TY - JOUR A1 - Kittler, Katrin A1 - Hurtaud-Pessel, D. A1 - Maul, Ronald A1 - Kolrep, F. A1 - Fessard, V. T1 - In vitro metabolism of the cyanotoxin cylindrospermopsin in HepaRG cells and liver tissue fractions N2 - No evidence for phase I metabolites of the cyanotoxin cylindrospermopsin (CYN) was given using HepaRG cells and different liver tissue fractions when studying metabolic conversion. Although the application of ketoconazole, a CYP3A4 inhibitor, led to a decreased cytotoxicity of CYN, no metabolites were detected applying high resolution mass spectrometry. Quantification of non-modified CYN led to recovery rates of almost 100%. Consequently, reduction of CYN toxicity in the presence of metabolism inhibiting agents must be attributed to alternative pathways. KW - Cylindrospermopsin KW - Metabolism KW - Liver tissue fractions KW - HepaRG cells KW - LC-HRMS KW - Quantification KW - Cyanotoxin PY - 2016 DO - https://doi.org/10.1016/j.toxicon.2015.11.007 SN - 0041-0101 SN - 1879-3150 VL - 110 SP - 47 EP - 50 PB - Elsevier CY - Oxford [u.a.] AN - OPUS4-35222 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kittler, Katrin A1 - Fessard, V. A1 - Maul, Ronald A1 - Hurtaud-Pessel, D. T1 - CYP3A4 activity reduces the cytotoxic effects of okadaic acid in HepaRG cells N2 - The biotoxin okadaic acid (OA), produced by dinoflagellates in marine environment, can accumulate in sponges and shellfish. Consumption of contaminated shellfish induces acute toxic effects such as diarrhea, nausea, vomiting, and abdominal pain. CYP3A4, one of the most important human xenobiotic metabolizing enzymes, is supposed to be involved in the metabolism of OA. Aim of our study was to evaluate the role of CYP3A4 in OA in vitro metabolism as well as in cell cytotoxicity in parallel. Therefore, a metabolic competent HepaRG cell line was exposed to OA with and without addition of the CYP3A4 inhibitor ketoconazole. Without the inhibitor, two mono-hydroxylated metabolites could be identified, whereas in its presence, no metabolites could be detected. Confirmation of the formed metabolites was accomplished by measuring the exact masses and investigating the fragmentation pattern. Data obtained from cytotoxicity assays showed that OA cytotoxicity is reduced when CYP3A4 is active. Thus, hydroxylation appears to be a crucial step for metabolic OA detoxification. KW - Okadaic acid KW - Cytochrome P-450 KW - Hydroxylation KW - Stability KW - Detoxification KW - Phase I metabolism PY - 2014 DO - https://doi.org/10.1007/s00204-014-1206-x SN - 0340-5761 SN - 1432-0738 VL - 88 IS - 8 SP - 1519 EP - 1526 PB - Springer CY - Berlin ; Heidelberg [u.a.] AN - OPUS4-31567 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Esslinger, Susanne A1 - Becker, Roland A1 - Maul, Ronald A1 - Nehls, Irene T1 - Hexabromocyclododecane enantiomers: microsomal degradation and patterns of hydroxylated metabolites N2 - The degradation of the enantiomers of α-, β-, and γ-hexabromocyclododecane (HBCD) by phase I metabolism was investigated using induced rat liver microsomes. HBCD isomers were quantified using HPLC-MS/MS (ESI-) after separation on a combination of a reversed phase and a chiral analytical column. The degradation of all six isomers followed first-order kinetics and the estimated half-lives ranged from 6.3 min for both β-HBCD enantiomers to 32.3 min in case of (+)-γ-HBCD. (+)-α- and (–)-γ-HBCD displayed significantly shorter half-lives than their corresponding antipodes. It could be shown that this degradation led to a significant enrichment of the first eluting enantiomers (–)-α- and (+)-γ-HBCD. Individual patterns of mono- and dihydroxylated derivatives obtained from each α- and γ-HBCD enantiomer were seen to be distinctly characteristic. The patterns of monohydroxylated HBCD derivatives detected in liver and muscle tissues of pollack, mackerel and in herring gull eggs were largely similar to those observed in the in vitro experiments with rat liver microsomes. This enabled individual hydroxy-HBCDs to be assigned to their respective parent HBCD enantiomers. KW - Brominated flame retardant KW - Cytochromes KW - Phase I metabolism KW - Hydroxylation KW - HPLC-MS/MS PY - 2011 DO - https://doi.org/10.1021/es1039584 SN - 0013-936X SN - 1520-5851 VL - 45 IS - 9 SP - 3938 EP - 3944 PB - ACS Publ. CY - Washington, DC AN - OPUS4-23837 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schebb, N.H. A1 - Franze, B. A1 - Maul, Ronald A1 - Ranganathan, A. A1 - Hammock, B.D. T1 - In vitro glucuronidation