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Iwashita K, Hosokawa Y, Ihara R, Miyamoto T, Otani M, Abe J, Asano K, Mercier O, Miyata K, Barlow S. Flumioxazin, a PPO inhibitor: A weight-of-evidence consideration of its mode of action as a developmental toxicant in the rat and its relevance to humans. Toxicology 2022; 472:153160. [DOI: 10.1016/j.tox.2022.153160] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2022] [Revised: 03/15/2022] [Accepted: 03/17/2022] [Indexed: 10/18/2022]
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Asano K, Takahashi Y, Ueno M, Fukuda T, Otani M, Kitamoto S, Tomigahara Y. Lack of human relevance for rat developmental toxicity of flumioxazin is revealed by comparative heme synthesis assay using embryonic erythroid cells derived from human and rat pluripotent stem cells. J Toxicol Sci 2022; 47:125-138. [DOI: 10.2131/jts.47.125] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Affiliation(s)
- Koji Asano
- Environmental Health Science Laboratory, Sumitomo Chemical Co., Ltd
| | | | - Manako Ueno
- Bioscience Research Laboratory, Sumitomo Chemical Co., Ltd
| | - Takako Fukuda
- Bioscience Research Laboratory, Sumitomo Chemical Co., Ltd
| | - Mitsuhiro Otani
- Environmental Health Science Laboratory, Sumitomo Chemical Co., Ltd
| | - Sachiko Kitamoto
- Environmental Health Science Laboratory, Sumitomo Chemical Co., Ltd
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Abe J. Researches on the evaluation of pesticide safety in humans using a pharmacokinetic approach. JOURNAL OF PESTICIDE SCIENCE 2021; 46:290-296. [PMID: 34566464 PMCID: PMC8422259 DOI: 10.1584/jpestics.j21-02] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Accepted: 05/24/2021] [Indexed: 06/13/2023]
Abstract
Similar to the pharmaceutical compounds, pesticides require human safety assessment for their registration and distribution; however, it is absolutely impossible to assess human safety by dosing humans with pesticides. Thus, how to appropriately evaluate the safety of pesticides in humans remains a great subject of debate. In this article, we present some examples of pesticide toxicity studies that identify species differences in toxicity and evaluate human safety by applying combinations of novel in vivo, in vitro, and in silico techniques to separately assess the key toxicodynamic (i.e., sensitivity) and/or toxicokinetic (i.e., exposure) factors. Because it is scientifically sound, the safety assessment strategy illustrated for three compounds in this article is expected to play an important role in the human safety assessment of agricultural compounds.
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Affiliation(s)
- Jun Abe
- Environmental Health Science Laboratory, Sumitomo Chemical Co., Ltd., 1–98 Kasugade-naka 3, Konohana-ku, Osaka 554–8558, Japan
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Kawamura S, Otani M, Miyamoto T, Abe J, Ihara R, Inawaka K, Fantel AG. Different effects of an N-phenylimide herbicide on heme biosynthesis between human and rat erythroid cells. Reprod Toxicol 2021; 99:27-38. [PMID: 33249232 DOI: 10.1016/j.reprotox.2020.11.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Revised: 10/28/2020] [Accepted: 11/22/2020] [Indexed: 01/10/2023]
Abstract
Rat developmental toxicity including embryolethality and teratogenicity (mainly ventricular septal defects and wavy ribs) were produced by S-53482, an N-phenylimide herbicide that inhibits protoporphyrinogen oxidase (PPO) common to chlorophyll and heme biosynthesis. The sequence of key biological events in the mode of action has been elucidated as follows: inhibition of PPO interferes with normal heme synthesis, which causes loss of blood cells leading to fetal anemia, embryolethality and the development of malformations. In this study we investigated whether the rat is a relevant model for the assessment of the human hazard of the herbicide. To study effects on heme biosynthesis, human erythroleukemia, human cord blood, and rat erythroleukemia cells were treated with the herbicide during red cell differentiation. Protoporphyrin IX, a marker of PPO inhibition, and heme were determined. We investigated whether synchronous maturation of primitive erythropoiesis, which can contribute to massive losses of embryonic blood, occurs in rats. The population of primitive erythroblasts was observed on gestational days 11 through 14. Heme production was suppressed in rat erythroid cells. In contrast, heme reduction was not seen in both human erythroid cells when PPO was inhibited. Rats underwent synchronous maturation in primitive erythropoiesis. Our results combined with epidemiological findings that patients with deficient PPO are not anemic led us to conclude that human erythroblasts are resistant to the herbicide. It is suggested that the rat would be an inappropriate model for assessing the developmental toxicity of S-53482 in humans as rats are specifically sensitive to PPO inhibition by the herbicide.
