Interleukin‐4 antagonizes oncostatin M and transforming growth factor beta‐induced responses in articular chondrocytes

Abstract

Oncostatin M (OSM) stimulates cartilage degradation in rheumatoid arthritis (RA) by inducing matrix metalloproteinases (MMPs) and aggrecanases (ADAMTS; a disintegrin and metalloproteinase with thrombospondin motif). Transforming growth factor beta (TGF-beta1) induces cartilage repair in joints but in excessive amounts, promotes inflammation. OSM and TGF-beta1 also induce tissue inhibitor of metalloproteinase-3 (TIMP-3), an important natural inhibitor of MMPs, aggrecanases, and tumor necrosis factor alpha converting enzyme (TACE), the principal proteases involved in arthritic inflammation and cartilage degradation. We studied cartilage protective mechanisms of the antiinflammatory cytokine, interleukin-4 (IL-4). IL-4 strongly (MMP-13 and TIMP-3) or minimally (ADAMTS-4) suppressed OSM-induced gene expression in chondrocytes. IL-4 did not affect OSM-stimulated phosphorylation of extracellular signal-regulated kinases (ERKs), protein 38 (p38), c-Jun N-terminal kinase (JNK) and Stat1. Lack of additional suppression with their inhibitors suggested that MMP-13, ADAMTS-4, and TIMP-3 inhibition was independent of these mediators. IL-4 also downregulated TGF-beta1-induced TIMP-3 gene expression, Smad2, and JNK phosphorylation. Additional suppression of TIMP-3 RNA by JNK inhibitor suggests JNK implication. The cartilage protective effects of IL-4 in animal models of arthritis may be due to its inhibition of MMPs and ADAMTS-4 expression. However, suppression of TIMP-3 suggests caution for using IL-4 as a cartilage protective therapy.