The human aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that is a pivotal regulator of human physiology and pathophysiology. Allosteric inhibition of AhR was previously thought to be untenable. Here, we identify carvones as noncompetitive, insurmountable antagonists of AhR and characterize the structural and functional consequences of their binding. Carvones do not displace radiolabeled ligands from binding to AhR but instead bind allosterically within the bHLH/PAS-A region of AhR. Carvones do not influence the translocation of ligand-activated AhR into the nucleus but inhibit the heterodimerization of AhR with its canonical partner ARNT and subsequent binding of AhR to the promoter of CYP1A1. As a proof of concept, we demonstrate physiologically relevant Ahr-antagonism by carvones in vivo in female mice. These substances establish the molecular basis for selective targeting of AhR regardless of the type of ligand(s) present and provide opportunities for the treatment of disease processes modified by AhR.

• MeSH
• cytochrom P-450 CYP1A1 genetika   MeSH
• kůže * metabolismus   účinky záření   MeSH
• ligandy MeSH
• myši MeSH
• promotorové oblasti (genetika) MeSH
• receptory aromatických uhlovodíků - jaderný translokátor * genetika   metabolismus   MeSH
• receptory aromatických uhlovodíků * genetika   metabolismus   MeSH
• ultrafialové záření škodlivé účinky   MeSH
• zvířata MeSH
• Check Tag
• myši MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• cytochrom P-450 CYP1A1 MeSH
• ligandy MeSH
• receptory aromatických uhlovodíků - jaderný translokátor * MeSH
• receptory aromatických uhlovodíků * MeSH

We examined the effects of gut microbial catabolites of tryptophan on the aryl hydrocarbon receptor (AhR). Using a reporter gene assay, we show that all studied catabolites are low-potency agonists of human AhR. The efficacy of catabolites differed substantially, comprising agonists with no or low (i3-propionate, i3-acetate, i3-lactate, i3-aldehyde), medium (i3-ethanol, i3-acrylate, skatole, tryptamine), and high (indole, i3-acetamide, i3-pyruvate) efficacies. We displayed ligand-selective antagonist activities by i3-pyruvate, i3-aldehyde, indole, skatole, and tryptamine. Ligand binding assay identified low affinity (skatole, i3-pyruvate, and i3-acetamide) and very low affinity (i3-acrylate, i3-ethanol, indole) ligands of the murine AhR. Indole, skatole, tryptamine, i3-pyruvate, i3-acrylate, and i3-acetamide induced CYP1A1 mRNA in intestinal LS180 and HT-29 cells, but not in the AhR-knockout HT-29 variant. We observed a similar CYP1A1 induction pattern in primary human hepatocytes. The most AhR-active catabolites (indole, skatole, tryptamine, i3-pyruvate, i3-acrylate, i3-acetamide) elicited nuclear translocation of the AhR, followed by a formation of AhR-ARNT heterodimer and enhanced binding of the AhR to the CYP1A1 gene promoter. Collectively, we comprehensively characterized the interactions of gut microbial tryptophan catabolites with the AhR, which may expand the current understanding of their potential roles in intestinal health and disease.

• Klíčová slova
• aryl hydrocarbon receptor, indoles, microbiome, tryptophan,
• MeSH
• cytochrom P-450 CYP1A1 genetika   MeSH
• exprese genu MeSH
• indoly MeSH
• lidé MeSH
• ligandy MeSH
• metabolické sítě a dráhy MeSH
• multimerizace proteinu MeSH
• myši MeSH
• nádorové buněčné linie MeSH
• promotorové oblasti (genetika) MeSH
• receptory aromatických uhlovodíků agonisté   metabolismus   MeSH
• reportérové geny MeSH
• střevní mikroflóra * účinky léků   MeSH
• transkripční faktory bHLH agonisté   metabolismus   MeSH
• tryptofan metabolismus   MeSH
• vazba proteinů MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• AHR protein, human MeSH Prohlížeč
• CYP1A1 protein, human MeSH Prohlížeč
• cytochrom P-450 CYP1A1 MeSH
• indole MeSH Prohlížeč
• indoly MeSH
• ligandy MeSH
• receptory aromatických uhlovodíků MeSH
• transkripční faktory bHLH MeSH
• tryptofan MeSH

Mono-methylindoles (MMI) were described as agonists and/or antagonists of the human aryl hydrocarbon receptor (AhR). Here, we investigated the effects of MMI on AhR-CYP1A pathway in human hepatocytes and HepaRG cells derived from human progenitor hepatic cells. All MMI, except of 2-methylindole, strongly induced CYP1A1 and CYP1A2 mRNAs in HepaRG cells. Induction of CYP1A genes was absent in AhR-knock-out HepaRG cells. Consistently, CYP1A1 and CYP1A2 mRNAs and proteins were induced by all MMIs (except 2-methylindole), in human hepatocytes. The enzyme activity of CYP1A1 was inhibited by MMIs in human hepatocytes and LS180 colon cancer cells in a concentration-dependent manner (IC50 values from 1.2 μM to 23.8 μM and from 3.4 μM to 11.4 μM, respectively). Inhibition of CYP1A1 activity by MMI in human liver microsomes was much weaker as compared to that in intact cells. Incubation of parental MMI with human hepatocytes either diminished (4-methylindole, 6-methylindole) or enhanced (7-methylindole) their agonist effects on AhR in AZ-AHR reporter cells. In conclusion, overall effects of MMI on AhR-CYP1A pathway in human cells comprise the induction of CYP1A genes through AhR, the inhibition of CYP1A catalytic activity and possibly the metabolic transformation causing loss or gain of AhR agonist activity of parental compounds.

