Redox Modification of Thiols in Alcohol Hepatotoxicity

描述(申请人提供)：长期饮酒通过一个复杂的过程导致肝脏损伤，包括氧化和亚硝化应激，缺氧，促炎细胞因子上调，以及能量代谢缺陷。线粒体既是活性氧和氮物种(ROS/RNS)介导的修饰的来源和靶点，也是细胞应激反应中的关键部位。越来越多的证据表明，ROS/RNS介导的应激破坏了线粒体的功能。线粒体蛋白质的硫醇氧化还原状态的改变被认为在调节线粒体的一些功能方面具有重要意义，包括呼吸、细胞因子信号转导、线粒体通透性转换和细胞凋亡。长期饮酒的影响与线粒体蛋白质硫醇状态变化之间的相似性有力地支持了线粒体蛋白质硫醇氧化导致酒精诱导的细胞死亡的机制联系。最近的研究表明，S-腺苷甲硫氨酸对酒精性肝损伤的治疗作用是通过线粒体途径实现的。在这项建议中，假设长期饮酒期间服用SAM将通过硫醇依赖机制保护肝脏线粒体功能，以应对ROS/RNS的增加。因此，该项目的总体目标是确定将SAM介导的保护与ROS/RNS对慢性酒精反应中线粒体功能的影响联系起来的机制。这些概念将通过追求以下特定目的在一个具有良好特征的慢性酒精消费导致肝脏线粒体功能障碍的大鼠模型中得到验证：(1)确定SAM在慢性酒精介导的线粒体蛋白硫醇氧化还原状态调节中的作用。(2)测定补充SAM对慢性酒精所致线粒体呼吸NO依赖控制改变的影响。(3)研究SAM对酒精诱导的线粒体DNA损伤、线粒体蛋白质合成缺陷以及BAP37/BAP37在呼吸复合体组装中的调节作用。这些研究将为酒精中毒中线粒体蛋白硫醇的氧化还原调节机制提供新的信息。还将获得有关SAM分子靶点的新信息，这将使设计有效的治疗策略来治疗肝脏疾病。

DESCRIPTION (provided by applicant): Chronic alcohol consumption causes liver damage by a complex process involving oxidative and nitrosative stress, hypoxia, upregulation of proinflammatory cytokines, and defects in energy metabolism. As both a source for the formation and target of modifications mediated by reactive oxygen and nitrogen species (ROS/RNS), the mitochondrion is recognized as a site critical in cellular stress responses. Emerging evidence indicates that ROS/RNS-mediated stress disrupts mitochondrial function. Changes in the thiol redox status of mitochondrial proteins is proposed to be important in regulating several mitochondrial functions including respiration, cytokine signaling, the mitochondria permeability transition, and apoptosis. The similarity between the effects of chronic alcohol consumption and changes in mitochondrial protein thiol status strongly supports a mechanistic link for the oxidation of protein thiols in mitochondria contributing to alcohol-induced cell death. Recent studies have suggested that the therapeutic effects of S-adenosylmethionine (SAM) in treating alcohol-induced liver injury are mediated though mitochondrial pathways. In this proposal it is hypothesized that SAM administration during chronic alcohol consumption will preserve hepatic mitochondrial function in response to increases in ROS/RNS through thiol-dependent mechanisms. Thus, the overall goal of this project is to identify mechanisms that link SAM-mediated protection to the effects of ROS/RNS on mitochondrial function in response to chronic alcohol. These concepts will be tested by the pursuit of the following Specific Aims in a well characterized rat model of chronic alcohol consumption which produces mitochondrial dysfunction in liver: (1) Determine the effects of SAM on chronic alcohol-mediated modulation of mitochondrial protein thiol redox status. (2) Determine the effect of SAM supplementation on chronic alcohol-induced changes in NO-dependent control of mitochondrial respiration. (3) Characterize the influence of SAM administration on alcohol-induced mtDNA damage, mitochondrial protein synthesis defects, and the regulatory function of prohibitin/BAP37 in respiratory complex assembly. These studies will generate novel information on the mechanisms of redox regulation of mitochondrial protein thiols in alcohol toxicity. New information on the molecular targets of SAM will also be achieved, which will enable the design of effective therapeutic strategies to treat liver diseases.