Intestinal probiotic Lactobacillus reuteri MLR1103 alleviates PM2.5-induced lung injury through inhibiting NLRP3 inflammasome activation

Fine particulate matter (PM2.5) is responsible for millions of deaths globally each year. We evaluated the impact of the human gut probiotic strain Lactobacillus reuteri MLR1103 on PM2.5-induced lung inflammation and injury. In mice, pre-colonization with MLR1103 protected the lungs from alveolar tissue remodeling under prolonged PM2.5 exposure and reduced infiltration of inflammation-related factors. In vitro, MLR1103 ferment (LRF) suppressed PM2.5-induced apoptosis and the expression of pro-inflammatory factors in mouse primary lung cells and alveolar macrophages. Nuclear magnetic resonance identified six metabolites in LRF, four of which were detected in the lungs of mice with gut-colonized MLR1103. Transcriptomic analysis suggested that MLR1103 inhibits NLRP3 inflammasome activation by downregulating the regulatory protein NEK7 and inflammasome component proteins, including Pro-caspase-1, ASC, and NLRP3, decreasing NLRP3 effector expression. This study suggests that MLR1103, as a functional probiotic, can protect against lung injury induced by air pollutants via modulating the gut–lung axis.