RESUMEN
<p><b>BACKGROUND</b>Ischemic postconditioning (IPost), able to significantly attenuate myocardial ischemia reperfusion injury, is dependent on RISK signaling. Studies have shown that Notch signaling repairs damaged myocardium, and this study aimed to investigate the effect of Notch signaling in myocardial IPost.</p><p><b>METHODS</b>We used H9c2 cells to establish the myocardial IPost and Hypoxia/Reoxygenation (H/R) model in vitro. which were randomly divided into control, H/R, IPost, Hepatocyte growth factor (HGF)+IPost and DAPT+IPost, N1ICD+IPost, miRNA+IPost, and Mock treatment groups. The myocardial cell viability was assessed by MTT, the cell apoptosis was detected using Annexin V/PI double staining and flow cytometry analyses. The expression of N1ICD, Hes1, PTEN Phospho-Akt/Akt, Phospho-GSK-3β/GSK-3β were detected by Western blotting. Finally, we assessed the changes in ψm using the potential-sensitive dye JC-1 and measured using flow cytometry analyses.</p><p><b>RESULTS</b>The Notch1 signaling is activated by HGF and ectopic expression of N1ICD during myocardial IPost, which increased myocardial cell viability, prevented cardiomyocyte apoptosis, and reduced loss of the mitochondrial membrane potential. However, myocardial ischemia reperfusion injury was increased in IPost when Notch1 signaling was inhibited using DAPT or with knockdown by Notch1-miRNA. Western blotting found that PTEN was down-regulated by Hes1 when Notch1 was activated, which consequently promoted Akt and GSK-3β phosphorylation.</p><p><b>CONCLUSIONS</b>Notch1 crosstalk with RISK signaling may be dependent on PTEN, which plays a cardioprotective role during IPost. This mechanism could provide a promising therapeutic target for the treatment of ischemic heart disease.</p>