PARC: Partnership for the Assessment of Risks from Chemicals

Institutionen
  • AG Leist (In vitro Toxikologie und Biomedizin)
Publikationen
  Leist, Marcel; Buettner, Andrea; Diel, Patrick; Eisenbrand, Gerhard; Epe, Bernd; Först, Petra; Grune, Tilman; Haller, Dirk; Heinz, Volker; Hengstler, Jan G. (2024): Controversy on health-based guidance values for bisphenol A : the need of criteria for studies that serve as a basis for risk assessment Archives of Toxicology. Springer. 2024, 98(7), S. 1967-1973. ISSN 0340-5761. eISSN 1432-0738. Verfügbar unter: doi: 10.1007/s00204-024-03778-3

Controversy on health-based guidance values for bisphenol A : the need of criteria for studies that serve as a basis for risk assessment

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Since 2006, the responsible regulatory bodies have proposed five health-based guidance values (HBGV) for bisphenol A (BPA) that differ by a factor of 250,000. This range of HBGVs covers a considerable part of the range from highly toxic to relatively non-toxic substances. As such heterogeneity of regulatory opinions is a challenge not only for scientific risk assessment but also for all stakeholders, the Senate Commission on Food Safety (SKLM) of the German Research Foundation (DFG) analyzed the reasons for the current discrepancy and used this example to suggest improvements for the process of HBGV recommendations. A key aspect for deriving a HBGV is the selection of appropriate studies that allow the identification of a point of departure (PoD) for risk assessment. In the case of BPA, the HBGV derived in the 2023 EFSA assessment was based on a study that reported an increase of Th17 cells in mice with a benchmark dose lower bound (BMDL 40 ) of 0.53 µg/kg bw/day. However, this study does not comply with several criteria that are important for scientific risk assessment: (1) the selected end-point, Th17 cell frequency in the spleen of mice, is insufficiently understood with respect to health outcomes. (2) It is unclear, by which mechanism BPA may cause an increase in Th17 cell frequency. (3) It is unknown, if an increase of Th17 cell frequency in rodents is comparably observed in humans. (4) Toxicokinetics were not addressed. (5) Neither the raw data nor the experimental protocols are available. A further particularly important criterion (6) is independent data confirmation which is not available in the present case. Previous studies using other readouts did not observe immune-related adverse effects such as inflammation, even at doses orders of magnitude higher than in the Th17 cell-based study. The SKLM not only provides here key criteria for the use of such studies, but also suggests that the use of such a “checklist” requires a careful and comprehensive scientific judgement of each item. It is concluded that the Th17 cell-based study data do not represent an adequate basis for risk assessment of BPA.

Forschungszusammenhang (Projekte)

    Renner, Nadine; Schöb, Franziska; Pape, Regina; Suciu, Ilinca; Spreng, Anna-Sophie; Ückert, Anna-Katharina; Cöllen, Eike; Bovio, Federica; Leist, Marcel; Schildknecht, Stefan (2024): Modeling ferroptosis in human dopaminergic neurons : Pitfalls and opportunities for neurodegeneration research Redox Biology. Elsevier. 2024, 73, 103165. eISSN 2213-2317. Verfügbar unter: doi: 10.1016/j.redox.2024.103165

Modeling ferroptosis in human dopaminergic neurons : Pitfalls and opportunities for neurodegeneration research

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The activation of ferroptosis is being pursued in cancer research as a strategy to target apoptosis-resistant cells. By contrast, in various diseases that affect the cardiovascular system, kidneys, liver, and central and peripheral nervous systems, attention is directed toward interventions that prevent ferroptotic cell death. Mechanistic insights into both research areas stem largely from studies using cellular in vitro models. However, intervention strategies that show promise in cellular test systems often fail in clinical trials, which raises concerns regarding the predictive validity of the utilized in vitro models.



In this study, the human LUHMES cell line, which serves as a model for human dopaminergic neurons, was used to characterize factors influencing the activation of ferroptosis. Erastin and RSL-3 induced cell death that was distinct from apoptosis. Parameters such as the differentiation state of LUHMES cells, cell density, and the number and timing of medium changes were identified as determinants of sensitivity to ferroptosis activation. In differentiated LUHMES cells, interventions at mechanistically divergent sites (iron chelation, coenzyme Q10, peroxidase mimics, or inhibition of 12/15-lipoxygenase) provide almost complete protection from ferroptosis. LUHMES cells allowed the experimental modulation of intracellular iron concentrations and demonstrated a correlation between intracellular iron levels, the rate of lipid peroxidation, as well as the sensitivity of the cells to ferroptotic cell death.



