Characterization and time course of MPP+-induced apoptosis in human SH-SY5Y neuroblastoma cells

A genetic defect in complex I of the mitochondrial electron transport chain (ETC) is implicated in the etiology of Parkinson's disease (PD), and has been studied in cybrid mitochondrial transgene cells based on the SH-SY5Y neuroblastoma. We sought to characterize further the mechanisms and time course of cell death in cultures of human SH-SY5Y neuroblastoma cells exposed to the ETC complex I inhibitor methyl-pyridinium ion (MPP+). We verify previous reports that apoptosis occurs after MPP+ exposure in SH-SY5Y cells. Nuclear pyknosis, the end stage of apoptosis, is evident after 18-hr exposure to 5 mM MPP+ and reversible until 10 hr, providing a temporal window within which to look for molecular and physiological correlates of MPP+-induced apoptosis, We then looked for mitochondrial correlates of MPP+-induced apoptosis in SH-SY5Y cells, Using flow cytometry, we found that MPP+-induced increased reactive oxygen species (ROS) and lactate production consistent with inhibition of the ETC. rho degrees cells, lacking a functional ETC, showed no ROS production, compensatory lactate production or apoptosis after exposure to MPP+, Finally, we show a collapse in ROS production and mitochondrial potential that is temporally correlated with irreversibility of MPP+-induced apoptosis. (C) 1999 Wiley-Liss, Inc.