Chronic ozone exposure induces hippocampal microglia activation by microbial dysbiosis in rat lungs

Ozone (O₃) pollution has become a significant international public health issue with adverse effects on human health. Recent studies have confirmed that O₃ exposure induces neuroinflammation and cognitive dysfunction. It is hypothesized that O₃ exposure affects the pulmonary microbiome, triggering inflammatory responses that subsequently contribute to neuroinflammation. After 40 days of O₃ exposure in rats, distinct changes in the microbial community were identified using 16S rRNA gene sequencing. This was followed by an assessment of the impact of pulmonary microbiota on serum NETs (neutrophil extracellular traps). Additionally, changes in the hippocampal P2X4R/NLRP3 signaling pathway were investigated following O₃ exposure. In vitro experiments were conducted to evaluate the effects of O₃ on BV-2 cells. In vivo results indicated that O₃ exposure led to an increased abundance of Pseudomonas aeruginosa within the pulmonary microbiota and significantly increased NET levels in rat serum. O₃ exposure caused a loose arrangement of hippocampal neurons in rats, resulting in cell atrophy and even death. Compared to controls, O₃ exposure significantly upregulated the expression of P2X4R/NLRP3 and pro-inflammatory factors. Similarly, BV-2 cells treated with serum from 1.0 ppm O₃-exposed rats exhibited comparable changes. Treatment with a P2X4R inhibitor significantly reduced pathway protein and pro-inflammatory factors expression compared to O₃ serum intervention alone. In conclusion, O₃ exposure significantly alters the pulmonary microbiome, induces hippocampal damage, and NETs may act as a mediator between the lung and brain axes.