Iijima, Koji

Allergens from the fungus Alternaria alternata promote secretion of alarmins from the airway epithelium including ATP, IL-33 and both genomic and mitochondrial DNA fragments, which produce type 2 immune responses in airways. Alternaria -induced oxidative stress activates ATP release by opening apical voltage-dependent anion channels (VDAC-1) and stimulating exocytosis of ATP. This investigation demonstrated that treatment of human bronchial epithelial (hBE) cells with a selective peptide antagonist or small molecule inhibitor (FPS-ZM 1 ) of the receptor for advanced glycation end products (RAGE), reduced Alternaria -evoked ATP secretion, decreasing the initial rate by ~40%. Furthermore, the Alternaria -induced increase in intracellular Ca 2+ concentration ([Ca 2+ ] i ) was inhibited by ~75% following pretreatment with RAGE antagonist peptide. Intranasal administration of Alternaria extract (50 μg) produced a significant increase in IL-33 secretion into bronchoalveolar lavage (BAL) fluid, which was inhibited in RAGE-deficient ( Ager -/- ) mice. Moreover, Alternaria -induced increases in IL-5 and IL-13 secretion into BAL fluid were also significantly reduced in Ager -/- mice. These findings support the conclusion that Alternaria -dependent ATP release and Ca 2+ mobilization was dependent in part on RAGE activation and that RAGE antagonists have the potential of reducing type 2 immune responses in airways following Alternaria allergen exposure. This study was supported by grants from the NIH (R01A1128729 & 1R01AI169530) to HK and SMO and by the Minnesota Agricultural Experiment station grant (AES0016134) to SMO. This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.

Abstract The objective of this study was to test the hypothesis that the increasing global incidence of allergy and atopy are due in part to improved hygiene and decreased microbial exposure. We have adopted a novel mouse model of normalized microbial exposure to test the impact of immune experience on subsequent responses to airway allergens. In this model, specific pathogen free (SPF) B6 mice are cohoused with mice from pet stores and become “dirty” – many commensals and pathogens are transmitted through cohousing and influence the immune cell populations systemically and in the lungs. We treated mice intranasally with a single dose of A. alternata fungal extract (Alt) and assessed production of type 2 cytokines. IL5 and IL13 levels in the lungs and bronchoalveolar lavage fluid were dramatically elevated by Alt in SPF mice but were not significantly increased by Alt in dirty mice. Type 2 innate lymphoid cells (ILC2) are the cells responsible for IL5 and IL13 after acute Alt treatment, and interestingly the number of lung ILC2 was unaltered by cohousing and their activation status appeared similar in both housing conditions. We treated mice with recombinant IL33, the alarmin released by lung epithelial cells in response to allergens, and the results suggest an impaired response to IL33 by dirty lung ILC2. In a repeated Alt exposure model, ILC2 cells expanded in SPF lungs and recruited eosinophils, neutrophils, and T cells. Most dirty mouse lungs contained these cell populations at steady state but were only modestly recruited with repeated Alt exposure. Lung function experiments are in progress. This study suggests that increased microbial exposure leads to more type-2 associated immune cells in the lungs, however responses to airway allergens are dampened.