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Concentration-response assessment of ToxCast Phase II compounds on spontaneous neural network activity in vitro
Citation:
Strickland, J., K. Wallace, M. Martin, K. Houck, J. Ross, AND Tim Shafer. Concentration-response assessment of ToxCast Phase II compounds on spontaneous neural network activity in vitro. 2017 Society of Toxicology Annual Meeting, Baltimore, MD, March 12 - 16, 2017.
Impact/Purpose:
This abstract demonstrates the ability of neural networks grown on MEAs to screen ToxCast compounds and eventually will be incorporated into the toxcast database.
Description:
The NRC report on Toxicity Testing in the 21st Century called for development of alternative assays for toxicity hazard assessment. The current study continues to evaluate the ability of multi-well microelectrode array (mwMEA) systems to provide an efficient, high throughput in vitro screening method to prioritize large sets of compounds for potential neurotoxicity. A total of 384 compounds from EPA’s ToxCast phase II libraries were screened in primary cortical networks grown on mwMEA plates for their ability to alter neural network function and cell health following acute exposures (40 min). Concentration response (0.1 – 40 M) of all compounds was assessed to determine potency. On day in vitro 13 - 15, baseline activity (40 min) was recorded prior to exposure to each compound. DMSO and the GABAA antagonist bicuculline (BIC) were included as internal 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 exposure. Following normalization of MFR (nMFR) data, concentration-response functions were fit to the data if the median nMFR at any concentration exceeded three times the baseline median absolute deviation (3x BMAD). Preliminary analysis indicates that a total of 169 compounds exceeded 3xBMAD and were fit by concentration-response functions; 6 compounds (colchicine, heptachlor, isoproterenol, dieldrin, endrin and lindane) increased nMFR, while 160 compounds decreased nMFR and 3 compounds (SR125047, 4-(butan-2-yl)phenol and S-bioallethrin) resulted in biphasic changes in nMFR. Of these compounds, only 5 resulted in decreased cell viability in the LDH and Cell Titer Blue assays. These results demonstrate that mwMEAs can be used to screen compounds for potency of effects on neural network function. (This abstract does not represent EPA Policy).