Autoantibody against peroxiredoxin I, an antioxidant enzyme, in patients with systemic sclerosis: possible association with oxidative stress.

OBJECTIVES To determine the prevalence and clinical correlation of autoantibody to peroxiredoxin (Prx) I, an antioxidant enzyme, in patients with systemic sclerosis (SSc). METHODS Serum samples from SSc patients (n = 70) and healthy controls (n = 23) were examined by ELISA using human recombinant Prx I. The presence of anti-Prx I antibody was further evaluated by immunoblotting analysis. To determine the functional relevance of anti-Prx I antibody in vivo, we assessed whether anti-Prx I antibody was able to inhibit Prx I enzymatic activity using yeast thioredoxin reductase system. RESULTS IgG anti-Prx I antibody levels in SSc patients were significantly higher than healthy controls and this autoantibody was detected in 33% of SSc patients. The presence of IgG anti-Prx I antibody was associated with longer disease duration, more frequent presence of pulmonary fibrosis, heart involvement, and anti-topoisomerase I antibody and increased levels of serum immunoglobulin and erythrocyte sedimentation rates. IgG anti-Prx I antibody levels also correlated positively with renal vascular damage and negatively with pulmonary function tests. Furthermore, anti-Prx I antibody levels correlated positively with serum levels of 8-isoprostane, a marker of oxidative stress. Immunoblotting analysis confirmed the presence of anti-Prx I antibody. Remarkably, Prx I enzymatic activity was inhibited by IgG isolated from SSc sera containing IgG anti-Prx I antibody. CONCLUSIONS These results suggest that elevated IgG anti-Prx I autoantibody is associated with the disease severity of SSc and that anti-PrxI antibody may enhance the oxidative stress by inhibiting Prx I enzymatic activity.