Endothelial nitric oxide synthase haplotypes are related to blood pressure elevation, but not to resistance to antihypertensive drug therapy

The Role of Single Nucleotide Variants of NOS1, NOS2, and NOS3 Genes in the Development of the Phenotype of Migraine and Arterial Hypertension

Migraine (M) and arterial hypertension (AH) are very common diseases. Today, there are a number of studies confirming and explaining their comorbidity. We searched PubMed, Springer, Scopus, Web of Science, Clinicalkeys, and Google Scholar databases for full-text English publications over the past 15 years using keywords and their combinations. The present review provides a synthesis of information about single nucleotide variants (SNVs) of NOS1, NOS2, and NOS3 genes involved in the development of M and essential AH. The results of studies we have discussed in this review are contradictory, which might be due to different designs of the studies, small sample sizes in some of them, as well as different social and geographical environments. Despite a high prevalence of the M and AH phenotype, its genetic markers have not yet been sufficiently studied. Specifically, there are separate molecular genetic studies aimed to identify SNVs of NOS1, NOS2, and NOS3 genes responsible for the development of M and those responsible for the development of AH. However, these SNVs have not been studied in patients with the phenotype of M and AH. In this review, we identify the SNVs that would be the most interesting to study in this aspect. Understanding the role of environmental factors and genetic predictors will contribute to a better diagnostics and exploration of new approaches to pathogenetic and disease-modifying treatment of the M and AH phenotype.

The Role of Single-Nucleotide Variants of NOS1, NOS2, and NOS3 Genes in the Comorbidity of Arterial Hypertension and Tension-Type Headache

Patients with tension-type headache (TTH) have an increased risk of developing arterial hypertension (AH), while hypertensive subjects do seem to have an increased risk of TTH. We searched for full-text English publications in databases using keywords and combined word searches over the past 15 years. In addition, earlier publications of historical interest were included in the review. In our review, we summed up the single nucleotide variants (SNVs) of Nitric Oxide Synthases (NOSs) genes involved in the development of essential AH and TTH. The results of studies we discussed in this review are contradictory. This might be due to different designs of the studies, small sample sizes in some of them, as well as different social and geographical characteristics. However, the contribution of genetic and environmental factors remains understudied. This makes the issue interesting for researchers, as understanding these mechanisms can contribute to a search for new approaches to pathogenetic and disease-modifying treatment of the AH and TTH phenotype. New drugs against AH and TTH can be based on inhibition of nitric oxide (NO) production, blockade of steps in the NO-cGMP pathway, or NO scavenging. Indeed, selective neuronal NOS (n-NOS) and inducible NOS (i-NOS) inhibitors are already in early clinical development.

Does eNOS derived nitric oxide protect the young from severe COVID-19 complications?

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Aging is the largest risk factors for severity and mortality in adult COVID-19.

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Severe cases of COVID-19 are related to vascular damage with evidence of direct viral infection in the endothelial cells.

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Increase risk of COVID-19 death are also highly related to disease with lower vascular Nitric Oxide (NO) level.

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Vascular viral defence by endothelial nitric oxide synthase (eNOS) derive NO may be the protecting factor for the young.

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eNOS polymorphism could potentially explain the disparity of COVID-19 mortality between Asian and non-Asian countries.

The COVID-19 pandemic poses an imminent threat to humanity, especially to the elderly. The molecular mechanisms underpinning the age-dependent disparity for disease progression is not clear. COVID-19 is both a respiratory and a vascular disease in severe patients. The damage endothelial system provides a good explanation for the various complications seen in COVID-19 patients. These observations lead us to suspect that endothelial cells are a barrier that must be breached before progression to severe disease. Endothelial intracellular defences are largely dependent of the activation of the interferon (IFN) system. Nevertheless, low type I and III IFNs are generally observed in COVID-19 patients suggesting that other intracellular viral defence systems are also activated to protect the young. Intriguingly, Nitric oxide (NO), which is the main intracellular antiviral defence, has been shown to inhibit a wide array of viruses, including SARS-CoV-1. Additionally, the increased risk of death with diseases that have underlying endothelial dysfunction suggest that endothelial NOS-derived nitric oxide could be the main defence mechanism. NO decreases dramatically in the elderly, the hyperglycaemic and the patients with low levels of vitamin D. However, eNOS derived NO occurs at low levels, unless it is during inflammation and co-stimulated by bradykinin. Regrettably, the bradykinin-induced vasodilation also progressively declines with age, thereby decreasing anti-viral NO production as well. Intriguingly, the inverse correlation between the percentage of WT eNOS haplotype and death per 100K population could potentially explain the disparity of COVID-19 mortality between Asian and non-Asian countries. These changes with age, low bradykinin and NO, may be the fundamental reasons that intracellular innate immunity declines with age leading to more severe COVID-19 complications.

