Latest Publications

@article{vondracek_assessment_2017,

title = {Assessment of the aryl hydrocarbon receptor-mediated activities of polycyclic aromatic hydrocarbons in a human cell-based reporter gene assay.},

author = {Jan Vondráček and Kateřina Pěnčíková and Jiří Neča and Miroslav Ciganek and Aneta Grycová and Zdeněk Dvořák and Miroslav Machala},

doi = {10.1016/j.envpol.2016.09.064},

issn = {1873-6424 0269-7491},

year  = {2017},

date = {2017-01-01},

journal = {Environmental pollution (Barking, Essex : 1987)},

volume = {220},

number = {Pt A},

pages = {307–316},

abstract = {Activation of the aryl hydrocarbon receptor (AhR)-mediated activity is one of key events in toxicity of polycyclic aromatic hydrocarbons (PAHs). Although various classes of AhR ligands may differentially activate human and rodent AhR, there is presently a lack of data on the human AhR-inducing relative potencies (REPs) of PAHs. Here, we focused on estimation of the AhR-mediated activities of a large set of environmental PAHs in human gene reporter AZ-AhR cell line, with an aim to develop the human AhR-based REP values with potential implications for risk assessment of PAHs. The previously identified weakly active PAHs mostly failed to activate the AhR in human cells. The order for REPs of individual PAHs in human cells largely corresponded with the available data from rodent-based experimental systems; nevertheless, we identified differences up to one order of magnitude in REP values of PAHs between human and rodent cells. Higher REP values were found in human cells for some important environmental contaminants or suspected carcinogens, such as indeno[1,2,3-cd]pyrene, benz[a]anthracene or benzo[b]fluoranthene, while lower REP values were determined for methyl-substituted PAHs. Our results also indicate that a different rate of metabolism for individual PAHs in human vs. rodent cells may affect estimation of REP values in human cell-based assay, and potentially alter toxicity of some compounds, such as benzofluoranthenes, in humans. We applied the AZ-AhR assay to evaluation of the AhR-mediated activity of complex mixtures of organic compounds associated with diesel exhaust particles, and we identified the polar compounds present in these mixtures as being particularly highly active in human cells, as compared with rodent cells. The present data suggest that differences may exist between the AhR-mediated potencies of PAHs in human and rodent cells, and that the AhR-mediated effects of polar PAH derivatives and metabolites in human cell models deserve further attention.},

note = {Place: England},

keywords = {AhR, AhR-mediated activity, Aryl Hydrocarbon/metabolism/*physiology, Basic Helix-Loop-Helix Transcription Factors/metabolism/*physiology, Biological Assay/methods, Carcinogens/toxicity, Cell Line, Environmental Pollutants/*toxicity, Genes, Humans, PAH mixtures, PAHs, Polycyclic Aromatic Hydrocarbons/*toxicity, Receptors, Relative effective potency, Reporter, Vehicle Emissions/toxicity},

pubstate = {published},

tppubtype = {article}

}

@article{andrysik_activation_2011,

title = {Activation of the aryl hydrocarbon receptor is the major toxic mode of action of an organic extract of a reference urban dust particulate matter mixture: the role of polycyclic aromatic hydrocarbons.},

author = {Zdeněk Andrysík and Jan Vondráček and Soňa Marvanová and Miroslav Ciganek and Jiří Neča and Kateřina Pěnčíková and Brinda Mahadevan and Jan Topinka and William M. Baird and Alois Kozubík and Miroslav Machala},

