Photoprotective effect of black tea extracts against UVB-induced phototoxicity in skin

(I)n previous studies, we showed that green tea and black tea extracts and their major polyphenolic constituents protect against UVB light-induced car cinogenesis in murine skin. All of these studies required chronic administr ation of tea extracts or specific constituents either topically or orally. However, it is not known whether acute or subchronic administration of blac k tea extracts or constituents can ameliorate UVB-induced early effects in skin. In the present study, cultured keratinocytes and mouse and human skin were employed to assess the effect of both oral and topical administration of standardized black tea extract (SBTE) and its two major polyphenolic su bfractions namely BTF1 and BTF2 against UVB-induced photodamage, In SKH-1 h airless mice, topical application of SBTE (0.2 mg/cm(2)) prior to UVB expos ure (180 mJ/cm(2)) resulted in 40% reduced incidence and 64% reduced severi ty of erythema and 50% reduction in skinfold thickness by day 6 when compar ed to nontreated WE-exposed animals. The SBTE was also effective in protect ing against UVB-induced erythema in human volunteers. Administration of SBT E 5 min after UVB irradiation was similarly effective in reducing UVB-induc ed inflammation in both murine and human skin. The major polyphenolic subfr actions, BTF1 and BTF2 were also effective in protecting in mouse skin. The SBTE subfractions inhibited WE-induced tyrosine phosphorylation of epiderm al growth factor receptor (EGFR), The UVB irradiation of human epidermoid c arcinoma cells resulted in 3.3-fold induction of tyrosine phosphorylation o f EGFR, Pretreatment with BTF1 and BTF2 reduced tyrosine phosphorylation of EGFR by 53% and 31%, respectively. The WE-mediated enhanced expression of the early response genes, c-fos and c-jun in human epidermal keratinocytes was reduced in a dose-dependent manner by SBTE. Topical application of SBTE was also effective in reducing accumulation of c-fos and p53 proteins by 8 2% and 78%, respectively, in UVB-exposed mouse skin. These data provide evi dence that constituents of black tea can abrogate UVB-induced erythema and associated early events in murine and human skin.