Effect of 1-methyl-4-phenylpyridinium on glutathione in rat pheochromocytoma PC 12 cells

We investigated the effect of the selective dopaminergic neurotoxin 1-methyl-4-phenylpyridinium (MPP+) on glutathione redox status and the generation of reactive oxygen intermediates (ROI) in rat pheochromocytoma PC 12 cells in vitro. Treatment with MPP+ (250 microM) led to a 63% increase of reduced glutathione (GSH) after 24 h, while a 10-fold higher concentration of MPP+ (2.5 mM) depleted cellular GSH to 12.5% of control levels within that time. Similarly, the complex I-inhibitor rotenone induced a time-dependent loss of GSH at 1 and 10 microM, whereas treatment with lower concentrations of rotenone (0.1, 0.01 microM) increased cellular GSH. Both MPP+ and rotenone increased cellular levels of oxidised glutathione (GSSG) and the higher concentrations of both compounds led to an elevated ratio of oxidised glutathione (GSSG) vs total glutathione (GSH + GSSG) indicating a shift in cellular redox balance. MPP+ or rotenone did not induce the generation of ROI or significant elevation of intracellular levels of thiobabituric acid reactive substances (TBARS) for up to 48 h. Our data suggest that MPP+ has differential effects on glutathione homeostasis depending on the degree of complex I-inhibition and that inhibition of complex I is not sufficient to generate ROI in this paradigm.