Posts Tagged ‘vascular biology’

Curated/reported by : Aviral Vatsa PhD, MBBS

Based on : S Moncada et al

It was in 1980 that Furchgott & Zawadzki first described endothelium- dependent relaxation of the blood vessels by acetylcholine. Further studies in 1984 revealed that other factors such as bradykinin, histamine and 5-hydroxytryptamine release endothelium derived relaxing factor (EDRF), which can modulate vessel tone. EDRF was shown to stimulate soluble guanylate cyclase and was inhibited by haemoglobin. In 1986 it was demonstrated that superoxide (O2) anions mediated EDRF inactivation and that the inhibitors of EDRF generated superoxide (O2) anions in solution as a mean to inhibit EDRF. It was later established that all compounds that inhibit EDRF have one property in common, redox activity, which accounted for their inhibitory action on EDRF. One exception was haemoglobin, which inactivates EDRF by binding to it. In 1987 Furchgott proposed that EDRF might be nitric oxide (NO) based on a study of the transient relaxations of endothelium-denuded rings of rabbit aorta to ‘acidified’ inorganic nitrite (NO) solutions and the observations that superoxide dismutase (SOD, which removes O2) protected EDRF. Till then NO was not known to be produced in mammalian cells. In 1988 Palmer et al could detect NO production both biologically and chemically by chemiluminescence. The following year in 1989 the enzyme responsible for NO production, NO synthase, was discovered and L-arginine:NO pathway was proposed.

Roles of L-arginine:NO pathway

By 1987 it was proposed that NO is generated in tissues other than endothelium. Hibbs et al and Marletta et al proposed that NO was generated by macrophages. Moreover release of EDRF was demonstrated in cerebellar cells following activation with N-methyl-D- aspartate (NMDA ). Both noradrenergic and cholinergic responses are ‘controlled’ by the nitrergic system so that the release of NO (e.g., during electrical field stimulation) counteracts and dominates the response to the noradrenergic or cholinergic stimulus (Cellek & Moncada, 1997). Mechanism of penile erection was unveiled by the studies on nitrergic neurotransmission that led to therapeutic intervention. Selective damage of nitrergic nerves in disease states was proposed as a potent mechanism of pathophysiology. Broadly three areas of research based on three isoforms of NOS came into being;

  • cardiovascular
  • nervous
  • immunology

Identification of NG-monomethyl-L-arginine (L-NMMA) as an inhibitor of the synthesis of NO lay the basis of future research into investigating the role of NO in biological systems. In 1989 it was demonstrated that intravenous infusion of L-NMMA resulted in increase in blood pressure that was reversible by infusing L-arginine. NO was thus implicated in constantly maintaining blood vessel tone. eNOS knockout studies showed a hypertensive phenotypes in the animal models and over expression of eNOS led to lowering of the blood pressure. Furthermore, eNOS activation was attributed to phosphorylation of a specific tyrosine residue in the enzyme.

NO and Mitochondria 


NO reacts with some of the complexes of the respiratory chain, and inhibits mitochondrial respiration – this is a well accepted notion. Initially it was believed that the target for NO was soluble guanylate cyclase, which in vasculature would lead to elevation of cGMP that eventually results in NO mediated vasodilatation and platelet aggregation inhibition. In 1994, another potential target, cytochrome c oxidase, for inhibitory effects of NO was discovered. This was a reversible effect, in competition with oxygen concentrations. Increases in NO production were also shown to inhibit cellular respiration irreversibly by selectively inhibiting complex I . Hence in 2002 it was proposed that this might be a mechanism through which cell pathology was initiated in certain conditions. Furthermore, NO was proposed to be implicated in the activation of the grp78-dependent stress response , via modulating calcium-related interaction between mitochondria and endoplasmic reticulum . This host defence mechanism might also have role in vasculature. Further evidence was provided in 2003 to link the role of NO in mitochondrogenesis and thus indicating that NO might be involved in the regulation of the balance between glycolysis and oxidative phosphorylation in cells.

