eNOS T-786C polymorphism affects atorvastatin-induced changes in erythrocyte membrane fluidity

Purpose  Statins have pleiotropic effects, including endothelial nitric oxide synthase (eNOS) upregulation and increased nitric oxide formation, which can be modulated by a genetic polymorphism in the promoter region of the eNOS gene (T-786C). Here, we report our investigation of whether this polymorphism modulates the effects of atorvastatin on the fluidity of erythrocyte membranes. Methods  We genotyped 200 healthy subjects (males, 18–60 years of age) and then randomly selected 15 of these with the TT genotype and 15 with the CC genotype to receive placebo or atorvastatin (10 mg/day oral administration) for 14 days. Cell membrane fluidity was evaluated by electron paramagnetic resonance (EPR) and spin-labeling method. The EPR spectra were registered on a VARIAN-E4 spectrometer. Thiobarbituric acid-reactive species (TBA-RS) and plasma membrane cholesterol were determined in the erythrocytes. Results  Atorvastatin reduced membrane fluidity in CC subjects (P < 0.05) but not in those with the TT genotype (P > 0.05). While no significant differences were found in plasma membrane cholesterol concentrations, higher TBA-RS concentrations were found in the CC subjects than in the TT subjects (P < 0.05). Conclusions  These findings suggest that a short treatment with atorvastatin is disadvantageous to subjects with the CC genotype for the T-786C polymorphism compared to those with TT genotype, at least in terms of the hemorheological properties of erythrocytes.     

Adverse balance of nitric oxide/peroxynitrite in the dysfunctional endothelium can be reversed by statins

Vascular endothelial dysfunction is a complex phenomenon that might be caused by a deficiency of nitric oxide (NO) and an overproduction of peroxynitrite (ONOO-). This study used a nanotechnological approach to monitor the in vitro effect of statins on the [NO]/[ONOO-] balance in normal and dysfunctional endothelial cells. NO and (ONOO-) were measured by electrochemical nanosensors in a single human umbilical vein endothelial cell (HUVEC) treated with atorvastatin or simvastatin for 24 hours in the presence or absence of 50 microg/mL oxidized-LDL. An imbalance between [NO]/[ONOO-] concentrations was used as an indicator of endothelial dysfunction and correlated with endothelial nitric oxide synthase (eNOS) expression. Ox-LDL induced dysfunction of the endothelium by uncoupling eNOS. NO concentration decreased from 300 +/- 12 to 146 +/- 8 nmol/L and (ONOO-) increased from 200 +/- 9 to 360 +/- 13 nmol/L. The [NO]/[ONOO-] balance decreased from 1.50 +/- 0.04 (control) to 0.40 +/- 0.03 for cells co-incubated with ox-LDL. Treatment with statins reversed eNOS uncoupling, induced by oxidized-LDL and significantly increased the [NO]/[ONOO-] balance to 1.2 +/- 0.1. These results demonstrate that statins can restore endothelial function by increasing eNOS expression, decreasing eNOS uncoupling, reducing the (ONOO-) level (nitroxidative stress), and shifting the [NO]/[ONOO-] balance towards NO.     

Statins, nitric oxide and neovascularization

Several landmark clinical trials suggest that 3-hydroxyl-3-methylglutaryl coenzyme A reductase inhibitors (statins) have additional cardiovascular protective activity that may function independently of their ability to lower serum cholesterol. The cardiovascular protective effects of statins are partly caused by the activation of postnatal neovascularization. At therapeutic doses, statins promote proliferation, migration and survival of endothelial cells, induce mobilization and differentiation of bone marrow-derived endothelial progenitor cells by stimulating the serine/threonine protein kinase Akt (also known as protein kinase B) and nitric oxide (NO) signal pathway. However, at excessive doses, statins may decrease protein isoprenylation as well as inhibit endothelial cell growth and migration. NO is an important signaling molecule that regulates a wide range of physiological and pathological processes in different tissues. There is substantial evidence that effective neovascularization requires endothelium-derived NO. Statins have pleiotropic effects on the expression and activity of endothelial nitric oxide synthase (eNOS) and lead to improved NO bioavailability. NO plays an important role in the effects of statins on neovascularization. In this review, we focus on the effects of statins on neovascularization and highlight specific novel targets, such as endothelial progenitor cells and NO.     

