A soluble receptor for advanced glycation end-products inhibits myocardial apoptosis induced by ischemia/reperfusion via the JAK2/STAT3 pathway

sRAGE can protect cardiomyocytes from apoptosis induced by ischemia/reperfusion (I/R). However, the signaling mechanisms in cardioprotection by sRAGE are currently unknown. We investigated the cardioprotective effect and potential molecular mechanisms of sRAGE inhibition on apoptosis in the mouse myocardial I/R as an in vivo model and neonatal rat cardiomyocyte subjected to ischemic buffer as an in vitro model. Cardiac function and myocardial infarct size following by I/R were evaluated with echocardiography and Evans blue/2,3,5-triphenyltetrazolium chloride. Apoptosis was detected by TUNEL staining and caspase-3 activity. Expression of the apoptosis-related proteins p53, Bax, Bcl-2, JAK2/p-JAK2, STAT3/p-STAT3, AKT/p-AKT, ERK/p-ERK, STAT5A/p-STAT5A and STAT6/p-STAT6 were detected by western blot analysis in the presence and absence of the JAK2 inhibitor AG 490. sRAGE (100 A mu g/day) improved the heart function in mice with I/R: the left ventricular ejection fraction and fractional shortening were increased by 42 and 57 %, respectively; the infarct size was decreased by 52 %, the TUNEL-positive myocytes by 66 %, and activity of caspase-3 by 24 %, the protein expression of p53 and ratio of Bax to Bcl-2 by 29 and 88 %, respectively; protein expression of the p-JAK2, p-STAT3 and p-AKT were increased by 92, 280 and 31 %, respectively. sRAGE have no effect on protein expression of p-ERK1/2, p-STAT5A and p-STAT6 following by I/R. sRAGE (900 nmol/L) exhibited anti-apoptotic effects in cardiomyocytes by decreasing TUNEL-positive myocytes by 67 % and caspase-3 activity by 20 %, p53 protein level and the Bax/Bcl-2 ratio by 58 and 86 %, respectively; increasing protein expression of the p-JAK2 and p-STAT3 by 26 and 156 %, respectively, p-AKT protein level by 33 %. The anti-apoptotic effects of sRAGE following I/R were blocked by JAK2 inhibitor AG 490. The effect of sRAGE reduction on TUNEL-positive myocytes and caspase-3 activity were abolished by PI3K inhibitor LY294002, but not ERK 1/2 inhibitor PD98059. These results suggest that sRAGE protects cardiomyocytes from apoptosis induced by I/R in vitro and in vivo by activating the JAK2/STAT3 signaling pathway.