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van Tongeren TC, Carmichael PL, Rietjens IM, Li H. Next Generation Risk Assessment of the Anti-Androgen Flutamide Including the Contribution of Its Active Metabolite Hydroxyflutamide. FRONTIERS IN TOXICOLOGY 2022; 4:881235. [PMID: 35722059 PMCID: PMC9201820 DOI: 10.3389/ftox.2022.881235] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2022] [Accepted: 04/29/2022] [Indexed: 12/03/2022] Open
Abstract
In next generation risk assessment (NGRA), non-animal approaches are used to quantify the chemical concentrations required to trigger bioactivity responses, in order to assure safe levels of human exposure. A limitation of many in vitro bioactivity assays, which are used in an NGRA context as new approach methodologies (NAMs), is that toxicokinetics, including biotransformation, are not adequately captured. The present study aimed to include, as a proof of principle, the bioactivity of the metabolite hydroxyflutamide (HF) in an NGRA approach to evaluate the safety of the anti-androgen flutamide (FLU), using the AR-CALUX assay to derive the NAM point of departure (PoD). The NGRA approach applied also included PBK modelling-facilitated quantitative in vitro to in vivo extrapolation (QIVIVE). The PBK model describing FLU and HF kinetics in humans was developed using GastroPlus™ and validated against human pharmacokinetic data. PBK model-facilitated QIVIVE was performed to translate the in vitro AR-CALUX derived concentration-response data to a corresponding in vivo dose-response curve for the anti-androgenicity of FLU, excluding and including the activity of HF (-HF and +HF, respectively). The in vivo benchmark dose 5% lower confidence limits (BMDL05) derived from the predicted in vivo dose-response curves for FLU, revealed a 440-fold lower BMDL05 when taking the bioactivity of HF into account. Subsequent comparison of the predicted BMDL05 values to the human therapeutic doses and historical animal derived PoDs, revealed that PBK modelling-facilitated QIVIVE that includes the bioactivity of the active metabolite is protective and provides a more appropriate PoD to assure human safety via NGRA, whereas excluding this would potentially result in an underestimation of the risk of FLU exposure in humans.
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Affiliation(s)
- Tessa C.A. van Tongeren
- Division of Toxicology, Wageningen University and Research, Wageningen, Netherlands
- *Correspondence: Tessa C.A. van Tongeren,
| | - Paul L. Carmichael
- Unilever Safety and Environmental Assurance Centre, Sharnbrook, United Kingdom
| | | | - Hequn Li
- Unilever Safety and Environmental Assurance Centre, Sharnbrook, United Kingdom
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Collet B, Desalegn AA, Swart K, Naderman M, Iszatt N, Stigum H, Jensen TK, Brouwer A, Eggesbø M, van der Burg B. Anti-androgenic compounds in breast milk and cryptorchidism among Norwegian boys in the HUMIS birth cohort. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 803:149746. [PMID: 34525773 DOI: 10.1016/j.scitotenv.2021.149746] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2021] [Revised: 07/23/2021] [Accepted: 08/14/2021] [Indexed: 06/13/2023]
Abstract
The prevalence of cryptorchidism has increased over the past decades, yet its origins remain poorly understood. Testis descent is dependent on androgens and likely affected by endocrine disrupting compounds (EDCs), targeting the androgen receptor (AR). We investigated the association between anti-androgenic activity, not derived from natural hormones, in maternal breast milk and impaired testis descent among boys. We performed a case-control study based on 199 breast milk samples from 94 mothers of cryptorchid boys and 105 random non-cryptorchid boys participating in the Norwegian HUMIS (Human Milk Study) cohort. For each participant, apolar, and polar fractions were extracted, and combined to reconstitute a mixture. Anti-androgenic activity was measured in all three fractions using the human cell-based in vitro anti-AR CALUX® assay and expressed in μg of flutamide equivalent, a well-known antiandrogen. Results from fraction analyses were compared among boys with cryptorchidism and controls using multiple logistic regression, controlling for appropriate confounders identified using a directed acyclic graph. Children's daily exposure to anti-androgenic EDCs through breastfeeding was estimated to 78 μg flutamide eq./kg of body weigh/day. The activity was higher in the polar fraction (1.48 ± 1.37 μg flutamide eq./g of milk) mainly representing non-persistent chemicals, in contrast to other fractions. However, the activity in the polar extracts was decreased when in mixtures with the apolar fraction, indicating synergistic interactions. No significant difference in the activity was observed according to cryptorchid status for polar, apolar or mixed breast milk fractions. The study showed anti-androgenic activity in nearly all human milk samples, and at levels higher than the advisory threshold. However, no significant association was observed between cryptorchidism and antiandrogenic activity measured in either polar, apolar, or mixture fractions derived from breast milk.
