title: Serum amyloid A triggers the mosodium urate -mediated mature interleukin-1β production from human synovial fibroblasts.
abstract: BACKGROUND
  Monosodium urate (MSU) has been shown to promote inflammasome activation and interleukin-1β (IL-1β) secretion in monocyte/macrophages, but the cellular pathway and nod-like receptor family, pyrin domain containing 3 (NLRP3) inflammasome activation in synovial tissues, remain elusive. In this study, we investigated the effects of MSU on synovial fibroblasts to elucidate the process of MSU-mediated synovial inflammation.
  
  
  METHODS
  Human synovial fibroblasts were stimulated with MSU in the presence or absence of serum amyloid A (SAA). The cellular supernatants were analyzed by immunoblotting using anti-IL-1β or anti-caspase-1 antibodies. IL-1β or NLRP3 mRNA expressions were analyzed by real-time PCR or reverse transcription-PCR (RT-PCR) method.
  
  
  RESULTS
  Neither SAA nor MSU stimulation resulted in IL-1β or interleukin-1α (IL-1α) secretions and pro-IL-1β processing in synovial fibroblasts. However, in SAA-primed synovial fibroblasts, MSU stimulation resulted in the activation of caspase-1 and production of active IL-1β and IL-1α. The effect of SAA on IL-1β induction was impaired in cells by silencing NLRP3 using siRNA or treating with caspase-1 inhibitor. In addition, SAA induced the secretion of cathepsin B and NLRP3 mRNA expression in synovial fibroblasts.
  
  
  CONCLUSIONS
  Our data demonstrate that exposure of human synovial fibroblasts to SAA promotes MSU-mediated caspase-1 activation and IL-1β secretion in the absence of microbial stimulation. These findings provide insight into the molecular processes underlying the synovial inflammatory condition of gout.
authors.affiliation: Department of Rheumatology, Nagasaki Medical Center, Kubara 2-1001-1, Omura, Nagasaki 856-8562, Japan. migita@nmc.hosp.go.jp
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Migita
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Koga
authors.forename: Kenshi
authors.initials: K
authors.lastname: Satomura
authors.forename: Masahiro
authors.initials: M
authors.lastname: Izumi
authors.forename: Takafumi
authors.initials: T
authors.lastname: Torigoshi
authors.forename: Yumi
authors.initials: Y
authors.lastname: Maeda
authors.forename: Yasumori
authors.initials: Y
authors.lastname: Izumi
authors.forename: Yuka
authors.initials: Y
authors.lastname: Jiuchi
authors.forename: Taiichiro
authors.initials: T
authors.lastname: Miyashita
authors.forename: Satoshi
authors.initials: S
authors.lastname: Yamasaki
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Aiba
authors.forename: Atsumasa
authors.initials: A
authors.lastname: Komori
authors.forename: Minoru
authors.initials: M
authors.lastname: Nakamura
authors.forename: Satoru
authors.initials: S
authors.lastname: Motokawa
authors.forename: Atsushi
authors.initials: A
authors.lastname: Kawakami
authors.forename: Tadashi
authors.initials: T
authors.lastname: Nakamura
authors.forename: Hiromi
authors.initials: H
authors.lastname: Ishibashi
mesh_terms: D000975:Antioxidants / Q000494:pharmacology*; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism*; D006073:Gout / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D053583:Interleukin-1beta / Q000096:biosynthesis*; D034741:RNA, Small Interfering; D060888:Real-Time Polymerase Chain Reaction; D000685:Serum Amyloid A Protein / Q000378:metabolism*; D013583:Synovial Membrane / Q000187:drug effects / Q000378:metabolism*; D014527:Uric Acid / Q000494:pharmacology*
chemical_list: D000975:Antioxidants; D053583:Interleukin-1beta; D034741:RNA, Small Interfering; D000685:Serum Amyloid A Protein; D014527:Uric Acid