A novel cell-autonomous role for β-adrenergic receptor signaling in osteoclasts

破骨细胞中β-肾上腺素能受体信号传导的新型细胞自主作用

• 批准号: 10414883
• 负责人: Katherine Jean Motyl
• 金额: $ 36.48万
• 依托单位: MAINEHEALTH
• 依托单位国家: 美国
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-06-01 至 2026-05-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10414883
• 关键词: Adrenergic Antagonists; Adrenergic beta-Agonists; Age; Age-Related Bone Loss; Aging; Agonist; Albuterol; Alleles; Attenuated; Binding; Biological Assay; Bone Density; Bone Diseases; Bone Marrow; Bone Resorption; Bone remodeling; Ca(2+)-Calmodulin Dependent Protein Kinase; Calcineurin; Calcineurin inhibitor; Cells; Clinical; Cohort Studies; Cyclic AMP-Dependent Protein Kinases; Data; Dose; Ensure; G Protein-Coupled Receptor Signaling; Genes; Genetic; Goals; Hand; Human; In Vitro; Laboratories; Lead; Ligand Binding; Marrow; Mass Spectrum Analysis; Mediating; Mediator of activation protein; Meta-Analysis; Mus; Myelogenous; Nervous system structure; Osteoblasts; Osteoclasts; Osteogenesis; Osteoporosis; PPP3CA gene; Pathology; Pathway interactions; Pharmaceutical Preparations; Pharmacology; Phenotype; Physiological; Postmenopause; Propranolol; Receptor Signaling; Refractory; Role; Serum; Signal Pathway; Signal Transduction; Sympathetic Nervous System; TRANCE protein; Testing; Woman; Work; beta-adrenergic receptor; bone; bone loss; fracture risk; improved; in vivo; in vivo evaluation; monocyte; novel; nuclear factors of activated T-cells; osteoclastogenesis; preclinical study; prevent; prospective; receptor; recruit; transcriptome sequencing

The sympathetic nervous system (SNS) is an important regulator of bone, and may contribute to bone pathology during aging. SNS activity is also heightened in post-menopausal women, causing reduced bone formation by osteoblasts and increased bone resorption by osteoclasts, which leads to bone loss. Large meta- analyses, osteoporosis cohort studies (preliminary data from co-I Dr. Lary) and new prospective trials, consistently show that β-adrenergic receptor (βAR) antagonists (i.e. β-blockers) are associated with reduced fracture risk, increased bone mineral density (BMD), and reduced bone resorption. However, mechanistic studies have focused largely on the osteoblast as the target of SNS activity. Humans and mice have three βARs: β1AR, β2AR and β3AR. The gene encoding β2AR (Adrb2) is highly expressed in bone, which also expresses lower levels of Adrb1, but does not express Adrb3. In mice, Adrb2 deletion in osteoblasts improves bone formation and prevents receptor activator of nuclear factor-kappa B ligand (RANKL)-mediated osteoclast recruitment after stimulation with a β-agonist. In humans, β1-selective β-blockers are used most often, but their selectivity is not absolute, and many still bind β2AR. Propranolol, a non-selective β-blocker, increases BMD in the majority of preclinical studies. Results from our laboratory show that propranolol can limit bone resorption directly in vitro, and in vivo without changing RANKL levels. This is in contrast to the established dogma that osteoblast expression of β2AR regulates osteoclasts only indirectly via RANKL. Our proposed work will resolve the outstanding mechanistic questions of how β1AR and β2AR directly influence osteoclast differentiation and what their contributions are to age- and SNS-related bone loss. We propose a novel hypothesis that βAR signaling in osteoclasts promotes differentiation and resorption and contributes to bone loss in vivo. To fully characterize βAR receptor subtypes and novel signaling mechanisms in osteoclasts, and to determine the contribution of βAR subtypes to in vivo phenotypes of bone density and bone remodeling, we propose a combination of genetic and pharmacologic in vivo and in vitro approaches in the following Specific Aims. Specific Aim 1: We will identify signaling mechanisms activated by specific βARs in osteoclasts. We expect that we will identify novel and established target pathways to test in vivo for efficacy in modulating bone resorption. Specific Aim 2: We will test the relative contributions of osteoclast β1AR and β2AR to SNS- mediated and aging-related bone loss in vivo. The SNS has been implicated in osteoporosis, but the role of βARs in osteoclasts has never been investigated in this condition. We hypothesize that both deletion of β1AR and β2AR, specifically in the osteoclasts, will attenuate βAR agonist-induced and aging-related bone loss in mice. Our work will provide a more complete understanding of the role of SNS signaling in age-related bone loss in vivo, and will lead to studies targeting specific osteoclast βARs and downstream signaling pathways for treatment of bone diseases.

交感神经系统（SNS）是骨的重要调节器，并且可能有助于骨形成。 衰老过程中的病理绝经后妇女的SNS活动也会增加，导致骨质减少 通过成骨细胞形成和通过破骨细胞增加骨吸收，这导致骨丢失。大型Meta- 分析，骨质疏松症队列研究（来自共同研究者Lary博士的初步数据）和新的前瞻性试验， 一致表明，β-肾上腺素能受体（βAR）拮抗剂（即β-阻滞剂）与降低的 骨折风险、骨矿物质密度（BMD）增加和骨吸收减少。然而，机械 研究主要集中在成骨细胞作为SNS活性的靶。人类和老鼠有三个 β AR：β 1 AR、β 2 AR和β 3 AR。编码β 2 AR的基因（Adrb 2）在骨中高度表达， 表达较低水平的Adrb 1，但不表达Adrb 3。在小鼠中，成骨细胞中的Adrb 2缺失改善了 骨形成和阻止核因子-κ B配体受体激活剂（RANKL）介导的破骨细胞 用β-激动剂刺激后的募集。在人类中，β1-选择性β受体阻滞剂是最常用的，但其 选择性不是绝对的，许多仍然结合β2AR。普萘洛尔是一种非选择性β受体阻滞剂，可增加 大多数临床前研究。我们实验室的结果显示普萘洛尔可以限制骨吸收 直接在体外和体内，而不改变RANKL水平。这与既定的教条相反， 成骨细胞表达β 2 AR仅通过RANKL间接调节破骨细胞。我们提出的工作将解决 β 1 AR和β 2 AR如何直接影响破骨细胞分化的突出机制问题， 他们对年龄和SNS相关的骨质流失的贡献。我们提出了一个新的假说，即βAR 破骨细胞中的信号传导促进分化和再吸收，并导致体内骨丢失。充分 表征破骨细胞中βAR受体亚型和新的信号传导机制，并确定 βAR亚型对骨密度和骨重建的体内表型的贡献，我们提出了一个新的研究方法。 在以下特定目的中，将遗传学和药理学的体内和体外方法相结合。 具体目标1：我们将确定破骨细胞中特定β AR激活的信号传导机制。我们预计 我们将确定新的和已建立的靶向途径，以在体内测试调节骨的功效， 再吸收具体目标2：我们将测试破骨细胞β 1 AR和β 2 AR对SNS的相对贡献。 介导的和老化相关的骨丢失。SNS与骨质疏松症有牵连，但 在这种情况下，破骨细胞中的β AR从未被研究过。我们假设β1AR的缺失 和β 2 AR，特别是在破骨细胞中，将减弱βAR激动剂诱导的和衰老相关的骨丢失， 小鼠我们的工作将提供一个更完整的理解SNS信号在年龄相关的骨中的作用， 体内丢失，并将导致针对特定破骨细胞β AR和下游信号通路的研究， 治疗骨骼疾病。