Heme Oxygenase-1 and Hepatitis C

描述(申请人提供)：丙型肝炎病毒(丙型肝炎病毒)是一个全球性的健康问题，可导致慢性肝炎、肝硬变和肝细胞癌，在病毒感染过程中产生的超氧化物和过氧化氢，并损害肝细胞和周围细胞。肝细胞通常会上调氧化防御酶，以维持氧化还原平衡，防止损伤。一种重要的抗氧化酶是血红素加氧酶-1(HO-1)，它是在人类和动物模型中对氧化应激做出反应时诱导的。尽管HO-1在人类肝病中的作用尚未得到很好的研究，但现有证据表明，该酶通常在损伤反应中上调。相反，我们小组最近的数据显示，在丙型肝炎病毒感染的肝脏样本中，HO-1的表达下调，并且在体外，丙型肝炎病毒核心蛋白转录下调该酶。总之，这些数据表明，丙型肝炎病毒抑制HO-1的表达可能导致肝损伤。我们的总体目标是确定HO-1在丙型肝炎病毒肝病中的作用和重要性，以及当该酶被丙型肝炎病毒下调时所导致的病理后果。我们的中心假设是，HO-1是一种重要的肝细胞防御酶，总体上可以预防肝细胞损伤。在慢性感染过程中，丙型肝炎病毒转录下调HO-1的表达，从而改变肝细胞对损伤的敏感性和反应。利用大量的人肝脏样本库进行体内研究，利用体外构建的多种丙型肝炎病毒蛋白和全长病毒结构物，我们将检验中心假设，并通过三个特定目的的实验来实现主要目标：1)我们将检验HO-1在丙型肝炎肝病中下调与体内肝细胞损伤显著相关和重要的假说。2)我们将验证HO-1与HO-2在表达FL-HCV复制子的Huh-7.5肝细胞中转录下调的假设。3)我们将检验一种假设，即表达FL-丙型肝炎病毒复制子的肝细胞对细胞损伤和氧化应激更敏感。我们还假设，HO-1的过度表达至少可以部分逆转FL-HCV复制和表达对细胞氧化还原平衡的不利影响。这些实验将增加我们对HO-1在丙型肝炎和其他肝病中的重要性以及当该酶下调时可能导致的损害后果的理解。进一步研究丙型肝炎病毒对HO-1表达的调控将为改善慢性丙型肝炎患者的治疗选择，如靶向抗氧化剂基因治疗和选择性抗氧化剂治疗奠定基础。

DESCRIPTION (provided by applicant): Hepatitis C virus (HCV) is a global health problem, causing chronic hepatitis, cirrhosis, and hepatocellular carcinoma, superoxide and peroxide that arise during viral infection and damage hepatocytes and surrounding cells. Hepatocytes normally up-regulate oxidative defense enzymes to maintain redox balance and prevent injury. An important antioxidative enzyme is heme oxygenase-1 (HO-1) that is induced in response to oxidative stress in humans and animal models. Although the role of HO-1 in human liver disease has not been well-studied, available evidence suggests that the enzyme is usually up-regulated in response to injury. In contrast, recent data by our group have shown that HO-1 expression is down-regulated in HCV infected liver samples and that the HCV core protein transcriptionally down-regulates the enzyme in vitro. Collectively, these data suggest that suppression of HO-1 expression by HCV may contribute to hepatic injury. Our overall objective is to determine the role and importance of HO-1 in HCV liver disease and the pathologic consequences that result when the enzyme is down regulated by HCV. Our central hypothesis is that HO-1 is an important hepatocellular defense enzyme that overall prevents hepatocyte injury. Hepatitis C virus transcriptionally down regulates expression of HO-1 during chronic infection, which alters the susceptibility and response of the hepatocyte to injury. Using a large human liver sample bank for the in vivo studies and a variety of HCV protein and full length viral constructs in vitro, we will test the central hypothesis and accomplish the major objective by undertaking experiments of three specific aims: 1) We will test the hypothesis that down regulation of HO-1 in HCV liver disease is significantly related to, and important for hepatocyte injury in vivo. 2) We will test the hypothesis that HO-1 is transcriptionally down-regulated in contrast to HO-2 in Huh-7.5 hepatocytes expressing FL HCV replicons. 3) We will test the hypothesis that hepatocytes expressing FL HCV replicons are more sensitive to cellular injury and oxidative stress. We also hypothesize that over-expression of HO-1 will at least partially reverse the untoward effects of FL HCV replication and expression on cellular oxidative redox balance. These experiments will increase our understanding of the importance of HO-1 in HCV and other liver diseases and the putative injurious consequences that result when the enzyme is down-regulated. Further study of the regulation of HO-1 expression by HCV will lay the foundation for-improved therapeutic options1 for patients with chronic HCV disease such as targeted antioxidant gene therapy and selective antioxidants.