Microbiota Metabolism Promotes Synthesis of the Human Ah Receptor Agonist 2,8-Dihydroxyquinoline

Safety and effects of acetylated and butyrylated high amylose maize starch in recently diagnosed youths with type 1 diabetes; a Pilot Study

Acetylated and butyrylated high amylose starch (HAMS-AB) is a prebiotic shown to be effective in type 1 diabetes (T1D) prevention in mouse models and is safe in adults with established T1D. HAMS-AB alters the gut microbiome profile with increased bacterial fermenters that produce short chain fatty acids (SCFAs) with anti-inflammatory and immune-modulatory effects. We performed a pilot study using a cross-over design to assess the safety and efficacy of 4 weeks of oral HAMS-AB consumption by recently diagnosed (< 2 years of diagnosis) youths with T1D. Seven individuals completed the study. The mean±SD age was 15.0±1.2 years, diabetes duration 19.5±6.3 months, 5/7 were female and 4/7 were White, all with a BMI of < 85th%. The prebiotic was safe. Following prebiotic intake, gut microbiome changes were seen, including a notable increase in the relative abundance of fermenters such as Bifidobacterium and Faecalibacterium. Treatment was also associated with changes in bacterial functional pathways associated with either improved energy metabolism (upregulation of tyrosine metabolism) or anti-inflammatory effects (reduced geraniol degradation). There were no differences in stool SCFA levels. Plasma metabolites associated with improved glycemia, such as hippurate, were significantly increased after treatment and there were positive and significant changes in the immune regulatory function of mucosal associated invariant T cells. There was a significant decrease in the area under the curve glucose but not C-peptide, as measured during a mixed meal tolerance testing, following the prebiotic consumption. In summary, the prebiotic HAMS-AB was safe in adolescents with T1D and showed promising effects on the gut microbiome composition, function and immune regulatory function.

Activation of the aryl hydrocarbon receptor in inflammatory bowel disease: insights from gut microbiota

Inflammatory bowel disease (IBD) is a chronic inflammatory intestinal disease that affects more than 3.5 million people, with rising prevalence. It deeply affects patients' daily life, increasing the burden on patients, families, and society. Presently, the etiology of IBD remains incompletely clarified, while emerging evidence has demonstrated that altered gut microbiota and decreased aryl hydrocarbon receptor (AHR) activity are closely associated with IBD. Furthermore, microbial metabolites are capable of AHR activation as AHR ligands, while the AHR, in turn, affects the microbiota through various pathways. In light of the complex connection among gut microbiota, the AHR, and IBD, it is urgent to review the latest research progress in this field. In this review, we describe the role of gut microbiota and AHR activation in IBD and discussed the crosstalk between gut microbiota and the AHR in the context of IBD. Taken as a whole, we propose new therapeutic strategies targeting the AHR-microbiota axis for IBD, even for other related diseases caused by AHR-microbiota dysbiosis.

Aryl hydrocarbon receptor (AhR) and pregnane X receptor (PXR) play both distinct and common roles in the regulation of colon homeostasis and intestinal carcinogenesis

Both aryl hydrocarbon receptor (AhR) and pregnane X receptor (PXR) belong among key regulators of xenobiotic metabolism in the intestinal tissue. AhR in particular is activated by a wide range of environmental and dietary carcinogens. The data accumulated over the last two decades suggest that both of these transcriptional regulators play a much wider role in the maintenance of gut homeostasis, and that both transcription factors may affect processes linked with intestinal tumorigenesis. Intestinal epithelium is continuously exposed to a wide range of AhR, PXR and dual AhR/PXR ligands formed by intestinal microbiota or originating from diet. Current evidence suggests that specific ligands of both AhR and PXR can protect intestinal epithelium against inflammation and assist in the maintenance of epithelial barrier integrity. AhR, and to a lesser extent also PXR, have been shown to play a protective role against inflammation-induced colon cancer, or, in mouse models employing overactivation of Wnt/β-catenin signaling. In contrast, other evidence suggests that both receptors may contribute to modulation of transformed colon cell behavior, with a potential to promote cancer progression and/or chemoresistance. The review focuses on both overlapping and separate roles of the two receptors in these processes, and on possible implications of their activity within the context of intestinal tissue.