doi = {10.1016/j.mrfmmm.2011.06.011},

issn = {0027-5107},

year  = {2011},

date = {2011-09-01},

journal = {Mutation research},

volume = {714},

number = {1-2},

pages = {53–62},

abstract = {Many of the toxic and carcinogenic effects of urban air pollution have been linked to polycyclic aromatic hydrocarbons (PAHs) adsorbed to airborne particulate matter (PM). The carcinogenic properties of PAHs in complex organic mixtures derived from PM have been chiefly attributed to their mutagenicity. Nevertheless, PAHs are also potent activators of the aryl hydrocarbon receptor (AhR), which may contribute to their nongenotoxic effects, including tumor promotion. As the genotoxicity of carcinogenic PAHs in complex mixtures derived from urban PM is often inhibited by other mixture constituents, the AhR-mediated activity of urban PM extracts might significantly contribute to the carcinogenic activity of such mixtures. In the present study, we used an organic extract of the urban dust standard reference material, SRM1649a, as a model mixture to study a range of toxic effects related to DNA damage and AhR activation. Both the organic extract and its neutral aromatic fraction formed a low number of DNA adducts per nucleotide in the liver epithelial WB-F344 cells model, without inducing DNA damage response, such as tumor suppressor p53 activation and apoptosis. In contrast, we found that this extract, as well as its neutral and polar fractions, were potent inducers of a range of AhR-mediated responses, including induction of the AhR-mediated transcription, such as cytochrome P450 1A1/1B1 expression, and the AhR-dependent cell proliferation. Importantly, these toxic events occurred at doses one order of magnitude lower than DNA damage. The AhR-mediated activity of the neutral fraction was linked to PAHs and their derivatives, as polychlorinated dibenzo-p-dioxins, dibenzofurans and biphenyls were only minor contributors to the overall AhR-mediated activity. Taken together, our data suggest that more attention should be paid to the AhR-dependent nongenotoxic events elicited by urban PM constituents, especially PAHs and their derivatives.},

note = {Place: Netherlands},

keywords = {Animals, Apoptosis/drug effects, Aryl Hydrocarbon/*metabolism, Cell Line, Cell Proliferation/drug effects, Cytochrome P-450 CYP1A1/metabolism, DNA Adducts/drug effects, DNA Damage/*drug effects, Dose-Response Relationship, Drug, Genes, Liver/drug effects, Mutagens/*toxicity, Organic Chemicals/*toxicity, p53/drug effects, Particulate Matter/*toxicity, Polycyclic Aromatic Hydrocarbons/*toxicity, Rats, Receptors},

pubstate = {published},

tppubtype = {article}

}

@article{hruba_genotoxic_2010,

title = {Genotoxic polycyclic aromatic hydrocarbons fail to induce the p53-dependent DNA damage response, apoptosis or cell-cycle arrest in human prostate carcinoma LNCaP cells.},

author = {Eva Hrubá and Lenka Trilecová and Sona Marvanová and Pavel Krcmár and Lenka Vykopalová and Alena Milcová and Helena Líbalová and Jan Topinka and Andrea Starsíchová and Karel Soucek and Jan Vondrácek and Miroslav Machala},

doi = {10.1016/j.toxlet.2010.06.004},

issn = {1879-3169 0378-4274},

year  = {2010},

date = {2010-09-01},

journal = {Toxicology letters},

volume = {197},

number = {3},

pages = {227–235},

abstract = {Exposure to polycyclic aromatic hydrocarbons (PAHs) has been positively associated with prostate cancer, but knowledge of the formation of PAH-DNA adducts and related genotoxic events in prostatic cells is limited. In the present study, benzo[a]pyrene (BaP), a potent mutagenic PAH, formed significant levels of DNA adducts in cell lines derived from human prostate carcinoma. When analyzing the effect of BaP on the induction of CYP1 enzymes participating in the metabolic activation of PAHs in LNCaP cells, we found that BaP induced expression of CYP1A1 and CYP1A2, but not CYP1B1 enzyme. Despite a significant amount of DNA adducts being formed by BaP and, to a lesser extent also by another strong genotoxin, dibenzo[a,l]pyrene, neither apoptosis nor cell-cycle arrest were induced in LNCaP cells. LNCaP cells were not sensitized to the induction of apoptosis by PAHs even through inhibition of the phosphoinositide-3-kinase/Akt pro-survival pathway. The lack of apoptosis was not due a disruption of expression of pro-apoptotic and pro-survival members of the Bcl-2 family of apoptosis regulators. In contrast to other genotoxic stimuli, genotoxic PAHs failed to induce DNA double-strand breaks, as illustrated by the lack of phosphorylation of histone H2AX or checkpoint kinase-2. BaP did not activate p53, as evidenced by the lack of p53 accumulation, phosphorylation at Ser15, or induction of p53 transcriptional targets. Taken together, although genotoxic PAHs produced significant levels of DNA adducts in a model of human prostate carcinoma cells, they did not activate the mechanisms leading to elimination of cells with significant damage to DNA, presumably due to their failure to activate the p53-dependent DNA damage response.},