Endothelial Nitric Oxide Synthase Gene Polymorphisms (- 922A > G, - 786 T > C, Intron 4 b/a VNTR and 894 G > T) and Essential Hypertension: An Association Study with Haplotypes Analysis

Endothelial Nitric Oxide Synthase (eNOS) is an indispensable regulator of blood pressure through producing Nitric Oxide (NO). There is some evidence to suggest that eNOS gene polymorphisms are associated with Essential Hypertension (EHT). In this study, the potential association between eNOS 4a/4b, A922G, G894T, T786C gene polymorphisms and EHT as individual risk factors and as haplotypes are examined in the southern population of Iran (Bandar-Abbas). In this study, 200 EHT patients and 200 normotensive subjects which were matched for age and sex were included. Genotyping was performed by either utilizing Polymerase Chain Reaction (PCR) or PCR followed by Restriction Fragment length Polymorphism (RFLP) method. Our results demonstrated statistically significant associations between T786C, G894T, and 4a/4a and EHT (p < 0.05); however, A922G had no significant association with EHT (p > 0.05). Haplotype analysis also suggested that - 786C/- 922A/4a, - 786C/- 922A/4b and - 786C/- 922G/4a haplotypes were more frequent in EHT group than control group, hypothesizing a positive association with EHT. The present study has identified that the eNOS genetic variations are associated with EHT in southern population of Iran (Bandar-Abbas). These findings also suggested that a number of haplotypes of eNOS gene may be a driving factor for EHT susceptibility in respected population.

Pharmacogenetic Implications of eNOS Polymorphisms (Glu298Asp, T786C, 4b/4a) in Cardiovascular Drug Therapy

Endothelial nitric oxide synthase (NOS3 or eNOS) is the enzyme responsible for the highest production of nitric oxide, with the greatest impact on the cardiovascular system, encoded by the eNOS gene, which presents various polymorphisms. ENOS gene polymorphisms play an important role in the response to drugs affecting nitric oxide (NO) signaling. This review discusses the pharmacogenetic impact of eNOS polymorphisms on the response to drugs affecting NO activity: angiotensin converting enzyme inhibitors, angiotensin II receptor antagonists, calcium blockers, beta-blockers, diuretics, phosphodiesterase inhibitors, and statins. The identification of biomarkers that accurately predict particular phenotypes is a challenge that needs additional large studies, in different populations. Efforts should be oriented towards a more accurate evaluation of the effects of eNOS genetic variants on biochemical parameters reflecting eNOS gene expression and enzymatic activity, in different diseases, as well as following drug treatment. This approach will allow for a better understanding of the role of eNOS genetic variants in cardiovascular disease progression and for cardiovascular drug therapy optimization.

Genetic association study between T-786C NOS3 polymorphism and essential hypertension in an Algerian population of the Oran city

BACKGROUND

Essential hypertension is an important risk factor for the development of cardiovascular disease. Important candidate genes such as NOS3 gene have been widely studied and reported to be associated with essential hypertension (HTN) in human populations.

AIM

We aim in this study to analyze the relationship between NOS3 -786T/C, a common genetic variant and HTN in a sample of the Algerian population of the Oran city.

METHODS

A case-control study has been performed in 154 subjects including 77 hypertensives and 77 normotensives. The recruitment of these subjects was done in local Health Centers of the city of Oran, West Algeria. HTN was defined as elevated systolic blood pressure SBD≥140  mmHg and or sustained diastolic blood pressure DBP≥90  mmHg, measured using an Omron^® Automatic BP Monitor - M-3W machine. Consents were obtained from all participants. Polymerase chain reaction (PCR) combined with restrictive fragment length polymorphism (RFLP) was used to genotype the NOS -786T/C variant.

RESULTS

The distribution of the allelic frequencies did not differ between cases and controls (OR = 1.48; 95%CI [0.94-2.32], P = 0.09). However, after adjustment with the age, sex, and body mass index, we observed significant association between NOS -786C allele and HTN status (OR = 2.08; 95%CI [1.18-3.66], P = 0.01).

CONCLUSION

Our results indicate that the C allele of the NOS3 gene is associated with increased risk of essential hypertension in this sample of the Algerian population of the Oran city. Further validation in larger samples is needed to confirm this finding.

Resveratrol lowers blood pressure in spontaneously hypertensive rats via calcium-dependent endothelial NO production

OBJECTIVE

Resveratrol, a polyphenol of natural compounds, has beneficial cardiovascular effects, many of which are mediated by nitric oxide (NO). Resveratrol increases intracellular calcium and activates AMP-activated protein kinase (AMPK), all of which could increase NO production. We hypothesized that resveratrol via a calcium-dependent NO production lowers blood pressure (BP) in spontaneously hypertensive rats (SHR).

METHODS

Acetylcholine (Ach)-induced endothelium-dependent relaxations in rat aortas were examined by organ chamber. Blood pressures were determined by radiotelemetry methods.

RESULTS

Incubation of isolated aortas from SHR with resveratrol dramatically improved vasorelaxation induced by Ach. Preincubation of aortas with endothelial NO synthase (eNOS) inhibitor or calcium chelant blunted the effects of resveratrol on Ach-induced relaxation, as wells as NO production and eNOS phosphorylation. In animal studies, administration of resveratrol significantly lowered systemic BP in SHR.

