Biogenesis of short intronic repeat 27-nucleotide small RNA from endothelial nitric-oxide synthase gene

High Altitude Pregnancies and Vascular Dysfunction: Observations From Latin American Studies

An estimated human population of 170 million inhabit at high-altitude (HA, above 2,500 m). The potential pathological effects of HA hypobaric hypoxia during gestation have been the focus of several researchers around the world. The studies based on the Himalayan and Central/South American mountains are particularly interesting as these areas account for nearly 70% of the HA world population. At present, studies in human and animal models revealed important alterations in fetal development and growth at HA. Moreover, vascular responses to chronic hypobaria in the pregnant mother and her fetus may induce marked cardiovascular impairments during pregnancy or in the neonatal period. In addition, recent studies have shown potential long-lasting postnatal effects that may increase cardiovascular risk in individuals gestated under chronic hypobaria. Hence, the maternal and fetal adaptive responses to hypoxia, influenced by HA ancestry, are vital for a better developmental and cardiovascular outcome of the offspring. This mini-review exposes and discusses the main determinants of vascular dysfunction due to developmental hypoxia at HA, such as the Andean Mountains, at the maternal and fetal/neonatal levels. Although significant advances have been made from Latin American studies, this area still needs further investigations to reveal the mechanisms involved in vascular dysfunction, to estimate complications of pregnancy and postnatal life adequately, and most importantly, to determine potential treatments to prevent or treat the pathological effects of being developed under chronic hypobaric hypoxia.

Dynamic visualization of mRNA splicing variants with a transactivating reporter

Dynamic changes in intron sequences, with their loss and gain, are poorly detected due to the limited methods for the non-invasive monitoring of the pre-mRNA splicing process. Here, we describe the design of a two-step transcriptional activation (TSTA) reporter for the real-time imaging of the splicing process in living subjects. By taking advantage of the strong transactivating properties of the GAL4-VP16 fusion protein, which can target upstream activation sequence (UAS) elements to boost subsequent firefly luciferase reporter gene expression, we successfully and consistently detected the dynamic pre-mRNA splicing activity in response to exogenous splicing modulators in living cells and animals. Our findings provide a valuable tool for the high-throughput screening of splicing modulators, which could speed up the development of new drugs for the treatment of disordered splicing diseases.

Common Endothelial Nitric Oxide Synthase Single Nucleotide Polymorphisms are not Related With the Risk for Restless Legs Syndrome

Because nitric oxide and endothelial dysfunction could play a role in the pathogenesis of idiopathic restless legs syndrome (RLS), as was suggested by some preliminary data, we investigated the possible association between the rs2070744 variants in the endothelial nitric oxide synthase (eNOS or NOS3) gene (chromosome 7q36.1) and the risk for RLS in a Caucasian Spanish population. We assessed the frequencies of NOS3 single nucleotide polymorphisms (SNPs) rs2070744, rs1799983, and rs79467411 genotypes and allelic variants in 273 patients with idiopathic RLS and 325 healthy controls using a TaqMan-based qPCR assay. We also analyzed the possible influence of genotype frequency on age at onset of RLS symptoms, gender, family history of RLS, and response to drugs commonly used in the treatment of RLS such as dopaminergic drugs, clonazepam, and GABAergic drugs. The frequencies of genotypes and allelic variants were not associated with the risk for RLS and were not influenced by gender, age, and positive family history of RLS. We identified weak statistical associations of the SNP rs1799983 with the response to dopamine agonists (Pc = 0.018 for the rs1799983 G/T genotype) and of the SNP rs79467411 with the response to clonazepam (Pc = 0.018 for the rs79467411 G allele), although these findings should be cautiously interpreted and require further confirmation. These associations aside, our findings suggest that common NOS3 SNPs are not associated with the risk for idiopathic RLS in Caucasian Spanish people.

Vascular homeostasis at high-altitude: role of genetic variants and transcription factors

High-altitude pulmonary edema occurs most frequently in non-acclimatized low landers on exposure to altitude ≥2500 m. High-altitude pulmonary edema is a complex condition that involves perturbation of signaling pathways in vasoconstrictors, vasodilators, anti-diuretics, and vascular growth factors. Genetic variations are instrumental in regulating these pathways and evidence is accumulating for a role of epigenetic modification in hypoxic responses. This review focuses on the crosstalk between high-altitude pulmonary edema-associated genetic variants and transcription factors, comparing high-altitude adapted and high-altitude pulmonary edema-afflicted subjects. This approach might ultimately yield biomarker information both to understand and to design therapies for high-altitude adaptation.

Gene polymorphisms in calcium-calmodulin pathway: Focus on cardiovascular disease

Cardiovascular disease is the leading cause of death in industrialized countries and affects an increasing number of people. Several risk factors play an important role in the etiology of this disease, such as an unhealthy lifestyle. It is increasingly clear that genetic factors influencing the molecular basis of excitation-contraction mechanisms in the heart could contribute to modify the individual's risk. Thanks to the progress that has been made in understanding calcium signaling in the heart, it is assumed that calmodulin can play a crucial role in the excitation-contraction coupling. In fact, calmodulin (CaM) binds calcium and consequently regulates calcium channels. Several works show how some polymorphic variants can be considered predisposing factors to complex pathologies. Therefore, we hypothesize that the identification of polymorphic variants of proteins involved in the CaM pathway could be important for understanding how genetic traits can influence predisposition to myocardial infarction. This review considers each pathway of the three different isoforms of calmodulin (CaM1; CaM2; CaM3) and focuses on some common proteins involved in the three pathways, with the aim of analyzing the polymorphisms studied in the literature and understanding if they are associated with cardiovascular disease.

