title: The PI3K/AKT cell signaling pathway is involved in regulation of osteoporosis.
abstract: BACKGROUND
  Osteoporosis is a systemic skeletal disease with the high incidence, serious complications, financial burden, and heavily decrease in living quality.
  
  
  METHODS
  Proliferation of osteoblast was tested by 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) method, alkaline phosphatase (ALP) activity of osteoblasts was tested by ALP REAGENT, Calcium level was determined by a colorimetric assay, mRNA expression of phosphoinositide-3 kinase (PI3K), 3-phosphoinositide-dependent protein kinase 1 (PDK1), Akt, Caspase-3, Caspase-7, Caspase-9, osteocalcin (OCN), Osterix and Runx2 of osteoblasts was tested by RNA preparation and quantitative reverse transcription polymerase chain reaction (RT-PCR), and protein expression of phospho-PI3K, phospho-PDK1 and phospho-Akt was measured by Western Blot analysis.
  
  
  RESULTS
  In osteoporosis model rats, it found that mRNA expression of PI3K, PDK1 and Akt showed no changes while protein expression of phospho-PI3K, phospho-PDK1 and phospho-Akt in bone tissue was decreased dramatically. To further characterize the molecular mechanisms that regulate osteoporosis, we examined the contribution of the PI3K/Akt cell signaling pathway in cultured osteoblasts. It suggested that, the blockade of PI3K activation by LY294002, a specific inhibitor of the PI3K/Akt signaling pathway in osteoblasts, heavily inhibited cell proliferation, ALP activity, calcium accumulation, and mRNA expression of OCN, Osterix and Runx2. However, mRNA expression of Caspase-3 and Caspase-9 was promoted accordingly.
  
  
  CONCLUSIONS
  The in vivo and in vitro studies indicated that the PI3K/Akt cell signaling pathway is involved in the inhibition of osteoporosis through promoting osteoblast proliferation, differentiation and bone formation.
authors.affiliation: a Orthopaedic Department , 309 Hospital of People's Liberation Army , Beijing , China and.
authors.forename: Jian-Cheng
authors.initials: JC
authors.lastname: Xi
authors.affiliation: b Outpatient Department , Command College of Land Force of People's Liberation Army , Shijiazhuang City , China.
authors.forename: Hai-Yu
authors.initials: HY
authors.lastname: Zang
authors.affiliation: a Orthopaedic Department , 309 Hospital of People's Liberation Army , Beijing , China and.
authors.forename: Li-Xin
authors.initials: LX
authors.lastname: Guo
authors.affiliation: a Orthopaedic Department , 309 Hospital of People's Liberation Army , Beijing , China and.
authors.forename: Hai-Bin
authors.initials: HB
authors.lastname: Xue
authors.affiliation: a Orthopaedic Department , 309 Hospital of People's Liberation Army , Beijing , China and.
authors.forename: Xiang-Dong
authors.initials: XD
authors.lastname: Liu
authors.affiliation: a Orthopaedic Department , 309 Hospital of People's Liberation Army , Beijing , China and.
authors.forename: Yi-Bing
authors.initials: YB
authors.lastname: Bai
authors.affiliation: a Orthopaedic Department , 309 Hospital of People's Liberation Army , Beijing , China and.
authors.forename: Yuan-Zheng
authors.initials: YZ
authors.lastname: Ma
mesh_terms: D000818:Animals; D017209:Apoptosis; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism; D049109:Cell Proliferation; D002478:Cells, Cultured; D004195:Disease Models, Animal; D005260:Female; D010006:Osteoblasts / Q000166:cytology / Q000378:metabolism*; D010024:Osteoporosis / Q000209:etiology / Q000378:metabolism* / Q000473:pathology; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism*; D053245:RANK Ligand / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction
chemical_list: D053245:RANK Ligand; D012333:RNA, Messenger; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D002118:Calcium
keywords: Akt; PI3K; bone formation; differentiation; inhibitor; osteoporosis; proliferation