脑缺血再灌注损伤大鼠大脑皮质NR2A及NR2B受体表达变化

目的探讨N-甲基-D-天冬氨酸受体亚单位NR2A/2B表达与缺血再灌注损伤的关系。方法建立局灶性大脑中动脉阻塞大鼠模型观察缺血2 h再灌6～96 h的组织病理学改变,实时荧光定量PCR及Western印迹法测定大脑皮质NR2A/2B mRNA及蛋白表达。结果大鼠缺血再灌注后6 h,皮质开始出现明显病理学改变,12 h可见血管内有淤血,24 h梗死区锥体细胞出现严重的核固缩、核溶解,几乎看不到正常神经元,48 h出现大面积角质化,96 h可见炎症细胞浸润。与假手术组相比,再灌组NR2A/2B mRNA于再灌注6 h即开始一直持续明显下降(P<0.01),再灌12和24 hNR2A/2B mRNA比值均为1∶2,偏离正常的1∶1,48 h两者的表达开始上调,至96 h NR2A/2B mRNA比值达到1∶1;再灌24 h后NR2A蛋白表达显著降低(P<0.05);NR2B蛋白于再灌6 h开始明显降低,一直持续到24 h(P<0.01),48 h开始上调,96 h后蛋白表达接近假手术组水平。结论缺血2 h再灌注24 h后神经元损伤最严重,并与NR2A/2B表达改变存在时间一致性和受体亚型选择性。

Expression of NR2A and NR2B receptors in cerebral cortex of rats with local ischemia reperfusion injury

OBJECTIVE To observe relationship between cerebral ischemia reperfusion injury and expression of N-methyl-D-aspartate receptors NR2A/2B.METHODS Established middle cerebral artery occlusion(MCAO) model and investigated histopathological changes at different time points between 6 and 96 h after ischemia(2 h) reperfusion injury,as well as to test mRNA levels and expression of NR2A/2B protein in rat cortex by using real-time quantitative polymerase chain reaction(RT-qPCR) and Western blotting.RESULTS The obvious pathological changes of cortex and visible vascular congestion in rats respectively showed at 6 h and 12 h.There were almost no normal neurons cells in infarcted area and severe pyknosis and karyolysis were observed at 24 h.Area horny at 48 h and inflammatory cell infiltration at 96 h were observed.Compared with the sham group,mRNA levels of NR2A/2B began to decrease at 6 h after reperfusion(P<0.01),NR2A/2B mRNA ratio was 1∶2 at 12 h and 24 h,and reached to 1∶1 at 96 h.Expression of NR2A protein significantly reduced only at 24 h(P<0.05).Differently,expression of NR2B protein was reduced from 6 h and continued until 24 h(P<0.01),while they began to increase at 48 h,and then reached to normal level at 96 h after reperfusion.CONCLUSION The neurons are most damaged at 24 h after ischemia reperfusion injury and this damage is consistent with the expression of NR2A/2B and might have relationship with receptor subtype selectivity.