Toxicity testing of chemical substances is increasingly based on mechanisms of toxicity that are structured in Adverse Outcome Pathways (AOPs). This paradigm shift in toxicity testing requires the employment of whole organism models, both healthy and diseased. The zebrafish embryo provides an excellent model for this purpose.
Short video about RIVM's activities researching zebrafish for toxicity testing applications
video
The zebrafish in toxicity testing
Speaker: Dr. Harm Heusinkveld, neurotoxicologist
DR. HARM HEUSINKVELD: At RIVM, we use the zebrafish embryo as a whole organism model to test the effects of substances on various outcomes and diseases.
TEXT: The zebrafish in toxicity testing
VOICE OVER: Toxicity testing of chemical substances is increasingly based on mechanisms of toxicity that are structured in adverse outcome pathways, describing the chain of events leading to toxicity or disease.
DR. HARM HEUSINKVELD: To study the effect of chemical exposure on an adverse outcome in vitro and in silico assays are used or being developed to represent the different key events along the AOP. With knowledge on the relationships between the individual key events, the integration of the data from these assays will predict whether exposure in the end will lead to an adverse outcome. For certain diseases it is known that toxicity relies on the interaction between different organs or cell types. Prediction of such toxicity requires the use of more complex assays and models to cover the interplay.
VOICE OVER: To understand what exposure to a certain toxicant means for humans, whole organisms are needed in addition to simple in vitro models. There are only few models available for this purpose before entering the realm of in vivo rodent studies. And the zebrafish embryo is one of them.
DR. HARM HEUSINKVELD: Reasons for the increased recognition of the zebrafish as a useful model for toxicological research are related to its fast development, transparent body and above all: great resemblance of human biology. The zebrafish only takes five days from a fertilised egg to fully developed organism. This timeframe allows for the study of many developmental processes, using multiple readouts such as morphological scoring and imaging techniques to monitor functional endpoints in living organisms.
VOICE OVER: At RIVM, the zebrafish embryo model is used as whole organism model for testing the effect of chemical substances on several adverse outcomes and diseases.
DR. HARM HEUSINKVELD: We use it, for example, to study the effect of chemicals on the nervous system and its development using motor activity and behaviour as an endpoint. The same endpoint is also used to study the addictiveness of substances, such as drugs. Other techniques that are applied are imaging techniques and transcriptomics, to study effects on skeletal development, liver disease and to explore the assessment strategies for chemical mixtures. As such, zebrafish are used as a higher tier complex model in AOP-based testing strategies. When applied correctly the combination of in vitro and in silico techniques with zebrafish embryos shows great potential to reduce the need for toxicity testing in higher tier animals such as rodents.
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A whole organism to bridge the gap
To study the effect of chemical exposure on an adverse outcome, in vitro and in silico test systems can be used to represent the different key events along an AOP. For certain outcomes it is known that toxicity relies on the interaction between different organs and cell types. Prediction of such toxicity therefore requires the use of more complex models. There are only a few models available for covering this interplay, the zebrafish being one of them.
Zebrafish have a number of advantages, such as their fast development, transparent body and resemblance to human biology. These advantages allow for studying many developmental processes using multiple readouts, such as morphological scoring and imaging techniques to monitor functional endpoints in living organisms.
Developmental toxicity and addiction
At RIVM, the zebrafish embryo model is used for testing, for example, the effect of chemicals on the nervous system and its development using motor activity and behaviour as endpoint. This endpoint is also used to study the addictiveness of substances such as drugs. Other techniques include imaging techniques and transcriptomics to study effects on skeletal development and liver disease, and explore assessment strategies for chemical mixtures. The combination of in vitro and in silico techniques with zebrafish embryos shows great potential to reduce the need for toxicity testing in higher-tier animals such as rodents.
Projects
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Key publications
| Dose Addition in the Induction of Craniofacial Malformations in Zebrafish Embryos Exposed to a Complex Mixture of Food-Relevant Chemicals with Dissimilar Modes of Action | van der Ven, L.T.M., van Ommeren, P., Zwart, E.P., Gremmer, E.R., Hodemaekers, H.M., Heusinkveld, H.J., van Klaveren, J.D., Rorije, E. | Environmental Health Perspectives 2023; 130(4):047003-1 |
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Exploring Neurobehaviour in Zebrafish Embryos as a Screening Model for Addictiveness of Substances |
Havermans, A., Zwart, E.P., Cremers, H.W.J.M., van Schijndel, M.D.M., Constant, R.S., Meskovic, M., Worutowicz, L.X., Pennings, J.L.A., Talhout, R., van der Ven, L.T.M., Heusinkveld, H.J. | Toxics 2021: 9(10):250 |
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Developmental Neurotoxicity of Environmentally Relevant Pharmaceuticals and Mixtures Thereof in a Zebrafish Embryo Behavioural Test |
Atzei, A., Jense, I., Zwart, E.P., Legradi, J., Venhuis, B.J., van der Ven, L.T.M., Heusinkveld, H.J., Hessel, E.V.S. | International Journal of Environmental Research and Public Health 2021; 18(13):6717 |
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Distinguishing mode of action of compounds inducing craniofacial malformations in zebrafish embryos to support dose-response modeling in combined exposures |
Heusinkveld, H.J., Schoonen, W.G., Hodemaekers, H.M., Nugraha, A., Sirks, J.J., Veenma, V., Sujan, C., Pennings, J.L.A., Wackers, P.F., Palazzolo, L., Eberini, I., Rorije, E., van der Ven, L.T.M. | Reproductive Toxicology 2020; 96:114-27 |
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The effects of aliphatic alcohols and related acid metabolites in zebrafish embryos - correlations with rat developmental toxicity and with effects in advanced life stages in fish |
van der Ven, L.T.M., Schoonen, W.G., Groot, R.M., den Ouden, F., Heusinkveld, H.J., Zwart, E.P., Hodemaekers, H.M., Rorije, E., Knecht, J. de | Toxicology and Applied Pharmacology 2020; 407:115249 |