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

The small/short heterodimer partner (SHP, NR0B2) is a nuclear receptor corepressor lacking a DNA binding domain. SHP is induced by bile acid-activated farnesoid X receptor (FXR) resulting in CYP7A1 gene suppression. In contrast, Pregnane X receptor (PXR) activation by its ligands was recently suggested to inhibit SHP gene transactivation to maximize the induction of PXR target genes. However, there are also conflicting reports in literature whether PXR or rodent Pxr activation down-regulates SHP/Shp expression. Moreover, the PXR-mediated regulation of the SHP gene has been studied only at the SHP mRNA and transactivation (gene reporter assay) levels. In this study, we studied the effect of rifampicin, a prototype PXR ligand, on SHP mRNA, and protein expression in three primary human hepatocyte cultures. We found that SHP mRNA is not systematically down-regulated in hepatocyte in culture after 24 h treatment with rifampicin. Consistently, we did not observe down-regulation of SHP protein in primary human hepatocytes after 24 and 48 h of incubation with rifampicin. We can conclude that although we observed slight down-regulation of SHP mRNA and protein in several hepatocyte preparations, the phenomenon is unlikely critical for PXR-mediated induction of its target genes.

• Keywords
• CYP3A4, PXR, SHP, cytochrome P450, induction,
• Publication type
• Journal Article MeSH

Metformin is widely used in the treatment of type-2 diabetes. The pleotropic effects of metformin on glucose and lipid metabolism have been proposed to be mediated by the activation of AMP-activated protein kinase (AMPK) and the subsequent up-regulation of small heterodimer partner (SHP). SHP suppresses the functions of several nuclear receptors involved in the regulation of hepatic metabolism, including pregnane X receptor (PXR), which is referred to as a "master regulator" of drug/xenobiotic metabolism. In this study, we hypothesize that metformin suppresses the expression of CYP3A4, a main detoxification enzyme and a target gene of PXR, due to SHP up-regulation. We employed various gene reporter assays in cell lines and qRT-PCR in human hepatocytes and in Pxr(-/-) mice. We show that metformin dramatically suppresses PXR-mediated expression of CYP3A4 in hepatocytes. Consistently, metformin significantly suppressed the up-regulation of Cyp3a11 mRNA in the liver and intestine of wild-type mice, but not in Pxr(-/-) mice. A mechanistic investigation of the phenomenon showed that metformin does not significantly up-regulate SHP in human hepatocytes. We further demonstrate that AMPK activation is not involved in this process. We show that metformin disrupts PXR's interaction with steroid receptor coactivator-1 (SRC1) in a two-hybrid assay independently of the PXR ligand binding pocket. Metformin also inhibited vitamin D receptor-, glucocorticoid receptor- and constitutive androstane receptor (CAR)-mediated induction of CYP3A4 mRNA in human hepatocytes. We show, therefore, a suppressive effect of metformin on PXR and other ligand-activated nuclear receptors in transactivation of the main detoxification enzyme CYP3A4 in human hepatocytes.

• MeSH
• Transcriptional Activation MeSH
• Cytochrome P-450 CYP3A genetics   metabolism   MeSH
• Hepatocytes drug effects   metabolism   MeSH
• Hypoglycemic Agents pharmacology   MeSH
• Nuclear Receptor Coactivators metabolism   MeSH
• Constitutive Androstane Receptor MeSH
• Cells, Cultured MeSH
• Humans MeSH
• Membrane Proteins genetics   metabolism   MeSH
• RNA, Messenger metabolism   MeSH
• Metformin pharmacology   MeSH
• Mice, Inbred C57BL MeSH
• Mice, Knockout MeSH
• Mice MeSH
• Reflex, Righting drug effects   MeSH
• Pregnane X Receptor MeSH
• AMP-Activated Protein Kinases physiology   MeSH
• Receptors, Cytoplasmic and Nuclear metabolism   physiology   MeSH
• Receptors, Glucocorticoid physiology   MeSH
• Receptors, Calcitriol physiology   MeSH
• Genes, Reporter MeSH
• Signal Transduction MeSH
• Receptors, Steroid genetics   physiology   MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Research Support, N.I.H., Extramural MeSH
• Names of Substances
• Cyp3a11 protein, mouse MeSH Browser
• Cytochrome P-450 CYP3A MeSH
• Hypoglycemic Agents MeSH
• Nuclear Receptor Coactivators MeSH
• Constitutive Androstane Receptor MeSH
• Membrane Proteins MeSH
• RNA, Messenger MeSH
• Metformin MeSH
• nuclear receptor subfamily 0, group B, member 2 MeSH Browser
• Pregnane X Receptor MeSH
• AMP-Activated Protein Kinases MeSH
• Receptors, Cytoplasmic and Nuclear MeSH
• Receptors, Glucocorticoid MeSH
• Receptors, Calcitriol MeSH
• Receptors, Steroid MeSH