Latest Publications

@article{tylichova_n-3_2019,

title = {n-3 Polyunsaturated fatty acids alter benzo[a]pyrene metabolism and genotoxicity in human colon epithelial cell models.},

author = {Zuzana Tylichová and Jiří Neča and Jan Topinka and Alena Milcová and Jiřina Hofmanová and Alois Kozubík and Miroslav Machala and Jan Vondráček},

doi = {10.1016/j.fct.2018.12.021},

issn = {1873-6351 0278-6915},

year  = {2019},

date = {2019-02-01},

journal = {Food and chemical toxicology : an international journal published for the British Industrial Biological Research Association},

volume = {124},

pages = {374–384},

abstract = {Dietary carcinogens, such as benzo[a]pyrene (BaP), are suspected to contribute to colorectal cancer development. n-3 Polyunsaturated fatty acids (PUFAs) decrease colorectal cancer risk in individuals consuming diets rich in PUFAs. Here, we investigated the impact of eicosapentaenoic (EPA) and docosahexaenoic (DHA) acid on metabolism and genotoxicity of BaP in human cell models derived from the colon: HT-29 and HCT-116 cell lines. Both PUFAs reduced levels of excreted BaP metabolites, in particular BaP-tetrols and hydroxylated BaP metabolites, as well as formation of DNA adducts in HT-29 and HCT-116 cells. However, EPA appeared to be a more potent inhibitor of formation of some intracellular BaP metabolites, including BaP-7,8-dihydrodiol. EPA also reduced phosphorylation of histone H2AX (Ser139) in HT-29 cells, which indicated that it may reduce further forms of DNA damage, including DNA double strand breaks. Both PUFAs inhibited induction of CYP1 activity in colon cells determined as 7-ethoxyresorufin-O-deethylase (EROD); this was at least partly linked with inhibition of induction of CYP1A1, 1A2 and 1B1 mRNAs. The downregulation and/or inhibition of CYP1 enzymes by PUFAs could thus alter metabolism and reduce genotoxicity of BaP in human colon cells, which might contribute to known chemopreventive effects of PUFAs in colon epithelium.},

note = {Place: England},

keywords = {Anticarcinogenic Agents/*pharmacology, Benzo(a)pyrene/adverse effects/*metabolism, Cell Line, Colon cancer, Cytochrome P450 Family 1/metabolism, DNA Adducts/metabolism, DNA Damage, DNA Damage/drug effects, Docosahexaenoic acid, Docosahexaenoic Acids/*pharmacology, Eicosapentaenoic acid, Eicosapentaenoic Acid/*pharmacology, Epithelial Cells/*drug effects, Histones/metabolism, Humans, Mutagens/adverse effects/*metabolism, Polycyclic aromatic hydrocarbon, S Phase Cell Cycle Checkpoints/drug effects, Tumor},

pubstate = {published},

tppubtype = {article}

}

@article{zapletal_butyrate_2017,

title = {Butyrate alters expression of cytochrome P450 1A1 and metabolism of benzo[a]pyrene via its histone deacetylase activity in colon epithelial cell models.},

author = {Ondřej Zapletal and Zuzana Tylichová and Jiří Neča and Jiří Kohoutek and Miroslav Machala and Alena Milcová and Michaela Pokorná and Jan Topinka and Mary Pat Moyer and Jiřina Hofmanová and Alois Kozubík and Jan Vondráček},

