Detection of neutrophil extracellular traps in patients with systemic lupus erythematosus

Abstract

Objective To assay the level of neutrophil extracellular traps (NETs) in systemic lupus erythematosus (SLE) patients and healthy controls and compare the difference between SLE group and control group, and to analyze between the level of NETs and related laboratory parameters. Methods Forty-four females patients with SLE were recruited as research subjects, with 24 cases in the active stage and 20 in stable stage. Forty-two healthy female volunteers matched in age were enrolled as control subjects. The fluorescence intensity of NETs in neutrophils was detected by fluorospectrophotometry. The concentration of neutrophil elastase in plasma was quantitatively detected. Statistical analysis of the difference of level of NETs between the SLE group and control group was conducted. Then the correlation between the fluorescence intensity of NETs and erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), and anti-double-stranded DNA (dsDNA), and anti-histone, and anti-nucleosome, and systemic lupus erythematosus disease activity index (SLEDAI) was analyzed respectively. The same tests were conducted for the level of NE. The results of the two groups were compared using analysis of variance and the relevance was analyzed using Spearman correlation analysis. NETs morphosis was observated by immunoflurescence method, and the difference of NETs between SLE group and control group was analyzed. Results ① The fluorescence intensity of NETs was significantly increased in SLE group(241±139) than that in the control group (173±135), (t=2.31, P 0.05] and NE concentration [(104±43) vs (96±48), t=0.50, P>0.05] between SLE active stage and stable stage was detected. ③ The fluorescence intensity of NETs in SLE patients was positively correlated with SLEDAI, but had no obvious correlation with anti-dsDNA, anti-histone, anti-nucleosome, CRP or ESR, respectively. ④ Images under confocal microscope showed that more NETs generated by PMN from SLE patients than that from controls. Conclusion The generation of NETs is enhanced in female patients with SLE. And NETs may relate to disease activity. However, NETs may not induce the production of autoantibodies. Key words: Lupus erythematosus, systemic; Neutrophils; Proteinase inhibitory proteins, secretory