Regulation of cardiac stress responses by Rho kinase

描述（由申请人提供）：心力衰竭仍然是人类发病和死亡的主要原因。Rho激酶（也称为ROCK）最近成为治疗心脏病的潜在治疗靶点，在实验和临床研究中显示ROCK抑制剂的有益作用。然而，需要解决的一个重要问题是ROCK是否真正代表了治疗人类疾病的可行靶点，因为目前可用的ROCK抑制剂具有广泛的特异性。此外，ROCK家族的两个成员ROCK1和ROCK2被ROCK抑制剂具有相同的抑制效力，并且对ROCK在体内的异构体功能知之甚少。我们最近发现，全身的ROCK1缺乏对心脏失代偿有保护作用，而ROCK1缺乏的抗凋亡作用是一个关键因素。与ROCK1缺失的有益作用相反，我们观察到心脏特异性的ROCK2缺乏会导致自发性心脏肥大和功能障碍，这表明ROCK2在心脏保护中的新作用。我们使用ROCK1或ROCK2缺陷胚胎源性成纤维细胞进行的体外研究支持了一个新的机制概念，即ROCK1优先通过ROCK1/MYPT/MLC途径介导应激诱导的肌动蛋白收缩，从而增加细胞死亡，而ROCK2优先通过ROCK2/LIMK/cofilin途径促进肌动蛋白聚合，从而提高应激条件下的细胞存活率。本应用程序的目的是解剖岩石在肥厚性心脏重塑中的异构体功能，并验证一个新的中心假设，即岩石1和岩石2在心脏应激反应中调节心肌细胞死亡和心脏重塑的功能不同。Specific Aim 1将验证ROCK2促进心肌细胞存活和心脏保护的假设。这些研究将进一步表征心脏特异性ROCK2敲除小鼠自发性心肌肥厚的发生和进展，并将确定心肌细胞中条件性ROCK2缺失是否会加速心力衰竭的进展。特异性Aim 2将决定ROCK1在心脏失代偿中的最终作用。这些研究将确定，当慢性压力过载导致心脏肥厚或扩张型心肌病发生时，心肌细胞中条件性ROCK1缺失是否可以限制心衰的进展。特异性目的3将验证ROCK1和ROCK2在介导应激性心肌细胞死亡中发挥相反作用的假设，并描述其潜在机制。这些研究的结果将显著提高我们对ROCK异构体病理生理学的认识，并为ROCK泛型抑制剂的临床试验提供信息，最终为异构体选择性抑制剂的临床试验提供信息，最终目标是开发治疗干预措施，以防止心肌细胞死亡和减少心力衰竭的进展。

DESCRIPTION (provided by applicant): Heart failure remains a leading cause of human morbidity and mortality. Rho kinase (also named ROCK) has recently emerged as a potential therapeutic target for the treatment of cardiac diseases with the overall promising studies showing beneficial effects of ROCK inhibitors in experimental and clinical studies. However, one important question needing to be addressed is whether ROCK truly represents a viable target for the treatment of human disease as currently available ROCK inhibitors have broad specificity. In addition, the two members of the ROCK family, ROCK1 and ROCK2, are inhibited by ROCK inhibitors with equal potency, and little is known about ROCK isoform functions in vivo. We recent discovered that systemic ROCK1 deficiency is protective against cardiac decompensation and the anti-apoptotic effect of ROCK1 deficiency is a critical contributor. In contrast to the beneficial effects of ROCK1 deletion, we observed that cardiac-specific ROCK2 deficiency results in spontaneous cardiac hypertrophy and dysfunction, suggesting a novel role for ROCK2 in cardiac protection. Our in vitro studies using ROCK1 or ROCK2 deficient embryo-derived fibroblasts support a novel mechanistic concept that ROCK1 preferentially mediates stress-induced acto-myosin contraction via the ROCK1/MYPT/MLC pathway leading to increased cell death, while ROCK2 preferentially contributes to actin polymerization via the ROCK2/LIMK/cofilin pathway leading to improved cell survival under stress conditions. The goal of this application is to dissect isoform functions of ROCK in hypertrophic cardiac remodeling and to test a novel central hypothesis that ROCK1 and ROCK2 are functionally different in regulating cardiomyocyte death and cardiac remodeling in response to cardiac stress. Specific Aim 1 will test the hypothesis that ROCK2 promotes cardiomyocyte survival and cardiac protection. The studies will further characterize the onset and progression of spontaneous cardiac hypertrophy in cardiac-specific ROCK2 knockout mice, and will determine if conditional ROCK2 deletion in cardiomyocytes accelerates heart failure progression. Specific Aim 2 will determine the ultimate role of ROCK1 in cardiac decompensation. The studies will determine if conditional ROCK1 deletion in cardiomyocytes can limit the progression of heart failure when cardiac hypertrophy or dilated cardiomyopathy has already occurred through chronic pressure overload. Specific Aim 3 will test the hypothesis that ROCK1 and ROCK2 play opposite roles in mediating stress-induced cardiomyocyte death and characterize the underlying mechanisms. Results of these studies will significantly advance our knowledge in ROCK isoform pathophysiology and inform clinical trials testing ROCK pan- inhibitors, and eventually isoform selective inhibitors, with the ultimate goal of developing therapeutic interventions to prevent cardiomyocyte death and reduce heart failure progression.