NOS3 polymorphisms, cigarette smoking, and cardiovascular disease risk: the Atherosclerosis Risk in Communities study

Cross-Sectional Gene-Smoking Interaction Analysis in Relation to Subclinical Atherosclerosis-Results From the IMPROVE Study

BACKGROUND

Smoking is associated with carotid intima-media thickness (C-IMT). However, knowledge about how genetics may influence this association is limited. We aimed to perform nonhypothesis driven gene-smoking interaction analyses to identify potential genetic variants, among those included in immune and metabolic platforms, that may modify the effect of smoking on carotid intima-media thickness.

METHODS

We used baseline data from 1551 men and 1700 women, aged 55 to 79, included in a European multi-center study. Carotid intima-media thickness maximum, the maximum of values measured at different locations of the carotid tree, was dichotomized with cut point values ≥75, respectively. Genetic data were retrieved through use of the Illumina Cardio-Metabo- and Immuno- Chips. Gene-smoking interactions were evaluated through calculations of Synergy index (S). After adjustments for multiple testing, P values of <2.4×10-7 for S were considered significant. The models were adjusted for age, sex, education, physical activity, type of diet, and population stratification.

RESULTS

Our screening of 207 586 SNPs available for analysis, resulted in the identification of 47 significant gene-smoking synergistic interactions in relation to carotid intima-media thickness maximum. Among the significant SNPs, 28 were in protein coding genes, 2 in noncoding RNA and the remaining 17 in intergenic regions.

CONCLUSIONS

Through nonhypothesis-driven analyses of gene-smoking interactions, several significant results were observed. These may stimulate further research on the role of specific genes in the process that determines the effect of smoking habits on the development of carotid atherosclerosis.

Family History, Tobacco Smoking, and Risk of Ischemic Stroke

BACKGROUND AND PURPOSE

Both genetic factors and smoking are associated with ischemic stroke (IS) risk. However, little is known about the potential interaction of these factors. We aimed to assess whether smoking and a positive family history interact to increase the risk of IS.

METHODS

The nationwide prospective study recruited 210,000 men and 300,000 women in 2004 to 2008 at ages 30 to 79 years. During 9.7 years of follow-up, we documented 16,923 and 20,656 incident IS cases in men and women without major chronic diseases at baseline, respectively. Multivariable Cox regression models were used to examine associations between family history and IS. Likelihood ratio tests were used to test the smoking-family history interactions on IS.

RESULTS

About 67.8% (n=135,168) of men ever smoked regularly compared with 2.7% (n=7,775) of women. Among men, a significant interaction between family history and smoking on IS was observed (P for interaction=0.03), with more pronounced association between family history and IS among ever-regular smokers (hazard ratio [HR], 1.21; 95% confidence interval [CI], 1.16 to 1.27) than among never-smokers (HR, 1.11; 95% CI, 1.01 to 1.23). The association between family history and IS among ex-smokers after more than 10 years of cessation (HR, 1.01; 95% CI, 0.85 to 1.20) appeared similar to that among never-smokers. Among women, a similar but not significant interaction between family history and smoking on IS was observed. Ever-regular smokers who had a family history of stroke had the highest risk of IS.

CONCLUSIONS

Among Chinese men, the association of family history with IS was accentuated by smoking, and such accentuation tended to be lowered by cessation.

Effect of the +781C/T polymorphism in the interleukin-8 gene on atherosclerotic cerebral infarction, and its interaction with smoking and drinking

OBJECTIVE

The aims of this study were to investigate the association between the +781C/T polymorphism of interleukin-8 (IL-8) and atherosclerotic cerebral infarction and the interaction between the +781C/T polymorphism and smoking or drinking in cerebral infarction in the Han Chinese population.

METHODS

We investigated the +781C/T polymorphism of IL-8 in 308 consecutive Han Chinese patients who were diagnosed with atherosclerotic cerebral infarction and in 294 age- and gender-matched healthy control subjects. The patients were classified using the Oxfordshire Community Stroke Project (OCSP) classification. The patients and subjects' histories of smoking and drinking were recorded, and atherosclerosis (AS) of the internal carotid artery (ICA) was evaluated in the patients. The +781C/T polymorphism was determined by polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) analysis.

RESULTS

The +781C/T polymorphism and allele frequencies were not significantly different between the patients and controls and were not significantly associated with the OCSP classifications. We found that the 781C allele was significantly associated with AS of the ICA in the patients (p = 0.017), and the CT genotype was more prevalent in patients without AS of the ICA (p = 0.035). No interactions were observed between the +781C/T polymorphism and smoking or drinking.

