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)是骨骼的重要调节器，可能对骨骼有贡献 衰老过程中的病理变化。绝经后女性的SNS活性也会增加，导致骨质减少 由成骨细胞形成，破骨细胞增加骨吸收，导致骨丢失。大型Meta- 分析、骨质疏松症队列研究(来自co-I Dr.Lary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受体阻滞剂)与 骨折风险，增加骨密度(BMD)，减少骨吸收。然而，机械论 研究主要集中在成骨细胞作为SNS活性的靶点上。人类和老鼠都有三种 βAR：β1AR、β2AR和β3AR。编码β-2AR(ADRB2)的基因在骨骼中高度表达，这也是 表达较低水平的Adrb1，但不表达ADRB3。在小鼠中，成骨细胞中ADRB2的缺失改善了 核因子-kappa B配体(RANKL)介导的破骨细胞的骨形成和阻止受体激活剂 在用β激动剂刺激后重新招募。在人类中，最常用的是β1选择性β阻滞剂，但他们的 选择性不是绝对的，许多仍然与β2AR结合。非选择性β阻滞剂普萘洛尔增加大鼠骨密度 大多数临床前研究。我们实验室的结果显示心得安可以抑制骨吸收。 直接在体外，在体内不改变RANKL水平。这与既定的教条形成了鲜明对比，即 成骨细胞表达β-2AR只能通过RANKL间接调节破骨细胞。我们提议的工作将解决 β-1AR和β-2AR如何直接影响破骨细胞分化 他们对年龄和社交网络相关骨丢失的贡献是什么。我们提出了一个新的假设，即βAR 破骨细胞中的信号促进分化和吸收，并在体内促进骨丢失。充分地 鉴定破骨细胞中βAR受体亚型和新的信号机制，并确定 β受体亚型对体内骨密度和骨重建表型的贡献 结合遗传学和药理学的体内和体外方法，以达到下列特定目的。 具体目标1：我们将确定破骨细胞中特定β受体激活的信号机制。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骼的有效性 再吸收。具体目标2：我们将测试破骨细胞β1AR和β2AR在社交网络中的相对贡献。 体内介导性和衰老相关的骨丢失。社交网络被认为与骨质疏松症有关，但 破骨细胞中的β受体在这种情况下从未被研究过。我们假设β1AR的缺失 而β2AR，特别是在破骨细胞中，将减轻βAR激动剂诱导的和衰老相关的骨丢失 老鼠。我们的工作将对SNS信号在年龄相关骨骼中的作用提供更全面的理解 体内丢失，并将导致针对特定破骨细胞β受体和下游信号通路的研究 骨病的治疗。