Cellular thiols status and cell death in the effect of green tea polyphenols in Ehrlich ascites tumor cells

Epidemiological studies suggest that the consumption of green tea may help prevent cancers in humans, and also breast and prostate cancers in animal m odels are reduced by green tea, and several mechanisms have been proposed f or these effects. In this study the relationship between cellular sulfhydry l (SH) groups and the cytotoxicity of green tea polyphenols in Ehrlich asci tes tumor cells was examined. It was found that in the presence of green te a extract (GTE) (100 mu g/ml) and one of its polyphenolic components, epiga llocatechin (EGC; 100 mu M), both cellular non-protein (GSH) and protein-su lfhydryl (PSH) levels were significantly decreased and this was associated with a decrease in cell viability. Replenishing the thiol levels by using N -acetylcysteine (NAC) caused a recovery in cell viability, but this recover y was dependent on the time of thiol replenishment in the presence of EGC ( initial 15 min). These results identify SH groups as a novel target of gree n tea polyphenols cytotoxicity in tumor cells, and a regulatory role for gr een tea in terms of reducing sulfhydryls in tumor inhibition. (C) 1999 Else vier Science Ireland Ltd. All rights reserved.