Differential changes of bax, caspase-3 and p21 mRNA expression after transient focal brain ischemia in the rat

Recent studies of transient focal ischemia have focused interest on apoptot ic mechanisms of neuronal cell death involving constitutive pro-apoptotic p roteins. The finding of specific patterns of novel gene expression might in dicate the activation of pro-apoptotic genes in previously ischemic areas. Thus, we investigated gene expression for the pro-apoptotic regulators, Bar and caspase-3, after transient focal brain ischemia, together with the p53 -regulated cell cycle inhibitor, p21/WAF1/CIP1. Reversible occlusion of the middle cerebral artery for 2 h was carried out in halothane-anesthetized r ats using the poly-L-lysine coated filament method. In situ hybridization w as performed at 0, 1, 3, 6 h and 1, 3 and 7 d of recirculation and in sham controls. Radioactive antisense probes served for detection of bar, p21 and caspase-3 mRNAs on brain sections, and quantitative film autoradiography w as combined with image-averaging techniques. Bar mRNA tended to decline aft er focal brain ischemia within 1 d. p21 mRNA was upregulated with a perifoc al pattern at 3 h and 1 d after ischemia whereas the ischemic regions thems elves failed to show significant upregulation. Caspase-3 mRNA was elevated in the resistant dorsomedial cortex at 1 d. A pro-apoptotic pattern of nove l gene expression, involving Bar and caspase-3, was not observed after tran sient focal brain ischemia. Rather, the perifocal expression of p21 and cas pase-3 mRNAs observed at 1 d after ischemia points to reactive changes in r esistant brain areas. (C) 2000 Elsevier Science B.V. All rights reserved.