PREVENTION OF PHOTOCARCINOGENESIS AND UV-INDUCED IMMUNOSUPPRESSION INMICE BY TOPICAL TANNIC-ACID

Topical application of tannic acid, a phenolic antioxidant derived fro m plants, was found to inhibit the cutaneous carcinogenesis and the im munosuppression induced by ultraviolet B (UVB) irradiation with no vis ible toxicity. BALB/cAnNTacfBR mice were treated with 200 mu g of tann ic acid three times weekly for two weeks before UV treatments began an d throughout the experiment. UVB irradiation consisted of five 30-minu te exposures per week to banks of six FS40 Westinghouse sunlamps. In t he photocarcinogenesis study, mice received a total dose of approximat ely 1.09 x 10(6) J/m(2). Skin cancer incidence in UV-irradiated mice w as 75% at 26 weeks after the first UV exposure; tannic acid reduced th is to 42%. Immunosuppression induced by UVB irradiation normally preve nts the host from rejecting antigenic syngeneic UV-induced tumors. Imm unosuppression in these experiments was measured by a passive transfer assay. Tumor challenges grew to an average of 88 +/- 20, 36 +/- 11, a nd 20 +- 8 mm(2) in naive recipients of splenocytes from UVB-irradiate d mice, nonirradiated control mice, and UVB-irradiated mice treated wi th tannic acid, respectively. Thus topical tannic acid treatment preve nted the transfer of enhanced tumor susceptibility with splenocytes fr om UVB-irradiated mice.