Genetic evaluation of nitric oxide regulating genes in ischemic stroke

描述（由申请人提供）：一氧化氮（NO）是一种重要的、特征明确的血管扩张剂，对维持体循环和脑循环中的血管张力至关重要。NO的可用性在很大程度上取决于三种一氧化氮合酶（NOS）酶，其催化L-精氨酸为瓜氨酸，随后产生NO。我们最近已经表明，内皮一氧化氮合酶（NOS 3）基因启动子中的两种特异性变体（-922 G/A和-786 T/C）与年轻的非洲裔美国妇女中风的易感性相关（霍华德et al.，Stroke，2005）。具有这两种单核苷酸多态性（SNP）中任一种风险基因型的非裔美国女性与具有非风险基因型的女性相比，中风风险约为3倍（p = 0.005）。在同样参与了年轻女性卒中预防（SPYW）研究的一组相似的白人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一项重复研究。在两种启动子SNP中，在非裔美国妇女中观察到我们最初发现的复制证据（p = 0.066 - 0.083）。在这项随访研究中，在高加索女性中也观察到了边缘相关性（p = 0.058 - 0.071），尽管这种相关性是相反的。虽然NOS酶直接负责NO的产生，但它们的活性受底物L-精氨酸和其他调节剂如热休克蛋白90、钙调蛋白和小窝蛋白的可用性调节。细胞对L-精氨酸的利用率（主要通过饮食摄入获得）也取决于精氨酸转运蛋白（CAT 1）和尿素酶的活性，后者在尿素循环中将L-精氨酸分解代谢为瓜氨酸，并产生尿素。因此，在任何给定时间产生的NO的量是在该良好调节的途径中蛋白质和酶的丰度和活性的直接结果。我们之前在SPYW研究中的结果以及其他研究NOS 3变异性的研究结果强烈暗示了这一途径在脑和心血管疾病的发展中的作用。考虑到NO在调节血管紧张素中的重要性以及先前观察到的NOS 3 SNP与年轻非裔美国女性中风的相关性，我们假设NOS 3和其他影响内皮NO生成和调节的基因的多态性有助于内皮功能的变异性。这种变异性可能导致遗传易感个体患血管疾病（如缺血性中风）的风险增加。本研究的目的是评估NO通路中基因的变异及其与缺血性卒中和亚临床内皮功能障碍的关系。确定中风易感性的遗传成分是描述这种疾病的发病机制的重要一步。虽然环境风险因素起着重要作用，但遗传易感性和基因-环境相互作用代表了重要的贡献，可能会增加我们对中风的理解以及我们改变中风风险和结果的能力。总的来说，NO的生物学重要性和与NOS 3的相关研究强烈暗示NO的产生和调节是血管疾病的重要决定因素。增强对NO通路的遗传调控的理解可能具有重要的诊断和治疗价值，从而确定可能受益于特定预防干预或开发新治疗药物的高危人群。

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.