Ethanol-Induced VDAC Closure in Hepatocytes

乙醇诱导肝细胞中的 VDAC 关闭

• 批准号: 7270105
• 负责人: EKHSON Lukmanovich HOLMUHAMEDOV
• 金额: $ 16.83万
• 依托单位: UNIV OF NORTH CAROLINA CHAPEL HILL
• 依托单位国家: 美国
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-08-01 至 2009-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7270105
• 关键词: Acetaldehyde; Acetates; Acetoacetates; Acetylcarnitine; Acute; Address; Affect; Alcohol consumption; Alcohol dehydrogenase; Alcoholic Liver Diseases; Biochemical; Carnitine; Closure; Complex; Confocal Microscopy; Cyanamide; Cytochrome P450; Cytochromes; Cytosol; Data; Dextrans; Digitonin; Esters; Ethanol; Ethanol Metabolism; Ethanol dependence; Event; Exposure to; Fatty Liver; Fatty acid glycerol esters; Figs - dietary; Glycogen; Glycolysis; Hepatic; Hepatocyte; Hydroxybutyrates; In Situ; Intervention; Lipids; Liver; Malates; Measures; Mediating; Membrane; Metabolism; Methods; Microscopic; Mitochondria; Molecular Weight; Monitor; Movement; NADH; Nonesterified Fatty Acids; Outer Mitochondrial Membrane; Oxidation-Reduction; Oxygen; Pathway interactions; Permeability; Physiological; Principal Investigator; Proteins; Protons; Pyruvate; Pyruvates; Rattus; Reaction; Reactive Oxygen Species; Regulation; Respiration; Rhodamine; Rhodamines; Risk; Role; Succinates; System; Techniques; Transferase; Volatile Fatty Acids; Voltage-Dependent Anion Channel; Voltage-Dependent_Anion_Channel-1; Water; acetaldehyde dehydrogenase; adenylate kinase; alcohol effect; alcohol exposure; alcohol measurement; beta-Hydroxybutyrate; dextran; fatty acid oxidation; fomepizole; inhibitor/antagonist; long chain fatty acid; malate; mitochondrial dysfunction; novel; oxidation; prevent; programs; research study; respiratory; response; rhodamine dextran; solute; succinate

DESCRIPTION (provided by applicant): Ethanol ingestion produces rapid changes in hepatic mitochondrial metabolism. These changes include a swift increase in alcohol metabolism (SIAM) by alcohol dehydrogenase (ADH) and acetaldehyde dehydrogenase (ACDH), a near doubling of respiration, decreased ATP, activated glycolysis, glycogen depletion, inhibition of mitochondrial oxidation of medium and long chain fatty acids, and fatty liver changes (steatosis). The unifying hypothesis of this proposal is that closure of mitochondrial voltage dependent anion channels (VDAC) is a critical event leading to these acute alterations of mitochondrial metabolism after ethanol. VDAC is located in the mitochondrial outer membrane and conducts solutes of molecular weight less than 5 kDa into and out of the mitochondria. Open VDAC is essential for movement of respiratory substrates (e.g., medium and long chain fatty acids, pyruvate), ATP, ADP, Pi and other polar metabolites into and out of mitochondria. We specifically hypothesize that VDAC closure after ethanol blocks these exchanges. After VDAC closure, mitochondria still oxidize membrane permeant respiratory substrates, particularly acetaldehyde and short chain fatty acids. Inhibition of ATP release and the high redox potential of acetaldehyde/acetate then produce mitochondrial hyperpolarization, leading to non-ohmic proton leaks in the hperpolarized inner membrane and respiratory stimulation. Activation of uncoupling proteins and the weak uncoupling effect of acetate may also contribute to increased respiratory flux. Overall, accelerated respiration and selective oxidation of acetaldehyde have the physiological function of removing and detoxifying ethanol. Heretofore, examination of VDAC conductivity in situ has been very difficult. In our preliminary studies, we developed a novel confocal microscopic technique utilizing the distribution of a 3 kDa rhodamine-conjugated dextran in the mitochondria of permeabilized hepatocytes to assess the open/closed status of VDAC. These pilot experiments support the hypothesis that acute ethanol exposure induces VDAC closure. Accordingly,our Specific Aims are 1) to characterize changes of VDAC permeability in rat hepatocytes exposed to ethanol from measurements of respiration and RhoDex retention by permeabilized hepatocytes and isolated mitochondria; and 2). to determine which metabolites of ethanol oxidation (NADH, ROS, acetaldehyde,acetate) are responsible for ethanol-induced VDAC closure or whether closure is a direct effect of ethanol. Overall, this proposal addresses the high risk, high return hypothesis that VDAC closure after ethanol exposure causes mitochondrial dysfunction and promotes steatosis. If our preliminary data supporting this hypothesis can be extended, this new role of VDAC will represent a paradigm shift in our understanding of the effects of alcohol on the liver and the regulation of mitochondrial metabolism.

描述（由申请人提供）：乙醇摄入会引起肝脏线粒体代谢的快速变化。这些变化包括酒精脱氢酶（ADH）和乙醛脱氢酶（ACDH）的酒精代谢（SIAM）迅速增加，呼吸几乎加倍，ATP减少，糖酵解激活，糖原消耗，中链和长链脂肪酸的线粒体氧化抑制，以及脂肪肝变化（脂肪变性）。该提议的统一假设是，线粒体电压依赖性阴离子通道（VDAC）的关闭是导致乙醇后线粒体代谢急性改变的关键事件。VDAC位于线粒体外膜，引导分子量小于5kda的溶质进出线粒体。开放的VDAC对于呼吸底物（如中、长链脂肪酸、丙酮酸）、ATP、ADP、Pi等极性代谢物进出线粒体的运动至关重要。我们特别假设，乙醇后的VDAC关闭阻断了这些交换。在VDAC关闭后，线粒体仍然氧化膜透呼吸底物，特别是乙醛和短链脂肪酸。抑制ATP释放和高氧化还原电位