| Objective: The aim of this study was to evaluate the neuroprotective effect of dexmedetomidine in rats exposed to cerebral ischemia/reperfusion injury induced by middle cerebral artery occlusion(MCAO),investigate the roles of phosphatidylinositol 3-kinase(PI3K)/AKT signaling pathway and Wnt/?-catenin signaling pathway in this protective process and its related mechanisms.The purpose of this study is to provide new targets and theoretical support for prevention and treatment of perioperative cerebral ischemia reperfusion injury.In the first part of the study,we investigate the neuroprotective effects of different doses of dexmedetomidine against ischemia/reperfusion injury in order to evaluate the neuroprotective effects of dexmedetomidine in clinical dose.In the second part,we investigate the roles of PI3K/AKT signaling pathway and Wnt/?-catenin signaling pathway in this protective process and evaluate the correlation between them.In the third part of the study,we evaluate the effect of dexmedetomidine on neuron apoptosis in this process and investigate the contributions of PI3K/AKT signaling pathway and Wnt/?-catenin signaling pathway.Methods:1.Adult male Sprague-Dawley rats were subjected to MCAO for 120 min followed by reperfusion;2.Longa scores were applied to evaluate the neurologic deficit in rats at 24 h of reperfusion;3.TTC stain was used to show the infarct size of rat brain;4.Nissle stain was used for morphological observation of brain tissue;5.Western blot was used to detect key protein and apoptosis related protein expression in penumbra;6.Real-time PCR was used to detect the expression of Bax and Bcl-2 mRNA in penumbra.Results: 1.The first part of the study,in M group,dexmedetomidine showed remarkable protective effects on cerebral ischemia/reperfusion injury.Compared with I/R group,the neurological deficit score,cerebral infarct size and neuron count in the ischemic penumbra were all improved;In H or L group,compared with I/R group,there was no significant difference in the neurological deficit score,cerebral infarct size and neuron count.2.In the second part of the study,treatment of rats exposed to I/R injury with Dex caused significant improvements in Longa score,cerebral infarct size and neuron count in the ischemic penumbra,compared with I/R group;and at the same time the protein expression of pAKT?pGSK3???-catenin was all significantly increased,compared with I/R group;The Dex-induced improvements in Longa score,cerebral infarct size and neuron count in the ischemic penumbra were diminished by the PI3 K inhibitor LY294002 and ?-catenin inhibitor XAV939,respectively.The increasing expression of pAKT?pGSK3???-catenin induced by Dex in the ischemic penumbra was markedly inhibited by LY294002.The increasing expression of ?-catenin induced by Dex in the ischemic penumbra was markedly inhibited by LY294002.At the same time,treatment with GSK3? inhibitor SB216763 also caused improvements in Longa scores,cerebral infarct size and neuron count in the ischemic penumbra and an increasing expression of pGSK3? and ?-catenin in the ischemic penumbra,compared with I/R group.3.In the third part,treatment with Dex reduced the expression of cleaved caspase3 and Bax,increased the expression of Bcl-2.And these changes were diminished by LY294002 but not XAV939.Compared with I/R group,treatment with SB216763 also caused not only a reduction of the expression of cleaved caspase3 and Bax,but also an increment of the the expression of Bcl-2.Conclusion:1.Treatment with clinical dose of Dex reduced cerebral injury in rats exposed to cerebral I/R injury.2.PI3K/AKT signaling pathway and Wnt/?-catenin signaling pathway both participated the neuroprotection process by Dex against cerebral I/R injury in rats.In this process,Wnt/?-catenin signaling pathway was located at downstream of PI3K/AKT signaling pathway and was mediated by PI3K/AKT signaling pathway.3.Wnt/?-catenin signaling pathway played an important part in the protection against cerebral I/R injury in rats.4.In the protection process by Dex against I/R injury,the protective effect of PI3K/AKT signaling pathway was partly related to anti-apoptosis,however its downstream Wnt/?-catenin signaling pathway seemed related to other mechanisms.5.Treatment with GSK3? inhibitor showed a protective effect on cerebral I/R injury in rats.Antiapoptotic effect may be one of its mechanism,and the activation of Wnt/?-catenin signaling pathway may be the second mechanism for it. |
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