Role of Mitochondria in the Regulation of Iron metabolism by Alcohol

描述（申请人提供）：线粒体在铁代谢中起关键作用，并在酒精性肝损伤中发挥作用。酒精会改变线粒体功能，导致氧化应激。我们已经证明，酒精诱导的氧化应激下调hepcidin转录，而不会引起肝脏组织学的变化或甘油三酯的增加。Hepcidin是一种在肝脏中合成的循环肽。它通过调节肠道和网状内皮铁运输在铁稳态中起核心作用。因此，酒精处理的动物表现出十二指肠铁转运蛋白和肝脏铁储存蛋白铁蛋白表达的增加。酒精还使肝脏中的肝磷脂合成对体内铁水平不敏感。值得注意的是，hepcidin通过抑制铁转运来保护机体免受铁超载。因此，酒精可能破坏hepcidin的这种保护机制，这可能对酒精性肝病（ALD）有影响。值得注意的是，ALD患者和ALD动物模型显示铁超载，但潜在的机制尚不清楚。我们的研究结果表明，肝脏中hepcidin合成的失调可能是ALD中观察到的铁过载的潜在机制之一。抗氧化剂消除了酒精对hepcidin表达的影响。多种途径在酒精诱导的氧化应激中发挥作用，包括Kupffer细胞、CYP2E1酶的激活和线粒体功能的改变。我们的初步结果排除了Kupffer细胞、TNF α细胞因子和CYP2E1在酒精介导的肝脏氧化应激对hepcidin表达的调节中的作用。线粒体也参与了酒精介导的氧化应激。酒精诱导电子传递链蛋白质的损伤，减少线粒体中ATP/ADP的易位和ATP的合成。我们的初步结果表明线粒体在hepcidin表达调控中的作用。抑制线粒体中DNA和蛋白质的合成导致HepG2肝癌细胞中hepcidin的表达显著降低。线粒体在细胞凋亡中起关键作用，酒精介导的线粒体变化诱导细胞凋亡刺激。然而，凋亡在hepcidin表达调控中的作用尚不清楚。我们的初步研究结果表明，fas介导的细胞凋亡下调肝脏中hepcidin的表达。本应用的目的是确定线粒体通过酒精调节肝脏hepcidin表达和铁代谢的分子机制。我们的中心假设是乙醇诱导的线粒体结构和功能的修饰在酒精调节hepcidin转录中起关键作用。我们将利用缺乏线粒体抗氧化酶、腺嘌呤核苷酸转运、细胞色素c氧化酶活性或缺氧诱导转录因子二聚化的转基因小鼠模型，研究酒精介导的氧化应激对hepcidin转录的调控。从这些研究中获得的知识，描述了线粒体的关键作用，将使我们能够确定铁和酒精在ALD患者中引起肝损伤的机制。

DESCRIPTION (provided by applicant): Mitochondria are critical in iron metabolism and play a role in alcohol-induced liver injury. Alcohol alters mitochondrial function and leads to oxidative stress. We have demonstrated that alcohol-induced oxidative stress down-regulates hepcidin transcription without causing changes in liver histology or an increase in triglycerides. Hepcidin is a circulatory peptide synthesized in the liver. It plays a central role in iron homeostasis by regulating both intestinal and reticulo-endothelial iron transport. Accordingly, alcohol-treated animals exhibited an increase in the expression of iron transporters in the duodenum and the iron storage protein, ferritin in the liver. Alcohol also rendered hepcidin synthesis in the liver insensitive to body iron levels. It is noteworthy, that hepcidin protects the body from iron overload by inhibiting iron transport. Thus, alcohol may compromise this protective mechanism of hepcidin, which may have implications for alcoholic liver disease (ALD). Of note, ALD patients and animal models of ALD display iron overload but the underlying mechanisms are unclear. Our findings suggest that the deregulation of hepcidin synthesis in the liver may be one of the underlying mechanisms of iron overload observed in ALD. Treatment with antioxidants abolished the effect of alcohol on hepcidin expression. Multiple pathways play a role in alcohol-induced oxidative stress, including activation of Kupffer cells, CYP2E1 enzyme and changes to mitochondrial function. Our preliminary results exclude a role for Kupffer cells, TNF alpha cytokine and CYP2E1 in the regulation of hepcidin expression by alcohol-mediated oxidative stress in the liver. Mitochondria also are involved in alcohol-mediated oxidative stress. Alcohol induces lesions in the proteins of the electron transport chain, and reduces ATP/ADP translocation and ATP synthesis in the mitochondria. Our preliminary results suggest a role for mitochondria in the regulation of hepcidin expression. Inhibition of DNA and protein synthesis in the mitochondria caused a significant decrease in hepcidin expression in plain HepG2 hepatoma cells. Mitochondria play a key role in apoptosis and alcohol-mediated changes in mitochondria induce apoptotic stimuli. However, the role of apoptosis in the regulation of hepcidin expression is unknown. Our preliminary findings demonstrate that Fas-mediated apoptosis down-regulates hepcidin expression in the liver. The objective of this application is to identify the molecular mechanisms whereby mitochondria regulate liver hepcidin expression and iron metabolism by alcohol. Our central hypothesis is that ethanol-induced modifications of mitochondrial structure and function play a key role in the regulation of hepcidin transcription by alcohol. We will employ transgenic mouse models deficient in mitochondrial antioxidant enzymes, adenine nucleotide transport, cytochrome c oxidase activity or the dimerization of hypoxia-inducible transcription factors to study the regulation of hepcidin transcription by alcohol-mediated oxidative stress. The knowledge obtained from these studies, characterizing the pivotal role of mitochondria, will enable us to determine the mechanisms of liver injury caused by iron and alcohol in patients with ALD.