Fig. 7. Erythromycin down regulates NET formation of PMNs of cigarette smoke exposed mice in vitro.

a PMNs isolated from cigarette exposure mice were stimulated with 0.3% CSE for 4 h at 37 °C (±2 μg/mL erythromycin for 30 min). PMNs were then fixed with 4% paraformaldehyde for 20 min at room temperature and stained with PI (NETs: white arrows). Original magnification, ×400. Scale bars = 50 µm. b Neutrophils isolated from peripheral blood of cigarette smoke exposed mice were stimulated for NET formation with 0.3% CSE at 37 °C for 4 h. Neutrophils were then fixed with 4% paraformaldehyde. PMNs were stained with NE, MPO or CITH3 (green) and DNA was stained with 4′,6-Diamidino-2-phenylindole dihydrochloride (DAPI, blue), and examined by confocal laser scanning microscope (CLSM) (NETs: white arrows). Original magnification, ×400. Scale bars = 50 µm. c The concentrations of extracellular DNA, NET-associated NE and MPO between groups of CSE-stimulated PMNs treated with or without erythromycin. Data are expressed as medians (n = 5). The comparisons were determined by Kruskal–Wallis one-way ANOVA on ranks.*P < 0.05. NS not significant