Metyrapone-induced glucocorticoid depletion modulates tyrosine hydroxylase and phenylethanolamine N-methyltransferase gene expression in the rat adrenal gland by a noncholinergic transsynaptic activation

Optimal timing of oral metyrapone intake for the suppression of cold-pressor stress-induced cortisol release

BACKGROUND

Pharmacological manipulation of cortisol levels is instrumental in elucidating mechanisms underlying acute stress effects and for distinguishing the physiological and behavioral effects of cortisol from those of the adrenergic system. Administration (oral or IV) of hydrocortisone is a direct and efficient method to elevate cortisol, and thus, frequently used in psychobiological stress research. However, lowering of cortisol (i.e. blockade of stress cortisol) requires a more sophisticated approach, such as the administration of the corticostatic compound metyrapone (MET). However, there is insufficient knowledge about the temporal dynamics of MET for the blocking of stress-induced cortisol reactivity. Thus, the present study aimed to build up an experimental protocol suitable to suppress acute behavioral stress-induced cortisol secretion by MET.

METHODS

50 healthy young men were randomly assigned to one of five treatment groups. They received 750 mg oral MET either 30 (n = 9), 45 (n = 11), or 60 (n = 10) minutes before exposure to a combined cold pressor and mental arithmetic test (stress induction), or were subjected to two different control treatments (placebo 60 min before stress (n = 10) or MET 30 min before non-stressful warm-water condition (n = 10)). Salivary cortisol concentration, hemodynamics, and subjective ratings were assessed.

RESULTS

Suppression of cold stress-induced cortisol release was strongest when MET intake was scheduled 30 min prior to stress onset. Cardiovascular stress-responses and subjective ratings remained unaffected by MET.

CONCLUSION

In healthy young males, 750 mg of MET efficiently block cold stress-induced cortisol release when oral administration is scheduled 30 min prior to stress onset. This finding may guide future research in improving timing of suppression of stress-induced cortisol secretion.

Maternal anxiety affects embryo implantation via impairing adrenergic receptor signaling in decidual cells

Recurrent implantation failure (RIF) is defined as the failed pregnancy after good embryo transfer over 3 cycles during in vitro fertilization (IVF).The human endometrium plays a vital role in providing the site for embryo implantation, with several factors implicated in unsatisfactory endometrial receptivity in RIF. Our present results revealed that women with pregnancy loss or infertility have a higher serum epinephrine level, indicating a potential correlation between psychological stress and pregnancy failure. RNA-sequencing of the tissues collected at the endometrial receptive phase in normal and RIF women showed that stress hormones could affect the functional status of endometrial receptivity. Subsequent analysis revealed that the epinephrine signaling acts as an important regulator of endometrial receptivity through the PI3K-AKT and FOXO1 signaling pathways. We also found that patients with RIF show attenuated expression of the alpha-2C-adrenergic receptor (ADRA2C) and that its down regulation induced by high level epinephrine could inhibit the decidualization. Early pregnant mice treated with stress showed high serum epinephrine levels, defective uterine adrenergic receptor expression, and low pregnancy rates. Altogether, our findings indicate that mental stress during early pregnancy can alter the functional status of endometrial receptivity.

An Ethanolic Extract of Cucurbita pepo L. Seeds Modifies Neuroendocrine Disruption in Chronic Stressed Rats and Adrenal Expression of Inflammatory Markers and HSP70

Background: Pumpkins (Cucurbita pepo L.) were described to have antioxidant, anti-inflammatory, anti-fatigue, and antidepressant-like effect. The adrenal gland is an important stress-responsive organ that maintains homeostasis during stress.

Objectives: This study aimed to assess the efficacy of the administration of Cucurbita pepo L. (CP) extract in relieving behavioral, biochemical, and structural changes in the adrenal gland induced by exposure to chronic unpredictable mild stress (CUMS) and to explore the mechanism behind this impact.

Materials and Methods: Forty male albino rats were divided into 4 groups (n = 10): control, CUMS, fluoxetine-treated, and CP-treated groups. Behavioral changes, corticosterone level, pro-inflammatory cytokines TNF-α and IL-6, and oxidant/antioxidant profile were assessed in the serum at the end of the experiment. Adrenal glands were processed for histopathological and immunohistochemical assessment. Gene expression of caspase-3 and Ki67 and heat shock protein 70 (HSP70) were assessed in adrenal glands using RT-PCR.

Results: The CP extract significantly reduced the corticosterone level (p < 0.001), immobility time (p < 0.001), and inflammatory and oxidative changes associated with CUMS-induced depression compared to the untreated group. The CP extract alleviated CUMS-induced adrenal histopathological changes and significantly reduced apoptosis (p < 0.001) and significantly upregulated antioxidant levels in the serum.

Conclusion:Cucurbita pepo L. effectively ameliorated the chronic stress-induced behavioral, biochemical, and adrenal structural changes mostly through its antioxidant and anti-inflammatory effects.

