Methotrexate-loaded biodegradable nanoparticles exert anti-arthritic effect by downregulating pro-inflammatory cytokines in Freund’s complete adjuvant-induced arthritic rats

Methotrexate (MTX), the first-line drug for the treatment of rheumatoid arthritis (RA), can cause considerable toxicity, which limits effective dosage regimens. Moreover, it has rapid clearance, which leads to poor patient compliance. To mitigate such challenges, this study aimed to validate the use of MTX-loaded chitosan nanoparticles (NPs) in treating Freund’s complete adjuvant (FCA) arthritis in rats. Healthy Wistar rats ( n = 30) were divided into five groups. The first group served as healthy control, while the second group served as arthritic control. Group 3 was administered methotrexate, while groups 4 and 5 were MTX-loaded NP-treated groups. NPs were prepared by solvent evaporation method and characterized by zeta size, potential, polydispersity index (PDI), and Fourier-transform infrared spectroscopy. NPs were 190 nm in size, and PDI was 0.25, confirming the uniform distribution of NPs. A significant increase in paw thickness was noted up to the 21st day of the study, which was reversed by a high dose of MTX-loaded NPs. MTX NPs significantly reduced the level of pro-inflammatory markers, including TNF-α and IL-6, along with improving control of oxidative stress biomarkers. The findings of biochemical, haematological, radiological, and histopathological investigations further confirmed amelioration of necrosis and cellular infiltration. It can be concluded that MTX-loaded chitosan NPs are promising candidates for treating FCA-induced arthritis in a rat model.