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Zheng C, Collins A, Brunborg G, van Schooten FJ, Nordengen AL, Shaposhnikov S, Godschalk R. Assay conditions for estimating differences in base excision repair activity with Fpg-modified comet assay. Cell Biol Toxicol 2023; 39:2775-2786. [PMID: 36932276 PMCID: PMC10693524 DOI: 10.1007/s10565-023-09801-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2022] [Accepted: 03/06/2023] [Indexed: 03/19/2023]
Abstract
DNA repair is an essential agent in cancer development, progression, prognosis, and response to therapy. We have adapted a cellular repair assay based on the formamidopyrimidine DNA glycosylase (Fpg)-modified comet assay to assess DNA repair kinetics. The removal of oxidized nucleobases over time (0-480 min) was analyzed in peripheral blood mononuclear cells (PBMCs) and 8 cell lines. DNA damage was induced by exposure to either Ro19-8022 plus visible light or potassium bromate (KBrO3). The initial amount of damage induced by Ro 19-8022 plus light varied between cell lines, and this was apparently associated with the rate of repair. However, the amount of DNA damage induced by KBrO3 varied less between cell types, so we used this agent to study the kinetics of DNA repair. We found an early phase of ca. 60 min with fast removal of Fpg-sensitive sites, followed by slower removal over the following 7 h. In conclusion, adjusting the initial damage at T0 to an equal level can be achieved by the use of KBrO3, which allows for accurate analysis of subsequent cellular DNA repair kinetics in the first hour after exposure.
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Affiliation(s)
- Congying Zheng
- Department of Pharmacology and Toxicology, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University, 6200, Maastricht, Netherlands
- Norgenotech AS, 64/66, Ullernchassern, Oslo, Norway
- Oslo Cancer Cluster, 64/66, Ullernchassern, Oslo, Norway
| | | | | | - Frederik-Jan van Schooten
- Department of Pharmacology and Toxicology, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University, 6200, Maastricht, Netherlands
| | - Anne Lene Nordengen
- Norgenotech AS, 64/66, Ullernchassern, Oslo, Norway
- Department of Public Health, Sport and Nutrition, University of Agder, 4604, Kristiansand, Norway
- Department of Nutrition, University of Oslo, 0372, Oslo, Norway
| | - Sergey Shaposhnikov
- Norgenotech AS, 64/66, Ullernchassern, Oslo, Norway
- Oslo Cancer Cluster, 64/66, Ullernchassern, Oslo, Norway
| | - Roger Godschalk
- Department of Pharmacology and Toxicology, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University, 6200, Maastricht, Netherlands.
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2
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Röhl C, Batke M, Damm G, Freyberger A, Gebel T, Gundert-Remy U, Hengstler JG, Mangerich A, Matthiessen A, Partosch F, Schupp T, Wollin KM, Foth H. New aspects in deriving health-based guidance values for bromate in swimming pool water. Arch Toxicol 2022; 96:1623-1659. [PMID: 35386057 PMCID: PMC9095538 DOI: 10.1007/s00204-022-03255-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2021] [Accepted: 02/17/2022] [Indexed: 11/27/2022]
Abstract
Bromate, classified as a EU CLP 1B carcinogen, is a typical by-product of the disinfection of drinking and swimming pool water. The aim of this study was (a) to provide data on the occurrence of bromate in pool water, (b) to re-evaluate the carcinogenic MOA of bromate in the light of existing data, (c) to assess the possible exposure to bromate via swimming pool water and (d) to inform the derivation of cancer risk-related bromate concentrations in swimming pool water. Measurements from monitoring analysis of 229 samples showed bromate concentrations in seawater pools up to 34 mg/L. A comprehensive non-systematic literature search was done and the quality of the studies on genotoxicity and carcinogenicity was assessed by Klimisch criteria (Klimisch et al., Regul Toxicol Pharmacol 25:1-5, 1997) and SciRAP tool (Beronius et al., J Appl Toxicol, 38:1460-1470, 2018) respectively. Benchmark dose (BMD) modeling was performed using the modeling average mode in BMDS 3.1 and PROAST 66.40, 67 and 69 (human cancer BMDL10; EFSA 2017). For exposure assessment, data from a wide range of sources were evaluated for their reliability. Different target groups (infants/toddlers, children and adults) and exposure scenarios (recreational, sport-active swimmers, top athletes) were considered for oral, inhalation and dermal exposure. Exposure was calculated according to the frequency of swimming events and duration in water. For illustration, cancer risk-related bromate concentrations in pool water were calculated for different target groups, taking into account their exposure using the hBMDL10 and a cancer risk of 1 in 100,000. Convincing evidence was obtained from a multitude of studies that bromate induces oxidative DNA damage and acts as a clastogen in vitro and in vivo. Since statistical modeling of the available genotoxicity data is compatible with both linear as well as non-linear dose-response relationships, bromate should be conservatively considered to be a non-threshold carcinogen. BMD modeling with model averaging for renal cancer studies (Kurokawa et al., J Natl. Cancer Inst, 1983 and 1986a; DeAngelo et al., Toxicol Pathol 26:587-594, 1998) resulted in a median hBMDL10 of 0.65 mg bromate/kg body weight (bw) per day. Evaluation of different age and activity groups revealed that top athletes had the highest exposure, followed by sport-active children, sport-active adults, infants and toddlers, children and adults. The predominant route of exposure was oral (73-98%) by swallowing water, followed by the dermal route (2-27%), while the inhalation route was insignificant (< 0.5%). Accepting the same risk level for all population groups resulted in different guidance values due to the large variation in exposure. For example, for an additional risk of 1 in 100,000, the bromate concentrations would range between 0.011 for top athletes, 0.015 for sport-active children and 2.1 mg/L for adults. In conclusion, the present study shows that health risks due to bromate exposure by swimming pool water cannot be excluded and that large differences in risk exist depending on the individual swimming habits and water concentrations.
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Affiliation(s)
- C Röhl
- Institute of Toxicology and Pharmacology for Natural Scientists, Christiana Albertina University Kiel, Kiel, Germany.
- Department of Environmental Health Protection, State Agency for social Services (LAsD) Schleswig-Holstein, Neumünster, Germany.
