Endothelial Nitric Oxide Gene Haplotypes and Risk of Cerebral Small-Vessel Disease

Abstract

Background and Purpose-Genetic influences are important in multifactorial cerebral small-vessel disease (SVD) and may act via endothelial dysfunction. Nitric oxide (NO) synthesized by endothelial nitric oxide synthase (eNOS) is a key mediator of endothelial function. We determined the role of 3 potentially functional eNOS polymorphisms (T-786C, intron 4ab, G894T) located toward the 5Ј flanking end of the gene as risk factors for SVD and different SVD subtypes: isolated lacunar infarction (nϭ137) and ischemic leukoaraiosis (nϭ160). Methods-Three hundred patients with SVD and 600 community controls were studied. Genotypes were determined through polymerase chain reaction with or without restriction fragment digestion. Nitrate (NO x ) levels were determined in a subgroup by use of a Griess method. Polymorphisms were tested individually and in combination with haplotype analysis. Results-The intron 4a variant was protective against SVD. This effect was confined to isolated lacunar infarction (odds ratio, 0.55; 95% confidence interval, 0.35 to 0.86; Pϭ0.01). Haplotypes encountered were significantly different in this subtype compared with controls (Pϭ0.001), with the -786C promoter/intron 4a combination particularly underrepresented. NO x levels were associated with the T-786C locus (Pϭ0.03) but only in the presence of the intron 4a allele (Pϭ0.07 for interaction). Conclusions-The intron 4ab insertion/deletion genotype was associated with isolated lacunar infarction. Haplotype and functional studies suggested that the protective effect of the 4a variant could be mediated through changes in eNOS promoter activity and increased NO levels. The specific association with isolated symptomatic lacunar infarction and not ischemic leukoaraiosis may reflect different etiopathogeneses of the 2 subtypes. Lack of NO could predispose to localized microatheroma in proximal arterioles rather than diffuse arteriosclerosis affecting distal perforating vessels.

Association analysis of endothelial nitric oxide synthase gene polymorphism with primary hypertension in a Singapore population

“…24 Intron 4A variant was also shown to be protective against cerebral small-vessel diseases with a confined effect to isolated lacunar infarction and suggested that the protective effect of the intron 4A could be mediated through changes in the eNOS promoter activity and increased NO levels. 15 Our results also showed the significant association of intron 4BB genotype with primary Table 4 Comparison of endothelial nitric oxide gene polymorphisms with diabetes and dyslipidemia hypertension and the protective effect of intron 4A allele against the disease. A significant excess of homozygotes for the rare intron 4A allele in patients with severely stenosed arteries in Australian subjects was reported, but the study did not provide an association with hypertension.…”

“…28 Several other reports have suggested a combined protective effect of intron 4 and G894T or TÀ786C variants. 15,24,29 In our study, we observed a significant association of intron 4BB genotype with systolic blood pressure among subjects with BMI greater than 25 kg/m 2 . BMI is known to have an effect on blood pressure and atherosclerosis and insulin sensitivity.…”

“…The intron 4 locus could act as a marker for another functional polymorphism in linkage disequilibrium. 15 Another possibility is that intron 4A allele has intrinsic functional significance, which can be justified with plasma NO metabolites concentration. Although we did not detect a positive linear relationship of the 4A allele with plasma NO metabolites in our study, we found significantly higher levels of plasma NO metabolites in control normotensive subjects who had significantly increased 4A allele.…”

“…11 Another variant of eNOS promoter region (TÀ786C) with cytosine replacing thymidine at nucleotide À786 is reported to have increased risk of hypertension 12 and coronary spasm. 13 Variable number of tandem repeats (VNTR) of intron 4 has been shown to have a significant association with primary hypertension, 14 isolated lacunar infarction 15 and a smoking-dependent risk of coronary artery disease. 16 Two alleles of intron 4 VNTR have been reported: bigger allele 4B has five tandem 27 bp repeats and smaller allele 4A has four repeats.…”

Polymorphisms of genes in nitric oxide-forming pathway associated with ischemic stroke in Chinese Han population

“…The present results indicate that polymorphisms in GCH1 (rs841) are independently associated with an increased risk for IS. In contrast, we failed to detect significant independent association with the rest of SNPs even though they have been suggested to be associated with cardiovascular diseases such as hypertension, coronary heart disease or stroke [21][22][23] .…”