Dose-response effects of tomato lycopene on lipid peroxidation and enzymic antioxidants in the hamster buccal pouch carcinogenesis model

Abstract

We evaluated the chemopreventive efficacy of tomato lycopene at three different concentrations on DMBA-induced hamster buccal pouch (HBP) carcinogenesis. Hamsters were divided into eight groups. The right buccal pouches of animals in group 1 were painted with 0.5 per cent DMBA three times a week. Animals in groups 2 to 4 painted with DMBA as in group 1, received in addition, intragastric administration of tomato lycopene of concentrations 2.5, 5 and 10 mg/kg bw respectively three times a week on days alternate to DMBA application. Groups 5 through 7 were given tomato lycopene alone while group 8 served as untreated control. All the animals were killed after an experimental period of 14 weeks. Lipid peroxidation and the status of enzymic antioxidants in the buccal pouch, liver and erythrocytes of hamsters in all the groups were assessed. All the hamsters painted with DMBA alone, developed oral squamous cell carcinomas. Diminished lipid peroxidation in the HBP tumors was accompanied by decreased activities of superoxide dismutase and catalase with increase in glutathione peroxidase. However, in the liver and erythrocytes of tumor-bearing animals increased lipid peroxidation was associated with compromised antioxidant defenses. Administration of tomato paste containing 5mg/kg bw of lycopene inhibited HBP tumor development as revealed by decreased tumour incidence and tumour burden. We suggest that tomato lycopene exerts its chemopreventive effects by modulating the oxidant-antioxidant profile in the target organ as well as in the liver and erythrocytes.