Antioxidant balance and free radical generation in vitamin E-deficient mice after dermal exposure to cumene hydroperoxide

Organic peroxides are widely used in the chemical industry as initiators of oxidation for the production of polymers and fiber-reinforced plastics, in the manufacture of polyester resin coatings, and pharmaceuticals. Free radical production is considered to be one of the key factors contributing to skin tumor promotion by organic peroxides. In vitro experiments have demonstrated metal-catalyzed formation of alkoxyl, alkyl, and aryl radicals in keratinocytes incubated with cumene hydroperoxide. The present study investigated in vivo free radical generation in lipid extracts of mouse skin exposed to cumene hydroperoxide. The electron spin resonance (ESR) spin-trapping technique was used to detect the formation of alpha-phenyl-N-tertbutylnitrone (PBN) radical adducts, following intradermal injection of 180 mg/kg PBN. It was found that 30 min after topical exposure, cumene hydroperoxide (12 mmol/kg) induced free radical generation in the skin of female Balb/c mice kept for 10 weeks on vitamin E-deficient diets. In contrast, hardly discernible radical adducts were detected when cumene hydroperoxide was applied to the skin of mice fed a vitamin E-sufficient diet. Importantly, total antioxidant reserve and levels of GSH, ascorbate, and vitamin E decreased 34%, 46.5%. 27%, and 98%, respectively, after mice were kept for 10 weeks on vitamin E-deficient diet. PBN adducts detected by ESR in vitamin E-deficient mice provide direct evidence for in vivo free radical generation in the skin after exposure to cumene hydroperoxide.