Protective Effect of Black Tea Polyphenols Against 7,12-Dimethylbenz[A]Anthracene-Induced Genotoxicity and Oxidative Stress During Hamster Buccal Pouch Carcinogenesis

ABSTRACT This study was designed to evaluate the protective effect of black tea polyphenols (Polyphenon B) against genotoxicity and oxidative stress during 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal pouch (HBP) carcinogenesis. Since the bone marrow reflects hematopoietic stress caused by tumor cells, we used the frequency of micronuclei, the extent of lipid peroxidation, and the status of antioxidants in the bone marrow plasma as intermediate biomarkers of oxidative stress. All the hamsters painted with DMBA alone for 14 weeks developed buccal pouch carcinomas with a 75.4% increase in the incidence of bone marrow micronuclei as compared to untreated control (group 4). This was accompanied by an increase in lipid peroxidation as evidenced by the formation of thiobarbituric acid reactive substances (TBARS) and lipid hydroperoxides (LOOH) (61.3% and 17.8%, respectively) and a decrease in the ratio of reduced glutathione (GSH) to oxidized glutathione (GSSG) and the activities of GSH-dependent enzymes glutathione peroxidase (GPx) and glutathione S-transferase (GST) by 32.6%, 35.9%, and 62.8%, respectively, as compared to untreated control. Dietary administration of Polyphenon B significantly suppressed DMBA-induced HBP carcinomas by 20% and reduced the frequency of bone marrow micronuclei by 57.3% and TBARS and LOOH by 38.8% and 25.8%, respectively, compared to group 1 animals with significant elevations in the GSH:GSSG ratio (16.0%) and activities of GPx (29.8%) and GST (53.8%). Our results reveal that dietary supplementation of Polyphenon B exerts protection against DMBA-induced genotoxicity and oxidative stress by augmenting bone marrow antioxidant defense mechanisms.