These findings underscore the importance of understanding the various factors that influence ferroptosis activation and highlight the need for well-characterized in vitro models to enhance the reliability and predictive value of observations in ferroptosis research, particularly when translating findings into in vivo contexts.

Forschungszusammenhang (Projekte)

  Pamies, David; Ekert, Jason; Zurich, Marie-Gabrielle; Frey, Olivier; Werner, Sophie; Piergiovanni, Monica; Freedman, Benjamin S.; Keong Teo, Adrian Kee; Hartung, Thomas; Leist, Marcel (2024): Recommendations on fit-for-purpose criteria to establish quality management for microphysiological systems and for monitoring their reproducibility Stem Cell Reports. Elsevier. 2024, 19(5), pp. 604-617. eISSN 2213-6711. Available under: doi: 10.1016/j.stemcr.2024.03.009

Recommendations on fit-for-purpose criteria to establish quality management for microphysiological systems and for monitoring their reproducibility

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Cell culture technology has evolved, moving from single-cell and monolayer methods to 3D models like reaggregates, spheroids, and organoids, improved with bioengineering like microfabrication and bioprinting. These advancements, termed microphysiological systems (MPSs), closely replicate tissue environments and human physiology, enhancing research and biomedical uses. However, MPS complexity introduces standardization challenges, impacting reproducibility and trust. We offer guidelines for quality management and control criteria specific to MPSs, facilitating reliable outcomes without stifling innovation. Our fit-for-purpose recommendations provide actionable advice for achieving consistent MPS performance.

Forschungszusammenhang (Projekte)

    Cöllen, Eike; Tanaskov, Yaroslav; Holzer, Anna-Katharina; Dipalo, Michele; Schäfer, Jasmin; Kraushaar, Udo; Leist, Marcel (2024): Elements and development processes for test methods in toxicology and human health-relevant life science research Alternatives to Animal Experimentation : ALTEX. Springer. 2024, 41(1), pp. 142-148. ISSN 1868-596X. eISSN 1868-8551. Available under: doi: 10.14573/altex.2401041

Elements and development processes for test methods in toxicology and human health-relevant life science research

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Many laboratory procedures generate data on properties of chemicals, but they cannot be equated with toxicological “test methods”. This apparent discrepancy is not limited to in vitro testing, using animal-free new approach methods (NAM), but also applies to animal-based testing approaches. Here, we give a brief overview of the differences between data generation and the setup or use of a complete test method. While there is excellent literature available on this topic for specialists (GIVIMP guidance; ToxTemp overview), a brief overview and easily-accessible entry point may be useful for a broader community. We provide a single figure to summarize all test method elements and processes required in the development (setup and adaptation) of a test method. The exposure scheme, the endpoint, and the test system are briefly outlined as fundamental elements of any test method. A rationale is provided, why they are not sufficient. We then explain the importance and role of purpose definition (including some information on what is modelled) and the prediction model, aka data interpretation procedure, which depends on the purpose definition, as further essential elements. This connection exemplifies that all fundamental elements are interdependent, and none can be omitted. Finally, discussion is provided on validation as a measure to provide confidence in the reliability, performance, and relevance of a test method. In this sense, validation may be considered a sixth fundamental element for practical use of test methods.

Forschungszusammenhang (Projekte)

  Smirnova, Lena; Hogberg, Helena T.; Leist, Marcel; Hartung, Thomas (2024): Revolutionizing developmental neurotoxicity testing : a journey from animal models to advanced in vitro systems Alternatives to Animal Experimentation : ALTEX. ALTEX Edition. 2024, 41(2), pp. 152-178. ISSN 1868-596X. Available under: doi: 10.14573/altex.2403281

Revolutionizing developmental neurotoxicity testing : a journey from animal models to advanced in vitro systems

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Developmental neurotoxicity (DNT) testing has seen enormous progress over the last two decades. Preceding even the publication of the animal-based OECD test guideline for DNT testing in 2007, a series of non-animal technology workshops and conferences that started in 2005 has shaped a community that has delivered a comprehensive battery of in vitro test methods (DNT IVB). Its data interpretation is now covered by a very recent OECD guidance (No. 377). Here, we overview the progress in the field, focusing on the evolution of testing strategies, the role of emerging technol­ogies, and the impact of OECD test guidelines on DNT testing. In particular, this is an example of the targeted development of an animal-free testing approach for one of the most complex hazards of chemicals to human health. These developments started literally from a blank slate, with no proposed alternative methods available. Over two decades, cutting-edge science enabled the design of a testing approach that spares animals and enables throughput to address this challenging hazard. While it is evident that the field needs guidance and regulation, the massive economic impact of decreased human cognitive capacity caused by chemical exposure should be prioritized more highly. Beyond this, the claim to fame of DNT in vitro testing is the enormous scientific progress it has brought for understanding the human brain, its development, and how it can be perturbed.

