title: Interleukin-17: A new bone acting cytokine in vitro.
abstract: Interleukin-17 (IL-17) is a recently cloned cytokine that is exclusively produced by activated T cells, but its receptor has been found on several cells and tissues. Like other proinflammatory cytokines produced by activated T cells, IL-17 may affect osteoclastic resorption and thereby mediate bone destruction accompanying some inflammatory diseases. In the present study, we investigated whether osteogenic cells possess the receptor for IL-17 (IL-17R) and whether IL-17 affects osteoclastic resorption. We found that IL-17R mRNA is expressed both in mouse MC3T3-E1 osteoblastic cells and fetal mouse long bones, suggesting that osteogenic cells may be responsive to IL-17. In fetal mouse long bones, IL-17 had no effect on basal and IL-1beta-stimulated osteoclastic bone resorption, but when given together with tumor necrosis factor-alpha (TNF-alpha) it increased bone resorption dose dependently in serum-free conditions. In addition, IL-17 increased TNF-alpha-induced IL-1alpha, IL-1beta, and IL-6 mRNA expression in fetal mouse metatarsals and IL-1alpha and IL-6 mRNA expression in MC3T3-E1 cells. In conclusion, IL-17R mRNA was expressed by mouse osteoblastic cells and fetal mouse long bones, and IL-17 in combination with TNF-alpha, but not IL-1beta, increased osteoclastic resorption in vitro. IL-17 may therefore affect bone metabolism in pathological conditions characterized by the presence of activated T cells and TNF-alpha production such as rheumatoid arthritis and loosening of bone implants.
authors.affiliation: Department of Endocrinology and Metabolic Diseases, Leiden University Medical Center, Leiden, The Netherlands.
authors.forename: R L
authors.initials: RL
authors.lastname: Van bezooijen
authors.forename: H C
authors.initials: HC
authors.lastname: Farih-Sips
authors.forename: S E
authors.initials: SE
authors.lastname: Papapoulos
authors.forename: C W
authors.initials: CW
authors.lastname: Löwik
mesh_terms: D000818:Animals; D001862:Bone Resorption; D001842:Bone and Bones / Q000187:drug effects; D002478:Cells, Cultured; D020381:Interleukin-17 / Q000494:pharmacology*; D051379:Mice; D010006:Osteoblasts / Q000187:drug effects* / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D018123:Receptors, Interleukin / Q000096:biosynthesis / Q000235:genetics; D053722:Receptors, Interleukin-17; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000235:genetics; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
chemical_list: C491673:Il17ra protein, mouse; D020381:Interleukin-17; D012333:RNA, Messenger; D018123:Receptors, Interleukin; D053722:Receptors, Interleukin-17; D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha