title: IL-32gamma and Streptococcus pyogenes cell wall fragments synergise for IL-1-dependent destructive arthritis via upregulation of TLR-2 and NOD2.
abstract: OBJECTIVE
  To investigate the potential synergism between interleukin (IL) 32γ and Streptococcus pyogenes cell wall (SCW) fragments in the development of destructive arthritis.
  
  
  METHODS
  An adenoviral vector encoding human IL-32γ (AdIL-32γ) was constructed and validated in HeLa cells. Fibroblast-like synoviocytes (FLS) were transduced with AdIL-32γ and stimulated with Toll-like receptor 2 (TLR-2) and nucleotide oligomerisation domain (NOD) 2 ligands. Expression levels of several proinflammatory cytokines, chemokines, matrix degrading enzymes, TLR-2 and NOD2 were measured by quantitative real-time PCR. Furthermore, IL-6 and CXCL8 protein levels were determined. In-vivo synergy between IL-32γ and SCW was studied by intra-articular injection of AdIL-32γ in C57Bl/6 mice followed by SCW injection. The contribution of endogenous IL-1 was assessed in mice deficient for both IL-1α and IL-1β.
  
  
  RESULTS
  IL-32γ synergise with TLR-2/NOD2 ligands to induce proinflammatory cytokines, chemokines and matrix degrading enzymes in AdIL-32γ-transduced FLS. In mice, AdIL-32γ transduction followed by the injection of SCW displayed aggravated joint inflammation and cartilage destruction. However, IL-1-deficient mice were protected against IL-32γ/SCW-induced joint changes, indicating a requirement for IL-1 in downstream events triggered by IL-32γ plus SCW. To elucidate the synergistic mechanism, the authors investigated the expression of two pattern recognition receptors involved in sensing SCW fragments. TLR-2 and NOD2 receptor expression was enhanced by IL-32γ and Pam3Cys/muramyl dipeptide stimulation in FLS.
  
  
  CONCLUSIONS
  Here the authors show that IL-32γ aggravates SCW-induced arthritis by the upregulation of TLR-2/NOD2 expression and promotes severe joint erosion in an IL-1-dependent fashion. Targeting of IL-32γ may provide a novel therapy to prevent destructive arthritis.
authors.affiliation: Rheumatology Research and Advanced Therapeutics, Department of Rheumatology, Radboud University Nijmegen Medical Centre, PO Box 9101, 6500HB, Nijmegen, The Netherlands. s.heinhuis@reuma.umcn.nl
authors.forename: Bas
authors.initials: B
authors.lastname: Heinhuis
authors.forename: Marije I
authors.initials: MI
authors.lastname: Koenders
authors.forename: Fons A
authors.initials: FA
authors.lastname: van de Loo
authors.forename: Peter L E M
authors.initials: PL
authors.lastname: van Lent
authors.forename: Soo-Hyun
authors.initials: SH
authors.lastname: Kim
authors.forename: Charles A
authors.initials: CA
authors.lastname: Dinarello
authors.forename: Leo A B
authors.initials: LA
authors.lastname: Joosten
authors.forename: Wim B
authors.initials: WB
authors.lastname: van den Berg
mesh_terms: D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D000942:Antigens, Bacterial / Q000276:immunology; D001169:Arthritis, Experimental / Q000276:immunology* / Q000473:pathology; D002473:Cell Wall / Q000276:immunology; D016207:Cytokines / Q000096:biosynthesis / Q000235:genetics; D004357:Drug Synergism; D005822:Genetic Vectors; D006367:HeLa Cells; D006801:Humans; D007375:Interleukin-1 / Q000276:immunology*; D007378:Interleukins / Q000235:genetics / Q000276:immunology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D053473:Nod2 Signaling Adaptor Protein / Q000096:biosynthesis* / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D013297:Streptococcus pyogenes / Q000276:immunology*; D051195:Toll-Like Receptor 2 / Q000096:biosynthesis* / Q000235:genetics; D015854:Up-Regulation / Q000276:immunology
chemical_list: D000942:Antigens, Bacterial; D016207:Cytokines; C496971:IL32 protein, human; D007375:Interleukin-1; D007378:Interleukins; D053473:Nod2 Signaling Adaptor Protein; C495945:Nod2 protein, mouse; D012333:RNA, Messenger; C493486:Tlr2 protein, mouse; D051195:Toll-Like Receptor 2