TY - JOUR A1 - Knebel, Constanze A1 - Neeb, Jannika A1 - Zahn, Elisabeth A1 - Schmidt, Flavia A1 - Carazo, Alejandro A1 - Holas, Ondej A1 - Pavek, Petr A1 - Püschel, Gerhard Paul A1 - Zanger, Ulrich M. A1 - Süssmuth, Roderich A1 - Lampen, Alfonso A1 - Marx-Stoelting, Philip A1 - Braeuning, Albert T1 - Unexpected Effects of Propiconazole, Tebuconazole, and Their Mixture on the Receptors CAR and PXR in Human Liver Cells JF - Toxicological sciences N2 - Analyzing mixture toxicity requires an in-depth understanding of the mechanisms of action of its individual components. Substances with the same target organ, same toxic effect and same mode of action (MoA) are believed to cause additive effects, whereas substances with different MoAs are assumed to act independently. Here, we tested 2 triazole fungicides, propiconazole, and tebuconazole (Te), for individual and combined effects on liver toxicity-related endpoints. Both triazoles are proposed to belong to the same cumulative assessment group and are therefore thought to display similar and additive behavior. Our data show that Te is an antagonist of the constitutive androstane receptor (CAR) in rats and humans, while propiconazole is an agonist of this receptor. Both substances activate the pregnane X-receptor (PXR) and further induce mRNA expression of CYP3A4. CYP3A4 enzyme activity, however, is inhibited by propiconazole. For common targets of PXR and CAR, the activation of PXR by Te overrides CAR inhibition. In summary, propiconazole and Te affect different hepatotoxicity-relevant cellular targets and, depending on the individual endpoint analyzed, act via similar or dissimilar mechanisms. The use of molecular data based on research in human cell systems extends the picture to refine cumulative assessment group grouping and substantially contributes to the understanding of mixture effects of chemicals in biological systems. KW - triazole fungicides KW - constitutive androstane receptor KW - pregnane X-receptor KW - enzyme induction KW - liver toxicity KW - mixtures Y1 - 2018 U6 - https://doi.org/10.1093/toxsci/kfy026 SN - 1096-6080 SN - 1096-0929 VL - 163 IS - 1 SP - 170 EP - 181 PB - Oxford Univ. Press CY - Oxford ER - TY - CHAP A1 - Braun, Monique A1 - Sawada, Stefanie A1 - Pink, Mario A1 - Meckert, Christine A1 - Oberemm, Axel A1 - Braeuning, Albert A1 - Lampen, Alfonso T1 - Proteomic analysis of 3-MCPD and its palmitic ester in rat kidney using a refined tissue extraction method T2 - NAUNYN-SCHMIEDEBERGS ARCHIVES OF PHARMACOLOGY Y1 - 2015 SN - 0028-1298 SN - 1432-1912 VL - 388 SP - S88 EP - S88 PB - Springer CY - New York ER - TY - JOUR A1 - Luckert, Claudia A1 - Hessel, Stefanie A1 - Lenze, Dido A1 - Lampen, Alfonso T1 - Disturbance of gene expression in primary human hepatocytes by hepatotoxic pyrrolizidine alkaloids: A whole genome transcriptome analysis JF - Toxicology in vitro N2 - 1,2-unsaturated pyrrolizidine alkaloids (PA) are plant metabolites predominantly occurring in the plant families Asteraceae and Boraginaceae. Acute and chronic PA poisoning causes severe hepatotoxicity. So far, the molecular mechanisms of PA toxicity are not well understood. To analyze its mode of action, primary human hepatocytes were exposed to a non-cytotoxic dose of 100 mu M of four structurally different PA: echimidine, heliotrine, senecionine, senkirkine. Changes in mRNA expression were analyzed by a whole genome microarray. Employing cut-off values with a vertical bar fold change vertical bar of 2 and a q-value of 0.01, data analysis revealed numerous changes in gene expression. In total, 4556, 1806, 3406 and 8623 genes were regulated by echimidine, heliotrine, senecione and senkirkine, respectively. 1304 genes were identified as commonly regulated. PA affected pathways related to cell cycle regulation, cell death and cancer development. The transcription factors TP53, MYC, NF kappa B and NUPR1 were predicted to be activated upon PA treatment. Furthermore, gene expression data showed a considerable interference with lipid metabolism and bile acid flow. The associated transcription factors FXR, LXR, SREBF1/2, and PPAR alpha/gamma/delta were predicted to be inhibited. In conclusion, though structurally different, all four PA significantly regulated a great number of genes in common. This proposes similar molecular mechanisms, although the extent seems to differ between the analyzed PA as reflected by the potential hepatotoxicity and individual PA structure. (C) 2015 Elsevier Ltd. All rights reserved. KW - Pyrrolizidine alkaloids KW - Transcriptomics KW - Gene expression KW - Hepatotoxicity Y1 - 2015 U6 - https://doi.org/10.1016/j.tiv.2015.06.021 SN - 0887-2333 VL - 29 IS - 7 SP - 1669 EP - 1682 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Luckert, Claudia A1 - Hessel, Stefanie A1 - Lampen, Alfonso A1 - Braeuning, Albert T1 - Utility of an appropriate reporter assay: Heliotrine interferes with GAL4/upstream activation sequence-driven reporter gene systems JF - Analytical biochemistry : methods in the biological sciences N2 - Reporter gene assays are widely used for the assessment of transcription factor activation following xenobiotic exposure of cells. A critical issue with such assays is the possibility of interference of test compounds with the test system, for example, by direct inhibition of the reporter enzyme. Here we show that the pyrrolizidine alkaloid heliotrine interferes with reporter signals derived from GAL4-based nuclear receptor transactivation assays by a mechanism independent of luciferase enzyme inhibition. These data highlight the necessity to conduct proper control experiments in order to avoid perturbation of reporter assays by test chemicals. (C) 2015 Elsevier Inc. All rights reserved. KW - Firefly luciferase inhibition KW - Nuclear receptor KW - Transactivation assay Y1 - 2015 U6 - https://doi.org/10.1016/j.ab.2015.07.009 SN - 0003-2697 SN - 1096-0309 VL - 487 SP - 45 EP - 48 PB - Elsevier CY - San Diego ER -