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TLR ligands, but not modulators of histone modifiers, can induce the complex immune response pattern of endotoxin tolerance in mammary epithelial cells.

ABSTRACT: Excessive stimulation of the TLR4 axis through LPS reduces the expression of some cytokine genes in immune cells, while stimulating the expression of immune defense genes during a subsequent bacterial infection. This endotoxin tolerance (ET) is mediated via epigenetic mechanisms. Priming the udder of cows with LPS was shown to induce ET in mammary epithelial cells (MEC), thereby protecting the udder against reinfection for some time. Seeking alternatives to LPS priming we tried to elicit ET by priming MEC with either lipopeptide (Pam2CSK4) via the TLR2/6 axis or inhibitors of histone-modifying enzymes. Pre-incubation of MEC with Pam2CSK4 enhanced baseline and induced expression of bactericidal (?-defensin; SLPI) and membrane protecting factors ( SAA3, TGM3), while reducing the expression of cytokine- and chemokine-encoding genes ( TNF, IL1?) after a subsequent pathogen challenge, the latter, however, not as efficiently as after LPS priming. Pre-treating MEC with various inhibitors of histone H3 modifiers (for demethylation, acetylation or deacetylation) all failed to induce any of the protective factors and only resulted in some dampening of cytokine gene expression after the re-challenge. Hence, triggering immune functions via the TLR axis, but not through those histone modifiers, induced the beneficial phenomenon of ET in MEC.

SUBMITTER: Gunther J

PROVIDER: S-EPMC5410871 | biostudies-other | 2017 Feb

REPOSITORIES: biostudies-other

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TLR ligands, but not modulators of histone modifiers, can induce the complex immune response pattern of endotoxin tolerance in mammary epithelial cells.

Günther Juliane J Petzl Wolfram W Zerbe Holm H Schuberth Hans-Joachim HJ Seyfert Hans-Martin HM

Innate immunity 20161205 2

Excessive stimulation of the TLR4 axis through LPS reduces the expression of some cytokine genes in immune cells, while stimulating the expression of immune defense genes during a subsequent bacterial infection. This endotoxin tolerance (ET) is mediated via epigenetic mechanisms. Priming the udder of cows with LPS was shown to induce ET in mammary epithelial cells (MEC), thereby protecting the udder against reinfection for some time. Seeking alternatives to LPS priming we tried to elicit ET by p ...[more]

PMID: 27913794

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Project description:Among both healthy and immunocompromised patient populations, pneumonia is a leading cause of death worldwide. Yet, despite structural vulnerability resulting in recurrent exposure to pathogens, the lungs’ mucosal immunity successfully suppresses most infections. We recently reported that these innate defenses can be substantially augmented by inhalational exposure to a crude bacterial lysate, protecting broadly against respiratory pathogens, including lethal pneumonia caused by bacteria, fungi or viruses. The phenomenon of inducible resistance is associated with rapid pathogen killing in the lungs and persists in the absence of the typical leukocytes of innate immunity. Rather, the respiratory epithelium appears to be the predominant effector. Toll-like receptors (TLRs) are highly conserved pattern recognition receptors crucial to host defense through the sensing of pathogen associated molecular patterns. Given the importance of TLRs to mucosal immunity, the presence of numerous pathogen associated molecular patterns in the bacterial lysate, and the induction of many TLR-dependent genes following lysate treatment, we hypothesized that induced resistance follows simultaneous stimulation of multiple TLRs. To test this, we challenged mice deficient in TLR/IL1R adaptor proteins and found that resistance could not be induced in mice lacking MyD88. Having identified this phenomenon to be MyD88-dependent, we sought to determine whether the protective phenomenon could be recapitulated by treatment with synthetic TLR agonists. Mice were treated with aerosolized TLR ligands, alone and in combination, prior to infection with virulent pathogens. While limited protection against pneumonia was afforded by the individual TLR ligands, we discovered that the synergistic combination of diacylated lipopetide TLR2/6 agonist Pam2CSK4 and CpG oligodeoxynucleotide TLR9 agonist ODN2395 induced profound resistance against all tested pathogens. This combination also induced greater than additive pathogen killing in the lungs of challenged mice, and we found that the combination could effectively induce pathogen killing by respiratory epithelial cells in vitro. In order to better understand the mechanisms underlying the inducible pathogen killing by this unique combination of TLR agonists, we performed microarray analysis of murine MLE-15 respiratory epithelial cells following 4 h treatment with PBS (sham treatment), Pam2CSK4 alone, ODN2395 alone, or the combination of both agonists, using Illumina Sentrix MouseRef-8 v2 BeadChips. This allows for assessment of differential gene expression, not only between treated and untreated, but between single and combination treated. The intent of the experiment is to gain insight into the transcriptionally-regulated means by which TLR2/6 and TLR9 signaling pathways synergistically interact. Keywords: Differential expression, epithelium, in vitro

Dataset Information

TLR ligands, but not modulators of histone modifiers, can induce the complex immune response pattern of endotoxin tolerance in mammary epithelial cells.

Publications

TLR ligands, but not modulators of histone modifiers, can induce the complex immune response pattern of endotoxin tolerance in mammary epithelial cells.

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