CONCLUSION

Our results demonstrated that the +781C/T polymorphism of IL-8 did not play a role and had no interaction with smoking or drinking in the occurrence of cerebral infarction in the Han Chinese population. However, the C allele and the CT genotype might be associated with AS of the ICA in patients with ischemic stroke.

An updated meta-analysis of endothelial nitric oxide synthase gene: three well-characterized polymorphisms with ischemic stroke

Polymorphisms in the endothelial nitric oxide synthase (eNOS) gene may influence the risk of ischemic stroke (IS), but the results are still debatable. A meta-analysis was performed to investigate the association between the eNOS gene polymorphisms in IS risk. Case-control studies on the association between the G894T, T-786C, and 4b/a polymorphisms and IS were searched up to July 2012, and the genotype frequencies in the control group were found to be consistent with the Hardy-Weinberg equilibrium (HWE). The effect summary odds ratio (OR) and 95% confidence intervals (CIs) were obtained. Meta-regression was used to explore the potential sources of heterogeneity. Funnel plots and Egger's test was used to estimate small study biases, and heterogeneity was assessed by chi-square-based Q-test and I(2) test. There were total 6537/6475 cases/controls for G894T, 3459/3951 cases/controls for 4b/a, and 2125/2673 cases/controls for T-786C polymorphism. For G894T and 4b/a, a significant association of 894T allele and 4a allele with increased risk of IS was found in Asians (TT+GT vs. GG: p<0.00001, OR=1.60, 95% CI=1.38-1.79, Pheterogeneity=0.11; aa+ba vs. bb: P<0.00001, OR=1.60, 95% CI=1.30-1.97, Pheterogeneity=0.02), but not in Caucasians (TT+GT vs. GG: P=0.60, OR=0.94, 95% CI=0.75-1.19, Pheterogeneity=0.002; aa+ba vs. bb: P=0.13, OR=0.81, 95% CI=0.62-1.06, Pheterogeneity=0.63). For T-786C polymorphism, there were no significant differences in genotype distribution between IS and control in Asians (CC+TC vs. TT: P=0.15, OR=1.14, 95% CI=0.95-1.37, Pheterogeneity=0.94) and in Caucasians (CC+TC vs. TT: P=0.72, OR=0.96, 95% CI=0.75-1.22, Pheterogeneity=0.53). This analysis provides strong evidence that the eNOS T-786C gene polymorphism is not associated with IS, the G894T and 4b/a polymorphisms might be associated with IS, at least in Asians.

The biology behind the atherothrombotic effects of cigarette smoke

Cigarette smoke is an aerosol that contains >4,000 chemicals, including nicotine, carbon monoxide, acrolein, and oxidant compounds. Exposure to cigarette smoke induces multiple pathological effects in the endothelium, several of which are the result of oxidative stress initiated by reactive oxygen species, reactive nitrogen species, and other oxidant constituents of cigarette smoke. Cigarette-smoke exposure interferes adversely with the control of all stages of plaque formation and development and pathological thrombus formation. The reactive oxygen species in cigarette smoke contribute to oxidative stress, upregulation of inflammatory cytokines, and endothelial dysfunction, by reducing the bioavailability of nitric oxide. Plaque formation and the development of vulnerable plaques also result from exposure to cigarette smoke via the enhancement of inflammatory processes and the activation of matrix metalloproteases. Moreover, exposure to cigarette smoke results in platelet activation, stimulation of the coagulation cascade, and impairment of anticoagulative fibrinolysis. Many cigarette-smoke-mediated prothrombotic changes are quickly reversible upon smoking cessation. Public health efforts should urgently promote our understanding of current cigarette-smoke-induced cardiovascular pathology to encourage individuals to reduce their exposure to cigarette smoke and, therefore, the detrimental consequences of associated atherothrombotic disease.

The interaction of AGT and NOS3 gene polymorphisms with conventional risk factors increases predisposition to hypertension

Renin-angiotensin and kallikrein-kinin systems are interconnected, regulating blood pressure homeostasis. We have demonstrated the interactions among polymorphisms of the angiotensinogen (AGT) and endothelial nitric oxide synthase (NOS3) genes and conventional risk factors affecting the hypertension occurrence. Individuals were recruited (n=192) and classified into hypertensive (HG; n=140) and normotensive (NG; n=52) groups. The genotypic distribution of the Met235Thr (AGT) and Glu298Asp (NOS3) polymorphisms demonstrated that both are independent risk factors of hypertension (p=0.02 and p=0.008, respectively). The concomitant presence of these polymorphisms in the HG group was significantly different (p=0.001) from the NG. Both gene polymorphisms presented an additive effect for the unfavourable alleles T and A, respectively, and 95% of the double mutant homozygotes were classified into the HG. Specific interactions among certain conventional factors and the presence of at least one unfavourable allele presented significant odds towards hypertension. Blood pressure homeostasis was affected by genetic polymorphisms conditioned by the T and A alleles of the AGT and NOS3 genes, respectively, which acted independently. However, their interaction with smoking, sedentariness, age and total cholesterol may have increased the predisposition to hypertension, which may explain most of the hypertension cases.

