Peficitinib Inhibits the Chemotactic Activity of Monocytes via Proinflammatory Cytokine Production in Rheumatoid Arthritis Fibroblast-Like Synoviocytes

Background: This study was performed to examine the effects of the Janus kinase (JAK) inhibitor peficitinib on fibroblast-like synoviocytes (FLS) obtained from patients with rheumatoid arthritis (RA). Methods: To examine the expression of JAK1, JAK2, and JAK3 in RA synovial tissue (ST) and FLS, immunohistochemistry was performed. We investigated the effects of peficitinib on interleukin 6 and IL-6 receptor responses in RA FLS. Phosphorylation of STAT was determined by western blot. To examine the functional analysis of peficitinib, we performed a proliferation and chemotaxis assays with FLS using THP-1 and peripheral blood mononuclear cells (PBMC). The inflammatory mediator expression of FLS was estimated by enzyme-linked immunosorbent assay. Results: JAK1, JAK2, and JAK3 were expressed in RA STs and FLS. Phosphorylation of STAT1, STAT3, and STAT5 in RA FLS was suppressed by peficitinib in a concentration-dependent manner. Peficitinib-treated RA FLS-conditioned medium reduced THP-1 and PBMC migration (p < 0.05) and proliferation of RA FLS (p < 0.05). Peficitinib suppressed the secretion of MCP-1/CCL2 in the RA FLS supernatant (p < 0.05). Conclusion: Peficitinib suppressed the JAK-STAT pathway in RA FLS and also suppressed monocyte chemotaxis and proliferation of FLS through inhibition of inflammatory cytokines.