Phenyl N-tert-Butylnitrone Down-Regulates Interleukin-1beta-Stimulated Matrix Metalloproteinase-13 Gene Expression in Human Chondrocytes: Suppression of c-Jun NH_2-Terminal Kinase, p38-Mitogen-Activated Protein Kinase and Activating Protein-1

摘要

Cytokine-mediated induction and overexpression of matrix metalloproteinases (MMPs) is recognized as an important factor in the pathogenesis of arthritis. Interleukin (IL)-1beta is a proinflammatory cytokine that is known to superinduce the expression and production of MMP-13 in many cell types. Phenyl N-tert-butylnitrone (PBN), a spin trap agent, inhibited the IL-1beta-induced expression of MMP-13 in human osteoarthritis (OA) chondrocytes. Down regulation of MMP-13 expression correlated with the inhibition of mitogen-activated protein kinase (MPK) subgroups c-Jun NH_2-terminal kinase (JNK) and p38-MAPK activation, accumulation of phospho-c-jun, and the DAN binding activity of activating protein-1 (AP-1). Results of in vitro kinase assays showed that exogenously added PBN completely blocked the c-Jun phosphorylating activity of JNK. Interestingly, using in vitro kinase assay, we also found that chondrocyte p38-MAPK phosphorylate c-Jun and that PBN was not very effective in inhibiting c-Jun phosphorylating activity of P38-MAPK. In addition, PBN did not block the ATF-2 phosphorylating activity of p38-MAPK and Elk-1 phosphorylating activity of extracellular regulated kinase p44/p42 in vitro, indicating that PBN may act selectively to inhibit the phosphorylation of c-Jun in OA chondrocytes. Together, our results for the first time demonstrate that PBN suppress the IL-1beta-stimulated expression of MMP-13 in OA chondrocytes and that this was achieved by inhibiting the activation of JNK and AP-1. These results suggest that use of PBN or compounds derived from it may be of potential benefit in inhibiting signaling events associated with cartilage degradation in arthritis.