Triclocarban, Triclosan, Bromochlorophene, Chlorophene, and Climbazole Effects on Nuclear Receptors: An in Silico and in Vitro Study

BACKGROUND: Endocrine-disrupting chemicals can interfere, with hormonal homeostasis and have, adverse, effects for both humans and the environment. Their identification is increasingly difficult due to lack of adequate toxicological tests. This difficulty is particularly problematic for cosmetic ingredients, because in vivo testing is now banned completely in the European Union. OBJECTIVES: The, aim was to identify candidate preservatives as endocrine disruptors by in silico methods and to confirm endocrine receptors' activities through nuclear receptors in vitro. METHODS: We screened preservatives listed in Annex V in the European Union Regulation on cosmetic products to predict their binding to nuclear receptors using the Endocrine Disruptome and VirtualToxLab(TM) version 5.8 in silico tools. Five candidate preservatives were further evaluated for androgen receptor (AR), estrogen receptor (ER alpha), glucocorticoid receptor (GR), and thyroid receptor (TR) agonist and antagonist activities in cellbased luciferase reporter assays in vitro in AR-EcoScreen, hER alpha-HeLa-9903, MDA-kb2, and GH3.TRE-Luc cell lines. Additionally, assays to test for false, positives were used (nonspecific luciferase, gene induction and luciferase inhibition). RESULTS: Triclocarban had agonist activity on AR and ER alpha, at 1 mu M and antagonist activity on GR at 5 mu M and TR at 1 mu M. Triclosan showed antagonist effects on AR, ERa, GR at 10 Oil and TR at 5 mu M, and bromochlorophene at 1 mu M (AR and TR) and at 10 Oil (ER alpha, and GR). AR antagonist activity of chlorophene was observed [inhibitory concentration at 50% (1050) 1050 = 2.4 mu M], as for its substantial ERa agonist at >5 [CM and 7112 antagonist activity at 10 mu M. Climbazole showed AR antagonist (1050 = 13.6 mu M.), ERa agonist at >10 mu M., and TR antagonist activity at 10 mu M. DISCUSSION: These data support the concerns of regulatory authorities about the endocrine-disrupting potential of preservatives. These data also define the need to further determine, their effects on the endocrine system and the need to reassess the risks they pose to human health and the environment.