CONCLUSION

Resveratrol increases endothelial NO production to improve endothelial dysfunction and lowers BP in hypertensive rats, which depends on calcium-eNOS activation.

Endothelial nitric oxide synthase: From biochemistry and gene structure to clinical implications of NOS3 polymorphisms

Nitric oxide (NO) is an important vasodilator with a well-established role in cardiovascular homeostasis. While mediator is synthesized from L-arginine by neuronal, endothelial, and inducible nitric oxide synthases (NOS1,NOS3 and NOS2 respectively), NOS3 is the most important isoform for NO formation in the cardiovascular system. NOS3 is a dimeric enzyme whose expression and activity are regulated at transcriptional, posttranscriptional,and posttranslational levels. The NOS3 gene, which encodes NOS3, exhibits a number of polymorphic sites including single nucleotide polymorphisms (SNPs), variable number of tandem repeats (VNTRs), microsatellites, and insertions/deletions. Some NOS3 polymorphisms show functional effects on NOS3 expression or activity, thereby affecting NO formation. Interestingly, many studies have evaluated the effects of functional NOS3 polymorphisms on disease susceptibility and drug responses. Moreover, some studies have investigated how NOS3 haplotypes may impact endogenous NO formation and disease susceptibility. In this article,we carried out a comprehensive review to provide a basic understanding of biochemical mechanisms involved in NOS3 regulation and how genetic variations in NOS3 may translate into relevant clinical and pharmacogenetic implications.

Antihypertensive therapy in preeclampsia is not modulated by VEGF polymorphisms

INTRODUCTION

Vascular endothelial growth factor (VEGF) is relevant for healthy pregnancy, and abnormalities in VEGF functions have been associated with hypertensive disorders of pregnancy. Our group recently demonstrated that VEGF genetic polymorphisms affect the susceptibility to preeclampsia (PE).

OBJECTIVE

Therefore, in this study our aim is to examine whether VEGF polymorphisms affect the antihypertensive responses in women with PE.

METHODS

We studied 113 white PE women who were stratified according to blood pressure levels after antihypertensive treatment (46 responsive, R group and 67 non-responsive, NR group). We then compared the frequencies of two VEGF genetic polymorphisms (C-2578A and G-634C) between R and NR groups.

RESULTS

We found no significant differences in genotype or allele distributions between R and NR groups (P > 0.05). In addition, no difference was observed in overall distribution of haplotypes (P > 0.05).

CONCLUSION

Our data suggest that VEGF polymorphisms do not affect responsiveness to the antihypertensive therapy in PE.

Endothelial nitric oxide synthase gene polymorphisms and the risk of hypertension in an Indian population

Genetic variants of eNOS gene play a significant role in the pathogenesis of hypertension. Many environmental factors have, also, been implicated in the aetiology of hypertension. We carried out an age-matched case-control study among adults. Hypertension was defined according to JNC-VII criteria and eNOS gene polymorphisms were determined by PCR and PCR followed by PCR-RFLP. eNOS intron 4 aa genotype (adjusted OR 6.81; 95% CI 2.29–20.25) and eNOS 894TT genotype (adjusted OR 7.84; 95% CI 2.57–23.96) were associated with the risk of hypertension. Tobacco users (either smoking/chewing or both) with eNOS intron 4 aa genotype (OR 14.00: 95% CI 1.20–163.37), eNOS 894GG genotype (OR 5.56: 95% CI 3.72–8.31), and eNOS T-786C CC genotype (OR 9.00: 95% CI 1.14–71.04) were at an increased risk of hypertension. Similarly a significant gene-environment interaction was observed between individuals consuming alcohol with eNOS intron 4 aa genotype (OR 12.00: 95% CI 1.20–143.73) and eNOS 894GG genotype (OR 1.95: 95% CI 1.35–2.81). The present study identified few susceptible genotypes of the eNOS gene with the risk of hypertension. Moreover, the interactive effects between the environmental factors and the risk of hypertension were dependent on the eNOS genotypes.

The effects of endothelial nitric oxide synthase tagSNPs on nitrite levels and risk of hypertension and obesity in children and adolescents

Obesity and the nitric oxide synthase 3 (NOS3) gene polymorphisms are associated with nitrite levels and hypertension. However, no study has tested the hypothesis that NOS3 tagSNPs rs3918226, rs3918188, rs743506 and rs7830 affect nitrite levels and are associated with hypertension in childhood obesity. We investigated the association of these NOS3 tagSNPs and the haplotypes formed by them with hypertension and with nitrite levels in children and adolescents with obesity and with obesity plus hypertension. We studied 355 subjects: 174 healthy (controls), 109 normotensive obese, and 72 obese children and adolescents with obesity plus hypertension. Genotypes were determined by Taqman allele discrimination assay and real-time PCR. We compared the distribution of NOS3 tagSNP genotypes, alleles and haplotypes in the three groups of subjects. Nitrite levels were determined by ozone-based chemiluminescence. Nitrite levels were affected by the rs3918226 polymorphism (P<0.05) but not by NOS3 haplotypes. There was no association between the tagSNPs studied and hypertension in children and adolescents. Our findings show that the NOS3 tagSNP rs3918226 is associated with NO production in children and adolescents, and suggest that this polymorphism may have an impact on cardiovascular health. Further studies are needed to better clarify the effects of this polymorphism on cardiovascular risk.

