Prolonged opportunity for neuroprotection in experimental stroke with selective blockade of cyclooxygenase-2 activity

Abstract

The post-treatment effects of the selective cyclooxygenase (COX)-2 inhibitor, valdecoxib, were investigated in a rat model of temporary focal ischemia. Valdecoxib reduced basal brain prostaglandin E(2) concentrations at dosages that did not affect serum thromboxane B(2), consistent with a selective COX-2 effect. Temporary focal cerebral ischemia was produced in rats by middle cerebral artery occlusion for 90 min. There was increased expression of COX-2 protein detected by Western blot and immunocytochemistry within neurons in the ischemic cortex at 4 and 24 h after ischemia. Rats were treated with vehicle or valdecoxib 15 min before or 1.5, 3 and 6 h after cerebral ischemia. Rats were sacrificed and brain infarction volume determined 24 h after ischemia. Valdecoxib treatment was associated with a decrease in infarction volume when administered 15 min before, and 1.5 or 3 h but not 6 h after cerebral ischemia. There were no differences in physiological parameters during the procedure. Valdecoxib administered at 1.5 h after ischemia significantly reduced the concentrations of prostaglandin E(2) in ischemic penumbral cortex as compared to the vehicle-treated group and contralateral non-ischemic cortex. These results suggest that COX-2 inhibition with valdecoxib is effective when initiated both before and after middle cerebral artery occlusion.

Figure 1

Expression of COX-2 in penumbral cortical tissue 24h after cerebral ischemia. (A) Confocal images of immunostained sections of ischemic cortex stained with Dapi (blue) to detect nuclei, antiNeu-N antibody (green) to detect neurons and antiCOX-2 antibody (green) to detect COX-2 expression. (B) Immunoblot detecting COX-2 protein 4h and 24h of cerebral ischemia and corresponding (C). Graph summarizing densitometeric analysis of COX-2 expression. n=3. Ipsi or I: ipsilateral. Contra and C: contralateral.

Figure 2

Effect of valdecoxib on hippocampal prostaglandin E₂ and serum thromboxane B₂ concentrations in naïve rats. Rats received 0.001 – 10.0 mg/Kg. Valdecoxib or vehicle via gastric lavage and were sacrificed 3h later. n = 3 per group. Ipsi: ipsilateral; contra: contralateral.

Figure 3

Effect of valdecoxib pre- and post-treatment Infarction volume in rats after induction of cerebral ischemia. Representative TTC-stained sections showing reduction infarct volumes and B) Graphic representation of reduction in % corrected infarction volume. ** P < 0.001; * P < 0.05 vs vehicle. n = 6 per group.

Figure 4

Effect of valdecoxib post-treatment on PGE₂ production in penumbral cortex after cerebral ischemia. Rats were treated with vehicle or valdecoxib (1 mg/Kg) via gastric lavage 90 min after reperfusion and were sacrificed at 24h. * P <.05; ** P < 0.01. n = 8 per group. Ipsi: ipsilateral; contra: contralateral