Anti-neuropilin-1 peptide inhibition of synoviocyte survival, angiogenesis, and experimental arthritis

Objective. To delineate the role of neuropilin-1 (NP-1), a vascular endothelial growth factor receptor (VEGFR), in rheumatoid inflammation and to determine whether blockade of NP-1 could suppress synoviocyte survival and angiogenesis. Methods. VEGF_111-165 peptide, which encompasses the NP-1 binding domain of VEGF₁₆₅, was generated by cleaving VEGF ₁₆₅ with plasmin. The effect of this peptide on the interaction between VEGF₁₆₅ and its receptor was determined by ¹²⁵I-VEGFR binding assay. Assays to determine synoviocyte apoptosis, adhesion, and migration were performed in the presence of VEGF₁₆₅ and/or the peptide. VEGF₁₆₅-induced angiogenesis was assessed by measuring the proliferation, tube formation, and wounding migration of endothelial cells (ECs). Mice were immunized with type II collagen to induce experimental arthritis. Results. VEGF_111-165 peptide specifically inhibited the binding of ¹²⁵I-VEGF₁₆₅ to NP-1 on rheumatoid synoviocytes and ECs. The peptide eliminated the VEGF ₁₆₅-mediated increase in synoviocyte survival and activation of p-ERK and Bcl-2. The peptide also completely inhibited a VEGF₁₆₅-induced increase in synoviocyte adhesion and migration. In addition, the anti-NP-1 peptide blocked VEGF₁₆₅-stimulated proliferation, capillary tube formation, and wounding migration of ECs in vitro. VEGF₁₆₅-induced neovascularization in a Matrigel plug in mice was also blocked by treatment with the peptide. Finally, subcutaneous injection of anti-NP-1 peptide suppressed arthritis severity and autoantibody formation in mice with experimental arthritis and inhibited synoviocyte hyperplasia and angiogenesis in arthritic joints. Conclusion. Anti-NP-1 peptide suppressed VEGF₁₆₅-induced increases in synoviocyte survival and angiogenesis, and thereby blocked experimental arthritis. Our findings suggest that anti-NP-1 peptide could be useful in alleviating chronic arthritis.