Alcohol-induced changes in hepatic microtubules: mechanisms and consequences

描述(申请人提供)：每年有2万多人死于酒精性肝病，这是美国人的第七大死因。因为肝脏是酒精代谢的主要部位，所以它是最容易受到酒精损伤的器官。尽管酒精性肝病的进展在临床上已有很好的描述，但酒精性肝损伤的分子基础尚不清楚。我们的长期目标是了解导致酒精肝毒性的机制。我们最近的研究是在极化的肝脏WIF-B细胞上进行的，这是一种研究酒精性肝损伤的新兴模型系统。我们发现，在酒精处理的WIF-B细胞中，微管更加稳定和高乙酰化。我们还发现，微管乙酰化和稳定性的增加依赖于乙醇的代谢，可能是酒精诱导的内吞和分泌缺陷的原因。这些结果已经在酒精喂养的大鼠的肝脏和酒精处理的肝脏切片中得到证实，这表明了我们的WIF-B观察的生理学重要性。在这个提案中，我们探索了一个围绕着肿瘤坏死因子-1和白介素6介导的信号传递的有趣的悖论。在酒精中毒的人类患者和酒精喂养的动物中，这些细胞因子中的每一种水平都会增加，因为它们会产生促炎反应。然而，这两种配体也都已知可以促进肝脏保护活性，并且是肝脏再生所必需的。为什么在酒精处理的肝细胞中，尽管它们的循环水平很高，但肿瘤坏死因子-1和白介素6的保肝和促肝分裂作用却选择性地消失了？这一建议集中在两个主要问题上来解释这一悖论。首先，微管乙酰化和稳定性的增加是否会通过损害受体的转运来改变IL-6和TNF-1介导的信号传递(目标1)？其次，微管乙酰化和稳定性的增加是否会通过损害相关转录因子的核转位来改变IL-6和TNF-1介导的信号传递(目标2)？我们的研究将在WIF-B细胞中启动，并在精确切割的肝脏切片中得到证实，这是一种更具生理学相关性的模型系统。我们在WIF-B细胞生物学和极化肝蛋白运输方面的丰富专业知识使我们能够进行这些机械实验。这些新的研究领域有望使我们对酒精肝毒性有更深入的了解。 与公共健康相关：大约75%的美国人饮酒，每年有10万人死于饮酒。在这些死亡中，超过2万人是由肝硬变引起的，这是美国人的第七大死因。显然，酒精性肝病在美国是一个主要的生物医学健康问题。

DESCRIPTION (provided by applicant): More than 20,000 people each year die of alcoholic liver disease, the seventh largest cause of death in Americans. Because the liver is the major site of ethanol metabolism, it is the most susceptible organ to alcohol-induced injury. Although the progression of alcoholic liver disease is well-described clinically, the molecular basis for alcohol-induced liver injury is not understood. Our long-term goal is to understand the mechanisms that lead to alcohol-induced hepatotoxicity. Our recent studies have been performed in the polarized, hepatic WIF-B cells, an emerging model system for the study of alcohol-induced liver injury. We found that microtubules are more stable and hyperacetylated in alcohol-treated WIF-B cells. We also found that increased microtubule acetylation and stability is dependent on ethanol metabolism and is likely responsible for alcohol-induced defects in endocytosis and secretion. These results have been confirmed in livers from ethanol-fed rats and in ethanol-treated liver slices indicating the physiologic importance of our WIF- B observations. In this proposal we explore an interesting paradox surrounding TNF-1 and IL-6-mediated signaling. The levels of each of these cytokines are increased in alcoholic human patients and in ethanol-fed animals where they exert proinflammatory responses. However, both of these ligands are also known to promote hepatoprotective activities and are required for liver regeneration. Why are the hepatoprotective and hepatomitogenic effects of TNF-1 and IL-6 selectively lost in alcohol-treated hepatocytes despite their high circulating levels? This proposal focuses on two major questions to explain this paradox. First, does increased microtubule acetylation and stability alter IL-6 and TNF-1-mediated signaling by impairing receptor trafficking (Aim 1)? Secondly, does increased microtubule acetylation and stability alter IL-6 and TNF-1-mediated signaling by impairing the nuclear translocation of the associated transcription factors (Aim 2)? Our studies will be initiated in WIF-B cells and confirmed in precision-cut liver slices, a more physiologically relevant model system. Our considerable expertise in WIF-B cell biology and in polarized hepatic protein trafficking well- situates us to perform these mechanistic experiments. These novel research areas will hopefully lead to our further understanding of alcohol-induced hepatotoxicity. PUBLIC HEALTH RELEVANCE: Approximately 75% of all Americans consume alcohol and 100,000 deaths per year are attributed to alcohol consumption. Of those deaths, greater than 20,000 are caused by cirrhosis of the liver, the seventh largest cause of death in Americans. Clearly, alcoholic liver disease is a major biomedical health concern in the United States.