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Affiliation(s)
- Satoshi Kawamura
- Environmental Health Science Laboratory, Sumitomo Chemical Co., Ltd., 1-98, Kasugade-naka 3-chome, Konohana-ku, Osaka, 554-8558, Japan.
| | - Mitsuhiro Otani
- Environmental Health Science Laboratory, Sumitomo Chemical Co., Ltd., 1-98, Kasugade-naka 3-chome, Konohana-ku, Osaka, 554-8558, Japan
| | - Taiki Miyamoto
- Environmental Health Science Laboratory, Sumitomo Chemical Co., Ltd., 1-98, Kasugade-naka 3-chome, Konohana-ku, Osaka, 554-8558, Japan
| | - Jun Abe
- Environmental Health Science Laboratory, Sumitomo Chemical Co., Ltd., 1-98, Kasugade-naka 3-chome, Konohana-ku, Osaka, 554-8558, Japan
| | - Ryo Ihara
- Environmental Health Science Laboratory, Sumitomo Chemical Co., Ltd., 1-98, Kasugade-naka 3-chome, Konohana-ku, Osaka, 554-8558, Japan
| | - Kunifumi Inawaka
- Environmental Health Science Laboratory, Sumitomo Chemical Co., Ltd., 1-98, Kasugade-naka 3-chome, Konohana-ku, Osaka, 554-8558, Japan
| | - Alan G Fantel
- Department of Pediatrics, University of Washington, 1959 NE Pacific St. Box 366320, Seattle, WA 98195-6320, USA
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Features of oxa-bridge cleavage in hexahydro-3a,6-epoxyisoindol-1(4H)-ones: A concise method to access acetylisoindolones possessing anti-viral activity. Tetrahedron Lett 2019. [DOI: 10.1016/j.tetlet.2019.151204] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Teixidó E, Krupp E, Amberg A, Czich A, Scholz S. Species-specific developmental toxicity in rats and rabbits: Generation of a reference compound list for development of alternative testing approaches. Reprod Toxicol 2018; 76:93-102. [PMID: 29409988 DOI: 10.1016/j.reprotox.2018.01.005] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2017] [Revised: 12/05/2017] [Accepted: 01/26/2018] [Indexed: 11/19/2022]
Abstract
For regulatory information requirements, developmental toxicity testing is often conducted in two mammalian species. In order to provide a set of reference compounds that could be used to explore alternative approaches to supersede testing in a second species, a retrospective data analysis was conducted. The aim was to identify compounds for which species sensitivity differences between rats and rabbits are not caused by maternal toxicity or toxicokinetic differences. A total of 330 compounds were analysed and classified according to their species-specific differences. A lack of concordance between rat and rabbit was observed in 24% of the compounds, of which 10% were found to be selective developmental toxicants in one of the species. In contrast to previously published analyses the presented comparison is based entirely on publically data allowing validating and comparing alternative approaches for developmental toxicity testing. Furthermore, this list could be useful to identify mechanisms leading to species differences.
