Manganese superoxide dismutase deficiency exacerbates cerebral infarction after focal cerebral ischemia/reperfusion in mice: implications for the production and role of superoxide radicals.
OBJECTIVE
Superoxide anion radicals (O2*-) are implicated in ischemia/reperfusion injury, although a direct relationship has not been elucidated. Recently, a specific method of hydroethidine (HEt) oxidation by O2*- was developed to detect O2*- production in a variety of experimental brain injury models. To clarify the role of O2*- in the mechanism of ischemia/reperfusion, we investigated O2*- production after ischemia/reperfusion and ischemia/reperfusion injury in mutant mice deficient in mitochondrial manganese superoxide dismutase (MnSOD) and in wild-type littermates.


METHODS
Ischemia/reperfusion was performed for 60 minutes using intraluminal suture blockade of the middle cerebral artery in the mutant or wild-type mice. We evaluated fluorescent kinetics of HEt or ethidium, the oxidized form of HEt, in brains after an intravenous injection of HEt, followed by measurement of cellular O2*- production using specific HEt oxidation by O2*- before and after ischemia/reperfusion. Furthermore, we compared O2*- production and subsequent infarct volume in the mice using triphenyltetrazolium chloride after ischemia/reperfusion.


RESULTS
HEt oxidation to ethidium is primarily a result of mitochondrially produced O2*- under physiological conditions. Cerebral ischemia/reperfusion produced O2*- prominently in neurons shortly after reperfusion, followed by a delayed increase in endothelial cells. A deficiency in MnSOD in mutant mice increased mitochondrial O2*- production and exacerbated cerebral infarction, worsening neurological deficits after ischemia/reperfusion.


CONCLUSIONS
These results suggest that mitochondrial O2*- production may be a critical step underlying the mechanism of ischemia/reperfusion injury and that MnSOD may protect against ongoing oxidative cell death after ischemia/reperfusion.
Kim
Gyung W
GW
Department of Neurosurgery, Stanford University School of Medicine, Stanford, Calif, USA.
Kondo
Takeo
T
Noshita
Nobuo
N
Chan
Pak H
PH
D000818:Animals; D002544:Cerebral Infarction / Q000473:pathology / Q000503:physiopathology*; D019610:Cytoprotection; D004195:Disease Models, Animal; D004996:Ethidium / Q000032:analysis / Q000378:metabolism; D006579:Heterozygote; D006720:Homozygote; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008817:Mice, Mutant Strains; D008928:Mitochondria / Q000378:metabolism; D018384:Oxidative Stress; D010617:Phenanthridines / Q000378:metabolism; D015427:Reperfusion Injury / Q000503:physiopathology*; D013482:Superoxide Dismutase / Q000172:deficiency* / Q000235:genetics / Q000378:metabolism; D000072105:Superoxide Dismutase-1; D013481:Superoxides / Q000378:metabolism*; D015996:Survival Rate; D000099156:Superoxide Dismutase 2
D004996:Ethidium; D010617:Phenanthridines; D013482:Superoxide Dismutase; D000072105:Superoxide Dismutase-1; D013481:Superoxides; D000099156:Superoxide Dismutase 2; C058428:hydroethidine; C000606291:Sod1 protein, mouse