title: Organic dust augments nucleotide-binding oligomerization domain expression via an NF-{kappa}B pathway to negatively regulate inflammatory responses.
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.
authors.affiliation: Pulmonary, Critical Care, Sleep & Allergy Division; Dept. of Medicine, Univ. of Nebraska Medical Center, 985300 The Nebraska Medical Center, Omaha, NE 68198-5300, USA. japoole@unmc.edu
authors.forename: Jill A
authors.initials: JA
authors.lastname: Poole
authors.forename: Tammy
authors.initials: T
authors.lastname: Kielian
authors.forename: Todd A
authors.initials: TA
authors.lastname: Wyatt
authors.forename: Angela M
authors.initials: AM
authors.lastname: Gleason
authors.forename: Jeremy
authors.initials: J
authors.lastname: Stone
authors.forename: Kelsey
authors.initials: K
authors.lastname: Palm
authors.forename: William W
authors.initials: WW
authors.lastname: West
authors.forename: Debra J
authors.initials: DJ
authors.lastname: Romberger
mesh_terms: D000383:Agriculture; D000818:Animals; D004391:Dust; D006801:Humans; D007249:Inflammation; D015850:Interleukin-6 / Q000096:biosynthesis; D016209:Interleukin-8 / Q000096:biosynthesis; D016676:Macrophages, Alveolar / Q000378:metabolism*; D051379:Mice; D009000:Monocytes / Q000378:metabolism*; D016328:NF-kappa B / Q000502:physiology*; D053473:Nod2 Signaling Adaptor Protein / Q000096:biosynthesis*; D034741:RNA, Small Interfering / Q000494:pharmacology; D013552:Swine; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors
chemical_list: C508606:CXCL8 protein, human; D004391:Dust; C508600:IL6 protein, human; D015850:Interleukin-6; D016209:Interleukin-8; D016328:NF-kappa B; D053473:Nod2 Signaling Adaptor Protein; D034741:RNA, Small Interfering; D014409:Tumor Necrosis Factor-alpha