NO and Pathophysiology

Lack of NO: By 2000, NO was established as a haemostatic regulator in the vasculature. Its absence was implicated in pathological states such as hypertension and vasospasm. These pathophysiological states share a common beginning of endothelial dysfunction, which has low NO production as one of its characterstic features. This dysfunction has been observed prior to the appearance of cardiovascular disease in predisposed subjects with family history of essential hypertension and atherosclerosis. The most likely mechanism for endothelial dysfunction is that of a reduced bioavailability of NO . The mechanism of this aspect is discussed elsewhere on this site. Protection against reduction of NO bio-availability in the vasculature is a vital therapeutic target and is extensively explored. This can be achieved by the use of antioxidants and/or augmentation of eNOS expression. In 2003 statins were shown to increase the production of endothelial NO in endothelial cell cultures and in animals by the reduction of oxidative stress or by increasing the coupling of the eNOS. It was way back in 1994 that oestrogen was shown to increase both the activity and expression of eNOS. In addition, more recently in 2003, oestrogen was shown to reduce the breakdown of available NO.

Excess of NO: In 2000 it was shown that NO produced from iNOS in vasculature is involved in extensive vasodilatation in septic shock. Later it was demonstrated that inhibition of mitochondrial respiration is an important component of the NO-induced tissue damage. This inhibition of respiration, which is initially NO-dependent and reversible, becomes persistent with time as a result of oxidative stress . Such metabolic hypoxic states where in tissues cannot utilise available oxygen due to NO, could also contribute to other inflammatory and degenerative conditions. An obvious therapeutic target for reducing NO production in such conditions would be L-NMMA. L-NMM was tested in a clinical trial for septic shock in 2004. The results were however disappointing probably due to the blanket reduction in NO production from other NOS enzymes there by having deleterious effects on the treatment group. More specific inhibitors for NOS forms are being investigated for in different disease states.

In conclusion, the L-arginine: NO pathway has had a major impact in many areas of research, specially vascular biology. A lot has been understood about this pathway and its interactions, therapeutic targets are being aggressively investigated, but further investigations are required to delineate further the role of NO in human health and disease.

Further Reading


Nitric Oxide and Platelet Aggregation

Inhaled NO in Pulmonary Artery Hypertension and Right Sided Heart Failure

Cardiovascular Disease (CVD) and the Role of agent alternatives in endothelial Nitric Oxide Synthase (eNOS) Activation and Nitric Oxide Production

Nitric Oxide in bone metabolism

Nitric oxide and signalling pathways

Rationale of NO use in hypertension and heart failure

Interaction of Nitric Oxide and Prostacyclin in Vascular Endothelium

Nitric Oxide has a ubiquitous role in the regulation of glycolysis -with a concomitant influence on mitochondrial function

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


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


Classification of Fast Acting Therapies for Patients at High Risk for Macrovascular events

Macrovascular Disease – Therapeutic Potential of cEPCs


The two leading therapy classes are:

  1. Cell-based Therapies for angiogenesis and myocardial regeneration
  2. Intracoronary Delivery of Autologous Bone Marrow originating cells to restore Ischemic Tissue

The European Meeting on Vascular Medicine and Biology is a biannual international conference. The 3rd European Meeting on Vascular Medicine and Biology, took place in September 2005 and the next conference will be in 2007. All abstract presentations are published in Supplement 2, JOURNAL OF VASCULAR RESEARCH, Volume 42, 2005.

Review of 355 abstracts of posters presented at the conference has identified the following twenty Research Frontiers in Vascular Biology and Vascular Disease.

One abstract is of special interest to the line of research which focus on endogenous augmentation of cEPCs and to reduction of CVD risk by endogenous induction of regression of atherosclerotic plaques. It was selected by being judged to have the highest potential for commercialization and the potential to replace several therapeutic agents with higher efficacy.

P119 IgG1 antibodies against oxLDL epitopes induce regression of advanced atherosclerotic plaques in LDLR-/- APOBEC mice.

