Detection of potential (anti)progestagenic endocrine disruptors using a recombinant human progesterone receptor binding and transactivation assay

The present work describes the identification of (anti)progestin endocrine disrupting chemicals (EDC) using a two step screening system. In the first step a competitive binding assay was developed using recombinant human progesterone receptor (hPR). The tested chemicals were of various classes like insecticides, their metabolites, industrial chemicals and waste water treatment plant (WWTP) effluents. All the tested chemicals demonstrated a high affinity binding for hPR. The average IC50 values of the test chemicals were within the range of 1-25 mu M. In the second step of screening, a mammalian cellbased hPR transactivation assay was developed where HEK 293 cells were co-transfected with hPR and luciferase reporter gene under the control of progesterone-response element. Stimulation of the cells with progesterone resulted in about 25-fold up regulation of luciferase activity, with EC50 value of 4 nM. Potent anti-progesterone, RU486, significantly inhibited progesterone-induced transactivation and non-progestagenic steroids failed to transactivate hPR till 1 mu M concentrations. The chemicals showing high binding affinities in competitive binding assays were then tested in transactivation assay and all of them were found to be anti-progestative except WWTP effluents. Transactivation assays using extracted water samples from five different WWTP effluents showed that it was rich in progestative compounds. The levels of induction caused by these effluents were in the range of 15-25% of induction by progesterone and they represented about 6 ng/l equivalent progesterone activities. In conclusion, we demonstrated that this two step assay provides an efficient screening tool for the detection of (anti)progestative EDC in various samples. (C) 2008 Elsevier Ireland Ltd. All rights reserved.