DataSheet1_Bacteroides dorei BDX-01 alleviates DSS-induced experimental colitis in mice by regulating intestinal bile salt hydrolase activity and the FXR-NLRP3 signaling pathway.docx

Background: The relationships among intestinal dysbiosis, bile acid (BA) metabolism disorders, and ulcerative colitis pathogenesis are now recognized. However, how specific strains regulate BA metabolism to alleviate colitis is still unclear. This study investigated the effects of Bacteroides dorei on the development of acute colitis and elucidated the underlying mechanisms.Methods: The safety of BDX-01 was evaluated in vitro and in vivo. 2.5% dextran sulfate sodium (DSS) induced colitis in C57BL/6 mice, Caco-2, and J774A.1 cells were used to evaluate the anti-inflammatory effect of BDX-01. qPCR and Western blotting were used to detect the expression of inflammatory pathways. Microbiota composition was analyzed by 16S rRNA gene sequencing. Enzyme activity analysis and targeted metabolomics were used to analyze fecal bile salt hydrolase (BSH) and BA levels. Antibiotic-induced pseudo-germ-free mice were used to investigate the role of gut microbiota in the alleviation of colitis by BDX-01.Results: We confirmed the safety of novel strain Bacteroides dorei BDX-01 in vitro and in vivo. Oral BDX-01 administration significantly ameliorated the symptoms and pathological damage of DSS-induced acute colitis. Moreoever, 16S rRNA sequencing and enzyme activity analysis showed that BDX-01 treatment increased intestinal BSH activity and the abundance of bacteria harboring this enzyme. Targeted metabolomics revealed that BDX-01 significantly increased intestinal BA excretion and deconjugation. Certain BAs act as FXR agonists. The β-muricholic acid (βMCA): taurine β-muricholic acid (T-βMCA) and cholic acid (CA): taurocholic acid (TCA) ratios and the deoxycholic acid (DCA) level decreased markedly in the colitis models but increased substantially in BDX-01-treated mice. The colonic farnesoid X receptor (FXR) and fibroblast growth factor 15 (FGF15) were upregulated in mice treated with BDX-01. BDX-01 downregulated the expression of colonic proinflammatory cytokines pyrin domain-containing 3 (NLRP3), ASC, cleaved caspase-1, and IL-1β. Antibiotic treatment didn’t abolish the protective effect of BDX-01 on colitis. In vitro studies showed TβMCA abolished the effects of BDX-01 on FXR activation and inhibition of the NLRP3 inflammasome activation.Conclusion: BDX-01 improved DSS-induced acute colitis by regulating intestinal BSH activity and the FXR-NLRP3 signaling pathway. Our findings indicate that BDX-01 is a promising probiotic to improve the management of ulcerative colitis.

背景：肠易位、胆汁酸（BA）代谢紊乱与溃疡性结肠炎的发病机制之间的关系已得到广泛认可。然而，特定菌株如何调节BA代谢以缓解结肠炎尚不明确。本研究旨在探讨Bacteroides dorei对急性结肠炎发展的影响，并阐明其潜在机制。方法：通过体外和体内实验评估了BDX-01的安全性。以2.5%的硫酸葡聚糖（DSS）诱导的结肠炎小鼠、Caco-2和J774A.1细胞作为模型，评估了BDX-01的抗炎作用。利用qPCR和Western blotting技术检测炎症通路的表达。通过16S rRNA基因测序分析菌群组成。酶活性分析和靶向代谢组学用于分析粪便中的胆盐水解酶（BSH）和BA水平。采用抗生素诱导的拟无菌小鼠模型研究肠道菌群在BDX-01缓解结肠炎中的作用。结果：我们证实了新型菌株Bacteroides dorei BDX-01在体外和体内的安全性。口服BDX-01显著改善了DSS诱导的急性结肠炎的症状和病理损伤。此外，16S rRNA测序和酶活性分析表明，BDX-01治疗增加了肠道BSH活性和携带该酶的细菌丰度。靶向代谢组学揭示了BDX-01显著增加了肠道BA的排泄和脱结合。某些BA作为FXR激动剂。在结肠炎模型中，β-穆鲁酸（βMCA）：牛磺酸β-穆鲁酸（T-βMCA）和胆酸（CA）：牛磺胆酸（TCA）的比例以及脱氧胆酸（DCA）水平显著下降，而在BDX-01处理的小鼠中则显著增加。BDX-01处理的小鼠结肠中的胆汁酸X受体（FXR）和成纤维细胞生长因子15（FGF15）表达上调。BDX-01下调了结肠中促炎细胞因子如NLRP3（pyrin domain-containing 3）、ASC、裂解的caspase-1和IL-1β的表达。抗生素治疗并未消除BDX-01对结肠炎的保护作用。体外研究表明，TβMCA消除了BDX-01对FXR激活和NLRP3炎症小体激活的抑制作用。结论：BDX-01通过调节肠道BSH活性和FXR-NLRP3信号通路改善了DSS诱导的急性结肠炎。我们的研究结果指出，BDX-01是一种有潜力的益生菌，有望改善溃疡性结肠炎的管理。