Methotrexate-Loaded Nanoparticles Ameliorate Autoimmune Arthritis by Regulating the Balance of Interleukin-17-Producing T Cells and Regulatory T and B Cells

Abstract Background: Rheumatoid arthritis (RA) is a progressive systemic autoimmune disease that is characterized by infiltration of inflammatory cells into the hyperplastic synovial tissue, resulting in subsequent destruction of adjacent articular cartilage and bone. Methotrexate (MTX), the first conventional disease-modifying antirheumatic drug (DMARD), could alleviate articular damage in RA and is implicated in humoral and cellular immune responses. However, MTX has several side effects, so efficient delivery of low-dose MTX is important. Methods: To investigate the efficacy of MTX-loaded nanoparticles (MTX-NPs) against RA, free MTX or MTX-NPs were administered as subcutaneous route to mice with collagen-induced arthritis (CIA) at 3 weeks after CII immunization. The levels of inflammatory factors in tissues were determined by immunohistochemistry, confocal microscopy, real-time PCR, and flow cytometry. Results: MTX-NPs ameliorated arthritic severity and joint destruction in collagen-induced arthritis (CIA) mice compared to free MTX-treated CIA mice. The levels of inflammatory cytokines, including interleukin (IL)-1β, tumor necrosis factor-α, and vascular endothelial growth factor, were reduced in MTX-NPs-treated mice. Numbers of phosphorylated STAT3-positive CD4+ cells and CD4+IL-17+ cells were reduced whereas the number of CD4+CD25+Foxp3+ cells increased in spleens from MTX- NPs-treated CIA mice compared to MTX-treated CIA mice. The frequency of CD19+CD25+Foxp3+ regulatory B cells increased in ex vivo splenocytes from MTX-loaded NPs-treated CIA mice compared to MTX-treated CIA mice. Conclusion: The results suggest that MTX-loaded NPs have therapeutic potential for RA.