The Activation Of COX-2 And 5-LO Pathways During Cerebral Ischemia-reperfusion Injury And The Protect Effects Of Propyl Gallate

OBJECTIVE: To investigate the changes of AA metabolism and the effects of related factors, the neuronal protective effects and mechanism of cyclooxygenase-2 and 5-lipoxygenase inhibitor propyl gallate(PrG)on focal cerebral ischemia reperfusion injury in rats.METHODS: The right middle cerebral artery of the rat was occluded by inserting a thread through internal carotid artery for 2h, and then reperfused for 24h. The rats were divided into sham, vehicle, PrG5 mg?kg-1 and 7.5 mg?kg-1group (PrG5 and PrG7.5). PrG was interaperitoneally administered 0 and 2h after reperfusion. The neurofunctional score was given. The infarction size of brain tissue was measured by TTC staining technique. Morphological changes of brain were observed by HE staining technique. The degree of brain edema was measured by AutoCAD image analysis software. EB was used as labelled compound to detect the permeability of blood-brain barrier(BBB). The expressions of COX-2, 5-LO, NF-κB, iNOS and TNF-αwere measured by immunohistochemcial technique. The activities of reduced glutathione hormone(GSH), myeloperoxidase(MPO)and total-antioxidation capability(T-AOC) were measured by biochemical technique. The contents of thromboxane A2 (TXA2) and prostaglandin I2 (PGI2) in plasma were measured by radioimmune technique.The concentration of leukotriene B4 (LTB4) in serum was measured by enzyme linked immunosorbent assay (ELISA) technique.RESULTS: (1) The expressions of COX-2, 5-LO and NF-κB proteins of vehicle group were significantly increased compared with sham group after 2h ischemia and 24h reperfusion. The changes happened mainly in IP area, amygdala and hippocampus, especially in IP area. (2) Several changes were observed after CIRI, such as the nerve tissue damage and the brain edema, the concentrations of TXA2 and LTB4 were significantly increased and PGI2 was significantly reduced in peripheral blood, and then the ratio of TXA2 to PGI2 was disturb. The activity of GSH, T-AOC and MPO was dramatically reduced in the brain tissue. The expressions of TNF-αand iNOS proteins were remarkably induced in the brain tissue. (3) Compared with vehicle group, PrG5 and PrG7.5 groups can improve the morphological changes of the brain,minimize the infarct size,inhibit the degree of the brain edema. Meanwhile, it can relieve the destroy of the BBB, reduce the content of TXA2 and induce the activity of PGI2 in plasma and so regulate the ratio of TXA2 to PGI2 disturbance, decrease LTB4 concentration in serum, reduce the expressions of TNF-αand iNOS proteins in the brain tissue. Also it can induce the activity T-AOC, GSH and inhibit MPO activation in the brain tissue.CONCLUSIONS: The enzymes of the COX-2 and 5-LO pathways of AA mechanism were activated, then the active products were increased in the brain tissue of the rats after CIRI. Since the brain tissue will suffer from neuronal damage, inflammatory reaction and lipid peroxidation. PrG5, 7.5mg?kg-1 can protect the neuronal cells injury after CIRI and it would be better by using a large dose. The mechanisms may be as followings: PrG can inhibit the activation of COX-2 and 5-LO pathways, relieve the damage of BBB,inhibit the inflammatory reaction and lipid peroxidation, reduce the expressions of iNOS and TNF-αproteins in the brain tissue.