Cannabidiol synergizes with methotrexate to attenuate rheumatoid arthritis via STAT3/NF-κB signalling-mediated M1...

Methotrexate (MTX) is the anchor drug for rheumatoid arthritis (RA) treatment, but its clinical application is limited by dose-dependent adverse events, such as hepatotoxicity and gastrointestinal intolerance, and incomplete efficacy in some patients. Cannabidiol (CBD) is a nonpsychotropic cannabinoid that has powerful therapeutic efficacy in alleviating pain and inflammation, as well as favourable safety and tolerability profiles. However, whether CBD can synergize with MTX to enhance therapeutic outcomes and mitigate toxicity remains unclear. This study aimed to investigate the synergistic efficacy, safety profile, and underlying molecular mechanism of the CBD-MTX combination in the treatment of RA.

Mice were randomly divided into 8 groups (n = 5 per group): a normal control group (NC), a model control group (MC), 3 MTX monotherapy groups (low/medium/high dose), and 3 CBD + MTX combination groups (low/medium/high dose). Arthritis severity was assessed by clinical scoring and micro-CT. Systemic safety was evaluated via histopathological examination of the liver, kidney, and testis. Flow cytometry, ELISA and Western blotting were used to validate the mechanisms involved. Network pharmacology and molecular docking were used to predict potential targets.

Compared with MTX monotherapy, the CBD-MTX combination had dose-dependent synergistic effects, significantly attenuating joint swelling, inflammation, and bone erosion. The medium-dose combination approached the efficacy of high-dose MTX (dose-sparing effect). CBD mitigated MTX-induced testicular toxicity and spermatogenic failure. Mechanistically, the combination suppressed M1 macrophage polarization and proinflammatory cytokine (TNF-α, IL-6, and IL-1β) secretion by inhibiting STAT3 and NF-κB signalling (downregulation of p-STAT3 and p-NF-κB p65).

The CBD-MTX combination exerts superior antiarthritic effects by inhibiting STAT3/NF-κB-mediated M1 macrophage polarization and protecting against MTX-induced reproductive toxicity. This study provides a preclinical rationale for this novel combination strategy in RA management.