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Testing for developmental neurotoxicity using a battery of in vitro assays for key cellular events in neurodevelopment
Citation:
Harrill, J., T. Freudenrich, K. Wallace, K. Ball, Tim Shafer, AND W. Mundy. Testing for developmental neurotoxicity using a battery of in vitro assays for key cellular events in neurodevelopment. TOXICOLOGY AND APPLIED PHARMACOLOGY. Academic Press Incorporated, Orlando, FL, 354(1):24-39, (2018). https://doi.org/10.1016/j.taap.2018.04.001
Impact/Purpose:
The prevalence of neurodevelopmental disorders is increasing worldwide and environmental chemical exposure is strongly implicated as a contributing factor. Recognizing this problem, information on the potential developmental neurotoxicity of chemicals is a major need of the Agency. However, information on developmental neurotoxicity is known for only a few chemicals, and current testing strategies are both too slow and too costly to adequately address this need. Efficient and predictive methods are needed to screen environmental chemicals and prioritize them for further assessment. Working under the auspices of Chemical Safety for Sustainability project 16.01, development of medium- and high-throughput tests for developmental neurotoxicity, we have developed a suite of in vitro assays that examine chemical effects on key processes in the development of the nervous system. In this manuscript, we examined effects of 67 reference chemicals in assays for proliferation of neuroprogenitor cells, neurite initiation/outgrowth and maturation, apoptosis and synaptogenesis. Of the 67 compounds tested, 53 have evidence of developmental neurotoxicity in vivo, while 14 are lacking evidence and/or exhibited no activity in EPA ToxCast bioactivity assays; 4 of these compounds are generally considered safe or FDA pregnancy risk Category B. This suite of assays had a high degree of combined sensitivity (87%) for categorizing chemicals known to affect neurodevelopment as active and a moderate degree of combined specificity (71 %) for categorizing chemicals not associated with affects on neurodevelopment as inactive. The combined sensitivity of the assay battery was higher than for any individual assay while the combined specificity of the assay battery was lower than for any individual assay. Overall, this manuscript demonstrates the value of a battery of assays for screening and prioritizing compounds for the potential to cause developmental neurotoxicity.
Description:
Medium- to high-throughput in vitro assays that recapitulate the critical processes of nervous system development have been proposed as a means to facilitate rapid testing and identification of chemicals which may affect brain development. In vivo neurodevelopment is a complex progression of distinct cellular processes. Therefore, batteries of in vitro assays that model and quantify effects on a variety of neurodevelopmental processes have the potential to identify chemicals which may affect brain development at different developmental stages. In the present study, the results of concentration-response screening of 67 reference chemicals in a battery of high content imaging and microplate reader-based assays that evaluate neural progenitor cell proliferation, neural proginitor cell apoptosis, neurite initiation/outgrowth, neurite maturation and synaptogenesis are summarized and compared. The assay battery had a high degree of combined sensitivity (87%) for categorizing chemicals known to affect neurodevelopment as active and a moderate degree of combined specificity (71%) for categorizing chemicals not associated with affects on neurodevelopment as inactive. The combined sensitivity of the assay battery was higher compared to any individual assay while the combined specificity of the assay battery was lower compared to any individual assay. When selectivity of effects for a neurodevelopmental endpoint as compared to general cytotoxicity was taken into account, the combined sensitivity of the assay battery decreased (68%) while the combined specificity increased (93%). The identity and potency of chemicals identified as active varied across the assay battery, underscoring the need for use of a combination of diverse in vitro models to comprehensively screen chemicals and identify those which potentially affect neurodevelopment. Overall, these data indicate that a battery of assays which address many different processes in nervous system development may be used to identify potential developmental neurotoxicants and to distinguish specific from generalized cytotoxic effects with a high degree of success.
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DOI: Testing for developmental neurotoxicity using a battery of in vitro assays for key cellular events in neurodevelopment