Caspase-1-driven neutrophil pyroptosis and its role in host susceptibility to Pseudomonas aeruginosa

International audienceMultiple regulated neutrophil cell death programs contribute to host defense against infections. However, despite expressing all necessary inflammasome components, neutrophils are thought to be generally defective in Caspase-1-dependent pyroptosis. By screening different bacterial species, we found that several Pseudomonas aeruginosa ( P . aeruginosa ) strains trigger Caspase-1-dependent pyroptosis in human and murine neutrophils. Notably, deletion of Exotoxins U or S in P . aeruginosa enhanced neutrophil death to Caspase-1-dependent pyroptosis, suggesting that these exotoxins interfere with this pathway. Mechanistically, P . aeruginosa Flagellin activates the NLRC4 inflammasome, which supports Caspase-1-driven interleukin (IL)-1β secretion and Gasdermin D (GSDMD)-dependent neutrophil pyroptosis. Furthermore, P . aeruginosa -induced GSDMD activation triggers Calcium-dependent and Peptidyl Arginine Deaminase-4-driven histone citrullination and translocation of neutrophil DNA into the cell cytosol without inducing extracellular Neutrophil Extracellular Traps. Finally, we show that neutrophil Caspase-1 contributes to IL-1β production and susceptibility to pyroptosis-inducing P . aeruginosa strains in vivo . Overall, we demonstrate that neutrophils are not universally resistant for Caspase-1-dependent pyroptosis

EEF2-inactivating toxins engage the NLRP1 inflammasome and promote epithelial barrier disruption

Human airway and corneal epithelial cells, which are critically altered during chronic infections mediated by Pseudomonas aeruginosa, specifically express the inflammasome sensor NLRP1. Here, together with a companion study, we report that the NLRP1 inflammasome detects exotoxin A (EXOA), a ribotoxin released by P. aeruginosa type 2 secretion system (T2SS), during chronic infection. Mechanistically, EXOA-driven eukaryotic elongation factor 2 (EEF2) ribosylation and covalent inactivation promote ribotoxic stress and subsequent NLRP1 inflammasome activation, a process shared with other EEF2-inactivating toxins, diphtheria toxin and cholix toxin. Biochemically, irreversible EEF2 inactivation triggers ribosome stress-associated kinases ZAKα- and P38-dependent NLRP1 phosphorylation and subsequent proteasome-driven functional degradation. Finally, cystic fibrosis cells from patients exhibit exacerbated P38 activity and hypersensitivity to EXOA-induced ribotoxic stress-dependent NLRP1 inflammasome activation, a process inhibited by the use of ZAKα inhibitors. Altogether, our results show the importance of P. aeruginosa virulence factor EXOA at promoting NLRP1-dependent epithelial damage and identify ZAKα as a critical sensor of virulence-inactivated EEF2.Published versionThis project was supported by the ATIP-Avenir program (to E. Meunier), Fondation pour la Recherche Médicale “Amorçage Jeunes Equipes” (AJE20151034460 to E. Meunier), the Agence Nationale de la Recherche (ANR Psicopak to E. Meunier), the Agence nationale de recherche sur le sida et les hépatites-Maladies infectieuses émergentes (to E. Meunier), the European Research Council (StG INFLAME 804249 to E. Meunier), the European Society of Clinical Microbiology and Infectious Diseases (to R. Planès), Invivogen-Conventions industrielles de formation par la recherche PhD grant (to M. Pinilla), Vaincre La Mucoviscidose, and Region Occitanie (Groupement de Recherche pour des Applications INnovantes avec les Entreprises) grants to C. Cougoule