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
• Cytochrome P-450 CYP1A1 genetics   MeSH
• Skin * metabolism   radiation effects   MeSH
• Ligands MeSH
• Mice MeSH
• Promoter Regions, Genetic MeSH
• Aryl Hydrocarbon Receptor Nuclear Translocator * genetics   metabolism   MeSH
• Receptors, Aryl Hydrocarbon * genetics   metabolism   MeSH
• Ultraviolet Rays adverse effects   MeSH
• Animals MeSH
• Check Tag
• Mice MeSH
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Cytochrome P-450 CYP1A1 MeSH
• Ligands MeSH
• Aryl Hydrocarbon Receptor Nuclear Translocator * MeSH
• Receptors, Aryl Hydrocarbon * MeSH

Sesquiterpenes, the main components of plant essential oils, are bioactive compounds with numerous health-beneficial activities. Sesquiterpenes can interact with concomitantly administered drugs due to the modulation of drug-metabolizing enzymes (DMEs). The aim of this study was to evaluate the modulatory effects of six sesquiterpenes (farnesol, cis-nerolidol, trans-nerolidol, α-humulene, β-caryophyllene, and caryophyllene oxide) on the expression of four phase I DMEs (cytochrome P450 3A4 and 2C, carbonyl reductase 1, and aldo-keto reductase 1C) at both the mRNA and protein levels. For this purpose, human precision-cut liver slices (PCLS) prepared from 10 patients and transfected HepG2 cells were used. Western blotting, quantitative real-time PCR and reporter gene assays were employed in the analyses. In the reporter gene assays, all sesquiterpenes significantly induced cytochrome P450 3A4 expression via pregnane X receptor interaction. However in PCLS, their effects on the expression of all the tested DMEs at the mRNA and protein levels were mild or none. High inter-individual variabilities in the basal levels as well as in modulatory efficacy of the tested sesquiterpenes were observed, indicating a high probability of marked differences in the effects of these compounds among the general population. Nevertheless, it seems unlikely that the studied sesquiterpenes would remarkably influence the bioavailability and efficacy of concomitantly administered drugs.

• Keywords
• cytochrome P450 3A4, gene reporter assay, mRNA expression, precision-cut liver slices, pregnane X receptor, protein expression, sesquiterpene,
• MeSH
• Aldo-Keto Reductases metabolism   MeSH
• Hep G2 Cells MeSH
• Cytochrome P-450 CYP3A metabolism   MeSH
• Farnesol pharmacology   MeSH
• Hepatocytes metabolism   MeSH
• Liver enzymology   MeSH
• Carbonyl Reductase (NADPH) metabolism   MeSH
• Middle Aged MeSH
• Humans MeSH
• RNA, Messenger metabolism   MeSH
• Metabolic Clearance Rate MeSH
• Monocyclic Sesquiterpenes pharmacology   MeSH
• Polycyclic Sesquiterpenes pharmacology   MeSH
• Pregnane X Receptor agonists   metabolism   MeSH
• Receptors, Aryl Hydrocarbon agonists   metabolism   MeSH
• Cytochrome P450 Family 2 metabolism   MeSH
• Aged, 80 and over MeSH
• Aged MeSH
• Sesquiterpenes pharmacology   MeSH
• Cytochrome P-450 Enzyme System metabolism   MeSH
• Check Tag
• Middle Aged MeSH
• Humans MeSH
• Male MeSH
• Aged, 80 and over MeSH
• Aged MeSH
• Female MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Aldo-Keto Reductases MeSH
• caryophyllene oxide MeSH Browser
• caryophyllene MeSH Browser
• Cytochrome P-450 CYP3A MeSH
• cytochrome P-450 CYP2C subfamily MeSH Browser
• Farnesol MeSH
• humulene MeSH Browser
• Carbonyl Reductase (NADPH) MeSH
• RNA, Messenger MeSH
• Monocyclic Sesquiterpenes MeSH
• nerolidol MeSH Browser
• Polycyclic Sesquiterpenes MeSH
• Pregnane X Receptor MeSH
• Receptors, Aryl Hydrocarbon MeSH
• Cytochrome P450 Family 2 MeSH
• Sesquiterpenes MeSH
• Cytochrome P-450 Enzyme System MeSH

Dovitinib (TKI-258) is under development for the treatment of diverse cancer entities. No published information on its pharmacokinetic drug interaction potential is available. Thus, we assessed its interaction with important drug metabolising enzymes and drug transporters and its efficacy in multidrug resistant cells in vitro. P-glycoprotein (P-gp, MDR1, ABCB1) inhibition was evaluated by calcein assay, inhibition of breast cancer resistance protein (BCRP, ABCG2) by pheophorbide A efflux, and inhibition of organic anion transporting polypeptides (OATPs) by 8-fluorescein-cAMP uptake. Inhibition of cytochrome P450 3A4, 2C19, and 2D6 was assessed by using commercial kits. Induction of transporters and enzymes was quantified by real-time RT-PCR. Possible aryl hydrocarbon receptor (AhR) activating properties were assessed by a reporter gene assay. Substrate characteristics were evaluated by growth inhibition assays in cells over-expressing P-gp or BCRP. Dovitinib weakly inhibited CYP2C19, CYP3A4, P-gp and OATPs. The strongest inhibition was observed for BCRP (IC50 = 10.3 ± 4.5 μM). Among the genes investigated, dovitinib only induced mRNA expression of CYP1A1, CYP1A2, ABCC3 (coding for multidrug resistance-associated protein 3), and ABCG2 and suppressed mRNA expression of some transporters and drug metabolising enzymes. AhR reporter gene assay demonstrated that dovitinib is an activator of this nuclear receptor. Dovitinib retained its efficacy in cell lines over-expressing P-gp or BCRP. Our analysis indicates that dovitinib will most likely retain its efficacy in tumours over-expressing P-gp or BCRP and gives first evidence that dovitinib might act as a perpetrator drug in pharmacokinetic drug-drug interactions.

