Conazole fungicides inhibit Leydig cell testosterone secretion and androgen receptor activation in vitro

Maarke J.E. Roelofs; A. Roberto Temming; Aldert H. Piersma; Martin van den Berg; Majorie B.M. van Duursen

doi:10.1016/j.toxrep.2014.05.006

Toxicology Reports (Jan 2014)

Conazole fungicides inhibit Leydig cell testosterone secretion and androgen receptor activation in vitro

Maarke J.E. Roelofs,
A. Roberto Temming,
Aldert H. Piersma,
Martin van den Berg,
Majorie B.M. van Duursen

Affiliations

Maarke J.E. Roelofs: Endocrine Toxicology Research Group, Institute for Risk Assessment Sciences (IRAS), Utrecht University, P.O. Box 80.177, NL-3508 TD Utrecht, The Netherlands
A. Roberto Temming: Endocrine Toxicology Research Group, Institute for Risk Assessment Sciences (IRAS), Utrecht University, P.O. Box 80.177, NL-3508 TD Utrecht, The Netherlands
Aldert H. Piersma: Center for Health Protection, National Institute for Public Health and the Environment (RIVM), P.O. Box 1, 3720 BA Bilthoven, The Netherlands
Martin van den Berg: Endocrine Toxicology Research Group, Institute for Risk Assessment Sciences (IRAS), Utrecht University, P.O. Box 80.177, NL-3508 TD Utrecht, The Netherlands
Majorie B.M. van Duursen: Endocrine Toxicology Research Group, Institute for Risk Assessment Sciences (IRAS), Utrecht University, P.O. Box 80.177, NL-3508 TD Utrecht, The Netherlands

DOI: https://doi.org/10.1016/j.toxrep.2014.05.006
Journal volume & issue: Vol. 1, no. C
pp. 271 – 283

Abstract

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Conazole fungicides are widely used in agriculture despite their suspected endocrine disrupting properties. In this study, the potential (anti-)androgenic effects of ten conazoles were assessed and mutually compared with existing data. Effects of cyproconazole (CYPRO), fluconazole (FLUC), flusilazole (FLUS), hexaconazole (HEXA), myconazole (MYC), penconazole (PEN), prochloraz (PRO), tebuconazole (TEBU), triadimefon (TRIA), and triticonazole (TRIT) were examined using murine Leydig (MA-10) cells and human T47D-ARE cells stably transfected with an androgen responsive element and a firefly luciferase reporter gene. Six conazoles caused a decrease in basal testosterone (T) secretion by MA-10 cells varying from 61% up to 12% compared to vehicle-treated control. T secretion was concentration-dependently inhibited after exposure of MA-10 cells to several concentrations of FLUS (IC50 = 12.4 μM) or TEBU (IC50 = 2.4 μM) in combination with LH. The expression of steroidogenic and cholesterol biosynthesis genes was not changed by conazole exposure. Also, there were no changes in reactive oxygen species (ROS) formation that could explain the altered T secretion after exposure to conazoles. Nine conazoles decreased T-induced AR activation (IC50s ranging from 10.7 to 71.5 μM) and effect potencies (REPs) were calculated relative to the known AR antagonist flutamide (FLUT). FLUC had no effect on AR activation by T. FLUS was the most potent (REP = 3.61) and MYC the least potent (REP = 0.03) AR antagonist. All other conazoles had a comparable REP from 0.12 to 0.38. Our results show distinct in vitro anti-androgenic effects of several conazole fungicides arising from two mechanisms: inhibition of T secretion and AR antagonism, suggesting potential testicular toxic effects. These effects warrant further mechanistic investigation and clearly show the need for accurate exposure data in order to perform proper (human) risk assessment of this class of compounds.

Published in Toxicology Reports

ISSN: 2214-7500 (Online)
Publisher: Elsevier
Country of publisher: Ireland
LCC subjects: Medicine: Public aspects of medicine: Toxicology. Poisons
Website: http://www.journals.elsevier.com/toxicology-reports/

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