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Affiliation(s)
- E Teixidó
- Department of Bioanalytical Ecotoxicology, Helmholtz Centre for Environmental Research - UFZ, Permoserstraße 15, 04318, Leipzig, Germany.
| | - E Krupp
- Sanofi-Aventis Deutschland GmbH, Preclinical Safety, Industriepark Hoechst, D-65926, Frankfurt am Main, Germany
| | - A Amberg
- Sanofi-Aventis Deutschland GmbH, Preclinical Safety, Industriepark Hoechst, D-65926, Frankfurt am Main, Germany
| | - A Czich
- Sanofi-Aventis Deutschland GmbH, Preclinical Safety, Industriepark Hoechst, D-65926, Frankfurt am Main, Germany
| | - S Scholz
- Department of Bioanalytical Ecotoxicology, Helmholtz Centre for Environmental Research - UFZ, Permoserstraße 15, 04318, Leipzig, Germany
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Abe J, Isobe N, Mikata K, Nagahori H, Naito Y, Saji H, Ono M, Kawamura S. Flumioxazin metabolism in pregnant animals and cell-based protoporphyrinogen IX oxidase (PPO) inhibition assay of fetal metabolites in various animal species to elucidate the mechanism of the rat-specific developmental toxicity. Toxicol Appl Pharmacol 2017; 339:34-41. [PMID: 29198728 DOI: 10.1016/j.taap.2017.11.028] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2017] [Revised: 11/28/2017] [Accepted: 11/29/2017] [Indexed: 02/02/2023]
Abstract
Flumioxazin, an N-phenylimide herbicide, inhibits protoporphyrinogen oxidase (PPO), a key enzyme in heme biosynthesis in mammals, and causes rat-specific developmental toxicity. The mechanism has mainly been clarified, but no research has yet focused on the contribution of its metabolites. We therefore conducted in vivo metabolism studies in pregnant rats and rabbits, and found 6 major known metabolites in excreta. There was no major rat-specific metabolite. The most abundant component in rat fetuses was APF, followed by flumioxazin and 5 identified metabolites. The concentrations of flumioxazin and these metabolites in fetuses were lower in rabbits than in rats. In vitro PPO inhibition assays with rat and human liver mitochondria showed that flumioxazin is a more potent PPO inhibitor than the metabolites. There were no species differences in relative intensity of PPO inhibition among flumioxazin and these metabolites. Based on the results of these in vivo and in vitro experiments, we concluded that flumioxazin is the causal substance of the rat-specific developmental toxicity. As a more reliable test system for research on in vitro PPO inhibition, cell-based assays with rat, rabbit, monkey, and human hepatocytes were performed. The results were consistent with those of the mitochondrial assays, and rats were more sensitive to PPO inhibition by flumioxazin than humans, while rabbits and monkeys were almost insensitive. From these results, the species difference in the developmental toxicity was concluded to be due to the difference in sensitivity of PPO to flumioxazin, and rats were confirmed to be the most sensitive of these species.
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Affiliation(s)
- Jun Abe
- Environmental Health Science Laboratory, Sumitomo Chemical Co., Ltd., 1-98, 3-Chome, Kasugade-Naka, Konohana-Ku, Osaka 554-8558, Japan.
