Neuroprotective effects of the stable nitroxide compound Tempol on 1-methyl-4-phenylpyridinium ion-induced neurotoxicity in the Nerve Growth Factor-differentiated model of pheochromocytoma PC12 cells

Nerve growth factor (NGF) differentiated pheochromocytoma PC12 cells exposed to 1-methyl-4-phenylpyridinium (MPP⁺) toxin were used as an in vitro pharmacological model of Parkinson's disease to examine the neuroprotective effects of 4-hydroxy-2,2,6,6-tetramethyl piperidine-n-oxyl (Tempol), a free radical scavenger and a superoxide dismutase-mimetic compound. MPP⁺-induced PC12 cell death was measured 72 h after exposure to 1.5 mM MPP⁺ by the release of lactate dehydrogenease, caspase-3 activation and stimulation of survival and stress mitogen-activated protein kinases. Exposure of PC12 cells to MPP⁺ activated ERK1 and ERK2 (forty-fold over control after 72 h), JNK1 and JNK2 (fourfold after 48 h) and p-38α (tenfold after 24 h). Pretreatment of PC12 cells with 500 μM Tempol, 1 h before induction of the MPP⁺ insult, reduced by 70% the release of LDH into the medium, inhibited caspase-3 activity by 30% and improved by 33% mitochondrial function, effects correlated with a 70% reduction in ERK1 and ERK2 phosphorylation activity. These findings support the neuroprotective effect of Tempol in the MPP⁺-induced PC12 cell death model and its use as a potential drug for treatment of Parkinson's disease.