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Characterization of ToxCast Phase II compounds disruption of spontaneous network activity in cortical networks grown on multi-well microelectrode array (mwMEA) plates.
Citation:
Strickland, J., M. Martin, A. Richard, AND K. Houck. Characterization of ToxCast Phase II compounds disruption of spontaneous network activity in cortical networks grown on multi-well microelectrode array (mwMEA) plates. Society of Toxicology Annual Meeting, New Orleans, LA, March 13 - 17, 2016.
Impact/Purpose:
The purpose of these experiments was to collect in vitro data on functional effects of toxcast compounds on neural function for inclusion in the ToxCast program
Description:
The development of multi-well microelectrode array (mwMEA) systems has increased in vitro screening throughput making them an effective method to screen and prioritize large sets of compounds for potential neurotoxicity. In the present experiments, a multiplexed approach was used to determine compound effects on both neural function and cell health in primary cortical networks grown on mwMEA plates following exposure to ~1100 compounds from EPA’s Phase II ToxCast libraries. On DIV 13, baseline activity (40 min) was recorded prior to exposure to each compound at 40 µM. DMSO and the GABAA antagonist bicuculline (BIC) were included as controls on each mwMEA plate. Changes in spontaneous network activity (mean firing rate; MFR) and cell viability (lactate dehydrogenase; LDH and CellTiter Blue; CTB) were assessed within the same well following compound exposure. Activity calls (“hits”) were established using the 90th and 20th percentiles of the compound-induced change in MFR (medians of triplicates) across all tested compounds; compounds above (top 10% of compounds increasing MFR), and below (bottom 20% of compounds decreasing MFR) these thresholds, respectively were considered hits. MFR was altered beyond one of these thresholds by 322 compounds. Four compound categories accounted for 66% of the hits, including: insecticides (e.g. abamectin, lindane, prallethrin), pharmaceuticals (e.g. haloperidol, reserpine), fungicides (e.g. hexaconazole, fenamidone), and herbicides (e.g., imazapyr, metholachlor). Most changes in MFR occurred in the absence of cytotoxicity; with only 8 compounds causing decreased cell viability. Analysis for enrichment of chemical structural features using ToxPrint identified 19 chemotypes, accounting for ~33% of the hits in the mwMEA assay. All 322 hits, as well as a subset of ~50 inactive compounds, will be rescreened in a concentration-response experimental design to confirm activity and determine potency. The MEA data on acute neurotoxicity will be combined with the results of other ToxCast assays for chemical prioritization purposes. (This abstract does not reflect EPA policy).