Locally administered prostaglandin E2 prevents aeroallergen-induced airway sensitization in mice through immunomodulatory mechanisms.

Prostaglandin E2 attenuates airway pathology in asthmatic patients and exerts a protective effect in antigen-sensitized mice when administered systemically. We aimed to establish the consequences of intranasal PGE2 administration on airway reactivity to aeroallergens in mice and reveal the underlying immunoinflammatory mechanisms. PGE2 was administered either daily during a 10-day exposure to house dust mite (HDM) extracts or for limited intervals. Airway hyperreactivity was measured by whole-body and invasive plethysmography. The phenotypes of lung immune cells and cytokine production were analysed by flow cytometry and ELISA, respectively. Airway hyperreactivity was sustainably reduced only when PGE2 administration was restricted to the initial 5 days of exposure to HDM. Lung inflammation, IL-4 production, and airway mast cell activity were also prevented under this early short-term treatment with PGE2. Interestingly, a Th2 response was already committed on day 5 of exposure to HDM. This was paralleled by GM-CSF and osteopontin upregulation and a decreased number of plasmacytoid dendritic and T regulatory cells, as well as a trend towards reduced IL-10 expression. Local PGE2 administration prevented the increase of airway IL-13 and osteopontin and kept lung plasmacytoid dendritic cell counts close to baseline. GM-CSF and Tregs were unaffected by the treatment. These findings suggest that the protection provided by PGE2 is a result of the modulation of early lung immunomodulatory mechanisms, and possibly a shift in the balance of dendritic cells towards a tolerogenic profile.