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Posts Tagged ‘Calcium-Channel Blocker’


Calcium Signaling, Cardiac Mitochondria and Metabolic Syndrome

Larry H Bernstein: Author 

and

Reporter: Aviva Lev-Ari, PhD, RN

Mitochondria, the cardiovascular system and metabolic syndrome

Start date
April 24, 2013
End date
April 24, 2013
Venue
London, UK / Kennedy Lecture Theatre, Institute of Child Health
Location
London, UK
Topics
– Mitochondrial ROS metabolism in the heart
– Mitochondrial permeability transition pore
– Mitochondria in vascular smooth muscle
– Therapeutic targets for cardiac disease

Invited speakers

This event has now passed – please visit our Conference calendar for future Abcam events

Confirmed speakers:

Paolo Bernardi, University of Padova, Italy
‘The mitochondrial permeability transition pore: A mystery solved?’

Susan Chalmers, University of Strathclyde Glasgow
‘Mitochondria in vascular smooth muscle: from regulation of calcium signals to control of proliferation’

Andrew Hall, UCL
‘The role of sirtuin 3 in cardiac dysfunction’

Derek Hausenloy, UCL
‘Mitochondrial dynamics as a therapeutic target for cardiac disease’

Guy Rutter, Imperial College London
‘Mitochondria and insulin secretion – links to diabetes’ 

Michael Murphy, MRC Mitochondiral Biology Unit, Cambridge
‘Exploring mitochondrial ROS metabolism in the heart using targeted probes and bioactive molecules’

Toni Vidal Puig, Institute of Metabolic Science, University of Cambridge
‘Adipose tissue expandability, lipotoxicity and the metabolic syndrome’ 

 SOURCE

http://www.abcam.com/index.html?pageconfig=resource&rid=15722

It all happens in a heartbeat

Calcium signaling is instrumental for excitation-contraction coupling (ECC). The involvement of mitochondria  in establishing rapid cytosolic calcium transients in this process remain debated.

Two models have emerged:

  • slow integration versus rapid and
  • ample beat-to-beat changes of

cytosolic calcium transients into the mitochondria matrix.

a brief outline of cardiac calcium signaling » 

Mitochondrial Calcium transport mechanisms 

Calcium influx can be mediated by:

  • Mitochondrial Calcium Uniporter (MCU)
  • Mitochondrial Ryanodine receptor type 1 (mRyR1)
  • Leucine-zipper-EF-hand-containing transmembrane protein 1 (LETM1)
  • Proposed uptake by UCP2 and 3 and Coenzyme Q10

Calcium efflux can be mediated by:

  • Na-dependent calcium extrusion pathway, mNCX1
  • Mitochondrial permeability transistion pore (mPTP)

Inhibiting Calcium signaling 

Homeostasis of mitochondrial Ca2+ is crucial for balancing cell survival, death and energy production. Inhibitors of mitochondrial Ca2+ exchange are:

  1. CGP37157 – Selective mitochondrial Na+-Ca2+ exchange inhibitor
  2. Thapsigargin – Potent, cell-permeable Ca2+-ATPase inhibitor
  3. Ryanodine – Ca2+ release modulator

calcium signaling inhibitors (now available from Abcam Biochemicals)  » 

Quick tools for calcium detection 

You can now detect intracellular calcium mobilization directly in cultured cells in only 1 hour with Fluo-8 No Wash Calcium Assay Kit (ab112129):

  • increased signal with Fluo-8 – high affinity indicator (Kd = 389 nM)
  • no wash step needed
  • works on adherent and suspension cells

The Mitochondria, cardiovascular system and metabolic syndrome meeting took place on April 24 2013,  London, UK.

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Calcium-Channel Blocker, Calcium Release-related Contractile Dysfunction (Ryanopathy) and Calcium as Neurotransmitter Sensor

Author, and Content Consultant to e-SERIES A: Cardiovascular Diseases: Justin Pearlman, MD, PhD, FACC

Author and Curator: Larry H Bernstein, MD, FCAP

and Article Curator: Aviva Lev-Ari, PhD, RN

Introduction

Author: Larry H Bernstein, MD, FACC  

This Chapter is one of a series of articles on calcium activation, in this case, in the signaling of smooth muscle cells by the interacting neural innervation.    The process occurs by calcium triggering neurotransmitter release by initiating synaptic vesicle fusion.   The mechanism by which this occurs is addressed in detail, and involves the interaction of soluble N-acetylmaleimide-sensitive factor (SNARE) and SM proteins, and in addition, the discovery of a calcium-dependsent Syt1 (C) domain of protein- kinase C isoenzyme, which binds to phospholipids.
The 2013 Lasker Prize was awarded to Richard Schell (Genentech) and Thomas Sudolf (Stanford University) for their discoveries concerning the molecular machinery and regulatory mechanism that underlie the rapid release of neurotransmitters, a process that underlies all of the brain’s activities. They identified and isolated many of this reaction’s key elements, unraveled central aspects of its fundamental mechanism, and deciphered how cells govern it with extreme precision. These advances have provided a molecular framework for understanding some of the most devastating disorders that afflict humans as well as normal functions such as learning and memory, explaining unresolved hypotheses derived from the earlier work in the 1950sof the late Bernard Katz.  We also see that the work clarifies the debates initiated by the Nobelist Santiago Ramon y Cajal (1891) concerning the development of neural networks.  A biological relay system achieves these feats. Neurotransmission kicks off with an electrical pulse that runs down a nerve cell, or neuron. When that signal reaches the tip, calcium enters the cell. In response, the neuron liberates chemical messengers—neurotransmitters.
In the 1950s, the late Bernard Katz figured out that cells eject neurotransmitters in fixed amounts.  Balloon-like containers—vesicles—each hold set quantities of the chemicals. Calcium incites these lipid-bound sacs to fuse with the membrane that encases the cell, and their contents spill out. The picture that emerges from the later work is that synaptic vesicle exocytosis operates by a general mechanism of membrane fusion that revealed itself to be a model for all membrane fusion, but that is uniquely regulated by a calcium-sensor protein called synaptotagmin. The general membrane-fusion mechanism thus identified is mediated by SNARE- (for soluble NSF-receptors) and SM-proteins (for Sec1/Munc18-like proteins), largely discovered at the synapse, with synaptotagmin acting together with a molecular assistant called complexin as a clamp and activator of the membrane fusion mediated by the SNARE- and SM-proteins. Strikingly, the biochemical properties of synaptotagmin were found to precisely correspond to the extraordinary calcium-triggering properties of release, and to account for a regulatory pathway that also applies to other types of calcium-triggered fusion, for example fusion observed in hormone secretion and fertilization. At the synapse, finally, these interdependent machines — the fusion apparatus and its synaptotagmin-dependent control mechanism — are embedded in a proteinaceous active zone that links them to calcium channels, and regulates the docking and priming of synaptic vesicles for subsequent calcium-triggered fusion. Thus, work on neurotransmitter release revealed a hierarchy of molecular machines that mediate the fusion of synaptic vesicles, the calcium-control of this fusion, and the embedding of calcium-controlled fusion in the context of the presynaptic terminal at the synapse.
This portion of the discussion deals with the interaction of the neuronal endings interwoven into smooth muscle.   The calcium triggering of smooth muscle contractions is similar with respect to airways and arteries, urinary bladder, uterine contraction, and gastrointestinl tract.
The basic mechanism that underlie this MOTIF taken as variations of that described above are well described  by Michael J. Berridge in ‘Smooth muscle cell calcium activation mechanisms’. (J Physiol. 2008 Nov 1;586(Pt 21):5047-61.
http://dx.doi.org/10.1113/jphysiol.2008.160440.  Epub 2008 Sep 11.)
This is illustrated in his graphical examples.
Figure 1. The three main mechanisms responsible for generating the Ca2+ transients that trigger smooth muscle cell (SMC) contraction. From: Smooth muscle cell calcium activation mechanisms.
 Fig 1 Ca2+
A, receptor-operated channels (ROCs) or a membrane oscillator induces the membrane depolarization (ΔV) that triggers Ca2+ entry and contraction.
B, a cytosolic Ca2+ oscillator induces the Ca2+ signal that drives contraction.
C, a cytosolic Ca2+ oscillator in interstitial cells of Cajal (ICCs) or atypical SMCs induces the membrane depolarization that spreads through the gap junctions to activate neighbouring SMCs. Reproduced from Berridge (2008), with permission.
Michael J Berridge. J Physiol. 2008 November 1;586(Pt 21):5047-5061.  http://www.ncbi.nlm.nih.gov/pmc/articles/instance/2652144/bin/tjp0586-5047-f1.jpg

Figure 5. Vascular or airway SMCs are driven by a cytosolic oscillator that generates a periodic release of Ca2+ from the endoplasmic reticulum that usually appears as a propagating Ca2+ wave. From: Smooth muscle cell calcium activation mechanisms.

tjp0586-5047-f5   Vascular or airway SMCs are driven by a cytosolic oscillator that generates a periodic release of Ca2+ from the endoplasmic reticulum

The oscillator is induced/modulated by neurotransmitters such as acetylcholine (ACh), 5-hydroxytryptamine (5-HT), noradrenaline (NA) and endothelin-1 (ET-1), which act through inositol 1,4,5-trisphosphate (InsP3) that initiates the oscillatory mechanism. The sequence of steps 1–9 is described in the text. Reproduced from Berridge (2008), with permission.
Michael J Berridge. J Physiol. 2008 November 1;586(Pt 21):5047-5061.    http://www.ncbi.nlm.nih.gov/pmc/articles/instance/2652144/bin/tjp0586-5047-f5.jpg

Figure 7. The cytosolic Ca2+ oscillator responsible for pacemaker activity in interstitial cells of Cajal releases periodic pulses of Ca2+ that form a Ca2+ wave. From: Smooth muscle cell calcium activation mechanisms.

tjp0586-5047-f7 The cytosolic Ca2+ oscillator responsible for pacemaker activity in interstitial cells of Cajal releases periodic pulses of Ca2+ that form a Ca2+ wave.

The increase in Ca2+ activates Cl− channels (CLCA) to give the spontaneous transient inward currents (STICs) that sum to form the spontaneous transient depolarizations (STD) resulting in the slow waves of membrane depolarization (see inset). Current flow through gap junctions allows these waves to spread into neighbouring smooth muscle cells to activate contraction. See text for a description of the oscillator that drives this activation process. Reproduced from Berridge (2008), with permission.
Michael J Berridge. J Physiol. 2008 November 1;586(Pt 21):5047-5061.  http://www.ncbi.nlm.nih.gov/pmc/articles/instance/2652144/bin/tjp0586-5047-f7.gif

This article is the Part IX in a series of articles on Activation and Dysfunction of the Calcium Release Mechanisms in Cardiomyocytes and Vascular Smooth Muscle Cells.

The Series consists of the following articles:

Part I: Identification of Biomarkers that are Related to the Actin Cytoskeleton

Larry H Bernstein, MD, FCAP

https://pharmaceuticalintelligence.com/2012/12/10/identification-of-biomarkers-that-are-related-to-the-actin-cytoskeleton/

Part II: Role of Calcium, the Actin Skeleton, and Lipid Structures in Signaling and Cell Motility

Larry H. Bernstein, MD, FCAP, Stephen Williams, PhD and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/08/26/role-of-calcium-the-actin-skeleton-and-lipid-structures-in-signaling-and-cell-motility/

Part III: Renal Distal Tubular Ca2+ Exchange Mechanism in Health and Disease

Larry H. Bernstein, MD, FCAP, Stephen J. Williams, PhD
 and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/09/02/renal-distal-tubular-ca2-exchange-mechanism-in-health-and-disease/

Part IV: The Centrality of Ca(2+) Signaling and Cytoskeleton Involving Calmodulin Kinases and Ryanodine Receptors in Cardiac Failure, Arterial Smooth Muscle, Post-ischemic Arrhythmia, Similarities and Differences, and Pharmaceutical Targets

Larry H Bernstein, MD, FCAP, Justin Pearlman, MD, PhD, FACC and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/09/08/the-centrality-of-ca2-signaling-and-cytoskeleton-involving-calmodulin-kinases-and-ryanodine-receptors-in-cardiac-failure-arterial-smooth-muscle-post-ischemic-arrhythmia-similarities-and-differen/

Part V: Ca2+-Stimulated Exocytosis:  The Role of Calmodulin and Protein Kinase C in Ca2+ Regulation of Hormone and Neurotransmitter

Larry H Bernstein, MD, FCAP
and
Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/12/23/calmodulin-and-protein-kinase-c-drive-the-ca2-regulation-of-hormone-and-neurotransmitter-release-that-triggers-ca2-stimulated-exocytosis/

Part VI: Calcium Cycling (ATPase Pump) in Cardiac Gene Therapy: Inhalable Gene Therapy for Pulmonary Arterial Hypertension and Percutaneous Intra-coronary Artery Infusion for Heart Failure: Contributions by Roger J. Hajjar, MD

Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/08/01/calcium-molecule-in-cardiac-gene-therapy-inhalable-gene-therapy-for-pulmonary-arterial-hypertension-and-percutaneous-intra-coronary-artery-infusion-for-heart-failure-contributions-by-roger-j-hajjar/

Part VII: Cardiac Contractility & Myocardium Performance: Ventricular Arrhythmiasand Non-ischemic Heart Failure – Therapeutic Implications for Cardiomyocyte Ryanopathy (Calcium Release-related Contractile Dysfunction) and Catecholamine Responses

Justin Pearlman, MD, PhD, FACC, Larry H Bernstein, MD, FCAP and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/08/28/cardiac-contractility-myocardium-performance-ventricular-arrhythmias-and-non-ischemic-heart-failure-therapeutic-implications-for-cardiomyocyte-ryanopathy-calcium-release-related-contractile/

Part VIII: Disruption of Calcium Homeostasis: Cardiomyocytes and Vascular Smooth Muscle Cells: The Cardiac and Cardiovascular Calcium Signaling Mechanism

Justin Pearlman, MD, PhD, FACC, Larry H Bernstein, MD, FCAP and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/09/12/disruption-of-calcium-homeostasis-cardiomyocytes-and-vascular-smooth-muscle-cells-the-cardiac-and-cardiovascular-calcium-signaling-mechanism/

Part IX: Calcium-Channel Blockers, Calcium Release-related Contractile Dysfunction (Ryanopathy) and Calcium as Neurotransmitter Sensor

Justin Pearlman, MD, PhD, FACC, Larry H Bernstein, MD, FCAP and Aviva Lev-Ari, PhD, RN

Part X: Synaptotagmin functions as a Calcium Sensor: How Calcium Ions Regulate the fusion of vesicles with cell membranes during Neurotransmission

Larry H Bernstein, MD, FCAP and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/09/10/synaptotagmin-functions-as-a-calcium-sensor-how-calcium-ions-regulate-the-fusion-of-vesicles-with-cell-membranes-during-neurotransmission/

Part XI: Sensors and Signaling in Oxidative Stress

Larry H. Bernstein, MD, FCAP

https://pharmaceuticalintelligence.com/2013/11/01/sensors-and-signaling-in-oxidative-stress/

Part XII: Atherosclerosis Independence: Genetic Polymorphisms of Ion Channels Role in the Pathogenesis of Coronary Microvascular Dysfunction and Myocardial Ischemia (Coronary Artery Disease (CAD))

Larry H Bernstein, MD, FCAP and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/12/21/genetic-polymorphisms-of-ion-channels-have-a-role-in-the-pathogenesis-of-coronary-microvascular-dysfunction-and-ischemic-heart-disease/

This article has FIVE Sections:

Section One

Innovations in Combination Drug Therapy: Calcium-Channel Blocker –  Amlodipine (Norvasc) in single-pill combinations (SPCs) of drugs

Section Two

Calcium-Channel Blockers: Drug Class and Indications

Section Three

Brand and Generic Calcium Channel Blocking Agents

Section Four

Dysfunction of the Calcium Release Mechanism

Section Five

The Calcium Sensor: How Calcium Ions Regulate the fusion of vesicles with cell membranes during Neurotransmission

 Section One

Innovations in Combination Drug Therapy:

Calcium-Channel Blocker, Amlodipine (Norvasc) in Single-Pill Combinations (SPCs) of Drugs

Latest development on Cardiovascular Pharmacotherapy relates to the development of a Duo Combination Therapy to include a leading  Calcium-Channel Blocker, Amlodipine (Norvasc), as one of the two drug classes in one pill:The research investigated the therapeutic efficacy achieved via a comparison of a two single-pill combinations (SPCs) of drugs:

  • telmisartan/amlodipine (T/A) [ARB/CCB]

and

  • telmisartan/hydrochlorothiazide (T/H) [ARB/Diuterics]
Drug classes:
ARB – telmisartan
CCB – amlodipine
Diuretics – hydrochlorothiazide

A review of the benefits of early treatment initiation with single-pill combinations of telmisartan with amlodipine or hydrochlorothiazide

Authors: Segura J, Ruilope LM

Published Date September 2013 Volume 2013:9 Pages 521 – 528

http://www.dovepress.com/articles.php?article_id=14373

Published: 16 September 2013, Dovepress Journal: Vascular Health and Risk Management

Julian Segura, Luis Miguel Ruilope

Department of Nephrology, Hospital 12 de Octubre, Madrid, Spain

Abstract:

This review discusses the rationale for earlier use of single-pill combinations (SPCs) of antihypertensive drugs, with a focus on telmisartan/amlodipine (T/A) and telmisartan/hydrochlorothiazide (T/H) SPCs.
  • Compared with the respective monotherapies, the once-daily T/A and T/H SPCs have been shown to result in significantly higher blood pressure (BP) reductions, BP goal rates, and response rates in patients at all stages of hypertension.
  • As expected, BP reductions are highest with the highest dose (T80/A10 and T80/H25) SPCs. Subgroup analyses of the telmisartan trials have reported the efficacy of both SPCs to be consistent, regardless of the patients’ age, race, and coexisting diabetes, obesity, or renal impairment.
  • In patients with mild-to-moderate hypertension, the T/A combination provides superior 24-hour BP-lowering efficacy compared with either treatment administered as monotherapy.
  • Similarly, the T/H SPC treatment provides superior 24-hour BP-lowering efficacy, especially in the last 6 hours relative to other renin–angiotensin system inhibitor-based SPCs.
  • The T/A SPC is associated with a lower incidence of edema than amlodipine monotherapy, and
  • The T/H SPC with a lower incidence of hypokalemia than hydrochlorothiazide monotherapy
  • Existing evidence supports the use of the T/A SPC for the treatment of hypertensive patients with prediabetes, diabetes, or metabolic syndrome, due to the metabolic neutrality of both component drugs, and the use of the T/H SPC for those patients with edema or in need of volume reduction.
Keywords: angiotensin receptor blockers, or ARBs, calcium-channel blocker, or CCBs, essential hypertension, diuretic, , renin-angiotensin system inhibitor, or ACEI
http://www.dovepress.com/articles.php?article_id=14373
We reported on 5/29/2012

Triple Combination Therapy: ARB and Calcium Channel Blocker and Diuretics

In July 2010, a triple combination drug for hypertension was approved by the US Food and Drug Administration. Tribenzor contains olmesartan medoxomil, amlodipine and hydrochlorothiazide, according to Monthly Prescribing Reference.

TRIBENZOR is a Daiichi Sankyo’s product- ARB and Calcium Channel Blocker and Diuretic

How TRIBENZOR work

Tribenzor contains olmesartan medoxomil, amlodipine and hydrochlorothiazide. High blood pressure makes the heart work harder to pump blood through the body and causes damage to blood vessels. TRIBENZOR can help your blood vessels relax and reduce the amount of fluid in your blood. This can make your blood pressure lower. Medicines that lower blood pressure may lower your chance of having a stroke or a heart attack.

Some people may need more than 1—or even more than 2—medicines to help control their blood pressure. TRIBENZOR combines 3 effective medicines in 1 convenient pill. Read the following chart to learn how each medicine works in its own way to help lower blood pressure.

TRIBENZOR: 3 effective medicines in 1 pill

The medicine in TRIBENZOR How it works What it does
Angiotensin II receptor blocker Blocks a natural chemical in your body that causes blood vessels to narrow.

Lowers

Yours

blood

pressure

Calcium channel blocker Blocks the narrowing effect of calcium on your blood vessels. This helps your blood vessels relax.
Diuretic (water pill) Helps your kidneys flush extra fluid and salt from your body. This lowers the amount of fluid in your blood.

http://www.tribenzor.com/how_works.html

            Effectively lower blood pressure. People taking the 3 medicines in TRIBENZOR had greater reductions in blood pressure than did people taking any 2 of the medicines combined

            Start to work quickly. People taking TRIBENZOR saw results in as little as 2 weeks

AZOR is a Daiichi Sankyo’s product- ARB and Calcium Channel Blocker

How AZOR work

AZOR relaxes and widens blood vessels to help lower blood pressure.

You may have already tried another blood pressure medicine that works a certain way to lower blood pressure. But 1 blood pressure medicine may not be enough for you. You may find the help you need with the 2 effective medicines in AZOR.

AZOR combines 2 effective medicines in 1 convenient pill.

Learn how each medicine in AZOR works in its own way to help lower blood pressure.

The medicine in AZOR How it works What it does
Angiotensin II receptor blocker (ARB) Blocks a natural chemical in your body that causes blood vessels to narrow. This helps your blood vessels relax and widen.

Lowers

Your

Blood

pressure

Calcium channel blocker Blocks the narrowing effect of calcium on your blood vessels. This helps your blood vessels relax.

http://www.AZOR.com/how_works.html

Section Two

Calcium-Channel Blockers: Drug Class and Indications

In Sudhof’s Lasker Award presentation he refers to the biochemical properties of synaptotagmin were found to precisely correspond to the extraordinary calcium-triggering properties of release, and to account for a regulatory pathway that also applies to other types of calcium-triggered fusion, for example fusion observed in hormone secretion.  A CCB would have to block the calcium-triggering properties of release, and consequently, would block the release of neurohormones.  This is because the fusion apparatus and its synaptotagmin-dependent control mechanism linked to the calcium channels, docking and priming synaptic vesicles, being blocked, disables the calcium-control of the vesicle fusion that is necessary for neurotransmitter release. Consequently, the end result would be increased vascular flow from the inhibition.

What are calcium channel blockers and how do they work?

In order to pump blood, the heart needs oxygen. The harder the heart works, the more oxygen it requires. Angina (heart pain) occurs when the supply of oxygen to the heart is inadequate for the amount of work the heart must do. By dilating the arteries, CCBs reduce the pressure in the arteries. This makes it easier for the heart to pump blood, and, as a result, the heart needs less oxygen. By reducing the heart’s need for oxygen, CCBs relieve or prevent angina. CCBs also are used for treating high blood pressure because of their blood pressure-lowering effects. CCBs also slow the rate at which the heart beats and are therefore used for treating certain types of abnormally rapid heart rhythms.

For what conditions are calcium channel blockers used?

CCBs are used for treating high blood pressure, angina, and abnormal heart rhythms (for example, atrial fibrillationparoxysmal supraventricular tachycardia).

They also may be used after a heart attack, particularly among patients who cannot tolerate beta-blocking drugs, have atrial fibrillation, or require treatment for their angina.

Unlike beta blockers, CCBs have not been shown to reduce mortality or additional heart attacks after a heart attack.

CCBs are as effective as ACE inhibitors in reducing blood pressure, but they may not be as effective as ACE inhibitors in preventing the kidney failure caused by high blood pressure or diabetes.

They also are used for treating:

CCBs are also used in the prevention of migraine headaches.

Are there any differences among calcium channel blockers?

CCBs differ in their duration of action, the process by which they are eliminated from the body, and, most importantly, in their ability to affect heart rate and contraction. Some CCBs [for example, amlodipine (Norvasc)] have very little effect on heart rate and contraction so they are safer to use in individuals who have heart failure or bradycardia (a slow heart rate). Verapamil (Calan, Isoptin) and diltiazem (Cardizem) have the greatest effects on the heart and reduce the strength and rate of contraction. Therefore, they are used in reducing heart rate when the heart is beating too fast.

What are the side effects of calcium channel blockers?

  • The most common side effects of CCBs are constipationnausea,headacherashedema (swelling of the legs with fluid), low blood pressure, drowsiness, and dizziness.
  • Liver dysfunction and over growth of gums may also occur. When diltiazem (Cardizem) or verapamil (Calan, Isoptin) are given to individuals with heart failure, symptoms of heart failure may worsen because these drugs reduce the ability of the heart to pump blood.
  • Like other blood pressure medications, CCBs are associated with sexual dysfunction.

http://www.medicinenet.com/calcium_channel_blockers/article.htm

Section Three

Brand and Generic Calcium Channel Blocking Agents

A drug may be classified by the chemical type of the active ingredient or by the way it is used to treat a particular condition. Each drug can be classified into one or more drug classes.

Calcium channel blockers block voltage gated calcium channels and inhibits the influx of calcium ions into cardiac and smooth muscle cells. The decrease in intracellular calcium reduces the strength of heart muscle contraction, reduces conduction of impulses in the heart, and causes vasodilatation.

Decrease in intracellular calcium in the heart decreases cardiac contractility. Decreased calcium in the vascular smooth muscle reduces its contraction and therefore causes vasodilatation.

Decrease in cardiac contractility decreases cardiac output and vasodilatation decreases total peripheral resistance, both of which cause a drop in blood pressure.

Calcium channel blocking agents are used to treat hypertension.

Filter by: — all conditions –AnginaAngina Pectoris ProphylaxisArrhythmiaAtrial FibrillationAtrial FlutterBipolar DisorderCluster HeadachesCoronary Artery DiseaseHeart FailureHigh Blood PressureHypertensive EmergencyHypertrophic CardiomyopathyIdiopathic Hypertrophic Subaortic StenosisIschemic StrokeMigraine PreventionNocturnal Leg CrampsPremature LaborRaynaud’s SyndromeSubarachnoid HemorrhageSupraventricular Tachycardia

Drug Name ( View by: Brand | Generic )
Afeditab CR (Pro, More…)generic name: nifedipine
Diltia XT (Pro, More…)generic name: diltiazem
Diltiazem Hydrochloride SR (More…)generic name: diltiazem
Nimotop (Pro, More…)generic name: nimodipine
Verelan PM (Pro, More…)generic name: verapamil
Cartia XT (Pro, More…)generic name: diltiazem
Adalat (More…)generic name: nifedipine
Calan SR (Pro, More…)generic name: verapamil
Cardizem (Pro, More…)generic name: diltiazem
Diltiazem Hydrochloride CD (More…)generic name: diltiazem
Isoptin SR (Pro, More…)generic name: verapamil
Nifediac CC (Pro, More…)generic name: nifedipine
Tiazac (Pro, More…)generic name: diltiazem
Procardia (Pro, More…)generic name: nifedipine
Adalat CC (Pro, More…)generic name: nifedipine
Cardizem LA (Pro, More…)generic name: diltiazem
Calan (Pro, More…)generic name: verapamil
Procardia XL (Pro, More…)generic name: nifedipine
Isoptin (More…)generic name: verapamil
Nifedical XL (Pro, More…)generic name: nifedipine
Plendil (Pro, More…)generic name: felodipine
Taztia XT (Pro, More…)generic name: diltiazem
Cardizem CD (Pro, More…)generic name: diltiazem
Norvasc (Pro, More…)generic name: amlodipine
Verelan (Pro, More…)generic name: verapamil
Cardene SR (Pro, More…)generic name: nicardipine
DynaCirc CR (Pro, More…)generic name: isradipine
Sular (Pro, More…)generic name: nisoldipine
Cardene (Pro, More…)generic name: nicardipine
Cardene IV (Pro, More…)generic name: nicardipine
Cleviprex (Pro, More…)generic name: clevidipine
Covera-HS (Pro, More…)generic name: verapamil
Dilacor XR (Pro, More…)generic name: diltiazem
Dilt-XR (Pro, More…)generic name: diltiazem
Diltiazem Hydrochloride XR (More…)generic name: diltiazem
Diltiazem Hydrochloride XT (More…)generic name: diltiazem
Diltzac (Pro, More…)generic name: diltiazem
Dynacirc (Pro, More…)generic name: isradipine
Matzim LA (Pro, More…)generic name: diltiazem
Nymalize (Pro, More…)generic name: nimodipine
Vascor (More…)generic name: bepridil

Section Four

Dysfunction of the Calcium Release Mechanism

For Disruption of Calcium Homeostasis in Vascular Smooth Muscle Cells, see

Part IV: The Centrality of Ca(2+) Signaling and Cytoskeleton Involving Calmodulin Kinases and Ryanodine Receptors in Cardiac Failure, Arterial Smooth Muscle, Post-ischemic Arrhythmia, Similarities and Differences, and Pharmaceutical Targets

Larry H Bernstein, MD, FCAP, Justin Pearlman, MD, PhD, FACC and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/09/08/the-centrality-of-ca2-signaling-and-cytoskeleton-involving-calmodulin-kinases-and-ryanodine-receptors-in-cardiac-failure-arterial-smooth-muscle-post-ischemic-arrhythmia-similarities-and-differen/

Part V: Heart, Vascular Smooth Muscle, Excitation-Contraction Coupling (E-CC), Cytoskeleton, Cellular Dynamics and Ca2 Signaling

Larry H Bernstein, MD, FCAP, Justin Pearlman, MD, PhD, FACC and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/08/26/heart-smooth-muscle-excitation-contraction-coupling-cytoskeleton-cellular-dynamics-and-ca2-signaling/

For Disruption of Calcium Homeostasis in Cardiomyocyte Cells, see

Part VI: Calcium Cycling (ATPase Pump) in Cardiac Gene Therapy: Inhalable Gene Therapy for Pulmonary Arterial Hypertension and Percutaneous Intra-coronary Artery Infusion for Heart Failure: Contributions by Roger J. Hajjar, MD

Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/08/01/calcium-molecule-in-cardiac-gene-therapy-inhalable-gene-therapy-for-pulmonary-arterial-hypertension-and-percutaneous-intra-coronary-artery-infusion-for-heart-failure-contributions-by-roger-j-hajjar/

Part VII: Cardiac Contractility & Myocardium Performance: Ventricular Arrhythmias and Non-ischemic Heart Failure – Therapeutic Implications for Cardiomyocyte Ryanopathy (Calcium Release-related Contractile Dysfunction) and Catecholamine Responses

Justin Pearlman, MD, PhD, FACC, Larry H Bernstein, MD, FCAP and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/08/28/cardiac-contractility-myocardium-performance-ventricular-arrhythmias-and-non-ischemic-heart-failure-therapeutic-implications-for-cardiomyocyte-ryanopathy-calcium-release-related-contractile/

Part VIII: Disruption of Calcium Homeostasis: Cardiomyocytes and Vascular Smooth Muscle Cells: The Cardiac and Cardiovascular Calcium Signaling Mechanism

Justin Pearlman, MD, PhD, FACC, Larry H Bernstein, MD, FCAP and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/09/12/disruption-of-calcium-homeostasis-cardiomyocytes-and-vascular-smooth-muscle-cells-the-cardiac-and-cardiovascular-calcium-signaling-mechanism/

Section Five

The Calcium Sensor: How Calcium Ions Regulate the fusion of vesicles with cell membranes during Neurotransmission

This topic is covered in

Synaptotagmin functions as a Calcium Sensor: How Calcium Ions Regulate the fusion of vesicles with cell membranes during Neurotransmission

Larry H Bernstein, MD, FCAP and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/09/10/synaptotagmin-functions-as-a-calcium-sensor-how-calcium-ions-regulate-the-fusion-of-vesicles-with-cell-membranes-during-neurotransmission/

Part V: Heart, Vascular Smooth Muscle, Excitation-Contraction Coupling (E-CC), Cytoskeleton, Cellular Dynamics and Ca2 Signaling

Larry H Bernstein, MD, FCAP, Justin Pearlman, MD, PhD, FACC and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/08/26/heart-smooth-muscle-excitation-contraction-coupling-cytoskeleton-cellular-dynamics-and-ca2-signaling/

Summary

Work on neurotransmitter release revealed a hierarchy of molecular machines that mediate the fusion of synaptic vesicles, the calcium-control of this fusion, and the embedding of calcium-controlled fusion in the context of the presynaptic terminal at the synapse. The neural transmission is described as a biological relay system. Neurotransmission kicks off with an electrical pulse that runs down a nerve cell, or neuron. When that signal reaches the tip, calcium enters the cell. In response, the neuron liberates chemical messengers—neurotransmitters.  When the calcium-controlled fusion at the presynaptic junction is blocked, as with a CCB, neurotransmitters are not released.  The activity of the neurotransmitters would be to cause smaooth muscle contraction of the vessel.  The CCB would cause relaxation and flow.

http://www.nature.com/focus/Lasker/2013/pdf/ES-Lasker13-Sudhof.pdf

Part IX of this series of articles discussed the mechanism of the signaling of smooth muscle cells by the interacting parasympathetic neural innervation that occurs by calcium triggering neurotransmitter release by initiating synaptic vesicle fusion. It involves the interaction of soluble N-acetylmaleimide-sensitive factor (SNARE) and SM proteins, and in addition, the discovery of a calcium-dependent Syt1 (C) domain of protein- kinase C isoenzyme, which binds to phospholipids. It is reasonable to consider that it differs from motor neuron activation of skeletal muscles, mainly because the innervation is in the involuntary domain. The cranial nerve rooted innervation has evolved comes from the spinal ganglia at the corresponding level of the spinal cord. It is in this specific neural function that we find a mechanistic interaction with adrenergic hormonal function, a concept intimated by the late Richard Bing. Only recently has there been a plausible concept that brings this into serious consideration. Moreover, the review of therapeutic drugs that are used in blocking adrenergic receptors are closely related to the calcium-channels. Interesting too is the participation of a phospholipid bound protein-kinase isoenzyme C calcium-dependent domain Syt1. The neurohormonal connection lies in the observation by Katz in the 1950’s that the vesicles of the neurons hold and eject fixed amounts of neurotransmitters.  The mechanism of this action will be futher discussed in Part X.

