Netrin‐1 and its receptor Unc5b are novel targets for the treatment of inflammatory arthritis

Rheumatoid arthritis is an autoimmune disease that is characterized by chronic inflammation and destruction of joints. Netrin-1, a chemorepulsant, laminin-like matrix protein, promotes inflammation by preventing macrophage egress from inflamed sites and is required for osteoclast differentiation. We asked whether blockade of Netrin-1 or its receptors [Unc5b and DCC (deleted in colorectal carcinoma)] may be useful therapeutic targets for treatment of inflammatory arthritis. Arthritis was induced in 8-wk-old C57Bl/6 mice by intraperitoneal injection of K/BxN serum. Murine monoclonal antibodies against Netrin-1, Unc5b, or DCC (10 μg/mouse) were injectedweekly for 4 wk(n = 10). Paw swelling and thickness were assessed and following euthanasia 2–4 wk after serum transfer, paws were prepared for micro–computed tomography and histology. Paw inflammation was maximal 2 wk after injection. Anti–Netrin-1 or anti-Unc5b, but not anti-DCC, antibodies significantly reduced paw inflammation (clinical score: 9.8 ± 0.8, 10.4 ± 0.9, and 13.5 ± 0.5, respectively vs. 16 ± 0 for control; P < 0.001). Micro–computed tomography showed bony erosions in untreated or anti-DCC–treated mice, whereas there were no erosions in anti–Netrin-1/anti-Unc5β-treated-animals. Tartrate-resistant acid phosphatase staining demonstrated a marked decrease in osteoclasts in anti-Netrin-1/anti-Unc5b–treated animals. Immunofluorescence staining revealed a decrease in cathepsin K+ and CD68+ cells in anti–Netrin-1/anti-Unc5b–treated animals. Blockade of Netrin-1/Unc5b by monoclonal antibodies prevents bone destruction and reduces the severity of K/BxN serum transfer–induced arthritis. Netrin-1 may be a novel therapeutic target for treatment of inflammatory bone destruction.—Mediero, A., Wilder, T., Ramkhelawon, B., Moore, K. J., Cronstein, B. N. Netrin-1 and its receptor Unc5b are novel targets for the treatment of inflammatory arthritis. FASEB J. 30, 3835–3844 (2016) www.fasebj.org