Effects of organic peroxides on human epidermal keratinocytes

Abstract

Human epidermal keratinocytes cultured for about 10 days were incubated for 60 min with ferrous ions, ascorbic acid, H 2O 2 t-butyl hydroperoxide or benzoyl peroxide. Lipid peroxidation was determined by malondialdehyde and ethane formation and cytotoxicity by the trypan blue exclusion test. ADP complexed ferrous ions and ascorbic acid led to high lipid peroxidation of keratinocytes, but no cell damage occurred. In contrast, H 2O 2, t-butyl hydroperoxide and benzoyl peroxide were unable to induce lipid peroxidation. Cell viability decreased greatly with benzoyl peroxide. The addition of ferrous ions to keratinocytes incubated with H 2O 2, t-butyl hydroperoxide or benzoyl peroxide resulted in a significant increase in lipid peroxidation whereas only slight additional cell damage occurred. In keratinocytes incubated with benzoyl peroxide and simultaneously irradiated with UV-A, lipid peroxidation increased and was several times higher than with UV-A alone. (+)-Cyanidanol-3 inhibited lipid peroxidation in both systems whereas EDTA was effective only when keratinocytes were exposed to benzoyl peroxide and ferrous ions. The data indicate that in human epidermal keratinocytes lipid peroxidation is inducible, but that it is not related to cell damage. Cytotoxicity caused in keratinocytes by benzoyl peroxide must be due to a mechanism dissimilar to lipid peroxidation.