| | - M Batke
- University Emden/Leer, Emden, Germany
| | - G Damm
- Department of Hepatobiliary Surgery and Visceral Transplantation, University Hospital, Leipzig University, Leipzig, Germany
| | - A Freyberger
- Research and Development, Pharmaceuticals, RED-PCD-TOX-P&PC Clinical Pathology, Bayer AG, Wuppertal, Germany
| | - T Gebel
- Federal Institute for Occupational Safety and Health (BAuA), Dortmund, Germany
| | - U Gundert-Remy
- Institute for Clinical Pharmacology and Toxicology, Universitätsmedizin Berlin, Charité Berlin, Germany
| | - J G Hengstler
- Leibniz Research Centre for Working Environment and Human Factors (IfADo), TU Dortmund University, Dortmund, Germany
| | - A Mangerich
- Molecular Toxicology, Department of Biology, University of Konstanz, Konstanz, Germany
| | - A Matthiessen
- Central Unit for Environmental Hygiene, University Hospital Schleswig-Holstein (UKSH), Kiel, Germany
| | - F Partosch
- Department of Toxicology, Fraunhofer-Institute for Toxicology and Experimental Medicine (ITEM), Hannover, Germany
| | - T Schupp
- Department of Chemical Engineering, University of Applied Science Muenster, Steinfurt, Germany
| | - K M Wollin
- Formerly Public Health Agency of Lower Saxony, Hannover, Germany
| | - H Foth
- Institute of Environmental Toxicology, University of Halle, Halle/Saale, Germany
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3
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Reisinger K, Fieblinger D, Heppenheimer A, Kreutz J, Liebsch M, Luch A, Maul K, Poth A, Strauch P, Dony E, Schulz M, Wolf T, Pirow R. The hen's egg test for micronucleus induction (HET-MN): validation data set. Mutagenesis 2022; 37:61-75. [PMID: 34080017 PMCID: PMC9071061 DOI: 10.1093/mutage/geab016] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Accepted: 05/27/2021] [Indexed: 12/12/2022] Open
Abstract
The classical in vitro genotoxicity test battery is known to be sensitive for indicating genotoxicity. However, a high rate of 'misleading positives' was reported when three assays were combined as required by several legislations. Despite the recent optimisations of the standard in vitro tests, two gaps could hardly be addressed with assays based on 2D monolayer cell cultures: the route of exposure and a relevant intrinsic metabolic capacity to transform pro-mutagens into reactive metabolites. Following these considerations, fertilised chicken eggs have been introduced into genotoxicity testing and were combined with a classical read-out parameter, the micronucleus frequency in circulating erythrocytes, to develop the hen's egg test for micronucleus induction (HET-MN). As a major advantage, the test mirrors the systemic availability of compounds after oral exposure by reflecting certain steps of Absorption, Distribution, Metabolism, Excretion (ADME) without being considered as an animal experiment. The assay is supposed to add to a toolbox of assays to follow up on positive findings from initial testing with classical in vitro assays. We here report on a validation exercise, in which >30 chemicals were tested double-blinded in three laboratories. The specificity and sensitivity of the HET-MN were calculated to be 98 and 84%, respectively, corresponding to an overall accuracy of 91%. A detailed protocol, which includes a picture atlas detailing the cell and micronuclei analysis, is published in parallel (Maul et al. Validation of the hen's egg test for micronucleus induction (HET-MN): detailed protocol including scoring atlas, historical control data and statistical analysis).
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Affiliation(s)
| | - Dagmar Fieblinger
- Department of Chemical and Product Safety, German Federal Institute for Risk Assessment (BfR), Berlin, Germany
| | | | | | - Manfred Liebsch
- Department of Chemical and Product Safety, German Federal Institute for Risk Assessment (BfR), Berlin, Germany
| | - Andreas Luch
- Department of Chemical and Product Safety, German Federal Institute for Risk Assessment (BfR), Berlin, Germany
| | - Katrin Maul
- Department of Chemical and Product Safety, German Federal Institute for Risk Assessment (BfR), Berlin, Germany
| | - Albrecht Poth
- ICCR-Roßdorf GmbH (formerly Harlan CCR GmbH), Rossdorf, Germany
| | - Pamela Strauch
- ICCR-Roßdorf GmbH (formerly Harlan CCR GmbH), Rossdorf, Germany
| | - Eva Dony
- ICCR-Roßdorf GmbH (formerly Harlan CCR GmbH), Rossdorf, Germany
| | - Markus Schulz
- ICCR-Roßdorf GmbH (formerly Harlan CCR GmbH), Rossdorf, Germany
| | | | - Ralph Pirow
- Department of Chemical and Product Safety, German Federal Institute for Risk Assessment (BfR), Berlin, Germany
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Cho E, Allemang A, Audebert M, Chauhan V, Dertinger S, Hendriks G, Luijten M, Marchetti F, Minocherhomji S, Pfuhler S, Roberts DJ, Trenz K, Yauk CL. AOP report: Development of an adverse outcome pathway for oxidative DNA damage leading to mutations and chromosomal aberrations. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2022; 63:118-134. [PMID: 35315142 PMCID: PMC9322445 DOI: 10.1002/em.22479] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2021] [Accepted: 03/18/2022] [Indexed: 05/22/2023]
Abstract
The Genetic Toxicology Technical Committee (GTTC) of the Health and Environmental Sciences Institute (HESI) is developing adverse outcome pathways (AOPs) that describe modes of action leading to potentially heritable genomic damage. The goal was to enhance the use of mechanistic information in genotoxicity assessment by building empirical support for the relationships between relevant molecular initiating events (MIEs) and regulatory endpoints in genetic toxicology. Herein, we present an AOP network that links oxidative DNA damage to two adverse outcomes (AOs): mutations and chromosomal aberrations. We collected empirical evidence from the literature to evaluate the key event relationships between the MIE and the AOs, and assessed the weight of evidence using the modified Bradford-Hill criteria for causality. Oxidative DNA damage is constantly induced and repaired in cells given the ubiquitous presence of reactive oxygen species and free radicals. However, xenobiotic exposures may increase damage above baseline levels through a variety of mechanisms and overwhelm DNA repair and endogenous antioxidant capacity. Unrepaired oxidative DNA base damage can lead to base substitutions during replication and, along with repair intermediates, can also cause DNA strand breaks that can lead to mutations and chromosomal aberrations if not repaired adequately. This AOP network identifies knowledge gaps that could be filled by targeted studies designed to better define the quantitative relationships between key events, which could be leveraged for quantitative chemical safety assessment. We anticipate that this AOP network will provide the building blocks for additional genotoxicity-associated AOPs and aid in designing novel integrated testing approaches for genotoxicity.
