Study Of Mechanisms Underlying Inflammatory Injury After Focal Cerebral Ischemia And Reperfusion

Inflammatory reaction is the common pathological process of many diseases and trauma. It was considered a secondary symptom, which is related to clear the debris and tissue rehabilitation. There is abundant evidences that an acute inflammatory reaction associated with reperfusion and acute trauma contributes to edema and the development of secondary tissue damage. Excitotoxity, free radical production, lipid peroxidation, glial activation and inflammation all contribute secondary brain injury. Because secondary injury mechanisms reinforce each other, the inhibition of specific pathway can have profound beneficial effect, endothelial adhesion molecules mediate the adhesion of leukocytes to the endothelial , followed by transmigration into the brain parenchyma. Cyclooxygenase contribute to inflammation development in many diseases.In order to clarify the role of COX-2 in the mechanisms of inflammatory injury after reperfusion and the interaction of COX-2 with ICAM-1 and E-selectin. We made the focal ischemia and reperfusion model of rats to observe the change of myeloperoxidase, the induction of intercelluler adhesion molecule-1 (ICAM-1),E-selectin and COX-2 in the ischemic brain, and the change following reperfusin.Twenty-four Wister rats were divided four groups randomly. Reperfusion groups, 18 Of them received 2h ischemia with middlecerebral artery occlusion(MCAO)and reperfusion. Rats were killed at 4h, 22h and 46h after reperfusion respectively. Six of them received the same operation,but the thread length <15mm.ICAM-1 and E-selectin mRNA was determined by semi-quantity RT-PCR. The protein expression of ICAM-1, E-selectin and COX-2 were detected by Western-blotting. MPO kit was applied to detect MPO activity. The expression site of ICAM-1, E-selectin and COX-2 was examined by immunohistochemitry method. What the results demonstrate are:1.The injury areas of the focal cerebral ischemia and reperfusion model of rats , which was made with thread embolism of middle cerebral artery, were localized striatum and parietal-temporal cortex.2. The MPO activity was increased significantly in the striatum and cortex of rat from 4h to 46h after reperfusion.3. ICAM-1 mRNA was increased significantly in the cortex of rat from 4h to 46h after reperfusion. But in the striatum it returned to the basal level 46h after reperfusion. The outcome of the ICAM-1 protein expression accorded with those rules.4. E-selectin mRNA could be detected in the control brain, was increased significantly in the striatum and cortex of rat after reperfusion. It peaked at 4h after reperfusion in the cortex. The outcome of the E-selectin protein expression accorded with those rules in the cortex, but also peaked at 4h after reperfusion in the striatum.5. Examined by immunohistochemistry, the number of ICAM-1 and E-selectin positive vessel was increased in the border of ischemia.6. The level of COX-2 protein was increased after reperfusion. In the cortex, COX-2 positive cells almost were neurons. In the striatum, COX-2 positive cells were neurons, glias and vessel endothelium.7. Statistic analysis showed that in the cortex the level of COX-2 protein expression correlated well with the ICAM-1 in the cortex. In the striatum the level of COX-2 protein expression correlated well with the E-selectin.In conclusion:Post-ischeraic reperfusion could induce neutrophil increase in the injury brain. It indicates inflammatory reaction involved in secondary brain injury after reperfusion. The expression of ICAM-1, E-selectin and COX-2 all increased after reperfusion at the border of the infarct where the neutrophil infiltration happened. It indicates that the adhesion molecules play a important role in the inflammatory reaction after ischemic-reperfusion. COX-2 may be involved in inflammation by influencing the endothelial adhesion molecules expression.