CTLA4-Ig Directly Inhibits Osteoclastogenesis by Interfering With Intracellular Calcium Oscillations in Bone Marrow Macrophages |
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| Authors: | Hiroyuki Okada Hiroshi Kajiya Yasunori Omata Takumi Matsumoto Yuiko Sato Tami Kobayashi Satoshi Nakamura Yosuke Kaneko Shinya Nakamura Takuma Koyama Shunichi Sudo Masashi Shin Fujio Okamoto Hisato Watanabe Naohiro Tachibana Jun Hirose Taku Saito Toshiyuki Takai Morio Matsumoto Masaya Nakamura Koji Okabe Takeshi Miyamoto Sakae Tanaka |
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| Affiliation: | 1. Department of Orthopaedic Surgery, The University of Tokyo, Tokyo, Japan;2. Department of Physiological Science and Molecular Biology, Fukuoka Dental College, Fukuoka, Japan;3. Department of Orthopedic Surgery, Keio University School of Medicine, Tokyo, Japan;4. Department of Experimental Immunology, Institute of Development, Aging and Cancer, Tohoku University, Sendai, Fukuoka, Japan |
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| Abstract: | CTLA4-Ig (cytotoxic T-lymphocyte antigen 4-immunoglobulin; Abatacept) is a biologic drug for rheumatoid arthritis. CTLA4 binds to the CD80/86 complex of antigen-presenting cells and blocks the activation of T cells. Although previous reports showed that CTLA4-Ig directly inhibited osteoclast differentiation, the whole inhibitory mechanism of CTLA4-Ig for osteoclast differentiation is unclear. Bone marrow macrophages (BMMs) from WT mice were cultured with M-CSF and RANKL with or without the recombinant mouse chimera CTLA4-Ig. Intracellular calcium oscillations of BMMs with RANKL were detected by staining with calcium indicator fura-2 immediately after administration of CTLA4-Ig or after one day of treatment. Calcium oscillations were analyzed using Fc receptor gamma- (FcRγ-) deficient BMMs. CTLA4-Ig inhibited osteoclast differentiation and reduced the expression of the nuclear factor of activated T cells NFATc1 in BMMs in vitro. Calcium oscillations in BMMs were suppressed by CTLA4-Ig both immediately after administration and after one day of treatment. CTLA4-Ig did not affect osteoclastogenesis and did not cause remarkable changes in calcium oscillations in FcRγ-deficient BMMs. Finally, to analyze the effect of CTLA4-Ig in vivo, we used an LPS-induced osteolysis model. CTLA4-Ig suppressed LPS-induced bone resorption in WT mice, not in FcRγ-deficient mice. In conclusion, CTLA4-Ig inhibits intracellular calcium oscillations depending on FcRγ and downregulates NFATc1 expression in BMMs. © 2019 American Society for Bone and Mineral Research. |
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| Keywords: | CTLA4 ABATACEPT OSTEOCLAST DIFFERENTIATION CALCIUM OSCILLATION |
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