浅低温对脑缺血再灌注小鼠海马蛋白激酶R样内质网激酶活性的影响

Effect of mild hypothermia on activity of hippocampal protein kinase R-like endoplasmic reticulum kinase in a mouse model of cerebral ischemia-reperfusion

目的评价浅低温对脑缺血再灌注小鼠海马蛋白激酶R样内质网激酶（PERK）活性的影响。方法健康雄性C56BL6小鼠120只，体重20～30g，7周龄，采用随机数字表法，将其分为3组（n=40）：假手术组（s组）、脑缺血再灌注组（I／R组）和浅低温组（H组）。采用夹闭双侧颈总动脉15min时恢复脑血流的方法制备小鼠脑缺血再灌注损伤模型。H组于再灌注即刻行体表降温，维持直肠温度32～34qc3h；I／R组和S组维持直肠温度36．8～37．2℃。分别于再灌注6、12、24和72h时取10只小鼠，取海马，TUNEL染色法进行海马CA1区凋亡神经元计数，采用Western blot法测定磷酸化PERK（p-PERK）表达。结果与S组比较，I／R组和H组各时点海马凋亡神经元计数升高，P—PERK表达上调（P〈0．05）；与I／R组比较，H组海马凋亡神经元计数降低，p-PERK表达下调（P〈0．05）。结论浅低温通过抑制脑缺血再灌注小鼠海马PERK活性，从而减轻内质网应激反应，减轻脑损伤。

Objective To evaluate the effect of mild hypothermia on the activity of hippocampal protein kinase R-like endoplasmic reticulum kinase （PERK） in a mouse model of cerebral ischemia-reperfusion （I/ R）. Methods One hundred and twenty male C56BL6 mice, weighing 20-30 g, aged 7 weeks, were randomly divided into 3 groups （n = 40 each） using a random number table： sham operation group （group S）, I/R group, and mild hypothermia group （group H）. Cerebral I/R was induced by occlusion of bilateral common carotid arteries for 15 min followed by reperfusion in anesthetized mice. In group H, surface cooling was performed immediately after reperfusion, and the rectal temperature was maintained at 32-34 ℃ for 3 h. In I/R and S groups, the rectal temperature was maintained at 36. 8-37.2 ℃. At 6, 12, 24 and 72 h of reperfusion, 10 mice were sacrificed in each group, and the hippocampi were removed for determination of the number of apoptotic neurons in hippocampal CA1 region （by TUNEL）, and phosphorylated PERK （p-PERK） expression （by Western blot）. Results Compared with group S, the number of apoptotic neurons was significantly increased, and the expression of p-PERK was up-regulated at each time point in I/R and H groups （P〈0. 05）. Compared with group I/R, the number of apoptotic neurons was significantly decreased, and the expression of p-PERK was down- regulated at each time point in group H （P〈0. 05）. Conclusion Mild hypothermia can reduce endoplasmie reticulum stress through inhibiting hippoeampal PERK activity, thus attenuating cerebral injury in a mouse model of cerebral of cerebral I/R