Redox-activation of vascular stores of NO by vitamin C

维生素 C 对血管 NO 储存的氧化还原激活

• 批准号: 6844729
• 负责人: MARTIN FEELISCH
• 金额: $ 32.3万
• 依托单位: BOSTON UNIVERSITY MEDICAL CAMPUS
• 依托单位国家: 美国
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-01-01 至 2006-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6844729
• 关键词: antioxidants; ascorbate; atherosclerosis; bioaccumulation; bioassay; diabetes mellitus; dietary supplements; disease /disorder model; enzyme activity; glutathione; homeostasis; hypertension; laboratory rat; metabolism; microelectrodes; nitric oxide; nitric oxide synthase; nutrition related tag; oxidation reduction reaction; oxidative stress; vascular endothelium; vascular resistance; vitamin C deficiency

DESCRIPTION (provided by applicant): Early in atherosclerosis endothelium-dependent relaxation is impaired. The underlying endothelial dysfunction is thought to involve inadequate bioavailability of nitric oxide (NO). Mechanisms that underlie this effect remain uncertain but may include reaction of NO with free radicals and depletion of substrate. Since NO plays a crucial role in atherogenesis, it is important to determine if NO bioavailability can be enhanced. Recent clinical studies suggest that vitamin C (ascorbate) can reverse endothelial dysfunction by enhancing endogenous NO-mediated vasorelaxation. However, the molecular mechanisms underlying this effect are not clearly understood. The current concepts are that ascorbate acts as an antioxidant by either sparing intracellular thiols or by scavenging superoxide radicals produced during an enhanced oxidative stress. Preliminary data presented in this application suggest an alternative hypothesis that encompasses both aforementioned concepts. We propose a unique role for ascorbate in the vasculature based on the finding that, in addition to eliciting vasorelaxation, part of the NO produced from endothelial NO-synthase (eNOS) is stored in the tissue in the form of stable NO adducts. While the existence of such tissue stores of NO has been recognized earlier, its potential physiological and clinical implications have not yet been examined. We have observed that ascorbate relaxes vascular aortic rings in vitro by redox-activating tissue stores to release NO. Our preliminary data suggest that NO is bound in endothelial and smooth muscle cells in the form of S-nitrosothiols, which are cleaved by an increase in intracellular reduced glutathione. The intriguing and novel hypothesis built on these observations is that vitamin C reverses endothelial dysfunction by allowing the release of NO from a preformed vascular pooi. Using a combined biochemical/functional approach, the following three specific aims are proposed to address the above hypothesis: 1. To investigate the mechanism of ascorbate induced vasorelaxation and its relationship to the cellular redox status; 2. To identify the chemical nature and localization of NO stores in the vasculature and determine the factors that govern their stability and bioactivation to yield NO; and 3. To investigate the role of ascorbate in the maintenance of vascular homeostasis using different animal models of endothelial dysfunction. Results from these investigations are expected to significantly enhance our understanding of the role of NOS dependent and -independent NO production in endothelial dysfunction. Moreover, they should provide new insight into the actions of ascorbate beyond those of mere antioxidant nature and a rationale for vitamin C supplementation in disease states associated with an enhanced oxidative stress such as hypertension, hypercholesterolemia, and diabetes.

描述（由申请人提供）：动脉粥样硬化早期 内皮依赖性舒张受损。下面的内皮细胞 功能障碍被认为与一氧化氮的生物利用度不足有关 （否）。造成这种影响的机制仍然不确定，但可能包括 NO与自由基的反应和底物的消耗。由于NO播放A 在动脉粥样硬化形成中起着至关重要的作用，重要的是要确定NO是否 可以提高生物利用度。最近的临床研究表明，维生素C （抗坏血酸）可以通过增强内源性 NO介导的血管舒张。然而，这背后的分子机制 效果并不清楚。目前的概念是，抗坏血酸的行为， 作为一种抗氧化剂，通过保留细胞内的硫醇或通过清除 在增强的氧化应激过程中产生的超氧自由基。初步 本申请中提供的数据提出了另一种假设， 包括上述两个概念。我们提出了一个独特的作用， 抗坏血酸在血管系统的基础上，发现，除了 引起血管舒张，部分NO由内皮NO合酶产生 eNOS（eNOS）以稳定的NO加合物的形式储存在组织中。而 早期已经认识到存在这种NO的组织储存， 潜在的生理和临床意义尚未被研究。 我们已经观察到抗坏血酸在体外舒张血管主动脉环， 氧化还原激活组织储存释放NO。我们的初步数据表明， NO在内皮细胞和平滑肌细胞中以 S-亚硝基硫醇，其通过增加细胞内还原的 谷胱甘肽基于这些观察结果的有趣而新颖的假设是， 维生素C通过释放NO来逆转内皮功能障碍 从一个预先形成的血管池里。使用组合的生化/功能 为解决上述问题，提出了以下三个具体目标 假设：1.探讨抗坏血酸诱导血管舒张的机制 及其与细胞氧化还原状态的关系; 2.来鉴定这种化学物质 性质和定位的NO商店在脉管系统中，并确定 控制其稳定性和产生NO的生物活化的因素;和3.到 研究抗坏血酸在维持血管内稳态中的作用 使用不同的内皮功能障碍动物模型。从这些 调查预计将大大提高我们对 一氧化氮合酶依赖性和非依赖性一氧化氮生成在内皮细胞增殖中的作用 功能障碍此外，它们还应提供新的见解， 抗坏血酸超出那些仅仅抗氧化性质和维生素C的基本原理 在与增强的氧化应激相关的疾病状态中的补充 如高血压、高胆固醇血症和糖尿病。