Soluble RAGE attenuates myocardial I/R injuries via FoxO3-Bnip3 pathway

Soluble receptor for advanced glycation end-products (sRAGE) was reported to inhibit cardiac apoptosis through the mitochondrial pathway during myocardial ischemia/reperfusion (I/R) injury. Meanwhile, the proapoptotic protein Bcl2 and adenovirus E1B 19-kDa-interacting protein 3 (Bnip3) was reported to mediate mitochondrial depolarization and be activated by the Forkhead box protein O3 (FoxO3a). Therefore, it is supposed that FoxO3a-Bnip3 pathway might be involved in the inhibiting effects of sRAGE on mitochondrial apoptosis during I/R. I/R surgery or glucose deprivation/reoxygenation was adopted to explore mitochondrial depolarization, apoptosis and related signaling pathways in mice hearts and cultured cardiomyocytes. The results showed that overexpression of sRAGE in cardiomyocytes dramatically improved cardiac function and reduced infarct areas in I/R treated mice. sRAGE inhibited mitochondrial depolarization and cardiac apoptosis during I/R, which correlated with reduced expression of Bnip3, Sirt2, phosphorylation of Akt and FoxO3a which translocated into nucleus in cultured cardiomyocytes. Either Sirt2 or FoxO3a silencing enhanced the inhibiting effects of sRAGE on mitochondrial depolarization induced by I/R in cultured cardiomyocytes. Meanwhile, overexpression or silencing of FoxO3a affected the inhibiting effects of sRAGE on Bnip3 and cleaved caspase-3 in cultured cardiomyocytes. Therefore, it is suggested that sRAGE inhibited I/R injuries via reducing mitochondrial apoptosis through the FoxO3a-Bnip3 pathway.