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Muscular dystrophy has deficient stem cell dystrophin

Posted in Biological Networks, Ca2+ triggered activation, Ca2+ triggered activation, Cell Biology, Signaling & Cell Circuits, Clinical Genomics, Curation, Developmental biology, Disease Biology, Gene Regulation, Genetics & Innovations in Treatment, Genetics & Pharmaceutical, Genome Biology, Inflammasome, Interviews with Scientific Leaders, Investment in Technological Breakthrough, MS, Neurodegenerative Diseases, Neurohumoral Transmission, Neurological Diseases, Neuroscience, Pharmaceutical Analytics, Pharmaceutical Discovery, Population genetics, Proteins, Proteomics, Regenerative Biology and Medicine, Regulated Clinical Trials: Design, Methods, Components and IRB related issues, Skeletal muscle regeneration, Stem Cells for Regenerative Medicine, tagged blocking cell differentiation, Ca2+-regulation, Clinical trial, dystrophin, genomic expression, Muscular dystrophy, skeletal and cardiomyocyte, Stem cell on November 21, 2015| Leave a Comment »

Muscular dystrophy has deficient stem cell dystrophin

Larry H. Bernstein, MD, FCAP, Curator

LPBI

Dystrophin Deficient Stem Cell Pathology

Muscular Dystrophy is a Stem Cell-Based Disease

November 19, 2015 by mburatov

https://beyondthedish.wordpress.com/2015/11/19/muscular-dystrophy-is-a-stem-cell-based-disease/

Michael Rudnicki, who has done pioneering work in muscle stem cell biology and muscle regeneration, and whose work has been featured several times on this blog, has struck again. Rudnicki, who serves as director of the Regenerative Medicine Program at The Ottawa Hospital and a professor at the University of Ottawa and holds the prestigious Canada Research Chair in Molecular Genetics, teamed up with workers from the Sprott Centre for Stem Cell Research and the Sinclair Centre for Regenerative Medicine to investigate the role of muscle-specific stem cells in patients who suffer from Duchenne muscular dystrophy. This new earth-shaking study, which was published in the journal Nature Medicine (November 16, 2015), has changed the way we think about muscular dystrophy and will almost certainly force people to rethink the treatments and cures for this dreadful disease.

According to this new study, Duchenne muscular dystrophy directly affects muscle stem cells, and is, largely a disease of muscle stem cells.

Rudicki said: “For nearly 20 years, we’ve thought that the muscle weakness observed in patients with Duchenne muscular dystrophy is primarily due to problems in their muscle fibers, but our research shows that it is also due to intrinsic defects in the function of their muscle stem cells. This completely changes our understanding of Duchenne muscular dystrophy and could eventually lead to far more effective treatments.”

Muscular dystrophy comes in several different forms, but the predominant sign of muscular dystrophy is progressive muscle weakness. Altogether, muscular dystrophy refers to a group of more than 30 genetic diseases, all of which cause progressive weakness and degeneration of skeletal muscles used during voluntary movement. Approximately half of all who suffer from muscular dystrophy have Duchenne muscular dystrophy (DMD). Because muscular dystrophy results from mutations in the dystrophin gene, which is on the X chromosome, the vast majority of muscular dystrophy patients are male. Girls can be carriers of muscular dystrophy and can be mildly affected.

Interestingly, somewhere around one-third of boys who suffer from DMD have no family history of the disease. Because the dystrophin gene is so large, spontaneous mutations in it are probably relatively common.

The signs and symptoms typically appear between the ages of 2 and 3, and may include frequent falls, difficulty getting up from a lying or sitting position, trouble running and jumping, a strange, shuffling way of walking or having a tendency to walk on their toes, calf muscles that are abnormally large, muscle pain and stiffness, and some learning disabilities.

Muscular dystrophy affects all ethnic groups and occurs globally. It affects around 1 in every 3,500 to 6,000 male births each year in the United States. DMD affects approximately one in 3,600 boys.

Because DMD results from mutations in the dystrophin gene, the vast majority of muscular dystrophy research was based on a simple model in which the Dystrophin protein played a structural role in the structural integrity of muscle fibers. Abnormal versions of the Dystrophin protein caused the muscle fibers to become damaged and die as a result of contraction. Dystrophin anchors the cytoskeleton of the muscle fibers, which are essential for muscle contraction, to the muscle cell membrane, and then to the extracellular matrix outside the cell that serves as a foundation upon which the muscle cells are built.

However in this current study, Rudnicki and his team discovered that muscle stem cells also express the dystrophin protein. This is a revelation because Dystrophin was thought to be protein that ONLY appeared in mature muscle. However, in this study, it became exceedingly clear that in the absence of Dystrophin, muscle stem cells generated ten-fold fewer muscle precursor cells, and, consequently, far fewer functional muscle fibers. Dystrophin is also a component of a signal transduction pathway that allows muscle stem cells to properly ascertain if they need to replace dead or dying muscle. Muscle stem cells repair the muscle in response to injury or exercise by dividing to generate precursor cells that differentiate into muscle fibers.

Even though Rudnicki used mice as a model system in these experiments, the Dystrophin protein is highly conserved in most vertebrate animals. Therefore, it is highly likely that these results will also apply to human muscle stem cells.

Gene therapy experiments and trials are in progress and even show some promise, but Rudnicki’s work tells us that gene therapy approaches must target muscle stem cells as well as muscle fibers if they are to work properly.

“We’re already looking at approaches to correct this problem in muscle stem cells,” said Dr. Rudnicki.

This paper has received high praise from the likes of Ronald Worton, who was one of the co-discovers of the dystrophin gene with Louis Kunkel in 1987.

Early pathogenesis of Duchenne muscular dystrophy modelled in patient-derived human induced pluripotent stem cells

Emi Shoji, Hidetoshi Sakurai, Tokiko Nishino, Tatsutoshi Nakahata, Toshio Heike, Tomonari Awaya, Nobuharu Fujii, Yasuko Manabe, Masafumi Matsuo & Atsuko Sehara-Fujisawa

Scientific Reports 5, Article number: 12831 (2015) http://dx.doi.org:/10.1038/srep12831

Duchenne muscular dystrophy (DMD) is a progressive and fatal muscle degenerating disease caused by a dystrophin deficiency. Effective suppression of the primary pathology observed in DMD is critical for treatment. Patient-derived human induced pluripotent stem cells (hiPSCs) are a promising tool for drug discovery. Here, we report an in vitro evaluation system for a DMD therapy using hiPSCs that recapitulate the primary pathology and can be used for DMD drug screening. Skeletal myotubes generated from hiPSCs are intact, which allows them to be used to model the initial pathology of DMD in vitro. Induced control and DMD myotubes were morphologically and physiologically comparable. However, electric stimulation of these myotubes for in vitro contraction caused pronounced calcium ion (Ca²⁺) influx only in DMD myocytes. Restoration of dystrophin by the exon-skipping technique suppressed this Ca²⁺ overflow and reduced the secretion of creatine kinase (CK) in DMD myotubes. These results suggest that the early pathogenesis of DMD can be effectively modelled in skeletal myotubes induced from patient-derived iPSCs, thereby enabling the development and evaluation of novel drugs.

Duchenne muscular dystrophy (DMD) is characterised by progressive muscle atrophy and weakness that eventually leads to ambulatory and respiratory deficiency from early childhood¹. It is an X-linked recessive inherited disease with a relatively high frequency of 1 in 3500 males^1,2.DMD, which is responsible for DMD, encodes 79 exons and produces dystrophin, which is one of the largest known cytoskeletal structural proteins³. Most DMD patients have various types of deletions or mutations in DMD that create premature terminations, resulting in a loss of protein expression⁴. Several promising approaches could be used to treat this devastating disease, such as mutation-specific drug exon-skipping^5,6, cell therapy⁷, and gene therapy^1,2.

Myoblasts from patients are the most common cell sources for assessing the disease phenotypes of DMD^11,12. …Previous reports have shown that muscle cell differentiation from DMD patient myoblasts is delayed and that these cells have poor proliferation capacity compared to those of healthy individuals^11,12. Our study revealed that control and DMD myoblasts obtained by activating tetracycline-dependent MyoD transfected into iPS cells (iPS^tet-MyoD cells) have comparable growth and differentiation potential and can produce a large number of intact and homogeneous myotubes repeatedly.

The pathogenesis of DMD is initiated and progresses with muscle contraction. The degree of muscle cell damage at the early stage of DMD can be evaluated by measuring the leakage of creatine kinase (CK) into the extracellular space¹⁵. Excess calcium ion (Ca²⁺) influx into skeletal muscle cells, together with increased susceptibility to plasma membrane injury, is regarded as the initial trigger of muscle damage in DMD^{19,20,21,22,23,24}. Targeting these early pathogenic events is considered essential for developing therapeutics for DMD.

In this study, we established a novel evaluation system to analyse the cellular basis of early DMD pathogenesis by comparing DMD myotubes with the same clone but with truncated dystrophin-expressing DMD myotubes, using the exon-skipping technique. We demonstrated through in vitro contraction that excessive Ca²⁺ influx is one of the earliest events to occur in intact dystrophin-deficient muscle leading to extracellular leakage of CK in DMD myotubes.

Generation of tetracycline-inducible MyoD-transfected DMD patient-derived iPSCs (iPS^tet-MyoD cells)

Figure 1: Generation and characterization of control and DMD patient-derived Tet-MyoD-transfected hiPS cells. Full size image

Morphologically and physiologically comparable intact myotubes differentiated from control and DMD-derived hiPSCs

Figure 2: Morphologically and physiologically comparable skeletal muscle cells differentiated from Control-iPS^tet-MyoD and DMD-iPS^tet-MyoD. Full size image

Exon-skipping with AO88 restored expression of Dystrophin in DMD myotubes differentiated from DMD-iPS^tet-MyoD cells

Figure 3: Restoration of dystrophin protein expression by AO88. Full size image

Restored dystrophin expression attenuates Ca²⁺ overflow in DMD-Myocytes

Figure 4: Restored expression of dystrophin diminishes Ca²⁺ influx in DMD muscle in response to electric stimulation. Full size image

Ca²⁺ influx provokes skeletal muscle cellular damage in DMD muscle

Figure 5: Ca²⁺ influx induces prominent skeletal muscle cellular damage in DMD-Myocytes. Full size image

Skeletal muscle differentiation in myoblasts from DMD patients is generally delayed compared to that in healthy individuals^11,36,37. Our differentiation system successfully induced the formation of myotubes from DMD patients, and the myotubes displayed analogous morphology and maturity compared with control myotubes (Fig. 2a–c). Comparing myotubes generated from patient-derived iPS cells with those derived from the same DMD clones but expressing dystrophin by application of the exon-skipping technique enabled us to demonstrate the primary cellular phenotypes in skeletal muscle solely resulting from the loss of the dystrophin protein (Fig. 4b). Our results demonstrate that truncated but functional dystrophin protein expression improved the cellular phenotype of DMD myotubes.

In DMD, the lack of dystrophin induces an excess influx of Ca²⁺ , leading to pathological dystrophic changes²². We consistently observed excess Ca²⁺ influx in DMD-Myocytes compared to Control-Myocytes (Supplementary Figure S3a and S3b) in response to electric stimulation. TRP channels, which are mechanical stimuli-activated Ca²⁺ channels⁴⁰that are expressed in skeletal muscle cells⁴¹, can account for this pathogenic Ca²⁺ influx…

In conclusion, our study revealed that the absence of dystrophin protein induces skeletal muscle damage by allowing excess Ca²⁺ influx in DMD myotubes. Our experimental system recapitulated the early phase of DMD pathology as demonstrated by visualisation and quantification of Ca²⁺ influx using intact myotubes differentiated from hiPS cells. This evaluation system significantly expands prospective applications with regard to assessing the effectiveness of exon-skipping drugs and also enables the discovery of drugs that regulate the initial events in DMD.

Duchenne muscular dystrophy affects stem cells, University of Ottawa study finds

New treatments could one day be available for the most common form of muscular dystrophy after a study suggests the debilitating genetic disease affects the stem cells that produce healthy muscle fibres.

The findings are based on research from the University of Ottawa and The Ottawa Hospital, published Monday in the journal Nature Medicine.

For nearly two decades, doctors had thought the muscular weakness that is the hallmark of the disease was due to problems with human muscle fibers, said Dr. Michael Rudnicki, the study’s senior author.

The new research shows the specific protein characterized by its absence in Duchenne muscular dystrophy normally exists in stem cells.

Dystrophin protein found in stem cells

“The prevailing notion was that the protein that’s missing in Duchenne muscular dystrophy — a protein called dystrophin — was not involved at all in the function of the stem cells.”

http://soundcloud.com/cbcottawa1

When the genetic mutations caused by Duchenne muscular dystrophy inhibit the production of dystrophin in stem cells, those stem cells produce significantly fewer precursor cells — and thus fewer properly functioning muscle fibres. Further, stem cells need dystrophin to sense their environment to figure out if they need to divide to produce more stem cells or perform muscle repair work.

Genetic repair might treat Duchenne muscular dystrophy

July 25, 2011|By Thomas H. Maugh II, Los Angeles Times

A genetic technique that allows the body to work around a crucial mutation that causes Duchenne muscular dystrophy increased the mass and function of muscles in a small group of patients with the devastating disease, paving the way for larger clinical trials of the drug. The study in a handful of boys age 5 to 15 showed that patients receiving the highest level of the drug, called AVI-4658 or eteplirsen, had a significant increase in production of a missing protein and increases in muscle fibers. The study demonstrated that the drug is safe in the short term. Results were reported Sunday in the journal Lancet.

