Glucocorticoids can affectPseudomonas aeruginosa(ATCC 27853) internalization and intracellular calcium concentration in cystic fibrosis bronchial epithelial cells

Microbial uptake by the respiratory epithelium: outcomes for host and pathogen

Intracellular occupancy of the respiratory epithelium is a useful pathogenic strategy facilitating microbial replication and evasion of professional phagocytes or circulating antimicrobial drugs. A less appreciated but growing body of evidence indicates that the airway epithelium also plays a crucial role in host defence against inhaled pathogens, by promoting ingestion and quelling of microorganisms, processes that become subverted to favour pathogen activities and promote respiratory disease. To achieve a deeper understanding of beneficial and deleterious activities of respiratory epithelia during antimicrobial defence, we have comprehensively surveyed all current knowledge on airway epithelial uptake of bacterial and fungal pathogens. We find that microbial uptake by airway epithelial cells (AECs) is a common feature of respiratory host-microbe interactions whose stepwise execution, and impacts upon the host, vary by pathogen. Amidst the diversity of underlying mechanisms and disease outcomes, we identify four key infection scenarios and use best-characterised host-pathogen interactions as prototypical examples of each. The emergent view is one in which effi-ciency of AEC-mediated pathogen clearance correlates directly with severity of disease outcome, therefore highlighting an important unmet need to broaden our understanding of the antimicrobial properties of respiratory epithelia and associated drivers of pathogen entry and intracellular fate.

Clinical and microbiological characteristics of cystic fibrosis adults never colonized by Pseudomonas aeruginosa: Analysis of the French CF registry

Pseudomonas aeruginosa is the main cause of chronic airway infection in cystic fibrosis (CF). However, for unclear reasons some patients are never colonized by P. aeruginosa. The objectives of this study were to better define the clinical, genetic, and microbiological characteristics of such a subpopulation and to identify predictive factors of non-colonization with P. aeruginosa. The French CF patient registry 2013–2014 was used to identify CF patients aged ≥ 20 years. The clinical outcomes, CF Transmembrane conductance Regulator (CFTR) genotypes, and microbiological data of patients reported positive at least once for P. aeruginosa (“Pyo” group, n = 1,827) were compared to those of patients with no history of P. aeruginosa isolation (“Never” group, n = 303). Predictive factors of non-colonization by P. aeruginosa were identified by multivariate logistic regression model with backward selection. Absence of aspergillosis (odds ratio (OR) [95% CI] = 1.64 [1.01–2.66]), absence of diabetes (2.25 [1.21–4.18]), pancreatic sufficiency (1.81 [1.30–2.52]), forced expiratory volume 1 (FEV1) ≥ 80% (3.03 [2.28–4.03]), older age at CF diagnosis (1.03 [1.02–1.04]), and absence of F508del/F508del genotype (2.17 [1.48–3.19]) were predictive clinical factors associated with absence of infection (“Never” group). Microbiologically, this same group was associated with more frequent detection of Haemophilus influenzae and lower rates of Stenotrophomonas maltophilia, Achromobacter xylosoxidans and Aspergillus spp. (all p<0.01) in sputum. This study strongly suggests that the absence of pulmonary colonization by P. aeruginosa in a minority of CF adults (14.2%) is associated with a milder form of the disease. Recent progress in the development of drugs to correct CFTR deficiency thus may be decisive in the control of P. aeruginosa lung infection.

Lipoxin A4 prevents tight junction disruption and delays the colonization of cystic fibrosis bronchial epithelial cells by Pseudomonas aeruginosa

The specialized proresolution lipid mediator lipoxin A4 (LXA4) is abnormally produced in cystic fibrosis (CF) airways. LXA4 increases the CF airway surface liquid height and stimulates airway epithelial repair and tight junction formation. We report here a protective effect of LXA4 (1 nM) against tight junction disruption caused by Pseudomonas aeruginosa bacterial challenge together with a delaying action against bacterial invasion in CF airway epithelial cells from patients with CF and immortalized cell lines. Bacterial invasion and tight junction integrity were measured by gentamicin exclusion assays and confocal fluorescence microscopy in non-CF (NuLi-1) and CF (CuFi-1) bronchial epithelial cell lines and in primary CF cultures, grown under an air/liquid interface, exposed to either a clinical or laboratory strains of P. aeruginosa LXA4 delayed P. aeruginosa invasion and transepithelial migration in CF and normal bronchial epithelial cell cultures. These protective effects of LXA4 were inhibited by the ALX/FPR2 lipoxin receptor antagonist BOC-2. LXA4 prevented the reduction in mRNA biosynthesis and protein abundance of the tight junction protein ZO-1 and reduced tight junction disruption induced by P. aeruginsosa inoculation. In conclusion, LXA4 plays a protective role in bronchial epithelium by stimulating tight junction repair and by delaying and reducing the invasion of CF bronchial epithelial cells by P. aeruginsosa.