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Comparisons of network formation and acute in vitro assays for evaluating neurotoxicity
Citation:
Martin, M., K. Carstens, A. Carpenter, T. Shafer, AND K. Paul-Friedman. Comparisons of network formation and acute in vitro assays for evaluating neurotoxicity. Society of Toxicology 61st Annual Meeting and ToxExpo 2022, San Diego, CA, March 27 - 31, 2022. https://doi.org/10.23645/epacomptox.19413830
Impact/Purpose:
Poster presented to the Society of Toxicology 61st Annual Meeting and ToxExpo March 2022. New Approach Methodologies (NAMs) offer the opportunity to better characterize hazard and toxicity risk for thousands of compounds for which toxicity information is lacking. In particular, many chemicals lack information on neurotoxicity and developmental neurotoxicity. Assessment of Developmental Neurotoxicity (DNT) using animal-based Guideline studies is expensive, time consuming, and does not always yield actionable data. Further, DNT assessment is not required under TSCA and the Guideline DNT study is a triggered study under FIFRA. Consequently, few of the tens of thousands of chemicals to which humans may be exposed have been evaluated for DNT hazard. To address this issue, New Approach Methodologies (NAMs) are being developed that can help provide data for risk decisions under FIFRA and TSCA. As these methods become more widely utilized, they can also provide information for other types of environmental decision-making as well.
Description:
New approach methodologies (NAMs) have been developed to address the existing need for information on the potential neurotoxicity or developmental neurotoxicity (DNT) hazard for thousands of chemicals in the environment. One platform is the multi-well microelectrode array (MEA) to measure neuronal action potentials and network formation. The acute MEA assay uses dissociated rat cortical cells cultured at postnatal day 0 and evaluated for chemical effects on network activity at day in vitro (DIV) 13 during an acute (60-minute) chemical exposure. In contrast, the network formation assay (NFA) uses an exposure paradigm beginning at DIV 0 through DIV 12, when network development stabilizes; network activity is measured throughout network development (at DIV 5, 7, 9, and 12). Chemicals were tested at a single concentration (SC), multiple concentrations (MC), or both. Here, our aim was to evaluate the quantitative and qualitative concordance between assays by chemical. In general, the NFA demonstrates reductions in the majority of endpoints for active chemicals, whereas the acute assay has differential patterns of response that include increased and decreased neuronal activity. Overall, of 243 chemicals tested in the acute (MC+SC) and NFA (MC+SC), 125 chemicals were active in both. Subsequently, when the MC data were analyzed separately, of the 154 chemicals tested in both the MC acute and MC NFA, 133 chemicals (86%) were detected in the acute assay while 115 (75%) chemicals were detected in the NFA. For the 106 chemicals detected in both assays, the minimum AC50 potency values were not shifted by assay in a predictable pattern. Additionally, filtering NFA data to include only potency values less than cytotoxic concentrations did not reveal a linear trend between minimum acute and NFA potency values. This analysis indicates the acute and NFA may complement one another and inform neurotoxicity hazard as well as likely probe distinct neurobiological substrates and specific functional processes. Future work will determine whether there are differences in the general network activity as well as bursting and connectivity parameters across assays. This provides a basis for further chemical evaluation using both approaches. This abstract does not necessarily reflect U.S. EPA policy.
URLs/Downloads:
DOI: Comparisons of network formation and acute in vitro assays for evaluating neurotoxicity
MELISSAMARTIN_SOT_POSTER_2022_FINAL.PDF (PDF, NA pp, 4725.241 KB, about PDF)