Interleukin-1 Induction of Aggrecanase Gene Expression in Human Articular Chondrocytes is Mediated by Mitogen-Activated Protein Kinases

Background/Aims: We investigated the unknown molecular mechanisms of Interleukin-1 (IL-1 beta)-induced cartilage aggrecan degeneration by aggrecanase (ADAMTS-A Disintegrin And Metalloproteinase with ThromboSpondin motifs) in human articular chondrocytes, a model mimicking human arthritis. Methods: Chondrocytes were pretreated with various pharmacological inhibitors and then stimulated with IL-1 beta for 24 h. ADAMTS-4 expression or activity was studied by RT-PCR or ELISA and other proteins measured by Western blotting. Results: MAP kinase kinase-specific inhibitor, U0126 inhibited IL-1-induced phosphorylation of ERK1/2 and down-regulated ADAMTS-4 expression and activity. Protein 38 inhibitor, 5B203580 down-regulated the phosphorylation of p38 and its target, activating transcription factor-2 (ATF-2), ADAMTS-4 mRNA and activity. C-Jun N-terminal kinase (JNK) inhibitor, SP600125 diminished IL-1-stimulated JNK phosphorylation, ADAMTS-4 m RNA expression and enzyme activity. A c-fos/lipoxygenase pathway inhibitor and antioxidant, nordihydroguaiaretic acid (NDGA) significantly suppressed ADAMTS-4 mRNA induction and activity. Activating protein (AP-1) and nuclear factor kappa B (NF-kappa B) transcription factor inhibitors, curcumin and pyrrolidine dithiocarbamate (PDTC) partially inhibited ADAMTS-4 induction and activity. Conclusion: These results suggest partial involvement of ERK-, p38- and JNK-MAPKs as well as AP-1, ATF-2 and NF-kappa B transcription factors in IL-1-induced ADAMTS-4 in chondrocytes. Inhibition of these targets by the specific pharmacological agents could be useful for reducing aggrecanase-driven cartilage resorption in arthritis. Copyright (c) 2012 S. Karger AG, Basel