The Xenobiotic Transporter Mdr1 Enforces T Cell Homeostasis in the Presence of Intestinal Bile Acids.

CD4+ T cells are tightly regulated by microbiota in the intestine, but whether intestinal T cells interface with host-derived metabolites is less clear. Here, we show that CD4+ T effector (Teff) cells upregulated the xenobiotic transporter, Mdr1, in the ileum to maintain homeostasis in the presence of bile acids. Whereas wild-type Teff cells upregulated Mdr1 in the ileum, those lacking Mdr1 displayed mucosal dysfunction and induced Crohn's disease-like ileitis following transfer into Rag1-/- hosts. Mdr1 mitigated oxidative stress and enforced homeostasis in Teff cells exposed to conjugated bile acids (CBAs), a class of liver-derived emulsifying agents that actively circulate through the ileal mucosa. Blocking ileal CBA reabsorption in transferred Rag1-/- mice restored Mdr1-deficient Teff cell homeostasis and attenuated ileitis. Further, a subset of ileal Crohn's disease patients displayed MDR1 loss of function. Together, these results suggest that coordinated interaction between mucosal Teff cells and CBAs in the ileum regulate intestinal immune homeostasis.

Bile acid-sensitive human norovirus strains are susceptible to sphingosine-1-phosphate receptor 2 inhibition.

Human noroviruses (HuNoVs) are a diverse group of RNA viruses that cause endemic and pandemic acute viral gastroenteritis. Previously, we reported that many HuNoV strains require bile or bile acid (BA) to infect human jejunal intestinal enteroid cultures. BA was not essential for the replication of a pandemic-causing GII.4 HuNoV strain. We found the hydrophobic BA glycochenodeoxycholic acid (GCDCA) promotes the replication of the BA-dependent strain GII.3 in jejunal enteroids. Furthermore, we found that inhibition of the G-protein-coupled BA receptor, sphingosine-1-phosphate receptor 2 (S1PR2), by JTE-013, reduced GII.3 infection dose-dependently and inhibited GII.3 cellular uptake in enteroids. Herein, we sought to determine whether S1PR2 is required for other BA-dependent HuNoV strains, the BA-independent GII.4, and whether S1PR2 is required for BA-dependent HuNoV infection in HIEs from other small intestinal segments. We found a second S1PR2 inhibitor, GLPG2938, reduces GII.3 infection dose-dependently, and an S1PR2 agonist (CYM-5520) enhances GII.3 replication in the absence of GCDCA. GII.3 replication also is abrogated in the presence of JTE-013 and CYM-5520. JTE-013 inhibition of S1PR2 in jejunal HIEs reduces GI.1, GII.3, and GII.17 (BA-dependent) but not GII.4 Sydney (BA-independent) infection, providing additional evidence of strain-specific differences in HuNoV infection. Finally, GII.3 infection of duodenal, jejunal, and ileal lines derived from the same individual is reduced with S1PR2 inhibition, indicating a common mechanism of BA-dependent infection among multiple segments of the small intestine. Our results support a model where BA-dependent HuNoVs exploit BA effects on S1PR2 to infect the entire small intestine.IMPORTANCEHuman noroviruses (HuNoVs) are important viral human pathogens that cause both outbreaks and sporadic gastroenteritis. These viruses are diverse, and many strains are capable of infecting humans. Our previous studies have identified strain-specific requirements for hydrophobic bile acids (BAs) to infect intestinal epithelial cells. Moreover, we identified a BA receptor, sphingosine-1-phosphate receptor 2 (S1PR2), required for infection by a BA-dependent strain. To better understand how various HuNoV strains enter and infect the small intestine and the role of S1PR2 in HuNoV infection, we evaluated infection by additional HuNoV strains using an expanded repertoire of intestinal enteroid cell lines. We found that multiple BA-dependent strains, but not a BA-independent strain, all require S1PR2 for infection. In addition, BA-dependent infection requires S1PR2 in multiple segments of the small intestine. Together, these results indicate that S1PR2 has value as a potential therapeutic target for BA-dependent HuNoV infection.