note = {Place: Netherlands},

keywords = {Animals, Apoptosis/*drug effects, Carcinoma/*metabolism, Cell Line, DNA Damage/*drug effects, Environmental Pollutants/toxicity, Gene Expression Regulation, Male, Neoplastic/drug effects, Polycyclic Aromatic Hydrocarbons/*toxicity, Prostatic Neoplasms/*metabolism, Tumor, Tumor Suppressor Protein p53/*metabolism},

pubstate = {published},

tppubtype = {article}

}

@article{kummer_estrogenic_2008,

title = {Estrogenic activity of environmental polycyclic aromatic hydrocarbons in uterus of immature Wistar rats.},

author = {Vladimír Kummer and Jarmila Masková and Zdenek Zralý and Jirí Neca and Pavlína Simecková and Jan Vondrácek and Miroslav Machala},

doi = {10.1016/j.toxlet.2008.06.862},

issn = {0378-4274},

year  = {2008},

date = {2008-08-01},

journal = {Toxicology letters},

volume = {180},

number = {3},

pages = {212–221},

abstract = {Polycyclic aromatic hydrocarbons (PAHs) are an important group of environmental pollutants, known for their mutagenic and carcinogenic activities. Many PAHs are aryl hydrocarbon receptor (AhR) ligands and several recent studies have suggested that PAHs or their metabolites may activate estrogen receptors (ER). The present study investigated possible estrogenic/antiestrogenic effects of abundant environmental contaminants benzo[a]pyrene (BaP), benz[a]anthracene (BaA), fluoranthene (Fla) and benzo[k]fluoranthene (BkF) in vivo, using the immature rat uterotrophic assay. The present results suggest that BaA, BaP and Fla behaved as estrogen-like compounds in immature Wistar rats, when applied for 3 consecutive days at 10mg/kg/day, as documented by a significant increase of uterine weight and hypertrophy of luminal epithelium. These effects were likely to be mediated by ERalpha, a major subtype of ER present in uterus, as they were inhibited by treatment with ER antagonist ICI 182,780. BaA, the most potent of studied PAHs, induced a significant estrogenic effect within a concentration range 0.1-50mg/kg/day; however, it did not reach the maximum level induced by reference estrogens. The proposed antiestrogenicity of the potent AhR agonist BkF was not confirmed in the present in vivo study; the exposure to BkF did not significantly affect the uterine weight, although a weak suppression of ERalpha immunostaining was observed in luminal and glandular epithelium, possibly related to its AhR-mediated activity. The PAHs under study did not induce marked genotoxic damage in uterine tissues, as documented by the lack of Ser-15-phoshorylated p53 protein staining. With the exception of Fla, all three remaining compounds increased CYP1-dependent monooxygenation activities in liver at the doses used, suggesting that the potential tissue-specific antiestrogenic effects of PAHs mediated by metabolization of 17beta-estradiol also cannot be excluded. Taken together, these environmentally relevant PAHs induced estrogenic effects in vivo, which might affect their toxic impact and carcinogenicity.},

note = {Place: Netherlands},

keywords = {Animals, Cytochrome P-450 CYP1A1/metabolism, Endocrine Disruptors/*toxicity, Environmental Pollutants/*toxicity, Epithelium/drug effects, Estradiol/metabolism, Estrogen Receptor alpha/metabolism, Estrogens/*biosynthesis, Female, Hydroxylation, Immunohistochemistry, Liver/drug effects/metabolism, Microsomes, Organ Size/drug effects, Ovary/drug effects, Phosphorylation, Polycyclic Aromatic Hydrocarbons/*toxicity, Rats, Tumor Suppressor Protein p53/metabolism, Uterus/drug effects/*metabolism, Wistar},

pubstate = {published},

tppubtype = {article}

}

@article{andrysik_aryl_2007,

title = {The aryl hydrocarbon receptor-dependent deregulation of cell cycle control induced by polycyclic aromatic hydrocarbons in rat liver epithelial cells.},

author = {Zdenek Andrysík and Jan Vondrácek and Miroslav Machala and Pavel Krcmár and Lenka Svihálková-Sindlerová and Anne Kranz and Carsten Weiss and Dagmar Faust and Alois Kozubík and Cornelia Dietrich},

