Dissecting the Role of Unfolded Protein Response in Alcoholic Liver Disease

描述(申请人提供)：酗酒威胁美国数百万美国人的健康。酒精性脂肪性肝病或脂肪变性是过量饮酒最早和最常见的后果之一，可导致更严重的肝脏损伤，包括肝硬变、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意义和基础性意义。最近的研究表明，内质网应激反应(ER)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，因为内质网是脂质生物合成、脂滴生物发生和酒精解毒的主要部位，而且据报道肝脏内质网在酒精中扩大。然而，内质网应激与酒精性脂肪肝之间的因果关系尚未确定。我们和其他人最近发现，UPR途径的IRE11-XBP1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，急性酒精攻击在几分钟内使肝脏中IRE11的活性增加了一倍，这表明内质网应激发生在饮酒后的早期阶段。此外，在两种长期酗酒的小鼠模型中观察到了内质网应激，这些小鼠的肝脏损伤形式更严重。因此，这个R21提案的目标是描述IRE11-XBP1分支在酒精性脂肪性肝病发病机制中的作用。我们推测，UPR的IRE11-XBP1分支直接调节肝脏对长期酗酒的造脂程序，从而在酒精性脂肪性肝病的发病机制中发挥关键作用。这一假说认为，IRE11-XBP1分支和内质网稳态是连接长期酗酒和酒精性脂肪肝的关键成分。我们将使用最先进的方法(如腺病毒shRNA实现基因和肝脏特异性的时间敲除，基于PHOS-Tag的方法来定量生理条件下的内质网应激，以及组织芯片-qPCR来定量转录因子与肝脏中特定基因启动子的结合)来验证这一假说，目的如下：(1)确定IRE11-XBP1途径的调节如何影响酒精性脂肪肝的发病机制；(2)探讨IRE11-XBP1途径调节酒精反应中脂肪生成基因的基本机制。如果成功，据我们所知，这项研究将首次确定UPR和酒精性脂肪肝之间的因果关系。与人类健康相关：过量饮酒是全球慢性肝病的主要原因。在饮酒者(美国超过50%的成年人)中，约29%的人报告每月在多个场合狂饮(即慢性狂饮者)，这导致美国每年约有15亿次狂饮。脂肪肝是过量饮酒最早和最常见的后果之一，可导致更严重的肝脏损伤，包括肝炎、肝硬变和肝细胞癌。我们的研究将为酒精性脂肪性肝病的发病机制提供重要的见解。如果这项研究成功，可能会勾勒出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。 与公共健康相关：内质网(ER)是一种动态的细胞结构，在长期饮酒的基础上扩张。这项建议验证了一种新的假设，即饮酒后ER应激反应的IRE11-XBP1通路的激活通过直接调节造脂程序，在酒精性肝脂肪变性(脂肪肝)的发病机制中起重要作用。这项研究如果成功，可能会建立内质网应激与酒精性脂肪肝之间的因果关系，并为过度酗酒或酗酒加剧的情况下的药物干预提供一个或多个候选靶点。

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. PUBLIC HEALTH RELEVANCE: Endoplasmic reticulum (ER) is a dynamic cellular structure that expands upon chronic alcohol drinking. This proposal tests a novel hypothesis that the activation of the IRE11-XBP1 pathway of the ER stress response upon alcohol consumption contributes significantly to the pathogenesis of alcoholic hepatic steatosis (faty liver) through direct regulation of the lipogenic program. This study, if successful, may establish a causal relationship between ER stress and alcoholic fatty liver, and provide one or more candidate targets for drug intervention in conditions exacerbated by excessive heavy or binge drinking.