Statin mediated protection of the ischemic myocardium

Hypercholesterolemia is a major risk factor in the development of cardiovascular disease and HMG-CoA reductase inhibitors (i.e. statins) were originally designed to reduce serum cholesterol levels and thus reduce this risk factor. However, it has become increasingly apparent that the effects of statins extend well beyond their lipid lowering actions, and these pleiotropic effects have a major role in protecting the myocardium against ischemic injury. There have been a large number of clinical studies demonstrating the safety and efficacy of statins in reducing total mortality as well as many other secondary endpoint markers in patients with cardiovascular disease. In addition, statins appear to benefit patients with a variety of clinical conditions such as acute coronary syndromes and severe heart failure. Recent experimental studies demonstrated that stains can rapidly (i.e. within hours) upregulate endothelial nitric oxide synthase (eNOS) activity and nitric oxide (NO) production. These landmark studies of statins and eNOS function set the foundation for the investigation of the protective effects of statins. Many experimental studies investigating the effects of statins on eNOS and cardiac injury in the setting of ischemia and reperfusion have been performed in an attempt to determine the extent of the protection as well as the mechanism of the protection. This review article will focus on our current understanding of statin-mediated protection of the myocardium against ischemia-reperfusion injury and infarction.     

Beyond lipid-lowering: effects of statins on endothelial nitric oxide

Endothelial dysfunction is now recognised as an important process in the pathogenesis of atherosclerosis. Nitric oxide (NO) release by the endothelium regulates blood flow, inflammation and platelet aggregation, and consequently its disruption during endothelial dysfunction can decrease plaque stability and encourage the formation of atherosclerotic lesions and thrombi. Inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A reductase (statins) are often utilised in the prevention of coronary heart disease due to their efficacy at lowering lipid levels. However, statins may also prevent atherosclerotic disease by non-lipid or pleiotropic effects, for example, improving endothelial function by promoting the production of NO. There are various mechanisms whereby statins may alter NO release, such as inhibiting the production of mevalonate and important isoprenoid intermediates, thereby preventing the isoprenylation of the small GTPase Rho, which negatively regulates the expression of endothelial nitric oxide synthase (eNOS). Furthermore, statins may also increase eNOS activity via post-translational activation of the phosphatidylinositol 3-kinase/protein kinase Akt (PI3 K/Akt) pathway and/or through an interaction with the molecular chaperone heat-shock protein 90 (HSP90). Data suggest that statins may vary in their efficacy for enhancing the release of NO, and the mechanisms dictating these differences are not yet clear. By increasing NO production, statins may interfere with atherosclerotic lesion development, stabilise plaque, inhibit platelet aggregation, improve blood flow and protect against ischaemia. Therefore, the ability of statins to improve endothelial function through the release of NO may partially account for their beneficial effects at reducing the incidence of cardiovascular events.     

Efficacy of statins on sirtuin 1 and endothelial nitric oxide synthase expression: the role of sirtuin 1 gene variants in human coronary atherosclerosis

Statins are 3‐hydroxy‐3‐methylglutaryl coenzyme A reductase inhibitors and are used to reduce the risk of coronary artery disease (CAD) due to their pleiotropic effects. Recently, greater focus has been placed on the role of sirtuin 1 (SIRT1) in cardiovascular disease research. However, insufficient data exist on the relationships between statins, SIRT1 protein levels, and SIRT1 gene variants. In the present study, we investigated the effects of statins, atorvastatin and rosuvastatin, in CAD patients by analysing the associations between SIRT1 gene variants, rs7069102C>G and rs2273773C>T, and SIRT1/endothelial nitric oxide (eNOS) expression, as well as total antioxidant and oxidant status, and the oxidative stress index. SIRT1 expression was significantly higher, and eNOS expression was significantly lower in CAD patients when compared with controls. Statin treatment reduced SIRT1 expression and increased eNOS expression, similar to the levels found in the control population, independent from the studied SIRT1 gene variants. Oxidative stress parameters were significantly increased in CAD patients, and were decreased by statin treatment, demonstrating the antioxidative effects of statins on atherosclerosis. These results indicate that statin treatment could produce its protective effect on cardiovascular disease through the inhibition of SIRT1 expression. This is the first study reporting on the effect of statins, specifically atorvastatin and rosuvastatin, on SIRT1 expression in CAD patients.     