Polymorphisms of DNA repair pathway genes and cigarette smoking in relation to susceptibility to large artery atherosclerotic stroke among ethnic Chinese in Taiwan

AIM

Cigarette-smoking induced oxidative DNA damage to endothelial cells has been reported to play an etiological role in atherosclerosis development. Individual vulnerability to oxidative stress through smoking exposure and the ability to repair DNA damage, which plays a critical role in modifying the risk susceptibility of large artery atherosclerotic (LAA) stroke, is hypothesized. Thus, we examined the effect of genetic polymorphisms of DNA repair pathway genes and cigarette smoking in relation to risk susceptibility of LAA stroke.

METHODS

We enrolled 116 LAA stroke patients and 315 healthy controls from the Armed Forces Taoyuan General Hospital, Taoyuan, Taiwan. Genotyping of polymorphisms of the OGG1 (Ser326Cys), XRCC1 (Arg399Gln), ERCC2 (Lys751Gln), and ERCC5 (Asp1104His) genes was performed and used to evaluate LAA stroke susceptibility.

RESULTS

Of those non-synonymous polymorphisms, the ERCC2 Lys751Gln variant was found to be associated with LAA stroke risk (OR: 1.69, 95%CI: 1.02-2.86), and this association was more pronounced in smokers, manifesting a 2.73-fold increased risk of LAA stroke (p=0.027). A joint effect on risk elevation of LAA stroke was seen in those patients with OGG1 and ERCC2 polymorphisms (OR: 2.75, 95%CI: 1.26-6.00). Moreover, among smokers carrying the OGG1 Ser326Cys polymorphism, there was a tendency toward an increased risk of LAA stroke in those patients who had a greater number of high-risk genotypes of XRCC1, ERCC2, and ERCC5 polymorphisms (p(trend)=0.010).

CONCLUSION

The susceptible polymorphisms of DNA repair pathway genes may have a modifying effect on the elevated risk of LAA stroke in smokers among ethnic Chinese in Taiwan.

Correlation between common genetic variants and risk factors associated with prediction of cardiovascular diseases in dyslipidemic patients

AIMS

The aim of the study was to investigate genetic variants predicting cardiovascular events in patients with dyslipidemia and compare its relationship with common risk factors including hyperlipidemia, metabolic syndrome, history of acute myocardial infarction, thrombosis, obesity, and smoking.

MATERIALS AND METHODS

Five hundred two individuals divided into six groups corresponding with the risk factors and a control group of normolypidemic patients were analyzed for the presence of eight mutations and polymorphisms (endothelial nitric oxide synthase -786T → C and G894T; lymphotoxin A C804A; angiotensin-converting enzyme [ACE] ins/del; human platelet antigen 1 a/b; beta-fibrinogen -455G → A; apolipoprotein B [ApoB] R3500Q; APOE E2/E3/E4) using the ViennaLab CVD Strip assay.

RESULTS

ACE deletions are the most frequent genetic variants in risk groups of dyslipidemic patients (from 58% in cardiovascular events to 51% in smokers). We found a strong relationship between genetic variants and risk factors. G894T is significantly associated with smoking (value of odds ratio [OR] = 1.62, p = 0.04), and ACE deletions are negatively associated with cardiovascular events (OR = 0.62, p = 0.03).

CONCLUSION

Significant associations between genetic variants predicting cardiovascular events and common risk factors in dyslipidemic patients were found.

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.

The Role of -786T/C Polymorphism in the Endothelial Nitric Oxide Synthase Gene in Males with Clinical and Biochemical Features of the Metabolic Syndrome

Background. Extensive evidence, arising from models of endothelial nitric oxide synthase gene (NOS3)-knockout mice supports the role of endothelial malfunction in the pathogenesis of the metabolic syndrome (MS). Aims. The aim of this study was to evaluate the role of -786T/C polymorphism in the etiology of MS and assess previously reported interaction with cigarette smoking. Methods. Based on International Diabetes Federation 2005 criteria, we recruited randomly 152 subjects with MS and 75 subjects without MS. Results. Allelic and genotype frequencies did not differ significantly between both groups. Total cholesterol level (CHOLT) and intima-media thickness of carotid arteries were significantly higher in -786CC homozygotes, in comparison with -786TC and -786TT patients. Regarding current smoking status, -786C allele was associated with higher CHOLT than -786T allele. Conclusion. Our study indicates the putative role of -786T/C polymorphism in the development of hypercholesterolemia, in patients with MS, which might be enhanced by cigarette smoking.

