Immunological studies of oxidized superoxide dismutase in patients with systemic lupus erythematosus. Correlation with disease induction and progression.

OBJECTIVE To investigate the status and contribution of oxidized superoxide dismutase (SOD) in systemic lupus erythematosus (SLE), and to explore whether oxidized-SOD has a role in disease induction and progression. METHODS This study was performed in the College of Medicine, Qassim University, Buraidah, Kingdom of Saudi Arabia between October 2011 and May 2012. The study was designed to explore the role of oxidized-SOD in SLE autoimmunity. The SOD was modified by reactive oxygen species (ROS) and characterized. Binding characteristics of autoantibodies in SLE patients (n=50) with varying levels of disease activity according to the SLE Disease Activity Index (SLEDAI) against ROS-modified-SOD (ROS-SOD) were screened by immunoassays and the results were compared with healthy age-matched controls (n=34). RESULTS The ROS caused extensive damage of SOD. Serum analysis showed significantly higher levels of anti-ROS-SOD antibodies in SLE patients compared with controls. Interestingly, not only was there an increased number of subjects positive for anti-ROS-SOD antibodies, but also the levels of these antibodies were significantly higher among SLE patients, whose SLEDAI scores were >/=20. In addition, a significant correlation was observed between the levels of anti-ROS-SOD antibodies and the SLEDAI score (r=0.796). CONCLUSION Our findings show an association between oxidized-SOD and SLE. The stronger response observed in patients with higher SLEDAI scores suggests that oxidized-SOD may be a useful biomarker in evaluating the progression of SLE and in elucidating the mechanisms of disease pathogenesis.