title: Overexpression of copper/zinc superoxide dismutase in transgenic rats protects vulnerable neurons against ischemic damage by blocking the mitochondrial pathway of caspase activation.
abstract: Mitochondria are known to be involved in the early stage of apoptosis by releasing cytochrome c, caspase-9, and the second mitochondria-derived activator of caspases (Smac). We have reported that overexpression of copper/zinc superoxide dismutase (SOD1) reduced superoxide production and ameliorated neuronal injury in the hippocampal CA1 subregion after global ischemia. However, the role of oxygen free radicals produced after ischemia/reperfusion in the mitochondrial signaling pathway has not been clarified. Five minutes of global ischemia was induced in male SOD1-transgenic (Tg) and wild-type (Wt) littermate rats. Cytosolic expression of cytochrome c and Smac and activation of caspases were evaluated by immunohistochemistry, Western blot, and caspase activity assay. Apoptotic cell death was characterized by DNA nick end and single-stranded DNA labeling. In the Wt animals, early superoxide production, mitochondrial release of cytochrome c, Smac, and cleaved caspase-9 were observed after ischemia. Active caspase-3 was subsequently increased, and 85% of the hippocampal CA1 neurons showed apoptotic DNA damage 3 d after ischemia. Tg animals showed less superoxide production and cytochrome c and Smac release. Subsequent active caspase-3 expression was not evident, and only 45% of the neurons showed apoptotic DNA damage. A caspase-3 inhibitor (N-benzyloxycarbonyl-val-ala-asp-fluoromethyl ketone) reduced cell death only in Wt animals. These results suggest that overexpression of SOD1 reduced oxidative stress, thereby attenuating the mitochondrial release of cytochrome c and Smac, resulting in less caspase activation and apoptotic cell death. Oxygen free radicals may play a pivotal role in the mitochondrial signaling pathway of apoptotic cell death in hippocampal CA1 neurons after global ischemia.
authors.affiliation: Department of Neurosurgery, Stanford University School of Medicine, Stanford, California 94305-5487, USA.
authors.forename: Taku
authors.initials: T
authors.lastname: Sugawara
authors.forename: Nobuo
authors.initials: N
authors.lastname: Noshita
authors.forename: Anders
authors.initials: A
authors.lastname: Lewén
authors.forename: Yvan
authors.initials: Y
authors.lastname: Gasche
authors.forename: Michel
authors.initials: M
authors.lastname: Ferrand-Drake
authors.forename: Miki
authors.initials: M
authors.lastname: Fujimura
authors.forename: Yuiko
authors.initials: Y
authors.lastname: Morita-Fujimura
authors.forename: Pak H
authors.initials: PH
authors.lastname: Chan
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D017209:Apoptosis / Q000502:physiology; D051017:Apoptosis Regulatory Proteins; D002545:Brain Ischemia / Q000201:enzymology* / Q000473:pathology; D002352:Carrier Proteins / Q000378:metabolism; D053148:Caspase 3; D053453:Caspase 9; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism*; D003574:Cytochrome c Group / Q000378:metabolism; D019610:Cytoprotection / Q000502:physiology*; D004249:DNA Damage / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015870:Gene Expression; D006624:Hippocampus / Q000098:blood supply / Q000201:enzymology / Q000473:pathology; D007150:Immunohistochemistry; D008297:Male; D008928:Mitochondria / Q000201:enzymology*; D024101:Mitochondrial Proteins / Q000378:metabolism; D009474:Neurons / Q000201:enzymology* / Q000473:pathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000502:physiology; D013482:Superoxide Dismutase / Q000096:biosynthesis* / Q000235:genetics; D000072105:Superoxide Dismutase-1; D013481:Superoxides / Q000378:metabolism
chemical_list: D051017:Apoptosis Regulatory Proteins; D002352:Carrier Proteins; D061945:Caspase Inhibitors; D003574:Cytochrome c Group; C489013:DIABLO protein, rat; D004791:Enzyme Inhibitors; D024101:Mitochondrial Proteins; D013481:Superoxides; C000606292:Sod1 protein, rat; D013482:Superoxide Dismutase; D000072105:Superoxide Dismutase-1; C505410:Casp3 protein, rat; C506435:Casp9 protein, rat; D053148:Caspase 3; D053453:Caspase 9; D020169:Caspases