The Gut Microbiome and Metabolomics Profiles of dust- exposed rats

Abstract Background Pneumoconiosis is a disease caused by long-term inhalation of mineral dust. Its retention in the lungs during occupational activities, mainly characterized as diffuse fibrosis of lung tissue, is the most serious and common occupational disease in China. At present, the treatments of silicosis is limited. Therefore, the disease characteristics and pathophysiological mechanisms of pneumoconiosis require further study. This study starts with Metabolomics, studies the types, quantities and changing laws of metabolites, and explores potential biomarkers to further understand pneumoconiosis and its pathogenesis. Methods: This study discussed the pathogenesis of pneumoconiosis from the perspective of intestinal flora. SPF male SD rats were selected as the experimental objects to explore the types, quantities and changes of metabolites after dust exposure of rats, so as to explore potential metabolic markers and metabolic pathways. We established the relationship between intestinal flora and silicosis by studying the flora and metabolism of dust-contaminated rats, in order to find changes of specific flora or metabolites in the process of silicosis and provide new experimental evidence for the early diagnosis of silicosis. In order to construct pneumoconiosis model, rats were divided into three groups. Eighteen rats were randomly divided into coal dust group (1 mL of coal dust suspension), silica group (1 mL of silica suspension) and control group (1 mL of sterile saline). After 8 weeks of dust exposure, blood, lung tissue and feces were collected, and the weight was recorded. The pathological changes of lung tissue in dust-exposed rats were evaluated by hematoxylin-eosin staining. The level of inflammatory factors (IL-6 and IL-11) in blood was used to evaluate the changes of pulmonary inflammation level in dust-exposed rats. The 16S rDNA gene sequencing and UHPLC-QTOFMS non-targeted metabolomics were used to analyze the differences of intestinal flora and fecal metabolites among different populations. Results After being exposed to dust for 8 w, the weights of rats in the silica group were significantly lower than that in the control group (P<0.05), and the weights of rats in the coal mine dust group had no significant change compared with that in the control group. The levels of inflammatory factors in each group were observed, and it was concluded that the expression levels of IL-6 and IL-11 in the serum of silica group and coal dust group were higher than those of control group (P<0.05). The results of pathological sections of lung tissues showed that the alveolar structure in the control group was normal and inflammatory reactions was rare. In the silicon dioxide group, the alveolar structure of the lung tissue was damaged, and the inflammatory reaction was intensified with the formation of silicon nodules. In the coal dust group, the lung tissue structure changed, and there were cell nodules formed by fibroblasts aggregation. The results of α diversity analysis showed that the Shannon index of intestinal flora in coal dust group was significantly lower than that in control group. Compared with the control group, the Simpson index in coal dust group was significantly increased. Simpson index decreased significantly in silica group, and there was no difference in ACE and Chao 1 index of intestinal flora among the three groups. β diversity analysis showed that there were significant differences in intestinal microbial communities between the coal mine dust group and the control group, and between the silicon dioxide group and the control group.The differential metabolites in feces of the three groups of rats were obtained from metabolomics analysis. Fold change>2; VIP>1; P<0.05 was the screening criteria. In the positive and negative mode, we screened eleven kinds of differential metabolites. Conclusion After dust exposure, the intestinal flora of the body was disordered, and the metabolic state changes obviously. Two potential metabolic markers were identified in coal mine dust group, which mainly participated in the metabolism of fructose and mannose. Nine potential metabolic markers were identified in silica group, which mainly involved in sphingolipid metabolism.