Induction of cytochrome P450 1A1 gene expression, oxidative stress, and genotoxicity by carbaryl and thiabendazole in transfected human HepG2 and lymphoblastoid cells.
Carbaryl and thiabendazole, two widely used pesticides, have been shown to induce cytochrome P450 1A1 (CYP1A1) expression, but neither compound is capable of displacing [3H] 2,3,7,8-tetrachlorodibenzo-P-dioxin from its aryl hydrocarbon receptor binding site. In the present study, we investigated the transcriptional regulation of CYP1A1 as well as other genes in various human hepatoma HepG2 cell lines stably transfected with the chloramphenicol acetyl transferase (CAT) reporter gene and cloned under the control of each of 14 promoters or response elements from relevant stress genes. Carbaryl and thiabendazole were found to activate CYP1A1 at the level of transcription, as demonstrated by the dose-dependent increase in reporter CAT and CYP1A1 mRNAs. Moreover, this effect appeared to be mediated via the xenobiotic responsive element (XRE), because both pesticides specifically activated various fusion constructs containing XRE sequences (CYP1A, glutathione S-transferase, and XRE). Carbaryl and to a lesser extent thiabendazole also activated other stress genes such as c-fos and NF-kappaBRE, HSP70 and GRP78, and GADD153 at a transcriptional level. These data suggest that these molecules induce early alert genes, including those known to be sensitive to oxidative stress. This led us to examine the genotoxic effect of carbaryl and thiabendazole by an in vitro DNA repair solid-phase assay. Both compounds provoked a strong DNA-damaging activity in the human lymphoblastoid cell line that constitutively expresses human CYP1A1 cDNA, but not in the parental line, indicating that CYP1A1 is chiefly implicated in carbaryl and thiabendazole genotoxicity. This effect was confirmed on HepG2 cells. These observations support the notion that intracellular signals leading to CYP1A1 induction, oxidative stress, and genotoxicity are intimately related.
Laboratoire de Pharmaco-Toxicologie Cellulaire et Moléculaire, INRA, BP 2078, 06606, Antibes, France. rahmani@antibes.inra.fr
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Delescluse
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Ledirac
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Piechocki
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Hines
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Gidrol
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Rahmani
D012721:Carbaryl / Q000494:pharmacology*; D015500:Chloramphenicol O-Acetyltransferase / Q000096:biosynthesis; D002800:Cholinesterase Inhibitors / Q000494:pharmacology; D019363:Cytochrome P-450 CYP1A1 / Q000096:biosynthesis* / Q000235:genetics; D004249:DNA Damage; D000091342:Endoplasmic Reticulum Chaperone BiP; D004790:Enzyme Induction; D015870:Gene Expression / Q000187:drug effects*; D006360:Heat-Shock Proteins / Q000096:biosynthesis / Q000235:genetics; D006801:Humans; D009152:Mutagenicity Tests; D018384:Oxidative Stress; D013827:Thiabendazole / Q000494:pharmacology*; D014158:Transcription, Genetic / Q000187:drug effects; D014162:Transfection; D014407:Tumor Cells, Cultured
D002800:Cholinesterase Inhibitors; D000091342:Endoplasmic Reticulum Chaperone BiP; C000717247:HSPA5 protein, human; D006360:Heat-Shock Proteins; D019363:Cytochrome P-450 CYP1A1; D015500:Chloramphenicol O-Acetyltransferase; D013827:Thiabendazole; D012721:Carbaryl