Article révisé par les pairs
Résumé : ABSTRACT Objective Plasma and synovial myeloperoxidase (MPO) and its products were strongly associated with osteoarthritis (OA) and rheumatoid arthritis (RA). In addition, it is well known that there is a link between oxidative stress and cytokines. The present study aims at investigating the link between synovial MPO (and its products), IL-18, which is involved in the degradation of articular cartilage in RA, and IL-8, which is involved in recruitment and activation of neutrophils during inflammation. Effects of the treatment of RA on the biological parameters were also investigated. Methods Patients (n=105) were studied including 39 patients with OA, 33 with RA and 33 with RA receiving a specific treatment. DAS-28 was calculated whereas MPO antigen/activity, neutrophils, chloro-tyrosine, homocitrulline, IL-8 and IL-18 were measured in synovial fluid (SF) and CRP was measured in serum. Results DAS-28 and CRP level were not significantly different between groups. MPO activity, and MPO, chloro-tyrosine and homocitrulline levels were significantly higher in SF of RA patients than OA patients. MPO specific activity (MPO activity/antigen ratio) was significantly lower in treated than in untreated RA patients as was IL-8. MPO activity and concentration were correlated with IL-8 and IL-18 in untreated but not in treated RA patients. Conclusions MPO level is related to IL-8 and IL-18 levels in untreated RA patients. A link has been shown between treatment and decrease of IL-8, MPO specific activity and homocitrulline in SF. The causal role of MPO in SF inflammation and how treatment can affect MPO specific activity need further investigations.

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