• Klíčová slova
• Aryl hydrocarbon receptor, Entero-hepatic axis, Methylindoles, Microbial catabolites, Tryptophan,
• MeSH
• cytochrom P-450 CYP1A1 antagonisté a inhibitory   biosyntéza   genetika   MeSH
• enzymová indukce MeSH
• hepatocyty účinky léků   enzymologie   MeSH
• indoly farmakologie   MeSH
• induktory cytochromu P450 farmakologie   MeSH
• inhibitory cytochromu P450 farmakologie   MeSH
• jaterní mikrozomy účinky léků   enzymologie   MeSH
• lidé středního věku MeSH
• lidé MeSH
• mladý dospělý MeSH
• nádorové buněčné linie MeSH
• nádory tračníku enzymologie   MeSH
• receptory aromatických uhlovodíků agonisté   genetika   metabolismus   MeSH
• senioři MeSH
• transkripční faktory bHLH agonisté   genetika   metabolismus   MeSH
• vztah mezi dávkou a účinkem léčiva MeSH
• Check Tag
• lidé středního věku MeSH
• lidé MeSH
• mladý dospělý MeSH
• mužské pohlaví MeSH
• senioři MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• AHR protein, human MeSH Prohlížeč
• CYP1A1 protein, human MeSH Prohlížeč
• cytochrom P-450 CYP1A1 MeSH
• indoly MeSH
• induktory cytochromu P450 MeSH
• inhibitory cytochromu P450 MeSH
• receptory aromatických uhlovodíků MeSH
• transkripční faktory bHLH MeSH

Novel methylindoles were identified as endobiotic and xenobiotic ligands of the human aryl hydrocarbon receptor (AhR). We examined the effects of 22 methylated and methoxylated indoles on the transcriptional activity of AhRs. Employing reporter gene assays in AZ-AHR transgenic cells, we determined full agonist, partial agonist, or antagonist activities of tested compounds, having substantially variable EC50, IC50, and relative efficacies. The most effective agonists (EMAX relative to 5 nM dioxin) of the AhR were 4-Me-indole (134%), 6-Me-indole (91%), and 7-MeO-indole (80%), respectively. The most effective antagonists of the AhR included 3-Me-indole (IC50; 19 μM), 2,3-diMe-indole (IC50; 11 μM), and 2,3,7-triMe-indole (IC50; 12 μM). Reverse transcription polymerase chain reaction analyses of CYP1A1 mRNA in LS180 cells confirmed the data from gene reporter assays. The compound leads, 4-Me-indole and 7-MeO-indole, induced substantial nuclear translocation of the AhR and enriched binding of the AhR to the CYP1A1 promoter, as observed using fluorescent immunohistochemistry and chromatin immunoprecipitation assays, respectively. Molecular modeling and docking studies suggest the agonists and antagonists likely share the same binding pocket but have unique binding modes that code for their affinity. Binding pocket analysis further revealed that 4-methylindole and 7-methoxyindole can simultaneously bind to the pocket and produce synergistic interactions. Together, these data show a dependence on subtle and specific chemical indole structures as AhR modulators and furthermore underscore the importance of complete evaluation of indole compounds as nuclear receptor ligands.

• MeSH
• buňky Hep G2 MeSH
• cytochrom P-450 CYP1A1 metabolismus   MeSH
• indoly farmakologie   MeSH
• lidé MeSH
• ligandy MeSH
• messenger RNA metabolismus   MeSH
• nádorové buněčné linie MeSH
• promotorové oblasti (genetika) účinky léků   MeSH
• receptory aromatických uhlovodíků agonisté   antagonisté a inhibitory   MeSH
• reportérové geny účinky léků   MeSH
• transkripční faktory bHLH agonisté   antagonisté a inhibitory   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Research Support, N.I.H., Extramural MeSH
• Research Support, U.S. Gov't, Non-P.H.S. MeSH
• Názvy látek
• AHR protein, human MeSH Prohlížeč
• cytochrom P-450 CYP1A1 MeSH
• indole MeSH Prohlížeč
• indoly MeSH
• ligandy MeSH
• messenger RNA MeSH
• receptory aromatických uhlovodíků MeSH
• transkripční faktory bHLH MeSH

