Remote Postconditioning Of Trauma With Abdaominal Surgical Incision Induces Cerebroprotection Via Activation Of Akt/p-Akt/Gsk-3β Pathway In Rat Brain

Objective:This study aims to observe the protective effects of remote postconditioning of trauma against ischemic-reperfusion injury, and to investigate whether PI3K/Akt/GSK-3β pathway is involved in the cerebral protection in middle cerebral artery occlusion model in rats.Methods:Sixty adult male Sprague-Dawley rats weighing220-280g were randomly divided into four groups:Sham group, I/R group,3hRPoCT group and6hRPoCT group(n=15,each group).The rats in I/R group were underwent middle cerebral artery occlusion (MCAO) for90min referencing to Longa’s method. The rats in3hRPoCT and6hRPoCT group received abdominal incision as the stimulus for RPoCT at3/6hours after reperfusion. The incision was a2-cm longitudinal incision located on the abdominal midline, extending through the skin and muscle and into the visceral peritoneum which was immediately closed using3-0Mersilk sutures. The rats in Sham group were underwent the same operation as I/R group without MCAO. Modified Neurological Severity Score (mNSS) and cerebral infarct size in the four groups were examined at24h after middle cerebral artery reperfusion. Neuronal cell morphology and survival of neurons in ischemic selected vulnerable hippocampal CA1were observed respectively by HE staining and Nissl staining. The expression of p-Akt、GSK-3(3and p-GSK-3(3(ser9) in the selected vulnerable hippocampal CA1were measured via immunohistochemistry and Western blot analysis.Results:1.TTC staining:Compared with that in I/R group, the brain infarction volume in6hRPoCT group decreased significantly (P<0.05). The cerebral infarct size at24h after middle cerebral artery reperfusion in3hRPoCT group were smaller than that in the I/R group,the difference is not significant (P>0.05).2. HE staining:Normal morphological characteristics of neurons showed in Sham group by microscopic examination. There were a large number of dying neurons in the ischemic selected vulnerable hippocampal CA1, which exhibited pyknotic nucleus and chromatin margination. And the quantity of neurons were decreased significantly in both I/R group and RPoCT group compared with that in Sham group (P<0.05). But Compared with that in I/R group, the neurons in the ischemic selected vulnerable hippocampal CA1in RPoCT group were more clear and integrated, and the interstitial edema were alleviative.3. Nissl staining:the number of survival neurons of the ischemic selected vulnerable hippocampal CA1in6hRPoCT group increased significantly Compared with that in I/R group (P<0.05), the number of survival neurons in6hRPoCT group is more than that in I/R group, but the difference is not significant (P>0.05).4. Immunohistochemical analysis:The expression of p-Akt in both3hRPoCT group and6hRPoCT group increased than that in I/R group, but the difference is not significan (P>0.05)t. The expression of GSK-3β in and6hRPoCT group increased significantly than that in I/R group (P<0.05).5. western blotting:Compared with those in I/R group, the expression of p-Akt and GSK-3(3in both3hRPoCT group and6hRPoCT group increased significantly (P<0.05). However, the expression of p-GSK-3β (ser9) in6hRPoCT group is up-regulated significantly compared to I/R group, while the increasement in3hRPoCT group is not significant (P>0.05).6. The mNSS median in both3hRPoCT group and6hRPoCT group decreased compared with that in I/R group at24h after cerebral ischemia reperfusion, but there was no significant difference in mNSS between I/R group and3/6hRPoCT group (P>0.05).Conclusions:Remote postconditioning of trauma, especially excerted at6hours after reperfusion, may have protective effects against cerebral I/R injury, which may related to inhibiting or attenuating apoptosis of neurons by activating PI3K/Akt/GSK-3(3pathway.