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，这是美国第七大死因。由于肝脏是乙醇代谢的主要部位，它是最容易受到酒精性损伤的器官。尽管酒精性肝病的进展在临床上有很好的描述，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诱导肝毒性的机制。我们最近的研究是在极化的肝wi - b细胞中进行的，这是一种用于研究酒精性肝损伤的新兴模型系统。我们发现微管在酒精处理的wi - b细胞中更稳定和高乙酰化。我们还发现增加的微管乙酰化和稳定性依赖于乙醇代谢，并且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观察在生理学上的重要性。在本提案中，我们探讨了围绕TNF-1和il -6介导的信号传导的一个有趣的悖论。这些细胞因子的水平在酗酒的人类病人和酒精喂养的动物中都有所增加，因为它们会产生促炎反应。然而，这两种配体也被认为能促进肝脏保护活性，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TNF-1和IL-6的循环水平很高，但它们的肝保护和肝源性作用选择性地丧失了？这个建议集中在两个主要问题上来解释这个悖论。首先，微管乙酰化和稳定性的增加是否会通过损害受体运输来改变IL-6和tnf -1介导的信号传导（Aim 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易位来改变IL-6和tnf -1介导的信号传导（目的2）？我们的研究将从wi - b细胞开始，并在精确切割的肝脏切片中得到证实，这是一个更符合生理学的模型系统。我们在wi - b细胞生物学和极化肝蛋白运输方面的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进一步了解酒精引起的肝毒性。

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.