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Comparisons of Microelectrode Array Acute and Network Formation In Vitro Assays for Evaluating Neurotoxicity
Citation:
Shafer, T., M. Martin, A. Carpenter, K. Friedman, AND K. Carstens. Comparisons of Microelectrode Array Acute and Network Formation In Vitro Assays for Evaluating Neurotoxicity. Society of Toxicology 62nd Annual Meeting and ToxExpo 2023, Nashville, TN, March 19 - 23, 2023. https://doi.org/10.23645/epacomptox.22750703
Impact/Purpose:
Poster presented to the Society of Toxicology 62nd Annual Meeting and ToxExpo March 2023. 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) can address information gaps on the potential neurotoxicity or developmental neurotoxicity (DNT) hazard for data-poor chemicals. Two assays have been developed using the microelectrode array (MEA) platform, which measures electrical activity in the form of extracellularly-recorded neuronal action potentials. The acute network function (AcN) MEA assay uses dissociated rat cortical cells cultured at postnatal day 0 and evaluates chemical effects on network activity (e.g., mean firing rate (MFR)) at day in vitro (DIV) 14 during an acute (60-minute) chemical exposure. In contrast, the network formation (NFA) MEA assay uses a developmental exposure paradigm that begins on DIV 0 and continues through DIV 12. Network activity is measured in the NFA throughout network development (at DIV 5, 7, 9, and 12) and the area under the curve is calculated for each concentration and then used to determine concentration-response relationships. Here, we evaluated the hypothesis that chemicals with acute effects also produce developmental network effects (and vice-versa) by examining the quantitative and qualitative concordance between assays. Using both single and multi-concentration data, the 243 chemicals that were tested in both the AcN and NFA assays had a 75.3% concordance in altering network activity based on alteration of MFR. Of the 154 chemicals with concentration-response data in both assays, 93 chemicals were active. The minimum selective AC50 potency value (AC50 values less than the cytotoxicity AC50 value) was generally concordant between the two assays, with 70 chemicals having selective potency values within ±1 log unit. However, hierarchical clustering suggested that select groups of chemicals were differentially active in the NFA and AcN. Specifically, 15 chemicals were selectively active (activity below concentrations that cause cytotoxicity) in the NFA but were inactive in the AcN. Conversely, 21 chemicals were selectively active in the AcN but were inactive in the NFA. No specific classes of chemicals contributed to those active only in the AcN or NFA assay. Additionally, cytotoxicity was often observed as a sensitive endpoint in the NFA, whereas in the AcN cytotoxicity was rarely observed, possibly due to the limited exposure time of the latter assay. These analyses indicate that the AcN and NFA MEA assays may probe distinct neurobiological substrates and specific functional processes, though uncertainties remain regarding cellular concentrations in the NFA versus the AcN due to repeat dosing and extended duration in the NFA. Lessons from this work will inform future screening strategies for chemicals with unknown neurological hazard potential. This abstract does not necessarily reflect U.S. EPA policy.
URLs/Downloads:
DOI: Comparisons of Microelectrode Array Acute and Network Formation In Vitro Assays for Evaluating Neurotoxicity
SHAFER_SOT_POSTER_2023_FINAL_CLEAR.PDF (PDF, NA pp, 1622.476 KB, about PDF)