1
|
Goettel M, Werner C, Honarvar N, Gröters S, Fegert I, Haines C, Chatham LR, Vardy A, Lake BG. Mode of action analysis for fluxapyroxad-induced rat liver tumour formation: evidence for activation of the constitutive androstane receptor and assessment of human relevance. Toxicology 2024; 505:153828. [PMID: 38740169 DOI: 10.1016/j.tox.2024.153828] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2024] [Revised: 04/30/2024] [Accepted: 05/08/2024] [Indexed: 05/16/2024]
Abstract
The fungicide fluxapyroxad (BAS 700 F) has been shown to significantly increase the incidence of liver tumours in male Wistar rats at dietary levels of 1500 and 3000 ppm and in female rats at a dietary level of 3000 ppm via a non-genotoxic mechanism. In order to elucidate the mode of action (MOA) for fluxapyroxad-induced rat liver tumour formation a series of in vivo and in vitro investigative studies were undertaken. The treatment of male and female Wistar rats with diets containing 0 (control), 50, 250, 1500 and 3000 ppm fluxapyroxad for 1, 3, 7 and 14 days resulted in a dose-dependent increases in relative weight at 1500 and 3000 ppm from day 3 onwards in both sexes, with an increase in relative liver weight being also observed in male rats given 250 ppm fluxapyroxad for 14 days. Examination of liver sections revealed a centrilobular hepatocyte hypertrophy in some fluxapyroxad treated male and female rats. Hepatocyte replicative DNA synthesis (RDS) was significantly increased in male rats given 1500 and 3000 ppm fluxapyroxad for 3 and 7 days and in female rats given 50-3000 ppm fluxapyroxad for 7 days and 250-3000 ppm fluxapyroxad for 3 and 14 days; the maximal increases in RDS in both sexes being observed after 7 days treatment. The treatment of male and female Wistar rats with 250-3000 ppm fluxapyroxad for 14 days resulted in significant increases in hepatic microsomal total cytochrome P450 (CYP) content and CYP2B subfamily-dependent enzyme activities. Male Wistar rat hepatocytes were treated with control medium and medium containing 1-100 μM fluxapyroxad or 500 μM sodium phenobarbital (NaPB) for 4 days. Treatment with fluxapyroxad and NaPB increased CYP2B and CYP3A enzyme activities and mRNA levels but had little effect on markers of CYP1A and CYP4A subfamily enzymes and of the peroxisomal fatty acid β-oxidation cycle. Hepatocyte RDS was significantly increased by treatment with fluxapyroxad, NaPB and 25 ng/ml epidermal growth factor (EGF). The treatment of hepatocytes from two male human donors with 1-100 μM fluxapyroxad or 500 μM NaPB for 4 days resulted in some increases in CYP2B and CYP3A enzyme activities and CYP mRNA levels but had no effect on hepatocyte RDS, whereas treatment with EGF resulted in significant increase in RDS in both human hepatocyte preparations. Hepatocytes from male Sprague-Dawley wild type (WT) and constitutive androstane receptor (CAR) knockout (CAR KO) rats were treated with control medium and medium containing 1-16 μM fluxapyroxad or 500 μM NaPB for 4 days. While both fluxapyroxad and NaPB increased CYP2B enzyme activities and mRNA levels in WT hepatocytes, only minor effects were observed in CAR KO rat hepatocytes. Treatment with both fluxapyroxad and NaPB only increased RDS in WT and not in CAR KO rat hepatocytes, whereas treatment with EGF increased RDS in both WT and CAR KO rat hepatocytes. In conclusion, a series of in vivo and in vitro investigative studies have demonstrated that fluxapyroxad is a CAR activator in rat liver, with similar properties to the prototypical CAR activator phenobarbital. A robust MOA for fluxapyroxad-induced rat liver tumour formation has been established. Based on the lack of effect of fluxapyroxad on RDS in human hepatocytes, it is considered that the MOA for fluxapyroxad-induced liver tumour formation is qualitatively not plausible for humans.
