Delayed mitochondrial dysfunction in excitotoxic neuron death: cytochrome c release and a secondary increase in superoxide production.
An increased production of superoxide has been shown to mediate glutamate-induced neuron death. We monitored intracellular superoxide production of hippocampal neurons during and after exposure to the glutamate receptor agonist NMDA (300 microm). During a 30 min NMDA exposure, intracellular superoxide production increased significantly and remained elevated for several hours after wash-out of NMDA. After a 5 min exposure, superoxide production remained elevated for 10 min, but then rapidly returned to baseline. Mitochondrial membrane potential also recovered after wash-out of NMDA. However, recovery of mitochondria was transient and followed by delayed mitochondrial depolarization, loss of cytochrome c, and a secondary rise in superoxide production 4-8 hr after NMDA exposure. Treatment with a superoxide dismutase mimetic before the secondary rise conferred the same protection against cell death as a treatment before the first. The secondary rise could be inhibited by the complex I inhibitor rotenone (in combination with oligomycin) and mimicked by the complex III inhibitor antimycin A. To investigate the relationship between cytochrome c release and superoxide production, human D283 medulloblastoma cells deficient in mitochondrial respiration (rho(-) cells) were exposed to the apoptosis-inducing agent staurosporine. Treatment with staurosporine induced mitochondrial release of cytochrome c, caspase activation, and cell death in control and rho(-) cells. However, a delayed increase in superoxide production was only observed in control cells. Our data suggest that the delayed superoxide production in excitotoxicity and apoptosis occurs secondary to a defect in mitochondrial electron transport and that mitochondrial cytochrome c release occurs upstream of this defect.
Luetjens
C M
CM
Interdisciplinary Center for Clinical Research, Research Group "Apoptosis and Cell Death", Westphalian Wilhelms-University, Münster, Germany.
Bui
N T
NT
Sengpiel
B
B
Münstermann
G
G
Poppe
M
M
Krohn
A J
AJ
Bauerbach
E
E
Krieglstein
J
J
Prehn
J H
JH
D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D003574:Cytochrome c Group / Q000378:metabolism*; D004579:Electron Transport / Q000502:physiology; D014450:Electron Transport Complex III / Q000378:metabolism; D004583:Electrons; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D016166:Free Radical Scavengers / Q000494:pharmacology; D018698:Glutamic Acid / Q000378:metabolism; D006624:Hippocampus / Q000166:cytology; D006801:Humans; D008527:Medulloblastoma; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008665:Metalloporphyrins / Q000494:pharmacology; D008928:Mitochondria / Q000187:drug effects / Q000201:enzymology*; D016202:N-Methylaspartate / Q000494:pharmacology; D009474:Neurons / Q000166:cytology* / Q000201:enzymology; D009498:Neurotoxins / Q000378:metabolism*; D051381:Rats; D011916:Rats, Inbred F344; D017382:Reactive Oxygen Species / Q000378:metabolism; D013482:Superoxide Dismutase / Q000378:metabolism; D013481:Superoxides / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D003574:Cytochrome c Group; D018690:Excitatory Amino Acid Agonists; D016166:Free Radical Scavengers; D008665:Metalloporphyrins; D009498:Neurotoxins; D017382:Reactive Oxygen Species; C097284:manganese(III)-tetrakis(4-benzoic acid)porphyrin; D013481:Superoxides; D018698:Glutamic Acid; D016202:N-Methylaspartate; D013482:Superoxide Dismutase; D014450:Electron Transport Complex III