Latest Publications

@article{hyzdalova_aryl_2018,

title = {Aryl Hydrocarbon Receptor-Dependent Metabolism Plays a Significant Role in Estrogen-Like Effects of Polycyclic Aromatic Hydrocarbons on Cell Proliferation.},

author = {Martina Hýžd'alová and Jakub Pivnicka and Ondrej Zapletal and Gerardo Vázquez-Gómez and Jason Matthews and Jirí Neca and Katerina Pencíková and Miroslav Machala and Jan Vondrácek},

doi = {10.1093/toxsci/kfy153},

issn = {1096-0929 1096-6080},

year  = {2018},

date = {2018-10-01},

journal = {Toxicological sciences : an official journal of the Society of Toxicology},

volume = {165},

number = {2},

pages = {447–461},

abstract = {Polycyclic aromatic hydrocarbons (PAHs) are widespread environmental contaminants that interact in a complex manner with both the aryl hydrocarbon receptor (AhR) and estrogen receptors (ER). Their potential endocrine-disrupting activities may depend on both inhibitory AhR-ER cross-talk and on AhR-dependent metabolic production of estrogenic PAH metabolites. Here, we analyzed the impact of AhR on estrogen-like effects of PAHs, such as benzo[a]pyrene (BaP), in particular, on control of cell cycle progression/cell proliferation. Using AhR knockout variant of estrogen-sensitive human breast cancer MCF-7 cells (MCF-7 AhRKO cells), we observed that the AhR-dependent control of cytochrome P450 family 1 (CYP1) expression played a major role in formation of estrogenic BaP metabolites, most notably 3-OH-BaP, which contributed to the ER-dependent induction of cell cycle progression/cell proliferation. Both BaP metabolism and the BaP-induced S-phase transition/cell proliferation were inhibited in MCF-7 AhRKO cells, whereas these cells remained sensitive towards both endogenous estrogen 17β-estradiol or hydroxylated BaP metabolites. BaP was found to increase the activity of ER-dependent luciferase reporter gene in wild-type MCF-7 cells; however, unlike its hydroxylated metabolite, BaP failed to stimulate luciferase activity in MCF-7 AhRKO cells. Similarly, estrogen-like effects of other known estrogenic PAHs, such as benz[a]anthracene or 3-methylcholanthrene, were diminished in MCF-7 AhRKO cells. Ectopic expression of human CYP1A1 and CYP1B1 enzymes partly restored both BaP metabolism and its effects on cell proliferation. Taken together, our data suggest that the AhR-dependent metabolism of PAHs contributes significantly to the impact of PAHs on cell proliferation in estrogen-sensitive cells.},

note = {Place: United States},

keywords = {Aryl Hydrocarbon/genetics/*metabolism, Cell Culture Techniques, Cell Cycle/drug effects/genetics, Cell Proliferation/*drug effects/genetics, Cytochrome P-450 CYP1A1/genetics/metabolism, Cytochrome P-450 CYP1B1/genetics/metabolism, Endocrine Disruptors/metabolism/*toxicity, Estrogen/genetics/metabolism, Gene Expression/drug effects, Gene Knockdown Techniques, Genes, Genetic Vectors, Humans, MCF-7 Cells, Plasmids, Polycyclic Aromatic Hydrocarbons/metabolism/*toxicity, Receptors, Reporter, Transfection},

pubstate = {published},

tppubtype = {article}

}

@article{brenerova_pure_2016,

title = {Pure non-dioxin-like PCB congeners suppress induction of AhR-dependent endpoints in rat liver cells.},

author = {Petra Brenerová and Timo Hamers and Jorke H. Kamstra and Jan Vondráček and Simona Strapáčová and Patrik L. Andersson and Miroslav Machala},