A. Schiopu1, B. Jansson2, P.K. Shah3, R. Carlsson3, J. Nilsson1, G. Nordin Fredrikson1Department of Medicine, Malmö University Hospital, Lund University, Malmö, SE; 2 BioInvent International AB, Lund, SE; 3 Atherosclerosis Research Center, Cedars-Sinai Medical Center, UCLA School of Medicine, Los Angeles, US.

Objective: The purpose of our study was to assess the effects of recombinant human IgG1 antibodies against specific oxLDL epitopes on advanced atherosclerotic lesions in mice.

Methods: We have tested 2 recombinant human IgG1 antibodies directed to malondialdehyde (MDA)-modified ApoB-100 peptide sequences. Three weekly 1 mg antibody doses were injected intraperitoneally starting at 25 weeks in LDLR-/-Apobec mice, which were then sacrificed at 29 weeks of age. IgG1 antibodies directed against fluorescein isothiocyanate, which do not bind to either native or oxidized LDL, and a

baseline group sacrificed at 25 weeks of age, to asses plaque status before immunization, were used as controls.

Results: Both antibodies induced a significant regression of already present atherosclerotic plaques in the descending aorta as compared to baseline. This effect was not present in the isotype control group. The changes did not depend on alterations in weight, cholesterol or triacylglycerol content in mice plasma.

Conclusions: The present study suggests that antibody treatment has the ability to reduce the extent of already present, advanced atherosclerotic lesions. Passive immunization with antibodies directed against oxLDL epitopes might constitute a future fast acting therapy for patients at high risk for acute cardiovascular events.

Twenty Research Frontiers in Vascular Medicine of Human Endothelium


Research Frontiers in Vascular Biology and Vascular Disease 



International Research Projects

Stem Cell biology Embryonic stem cells in cardiovascularrepairEarly differentiation of human endothelial progenitor cellsVessels transmigration of stem cells depends on activation of the endothelium.

Interaction of embryonal endothelial progenitor cells with platelets

Role of smooth muscle cell progenitors on atherosclerotic plaque development and stability.


Ischemia  and Reperfusion Connexin 43 and myocardial ischemia/reperfusioninjuryEndothelialreperfusion injuryA possible role for hypoxia-inducible factor 1• in protection against reperfusion injury


Genetic Basis of Vascular Disease Cardiovascular genomics and oxidative stressNox1 mediates basic fibroblast growth factor induced vascular smooth muscle cell migrationReactive oxygen species upregulate NOX4, but not NOX2, in endothelial cells

Induction of prolyl hydroxylase 2 by nitric oxide interferes with the hypoxia induced feedback loop of HIF-1• regulation

Protein disulfide isomerase is a central

regulator of NADPH oxidase activity


Inflammation Inflammatory mediatorsofvascularInflammationIsoprostanes inhibit in vitro migration and tube formation of endothelial cells via the thromboxane A2 receptor.

Heme oxygenase-1-dependent and

-independent regulation of angiogenic and inflammatory genes expression in human microvascular endothelial cells


Tissue Engineering Engineered heart tissueEndothelial tissue engineeringBlood vessel growth and remodeling in in-vivo tissue engineering

The effects of cyclic strain on the cytoskeleton of vascular smooth muscle cells


Atherosclerosis Imaging Experimental In vivo imaging ofatherosclerosisHoming ofCD34+ progenitor cells to sites ofangiogenic tube formation using real-time video microscopy.Relation between lipoprotein(a) and fibrinogen and serial intravascular ultrasound plaque progression in left main stems

Cardiovascular Development Controlled by Fluid Shear Stress. A Functionomic Approach.

Dynamics in microvascular alterations in UCP/DTA mice in vivo – from metabolic syndrome to diabetes mellitus type 2

Vascular Cell Signaling TGF-beta in endothelial cell functionandvascular developmentVEGF signaling


Atherosclerosis (Clinical / In Vivo) Pathophysiology of cigarette smoking-inducedatherosclerosisThe homeostatic benefits of plaque ruptureEarly coronary atherogenesis as a

consequence of chronic in-vivo proteasome inhibition.


