title: Oxidative stress antagonizes Wnt signaling in osteoblast precursors by diverting beta-catenin from T cell factor- to forkhead box O-mediated transcription.
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.
authors.affiliation: Division 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, Arkansas 72205.
authors.forename: Maria
authors.initials: M
authors.lastname: Almeida
authors.affiliation: Division 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, Arkansas 72205.
authors.forename: Li
authors.initials: L
authors.lastname: Han
authors.affiliation: Division 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, Arkansas 72205.
authors.forename: Marta
authors.initials: M
authors.lastname: Martin-Millan
authors.affiliation: Division 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, Arkansas 72205.
authors.forename: Charles A
authors.initials: CA
authors.lastname: O'Brien
authors.affiliation: Division 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, Arkansas 72205. Electronic address: manolagasstavros@uams.edu.
authors.forename: Stavros C
authors.initials: SC
authors.lastname: Manolagas
mesh_terms: D000375:Aging / Q000502:physiology; D000818:Animals; D002454:Cell Differentiation; D002478:Cells, Cultured; D005260:Female; D000071161:Forkhead Box Protein O1; D051858:Forkhead Transcription Factors / Q000502:physiology*; D006861:Hydrogen Peroxide / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL; D010006:Osteoblasts / Q000166:cytology / Q000378:metabolism*; D018384:Oxidative Stress; D015398:Signal Transduction / Q000502:physiology*; D013234:Stem Cells / Q000166:cytology / Q000378:metabolism*; D051820:TCF Transcription Factors / Q000502:physiology*; D014158:Transcription, Genetic; D051153:Wnt Proteins / Q000502:physiology*; D051176:beta Catenin / Q000502:physiology*
chemical_list: D000071161:Forkhead Box Protein O1; D051858:Forkhead Transcription Factors; C467200:Foxo1 protein, mouse; D051820:TCF Transcription Factors; D051153:Wnt Proteins; D051176:beta Catenin; D006861:Hydrogen Peroxide