Homocysteine and Alcoholic Liver Disease

描述(由申请人提供)：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。尽管与酒精相关的研究已经进行了几十年，但关于酒精所致组织损伤的机制仍有许多悬而未决的问题。血液同型半胱氨酸升高(高同型半胱氨酸血症)与慢性酒精中毒密切相关。然而，酒精滥用者同型半胱氨酸升高的分子机制在很大程度上还不清楚。更重要的是高同型半胱氨酸血症对这些人的病理影响和临床后果。本研究将为甲硫氨酸合成酶(MS)在酒精性高同型半胱氨酸血症、酒精性肝病(ALD)模型中同型半胱氨酸诱导的氧化和内质网(ER)应激以及酒精处理细胞和肝脏的单碳蛋白质组和代谢组改变中的作用提供新的信息。推动该项目的核心假设是：1)酒精诱导的肝脏氧化应激将导致依赖B12的MS失活；2)同型半胱氨酸的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的分子靶向导致活性氧物种(ROS)的产生增加，内质网应激和细胞凋亡；以及，4)ALD时肝脏的单碳蛋白质组和代谢组显著改变。本项目的具体目的是：1.确定酒精处理细胞和酒精喂养大鼠肝脏中依赖B12的MS失活的机制；2.确定L同型半胱氨酸针对特定蛋白质的分子靶向在酒精处理细胞和大鼠氧化应激产生和诱导ER应激中的作用；以及3.确定酒精或其代谢产物对蛋氨酸循环酶水平和/或活性的影响是否(A)酒精或其代谢产物对蛋氨酸循环酶水平和/或活性的直接结果，或(B)伴随酒精摄入量增加的高同型半胱氨酸血症的间接结果。这些假说将通过酒精处理或未处理的培养的HepG2 E47和C34细胞在细胞水平上进行测试，并在体内使用Lieber-DeCarli乙醇喂养模型和配对喂养对照组的大鼠肝脏进行验证。从这一建议中获得的机制洞察力可能有助于建立治疗酒精性肝病的新的治疗干预措施。与公共健康相关：与酗酒相关的公共健康问题、经济影响和人类痛苦令人震惊。血液同型半胱氨酸升高(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调节组织损伤中的作用在很大程度上是未知的。这项提议将为慢性酒精滥用中高同型半胱氨酸血症的原因及其对组织的有害影响提供机械性的见解。

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.