| Objective:To investigate the effect of ischemia or pinacidil postconditioning on function of Langendorff perfused rat hearts,and to explore the protective mechanisms of Nuclear factor-E2 related factor2(Nrf2)-Antioxidant response element(ARE) pathway on postconditioning.Methods:56 Langendorff-perfused isolated Sprague-Dawley male rat hearts were divided into 7 groups (n=8, each group). After 20 min equilibration ischemia (40 min)/reperfusion (60 min) (I/R) was induced(group C), rat hearts were perfused with Krebs-Henseleit buffer containing different concentrations of pinacidil (5,10,30,50μM) for 5 min(group P) or subjected to six 10s cycles of ischemia/reperfusion(group IPO) at the beginning of reperfusion, the hearts were then reperfused for 55 or 58 min. Normal hearts were left untreated. Heart function was assessed by developed pressure (LVDP),±dp/dtmax, DP, heart rate (HR) and left ventricular end-diastolic pressure (LVEDP) at the point of equilibration and reperfusion end. To detect the gene and protein expression of Nrf2, quinone oxidoreductase 1(NQO1), Heme oxygenase 1(HO-1) and superoxide dismutase 1(SOD1) of the samples from left ventricle obtained after reperfusion, we used the methods of RT-PCR and Western blotting.Results:1. The cardiac function index There was no obvious difference in the cardiac function between each group after equilibrium (P> 0.05). After reperfusion, the cardiac function in group N, IPO, P(30,50μM) were obviously better than group C and P5μM (P<0.01 or 0.05), group PlOμM were obviously better than group P5μM on LVDP,-dp/dtmax and LVEDP (P<0.01 or 0.05) while group P5μM were obviously better than group C on LVDP,+ dp/dtmax and LVEDP (P<0.01 or 0.05). Ischemia hearts treated with pinacidil improved cardiac function in a concentration-dependent manner.2. The mRNA expressions of Nrf2, HO-1, SOD1 and NQO1 The mRNA expressions of Nrf2, HO-1, SOD1 and NQO1 in group C, IPO, P(5,10,30,50μM) were obviously higher than group N (P<0.01 or 0.05). The mRNA expressions of Nrf2, HO-1, SOD1 and NQO1 were induced in pinacidil-treated hearts in a concentration-dependent manner. Nrf2:The mRNA expressions in group IPO, P(30, P50μM) were obviously higher than other groups (P<0.01 or 0.05) and there were no obvious difference between them. SOD1:The mRNA expressions in group IPO, P50μM were obviously higher than group C and P5μM (P<0.01 or 0.05), P30μM were obviously higher than group C (P< 0.05). NQO1:The mRNA expressions in group C, IPO, P(5,10,30,50μM) were no obviously difference(P>0.05). HO-1:The mRNA expressions in group IPO, P50μM were obviously higher than group C and P5μM (P<0.01 or 0.05).3. The protein expressions of Nrf2, HO-1, SOD1 and NQO1 The protein expressions of Nrf2, HO-1, SOD1 and NQO1 in group C, IPO, P(5,10,30,50μM) were obviously higher than group N (P<0.01). The protein expressions of Nrf2, HO-1, SOD1 and NQO1 were induced in pinacidil-treated hearts in a concentration-dependent manner. Nrf2 and NQO1: The protein expressions in group IPO, P(30,50μM) were obviously higer than other groups (P<0.01 or 0.05), the protein expressions in group C, P(5, 10μM) were no obvious difference (P>0.05). HO-1 and SOD1:The protein expressions of HO-1 and SOD1 in group IPO, P(30,50μM) were obviously higer than group C and P5μM (P<0.01 or 0.05), the protein expressions of SOD1 in group P10μM were obviously higer than group P5μM (P<0.05).Conclusion:Ischemia or pinacidil postconditioning could relieve ischemia reperfusion injury of isolated ischemia hearts, pinacidil could improve the cardiac function in a concentration-dependent manner in this experiment. Nrf2 which could upregulate antioxidants contributed to the effect of myocardial protection produced by ischemia or pinacidil postconditioning, and both mRNA and protein expression of Nrf2 and antioxidants are induced in pinacidil-treated hearts in a concentration-dependent fashion, the protective mechanisms of postconditioning may be partly mediated by Nrf2 activation, and then upregulate antioxidants through Nrf2-ARE pathway. Ischemia reperfusion may activate Nrf2-ARE pathway to survive ischemia myocardium. |
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