Lung microbiota dysbiosis mediates PM_2.5-induced pulmonary inflammation through antibiotic-reversible mechanisms

Fine particulate matter (PM_2.5) exposure contributes to over 4 million premature deaths annually, yet the mechanistic role of lung microbiota in PM_2.5-induced pulmonary inflammation remains poorly understood. In collaboration of 16S rRNA and single-cell RNA multi-omics analysis and in vivo/in vitro experimental validation with antibiotic intervention strategies, the study here examined PM_2.5-microbiota interactions in murine PM_2.5 exposure models and cellular systems. It was found that PM_2.5 exposure induced lung microbiota dysbiosis characterized by Gram-negative bacterial expansion, particularly Proteobacteria dominance, accompanied by reduced microbial diversity. scRNA analysis revealed coordinated activation of TLR4/MyD88/NLRP3 inflammatory signaling pathways and p53/p21/p16-mediated cell cycle arrest. Moreover, PM_2.5 exposure activated NLRP3 inflammosome-dependent macrophage pyroptosis as evidenced by increased interleukin (IL)-1β, IL-18, caspase-1, and GSDMD expression. In vitro studies demonstrated that the inflammatory changes induced by PM_2.5 exposure were statistically indistinguishable from those of LPS-positive controls, confirming endotoxin-like mechanisms. Critically, antibiotic pretreatment effectively attenuated PM_2.5-induced inflammatory responses, cell cycle arrest, and tissue pathology, which established causality between microbiota disruption and pulmonary dysfunction. In conclusion, this study revealed lung microbiota dysbiosis as a critical mediator of PM_2.5-induced pulmonary inflammation through Gram-negative bacterial expansion and subsequent endotoxin-like activation of inflammatory cascades, thereby providing novel mechanistic insights and potential microbiome-targeted therapeutic strategies for air pollution-associated respiratory diseases.