Thymic stromal lymphopoietin contributes to airway responses to ozone via dendritic cells

<bold>Background:</bold> Ozone induces airway hyper responsiveness (AHR), neutrophilic airway inflammation and thymic stromal lymphopoietin (TSLP) is important molecule in severe asthma. The purpose of the present study is to examine whether TSLP contributes to ozone-induced pulmonary responses and to clarify the mechanisms. <bold>Methods:</bold> WT and TSLPR-/- mice were exposed ozone at 2 ppm for 3 hours. AHR to methacholine and airway inflammation were assessed by inflammatory cell counts in bronchoalveolar lavage (BAL). Airway epithelial cell injury was examined by cytotoxicity in BAL and TSLP concentration in lung was examined by ELISA. Single cell RNA sequencing analysis of lung tissue was performed. Clodronate was treated to deplete dendritic cell and NP-G2-044 was administrated to inhibit fascin. <bold>Results:</bold> WT mice showed significantly increasing of AHR and neutrophils in BAL along with airway epithelial cell injury and elevation of TSLP concentration by ozone. In ozone-exposed mice, AHR and BAL neutrophils were significantly attenuated in TSLPR-/- mice (Figs. 1A,B). Single cell RNA sequencing indicated that gene expression levels such as <italic>fscn1</italic> in dendritic cells (DCs), especially conventional DC type 1 were altered by ozone exposure and blockade of TSLP signal (Figs. 1C,D). Partially depletion of dendritic cells by clodoronate attenuated ozone induced AHR and BAL neutrophils(Figs. 2A,B). Finally, NP-G2-044, inhibitor of fascin, a protein coding <italic>fscn1</italic> gene attenuated ozone induced BAL neutrophils(Fig. 2C). <bold>Conclusion:</bold> TSLP is crucial for ozone-induced AHR and neutrophilic airway inflammation via DCs. As the mechanisms, fascin derived from cDC1 is associated with neutrophilic airway inflammation (Fig 2D).