伊立替康（CPT-11，卡姆拓萨）是治疗转移性结直肠癌的一线药物。CPT-11引起的腹泻与肠道中β-葡萄糖苷酶（β-GUS）和SN-38浓度密切相关，限制了其临床应用。因此，本研究采用了具有传统中药配方的小柴胡汤（XCHT）来减轻CPT-11引起的毒性反应。本研究首先探讨了XCHT缓解腹泻的机制，特别是与肠道微生物群落中的β-GUS有关的机制。首先，我们检测了肠道中促炎症细胞因子和抗炎症细胞因子的水平。此外，我们还利用16S rRNA高通量测序技术研究了CPT-11和XCHT处理小鼠肠道微生物群落的相对丰度。同时，我们检测了肠道中SN-38的水平和β-GUS的浓度。我们还利用X射线晶体学技术解析了来自肠道微生物群落的β-GUS的三维结构。此外，我们还使用虚拟筛选、SPR分析和酶活性测定确认了XCHT中的主要活性成分是否能够选择性地抑制β-GUS。在接受XCHT治疗的小鼠中，促炎症细胞因子的水平降低，抗炎症细胞因子的水平增加，并且有益的厚壁菌门和拟杆菌门在肠道微生物群落中的丰度得到改善。我们还发现，在联合应用XCHT和CPT-11后，肠道中β-GUS的浓度和导致腹泻的主要成分SN-38的水平明显降低。此外，我们揭示了来自不同肠道微生物群落的β-GUS的结构差异。最后，我们发现EcGUS与黄芩素具有良好的亲合力，并且能够被XCHT中的黄芩素选择性地抑制。综上所述，XCHT通过改善有益的肠道微生物群落和减少炎症反应来缓解CPT-11引起的迟发性腹泻。此外，根据三维结构，特别是黄芩素可以作为候选的EcGUS抑制剂来缓解CPT-11引起的腹泻。 版权所有 © 2023 Elsevier GmbH出版。

Irinotecan (CPT-11, Camptosar@) is a first-line drug for metastatic colorectal cancer. CPT-11-induced diarrhea, which is closely related to the concentrations of β-glucuronidase (β-GUS) and SN-38 in the gut, largely limits its clinical application.Herein, Xiao-Chai-Hu-Tang (XCHT), a traditional Chinese formula, was applied to mitigate CPT-11-induced toxicity. This study initially explored the mechanism by which XCHT alleviated diarrhea, especially for β-GUS from the gut microbiota.First, we examined the levels of the proinflammatory cytokines and the anti-inflammatory cytokines in the intestine. Furthermore, we researched the community abundances of the gut microbiota in the CPT-11 and XCHT-treated mice based on 16S rRNA high-throughput sequencing technology. Meanwhile, the level of SN-38 and the concentrations of β-GUS in intestine were examined. We also resolved the 3D structure of β-GUS from gut microbiota by X-ray crystallography technology. Moreover, we used virtual screening, SPR analysis, and enzyme activity assays to confirm whether the main active ingredients from XCHT could selectively inhibit β-GUS.In XCHT-treated mice, the levels of the proinflammatory cytokines decreased, the anti-inflammatory cytokines increased, and the community abundances of beneficial Firmicutes and Bacteroidota improved in the gut microbiota. We also found that the concentrations of β-GUS and the level of SN-38, the major ingredient that induces diarrhea in the gut, significantly decreased after coadministration of XCHT with CPT-11 in the intestine. Additionally, we revealed the structural differences of β-GUS from different gut microbiota. Finally, we found that EcGUS had good affinity with baicalein and meanwhile could be selectively inhibited by baicalein from XCHT.Overall, XCHT could relieve the delayed diarrhea induced by CPT-11 through improving the abundance of beneficial gut microbiota and reduced inflammation. Furthermore, based on the three-dimensional structure, baicalein, especially, could be used as a candidate EcGUS inhibitor to alleviate CPT-11-induced diarrhea.Copyright © 2023. Published by Elsevier GmbH.