Anti-infective bile acids bind and inactivate a Salmonella virulence regulator.

Bile acids are prominent host and microbiota metabolites that modulate host immunity and microbial pathogenesis. However, the mechanisms by which bile acids suppress microbial virulence are not clear. To identify the direct protein targets of bile acids in bacterial pathogens, we performed activity-guided chemical proteomic studies. In Salmonella enterica serovar Typhimurium, chenodeoxycholic acid (CDCA) most effectively inhibited the expression of virulence genes and invasion of epithelial cells and interacted with many proteins. Notably, we discovered that CDCA can directly bind and inhibit the function of HilD, an important transcriptional regulator of S. Typhimurium virulence and pathogenesis. Our characterization of bile acid-resistant HilD mutants in vitro and in S. Typhimurium infection models suggests that HilD is one of the key protein targets of anti-infective bile acids. This study highlights the utility of chemical proteomics to identify the direct protein targets of microbiota metabolites for mechanistic studies in bacterial pathogens.

Bile Acid Receptor Agonist Reverses Transforming Growth Factor-ß1-Mediated Fibrogenesis in Human Induced Pluripotent Stem Cells-Derived Kidney Organoids.

Chronic kidney disease progresses through the replacement of functional tissue compartments with fibrosis, a maladaptive repair process. Shifting kidney repair toward a physiologically intact architecture, rather than fibrosis, is key to blocking chronic kidney disease progression. Much research into the mechanisms of fibrosis is performed in rodent models with less attention to the human genetic context. Recently, human induced pluripotent stem cell (iPSC)-derived organoids have shown promise in overcoming the limitation. In this study, we developed a fibrosis model that uses human iPSC-based 3-dimensional renal organoids, in which exogenous transforming growth factor-ß1 (TGF-ß1) induced the production of extracellular matrix. TGF-ß1-treated organoids showed tubulocentric collagen 1α1 production by regulating downstream transcriptional regulators, Farnesoid X receptor, phosphorylated mothers against decapentaplegic homolog 3 (p-SMAD3), and transcriptional coactivator with PDZ-binding motif (TAZ). Increased nuclear TAZ expression was confirmed in the tubular epithelium in human kidney biopsies with tubular injury and early fibrosis. A dual bile acid receptor agonist (INT-767) increased Farnesoid X receptor and reduced p-SMAD3 and TAZ, attenuating TGF-ß1-induced fibrosis in kidney organoids. Finally, we show that TAZ interacted with TEA-domain transcription factors and p-SMAD3 with TAZ and TEA-domain transcription factor 4 coregulating collagen 1α1 gene transcription. In summary, we establish a novel, readily manipulable fibrogenesis model and posit a role for bile acid receptor agonism early in renal parenchymal fibrosis.

Human Sapovirus Replication in Human Intestinal Enteroids.

Human sapoviruses (HuSaVs), like human noroviruses (HuNoV), belong to the Caliciviridae family and cause acute gastroenteritis in humans. Since their discovery in 1976, numerous attempts to grow HuSaVs in vitro were unsuccessful until 2020, when these viruses were reported to replicate in a duodenal cancer cell-derived line. Physiological cellular models allowing viral replication are essential to investigate HuSaV biology and replication mechanisms such as genetic susceptibility, restriction factors, and immune responses to infection. In this study, we demonstrate replication of two HuSaV strains in human intestinal enteroids (HIEs) known to support the replication of HuNoV and other human enteric viruses. HuSaVs replicated in differentiated HIEs originating from jejunum, duodenum and ileum, but not from the colon, and bile acids were required. Between 2h and 3 to 6 days postinfection, viral RNA levels increased up from 0.5 to 1.8 log10-fold. Importantly, HuSaVs were able to replicate in HIEs independent of their secretor status and histo-blood group antigen expression. The HIE model supports HuSaV replication and allows a better understanding of host-pathogen mechanisms such as cellular tropism and mechanisms of viral replication. IMPORTANCE Human sapoviruses (HuSaVs) are a frequent but overlooked cause of acute gastroenteritis, especially in children. Little is known about this pathogen, whose successful in vitro cultivation was reported only recently, in a cancer cell-derived line. Here, we assessed the replication of HuSaV in human intestinal enteroids (HIEs), which are nontransformed cultures originally derived from human intestinal stem cells that can be grown in vitro and are known to allow the replication of other enteric viruses. Successful infection of HIEs with two strains belonging to different genotypes of the virus allowed discovery that the tropism of these HuSaVs is restricted to the small intestine, does not occur in the colon, and replication requires bile acid but is independent of the expression of histo-blood group antigens. Thus, HIEs represent a physiologically relevant model to further investigate HuSaV biology and a suitable platform for the future development of vaccines and antivirals.

Comparative analysis of proteomic adaptations in Enterococcus faecalis and Enterococcus faecium after long term bile acid exposure.

BACKGROUND: All gastrointestinal pathogens, including Enterococcus faecalis and Enterococcus faecium, undergo adaptation processes during colonization and infection. In this study, we investigated by data-independent acquisition mass spectrometry (DIA-MS) two crucial adaptations of these two Enterococcus species at the proteome level. Firstly, we examined the adjustments to cope with bile acid concentrations at 0.05% that the pathogens encounter during a potential gallbladder infection. Therefore, we chose the primary bile acids cholic acid (CA) and chenodeoxycholic acid (CDCA) as well as the secondary bile acid deoxycholic acid (DCA), as these are the most prominent bile acids. Secondly, we investigated the adaptations from an aerobic to a microaerophilic environment, as encountered after oral-fecal infection, in the absence and presence of deoxycholic acid (DCA). RESULTS: Our findings showed similarities, but also species-specific variations in the response to the different bile acids. Both Enterococcus species showed an IC50 in the range of 0.01- 0.023% for DCA and CDCA in growth experiments and both species were resistant towards 0.05% CA. DCA and CDCA had a strong effect on down-expression of proteins involved in translation, transcription and replication in E. faecalis (424 down-expressed proteins with DCA, 376 down-expressed proteins with CDCA) and in E. faecium (362 down-expressed proteins with DCA, 391 down-expressed proteins with CDCA). Proteins commonly significantly altered in their expression in all bile acid treated samples were identified for both species and represent a "general bile acid response". Among these, various subunits of a V-type ATPase, different ABC-transporters, multi-drug transporters and proteins related to cell wall biogenesis were up-expressed in both species and thus seem to play an essential role in bile acid resistance. Most of the differentially expressed proteins were also identified when E. faecalis was incubated with low levels of DCA at microaerophilic conditions instead of aerobic conditions, indicating that adaptations to bile acids and to a microaerophilic atmosphere can occur simultaneously. CONCLUSIONS: Overall, these findings provide a detailed insight into the proteomic stress response of two Enterococcus species and help to understand the resistance potential and the stress-coping mechanisms of these important gastrointestinal bacteria.

Melatonin improves cholestatic liver disease via the gut-liver axis.

