Inhibitory effect of synthetic cannabinoids on cytokine production in rheumatoid fibroblast-like synoviocytes

OBJECTIVE: To verify whether synthetic cannabinoids (CP55,940 and WIN55,212-2) are able to exert an anti-inflammatory effect on rheumatoid fibroblast-like synoviocytes (FLS) by down-regulating cytokine production, and determine whether this effect could be mediated by CB1/CB2 cannabinoid receptors. METHODS: Interleukin-6 (IL-6) and interleukin-8 (IL-8) were assayed in the supernatant from cultured FLS by ELISA method before and after 3 hours of incubation with CP55,940 (10 microM) and WIN55,212-2 (10 microM). Co-stimulation of cells with the cannabinoid receptor antagonists was performed to evaluate receptor involvement in cytokine modulation. All the experiments were conducted in basal conditions and after 1 hour pre-incubation with 0.1 ng/ml IL-1beta. FLS expression of CB1 and CB2 receptor was studied by Western Blot analyses. RESULTS: Both CP55,940 and WIN55,212-2 induced a potent and significant reduction in IL-6 and IL-8 secretion from IL-1beta. stimulated FLS. Although FLS express CB1 and CB2 receptor, cannabinoid receptor antagonists did not significantly modify the inhibition of cytokines secretion induced by CP55,940 and WIN55,212-2. CONCLUSIONS: In vitro, CP55,940 and WIN55,212-2 exert a potent anti-inflammatory effect on rheumatoid FLS via a non-CB1/CB2 receptor mediated mechanism.