Latest Publications

@article{zapletal_butyrate_2019,

title = {Butyrate interacts with benzo[a]pyrene to alter expression and activities of xenobiotic metabolizing enzymes involved in metabolism of carcinogens within colon epithelial cell models.},

author = {Ondřej Zapletal and Jiřina Procházková and Vít Dubec and Jiřina Hofmanová and Alois Kozubík and Jan Vondráček},

doi = {10.1016/j.tox.2018.11.001},

issn = {1879-3185 0300-483X},

year  = {2019},

date = {2019-01-01},

journal = {Toxicology},

volume = {412},

pages = {1–11},

abstract = {Butyrate helps to maintain colon homeostasis and exhibits chemopreventive effects in colon epithelium. We examined the interactive effects of butyrate and benzo[a]pyrene (BaP), dietary carcinogen, in regulation of expression of a panel of phase I and II xenobiotic metabolizing enzymes (XMEs) in human colon cells. In human colon carcinoma HCT-116 and HT-29 cell lines, butyrate alone increased mRNA levels of some enzymes, such as N-acetyltransferases (in particular NAT2). In combination with BaP, butyrate potentiated induction of cytochrome P450 family 1 enzymes (CYP1A1), aldo-keto reductases (AKR1C1) or UDP-glucuronosyltransferases (UGT1A1). There were some notable differences between cell lines, as butyrate potentiated induction of NAD(P)H:quinone oxidoreductase 1 (NQO1) and UGT1A4 only in HCT-116 cells, and it even repressed AKR1C3 induction in HT-29 cells. Butyrate also promoted induction of CYP1, NQO1, NAT2, UGT1A1 or UGT1A4 in human colon Caco-2 cells, in a differentiation-dependent manner. Differentiated Caco-2 cells exhibited a higher inducibility of selected XME genes than undifferentiated cells. Butyrate increased induction of enzymatic activities of NATs, NQO1 and UGTs by BaP in HCT-116 and HT29 cells, whereas in differentiated Caco-2 cells it helped to increase only enzymatic activity of NQO1 and UGTs. Together, the present data suggest that butyrate may modulate expression/activities of several enzymes involved in metabolism of carcinogens in colon. In some cases (NAT2, UGT1 A1), this was linked to inhibition of histone deacetylases (HDAC), as confirmed by using HDAC inhibitor trichostatin A. These results may have implications for our understanding of the role of butyrate in regulation of XMEs and carcinogen metabolism in colon.},

note = {Place: Ireland},

keywords = {Benzo(a)pyrene/*toxicity, Butyrate, Butyrates/*pharmacology, Carcinogens/*toxicity, Cell Line, Colon epithelium, Colon/cytology, Epithelial Cells/drug effects/metabolism, Humans, N-acetyltransferases, NAD(P)H:quinone oxidoreductase 1, Oxidoreductases/genetics/*metabolism, Polycyclic aromatic hydrocarbons, Transferases/genetics/*metabolism, UDP-glucuronosyltransferases, Xenobiotics/metabolism},

pubstate = {published},

tppubtype = {article}

}

@article{andrysik_aryl_2013,

title = {Aryl hydrocarbon receptor-mediated disruption of contact inhibition is associated with connexin43 downregulation and inhibition of gap junctional intercellular communication.},

author = {Zdeněk Andrysík and Jiřina Procházková and Markéta Kabátková and Lenka Umannová and Pavlína Simečková and Jiří Kohoutek and Alois Kozubík and Miroslav Machala and Jan Vondráček},

doi = {10.1007/s00204-012-0963-7},

issn = {1432-0738 0340-5761},

year  = {2013},

date = {2013-03-01},

journal = {Archives of toxicology},

volume = {87},

number = {3},

pages = {491–503},

abstract = {The aryl hydrocarbon receptor (AhR) contributes to the control of cell-to-cell communication, cell adhesion, migration or proliferation. In the present study, we investigated the regulation of connexin43 (Cx43) and Cx43-mediated gap junctional intercellular communication (GJIC) during the AhR-dependent disruption of contact inhibition in non-tumorigenic liver epithelial cells. The contact inhibition of cell proliferation is a process restricting the cell division of confluent non-transformed cells, which is frequently abolished in cancer cells; however, the mechanisms contributing to its disruption are still only partially understood. Disruption of contact inhibition, which was induced by toxic AhR ligands 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) or polycyclic aromatic hydrocarbons in epithelial WB-F344 cells, reduced Cx43 protein levels, possibly via enhanced proteasomal degradation, significantly decreased the amount of gap junction plaques and downregulated GJIC, in an AhR-dependent manner. Although both intracellular and membrane Cx43 pools were markedly reduced in cells released from contact inhibition by TCDD, siRNA-mediated Cx43 knock-down was not sufficient to stimulate proliferation in contact-inhibited cells. Our data suggest that downregulation of Cx43/GJIC in non-transformed epithelial cells is an inherent part of disruption of contact inhibition, which occurs at the post-transcriptional level. This process runs in parallel with alterations of other forms of cell-to-cell communication, thus suggesting that toxic AhR agonists may simultaneously abrogate contact inhibition and reduce GJIC, two essential mechanisms linked to deregulation of cell-to-cell communication during tumor promotion and progression.},

