Latest Publications

@article{simeckova_224455-hexachlorobiphenyl-enhanced_2009,

title = {The 2,2',4,4',5,5'-hexachlorobiphenyl-enhanced degradation of connexin 43 involves both proteasomal and lysosomal activities.},

author = {Pavlína Simecková and Jan Vondrácek and Zdenek Andrysík and Jirina Zatloukalová and Pavel Krcmár and Alois Kozubík and Miroslav Machala},

doi = {10.1093/toxsci/kfn202},

issn = {1096-0929},

year  = {2009},

date = {2009-01-01},

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

volume = {107},

number = {1},

pages = {9–18},

abstract = {One of the toxic effects of non-dioxin-like polychlorinated biphenyls (NDL-PCBs) is the acute inhibition of gap junctional intercellular communication (GJIC), an event possibly associated with tumor promotion. The model NDL-PCB-2,2',4,4',5,5'-hexachlorobiphenyl (PCB 153)-induces a sustained GJIC inhibition in rat liver epithelial WB-F344 cells. As this effect might be related to deregulation of connexin 43 (Cx43) synthesis, trafficking, or degradation, we investigated the impact of PCB 153 on these events. Although PCB 153 had no effect on Cx43 mRNA levels, it induced a gradual loss of Cx43 protein and significantly decreased the amount of gap junction plaques in plasma membrane. PCB 153 contributed to extracellular signal-regulated kinases 1 and 2 (ERK1/2)-dependent accumulation of hyperphosphorylated Cx43-P3 form, thus indicating that ERK1/2 activation by PCB 153 might contribute to its effects on Cx43 internalization or degradation. Inhibition of either proteasomes or lysosomes with their specific inhibitors largely restored total Cx43 protein levels, thus suggesting that both proteasomes and lysosomes may participate in the PCB 153-enhanced Cx43 internalization and degradation. However, neither the proteasomal nor the lysosomal inhibitors restored normal GJIC or number/size of gap junction plaques. Finally, PCB 153 also interfered with restoration of gap junction plaques following the inhibition of Cx43 transport to plasma membrane. Taken together, multiple modes of action seem to contribute to downregulation of Cx43 in PCB 153-treated rat liver epithelial cells. The enhanced degradation of Cx43, together with persistent inhibition of GJIC, might contribute to tumor-promoting effects of NDL-PCBs.},

note = {Place: United States},

keywords = {Analysis of Variance, Animals, Cell Communication/drug effects, Cell Line, Cell Membrane/drug effects, Connexin 43/genetics/*metabolism, Extracellular Signal-Regulated MAP Kinases/antagonists & inhibitors/metabolism, Gap Junctions/*drug effects/metabolism, Leupeptins/pharmacology, Liver/metabolism, Lysosomes/*drug effects/metabolism, Metabolic Networks and Pathways/drug effects, Polychlorinated Biphenyls/*pharmacology, Proteasome Endopeptidase Complex/*drug effects/metabolism, Proteasome Inhibitors, Rats},

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{machala_toxicity_2004,

title = {Toxicity of hydroxylated and quinoid PCB metabolites: inhibition of gap junctional intercellular communication and activation of aryl hydrocarbon and estrogen receptors in hepatic and mammary cells.},

author = {Miroslav Machala and Ludek Bláha and Hans-Joachim Lehmler and Martina Plísková and Zuzana Májková and Petra Kapplová and Iva Sovadinová and Jan Vondrácek and Tina Malmberg and Larry W. Robertson},

doi = {10.1021/tx030034v},

issn = {0893-228X},

year  = {2004},

date = {2004-03-01},

journal = {Chemical research in toxicology},

volume = {17},

number = {3},

pages = {340–347},

abstract = {In the present study, a series of 32 hydroxy- and dihydroxy-polychlorinated biphenyls (OH-PCBs) and PCB-derived quinones were prepared and evaluated for their in vitro potencies to downregulate gap junctional intercellular communication (GJIC) and to activate the aryl hydrocarbon receptor (AhR) and the estrogen receptor alpha (ER) in well-established liver and mammary cell models. The rat liver epithelial cell line WB-F344 was used for in vitro determination of GJIC inhibition; the AhR-inducing activity was determined in the rat hepatoma H4IIE.Luc cells stably transfected with a luciferase reporter gene; ER-mediated activity was measured in two breast carcinoma cell lines, MVLN and T47D.Luc, stably transfected with luciferase under the control of estrogen responsive element. Acute inhibition of GJIC, potentially associated with tumor promotion, was detected after treatment with all OH-PCBs under study, with the persistent OH-PCBs being the strongest ones. Several compounds were found to significantly induce the AhR-mediated activity, including 4'-OH-PCB 79, a metabolite of PCB 77, and 2-(4'-chloro)- and 2-(3',4'-dichloro)-1,4-benzoquinones and 1,4-hydroquinones. Low molecular weight OH-PCBs, such as 3'-hydroxy, 4'-, and 3',4'-dihydroxy-4-chlorobiphenyl, elicited significant estrogenic activity and potentiated effect of 17beta-estradiol. Antiestrogenic potencies, determined in the presence of 17beta-estradiol, were found for persistent 4-OH-PCB 187, 4-OH-PCB 146, and some low chlorinated PCB derivatives. However, no apparent association between induction of AhR activity and antiestrogenicity was observed. The majority of the OH-PCBs suppressed the 17beta-estradiol response only at cytotoxic concentrations. Spearman's rank correlations were calculated for these biological data and the physicochemical descriptors, hydrophobicity (log P), molar volume, pKa, log D, and dihedral angle. Significant correlations were found between potency to downregulate GJIC and log P and molar volume (R = -0.7, p < 0.0001). Antiestrogenic effects were also negatively correlated with hydrophobicity and molar volume. No significant correlations among other biological end points and the physicochemical descriptors were observed for the entire set of compounds. These results show that oxygenated PCB metabolites are capable of multiple adverse effects, including gap junction inhibition, AhR-mediated activity, and (anti)estrogenicity. The inhibition of GJIC by OH-PCBs represents a novel mode of action of both the lower chlorinated and the persisting high molecular weight OH-PCBs.},

note = {Place: United States},

keywords = {Adenocarcinoma/metabolism/pathology, Animals, Aryl Hydrocarbon/*biosynthesis, Breast Neoplasms/metabolism/pathology, Carcinoma, Cell Line, Cell Survival/drug effects, Dose-Response Relationship, Down-Regulation, Drug, Environmental Pollutants/*toxicity, Epithelial Cells/drug effects/metabolism, Estrogen/*biosynthesis, Gap Junctions/*drug effects/metabolism, Hepatocellular/metabolism/pathology, Humans, Hydroquinones, Hydroxylation, Liver Neoplasms/metabolism/pathology, Neoplasms/*metabolism/pathology, Polychlorinated Biphenyls/*toxicity, Quinones/*toxicity, Rats, Receptors, Tumor},

pubstate = {published},

tppubtype = {article}

}