[Prevalence of dyslipidemia in middle-aged adults with NOS3 gene polymorphism and low cardiorespiratory fitness]

OBJECTIVE

To evaluate the influence of the interaction between endothelial nitric oxide synthase gene (NOS3) polymorphisms at positions -786T>C, Glu298Asp and intron 4b/a, and cardiorespiratory fitness on plasma nitrite/nitrate levels, blood pressure, lipid profile, and prevalence of cardiometabolic disorders.

SUBJECTS AND METHODS

Ninety-two volunteers were genotyped for NOS3 polymorphisms at positions (-786T>C and Glu298Asp) and (intron 4b/a) and divided according to the genotype: non-polymorphic (NP) and polymorphic (P). After that, they were subdivided according to the cardiorespiratory fitness associated with genotype: high (HNP and HP) and low (LNP and LP).

RESULTS

The subjects with polymorphism for the interactions at positions Glu298Asp + intron 4b/a, and Glu298Asp+-786T>C showed the highest values in total cholesterol, as well as dyslipidemia.

CONCLUSION

Our findings show that NOS3 gene polymorphisms at positions -786T>C, Glu298Asp, and intron 4b/a exert negative effects on the lipid profile compared with those who do not carry polymorphisms.

Endothelial nitric oxide synthase gene polymorphisms and renal responsiveness to RAS inhibition therapy in type 2 diabetic Asian Indians

AIM

To investigate the association of functional single nucleotide polymorphisms (SNPs) of the endothelial nitric oxide synthase gene (eNOS) gene (T-786C, G894T) and one variable number tandem repeat polymorphism (aa 27VNTR bb) with reno-protective response to angiotensin converting enzyme inhibitors (ACEI) and angiotensin receptor blockers (ARB) therapy in North Indian type 2 diabetic mellitus (T2DM) subjects with cases having diabetic nephropathy (DN) and controls without DN.

METHOD

We genotyped three polymorphisms of eNOS (two SNPs: T-786C, G894T and one 27 VNTR) in T2DM patients with overt nephropathy (cases: n=320) and T2DM patients without overt nephropathy (controls: n=490), using validated PCR-RFLP assays. These 810 North Indian T2DM patients treated with ACEI or ARB after diagnosis were followed up for 3 years. Percent changes in eGFR, urinary albumin excretion (UAE), serum creatinine at the end of 3 years of treatment were taken as end points of renoprotective response.

RESULT

We observed that in normoalbuminuric patients, eNOS -786 CC genotype and haplotypes C-b-G and C-b-T were associated with lesser renoprotective response to ACEI. While, in macroalbuminurics, eNOS -786 CC genotype, haplotypes C-b-G and C-b-T and 27VNTR aa were associated with better renoprotective response to ACEI/ARB.

CONCLUSION

Our results showed that eNOS T-786C CC genotype and 27VNTR individually and in interaction with other eNOS SNPs modulate renoprotective efficacy of ACEI and ARB in T2DM patients, depending on the status of proteinuria.

Inducible nitric oxide synthase haplotype associated with hypertension and responsiveness to antihypertensive drug therapy

Hypertension is a multifactorial disorder associated with increased inducible nitric oxide synthase (iNOS) expression and activity. While genetic polymorphisms affect iNOS expression, it is not known whether iNOS gene polymorphisms affect the susceptibility to hypertension and the responses to antihypertensive therapy. This study aimed at assessing whether iNOS polymorphisms ((CCTTT)(n), g.-1026C>A, and g.2087G>A) and haplotypes are associated with hypertension and with responsiveness to drug therapy. We studied 115 well controlled hypertensive patients (HTN), 82 hypertensive patients resistant to optimized antihypertensive therapy (RHTN), and 113 normotensive healthy subjects (NT). Genotypings were carried out using real-time polymerase chain reaction (PCR) and PCR amplification followed by capillary electrophoresis. The software PHASE 2.1 was used to estimate the haplotype frequencies in each group. Variant genotypes (GA+AA) for the g.2087G>A polymorphism were more commonly found in hypertensive patients (HTN+RHTN) than in normotensives (P=0.016; OR=2.05). We found no associations between genotypes and responsiveness to therapy (P>0.05). The S-C-A haplotype was more commonly found in hypertensive patients (HTN+RHTN) than in normotensives (P=0.014; OR=6.07). Interestingly, this haplotype was more commonly found in the HTN group than in the RHTN group (P=0.012; OR=0.14). Our findings indicate that the g.2087G>A polymorphism in the iNOS gene affects the susceptibility to hypertension. Moreover, while the S-C-A haplotype is associated with hypertension, it is also associated with responsiveness to antihypertensive therapy.

