AIMS: Cellular repressor of E1A-stimulated genes (CREG) is a homeostasis-modulating gene abundantly expressed in adult artery endothelium. Previous studies have demonstrated a protective effect of CREG against atherosclerosis through prevention of vascular smooth muscle cell apoptosis. However, the role of CREG in endothelial cells (ECs) apoptosis and the underlying signaling mechanisms are unknown. METHOD AND RESULTS: We ascertained that CREG expression was decreased in atherogenesis-prone endothelium in apolipoprotein E-null (apoE(-/-)) mice compared with their wild-type littermates using in situ immunofluorescent staining. Terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling (TUNEL) staining and caspase-3 activity assays determined that treatment of apoE(-/-) mice arteries with staurosporine (STS) significantly induced endothelial apoptosis associated with a reduction of CREG expression. Gain- and loss-of-function analyses revealed that silencing CREG expression significantly enhanced ECs apoptosis, whereas CREG overexpression abrogated apoptosis stimulated by STS or etoposide (VP-16). Blocking assays using the neutralizing antibody for vascular endothelial growth factor (VEGF) and the specific inhibitor of phosphoinositide 3-kinase (PI3K), such as LY294002 or wortmannin, demonstrated that the protective effect of CREG on ECs apoptosis was mainly mediated by activation of the VEGF/PI3K/AKT signaling pathway. CONCLUSIONS: These data demonstrate that CREG plays a critical role in protecting the vascular endothelium from apoptosis, and the protective effort of CREG against ECs apoptosis is through the activation of the VEGF/PI3K/AKT signaling pathway.
AIMS: Cellular repressor of E1A-stimulated genes (CREG) is a homeostasis-modulating gene abundantly expressed in adult artery endothelium. Previous studies have demonstrated a protective effect of CREG against atherosclerosis through prevention of vascular smooth muscle cell apoptosis. However, the role of CREG in endothelial cells (ECs) apoptosis and the underlying signaling mechanisms are unknown. METHOD AND RESULTS: We ascertained that CREG expression was decreased in atherogenesis-prone endothelium in apolipoprotein E-null (apoE(-/-)) mice compared with their wild-type littermates using in situ immunofluorescent staining. Terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling (TUNEL) staining and caspase-3 activity assays determined that treatment of apoE(-/-) mice arteries with staurosporine (STS) significantly induced endothelial apoptosis associated with a reduction of CREG expression. Gain- and loss-of-function analyses revealed that silencing CREG expression significantly enhanced ECs apoptosis, whereas CREG overexpression abrogated apoptosis stimulated by STS or etoposide (VP-16). Blocking assays using the neutralizing antibody for vascular endothelial growth factor (VEGF) and the specific inhibitor of phosphoinositide 3-kinase (PI3K), such as LY294002 or wortmannin, demonstrated that the protective effect of CREG on ECs apoptosis was mainly mediated by activation of the VEGF/PI3K/AKT signaling pathway. CONCLUSIONS: These data demonstrate that CREG plays a critical role in protecting the vascular endothelium from apoptosis, and the protective effort of CREG against ECs apoptosis is through the activation of the VEGF/PI3K/AKT signaling pathway.