Luteinizing hormone receptor (lhcgr) as a marker gene for characterizing estrogenic endocrine-disrupting chemicals in zebrafish ovarian follicle cells.

The adverse effects of endocrine-disrupting chemicals (EDCs) have been well documented; however, the action mechanisms of many EDCs remain elusive and controversial. Furthermore, the highly diversified chemical structures and low environmental concentrations of EDCs present a major challenge to their chemical detection. Clearly, there is an urgent need for simple and reliable bioassays to detect EDCs in the environment and unravel their action mechanisms. We have recently identified luteinizing hormone receptor (lhcgr) as a robust estradiol (E2)-responsive gene in cultured zebrafish ovarian follicle cells. The expression of lhcgr exhibited a distinct biphasic response to E2 over a 24-h time-course treatment, making this a unique system for characterizing estrogenic EDCs. This study was undertaken to validate this platform by testing a wide range of EDCs, including 17α-ethinylestradiol (EE2), diethylstilbestrol (DES), bisphenol A (BPA), genistein (GEN), 1,1,1-trichloro-2-(2-chlorophenyl)-2-(4-chlorophenyl)ethane (o,p'-DDT), vinclozolin (VIN), bis(2-ethylhexyl) phthalate (DEHP), 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), and 2,2',4,4'-tetrabromodiphenyl ether (BDE-47). Diethylstilbestrol (DES), EE2 and o,p'-DDT mimicked E2 and induced a biphasic expression of lhcgr while BPA and GEN stimulated a monophasic expression in the 24-h time-course. In contrast, BDE-47, DEHP and VIN had no effect, whereas TCDD decreased lhcgr expression. Dose-response experiment showed that E2, EE2 and DES had the highest potency, which was followed by GEN, BPA and o,p'-DDT. The effects of estrogenic EDCs were further confirmed by their potentiation of hCG-induced activin βA2 subunit (inhbab) expression. In conclusion, the present study showed that the expression of lhcgr in cultured zebrafish follicle cells and its biphasic response to estrogens provide a unique in vitro platform for screening and categorizing estrogenic substances and deciphering their action mechanisms.