Hepatocyte NAD(P)H Oxidases as an Endogenous Source of Reactive Oxygen Species During Hepatitis C Virus Infection

School of Natural Sciences, University of California, Merced, CA 95343, USA.
Hepatology (Impact Factor: 11.06). 07/2010; 52(1):47-59. DOI: 10.1002/hep.23671
Source: PubMed


Oxidative stress has been identified as a key mechanism of hepatitis C virus (HCV)-induced pathogenesis. Studies have suggested that HCV increases the generation of hydroxyl radical and peroxynitrite close to the cell nucleus, inflicting DNA damage, but the source of reactive oxygen species (ROS) remains incompletely characterized. We hypothesized that HCV increases the generation of superoxide and hydrogen peroxide close to the hepatocyte nucleus and that this source of ROS is reduced nicotinamide adenine dinucleotide phosphate (NAD(P)H) oxidase 4 (Nox4). Huh7 human hepatoma cells and telomerase-reconstituted primary human hepatocytes, transfected or infected with virus-producing HCV strains of genotypes 2a and 1b, were examined for messenger RNA (mRNA), protein, and subcellular localization of Nox proteins along with the human liver. We found that genotype 2a HCV induced persistent elevations of Nox1 and Nox4 mRNA and proteins in Huh7 cells. HCV genotype 1b likewise elevated the levels of Nox1 and Nox4 in telomerase-reconstituted primary human hepatocytes. Furthermore, Nox1 and Nox4 proteins were increased in HCV-infected human liver versus uninfected liver samples. Unlike Nox1, Nox4 was prominent in the nuclear compartment of these cells as well as the human liver, particularly in the presence of HCV. HCV-induced ROS and nuclear nitrotyrosine could be decreased with small interfering RNAs to Nox1 and Nox4. Finally, HCV increased the level of transforming growth factor beta 1 (TGFbeta1). TGFbeta1 could elevate Nox4 expression in the presence of infectious HCV, and HCV increased Nox4 at least in part through TGFbeta1. CONCLUSION: HCV induced a persistent elevation of Nox1 and Nox4 and increased nuclear localization of Nox4 in hepatocytes in vitro and in the human liver. Hepatocyte Nox proteins are likely to act as a persistent, endogenous source of ROS during HCV-induced pathogenesis.

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Available from: Jinah Choi, Jan 17, 2014
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    • "are well-known targets of HCV protein actions; however, also extramitochondrial sources of ROS are involved in HCVrelated OS onset: ER, peroxisomes and other cell compartments [11] [12], xanthine oxidase or NADPH oxidases [13], cytochromes P450, and resident immune cell populations in the liver (e.g., Kupffer cells). To avoid the deleterious effects of ROS, biological systems have developed several mechanisms of detoxification that use a wide number of small molecules, peptides, and enzymes, like glutathione (GSH) or superoxide dismutases (SODs), respectively. "
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    • "This is indirectly demonstrated by the fact that mitochondrial DNA (mtDNA) shows increasing amounts of damage with increasing age, likely attributed to the proximity of the mtDNA to the source of ROS [46]. Mitochondria are not the only ROS sources that could become displaced, another potential source is NADPH oxidase 4 (NOX4), which contributes to superoxide (O 2 À ) and H 2 O 2 generation, and has been shown to colocalize with lamin A/C, especially after hepatitis C virus infection [47] [48]. "
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