Diethylstilbestrol decreased adrenal cholesterol and corticosterone in rats

Rapid prolactin induction in adult male rats after treatment with diethylstilbestrol

Diethylstilbestrol (DES) is a synthetic oestrogen known to disrupt the endocrine system and to cause reproductive toxicity mediated via the hypothalamic-pituitary-adrenal axis; however, its molecular mechanism of action is poorly understood. In the present study, we found that, after only 1 week of exposure to DES, blood testosterone dramatically decreased and that this decrease was associated with a strong induction of prolactin (PRL). Even with the increase in PRL, the luteinising hormone and follicle-stimulating hormone mRNAs slightly decreased. Our results show that, after 48 hours of a single dose of DES, there was a six-fold increase in PRL expression. After exploring the upstream mechanisms, we determined that dopamine, which inhibits PRL secretion in male rats, did not decrease in the pituitary gland of DES-treated rats, whereas vasoactive intestinal peptide (VIP), which mediates the acute release of PRL, was elevated. Serotonin (5-HT) increased in the brain of male rats 24 hours after a single DES treatment; however, PRL, VIP or 5-HT was not induced by DES in female rats. Our results indicate that DES induces the expression of pituitary PRL in male rats by stimulating VIP in the hypothalamus and 5-HT in the central nervous system.

Suppression of liver Apo E secretion leads to HDL/cholesterol immaturity in rats administered ethinylestradiol

Ethinylestradiol (EE), a main component of the combined oral contraceptive pill, is associated with an increased risk of arterial diseases. However, the toxicity mechanism of EE is poorly understood. In this study, we found that the exposure to EE reduced the serum apolipoprotein E (Apo E) level and high-density lipoprotein (HDL)/cholesterol concentration in adult female rats. Diethylstilbestrol showed the same effects and both reductions were suppressed by coadministration of tamoxifen (TAM). Liver perfusion experiments revealed that the secretion rate of Apo E from the liver was significantly reduced. It is concluded that EE damages the maturation of HDL/cholesterol by delaying Apo E secretion from the liver, and this may lead to an increased risk of arterial diseases, such as atheromas.

Adrenal steroidogenesis disruption caused by HDL/cholesterol suppression in diethylstilbestrol-treated adult male rat

The synthetic estrogen diethylstilbestrol is used to prevent miscarriages and as a therapeutic treatment for prostate cancer, but it has been reported to have adverse effects on endocrine homeostasis. However, the toxicity mechanism is poorly understood. Recently, we reported that diethylstilbestrol impairs adrenal steroidogenesis via cholesterol insufficiency in adult male rats. In the present study, we found that the adrenal cholesterol level was significantly reduced without of the decrease in other precursors in the adrenal steroidogenesis 24 h after a single dose of diethylstilbestrol (0.33 μg/g body mass). The serum HDL/cholesterol level was also reduced only 12 h after the diethylstilbestrol exposure. The level of Apo E, which is indispensable for HDL/cholesterol maturation, was decreased in both the HDL and VLDL/LDL fractions, whereas the level of Apo A1, which is an essential constituent of HDL, was not altered in the HDL fraction. Because the liver is a major source of Apo E and Apo A1, the secretion rates of these proteins were examined using a liver perfusion experiment. The secretion rate of Apo A1 from the liver was consistent between DES-treated and control rats, but that of Apo E was comparatively suppressed in the DES-treated rats. The disruption of adrenal steroidogenesis by diethylstilbestrol was caused by a decrease in serum HDL/cholesterol, which is the main source of adrenal steroidogenesis, due to the inhibition of Apo E secretion from the liver.

DNA hypermethylation of acetoacetyl-CoA synthetase contributes to inhibited cholesterol supply and steroidogenesis in fetal rat adrenals under prenatal nicotine exposure

