Thymic Stromal Lymphopoietin Promotes Ozone-induced Inflammation in the Airway

Ozone is associated with induction of airway hyperresponsiveness (AHR) and neutrophilic airway inflammation which is the characteristic of type 2 low inflammatory phenotype. Recently, epithelial cell-derived cytokines such as thymic stromal lymphopoietin (TSLP) have been recognized as therapeutic targets for asthma with type 2 low inflammation, but the mechanisms remain unknown. In the present study, BALB/c mice and TSLP receptor-deficient mice were exposed to ozone at 2 ppm for 3 hours. AHR, cell counts, and cytokine analyses of bronchoalveolar lavage fluid (BALF) were examined. Single-cell RNA sequencing was performed to explore targeted cell clusters and genes. Batf3-deficient mice were analyzed to assess the effects of conventional type 1 dendritic cells (cDC1s), and treatment with NP-G2-044 was given to evaluate the impact of Fscn1 on ozone-induced airway responses. Ozone-exposed BALB/c mice showed greater AHR and neutrophils in BALF, with higher levels of TSLP in lungs than air-exposed BALB/c mice. Ozone-exposed TSLP receptor-deficient mice showed lower AHR and neutrophil counts in BALF than BALB/c mice. Single-cell RNA sequencing showed that DCs, especially cDC1s, were modified by ozone exposure and blockade of TSLP in terms of gene expressions including Fscn1. Ozone-exposed Batf3-deficient mice showed lower AHR and neutrophil counts in BALF, with depletion of cDC1s compared with C57BL/6J mice. Expression of Fscn1 was greater in bone marrow-derived cDC1s stimulated by TSLP, and ozone-exposed BALB/c mice treated with NP-G2-044 showed lower neutrophils in BALF than BALB/c mice treated with placebo. For conclusion, cDC1 derived Fscn1 was a potential target for ozone-induced neutrophilic airway inflammation via TSLP.