Epigallocatechin gallate inhibits histamine release from rat basophilic leukemia (RBL-2H3) cells: Role of tyrosine phosphorylation pathway

Some tea polyphenolic compounds including (-)epigallocatechin gallate (EGCG ) have been shown, to inhibit histamine release from mast cells through poo rly understood mechanisms. By using a mast cell model rat basophilic leukem ia (RBL-2H3) cells we explored the mechanism of the inhibition. EGCG inhibi ted histamine release from RBL-2H3 cells in response to antigen or the calc ium-ionophore A23187, while (-)epicatechin (EC) had little effect, Increase d tyrosine phosphorylation of several proteins including similar to 120 kDa proteins occurred in parallel with the secretion induced by either stimula tion. EGCG; also inhibited tyrosine phosphorylation of the similar to 120-k Da proteins induced by either stimulation, whereas EC did not. The tyrosine kinase-specific inhibitor piceatannol inhibited the secretion and tyrosine phosphorylation of these proteins induced by either stimulation also. Furt her analysis showed that the focal adhesion kinase pp125(FAK) was one of th e similar to 120-kDa proteins. These findings suggest that EGCG; prevents h istamine release from mast cells mainly by inhibiting tyrosine phosphorylat ion of proteins including pp125FAK (C) 2000 Academic Press.