Pseudomonas aeruginosa infection reveals a Caspase-1-dependent neutrophil pyroptosis pathway that restrains damaging Histone release

Neutrophils mediate essential immune and microbicidal processes. Consequently, to counteract neutrophil attack, pathogens have developed various virulence strategies. Here, we showed that Pseudomonas aeruginosa (P. aeruginosa) phospholipase ExoU drives pathological NETosis in neutrophils. Surprisingly, inhibition of ExoU activity uncovered a fully functional Caspase-1-driven pyroptosis pathway in neutrophils. Mechanistically, activated NLRC4 inflammasome promoted Caspase-1-dependent Gasdermin-D activation, IL-1{beta} cytokine release and neutrophil pyroptosis. Whereas both pyroptotic and netotic neutrophils released alarmins, only NETosis liberated the destructive DAMPs Histones, which exacerbated Pseudomonas-induced mouse lethality. To the contrary, subcortical actin allowed pyroptotic neutrophils to physically limit poisonous inflammation by keeping Histones intracellularly. Finally, mouse models of infection highlighted that both NETosis and neutrophil Caspase-1 contributed to P. aeruginosa spreading. Overall, we established the host deleterious consequences of Pseudomonas-induced-NETosis but also uncovered an unsuspected ability of neutrophils to undergo Caspase-1-dependent pyroptosis, a process where neutrophils exhibit a self-regulatory function that limit Histone release. Graphical abstractP.aeruginosaExoU (right) triggers phospholipid degradation and subsequent neutrophil lysis that associates to NETosis through F-Actin collapse/degradation and PAD4-dependent DNA decondensation. P.aeruginosaExoU- (left) triggers NLRC4-dependent pyroptosis in neutrophils, which leads to PAD4- depndent DNA decondensation but not expulsion due to a still function subcortical F- Actin network. Created with Biorender.com. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=124 SRC="FIGDIR/small/450116v1_ufig1.gif" ALT="Figure 1"> View larger version (29K): org.highwire.dtl.DTLVardef@16b15ecorg.highwire.dtl.DTLVardef@16c5d95org.highwire.dtl.DTLVardef@17405d5org.highwire.dtl.DTLVardef@2af107_HPS_FORMAT_FIGEXP M_FIG C_FIG