Autophagy is induced by anti-neutrophil cytoplasmic Abs and promotes neutrophil extracellular traps formation

Dysregulated neutrophil extracellular traps (NETs) formation contributes to the pathogenesis of anti-neutrophil cytoplasmic Ab (ANCA)-associated vasculitis (AAV). Increasing evidence indicates that autophagy is involved in the process of NETs formation. In this study, we aimed to investigate whether ANCA could induce autophagy in the process of NETs formation. Autophagy was detected using live cell imaging, microtubule-associated protein light chain 3B (LC3B) accumulation and Western blotting. The results showed that autophagy vacuolization was detected in neutrophils treated with ANCA-positive IgG by live cell imaging. This effect was enhanced by rapamycin, the autophagy inducer, and weakened by 3-methyladenine (3-MA), the autophagy inhibitor. In line with these results, the autophagy marker, LC3B, showed a punctate distribution pattern in the neutrophils stimulated with ANCA-positive IgG. In the presence of rapamycin, LC3B accumulation was further increased; however, this effect was attenuated by 3-MA. Moreover, incubated with ANCA-positive IgG, the NETosis rate significantly increased compared with the unstimulated group. And, the rate significantly increased or decreased in the neutrophils pretreated with rapamycin or 3-MA, respectively, as compared with the cells incubated with ANCA-positive IgG. Overall, this study demonstrates that autophagy is induced by ANCA and promotes ANCA-induced NETs formation.