Role of STAT3 signal transduction pathway in diazoxide cardioplegic solution-induced reduction of ischemia-reperfusion injury in isolated rat hearts

Objective To evaluate the role of signal transducer and activator of transcription 3 (STAT3) signal transduction pathway in diazoxide cardioplegic solution-induced reduction of ischemia-reperfusion (I/R) injury in isolated rat hearts.Methods Sixty adult male Sprague-Dawley rats,aged 2-3 months,weighing 240-260 g,were used in this study.Their hearts were excised and perfused in a Langendorff apparatus and then randomly divided into 5 groups (n=12 each):control group (group C),group I/R,cardioplegic solution group (group P),diazoxide cardioplegic solution group (group DZX),and STAT3 signal transduction pathway blocker Stattic group (group Stattic).The hearts were continuously perfused for 90 min after 15 min of equilibration in group C.Perfusion was stopped after 15 min of equilibration and restored 30 min later in I/R,P,DZX and Stattic groups.In P and DZX groups,the hearts were perfused with the cardioplegic solution containing 0.4％ dimethyl sulfoxide and 50μmol/L diazoxide,respectively,before perfusion was stopped.In group Stattic,the hearts were perfused with 10μmol/L Stattic for 5 min before perfusion with diazoxide.At 60 min of reperfusion,the hearts were sliced and stained for determination of myocardial infarct size (IS) as a percentage of area at risk (AAR) (IS/AAR),cell apoptosis and expression of phosphorylated STAT3 (p-STAT3) protein (by Western blot) and STAT3 mRNA (using RT-PCR).Apoptotic index (AI) was calculated.Results Compared with group C,the IS/AAR and AI were significantly increased in the other four groups,the expression of p-STAT3 and STAT3 mRNA was down-regulated in I/R and Stattic groups,and the expression of p-STAT3 was down-regulated and STAT3 mRNA was up-regulated in P and DZX groups (P ＜ 0.05).Compared with group I/R,the IS/AAR and AI were significantly decreased,and the expression of p-STAT3 and STAT3 mRNA was up-regulated in P and DZX groups (P ＜ 0.05),and no significant changes were found in the parameters mentioned above in Stattic group (P ＞ 0.05).The IS/AAR and AI were significantly lower,and the expression of p-STAT3 and STAT3 mRNA was higher in DZX group than in P group (P ＜ 0.05).Conclusion STAT3 signal transduction pathway is involved in diazoxide cardioplegic solution-induced reduction of I/R injury in isolated rat hearts. Key words: STAT3 transcription factor;  Diazoxide;  Myocardial reperfusion injury