Bacterial infection induces pyroptotic signaling-mediated neutrophil extracellular traps (NETs) formation in turbot (Scophthalmus maximus)

Neutrophils can capture and kill pathogens by releasing neutrophils extracellular traps (NETs), which play critical roles in anti-microbial infection in mammals; however, the mechanisms involved in NETs formation and its role in anti-bacterial infection in teleost fish remains largely unknown. In this study, to explore the function of NETs in turbot , we established an in vitro bacterial infection model in head kidney derived neutrophils, and found that the haemolysin over-expressed Edwardsiella piscicida ( ethA + ) could induce a robust phenotype of NETs, compared with that in wild type or ethA mutant ( ethA +  - ΔethA ) strains. Besides, the NETosis was mediated by ethA +  -induced pyroptosis , and arms the ability of bacterial killing in neutrophils of turbot. Moreover, we found that neutrophils elastase (NE) might involves in this pyroptotic signaling, rather than inflammatory Sm caspase . Taken together, this study reveals the important role of pyroptosis in NETs formation in turbot neutrophils, suggesting that NETs formation is a critical immune response during bacterial infection in teleost fish.