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Published online before print June 15, 2007

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(Journal of Leukocyte Biology. 2007;82:657-665.)
© 2007 by Society for Leukocyte Biology

The extra domain A of fibronectin stimulates murine mast cells via Toll-like receptor 4

Srie Prihianti Gondokaryono^*,, Hiroko Ushio^*,1, François Niyonsaba^*, Mutsuko Hara^*,, Hiroshi Takenaka^*,, Sumanasiri T. M. Jayawardana^*,, Shigaku Ikeda, Ko Okumura^*, and Hideoki Ogawa^*

^* Atopy (Allergy) Research Center, Departments of
Dermatology and
Immunology,
Division of Molecular and Biochemical Research, Biomedical Center, Juntendo University School of Medicine, Bunkyo-ku, Tokyo, Japan

¹ Correspondence: Atopy (Allergy) Research Center, Juntendo University School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo, 113-8421, Japan. E-mail: hushio{at}med.juntendo.ac.jp

The activation of mast cells by extra domain A of fibronectin (FN-EDA), an endogenous ligand of TLR4, and its contribution to the pathogenesis of rheumatoid arthritis (RA) in vivo were examined. FN-EDA, but no other domain of the fibronectin fragment, III₁₁ (FN-III₁₁) and III₁₂ (FN-III₁₂), stimulated bone marrow-derived murine mast cells (BMMCs) dose-dependently to secret cytokines (TNF-, IL-6, and IL-1ß), similar to the pattern produced by LPS. FN-EDA-induced cytokine production was mediated by TLR4, as cytokine production by FN-EDA was absent in TLR4-deficient (TLR4–/–) BMMCs. We examined the roles of TLR4-mediated mast cell activation by this form of fibronectin fragment in the pathogenesis of RA in vivo. The injection of FN-EDA, but not FN-III₁₁and FN-III₁₂, to joints resulted in joint swelling of mice in vivo. Genetically mast cell-deficient WBB6F₁-W/W^v mice exhibited significantly less swelling and cytokine production compared with mast cell-sufficient +/+ mice, suggesting that swelling and inflammatory cytokine production were partially dependent on tissue mast cells. Reduced swelling and cytokine production were recovered by the reconstitution of tissue mast cells by the injection of BMMCs from wild-type mice but not from TLR4–/– mice. Altogether, these results suggest that the TLR4-mediated activation of mast cells by endogenous ligand FN-EDA might contribute to the pathogenesis of RA through proinflammatory cytokine production.

Key Words: basophil • rheumatoid arthritis