In vitro assessment of thyroid and estrogenic endocrine disruptors in wastewater treatment plants, rivers and drinking water supplies in the greater Paris area (France).

The presence of estrogenomimetic compounds in the environment, and particularly in water resources, is well known. In contrast, little data is available about the disruption of the thyroid system, even though thyroid hormones are strongly involved in regulating metabolism, growth and development. The aim of this study was to carry out a parallel evaluation of the disruptions of thyroid and estrogenic hormone receptor transcriptional activities, induced by water samples from two wastewater treatment plants (WWTPs), in the river Seine, and from four drinking treatment plants located in the Paris area. Two in vitro bioassays were used for the evaluation of thyroid (PC-DR-LUC) and estrogenic (MELN) disruption. Our observations of thyroidal activity show that a disruption potential was only present in the WWTPs influents, whereas estrogenicity was systematically detected in both influents and effluents. The great majority of endocrine activity was removed during the biological process. In the river Seine, only estrogenicity was detected, and no activity was observed in drinking water supplies. Fractionation of the influents revealed that most of the thyroidal effect was associated with compounds with low polarity, and could be partly attributable to 4-nonylphenol.

A new bioluminescent cellular assay to measure the transcriptional effects of chemicals that modulate the alpha-1 thyroid hormone receptor.

Interactions of environmental pollutants with the thyroid endocrine axis have received much attention especially because thyroid hormones (THs) play a major role in mammalian brain development. In order to screen for compounds that act on the triiodothyronine (T3) signaling pathway, we developed a new reporter gene assay expressing luciferase under the control of the TH receptor (TR). PC12 cells expressing the alpha1-isoform of TR of avian origin were stably transfected with a luciferase gene controlled by the SV40 promoter, and enhanced by a four-spaced direct repeat (DR4) thyroid response element (TRE). The resulting PC-DR-LUC cells were used to optimize a T3 assay in multiwell microplates. This assay was highly sensitive (30 pM T3) and reproducible, and responded as expected to TH analogues. Several halogenated phenolic (3,3',5,5'-tetrabromobisphenol A, 3,3',5,5'-tetrachlorobisphenol A, 4-hydroxy-2',3,4',5,6'-pentachlorobiphenyl) and phenol (pentachlorophenol, 2,4,6-triiodophenol) compounds suspected of being thyroid-disrupting environmental chemicals induced partial agonistic and/or complex competitive/uncompetitive antagonistic responses in PC-DR-LUC cells at micromolar concentrations. A cell viability test indicated that these effects were not related to cytotoxicity of the chemicals. These results suggest that the PC-DR-LUC assay could be a valuable tool for the large-scale screening for thyroid receptor agonists and antagonists in vitro, and for detecting thyroid disruptors in the environment.