doi = {10.1007/s11356-015-4819-6},

issn = {1614-7499 0944-1344},

year  = {2016},

date = {2016-02-01},

journal = {Environmental science and pollution research international},

volume = {23},

number = {3},

pages = {2099–2107},

abstract = {The relative potencies of non-ortho-substituted coplanar polychlorinated biphenyl (PCB) congeners to activate the aryl hydrocarbon receptor (AhR) and to cause the AhR-dependent toxic events are essential for their risk assessment. Since some studies suggested that abundant non-dioxin-like PCB congeners (NDL-PCBs) may alter the AhR activation by PCB mixtures and possibly cause non-additive effects, we evaluated potential suppressive effects of NDL-PCBs on AhR activation, using a series of 24 highly purified NDL-PCBs. We investigated their impact on the model AhR agonist-induced luciferase reporter gene expression in rat hepatoma cells and on induction of CYP1A1/1B1 mRNAs and deregulation of AhR-dependent cell proliferation in rat liver epithelial cells. PCBs 128, 138, and 170 significantly suppressed AhR activation (with IC50 values from 1.4 to 5.6 μM), followed by PCBs 28, 47, 52, and 180; additionally, PCBs 122, 153, and 168 showed low but still significant potency to reduce luciferase activity. Detection of CYP1A1 mRNA levels in liver epithelial cells largely confirmed these results for the most abundant NDL-PCBs, whereas the other AhR-dependent events (CYP1B1 mRNA expression, induction of cell proliferation in confluent cells) were less sensitive to NDL-PCBs, thus indicating a more complex regulation of these endpoints. The present data suggest that some NDL-PCBs could modulate overall dioxin-like effects in complex mixtures.},

note = {Place: Germany},

keywords = {Animals, Aryl hydrocarbon receptor, Aryl Hydrocarbon/genetics/*metabolism, Cell Line, Cell Proliferation/drug effects, Cytochrome P-450 CYP1A1/genetics/metabolism, Cytochrome P450, Disruption of contact inhibition, DR-CALUX® assay, Epithelial Cells/cytology/drug effects/metabolism, Gene Expression/drug effects, Hepatocytes/cytology/drug effects/metabolism, Liver/*drug effects/metabolism, NDL-PCBs, Polychlorinated Biphenyls/*chemistry/*toxicity, Rats, Receptors, Relative effect potency, Signal Transduction/drug effects},

pubstate = {published},

tppubtype = {article}

}

@article{prochazkova_interplay_2011,

title = {The interplay of the aryl hydrocarbon receptor and β-catenin alters both AhR-dependent transcription and Wnt/β-catenin signaling in liver progenitors.},

author = {Jirina Procházková and Markéta Kabátková and Vítezslav Bryja and Lenka Umannová and Ondrej Bernatík and Alois Kozubík and Miroslav Machala and Jan Vondrácek},

doi = {10.1093/toxsci/kfr129},

issn = {1096-0929},

year  = {2011},

date = {2011-08-01},

journal = {Toxicological sciences : an official journal of the Society of Toxicology},

volume = {122},

number = {2},

pages = {349–360},

abstract = {β-catenin is a key integrator of cadherin-mediated cell-cell adhesion and transcriptional regulation through the Wnt/β-catenin pathway, which plays an important role in liver biology. Using a model of contact-inhibited liver progenitor cells, we examined the interactions of Wnt/β-catenin signaling with the aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor, which mediates the toxicity of dioxin-like compounds, including their effects on development and hepatocarcinogenesis. We found that AhR and Wnt/β-catenin cooperated in the induction of AhR transcriptional targets, such as Cyp1a1 and Cyp1b1. However, simultaneously, the activation of AhR led to a decrease of dephosphorylated active β-catenin pool, as well as to hypophosphorylation of Dishevelled, participating in regulation of Wnt signaling. A sustained AhR activation by its model ligand, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), led to a downregulation of a number of Wnt/β-catenin pathway target genes. TCDD also induced a switch in cytokeratin expression, where downregulation of cytokeratins 14 and 19 was accompanied with an increased cytokeratin 8 expression. Together with a downregulation of additional markers associated with stem-like phenotype, this indicated that the AhR activation interfered with differentiation of liver progenitors. The downregulation of β-catenin was also related to a reduced cell adhesion, disruption of E-cadherin-mediated cell-cell junctions and an increased G1-S transition in liver progenitor cell line. In conclusion, although β-catenin augmented the expression of selected AhR target genes, the persistent AhR activation may lead to downregulation of Wnt/β-catenin signaling, thus altering differentiation and/or proliferative status of liver progenitor cells.},