Cholestatic liver disease is characterized by disturbances in the intestinal microbiota and excessive accumulation of toxic bile acids (BA) in the liver. Melatonin (MT) can improve liver diseases. However, the underlying mechanism remains unclear. This study aimed to explore the mechanism of MT on hepatic BA synthesis, liver injury, and fibrosis in 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC)-fed and Mdr2-/- mice. MT significantly improved hepatic injury and fibrosis with a significant decrease in hepatic BA accumulation in DDC-fed and Mdr2-/- mice. MT reprogramed gut microbiota and augmented fecal bile salt hydrolase activity, which was related to increasing intestinal BA deconjugation and fecal BA excretion in both DDC-fed and Mdr2-/- mice. MT significantly activated the intestinal farnesoid X receptor (FXR)/fibroblast growth factor 15 (FGF-15) axis and subsequently inhibited hepatic BA synthesis in DDC-fed and Mdr2-/- mice. MT failed to improve DDC-induced liver fibrosis and BA synthesis in antibiotic-treated mice. Furthermore, MT provided protection against DDC-induced liver injury and fibrosis in fecal microbiota transplantation mice. MT did not decrease liver injury and fibrosis in DDC-fed intestinal epithelial cell-specific FXR knockout mice, suggesting that the intestinal FXR mediated the anti-fibrosis effect of MT. In conclusion, MT ameliorates cholestatic liver diseases by remodeling gut microbiota and activating intestinal FXR/FGF-15 axis-mediated inhibition of hepatic BA synthesis and promotion of BA excretion in mice.

Bile salts and proinflammatory cytokines inhibit MCT1-mediated cellular uptake of butyrate and interfere with its antiproliferative properties.

Butyrate (BT) is important in the prevention and inhibition of colorectal cancer (CRC). Inflammatory bowel disease, a risk factor for CRC, is associated with higher levels of proinflammatory cytokines and bile acids. The aim of this work was to investigate the interaction of these compounds in inhibiting BT uptake by Caco-2 cells, as a mechanism contributing to the link between IBD and CRC. TNF-α, IFN-γ, chenodeoxycholic acid (CDCA) and deoxycholic acid (DCA) markedly reduce 14C-BT uptake. All these compounds appear to inhibit MCT1-mediated BT cellular uptake at a posttranscriptional level, and, because their effect is not additive, they are most probably inhibiting MCT1 by a similar mechanism. Correspondingly, the antiproliferative effect of BT (MCT1-dependent) and of the proinflammatory cytokines and CDCA were not additive. In contrast, the cytotoxic effect of BT (MCT1-independent) and of the proinflammatory cytokines and CDCA were additive. In conclusion, proinflammatory cytokines (TNF-α and IFN-γ) and bile acids (DCA and CDCA) inhibit MCT1-mediated BT cellular uptake. These proinflammatory cytokines and CDCA were found to interfere with the antiproliferative effect of BT, mediated by an inhibitory effect upon MCT1-mediated cellular uptake of BT.

Bovine milk osteopontin improved intestinal health of pregnant rats fed a high-fat diet through improving bile acid metabolism.

The main purpose of the current study was to investigate the ameliorative effects of bovine milk osteopontin (bmOPN) on the gut dysfunction of pregnant rats fed a high-fat diet (HFD). Bovine milk osteopontin was supplemented at a dose of 6 mg/kg body weight. Bovine milk osteopontin supplementation during pregnancy reduced colonic inflammation of HFD dams, and it also increased the colonic expression of ZO-1 and claudin-4 of HFD dams. Bovine milk osteopontin significantly enriched the relative abundance of Bacteroidetes, whereas it decreased Proteobacteria, Helicobacteraceae, and Desulfovibrionaceae in feces of HFD dams. The levels of isobutyric acid and pentanoic acid in the HFD + bmOPN group were higher than that of the HFD group. Functional predication analysis of microbial genomes revealed that bmOPN supplementation to HFD pregnancies changed 4 Kyoto Encyclopedia of Genes and Genomes pathways including bile acid biosynthesis. Further, bmOPN enriched hepatic taurochenodeoxycholic acid and tauroursodeoxycholic acid plus taurohyodeoxycholic acid in the gut of HFD maternal rats. Our findings suggested that bmOPN improved the gut health of HFD pregnant rats partially through modulating bile acid biosynthesis.

Bacteroides and related species: The keystone taxa of the human gut microbiota.

