ABSTRACT
ObjectiveTo explore the protective effect of polysaccharide from Inonotus obliquus （IOP） on lipopolysaccharide （LPS）-induced acute lung injury （ALI） in mice. MethodA total of 40 male C57BL/6 mice were randomly divided into normal group， model group， dexamethasone group， and high-dose and low-dose IOP groups， with eight mice in each group. The high-dose and low-dose IOP groups were administered intragastrically with IOP at 20 and 10 mg·kg-1， respectively. The normal group and the model group were intragastrically administered with normal saline in equal volumes， and the dexamethasone group was intraperitoneally injected with dexamethasone phosphate injection of 30 mg·kg-1 for 21 days. An ALI mouse model induced by LPS was constructed， and hematoxylin-eosin （HE） staining， immunofluorescence staining， and blood routine were used to detect pathological damage of lung tissue and blood cell content. Enzyme-linked immunosorbent assay （ELISA） and Real-time fluorescence quantitative polymerase chain reaction （Real-time PCR） were used to detect the expression levels of various inflammatory factors. Changes in gut microbiota and plasma differential metabolites in mice were detected using 16S rRNA sequencing and ultra-high performance liquid chromatography-quadrupole-time of flight tandem mass spectrometry （UPLC-Q-TOF-MS）. ResultCompared with the model group， the lung tissue lesions of ALI mice were significantly improved after IOP administration， and the spleen and thymus index were dramatically increased （P<0.05， P<0.01）. The ratio of wet-to-dry weight of lung tissue was sensibly decreased （P<0.05， P<0.01）， and the number of lymphocytes was substantially increased （P<0.05， P<0.01）. The number of neutrophils was markedly decreased （P<0.01）. The expression level of interleukin-6 （IL-6）， interleukin-8 （IL-8）， interleukin-1β （IL-1β）， nuclear factor-κB（NF-κB）， and nucleotide-binding oligomerization domain-like receptor 3 （NLRP3） decreased prominently （P<0.05， P<0.01） and the expression level of interleukin-10 （IL-10） increased memorably （P<0.01）. The 16S rRNA sequencing results show that IOP can regulate and improve intestinal microbial disorders. The UPLC-Q-TOF-MS results indicate that the treatment of ALI mice with IOP may involve pathways related to mitochondrial， sugar， and amino acid metabolism， such as nucleotide sugar metabolism， histidine metabolism， ubiquinone， and other terpenoid compound-quinone biosynthesis， as well as starch and sucrose metabolism. ConclusionThe improvement of lung tissue lesions and inflammatory response by IOP in ALI mice may be related to maintaining intestinal microbiota balance， regulating mitochondrial electron oxidation respiratory chain， as well as sugar and amino acid metabolism pathways， and affecting the production of related microbial metabolites and tricarboxylic acid cycle metabolites.