Bile Acid Profile and its Changes in Response to Cefoperazone Treatment in MR1 Deficient Mice

Abstract

Mucosal associated invariant T-cells (MAIT cells) are activated following recognition of bacterial antigens (riboflavin intermediates) presented on major histocompatibility complex class I-related molecule (MR1). Our previous study showed that MR1−/− knock-out (KO) mice (lacking MAIT cells) harbor a unique microbiota that is resistant to antibiotic disruption and Clostridioides difficile colonization. While we have characterized the microbiota of this mouse strain, changes in global metabolic activity in these KO mice have not been assessed. Here, LC/MS-based untargeted metabolomics was applied to investigate the differences in the metabolome, specifically in the bile acid (BA) profile of wild-type (WT) and MR1−/− KO mice, as well as how antibiotics change these profiles. BA changes were evaluated in the intestinal content, cecum content, and stool samples from MR1−/− mice and WT mice treated with cefoperazone (Cef). Fecal pellets were collected daily and both intestinal and cecal contents were harvested at predetermined endpoints on day 0 (D0), day 1 (D1), day 3 (D3), and day 5 (D5). KO mice exhibited no changes in 6-hydroxymethyl-8-D-ribityllumazine (rRL-6-CH2OH; an MR1-restricted riboflavin derivative) in the stool samples at either time point vs. D0, while WT mice showed significant decreases in rRL-6-CH2OH in the stool samples on all treatment days vs. D0. Metabolomics analysis from cecal and stool samples showed that KO mice had more total BA intensity (KO/WT = ~1.7 and ~3.3 fold higher) than that from WT mice prior to Cef treatment, while the fold change difference (KO/WT = ~4.5 and ~4.4 fold) increased after five days of Cef treatment. Both KO and WT mice showed decreases in total BA intensity in response to Cef treatment, however, less dramatic decreases were present in KO vs. WT mice. Increases in taurocholic acid (TCA) intensity and decreases in deoxycholic acid (DCA) intensity in the stool samples from WT mice were associated with the depletion of certain gut bacteria, which was consistent with the previously reported microbiome data. Furthermore, the non-detected TCA and relatively higher DCA intensity in the KO mice might be related to Clostridioides difficile infection resistance, although this needs further investigation.

Evaluating Cefoperazone-Induced Gut Metabolic Functional Changes in MR1-Deficient Mice

“…These were reflected by the intestinal metabolome changes, specifically, decreases in secondary bile acids, glucose, free fatty acids, and dipeptides, whereas increases in primary bile acids and sugar alcohols were also reported [ 15 ]. Our previous study showed similar results, where increases in primary bile acids and decreases in secondary bile acids were observed in mice after Cef administration [ 17 ]. Another study also showed that decreases in many host-gut microbiota co-metabolites (indole- and phenyl-containing metabolites, amino acids, vitamins, nucleotides, and bile acids) were observed in the urine from mice treated with penicillin (an antibiotic used to treat Gram-positive bacterial infections) [ 18 ].…”

Antibiotic perturbation of the murine gut microbiome introduces inter-individual susceptibility to arsenic

“…Antibiotics in general can indirectly impact host metabolism, immunity, the nervous system, and other key aspects of normal physiology through their influence on the diversity and function of microbial communities ( Clemente et al, 2012 ; Cryan et al, 2020 ; Rooks and Garrett, 2016 ; Tang et al, 2019 ). Cefoperazone has been well-studied in C57BL/6 J mice, where it decreases the abundance of bacterial taxa that numerically dominate the gut of untreated animals ( Firmicutes and Bacteroides ) ( Reeves et al, 2011 ); decreases the total bacterial load in the gut by ∼3 orders of magnitude ( Antonopoulos et al, 2009 ); significantly alters bile acid levels and composition ( Sun et al, 2020 ; Theriot et al, 2016 ); and opens niches for opportunistic pathogens like Clostridioides difficile ( Jenior et al, 2018 ) and Candida albicans ( Antonopoulos et al, 2009 ; Gutierrez et al, 2020 ). We hypothesized that the combination of gut microbiome perturbation and arsenic would be detrimental compared to mice treated with either antibiotic or arsenic alone, and while this was certainly the case, we did not necessarily expect to observe such interindividual variability in host response and outcome.…”

Taming the Sentinels: Microbiome-Derived Metabolites and Polarization of T Cells

“…Secondary bile acids can act in multiple ways as signaling molecules, through activation of the nuclear Farnesoid X receptor (FXR), vitamin D receptor, and through surface expressed GPCRs. The spectrum and distribution of gut bile acids and their derivatives depends, to a large extent, on the composition of the microbiome [ 121 ]. Engagement of these compounds in many physiological aspects has been appreciated for some time, but a role for bile acids as controllers of the Treg–Th17 axis has emerged only recently.…”