Endothelial nitric oxide synthase polymorphisms/haplotypes are strong modulators of oral cancer risk in Serbian population

Oral carcinoma is the sixth most common malignancy worldwide, with survival rates of approximately 50%. The major type of oral cancer, present in 90% of the cases, is oral squamous cell carcinoma (OSCC). The genetic background predisposing an individual to OSCC is complex and largely unknown. Studies have suggested that endothelial nitric oxide synthase (eNOS) gene polymorphisms modulate the cancer risk, prompting us to assess the impact of three functional eNOS gene polymorphisms on OSCC risk. The present study included 50 patients with OSCC and 110 controls. Polymerase chain reaction and restriction fragment length polymorphism analysis were used for genotyping of single-nucleotide polymorphisms -786 T/C (rs2070744) and 894 G/T (rs1799983) and variable number of tandem repeats (VNTR) intron 4b/a polymorphism. Homozygous carriers of -786 T/C and intron 4b/a VNTR variant alleles paired with a significant increase of oral cancer risk [odds ratio (OR): 3.63, 95% confidence interval (CI): 1.08-12.21; P = 0.045 and OR: 11.29, 95% CI: 2.71-47.11; P < 0.001, respectively]. When combined, CC and 4b4a genotypes together led to a 21-fold OSCC risk increase (OR: 21, 95% CI: 2.07-213.29; P = 0.006). Haplotype analysis showed that the C-G-4b haplotype conferred an 11-fold increase in OSCC risk. In conclusion, eNOS polymorphisms considerably influence levels of OSCC risk in the Serbian population.

Relation of nitric oxide synthase gene (NOS3) polymorphisms to varicocele risk and post-varicocelectomy seminal oxidative stress reduction

The pathophysiology of varicocele remains to be unknown. Several genetic factors have been implicated in varicocele etiopathogenesis. We studied the relationship between NOS3 c.894G>T, c.786T>C and 4b/a polymorphisms to varicocele risk and their prognostic value as regards improvement of the post-operative seminal parameters &/or seminal malonaldehyde levels. The three NOS3 polymorphisms were evaluated in 100 patients with varicocele and 100 healthy subjects by RT-PCR. Seminal plasma MDA level was measured pre-operatively and 3 months after varicocelectomy by the thiobarbituric acid method. The GT, TT, TC and bb genotypes of NOS3 polymorphism were more commonly observed in varicocele patients (30%, 9%, 28% and 70% respectively) compared to normal controls (12%, 0%, 10% and 50% respectively). The mean percentage of post-varicocelectomy seminal MDA reduction was highest with the GT genotype (p < .001). Genotypes GT+TT, TC and bb were associated with varicocele occurrence in our patients. The T (c.894G>T), C (c.786T>C) and b (NOS3 intron 4 VNTR) alleles were significantly associated with varicocele occurrence in our cohort of patients. We also report a better response regarding the reduction of seminal MDA after varicocelectomy with the GT and ba genotypes.

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.

Pharmacogenetic relevance of endothelial nitric oxide synthase polymorphisms and gene interactions

Endothelial nitric oxide synthase (NOS3) is a key enzyme responsible for nitric oxide (NO) generation in the vascular endothelium. Endothelial dysfunction is characterized by reduced NO production, and is a hallmark of cardiovascular diseases. Drugs with cardiovascular action may activate NOS3 and result in NO release and vasodilation. Moreover, genetic variations affect NOS3 expression and activity, and may partially explain the variability in the responses to cardiovascular drugs. We reviewed NO signaling and genetic effects on NO formation, and the effects of NOS3 polymorphisms, haplotypes and gene-gene interactions within NO signaling pathways on the responses to cardiovascular drugs. We discuss the role of rare NOS3 variants and further gene-gene interactions analysis for the development of novel therapies for cardiovascular diseases.

Poly (ADP-Ribose) Polymerase 1 Mediated Arginase II Activation Is Responsible for Oxidized LDL-Induced Endothelial Dysfunction

It is well known that arginase II leads to decreased synthesis of nitric oxide (NO) by competing with endothelial nitric oxide synthase (eNOS) for their same substrate L-arginine. However, the regulatory mechanisms of arginase II production remain unclear. In this study, we hypothesized that poly- (ADP-ribose) transferase/polymerase-1 (PARP-1) may be a critical factor responsible for ox-LDL (oxidized Low Density Lipoprotein)-enhanced arginase II activity. We used serial deletions within plasmid constructs and found that a core promoter region of arginase II was located at the element of -774 to -738 bp and PARP-1 was identified specifically binding to this region. Inhibition of PARP-1 markedly reduced the endogenous arginase II expression and enhanced eNOS and NO production. Similarly, ox-LDL-induced increase in arginase II production and eNOS and NO reduction was substantially abolished by PARP-1 inhibition both in vitro and in vivo. Significant decrease in arginase II expression and increase in eNOS expression and NO levels, as well as improved endothelial function were observed in PARP-1-/- mice. The underlying mechanisms of ox-LDL-induced changes of PARP-1 expression involved migration of phosphorylated ERK2 into nuclei and direct interaction with PARP-1 which dramatically enhanced PARP-1 production, followed by histone acetylation to activate arginase II transcription process. Our studies demonstrated for the first time that PARP-1 regulates basal transcription process and ox-LDL-induced up-regulation of arginase II. These results demonstrated that PARP-1 offers a promising therapeutic target for endothelial dysfunction and atherosclerosis.

