Evaluation of 5-day In Vivo Rat Liver and Kidney With High-throughput Transcriptomics for Estimating Benchmark Doses of Apical Outcomes

Abstract

A 5-day in vivo rat model was evaluated as an approach to estimate chemical exposures that may pose minimal risk by comparing benchmark dose (BMD) values for transcriptional changes in the liver and kidney to BMD values for toxicological endpoints from traditional toxicity studies. Eighteen chemicals, most having been tested by the NTP in 2-year bioassays, were evaluated. Some of these chemicals are potent hepatotoxicants (e.g. DE71, PFOA, and furan) in rodents, some exhibit toxicity but have minimal hepatic effects (e.g. acrylamide and α,β-thujone), and some exhibit little overt toxicity (e.g. ginseng and milk thistle extract) based on traditional toxicological evaluations. Male Sprague Dawley rats were exposed once daily for 5 consecutive days by oral gavage to 8-10 dose levels for each chemical. Liver and kidney were collected 24 hours after the final exposure and total RNA was assayed using HTT with the rat S1500+ platform. HTT data were analyzed using BMD Express 2 to determine transcriptional gene set BMD values. BMDS was used to determine BMD values for histopathological effects from chronic or sub-chronic toxicity studies. For many of the chemicals, the lowest transcriptional BMDs from the 5-day assays were within a factor of 5 of the lowest histopathological BMDs from the toxicity studies. These data suggest that using HTT in a 5-day in vivo rat model provides reasonable estimates of BMD values for traditional apical endpoints. This approach may be useful to prioritize chemicals for further testing while providing actionable data in a timely and cost-effective manner.

AmicroRNAor messengerRNApoint of departure estimates an apical endpoint point of departure in a rat developmental toxicity model

“…The concordance of dam molecular and apical POD values reported here align with published data showing adult rat general toxicity molecular POD values are typically within an order of magnitude of general toxicity apical POD values (Chepelev et al, 2018;Gwinn et al, 2020;Jackson et al, 2014;Johnson et al, 2020;LaRocca et al, 2020;Moffat et al, 2015;Thomas et al, 2011;Thomas et al, 2013). Interestingly, the dam liver molecular POD values were approximately 30X lower than the dam liver apical POD values (Figure 2).…”

“…Since the pioneering work developing quantitative measures of transcriptome change in toxicology studies (Thomas et al, 2007; Yu et al, 2006), mRNA‐based transcriptome POD values have been compared to traditional apical endpoint POD values across a number of general toxicity studies. These comparisons have led to a developing consensus that a transcriptome POD from a short‐term to subchronic exposure of adult rodents approximates with reasonable accuracy a concurrent and/or chronic exposure apical endpoint POD (Bianchi et al, 2021; Gwinn et al, 2020; Jackson et al, 2014; Johnson et al, 2020; LaRocca, Costa, Sriram, Hannas, & Johnson, 2020; Moffat et al, 2015; Thomas et al, 2011; Thomas et al, 2013). To our knowledge, comparison of a maternal transcriptome POD to an embryofetal apical POD within a developmental toxicity study design and derivation of a POD based upon changes in miRNA have not been published.…”

“…The data reported here support the hypothesis that high content data from different types of molecular endpoints (e.g., transcriptomic and epigenomic) that are collapsed to a single value can be used interchangeably to derive a molecular POD for estimation of an apical endpoint POD. For mRNA‐based POD derivation there are numerous examples of the transcriptome POD to apical POD concordance for general toxicity study designs in the literature (Chepelev et al, 2018; Gwinn et al, 2020; Jackson et al, 2014; Johnson et al, 2020; LaRocca et al, 2020; Moffat et al, 2015; Thomas et al, 2011; Thomas et al, 2013). For epigenetic data such as miRNA, the scientific literature is much sparser.…”

“…Using this process, a limited number of studies have examined the concordance between transcriptome and apical POD values. Target organ transcriptome POD values typically are within an order of magnitude of apical endpoint POD values for rodent carcinogenicity or subchronic general toxicity study designs (Bianchi et al, 2021; Chepelev et al, 2018; Gwinn et al, 2020; Jackson et al, 2014; Moffat et al, 2015; Thomas et al, 2011; Thomas et al, 2013). To date, a comparison of transcriptome and apical POD values for a developmental toxicity phenotype has not been performed.…”

A Modern Genotoxicity Testing Paradigm: Integration of the High-Throughput CometChip® and the TGx-DDI Transcriptomic Biomarker in Human HepaRG™ Cell Cultures

“…The field of genetic toxicology is shifting toward more quantitative analyses of genetic toxicology data for potency assessments (94)(95)(96)(97). Previous work has shown that transcriptional PODs are well-aligned with apical PODs (98)(99)(100)(101). Moreover, Bemis et al (102) demonstrated the correlation between in vitro and in vivo BMDs for flow cytometric micronucleus data and suggested that the clastogenic potential of a chemical can be calculated from animal studies or cell-based models of chromosome damage.…”