Glucocorticoid withdrawal affects stress-induced changes of urocortin 2 gene expression in rat adrenal medulla and brain

Corticotropin-releasing factor is well known activator of the hypothalamic-pituitary-adrenocortical axis, that represents crucial system participating on stress response of the organism. Urocortins are members of the corticotropin-releasing factor family of peptides with proposed effects on neuroendocrine and behavioral stress response mechanisms. Urocortin 2, one of three known urocortins, is present in central and peripheral stress response system and its expression can be augmented by glucocorticoids. In the present study we have examined how glucocorticoid withdrawal affects urocortin 2 gene expression after acute immobilization in the adrenal medulla and selected brain areas in rats. We used pharmacological adrenalectomy to block synthesis of corticosterone. Our results show that the immobilization-induced rise in urocortin 2 mRNA levels in rat adrenal medulla was not inhibited by glucocorticoid withdrawal. On the other hand, observed changes in the brain indicate that the effect of stress and pharmacological adrenalectomy on urocortin 2 gene expression is site-specific. While in the paraventricular nucleus and locus coeruleus the immobilization induced rise of urocortin 2 was not inhibited by pharmacological adrenalectomy in the arcuate nucleus and central amygdala it was. Moreover, we have seen a significant depletion of urocortin 2 plasma levels after immobilization. The immobilization induced rise of urocortin 2 gene expression in rat adrenal medulla and brain areas regulating stress response pathways and preservation of its induction after adrenalectomy suggests a role of urocortin 2 in the neuroendocrine stress response of an organism. This article is protected by copyright. All rights reserved.

On the origin of information in epigenetic structures in metazoans

Epigenetic inheritance implies the existence of epigenetic information. Great progress has been made in recent years in understanding the role of the changes in epigenetic structures (methylated DNA, histone acetylation/deacetylation and chromatin remodelling) as well as the role of miRNA (MIR) expression patterns in epigenetic processes. However, as of yet, we do not have a satisfactory understanding of the origin of epigenetic information stored in, and conveyed by, these structures. We do not know whether these structures are the ultimate source of the information or whether they are simply media for storing and transmitting epigenetic information for gene expression from upstream sources to the phenotype. Herein an attempt is made to ascertain the ultimate sources of the epigenetic information they contain and transmit by tracing back the causal chain leading to the changes in epigenetic structures.

Pathway analysis reveals common pro-survival mechanisms of metyrapone and carbenoxolone after traumatic brain injury

Developing new pharmacotherapies for traumatic brain injury (TBI) requires elucidation of the neuroprotective mechanisms of many structurally and functionally diverse compounds. To test our hypothesis that diverse neuroprotective drugs similarly affect common gene targets after TBI, we compared the effects of two drugs, metyrapone (MT) and carbenoxolone (CB), which, though used clinically for noncognitive conditions, improved learning and memory in rats and humans. Although structurally different, both MT and CB inhibit a common molecular target, 11β hydroxysteroid dehydrogenase type 1, which converts inactive cortisone to cortisol, thereby effectively reducing glucocorticoid levels. We examined injury-induced signaling pathways to determine how the effects of these two compounds correlate with pro-survival effects in surviving neurons of the injured rat hippocampus. We found that treatment of TBI rats with MT or CB acutely induced in hippocampal neurons transcriptional profiles that were remarkably similar (i.e., a coordinated attenuation of gene expression across multiple injury-induced cell signaling networks). We also found, to a lesser extent, a coordinated increase in cell survival signals. Analysis of injury-induced gene expression altered by MT and CB provided additional insight into the protective effects of each. Both drugs attenuated expression of genes in the apoptosis, death receptor and stress signaling pathways, as well as multiple genes in the oxidative phosphorylation pathway such as subunits of NADH dehydrogenase (Complex1), cytochrome c oxidase (Complex IV) and ATP synthase (Complex V). This suggests an overall inhibition of mitochondrial function. Complex 1 is the primary source of reactive oxygen species in the mitochondrial oxidative phosphorylation pathway, thus linking the protective effects of these drugs to a reduction in oxidative stress. The net effect of the drug-induced transcriptional changes observed here indicates that suppressing expression of potentially harmful genes, and also, surprisingly, reduced expression of pro-survival genes may be a hallmark of neuroprotective therapeutic effects.

Chronic stress induces adrenal hyperplasia and hypertrophy in a subregion-specific manner

The adrenal gland is an essential stress-responsive organ that is part of both the hypothalamic-pituitary-adrenal axis and the sympatho-adrenomedullary system. Chronic stress exposure commonly increases adrenal weight, but it is not known to what extent this growth is due to cellular hyperplasia or hypertrophy and whether it is subregion specific. Moreover, it is not clear whether increased production of adrenal glucocorticoid after chronic stress is due to increased sensitivity to adrenocorticotropic hormone (ACTH) vs. increased maximal output. The present studies use a 14-day chronic variable stress (CVS) paradigm in adult male rats to assess the effects of chronic stress on adrenal growth and corticosterone steroidogenesis. Exogenous ACTH administration (0-895 ng/100 g body wt) to dexamethasone-blocked rats demonstrated that CVS increased maximal plasma and adrenal corticosterone responses to ACTH without affecting sensitivity. This enhanced function was associated with increased adrenal weight, DNA and RNA content, and RNA/DNA ratio after CVS, suggesting that both cellular hyperplasia and hypertrophy occurred. Unbiased stereological counting of cells labeled for Ki67 (cell division marker) or 4,6-diamidino-2-phenylindole (nuclear marker), combined with zone specific markers, showed that CVS induced hyperplasia in the outer zona fasciculata, hypertrophy in the inner zona fasciculata and medulla, and reduced cell size in the zona glomerulosa. Collectively, these results demonstrate that increased adrenal weight after CVS is due to hyperplasia and hypertrophy that occur in specific adrenal subregions and is associated with increased maximal corticosterone responses to ACTH. These chronic stress-induced changes in adrenal growth and function may have implications for patients with stress-related disorders.