Correlation Between Intron 4 Polymorphism of the Endothelial Nitric Oxide Synthase Gene and Cardiovascular Risk with the Numbers of Circulating Endothelial Progenitor Cells in Healthy Subjects

In the present study, we investigated the relationship between an important 27 bp repeat polymorphism in intron 4 of eNOS and numbers of circulating EPCs in presence of cardiovascular disease (CVD) risk factors in a group of healthy human volunteers. The study comprised of 45 healthy subjects (30-50 years). These subjects had various degrees of CVD risk but no history of CVD. The repeat polymorphism of eNOS was detected by polymerase chain reaction and EPC levels were analyzed by flow cytometry. We observed a good association between the intronic 4 mutant a/b genotype and the combined Framingham risk factor score in our subjects (χ² = 3.2, P = 0.07). EPC numbers in subjects with mutant eNOS a/b genotype were also less than those observed in subjects with normal eNOS b/b genotype (P = 0.06). Interestingly, subjects with eNOS a/b genotype showed a significant inverse correlation between framingham risk score and EPC numbers (R = -0.57, P < 0.05). The study suggests that the presence of CVD risk factors in subjects with eNOS intron 4 polymorphism results in reduced number of circulating EPCs, which may significantly predispose them to CVD and aberrant endothelial repair.

Endothelial nitric oxide synthase polymorphisms affect the changes in blood pressure and nitric oxide bioavailability induced by propofol

Propofol anesthesia is usually accompanied by hypotension, which is at least in part related to enhanced endothelial nitric oxide synthase (NOS3)-derived NO bioavailability. We examined here whether NOS3 polymorphisms (rs2070744, 4b/4a VNTR, rs3918226 and rs1799983) and haplotypes affect the changes in blood pressure and NO bioavailability induced by propofol. Venous blood samples were collected from 168 patients at baseline and after 10 min of anesthesia with propofol 2 mg/kg administered intravenously by bolus injection. Genotypes were determined by polymerase chain reaction and haplotype frequencies were estimated. Nitrite concentrations were measured by using an ozone-based chemiluminescence assay, while NOx (nitrites + nitrates) levels were determined by using the Griess reaction. We found that CT + TT genotypes for the rs3918226 polymorphism, the ba + aa genotypes for the 4b/4a VNTR and the CTbT haplotype were associated with lower decreases in blood pressure and lower increases in nitrite levels after propofol anesthesia. On the other hand, the TCbT and CCbT haplotypes were associated with more intense decreases in blood pressure and higher increases in nitrite levels in response to propofol. Our results suggest that NOS3 polymorphisms and haplotypes influence the hypotensive responses to propofol, possibly by affecting NO bioavailability.

Distinct role of endothelial nitric oxide synthase gene polymorphisms from menopausal status in the patients with sporadic breast cancer in Taiwan

Breast cancer has a high incidence in Taiwanese women and worldwide. Previous studies have indicated that NO has multiple independent roles in carcinogenesis; genetic polymorphisms in the endothelial nitric oxide synthase (eNOS) gene could modify its transcription and endogenous NO production. Previous studies have reported conflicting results for the relationship between polymorphisms in the eNOS gene and breast cancer risk. Estrogen levels are associated with eNOS expression; accordingly, variation in estrogen levels may contribute to the discordant results. Therefore, in this study, the effects of eNOS polymorphisms on breast cancer susceptibility were examined in terms of menopausal status in Taiwanese women. Three eNOS polymorphisms (-786T > C, VNTR, and 894G > T) were genotyped in 283 patients with breast cancer (139 premenopausal and 144 postmenopausal) and 200 cancer-free controls (100 premenopausal and 100 postmenopausal) by PCR-RFLP. There was a significantly higher breast cancer risk in premenopausal women carrying 894G > T T than in those with the 894G > T GG genotype; however, postmenopausal women carrying 894G > T T had a lower risk of developing breast cancer. In addition, based on a binary logistic regression analysis, interaction effects of these polymorphisms differed according to menopausal status. The relationship between eNOS polymorphisms and breast cancer hazard depended on menopause status, especially for the 894G > T polymorphism, which may provide an explanation for previous conflicting results.

Phenotypic Variability in Synthetic Biology Applications: Dealing with Noise in Microbial Gene Expression

The stochasticity due to the infrequent collisions among low copy-number molecules within the crowded cellular compartment is a feature of living systems. Single cell variability in gene expression within an isogenic population (i.e., biological noise) is usually described as the sum of two independent components: intrinsic and extrinsic stochasticity. Intrinsic stochasticity arises from the random occurrence of events inherent to the gene expression process (e.g., the burst-like synthesis of mRNA and protein molecules). Extrinsic fluctuations reflect the state of the biological system and its interaction with the intra and extracellular environments (e.g., concentration of available polymerases, ribosomes, metabolites, and micro-environmental conditions). A better understanding of cellular noise would help synthetic biologists design gene circuits with well-defined functional properties. In silico modeling has already revealed several aspects of the network topology’s impact on noise properties; this information could drive the selection of biological parts and the design of reliably engineered pathways. Importantly, while optimizing artificial gene circuitry for industrial applications, synthetic biology could also elucidate the natural mechanisms underlying natural phenotypic variability. In this review, we briefly summarize the functional roles of noise in unicellular organisms and address their relevance to synthetic network design. We will also consider how noise might influence the selection of network topologies supporting reliable functions, and how the variability of cellular events might be exploited when designing innovative biotechnology applications.

Associations between nitric oxide synthase 3 gene polymorphisms and preeclampsia risk: a meta-analysis

Previous studies have examined the role of three NOS3 gene polymorphisms [G894T, T-786C, and the variable number of tandem repeats 4b/a (VNTR 4b/a)] in the susceptibility to preeclampsia with inconclusive findings. We therefore conducted an updated meta-analysis by including more studies. The most appropriate genetic model was chosen for each polymorphism by using a well-established method. Pooled results indicated that, compared with the GT + GG genotype, the TT genotype of G894T was associated with an increased risk of preeclampsia (odds ratio (OR) = 1.46; 95% confidence interval (CI) = 1.21–1.77, P < 0.001; I² = 40.2%). The CC genotype of T-786C was also associated with a higher risk of preeclampsia (OR = 1.30; 95% CI = 1.07–1.58, P = 0.034; I² = 46.9%) than the CT + TT genotype. No association was found for VNTR 4b/a. Stratified analysis indicated that the increased risk was evident for high-quality studies both for G894T and T-786C, and for studies conducted among Caucasians and Africans for T-786C. However, the increased risk for T-786C among Africans needs further confirmation due to the high probability of false-positive reports. Our results suggested that G894T and T-786C polymorphisms, but not VNTR 4b/a, were associated with an increased risk of preeclampsia.

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.

Lungs at high-altitude: genomic insights into hypoxic responses

Hypobaric hypoxia at high altitude (HA) results in reduced blood arterial oxygen saturation, perfusion of organs with hypoxemic blood, and direct hypoxia of lung tissues. The pulmonary complications in the cells of the pulmonary arterioles due to hypobaric hypoxia are the basis of the pathophysiological mechanisms of high-altitude pulmonary edema (HAPE). Some populations that have dwelled at HA for thousands of years have evolutionarily adapted to this environmental stress; unadapted populations may react with excessive physiological responses that impair health. Individual variations in response to hypoxia and the mechanisms of HA adaptation provide insight into physiological responses. Adaptive and maladaptive responses include alterations in pathways such as oxygen sensing, hypoxia signaling, K+- and Ca2+-gated channels, redox balance, and the renin-angiotensin-aldosterone system. Physiological imbalances are linked with genetic susceptibilities, and nonhomeostatic responses in gene regulation that occur by small RNAs, histone modification, and DNA methylation predispose susceptible humans to these HA illnesses. Elucidation of the interaction of these factors will lead to a more comprehensive understanding of HA adaptations and maladaptations and will lead to new therapeutics for HA disorders related to hypoxic lungs.

A critical update on endothelial nitric oxide synthase gene variations in women with idiopathic recurrent spontaneous abortion: genetic association study, systematic review and meta-analyses

A number of case-control studies investigated the association between idiopathic recurrent spontaneous abortion (IRSA) and variations in the gene encoding endothelial nitric oxide synthase (NOS3), but yielded contradictory results. Our aim was to test the association of the NOS3 variable number of tandem repeats (VNTR) in intron 4 and +894 G/T single-nucleotide polymorphism (SNP) with IRSA in Slovenian women (148 IRSA and 149 control women), conduct a systematic review of literature on the association between NOS3 gene variations and IRSA, and perform meta-analyses of studies that met the inclusion criteria, defined by virtue of the European Society for Human Reproduction and Embryology evidence-based guidelines for recurrent spontaneous abortion. Genotyping was performed using PCR and restriction fragment length polymorphism methods. The systematic review of literature (English language) was conducted using PubMed and Scopus databases, to 1 November 2014. We determined no association of IRSA with the VNTR in intron 4 and +894 G/T SNP in Slovenian women. Furthermore, 16 case-control studies were identified on the association between 15 NOS3 gene variations and IRSA. However, significant inconsistencies exist in the selection criteria of patients and controls between studies. The meta-analysis of VNTR in intron 4 was performed on five studies (894 patients, 944 controls), whereas the meta-analysis of +894 G/T SNP included six studies (1111 patients, 1121 controls). The association with IRSA was significant for the +894 G/T SNP under the dominant genetic model (GT+TT versus GG) based on fixed (odds ratio (OR) = 1.54, 95% confidence interval (CI) = 1.28-1.86, P = <0.01) and random effects models (OR = 1.54, 95% CI = 1.03-2.31, P = 0.03). In conclusion, the GT and TT genotypes of the +894 G/T SNP in women might contribute to a predisposition to IRSA. Additional genetic association and functional studies in different populations with larger numbers of participants and a uniformly defined IRSA are needed to clarify the contribution of NOS3 +894 G/T gene variation to IRSA.

CpG signalling, H2A.Z/H3 acetylation and microRNA-mediated deferred self-attenuation orchestrate foetal NOS3 expression

BACKGROUND

An adverse intrauterine environment leads to permanent physiological changes including vascular tone regulation, potentially influencing the risk for adult vascular diseases. We therefore aimed to monitor responsive NOS3 expression in human umbilical artery endothelial cells (HUAEC) and to study the underlying epigenetic signatures involved in its regulation.

RESULTS

NOS3 and STAT3 mRNA levels were elevated in HUAEC of patients who suffered from placental insufficiency. 5-hydroxymethylcytosine, H3K9ac and Histone 2A (H2A).Zac at the NOS3 transcription start site directly correlated with NOS3 mRNA levels. Concomitantly, we observed entangled histone acetylation patterns and NOS3 response upon hypoxic conditions in vitro. Knock-down of either NOS3 or STAT3 by RNAi provided evidence for a functional NOS3/STAT3 relationship. Moreover, we recognized massive turnover of Stat3 at a discrete binding site in the NOS3 promoter. Interestingly, induced hyperacetylation resulted in short-termed increase of NOS3 mRNA followed by deferred decrease indicating that NOS3 expression could become self-attenuated by co-expressed intronic 27 nt-ncRNA. Reporter assay results and phylogenetic analyses enabled us to propose a novel model for STAT3-3'-UTR targeting by this 27-nt-ncRNA.

