L' interleukine-33, cytokine de la famille IL-1 (régulation par les protéases inflammatoires)

TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

Neutralisation of the interleukin-33/ST2 pathway ameliorates experimental colitis through enhancement of mucosal healing in mice

Objective: Inflammatory bowel diseases (IBD) have been intrinsically linked to a deregulated cytokine network, but novel therapeutic principles are urgently needed. Here we identify the interleukin (IL)-33 and its receptor ST2 as key negative regulators of wound healing and permeability in the colon of mice. Design: Expression of IL-33 and ST2 was determined by qRT-PCR, ELISA, immunohistochemistry and western-blot analysis. Wild-type and St2-/-mice were used in wound healing experiments and in two experimental models of IBD triggered by 2,4,6-trinitrobenzene sulphonic acid or dextran sodium sulphate (DSS). Neutralisation of ST2 was performed by using a specific blocking antibody. Results: Nuclear localisation and enhanced expression of IL-33 in myofibroblasts and enterocytes was linked to disease involvement independently of inflammation, while the expression of ST2 was primarily restricted to the colonic epithelia. In two experimental models of IBD, genetic ablation of ST2 significantly improved signs of colitis, while a sustained epithelial expression of the cyto-protective factor connexin-43 was observed in DSStreated St2-deficient mice. Unexpectedly, absence of ST2 in non-hematopoietic cells was sufficient to protect against colitis. Consistently, specific inhibition of endogenous ST2-mediated signalling by treatment with neutralising antibody improved DSS-induced colitis. In addition, IL-33 treatment impaired epithelial barrier permeability in vitro and in vivo, whereas absence of ST2 enhanced wound healing response upon acute mechanical injury in the colon. Conclusions: Our study unveiled a novel nonhematopoietic function of IL-33 in epithelial barrier function and wound healing. Therefore, blocking the IL-33/ST2 axis may represent an efficient therapy in IBD

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

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

Abstract 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-1β 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 abstract P.aeruginosa ExoU (right) triggers phospholipid degradation and subsequent neutrophil lysis that associates to NETosis through F-Actin collapse/degradation and PAD4-dependent DNA decondensation. P.aeruginosa ExoU- (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