Abstract
Green tea polyphenol epigallocatechin-3-gallate (EGCG) is reported to have antioxidant abilities and to counteract beneficially mitochondrial impairment and oxidative stress. The present study was designed to investigate neuroprotective effects of EGCG on rotenone-treated dissociated mesencephalic cultures and organotypic striatal cultures. Rotenone is a potent inhibitor of complex I of the respiratory chain, which in vitro causes pathological and neurochemical characteristics of diseases in which mitochondrial impairment is involved, e.g., Parkinson's disease. Treatment with EGCG (0.1, 1, 10 mu M) alone had no significant effects on mesencephalic cultures. In striatal slice cultures, EGCG led to a significant increase of propidium iodide (PI) uptake and 4-amino-5-methylamino-2',7'-difluorofluorescein diacetate (DAF-FM), but not dihydroethidium (DHE) fluorescence intensity. Rotenone (20 nM on the eighth DIV for 48 h) significantly decreased the numbers and the neurite lengths of TH ir neurons by 23 and 34% in dissociated mesencephalic cell cultures compared to untreated controls. Exposure of striatal slices to rotenone (0.5 mM for 48 h) significantly increased PI uptake, and DAF-FM and DHE fluorescence intensities by 41 and 136 and 19%, respectively, compared to controls. Against rotenone, in dissociated mesencephalic cultures, EGCG produced no significant effect on either the number or neurite lengths of THir neurons compared to rotenone-treated cultures, but EGCG significantly decreased PI uptake by 19% and DAF-FM fluorescence intensity by 19 and 58%, respectively, compared to increase in rotenone-exposed striatal slices. On the other hand, EGCG did not affect superoxide (O-2 (-)) formation as detected with DHE. These data indicate that EGCG slightly protects striatal slices by counteracting nitric oxide (NO center dot) production by rotenone. In conclusion, EGCG partially protects striatal slices but not dissociated cells against rotenone toxicity.