Fetal hypothalamus-pituitary-adrenal responses to estradiol sulfate

Steroid Sulfation in Adrenal Tumors

CONTEXT

The adrenal cortex produces specific steroid hormones including steroid sulfates such as dehydroepiandrosterone sulfate (DHEAS), the most abundant steroid hormone in the human circulation. Steroid sulfation involves a multistep enzyme machinery that may be impaired by inborn errors of steroid metabolism. Emerging data suggest a role of steroid sulfates in the pathophysiology of adrenal tumors and as potential biomarkers.

EVIDENCE ACQUISITION

Selective literature search using "steroid," "sulfat*," "adrenal," "transport," "mass spectrometry" and related terms in different combinations.

EVIDENCE SYNTHESIS

A recent study highlighted the tissue abundance of estrogen sulfates to be of prognostic impact in adrenocortical carcinoma tissue samples using matrix-assisted laser desorption ionization mass spectrometry imaging. General mechanisms of sulfate uptake, activation, and transfer to substrate steroids are reasonably well understood. Key aspects of this pathway, however, have not been investigated in detail in the adrenal; these include the regulation of substrate specificity and the secretion of sulfated steroids. Both for the adrenal and targeted peripheral tissues, steroid sulfates may have relevant biological actions beyond their cognate nuclear receptors after desulfation. Impaired steroid sulfation such as low DHEAS in Cushing adenomas is of diagnostic utility, but more comprehensive studies are lacking. In bioanalytics, the requirement of deconjugation for gas-chromatography/mass-spectrometry has precluded the study of steroid sulfates for a long time. This limitation may be overcome by liquid chromatography/tandem mass spectrometry.

CONCLUSIONS

A role of steroid sulfation in the pathophysiology of adrenal tumors has been suggested and a diagnostic utility of steroid sulfates as biomarkers is likely. Recent analytical developments may target sulfated steroids specifically.

A transcriptomics model of estrogen action in the ovine fetal hypothalamus: evidence for estrogenic effects of ICI 182,780

Estradiol plays a critical role in stimulating the fetal hypothalamus-pituitary-adrenal axis at the end of gestation. Estradiol action is mediated through nuclear and membrane receptors that can be modulated by ICI 182,780, a pure antiestrogen compound. The objective of this study was to evaluate the transcriptomic profile of estradiol and ICI 182,780, testing the hypothesis that ICI 182,780 antagonizes the action of estradiol in the fetal hypothalamus. Chronically catheterized ovine fetuses were infused for 48 h with: vehicle (Control, n = 6), 17β-estradiol 500 μg/kg/day (Estradiol, n = 4), ICI 182,780 5 μg/kg/day (ICI 5 μg, n = 4) and ICI 182,780 5 mg/kg/day (ICI 5 mg, n = 5). Fetal hypothalami were collected afterward, and gene expression was measured through microarray. Statistical analysis of transcriptomic data was performed with Bioconductor-R and Cytoscape software. Unexpectedly, 35% and 15.5% of the upregulated differentially expressed genes (DEG) by Estradiol significantly overlapped (P < 0.05) with upregulated DEG by ICI 5 mg and ICI 5 μg, respectively. For the downregulated DEG, these percentages were 29.9% and 15.5%, respectively. There was almost no overlap for DEG following opposite directions between Estradiol and ICI ICI 5 mg or ICI 5 μg. Furthermore, most of the genes in the estrogen signaling pathway - after activation of the epidermal growth factor receptor - followed the same direction in Estradiol, ICI 5 μg or ICI 5 mg compared to Control. In conclusion, estradiol and ICI 182,780 have estrogenic genomic effects in the developing brain, suggesting the possibility that the major action of estradiol on the fetal hypothalamus involves another receptor system rather than estrogen receptors.

