Effect of mild hypothermia on glucose regulated protein 78 expression in hippocampus following transient cerebral ischemia-reperfusion in aged rats

Abstract

Objective To investigate the effect of mild hypothermia on glucose regulated protein 78 (GRP78) expression in hippocampus following transient cerebral ischemia-reperfusion (I/R) in aged rats.Methods One hundred and forty-four male aged Sprague-Dawley rats,weighing 450-550 g,were randomly divided into 3 groups (n=48 each): sham operation group (group S),I/R group and mild hypothermia group (group H).Global cerebral I/R was induced by 4-vessel occlusion method.Bilateral vertebral arteries were permanently occluded by cauterization,and bilateral carotid arteries were occluded for 5 min.The surface cooling was started immediately after reperfusion and maintained for 3 h.During surface cooling,the body temperature was maintained at 32-34 ℃(rectal).At 6,12,24 and 48 h of reperfusion,the expression of GRP78 was determined using immuno-histochemisty and Western blot,and the viable neurons in CA1 area were counted.Results The number of viable neurons was significantly smaller at each time point,and the expression of GRP78 was significantly higher at 6,12 and 24 h of reperfusion,while lower at 48 h of reperfusion in I/R group,and the number of viable neurons was significantly smaller,and the expression of GRP78 was significantly higher at each time point in group H than in group S (P＜ 0.05).The number of viable neurons was significantly larger at 12,24 and 48 h of reperfusion,and the expression of GRP78 was significantly higher at each time point in group H than in group I/R (P ＜ 0.05).Conclusion Mild hypothermia can further up-regulate GRP78 expression in hippocampus following transient cerebral I/R in aged rats,thus reducing endoplasmic reticulum stress and cerebral I/R injury. Key words: Hypothermia,induced; Heat-shock proteins; Reperfusion injury; Brain; Aged