Open AccessGlycoprotein 96 perpetuates the persistent inflammation of rheumatoid arthritis
Author(s) -
Huang QiQuan,
Koessler Renee E.,
Birkett Robert,
Dorfleutner Andrea,
Perlman Harris,
Haines G. Kenneth,
Stehlik Christian,
Nicchitta Christopher V.,
Pope Richard M.
Publication year - 2012
Publication title -
arthritis & rheumatism
Language(s) - English
Resource type - Journals
eISSN - 1529-0131
pISSN - 0004-3591
DOI - 10.1002/art.34610
Subject(s) - synovial fluid , hek 293 cells , tumor necrosis factor alpha , inflammation , synovial membrane , arthritis , antibody , immunology , macrophage , cd14 , receptor , microbiology and biotechnology , chemistry , medicine , immune system , biology , osteoarthritis , pathology , in vitro , biochemistry , alternative medicine
Objective The mechanisms that contribute to the persistent activation of macrophages in rheumatoid arthritis (RA) are incompletely understood. The aim of this study was to determine the contribution of endogenous gp96 in Toll‐like receptor (TLR)–mediated macrophage activation in RA. Methods RA synovial fluid was used to activate macrophages and HEK–TLR‐2 and HEK–TLR‐4 cells. Neutralizing antibodies to TLR‐2, TLR‐4, and gp96 were used to inhibit activation. RA synovial fluid macrophages were isolated by CD14 negative selection. Cell activation was measured by the expression of tumor necrosis factor α (TNFα) or interleukin‐8 messenger RNA. Arthritis was induced in mice by K/BxN serum transfer. The expression of gp96 was determined by immunoblot analysis, enzyme‐linked immunosorbent assay, and immunohistochemistry. Arthritis was treated with neutralizing anti‐gp96 antiserum or control serum. Results RA synovial fluid induced the activation of macrophages and HEK–TLR‐2 and HEK–TLR‐4 cells. RA synovial fluid–induced macrophage and HEK–TLR‐2 activation was suppressed by neutralizing anti‐gp96 antibodies only in the presence of high (>800 ng/ml) rather than low (<400 ng/ml) concentrations of gp96. Neutralization of RA synovial fluid macrophage cell surface gp96 inhibited the constitutive expression of TNFα. Supporting the role of gp96 in RA, joint tissue gp96 expression was induced in mice with the K/BxN serum–induced arthritis, and neutralizing antibodies to gp96 ameliorated joint inflammation, as determined by clinical and histologic examination. Conclusion These observations support the notion that gp96 plays a role as an endogenous TLR‐2 ligand in RA and identify the TLR‐2 pathway as a therapeutic target.