Ozone Exposure Induces Pulmonary Microbiota Dysbiosis and Associated Inflammatory Responses in Mice

Ozone (O₃) is a prevalent environmental pollutant that can induce oxidative stress and respiratory epithelial injury. Dysregulation of pulmonary microbiota homeostasis plays an important role in the progression of lung damage and inflammatory responses. However, there remains a lack of systematic research on the effects of O₃ exposure on pulmonary microecology and its potential association with pulmonary inflammation. In this study, twenty-three SPF-grade C57BL/6N male mice (aged 6-7 weeks) were randomly divided into a filtered air control group (n = 11) and an O₃ exposure group (n = 12). Mice in the O₃ group underwent whole-body inhalation exposure to 1 ppm O₃ for 4 h daily over 8 consecutive weeks, while control mice were maintained under identical conditions with filtered air exposure. The 1 ppm concentration (equivalent to 0.2-0.3 ppm in humans) and 8-week daily 4 h exposure regimen was selected to model the 2-month summer high-O₃ season with typical afternoon O₃ peaks. The results showed that the O₃-exposed group exhibited marked inflammatory infiltrates in the lung, as well as significantly elevated macrophage inflammatory protein-2 (MIP-2) and tumor necrosis factor-alpha (TNF-α) in bronchoalveolar lavage fluids compared with controls. Pulmonary microbiota sequencing revealed that O₃ exposure significantly elevated the Shannon index of pulmonary microbiota in mice, and four differential genera including Deinococcus, Aerococcus, Enterococcus and Proteiniphilum were identified. Correlation analysis revealed that MIP-2 was significantly correlated with Aerococcus. In conclusion, the findings of this study suggest that exposure to O₃ induces inflammation and significant changes in the microbial composition of the lungs, which provides an experimental basis for further investigating mechanisms linking microbiota dysbiosis to lung injury triggered by ambient air pollutants.