NLRC4 inflammasome-mediated production of IL-1β modulates mucosal immunity in the lung against gram-negative bacterial infection

J Immunol. 2012 Jun 1;188(11):5623-35. doi: 10.4049/jimmunol.1200195. Epub 2012 Apr 30.

Abstract

Bacterial flagellin is critical to mediate NLRC4 inflammasome-dependent caspase-1 activation. However, Shigella flexneri, a nonflagellated bacterium, and a flagellin (fliC) knockout strain of Pseudomonas aeruginosa are known to activate NLRC4 in bone marrow-derived macrophages. Furthermore, the flagellin-deficient fliC strain of P. aeruginosa was used in a mouse model of peritonitis to show the requirement of NLRC4. In a model of pulmonary P. aeruginosa infection, flagellin was shown to be essential for the induction of NLRC4-dependent caspase-1 activation. Moreover, in all P. aeruginosa studies, IL-1β production was attenuated in NLRC4(-/-) mice; however, the role of IL-1β in NLRC4-mediated innate immunity in the lungs against a nonflagellated bacterium was not explored. In this article, we report that NLRC4 is important for host survival and bacterial clearance, as well as neutrophil-mediated inflammation in the lungs following Klebsiella pneumoniae infection. NLRC4 is essential for K. pneumoniae-induced production of IL-1β, IL-17A, and neutrophil chemoattractants (keratinocyte cell-derived chemokines, MIP-2, and LPS-induced CXC chemokines) in the lungs. NLRC4 signaling in hematopoietic cells contributes to K. pneumoniae-induced lung inflammation. Furthermore, exogenous IL-1β, but not IL-18 or IL-17A, partially rescued survival, neutrophil accumulation, and cytokine/chemokine expression in the lungs of NLRC4(-/-) mice following infectious challenge. Furthermore, IL-1R1(-/-) mice displayed a decrease in neutrophilic inflammation in the lungs postinfection. Taken together, these findings provide novel insights into the role of NLRC4 in host defense against K. pneumoniae infection.

Publication types

  • Research Support, American Recovery and Reinvestment Act
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis Regulatory Proteins / deficiency
  • Apoptosis Regulatory Proteins / physiology*
  • Calcium-Binding Proteins / deficiency
  • Calcium-Binding Proteins / physiology*
  • Caspase 1 / metabolism
  • Female
  • Humans
  • Immunity, Mucosal / immunology
  • Inflammasomes / deficiency
  • Inflammasomes / physiology*
  • Inflammation Mediators / physiology
  • Interleukin-1beta / biosynthesis*
  • Klebsiella Infections / enzymology
  • Klebsiella Infections / immunology*
  • Klebsiella Infections / pathology
  • Macrophages, Alveolar / immunology
  • Macrophages, Alveolar / microbiology
  • Macrophages, Alveolar / pathology
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Neutrophils / immunology
  • Neutrophils / microbiology
  • Neutrophils / pathology
  • Pneumonia, Bacterial / immunology*
  • Pneumonia, Bacterial / microbiology
  • Pneumonia, Bacterial / pathology
  • Respiratory Tract Infections / immunology*
  • Respiratory Tract Infections / microbiology*
  • Respiratory Tract Infections / pathology

Substances

  • Apoptosis Regulatory Proteins
  • Calcium-Binding Proteins
  • Inflammasomes
  • Inflammation Mediators
  • Interleukin-1beta
  • Ipaf protein, mouse
  • Caspase 1