CONCLUSIONS

An adverse intrauterine environment leads to adaptive changes of NOS3 expression. Apparently, a rapid NOS3 self-limiting response upon ectopic triggers co-exists with longer termed expression changes in response to placental insufficiency involving differential epigenetic signatures. Their persistence might contribute to impaired vascular endothelial response and consequently increase the risk of cardiovascular disease later in life.

Association of the NOS3 intron-4 VNTR polymorphism with aneurysmal subarachnoid hemorrhage

OBJECT

The nitric oxide system has been linked to the pathogenesis of aneurysmal subarachnoid hemorrhage (SAH). The authors performed a case-control study to investigate the association between SAH and common genetic variants within the endothelial nitric oxide synthase gene (NOS3).

METHODS

Three hundred thirty-three Caucasian SAH patients and 498 controls were genotyped for the -922A > G (rs 1800779), -786T > C (rs2070744), and 894G > T (rs1799983) single nucleotide polymorphisms and the intron-4 27-bp variable number of tandem repeats polymorphism (27-bp-VNTR).

RESULTS

The b/b (5 repeats) genotype of the 27-bp-VNTR was overrepresented in cases (77%) versus controls (69%) (p = 0.02). In male patients the b/b genotype was found in 85% compared with 67% in male controls, whereas in women, the frequencies were 73% and 72%, respectively. This corresponds to an odds ratio of 2.8 (95% CI 1.5-5.6, p = 0.0005) for SAH in men with the b/b genotype versus men with a/b or a/a. In women, no such association was found (OR 1.1, 95% CI 0.7-1.6, p = 0.76). Stepwise logistic regression including arterial hypertension, smoking, sex, and age with interactions yielded similar effect estimates of the 27-bp-VNTR. Haplotype analysis revealed that no single haplotype containing the b-allele was responsible for the observed genotype effect.

CONCLUSIONS

The authors' results suggest that the NOS3 27-bp-VNTR b/b genotype independent of other risk factors act in concert with male sex to substantially increase risk of SAH. This effect is not mediated by any single NOS3 haplotype.

The presence of the NOS3 gene polymorphism for intron 4 mitigates the beneficial effects of exercise training on ambulatory blood pressure monitoring in adults

The number of studies that have evaluated exercise training (ET) and nitric oxide synthase (NOS)3 gene polymorphisms is scarce. The present study was designed to evaluate the relationship between exercise training and NOS3 polymorphisms at -786T>C, 894G>T, and intron 4b/a on blood pressure (BP) using 24-h ambulatory BP monitoring (ABPM), nitrate/nitrite levels (NOx), and redox state. Eighty-six volunteers (51 ± 0.6 yr old) were genotyped into nonpolymorphic and polymorphic groups for each of the three positions of NOS3 polymorphisms. Auscultatory BP, ABPM, SOD activity, catalase activity, NOx levels, and malondialdehyde levels were measured. DNA was extracted from leukocytes, and PCR followed by sequencing was applied for genotype analysis. Aerobic ET consisted of 24 sessions for 3 days/wk for 40 min at moderate intensity. This study was performed in a double-blind and crossover format. ET was effective in lowering office BP (systolic BP: 3.2% and diastolic BP: 3%) as well as ABPM (systolic BP: 2% and diastolic BP: 1.3%). Increased SOD and catalase activity (42.6% and 15.1%, respectively) were also observed. The NOS3 polymorphism for intron 4 mitigated the beneficial effect of ET for systolic BP (nonpolymorphic group: -3.0% and polymorphic group: -0.6%) and diastolic BP (nonpolymorphic group: -3.2% and polymorphic group: -0.5%), but it was not associated with NOx level and redox state. Paradoxical responses were found for positions T786-C and G894T for the NOS3 gene. Consistently, the presence of the polymorphism for intron 4 blunted the beneficial effects of ET in middle-aged adults. Possibly, this effect might be as consequence of intron 4 acting as a short intronic repeat RNA controlling endothelial NOS activity epigenetically.

Nitric oxide (NO) in alleviation of heavy metal induced phytotoxicity and its role in protein nitration

Nitric oxide (NO) is recognized as a biological messenger in various tissues to regulate diverse range of physiological process including growth, development and response to abiotic and biotic factors. The NO emission from plants is known since the 1970s, and there is copious information on the multiple effects of exogenously applied NO on different physiological and biochemical processes of plants. Heavy metal toxicity is one of the major abiotic stresses leading to hazardous effects in plants and its toxicity is based on chemical and physical property. A common consequence of heavy metal toxicity is the uncontrolled and excessive accumulation of reactive oxygen species (ROS) which leads to peroxidation of lipids, oxidation of protein, inactivation of enzymes, DNA damage and/or interact with other vital constituents of plant cells. Recently, an increasing number of articles have reported the effects of exogenous NO on alleviating heavy metal toxicity in plants but knowledge of physiological mechanisms of NO in alleviating heavy metal toxicity is quite limited, and some results contradict one another. Therefore, to help clarify the roles of NO in heavy metal tolerance, it is important to review and discuss the recent advances on this area of research. NO can provoke both beneficial and harmful effects, which depend on the concentration and location of NO in the plant cells. NO alleviates the harmfulness of the ROS, and reacts with other target molecules, and regulates the expression of stress responsive genes under various stress conditions. This manuscript includes, the latest advances in understanding the effects of endogenous NO on heavy metal toxicity and the mechanisms and role of NO as an antioxidant as well as in protein nitration are highlighted.

