title: Arthritis is associated with T-cell-induced upregulation of Toll-like receptor 3 on synovial fibroblasts.
abstract: BACKGROUND
  Toll-like receptors (TLRs) are likely to play crucial roles in the pathogenesis of rheumatoid arthritis (RA). The aim of this study was to determine the key TLRs in synovium and explore their roles in the activation of fibroblast-like synoviocytes (FLSs) mediated by T cells in arthritis.
  
  
  METHODS
  Pristane-induced arthritis (PIA) was established by subcutaneous injection with pristane at the base of the rat's tail. TLR expression in synovium from PIA rats was detected at different time points by performing real-time PCR. Polyinosinic:polycytidylic acid (poly(I:C)) was intra-articularly administrated to PIA rats, and arthritis was monitored macroscopically and microscopically. Synovial TLR3 was detected by immunohistochemical staining. Rat FLSs were stimulated with pristane-primed T cells or pristane-primed, T-cell conditioned medium. The intervention of TLR3 in FLSs was achieved by specific short-hairpin RNA (shRNA) or an antibody. The migration ability of FLSs was measured by using the scratch test, and gene expression was detected by using real-time PCR. FLSs from RA patients were stimulated with various cytokines and TLR ligands, and TLR3 expression was detected by performing real-time PCR. In addition, with different concentrations of poly(I:C) stimulation, TLR3 expression of FLSs from RA patients and patients with osteoarthritis (OA) was compared.
  
  
  RESULTS
  Synovium TLR3 displayed early and persistent overexpression in PIA rats. TLR3 was expressed in FLSs, and local treatment with poly(I:C) synergistically aggravated the arthritis. Rat FLSs co-cultured with pristane-primed T cells showed strengthened migration ability and significant upregulation of TLR3, IFN-β, IL-6 and matrix metalloproteinase 3 (MMP3) expression, which could also be induced by pristane-primed, T-cell conditioned medium. The upregulation of cytokines and MMPs was blocked by shRNA or TLR3 antibodies. In RA FLSs with cytokine or TLR ligand stimulation, TLR3 expression exhibited remarkable upregulation. Furthermore, RA FLSs showed higher reactivity than OA FLSs to poly(I:C).
  
  
  CONCLUSIONS
  TLR3 in the synovium of PIA rats was overexpressed, and activation of the TLR3 signaling pathway could aggravate this arthritis. The induction of TLR3 in FLSs resulted from T cell-derived inflammatory stimulation and could further mediate FLS activation in arthritis. We conclude that TLR3 upregulation of FLSs activated by T cells results in articular inflammation.
authors.affiliation: Department of Genetics and Molecular Biology, Xi'an Jiaotong University School of Medicine, Yanta West Road 76, Xi'an, Shaanxi 710061, People's Republic of China.
authors.forename: Wenhua
authors.initials: W
authors.lastname: Zhu
authors.forename: Liesu
authors.initials: L
authors.lastname: Meng
authors.forename: Congshan
authors.initials: C
authors.lastname: Jiang
authors.forename: Xiaojing
authors.initials: X
authors.lastname: He
authors.forename: Weikun
authors.initials: W
authors.lastname: Hou
authors.forename: Peng
authors.initials: P
authors.lastname: Xu
authors.forename: Heng
authors.initials: H
authors.lastname: Du
authors.forename: Rikard
authors.initials: R
authors.lastname: Holmdahl
authors.forename: Shemin
authors.initials: S
authors.lastname: Lu
mesh_terms: D000818:Animals; D001169:Arthritis, Experimental / Q000139:chemically induced / Q000276:immunology* / Q000378:metabolism; D001172:Arthritis, Rheumatoid / Q000276:immunology* / Q000378:metabolism; D002465:Cell Movement / Q000276:immunology; D002478:Cells, Cultured; D017077:Culture Media, Conditioned / Q000494:pharmacology; D004195:Disease Models, Animal; D005260:Female; D005347:Fibroblasts / Q000276:immunology* / Q000378:metabolism; D015870:Gene Expression / Q000276:immunology; D006801:Humans; D007166:Immunosuppressive Agents / Q000633:toxicity; D008297:Male; D010003:Osteoarthritis / Q000276:immunology / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D012720:Severity of Illness Index; D015398:Signal Transduction / Q000276:immunology; D013583:Synovial Membrane / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D013601:T-Lymphocytes / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D013729:Terpenes / Q000633:toxicity; D051196:Toll-Like Receptor 3 / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D015854:Up-Regulation / Q000276:immunology
chemical_list: D017077:Culture Media, Conditioned; D007166:Immunosuppressive Agents; C495344:TLR3 protein, human; C530472:TLR3 protein, rat; D013729:Terpenes; D051196:Toll-Like Receptor 3; C009042:pristane