Mitochondrial aconitase knockdown attenuates paraquat-induced dopaminergic cell death via decreased cellular metabolism and release of iron and H2O2

Mitochondrial oxidative stress is a contributing factor in the etiology of numerous neuronal disorders. However, the precise mechanism(s) by which mitochondrial reactive oxygen species modify cellular targets to induce neurotoxicity remains unknown. In this study, we determined the role of mitochondrial aconitase (m-aconitase) in neurotoxicity by decreasing its expression. Incubation of the rat dopaminergic cell line, N27, with paraquat (PQ(2+)) resulted in aconitase inactivation, increased hydrogen peroxide (H2O2) and increased ferrous iron (Fe2+) at times preceding cell death. To confirm the role of m-aconitase in dopaminergic cell death, we knocked down m-aconitase expression via RNA interference. Incubation of m-aconitase knockdown N27 cells with PQ(2+) resulted in decreased H2O2 production, Fe2+ accumulation, and cell death compared with cells expressing basal levels of m-aconitase. To determine the metabolic role of m-aconitase in mediating neuroprotection, we conducted a complete bioenergetic profile. m-Aconitase knockdown N27 cells showed a global decrease in metabolism (glycolysis and oxygen consumption rates) which blocked PQ(2+)-induced H+ leak and respiratory capacity deficiency. These findings suggest that dopaminergic cells are protected from death by decreasing release of H2O2 and Fe2+ in addition to decreased cellular metabolism.