Infarct reduction in rats following intraventricular administration of either tissue plasminogen activator (tPA) or its non-protease mutant S478A-tPA.
In addition to its thrombolytic effect, human recombinant tissue plasminogen activator (tPA) may have parenchymal effects such as protease-dependent neurotoxic and protease-independent neuroprotective effects. The purpose of this study was to examine parenchymal effects of tPA and its non-protease mutant S478A-tPA in permanent focal cerebral ischemia in rats. However, before doing in vivo experiments, effects of tPA and S478A-tPA on zinc or NMDA toxicity were first studied in cortical cultures. Like tPA, which has protease-independent cytoprotective effects, the non-protease mutant S478A-tPA blocked zinc toxicity in cortical cell cultures, but did not affect calcium-mediated NMDA toxicity. Then, effects of tPA and S478A-tPA on infarcts induced by permanent occlusion of middle cerebral artery (MCA) were investigated. tPA and S478A-tPA were administered into the cerebral ventricle 15 min or 1 h after MCA occlusion. Both tPA and its non-protease mutant S478A-tPA, when given 15 min after ischemia, substantially reduced infarcts and ameliorated motor deficits in the MCA occlusion model of focal cerebral ischemia. However, when administered 1 h after MCA occlusion, neither showed protective effects. The protective effects of tPA or S478A-tPA remained unchanged at 7 days after MCA occlusion. Indicating that the native protein conformation is necessary for the protective effect of tPA and S478A-tPA, heat-denatured tPA did not exhibit any protective effect. Since S478A-tPA lacks protease activity, which has been implicated in causing cerebral hemorrhage or aggravating excitotoxicity, its parenchymal neuroprotective effect may be useful in treatment of ischemic stroke.
Yi
Jung-Sun
JS
National Creative Research Initiative Center for the Study of CNS Zinc, University of Ulsan College of Medicine, Seoul 138-736, South Korea.
Kim
Yang-Hee
YH
Koh
Jae-Young
JY
D000818:Animals; D001921:Brain / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D020520:Brain Infarction / Q000188:drug therapy* / Q000378:metabolism / Q000503:physiopathology; D002545:Brain Ischemia / Q000188:drug therapy* / Q000378:metabolism / Q000503:physiopathology; D002478:Cells, Cultured; D018920:Coculture Techniques; D004195:Disease Models, Animal; D010450:Endopeptidases / Q000009:adverse effects; D005333:Fetus; D020244:Infarction, Middle Cerebral Artery / Q000188:drug therapy / Q000378:metabolism / Q000503:physiopathology; D007276:Injections, Intraventricular; D008297:Male; D051379:Mice; D009069:Movement Disorders / Q000188:drug therapy / Q000209:etiology; D009154:Mutation / Q000235:genetics; D016202:N-Methylaspartate / Q000037:antagonists & inhibitors / Q000633:toxicity; D011487:Protein Conformation; D051381:Rats; D017207:Rats, Sprague-Dawley; D010959:Tissue Plasminogen Activator / Q000235:genetics / Q000494:pharmacology*; D016896:Treatment Outcome; D015032:Zinc / Q000037:antagonists & inhibitors / Q000633:toxicity
D016202:N-Methylaspartate; D010450:Endopeptidases; D010959:Tissue Plasminogen Activator; D015032:Zinc