doi = {10.1007/s00204-016-1887-4},

issn = {1432-0738 0340-5761},

year  = {2017},

date = {2017-05-01},

journal = {Archives of toxicology},

volume = {91},

number = {5},

pages = {2135–2150},

abstract = {Butyrate, a short-chain fatty acid produced by fermentation of dietary fiber, is an important regulator of colonic epithelium homeostasis. In this study, we investigated the impact of this histone deacetylase (HDAC) inhibitor on expression/activity of cytochrome P450 family 1 (CYP1) and on metabolism of carcinogenic polycyclic aromatic hydrocarbon, benzo[a]pyrene (BaP), in colon epithelial cells. Sodium butyrate (NaBt) strongly potentiated the BaP-induced expression of CYP1A1 in human colon carcinoma HCT116 cells. It also co-stimulated the 7-ethoxyresorufin-O-deethylase (EROD) activity induced by the 2,3,7,8-tetrachlorodibenzo-p-dioxin, a prototypical ligand of the aryl hydrocarbon receptor. Up-regulation of CYP1A1 expression/activity corresponded with an enhanced metabolism of BaP and formation of covalent DNA adducts. NaBt significantly potentiated CYP1A1 induction and/or metabolic activation of BaP also in other human colon cell models, colon adenoma AA/C1 cells, colon carcinoma HT-29 cells, or in NCM460D cell line derived from normal colon mucosa. Our results suggest that the effects of NaBt were due to its impact on histone acetylation, because additional HDAC inhibitors (trichostatin A and suberanilohydroxamic acid) likewise increased both the induction of EROD activity and formation of covalent DNA adducts. NaBt-induced acetylation of histone H3 (at Lys14) and histone H4 (at Lys16), two histone modifications modulated during activation of CYP1A1 transcription, and it reduced binding of HDAC1 to the enhancer region of CYP1A1 gene. This in vitro study suggests that butyrate, through modulation of histone acetylation, may potentiate induction of CYP1A1 expression, which might in turn alter the metabolism of BaP within colon epithelial cells.},

note = {Place: Germany},

keywords = {Benzo(a)pyrene/metabolism/*pharmacokinetics, beta Catenin/metabolism, Butyrate, Butyric Acid/*pharmacology, Colon epithelial cells, Colon/*drug effects/metabolism, CYP1A1, Cytochrome P-450 CYP1A1/genetics/*metabolism, DNA adducts, DNA Adducts/drug effects/metabolism, Enhancer Elements, Genetic/drug effects, HCT116 Cells, Histone Deacetylase 1/antagonists & inhibitors/metabolism, Histone Deacetylase Inhibitors/pharmacology, Histone deacetylases, Histones/metabolism, HT29 Cells, Humans, Inactivation, Metabolic, Polycyclic aromatic hydrocarbons},

pubstate = {published},

tppubtype = {article}

}

@article{gabelova_genotoxicity_2011,

title = {Genotoxicity of 7H-dibenzo[c,g]carbazole and its tissue-specific derivatives in human hepatoma HepG2 cells is related to CYP1A1/1A2 expression.},

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

doi = {10.1002/em.20664},

issn = {1098-2280 0893-6692},

year  = {2011},

date = {2011-10-01},

journal = {Environmental and molecular mutagenesis},

volume = {52},

number = {8},

pages = {636–645},

abstract = {The goal of this study was to investigate the genotoxicity of 7H-dibenzo[c,g]carbazole (DBC), a ubiquitous environmental pollutant, and its methyl derivatives, 5,9-dimethylDBC (DiMeDBC), a strict hepatocarcinogen, and N-methylDBC (N-MeDBC), a specific sarcomagen in human hepatoma HepG2 cells, and to infer potential mechanisms underlying the biological activity of particular carcinogen. All dibenzocarbazoles, regardless the tissue specificity, induced significant DNA strand break levels and micronuclei in HepG2 cells; though a mitotic spindle dysfunction rather than a chromosome breakage was implicated in N-MeDBC-mediated micronucleus formation. While DBC and N-MeDBC produced stable DNA adducts followed with p53 protein phosphorylation at Ser-15, DiMeDBC failed. A significant increase in DNA strand breaks following incubation of exposed cells with a repair-specific endonuclease (Fpg protein) suggested that either oxidative DNA damage or unstable DNA-adducts might underlie DiMeDBC genotoxicity in human hepatoma cells. DiMeDBC and N-MeDBC increased substantially also the amount of CYP1A1/2 expression in HepG2 cells. Pretreatment of cells with substances affecting AhR-mediated CYP1A family of enzymes expression; however, diminished DiMeDBC and N-MeDBC genotoxicity. Our data clearly demonstrated differences in the mechanisms involved in the biological activity of DiMeDBC and N-MeDBC in human hepatoma cells; the genotoxicity of these DBC derivatives is closely related to CYP1A1/2 expression.},

note = {Place: United States},

keywords = {Base Sequence, Blotting, Carbazoles/*toxicity, Cell Survival/drug effects, Chromosome-Defective/chemically induced/statistics & numerical data, Comet assay, Cytochrome P-450 CYP1A1/*genetics, Cytochrome P-450 CYP1A2/*genetics, DNA adducts, DNA Breaks, Dose-Response Relationship, Drug, Hep G2 Cells, Histones/metabolism, Humans, Micronuclei, Micronucleus Tests, Mitotic Index, Molecular Sequence Data, Mutagens/*toxicity, Phosphorylation, Real-Time Polymerase Chain Reaction, Tumor Suppressor Protein p53/metabolism, Western},

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}

}