Studies on the Antioxidative and Cytotoxic Actions of Epigallocatechin Gallate in Murine Cerebral Cortical Cell Cultures

ABSTRACT

OBJECTIVE: Epigallocatethin gallate(EGCG) is a major green tea polyphenol and is known to have potent antioxidative and antiproliferative actions. This study is performed to investigate the antioxidative effect of EGCG on the various oxidative insults in mouse cerebral cortical cell cultures. METHODS: Mixed cortical cell cultures containing both neuron and glia prepared by plating fetal mice cortical cells on to an established glia of 24 well vessels. At 13-15 days in vitro, oxidative neuronal deaths were induced by the addition of oxidants into the cortical cultures. Iron ion(FeCl2), copper ion(CuCl2), sodium nitroprusside(SNP) and buthionine sulfoximine(BSO, a glutathione depletor) were used as oxidants. Cell death was assessed by LDH assay after microscopic examination. RESULTS: All four oxidants induced neuronal cell death associated with cell body swelling, which was markedly inhibited by Trolox(100muM), a vitamin E analog. EGCG(1-10muM) markedly inhibited the neuronal cell death induced by 20muM CuCl2, 1muM SNP, or 1mM BSO. Unexpectedly the neuronal cell death induced by 20muM FeCl2 was augmented by treatment with 1 or 3muM EGCG. EGCG itself induced concentration- and exposure time-dependent cell death at more than 30muM concentrations. EGCG(30, 100muM) injured not only neuronal cells but glial cells after 48 hour exposure. The EGCG-induced cytotoxicity was partially inhibited by protein synthesis inhibitors, cycloheximide(0.1 or 1mug/ml) and emetine (1mug/ml) or high potassium media(10 or 25mM) but was not affected by Trolox. CONCLUSION: These results suggest that the dual antioxidative-cytotoxic actions of EGCG are concentration-dependent and that the antioxidative aciton depends on the kind of oxidative insults, and that the EGCG-induced cytotoxicity be relevant to protein synthesis and/or membrane depolarization.