Interleukin-17-induced gene expression in articular chondrocytes is associated with activation of mitogen-activated protein kinases and NF-kappaB.

This study examines intracellular signaling events associated with the activation of chondrocytes by the cytokine interleukin-17 (IL-17). Stimulation of normal human articular chondrocytes with IL-17 induced nitric oxide (NO) production, concomitant with an increase in transcripts and de novo translation products of the inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) genes. Several other genes associated with inflammation and cartilage degradation, such as IL-1beta, IL-6, and stromelysin, were also up-regulated in IL-17-treated chondrocytes. Among signaling events displaying early response to IL-17 in chondrocytes were the mitogen-activated protein (MAP) kinases ERK1, ERK2, JNK, and p38. DNA binding activity of NF-kappaB was also significantly induced. IL-17 effects on NO release, as well as iNOS, COX-2, and IL-6 protein expression, were inhibited by the anti-inflammatory drug dexamethasone. Importantly, dexamethasone blunted IL-17-dependent activation of MAP kinases, suggesting a mechanistic relationship between these activities and the aforementioned gene expression responses. Similar effects of a lesser extent were observed with the p38-specific inhibitor SB203580. These results suggest that IL-17 activation of chondrocytes is associated with and depends at least in part on the activation of MAP kinases and NF-kappaB.