Renin-Angiotensin System ACE inhibitorsstimulate endothelialCOX-2expression by aJNK-dependent ACE signalling pathway.A new ACE on the table: ACE2 expression in human atherosclerosis

Role of the ACE gene in renal and vascular complications of diabetes mellitus, experimental study in the mouse.

Bone marrow molecular alterations after

myocardial infarction: impact on endothelial progenitor cells and modulation by ACE inhibition or statin treatment.

Anti-inflammatory properties of Ramiprilat: reduction of monocyte adhesion to angiotensin II-stimulated endothelium is associated with AT1 downregulation.

Activation of phospholipase D by angiotensin II in HUVECS and HMVECS

Pathogenesis of Atherosclerosis Metalloproteinases in vascular pathologywhat we know and what we don’t know.
Stem Cell Therapy Functional assessment of circulatingcellsHuman fetal vascular progenitor cellsaccelerate the healing of ischemic diabetic ulcers

Peri-infarct gene transfer of human tissue kallikrein gene prevents left ventricle dysfunction by stimulating

angiogenesis/arteriogenesis and cardiac stem cell activation and by inhibiting cardiomyocyte apoptosis.


Genomics / Proteomics in Vascular Biology Genomic analysis of animal modelsforatherosclerosis.Differential gene expression analysis of tube forming and non-tube forming microvascular endothelial cells in vitro, separated by differences in morphology

Proteomic and metabolomic analysis of

atherosclerotic vessels in ApoE-/- mice

Hypoxic angiogenic transcriptome in human keratinocytes and microvascular endothelial cells: macroarray and real-time PCR analysis.

Gene expression profiling of human red blood cells.


Oxidant and Lipid Signaling Lipid modifications in atherogenesis.Epoxyeicosatrienoic acids in vascularHomeostasis

Oxidized phospholipids as modulators of


Chemokines — Cell-Cell Interactions Endothelial cell-to-celljunctionsInterplay ofchemokines and platelets invascular cell recruitment


Vascular Development Embryonic vesseldeterminationVascular remodeling: differentiation ofarteries, veins and lymph vessels


Vascular Aneurysms and VascularDegradation MMP in aneurysmdevelopmentFurin-likeproproteinconvertases regulate membrane type-1 matrixmetalloproteinase in atherosclerosisNon-viral, electroporation mediated gene

transfer of TIMP-1.ATF, a cell-surface directed MMP inhibitor, suppresses intimal hyperplasia in vein grafts more efficiently than TIMP-1 in vivo.

EMMPRIN regulates MMP activity in

cardiovascular cells. Implications in Acute Myocardial Infarction.

NF-kB promotes monocyte adhesion in vessels exposed to high intraluminal pressure

Diabetes Mellitus and InsulinResistance The endothelial cellglycocalyx indiabetesVasocrine signaling and insulin resistanceEarly arteriogenic defects in a diabetic

ischemic hindlimb model

Diabetes-induced overproduction of reactive oxygen species impairs post-ischemic neovascularization


Microparticles / Platelets The significance of membranemicroparticles in vascular pathophysiology andintercellularcommunication.Influences of nuclear receptors on platelet function.

Cellular origin of microparticles in human

atherosclerotic plaques

Apoptotic microparticles derived from

endothelial cells, smooth muscle cells and monocytes induce thrombin generation via different pathways

Smooth Muscle Cells Role of epigenetic mechanisms in control of SMC differentiation in development anddiseaseThe cytoskeletal proteinzyxin is amechanosensitive signaltransducer in vascular smooth muscle cells.Leukotriene-induced migration and

proliferation of vascular smooth muscle cells: implications for atherosclerosis and restenosis


Stem Cells Transfer of stem cell-derived endothelial cells retardedneointimal lesions in the injured artery.Stimulation ofreendothelialization viarecruitment of endothelial progenitor cells with selective antibodies against progenitor cell surface markers

Caspase-8 activity is essential for endothelial progenitor cell adherence

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