Alleviation of Reperfusion-Mediated Cardiac Dysfunction

描述（由申请人提供）：每150个新生儿中就有一个患有先天性心脏病，这仍然是婴儿死亡的主要原因。随着诊断和支持系统的改善，越来越多的儿童在生命早期接受心脏手术来缓解复杂的先天性缺陷。未成熟心肌对缺血的易感性增加以及修复先天性缺陷所需的体外循环（CPB）时间延长往往导致小儿心脏手术后心肌功能障碍。婴儿和儿童的心肌保护策略缺乏，往往只是成人治疗的外推。缺血心脏的再灌注刺激心肌细胞中半胱氨酸蛋白酶钙蛋白酶及其内源性抑制剂钙pastatin的活性。钙蛋白酶活性与钙调控的心肌细胞收缩中断、心肌收缩蛋白降解和细胞死亡增强有关。这项应用的长期目标是明确儿童缺血再灌注后心肌功能障碍的机制。当前的目标是确定心肌通路，以促进干预措施的发展，以减少术后再灌注损伤。假设calpain和calpastatin通路是未成熟心肌再灌注损伤的关键介质。本项目的具体目的是：1)在未成熟动物模型中确定calpastatin表达增强对缺血再灌注心肌功能障碍的减轻程度；2)明确calpastatin在介导心肌再灌注损伤相关细胞凋亡中的作用；3)建立calpain和calpastatin调节缺血心肌再灌注后收缩蛋白变化的机制。腺病毒介导的钙pastatin结构域的基因转移介导钙内流和抑制钙蛋白酶活性的两种不同功能，研究了钙蛋白酶和钙蛋白酶在仔猪再灌注损伤模型中的作用。确定钙蛋白酶和钙pastatin对细胞死亡级联和心肌收缩蛋白（如肌钙蛋白I）降解的调节作用，为减少儿科患者术后心肌功能障碍的干预确定新的治疗靶点。

DESCRIPTION (provided by applicant): One child in 150 births suffers from congenital heart disease, which remains a leading cause of infant mortality. As diagnoses and support systems improve, more children are undergoing cardiac surgery to palliate complex congenital defects earlier in life. The increased susceptibility of the immature myocardium to ischemia and the prolonged cardiopulmonary bypass (CPB) period required for repair of congenital defects often result in myocardial dysfunction after pediatric cardiac surgery. Myocardial protective strategies for infants and children are lacking and often are only extrapolations of adult therapies. Reperfusion of ischemic heart stimulates the activity of cysteine proteases called calpains and their endogenous inhibitor, calpastatin, in cardiomyocytes. Calpain activity is associated with interruption of calcium-regulated myocyte contraction, degradation of myocardial contractile proteins, and enhanced cell death. The long-term goal of this application is to define mechanisms contributing to myocardial dysfunction after ischemia and reperfusion in children. The immediate goal is to identify pathways in myocardium that can facilitate development of interventions to reduce postoperative reperfusion injury. The hypothesis is that calpain and calpastatin pathways are critical mediators of reperfusion injury in immature myocardium. The specific aims of this project are: 1) determine the degree to which augmentation of calpastatin expression can reduce myocardial dysfunction associated with ischemia and reperfusion in an immature animal model, 2) define the role of calpastatin in mediating cardiac apoptosis associated with reperfusion injury, and 3) establish mechanisms by which calpain and calpastatin regulate changes in contractile proteins after reperfusion of ischemic myocardium. Adenoviral-mediated gene transfer of calpastatin domains with two distinct functions for mediating calcium influx and inhibiting calpain activity examines the roles of calpain and calpastatin in a clinically relevant piglet model of reperfusion injury. Determining calpain and calpastatin regulation of the cell death cascade and degradation of myocardial contractile proteins, such as troponin I, identifies new therapeutic targets for intervention to reduce postoperative myocardial dysfunction in pediatric patients.