of the antibacterial triclocarban and its oxidative metabolites N2 - Triclocarban (3,4,4'-trichlorocarbanilide; TCC) is widely used as an antibacterial in bar soaps. During use of these soaps, a significant portion of TCC is absorbed by humans. For the elimination from the body, glucuronidation plays a key role in both biliary and renal clearance. To investigate this metabolic pathway, we performed microsomal incubations of TCC and its hydroxylated metabolites 2'-OH-TCC, 3'-OH-TCC, and 6-OH-TCC. Using a new liquid chromatography-UV-mass spectrometry method, we could show a rapid glucuronidation for all OH-TCCs by the uridine-5'-diphosphate-glucuronosyltransferases (UGT) present in liver microsomes of humans (HLM), cynomolgus monkeys (CLM), rats (RLM), and mice (MLM). Among the tested human UGT isoforms, UGT1A7, UGT1A8, and UGT1A9 showed the highest activity for the conjugation of hydroxylated TCC metabolites followed by UGT1A1, UGT1A3, and UGT1A10. Due to this broad pattern of active UGTs, OH-TCCs can be efficiently glucuronidated in various tissues, as shown for microsomes from human kidney (HKM) and intestine (HIM). The major renal metabolites in humans, TCC-N-glucuronide and TCC-N'-glucuronide, were formed at very low conversion rates (<1%) by microsomal incubations. Low amounts of N-glucuronides were generated by HLM, HIM, and HKM, as well as by MLM and CLM, but not by RLM, according to the observed species specificity of this metabolic pathway. Among the human UGT isoforms, only UGT1A9 had activity for the N-glucuronidation of TCC. These results present an anomaly where in vivo the predominant urinary metabolites of TCC are N and N'-glucuronides, but these compounds are slowly produced in vitro. KW - 3,4,4'-trichlorocarbanilide KW - Metabolism KW - Glucuronidation PY - 2012 DO - https://doi.org/10.1124/dmd.111.042283 SN - 0090-9556 SN - 1521-009X VL - 40 IS - 1 SP - 25 EP - 31 PB - ASPET CY - Bethesda, Md., USA AN - OPUS4-25731 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Maul, Ronald A1 - Warth, B. A1 - Kant, Jill-Sandra A1 - Schebb, N.H. A1 - Krska, R. A1 - Koch, Matthias A1 - Sulyok, M. T1 - Investigation of the hepatic glucuronidation pattern of the fusarium mycotoxin deoxynivalenol in various species N2 - Deoxynivalenol (DON) is one of the most abundant mycotoxins contaminating food and feed worldwide. Upon absorption, the major portion of the toxin is excreted by humans and animal species as glucuronide. However, consistent in vitro data on DON glucuronidation are lacking. In the present study, the metabolism of DON was investigated using liver microsomes from humans and six different animal species. It was shown that all animal and human liver microsomes led to the formation of up to three different mono-O-glucuronides with significant interspecies differences. While the activity of human liver microsomes was low (0.8 to 2.2 pmol·min–1·mg–1), bovine liver and rat liver microsomes conjugated DON with activities of 525 pmol·min–1·mg–1 and 80 pmol·min–1·mg–1, respectively. KW - Deoxynivalenol KW - Hepatic metabolism KW - Microsomes KW - Glucuronidation KW - Inter-species comparison PY - 2012 DO - https://doi.org/10.1021/tx300348x SN - 0893-228X SN - 1520-5010 VL - 25 IS - 12 SP - 2715 EP - 2717 PB - Soc. CY - Washington, DC, USA AN - OPUS4-27604 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kittler, Katrin A1 - Schreiner, M. A1 - Krumbein, A. A1 - Manzei, S. A1 - Koch, Matthias A1 - Rohn, S. A1 - Maul, Ronald T1 - Uptake of the cyanobacterial toxin cylindrospermopsin in brassica vegetables N2 - Toxin-producing cyanobacterial species are increasingly being found in freshwater systems. However, literature on the impact of many cyanobacterial toxins on plants is scarce. Cylindrospermosin (CYN), a secondary metabolite of cyanobacteria such as Cylindrospermopsis and Aphanizomenon species, is a potent hepatotoxin and protein synthesis inhibitor. Worryingly, CYN is increasingly found in surface and drinking water worldwide causing human and animal intoxications. Further, exposure of crop plants to CYN by irrigation with contaminated water has already been shown. Therefore, in this study, horticulturally important and highly consumed Brassica species were investigated to determine the level of CYN in the leaves after exposure of the roots to the toxin. Treatment of Brassica oleracea var. sabellica, Brassica juncea, and Sinapis alba under varying experimental conditions showed significant CYN uptake, with CYN levels ranging from 