The Study Of PERK/eIF2α Signal Transduction Pathways Induced By Endoplasmic Reticulum Stress And Postconditioning Intervention In Cerebral Ischemic Injury

Objective:To observe the changes of PERK and GRP78expression in focal thrombotic ischemic cerebral cortex and hippocampus, and the effects of postconditioning intervention on endoplasmic reticulum stress in vivo, it is intended to explore the possible mechanism of PERK/e1F2a signal transduction pathway induced by endoplasmic reticulum stress and the neuronal protection of postconditioning intervention after cerebral ischemia.Methods:The focal thrombotic cerebral ischemia was established by photochemical method in tree shrew. At4h after ischemia the right common carotid arteiy was clamped for5min and then opened for5min, altogether alternating3cycles to duplicate the animal model of ischemia and postconditioning. The samples were respectively taken out at4h,24h and72h after cerebral ischemia or with postconditioning intervention. The morphological changes in ischemic cerebral cortex and hippocampus were observed by HE staining and the electronic microscope. The protein expressions of PERK and GRP78in ischemic cerebral cortex and hippocampus were assessed by immunohistocheniistiy and western blotting assay. The PERK and GRP78mRNAs.were analyzed by reverse transcriptase polymerase chain reaction.Results:The expressions of PERK mRNA and protein in ischemic cortex induced by focal thrombotic cerebral ischemia in tree shrews increased at4h after ischemia with a significance (P<0.05), compared with sham operation group, while decreased at24h (P<0.05); Compared with ischemia group, PERK expression in ischemic cortex treated with ischemia and postconditioning (IP) increased at IP24h with a significance (P<0.05) and IP72h while decreased at IP4h. The expressions of PERK mRNA and protein in ischemic hippocampus markedly increased at4h,24h and72h with the significance (P<0.05), compared with sham operation group; Compared with ischemia group, PERK expression in ischemic hippocampus treated with ischemia and postconditioning decreased at IP4h, IP24h and IP72h, but only at IP24h with a significance (P<0.05). The expressions of GRP78mRNA and protein in ischemic cortex increased at4h with a significance (P<0.05). gradually decreased with the prolonged ischemic time, which was compared with sham operation group; Compared with ischemia group, GRP78expression in ischemic cortex treated with ischemia and postconditioning increased at IP24h and1P72h, but only at IP24h with a significance (P<0.05). The expressions of GRP78mRNA and protein in ischemic hippocampus increased at4h, gradually decreased with the prolonged ischemic time; Compared with ischemia group, GRP78expression of ischemic hippocampus treated with ischemia and postconditioning increased at IP24h and IP72h, but only at IP24h with a significance (P<0.05), while decreased at IP4h.Conclusion:1. Focal thrombotic cerebral ischemia may induce endoplasmic reticulum stress response of ischemic cortex and hippocampus in tree shrew, leading to the changes in expression of PERK and GRP78mRNA and protein in PERK/eIF2a signal transduction pathway stimulated by endoplasmic reticulum stress.2Ischemia and postconditioning can activate PERK/eIF2a signal transduction pathway of endoplasmic reticulum stress, thereby blocking the translation of new protein, preventing the accumulation of misfolded proteins, alleviating endoplasmic reticulum stress response, reducing death and apoptosis of neural cells via influencing PERK and GRP78, may play a certain role in protecting brain function.