Alterations and associations between lung microbiota and metabolite profiles in silica-induced lung injury

Silicosis, caused by silica exposure, is the most widespread and deadliest occupational disease. However, effective treatments are lacking. Therefore, it is crucial to elucidate the mechanisms and targets involved in the development of silicosis. We investigated the basic processes of silicosis development and onset at different exposure durations (2 or 4 weeks) using various techniques such as histopathology, immunohistochemistry, Enzyme linked immunosorbent assay(ELISA),16 S rRNA, and untargeted metabolomics.These results indicate that exposure to silica leads to progressive damage to lung tissue with significant deterioration observed over time. Time-dependent cytokines such as the IL-4, IL-13, and IL-6 are detected in lung lavage fluid, the model group consistently exhibited elevated levels of these cytokines, indicating a persistent and worsening inflammatory response in the lungs. Meanwhile, HE and Masson results show that 4-week exposure to silica causes more obvious lung injury and pulmonary fibrosis. Besides, the model group consistently exhibited a distinct lung bacterial population, known as the Lachnospiraceae_NK4A136_group, regardless of exposure duration. However, with increasing exposure duration, specific temporal changes were observed in lung bacterial populations, including Haliangium, Allobaculum, and Sandaracinus (at 4 weeks; p < 0.05). Furthermore, our study revealed a strong correlation between the mechanism of silica-induced lung injury and three factors: oxidative stress, impaired lipid metabolism, and imbalanced amino acid metabolism. We observed a close correlation between cytokine levels, changes in lung microbiota, and metabolic disturbances during various exposure periods. These findings propose that a possible mechanism of silica-induced lung injury involves the interplay of cytokines, lung microbiota, and metabolites.