LAUSR

Glucocorticoids (GCs) are steroid hormones that have systemic effects that are mediated by the glucocorticoid receptor (GR). Environmental chemicals that disrupt GR signaling and/or GC homeostasis could adversely affect the health of human and non-human vertebrates. A major challenge in identifying environmental chemicals that alter GR signaling and/or GC homeostasis is a lack of adequate screening methods. Here, we developed a cell-based bioassay to measure total glucocorticogenic activity (TGA) of environmental chemicals and human serum. Human MDA-MB-231 breast cancer cells were stably transfected with a luciferase reporter gene driven by three tandem glucocorticoid-response elements. Dose-response curves for 6 GCs and 4 non-GC steroid hormones were generated to evaluate specificity of the bioassay. Cells were also optimized to measure TGA of 176 structurally diverse environmental chemicals and human serum samples in a high-throughput format. Reporter activity was GC specific and induced 400-fold by 1 μM dexamethasone. Furthermore, three of the screened chemicals (3,4,4'-trichlorocarbanilide, isopropyl-N-phenylcarbamate, and benzothiazole derivative 2-(4-chlorophenyl)-benzothiazole) potentiated cortisol-induced GR activity. Serum TGA estimates from the bioassay were highly correlated with a cortisol enzyme-linked immunosorbent assay. This work establishes an in vitro method to rapidly screen environmental chemicals and human serum for altered glucocorticogenic activity. Future studies can utilize this tool to quantify the joint effect of endogenous GCs and environmental chemicals. This article is protected by copyright. All rights reserved.