Duchenne muscular dystrophy affects about one in every 3,500 males worldwide. It is caused by any one of several different mutations that affect production of a protein called dystrophin, which is important for the production and maintenance of muscle fibers. Affected patients become unable to walk and must use a wheelchair by age 8 to 12. Deterioration continues through their teens and 20s, and the condition typically proves fatal as muscle failure impairs their ability to breathe.

This study is designed to assess the efficacy, safety, tolerability, and pharmacokinetics (PK) of AVI-4658 (eteplirsen) in both 50.0 mg/kg and 30.0 mg/kg doses administered over 24 weeks in subjects diagnosed with Duchenne muscular dystrophy (DMD).

Condition	Intervention	Phase
Duchenne Muscular Dystrophy	Drug: AVI-4658 (Eteplirsen) Other: Placebo	Phase 2

Study Type:	Interventional
Study Design:	Allocation: Randomized Endpoint Classification: Safety/Efficacy Study Intervention Model: Parallel Assignment Masking: Double Blind (Subject, Caregiver, Investigator, Outcomes Assessor) Primary Purpose: Treatment
Official Title:	A Randomized, Double-Blind, Placebo-Controlled, Multiple Dose Efficacy, Safety, Tolerability and Pharmacokinetics Study of AVI-4658(Eteplirsen),in the Treatment of Ambulant Subjects With Duchenne Muscular Dystrophy

Resource links provided by NLM:

Genetics Home Reference related topics: Duchenne and Becker muscular dystrophy

MedlinePlus related topics: Muscular Dystrophy

Genetic and Rare Diseases Information Center resources: Becker Muscular Dystrophy Duchenne Muscular Dystrophy Muscular Dystrophy

U.S. FDA Resources

Dystrophin expression in muscle stem cells regulates their polarity and asymmetric division

Nicolas A Dumont, Yu Xin Wang, Julia von Maltzahn, Alessandra Pasut, C Florian Bentzinger, Caroline E Brun & Michael A Rudnicki

Nature Medicine(2015) http://dx.doi.org:/10.1038/nm.3990

Dystrophin is expressed in differentiated myofibers, in which it is required for sarcolemmal integrity, and loss-of-function mutations in the gene that encodes it result in Duchenne muscular dystrophy (DMD), a disease characterized by progressive and severe skeletal muscle degeneration. Here we found that dystrophin is also highly expressed in activated muscle stem cells (also known as satellite cells), in which it associates with the serine-threonine kinase Mark2 (also known as Par1b), an important regulator of cell polarity. In the absence of dystrophin, expression of Mark2 protein is downregulated, resulting in the inability to localize the cell polarity regulator Pard3 to the opposite side of the cell. Consequently, the number of asymmetric divisions is strikingly reduced in dystrophin-deficient satellite cells, which also display a loss of polarity, abnormal division patterns (including centrosome amplification), impaired mitotic spindle orientation and prolonged cell divisions. Altogether, these intrinsic defects strongly reduce the generation of myogenic progenitors that are needed for proper muscle regeneration. Therefore, we conclude that dystrophin has an essential role in the regulation of satellite cell polarity and asymmetric division. Our findings indicate that muscle wasting in DMD not only is caused by myofiber fragility, but also is exacerbated by impaired regeneration owing to intrinsic satellite cell dysfunction.

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Summary of Signaling and Signaling Pathways

Posted in Academic Publishing, Alzheimer's Disease, Best evidence, Biochemical pathways, Bone Disease and Musculoskeletal Disease, Ca2+ triggered activation, Calcium Signaling, Calmodulin Kinase and Contraction, Cardiac muscle regeneration, Cardiomyopathy, Cardiovascular Research, Cerebrovascular and Neurodegenerative Diseases, Chemical Biology and its relations to Metabolic Disease, Curation, Cytoskeleton, Developmental biology, Dialectic, Discovery process, Disease Biology, Electrophysiology, Endocrine Diseases, Enzyme Induction, Epigenetics and Cardiovascular Risks, Experimental validation, Explanatory, Fatty acids, Frontiers in Cardiology and Cardiovascular Disorders, Gene Regulation, Genomic Expression, Human Immune System in Health and in Disease, Inferential analysis, Kinase, Lipid metabolism, Lipids, Mechanical Assist Devices: LVAD, Metabolism, Metabolomics, Mg++, MS, Mutant Gene Expression, Myocardial Metabolism, Neurohumoral Transmission, Neurological Diseases, Nitric Oxide in Health and Disease, Nutrition, Nutritional Supplements: Atherogenesis, Pharmaceutical Analytics, Pharmaceutical Discovery, Pharmaceutical R&D Investment, Pharmacodynamics and Pharmacokinetics, Phosphorylase, Phosphorylation, PKC, Population Health Management, Proteins, Proteomics, RNA Biology, Signaling, Signaling & Cell Circuits, Skeletal muscle regeneration, Small Molecules in Development of Therapeutic Drugs, Systemic Inflammatory Response Related Disorders, Transcriptomics, Translational Research, Translational Science, Ubiquitinylation, tagged Alzheimers Disease, a_b catenin, cell signaling, Cytoskeleton, Extracellular matrix, G-protein coupled receptors (GPCR), integrin, intracellular localization, myasthenia gravis, N-glycosylation, neuroendocrine signal, Neuroendocrine Transcriptome, nuclear receptor, Phosphorylation, protein signals, Receptor tyrosine kinases, second messenger, signaling, signaling cascades, transduction, Tyrosine Kinase, zinc on November 1, 2014| Leave a Comment »

Summary of Signaling and Signaling Pathways

Author and Curator: Larry H Bernstein, MD, FCAP

In the imtroduction to this series of discussions I pointed out JEDS Rosalino’s observation about the construction of a complex molecule of acetyl coenzyme A, and the amount of genetic coding that had to go into it. Furthermore, he observes – Millions of years later, or as soon as, the information of interaction leading to activity and regulation could be found in RNA, proteins like reverse transcriptase move this information to a more stable form (DNA). In this way it is easier to understand the use of CoA to make two carbon molecules more reactive.

acetylCoA

In the tutorial that follows we find support for the view that mechanisms and examples from the current literature, which give insight into the developments in cell metabolism, are achieving a separation from inconsistent views introduced by the classical model of molecular biology and genomics, toward a more functional cellular dynamics that is not dependent on the classic view. The classical view fits a rigid framework that is to genomics and metabolomics as Mendelian genetics if to multidimentional, multifactorial genetics. The inherent difficulty lies in two places:

Interactions between differently weighted determinants
A large part of the genome is concerned with regulatory function, not expression of the code

The goal of the tutorial was to achieve an understanding of how cell signaling occurs in a cell. Completion of the tutorial would provide

a basic understanding signal transduction and
the role of phosphorylation in signal transduction.

Regulation of the integrity of endothelial cell–cell contacts by phosphorylation of VE-cadherin

In addition – detailed knowledge of –

the role of Tyrosine kinases and
G protein-coupled receptors in cell signaling.

serine

threonine

protein kinase

We are constantly receiving and interpreting signals from our environment, which can come

in the form of light, heat, odors, touch or sound.

The cells of our bodies are also

constantly receiving signals from other cells.

These signals are important to

keep cells alive and functioning as well as
to stimulate important events such as
cell division and differentiation.

Signals are most often chemicals that can be found

in the extracellular fluid around cells.

These chemicals can come

from distant locations in the body (endocrine signaling by hormones), from
nearby cells (paracrine signaling) or can even
be secreted by the same cell (autocrine signaling).

Signaling molecules may trigger any number of cellular responses, including

changing the metabolism of the cell receiving the signal or
result in a change in gene expression (transcription) within the nucleus of the cell or both.

controlling the output of ribosomes.

To which I would now add..

result in either an inhibitory or a stimulatory effect

The three stages of cell signaling are:

Cell signaling can be divided into 3 stages:

Reception: A cell detects a signaling molecule from the outside of the cell.

Transduction: When the signaling molecule binds the receptor it changes the receptor protein in some way. This change initiates the process of transduction. Signal transduction is usually a pathway of several steps. Each relay molecule in the signal transduction pathway changes the next molecule in the pathway.

Response: Finally, the signal triggers a specific cellular response.

signal transduction

http://www.hartnell.edu/tutorials/biology/images/signaltransduction_simple.jpg

The initiation is depicted as follows:

Signal Transduction – ligand binds to surface receptor

Membrane receptors function by binding the signal molecule (ligand) and causing the production of a second signal (also known as a second messenger) that then causes a cellular response. These types of receptors transmit information from the extracellular environment to the inside of the cell.

by changing shape or
by joining with another protein
once a specific ligand binds to it.

Examples of membrane receptors include

G Protein-Coupled Receptors and

Understanding these receptors and identifying their ligands and the resulting signal transduction pathways represent a major conceptual advance.

Receptor Tyrosine Kinases.

intracellular signaling

http://www.hartnell.edu/tutorials/biology/images/membrane_receptor_tk.jpg

Intracellular receptors are found inside the cell, either in the cytopolasm or in the nucleus of the target cell (the cell receiving the signal).

Note that though change in gene expression is stated, the change in gene expression does not here imply a change in the genetic information – such as – mutation. That does not have to be the case in the normal homeostatic case.

This point is the differentiating case between what JEDS Roselino has referred as

a fast, adaptive reaction, that is the feature of protein molecules, and distinguishes this interaction from
a one-to-one transcription of the genetic code.

The rate of transcription can be controlled, or it can be blocked. This is in large part in response to the metabolites in the immediate interstitium.

This might only be

a change in the rate of a transcription or a suppression of expression through RNA.
Or through a conformational change in an enzyme

Swinging domains in HECT E3 enzymes

Since signaling systems need to be

responsive to small concentrations of chemical signals and act quickly,
cells often use a multi-step pathway that transmits the signal quickly,
while amplifying the signal to numerous molecules at each step.

Signal transduction pathways are shown (simplified):

Signal Transduction

Signal transduction occurs when an

extracellular signaling molecule activates a specific receptor located on the cell surface or inside the cell.
In turn, this receptor triggers a biochemical chain of events inside the cell, creating a response.
Depending on the cell, the response alters the cell’s metabolism, shape, gene expression, or ability to divide.
The signal can be amplified at any step. Thus, one signaling molecule can cause many responses.

In 1970, Martin Rodbell examined the effects of glucagon on a rat’s liver cell membrane receptor. He noted that guanosine triphosphate disassociated glucagon from this receptor and stimulated the G-protein, which strongly influenced the cell’s metabolism. Thus, he deduced that the G-protein is a transducer that accepts glucagon molecules and affects the cell. For this, he shared the 1994 Nobel Prize in Physiology or Medicine with Alfred G. Gilman.

Guanosine monophosphate structure

In 2007, a total of 48,377 scientific papers—including 11,211 e-review papers—were published on the subject. The term first appeared in a paper’s title in 1979. Widespread use of the term has been traced to a 1980 review article by Rodbell: Research papers focusing on signal transduction first appeared in large numbers in the late 1980s and early 1990s.

Signal transduction involves the binding of extracellular signaling molecules and ligands to cell-surface receptors that trigger events inside the cell. The combination of messenger with receptor causes a change in the conformation of the receptor, known as receptor activation.

This activation is always the initial step (the cause) leading to the cell’s ultimate responses (effect) to the messenger. Despite the myriad of these ultimate responses, they are all directly due to changes in particular cell proteins. Intracellular signaling cascades can be started through cell-substratum interactions; examples are the integrin that binds ligands in the extracellular matrix and steroids.

Integrin

Most steroid hormones have receptors within the cytoplasm and act by stimulating the binding of their receptors to the promoter region of steroid-responsive genes.

steroid hormone receptor

Various environmental stimuli exist that initiate signal transmission processes in multicellular organisms; examples include photons hitting cells in the retina of the eye, and odorants binding to odorant receptors in the nasal epithelium. Certain microbial molecules, such as viral nucleotides and protein antigens, can elicit an immune system response against invading pathogens mediated by signal transduction processes. This may occur independent of signal transduction stimulation by other molecules, as is the case for the toll-like receptor. It may occur with help from stimulatory molecules located at the cell surface of other cells, as with T-cell receptor signaling. Receptors can be roughly divided into two major classes: intracellular receptors and extracellular receptors.

Signal transduction cascades amplify the signal output

G protein-coupled receptors (GPCRs) are a family of integral transmembrane proteins that possess seven transmembrane domains and are linked to a heterotrimeric G protein. Many receptors are in this family, including adrenergic receptors and chemokine receptors.

Arrestin binding to active GPCR kinase (GRK)-phosphorylated GPCRs blocks G protein coupling

signal transduction pathways

Arrestin binding to active GPCR kinase (GRK)-phosphorylated GPCRs blocks G protein coupling

Signal transduction by a GPCR begins with an inactive G protein coupled to the receptor; it exists as a heterotrimer consisting of Gα, Gβ, and Gγ. Once the GPCR recognizes a ligand, the conformation of the receptor changes to activate the G protein, causing Gα to bind a molecule of GTP and dissociate from the other two G-protein subunits.

