Polysaccharide From Ficus pumila Alleviates Acute Lung Injury in Mice Through Regulating MAPK/NF-κB 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.