Protective effect of dl-alpha-tocopherol on the cytotoxicity of ultraviolet B against human skin fibroblasts in vitro

The effect of dl-alpha-tocopherol on ultraviolet light, 280-320 nm (UVB)-induced damage of human skin fibroblasts was studied by measuring the colony-forming ability, unscheduled DNA synthesis (UDS) and malondialdehyde (MDA) production. Regarding the cell toxicity, the values of the mean lethal dose (D0) of UV in fibroblast strains from 5 normal subjects were examined. D0 increased dose-dependently when the cells were cultured in the presence of dl-alpha-tocopherol at the concentration of 10-1000 micrograms/ml. UDS induced by 500 J/m2 UVB irradiation was not altered by treatment of 100 micrograms/ml dl-alpha-tocopherol. MDA did not increase after 500 J/m2 UVB irradiation in the fibroblasts cultured with 100 micrograms/ml dl-alpha-tocopherol, while MDA in the fibroblasts cultured without dl-alpha-tocopherol increased after irradiation. These results suggest that dl-alpha-tocopherol protects human skin fibroblasts against the cytotoxic effect of UVB, and its mechanism seems to be related to inhibition of UV-induced lipid peroxidation or to the antioxidation effect of dl-alpha-tocopherol.