note = {Place: Germany},

keywords = {Animals, Aryl Hydrocarbon/*agonists/genetics/metabolism, Benz(a)Anthracenes/toxicity, Carcinogens/*toxicity, Cell Communication/*drug effects, Cell Line, Cell Proliferation, Cell Transformation, Connexin 43/genetics/*metabolism, Contact Inhibition/*drug effects, Dose-Response Relationship, Down-Regulation, Drug, Epithelial Cells/*drug effects/metabolism/pathology, Fluorenes/toxicity, Gap Junctions/*drug effects/metabolism/pathology, Gene Knockdown Techniques, Indoles/pharmacology, Ligands, Liver Neoplasms/chemically induced/metabolism/pathology, Liver/*drug effects/metabolism/pathology, Neoplastic/chemically induced/metabolism/pathology, Phloroglucinol/analogs & derivatives/pharmacology, Phosphorylation, Polychlorinated Dibenzodioxins/toxicity, Proteasome Endopeptidase Complex/metabolism, Rats, Receptors, RNA Interference, Signal Transduction/*drug effects, Time Factors, Transfection},

pubstate = {published},

tppubtype = {article}

}

@article{valovicova_genotoxicity_2012,

title = {Genotoxicity of 7H-dibenzo[c,g]carbazole and its methyl derivatives in human keratinocytes.},

author = {Zuzana Valovičová and Monika Mesárošová and Lenka Trilecová and Eva Hrubá and Soňa Marvanová and Pavel Krčmář and Alena Milcová and Jana Schmuczerová and Jan Vondráček and Miroslav Machala and Jan Topinka and Alena Gábelová},

doi = {10.1016/j.mrgentox.2011.12.030},

issn = {0027-5107},

year  = {2012},

date = {2012-03-01},

journal = {Mutation research},

volume = {743},

number = {1-2},

pages = {91–98},

abstract = {Differences between tissues in the expression of drug-metabolizing enzymes may substantially contribute to tissue-specificity of chemical carcinogens. To verify this hypothesis, the spontaneously immortalized human keratinocytes HaCaT were used, in order to evaluate the genotoxic potential of 7H-dibenzo[c,g]carbazole (DBC), a known hepatocarcinogen and sarcomagen, and its synthetic tissue-specific derivatives, 5,9-dimethyl-DBC (DiMeDBC) and N-methyl-DBC (N-MeDBC), which manifest specific tropism to the liver and skin, respectively. HaCaT cells mainly express cytochrome P4501A1 (CYP1A1), which is involved in metabolism of DBC and N-MeDBC, but not DiMeDBC [10]. Both DBC and the sarcomagen N-MeDBC induced significant levels of DNA strand-breaks, micronuclei, and DNA adducts followed by the phosphorylation of the p53 protein and histone H2AX in HaCaT cells. In contrast, the specific hepatocarcinogen DiMeDBC was devoid of any significant genotoxic activity in this cell line. Our study demonstrates that the absence of drug-metabolizing enzyme(s) involved in DiMeDBC metabolism may contribute substantially to the tissue-specific genotoxicity of this hepatocarcinogen.},

note = {Place: Netherlands},

keywords = {Carbazoles/chemistry/*toxicity, Carcinogens/*toxicity, Cell Line, Cytochrome P-450 CYP1A1/metabolism, DNA Breaks, Humans, Keratinocytes/*drug effects/metabolism, Mutagenicity Tests, Mutagens/*toxicity, Organ Specificity, Single-Stranded},

pubstate = {published},

tppubtype = {article}

}

@article{valovicova_differences_2009,

title = {Differences in DNA damage and repair produced by systemic, hepatocarcinogenic and sarcomagenic dibenzocarbazole derivatives in a model of rat liver progenitor cells.},