Collapse
MESH Headings
- Animals
- Male
- Female
- Rats, Wistar
- Rats
- Fungicides, Industrial/toxicity
- Receptors, Cytoplasmic and Nuclear/metabolism
- Receptors, Cytoplasmic and Nuclear/genetics
- Constitutive Androstane Receptor
- Humans
- Hepatocytes/drug effects
- Hepatocytes/metabolism
- Hepatocytes/pathology
- Liver/drug effects
- Liver/metabolism
- Liver/pathology
- Dose-Response Relationship, Drug
- Organ Size/drug effects
- Liver Neoplasms, Experimental/chemically induced
- Liver Neoplasms, Experimental/pathology
- Liver Neoplasms, Experimental/metabolism
- DNA Replication/drug effects
- Cytochrome P-450 Enzyme System/metabolism
- Cytochrome P-450 Enzyme System/genetics
- Microsomes, Liver/drug effects
- Microsomes, Liver/metabolism
- Liver Neoplasms/chemically induced
- Liver Neoplasms/metabolism
- Liver Neoplasms/pathology
Collapse
Affiliation(s)
- Manuela Goettel
- BASF SE, Global Toxicology Agricultural Solutions, Speyerer Strasse 2, Limburgerhof 67117, Germany.
| | - Christoph Werner
- BASF SE, Global Toxicology Agricultural Solutions, Speyerer Strasse 2, Limburgerhof 67117, Germany
| | - Naveed Honarvar
- BASF SE, Experimental Toxicology and Ecology, Carl-Bosch-Strasse 38, Ludwigshafen am Rhein 67056, Germany
| | - Sibylle Gröters
- BASF SE, Experimental Toxicology and Ecology, Carl-Bosch-Strasse 38, Ludwigshafen am Rhein 67056, Germany
| | - Ivana Fegert
- BASF SE, Global Toxicology Agricultural Solutions, Speyerer Strasse 2, Limburgerhof 67117, Germany
| | - Corinne Haines
- Concept Life Sciences Ltd., 2, James Lindsay Place, Dundee Technopole, Dundee DD1 5JJ, United Kingdom
| | - Lynsey R Chatham
- Concept Life Sciences Ltd., 2, James Lindsay Place, Dundee Technopole, Dundee DD1 5JJ, United Kingdom
| | - Audrey Vardy
- Concept Life Sciences Ltd., 2, James Lindsay Place, Dundee Technopole, Dundee DD1 5JJ, United Kingdom
| | - Brian G Lake
- School of Biosciences and Medicine, Faculty of Health and Medical Sciences, University of Surrey, Guildford, Surrey GU2 7XH, UK
| |
Collapse
|
2
|
Goettel M, Fegert I, Honarvar N, Vardy A, Haines C, Chatham LR, Lake BG. Comparative studies on the effects of sodium phenobarbital and two other constitutive androstane receptor (CAR) activators on induction of cytochrome P450 enzymes and replicative DNA synthesis in cultured hepatocytes from wild type and CAR knockout rats. Toxicology 2020; 433-434:152394. [PMID: 32027962 DOI: 10.1016/j.tox.2020.152394] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2019] [Revised: 01/31/2020] [Accepted: 02/01/2020] [Indexed: 10/25/2022]
Abstract
Nongenotoxic chemicals can produce liver tumours in rats and mice by a mitogenic mode of action involving activation of the constitutive androstane receptor (CAR). The aim of this study was to evaluate the usefulness of cultured hepatocytes from normal (wild type; WT) and CAR knockout (KO) rats to screen compounds as potential activators of rat CAR and to validate this test system. Cultured hepatocytes from male Sprague-Dawley WT and CAR KO rats were treated with either 100 and 1000 μM sodium phenobarbital (NaPB), 3-100 μM fluquinconazole (FQZ), or 3-300 μM 3-(difluoromethyl)-1-methyl-N-(3´,4´,6-trifluoro[1,1´-biphenyl]-2-yl)-1H-pyrazole-4-carboxamide (TI1) for 96 h. Induction of cytochrome P450 (CYP) enzymes was monitored by measurement of 7-pentoxyresorufin O-depentylase (PROD), 7-benzyloxyresorufin O-debenzylase (BROD) and 7-benzyloxyquinoline O-debenzylase (BQ) activities. Hepatocytes undergoing replicative DNA synthesis (RDS) were labelled by adding 10 μM 5-bromo-2´-deoxyuridine to the culture medium for determination of the hepatocyte labelling index. The treatment of WT, but not of CAR KO, rat hepatocytes with NaPB, FQZ and TI1 increased hepatocyte RDS and induced CYP2B-dependent PROD activity. In contrast, all three compounds increased CYP2B/3A-dependent BROD and CYP3A-dependent BQ activities in both WT and CAR KO rat hepatocytes. Hepatocyte RDS was increased in both WT and CAR KO rat hepatocytes by treatment with 25 ng/ml epidermal growth factor as a positive control. Overall, these results demonstrate that the effects of three CAR activators on RDS and CYP2B enzyme induction are abolished in cultured CAR KO rat hepatocytes. As demonstrated by this validation study, the CAR KO hepatocyte model is a useful in vitro mechanistic tool for the rapid screening of chemicals as potential activators of rat CAR.
