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Integrating in silico and in vitro data for New Approach Methods evaluation: Application to Tox21 TRHR assay results
Citation:
Shobair, Mahmoud A., Chris Grulke, D. Chang, R. Lougee, K. Paul-Friedman, AND A. Richard. Integrating in silico and in vitro data for New Approach Methods evaluation: Application to Tox21 TRHR assay results. The American Society for Cellular and Computational Toxicology (ASCCT) 2020 annual meeting, DURHAM, North Carolina, October 21 - 22, 2020. https://doi.org/10.23645/epacomptox.13148168
Impact/Purpose:
Poster presented to the The American Society for Cellular and Computational Toxicology (ASCCT) annual meeting October 2020. Application of high-throughput screening (HTS) to toxicology faces the challenge of relating HTS data to molecular initiating events (MIEs) and adverse outcome pathways (AOP) even when the relationship between the HTS output and MIE is indirect. Thyrotropin-Release Hormone Receptor (TRHR) activation is a MIE in the AOP network for thyroid hormone (TH) disruption, but the ability of environmental chemicals to perturb TRHR signaling is unknown. A Tox21 HTS biochemical assay is available, but no orthogonal or confirmatory Tox21 or ToxCast assays can be used to differentiate TRHR true positive responses. To test the hypothesis that environmentally-relevant chemicals can directly interact with TRHR, we developed an in silico cheminformatic workflow to identify chemicals predicted to interfere with TRH binding.
Description:
With the availability of high-throughput screening (HTS) data, such as in the cross-federal Tox21 partnership or EPA’s ToxCast program, the challenge of relating biochemical outputs to molecular initiating events (MIEs) and adverse outcome pathways (AOPs) must be addressed to answer toxicology questions. Data-enrichment approaches can identify relevant in vitro HTS hits, and domain knowledge can be used to build models with high confidence and specificity. Whether modulation of thyrotropin-release hormone receptor (TRHR) activity is a relevant MIE for environmental chemicals is unknown. To evaluate the utility of the Tox21_TRHR assay for hazard evaluation, we developed an in silico cheminformatic workflow that enriches for signals in the data predicted to impact TRHR activity. The tiered approach identifies both potential artifacts and binders using chemotype enrichment analysis, 2D structure filters, and 3D modeling. To build a training set, we created a curated reference dataset from literature reports of a competitive binding assay that measures chemical concentration required to displace binding of radiolabeled TRH. Using pharmacophore modeling, we generated 3D descriptors that can discriminate between binders and non-binders. Preliminary results suggest that less than 10% of the actives in the Tox21 biochemical assay contain TRH-like binding features, likely due to the conservation of the TRHR ligand binding site and the structural similarity of these substances to known TRHR modulators. Our findings suggest that combining structure-based methods and data enrichment analysis can increase confidence in HTS results and aid in prioritization and identification of data gaps. This abstract does not reflect EPA policy.
URLs/Downloads:
DOI: Integrating in silico and in vitro data for New Approach Methods evaluation: Application to Tox21 TRHR assay results
SHOBAIR_ASCCT2020_EPOSTER_20201019_FINAL.PDF (PDF, NA pp, 603.315 KB, about PDF)
ASCCT2020_TRHR_FLASHPOSTER_SHOBAIR.PDF (PDF, NA pp, 846.708 KB, about PDF)