Nitrite Mediated Cardioprotection

描述(申请人提供)：一氧化氮(NO)在缺血再灌注(I/R)损伤中的作用已被广泛研究。以往的研究表明，eNOS的缺乏加重了心肌I/R损伤，而eNOS的过度表达、NO供体或吸入NO气体治疗对心肌有明显的保护作用。NO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。这些包括血管扩张和抑制氧化应激，血小板聚集，白细胞趋化和细胞凋亡。如果没有足够的底物和辅助因子(在缺血期间肯定存在于心脏中的情况)，一氧化氮合酶就不再能够产生NO。因此，需要在缺血组织中替代产生NO的方法来限制I/R损伤。我们实验室以前的研究表明，急性给予亚硝酸盐可以保护心肌I/R损伤。此外，我们的初步数据显示，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酸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产生了深远的影响。此外，我们的初步数据表明，观察到的心脏保护作用在一定程度上是通过在口服补充期间和缺血期将亚硝酸盐还原为NO来实现的。这项提议的目的是检验亚硝酸盐作为NO的内源性存储形式，通过其转化为NO的能力而起到心脏保护作用的总体假设。为了验证这一假设，我们提出了以下四个具体目标。具体目标1将通过评估不同剂量和持续时间的亚硝酸盐补充来研究在心肌I/R环境中实现心脏保护所需的最佳治疗策略。具体目标2将通过研究肌红蛋白将亚硝酸盐还原为NO来开始我们的亚硝酸盐补充治疗的机制研究。建议的研究将评估一种新的治疗药物(即口服亚硝酸盐疗法)在临床相关的急性心肌梗死实验模型系统中的保护作用。这项拟议的研究将极大地提高我们目前对心脏病发作期间心肌细胞死亡机制的理解。

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. Public Health Relevance: Despite numerous advances in health care, cardiovascular disease remains the number one killer in the United States and acute myocardial infarction (i.e., heart attack) affects nearly 1.1 million people every year and is responsible for approximately 220,000 deaths per year. The proposed studies will evaluate the protective actions of a novel therapeutic agent (i.e., oral nitrite therapy) in a clinically relevant experimental model system of acute myocardial infarction. The proposed studies will significantly advance our current understanding of the mechanisms responsible for myocardial cell death during a heart attack