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An inter-laboratory case study to determine the added value of the Zebrafish Light-dark transition test to predict developmental neurotoxicity (DNT5)
Citation:
Truong, L., J. Hsieh, L. Ellis, V. Schiavone, A. Alzualde, J. Legradi, D. Rubbini, C. Woodland, K. Ryan, B. Hill, S. Padilla, M. Behl, J. Terriente, A. Muriana, R. Tanguay, M. Sachana, A. Price, T. Shafer, AND E. Hessel. An inter-laboratory case study to determine the added value of the Zebrafish Light-dark transition test to predict developmental neurotoxicity (DNT5). 5th International Conference on Developmental Neurotoxicity Testing (DNT5), Konstanz, GERMANY, April 05 - 08, 2020.
Impact/Purpose:
The Organisation for Economic Co-operation and Develoment (OECD) building a guidance document containing a testing strategy to predict developmental neurotoxicity which, at present, consists of a combination of in vitro tests encompassing the critical processes in brain development. The aim of this study is to investigate the added value of the zebrafish developmental neurotoxicity testing behavioral model in this testing strategy.
Description:
Developmental neurotoxicity (DNT) entails one of the most complex areas in toxicology. Development of the central nervous system is a complex process involving many different events within strictly controlled time frames and therefore each event might create a different window of vulnerability to chemical exposure. OECD test guidelines for DNT (TG 426 and 443) are only occasionally carried out and the predictivity of these in vivo animal tests for human health effects may be limited. There is a high need for human-relevant in vitro models to assess DNT potential of chemicals. OECD is, therefore, building a guidance document containing a testing strategy to predict DNT. This testing strategy consists of a combination of in vitro tests encompassing the critical processes in brain development. The aim of this study is to investigate the added value of the zebrafish DNT behavioral model in this testing strategy. Up until 120 hours post-fertilization (hpf) zebrafish are not considered as experimental animals under the current European animal directive (2010/63/EU). The neurological system, the different neuron types, and neurotransmitters are well studied and well conserved among zebrafish and other species, including humans. The advantage of the zebrafish model in comparison to other in vitro assays is that whole brain development occurs within a relatively short period and effects of chemicals on brain development and behaviour can be tested. A group of experts agreed on a protocol for the light-dark transition test to predict DNT. At 120 hpf, zebrafish are tested in the light-dark transition test after chemical exposure from 6-120 hpf in a 96 well plate, 7 concentrations and 12 larvae per concentration. Twenty-eight known DNT compounds will be tested in five different laboratories. Data analysis will focus on locomotor activity (distance moved) of the larvae during the testing period. Benchmark dose analysis will be performed to determine the critical effect dose of each compound and for comparison of results across laboratories. Based on the results of this inter-laboratory case study, the robustness, biological domain and addition of the light dark-transition assay to predict DNT will be discussed and determined. Future experiments will test more compounds in the light-dark transition tests and the added value of other zebrafish DNT behavioral test tests will be discussed. The future goal is to add the zebrafish DNT assays to the OECD guidance document and to use this model to predict DNT. (This abstract does not necessarily reflect EPA policy).