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Microbial Bile Acid Metabolites regulate Central Nervous System autoimmunity

ABSTRACT: the commensal gut microbiota modulates multiple sclerosis with unknown mechanisms. Commensal bacteria producing bile acid-deconjugating enzymes are fundamental to generate secondary bile acid metabolites (BAM) with immunoregulatory function. We show that immune regulatory BAM prevent autoimmunity in the central nervous system by inducing immune tolerance at the intestinal level and peripherally limiting effector function and aggressiveness of myelin-reactive T cells. We validated the key role of microbiota-induced BAM in humans by showing that relapsing-remitting multiple sclerosis patients have significantly reduced level of an important immune regulatory BAM (deoxycholic acid) and lower abundance of BAM-producing bacteria that correlate with increased percentages of peripheral effector Th17 cells. Our data indicate that the immune regulatory biliary network is crucial for the prevention of central nervous system autoimmunity.

ORGANISM(S): Homo sapiens

PROVIDER: GSE233771 | GEO | 2025/03/17

REPOSITORIES: GEO

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Project description:Commensal microbes are exposed to enterohepatically circulated steroids such as bile acids and hormones in the gastrointestinal, vaginal, and urinary tracts. Since commensal microbes are exposed to these molecules exclusively in association with their host, we hypothesized that they may serve as effectors to identify and characterize genetic pathways involved in the commensal-host relationship. Host specific and some ingested steroids (phytoestrogens) are enterohepatically circulated through the lumen of the small intestine. Bile acid steroids are present at high concentrations, approximating 4 to 20 mM in the duodenum, and are released in bile from the common bile duct. Steroid hormones are secreted in bile at levels approximating 6 to 13 mg per day once conjugated to glucuronide or sulfate by the liver. Re-absorption of steroids by the terminal ileum is an incomplete process: for example, 200 to 600 mg of bile acid steroids per day in humans escape to the colon where complex microbial populations exist. We have shown that steroid hormones estradiol, progesterone, and hydrocortisone serve as strong substrates for the major RND- and MFS-type (except hydrocortisone) tripartite multidrug efflux systems, AcrAB-TolC and EmrAB-TolC respectively, even though such molecules fail to demonstrate antimicrobial properties in this bacterial background (Elkins and Mullis [2006] J. Bacteriol. 188:1191-1195). Although bile acids are subject to efflux, they are also known to directly interact with intracellular global regulators such as MarR (Prouty et al. [2004] Microbiol. 150:775-783) and Rob (Rosenberg et al., [2003] Mol. Microbiol. 48:1609-1619) consequently altering antimicrobial and bile resistance profiles. In our present study, whole-genome DNA microarrays of E. coli were used to determine what general effect steroids, both bile acid and hormones, may have on the transcriptome in relation to the human commensal environment. Keywords: Comparative Chemical Class Treatment

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Microbial Bile Acid Metabolites regulate Central Nervous System autoimmunity

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