Signal transduction pathways involving p38 MAPK, JNK, NFκB and AP-1 influences the response of chondrocytes cultured in agarose constructs to IL-1β and dynamic compression

Objective and Design: To examine whether inhibitors of the MAPK pathways will influence the response of bovine chondrocytes cultured in agarose constructs to IL-1 beta and dynamic compression. Methods: Dose-response studies were conducted under IL-1 beta conditions with either SB203580, SP600125, PDTC or curcumin. In separate experiments, constructs were treated with IL-1 beta and an appropriate concentration of inhibitor and subjected to 15% dynamic compression. Nitrite and PGE(2) release, (SO4)-S-35 and [H-3]-thymidine incorporation were subsequently measured using biochemical assays. Results: All inhibitors reduced the IL-1 beta induced nitrite and PGE(2) release in a dose-dependent manner. The inhibition of [H-3]-thymidine incorporation by IL-1 beta was partially reversed with SB203580, SP600125 or curcumin, but not PDTC. In most cases, the inhibitors reduced (SO4)-S-35 incorporation with IL-1 beta. For the mechanical loading studies, the inhibitors reduced the compression-induced inhibition of nitrite and PGE(2) release and restored [H-3] -thymidine and (SO4)-S-35 incorporation. Conclusions: The MAPK, AP-1 and NF-kappa B signalling pathways are involved in the upregulation of NO and PGE(2) release by IL-1 beta. Dynamic compression stimulates cell proliferation and proteoglycan synthesis in the presence of IL-1 beta and/or inhibitors of the MAPKs and NF kappa B and AP-1 signalling pathways. This experimental approach could provide valuable information for the biophysical/pharmacological treatment of OA.