Serum DNase I activity in systemic lupus erythematosus: correlation with immunoserological markers, the disease activity and organ involvement

Background: Decreased activity of serum desoxyribonuclease I (DNase I) in systemic lupus erythematosus (SLE) has been reported, but its role as a biomarker in SLE is still unelucidated. Methods: Seventy-seven SLE patients (aged 39.6 +/- 13.1 years) were studied for serum DNase I activity, levels of antinuclear (ANA), anti-dsDNA [high-avidity ELISA, conventional ELISA and indirect immunofluorescence (IIF)], anti-nucleosome, anti-histone antibodies, complement components C3 and C4. SLE disease activity was evaluated by disease activity index (SLEDAI-2K). Thirty-five patients were serologically and clinically followed for 3-12 months (mean 5.6 +/- 2.8). Thirty-seven healthy blood donors were the control group. Results: DNase I activity in SLE patients was lower than in healthy controls (p < 0.01). DNase I activity was in positive correlation with SLEDAI-2K (p < 0.01), levels of ANA, anti-dsDNA, anti-nucleosome and anti-histone antibodies (p < 0.01) and in negative correlation with C3 concentration (p < 0.05). The highest correlation was found between DNase I activity and anti-dsDNA concentrations determined by high-avidity ELISA (r = 0.624), followed by IIF (r = 0.541) and conventional ELISA (r = 0.405). In the follow-up study, DNase I activity also correlated with SLEDAI-2K (p < 0.01). SLE patients with low DNase I activity more frequently had SLE-specific cutaneous lesions (p < 0.05). Conclusions: Monitoring of DNase I activity simultaneously with SLEDAI-2K might be a useful tool in the follow-up of SLE. An increase of DNase I activity characterized relapse in most SLE patients, although it did not reach the levels of healthy individuals. A decrease of DNase I activity in SLE flare-ups might be a functional biomarker of a subset of patients with specific dysfunction of apoptotic chromatin degradation.