The dissociation exposes sites on the subunits that can interact with other molecules. The activated G protein subunits detach from the receptor and initiate signaling from many downstream effector proteins such as phospholipases and ion channels, the latter permitting the release of second messenger molecules.

Receptor tyrosine kinases (RTKs) are transmembrane proteins with an intracellular kinase domain and an extracellular domain that binds ligands; examples include growth factor receptors such as the insulin receptor.

insulin receptor and and insulin receptor signaling pathway (IRS)

To perform signal transduction, RTKs need to form dimers in the plasma membrane; the dimer is stabilized by ligands binding to the receptor.

RTKs

The interaction between the cytoplasmic domains stimulates the autophosphorylation of tyrosines within the domains of the RTKs, causing conformational changes.

Subsequent to this, the receptors’ kinase domains are activated, initiating phosphorylation signaling cascades of downstream cytoplasmic molecules that facilitate various cellular processes such as cell differentiation and metabolism.

Signal-Transduction-Pathway

As is the case with GPCRs, proteins that bind GTP play a major role in signal transduction from the activated RTK into the cell. In this case, the G proteins are

members of the Ras, Rho, and Raf families, referred to collectively as small G proteins.

They act as molecular switches usually

tethered to membranes by isoprenyl groups linked to their carboxyl ends.

Upon activation, they assign proteins to specific membrane subdomains where they participate in signaling. Activated RTKs in turn activate

small G proteins that activate guanine nucleotide exchange factors such as SOS1.

Once activated, these exchange factors can activate more small G proteins, thus

amplifying the receptor’s initial signal.

The mutation of certain RTK genes, as with that of GPCRs, can result in the expression of receptors that exist in a constitutively activate state; such mutated genes may act as oncogenes.

Integrin

Integrin

Integrin-mediated signal transduction

An overview of integrin-mediated signal transduction, adapted from Hehlgens et al. (2007).

Integrins are produced by a wide variety of cells; they play a role in

cell attachment to other cells and the extracellular matrix and
in the transduction of signals from extracellular matrix components such as fibronectin and collagen.

Ligand binding to the extracellular domain of integrins

changes the protein’s conformation,
clustering it at the cell membrane to
initiate signal transduction.

Integrins lack kinase activity; hence, integrin-mediated signal transduction is achieved through a variety of intracellular protein kinases and adaptor molecules, the main coordinator being integrin-linked kinase.

As shown in the picture, cooperative integrin-RTK signaling determines the

timing of cellular survival,
apoptosis,
proliferation, and
differentiation.

integrin-mediated signal transduction

Integrin signaling

ion channel

A ligand-gated ion channel, upon binding with a ligand, changes conformation

to open a channel in the cell membrane
through which ions relaying signals can pass.

An example of this mechanism is found in the receiving cell of a neural synapse. The influx of ions that occurs in response to the opening of these channels

induces action potentials, such as those that travel along nerves,
by depolarizing the membrane of post-synaptic cells,
resulting in the opening of voltage-gated ion channels.

RyR and Ca+ release from SR

An example of an ion allowed into the cell during a ligand-gated ion channel opening is Ca2+;

it acts as a second messenger
initiating signal transduction cascades and
altering the physiology of the responding cell.

This results in amplification of the synapse response between synaptic cells

by remodelling the dendritic spines involved in the synapse.

In eukaryotic cells, most intracellular proteins activated by a ligand/receptor interaction possess an enzymatic activity; examples include tyrosine kinase and phosphatases. Some of them create second messengers such as cyclic AMP and IP3,

cAMP

Inositol_1,4,5-trisphosphate.svg

the latter controlling the release of intracellular calcium stores into the cytoplasm.

Many adaptor proteins and enzymes activated as part of signal transduction possess specialized protein domains that bind to specific secondary messenger molecules. For example,

calcium ions bind to the EF hand domains of calmodulin,
allowing it to bind and activate calmodulin-dependent kinase.

calcium movement and RyR2 receptor

PIP3 and other phosphoinositides do the same thing to the Pleckstrin homology domains of proteins such as the kinase protein AKT.

Signals can be generated within organelles, such as chloroplasts and mitochondria, modulating the nuclear
gene expression in a process called retrograde signaling.

Recently, integrative genomics approaches, in which correlation analysis has been applied on transcript and metabolite profiling data of Arabidopsis thaliana, revealed the identification of metabolites which are putatively acting as mediators of nuclear gene expression.

http://fpls.com/unraveling_retrograde_signaling_pathways:_finding_candidate_signaling_molecules_via_metabolomics_and_systems_biology_driven_approaches

Systems Biology Approach Reveals Genome to Phenome Correlation in Type 2 Diabetes (plosone.org)
Gene Expression and Thiopurine Metabolite Profiling in Inflammatory Bowel Disease – Novel Clues to Drug Targets and Disease Mechanisms? (plosone.org)
Activation of the Jasmonic Acid Plant Defence Pathway Alters the Composition of Rhizosphere

Nutrients 2014, 6, 3245-3258; http://dx.doi.org:/10.3390/nu6083245

Omega-3 (ω-3) fatty acids are one of the two main families of long chain polyunsaturated fatty acids (PUFA). The main omega-3 fatty acids in the mammalian body are

α-linolenic acid (ALA), docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA).

Central nervous tissues of vertebrates are characterized by a high concentration of omega-3 fatty acids. Moreover, in the human brain,

DHA is considered as the main structural omega-3 fatty acid, which comprises about 40% of the PUFAs in total.

DHA deficiency may be the cause of many disorders such as depression, inability to concentrate, excessive mood swings, anxiety, cardiovascular disease, type 2 diabetes, dry skin and so on.

On the other hand,

zinc is the most abundant trace metal in the human brain.

There are many scientific studies linking zinc, especially

excess amounts of free zinc, to cellular death.

Neurodegenerative diseases, such as Alzheimer’s disease, are characterized by altered zinc metabolism. Both animal model studies and human cell culture studies have shown a possible link between

omega-3 fatty acids, zinc transporter levels and
free zinc availability at cellular levels.

Many other studies have also suggested a possible

omega-3 and zinc effect on neurodegeneration and cellular death.

Therefore, in this review, we will examine

the effect of omega-3 fatty acids on zinc transporters and
the importance of free zinc for human neuronal cells.

Moreover, we will evaluate the collective understanding of

mechanism(s) for the interaction of these elements in neuronal research and their
significance for the diagnosis and treatment of neurodegeneration.

Epidemiological studies have linked high intake of fish and shellfish as part of the daily diet to

reduction of the incidence and/or severity of Alzheimer’s disease (AD) and senile mental decline in

Omega-3 fatty acids are one of the two main families of a broader group of fatty acids referred to as polyunsaturated fatty acids (PUFAs). The other main family of PUFAs encompasses the omega-6 fatty acids. In general, PUFAs are essential in many biochemical events, especially in early post-natal development processes such as

cellular differentiation,
photoreceptor membrane biogenesis and
active synaptogenesis.

Despite the significance of these

two families, mammals cannot synthesize PUFA de novo, so they must be ingested from dietary sources. Though belonging to the same family, both

omega-3 and omega-6 fatty acids are metabolically and functionally distinct and have
opposing physiological effects. In the human body,
high concentrations of omega-6 fatty acids are known to increase the formation of prostaglandins and
thereby increase inflammatory processes [10].

the reverse process can be seen with increased omega-3 fatty acids in the body.

Many other factors, such as

thromboxane A2 (TXA2),
leukotriene
B4 (LTB4),
IL-1,
IL-6,
tumor necrosis factor (TNF) and
C-reactive protein,

which are implicated in various health conditions, have been shown to be increased with high omega-6 fatty acids but decreased with omega-3 fatty acids in the human body.

Dietary fatty acids have been identified as protective factors in coronary heart disease, and PUFA levels are known to play a critical role in

immune responses,
gene expression and
intercellular communications.

omega-3 fatty acids are known to be vital in

the prevention of fatal ventricular arrhythmias, and
are also known to reduce thrombus formation propensity by decreasing platelet aggregation, blood viscosity and fibrinogen levels

.Since omega-3 fatty acids are prevalent in the nervous system, it seems logical that a deficiency may result in neuronal problems, and this is indeed what has been identified and reported.

The main

In another study conducted with individuals of 65 years of age or older (n = 6158), it was found that

only high fish consumption, but
not dietary omega-3 acid intake,
had a protective effect on cognitive decline

In 2005, based on a meta-analysis of the available epidemiology and preclinical studies, clinical trials were conducted to assess the effects of omega-3 fatty acids on cognitive protection. Four of the trials completed have shown

a protective effect of omega-3 fatty acids only among those with mild cognitive impairment conditions.

A trial of subjects with mild memory complaints demonstrated

an improvement with 900 mg of DHA.

We review key findings on

the effect of the omega-3 fatty acid DHA on zinc transporters and the
importance of free zinc to human neuronal cells.

DHA is the most abundant fatty acid in neural membranes, imparting appropriate

fluidity and other properties,

and is thus considered as the most important fatty acid in neuronal studies. DHA is well conserved throughout the mammalian species despite their dietary differences. It is mainly concentrated

in membrane phospholipids at synapses and
in retinal photoreceptors and
also in the testis and sperm.

In adult rats’ brain, DHA comprises approximately

17% of the total fatty acid weight, and
in the retina it is as high as 33%.

DHA is believed to have played a major role in the evolution of the modern human –

in particular the well-developed brain.

Premature babies fed on DHA-rich formula show improvements in vocabulary and motor performance.

Analysis of human cadaver brains have shown that

people with AD have less DHA in their frontal lobe
and hippocampus compared with unaffected individuals

Furthermore, studies in mice have increased support for the

protective role of omega-3 fatty acids.

Mice administrated with a dietary intake of DHA showed

an increase in DHA levels in the hippocampus.

Errors in memory were decreased in these mice and they demonstrated

reduced peroxide and free radical levels,
suggesting a role in antioxidant defense.

Another study conducted with a Tg2576 mouse model of AD demonstrated that dietary

DHA supplementation had a protective effect against reduction in
drebrin (actin associated protein), elevated oxidation, and to some extent, apoptosis via
decreased caspase activity.

Zinc

Zinc is a trace element, which is indispensable for life, and it is the second most abundant trace element in the body. It is known to be related to

growth,
development,
differentiation,
immune response,
receptor activity,
DNA synthesis,
gene expression,
neuro-transmission,
enzymatic catalysis,
hormonal storage and release,
tissue repair,
memory,
the visual process

and many other cellular functions. Moreover, the indispensability of zinc to the body can be discussed in many other aspects, as

a component of over 300 different enzymes
an integral component of a metallothioneins
a gene regulatory protein.

Approximately 3% of all proteins contain

zinc binding motifs .

The broad biological functionality of zinc is thought to be due to its stable chemical and physical properties. Zinc is considered to have three different functions in enzymes;

catalytic,
coactive and

Indeed, it is the only metal found in all six different subclasses

of enzymes. The essential nature of zinc to the human body can be clearly displayed by studying the wide range of pathological effects of zinc deficiency. Anorexia, embryonic and post-natal growth retardation, alopecia, skin lesions, difficulties in wound healing, increased hemorrhage tendency and severe reproductive abnormalities, emotional instability, irritability and depression are just some of the detrimental effects of zinc deficiency.

Proper development and function of the central nervous system (CNS) is highly dependent on zinc levels. In the mammalian organs, zinc is mainly concentrated in the brain at around 150 μm. However, free zinc in the mammalian brain is calculated to be around 10 to 20 nm and the rest exists in either protein-, enzyme- or nucleotide bound form. The brain and zinc relationship is thought to be mediated

through glutamate receptors, and
it inhibits excitatory and inhibitory receptors.

Vesicular localization of zinc in pre-synaptic terminals is a characteristic feature of brain-localized zinc, and

its release is dependent on neural activity.

Retardation of the growth and development of CNS tissues have been linked to low zinc levels. Peripheral neuropathy, spina bifida, hydrocephalus, anencephalus, epilepsy and Pick’s disease have been linked to zinc deficiency. However, the body cannot tolerate excessive amounts of zinc.

The relationship between zinc and neurodegeneration, specifically AD, has been interpreted in several ways. One study has proposed that β-amyloid has a greater propensity to

form insoluble amyloid in the presence of
high physiological levels of zinc.

Insoluble amyloid is thought to

aggregate to form plaques,

which is a main pathological feature of AD. Further studies have shown that

chelation of zinc ions can deform and disaggregate plaques.

In AD, the most prominent injuries are found in

hippocampal pyramidal neurons, acetylcholine-containing neurons in the basal forebrain, and in
somatostatin-containing neurons in the forebrain.

All of these neurons are known to favor

rapid and direct entry of zinc in high concentration
leaving neurons frequently exposed to high dosages of zinc.

This is thought to promote neuronal cell damage through oxidative stress and mitochondrial dysfunction. Excessive levels of zinc are also capable of

inhibiting Ca2+ and Na+ voltage gated channels
and up-regulating the cellular levels of reactive oxygen species (ROS).

High levels of zinc are found in Alzheimer’s brains indicating a possible zinc related neurodegeneration. A study conducted with mouse neuronal cells has shown that even a 24-h exposure to high levels of zinc (40 μm) is sufficient to degenerate cells.

If the human diet is deficient in zinc, the body

efficiently conserves zinc at the tissue level by compensating other cellular mechanisms

to delay the dietary deficiency effects of zinc. These include reduction of cellular growth rate and zinc excretion levels, and

redistribution of available zinc to more zinc dependent cells or organs.

