Surface RANKL of Toll-like receptor 4–stimulated human neutrophils activates osteoclastic bone resorption

• Published in: Blood Vol. 114; no. 8; pp. 1633 - 1644
• Main Authors: Chakravarti, Arpita, Raquil, Marie-Astrid, Tessier, Philippe, Poubelle, Patrice E.
• Format: Journal Article
• Language: English
• Published: Washington, DC Elsevier Inc 20.08.2009; Americain Society of Hematology
• Subjects: Animals; Antigens, Surface - metabolism; Antigens, Surface - physiology; Biological and medical sciences; Bone Resorption - etiology; Bone Resorption - metabolism; Cell Adhesion - drug effects; Cell Adhesion - physiology; Cell Differentiation - drug effects; Cell Differentiation - physiology; Cell Movement - drug effects; Cell Movement - physiology; Cell physiology; Cells, Cultured; Fundamental and applied biological sciences. Psychology; Humans; Ligands; Lipopolysaccharides - pharmacology; Mice; Miscellaneous; Molecular and cellular biology; Neutrophils - drug effects; Neutrophils - metabolism; Neutrophils - physiology; Osteoclasts - drug effects; Osteoclasts - metabolism; Osteoclasts - physiology; RANK Ligand - antagonists & inhibitors; RANK Ligand - metabolism; RANK Ligand - physiology; RNA, Small Interfering - pharmacology; Toll-Like Receptor 4 - metabolism; Toll-Like Receptor 4 - physiology; Toll-Like Receptors - metabolism; Human; Toll like receptor 4; Receptor activator Nfkb ligand; Cytokine; Rodentia; Granulocyte; Resorption; Natural immunity; Activation; Osteoclast; Osteoarticular system; Vertebrata; Mammalia; Mouse; Animal; Neutrophil; Bone
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood-2008-09-178301

Inflammatory bone loss in septic and inflammatory conditions is due to increased activity of osteoclasts that requires receptor activator of NF-kappa B-ligand (RANKL). Neutrophils are the predominant infiltrating cells in these conditions. Although disease severity is linked to neutrophils, their role in evolution of bony lesions is not clear. We show that lipopolysaccharide (LPS), a toll-like receptor 4 ligand, up-regulated the expression of membrane RANKL in human blood neutrophils and murine air pouch–derived neutrophils. LPS-activated human and murine neutrophils, cocultured with human monocyte-derived osteoclasts and RAW 264.7 cells, respectively, stimulated bone resorption. Transfection of PLB-985 neutrophil-like cells with RANKL antisense RNA reduced osteoclastogenesis. Synovial fluid neutrophils of patients with exacerbation of rheumatoid arthritis strongly expressed RANKL and activated osteoclastogenesis in coculture systems. Osteoprotegerin, the RANKL decoy receptor, suppressed osteoclast activation by neutrophils from these different sources. Moreover, direct cell-cell contact between neutrophils and osteoclasts was visualized by confocal laser microscopy. Activation of neutrophil membrane-bound RANKL was linked to tyrosine phosphorylation of Src-homology domain–containing cytosolic phosphatase 1 with concomitant down-regulation of cytokine production. The demonstration of these novel functions of neutrophils highlights their potential role in osteoimmunology and in therapeutics of inflammatory bone disease.