title: CYP24 promoter activity is affected by mechanical stress and mitogen-activated protein kinase in MG63 osteoblast-like cells.
abstract: OBJECTIVE
  For bone homeostasis, vitamin D plays an important role in the regulation of calcium. The enzyme CYP24 inactivates vitamin D and is involved in its regulation. However, the mechanism of expression of CYP24 in osteoblastic cells under mechanical stress is not clear. In this study we investigated CYP24 promoter activity in stretched osteoblastic cells and the participation of mitogen-activated protein kinase (MAPK) in expression of CYP24.
  
  
  METHODS
  MG63 osteoblastic cells were cultured on silicon-bottomed plates. Cells were transfected with a reporter gene that contained a CYP24 promoter. After activated vitamin D, 1,25(OH)2D3, was added or not added, cells were stretched. Stretched and non-stretched cells were investigated by luciferase dual assay. Cells were also investigated similarly using medium with an ERK1/2 inhibitor or p38 inhibitor.
  
  
  RESULTS
  The CYP24 promoter was activated by 1,25(OH)2D3 and the promoter activity decreased in stretched cells. Inhibitor of MAPK decreased CYP24 promoter activity. However, CYP24 promoter activity decreased with mechanical stress after addition of p38 inhibitor, while it did not decrease with mechanical stress after addition of ERK1/2 inhibitor. The CYP24 promoter was not activated without 1,25(OH)2D3 in any case.
  
  
  CONCLUSIONS
  Mechanical stress and MAPK control CYP24 promoter activity in the presence of Vitamin D in MG63 osteoblast-like cells.
authors.affiliation: Department of Oral Rehabilitation, Division of Occlusion and Removable Prosthodontics, Health Sciences University of Hokkaido School of Dentistry, Hokkaido, Japan. toyosita@hoku-iryo-u.ac.jp
authors.forename: Yoshifumi
authors.initials: Y
authors.lastname: Toyoshita
authors.forename: Shunji
authors.initials: S
authors.lastname: Iida
authors.forename: Hisashi
authors.initials: H
authors.lastname: Koshino
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Hirai
authors.forename: Atsuro
authors.initials: A
authors.lastname: Yokoyama
mesh_terms: D002117:Calcitriol; D045744:Cell Line, Tumor; D006801:Humans; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology*; D012516:Osteosarcoma / Q000235:genetics; D013250:Steroid Hydroxylases / Q000378:metabolism*; D013314:Stress, Mechanical; D065668:Vitamin D3 24-Hydroxylase
chemical_list: D013250:Steroid Hydroxylases; D065668:Vitamin D3 24-Hydroxylase; D020928:Mitogen-Activated Protein Kinases; D002117:Calcitriol