Environmental exposures, nitric oxide synthase genes, and exhaled nitric oxide in asthmatic children

Exhaled nitric oxide (FeNO), a measure of airway inflammation, is being explored as a tool to guide asthma management in children. Investigators have identified associations of genetic polymorphisms in nitric oxide synthase genes (NOS1 and NOS3) with FeNO levels; however, none have explored whether these polymorphisms modify the relationship of environmental exposures with FeNO. The objective of this project was to evaluate the association of NOS polymorphisms and environmental exposures with FeNO levels among children with asthma. We conducted a 12-month prospective cohort study of 225 tobacco-smoke exposed children (6-12 years) with doctor-diagnosed asthma. We assessed environmental exposures (tobacco, indoor allergens, & airborne particulates), polymorphisms in NOS1 (an intronic AAT tandem repeat) and NOS3 (G894T), and FeNO levels. There was no association of NOS1 or NOS3 polymorphisms with FeNO levels. There were no significant interactions of environmental exposures and the NOS1 polymorphism with FeNO levels. In contrast, there was an interaction of the NOS3 polymorphism and airborne nicotine concentration with FeNO levels (P = 0.01). Among GG genotype individuals, nicotine exposure did not affect FeNO levels; however, among individuals with at least one T allele, higher nicotine exposure was associated with lower FeNO levels (approximately 5 ppb decrease from the lowest to the highest quartile). We conclude that genetic differences may explain some of the conflicting results in studies of the effects of tobacco smoke exposure on FeNO levels and may make FeNO interpretation difficult for a subset of children with asthma.

Genetic and pharmacogenetic associations between NOS3 polymorphisms, blood pressure, and cardiovascular events in hypertension

BACKGROUND

Polymorphisms in the endothelial nitric oxide synthase (NOS3) gene increase susceptibility to hypertension and cardiovascular disease. We examined genetic and pharmacogenetic associations between NOS3 polymorphisms, blood pressure (BP) control, and cardiovascular events in elderly, hypertensive coronary artery disease (CAD) patients.

METHODS

Patients with CAD were randomly assigned to either verapamil SR- or atenolol-based antihypertensive treatment and followed for cardiovascular events. Cases (all-cause death, nonfatal myocardial infarction (MI), or nonfatal stroke) and an age-, sex-, race/ethnicity-matched control population were genotyped for the -786T>C and Glu298>Asp polymorphisms in NOS3. On-treatment BP and BP control were compared across genotype groups. Logistic regression was performed to estimate odds ratios (ORs) for the -786T>C and Glu298>Asp polymorphisms in the combined population and in randomized treatment groups.

RESULTS

Genotype data were available for 256 cases and 769 controls. Among controls, mean on-treatment BP differed according to -786T>C genotype (T/T 137/78 mm Hg, T/C 133/76 mm Hg, C/C 133/75 mm Hg; P = 0.0007 for systolic, P = 0.09 for diastolic) which corresponded to differing rates of BP control (T/T 63%, T/C 72%, C/C 88%; P = 0.002). Neither polymorphisms was associated with case status, with or without regard to assigned treatment.

CONCLUSIONS

The -786T>C, but not the Glu298>Asp variant of NOS3, may correlate with BP but do not appear to be associated with incident cardiovascular events in patients with established cardiovascular disease. The antihypertensive treatment approach did not appear to alter the genetic contribution to either BP control or cardiovascular events.

Is Polymorphism within eNOS Gene Associated With the Late Onset of Myocardial Infarction? A Pilot Study

Introduction

Nitric oxide (NO) produced by endothelial nitric oxide synthase (eNOS) is a potent vasodilator. Several polymorphisms in the eNOS gene have been described, some of them being linked with the increased risk of cardiovascular disease, coronary heart disease (CHD), and coronary spasm.

Methods and Results

We studied 3 polymorphisms within the gene of eNOS (-786T/C, G10T, and 894 G/T) in patients with their first myocardial infarction (MI) younger than 45 years and in healthy volunteers. We found the relation between the occurrence of eNOS 894G allele and the Gensini score, which describes the severity of CHD ( P = .020).

