Inhibition of ultraviolet B-induced AP-1 activation by theaflavins from black tea

Theaflavins are believed to be key active components in black tea for chemo prevention of cancer. However, the molecular mechanisms underlying the inhi bitory effects of theaflavins are not clear. With the JB6 mouse epidermal c ell line, we investigated the effects of theaflavins on ultraviolet (UV) B radiation-induced activator protein-1 (AP-1)-dependent transcriptional acti vation and compared them with (-)-epigallocatechin-3-gallate (EGCG), a majo r green tea polyphenol that has cancer chemopreventative activity. Theaflav ins and EGCG inhibited UVB-induced AP-1 activation in a concentration-depen dent manner. The inhibitory effects of theaflavins were stronger than those of EGCG. We found that theaflavins significantly inhibited activation of e xtracellular signal-regulated protein kinases and c-jun NH2-terminal kinase s. Because the transcription factor AP-1 is important in the process of tum or promotion, the inhibitory effect of these polyphenols on AP-1 activation may further explain the anti-tumor promotion action of these tea constitue nts. (C) 2000 Wiley-Liss, Inc.