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J Biol Chem. 2007 Sep 14;282(37):27298-305. Epub 2007 Jul 10.

Oxidative stress antagonizes Wnt signaling in osteoblast precursors by diverting beta-catenin from T cell factor- to forkhead box O-mediated transcription.

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  • 1Division of Endocrinology and Metabolism, Center for Osteoporosis and Metabolic Bone Diseases, University of Arkansas for Medical Sciences and the Central Arkansas Veterans Healthcare System, Little Rock, AR 72205, USA.

Abstract

We have elucidated that oxidative stress is a pivotal pathogenetic factor of age-related bone loss and strength in mice, leading to, among other changes, a decrease in osteoblast number and bone formation. To gain insight into the molecular mechanism by which oxidative stress exerts such adverse effects, we have tested the hypothesis that induction of the Forkhead box O (FoxO) transcription factors by reactive oxygen species may antagonize Wnt signaling, an essential stimulus for osteoblastogenesis. In support of this hypothesis, we report herein that the expression of FoxO target genes increases, whereas the expression of Wnt target genes decreases, with increasing age in C57BL/6 mice. Moreover, we show that in osteoblastic cell models, oxidative stress (exemplified by H(2)O(2)) promotes the association of FoxOs with beta-catenin, beta-catenin is required for the stimulation of FoxO target genes by H(2)O(2), and H(2)O(2) promotes FoxO-mediated transcription at the expense of Wnt-/T-cell factor-mediated transcription and osteoblast differentiation. Furthermore, beta-catenin overexpression is sufficient to prevent FoxO-mediated suppression of T-cell factor transcription. These results demonstrate that diversion of the limited pool of beta-catenin from T-cell factor- to FoxO-mediated transcription in osteoblastic cells may account, at least in part, for the attenuation of osteoblastogenesis and bone formation by the age-dependent increase in oxidative stress.

PMID:
17623658
[PubMed - indexed for MEDLINE]
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