Alterations of Antioxidant Enzyme Expression in Response to Hydrogen Peroxide

Abstract

The effect of hydrogen peroxide (H 2O 2) on the expression of different antioxidant enzymes was investigated in primary rat hepatocytes and the rat hepatoma H4IIE cell line. Catalase mRNA expression and enzyme activity decreased during rat hepatocyte culture. Exposure of hepatocytes to H 2O 2 prevented this decrease in catalase mRNA expression, catalase expression was induced 2-fold. MnSOD message levels showed a peak after 12 h of culture and MnSOD enzyme activity increased similarly. MnSOD mRNA expression was also induced after exposure to H 2O 2. Cu/ZnSOD mRNA expression remained constant during culturing and was not affected by H 2O 2 treatment. In confluent hepatoma H4IIE cells catalase mRNA expression was lower than in early hepatocyte cultures and could be induced 2-fold upon treatment with H 2O 2. Actinomycin D alone caused the same amount of induction of catalase mRNA in rat hepatocytes as in combination with H 2O 2. Exposure of hepatocytes to cycloheximide did not influence the induction of catalase mRNA by H 2O 2. In rat hepatoma H4IIE cells the induction of catalase mRNA by H 2O 2 was prevented by the addition of actinomycin D or cycloheximide. Although induction of catalase mRNA by H 2O 2 was found in rat hepatocytes and H4IIE cells, gene expression of catalase does not appear to be regulated in both cell types in the same manner.