eNOS polymorphism associated with metabolic syndrome in children and adolescents

We investigated whether genetic polymorphisms in the endothelial nitric oxide (eNOS) gene (T(786)C in the promoter region, Glu298Asp in exon 7, and 4b/4a in intron 4) or eNOS haplotypes are associated with metabolic syndrome (MetS) in obese children and adolescents. We studied 242 subjects: 108 healthy (controls), 64 normotensive obese, and 70 obese children and adolescents with MetS. Genotypes were determined by Taqman(®) allele discrimination assay and real-time polymerase chain reaction (PCR), and PCR followed by fragment separation by electrophoresis. We compared the distribution of eNOS genotypes, alleles, and haplotypes in the three groups of subjects. The CC genotype for the T(786)C polymorphism was more common in the MetS group than in the control group (OR = 3.27; CI 1.81-9.07; P < 0.05). However, we found no significant differences in the distribution of eNOS haplotypes (P > 0.00625; P for significance after correction for multiple comparisons). Our findings suggest that while eNOS haplotypes are not relevant, the CC genotype for the T(786)C polymorphism is associated with MetS in obese children and adolescents. Further studies examining interactions of eNOS haplotypes with environmental factors and other genetic markers are warranted.

Resequencing and association analysis of arylalkylamine N-acetyltransferase (AANAT) gene and its contribution to major depression susceptibility

Circadian rhythms disruptions, including abnormalities of circadian phase position and melatonin secretion, have been described in major depression (MD). Arylalkylamine N-acetyltransferase (AANAT) is a key enzyme of the melatonin pathway involved in circadian oscillations of melatonin levels. We assessed the contribution of AANAT gene variability to susceptibility to MD considering common and rare genetic variations through a sequential sequencing and single nucleotide polymorphism (SNP)-based genotyping approach in a sample of 445 unrelated patients with MD (257 unipolar MD, 188 bipolar depression) and 440 community-based screened control subjects. We identified 17 sequence changes, thirteen of which represented novel sequence variations. We did not observe an over-representation of patients carrying rare variants compared with the healthy controls. Common variants (MAF > 2%) were included in a case-control association analysis that showed significant association after multiple testing correction of two SNPs located in the promoter region of AANAT with MD: rs3760138 (P = 0.00006) and rs4238989 (P = 0.005). Multimarker analysis found significant associations between two three-marker protective haplotypes and a susceptibility three-marker haplotype containing the rare alleles of rs3760138-rs4238989-rs8150 and MD. We present evidence of the association of genetic variability in the AANAT gene with susceptibility to MD. Our results support the hypothesis that the melatonin-signaling pathway and circadian clock mechanisms may contribute to the pathophysiology of MD.

Effects of eNOS polymorphisms on nitric oxide formation in healthy pregnancy and in pre-eclampsia

Pre-eclampsia (PE) is associated with decreased nitric oxide (NO) formation. However, no previous study has examined whether genetic variations in the endothelial NO synthase (eNOS) affect this alteration. We hypothesized that PE decreases NO formation depending on eNOS polymorphisms. We examined how three eNOS polymorphisms [T-786C, rs2070744; Glu298Asp, rs1799983; 27 bp variable number of tandem repeats (VNTR) in intron 4] affect plasma nitrite concentrations in 205 pregnant women [107 healthy pregnant (HP) and 98 PE]. Genotypes were determined and eNOS haplotypes were inferred using the PHASE 2.1 program. The plasma nitrite concentrations were determined using an ozone-based chemiluminescence assay. The Glu298Asp polymorphism had no effects on the plasma nitrite concentrations. Higher nitrite levels were found in HP women with the CC versus TT genotype for the T-786C polymorphism (277.9 +/- 19.5 versus 140.6 +/- 8.2 nM; P < 0.05). Lower nitrite levels were found in healthy women with the 4a4a versus 4b4b genotype for the VNTR polymorphism (95.1 +/- 3.3 versus 216.1 +/- 16.8 nM; P < 0.05). No effects of genotypes were found in PE women (all P > 0.05). The 'C Glu b' haplotype was more frequent in the HP group than in the PE group (20 versus 5; P = 0.0044). This haplotype was associated with higher nitrite concentrations than the other haplotypes in healthy pregnancies (P < 0.05). No differences in nitrite concentrations were found among PE women with different eNOS haplotypes (P > 0.05). These findings indicate that eNOS polymorphisms affect endogenous NO formation in normal pregnancy, but not in PE, and that the 'C Glu b' haplotype may protect against the development of PE by increasing endogenous NO formation.

Endothelial nitric oxide synthase haplotypes associated with hypertension do not predispose to cardiac hypertrophy

Left ventricular hypertrophy (LVH) is a complication that may result from chronic hypertension. While nitric oxide (NO) deficiency has been associated with LVH, inconsistent results have been reported with regards to the association of endothelial NO synthase (eNOS) polymorphisms and LVH in hypertensive patients. This study aims to assess whether eNOS haplotypes are associated with LVH in hypertensive patients. This study included 101 healthy controls and 173 hypertensive patients submitted to echocardiography examination. Genotypes for three eNOS polymorphisms were determined: a single-nucleotide polymorphism in the promoter region (T-786C) and in exon 7 (Glu298Asp), and variable number of tandem repeats in intron 4. We found no significant association between eNOS genotypes and hypertension or with LVH (all p > 0.05). However, while we found two eNOS haplotypes associated with variable risk of hypertension (all p < 0.05), we found no significant associations between eNOS haplotypes and LVH (all p > 0.05), even after adjustment in multiple linear regression analysis. These findings suggest that eNOS haplotypes that have been associated with variable susceptibility to hypertension were not associated with LVH in hypertensive patients. Further studies are necessary to examine whether other genes downstream may interact with eNOS polymorphisms and predispose to LVH in hypertensive patients.

