title: [Dexamethasone inhibits osteoblastic differentiation by down-regulation of LIM mineralization protein 1].
abstract: To investigate the mechanisms of the inhibition of osteoblastic differentiation by dexamethasone (DEX), the effects of different doses of DEX on the activity of alkaline phosphatase (ALP), the synthesis of osteocalcin (OC) and the expression of collagen type I were observed in the cultured rat osteoblasts. The LIM mineralization protein-1 (LMP-1) mRNA, a positive regulator of osteoblasts, was semi-quantified by RT-PCR. The results showed that a lower dose (10(-9) mol/L) of DEX could enhance the activity of ALP, the synthesis of OC and the expression of collagen type I. However, a higher dose (10(-7) mol/L) of DEX inhibited them and down-regulated the expression of LMP-1 mRNA in osteoblasts. It is suggested that DEX stimulates osteoblast differentiation at lower dose, while at higher dose it inhibits osteoblast differentiation. The inhibitory action of DEX on osteoblast differentiation might be mediated by the down-regulation of LMP-1 mRNA.
authors.affiliation: Department of Biochemistry, Hebei Medical University, Shijiazhuang 050017; liusucai@163.net
authors.forename: Su-Cai
authors.initials: SC
authors.lastname: Liu
authors.forename: Zhi-Yong
authors.initials: ZY
authors.lastname: Zhang
authors.forename: En
authors.initials: E
authors.lastname: Li
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D002454:Cell Differentiation / Q000187:drug effects*; D002478:Cells, Cultured; D003907:Dexamethasone / Q000008:administration & dosage / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D018398:Homeodomain Proteins / Q000096:biosynthesis*; D060850:LIM-Homeodomain Proteins; D010006:Osteoblasts / Q000166:cytology / Q000378:metabolism*; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D014157:Transcription Factors
chemical_list: D018398:Homeodomain Proteins; D060850:LIM-Homeodomain Proteins; C499522:Lhx1 protein, rat; D012333:RNA, Messenger; D014157:Transcription Factors; D003907:Dexamethasone