Stroke outcome in double-mutant antioxidant transgenic mice

Background and Purpose-Both NO and superoxide cytotoxicity are important in experimental stroke; however, it is unclear whether these molecules act wi thin parallel pathological pathways or as coreagents in a common reaction. We examined these alternatives by comparing outcomes after middle cerebral artery occlusion in male and female neuronal NO synthase (nNOS)-deficient ( nNOS -/-) or human CuZn superoxide dismutase- overexpressing (hSOD 1 +/-) m ice and a novel strain with both mutations. Methods-Permanent middle cerebral artery occlusion was performed by use of the intraluminal filament technique (18 hours). Neurological status was sco red, and tissue infarction volume was determined by 2,3,5-triphenyltetrazol ium staining and image analysis. Results-Hemispheric infarction volume was reduced in each transgenic strain relative to the genetically matched, wild-type, control cohorts (WT mice): nNOS -/- (80+/-6 mm(3)) and double-mutant (49+6 mm3) mice versus WT mice ( 114+/-7 mm(3)) and hSOD1+/- mice (52+7 mm(3)) versus WT mice (95+/-5 mm(3)) . Human CuZn superoxide dismutase had a larger effect on mean infarction vo lume (30% of contralateral hemisphere) than did nNOS deficiency (46%). Alth ough infarction volume was less in double-mutant mice compared with nNOS -/ - mice, injury was not improved relative to hSOD1+/- mice. There was no dif ference in histological damage by sex within each strain; however, female n NOS -/- mice were not protected from ischemic injury, unlike male mutants. Conclusions-Superoxide generation contributes to severe ischemic brain inju ry in vivo to a greater extent than does neuronally derived NO. In vivo, si gnificant superoxide scavenging by CuZn superoxide dismutase occurs within cellular compartments or through biochemical pathways that are not restrict ed to, and may be distinct from, neuronal NO/superoxide reaction and peroxy nitrite synthesis.