Effects of Maxing Shigan Decoction on Pulmonary Microbiota and Metabolites in the Immunosuppressed Influenza Pneumonia Mouse Model

Objective This study investigates the microecological mechanisms of Maxing Shigan Decoction in treating influenza pneumonia through pulmonary Microbiomics and Metabolomics.Methods A total of 40 BALB/c mice were randomly divided into four groups: normal control (NC), model control (MO), Maxing Shigan Decoction (MA)and oseltamivir (AO). Except for the NC group, all mice received a single intraperitoneal injection of cyclophosphamide (80 mg/kg). After 24 hours, influenza virus was intranasally inoculated to establish an immunosuppressed influenza pneumonia model. The mice were then administered the corresponding drug or normal saline via gavage for five days. Body weight and lung index were measured, influenza viral load in lung tissues was detected using RT-qPCR, serum inflammatory cytokine levels were determined by ELISA, pulmonary microbiota composition was analyzed using 16S rRNA, and untargeted metabolomics analysis of lung tissue was performed using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS).Results Compared to the NC group, the MO group exhibited a significant decrease in body weight and a marked increase in lung index (P<0.001 or P<0.01), along with significantly elevated influenza viral load and increased expression of inflammatory cytokines (IL-1β, IL-6, TNF-α) in lung tissue (P<0.05 or P<0.01). Compared to the MO group, the MA group demonstrated a significant increase in body weight and a reduction in lung index (P<0.01 or P<0.05), as well as significantly lower influenza viral load and reduced expression of inflammatory cytokines (IL-6, TNF-α) (P<0.05).16S rRNA sequencing results showed that, compared to the NC group, the MO group had a significantly decreased abundance of Blautia and Ruminococcus (P<0.05), while the abundance of Streptococcus was significantly increased (P<0.05). Compared to the MO group, the MA group showed a significant increase in the abundance of Blautia and Ruminococcus (P<0.05), which were identified as potential biomarkers of MA. Lung metabolomics analysis identified 166 differential metabolites between the NC and MO groups, mainly affecting tricarboxylic acid (TCA) cycle. Compared to the MO group, the MA group significantly regulated 35 differential metabolites (P<0.05), including citric acid, trans-itaconic acid, L-malate, and 2-DG primarily affecting the citric acid cycle. Microbiota-metabolite correlation analysis revealed that the differential microbial taxa were significantly associated with metabolites involved in the TCA cycle.Conclusion Maxing Shigan Decoction may alleviate immune-inflammatory lung injury caused by influenza pneumonia by effectively modulating the pulmonary microecology, potentially through regulating Blautia, Ruminococcus, and metabolites associated with the TCA cycle.