Mitochondrial Regulated Cardiac Myocyte Death

描述(申请人提供)：线粒体约占哺乳动物心肌细胞内总体积的30%。毫不奇怪，线粒体功能或膜电位的细微变化可以对心肌细胞的能量产生产生戏剧性的影响，并最终影响单个细胞的生死。事实上，细胞损伤或应激刺激直接引起线粒体结构、膜电位和氧化能力的改变，这可能与线粒体基质内容物和细胞色素C氧化酶等完整膜蛋白成分的不可逆转损失有关，随后很快就会激活与细胞凋亡和坏死相关的细胞内蛋白酶和DNA碎裂酶。一种新的范式将线粒体通透性转换孔(MPTP)的形成作为一种中心事件，在缺血损伤后和进展性心力衰竭期间引发心肌细胞凋亡或坏死。该项目将测试MPTP是导致缺血再灌注损伤或长期心肌病后心肌细胞死亡的主要机制这一假说。获得和丧失功能的方法都将在小鼠身上实施，作为剖析MPTP的分子决定因素和潜在治疗机会的一种手段。具体目标1将明确MPTP的形成机制及其在调节心肌细胞凋亡中的功能后果。特异性靶点2将确定可诱导的MPTP形成是否调节体内心肌细胞的凋亡，而特异性靶点3将靶向VDAC1/3和亲环素D作为阻断心脏MPTP形成的一种手段。尽管用药物抑制MPTP的形成通常可以防止不同细胞类型的灾难性刺激后的细胞死亡，但MPTP的形成在介导缺血损伤或长期心肌病后心肌细胞死亡的必要性尚未阐明。此外，推测的MPTP组分的身份和关键功能还没有在体内进行遗传功能获得或丧失的分析，留下了复杂的真实身份尚未解决。更深入地了解MPTP的关键成分，以及进一步表征其在心脏中的功能优势，可能会为治疗与细胞死亡相关的人类心脏病提供新的方法。

DESCRIPTION (provided by applicant): Mitochondria comprise approximately 30% of the total intracellular volume of a mammalian cardiomyocyte. Not surprisingly, subtle alterations in mitochondrial function or membrane potential can have a dramatic influence on cardiomyocyte energy production and ultimately, the life or death individual cell. Indeed, cellular injury or stress stimulation directly elicit alterations in mitochondrial architecture, membrane potential, and oxidative capacity, which can be associated with ah irreversible loss of mitochondrial matrix contents and integral membrane protein constituents such as cytochrome C oxidase, followed soon thereafter by activation of intracellular proteases and DNA fragmentation enzymes associated with apoptosis and necrosis. An emerging paradigm places mitochondrial permeability transition pore (MPTP) formation as a central event precipitating cardiac myocyte apoptosis or necrosis following ischemic injury and during progressive heart failure. This project will test the hypothesis that MPTP is a primary mechanism responsible for driving myocardial cell death following ischemia- reperfusion injury or in response to long-standing cardiomyopathy. Both gain- and loss-of-function approaches will be implemented in the mouse as a means of dissecting the molecular determinants of MPTP and potential therapeutic opportunities. Specific aim 1 will define the mechanism of MPTP formation and its functional consequence in regulating cardiac myocyte apoptosis. Specific aim 2 will determine if inducible MPTP formation regulates cardiac myocyte apoptosis in vivo, while Specific aim 3 will target VDAC1/3 and cyclophilin D as a means of blocking MPTP formation in the heart. Even though inhibition of MPTP formation with pharmacologic agents often prevents cell death following catastrophic stimuli in diverse cell-types, the necessity of MPTP formation in mediating cardiomyocyte cell death following ischemic injury or long-standing cardiomyopathy has not been elucidated. Moreover, the identity and key functions of the putative MPTP components have not been subjected to genetic gain- or loss-of-function analysis in vivo, leaving the true identity of the complex unresolved. A greater understanding of the key constituents that comprise the MPTP, as well as further characterizing its functional dominance in the heart, will likely suggest novel approaches for treating human heart disease associated with cell death.