title: RANKL-stimulated osteoclast-like cell formation in vitro is partially dependent on endogenous interleukin-1 production.
abstract: Receptor activator of NF-kappaB ligand (RANKL) and interleukin-1 (IL-1) individually plays a critical role in the differentiation and activation of osteoclasts in bone. In addition, both RANKL and IL-1 activate similar signal transduction pathways including p38 MAP kinase and c-Jun NH(2) terminal kinase (JNK). We examined if endogenously produced IL-1 influenced osteoclast-like cell (OCL) formation in murine bone marrow and bone marrow monocyte (BMM) cultures that were stimulated with M-CSF and RANKL. RANKL stimulated OCL formation in a dose-dependent manner in bone marrow cultures, and this response was significantly inhibited by IL-1 RA (100 ng/ml), a specific IL-1 antagonist. Interleukin-1 further increased OCL formation in BMM cultures that were treated with M-CSF (30 ng/ml) and RANKL (1, 3, 10 and 30 ng/ml). In addition, BMM cultures from IL-1 type I receptor-deficient mice, which do not respond to IL-1, demonstrated significantly less OCL formation compared to wild-type BMM cultures. We examined the time course and dose response of IL-1alpha protein expression by ELISA in BMM cultures that were treated with or without M-CSF and RANKL. RANKL dose dependently stimulated IL-1alpha protein significantly (up to 46%) in 6-day cultures. The interaction of RANKL and IL-1 on osteoclastogenesis did not appear significantly dependent on prostaglandin synthesis since PGE(2) expression in the conditioned medium of BMM cultures was nearly undetectable and the PGHS-2 specific inhibitor, NS-398, was without effect. We also investigated the effect of IL-1 on p38 MAP kinase and JNK in BMM cultures. The combination of RANKL and IL-1 had additive effects on JNK but not p38 MAP kinase compared to results in cultures treated with RANKL or IL-1 alone. In addition, SP600125, a specific JNK inhibitor, markedly reduced OCL formation in BMM cultures that were treated with RANKL or the combination of RANKL and IL-1. These findings demonstrate that endogenously produced IL-1 augments the response of bone marrow cells to RANKL, and this effect appears mediated by mechanisms that are associated with enhancement of JNK activity.
authors.affiliation: Division of Endocrinology, Department of Medicine, MC-1850, University of Connecticut Health Center, 263 Farmington Avenue, Farmington, CT 06030-1850, USA. slee@neuron.uchc.edu
authors.forename: Sun-Kyeong
authors.initials: SK
authors.lastname: Lee
authors.forename: Amy E
authors.initials: AE
authors.lastname: Gardner
authors.forename: Judith F
authors.initials: JF
authors.lastname: Kalinowski
authors.forename: Sandra L
authors.initials: SL
authors.lastname: Jastrzebski
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Lorenzo
mesh_terms: D000818:Animals; D001854:Bone Marrow Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D002352:Carrier Proteins / Q000494:pharmacology*; D002454:Cell Differentiation; D053590:Interleukin 1 Receptor Antagonist Protein; D007375:Interleukin-1 / Q000037:antagonists & inhibitors / Q000494:pharmacology / Q000502:physiology*; D048670:MAP Kinase Kinase 4 / Q000037:antagonists & inhibitors / Q000378:metabolism; D016173:Macrophage Colony-Stimulating Factor / Q000494:pharmacology; D008562:Membrane Glycoproteins / Q000494:pharmacology*; D051379:Mice; D008810:Mice, Inbred C57BL; D010010:Osteoclasts / Q000166:cytology* / Q000378:metabolism; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; D012795:Sialoglycoproteins / Q000494:pharmacology; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D002352:Carrier Proteins; C507764:Il1rn protein, mouse; D053590:Interleukin 1 Receptor Antagonist Protein; D007375:Interleukin-1; D008562:Membrane Glycoproteins; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; D012795:Sialoglycoproteins; C505687:Tnfrsf11a protein, mouse; C505689:Tnfsf11 protein, mouse; D016173:Macrophage Colony-Stimulating Factor; D048051:p38 Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4