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Affiliation(s)
- Eunnara Cho
- Environmental Health Science and Research BureauHealth CanadaOttawaOntarioCanada
- Department of BiologyCarleton UniversityOttawaOntarioCanada
| | | | | | - Vinita Chauhan
- Consumer and Clinical Radiation Protection BureauHealth CanadaOttawaOntarioCanada
| | | | | | - Mirjam Luijten
- Centre for Health ProtectionNational Institute for Public Health and the Environment (RIVM)BilthovenThe Netherlands
| | - Francesco Marchetti
- Environmental Health Science and Research BureauHealth CanadaOttawaOntarioCanada
- Department of BiologyCarleton UniversityOttawaOntarioCanada
| | - Sheroy Minocherhomji
- Amgen Research, Translational Safety and Bioanalytical SciencesAmgen Inc.Thousand OaksCaliforniaUSA
| | | | | | | | - Carole L. Yauk
- Environmental Health Science and Research BureauHealth CanadaOttawaOntarioCanada
- Department of BiologyCarleton UniversityOttawaOntarioCanada
- Department of BiologyUniversity of OttawaOttawaOntarioCanada
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5
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Dural E, Shah UK, Pritchard D, Chapman KE, Doak SH, Jenkins GJS. The effect of chronic dosing and p53 status on the genotoxicity of pro-oxidant chemicals in vitro. Mutagenesis 2020; 35:479-489. [PMID: 33259605 DOI: 10.1093/mutage/geaa024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Accepted: 09/07/2020] [Indexed: 11/12/2022] Open
Abstract
In this study, we have studied the cytotoxicity and genotoxic potency of 3 pro-oxidants; H2O2, menadione and KBrO3 in different dosing scenarios, namely acute (1-day dosing) and chronic (5-days). For this purpose, relative population doubling (RPD%) and mononucleated micronucleus (MN) test were used. TK6 cells and NH32 were employed in in vitro experiments. In the study, the total acute dose was divided into 5 days for each prooxidant chemicals by dose fractionation (1/5th per day) method. Acute dosing was compared to chronic dosing. The oxidative stress caused by the exposure of cells with pro-oxidant chemicals to the cells was determined by an optimized 2',7'-dichlorofluorescein diacetate (DCFHDA) test method. The antioxidant levels of the cell lines were altered with buthionine sulfoxide (BSO) and N-acetyl cysteine (NAC), and the effect of antioxidant capacity on the MN formation in the cells was observed with this method. In the case of H2O2 and menadione, fractional dosing has been observed to result in lower toxicity and lower genotoxicity. But in the case of KBrO3, unlike the other 2 pro-oxidants, higher MN induction was observed with fractionated doses. DCFHDA test clearly demonstrated ROS induction with H2O2 and menadione but not with KBrO3. Unexpectedly, DCFHDA test demonstrated that KBrO3 did not cause an increase ROS levels in both acute and chronic dosing, suggesting an alternative ROS induction mechanism. It was also observed that, treatment with BSO and NAC, caused increasing and decreasing of MN fold change respectively, allowing further ROS specific mechanisms to be explored. Hence, dose fractionation expectedly caused less MN, cytotoxicity and ROS formation with H2O2 and menadione exposure, but not with KBrO3. This implies a unique mechanism of action for KBrO3 induced genotoxicity. Chronic dosing in vitro may be a valuable approach allowing better understanding of how chemicals damage DNA and pose human hazards.
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Affiliation(s)
- Emrah Dural
- In vitro Toxicology Group, Institute of Life Science, College of Medicine, Swansea University, Swansea, U.K
- Sivas Cumhuriyet University, Department of Pharmaceutical Toxicology, Faculty of Pharmacy, Sivas, Turkey
| | - Ume-Kulsoom Shah
- In vitro Toxicology Group, Institute of Life Science, College of Medicine, Swansea University, Swansea, U.K
| | - Demi Pritchard
- In vitro Toxicology Group, Institute of Life Science, College of Medicine, Swansea University, Swansea, U.K
| | - Katherine Emma Chapman
- In vitro Toxicology Group, Institute of Life Science, College of Medicine, Swansea University, Swansea, U.K
| | - Shareen Heather Doak
- In vitro Toxicology Group, Institute of Life Science, College of Medicine, Swansea University, Swansea, U.K
| | - Gareth James Scott Jenkins
- In vitro Toxicology Group, Institute of Life Science, College of Medicine, Swansea University, Swansea, U.K
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6
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Aoki Y, Taniguchi Y, Matsumoto M, Matsumoto M, Ohno M, Masumura K, Sasaki S, Tsuzuki T, Yamamoto M, Nohmi T. Oxidative-stress-driven mutagenesis in the small intestine of the gpt delta mouse induced by oral administration of potassium bromate. MUTATION RESEARCH. GENETIC TOXICOLOGY AND ENVIRONMENTAL MUTAGENESIS 2020; 850-851:503136. [PMID: 32247553 DOI: 10.1016/j.mrgentox.2020.503136] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2019] [Revised: 01/08/2020] [Accepted: 01/09/2020] [Indexed: 06/11/2023]
Abstract
Tumorigenesis induced by oxidative stress is thought to be initiated by mutagenesis, but via an indirect mechanism. The dose-response curves for agents that act by this route usually show a threshold, for unknown reasons. To gain insight into these phenomena, we have analyzed the dose response for mutagenesis induced by the oral administration of potassium bromate, a typical oxidative-stress-generating agent, to gpt delta mice. The agent was given orally for 90 d to either Nrf2+ or Nrf2-knockout (KO) mice and mutants induced in the small intestine were analyzed. In Nrf2+mice, the mutant frequency was significantly greater than in the vehicle controls at a dose of 0.6 g/L but not at 0.2 g/L, indicating that a practical threshold for mutagenesis lies between these doses. At 0.6 g/L, the frequencies of G-to-T transversions (landmark mutations for oxidative stress) and G-to-A transitions were significantly elevated. In Nrf2-KO mice, too, the total mutant frequency was increased only at 0.6 g/L. G-to-T transversions are likely to have driven tumorigenesis in the small intestine. A site-specific G-to-T transversion at guanine (nucleotide 406) in a 5'-TGAA-3' sequence in gpt, and our primer extension reaction showed that formation of the oxidative DNA base modification 8-oxo-deoxyguanosine (8-oxo-dG) at nucleotide 406 was significantly increased at doses of 0.6 and 2 g/L in the gpt delta mice. In the Apc oncogene, guanine residues in the same or similar sequences (TGAA or AGAA) are highly substituted by thymine (G-to-T transversions) in potassium bromate-induced tumors. We propose that formation of 8-oxo-dG in the T(A)GAA sequence is an initiating event in tumor formation in the small intestine in response to oxidative stress.
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Affiliation(s)
- Yasunobu Aoki
- National Institute for Environmental Studies, Center for Health and Environmental Risk Research, Onogawa, Tsukuba, Ibaraki 305-8506, Japan.
| | - Yosuke Taniguchi
- Kyushu University, Graduate School of Pharmaceutical Sciences, Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan
| | - Michiyo Matsumoto
- National Institute for Environmental Studies, Center for Health and Environmental Risk Research, Onogawa, Tsukuba, Ibaraki 305-8506, Japan
| | - Michi Matsumoto
- National Institute for Environmental Studies, Center for Health and Environmental Risk Research, Onogawa, Tsukuba, Ibaraki 305-8506, Japan
| | - Mizuki Ohno
- Kyushu University, Faculty of Medical Sciences, Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan
| | - Kenichi Masumura
- National Institute of Health Sciences, Division of Genetics and Mutagenesis, Tonomachi, Kawasaki-ku, Kawasaki, Kanagawa 210-9501, Japan
| | - Shigeki Sasaki
- Kyushu University, Graduate School of Pharmaceutical Sciences, Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan
| | - Teruhisa Tsuzuki
- Kyushu University, Faculty of Medical Sciences, Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan
| | - Masayuki Yamamoto
- Tohoku University, Graduate School of Medicine, Seiryo-machi, Aoba-ku, Sendai, Miyagi 980-8575, Japan
| | - Takehiko Nohmi
- National Institute of Health Sciences, Division of Genetics and Mutagenesis, Tonomachi, Kawasaki-ku, Kawasaki, Kanagawa 210-9501, Japan
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7
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Nohmi T, Matsumoto K. Effects of DNA polymerase kappa and mismatch repair on dose-responses of chromosome aberrations induced by three oxidative genotoxins in human cells. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2020; 61:193-199. [PMID: 31294882 DOI: 10.1002/em.22315] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2019] [Revised: 06/25/2019] [Accepted: 06/27/2019] [Indexed: 06/09/2023]
Abstract
Genotoxic carcinogens are regulated under the policy that there is no threshold or safe dose. It has been pointed out, however, that self-defense mechanisms, such as detoxification, DNA repair, and error-free translesion synthesis, may protect chromosome DNA from genotoxic insults, thereby constituting practical threshold. In this study, we examined dose responses of chromosome aberrations induced by three oxidative genotoxins, that is, hydrogen peroxide (H2 O2 ), menadione and paraquat, with or without DNA polymerase kappa (Polκ) activities and mismatch repair capacities in human cells. Polκ is involved in translesion synthesis across DNA damage and mismatch repair is responsible for correction of base-base mismatch in DNA. Polκ activity of the cells was inactivated either by point mutations in the catalytically essential amino acids (catalytically dead or CD) or by deletion of the POLK gene (knockout or KO). In the absence of mismatch repair, frequencies of chromosome aberrations induced by H2 O2 and menadione were not significantly different among CD, KO, and the wild type (WT) cells. In the presence of mismatch repair, however, cytotoxicity and clastogenicity were enhanced and Polκ modulated the sensitivity of the cells. No-observed-genotoxic-effect-levels (NOGELs) for H2 O2 and menadione were CD = KO < WT cells. In contrast, the sensitivities of the cells to paraquat were not significantly affected by the status of mismatch repair or Polκ activity. The results suggest that mismatch repair and Polκ coordinately modulate NOGELs for the clastogenicity of H2 O2 and menadione and also that DNA lesion(s) responsible for paraquat-induced chromosome aberrations are different from those induced by H2 O2 and menadione. Environ. Mol. Mutagen. 61:193-199, 2020. © 2019 Wiley Periodicals, Inc.
