Airborne PM2.5 from pig houses induces piglet respiratory epithelial barrier injury by activating the NLRP3 inflammasome through Drp1-mediated mitochondrial dysfunction

Airborne PM2.5 in pig houses contains diverse toxic substances and pathogenic microorganisms, which can induce respiratory inflammation and act as a major vector for disease transmission, posing a serious threat to swine health and productivity. The respiratory epithelial barrier serves as the first line of defense against environmental pollutants. This study employed a whole-body exposure model in piglets and primary tracheal epithelial cells from neonatal piglets (PTEC) to investigate the effects of PM2.5 on the respiratory epithelial barrier and its underlying mechanisms. PM2.5 exposure did not significantly influence growth performance or organ indices in piglets, but caused pronounced alveolar damage, inflammatory cell infiltration, goblet cell hyperplasia, and aggravated pulmonary fibrosis. These lesions were accompanied by decreased expression of tight junction proteins, increased apoptosis, and elevated proinflammatory cytokines. Further analyses revealed a dose-dependent upregulation of the NLRP3 inflammasome components and the mitochondrial fission protein Drp1 in lung tissues. In vitro, PM2.5 decreased PTEC viability and barrier integrity, evidenced by reduced transepithelial electrical resistance and increased FITC-dextran permeability. PM2.5 exposure also induced mitochondrial dysfunction, including elevated intracellular ROS levels, decreased mitochondrial membrane potential, and severe ultrastructural damage. Inhibition of NLRP3 alleviated PM2.5-induced barrier disruption and inflammation, while Drp1 inhibition suppressed NLRP3 activation, suggesting that Drp1-mediated mitochondrial dysfunction acts upstream of NLRP3 activation. Collectively, these findings demonstrate that pig-house PM2.5 compromises respiratory epithelial barrier structure and function by activating the NLRP3 inflammasome through Drp1-mediated mitochondrial dysfunction, providing novel insights and potential therapeutic targets for respiratory disorders associated with PM2.5 pollution in intensive livestock production systems.