Effects of Methoxychlor and Its Metabolite Hydroxychlor on Human Placental 3β-Hydroxysteroid Dehydrogenase 1 and Aromatase in JEG-3 Cells

Abstract

Progesterone and estradiol produced by the human placenta are critical for maintenance of pregnancy and fetal development. In the human placenta, 3β-hydroxysteroid dehydrogenase 1 (HSD3B1) is responsible for the formation of progesterone from pregnenolone and aromatase (CYP19A1) for the production of estradiol from androgen. Insecticide methoxychlor (MXC) and its metabolite hydroxychlor (HPTE) may disrupt the activities of these 2 enzymes. In this study, we investigated the effects of MXC and HPTE on steroid production in human placental JEG-3 cells and on HSD3B1 and CYP19A1 activities. MXC and HPTE inhibited progesterone and estradiol production in JEG-3 cells. MXC and HPTE were potent HSD3B1 inhibitors with the half maximal inhibitory concentration (IC₅₀) values of 2.339 ± 0.096 and 1.918 ± 0.078 μmol/l, respectively. MXC had no inhibition on CYP19A1 at 100 μmol/l, while HPTE was a weak inhibitor with IC₅₀ of 97.16 ± 0.10 μmol/l. When pregnenolone was used to determine the inhibitory mode, MXC and HPTE were found to be competitive inhibitors of HSD3B1. When cofactor NAD⁺ was used, MXC and HPTE were the noncompetitive inhibitors of HSD3B1. When testosterone was used, HPTE was a mixed inhibitor of CYP19A1. In conclusion, MXC and HPTE are potent inhibitors of human HSD3B1, and HPTE is a weak CYP19A1 inhibitor.

Triclocarban and Triclosan Inhibit Human Aromatase via Different Mechanisms

“…JEG-3 cells secreted estrone (1 ± 0.16 ng/ml) and estradiol (11 ± 3.1 ng/ml) in the presence of excess DHEA [ 14 ]. The JEG-3 cell culture and DHEA treatment were performed as previously described [ 15 ]. JEG-3 cells were seeded at 10 5 cells per well in 24-well plates and cultured in MEM medium with phenol red containing 10% fetal calf serum at 37°C and 5% CO2 in the presence of various concentrations of triclocarban or triclosan with 10 μ M DHEA (for estradiol assay) for 12 h. For cytotoxicity analysis, cells were treated with 100 μ M triclosan or triclocarban and the cells were tested for their viability as discussed below.…”

Physiology and Pathophysiology of Steroid Biosynthesis, Transport and Metabolism in the Human Placenta

“…Pregnenolone is converted to progesterone by 3β-HSD1 in the ER ( Figures 5 , 6 ; Miller and Auchus, 2011 ; Liu et al, 2016 ). 3β-HSD1 is exclusively expressed in the placental STB ( Ian Mason, 1993 ; Li et al, 2005 ), while 3β-HSD2 is predominantly expressed in the adrenal gland and gonads ( Labrie et al, 1992 ; Ian Mason, 1993 ).…”

“…The fungicide tributyltin lowers progesterone production and acts as a moderate inhibitor of 3β-HSD1 ( Cao et al, 2017 ). Likewise, the insecticides methoxychlor and its metabolite hydroxychloroquine inhibit progesterone as well as estradiol production; these substances are potent 3β-HSD1 inhibitors ( Liu et al, 2016 ). In contrast, ochratoxin A, a common food-borne mycotoxin, induces the expression of 3β-HSD1, leading to a significant increase of progesterone production ( Woo et al, 2013 ).…”

Triphenyltin Chloride Delays Leydig Cell Maturation During Puberty in Rats

“…Leydig cells were identified by staining HSD11B1 as above. The Leydig cell size, nuclear size, and cytoplasmic size were calculated as previously described ( Liu et al, 2016 ). Six randomly selected fields in each of three non-adjacent sections per testis were captured using a BX53 Olympus microscope (Tokyo, Japan) equipped with a digital camera interfaced to a computer.…”

“…CYP11A1 and HSD11B1 are the proteins of Leydig cells and SOX9 is the Sertoli cell protein. CYP11A1, HSD11B1, and SOX9 protein levels were measured using semi-quantitative measurement of the density for cell per se as previously described ( Liu et al, 2016 ). Immunohistochemical stainings of CYP11A1, HSD11B1, and SOX9 were performed as above.…”