Myeloperoxidase and its products in synovial fluid of patients with treated or untreated rheumatoid arthritis

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A. Nzeusseu Toukapa, C. Delporte*bc, C. Noyonb, T. Franckd, A. Rousseaue, D. Serteynd, M. Raesf, M. Vanhaeverbeeke, N. Moguilevskyg, J. Nèveb, L. Vanhammeh, P. Dureza, P. Van Antwerpenbc & K. Zouaoui Boudjeltiaea Institut de Recherche Expérimentale et Clinique and Service de Rhumatologie, Cliniques Universitaires St-Luc, Université Catholique de Louvain, Brussels, Belgiumb Laboratory of Pharmaceutical Chemistry, Faculty of Pharmacy, Université Libre de Bruxelles, Brussels, Belgiumc Analytical Platform, Faculty of Pharmacy, Université Libre de Bruxelles, Brussels, Belgiumd Center of Oxygen, Research and Development, Institute of Chemistry, University of Liège, Belgiume Laboratory of Experimental Medicine (ULB 222 UNIT), CHU de Charleroi, A. Vésale Hospital, Faculty of Medicine, Université Libre de Bruxelles, Montigny-le-Tilleul, Belgiumf Research Unit of Cellular Biology-Narilis, Faculty of Sciences, University of Namur, Namur, Belgiumg Technology Transfer Office, University of Namur, Namur, Belgiumh Laboratory of Molecular Parasitology, IBMM, Faculty of Sciences, Université Libre de Bruxelles, Gosselies, Belgium†These authors contributed equally to this work.Correspondence: Cédric Delporte, PhD, Laboratory of Pharmaceutical Chemistry, Faculty of Pharmacy, Université Libre de Bruxelles, Campus Plaine CP 205/5, B-1050 Bruxelles, Brussels, Belgium. Tel: + 3226505277. Fax: + 3226505249. E-mail: cedric.delporte@ulb.ac.beAbstractObjective. 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), interleukin (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. Disease activity score (DAS-28) was calculated whereas MPO antigen/activity, neutrophils, chloro-tyrosine (Cl-Tyr), homocitrulline (Hcit), IL-8, and IL-18 were measured in synovial fluid (SF) and CRP was measured in serum. Results. DAS-28 and CRP levels were not significantly different between groups. MPO activity, and MPO, Cl-Tyr, and Hcit 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 Hcit in SF. The causal role of MPO in SF inflammation and how treatment can affect MPO specific activity need further investigations.