In depth study on the mechanism of Xiao-Chai-Hu-Tang in ameliorating irinotecan-induced intestinal toxicity and enhancing antitumor immunity via intestinal microbiota and fecal metabolomics.

Irinotecan (CPT-11) is a cornerstone chemotherapeutic for advanced colorectal cancer (CRC), but its clinical use is limited by dose-dependent gastrointestinal (GI) toxicity. Xiao-Chai-Hu-Tang (XCHT), a classical traditional Chinese medicine formula, alleviates CPT-11-induced adverse effects, yet its mechanism remains unclear. This study established a CPT-11-induced intestinal toxicity model in CRC rats, using multi-omics analyses (16S rRNA sequencing, fecal metabolomics, SCFA quantification) and an antibiotic depletion model to explore XCHT's mechanism via the gut microbiota-metabolite axis. XCHT significantly alleviated intestinal toxicity, reduced inflammation, and restored intestinal barrier integrity. It also enhanced antitumor immunity, as evidenced by an increased CD4⁺/CD8⁺ ratio and promoted Th1 polarization, and potentiated CPT-11's antitumor effects. XCHT alleviated CPT-11-induced dysbiosis of key bacterial genera and substantially restored the disturbed metabolome, with the restored metabolites primarily enriched in unsaturated fatty acid biosynthesis and linoleic acid metabolism. It also restored SCFA levels and upregulated colonic SCFA receptors/transporter. Correlation analysis revealed that these microbial and metabolic shifts were closely associated with the improvement of intestinal toxicity and antitumor immunity, and XCHT's protective effects depended on an intact gut microbiota. In conclusion, XCHT mitigates CPT-11-induced intestinal injury and enhances immunity by restoring gut microbiota balance and metabolic reprogramming, providing scientific evidence for its clinical use as a complementary therapy for CRC patients on CPT-11.