• Publication type
• Journal Article 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
• Enzyme Activation drug effects   MeSH
• Aryl Hydrocarbon Hydroxylases metabolism   MeSH
• Cell Line MeSH
• Cytochrome P-450 CYP1A1 genetics   metabolism   MeSH
• Gene Expression MeSH
• Hepatocytes drug effects   metabolism   MeSH
• Khellin pharmacology   MeSH
• Humans MeSH
• Receptors, Aryl Hydrocarbon metabolism   MeSH
• Gene Expression Regulation drug effects   MeSH
• Genes, Reporter MeSH
• Signal Transduction drug effects   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Aryl Hydrocarbon Hydroxylases MeSH
• Cytochrome P-450 CYP1A1 MeSH
• Khellin MeSH
• Receptors, Aryl Hydrocarbon MeSH
• visnagin MeSH Browser

Anthocyanins are plant pigments occurring in flowers and berry fruits. Since a phenomenon of food-drug interactions is increasingly emerging, we examined the effects of 21 major anthocyanins and the extracts from 3 food supplements containing anthocyanins on the aryl hydrocarbon receptor (AhR)-cytochrome P450 CYP1A1 signaling pathway in human hepatocytes and human hepatic HepG2 and intestinal LS174T cancer cells. Pelargonidin-3-O-rutinoside (PEL-2) and cyanidin-3,5-O-diglucoside (CYA-3) dose-dependently activated AhR, as revealed by gene reporter assay. PEL-2 and CYA-3 induced CYP1A1 mRNA but not protein in HepG2 and LS174T cells. Neither compounds induced CYP1A1 mRNA and protein in four different primary human hepatocytes cultures. The effects of PEL-2 and CYA-3 on AhR occurred by ligand-dependent and ligand-independent mechanisms, respectively, as demonstrated by ligand binding assay. In a direct enzyme inhibition assay, none of the antocyanins tested inhibited the CYP1A1 marker activity to less than 50% even at 100 μM concentration. PEL-2 and CYA-3 at 100 μM inhibited CYP1A1 to 79% and 65%, respectively. In conclusion, with exception of PEL-2 and CYA-3, there were no effects of 19 major anthocyanins and 3 food supplements containing anthocyanins on AhR-CYP1A1 signaling, implying zero potential of these compounds for food-drug interactions with respect to AhR-CYP1A1 pathway.

• Keywords
• 2,3,7,8-tetrachlorodibenzo-p-dioxin, AhR, Anthocyanins, Aryl hydrocarbon receptor, Cytochrome P450, Food supplements, Food–drug interactions, TCDD, aryl hydrocarbon receptor,
• MeSH
• Anthocyanins chemistry   toxicity   MeSH
• Hep G2 Cells MeSH
• Cytochrome P-450 CYP1A1 metabolism   MeSH
• Adult MeSH
• Glucosides chemistry   toxicity   MeSH
• Hepatocytes drug effects   metabolism   MeSH
• Enzyme Inhibitors toxicity   MeSH
• Food-Drug Interactions MeSH
• Microsomes, Liver drug effects   enzymology   MeSH
• Middle Aged MeSH
• Humans MeSH
• Dietary Supplements MeSH
• Receptors, Aryl Hydrocarbon drug effects   metabolism   MeSH
• Gene Expression Regulation, Enzymologic drug effects   MeSH
• Signal Transduction drug effects   MeSH
• Protein Binding MeSH
• Cell Survival drug effects   MeSH
• Check Tag
• Adult MeSH
• Middle Aged MeSH
• Humans MeSH
• Male MeSH
• Female MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Research Support, N.I.H., Extramural MeSH
• Names of Substances
• Anthocyanins MeSH
• cyanidin-3-O-beta-glucopyranoside MeSH Browser
• Cytochrome P-450 CYP1A1 MeSH
• Glucosides MeSH
• Enzyme Inhibitors MeSH
• pelargonidin MeSH Browser
• Receptors, Aryl Hydrocarbon MeSH

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
• Transcriptional Activation drug effects   MeSH
• Anthocyanins pharmacology   MeSH
• Hep G2 Cells MeSH
• Cytochrome P-450 CYP1A1 biosynthesis   MeSH
• Enzyme Induction MeSH
• Hepatocytes drug effects   enzymology   MeSH
• Microsomes, Liver enzymology   MeSH
• Kinetics MeSH
• Humans MeSH
• Ligands MeSH
• RNA, Messenger biosynthesis   MeSH
• Liver Neoplasms enzymology   MeSH
• Polychlorinated Dibenzodioxins pharmacology   MeSH
• Primary Cell Culture MeSH
• Promoter Regions, Genetic drug effects   MeSH
• Receptors, Aryl Hydrocarbon drug effects   metabolism   MeSH
• Signal Transduction drug effects   MeSH
• Intestinal Neoplasms enzymology   MeSH
• Transfection MeSH
• Basic Helix-Loop-Helix Transcription Factors drug effects   metabolism   MeSH
• Dose-Response Relationship, Drug MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Research Support, N.I.H., Extramural MeSH
• Names of Substances
• AHR protein, human MeSH Browser
• Anthocyanins MeSH
• CYP1A1 protein, human MeSH Browser
• Cytochrome P-450 CYP1A1 MeSH
• Ligands MeSH
• RNA, Messenger MeSH
• pelargonidin MeSH Browser
• Polychlorinated Dibenzodioxins MeSH
• Receptors, Aryl Hydrocarbon MeSH
• Basic Helix-Loop-Helix Transcription Factors MeSH