NOR-1 is involved in VEGF-induced endothelial cell growth

Neuron-derived orphan receptor-1 (NOR-1) is a transcription factor over-expressed in human atherosclerotic plaques that is involved in vascular smooth muscle cell proliferation. The aim of this study was to analyze whether NOR-1 plays a role in vascular endothelial growth factor (VEGF) induced endothelial cell growth. VEGF induced an early and transient up-regulation of NOR-1 in human umbilical vein endothelial cells (HUVEC). NOR-1 up-regulation by VEGF is processed through VEGF receptor-2 (VEGFR-2) and involves different signaling pathways including increase in cytosolic Ca2+, activation of protein kinase C and mitogen-activated protein kinase (MAPK) pathways (both extracellular-signaling regulated kinase [ERK] and p38 MAPK). VEGF induced CREB activation (phosphorylation in Ser133). In transfection assays, a dominant-negative of CREB inhibited NOR-1 promoter activity, while mutation of the three CRE sites in the NOR-1 promoter abolished VEGF-induced NOR-1 promoter activity. Antisense oligonucleotides against NOR-1 inhibited VEGF-induced endothelial cell growth (reduced DNA synthesis, and inhibited cell cycle progression and endothelial cell wound repair after mechanical injury). These results indicate that NOR-1 could be a key transcription factor regulating endothelial cell growth induced by VEGF.