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Pseudomonas aeruginosa type-3 secretion system dampens host defense by exploiting the NLRC4-coupled inflammasome.
Pseudomonas aeruginosa type-3 secretion system dampens host defense by exploiting the NLRC4-coupled inflammasome.
- Source :
-
American journal of respiratory and critical care medicine [Am J Respir Crit Care Med] 2014 Apr 01; Vol. 189 (7), pp. 799-811. - Publication Year :
- 2014
-
Abstract
- Rationale: Pseudomonas aeruginosa, a major problem pathogen responsible for severe infections in critically ill patients, triggers, through a functional type-3 secretion system (T3SS), the activation of an intracellular cytosolic sensor of innate immunity, NLRC4. Although the NLRC4-inflammasome-dependent response contributes to increased clearance of intracellular pathogens, it seems that NLRC4 inflammasome activation decreases the clearance of P. aeruginosa, a mainly extracellular pathogen.<br />Objectives: We sought to determine the underlying mechanisms of this effect of the activation of NLRC4 by P. aeruginosa.<br />Methods: We established acute lung injury in wild-type and Nlrc4(-/-) mice using sublethal intranasal inocula of P. aeruginosa strain CHA expressing or not a functional T3SS. We studied 96-hour survival, lung injury, bacterial clearance from the lungs, cytokine secretion in bronchoalveolar lavage, lung antimicrobial peptide expression by quantitative polymerase chain reaction, and flow cytometry analysis of lung cells.<br />Measurements and Main Results: Nlrc4(-/-) mice showed enhanced bacterial clearance and decreased lung injury contributing to increased survival against extracellular P. aeruginosa strain expressing a functional T3SS. The mechanism involved decreased NLRC4-inflammasome-driven IL-18 secretion attenuating lung injury caused by excessive neutrophil recruitment. Additionally, in the lungs of Nlrc4(-/-) mice secretion of IL-17 by innate immune cells was increased and responsible for increased expression of lung epithelial antimicrobial peptides. Furthermore, IL-18 secretion was found to repress IL-17 and IL-17-driven lung antimicrobial peptide expression.<br />Conclusions: We report a new role of the T3SS apparatus itself, independently of exotoxin translocation. Through NLRC4 inflammasome activation, the T3SS promotes IL-18 secretion, which dampens a beneficial IL-17-mediated antimicrobial host response.
- Subjects :
- Acute Lung Injury immunology
Acute Lung Injury metabolism
Animals
Biomarkers metabolism
Bronchoalveolar Lavage Fluid chemistry
Caspase 1 metabolism
Cells, Cultured
Female
Flow Cytometry
Immunity, Innate
Interleukin-17 metabolism
Interleukin-18 metabolism
Macrophages immunology
Macrophages metabolism
Macrophages microbiology
Male
Mice
Mice, Inbred C57BL
Mice, Knockout
Pseudomonas Infections immunology
Pseudomonas Infections metabolism
Pseudomonas aeruginosa metabolism
Reverse Transcriptase Polymerase Chain Reaction
Acute Lung Injury microbiology
Apoptosis Regulatory Proteins metabolism
Calcium-Binding Proteins metabolism
Inflammasomes metabolism
Pseudomonas Infections microbiology
Pseudomonas aeruginosa pathogenicity
Subjects
Details
- Language :
- English
- ISSN :
- 1535-4970
- Volume :
- 189
- Issue :
- 7
- Database :
- MEDLINE
- Journal :
- American journal of respiratory and critical care medicine
- Publication Type :
- Academic Journal
- Accession number :
- 24555512
- Full Text :
- https://doi.org/10.1164/rccm.201307-1358OC