The Effect of Alcohol and Hydrogen Peroxide on Liver Hepcidin Gene Expression in Mice Lacking Antioxidant Enzymes, Glutathione Peroxidase-1 or Catalase

This study investigates the regulation of hepcidin, the key iron-regulatory molecule, by alcohol and hydrogen peroxide (H(2)O(2)) in glutathione peroxidase-1 (gpx-1(−/−)) and catalase (catalase(−/−)) knockout mice. For alcohol studies, 10% ethanol was administered in the drinking water for 7 days. Gpx-1(−/−) displayed significantly higher hepatic H(2)O(2) levels than catalase(−/−) compared to wild-type mice, as measured by 2'-7'-dichlorodihydrofluorescein diacetate (DCFH-DA). The basal level of liver hepcidin expression was attenuated in gpx-1(−/−) mice. Alcohol increased H(2)O(2) production in catalase(−/−) and wild-type, but not gpx-1(−/−), mice. Hepcidin expression was inhibited in alcohol-fed catalase(−/−) and wild-type mice. In contrast, alcohol elevated hepcidin expression in gpx-1(−/−) mice. Gpx-1(−/−) mice also displayed higher level of basal liver CHOP protein expression than catalase(−/−) mice. Alcohol induced CHOP and to a lesser extent GRP78/BiP expression, but not XBP1 splicing or binding of CREBH to hepcidin gene promoter, in gpx-1(−/−) mice. The up-regulation of hepatic ATF4 mRNA levels, which was observed in gpx-1(−/−) mice, was attenuated by alcohol. In conclusion, our findings strongly suggest that H(2)O(2) inhibits hepcidin expression in vivo. Synergistic induction of CHOP by alcohol and H(2)O(2,) in the absence of gpx-1, stimulates liver hepcidin gene expression by ER stress independent of CREBH.