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Disruption of Calcium Homeostasis: Cardiomyocytes and Vascular Smooth Muscle Cells: The Cardiac and Cardiovascular Calcium Signaling Mechanism

 

Author, Introduction: Larry H Bernstein, MD, FCAP

Author, Summary: Justin Pearlman, MD, PhD, FACC 

and

Article Curator: Aviva Lev-Ari, PhD, RN

This article is the Part VIII in a series of articles on Activation and Dysfunction of the Calcium Release Mechanisms in Cardiomyocytes and Vascular Smooth Muscle Cells. Calcium has a storage and release cycle that flags activation of important cellular activities that include in particular the cycle activation of muscle contraction both to circulate blood and control its pressure and distribution. Homeostasis – the maintenance of status – requires controlled release of calcium from storage and return of calcium to storage. Such controls are critical both within cells, and for the entire biologic system. Thus the role of kidneys in maintaining the correct total body load of available calcium is just as vital as the subcellular systems of calcium handling in heart muscle and in the muscles that line arteries to control blood flow. The practical side to this knowledge includes not only identifying abnormalities at the cellular as well as system levels, but also identifying better opportunities to characterize disease and to intervene.

The Series consists of the following articles:

Part I: Identification of Biomarkers that are Related to the Actin Cytoskeleton

Larry H Bernstein, MD, FCAP

https://pharmaceuticalintelligence.com/2012/12/10/identification-of-biomarkers-that-are-related-to-the-actin-cytoskeleton/

Part II: Role of Calcium, the Actin Skeleton, and Lipid Structures in Signaling and Cell Motility

Larry H. Bernstein, MD, FCAP, Stephen Williams, PhD and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/08/26/role-of-calcium-the-actin-skeleton-and-lipid-structures-in-signaling-and-cell-motility/

Part III: Renal Distal Tubular Ca2+ Exchange Mechanism in Health and Disease

Larry H. Bernstein, MD, FCAP, Stephen J. Williams, PhD
 and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/09/02/renal-distal-tubular-ca2-exchange-mechanism-in-health-and-disease/

Part IV: The Centrality of Ca(2+) Signaling and Cytoskeleton Involving Calmodulin Kinases and Ryanodine Receptors in Cardiac Failure, Arterial Smooth Muscle, Post-ischemic Arrhythmia, Similarities and Differences, and Pharmaceutical Targets

Larry H Bernstein, MD, FCAP, Justin Pearlman, MD, PhD, FACC and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/09/08/the-centrality-of-ca2-signaling-and-cytoskeleton-involving-calmodulin-kinases-and-ryanodine-receptors-in-cardiac-failure-arterial-smooth-muscle-post-ischemic-arrhythmia-similarities-and-differences/

Part V: Ca2+-Stimulated Exocytosis:  The Role of Calmodulin and Protein Kinase C in Ca2+ Regulation of Hormone and Neurotransmitter

Larry H Bernstein, MD, FCAP
and
Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/12/23/calmodulin-and-protein-kinase-c-drive-the-ca2-regulation-of-hormone-and-neurotransmitter-release-that-triggers-ca2-stimulated-exocytosis/

Part VI: Calcium Cycling (ATPase Pump) in Cardiac Gene Therapy: Inhalable Gene Therapy for Pulmonary Arterial Hypertension and Percutaneous Intra-coronary Artery Infusion for Heart Failure: Contributions by Roger J. Hajjar, MD

Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/08/01/calcium-molecule-in-cardiac-gene-therapy-inhalable-gene-therapy-for-pulmonary-arterial-hypertension-and-percutaneous-intra-coronary-artery-infusion-for-heart-failure-contributions-by-roger-j-hajjar/

Part VII: Cardiac Contractility & Myocardium Performance: Ventricular Arrhythmias and Non-ischemic Heart Failure – Therapeutic Implications for Cardiomyocyte Ryanopathy (Calcium Release-related Contractile Dysfunction) and Catecholamine Responses

Justin Pearlman, MD, PhD, FACC, Larry H Bernstein, MD, FCAP and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/08/28/cardiac-contractility-myocardium-performance-ventricular-arrhythmias-and-non-ischemic-heart-failure-therapeutic-implications-for-cardiomyocyte-ryanopathy-calcium-release-related-contractile/

Part VIII: Disruption of Calcium Homeostasis: Cardiomyocytes and Vascular Smooth Muscle Cells: The Cardiac and Cardiovascular Calcium Signaling Mechanism

Justin Pearlman, MD, PhD, FACC, Larry H Bernstein, MD, FCAP and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/09/12/disruption-of-calcium-homeostasis-cardiomyocytes-and-vascular-smooth-muscle-cells-the-cardiac-and-cardiovascular-calcium-signaling-mechanism/

Part IXCalcium-Channel Blockers, Calcium Release-related Contractile Dysfunction (Ryanopathy) and Calcium as Neurotransmitter Sensor

Justin Pearlman, MD, PhD, FACC, Larry H Bernstein, MD, FCAP and Aviva Lev-Ari, PhD, RN

Part X: Synaptotagmin functions as a Calcium Sensor: How Calcium Ions Regulate the fusion of vesicles with cell membranes during Neurotransmission

Larry H Bernstein, MD, FCAP and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/09/10/synaptotagmin-functions-as-a-calcium-sensor-how-calcium-ions-regulate-the-fusion-of-vesicles-with-cell-membranes-during-neurotransmission/

Part XI: Sensors and Signaling in Oxidative Stress

Larry H. Bernstein, MD, FCAP

https://pharmaceuticalintelligence.com/2013/11/01/sensors-and-signaling-in-oxidative-stress/

Part XII: Atherosclerosis Independence: Genetic Polymorphisms of Ion Channels Role in the Pathogenesis of Coronary Microvascular Dysfunction and Myocardial Ischemia (Coronary Artery Disease (CAD))

Larry H Bernstein, MD, FCAP and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/12/21/genetic-polymorphisms-of-ion-channels-have-a-role-in-the-pathogenesis-of-coronary-microvascular-dysfunction-and-ischemic-heart-disease/

 

This article has three Sections:

Section One:

Vascular Smooth Muscle Cells: The Cardiovascular Calcium Signaling Mechanism

Section Two:

Cardiomyocytes Cells: The Cardiac Calcium Signaling Mechanism

Section Three:

The Calcium Sensor: How Calcium Ions Regulate the fusion of vesicles with cell membranes during Neurotransmission

Introduction

by Larry H Bernstein, MD, FACC   

Introduction

This discussion in two Sections brings to a conclusion the two main aspects of calcium signaling and transient current induction in the cardiovascular system – involving vascular smooth muscle and cardiomyocyte.  In this first Section, it extends the view of smooth muscle beyond the vascular smooth muscle to contraction events in gastrointestinal tract, urinary bladder, and uterus, but by inference, to ductal structures (gallbladder, parotid gland, etc.).  This discussion also reinforces the ECONOMY of the evolutionary development of these functional MOTIFS, as a common thread is used again, and again, in specific contexts.  The main elements of this mechanistic framework are:

  • the endoplasmic (sarcoplasmic) reticulum as a strorage depot for calcium needed in E-C coupling
  • the release of Ca(2+) into the cytoplasm
  • the generation of a voltage and current with contraction of the muscle cell unit
  • the coordination of smooth muscle cell contractions (in waves)
    • this appears to be related to the Rho/Rho kinase pathway
  • there is also a membrane depolarization inherent in the activation mechanism
  • whether there is an ordered relationship between the calcium release and the membrane polarization, and why this would be so, in not clear
  • three different models of calcium release are shown from the MJ Berridge classification article below in Figure 1.
  • Model C is of special interest because of the focus on cytosolic (Ca+) ion transfers involving the interstitial cells of Cajal (Ramin e’ Cajal) through gap junctions

Santiago Ramón y Cajal  (Spanish: [sanˈtjaɣo raˈmon i kaˈxal]; 1 May 1852 – 18 October 1934) was a Spanish pathologist, histologist and neuroscientist. He was awarded  the Nobel Prize in Physiology or Medicine in 1906 together with Italian Camillo Golgi “in recognition of their work on the structure of the nervous system”.  Relevant to this discussion, he discovered a new type of cell, to be named after him: the interstitial cell of Cajal (ICC). This cell is found interleaved among neurons embedded within the smooth muscles lining the gut, serving as the generator and pacemaker of the slow waves of contraction that move material along the gastrointestine, vitally mediating neurotransmission from motor nerves to smooth muscle cells . Cajal also described in 1891 slender horizontal bipolar cells in the developing marginal zone of lagomorphs.(See the Cajal’s original drawing of the cells) , considered by Retzius as homologues to the cells he found in humans and in other mammals (Retzius, 1893, 1894).  The term Cajal–Retzius cell is applied to reelin-producing neurons of the human embryonic marginal zone.  

240px-Cajal-Retzius_cell_drawing_by_Cajal_1891

Section One

Vascular Smooth Muscle Cells: The Cardiovascular Calcium Signaling Mechanism

Smooth Muscle Cell Calcium Activation Mechanisms

Michael J. Berridge

J Physiol 586.21 (2008) pp 5047–5061

http://jp.physoc.org/content/586/21/5047.full.pdf

Classification of Smooth Muscle Ca2+ Activation Mechanisms

Excitation–contraction coupling in SMCs occurs through two main mechanisms. Many SMCs are activated by Ca2+ signalling cascades (Haddock & Hill, 2005; Wray et al.  2005).  In addition, there is a Rho/Rho kinase signaling pathway that acts by altering the Ca2+ sensitivity of the contractile system (Somlyo & Somlyo, 2003). Since the latter appears to have more of a modulatory function,most attention will focus on how Ca2+ signalling is activated.  Since membrane depolarization is a key element for the activation of many SMCs,much attention will focus on the mechanisms responsible for depolarizing the membrane.  However, there are other SMCs where activation depends on the periodic release of Ca2+ from internal stores. These different Ca2+ activation mechanisms fall into the following three main groups (Fig. 1).

 

Fig 1 Ca2+

Figure 1. The three main mechanisms responsible for generating the Ca2+ transients that trigger smooth

muscle cell (SMC) contraction

A, receptor-operated channels (ROCs) or a membrane oscillator induces the membrane depolarization (_V) that

triggers Ca2+ entry and contraction.

B, a cytosolic Ca2+ oscillator induces the Ca2+ signal that drives contraction.

C, a cytosolic Ca2+ oscillator in interstitial cells of Cajal (ICCs) or atypical SMCs induces the membrane depolarization

that spreads through the gap junctions to activate neighbouring SMCs. Reproduced from Berridge (2008), with permission

SOURCE for Figure 1: J Physiol 586.21 M. J. Berridge Smooth muscle cell calcium activation mechanisms 5048

http://jp.physoc.org/content/586/21/5047.full.pdf

Mechanism A.

Many SMCs are activated by membrane depolarization (_V) that opens L-type voltage-operated channels (VOCs) allowing external Ca2+ to flood into the cell to trigger contraction. This depolarization is induced either by ionotropic receptors (vas deferens) or a membrane oscillator (bladder and uterus). Themembrane oscillator, which resides in the plasma membrane, generates the periodic pacemaker depolarizations responsible for the action potentials that drive contraction. The depolarizing signal that activates gastrointestinal, urethral and ureter SMCs is described in mechanism C.

Mechanism B.

The rhythmical contractions of vascular, lymphatic, airway and corpus cavernosum SMCs depend on an endogenous pacemaker driven by a cytosolic Ca2+ oscillator that is responsible for the periodic release of Ca2+  from the endoplasmic reticulum. The periodic pulses of Ca2+ often cause membrane depolarization, but this is not part of the primary activation mechanism but has a secondary role to synchronize and amplify the oscillatory mechanism. Neurotransmitters and hormones act by modulating the frequency of the cytosolic oscillator.

Mechanism C.

A number of SMCs are activated by pacemaker cells such as the interstitial cells of Cajal (ICCs)  (gastrointestinal and urethral SMCs) or atypical SMCs (ureter). These pacemaker cells have a cytosolic oscillator that generates the repetitive Ca2+  transients that activate inward currents that spread through the gap junctions to provide the depolarizing signal (_V) that triggers contraction through mechanism A.  In the following sections, some selected SMC types will illustrate how these signalling mechanisms have been adapted to control different contractile functions with particular emphasis on how Ca2+ signals are activated.

Vascular, Lymphatic and Airway Smooth Muscle Cells

Vascular, lymphatic and airway smooth muscle, which generate rhythmical contractions over an extended period of time, have an endogenous pacemaker mechanism driven by a cytosolic Ca2+ oscillator. In addition, these SMCs also respond to neurotransmitters released from the neural innervation. In the case of mesenteric arteries, the perivascular nerves release both ATP and noradrenaline  (NA). The ATP acts first to produce a small initial contraction that is then followed by a much larger contraction when NA initiates a series of Ca2+ transients (Lamont et al. 2003). Such agonist-induced Ca2+ oscillations are a characteristic feature of the activation mechanisms of vascular (Iino et al. 1994; Lee et al.  2001; Peng et al. 2001; Perez & Sanderson, 2005b; Shaw et al. 2004) and airway SMCs (Kuo et al. 2003; Perez & Sanderson, 2005a; Sanderson et al. 2008). In some blood vessels, a specific tone is maintained by the spatial averaging of asynchronous oscillations. However, there are some vessels where the oscillations in groups of cells are synchronized resulting in the pulsatile contractions known as vasomotion (Mauban et al. 2001; Peng et al.  2001; Lamboley et al. 2003; Haddock & Hill, 2005).  Such vasomotion is also a feature of lymphatic vessels (Imtiaz et al. 2007). Another feature of this oscillatory activity is that variations in transmitter concentration are translated into a change in contractile tone through a mechanism of frequency modulation (Iino et al.  1994; Kuo et al. 2003; Perez & Sanderson, 2005a,b).  Frequency modulation is one of the mechanisms used for encoding and decoding signalling information through Ca2+ oscillations (Berridge, 2007).

The periodic pulses of Ca2+ that drive these rhythmical SMCs are derived from the internal stores through the operation of a cytosolic Ca2+  oscillator (Haddock & Hill, 2005; Imtiaz et al. 2007;  Sanderson et al. 2008). The following general model, which applies to vascular, lymphatic, airway and perhaps also to corpus cavernosum SMCs, attempts to describe the nature of this oscillator and how it can be induced or modulated by neurotransmitters. A luminal loading Ca2+ oscillation mechanism (Berridge & Dupont, 1994; Berridge, 2007)  forms the basis of this cytosolic oscillator model that depends upon the following sequential series of events  (Fig. 5).

 Fig 2 Ca2+

Figure 5. Vascular or airway SMCs are driven by a cytosolic oscillator that generates a periodic release

of Ca2+ from the endoplasmic reticulum that usually appears as a propagating Ca2+ wave

The oscillator is induced/modulated by neurotransmitters such as acetylcholine (ACh), 5-hydroxytryptamine (5-HT),

noradrenaline (NA) and endothelin-1 (ET-1), which act through inositol 1,4,5-trisphosphate (InsP3) that initiates

the oscillatory mechanism. The sequence of steps 1–9 is described in the text. Reproduced from Berridge (2008),

with permission.

SOURCE for Figure 5: J Physiol 586.21 M. J. Berridge Smooth muscle cell calcium activation mechanisms 5053

http://jp.physoc.org/content/586/21/5047.full.pdf

For Disruption of Calcium Homeostasis in Vascular Smooth Muscle Cells, see

Part IV: The Centrality of Ca(2+) Signaling and Cytoskeleton Involving Calmodulin Kinases and Ryanodine Receptors in Cardiac Failure, Arterial Smooth Muscle, Post-ischemic Arrhythmia, Similarities and Differences, and Pharmaceutical Targets

Larry H Bernstein, MD, FCAP, Justin Pearlman, MD, PhD, FACC and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/09/08/the-centrality-of-ca2-signaling-and-cytoskeleton-involving-calmodulin-kinases-and-ryanodine-receptors-in-cardiac-failure-arterial-smooth-muscle-post-ischemic-arrhythmia-similarities-and-differen/

Part V: Heart, Vascular Smooth Muscle, Excitation-Contraction Coupling (E-CC), Cytoskeleton, Cellular Dynamics and Ca2 Signaling

Larry H Bernstein, MD, FCAP, Justin Pearlman, MD, PhD, FACC and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/08/26/heart-smooth-muscle-excitation-contraction-coupling-cytoskeleton-cellular-dynamics-and-ca2-signaling/

 

Section Two

Cardiomyocytes Cells: The Cardiac Calcium Signaling Mechanism

Cardiomyocytes and Ca2+ Channels

Published August 8, 2011 // JCB vol. 194 no. 3 355-365 
The Rockefeller University Press, doi: 10.1083/jcb.201101100

Cellular mechanisms of cardiomyopathy
  1. Pamela A. Harvey and
  2. Leslie A. Leinwand

+Author Affiliations


  1. Department of Molecular, Cellular, and Developmental Biology, University of Colorado at Boulder, Boulder, CO 80309
  1. Correspondence to Leslie Leinwand: leslie.leinwand@colorado.edu

Abbreviations

DCM dilated cardiomyopathy

HCM hypertrophic cardiomyopathy

MyH Cmyosin heavy chain

RCM restrictive cardiomyopathy

Introduction

The heart relies on a complex network of cells to maintain appropriate function. Cardiomyocytes, the contracting cells in the heart, exist in a three-dimensional network of endothelial cells, vascular smooth muscle, and an abundance of fibroblasts as well as transient populations of immune cells. Gap junctions electrochemically coordinate the contraction of individual cardiomyocytes, and their connection to the extracellular matrix (ECM) transduces force and coordinates the overall contraction of the heart. Intracellularly, repeating units of actin and myosin form the backbone of sarcomere structure, the basic functional unit of the cardiomyocyte (Fig. 1). The sarcomere itself consists of ∼20 proteins; however, more than 20 other proteins form connections between the myocytes and the ECM and regulate muscle contraction (Fig. 1 B). Given the complexity of the coordinated efforts of the many proteins that exist in multimeric complexes, dysfunction occurs when these interactions are disrupted.

Figure 1.

View larger version:

Figure 1. Anatomy of the cardiac sarcomere(A) Diagram of the basic organization of the sarcomere. The sarcomere forms the basic contractile unit in the cardiomyocytes of the heart. Thin filaments composed of actin are anchored at the Z line and form transient sliding interactions with thick filaments composed of myosin molecules. The M Line, I Band, and A Band are anatomical features defined by their components (actin, myosin, and cytoskeletal proteins) and appearance in polarized light. Titin connects the Z line with the M line and contributes to the elastic properties and force production of the sarcomere through its extensible region in the I Band. Coordinated shortening of the sarcomere creates contraction of the cardiomyocyte. (B) Representation of the major proteins of the cardiac sarcomere. Attachment to the ECM is mediated by costameres composed of the dystroglycan–glycoprotein complex and the integrin complex. Force transduction and intracellular signaling are coordinated through the costamere. The unique roles of each of these proteins are critical to appropriate function of the heart. T-cap, titin cap; MyBP-C, myosin-binding protein C; NOS, nitric oxide synthase.

Although the heart may functionally tolerate a variety of pathological insults, adaptive responses that aim to maintain function eventually fail, resulting in a wide range of functional deficits or cardiomyopathy. Although a multitude of intrinsic and extrinsic stimuli promote cardiomyopathies, the best described causes are the >900 mutations in genes expressed in the cardiomyocyte (Fig. 1 BWang et al., 2010). Mutations in most of these genes cause a diverse range of cardiomyopathies, many with overlapping clinical phenotypes. Mutations in sarcomeric genes are usually inherited in an autosomal-dominant manner and are missense mutations that are incorporated into sarcomeres (Seidman and Seidman, 2001). Thus far >400 mutations in 13 sarcomeric proteins including β-myosin heavy chain (β-MyHC), α-cardiac actin, tropomyosin, and troponin have been associated with cardiomyopathy (www.cardiogenomics.med.harvard.edu). Table I summarizes these mutated proteins.

Ca2+ regulation and calcineurin signaling

Ca2+ concentrations inside the cardiomyocyte are critically important to actin–myosin interactions. Ca2+ is sequestered within the sarcoplasmic reticulum and the sarcomere itself, which serves as an intracellular reserve that is released in response to electrical stimulation of the cardiomyocyte. After contraction, sarco/endoplasmic reticulum Ca2+-ATPase sequesters the Ca2+ back into the sarcoplasmic reticulum to restore Ca2+balance. There is a clear correlation between force production and perturbation of Ca2+regulation, alterations of which might directly induce pathological, anatomical, and functional alterations that lead to heart failure via activation of GPCRs (Minamisawa et al., 1999).

Ca2+ in the cytosol can be increased to modulate sarcomere contractility by signaling through Gαq recruitment and activation of PLCβ. Ca2+ released from the sarcoplasmic reticulum activates calmodulin, which phosphorylates calcineurin, a serine/threonine phosphatase. Upon activation, calcineurin interacts with and dephosphorylates nuclear factor of activated T cells (NFAT), which then translocates into the nucleus. Calcineurin activation exacerbates hypertrophic signals and expedites the transition to a decompensatory state. Indeed, cardiac-specific overexpression of calcineurin or NFAT leads to significant cardiac hypertrophy that progresses rapidly to heart failure (Molkentin et al., 1998). Administration of antagonists of calcineurin attenuates the hypertrophic response of neonatal rat ventricular myocytes to stimuli such as phenylephrine (PE) and angiotensin II (Taigen et al., 2000).

Mechanotransduction and signaling in the cardiomyocyte

The responses of cardiomyocytes to systemic stress or genetic abnormalities are modulated by mechanosensitive mechanisms within the cardiomyocyte (Molkentin and Dorn, 2001Seidman and Seidman, 2001Frey and Olson, 2003). A complex network of proteins that connects the sarcomere to the ECM forms the basis of the mechanotransduction apparatus. For example, components of the costamere complex, which form the connection between the sarcomere and the ECM via integrins, initiate intracellular signaling and subsequently alter contractile properties and transcriptional regulation in response to membrane distortion. Mechanosensitive ion channels are also implicated in signal initiation in response to systemic stress (Le Guennec et al., 1990;Zhang et al., 2000de Jonge et al., 2002). These channels are likely responsible for acute changes that might initiate other longer-term responses in the heart but are nonetheless important to consider when examining possible transducers of systemic and tissue alterations to the cardiomyocyte.

Changes in wall stress induce signaling pathways that are associated with the development of cardiac pathology. The many intracellular signaling pathways that mediate responses to increased demand on the heart have been extensively reviewed elsewhere (Force et al., 1999Molkentin and Dorn, 2001Heineke and Molkentin, 2006). Here, we focus on pathways that are intimately involved in pathogenesis (Fig. 4). Although their effects in compensatory responses early in pathology initially increase function by promoting growth and contractility, persistent responses eventually compromise function.

Figure 4.

View larger version:

Figure 4. Signaling pathways associated with cardiac hypertrophy.

Although many pathways are associated with cardiomyopathy, up-regulation of transcription and induction of apoptosis are major mediators of pathogenic responses in the heart. The GPCR-associated pathway (dark red) can be activated by ET-1 and AngII, which are released in response to reduced contractility, and mediates contractile adaptation through increased calcium release from the sarcoplasmic reticulum. Increased intracellular calcium activates calmodulin and induces activation of the transcription factor MEF2. Incorporation into the sarcomere of mutant proteins that exhibit reduced ATP efficiency inhibits the sequestration of calcium from the cytosol and further enhances increases in intracellular calcium concentration. GPCR signaling is also associated with activation of the Akt signaling pathway (light green) that induces fetal gene expression and the cardiac hypertrophic response through inhibition of GSK3β. Apoptotic pathways (light blue) are induced by cytochrome c (CytC) release from mitochondria and activation of death receptors (like FasR) by cytokines such as TNF. Calcium overload and myocyte loss significantly contribute to reduced contractility in many forms of cardiomyopathy. ET-1, endothelin-1; HDAC, histone deacetylase; NFAT, nuclear factor of activated T cells; MEF-2, myocyte enhancer factor 2; SERCA, sarco/endoplasmic reticulum calcium-ATPase; cFLIP, cellular FLICE-inhibitory protein; AngII, angiotensin II; FasR, Fas receptor.

http://jcb.rupress.org/content/194/3/355.full

For Disruption of Calcium Homeostasis in Cardiomyocyte Cells, see

Part VI: Calcium Cycling (ATPase Pump) in Cardiac Gene Therapy: Inhalable Gene Therapy for Pulmonary Arterial Hypertension and Percutaneous Intra-coronary Artery Infusion for Heart Failure: Contributions by Roger J. Hajjar, MD

Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/08/01/calcium-molecule-in-cardiac-gene-therapy-inhalable-gene-therapy-for-pulmonary-arterial-hypertension-and-percutaneous-intra-coronary-artery-infusion-for-heart-failure-contributions-by-roger-j-hajjar/

Part VII: Cardiac Contractility & Myocardium Performance: Ventricular Arrhythmias and Non-ischemic Heart Failure – Therapeutic Implications for Cardiomyocyte Ryanopathy (Calcium Release-related Contractile Dysfunction) and Catecholamine Responses

Justin Pearlman, MD, PhD, FACC, Larry H Bernstein, MD, FCAP and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/08/28/cardiac-contractility-myocardium-performance-ventricular-arrhythmias-and-non-ischemic-heart-failure-therapeutic-implications-for-cardiomyocyte-ryanopathy-calcium-release-related-contractile/

Section Three

The Calcium Sensor: How Calcium Ions Regulate the fusion of vesicles with cell membranes during Neurotransmission

This topic is covered in

Synaptotagmin functions as a Calcium Sensor: How Calcium Ions Regulate the fusion of vesicles with cell membranes during Neurotransmission

Larry H Bernstein, MD, FCAP and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/09/10/synaptotagmin-functions-as-a-calcium-sensor-how-calcium-ions-regulate-the-fusion-of-vesicles-with-cell-membranes-during-neurotransmission/

Summary

Justin D Pearlman, MD, PhD, FACC  PENDING

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Renal Distal Tubular Ca2+ Exchange Mechanism in Health and Disease

Author and Curator: Larry H. Bernstein, MD, FCAP

Curator:  Stephen J. Williams, PhD
and

Curator: Aviva Lev-Ari, PhD, RN

This is Part III in a series of articles on the role of Calcium Release Mechanism in cell biology and physiology.

The Series consists of the following articles:

Part I: Identification of Biomarkers that are Related to the Actin Cytoskeleton

Larry H Bernstein, MD, FCAP

https://pharmaceuticalintelligence.com/2012/12/10/identification-of-biomarkers-that-are-related-to-the-actin-cytoskeleton/

Part II: Role of Calcium, the Actin Skeleton, and Lipid Structures in Signaling and Cell Motility

Larry H. Bernstein, MD, FCAP, Stephen Williams, PhD and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/08/26/role-of-calcium-the-actin-skeleton-and-lipid-structures-in-signaling-and-cell-motility/

Part III: Renal Distal Tubular Ca2+ Exchange Mechanism in Health and Disease

Larry H. Bernstein, MD, FCAP, Stephen J. Williams, PhD
 and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/09/02/renal-distal-tubular-ca2-exchange-mechanism-in-health-and-disease/

Part IV: The Centrality of Ca(2+) Signaling and Cytoskeleton Involving Calmodulin Kinases and Ryanodine Receptors in Cardiac Failure, Arterial Smooth Muscle, Post-ischemic Arrhythmia, Similarities and Differences, and Pharmaceutical Targets

Larry H Bernstein, MD, FCAP, Justin Pearlman, MD, PhD, FACC and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/09/08/the-centrality-of-ca2-signaling-and-cytoskeleton-involving-calmodulin-kinases-and-ryanodine-receptors-in-cardiac-failure-arterial-smooth-muscle-post-ischemic-arrhythmia-similarities-and-differen/

Part V: Ca2+-Stimulated Exocytosis:  The Role of Calmodulin and Protein Kinase C in Ca2+ Regulation of Hormone and Neurotransmitter

Larry H Bernstein, MD, FCAP
and
Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/12/23/calmodulin-and-protein-kinase-c-drive-the-ca2-regulation-of-hormone-and-neurotransmitter-release-that-triggers-ca2-stimulated-exocytosis/

Part VI: Calcium Cycling (ATPase Pump) in Cardiac Gene Therapy: Inhalable Gene Therapy for Pulmonary Arterial Hypertension and Percutaneous Intra-coronary Artery Infusion for Heart Failure: Contributions by Roger J. Hajjar, MD

Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/08/01/calcium-molecule-in-cardiac-gene-therapy-inhalable-gene-therapy-for-pulmonary-arterial-hypertension-and-percutaneous-intra-coronary-artery-infusion-for-heart-failure-contributions-by-roger-j-hajjar/

Part VII: Cardiac Contractility & Myocardium Performance: Ventricular Arrhythmias and Non-ischemic Heart Failure – Therapeutic Implications for Cardiomyocyte Ryanopathy (Calcium Release-related Contractile Dysfunction) and Catecholamine Responses

Justin Pearlman, MD, PhD, FACC, Larry H Bernstein, MD, FCAP and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/08/28/cardiac-contractility-myocardium-performance-ventricular-arrhythmias-and-non-ischemic-heart-failure-therapeutic-implications-for-cardiomyocyte-ryanopathy-calcium-release-related-contractile/

Part VIII: Disruption of Calcium Homeostasis: Cardiomyocytes and Vascular Smooth Muscle Cells: The Cardiac and Cardiovascular Calcium Signaling Mechanism

Justin Pearlman, MD, PhD, FACC, Larry H Bernstein, MD, FCAP and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/09/12/disruption-of-calcium-homeostasis-cardiomyocytes-and-vascular-smooth-muscle-cells-the-cardiac-and-cardiovascular-calcium-signaling-mechanism/

Part IX: Calcium-Channel Blockers, Calcium Release-related Contractile Dysfunction (Ryanopathy) and Calcium as Neurotransmitter Sensor

Justin Pearlman, MD, PhD, FACC, Larry H Bernstein, MD, FCAP and Aviva Lev-Ari, PhD, RN

Part X: Synaptotagmin functions as a Calcium Sensor: How Calcium Ions Regulate the fusion of vesicles with cell membranes during Neurotransmission

Larry H Bernstein, MD, FCAP and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/09/10/synaptotagmin-functions-as-a-calcium-sensor-how-calcium-ions-regulate-the-fusion-of-vesicles-with-cell-membranes-during-neurotransmission/

Part XI: Sensors and Signaling in Oxidative Stress

Larry H. Bernstein, MD, FCAP

https://pharmaceuticalintelligence.com/2013/11/01/sensors-and-signaling-in-oxidative-stress/

Part XII: Atherosclerosis Independence: Genetic Polymorphisms of Ion Channels Role in the Pathogenesis of Coronary Microvascular Dysfunction and Myocardial Ischemia (Coronary Artery Disease (CAD))

Larry H Bernstein, MD, FCAP and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/12/21/genetic-polymorphisms-of-ion-channels-have-a-role-in-the-pathogenesis-of-coronary-microvascular-dysfunction-and-ischemic-heart-disease/

 

Renal Distal Tubular Ca2+ Exchange Mechanism

This is the Third article of a multipart series covering Ca(2+) signaling and the cytoskeleton, and two on Ca2+ in cardiac contractility governed by the activations involving a ryanodine (RyR2) receptor and a specific calmodulin protein CaKIIδ with B and C splice variants.  In all of these discussions, Ca(2+) has a crucial role in many cellular events, not all of which are detailed, and its importance to cardiac function and function disorders is critical.   We shall next undertake the difficult examination of Ca(2+) movements in the kidney, which has a special relationship to vitamin D and bone mineral metabolism that is not of interest here.   Nor will we go into any depth on the importance of the kidney to maintenance of plasma H+ and K+ balance and metabolic acidosis.   Whereas the lung has a large role in pH maintenance by the respiratory rate (under sympathetic control), it maintains the balance through the expiration of CO2, with H+ tied up in water via the carbonic anhydrase reaction.

