Roles Of TGF-?1/Smad2/3 Signaling Pathway And Cx43 In Isoflurane Post-conditioning Of Cerebral Ischemia/reperfusion Injury In Rats

Object: After 90 minutes of cerebral ischemia,rats inhaled a concentration of 1 MAC(1.5%)isoflurane immediately for 60 minutes.After a reperfusion of 24 hours,we investigated the role of Cx43 and transforming growth factor ?1 in cerebral ischemia/reperfusion injury in rats.Methods: Healthy male Sprague Dawley rats,which weigh 250-300 g,was used to establish the MCAO model,the middle cerebral artery was blocked for 90 minutes and then we removed the thread for a reperfusion of 24 hours.Rats with cerebral ischemia/reperfusion injury were treated with1.5% isoflurane at the starting time point of reperfusion for 1 hour.The protective effects of 1.5%isoflurane post-conditioning was tested by neurological deficit scoring and 2,3,5-triphenyl tetrazolium chloride staining(TTC staining).TUNEL and HE staining were both used to observe the apoptosis of CA1 area cells in the hippocampus tissue of the rats.Function of protein synthesis in neurons was tested by Nissl's staining.Expression levels of Cx43,p-Cx43,Smad2/3,TGF-?1,p-Smad2/3 were all measured by the western-blot analysis,q RT-PCR and immunofluorescence technology(IF).Results: Compared with the Sham group,brain infarct size,neurological deficit scores and damaged cells in ischemic/reperfusion(I/R)injury group were increased evidently(P<0.05).Nevertheless,in the ISO group,damage of brain was significantly ameliorated(P<0.05).q RT-PCR showed a higher TGF-?1 m RNA expression in the hippocampal tissue of ISO group than I/R group(P<0.05);Western blot and immunofluorescence results showed similar changes of p-Cx43 in ISO group(P<0.05).The expression levels of TGF-?1 and p-Smad2/3 both increased in the ISO group(P<0.05),whereas unphosphorylated Smad2/3 and total Cx43 expression didn't change in all groups(P>0.05).However,when TGF-?1 inhibitor(LY2157299)was applied,expression levels of p-Cx43 significantly decreased as well as neuronal density(P<0.05).By contrast,the expression level of TGF-?1 did not change significantly after the application of p-Cx43 inhibitor(Ro318220)(P>0.05).Conclusion: The concentration of 1MAC isoflurane post-conditioning(ISO)may alleviate cerebral I/R injury through up-regulating the expression of p-Cx43 and TGF-?1/Smad2/3 signaling pathway may be involved in the process.