Genetic evaluation of nitric oxide regulating genes in ischemic stroke

说明(申请人提供)：一氧化氮(NO)是一种重要的、特征明确的血管扩张剂，在维持全身和大脑循环中的血管张力方面是必不可少的。NO的可获得性在很大程度上依赖于催化L精氨酸生成瓜氨酸的三种一氧化氮合酶，进而产生NO。我们最近发现，内皮型一氧化氮合酶(NOS3)基因启动子中的两个特定变异(-922G/A和-786T/C)与年轻的非裔美国女性中风的易感性有关(Howard等，Stroke，2005)。具有这两种单核苷酸多态(SNP)中任何一种的风险基因的非裔美国女性患中风的风险大约是非风险基因女性的三倍(p=0.005)。在同样参与年轻女性中风预防(SPYW)研究的高加索女性中，没有观察到这种关联。我们最近在一组同样确定和评估的妇女中进行了重复研究。在两个启动子SNPs中，在非裔美国女性中观察到了我们最初发现的重复证据(p=0.066-0.083)。在这项跟踪研究中，高加索女性中也观察到了边缘关联(p=0.058-0.071)，尽管这种关联是相反的。虽然一氧化氮合酶直接负责一氧化氮的产生，但它们的活性受到底物L精氨酸和其他调节因子的调节，如热休克蛋白90、钙调蛋白和小窝蛋白。细胞对L精氨酸的利用主要是通过膳食摄入获得的，它还取决于精氨酸转运体(CAT1)和精氨酸酶的活性，精氨酸酶在尿素循环中将L精氨酸分解为瓜氨酸，同时产生尿素。因此，在任何给定的时间产生的NO的数量是蛋白质和酶在这一调节良好的途径中的丰度和活性的直接结果。我们之前在SPYW研究和其他研究NOS3变异的研究中的结果强烈地表明，这一途径与大脑和心血管疾病的发展有关。鉴于NO在血管舒缩张力调节中的重要性，以及先前观察到的NOS3 SNPs与年轻非裔美国女性中风的关联，我们假设NOS3和其他影响内皮NO生成和调节的基因的多态有助于内皮功能的可变性。这种变异可能会导致遗传易感个体患血管疾病(如缺血性中风)的风险增加。这项建议的目的是评估NO途径中的基因变异及其与缺血性中风和亚临床血管内皮细胞功能障碍的关系。确定卒中易感性的遗传成分是阐明该疾病发病机制的重要一步。虽然环境风险因素发挥着重要作用，但遗传易感性和基因-环境相互作用是重要的贡献，可能会增加我们对中风的理解，以及我们改变中风风险和预后的能力。总体而言，NO的生物学重要性及其与NOS3的相关性研究强烈表明，NO的产生和调控是血管疾病的重要决定因素。加强对NO途径基因调控的了解可能具有重要的诊断和治疗价值，有助于识别可能受益于特定预防干预措施的高危人群或开发新的治疗药物。

DESCRIPTION (provided by applicant): Nitric oxide (NO) is an important and well-characterized vasodilator essential in maintaining vascular tone in the systemic and cerebral circulation. The availability of NO is largely dependent upon three nitric oxide synthase (NOS) enzymes that catalyze L-arginine to citrulline, with the subsequent production of NO. We have recently shown that two specific variants in the promoter of the endothelial nitric oxide synthase (NOS3) gene (-922 G/A and -786 T/C) are associated with susceptibility to stroke in young, African-American women (Howard et al., Stroke, 2005). African-American women with the risk genotype for either of these two single nucleotide polymorphisms (SNPs) had approximately three times the risk of stroke compared to women with the non-risk genotypes (p = 0.005). This association was not observed in a similar group of Caucasian women, also taking part in the Stroke Prevention in Young Women (SPYW) study. We have recently performed a replication study in a group of women similarly ascertained and evaluated. With both promoter SNPs, evidence for replication of our original finding was observed in African-American women (p = 0.066 - 0.083). Borderline association was also observed in Caucasian women in this follow-up study (p = 0.058 - 0.071), although the association was in the opposite direction. While the NOS enzymes are directly responsible for the generation of NO, their activity is modulated by the availability of the substrate, L-arginine, and other regulators such as heat shock protein 90, calmodulin, and caveolin. The availability of L-arginine to cells, which is primarily obtained through dietary intake, is also determined by the arginine transporter (CAT1) and the activity of arginase, which catabolizes L-arginine to citrulline, with the production of urea, in the urea cycle. Therefore, the amount of NO produced at any given time is a direct result of the abundance and activity of the proteins and enzymes in this well-regulated pathway. Our previous results in the SPYW study and those of others investigating variability of NOS3 strongly implicate this pathway in the development of cerebro- and cardiovascular disease. Given the importance of NO in the regulation of vasomotor tone and the previously observed association of NOS3 SNPs with stroke in young African-American women, we hypothesize that polymorphisms in NOS3 and other genes affecting the generation and regulation of endothelial NO contribute to variability in endothelial function. This variability may lead to an increased risk of vascular diseases, such as ischemic stroke, in genetically susceptible individuals. The goal of this proposal is to evaluate variation in genes in the NO pathway and their relationship to ischemic stroke and subclinical endothelial dysfunction. Determining the genetic components of stroke susceptibility is an important step in delineating the pathogenesis of this disease. While environmental risk factors play an important role, genetic predisposition and gene-environment interactions represent important contributions that may increase our understanding of stroke and our ability to modify stroke risk and outcome. Collectively, the biological importance of NO and association studies with NOS3 strongly implicate NO generation and regulation as an important determinant of vascular disease. Enhanced understanding of the genetic regulation of the NO pathway may have important diagnostic and therapeutic value, leading to the identification of high-risk groups that might benefit from specific preventive interventions or to the development of new therapeutic drugs.