Citation:

MedlockKakaley, E., M. Cardon, P. Hartig, AND V. Wilson. Carolinas SETAC: Validation of a Glucocorticoid Receptor Effects-Based Environmental Sample Screening Tool. Carolinas Society of Environmental Toxicology and Chemistry, Charleston, SC, May 17 - 19, 2017.

Impact/Purpose:

Glucocorticoid activity has been detected, using in vitro effects-based monitoring tools (e.g. transcriptional activation bioassays), in waste and surface waters. We have developed and optimized an in vitro transcriptional activation assay that can be used as an effects-based monitoring tool for the detection of GR-mediated biological activity. A review of the existing literature confirms that many different glucocorticoid receptor-specific pharmaceuticals have been detected in water samples. Therefore, we have further validated the sensitivity of the glucocorticoid receptor transcriptional activation bioassay using 18 GR agonists detected in surface water samples. Determination of individual potencies will allow prediction of the expected biological activity of environmental mixture in present in water samples.

Description:

Glucocorticoid activity has been detected, using in vitro effects-based monitoring tools (e.g. transcriptional activation bioassays), in waste and surface waters domestically and around the world. A review of the existing literature confirms that many different glucocorticoid receptor-specific pharmaceuticals have been detected in water samples. Therefore, we have further validated the sensitivity of the glucocorticoid receptor transcriptional activation bioassay using 18 known GR agonists (15 of the commonly detected pharmaceuticals and 3 endogenous hormones) as well as one antagonist. CV1a cells, devoid of endogenous GR and androgen receptor, were adenovirally transduced with the human GR and MMTV-luciferase genes. Cells were then treated with individual GR agonist or dexamethasone + antagonist (mifepristone) to determine individual compound potency and efficacy. Efficacy (%maximum response) varied between compounds and potency, noted by nominal EC50 values, ranged over several orders of magnitude; triamcinolone acetonide (8.895x10-11M) < flucinonide (1.278x10-10M) < fluticasone propionate (1.734x10-10M) < dexamethasone (2.118x10-10M) < fludrocortisone (3.025x10-10M) < prednisolone (3.873x10-9m) < corticosterone (1.18x10-8M) < 21-hydroxyprogesterone (1.117x10-7M) < cortisone (1.036x10-4M). Further, a GR antagonist standard curve, suited to evaluate GR antagonistic activity (MifEqs) in environmental mixture samples, was optimized by co-exposing cells to dexamethasone with a range of mifepristone concentrations. The IC50 of mifepristone, in the presence of 1pM dexamethasone, was 8.355x10-10. Validating this screening tool using commonly detected GR-specific pharmaceuticals will allow the determination of individual contributions of detected GR agonists and antagonists in future surface and waste water samples. Disclaimer: This abstract does not necessarily reflect USEPA policy. Funded by USEPA/UNC Toxicology Training Agreement CR-83591401 with the Curriculum in Toxicology, University of North Carolina, Chapel Hill

Record Details: