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

BackgroundTraffic-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.ObjectiveWe sought to determine the expression, function, and regulation of pathways involved in promotion of allergic airway inflammation by PM.MethodsWe used gene expression transcriptional profiling, in vitro culture assays, and in vivo murine models of allergic airway inflammation.ResultsWe 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.ConclusionPM activates an AhR-Jag1-Notch cascade to promote allergic airway inflammation in concert with proasthmatic alleles.