Novel allele of the endothelial nitric oxide synthase gene polymorphism in Caucasian asthmatics

Association between eNOS Gene Polymorphism (T786C and VNTR) and Sickle Cell Disease Patients in Ghana

Endothelial nitric oxide synthase (eNOS) variants have been found to be associated with several vascular disorders as well as the pathogenesis of sickle cell disease (SCD) complications such as vaso-occlusive crises (VOC). Studies on eNOS gene variants among SCD patients are rare in Ghana and several other African countries. The current study aimed to determine a possible association between variants of the eNOS gene (variable number of tandem repeats in intron 4 and T786C) in SCD complications among Ghanaian patients. This was a cross-sectional study involving 89 HbSS patients with complications and 46 HbSS patients without complications. Genomic DNA was extracted from leukocytes in the buffy coat and separated from collected whole blood samples of the study participants. PCR amplification, followed by restriction fragment length polymorphism (RFLP) was used to genotype T786C (rs2070744) variants. Variable number of tandem repeats (VNTR) in intron 4 was genotyped by PCR and direct electrophoresis. There was a significant difference in the genotype frequency of the T786C variant between HbSS patients with complications and those without complications (p = 0.0165). However, there was no significant difference in the VNTR intron 4 variant of the eNOS gene between patients with complications and those without complications (p > 0.05). The study shows an association between the eNOS gene variant (T786C) and complications in SCD.

Nitric oxide and hyperoxic acute lung injury

Hyperoxic acute lung injury (HALI) refers to the damage to the lungs secondary to exposure to elevated oxygen partial pressure. HALI has been a concern in clinical practice with the development of deep diving and the use of normobaric as well as hyperbaric oxygen in clinical practice. Although the pathogenesis of HALI has been extensively studied, the findings are still controversial. Nitric oxide (NO) is an intercellular messenger and has been considered as a signaling molecule involved in many physiological and pathological processes. Although the role of NO in the occurrence and development of pulmonary diseases including HALI has been extensively studied, the findings on the role of NO in HALI are conflicting. Moreover, inhalation of NO has been approved as a therapeutic strategy for several diseases. In this paper, we briefly summarize the role of NO in the pathogenesis of HALI and the therapeutic potential of inhaled NO in HALI.

Intron 4 VNTR (4a/b) polymorphism of the endothelial nitric oxide synthase gene is associated with breast cancer in Mexican women

The endothelial nitric oxide synthase (eNOS) gene plays an important role in several biological functions. Polymorphisms of the eNOS gene have been associated with cancer. It has been suggested that the VNTR 4 a/b polymorphism may affect the expression of eNOS and contributes to tumor promotion in the mammary gland. We examined the role of the eNOS4 a/b polymorphism by comparing the genotypes of 281 healthy Mexican women with the genotypes of 429 Mexican women with breast cancer (BC). The observed genotype frequencies for control and BC patients were 0.6% and 0.7% for a/a (polymorphic); 87% and 77% for a/a (wild type); and 12% and 22% for a/b respectively. We found that the odds ratio (OR) was 1.9, with a 95% confidence interval (95%CI) of 1.29-2.95, P = 0.001 for genotypes a/a-a/b, b/c. The association was also evident when comparing the distribution of the a/a-a/b genotypes in patients with high levels of glutamate-oxaloacetate transaminase (SGOT) (OR, 1.93; 95% CI, 1.14-3.28; P = 0.015); undergoing menopause with high levels of SGOT (OR, 2.0; 95% CI, 1.1-3.84); and with high levels of glutamic-pyruvic transaminase (SGPT) (OR, 3.5; 95% CI, 1.56-8.22). The genotypes a/a-a/b are associated with BC susceptibility in the analyzed samples from the Mexican population.

Extensive ethnogenomic diversity of endothelial nitric oxide synthase (eNOS) polymorphisms

Nitric oxide (NO) is highly reactive, produced in endothelial cells by endothelial NO synthase (eNOS) and has been implicated in sickle cell pathophysiology. We evaluated the distribution of functionally significant eNOS variants (the T786C variant in the promoter region, the Glu298Asp variant in exon 7, and the variable number of tandem repeats (VNTR) in intron 4) in Africans, African Americans and Caucasians. The C-786 variant was more common in Caucasians than in Africans and African Americans. Consistent with other findings, the Asp-298 variant had the highest frequency in Caucasians followed by African Americans, but was completely absent in Africans. The very rare intron 4 allele, eNOS 4c, was found in some Africans and African Americans, but not in Caucasians. eNOS 4d allele was present in 2 Africans. These findings suggest a consistent and widespread genomic diversity in the distribution of eNOS variants in Africans, comparative to African Americans and Caucasians.

