Bile acids in intestinal homeostasis and allogeneic hematopoietic transplantation

项目摘要/摘要--项目2 胆汁酸(BA)是在肝脏中从胆固醇合成，与牛磺酸或甘氨酸结合，储存 在胆囊中，并释放到十二指肠作为对食物摄取的反应。在肠道中， 细菌胆盐水解酶(BSHS)对结合的初级BA的氨基酸去共轭作用 然后经过几次修饰，包括由厌氧细菌进行7次α-脱羟基，以产生 次要低音。虽然BAS的主要功能是促进肠道吸收和转运 饮食中的脂质，现在被认为也调节不同的生理过程。万古霉素- 耐药肠球菌(VRE)是引起患者血液感染的主要原因之一。 异基因造血细胞移植(allo-HCT)在包括美国在内的世界各地的医院 各州。接受allo-HCT患者的优势肠道定植可导致血流VRE 感染、高死亡率和医院内的病人间传播。值得注意的是，VRE可以是 通过粪便移植从肠道中根除，几个共生细菌物种已经被 显示可促进VRE的肠道清除。然而，成员通过的机制 微生物区系抑制VRE定植仍不清楚。了解VRE的调节机制 微生物群的定植以及VRE在allo-HCT中对肠道的影响，我们开发了一种 从人VRE株转导万古霉素耐药质粒至小鼠VRE模型 一株接合的小鼠粪肠球菌。在使用抗生素治疗后，小鼠VRE 在接受allo-HCT的患者中，在小鼠肠道中的累积水平与人类VRE相当。 利用小鼠VRE模型，我们已经确定了bas在VRE定植调控中的作用。 肠子。甘氨酸或牛磺酸偶联BA的去共轭是BA的关键限速步骤 由细菌BSH酶介导的代谢。我们已经鉴定出小鼠的共生菌 介导BA去共轭并促进共轭产物胆酸和DCA的合成 BAS与VRE抑制活性的产生相关。我们还发现， Allo-HCT后肠道原发和继发bas减少。越界假说 是特定BA加工菌、BA和宿主因素包括胆汁酸受体FXR调节 异基因造血干细胞移植后VRE定植与移植物抗宿主病(GVHD)的关系。为了解决这些假设， 我们提出了三个具体的目标来理解BA和BA诱导的信号在VRE中的作用 殖民和GVHD。

PROJECT SUMMARY/ABSTRACT – PROJECT 2 Bile acids (BAs) are synthesized in the liver from cholesterol, conjugated with taurine or glycine, stored in the gallbladder and released into the duodenum in response to food ingestion. In the intestine, conjugated primary BAs undergo amino acid deconjugation by bacterial bile salt hydrolases (BSHs) followed by several modifications including 7α-dehydroxylation by anaerobic bacteria to produce secondary BAs. Although a main function of BAs is to promote the intestinal absorption and transport of dietary lipids, it is now recognized that BAs also regulate diverse physiological processes. Vancomycin- resistant enterococcus (VRE) is one of the leading causes of bloodstream infection in patients undergoing allogeneic hematopoietic cell transplantation (allo-HCT) in hospitals around the world including the United States. Dominant intestinal colonization in patients undergoing allo-HCT can lead to bloodstream VRE infection, high mortality rates, and patient-to-patient transmission in hospitals. Notably, VRE can be eradicated from the intestine by fecal transplantation and several symbiotic bacterial species have been shown to promote VRE intestinal clearance. However, the mechanism by which members of the microbiota inhibit VRE colonization remains unknown. To understand the mechanism that regulates VRE colonization by the microbiota and how VRE affects the intestine during allo-HCT, we have developed a VRE model in the mouse by transferring a vancomycin-resistance plasmid from a human VRE strain to a mouse Enterococcus fecalis strain by conjugation. Upon treatment with antibiotics, mouse VRE accumulated in the mouse intestine to levels comparable to human VRE in patients undergoing allo-HCT. Using the mouse VRE model, we have identified a role for BAs in the regulation of VRE colonization in the intestine. Deconjugation of glycine or taurine-conjugated BAs is the key rate-limiting step in BA metabolism which is mediated by bacterial BSH enzymes. We have identified mouse symbiotic bacteria that mediate BA deconjugation and promote the production of cholic acid (CA) and DCA from conjugated BAs which correlates with the generation of VRE-inhibitory activity. We also found that the amounts of primary and secondary BAs in the intestine are decreased after allo-HCT. The overreaching hypothesis is that specific BA-processing bacteria, BAs and host factors including the bile acid receptor FXR regulate VRE colonization and graft-versus-host disease (GVHD) after allo-HCT. To address these hypotheses, we propose three specific Aims to understand the role of BAs and BA-induced signaling in VRE colonization and GVHD.