Korean Red Ginseng Water Extract Restores Impaired Endothelial Function by Inhibiting Arginase Activity in Aged Mice

Cardiovascular disease is the prime cause of morbidity and mortality and the population ages that may contribute to increase in the occurrence of cardiovascular disease. Arginase upregulation is associated with impaired endothelial function in aged vascular system and thus may contribute to cardiovascular disease. According to recent research, Korean Red Ginseng water extract (KRGE) may reduce cardiovascular disease risk by improving vascular system health. The purpose of this study was to examine mechanisms contributing to age-related vascular endothelial dysfunction and to determine whether KRGE improves these functions in aged mice. Young (10±3 weeks) and aged (55±5 weeks) male mice (C57BL/6J) were orally administered 0, 10, or 20 mg/mouse/day of KRGE for 4 weeks. Animals were sacrificed and the aortas were removed. Endothelial arginase activity, nitric oxide (NO) generation and reactive oxygen species (ROS) production, endothelial nitric oxide synthase (eNOS) coupling, vascular tension, and plasma peroxynitrite production were measured. KRGE attenuated arginase activity, restored nitric oxide (NO) generation, reduced ROS production, and enhanced eNOS coupling in aged mice. KRGE also improved vascular tension in aged vessels, as indicated by increased acetylcholine-induced vasorelaxation and improved phenylephrine-stimulated vasoconstriction. Furthermore, KRGE prevented plasma peroxynitrite formation in aged mice, indicating reduced lipid peroxidation. These results suggest KRGE exerts vasoprotective effects by inhibiting arginase activity and augmenting NO signaling and may be a useful treatment for age-dependent vascular diseases.     

Influence of statin use on endothelial function: from bench to clinics

Endothelial dysfunction has been shown to be a prognostic factor for cardiovascular disease and improvement of endothelial dysfunction prevents cardiovascular event presentation. Endothelial dysfunction is associated to a reduced nitric oxide (NO) bioactivity, as a result of the impairment of NO synthesis/release by the endothelial NO synthase (eNOS) or by inactivation of NO. Endothelial dysfunction measurements are valuable surrogate markers to assess the effectiveness of interventions addressed to prevent or treat coronary heart disease (CHD). Dyslipemia and other cardiovascular risk factors promote endothelial dysfunction and life style changes and pharmacological treatment, particularly HMG-CoA reductase inhibitors (statins), have shown early improve of endothelial-dependent vasomotion. Statins efficiently reduce plasma LDL cholesterol, an effect that may account for their beneficial effect on endothelial function, but they also reduce cellular levels of isoprenoid compounds relevant for the bioavailability of NO. Statins restore NO production by several mechanisms, including up-regulation of eNOS mRNA and protein levels and preservation of NO inactivation by reactive oxygen species (ROS). These effects are mediated, at least in a part, through mechanisms independent of their lipid lowering effect (pleiotropic effects). In this article we discuss the relevance of endothelium-dependent effects on the early and delayed clinical benefit of statins, as well as the multiple ways by which statins may restore endothelial function acting not only on the endothelium but also on endothelial progenitor cells (EPC), which likely could contribute to both ischemia-induced neovascularization and endothelial regeneration after injury.     

The soy isoflavone genistein induces a late but sustained activation of the endothelial nitric oxide-synthase system in vitro

Cardiovascular diseases are known as the major causes of death or disability in western countries. Decreased bioavailability of endothelial derived nitric oxide (NO) is recognized as an important promoter in cardiovascular disease. In vivo studies suggest that phytoestrogens, especially isoflavones from soy, enhance endothelium-dependent vasoreactivity. We hypothesized that isoflavones may affect the expression of endothelial-type nitric oxide synthase (eNOS) and thereby NO formation in vitro. Human EA.hy926 endothelial cells were treated with the soybean isoflavones biochanin A and formononetin and with their metabolites genistein and daidzein. eNOS promoter activity was examined by a luciferase reporter gene assay (20 h). Active eNOS was detected by quantifying conversion of L-arginine to L-citrulline and by measuring NO released from endothelial cells using the fluorescent probe DAF-2 (20-96 h).eNOS promoter activity increased in response to isoflavone treatment (20 h). NO and L-citrulline production by EA.hy926 cells rose up to 1.7-fold of control levels after stimulation with genistein for 48-96 h. From these results, we conclude that the suggested positive effects of soy isoflavones on vascular reactivity may be indeed mediated via a long-term effect on the eNOS system.     

