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Prioritization of chemicals for effects on steroidogenesis using an integrated statistical approach to high-throughput H295R data (SOT)
Citation:
Haggard, D., Woodrow Setzer, R. Judson, AND K. Paul-Friedman. Prioritization of chemicals for effects on steroidogenesis using an integrated statistical approach to high-throughput H295R data (SOT). Presented at Society of Toxicology annual meeting, Baltimore, MD, March 10 - 14, 2019. https://doi.org/10.23645/epacomptox.7873802
Impact/Purpose:
Endocrine disruption is a toxicity of both physiological and regulatory importance; as steroid hormones regulate reproduction, development, and other biological processes, it is a priority to identify chemicals that may interact with production of these hormones. A high-throughput H295R assay (HT-H295R) was developed as part of the U.S. EPA’s ToxCast program that includes measurement of 11 hormones across the steroid hormone biosynthesis pathway in H295R cells, including progestagens, corticosteroids, androgens, and estrogens. HT-H295R has been used to screen a total of 2012 chemicals in single-concentration and 656 chemicals in multi-concentration. Poster for presentation at Society of Toxicology annual meeting March 2019.
Description:
Synthesis of 11 steroid hormones in the human adrenocortical carcinoma cell line, H295R, was measured in a high-throughput steroidogenesis assay (HT-H295R) as part of the US Environmental Protection Agency’s ToxCast program for 656 chemicals in multi-concentration response. This work examined the utility of a novel prioritization metric that reduced these 11-dimensional data to 1-dimension via calculation of a mean Mahalanobis distance (mMd) at for all steroid hormones measured at each chemical concentration. First, we demonstrated the robustness of estimated mMd values via a data simulation to quantify the influence of the covariance matrix on the mMd, the type I error rate, and the relative power to identify different steroid hormone responses. Second, steroid hormone response patterns of prototypical aromatase inhibitors in the HT-H295R assay were examined. Third, a prioritization metric was developed using the mMd, ToxCast/Tox21 assay indicators of mitochondrial and cytotoxicity, and the parallel HT-H295R cell viability assay. The covariance structure among hormones was stable, and mMd values were reproducible and similar from simulation to experiment, with sufficient power to detect ≥1.5-fold changes in a variety of hormone responses. Aromatase inhibitors decreased estrogen synthesis but demonstrated variable effects on other hormones. Using mitochondrial and cytotoxicity filters, 422 of 623 chemical samples with sufficient ToxCast assay information demonstrated selective activity in the HT-H295R assay, i.e. with potency values ≥0.5 log10-micromolar units lower in the HT-H295R assay. Test chemicals with the greatest selectivity and potency included pharmacological aromatase inhibitors (e.g. letrozole), steroid hormones (e.g. androstenedione, estrone, and corticosterone), inhibitors of cholesterol synthesis (e.g. cerivastatin sodium) and other drugs with roles in steroidogenesis (e.g. mifepristone and danazol). The resultant analyses inform development of a relative prioritization scheme using a robust metric, the maximum mMd, and indicators of mitochondrial and cytotoxicity. This abstract does not necessarily reflect U.S. EPA policy.
URLs/Downloads:
DOI: Prioritization of chemicals for effects on steroidogenesis using an integrated statistical approach to high-throughput H295R data (SOT)
HAGGARD_SOT2019_POSTER_02282019.PDF (PDF, NA pp, 2108.897 KB, about PDF)