Conclusions

The fact that first clinical manifestation of MI occurred in G carriers when the atherosclerotic plaque was much more advanced than in T carriers may suggest that wild-type genotype provided a better compensatory mechanisms due to NO synthesis and/or release. The polymorphisms within eNOS gene G10T, 894G/T, and −786T/C were not associated with the increased risk of MI.

Why study gene-environment interactions?

PURPOSE OF REVIEW

We examine the reasons for investigating gene-environment interactions and address recent reports evaluating interactions between genes and environmental modulators in relation to cardiovascular disease and its common risk factors.

RECENT FINDINGS

Studies focusing on smoking, physical activity, and alcohol and coffee consumption are observational and include relatively large sample sizes. They tend to examine single genes, however, and fail to address interactions with other genes and other correlated environmental factors. Studies examining gene-diet interactions include both observational and interventional designs. These studies are smaller, especially those including dietary interventions. Among the reported gene-diet interactions, it is important to highlight the strengthened position of APOA5 as a major gene that is involved in triglyceride metabolism and modulated by dietary factors, and the identification of APOA2 as a modulator of food intake and obesity risk.

SUMMARY

The study of gene-environment interactions is an active and much needed area of research. Although technical barriers of genetic studies are rapidly being overcome, inclusion of comprehensive and reliable environmental information represents a significant shortcoming of genetics studies. Progress in this area requires inclusion of larger populations but also more comprehensive, standardized, and precise approaches to capturing environmental information.

CYP2J2 and CYP2C8 polymorphisms and coronary heart disease risk: the Atherosclerosis Risk in Communities (ARIC) study

OBJECTIVE

The cytochromes P450 epoxygenases CYP2J2 and CYP2C8 synthesize epoxyeicosatrienoic acids, which regulate endothelial function. We sought to determine if genetic variation in CYP2J2 and CYP2C8 was associated with coronary heart disease risk.

METHODS

We genotyped 2065 Atherosclerosis Risk in Communities study participants (1085 incident coronary heart disease cases, 980 noncases) for polymorphisms in CYP2J2 and CYP2C8. Using a case-cohort design, associations between genotype and incident coronary heart disease risk were evaluated using proportional hazards regression. The influence of cigarette smoking on these associations was also evaluated. False discovery rate q-values were estimated to minimize the impact of the multiple statistical comparisons completed. All analyses were race stratified.

RESULTS

The CYP2J2 G-50T polymorphism variant -50T allele was associated with significantly lower risk of incident coronary heart disease in African-Americans (adjusted hazard rate ratio 0.58, 95% confidence interval 0.35-0.96, P=0.036, q=0.051); however, no significant association was observed in Caucasians. Overall, the I264M, I269F, and K399R polymorphisms in CYP2C8 were not significantly associated with risk of incident coronary heart disease. In Caucasians, the relationship between the I264M and K399R polymorphisms and incident coronary heart disease risk was significantly modified by cigarette smoking status (P for interaction=0.008, q=0.064), with the highest risk observed in smokers carrying at least one variant allele.

CONCLUSIONS

The G-50T polymorphism in CYP2J2 may be an important risk factor for the development of coronary heart disease events in African-Americans, whereas cigarette smoking may modify the relationship between the I264M and K399R polymorphisms in CYP2C8 and coronary heart disease risk in Caucasians. Confirmation of these findings in an independent population is warranted.

Cyclooxygenase polymorphisms and risk of cardiovascular events: the Atherosclerosis Risk in Communities (ARIC) study

Cyclooxygenase-derived prostaglandins modulate cardiovascular disease risk. We genotyped 2212 Atherosclerosis Risk in Communities study participants (1,023 incident coronary heart disease (CHD) cases; 270 incident ischemic stroke cases; 919 non-cases) with available DNA for polymorphisms in PTGS1 and PTGS2. Using a case-cohort design, associations between genotype and CHD or stroke risk were evaluated using proportional hazards regression. In Caucasians, the reduced function PTGS1 -1006A variant allele was significantly more common among stroke cases compared to non-cases (18.2 versus 10.6%, P=0.027). In African Americans, the reduced function PTGS2 -765C variant allele was significantly more common in stroke cases (61.4 versus 49.4%, P=0.032). No significant relationships with CHD risk were observed. However, aspirin utilization appeared to modify the relationship between the PTGS2 G-765C polymorphism and CHD risk (interaction P=0.072). These findings suggest that genetic variation in PTGS1 and PTGS2 may be important risk factors for the development of cardiovascular disease events. Confirmation in independent populations is necessary.