title: Hepatitis C virus (HCV) proteins induce NADPH oxidase 4 expression in a transforming growth factor beta-dependent manner: a new contributor to HCV-induced oxidative stress.
abstract: Viral hepatitis-induced oxidative stress accompanied by increased levels of transforming growth factor beta (TGF-beta) and hepatic fibrosis are hallmarks of hepatitis C virus (HCV) infection. The mechanisms of redox regulation in the pathogenesis of HCV-induced liver disease are not clearly understood. The results of our current studies suggest that reactive oxygen species (ROS) derived from Nox4, a member of the NADPH oxidase (Nox) family, could play a role in HCV-induced liver disease. We found that the expression of HCV (genotype 1a) cDNA constructs (full-length and subgenomic), core protein alone, viral RNA, or replicating HCV (JFH-AM2) induced Nox4 mRNA expression and ROS generation in human hepatocyte cell lines (Huh-7, Huh-7.5, HepG2, and CHL). Conversely, hepatocytes expressing Nox4 short hairpin RNA (shRNA) or an inactive dominant negative form of Nox4 showed decreased ROS production when cells were transfected with HCV. The promoters of both human and murine Nox4 were used to demonstrate transcriptional regulation of Nox4 mRNA by HCV, and a luciferase reporter tied to an approximately 2-kb promoter region of Nox4 identified HCV-responsive regulatory regions modulating the expression of Nox4. Furthermore, the human Nox4 promoter was responsive to TGF-beta1, and the HCV core-dependent induction of Nox4 was blocked by antibody against TGF-beta or the expression of dominant negative TGF-beta receptor type II. These findings identified HCV as a regulator of Nox4 gene expression and subsequent ROS production through an autocrine TGF-beta-dependent mechanism. Collectively, these data provide evidence that HCV-induced Nox4 contributes to ROS production and may be related to HCV-induced liver disease.
authors.affiliation: Laboratory of Host Defenses, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 12441 Parklawn Drive, Rockville, MD 20852, USA.
authors.forename: Howard E
authors.initials: HE
authors.lastname: Boudreau
authors.forename: Suzanne U
authors.initials: SU
authors.lastname: Emerson
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Korzeniowska
authors.forename: Meghan A
authors.initials: MA
authors.lastname: Jendrysik
authors.forename: Thomas L
authors.initials: TL
authors.lastname: Leto
mesh_terms: D000818:Animals; D015971:Gene Expression Regulation, Enzymologic; D056945:Hep G2 Cells; D016174:Hepacivirus / Q000502:physiology*; D006801:Humans; D051379:Mice; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases / Q000235:genetics* / Q000502:physiology; D018384:Oxidative Stress; D017382:Reactive Oxygen Species / Q000378:metabolism; D013481:Superoxides / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000502:physiology*; D014764:Viral Proteins / Q000502:physiology*
chemical_list: D017382:Reactive Oxygen Species; D016212:Transforming Growth Factor beta; D014764:Viral Proteins; D013481:Superoxides; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases; C498910:NOX4 protein, human