Contribution of the Alkylquinolone Quorum-Sensing System to the Interaction of Pseudomonas aeruginosa With Bronchial Epithelial Cells.

Yi-Chia Liu,Ana Carolina Paiva,Miguel Cámara,Paddy Tighe,Jeni Luckett,Paul Williams,Sonali Singh,Ola Negm,Sirina Muntaka,Nigel Halliday,Cynthia Bosquillon,Jean-Frédéric Dubern,Lee Wheldon,Luisa Martínez-Pomares,Farah Hussain

doi:10.3389/fmicb.2018.03018

Yi-Chia Liu, Ana Carolina Paiva + Show 13 more

Open Access

https://doi.org/10.3389/fmicb.2018.03018

Copy DOI

Abstract

Pseudomonas aeruginosa causes infections in patients with compromised epithelial barrier function. Multiple virulence factors produced by P. aeruginosa are controlled by quorum sensing (QS) via 2-alkyl-4(1H)-quinolone (AQ) signal molecules. Here, we investigated the impact of AQs on P. aeruginosa PAO1 infection of differentiated human bronchial epithelial cells (HBECs). The pqsA-E operon is responsible for the biosynthesis of AQs including the 2-alkyl-3-hydroxy-4-quinolones, 4-hydroxy-2-alkylquinolines, and 4-hydroxy-2-alkylquinoline N-oxides as exemplified by pseudomonas quinolone signal (PQS), 2-heptyl-4-hydroxyquinoline (HHQ), and 2-heptyl-4-hydroxyquinoline N-oxide (HQNO), respectively. PQS and HHQ both act as QS signal molecules while HQNO is a cytochrome inhibitor. PqsE contributes both to AQ biosynthesis and promotes virulence in a PQS-independent manner. Our results show that PQS, HHQ, and HQNO were produced during PAO1 infection of HBECs, but no differences in growth or cytotoxicity were apparent when PAO1 and an AQ-negative ΔpqsA mutant were compared. Both strains promoted synthesis of inflammatory cytokines TNF-α, interleukin (IL)-6, and IL-17C by HBECs, and the provision of exogenous PQS negatively impacted on this response without affecting bacterial growth. Expression of pqsE and the PQS-independent PqsE-regulated genes mexG and lecA was detected during HBEC infection. Levels were reduced in the ΔpqsA mutant, that is, in the absence of PQS, and increased by exogenous PQS. These results support an AQ-independent role for PqsE during initial infection of HBEC by P. aeruginosa and for PQS as an enhancer of PqsE and PqsE-controlled virulence determinants and as an immunomodulator.

Highlights

Pseudomonas aeruginosa is an opportunistic pathogen that causes acute infections in patients with ventilator-acquired pneumonia and is a major cause of chronic respiratory infections in patients with cystic fibrosis (CF) (Kipnis et al, 2006; Folkesson et al, 2012)
To determine whether AQs are produced during infection of differentiated human bronchial epithelial cells (HBECs), differentiated Calu-3 cells in air-liquid interface cultures (Calu-3-ALI; Figure S1) were infected with PAO1 or the isogenic AQ-negative ΔpqsA mutant (Figure S2) at MOI 50 and AQs in the infected cultures were quantified by LC-MS/MS as described in Materials and Methods
The results show that HHQ, pseudomonas quinolone signal (PQS), and hydroxyquinoline N-oxide (HQNO) are all detectable in Calu-3-ALI cultures infected

Summary

Introduction

Pseudomonas aeruginosa is an opportunistic pathogen that causes acute infections in patients with ventilator-acquired pneumonia and is a major cause of chronic respiratory infections in patients with cystic fibrosis (CF) (Kipnis et al, 2006; Folkesson et al, 2012). The 2-alkyl4(1H)-quinolones (AQs) including 2-heptyl-3-hydroxy-4(1H)quinolone (PQS, pseudomonas quinolone signal) and its biosynthetic precursor 2-heptyl-4-hydroxyquinoline (HHQ) regulate gene expression through interactions with PqsR (MvfR) (Heeb et al, 2011; Ilangovan et al, 2013; Drees and Fetzner, 2015). PqsA catalyzes the formation of anthraniloyl-CoA (Coleman et al, 2008) that is condensed with malonyl-CoA by PqsD to form 2-aminobenzoylacetyl-CoA (2-ABA-CoA). The latter is converted into 2-aminobenzoylacetate (2-ABA) via the thioesterase activity of PqsE (Drees and Fetzner, 2015). Inhibition of AQ signaling supports the importance of PQS in both acute and persistent P. aeruginosa infections in mice (Starkey et al, 2014)

Methods

Results

Conclusion