note = {Place: United States},

keywords = {Animals, Aryl Hydrocarbon Hydroxylases/genetics/metabolism, Aryl Hydrocarbon/genetics/*metabolism, beta Catenin/genetics/*metabolism, Cadherins/genetics, Cell Adhesion, Cell Differentiation, Cell Line, Cytochrome P-450 CYP1A1/genetics/metabolism, Cytochrome P-450 CYP1B1, Down-Regulation/drug effects, Hepatocytes/drug effects, Inbred F344, Liver/*drug effects, Polychlorinated Dibenzodioxins/toxicity, Rats, Receptors, Wnt Proteins/genetics/*metabolism, Wnt Signaling Pathway},

pubstate = {published},

tppubtype = {article}

}

@article{zatloukalova_beta-naphthoflavone_2007,

title = {beta-Naphthoflavone and 3'-methoxy-4'-nitroflavone exert ambiguous effects on Ah receptor-dependent cell proliferation and gene expression in rat liver 'stem-like' cells.},

author = {Jirina Zatloukalová and Lenka Svihálková-Sindlerová and Alois Kozubík and Pavel Krcmár and Miroslav Machala and Jan Vondrácek},

doi = {10.1016/j.bcp.2007.01.032},

issn = {0006-2952},

year  = {2007},

date = {2007-05-01},

journal = {Biochemical pharmacology},

volume = {73},

number = {10},

pages = {1622–1634},

abstract = {Both natural and synthetic flavonoids are known to interact with the aryl hydrocarbon receptor (AhR); however, their agonist/antagonist properties in vitro have been so far studied mostly in the context of cytochrome P450 1A1 gene (Cyp1a1) regulation. We investigated effects of two synthetic flavones known either as AhR agonist (beta-naphthoflavone; BNF) or antagonist (3'-methoxy-4'-nitroflavone; 3M4NF), using an in vitro model of liver 'stem-like' cells, on expression of various AhR target genes and AhR-dependent cell proliferation. We found that the presumed antagonist 3M4NF induces a partial nuclear translocation and activation of AhR. Although inhibiting the 2,3,7,8-tetrachlorodibenzo-p-dioxin-induced Cyp1a1 expression, 3M4NF alone induced a minor increase of CYP1A1 mRNA and protein. However, 3M4NF did not induce AhR binding to synthetic dioxin response elements (DRE). In contrast to Cyp1a1, 3M4NF induced a marked expression of other AhR-regulated genes, such as Cyp1b1 and Nqo1, as well as transcriptional repression of Cdh13 gene, confirming that its effects may be promoter-context specific. Like BNF, 3M4NF induced AhR-dependent cell proliferation of contact-inhibited rat liver 'stem-like' WB-F344 cells, associated with a marked upregulation of Cyclin A, as well as the downregulation of proteins involved in formation of cell-cell contacts. Based on these experimental findings, we conclude that partial agonists/antagonists of AhR can increase cell proliferation rate and AhR-dependent genes expression in both cell type- and gene-specific manner. The specificity of effects of flavones on diverse AhR targets should be taken into account, when studying AhR signaling using presumed AhR antagonists.},

note = {Place: England},

keywords = {Animals, Aryl Hydrocarbon/genetics/*metabolism, beta-Naphthoflavone/*pharmacology, Cadherins/genetics/metabolism, Cell Proliferation/*drug effects, Cells, Cultured, Cytochrome P-450 CYP1A1/genetics/metabolism, Flavonoids/*pharmacology, Gene Expression/*drug effects/physiology, Hepatocytes/*drug effects/physiology, Inbred F344, Liver/cytology, NAD(P)H Dehydrogenase (Quinone)/genetics/metabolism, Rats, Receptors},

pubstate = {published},

tppubtype = {article}

}