Organic dust augments nucleotide-binding oligomerization domain expression via an NF-{kappa}B pathway to negatively regulate inflammatory responses

Am J Physiol Lung Cell Mol Physiol. 2011 Sep;301(3):L296-306. doi: 10.1152/ajplung.00086.2011. Epub 2011 Jun 10.

Abstract

Nucleotide-binding oligomerization domain 2 (NOD2) is involved in innate immune responses to peptidoglycan degradation products. Peptidoglycans are important mediators of organic dust-induced airway diseases in exposed agriculture workers; however, the role of NOD2 in response to complex organic dust is unknown. Monocytes/macrophages were exposed to swine facility organic dust extract (ODE), whereupon NOD2 expression was evaluated by real-time PCR and Western blot. ODE induced significant NOD2 mRNA and protein expression at 24 and 48 h, respectively, which was mediated via a NF-κB signaling pathway as opposed to a TNF-α autocrine/paracrine mechanism. Specifically, NF-κB translocation increased rapidly following ODE stimulation as demonstrated by EMSA, and inhibition of the NF-κB pathway significantly reduced ODE-induced NOD2 expression. However, there was no significant reduction in ODE-induced NOD2 gene expression when TNF-α was inhibited or absent. Next, it was determined whether NOD2 regulated ODE-induced inflammatory cytokine production. Knockdown of NOD2 expression by small interfering RNA resulted in increased CXCL8 and IL-6, but not TNF-α production in response to ODE. Similarly, primary lung macrophages from NOD2 knockout mice demonstrated increased IL-6, CXCL1, and CXCL1, but not TNF-α, expression. Lastly, a higher degree of airway inflammation occurred in the absence of NOD2 following acute (single) and repetitive (3 wk) ODE exposure in an established in vivo murine model. In summary, ODE-induced NOD2 expression is directly dependent on NF-κB signaling, and NOD2 is a negative regulator of complex, organic dust-induced inflammatory cytokine/chemokine production in mononuclear phagocytes.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Agriculture
  • Animals
  • Dust*
  • Humans
  • Inflammation
  • Interleukin-6 / biosynthesis
  • Interleukin-8 / biosynthesis
  • Macrophages, Alveolar / metabolism*
  • Mice
  • Monocytes / metabolism*
  • NF-kappa B / physiology*
  • Nod2 Signaling Adaptor Protein / biosynthesis*
  • RNA, Small Interfering / pharmacology
  • Swine
  • Tumor Necrosis Factor-alpha / antagonists & inhibitors

Substances

  • CXCL8 protein, human
  • Dust
  • IL6 protein, human
  • Interleukin-6
  • Interleukin-8
  • NF-kappa B
  • Nod2 Signaling Adaptor Protein
  • RNA, Small Interfering
  • Tumor Necrosis Factor-alpha