Green tea polyphenol epigallocatechin gallate activates TRPA1 in an intestinal enteroendocrine cell line, STC-1.

A characteristic astringent taste is elicited by polyphenols. Among the polyphenols, catechins and their polymers are the most abundant polyphenols in wine and tea. A typical green tea polyphenol is epigallocatechin gallate (EGCG). Currently, the mechanism underlying the sensation of astringent taste is not well understood. We observed by calcium imaging that the mouse intestinal endocrine cell line STC-1 responds to the astringent compound, EGCG. Among major catechins of green tea, EGCG was most effective at eliciting a response in this cell line. This cellular response was not observed in HEK293T or 3T3 cells. Further analyses demonstrated that the 67-kDa laminin receptor, a known EGCG receptor, is not directly involved. The Ca(2+) response to EGCG in STC-1 cells was decreased by inhibitors of the transient receptor potential A1 (TRPA1) channel. HEK293T cells transfected with the mouse TRPA1 (mTRPA1) cDNA showed a Ca(2+) response upon application of EGCG, and their response properties were similar to those observed in STC-1 cells. These results indicate that an astringent compound, EGCG, activates the mTRPA1 in intestinal STC-1 cells. TRPA1 might play an important role in the astringency taste on the tongue.