FTY720 induces neutrophil extracellular traps via a NADPH oxidase-independent pathway.

FTY720 is an immunosuppressive agent which has been approved to treat multiple sclerosis (MS). The main object of the present study is to investigate whether FTY720 has the potential to induce the formation of neutrophil extracellular traps (NETs) in vitro. Using Sytox Green assay and fluorescence microscopy, our results showed that FTY720 trigged the NET formation. In contrast to classic NET formation induced by Phorbol 12-myristate 13-acetate (PMA), FTY720-induced NETs were detected earlier and independent of NADPH oxidase (NOX) activity. Pharmacological inhibitor experiments indicated that autophagy was also required for the NET formation induced by FTY720. Moreover, p38 and AKT inhibitor significantly suppressed the NET formation by FTY720, whereas ERK inhibitor had no effect, suggesting that FTY720-induced NETs depended on the activation of p38 and AKT. We further found that citrullination of histone H3 and peptidylarginine deiminase 4 (PAD4) did not mediated FTY720-induced NET formation. Interestingly, necroptosis signaling activation was involved in the vital NET formation by FTY720, however, plasma membrane rupture resulting from necroptosis was not a major component of NET formation described here. Collectively, these findings indicated that FTY720 could be a potential antibacterial drug to protect host against pathogen infection.