Triclocarban, triclosan, bromochlorophene, chlorophene, and climbazole effects on nuclear receptors

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 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 cell-based 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[micro]M and antagonist activity on GR at 5[micro]M and TR at 1[micro]M. Triclosan showed antagonist effects on AR, ER[alpha], GR at 10[micro]M and TR at 5[micro]M, and bromochlorophene at 1[micro]M (AR and TR) and at 10[micro]M (ER[alpha] and GR). AR antagonist activity of chlorophene was observed [inhibitory concentration at 50% (IC50) IC50=2.4[micro]M], as for its substantial ER[alpha] agonist at >5[micro]M and TR antagonist activity at 10[micro]M. Climbazole showed AR antagonist (IC50=13.6[micro]M), ER[alpha] agonist at >10[micro]M, and TR antagonist activity at 10[micro]M