Dynamic compression alters NFκB activation and IκB-α expression in IL-1β-stimulated chondrocyte/agarose constructs

Determine the effect of IL-1 beta and dynamic compression on NF kappa B activation and I kappa B-alpha gene expression in chondrocyte/agarose constructs. Constructs were cultured under free-swelling conditions or subjected to dynamic compression for up to 360 min with IL-1 beta and/or PDTC (inhibits NF kappa B activation). Nuclear translocation of NF kappa B-p65 was analysed by immunofluoresence microscopy. Gene expression of I kappa B-alpha, iNOS, IL-1 beta and IL-4 was assessed by real-time qPCR. Nuclear translocation of NF kappa B-p65 was concomitant with an increase in nuclear fluorescence intensity which reached maximum values at 60 min with IL-1 beta (p < 0.001). Dynamic compression or PDTC reduced nuclear fluorescence and NF kappa B nuclear translocation in cytokine-treated constructs (p < 0.001 and p < 0.01 respectively). IL-1 beta increased I kappa B-alpha expression (p < 0.001) at 60 min and either induced iNOS (p < 0.001) and IL-1 beta (p < 0.01) or inhibited IL-4 (p < 0.05) expression at 360 min. These time-dependent events were partially reversed by dynamic compression or PDTC (p < 0.01) with IL-1 beta. Co-stimulation by dynamic compression and PDTC favoured suppression (I kappa B-alpha, iNOS, IL-1 beta) or induction (IL-4) of gene expression. NF kappa B is one of the key players in the mechanical and inflammatory pathways, and its inhibition by a biophysical/therapeutic approach could be a strategy for attenuating the catabolic response in osteoarthritis.