Influence of aryl hydrocarbon- (Ah) receptor and genotoxins on DNA repair gene expression and cell survival of mouse hepatoma cells.

2.50
Hdl Handle:
http://hdl.handle.net/10146/83595
Title:
Influence of aryl hydrocarbon- (Ah) receptor and genotoxins on DNA repair gene expression and cell survival of mouse hepatoma cells.
Authors:
Schreck, Ilona; Chudziak, Doreen; Schneider, Sandra; Seidel, Albrecht; Platt, Karl L.; Oesch, Franz; Weiss, Carsten
Abstract:
The aryl hydrocarbon receptor (AhR) mediates toxicity of a variety of environmental pollutants such as polycyclic aromatic hydrocarbons (PAHs) and dioxins. However, the underlying mechanisms and genetic programmes regulated by AhR to cause adverse effects but also to counteract poisoning are still poorly understood. Here we analysed the effects of two AhR ligands, benzo[a]pyrene (B[a]P), a DNA damaging tumour initiator and promotor and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a pure tumour promoter, on cell survival and on nucleotide excision repair (NER) gene expression. NER deals with so called "bulky" DNA adducts including those generated by enzymatically activated B[a]P. Therefore, the hypothesis that AhR may enhance NER gene expression to trigger DNA repair in the presence of genotoxic AhR ligands was tested. Furthermore, we investigated a potential cytoprotective effect of AhR activation by the non-genotoxic ligand TCDD against cell death induced by various genotoxins. Finally, the actions of genotoxins themselves on NER gene expression were studied. As a cell culture model we used mouse hepatoma cells (Hepa-c7) proficient for AhR and its partner protein ARNT as well as subclones deficient in AhR (Hepa-c12) or ARNT (Hepa-c4) to study involvement of AhR and ARNT in response to B[a]P and TCDD. Indeed, the mRNA levels of the two NER genes XP-C and DNA polymerase kappa were increased by B[a]P and TCDD, however, this was not accompanied by an increase in the amount of the respective proteins. Pretreatment of cells with TCDD did not reduce cytotoxicity induced by various genotoxins. Thus, in Hepa-c7 cells AhR has no major effects on the expression of these crucial NER proteins and does not prevent genotoxin-provoked cell death. As expected, the genotoxins B[a]P and cis-platin led to p53 accumulation and induction of its target p21. Interestingly, however, NER gene expression was not enhanced but rather decreased. As two NER genes, XP-C and DNA damage binding protein ddb2, are up-regulated by p53 and ultraviolet radiation in human cells these findings suggest cell type, species or lesion specific actions of p53 on DNA repair gene expression. Importantly, in cells with damaged DNA up-regulation of p53 may not suffice to enhance DNA repair gene expression.
Citation:
Toxicology 2009, 259 (3):91-96
Journal:
Toxicology
Issue Date:
17-May-2009
URI:
http://hdl.handle.net/10146/83595
DOI:
10.1016/j.tox.2009.02.006
PubMed ID:
19428948
Additional Links:
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TCN-4VR24B9-2&_user=1843694&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_acct=C000055040&_version=1&_urlVersion=0&_userid=1843694&md5=87626e928d5a9c3fc6e680f726340df7
Type:
Article
Language:
en
ISSN:
0300-483X
Sponsors:
This work was supported by ECNIS (Environmental Cancer Risk, Nutrition and Individual Susceptibility), a network of excellence operating within the European Union 6th Framework Program, Priority 5: “Food Quality and Safety” (Contract No. 513943).
