The role of IL-4 and IL-6 in IL-1-dependent cartilage matrix degradation.

The objective of this paper was to study the effects of interleukin 4 (IL-4) and interleukin 6 (IL-6) on cartilage matrix degradation, the production of chondroitin-4-sulphate (C4S) and chondroitin-6-sulphate (C6S), metalloproteinase (stromelysin 1 = MMP-3) and metalloproteinase inhibitor (TIMP-1) production. Cartilage matrix degradation was assayed the release of 35SO4 from chondrocyte cultures. TIMP-1 and MMP-3 were measured by ELISA. C6S and C4S were measured by HPLC analysis. IL-1 beta significantly enhanced C4S production and significantly suppressed C6S production. Thus, the C4S/C6S ratio was significantly enhanced by IL-1 beta, and significantly suppressed by IL-4. IL-4 removed the suppressing effects of IL-1 beta for C6S and the enhancing effects of IL-1 beta for the C4S/C6S ratio. Whereas IL-1 beta stimulated the production of MMP-3, IL-4 and IL-6 had no effect on enzyme activity. IL-4, but not IL-6, removed the enhancing effects of IL-1 beta for MMP-3. In contrast, IL-4 and IL-6 significantly enhanced TIMP-1 production in chondrocytes, IL-4, but not IL-6, also significantly suppressed IL-1 beta-mediated cartilage matrix degradation. On the other hand, IL-6 significantly suppressed spontaneous cartilage matrix degradation which is supposed to be mediated by the autocrine IL-1 mechanisms. In conclusion our results suggest that IL-4 and IL-6 both protect the cartilage matrix degradation induced by IL-1.