The Roles Of Aquaporin-4 And ERK1/2 Pathway In Protective Effect Of Remifentanil Postconditioning Against Adult Myocardial Hypoxia/Reoxygenation Injury

Objective By using the model of myocardial hypoxia/reoxygenation injury in adult.This paper is going to investigate the protective effect of remifentanil postconditioning on myocardial hypoxia/reoxygenation injury in adult,and to further observe the role of three opioid receptors（μ,δ,κ）in this effect,and also to discover whether this effect is transduced by extracellular signal-regulated kinase（ERK1/2）signaling pathway,to regulate the expression of AQP-4 and to alleviate the degree of cardiac edema.Methods Myocardial hypoxia/reoxygenation injury model is established by cutting the intact trabeculae of adult right atrial appendage.66 trabecular muscles are randomly divided into 11 groups,The normal control group（Group C）:being perfused reoxygenation liquid for 210 min,no hypoxia/reoxygenation;hypoxia/reoxygenation group（Group HR）:trabecular muscles hypoxia for 90 min/reoxygenation for 120 min;10^-11,10^-10 or 10^-99 M remifentanil postconditioning group（Group LRP,MRP or HRP）:trabecular muscles hypoxia for 90 min/reoxygenation for 120 min,infusion 10^-11,10^-10 or 10^-99 M remifentanil between 10min before the end of hypoxia to 10 min after the start of reoxygenation;μ,δorκreceptor Antagonist group（CTOP,NTD or nor-BNI group）:trabecular muscles hypoxia for 90 min/reoxygenation for 120 min,infusion of 2 nM CTOP,10 nM NTD or 1 nM nor-BNI between 20 min before the end of hypoxia to 10 min after the start of reoxygenation;μ,δorκreceptor antagonist+10^-10 M remifentanil postconditioning group（CTOP+MRP,NTD+MRP or nor-BNI+MRP group）:trabecular muscles hypoxia for 90 min/reoxygenation for 120 min,2 nM CTOP,10 nM NTD,1 nM nor-BNI,10^-10 M remifentanil were perfused spectively at the corresponding time.During the experiment,the contractile tension of trabecular muscles is monitored.After the end of reoxygenation,the trabecular muscles were randomly divided into two parts.One was observed and graded under light microscopes,and the other was used to detect the expressions of AQP-4,t-ERK1/2,p-ERK1/2 by Western Blot.Results（1）Comparison of trabecular muscle tension changes:compared within group,trabecular muscle tension of group C remained basically the same（P>0.05）;the trabecular contractile tension of group HR decreased with the prolongation of hypoxia time（P<0.05）,but partially restored in the reoxygenation stage（P<0.05）.Inter-group comparison:In hypoxia phase,there was no difference in muscle trabecular tension between each group except the group C（P>0.05）.In reoxygenation stage,the trabecular contraction tension of MRP and HRP groups was significantly improved compared with HR group（P<0.05）;In the same stage,the trabecular contraction tension recovery of CTOP and NTD group was lower than HR group（P<0.05）,while there was no difference between HR group and nor-BNI group in it（P>0.05）.In the same stage,there was no difference in the recovery of trabecular tension between CTOP+MRP and NTD+MRP groups（P>0.05）.（2）Comparison of edema degree:Compared with group C,myocardial cells and intercellular spaces in HR group were significantly swollen,and the cross-sectional area of cells was significantly increased（P<0.05）.Compared with the HR group,the degree of myocardial cell and intercellular swelling and the area of cell crosscutting were decreased in the MRP,HRP and nor-BNI+MRP group（P<0.05）.（3）Comparison of relative expression of AQP-4:Compared with group C,the expression level of AQP-4 in HR group was increased（P<0.05）;Compared with HR group,the expression level of AQP-4 in MRP and HRP group were down-regulated（P<0.05）.There was no difference between MRP and HRP group（P>0.05）and there was also no difference among CTOP+MRP group,NTD+MRP group and HR group（P>0.05）.There was no difference between nor-BNI+MRP group and MRP group either.（P>0.05）.（4）the comparison of the relative expression of p-ERK:Compared to group C,the relative expression level of p-ERK in HR group has decreased（P<0.05）;multiple comparisons among the groups showed that compared to HR group,the expression level of p-ERK in MRP and HRP group was up-regulated（P<0.05）;there was no difference between MRP group and HRP group（P>0.05）;and compared with HR group,there was no difference among CTOP+MRP,NTD+MRP group and MRP group（P>0.05）and there was no difference between not-BNI+MRP group and MPR group（P>0.05）.Conclusion（1）Remifentanil postconditioning,relating to the activation ofμandδopioid receptor,is able to alleviate myocardial hypoxia/reoxygenation injury in adult.（2）It is possible that AQP-4 may be involved in myocardial hypoxia/reoxygenation injury process,remifentanil postconditioning can decrease the expression of AQP-4.（3）Remifentanil postconditioning regulate AQP-4 may be associated with ERK1/2 signaling pathway in myocardial hypoxia/reoxygenation.