Synergistic interactions of proinflammatory cytokines with oncostatin M: production of active collagenases and implications for joint destruction
- TE Cawston1
© The Author(s) 2004
Published: 13 September 2004
Oncostatin M (OSM) is a member of the IL-6 family that we previously showed could synergise with IL-1 to induce cartilage proteoglycan and collagen degradation in a cartilage explant culture system ; these observations now extend to IL-6 in the presence of its soluble receptor. A significant finding was the synergistic induction of the collagenase, matrix metalloproteinase (MMP)-1, which occurs via interplay between the janus-activated kinase/signal transducer and activator of transcription, activator protein 1 and mitogen-activated protein kinase pathways. Other collagenases such as MMP-8 and MMP-13 are also upregulated along with MMP-14 and MMP-3. This latter enzyme can activate the collagenases and an important feature of OSM may be its ability to activate enzymes that initiate the activation cascades that lead to the production of active collagenases. These studies have important implications for inflammatory joint disease since OSM (and indeed IL-6) have been proposed to be protective in rheumatoid arthritis. We also demonstrated that OSM can also exacerbate the effects of other important proinflammatory mediators such as tumour necrosis factor alpha (TNF-α) and IL-17.
We have continued molecular and cellular studies to discover the mechanism of action that leads to synergy. Using Affymetrix microarrays we have shown that a specific cohort of genes are upregulated by these cytokine mixtures that include MMPs, a disintegrin and metalloproteinases, activators, cell surface proteins and cytokines. Analysis using two-dimensional gel electrophoresis and proteomic analysis has confirmed that many of the corresponding proteins are made by chondrocytes after stimulation. Purification of specific proteins from conditioned culture medium has been undertaken to try and determine the specific collagenase responsible for collagen turnover.
In order to assess the effects of these cytokine combinations in vivo, we have assessed the effects of intra-articular gene transfer of OSM in combination with either IL-1 or TNF-α on murine knee joints using recombinant adenovirus. Engineered adenoviruses were administered for only 7 days, after which time joints were fixed, decalcified and sectioned. Histological analyses indicated marked synovial hyperplasia and inflammatory cell infiltration for IL-1, TNF-α and OSM treated joints but not in controls (joints treated with an 'empty' adenovirus). The inflammation was more pronounced for both the OSM + IL-1 and OSM + TNF-α combinations with evidence of extensive cartilage and bone destruction. Significant loss of both proteoglycan and collagen was also seen for these combinations, and immunohistochemistry revealed an increased expression of MMPs with decreased tissue inhibitors of metalloproteinases in both articular cartilage and synovium. The effects of these combinations were significantly greater than those seen with any of the cytokines alone. Cytokine combinations also upregulated receptor activator of NF-κB/receptor activator of NF-κB ligand (RANK/RANKL) and increased the number of TRAP-positive cells. A significant increase in osteoclast formation and activation and bone damage was accompanied by marked upregulation of RANK/RANKL in inflammatory cells within the synovial tissue. Taken together, these data confirm that, in vivo, OSM can significantly exacerbate the effects of both IL-1 and TNF-α, resulting in inflammation and tissue destruction characteristic of that seen in rheumatoid arthritis. In vitro data showed that the damage to cartilage in the cartilage model system can be blocked by both transforming growth factor beta and insulin like growth factor-1.
These studies provide further evidence to implicate the upregulation of collagenases as a key factor in the destruction of collagen that occurs in joint pathology, and suggests that OSM is a potent mediator when found in the joint with other proinflammatory cytokines.
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