P-STAT3Mediated Apoptosis Effect Is Involved In Cerebral Protection Induced By Noninvasive Limb Remote Ischemic Postconditioning In MCAO Rats

Objective:To observe the protective effects of noninvasive limb remote ischemic postconditioning against ischemic-reperfusion injury, and to investigate whether p-STAT3mediated apoptosis effect is involved in this cerebral protection in MACO rats.Methods:Forty-five adult male Sprague-Dawley rats were divided randomly into three groups (n=15, each group):Sham group, I/R goup and NRIPoC group. The rats in I/R and NRIPoC group were received right middle cerebral artery occlusion (MCAO), and the rats in NRIPoC group were accepted3cycles of5minutes reperfusion followed by5minutes ischemia on right hind limb at the beginning of reperfusion in middle cerebral artery. The rats in Sham group were isolated the vessels, but didn’t receive right middle cerebral artery occlusion. At24h after cerebral reperfusion, the neurologic deficit scores (NDS) of the rats in three groups were evaluated by the methods of Longa’s. Five rats were randomly selected to measure their cerebral infarct size by TTC staining; and another five rats were randomly selected to observe the tissue morphology by HE staining, detect the survival nerve cells by Nissl staining, while the neuronal apoptosis was determined by TUNEL staining. The expression of Bcl-2, Bax and p-STAT3in the penumbra cortex were surveyed by immunohistochemical analysis and Western blot analysis.Results:1.TTC staining:Compared with that in I/R group, the brain infarction volume in NRIPoC group decreased significantly (P<0.05). There was no brain infarction in sham group.2.HE staining:The neurons of cerebral cortex were eumorphism in Sham group. Compared with that in I/R group, the neurons in penumbra cortex in NRIPoC group were more clear and integrated. Contrarily, the quantity of neurons was also more but the interstitial edema were alleviative in penumbra cortex in NRIPoC group. Furthermore, the quantity of neurons in core area in both NRIPoC group and I/R group were fewer and the tissues were loose.3.Nissl staining:the number of survival neurons of penumbra cortex in NRIPoC group increased significantly Compared with that in I/R group (P<0.05).4. TUNEL staining:Compared with that in Sham group, the number of apoptotic cells in the penumbra cortex in I/R group and NRIPoC group increased significantly (P<0.05). Furthermore, the number of apoptotic cells in NRIPoC group were decreased significantly compared with that in I/R group (P<0.05).5. Immunohistochemical analysis and western blotting:Compared with that in Sham group, the expression of Bcl-2、Bax and p-STAT3in the penumbra cortex in I/R group and NRIPoC group increased significantly (P<0.05). Compared with that in I/R group, the expression of Bcl-2、p-STAT3were up-regulated (P<0.05). Contrarily, the expression of Bax were down-regulated significantly(P<0.05).6. The NDS in NRIPoC group was lower than that in I/R group, but there was no significant difference between two groups (P>0.05).Conclusion:Noninvasive limb remote ischemic postconditioning may have protective effects against cerebral I/R injury, which may related to inhibiting or attenuating apoptosis of neurons by activating STAT3and regulating Bcl-2/Bax ratio.