eNOS Gene Variant in Patients with Coronary Artery Disease

Subject & Aim. Endothelial nitric oxide synthase (eNOS) is one of the most important candidate genes in CAD. A functional polymorphism within eNOS gene is a 27 bp VNTR on its intron 4 which has been shown to be associated with various diseases. In this study we investigated eNOS VNTR polymorphism in addition to eNOS gene expression profile in patients with CAD. Material and Methods. The study comprised patients with angiographically confirmed CAD (CAD⁺) and individuals with normal coronary as CAD⁻. eNOS VNTR polymorphism frequencies were determined in both groups. In addition eNOS gene expression profile was examined using a quantitative real-time PCR. Results. We have found that aa genotype was significantly increasing the risk of CAD in our patients (aa versus ab + bb, P = 0.02, OR = 3.5; 95% CI: = 0.98 to 16.2). The differences in eNOS expression were not significant between patients and normal group; however in CAD⁺ patients eNOS expression was higher than the expression level of patients carrying other genotypes (P = 0.16). Conclusion. We have observed that eNOS gene polymorphism was associated with CAD in angiography-confirmed patients. However, the difference in eNOS gene expression was not statistically significant between patients and control which might be due to the contribution of other confounding factors which require further investigations.

eNOS tag SNP haplotypes in hypertensive disorders of pregnancy

Haplotypes formed by polymorphisms (T-786C, rs2070744; a variable number of tandem repeats in intron 4, and Glu298Asp, rs1799983) of the eNOS gene were associated previously with gestational hypertension (GH) and preeclampsia (PE). However, no study has explored the Tag SNPs rs743506 and rs7830 in these disorders. The aim of the current study was to compare the distribution of the genotypes and haplotypes formed by the five eNOS polymorphisms mentioned among healthy pregnant (HP, n=122), GH (n=138), and PE (n=157). The haplotype formed by "C b G G C" was more frequent in HP compared to GH and PE (p=0.0071), which is supported by previous findings that demonstrated the association of the combination "C b G" with a higher level of nitrite (NO marker). Our results suggest a protective effect of the haplotype "C b G G C" against the development of hypertensive disorders of pregnancy.

Negative feedback through mRNA provides the best control of gene-expression noise

Genetically identical cell populations exposed to the same environment can exhibit considerable cell-to-cell variation in the levels of specific proteins. This variation or expression noise arises from the inherent stochastic nature of biochemical reactions that constitute gene expression. Negative feedback loops are common motifs in gene networks that reduce expression noise and intercellular variability in protein levels. Using stochastic models of gene expression we here compare different feedback architectures in their ability to reduce stochasticity in protein levels. A mathematically controlled comparison shows that in physiologically relevant parameter regimes, feedback regulation through the mRNA provides the best suppression of expression noise. Consistent with our theoretical results we find negative feedback loops though the mRNA in essential eukaryotic genes, where feedback is mediated via intron-derived microRNAs. Finally, we find that contrary to previous results, protein-mediated translational regulation may not always provide significantly better noise suppression than protein-mediated transcriptional regulation.

Co-transcriptional regulation of alternative pre-mRNA splicing

While studies of alternative pre-mRNA splicing regulation have typically focused on RNA-binding proteins and their target sequences within nascent message, it is becoming increasingly evident that mRNA splicing, RNA polymerase II (pol II) elongation and chromatin structure are intricately intertwined. The majority of introns in higher eukaryotes are excised prior to transcript release in a manner that is dependent on transcription through pol II. As a result of co-transcriptional splicing, variations in pol II elongation influence alternative splicing patterns, wherein a slower elongation rate is associated with increased inclusion of alternative exons within mature mRNA. Physiological barriers to pol II elongation, such as repressive chromatin structure, can thereby similarly impact splicing decisions. Surprisingly, pre-mRNA splicing can reciprocally influence pol II elongation and chromatin structure. Here, we highlight recent advances in co-transcriptional splicing that reveal an extensive network of coupling between splicing, transcription and chromatin remodeling complexes. This article is part of a Special Issue entitled: Chromatin in time and space.

Intron 4 polymorphism of the endothelial nitric oxide synthase (eNOS) gene is associated with decreased NO production in a mercury-exposed population

Nitric oxide (NO), produced by endothelial nitric oxide synthase (eNOS), is a potent vasodilator and plays a prominent role in regulating the cardiovascular system. Decreased basal NO release may predispose to cardiovascular diseases. Evidence suggests that the 27 nt repeat polymorphism of the intron 4 in the eNOS gene may regulate eNOS expression. On the other hand, some recent reports strongly suggest an association between methylmercury (MeHg) exposures and altered NO synthesis. In the present study, we investigate the contribution of the 27-pb tandem repeat polymorphism on nitric oxide production, which could enhance susceptibility to cardiovascular disease in the MeHg-exposed study population. Two-hundred-two participants (98 men and 104 women), all chronically exposed to MeHg through fish consumption were examined. Mean blood Hg concentration and nitrite plasma concentration were 50.5 ± 35.4 μg/L and 251.4 ± 106.3n M, respectively. Mean systolic and diastolic blood pressure were 120.1 ± 19.4mm Hg and 72.0 ± 10.6mm Hg, respectively. Mean body mass index was 24.5 ± 4.3 kg/m(2) and the mean heart rate was 69.8 ± 11.8 bpm. There were no significant differences in age, arterial blood pressure, body mass index or cardiac frequency between genotype groups (all P>0.05). However, we observed different nitrite concentrations in the genotypes groups, with lower nitrite levels for the 4a4a genotype carriers. Age, gender and the presence of intron 4 polymorphism contributed to nitrite reduction as a result of blood Hg concentration. Taken together, our results show that the 27 nt repeat polymorphism of the intron 4 in the eNOS gene increases susceptibility to cardiovascular diseases after MeHg exposure by modulating nitric oxide levels.

