Folate-modified liposomal celastrol for rheumatoid arthritis: therapeutic efficacy and modulation of ROS/NF-κB/COX-2-related inflammatory signaling.

BACKGROUND: Rheumatoid arthritis (RA) is a chronic autoimmune disorder characterized by severe synovial inflammation, joint deformities, and progressive tissue destruction. Celastrol (Cel), a natural triterpenoid with anti-inflammatory and antioxidant activity, is a promising therapeutic candidate for RA; however, its application is limited by poor aqueous solubility, low bioavailability, and systemic toxicity. PURPOSE: This study aimed to develop folate-modified liposomes encapsulating Cel (FA-Cel-LPs) to improve its solubility, stability, and joint accumulation, and to evaluate their anti-inflammatory efficacy and associated molecular changes in LPS-activated RAW264.7 macrophages and collagen-induced arthritis (CIA) rats. METHODS: FA-Cel-LPs were prepared by thin-film hydration followed by extrusion and characterized for particle size, morphology, polydispersity index (PDI), encapsulation efficiency (EE), and in vitro release behavior. In LPS-activated RAW264.7 cells, cellular uptake, intracellular ROS levels, NF-κB nuclear translocation, COX-2/iNOS expression, and cytokine secretion were evaluated. In CIA rats, therapeutic efficacy was assessed by paw swelling, arthritis scores, in vivo fluorescence imaging, MRI, histological analysis, and micro-CT-based bone parameters. Safety was evaluated using hemolysis, serum biochemical analysis, and organ histology. RESULTS: FA-Cel-LPs showed a mean particle size of 110.65 ± 1.24 nm, an EE of 84.67 ± 2.55%, a PDI of 0.230 ± 0.018, and a sustained release profile with pH-dependent differences in vitro. In RAW264.7 cells, folate-modified liposomes showed greater cellular uptake and were associated with reduced ROS levels, attenuated NF-κB activation, and decreased COX-2, iNOS, and pro-inflammatory cytokine expression, with low cytotoxicity. In CIA rats, in vivo imaging suggested greater accumulation of FA-Cel-LPs in inflamed joints. Compared with free Cel and Cel-LPs, FA-Cel-LPs more effectively reduced paw swelling and joint inflammation while attenuating bone erosion and preserving joint architecture. Serum ALT and AST levels in the FA-Cel-LPs group remained within physiological ranges and were significantly lower than those in the free Cel group. Organ histology showed no obvious treatment-related injury, suggesting acceptable preliminary safety. CONCLUSION: FA-Cel-LPs improved the solubility, formulation stability, and apparent joint accumulation of Cel and enhanced its anti-inflammatory and bone-protective effects in experimental RA. These effects were associated with reduced ROS/NF-κB/COX-2-related inflammatory changes, suggesting FA-Cel-LPs may represent a promising liposomal strategy for RA.