Dual function of (−)-epigallocatechin gallate (EGCG) in healthy human lymphocytes

(−)-Epigallocatechin gallate (EGCG), a catechin polyphenol component, is the main ingredient of green tea extract. Recently, increasing attention has been given to its anti-oxidant effects. However, several studies reported the oxidative effects of EGCG, suggesting that EGCG had a dual function of anti-oxidant and pro-oxidant potentials. In this study, we examined the influences of EGCG on healthy human whole blood lymphocytes and purified blood lymphocytes using a single-cell gel electrophoresis (SCG) assay. The results showed that EGCG suppressed the DNA strand breakage in whole blood lymphocytes at concentrations from 10−8 to 10−5 M, while it induced DNA strand breakage at concentration of 10−3 M. Furthermore, EGCG at concentrations of 10−6–10−4 M suppressed the DNA strand breakage induced by bleomycin (BLM) and H2O2 in whole blood lymphocytes. In the same range of 10−6–10−4 M, EGCG increased DNA strand breakage in purified blood lymphocytes, but suppressed the DNA breakage induced by BLM at lower concentrations from 10−8 to10−7 M. From these findings, we propose that EGCG might have a dual function of anti-oxidant and pro-oxidant in healthy human lymphocytes, which would involved in its inhibitory effects against DNA strand breakage induced by BLM and H2O2.