Microbial communities play a significant role in maintaining ecosystems in a healthy homeostasis. Presently, in the human gastrointestinal tract, there are certain taxonomic groups of importance, though there is no single species that plays a keystone role. Bacteroides spp. are known to be major players in the maintenance of eubiosis in the human gastrointestinal tract. Here we review the critical role that Bacteroides play in the human gut, their potential pathogenic role outside of the gut, and their various methods of adapting to the environment, with a focus on data for B. fragilis and B. thetaiotaomicron. Bacteroides are anaerobic non-sporing Gram negative organisms that are also resistant to bile acids, generally thriving in the gut and having a beneficial relationship with the host. While they are generally commensal organisms, some Bacteroides spp. can be opportunistic pathogens in scenarios of GI disease, trauma, cancer, or GI surgery, and cause infection, most commonly intra-abdominal infection. B. fragilis can develop antimicrobial resistance through multiple mechanisms in large part due to its plasticity and fluid genome. Bacteroidota (formerly, Bacteroidetes) have a very broad metabolic potential in the GI microbiota and can rapidly adapt their carbohydrate metabolism to the available nutrients. Gastrointestinal Bacteroidota species produce short-chain fatty acids such as succinate, acetate, butyrate, and occasionally propionate, as the major end-products, which have wide-ranging and many beneficial influences on the host. Bacteroidota, via bile acid metabolism, also play a role in in colonization-resistance of other organisms, including Clostridioides difficile, and maintenance of gut integrity.

Aspirin Caused Intestinal Damage through FXR and ET-1 Signaling Pathways.

Aspirin is a non-steroidal, anti-inflammatory drug often used long term. However, long-term or large doses will cause gastrointestinal adverse reactions. To explore the mechanism of intestinal damage, we used non-targeted metabolomics; farnesoid X receptor (FXR) knockout mice, which were compared with wild-type mice; FXR agonists obeticholic acid (OCA) and chenodeoxycholic acid (CDCA); and endothelin-producing inhibitor estradiol to explore the mechanisms of acute and chronic intestinal injuries induced by aspirin from the perspective of molecular biology. Changes were found in the bile acids taurocholate acid (TCA) and tauro-ß-muricholic acid (T-ß-MCA) in the duodenum, and we detected a significant inhibition of FXR target genes. After additional administration of the FXR agonists OCA and CDCA, duodenal villus damage and inflammation were effectively improved. The results in the FXR knockout mice and wild-type mice showed that the overexpression of endothelin 1 (ET-1) was independent of FXR regulation after aspirin exposure, whereas CDCA was able to restore the activation of ET-1, which was induced by aspirin in wild-type mice in an FXR-dependent manner. The inhibition of ET-1 production could also effectively protect against small bowel damage. Therefore, the study revealed the key roles of the FXR and ET-1 pathways in acute and chronic aspirin-induced intestinal injuries, as well as strategies on alleviating aspirin-induced gastrointestinal injury by activating FXR and inhibiting ET-1 overexpression.

Anti-Neuroinflammatory Effects of a Novel Bile Acid Derivative.

In the search for novel potent immunomodulatory nuclear factor-erythroid 2 related factor 2 (Nrf2) activators, a derivative of cholic bile acid, SB140, was synthesized. The synthesis of SB140 aimed to increase the electrophilic functionality of the compound, enhancing its ability to activate Nrf2. Effects of SB140 on microglial cells, myeloid-derived cells (MDC), and T cells were explored in the context of (central nervous system) CNS autoimmunity. SB140 potently activated Nrf2 signaling in MDC and microglia. It was efficient in reducing the ability of microglial cells to produce inflammatory nitric oxide, interleukin (IL)-6, and tumor necrosis factor (TNF). Also, SB140 reduced the proliferation of encephalitogenic T cells and the production of their effector cytokines: IL-17 and interferon (IFN)-γ. On the contrary, the effects of SB140 on anti-inflammatory IL-10 production in microglial and encephalitogenic T cells were limited or absent. These results show that SB140 is a potent Nrf2 activator, as well as an immunomodulatory compound. Thus, further research on the application of SB140 in the treatment of neuroinflammatory diseases is warranted. Animal models of multiple sclerosis and other inflammatory neurological disorders will be a suitable choice for such studies.