A novel method of measuring metallothionein (MT) levels was introduced as a biomarker for the

assessment of the zinc status of individuals and populations.

In humans, erythrocyte metallothionein (E-MT) levels may be considered as an indicator of zinc depletion and repletion, as E-MT levels are sensitive to dietary zinc intake. It should be noted here that MT plays an important role in zinc homeostasis by acting

as a target for zinc ion binding and thus
assisting in the trafficking of zinc ions through the cell,
which may be similar to that of zinc transporters

Zinc Transporters

Deficient or excess amounts of zinc in the body can be catastrophic to the integrity of cellular biochemical and biological systems. The gastrointestinal system controls the absorption, excretion and the distribution of zinc, although the hydrophilic and high-charge molecular characteristics of zinc are not favorable for passive diffusion across the cell membranes. Zinc movement is known to occur

via intermembrane proteins and zinc transporter (ZnT) proteins

These transporters are mainly categorized under two metal transporter families; Zip (ZRT, IRT like proteins) and CDF/ZnT (Cation Diffusion Facilitator), also known as SLC (Solute Linked Carrier) gene families: Zip (SLC-39) and ZnT (SLC-30). More than 20 zinc transporters have been identified and characterized over the last two decades (14 Zips and 8 ZnTs).

Members of the SLC39 family have been identified as the putative facilitators of zinc influx into the cytosol, either from the extracellular environment or from intracellular compartments (Figure 1).

The identification of this transporter family was a result of gene sequencing of known Zip1 protein transporters in plants, yeast and human cells. In contrast to the SLC39 family, the SLC30 family facilitates the opposite process, namely zinc efflux from the cytosol to the extracellular environment or into luminal compartments such as secretory granules, endosomes and synaptic vesicles; thus decreasing intracellular zinc availability (Figure 1). ZnT3 is the most important in the brain where

it is responsible for the transport of zinc into the synaptic vesicles of
glutamatergic neurons in the hippocampus and neocortex,

Figure 1: Subcellular localization and direction of transport of the zinc transporter families, ZnT and ZIP. Arrows show the direction of zinc mobilization for the ZnT (green) and ZIP (red) proteins. A net gain in cytosolic zinc is achieved by the transportation of zinc from the extracellular region and organelles such as the endoplasmic reticulum (ER) and Golgi apparatus by the ZIP transporters. Cytosolic zinc is mobilized into early secretory compartments such as the ER and Golgi apparatus by the ZnT transporters. Figures were produced using Servier Medical Art, http://www.servier.com/. http://www.hindawi.com/journals/jnme/2012/173712.fig.001.jpg

Figure 2: Early zinc signaling (EZS) and late zinc signaling (LZS). EZS involves transcription-independent mechanisms where an extracellular stimulus directly induces an increase in zinc levels within several minutes by releasing zinc from intracellular stores (e.g., endoplasmic reticulum). LSZ is induced several hours after an external stimulus and is dependent on transcriptional changes in zinc transporter expression. Components of this figure were produced using Servier Medical Art, http://www.servier.com/ and adapted from Fukada et al. [30].

omega-3 fatty acids in the mammalian body are

α-linolenic acid (ALA),
docosahexenoic acid (DHA) and
eicosapentaenoic acid (EPA).

In general, seafood is rich in omega-3 fatty acids, more specifically DHA and EPA (Table 1). Thus far, there are nine separate epidemiological studies that suggest a possible link between

increased fish consumption and reduced risk of AD
and eight out of ten studies have reported a link between higher blood omega-3 levels

DHA and Zinc Homeostasis

Many studies have identified possible associations between DHA levels, zinc homeostasis, neuroprotection and neurodegeneration. Dietary DHA deficiency resulted in

increased zinc levels in the hippocampus and
elevated expression of the putative zinc transporter, ZnT3, in the rat brain.

Altered zinc metabolism in neuronal cells has been linked to neurodegenerative conditions such as AD. A study conducted with transgenic mice has shown a significant link between ZnT3 transporter levels and cerebral amyloid plaque pathology. When the ZnT3 transporter was silenced in transgenic mice expressing cerebral amyloid plaque pathology,

a significant reduction in plaque load
and the presence of insoluble amyloid were observed.

In addition to the decrease in plaque load, ZnT3 silenced mice also exhibited a significant

reduction in free zinc availability in the hippocampus
and cerebral cortex.

Collectively, the findings from this study are very interesting and indicate a clear connection between

zinc availability and amyloid plaque formation,

thus indicating a possible link to AD.

DHA supplementation has also been reported to limit the following:

amyloid presence,
synaptic marker loss,
hyper-phosphorylation of Tau,
oxidative damage and
cognitive deficits in transgenic mouse model of AD.

In addition, studies by Stoltenberg, Flinn and colleagues report on the modulation of zinc and the effect in transgenic mouse models of AD. Given that all of these are classic pathological features of AD, and considering the limiting nature of DHA in these processes, it can be argued that DHA is a key candidate in preventing or even curing this debilitating disease.

In order to better understand the possible links and pathways of zinc and DHA with neurodegeneration, we designed a study that incorporates all three of these aspects, to study their effects at the cellular level. In this study, we were able to demonstrate a possible link between omega-3 fatty acid (DHA) concentration, zinc availability and zinc transporter expression levels in cultured human neuronal cells.

When treated with DHA over 48 h, ZnT3 levels were markedly reduced in the human neuroblastoma M17 cell line. Moreover, in the same study, we were able to propose a possible

neuroprotective mechanism of DHA,

which we believe is exerted through

a reduction in cellular zinc levels (through altering zinc transporter expression levels)
that in turn inhibits apoptosis.

DHA supplemented M17 cells also showed a marked depletion of zinc uptake (up to 30%), and

free zinc levels in the cytosol were significantly low compared to the control

This reduction in free zinc availability was specific to DHA; cells treated with EPA had no significant change in free zinc levels (unpublished data). Moreover, DHA-repleted cells had

low levels of active caspase-3 and
high Bcl-2 levels compared to the control treatment.

These findings are consistent with previous published data and further strengthen the possible

correlation between zinc, DHA and neurodegeneration.

On the other hand, recent studies using ZnT3 knockout (ZnT3KO) mice have shown the importance of

ZnT3 in memory and AD pathology.

For example, Sindreu and colleagues have used ZnT3KO mice to establish the important role of

ZnT3 in zinc homeostasis that modulates presynaptic MAPK signaling
required for hippocampus-dependent memory

Results from these studies indicate a possible zinc-transporter-expression-level-dependent mechanism for DHA neuroprotection.

Read Full Post »

Complex Models of Signaling: Therapeutic Implications

Posted in Academic Publishing, Alzheimer's Disease, Best evidence, Biological Networks, Gene Regulation and Evolution, Biomarkers & Medical Diagnostics, Bone Disease and Musculoskeletal Disease, Cancer and Current Therapeutics, Cell Biology, Signaling & Cell Circuits, Cerebrovascular and Neurodegenerative Diseases, Chemical Biology and its relations to Metabolic Disease, Curation, Cytoskeleton, Developmental biology, Disease Biology, Small Molecules in Development of Therapeutic Drugs, Drug Toxicity, Electrophysiology, Epigenetics and Cardiovascular Risks, Etiology, Experimental validation, Explanatory, Fatty acids, Frontiers in Cardiology and Cardiovascular Disorders, Gene Regulation, Human Immune System in Health and in Disease, Inferential analysis, Innovation in Immunology Diagnostics, Innovations in Neurophysiology & Neuropsychology, Kinase, Lipid metabolism, Liver & Digestive Diseases Research, Metabolism, Metabolomics, MS, Myocardial Ischemia, Neurodegenerative Diseases, Neurohumoral Transmission, Nitric Oxide in Health and Disease, Nutrition, Nutritional Supplements: Atherogenesis, lipid metabolism, Personalized and Precision Medicine & Genomic Research, Pharmaceutical Analytics, Pharmaceutical Discovery, Pharmacologic toxicities, Phosphorylation, Population Health Management, Proteins, Proteomics, Regenerative Biology and Medicine, Signaling, Signaling & Cell Circuits, Small Molecules in Development of Therapeutic Drugs, Translational Effectiveness, Translational Research, Translational Science, Ubiquitinylation, tagged Alzheimers Disease, Amyloid, B-type natriuretic peptide, cell differentiation, cell signaling, DHA, Extracellular matrix, Heart Failure, intracellular localization, multiple schlerosis, neuritogenesis, Omega-3 fatty acid, plasticity, prion protein, zinc on October 31, 2014| Leave a Comment »

Complex Models of Signaling: Therapeutic Implications

Curator: Larry H. Bernstein, MD, FCAP

Updated 6/24/2019

Fishy Business: Effect of Omega-3 Fatty Acids on Zinc Transporters and Free Zinc Availability in Human Neuronal Cells

Damitha De Mel and Cenk Suphioglu *

NeuroAllergy Research Laboratory (NARL), School of Life and Environmental Sciences, Faculty of Science, Engineering and Built Environment, Waurn Ponds, Victoria, Australia.

Nutrients 2014, 6, 3245-3258; http://dx.doi.org:/10.3390/nu6083245

Omega-3 (ω-3) fatty acids are one of the two main families of long chain polyunsaturated fatty acids (PUFA). The main omega-3 fatty acids in the mammalian body are

α-linolenic acid (ALA), docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA).

Central nervous tissues of vertebrates are characterized by a high concentration of omega-3 fatty acids. Moreover, in the human brain,

DHA is considered as the main structural omega-3 fatty acid, which comprises about 40% of the PUFAs in total.

DHA deficiency may be the cause of many disorders such as depression, inability to concentrate, excessive mood swings, anxiety, cardiovascular disease, type 2 diabetes, dry skin and so on.

On the other hand,

zinc is the most abundant trace metal in the human brain.

There are many scientific studies linking zinc, especially

excess amounts of free zinc, to cellular death.

Neurodegenerative diseases, such as Alzheimer’s disease, are characterized by altered zinc metabolism. Both animal model studies and human cell culture studies have shown a possible link between

omega-3 fatty acids, zinc transporter levels and
free zinc availability at cellular levels.

Many other studies have also suggested a possible

omega-3 and zinc effect on neurodegeneration and cellular death.

Therefore, in this review, we will examine

the effect of omega-3 fatty acids on zinc transporters and
the importance of free zinc for human neuronal cells.

Moreover, we will evaluate the collective understanding of

mechanism(s) for the interaction of these elements in neuronal research and their
significance for the diagnosis and treatment of neurodegeneration.

Epidemiological studies have linked high intake of fish and shellfish as part of the daily diet to

reduction of the incidence and/or severity of Alzheimer’s disease (AD) and senile mental decline in

cellular differentiation,
photoreceptor membrane biogenesis and
active synaptogenesis.

Despite the significance of these

two families, mammals cannot synthesize PUFA de novo, so they must be ingested from dietary sources. Though belonging to the same family, both

omega-3 and omega-6 fatty acids are metabolically and functionally distinct and have
opposing physiological effects. In the human body,
high concentrations of omega-6 fatty acids are known to increase the formation of prostaglandins and
thereby increase inflammatory processes [10].

the reverse process can be seen with increased omega-3 fatty acids in the body.

Many other factors, such as

thromboxane A2 (TXA2),
leukotriene
B4 (LTB4),
IL-1,
IL-6,
tumor necrosis factor (TNF) and
C-reactive protein,

which are implicated in various health conditions, have been shown to be increased with high omega-6 fatty acids but decreased with omega-3 fatty acids in the human body.

Dietary fatty acids have been identified as protective factors in coronary heart disease, and PUFA levels are known to play a critical role in

immune responses,
gene expression and
intercellular communications.

omega-3 fatty acids are known to be vital in

the prevention of fatal ventricular arrhythmias, and
are also known to reduce thrombus formation propensity by decreasing platelet aggregation, blood viscosity and fibrinogen levels

.Since omega-3 fatty acids are prevalent in the nervous system, it seems logical that a deficiency may result in neuronal problems, and this is indeed what has been identified and reported.

The main omega-3 fatty acids in the mammalian body are

α-linolenic acid (ALA),
docosahexenoic acid (DHA) and
eicosapentaenoic acid (EPA).

In general, seafood is rich in omega-3 fatty acids, more specifically DHA and EPA (Table 1). Thus far, there are nine separate epidemiological studies that suggest a possible link between

increased fish consumption and reduced risk of AD
and eight out of ten studies have reported a link between higher blood omega-3 levels

Table 1. Total percentage of omega-3 fatty acids in common foods and supplements.

Food/Supplement	EPA	DHA	ALA	Total %
Fish
SalmonSardine Anchovy Halibut Herring Mackerel Tuna Fresh Bluefin	XX X X X X X X	XX X X X X X X		>50%>50% >50% >50% >50% >50% >50% >50%
Oils/Supplements
Fish oil capsulesCod liver oils Salmon oil Sardine oil	XX X X	XX X X		>50%>50% >50% >50%
Black currant oilCanola oil Mustard seed oils Soybean oil Walnut oil Wheat germ oil			XX X X X X	10%–50%10%–50% 10%–50% 10%–50% 10%–50% 10%–50%
Seeds and other foods
Flaxseeds/LinseedsSpinach Wheat germ Human milk Peanut butter Soybeans Olive oil Walnuts			XX X X X X X X	>50%>50% 10%–50% 10%–50% <10% <10% <10% <10%

Table adopted from Maclean C.H. et al. [18].

