Des-acyl ghrelin protects microvascular endothelial cells from oxidative stress-induced apoptosis through sirtuin 1 signaling pathway

ObjectiveGhrelin is a stomach-derived hormone. Acylation of ghrelin has been essential for its biological activities such as stimulating appetite. On the other hand, the function of des-acyl ghrelin (Des-G) has not been fully elucidated. The aim of the present study is to examine the anti-apoptotic effect of Des-G on endothelial cells.Materials/MethodsAfter human retinal microvascular endothelial cells (RMECs) were pretreated with or without 100 nmol/L Des-G, apoptosis was induced with 0.1 mmol/L hydrogen peroxide (H₂O₂). For pharmacological inhibition of surtuin 1 (SIRT1) catalytic activity, the cells were treated with 10 μmol/L Ex-527. Inhibition of SIRT1 with siRNA was also performed. The quantitative estimation of DNA fragmentation was used as a marker of apoptosis. Furthermore, total SIRT activity in nuclear extracts, mRNA and protein levels of SIRT1, manganese superoxide dismutase (MnSOD) and catalase were determined.ResultsDes-G pretreatment protected RMECs from oxidative stress-induced apoptosis and increased SIRTs deacetylase activity in nuclear extracts. On the other hand, both pharmacological and siRNA mediated inhibition of SIRT1 attenuated the anti-apoptotic effect of Des-G. Moreover, Des-G increased mRNA and protein levels of SIRT1 and antioxidant enzymes such as MnSOD and CAT, which are downstream targets of SIRT1. Although the treatment of Ex-527 did not alter mRNA expression levels of SIRT1, it decreased mRNA expression levels of antioxidant enzymes in the cells with Des-G pretreatment.ConclusionsOur results suggest that SIRT1 signaling pathway contributes to protective effect of Des-G against oxidative stress-induced apoptosis.