Role of Nrf2/ARE singling pathway in reduction of myocardial ischemia-reperfusion injury by zinc sulfate preconditioning in rats

Objective To evaluate the role of nuclear factor erythroid 2-related factor 2(Nrf2)/antioxidant response element(ARE)signaling pathway in reduction of myocardial ischemia-reperfusion(I/R)injury by ischemic preconditioning in the rats. Methods Healthy male Sprague-Dawley rats, weighing 250-300 g, aged 4-6 months, were used in the study.Their hearts were excised, and retrogradely perfused with K-H solution at 37 ℃ in a Langendorff apparatus.Forty isolated hearts were randomly divided into 4 groups(n=10 each)using a random number table: control group(group C), I/R group, ischemic preconditioning group(group IPC), and ischemic preconditioning+ Nrf2/ARE signaling pathway blocker luteolin group(group IPC+ L). After 20 min of equilibration, the hearts were continuously perfused for 100 min in group C. After 20 min of equilibration, the hearts were subjected to 40 min ischemia at 32 °C followed by 60 min of reperfusion in group I/R.In group IPC, ischemic preconditioning was induced by 6 cycles of 10 s ischemia followed by 10 s reperfusion starting from the time point immediately after 20 min of equilibration, and then the hearts were subjected to 40 min ischemia at 32 ℃ followed by 58 min of reperfusion.In group IPC+ L, after 20 min of equilibration, the hearts were perfused with K-H solution containing lueolin 50 μmol/L for 3 min before ischemia, and the other treatments were similar to those previously described in group IPC.Left ventricular developed pressure(LVDP), left ventricular end-diastolic pressure(LVDEP), heart rate(HR), and the maximum rate of increase of left ventricular pressure(+ dp/dtmax)were recorded at the end of equilibration and reperfusion.At the end of reperfusion, left ventricular myocardial tissues were obtained for examination of the ultrastructure of myocardial cells and for determination of the expression of Nrf2, heme oxygenase-1(HO-1), quinone oxidoreductase 1(NQO1), and superoxide dismutase 1(SOD1) mRNA and protein(by real-time polymerase chain reaction and Western blot, respectively). Results Compared with group C, the HR, + dp/dtmax and LVDP were significantly decreased, and LVEDP was significantly increased at the end of reperfusion in I/R and IPC+ L groups, and the expression of Nrf2, HO-1, NQO1 and SOD1 mRNA and protein was significantly up-regulated in I/R, IPC and IPC+ L groups(P 0.05). Compared with group IPC, the HR, + dp/dtmax and LVDP were significantly decreased, and LVEDP was significantly increased at the end of reperfusion, and the expression of HO-1, NQO1, SOD1 mRNA and protein was significantly down-regulated(P 0.05), and the pathological changes were significantly aggravated in group IPC+ L. Conclusion Ischemic preconditioning reduces myocardial I/R injury through activating Nrf2/ARE signaling pathway in the rats. Key words: Ischemic preconditioning; Myocardial reperfusion injury; Nuclear factor-E2 related factor 2; Response elements