doi = {10.1016/j.mrfmmm.2006.10.004},

issn = {0027-5107},

year  = {2007},

date = {2007-02-01},

journal = {Mutation research},

volume = {615},

number = {1-2},

pages = {87–97},

abstract = {Disruption of cell proliferation control by polycyclic aromatic hydrocarbons (PAHs) may contribute to their carcinogenicity. We investigated role of the aryl hydrocarbon receptor (AhR) in disruption of contact inhibition in rat liver epithelial WB-F344 'stem-like' cells, induced by the weakly mutagenic benz[a]anthracene (BaA), benzo[b]fluoranthene (BbF) and by the strongly mutagenic benzo[a]pyrene (BaP). There were significant differences between the effects of BaA and BbF, and those of the strongly genotoxic BaP. Both BaA and BbF increased percentage of cells entering S-phase and cell numbers, associated with an increased expression of Cyclin A and Cyclin A/cdk2 complex activity. Their effects were significantly reduced in cells expressing a dominant-negative AhR mutant (dnAhR). Roscovitine, a chemical inhibitor of cdk2, abolished the induction of cell proliferation by BbF. However, neither BaA nor BbF modulated expression of the principal cdk inhibitor involved in maintenance of contact inhibition, p27(Kip1), or pRb phosphorylation. The strongly mutagenic BaP induced apoptosis, a decrease in total cell numbers and significantly higher percentage of cells entering S-phase than either BaA or BbF. Given that BaP induced high levels of Cyclin A/cdk2 activity, downregulation of p27(Kip1) and hyperphosphorylation of pRb, the accumulation of cells in S-phase was probably due to cell proliferation, although S-phase arrest due to blocked replication forks can not be excluded. Both types of effects of BaP were significantly attenuated in dnAhR cells. Transfection of WB-F344 cells with siRNA targeted against AhR decreased induction of Cyclin A induced by BbF or BaP, further supporting the role of AhR in proliferative effects of PAHs. This suggest that activation of AhR plays a significant role both in disruption of contact inhibition by weakly mutagenic PAHs and in genotoxic effects of BaP possibly leading to enhanced cell proliferation. Thus, PAHs may increase proliferative rate and the likelihood of fixation of mutations.},

note = {Place: Netherlands},

keywords = {Animals, Apoptosis/drug effects, Aryl Hydrocarbon/antagonists & inhibitors/genetics/*metabolism, Base Sequence, Benz(a)Anthracenes/toxicity, Benzo(a)pyrene/toxicity, Cell Cycle Proteins/metabolism, Cell Cycle/*drug effects/*physiology, Cell Line, Cell Proliferation/drug effects, Cyclin A/metabolism, Cyclin-Dependent Kinase 2/metabolism, Cytochrome P-450 CYP1A1/genetics, Epithelial Cells/cytology/drug effects/metabolism, Fluorenes/toxicity, Gene Expression/drug effects, Hepatocytes/cytology/*drug effects/*metabolism, Messenger/genetics/metabolism, Multiprotein Complexes, Mutagens/toxicity, Mutation, Polycyclic Aromatic Hydrocarbons/*toxicity, Rats, Receptors, RNA, Small Interfering/genetics},

pubstate = {published},

tppubtype = {article}

}

@article{andrysik_activation_2006,

title = {Activation of ERK1/2 and p38 kinases by polycyclic aromatic hydrocarbons in rat liver epithelial cells is associated with induction of apoptosis.},

author = {Zdenek Andrysík and Miroslav Machala and Katerina Chramostová and Jirina Hofmanová and Alois Kozubík and Jan Vondrácek},

