1. Hepatocyte Nicotinamide Adenine Dinucleotide Phosphate Reduced Oxidase 4 Regulates Stress Signaling, Fibrosis, and Insulin Sensitivity During Development of Steatohepatitis in Mice.
- Author
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Bettaieb A, Jiang JX, Sasaki Y, Chao TI, Kiss Z, Chen X, Tian J, Katsuyama M, Yabe-Nishimura C, Xi Y, Szyndralewiez C, Schröder K, Shah A, Brandes RP, Haj FG, and Török NJ
- Subjects
- Animals, Biomarkers metabolism, Biopsy, Diet methods, Disease Models, Animal, Fatty Liver chemically induced, Fatty Liver genetics, Fatty Liver metabolism, Hepatocytes metabolism, Humans, Lipid Peroxidation drug effects, Liver cytology, Liver pathology, Liver Cirrhosis pathology, Mice, Mice, Inbred C57BL, Mice, Knockout, NADP administration & dosage, NADPH Oxidase 4, Obesity drug therapy, Obesity metabolism, Protein Phosphatase 1 metabolism, Pyrazoles metabolism, Pyrazolones, Pyridines metabolism, Pyridones, Stress, Physiological drug effects, Fatty Liver drug therapy, Hepatocytes drug effects, Insulin Resistance, Liver Cirrhosis drug therapy, NADP pharmacology, NADPH Oxidases metabolism, Oxidative Stress drug effects
- Abstract
Background & Aims: Reactive oxidative species (ROS) are believed to be involved in the progression of nonalcoholic steatohepatitis (NASH). However, little is known about the sources of ROS in hepatocytes or their role in disease progression. We studied the effects of nicotinamide adenine dinucleotide phosphate reduced oxidase 4 (NOX4) in liver tissues from patients with NASH and mice with steatohepatitis., Methods: Liver biopsy samples were obtained from 5 patients with NASH, as well as 4 patients with simple steatosis and 5 patients without steatosis (controls) from the University of California, Davis Cancer Center Biorepository. Mice with hepatocyte-specific deletion of NOX4 (NOX4(hepKO)) and NOX4(floxp+/+) C57BL/6 mice (controls) were given fast-food diets (supplemented with high-fructose corn syrup) or choline-deficient l-amino acid defined diets to induce steatohepatitis, or control diets, for 20 weeks. A separate group of mice were given the NOX4 inhibitor (GKT137831). Liver tissues were collected and immunoblot analyses were performed determine levels of NOX4, markers of inflammation and fibrosis, double-stranded RNA-activated protein kinase, and phospho-eIF-2α kinase-mediated stress signaling pathways. We performed hyperinsulinemic-euglycemic clamp studies and immunoprecipitation analyses to determine the oxidation and phosphatase activity of PP1C., Results: Levels of NOX4 were increased in patients with NASH compared with controls. Hepatocyte-specific deletion of NOX4 reduced oxidative stress, lipid peroxidation, and liver fibrosis in mice with diet-induced steatohepatitis. A small molecule inhibitor of NOX4 reduced liver inflammation and fibrosis and increased insulin sensitivity in mice with diet-induced steatohepatitis. In primary hepatocytes, NOX4 reduced the activity of the phosphatase PP1C, prolonging activation of double-stranded RNA-activated protein kinase and phosphorylation of extracellular signal-regulated kinase-mediated stress signaling. Mice with hepatocyte-specific deletion of NOX4 and mice given GKT137831 had increased insulin sensitivity., Conclusions: NOX4 regulates oxidative stress in the liver and its levels are increased in patients with NASH and mice with diet-induced steatohepatitis. Inhibitors of NOX4 reduce liver inflammation and fibrosis and increase insulin sensitivity, and might be developed for treatment of NASH., (Copyright © 2015 AGA Institute. Published by Elsevier Inc. All rights reserved.)
- Published
- 2015
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