Comparison of xanthine oxidase levels in synovial fluid from patients with rheumatoid arthritis and other joint inflammations

OBJECTIVE

To search whether xanthine oxido-reductase (XOR) present in the synovium is also liberated, to determine its activity in synovial fluid and to establish a possible relationship between XOR levels in rheumatoid arthritis (RA) and non-RA patients.

METHODS

This study was carried out in the Laboratory of Immunology, University Ferhat Abbas, Setif, Algeria from 2001-2008. This study is a retrospective controlled study matching cases with RA to non rheumatoid joint inflammations. Synovial fluid (SF) samples were collected with consent of the patients, at Setif University Hospital, from adults suffering from RA (n=36) or only with joint inflammations (n=52). After its detection in SF with indirect enzyme-linked immunosorbent assay (ELISA) and dot-immunobinding, using anti-bovine XOR as first antibodies, XOR was assayed with capture ELISA.

RESULTS

Xanthine oxidoreductase is found in all studied SF. Capture ELISA showed levels up to 0.762 and 0.143 mg/mL in SF of RA and other joint inflammations patients, respectively. In most cases, more than 50% of synovial XOR is present as oxidase form. Positive correlation was observed between enzyme level and the disease severity since RA patients had a significantly high enzyme amount compared to patients with other less severe arthritic pathologies.

CONCLUSION

These results suggest that the enzyme could well be involved in joint inflammation probably by producing reactive oxygen species.

Anti-xanthine oxidase antibodies in sera and synovial fluid of patients with rheumatoid arthritis and other joint inflammations

OBJECTIVE

To study anti-bovine milk xanthine oxidoreductase XOR antibody levels in synovial fluid as well as in serum of patients suffering from rheumatoid affections to assess a possible correlation between antibody titres and severity of disease.

METHODS

Sera and synovial fluids were collected from volunteer donors at Setif University Hospital, Setif, Algeria from 2001--2007 with the consent of patients. Human IgG and IgM levels of free and bound anti-bovine milk XOR antibodies were determined using bovine XOR as antigen, with enzyme-linked immunosorbent assay ELISA.

RESULTS

Serum IgG anti-bovine milk XOR titres in 30 healthy normal subjects 2.74+/-2.31 microgram/mL are in agreement with that reported in the literature. Immunoglobulin G and IgM anti-bovine milk XOR antibody titres were found to be significantly higher in serum from patients with rheumatoid arthritis RA, and latex positives subjects. Synovial IgM antibody titres to bovine XOR were found to be significantly higher in rheumatoid arthritis patients compared to patients with other joint inflammations.

CONCLUSION

In rheumatoid arthritis patients, high concentrations of antibodies against XOR were noticed. These antibodies may play a major role in RA by inhibiting both xanthine and NADH oxidase activities of XOR. They may also play a key role in eliminating XOR from serum and synovial fluid positive role but unfortunately, immune complex formation could also activate complement and participate in self maintenance of inflammation.