doi = {10.1016/j.taap.2005.06.007},

issn = {0041-008X},

year  = {2006},

date = {2006-03-01},

journal = {Toxicology and applied pharmacology},

volume = {211},

number = {3},

pages = {198–208},

abstract = {Deregulation of various signaling pathways, linked either to induction of cell proliferation or to modulation of cellular differentiation and apoptosis, has been proposed to contribute to carcinogenicity of polycyclic aromatic hydrocarbons (PAHs). In the present study, we investigated effects of the PAHs previously shown to induce cell proliferation and/or apoptosis in contact-inhibited rat liver epithelial WB-F344 cells, with an aim to define the role of mitogen-activated protein kinases in both events. We found that only strong genotoxin dibenzo[a,l]pyrene (DBalP) activated extracellular signal-regulated kinases 1 and 2 (ERK1/2) and p38 kinase, but not c-Jun N-terminal kinases (JNKs), at concentrations inducing both apoptosis and phosphorylation of p53 tumor suppressor at serine 15 residue. In contrast, the PAHs stimulating cell proliferation in WB-F344 cell line had no effect on activation of ERK1/2, p38 or JNKs. Synthetic inhibitors of ERK1/2 activation (U0126) or p38 kinase activity (SB203580) prevented both apoptosis and induction of p53 phosphorylation by DBalP. Pifithrin-alpha, inhibitor of p53 transcriptional activity, prevented induction of apoptosis and activation of ERK1/2 and p38. Taken together, our data suggest that both ERK1/2 and p38 are activated in response to DBalP and that they might be involved in regulation of cellular response to DNA damage induced by DBalP, while neither kinase is involved in the release from contact inhibition induced by PAHs.},

note = {Place: United States},

keywords = {*Epithelial Cells/cytology/drug effects/enzymology, *Liver/cytology/drug effects/enzymology, Animals, Apoptosis/*drug effects, Cell Cycle/drug effects, Cell Line, Cell Proliferation/drug effects, Enzyme Activation/drug effects, Enzyme Inhibitors/pharmacology, Extracellular Signal-Regulated MAP Kinases/*metabolism, JNK Mitogen-Activated Protein Kinases/metabolism, p38 Mitogen-Activated Protein Kinases/*metabolism, Phosphorylation, Polycyclic Aromatic Hydrocarbons/*toxicity, Rats},

pubstate = {published},

tppubtype = {article}

}

@article{chramostova_polycyclic_2004,

title = {Polycyclic aromatic hydrocarbons modulate cell proliferation in rat hepatic epithelial stem-like WB-F344 cells.},

author = {Katerina Chramostová and Jan Vondrácek and Lenka Sindlerová and Borivoj Vojtesek and Alois Kozubík and Miroslav Machala},

doi = {10.1016/j.taap.2003.12.008},

issn = {0041-008X},

year  = {2004},

date = {2004-04-01},

journal = {Toxicology and applied pharmacology},

volume = {196},

number = {1},

pages = {136–148},

abstract = {Although many polycyclic aromatic hydrocarbons (PAHs) are recognized as potent mutagens and carcinogens, relatively little is known about their role in the tumor promotion. It is known that 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) can induce release of rat hepatic oval epithelial cells from contact inhibition by a mechanism possibly involving the aryl hydrocarbon receptor (AhR) activation. Many PAHs are AhR ligands and are known to act as transient inducers of AhR-mediated activity. In this study, effects of 19 selected PAHs on proliferation of confluent rat liver epithelial WB-F344 cells were investigated. Non-mutagens that are weak activators or nonactivators of AhR-mediated activity had no effect on cell proliferation. Relatively strong or moderate AhR ligands with low mutagenic potencies, such as benzofluoranthenes, benz[a]anthracene, and chrysene, were found to increase cell numbers, which corresponded to an increased percentage of cells entering S-phase. Strong mutagens, including benzo[a]pyrene and dibenzo[a,l]pyrene, increased a percentage of cells in S-phase without inducing a concomitant increase in cell numbers. The treatment with mutagenic PAHs was associated with an increased DNA synthesis and induction of cell death, which corresponded with the activation of p53 tumor suppressor. Apoptosis was blocked by pifithrin-alpha, the chemical inhibitor of p53. Both weakly and strongly mutagenic PAHs known as AhR ligands were found to induce significant increase of cytochrome P4501A activity, suggesting a presence of functional AhR. The results of the present study seem to suggest that a release from contact inhibition could be a part of tumor promoting effects of AhR-activating PAHs; however, the genotoxic effects of some PAHs associated with p53 activation might interfere with this process.},

note = {Place: United States},

keywords = {Animals, Apoptosis/drug effects, Aryl Hydrocarbon/metabolism, Cell Division/drug effects, Cells, Cultured, Cytochrome P-450 CYP1A1/metabolism, Dose-Response Relationship, Drug, Epithelial Cells/*drug effects/enzymology/metabolism, Liver/*cytology, Mutagens/*toxicity, Polycyclic Aromatic Hydrocarbons/*toxicity, Rats, Receptors, Stem Cells/*drug effects/enzymology/metabolism, Tumor Suppressor Protein p53/biosynthesis},

pubstate = {published},

tppubtype = {article}

}