Exploring flagellar contributions to motility and virulence in Arcobacter butzleri.

Flagella is a well-known bacterial structure crucial for motility, which also plays pivotal roles in pathogenesis. Arcobacter butzleri, an enteropathogen, possesses a distinctive polar flagellum whose functional aspects remain largely unexplored. Upon investigating the factors influencing A. butzleri motility, we uncovered that environmental conditions like temperature, oxygen levels, and nutrient availability play a significant role. Furthermore, compounds that are found in human gut, such as short-chain fatty acids, mucins and bile salts, have a role in modulating the motility, and in turn, the pathogenicity of A. butzleri. Further investigation demonstrated that A. butzleri ΔflaA mutant showed a reduction in motility with a close to null average velocity, as well as a reduction on biofilm formation. In addition, compared with the wild-type, the ΔflaA mutant showed a decreased ability to invade Caco-2 cells and to adhere to mucins. Taken together, our findings support the role of environmental conditions and gut host associated compounds influencing key physiological aspects of the gastrointestinal pathogen A. butzleri, such as motility, and support the role of the flagellum on bacterial virulence.

The microbial-derived bile acid lithocholate and its epimers inhibit Clostridioides difficile growth and pathogenicity while sparing members of the gut microbiota.

Clostridioides difficile is a Gram-positive, spore-forming anaerobe that causes clinical diseases ranging from diarrhea and pseudomembranous colitis to toxic megacolon and death. C. difficile infection (CDI) is associated with antibiotic usage, which disrupts the indigenous gut microbiota and causes the loss of microbial-derived secondary bile acids that normally provide protection against C. difficile colonization. Previous work has shown that the secondary bile acid lithocholate (LCA) and its epimer isolithocholate (iLCA) have potent inhibitory activity against clinically relevant C. difficile strains. To further characterize the mechanisms by which LCA and its epimers iLCA and isoallolithocholate (iaLCA) inhibit C. difficile, we tested their minimum inhibitory concentration against C. difficile R20291 and a commensal gut microbiota panel. We also performed a series of experiments to determine the mechanism of action by which LCA and its epimers inhibit C. difficile through bacterial killing and effects on toxin expression and activity. Additionally, we tested the cytotoxicity of these bile acids through Caco-2 cell apoptosis and viability assays to gauge their effects on the host. Here, we show that the epimers iLCA and iaLCA strongly inhibit C. difficile growth in vitro while sparing most commensal Gram-negative gut microbes. We also show that iLCA and iaLCA have bactericidal activity against C. difficile, and these epimers cause significant bacterial membrane damage at subinhibitory concentrations. Finally, we observe that iLCA and iaLCA decrease the expression of the large cytotoxin tcdA, while LCA significantly reduces toxin activity. Although iLCA and iaLCA are both epimers of LCA, they have distinct mechanisms for inhibiting C. difficile. LCA epimers, iLCA and iaLCA, represent promising compounds that target C. difficile with minimal effects on members of the gut microbiota that are important for colonization resistance. IMPORTANCE In the search for a novel therapeutic that targets Clostridioides difficile, bile acids have become a viable solution. Epimers of bile acids are particularly attractive as they may provide protection against C. difficile while leaving the indigenous gut microbiota largely unaltered. This study shows that LCA epimers isolithocholate (iLCA) and LCA epimers isoallolithocholate (iaLCA) specifically are potent inhibitors of C. difficile, affecting key virulence factors including growth, toxin expression, and activity. As we move toward the use of bile acids as therapeutics, further work will be required to determine how best to deliver these bile acids to a target site within the host intestinal tract.

CsbD, a Novel Group B Streptococcal Stress Response Factor That Contributes to Bacterial Resistance against Environmental Bile Salts.

