Role of FoxOs in Skeletal Homeostasis

FoxOs 在骨骼稳态中的作用

• 批准号: 8063571
• 负责人: Maria Jose Almeida
• 金额: $ 31.32万
• 依托单位: UNIV OF ARKANSAS FOR MED SCIS
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-04-15 至 2015-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8063571
• 关键词: Acetylation; Adult; Adverse effects; Affect; Aging; Antioxidants; Apoptosis; Binding; Biological Assay; Bone remodeling; Cell Cycle; Cell Death; Cell Line; Cell Respiration; Cells; DNA Repair; DNA Repair Enzymes; DNA lesion; Defense Mechanisms; Electron Transport; Enzymes; Family; Foundations; Free Radical Scavenging; Gene Expression; Gene Targeting; Generations; Genes; Genetic Transcription; Glucocorticoids; Health; Histone Deacetylase; Homeostasis; Immunoprecipitation; In Vitro; Inflammatory; Interferons; Knowledge; Lead; Lipid Peroxidation; Longevity; Mediating; Mediator of activation protein; Mitochondria; Modeling; Mus; Osteoblasts; Osteoclasts; Osteocytes; Osteogenesis; Oxidative Stress; Peroxides; Phenotype; Phosphorylation; Play; Post-Translational Protein Processing; Prevalence; Protein Isoforms; Proteins; Reactive Oxygen Species; Risk; Role; Signal Transduction; Signaling Molecule; Site; Stem cells; Stress; Testing; Transgenes; Vertebral Bone; Work; age related; base; biological adaptation to stress; bone; bone loss; bone mass; bone strength; catalase; chromatin immunoprecipitation; cytokine; in vivo; mutant; novel; osteoblast differentiation; osteoclastogenesis; osteoporosis with pathological fracture; overexpression; prevent; progenitor; promoter; protein function; public health relevance; recombinase; skeletal; therapy development; transcription factor

DESCRIPTION (provided by applicant): Wnt/2-catenin signaling is indispensable for osteoblastogenesis and bone formation. In studies leading to this application, a novel mechanism of Wnt/2-catenin antagonism, whereby activation of FoxO transcription factors diverts the limited pool of 2-catenin from Wnt induced TCF/Lef- transcription to FoxO-mediated transcription was elucidated. This antagonistic cascade in bone is initiated by reactive oxygen species (ROS) and represents both a mediator of, and a defense mechanism against, oxidative stress. FoxOs mediate oxidative stress responses by regulating the expression of genes involved in cell cycle, DNA repair, and lifespan. The involvement of the histone deacetylase Sirt1 in the inhibition of Wnt/2-catenin by ROS; and co- activation by 2-catenin of the expression of FoxO-target genes that promote osteoblast survival under stress conditions was also established. Moreover, evidence was obtained that the actions of glucocorticoids or TNF1 on bone are mediated, at least in part, by ROS-induced FoxO activation. The above observations form the foundation of the hypothesis that activation of FoxO transcription factors by oxidative stress represents a previously unappreciated cell-autonomous mechanism of Wnt/2-catenin antagonism which contributes to the adverse effects of aging, glucocorticoid excess and inflammatory cytokines on bone, by diverting 2-catenin from TCF- to FoxO-mediated transcription. To test this hypothesis, the role of ROS-induced FoxO post- translational modifications on the binding of FoxOs to 2-catenin, in osteoblastic cells, and whether ROS lead to recruitment of 2-catenin to the promoter of FoxO-target genes will be investigated (Aim 1). In addition, in vitro studies will be done to establish the consequences of FoxO activation in osteoblast lifespan and differentiation (Aim 2). Finally, mice overexpressing FoxO3a in osteoblast precursors and their progeny (osteoblasts, osteocytes); and mice in which the three main FoxO isoforms FoxO1, 3a, and 4 are conditionally deleted will be used to examine the role of FoxOs in skeletal homeostasis (Aim 3). This work should advance knowledge of how aging, glucocorticoid excess or inflammatory cytokines decrease bone mass. Furthermore, it should provide a better understanding of how to optimize the treatment of this condition. PUBLIC HEALTH RELEVANCE: The proposed studies seek to identify the means by which aging, glucocorticoid excess or inflammatory cytokines cause bone loss. This will be accomplished by studying changes in the function of proteins that control bone-forming cells. Increased understanding of the mechanisms that control bone formation will provide important information for the development of therapies to maintain or increase bone mass and strength, thereby reducing the risk of osteoporotic fractures

描述（由申请人提供）：Wnt/2-连环蛋白信号传导对于成骨细胞发生和骨形成是不可或缺的。在导致该应用的研究中，阐明了 Wnt/2-连环蛋白拮抗作用的新机制，即 FoxO 转录因子的激活将有限的 2-连环蛋白池从 Wnt 诱导的 TCF/Lef 转录转移到 FoxO 介导的转录。骨中的这种拮抗级联是由活性氧 (ROS) 引发的，既是氧化应激的介体，又是氧化应激的防御机制。 FoxOs 通过调节参与细胞周期、DNA 修复和寿命的基因表达来介导氧化应激反应。组蛋白脱乙酰酶 Sirt1 参与 ROS 对 Wnt/2-catenin 的抑制；并且还建立了2-连环蛋白共激活FoxO靶基因的表达，从而促进成骨细胞在应激条件下的存活。此外，有证据表明糖皮质激素或 TNF1 对骨的作用至少部分是由 ROS 诱导的 FoxO 激活介导的。上述观察结果构成了以下假设的基础：氧化应激对 FoxO 转录因子的激活代表了一种以前未被认识到的 Wnt/2-catenin 拮抗细胞自主机制，通过将 2-catenin 从 TCF 介导的转录转移到 FoxO 介导的转录，导致衰老、糖皮质激素过量和炎症细胞因子对骨的不利影响。为了检验这一假设，将研究 ROS 诱导的 FoxO 翻译后修饰对成骨细胞中 FoxO 与 2-catenin 结合的作用，以及 ROS 是否导致 2-catenin 募集到 FoxO 靶基因的启动子上（目标 1）。此外，还将进行体外研究以确定 FoxO 激活对成骨细胞寿命和分化的影响（目标 2）。最后，在成骨细胞前体及其后代（成骨细胞、骨细胞）中过度表达 FoxO3a 的小鼠；条件性删除三种主要 FoxO 同工型 FoxO1、3a 和 4 的小鼠将用于检查 FoxO 在骨骼稳态中的作用（目标 3）。这项工作应该增进人们对衰老、糖皮质激素过量或炎症细胞因子如何减少骨量的认识。此外，它应该可以让人们更好地了解如何优化这种情况的治疗。 公共健康相关性：拟议的研究旨在确定衰老、糖皮质激素过量或炎症细胞因子导致骨质流失的方式。这将通过研究控制骨形成细胞的蛋白质功能的变化来实现。进一步了解控制骨形成的机制将为开发维持或增加骨量和强度的疗法提供重要信息，从而降低骨质疏松性骨折的风险