2004
Machala, Miroslav; Bláha, Ludek; Lehmler, Hans-Joachim; Plísková, Martina; Májková, Zuzana; Kapplová, Petra; Sovadinová, Iva; Vondrácek, Jan; Malmberg, Tina; Robertson, Larry W.
In: Chemical research in toxicology, vol. 17, no. 3, pp. 340–347, 2004, ISSN: 0893-228X, (Place: United States).
Abstract | Links | BibTeX | Tags: 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
@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}
}
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.
2003
Machala, Miroslav; Bláha, Ludek; Vondrácek, Jan; Trosko, James E.; Scott, Jacob; Upham, Brad L.
In: Toxicological sciences : an official journal of the Society of Toxicology, vol. 76, no. 1, pp. 102–111, 2003, ISSN: 1096-6080 1096-0929, (Place: United States).
Abstract | Links | BibTeX | Tags: Animals, Blotting, Cell Line, Epidermal Growth Factor/toxicity, Epithelial Cells/drug effects/enzymology, Gap Junctions/*drug effects/enzymology, Liver/cytology, Mitogen-Activated Protein Kinases/metabolism, Polychlorinated Biphenyls/*toxicity, Rats, Signal Transduction/*drug effects, Sphingomyelin Phosphodiesterase/metabolism, src-Family Kinases/metabolism, Tetradecanoylphorbol Acetate/toxicity, Western
@article{machala_inhibition_2003,
title = {Inhibition of gap junctional intercellular communication by noncoplanar polychlorinated biphenyls: inhibitory potencies and screening for potential mode(s) of action.},
author = {Miroslav Machala and Ludek Bláha and Jan Vondrácek and James E. Trosko and Jacob Scott and Brad L. Upham},
doi = {10.1093/toxsci/kfg209},
issn = {1096-6080 1096-0929},
year = {2003},
date = {2003-11-01},
journal = {Toxicological sciences : an official journal of the Society of Toxicology},
volume = {76},
number = {1},
pages = {102–111},
abstract = {Polychlorinated biphenyls (PCBs), a structurally diverse group of environmental pollutants, are effective promoters in two-stage cancer models, which implies that epigenetic mechanisms are involved. Inhibition of gap junctional intercellular communication (GJIC) belongs among critical epigenetic events of tumor promotion. We determined the relative potencies of a series of environmentally relevant PCB congeners to inhibit GJIC in vitro in a rat liver epithelial cell line with pluripotent oval cell characteristics. The nonplanar PCBs were potent inhibitors of GJIC, whereas the coplanar PCBs did not inhibit GJIC. We then compared the effects of the coplanar PCB 126 (3,3',4,4',5-pentachlorobiphenyl) and the noncoplanar PCB 153 (2,2',4,4',5,5'-hexachlorobiphenyl) with effects of two model GJIC inhibitors, a tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) and epidermal growth factor (EGF). In contrast to TPA or EGF, PCB 153 elicited a long-term downregulation of GJIC (up to 48 h). Using Western blot analysis with phospho-specific antibodies, it was found that PCB 153, and not PCB 126, activated mitogen-activated protein kinases ERK1/2; however in contrast to TPA and EGF, this activation was observed at the time points subsequent to GJIC inhibition. Moreover, blocking of ERK1/2 activation did not prevent the GJIC inhibition induced by PCB 153. Therefore, additional intracellular signaling pathways potentially involved in the downregulation of GJIC by PCBs were screened by using specific chemical probes inhibiting serine/threonine kinases, tyrosine kinases, and phospholipases. The inhibition of diacylglycerol lipase partially blocked and the selective inhibition of Src kinases and phosphatidylcholine-specific phospholipase C (PC-PLC) completely blocked the inhibitory effects of the noncoplanar PCB on GJIC, indicating that PC-PLC or sphingomyelinase and Src might be upstream regulators of noncoplanar PCB-induced inhibition of GJIC.},
note = {Place: United States},
keywords = {Animals, Blotting, Cell Line, Epidermal Growth Factor/toxicity, Epithelial Cells/drug effects/enzymology, Gap Junctions/*drug effects/enzymology, Liver/cytology, Mitogen-Activated Protein Kinases/metabolism, Polychlorinated Biphenyls/*toxicity, Rats, Signal Transduction/*drug effects, Sphingomyelin Phosphodiesterase/metabolism, src-Family Kinases/metabolism, Tetradecanoylphorbol Acetate/toxicity, Western},
pubstate = {published},
tppubtype = {article}
}
Polychlorinated biphenyls (PCBs), a structurally diverse group of environmental pollutants, are effective promoters in two-stage cancer models, which implies that epigenetic mechanisms are involved. Inhibition of gap junctional intercellular communication (GJIC) belongs among critical epigenetic events of tumor promotion. We determined the relative potencies of a series of environmentally relevant PCB congeners to inhibit GJIC in vitro in a rat liver epithelial cell line with pluripotent oval cell characteristics. The nonplanar PCBs were potent inhibitors of GJIC, whereas the coplanar PCBs did not inhibit GJIC. We then compared the effects of the coplanar PCB 126 (3,3',4,4',5-pentachlorobiphenyl) and the noncoplanar PCB 153 (2,2',4,4',5,5'-hexachlorobiphenyl) with effects of two model GJIC inhibitors, a tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) and epidermal growth factor (EGF). In contrast to TPA or EGF, PCB 153 elicited a long-term downregulation of GJIC (up to 48 h). Using Western blot analysis with phospho-specific antibodies, it was found that PCB 153, and not PCB 126, activated mitogen-activated protein kinases ERK1/2; however in contrast to TPA and EGF, this activation was observed at the time points subsequent to GJIC inhibition. Moreover, blocking of ERK1/2 activation did not prevent the GJIC inhibition induced by PCB 153. Therefore, additional intracellular signaling pathways potentially involved in the downregulation of GJIC by PCBs were screened by using specific chemical probes inhibiting serine/threonine kinases, tyrosine kinases, and phospholipases. The inhibition of diacylglycerol lipase partially blocked and the selective inhibition of Src kinases and phosphatidylcholine-specific phospholipase C (PC-PLC) completely blocked the inhibitory effects of the noncoplanar PCB on GJIC, indicating that PC-PLC or sphingomyelinase and Src might be upstream regulators of noncoplanar PCB-induced inhibition of GJIC.