The 27-bp VNTR polymorphism in intron 4 of the human eNOS gene in healthy Singaporean Chinese, Indians, and Malays

Human endothelial nitric oxide synthase (eNOS) is one isoform of the nitric oxide synthases that are responsible for nitric oxide synthesis from L-arginine. The gene encoding eNOS contains a 27-bp VNTR polymorphism in intron 4. We report here for the first time the presence of a novel allele 3, which was absent in all other populations studied to date, in 1.7% each of Singaporean Indians and Malays. We also detected the presence of a novel genotype 3/5 in 3.4% each of Singaporean Indians and Malays. Allele 6, which was absent in Han Chinese from northern China and Taiwan and was also absent in Indians from the Indian subcontinent, was found in 2.1% of Singaporean Chinese and in 0.3% of Singaporean Indians.

Endothelial nitric oxide synthase genotypes in the etiology of retinopathy of prematurity in premature infants

PURPOSE

Retinopathy of Prematurity (ROP) is a vasoproliferative disorder affecting preterm infants leading to visual impairment. ROP is more common in Caucasians than African Americans. Very low birth weight infants have immature retinas and are susceptible to ROP. Because of differences in individual responses to the treatment, various genetic factors have been looked into to understand the etiology of ROP. Endothelial nitric oxide (eNO) serves as a vasodilator, relaxes smooth muscle, prevents platelet aggregation, and facilitates improved blood flow and vascular tonicity. Mutant eNO synthase (eNOS) genotypes result in reduced nitric oxide levels by decreasing enzyme activity. Since eNO affects vasculature and ROP is a vascular disease, the present investigation was aimed at studying the association of genotypes with ROP.

METHODS

Two eNOS gene single nucleotide polymorphisms (SNPs) (T-786C, and G894T) were studied by microplate-Restriction Fragment Length Polymorphism Polymerase Chain Reaction (RFLP PCR) method. Genotypes were studied in 146 premature infants.

RESULTS

The present data showed significant differences in the baseline gene frequencies between Caucasians and African Americans. ROP patients displayed 3-fold higher frequencies of mutant -786C and 894T alleles in both ethnicities compared to respective controls.

CONCLUSIONS

The present data suggest ethnic stratification of genotypes. Mutant -786C and 894T alleles are significant risk factors in the development of ROP, and suggest a strong association between eNOS polymorphisms and the disease. It is interesting to know if a larger dataset of ROP patients can confirm our initial findings.

Subcellular and cellular locations of nitric oxide synthase isoforms as determinants of health and disease

The effects of nitric oxide in biological systems depend on its steady-state concentration and where it is being produced. The organ where nitric oxide is produced is relevant, and within the organ, which types of cells are actually contributing to this production seem to play a major determinant of its effect. Subcellular compartmentalization of specific nitric oxide synthase enzymes has been shown to play a major role in health and disease. Pathophysiological conditions affect the cellular expression and localization of nitric oxide synthases, which in turn alter organ cross talk. In this study, we describe the compartmentalization of nitric oxide in organs, cells, and subcellular organelles and how its localization relates to several relevant clinical conditions. Understanding the complexity of the compartmentalization of nitric oxide production and the implications of this compartmentalization in terms of cellular targets and downstream effects will eventually contribute toward the development of better strategies for treating or preventing pathological events associated with the increase, inhibition, or mislocalization of nitric oxide production.

Is an endothelial nitric oxide synthase gene mutation a risk factor in the origin of intraventricular hemorrhage?

OBJECT

Studies have shown decreased levels of nitric oxide (NO), the product of endothelial NO synthase (eNOS) gene activity, in infants with respiratory conditions and intraventricular hemorrhage (IVH). The authors evaluated the association of the eNOS gene promoter polymorphism T-786C with the cause of these conditions (respiratory conditions and IVH) in premature infants.

METHODS

Blood samples from 124 African American premature infants were studied. The DNA was isolated and microplate polymerase chain reaction-restriction fragment length polymorphism assay was performed. Genotypes were scored as: TT homozygotes with 140 bp and 40 bp; CC homozygotes with 90 bp, 50 bp, and 40 bp; and TC heterozygotes with 140 bp, 90 bp, 50 bp, and 40 bp. Genotypes were stratified according to ethnicity, preterm status, and prematurity conditions.