Intronic microRNA suppresses endothelial nitric oxide synthase expression and endothelial cell proliferation via inhibition of STAT3 signaling

Intronic microRNA (miRNAs) suppressed the expression of endothelial nitric oxide synthase (eNOS) gene in endothelial cells (ECs). This study was to investigate the role of signal transducer and activator of transcription 3 (STAT3) in the regulation of eNOS expression and vascular EC proliferation by the intronic 27-nucleotide (nt) miRNA derived from the 27-base pair repeats in intron 4 of eNOS gene. A detectable level of the 27-nt miRNA was present in the control ECs. Overexpression of the 27-nt miRNA dramatically suppressed the expression of eNOS and STAT3 at both transcription and translation levels in ECs in association with significant inhibition of EC proliferation. Mutation of the 27-nt miRNA at the 3'-terminal region resulted in substantial reduction of the inhibitory effect of miRNA on eNOS and STAT3 expression, and EC proliferation. Overexpression of active STAT3 significantly reversed the inhibitory effect of the 27-nt miRNA on eNOS expression and EC proliferation. In summary, we demonstrated that the 27-nt intronic miRNA functioned as a negative regulator for the expression of its host gene eNOS and cell proliferation in ECs. The sequence in 3'-terminal region played a key role in the function of the 27-nt miRNA. The regulatory effect of the intronic miRNA on eNOS gene expression was associated with miRNA polymorphisms, and mediated through inhibition of STAT3 signaling in ECs.

Endothelial nitric oxide synthase haplotypes associated with aura in patients with migraine

There is strong evidence implicating nitric oxide (NO) in the pathophysiology of migraine and aura. Therefore, genetic polymorphisms in the endothelial NO synthase (eNOS) gene have been studied as candidate markers for migraine susceptibility. We compared for the first time the distribution of eNOS haplotypes including the three clinically relevant eNOS polymorphisms (T(-786)C in the promoter, rs2070744; Glu298Asp in exon 7, rs1799983; and a 27 bp variable number of tandem repeats in intron 4) and two additional tagging single-nucleotide polymorphisms (rs3918226 and rs743506) in 178 women with migraine (134 without aura and 44 with aura) and 117 healthy controls (control group). Genotypes were determined by TaqMan allele discrimination assay, real-time polymerase chain reaction, and polymerase chain reaction followed by fragment separation by electrophoresis. The GA (rs743506) genotype was more common in the control group than in women with migraine (odds ratio = 0.47, 95% confidence interval [CI] = 0.29-0.78, p < 0.01). No significant differences were found in allele distributions for the five eNOS polymorphisms. However, the haplotypes including the variants "C C a Glu G" and the variants "C C b Glu G" were more common in women with migraine with aura than in women with migraine without aura (odds ratio = 30.71, 95% CI = 1.61-586.4 and odds ratio = 17.26, 95% CI = 1.94-153.4, respectively; both p < 0.0015625). These findings suggest that these two eNOS haplotypes affect the susceptibility to the presence of aura in patients with migraine.

Influence of endothelial nitric oxide synthase polymorphisms in psoriasis risk

Nitric oxide (NO) is a potent regulator of keratinocyte growth and differentiation that has been implicated in the pathogenesis of psoriasis (Ps). The NOS3 -786 T/C (SNP id rs2070744; http://www.ensembl.org ), intron 4 variable number tandem repeat (VNTR), and Glu298Asp (SNP id rs1799983) polymorphisms, have been associated with differences in NO plasma concentrations and with the risk of hypertension (HT) and ischemic cardiac disease. The aim of this study was to determine whether the above-mentioned NOS3 variants contributed to the risk of Ps, and were associated with the risk for HT and CAD in these patients. A total of 368 patients with chronic plaque Ps and 400 healthy controls were genotyped for the NOS3 -786 T/C, intron 4 VNTR, and Glu298Asp polymorphisms. Carriers of the -786 C allele were significantly more frequent among the patients (p < 0.001). Carriers of the 4-repeats allele (45 + 44 genotypes) were also more frequent a (p < 0.001). No significant difference was found for the Glu298Asp polymorphism. None of the NOS3 variants was associated with Ht and CAD in our population. In conclusion, NOS3 gene polymorphism would be risk factors for developing Ps.

Genetic polymorphisms in the endothelial nitric oxide synthase gene correlate with overall survival in advanced non-small-cell lung cancer patients treated with platinum-based doublet chemotherapy

Background

Nitric oxide (NO) is a free radical that is involved in carcinogenesis. Endothelial NO, synthesized from L-arginine by endothelial NO synthase (eNOS), inhibits apoptosis and promotes angiogenesis, tumor cell proliferation and metastasis. The aim of this study was to evaluate the influence of polymorphisms in the eNOS gene on prognosis of patients with advanced stage non-small-cell lung cancer (NSCLC).

Methods

Unresectable, chemotherapy naïve stage III or IV NSCLC patients who were treated with standard platinum-containing doublet regimens were analyzed. All individuals were genotyped for the single-nucleotide polymorphism G894T in exon 7 of the eNOS gene and for a variable number of tandem repeats (VNTR) polymorphism in intron 4 that results in a rare smaller allele (a) and a common larger allele (b), to investigate the association between these polymorphisms and clinical outcomes. The primary endpoint was correlation with overall survival.

Results

From October 2004 to December 2007, 108 patients (male/female, 66/42; Stage IIIA/IIIB/IV, 6/30/72) aged 29-77 years (median 63) with good performance status were consecutively enrolled in this study. Using Kaplan-Meier estimates, we showed that 5-year overall survival was significantly increased in patients carrying the VNTR a-allele compared with VNTR b/b patients (P = 0.015). In multivariate Cox proportional hazard analysis, the VNTR polymorphism was an independent prognostic factor for survival.