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Affiliation(s)
- Bérénice Collet
- Vrije Universiteit Amsterdam, Department of Ecological Science, 1081HV Amsterdam, the Netherlands; BioDetection Systems BV, Science Park 406, 1098XH Amsterdam, the Netherlands
| | - Anteneh A Desalegn
- Norwegian Institute of Public Health, P.O. Box 4404, Nydalen, N-0403 Oslo, Norway; Faculty of Medicine, University of Oslo, Oslo, Norway.
| | - Kees Swart
- BioDetection Systems BV, Science Park 406, 1098XH Amsterdam, the Netherlands.
| | - Matthijs Naderman
- BioDetection Systems BV, Science Park 406, 1098XH Amsterdam, the Netherlands.
| | - Nina Iszatt
- Norwegian Institute of Public Health, P.O. Box 4404, Nydalen, N-0403 Oslo, Norway.
| | - Hein Stigum
- Department of Non-communicable Disease, Norwegian Institute of Public Health, PO Box 222, Skøyen, 0213 Oslo, Norway.
| | - Tina K Jensen
- Department of Clinical Pharmacology, Pharmacy and Environmental Medicine, University of Southern Denmark, 5000 Odense, Denmark.
| | - Abraham Brouwer
- Vrije Universiteit Amsterdam, Department of Ecological Science, 1081HV Amsterdam, the Netherlands; BioDetection Systems BV, Science Park 406, 1098XH Amsterdam, the Netherlands.
| | - Merete Eggesbø
- Norwegian Institute of Public Health, P.O. Box 4404, Nydalen, N-0403 Oslo, Norway.
| | - Bart van der Burg
- BioDetection Systems BV, Science Park 406, 1098XH Amsterdam, the Netherlands.
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Schreiber E, Garcia T, González N, Esplugas R, Sharma RP, Torrente M, Kumar V, Bovee T, Katsanou ES, Machera K, Domingo JL, Gómez M. Maternal exposure to mixtures of dienestrol, linuron and flutamide. Part I: Feminization effects on male rat offspring. Food Chem Toxicol 2020; 139:111256. [DOI: 10.1016/j.fct.2020.111256] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Revised: 03/06/2020] [Accepted: 03/08/2020] [Indexed: 12/23/2022]
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Sharma RP, Kumar V, Schuhmacher M, Kolodkin A, Westerhoff HV. Development and evaluation of a harmonized whole body physiologically based pharmacokinetic (PBPK) model for flutamide in rats and its extrapolation to humans. ENVIRONMENTAL RESEARCH 2020; 182:108948. [PMID: 31841869 DOI: 10.1016/j.envres.2019.108948] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Revised: 10/25/2019] [Accepted: 11/17/2019] [Indexed: 06/10/2023]
Abstract
By their definition, inadvertent exposure to endocrine disrupting compounds (EDCs) intervenes with the endocrine signalling system, even at low dose. On the one hand, some EDCs are used as important pharmaceutical drugs that one would not want to dismiss. On the other hand, these pharmaceutical drugs are having off-target effects and increasingly significant exposure to the general population with unwanted health implications. Flutamide, one of the top pharmaceutical products marketed all over the world for the treatment of prostate cancer, is also a pollutant. Its therapeutic action mainly depends on targeting the androgen receptors and inhibiting the androgen action that is essential for growth and survival of prostate tissue. Currently flutamide is of concern with respect to its categorization as an endocrine disruptor. In this work we have developed a physiologically based pharmacokinetic (PBPK) model of flutamide that could serve as a standard tool for its human risk assessment. First we built the model for rat (where many parameters have been measured). The rat PBPK model was extrapolated to human where the re-parameterization involved human-specific physiology, metabolic kinetics derived from in-vitro studies, and the partition coefficient same as the rat model. We have harmonized the model by integrating different sets of in-vitro, in-vivo and physiological data into a PBPK model. Then the model was used to simulate different exposure scenarios and the results were compared against the observed data. Both uncertainty and sensitivity analysis was done. Since this new whole-body PBPK model can predict flutamide concentrations not only in plasma but also in various organs, the model may have clinical applications in efficacy and safety assessment of flutamide. The model can also be used for reverse dosimetry in the context of interpreting the available biomonitoring data to estimate the degree to which the population is currently being exposed, and a tool for the pharmaceutical companies to validate the estimated Permitted Daily Exposure (PDE) for flutamide.
