Role of nitric oxide in mitigation of autophagy and cell apoptosis by sevoflurane postconditioning during ischemia-reperfusion in isolated rat hearts

Objective To evaluate the role of nitric oxide in sevoflurane postconditioning-induced mitigation of autophagy and cell apoptosis during ischemia/reperfusion (I/R) in isolated rat hearts.Methods The hearts of male Sprague-Dawley rats,aged 2-3 months,weighing 250-300 g,were excised and retrogradely perfused in a Langendorff apparatus.One hundred and eight isolated rat hearts,which were successfully perfused in a Langendorff apparatus,were equally and randomly divided into 6 groups:control group (C group),sevoflurane group (S group),I/R group,sevoflurane postconditioning group (SSP group),sevoflurane postconditioning + L-NAME (non-selective nitric oxide synthase (NOS) inhibitor group (SSP + L group),and L-NAME group (L group).The hearts were perfused with K-H solution for 150 min in C group.The hearts were continuously perfused for 180 min and perfused with K-H solution containing 3％ sevoflurane for 15 min starting from 60 min of perfusion in S group.After being perfused with K-H solution for 30 min,the hearts were subjected to occlusion for 30 min followed by reperfusion for 120 min in the other groups except C and S groups.After onset of reperfusion,the hearts were perfused with K-H solution containing 3％ sevoflurane for 15 min in SSP group,the hearts were perfused with K-H solution containing 3％ sevoflurane and L-NAME 100 μmol/L for 15 and 60 min,respectively,in SSP + L group,and the hearts were perfused with K-H solution containing L-NAME 100μmol/L for 60 min in L group.Inn ediately before ischemia,and at 30,60,90 and 120 min of reperfusion,each parameter of cardiac function was recorded.At the end of reperfusion,myocardial specimens were obtained at the end of reperfusion for measurement of the infarct size,NOS activity,NO content,and expression of Bcl-2,Beclin 1 and caspase-3,for observation of formation of autophagosomes,and for examination of the pathological changes.Results Compared with C group,LVSP,+ dp/dtmax,-dp/dtmax,NOS activity and NO content were significantly decreased,and LVEDP was increased in I/R and SSP groups.Compared with I/R group,LVSP,+ dp/dtmax,-dp/dtmax,NOS activity and NO content were significantly increased,LVEDP was decreased,Bcl-2 expression was down-regulated,and the expression of Beclin 1 and caspase-3 was up-regulated in SSP group,and no significant changes were found in each index in SSP+ L and L groups.Compared with SSP group,LVSP,+ dp/dtmax,-dp/dtmax,NOS activity and NO content were significantly decreased,LVEDP was increased,Bcl-2 expression was down-regulated,and the expression of Beclin 1 and caspase-3 was up-regulated in SSP + L group.Conclusion The mechanism by which sevoflurane postconditioning reduces I/R injury may be related to promoted NO product and inhibited autophagy and cell apoptosis in isolated rat hearts. Key words: Nitric oxide;  Autophagy;  Apoptosis;  Anesthetics, inhalation;  Myocardial reperfusion injury