RRC ID 42226
Author Fujita T, Fukuyama R, Enomoto H, Komori T.
Title Dexamethasone inhibits insulin-induced chondrogenesis of ATDC5 cells by preventing PI3K-Akt signaling and DNA binding of Runx2.
Journal J Cell Biochem
Abstract Glucocorticoids play important roles in cell growth and differentiation. In this study, we investigated the effect of application of dexamethasone (DEX) at the early stage of chondrogenesis using the prechondrogenic cell line, ATDC5, which differentiates into chondrocytes in the presence of insulin. When ATDC5 cells were cultured in the presence of DEX and insulin, DEX inhibited insulin-induced cellular condensation and subsequent cartilaginous nodule formation, and reduced proteoglycan synthesis and type II collagen expression dose-dependently. Pretreatment with 10(-8) M DEX for 1 day inhibited insulin-induced Akt phosphorylation, but not ERK1/2 phosphorylation, in ATDC5 cells. Treatment of ATDC5 cells with insulin for more than 2 days upregulated the levels of phosphatidylinositol 3-kinase (PI3K) subunit proteins, p85 and p110, and Akt, whereas the upregulation was inhibited in the presence of 10(-8) M DEX. In electrophoresis mobility shift assays (EMSAs), treatment with 10(-8) M DEX inhibited DNA binding of Runx2 during culture of ATDC5 cells with insulin. Reporter assays using osteocalcin promoter showed that DEX inhibited Runx2-dependent transcription dose-dependently. Adenoviral introduction of dominant-negative (dn)-Akt or dn-Runx2 into ATDC5 cells inhibited cellular condensation and reduced proteoglycan synthesis upon incubation with insulin, whereas adenoviral introduction of Akt or Runx2 prevented the inhibition of chondrogenesis by DEX. These findings indicate that DEX inhibits chondrogenesis of ATDC5 cells at the early stage by downregulating Akt phosphorylation as well as the protein levels of PI3K subunits and Akt, thereby suppressing PI3K-Akt signaling, and by inhibiting DNA binding of Runx2 and Runx2-dependent transcription.
Volume 93(2)
Pages 374-83
Published 2004-10-1
DOI 10.1002/jcb.20192
PMID 15368363
MeSH Adenoviridae / genetics Animals Cell Line, Tumor Chondrocytes / cytology Chondrocytes / drug effects Chondrocytes / enzymology Chondrocytes / metabolism Chondrogenesis / drug effects* Core Binding Factor Alpha 1 Subunit DNA / metabolism* DNA-Binding Proteins / genetics DNA-Binding Proteins / metabolism* Dexamethasone / pharmacology* Down-Regulation / drug effects Gene Expression Regulation Insulin / pharmacology* Insulin Antagonists / pharmacology Mice Osteocalcin / genetics Osteocalcin / metabolism Phosphatidylinositol 3-Kinases / metabolism* Phosphoinositide-3 Kinase Inhibitors Phosphorylation / drug effects Promoter Regions, Genetic / genetics Protein Binding / drug effects Protein-Serine-Threonine Kinases / antagonists & inhibitors Protein-Serine-Threonine Kinases / genetics Protein-Serine-Threonine Kinases / metabolism* Proto-Oncogene Proteins / antagonists & inhibitors Proto-Oncogene Proteins / genetics Proto-Oncogene Proteins / metabolism* Proto-Oncogene Proteins c-akt Signal Transduction / drug effects Transcription Factor AP-2 Transcription Factors / genetics Transcription Factors / metabolism* Transcription, Genetic / drug effects
IF 3.448
Times Cited 46
Human and Animal Cells