Study On The Mechanism Of Pulmonary Inflammation Due To Ozone Exposure-induced Disruption Of Lung Flora

Studies have shown that ozone exposure is associated with an increased risk of respiratory disease and mortality.Imbalance in lung flora homeostasis has a potential regulatory role on host immune response and inflammation.However,studies on the effects of O₃（ozone）on lung immune defence and its mechanisms of interaction with the microflora have been rarely reported.In this study,we developed a mouse O₃ inhalation exposure model to characterize the dynamic changes of O₃ on lung flora and its response mechanism;to identify the pathways through which O₃ induces inflammatory health outcomes in the lung through lung flora disorders,and to investigate the toxicological mechanisms affecting lung health in mice.（1）The alveolar lavage fluid of mice was extracted and sequenced with 16S rRNA in this study.The results showed that the diversity of the flora increased significantly and the species richness decreased significantly after O₃ exposure;the community structure of the flora showed significant differences as the duration of O₃ exposure increased.In addition,O₃ exposure altered the composition of the lung flora in mice,resulting in the succession of dominant genera.Analysis of the major pathogens revealed a significant reduction in abundance and a turnover of the major pathogens after O₃ exposure.Phenotypic and functional predictions revealed a significant decrease in the phenotype of pathogenic and parthenogenic anaerobic bacteria and an increase in the phenotype of the anaerobic flora;the proportion of Staphylococcus aureus infections in mice was reduced as a function.Co-occurrence network analysis indicated a decrease in the stability of the lung flora network after O₃ exposure and a weakened resistance to changes in the lung microenvironment,which may increase health risks.（2）In this study,lung tissues from mice were taken to examine the effects of O₃ exposure on lung pathology,inflammatory damage and neutrophil-related indices in mice.The results showed that O₃ exposure slowed body weight gain,increased lung-to-body ratio and led to inflammatory cell infiltration and fibrillar collagen deposition in lung tissue.PCR showed that mRNA levels of the inflammatory factors IL-1βand TNF-αtended to increase after exposure.After O₃ exposure stimulated inflammatory injury in the lung,monocytes and epithelial cells released neutrophil chemokines（GM-CSF,CXCL1 and CXCL2）,which activated neutrophils and mediated neutrophil migration;subsequently pro-inflammatory and neutrophil recruitment factors（IL-6,IL-8 and LTB4）promoted neutrophil production in the bone marrow and neutrophil recruitment and accumulation to the site of lung injury,triggering an innate immune response.Large numbers of aggregated mature neutrophils form NETs and release MPO,which induce increased mucus secretion from lung tissue and disrupt alveolar structures,further worsening and amplifying neutrophil inflammation.Increased levels of pro-inflammatory factors promote the development and expression of Th17 cells;Th17 cells secrete cytokines and induce the expression of neutrophil chemokines,which recruit more neutrophils to the site of inflammation,and a vicious cycle of lung injury and inflammation occurs.Our further analysis revealed a strong correlation between both mucin and neutrophil chemotaxis and recruitment-related factors and pathogenic bacteria,suggesting that alterations in lung microbes may lead to impaired host defences through pathological crosstalk with the immune system.In conclusion,this study combined the analysis of lung flora changes and immune response indicators after O₃ exposure to elucidate the possible mechanisms by which O₃exposure disturbs lung microecology and triggers lung inflammation in mice.The results of this study provide a scientific basis for understanding the mechanisms of O₃ respiratory toxicity.