Collapse
Affiliation(s)
- Manuela Goettel
- BASF SE, Carl-Bosch-Strasse 38, 67056 Ludwigshafen, Germany.
| | - Ivana Fegert
- BASF SE, Carl-Bosch-Strasse 38, 67056 Ludwigshafen, Germany
| | | | - Audrey Vardy
- Concept Life Sciences (formerly CXR Biosciences Ltd.), 2, James Lindsay Place, Dundee Technopole, Dundee DD1 5JJ, United Kingdom
| | - Corinne Haines
- Concept Life Sciences (formerly CXR Biosciences Ltd.), 2, James Lindsay Place, Dundee Technopole, Dundee DD1 5JJ, United Kingdom
| | - Lynsey R Chatham
- Concept Life Sciences (formerly CXR Biosciences Ltd.), 2, James Lindsay Place, Dundee Technopole, Dundee DD1 5JJ, United Kingdom
| | - Brian G Lake
- Concept Life Sciences (formerly CXR Biosciences Ltd.), 2, James Lindsay Place, Dundee Technopole, Dundee DD1 5JJ, United Kingdom; Faculty of Health and Medical Sciences, University of Surrey, Guildford, Surrey, GU2 7XH, UK
| |
Collapse
|
3
|
Hu J, Tian J, Zhang F, Wang H, Yin J. Pxr- and Nrf2- mediated induction of ABC transporters by heavy metal ions in zebrafish embryos. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2019; 255:113329. [PMID: 31600704 DOI: 10.1016/j.envpol.2019.113329] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Revised: 08/27/2019] [Accepted: 09/29/2019] [Indexed: 05/13/2023]
Abstract
Transcription factors including pregnane X receptor (Pxr) and nuclear factor-erythroid 2-related factor-2 (Nrf2) are important modulators of Adenosine triphosphate-binding cassette (ABC) transporters in mammalian cells. However, whether such modulation is conserved in zebrafish embryos remains largely unknown. In this manuscript, pxr- and nrf2-deficient models were constructed with CRISPR/Cas9 system, to evaluate the individual function of Pxr and Nrf2 in the regulation of ABC transporters and detoxification of heavy metal ions like Cd2+ and Ag+. As a result, both Cd2+ and Ag+ conferred extensive interactions with ABC transporters in wild type (WT) embryos: their accumulation and toxicity were affected by the activity of ABC transporters, and they significantly induced the mRNA expressions of ABC transporters. These induction effects were reduced by the mutation of pxr and nrf2, but elevations in the basal expression of ABC transporters compensated for the loss of their inducibility. This could be an explanation for remaining transporter function in both mutant models as well as the unaltered toxicity of metal ions in pxr-deficient embryos. However, mutation of nrf2 disrupted the production of glutathione (GSH), resulting in the enhanced toxicity of Cd2+/Ag+ in zebrafish embryos. In addition, elevated expressions of other transcription factors like aryl hydrocarbon receptor (ahr) 1b, peroxisome proliferator-activated receptor (ppar)-β, and nrf2 were found in pxr-deficient models without any treatment, while enhanced induction of ahr1b, ppar-β and pxr could only be seen in nrf2-deficient embryos after the treatment of metal ions, indicating different compensation phenomena for the absence of transcription factors. After all, pxr-deficient and nrf2-deficient zebrafish embryos are useful tools in the functional investigation of Pxr and Nrf2 in the early life stages of aquatic organisms. However, the compensatory mechanisms should be taken into consideration when interpreting the results and need in-depth investigations.