Khellin and visnagin are two furanochromones that can be frequently found in ethnomedical formulations in Asia and the Middle East. Both compounds possess anti-inflammatory and analgesic properties, therefore modern medicine uses these compounds or structurally related derivatives for treatment of vitiligo, bronchial asthma and renal colics. Despite their frequent usage, the potential toxic properties of visnagin and khellin are not well characterized up-to-now. Many natural compounds modulate the expression and activity of cytochrome P450 1A1 (CYP1A1), which is well-known to bioactivate pro-carcinogens. The expression of this enzyme is controlled by the aryl hydrocarbon receptor (AHR), a ligand-activated transcription factor and regulator of drug metabolism. Here, we investigated the influence of both furanochromones on AHR signaling in human HepG2 hepatocarcinoma cells and primary human hepatocytes. Both compounds transactivated xenobiotic response element (XRE)-driven reporter gene activity in a dose-dependent manner and induced CYP1A1 transcription in HepG2 cells and primary hepatocytes. The latter was abolished in presence of a specific AHR antagonist. CYP1A enzyme activity assays done in HepG2 cells and primary hepatocytes revealed an inhibition of enzyme activity by both furanochromones, which may become relevant regarding the metabolism of xenobiotics and co-administered therapeutic drugs. The observed induction of several other members of the AHR gene battery, whose gene products are involved in regulation of cell growth, differentiation and migration, indicates that a further toxicological characterization of visnagin and khelllin is urgently required in order to minimize potential drug-drug interactions and other toxic side-effects that may occur during therapeutic usage of these furanochromones.

• MeSH
• aktivace enzymů účinky léků   MeSH
• aromatické hydroxylasy metabolismus   MeSH
• buněčné linie MeSH
• cytochrom P-450 CYP1A1 genetika   metabolismus   MeSH
• exprese genu MeSH
• hepatocyty účinky léků   metabolismus   MeSH
• khelin farmakologie   MeSH
• lidé MeSH
• receptory aromatických uhlovodíků metabolismus   MeSH
• regulace genové exprese účinky léků   MeSH
• reportérové geny MeSH
• signální transdukce účinky léků   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• aromatické hydroxylasy MeSH
• cytochrom P-450 CYP1A1 MeSH
• khelin MeSH
• receptory aromatických uhlovodíků MeSH
• visnagin MeSH Prohlížeč

We examined the effects of anthocyanidins (cyanidin, delphinidin, malvidin, peonidin, petunidin, pelargonidin) on the aryl hydrocarbon receptor (AhR)-CYP1A1 signaling pathway in human hepatocytes, hepatic HepG2 and intestinal LS174T cancer cells. AhR-dependent reporter gene expression in transfected HepG2 cells was increased by pelargonidin in a concentration-dependent manner at 24h. Similarly, pelargonidin induced the expression of CYP1A1 mRNA up to 5-fold in HepG2 and LS174T cells relative to the induction by 5 nM 2,3,7,8-tetrachlorodibenzodioxin (TCDD), the most potent activator of AhR. CYP1A1 and CYP1A2 mRNAs were also increased by pelargonidin in three primary human hepatocytes cultures (approximately 5% of TCDD potency) and the increase in CYP1A1 protein in HepG2 and LS174T cells was comparable to the increase in catalytic activity of CYP1A1 enzyme. Ligand binding analysis demonstrated that pelargonidin was a weak ligand of AhR. Enzyme kinetic analyses using human liver microsomes revealed inhibition of CYP1A1 activity by delphinidin (IC50 78 μM) and pelargonidin (IC50 33 μM). Overall, although most anthocyanidins had no effects on AhR-CYP1A1 signaling, pelargonidin can bind to and activate the AhR and AhR-dependent gene expression, and pelargonidin and delphinidin inhibit the CYP1A1 catalytic activity.

• MeSH
• aktivace transkripce účinky léků   MeSH
• anthokyaniny farmakologie   MeSH
• buňky Hep G2 MeSH
• cytochrom P-450 CYP1A1 biosyntéza   MeSH
• enzymová indukce MeSH
• hepatocyty účinky léků   enzymologie   MeSH
• jaterní mikrozomy enzymologie   MeSH
• kinetika MeSH
• lidé MeSH
• ligandy MeSH
• messenger RNA biosyntéza   MeSH
• nádory jater enzymologie   MeSH
• polychlorované dibenzodioxiny farmakologie   MeSH
• primární buněčná kultura MeSH
• promotorové oblasti (genetika) účinky léků   MeSH
• receptory aromatických uhlovodíků účinky léků   metabolismus   MeSH
• signální transdukce účinky léků   MeSH
• střevní nádory enzymologie   MeSH
• transfekce MeSH
• transkripční faktory bHLH účinky léků   metabolismus   MeSH
• vztah mezi dávkou a účinkem léčiva MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Research Support, N.I.H., Extramural MeSH
• Názvy látek
• AHR protein, human MeSH Prohlížeč
• anthokyaniny MeSH
• CYP1A1 protein, human MeSH Prohlížeč
• cytochrom P-450 CYP1A1 MeSH
• ligandy MeSH
• messenger RNA MeSH
• pelargonidin MeSH Prohlížeč
• polychlorované dibenzodioxiny MeSH
• receptory aromatických uhlovodíků MeSH
• transkripční faktory bHLH MeSH