Key words, abbreviations:

calcium, magnesium, phosphate, renal calcium transport, calcium channels, diltiazem, mibefradil, ω-conotoxin. FGF23, Parathyroid hormone (PTH), Thick Ascending Loop (TAL), cTAL, proximal tubule, distal convoluted tubule (DCL), chronic kidney disease, Ca2+-ATPase, Ca2+-stimulated adenosine triphosphatase, Na++K-E-ATPase: (Na++K+)-stimulated adenosine triphosphatase, Na+-K+-2Cl cotransporter (NKCC@),TRPV6, calbindin- D9K, Ca2+ – ATPase, 4-(2-hydroxyethyl)-1-piperazine-ethanesulphonic acid, Non-hypertensive uremic, de novo cardiomyopathy, renal transplantation, karyotypes, isoform, Angiotensin converting enzyme (ACE), Basic fibroblast growth factor (BFGF), Extracellular signal regulated kinase (ERK), Friend leukemia integration-1 transcription factor (Fli-1), Growth hormone (GSH),  oxidative stress, Nitric oxide (NO),  Protein kinase C (PKC),angiotensin II,  Renin-angiotensin system (RAS), Transforming growth factor-beta (TGF-b), Vascular endothelial growth factor (VEGF), 22-oxacalcitriol (OCT), Calcium-sensing receptor (CaSR),  Claudin14, Claudin 16, bradykinin,  bradykinin B2 receptor antagonists, inosine,  marino-bufagenin (MBG),  ramipril, nifedipine or moxonidine, calcitriol, Vitamin D receptor (VDR), Alpha-Kloth and FGf23

The first part in the Series, excludes calcium related heart failure and  arrhythmias of calcium  and includes the following:

(Part I) Identification of Biomarkers that are Related to the Actin Cytoskeleton
Curator: Larry H Bernstein, MD, FCAP

https://pharmaceuticalintelligence.com/2012/12/10/identification-of-biomarkers-that-are-related-to-the-actin-cytoskeleton/

(Part II) Role of Calcium, the Actin Skeleton, and Lipid Structures in Signaling and Cell Motility  
Larry H. Bernstein, MD, FCAP, Stephen Williams, PhD and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/08/26/role-of-calcium-the-actin-skeleton-and-lipid-structures-in-signaling-and-cell-motility/

(Part III) Renal Distal Tubular Ca2+ Exchange Mechanism in Health and Disease Larry H. Bernstein, MD, FCAP, Stephen J. Williams, PhD
 and

Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/09/02/renal-distal-tubular-ca2-exchange-mechanism-in-health-and-disease/ 

This article is a continuation to the following article series on tightly related topics:

Part I: Identification of Biomarkers that are Related to the Actin Cytoskeleton

Larry H Bernstein, MD, FCAP

https://pharmaceuticalintelligence.com/2012/12/10/identification-of-biomarkers-that-are-related-to-the-actin-cytoskeleton/

(Part II) Role of Calcium, the Actin Skeleton, and Lipid Structures in Signaling and Cell Motility  
Larry H. Bernstein, MD, FCAP, Stephen Williams, PhD and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/08/26/role-of-calcium-the-actin-skeleton-and-lipid-structures-in-signaling-and-cell-motility/

 (Part III) Renal Distal Tubular Ca2+ Exchange Mechanism in Health and Disease

Larry H. Bernstein, MD, FCAP, Stephen J. Williams, PhD
 and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/09/02/renal-distal-tubular-ca2-exchange-mechanism-in-health-and-disease/ 

(Part IV) The Centrality of Ca(2+) Signaling and Cytoskeleton Involving Calmodulin Kinases and Ryanodine Receptors in Cardiac Failure, Arterial Smooth Muscle, Post-ischemic Arrhythmia, Similarities and Differences, and Pharmaceutical Targets

Larry H Bernstein, MD, FCAP, Justin Pearlman, MD, PhD, FACC and Aviva Lev-Ari, PhD, RN

http:/pharmaceuticalintelligence.com/2013.09.089/lhbern/The Centrality of Ca(2+) Signaling and Cytoskeleton Involving Calmodulin Kinases and Ryanodine Receptors in Cardiac Failure, Arterial Smooth Muscle, Post-ischemic Arrhythmia, Similarities and Differences, and Pharmaceutical Targets

Part V:  Heart Failure and Arrhythmia: Potential for Targeted Intervention — The Effects of Ca 2+ -calmodulin (Ca-CaM) phosphorylation/dephosphorylation/hyperphosphorylation

Larry H Bernstein, MD, FCAP, Justin Pearlman, MD, PhD, FACC and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/08/29/ryanodine-receptor-ryr2-subunits-in-heart-failure-and-arrhythmia-potential-for-targeted-intervention-the-effects-of-ca-2-calmodulin-ca-cam-phosphorylationdephosphorylationhyperphosphoryla/

(VI) Calcium Cycling (ATPase Pump) in Cardiac Gene Therapy: Inhalable Gene Therapy for Pulmonary Arterial Hypertension and Percutaneous Intra-coronary Artery Infusion for Heart Failure: Contributions by Roger J. Hajjar, MD
Curator: Aviva Lev-Ari, PhD, RN
https://pharmaceuticalintelligence.com/2013/08/01/calcium-molecule-in-cardiac-gene-therapy-inhalable-gene-therapy-for-pulmonary-arterial-hypertension-and-percutaneous-intra-coronary-artery-infusion-for-heart-failure-contributions-by-roger-j-hajjar/

Cardiac Contractility & Myocardium Performance: Ventricular Arrhythmias and Non-ischemic Heart Failure – Therapeutic Implications for Cardiomyocyte Ryanopathy (Calcium Release-related Contractile Dysfunction) and Catecholamine Responses in the Human Heart

Justin Pearlman, MD, PhD, FACC, Larry H Bernstein, MD, FCAP and Aviva Lev-Ari, PhD, RN
https://pharmaceuticalintelligence.com/2013/08/28/cardiac-contractility-myocardium-performance-ventricular-arrhythmias-and-non-ischemic-heart-failure-therapeutic-implications-for-cardiomyocyte-ryanopathy-calcium-release-related-contractile/

Calcium Ion Transport across Plasma Membranes

Basal-lateral-plasma-membrane vesicles and brush-border-membrane vesicles were isolated from rat kidney cortex by differential centrifugation followed by free-flow electrophoresis. Ca2+ uptake into these vesicles was investigated by a rapid filtration method. Both membranes show a considerable binding of Ca2+ to the vesicle interior, making the analysis of passive fluxes in uptake experiments difficult. Only the basal-lateral-plasma-membrane vesicles exhibit an ATP-dependent pump activity which can be distinguished from the activity in mitochondrial and endoplasmic reticulum by virtue of the different distribution during free-flow electrophoresis and its lack of sensitivity to oligomycin. The basal-lateral plasma membranes contain in addition a Na+/Ca2+-exchange system which mediates a probably rheogenic counter-transport of Ca2+ and Na+ across the basal cell border. The latter system is probably involved in the secondary active Na+-dependent and ouabain-inhibitable Ca2+ reabsorption in the proximal tubule, the ATP-driven system is probably more important for the maintenance of a low concentration of intracellular Ca2+.

In recent micropuncture studies using simultaneously tubular and capillary perfusion it could be demonstrated that in the rat kidney proximal tubule Ca2+ reabsorption is dependent on the presence of Na+- ions and sensitive to ouabain (Ullrich et al., 1976). On the other hand cell-fractionation studies on the distribution of plasma-membrane-bound enzymes in rat proximal tubular epithelial cells revealed a contraluminal localization of a Ca2+-stimulated ATPase (Kinne-Saffran & Kinne, 1974). These results suggested that both Na+-driven and ATP-driven Ca2+ transport systems might be involved in proximal tubular transepithelial Ca2+ transport. Considering the low concentration of intracellular Ca2+ one could expect that these active steps in Ca2+ reabsorption are located at the basal cell pole.

To our knowledge there have been two attempts to study the role of ATP in the Ca2+ transport of renal membranes. In one study increase in Ca2+ uptake by rabbit kidney membranes was observed, but this increase was attributed to a phosphorylation of the membranes and a concomitant binding of Ca2+ to the negative charges newly generated at the membrane surface. Moore et al. (1974) observed an ATP-dependent Ca2+ uptake distinct from that of the mitochondria in a crude fraction of renal plasma membranes as well as in rat renal microsomes. The two uptake systems differed in their capacity, their sensitivity to Na+ and their apparent Km values for Mg2+-ATP.

Experiments are described on the Ca2+ transport into brush-border-membrane vesicles and basal-lateral plasma-membrane vesicles isolated from rat renal cortex. The results show that a primary active ATP-driven Ca2+ pump and an Na+/Ca2+-exchange system are present in the basal-lateral plasma membranes, but not in the brush-border membrane.

These findings indicate that trans-epithelial Ca2+ transport in rat proximal tubule can be

  1. primarily active via the ATP-driven system as well as
  2. secondarily active if the Na+/Ca2+ exchange system is involved.

It appears that the Na+/Ca2+ exchange system

  • is responsible for the bulk flow of Ca2+ across the epithelium, whereas
  • the ATP-driven system might be involved in the fine regulation of the concentration of intracellular Ca2+.

(Gmaj P, Murer  H, and Kinne R. 1979)

The Renal Na+/Ca2+ Exchange System of the Nephron

The movement of Ca2+ across the basolateral plasma membrane was studied from rabbit proximal and distal convoluted tubules and ATP-dependent Ca2+ uptake was found in both. But the activity was higher distal.  The distal tubular membranes had a very active Na+/Ca2+ exchange system, which was absent in the proximal segment. The ATP-dependent Ca2+ uptake in the distal tubular membrane preparations was gradually inhibited by Na+ outside the vesicles, and was a function of the imposed Na+ gradient.  The results indicate that an active Na+/Ca2+ exchange system is absent in the proximal tubule. Ramachandram & Brunette, 1989).  Parathyroid hormone (PTH) and calcitonin increase Ca2+ uptake by purified distal tubular luminal membranes (DTLM), and both hormone stimulate adenylate cyclase and phospholipase C.  Therefore, distal tubules were incubated with dibutyryl cAMP (dbcAMP) and the result was that dbcAMP increased the Ca2+ transport by luminal membranes, but phorbol 12-myristate 13 acetate (PMA) had no such effect. But when PMA was added to low concentrations of dbcAMP the uptake significantly increased. Protein kinase C inhibitors prevented the effect. This indicated that in the distal tubule Ca2+ transport required both the combined effect of PK  A and C involves both components of the transport kinetics.  (Hila, Claveau, Laclerc, Brunette, 1997)

In the rabbit, calcitonin enhances Ca2+ reabsorption in the distal tubule.  Tubules were incubated with or in the absence of calcitonin, and the luminal or basolateral membranes were purified and Ca2+ transport was measured through the vesicles.  The results were compared with those obtained from proximal tubule membranes, and the results were no effect of calcitonin on Ca2+ uptake in the proximal tubules.  In the distal tubules there was the expected uptake, but the presence of Na+ in the suspension decreased the Ca2+ uptake.  The uptake was partially restored by preincubation with calcitonin.  Recall the experiment demonstrating a requirement for PK A and C in Ca2+ uptake indicating a dual kinetics of Ca2+ uptake by the distal luminal membranes.  Calcitonin enhanced Ca2+ transport by the low affinity component, increasing the Vmax and leaving the K(m) unchanged. Renal calcitonin receptors usually couple to both adenylate cyclase and phospholipase C.  Calcitonin stimulates cAMP and IP3 release. Incubation of the distal tubules with 10(-7) M calcitonin significantly increased both messengers. In contrast, calcitonin did not influence the IP3 nor the cAMP content of proximal tubules.  Incubation of distal tubule suspensions with dbcAMP significantly increased Ca2+ uptake by the luminal membranes. However, incubation of these tubules with various concentrations of PMA (10 nM, 100 nM and 1 microM) had no effect on this uptake.  Calcitonin also influenced Ca2+ transport by the distal basolateral membrane. Incubation of distal tubule suspensions with 10(-7) M calcitonin activated the Na+/Ca2+ exchanger activity, almost doubling the Na+ dependent Ca2+ uptake. Here again this action was mimicked by cAMP. The researchers concluded that calcitonin increases Ca2+ transport by the distal tubule through two mechanisms:

  1. the opening of low affinity Ca2+ channels in the luminal membrane and
  2. the stimulation of the Na+/Ca2+ exchanger in the basolateral membrane, both actions depending on the activation of adenylate cyclase.
    (Zuo Q, Claveau D, Hilal G, Leclerc M, Brunette MG. 1997)

Calcium (Ca2+) filtered in the glomerulus is reabsorbed by the luminal membrane of the proximal and distal nephron. Ca2+ enters cells across apical plasma membranes along a steep electrochemical gradient, through Ca2+ channels. Regulation by hormones requires

  1. binding of these hormones to the basolateral membrane,
  2. interaction with G proteins,
  3. liberation of messengers,
  4. activation of kinases
  5. opening of the channels at the opposite pole of the cells.

It follows that if the Ca2+ entry through the luminal membranes of proximal and distal tubules is a membrane-limited process, then G proteins have a regulatory role. Luminal membranes were purified from rabbit proximal and distal tubule suspensions, and their vesicles were loaded with GTPγs or the carrier. Then, the 45Ca2+ uptake by these membrane vesicles was measured in the presence and absence of 100 mM NaCl. In the absence of Na+, intravesicular GTPγs significantly enhanced 0.5 mM Ca2+ uptake by the proximal membrane vesicles (p < 0.05). In the presence of Na+, however, this effect disappeared. In the distal tubules, intravesicular GTPγs increased 0.5 mM Ca2+ uptake in the absence (p < 0.02) and in the presence (p < 0.02) of Na+. The action of GTPγs, when present, was dose dependent. The distal luminal membrane is the site of two Ca2+ channels with different kinetics parameters. GTPγs increased the Vmax value of the low-affinity component exclusively, in the presence as in the absence of Na+. Finally, Ca2+ uptake by the membranes of the two segments was differently influenced by toxins: cholera toxin slightly stimulated transport by the proximal membrane, but had no influence on the distal membrane, whereas pertussis toxin decreased the cation uptake by the distal tubule membrane exclusively. We conclude that the nature of Ca2+ channels differs in the proximal and distal luminal membranes: Ca2+ channels present in the proximal tubule and the low-affinity Ca2+ channels present in the distal tubule membranes are directly regulated by Gs and Gi proteins respectively, whereas the high-affinity Ca2+ channel in the distal tubule membrane is insensitive to any of them.
(Brunette MG, Hilal G, Mailloux J, Leclerc M. 2000)

We previously reported a dual kinetics of Ca2+ transport by the distal tubule luminal membrane of the kidney, suggesting the presence of several types of channels. We, therefore, examined the effects of specific inhibitors (i.e., diltiazem, an L-type channel; ω-conotoxin MVIIC, a P/Q-type channel; and mibefradil, a T-type channel antagonist) on Ca2+ uptake by rabbit nephron luminal membranes. None of these inhibitors influenced Ca2+ uptake by the proximal tubule membranes. In contrast, in the absence of sodium (Na+), the three channel antagonists decreased Ca2+ transport by the distal membranes, and their action depended on the substrate concentrations: (P < 0.05) without influencing 0.5 mM Ca2+ transport, whereas ω-conotoxin MVIIC decreased 0.5 mM Ca2+ (P < 0.02) and 1 µM mibefradil decreased it (P < 0.05); the latter two inhibitors [P/Q type, T-type] left 0.1 mM Ca2+ transport unchanged. Diltiazem [L-type] decreased the Vmax of the high-channels, whereas ω-conotoxin MVIIC and mibefradil influenced exclusively the Vmax of the low-affinity channels. These results not only confirm that the distal luminal membrane is the site of Ca2+ channels, but they suggest that these channels belong to the L, P/Q, and T types. (M G Brunette, M Leclerc, D Couchourel, J Mailloux, Y Bourgeois. 2000)

Calcium (Ca2+) transport by the distal tubule (DT) luminal membrane

Calcium (Ca2+) transport by the distal tubule (DT) luminal membrane is regulated by

  • the parathyroid hormone (PTH) and calcitonin (CT) through the action of messengers,
  • protein kinases, and
  • ATP as the phosphate donor.

Could ATP itself, when directly applied to the cytosolic surface of the membrane influence the Ca2+ channels previously detected in this membrane. We purified the luminal membranes of rabbit proximal (PT) and DT separately and measured Ca2+ uptake by these vesicles loaded with ATP or the carrier. The presence of 100 μM ATP in the DT membrane vesicles significantly enhanced 0.5 mM Ca2+ uptake           in the absence of Na+ (P < 0.01) and in the presence of 100 mM Na+ (P < 0.01). This effect was dose dependent with an EC50 value of approximately 40 μM. ATP action involved the high-affinity component of Ca2+ transport, decreasing the Km from 0.08 ± 0.01 to 0.04 ± 0.01 mM (P< 0.02). Replacement of the nucleotide by the nonhydrolyzable ATPγs abolished this action. Because ATP has been reported to be necessary for cytoskeleton integrity, they investigated the effect of intravesicular cytochalasin on Ca2+ transport. Cytochalasin B decreased 0.5 mM Ca2+ uptake (P< 0.01). However, when both ATP and cytochalasin were present in the vesicles, the uptake was not different from that observed with ATP alone. Neither ATP nor cytochalasin had any influence on Ca2+ uptake by the PT luminal membrane. They conclude from this that the high-affinity Ca2+ channel of the DT luminal membrane is regulated by ATP and that ATP plays a crucial role in the integrity of the cytoskeleton which is also involved in the control of Ca2+ channels within this membrane. (MG. Brunette*, J Mailloux, G Hilal. 1999)

Proximal tubular sodium-calcium exchanger

The functional expression of the renal sodium-calcium exchanger has been amply documented in studies on renal cortical basolateral membranes. In perfused renal tubules, other investigators have shown sodium-calcium exchange activity in the

  • proximal convolution
  • in the distal convolution,
  • the connecting tubule, and
  • the collecting tubule of the rabbit.

In rat proximal tubules, we found that the sodium-calcium exchanger is an important determinant of cytosolic calcium homeostasis, since

  • inhibition of sodium-dependent calcium efflux mode caused a large accumulation of tubular calcium.

In membranes from rat proximal tubules sodium-calcium activity was high, and in intact proximal tubules,

  • the tubular sodium-calcium exchanger exhibited a high affinity for cytosolic calcium

and had a substantial transport capacity, which may be absolute requirements for the maintenance of stable cytosolic calcium in proximal tubules. (Dominguez JH, Juhaszova M, Feister HA. 1992.)

Proximal tubule Na(+)-Ca2+ exchanger protein is same as the cardiac protein

The activity of the Na(+)-Ca2+ exchanger, a membrane transporter that mediates Ca2+ efflux, has been described in amphibian and mammalian renal proximal tubules. However, demonstration of cell-specific

  • expression of the Na(+)-Ca2+ exchanger in proximal renal tubules has been restricted to functional assays.

In this work, Na(+)-Ca2+ exchanger gene expression in rat proximal tubules was characterized by three additional criteria:

  1. functional assay of transport activity in membrane vesicles derived from proximal tubules, expression of
  2. specific Na(+)-Ca2+ exchanger protein detected on Western blots, and
  3. determination of specific mRNA encoding Na(+)-Ca2+ exchanger protein on Northern blots.

A new transport activity assay showed that proximal tubule membranes

  • contained the highest Na(+)-Ca2+ exchanger transport activity reported in renal tissues.

In dog renal proximal tubules and sarcolemma, a specific protein of approximately 70 kDa was detected, whereas in rat proximal tubules and sarcolemma, the specific protein approximated 65 kDa and was localized to the basolateral membrane. On Northern blots, a single 7-kb transcript isolated from rat

  • proximal tubules,
  • whole kidney, and
  • heart

hybridized with rat heart cDNA.

These data indicate that Na(+)-Ca2+ exchanger protein expressed in rat proximal tubule is similar, if not identical, to the cardiac protein. We suggest that the tubular Na(+)-Ca2+ exchanger characterized herein represents the Na(+)-Ca2+ exchanger described in functional assays of renal proximal tubules. (Dominguez JH, Juhaszova M, Kleiboeker SB, Hale CC, Feister HA. 1992.)

Calcium reabsorption regulated by the distal tubules

Extracellular calcium homeostasis involves coordinated calcium absorption by

  1. the intestine,
  2. calcium resorption from bone, and
  3. calcium reabsorption by the kidney.

This review addresses the mechanism and regulation of renal calcium transport. Calcium reabsorption occurs throughout the nephron. However, distal tubules are the nephron site at which calcium reabsorption is regulated by

  1. parathyroid hormone,
  2. calcitonin, and
  3. 1 alpha,25-dihydroxyvitamin D3 and

where the magnitude of net reabsorption is largely determined. These and related observations underscore the view that distal tubules are highly specialized

  • to permit fine regulation of calcium excretion in response to
  • alterations in extracellular calcium levels.

Progress in understanding the mechanism and regulation of calcium transport has emerged from application of

  • single cell fluorescence,
  • patch clamp, and
  • molecular biological approaches.

These techniques permit the examination of

  1. ion transport at the cellular level and
  2.  its regulation at subcellular and molecular levels.

This editorial review focuses on recent and emerging observations and attempts to integrate them into models of cellular calcium transport. (Friedman PA , Gesek FA.  1993)

Calcium-Sensing Receptor (CSR)

Renal tubular calcium reabsorption is a critical determinant of extracellular fluid (ECF) calcium concentration; for the need of constancy of ECF calcium concentration,

  • the renal tubular handling of calcium is tightly controlled
  • in order to match renal calcium excretion to the net amount of calcium entering the ECF.

Both parathyroid hormone (PTH) and vitamin D metabolites are involved in

  1. the control of renal tubular calcium reabsorption and
  2. ECF calcium concentration [1].

Besides this hormonal control, it has been recognized recently that

  • ECF calcium is able to regulate its own reabsorption by the mammalian tubule.

Indeed, a large body of evidence supports the view that ECF calcium exerts this action

  • by activating the calcium/polyvalent cation-sensing receptor (CaSR)
  • located in the plasma membrane of many tubular cell types.

First, increasing ECF calcium concentration

  • elicits a marked increase in urinary calcium (and magnesium) excretion [2,3] and
  • this occurs independently of any change in the calcium-regulating hormones [2,3].

Second, the inhibitory effect of ECF calcium on its own reabsorption is shared by other CaSR agonists, e.g. magnesium [4].

Third, the relationship between ECF calcium and urinary calcium excretion

is altered in patients bearing mutations of the CASR gene: renal tubular calcium reabsorption

  • is enhanced in patients with inactivating mutations [5,6]
  • and decreased in patients with activating mutations.

Therefore, there is abundant evidence that renal tubular CaSR plays a role

  • in the control of divalent cations reabsorption under
  • both normal and pathological conditions.

Localization of the extracellular CaSR

Transcripts of the CASR gene are expressed in many nephron segments of rat kidney, extending from glomeruli to the inner medullary collecting duct (IMCD) [7]. The CaSR protein is expressed in

  • the proximal tubule,
  • medullary and cortical thick ascending limb (TAL) segments,
  • macula densa cells,
  • distal convoluted tubule (DCT) and
  • type-A intercalated cells in the distal tubule and cortical collecting duct [8]
  • and in inner medullary collecting duct cells [9].

The polarity of expression varies from segment to segment, the protein being expressed in

  • the apical membrane of proximal tubule and
  • IMCD cells and
  • in the basolateral membrane of TAL and DCT cells [8,9].

Interestingly, the highest density of protein expression has been observed in the cortical TAL (cTAL),

  • known to reabsorb calcium and magnesium in a regulated manner.

CaSR under physiological conditions

Consistent with its polarized plasma membrane localization,

  • CaSR has been shown to be involved in the control of thick ascending limb (TAL) calcium and magnesium reabsorption.

In the mouse and rat TAL,

  • both calcium and magnesium are reabsorbed selectively in the cortical portion (cTAL) [10]
  • and this reabsorption is passive along an electrical gradient

through the paracellular pathway [10,11]. The electrical gradient is related to

  • transcellular NaCl reabsorption.

The first step is NaCl entry into the cell via

  • the electroneutral apical Na- K-2Cl co-transporter BSC1 (NKCC2).

Subsequently, most of the potassium recycles back to the lumen, through an apical potassium channel,

  • necessary to maintain NaCl absorption via BSC1 (NKCC2).

In the absence of recycling, NaCl absorption is inhibited because of

  • the low availability of potassium in luminal fluid.

In addition, potassium recycling hyperpolarizes the apical membrane.

Chloride exits the cell

  • across the basolateral membrane
  • mainly via the CLC-Kb channel,
  • which depolarizes the basolateral membrane.

The overall consequence is a lumen-positive transepithelial voltage that

  • drives calcium, magnesium and also sodium through the paracellular pathway.

The pathway permeability for calcium and magnesium requires the presence of a specific protein,

  • paracellin-1 (also known as claudin-16),
  • co-expressed with occludin
    • in the tight junctions of thick ascending limb (TAL) [12].

Inactivating mutations of the paracellin-1 gene cause a specific

  1. decrease in cTAL calcium and magnesium reabsorption and
  2. renal loss of both cations without renal sodium loss,

which is the landmark of an inherited disease referred to as hypercalciuric hypomagnesaemia with nephrocalcinosis [4].

Calcium and magnesium reabsorption in the cTAL is tightly regulated. Micropuncture studies have shown that peptide hormones, such as

  • PTH,
  • arginine vasopressin,
  • calcitonin and
  • glucagon,

stimulate NaCl as well as calcium and magnesium reabsorption in the loop of Henle and decrease their excretion in final urine. PTH, the most important peptide hormone for the stimulation of renal calcium transport, elicits an increase in calcium and magnesium reabsorption cTAL.
Wittner et al. [14] demonstrated that PTH stimulation of calcium and magnesium transport

  • involves an increase in paracellular pathway permeability.

The activation of CaSR also affects a number of intracellular events in TAL cells and

  • modulates transport processes along the cTAL epithelium.

Activating CaSR increases intracellular free calcium concentration in

  • cTAL,
  • DCT and
  • cortical as well as
  • outer medullary collecting duct.

This also decreases hormone-dependent cAMP accumulation in cTAL by

  • inhibition of type-6 adenylyl cyclase [20],
  • increases inositol phosphate formation [21] and
  • elicits an increase in phospholipase A2 activity and
  • in intracellular cellular production of 20-hydroxyeicosatetraenoic acid [22].   ….

In conclusion, a large body of evidence supports the view that CaSR is

  • a major regulator of calcium and magnesium reabsorption in the cTAL and,
  • of overall tubular divalent cation handling.

However, several issues remain unresolved. It is still unclear whether CaSR activation in the cTAL decreases NaCl reabsorption in this segment or not. The mechanism through which CaSR activation could alter the function of paracellin-1 and the paracellular pathway permeability also remains unsettled. Finally, the role of CaSR in the medullary part of TAL should be investigated: a CaSR-dependent inhibition of NaCl reabsorption could explain at least part of the polyuria that accompanies hypercalcaemic states.   (P Houillier and M Paillar. 2003)

Alpha-Kloth and FGf23

Recent advances that have given rise to marked progress in clarifying actions of alpha(α)-Klotho (alpha-Kl) and FGf23 can be summarized as follows ;

(i) α-Kl binds to Na(+), K(+)-ATPase, and Na(+), K(+)-ATPase is recruited to the plasma membrane by a novel α-Kl dependent pathway in correlation with cleavage and secretion of α-Kl in response to extracellular Ca(2+) fluctuation.

(ii) The increased Na(+) gradient created by Na(+), K(+)-ATPase activity drives the transepithelial transport of Ca(2+) in the choroid plexus and the kidney, this is defective in α-kl(-/-) mice.

(iii) The regulated PTH secretion in the parathyroid glands is triggered via recruitment of Na(+), K(+)-ATPase to the cell surface in response to extracellular Ca(2+) concentrations.

(iv) α-Kl, in combination with FGF23, regulates the production of 1,25 (OH) (2)D in the kidney. In this pathway, α-Kl binds to FGF23, and α-Kl converts the canonical FGF receptor 1c to a specific receptor for FGF23, enabling the high affinity binding of FGF23 to the cell surface of the distal convoluted tubule where α-Kl is expressed.

(v) FGF23 signal down-regulates serum phosphate levels, due to decreased NaPi-IIa abundance in the apical membrane of the kidney proximal tubule cells.

(vi) α-Kl in urine increases TRPV5 channel abundance at the luminal cell surface by hydrolyzing the N-linked extracellular sugar residues of TRPV5, resulting in increased Ca(2+) influx from the lumen.

These findings revealed a comprehensive regulatory scheme of mineral homeostasis that is illustrated by the mutually regulated positive/negative feedback actions of α-Kl, FGF23, PTH and 1,25 (OH) (2)D. In this regard, α-Kl and FGF23 might play pivotal roles in mineral metabolism as regulators that integrate calcium and phosphate homeostasis, although this concept requires further verification in the light of related findings. Here, the unveiling of the molecular functions of α-Klotho and FGF23 has recently given new insight into the field of calcium and phosphate homeostasis. Unveiled molecular functions of α-Kl and FGF23 provided answers for several important questions regarding the mechanisms of calcium and phosphate homeostasis that remained to be solved, such as :

(i) what is the non-hormonal regulatory system that directly responds to the fluctuation of extracellular Ca(2+),
(ii) how is Na(+), K(+)-ATPase activity enhanced in response to low calcium stimuli in the parathyroid glands,
(iii) what is the exact role of FGF23 in calcium and phosphorus metabolism,
(iv) how is Ca(2+) influx through TRPV5 controlled in the DCT nephron, and finally
(v) how is calcium homeostasis regulated in cerebrospinal fluid. However, several critical questions still remain to be solved. So far reported,

  • α-Kl binds to Na(+),
  • K(+)-ATPase,
  • FGF receptors and FGF23, and
  • α-Kl hydrolyzes the sugar moieties of TRPV5.