In another study conducted with individuals of 65 years of age or older (n = 6158), it was found that

only high fish consumption, but
not dietary omega-3 acid intake,
had a protective effect on cognitive decline

a protective effect of omega-3 fatty acids only among those with mild cognitive impairment conditions.

A trial of subjects with mild memory complaints demonstrated

an improvement with 900 mg of DHA.

We review key findings on

the effect of the omega-3 fatty acid DHA on zinc transporters and the
importance of free zinc to human neuronal cells.

DHA is the most abundant fatty acid in neural membranes, imparting appropriate

fluidity and other properties,

and is thus considered as the most important fatty acid in neuronal studies. DHA is well conserved throughout the mammalian species despite their dietary differences. It is mainly concentrated

in membrane phospholipids at synapses and
in retinal photoreceptors and
also in the testis and sperm.

In adult rats’ brain, DHA comprises approximately

17% of the total fatty acid weight, and
in the retina it is as high as 33%.

DHA is believed to have played a major role in the evolution of the modern human –

in particular the well-developed brain.

Premature babies fed on DHA-rich formula show improvements in vocabulary and motor performance.

Analysis of human cadaver brains have shown that

people with AD have less DHA in their frontal lobe
and hippocampus compared with unaffected individuals

Furthermore, studies in mice have increased support for the

protective role of omega-3 fatty acids.

Mice administrated with a dietary intake of DHA showed

an increase in DHA levels in the hippocampus.

Errors in memory were decreased in these mice and they demonstrated

reduced peroxide and free radical levels,
suggesting a role in antioxidant defense.

Another study conducted with a Tg2576 mouse model of AD demonstrated that dietary

DHA supplementation had a protective effect against reduction in
drebrin (actin associated protein), elevated oxidation, and to some extent, apoptosis via
decreased caspase activity.

Zinc

Zinc is a trace element, which is indispensable for life, and it is the second most abundant trace element in the body. It is known to be related to

growth,
development,
differentiation,
immune response,
receptor activity,
DNA synthesis,
gene expression,
neuro-transmission,
enzymatic catalysis,
hormonal storage and release,
tissue repair,
memory,
the visual process

and many other cellular functions. Moreover, the indispensability of zinc to the body can be discussed in many other aspects, as

a component of over 300 different enzymes
an integral component of a metallothioneins
a gene regulatory protein.

Approximately 3% of all proteins contain

zinc binding motifs .

The broad biological functionality of zinc is thought to be due to its stable chemical and physical properties. Zinc is considered to have three different functions in enzymes;

catalytic,
coactive and

Indeed, it is the only metal found in all six different subclasses

through glutamate receptors, and
it inhibits excitatory and inhibitory receptors.

Vesicular localization of zinc in pre-synaptic terminals is a characteristic feature of brain-localized zinc, and

its release is dependent on neural activity.

The relationship between zinc and neurodegeneration, specifically AD, has been interpreted in several ways. One study has proposed that β-amyloid has a greater propensity to

form insoluble amyloid in the presence of
high physiological levels of zinc.

Insoluble amyloid is thought to

aggregate to form plaques,

which is a main pathological feature of AD. Further studies have shown that

chelation of zinc ions can deform and disaggregate plaques.

In AD, the most prominent injuries are found in

hippocampal pyramidal neurons, acetylcholine-containing neurons in the basal forebrain, and in
somatostatin-containing neurons in the forebrain.

All of these neurons are known to favor

rapid and direct entry of zinc in high concentration
leaving neurons frequently exposed to high dosages of zinc.

This is thought to promote neuronal cell damage through oxidative stress and mitochondrial dysfunction. Excessive levels of zinc are also capable of

inhibiting Ca2+ and Na+ voltage gated channels
and up-regulating the cellular levels of reactive oxygen species (ROS).

If the human diet is deficient in zinc, the body

efficiently conserves zinc at the tissue level by compensating other cellular mechanisms

to delay the dietary deficiency effects of zinc. These include reduction of cellular growth rate and zinc excretion levels, and

redistribution of available zinc to more zinc dependent cells or organs.

A novel method of measuring metallothionein (MT) levels was introduced as a biomarker for the

assessment of the zinc status of individuals and populations.

as a target for zinc ion binding and thus
assisting in the trafficking of zinc ions through the cell,
which may be similar to that of zinc transporters

Zinc Transporters

via intermembrane proteins and zinc transporter (ZnT) proteins

Members of the SLC39 family have been identified as the putative facilitators of zinc influx into the cytosol, either from the extracellular environment or from intracellular compartments (Figure 1).

it is responsible for the transport of zinc into the synaptic vesicles of
glutamatergic neurons in the hippocampus and neocortex,

Figure 1. Putative cellular localization of some of the different human zinc transporters (i.e., Zip1- Zip4 and ZnT1- ZnT7). Arrows indicate the direction of zinc passage by the appropriate putative zinc transporters in a generalized human cell. Although there are fourteen Zips and eight ZnTs known so far, only the main zinc transporters are illustrated in this figure for clarity and brevity.

zinc transporters

Early zinc signaling (EZS) and late zinc signaling (LZS)

http://www.hindawi.com/journals/jnme/2012/floats/173712/thumbnails/173712.fig.002_th.jpg

DHA and Zinc Homeostasis

Many studies have identified possible associations between DHA levels, zinc homeostasis, neuroprotection and neurodegeneration. Dietary DHA deficiency resulted in

increased zinc levels in the hippocampus and
elevated expression of the putative zinc transporter, ZnT3, in the rat brain.

a significant reduction in plaque load
and the presence of insoluble amyloid were observed.

In addition to the decrease in plaque load, ZnT3 silenced mice also exhibited a significant

reduction in free zinc availability in the hippocampus
and cerebral cortex.

Collectively, the findings from this study are very interesting and indicate a clear connection between

zinc availability and amyloid plaque formation,

thus indicating a possible link to AD.

DHA supplementation has also been reported to limit the following:

amyloid presence,
synaptic marker loss,
hyper-phosphorylation of Tau,
oxidative damage and
cognitive deficits in transgenic mouse model of AD.

When treated with DHA over 48 h, ZnT3 levels were markedly reduced in the human neuroblastoma M17 cell line. Moreover, in the same study, we were able to propose a possible

neuroprotective mechanism of DHA,

which we believe is exerted through

a reduction in cellular zinc levels (through altering zinc transporter expression levels)
that in turn inhibits apoptosis.

DHA supplemented M17 cells also showed a marked depletion of zinc uptake (up to 30%), and

free zinc levels in the cytosol were significantly low compared to the control

This reduction in free zinc availability was specific to DHA; cells treated with EPA had no significant change in free zinc levels (unpublished data). Moreover, DHA-repleted cells had

low levels of active caspase-3 and
high Bcl-2 levels compared to the control treatment.

These findings are consistent with previous published data and further strengthen the possible

correlation between zinc, DHA and neurodegeneration.

On the other hand, recent studies using ZnT3 knockout (ZnT3KO) mice have shown the importance of

ZnT3 in memory and AD pathology.

For example, Sindreu and colleagues have used ZnT3KO mice to establish the important role of

ZnT3 in zinc homeostasis that modulates presynaptic MAPK signaling
required for hippocampus-dependent memory

Results from these studies indicate a possible zinc-transporter-expression-level-dependent mechanism for DHA neuroprotection.

Collectively from these studies, the following possible mechanism can be proposed (Figure 2).

possible benefits of DHA in neuroprotection through reduction of ZnT3 transporter

Figure 2. Proposed neuroprotection mechanism of docosahexaenoic acid (DHA) in reference to synaptic zinc. Schematic diagram showing possible benefits of DHA in neuroprotection through reduction of ZnT3 transporter expression levels in human neuronal cells, which results in a reduction of zinc flux and thus lowering zinc concentrations in neuronal synaptic vesicles, and therefore contributing to a lower incidence of neurodegenerative diseases (ND), such as Alzheimer’s disease (AD).

More recent data from our research group have also shown a link between the expression levels of histone H3 and H4 proteins in human neuronal cells in relation to DHA and zinc. Following DHA treatment, both H3 and H4 levels were up-regulated. In contrast, zinc treatment resulted in a down-regulation of histone levels. Both zinc and DHA have shown opposing effects on histone post-translational modifications, indicating a possible distinctive epigenetic pattern. Upon treatment with zinc, M17 cells displayed an increase in histone deacetylase (HDACs) and a reduction in histone acetylation. Conversely, with DHA treatment, HDAC levels were significantly reduced and the acetylation of histones was up-regulated. These findings also support a possible interaction between DHA and zinc availability.

Conclusions

It is possible to safely claim that there is more than one potential pathway by which DHA and zinc interact at a cellular level, at least in cultured human neuronal cells. Significance and importance of both DHA and zinc in neuronal survival is attested by the presence of these multiple mechanisms.
Most of these reported studies were conducted using human neuroblastoma cells, or similar cell types, due to the lack of live mature human neuronal cells. Thus, the results may differ from results achieved under actual human physiological conditions due to the structural and functional differences between these cells and mature human neurons. Therefore, an alternative approach that can mimic the human neuronal cells more effectively would be advantageous.

Sphingosine-1-phosphate signaling as a therapeutic target

E Giannoudaki, DJ Swan, JA Kirby, S Ali

Applied Immunobiology and Transplantation Research Group, Institute of Cellular Medicine, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, UK

Cell Health and Cytoskeleton 2012; 4: 63–72

S1P is a 379Da member of the lysophospholipid family. It is the direct metabolite of sphingosine through the action of two sphingosine kinases, SphK1 and SphK2. The main metabolic pathway starts with the hydrolysis of sphingomyelin, a membrane sphingolipid, into ceramide by the enzyme sphingomyelinase and the subsequent production of sphingosine by ceramidase (Figure 1). Ceramide can also be produced de novo in the endoplasmic reticulum (ER) from serine and palmitoyl coenzyme A through multiple intermediates. S1P production is regulated by various S1P-specific and general lipid phosphatases, as well as S1P lyase, which irreversibly degrades S1P into phosphoethanolamine and hexadecanal. The balance between intracellular S1P and its metabolite ceramide can determine cellular fate. Ceramide promotes apoptosis, while S1P suppresses cell death and promotes cell survival. This creates an S1P ceramide “rheostat” inside the cells. S1P lyase expression in tissue is higher than it is in erythrocytes and platelets, the main “suppliers” of S1P in blood. This causes a tissue–blood gradient of S1P, which is important in many S1P-mediated responses, like the lymphocyte egress from lymphoid organs.

S1P signaling overview

S1P is produced inside cells; however, it can also be found extracellularly, in a variety of different tissues. It is abundant in the blood, at concentrations of 0.4–1.5 μM, where it is mainly secreted by erythrocytes and platelets. Blood S1P can be found separately, but mainly it exists in complexes with high-density lipoprotein (HDL) (∼60%). Many of the cardioprotective effects of HDL are hypothesized to involve S1P. Before 1996, S1P was thought to act mainly intracellularly as a second messenger. However, the identification of several GPCRs that bind S1P led to the initiation of many studies on

extracellular S1P signaling through those receptors.

There are five receptors that have been identified currently. These can be coupled with different G-proteins. Assuming that each receptor coupling with a G protein has a slightly different function, one can recognize the complexity of S1P receptor signaling.

S1P as a second messenger

S1P is involved in many cellular processes through its GPCR signaling; studies demonstrate that S1P also acts at an intracellular level. Intracellular S1P plays a role in maintaining the balance of cell survival signal toward apoptotic signals, creating a

cell “rheostat” between S1P and its precursor ceramide.

Important evidence that S1P can act intracellularly as a second messenger came from yeast (Saccharomyces cerevisiae) and plant (Arabidopsis thaliana) cells. Yeast cells do not express any S1P receptors, although they can be affected by S1P during heat-shock responses. Similarly, Arabidopsis has only one GPCR-like protein, termed “GCR1,” which does not bind S1P, although S1P regulates stomata closure during drought.

Sphingosine-1-phosphate

In mammals, the sphingosine kinases have been found to localize in different cell compartments, being responsible for the accumulation of S1P in those compartments to give intracellular signals. In mitochondria, for instance,

S1P was recently found to interact with prohibitin 2,

a conserved protein that maintains mitochondria assembly and function. According to the same study,

SphK2 is the major producer of S1P in mitochondria and the knockout of its gene can cause

disruption of mitochondrial respiration and cytochrome c oxidase function.

SphK2 is also present in the nucleus of many cells and has been implicated to cause cell cycle arrest, and it causes S1P accumulation in the nucleus. It seems that nuclear S1P is affiliated with the histone deacetylases HDAC1 and HDAC2,

inhibiting their activity, thus having an indirect effect in epigenetic regulation of gene expression.

In the ER, SphK2 has been identified to translocate during stress, and promote apoptosis. It seems that S1P has specific targets in the ER that cause apoptosis, probably through calcium mobilization signals.

Sphingosine 1-phosphate (S1P) is a small bioactive lipid molecule that is involved in several processes both intracellularly and extracellularly. It acts intracellularly

to promote the survival and growth of the cell,

through its interaction with molecules in different compartments of the cell.

