Studies on the genotoxicity of mycotoxins focus primarily on the native compounds. 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 DNACtopoisomerase 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. Electronic supplementary material The online version of this article (doi:10.1007/s00204-016-1801-0) contains supplementary material, which is available to authorized users. are ubiquitously present in nature, causing a diversity of plant diseases (Mikami et al. 1971; Tsuge et al. 2013). As a result of their wide sporulation and growth range, they infect plants and food crops in nearly every stage of production, even during storage at low temperatures. The excessive production of secondary metabolites by spp. under diverse conditions enables them to be hazardous to the health of humans and animals (Asam and Rychlik 2013; CONTAM 2011; Lee et al. 2015). Seventy of these secondary metabolites have been classified as mycotoxins or phytotoxins (Barkai-Golan 2008). Alternariol (AOH) and alternariol monomethyl ether (AME) (Fig.?1) represent two of the major mycotoxins produced by that have been ascribed as cytotoxic and genotoxic in vitro (Pfeiffer et al. 2007a). Fehr et al. (2009, 2010) reported DNA strand-breaking properties of AOH and AME in vitro in consequence of topoisomerase poisoning. Additionally, mutagenic and estrogenic effects in cell culture were described by Lehmann et al. (2006) and Brugger et al. (2006). Some of these activities might be caused by phase I metabolites of AOH and AME. Pfeiffer et al. (2007b) postulated that during xenobiotic metabolism, metabolites of AOH or AME, arising from hydroxylation through cytochrome P450 (CYP) enzymes, have a reactive catechol or hydroquinone structure. Such compounds are supposed to undergo redox cycling inducing the generation of reactive oxygen species potentially leading to DNA damage. Thus, despite data concerning toxicity and other effects of AOH and AME, their phase I metabolites should not be neglected for a proper risk evaluation. Fig.?1 a Chemical structure of alternariol (AOH), alternariol monomethyl ether (AME), 4-hydroxy alternariol (4-OH-AOH) and 4-hydroxy alternariol monomethyl ether (4-OH-AME), b chemical synthesis of 4-OH-AOH and 4-OH-AME. ethyl, tert. Butyl, N,N-dimethylformamide, … Pfeiffer et al. (2007b, 2008) incubated human microsomes with AOH and AME confirming the formation of metabolites hydroxylated at C-2, C-4 and C-8. Furthermore, CYP1A1, commonly Rivaroxaban occurring in extrahepatic tissues such as the esophagus (Lechevrel et al. 1999), was the most active monooxygenase for AOH and especially for AME (Pfeiffer et al. 2008; Schreck et al. 2012). Thus, phase I metabolites may be generated in a tissue-specific manner after ingestion of AOH or AME and may at least contribute to the induction of esophageal cancer (Liu et al. 1991). CYP1A1 belongs to the isoenzyme family of CYPs which is mainly regulated by the aryl hydrocarbon receptor (AhR) pathway. As hypothesized by Schreck et al. (2012), AOH and AME are inducers of the AhR pathway, which enhances the expression of several metabolizing enzymes especially CYP monooxygenases. Experiments with murine AhR-deficient Hepa-1c1c12 cells did not show induction of CYP expression after incubation with AOH or AME supporting the hypothesis. Also in line are the findings of Pahlke et al. (2015), who analyzed the impact of toxins on CYP1A transcription and activity in different human tumor cells with the objective to identify Rivaroxaban potential organ specificity. AOH caused an Mouse monoclonal to WNT10B induction of CYP1A most prominently Rivaroxaban in esophageal cells (KYSE510) after 24-h incubation, whereas AME only mediated an increase in liver cells. Because of the enhanced sensitivity of KYSE510 cells toward AOH, the experiments were repeated in AhR-suppressed KYSE510 cells. CYP1A1 induction by AOH was significantly reduced compared to the AhR-expressing cells, but Rivaroxaban AhR suppression was of no relevance for the DNA-damaging properties of AOH. The data suggest that at least AOH promotes its xenobiotic metabolism by AhR-dependent induction of CYP enzymes in cells. The lacking impact of AhR suppression on DNA damage might be due to the initiation of cellular defense mechanisms. As recently reported, AME and, to a greater extent, AOH were found to.