Evaluation of a multiplexed, multispecies nuclear receptor assay for chemical hazard assessment

Sensitivity to potential endocrine disrupting chemicals in the environment varies across species and is influenced by sequence conservation of their nuclear receptor targets. Here, we evaluated a multiplexed, in vitro assay testing receptors relevant to endocrine and metabolic disruption from five species. The TRANS-FACTORIAL (TM) system of human nuclear receptors was modified to include additional species: mouse (Mus musculus), frog (Xenopus laevis), zebrafish (Danio rerio), chicken (Gallus gallus), and turtle (Chrysemys picta). Receptors regulating endocrine function and xenobiotic recognition were included, specifically: ER alpha, ER beta, AR, TR alpha, TR beta, PPAR gamma and PXR. The assay, ECOTOX-FACTORIAL (TM), was evaluated with 191 chemicals enriched with known receptor ligands. Hierarchical clustering of potency values demonstrated strong coherence of receptor families. Interspecies comparisons of responses within a receptor family showed moderate to high concordance for potencies under 50 mu M. PPAR gamma showed high concordance between mammalian species, 89%, but only 63% between mammalian and zebrafish. For chemicals with potencies below 1 mu M, concordances were 89-100% for all receptors except PXR. Concordance showed a strong positive relationship to ligand-binding domain sequence similarity and critical amino acid residues obtained by the Sequence Alignment to Predict Across Species Susceptibility (SeqAPASS) tool. In combination with SeqAPASS, ECOTOX-FACTORIAL may provide efficient screening of important receptors to identify species of high priority for effects monitoring.

Automated summary

Sensitivity to potential endocrine disrupting chemicals varies across species, influenced by sequence conservation of nuclear receptor targets. In vitro assays testing receptors from five species showed strong coherence of receptor families in potency values, with varying levels of interspecies concordance in response to different receptors. Concordance was positively related to ligand-binding domain sequence similarity and critical amino acid residues, indicating potential for efficient screening of important receptors for species prioritization in effects monitoring.