Bile acids play crucial roles in host physiology by acting both as detergents that aid in digestion and as signaling molecules that bind to host receptors. Gut bacterial bile salt hydrolase (BSH) enzymes perform the gateway reaction leading to the conversion of host-produced primary bile acids into bacterially modified secondary bile acids. Small molecule probes that target BSHs will help elucidate the causal roles of these metabolites in host physiology. We previously reported the development of a covalent BSH inhibitor with low gut permeability. Here, we build on our previous findings and describe the development of a second-generation gut-restricted BSH inhibitor with enhanced potency, reduced off-target effects, and durable in vivo efficacy. Structure–activity relationship (SAR) studies focused on the bile acid core identified a compound, AAA-10, containing a C3-sulfonated lithocholic acid scaffold and an alpha-fluoromethyl ketone warhead as a potent pan-BSH inhibitor. This compound inhibits BSH activity in mouse and human fecal slurry, bacterial cultures, and purified BSH proteins and displays reduced toxicity against mammalian cells compared to first generation compounds. Oral administration of AAA-10 to wild-type mice for 5 days resulted in a decrease in the abundance of the secondary bile acids deoxycholic acid (DCA) and lithocholic acid (LCA) in the mouse GI tract with low systemic exposure of AAA-10, demonstrating that AAA-10 is an effective tool for inhibiting BSH activity and modulating bile acid pool composition in vivo.

中文翻译：

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作为肠道细菌胆汁盐水解酶抑制剂的肠道限制性石胆酸类似物

胆汁酸作为帮助消化的去污剂和与宿主受体结合的信号分子，在宿主生理学中起着至关重要的作用。肠道细菌胆汁盐水解酶 (BSH) 酶执行网关反应，导致宿主产生的初级胆汁酸转化为细菌修饰的次级胆汁酸。针对 BSH 的小分子探针将有助于阐明这些代谢物在宿主生理学中的因果作用。我们之前报道了一种具有低肠道通透性的共价 BSH 抑制剂的开发。在这里，我们以我们之前的研究结果为基础，描述了第二代肠道限制性 BSH 抑制剂的开发，该抑制剂具有增强的效力、减少的脱靶效应和体内持久性功效。专注于胆汁酸核心的构效关系 (SAR) 研究确定了一种化合物 AAA-10，该化合物含有 C3-磺化石胆酸支架和 α-氟甲基酮弹头作为有效的泛 BSH 抑制剂。与第一代化合物相比，该化合物可抑制小鼠和人类粪便浆液、细菌培养物和纯化的 BSH 蛋白中的 BSH 活性，并显示出对哺乳动物细胞的毒性降低。向野生型小鼠口服 AAA-10 5 天导致小鼠胃肠道中二级胆汁酸脱氧胆酸 (DCA) 和石胆酸 (LCA) 的丰度降低，全身暴露 AAA-10 ，证明 AAA-10 是抑制 BSH 活性和调节体内胆汁酸池组成的有效工具。