title: The S100A8/A9 heterodimer amplifies proinflammatory cytokine production by macrophages via activation of nuclear factor kappa B and p38 mitogen-activated protein kinase in rheumatoid arthritis.
abstract: S100A8 and S100A9, two Ca2+-binding proteins of the S100 family, are secreted as a heterodimeric complex (S100A8/A9) from neutrophils and monocytes/macrophages. Serum and synovial fluid levels of S100A8, S100A9, and S100A8/A9 were all higher in patients with rheumatoid arthritis (RA) than in patients with osteoarthritis (OA), with the S100A8/A9 heterodimer being prevalent. By two-color immunofluorescence labeling, S100A8/A9 antigens were found to be expressed mainly by infiltrating CD68+ macrophages in RA synovial tissue (ST). Isolated ST cells from patients with RA spontaneously released larger amounts of S100A8/A9 protein than did the cells from patients with OA. S100A8/A9 complexes, as well as S100A9 homodimers, stimulated the production of proinflammatory cytokines, such as tumor necrosis factor alpha, by purified monocytes and in vitro-differentiated macrophages. S100A8/A9-mediated cytokine production was suppressed significantly by p38 mitogen-activated protein kinase (MAPK) inhibitors and almost completely by nuclear factor kappa B (NF-kappaB) inhibitors. NF-kappaB activation was induced in S100A8/A9-stimulated monocytes, but this activity was not inhibited by p38 MAPK inhibitors. These results indicate that the S100A8/A9 heterodimer, secreted extracellularly from activated tissue macrophages, may amplify proinflammatory cytokine responses through activation of NF-kappaB and p38 MAPK pathways in RA.
authors.affiliation: Department of Medicine and Clinical Science, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, 2-5-1 Shikata-cho, Okayama 700-8558, Japan.
authors.forename: Katsue
authors.initials: K
authors.lastname: Sunahori
authors.forename: Masahiro
authors.initials: M
authors.lastname: Yamamura
authors.forename: Jiro
authors.initials: J
authors.lastname: Yamana
authors.forename: Kouji
authors.initials: K
authors.lastname: Takasugi
authors.forename: Masanori
authors.initials: M
authors.lastname: Kawashima
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Yamamoto
authors.forename: Walter J
authors.initials: WJ
authors.lastname: Chazin
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Nakatani
authors.forename: Satoru
authors.initials: S
authors.lastname: Yui
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Makino
mesh_terms: D000368:Aged; D001172:Arthritis, Rheumatoid / Q000276:immunology / Q000503:physiopathology*; D040501:Calgranulin A / Q000378:metabolism*; D040502:Calgranulin B / Q000378:metabolism*; D016207:Cytokines / Q000096:biosynthesis*; D019281:Dimerization; D005260:Female; D006801:Humans; D008264:Macrophages / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D009000:Monocytes / Q000276:immunology; D016328:NF-kappa B / Q000378:metabolism*; D013582:Synovial Fluid / Q000166:cytology / Q000502:physiology*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
chemical_list: D040501:Calgranulin A; D040502:Calgranulin B; D016207:Cytokines; D016328:NF-kappa B; D048051:p38 Mitogen-Activated Protein Kinases