Dependence of excitotoxic neurodegeneration on mitochondrial aconitase inactivation.
Using the inactivation of mitochondrial and cytosolic aconitases as markers of compartment-specific superoxide (O2(-)) production, we show that oxygen-glucose deprivation (OGD) or excitotoxin exposure produce a time-dependent inactivation of mitochondrial, but not cytosolic, aconitase in cortical cultures. To determine if mitochondrial O2(-) production was an important determinant in neuronal death resulting from OGD, metalloporphyrins with varying superoxide dismutase (SOD) activity were tested for their ability to protect against mitochondrial aconitase inactivation and cell death. OGD-induced mitochondrial aconitase inactivation and cell death was inhibited by manganese tetrakis (4-benzoic acid) porphyrin (MnTBAP), manganese tetrakis (N-ethylpyridinium-2-yl) porphyrin (MnTE-2-PyP) and NMDA receptor antagonists. By contrast, NMDA- or kainate (KA)-induced mitochondrial aconitase inactivation and cell death was inhibited by MnTBAP, but not MnTE-2-PyP. Moreover, both MnTBAP and MnTE-2-PyP penetrated mitochondrial fractions of cortical cells. These data suggest that mitochondrial aconitase inactivation closely correlates with subsequent neuronal death following excitotoxicity produced by OGD or NMDA/KA exposure. Assessment of biological rather biochemical antioxidant activities better predicted neuroprotection by metalloporphyrins. Moreover, antioxidants that protect oxidant-sensitive mitochondrial targets such as aconitase may be useful as therapies for disease states involving excitotoxicity.
Li
Q Y
QY
Department of Medicine, National Jewish Medical and Research Center, Denver, Colorado 80206, USA.
Pedersen
C
C
Day
B J
BJ
Patel
M
M
D000154:Aconitate Hydratase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000818:Animals; D001253:Astrocytes / Q000166:cytology / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D016923:Cell Death; D002458:Cell Fractionation; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005649:Fumarate Hydratase / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D007608:Kainic Acid / Q000494:pharmacology*; D008665:Metalloporphyrins / Q000378:metabolism / Q000494:pharmacology; D008928:Mitochondria / Q000187:drug effects / Q000201:enzymology*; D016202:N-Methylaspartate / Q000494:pharmacology*; D009410:Nerve Degeneration; D009474:Neurons / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism*; D018696:Neuroprotective Agents / Q000494:pharmacology; D009498:Neurotoxins / Q000494:pharmacology; D010100:Oxygen / Q000378:metabolism; D010269:Paraquat / Q000494:pharmacology; D051381:Rats; D013481:Superoxides / Q000378:metabolism*
D004791:Enzyme Inhibitors; D008665:Metalloporphyrins; D018696:Neuroprotective Agents; D009498:Neurotoxins; D013481:Superoxides; D016202:N-Methylaspartate; D005649:Fumarate Hydratase; D000154:Aconitate Hydratase; D005947:Glucose; D010269:Paraquat; D010100:Oxygen; D007608:Kainic Acid