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Affiliation(s)
- Takehiko Nohmi
- Biological Safety Research Center, National Institute of Health Sciences, Kawasaki-shi, Kanagawa, Japan
| | - Kyomu Matsumoto
- Toxicology Division, The Institute of Environmental Toxicology, Joso-shi, Ibaraki, Japan
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8
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Liu H, Wu Y, He F, Cheng Z, Zhao Z, Xiang C, Feng X, Bai X, Takeda S, Wu X, Qing Y. Brca1 is involved in tolerance to adefovir dipivoxil‑induced DNA damage. Int J Mol Med 2019; 43:2491-2498. [PMID: 31017265 DOI: 10.3892/ijmm.2019.4164] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2018] [Accepted: 03/29/2019] [Indexed: 02/05/2023] Open
Abstract
Nucleos(t)ide analogues (NAs) are currently the most important anti‑viral treatment option for patients with chronic hepatitis B (CHB). Adefovir dipivoxil (ADV), a diester pro‑drug of adefovir, has been widely used for the clinical therapy of hepatitis B virus infection. It has been previously reported that adefovir induced chromosomal aberrations (CAs) in the in vitro human peripheral blood lymphocyte assay, while the genotoxic mechanism remains elusive. To evaluate the possible mechanisms, the genotoxic effects of ADV on the TK6 and DT40 cell lines, as well as DNA repair‑deficient variants of DT40 cells, were assessed in the present study. A karyotype assay revealed ADV‑induced CAs, particularly chromosomal breaks, in wild‑type DT40 and TK6 cells. A γ‑H2AX foci formation assay confirmed the presence of DNA damage following treatment with ADV. Furthermore, Brca1‑/‑ DT40 cells exhibited an increased sensitivity to ADV, while the knockdown of various other DNA damage‑associated genes did not markedly affect the sensitivity. These comprehensive genetic studies identified the genotoxic capacity of ADV and suggested that Brca1 may be involved in the tolerance of ADV‑induced DNA damage. These results may contribute to the development of novel drugs against CHB with higher therapeutic efficacy and less genotoxicity.
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Affiliation(s)
- Hao Liu
- Department of Pharmacology, West China School of Pharmacy, Sichuan University, Chengdu, Sichuan 610041, P.R. China
| | - Yang Wu
- State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, P.R. China
| | - Fang He
- Center of Infectious Diseases, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, P.R. China
| | - Ziyuan Cheng
- Department of Pharmacology, West China School of Pharmacy, Sichuan University, Chengdu, Sichuan 610041, P.R. China
| | - Zilu Zhao
- Department of Pharmacology, West China School of Pharmacy, Sichuan University, Chengdu, Sichuan 610041, P.R. China
| | - Cuifang Xiang
- Department of Pharmacology, West China School of Pharmacy, Sichuan University, Chengdu, Sichuan 610041, P.R. China
| | - Xiaoyu Feng
- Department of Pharmacology, West China School of Pharmacy, Sichuan University, Chengdu, Sichuan 610041, P.R. China
| | - Xin Bai
- Department of Pharmacology, West China School of Pharmacy, Sichuan University, Chengdu, Sichuan 610041, P.R. China
| | - Shunichi Takeda
- Department of Radiation Genetics, Graduate School of Medicine, Kyoto University, Kyoto 606‑8501, Japan
| | - Xiaohua Wu
- State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, P.R. China
| | - Yong Qing
- Department of Pharmacology, West China School of Pharmacy, Sichuan University, Chengdu, Sichuan 610041, P.R. China
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9
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Spassova MA. Statistical Approach to Identify Threshold and Point of Departure in Dose-Response Data. RISK ANALYSIS : AN OFFICIAL PUBLICATION OF THE SOCIETY FOR RISK ANALYSIS 2019; 39:940-956. [PMID: 30253453 DOI: 10.1111/risa.13191] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2018] [Revised: 08/09/2018] [Accepted: 08/18/2018] [Indexed: 06/08/2023]
Abstract
The study presents an integrated, rigorous statistical approach to define the likelihood of a threshold and point of departure (POD) based on dose-response data using nested family of bent-hyperbola models. The family includes four models: the full bent-hyperbola model, which allows for transition between two linear regiments with various levels of smoothness; a bent-hyperbola model reduced to a spline model, where the transition is fixed to a knot; a bent-hyperbola model with a restricted negative asymptote slope of zero, named hockey-stick with arc (HS-Arc); and spline model reduced further to a hockey-stick type model (HS), where the first linear segment has a slope of zero. A likelihood-ratio test is used to discriminate between the models and determine if the more flexible versions of the model provide better or significantly better fit than a hockey-stick type model. The full bent-hyperbola model can accommodate both threshold and nonthreshold behavior, can take on concave up and concave down shapes with various levels of curvature, can approximate the biochemically relevant Michaelis-Menten model, and even be reduced to a straight line. Therefore, with the use of this model, the presence or absence of a threshold may even become irrelevant and the best fit of the full bent-hyperbola model be used to characterize the dose-response behavior and risk levels, with no need for mode of action (MOA) information. Point of departure (POD), characterized by exposure level at which some predetermined response is reached, can be defined using the full model or one of the better fitting reduced models.
