Myeloperoxidase-derived hypochlorous acid promotes ox-LDL-induced senescence of endothelial cells through a mechanism involving β-catenin signaling in hyperlipidemia

Myeloperoxidase (MPO)-derived product hypochlorous acid (HOCl) is able to induce cellular senescence and MPO is also expressed in endothelial cells besides the well-recognized immune cells. This study aims to clarify the association of endothelium-derived MPO with endothelial senescence in hyperlipidemia. The rats were fed with high-fat diet for 8 weeks to establish a hyperlipidemic model, which showed an increase in plasma lipids, endothelium-derived MPO expression, endothelial senescence and endothelial dysfunction concomitant with a reduction in glycogen synthase kinase 3 beta (GSK-3 beta) activity and phosphorylated beta-catenin (p-beta-catenin) level as well as an increase in beta-catenin and p53 levels within the endothelium. Next, human umbilical vein endothelial cells (HUVECs) were incubated with oxidized low density lipoprotein (ox-LDL, 100 mu g/ml) for 24 h to establish a senescent cell model in vitro. Consistent with the finding in vivo, ox-LDL-induced MPO expression and HUVECs senescence, accompanied by a decrease in GSK-3 beta activity and p-beta-catenin level as well as an increase in HOCl content, beta-catenin and p53 levels; these phenomena were attenuated by MPO inhibitor. Replacement of ox-LDL with HOCl could also induce HUVECs senescence and activate the beta-catenin/p53 pathway. Based on these observations, we conclude that endothelium-derived MPO is upregulated in hyperlipidemic rats, which may contribute to the accelerated vascular endothelial senescence through a mechanism involving the beta-catenin/p53 pathway. (C) 2015 Elsevier Inc. All rights reserved.