Ketamine modulates fetal hemodynamic and endocrine responses to umbilical cord occlusion

Umbilical cord occlusion (UCO) is a hypoxic insult that has been used to model birth asphyxia and umbilical cord compression in utero. UCO triggers vigorous neural and endocrine responses that include increased plasma ACTH and cortisol concentrations, increased blood pressure (BP), and decreased heart rate (HR). We have previously reported that ketamine, a noncompetitive N‐methyl‐D‐aspartate receptor antagonist, can modify the fetal hemodynamic and ACTH responses to ventilatory hypoxia and cerebral ischemia‐reperfusion. We performed the present experiments to test the hypothesis that ketamine has similar effects on the neuroendocrine and cardiovascular responses to UCO. Fetal sheep were chronically catheterized at gestational day 125. Ketamine (3 mg/kg) was administered intravenously to the fetus 10 min prior to the insult. UCO was induced for 30 min by reducing the umbilical vein blood flow until fetal P_aO₂ levels were reduced from 17 ± 1 to 11 ± 1 mm Hg. UCO produced an initial increase on fetal BP in both control and ketamine groups (P = 0.018 time), followed by a decrease in the control group, but values remained higher with ketamine. HR decreased after UCO (P = 0.041 stimulus*time) in both groups, but the reduction was greater initially in control compared to ketamine groups. Fetal P_aCO₂ levels increased after UCO (P < 0.01 stimulus*time), but values were higher in the control versus ketamine groups. UCO significantly decreased fetal pH values (P < 0.01 stimulus*time) with a greater effect on the control versus ketamine group. Ketamine delayed the cortisol responses to UCO (P < 0.001 stimulus*time), and UCO produced a robust increase in ACTH levels from 19 ± 2 to 280 ± 27 pg/mL (P < 0.001 stimulus*time), but there were no differences in ACTH levels between UCO groups. We conclude that ketamine augmented the cardiovascular response to UCO, but did not alter the ACTH response to UCO.

Accurate determination of tissue steroid hormones, precursors and conjugates in adult male rat

The actual levels of steroid hormones in organs are vital for endocrine, reproductive and neuronal health and disorders. We developed an accurate method to determine the levels of steroid hormones and steroid conjugates in various organs by an efficient preparation using a solid-phase-extraction cartridge. Each steroid was identified by the precursor ion spectra using liquid chromatography-electrospray ionization time-of-flight mass spectrometry, and the respective steroids were quantitatively analysed in the selected reaction monitoring mode by liquid chromatograph-mass spectrometry/mass spectrometry (LC-MS/MS). The data showed that significant levels of testosterone, corticosterone and precursors of both hormones were detected in all organs except liver. The glucuronide conjugates of steroid hormones and the precursors were detected in all organs except liver, but sulfate conjugates of these steroids were observed only in the target organs of the hormones and kidney. Interestingly, these steroids and the conjugates were not observed in the liver except pregnenolone. In conclusion, an accurate determination of tissue steroids was developed using LC-MS analysis. Biosynthesis of steroid hormones from the precursors was estimated even in the target organs, and the delivery of these steroid conjugates was also suggested via the circulation without any significant hepatic participation.

Genomics of estradiol-3-sulfate action in the ovine fetal hypothalamus

In fetal sheep during late gestation sulfoconjugated estrogens in plasma reach a concentration 40-100 times greater than unconjugated estrogens. The objective of the present study was to determine the genomics of estradiol-3-sulfate (E(2)S) action in the ovine fetal brain. The hypothesis was that E(2)S stimulates genes involved in the neuroendocrine pathways that direct or facilitate fetal development at the end of gestation. Four sets of chronically catheterized ovine twin fetuses were studied (gestational age: 120-127 days gestation) with one infused with E(2)S intracerebroventricularly (1 mg/day) and the other remaining untreated (control). After euthanasia, mRNA samples were extracted from fetal brains. Only hypothalamic samples were employed for this study given the important function of this brain region in the control of the hypothalamus-pituitary-adrenal axis. Microarray analysis was performed following the Agilent protocol for one-color 8 × 15 microarrays, designed for Ovis aries. A total of 363 known genes were significantly upregulated by the E(2)S treatment (P < 0.05). Network and enrichment analyses were performed using the Cytoscape/Bingo software, and the results validated by quantitative real-time PCR. The main overrepresented biological processes resulting from this analysis were feeding behavior, hypoxia response, and transforming growth factor signaling. Notably, the genes involved in the feeding behavior (neuropeptide Y and agouti-related protein) were the most strongly induced by the E(2)S treatment. In conclusion, E(2)S may be an important component of the mechanism for activating orexigenic, hypoxia responsiveness and neuroprotective pathways in the lamb as it approaches postnatal life.