The following questions are unresolved:

Does alpha-Kl recognize these proteins directly or indirectly?
Is there any common mechanism?
How can we reconcile such diverse functions of alpha-Kl?What is the Ca(2+) sensor machinery and how can we isolate it?
How do hypervitaminosis D and the subsequently altered mineral-ion balance lead to the multiple phenotypes?
What is the phosphate sensor machinery and how can we isolate it?
How does the Fgf23/α-Kl system regulate phosphorus homeostasis?
How are serum concentrations of Ca(2+) and phosphate mutually regulated?
(Nabeshima Y. 2008)

Cilium and Calcium Signal

We tested the hypothesis that the primary cilium of renal epithelia is mechanically sensitive and serves as a flow sensor in MDCK cells using differential interference contrast and fluorescence microscopy. Bending the cilium, either by suction with a micropipette or by increasing the flow rate of perfusate, causes intracellular calcium to substantially increase as indicated by the fluorescent indicator, Fluo-4. This calcium signal is initiated by Ca2+-influx through mechanically sensitive channels that probably reside in the cilium or its base. The influx is followed by calcium release from IP3-sensitive stores. The calcium signal then spreads as a wave from the perturbed cell to its neighbors by diffusion of a second messenger through gap junctions. This spreading of the calcium wave points to flow sensing as a coordinated event within the tissue, rather than an isolated phenomenon in a single cell. Measurement of the membrane potential difference by microelectrode during perfusate flow reveals a profound hyperpolarization during the period of elevated intracellular calcium. We conclude that the primary cilium in MDCK cells is mechanically sensitive and responds to flow by greatly increasing intracellular calcium.  (Praetorius HA, Spring KR. 2001)

Fgf23 regulation in chronic renal disease

The mechanism of FGF23 action in calcium/phosphorus metabolism of patients with chronic kidney disease (CKD) was studied using a mathematical model and clinical data in a public domain. We have previously built a physiological model that describes interactions of PTH, calcitriol, and FGF23 in mineral metabolism encompassing organs such as bone, intestine, kidney, and parathyroid glands. Since an elevated FGF23 level in serum is a characteristic symptom of CKD patients, we evaluate herein potential metabolic alterations in response to administration of a neutralizing antibody against FGF23. Using the parameters identified from available clinical data, we observed that a transient decrease in the FGF23 level elevated the serum concentrations of PTH, calcitriol, and phosphorus. The model also predicted that the administration reduced a urinary output of phosphorous. This model-based prediction indicated that the therapeutic reduction of FGF23 by the neutralizing antibody did not reduce phosphorus burden of CKD patients and decreased the urinary phosphorous excretion. Thus, the high FGF23 level in CKD patients was predicted to be a failure of FGF23-mediated phosphorous excretion. The results herein indicate that it is necessary to understand the mechanism in CKD in which the level of FGF23 is elevated without effectively regulating phosphorus.

A traditional, physiological model with PTH and calcitriol needs to be rebuilt in accordance with the emerging role of FGF23 and its interacting molecules. To understand probable interactions among FGF23, PTH and calcitriol, we previously developed a minimum physiological model of calcium/phosphorus metabolism and investigated potential influences of FGF23 on the observable state variables such as the serum concentrations of PTH, calcitriol, calcium (Ca), and phosphorous (P), as well as the urinary excretion of Ca and P.3 In this study, we extended the model and evaluated the mechanism of FGF23-mediated regulation in chronic kidney diseases (CKD).

The FGF23 gene was identified by its mutations associated with autosomal dominant hypophosphatemic rickets (ADHR), which is an inherited phosphate wasting disorder.4 Thereafter, a variety of disorders resulting from gain or loss of FGF23 bioactivity have been reported.5 These disorders, which are caused by mutations in the genes that directly or indirectly interact with FGF23, include hyperphosphatemic familial tumoral calcinosis (HFTC), hereditary hypo-phosphatemic rickets with hypercalciuria (HHRH), autosomal recessive hypophosphatemic rickets (ARHR), and X-linked dominant hypophosphatemic rickets (XLH, HYP). CKD patients who need dialysis have very high levels of FGF23 in serum that are linked with increased rates of death.6
We examined the effect of reduction of FGF23 by neutralizing antibody would modulate phosphorus balance of CKD patients. We evaluated the levels of physiological variables such as the levels of PTH, calcitriol, FGF23, Ca, and P in serum as well as urinary outputs of Ca and P using clinical data. Since a glomerular filtration rate (GFR) is a good indicator of severity of CKD, data were processed as a function of GFR. We then employed the previously developed mathematical model for mineral metabolism, and conducted numerical simulations in response to the modulation of FGF23 by neutralizing antibody.

Estimation of the relationship of the FGF23 level to other physiological variables

The FGF23 concentrations, reported in literature, considerably varied among available datasets, presumably caused by differential baseline levels or sensitivity variations among individual assays. To predict a quantitative relationship among the FGF23 level and other physiological variables, the reported FGF23 level was linearly modified:

[FGF23]AB = {[FGF23]-A}/B         (1)

in which [FGF23] = reported FGF23 level, [FGF23]AB = linearly modified FGF23 level, and A and B = two correction factors. Note that these correction factors are constant and they were chosen independently for each of the physiological variables such as the serum level of PTH and the urinary output of P. The “+” and “-” values of the factor B indicate positive and negative correlations to the FGF23 level, respectively. We applied the described modification in analyzing clinical data since the observed FGF23 variation was larger than others. Without this procedure, it was difficult to estimate a quantitative relationship of its concentrations to other variables.  [With the significant variation around the linear fit, it might well have been warranted to use the log transform of the modified level, LHB].

Mathematical model and prediction of effects of FGF23 antibody

We previously developed a pair of metabolism models of calcium and phosphorus with and without including the predicted action of FGF23.3,20 In this study we considered an additional state variable, GFRf, as a multiplicative term pertaining to the calcium and phosphorus renal thresholds and the kidney production of calcitriol:

GFRf = (GFR/GFR0)k       (2)

in which GFR0 and GFR = glomerular filtration rates in the control state and at any given degree of renal failure, respectively, and a factor k (>0) was chosen so as to fit the clinical data as described previously.7

To predict the effects of intravenous administration of a neutralizing antibody against FGF23, we numerically examined 5 different dosages for i.v. administration at 0.003, 0.01, 0.03, 0.1 and 0.3 mg/kg (dosage levels 1–5). These dosages corresponded to a clinical trial study being proposed for a dose-escalation study of KRN23 (Kyowa Hakko Kirin Pharma Inc.). A primary outcome measure of this Phase I clinical trial is a change in a serum phosphate level, and a single dose by intravenous or subcutaneous administration is planned. The initial target is X-linked hypophosphatemia but no clinical data regarding efficacy and side effects are available. To simulate a probable injection procedure, we assumed a form of a single, smoothed-out pulse. The rise in the antibody concentration was modeled using a Gaussian type diffusion profile with a period dependent on the distribution volume and cardiac output.

Glomerular filtration rate (GFR) as an indicator in cKD patients

We plotted physiological variables of CKD patients as a function of GFR in ml/min/1.73 m2. Figure 1 illustrated the levels of PTH (pg/ml), calcitriol (pg/ml), Ca (mg/dl), and P (mg/dl) in serum as well as urinary outputs of Ca and P expressed as a fraction of the glomerular loads. The numbers in the brackets in Figure 1 were the numbers of patients. The average and SEM values were obtained in each of the sampling bins. As GFR was normal above 90, the levels of PTH and P in serum as well as the fractions of urinary Ca and P outputs were lowered. On the contrary, the level of calcitriol in serum was higher as GFR increased.

Estimation of FGF23 levels in serum in cKD patients

The relationships of the linearly modified FGF23 concentration in serum, [FGF23]AB, to the selected physiological variables in CKD patients were illustrated in Figure 2. First, a strong correlation was observed between log.e(GFR) and a negative form of log.e[FGF23]AB, indicating that the FGF23 level was sharply elevated in CKD patients with reduction in GFR. Second, an increase in [FGF23]AB was correlated to the levels of PTH, calcitriol, P in serum, and the renal threshold for P. Note that a positive correlation (i.e. B > 0) was observed for the levels of PTH and P in serum, while a negative correlation (i.e. B < 0) for the serum level of calcitriol and the renal threshold for P. Note that a majority of data points had the PTH level above 50 pg/ml, indicating a poor balance of mineral metabolism in CKD patients.

 Linkage of FGF23 and P levels in serum

In all groups, a positive correction was observed between the level of P and the modified level of FGF23 in serum. Note that CKD data in Figure 2D showed the elevated P level up to 6 mg/dl, while the higher bound of the P level was ∼2 mg/dl (Tumor Induced Osteomalacia), 3.5 ∼4 mg/dl (Fibrous Dysplasia and XLH), and 4.5 mg/dl (healthy populations).

Predicted effects of the antibody specific to FGF23

Although the observed increase of FGF23 in CKD is apparently a physiological response to hyperphos-phatemia, the use of FGF23 antibody is suggested for transplanted hypophosphatemic patients of CKD with a high level of FGF23.21 In response to intravenous administration of the antibody specific to FGF23, we evaluated the predicted changes in the serum levels of PTH, calcitriol, and P as well as a normalized urinary output of P.  The results were positive.
(Yokota H, Pires A, Raposa JF, Ferreira HG. 2010.)

Overview of renal Ca2+ handling

About 50% of plasma calcium (ionized and complexed form; ultrafilterable fraction, excluding the protein bound form) is freely filtered through the renal glomerulus, and 99% of the filtered calcium is actually reabsorbed along renal tubules (Table 1- see Fig below on right)). The excreted calcium in the final urine is about 200 mg per day in an adult person with an average diet. Several factors are involved in the regulation of calcium in renal tubules. PTH and activated vitamin D enhance calcium reabsorption in the thick ascending limb (TAL), distal convoluted tubule (DCT) and/or connecting tubule (CNT).

Acidosis contributes to hypercalciuria by reducing calcium reabsorption in the proximal tubule (PT) and DCT, and alkalosis vice versa3). Diuretics like thiazide and furosemide also alter calcium absorption in the renal tubules; thiazide promotes calcium reabsorption and furosemide inhibits it. Plasma calcium itself also controls renal calcium absorption through altered PTH secretion as well as via binding to the calcium sensing receptor (CaSR) in the TAL.

To facilitate Ca2+ reabsorption along renal tubules;

(i) voltage difference between the lumen and blood compartment should be favorable for Ca2+ passage, i.e., a positive voltage in the lumen;
(ii) concentration difference should be favorable for Ca2+ passage with a higher Ca2+ concentration in the lumen;
(iii) an active transporter should exist if the voltage or concentration difference is not favorable for Ca2+ reabsorption. Each renal tubular segment has a different Ca2+ concentration difference or voltage environment for its unique mechanism for calcium re-absorption.

Calcium handling along the tubules

Fifty to sixty percent of filtered calcium is absorbed in parallel with sodium and water in the PT, suggesting that the passive pathway is the main route of Ca2+ absorption in this segment. Claudin-2 is especially concentrated in the tight junction and also expressed in the basolateral membrane of the PT as the candidate for paracellular Ca2+ channel in the PT. There is no evidence that Ca2+ reabsorption occurs in the thin descending and ascending limb. In the TAL, 15% of filtered calcium is absorbed, and the passive absorption through paracellular space is known as the main mechanism (Fig. 1). Paracellin-1 (claudin-16) is exclusively expressed in the tight junction of TAL and has been known as the important magnesium channel in the TAL. Paracellin-1 mutation caused hypercalciuria and nephrocalcinosis in addition to hypomagnesemia. This finding supports that paracellin-1 is not only the main Mg2+ channel, but also works as the paracellular Ca2+ channel in the TAL. There are some evidences that active transport occurs in the TAL, but no specific channel has yet been identified). The CaSR is a member of G protein-coupled receptors and suppresses PTH secretion by sensing high plasma Ca2+ level in the parathyroid glands). In the kidney, the CaSR is most highly expressed in the TAL..
Although only 10-15% of filtered Ca2+ is absorbed in the DCT and CNT, these are the main sites in which the fine regulation of Ca2+ excretion and the major action of PTH and activated vitamin D occur. In the DCT and CNT, the luminal voltage is negative and Ca2+ concentration in the lumen is lower than that of plasma. Thus, active transport mechanism against voltage and concentration gradient should exist in these segments. Several Ca2+ transporting proteins are involved in this active transmembrane transport of Ca2+ in the DCT and CNT. Transcellular Ca2+ re-absorption can occur by three steps;
(i) entry of Ca2+ through the calcium channels (TRPV5, TRPV6) in the apical membrane,
(ii) binding of Ca2+ with calcium-binding protein (calbindin) and diffusion in the cytoplasm (which enables no significant change in the intracellular i[Ca2+], and
(iii) Ca2+ extrusion via an ATP-dependent plasma membrane Ca2+-ATPase (PMCA1b) and an Na2+/Ca2+ exchanger (NCX1) in the basolateral membrane (see Fig below on right).
  • In the collecting duct (CD), there is no evidence that Ca2+ reabsorption occurs even though calcium channel (TRPV6) was documented to be expressed in CD cells.
  • Each renal tubule has a unique environment and plays a different role in Ca2+ reabsorption.
  • The coordinated play of different renal tubules could maintain harmony of renal Ca2+ handling.

Transient receptor potential (TRP) channel is a super-family of ion channels permeable to monovalent and/or divalent cations with six-transmembrane domains. The mammalian TRP family consists of six subfamilies like TRPC (canonical), TRPV (vanilloid), TRPM (melastatin), TRPP (polycystin), TRPML (mucolipin), and TRPA (ankyrin). TRPV is one of them and consists of six members in mammalians; TRPV1 to TRPV6. TRPV5 (previously known as ECaC1) and TRPV6 (ECaC2), both cloned in 1999, have characteristics distinguished from other TRPV channels; (i) constitutively active at low intracellular Ca2+ concentration, and (ii) exclusively selective for Ca2+ (PCa/PNa >100)9). TRPV5 and TRPV6 have the highest sequence homology (~730 amino acids, amino-terminal ankyrin repeats, TM5 and TM6 each forming the pore-region composed with tetramer, on human chromosome 7q34-35) (Fig. 3a). TRPV5 is exclusively expressed in the DCT and CNT in the kidney10) (Fig. 3b). On the contrary, TRPV6 is more ubiquitously distributed, especially in the intestine, and also found from the DCT to the CD in the kidney11) (Fig. 3b). Both TRPV5 and TRPV6 are located in the apical plasma membrane of the tubular epithelium, and serve as the entrance of Ca2+ from the lumen into the cytoplasm. TRPV5 knockout mice exhibited severe hypercalciuria (more than 6 times of wild type mouse) and low bone densities, but without hypocalcemia due to the compensatory elevation of activated vitamin D, clearly demonstrating that TRPV5 plays a crucial role in renal calcium reabsorption12). TRPV6 knockout mice also showed significant hypercalciuria and bone disease13). Even though TRPV5 and TRPV6 knockout mice showed congenital hypercalciuria, the mutation of the proteins has not been found in the human. Until now, TRPV5 is known
as the main entry of Ca2+ in renal tubular epithelial cells in the DCT and CNT, and TRPV6 is also known to contribute to renal Ca2+ reabsorption in the distal nephron.
Several factors (PTH, 1,25(OH)2D3, calcitonin, estrogen, i[Ca2+], acid-base status, klotho, diuretics, and im-munosuppressive drugs, etc) are involved in the regulation of both TRPV5 and TRPV610) (Table 2). Alteration of TRPV5 and TRPV6 by these factors contributes in disturbance of calcium metabolism: dyscalcemia, hypo- and hypercalciuria. 1,25(OH)2D3-depleted rats showed decreased expression of TRPV5 and calbindin-D28K mRNA and protein, and repletion of the hormone restored the expression of them.

TRPV

Transient receptor potential (TRP) channel is a super-family of ion channels permeable to monovalent and/or divalent cations with six-transmembrane domains. The mammalian TRP family consists of six subfamilies like TRPC (canonical), TRPV (vanilloid), TRPM (melastatin), TRPP (polycystin), TRPML (mucolipin), and TRPA (ankyrin). TRPV is one of them and consists of six members in mammalians; TRPV1 to TRPV6. TRPV5 (previously known as ECaC1) and TRPV6 (ECaC2), both cloned in 1999, have characteristics distinguished from other TRPV channels;
(i) constitutively active at low intracellular Ca2+ concentration, and
(ii) exclusively selective for Ca2+ (PCa/PNa >100)9). TRPV5 and TRPV6 have the highest sequence homology (~730 amino acids, amino-terminal ankyrin repeats, TM5 and TM6 each forming the pore-region composed with tetramer, on human chromosome 7q34-35). TRPV5 is exclusively expressed in the DCT and CNT in the kidney.
  • On the contrary, TRPV6 is more ubiquitously distributed, especially in the intestine, and also found from the DCT to the CD in the kidney
  • Both TRPV5 and TRPV6 are located in the apical plasma membrane of the tubular epithelium, and serve as the entrance of Ca2+ from the lumen into the cytoplasm.
TRPV5 knockout mice exhibited severe hypercalciuria (more than 6 times of wild type mouse) and low bone densities, but without hypocalcemia due to the compensatory elevation of activated vitamin D, clearly demonstrating that TRPV5 plays a crucial role in renal calcium reabsorption. TRPV6 knockout mice also showed significant hypercalciuria and bone disease. Even though TRPV5 and TRPV6 knockout mice showed congenital hypercalciuria, the mutation of the proteins has not been found in the human. Until now, TRPV5 is known  as the main entry of Ca2+ in renal tubular epithelial cells in the DCT and CNT, and TRPV6 is also known to contribute to renal Ca2+ reabsorption in the distal nephron.
Several factors (PTH, 1,25(OH)2D3, calcitonin, estrogen, i[Ca2+], acid-base status, klotho, diuretics, and im-munosuppressive drugs, etc) are involved in the regulation of both TRPV5 and TRPV6. Alteration of TRPV5 and TRPV6 by these factors contributes in disturbance of calcium metabolism: dyscalcemia, hypo- and hypercalciuria. 1,25(OH)2D3-depleted rats showed decreased expression of TRPV5 and calbindin-D28K mRNA and protein, and repletion of the hormone restored the expression of them.
Table . The regulation of calcium transporting proteins in the DCT and CNT
Factors TRPV5  TRPV6  Calbindin- Mechanisms

D28K

PTH + NC + transcription
Vit D + + + transcription
Estrogen + + + transcription
Low Ca2+ diet + + NC transcription
Acidosis ND transcription
Thiazide C ND C transcription
Furosemide + + + transcription
Tacrolimus ND transcription
[Ca2+] Channel activity
Calbindin-D28K + NC Channel activity
Klotho + + ND trafficking

FGF23

FGF23, a member of the FGF family (type I trans-membrane phosphotyrosine kinase receptors), is a 30 kDa secreted protein and inactivated by cleavage into two smaller fragments (N-terminal 18 kDa fragment and C-terminal 12 kDa fragment) by a pro-convertase enzyme, furin . It was first cloned as the candidate gene for autosomal dominant hypophosphatemic rickets (ADHR). FGF23 is primarily expressed in the osteoblasts and osteocytes. Because Fgf23 knockout mice showed very similar phenotype to Klotho knockout mice including severe hyperphophatemia and osteoporosis, and gain of function mutation of Fgf23 gene was observed in ADHR patients. The main studies about the role of FGF23 in the kidney have focused on phosphate metabolism rather than calcium metabolism.

It is unknown how the FGF23:klotho complex from the DCT acts in the PT because the main action site of FGF23 in the kidney is the PT, whereas the FGF23:klotho complex is most abundant in the DCT. Both overexpression and deficiency of FGF23 cause several clinical diseases including ADHR and HFTC (hyperphosphatemic familial tumorial calcino-sis). Recently, FGF23 was suggested as a potential bio-marker for management of phosphate balance in chronic kidney disease (CKD) patients because the circulating FGF23 level was higher in CKD patients than healthy controls and the increased FGF23 level was an independent risk factor for higher mortality among dialysis patients26). FGF23 also plays some roles in the parathyroid glands and other organs like the choroid plexus, pituitary gland, and bone. However, further studies are needed to clarify the roles and the mechanisms.

Conclusion

The kidney has been known as the central organ for calcium homeostasis through fine regulation of renal calcium excretion. For the past decade, there has been big progress in the understanding of the roles of the kidney in calcium homeostasis. The identification of calcium transport proteins and the molecular approach to the regulatory mechanisms achieved a major contribution to this progress. TRPV5, TRPV6, calbindin-D28K, NCX1, and PMCA1b have been identified as the main calcium transport proteins in the distal nephron. PTH, vitamin D, i[Ca2+], CaSR, and other various conditions control renal calcium excretion through the regulation of these transport proteins. Klotho and FGF23 emerged as new players in calcium metabolism in the kidney. Thus, the role of the klotho-FGF23 axis in the regulatory mechanisms of calcium transport needs to be addressed.

Disorders of Calcium, Phosphorus and Magnesium Metabolism

Infrequently patients might present in the outpatient settings with non-specific symptoms that might be due to abnormalities of divalent cation (magnesium, calcium) or phosphorous metabolism. Several inherited disorders have been identified that result in renal or intestinal wasting of these elements. Physicians need to have a thorough understanding of the mechanism of calcium, magnesium and phosphorous metabolism and diagnoses disorders due to excess or deficiency of these elements. Prompt identification and treatment of the underlying disorders result in prevention of serious morbidity and mortality.

Maintenance of serum calcium in the extra cellular fluid space (ECF) is tightly regulated. Most calcium (around 99%) is bound and complexed in the bones. Calcium in the ECF is found in three fractions, of which 45% is in biological ionized fraction, 45% is protein bound and not filterable in the kidney and 10% is complexed with anions such as bicarbonate, citrate, phosphate, and lactate (Fig. 1 ). Most of the protein bound calcium is complexed with albumin, and a smaller amount to globulin. Each 1 g/dL of albumin binds 0.8 mg/dL (0.2 mmol/L) calcium. Hence, for each 1g/ dl decrease in serum albumin below normal value of 4.0 g/dl, one needs to add 0.8 mg/ dl to the measured serum calcium. Levels of calcium are also influenced by acid-base status, with acidosis increasing serum calcium while alkalosis decreases serum calcium levels.

Maintenance of normal calcium in ECF is dependent on fluxes of calcium between the intestine, kidneys and bone. The regulation of calcium in serum is regulated by calcium itself, through a calcium sensing receptor (Ca RG) and hormones like parathormone (PTH) and 1, 25-dihydroxyvitamin D3.

Calcium transport across the intestine occurs in two directions, absorption and secretion. The factors that influence calcium absorption in the intestine include daily amount of calcium that is ingested and 1, 25-dihydroxyvitamin D3 that binds to and activates the Vitamin D receptor (VDR) and induces the expression of calcium channel TRPV6, calbindin- D9K, and Ca2+ – ATPase. Other hormones like PTH, estrogen, prolactin and growth hormone may play a minor role in calcium absorption. Conditions that result in decreased intestinal calcium transport include high vegetable fiber and fat content of food, corticosteroid deficiency, estrogen deficiency, advanced age, gastrectomy, intestinal malabsorption, diabetes mellitus, renal failure and low Ca2+ phosphate ratio in the food.

PTH and 1, 25- dihydroxyvitamin D3 stimulate osteoclasts in bones and promote release of calcium in ECF. PTH promotes hydroxylation of 25(OH) D3 to 1, 25(OH) D3 and distal tubular calcium reabsorption.

Hypocalcaemia occurs when the loss of calcium from the ECF via renal excretion is greater than influx of Ca 2+ from intestine or bones. One of the commonest cause of low calcium is hypoalbuminemia, though the level of ionized Ca2+ is normal. The causes of hypocalcaemia is summarized in Table 1 . Acute hypocalcaemia is often seen in acute respiratory alkalosis due to hyperventilation. Idiopathic or acquired (post surgery, radiotherapy) hypoparathyroid states are usually accompanied with elevated phosphate level. Pseudo hypoparathyroidism is characterized by short neck, round face and short metacarpal and results from end-organ resistance to PTH. Chronic kidney disease and massive phosphate administration can result in hypocalcaemia with high serum phosphate levels. Familial hypocalcaemia is linked with activating mutation of Ca RG.  Hypocalcaemia with low phosphate levels occur in Vitamin D deficiency, resistance to calcitriol (Type 2 vitamin D- dependent rickets) acute pancreatitis and magnesium deficiency.

Table 1 : Causes of Hypocalcemia
Idiopathic Hypoparathyroidism
Post parathyroidectomy (Hungry bones syndrome)
Pseudo-hypoparathyroidism
Familial hypocalcemia
Rapid correction of severe acidosis with dialysis
Acute respiratory and metabolic alkalosis
Acute pancreatitis
Rhabdomyolysis
Hypomagnesemia
Septic shock
Ethylene glycol toxicity
Vitamin D deficiency
Chronic kidney disease
Massive transfusion- Citrate toxicity

Hypercalcemia occurs when in influx of calcium into the ECF exceeds the efflux of calcium from intestine and kidneys. The normal calcium level ranges from 8.9- 10.1 mg/ dL. The range of serum calcium levels in mild hypercalcemia is (10.1- 12.0 mg/dL), moderate hypercalcemia (12.0 – 14.0 mg/dl) and severe hypercalcemia > 14.0 mg/ dL respectively. The various causes of hypercalcemia is depicted in Table 2. Mutation of the gene for Ca RG results in hypercalcemia in few cases.

Table 2. : Causes of hypercalcemia
Parathormone             Primary hyperparathyroidism
(PTH) mediated           Lithium induced
Familial hypocalciuric hypercalcemia
Tertiary hyperparathyroidism
Cancer                          Multiple myeloma
PTHrp mediated-Breast, lung,
Exogenous Vitamin D
Dialysis patients (exogenous Vit D)
Other causes               Vitamin A toxicity
Thyrotoxicosis
Paget’s disease
Adrenal insufficiency
Thiazide use

Deficiency of calcium, magnesium and phosphorous are common in general practice. A thorough understanding of pathophysiology of these elements, common dietary sources of these elements and pharmacological measures that might be necessary to correct these deficiencies could guide the physician to make an accurate diagnosis, initiate appropriate treatment and prevent future recurrences.  (Ghosh AK*, Joshi SR. 2008.)

Renal Disease and the Cardiovascular System

Cardiovascular disease is a leading cause of death among patients with end stage renal failure. Animal models have played a crucial role in teasing apart the complex pathological processes involved. In addition to the anatomical and histological characteristics humans share with other species, human diseases can be reproduced in these species using pharmacological, surgical or genetic manipulation. Experimentation still provides the best evidence for disease causation, and only with this evidence can clinical science proceed to developing treatments. However, experimentation is often not possible or ethical in human subjects, and thus without these animal models the advancement in knowledge of the patho-physiology of disease would come to a standstill.

The way in which kidneys succumb to disease and the development of renal failure involves complex interactions between numerous different systems, mediated by a multitude of chemicals. Current understanding of renal disease is merely the tip of the metaphorical iceberg. The history of renal pathology is plagued by controversy, and nowhere is this more evident than in the development of cardiovascular disease in patients with chronic renal failure. Impairment of renal function increases the risk of cardiac disease to 15-20 times that of individuals with normal renal function. The result is that cardiac disease causes 40% of deaths in patients on dialysis.

This review discusses the principles of using animal models, the history of their use in the study of renal hypertension, the controversies arising from experimental models of non-hypertensive uraemic cardiomyopathy and the lessons learned from these models, and highlights important areas of future research in this field, including de novo cardiomyopathy secondary to renal transplantation.

Myocardial Interstitial Fibrosis, Cardiac Compliance and Vascular Architecture

Using subtotally nephrectomised Sprague-Dawley rats, Mall et al. showed that the increase in total heart weight demonstrated by Rambausek et al. after 21 days of uremia (as well as an increase in both right and left ventricular weight) was secondary to an increase in true interstitial volume, both cellular and non-cellular, with increased deposition of collagen. This was associated with activated interstitial cells, and a reduced capillary cross-sectional area. In 1992, this latter point was confirmed using stereological techniques to analyse perfusion-fixed hearts of subtotally nephrectomised Sprague-Dawley rats. Uremia resulted in increased blood pressure and reduced capillary length per unit myocardial volume, as well as reduced capillary luminal surface density and volume density, compared to control rats. The same group found a blood pressure-independent increase in the wall to lumen ratio of intramyocardial arteries, and in the aorta media thickness of subtotally nephrectomised rats. The intramyocardial arterial wall thickening has been found to be due to hypertrophy rather than hyperplasia, independent of blood pressure.  These architectural changes were reported again in 1996. In that experiment, nephrectomised Sprague-Dawley rats were given ramipril, nifedipine or moxonidine to normalise blood pressure; these drugs had differential effects on the above architectural changes, and also acted to prevent these changes.  The different changes in interstitial and capillary density in uremic cardiomyopathy have not yet been explained, but the role of growth factors such as basic fibroblast growth factor (BFGF) and vascular endothelial growth factor (VEGF) has been proposed.

Cardiac Function and Energetics in Uremia

The above experiments provided some insight into the structural changes seen in uraemic hearts. They were followed by a study using the subtotal (5/6) nephrectomy model on Wistar rats, in which the authors focused on the mechanical effects of these structural changes in vitro, thereby removing neurohormonal influences on cardiac contractility. Four weeks after surgery, isolated perfusing working heart preparations demonstrated reduced cardiac output. However, blood pressure was not controlled during the four weeks post-operatively, and could have contributed to the effects. An increased susceptibility to ischemic damage was also shown via decreased phosphocreatine content, and an increased release of inosine (a marker of ischaemic damage). These hearts failed in response to increases in calcium; the authors proposed that impaired cytosolic calcium control played a role in the relationship between renal failure and impaired cardiac function.

This in vitro experiment demonstrated the fact that impaired cardiac function was independent of circulating urea and creatinine, as the hearts were perfused with physiological saline, with no effect from the addition of urea and creatinine. The opposite has been shown in spontaneously beating mouse cardiac myocytes, in response to sera from patients on haemodialysis for chronic renal failure. Urea, creatinine, and combinations of the two reduced the cardiac inotropy and resulted in arrhythmias and asynchronies.

These experiments make a good case for uremic cardiomyopathy to be a distinct entity from hypertensive cardiac dysfunction and atherosclerotic cardiac disease secondary to the risk factors common to both heart and kidney disease. The cause of this phenomenon is still controversial, with parathyroid hormone (PTH), angiotensin II, marino-bufagenin (MBG), oxidative stress, and growth hormone.

The Role of Calcium in Uremic Cardiomyopathy

Calcium ions play a crucial role in cardiac physiology, particularly in myocardial excitation-contraction coupling. Therefore, PTH was one of the first culprits to be suspected of playing a role in the pathophysiology of uremic cardiomyopathy; this was as early as 1984. As reviewed by Rostand and Drüeke, there are numerous theories pertaining to the mechanisms whereby PTH could act as an intermediary between renal impairment and cardiomyopathy. These include

  • direct trophic effects on myocytes
  • interstitial fibroblasts,
  • indirect effects via anaemia or large and small vessel changes.

Rostand and Drüeke suggest an increase in blood pressure via hypercalcemia, but the effects on the heart appear to be independent of blood pressure.

Rambausek et al. noted increased cardiac calcium content in experimental rats, and that an increase in heart weight still occurred after parathyroidectomy with calcium supplementation. This was followed in the 1990s by in vitro experiments that demonstrated; an increased cytosolic calcium concentration in isolated rat myocytes in response to PTH, a reduced expression of PTH-related peptide receptor mRNA in rat hearts secondary to hyperparathyroidism due to chronic renal failure, and increased force and frequency of contraction of isolated, beating rat cardiomyocytes.

