Mechanisms regulating autophagy in alcohol-induced liver injury

描述（由申请人提供）：自噬是一种遗传编程，进化保守的过程，降解长寿命的细胞蛋白质和受损的细胞器，包括线粒体，是细胞应对应激的关键生存机制。我们最近报道了乙醇诱导自噬，减少乙醇引起的肝损伤（Ding et al., 2010a）。这是一个重要的发现，因为酒精滥用是导致肝脏疾病的主要原因，也是美国的一个主要健康问题。氧化应激和线粒体损伤在酒精引起的肝毒性中起重要作用。细胞可以通过自噬等机制清除受损的线粒体来保护自己。因此，调节自噬过程可能为酒精性肝病提供新的治疗方法。然而，乙醇诱导自噬的机制以及自噬如何防止乙醇诱导的肝脏发病机制尚不清楚。没有这样的认识，最终使用自噬治疗酒精相关肝病的潜力将受到限制。我们的初步研究表明叉头转录因子FoxO3a可能在乙醇诱导的自噬中起主要作用。因此，核心假设是乙醇通过激活FoxO3a诱导自噬，自噬清除乙醇诱导的受损线粒体对于防止乙醇诱导的肝脏发病至关重要。为了验证我们的假设，提出了三个具体目标：1)确定乙醇激活肝细胞中FoxO3a的机制，2)确定乙醇激活的FoxO3a如何诱导肝细胞自噬，以及3)确定去除受损线粒体保护免受乙醇诱导的肝毒性的机制。本申请中提出的研究在概念上是创新的，乙醇可以激活自噬，作为一种保护机制，对抗其对肝脏的已知有害影响。此外，我们将利用GFP-LC3转基因小鼠和Atg5肝脏特异性敲除小鼠等新型遗传动物模型，专门研究自噬在酒精性肝损伤中的作用。此外，本研究重点关注foxo3a介导的自噬通路在酒精性肝病中的作用，这一途径尚未得到研究。这项研究的意义在于，其结果将有助于理解自噬在酒精性肝脏发病机制中的作用。最终，这些知识有可能为通过调节自噬来治疗酒精性肝的发病机制提供新的治疗方法。

DESCRIPTION (provided by applicant): Autophagy is a genetically programmed, evolutionarily conserved process that degrades long-lived cellular proteins and damaged organelles, including mitochondria, as a critical cell survival mechanism in response to stress. We recently reported that ethanol induces autophagy, which reduces ethanol-induced liver injury (Ding et al., 2010a). This is an important finding because alcohol abuse is a major cause of liver disease and a major health problem in the United States. Oxidative stress and mitochondrial damage play important roles in alcohol-induced hepatotoxicity. Cells may protect themselves by removing damaged mitochondria by mechanisms such as autophagy. Therefore modulating the autophagy process could offer new therapeutic treatments for alcoholic liver diseases. However, the mechanisms by which ethanol induces autophagy and how autophagy protects against ethanol-induced liver pathogenesis are not clear. Without such understanding, the potential to ultimately use autophagy in the treatment of alcohol-related liver disease will be limited. Our preliminary studies suggest that the forkhead transcription factor FoxO3a could play a major role in ethanol- induced autophagy. Therefore, the central hypothesis is that ethanol induces autophagy by activating FoxO3a, and autophagic removal of ethanol-induced damaged mitochondria is crucial to protect against ethanol- induced liver pathogenesis. To examine our hypothesis, three specific aims are proposed: 1) determine the mechanisms by which ethanol activates FoxO3a in hepatocytes, 2) determine how ethanol-activated FoxO3a induces autophagy in hepatocytes, and 3) determine the mechanisms by which removal of damaged mitochondria protects against ethanol-induced hepatotoxicity. The research proposed in this application is innovative in the concept that ethanol can activate autophagy as a protective mechanism against its known detrimental effects on the liver. Moreover, we will utilize novel genetic animal models such as GFP-LC3 transgenic and Atg5 liver-specific knockout mice to specifically study the role of autophagy in alcohol-induced liver injury. Furthermore, it focuses on the role of FoxO3a-mediated autophagy pathway in alcoholic liver disease, which has not been studied. The proposed research is significant because the results from this study will lead to the understanding of mechanisms and roles of autophagy in alcohol-induced liver pathogenesis. Ultimately, such knowledge has the potential of offering novel therapeutic approaches for treating alcoholic liver pathogenesis by modulating autophagy.