author = {Zuzana Valovicová and Sona Marvanová and Monika Mészárosová and Annamária Srancíková and Lenka Trilecová and Alena Milcová and Helena Líbalová and Jan Vondrácek and Miroslav Machala and Jan Topinka and Alena Gábelová},

doi = {10.1016/j.mrfmmm.2009.02.014},

issn = {0027-5107},

year  = {2009},

date = {2009-06-01},

journal = {Mutation research},

volume = {665},

number = {1-2},

pages = {51–60},

abstract = {Liver progenitor (oval) cells are a potential target cell population for hepatocarcinogens. Our recent study showed that the liver carcinogens 7H-dibenzo[c,g]carbazole (DBC) and 5,9-dimethyldibenzo[c,g]carbazole (DiMeDBC), but not the sarcomagen N-methyldibenzo[c,g]carbazole (N-MeDBC), induced several cellular events associated with tumor promotion in WB-F344 cells, an in vitro model of liver oval cells [J. Vondracek, L. Svihalkova-Sindlerova, K. Pencikova, P. Krcmar, Z. Andrysik, K. Chramostova, S. Marvanova, Z. Valovicova, A. Kozubik, A. Gabelova, M. Machala, 7H-Dibenzo[c,g]carbazole and 5,9-dimethyldibenzo[c,g]carbazole exert multiple toxic events contributing to tumor promotion in rat liver epithelial 'stem-like' cells, Mutat. Res. Fundam. Mol. Mech. Mutagen. 596 (2006) 43-56]. In this study, we focused on the genotoxic effects generated by these dibenzocarbazoles in WB-F344 cells to better understand the cellular and molecular mechanisms involved in hepatocarcinogenesis. Lower IC(50) values determined for DBC and DiMeDBC, as compared with N-MeDBC, indicated a higher sensitivity of WB-F344 cells towards hepatocarcinogens. Accordingly, DBC produced a dose-dependent DNA-adduct formation resulting in substantial inhibition of DNA replication and transcription. In contrast, DNA-adduct number detected in DiMeDBC-exposed cells was almost negligible, whereas N-MeDBC produced a low level of DNA adducts. Although all dibenzocarbazoles significantly increased the level of strand breaks (p<0.05) and micronuclei (p<0.001) after 2-h treatment, differences in the kinetics of strand break rejoining were found. The strand break level in DiMeDBC- and N-MeDBC-exposed cells returned to near the background level within 24h after treatment, whereas a relatively high DNA damage level was detected in DBC-treated cells up to 48h after exposure. Additional breaks detected after incubation of DiMeDBC-exposed WB-F344 cells with a repair-specific endonuclease, along with a nearly 3-fold higher level of reactive oxygen species found in these cells as compared with control, suggest a possible role of oxidative stress in DiMeDBC genotoxicity. We demonstrated qualitative differences in the DNA damage profiles produced by hepatocarcinogens DBC and DiMeDBC in WB-F344 cells. Different lesions may trigger distinct cellular pathways involved in hepatocarcinogenesis. The low amount of DNA damage, together with an efficient repair, may explain the lack of hepatocarcinogenicity of N-MeDBC.},

note = {Place: Netherlands},

keywords = {*DNA Damage, *DNA Repair, Animals, Biological, Carbazoles/*toxicity, Carcinogens/*toxicity, Cell Line, DNA Adducts/metabolism, Experimental/chemically induced, Histones/metabolism, Kinetics, Liver Neoplasms, Liver/cytology/*drug effects/*metabolism, Models, Mutagens/toxicity, Oxidative Stress/drug effects, Rats, Sarcoma, Stem Cells/cytology/*drug effects/*metabolism},

pubstate = {published},

tppubtype = {article}

}

@article{vondracek_concentrations_2007,

title = {Concentrations of methylated naphthalenes, anthracenes, and phenanthrenes occurring in Czech river sediments and their effects on toxic events associated with carcinogenesis in rat liver cell lines.},

author = {Jan Vondrácek and Lenka Svihálková-Sindlerová and Katerina Pencíková and Sona Marvanová and Pavel Krcmár and Miroslav Ciganek and Jirí Neca and James E. Trosko and Brad Upham and Alois Kozubík and Miroslav Machala},

