Oxidative Inactivation of Mitochondrial Aconitase Results in Iron and H(2)O(2)-Mediated Neurotoxicity in Rat Primary Mesencephalic Cultures

BACKGROUND: 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 (ROS) modify cellular targets to induce the death of neurons remains unknown. The goal of this study was to determine if oxidative inactivation of mitochondrial aconitase (m-aconitase) resulted in the release of redox-active iron (Fe(2+)) and hydrogen peroxide (H(2)O(2)) and whether this contributes to cell death. METHODOLOGY/PRINCIPAL FINDINGS: Incubation of rat primary mesencephalic cultures with the redox cycling herbicide paraquat (PQ(2+)) resulted in increased production of H(2)O(2) and Fe(2+) at times preceding cell death. To confirm the role of m-aconitase as a source of Fenton reagents and death, we overexpressed m-aconitase using an adenoviral construct thereby increasing the target available for inactivation by ROS. Co-labeling studies identified astrocytes as the predominant cell type expressing transduced m-aconitase although neurons were identified as the primary cell type dying. Oxidative inactivation of m-aconitase overexpressing cultures resulted in exacerbation of H(2)O(2) production, Fe(2+) accumulation and increased neuronal death. Increased cell death in m-aconitase overexpressing cultures was attenuated by addition of catalase and/or a cell permeable iron chelator suggesting that neuronal death occurred in part via astrocyte-derived H(2)O(2). CONCLUSIONS: These results suggest a role of ROS-sensitive m-aconitase as a source of Fe(2+) and H(2)O(2) and as a contributing factor to neurotoxicity.