Angiogenesis is the development of blood capillaries from pre-existing vessels. Vascular endothelial growth factor (VEGF) is a key regulator of vessel growth and regression, and acts as an endothelial survival factor by protecting endothelial cells from apoptosis. Many genes involved in cell proliferation and apoptosis are regulated by the nuclear factor kappa B (NF kappa B) transcription factor family. This study aimed to address the hypothesis that VEGF-mediated survival effects on endothelium involve NF kappa B. Using an NF kappa B-luciferase reporter adenovirus, we observed activation of NF kappa B following VEGF treatment of human umbilical vein endothelial cells. This was confirmed using electrophoretic mobility shift assay and found to involve nuclear translocation of NF kappa B sub-unit p65. However, NF kappa B activation Occurred without degradation of inhibitory I kappa B proteins (I kappa B alpha, I kappa B beta, and I kappa B epsilon). Instead, tyrosine phosphorylation of I kappa B alpha was observed following VEGF treatment, suggesting NF kappa B activation was mediated by degradation-independent dissociation of I kappa B alpha from NF kappa B. Adenovirus-mediated over-exprcssion of either native I kappa B alpha, or of I kappa B alpha in which tyrosine residue 42 was mutated to phenylalanine, inhibited induction of NF kappa B-dependent luciferase activity in response to VEGF. Further-more, VEGF-induced upregulation of mRNA for the anti-apoptotic protein Bcl-2 and cell survival following serum withdrawal was reduced following I kappa B alpha over-expression. This Study highlights that different molecular mechanisms of NF kappa B activation may be involved downstream of stimuli which activate the endothelial lining of blood vessels. (c) 2005 Elsevier Inc. All rights reserved.