Abstract: Objective　To explore the role of Keap1-Nrf2/ARE signaling pathway in fecal microbiota transplantation (FMT) intervention in endotoxin-induced acute lung injury (ALI) in rats. Methods　Fifteen adult healthy male SD rats were randomly divided into control group (NS) , model group (LPS) and FMT group with 5 in each group. LPS group and FMT group were intraperitoneally injected with lipopolysaccharide (LPS) to build the model of ALI, and NS group was injected with the same volume of normal saline. After 24 h of modeling, self-made fecal fluid (10 mL/kg) was given to the FMT group (twice a day for 2 days), while the NS group and the LPS group were given the same volume of normal saline. After 24 h of the last FMT intervention, samples of celiac arterial blood, lung tissue and fresh fecal specimens were collected from each group. The lung wet/dry weight ratio (W/D), the arterial blood oxygen partial pressure［p(O)2］in celiac arterial blood, and the content of superoxide dismutase (SOD), malondialdehyde (MDA), protein carbonyl (PCO) in serum were measured by enzyme-linked immunosorbent (ELISA) method. Fresh fecal specimens were used for high-throughput sequencing of intestinal flora. HE staining was used to observe the changes of lung tissue and pathological score. Immunohistochemical detection was used for the nuclear factor-erythroid 2 related factor 2 (Nrf2) expression in lung tissue. Western blot assay was used to detect the expression of Keap1-Nrf2/ARE pathway related proteins. Results　Compared with NS group, the lung W/D and lung histopathological score were increased in LPS group, and p(O) 2 was decreased. At the same time, the serum content of SOD were lower in LPS group than that of NS group, while the serum levels of MDA and PCO and the expression levels of Nrf2, heme oxygenase-1 (HO-1) protein in lung tissue were increased in LPS group than those of NS group (all P＜0.05). Following treatment with FMT, the lung W/D and lung histopathological score decreased and p(O)2 increased in LPS group than those of FMT group, which accompanied by the increased content of SOD and the decreased levels of MDA and PCO. Notably, the expression levels of Nrf2 and HO-1 in lung tissue were significantly increased following the treatment with FMT (all P＜0.05). Compared with NS group and FMT group, the Beta diversity of the intestinal flora was different in LPS group, in which the Lactobacillaceae and Peptostreptococcaceae decreased and the Porphyromonadaceae increased significantly. Alpha diversity and Beta diversity of intestinal flora were similar in NS group and LPS group. Conclusion　FMT might attenuate LPS-induced lung injury in rats by regulating the intestinal flora acting on Keap1-Nrf2/ARE signal pathway, enhancing anti-oxidative stress response and reducing oxidative damage-related products.

Key words: acute lung injury, fecal microbiota transplantation, NF-E2-related factor 2, oxidative stress