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Effects of nimesulide and sodium diclofenac on interleukin-6, interleukin-8, proteoglycans and prostaglandin E2 production by human articular chondrocytes in vitro

Y.E. Henrotin¹, A.H. Labasse¹, P.E. Simonis¹, S.-X. Zheng¹, G.P. Deby², J.-P.Famaey³, J.-M.R. Crielaard¹, J.-Y.L. Reginster¹

¹Bone and Cartilage Metabolism Research Unit, Institute of Pathology, University of Liège; ²Center for the Biochemistry of Oxygen, Institute of Chemistry, Liège, Belgium; ³Therabel Research, Bruxelles, Belgium.

ABSTRACT
Objectives
The aim of this study was to investigate the effects of two nonsteroidal anti-inflammatory drugs (NSAIDs), nimesulide and sodium diclofenac, on the production of proteoglycans (PG), prostaglandin E2 (PGE2) and cytokines (IL-6 and IL-8) by human articular chondrocytes in vitro.

Methods
Enzymatically isolated chondrocytes were cultured under constant agitation in a well defined culture medium. Specific radioimmunoassays were used to quantify PG and PGE2 production. Cytokine production (IL-6 and IL-8) was assayed by enzyme amplified sensitivity immunoassays (EASIAs).

Results
At a concentration of 3 µg/ml, nimesulide did not affect the PG production by chondrocytes. This concentration was superior to the highest level of nimesulide found in the synovial fluid of patients with rheumatoid arthritis 3 hours after the last oral administration of nimesulide (100 mg twice daily for 7 days). At 6 µg/ml a significant reduction in the PG content was obtained in the cellular phase in 5 out of the 8 cultures investigated. No similar effect was observed in the culture supernatants. Above this concentration nimesulide inhibited PG production in a dose-dependent manner.
At concentrations ranging from 0.005 to 1 µg/ml diclofenac did not significantly alter PG production. At therapeutic concentrations PGE2 production was totally inhibited by nimesulide, thus suggesting that PG inhibition is not linked to PGE2 production. Nimesulide inhibited PGE2 production by unstimulated (IC50 = 6 ng/ml) and IL-1b-stimulated (IC50 = 6.9 ng/ml) chondrocytes. At these concentrations, PGE2 production was fully inhibited by diclofenac. Furthermore, both nimesulide and diclofenac at therapeutic concentrations significantly decreased spontaneous and IL-1b-stimulated IL-6 production by human chondrocytes, but did not modify IL-8 production.

Conclusion
From the results of this study we conclude that nimesulide and diclofenac at therapeutic concentrations are potent inhibitors of PGE2 and IL-6 production, while they do not modify proteoglycan or IL-8 production.

Key words
Osteoarthritis, chondrocytes, cytokines, nimesulide, diclofenac.

Please address correspondence and reprint requests to: Dr Y. Henrotin, Bone and Cartilage Metabolism Research Unit, Institute of Pathology, C.H.U., Bat. B23, Sart-Tilman, B-4000 Liège, Belgium.