Subsequent to “chance observations” in the laboratory, Amann et al. argued for the role of PTH in the wall thickening of intramyocardial arterioles and for fibroblast activation and subsequent cardiac fibrosis. Abolishing hyperparathyroidism prevented the cardiac fibrosis and capillary changes normally seen in nephrectomised rats, which was independent of blood pressure.

The Renin-Angiotensin System (RAS) and Endothelin

Many studies have highlighted the importance of the RAS in the development of uremic cardiomyopathy. Tornig et al. showed that in nephrectomised rats, ramipril, an ACE inhibitor, prevented the increased wall thickness of the intramyocardial arterioles, as well as the expansion of nonvascular cardiac interstitial volume and the aortic wall and lumen changes, but not the reduced capillary length density. The same group subsequently repeated these observations, and demonstrated that the beneficial effects of ramipril were prevented by the use of specific bradykinin B2 receptor antagonists, suggesting a role for increased bradykinin as a mediator for the effects of ramipril.

CONCLUSIONS

Experimental models have played a crucial role in the study of the complex interplay between the heart and the kidney in chronic renal disease. In view of the numerous differences in animal and human anatomy, physiology and pathology, the results of these experiments should be interpreted with caution, but in some areas, these studies have led directly to advances in therapeutics.
(RC Grossman. 2010.)

Deficiency of the Calcium-Sensing Receptor

Rare loss-of-function mutations in the calcium-sensing receptor (Casr) gene lead to decreased urinary calcium excretion in the context of parathyroid hormone (PTH)–dependent hypercalcemia, but the role of Casr in the kidney is unknown. Using animals expressing Cre recombinase driven by the Six2 promoter, we generated mice that appeared grossly normal but had undetectable levels of Casr mRNA and protein in the kidney. Baseline serum calcium, phosphorus, magnesium, and PTH levels were similar to control mice. When challenged with dietary calcium supplementation, however, these mice had significantly lower urinary calcium excretion than controls (urinary calcium to creatinine, 0.31±0.03 versus 0.63±0.14; P=0.001). Western blot analysis on whole-kidney lysates suggested an approximately four-fold increase in activated Na+-K+-2Cl cotransporter (NKCC2). In addition, experimental animals exhibited significant downregulation of Claudin14, a negative regulator of paracellular cation permeability in the thick ascending limb, and small but significant upregulation of Claudin16, a positive regulator of paracellular cation permeability. Taken together, these data suggest that renal Casr regulates calcium reabsorption in the thick ascending limb, independent of any change in PTH, by increasing the lumen-positive driving force for paracellular Ca2+ transport.
(Toka HR, Al-Romaih K, Koshy JM, DiBartolo, III S, et al. 2012)

References:

The renal sodium-calcium exchanger.
Dominguez JH, Juhaszova M, Feister HA.
J Lab Clin Med. 1992 Jun;119(6):640-9.
http://www.ncbi.nlm.nih.gov/pubmed/1593210

Na(+)-Ca2+ exchanger of rat proximal tubule: gene expression and subcellular localization.
Dominguez JH, Juhaszova M, Kleiboeker SB, Hale CC, Feister HA.
Am J Physiol. 1992 Nov;263(5 Pt 2):F945-50.
http://www.ncbi.nlm.nih.gov/pubmed/1443182

Calcium transport in renal epithelial cells
PA Friedman, FA Gesek
Am J Physiol – Renal Physiology 1993; 264(F181-F198)
http://ajprenal.physiology.org/content/264/2/F181

Effect of calcitonin on calcium transport by the luminal and basolateral membranes of the rabbit nephron.
Zuo Q, Claveau D, Hilal G, Leclerc M, Brunette MG.
Kidney Int. 1997; 51(6):1991-9.
http://www.ncbi.nlm.nih.gov/pubmed/9186893

Ca2+ transport by the luminal membrane of the distal nephron: action and interaction of protein kinases A and C.
Hilal G, Claveau D, Leclerc M, Brunette MG.
Biochem J. 1997 Dec 1;328 ( Pt 2):371-5
http://www.ncbi.nlm.nih.gov/pubmed/9371690

Calcium-sensing receptor and renal cation handling
Pascal Houillier and Michel Paillar
Nephrol. Dial. Transplant. (2003) 18 (12): 2467-2470. http://ndt.oxfordjournals.org/content/18/12/2467.full
http://dx.doi.org/10.1093/ndt/gfg420

Patch-clamp evidence for calcium channels in apical membranes of rabbit kidney connecting tubules.
S Tan and K Lau
J Clin Invest. 1993; 92(6): 2731–2736
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC288471/
http://dx.doi.org/10.1172/JCI116890

Bending the MDCK Cell Primary Cilium Increases Intracellular Calcium
H.A. Praetorius, K.R. Spring
J Membrane Biol 2001; 184(1), pp 71-7
http://link.springer.com/article/10.1007/s00232-001-0075-4

Branching points of renal resistance arteries are enriched in L-type calcium channels and initiate vasoconstriction.
M S Goligorsky, D Colflesh, D Gordienko, L C Moore
Am J Physiol 03/1995; 268(2 Pt 2):F251-7.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC9186893/

G proteins regulate calcium channels in the luminal membranes of the rabbit nephron
Brunette MG, Hilal G, Mailloux J, Leclerc M.
Nephron. 2000 Jul;85(3):238-47.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC10867539/

Characterization of three types of calcium channel in the luminal membrane of the distal nephron
MG Brunette, M Leclerc, D Couchourel, J Mailloux, Y Bourgeois
Can J Phy Pharma 2004; 82(1): 30-37     http://dx.doi.org/10.1139/y03-127

ATP directly enhances calcium channels in the luminal membrane of the distal nephron
MG Brunette, J Mailloux, G Hilal
J Cell Phys 1999; 181(3), pp 416–423
http://dx.doi.org/10.1002/(SICI)1097-4652(199912)181:3<416::AID-JCP5>3.0.CO;2-X

Discovery of alpha-Klotho and FGF23 unveiled new insight into calcium and phosphate homeostasis
Nabeshima Y.
Clin Calcium. 2008;18(7):923-34. http://dx.doi.org/CliCa0807923934

Deficiency of the calcium-sensing receptor in the kidney causes parathyroid hormone-independent hypocalciuria
Toka HR, Al-Romaih K, Koshy JM, DiBartolo S, III, Kos, CH, et al.
J Am Soc Nephrol 2012; 23: 1879-1890.   http://dx.doi.org/10.1681/ASN.2012030323

The renal Na+/Ca2+ exchange system is located exclusively in the distal tubule
Ramachandram C, Brunette MG.
Biochem J 1989;257:259-264

Calcium ion transport across plasma membranes isolated from rat kidney cortex
Gmaj P, Murer H, Kinne R
Biochem J 1979; 178:549-557

Model-based analysis of Fgf23 regulation in chronic renal disease
Yokota H, Pires A, Raposo JF, Ferreira HG.
Gene Reg and Systems Biol 2010; 4: 53-60

Kidney and Calcium Homeostasis
Un Sil Jeon
Electrolyte & Blood Pressure  2008; 6:68-76

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68-76.hwp

1 Ca2+ absorption in the thick ascending limb of Henle (TAL).
 The schematic view of Ca2+ reabsorption in the TAL.
Paracellin-1 (claudin-16) is located in the tight junction of
TAL  and serves as the paracellular route for divalent cations.
The mechanism of Ca2+ absorption in the renal epithelium.  Transcellular Ca2+

reabsorption in the distal convoluted tubule (DCT) and connecting tubule (CNT)
occurs by three steps;
(i) entry of Ca2+ through the calcium channels [transient receptor potential
vanilloid (TRPV) 5, TRPV6] in the apical membrane,
(ii) binding of Ca2+ with calcium-binding protein (calbindin) and diffusion in the
cytoplasm (without significant change in the intracellular i[Ca2+]), and
(iii) Ca2+ extrusion via an ATP-dependent Ca2+-ATPase (PMCA1b) or an
Na2+/Ca2+ exchanger (NCX1) in the basolateral membrane.

Read Full Post »


Role of Calcium, the Actin Skeleton, and Lipid Structures in Signaling and Cell Motility

Author: Larry H. Bernstein, MD

Author: Stephen Williams, PhD

and

Curator: Aviva Lev-Ari, PhD, RN

This article is Part II in a series of articles on Calcium and its role in Cell motility

The Series consists of the following articles:

Part I: Identification of Biomarkers that are Related to the Actin Cytoskeleton

Larry H Bernstein, MD, FCAP

https://pharmaceuticalintelligence.com/2012/12/10/identification-of-biomarkers-that-are-related-to-the-actin-cytoskeleton/

Part II: Role of Calcium, the Actin Skeleton, and Lipid Structures in Signaling and Cell Motility

Larry H. Bernstein, MD, FCAP, Stephen Williams, PhD and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/08/26/role-of-calcium-the-actin-skeleton-and-lipid-structures-in-signaling-and-cell-motility/

Part III: Renal Distal Tubular Ca2+ Exchange Mechanism in Health and Disease

Larry H. Bernstein, MD, FCAP, Stephen J. Williams, PhD
 and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/09/02/renal-distal-tubular-ca2-exchange-mechanism-in-health-and-disease/

Part IV: The Centrality of Ca(2+) Signaling and Cytoskeleton Involving Calmodulin Kinases and Ryanodine Receptors in Cardiac Failure, Arterial Smooth Muscle, Post-ischemic Arrhythmia, Similarities and Differences, and Pharmaceutical Targets

Larry H Bernstein, MD, FCAP, Justin Pearlman, MD, PhD, FACC and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/09/08/the-centrality-of-ca2-signaling-and-cytoskeleton-involving-calmodulin-kinases-and-ryanodine-receptors-in-cardiac-failure-arterial-smooth-muscle-post-ischemic-arrhythmia-similarities-and-differen/

Part V: Ca2+-Stimulated Exocytosis:  The Role of Calmodulin and Protein Kinase C in Ca2+ Regulation of Hormone and Neurotransmitter

Larry H Bernstein, MD, FCAP
and
Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/12/23/calmodulin-and-protein-kinase-c-drive-the-ca2-regulation-of-hormone-and-neurotransmitter-release-that-triggers-ca2-stimulated-exocytosis/

Part VI: Calcium Cycling (ATPase Pump) in Cardiac Gene Therapy: Inhalable Gene Therapy for Pulmonary Arterial Hypertension and Percutaneous Intra-coronary Artery Infusion for Heart Failure: Contributions by Roger J. Hajjar, MD

Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/08/01/calcium-molecule-in-cardiac-gene-therapy-inhalable-gene-therapy-for-pulmonary-arterial-hypertension-and-percutaneous-intra-coronary-artery-infusion-for-heart-failure-contributions-by-roger-j-hajjar/

Part VII: Cardiac Contractility & Myocardium Performance: Ventricular Arrhythmias and Non-ischemic Heart Failure – Therapeutic Implications for Cardiomyocyte Ryanopathy (Calcium Release-related Contractile Dysfunction) and Catecholamine Responses

Justin Pearlman, MD, PhD, FACC, Larry H Bernstein, MD, FCAP and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/08/28/cardiac-contractility-myocardium-performance-ventricular-arrhythmias-and-non-ischemic-heart-failure-therapeutic-implications-for-cardiomyocyte-ryanopathy-calcium-release-related-contractile/

Part VIII: Disruption of Calcium Homeostasis: Cardiomyocytes and Vascular Smooth Muscle Cells: The Cardiac and Cardiovascular Calcium Signaling Mechanism

Justin Pearlman, MD, PhD, FACC, Larry H Bernstein, MD, FCAP and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/09/12/disruption-of-calcium-homeostasis-cardiomyocytes-and-vascular-smooth-muscle-cells-the-cardiac-and-cardiovascular-calcium-signaling-mechanism/

Part IX: Calcium-Channel Blockers, Calcium Release-related Contractile Dysfunction (Ryanopathy) and Calcium as Neurotransmitter Sensor

Justin Pearlman, MD, PhD, FACC, Larry H Bernstein, MD, FCAP and Aviva Lev-Ari, PhD, RN

Part X: Synaptotagmin functions as a Calcium Sensor: How Calcium Ions Regulate the fusion of vesicles with cell membranes during Neurotransmission

Larry H Bernstein, MD, FCAP and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/09/10/synaptotagmin-functions-as-a-calcium-sensor-how-calcium-ions-regulate-the-fusion-of-vesicles-with-cell-membranes-during-neurotransmission/

Part XI: Sensors and Signaling in Oxidative Stress

Larry H. Bernstein, MD, FCAP

https://pharmaceuticalintelligence.com/2013/11/01/sensors-and-signaling-in-oxidative-stress/

Part XII: Atherosclerosis Independence: Genetic Polymorphisms of Ion Channels Role in the Pathogenesis of Coronary Microvascular Dysfunction and Myocardial Ischemia (Coronary Artery Disease (CAD))

Larry H Bernstein, MD, FCAP and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/12/21/genetic-polymorphisms-of-ion-channels-have-a-role-in-the-pathogenesis-of-coronary-microvascular-dysfunction-and-ischemic-heart-disease/

 

This article, constitute, Part II, it is a broad, but not complete review of the emerging discoveries of the critical role of calcium signaling on cell motility and by extension, embryonic development, cancer metastasis, changes in vascular compliance at the junction between the endothelium and the underlying interstitial layer.  The effect of calcium signaling on the heart in arrhtmogenesis and heart failure will be a third in this series, while the binding of calcium to troponin C in the synchronous contraction of the myocardium had been discussed by Dr. Lev-Ari in Part I.

Universal MOTIFs essential to skeletal muscle, smooth muscle, cardiac syncytial muscle, endothelium, neovascularization, atherosclerosis and hypertension, cell division, embryogenesis, and cancer metastasis. The discussion will be presented in several parts:
1.  Biochemical and signaling cascades in cell motility
2.  Extracellular matrix and cell-ECM adhesions
3.  Actin dynamics in cell-cell adhesion
4.  Effect of intracellular Ca++ action on cell motility
5.  Regulation of the cytoskeleton
6.  Role of thymosin in actin-sequestration
7.  T-lymphocyte signaling and the actin cytoskeleton

Part 1.  Biochemical and Signaling Cascades in Cell Motility

BIOCHEMISTRY AND BIOMECHANICS OF CELL MOTILITY

Song Li, Jun-Lin Guan, and Shu Chien
Annu. Rev. Biomed. Eng. 2005. 7:105–50   [doi:10.1146/annurev.bioeng.7.060804.100340]
Cell motility or migration is an essential cellular process for a variety of biological events. In embryonic development, cells migrate to appropriate locations for the morphogenesis of tissues and organs. Cells need to migrate to heal the wound in repairing damaged tissue. Vascular endothelial cells (ECs) migrate to form new capillaries during angiogenesis. White blood cells migrate to the sites of inflammation to kill bacteria. Cancer cell metastasis involves their migration through the blood vessel wall to invade surrounding tissues.

Variety of important roles for cell migration:

1. Embryogenesis
2. Wound healing (secondary extension)
3. Inflammatory infiltrate (chemotaxis)
4. Angiogenesis
5. Cancer metastasis
6. Arterial compliance
7. Myocardial and skeletal muscle contraction
8. Cell division

Portrait of Cell in Migration:

1. protrusion of leading edge
2. Formation of new adhesions at front
3. Cell contraction
4. Release of adhesions at rear
Microenvironmental factor:
1. Concentration gradient of chemoattractants
2. Gradient of immobilized ECM proteins
3. Gradient of matrix rigidity
4. Mechanotaxis
Extracellular signals are sensed by receptors or mechanosensors on cell surface or in cell interior to initiate migration. Actin polymerization is the key event leading to protrusion at the leading edge and new focal adhesions anchor the actin filaments and the cell to the underlying surface.  This is followed by contraction of the actin filaments.  The contraction of actomyosin filaments pulls the elongate body forward and at the same time the tail retracts.

Part 2.  Cell-ECM Adhesions

Cytoskeleton and cell-ECM adhesions are two major molecular machineries involved in mechano-chemical signal transduction during cell migration. Although all three types of cytoskeleton (actin microfilaments, microtubules, and intermediate filaments) contribute to cell motility, actin cytoskeleton plays the central role. The polymerization of actin filaments provides the driving force for the protrusion of the leading edge as lamellipodia (sheet-like protrusions) or filopodia (spike-like protrusions), and actomyosin contraction generates the traction force at (focal adhesions) FAs and induces the retraction at the rear. It is generally accepted that actin filaments interact with the double-headed myosin to generate the force for cell motility and that actomyosin contraction/relaxation involves the modulation of myosin light chain (MLC) phosphorylation.  Rho family GTPases, including Cdc42, Rac, and Rho, are the key regulators of actin polymerization, actomyosin contraction, and cell motility.  Cdc42 activation induces the formation of filopodia; Rac activation induces lamellipodia; and Rho activation increases actin polymerization, stress fiber formation, and actomyosin contractility. All three types of Rho GTPases stimulate new FA formation.
Integrins are the major receptors for ECM proteins. The integrin family includes more than 20  transmembrane heterodimers composed of α and β subunits with noncovalent association. The extracellular domain of integrin binds to specific ligands, e.g., ECM proteins such as fibronectin (FN), vitronectin, collagen, and laminin. The cytoplasmic domain interacts with cytoskeletal proteins (e.g., paxillin, talin, vinculin, and actin) and signaling molecules in the focal adhesion (FA) sites. The unique structural features of integrins enable them to mediate outside-in signaling, in which extracellular stimuli induce the intracellular signaling cascade via integrin activation, and inside-out signaling, in which intracellular signals modulate integrin activation and force generation through FAs.

Part 3. Actin Dynamics in Cell-cell Adhesion

Actin filaments are linked to the focal adhesions (Fas) between cell and ECM through a protein complex that includes talin, vinculin, α-actinin, and filamin. Such a complex couples the actomyosin contractile apparatus to FAs, and plays an important role in the force transmission between ECM and the cell.

3a. Actin dynamics and cell–cell adhesion in epithelia

Valeri Vasioukhin and Elaine Fuchs
Howard Hughes Medical Institute, Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL
Current Opinion in Cell Biology 2001, 13:76–84
Recent advances in the field of intercellular adhesion highlight the importance of adherens junction association with the underlying actin cytoskeleton. In skin epithelial cells a dynamic feature of adherens junction formation involves filopodia, which physically project into the membrane of adjacent cells, catalyzing the clustering of adherens junction protein complexes at their tips. In turn, actin polymerization is stimulated at the cytoplasmic interface of these complexes. Although the mechanism remains unclear, the VASP/Mena family of proteins seems to be involved in organizing actin polymerization at these sites. In vivo, adherens junction formation appears to rely upon filopodia in processes where epithelial sheets must be physically moved closer to form stable intercellular connections, for example, in ventral closure in embryonic development or wound healing in the postnatal animal.
Located at cell–cell borders, adherens junctions are electron dense transmembrane structures that associate with the actin cytoskeleton. In their absence, the formation of other cell–cell adhesion structures is dramatically reduced. The transmembrane core of adherens junctions consists of cadherins, of which E-cadherin is the epithelial prototype. Its extracellular domain is responsible for homotypic, calcium-dependent, adhesive interactions with E-cadherins on the surface of opposing cells. Its cytoplasmic domain is important for associations with other intracellular proteins involved in the clustering of surface cadherins to form a junctional structure.
The extracellular domain of the transmembrane E-cadherin dimerizes and interacts in a calcium-dependent manner with similar molecules on neighboring cells. The intracellular juxtamembrane part of E-cadherin binds to p120ctn, an armadillo repeat protein capable of modulating E-cadherin clustering. The distal segment of E-cadherin’s cytoplasmic domain can interact with β-catenin or plakoglobin, armadillo repeat proteins which in turn bind to α-catenin. The carboxyl end of α-catenin binds directly to f-actin, and, through a direct mechanism, α-catenin can link the membrane-bound cadherin–catenin complex to the actin cytoskeleton. Additionally, α-catenin can bind to either vinculin or ZO1, and it is required for junctional localization of zyxin. Vinculin and zyxin can recruit VASP (and related family members), which in turn can associate with the actin cytoskeleton, providing the indirect mechanism to link the actin cytoskeleton to adherens junctions. ZO1 is also a member of tight junctions family, providing a means to link these junctions with adherens junctions.
Through a site near its transmembrane domain, cadherins bind directly to the catenin p120ctn, and through a more central site within the cytoplasmic domain, cadherins bind preferentially to β-catenin. Cell migration appears to be promoted by p120ctn through recruiting and activating small GTPases. β-catenin is normally involved in adherens junction formation through its ability to bind to β-catenin and link cadherins to the actin cytoskeleton. However, β-catenin leads a dual life in that it can also act as a transcriptional cofactor when stimulated by the Wnt signal transduction pathway

α-Catenin: More than just a Bridge between Adherens Junctions and the Actin Cytoskeleton

α-catenin was initially discovered as a member of the E-cadherin–catenin complex.  It is related to vinculin, an actin-binding protein that is found at integrin-based focal contacts. The amino-terminal domain of α-catenin is involved in α-catenin/plakoglobin binding and is also important for dimerization. Its central segment can bind to α-actinin and to vinculin, and it partially encompasses the region of the protein necessary for cell adhesion (which is the adhesion-modulation domain; amino acids 509–643). The carboxy-terminal domain of both vinculin and α-catenin is involved in filamentous actin (f-actin) binding, and for α-catenin, this domain is also involved in binding to ZO1.  VH1, VH2 and VH3 are three regions sharing homology to vinculin. The percentage amino acid identity and the numbers correspond to the amino acid residues of the α-catenin polypeptide.
α-catenin is the only catenin that can directly bind to actin filaments , and E-cadherin–catenin complexes do not associate with the actin cytoskeleton after α-catenin is removed by extraction with detergent. Cancer cell lines lacking α-catenin still express E-cadherin and β-catenin, but do not show proper cell–cell adhesion unless the wild-type gene is reintroduced into the cancer cell. This provides strong evidence that clustering of the E-cadherin–catenin complex and cell–cell adhesion requires the presence of α-catenin.
Although intercellular adhesion is dependent upon association of the E-cadherin–β-catenin protein complex with α-catenin and the actin cytoskeleton, it is unclear whether α-catenin’s role goes beyond linking the two structures. Fusion of a nonfunctional tailless E-cadherin (E C71) with α-catenin resulted in a chimeric protein able to confer cell–cell adhesion on mouse fibroblasts in vitro, and generation of additional chimeric proteins enabled delineation of the region of α-catenin that is important for cell aggregation. Not surprisingly, the essential domain of α-catenin was its carboxy-terminal domain (~amino acids 510–906), containing the actin-binding site, which encompasses residues 630–906 of this domain.
The binding of α-catenin to the actin cytoskeleton is required for cell–cell adhesion,  but α-catenin appears to have additional function(s) beyond its ability to link E-cadherin–β-catenin complexes to actin filaments.  The domain encompassing residues 509–643 of α-catenin has been referred to as an adhesion-modulation domain to reflect this added, and as yet unidentified, function.  Besides its association with β-catenin and f-actin, α-catenin binds to a number of additional proteins, some of which are actin binding proteins themselves.  Additionally, the localization of vinculin to cell–cell borders is dependent upon the presence of α-catenin. α-catenin can also bind to the MAGUK (membrane-associated guanylate kinase) family members ZO1 and ZO2.  Thus, the role for α-catenin might not simply be to link E-cadherin–catenin complexes to the actin cytoskeleton but rather to organize a multiprotein complex with multiple actin-binding, bundling and polymerization activities.
The decisive requirement for α-catenin’s actin-binding domain in adherens junction formation underscores the importance of the actin cytoskeleton in intercellular adhesion. Thus, it is perhaps not surprising that the majority of f-actin in epithelial cells localizes to cell–cell junctions.  When epidermal cells are incubated in vitro in culture media with calcium concentrations below 0.08 mM they are unable to form adherens junctions. However, when the calcium concentrations are raised to the levels naturally occurring in skin (1.5–1.8 mM), intercellular adhesion is initiated.
This switch in part promotes a calcium-dependent conformational change in the extracellular domain of E-cadherin that is necessary for homotypic interactions to take place.  It appears that the actin cytoskeleton has a role in facilitating the process that brings opposing membranes together and stabilizing them once junction formation has been initiated. In this regard, the formation of cell–cell adhesion can be divided into two categories:
  • active adhesion, a process that utilizes the actin cytoskeleton to generate the force necessary to bring opposing membranes together, and
  • passive adhesion, a process which may not require actin if the membranes are already closely juxtaposed and stabilized by the deposition of cadherin–catenin complexes.
Upon a switch from low to high calcium, cadherin-mediated intercellular adhesion is activated. Passive adhesion: in cells whose actin cytoskeleton has been largely disrupted by cytochalasin D, cadherin–catenin complexes occur at sites where membranes of neighboring cells directly contact each other. Active adhesion: neighboring cells with functional actin cytoskeletons can draw their membranes together, forming a continuous epithelial sheet.  Upon initial membrane contact, E-cadherin forms punctate aggregates or puncta along regions where opposing membranes are in contact with one another. Each of these puncta is contacted by a bundle of actin filaments that branch off from the cortical belt of actin filaments underlying the cell membrane. At later stages in the process, those segments of the circumferential actin cables that reside along the zone of cell–cell contacts disappear, and the resulting semi-circles of cortical actin align to form a seemingly single circumferential cable around the perimeter of the two cells. At the edges of the zone of cell–cell contact, plaques of E-cadherin–catenin complexes connect the cortical belt of actin to the line of adhesion. At the center of the developing zone of adhesion, E-cadherin puncta associate with small bundles of actin filaments oriented perpendicular to the zone.
Multiple E-cadherin-containing puncta that form along the developing contact rapidly associate with small bundles of actin filaments. As the contact between cells lengthens, puncta continue to develop at a constant average density, with new puncta at the edges of the contact. The segment of the circumferential actin cable that underlies the developing contact gradually ‘dissolves’, and merges into a large cable, encompassing both cells. This is made possible through cable-mediated connections to the E-cadherin plaques at the edges of the contact. As contact propagates, E-cadherin is deposited along the junction as a continuous line. The actin cytoskeleton reorganizes and is now oriented along the cell–cell contact. In primary keratinocytes, two neighboring cells send out filopodia, which, upon contact, slide along each other and project into the opposing cell’s membrane. Filopodia are rich in f-actin. Embedded tips of filopodia are stabilized by puncta, which are transmembrane clusters of adherens junction proteins.
This process draws regions of the two cell surfaces together, which are then clamped by desmosomes. Radial actin fibers reorganize at filopodia tips in a zyxin-, vinculin-, VASP-, and Mena-dependent fashion.  Actin polymerization is initiated at stabilized puncta, creating the directed reverse force needed to push and merge puncta into a single line as new puncta form at the edges. The actin-based movement physically brings remaining regions of opposing membranes together and seals them into epithelial sheets. As filopodia contain actin rather than keratin intermediate filaments, they become natural zones of adherens junctions, whereas the cell surface flanking filopodia becomes fertile ground for desmosome formation, alternating adherens junctions and desmosomes.

Possible Roles of Myosin in Cell–cell Adhesion.

[a] A hypothetical ‘purse string’ model for myosin-driven epithelial sheet closure at a large circular wound site in the cornea of an adult mouse. At the edge of wound site epithelial cables of actin appear to extend from cell to cell, forming a ring around the wound circumference. Contraction of actin cables  driven by myosin can lead to wound closure.
[b] Inside out ‘purse string’ model for contact propagation (compaction) in MDCK cells. During contact formation in MDCK cells, circumferential actin cables contact cadherin–catenin plaques at the edges of the contact. Contraction of actin cables driven by myosin can lead to the contact expansion.

What Regulates the Actin Dynamics that are Important for Cell–cell Adhesion?

The answer to this remains uncertain, but the small GTPases of the Rho family seem to be likely candidates, given that Rho, Rac1 and Cdc42 promote stress fiber, lamellipodia and filopodia formation, respectively.
In vivo mutagenesis studies in Drosophila reveal a role for Rac1 and Rho in dorsal closure and/or in head involution, processes that involve complex and well orchestrated rearrangements of cells. In contrast, Cdc42 appears to be involved in regulating polarized cell shape changes. In vitro, keratinocytes microinjected with dominant negative Rac1 or with C3 toxin, a specific inhibitor of Rho, are unable to form cadherin-based cell–cell contacts.  Similarly, overexpression of a constitutively active form of Rac1 or Cdc42 in MDCK cells increases junctional localization of E-cadherin–catenin complexes, whereas the dominant negative forms of Rac1 and Cdc42, or C3 microinjection, have the opposite effect. The finding that Tiam1, a guanine nucleotide exchange factor for Rac1, increases E-cadherin mediated cell–cell adhesion, inhibits hepatocyte growth-factor-induced cell scattering and reverses the loss of adhesion in Ras-transformed cells is consistent with the above.  Together, these findings provide compelling evidence that activation of the Rho family of small GTPases plays a key role in the actin dynamics that are necessary for adherens junction formation.
We found that E-cadherin–catenin-enriched puncta, which assemble during the first stages of epithelial sheet formation, are sites of de novo actin polymerization. This led us to postulate that actin polymerization might provide the force that is subsequently necessary to merge the double role of puncta into a single row and ultimately into an epithelial sheet. Knowledge of how actin polymerization might generate movement comes largely from studies of the mechanism by which the pathogen Listeria monocytogenes pirates actin polymerization and utilizes it for intracellular propulsion. For this endeavor, these bacteria recruit two types of cellular components, the VASP family of proteins and the Arp2/3 complex. The Arp2/3 protein complex is required for de novo nucleation of actin filament polymerization, whereas VASP appears to accelerate bacterial movement by about 10 fold.
Although most studies have revealed positive roles for VASP and its cousins in actin reorganization/ polymerization, recent experiments have shown that in certain instances these proteins act negatively in directing cell movement. A further complication is the finding that VASP family proteins can be phosphorylated, thereby inhibiting their actin nucleation and f-actin binding ability. A  role for VASP may be in the actin polymerization necessary for filopodia  extensions. In this regard, VASP family proteins localize to the tips of filopodia during neural growth and in calcium-stimulated keratinocytes. VASP family proteins in this process might provide directionality to the process of actin polymerization, reshaping f-actin into parallel bundles to produce and extend filopodia-like structures from branched lamellipodial networks.

The Might of Myosins

Although actin polymerization seems to be important in generating the cellular movement necessary for intercellular adhesion, this does not rule out the possibility that the myosin family of actin motor proteins may also play a role.  It is known, for instance, that cells can use myosin–actin contractile forces to alter cell shape, and myosin II is a ubiquitously expressed protein involved in such diverse processes as cell spreading, cytokinesis, cell migration, generation of tension within actin stress fiber networks and retrograde flow of actin filaments at the leading edge of moving cells. Interestingly, mouse corneal cells at a wound edge assemble cables of actin filaments anchored to E-cadherin–catenin complexes. The cells surrounding the wound site display myosin-II-associated actin filaments that are aligned in a structure resembling a purse string. It has been postulated that closure of the wound may be achieved through myosin-directed contraction of the actin filaments, in a mechanism similar to that of pulling on a purse string.
Overall, through guilt by association, myosins have been implicated in cell–cell adhesion and in adherens junction formation and although the models proposed are attractive, direct experimental evidence is still lacking. BDM (2,3-butanedione monoxime), a general inhibitor of myosin function, had no obvious effect on intercellular junction formation in our keratinocyte adhesion assays (V Vasioukhin, E Fuchs, unpublished data). However, the role of myosins clearly deserves a more detailed investigation, and this awaits the development of new and improved inhibitors and activators of myosin action.

