Mitochondria and NO? in Cardiac Ischemic Preconditioning

描述（由申请人提供）：在美国，心肌梗死（MI）每年导致220，000例死亡[35]。心肌缺血-再灌注损伤是心肌梗死后心肌收缩功能障碍的病理过程.线粒体Ca 2+超载和活性氧（ROS）的过度产生是心脏IR的关键病理事件，导致线粒体通透性转换（PT）孔开放和随后的心肌细胞死亡。相反，线粒体也参与缺血预处理（IPC）的机制，其中短暂的非致死性缺血期保护心脏免受长期IR损伤。IPC中涉及的另一个因素是一氧化氮（NO），我们最近已经确定了在线粒体水平的NO信号传导的两种新机制，这在IPC中具有潜在的重要性：（i）通过NO依赖性蛋白质S-亚硝化对呼吸链的可逆抑制;（ii）通过解偶联蛋白（UCP）或其他靶点的硝化脂质活化介导的轻度解偶联（H+泄漏）。这两种事件随后都可以抑制线粒体Ca 2+过载和ROS产生，从而抑制PT孔开放。为了利用这一保护途径，已经开发了一系列靶向NO供体，其在IR损伤的心肌细胞和灌注心脏模型中表现出有效的心脏保护作用。基于这些发现，我们假设可逆的呼吸链抑制和H+泄漏的小调节增加是NO介导的心脏保护机制。该假设将通过追求以下具体目标进行测试：目标1：测试呼吸链S-亚硝化介导NO的心脏保护作用的假设。目标2：测试硝基脂质的H+泄漏激活介导NO的心脏保护作用的假设。目标3：测试作为心脏保护剂的靶向NO供体。预期解决目标1和2将定义NO介导心脏保护的新机制，并且目标3将导致用于治疗心脏IR损伤的新疗法。

DESCRIPTION (provided by applicant): Myocardial infarction (MI) is responsible for 220,000 deaths annually in the USA [35]. Cardiac ischemia- reperfusion (IR) injury is the pathologic process that links MI to contractile dysfunction. Mitochondrial Ca2+ overload and excessive generation of reactive oxygen species (ROS) are key pathologic events in cardiac IR, leading to opening of the mitochondrial permeability transition (PT) pore and subsequent death of cardiomyocytes. In contrast mitochondria are also implicated in the mechanism of ischemic preconditioning (IPC), in which short non-lethal periods of ischemia protect the heart from prolonged IR injury. An additional factor implicated in IPC is nitric oxide (NO), and we have recently identified two novel mechanisms of NO signaling at the mitochondrial level which are of potential importance in IPC: (i) reversible inhibition of the respiratory chain by NO dependent protein S-nitrosation; (ii) mild uncoupling (H+ leak) mediated via nitrated lipid activation of uncoupling proteins (UCPs) or other targets. Both these events can subsequently inhibit mitochondrial Ca2+ overload and ROS generation, and thus inhibit PT pore opening. To exploit this protective pathway a series of mitochondrially-targeted NO donors have been developed, which exhibit potent cardioprotective effects in cardiomyocyte and perfused heart models of IR injury. Based on these findings, it is hypothesized that reversible respiratory chain inhibition and small regulated increases in H+ leak are mechanisms of NO mediated cardioprotection. This hypothesis will be tested through pursuit of the following specific aims: Aim 1: Test the hypothesis that respiratory chain S-nitrosation mediates the cardioprotective effects of NO. Aim 2: Test the hypothesis that H+ leak activation by nitro-lipids mediates the cardioprotective effects of NO. Aim 3: Test mitochondrially-targeted NO donors as cardioprotective agents. It is anticipated that addressing Aims 1 & 2 will define new mechanisms by which NO mediates cardioprotection, and that Aim 3 will lead to novel therapies for the treatment of cardiac IR injury.