Regulation of Pseudomonas aeruginosa-Mediated Neutrophil Extracellular Traps

Abstract

Pseudomonas aeruginosa is the most prevalent opportunistic pathogen in the airways of cystic fibrosis (CF) patients. The pulmonary disorder is characterized by recurrent microbial infections and an exaggerated host inflammatory immune response led primarily by influx of neutrophils. Under these conditions, chronic colonization with P. aeruginosa is associated with diminished pulmonary function and increased morbidity and mortality. P. aeruginosa has a wide array of genetic mechanisms that facilitate its persistent colonization of the airway despite extensive innate host immune responses. Loss of function mutations in the quorum sensing regulatory gene lasR have been shown to confer survival advantage and a more pathogenic character to P. aeruginosa in CF patients. However, the strategies used by LasR-deficient P. aeruginosa to modulate neutrophil-mediated bactericidal functions are unknown. We sought to understand the role of LasR in P. aeruginosa -mediated neutrophil extracellular trap (NET) formation, an important anti-microbial mechanism deployed by neutrophils, the first-line responder in the infected airway. We observe mechanistic and phenotypic differences between NETs triggered by LasR-sufficient and LasR-deficient P. aeruginosa strains. We uncover that LasR-deficient P. aeruginosa strains fail to induce robust NET formation in both human and murine neutrophils, independently of bacterial motility or LPS expression. LasR does not mediate NET release via downstream quorum sensing signaling pathways but rather via transcriptional regulation of virulence factors, including, but not restricted to, LasB elastase and LasA protease. Finally, our studies uncover the differential requirements for NADPH oxidase in NET formation triggered by different P. aeruginosa strains.

A Refined View of Airway Microbiome in Chronic Obstructive Pulmonary Disease at Species and Strain-Levels

“…For example, non-typeable H. influenzae evades host immune recognition and clearance by neutrophil extracellular traps (NETs) through invading host epithelial cells, forming biofilms, altering gene expression and displaying surface antigenic variation ( Ahearn et al, 2017 ). P. aeruginosa is able to modify its motility, alginate production, biofilm formation or susceptibility to host anti-microbial defenses to establish niches of persistent infection ( Skopelja-Gardner et al, 2019 ). N. meningitidis can be resistant against NETs through a series of mechanisms including modification of LPS and escape from NET-mediated nutritional immunity ( Lappann et al, 2013 ).…”

Understanding Pseudomonas aeruginosa–Host Interactions: The Ongoing Quest for an Efficacious Vaccine

“…Both receptors are critical in the response to P. aeruginosa as they recruit neutrophils that aid in bacterial clearance and are well reviewed elsewhere [77,80]. The neutrophils act to kill P. aeruginosa, but can also contribute to host lung damage due to the production of reactive oxygen species (ROS) and the release of bactericidal proteins from their acidophilic granules [81]. Hence, an appropriate level of neutrophil recruitment is essential to achieve bacterial clearance without causing excessive tissue damage during the control of the infection.…”

Silver Nanoparticles Induce Neutrophil Extracellular Traps Via Activation of PAD and Neutrophil Elastase

“…Before the treatment of cells with AgNPs, polymyxin B was added to the culture medium as an endotoxin neutralizer to remove the potential contamination of NPs. Neutrophils express the endotoxin receptor toll-like receptor 4, which can activate neutrophils and induce NETs [ 23 ].…”

“…Mia Philipson and Paul Kubes have classified NETs into three types [ 22 ]. The first type includes suicidal NETs, which use the rupture of the plasma membrane for DNA release [ 12 , 23 ]. These NETs require ROS and peptidyl arginine deiminase type IV (PAD4)-mediated citrullination of histones.…”