Protein oxidation markers in the serum and synovial fluid of psoriatic arthritis patients

The role of oxidative stress has been studied in rheumatoid arthritis (RA) and other inflammatory joint diseases to some extent, but its importance in psoriatic arthritis (PsA) has rarely been investigated. The aim of this study was to analyze the levels of protein oxidation markers, sulfhydryl (SH) and carbonyl (CO) groups, in the synovial fluid (SF) and serum of PsA patients and compare them with the findings in RA and osteoarthritis (OA) patients. A total of 49 subjects with a knee-joint effusion including 16 PsA, 18 RA, and 15 OA patients were studied. In all patients, the levels of SH groups measured in the serum and SF inversely correlated with the number of white blood cells (WBC) (P < 0.05) and the percentage of polymorphonuclear leukocytes (PMN) (P < 0.01) in SF. Serum SH levels inversely correlated with serum erythrocyte sedimentation rate (ESR) (P < 0.02) and C-reactive protein (CRP) (P < 0.05) values. The SH levels in SF were significantly lower in patients affected by PsA and RA compared to OA cases (P < 0.02). The serum SH levels in PsA were lower than OA (P < 0.001) and higher than RA patients (P < 0.05). The serum and synovial levels of CO groups in PsA, RA, and OA patients were similar. Our study provides novel evidence on the involvement of protein oxidation in PsA and confirms the important role of oxidative stress in the pathogenesis of RA. These data suggest that antioxidant agents can potentially be a useful addition to the conventional therapy in the management of these diseases.