The role of RASSF1A in myocardial ischemia/reperfusion injury

描述（由申请人提供）：心肌细胞在缺血再灌注（I/R）反应中通过坏死和凋亡的损失是导致心肌重塑和心功能丧失的关键因素。然而，通过广泛的抑制剂来限制心肌细胞死亡的尝试尚未对急性心肌梗死患者产生有效的治疗。我们认为，这种方法忽略了细胞类型之间的独特功能和串扰，因此无法提供心脏保护。换句话说，心肌细胞的死亡对I/R期间的心肌是有害的，而部分细胞的凋亡是有益的。尽管是无菌环境，先天性和适应性免疫反应都是由心肌中的I/R激活的。这一点很重要，因为精心安排的炎症反应是清除碎片、激活修复细胞和促进I/R后伤口愈合所必需的。然而，过度和/或长时间的炎症可增强基质降解，损害胶原沉积，引起更大的CM损失，扩展浸润到非梗死心肌，增加纤维化和心功能恶化。因此，维持平衡的炎症反应对于提供最大的心脏保护至关重要。因此，我们有理由假设，有缺陷的炎症细胞凋亡可能起着“失灵刹车”的作用，导致过度的免疫反应和恶化的损伤。RASSF1A是一种促凋亡分子和已知的肿瘤抑制因子，但RASSF1A与炎症的关系尚不清楚。我们的初步结果表明RASSF1A是I/R期间心肌炎症的重要调节剂。本研究将探讨RASSF1A下调导致炎症细胞凋亡改变导致I/R后心肌损伤的可能性。我们假设，在I/R期间，造血细胞中一个关键的内源性凋亡信号级联的消融，即对细胞死亡的增强抵抗，对心肌有害。为了验证我们的假设，我们将采用WT和Rassf1A KO小鼠的原代巨噬细胞和巨噬细胞系的培养来获得巨噬细胞在体外激活和存活的机制。重要的是，这些研究将得到体内实验的补充

DESCRIPTION (provided by applicant): The loss of cardiomyocytes through necrosis and apoptosis in response to ischemia and reperfusion (I/R) is a critical factor leading to myocardial remodeling and loss of cardiac function. However, attempts at limiting cardiomyocyte death through broad-based inhibitors have yet to produce an effective treatment for patients with acute MI. We propose that this approach ignores the unique functionality and crosstalk that occurs between cell types and therefore fails to provide cardioprotection. In other words, while death of cardiomyocytes is deleterious to the myocardium during I/R, apoptosis of select cells is beneficial. Despite being a sterile environment, both innate and adaptive immune responses are activated by I/R in the myocardium. This is important because a well-orchestrated inflammatory response is necessary to clear debris, activate reparative cells and promote wound healing after I/R. However, excessive and/or prolonged inflammation can augment matrix degradation, impair collagen deposition, cause greater CM loss, extend infiltrate to non-infarcted myocardium, increase fibrosis and worsen heart function. Therefore, maintaining a balanced inflammatory response is critical to provide maximum cardioprotection. It is reasonable to posit, then, that defective inflammatory cell apoptosis could function as a "faulty brake" and cause an excessive immune response and worsened injury. RASSF1A is a pro-apoptotic molecule and known tumor suppressor, yet nothing is known regarding RASSF1A and inflammation. Our preliminary results implicate RASSF1A as an important modulator of inflammation in the myocardium during I/R. This proposal will examine the possibility that altered inflammatory cell apoptosis due to RASSF1A downregulation contributes to myocardial injury following I/R. We hypothesize that the ablation of a critical endogenous apoptotic signaling cascade, i.e. a heightened resistance to cell death, in cells of hematopoietic origin is detrimental to the myocardium during I/R. To test our hypothesis, we will employ the culture of primary macrophages from WT and Rassf1A KO mice and a macrophage cell line to attain mechanistic insight regarding their activation and survival in vitro. Importantly, these studies will be complimented by in vivo experiments utilizing bone marrow transplantation and simulated I/R in WT and KO mice. Importantly, the findings obtained upon successful completion of this proposal will have the potential to shift the medical paradigm away from general inhibitors of cell death toward cell type-specific therapies for ischemic heart disease and acute MI.