title: Tumor necrosis factor alpha-induced interleukin-32 is positively regulated via the Syk/protein kinase Cdelta/JNK pathway in rheumatoid synovial fibroblasts.
abstract: OBJECTIVE
  Interleukin-32 (IL-32) is a recently discovered cytokine that appears to play a critical role in human rheumatoid arthritis (RA). It is highly expressed in synovium and fibroblast-like synoviocytes (FLS) from RA patients, but not in patients with osteoarthritis (OA). This study was undertaken to assess IL-32 levels in RA synovial fluid (SF) and to investigate the secretion and regulation of IL-32 in RA FLS.
  
  
  METHODS
  FLS and SF were obtained from the joints of RA patients. The secretion and expression of IL-32 and activation of signaling molecules were examined by enzyme-linked immunosorbent assay, immunoblotting, immunoprecipitation, reverse transcriptase-polymerase chain reaction, and small interfering RNA (siRNA) transfection.
  
  
  RESULTS
  IL-32 levels were high in RA SF compared with OA SF. Furthermore, RA FLS expressed and secreted IL-32 when stimulated with tumor necrosis factor alpha (TNFalpha). TNFalpha-induced expression of IL-32 was significantly suppressed, in a dose-dependent manner, by inhibitors of Syk, protein kinase Cdelta (PKCdelta), and JNK and by knockdown of these kinases and c-Jun with siRNA. We also observed that PKCdelta mediated the activation of JNK and c-Jun, and experiments using specific inhibitors and siRNA demonstrated that Syk was the upstream kinase for the activation of PKCdelta.
  
  
  CONCLUSIONS
  The present findings suggest that IL-32 may be a newly identified prognostic biomarker in RA, thereby adding valuable knowledge to the understanding of this disease. The results also demonstrate that the production of IL-32 in RA FLS is regulated by Syk/PKCdelta-mediated signaling events.
authors.affiliation: Konkuk University, Chungju, Korea.
authors.forename: Se Hwan
authors.initials: SH
authors.lastname: Mun
authors.forename: Jie Wan
authors.initials: JW
authors.lastname: Kim
authors.forename: Seong Su
authors.initials: SS
authors.lastname: Nah
authors.forename: Na Young
authors.initials: NY
authors.lastname: Ko
authors.forename: Jun Ho
authors.initials: JH
authors.lastname: Lee
authors.forename: Ju Dong
authors.initials: JD
authors.lastname: Kim
authors.forename: Do Kyun
authors.initials: DK
authors.lastname: Kim
authors.forename: Hyuk Soon
authors.initials: HS
authors.lastname: Kim
authors.forename: Ji Da
authors.initials: JD
authors.lastname: Choi
authors.forename: Soo Hyun
authors.initials: SH
authors.lastname: Kim
authors.forename: Chang Keun
authors.initials: CK
authors.lastname: Lee
authors.forename: Seung Hwa
authors.initials: SH
authors.lastname: Park
authors.forename: Bo Kyung
authors.initials: BK
authors.lastname: Kim
authors.forename: Hyung Sik
authors.initials: HS
authors.lastname: Kim
authors.forename: Young Mi
authors.initials: YM
authors.lastname: Kim
authors.forename: Wahn Soo
authors.initials: WS
authors.lastname: Choi
mesh_terms: D000368:Aged; D001172:Arthritis, Rheumatoid / Q000378:metabolism* / Q000473:pathology; D015415:Biomarkers / Q000378:metabolism; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation / Q000187:drug effects; D005260:Female; D005347:Fibroblasts / Q000378:metabolism / Q000473:pathology; D006801:Humans; D007378:Interleukins / Q000378:metabolism*; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D048670:MAP Kinase Kinase 4 / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D010003:Osteoarthritis / Q000378:metabolism / Q000473:pathology; D051745:Protein Kinase C-delta / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D034741:RNA, Small Interfering / Q000494:pharmacology; D015398:Signal Transduction / Q000502:physiology; D000072377:Syk Kinase; D013582:Synovial Fluid / Q000378:metabolism; D013583:Synovial Membrane / Q000378:metabolism* / Q000473:pathology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
chemical_list: D015415:Biomarkers; C496971:IL32 protein, human; D007378:Interleukins; D047908:Intracellular Signaling Peptides and Proteins; D016755:Proto-Oncogene Proteins c-jun; D034741:RNA, Small Interfering; D014409:Tumor Necrosis Factor-alpha; D011505:Protein-Tyrosine Kinases; C000606896:SYK protein, human; D000072377:Syk Kinase; D051745:Protein Kinase C-delta; D048670:MAP Kinase Kinase 4