HMGB1 induces endothelial progenitor cells apoptosis via RAGE-dependent PERK/eIF2α pathway

Studies have demonstrated that the high-mobility group 1B protein (HMGB1) could regulate endothelial progenitor cell (EPC) homing, but the effect of HMGB1 on EPC apoptosis and associated mechanisms are still unclear. The aim of this study was to investigate the effects of HMGB1 on EPC apoptosis and the possible involvement of the endoplasmic reticulum (ER) stress pathway. EPC apoptosis was determined by flow cytometry. The expressions of PERK, eIF2 alpha, and CHOP were detected by western blotting. Additionally, the effects of PERK shRNA on the biological behaviors of EPCs were assessed. Our results showed that incubation of EPCs with HMGB1 (0.1-1 mu g/ml) for 12-48 h induced apoptosis as well as activated ER stress transducers, as assessed by up-regulating PERK protein expression and eIF2 alpha phosphorylation in a dose or time-dependent manner. Moreover, HMGB1-mediated EPC apoptosis and CHOP expression were dramatically suppressed by PERK shRNA or a specific eIF2 alpha inhibitor (salubrinal). Importantly, a blocking antibody specifically targeted against RAGE (anti-RAGE antibody) markedly inhibited HMGB1-induced EPC apoptosis and ER stress marker protein (PERK, eIF2 alpha, and CHOP) expression levels. Our novel findings suggest that HMGB1 triggered EPC apoptosis in a manner of RAGE-mediated activation of the PERK/eIF2 alpha pathway.