 Key references:

1. Imamura Y, Itoh M, Maeno Y, Tsukita S, Nagafuchi A: Functional  domains of α-catenin required for the strong state of cadherin based cell adhesion. J Cell Biol 1999, 144:1311-1322.
Three distinct functional domains for α-catenin were identified: a vinculin binding domain, a ZO-1-binding domain and an adhesion modulation domain. Both ZO1-binding (also actin binding) and adhesion modulation domains are necessary for strong adhesion.
2. Vasioukhin V, Bauer C, Yin M, Fuchs E: Directed actin polymerization is the driving force for epithelial cell–cell adhesion. Cell 2000, 100:209-219.
A dynamic filopodia-driven process of cell–cell adhesion is described in primary mouse keratinocyte cultures. Newly forming adherens junctions were identified as sites of actin polymerization and/or reorganization, involving VASP/Mena family members.
3. Raich WB, Agbunag C, Hardin J: Rapid epithelial-sheet sealing in the Caenorhabditis elegans embryo requires cadherin-dependent filopodial priming. Curr Biol 1999, 9:1139-1146.
An elegant in vivo analysis of filopodia-based cell–cell junction formation during epithelial-sheet closure in embryonic development of C. elegans.
4. Loisel TP, Boujemaa R, Pantaloni D, Carlier MF: Reconstitution of actin-based motility of Listeria and Shigella using pure proteins.  Nature 1999, 401:613-616.
Using an in vitro reconstitution approach, the authors show that Arp2/3, actin, cofilin and capping proteins are required for motility of Listeria, in contrast VASP seems to act by increasing the speed of movement by about 10 fold.

3b.  Role for Gelsolin in Actuating Epidermal Growth Factor Receptor-mediated Cell Motility

Philip Chen,  Joanne E. Murphy-Ullrich, and Alan Wells
Department of Pathology, University of Alabama at Birmingham, AL
J Cell Biology Aug 1996; 134(3): 689-698
Phospholipase C-~/(PLC~/) is required for EGF-induced motility (Chen, P., H. Xie, M.C. Sekar, K.B. Gupta, and A. Wells. J. Cell Biol. 1994. 127:847-857); however, the molecular basis of how PLC~/modulates the actin filament network underlying cell motility remains undetermined. One connection to the actin cytoskeleton may be direct hydrolysis of PIP 2 with subsequent mobilization of membrane-associated actin modifying proteins. We used signaling restricted EGFR mutants expressed in receptor-devoid NR6 fibroblast cells to investigate whether EGFR activation of PLC causes gelsolin mobilization from the cell membrane in vivo and whether this translocation facilitates cell movement. Gelsolin anti-sense  oligonucleotide (20 p,M) treatment of NR6 ceils expressing the motogenic full-length (WT) and  truncated c’ 1000 EGFR decreased endogenous gelsolin by 30–60%; this resulted in preferential reduction of EGF (25 nM)-induced cell movement by >50% with little effect on the basal motility. As 14 h of EGF stimulation of cells did not increase total cell gelsolin content, we determined whether EGF induced redistribution of gelsolin from the membrane fraction. EGF treatment decreased the gelsolin mass associated with the membrane fraction in motogenic WT and c’1000 EGFR NR6 cells but not in cells expressing the fully mitogenic, but nonmotogenic c’973 EGFR. Blocking PLC activity with the pharmacologic agent U73122 (1 ~M) diminished both this mobilization of gelsolin and EGF-induced motility, suggesting that gelsolin mobilization is downstream of PLC. Concomitantly observed was reorganization of submembranous actin filaments correlating directly with PLC activation and gelsolin mobilization. In vivo expression of a peptide that is reported to compete in vitro with gelsolin in binding to PIP2 dramatically increased basal cell motility in NR6 cells expressing either motogenic (WT and c’1000) or nonmotogenic (c’973) EGFR; EGF did not further augment cell motility and gelsolin mobilization. Cells expressing this peptide demonstrated actin reorganization similar to that observed in EGF-treated control cells; the peptide-induced changes were unaffected by U73122. These data suggest that much of the EGF induced motility and cytoskeletal alterations can be reproduced by displacement of select actin-modifying proteins from a PIP2-bound state. This provides a signaling mechanism for translating cell surface receptor mediated biochemical reactions to the cell movement machinery.

3c.  Actomyosin Contraction at the Cell Rear Drives Nuclear Translocation in Migrating Cortical Interneurons

Francisco J. Martini and Miguel Valdeolmillos
Instituto de Neurociencias de Alicante, Universidad Miguel Hernandez, Alacant, Spain
Journal of Neuroscience 2010 • 30(25):8660–8670
Neuronal migration is a complex process requiring the coordinated interaction of cytoskeletal components and regulated by calcium signaling among other factors. Migratory neurons are polarized cells in which the largest intracellular organelle, the nucleus, has to move repeatedly. Current views support a central role for pulling forces that drive nuclear movement. By analyzing interneurons migrating in cortical slices of mouse brains, we have found that nucleokinesis is associated with a precise pattern of actin dynamics characterized by the initial formation of a cup-like actin structure at the rear nuclear pole. Time-lapse experiments show that progressive actomyosin contraction drives the nucleus forward. Nucleokinesis concludes with the complete contraction of the cup-like structure, resulting in an actin spot at the base of the retracting trailing process. Our results demonstrate that this actin remodeling requires a threshold calcium level provided by low-frequency spontaneous fast intracellular calcium transients. Microtubule stabilization with taxol treatment prevents actin remodeling and nucleokinesis, whereas cells with a collapsed microtubule cytoskeleton induced by nocodazole treatment, display nearly normal actin dynamics and nucleokinesis. In summary, the results presented here demonstrate that actomyosin forces acting at the rear side of the nucleus drives nucleokinesis in tangentially migrating interneurons in a process that requires calcium and a dynamic cytoskeleton of microtubules.

3d. Migration of Zebrafish Primordial Germ Cells: A Role for Myosin Contraction and Cytoplasmic Flow

H Blaser, M Reichman-Fried, I Castanon, K Dumstrei, F L Marlow, et al.
Max Planck Institute, Gottingen & Dresden, Germany;  Vanderbilt University, Nashville, Tenn; National Institute of Genetics, Shizuoka, Japan
Developmental Cell 2006; 11: 613–627 [DOI 10.1016/j.devcel.2006.09.023]
The molecular and cellular mechanisms governing cell motility and directed migration in response to the chemokine SDF-1 are largely unknown. Here, we demonstrate that zebrafish primordial germ cells whose migration is guided by SDF-1 generate bleb-like protrusions that are powered by cytoplasmic flow. Protrusions are formed at sites of higher levels of free calcium where activation of myosin contraction occurs. Separation of the acto-myosin cortex from the plasma membrane at these sites is followed by a flow of cytoplasm into the forming bleb. We propose that polarized activation of the receptor CXCR4 leads to a rise in free calcium that in turn activates myosin contraction in the part of the cell responding to higher levels of the ligand SDF-1. The biased formation of new protrusions in a particular region of the cell in response to SDF-1 defines the leading edge and the direction of cell migration.

Part 4.  Calcium Signaling

4a. Indirect Association of Ezrin with F-Actin: Isoform Specificity and Calcium Sensitivity

Charles B. Shuster and Ira M. Herman
Tufts University Health Science Schools, Boston, MA
J Cell Biology Mar 1995; 128(5): 837-848
Muscle and nonmuscle isoactins are segregated into distinct cytoplasmic domains,  but the mechanism regulating subcellular sorting is unknown (Herman, 1993a). To reveal whether isoform-specific actin-binding proteins function to coordinate these events, cell extracts derived from motile (Era) versus stationary (Es) cytoplasm were selectively and sequentially fractionated over filamentous isoactin affinity columns prior to elution with a KC1 step gradient.  A polypeptide of interest, which binds specifically to/3-actin filament columns, but not to muscle actin columns has been conclusively identified as the ERM family member, ezrin. We studied ezrin-/3 interactions in vitro by passing extracts (Era) over isoactin affinity matrices in the presence of Ca2+-containing versus Ca2+-free buffers, with or without cytochalasin D. Ezrin binds and can be released from/3-actin Sepharose-4B in the presence of Mg2+/EGTA and 100 mM NaC1 (at 4°C and room temperature), but not when affinity fractionation of Em is carried out in the presence of 0.2 mM CaC12 or 2/~M cytochalasin D. N-acetyl-(leucyl)2-norleucinal and E64, two specific inhibitors of the calcium-activated protease, calpain I, protect ezrin binding to β-actin in the presence of calcium. Biochemical analysis of endothelial lysates reveals that a calpain I cleavage product of ezrin emerges when cell locomotion is stimulated in response to monolayer injury. Immunofluorescence analysis shows that anti-ezrin and anti-β-actin IgGs can be simultaneously co-localized, extending the results of isoactin affinity fractionation of Em-derived extracts and suggesting that ezrin and β-actin interact in vivo. To test the hypothesis that ezrin binds directly to β-actin, we performed three sets of studies under a wide range of physiological conditions (pH 7.0-8.5) using purified pericyte ezrin and either α- or β-actin. Results of these experiments reveal that purified ezrin does not directly bind to β-actin filaments. We mapped cellular free calcium in endothelial monolayers crawling in response to injury. Confocal imaging of fluo-3 fluorescence followed by simultaneous double antibody staining reveals a transient rise of free calcium within ezrin-/3-actin-enriched domains in the majority of motile cells bordering the wound edge. These results support the notion that calcium and calpain I modulate ezrin and β-actin interactions during forward protrusion formation.

4b.  Calcium channel and glutamate receptor activities regulate actin organization in salamander retinal neurons

Massimiliano Cristofanilli and Abram Akopian
New York University School of Medicine, New York, NY
J Physiol 575.2 (2006) pp 543–554
Intracellular Ca2+ regulates a variety of neuronal functions, including neurotransmitter release, protein phosphorylation, gene expression and synaptic plasticity. In a variety of cell types, including neurons, Ca2+ is involved in actin reorganization, resulting in either actin polymerization or depolymerization. Very little, however, is known about the relationship between Ca2+ and the actin cytoskeleton organization in retinal neurons. We studied the effect of high-K+-induced depolarization on F-actin organization in salamander retina and found that Ca2+ influx through voltage-gated L-type channels causes F-actin disruption, as assessed by 53±5% (n=23, P <0.001) reduction in the intensity of staining with Alexa-Fluor488-phalloidin, a compound that permits visualization and quantification of polymerized actin. Calcium-induced F-actin depolymerization was attenuated in the presence of protein kinase C antagonists, chelerythrine or bis-indolylmaleimide hydrochloride (GF 109203X). In addition, phorbol 12-myristate 13-acetate (PMA), but not 4α-PMA, mimicked the effect of Ca2+ influx on F-actin. Activation of ionotropic AMPA and NMDA glutamate receptors also caused a reduction in F-actin. No effect on F-actin was exerted by caffeine or thapsigargin, agents that stimulate Ca2+ release from internal stores. In whole-cell recording from a slice preparation, light-evoked ‘off’ but not ‘on’ EPSCs in ‘on–off’ ganglion cells were reduced by 60±8% (n=8, P <0.01) by cytochalasin D. These data suggest that elevation of intracellular Ca2+ during excitatory synaptic activity initiates a cascade for activity-dependent  actin remodelling, which in turn may serve as a feedback mechanism to attenuate excite-toxic Ca2+ accumulation induced by synaptic depolarization.

4c.  Electric Field-directed Cell Shape Changes, Displacement, and Cytoskeletal Reorganization Are Calcium Dependent

Edward K. Onuma and Sek-Wen Hui
Roswell Park Memorial Institute, Buffalo, New York
J Cell Biology 1988; 106: 2067-2075

C3H/10T1/2 mouse embryo fibroblasts were stimulated by a steady electric field ranging up to 10 V/cm. Some cells elongated and aligned perpendicular to the field direction. A preferential positional shift toward the cathode was observed which was inhibited by the calcium channel blocker D-600 and the calmodulin antagonist trifluoperazine. Rhodaminephalloidin labeling of actin filaments revealed a field induced disorganization of the stress fiber pattern, which was reduced when stimulation was conducted in calcium-depleted buffer or in buffer containing calcium antagonist CoC12, calcium channel blocker D-600, or calmodulin antagonist trifluoperazine. Treatment with calcium ionophore A23187 had similar effects, except that the presence of D-600 did not reduce the stress fiber disruption. The calcium-sensitive photoprotein aequorin was used to monitor changes in intracellular-free calcium. Electric stimulation caused an increase of calcium to the micromolar range. This increase was inhibited by calcium-depleted buffer or by CoC12, and was reduced by D-600. A calcium-dependent mechanism is proposed to explain the observed field-directed cell shape changes, preferential orientation, and displacement.

4d. Local Calcium Elevation and Cell Elongation Initiate Guided Motility in Electrically Stimulated osteoblast-Like Cells

N Ozkucur, TK Monsees, S Perike, H Quynh Do, RHW Funk.
Carl Gustav Carus, TU-Dresden, Dresden, Germany; University of the Western Cape, SAfrica.
Plos ONE 2009; 4 (7): e6131

Investigation of the mechanisms of guided cell migration can contribute to our understanding of many crucial biological processes, such as development and regeneration. Endogenous and exogenous direct current electric fields (dcEF) are known to induce directional cell migration, however the initial cellular responses to electrical stimulation are poorly understood. Ion fluxes, besides regulating intracellular homeostasis, have been implicated in many biological events, including regeneration. Therefore understanding intracellular ion kinetics during EF-directed cell migration can provide useful information for development and regeneration.
We analyzed the initial events during migration of two osteogenic cell types, rat calvarial and human SaOS-2 cells, exposed to strong (10–15 V/cm) and weak (#5 V/cm) dcEFs. Cell elongation and perpendicular orientation to the EF vector occurred in a time- and voltage-dependent manner. Calvarial osteoblasts migrated to the cathode as they formed new filopodia or lamellipodia and reorganized their cytoskeleton on the cathodal side. SaOS-2 cells showed similar responses except towards the anode. Strong dcEFs triggered a rapid increase in intracellular calcium levels, whereas a steady state level of intracellular calcium was observed in weaker fields. Interestingly, we found that dcEF induced intracellular calcium elevation was initiated with a local rise on opposite sides in calvarial and SaOS-2 cells, which may explain their preferred directionality. In calcium-free conditions, dcEFs induced neither intracellular calcium elevation nor directed migration, indicating an important role for calcium ions. Blocking studies using cadmium chloride revealed that voltage-gated calcium channels (VGCCs) are involved in dcEF-induced intracellular calcium elevation. Taken together, these data form a time scale of the morphological and physiological rearrangements underlying EF-guided migration of osteoblast-like cell types and reveal a requirement for calcium in these reactions. We show for the first time here that dcEFs trigger different patterns of intracellular calcium elevation and positional shifting in osteogenic cell types that migrate in opposite directions.

4e. TRPM4 Regulates Migration of Mast Cells in Mice

T Shimizua, G Owsianik, M Freichelb, V Flockerzi, et al.
Laboratory of Ion Channel Research, KU Leuven, Leuven, Belgium; Universität des Saarlandes, Homburg, Germany; National Institute for Physiological Sciences,Okazaki, Japan
Cell Calcium 2008; xxx–xxx

We demonstrate here that the transient receptor potential melastatin subfamily channel, TRPM4, controls migration of bone marrow-derived mast cells (BMMCs), triggered by dinitrophenylated human serum albumin (DNP-HSA) or stem cell factor (SCF). Wild-type BMMCs migrate after stimulation with DNPHSA or SCF whereas both stimuli do not induce migration in BMMCs derived from TRPM4 knockout mice (trpm4−/−). Mast cell migration is a Ca2+-dependent process, and TRPM4 likely controls this process by setting the intracellular Ca2+ level upon cell stimulation. Cell migration depends on filamentous actin (F-actin) rearrangement, since pretreatment with cytochalasin B, an inhibitor of F-actin formation, prevented both DNP-HSA- and SCF-induced migration in wild-type BMMC. Immunocytochemical experiments using fluorescence-conjugated phalloidin demonstrate a reduced level of F-actin formation in DNP-HSA-stimulated BMMCs from trpm4−/− mice. Thus, our results suggest that TRPM4 is critically involved in migration of BMMCs by regulation of Ca2+-dependent actin cytoskeleton rearrangements.
4f. Nuclear and cytoplasmic free calcium level changes induced by elastin peptides in human endothelial cells
G FAURY, Y USSON, M ROBERT-NICOUD, L ROBERT, AND J VERDETTI.
Institut Albert Bonniot, Universite´ J. Fourier, Grenoble, Fr; and Universite´ Paris, Paris, Fr
PNAS: Cell Biology 1998; 95: pp. 2967–2972.

The extracellular matrix protein ‘‘elastin’’ is the major component of elastic fibers present in the arterial wall. Physiological degradation of elastic fibers, enhanced in vascular pathologies, leads to the presence of circulating elastin peptides (EP). EP have been demonstrated to influence cell migration and proliferation. EP also induce, at circulating pathophysiological concentrations (and not below), an endothelium-and NO- dependent vasorelaxation mediated by the 67-kDa subunit of the elastin-laminin receptor. Here, by using the techniques of patch-clamp, spectrofluorimetry and confocal microscopy, we demonstrate that circulating concentrations of EP activate low specificity calcium channels on human umbilical venous endothelial cells, resulting in increase in cytoplasmic and nuclear free calcium concentrations. This action is independent of phosphoinositide metabolism. Furthermore, these effects are inhibited by lactose, an antagonist of the elastin-laminin receptor, and by cytochalasin D, an actin microfilament depolymerizer. These observations suggest that EP-induced signal transduction is mediated by the elastin-laminin receptor via coupling of cytoskeletal actin microfilaments to membrane channels and to the nucleus. Because vascular remodeling and carcinogenesis are accompanied by extracellular matrix modifications involving elastin, the processes here described could play a role in the elastin-laminin receptor-mediated cellular migration, differentiation, proliferation, as in atherogenesis, and metastasis formation.

Part 5. Regulation of the Cytoskeleton

5a Regulation of the Actin Cytoskeleton by PIP2 in Cytokinesis

MR Logan and CA Mandato
McGill University, Montreal, Ca
Biol. Cell (2006) 98, 377–388 [doi:10.1042/BC20050081]

Cytokinesis is a sequential process that occurs in three phases:

  • assembly of the cytokinetic apparatus, 
  • furrow progression and 
  • fission (abscission) of the newly formed daughter cells.

The ingression of the cleavage furrow is dependent on the constriction of an equatorial actomyosin ring in many cell types. Recent studies have demonstrated that this structure is highly dynamic and undergoes active polymerization and depolymerization throughout the furrowing process. Despite much progress in the identification of contractile ring components, little is known regarding the mechanism of its assembly and structural rearrangements. PIP2 (phosphatidylinositol 4,5-bisphosphate) is a critical regulator of actin dynamics and plays an essential role in cell motility and adhesion. Recent studies have indicated that an elevation of PIP2 at the cleavage furrow is a critical event for furrow stability. We discuss the role of PIP2-mediated signaling in the structural maintenance of the contractile ring and furrow progression. In addition, we address the role of other phosphoinositides, PI(4)P (phosphatidylinositol-4-phosphate) and PIP3 (phosphatidylinositol 3,4,5-triphosphate) in these processes.

Regulation of the actin cytoskeleton by PIPKs (phosphatidylinositol phosphate kinases) and PIP2 (phosphatidylinositol 4,5-bisphosphate)

PIP2 is generated by the activity of type I (PIPKIs) or type II (PIPKII) kinase isoforms (α, β, γ) which utilize PI(4)P (phosphatidylinositol 4-phosphate) and PI(5)P (phosphatidylinositol 5-phosphate) as substrates respectively. PIPKIs are localized to the plasma membrane and are thought to account for the majority of PIP2 synthesis, whereas PIPKIIs are predominantly localized to intracellular sites. PIP2 plays a key role in re-structuring the actin cytoskeleton in several ways. In general, high levels of PIP2 are associated with actin polymerization, whereas low levels block assembly or promote actin severing activity. PIP2 facilitates actin polymerization in multiple ways such as:

(i) activating N-WASp (neuronal Wiskott–Aldrich syndrome protein)- and Arp2/3 (actin-related protein 2/3)-mediated actin branching, 
(ii) binding and impairing the activity of actin-severing proteins, such as gelsolin and cofilin/ADF (actin depolymerizing factor); and
(iii) uncapping actin filaments for the addition on new actin monomers

This polymerization signal is counteracted by the generation of IP3 (inositol 1,4,5-triphosphate) and DAG (diacylglycerol), following PLC (phospholipase C)-mediated hydrolysis of PIP2. IP3-mediated activation of Ca2+/CaM (calmodulin) promotes the activation of severing proteins such as gelsolins and cofilin, which lead to solubilization of the actin network (Figure 1). In addition to influencing actin polymerization, PIP2 modulates the function of several actin cross-linking and regulatory proteins which are critical for the assembly of stress fibres, gel meshworks and membrane attachment. For example, PIP2 negatively regulates cross-linking mediated by filamin and the actin-bundling activity of α-actinin. In contrast, PIP2 induces conformational changes in vinculin, talin and ERM (ezrin/radixin/moesin) family proteins to promote anchoring of the actin cytoskeleton to the plasma membrane. PLC-mediated hydrolysis of PIP2 and the downstream activation of Ca2+/CaM and PKC (protein kinase C) also influences actin-myosin based contractility. Ca2+/CaM activates MLCK (myosin regulatory light chain kinase), leading to phosphorylation of the MLC (myosin regulatory light chain). Similarly, PKC has been shown to phosphorylate and activate MLC (Figure 1).

Figure 1 Summary of PIP2-mediated regulation of the actin cytoskeleton

Role of PIP2-mediated signaling in cell division

Prior to cell division cells undergo a global cell rounding which is a prerequisite step for the initiation of the cleavage furrow. In frog, sea urchin and newt eggs these shape changes correlate with an increase in cortical tension that precedes or occurs near the onset of the cleavage furrow.  Precise mapping of the changes in cortical tension have shown that peaks of tension are propagated in waves that occur in front of and at the same time as furrow initiation. These tension waves are generated by actomyosin-based contractility and subside after the furrow has passed. Experiments in Xenopus eggs, zebrafish and  Xenopus embryos indicated that site-specific Ca2+ waves were generated within the cleavage furrow that would be predicted to coincide with peaks of cortical tension. The injection of heparin, a competitive inhibitor of IP3 receptors, or Ca2+ chelators were both demonstrated to significantly delay or arrest furrowing , and a similar inhibitory effect was observed of microinjected PIP2 antibodies that caused a depletion of the intracellular pool of DAG and Ca2+ in Xenopus blastomeres. In addition, the increase in cortical contractility of Xenopus oocytes has been shown to occur via a PKC-dependent pathway. Together, these studies demonstrate a role for PIP2-mediated signaling at the early stages of cytokinesis.
Recent studies have supported that PIP2-mediated signaling also plays a critical role in ingression of the cleavage furrow, although significant differences have been shown in the localization of PIP2 and the role of PLC. Lithium and the PLC inhibitor, U73122, caused a rapid (within minutes) regression of cleavage furrows in crane fly spermatocytes, but did not block their initial formation. PIP2 may become concentrated within the cleavage furrow and could facilitate anchoring of the plasma membrane to structural components of the actomyosin ring. A PIPKI homologue, its3, and PIP2 were reported at the septum of dividing fission yeast, Schizosaccharomyces pombe. A temperature sensitive mutant of its3 exhibited disrupted actin patches, following a shift to the restrictive temperature, and also impaired cytokinesis. Although a contractile ring was still evident in these cells, abnormalities, such as an extra ring, were found. Two recent studies demonstrated an increase in PIP2-specific GFP-labeled PH domains within the cleavage furrow of mammalian cells. Both of these reports suggested de novo synthesis of PIP2 occurs within the furrow. Another study found that endogenous and over-expressed PIPKIβ, but not PIPKIγ, concentrated in the cleavage furrow of CHO (Chinese hamster ovary) cells. The expression of a kinase-dead mutant of this isoform and microinjection of PIP2-specific antibodies both caused a significant increase in the number of multinucleated cells. A multinucleated phenotype was, similarly, observed in multiple cell lines (CHO, HeLa, NIH 3T3 and 293T) transfected with high levels of PIP2-specific PH domains, synaptojanin [which dephosphorylates PIP2 to PI(4)P], or a kinase-dead mutant of PIPKIα. In addition, a small percentage of CHO and HeLa cells expressing high levels of PIP2-specific PH domains or synaptojanin showed signs of F-actin dissociation from the plasma membrane.  CHO cells transfected with PIP2 PH domains, but not PH domains specific for PI(3,4)P2 (phosphatidylinositol 3,4-bisphosphate) and PIP3, also exhibited impaired furrow expansion induced by the application of hypotonic buffer. This suggests one of the primary roles of PIP2 is to promote cytoskeleton–membrane anchoring at the furrow.
Role of PI3Ks (phosphoinositide 3-kinases) and PI4Ks (phosphoinositide 4-kinases) in cytokinesis PI4Ks generate the PIPKI substrate, PI(4)P, and play a critical role in PIP2 generation.  Studies in lower organisms support  the requirement of PI4Ks for cytokinesis. In Saccharomyces cerevisiae two PI4Ks, STT4 and PIK1, have non-overlapping functions in Golgi-tomembrane trafficking and cell-wall integrity respectively.  Both genes are also required for cell division. Conditional mutants of Pik1p exhibited a cytokinesis defect: cells arrest with large buds and fully divided nuclei. In addition, STT4 was identified as a gene implicated in reorientation of the mitotic spindle prior to cytokinesis.  Spermatocytes derived from fwd mutant males had unstable furrows that failed to ingress and abnormal contractile rings with dissociated myosin II and F-actin, fwd has homology with yeast PIK1 and human PI4KIIIβ. Although PIK1 is an essential gene in yeast, the deletion of fwd was not lethal and female flies were fertile.  A study in fission yeast suggests that PI4Ks may be recruited to the furrow, as reported for PIPKs. Desautels et al. (2001) identified a PI4K as a binding partner of Cdc4p, a contractile ring protein with homology to the myosin essential light chain. A Cdc4p mutant, G107S, abolished the interaction with PI4K and induced the formation of multinucleated cells with defects in septum formation. This finding suggests that, at least for fission yeast, anchoring of PI4K to the contractile ring may concentrate PI(4)P substrate within the furrow for subsequent PIP2 generation.
An increased synthesis of PIP2 by PIPKIs at the cleavage furrow is anticipated to promote both actin polymerization and structural support to the contractile ring. Structural proteins of the contractile ring regulated by PIP2 include anillin, septin and ERM proteins. The concentration of PIP2 at the cleavage furrow is postulated to be a critical molecule in the recruitment of these proteins and their integration with the actomyosin ring. Anillin exhibits actin-bundling activity and is required at the terminal stages of cytokinesis in Drosophila and human cells.  The depletion of anillin in Drosophila and human cells causes cytokinesis failure, which is correlated with uncoordinated actomyosin contraction of the medial ring. Anillin also functions as a cofactor to promote the recruitment of septins to actin bundles. Mutations within the PH domain of anillin were recently demonstrated to impair septin localization to both the furrow canal and the contractile ring in Drosophila cells, blocking cellularization and furrow progression. Septins have also been shown to bind to phosphoinositides and this interaction regulates their subcellular localization. The mammalian septin, H5, bound PIP2 and PIP3 liposomes at its N-terminal basic region, which is conserved in most septin proteins. The over-expression of synaptojanin and treatment with neomycin (which depletes cellular PIP2) both caused disruption of actin stress fibres and dissociation of H5 from filamentous structures in Swiss 3T3 cells. Septins are co-localized with actin at the cleavage furrow and form ring structures that are postulated to structurally support  the contractile ring.
Studies suggest that PLC-mediated hydrolysis of PIP2 and the subsequent release of intracellular Ca2+ stores is a necessary event for furrow stability and ingression.  A role for Ca2+ is similarly supported by previous findings that Ca2+ waves were localized to the cleavage furrow in frog embryos, eggs and fish. PLC second messengers have also been implicated in cytokinesis. For example, CaM was localized to mitotic spindles of HeLa cells and the inhibition of its activity was reported to cause cytokinesis defects. A recent RNAi (RNA interference) screen also identified PI4Ks and PIPKs, but not PLC genes, as critical proteins for cytokinesis in Drosophila.  This may indicate PLC is required for completion of furrowing, rather than its initiation.
It is hypothesized that PLC activity may promote actin filament severing through the activation of Ca2+-dependent actin-severing proteins, such as gelsolin and cofilin. Depending on the localization of PLC, this could either drive disassembly of actin filaments of the medial ring or the cortical actin network. Furthermore, the activation of PKC and CaM would activate actomyosin contraction via the phosphorylation of MLCK. At the furrow, PKC and CaM could act in concert with the Rho effectors ROCK and Citron kinase, which also phosphorylate and activate MLC.
The activation of CaM and/or PKC may also provide positive feedback for the recruitment of PIP2 effectors and regulate GTPase-mediated actin polymerization. Both PKC and CaM have been shown to promote the dissociation of MARCKS (myristoylated alanine-rich C kinase substrates) family proteins from PIP2. MARCKS are postulated to play a major regulatory role in phosphoinositide signalling by sequestering PIP2 at the membrane. Thus the activation of PKC and CaM promotes PIP2 availability for the recruitment of PH-domain-containing effector proteins. Studies in yeast and mammalian cells have supported that CaM and PKC can mediate positive feedback for PIP2 synthesis by activating PIPKs.

Signaling Crosstalk: Role of GTPases and Phosphoinositides

On the basis of the present available data, PIP2 has been shown to be a critical molecule for structural integrity of the contractile ring and furrow stability. However, the observation that furrows are initiated in cells treated with agents that either sequester PIP2 or prevent its hydrolysis suggests PIP2 does not provide the originating signal for furrow formation. Recent studies suggest that the recruitment and activation of RhoA may provide this early signal.

Figure 2 Proposed model of PIP2 and GTPase signaling at the cleavage furrow

Ect2, is recruited to the cleavage furrow via its interaction withMgcRacGAP at the central spindle. Ect2 and MgcRacGAP regulate the activities of Rho GTPases (RhoA, Cdc42 and Rac) and are functionally implicated in the assembly of the contractile ring. Active RhoA and Cdc42 are increased at the furrow, whereas Rac is suppressed (grey). Furrow-recruited GTPases (RhoA, ARF6 and Cdc42) are predicted to activate PIPKI, leading to the generation of PIP2. PI3K activity is suppressed at the furrow (grey), which may be due to MgcRacGAP-mediated inhibition of Rac and/or the activity of the PIP3 phosphatase, PTEN. Cycles of PIP2 synthesis and hydrolysis by PLC are thought to play a critical role in re-structuring the contractile ring throughout the duration of furrowing. PIP2-mediated activation of anillin, septins and ERM proteins promotes cross-linking and membrane anchoring of the contractile ring. PLC-mediated activation of PKC and CaM can facilitate the contraction of the actomyosin ring, similar to RhoA effectors, ROCK and Citron kinase. CaM may also regulate IQGAP–Cdc42 interactions, and thereby modulate actin organization. It is hypothesized that Cdc42-mediated actin polymerization via effectors, such as N-WASp (neuronalWiskott–Aldrich syndrome protein) and Arp2/3 (actin-related protein 2/3), may reduce membrane tension outside the inner region of RhoA-mediated contractility.
Actin core bundle fimbrin

Actin core bundle fimbrin (Photo credit: Wikipedia)

English: Diagram showing Actin-Myosin filament...

English: Diagram showing Actin-Myosin filaments in Smooth muscle. The actin fibers attach to the cell wall and to dense bodies in the cytoplasm. When activated the slide over the myosin bundles causing shortening of the cell walls (Photo credit: Wikipedia)

English: Figure 2: The matrix can play into ot...