Group B Streptococcus (GBS) can cause many serious infections and result in severe symptoms depending on the infected organs. To survive and initiate infection from the gastrointestinal tract, GBS must resist physiochemical factors, such as bile salts, a potent antibacterial compound in the intestine. We found that GBS isolated from diverse sources all possess the capability to defend bile salts and permit survival. By constructing the GBS A909 transposon mutant library (A909Tn), we identified several candidate genes that might participate in the bile salt resistance of GBS. The rodA and csbD genes were validated as relevant to bile salt resistance. The rodA gene was anticipated to be related to peptidoglycan synthesis and influence the bile salt resistance of GBS by cell wall construction. Notably, we found that the csbD gene worked as a bile salt resistance response factor and influenced several ABC transporter genes, specifically at the later growth period of GBS under bile salt stress. We further detected the marked intracellular bile salt accumulation in ΔcsbD by hydrophilic interaction chromatography-liquid chromatography/mass spectrometry (HILIC-LC/MS). Collectively, we showed a novel GBS stress response factor, csbD, contributes to bacterial survival in bile salts by sensing bile salt stress and subsequently induces transcription of transporter genes to excrete bile salts. IMPORTANCE GBS, a conditional pathogenetic colonizer of the human intestinal flora, can cause severe infectious diseases in immunocompromised patients. Therefore, it is critical to understand the factors that contribute to the resistance to bile salts, which are abundant in the intestine but harmful to bacteria. We identified rodA and csbD genes involved in bile salt resistance using a transposon insertion site sequencing (TIS-seq) based screen. The rodA gene products might be involved in peptidoglycan synthesis as important contributors to stress resistance including bile salts. However, the csbD gene conferred bile salt resistance by promoting transporter genes transcription at the later growth period of GBS in response to bile salts. These findings developed a better understanding of the stress response factor csbD on the bile salt resistance of GBS.

Staphylococcus aureus FadB is a dehydrogenase that mediates cholate resistance and survival under human colonic conditions.

Staphylococcus aureus is a common colonizer of the human gut and in doing so it must be able to resist the actions of the host's innate defences. Bile salts are a class of molecules that possess potent antibacterial activity that control growth. Bacteria that colonize and survive in that niche must be able to resist the action of bile salts, but the mechanisms by which S. aureus does so are poorly understood. Here we show that FadB is a bile-induced oxidoreductase which mediates bile salt resistance and when heterologously expressed in Escherichia coli renders them resistant. Deletion of fadB attenuated survival of S. aureus in a model of the human distal colon.

Pregnane X receptor as a therapeutic target for cholestatic liver injury.

Cholestatic liver injury (CLI) is caused by toxic bile acids (BAs) accumulation in the liver and can lead to inflammation and liver fibrosis. The mechanisms underlying CLI development remain unclear, and this disease has no effective cure. However, regulating BA synthesis and homeostasis represents a promising therapeutic strategy for CLI treatment. Pregnane X receptor (PXR) plays an essential role in the metabolism of endobiotics and xenobiotics via the transcription of metabolic enzymes and transporters, which can ultimately modulate BA homeostasis and exert anticholestatic effects. Furthermore, recent studies have demonstrated that PXR exhibits antifibrotic and anti-inflammatory properties, providing novel insights into treating CLI. Meanwhile, several drugs have been identified as PXR agonists that improve CLI. Nevertheless, the precise role of PXR in CLI still needs to be fully understood. This review summarizes how PXR improves CLI by ameliorating cholestasis, inhibiting inflammation, and reducing fibrosis and discusses the progress of promising PXR agonists for treating CLI.

Manipulating the growth environment through co-culture to enhance stress tolerance and viability of probiotic strains in the gastrointestinal tract.

IMPORTANCE: The viability of probiotics in the human gastrointestinal tract is important, as some reports indicate that the health benefits of live bacteria are greater than those of dead ones. Therefore, the higher the viability of the probiotic strain, the better it may be. However, probiotic strains lose their viability due to gastrointestinal stress such as gastric acid and bile. This study provides an example of the use of co-culture or pH-controlled monoculture, which uses more stringent conditions (lower pH) than normal monoculture to produce probiotic strains that are more resistant to gastrointestinal stress. In addition, co-cultured beverages showed higher viability of the probiotic strain in the human gastrointestinal tract than monocultured beverages in our human study.