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Herrera N, Herrera C, Ortíz I, Orozco L, Robledo S, Agudelo D, Echeverri F. Genotoxicity and cytotoxicity of three microcystin-LR containing cyanobacterial samples from Antioquia, Colombia. Toxicon 2018; 154:50-59. [PMID: 30273704 DOI: 10.1016/j.toxicon.2018.09.011] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2018] [Revised: 09/19/2018] [Accepted: 09/25/2018] [Indexed: 01/09/2023]
Abstract
The presence of cyanobacterial blooms and cyanotoxins in water presents a global problem due to the deterioration of ecosystems and the possibility of poisoning in human and animals. Microcystin LR is the most widely distributed cyanotoxin and liver cells are its main target. In the present study, HepG2 cells were used to determine DNA damage of three crude extracts of cyanobacterial blooms containing MC-LR, through comet assay. The results show that all extracts at a concentration of 500 μg mL-1 caused low damage in hepatocytes exposed for 24 h, but produced total mortality even at low concentrations at 48 h. Moreover, balloons corresponding to cell apoptosis were found. Through HPLC/MS, MC-LR was detected in all samples of cyanobacterial blooms at concentrations of (5,65 μg ml-1) in sample 1, (1,24 μg ml-1) in sample 2 and (57,29 μg ml-1) in sample 3. In addition, in all samples high molecular weights peaks were detected, that may correspond to other microcystins. Besides, the cytotoxic effect of a cyanobacterial bloom and some of its chromatographic fractions from the crude extracts were evaluated in U-937, J774, Hela and Vero cell lines, using the enzymatic micromethod (MTT). The highest toxicity was detected in U-937 cells (LC50 = 29.7 μg mL-1) and Vero cells (LC50 = 39.7 μg mL-1). Based on these results, it is important to remark that genotoxic and cytotoxicity assays are valuable methods to predict potential biological risks in waters contaminated with blooms of cyanobacteria, since chemical analysis can only describe the presence of cyanotoxins, but not their biological effects.
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Affiliation(s)
- Natalia Herrera
- Grupo de Química Organica de Productos Naturales, Instituto de Química, Universidad de Antioquia, Calle 67 No. 53-10, Medellín, 050010, Colombia.
| | - Carolina Herrera
- Grupo de Química Organica de Productos Naturales, Instituto de Química, Universidad de Antioquia, Calle 67 No. 53-10, Medellín, 050010, Colombia
| | - Isabel Ortíz
- Universidad Pontificia Bolivariana, Medellín, Colombia
| | - Luz Orozco
- Universidad Pontificia Bolivariana, Medellín, Colombia
| | - Sara Robledo
- Programa de Estudio y Control de Enfermedades Tropicales, Instituto de Investigaciones Médicas, Facultad de Medicina, Universidad de Antioquia, Medellín, Colombia
| | - Diana Agudelo
- Grupo de investigación en Gestión y Modelación Ambiental (GAIA), Universidad de Antioquia, Medellín, Colombia
| | - Fernando Echeverri
- Grupo de Química Organica de Productos Naturales, Instituto de Química, Universidad de Antioquia, Calle 67 No. 53-10, Medellín, 050010, Colombia.
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Kinetic Modeling Reveals the Roles of Reactive Oxygen Species Scavenging and DNA Repair Processes in Shaping the Dose-Response Curve of KBrO₃-Induced DNA Damage. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2015; 2015:764375. [PMID: 26448819 PMCID: PMC4581570 DOI: 10.1155/2015/764375] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/12/2015] [Accepted: 07/21/2015] [Indexed: 11/24/2022]
Abstract
We have developed a kinetic model to investigate how DNA repair processes and scavengers of reactive oxygen species (ROS) can affect the dose-response shape of prooxidant induced DNA damage. We used as an example chemical KBrO3 which is activated by glutathione and forms reactive intermediates that directly interact with DNA to form 8-hydroxy-2-deoxyguanosine DNA adducts (8-OH-dG). The single strand breaks (SSB) that can result from failed base excision repair of these adducts were considered as an effect downstream from 8-OH-dG. We previously demonstrated that, in the presence of effective base excision repair, 8-OH-dG can exhibit threshold-like dose-response dependence, while the downstream SSB can still exhibit a linear dose-response. Here we demonstrate that this result holds for a variety of conditions, including low levels of GSH, the presence of additional SSB repair mechanisms, or a scavenger. It has been shown that melatonin, a terminal scavenger, inhibits KBrO3-caused oxidative damage. Our modeling revealed that sustained exposure to KBrO3 can lead to fast scavenger exhaustion, in which case the dose-response shapes for both endpoints are not substantially affected. The results are important to consider when forming conclusions on a chemical's toxicity dose dependence based on the dose-response of early genotoxic events.
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Rivara MB, Ikizler TA, Ellis CD, Mehrotra R, Himmelfarb J. Association of plasma F2-isoprostanes and isofurans concentrations with erythropoiesis-stimulating agent resistance in maintenance hemodialysis patients. BMC Nephrol 2015; 16:79. [PMID: 26045064 PMCID: PMC4455324 DOI: 10.1186/s12882-015-0074-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2014] [Accepted: 05/21/2015] [Indexed: 12/21/2022] Open
Abstract
Background In patients undergoing maintenance hemodialysis (HD), hyporesponsiveness to erythropoiesis stimulating agents (ESAs) is associated with adverse clinical outcomes. Systemic inflammation is highly prevalent in HD patients and is associated with ESA hyporesponsiveness. Oxidative stress is also highly prevalent in HD patients, but no previous study has determined its association with ESA response. This study assessed the association of plasma markers of oxidative stress and inflammation with ESA resistance in patients undergoing maintenance HD. Methods We analyzed data from 165 patients enrolled in the Provision of Antioxidant Therapy in Hemodialysis study, a randomized controlled trial evaluating antioxidant therapy in prevalent HD patients. Linear and mixed-effects regression were used to assess the association of baseline and time-averaged high sensitivity F2-isoprostanes, isofurans, C-reactive protein (hsCRP), and interleukin-6 (IL-6) with ESA resistance index (ERI), defined as the weekly weight-adjusted ESA dose divided by blood hemoglobin level. Unadjusted models as well as models adjusted for potential confounders were examined. Predicted changes in ERI per month over study follow-up among baseline biomarker quartiles were also assessed. Results Patients with time-averaged isofurans in the highest quartile had higher adjusted mean ERI compared with patients in the lowest quartile (β = 14.9 ng/ml; 95 % CI 7.70, 22.2; reference group <0.26 ng/ml). The highest quartiles of hsCRP and IL-6 were also associated with higher adjusted mean ERI (β = 10.8 mg/l; 95 % CI 3.52, 18.1 for hsCRP; β = 10.2 pg/ml; 95 % CI 2.98, 17.5 for IL-6). No significant association of F2-isoprostanes concentrations with ERI was observed. Analyses restricted to baseline exposures and ERI showed similar results. Baseline hsCRP, IL-6, and isofurans concentrations in the highest quartiles were associated with greater predicted change in ERI over study follow-up compared to the lowest quartiles (P = 0.008, P = 0.004, and P = 0.04, respectively). There was no association between baseline F2-isoprostanes quartile and change in ERI. Conclusions In conclusion, higher concentrations of isofurans, hsCRP and IL-6, but not F2-isoprostanes, were associated with greater resistance to ESAs in prevalent HD patients. Further research is needed to test whether interventions that successfully decrease oxidative stress and inflammation in patients undergoing maintenance HD improve ESA responsiveness. Electronic supplementary material The online version of this article (doi:10.1186/s12882-015-0074-9) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Matthew B Rivara
- Division of Nephrology, Department of Medicine, University of Washington, Box 359606, 325 9th Ave., Seattle, WA, 98104, USA. .,Kidney Research Institute, Seattle, WA, USA.
