Fig. 4

Dipyridamole suppresses NETosis via activation of the adenosine A_2A receptor. a, b Neutrophils were isolated from healthy volunteers and then treated with either control IgG or APS IgG for 3 h. Some samples were additionally treated with dipyridamole as indicated. In panel a, total extracellular DNA was measured as relative fluorescence units upon the addition of Sytox Green. In panel b, an independent set of experiments was performed, with NETosis quantified by measuring the enzymatic activity of nuclease-liberated myeloperoxidase (MPO). Mean and standard deviation are presented for n = 3 independent experiments; *p < 0.05, **p < 0.01, and ***p < 0.001 as compared with the 0 µM group by one-way ANOVA corrected with Dunnett’s test. c, d Neutrophils were treated with APS IgG in the presence of different combinations of dipyridamole and the A_2A receptor antagonist SCH58261. Extracellular DNA (c) or NETs (d) were quantified as above. Mean and standard deviation are presented for n = 3 independent experiments; *p < 0.05 and **p < 0.01 by one-way ANOVA. e Neutrophils were treated with APS IgG (black bars) and dipyridamole as indicated. Adenosine was quantified in culture supernatants. Mean and standard deviation are presented for n = 4 independent experiments; *p < 0.05 by one-way ANOVA corrected with Sidak’s test. f, g Neutrophils were isolated from patients with primary APS and immediately placed in culture. Some samples were additionally treated with drugs as indicated. Extracellular DNA (f) or NETs (g) were quantified as above. Mean and standard deviation are presented for n = 9 patients; **p < 0.01 and ***p < 0.001 as compared with the no-drug group by one-way ANOVA corrected with Dunnett’s test