Alcohol-induced changes in hepatic microtubules: mechanisms and consequences

描述（由申请人提供）：每年有超过20，000人死于酒精性肝病，这是美国人的第七大死因。由于肝脏是乙醇代谢的主要场所，因此它是最易受酒精诱导损伤的器官。虽然酒精性肝病的进展在临床上得到了很好的描述，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诱导的肝毒性的机制。我们最近的研究是在极化的肝WIF-B细胞中进行的，这是一种用于研究酒精诱导的肝损伤的新兴模型系统。我们发现，微管在酒精处理的WIF-B细胞中更稳定和高度乙酰化。我们还发现，增加微管乙酰化和稳定性是依赖于乙醇代谢，并可能是负责酒精诱导的缺陷，内吞和分泌。这些结果已在乙醇喂养大鼠的肝脏和乙醇处理的肝脏切片中得到证实，表明我们的WIF- B观察结果的生理重要性。在这个建议中，我们探讨了一个有趣的悖论周围TNF-1和IL-6介导的信号。这些细胞因子中的每一种的水平在酗酒的人类患者和乙醇喂养的动物中增加，其中它们发挥促炎反应。然而，这两种配体也已知促进肝保护活性，并且是肝再生所需的。为什么TNF-1和IL-6的肝保护和促肝细胞有丝分裂作用在酒精处理的肝细胞中选择性丧失，尽管它们的循环水平很高？这个建议集中在两个主要问题来解释这个悖论。首先，增加微管乙酰化和稳定性是否通过损害受体运输改变IL-6和TNF-1介导的信号传导（目的1）？其次，增加微管乙酰化和稳定性是否通过损害相关转录因子的核转位来改变IL-6和TNF-1介导的信号传导（目的2）？我们的研究将在WIF-B细胞中开始，并在精确切割的肝脏切片中得到证实，这是一种生理学上更相关的模型系统。我们在WIF-B细胞生物学和极化肝蛋白运输方面的大量专业知识使我们能够进行这些机制实验。这些新的研究领域将有望导致我们进一步了解酒精诱导的肝毒性。 公共卫生相关性：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20，000人是由肝硬化引起的，肝硬化是美国人的第七大死亡原因。显然，酒精性肝病是美国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.