Essential role of the cryptic epitope SLAYGLR within osteopontin in a murine model of rheumatoid arthritis
Nobuchika Yamamoto, … , Takashi Fujii, Toshimitsu Uede
Nobuchika Yamamoto, … , Takashi Fujii, Toshimitsu Uede
Published July 15, 2003
Citation Information: J Clin Invest. 2003;112(2):181-188. https://doi.org/10.1172/JCI17778.
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Article Immunology

Essential role of the cryptic epitope SLAYGLR within osteopontin in a murine model of rheumatoid arthritis

Abstract

It has been shown that osteopontin (OPN) plays a pivotal role in the pathogenesis of rheumatoid arthritis (RA). However, the molecular mechanism of OPN action is yet to be elucidated. Splenic monocytes obtained from arthritic mice exhibited a significant capacity for cell migration toward thrombin-cleaved OPN but not toward full-length OPN. Migratory monocytes expressed α9 and α4 integrins. Since cleavage of OPN by thrombin exposes the cryptic epitope recognized by α9 and α4 integrins, we investigated the role of the cryptic epitope SLAYGLR in a murine RA model by using a specific antibody (M5) reacting to SLAYGLR sequence. The M5 antibody could abrogate monocyte migration toward the thrombin-cleaved form of OPN. Importantly, M5 antibody could inhibit the proliferation of synovium, bone erosion, and inflammatory cell infiltration in arthritic joints. Thus, we demonstrated that a cryptic epitope, the SLAYGLR sequence of murine OPN, is critically involved in the pathogenesis of a murine model of RA.

Authors

Nobuchika Yamamoto, Fumihiko Sakai, Shigeyuki Kon, Junko Morimoto, Chiemi Kimura, Harumi Yamazaki, Ikuko Okazaki, Nobuo Seki, Takashi Fujii, Toshimitsu Uede

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Figure 5

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M5 Ab prevented osteoclast-mediated bone resorption and osteoclast forma...
M5 Ab prevented osteoclast-mediated bone resorption and osteoclast formation in vitro. (a and b) PTH or IL-1α induced calcium releases. PTH and IL-1 induced calcium release from bone in murine neonatal calvaria culture in the presence of M5 Ab (a and b) or anti-β3 integrin Ab (c). Results are expressed as means ± SEM. **P < 0.01 for comparison by Dunnet’s multiple-comparison test with isotype control IgG plus PTH or IL-1α. (d) Mouse bone marrow cells were cultured for 7 days in the presence of M-CSF and RANKL in the presence of control antibody or M5 Ab (200 μg/ml), and TRAP-positive mature osteoclasts numbers were counted and expressed as mean numbers ± SEM of cells. (e) Arthritic mice prophylactically treated with M5 Ab on day 0 and 3 in Figure 3 were used. Expressions of proinflammatory cytokines, OPN, and integrin mRNA in joint extracts were analyzed using RT-PCR and GAPDH as a housekeeping gene. These are representative data from three separate experiments.