Abstract
A role for the NADPH oxidases NOX1 and NOX2 in liver fibrosis has been proposed, but the implication of NOX4 is poorly understood yet. The aim of this work was to study the functional role of NOX4 in different cell populations implicated in liver fibrosis: hepatic stellate cells (HSC), myofibroblats (MFBs) and hepatocytes. Two different mice models that develop spontaneous fibrosis (Mdr2(-/-)/p19(ARF-/-), Stat3(Δhc)/Mdr2(-/-)) and a model of experimental induced fibrosis (CCl(4)) were used. In addition, gene expression in biopsies from chronic hepatitis C virus (HCV) patients or non-fibrotic liver samples was analyzed. Results have indicated that NOX4 expression was increased in the livers of all animal models, concomitantly with fibrosis development and TGF-β pathway activation. In vitro TGF-β-treated HSC increased NOX4 expression correlating with transdifferentiation to MFBs. Knockdown experiments revealed that NOX4 downstream TGF-β is necessary for HSC activation as well as for the maintenance of the MFB phenotype. NOX4 was not necessary for TGF-β-induced epithelial-mesenchymal transition (EMT), but was required for TGF-β-induced apoptosis in hepatocytes. Finally, NOX4 expression was elevated in patients with hepatitis C virus (HCV)-derived fibrosis, increasing along the fibrosis degree. In summary, fibrosis progression both in vitro and in vivo (animal models and patients) is accompanied by increased NOX4 expression, which mediates acquisition and maintenance of the MFB phenotype, as well as TGF-β-induced death of hepatocytes.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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ATP Binding Cassette Transporter, Subfamily B / deficiency
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ATP Binding Cassette Transporter, Subfamily B / genetics
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ATP-Binding Cassette Sub-Family B Member 4
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Animals
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Apoptosis / drug effects
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Biopsy
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Carbon Tetrachloride
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Cell Transdifferentiation / drug effects
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Cyclin-Dependent Kinase Inhibitor p16 / deficiency
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Cyclin-Dependent Kinase Inhibitor p16 / genetics
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Gene Expression / drug effects
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Hepacivirus / physiology
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Hepatic Stellate Cells / drug effects
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Hepatic Stellate Cells / enzymology*
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Hepatic Stellate Cells / virology
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Hepatitis C, Chronic / enzymology*
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Hepatitis C, Chronic / pathology
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Hepatitis C, Chronic / virology
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Hepatocytes / drug effects
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Hepatocytes / enzymology*
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Hepatocytes / virology
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Humans
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Liver / drug effects
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Liver / enzymology*
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Liver / virology
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Liver Cirrhosis / chemically induced
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Liver Cirrhosis / enzymology*
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Liver Cirrhosis / pathology
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Liver Cirrhosis / virology
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Mice
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Mice, Knockout
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Myofibroblasts / drug effects
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Myofibroblasts / enzymology*
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Myofibroblasts / virology
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NADPH Oxidase 4
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NADPH Oxidases / genetics*
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NADPH Oxidases / metabolism
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STAT3 Transcription Factor / deficiency
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STAT3 Transcription Factor / genetics
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Signal Transduction / drug effects
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Transforming Growth Factor beta / pharmacology
Substances
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ATP Binding Cassette Transporter, Subfamily B
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Cdkn2a protein, mouse
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Cyclin-Dependent Kinase Inhibitor p16
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STAT3 Transcription Factor
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Stat3 protein, mouse
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Transforming Growth Factor beta
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Carbon Tetrachloride
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NADPH Oxidase 4
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NADPH Oxidases
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Nox4 protein, mouse
Grants and funding
This work was supported by grants to IF from the Ministerio de Ciencia e Innovación (MICINN), Spain (BFU2009-07219 and ISCIII-RTICC RD06/0020) and AGAUR-Generalitat de Catalunya (2009SGR-312). The work of WM was supported by the European Union, FP7 Health Research project number HEALTH-F4-2008-202047. JM and EC-M were recipients of pre-doctoral fellowships from the FPI and FPU programs, respectively, MICINN, Spain. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.