RESULTS

The mutant allele -786C was present in 15.3% of premature infants with respiratory distress syndrome, bronchopulmonary dysplasia, and IVH, compared with 7.25% in those premature infants without these conditions. A significant 2-fold increase of the mutant allele in patients compared with controls (p = 0.04, OR 2.3) reveals that the eNOS -786C allele could be a significant risk factor in the origin of respiratory conditions and IVH in premature infants.

CONCLUSIONS

These results suggest that the mutant eNOS -786C allele is a significant risk factor in the origin of respiratory and IVH diseases, probably mediating an insufficient supply of endogenous NO in premature infants.

Haplotype analysis of the endothelial nitric oxide synthase gene in asthma

Nitric oxide (NO) is an important mediator of physiologic processes in the airways. Evidence exists that genetic factors affect NO formation and contribute to the pathophysiology of asthma. The aims of this study were to determine the endothelial NO synthase (eNOS) haplotypes in Czech asthmatics and control subjects and examine their relation to asthma. We analyzed a total of six polymorphisms. Two SNPs in the promoter (C-786T and C-691T), two variants in the introns (27-bp repeat in intron 4 and G11T in intron 23), and two others in the exons (C774T in exon 6 and G894T in exon 7) were genotyped in 610 subjects (asthma, n = 294; healthy controls, n = 316), and a case-control association study was conducted. No significant differences in allele or genotype frequencies for individual polymorphisms were observed between patients with asthma and controls after correction for multiple comparisons. Nevertheless, a G to T exchange in intron 23 was related with specific sensitization for feather (p = 0.008, p(corr) < 0.05). However, the common haplotype -786T/-691C/27-bp 5 repeat variant/774C/894G/11T was associated with lower risk of asthma (p = 0.001, p(corr) < 0.05, odds ratio = 0.58, 95% confidence interval = 0.46-0.73). These findings suggest that endothelial NOS variants may be one of the factors participating in protection or susceptibility to asthma in our population.

The intron 4c allele of the NOS3 gene is associated with ischemic stroke in African Americans

BACKGROUND

Ischemic stroke is the most common cause of disability in North America and in addition to the generally accepted risk factors, there is increasing evidence for the potential pathophysiological role of genes. One of these genes, the endothelial nitric oxide synthase gene (NOS3) has been reported as a genetic risk factor for ischemic stroke. To independently confirm and extend the results of these previous reports, we investigated this gene as a risk factor for stroke in an ethnically diverse study population.

METHODS

Using the TOAST classification, we characterized and studied 377 patients with ischemic stroke. We genotyped two common variants in the NOS3 gene, the intron 4 insertion/deletion and an exonic single nucleotide polymorphism (SNP), G894T, in these patients and compared them with 502 controls. Chi-square or Fisher's exact tests were used to examine allele effects on stroke and stroke subtypes. Logistic regression analysis was used to adjust for confounding covariate effects.

RESULTS

All genotypes are in Hardy-Weinberg equilibrium except for intron 4c, which is overrepresented in ischemic stroke patients. In pooled analysis of all patients, intron 4c, but not intron 4a, intron 4b or G894T alleles are associated with stroke (p < 0.01). In subgroup analysis by race, the intron 4c allele is most strongly associated with large artery ischemic stroke in African Americans (p < 0.01).

CONCLUSION

We are unable to confirm previous reports of an association of the intron 4a or the G894T alleles with ischemic stroke. However, although limited by a relatively small sample size, our study suggests a potentially important role of the intron 4c allele as a genetic marker of ischemic stroke in African Americans.

Genome-wide linkage analysis of pulmonary function in families of children with asthma in Costa Rica

BACKGROUND

Although asthma is highly prevalent among certain Hispanic subgroups, genetic determinants of asthma and asthma-related traits have not been conclusively identified in Hispanic populations. A study was undertaken to identify genomic regions containing susceptibility loci for pulmonary function and bronchodilator responsiveness (BDR) in Costa Ricans.

METHODS

Eight extended pedigrees were ascertained through schoolchildren with asthma in the Central Valley of Costa Rica. Short tandem repeat (STR) markers were genotyped throughout the genome at an average spacing of 8.2 cM. Multipoint variance component linkage analyses of forced expiratory volume in 1 second (FEV(1)) and FEV(1)/ forced vital capacity (FVC; both pre-bronchodilator and post-bronchodilator) and BDR were performed in these eight families (pre-bronchodilator spirometry, n = 640; post-bronchodilator spirometry and BDR, n = 624). Nine additional STR markers were genotyped on chromosome 7. Secondary analyses were repeated after stratification by cigarette smoking.