English: Figure 2: The matrix can play into other pathways inside the cell even through just its physical state. Matrix immobilization inhibits the formation of fibrillar adhesions and matrix reorganization. Likewise, players of other signaling pathways inside the cell can affect the structure of the cytoskeleton and thereby the cell’s interaction with the ECM. (Photo credit: Wikipedia)

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Calcium Cycling (ATPase Pump) in Cardiac Gene Therapy: Inhalable Gene Therapy for Pulmonary Arterial Hypertension and Percutaneous Intra-coronary Artery Infusion for Heart Failure: Contributions by Roger J. Hajjar, MD


Calcium Cycling (ATPase Pump) in Cardiac Gene Therapy: Inhalable Gene Therapy for Pulmonary Arterial Hypertension and Percutaneous Intra-coronary Artery Infusion for Heart Failure: Contributions by Roger J. Hajjar, MD

Curator: Aviva Lev-Ari, PhD, RN

This article is Part VI in a Series of articles on Calcium Release Mechanism, the series consists of the following articles:

Part I: Identification of Biomarkers that are Related to the Actin Cytoskeleton

Larry H Bernstein, MD, FCAP

https://pharmaceuticalintelligence.com/2012/12/10/identification-of-biomarkers-that-are-related-to-the-actin-cytoskeleton/

Part II: Role of Calcium, the Actin Skeleton, and Lipid Structures in Signaling and Cell Motility

Larry H. Bernstein, MD, FCAP, Stephen Williams, PhD and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/08/26/role-of-calcium-the-actin-skeleton-and-lipid-structures-in-signaling-and-cell-motility/

Part III: Renal Distal Tubular Ca2+ Exchange Mechanism in Health and Disease

Larry H. Bernstein, MD, FCAP, Stephen J. Williams, PhD
 and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/09/02/renal-distal-tubular-ca2-exchange-mechanism-in-health-and-disease/

Part IV: The Centrality of Ca(2+) Signaling and Cytoskeleton Involving Calmodulin Kinases and Ryanodine Receptors in Cardiac Failure, Arterial Smooth Muscle, Post-ischemic Arrhythmia, Similarities and Differences, and Pharmaceutical Targets

Larry H Bernstein, MD, FCAP, Justin Pearlman, MD, PhD, FACC and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/09/08/the-centrality-of-ca2-signaling-and-cytoskeleton-involving-calmodulin-kinases-and-ryanodine-receptors-in-cardiac-failure-arterial-smooth-muscle-post-ischemic-arrhythmia-similarities-and-differen/

Part V: Ca2+-Stimulated Exocytosis:  The Role of Calmodulin and Protein Kinase C in Ca2+ Regulation of Hormone and Neurotransmitter

Larry H Bernstein, MD, FCAP
and
Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/12/23/calmodulin-and-protein-kinase-c-drive-the-ca2-regulation-of-hormone-and-neurotransmitter-release-that-triggers-ca2-stimulated-exocytosis/

Part VI: Calcium Cycling (ATPase Pump) in Cardiac Gene Therapy: Inhalable Gene Therapy for Pulmonary Arterial Hypertension and Percutaneous Intra-coronary Artery Infusion for Heart Failure: Contributions by Roger J. Hajjar, MD

Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/08/01/calcium-molecule-in-cardiac-gene-therapy-inhalable-gene-therapy-for-pulmonary-arterial-hypertension-and-percutaneous-intra-coronary-artery-infusion-for-heart-failure-contributions-by-roger-j-hajjar/

Part VII: Cardiac Contractility & Myocardium Performance: Ventricular Arrhythmias and Non-ischemic Heart Failure – Therapeutic Implications for Cardiomyocyte Ryanopathy (Calcium Release-related Contractile Dysfunction) and Catecholamine Responses

Justin Pearlman, MD, PhD, FACC, Larry H Bernstein, MD, FCAP and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/08/28/cardiac-contractility-myocardium-performance-ventricular-arrhythmias-and-non-ischemic-heart-failure-therapeutic-implications-for-cardiomyocyte-ryanopathy-calcium-release-related-contractile/

Part VIII: Disruption of Calcium Homeostasis: Cardiomyocytes and Vascular Smooth Muscle Cells: The Cardiac and Cardiovascular Calcium Signaling Mechanism

Justin Pearlman, MD, PhD, FACC, Larry H Bernstein, MD, FCAP and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/09/12/disruption-of-calcium-homeostasis-cardiomyocytes-and-vascular-smooth-muscle-cells-the-cardiac-and-cardiovascular-calcium-signaling-mechanism/

Part IXCalcium-Channel Blockers, Calcium Release-related Contractile Dysfunction (Ryanopathy) and Calcium as Neurotransmitter Sensor

Justin Pearlman, MD, PhD, FACC, Larry H Bernstein, MD, FCAP and Aviva Lev-Ari, PhD, RN

Part X: Synaptotagmin functions as a Calcium Sensor: How Calcium Ions Regulate the fusion of vesicles with cell membranes during Neurotransmission

Larry H Bernstein, MD, FCAP and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/09/10/synaptotagmin-functions-as-a-calcium-sensor-how-calcium-ions-regulate-the-fusion-of-vesicles-with-cell-membranes-during-neurotransmission/

Part XI: Sensors and Signaling in Oxidative Stress

Larry H. Bernstein, MD, FCAP

https://pharmaceuticalintelligence.com/2013/11/01/sensors-and-signaling-in-oxidative-stress/

Part XII: Atherosclerosis Independence: Genetic Polymorphisms of Ion Channels Role in the Pathogenesis of Coronary Microvascular Dysfunction and Myocardial Ischemia (Coronary Artery Disease (CAD))

Larry H Bernstein, MD, FCAP and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/12/21/genetic-polymorphisms-of-ion-channels-have-a-role-in-the-pathogenesis-of-coronary-microvascular-dysfunction-and-ischemic-heart-disease/

This article has THREE parts:

Part I: Scientific Leader in Cardiology, Contributions by Roger J. Hajjar, MD to Gene Therapy

Part II: Cardiac Gene Therapy: Inhalable Gene Therapy for Pulmonary Arterial Hypertension

Part III: Cardiac Gene Therapy: Percutaneous Intra-coronary Artery Infusion for Heart Failure

The following two discoveries in Cardiac Gene Therapies represent the FRONTIER IN CARDIOLOGY for 2012 – 2013: Solution Advancement for Improving Myocardial Contractility

Part I: Scientific Leader in Cardiology, Contributions by Roger J. Hajjar, MD to Gene Therapy

Roger J. Hajjar, MD, a pioneering Mount Sinai researcher who has published cutting-edge studies on heart failure, has been named the recipient of the 2013 BCVS Distinguished Achievement Award by theAmerican Heart Association and the Council on Basic Cardiovascular Sciences. Dr. Hajjar, who is The Arthur and Janet C. Ross Professor of Medicine and Director of The Helmsley Trust Translational Research Center, will be honored at the American Heart Association’s Scientific Sessions Annual Conference later this year.

“Dr. Hajjar will receive the award for his groundbreaking contributions to developing gene therapy treatments for cardiac disease,” says Joshua Hare, MD, who is President-elect of the Council on Basic Cardiovascular Sciences. He will also be recognized for his work on behalf of the Council.

Over the years, Dr. Hajjar’s laboratory has made important basic science discoveries that were translated into clinical trials. Most recently, Dr. Hajjar and his researchers identified a possible new drug target for treating or preventing heart failure. Says Mark A. Sussman, PhD, a former president of the Council, “Dr. Hajjar was among the first, and certainly the most successful, in combining gene therapy and treatment of heart failure. He shows a relentless pursuit of translating basic science into real-world treatment of heart disease.”

This article was first published in Inside Mount Sinai.

http://blog.mountsinai.org/blog/roger-j-hajjar-md-to-be-honored-for-research/

John Hopkins, Distinguished Alumnus Award 2011

Roger J. Hajjar, Engr ’86
Dr. Roger Hajjar received his bachelor’s degree in biomedical engineering from Johns Hopkins University in 1986. A cardiologist and translational scientist, he is a leader in gene therapy techniques and model testing for cardiovascular diseases. Dr. Hajjar is professor of medicine and cardiology, and professor of gene and cell medicine at Mount Sinai Medical Center in New York, as well as research director of Mount Sinai’s Wiener Family Cardiovascular Research Laboratories. Dr. Hajjar was recruited to Mt. Sinai from Harvard Medical School where he was assistant professor of medicine and staff cardiologist in the Heart Failure & Cardiac Transplantation Center. He received his medical degree from Harvard Medical School and trained in internal medicine and cardiology at Massachusetts General Hospital in Boston. Dr. Hajjar has concentrated his research efforts on understanding the basic mechanisms of heart failure. He has developed gene transfer methods and techniques in the heart to improve contractility. Dr. Hajjar’s laboratory focuses on targeting signaling pathways in cardiac myocytes to improve contractile function in heart failure and to block signaling pathways in hypertrophy and apoptosis. Dr. Hajjar has significant expertise in gene therapy. In 1996, he won the Young Investigator Award of the American Heart Association (Council on Circulation). In 1999, Dr. Hajjar was awarded the prestigious Doris Duke Clinical Scientist award and won first prize at the Astra Zeneca Young Investigator Forum. Dr. Hajjar holds a number of NIH grants.

http://alumni.jhu.edu/distinguishedalumni2011

Dr Hajjar is the Director of the Cardiovascular Research Center, and the Arthur & Janet C. Ross Professor of Medicine at Mount Sinai School of Medicine, New York, NY. He received his BS in Biomedical Engineering from Johns Hopkins University and his MD from Harvard Medical School and the Harvard-MIT Division of Health Sciences & Technology. He completed his training in internal medicine, cardiology and research fellowships at Massachusetts General Hospital in Boston.

Dr. Hajjar is an internationally renowned scientific leader in the field of cardiac gene therapy for heart failure. His laboratory focuses on molecular mechanisms of heart failure and has validated the cardiac sarcoplasmic reticulum calcium ATPase pump, SERCA2a, as a target in heart failure, developed methodologies for cardiac directed gene transfer that are currently used by investigators throughout the world, and examined the functional consequences of SERCA2a gene transfer in failing hearts. His basic science laboratory remains one of the preeminent laboratories for the investigation of calcium cycling in failing hearts and targeted gene transfer in various animal models. The significance of Dr Hajjar’s research has been recognized with the initiation and recent successful completion of phase 1 and phase 2 First-in-Man clinical trials of SERCA2a gene transfer in patients with advanced heart failure under his guidance.

Prior to joining Mount Sinai, Dr. Hajjar served as Director of the Cardiovascular Laboratory of Integrative Physiology and Imaging at Massachusetts General Hospital and Associate Professor of Medicine at Harvard Medical School. Dr. Hajjar has also been a staff cardiologist in the Heart Failure & Cardiac Transplantation Center at Massachusetts General Hospital.

Dr. Hajjar has won numerous awards and distinctions, including the Young Investigator Award of the American Heart Association. He was awarded a Doris Duke Clinical Scientist award and has won first prize at the Astra Zeneca Young Investigator Forum. He is a member of the American Society for Clinical Investigation. He was recently awarded the Distinguished Alumnus Award from Johns Hopkins University and the Mount Sinai Dean’s award for Excellence in Translational Science. He has authored over 260 peer-reviewed publications.

http://heart.sdsu.edu/~website/IRRI/Pages/faculty/roger-hajjar-md.html

Meet the Director of Mount Sinai’s Cardiovascular Research Center

“Cardiovascular diseases are the number one cause of death globally. In order to tackle them in all aspects, we must unite improved diagnostic techniques with more refined therapies.”

Roger J. Hajjar, MD, Director of the Cardiovascular Research Center, the Arthur & Janet C. Ross Professor of Medicine, Professor of Gene & Cell Medicine, Director of the Cardiology Fellowship Program, and Co-Director of the Transatlantic Cardiovascular Research Center, which combines Mount Sinai Cardiology Laboratories with those of the Universite de Paris – Madame Curie.

In the late 1990s, the possibility that discoveries in genetics and genomics could have a positive impact on the diagnosis, treatment, and prevention of cardiovascular diseases seemed to be just a distant promise. Today, a little more than a decade later, the promise is beginning to take shape. Roger J. Hajjar, MD and his multidisciplinary team of investigators are beginning to translate scientific findings into real therapies for cardiovascular diseases. As Director of the Cardiovascular Research Institute and a cardiologist by training, Dr. Hajjar guides the growth of a cutting-edge translational research laboratory, which is positioning Mount Sinai as the leader in cardiovascular genomics.

An internationally recognized scientific leader in the field of cardiac gene therapy for heart failure, Dr. Hajjar is expanding studies of the basic mechanisms of cardiac diseases and identification of high-risk groups and genomic predictors so that they can be part of the daily clinical care of patients. Unique biorepositories combined with cardiovascular areas of excellence across Mount Sinai make possible crucial genetic studies.

First Gene Therapy for Heart Failure

Under Dr. Hajjar’s leadership, the Cardiovascular Research Center has already developed the world’s first potential gene therapy for heart failure. Known as AAV1.SERCA2a, this therapy actually revives heart tissue that has stopped working properly. It has led to new treatment possibilities for patients with advanced heart failure, whose options used to be severely limited. The significance of this research has been recognized with the initiation and successful completion Phase 1 and Phase 2 First-in-Man clinical trials of SERCA2a gene transfer in patients with advanced heart failure. Phase 3 validation begins in 2011.

The Cardiovascular Research Center’s next research projects, already underway, focus on using novel gene therapy vectors to target diastolic heart failure, ventricular arrhythmias, pulmonary hypertension, and myocardial infarctions.

In addition to targeting signaling pathways to aid failing heart cells, ongoing work at the Cardiovascular Research Center involves studying how to block signaling pathways in cardiac hypertrophy as well as apoptosis. The laboratory team is also targeting a number of signaling pathways in the aging heart to improve dystolic function.

Prior to joining Mount Sinai in 2007, Dr. Hajjar served as Director of the Cardiovascular Laboratory of Integrative Physiology and Imaging at Massachusetts General Hospital and Associate Professor of Medicine at Harvard Medical School. Dr. Hajjar has also been a staff cardiologist in the Heart Failure & Cardiac Transplantation Center at Massachusetts General Hospital. After earning a bachelors of science degree in Biomedical Engineering from Johns Hopkins University and a medical degree from Harvard Medical School and the Harvard-MIT Division of Health Sciences and Technology, he completed his training in internal medicine, cardiology and research fellowships at Massachusetts General Hospital in Boston.

Scientific Advisors

Roger J. Hajjar, MD, Co-Founder and a Scientific Advisor of Celladon Co, plans to commercialize AAV1.SERCA2a for the treatment of heart failure.
Dr. Roger J. Hajjar is the Director of the Cardiovascular Research Center at the Mt. Sinai School of Medicine. Previously, he was the Director of the Cardiovascular Laboratory of Integrative Physiology and Imaging at Massachusetts General Hospital (MGH) and Associate Professor of Medicine at Harvard Medical School. Dr. Hajjar has an active basic science laboratory and concentrates his research efforts on understanding the basic mechanisms of heart failure. He has developed gene transfer methods and techniques targeting the heart as a therapeutic modality to improve contractility in heart failure. Dr. Hajjar’s laboratory focuses on targeting signaling pathways in cardiac myocytes to improve contractile function in heart failure and to block signaling pathways in hypertrophy and apoptosis.

Gene Therapy: Volume 19, Issue 6 (June 2012)

Special Issue: Cardiovascular Gene Therapy

Guest Editor

Roger J Hajjar MD, Mount Sinai School of Medicine, New York, NY Director, Cardiovascular Research Institute, Arthur & Janet C Ross Professor of Medicine

SDF-1 in myocardial repair  

M S Penn, J Pastore, T Miller and R Aras

Gene Ther 19: 583-587; doi:10.1038/gt.2012.32

Abstract | Full Text | PDF

Gene- and cell-based bio-artificial pacemaker: what basic and translational lessons have we learned?  

R A Li

Gene Ther 19: 588-595; doi:10.1038/gt.2012.33

Abstract | Full Text | PDF

Sarcoplasmic reticulum and calcium cycling targeting by gene therapy  

J-S Hulot, G Senyei and R J Hajjar

Gene Ther 19: 596-599; advance online publication, May 17, 2012; doi:10.1038/gt.2012.34

Abstract | Full Text | PDF

Gene therapy for ventricular tachyarrhythmias  

J K Donahue

Gene Ther 19: 600-605; advance online publication, April 26, 2012; doi:10.1038/gt.2012.35

Abstract | Full Text | PDF

Prospects for gene transfer for clinical heart failure  

T Tang, M H Gao and H Kirk Hammond

Gene Ther 19: 606-612; advance online publication, April 26, 2012; doi:10.1038/gt.2012.36

Abstract | Full Text | PDF

Targeting S100A1 in heart failure  

J Ritterhoff and P Most

Gene Ther 19: 613-621; advance online publication, February 16, 2012; doi:10.1038/gt.2012.8

Abstract | Full Text | PDF

VEGF gene therapy: therapeutic angiogenesis in the clinic and beyond  

M Giacca and S Zacchigna

Gene Ther 19: 622-629; advance online publication, March 1, 2012; doi:10.1038/gt.2012.17

Abstract | Full Text | PDF

Vein graft failure: current clinical practice and potential for gene therapeutics  

S Wan, S J George, C Berry and A H Baker

Gene Ther 19: 630-636; advance online publication, March 29, 2012; doi:10.1038/gt.2012.29

Abstract | Full Text | PDF

Percutaneous methods of vector delivery in preclinical models  

D Ladage, K Ishikawa, L Tilemann, J Müller-Ehmsen and Y Kawase

Gene Ther 19: 637-641; advance online publication, March 15, 2012; doi:10.1038/gt.2012.14

Abstract | Full Text | PDF

Lentiviral vectors and cardiovascular diseases: a genetic tool for manipulating cardiomyocyte differentiation and function  

E Di Pasquale, M V G Latronico, G S Jotti and G Condorelli

Gene Ther 19: 642-648; advance online publication, March 1, 2012; doi:10.1038/gt.2012.19

Abstract | Full Text | PDF

Intracellular transport of recombinant adeno-associated virus vectors  

M Nonnenmacher and T Weber

Gene Ther 19: 649-658; advance online publication, February 23, 2012; doi:10.1038/gt.2012.6

Abstract | Full Text | PDF

Gene delivery technologies for cardiac applications  

M G Katz, A S Fargnoli, L A Pritchette and C R Bridges

Gene Ther 19: 659-669; advance online publication, March 15, 2012; doi:10.1038/gt.2012.11

Abstract | Full Text | PDF

Cardiac gene therapy in large animals: bridge from bench to bedside  

K Ishikawa, L Tilemann, D Ladage, J Aguero, L Leonardson, K Fish and Y Kawase

Gene Ther 19: 670-677; advance online publication, February 2, 2012; doi:10.1038/gt.2012.3

Abstract | Full Text | PDF

Progress in gene therapy of dystrophic heart disease  

Y Lai and D Duan

Gene Ther 19: 678-685; advance online publication, February 9, 2012; doi:10.1038/gt.2012.10

Abstract | Full Text | PDF

Targeting GRK2 by gene therapy for heart failure: benefits above β-blockade  

J Reinkober, H Tscheschner, S T Pleger, P Most, H A Katus, W J Koch and P W J Raake

Gene Ther 19: 686-693; advance online publication, February 16, 2012; doi:10.1038/gt.2012.9

Abstract | Full Text | PDF

Directed evolution of novel adeno-associated viruses for therapeutic gene delivery  

M A Bartel, J R Weinstein and D V Schaffer

Gene Ther 19: 694-700; advance online publication, March 8, 2012; doi:10.1038/gt.2012.20

Abstract | Full Text | PDF

http://www.nature.com/gt/journal/v19/n6/index.html

Part II: Cardiac Gene Therapy: Inhalable Gene Therapy for Pulmonary Arterial Hypertension

Public release date: 30-Jul-2013

Contact: Lauren Woods
lauren.woods@mountsinai.org
212-241-2836
The Mount Sinai Hospital / Mount Sinai School of Medicine

Inhalable gene therapy may help pulmonary arterial hypertension patients

Gene therapy when inhaled may restore function of a crucial enzyme in the lungs to reverse deadly PAH

The deadly condition known as pulmonary arterial hypertension (PAH), which afflicts up to 150,000 Americans each year, may be reversible by using an inhalable gene therapy, report an international team of researchers led by investigators at the Cardiovascular Research Center at Icahn School of Medicine at Mount Sinai.

In their new study, reported in the July 30 issue of the journal Circulation, scientists demonstrated that gene therapy administered through a nebulizer-like inhalation device can completely reverse PAH in rat models of the disease. In the lab, researchers also showed in pulmonary artery PAH patient tissue samples reduced expression of the SERCA2a, an enzyme critical for proper pumping of calcium in calcium compartments within the cells. SERCA2a gene therapy could be sought as a promising therapeutic intervention in PAH.

“The gene therapy could be delivered very easily to patients through simple inhalation — just like the way nebulizers work to treat asthma,” says study co-senior investigator Roger J. Hajjar, MD, Director of the Cardiovascular Research Center and the Arthur & Janet C. Ross Professor of Medicine and Professor of Gene & Cell at Icahn School of Medicine at Mount Sinai. “We are excited about testing this therapy in PAH patients who are in critical need of intervention.”

This same SERCA2a dysfunction also occurs in heart failure. This new study utilizes the same gene therapy currently being tested in patients to reverse congestive heart failure in a large phase III clinical trial in the United States and Europe.

“What we have shown is that gene therapy restores function of this crucial enzyme in diseased lungs,” says Dr. Hajjar. “We are delighted with these new findings because it suggests that a gene therapy that is already showing great benefit in congestive heart failure patients may be able to help PAH patients who currently have no good treatment options — and are in critical need of a life sustaining therapy.”

When SERCA2a is down-regulated, calcium stays longer in the cells than it should, and it induces pathways that lead to overgrowth of new and enlarged cells. According to researchers, the delivery of the SERCA2a gene produces SERCA2a enzymes, which helps both heart and lung cells restore their proper use of calcium.

“We are now on a path toward PAH patient clinical trials in the near future,” says Dr. Hajjar, who developed the gene therapy approach. Studies in large animal models are now underway. SERCA2a gene therapy has already been approved by the National Institutes of Health for human study.

A Simple Inhalation Corrects Deadly Dysfunction

PAH most commonly results from heart failure in the left side of the heart or from a pulmonary embolism, when clots in the legs travel to the lungs and cause blockages. When the lung is damaged from these conditions, the tissue starts to quickly produce new and enlarged cells, which narrows pulmonary arteries. This increases the pressure inside them. The high pressure in these arteries resists the heart’s effort to pump through them and the blood flow between the heart and lungs is reduced. The right side of the heart then must overcome the resistance and work harder to push the blood through the pulmonary arteries into the lungs. Over time, the right ventricle becomes thickened and enlarged and heart failure develops.

The gene therapy that Dr. Hajjar developed uses a modified adeno-associated viral-vector that is derived from a parvovirus. It works by introducing a healthy SERCA2a gene into cells, but this gene does not incorporate into a patient’s chromosome, according to the study’s lead author, Lahouaria Hadri, PhD, an Instructor of Medicine in Cardiology at Icahn School of Medicine at Mount Sinai.

“The clinical trials in congestive heart failure have shown already that the gene therapy is very safe,” says Dr. Hadri. Between 40-50 percent of individuals have antecedent antibodies to the adeno-associated vectors, so potential patients need to be screened before gene therapy to make sure they are eligible to receive the vectors. In patients without antibodies, the restorative enzyme gene therapy does not cause an immune response, according to Dr. Hadri.

The clinical application of the gene therapy for patients with PAH will most likely differ from those with heart failure. The replacement gene needs to be injected through the coronary arteries of heart failure patients using catheters, while in PAH patients, the gene will need to be administered through inhalation.

This study was supported by National Institutes of Health grants (K01HL103176, K08111207, R01 HL078691, HL057263, HL071763, HL080498, HL083156, and R01 HL105301).

Other study co-authors include Razmig G. Kratlian, MD, Ludovic Benard, PhD, Kiyotake Ishikawa, MD, Jaume Aguero, MD, Dennis Ladage, MD, Irene C.Turnbull, MD, Erik Kohlbrenner, BA, Lifan Liang, MD, Jean-Sébastien Hulot, MD, PhD, and Yoshiaki Kawase, MD, from Icahn School of Medicine at Mount Sinai; Bradley A. Maron, MD and the study’s co-senior author Jane A. Leopold, MD, from Brigham and Women’s Hospital and Harvard Medical School in Boston, MA; Christophe Guignabert, PhD, from Hôpital Antoine-Béclère, Clamart, France; Peter Dorfmüller, MD, PhD, and Marc Humbert, MD, PhD, both of the Hôpital Antoine-Béclère and INSERM U999, Centre Chirurgical Marie-Lannelongue, Le Plessis-Robinson, France; Borja Ibanez, MD, from Fundación Centro Nacional de Investigaciones Cardiovasculares, Carlos III (CNIC), Madrid, Spain; and Krisztina Zsebo, PhD, of Celladon Corporation, San Diego, CA.

  • Dr. Hajjar and co-author Dr. Zsebo, have ownership interest in Celladon Corporation, which is developing AAV1.SERCA2a for the treatment of heart failure. Also,
  • Dr. Hajjar and co-authors Dr. Kawase and Dr. Ladage hold intellectual property around SERCA2a gene transfer as a treatment modality for PAH. In addition,
  • co-author Dr. Maron receives funding from Gilead Sciences, Inc. to study experimental pulmonary hypertension.
  • Other study co-authors have no financial interests to declare.

Therapeutic Efficacy of AAV1.SERCA2a in Monocrotaline-Induced Pulmonary Arterial Hypertension

  1. Lahouaria Hadri, PhD;
  2. Razmig G. Kratlian, MD;
  3. Ludovic Benard, PhD;
  4. Bradley A. Maron, MD;
  5. Peter Dorfmüller, MD, PhD;
  6. Dennis Ladage, MD;
  7. Christophe Guignabert, PhD;
  8. Kiyotake Ishikawa, MD;
  9. Jaume Aguero, MD;
  10. Borja Ibanez, MD;
  11. Irene C. Turnbull, MD;
  12. Erik Kohlbrenner, BA;
  13. Lifan Liang, MD;
  14. Krisztina Zsebo, PhD;
  15. Marc Humbert, MD, PhD;
  16. Jean-Sébastien Hulot, MD, PhD;
  17. Yoshiaki Kawase, MD;
  18. Roger J. Hajjar, MD*;
  19. Jane A. Leopold, MD*

+Author Affiliations


  1. From the Cardiovascular Research Center, Icahn School of Medicine at Mount Sinai, New York, NY (L.H., R.G.K., L.B., D.L., K.I., J.A., I.C.T., E.K., L.L., J.-S.H., Y.K., R.J.H.); Cardiovascular Medicine Division, Brigham and Women’s Hospital and Harvard Medical School, Boston, MA (B.A.M., J.A.L.); Hôpital Antoine-Béclère, Clamart, France (P.D., C.G., M.H.); INSERM U999, Centre Chirurgical Marie-Lannelongue, Le Plessis-Robinson, France (P.D., M.H.); Fundación Centro Nacional de Investigaciones Cardiovasculares, Carlos III (CNIC), Madrid, Spain (B.I.); and Celladon Corporation, San Diego, CA (K.Z.).
  1. Correspondence to Lahouaria Hadri, PhD, Cardiovascular Research Center, Box 1030, Icahn School of Medicine at Mount Sinai, 1470 Madison Ave, New York, NY 10029. E-mail lahouaria.hadri@mssm.edu

Abstract

Background—Pulmonary arterial hypertension (PAH) is characterized by dysregulated proliferation of pulmonary artery smooth muscle cells leading to (mal)adaptive vascular remodeling. In the systemic circulation, vascular injury is associated with downregulation of sarcoplasmic reticulum Ca2+-ATPase 2a (SERCA2a) and alterations in Ca2+homeostasis in vascular smooth muscle cells that stimulate proliferation. We, therefore, hypothesized that downregulation of SERCA2a is permissive for pulmonary vascular remodeling and the development of PAH.

Methods and Results—SERCA2a expression was decreased significantly in remodeled pulmonary arteries from patients with PAH and the rat monocrotaline model of PAH in comparison with controls. In human pulmonary artery smooth muscle cells in vitro, SERCA2a overexpression by gene transfer decreased proliferation and migration significantly by inhibiting NFAT/STAT3. Overexpresion of SERCA2a in human pulmonary artery endothelial cells in vitro increased endothelial nitric oxide synthase expression and activation. In monocrotaline rats with established PAH, gene transfer of SERCA2a via intratracheal delivery of aerosolized adeno-associated virus serotype 1 (AAV1) carrying the human SERCA2a gene (AAV1.SERCA2a) decreased pulmonary artery pressure, vascular remodeling, right ventricular hypertrophy, and fibrosis in comparison with monocrotaline-PAH rats treated with a control AAV1 carrying β-galactosidase or saline. In a prevention protocol, aerosolized AAV1.SERCA2a delivered at the time of monocrotaline administration limited adverse hemodynamic profiles and indices of pulmonary and cardiac remodeling in comparison with rats administered AAV1 carrying β-galactosidase or saline.

Conclusions—Downregulation of SERCA2a plays a critical role in modulating the vascular and right ventricular pathophenotype associated with PAH. Selective pulmonary SERCA2a gene transfer may offer benefit as a therapeutic intervention in PAH.

Key Words:

  • Received January 24, 2013.
  • Accepted June 13, 2013.

http://circ.ahajournals.org/content/128/5/512.abstract?sid=9b3b4fcc-e158-4e5d-bb8b-125586e2ec12

Circulation.2013; 128: 512-523 Published online before print June 26, 2013,doi: 10.1161/​CIRCULATIONAHA.113.001585

Part III: Cardiac Gene Therapy: Percutaneous Intra-coronary Artery Infusion for Heart Failure

Etiology of Heart Failure

  • Alcoholic
  • Hypertensive
  • Idiopathic
  • Inflammatory
  • Ischemic
  • Pregnancy-related
  • Toxic
  • Valvular Heart DIsease

Administration of Cardiac Gene Therapy for Heart Failure: via Percutaneous Intra-coronary Artery Infusion

  • Gene delivery to viable myocardium

dominance and coronary artery anatomy from angiography determines infusion scenario

  • Antegrade epicardial coronary artery infusion over 10 minutes

60 mL divided into 1,2,3 infusions depending on anatomy

Delivered via commercially available angiographic injection system & guide or diagnostic catheters

Dr. Roger J. Hajjar of the Mount Sinai School of Medicine will present at the ASGCT 15th Annual Meeting during a Scientific Symposium entitled: Cell and Gene Therapy in Cardiovascular Disease on Wednesday, May 16, 2012 at 8:00 am. Below is a brief preview of his presentation.

Roger J. Hajjar, MD

Mount Sinai School of Medicine

New York, NY

Novel Developments in Gene Therapy for Cardiovascular Diseases

Chronic heart failure is a leading cause of hospitalization affecting nearly 6 million people in the U.S. with 670,000 new cases diagnosed every year. Heart failure leads to about 280,000 deaths annually.

Congestive heart failure remains a progressive disease with a desperate need for innovative therapies to reverse the course of ventricular dysfunction. The most common symptoms of heart failure are shortness of breath, feeling tired and swelling in the ankles, feet, legs and sometimes the abdomen. Recent advances in understanding the molecular basis of myocardial dysfunction, together with the evolution of increasingly efficient gene transfer technology have placed heart failure within reach of gene-based therapies.

One of the key abnormalities in both human and experimental HF is a defect in sarcoplasmic reticulum (SR) function, which controls Ca2+ handling in cardiac myocytes on a beat to beat basis. Deficient SR Ca2+ uptake during relaxation has been identified in failing hearts from both humans and animal models and has been associated with a decrease in the activity of the SR Ca2+-ATPase (SERCA2a).