doi = {10.1897/07-161R.1},

issn = {0730-7268},

year  = {2007},

date = {2007-11-01},

journal = {Environmental toxicology and chemistry},

volume = {26},

number = {11},

pages = {2308–2316},

abstract = {Alkylated polycyclic aromatic hydrocarbons (PAHs) are important environmental pollutants. In the present study, we determined levels of monomethylated naphthalenes (MeNap), phenanthrenes (MePhe), and anthracenes (MeAnt) in Czech river sediments. The levels of MePhe generally were lower than the concentrations of phenanthrene. In contrast, both MeNap and MeAnt were found at levels higher than their respective parent compounds in the majority of sampling sites. We then investigated their aryl hydrocarbon receptor (AhR)-mediated activity, accumulation of phosphorylated p53 protein, induction of expression of cytochrome P450 1A1 (CYP1A1), inhibition of gap junctional intercellular communication (GJIC), and effects on cell proliferation in rat liver cell models to evaluate the relative importance of these toxicity mechanisms of low-molecular-weight methylated PAHs. Methylated phenanthrene and anthracene compounds were weak inducers of AhR-mediated activity as determined both in a reporter gene assay system and by detection of the endogenous gene (Cyp1a1) induction. 2-Methylphenanthrene was the most potent AhR ligand. Contribution of MeAnt and MePhe to overall AhR-inducing potencies should be taken into account in PAH-contaminated environments. Nevertheless, their effects on AhR were not sufficient to modulate cell proliferation in a normal rat liver progenitor cell model system. These PAHs only had a marginal effect on p53 phosphorylation at high doses of 1-, 3-, and 9-MePhe as well as 1 MeAnt. On the other hand, both 2- and 9-MeAnt as well as all the MePhe under study were efficient inhibitors of GJIC, suggesting that these compounds might act as tumor promoters. In summary, inhibition of GJIC and partial activation of AhR seem to be the most prominent toxic effects of the methylated PAHs in the present study.},

note = {Place: United States},

keywords = {Animals, Anthracenes/toxicity, Aryl Hydrocarbon/metabolism, Carcinogens/*toxicity, Cell Line, Cell Proliferation/*drug effects, Cytochrome P-450 CYP1A1/genetics/metabolism, Czech Republic, Dose-Response Relationship, Drug, Environmental Pollutants/*toxicity, Gap Junctions/*drug effects/metabolism, Gene Expression Regulation/*drug effects/physiology, Geologic Sediments/*chemistry, Liver/cytology/pathology, Methylation, Naphthalenes/toxicity, Phenanthrenes/toxicity, Rats, Receptors, Rivers/*chemistry, Tumor, Tumor Suppressor Protein p53/metabolism},

pubstate = {published},

tppubtype = {article}

}

@article{vondracek_7h-dibenzocgcarbazole_2006,

title = {7H-Dibenzo[c,g]carbazole and 5,9-dimethyldibenzo[c,g]carbazole exert multiple toxic events contributing to tumor promotion in rat liver epithelial 'stem-like' cells.},

author = {Jan Vondrácek and Lenka Svihálková-Sindlerová and Katerina Pencíková and Pavel Krcmár and Zdenek Andrysík and Katerina Chramostová and Sona Marvanová and Zuzana Valovicová and Alois Kozubík and Alena Gábelová and Miroslav Machala},

doi = {10.1016/j.mrfmmm.2005.11.005},

issn = {0027-5107},

year  = {2006},

date = {2006-04-01},

journal = {Mutation research},

volume = {596},

number = {1-2},

pages = {43–56},

abstract = {Immature liver progenitor cells have been suggested to be an important target of hepatotoxins and hepatocarcinogens. The goal of the present study was to assess the impact of 7H-dibenzo[c,g]carbazole (DBC) and its tissue-specific carcinogenic N-methyl (N-MeDBC) and 5,9-dimethyl (DiMeDBC) derivatives on rat liver epithelial WB-F344 cells, in vitro model of liver progenitor cells. We investigated the cellular events associated with both tumor initiation and promotion, such as activation of aryl hydrocarbon receptor (AhR), changes in expression of enzymes involved in metabolic activation of DBC and its derivatives, effects on cell cycle, cell proliferation/apoptosis and inhibition of gap junctional intercellular communication (GJIC). N-MeDBC, a tissue-specific sarcomagen, was only a weak inhibitor of GJIC or inducer of AhR-mediated activity, and it did not affect either cell proliferation or apoptosis. DBC was efficient GJIC inhibitor, while DiMeDBC manifested the strongest AhR inducing activity. Accordingly, DiMeDBC was also the most potent inducer of cytochrome P450 1A1 (CYP1A1) and CYP1A2 expression among the three compounds tested. Both DBC and DiMeDBC induced expression of CYP1B1 and aldo-keto reductase 1C9 (AKR1C9). N-MeDBC failed to significantly upregulate CYP1A1/2 and it only moderately increased CYP1B1 or AKR1C9. Only the potent liver carcinogens, DBC and DiMeDBC, caused a significant increase of p53 phosphorylation at Ser15, an increased accumulation of cells in S-phase and apoptosis at micromolar concentrations. In addition, DiMeDBC was found to stimulate cell proliferation of contact-inhibited WB-F344 cells at 1 microM concentration, which is a mode of action that might further contribute to its hepatocarcinogenicity. The present data seem to suggest that the AhR activation, induction of enzymes involved in metabolic activation, inhibition of GJIC or stimulation of cell proliferation might all contribute to the hepatocarcinogenic effects of DBC and DiMeDBC.},

