Anti-arthritic effect of spirocyclopiperazinium bromide DXL-A-24 in CFA-induced arthritic rats and its mechanism

This study aimed to investigate the effect of spirocyclopiperazinium bromide DXL-A-24 on complete Freund's adjuvant (CFA)-induced arthritis and its underlying mechanism in rats. A rheumatoid arthritis model was established by the intradermal injection of CFA into the paws of rats. Mechanical withdrawal threshold (MWT), thermal withdrawal latency (TWL), ankle swelling and paw edema were used to evaluate the effects of DXL-A-24. Bone erosion and bone mineral density (BMD) were observed using micro-computed tomography. Receptor blocking test, western blotting, and enzyme-linked immunosorbent assay were performed to explore the mechanisms. Administration of DXL-A-24 (1, 0.5, 0.25 mg/kg, i.g.) dose-dependently increased the MWT and TWL, while alleviating ankle and paw swelling in CFA rats. The effects were blocked by peripheral α7 nicotinic or M4 muscarinic receptor antagonists. DXL-A-24 improved bone erosion and BMD, as well as downregulated the overexpression of Cav3.2, pJAK2, pSTAT3, pIκBα, pNF-κB p65, c-Fos and TNF-α proteins that were induced by CFA. In conclusion, this study shows, for the first time, that DXL-A-24 improves bone erosion and BMD and exhibits obvious anti-arthritic effects in CFA rats. The mechanism may be related to activating the peripheral α7 nicotinic and M4 muscarinic receptors, reducing Cav3.2 expression, and suppressing JAK2/STAT3 and IκBα/NF-κB p65 inflammatory signaling pathways, ultimately inhibiting inflammation-related proteins TNF-α and c-Fos.