title: Requirement of type I interferon signaling for arthritis triggered by double-stranded RNA.
abstract: OBJECTIVE
  Arthralgias and overt arthritides are often associated with viral infections. Viral infections expose the infected host to proinflammatory double-stranded RNA (dsRNA), which can cause joint inflammation and is a potent activator of interferon-alpha (IFNalpha). The aim of this study was to determine the role of IFNalpha and dsRNA-related signaling molecules in the onset of joint inflammation induced by viral dsRNA.
  
  
  METHODS
  IFNalpha and different forms of RNA were injected into the knee joints of wild-type mice, mice lacking the type I interferon receptor (IFNAR(-/-)), and mice deficient in dsRNA-dependent protein kinase (PKR(-/-)). Histologic evidence of joint damage and the ability of splenocytes to produce cytokines in response to dsRNA or IFNalpha were assessed.
  
  
  RESULTS
  Viral dsRNA, but not short single-stranded RNA, induced arthritis. The arthritis was aggravated by intracellular delivery of dsRNA. The expression of PKR was not mandatory for dsRNA-induced joint inflammation. In contrast, IFNalpha/beta signaling was important for dsRNA-induced joint inflammation because IFNAR(-/-) mice did not develop arthritis. Furthermore, intraarticular deposition of IFNalpha induced arthritis in PKR(-/-) and control mice, whereas IFNAR(-/-) mice were protected. The arthritogenic effect of IFNalpha was attenuated by in vivo depletion of monocyte/macrophages.
  
  
  CONCLUSIONS
  Arthritis triggered by dsRNA is not dependent on the expression of the dsRNA-signaling molecule PKR (or Toll-like receptor 3, as previously shown), but is associated with the ability to produce type I IFN and is critically dependent on type I IFN receptor signaling. The intrinsic arthritogenic properties of IFNalpha implicate a role of this cytokine in joint manifestations triggered by various interferogenic stimuli.
authors.affiliation: Internal Medicine, Rheumatology and Inflammation Research, Sahlgrandka Academy at Göteborg University, Guldhedsgatan 10A, 413-46 Gothenburg, Sweden. Mattias.Magnusson@rheuma.gu.se
authors.forename: Mattias
authors.initials: M
authors.lastname: Magnusson
authors.forename: Fariba
authors.initials: F
authors.lastname: Zare
authors.forename: Andrej
authors.initials: A
authors.lastname: Tarkowski
mesh_terms: D000818:Animals; D001168:Arthritis / Q000209:etiology* / Q000821:virology; D005260:Female; D016898:Interferon-alpha / Q000502:physiology*; D051379:Mice; D012330:RNA, Double-Stranded / Q000502:physiology*; D012367:RNA, Viral / Q000502:physiology*
chemical_list: D016898:Interferon-alpha; D012330:RNA, Double-Stranded; D012367:RNA, Viral