Prenatal nicotine exposure is a risk factor for intrauterine growth retardation (IUGR). Steroid hormones synthesized from cholesterol in the fetal adrenal play an important role in the fetal development. The aim of this study is to investigate the effects of prenatal nicotine exposure on steroidogenesis in fetal rat adrenals from the perspective of cholesterol supply and explore the underlying epigenetic mechanisms. Pregnant Wistar rats were administered 1.0mg/kg nicotine subcutaneously twice a day from gestational day (GD) 7 to GD17. The results showed that prenatal nicotine exposure increased IUGR rates. Histological changes, decreased steroid hormone concentrations and decreased cholesterol supply were observed in nicotine-treated fetal adrenals. In the gene expression array, the expression of genes regulating ketone metabolic process decreased in nicotine-treated fetal adrenals. The following conjoint analysis of DNA methylation array with these differentially expressed genes suggested that acetoacetyl-CoA synthetase (AACS), the enzyme utilizing ketones for cholesterol supply, may play an important role in nicotine-induced cholesterol supply deficiency. Moreover, the decreased expression of AACS and increased DNA methylation in the proximal promoter of AACS in the fetal adrenal was verified by real-time reverse-transcription PCR (RT-PCR) and bisulfite sequencing PCR (BSP), respectively. In conclusion, prenatal nicotine exposure can cause DNA hypermethylation of the AACS promoter in the rat fetal adrenal. These changes may result in decreased AACS expression and cholesterol supply, which inhibits steroidogenesis in the fetal adrenal.

Analysis of endocrine disruption effect of Roundup® in adrenal gland of male rats

The effect of Roundup^® on adrenal gland steroidogenesis and signaling pathway associated with steroid production was investigated. Doses of 10, 50, 100 and 250 mg/kg bw/d Roundup^® were administered for two weeks to adult male rats. The 10 mg/kg bw/d dose which reduced circulatory corticosterone levels, but did not change food consumption and body weight, was selected for further study. The expression of cholesterol receptor (low density lipoprotein receptor), de novo cholesterol synthesis enzyme (3-hydroxy-3-methylglutaryl-coenzyme A synthase), hormone-sensitive lipase, steroidogenic acute regulatory protein (StAR) mRNA and phosphorylated form was decreased. Adrenocorticotropic hormone receptor (ACTH), melanocortin-2 receptor, expression was not changed but circulatory ACTH levels and adrenal cortex protein kinase A (PKA) activity were reduced. Surprisingly, exogenous ACTH treatment rescued steroidogenesis in Roundup^®-treated animals. Apoptosis was evident at 250 mg/kg bw/d, but not at 10 mg/kg bw/d dose. These results suggest that Roundup^® may be inhibitory to hypothalamic–pituitary axis leading to reduction in cyclic adenosine monophosphate (cAMP)/PKA pathway, StAR phosphorylation and corticosterone synthesis in the adrenal tissue.

Increased DNA methylation of scavenger receptor class B type I contributes to inhibitory effects of prenatal caffeine ingestion on cholesterol uptake and steroidogenesis in fetal adrenals

Steroid hormones synthesized from cholesterol in the fetal adrenal are crucial for fetal development. We have observed the inhibited fetal adrenal corticosterone synthesis and increased intrauterine growth retardation (IUGR) rate in rats under prenatal caffeine ingestion. The aim of this study is to evaluate the effects of prenatal caffeine ingestion on cholesterol supply in fetal adrenal steroidogenesis in rats and explore the underlying epigenetic mechanisms. Pregnant Wistar rats were treated with 60 mg/kg · d caffeine from gestational day (GD) 7 to GD17. Histological changes of fetal adrenals and increased IUGR rates were observed in the caffeine group. There were significantly decreased steroid hormone contents and cholesterol supply in caffeine-treated fetal adrenals. Data from the gene expression array suggested that prenatal caffeine ingestion caused increased expression of genes related to DNA methylation and decreased expression of genes related to cholesterol uptake. The following conjoint analysis of DNA methylation array with these differentially expressed genes suggested that scavenger receptor class B type I (SR-BI) may play an important role in caffeine-induced cholesterol supply deficiency. Moreover, real-time RT-PCR and immunohistochemical detection certified the inhibitory effects of caffeine on both mRNA expression and protein expression of SR-BI in the fetal adrenal. And the increased DNA methylation frequency in the proximal promoter of SR-BI was confirmed by bisulfite-sequencing PCR. In conclusion, prenatal caffeine ingestion can induce DNA hypermethylation of the SR-BI promoter in the rat fetal adrenal. These effects may lead to decreased SR-BI expression and cholesterol uptake, which inhibits steroidogenesis in the fetal adrenal.