Afa/Dr Diffusely Adhering Escherichia coli Strain C1845 Induces Neutrophil Extracellular Traps That Kill Bacteria and Damage Human Enterocyte-Like Cells

Abstract

<jats:title>ABSTRACT</jats:title><jats:p>We recently documented the neutrophil response to enterovirulent diffusely adherent<jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus-species" xlink:type="simple">Escherichia coli</jats:named-content>expressing Afa/Dr fimbriae (Afa/Dr DAEC), using the human myeloid cell line PLB-985 differentiated into fully mature neutrophils. Upon activation, particularly during infections, neutrophils release neutrophil extracellular traps (NETs), composed of a nuclear DNA backbone associated with antimicrobial peptides, histones, and proteases, which entrap and kill pathogens. Here, using fluorescence microscopy and field emission scanning electron microscopy, we observed NET production by PLB-985 cells infected with the Afa/Dr wild-type (WT)<jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus-species" xlink:type="simple">E. coli</jats:named-content>strain C1845. We found that these NETs were able to capture, immobilize, and kill WT C1845 bacteria. We also developed a coculture model of human enterocyte-like Caco-2/TC7 cells and PLB-985 cells previously treated with WT C1845 and found, for the first time, that the F-actin cytoskeleton of enterocyte-like cells is damaged in the presence of bacterium-induced NETs and that this deleterious effect is prevented by inhibition of protease release. These findings provide new insights into the neutrophil response to bacterial infection via the production of bactericidal NETs and suggest that NETs may damage the intestinal epithelium, particularly in situations such as inflammatory bowel diseases.</jats:p>

Neutrophil Extracellular Traps Downregulate Lipopolysaccharide-Induced Activation of Monocyte-Derived Dendritic Cells

“…PMN kill pathogens through various strategies, including phagocytosis, degranulation, the oxidative burst, and release of neutrophil extracellular traps (NETs), a process called netosis (1,2). NETs are released by activated PMN in response to pathogenic bacteria, fungi, viruses, and protozoa (1,(3)(4)(5) [reviewed in (6,7)] and also in response to endogenous mediators of inflammation (3,4) and pharmacological agents such as PMA and calcium ionophore (1,3,(5)(6)(7). Netosis was initially described as a suicide-like mechanism, but a concept of "vital netosis" is also emerging (8).…”

“…However, NET accumulation can also have adverse consequences in in vitro and in vivo, such as epithelial and endothelial cell injury (6,11,(14)(15)(16) and thrombus formation (17,18) [reviewed in (10,13)]. Moreover, by exposing self-Ags, NETs might be involved in autoimmune disorders, including small-vessel vasculitis, rheumatoid arthritis, type 1 diabetes, and systemic lupus erythematosus (SLE) (14,(19)(20)(21).…”

Beneficial and Deleterious Effects of Neutrophil Extracellular Traps on Infection

“…The proposed mechanisms for the formation of NETs depend on the bacteria strain and its pathogenesis. In the case of E. coli involved in liver sepsis, the infection can be controlled by histones H2B or by activating the intravascular NETs release through the integrin lymphocyte function-associated antigen 1 (LFA-1) [19,20].…”

La pêche miraculeuse des filets du neutrophile

“…Il est également possible que les modifications protéiques (oxydation, protéolyse, citrullination) induites par le processus de nétose conduisent à la génération de néoantigènes, participant ainsi à la rupture de la tolérance immunitaire [1]. En plus de leur immunogénicité probable, il a été montré que les NET, via les protéases ou les histones fixées à leur surface, participent à l'inflammation et aux dommages tissulaires caractérisant la phase effectrice des manifestations auto-immunes [14].…”

“…Au cours des pathologies pulmonaires inflammatoires aiguës comme le syndrome de détresse respiratoire aiguë ou le syndrome respiratoire aigu post-transfusionnel, les plaquettes activées induisent la formation de NET qui s'accumulent au niveau alvéolaire et participent aux lésions épithéliales et endothéliales. En effet, il a été montré que les histones sont capables d'induire une apoptose cellulaire dépendante de la dose [14], et que l'élastase augmente la perméabilité de la barrière alvéolo-capillaire par altération du cytosquelette endothélial. Au cours du sepsis et du syndrome respiratoire aigu post-transfusionnel, des marqueurs circulants de nétose sont présents [29].…”