内皮型一氧化氮合酶脱偶联的研究进展

血管内皮功能障碍(endothelial dysfunction)是多种心脑血管疾病的共同病理机制,其突出表现为内皮依赖性血管舒张功能障碍,主要由NO减少及氧自由基增加所致。最新研究发现,内皮型一氧化氮合酶脱偶联(eNOS uncoup ling)是导致NO水平下降和氧自由基水平升高的重要机制,是高血压、糖尿病、动脉粥样硬化等疾病中内皮功能障碍的重要原因。通过纠正eNOS脱偶联可有效改善内皮功能,有望为保护血管内皮功能提供有效途径。     

Therapeutic strategies targeting endothelial function in humans: clinical implications

Persistent oxidative stress in the vascular wall may lead to endothelial dysfunction, a pathological process widely implicated in the morbidities observed in a spectrum of cardiovascular disease. The production of reactive oxygen species (ROS) is regulated by various oxidase enzymes and mitochondrial electron transport mechanisms. Nitric oxide (NO) is a key mediator of endothelial function via its effect on endothelium dependent vascular relaxation. Therapeutic interventions aimed to increase NO bioavailability in the vasculature may improve the long term cardiovascular outcome for healthy individuals, high-risk subjects, and patients with advanced atherosclerosis. Current therapeutic strategies focus on enhancing synthesis or lowering oxidative inactivation of NO in human vasculature. Of the available therapeutic agents, angiotensin converting enzyme inhibitors and statins have shown most promise at improving endothelial function and cardiovascular outcome after long term administration. Other therapeutic approaches may also be useful towards improving endothelial dysfunction. These strategies include targeting NO synthesis by modulation of endothelial nitric oxide synthase (eNOS) coupling, such as folates and tetrahydrobiopterin. Evidence for the benefits of gene therapy to improve endothelial function is also emerging. However, the long term direct clinical benefit of these strategies aimed to improve endothelial function still remains unclear.     

Homocysteine impaired endothelial function through compromised vascular endothelial growth factor/Akt/endothelial nitric oxide synthase signalling

1. Hyperhomocysteinaemia (HHcy) is associated with endothelial dysfunction and has been recognized as a risk factor of cardiovascular disease. The present study aimed to investigate the effect of homocysteine (Hcy) on endothelial function in vivo and in vitro, and the underlying signalling pathways. 2. The HHcy animal model was established by intragastric administration with l ‐methionine in rats. Plasma Hcy and nitric oxide (NO) concentration were measured by fluorescence immunoassay or nitrate reductase method, respectively. Vasorelaxation in response to acetylcholine and sodium nitroprusside were carried out on aortic rings. Human umbilical vein endothelial cells (HUVEC) were treated with indicated concentrations of Hcy in the in vitro experiments. Intracellular NO level and NO concentration in culture medium were assayed. The alterations of possible signalling proteins were detected by western blot analysis. 3. l ‐methionine administration induced a significant increase in plasma Hcy and decrease in plasma NO. Endothelium‐dependent relaxation of aortic rings in response to acetylcholine was impaired in l ‐methionine‐administrated rats. The in vitro study showed that Hcy reduced both intracellular and culture medium NO levels. Furthermore, Hcy decreased phosphorylation of endothelial nitric oxide synthase (eNOS) at serine‐1177 and phosphorylation of Akt at serine‐473. Hcy‐induced dephosphorylation of eNOS at Ser‐1177 was partially reversed by insulin (Akt activator) and GF109203X (PKC inhibitor). Furthermore, Hcy reduced vascular endothelial growth factor (VEGF) expression in a dose‐dependent manner. 4. In conclusion, Hcy impaired endothelial function through compromised VEGF/Akt/endothelial nitric oxide synthase signalling. These findings will be beneficial for further understanding the role of Hcy in cardiovascular disease.     

Understanding eNOS for pharmacological modulation of endothelial function: a translational view

