PROTECTION AGAINST ULTRAVIOLET-B RADIATION-INDUCED EFFECTS IN THE SKIN OF SKH-1 HAIRLESS MICE BY A POLYPHENOLIC FRACTION ISOLATED FROM GREEN TEA

In prior studies we and others have shown that oral feeding of a poryp henolic fraction isolated from green tea (GTP) or water extract of gre en tea affords protection against ultraviolet B (UVB) radiation-induce d carcinogenesis in SKH-1 hairless mice (Wang et al., Carcinogenesis 1 2, 1527-1530, 1991). It is known that exposure of murine skin to UVB r adiation results in cutaneous edema, depletion of the antioxidant-defe nse system and induction of ornithine decarboxylase (ODC) and cyclooxy genase activities. In this study we assessed the protective effect of GTP on these UVB radiation-caused changes in murine skin. Oral feeding of 0.2% GTP (wt/vol) as the sole source of drinking water for 30 days to SKH-1 hairless mice followed by irradiation with UVB (900 mJ/cm(2) ) resulted in significant protection against UVB radiation-caused cuta neous edema (P < 0.0005) and depletion of the antioxidant-defense syst em in epidermis (P < 0.01-0.02). The oral feeding of GTP also resulted in significant protection against UVB radiation-caused induction of e pidermal ODC (P < 0.005-0.01) and cyclooxygenase activities (P < 0.000 1) in a time-dependent manner. Our data indicate that the inhibition o f UVB radiation-caused changes in these markers of tumor promotion in murine skin by GTP may be one of the possible mechanisms of chemopreve ntive effects associated with green tea against UVB-induced tumorigene sis. The results of this study suggest that green tea, specifically po lyphenols present therein, may be useful against inflammatory response s associated with the exposure of skin to solar radiation.