Glucocorticoid suppresses the canonical Wnt signal in cultured human osteoblasts

https://doi.org/10.1016/j.bbrc.2005.01.117Get rights and content

Abstract

To explore the mechanism of glucocorticoid-induced osteoporosis, we investigated the effect of glucocorticoid on canonical Wnt signaling that emerged as a novel key pathway for promoting bone formation. Wnt3a increased the T-cell factor (Tcf)/lymphoid enhancer factor (Lef)-dependent transcriptional activity in primary cultured human osteoblasts. Dexamethasone suppressed this transcriptional activity in a dose-dependent manner, while 1,25-dihydroxyvitamin D3 increased this transcriptional activity. LiCl, an inhibitor of glycogen synthase kinase-3β, also enhanced the Tcf/Lef-dependent transcriptional activity, which was, however, not inhibited by dexamethasone. The addition of anti-dickkopf-1 antibody partially restored the transcriptional activity suppressed by dexamethasone. Dexamethasone decreased the cytosolic amount of β-catenin accumulated by Wnt3a and also inhibited the nuclear translocation of β-catenin induced by Wnt3a. These data suggest that glucocorticoid suppresses the canonical Wnt signal in cultured human osteoblasts, partially through the enhancement of the dickkopf-1 production.

Section snippets

Materials and methods

Materials. Eagle’s α-MEM, penicillin, and streptomycin were obtained from Invitrogen (Carlsbad, CA). Fetal calf serum (FCS) was purchased from Sanko Junyaku (Tokyo, Japan). Dexamethasone, 17β-estradiol, dihydrotestosterone, 1,25-dihydroxyvitamin D3, LiCl, and goat immunoglobulin (IgG) were purchased from Sigma (St. Louis, MI). Anti-β-catenin monoclonal antibody and anti-Dkk-1 goat polyclonal antibody were purchased from Transduction Laboratories (Lexington, KY) and Santa Cruz Biotechnology

Results

To investigate the effect of glucocorticoid on canonical Wnt signaling, we first examined whether glucocorticoid would affect the Tcf/Lef-dependent transcriptional activity by a Tcf-reporter gene (luciferase) assay in cultured osteoblasts (Fig. 1A). In primary cultured human osteoblasts, the addition of Wnt3a-conditioned medium (Wnt3a-CM) enhanced the Tcf/Lef-dependent transcriptional activity (approximately 3.5-fold). Dexamethasone suppressed the Wnt3a-induced Tcf/Lef-dependent transcriptional

Discussion

In the present study, we demonstrated that dexamethasone suppressed the Tcf/Lef-dependent canonical Wnt signaling pathway in primary cultured human osteoblasts. This effect was in part attributed to the increase of Dkk-1 expression by dexamethasone.

Glucocorticoid suppresses osteoblastic differentiation and proliferation by affecting multiple aspects of osteoblast function [1], [2], [3]. One well-known effect of glucocorticoid on osteoblast is the inhibition of the expression for Runx2/Cbfa1 [17]

Acknowledgments

This work was supported in part by Grants-in-Aid for Scientific Research (B), Scientific Research (C) and Exploratory Research, and a grant for the 21st Century Center of Excellence (COE) Program (Kyushu University) from the Japanese Ministry of Education, Culture, Sports, Science and Technology.

Cited by (227)

  • Pathogenic mechanisms of glucocorticoid-induced osteoporosis

    2023, Cytokine and Growth Factor Reviews
  • Glucocorticoid action in osteoblasts and systemic energy metabolism

    2023, Current Opinion in Endocrine and Metabolic Research
  • Risk for osteoporosis and fracture with glucocorticoids

    2022, Best Practice and Research: Clinical Rheumatology
View all citing articles on Scopus
View full text