Effects of calpain inhibitor on delayed neuronal death after global forebrain ischemia

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Transient forebrain ischemia induces activation of calpain and proteolysis of a neuronal cytoskeleton, fodrin, in gerbil hippocampus. This phenomenon precedes delayed neuronal death in hippocampal CAl neurons. We examined effects of a calpain inhibitor on delayed neuronal death after transient forebrain ischemia. In gerbils, a selective calpain inhibitor entrapped in liposome was given transvenously and 30 minutes later, 5-minute forebrain ischemia was produced by occlusion of both common carotid arteries. On day 7, CAl neuronal damage was examined in the hippocampal slices stained with cresyl-violet. Calpain-induced proteolysis of fodrin was also examined by immunohistochemistry and immunoblot. Additionally, to assure entrapment of the inhibitor by CAl neurons, the inhibitor-liposome complex was labeled with FITC and given to gerbils. Fluorescence in the hippocampal slices was examined by confocal laser scanning microscope. Selective CAl neuronal damage induced by forebrain ischemia w … More as prevented by administration of the inhibitor in a dose-dependent manner but not completely even in dose of 60mg/kg. Calpain-induced proteolysis of fodrin was also extinguished by the calpain inhibitor in a dose-dependent manner and completely abolished in dose of 60mg/kg. Bright fluorescence of the FITC-labeled inhibitor was observed in the CAl neurons. The data show an important role of calpain in development of the ischemic delayed neuronal death. Calpain seems to produce neuronal damage by degrading neuronal cytoskeleton. Our data also show a palliative effect of the calpain inhibitor on the neurotoxic damage. Although the calpain inhibitor does not completely block the ischemic neuronal damage, it offers a new and potent treatment of transient forebrain cerebral ischemia.As an additional experimet, alteration of endogenous calpain inhibitor, calpastatin, in forebrain ischemia was examined by immunohistochemical and immunobloting methods. The immunoreactivity of calpastatin in hippocampal neurons increased 4 hours after the ischemic insult and then decreased. The result suggested that calpastatin may participate in the stress responses. Less