Nitrite Mediated Cardioprotection

描述（由申请人提供）：一氧化氮（NO）在缺血再灌注（I/R）损伤的情况下被广泛研究。既往研究清楚地表明，eNOS缺乏会加重心肌I/R损伤，而eNOS过表达、NO供体或吸入NO气体治疗均能显著保护心肌。一氧化氮具有许多生理特性，使其成为一种有效的心脏保护信号分子。这些包括血管舒张和氧化应激抑制，血小板聚集，白细胞趋化和凋亡。NO的合成受到多种辅助因子的严重影响，如四氢生物蝶呤、黄素单核苷酸和黄素腺嘌呤二核苷酸、还原性硫醇、内源性NOS抑制剂不对称二甲基精氨酸（ADMA）的存在，以及底物和氧的可用性。如果没有足够的底物和辅助因子（缺血时心脏中肯定存在的条件）的递送，NOS不再能够产生no。因此，需要在缺血组织中产生NO的替代方法来限制I/R损伤。我们实验室先前的研究表明，急性亚硝酸盐治疗可防止心肌I/R损伤。此外，我们的初步数据表明，饮食中亚硝酸盐摄入量的适度变化显著改变了亚硝酸盐、亚硝基修饰蛋白和亚硝基血红素产物的稳态浓度，这些生化变化对急性心肌梗死的严重程度有深远的影响。此外，我们的初步数据表明，观察到的心脏保护作用部分是通过在口服补充和缺血期间将亚硝酸盐还原为NO介导的。本提案的目的是测试整体假设，即亚硝酸盐作为一氧化氮的内源性储存形式，通过其转化为一氧化氮的能力来提供心脏保护。为了验证这一假设，我们提出了以下四个具体目标。特异性目的1将通过评估亚硝酸盐补充的不同剂量和持续时间，研究在心肌I/R情况下实现心脏保护所需的最佳治疗策略。特异性目标2将通过研究肌红蛋白将亚硝酸盐还原为NO开始我们的亚硝酸盐补充疗法的机制研究。特异性目的3将探讨亚硝酸盐补充治疗的一些分子机制，包括亚硝酸盐对心肌I/R后凋亡通路的影响。具体目的4将探讨口服亚硝酸盐治疗对心肌I/R后线粒体结构和功能的影响。

DESCRIPTION (provided by applicant): Nitric oxide (NO) has been extensively studied in the setting of ischemia-reperfusion (I/R) injury. Previous studies clearly demonstrate that the deficiency of eNOS exacerbates myocardial I/R injury whereas the overexpression of eNOS, NO donor or inhaled NO gas therapy significantly protect the myocardium. NO possesses a number of physiological properties that makes it a potent cardioprotective-signaling molecule. These include vasodilation and the inhibition of oxidative stress, platelet aggregation, leukocyte chemotaxis and apoptosis. The synthesis of NO is critically influenced by various cofactors such as tetrahydrobiopterin, flavin mononucleotide and flavin adenine dinucleotide, the presence of reduced thiols, and the endogenous NOS inhibitor asymmetric dimethylarginine (ADMA), as well as, substrate and oxygen availability. Without an adequate delivery of substrate and co-factors (conditions that certainly exist in the heart during ischemia), NOS is no longer able to produce NO. Therefore, alternate means to produce NO in ischemic tissues are needed to limit I/R injury. Previous studies in our lab have shown that an acute administration of nitrite protects against myocardial I/R injury. Additionally, our preliminary data demonstrates that modest changes in dietary nitrite intake significantly alter steady-state concentrations of nitrite, nitroso modified proteins, and nitrosyl-heme products and that these biochemical changes have a profound outcome on the severity of acute myocardial infarction. Furthermore, our preliminary data suggests that the observed cardioprotection is mediated, in part, by the reduction of nitrite to NO during both the oral supplementation and ischemic periods. The objective of this proposal is to test the overall hypothesis that nitrite serves as an endogenous storage form of NO that renders cardioprotection through its ability to be converted to NO. To test this hypothesis, we have proposed the following four Specific Aims. Specific Aim 1 will investigate the optimal therapeutic strategy needed to achieve cardioprotection in the setting of myocardial I/R by evaluating different doses and durations of nitrite supplementation. Specific Aim 2 will begin our mechanistic studies of nitrite supplementation therapy by investigating the reduction of nitrite to NO by myoglobin. Specific Aim 3 will investigate some of the molecular mechanisms of nitrite supplementation therapy, including the effects of nitrite on the apoptotic pathway following myocardial I/R. Specific aim 4 will investigate the effects of oral nitrite therapy on the structure and function of mitochondria following myocardial I/R.