Impact of Pseudomonas aeruginosa quorum sensing signaling molecules on adhesion and inflammatory markers in endothelial cells

Carmen Curutiu,Alina Maria Hoban,Veronica Lazar,Mariana Carmen Chifiriuc,Aurelia Magdalena Pisoschi,Aneta Pop,Florin Iordache

doi:10.3762/bjoc.14.235

Abstract

Pseudomonas aeruginosa relies on the quorum sensing (QS) signaling system as a central regulator mechanism of virulence expression that contributes to the formation and maintenance of biofilms and tolerance to conventional antimicrobials. QS Signaling molecules (QSSMs) may be recognized and may function also within the host cells, being potentially involved in the progression of the infectious process. In this study we evaluate the expression of adhesion and inflammatory molecules in endothelial cells treated with P. aeruginosa QSSMs, in order to bring new insights on the mechanisms involved in the interaction of P. aeruginosa with host cells during the infectious process. Endothelial cells were stimulated with 20 µM of main P. aeruginosa QSSMs (OdDHL = N-(3-oxododecanoyl)-L-homoserine lactone, C4HSL = N-butyryl-L-homoserine lactone, PQS = 2-heptyl-3-hydroxy-4(1H)-quinolone and HHQ = 2-heptyl-4-quinolone). Adherence to endothelial cells, inert substratum and biofilm formation was evaluated. The expression of adhesion molecules (VE-cadherin, PECAM-1, ICAM-1, and P-selectin) and inflammatory response molecules (IL-1β, IL-6, TNFα, TGFβ, and eNOS) was assessed by qRT-PCR and flow cytometry. Our results showed that bacterial adherence to inert substratum and biofilm were decreased in the presence of all tested QSSMs. The adherence index of PAO1 laboratory strain to host cells was decreased between 10–40% in the presence of QSSMs, as compared to untreated control. Expression of eukaryotic cells adhesion molecules ICAM-1 and P-selectin was stimulated by QSSMs, whereas VE-cadherin and PECAM-1 levels were increased only by C4HSL. The inflammatory response of endothelial cells was also modulated, as observed by the modified expression of IL-1β (for C4HSL, PQS and HHQ), IL-6 (for C4HSL and HHQ), TNFα (for C4HSL and HHQ), TGFβ, and eNOS factors. Our results demonstrate that the main pseudomonadal QSSMs differentially modulate endothelial cells adhesion and proinflammatory cytokine expression. These observations provide new insights in the mechanisms by which different QSSMs activate endothelial cells and modulate the infectious process, and support the importance of recent studies aiming to develop anti-QS therapeutic strategies to fight against P. aeruginosa infections.

Highlights

Pseudomonas (P.) aeruginosa is an opportunistic pathogen that causes severe and persistent infections in immune compromised individuals and in patients with bronchiectasis or cystic fibrosis
The aim of this study was to evaluate the expression of adhesion and inflammatory molecules in endothelial cells treated with P. aeruginosa quorum-sensing (QS) molecules, in order to elucidate their role in the occurrence of tissue damages, in which endothelial cells are involved, such as: wound healing, transepithelial migration of neutrophils, lung inflammation and permeability
It is known that prostaglandin E2 (PGE2) plays a role in inducing mucus secretion, vasodilatation and edema, acting as a lipid mediator in immunomodulation [17]. These results indicate that OdDHL contributes to the induction of inflammation and pulmonary pathology in P. aeruginosa infections, which is mainly visible in cystic fibrosis patients

Summary

Introduction

Pseudomonas (P.) aeruginosa is an opportunistic pathogen that causes severe and persistent infections in immune compromised individuals and in patients with bronchiectasis or cystic fibrosis. Pseudomonas aeruginosa is recognized as the principal pathogen responsible of high morbidity and mortality in patients with cystic fibrosis, one of the most common life-threatening autosomal recessive genetic disease in Northwest European populations, determined by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene [1]. This mutation determines alteration of ion transport and subsequent dehydration of the airway surface liquid, resulting in a viscous mucus layer on the airway surface of cystic fibrosis patients that deteriorate the mucociliary clearance and enhance the infection, inflammation and respiratory insufficiency [2]. The elucidation of the intimate QSSM mechanisms could contribute to the development of new anti-QS therapeutic strategies against P. aeruginosa infections, which are very difficult to treat

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