Effect of emulsified isoflurane postconditioning on Nrf2-ARE signaling pathway during myocardial ischemia-reperfusion in rats in vitro

Abstract

Objective To evaluate the effect of emulsified isoflurane postconditioning on nuclear factor-E2 related factor 2 (Nrf2) -antioxidant response element (ARE) signaling pathway during myocardial ischemia-reperfusion (I/R) in rats in vitro. Methods Healthy male Sprague-Dawley rats, aged 4-5 months, weighing 250-300 g, were heparinized and anesthetized with intraperitoneal 1% amobarbital sodium 40 mg/kg.Their hearts were excised and perfused in a Langendorff apparatus with K-H solution.Thirty-two isolated rat hearts were randomly divided into 4 groups (n=8 each) using a random number table: control group (group C) , group I/R, emulsified isoflurane postconditioning group (EIP group) and fat emulsion group (group F) . After 20 min of equilibration, group C was continuously perfused with K-H solusion for 100 min.Group I/R underwent 40 min of ischemia at 32 ℃, followed by reperfusion for 60 min.In EIP and F groups, after undergoing 40 min of global ischemia, the isolated hearts were perfused for 2 min with K-H solution containing 1.68 mmol/L emulsified isoflurane and 712 mg/L intralipid, respectively, starting from the onset of reperfusion, and then were continuously perfused with K-H solution containing oxygen at 37 ℃ for 58 min.Heart rate (HR) , left ventricular developed pressure (LVDP) , left ventricular end-diastolic pressure (LVEDP) , and positive maximal pressure of left ventricular increase (+ dp/dtmax) were recorded at the end of equilibration and reperfusion.At the end of reperfusion, myocardial specimens were obtained from the left ventricle for examination of the ultrastructure of myocardial cells and for determination of Nrf2, heme oxygenase-1 (HO-1) , quinone oxidoreductase 1 (NQO1) , and superoxide dismutase 1 (SOD1) and mRNA expression using Western blot and real-time PCR. Results Compared with group C, HR, + dp/dtmax and LVDP were significantly decreased, and LVEDP was increased at the end of reperfusion in I/R and F groups, LVDP was significantly decreased, LVEDP was increased, and no significant changes were found in HR and + dp/dtmax at the end of reperfusion in EIP group, and Nrf2, HO-1, NQO1 and SOD1 and mRNA expression was down-regulated at the end of reperfusion in I/R, EIP and F groups.Compared with group I/R, HR, + dp/dtmax and LVDP were significantly increased, and LVEDP was decreased at the end of reperfusion in EIP and F groups, Nrf2, HO-1, NQO1 and SOD1 and mRNA expression was significantly up-regulated at the end of reperfusion in EIP group, and Nrf2, HO-1, NQO1 and SOD1 mRNA expression was significantly up-regulated, Nrf2 and HO-1 expression was up-regulated, and no significant changes were found in NQO1 and SOD1 expression at the end of reperfusion in group F. Compared with group EIP, HR, + dp/dtmax and LVDP were significantly decreased, LVEDP was increased, and Nrf2, HO-1, NQO1 and SOD1 and mRNA expression was down-regulated in group F. Conclusion Emulsified isoflurane postconditioning attenuates myocardial I/R injury probably by activating Nrf2-ARE signaling pathway in isolated rat hearts. Key words: Isoflurane; Fat emulsions, intravenous; Ischemic postconditioning; Myocardial reperfusion injury; Nuclear factor-E2 related factor 2; Response elements