RESULTS

Among all subjects, the highest logarithm of the odds of linkage (LOD) score for FEV(1) (post-bronchodilator) was found on chromosome 7q34-35 (LOD = 2.45, including the additional markers). The highest LOD scores for FEV(1)/FVC (pre-bronchodilator) and BDR were found on chromosomes 2q (LOD = 1.53) and 9p (LOD = 1.53), respectively. Among former and current smokers there was near-significant evidence of linkage to FEV(1)/FVC (post-bronchodilator) on chromosome 5p (LOD = 3.27) and suggestive evidence of linkage to FEV(1) on chromosomes 3q (pre-bronchodilator, LOD = 2.74) and 4q (post-bronchodilator, LOD = 2.66).

CONCLUSIONS

In eight families of children with asthma in Costa Rica, there is suggestive evidence of linkage to FEV(1) on chromosome 7q34-35. In these families, FEV(1)/FVC may be influenced by an interaction between cigarette smoking and a locus (loci) on chromosome 5p.

Association study of promoter polymorphisms within the NOS3 gene and allergic diseases

BACKGROUND

Nitric oxide (NO) is an important mediator of physiologic and pathologic processes in the airways. On this basis, we hypothesized that polymorphisms in the NOS3 gene could be associated with the disease process.

METHODS

Two promoter variants (-786C/T and -691C/T) were examined in a Caucasian Czech population of allergic patients [n = 671, with a subgroup of asthmatics (n = 305)] and healthy controls (n = 334) using PCR-RFLP analyses.

RESULTS

NOS3 -786C/T and -691C/T were not associated with allergic diseases or asthma. However, the -786 variant was significantly associated with asthma in men (p < 0.01, p(corr) < 0.05) but not in women. NOS3 -691C/T was found to be in strong linkage disequilibrium with -786C/T, and the distribution of combined genotypes was marginally different between the asthmatic and control men.

CONCLUSION

Our results suggest that NOS3 gene variants may be one of the factors that participate in the pathogenesis of asthma in men.

Overexpression of endothelial nitric oxide synthase suppresses features of allergic asthma in mice

Background

Asthma is associated with airway hyperresponsiveness and enhanced T-cell number/activity on one hand and increased levels of exhaled nitric oxide (NO) with expression of inducible NO synthase (iNOS) on the other hand. These findings are in paradox, as NO also relaxes airway smooth muscle and has immunosuppressive properties. The exact role of the endothelial NOS (eNOS) isoform in asthma is still unknown. We hypothezised that a delicate regulation in the production of NO and its bioactive forms by eNOS might be the key to the pathogenesis of asthma.

Methods

The contribution of eNOS on the development of asthmatic features was examined. We used transgenic mice that overexpress eNOS and measured characteristic features of allergic asthma after sensitisation and challenge of these mice with the allergen ovalbumin.

Results

eNOS overexpression resulted in both increased eNOS activity and NO production in the lungs. Isolated thoracic lymph nodes cells from eNOS overexpressing mice that have been sensitized and challenged with ovalbumin produced significantly less of the cytokines IFN-γ, IL-5 and IL-10. No difference in serum IgE levels could be found. Further, there was a 50% reduction in the number of lymphocytes and eosinophils in the lung lavage fluid of these animals. Finally, airway hyperresponsiveness to methacholine was abolished in eNOS overexpressing mice.

Conclusion

These findings demonstrate that eNOS overexpression attenuates both airway inflammation and airway hyperresponsiveness in a model of allergic asthma. We suggest that a delicate balance in the production of bioactive forms of NO derived from eNOS might be essential in the pathophysiology of asthma.

Modulation of nitric oxide pathways: therapeutic potential in asthma and chronic obstructive pulmonary disease

Nitric oxide (NO) is present in the exhaled breath of humans and other mammalian species. It is generated in the lower airways by enzymes of the nitric oxide synthase (NOS) family, although nonenzymatic synthesis and consumptive processes may also influence levels of NO in exhaled breath. The biological properties of NO in the airways are multiple, complex, and bidirectional. Under physiological conditions, NO appears to play a homeostatic bronchoprotective role. However, its proinflammatory properties could also potentially cause tissue injury and contribute to airway dysfunction in disease states such as asthma and chronic obstructive pulmonary disease (COPD). This article will review the physiological and pathophysiological roles of NO in the airways, discuss the rationale for the use of drugs that modulate NO pathways--nitric oxide synthase inhibitors and NO donors--to treat inflammatory airway diseases, and attempt to predict the likely therapeutic benefit of such agents.