Knowledge about the function of endothelial nitric oxide synthase (eNOS), and its regulation in pathophysiological states has tremendously increased. It is now clear that diminished activity of nitric oxide (NO) contributes to endothelial dysfunction, which is a characteristic of impeding atherosclerosis. This review aims to summarize the available knowledge about the impact of important cardiovascular risk factors on NO production by eNOS. There are 4 principle causes of diminished NO bio-activity: decreased expression and/or activity of the eNOS enzyme, eNOS uncoupling, enhanced breakdown or scavenging of NO and impaired transmission of NO-mediated signaling events (failure of the effector mechanisms). From the analysis, it becomes clear, that several aspects of eNOS functionality have only scarcely been tested under conditions of increased (experimental) cardiovascular risk. These aspects include palmitoylation, myristoylation and phosphorylation of the eNOS enzyme. Clear is that enhanced production of reactive oxygen species (ROS) and eNOS uncoupling are relatively important causes of reduced NO-bioactivity in cardiovascular disease states. Ideally, eNOS is sufficiently expressed, produces NO sufficiently and not abundantly, does not produce superoxide and is not scavenged by ROS; the produced NO then reaches its signaling target, mainly soluble guanylyl cyclase (sGC) and elicits a cellular response. Considering which aspects of eNOS are now assessable in a clinical setting and which therapeutic measures are available, there is a great challenge ahead.     

Functional effects of endothelial nitric oxide synthase genetic polymorphisms on haemorheological parameters in healthy human individuals

The constitutive endothelial nitric oxide synthase (eNOS) plays a major role in circulatory homoeostasis and shows genetic polymorphism. eNOS is expressed and functional in blood cells, including erythrocytes. There is limited knowledge about the consequences of eNOS genetic variability in haemorheological parameters and erythrocyte functioning. The purpose of this study was to investigate the effects of three eNOS genetic polymorphisms, namely exonic G894T (Glu298Asp), intronic VNTR (27-bp repeat) and 5'-flanking T(-786)C polymorphisms on haemorheological variables, such as erythrocyte deformability and erythrocyte aggregation (rouleaux formation) in healthy non-smoking volunteers. Sixty subjects (19 women, 41 men) were examined for genotypes and haemorheological variables. Genotypes were determined by polymerase chain reaction and restriction analysis. Haemorheological variables were measured by means of a laser-assisted optical rotational cell analyser (LORCA). Erythrocyte aggregation was significantly decreased in individuals with 894TT genotype when compared to subjects with the (G) allele. Aggregation indices (AI) were 54.7±3.2% versus 61.0±0.9% (p=0.026), and the half-lives (t(1/2) ) for aggregation formation were 3.43±0.43 versus 2.55±0.12 sec. (p=0.024), respectively. Similarly, VNTR-bb genotype significantly altered erythrocyte aggregability. AI values were 58.7±1.1% in subjects with VNTR-a allele versus 63.7±1.2% in subjects with bb genotype (p=0.011); t(1/2) values were 2.86±0.16 versus 2.20±0.13 sec., respectively (p=0.016). T(-786)C polymorphism did not change any haemorheological parameters. These findings suggest that eNOS 894TT genotype is associated with decreased erythrocyte aggregation, while VNTR-bb genotype increases aggregability in healthy human individuals. eNOS genetic variants may contribute in the pathogenesis of microvascular disorders by altering erythrocyte functions in human beings.     

Effects of angiotensin receptor blockers on endothelial nitric oxide release: the role of eNOS variants

AIM

Angiotensin II receptor blockers (ARBs) improve endothelial cell (EC)-dependent vasodilation in patients with hypertension through suppression of angiotensin II type 1 receptors but may have additional and differential effects on endothelial nitric oxide (NO) synthase (eNOS) function. To investigate this question, we tested the effects of various ARBs on NO release in ECs from multiple donors, including those with eNOS genetic variants linked to higher cardiovascular risk.

METHODS

The effects of ARBs (losartan, olmesartan, telmisartan, valsartan), at 1 µm, on NO release were measured with nanosensors in human umbilical vein ECs obtained from 18 donors. NO release was stimulated with calcium ionophore (1 µm) and its maximal concentration was correlated with eNOS variants. The eNOS variants were determined by a single nucleotide polymorphism in the promoter region (T-786C) and in the exon 7 (G894T), linked to changes in NO metabolism.

RESULTS

All of the ARBs caused an increase in NO release as compared with untreated samples (P < 0.01, n = 4–5 in all eNOS variants). However, maximal NO production was differentially influenced by eNOS genotype. Olmesartan increased maximal NO release by 30%, which was significantly greater (P < 0.01, n = 4–5 in all eNOS variants) than increases observed with other ARBs.

CONCLUSIONS

The ARBs differentially enhanced NO release in ECs in a manner influenced by eNOS single nucleotide polymorphisms. These findings provide new insights into the effects of ARBs on EC-dependent vasodilation and eNOS function.     

Endothelial caveolar subcellular domain regulation of endothelial nitric oxide synthase

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