Effect Of Sevoflurane Postconditioning On Inositol-requiring Enzyme 1 Signaling Pathway In Brain Tissues In A Rat Model Of Hemorrhagic Shock And Resuscitation

Objective To evaluate the effect of sevoflurane postconditioning on inositol-requiring enzyme 1(IRE 1)signaling pathway in the brain tissues in a rat model of hemorrhagic shock and resuscitation(HSR).Methods Sixty healthy adult male Sprague-Dawley rats,weighing 300-320 g,were randomly divided into 5 groups(n=12)using the method number table:sham operated group(group Sham): only treated with catheterization(right common carotid artery and left external jugular vein)without suffering hemorrhagic shock and resuscitation;hemorrhagic shock and resuscitation group(group HSR): treated with catheterization following hemorrhagic shock and resuscitation;sevoflurane postconditioning(SP)group(group S): in the SP1,SP2 and SP3 group,the rats were post-conditioned with inhaling sevoflurane at three levels(1.2%,2.4% and 3.6%),respectively,for 30 min immediately at the onset of infusion of the shed blood.Hemorrhagic shock was induced by withdrawing blood(40%of the rat’s total blood volume)from the right common carotid artery over 30 min,followed by resuscitation 1 h after the shock with infusion of the shed blood via the left external jugular vein within 30 min.Heart rate(HR)and mean arterial pressure(MAP)were monitored continuously during the study,in which the values of MAP before withdrawing blood,immediately after the end of withdrawing blood(or 30 min after the catheterization in Sham),30 min after the end of withdrawing blood(60 min after the catheterization in Sham),before infusion of theshed blood(90 min after the catheterization in Sham),and immediately at the onset of infusion of the shed blood(120 min after the catheterization in Sham)were recorded as T0,T1,T2,T3 and T4 respectively.0.2 ml arterial blood samples were obtained at T0、T1、T3 and T4 for blood gas analysis.At 72 h after the end of infusion of the shed blood,6 rats from each group were selected randomly to perform the assessment of the spatial learning and memory ability by Morris water maze test.Then,the animals were sacrificed,and brains were acquired and sliced for determination of the expression of cysteine-containing aspartate-specific proteases 3(caspase-3)in hippocampal CA1 region by immune-histochemistry.The rest 6 rats in each group were sacrificed at 72 h after infusion of the shed blood,and the hippocampus was isolated for determination of the protein level of IRE1 and XBP1 by Western blot.Results1.Hemodynamics parameters There were no significant differences of MAP values among the five groups at T0 and T4.The MAP values of HSR and S1~3 groups at T0-3 were decreased when comparing with the Sham group(P<0.05);and the MAP values of HSR and S1~3groups at T1-3 were repressed as compared with the T0(P<0.05).2.Blood gas analysis There were no significant differences of PH,Lac and BE among the five groups at T0 and T4.Compared with the Sham group,the values of pH and BE were significantly reduced while the blood Lac was significantly increased at T1,3 in HSR and SP1~3groups(P<0.05);compared with the T0,the values of pH and BE were significantly decreased while the Lac was significantly elevated at T1,3 in HSR and SP1~3 groups(P<0.05).3.Morris water maze task Compared with Sham group,the escape latency was markedly prolonged and the number of crossing the original platform was decreased in HSR group and SP1 group(P<0.05).There was no significant difference in SP2 and SP3 groups(P>0.05).Interestingly,the changes in the escape latency and the number of crossing the original platform were both reversed in the groups of SP2 and S3 as compared with HSR group,(P<0.05).There was no significant difference in SP1 group(P> 0.05).There was no noticeable difference in escaping latency and the number of crossing the original platform between SP2 group and SP3 group(P> 0.05).4.Immunohistochemistry Compared with the Sham group,the expression of caspase-3 in hippocampal CA1 region was significantly up-regulated in group HSR and SP1(P<0.05);while this up-regulation was significantly attenuated in group SP2 and SP3 when comparing to the HSR group(P<0.05).5.Western blotting Compared with the Sham group,the protein levels of IRE1 and XBP1 were significantly up-regulated in group HSR and SP1(P<0.05);while the up-regulation of IRE1 and XBP1 were significantly inhibited in group SP2 and SP3 as compared with the HSR group(P<0.05).Conclusion Postconditioning with sevoflurane at the concentrations of 2.4% and 3.6%mitigates the hemorrhage shock and resuscitation-induced brain injury,and this protective effect may be induced by decreasing the protein level of IRE1 and XBP1 in hippocampus.