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Screening and prioritization of surface waters using high throughput in vitro assays as effects-based monitoring tools
Citation:
Blackwell, B., S. Corsi, AND Dan Villeneuve. Screening and prioritization of surface waters using high throughput in vitro assays as effects-based monitoring tools. National Monitoring Conference, Denver, CO, March 25 - 29, 2019.
Impact/Purpose:
High throughput screening (HTS) technologies have been successfully applied to single chemical toxicity screening. These same HTS approaches can be used as effects-based monitoring tools to screen complex environmental mixtures. As part of the Great Lakes Restoration Initiative (GLRI), the use of high throughput in vitro assays as an effects-based monitoring tool was piloted and later expanded to study other surface waters across the US. Water extracts were tested using HTS assays to identify prominent bioactivities, sites of concern, and to assess how well measured chemicals predicted bioassay response. Extracts were screened through up to three multiplexed in vitro HTS assays, two of which are included in the USEPA ToxCast program. Overall, the results highlight the applicability of HTS bioassays to environmental monitoring and identify biological targets to focus development of adverse outcome pathways (AOPs) to better understand the consequence of increased biological activity in surface waters.
Description:
Chemical monitoring approaches have historically been limited by a priori knowledge of a contaminant and availability of analytical methods. Advancements in non-targeted chemical analysis have expanded the potential of chemical monitoring to include identification of “unknowns”; however, application of comprehensive non-targeted analysis to routine environmental monitoring remains unfeasible. Effects-based monitoring uses biological systems, from in vivo vertebrate and invertebrate bioassays to in vitro cell-based bioassays, to evaluate the integrated effects of complex mixtures of both known and unidentified contaminants present in environmental samples. As such, bioassays provide a practical, cost-effective tool for evaluation of complex chemical mixtures. As part of the Great Lakes Restoration Initiative (GLRI), the use of high throughput in vitro assays as an effects-based monitoring tool was piloted and later expanded to study other surface waters across the US. Water extracts were tested using high throughput screening (HTS) assays to identify prominent bioactivities, sites of concern, and to assess how well measured chemicals predicted bioassay response. Extracts were screened through up to three multiplexed in vitro HTS assays, two of which are included in the USEPA ToxCast program. Across all three assays, 93 target endpoints were screened covering 83 unique gene targets. To date, over 300 individual water samples have been screened through one or more HTS assays. The most commonly activated biological endpoints targets include aryl hydrocarbon receptor, pregnane X receptor, estrogen receptor, glucocorticoid receptor, PPARã receptor. Exposure-activity ratios were calculated for samples with corresponding measured contaminant concentrations, to compare predicted bioactivity with observed bioassay response. Overall, estrogen receptor activity was the only endpoint well predicted through exposure-activity analysis. Sparse partial least squares (SPLS) analysis identified additional contaminants associated with bioactivity, suggesting potential surrogates of biological effect that could be used to prioritize locations with available chemical monitoring data. Overall, the results highlight the applicability of HTS bioassays to environmental monitoring and identify biological targets to focus development of adverse outcome pathways (AOPs) to better understand the consequence of increased biological activity in surface waters.