10% to 21% in the leaves compared to the CYN concentration applied to the roots (18–35 µg/l). In seedlings, CYN concentrations of up to 49 µg/g fresh weight were observed. Thus, crop plants irrigated with CYN-containing water may represent a significant source of this toxin within the food chain. KW - Cylindrospermopsin KW - Plant systemic availability KW - Cyanobacterial toxin KW - Brassicaceae KW - Exposure source PY - 2012 DO - https://doi.org/10.1016/j.foodchem.2012.01.107 SN - 0308-8146 VL - 133 IS - 3 SP - 875 EP - 879 PB - Elsevier CY - Amsterdam [u.a.] ; Jena AN - OPUS4-25730 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Maul, Ronald A1 - Warth, B. A1 - Schebb, N.H. A1 - Krska, R. A1 - Koch, Matthias A1 - Sulyok, M. T1 - In vitro glucuronidation kinetics of deoxynivalenol by human and animal microsomes and recombinant human UGT enzymes N2 - The mycotoxin deoxynivalenol (DON), formed by Fusarium species, is one of the most abundant mycotoxins contaminating food and feed worldwide. Upon ingestion, the majority of the toxin is excreted by humans and animal species as glucuronide conjugate. First in vitro data indicated that DON phase II metabolism is strongly species dependent. However, kinetic data on the in vitro metabolism as well as investigations on the specific enzymes responsible for DON glucuronidation in human are lacking. In the present study, the DON metabolism was investigated using human microsomal fractions and uridine-diphosphoglucuronyltransferases (UGTs) as well as liver microsomes from five animal species. Only two of the twelve tested human recombinant UGTs led to the formation of DON glucuronides with a different regiospecificity. UGT2B4 predominantly catalyzed the formation of DON-15-O-glucuronide (DON-15GlcA), while for UGT2B7 the DON-3-O-glucuronide (DON-3GlcA) metabolite prevailed. For human UGTs, liver, and intestinal microsomes, the glucuronidation activities were low. The estimated apparent intrinsic clearance (Clapp,int) for all human UGT as well as tissue homogenates was <1 mL/min mg protein. For the animal liver microsomes, moderate Clapp,int between 1.5 and 10 mL/min mg protein were calculated for carp, trout, and porcine liver. An elevated glucuronidation activity was detected for rat and bovine liver microsomes leading to Clapp,int between 20 and 80 mL/min mg protein. The obtained in vitro data points out that none of the animal models is suitable for estimating the human DON metabolism with respect to the metabolite pattern and formation rate. KW - Deoxynivalenol KW - Glucuronidation KW - Uridine-diphosphoglucuronyltransferases (UGT) KW - Human recombinant UGT KW - Trichothecene KW - Phase II metabolism PY - 2015 DO - https://doi.org/10.1007/s00204-014-1286-7 SN - 0340-5761 SN - 1432-0738 VL - 89 IS - 6 SP - 949 EP - 960 PB - Springer CY - Berlin ; Heidelberg [u.a.] AN - OPUS4-33204 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Merkel, Stefan A1 - Dib, Baha A1 - Maul, Ronald A1 - Köppen, Robert A1 - Koch, Matthias A1 - Nehls, Irene T1 - Degradation and epimerization of ergot alkaloids after baking and in vitro digestion N2 - The degradation and epimerization of ergot alkaloids (EAs) in rye flour were investigated after baking cookies and subsequently subjecting them to an in vitro digestion model. Different steps of digestion were analyzed using salivary, gastric, and duodenal juices. The degradation and bidirectional conversion of the toxicologically relevant (R)-epimers and the biologically inactive (S)-epimers for seven pairs of EAs were determined by a HPLC method coupled with fluorescence detection. Baking cookies resulted in degradation of EAs (2–30 %) and a shift in the epimeric ratio toward the (S)-epimer for all EAs. The applied digestion model led to a selective toxification of ergotamine and ergosine, two ergotamine-type EAs. The initial percentage of the toxic (R)-epimer in relation to the total toxin content was considerably increased after digestion of cookies. Ergotamine and ergosine increased from 32 to 51 % and 35 to 55 %, respectively. In contrast, EAs of the ergotoxine type (ergocornine, α- and β-ergocryptine, and ergocristine) showed an epimeric shift toward their biologically inactive (S)-epimers. Further experiments indicated that the selective epimerization of ergotamine EAs occurs in the duodenal juice only. These results demonstrate that toxification of EAs in the intestinal tract should be taken into consideration. KW - HPLC-FLD KW - Claviceps purpurea KW - Rye KW - Ergotoxine KW - Ergotamine KW - Deoxynivalenol KW - Nivalenol KW - Zearalenone KW - Food KW - ERM KW - Quality assurance PY - 2012 DO - https://doi.org/10.1007/s00216-012-6386-8 SN - 1618-2642 SN - 1618-2650 VL - 404 IS - 8 SP - 2489 EP - 2497 PB - Springer CY - Berlin AN - OPUS4-27119 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Drzymala, Sarah A1 - Herrmann, Antje A1 - Maul, Ronald A1 - Pfeifer, Dietmar A1 - Garbe, L.