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Affiliation(s)
- Raju Prasad Sharma
- Environmental Engineering Laboratory, Departament d'Enginyeria Quimica, Universitat Rovira i Virgili, Av. Països Catalans 26, 43007, Tarragona, Catalonia, Spain; Molecular Cell Physiology, VU University Amsterdam, the Netherlands; Infrastructure for Systems Biology Europe (ISBE), Europe
| | - Vikas Kumar
- Environmental Engineering Laboratory, Departament d'Enginyeria Quimica, Universitat Rovira i Virgili, Av. Països Catalans 26, 43007, Tarragona, Catalonia, Spain.
| | - Marta Schuhmacher
- Environmental Engineering Laboratory, Departament d'Enginyeria Quimica, Universitat Rovira i Virgili, Av. Països Catalans 26, 43007, Tarragona, Catalonia, Spain
| | - Alexey Kolodkin
- Molecular Cell Physiology, VU University Amsterdam, the Netherlands; Infrastructure for Systems Biology Europe (ISBE), Europe; Luxembourg Centre for Systems Biomedicine, University of Luxembourg, Luxembourg
| | - Hans V Westerhoff
- Molecular Cell Physiology, VU University Amsterdam, the Netherlands; Infrastructure for Systems Biology Europe (ISBE), Europe; Synthetic Systems Biology and Nuclear Organization, Swammerdam Institute for Life Sciences, University of Amsterdam, the Netherlands; Manchester Centre for Integrative Systems Biology, UK.
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Singam ERA, Tachachartvanich P, Merrill MAL, Smith MT, Durkin KA. Structural Dynamics of Agonist and Antagonist Binding to the Androgen Receptor. J Phys Chem B 2019; 123:7657-7666. [PMID: 31431014 PMCID: PMC6742532 DOI: 10.1021/acs.jpcb.9b05654] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Androgen receptor (AR) is a steroid hormone nuclear receptor which upon binding its endogenous androgenic ligands (agonists), testosterone and dihydrotestosterone (DHT), alters gene transcription, producing a diverse range of biological effects. Antiandrogens, such as the pharmaceuticals bicalutamide and hydroxyflutamide, act as agonists in the absence of androgens and as antagonists in their presence or in high concentration. The atomic level mechanism of action by agonists and antagonists of AR is less well characterized. Therefore, in this study, multiple 1 μs molecular dynamics (MD), docking simulations, and perturbation-response analyses were performed to more fully explore the nature of interaction between agonist or antagonist and AR and the conformational changes induced in the AR upon interaction with different ligands. We characterized the mechanism of the ligand entry/exit and found that helix-12 and nearby structural motifs respond dynamically in that process. Modeling showed that the agonist and antagonist/agonist form a hydrogen bond with Thr877/Asn705 and that this interaction is absent for antagonists. Agonist binding to AR increases the mobility of residues at allosteric sites and coactivator binding sites, while antagonist binding decreases mobility at these important sites. A new site was also identified as a potential surface for allosteric binding. These results shed light on the effect of agonists and antagonists on the structure and dynamics of AR.
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Affiliation(s)
| | | | | | - Martyn T. Smith
- Division of Environmental Health Sciences, School of Public Health, University of California, Berkeley, CA, USA
| | - Kathleen A. Durkin
- Molecular Graphics and Computation Facility, College of Chemistry, University of California, Berkeley, CA, USA
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