Mechanisms of Sensitization to TNF hepatotoxicity in ALD

ALD 中 TNF 肝毒性的致敏机制

• 批准号: 6970454
• 负责人: ZHENYUAN SONG
• 金额: $ 10.02万
• 依托单位: UNIVERSITY OF LOUISVILLE
• 依托单位国家: 美国
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-09-15 至 2010-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6970454
• 关键词: S adenosylmethionine; alcoholic beverage consumption; alcoholic fatty liver; alcoholic liver cirrhosis; alcoholism /alcohol abuse; cysteine endopeptidases; enzyme activity; enzyme inhibitors; enzyme linked immunosorbent assay; gel mobility shift assay; hepatotoxin; laboratory rat; liver toxic disorder; methionine; polymerase chain reaction; terminal nick end labeling; tissue /cell culture; transmethylation; tumor necrosis factor alpha

DESCRIPTION (provided by applicant): Alcoholic liver disease (ALD) continues to be an important health problem in the United States. Abnormal hepatic methionine metabolism is an acquired metabolic abnormality in ALD and the effects of chronic alcohol intake on hepatic methionine metabolism are initially seemingly paradoxic. Whereas alcohol consumption causes hepatic deficiency of S-adenosylmethionie (SAMe), it elevates hepatic homocysteine levels, a product of SAMe metabolism. Decreased SAMe levels and elevated homocysteine levels may contribute to alcohol induced liver injury. The effect of alcohol on S-adenosylhomocysteine (SAH) levels, another metabolite in the methionine metabolism pathway, has received little investigative attention. It is our working hypothesis that tumor necrosis factor (TNF) in conjunction with certain metabolic abnormalities observed in ALD, such as altered intracellular methylation status due to abnormal methionine/SAMe/SAH metabolism play an etiologic role in the development of liver injury in ALD. We postulate that chronic alcohol abuse causes increased gut permeability and endotoxemia, generation of reactive oxygen intermediates, activation of Kupffer cell NFkB with increased TNF production, decreased hepatocyte MAT activity with subsequent SAMe deficiency, increased S-adenosylhomocysteine (SAH) concentrations, inhibition of transmethylation reactions, decreased hepatic methylation status, elevated expression/ activation/activity of proteins sensitive to intracellular methylation status such as caspase-8, mitochondrial dysfunction, increased susceptibility to hepatic TNF cytotoxicity, and subsequent liver injury. In this proposal, we will evaluate inhibition of hepatic transmethylation reactions by chronic alcohol exposure as a mechanism for hepatic sensitization to TNF-induced cytotoxicity in a relevant model of ALD. The specific objectives of this project are as follows: 1. Evaluate the effects of inhibition of hepatic transmethylation reactions on "sensitization" to TNF hepatotoxicity; 2. Investigate possible mechanisms by which inhibition of transmethylation reactions sensitizes hepatocytes to TNF hepatotoxicity; and 3. Evaluate the effects of chronic alcohol consumption (+/- SAMe supplementation) on hepatic methylation status and sensitization to TNF-hepatotoxicity in rats intragastrically fed alcohol. This research will be performed with structured mentoring support and a detailed training program designed to maximize my opportunity to become an independent NIH-funded investigator.

描述（由申请人提供）：酒精性肝病（ALD）仍然是美国的一个重要健康问题。肝脏蛋氨酸代谢异常是 ALD 中的一种获得性代谢异常，长期饮酒对肝脏蛋氨酸代谢的影响最初似乎是矛盾的。饮酒会导致肝脏缺乏 S-腺苷甲硫氨酸 (SAMe)，但它会升高肝脏同型半胱氨酸水平（SAMe 代谢的产物）。 SAMe 水平降低和同型半胱氨酸水平升高可能导致酒精性肝损伤。酒精对蛋氨酸代谢途径中另一种代谢物 S-腺苷高半胱氨酸 (SAH) 水平的影响很少受到研究关注。我们的工作假设是，肿瘤坏死因子 (TNF) 与 ALD 中观察到的某些代谢异常（例如由于蛋氨酸/SAMe/SAH 代谢异常导致的细胞内甲基化状态改变）一起在 ALD 肝损伤的发生中发挥病因作用。我们假设长期酗酒会导致肠道通透性增加和内毒素血症、活性氧中间体的产生、库普弗细胞NFkB的激活以及TNF产生的增加、肝细胞MAT活性的降低以及随后的SAMe缺乏、S-腺苷同型半胱氨酸（SAH）浓度的增加、转甲基化的抑制反应、肝甲基化状态降低、对细胞内甲基化状态敏感的蛋白质（如 caspase-8）的表达/激活/活性升高、线粒体功能障碍、增加对肝脏 TNF 细胞毒性和随后的肝损伤的易感性。在本提案中，我们将评估慢性酒精暴露对肝转甲基化反应的抑制作用，作为肝脏对 TNF 诱导的细胞毒性敏感的相关 ALD 模型中的机制。该项目的具体目标如下： 1. 评估抑制肝转甲基反应对TNF肝毒性“致敏”的影响； 2. 研究抑制转甲基反应使肝细胞对TNF肝毒性敏感的可能机制； 3. 评估长期饮酒（+/- SAMe 补充）对灌胃酒精大鼠的肝甲基化状态和 TNF-肝毒性敏感性的影响。 这项研究将在结构化的指导支持和详细的培训计划下进行，旨在最大限度地提高我成为 NIH 资助的独立研究者的机会。