Hepatitis C virus induces oxidative stress, DNA damage and modulates the DNA repair enzyme NEIL1.
OBJECTIVE
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.


METHODS
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.


RESULTS
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.


CONCLUSIONS
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.
Pal
Sampa
S
Department of Laboratory Medicine, University of Washington, Seattle, Washington 98195-7110 USA. sampa@u.washington.edu
Polyak
Stephen J
SJ
Bano
Nazneen
N
Qiu
Wan Chong
WC
Carithers
Robert L
RL
Shuhart
Margaret
M
Gretch
David R
DR
Das
Aditi
A
D001706:Biopsy; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000378:metabolism* / Q000473:pathology / Q000821:virology; D004249:DNA Damage; D045647:DNA Glycosylases / Q000378:metabolism*; D011088:DNA Ligases; D018450:Disease Progression; D016174:Hepacivirus / Q000378:metabolism / Q000472:pathogenicity*; D006801:Humans; D008103:Liver Cirrhosis / Q000235:genetics / Q000378:metabolism* / Q000473:pathology / Q000821:virology; D008113:Liver Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology / Q000821:virology; D009154:Mutation; D018384:Oxidative Stress; D017382:Reactive Oxygen Species / Q000378:metabolism
D017382:Reactive Oxygen Species; D045647:DNA Glycosylases; C473634:NEIL1 protein, human; D011088:DNA Ligases