Polysaccharide From Ficus pumila Alleviates Acute Lung Injury in Mice Through Regulating MAPK/NF‐ κ B Pathway and Gut Microbiota

Background Lihuabidouyan Tablet is a compound Chinese herb preparation used for the treatment of respiratory diseases. As the main active ingredient in it, Ficus pumila ( F . pumila ) contains polysaccharides that exert unique biological activity. In this study, polysaccharides in F . pumila were extracted and purified, and the protective effect and mechanism of action of F . pumila polysaccharide 1‐1 (FPP1‐1) in lipopolysaccharide (LPS)‐induced acute lung injury (ALI) mice were discussed. Methods BALB/c mice were randomly divided into control, model, dexamethasone (DEX), and FPP‐1‐1 groups (50, 100, and 200 mg/kg), and the drug was administered by gavage for one week. Hematoxylin–eosin staining (H&E) and wet/dry ratio were used to evaluate lung injury and pulmonary edema. The ELISA was used to detect inflammatory factors. qRT‐PCR was used to examine mRNA expression in tissues. Proteins related to inflammation were evaluated by western blotting. 16S rDNA sequencing was used to analyze the gut microbiota. Results FPP‐1‐1 significantly reduced lung injury in the ALI mice and significantly reduced levels of the proinflammatory factors interleukin (IL)‐6 and tumor necrosis (TNF)‐ α and promoted the anti‐inflammatory factor IL‐10 in bronchoalveolar lavage fluid. FPP‐1‐1 inhibited the expression of phospho‐ERK1/2, phospho‐P38, and phospho‐NF‐ κ B p65 proteins. FPP‐1‐1 also increased the diversity of the gut microbiota and increased the abundance of Lachnospiraceae in the ALI mice. Correlation analysis results showed that there was a significant correlation between the MAPK/NF‐ κ B pathway and inflammatory cytokines and gut microbiota in ALI mice. Conclusion The present study characterized the structure and molecular weight of a novel homogeneous polysaccharide, FPP‐1‐1, isolated from F. pumila . In addition, FPP‐1‐1 affected the expression of inflammatory factors by inhibiting the MAPK/NF‐ κ B pathway. FPP‐1‐1 also restored the diversity of gut microbiota and changed the relative abundance of key bacterial genera such as Lachnospiraceae and Alloprevotella , suggesting that the “gut–lung” axis may serve as a crucial pathway through which FPP‐1‐1 exerts its effect.