Probiotic and technological characterization of selected Lactobacillus strains isolated from different egyptian cheeses.

BACKGROUND: Fresh milk and natural environmental conditions are used to produce traditional cheeses. Such cheeses are produced by dozens of different types of microbes. Non-starter lactobacilli are the most responsible genus of lactic acid bacteria exhibiting key technological and health promoting traits. The purpose of this study is to isolate Lactobacillus bacteria from conventional Egyptian cheeses and analyse their probiotic potential and technological properties. RESULTS: Lactobacillus isolates (33 isolates) were isolated from different Egyptian cheeses. Our results revealed that 18.18% of the isolates were fast-acidifying, 30.3% were medium-acidifying and 51.5% were slow-acidifying isolates. The results of autolytic activity showed that 24.3% of the isolates were good autolysis, 33.3% were fair autolysis, while 42.4% were poor autolysis. Fifteen isolates produced exopolysaccharides, while 9 isolates exhibited antimicrobial activities against Lactobacillus bulgaricus 340. All the isolates were resistant to pH 3 for 3 h except isolate No. 15 (MR4). The growth rate of the isolates ranged from 42.25 to 85.25% at 0.3% bile salts after 3 h of incubation. The surviving percentage of the Lactobacillus isolates decreased with increasing incubation time or the percentage of bile salts greater than 0.3%. All the isolates grew after incubation in artificial gastric and intestinal fluids. The auto-aggregation of 15 isolates ranged from 43.13 to 72.77%. Lacticaseibacillus paracasei BD3, Lactiplantibacillus plantarum BR4 and Limosilactobacillus fermentum MR2 were sensitive to the majority of the tested antibiotics and showed good bile salt hydrolase activity. CONCLUSION: L. paracasei BD3, L. plantarum BR4 and L. fermentum MR2 were isolated from Egyptian cheeses and showed probiotic and technological characterization, which are valuable for their practical application as starters, adjunct and protective cultures in cheese making.

Metabolic reprogramming of the intestinal microbiome with functional bile acid changes underlie the development of NAFLD.

BACKGROUND AND AIMS: Bile acids are hepatic metabolites and have many properties considered to be relevant to the pathophysiology of NAFLD. Circulating levels of the intestinal microbiome-modified bile acid deoxycholate are increased in cirrhosis. APPROACH AND RESULTS: To further elucidate the role of bile acids and intestinal microbiota linked to bile acids in progressively severe NAFLD, a multiomic study of feces including 16S rRNA sequencing, microbial transcriptomics and metabolomics was performed in a cohort with varying phenotypes of NAFLD. Several bile acids of microbial origin derived from deoxycholic acid (DCA) (glycodeoxycholate, 7-ketodeoxycholic acid, dehydrocholic acid) increased with disease activity and fibrosis stage. These were linked to increased expression of microbial bile salt hydrolase, bile acid operon (BaiCD) and hydroxysteroid dehydrogenases (hdhA) required for DCA and downstream metabolite synthesis providing a mechanistic basis for altered bile acid profiles with disease progression. Bacteroidetes and several genera of Lachnospiraceae family containing DCA generating genes increased with increasing disease severity, whereas several potentially beneficial microbes sensitive to antibacterial effects of DCA e.g., Ruminococcaceae were decreased. The clinical relevance of these data was confirmed in an independent cohort enrolled in a clinical trial for NASH where at entry DCA and its conjugates were associated with advanced fibrosis. In patients treated with placebo, DCA declined in those with fibrosis regression and increased in those with fibrosis progression. DCA rose further in those with compensated cirrhosis when they experienced decompensation. CONCLUSIONS: These findings demonstrate a role for bile acids and the bile acid dependent microbiome in the development and progression of NAFLD and set the stage to leverage these findings for NASH biomarker development and for therapeutics.