It can also exist at high concentrations extracellularly, in the blood plasma and lymph. This causes an S1P gradient important for cell migration. S1P signals through five G protein-coupled receptors, S1PR1–S1PR5, whose expression varies in different types of cells and tissue. S1P signaling can be involved in physiological and pathophysiological conditions of the cardiovascular, nervous, and immune systems and diseases such as ischemia/reperfusion injury, autoimmunity, and cancer. In this review, we discuss how it can be used to discover novel therapeutic targets.

The involvement of S1P signaling in disease

In a mouse model of myocardial ischemia-reperfusion injury (IRI), S1P and its carrier, HDL, can help protect myocardial tissue and decrease the infarct size. It seems they reduce cardiomyocyte apoptosis and neutrophil recruitment to the ischemic tissue and may decrease leukocyte adhesion to the endothelium. This effect appears to be S1PR3 mediated, since in S1PR3 knockout mice it is alleviated.

Ischemia activates SphK1, which is then translocated to the plasma membrane. This leads to an increase of intracellular S1P, helping to promote cardiomyocyte survival against apoptosis, induced by ceramide. SphK1 knockout mice cannot be preconditioned against IRI, whereas SphK1 gene induction in the heart protects it from IRI. Interestingly, a recent study shows SphK2 may also play a role, since its knockout reduces the cardioprotective effects of preconditioning. Further, administration of S1P or sphingosine during reperfusion results in better recovery and attenuation of damage to cardiomyocytes. As with preconditioning, SphK1 deficiency also affects post-conditioning of mouse hearts after ischemia reperfusion (IR).

S1P does not only protect the heart from IRI. During intestinal IR, multiple organs can be damaged, including the lungs. S1P treatment of mice during intestinal IR seems to have a protective effect on lung injury, probably due to suppression of iNOS-induced nitric oxide generation. In renal IRI, SphK1 seems to be important, since its deficiency increased the damage in kidney tissue, whereas the lentiviral overexpression of the SphK1 gene protected from injury. Another study suggests that, after IRI, apoptotic renal cells release S1P, which recruits macrophages through S1PR3 activation and might contribute to kidney regeneration and restoration of renal epithelium. However, SphK2 is negatively implicated in hepatic IRI, its inhibition helping protect hepatocytes and restoring mitochondrial function.

Further studies are implicating S1P signaling or sphingosine kinases in several kinds of cancer as well as autoimmune diseases.

Figure 2 FTY720-P causes retention of T cells in the lymph nodes.

Notes: C57BL/6 mice were injected with BALB/c splenocytes in the footpad to create an allogenic response then treated with FTY720-P or vehicle every day on days 2 to 5. On day 6, the popliteal lymph nodes were removed. Popliteal node-derived cells were mixed with BALB/c splenocytes in interferon gamma (IFN-γ) cultured enzyme-linked immunosorbent spot reactions. Bars represent the mean number of IFN-γ spot-forming cells per 1000 popliteal node-derived cells, from six mice treated with vehicle and seven with FTY720-P. **P , 0.01. (not shown)

Fingolimod (INN, trade name Gilenya, Novartis) is an immunomodulating drug, approved for treating multiple sclerosis. It has reduced the rate of relapses in relapsing-remitting multiple sclerosis by over half. Fingolimod is a sphingosine-1-phosphate receptor modulator, which sequesters lymphocytes in lymph nodes, preventing them from contributing to an autoimmune reaction.

Fingolimod3Dan

http://upload.wikimedia.org/wikipedia/commons/thumb/4/48/Fingolimod3Dan.gif/200px-Fingolimod3Dan.gif

The S1P antagonist FTY720 has been approved by the US Food and Drug Administration to be used as a drug against multiple sclerosis (MS). FTY720 is in fact a prodrug, since it is phosphorylated in vivo by SphK2 into FTY720-P, an S1P structural analog, which can activate S1PR1, 3, 4, and 5. FTY720-P binding to S1PR1 causes internalization of the receptor, as does S1P – but instead of recycling it back to the cell surface, it promotes its ubiquitination and degradation at the proteasome. This has a direct effect on lymphocyte trafficking through the lymph nodes, since it relies on S1PR1 signaling and S1P gradient (Figure 2). In MS, it stops migrating lymphocytes into the brain, but it may also have direct effects on the CNS through neuroprotection. FTY720 can pass the blood–brain barrier and it could be phosphorylated by local sphingosine kinases to act through S1PR1 and S1PR3 receptors that are mainly expressed in the CNS. In MS lesions, astrocytes upregulate those two receptors and it has been shown that FTY720-P treatment in vitro inhibits astrocyte production of inflammatory cytokines. A recent study confirms the importance of S1PR3 signaling on activated astrocytes, as well as SphK1, that are upregulated and promote the secretion of the potentially neuroprotective cytokine CXCL-1.

There are several studies implicating the intracellular S1P ceramide rheostat to cancer cell survival or apoptosis and resistance to chemotherapy or irradiation in vitro. Studies with SphK1 inhibition in pancreatic, prostate cancers, and leukemia, show increased ceramide/S1P ratio and induction of apoptosis. However, S1P receptor signaling plays conflicting roles in cancer cell migration and metastasis.

Modulation of S1P signaling: therapeutic potential

S1P signaling can be involved in many pathophysiological conditions. This means that we could look for therapeutic targets in all the molecules taking part in S1P signaling and production, most importantly the S1P receptors and the sphingosine kinases. S1P agonists and antagonists could also be used to modulate S1P signaling during pathological conditions.

S1P can have direct effects on the cardiovascular system. During IRI, intracellular S1P can protect the cardiomyocytes and promote their survival. Pre- or post-conditioning of the heart with S1P could be used as a treatment, but upregulation of sphingosine kinases could also increase intracellular S1P bioavailability. S1P could also have effects on endothelial cells and neutrophil trafficking. Vascular endothelial cells mainly express S1PR1 and S1PR3; only a few types express S1PR2. S1PR1 and S1PR3 activation on these cells has been shown to enhance their chemotactic migration, probably through direct phosphorylation of S1PR1 by Akt, in a phosphatidylinositol 3-kinase and Rac1-dependent signaling pathway. Moreover, it stimulates endothelial cell proliferation through an ERK pathway. S1PR2 activation, however, inhibits endothelial cell migration, morphogenesis, and angiogenesis, most likely through Rho-dependent inhibition of Rac signaling pathway, as Inoki et al showed in mouse cells with the use of S1PR1 and S1PR3 specific antagonists.

Regarding permeability of the vascular endothelium and endothelial barrier integrity, S1P receptors can have different effects. S1PR1 activation enhances endothelial barrier integrity by stimulation of cellular adhesion and upregulation of adhesion molecules. However, S1PR2 and S1PR3 have been shown to have barrier-disrupting effects in vitro, and vascular permeability increasing effects in vivo. All the effects S1P can have on vascular endothelium and smooth muscle cells suggest that activation of S1PR2, not S1PR1 and S1PR3, signaling, perhaps with the use of S1PR2 specific agonists, could be used therapeutically to inhibit angiogenesis and disrupt vasculature, suppressing tumor growth and progression.

An important aspect of S1P signaling that is being already therapeutically targeted, but could be further investigated, is immune cell trafficking. Attempts have already been made to regulate lymphocyte cell migration with the use of the drug FTY720, whose phosphorylated form can inhibit the cells S1PR1-dependent egress from the lymph nodes, causing lymphopenia. FTY720 is used as an immunosuppressant for MS but is also being investigated for other autoimmune conditions and for transplantation. Unfortunately, Phase II and III clinical trials for the prevention of kidney graft rejection have not shown an advantage over standard therapies. Moreover, FTY720 can have some adverse cardiac effects, such as bradycardia. However, there are other S1PR1 antagonists that could be considered instead, including KRP-203, AUY954, and SEW2871. KRP-203 in particular has been shown to prolong rat skin and heart allograft survival and attenuate chronic rejection without causing bradycardia, especially when combined with other immunomodulators.

There are studies that argue S1P pretreatment has a negative effect on neutrophil chemotaxis toward the chemokine CXCL-8 (interleukin-8) or the potent chemoattractant formyl-methionyl-leucyl-phenylalanine. S1P pretreatment might also inhibit trans-endothelial migration of neutrophils, without affecting their adhesion to the endothelium. S1P effects on neutrophil migration toward CXCL-8 might be the result of S1PRs cross-linking with the CXCL-8 receptors in neutrophils, CXCR-1 and CXCR-2. Indeed, there is evidence suggesting S1PR4 and S1PR3 form heterodimers with CXCR-1 in neutrophils. Another indication that S1P plays a role in neutrophil trafficking is a recent paper on S1P lyase deficiency, a deficiency that impairs neutrophil migration from blood to tissue in knockout mice.

S1P lyase and S1PRs in neutrophils may be new therapeutic targets against IRI and inflammatory conditions in general. Consistent with these results, another study has shown that inhibition of S1P lyase can have a protective effect on the heart after IRI and this effect is alleviated when pretreated with an S1PR1 and S1PR3 antagonist. Inhibition was achieved with a US Food and Drug Administration-approved food additive, 2-acetyl-4-tetrahydroxybutylimidazole, providing a possible new drug perspective. Another S1P lyase inhibitor, LX2931, a synthetic analog of 2-acetyl-4-tetrahydroxybutylimidazole, has been shown to cause peripheral lymphopenia when administered in mice, providing a potential treatment for autoimmune diseases and prevention of graft rejection in transplantation. This molecule is currently under Phase II clinical trials in rheumatoid arthritis patients.

S1P signaling research has the potential to discover novel therapeutic targets. S1P signaling is involved in many physiological and pathological processes. However, the complexity of S1P signaling makes it necessary to consider every possible pathway, either through its GPCRs, or intracellularly, with S1P as a second messenger. Where the activation of one S1P receptor may lead to the desired outcome, the simultaneous activation of another S1P receptor may lead to the opposite outcome. Thus, if we are to target a specific signaling pathway, we might need specific agonists for S1P receptors to activate one S1P receptor pathway, while, at the same time, we might need to inhibit another through S1P receptor antagonists.

Evidence of sphingolipid signaling in cancer

Biologically active lipids are important cellular signaling molecules and play a role in cell communication and cancer cell proliferation, and cancer stem cell biology. A recent study in ovarian cancer cell lines shows that exogenous sphingosine 1 phosphate (SIP1) or overexpression of the sphingosine kinase (SPHK1) increases ovarian cancer cell proliferation, invasion and contributes to cancer stem cell like phenotype. The diabetes drug metformin was shown to be an inhibitor of SPHK1 and reduce ovarian cancer tumor growth.

2019 Apr;17(4):870-881. doi: 10.1158/1541-7786.MCR-18-0409. Epub 2019 Jan 17.

SPHK1 Is a Novel Target of Metformin in Ovarian Cancer.

Hart PC^#¹, Chiyoda T^#^1,², Liu X³, Weigert M¹, Curtis M¹, Chiang CY¹, Loth R¹, Lastra R⁴, McGregor SM^4,⁵, Locasale JW³, Lengyel E¹, Romero IL⁶.

Author information

Abstract

The role of phospholipid signaling in ovarian cancer is poorly understood. Sphingosine-1-phosphate (S1P) is a bioactive metabolite of sphingosine that has been associated with tumor progression through enhanced cell proliferation and motility. Similarly, sphingosine kinases (SPHK), which catalyze the formation of S1P and thus regulate the sphingolipid rheostat, have been reported to promote tumor growth in a variety of cancers. The findings reported here show that exogenous S1P or overexpression of SPHK1 increased proliferation, migration, invasion, and stem-like phenotypes in ovarian cancer cell lines. Likewise, overexpression of SPHK1 markedly enhanced tumor growth in a xenograft model of ovarian cancer, which was associated with elevation of key markers of proliferation and stemness. The diabetes drug, metformin, has been shown to have anticancer effects. Here, we found that ovarian cancer patients taking metformin had significantly reduced serum S1P levels, a finding that was recapitulated when ovarian cancer cells were treated with metformin and analyzed by lipidomics. These findings suggested that in cancer the sphingolipid rheostat may be a novel metabolic target of metformin. In support of this, metformin blocked hypoxia-induced SPHK1, which was associated with inhibited nuclear translocation and transcriptional activity of hypoxia-inducible factors (HIF1α and HIF2α). Further, ovarian cancer cells with high SPHK1 were found to be highly sensitive to the cytotoxic effects of metformin, whereas ovarian cancer cells with low SPHK1 were resistant. Together, the findings reported here show that hypoxia-induced SPHK1 expression and downstream S1P signaling promote ovarian cancer progression and that tumors with high expression of SPHK1 or S1P levels might have increased sensitivity to the cytotoxic effects of metformin. IMPLICATIONS: Metformin targets sphingolipid metabolism through inhibiting SPHK1, thereby impeding ovarian cancer cell migration, proliferation, and self-renewal.

Nrf2:INrf2(Keap1) Signaling in Oxidative Stress

James W. Kaspar, Suresh K. Niture, and Anil K. Jaiswal*

Department of Pharmacology, University of Maryland School of Medicine, Baltimore, MD

Free Radic Biol Med. 2009 Nov 1; 47(9): 1304–1309. http://dx.doi.org:/10.1016/j.freeradbiomed.2009.07.035

Nrf2:INrf2(Keap1) are cellular sensors of chemical and radiation induced oxidative and electrophilic stress. Nrf2 is a nuclear transcription factor that

controls the expression and coordinated induction of a battery of defensive genes encoding detoxifying enzymes and antioxidant proteins.

