title: Impact of phase I metabolism on uptake, oxidative stress and genotoxicity of the emerging mycotoxin alternariol and its monomethyl ether in esophageal cells.
abstract: Studies on the genotoxicity of Alternaria mycotoxins focus primarily on the native compounds. Alternariol (AOH) and its methyl ether (AME) have been reported to represent substrates for cytochrome P450 enzymes, generating hydroxylated metabolites. The impact of these phase I metabolites on genotoxicity remains unknown. In the present study, the synthesis and the toxicological effects of the metabolites 4-hydroxy alternariol (4-OH-AOH) and 4-hydroxy alternariol monomethyl ether (4-OH-AME) are presented and compared to the effects of the parent molecules. Although the two phase I metabolites contain a catecholic structure, which is expected to be involved in redox cycling, only 4-OH-AOH increased reactive oxygen species (ROS) in human esophageal cells (KYSE510), 4 times more pronounced than AOH. No ROS induction was observed for 4-OH-AME, although the parent compound showed some minor impact. Under cell-free conditions, both metabolites inhibited topoisomerase II activity comparable to their parent compounds. In KYSE510 cells, both metabolites were found to enhance the level of transient DNA-topoisomerase complexes in the ICE assay. Although the level of ROS was significantly increased by 4-OH-AOH, neither DNA strand breaks nor enhanced levels of formamidopyrimidine-DNA-glycosylase (FPG)-sensitive sites were observed. In contrast, AOH induced significant DNA damage in KYSE510 cells. Less pronounced or even absent effects of hydroxylated metabolites compared to the parent compounds might at least partly be explained by their poor cellular uptake. Glucuronidation as well as sulfation appear to have only a minor influence. Instead, methylation of 4-OH-AOH seems to be the preferred way of metabolism in KYSE510 cells, whereby the toxicological relevance of the methylation product remains to be clarified.
authors.affiliation: Department of Food Chemistry and Toxicology, Faculty of Chemistry, University of Vienna, Waehringer Str. 38, 1090, Vienna, Austria.
authors.forename: Christine
authors.initials: C
authors.lastname: Tiessen
authors.affiliation: Institute of Applied Synthetic Chemistry, Vienna University of Technology, Getreidemarkt 9/163, 1060, Vienna, Austria.
authors.forename: Doris
authors.initials: D
authors.lastname: Ellmer
authors.affiliation: Institute of Applied Synthetic Chemistry, Vienna University of Technology, Getreidemarkt 9/163, 1060, Vienna, Austria.
authors.forename: Hannes
authors.initials: H
authors.lastname: Mikula
authors.affiliation: Department of Food Chemistry and Toxicology, Faculty of Chemistry, University of Vienna, Waehringer Str. 38, 1090, Vienna, Austria.
authors.forename: Gudrun
authors.initials: G
authors.lastname: Pahlke
authors.affiliation: Department of Food Chemistry and Toxicology, Faculty of Chemistry, University of Vienna, Waehringer Str. 38, 1090, Vienna, Austria.
authors.forename: Benedikt
authors.initials: B
authors.lastname: Warth
authors.affiliation: Department of Food Chemistry and Toxicology, Faculty of Chemistry, University of Vienna, Waehringer Str. 38, 1090, Vienna, Austria.
authors.forename: Helge
authors.initials: H
authors.lastname: Gehrke
authors.affiliation: Department of Pharmacognosy, Faculty of Life Sciences, University of Vienna, Althanstrasse 14, 1090, Vienna, Austria.
authors.forename: Kristin
authors.initials: K
authors.lastname: Zimmermann
authors.affiliation: Department of Pharmacognosy, Faculty of Life Sciences, University of Vienna, Althanstrasse 14, 1090, Vienna, Austria.
authors.forename: Elke
authors.initials: E
authors.lastname: Heiss
authors.affiliation: Institute of Applied Synthetic Chemistry, Vienna University of Technology, Getreidemarkt 9/163, 1060, Vienna, Austria.
authors.forename: Johannes
authors.initials: J
authors.lastname: Fröhlich
authors.affiliation: Department of Food Chemistry and Toxicology, Faculty of Chemistry, University of Vienna, Waehringer Str. 38, 1090, Vienna, Austria. doris.marko@univie.ac.at.
authors.forename: Doris
authors.initials: D
authors.lastname: Marko
mesh_terms: D000951:Antigens, Neoplasm / Q000378:metabolism; D045744:Cell Line, Tumor; D002474:Cell-Free System; D004249:DNA Damage / Q000187:drug effects; D004250:DNA Topoisomerases, Type II / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D004938:Esophageal Neoplasms / Q000188:drug therapy / Q000473:pathology; D006801:Humans; D006900:Hydroxylation; D007783:Lactones / Q000378:metabolism / Q000493:pharmacokinetics* / Q000633:toxicity*; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D009152:Mutagenicity Tests / Q000379:methods; D051267:NF-E2-Related Factor 2 / Q000235:genetics / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects*; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D000951:Antigens, Neoplasm; D004268:DNA-Binding Proteins; D007783:Lactones; D051267:NF-E2-Related Factor 2; C495635:NFE2L2 protein, human; D017382:Reactive Oxygen Species; D004250:DNA Topoisomerases, Type II; C005197:alternariol; C018206:alternariol monomethyl ether
keywords: Alternaria alternata; Human phase I and II metabolism; KYSE510; Mycotoxin conjugates; Reactive oxygen species; Topoisomerase inhibition