EFFECT OF IL-13 ON CYTOKINES, CYTOKINE RECEPTORS AND INHIBITORS ON HUMAN OSTEOARTHRITIS SYNOVIUM AND SYNOVIAL FIBROBLASTS

Objective: In this study we investigated the effect of interleukin-13 (IL-13), an anti-inflammatory cytokine, for potential therapeutic use in osteoarthritis (OA). Design: We examined the effect of IL-13 on the synthesis and expression of interleukin-1 beta (IL-1 beta), tumor nec rosis factor-alpha (TNF-alpha), IL-1 receptor antagonist (IL-1Ra) and stromelysin-1 on human OA synovial membrane in ex vivo cultures. In ad dition, we explored the effect of IL-13 on both the IL-1 receptor (IL- 1R) and TNF-receptor (TNF-R) systems on OA synovial fibroblasts. This included determination of the levels of IL-1 beta and TNF-alpha recept or binding, IL-1Ra and TNF-soluble receptors 55 and 75 (TNF-sR55 and T NF-sR75). Results: In OA synovial membrane treated with LPS, IL-13 inh ibited the synthesis of IL-1 beta, TNF-alpha and stromelysin-1. but in creased IL-1Ra production. In addition, IL-13 reduced the level of IL- 1 beta mRNA and stimulated the level of IL-1Ra mRNA. In synovial fibro blasts, IL-13 decreased the level of IL-1 binding, an effect related t o the increased production of IL-1Ra. Although IL-13 had no effect on the TNF-R level, this cytokine markedly decreased the shedding of TNF- R75. Conclusion: These experiments suggest that IL-13 is potentially u seful in the therapeutic treatment of OA, as it could regulate the maj or pathological process of this disease by reducing the production of proinflammatory cytokines and metalloproteases, and favoring the produ ction of IL-1Ra.