-A. A1 - Koch, Matthias T1 - In vitro phase I metabolism of cis-zearalenone N2 - The present study investigates the in vitro phase I metabolism of cis-zearalenone (cis-ZEN) in rat liver microsomes and human liver microsomes. cis-ZEN is an often ignored isomer of the trans-configured Fusarium mycotoxin zearalenone (trans-ZEN). Upon the influence of (UV-) light, trans-ZEN isomerizes to cis-ZEN. Therefore, cis-ZEN is also present in food and feed. The aim of our study was to evaluate the in vitro phase I metabolism of cis-ZEN in comparison to that of trans-ZEN. As a result, an extensive metabolization of cis-ZEN is observed for rat and human liver microsomes as analyzed by HPLC-MS/MS and high-resolution MS. Kinetic investigations based on the substrate depletion approach showed no significant difference in rate constants and half-lives for cis- and trans-ZEN in rat microsomes. In contrast, cis-ZEN was depleted about 1.4-fold faster than trans-ZEN in human microsomes. The metabolite pattern of cis-ZEN revealed a total of 10 phase I metabolites. Its reduction products, α- and β-cis-zearalenol (α- and β-cis-ZEL), were found as metabolites in both species, with α-cis-ZEL being a major metabolite in rat liver microsomes. Both compounds were identified by co-chromatography with synthesized authentic standards. A further major metabolite in rat microsomes was monohydroxylated cis-ZEN. In human microsomes, monohydroxylated cis-ZEN is the single dominant peak of the metabolite profile. Our study discloses three metabolic pathways for cis-ZEN: reduction of the keto-group, monohydroxylation, and a combination of both. Because these routes have been reported for trans-ZEN, we conclude that the phase I metabolism of cis-ZEN is essentially similar to that of its trans isomer. As trans-ZEN is prone to metabolic activation, leading to the formation of more estrogenic metabolites, the novel metabolites of cis-ZEN reported in this study, in particular α-cis-ZEL, might also show higher estrogenicity. KW - Cis-ZEN KW - Phase I metabolism KW - LC-MS/MS KW - HRMS KW - Depletion kinetics PY - 2014 DO - https://doi.org/10.1021/tx500312g SN - 0893-228X SN - 1520-5010 VL - 27 IS - 11 SP - 1972 EP - 1978 PB - Soc. CY - Washington, DC, USA AN - OPUS4-32071 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Maul, Ronald A1 - Müller, C. A1 - Rieß, Stephanie A1 - Koch, Matthias A1 - Methner, F.-J. A1 - Nehls, Irene T1 - Germination induces the glucosylation of the Fusarium mycotoxin deoxynivalenol in various grains N2 - In food, the mycotoxin deoxynivalenol (DON) often occurs in conjunction with its 3-β-D-glucopyranoside (D3G). The transformation of DON to D3G through glucosylation is catalysed by plant enzymes, however, the exact circumstances are not well understood. In order to investigate the role of enzymatic glucosylation in germinating grains, DON treated kernels were steeped and germinated under laboratory conditions. Furthermore, the effect of malting on the DON content of the contaminated barley was investigated. In all cases, DON and its derivatives were quantified by HPLC-MS/MS before, during and after the experiments. Amongst the six tested cereals; wheat, rye, barley, spelt, and millet transformed DON to D3G during germination whilst the oats were inactive. For wheat, barley, and spelt the initial DON content was reduced by 50%, with the loss being almost entirely accounted for by D3G formation. As D3G might be cleaved during digestion, the elevated D3G concentration may obscure the toxicologically relevant DON content in processed food and beer. The germination process has a major influence on the 'masking' of DON, leading to high quantities of D3G that may be missed in common mycotoxin analyses. KW - Mycotoxins KW - Masked mycotoxins KW - Deoxynivalenol (DON) KW - DON-3-glucoside KW - Acetyl-DON KW - Germination KW - Malting PY - 2012 DO - https://doi.org/10.1016/j.foodchem.2011.08.077 SN - 0308-8146 VL - 131 IS - 1 SP - 274 EP - 279 PB - Elsevier CY - Amsterdam [u.a.] ; Jena AN - OPUS4-25732 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -