Homocysteine and Alcoholic Liver Disease

描述（由申请人提供）：与酒精滥用相关的公共卫生问题，经济影响和人类痛苦是惊人的。尽管酒精相关的研究已经进行了几十年，但关于酒精诱导的组织损伤机制仍有许多未解之谜。血中高同型半胱氨酸（高同型半胱氨酸血症）与慢性酒精中毒密切相关。然而，酗酒者同型半胱氨酸升高的分子机制在很大程度上是未知的。更重要的是高同型半胱氨酸血症在这些个体中的病理影响和临床后果。该提案将提供新的信息蛋氨酸合成酶（MS）在酒精相关的高同型半胱氨酸血症，同型半胱氨酸诱导的氧化和内质网（ER）应激模型中的酒精性肝病（ALD），和酒精处理的细胞和肝脏的一碳蛋白质组和代谢组的变化的作用。本研究的核心假设是：1）酒精诱导的肝脏氧化应激将导致B12依赖性MS的失活; 2）同型半胱氨酸的再甲基化受损导致细胞内同型半胱氨酸升高和高同型半胱氨酸血症; 3）同型半胱氨酸对特定细胞内蛋白质的分子靶向作用导致活性氧（ROS）产生增加、内质网应激和细胞凋亡;和，4）肝脏的一碳蛋白质组和代谢组在ALD中显著改变。该项目的具体目标是：1。确定B12依赖性MS在培养的乙醇处理细胞和乙醇喂养大鼠肝脏中失活的机制; 2.确立L-高半胱氨酸对特定蛋白质的分子靶向在酒精处理的细胞和大鼠中氧化应激的产生和ER应激的诱导中的作用;以及，3.以确定伴随ALD的SAM/SAH比率降低是否是（a）酒精或其代谢物对甲硫氨酸循环酶的水平和/或活性的直接结果，或（B）伴随酒精消耗增加的高同型半胱氨酸血症的间接结果。这些假设将在细胞水平上使用培养的酒精处理或未处理的HepG 2 E47和C34细胞进行测试，并在体内使用Lieber-DeCarli乙醇喂养模型和成对喂养对照大鼠的肝脏进行测试。从这一建议中获得的机制见解可能有助于建立新的治疗干预酒精性肝病的治疗。公共卫生相关性：与酗酒相关的公共卫生问题、经济影响和人类痛苦令人震惊。血中高同型半胱氨酸（高同型半胱氨酸血症）与慢性酒精中毒密切相关。然而，同型半胱氨酸升高的分子原因及其在酒精中毒中介导组织损伤的作用在很大程度上是未知的。这一建议将提供高同型半胱氨酸血症的原因及其对慢性酒精滥用组织的有害影响的机制的见解。

DESCRIPTION (provided by applicant): The public health issues, economic impact and human suffering associated with alcohol abuse are staggering. Although alcohol-related research has been on-going for decades, there are many unanswered questions concerning mechanisms of alcohol-induced tissue injury. Elevated blood homocysteine (hyperhomocysteinemia) is strongly associated with chronic alcoholism. However, the molecular mechanism of elevated homocysteine in alcohol abusers is largely unknown. Of greater importance is the pathological impact and clinical consequences of hyperhomocysteinemia in these individuals. This proposal will provide novel information on the role of methionine synthase (MS) in alcohol-associated hyperhomocysteinemia, homocysteine-induced oxidative and endoplasmic reticulum (ER) stress in models of alcoholic liver disease (ALD), and changes in the one-carbon proteome and metabolome of alcohol-treated cells and liver. The central hypotheses that drive this project are: 1) alcohol-induced oxidative stress in the liver will lead to the inactivation of B12-dependent MS; 2) impaired remethylation of homocysteine results in elevated intracellular homocysteine and hyperhomocysteinemia; 3) molecular targeting of specific intracellular proteins by homocysteine causes enhanced production of reactive oxygen species (ROS), ER stress, and apoptosis; and, 4) the one-carbon proteome and metabolome of the liver is substantially altered in ALD. The specific aims of this project are: 1. to determine the mechanism of inactivation of B12-dependent MS in alcohol-treated cells in culture and in livers from ethanol-fed rats; 2. to establish the role that molecular targeting of specific proteins by L-homocysteine has in the generation of oxidative stress and in the induction of ER stress in alcohol-treated cells and rats; and, 3. to determine whether the decreased SAM/SAH ratio that accompanies ALD is (a) a direct result of alcohol or its metabolites on the levels and/or activities of the methionine cycle enzymes, or (b) an indirect result of the hyperhomocysteinemia that accompanies increased alcohol consumption. These hypotheses will be tested at the cellular level using cultured alcohol-treated or untreated HepG2 E47 and C34 cells and in vivo using livers from rats on the Lieber-DeCarli ethanol feeding model and pair-fed controls. The mechanistic insight gained from this proposal may be useful for establishing novel therapeutic interventions in the treatment of alcoholic liver disease. PUBLIC HEALTH RELEVANCE: The public health issues, economic impact and human suffering associated with alcohol abuse are staggering. Elevated blood homocysteine (hyperhomocysteinemia) is strongly associated with chronic alcoholism. However, the molecular cause of elevated homocysteine and its role in mediating tissue injury in alcoholism is largely unknown. This proposal will provide mechanistic insight on the cause of hyperhomocysteinemia and its deleterious effects to tissues in chronic alcohol abuse.