Androgen inhibition of MAP kinase pathway and Elk-1 activation in proliferating osteoblasts

Kristine Wiren, A. R. Toombs, X. W. Zhang

Research output: Contribution to journalArticle

27 Citations (Scopus)

Abstract

Non-aromatizable androgens have significant beneficial effects on skeletal homeostasis independently of conversion to estradiol, but the effects of androgens on bone cell metabolism and cell proliferation are still poorly understood. Using an osteoblastic model with enhanced androgen responsiveness, MC3T3-E1 cells stably transfected with androgen receptor (AR) under the control of the type I collagen promoter (colAR-MC3T3), the effects of androgens on mitogenic signaling were characterized. Cultures were treated with the non-aromatizable androgen 5α-dihydrotestosterone (DHT) and the effects on osteoblast viability were determined as measured by an MTT assay. A complex response was observed in that continuous short-term DHT treatment enhanced osteoblast viability, but with longer-term DHT treatment inhibition was observed. The inhibition by DHT was prevented by the specific AR antagonist hydroxyflutamide, and was also observed in primary cultures of normal rat calvarial osteoblasts. In order to identify potential mediators of this effect, mitogenic pathway-specific cDNA microarrays were interrogated. Reduced hybridization of several genes important in MAP kinase-mediated signaling was observed, with the most dramatic effect on Elk-1 expression. Analysis of phosphorylation cascades demonstrated that DHT treatment inhibited phosphoERK1/2 levels, MAP kinase activation of Elk-1, Elk-1 protein and phosphoElk-1 levels, and downstream AP-1/luciferase reporter activity. Together, these data provide the first evidence that androgen inhibition of the MAP kinase signaling pathway is a potential mediator of osteoblast growth, and are consistent with the hypothesis that the MAP cascade may be a specific downstream target of DHT.

Original languageEnglish (US)
Pages (from-to)209-226
Number of pages18
JournalJournal of Molecular Endocrinology
Volume32
Issue number1
DOIs
StatePublished - Feb 2004

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Dihydrotestosterone
Osteoblasts
Androgens
Phosphotransferases
Androgen Receptor Antagonists
MAP Kinase Signaling System
Mitogen-Activated Protein Kinase 1
Transcription Factor AP-1
Androgen Receptors
Collagen Type I
Oligonucleotide Array Sequence Analysis
Luciferases
Estradiol
Homeostasis
Phosphorylation
Cell Proliferation
Bone and Bones
Growth
Genes
Proteins

ASJC Scopus subject areas

  • Endocrinology

Cite this

Androgen inhibition of MAP kinase pathway and Elk-1 activation in proliferating osteoblasts. / Wiren, Kristine; Toombs, A. R.; Zhang, X. W.

In: Journal of Molecular Endocrinology, Vol. 32, No. 1, 02.2004, p. 209-226.

Research output: Contribution to journalArticle

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