Endogenous Glucagon‐Like Peptide‐1 Receptor and Glucose‐Dependent Insulinotropic Polypeptide Receptor Signaling Inhibits Aeroallergen‐Induced Innate Airway Inflammation

ABSTRACT Background Anti‐inflammatory effects of incretin signaling through the glucagon‐like peptide‐1 receptor (GLP‐1R) and the glucose‐dependent insulinotropic polypeptide receptor (GIPR) in mice have been reported. Therefore, we hypothesized that signaling through the endogenous GLP‐1R and the GIPR individually decreases allergic airway inflammation and that the combination of GLP‐1R and GIPR signaling together additively inhibits allergen‐induced lung and airway inflammation. Methods WT (C57BL/6J), GLP‐1R knockout (KO), GIPR KO, and GLP‐1R/GIPR double KO (DKO) mice were challenged intranasally with Alternaria alternata extract (Alt‐Ext) or vehicle to evaluate the impact of signaling through these receptors on the innate allergen‐induced inflammatory response that is primarily driven by group 2 innate lymphoid cells (ILC2). Results Alt‐Ext‐induced IL‐33 release in the bronchoalveolar lavage fluid (BALF) was not different between the mouse strains, but thymic stromal lymphopoietin (TSLP) was significantly increased in GLP‐1R/GIPR DKO mice challenged with Alt‐Ext compared to the other strains. Furthermore, Alt‐Ext‐induced protein expression of IL‐5, IL‐13, CCL11, and CCL24 in the lung homogenates, the number of eosinophils, lymphocytes, and neutrophils in the BALF, and the number of lung GATA3+ ILC2 were significantly increased in GLP‐1R/GIPR DKO mice compared to the other 3 strains. Furthermore, ICAM‐1 expression on lung epithelial cells was increased in GLP‐1R/GIPR DKO mice challenged with Alt‐Ext compared to the other 3 strains. Conclusions Deficiency of both GLP‐1R and GIPR signaling together increased TSLP release, ILC2 activation, and early type 2 innate immune responses to aeroallergen exposure. Combined GLP‐1R and GIPR signaling should be explored for the treatment of asthma.