Forschungszusammenhang (Projekte)

    Ückert, Anna-Katharina; Rütschlin, Sina; Gutbier, Simon; Hauer, Isa; Holzer, Anna-Katharina; Meyburg, Birthe; Mix, Ann-Kathrin; Hauck, Christof R.; Böttcher, Thomas; Leist, Marcel (2023): Identification of the bacterial metabolite aerugine as potential trigger of human dopaminergic neurodegeneration Environment International. Elsevier. 2023, 180, 108229. ISSN 0160-4120. eISSN 1873-6750. Available under: doi: 10.1016/j.envint.2023.108229

Identification of the bacterial metabolite aerugine as potential trigger of human dopaminergic neurodegeneration

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The causes of nigrostriatal cell death in idiopathic Parkinson’s disease are unknown, but exposure to toxic chemicals may play some role. We followed up here on suggestions that bacterial secondary metabolites might be selectively cytotoxic to dopaminergic neurons. Extracts from Streptomyces venezuelae were found to kill human dopaminergic neurons (LUHMES cells). Utilizing this model system as a bioassay, we identified a bacterial metabolite known as aerugine (C10H11NO2S; 2-[4-(hydroxymethyl)-4,5-dihydro-1,3-thiazol-2-yl]phenol) and confirmed this finding by chemical re-synthesis. This 2-hydroxyphenyl-thiazoline compound was previously shown to be a product of a wide-spread biosynthetic cluster also found in the human microbiome and in several pathogens. Aerugine triggered half-maximal dopaminergic neurotoxicity at 3-4 µM. It was less toxic for other neurons (10-20 µM), and non-toxic (at <100 µM) for common human cell lines. Neurotoxicity was completely prevented by several iron chelators, by distinct anti-oxidants and by a caspase inhibitor. In the Caenorhabditis elegans model organism, general survival was not affected by aerugine concentrations up to 100 µM. When transgenic worms, expressing green fluorescent protein only in their dopamine neurons, were exposed to aerugine, specific neurodegeneration was observed. The toxicant also exerted functional dopaminergic toxicity in nematodes as determined by the “basal slowing response” assay. Thus, our research has unveiled a bacterial metabolite with a remarkably selective toxicity toward human dopaminergic neurons in vitro and for the dopaminergic nervous system of Caenorhabditis elegans in vivo. These findings suggest that microbe-derived environmental chemicals should be further investigated for their role in the pathogenesis of Parkinson's disease.

Forschungszusammenhang (Projekte)

    Holzer, Anna-Katharina; Dreser, Nadine; Pallocca, Giorgia; Mangerich, Aswin; Stacey, Glyn; Dipalo, Michael; Rovida, Costanza; Wirtz, Petra H.; Hartung, Thomas; Leist, Marcel (2023): Acceptance criteria for new approach methods in toxicology and human health-relevant life science research – part I Alternatives to Animal Experimentation : ALTEX. Springer Spektrum. 2023, 40(4), pp. 706-712. eISSN 1868-596X. Available under: doi: 10.14573/altex.2310021

Acceptance criteria for new approach methods in toxicology and human health-relevant life science research – part I

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Every test procedure, scientific and non-scientific, has inherent uncertainties, even when performed according to a standard operating procedure (SOP). In addition, it is prone to errors, defects, and mistakes introduced by operators, laboratory equipment, or materials used. Adherence to an SOP and comprehensive validation of the test method cannot guarantee that each test run produces data within the acceptable range of variability and with the precision and accuracy determined during the method validation. We illustrate here (part I) why controlling the validity of each test run is an important element of experimental design. The definition and application of acceptance criteria (AC) for the validity of test runs is important for the setup and use of test methods, particularly for the use of new approach methods (NAM) in toxicity testing. AC can be used for decision rules on how to handle data, e.g., to accept the data for further use (AC fulfilled) or to reject the data (AC not fulfilled). The adherence to AC has important requirements and consequences that may seem surprising at first sight: (i) AC depend on a test method’s objectives, e.g., on the types/concentrations of chemicals tested, the regulatory context, the desired throughput; (ii) AC are applied and documented at each test run, while validation of a method (including the definition of AC) is only performed once; (iii) if AC are altered, then the set of data produced by a method can change. AC, if missing, are the blind spot of quality assurance: Test results may not be reliable and comparable. The establishment and uses of AC will be further detailed in part II of this series.

Forschungszusammenhang (Projekte)

Mittelgeber
Name Finanzierungstyp Kategorie Kennziffer
Europäische Union Drittmittel Forschungsförderprogramm 636/22
Weitere Informationen
Laufzeit: 01.05.2022 – 30.04.2028