Latest Publications

@article{machala_changes_2021,

title = {Changes in Sphingolipid Profile of Benzo[a]pyrene-Transformed Human Bronchial Epithelial Cells Are Reflected in the Altered Composition of Sphingolipids in Their Exosomes.},

author = {Miroslav Machala and Josef Slavík and Ondrej Kováč and Jiřina Procházková and Kateřina Pěnčíková and Martina Pařenicová and Nicol Straková and Jan Kotouček and Pavel Kulich and Steen Mollerup and Jan Vondráček and Martina Hýžďalová},

doi = {10.3390/ijms22179195},

issn = {1422-0067},

year  = {2021},

date = {2021-08-01},

journal = {International journal of molecular sciences},

volume = {22},

number = {17},

abstract = {Sphingolipids (SLs), glycosphingolipids (GSLs), and eicosanoids are bioactive lipids, which play important roles in the etiology of various diseases, including cancer. However, their content and roles in cancer cells, and in particular in the exosomes derived from tumor cells, remain insufficiently characterized. In this study, we evaluated alterations of SL and GSL levels in transformed cells and their exosomes, using comparative HPLC-MS/MS analysis of parental human bronchial epithelial cells HBEC-12KT and their derivative, benzo[a]pyrene-transformed HBEC-12KT-B1 cells with the acquired mesenchymal phenotype. We examined in parallel SL/GSL contents in the exosomes released from both cell lines. We found significant alterations of the SL/GSL profile in the transformed cell line, which corresponded well with alterations of the SL/GSL profile in exosomes derived from these cells. This suggested that a majority of SLs and GSLs were transported by exosomes in the same relative pattern as in the cells of origin. The only exceptions included decreased contents of sphingosin, sphingosin-1-phosphate, and lactosylceramide in exosomes derived from the transformed cells, as compared with the exosomes derived from the parental cell line. Importantly, we found increased levels of ceramide phosphate, globoside Gb3, and ganglioside GD3 in the exosomes derived from the transformed cells. These positive modulators of epithelial-mesenchymal transition and other pro-carcinogenic processes might thus also contribute to cancer progression in recipient cells. In addition, the transformed HBEC-12KT-B1 cells also produced increased amounts of eicosanoids, in particular prostaglandin E2. Taken together, the exosomes derived from the transformed cells with specifically upregulated SL and GSL species, and increased levels of eicosanoids, might contribute to changes within the cancer microenvironment and in recipient cells, which could in turn participate in cancer development. Future studies should address specific roles of individual SL and GSL species identified in the present study.},

note = {Place: Switzerland},

keywords = {*Cell Transformation, Benzo(a)pyrene/toxicity, Bronchi/cytology, Carcinogens/toxicity, Cell Line, eicosanoids, exosomes, Exosomes/*metabolism, glycosphingolipid, Humans, in vitro cell transformation, Neoplastic, Respiratory Mucosa/drug effects/*metabolism, sphingolipid, Sphingolipids/*metabolism},

pubstate = {published},

tppubtype = {article}

}

@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{smerdova_upregulation_2014,

title = {Upregulation of CYP1B1 expression by inflammatory cytokines is mediated by the p38 MAP kinase signal transduction pathway.},

author = {Lenka Smerdová and Jana Šmerdová and Markéta Kabátková and Jiří Kohoutek and Dalibor Blažek and Miroslav Machala and Jan Vondráček},

