Cellular repressor of E1A stimulated genes enhances endothelial monolayer integrity

Cellular repressor of E1A stimulated genes (CREG) is a novel modulator that maintains the homeostasis of vascular cells. The present study aimed to investigate the effects of CREG on tumor necrosis factor (TNF)-alpha-mediated inflammatory injury of vascular endothelial cells. Human umbilical vein endothelial cells (HUVECs) were cultured and CREG overexpressing (VC), knockdown (VS) and mock-transfected (VE) HUVECs were challenged with TNF-alpha. We demonstrated that TNF-alpha prompted robust intercellular filamentous actin (F-actin) stress fiber formation as examined by rhodamin-phalloidin staining. Transwell assay and rhodamine B isothiocyanate-dextran staining indicated that TNF-alpha induced intercellular hyperpermeability of the HUVEC monolayers. These effects were attenuated in VC cells with forced CREG overexpression but significantly potentiated in VS cells with CREG silencing. After TNF-alpha stimulation, interleukin (IL)-6 and IL-8 secretions in VE cells were markedly increased and inducible nitric oxidase (iNOS) expression substantially elevated, whereas these effects were pronouncedly damped in VC cells. Conversely, in VS cells, the increase in inflammatory markers was substantially potentiated. Immunofluorescence staining demonstrated that nuclear factor kappa B (NF-kappa B) slowly and transiently translocated into the nuclei of VC cells upon TNF-alpha stimulation. However, a more swift and sustained nuclear translocation was observed in VS as compared to VE cells. Corresponding changes in the pattern of its protein expression was also observed. These data suggested that CREG can inhibit NF-kappa B activation, TNF-alpha-induced inflammatory responses and the hyperpermeability of endothelial cells, and may therefore represent a potential therapeutic target for pathological vascular injury.