title: Class A Scavenger Receptor Exacerbates Osteoclastogenesis by an Interleukin-6-Mediated Mechanism through ERK and JNK Signaling Pathways.
abstract: Osteoclasts originate from bone marrow monocyte/macrophage lineage cells, which are important for bone health. Class A scavenger receptor (SR-A) is a multifunctional molecule that functions during differentiation of monocyte into macrophages and osteoclasts. To further characterize the role of SR-A in osteoclasts, we used the murine tooth movement model (TM) and the murine anterior cruciate ligament transection model of osteoarthritis (ACLT OA). In these two models the bones involved are of different origin and have different properties. Bone resorption was decreased in SR-A-/-mice compared to SR-A+/+mice. Further evaluation showed that the number of multinucleated osteoclasts in SR-A-/-mice, compared to SR-A+/+mice, was significantly decreased bothin vivoandin vitro. The levels of interleukin-6 (IL-6) produced by osteoclasts were reduced in SR-A-/-mice compared to SR-A+/+mice. In thein vitromarrow-derived osteoclast formation assay and in both mouse models, osteoclastogenesis was restored to normal in SR-A-/-mice by administration of recombinant murine IL-6. Moreover, neutralization of IL-6 reduced the number of osteoclasts formed in SR-A+/+mice of TM model. Both extracellular signal-regulated kinase (ERK) and c-Jun N-terminal protein kinase (JNK), but not p38, signaling pathways were downregulated in receptor activator of nuclear factor-κB ligand (RANKL)-stimulated SR-A-/-osteoclasts. Importantly, when treated with either ERK or JNK inhibitor, the numbers of osteoclasts generated from RANKL-induced bone marrow derived-macrophages of SR-A+/+mice, and their IL-6 production, were significantly decreased. This suggests that SR-A activates the ERK and JNK signaling pathways, and promotes production of IL-6 by osteoclasts to further stimulate osteoclast formation.
authors.affiliation: Jiangsu Key Laboratory of Oral Diseases, Nanjing Medical University, Nanjing, China.
authors.forename: Shuyu
authors.initials: S
authors.lastname: Guo
authors.affiliation: Jiangsu Key Laboratory of Oral Diseases, Nanjing Medical University, Nanjing, China.
authors.forename: Yuanyuan
authors.initials: Y
authors.lastname: Ni
authors.affiliation: Atherosclerosis Research Center, Key Laboratory of Cardiovascular Disease and Molecular Intervention, Nanjing Medical University, Nanjing, China.
authors.forename: Jingjing
authors.initials: J
authors.lastname: Ben
authors.affiliation: Jiangsu Key Laboratory of Oral Diseases, Nanjing Medical University, Nanjing, China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Xia
authors.affiliation: Jiangsu Key Laboratory of Oral Diseases, Nanjing Medical University, Nanjing, China.
authors.forename: Tingting
authors.initials: T
authors.lastname: Zhou
authors.affiliation: Jiangsu Key Laboratory of Oral Diseases, Nanjing Medical University, Nanjing, China.
authors.forename: Dongyue
authors.initials: D
authors.lastname: Wang
authors.affiliation: Jiangsu Key Laboratory of Oral Diseases, Nanjing Medical University, Nanjing, China.
authors.forename: Jieli
authors.initials: J
authors.lastname: Ni
authors.affiliation: Atherosclerosis Research Center, Key Laboratory of Cardiovascular Disease and Molecular Intervention, Nanjing Medical University, Nanjing, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Bai
authors.affiliation: Jiangsu Key Laboratory of Oral Diseases, Nanjing Medical University, Nanjing, China.
authors.forename: Lin
authors.initials: L
authors.lastname: Wang
authors.affiliation: Jiangsu Key Laboratory of Oral Diseases, Nanjing Medical University, Nanjing, China.
authors.forename: Junqing
authors.initials: J
authors.lastname: Ma
authors.affiliation: Atherosclerosis Research Center, Key Laboratory of Cardiovascular Disease and Molecular Intervention, Nanjing Medical University, Nanjing, China.
authors.forename: Qi
authors.initials: Q
authors.lastname: Chen
mesh_terms: D000818:Animals; D004797:Enzyme-Linked Immunosorbent Assay; D048049:Extracellular Signal-Regulated MAP Kinases / Q000235:genetics / Q000378:metabolism*; D015850:Interleukin-6 / Q000235:genetics / Q000378:metabolism*; D048031:JNK Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D008264:Macrophages / Q000166:cytology / Q000378:metabolism; D051379:Mice; D010003:Osteoarthritis / Q000378:metabolism; D010010:Osteoclasts / Q000166:cytology* / Q000378:metabolism; D010012:Osteogenesis / Q000235:genetics / Q000502:physiology*; D053245:RANK Ligand / Q000235:genetics / Q000378:metabolism; D051117:Scavenger Receptors, Class A / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology; D055114:X-Ray Microtomography
chemical_list: D015850:Interleukin-6; D053245:RANK Ligand; D051117:Scavenger Receptors, Class A; D048049:Extracellular Signal-Regulated MAP Kinases; D048031:JNK Mitogen-Activated Protein Kinases
keywords: ERK; IL-6; JNK.; Osteoclasts; SR-A