title: Interleukin-18 induces serum amyloid A (SAA) protein production from rheumatoid synovial fibroblasts.
abstract: Interleukin-18 (IL-18) is a novel proinflammatory cytokine that was recently found in synovial fluids and synovial tissues from patients with rheumatoid arthritis (RA). To investigate the role of IL-18 in rheumatoid synovitis, the levels of IL-18 and serum amyloid A (SAA) were measured in synovial fluids from 24 patients with rheumatoid arthritis (RA) and 13 patients with osteoarthritis (OA). The levels of IL-18 and SAA in the synovial fluids were elevated in RA patients. In contrast, the levels of IL-18 in synovial fluids from OA patients were significantly lower compared to those of RA patients. SAA was not detected in synovial fluids from OA patients. The expression of SAA mRNA in rheumatoid synovial cells was also examined. SAA4 mRNA, which was constitutively expressed by rheumatoid synovial cells, was not affected by IL-18 stimulation. Although acute phase SAA (A-SAA, SAA1 + 2) mRNA was not detected in unstimulated synovial cells, its expression was induced by IL-18 stimulation. By immunoblot, we demonstrated that IL-18 induced the SAA protein synthesis from rheumatoid synovial cells in a dose-dependent manner. These results indicate a novel role for IL-18 in rheumatoid inflammation through the synovial SAA production.
authors.affiliation: First Department of Internal Medicine, Nagasaki University School of Medicine, Sakamoto 1-7-1, Nagasaki, Japan.
authors.forename: Fumiko
authors.initials: F
authors.lastname: Tanaka
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Migita
authors.forename: Yojiro
authors.initials: Y
authors.lastname: Kawabe
authors.forename: Takahiko
authors.initials: T
authors.lastname: Aoyagi
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Ida
authors.forename: Atsushi
authors.initials: A
authors.lastname: Kawakami
authors.forename: Katsumi
authors.initials: K
authors.lastname: Eguchi
mesh_terms: D001172:Arthritis, Rheumatoid / Q000276:immunology / Q000378:metabolism* / Q000473:pathology; D002478:Cells, Cultured; D005347:Fibroblasts / Q000166:cytology / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D020382:Interleukin-18 / Q000276:immunology / Q000378:metabolism*; D053727:Interleukin-18 Receptor alpha Subunit; D018123:Receptors, Interleukin / Q000235:genetics / Q000378:metabolism; D053724:Receptors, Interleukin-18; D000685:Serum Amyloid A Protein / Q000276:immunology / Q000378:metabolism*; D013223:Statistics as Topic; D013582:Synovial Fluid / Q000737:chemistry; D013583:Synovial Membrane / Q000166:cytology* / Q000473:pathology
chemical_list: C508572:IL18R1 protein, human; D020382:Interleukin-18; D053727:Interleukin-18 Receptor alpha Subunit; D018123:Receptors, Interleukin; D053724:Receptors, Interleukin-18; D000685:Serum Amyloid A Protein