This is a mechanism of critical importance for cellular protection and cell survival. Nrf2 is retained in the cytoplasm by an inhibitor INrf2. INrf2 functions as an adapter for

Cul3/Rbx1 mediated degradation of Nrf2.
In response to oxidative/electrophilic stress,
Nrf2 is switched on and then off by distinct

early and delayed mechanisms.

Oxidative/electrophilic modification of INrf2cysteine151 and/or PKC phosphorylation of Nrf2serine40 results in the escape or release of Nrf2 from INrf2. Nrf2 is stabilized and translocates to the nucleus, forms heterodimers with unknown proteins, and binds antioxidant response element (ARE) that leads to coordinated activation of gene expression. It takes less than fifteen minutes from the time of exposure

to switch on nuclear import of Nrf2.

This is followed by activation of a delayed mechanism that controls

switching off of Nrf2 activation of gene expression.

GSK3β phosphorylates Fyn at unknown threonine residue(s) leading to

nuclear localization of Fyn.

Fyn phosphorylates Nrf2tyrosine568 resulting in

nuclear export of Nrf2,
binding with INrf2 and
degradation of Nrf2.

The switching on and off of Nrf2 protects cells against free radical damage, prevents apoptosis and promotes cell survival.

NPRA-mediated suppression of AngII-induced ROS production contributes to the antiproliferative effects of B-type natriuretic peptide in VSMC

Pan Gao, De-Hui Qian, Wei Li, Lan Huang
Mol Cell Biochem (2009) 324:165–172

http://dx.doi.org/10.1007/s11010-008-9995-y

Excessive proliferation of vascular smooth cells (VSMCs) plays a critical role in the pathogenesis of diverse vascular disorders, and inhibition of VSMCs proliferation has been proved to be beneficial to these diseases.

In this study, we investigated the antiproliferative effect of

B-type natriuretic peptide (BNP), a natriuretic peptide with potent antioxidant capacity,

on rat aortic VSMCs, and the possible mechanisms involved. The results indicate that

BNP potently inhibited Angiotensin II (AngII)-induced VSMCs proliferation,

as evaluated by [3H]-thymidine incorporation assay. Consistently, BNP significantly decreased

AngII-induced intracellular reactive oxygen species (ROS)
and NAD(P)H oxidase activity.

8-Br-cGMP, a cGMP analog,

mimicked these effects.

To confirm its mechanism, siRNA of natriuretic peptide receptor-A(NRPA) strategy technology was used

to block cGMP production in VSMCs, and
siNPRA attenuated the inhibitory effects of BNP in VSMCs.

Taken together, these results indicate that

BNP was capable of inhibiting VSMCs proliferation by
NPRA/cGMP pathway,

which might be associated with

the suppression of ROS production.

These results might be related, at least partly, to the anti-oxidant property of BNP.

Cellular prion protein is required for neuritogenesis: fine-tuning of multiple signaling pathways involved in focal adhesions and actin cytoskeleton dynamics

A Alleaume-Butaux, C Dakowski, M Pietri, S Mouillet-Richard, Jean-Marie Launay, O Kellermann, B Schneider

1INSERM, UMR-S 747, 2Paris Descartes University, Sorbonne Paris, 3Public Hospital of Paris, Department of Biochemistry, Paris, France; 4Pharma Research Department, Hoffmann La Roche Ltd, Basel, Switzerland

Cell Health and Cytoskeleton 2013; 5: 1–12

Neuritogenesis is a complex morphological phenomena accompanying neuronal differentiation. Neuritogenesis relies on the initial breakage of the rather spherical symmetry of neuroblasts and the formation of buds emerging from the postmitotic neuronal soma. Buds then evolve into neurites, which later convert into an axon or dendrites. At the distal tip of neurites, the growth cone integrates extracellular signals and guides the neurite to its target. The acquisition of neuronal polarity depends on deep modifications of the neuroblast cytoskeleton characterized by the remodeling and activation of focal adhesions (FAs) and localized destabilization of the actin network in the neuronal sphere.Actin instability in unpolarized neurons allows neurite sprouting, ie, the protrusion of microtubules, and subsequent neurite outgrowth. Once the neurite is formed, actin microfilaments recover their stability and exert a sheathed action on neurites, a dynamic process necessary for the maintenance and integrity of neurites.

A combination of extrinsic and intrinsic cues pilots the architectural and functional changes in FAs and the actin network along neuritogenesis. This process includes neurotrophic factors (nerve growth factor, brain derived neurotrophic factor, neurotrophin, ciliary neurotrophic factor, glial derived neurotrophic factor) and their receptors, protein components of the extracellular matrix (ECM) (laminin, vitronectin, fibronectin), plasma membrane integrins and neural cell adhesion molecules (NCAM), and intracellular molecular protagonists such as small G proteins (RhoA, Rac, Cdc42) and their downstream targets.

Neuritogenesis is a dynamic phenomenon associated with neuronal differentiation that allows a rather spherical neuronal stem cell to develop dendrites and axon, a prerequisite for the integration and transmission of signals. The acquisition of neuronal polarity occurs in three steps:

(1) neurite sprouting, which consists of the formation of buds emerging from the postmitotic neuronal soma;

(2) neurite outgrowth, which represents the conversion of buds into neurites, their elongation and evolution into axon or dendrites; and

(3) the stability and plasticity of neuronal polarity.

In neuronal stem cells, remodeling and activation of focal adhesions (FAs) associated with deep modifications of the actin cytoskeleton is a prerequisite for neurite sprouting and subsequent neurite outgrowth. A multiple set of growth factors and interactors located in the extracellular matrix and the plasma membrane orchestrate neuritogenesis

by acting on intracellular signaling effectors,
notably small G proteins such as RhoA, Rac, and Cdc42,
which are involved in actin turnover and the dynamics of FAs.

The cellular prion protein (PrPC), a glycosylphosphatidylinositol

(GPI)-anchored membrane protein

mainly known for its role in a group of fatal

neurodegenerative diseases,

has emerged as a central player in neuritogenesis.

Here, we review the contribution of PrPC to neuronal polarization and detail the current knowledge on the

signaling pathways fine-tuned by PrPC
to promote neurite sprouting, outgrowth, and maintenance.

We emphasize that PrPC-dependent neurite sprouting is a process in which PrPC

governs the dynamics of FAs and the actin cytoskeleton
via β1 integrin signaling.

The presence of PrPC is necessary to render neuronal stem cells

competent to respond to neuronal inducers and
to develop neurites.

In differentiating neurons, PrPC exerts

a facilitator role towards neurite elongation.

This function relies on the interaction of PrPC with a set of diverse partners such as

elements of the extracellular matrix,
plasma membrane receptors,
adhesion molecules, and
soluble factors that control actin cytoskeleton turnover through Rho-GTPase signaling.

Once neurons have reached their terminal stage of differentiation and acquired their polarized morphology, PrPC also

takes part in the maintenance of neurites.

By acting on tissue nonspecific alkaline phosphatase, or

matrix metalloproteinase type 9,

PrPC stabilizes interactions between

neurites and the extracellular matrix.

Keywords: prion, neuronal differentiation

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ENDORSE Positive Results Continued over Five Years with TECFIDERA® (Dimethyl Fumarate, Biogen Idec) in a Wide Range of Multiple Sclerosis Patients

Posted in MS, Neurodegenerative Diseases on September 12, 2014| Leave a Comment »

ENDORSE Positive Results Continued over Five Years with TECFIDERA® (Dimethyl Fumarate, Biogen Idec) in a Wide Range of Multiple Sclerosis Patients

Reporter: Aviva Lev-Ari, PhD, RN

UPDATED on 7/30/2022

Tecfidera® is an oral therapy contained in capsules taken two times per day. Tecfidera, formerly known as BG-12, is dimethyl fumarate, a formulation that was developed specifically for use by people with multiple sclerosis. A chemically related compound, called Fumaderm (dimethyl fumarate and fumaric acid esters), has been used at higher doses for decades in Germany to treat acute flare-ups of psoriasis. Although its exact mechanism of action is not known, Tecfidera is thought to modulate the immune response to be less inflammatory and may have antioxidant properties that could be protective against damage to the brain and spinal cord.

Tecfidera is approved by the FDA for the treatment of relapsing forms of multiple sclerosis to include clinically isolated syndrome, relapsing-remitting disease and active secondary progressive disease in adults.

Click here to read the Tecfidera Prescribing Information for healthcare professionals.

Click here to read the Tecfidera Patient Information.

SOURCE

https://www.nationalmssociety.org/Treating-MS/Medications/Tecfidera%E2%84%A2

New Data from ENDORSE Show Positive Results Continued over Five Years with TECFIDERA® (Dimethyl Fumarate) in a Wide Range of Multiple Sclerosis Patients

CAMBRIDGE, Mass.Today Biogen Idec (NASDAQ: BIIB) announced that five-year results from the ENDORSE Phase 3 extension study show TECFIDERA® (dimethyl fumarate) provides strong and sustained efficacy in a broad range of people living with relapsing-remitting multiple sclerosis (RRMS). These data will be presented at the Sixth Triennial Joint Meeting of the Americas Committee for Treatment and Research in Multiple Sclerosis and the European Committee for Treatment and Research in Multiple Sclerosis (ACTRIMS-ECTRIMS).

Across all patients in the ENDORSE study who received TECFIDERA, including some patients who were treated for up to seven and a half years, the safety profile remained consistent with no new or worsening safety signals. Additional analyses in patients who were newly diagnosed with multiple sclerosis (MS) when the parent studies DEFINE and CONFIRM began indicate that TECFIDERA had a robust long-term effect on MS relapse rates, disability progression and MRI measures in these patients.

ENDORSE is a global, dose-blind extension study evaluating the long-term safety and efficacy of TECFIDERA (240 mg, dosed twice a day [BID] or three times a day [TID]). Patients who received up to two years of TECFIDERA in the pivotal Phase 3 DEFINE and CONFIRM studies continued on the same dose in ENDORSE. Patients who previously received placebo or glatiramer acetate (GA; 20 mg subcutaneous daily injection; CONFIRM only) in DEFINE and CONFIRM were randomized 1:1 to TECFIDERA BID or TID.

At five years (two years in DEFINE or CONFIRM and three years in ENDORSE), interim results show that patients who continued on TECFIDERA BID treatment experienced sustained clinical efficacy on relapse and disability progression endpoints as measured by annualized relapse rate (ARR) and 24-week Expanded Disability Status Scale (EDSS), similar to what was observed after two years in DEFINE and CONFIRM. These patients also maintained a low frequency of brain lesions over five years as measured by new or enlarging T2-hyperintense lesions, new non-enhancing T1-hypointense lesions and gadolinium-enhanced [Gd+] lesions.

These data will be presented in poster presentations on Thursday, Sept.11 at 3:30 p.m. ET:

Five-Year Follow-up of Delayed-Release Dimethyl Fumarate in RRMS: Integrated Clinical Efficacy Data from the DEFINE, CONFIRM, and ENDORSE Studies (P110)Five-Year Follow-up of Delayed-Release Dimethyl Fumarate in Relapsing-Remitting Multiple Sclerosis: MRI Outcomes from DEFINE, CONFIRM, and ENDORSE (P059)

Clinical Efficacy in Newly Diagnosed Patients

An analysis of data from ENDORSE evaluated the long-term efficacy of TECFIDERA in newly diagnosed patients, defined as those diagnosed within one year prior to enrolling in DEFINE or CONFIRM and either disease modifying treatment-naïve or previously treated with corticosteroids alone.

Over the five-year observation period, newly diagnosed patients taking TECFIDERA BID experienced sustained reductions in relapses (measured by ARR and proportion of patients who relapsed), disability progression (measured by 24-week EDSS) and number of brain lesions. These effects are similar to the results reported for the overall ENDORSE study population, supporting the consistent efficacy of TECFIDERA in this subpopulation.

These data will be presented in a poster presentation on Thursday, Sept. 11 at 3:30 p.m. ET:

Long-Term Efficacy of Delayed-Release Dimethyl Fumarate in Newly Diagnosed Patients With RRMS: An Integrated Analysis of DEFINE, CONFIRM and ENDORSE (P064)

“As shown in the ENDORSE study, TECFIDERA provides consistent outcomes across a broad range of relapsing-remitting MS patients, including those who are newly diagnosed, highlighting its utility in the range of patients we see in practice,” said Ralf Gold, M.D., professor and chair of the Department of Neurology at St. Josef-Hospital, Ruhr-University in Bochum, Germany. “The long-term efficacy of TECFIDERA in reducing key measures of disease activity and its favorable safety profile help support its role as an important therapeutic option for people living with MS.”

Effect of TECFIDERA on No Evidence of Disease Activity

Another analysis from ENDORSE evaluated the long-term effects of TECFIDERA on the emerging measure of No Evidence of Disease Activity (NEDA) over five years. Patients were assessed annually and were considered to have NEDA if they had: no relapses, no 24-week confirmed disability progression, no Gd+ lesions, and no new or enlarging T2-hyperintense lesions.

Results over five years show that the proportion of patients achieving NEDA annually was maintained in patients who continued on TECFIDERA, and was improved in patients who switched from placebo to treatment with TECFIDERA BID in the ENDORSE study.

