Prevention of heart failure and remodeling through calcium channel modulation

 描述(由申请人提供)：心肌梗死(MI)后立即丧失的心输出量会触发较长期的心脏重构。MI重构包括收缩能力的丧失和导致心力衰竭(HF)的心室扩张。保持心肌梗死后较高收缩功能的策略可能会绕过最终导致心衰的刺激。一个潜在的治疗靶点是Rad，一种作为L类型钙通道调节器的小GTP酶；Rad丢失促进更大的内向电流、更高的抽动钙水平、更大的心室肌细胞缩短分数和增加的心脏收缩能力。这是假设，这种钙稳态和收缩的改善可以减轻心肌梗塞后收缩能力的丧失。为了验证这一假设，Rad基因缺失的小鼠将接受冠状动脉结扎，并进行一系列超声心动图以监测心脏大小和功能。瘢痕大小将通过组织学进行评估，细胞内钙离子将在受刺激的分离的心室肌细胞中进行测量，以确定Rad基因缺失的小鼠是否受到保护，免受心肌梗死引起的钙调节失调的影响，防止瞬时幅度的损失和重新摄取到SR的速度减缓。此外，Rad基因缺失的小鼠可以免受急性心肌梗死引起的坏死和细胞凋亡的假设将通过缺血的离体灌流心脏进行测试，随后将对其进行染色并分析其梗塞发展情况。这些结果也将在活体内使用晚期Gd增强MRI进行研究。假设Rad GTP酶的缺失将通过保存心肌梗死后的心输出量以及通过细胞保护途径启动心脏以减少梗塞的发展来预防心肌梗死所致的心力衰竭。这些实验将使人们更好地了解一种潜在有益的治疗性蛋白质，这种蛋白质可能既能预防急性细胞毒性，又能促进心肌梗死后的功能改善。

 DESCRIPTION (provided by applicant): The loss of cardiac output immediately post-myocardial infarction (MI) triggers longer-term cardiac remodeling. MI remodeling consists of a loss of contractility and ventricular dilation leading to heart failure (HF). Strategies that maintin higher systolic function post-MI may circumvent the stimulus that ultimately leads to HF. One potential therapeutic target is Rad, a small GTPase that acts as a regulator of the L-type calcium channel; Rad loss promotes greater inward current, higher twitch calcium levels, greater fractional shortening of ventricular myocytes, and increased heart contractility. It is hypothesize that this improvement in calcium homeostasis and contraction can mitigate the loss of contractility post-MI. To test this hypothesis, Rad null mice will be subjected to coronary artery ligation, and serial echocardiography to monitor heart dimensions and function. Scar size will be evaluated using histology, and cytosolic calcium will be measured in stimulated isolated ventricular myocytes to determine if Rad null mice are protected from MI-induced calcium dysregulation, preventing loss of transient amplitude and the slowing of reuptake into the SR. In addition, the hypothesis that Rad null mice are protected from acute MI-induced necrosis and apoptosis will be tested using isolated perfused hearts subjected to ischemia, which will subsequently be stained and analyzed for infarct development. These results will also be investigated in vivo using late gadolinium enhanced MRI. It is hypothesized that deletion of Rad GTPase will prevent MI-induced heart failure through both preservation of cardiac output post-MI, and through the priming of the heart to reduce infarct development through cytoprotective pathways. These experiments will enable a better understanding of a potentially beneficial therapeutic protein that may both prevent acute cytotoxicity, as well as promote functional improvement after MI.