Conclusions

The results support the role of the VNTR polymorphism in intron 4 as a marker for survival in patients with advanced stage NSCLC who are candidates for standard chemotherapy.

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.

Epigenetics of the vascular endothelium

Classical models of transcription in vascular endothelial cells, specifically the cis/trans paradigm, have limitations. For instance, how does the environment have chronic effects on gene expression in endothelial cells after weeks or years? When an endothelial cell divides, how is this information transmitted to daughter cells? Epigenetics refers to chromatin-based pathways important in the regulation of gene expression and includes three distinct, but highly interrelated, mechanisms: DNA methylation, histone density and posttranslational modifications, and RNA-based mechanisms. Together they offer a newer perspective on transcriptional control paradigms in vascular endothelial cells and provide a molecular basis for understanding how the environment impacts the genome to modify disease susceptibility. This alternative viewpoint for transcriptional regulation allows a reassessment of the cis/trans model and even helps explain some of its limitations. This review provides an introduction to epigenetic concepts for vascular biologists and uses topical examples in cell biology to provide insight into how cell types or even whole organisms, such as monozygotic human twins with the same DNA sequence, can exhibit heterogeneous patterns of gene expression, phenotype, or diseases prevalence. Using endothelial nitric oxide synthase (NOS3) as an example, we examine the growing body of evidence implicating epigenetic pathways in the control of vascular endothelial gene expression in health and disease.

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.

Control of alternative splicing through siRNA-mediated transcriptional gene silencing

When targeting promoter regions, small interfering RNAs (siRNAs) trigger a previously proposed pathway known as transcriptional gene silencing by promoting heterochromatin formation. Here we show that siRNAs targeting intronic or exonic sequences close to an alternative exon regulate the splicing of that exon. The effect occurred in hepatoma and HeLa cells with siRNA antisense strands designed to enter the silencing pathway, suggesting hybridization with nascent pre-mRNA. Unexpectedly, in HeLa cells the sense strands were also effective, suggesting that an endogenous antisense transcript, detectable in HeLa but not in hepatoma cells, acts as a target. The effect depends on Argonaute-1 and is counterbalanced by factors favoring chromatin opening or transcriptional elongation. The increase in heterochromatin marks (dimethylation at Lys9 and trimethylation at Lys27 of histone H3) at the target site, the need for the heterochromatin-associated protein HP1alpha and the reduction in RNA polymerase II processivity suggest a mechanism involving the kinetic coupling of transcription and alternative splicing.

An intron 4 VNTR polymorphism of the endothelial nitric oxide synthase gene is associated with early-onset colorectal cancer

Endothelial-derived nitric oxide, which is produced by endothelial nitric oxide synthase (eNOS), may play an important role in colorectal carcinogenesis. However, the putative contribution of common eNOS genetic polymorphisms to colorectal cancer risk remains unknown. We genotyped 3 polymorphisms of eNOS (T-786C, G894T, and intron4b/a) in 727 colorectal adenocarcinoma cases and 736 age- and sex-matched healthy controls in Taiwan. Genotypes of the T-786C and G894T polymorphisms were determined by fluorescence polarization assays and the 27-bp variable number of tandem repeat (VNTR) polymorphism in intron 4 (intron4b/a) was analyzed by PCR. Logistic regression was used to calculate odds ratios (ORs) and 95% confidence intervals (CIs). Among younger participants (< or =60 yrs), the intron4a variant genotype was associated with a significantly increased risk of colorectal cancer, compared with the intron4bb genotype (OR = 1.60, 95% CI = 1.04-2.46). In addition, those young individuals bearing a greater number of high-risk genotypes (OR > 1, i.e., CT+TT for T-786C, ba+aa for intron4b/a, and GG for G894T) of eNOS had a higher colorectal cancer risk (p(trend) = 0.039). Compared with younger individuals without any putative high-risk genotypes, those with 3 high-risk genotypes had a significantly greater cancer risk (OR = 1.89, 95% CI = 1.04-3.43). Our results suggest that the eNOS intron4b/a polymorphism may contribute to early-onset colorectal cancer risk in the Taiwanese population.

Effect of 27nt small RNA on endothelial nitric-oxide synthase expression

We have reported previously that the 27nt repeat polymorphism in endothelial nitric-oxide synthase (eNOS) intron 4--a source of 27nt small RNA--inhibits eNOS expression. In the current study, we have investigated how 27nt small RNA suppresses eNOS expression. Using a chromatin immunoprecipitation assay, we examined histone acetylation in the 27nt repeat element of eNOS intron 4, the promoter region up to -1486 bp, and the 5' enhancer region (-4583/-4223bp) in human aortic endothelial cells (HAECs) treated with 27nt RNA duplex. 27nt RNA duplex induced hyperacetylation in H3 (lysine8, 12, and 23) and H4 (lysine 9 and 12) at the 27nt repeat element, which then interacted with nuclear actin, histone deacetylase 3 (HDAC3), and NonO proteins. In contrast, the histone H3 and H4 became hypoacetylated at the eNOS core promoter. HAECs treated with 27nt RNA duplex had reduced eNOS expression, but treatment with either HDAC3 small interfering RNA or NonO siRNA significantly attenuated the 27nt small RNA-induced suppression. We further found that 27nt small RNA induced DNA methylation in a region approximately 750nt upstream of the intron 4 repeats, and a methyltransferase inhibitor reversed the effect on methylation and eNOS expression. Our study demonstrates that 27nt small RNA may suppress eNOS expression by altering histone acetylation and DNA methylation in regions adjacent to the 27nt repeat element and core promoter.