Chemical Genomics Profiling of Environmental Chemical Modulation of Human Nuclear Receptors

Abstract

Background: The large and increasing number of chemicals released into the environment demands more efficient and cost-effective approaches for assessing environmental chemical toxicity. The U.S. Tox21 program has responded to this challenge by proposing alternative strategies for toxicity testing, among which the quantitative high-throughput screening (qHTS) paradigm has been adopted as the primary tool for generating data from screening large chemical libraries using a wide spectrum of assays.Objectives: The goal of this study was to develop methods to evaluate the data generated from these assays to guide future assay selection and prioritization for the Tox21 program.Methods: We examined the data from the Tox21 pilot-phase collection of approximately 3,000 environmental chemicals profiled in qHTS format against a panel of 10 human nuclear receptors (AR, ERα, FXR, GR, LXRβ, PPARγ, PPARδ, RXRα, TRβ, and VDR) for reproducibility, concordance of biological activity profiles with sequence homology of the receptor ligand binding domains, and structure–activity relationships.Results: We determined the assays to be appropriate in terms of biological relevance. We found better concordance for replicate compounds for the agonist-mode than for the antagonist-mode assays, likely due to interference of cytotoxicity in the latter assays. This exercise also enabled us to formulate data-driven strategies for discriminating true signals from artifacts, and to prioritize assays based on data quality.Conclusions: The results demonstrate the feasibility of qHTS to identify the potential for environmentally relevant chemicals to interact with key toxicity pathways related to human disease induction.

A Quantitative Approach to Screen for Nephrotoxic Compounds In Vitro

“…33 However, despite the fact that HO-1 increase was more pronounced and reliable in primary human compared with immortalized kidney cells (Supplemental Figure 2C), the 2D system for kidney suffers from certain limitations. Those include: lack of estimating toxicity of compounds that require metabolism and bioactivation by the liver, for example compounds such as acetaminophen, an analgesic with nephrotoxicity attributed to its hepatic metabolite N-acetyl-p-benzoquinone imine; lack of apical to basolateral polarity when cultured on a flat surface, which might not allow the uptake of certain antiviral drugs therefore misrepresenting its safety, for example OAT1 and OAT3, expressed at the basolateral membrane of proximal tubular epithelial cells mediating the uptake of antiviral agents tenofovir and acyclovir.…”

Effect-based trigger values for in vitro bioassays: Reading across from existing water quality guideline values

“…In vitro assays included in Tox21 are phenotypic assays (e.g., targeting mitochondrial toxicity (Attene-Ramos et al, 2013a)), pathway assays (e.g., targeting cell viability in specific cell lines) and nuclear receptor assays (e.g., targeting hormone receptors and metabolic pathways (Huang et al, 2011)) and various other endpoints (Tice et al, 2013). The chemicals and pathways screened for Tox21 are also relevant for water quality and some of the assays have been applied successfully to water quality testing together with more established in vitro assays .…”

Performance of the BG1Luc ER TA method in a qHTS format

“…One of the goals of the Tox21 program is to develop, validate and translate test methods that characterize toxicity pathways while reducing cost and animal use (Shukla et al, 2010;Huang et al, 2011). Tox21 is using qHTS methods to reach this goal.…”