Manganese superoxide dismutase mediates the early release of mitochondrial cytochrome C and subsequent DNA fragmentation after permanent focal cerebral ischemia in mice.
Recent studies have shown that release of mitochondrial cytochrome c is a critical step in the apoptosis process. We have reported that cytosolic redistribution of cytochrome c in vivo occurred after transient focal cerebral ischemia (FCI) in rats and preceded the peak of DNA fragmentation. Although the involvement of reactive oxygen species in the cytosolic redistribution of cytochrome c in vitro has been suggested, the detailed mechanism by which cytochrome c release is mediated in vivo has not yet been established. Also, the role of mitochondrial oxidative stress in cytochrome c release is unknown. These issues can be addressed using knock-out mutants that are deficient in the level of the mitochondrial antioxidant manganese superoxide dismutase (Mn-SOD). In this study we examined the subcellular distribution of the cytochrome c protein in both wild-type mice and heterozygous knock-outs of the Mn-SOD gene (Sod2 -/+) after permanent FCI, in which apoptosis is assumed to participate. Cytosolic cytochrome c was detected as early as 1 hr after ischemia, and correspondingly, mitochondrial cytochrome c showed a significant reduction 2 hr after ischemia (p < 0.01). Cytosolic accumulation of cytochrome c was significantly higher in Sod2 -/+ mice compared with wild-type animals (p < 0.05). N-benzyloxycarbonyl-val-ala-asp-fluoromethyl ketone (z-VAD.FMK), a nonselective caspase inhibitor, did not affect cytochrome c release after ischemia. A significant amount of DNA laddering was detected 24 hr after ischemia and increased in Sod2 -/+ mice. These data suggest that Mn-SOD blocks cytosolic release of cytochrome c and could thereby reduce apoptosis after permanent FCI.
Fujimura
M
M
Departments of Neurosurgery, Neurology and Neurological Sciences, and Program in Neurosciences, Stanford University School of Medicine, Palo Alto, California 94304, USA.
Morita-Fujimura
Y
Y
Kawase
M
M
Copin
J C
JC
Calagui
B
B
Epstein
C J
CJ
Chan
P H
PH
D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis; D001794:Blood Pressure; D001921:Brain / Q000378:metabolism*; D002545:Brain Ischemia / Q000235:genetics / Q000378:metabolism* / Q000503:physiopathology; D002311:Cardiomyopathy, Dilated / Q000235:genetics; D002540:Cerebral Cortex / Q000378:metabolism / Q000473:pathology; D002544:Cerebral Infarction / Q000378:metabolism; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D003574:Cytochrome c Group / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D053938:DNA Fragmentation; D006579:Heterozygote; D002546:Ischemic Attack, Transient / Q000235:genetics / Q000378:metabolism* / Q000503:physiopathology; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008928:Mitochondria / Q000378:metabolism*; D018384:Oxidative Stress; D051381:Rats; D013482:Superoxide Dismutase / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D013481:Superoxides / Q000378:metabolism
D000590:Amino Acid Chloromethyl Ketones; D015853:Cysteine Proteinase Inhibitors; D003574:Cytochrome c Group; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; D013481:Superoxides; D013482:Superoxide Dismutase