| Objective: Aquaporins,a family of proteins with the function of transmembrane transport of water,play an important role in maintaining the dynamic balance of water in the brain and cerebral edema caused by stroke.This study observe the effect of isoflurane post-conditioning on brain edema and cell damage during focal cerebral ischemia/reperfusion(I/R)injury in rats,and investigate the role of AQP4 in the treatment of cerebral I/R injury in rats and its relationship with BMP4/Smad1/5/8 signal pathway though using inhibitors of AQP4 channel and BMP4/Smad1/5/8 signal pathway.Methods: A model of middle cerebral artery occlusion(MCAO)in male adult Sprague–Dawley rats was established to simulate cerebral I/R injury.After 90 minutes of middle cerebral artery embolization,rats in the isoflurane post-conditioning(ISO)group were put into 1.5% isoflurane immediately after reperfusion.The rats of inhibitor group received intraperitoneal injection of related inhibitor before any ischemic treatment.After 24 hours of ischemia,the specimens were collected.Brain injury and cerebral infarction in rats were determined by using neurobehavioral evaluation and2,3,5-triphenyl tetrazolium chloride(TTC)staining.Brain water content were used as an index for brain edema.HE and thionine staining were determined to evaluate brain cells and neuronal injury.The expression levels of AQP4,BMP4,Smad1/5/8 and phosphorylated Smad1/5/8 were detected by Western blot,immunofluorescence(IF)and real-time quantitative PCR(q RT-PCR).Results:(1)compared with the Sham group,the neurobehavioral score of I/R group was generally higher.The cerebral infarction volume and water content were increased after I/R injury,while these in ISO group were significantly ameliorated(P<0.01).(2)q RT-PCR suggested that the level of AQP4 m RNA in hippocampus of rats in ISO group was significantly lower than that in I/R group(P<0.01).The results of Western blot and IF showed that expression of AQP4 protein in brain was significantly increased as well as the fluorescence intensity increased in I/R group,whereas in the ISO group,the expression of AQP4 protein was decreased(P<0.05).(3)Compared with I/R group,the expression of BMP4 protein and phosphorylated Smad1/5/8 protein increased significantly(P<0.01),but there was no significant change in the expression of total Smad1/5/8 protein(P>0.05).The expression level of AQP4 protein increased after intraperitoneal injection of BMP4inhibitor(LDN193189).But the expression of BMP4 protein and the density of neurons in the CA1 area of hippocampus decreased with lessened Nissl corpuscles(P<0.05).However,the expression level of BMP4 did not change significantly after the application of AQP4 inhibitor(TGN020)(P>0.05),but the expression and intensity of fluorescence of AQP4 decreased with neuron density and Nissl corpuscles in the CA1 area of hippocampus increased(P>0.05).Conclusion:(1)Isoflurane post-conditioning can assuredly ameliorate brain cell injury and edema after cerebral I/R injury in rats.(2)AQP4 may take part in the formation of cerebral edema after cerebral I/R injury.Isoflurane post-conditioning can inhibit the occurrence of brain edema and reduce brain injury by reducing the expression of AQP4 protein.(3)BMP4/Smad1/5/8 signaling pathway may display a certain function in the neuroprotection of isoflurane post-conditioning. |
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