Dissecting the Role of Unfolded Protein Response in Alcoholic Liver Disease

描述（由申请人提供）：酗酒威胁着美国数百万美国人的健康。酒精性脂肪肝或脂肪变性是过量饮酒最早和最常见的后果之一，可导致更严重的肝损伤，包括肝硬化，糖尿病，肝炎，纤维化和肝细胞癌。因此，了解酒精性脂肪肝的发病机制具有重要的临床和基础意义。最近的研究表明，内质网（ER）对应激的反应或未折叠蛋白反应（UPR）可能参与了酒精性肝病的发病机制。这是一个非常有吸引力的模型，因为ER是脂质生物合成、脂滴生物发生和酒精解毒的主要位点，并且因为据报道肝脏ER在酗酒者中扩增。然而，ER应激和酒精性脂肪肝之间的因果关系尚未建立。我们和其他人最近已经表明，UPR途径的IRE 11-XBP 1分支在脂质代谢中起着关键作用。令人兴奋的是，我们的初步数据显示，急性酒精挑战在几分钟内使肝脏中IRE 11的活性增加了一倍，这表明ER应激发生在饮酒后的早期阶段。此外，在两种慢性酗酒小鼠模型中观察到ER应激，这些小鼠具有更严重的肝损伤形式。因此，这项R21提案的目标是描述IRE 11-XBP 1分支在酒精性脂肪肝发病机制中的作用。我们推测UPR的IRE 11-XBP 1分支直接调节肝脏对慢性酗酒的反应，从而在酒精性脂肪肝的发病机制中发挥关键作用。这一假说将IRE 11-XBP 1分支和ER稳态确定为连接慢性酗酒和酒精性脂肪肝疾病的关键组分。使用最先进的方法（例如，腺病毒shRNA以实现基因和肝脏特异性时间敲低，基于Phos标签的方法以定量生理条件下的ER应激，以及组织ChIP-qPCR以定量转录因子与肝脏中特异性基因启动子的结合），我们将以以下目的测试该假设：（1）确定IRE 11-XBP 1通路的调节如何影响酒精性脂肪肝的发病机制;（2）探讨IRE 11-XBP 1通路调节脂肪生成基因响应酒精的基本机制。如果成功，这项研究将首次建立UPR与酒精性脂肪肝之间的因果关系。与人类健康的相关性：过量饮酒是全球慢性肝病的主要原因。在饮酒者中（超过50%的美国成年人），约29%的人报告每月多次饮酒（即慢性饮酒者），这导致美国每年约有15亿次饮酒。脂肪肝是过量饮酒或酗酒最早和最常见的后果之一，可导致更严重的肝损伤，包括肝炎，肝硬化和肝细胞癌。我们的研究将为酒精性脂肪肝的发病机制提供重要的见解。这项研究如果成功，可能会描绘酒精性肝病的关键信号通路，并确定预防和治疗酒精性肝病以及其他形式的肝病的新靶点。

DESCRIPTION (provided by applicant): Alcoholism threatens the health of millions of Americans in the United States. Alcoholic fatty liver disease, or steatosis, is one of the earliest and most common consequences of excess alcohol consumption and can lead to more severe forms of liver injury, including cirrhosis, diabetes, hepatitis, fibrosis and hepatocellular carcinoma. Therefore, understanding the pathogenesis of alcohol-induced fatty liver disease is of great clinical and basic importance. Recent studies have suggested that response to stress in the endoplasmic reticulum (ER), or unfolded protein response (UPR) may be involved in the pathogenesis of alcoholic liver disease. This is a very attractive model because the ER is the predominant site for lipid biosynthesis, lipid droplet biogenesis, and alcohol detoxification, and because hepatic ER has been reported to expand in alcoholics. However, the causal relationship between ER stress and alcoholic fatty liver has yet to be established. We and others have recently shown that the IRE11-XBP1 branch of the UPR pathway plays a critical role in lipid metabolism. Excitingly, our preliminary data reveal that acute alcohol challenge doubled the activity of IRE11 in the liver within minutes, suggesting that ER stress occurs at an early stage following alcohol consumption. Moreover, ER stress was observed in two chronic-binge drinking mouse models with more severe forms of liver injury. Hence, the goal of this R21 proposal is to delineate the role of the IRE11-XBP1 branch in the pathogenesis of alcoholic fatty liver disease. We hypothesize that the IRE11-XBP1 branch of UPR directly regulates the lipogenic program in the liver in response to chronic-binge alcohol drinking, thereby playing a key role in the pathogenesis of alcoholic fatty liver disease. This hypothesis identifies the IRE11-XBP1 branch and ER homoeostasis as key components linking chronic-binge alcohol drinking and alcoholic fatty liver disease. Using state of the art methodology (e.g. adenoviral shRNA to achieve gene- and liver-specific temporal knockdown, Phos-tag-based method to quantitate ER stress under physiological conditions and tissue ChIP-qPCR to quantitate the binding of a transcription factor to specific gene promoters in the liver), we will test this hypothesis with the following Aims: (1) To determine how modulation of the IRE11-XBP1 pathway affects the pathogenesis of alcoholic fatty liver; (2) To explore the fundamental mechanism by which the IRE11-XBP1 pathway regulates lipogenic genes in response to alcohol. If successful, this study will establish, for the first time to our knowledge, a causal relationship between the UPR and alcoholic fatty liver disease. Relevance to human health: Excessive alcohol intake is a leading cause of chronic liver disease worldwide. Of those who drink (over 50% adults in US), about 29% report binge drinking on multiple occasions each month (i.e. chronic-binge drinkers), which results in about 1.5 billion episodes of binge drinking in the US each year. Fatty liver disease, one of the earliest and most common consequences of excessive heavy or binge drinking, can lead to more severe forms of liver injuries, including hepatitis, cirrhosis, and hepatocellular carcinoma. Our study will provide critical insights into the pathogenesis of alcohol-induced fatty liver disease. This study, if successful, may delineate key signaling pathways in alcoholic liver disease and identify new targets for preventing and treating alcoholic liver diseases as well as other forms of liver diseases.