In vitro effects of tea polyphenols on redox metabolism, oxidative stress, and apoptosis in PC12 cells.

Tea polyphenols, especially catechins, have been reported to be potent antioxidants and beneficial in oxidative stress-related diseases including cancer. Numerous animal and cell culture models demonstrate anticancer effects of tea catechins. Experimental and epidemiological evidence suggests the use of black tea polyphenols (BTP), green tea catechins (especially epigallocatechin gallate [EGCG]), and other polyphenols in preventing the progression of cancer both in animal and human populations. In the present study, we have demonstrated alterations in oxidative stress and redox metabolism using an isolated cell-free system and also in PC12 cancer cells after treatment with EGCG and BTP. We have demonstrated that tea catechins, alter the production of reactive oxygen species, glutathione metabolism, lipid peroxidation, and protein oxidation under in vitro conditions. We have also demonstrated that EGCG and BTP affect redox metabolism under cell culture conditions. Induction of apoptosis was observed, after the treatment with tea polyphenols, as shown by increased DNA breakdown and activation of the apoptotic markers, cytochrome c, caspase 3, and poly-(ADP-ribose) polymerase. These results may have implications in determining the chemopreventive and therapeutic use of tea catechins in vivo.