Soluble Siglec-9 suppresses arthritis in a collagen-induced arthritis mouse model and inhibits M1 activation of RAW264.7 macrophages.
The aim of this study was to assess the effects of soluble sialic acid-binding immunoglobulin-type lectin (sSiglec)-9 on joint inflammation and destruction in a murine collagen-induced arthritis (CIA) model and in monolayer cultures of murine macrophages (RAW264.7 cells and peritoneal macrophages) and fibroblast-like synoviocytes (FLS) derived from patients with rheumatoid arthritis.



DBA/1J mice were immunized with type II collagen. Effects of sSiglec-9 were evaluated using a physiologic arthritis score, histological analysis, serum tumor necrosis factor (TNF)-α concentration, and the proportion of forkhead box P3 (Foxp3)-positive regulatory T (Treg) cells. In vivo biofluorescence imaging was used to assess the distribution of sSiglec-9. Levels of M1 (TNF-α, interleukin [IL]-6, and inducible nitric oxide synthase) and M2 (CD206, Arginase-1, and IL-10) macrophage markers and phosphorylation of intracellular signaling molecules were examined in macrophages, and levels of matrix metalloproteinase (MMP)-1, MMP-3, and MMP-13 were examined in FLS.



sSiglec-9 significantly suppressed the clinical and histological incidence and severity of arthritis. The proportion of Foxp3-positive Treg cells significantly improved and serum TNF-α concentration decreased in vivo. Although sSiglec-9 reduced the expression of M1 markers in macrophages, it did not affect the expression of M2 markers and MMPs in FLS. Nuclear factor (NF)-kB p65 phosphorylation was attenuated by sSiglec-9, and chemical blockade of the NF-kB pathway reduced M1 marker expression in RAW264.7 cells.



In this study, we have demonstrated the therapeutic effects of sSiglec-9 in a murine CIA model. The mechanism underlying these effects involves the suppression of M1 proinflammatory macrophages by inhibiting the NF-kB pathway. sSiglec-9 may provide a novel therapeutic option for patients with rheumatoid arthritis refractory to currently available drugs.
Department of Orthopedic Surgery and Rheumatology, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, Aichi, 466-8550, Japan.
Takuya
T
Matsumoto
Department of Orthopedic Surgery and Rheumatology, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, Aichi, 466-8550, Japan. nobunori@med.nagoya-u.ac.jp.
Nobunori
N
Takahashi
Department of Orthopedic Surgery and Rheumatology, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, Aichi, 466-8550, Japan.
Toshihisa
T
Kojima
Department of Orthopedic Surgery and Rheumatology, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, Aichi, 466-8550, Japan.
Yutaka
Y
Yoshioka
Department of Oral and Maxillofacial Surgery/Protective Care for Masticatory Disorders, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, Aichi, 466-8550, Japan.
Jun
J
Ishikawa
Department of Biochemistry II, Nagoya University Graduate School of Medicine, Nagoya, 466-0065, Japan.
Koichi
K
Furukawa
Research Institute of Environmental Medicine, Nagoya University, Nagoya, 464-8601, Japan.
Kenji
K
Ono
Research Institute of Environmental Medicine, Nagoya University, Nagoya, 464-8601, Japan.
Makoto
M
Sawada
Department of Orthopedic Surgery and Rheumatology, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, Aichi, 466-8550, Japan.
Naoki
N
Ishiguro
Department of Oral and Maxillofacial Surgery/Protective Care for Masticatory Disorders, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, Aichi, 466-8550, Japan.
Akihito
A
Yamamoto
D000818:Animals; D015703:Antigens, CD / Q000378:metabolism / Q000494:pharmacology*; D001169:Arthritis, Experimental / Q000276:immunology / Q000473:pathology*; D001172:Arthritis, Rheumatoid / Q000276:immunology / Q000473:pathology*; D015153:Blotting, Western; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D006801:Humans; D007150:Immunohistochemistry; D008262:Macrophage Activation / Q000187:drug effects* / Q000276:immunology; D008264:Macrophages / Q000187:drug effects; D008297:Male; D051379:Mice; D008811:Mice, Inbred DBA; D016133:Polymerase Chain Reaction; D000067996:RAW 264.7 Cells; D011897:Random Allocation; D063265:Sialic Acid Binding Immunoglobulin-like Lectins / Q000378:metabolism / Q000494:pharmacology*
D015703:Antigens, CD; C412227:SIGLEC9 protein, human; D063265:Sialic Acid Binding Immunoglobulin-like Lectins
Collagen-induced arthritis; Rheumatoid arthritis; Siglec-9