Modified Dachengqi Decoction ameliorates sepsis-induced lung injury via the gut microbiota-bile acid axis.

BACKGROUND: Sepsis-induced acute lung injury (SI-ALI) is associated with high mortality. The gut microbiota-bile acid axis plays a critical role in regulating host inflammatory responses; however, the mechanism of action of traditional Chinese medicine (TCM) compounds targeting this axis remains unclear. AIM: This study aimed to systematically evaluate the protective effects of Modified DaChengqi Decoction (MDD) against lipopolysaccharide (LPS)-induced SI-ALI and to elucidate its underlying mechanism in modulating inflammation and neutrophil extracellular traps (NETs) through the regulation of gut microbiota and bile acid metabolism. METHODS: An LPS-induced mouse model of SI-ALI was established. Mice were orally administered MDD, and 72-h survival rate, lung function, histopathology, and inflammatory cytokine levels were assessed. Fecal 16S rRNA sequencing and targeted bile acid metabolomics were combined to analyze changes in the microbiota and metabolites. Network pharmacology was employed to screen key targets, followed by experimental validation using Western blotting, immunohistochemistry, and ELISA to confirm candidate pathways. RESULTS: Compared with the model group, MDD significantly improved survival and lung function, alleviated pulmonary inflammation and vascular permeability. Microbiomic analysis revealed that MDD downregulated the abundance of Parabacteroides and Bacteroides. Targeted metabolomics showed that MDD markedly altered the levels of several primary and secondary bile acids, mainly including glycoursodeoxycholic acid (GUDCA), taurochenodesoxycholic acid (TCDCA), chenodeoxycholic acid (CDCA), and taurocholic acid (TCA). Molecular validation demonstrated that the nuclear receptor FXR was significantly upregulated, while the TLR4 and downstream MYD88-NF-κB/JNK signaling pathways were inhibited. Additionally, the expression of PAD4 and CitH3 as well as NETs formation were reduced. CONCLUSION: MDD can alleviate LPS-induced SI-ALI by modulating the gut microbiota-bile acid metabolism, activating FXR, and thereby suppressing the TLR4/MYD88-mediated inflammatory cascade and NETs generation.