A pharmacogenetics-based approach to reduce cardiovascular mortality with the prophylactic use of statins

Nitric oxide (NO) is the main endothelial-derived relaxation factor and plays a major role in cardiovascular homeostasis. This key signalling molecule is synthesised by a family of nitric oxide synthases (NOS), and the endothelial isoform (eNOS) is the most important for nitric oxide formation in the cardiovascular system. Cardiovascular drugs including statins increase eNOS expression and up-regulate NO formation, and this effect may be responsible for protective, pleiotropic effects produced by statins. However, the genetic background may also affect NO formation in the cardiovascular system, and recent studies have shown that genetic polymorphisms in the eNOS gene modify endogenous NO formation and the risk of developing cardiovascular diseases. For example, cases with the CC genotype for the T(-786)C polymorphism in the eNOS gene are at increased cardiovascular risk when compared with those with the TT genotype. Interestingly, pharmacogenetic studies have recently indicated that atorvastatin improves NO formation more clearly in these individuals. However, it is not known whether this polymorphism really increases cardiovascular morbidity and mortality, and whether atorvastatin or other statins attenuate the morbidity and mortality rates in cases with the CC genotype. If proved true, then statins-induced up-regulation of eNOS and increased NO formation could compensate for a genetic 'disadvantage' in cases with the CC genotype. This could be a significant advance in the prevention of cardiovascular events. It is necessary although to validate this hypothesis with clinical trials which will require a long follow-up to assess relevant clinical events and not only surrogate biomarkers.

AnNOS3Haplotype Is Protective against Hypertension in a Caucasian Population

The endothelial nitric oxide synthase gene (NOS3) has been implicated in the development of hypertension, although the specific role of variants and haplotypes has not been clarified. In this study, the association of three polymorphisms (promoter T786C, intronic 4a/b, and nonsynonymous G894T) was tested in a case-control sample of 230 patients with essential hypertension and 306 healthy controls. Haplotype analysis was also performed. The mutant allele a^∗ of the 4a/b polymorphism showed a protective effect against hypertension under a dominant model (odds ratio = 0.64, 95% confidence interval (0.44–0.93)), although this effect was not significant after the adjustment for covariates (P = 0.06). The estimated frequency of the haplotype composed of the T786^∗, 4a^∗, and G894^∗ alleles was significantly higher in controls (5.5%) compared to cases (2%). These results indicate that although individual NOS3 polymorphisms are not associated with hypertension, a rare haplotype of the gene might be protective against the development of hypertension.

eNOS haplotypes affect the responsiveness to antihypertensive therapy in preeclampsia but not in gestational hypertension

Variations of the endothelial nitric oxide synthase (eNOS) gene have been associated with hypertensive disorders of pregnancy. We examined whether eNOS polymorphisms affect the therapeutic responses of women with gestational hypertension (GH) or preeclampsia (PE). We studied 304 hypertensive pregnant women (152 GH and 152 PE), who were stratified according to clinical and laboratorial parameters of therapeutic responsiveness. We compared the frequencies of three eNOS genetic polymorphisms (T-786C, Glu298Asp and b/a intron 4) in responsive and nonresponsive PE and GH patients. We found no significant differences in genotype or allele distributions when responsive and nonresponsive groups were compared (both PE or GH; all P>0.05). However, the eNOS haplotype distribution differed in PE (but not in GH)-responsive and -nonresponsive groups (P=0.0003). The 'C-Glu-a' and 'T-Asp-a' hapotypes were associated with responsiveness and nonresponsiveness to therapy, respectively (both P<0.001), thus suggesting that eNOS haplotypes affect the responsiveness to antihypertensive therapy in PE.

Association between -T786C NOS3 polymorphism and resistant hypertension: a prospective cohort study

Background

It is estimated that 5% of the hypertensive patients are resistant to conventional antihypertensive therapy. Polymorphisms in the endothelial nitric oxide synthase (NOS3) gene have been associated with high blood pressure levels, but not with resistant hypertension. The aim of the present study was to investigate if the -786T>C and G894T (Glu298Asp) polymorphisms of the NOS3 gene were associated with resistant hypertension.

Methods

A prospective case-control observational study was performed. From a series of 950 consecutive patients followed up during 42 months, 48 patients with resistant hypertension were detected. 232 patients with controlled high blood pressure were also included.

Results

No differences were observed in the distribution of G894T (Glu298Asp) NOS3 genotypes between the resistant hypertension group and the controlled hypertension patients. However, genotype -786CC was more frequent in the group of patients with resistant hypertension (33.3%) than in the group of patients with controlled high blood pressure (17.7%) (p 0.03). Furthermore carriers of allele T (-786TC and -786TT) were more frequent in patients with controlled hypertension (82.3%) than those with resistant hypertension (66.7%) (Multivariate analysis; RR 2.09; 95% CI 1.03–4.24; p 0.004).

