Effects and mechanism of fecal transplantation on acute lung injury induced by lipopolysaccharide in rats

To investigate the effect of fecal microbiota transplantation (FMT) on acute lung injury (ALI) induced by lipopolysaccharide (LPS) and its regulatory mechanism. Fifteen rats were divided into control group, LPS group and LPS+FMT group by random number table method. LPS group and LPS+FMT group were intraperitoneally injected with LPS to generate rat ALI model. After 24 h of modeling, feces (10 ml/kg) were given to the LPS+FMT group twice a day, and the control group and LPS group were given the same amount of normal saline. The intervention lasted for 2 days. After 24 h of the last fecal microbiota transplantation, arterial blood gas analysis was performed in each group. Then rats were sacrificed and enzyme-linked immunosorbent (ELISA) method was used to detect intercellular adhesion molecule 1 (ICAM-1) content in the serum and bronchoalveolar lavage fluid (BALF). The lung wet-dry weight ratio (W/D) was evaluated; HE staining and lung tissue pathology scoring, immunohistochemical detection of nuclear factor-kappa B (NF-κB) predominate nuclear expression and expression of ICAM-1 of alveolar epithelial cells were conducted; Western blot was used to detect the expression of proteins related to the intracellular phosphatidylinositol kinase (PI3K)/protein kinase (AKT) signaling pathway. Samples of rat feces were collected and DNA was extracted. Polymerase chain reaction (PCR) products of the V3 and V4 regions of the 16S ribosomal RNA gene (16SrDNA) were sequenced at high throughput, and bioinformatics analysis was conducted on the microbial community based on the operational classification unit. The lung W/D and lung histopathological score of the LPS group were significantly higher than those of the control group, while the arterial partial oxygen pressure (PaO(2)) of the LPS group was significantly lower than that of the control group [(79.2±5.89 vs 95.2±2.77) mmHg, 1 mmHg=0.133 kPa](all 0.05). The results of intestinal flora sequencing revealed that the diversity index of LPS group was significantly higher than that of the control group, while the lactobacillus of LPS group rats was significantly lower than that of the control group. The content of ICAM-1 in serum, BALF and its relative expression on the cell membrane in the LPS group was significantly higher than that in the control group [(8.64±0.87) vs (7.40±0.32) ng/L; (0.941±0.035) vs (0.739±0.079) ng/L; (0.250±0.010) vs (0.076±0.010)] (all 0.05). Moreover, the relative expression levels of phosphorylate