Molecular networking identifies an AHR-modulating benzothiazole from white button mushrooms (Agaricus bisporus)

Diet-derived aryl hydrocarbon receptor (AHR) ligands have potential to maintain gut health. However, among the myriad bioactive compounds from foods, identifying novel functional ligands which would significantly impact gastrointestinal health is a challenge. In this study, a novel AHR modulator is predicted, identified, and characterized in the white button mushroom (Agaricus bisporus). Using a molecular networking approach, a methylated analog to benzothiazole was indicated in white button mushrooms, which was subsequently isolated and identified as 2-amino-4-methyl-benzothiazole(2A4). Cell-based AHR transcriptional assays revealed that 2-amino-4-methyl-benzothiazole possesses agonistic activity and upregulated CYP1A1 expression. This contrasts with previous findings that whole white button mushroom extract has overall antagonistic activity in vivo, underscoring the importance of studying the roles each chemical component plays in a whole food. The findings suggest that 2-amino-4-methyl-benzothiazole is a previously unidentified AHR modulator from white button mushroom and demonstrate that molecular networking has potential to identify novel receptor modulators from natural products.

Aryl hydrocarbon receptor (AHR): towards understanding intestinal microbial ligands including vitamin B12 and folic acid as natural antagonists

AHR has been identified as ligand-modulated transcription factor and environmental sensor. However, explanation of its multiple agonistic and antagonistic ligands is far from complete. Studies of AHR's role in host-microbiome interaction are currently a fruitful area of research. Microbial products and virulence factors have been identified as AHR agonists. In steady state they are involved in safeguarding intestinal barrier integrity. When virulence factors from pathogenic bacteria are identified by AHR of intestinal immune cells, anti-microbial defense mechanisms are activated by generating reactive oxygen species (ROS) in intestinal epithelial cells and recruited immune cells. ROS production has to be strictly controlled, and anti-inflammatory responses have to be initiated timely in the resolution phase of inflammation to avoid tissue damage and chronic inflammatory responses. Surprisingly, bacteria-generated vitamin B12/cobalamin and vitamin B9/folic acid have been identified as natural AHR antagonists, stimulating the interest of biochemists. Hints for AHR-cobalamin antagonism are pointing to cobalamin-dependent enzymes leading to alterations of TCA cycle intermediates, and TCDD-mediated loss of serum cobalamin. Although we are still at the beginning to understand mechanisms, it is likely that scientific efforts are on a rewarding path to understand novel AHR functions.

Targeting the aryl hydrocarbon receptor by gut phenolic metabolites: A strategy towards gut inflammation

The Aryl Hydrocarbon Receptor (AHR) is a ligand-dependent transcription factor able to control complex transcriptional processes in several cell types, which has been correlated with various diseases, including inflammatory bowel diseases (IBD). Numerous studies have described different compounds as ligands of this receptor, like xenobiotics, natural compounds, and several host-derived metabolites. Dietary (poly)phenols have been studied regarding their pleiotropic activities (e.g., neuroprotective and anti-inflammatory), but their AHR modulatory capabilities have also been considered. However, dietary (poly)phenols are submitted to extensive metabolism in the gut (e.g., gut microbiota). Thus, the resulting gut phenolic metabolites could be key players modulating AHR since they are the ones that reach the cells and may exert effects on the AHR throughout the gut and other organs. This review aims at a comprehensive search for the most abundant gut phenolic metabolites detected and quantified in humans to understand how many have been described as AHR modulators and what could be their impact on inflammatory gut processes. Even though several phenolic compounds have been studied regarding their anti-inflammatory capacities, only 1 gut phenolic metabolite, described as AHR modulator, has been evaluated on intestinal inflammatory models. Searching for AHR ligands could be a novel strategy against IBD.

Current Therapeutic Landscape and Safety Roadmap for Targeting the Aryl Hydrocarbon Receptor in Inflammatory Gastrointestinal Indications

Target modulation of the AhR for inflammatory gastrointestinal (GI) conditions holds great promise but also the potential for safety liabilities both within and beyond the GI tract. The ubiquitous expression of the AhR across mammalian tissues coupled with its role in diverse signaling pathways makes development of a “clean” AhR therapeutically challenging. Ligand promiscuity and diversity in context-specific AhR activation further complicates targeting the AhR for drug development due to limitations surrounding clinical translatability. Despite these concerns, several approaches to target the AhR have been explored such as small molecules, microbials, PROTACs, and oligonucleotide-based approaches. These various chemical modalities are not without safety liabilities and require unique de-risking strategies to parse out toxicities. Collectively, these programs can benefit from in silico and in vitro methodologies that investigate specific AhR pathway activation and have the potential to implement thresholding parameters to categorize AhR ligands as “high” or “low” risk for sustained AhR activation. Exploration into transcriptomic signatures for AhR safety assessment, incorporation of physiologically-relevant in vitro model systems, and investigation into chronic activation of the AhR by structurally diverse ligands will help address gaps in our understanding regarding AhR-dependent toxicities. Here, we review the role of the AhR within the GI tract, novel therapeutic modality approaches to target the AhR, key AhR-dependent safety liabilities, and relevant strategies that can be implemented to address drug safety concerns. Together, this review discusses the emerging therapeutic landscape of modalities targeting the AhR for inflammatory GI indications and offers a safety roadmap for AhR drug development.