These data will be presented in a platform presentation on Friday, Sept. 12 at 9:00 a.m. ET:

Long-term Follow-up of the Effect of Delayed-Release Dimethyl Fumarate on No Evident Disease Activity in Patients with Multiple Sclerosis (FC3.5)

Source: www.biogenidec.com

See on Scoop.it – Cardiotoxicity

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Advances in Stem Cell Research

Posted in Alzheimer's Disease, Autologous Cell Therapy, Automated Cell Processing, Cardiac & Vascular Repair Tools Subsegment, Cell Biology, Signaling & Cell Circuits, Genome Biology, hNPCs, hNPCs, Human neural progenitor cells, MS, Neurodegenerative Diseases, Pharmacologic toxicities, Pre-Clinical Animal Model Development, Stem Cells for Regenerative Medicine, Technology Transfer: Biotech and Pharmaceutical, Translational Science, tagged alzheimer's, autologous transplant, Automated Cell Processing, cell ontology, human neural pleuripotential cells (hPNCs), mutiple sclerosis (MS), regererative medicine, stemm cells on December 7, 2013| Leave a Comment »

Larry H Bernstein, MD, FCAP, reporter and curator

htto://pharmaceuticalintelligence.com/2013-12-07/larryhbern/Advances-in-Stem-Cell-Research

The amount of success in stem cell research and recent successes is notable.

GEN News Dec 5, 2013
Stem Cell Leaders Call for Human Embryome Project

Just as an international consortium was formed to map and sequence the human genome, now a group of stem cell and regenerative medicine scientists say it’s critical that such an effort be ramped up to do a similar project focused on the human embryome.

This was the key message of a panel discussion, “From Mapping the Genome to Mapping the Embryome: The Urgent Need for an International Initiative,” moderated by Michael West, Ph.D., CEO of Biotime. It took place at the World Stem Cell Summit, which is taking place this week in San Diego.

“It is becoming increasingly clear in regenerative medicine that pluripotent stem cells, embryonic stem cells, and IPs cells will be as fundamentally important to medicine as was DNA. Maybe even bigger because you can genetically engineer these cells,” said Dr. West.

Dr. West and his colleagues adamantly believe that there needs to be a large international effort aimed at mapping the cellular and molecular basis of all human life starting with the fertilized egg and working its way up to the body of the adult. This is what it is termed the embryome.

“The opportunity presented by pluripotent stem cells to manufacture for the first time in the history of medicine all of the cellular components of the human body on an industrial scale is at once both an opportunity and a challenge,” said Dr. West. “The opportunity is to build a new field we call regenerative medicine in which many currently incurable diseases are treated with cells capable of regenerating tissues afflicted with disease. The challenge relates to the complexity of the cell types in the body and our ability to manufacture products with precisely defined compositions for human clinical use.”

Dr. West went on to say that to get these different types of stem cells into the clinic, and approved by the FDA, researchers will fully need to understand all aspects of the biology of these cells. An identification and understanding of any contaminating cells will also be essential to success in this field. The question to ask is “What is in the syringe?”

Unlike recombinant DNA, continued Dr. West, the contaminants in pluripotent stem cells are alive and may make things that are undesirable at the intended point of therapy. For example, you might have a bioreactor full of cells that are making heart muscle to regenerate heart function in a patient. But you have to be careful that your cells are not contaminated with neural crest cells from the head area which could generate a tooth along with the heart muscle.

“These contaminants, if you do not remove them, can lead to years of delay in filing an IND and a runup in costs as you try to identify these cells,” explained Dr. West.

The major problem in identifying them, according to Dr. West, is that no one has ever mapped the molecular markers or even a rudimentary cell ontology tree, i.e., mapped out the tree from the fertilized egg to the cells of the human body.

“If [there were] a detailed map of all the cellular and molecular components of life from the fertilized egg to adulthood, and then databased in a manner to the information in the human genome, medicine would be the true beneficiary,” added Dr. West. “That’s why we have made this call for an international initiative.”

Also, watch our video “A Brief History of Stem Cells” to see a timeline spanning over 60 years of stem cell research.

Mary Ann Liebert Wins Stem Cell Education Award

Mary Ann Liebert, president and CEO of Mary Ann Liebert Inc., and publisher of GEN, was presented with the Stem Cell Education Award by the Genetics Policy Institute. The award was given during a ceremony at dinner which took place at the World Stem Cell Summit, which is being held in San Diego this week.

Liebert was cited for her outstanding “work in educating patients, researchers, and the broader stem cell community, and in raising the standard in medical research journalism.” Among the seventy journals the Liebert company publishes is the peer-reviewed Stem Cells and Development.

In her acceptance speech Liebert told the audience that she was extremely gratified in being so recognized and thanked the entire staff at her company for their dedication in helping to promote excellence in medical publishing.

In his introductory remarks during the award ceremony GEN’s long-time editor in chief John Sterling noted that Mary Ann always encourages her editors and writers “to inform, enlighten when they can, and educate as much as possible.”

Sterling added that while she started her company 33 years ago her vision for her publications remains the same: “to help advance our knowledge of science and medicine in the best ways possible.”

Neural Precursors “Cure MS” in Mice

During a session at the this week’s World Stem Cell Summit in San Diego, an international research team described an “astonishing” experiment in which a mouse model of multiple sclerosis was able to virtually totally recover and move normally after being transplanted with human neural precursor cells (hNPC). The scientists were able to show almost full recovery in the mice up to six months later.

The investigators, led by Jeanne Loring, Ph.D., from the Scripps Research Institute, included scientists from the University of California, Irvine and a group from Australia.

“Our goal was to demonstrate cell therapy for MS,” Dr. Loring told the audience.

According to Ronald Coleman, a graduate student working with Dr. Loring and who is at UC-Irvine, the team used mice infected with a neurotropic JHM variant of mouse hepatitis virus (JHMV) as a model for MS. They injected hNPCs derived from human pluripotent stem cells (hPSC) into the mice to explore treatment options for the disease.

The results were indeed astonishing, said Dr. Loring. Non-control mice were able to move about in a manner that can be described as consistent and long lasting. T-cell proliferation was reduced and T regulatory cell induction took place. The spinal cords of the mice not only did not undergo further demyelination but actually exhibited remyelination. The control mice dragged their legs around when they tried to move.

“The only problem was that the hNPCs themselves are not directly responsible for the cure. They are not even there when the mice start walking,” explained Dr. Loring. “Those cells are rejected after seven days and we start to see a therapeutic response in three weeks.”

Both Dr. Loring and Coleman believe that the hNPCs are secreting proteins, like cytokines, that do the actual repair work in the CNS of the mice.

“We identified a set of candidate proteins secreted by hNPCs and not by undifferentiated pluripotent stem cells,” continued Dr. Loring, who said the team plans to continue building on this initial research.

World Stem Cell Summit: December 4, 2013 Update

GEN is on the scene at the World Stem Cell Summit in San Diego. Here are some highlights from the conference so far:

Bernard Siegel, J.D., founder and co-chair of the World Stem Cell Summit (WSCS) and executive director of Genetics Policy Institute, today welcomed attendees of WSCS 2013, being held December 4–6, in San Diego, CA.

“Stem cell science represents, to those afflicted with chronic disease, a vehicle for modeling disease and therapeutic development,” states Siegel in World Stem Cell Report 2013, a supplement to Stem Cells and Development (2013;22;Suppl1). “The field is a true scientific revolution and reflects the transformative power of hope, a powerful engine for progress.”

“The future is here now,” says Mahendra Rao, M.D., Ph.D., director, NIH Center for Regenerative Medicine, who delivered a plenary keynote and moderated the plenary panel discussion, “How Stem Cells are Transforming Medicine.” Cell therapies have been used to treat people safely and effectively; the technical barriers have been addressed. The challenge now is to reduce the cost of manufacturing. To drive routine adoption of cell therapy it must be cost effective and must demonstrate more than incremental benefit, according to Dr. Rao.

Professor Teruo Okano, Ph.D., Tokyo Women’s Medical University, described his group’s Cell Sheet Tissue Engineering strategy that involves enzymatic membrane disruption during cell harvesting and growth of an autologous cell sheet for transplantation on an “intelligent surface” that reversibly changes properties from hydrophobic to hydrophilic with a reversible in temperature from 37°C to 20°C. Dr. Okano further described the development of an automatic tissue factory and thick tissue evaluation system for fully automated, industrialized GMP cell processing.

Andre Terzic, M.D., Ph.D., Center for Regenerative Medicine, Mayo Clinic, noted during the opening session of the WSCS that “the Mayo Clinic has embraced regenerative medicine as a strategy for the future of medicine,” and he described their blueprint for moving from knowledge to delivery of treatments and procedures. Education is a critical dimension of this process. Another important component, according to Dr. Terzic, is the Regenerative Medicine Biotrust, in which “the patient is the center of the solution” to develop combinations of diagnostics and therapeutics and conduct clinical trials.

Regardless of the outcomes of current or future clinical trials, “I would argue that we have already seen breakthroughs,” said Evan Snyder, Ph.D., Sanford-Burnham Medical Research Institute, as stem cells “have completely changed the way medicine thinks about disease and development.” They have led to new views on plasticity and regeneration and the development of different types of drug targets.

WSCS 2013 is organized by the Genetics Policy Institute (GPI), California Institute for Regenerative Medicine (CIRM), Institute for Integrated Cell-Material Sciences at Kyoto University (iCeMS), Mayo Clinic, Sanford-Burnham Medical Research Institute, and The Scripps Research Institute. Mary Ann Liebert, Inc. publishers and Genetic Engineering & Biotechnology News (GEN) are sponsors of the summit.

Drug Testing Should Be with Human iPS Cells
Fri, 12/06/2013 – drug discovery & development (DDD)

Once established such neural stem cells can be used to continuously generate neurons for drug testing and disease modeling. Depicted is an immunofluorescence staining where proteins characteristic of neural stem cells are labeled with fluorescing antibodies (Nestin in green, Dach1 in red). (Source: Jerome Mertens / Uni Bonn)Once established such neural stem cells can be used to continuously generate neurons for drug testing and disease modeling. Depicted is an immunofluorescence staining where proteins characteristic of neural stem cells are labeled with fluorescing antibodies (Nestin in green, Dach1 in red). (Source: Jerome Mertens / Uni Bonn)Why do certain Alzheimer medications work in animal models but not in clinical trials in humans? A research team from the University of Bonn and the biomedical enterprise Life & Brain GmbH has been able to show that results of established test methods with animal models and cell lines used up until now can hardly be translated to the processes in the human brain. Drug testing should therefore be conducted with human nerve cells, conclude the scientists. The results are published by Cell Press in the journal Stem Cell Reports.

In the brains of Alzheimer’s patients, deposits form that consist essentially of beta-amyloid and are harmful to nerve cells. Scientists are therefore searching for pharmaceutical compounds that prevent the formation of these dangerous aggregates. In animal models, certain non-steroidal anti-inflammatory drugs (NSAIDs) were found to a reduced formation of harmful beta-amyloid variants. Yet, in subsequent clinical studies, these NSAIDs failed to elicit any beneficial effects.

“The reasons for these negative results have remained unclear for a long time”, said Oliver Brüstle, director of the Institute for Reconstructive Neurobiology of the University of Bonn and CEO of Life & Brain GmbH. “Remarkably, these compounds were never tested directly on the actual target cells—the human neuron”, added lead author Jerome Mertens of Brüstle’s team, who now works at the Laboratory of Genetics in La Jolla (USA). This is because, so far, living human neurons have been extremely difficult to obtain. However, with the recent advances in stem cell research it has become possible to derive limitless numbers of brain cells from a small skin biopsy or other adult cell types.

Scientists transform skin cells into nerve cells

Now a research team from the Institute for Reconstructive Neurobiology and the Department of Neurology of the Bonn University Medical Center together with colleagues from the Life & Brain GmbH and the University of Leuven (Belgium) has obtained such nerve cells from humans. The researchers used skin cells from two patients with a familial form of Alzheimer’s Disease to produce so-called induced pluripotent stem cells (iPS cells), by reprogramming the body’s cells into a quasi-embryonic stage. They then transformed the resulting iPS cells into nerve cells.

Using these human neurons, the scientists tested several compounds in the group of NSAIDs. As control, the researchers used nerve cells they had obtained from iPS cells of donors who did not have the disease. Both in the nerve cells obtained from the Alzheimer’s patients and in the control cells, the NSAIDs that had previously tested positive in the animal models and cell lines typically used for drug screening had practically no effect: The values for the harmful beta-amyloid variants that form the feared aggregates in the brain remained unaffected when the cells were treated with clinically relevant dosages of these compounds.

Metabolic processes in animal models differ from humans

“In order to predict the efficacy of Alzheimer drugs, such tests have to be performed directly on the affected human nerve cells”, concluded Brüstle’s colleague Philipp Koch, who led the study. Why do NSAIDs decrease the risk of aggregate formation in animal experiments and cell lines but not in human neurons? The scientists explain this with differences in metabolic processes between these different cell types. “The results are simply not transferable”, says Koch.

The scientists now hope that in the future, testing of potential drugs for the treatment of Alzheimer’s disease will be increasingly conducted using neurons obtained from iPS cells of patients. “The development of a single drug takes an average of ten years”, said Brüstle. “By using patient-specific nerve cells as a test system, investments by pharmaceutical companies and the tedious search for urgently needed Alzheimer medications could be greatly streamlined”.

Date: November 6, 2013
Source: University of Bonn