Interaction between death and MAPK pathways with myocardial ischemia

心肌缺血/再灌注（I/R）是一种强有力的刺激，可诱导心肌细胞凋亡和坏死。虽然凋亡是细胞有目的的行为，但考虑到成年心肌细胞增殖能力有限，心肌细胞凋亡可能导致心功能下降。因此，了解I/R介导的细胞凋亡信号转导机制具有重要意义。心肌I/R激活应激反应性丝裂原活化蛋白激酶（mitogen activated protein kinases，MAPK），使其活性增强，并刺激细胞凋亡，从而启动“死亡”和“SR-MAPK”通路之间的正反馈机制。尽管细胞凋亡与SR-MAPKs之间存在密切的关系，但“死亡”信号通路在I/R诱导的SR-MAPKs激活中的运动以及“SR-MAPKs”在I/R诱导的心肌细胞凋亡中的作用仍不清楚。我们假设心肌I/R启动了“死亡”信号通路和“SR-MAPKs”通路之间的相互作用，这放大了心肌细胞的凋亡。caspase对MEKK 1和Mst 1的切割和激活是两条途径相互作用的节点，这种放大机制在I/R诱导的心肌细胞凋亡中起着重要作用。本研究将利用分子生物学技术和腺病毒介导的转导技术，在体内外I/R模型、转基因动物和慢性清醒猪I/R模型中，从器官和细胞水平研究心肌细胞凋亡的信号转导机制。我们将问1）半胱天冬酶是否参与I/R对MEKK 1和Mst 1的切割/激活; 2）SR-MAPK的激活，包括半胱天冬酶切割的MEKK 1和Mst 1，是否足以促进凋亡; 3）SR-MAPK的激活/切割，包括半胱天冬酶/切割的MEKK 1和Mst 1，是否足以促进凋亡;（3）SR-MAPKs的激活/裂解是否是I/R心肌细胞凋亡所必需的。本研究将有助于进一步了解I/R引起心肌细胞凋亡的机制，并为预防I/R引起的心肌细胞丢失和心功能下降提供线索。

Myocardial ischemia/reperfusion (I/R) is a potent stimulus which induces apoptosis and necrosis of cardiac myocytes. Although apoptosis should be a purposeful behavior of cells, considering the limited capacity of cell proliferation in adult cardiac myocytes, myocyte apoptosis may lead to reduced cardiac function. Thus, understanding the signaling mechanism of apoptosis by I/R is important. Myocardial I/R activates stress- responsive mitogen activated protein kinases exhibit higher activities and stimulate apoptosis, thereby initiating positive feedback mechanism between "death" and "SR-MAPK" pathways. Although there are close relations between apoptosis and SR-MAPKs, the movement of "death" signaling pathways in I/R-induced activation of SR-MAPKs, and conversely the role of "SR-MAPKs" in I/R induced myocyte apoptosis, remain unclear. We hypothesize that myocardial I/R initiates an interaction between the "death" signaling pathways, and the "SR- MAPKs" pathways, which amplifies apoptosis of cardiac myocytes. Cleavage and activation of MEKK1 and Mst1 by caspases are the nodal points of the interaction between two pathways, and such an amplification mechanism plays an essential role in I/R induced myocyte apoptosis. Using molecular biological techniques and adenovirus- mediated transduction in in vivo and in vitro models of I/R as well as transgenic animals and the chronically instrumented conscious pig model of I/R, we will study signaling mechanisms of myocyte apoptosis at both organ and cellular levels. We will ask 1) if caspases are involved in cleavage/activation of MEKK1 and Mst1 by I/R; 2) if activation of SR- MAPKs, including caspase-cleaved MEKK1 and Mst1, is sufficient to promote apoptosis; 3) if activation/cleavage of SR-MAPKs, including caspase/cleaved MEKK1 and Mst1, is sufficient to promote apoptosis; 3) if activation/cleavage of SR-MAPKs is required for cardiac myocyte apoptosis by I/R. Our study will contribute to the understanding of the mechanism of cardiac myocyte apoptosis by I/R and may provide clues to prevent myocyte loss and reduced cardiac function alter myocardial I/R.