Toll-like receptor 9 deficiency protects mice against Pseudomonas aeruginosa lung infection

PLoS One. 2014 Mar 4;9(3):e90466. doi: 10.1371/journal.pone.0090466. eCollection 2014.

Abstract

Pseudomonas aeruginosa is an opportunistic pathogen involved in nosocomial infections. While a number of studies have demonstrated the roles of TLR2, TLR4 and TLR5 in host defense againt P. aeruginosa infection, the implication of TLR9 in this process has been overlooked. Here, we show that P. aeruginosa DNA stimulates the inflammatory response through TLR9 pathway in both a cell line and primary alveolar macrophages (AMs). This activation requires asparagine endopeptidase- and endosomal acidification. Interestingly, TLR9-/- mice resisted to lethal lung infection by P. aeruginosa, compared to WT C57BL/6 mice. The resistance of TLR9-/- mice to P. aeruginosa infection was associated with: (i) a higher ability of TLR9-/- AMs to kill P. aeruginosa; (ii) a rapid increase in the pro-inflammatory cytokines such as TNFα, IL-1β and IL-6 production; and (iii) an increase in nitric oxide (NO) production and inductible NO synthase expression in AMs. In addition, inhibition of both IL-1β and NO production resulted in a significant decrease of P. aeruginosa clearance by AMs. Altogether these results indicate that TLR9 plays a detrimental role in pulmonary host defense toward P. aeruginosa by reducing the AMs clearance activity and production of IL-1β and NO necessary for bacteria killing.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Separation
  • Cytokines / biosynthesis
  • DNA, Bacterial / metabolism
  • Endosomes / drug effects
  • Endosomes / metabolism
  • Female
  • Hydrogen-Ion Concentration
  • Immunity, Innate / drug effects
  • Lung / drug effects
  • Lung / immunology
  • Lung / microbiology*
  • Lung / pathology*
  • Macrophages, Alveolar / drug effects
  • Macrophages, Alveolar / metabolism
  • Male
  • Mice, Inbred C57BL
  • Microbial Viability / drug effects
  • Nitric Oxide / metabolism
  • Nitric Oxide Synthase Type II / metabolism
  • Oligodeoxyribonucleotides / pharmacology
  • Pneumonia / immunology
  • Pneumonia / microbiology
  • Pneumonia / pathology
  • Pseudomonas Infections / immunology
  • Pseudomonas Infections / microbiology*
  • Pseudomonas Infections / pathology
  • Pseudomonas Infections / prevention & control*
  • Pseudomonas aeruginosa / drug effects
  • Pseudomonas aeruginosa / physiology*
  • Signal Transduction / drug effects
  • Survival Analysis
  • Toll-Like Receptor 4 / metabolism
  • Toll-Like Receptor 9 / deficiency*
  • Toll-Like Receptor 9 / metabolism

Substances

  • CPG-oligonucleotide
  • Cytokines
  • DNA, Bacterial
  • Oligodeoxyribonucleotides
  • Tlr4 protein, mouse
  • Tlr9 protein, mouse
  • Toll-Like Receptor 4
  • Toll-Like Receptor 9
  • Nitric Oxide
  • Nitric Oxide Synthase Type II

Grants and funding

This work was supported by ANR (ANR 2010 MIDI 008 01) and the Association Vaincre la Mucoviscidose (RF20120600716). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.