title: Complementary action of granulocyte macrophage colony-stimulating factor and interleukin-17A induces interleukin-23, receptor activator of nuclear factor-κB ligand, and matrix metalloproteinases and drives bone and cartilage pathology in experimental arthritis: rationale for combination therapy in rheumatoid arthritis.
abstract: BACKGROUND
  Type 17 T helper cells and interleukin (IL)-17 play important roles in the pathogenesis of human and murine arthritis. Although there is a clear link between IL-17 and granulocyte macrophage colony-stimulating factor (GM-CSF) in the inflammatory cascade, details about their interaction in arthritic synovial joints are unclear. In view of the introduction of GM-CSF and IL-17 inhibitors to the clinic, we studied how IL-17 and GM-CSF orchestrate the local production of inflammatory mediators during experimental arthritis.
  
  
  METHODS
  To allow detection of additive, complementary or synergistic effects of IL-17 and GM-CSF, we used two opposing experimental approaches: treatment of arthritic mice with neutralising antibodies to IL-17 and GM-CSF and local overexpression of these cytokines in naive synovial joints. Mice were treated for 2 weeks with antibodies against IL-17 and/or GM-CSF after onset of collagen-induced arthritis. Naive mice were injected intraarticularly with adenoviral vectors for IL-17 and/or GM-CSF, resulting in local overexpression. Joint inflammation was monitored by macroscopic scoring, X-rays and histology. Joint washouts, synovial cell and lymph node cultures were analysed for cytokines, chemokines and inflammatory mediators by Luminex analysis, flow cytometry and quantitative polymerase chain reaction.
  
  
  RESULTS
  Combined therapeutic anti-IL-17 and anti-GM-CSF ameliorated arthritis progression, and joint damage was dramatically reduced compared with treatment with anti-IL-17 or anti-GM-CSF alone. Anti-IL-17 specifically reduced synovial IL-23 transcription, whereas anti-GM-CSF reduced transcription of matrix metalloproteinases (MMPs) and receptor activator of nuclear factor κB ligand (RANKL). Overexpression of IL-17 or GM-CSF in naive knee joints elicited extensive inflammatory infiltrate, cartilage damage and bone destruction. Combined overexpression revealed additive and synergistic effects on the production of MMPs, RANKL and IL-23 in the synovium and led to complete destruction of the joint structure within 7 days.
  
  
  CONCLUSIONS
  IL-17 and GM-CSF differentially mediate the inflammatory process in arthritic joints and show complementary and local additive effects. Combined blockade in arthritic mice reduced joint damage not only by direct inhibition of IL-17 and GM-CSF but also by indirect inhibition of IL-23 and RANKL. Our results provide a rationale for combination therapy in autoinflammatory conditions, especially for patients who do not fully respond to inhibition of the separate cytokines.
authors.affiliation: Experimental Rheumatology, Radboud University Medical Centre, Route 272, Geert Grooteplein 28, 6525, GA, Nijmegen, The Netherlands. annemarie.vannieuwenhuijze@vib-kuleuven.be.|Reid Rheumatology Laboratory, The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville 3050, Melbourne, Australia. annemarie.vannieuwenhuijze@vib-kuleuven.be.|Autoimmune Genetics Laboratory, Vlaams Instituut voor Biotechnologie (VIB), and Department of Microbiology and Immunology, University of Leuven, Campus Gasthuisberg, Herestraat 49, Leuven, 3000, Belgium. annemarie.vannieuwenhuijze@vib-kuleuven.be.
authors.forename: Annemarie E M
authors.initials: AE
authors.lastname: van Nieuwenhuijze
authors.affiliation: Experimental Rheumatology, Radboud University Medical Centre, Route 272, Geert Grooteplein 28, 6525, GA, Nijmegen, The Netherlands. fons.vandeloo@radboudumc.nl.
authors.forename: Fons A
authors.initials: FA
authors.lastname: van de Loo
authors.affiliation: Experimental Rheumatology, Radboud University Medical Centre, Route 272, Geert Grooteplein 28, 6525, GA, Nijmegen, The Netherlands. birgitte.walgreen@radboudumc.nl.
authors.forename: Birgitte
authors.initials: B
authors.lastname: Walgreen
authors.affiliation: Experimental Rheumatology, Radboud University Medical Centre, Route 272, Geert Grooteplein 28, 6525, GA, Nijmegen, The Netherlands. miranda.bennink@radboudumc.nl.
authors.forename: Miranda
authors.initials: M
authors.lastname: Bennink
authors.affiliation: Experimental Rheumatology, Radboud University Medical Centre, Route 272, Geert Grooteplein 28, 6525, GA, Nijmegen, The Netherlands. monique.helsen@radboudumc.nl.
authors.forename: Monique
authors.initials: M
authors.lastname: Helsen
authors.affiliation: Experimental Rheumatology, Radboud University Medical Centre, Route 272, Geert Grooteplein 28, 6525, GA, Nijmegen, The Netherlands. liduine.vandenbersselaar@radboudumc.nl.
authors.forename: Liduine
authors.initials: L
authors.lastname: van den Bersselaar
authors.affiliation: Reid Rheumatology Laboratory, The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville 3050, Melbourne, Australia. wicks@wehi.edu.au.
authors.forename: Ian P
authors.initials: IP
authors.lastname: Wicks
authors.affiliation: Experimental Rheumatology, Radboud University Medical Centre, Route 272, Geert Grooteplein 28, 6525, GA, Nijmegen, The Netherlands. wim.vandenberg@radboudumc.nl.
authors.forename: Wim B
authors.initials: WB
authors.lastname: van den Berg
authors.affiliation: Experimental Rheumatology, Radboud University Medical Centre, Route 272, Geert Grooteplein 28, 6525, GA, Nijmegen, The Netherlands. marije.koenders@radboudumc.nl.
authors.forename: Marije I
authors.initials: MI
authors.lastname: Koenders
mesh_terms: D000818:Animals; D001169:Arthritis, Experimental / Q000276:immunology* / Q000473:pathology; D001172:Arthritis, Rheumatoid / Q000276:immunology* / Q000473:pathology; D001842:Bone and Bones / Q000473:pathology; D002358:Cartilage, Articular / Q000473:pathology; D005434:Flow Cytometry; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000276:immunology*; D020381:Interleukin-17 / Q000276:immunology*; D053759:Interleukin-23 / Q000276:immunology; D008297:Male; D020782:Matrix Metalloproteinases / Q000276:immunology; D051379:Mice; D060888:Real-Time Polymerase Chain Reaction; D053246:Receptor Activator of Nuclear Factor-kappa B / Q000276:immunology; D015398:Signal Transduction / Q000276:immunology*; D058504:Th17 Cells / Q000276:immunology
chemical_list: D020381:Interleukin-17; D053759:Interleukin-23; D053246:Receptor Activator of Nuclear Factor-kappa B; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D020782:Matrix Metalloproteinases