The Aryl Hydrocarbon Receptor (AHR) as a Potential Target for the Control of Intestinal Inflammation: Insights from an Immune and Bacteria Sensor Receptor

The aryl hydrocarbon receptor (AHR) is widely expressed in immune and non-immune cells of the gut and its activation has been correlated to the outcome of inflammatory bowel diseases (IBD). In ulcerative colitis and Crohn's disease, there is an excessive chronic inflammation with massive accumulation of leukocytes in the gut, in an attempt to constrain the invasion of pathogenic microorganisms on the damaged organ. Accordingly, it is known that dietary components, xenobiotics, and some chemicals or metabolites can activate AHR and induce the modulation of inflammatory responses. In fact, the AHR triggering by specific ligands during inflammatory conditions results in decreased IFNγ, IL-6, IL-12, TNF, IL-7, and IL-17, along with reduced microbial translocation and fibrosis in the gut. Moreover, upon AHR activation, there are increased regulatory mechanisms such as IL-10, IL-22, prostaglandin E₂, and Foxp3, besides the production of anti-microbial peptides and epithelial repair. Most interestingly, commensal bacteria or their metabolites may also activate this receptor, thus contributing to the restoration of gut normobiosis and homeostasis. In line with that, Lactobacillus reuteri, Lactobacillus bulgaricus, or microbial products such as tryptophan metabolites, indole-3-pyruvic acid, urolithin A, short-chain fatty acids, dihydroxyquinoline, and others may regulate the inflammation by mechanisms dependent on AHR activation. Hence, here we discussed the potential modulatory role of AHR on intestinal inflammation, focused on the reestablishment of homeostasis through the receptor triggering by microbial metabolites. Finally, the development of AHR-based therapies derived from bacteria products could represent an important future alternative for controlling IBD.

Untargeted fecal metabolome analysis in obese dogs after weight loss achieved by feeding a high-fiber-high-protein diet

INTRODUCTION

In humans and companion animals, obesity is accompanied by metabolic derangements. Studies have revealed differences in the composition of the fecal microbiome between obese dogs and those with an ideal body weight.

OBJECTIVES

We have previously reported that the fecal microbiome in obese dogs changes after controlled weight reduction, induced by feeding a diet high in fiber and protein. Despite these findings, it is unclear if taxonomic differences infer differences at the functional level between obese dogs and those with an ideal body weight.

METHODOLOGY

Untargeted fecal metabolome analysis was performed on dogs with obesity before and after weight loss achieved by feeding a high-fiber-high-protein diet.

RESULTS

Fecal metabolome analysis revealed a total of 13 compounds that changed in concentration in obese dogs after weight loss. Of these compounds, metabolites associated with bacterial metabolism decreased after weight loss including purine, L-(-)-methionine, coumestrol, and the alkaloids 1-methylxanthine and trigonelline. Conversely, the polyphenols (-)-epicatechin and matairesinol and the quinoline derivatives 1,5-isoquinolinediol and 2-hydroxiquinoline increased after weight loss.

CONCLUSION

These results suggest differences in intestinal microbiome at the functional level after weight loss, but further studies are needed to determine the role of these compounds in the etiology of obesity and weight loss.

Intestinal interplay of quorum sensing molecules and human receptors

Human gut is in permanent contact with microorganisms that play an important role in many physiological processes including metabolism and immunologic activity. These microorganisms communicate and manage themself by the quorum sensing system (QS) that helps to coordinate optimal growth and subsistence by activating signaling pathways that regulate bacterial gene expression. Diverse QS molecules produced by pathogenic as well as resident microbiota have been found throughout the human gut. However, even a host can by affected by these molecules. Intestinal and immune cells possess a range of molecular targets for QS. Our present knowledge on bacteria-cell communication encompasses G-protein-coupled receptors, nuclear receptors and receptors for bacterial cell-wall components. The QS of commensal bacteria has been approved as a protective factor with favourable effects on intestinal homeostasis and immunity. Signaling molecules of QS interacting with above-mentioned receptors thus parcipitate on maintaining of barrier functions, control of inflammation processes and increase of resistance to pathogen colonization in host organisms. Pathogens QS molecules can have a dual function. Host cells are able to detect the ongoing infection by monitoring the presence and changes in concentrations of QS molecules. Such information can help to set the most effective immune defence to prevent or overcome the infection. Contrary, pathogens QS signals can target the host receptors to deceive the immune system to get the best conditions for growth. However, our knowledge about communication mediated by QS is still limited and detailed understanding of molecular mechanisms of QS signaling is desired.

How Ah Receptor Ligand Specificity Became Important in Understanding Its Physiological Function

Increasingly, the aryl hydrocarbon receptor (AHR) is being recognized as a sensor for endogenous and pseudo-endogenous metabolites, and in particular microbiota and host generated tryptophan metabolites. One proposed explanation for this is the role of the AHR in innate immune signaling within barrier tissues in response to the presence of microorganisms. A number of cytokine/chemokine genes exhibit a combinatorial increase in transcription upon toll-like receptors and AHR activation, supporting this concept. The AHR also plays a role in the enhanced differentiation of intestinal and dermal epithelium leading to improved barrier function. Importantly, from an evolutionary perspective many of these tryptophan metabolites exhibit greater activation potential for the human AHR when compared to the rodent AHR. These observations underscore the importance of the AHR in barrier tissues and may lead to pharmacologic therapeutic intervention.

Neonatal Mouse Gut Metabolites Influence Cryptosporidium parvum Infection in Intestinal Epithelial Cells

Cryptosporidium sp. occupies a unique intracellular niche that exposes the parasite to both host cell contents and the intestinal lumen, including metabolites from the diet and produced by the microbiota. Both dietary and microbial products change over the course of early development and could contribute to the changes seen in susceptibility to cryptosporidiosis in humans and mice.

The protozoan parasite Cryptosporidium sp. is a leading cause of diarrheal disease in those with compromised or underdeveloped immune systems, particularly infants and toddlers in resource-poor localities. As an enteric pathogen, Cryptosporidium sp. invades the apical surface of intestinal epithelial cells, where it resides in close proximity to metabolites in the intestinal lumen. However, the effect of gut metabolites on susceptibility to Cryptosporidium infection remains largely unstudied. Here, we first identified which gut metabolites are prevalent in neonatal mice when they are most susceptible to Cryptosporidium parvum infection and then tested the isolated effects of these metabolites on C. parvum invasion and growth in intestinal epithelial cells. Our findings demonstrate that medium or long-chain saturated fatty acids inhibit C. parvum growth, perhaps by negatively affecting the streamlined metabolism in C. parvum, which is unable to synthesize fatty acids. Conversely, long-chain unsaturated fatty acids enhanced C. parvum invasion, possibly by modulating membrane fluidity. Hence, gut metabolites, either from diet or produced by the microbiota, influence C. parvum growth in vitro and may also contribute to the early susceptibility to cryptosporidiosis seen in young animals.

Intestinal microbiota-derived tryptophan metabolites are predictive of Ah receptor activity

Commensal microbiota-dependent tryptophan catabolism within the gastrointestinal tract is known to exert profound effects upon host physiology, including the maintenance of epithelial barrier and immune function. A number of abundant microbiota-derived tryptophan metabolites exhibit activation potential for the aryl hydrocarbon receptor (AHR). Gene expression facilitated by AHR activation through the presence of dietary or microbiota-generated metabolites can influence gastrointestinal homeostasis and confer protection from intestinal challenges. Utilizing untargeted mass spectrometry-based metabolomics profiling, combined with AHR activity screening assays, we identify four previously unrecognized tryptophan metabolites, present in mouse cecal contents and human stool, with the capacity to activate AHR. Using GC/MS and LC/MS platforms, quantification of these novel AHR activators, along with previously established AHR-activating tryptophan metabolites, was achieved, providing a relative order of abundance. Using physiologically relevant concentrations and quantitative gene expression analyses, the relative efficacy of these tryptophan metabolites with regard to mouse or human AHR activation potential is examined. These data reveal indole, 2-oxindole, indole-3-acetic acid and kynurenic acid as the dominant AHR activators in mouse cecal contents and human stool from participants on a controlled diet. Here we provide the first documentation of the relative abundance and AHR activation potential of a panel of microbiota-derived tryptophan metabolites. Furthermore, these data reveal the human AHR to be more sensitive, at physiologically relevant concentrations, to tryptophan metabolite activation than mouse AHR. Additionally, correlation analyses indicate a relationship linking major tryptophan metabolite abundance with AHR activity, suggesting these cecal/fecal metabolites represent biomarkers of intestinal AHR activity.

The aryl hydrocarbon receptor as a mediator of host-microbiota interplay

Increasing evidence suggests a significant role for microbiota dependent metabolites and co-metabolites, acting as aryl hydrocarbon receptor (AHR) ligands, to facilitate bidirectional communication between the host and the microbiota and thus modulate physiology. Such communication is particularly evident within the gastrointestinal tract. Through binding to or activating the AHR, these metabolites play fundamental roles in various physiological processes and likely contribute to the maintenance of intestinal homeostasis. In recent years, tryptophan metabolites were screened to identify physiologically relevant AHR ligands or activators. The discovery of specific microbiota-derived indole-based metabolites as AHR ligands may provide insight concerning how these metabolites affect interactions between gut microbiota and host intestinal homeostasis and how this relates to chronic GI disease and overall health. A greater understanding of the mechanisms that modulate the production of such metabolites and associated AHR activity may be utilized to effectively treat inflammatory diseases and promote human health. Here, we review microbiota-derived AHR ligands generated from tryptophan that modulate host-gut microbiota interactions and discuss possible intervention strategies for potential therapies in the future.

Dysregulated bile acid receptor-mediated signaling and IL-17A induction are implicated in diet-associated hepatic health and cognitive function

BACKGROUND

Chronic consumption of high sugar and high fat diet associated with liver inflammation and cognitive decline. This paper tests a hypothesis that the development and resolution of diet-induced nonalcoholic fatty liver disease (NAFLD) has an impact on neuroplasticity and cognition.

METHODS

C57BL/6 wild-type mice were fed with either a healthy control diet (CD) or a fructose, palmitate, and cholesterol (FPC)-enriched diet since weaning. When mice were 3-months old, FPC diet-fed mice were randomly assigned to receive either FPC-enriched diet with or without 6% inulin supplementation. At 8 months of age, all three groups of mice were euthanized followed by analysis of inflammatory signaling in the liver and brain, gut microbiota, and cecal metabolites.

RESULTS

Our data showed that FPC diet intake induced hepatic steatosis and inflammation in the liver and brain along with elevated RORγ and IL-17A signaling. Accompanied by microglia activation and reduced hippocampal long-term potentiation, FPC diet intake also reduced postsynaptic density-95 and brain derived neurotrophic factor, whereas inulin supplementation prevented diet-reduced neuroplasticity and the development of NAFLD. In the gut, FPC diet increased Coriobacteriaceae and Erysipelotrichaceae, which are implicated in cholesterol metabolism, and the genus Allobaculum, and inulin supplementation reduced them. Furthermore, FPC diet reduced FXR and TGR5 signaling, and inulin supplementation reversed these changes. Untargeted cecal metabolomics profiling uncovered 273 metabolites, and 104 had significant changes due to FPC diet intake or inulin supplementation. Among the top 10 most affected metabolites, FPC-fed mice had marked increase of zymosterol, a cholesterol biosynthesis metabolite, and reduced 2,8-dihydroxyquinoline, which has known benefits in reducing glucose intolerance; these changes were reversible by inulin supplementation. Additionally, the abundance of Barnesiella, Coprobacter, Clostridium XIVa, and Butyrivibrio were negatively correlated with FPC diet intake and the concentration of cecal zymosterol but positively associated with inulin supplementation, suggesting their benefits.

CONCLUSION

Taken together, the presented data suggest that diet alters the gut microbiota and their metabolites, including bile acids. This will subsequently affect IL-17A signaling, resulting in systemic impacts on both hepatic metabolism and cognitive function.

Reversal of obesity and liver steatosis in mice via inhibition of aryl hydrocarbon receptor and altered gene expression of CYP1B1, PPARα, SCD1, and osteopontin

BACKGROUND/OBJECTIVES

Obesity is a global epidemic and the underlying basis for numerous comorbidities. We report that the aryl hydrocarbon receptor (AHR) plays a key role in the metabolism of obesity. The AHR is a promiscuous, ligand-activated nuclear receptor primarily known for regulating genes involved in xenobiotic metabolism and T cell polarization. The aims of the work reported here were to understand the underlying mechanism of AHR-based obesity and to determine whether inhibition of AHR activity would reverse obesity.

METHODS

Mice were fed control (low fat) and Western (high fat) diets with and without the AHR antagonist alpha-naphthoflavone (aNF). Gene expression of identified AHR-regulated genes from liver and adipose tissue was characterized. To determine the role of the AHR in obesity reversal, selected mice in control and Western diet regimens were switched at midpoint to the respective control and Western diets containing aNF, and the identified AHR-regulated genes characterized.

RESULTS

AHR inhibition prevented obesity in mice on a 40-week diet regimen. The likely AHR-regulated and cross-regulated downstream effectors of AHR-based obesity were shown to be CYP1B1, PPARα-target genes, SCD1, and SPP1 (osteopontin). Western diet caused an increase of mRNA and protein expression of the Cyp1b1, Scd1, and Spp1, and PPARα-target genes in the liver, and inhibition of the AHR maintained expression of these genes near control levels. The body weight of obese mice on Western diet switched to Western diet containing aNF decreased to that of mice on control diet concurrently with a reduction in the expression of liver CYP1B1, PPARα-target genes, SCD1, and SPP1. AHR inhibition prevented hypertrophy and hyperplasia in visceral adipose tissue and limited expression levels of CYP1B1 and SPP1 to that of mice on control diet.

CONCLUSIONS

AHR inhibition prevents and reverses obesity by likely reducing liver expression of the Cyp1b1, Scd1, Spp1, and PPARα-target genes; and the AHR is a potentially potent therapeutic target for the treatment and prevention of obesity and linked diseases.

Microbiome is a functional modifier of P450 drug metabolism

Host cytochrome P450s (P450s) play important roles in the bioactivation and detoxification of numerous therapeutic drugs, environmental toxicants, dietary factors, as well as endogenous compounds. Gut microbiome is increasingly recognized as our "second genome" that contributes to the xenobiotic biotransformation of the host, and the first pass metabolism of many orally exposed chemicals is a joint effort between host drug metabolizing enzymes including P450s and gut microbiome. Gut microbiome contributes to the drug metabolism via two distinct mechanisms: direct mechanism refers to the metabolism of drugs by microbial enzymes, among which reduction and hydrolysis (or deconjugation) are among the most important reactions; whereas indirect mechanism refers to the influence of host receptors and signaling pathways by microbial metabolites. Many types of microbial metabolites, such as secondary bile acids (BAs), short chain fatty acids (SCFAs), and tryptophan metabolites, are known regulators of human diseases through modulating host xenobiotic-sensing receptors. To study the roles of gut microbiome in regulating host drug metabolism including P450s, several models including germ free mice, antibiotics or probiotics treatments, have been widely used. The present review summarized the current information regarding the interactions between microbiome and the host P450s in xenobiotic biotransformation organs such as liver, intestine, and kidney, highlighting the remote sensing mechanisms underlying gut microbiome mediated regulation of host xenobiotic biotransformation. In addition, the roles of bacterial, fungal, and other microbiome kingdom P450s, which is an understudied area of research in pharmacology and toxicology, are discussed.

Isolation and Identification of Aryl Hydrocarbon Receptor Modulators in White Button Mushrooms (Agaricus bisporus)

Natural aryl hydrocarbon (AHR) ligands have been identified in food and herbal medicines, and they may exhibit beneficial activity in humans. In this study, white button (WB) feeding significantly decreased AHR target gene expression in the small intestine of both conventional and germ-free mice. High-performance liquid chromatography (HPLC) fractionation and ultra-high-performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) combined with an AHR-responsive cell-based luciferase gene reporter assay were used to isolate and characterize benzothiazole (BT) derivatives and 6-methylisoquinoline (6-MIQ) as AHR modulators from WB mushrooms. The study showed dose-dependent changes of AHR transformation determined by the cell-based luciferase gene reporter assay and transcription of CYP1A1 in human Caco-2 cells by BT derivatives and 6-MIQ. These findings suggested that WB mushroom contains new classes of natural AHR modulators and demonstrated HPLC fractionation and UHPLC-MS/MS combined with a cell-based luciferase gene reporter assay as a useful approach for isolation and characterization of the previously unidentifed AHR modulators from natural products.