ABSTRACT
Objective To evaluate the effect of sevoflurane preconditioning on autophagy during ischemiareperfusion (I/R) injury to isolated rat hearts and the role of PI3K/Akt signaling pathway.Methods Healthy adult male Wistar rats,aged 6-8 weeks,weighing 250-280 g,were anesthetized.Their hearts were excised and perfused in a Langendorff apparatus.Eighty-four isolated rat hearts with I/R injury were randomly divided into 7 groups (n =12 each):normal control group (NC group),I/R group,sevoflurane preconditioning group (S + I/R group),normal control plus wortmannin group (NC + W group),I/R plus wortmannin group (I/R + W group),sevoflurane preconditioning plus wortmannin group (S + I/R + W group),and solvent group (S + I/R + D group).In NC group,the hearts were continuously perfused with K-H solution for 180 min.In I/R group,the hearts were perfused with K-H solution for 30 min,and then subjected to ischemia for 30 min followed by 120 min of reperfusion.In S+ I/R group,the hearts were perfused with K-H solution for 10 min,and then with K-H solution saturated with 2.5％ sevoflurane for 15 min,followed by 5 min washout with K-H solution before ischemia.In NC + W group,wortmannin (PI3K inhibitor) 15 μg/kg was injected intraperitoneally at 30 min before chest opening,and the other procedures were similar to those previously described in group NC.In I/R + W group,wortmarnin 15 μg/kg was injected intraperitoneally at 30 min before chest opening,and the other procedures were similar to those previously described in group I/R.In S + I/R + W group,wortmannin 15 μg/kg was injected intraperitoneally at 30 min before chest opening,and the other procedures were similar to those previously described in S + I/R group.In S + I/R + D group,dimethyl sulfoxide 1.5 ml/kg was injected intraperitoneally at 30 min before chest opening,and the other procedures were similar to those previously described in group S + I/R.The HR,± dp/dtmax,left ventricular developed pressure (LVDP) and left ventricular end-diastolic pressure (LVEDP) were recorded at the end of equilibration and reperfusion.At the end of reperfusion,coronary effluent was collected to detect lactate dehydrogenase (LDH) activity,and myocardial specimens were obtained to calculate the percentage of myocardial infract size.The expression of autophagy marker LC3-Ⅱ and Akt,phosphor-Akt (p-Akt),mammalian target of rapamycin (mTOR),and phosphor-mTOR (p-mTOR) was determined by Western blot.Results Compared with NC group,no significant change was found in the parameters of hemodynamics in NC + W group,and HR,± dp/dtmax and LVDP were significantly decreased,LVEDP,myocardial infract size,and LDH activity were increased,LC3-Ⅱ expression was up-regulated,and the expression of p-Akt and p-mTOR was down-regulated in the other groups.Compared with group I/R,HR,± dp/dtmax,and LVDP were significantly increased,LVEDP,myocardial infract size,and LDH activity were decreased,LC3-Ⅱ expression was downregulated,and the expression of p-Akt and p-mTOR was up-regulated in S + I/R and S + I/R + D groups,and no significant change was found in each parameter in S+ I/R+ W group.Compared with S + I/R group,HR,± dp/ dtmax and LVDP were significantly decreased,LVEDP,myocardial infract size and LDH activity were increased,LC3-Ⅱ expression was up-regulated,and the expression of p-Akt and p-mTOR was down-regulated in S + I/R + W group,and no significant change was found in each parameter in S + I/R + D group.Conclusion Sevoflurane preconditioning can decrease autophagy of myocardial cells during I/R through activating PI3K/Akt signaling pathway and enhancing mTOR activity in the downstream,thus protecting isolated rat hearts against I/R injury.