Modulation of Tea and Tea Polyphenols on Benzo(a)pyrene-induced DNA Damage in Chang Liver Cells

Abstract

The protective effects of three tea extracts (green tea, GTE; oolong tea, OTE; and black tea, BTE) and five tea polyphenols (epicatechin, EC; epicatechin gallate, ECG; epigallocatechin, EGC; epigallocatechin gallate, EGCG; and theaflavins, THFs) on benzo[a]pyrene (B[a]P)-induced DNA damage in Chang liver cells were evaluated using the comet assay. B[a]P-induced DNA damage in Chang liver cells was significantly (p<0.05) inhibited by GTE and OTE at a concentration of 10 μg/ml and by BTE at 25 μg/ml. At a concentration of 100 μg/ml, the % tail DNA was reduced from 33% (B[a]P treated only) to 10, 9, 13%, by GTE, OTE and BTE, respectively. EC and ECG did not cause DNA damage in cells according to the results of the comet assay; however, EGC, EGCG and theaflavins caused DNA damage in cells at a concentration of 100 μM. The results indicated that EC and ECG had protective effects against B[a]P-induced DNA damage in cells at a concentration of 10–100 μM. Although EGC, EGCG and the theaflavins caused DNA damage at a high concentration, but they had protective effects against B[a]P-induced DNA damage in cells at a low concentration of 10–50 μM. The results also showed that the DNA damage in cells induced by EGC, EGCG, and the theaflavins was due to the generation of superoxide during incubation with cells at a higher concentration. Therefore, tea catechins and THFs play an important role in enabling tea extracts to inhibit DNA damage in Chang liver cells.