Conclusion

Our results indicate that genotype -786CC of the NOS3 gene increase the susceptibility to suffer resistant hypertension, which suggest that resistance to conventional therapy could be determined at the endothelial level.

eNOS haplotypes associated with gestational hypertension or preeclampsia

AIMS

Polymorphisms in the endothelial nitric oxide synthase (eNOS) gene have been inconsistently associated with preeclampsia. We compared genotype and haplotype frequencies of three eNOS gene polymorphisms in normotensive and hypertensive pregnancies.

METHODS

Genotypes and haplotypes for eNOS polymorphisms (T-786C, Glu298Asp and intron 4 b/a) were determined in 326 pregnant women (110 healthy pregnancies, 103 gestational hypertensives and 113 preeclamptic).

RESULTS

No differences were observed in the frequencies of genotypes and alleles of the three polymorphisms among the groups (all p > 0.05). However, the haplotype 'T Glu a' was more common in healthy pregnancies than in gestational hypertensives or preeclamptic (20 vs 6 and 6%, respectively; p < 0.0032). Conversely, the haplotype 'C Glu a' was more common in gestational hypertensives and preeclamptic than in healthy pregnancies (17 vs 17 and 5%; p = 0.0061).

CONCLUSION

These findings suggest a contribution of eNOS haplotypes to the development of hypertensive disorders of pregnancy that is obscured when specific eNOS genotypes alone are considered.

Impact of the endothelial nitric oxide synthase gene G894T polymorphism on renal endothelial function in patients with type 2 diabetes

OBJECTIVE

Endothelial dysfunction and increased oxidative stress contribute to the progression of diabetic nephropathy. To analyze the functional significance of the G894T polymorphism of NOS3, the gene encoding endothelial nitric oxide synthase (NOS), we assessed basal nitric oxide activity and the amount of oxidative stress in the renal circulation of patients with type 2 diabetes.

METHODS

Renal plasma flow (RPF) was assessed by steady-state input clearance technique with sodium para-aminohippurate in 84 patients with type 2 diabetes and 84 patients without diabetes. RPF was measured at baseline and after the infusion of the NOS inhibitor N-monomethyl-L-arginine (4.25 mg/kg); the substrate of NOS L-arginine (100 mg/kg); and coinfusion of vitamin C (3 g) with L-arginine (100 mg/kg).

RESULTS

The decrease of RPF to N-monomethyl-L-arginine was similar between carriers of the T allele and homozygous carriers of the G allele in patients with diabetes (-56+/-40 vs. -68.1+/-74 ml/min/1.73 m, P=0.342) and patients without diabetes (-66.7+/-81 vs. -58.3+/-63 ml/min/1.73 m, P=0.606). In patients with diabetes, however, carriers of the T allele revealed a more pronounced increase of RPF to coinfusion of vitamin C with L-arginine than homozygous carriers of the G allele (61.8+/-75 vs. 22.3+/-73 ml/min/1.73 m, P=0.021), whereas in patients without diabetes the response of RPF to coinfusion of vitamin C with L-arginine was similar between both groups (46.2+/-80 vs. 70.7+/-86 ml/min/1.73 m, P=0.217). Gene-environment interaction between disease (diabetes) and genotype (genotype GG vs. genotype GT/TT) was observed for increase of RPF to coinfusion of vitamin C with L-arginine (P=0.020).

CONCLUSION

G894T polymorphism of NOS3 has no impact on the basal nitric oxide activity of renal circulation. In contrast, the T allele is associated with increased oxidative stress in the renal circulation in patients with diabetes suggesting a specific role of the G894T polymorphism in the pathogenesis of diabetic nephropathy.

Acute inhibition of guanosine triphosphate cyclohydrolase 1 uncouples endothelial nitric oxide synthase and elevates blood pressure

GTP cyclohydrolase 1 (GTPCH1) is the rate-limiting enzyme in de novo synthesis of tetrahydrobiopterin (BH4), an essential cofactor for endothelial NO synthase (eNOS) dictating, at least partly, the balance of NO and superoxide produced by this enzyme. The aim of this study was to determine the effect of acute inhibition of GTPCH1 on BH4, eNOS function, and blood pressure (BP) in vivo. Exposure of bovine or mouse aortic endothelial cells to GTPCH1 inhibitors (2,4-diamino-6-hydroxypyrimidine or N-acetyl-serotonin) or GTPCH1 small-interference RNA (siRNA) significantly reduced BH4 and NO levels but increased superoxide levels. This increase was abolished by sepiapterin (BH4 precursor) or N(G)-nitro-L-arginine methyl ester (nonselective NOS inhibitor). Incubation of isolated murine aortas with 2,4-diamino-6-hydroxypyrimidine or N-acetyl-serotonin impaired acetylcholine-induced endothelium-dependent relaxation but not endothelium-independent relaxation. Aortas from GTPCH1 siRNA-injected mice, but not their control-siRNA injected counterparts, also exhibited impaired endothelium-dependent relaxation. BH4 reduction induced by GTPCH1 siRNA injection was associated with increased aortic levels of superoxide, 3-nitrotyrosine, and adhesion molecules (intercellular adhesion molecule 1 and vascular cell adhesion molecule 1), as well as a significantly elevated systolic, diastolic, and mean BP in C57BL6 mice. GTPCH1 siRNA was unable to elicit these effects in eNOS(-/-) mice. Sepiapterin supplementation, which had no effect on high BP in eNOS(-/-) mice, partially reversed GTPCH1 siRNA-induced elevation of BP in wild-type mice. In conclusion, GTPCH1 via BH4 maintains normal BP and endothelial function in vivo by preserving NO synthesis by eNOS.

