Effects of cannabinoids on IL-1alpha-induced bovine chrondrocyte metabolism and cartilage resorption.

Cannabinoids reported to have analgesic, anti-inflammatory and immunosuppressive effects were also shown to reduce joint damage in animal models of arthritis, suggesting that they have a potential as anti-arthritic agents. Therefore in this thesis, the effects of cannabinoids were studied to determine the mechanisms involved in their joint protective effects by making use of IL-1alpha-induced bovine articular chondrocytes and nasal cartilage explants. IL-1alpha induction of the inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2) and 5-lipooxygenase (5-LOX) pathways and effects of cannabinoids on these was studied using immunofluorescence, immunoblotting as well as ELISAs. Effects of cannabinoids on IL-1-induced activation of nuclear factor-kappa B (NF-kappaB) as well as p38 mitogen activated protein kinase (MAPK) were determined by immunofluorescence and fast activated cell-based ELISA (FACE). Cartilage explant cultures were stimulated with IL-1alpha to resorb and effects of cannabinoids on the release of collagen (using hydroxyproline assay), cartilage oligomeric matrix protein (COMP) (using an ELISA) and proteoglycan (using dimethylmethylene blue assay) were studied as well. Expression of cannabinoid receptors in chondrocytes was also determined by immublotting and immunofluorescence. Cannabinoids inhibited IL-1alpha-induced iNOS, COX-2 expression, NF-kappaB and p38 MAPK activation in chondrocytes. They also protected the explants from resorption stimulated by IL-1. Chondrocytes were also shown for the first time to express cannabinoid receptors. The results suggested that cannabinoids protected cartilage from cytokine-induced degradation, in part, by inhibiting NO and PGE2 production and their pathways. These effects were possibly receptor mediated. Cannabinoids appear to have a significant potential as anti-arthritic therapeutics.