The effects of Brassica oleraceae var capitata on epidermal glutathione and lipid peroxides in DMBA-initiated-TPA-promoted mice

Background: The objective of the present study was to determine if modulati on of GSH-dependent antioxidant protective system by Brassica oleraceae var capitata might inhibit the molecular mechanism of skin tumor promotion. Ma terials and Methods: In a two stages skin carcinogenesis model the protocol used included a single topical application of 200 nmol of the initiator 7, 12-dimethyl-benz(a)anthracene (DMBA) to the backs of mice, followed I week later by promotion with 10 nmol of 12-O-tetradecanoyl-phorbol-13 acetate ( TPA) twice weekly for 30 weeks. In addition to this regimen, 0.1 g/L brassi ca extract was added water week prior to the initiating dose of DMBA in the treatment group. Tissue glutathione (GSH) contents and levels of lipid per oxidation products (measured as thiobarbituric acid (TBA)-reactive substanc es) were quantitated in the skin tumors generated by the initiation-promoti on protocol. Results: It was observed that the tumor incidence and tumor mu ltiplicity in the treatment group was highly significantly low compared to the first group of mice (p <0.001 and p <0.001, respectively). In! the trea tment group, GSH content in the papillomas was higher than in the non-invol ved skin surrounding the papillomas. Conclusions: We suggest that the antic arcinogenicity of Brassica may be linked to its ability to facilitate or en hance the activity of the natural GSH-dependent antioxidant protective syst em of the epidermal cells during the later stages of skin tumor promotion.