Functional single nucleotide polymorphism-1026C/A of inducible nitric oxide synthase gene with increased YY1-binding affinity is associated with hypertension in a Chinese Han population

Abstract

In our previous linkage analysis of Chinese hypertensive families, a hypertension susceptibility region on chromosome 17 was located at D17S1878, which encompasses the inducible nitric oxide synthase (iNOS) gene. The aim of this study was to investigate the association between variant in the human iNOS gene and susceptibility to hypertension in Chinese Han. We detected the -1026C/A polymorphism of the iNOS promoter in 463 hypertensive patients and 432 normotensive individuals for purposes of an association analysis and in 76 hypertensive families with 318 members for purposes of transmission disequillibrium test analysis via real-time PCR with a Taqman-minor groove binder probe. There were significant differences in the genotype and allele frequencies of the iNOS-1026C/A (P<0.05); the genotype CC was associated with hypertension after adjusting for environmental risk factors via a nonconditional logistic regression analysis [adjusted odds ratio, 2.90; 95% confidence interval, 2.14-3.93]. A transmission disequillibrium test-sib transmission disequillibrium test analysis demonstrated that the allele C was preferentially transmitted within a pedigree (combined Z score 2.257, P<0.05). The iNOS-1026C/A was identified by a construct reporter assay as a functional variant, and the transcriptional activity of the promoter with allele C was 4.73-fold lower than that with allele A. Furthermore, electrophoresis mobility shift assay showed that the -1026C/A changed the Y in Yang 1 (YY1)-binding pattern in vitro, whereas chromatin immunoprecipitation showed that transcription factor YY1 was bound to the -1026C element in vivo. Lipopolysaccharide, an inflammatory stimulating factor, could induce YY1 to augment DNA-binding affinity; it could also be involved in the inhibited transcriptional activity of the iNOS promoter with allele C. We thus conclude that iNOS-1026C/A with a change in YY1-binding affinity is associated with hypertension under the affect of inflammatory-stimulating factors.