Serum level of DNase1l3 in patients with dermatomyositis/polymyositis, systemic lupus erythematosus and rheumatoid arthritis, and its association with disease activity.

DNase1l3 is an endonuclease to degrade the chromatin of apoptotic or necrotic cells. Serum DNase1l3 may fulfill the function of clearance of chromatin released into the circulation by dying cells, which can trigger autoimmune responses. To date, it remains unclear whether serum DNase1l3 level associates with the pathogenesis of autoimmune diseases. Sixty-eight patients with dermatomyositis/polymyositis (DM/PM, n = 30), systemic lupus erythematosus (SLE, n = 20) and rheumatoid arthritis (RA, n = 18), as well as 26 healthy blood donors were enrolled in the present study. Serum levels of DNase1l3 were quantified by enzyme-linked immunosorbent assay. DNASE1L3 activity in serum was estimated by the capability of serum to digest nucleosomal DNA. Clinical, biochemical, serological and other markers of disease activity (CRP, ESR, C3, C4, anti-Jo-1 and anti-dsDNA, etc.) were measured by standard laboratory procedure. We found a decrease in DNase1l3 level in the DM/PM and SLE patients, resulting in the reduction in serum activity to digest nucleosome DNA. In contrast, the level and activity of DNase1l3 remained unchanged in the RA patients. The DNase1l3 level was relatively lower in the DM/PM patients with anti-Jo-1 antibody and interstitial lung disease, and in the SLE patients with SLE disease activity index higher than 6, renal involvement and anti-dsDNA antibody. DNase1l3 level negatively correlated with CRP and IgG in the PM/DM patients and correlated with ESR in the SLE patients. We found a significant reduction in serum DNase1l3 level in DM/PM and SLE, which may associate with clinic features and disease activity.