Expression and distribution of glucocorticoid receptors in the ovine fetal adrenal cortex: effect of long-term hypoxia

Evaluation of fetal middle adrenal artery Doppler and fetal adrenal gland size in pregnancies with fetal growth restriction: a case-control study

OBJECTIVES

This study aims to evaluate sonographic measurements of fetal adrenal gland size and middle adrenal artery Doppler in pregnancies with fetal growth restriction (FGR) and in a healthy control group.

METHODS

This prospective study included 107 singleton pregnancies with FGR between 24 and 42 weeks of gestation and 107 pregnancies with fetuses whose growth was appropriate for gestational age (AGA). Adrenal gland size and Doppler parameters of the adrenal artery were measured and the values and obstetric outcomes were compared between the study and control groups.

RESULTS

In the study group, the Z-scores of total adrenal width-length and height, fetal zone width-length and middle adrenal artery-peak systolic velocity (MAA-PSV) were significantly higher than those in the control group (p<0.05). The Z-scores of middle adrenal artery-pulsatility index (MAA-PI) were significantly lower in the study group than in the control group (p<0.05). The rate of neonatal intensive care unit admission in fetuses with high adrenal artery PI scores was higher in the FGR group (p<0.05).

CONCLUSIONS

In the present study, we observed decreased adrenal artery PI, increased adrenal blood flow, and increased fetal adrenal volume in fetuses diagnosed with fetal growth restriction, most likely in response to placental insufficiency and chronic hypoxia.

Effects of maternal dexamethasone treatment early in pregnancy on glucocorticoid receptors in the ovine placenta

The effects of endogenous cortisol on binucleate cells (BNCs), which promote fetal growth, may be mediated by glucocorticoid receptors (GRs), and exposure to dexamethasone (DEX) in early pregnancy stages of placental development might modify this response. In this article, we have investigated the expression of GR as a determinant of these responses. Pregnant ewes carrying singleton fetuses (n = 119) were randomized to control (2 mL saline/ewe) or DEX-treated groups (intramuscular injections of 0.14 mg/kg ewe weight per 12 hours) at 40 to 41 days of gestation (dG). Placental tissue was collected at 50, 100, 125, and 140 dG. Total glucocorticoid receptor protein (GRt) was increased significantly by DEX at 50 and 125 dG in females only, but decreased in males at 125 dG as compared to controls. Glucocorticoid receptor α (GRα) protein was not changed after DEX treatment. Three BNC phenotypes were detected regarding GRα expression (++, +-, --), DEX increased the proportion of (++) and decreased (--) BNC at 140 dG. Effects were sex- and cell type dependent, modifying the responsiveness of the placenta to endogenous cortisol. We speculate that 3 maturational stages of BNCs exist and that the overall activity of BNCs is determined by the distribution of these 3 cell types, which may become altered through early pregnancy exposure to elevated glucocorticoids.

Glucocorticoid receptor and molecular chaperones in the pathogenesis of adrenal incidentalomas: potential role of reduced sensitivity to glucocorticoids

Glucocorticoid (GC) sensitivity depends on glucocorticoid receptor (GR) and heat shock proteins (Hsps). We investigated whether common GR genes (ER22/23EK, N363S, Bcl I, and 9β) and adrenocorticotropin receptor promoter polymorphisms influence susceptibility for unilateral adrenal incidentaloma (AI), plus GR and Hsp expression in tumorous (n = 19), peritumorous (n = 13) and normal adrenocortical (n = 11) tissues. Patients (n = 112), population-matched controls (n = 100) and tumor tissues (n = 32) were genotyped for these polymorphisms. Postdexamethasone serum cortisol was higher in patients (p < 0.001). GR gene variants, larger allele of Bcl I (odds ratio [OR] 2.9; 95% confidence interval [CI] 1.7-5.1; p < 0.001] and minor allele of 9β (OR 3.0; 95% CI 1.6-5.7; p < 0.001) were independent predictors of AI. In patients, the first allele is linked with larger tumors (p = 0.002) and the latter with higher postdexamethasone cortisol levels (p = 0.025). Both allele carriers had lesser waist circumference (p = 0.02), similar adrenocorticotropin and higher basal (p = 0.024) and postdexamethasone cortisol concentrations (p < 0.001). Tumorous and constitutional genotypes were similar. GR-D is the major receptor isoform in normal adrenal cortex by Western blotting. Loss of other receptor isoforms, decrease in immunostaining for GR (p < 0.0001), underexpression of chaperones (p ≤ 0.01) and the presence of inducible Hsp70 were found in adenomas. In conclusion, GR gene variants, C allele of Bcl I and minor allele of 9β, are associated with AIs. Their concurrent presence in patients reduces GC sensitivity. Normal adrenal cortex preferentially expresses GR-D. In adenomas, the lack of other GR isoforms and underexpression of heat shock proteins perhaps permanently impair GC signaling, which could promote dysregulated cortisol production and tumor growth. The innate GC sensitivity probably modifies these effects.

