Cox-2 Regulation of Bone Responses to PTH: Role of Osteoclasts

Cox-2 调节骨对 PTH 的反应：破骨细胞的作用

• 批准号: 9176254
• 负责人: CAROL C. PILBEAM
• 金额: $ 34.8万
• 依托单位: UNIVERSITY OF CONNECTICUT SCH OF MED/DNT
• 依托单位国家: 美国
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-07-01 至 2021-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9176254
• 关键词: Acute; Acute-Phase Proteins; Age-Months; Amyloid; Back; Bone Density; Bone Marrow; Bone Resorption; Bone remodeling; Calcium; Cell Culture Techniques; Cell Lineage; Cell model; Clinical; Coculture Techniques; Conditioned Culture Media; Cyclic AMP; Cyclic AMP-Dependent Protein Kinases; Data; Defect; Development; Diet; Dinoprostone; Dose; EP4 receptor; Environment; Enzymes; Female; Gene Expression; Gene Targeting; Genes; ITGAM gene; In Vitro; Infection; Inflammation; Inflammatory; Infusion procedures; Interleukin-1; Knock-out; Knockout Mice; Lead; Ligands; Mediating; Modeling; Molecular; Mus; New Agents; Nuclear; Osteoblasts; Osteoclasts; Osteogenesis; Osteoporosis; PTH gene; Pathway interactions; Phenotype; Production; Protein Kinase C; Proteins; Regulation; Role; Secondary Hyperparathyroidism; Serum; Signal Pathway; Signal Transduction; Stromal Cells; TNFSF11 gene; Testing; Wild Type Mouse; base; bone; bone loss; bone turnover; cyclooxygenase 2; cytokine; feeding; in vitro Model; in vivo; in vivo Model; inhibitor/antagonist; macrophage; male; novel; osteoblast differentiation; receptor; receptor expression; response; skeletal; skeletal disorder

Project Summary Intermittently injected parathyroid hormone (PTH) is a key anabolic therapy for osteoporosis, stimulating bone formation more than resorption. Paradoxically, continuously elevated PTH causes bone loss. We have identified a factor that may explain the paradox. PTH is a potent inducer in osteoblastic lineage cells of both cyclooxygenase 2 (Cox2), the major enzyme producing prostaglandin E2 (PGE2), and receptor activator of nuclear factor κB ligand (RANKL), which is required to commit bone marrow macrophages (BMMs) to become osteoclasts. RANKL and Cox2/PGE2 together cause BMMs to secrete a factor that suppresses the ability of continuous PTH to stimulate differentiation of osteoblasts. Using in vitro cell models, we identified the inhibitory factor as serum amyloid A3 (Saa3), an acute phase protein generally associated with inflammation or infection, and showed that Saa3 inhibited PTH-stimulated osteoblast differentiation by blocking PTH-stimulated cAMP production. As predicted by the in vitro models, PTH infusion in wild type (WT) mice suppressed bone formation and caused bone loss, but PTH infusion in in Cox2 knockout (KO) mice was markedly anabolic for bone. In contrast to the effects on formation, PTH infusion stimulated bone resorption equally in WT and Cox2 KO mice. We have generated a mouse with global KO of Saa3. We will test the hypothesis that Saa3 suppresses the anabolic, but not the catabolic, responses to continuously elevated PTH in vivo. Specific aim 1 will examine effects on bone formation and resorption of Saa3 in in vivo models for elevating PTH. Aim 2 will examine the effect of Saa3 on PTH-stimulated osteoblast and osteoclast differentiation in vitro and the cAMP- dependent actions by which PTH regulates Wnt signaling and the cAMP–independent signaling pathways by which PTH regulates RANKL signaling in our models. Aim 3 will examine the requirement for PGE2 and its EP4 receptor in the induction of Saa3 in BMMs and the role of Saa3 in stimulating other cytokines that can regulate the bone environment. We are proposing a novel role for Saa3; a new means by which osteoclasts regulate osteoblasts; and a novel role for Cox2/PGE2. The results of this study should strengthen our understanding of the molecular mechanisms underlying actions of PTH and may help us target bone remodeling more effectively to treat osteoporosis and other skeletal diseases.

项目摘要 间歇性注射甲状旁腺激素（PTH）是骨质疏松症的关键合成代谢疗法， 形成多于吸收。奇怪的是，持续升高的PTH会导致骨质流失。我们有 发现了一个可以解释这个悖论的因素。PTH是成骨细胞系细胞的有效诱导剂， 环氧合酶2（Cox 2）是产生前列腺素E2（PGE 2）的主要酶，也是前列腺素E2受体激活剂。 核因子κB配体（RANKL），其是使骨髓巨噬细胞（BMPs）成为 破骨细胞RANKL和Cox 2/PGE 2共同导致Bctin分泌一种抑制RANKL和Cox 2/PGE 2的能力的因子。 持续的甲状旁腺激素刺激成骨细胞的分化。使用体外细胞模型，我们鉴定了抑制性的 血清淀粉样蛋白A3（Saa 3），一种通常与炎症或感染相关的急性期蛋白， Saa 3通过阻断PTH刺激的cAMP抑制PTH刺激的成骨细胞分化， 生产正如体外模型所预测的那样，在野生型（WT）小鼠中，PTH输注抑制了骨形成。 但在Cox 2基因敲除（KO）小鼠中，PTH输注对骨形成和骨丢失具有显著的合成代谢作用， 骨头与对骨形成的影响相反，PTH输注在WT和Cox 2中同样刺激骨吸收 KO小鼠。我们已经产生了具有Saa 3的全局KO的小鼠。我们将测试假设Saa 3 抑制体内对持续升高的PTH的合成代谢而不是分解代谢反应。具体目标1 将在用于升高PTH的体内模型中检查Saa 3对骨形成和再吸收的影响。目标2将 检测Saa 3对体外PTH刺激的成骨细胞和破骨细胞分化的影响，以及cAMP- PTH调节Wnt信号和cAMP非依赖性信号通路的依赖性作用， 在我们的模型中PTH调节RANKL信号。目标3将审查对PGE 2的需求及其 EP 4受体在诱导BMP 3中Saa 3的作用以及Saa 3在刺激其他细胞因子中的作用， 调节骨环境。我们提出了Saa 3的一个新作用，一种破骨细胞 调节成骨细胞;以及Cox 2/PGE 2的新作用。这项研究的结果应该加强我们的 了解PTH作用的分子机制，可能有助于我们靶向骨 重塑更有效地治疗骨质疏松症和其他骨骼疾病。