Over the last ten years we have undertaken a program of targeting important calcium cycling proteins in experimental models of heart by somatic gene transfer. This has led to the completion of a first-in-man phase 1 clinical trial of gene therapy for heart failure using adeno-associated vector (AAV) type 1 carrying SERCA2a. In this Phase I trial, there was evidence of clinically meaningful improvements in functional status and/or cardiac function which were observed in the majority of patients at various time points. The safety profile of AAV gene therapy along with the positive biological signals obtained from this phase 1 trial has led to the initiation and recent completion of a phase 2 trial of AAV1.SERCA2a in NYHA class III/IV patients. In the phase 2 trial, gene transfer of SERCA2a was found to be safe and associated with benefit in clinical outcomes, symptoms, functional status, NT-proBNP and cardiac structure.

The 12 month data presented showed that heart failure, which is a progressive disease, became stabilized in high dose AAV1.SERCA2a-treated patients: heart failure symptoms, exercise tolerance, serum biomarkers and cardiac function essentially improved or remained the same while these parameters deteriorated substantially in patients treated with placebo and concurrent optimal drug and device therapy. More recently, the 2-year CUPID data from long-term follow-up demonstrate a durable benefit in preventing major cardiovascular events.

The recent successful and safe completion of the CUPID trial along with the start of more recent phase 1 trials usher a new era for gene therapy for the treatment of heart failure. Furthermore, novel AAV derivatives with high cardiotropism and resistant to neutralizing antibodies are being developed to target a large number of cardiovascular diseases.

http://www.execinc.com/hosted/emails/asgct/file/Hajjar2(1).pdf

Power Point Presentation on Cardiac Gene Therapy –

VIEW SLIDE SHOW

http://my.americanheart.org/idc/groups/heart-public/@wcm/@global/documents/downloadable/ucm_311680.pdf

Gene Therapy for Heart Failure

  1. Lisa Tilemann,
  2. Kiyotake Ishikawa,
  3. Thomas Weber,
  4. Roger J. Hajjar

+Author Affiliations


  1. From the Cardiovascular Research Center, Mount Sinai Medical Center, New York, NY.
  1. Correspondence to Roger J. Hajjar, MD, Mount Sinai Medical Center, One Gustave Levy Place, Box 1030, New York, NY 10029. E-mail roger.hajjar@mssm.edu

Abstract

Congestive heart failure accounts for half a million deaths per year in the United States. Despite its place among the leading causes of morbidity, pharmacological and mechanic remedies have only been able to slow the progression of the disease. Today’s science has yet to provide a cure, and there are few therapeutic modalities available for patients with advanced heart failure. There is a critical need to explore new therapeutic approaches in heart failure, and gene therapy has emerged as a viable alternative. Recent advances in understanding of the molecular basis of myocardial dysfunction, together with the evolution of increasingly efficient gene transfer technology, have placed heart failure within reach of gene-based therapy. The recent successful and safe completion of a phase 2 trial targeting the sarcoplasmic reticulum calcium ATPase pump (SERCA2a), along with the start of more recent phase 1 trials, opens a new era for gene therapy for the treatment of heart failure.

Circulation Research.2012; 110: 777-793 doi: 10.1161/​CIRCRESAHA.111.252981

Key Words:

  • Received December 8, 2011.
  • Revision received January 29, 2012.
  • Accepted January 30, 2012.

Conclusions 

With a better understanding of the molecular mechanisms associated with heart failure and improved vectors with cardiotropic properties, gene therapy can now be considered as a viable adjunctive treatment to mechanical and pharmacological therapies for heart failure. In the coming years, more targets will emerge that are amenable to genetic manipulations, along with more advanced vector systems, which will undoubtedly lead to safer and more effective clinical trials in gene therapy for heart failure.

http://circres.ahajournals.org/content/110/5/777.full.pdf+html

Hijjar1
Figure 1.

AAV entry. 1 indicates receptor binding and endocytosis; 2, escape into cytoplasm; 3, nuclear import; 4, capsid disassembly; 5, double-strand synthesis; and 6, transcription.

Hijjar2

Figure 2.

Generation of mutant AAV library and directed evolution to identify cardiotropic AAVs. A, Creation of a library of AAVs through DNA shuffling.B, Selection of cardiotropic AAVs through directed evolution.

Hijjar3

Figure 3.

Antegrade coronary artery infusion. A, Coronary artery infusion. The vector is injected through a catheter without interruption of the coronary flow. B, Coronary artery infusion with occlusion of a coronary artery: The vector is injected through the lumen of an inflated angioplasty catheter. C, Coronary artery infusion with simultaneous blocking of a coronary artery and a coronary vein: The vector is injected through an inflated angioplasty catheter and resides in the coronary circulation until both balloons are deflated.

Hijjar4

Figure 4.

V-Focus system and retrograde coronary venous infusion. A, Recirculating antegrade coronary artery infusion: The vector is injected into a coronary artery, collected from the coronary sinus and after oxygenation readministered into the coronary artery. B, Retrograde coronary venous infusion with simultaneous blocking of a coronary artery and a coronary vein: The vector is injected into a coronary vein and resides in the coronary circulation until both balloons are deflated.

Hijjar5

Figure 5.

Direct myocardial injection and pericardial injection. A, Percutaneous myocardial injection: The vector is injected with an injection catheter via an endocardial approach.B, Surgical myocardial injection: The vector is injected via an epicardial approach. C, Percutaneous pericardial injection: The vector is injected via a substernal approach.

Hijjar6

Figure 6.

Excitation-contraction coupling in cardiac myocytes provides multiple targets for gene therapy.

SOURCE

http://circres.ahajournals.org/content/110/5/777.figures-only

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  • ‘Ryanopathy’: causes and manifestations of RyR2 dysfunction in heart failureCardiovasc Res. 2013;98:240-247,
  • Up-regulation of sarcoplasmic reticulum Ca2+ uptake leads to cardiac hypertrophy, contractile dysfunction and early mortality in mice deficient in CASQ2Cardiovasc Res. 2013;98:297-306,
  • Myocardial Delivery of Stromal Cell-Derived Factor 1 in Patients With Ischemic Heart Disease: Safe and PromisingCirc. Res.. 2013;112:746-747,
  • Circulation Research Thematic Synopsis: Cardiovascular GeneticsCirc. Res.. 2013;112:e34-e50,
  • Gene and cytokine therapy for heart failure: molecular mechanisms in the improvement of cardiac functionAm. J. Physiol. Heart Circ. Physiol.. 2012;303:H501-H512,
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http://circres.ahajournals.org/content/110/5/777.full.pdf+html

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Identification of Biomarkers that are Related to the Actin Cytoskeleton

Curator and Writer: Larry H Bernstein, MD, FCAP

This is Part I in a series of articles on Calcium and Cell motility.

The Series consists of the following articles:

Part I: Identification of Biomarkers that are Related to the Actin Cytoskeleton

Larry H Bernstein, MD, FCAP

https://pharmaceuticalintelligence.com/2012/12/10/identification-of-biomarkers-that-are-related-to-the-actin-cytoskeleton/

Part II: Role of Calcium, the Actin Skeleton, and Lipid Structures in Signaling and Cell Motility

Larry H. Bernstein, MD, FCAP, Stephen Williams, PhD and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/08/26/role-of-calcium-the-actin-skeleton-and-lipid-structures-in-signaling-and-cell-motility/

Part III: Renal Distal Tubular Ca2+ Exchange Mechanism in Health and Disease

Larry H. Bernstein, MD, FCAP, Stephen J. Williams, PhD
 and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/09/02/renal-distal-tubular-ca2-exchange-mechanism-in-health-and-disease/

Part IV: The Centrality of Ca(2+) Signaling and Cytoskeleton Involving Calmodulin Kinases and Ryanodine Receptors in Cardiac Failure, Arterial Smooth Muscle, Post-ischemic Arrhythmia, Similarities and Differences, and Pharmaceutical Targets

Larry H Bernstein, MD, FCAP, Justin Pearlman, MD, PhD, FACC and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/09/08/the-centrality-of-ca2-signaling-and-cytoskeleton-involving-calmodulin-kinases-and-ryanodine-receptors-in-cardiac-failure-arterial-smooth-muscle-post-ischemic-arrhythmia-similarities-and-differen/

Part V: Ca2+-Stimulated Exocytosis:  The Role of Calmodulin and Protein Kinase C in Ca2+ Regulation of Hormone and Neurotransmitter

Larry H Bernstein, MD, FCAP
and
Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/12/23/calmodulin-and-protein-kinase-c-drive-the-ca2-regulation-of-hormone-and-neurotransmitter-release-that-triggers-ca2-stimulated-exocytosis/

Part VI: Calcium Cycling (ATPase Pump) in Cardiac Gene Therapy: Inhalable Gene Therapy for Pulmonary Arterial Hypertension and Percutaneous Intra-coronary Artery Infusion for Heart Failure: Contributions by Roger J. Hajjar, MD

Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/08/01/calcium-molecule-in-cardiac-gene-therapy-inhalable-gene-therapy-for-pulmonary-arterial-hypertension-and-percutaneous-intra-coronary-artery-infusion-for-heart-failure-contributions-by-roger-j-hajjar/

Part VII: Cardiac Contractility & Myocardium Performance: Ventricular Arrhythmias and Non-ischemic Heart Failure – Therapeutic Implications for Cardiomyocyte Ryanopathy (Calcium Release-related Contractile Dysfunction) and Catecholamine Responses

Justin Pearlman, MD, PhD, FACC, Larry H Bernstein, MD, FCAP and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/08/28/cardiac-contractility-myocardium-performance-ventricular-arrhythmias-and-non-ischemic-heart-failure-therapeutic-implications-for-cardiomyocyte-ryanopathy-calcium-release-related-contractile/

Part VIII: Disruption of Calcium Homeostasis: Cardiomyocytes and Vascular Smooth Muscle Cells: The Cardiac and Cardiovascular Calcium Signaling Mechanism

Justin Pearlman, MD, PhD, FACC, Larry H Bernstein, MD, FCAP and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/09/12/disruption-of-calcium-homeostasis-cardiomyocytes-and-vascular-smooth-muscle-cells-the-cardiac-and-cardiovascular-calcium-signaling-mechanism/

Part IXCalcium-Channel Blockers, Calcium Release-related Contractile Dysfunction (Ryanopathy) and Calcium as Neurotransmitter Sensor

Justin Pearlman, MD, PhD, FACC, Larry H Bernstein, MD, FCAP and Aviva Lev-Ari, PhD, RN

Part X: Synaptotagmin functions as a Calcium Sensor: How Calcium Ions Regulate the fusion of vesicles with cell membranes during Neurotransmission

Larry H Bernstein, MD, FCAP and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/09/10/synaptotagmin-functions-as-a-calcium-sensor-how-calcium-ions-regulate-the-fusion-of-vesicles-with-cell-membranes-during-neurotransmission/

Part XI: Sensors and Signaling in Oxidative Stress

Larry H. Bernstein, MD, FCAP

https://pharmaceuticalintelligence.com/2013/11/01/sensors-and-signaling-in-oxidative-stress/

Part XII: Atherosclerosis Independence: Genetic Polymorphisms of Ion Channels Role in the Pathogenesis of Coronary Microvascular Dysfunction and Myocardial Ischemia (Coronary Artery Disease (CAD))

Larry H Bernstein, MD, FCAP and Aviva Lev-Ari, PhD, RN

https://pharmaceuticalintelligence.com/2013/12/21/genetic-polymorphisms-of-ion-channels-have-a-role-in-the-pathogenesis-of-coronary-microvascular-dysfunction-and-ischemic-heart-disease/

 

In this article the Author will cover two types of biomarker on the function of actin in cytoskeleton mobility in situ.

  • First, is an application in developing the actin or other component, for a biotarget and then, to be able to follow it as

(a) a biomarker either for diagnosis, or

(b) for the potential treatment prediction of disease free survival.

  • Second, is mostly in the context of MI, for which there is an abundance of work to reference, and a substantial body of knowledge about

(a) treatment and long term effects of diet, exercise, and

(b) underlying effects of therapeutic drugs.

1.  Cell Membrane (cytoskeletal) Plasticity

Refer to … Squeezing Ovarian Cancer Cells to Predict Metastatic Potential: Cell Stiffness as Possible Biomarker

Reporter/curator: Prabodh Kandala, PhD

New Georgia Tech research shows that cell stiffness could be a valuable clue for doctors as they search for and treat cancerous cells before they’re able to spread. The findings, which are published in the journal PLoS One, found that highly metastatic ovarian cancer cells are several times softer than less metastatic ovarian cancer cells. This study used atomic force microscopy (AFM) to study the mechanical properties of various ovarian cell lines. A soft mechanical probe “tapped” healthy, malignant and metastatic ovarian cells to measure their stiffness. In order to spread, metastatic cells must push themselves into the bloodstream. As a result, they must be highly deformable and softer. This study results indicate that cell stiffness may be a useful biomarker to evaluate the relative metastatic potential of ovarian and perhaps other types of cancer cells.

Comparative gene expression analyses indicate that the reduced stiffness of highly metastatic HEY A8 cells is associated with actin cytoskeleton remodeling and microscopic examination of actin fiber structure in these cell lines is consistent with this prediction.   The results suggest either of two approaches. Atomic Force Microscopy is not normally used by pathologists in diagnostics. Electron microscopy requires space for making and cutting the embedded specimen, and a separate room for the instrument. The instrument is large and the technique was not suitable for anything other than research initially until EM gained importance in Renal Pathology. It has not otherwise been used.  This new method looks like it might be more justified over a spectrum of cases.

A.  Atomic Force Microscopy

So the first point related to microscopy is whether AFM has feasibility for routine clinical use in the pathologists’ hands. This requires:

  1. suitable size of equipment
  2.  suitable manipulation of the specimen
  3. The question of whether you are using overnight fixed specimen, or whether the material is used unfixed
  4. Nothing is said about staining of cells for identification.
  5. Then there is the question about whether this will increase the number of Pathologist Assistants used across the country, which I am not against.   This would be the end of “house” trained PAs, and gives more credence to the too few PA programs across the country. The PA programs have to be reviewed and accredited by NAACLS (I served 8 years on the Board). A PA is represented on the Board, and programs are inspected by qualified peers.   There is no academic recognition given to this for tenure and promotion in Pathology Departments, and a pathologist is selected for a medical advisory role by the ASCP, and must be a Medical Advisor to a MLS accredited Program.   The fact is that PAs do gross anatomic dictation of selected specimens, and they do autopsies under the guidance of a pathologist. This is the reality of the profession today. The pathologist has to be in attendance at a variety of quality review conferences, for surgical morbidity and mortality to obstetrics review, and the Cancer Review. Cytopathology and cytogenetics are in the pathology domain.   In the case of tumors of the throat, cervix, and accessible orifices, it seems plausible to receive a swab for preparation. However, sampling error is greater than for a biopsy. A directed needle biopsy or a MIS specimen is needed for the ovary.

B.  identification of biomarkers that are related to the actin cytoskeleton

The alternative to the first approach is the identification of biomarkers that are related to the actin cytoskeleton, perhaps in the nature of the lipid or apoprotein isoform that gives the cell membrane deformability. The method measuring by Atomic Force Microscopy is shown with the current method of cytological screening, and I call attention to cells clustered together that have a scant cytoplasm surrounding nuclei occupying 1/2 to 3/4 of the cell radius.  The cells are not anaplastic, but the clumps are suggestive of glnad forming epithelium.

English: Animation showing 3-D nature of clust...

English: Animation showing 3-D nature of cluster. Image:Serous carcinoma 2a – cytology.jpg (Photo credit: Wikipedia)

The cell membrane, also called the plasma memb...

The cell membrane, also called the plasma membrane or plasmalemma, is a semipermeable lipid bilayer common to all living cells. It contains a variety of biological molecules, primarily proteins and lipids, which are involved in a vast array of cellular processes. It also serves as the attachment point for both the intracellular cytoskeleton and, if present, the cell wall. (Photo credit: Wikipedia)

English: AFM bema detection

AFM non contact mode

AFM non contact mode (Photo credit: Wikipedia)

C.  The diagnosis of ovarian cancer can be problematic because it can have a long period of growth undetected.

On the other hand, it is easily accessible once there is reason to suspect it. They are terrible to deal with because they metastasize along the abdominal peritoneum and form a solid cake. It is a problem of location and silence until it is late. Once they do announce a presence on the abdominal wall, there is probably a serous effusion. It was not possible to rely on a single marker, but when CA125 was introduced, Dr. Marguerite Pinto, Chief of Cytology at Bridgeport Hospital-Yale New Haven Health came to the immnunochemistry lab and we worked out a method for analyzing effusions, as we had already done with carcinoembryonic antigen.       The use of CEA and CA125 was published by Pinto and Bernstein as a first that had an impact.  This was followed by a study with the Chief of Oncology, Dr. Martin Rosman, that showed that the 30 month survival of patients post treatment is predicted by the half-life of disappearance of CA125 in serum.  At the time of this writing, I am not sure of the extent of its use 20 years later. History has taught us that adoption can be slow, depending very much on dissemination from major academic medical centers.  On the other hand, concepts can also be stuck at academic medical centers because of a rigid and unprepared mindset in the professional community.  The best example of this is the story of Ignaz Semmelweis, the best student of Rokitansky in Vienna for discovering the cause and prevention of childbirth fever at a time that nursemaids had far better results at obstetrical delivery than physicians.  Contrary to this, Edward Jenner, the best student of John Hunter (anatomist, surgeon, and physician to James Hume), discovered vaccination from the observation that milkmaids did not get smallpox (cowpox was a better alternative).
Only this year a Nobel Prize in Physics was awarded to an Israeli scientist who, working in the US, was unable to convince his associates of his discovery of PSEUDOCRYSTALS. – Diagnostic efficiency of carcinoembryonic antigen and CA125 in the cytological evaluation of effusions. M M Pinto, L H Bernstein, R A Rudolph, D A Brogan, M Rosman Arch Pathol Lab Med 1992; 116(6):626-631 ICID: 825503 Article type: Review article – Immunoradiometric assay of CA 125 in effusions. Comparison with carcinoembryonic antigen. M M Pinto, L H Bernstein, D A Brogan, E Criscuolo Cancer 1987; 59(2):218-222 ICID: 825555 Article type: Review article – Carcinoembryonic antigen in effusions. A diagnostic adjunct to cytology. M M Pinto, L H Bernstein, D A Brogan, E M Criscuolo Acta Cytologica 1987; 31(2):113-118 ICID: 825557

Predictive Modeling

Ovarian Cancer a plot of the CA125 elimination half-life vs the Kullback-Liebler distance

Ca125 half-life vs Kullback Entropy                                                          HL vs Survival KM plot 

Troponin(s) T, I, C  and the contractile apparatus  (contributed by Aviva Lev-Ari, PhD, RN)

 

For 2012 – 2013 Frontier Contribution in Cardiology on Gene Therapy Solutions for Improving Myocardial Contractility, see

Lev-Ari, A. 8/1/2013 Calcium Cycling (ATPase Pump) in Cardiac Gene Therapy: Inhalable Gene Therapy for Pulmonary Arterial Hypertension and Percutaneous Intra-coronary Artery Infusion for Heart Failure: Contributions by Roger J. Hajjar, MD

https://pharmaceuticalintelligence.com/2013/08/01/calcium-molecule-in-cardiac-gene-therapy-inhalable-gene-therapy-for-pulmonary-arterial-hypertension-and-percutaneous-intra-coronary-artery-infusion-for-heart-failure-contributions-by-roger-j-hajjar/

For explanation of Conduction prior to Myocardial Contractility, see

Lev-Ari, A. 4/28/2013 Genetics of Conduction Disease: Atrioventricular (AV) Conduction Disease (block): Gene Mutations – Transcription, Excitability, and Energy Homeostasis

https://pharmaceuticalintelligence.com/2013/04/28/genetics-of-conduction-disease-atrioventricular-av-conduction-disease-block-gene-mutations-transcription-excitability-and-energy-homeostasis/

The contraction of skeletal muscle is triggered by nerve impulses, which stimulate the release of Ca2+ from the sarcoplasmic reticulum—a specialized network of internal membranes, similar to the endoplasmic reticulum, that stores high concentrations of Ca2+ ions. The release of Ca2+ from the sarcoplasmic reticulum increases the concentration of Ca2+ in the cytosol from approximately 10-7 to 10-5 M. The increased Ca2+ concentration signals muscle contraction via the action of two accessory proteins bound to the actin filaments: tropomyosin and troponin (Figure 11.25). Tropomyosin is a fibrous protein that binds lengthwise along the groove of actin filaments. In striated muscle, each tropomyosin molecule is bound to troponin, which is a complex of three polypeptides: troponin C (Ca2+-binding), troponin I (inhibitory), and troponin T (tropomyosin-binding).

  • When the concentration of Ca2+ is low, the complex of the troponins with tropomyosin blocks the interaction of actin and myosin, so the muscle does not contract.
  • At high concentrations, Ca2+ binding to troponin C shifts the position of the complex, relieving this inhibition and allowing contraction to proceed.

Figure 11.25

Association of tropomyosin and troponins with actin filaments. (A) Tropomyosin binds lengthwise along actin filaments and, in striated muscle, is associated with a complex of three troponins: troponin I (TnI), troponin C (TnC), and troponin T (TnT). In (more…)
Contractile Assemblies of Actin and Myosin in Nonmuscle Cells

Contractile assemblies of actin and myosin, resembling small-scale versions of muscle fibers, are present also in nonmuscle cells. As in muscle, the actin filaments in these contractile assemblies are interdigitated with bipolar filaments of myosin II, consisting of 15 to 20 myosin II molecules, which produce contraction by sliding the actin filaments relative to one another (Figure 11.26). The actin filaments in contractile bundles in nonmuscle cells are also associated with tropomyosin, which facilitates their interaction with myosin II, probably by competing with filamin for binding sites on actin.

Figure 11.26

Contractile assemblies in nonmuscle cells. Bipolar filaments of myosin II produce contraction by sliding actin filaments in opposite directions.

Two examples of contractile assemblies in nonmuscle cells, stress fibers and adhesion belts, were discussed earlier with respect to attachment of the actin cytoskeleton to regions of cell-substrate and cell-cell contacts (see Figures 11.13 and 11.14). The contraction of stress fibers produces tension across the cell, allowing the cell to pull on a substrate (e.g., the extracellular matrix) to which it is anchored. The contraction of adhesion belts alters the shape of epithelial cell sheets: a process that is particularly important during embryonic development, when sheets of epithelial cells fold into structures such as tubes.

The most dramatic example of actin-myosin contraction in nonmuscle cells, however, is provided by cytokinesis—the division of a cell into two following mitosis (Figure 11.27). Toward the end of mitosis in animal cells, a contractile ring consisting of actin filaments and myosin II assembles just underneath the plasma membrane. Its contraction pulls the plasma membrane progressively inward, constricting the center of the cell and pinching it in two. Interestingly, the thickness of the contractile ring remains constant as it contracts, implying that actin filaments disassemble as contraction proceeds. The ring then disperses completely following cell division.

Figure 11.27

Cytokinesis. Following completion of mitosis (nuclear division), a contractile ring consisting of actin filaments and myosin II divides the cell in two.

http://www.ncbi.nlm.nih.gov/books/NBK9961/

2.  Use of Troponin(s) in Diagnosis

Troponins T and I are released into the circulation at the time of an acute coronary syndrome (ACS).  Troponin T was first introduced by Roche (developed in Germany) for the Roche platform as a superior biomarker for identifying acute myocardial infarction (AMI), because of a monoclonal specificity to the cardiac troponin T.  It could not be measured on any other platform (limited license patent), so the Washington University Clinical Chemistry group developed a myocardiocyte specific troponin I that quickly became widely available to Beckman, and was adapted to other instruments.  This was intended to replace the CK isoenzyme MB, that is highly elevated in rhabdomyolysis associated with sepsis or with anesthesia in special cases.

The troponins I and T had a tenfold scale difference, and the Receiver Operator Curve Generated cutoff was accurate for AMI, but had significant elevation with end-stage renal disease.  The industry worked in concert to develop a high sensitivity assay for each because there were some missed AMIs just below the ROC cutoff, which could be interpreted as Plaque Rupture.  However, the concept of plaque rupture had to be reconsidered, and we are left with type1 and type 2 AMI (disregarding the case of post PCI or CABG related).   This led to the current establishment of 3 standard deviations above the lowest measureable level at 10% coefficient of variation.  This has been discussed sufficiently elsewhere.  It did introduce a problem in the use of the test as a “silver bullet” once the finer distinctions aqnd the interest in using the test for prognosis as well as diagnosis.   This is where the use of another protein associated with heart failure came into play – either the B type natriuretic peptide, or its propeptide, N-terminal pro BNP.  The prognostic value of using these markers, secreted by the HEART and acting on the kidneys (sodium reabsorption) has proved useful.  But there has not been a multivariate refinement of the use of a two biomarker approach.  In the following part D, I illustrate what can be done with an algorithmic approach to multiple markers.

Software Agent for Diagnosis of AMI

Isaac E. Mayzlin, Ph.D., David Mayzlin, Larry H. Bernstein, M.D. The so called gold standard of proof of a method is considered the Receiver-Operating Characteristic Curve, developed for detecting “enemy planes or missiles”, and adopted first by radiologists in medicine.  This matches the correct “hits” to the actual calssification and it is generally taught as a plot of sensitivity vs (1 – specifity).  But what if you had no “training” variable?  Work inspired by Eugene Rypka’s bacterial classification led to Rosser Rudolph’s application of the Entropy of Shannon and Weaver to identify meaningful information, referring to what was Kullback-Liebler distance as “effective information”.  This allowed Rudolph and Bernstein to classify using disease biomarkers obtaing the same results as the ROC curve using an apl program.  The same data set was used by Bernstein, Adan et al. previously, and was again used by Izaak Mayzlin from University of Moscow with a new wrinkle.  Dr. Mayzlin created a neural network (Maynet), and then did a traditional NN with training on the data, and also clustered the data using geometric distance clustering and trained on the clusters.  It was interesting to see that the optimum cluster separation was closely related to the number of classes and the accuracy of classification.  An earlier simpler model using the slope of the MB isoenzyme increase and percent of total CK activity was perhaps related to Burton Sobel’s work on CK-MB disappearance rate for infarct size. The main process consists of three successive steps: (1)       clustering performed on training data set, (2)       neural network’s training on clusters from previous step, and (3)       classifier’s accuracy evaluation on testing data. The classifier in this research will be the ANN, created on step 2, with output in the range [0,1], that provides binary result (1 – AMI, 0 – not AMI), using decision point 0.5. Table  1.  Effect  of  selection  of  maximum  distance  on  the  number  of  classes  formed  and  on  the accuracy of recognition by ANN

Clustering Distance Factor F(D = F * R) Number ofClasses Number of Nodes in The Hidden Layers Number of Misrecognized Patterns inThe TestingSet of 43 Percent ofMisrecognized
10.90.80.7 2414135 1,  02,  03,  01,  02,  03,  0 3,  2 3,  2 121121 1 1 2.34.62.32.34.62.3 2.3 2.3

Creatine kinase B-subunit activity in serum in cases of suspected myocardial infarction: a prediction model based on the slope of MB increase and percentage CK-MB activity. L H Bernstein, G Reynoso Clin Chem 1983; 29(3):590-592 ICID: 825549 Diagnosis of acute myocardial infarction from two measurements of creatine kinase isoenzyme MB with use of nonparametric probability estimation. L H Bernstein, I J Good, G I Holtzman, M L Deaton, J Babb.  Clin Chem 1989; 35(3):444-447 ICID: 825570 – Information induction for predicting acute myocardial infarction. R A Rudolph, L H Bernstein, J Babb. Clin Chem 1988; 34(10):2031-2038 ICID: 825568

Related articles

Related articles published on this Open Access Online Scientific Journal, include the following:

Calcium Cycling (ATPase Pump) in Cardiac Gene Therapy: Inhalable Gene Therapy for Pulmonary Arterial Hypertension and Percutaneous Intra-coronary Artery Infusion for Heart Failure: Contributions by Roger J. Hajjar, MD

Aviva Lev-Ari, PhD, RN 8/1/2013

https://pharmaceuticalintelligence.com/2013/08/01/calcium-molecule-in-cardiac-gene-therapy-inhalable-gene-therapy-for-pulmonary-arterial-hypertension-and-percutaneous-intra-coronary-artery-infusion-for-heart-failure-contributions-by-roger-j-hajjar/

High-Sensitivity Cardiac Troponin Assays- Preparing the United States for High-Sensitivity Cardiac Troponin Assays

Larry Bernstein, MD, FCAP 6/13/2013

https://pharmaceuticalintelligence.com/2013/06/13/high-sensitivity-cardiac-troponin-assays/

Dealing with the Use of the High Sensitivity Troponin (hs cTn) Assays

Larry Bernstein and Aviva Lev-Ari  5/18/2013

https://pharmaceuticalintelligence.com/2013/05/18/dealing-with-the-use-of-the-hs-ctn-assays/

Acute Chest Pain/ER Admission: Three Emerging Alternatives to Angiography and PCI – Corus CAD, hs cTn, CCTA

Aviva Lev-Ari  3/10/2013

https://pharmaceuticalintelligence.com/2013/03/10/acute-chest-painer-admission-three-emerging-alternatives-to-angiography-and-pci/

  • Redberg’s conclusions are correct for the initial screening. The issue has been whether to do further testing for low or intermediate risk patients.
  • The most intriguing finding that is not at all surprising is that the CCTA added very little in the suspect group with small or moderate risk.
  • The ultra sensitive troponin threw the ROC out the window
  • The improved assay does pick up minor elevations of troponin in the absence of MI.

Critical Care | Abstract | Cardiac ischemia in patients with septic …
Aviva Lev-Ari  6/26/2013
https://pharmaceuticalintelligence.com/2013/06/26/critical-care-abstract-cardiac-ischemia-in-patients-with-septic/

  • refer to:  Cardiac ischemia in patients with septic shock randomized to vasopressin or norepinephrine

Mehta S, Granton J,  Gordon AC, Cook DJ, et al.
Critical Care 2013, 17:R117   http://dx.doi.org/10.1186/cc12789
Troponin and CK levels, and rates of ischemic ECG changes were similar in the VP and NE groups. In multivariable analysis

  • only APACHE II was associated with 28-day mortality (OR 1.07, 95% CI 1.01-1.14, p=0.033).

Assessing Cardiovascular Disease with Biomarkers

Larry H Bernstein, MD, FCAP 12/25/2012

https://pharmaceuticalintelligence.com/2012/12/25/assessing-cardiovascular-disease-with-biomarkers/

Vascular Medicine and Biology: CLASSIFICATION OF FAST ACTING THERAPY FOR PATIENTS AT HIGH RISK FOR MACROVASCULAR EVENTS Macrovascular Disease – Therapeutic Potential of cEPCs

Aviva Lev-Ari, PhD, RN 8/24/2012

https://pharmaceuticalintelligence.com/2012/08/24/vascular-medicine-and-biology-classification-of-fast-acting-therapy-for-patients-at-high-risk-for-macrovascular-events-macrovascular-disease-therapeutic-potential-of-cepcs/

 PENDING Integration

  • ‘Ryanopathy’: causes and manifestations of RyR2 dysfunction in heart failureCardiovasc Res. 2013;98:240-247,
  • Up-regulation of sarcoplasmic reticulum Ca2+ uptake leads to cardiac hypertrophy, contractile dysfunction and early mortality in mice deficient in CASQ2Cardiovasc Res. 2013;98:297-306,
  • Myocardial Delivery of Stromal Cell-Derived Factor 1 in Patients With Ischemic Heart Disease: Safe and PromisingCirc. Res.. 2013;112:746-747,
  • Circulation Research Thematic Synopsis: Cardiovascular GeneticsCirc. Res.. 2013;112:e34-e50,
  • Gene and cytokine therapy for heart failure: molecular mechanisms in the improvement of cardiac functionAm. J. Physiol. Heart Circ. Physiol.. 2012;303:H501-H512,
  • Ryanodine Receptor Phosphorylation and Heart Failure: Phasing Out S2808 and “Criminalizing” S2814Circ. Res.. 2012;110:1398-1402,

http://circres.ahajournals.org/content/110/5/777.figures-only

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