title: β-Adrenergic signaling stimulates osteoclastogenesis via reactive oxygen species.
abstract: Sympathetic signaling regulates bone resorption through receptor activator of nuclear factor-κB ligand (RANKL) expression via the β-adrenergic receptor (β-AR) on osteoblasts. Reactive oxygen species (ROS) are known as one type of osteoclast regulatory molecule. Here we show that an antioxidant, α-lipoic acid (α-LA), treatment prevent the β-adrenergic signaling-induced bone loss by suppressing osteoclastogenesis, and sympathetic signaling directly regulates osteoclastogenesis through β2-AR expressed on osteoclasts via intracellular ROS generation. In an in vitro study, the β-AR agonist isoprenaline increased intracellular ROS generation in osteoclasts prepared from bone marrow macrophages (BBMs) and RAW 264.7 cells. Isoprenaline enhanced osteoclastogenesis through β2-AR expressed on BMMs and RAW 264.7 cells. The antioxidant α-LA inhibited isoprenaline-enhanced osteoclastogenesis. Isoprenaline increased the expression of osteoclast-related genes such as nuclear factor of activated T cells, cytoplasmic, calcineurin-dependent 1, tartrate-resistant acid phosphatase, and cathepsin K on osteoclasts. α-LA also inhibited isoprenaline-induced increases of these gene expressions. These in vitro results led to the hypothesis that β-adrenergic signaling directly stimulates osteoclastogenesis via ROS generation. In an in vivo study, isoprenaline treatment alone caused oxidative damage in local bone and reduced bone mass because of an increase in bone resorption, and, in α-LA-treated mice, isoprenaline did not increase tibial osteoclast number even though the RANKL-to-osteoprotegerin ratio increased. These in vitro and in vivo results indicate that β-adrenergic signaling, at least in part, directly stimulates osteoclastogenesis through β2-AR on osteoclasts via ROS generation.
authors.affiliation: Department of Pharmacology, School of Dentistry, Aichi-Gakuin University, Nagoya, Japan.
authors.forename: Hisataka
authors.initials: H
authors.lastname: Kondo
authors.forename: Shoko
authors.initials: S
authors.lastname: Takeuchi
authors.forename: Akifumi
authors.initials: A
authors.lastname: Togari
mesh_terms: D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D001835:Body Weight / Q000187:drug effects; D001854:Bone Marrow Cells / Q000187:drug effects; D002460:Cell Line; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D010010:Osteoclasts / Q000378:metabolism / Q000502:physiology*; D010012:Osteogenesis / Q000502:physiology*; D018384:Oxidative Stress; D053245:RANK Ligand / Q000096:biosynthesis; D017382:Reactive Oxygen Species / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction; D011943:Receptors, Adrenergic, beta / Q000502:physiology*; D018343:Receptors, Adrenergic, beta-2 / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects; D008063:Thioctic Acid / Q000494:pharmacology; D014057:Tomography, X-Ray Computed
chemical_list: D000318:Adrenergic beta-Agonists; D000975:Antioxidants; D053245:RANK Ligand; D017382:Reactive Oxygen Species; D011943:Receptors, Adrenergic, beta; D018343:Receptors, Adrenergic, beta-2; C505689:Tnfsf11 protein, mouse; D008063:Thioctic Acid; D007545:Isoproterenol