Endothelial nitric oxide synthase gene haplotypes and circulating nitric oxide levels significantly associate with risk of essential hypertension

Nitric oxide (NO), a potent vasodilator, plays a pivotal role in blood pressure regulation. Endothelial NO synthase gene (NOS3) polymorphisms influence NO levels. Here, we investigated the role of the -922A/G, -786T/C, 4b/4a, and 894G/T polymorphisms of the NOS3 and NO(x) levels in 800 consecutive unrelated subjects comprising 455 patients of essential hypertension and 345 controls. The polymorphisms were investigated independently and as haplotypes. Plasma NO(x) levels (nitrate and nitrite) were estimated by the Griess method. Genotype frequencies for the -786T/C, 4b/4a, and 894G/T polymorphisms differed significantly (P<0.001) between patients and controls and were associated with an increased risk of hypertension (OR=2.0, OR=3.8, OR=1.6, respectively). The 4-locus haplotypes ATaG (H1), ATaT (H2), and GCaG (H3) were significantly associated with essential hypertension and served as susceptible haplotypes (P<or=0.0001). On the other hand, haplotypes ATbG (H4) and GTbG (H5) were negatively associated with hypertension and served as protective haplotypes (P<0.0001). NO(x) levels were significantly lower in patients than controls (P<0.0001). The individual polymorphisms showed marginal association with NO(x) level; however, the susceptible haplotype H2 associated significantly with lower NO(x) levels in patients (P<0.001) and conversely the haplotype H4 with higher NO(x) levels in controls (P<0.001). In conclusion, the 4b/4a and likely -786T/C polymorphisms were identified as the determinants modifying the risk of hypertension. This study identifies the NOS3 variants and haplotypes as genetic risk factors and as useful markers of increased susceptibility to the risk of essential hypertension.

Racial differences in nitric oxide-dependent vasorelaxation

Along with the growing heterogeneity of the American population, ethnic/racial disparity is becoming a clear health issue in the United States. The awareness of ethnic/racial disparities has been growing because of considerable data gathered from recent clinical and epidemiological studies. These studies have highlighted the importance of addressing these differences in the diagnosis and treatment of various diseases potentially according to race. It is becoming particularly clear that there is a 2- to 3-fold racial difference in certain cardiovascular diseases (eg, preeclampsia) associated with dysfunctional nitric oxide-mediated vasodilation. In this review, the authors summarize the current literature on racial disparities in nitric oxide-mediated vasodilation in relation to cardiovascular health with an emphasis on vascular nitric oxide bioavailability as a balance between production via endothelial nitric oxide synthase and degradation through reactive oxygen species. The major hypotheses postulated on the biological basis of these differences are also highlighted.

Influence of eNOS haplotypes on the plasma nitric oxide products concentrations in hypertensive and type 2 diabetes mellitus patients

Endothelial nitric oxide synthase (eNOS) haplotypes are associated with hypertension (HT) in patients with or without type 2 diabetes mellitus (T2DM). We evaluated the association of eNOS genotypes/haplotypes with the plasma concentrations of nitrite/nitrate (NO(x)), which are products of nitric oxide in HT, T2DM, and T2DM+HT patients. We studied eNOS polymorphisms in the promoter region (T-786C), in exon 7 (Glu298Asp), and in intron 4 (b/a) in 98 controls, 68 patients with HT, 66 patients with T2DM, and 86 patients with T2DM+HT. NO(x) concentrations were assessed using a chemiluminescence assay. No differences were found in genotype/allele distribution among groups. Genotypes were not associated with NO(x) concentrations. The "C-Glu-b" haplotype was more common in controls than in HT/T2DM+HT groups (21% versus 9/5%, respectively, P<0.006). This haplotype was more common in HT and T2DM+HT groups among subjects with high (82+/-38 and 90+/-33 microM, respectively) than with low (35+/-7 and 34+/-7 microM, respectively) NO(x) concentrations. Conversely, the "C-Asp-b" haplotype was more common in HT/T2DM+HT groups than healthy (21/21% versus 10%, respectively, P<0.006). The haplotype associated with lower risk of developing hypertension is also associated with higher NO(x) levels among hypertensives. Conversely, the haplotype increasing the risk of developing hypertension is associated with lower NO(x) levels in hypertensives.