Maternal undernutrition programs offspring adrenal expression of steroidogenic enzymes

The aim of this study was to determine the influence of maternal undernutrition (MUN) on maternal and offspring adrenal steroidogenic enzymes. Pregnant Sprague-Dawley rats were 50% food-restricted from day 10 of gestation until delivery. Control animals received ad libitum food. Offspring were killed on day 1 of life (P1) and at 9 months. We determined the messenger RNA (mRNA) expression of steroidogenic enzymes by real-time reverse transcriptase polymerized chain reaction (RT-PCR). Maternal undernutrition inhibited maternal adrenal expression of P450 cholesterol side-chain cleavage enzyme (CYP11A1), 11 beta-hydroxylase (CYP11B1), aldosterone synthase (CYP11B2), and adrenocorticotropic hormone (ACTH) receptor (ACTH-R; MC2 gene) compared with control offspring. There was a marked downregulation in the expression of CYP11B1, CYP11B2, 11 β-hydroxysteroid dehydrogenase type 1 and 2 (HSD1 and HSD2), CYP11A1, ACTH receptor, steroidogenic acute regulatory protein (STAR), and mineralocorticoid receptor (MCR; NR3C2 gene) mRNA in P1 MUN offspring (both genders), with no changes in glucocorticoid receptor (GCR). Quantitative immunohistochemical analysis confirmed the PCR data for GCR and MCR in P1 offspring and demonstrated lower expression of leptin receptor protein (Ob-Ra/Ob-Rb) and mRNA in P1 MUN offspring. In 9-month adult male MUN offspring, the expression of HSD1, CYP11A1, CYP11B2, Ob-Ra/Ob-Rb, and GCR mRNA were significantly upregulated with a trend toward an increase in ACTH-R and a decrease in 17 alpha-hydroxylase (CYP17A1) expression. In adult female MUN offspring, similar to males, the expression of CYP11A1, ACTH-R, and Ob-Rb mRNA were increased, whereas GCR and CYP17A1 mRNA were decreased. These results indicate that the adrenal gland is a target of nutritional programming. In utero undernutrition has a global suppressive effect on maternal and P1 offspring adrenal steroidogenic enzymes in association with reduced circulating corticosterone levels in P1 offspring, which may be secondary to a negative feedback from elevated maternal GC levels and or leptin levels in MUN dams. Gender-specific differences in steroidogenic enzyme expression were found in adult MUN offspring. The common finding of increased ACTH receptor expression in MUN adults of both genders suggests an increased sensitivity of these offspring to stress.

Discovery of glucocorticoid receptor-beta in mice with a role in metabolism

Glucocorticoid hormones control diverse physiological processes, including metabolism and immunity, by activating the major glucocorticoid receptor (GR) isoform, GRalpha. However, humans express an alternative isoform, human (h)GRbeta, that acts as an inhibitor of hGRalpha to produce a state of glucocorticoid resistance. Indeed, evidence exists that hGRbeta contributes to many diseases and resistance to glucocorticoid hormone therapy. However, rigorous testing of the GRbeta contribution has not been possible, because rodents, especially mice, are not thought to express the beta-isoform. Here, we report expression of GRbeta mRNA and protein in the mouse. The mGRbeta isoform arises from a distinct alternative splicing mechanism utilizing intron 8, rather than exon 9 as in humans. The splicing event produces a form of beta that is similar in structure and functionality to hGRbeta. Mouse (m)GRbeta has a degenerate C-terminal region that is the same size as hGRbeta. Using a variety of newly developed tools, such as a mGRbeta-specific antibody and constructs for overexpression and short hairpin RNA knockdown, we demonstrate that mGRbeta cannot bind dexamethasone agonist, is inhibitory of mGRalpha, and is up-regulated by inflammatory signals. These properties are the same as reported for hGRbeta. Additionally, novel data is presented that mGRbeta is involved in metabolism. When murine tissue culture cells are treated with insulin, no effect on mGRalpha expression was observed, but GRbeta was elevated. In mice subjected to fasting-refeeding, a large increase of GRbeta was seen in the liver, whereas mGRalpha was unchanged. This work uncovers the much-needed rodent model of GRbeta for investigations of physiology and disease.

Long-term hypoxia increases endothelial nitric oxide synthase expression in the ovine fetal adrenal

This study was designed to test the hypothesis that fetal adrenal nitric oxide synthase (NOS) is elevated in response to long-term hypoxia (LTH). Pregnant ewes were maintained at high altitude (3820 m) for approximately the last 100 days of gestation. Between days 138 and 141 of gestation, adrenal glands were collected from LTH fetuses and age-matched normoxic controls. Quantitative real-time polymerase chain reaction (qRT-PCR) and Western analysis were used to quantify NOS expression, and NOS distribution was examined by immunohistochemistry and double-staining immunofluorescence for endothelial NOS (eNOS) and 17alpha-hydroxylase (CYP17). Neuronal NOS (nNOS) was expressed at very low levels and with no differences between groups. Expression of eNOS was significantly greater in the LTH group compared with control. Neuronal NOS was distributed throughout the cortex while the greatest density of eNOS was observed in the zona fasciculata/reticularis area and eNOS co-localized with CYP17. We conclude that LTH enhances eNOS expression in the inner adrenal cortex which may play a role in regulation of cortisol biosynthesis in the LTH fetus.