Mitochondria and NO? in Cardiac Ischemic Preconditioning

描述（由申请人提供）：心肌梗死（MI）在美国每年造成22万人死亡。心脏缺血再灌注损伤是心肌梗死与心肌收缩功能障碍之间的病理联系。线粒体Ca2+过载和活性氧（ROS）的过量产生是心脏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，在IPC中，短时间的非致死缺血可以保护心脏免受长时间的IR损伤。另一个与IPC相关的因素是一氧化氮（NO），我们最近在线粒体水平发现了两种新的NO信号传导机制，它们在IPC中具有潜在的重要性：(i) NO依赖蛋白s -亚硝化对呼吸链的可逆抑制；（ii）通过解偶联蛋白（UCPs）或其他靶标的硝化脂质活化介导的轻度解偶联（H+泄漏）。这两个事件随后都可以抑制线粒体Ca2+过载和ROS的产生，从而抑制PT孔开放。为了利用这一保护途径，研究人员开发了一系列线粒体靶向NO供体，它们在IR损伤的心肌细胞和灌注心脏模型中表现出强大的心脏保护作用。基于这些发现，我们假设可逆呼吸链抑制和H+泄漏的小调控增加是NO介导的心脏保护机制。这一假设将通过追求以下具体目的来验证：目的1：验证呼吸链s -亚硝化介导NO的心脏保护作用的假设。目的2：验证硝基脂质激活H+泄漏介导NO心脏保护作用的假设。目的3：检测线粒体靶向NO供体作为心脏保护剂的作用。研究目标1和2将定义NO介导心脏保护的新机制，而目标3将导致心脏IR损伤治疗的新疗法。

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.