Vehicular exhaust particles promote allergic airway inflammation through an aryl hydrocarbon receptor-notch signaling cascade

Abstract

Background: Traffic-related particulate matter (PM) has been linked to a heightened incidence of asthma and allergic diseases. However, the molecular mechanisms by which PM exposure promotes allergic diseases remain elusive.

Objective: We sought to determine the expression, function, and regulation of pathways involved in promotion of allergic airway inflammation by PM.

Methods: We used gene expression transcriptional profiling, in vitro culture assays, and in vivo murine models of allergic airway inflammation.

Results: We identified components of the Notch pathway, most notably Jagged 1 (Jag1), as targets of PM induction in human monocytes and murine dendritic cells. PM, especially ultrafine particles, upregulated TH cytokine levels, IgE production, and allergic airway inflammation in mice in a Jag1- and Notch-dependent manner, especially in the context of the proasthmatic IL-4 receptor allele Il4raR576. PM-induced Jag1 expression was mediated by the aryl hydrocarbon receptor (AhR), which bound to and activated AhR response elements in the Jag1 promoter. Pharmacologic antagonism of AhR or its lineage-specific deletion in CD11c(+) cells abrogated the augmentation of airway inflammation by PM.

Conclusion: PM activates an AhR-Jag1-Notch cascade to promote allergic airway inflammation in concert with proasthmatic alleles.

Keywords: Jagged 1; Notch; Traffic-related particulate matter; airway hyperresponsiveness; allergic airway inflammation; aryl hydrocarbon receptor; asthma; diesel exhaust particles; ultrafine particles.