| | - T Alp Ikizler
- Division of Nephrology, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, USA. .,Vanderbilt Center for Kidney Disease, Vanderbilt University Medical Center, Nashville, TN, USA.
| | - Charles D Ellis
- Division of Nephrology, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, USA. .,Vanderbilt Center for Kidney Disease, Vanderbilt University Medical Center, Nashville, TN, USA.
| | - Rajnish Mehrotra
- Division of Nephrology, Department of Medicine, University of Washington, Box 359606, 325 9th Ave., Seattle, WA, 98104, USA. .,Kidney Research Institute, Seattle, WA, USA.
| | - Jonathan Himmelfarb
- Division of Nephrology, Department of Medicine, University of Washington, Box 359606, 325 9th Ave., Seattle, WA, 98104, USA. .,Kidney Research Institute, Seattle, WA, USA.
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Guérard M, Baum M, Bitsch A, Eisenbrand G, Elhajouji A, Epe B, Habermeyer M, Kaina B, Martus H, Pfuhler S, Schmitz C, Sutter A, Thomas A, Ziemann C, Froetschl R. Assessment of mechanisms driving non-linear dose–response relationships in genotoxicity testing. MUTATION RESEARCH-REVIEWS IN MUTATION RESEARCH 2015; 763:181-201. [DOI: 10.1016/j.mrrev.2014.11.001] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2014] [Revised: 10/31/2014] [Accepted: 11/01/2014] [Indexed: 01/15/2023]
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Guha N, Roy A, Kopylev L, Fox J, Spassova M, White P. Nonparametric Bayesian methods for benchmark dose estimation. RISK ANALYSIS : AN OFFICIAL PUBLICATION OF THE SOCIETY FOR RISK ANALYSIS 2013; 33:1608-19. [PMID: 23339666 DOI: 10.1111/risa.12004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
The article proposes and investigates the performance of two Bayesian nonparametric estimation procedures in the context of benchmark dose estimation in toxicological animal experiments. The methodology is illustrated using several existing animal dose-response data sets and is compared with traditional parametric methods available in standard benchmark dose estimation software (BMDS), as well as with a published model-averaging approach and a frequentist nonparametric approach. These comparisons together with simulation studies suggest that the nonparametric methods provide a lot of flexibility in terms of model fit and can be a very useful tool in benchmark dose estimation studies, especially when standard parametric models fail to fit to the data adequately.
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Affiliation(s)
- Nilabja Guha
- Department of Mathematics and Statistics, University of Maryland Baltimore County, Baltimore, MD, USA
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Bhattacharya R, Lin L. RECENT PROGRESS IN THE NONPARAMETRIC ESTIMATION OF MONOTONE CURVES -WITH APPLICATIONS TO BIOASSAY AND ENVIRONMENTAL RISK ASSESSMENT. Comput Stat Data Anal 2013; 63:63-80. [PMID: 23997381 DOI: 10.1016/j.csda.2013.01.023] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Three recent nonparametric methodologies for estimating a monotone regression function F and its inverse F-1 are (1) the inverse kernel method DNP (Dette et al. (2005), Dette and Scheder (2010)), (2) the monotone spline (Kong and Eubank (2006)) and (3) the data adaptive method NAM (Bhattacharya and Lin (2010), (2011)), with roots in isotonic regression (Ayer et al. (1955), Bhattacharya and Kong (2007)). All three have asymptotically optimal error rates. In this article their finite sample performances are compared using extensive simulation from diverse models of interest, and by analysis of real data. Let there be m distinct values of the independent variable x among N observations y. The results show that if m is relatively small compared to N then generally the NAM performs best, while the DNP outperforms the other methods when m is O(N) unless there is a substantial clustering of the values of the independent variable x.
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Spassova MA, Miller DJ, Eastmond DA, Nikolova NS, Vulimiri SV, Caldwell J, Chen C, White PD. Dose-response analysis of bromate-induced DNA damage and mutagenicity is consistent with low-dose linear, nonthreshold processes. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2013; 54:19-35. [PMID: 23015362 DOI: 10.1002/em.21737] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2012] [Revised: 08/21/2012] [Accepted: 08/21/2012] [Indexed: 06/01/2023]
Abstract
Mutagenic agents have long been inferred to act through low-dose linear, nonthreshold processes. However, there is debate about this assumption, with various studies interpreting datasets as showing thresholds for DNA damage and mutation. We have applied rigorous statistical analyses to investigate the shape of dose-response relationships for a series of in vitro and in vivo genotoxicity studies using potassium bromate (KBrO(3) ), a water ozonation byproduct that is bioactivated to a reactive species causing oxidative damage to DNA. We analyzed studies of KBrO(3) genotoxicity where no-effect/threshold levels were reported as well as other representative datasets. In all cases, the data were consistent with low-dose linear models. In the majority of cases, the data were fit either by a linear (straight line) model or a model which was linear at low doses and showed a saturation-like downward curvature at high doses. Other datasets with apparent upward curvature were still adequately represented by models that were linear at low dose. Sensitivity analysis of datasets showing upward curvature revealed that both low-dose linear and nonlinear models provide adequate fits. Additionally, a simple biochemical model of selected key processes in bromate-induced DNA damage was developed and illustrated a situation where response for early primary events suggested an apparent threshold while downstream events were linear. Overall, the statistical analyses of DNA damage and mutations induced by KBrO(3) are consistent with a low-dose linear response and do not provide convincing evidence for the presence of a threshold.
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Affiliation(s)
- Maria A Spassova
- National Center for Environmental Assessment (NCEA), Office of Research and Development (ORD), U.S. Environmental Protection Agency (U.S.EPA), Washington, DC, USA.
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Existe-t-il une dose seuil pour les effets génotoxiques ? ARCH MAL PROF ENVIRO 2012. [DOI: 10.1016/j.admp.2012.06.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Le Hégarat L, Huet S, Fessard V. A co-culture system of human intestinal Caco-2 cells and lymphoblastoid TK6 cells for investigating the genotoxicity of oral compounds. Mutagenesis 2012; 27:631-6. [PMID: 22844081 DOI: 10.1093/mutage/ges028] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Here, we assessed a co-culture system of intestinal Caco-2 cells and lymphoblastoid TK6 cells for modelling the role of intestinal first-pass effects, i.e. absorption and metabolism, in the genotoxicity of oral drugs and food contaminants. Caco-2 cells were seeded onto semipermeable culture inserts for 21 days until differentiation, and then TK6 cells were added to the basal compartment. After apical loading with mutagenic compounds [methylmethanesulfonate (MMS), benzo[a]-pyrene (BaP) and aflatoxin B1 (AFB1)], comet and micronucleus assays were performed on both cell lines. MMS (10 µg/ml) showed positive results in the micronucleus assays in both cell lines, even though DNA damage was only detected in the Caco-2 cells with the comet assay. At concentrations of 0.5-50 µM, BaP induced dose-dependent comet and micronucleus formation at 24h in Caco-2 cells, but no DNA damage was observed in TK6 cells. Although AFB1 failed to induce comet formation, it resulted in a high level of micronuclei in both cell lines. Treatment of Caco-2 cells with the CYP3A4 inhibitor, ketoconazole, inhibited the AFB1-induced cytotoxicity and micronucleus formation in TK6 cells, suggesting that intestinal metabolism is involved in the AFB1 genotoxic response in TK6 cells. Our results suggest that the Caco-2/TK6 co-culture model is suitable for modelling the role of intestinal biotransformation and transport processes in the genotoxic potential of oral drugs and food contaminants in target blood cells.
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Affiliation(s)
- Ludovic Le Hégarat
- ANSES, Laboratoire de Fougères, Unité de Toxicologie des contaminants BP 90203, 35302 Fougères Cedex, France.
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Geter DR, Zhang F, Schisler MR, Wood AJ, Kan HL, Jeong YC, Bartels MJ, McFadden L, Gollapudi BB. Genetic damage, but limited evidence of oxidative stress markers in diethyl maleate-induced glutathione depleted mouse lymphoma L5178Y (TK(+/-)) cell cultures. Toxicol Mech Methods 2012; 22:547-54. [PMID: 22564015 DOI: 10.3109/15376516.2012.692111] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Depletion of glutathione (GSH) in cells exposed to certain xenobiotics has been proposed to result in oxidative stress, which could lead to damage of cellular macromolecules such as proteins, lipids, and DNA. Diethyl maleate (DEM) is known to conjugate with GSH and rapidly lower cellular GSH levels. The objective of this study was to investigate the influence of DEM-induced GSH depletion on various genotoxicity and gene expression end points in mouse lymphoma L5178Y (TK(+/-)) cell cultures. Cells were exposed to DEM for 4 h at concentrations of 0, 6.7, 13.5, 26.9, 53.8, 107.6, 215.3, and 430.6 µg/mL (0.039-2.5 mM). Genotoxicity was evaluated by examining the induction of in vitro micronuclei (20 h post-treatment) and DNA strand breaks as measured by comet (immediately following treatment), and correlating these observations to cellular GSH levels. In the current study, GSH was decreased more than 50% at the lowest test concentration (6.7 µg/mL) and more than 95% at ≥ 107.6 µg/mL. A significant increase in micronuclei and DNA strand breaks was observed at concentrations of ≥ 26.9 µg/mL. Gene expression of seven apoptosis and oxidative-stress related genes showed significant alterations in only three genes only at the highest test concentration. Quantifiable levels of 8-OH-dG (≥ 2 adducts per 1 × 10(8) NT) were not detected at any treatment concentration. These results demonstrate an association between DEM-induced genotoxicity and GSH depletion in mouse lymphoma L5178Y (TK(+/-)) cells, but not with other oxidative markers.
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Affiliation(s)
- David R Geter
- Toxicology and Environmental Research & Consulting, The Dow Chemical Company, Midland, Michigan, USA
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Alves JM, Munari CC, de Azevedo Bentes Monteiro Neto M, Furtado RA, Senedese JM, Bastos JK, Tavares DC. In vivo protective effect of Copaifera langsdorffii hydroalcoholic extract on micronuclei induction by doxorubicin. J Appl Toxicol 2012; 33:854-60. [PMID: 22611044 DOI: 10.1002/jat.2777] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2012] [Revised: 04/18/2012] [Accepted: 04/18/2012] [Indexed: 11/06/2022]
Abstract
Copaifera lansdorffii Desf. is known as 'copaíba', 'copaiva' or 'paú-de-óleo', and is found in part of Brazil. The present study was undertaken to evaluate the genotoxic potential of C. langsdorffii leaf hydroalcoholic extract (CLE) and its influence on the genotoxicity induced by the chemotherapeutic agent doxorubicin (DXR) using the Swiss mouse peripheral blood micronucleus test. HPLC analysis of CLE using two monolithic columns linked in series allowed quantification of two major flavonoid heterosides, quercitrin and afzelin. Animals were treated with CLE by gavage at doses of 10, 20, 40 and 80 mg kg(-1) body weight per day, each for 20 days. Peripheral blood samples were collected at 24 and 48 h, and 7, 15 and 21 days after the beginning of the treatment. For the antigenotoxicity evaluation, the animals treated with different concentrations of CLE received DXR (15 mg kg(-1) body weight, intraperitoneal) at day 20. The peripheral blood samples were collected 24 and 48 h after the treatment with DXR. The results demonstrated that CLE itself was not genotoxic in the mouse micronucleus assay. In animals treated with CLE and DXR, the number of micronucleus was significantly decreased compared with animals receiving DXR alone. The putative antioxidant activity of one or more of the active compounds of CLE may explain the effect of this plant on DXR genotoxicity.
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Affiliation(s)
- Jacqueline Morais Alves
- Universidade de Franca, Avenida Dr. Armando Salles de Oliveira, 201 Parque Universitário, 14404-600, Franca, São Paulo, Brazil
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Seager AL, Shah UK, Mikhail JM, Nelson BC, Marquis BJ, Doak SH, Johnson GE, Griffiths SM, Carmichael PL, Scott SJ, Scott AD, Jenkins GJS. Pro-oxidant induced DNA damage in human lymphoblastoid cells: homeostatic mechanisms of genotoxic tolerance. Toxicol Sci 2012; 128:387-97. [PMID: 22539617 DOI: 10.1093/toxsci/kfs152] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Oxidative stress contributes to many disease etiologies including ageing, neurodegeneration, and cancer, partly through DNA damage induction (genotoxicity). Understanding the i nteractions of free radicals with DNA is fundamental to discern mutation risks. In genetic toxicology, regulatory authorities consider that most genotoxins exhibit a linear relationship between dose and mutagenic response. Yet, homeostatic mechanisms, including DNA repair, that allow cells to tolerate low levels of genotoxic exposure exist. Acceptance of thresholds for genotoxicity has widespread consequences in terms of understanding cancer risk and regulating human exposure to chemicals/drugs. Three pro-oxidant chemicals, hydrogen peroxide (H(2)O(2)), potassium bromate (KBrO(3)), and menadione, were examined for low dose-response curves in human lymphoblastoid cells. DNA repair and antioxidant capacity were assessed as possible threshold mechanisms. H(2)O(2) and KBrO(3), but not menadione, exhibited thresholded responses, containing a range of nongenotoxic low doses. Levels of the DNA glycosylase 8-oxoguanine glycosylase were unchanged in response to pro- oxidant stress. DNA repair-focused gene expression arrays reported changes in ATM and BRCA1, involved in double-strand break repair, in response to low-dose pro-oxidant exposure; however, these alterations were not substantiated at the protein level. Determination of oxidatively induced DNA damage in H(2)O(2)-treated AHH-1 cells reported accumulation of thymine glycol above the genotoxic threshold. Further, the H(2)O(2) dose-response curve was shifted by modulating the antioxidant glutathione. Hence, observed pro- oxidant thresholds were due to protective capacities of base excision repair enzymes and antioxidants against DNA damage, highlighting the importance of homeostatic mechanisms in "genotoxic tolerance."
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Affiliation(s)
- Anna L Seager
- DNA Damage Research Group, Institute of Life Science, College of Medicine, Swansea University, SA2 8PP, UK
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Platel A, Nesslany F, Gervais V, Claude N, Marzin D. Study of oxidative DNA damage in TK6 human lymphoblastoid cells by use of the thymidine kinase gene-mutation assay and the in vitro modified comet assay: Determination of No-Observed-Genotoxic-Effect-Levels. MUTATION RESEARCH-GENETIC TOXICOLOGY AND ENVIRONMENTAL MUTAGENESIS 2011; 726:151-9. [DOI: 10.1016/j.mrgentox.2011.09.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2009] [Revised: 08/26/2011] [Accepted: 09/04/2011] [Indexed: 11/27/2022]
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Elhajouji A, Lukamowicz M, Cammerer Z, Kirsch-Volders M. Potential thresholds for genotoxic effects by micronucleus scoring. Mutagenesis 2010; 26:199-204. [DOI: 10.1093/mutage/geq089] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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Bryce SM, Avlasevich SL, Bemis JC, Phonethepswath S, Dertinger SD. Miniaturized flow cytometric in vitro micronucleus assay represents an efficient tool for comprehensively characterizing genotoxicity dose-response relationships. Mutat Res 2010; 703:191-9. [PMID: 20826227 DOI: 10.1016/j.mrgentox.2010.08.020] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2010] [Revised: 08/26/2010] [Accepted: 08/27/2010] [Indexed: 01/14/2023]
Abstract
This laboratory has developed a flow cytometric approach for scoring in vitro micronuclei (In Vitro MicroFlow(®)) whose characteristics are expected to benefit studies designed to comprehensively investigate genotoxicity dose-response relationships. In particular, new experimental designs become possible when automated scoring is combined with treatment, processing and sampling that all occur in microtiter plates. To test this premise, experiments described herein investigated micronucleus (MN) formation in TK6 cells treated with genotoxic agents applied at 22 closely spaced concentrations in quadruplicate, with 10,000 cells analyzed per replicate. The genotoxicants colchicine, vinblastine sulfate, ethyl methanesulfonate, methyl methanesulfonate, ethyl nitrosourea, methyl nitrosourea, and bleomycin were applied continuously for 24-30 h. Following treatment, all cell processing, sampling and data acquisition steps were accomplished in the same 96-well plate. Data acquisition occurred in a walk-away mode via the use of a high throughput sampling device. The resulting flow cytometric MN values were evaluated with a statistical model that indicated non-linear relationships describe the data better than linear fits. The one exception was bleomycin, where MN induction was consistently best described by a linear dose-response relationship. Collectively, these results suggest that flow cytometry represents a practical and efficient approach for thoroughly examining the dose-response relationship, and clearly benefits studies that seek to characterize no observable genotoxic effect levels, lowest observable genotoxic effect levels, and/or benchmark doses.
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Hashimoto K, Nakajima Y, Matsumura S, Chatani F. Comparison of four different treatment conditions of extended exposure in the in vitro micronucleus assay using TK6 lymphoblastoid cells. Regul Toxicol Pharmacol 2010; 59:28-36. [PMID: 20800082 DOI: 10.1016/j.yrtph.2010.08.016] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2010] [Revised: 08/19/2010] [Accepted: 08/20/2010] [Indexed: 11/27/2022]
Abstract
In the OECD Guideline 487, a total of four extended exposure treatment conditions are proposed for the in vitro micronucleus (MNvit) assay in the presence and absence of a cytokinesis block and with or without a recovery period. This guideline also states that rodent cell lines and human lymphocytes can be used as shown by many validated studies but that human cell lines such as TK6 and HepG2 are not yet validated. In this present study each extended exposure condition was characterized by investigation using TK6 cells and nine chemicals known to be able to induce micronucleus (MN) in rodent cell lines. The results revealed two concerns: six chemicals did not show significant MN induction in the 'cytokinesis block without recovery period'; two aneugens showed no dose-dependent cytotoxicity in the 'cytokinesis block with recovery period'. Further investigation revealed that 3-4 times higher spontaneous MN frequency than that in the other conditions is a possible reason for the low sensitivity, and this high spontaneous MN frequency was not observed in Chinese hamster lung cells under the identical treatment condition. With regard to the two conditions without cytokinesis block, two negative substances were evaluated and found to be negative, suggesting the validity of the TK6 test system for these conditions. Although our findings showed a few concerns for the treatment with cytokinesis block, the TK6 cells were considered to be a reliable cell line to be used for detecting potential inducers of MN in the in vitro micronucleus assay based on the overall results.
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Affiliation(s)
- Kiyohiro Hashimoto
- Development Research Center, Pharmaceutical Research Division, Takeda Pharmaceutical Company Limited, 17-85, Jusohonmachi 2-chome, Yodogawa-ku, Osaka 532-8686, Japan.
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Platel A, Gervais V, Sajot N, Nesslany F, Marzin D, Claude N. Study of gene expression profiles in TK6 human cells exposed to DNA-oxidizing agents. Mutat Res 2010; 689:21-49. [PMID: 20466008 DOI: 10.1016/j.mrfmmm.2010.04.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2009] [Revised: 04/28/2010] [Accepted: 04/30/2010] [Indexed: 05/29/2023]
Abstract
During the last decade, there has been clear progress in using threshold in risk assessment but its acceptance by scientists is still under debate. Contrary to indirect DNA-damaging agents, DNA-reactive agents have been assumed to have a non-threshold mode of action, as they directly induce DNA lesions that potentially can be converted into mutations. However, in recent years there is a growing number of data establishing threshold doses even for these DNA-reactive compounds. Indeed, there are several defence and repair mechanisms that provide protection and that may be responsible for genotoxic thresholds. In this context, we recently showed that DNA-oxidizing agents exhibit a thresholded dose-response in vitro with respect to chromosomal alterations. We have hypothesized the involvement of different cellular responses whose nature and efficiency depend on the stress level. The aim of this study was to develop a more complete understanding of these underlying mechanisms. We investigated global gene expression profiles of human lymphoblastoid TK6 cells after exposure to potassium bromate and hydrogen peroxide (via glucose oxidase). Cells were treated for 1h and mRNAs were isolated either immediately at the end of the treatment or after a 23-h recovery period. Our results showed that cells have developed elaborate cellular responses to oxidative stress in order to maintain genomic integrity. Many of altered genes were redox-sensitive transcription factors such as p53, NF-kappaB, AP-1 and Nrf2. Their downstream target genes and signalling pathways were subsequently activated leading mainly to the induction of antioxidant defenses, inflammation, cell cycle arrest, DNA repair and cell death. Overall, our study allowed the identification of key events involved in the thresholded response observed after DNA-oxidizing agents exposure and shows the usefulness of the combination of standard in vitro genotoxicity assays with gene expression profiling technology to determine modes of action, particularly for critical risk assessment.
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Affiliation(s)
- Anne Platel
- Biologie Servier, 905 Route de Saran, 45403 Gidy, France
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