| | - Naohiko Isobe
- Environmental Health Science Laboratory, Sumitomo Chemical Co., Ltd., 1-98, 3-Chome, Kasugade-Naka, Konohana-Ku, Osaka 554-8558, Japan
| | - Kazuki Mikata
- Environmental Health Science Laboratory, Sumitomo Chemical Co., Ltd., 1-98, 3-Chome, Kasugade-Naka, Konohana-Ku, Osaka 554-8558, Japan
| | - Hirohisa Nagahori
- Environmental Health Science Laboratory, Sumitomo Chemical Co., Ltd., 1-98, 3-Chome, Kasugade-Naka, Konohana-Ku, Osaka 554-8558, Japan
| | - Yoshikazu Naito
- Environmental Health Science Laboratory, Sumitomo Chemical Co., Ltd., 1-98, 3-Chome, Kasugade-Naka, Konohana-Ku, Osaka 554-8558, Japan
| | - Hideo Saji
- Department of Patho-Functional Bioanalysis, Graduate School of Pharmaceutical Sciences, Kyoto University, 46-29, Yoshida Shimoadachi-cho, Sakyo-ku, Kyoto 606-8501, Japan
| | - Masahiro Ono
- Department of Patho-Functional Bioanalysis, Graduate School of Pharmaceutical Sciences, Kyoto University, 46-29, Yoshida Shimoadachi-cho, Sakyo-ku, Kyoto 606-8501, Japan
| | - Satoshi Kawamura
- Environmental Health Science Laboratory, Sumitomo Chemical Co., Ltd., 1-98, 3-Chome, Kasugade-Naka, Konohana-Ku, Osaka 554-8558, Japan
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Kawamura S, Yoshioka T, Mito N, Kishimoto N, Nakaoka M, Fantel AG. Mechanism of Developmental Effects in Rats Caused by an N-Phenylimide Herbicide: Transient Fetal Anemia and Sequelae during Mid-to-Late Gestation. ACTA ACUST UNITED AC 2016; 107:45-59. [PMID: 26865470 DOI: 10.1002/bdrb.21172] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2015] [Accepted: 01/20/2016] [Indexed: 12/14/2022]
Abstract
BACKGROUND Rat developmental toxicity including embryolethality and teratogenicity (mainly ventricular septal defects [VSDs] and wavy ribs) was produced by an N-phenylimide herbicide that inhibits protoporphyrinogen oxidase (PPO) common to chlorophyll and heme biosynthesis. Major characteristics of the developmental toxicity included species difference between rats and rabbits, compound-specific difference among structurally similar herbicides, and sensitive period. Protoporphyrin accumulation in treated fetuses closely correlated with the major characteristics. Iron deposits in erythroblastic mitochondria and degeneration of erythroblasts were observed in treated rat fetuses. In this study we investigated fetal anemia and subsequent developmental effects in rats, and inhibition of PPO in rats, rabbits, and humans by the herbicides in vitro. METHODS Fetuses were treated on gestational day (GD) 12 and removed on GDs 13 through 20. All litters were examined externally. One half of litters were examined for blood and skeletal development, and the other half for interventricular foramen closure. Effects on PPO were determined in mitochondria from embryos and adult livers. RESULTS Fetal anemia in rats was evident on GDs 13 through 16. Subsequently, enlarged heart, delayed closure of the foramen, reduced serum protein, and retarded rib ossification were observed. In vitro PPO inhibition exhibited species- and compound-specific differences corresponding to the developmental toxicity. CONCLUSION We propose that developmental toxicity results from PPO inhibition in primitive erythroblasts, causing transient fetal anemia followed by death. Compensatory enlargement of the fetal heart results in failure of interventricular foramen closure and VSD. Reduced serum protein leads to delayed ossification and wavy ribs.
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Affiliation(s)
- Satoshi Kawamura
- Environmental Health Science Laboratory, Sumitomo Chemical Co. Ltd, Konohana-ku, Osaka, Japan
| | - Takafumi Yoshioka
- Environmental Health Science Laboratory, Sumitomo Chemical Co. Ltd, Konohana-ku, Osaka, Japan
| | - Nobuaki Mito
- Intellectual Property Department, Sumitomo Chemical Co. Ltd, Chuo-ku, Tokyo, Japan
| | - Noriyuki Kishimoto
- Environmental Health Science Laboratory, Sumitomo Chemical Co. Ltd, Konohana-ku, Osaka, Japan
| | - Masanao Nakaoka
- Environmental Health Science Laboratory, Sumitomo Chemical Co. Ltd, Konohana-ku, Osaka, Japan
| | - Alan G Fantel
- Department of Pediatrics, University of Washington, Seattle, Washington
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