note = {Place: Netherlands},

keywords = {Animals, Aryl Hydrocarbon Hydroxylases/genetics, Base Sequence, Carbazoles/*toxicity, Carcinogens/*toxicity, Cell Death/drug effects, Cytochrome P-450 CYP1A1/genetics, Cytochrome P-450 CYP1A2/genetics, Cytochrome P-450 CYP1B1, DNA Primers, Epithelial Cells/drug effects/*pathology, Inbred F344, Liver/*cytology/drug effects, Methylation, Molecular Structure, Mutagens, Rats, Reverse Transcriptase Polymerase Chain Reaction},

pubstate = {published},

tppubtype = {article}

}

@article{pliskova_deregulation_2005,

title = {Deregulation of cell proliferation by polycyclic aromatic hydrocarbons in human breast carcinoma MCF-7 cells reflects both genotoxic and nongenotoxic events.},

author = {Martina Plísková and Jan Vondrácek and Borivoj Vojtesek and Alois Kozubík and Miroslav Machala},

doi = {10.1093/toxsci/kfi040},

issn = {1096-6080 1096-0929},

year  = {2005},

date = {2005-02-01},

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

volume = {83},

number = {2},

pages = {246–256},

abstract = {Polycyclic aromatic hydrocarbons (PAHs), such as benzo[a]pyrene (BaP), are carcinogens suggested to be involved in development of human cancer. Several recent studies have reported that PAHs can activate estrogen receptors (ER), either directly or indirectly by producing estrogenic metabolites. We hypothesized that the activation of ER by PAHs or their metabolites could induce cell proliferation in estrogen-sensitive cells. In the present study, we found that two PAHs, benz[a]anthracene (BaA) and BaP, can stimulate proliferation of human breast carcinoma MCF-7 cells at concentrations 100 nM and higher. This effect was ER-dependent, because it was blocked by the pure antiestrogen ICI 182,780. Although both PAHs partially inhibited S-phase entry and DNA synthesis induced by 17beta-estradiol, they stimulated S-phase entry when applied to MCF-7 cells synchronized by serum deprivation. This was in contrast with model antiestrogenic aryl hydrocarbon receptor ligand, 2,3,7,8-tetrachlorodibenzo-p-dioxin, which fully suppressed S-phase entry. BaP, which is a strong mutagen, was found to induce p53 tumor suppressor expression, a partial S-phase arrest and at higher concentrations also cell death. Pifithrin-alpha, a synthetic inhibitor of p53 activity, abolished both S-phase arrest and apoptosis induced by genotoxic PAHs, and it potentiated the proliferative effect of BaP. Thus, both genotoxic and nongenotoxic events seem to interact in the effects of BaP on cell proliferation. Taken together, our data indicate that both BaA and BaP can stimulate cell proliferation through activation of ER. The proliferative effects of these carcinogenic compounds might contribute to tumor promotion in estrogen-sensitive tissues.},

note = {Place: United States},

keywords = {Benz(a)Anthracenes/*toxicity, Benzo(a)pyrene/*toxicity, Benzothiazoles, Breast Neoplasms/drug therapy/*genetics/metabolism, Bromodeoxyuridine/metabolism, Carcinogens/*toxicity, Carcinoma/drug therapy/*genetics/metabolism, Cell Cycle/drug effects, Cell Line, Cell Proliferation/*drug effects, Cell Survival/drug effects, DNA Replication/drug effects, Dose-Response Relationship, Drug, Drug Interactions, Epigenesis, Estradiol/*analogs & derivatives/pharmacology, Estrogen, Estrogen Antagonists/pharmacology, Female, Fulvestrant, Genetic, Humans, Receptors, Thiazoles/pharmacology, Toluene/*analogs & derivatives/pharmacology, Tumor, Tumor Suppressor Protein p53/antagonists & inhibitors/genetics/metabolism},

pubstate = {published},

tppubtype = {article}

}