Oxidative inactivation of mitochondrial aconitase results in iron and H2O2-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 (Fe2+) and hydrogen peroxide (H2O2) and whether this contributes to cell death.


RESULTS
Incubation of rat primary mesencephalic cultures with the redox cycling herbicide paraquat (PQ2+) resulted in increased production of H2O2 and Fe2+ 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 H2O2 production, Fe2+ 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 H2O2.


CONCLUSIONS
These results suggest a role of ROS-sensitive m-aconitase as a source of Fe2+ and H2O2 and as a contributing factor to neurotoxicity.
Cantu
David
D
Neuroscience Program, University of Colorado Denver, Anschutz Medical Campus, Aurora, Colorado, USA.
Schaack
Jerome
J
Patel
Manisha
M
D000154:Aconitate Hydratase / Q000378:metabolism*; D000818:Animals; D002478:Cells, Cultured; D006861:Hydrogen Peroxide / Q000737:chemistry / Q000378:metabolism*; D007501:Iron / Q000737:chemistry / Q000378:metabolism*; D008636:Mesencephalon / Q000378:metabolism*; D008928:Mitochondria / Q000201:enzymology* / Q000378:metabolism; D009474:Neurons / Q000378:metabolism; D018384:Oxidative Stress; D010100:Oxygen / Q000737:chemistry*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species; D020133:Reverse Transcriptase Polymerase Chain Reaction
C045076:Fenton's reagent; D017382:Reactive Oxygen Species; D006861:Hydrogen Peroxide; D007501:Iron; D000154:Aconitate Hydratase; D010100:Oxygen