title: Implication of interleukin 18 in production of matrix metalloproteinases in articular chondrocytes in arthritis: direct effect on chondrocytes may not be pivotal.
abstract: OBJECTIVE
  To clarify the effect of interleukin (IL) 18 on cartilage degeneration by studying the profile of IL18 receptor (IL18R) on chondrocytes and the direct effect of IL18 on production of matrix metalloproteinases (MMPs), aggrecanases, and tissue inhibitors of metalloproteinases (TIMPs) in articular chondrocytes.
  
  
  METHODS
  Monolayer cultured human articular chondrocytes were isolated from non-arthritic subjects and patients with rheumatoid arthritis or osteoarthritis. Gene expression of IL18, IL18Ralpha, IL18Rbeta, MMPs, and aggrecanases was detected by RT-PCR. Protein levels of IL18Ralpha were analysed by flow cytometry. Protein levels of IL18, MMPs, and TIMPs were measured by ELISA. Aggrecanase-2 mRNA expression was quantitatively analysed by real time RT-PCR. Protein levels of signalling molecules were assayed by western blotting.
  
  
  RESULTS
  IL18 mRNA was constitutively expressed in chondrocytes, and was enhanced by IL1beta stimulation. Flow cytometric analysis showed that IL1beta, tumour necrosis factor alpha, and IL18 up regulated IL18Ralpha expression levels. The level of IL18Rbeta mRNA was much lower than that of IL18Ralpha, and was slightly up regulated by IL1beta. In chondrocytes responding to IL18, IL18 (1-100 ng/ml) slightly increased the production of MMP-1, MMP-3, and MMP-13, which was blocked by NF-kappaB inhibitor and p38 mitogen activated protein kinase inhibitor. IL18 up regulated mRNA expression of aggrecanase-2, but not aggrecanase-1. IL18 also slightly stimulated TIMP-1 production?through extracellular signal regulated kinase activation.
  
  
  CONCLUSIONS
  IL18 induces production of MMPs from chondrocytes in inflammatory arthritis. Although the direct effect of IL18 on chondrocytes may not be pivotal for the induction of cartilage degeneration, IL18 seems to play some part in the degradation of articular cartilage in arthritis.
authors.affiliation: Department of Bioregulation, Institute of Medical Science, St Marianna University School of Medicine, 2-16-1 Sugao, Miyamae-ku, Kawasaki, Kanagawa 216-8512, Japan.
authors.forename: S-M
authors.initials: SM
authors.lastname: Dai
authors.forename: Z-Z
authors.initials: ZZ
authors.lastname: Shan
authors.forename: K
authors.initials: K
authors.lastname: Nishioka
authors.forename: K
authors.initials: K
authors.lastname: Yudoh
mesh_terms: D051722:ADAM Proteins; D000071116:ADAMTS5 Protein; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001168:Arthritis / Q000201:enzymology / Q000378:metabolism / Q000473:pathology; D001172:Arthritis, Rheumatoid / Q000201:enzymology* / Q000378:metabolism / Q000473:pathology; D002358:Cartilage, Articular / Q000201:enzymology* / Q000473:pathology; D002478:Cells, Cultured; D019902:Chondrocytes / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D020382:Interleukin-18 / Q000096:biosynthesis / Q000235:genetics / Q000494:pharmacology*; D020782:Matrix Metalloproteinases / Q000096:biosynthesis*; D008666:Metalloendopeptidases / Q000096:biosynthesis / Q000235:genetics; D008875:Middle Aged; D010003:Osteoarthritis / Q000201:enzymology* / Q000378:metabolism / Q000473:pathology; D012333:RNA, Messenger / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D015398:Signal Transduction; D019715:Tissue Inhibitor of Metalloproteinase-1 / Q000096:biosynthesis
chemical_list: D020382:Interleukin-18; D012333:RNA, Messenger; D019715:Tissue Inhibitor of Metalloproteinase-1; D051722:ADAM Proteins; D000071116:ADAMTS5 Protein; C121532:ADAMTS5 protein, human; D020782:Matrix Metalloproteinases; D008666:Metalloendopeptidases