Roles of Catalase and Hydrogen Peroxide in Green Tea Polyphenol-Induced Chemopreventive Effects

Abstract

The green tea polyphenol ()-epigallocatechin-3-gallate (EGCG) possesses promising anticancer potential. Although in vivo stud-ies unveiled the metabolic routes and pharmacokinetics of EGCG and showed no adverse effects, in vitro studies at high concen-trations demonstrated oxidative stress. EGCG causes differential oxidative environments in tumor versus normal epithelial cells, but the roles that EGCG, hydrogen peroxide (H2O2), and intracellular catalase play in the epithelial system are largely unknown. The current study employed enzyme activity assays, reactive oxygen species quantification, and immunoblotting to investigate whether EGCG-induced differential effects correlate with levels of key an-tioxidant enzymes and H2O2. It was found that normal human keratinocytes with high catalase activity are least susceptible to H2O2, whereas H2O2 caused significant cytotoxicity in oral carci