Effect of mild hypothermia on IRE1-XBP1 signaling pathway in endoplasmic reticulum in cortex in a rat model of focal cerebral ischemia-reperfusion / 中华麻醉学杂志

ABSTRACT

Objective:To evaluate the effect of mild hypothermia on inositol requiring enzyme 1-X-box binding protein 1 (IRE1-XBP1) signaling pathway in endoplasmic reticulum in cortex in a rat model of focal cerebral ischemia-reperfusion (I/R).Methods:Fifty-four clean-grade healthy male Sprague-Dawley rats, aged 8-10 weeks, weighing 200-230 g, were divided into 3 groups ( n=18 each) using a random number table method: sham operation group (group S), cerebral I/R group (group I) and mild hypothermia group (group T). Cerebral I/R was induced by inserting a nylon thread with rounded tip into the internal carotid artery which was occluded for 2 h and then released for reperfusion.The surface cooling was started immediately after reperfusion, and the rectal temperature was maintained at 32-34 ℃ for 3 h in group T. Blood vessels were only exposed, without occlusion in group S. The neurologic deficit was assessed and scored at 24 h of reperfusion.The animals were then sacrificed and the ischemic area of the cerebral cortex was removed for examination of the ultrastructure of the cells (with a transmission electron microscope), for determination of nerve cell apoptosis (using TUNEL), for detection of the expression of IRE1 and XBP1 (by Western blot) and for determination of the expression of IRE1 and XBP1 protein mRNA (using quantitative real-time polymerase chain reaction). Results:Compared with group S, the neurologic deficit scores were significantly increased, nerve cell apoptosis in the ischemic area of the cerebral cortex was increased, the expression of IRE1, XBP1 protein and mRNA was up-regulated ( P<0.05), the neuronal nuclei was degenerated and swollen, the nuclear membrane was fragmented and defective, the chromatin was pyknotic and marginalized, and the endoplasmic reticulum was dilated and cisternal in group I and group T. Compared with group I, the neurologic deficit scores were significantly decreased, nerve cell apoptosis in the ischemic area of the cerebral cortex was decreased, the expression of IRE1, XBP1 protein and mRNA was up-regulated ( P<0.05), and the damage to the ultrastructure of nerve cells was reduced in group T. Conclusion:The mechanism by which mild hypothermia alleviates focal cerebral I/R injury is associated with further activation of neuronal IRE1-XBP1 signaling pathway and alleviation of endoplasmic reticulum stress response in rats.