BETA-CYCLODEXTRIN POLYSULPHATE REPRESSES TNFALPHA-MEDIATED IL-1BETA CASCADES IN OSTEOARTHRITIC CHONDROCYTES

S. Groeneboer, D. Elewaut, E.M. Veys, G. VerbruggenRheumatology, Ghent University Hospital, Ghent, BelgiumObjectives: In osteoarthritic (OA) articular chondrocytes, the anabolic IGFRI/insulin-like growth factor 1 (IGF-1) pathway was shown to be overruled by the catabolic effects of the IL-1/IL-1RI pathway. As a consequence less of the produced extracellular matrix macromolecules may persist in the CAM of the OA chondrocytes (1). The influence of beta-cyclodextrin polysulphate on this TNFa-mediated auto/paracrine IL-1/IL-1RI pathway has been evaluated.Methods: Chondrocytes were isolated from both visually intact and fibrillated femoral condyle cartilage of human knee joints and cultured separately in gelled alginate to maintain their differentiated phenotype. During 1 week of culture, the cells were exposed to 5 microg/ml of beta-cyclodextrin polysulphate. Additionally, normal chondrocyte cultures with and without cyclodextrin polysulphate were exposed to 180 pg/ml TNFa during the last 48 hours. The release of IL-6 in the culture media was used as a variable reflecting the auto/paracrine IL-1b activity of the cells in different experimental conditions (2,3).Results: Chondroctyes from OA regions secreted 2 to 3 times more IL-6 in the supernatant media compared to cells from intact cartilage. When exposed to 180 pg/ml of TNFa, the cells of intact cartilage show a fourfold increase in IL-6 release. 5.0 microg/ml of beta-cyclodextrin polysulphate caused a 50% decrease of the IL-6 concentration in the supernatant of normal and osteoarthritic chondrocytes. The release of IL-6 by the TNFa primed chondrocytes treated with 5.0 microg/ml beta-cyclodextrin polysulphate was repressed by 30%.Conclusion: OA cells secreted significantly more IL-6 than normal chondrocytes, illustrating the increase of the auto/paracrine IL-1b activity in OA chondrocytes. beta-cyclodextrin polysulphate inhibited the synthesis of IL-6 in both normal and OA chondrocytes. Although the experiments were not performed in the presence of IL-1b blocking antibodies, it is supposed that beta-cyclodextrin affected the IL-1b loop and did not directly interfere with the production of IL-6. We hypothesise that the IL-6 decrease by b-cyclodextrin treated TNFa primed chondrocytes was obtained through an interference with IL-1, although this does not excludes the possibility of a downmodulation of TNFa effects in the inhibition of IL-6 release. Considering IL-1b as the major auto/paracrine cytokine inducing catabolic processes in cartilage, its downregulation by beta-cyclodextrin polysulphate may be a novel approach in enhancing repair of osteoarthritic cartilage.References: 1. Wang J, Verdonk P, Elewaut D, Veys E M, Verbruggen G. Homeostasis of the extracellular matrix of normal and osteoarthritic human articular cartilage chondrocytes in vitro. Osteoarthritis Cart 2003,11:801-92. Malfait AM, Verbruggen G, Veys EM, Lambert J, De Ridder L, Cornelissen M. Comparative and combined effects of interleukin 6, interleukin 1b, and tumor necrosis factor a on proteoglycan metabolism of human articular chondrocytes cultured in agarose. J Rheumatol. 1994;21:314-20.3. Henrotin YE, De Grootte DD, Labasse AH, Gaspar SE Zheng SX, Geenen VG, Reginster JY. Effects of exogenous IL-1 beta, TNF alpha, IL-6, IL-8 and LIF on cytokine production by human articular chondrocytes. Osteoarthritis Cartilage. 1996;4:163-73.Citation: Ann Rheum Dis, volume 64, supplement III, year 2005, page 138Session: Cytokines and inflammatory mediators