Differential role of catalase and glutathione peroxidase in cultured human fibroblasts under exposure of H₂O₂ or ultraviolet B light

Abstract

The purpose of this study was to elucidate the differential contribution of catalase and glutathione peroxidase (GSH-Px) to H ₂ O ₂ scavenging in cultured human dermal fibroblasts. Responses of the cells in terms of both enzyme activities were examined by using two sorts of inhibitors, 3-amino-1H-1,2,4-triazole (AT) for catalase and dl -buthionine-[ S, R ]-sulfoximine (BSO) for GSH-Px, under exposure to H ₂ O ₂ or ultraviolet (UV) B radiation. AT treatment resulted in a decrease in H ₂ O ₂ scavenging activity, while BSO treatment did not affect H ₂ O ₂ scavenging. When fibroblasts were exposed to a low concentration of H ₂ O ₂ (100 Ì M ). AT treatment resulted in a significant decrease in cell survival, but BSO treatment did not affect survival. At higher concentrations of H ₂ O ₂ ranging from 500 Ì M to 1 m M , BSO-treated fibroblasts showed reduced survival. In addition, AT treatment was much more cytotoxic in the presence of UVB than BSO treatment. The intracellular levels of H ₂ O ₂ in fibroblasts treated with AT or BSO were also determined. BSO-treated cells showed similar H ₂ O ₂ levels to control cells, but the intracellular H ₂ O ₂ levels of AT-treated fibroblasts were 1.4-fold higher than found in control cells. These results with human dermal fibroblasts indicate that catalase acts as a primary defence against oxidative stress from exogenous or endogenous H ₂ O ₂ at low concentrations. In contrast, GSH-Px helps protect the cell from damage during exposure to high concentrations of H ₂ O ₂ .