Environmentally persistent free radicals (EPFRs), generated during thermal combustion processes including hazardous waste remediation, are emerging redox-active pollutants linked to adverse respiratory outcomes. EPFR inhalation induces neutrophilic asthma characterized by substantial lung injury. Neutrophilic asthma is driven by T helper 17 (Th17) cells which secrete IL-17. We identified aryl hydrocarbon receptor (AHR) as a key mediator of EPFR-induced pulmonary Th17 responses. Building on this, we discovered that club cells, specialized airway epithelial cells, are a primary site of AHR activation following EPFR exposure. To dissect the specific role of AHR in club cells, we generated mice with a conditional deletion of Ahr in club cells ( Ahr ΔCC) by crossing Ahr fx mice Ahr tm3.1Bra /J strain with Scgb1a1-CreER TM mice B6N.129S6(Cg)- Scgb1a1 tm1(cre/ERT)Blh /J strain. Littermate (LM; Cre-negative Ahr fl/fl ) control and Ahr ΔCC mice were exposed to air or EPFRs via inhalation. Flow cytometry and immunofluorescence confirmed loss of AHR in club cells of Ahr ΔCC mice. As expected, EPFR-exposed LM mice exhibited a pronounced Th17-biased pulmonary immune response accompanied by increased neutrophils in the bronchoalveolar lavage fluid (BALF) compared to air-controls. In contrast, EPFR-exposed Ahr ΔCC mice failed to induce Th17 responses or neutrophilia. Supporting these findings, BALF analysis showed increased cytokines associated with Th17 signaling and neutrophil recruitment (IL-17, IL-6, IL-1β, KC/GRO) in EPFR-exposed LM mice but not in Ahr ΔCC mice. Histopathology revealed that EPFR exposure induced airspace enlargement, fibrosis, and mucus hyperproduction in LM mice, whereas Ahr ΔCC mice were protected. Pulmonary function testing further demonstrated increased airway hyperresponsiveness in EPFR-exposed LM mice which was attenuated in Ahr ΔCC mice. Collectively, these findings highlight a key epithelial-immune crosstalk in the lung triggered by EPFRs and suggest that AHR signaling in club cells is critical for mediating lung inflammation and functional decline following EPFR exposure. Targeting this pathway may offer a promising therapeutic strategy to prevent or reverse EPFR-induced lung injury. • Club cell AHR drives EPFR-induced Th17 responses, neutrophilic inflammation, and lung remodeling; its deletion prevents these immunopathological changes. • Male mice showed a trend toward greater susceptibility to EPFR-induced Th17 responses and airway hyperresponsiveness driven by club cell AHR, suggesting potential sex-specific effects in pollutant-induced lung injury. • This study reveals a novel epithelial-immune axis linking pollutant sensing to Th17-mediated lung injury.
Pathak et al. (Sun,) studied this question.
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