title: Deficiency of the NR4A neuron-derived orphan receptor-1 attenuates neointima formation after vascular injury.
abstract: BACKGROUND
  The neuron-derived orphan receptor-1 (NOR1) belongs to the evolutionary highly conserved and most ancient NR4A subfamily of the nuclear hormone receptor superfamily. Members of this subfamily function as early-response genes regulating key cellular processes, including proliferation, differentiation, and survival. Although NOR1 has previously been demonstrated to be required for smooth muscle cell proliferation in vitro, the role of this nuclear receptor for the proliferative response underlying neointima formation and target genes trans-activated by NOR1 remain to be defined.
  
  
  RESULTS
  Using a model of guidewire-induced arterial injury, we demonstrate decreased neointima formation in NOR1(-/-) mice compared with wild-type mice. In vitro, NOR1-deficient smooth muscle cells exhibit decreased proliferation as a result of a G(1)-->S phase arrest of the cell cycle and increased apoptosis in response to serum deprivation. NOR1 deficiency alters phosphorylation of the retinoblastoma protein by preventing mitogen-induced cyclin D1 and D2 expression. Conversely, overexpression of NOR1 induces cyclin D1 expression and the transcriptional activity of the cyclin D1 promoter in transient reporter assays. Gel shift and chromatin immunoprecipitation assays identified a putative response element for NR4A receptors in the cyclin D1 promoter, to which NOR1 is recruited in response to mitogenic stimulation. Finally, we provide evidence that these observations are applicable in vivo by demonstrating decreased cyclin D1 expression during neointima formation in NOR1-deficient mice.
  
  
  CONCLUSIONS
  These experiments characterize cyclin D1 as an NOR1-regulated target gene in smooth muscle cells and demonstrate that NOR1 deficiency decreases neointima formation in response to vascular injury.
authors.affiliation: 575 Wethington Bldg, 900 S Limestone St, Lexington, KY 40536-0200, USA.
authors.forename: Takashi
authors.initials: T
authors.lastname: Nomiyama
authors.forename: Yue
authors.initials: Y
authors.lastname: Zhao
authors.forename: Florence
authors.initials: F
authors.lastname: Gizard
authors.forename: Hannes M
authors.initials: HM
authors.lastname: Findeisen
authors.forename: Elizabeth B
authors.initials: EB
authors.lastname: Heywood
authors.forename: Karrie L
authors.initials: KL
authors.lastname: Jones
authors.forename: Orla M
authors.initials: OM
authors.lastname: Conneely
authors.forename: Dennis
authors.initials: D
authors.lastname: Bruemmer
mesh_terms: D000818:Animals; D001011:Aorta / Q000166:cytology; D017209:Apoptosis / Q000502:physiology; D002455:Cell Division / Q000502:physiology; D002470:Cell Survival / Q000502:physiology; D002478:Cells, Cultured; D003331:Coronary Vessels / Q000166:cytology; D019938:Cyclin D1 / Q000235:genetics; D056742:Cyclin D2; D016213:Cyclins / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D050684:E2F Transcription Factors / Q000378:metabolism; D015870:Gene Expression / Q000502:physiology; D006801:Humans; D051379:Mice; D008817:Mice, Mutant Strains; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000293:injuries* / Q000502:physiology*; D057105:Nuclear Receptor Subfamily 4, Group A, Member 1; D010766:Phosphorylation / Q000502:physiology; D011401:Promoter Regions, Genetic / Q000502:physiology; D051381:Rats; D011987:Receptors, Steroid / Q000235:genetics* / Q000378:metabolism; D016160:Retinoblastoma Protein / Q000378:metabolism; D017539:Tunica Intima / Q000166:cytology / Q000293:injuries / Q000502:physiology; D014945:Wound Healing / Q000502:physiology*
chemical_list: C486196:Ccnd2 protein, mouse; D056742:Cyclin D2; D016213:Cyclins; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; C539821:NR4A1 protein, human; C539818:Nr4a1 protein, mouse; C539820:Nr4a1 protein, rat; D057105:Nuclear Receptor Subfamily 4, Group A, Member 1; D011987:Receptors, Steroid; D016160:Retinoblastoma Protein; D019938:Cyclin D1