酒精导致心肌损伤的新机制--PINK1/Parkin通路与FUNDC1相互作用调节的线粒体自噬

Although light to moderate drinking may be beneficial to the heart, chronic alcohol consumption and binge drinking are considered an independent risk factor for heart diseases, representing a major health threat. Alcohol intake or alcoholism is known to trigger the development of alcoholic cardiomyopathy, or alcoholic heart disease, which is manifested as reduced cardiac contractility, delayed sarcoplasmic reticulum Ca2+ reuptake, cardiomyocyte cell death and aberrant myocardial morphology. Evidence from our lab as well as others has shown that accumulation of reactive oxygen species (ROS) and excessive autophagy play an important role in the onset and pathogenesis of alcoholic cardiomyopathy. However, the precise mechanism(s) behind autophagy-mediated cardiac anomalies following alcohol intake remains poorly understood. It is pertinent to seek strategy to minimize cellular injury machineries triggered by buildup of ROS and excessive autophagy. Autophagy is increasingly recognized as an important mechanism regulating the response of cells to stress and energy deficit including regulation of heart function. Moreover, autophagy is considered as a double-edged sword for cell survival and death. Data from our lab revealed that mitochondrial isoform aldehyde dehydrogenase (ALDH2, which detoxifies acetaldehyde) and antioxidants alleviate, whereas alcohol dehydrogenase (ADH, which produces acetaldehyde) exacerbates alcohol intake-induced changes in autophagy, cardiac and mitochondrial function in the heart. However, little is known with regards to the precise role of autophagy in alcohol and alcohol metabolite acetaldehyde-induced myocardial geometric and functional changes. This proposal is designed to examine the hypothesis that PINK1 and Parkin-mediated mitochondrial autophagy (mitophagy), is responsible for alcohol-induced myocardial injury. We hypothesize that excessive autophagy triggers mitochondrial injury, leading to the development of alcoholic cardiomyopathy. State-of-the art cell physiology and molecular biology techniques will be employed. This interdisciplinary approach should shed some critical new light on a potential novel therapeutic approach for treating or preventing heart diseases developed as a result of alcoholism. Successful completion of these studies will provide the scientific framework for translational approaches using small molecule regulators of autophagy and mitochondrial function with the long-term goal of limiting alcoholism-induced heart defect.

乙醇和其代谢物乙醛的毒性作用是酒精性心肌病发病的主要原因，但目前其发病机制不明。线粒体自噬通过清除受损线粒体实现心肌保护作用，然而过度的线粒体自噬诱发细胞程序性死亡，导致最终心肌功能受损。我们前期研究发现酒精刺激可导致心肌组织中自噬体的蓄积，同时发现酒精刺激可引起心肌线粒体膜电位下降、线粒体功能障碍及ROS的蓄积，提示线粒体损伤及其导致的氧化应激是酒精性心肌损伤的重要机制。本研究拟采用模式动物和细胞基因沉默技术相结合，证实酒精刺激通过PINK1/Parkin通路诱导的线粒体自噬，而过度的线粒体自噬最终导致心肌细胞的程序性死亡，并明确Parkin信号通路与FUNDC1线粒体膜蛋白相互作用在线粒体自噬中的调节作用，进一步深化对酒精性心肌病发病机制的认识，为新的治疗靶点的选择提供理论依据。

根据本研究的研究目标，我们采用模式动物和细胞基因沉默技术相结合，主要证实PINK1-Parkin信号通路在酒精性心脏毒性作用中的调控机制。我们的结果显示，酒精摄入导致心脏收缩功能障碍，心肌细胞增大和间质纤维化，线粒体肿胀伴嵴排列紊乱和线粒体去极化，而Parkin缺乏加重了这种作用（Parkin敲除小鼠）。饮酒可促进自噬和PINK1-Parkin介导的线粒体自噬，Parkin基因敲除可消除自噬和PINK1-Parkin介导的线粒体自噬。免疫共沉淀结果显示Parkin和Ambra1（自噬和Beclin1调节因子1）之间存在紧密的相互作用。利用乳鼠心肌细胞进行的体外研究表明，Parkin过表达改善了乙醇诱导的自噬增强。然而，Ambra1基因沉默逆转了Parkin对乙醇诱导自噬的保护作用。综上所述，这些数据表明Parkin通过与自噬蛋白Ambra1的相互作用来保护酒精引起的心脏损伤，从而促进自噬维持线粒体稳态。本研究阐明了Parkin缺失恶化酒精性心肌损伤的主要机制，进一步深化对酒精性心肌病发病机制的认识，为新的治疗靶点的选择提供理论依据。