EFFECT OF BETA-CAROTENE AND CANTHAXANTHIN ON TERT-BUTYL HYDROPEROXIDE-INDUCED LIPID-PEROXIDATION IN MURINE NORMAL AND TUMOR THYMOCYTES

It has been reported that the anticarcinogenic effect of carotenoids c ould be related to an antioxidant mechanism. The antioxidant efficienc y of beta-carotene and canthaxanthin was evaluated in murine normal an d tumor thymocytes. Normal and tumor cells were exposed under air to t ert-butyl hydroperoxide (t-BOOH) and lipid peroxidation was measured i n the absence or in the presence of the two carotenoids. Our results s how that: (a) Both carotenoids, added at effective and comparable conc entrations (from 1 to 50 mu M), were able to inhibit t-BOOH-induced ma londialdehyde formation in a dose-dependent manner. (b) Canthaxanthin was a more potent antioxidant than beta-carotene. (c) The inhibition o f lipid peroxidation was greater in tumor thymocytes. (d) Carotenoids were consumed differentially during the incubation with the prooxidant . beta-Carotene was consumed faster than canthaxanthin and in a larger amount in tumor than in normal thymocytes. The addition of the iron c helator deferoxamine or the SH group reducing agent dithiothreitol red uced t-BOOH-induced beta-carotene consumption in tumor cells but not i n normal ones. (e) The loss of endogeneous alpha-tocopherol induced by t-BOOH was enhanced by the addition of beta-carotene, suggesting the possibility of oxidative interactions between the two antioxidants. Th ese results confirmed the antioxidant effectiveness of carotenoids in normal and tumor cells, although differences depending on the kind of cells and carotenoids used were found. (C) 1996 Academic Press, Inc.