doi = {10.1093/carcin/bgu190},

issn = {1460-2180 0143-3334},

year  = {2014},

date = {2014-11-01},

journal = {Carcinogenesis},

volume = {35},

number = {11},

pages = {2534–2543},

abstract = {Cytochrome P450 1B1 (CYP1B1) is an enzyme that has a unique tumor-specific pattern of expression and is capable of bioactivating a wide range of carcinogenic compounds. We have reported previously that coordinated upregulation of CYP1B1 by inflammatory cytokines, such as tumor necrosis factor-α (TNF-α) and the aryl hydrocarbon receptor ligands, may increase bioactivation of promutagens, such as benzo[a]pyrene (BaP) in epithelial cells. Here, we extend those studies by describing a novel mechanism participating in the regulation of CYP1B1 expression, which involves activation of the p38 mitogen-activated protein kinase (p38) and mitogen- and stress-activated protein kinase 1 (MSK1). Using inhibitors of p38 and MSKs, as well as mouse embryonic cells derived from p38α-deficient and MSK1/2 double knockout mice, we show here that TNF-α potentiates CYP1B1 upregulation via the p38/MSK1 kinase cascade. Effects of this inflammatory cytokine on CYP1B1 expression further involve the positive transcription elongation factor b (P-TEFb). The inhibition of the P-TEFb subunit, cyclin-dependent kinase 9 (CDK9), which phosphorylates RNA polymerase II (RNAPII), prevented the enhanced CYP1B1 induction by a combination of BaP and inflammatory cytokine. Furthermore, using chromatin immunoprecipitation assays, we found that cotreatment of epithelial cells with TNF-α and BaP resulted in enhanced recruitment of both CDK9 and RNAPII to the Cyp1b1 gene promoter. Overall, these results have implications concerning the contribution of inflammatory factors to carcinogenesis, since enhanced CYP1B1 induction during inflammation may alter metabolism of exogenous carcinogens, as well as endogenous CYP1B1 substrates playing role in tumor development.},

note = {Place: England},

keywords = {Animals, Carcinogenesis/drug effects/*genetics, Carcinogens/toxicity, Cyclin-Dependent Kinase 9/genetics, Cytochrome P-450 CYP1B1/*biosynthesis/genetics, Cytokines/metabolism, Gene Expression Regulation, Humans, Mice, Neoplasms/chemically induced/*genetics/pathology, Neoplastic/drug effects, p38 Mitogen-Activated Protein Kinases/antagonists & inhibitors/*genetics/metabolism, Positive Transcriptional Elongation Factor B/genetics, RNA Polymerase II/genetics, Signal Transduction/drug effects, Tumor Necrosis Factor-alpha/metabolism},

pubstate = {published},

tppubtype = {article}

}

@article{blaha_inhibition_2002,

title = {Inhibition of gap-junctional intercellular communication by environmentally occurring polycyclic aromatic hydrocarbons.},

author = {Ludek Bláha and Petra Kapplová and Jan Vondrácek and Brad Upham and Miroslav Machala},

doi = {10.1093/toxsci/65.1.43},

issn = {1096-6080 1096-0929},

year  = {2002},

date = {2002-01-01},

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

volume = {65},

number = {1},

pages = {43–51},

abstract = {Polycyclic aromatic hydrocarbons (PAHs) are a broad class of ubiquitous environmental pollutants with known or suspected carcinogenic properties. Tumor promotion is a cell-proliferative step of cancer that requires the removal of cells from growth suppression via the inhibition of gap-junctional intercellular communication (GJIC). Inhibition of GJIC measured with an in vitro WB-F344 rat liver epithelial cell system was used to assess the relative potencies of 13 PAHs suggested by the U.S. Environmental Protection Agency (EPA) as the principal contaminants and 22 other PAHs, most of them identified in environmental samples. Maximal inhibition of GJIC was detected after 30 min of exposure, followed by a recovery in intercellular communication after an additional 30 min of exposure, suggesting a transient character of inhibition. Although microM concentrations of PAHs were required to reach the inhibition level equal to the model tumor promoter phorbol 12-myristate 13-acetate (IC50 = 8 nM), 12 of the PAHs under study were found to be strong inhibitors of GJIC (strongest effects were observed with fluoranthene, picene, 5-methylchrysene and nine additional PAHs). The other nine PAHs, including benzo[a]pyrene, inhibited GJIC only up to 50-75% of the control level. Interestingly, several high molecular weight PAHs with known strong carcinogenic properties possessed only weak (dibenzopyrenes) or no inhibition potency (dibenzofluoranthenes, naphtho[2,3-a]pyrene and benzo[a]perylene). Based on the IC50 values related to the reference PAH benzo[a]pyrene, we suggested arbitrary values of inhibition equivalency factors (GJIC-IEFs) ranging from 0 (noninhibiting PAHs) to 10.0 (strongest inhibitors), suitable for the purposes of environmental risk assessment.},

note = {Place: United States},

keywords = {Animals, Carcinogens/toxicity, Cell Communication/*drug effects, Cell Line, Dose-Response Relationship, Drug, Environmental Pollutants/*toxicity, Epithelium/drug effects, Gap Junctions/*drug effects, Liver/cytology/drug effects, Molecular Structure, Polycyclic Aromatic Hydrocarbons/chemistry/*toxicity, Rats, Tetradecanoylphorbol Acetate/toxicity, United States, United States Environmental Protection Agency/standards},

pubstate = {published},

tppubtype = {article}

}