Toll-like receptor 2 regulates organic dust-induced airway inflammation

Am J Respir Cell Mol Biol. 2011 Oct;45(4):711-9. doi: 10.1165/rcmb.2010-0427OC. Epub 2011 Jan 28.

Abstract

Organic dust exposure in agricultural environments results in significant airway inflammatory diseases. Gram-positive cell wall components are present in high concentrations in animal farming dusts, but their role in mediating dust-induced airway inflammation is not clear. This study investigated the role of Toll-like receptor (TLR) 2, a pattern recognition receptor for gram-positive cell wall products, in regulating swine facility organic dust extract (DE)-induced airway inflammation in mice. Isolated lung macrophages from TLR2 knockout mice demonstrated reduced TNF-α, IL-6, keratinocyte chemoattractant/CXCL1, but not macrophage inflammatory protein-2/CXCL2 expression, after DE stimulation ex vivo. Next, using an established mouse model of intranasal inhalation challenge, we analyzed bronchoalveolar lavage fluid and lung tissue in TLR2-deficient and wild-type (WT) mice after single and repetitive DE challenge. Neutrophil influx and select cytokines/chemokines were significantly lower in TLR2-deficient mice at 5 and 24 hours after single DE challenge. After daily exposure to DE for 2 weeks, there were significant reductions in total cellularity, neutrophil influx, and TNF-α, IL-6, CXCL1, but not CXCL2 expression, in TLR2-deficient mice as compared with WT animals. Lung pathology revealed that bronchiolar inflammation, but not alveolar inflammation, was reduced in TLR2-deficient mice after repetitive exposure. Airway hyperresponsiveness to methacholine after dust exposure was similar in both groups. Finally, airway inflammatory responses in WT mice after challenge with a TLR2 agonist, peptidoglycan, resembled DE-induced responses. Collectively, these results demonstrate that the TLR2 pathway is important in regulating swine facility organic dust-induced airway inflammation, which suggests the importance of TLR2 agonists in mediating large animal farming-induced airway inflammatory responses.

Publication types

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

MeSH terms

  • Animal Husbandry
  • Animals
  • Bronchial Hyperreactivity / immunology
  • Bronchial Hyperreactivity / physiopathology
  • Bronchoalveolar Lavage Fluid / immunology
  • Bronchoconstrictor Agents / pharmacology
  • Chemokines / metabolism
  • Cytokines / metabolism
  • Disease Models, Animal
  • Dose-Response Relationship, Drug
  • Dust*
  • Housing, Animal
  • Inflammation Mediators / metabolism
  • Inhalation Exposure
  • Lipopolysaccharides / pharmacology
  • Lung / drug effects
  • Lung / immunology*
  • Lung / physiopathology
  • Macrophages, Alveolar / immunology
  • Methacholine Chloride / pharmacology
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Neutrophil Infiltration
  • Neutrophils / immunology
  • Nitric Oxide / metabolism
  • Peptidoglycan / pharmacology
  • Pneumonia / chemically induced
  • Pneumonia / immunology*
  • Pneumonia / physiopathology
  • Pneumonia / prevention & control
  • Swine
  • Time Factors
  • Toll-Like Receptor 2 / agonists
  • Toll-Like Receptor 2 / deficiency
  • Toll-Like Receptor 2 / genetics
  • Toll-Like Receptor 2 / metabolism*

Substances

  • Bronchoconstrictor Agents
  • Chemokines
  • Cytokines
  • Dust
  • Inflammation Mediators
  • Lipopolysaccharides
  • Peptidoglycan
  • Tlr2 protein, mouse
  • Toll-Like Receptor 2
  • Methacholine Chloride
  • Nitric Oxide