The activation mechanism of Nrf2-ARE pathway in protective effect of ischemia and pinacidil postconditioning on isolated rat hearts / 中华胸心血管外科杂志

ABSTRACT

Objective To observe the activation mechanism of Nrf2-ARE pathway in protective effect of ischemia and pinacidil postconditioning on isolated rat hearts.Methods The hearts of adult male Sprague Dawley rats were established ischemia-reperfusion injury model,and devided into six groups(n =8,each group),i.e.Normal group(Group N),ischemiareperfusion group (Group Con,I/R),ischemic postconditioning group (Group IPO),pinacidil postconditioning group (Group P50),N-(2-mercaptopropionyl)-glycine(MPG,2mmol/L) + IPO group(Group M + IPO),MPG + P50 group(Group M + P50).Rat hearts were perfused with Krebs-Henseleit(K-H) buffer for 20 minutes for equilibration.Subsequently,Group N was perfused with K-H buffer for 100 minutes after equilibration,Group Con was perfused with 4℃ ST.Thomas solution to stop the heart beating after equilibration,then the hearts were underwent 40 minutes global ischemia under 32℃,and followed by the K-H solution for 60 minutes.Group IPO after global ischemia period,the hearts were subjected to six 10-seconds cycles of ischemia/reperfusion at the beginning of reperfusion,then were reperfused for 58 minutes.Group P50 after global ischemia,rat hearts were perfused with K-H buffer containing pinacidil(50.μmol/L) for 2 minutes before reperfusion.Group M + IPO after global ischemia,the hearts were subjected to perfuse with K-H buffer containing MPG(2 mmol/L) for 3 minutes,and then underwent six 10-seconds cycles of ischemia/reperfusion before reperfusion.Group M + P50 after global ischemia,the hearts were perfused with K-H buffer containing MPG(2 mmol/L) for 3 minutes,and then subjected to perfuse with K-H buffer containing pinacidil(50 μmol/L) for 2 minutes before reperfusion.Cardiac function indexes(such as HR,LVDP,LVEDP,and the Max dp/dt) at the end point of equilibration and repeffusion were observed and recorded.The ultrastructure of myocardial tissue was observed by electron microscopy and the mitochondrial Flameng score was calculated.RT-PCR and western-blot were applied to detect the gene transcription and protein expression of HO-1,NQO1,SOD1,and Nrf2 in left ventricular myocardial tissue after reperfusion.Results The HR,LVDP and + dp/dtmax at the end of reperfusionthe cardiac function indexes are lower among each group compared with group N,group 1PO and group P50 are better than group Con (P ＜ 0.05).Compared with group IPO,there is no significant difference in group group P50,but group M + IPO is obviously decreased(P ＜ 0.05).Compared with group P50,group M + P50 index is decreased significantly(P ＜ 0.05).The LVEDP at the end of reperfusion is lower than that among each group as compared with group Con,which is significantly increased in group Con (P ＜ 0.05).Compared with group IPO,there is no significant difference in group P50,but group M + IPO is significantly increased(P ＜ 0.05).Compared with group P50,the group M + P50 is obviously decreased(P ＜ 0.05).The ultrastructure of myocardial tissue in group N is mostly normal,group Con presence serious damage.The ultrastructure damage of myocardial tissue is improved in group IPO and group P50 as compared with that in group Con,while group M + IPO is more serious than group IPO,group M + P50 is more serious group P50.The mitochondrial Flameng score is higher among each group as compared with group N (P ＜ 0.05),the score is lower in group IPO and group P50 as compared with group Con and corresponding nonblocking group (M + IPO,M + P50,P ＜0.05).The mRNA and the protein expressions of HO-1,NQO1,SOD1 and Nrf2 among each group are lower as compared with group N(P ＜0.05).Compared with those in group Con,the mRNA and the protein expressions in group IPO and group P50 are obviously increased(P ＜ 0.05),group IPO and group P50 are higher than those in group adding active oxygen scavenger(MPG) (P ＜ 0.05).Conclusion Ischemic postconditioning and pinacidil postconditioning have protective effect of myocardial tissue from ischemia reperfusion injury,while improve the cardiac function index.The cardiac protective effect of Ischemic and Pinacidil postconditioning methods may be involved the ROS in early reperfusion,which activate the Nrf2-ARE pathway,and up-regulate the expression downstream antioxidant protein and phase Ⅱ detoxifying enzyme,ultimately improve the cardiac function index during the reperfusion period.