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Pseudomonas aeruginosa quorum-sensing molecule homoserine lactone modulates inflammatory signaling through PERK and eI-F2?.

ABSTRACT: Pseudomonas aeruginosa secrete N-(3-oxododecanoyl)-homoserine lactone (HSL-C12) as a quorum-sensing molecule to regulate bacterial gene expression. Because HSL-C12 is membrane permeant, multiple cell types in P. aeruginosa-infected airways may be exposed to HSL-C12, especially adjacent to biofilms where local (HSL-C12) may be high. Previous reports showed that HSL-C12 causes both pro- and anti-inflammatory effects. To characterize HSL-C12's pro- and anti-inflammatory effects in host cells, we measured protein synthesis, NF-?B activation, and KC (mouse IL-8) and IL-6 mRNA and protein secretion in wild-type mouse embryonic fibroblasts (MEF). To test the role of the endoplasmic reticulum stress inducer, PERK we compared these responses in PERK(-/-) and PERK-corrected PERK(-/-) MEF. During 4-h treatments of wild-type MEF, HSL-C12 potentially activated NF-?B p65 by preventing the resynthesis of I?B and increased transcription of KC and IL-6 genes (quantitative PCR). HSL-C12 also inhibited secretion of KC and/or IL-6 into the media (ELISA) both in control conditions and also during stimulation by TNF-?. HSL-C12 also activated PERK (as shown by increased phosphorylation of eI-F2?) and inhibited protein synthesis (as measured by incorporation of [(35)S]methionine by MEF). Comparisons of PERK(-/-) and PERK-corrected MEF showed that HSL-C12's effects were explained in part by activation of PERK?phosphorylation of eI-F2??inhibition of protein synthesis?reduced I?B? production?activation of NF-?B?increased transcription of the KC gene but reduced translation and secretion of KC. HSL-C12 may be an important modulator of early (up to 4 h) inflammatory signaling in P. aeruginosa infections.

SUBMITTER: Grabiner MA

PROVIDER: S-EPMC4113911 | biostudies-literature | 2014 Aug

REPOSITORIES: biostudies-literature

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Pseudomonas aeruginosa quorum-sensing molecule homoserine lactone modulates inflammatory signaling through PERK and eI-F2α.

Grabiner Mark A MA Fu Zhu Z Wu Tara T Barry Kevin C KC Schwarzer Christian C Machen Terry E TE

Journal of immunology (Baltimore, Md. : 1950) 20140702 3

Pseudomonas aeruginosa secrete N-(3-oxododecanoyl)-homoserine lactone (HSL-C12) as a quorum-sensing molecule to regulate bacterial gene expression. Because HSL-C12 is membrane permeant, multiple cell types in P. aeruginosa-infected airways may be exposed to HSL-C12, especially adjacent to biofilms where local (HSL-C12) may be high. Previous reports showed that HSL-C12 causes both pro- and anti-inflammatory effects. To characterize HSL-C12's pro- and anti-inflammatory effects in host cells, we me ...[more]

PMID: 24990083

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Project description:The opportunistic pathogen Pseudomonas aeruginosa is a leading cause of airway infection in cystic fibrosis (CF) patients. P. aeruginosa employs several hierarchically arranged and interconnected quorum sensing (QS) regulatory circuits to produce a battery of virulence factors such as elastase, phenazines, and rhamnolipids. The QS transcription factor LasR sits atop this hierarchy and activates the transcription of dozens of genes, including that encoding the QS regulator RhlR. Paradoxically, inactivating lasR mutations are frequently observed in isolates from CF patients with chronic P. aeruginosa infections. In contrast, mutations in rhlR are rare. We have recently shown that in CF isolates, the QS circuitry is often rewired such that RhlR acts in a LasR-independent manner. To begin understanding how QS activity differs in this rewired background, we characterized QS activation and RhlR-regulated gene expression in P. aeruginosa E90, a LasR-null, RhlR-active chronic infection isolate. In this isolate, RhlR activates the expression of 53 genes in response to increasing cell density. The genes regulated by RhlR include several that encode virulence factors. Some, but not all, of these genes are present in the QS regulon described in the well-studied laboratory strain PAO1. We also demonstrate that E90 produces virulence factors at similar concentrations as PAO1, and in E90, RhlR plays a significant role in mediating cytotoxicity in a three-dimensional lung epithelium cell model. These data illuminate a rewired LasR-independent RhlR regulon in chronic infection isolates and suggest further investigation of RhlR as a possible target for therapeutic development in chronic infections.IMPORTANCE Pseudomonas aeruginosa is a prominent cystic fibrosis (CF) pathogen that uses quorum sensing (QS) to regulate virulence. In laboratory strains, the key QS regulator is LasR. Many isolates from patients with chronic CF infections appear to use an alternate QS circuitry in which another transcriptional regulator, RhlR, mediates QS. We show that a LasR-null CF clinical isolate engages in QS through RhlR and remains capable of inducing cell death in an in vivo-like lung epithelium cell model. Our findings support the notion that LasR-null clinical isolates can engage in RhlR QS and highlight the centrality of RhlR in chronic P. aeruginosa infections.

Dataset Information

Pseudomonas aeruginosa quorum-sensing molecule homoserine lactone modulates inflammatory signaling through PERK and eI-F2?.

Publications

Pseudomonas aeruginosa quorum-sensing molecule homoserine lactone modulates inflammatory signaling through PERK and eI-F2α.

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