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Full metadata record

DC FieldValue Language
dc.contributor.authorSchreck, Ilonaen
dc.contributor.authorChudziak, Doreenen
dc.contributor.authorSchneider, Sandraen
dc.contributor.authorSeidel, Albrechten
dc.contributor.authorPlatt, Karl L.en
dc.contributor.authorOesch, Franzen
dc.contributor.authorWeiss, Carstenen
dc.date.accessioned2009-10-06T10:52:23Z-
dc.date.available2009-10-06T10:52:23Z-
dc.date.issued2009-05-17-
dc.identifier.citationToxicology 2009, 259 (3):91-96en
dc.identifier.issn0300-483X-
dc.identifier.pmid19428948-
dc.identifier.doi10.1016/j.tox.2009.02.006-
dc.identifier.urihttp://hdl.handle.net/10146/83595-
dc.description.abstractThe aryl hydrocarbon receptor (AhR) mediates toxicity of a variety of environmental pollutants such as polycyclic aromatic hydrocarbons (PAHs) and dioxins. However, the underlying mechanisms and genetic programmes regulated by AhR to cause adverse effects but also to counteract poisoning are still poorly understood. Here we analysed the effects of two AhR ligands, benzo[a]pyrene (B[a]P), a DNA damaging tumour initiator and promotor and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a pure tumour promoter, on cell survival and on nucleotide excision repair (NER) gene expression. NER deals with so called "bulky" DNA adducts including those generated by enzymatically activated B[a]P. Therefore, the hypothesis that AhR may enhance NER gene expression to trigger DNA repair in the presence of genotoxic AhR ligands was tested. Furthermore, we investigated a potential cytoprotective effect of AhR activation by the non-genotoxic ligand TCDD against cell death induced by various genotoxins. Finally, the actions of genotoxins themselves on NER gene expression were studied. As a cell culture model we used mouse hepatoma cells (Hepa-c7) proficient for AhR and its partner protein ARNT as well as subclones deficient in AhR (Hepa-c12) or ARNT (Hepa-c4) to study involvement of AhR and ARNT in response to B[a]P and TCDD. Indeed, the mRNA levels of the two NER genes XP-C and DNA polymerase kappa were increased by B[a]P and TCDD, however, this was not accompanied by an increase in the amount of the respective proteins. Pretreatment of cells with TCDD did not reduce cytotoxicity induced by various genotoxins. Thus, in Hepa-c7 cells AhR has no major effects on the expression of these crucial NER proteins and does not prevent genotoxin-provoked cell death. As expected, the genotoxins B[a]P and cis-platin led to p53 accumulation and induction of its target p21. Interestingly, however, NER gene expression was not enhanced but rather decreased. As two NER genes, XP-C and DNA damage binding protein ddb2, are up-regulated by p53 and ultraviolet radiation in human cells these findings suggest cell type, species or lesion specific actions of p53 on DNA repair gene expression. Importantly, in cells with damaged DNA up-regulation of p53 may not suffice to enhance DNA repair gene expression.en
dc.description.sponsorshipThis work was supported by ECNIS (Environmental Cancer Risk, Nutrition and Individual Susceptibility), a network of excellence operating within the European Union 6th Framework Program, Priority 5: “Food Quality and Safety” (Contract No. 513943).en
dc.language.isoenen
dc.relation.urlhttp://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TCN-4VR24B9-2&_user=1843694&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_acct=C000055040&_version=1&_urlVersion=0&_userid=1843694&md5=87626e928d5a9c3fc6e680f726340df7en
dc.subjectAryl hydrocarbon receptoren
dc.subjectNucleotide excision repairen
dc.subjectBenzo[a]pyreneen
dc.subject2,3,7,8-Tetrachlorodibenzo-p-dioxinen
dc.subjectcis-Platinen
dc.subjectp53en
dc.subject.meshAnimals-
dc.subject.meshAryl Hydrocarbon Receptor Nuclear Translocator-
dc.subject.meshBlotting, Western-
dc.subject.meshCell Line, Tumor-
dc.subject.meshCell Survival-
dc.subject.meshDNA Repair-
dc.subject.meshDNA-Directed DNA Polymerase-
dc.subject.meshEnvironmental Pollutants-
dc.subject.meshGene Expression Profiling-
dc.subject.meshGene Expression Regulation-
dc.subject.meshGenes, p53-
dc.subject.meshLiver Neoplasms, Experimental-
dc.subject.meshMice-
dc.subject.meshMutagens-
dc.subject.meshReceptors, Aryl Hydrocarbon-
dc.titleInfluence of aryl hydrocarbon- (Ah) receptor and genotoxins on DNA repair gene expression and cell survival of mouse hepatoma cells.en
dc.typeArticleen
dc.identifier.journalToxicologyen
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