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.

Oxidative stress parameters in different systemic rheumatic diseases.

The involvement of oxidative stress in the pathogenesis of rheumatic disorders, such as systemic sclerosis (SSc) and chronic polyarthritides, has been suggested yet not thoroughly verified experimentally. We analysed 4 plasmatic parameters of oxidative stress in patients with SSc (n = 17), psoriatic arthritis (PsA) (n = 10) and rheumatoid arthritis (RA) (n = 9) compared with healthy subjects (n = 22). The biomarkers were: total antioxidant capacity (TAC) measured by ferric reducing antioxidant power (FRAP) method, hydroperoxides determined by ferrous ion oxidation in presence of xylenol orange (FOX) method and sulfhydryl and carbonyl groups assessed by spectrophotometric assays. The results showed significantly increased hydroperoxides in SSc, PsA and RA (3.97 +/- 2.25, 4.87 +/- 2.18 and 5.13 +/- 2.36 micromol L(-1), respectively) compared with the control group (2.31 +/- 1.40 micromol L(-1); P < 0.05). Sulfhydryls were significantly lower in SSc (0.466 +/- 0.081 mmol L(-1)), PsA (0.477 +/- 0.059 mmol L(-1)) and RA (0.439 +/- 0.065 mmol L(-1)) compared with the control group (0.547 +/- 0.066 mmol L(-1); P < 0.05). TAC in all three diseases showed no difference in comparison with controls. Carbonyls were significantly higher in RA than in the control group (32.1 +/- 42 vs 2.21 +/- 1.0 nmol (mg protein)(-1); P < 0.05). The obtained data indicate augmented free radical-mediated injury in these rheumatic diseases and suggest a role for the use of antioxidants in prevention and treatment of these pathologies.