title: α1B -Adrenoceptor signalling regulates bone formation through the up-regulation of CCAAT/enhancer-binding protein δ expression in osteoblasts.
abstract: OBJECTIVE
  The sympathetic nervous system regulates bone remodelling, in part, through ß2 -adrenoceptor signalling. However, the physiological role of α1 -adrenoceptor signalling in bone in vivo remains unclear. Therefore, to obtain a deeper understanding of bone remodelling by the sympathetic nervous system, we investigated the role of α1B -adrenoceptor signalling in bone metabolism.
  
  
  METHODS
  Prazosin, a nonspecific α1 -adrenoceptor antagonist, was administered for 2 weeks in C57BL6 mice, and efficacy was evaluated by bone microarchitecture using microcomputed tomography and determination of bone formation by fluorescent labelling of bone. We also compared the bone phenotype of α1B -adrenoceptor null mice (α1B (-/-) ) with that of wild-type littermates.
  
  
  RESULTS
  We demonstrated that the systemic administration of prazosin decreased bone formation. In addition, α1B -adrenoceptor-deficient mice had a lower bone mass due to decreased bone formation but did not exhibit any changes in bone-resorbing activity. Furthermore, stimulation with phenylephrine, a non-specific α1 -adrenoceptor agonist, increased the expression of the transcriptional factor CCAAT/enhancer-binding protein δ (Cebpd) in MC3T3-E1 osteoblastic cells. The overexpression of Cebpd induced cellular proliferation in MC3T3-E1 cells, whereas the silencing of Cebpd suppressed it.
  
  
  CONCLUSIONS
  Taken together, these results suggested that α1B -adrenoceptor signalling is required for bone formation and regulated cellular proliferation through a mechanism relevant to the up-regulation of Cebpd in osteoblasts and, thus, provide new evidence for the physiological importance of α1B -adrenoceptor signalling in bone homeostasis.
authors.affiliation: Department of Pharmacology, School of Dentistry, Aichi Gakuin University, Nagoya, 464-8650, Japan.
authors.forename: Kenjiro
authors.initials: K
authors.lastname: Tanaka
authors.affiliation: Department of Pharmacology, School of Dentistry, Aichi Gakuin University, Nagoya, 464-8650, Japan.
authors.forename: Takao
authors.initials: T
authors.lastname: Hirai
authors.affiliation: Department of Pharmacology, School of Dentistry, Aichi Gakuin University, Nagoya, 464-8650, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Kodama
authors.affiliation: Department of Pharmacology, School of Dentistry, Aichi Gakuin University, Nagoya, 464-8650, Japan.
authors.forename: Hisataka
authors.initials: H
authors.lastname: Kondo
authors.affiliation: Department of Pharmacology, School of Dentistry, Aichi Gakuin University, Nagoya, 464-8650, Japan.
authors.forename: Kazunori
authors.initials: K
authors.lastname: Hamamura
authors.affiliation: Department of Pharmacology, School of Dentistry, Aichi Gakuin University, Nagoya, 464-8650, Japan.
authors.forename: Akifumi
authors.initials: A
authors.lastname: Togari
mesh_terms: D058646:Adrenergic alpha-1 Receptor Agonists / Q000494:pharmacology; D058668:Adrenergic alpha-1 Receptor Antagonists / Q000494:pharmacology; D000818:Animals; D051743:CCAAT-Enhancer-Binding Protein-delta / Q000235:genetics*; D002460:Cell Line; D005269:Femur / Q000378:metabolism; D008297:Male; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010006:Osteoblasts / Q000378:metabolism*; D010012:Osteogenesis / Q000502:physiology*; D010656:Phenylephrine / Q000494:pharmacology; D011224:Prazosin / Q000494:pharmacology; D018340:Receptors, Adrenergic, alpha-1 / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D015854:Up-Regulation
chemical_list: D058646:Adrenergic alpha-1 Receptor Agonists; D058668:Adrenergic alpha-1 Receptor Antagonists; D018340:Receptors, Adrenergic, alpha-1; D051743:CCAAT-Enhancer-Binding Protein-delta; D010656:Phenylephrine; D011224:Prazosin