In addition to its chemopreventive activity, phase 2 enzyme inducers have been recently found to have anti-inflammatory activity. In this study, we examined the influence of sulphoraphane (SPN), one of the most potent inducers of the phase II enzymes on the production of MMPs by pro-inflammatory cytokines in human articular chondrocytes.
Articular cartilages were obtained from knee OA patients and were cultured in monolayers and explants. Induction of a phase II enzyme, NAD(P)H:quinone oxidoreductase 1 (NQO1), in chondrocytes was assayed after incubation with various concentrations of SPN. Chondrocytes were stimulated with IL-1 or TNF-alpha with or without pre-incubation with SPN. The expression and activation of MMP-1, -3 and -13 was evaluated by an ELISA, gel zymography and RT-PCR. MAP kinases [p38, extracellular signal-regulated protein kinase (ERK) and C-Jun N terminal kinase (JNK)] and NF-kappaB activation were evaluated by western blotting and by an electrophoretic mobility shift assay, respectively.
SPN significantly induced NQO1 activity in chondrocytes and the induction was maximal at 24 h. SPN inhibited the production of MMP-1, -3 and -13 protein and mRNA induced by either IL-1 or TNF-alpha in a dose-dependent manner. This inhibition of MMP by SPN was accompanied by the inhibition of NF-kappaB and JNK activation.
SPN was found to inhibit MMP production in pro-inflammatory cytokine-stimulated chondrocytes. Delineation of the biochemical mechanism regulating cartilage catabolism by SPN may identify safe and effective therapeutic targets for the inhibition of cartilage degradation.