6-hydroxydopamine toxicity towards human SH-SY5Y dopaminergic neuroblastoma cells: independent of mitochondrial energy metabolism

6-Hydroxydopamine (6-OHDA) is widely used to generate animal models of Park inson's disease. However, little is known about the intracellular events le ading to cell death of dopaminergic neurones. Here we correlate indices oil energy production and cell viability in human dopaminergic neuroblastoma S H-SY5Y cells after exposure to 6-OHDA. The toxin induces a time and dose-de pendent decrease in cell survival with an IC50 value of 25 mu M after 24h. In contrast to the mitochondrial complex I inhibitor 1-methyl-4-phenylpyrid inium (MPP+), 6-OHDA-induced reduction of cell viability is not associated with a decrease of intracellular ATP content, intracellular ATP/ADP ratio o r NAD(+) content. In addition, preventing or forcing glycolysis do not alte r 6-OHDA toxicity. The antioxidant D-alpha-tocopherol can attenuate cell de ath induced by 6-OHDA. These results suggest that cell death induced by 6-O HDA is not due to an inhibition of mitochondrial energy supply, but probabl y involves production of free radicals.