HSP70 Gene Expression after Mild Transient Global Cerebral Ischemia in Rats

ABSTRACT

PURPOSE: Cerebral ischemia lead to neuronal damage in a specific area of the brain of both rodents and humans. After ischemia, the pyramidal cells in area CA1 of the hippocampus are particularly sensitive, but death of these pyramidal cells is delayed to at least 3~4 days after the transient cerebral ischemia. Induction of HSP70 has been mainly observed in resistant areas, so a protective effect has been proposed for HSP70. The presence of HSP70 is a good indicator of the general pathophysiologic stress response to ischemia, but not necessarily a marker for neuronal survival. METHODS: Fisher rats (344) were used in the present experiments. Mild Transient ischemia was induced by using two common methods, carotid artery occlusion and reperfusion. For immunostaining, brain tissues were prepared following intracranial perfusion, and frozen sections were cut on a crystal. Section were incubated with mouse monoclonal antibodies by using a free-float method. Hippocampal tissues at the indicated times were prepared for Western blot analysis. For the determination of the protein levels of HSP70, tissue extracts were subjected to ECL Western blot analysis using primary antibodies. The result from Western blotting was expressed numerically through an image analysis. RESULTS: HSP70 expression markedly increased in 2-day group of transient mild cerebral ischemia after reperfusion. HSP70-positive cells were observed in the cerebral cortex, the striata terminalis, and the hippocampus 2 days after the onset of ischemia. In preconditioned ischemia, no ischemic cell death due to necrosis and apoptosis was noted. CONCLUSION: Preconditioning is induced by mild transient cerebral ischemia, and that is a potent stimulator of HSP70 gene expression.