Adenosine and Pyruvate Protection During Heart Surgery

描述（由申请人提供）： 严重心室功能障碍、心肌梗死（MI）、心力衰竭和心脏手术后死亡的并发症发生率，包括高危CABG手术患者的某些子集，可能超过10- 15%。虽然心脏手术后心肌损伤的原因有很多，但缺血/再灌注损伤和缺乏最佳心肌保护是值得改善的重要因素。我们实验室的新发现表明，腺苷和丙酮酸的心脏保护作用可能是通过调节丝裂原活化蛋白激酶（MAPK）介导的。本研究的目的是进一步阐明缺血/再灌注损伤的机制，并评估MAPKs与急性和延迟腺苷受体激活和中间代谢产物丙酮酸的心脏保护作用之间的关系。具体目标1将测试缺血再灌注期间心肌细胞的急性和延迟A1受体预处理是通过线粒体功能和细胞内Ca++稳态的MAPK调节介导的假设。具体目标2将确定腺苷受体介导的急性和延迟的梗死面积减少在体内是如何通过一个或多个MAPK信号转导介导的。具体目标3将确定腺苷受体介导的急性和延迟衰减心肌顿抑在体内和一个或多个MAPK家族（p38，ERK，JNK）的激活之间的关系。具体目标4将确定丙酮酸在可逆和不可逆损伤心肌中的有益作用是否是由于MAPK信号传导的氧化还原调节。实验将在模拟缺血条件下在分离的大鼠心室肌细胞中进行，并在体内大鼠梗死和体内猪顿抑制备物中进行。在分离的肌细胞研究中，将使用荧光成像和共聚焦显微镜同时测量肌细胞氧化应激、线粒体内游离[Ca++]、线粒体渗透性转换孔（MPTP）、线粒体膜电位的变化和线粒体氧化还原状态的变化。在体内研究中，梗死面积和心肌功能的变化将与亚细胞组分中MAPK的表达和活性相关。预计这些研究的结果将提供有关腺苷和丙酮酸有益作用的机制的新见解。最终，研究结果应导致的战略，将允许放大这些内源性药物的心脏保护作用和/或开发新的和特定的治疗方案，旨在改善心脏手术后的病人的结果。

DESCRIPTION (provided by applicant): The complication rates of severe ventricular dysfunction, myocardial infarction (MI), heart failure and death after heart surgery, including certain subsets of high-risk CABG surgery patients, may exceed 10-15%. While there are many causes of myocardial injury after heart surgery, ischemia/reperfusion injury and the lack of optimal myocardial protection are important contributing factors that are amenable to improvement. New findings from our laboratory indicate that the cardioprotective effects of adenosine and pyruvate may be mediated via the modulation of mitogen activated protein kinases (MAPK). The purpose of the proposed research is to further elucidate the mechanisms underlying ischemia/reperfusion injury and evaluate the relationship between MAPKs and the cardioprotective effects of acute and delayed adenosine receptor activation and the intermediary metabolite pyruvate. Specific Aim 1 will test the hypothesis that acute and delayed A1receptor preconditioning of the cardiac myocyte during ischemia-reperfusion is mediated via MAPK modulation of mitochondrial function and intracellular Ca++ homeostasis. Specific Aim 2 will determine how adenosine receptor-mediated acute and delayed reduction of infarct size in vivo is mediated via signaling through one or more of the MAPKs. Specific Aim 3 will determine the relationship between adenosine receptor-mediated acute and delayed attenuation of myocardial stunning in vivo and activation of one or more of the MAPK families (p38, ERK, JNK). Specific Aim 4 will determine whether the beneficial effects of pyruvate in reversibly and irreversibly injured myocardium are due to redox modulation of MAPK signaling. Experiments will be performed in isolated rat ventricular myocytes under conditions of simulated ischemia and in in vivo rat infarct and in vivo porcine stunning preparations. In the isolated myocyte studies, fluorescence imaging and confocal microscopy will be used to simultaneously measure changes in myocyte oxidative stress, intramitochondrial free [Ca++], the mitochondria] permeability transition pore (MPTP), mitochondrial membrane potential and changes in mitochondrial redox status. In the in vivo studies, changes in infarct size and myocardial function will be correlated with the expression and activity of the MAPKs in subcellular fractions. It is anticipated the results of these studies will provide new insights regarding mechanisms underlying the salutary effects of adenosine and pyruvate. Ultimately the findings should lead to strategies that will allow for the amplification of the cardioprotective effects of these endogenous agents and/or the development of new and specific therapeutic regimens designed to improve patient outcomes after heart surgery.