Peroxynitrite in Cardiac Ischemia/Reperfusion Injury

硝基化合物（如硝酸甘油）作为外源性NO供体，用于治疗心肌梗死已有一百多年的历史。然而，一氧化氮治疗在再灌注中的益处最近受到了挑战。生化证据表明，NO与O2的反应产物ONOO-是一种高活性片段，可引起与OH相当的组织损伤。尽管这些体外研究支持ONOO-在心肌再灌注损伤中的作用，但缺乏将这些观察结果扩展到相关的全器官或体内模型。更重要的是，最近的研究表明，ONOO-的作用严重依赖于这种氧化剂产生的微环境。该项目的长期目标是提高对ONOO- in再灌注损伤的认识。在具体目标1中，化学合成的ONOO-将在冠状动脉闭塞或再灌注期间以不同剂量和时间间隔持续注入家兔左心房。这种外源性ONOO-对梗死面积、心功能和PMN积累的影响将在临床相关的体内模型中进行评估。在具体目标2中，内源性ONOO-将被超氧化物、一氧化氮或ONOO-清除剂抑制。将评估内源性形成的ONOO-在再灌注中的作用，并研究旨在将ONOO-浓度降低到可防止再灌注损伤的水平的不同策略。在特定目标3中，将在分离的兔中性粒细胞和培养的兔微血管内皮细胞中确定ONOO-影响PMN-EC相互作用的机制。提出的研究具有临床相关性，因为结果可能改变未来心脏缺血的治疗。本提案中概述的研究是理解NO在缺血-再灌注损伤中的作用的基础，也是通过操纵NO的产生来减少再灌注损伤的临床试验的前提。

Nitro-compounds (e.g., nitroglycerin), as exogenous NO donors, have been used to treat MI for over one hundred years. The benefits of NO- treatment in reperfusion, however, have recently been challenged. Biochemical evidence reveals that ONOO-, the reaction product of NO with O2, is a highly reactive moiety that causes tissue damage comparable to that caused by OH Although these in vitra studies support a role for ONOO- in myocardial reperfusion injury, extension of these observations to relevant whole organs or to in viva models is lacking. More importantly, recent studies suggest that the effects of ONOO- are critically dependent on the microenvironment in which this oxidant is produced. The long-term goal of this project is to enhance the understanding of ONOO- in reperfusion injury. In specific aim number 1, chemically-synthesized ONOO- will be continually infused into the left atrium of rabbits at various doses and intervals during coronary occlusion or reperfusion. The effects of this exogenous ONOO- on infarct size, cardiac function, and PMN accumulation will be evaluated in a clinically relevant in vivo model. In specific aim number 2, endogenous ONOO- will be inhibited by administration of superoxide, nitric oxide, or ONOO- scavenger. The role of endogenously formed ONOO- in reperfusion will be evaluated and different strategies aimed at decreasing ONOO- concentration to a level that protects against reperfusion injury will be studied- In specific aim number3, the mechanisms by which ONOO- influences PMN-EC interactions will be determined in isolated rabbit neutrophils and cultured rabbit microvascular endothelial cells. The proposed studies are clinically relevant because the results may alter future treatment of cardiac ischemia. The studies outlined in this proposal are fundamental to understanding the role of NO in ischemia-reperfusion injury, and are prerequisite to clinical trials designed to decrease reperfusion injury through the manipulation of NO production.