Neuron-derived orphan receptor-1 (NOR-1) is induced by thrombin and mediates vascular endothelial cell growth.
OBJECTIVE
Neuron-derived orphan receptor-1 (NOR-1) is a transcription factor overexpressed in human atherosclerotic plaques that is involved in vascular smooth muscle cell (VSMC) proliferation. The aim of this study was to analyze the role of NOR-1 in thrombin-induced endothelial cell growth.


RESULTS
Thrombin induced an early and transient up-regulation of NOR-1 in human umbilical vein endothelial cells (HUVEC). NOR-1 up-regulation by thrombin is dependent on multiple pathways, including cytosolic Ca(2+), activation of protein kinase C (PKC), mitogen-activated protein kinase (MAPK) pathways [both extracellular-regulated kinase (ERK) and p38 MAPK], and downstream activation of cAMP response element binding protein (CREB). The critical role of CREB in the induction of NOR-1 by thrombin was demonstrated using a dominant-negative of CREB. By site-direct mutagenesis we identified two CRE sites present at -79 and -53 bp in the NOR-1 promoter involved in the up-regulation of NOR-1 by thrombin. Inhibition of thrombin receptor PAR-1 abolished CREB activation, NOR-1 up-regulation and DNA synthesis (used as an index of cell proliferation). TRAP-6 mimicked both NOR-1 up-regulation and CREB activation induced by thrombin, while PPACK (an irreversible thrombin inhibitor) prevented such an effect. Direct inhibition of thrombin-induced NOR-1 up-regulation, using antisense oligonucleotides or siRNA against NOR-1, reduced DNA synthesis and endothelial cell re-growth after injury in an in vitro model of wound repair.


CONCLUSIONS
These results indicate that NOR-1 up-regulation plays a key role in thrombin-induced endothelial cell growth. Strategies aimed to block NOR-1 could be useful to prevent vascular effects triggered by thrombin.
Martorell
L
L
Centro de Investigación Cardiovascular, CSIC/ICCC, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain.
Martínez-González
J
J
Crespo
J
J
Calvayrac
O
O
Badimon
L
L
D049109:Cell Proliferation; D004268:DNA-Binding Proteins / Q000502:physiology*; D042783:Endothelial Cells / Q000166:cytology*; D004730:Endothelium, Vascular / Q000166:cytology; D005786:Gene Expression Regulation; D006801:Humans; D016297:Mutagenesis, Site-Directed; D009474:Neurons / Q000378:metabolism; D011401:Promoter Regions, Genetic; D034741:RNA, Small Interfering / Q000378:metabolism; D011987:Receptors, Steroid / Q000502:physiology*; D018179:Receptors, Thrombin / Q000378:metabolism; D011988:Receptors, Thyroid Hormone / Q000502:physiology*; D015398:Signal Transduction; D013917:Thrombin / Q000378:metabolism*; D015854:Up-Regulation; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
D004268:DNA-Binding Proteins; C490412:NR4A3 protein, human; D034741:RNA, Small Interfering; D011987:Receptors, Steroid; D018179:Receptors, Thrombin; D011988:Receptors, Thyroid Hormone; D048051:p38 Mitogen-Activated Protein Kinases; D013917:Thrombin