Collapse
Affiliation(s)
- Jia Hu
- School of Biology & Basic Medical Sciences, Medical College, Soochow University, Suzhou, Jiangsu 215123, PR China
| | - Jingjing Tian
- CAS Key Lab of Bio-Medical Diagnostics, Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences, Suzhou, Jiangsu 215163, PR China; Academy for Engineering & Technology, Fudan University, Shanghai 200433, PR China
| | - Feng Zhang
- Suzhou GCL Photovoltaic Technology Co., Ltd, Suzhou, Jiangsu 215163, PR China
| | - Han Wang
- School of Biology & Basic Medical Sciences, Medical College, Soochow University, Suzhou, Jiangsu 215123, PR China
| | - Jian Yin
- CAS Key Lab of Bio-Medical Diagnostics, Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences, Suzhou, Jiangsu 215163, PR China; Shandong Guo Ke Medical Technology Development Co., Ltd, PR China.
| |
Collapse
|
4
|
Wiemann C, Goettel M, Vardy A, Elcombe BM, Elcombe CR, Chatham LR, Wang H, Li L, Buesen R, Honarvar N, Treumann S, Marxfeld H, Groeters S, Lake BG. Metazachlor: Mode of action analysis for rat liver tumour formation and human relevance. Toxicology 2019; 426:152282. [DOI: 10.1016/j.tox.2019.152282] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2019] [Revised: 08/20/2019] [Accepted: 08/25/2019] [Indexed: 12/19/2022]
|
5
|
Lake BG. Human relevance of rodent liver tumour formation by constitutive androstane receptor (CAR) activators. Toxicol Res (Camb) 2018; 7:697-717. [PMID: 30090615 PMCID: PMC6060665 DOI: 10.1039/c8tx00008e] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2018] [Accepted: 03/09/2018] [Indexed: 01/01/2023] Open
Abstract
A large number of nongenotoxic chemicals have been shown to increase the incidence of liver tumours in rats and/or mice by a mode of action (MOA) involving activation of the constitutive androstane receptor (CAR). Studies with the model CAR activator phenobarbital (PB) and its sodium salt (sodium phenobarbital; NaPB) have demonstrated that the key and associative events for rat and mouse liver tumour formation include CAR activation, increased hepatocyte replicative DNA synthesis (RDS), induction of cytochrome P450 CYP2B subfamily enzymes, liver hypertrophy, increased altered hepatic foci and hepatocellular adenomas/carcinomas. The key species difference between the rat and mouse compared to humans, is that human hepatocytes are refractory to the mitogenic effects of PB/NaPB and other CAR activators. While PB/NaPB and other CAR activators stimulate RDS in rat and mouse hepatocytes in both in vitro and in vivo studies, such compounds do not stimulate RDS in cultured human hepatocytes and in in vivo studies performed in chimeric mice with humanised livers. In terms of species differences in RDS, unlike the rat and mouse, humans are similar to other species such as the Syrian hamster and guinea pig in being nonresponsive to the mitogenic effects of CAR activators. Overall, the MOA for rat and mouse liver tumour formation by PB/NaPB and other CAR activators is considered qualitatively not plausible for humans. This conclusion is supported by data from a number of epidemiological studies, which demonstrate that chronic treatment with PB does not increase the incidence of liver cancer in humans.
Collapse
Affiliation(s)
- Brian G Lake
- Centre for Toxicology , Faculty of Health and Medical Sciences , University of Surrey , Guildford , Surrey GU2 7XH , UK .
| |
Collapse
|
6
|
Haines C, Chatham LR, Vardy A, Elcombe CR, Foster JR, Lake BG. Comparison of the hepatic and thyroid gland effects of sodium phenobarbital in wild type and constitutive androstane receptor (CAR) knockout rats and pregnenolone-16α-carbonitrile in wild type and pregnane X receptor (PXR) knockout rats. Toxicology 2018; 400-401:20-27. [DOI: 10.1016/j.tox.2018.03.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2017] [Revised: 03/05/2018] [Accepted: 03/06/2018] [Indexed: 12/21/2022]
|
7
|
Haines C, Chatham LR, Vardy A, Elcombe CR, Foster JR, Lake BG. Comparison of the hepatic and thyroid gland effects of sodium phenobarbital and pregnenolone-16α-carbonitrile in wild-type and constitutive androstane receptor (CAR)/pregnane X receptor (PXR) knockout rats. Xenobiotica 2018; 49:227-238. [DOI: 10.1080/00498254.2018.1437300] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Corinne Haines
- Concept Life Sciences (formerly CXR Biosciences Ltd.), Dundee, UK
| | | | - Audrey Vardy
- Concept Life Sciences (formerly CXR Biosciences Ltd.), Dundee, UK
| | | | | | - Brian G. Lake
- Concept Life Sciences (formerly CXR Biosciences Ltd.), Dundee, UK
- Centre for Toxicology, Faculty of Health and Medical Sciences, University of Surrey, Guildford, UK
| |
Collapse
|