A Jagged 1-Notch 4 molecular switch mediates airway inflammation induced by ultrafine particles

Exposure to traffic-related particulate matter promotes asthma and allergic diseases. However, the precise cellular and molecular mechanisms by which particulate matter exposure acts to mediate these effects remain unclear.

We sought to elucidate the cellular targets and signaling pathways critical for augmentation of allergic airway inflammation induced by ambient ultrafine particles (UFP).

We used in vitro cell-culture assays with lung-derived antigen-presenting cells and allergen-specific T cells and in vivo mouse models of allergic airway inflammation with myeloid lineage-specific gene deletions, cellular reconstitution approaches, and antibody inhibition studies.

We identified lung alveolar macrophages (AM) as the key cellular target of UFP in promoting airway inflammation. Aryl hydrocarbon receptor-dependent induction of Jagged 1 (Jag1) expression in AM was necessary and sufficient for augmentation of allergic airway inflammation by UFP. UFP promoted T_H2 and T_H17 cell differentiation of allergen-specific T cells in a Jag1- and Notch 4-dependent manner. Treatment of mice with an anti-Notch 4 antibody abrogated exacerbation of allergic airway inflammation induced by UFP.

UFP exacerbate allergic airway inflammation by promoting a Jag1-Notch 4-dependent interaction between AM and allergen-specific T cells, leading to augmented T_H cell differentiation.