Effect of the S100A9/AMPK pathway on PM2.5-mediated mouse lung injury.

Objectives: Particulate matter 2.5 (PM2.5), particles with an aerodynamic diameter less than 2.5 µm, affect lung function and increase respiratory disease incidence and mortality rate. The molecular mechanism of lung injury and epithelial damage after PM2.5 exposure is not completely clear. Materials and Methods: Mouth-nose exposure of mice was performed with PM2.5 or neutral saline. Results: PM2.5 exposure in mice caused lung epithelial damage, alveolar wall thickening, and alveolar wall structure destruction. The 16S rRNA sequencing results suggested that the microecology structure of lung tissue was altered after PM2.5 exposure. Proteomic sequencing was performed to explore the underlying mechanism, and 71 differentially expressed proteins were identified. KEGG database analysis of the up-regulated differential proteins revealed regulatory networks, including fat digestion and absorption, the AMPK signaling pathway, and the PPAR signaling pathway. Moreover, PM2.5 exposure in mice increased the level of S100A9 and ROS, leading to reduction of the ATP level. To achieve a sufficient energy supply by increasing fatty acid transfer and oxidation, activated AMPK up-regulates CD36 and CPT1, which leads to mitochondrial damage of PM2.5-exposed cells and injury or death of lung epithelial cells. siRNA-S100A9 and AMPK inhibitors significantly reduced the occurrence of cell damage. Conclusion: These results may help to clarify biomarkers and specific mechanisms of lung tissue injury induced by PM2.5 exposure.