Department of Laboratory Medicine, University of Washington, Seattle, Washington 98195-7110 USA.
J Gastroenterol Hepatol. 2010 Mar;25(3):627-34. doi: 10.1111/j.1440-1746.2009.06128.x. Epub 2010 Jan 14.
Hepatitis C virus (HCV)-induced chronic inflammation may induce oxidative stress which could compromise the repair of damaged DNA, rendering cells more susceptible to spontaneous or mutagen-induced alterations, the underlying cause of liver cirrhosis and hepatocellular carcinoma. In the current study we examined the induction of reactive oxygen species (ROS) resulting from HCV infection and evaluated its effect on the host DNA damage and repair machinery.
HCV infected human hepatoma cells were analyzed to determine (i) ROS, (ii) 8-oxoG and (iii) DNA glycosylases NEIL1, NEIL2, OGG1. Liver biopsies were analyzed for NEIL1.
Human hepatoma cells infected with HCV JFH-1 showed 30-60-fold increases in ROS levels compared to uninfected cells. Levels of the oxidatively modified guanosine base 8-oxoguanine (8-oxoG) were significantly increased sixfold in the HCV-infected cells. Because DNA glycosylases are the enzymes that remove oxidized nucleotides, their expression in HCV-infected cells was analyzed. NEIL1 but not OGG1 or NEIL2 gene expression was impaired in HCV-infected cells. In accordance, we found reduced glycosylase (NEIL1-specific) activity in HCV-infected cells. The antioxidant N-acetyl cystein (NAC) efficiently reversed the NEIL1 repression by inhibiting ROS induction by HCV. NEIL1 expression was also partly restored when virus-infected cells were treated with interferon (IFN). HCV core and to a lesser extent NS3-4a and NS5A induced ROS, and downregulated NEIL1 expression. Liver biopsy specimens showed significant impairment of NEIL1 levels in HCV-infected patients with advanced liver disease compared to patients with no disease.
Collectively, the data indicate that HCV induction of ROS and perturbation of NEIL1 expression may be mechanistically involved in progression of liver disease and suggest that antioxidant and antiviral therapies can reverse these deleterious effects of HCV in part by restoring function of the DNA repair enzyme/s.
丙型肝炎病毒（HCV）引起的慢性炎症可能会导致氧化应激，从而损害受损 DNA 的修复，使细胞更容易受到自发或诱变引起的改变，这是肝硬化和肝细胞癌的根本原因。在目前的研究中，我们研究了 HCV 感染引起的活性氧（ROS）的诱导，并评估了其对宿主 DNA 损伤和修复机制的影响。
分析 HCV 感染的人肝癌细胞以确定 (i) ROS、(ii) 8-oxoG 和 (iii) DNA 糖苷酶 NEIL1、NEIL2、OGG1。分析肝活检标本中的 NEIL1。
与未感染细胞相比，感染 HCV JFH-1 的人肝癌细胞的 ROS 水平增加了 30-60 倍。感染 HCV 的细胞中氧化修饰的鸟嘌呤碱基 8-氧鸟嘌呤（8-oxoG）的水平显著增加了六倍。由于 DNA 糖苷酶是去除氧化核苷酸的酶，因此分析了它们在 HCV 感染细胞中的表达。与 OGG1 或 NEIL2 基因表达不同，NEIL1 基因表达在 HCV 感染细胞中受损。相应地，我们发现 HCV 感染细胞中的糖苷酶（NEIL1 特异性）活性降低。抗氧化剂 N-乙酰半胱氨酸 (NAC) 通过抑制 HCV 诱导的 ROS 诱导，有效地逆转了 NEIL1 的抑制作用。当用干扰素 (IFN) 处理病毒感染的细胞时，NEIL1 的表达也部分恢复。HCV 核心蛋白以及在较小程度上的 NS3-4a 和 NS5A 诱导 ROS，下调 NEIL1 表达。与没有疾病的患者相比，患有晚期肝病的 HCV 感染患者的肝活检标本显示 NEIL1 水平显著受损。
总之，这些数据表明，HCV 诱导的 ROS 和 NEIL1 表达的改变可能在肝病的进展中具有机制性作用，并表明抗氧化和抗病毒疗法可以通过部分恢复 DNA 修复酶的功能来逆转 HCV 的这些有害影响。
