Peroxynitrite in Cardiac Ischemia/Reperfusion Injury

硝基化合物（例如，硝酸甘油）作为外源性NO供体，已经被用于治疗MI超过一百年。 然而，NO-治疗在再灌注中的益处最近受到了挑战。生化证据表明，ONOO-，与O2的NO的反应产物，是一个高度反应性的部分，导致组织损伤的OH所造成的。虽然这些在体外研究支持的作用，ONOO-在心肌再灌注损伤，这些观察扩展到相关的整个器官或在体内模型是缺乏的。 更重要的是，最近的研究表明，ONOO-的影响严重依赖于产生这种氧化剂的微环境。 本项目的长期目标是提高对ONOO-在再灌注损伤中的理解。 在具体目标1中，在冠状动脉闭塞或再灌注期间，将化学合成的ONOO-以各种剂量和间隔连续输注到兔的左心房中。将在临床相关的体内模型中评价这种外源性ONOO-对梗死面积、心脏功能和PMN积累的影响。 在具体目标2中，内源性ONOO-将通过施用超氧化物、一氧化氮或ONOO-清除剂来抑制。 将评价内源性形成的ONOO-在再灌注中的作用，并研究旨在将ONOO-浓度降低至保护免受再灌注损伤的水平的不同策略。在具体目标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。 拟议的研究具有临床相关性，因为结果可能会改变未来的心脏缺血治疗。本提案中概述的研究是了解NO在缺血-再灌注损伤中的作用的基础，并且是旨在通过操纵NO产生来减少再灌注损伤的临床试验的先决条件。

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.