Altered hypothalamo-pituitary-adrenal and sympatho-adrenomedullary activities in rats bred for high anxiety: central and peripheral correlates

Wistar rats have been selectively bred for high (HABs) or low (LABs) anxiety-related behavior based on results obtained in the elevated-plus maze. They also display robust behavioral differences in a variety of additional anxiety tests. The present study was undertaken to further characterize physiological substrates that contribute to the expression of this anxious trait. We report changes in brain and peripheral structures involved in the regulation of both the hypothalamo-pituitary-adrenal (HPA) and sympatho-adrenal systems. Following exposure to a mild stressor, HABs displayed a hyper-reactivity of the HPA axis associated with a hypo-reactivity of the sympatho-adrenal system and a lower serotonin turnover in the lateral septum and amygdala. At rest, HABs showed a higher adrenal weight and lower tyrosine hydroxylase and phenylethanolamine-N-methyltransferase mRNAs expression in their adrenals than LABs. In the anterior pituitary, HABs also exhibited increased proopiomelanocortin and decreased vasopressin V1b receptor mRNAs expression, whereas glucocorticoid receptor mRNA levels remained unchanged. These results indicate that the behavioral phenotype of HABs is associated with peripheral and central alterations of endocrine mechanisms involved in stress response regulation. Data are discussed in relation to coping strategies adopted to manage stressful situations. In conclusion, HABs can be considered as an useful model to study the etiology and pathophysiology of stress-related disorders and their neuroendocrine substrates.

The adrenal gland of newt Triturus carnifex (Amphibia, Urodela) following in vivo betamethasone administration

The response of the adrenal gland of Triturus carnifex to betamethasone administration was studied; the effects were evaluated by examination of the ultrastructural morphological features of the tissues as well as the serum levels of aldosterone, corticosterone, norepinephrine and epinephrine. In March and June, betamethasone significantly decreased the serum levels of aldosterone and corticosterone and the lipid droplet content in the steroidogenic cells. Moreover, betamethasone influenced the chromaffin tissue, enhancing in March (when the chromaffin cells produce norepinephrine and epinephrine in almost equal quantities) epinephrine serum levels and the numeric ratio between norepinephrine and epinephrine granules in the chromaffin cells. In June, (when the chromaffin cells contain almost exclusively norepinephrine granules) betamethasone administration raised norepinephrine serum levels, whereas a decrease in the numeric ratio between norepinephrine and epinephrine granules in the chromaffin cells was found. Finally, betamethasone administration did not evoke in June any increase in the mean number of epinephrine granules in the chromaffin cells and/or in epinephrine serum levels, as would be expected if phenyletanolamine-N-methyl transferase (PNMT) enzyme, converting norepinephrine into epinephrine, were activated by corticosteroids. The results of this study showed that betamethasone decreased aldosterone and corticosterone serum levels and enhanced catecholamine serum concentrations. Moreover, the present results suggest that a stimulatory role of glucocorticoids on PNMT enzyme may be ruled out.

Prenatal morphine exposure affects sympathoadrenal axis activity and serotonin metabolism in adult male rats both under basal conditions and after an ether inhalation stress

We have previously shown that prenatal morphine exposure inhibited the hypothalamo-pituitary-adrenal (HPA) axis and altered the hypothalamic metabolism of serotonin during the early postnatal period in the rat and induced a chronic sympathoadrenal hyperactivity under resting conditions in adult male rats. In this study, we examined the effects of prenatal morphine exposure on the responsiveness to an acute ether inhalation stress of the sympathoadrenal and HPA axis and the hippocampal and hypothalamic concentrations of serotonin (5HT) and 5-hydroxylindoleacetic acid (5HIAA) in 3-month-old male rats. The plasma levels of adrenocorticopic hormone (ACTH) and corticosterone (B) did not differ between the two groups both under resting conditions and after ether exposure. Ether inhalation increased adrenal tyrosine hydroxylase (TH) and phenylethanolamine N-methyltransferase (PNMT) mRNA expression as well as adrenal epinephrine (E) concentration in control rats but not in prenatally morphine-exposed (PM) animals. Under basal conditions, hypothalamic concentrations of 5HT and 5HIAA increased in PM animals. In contrast to control animals, PM rats showed, in response to stress, an increased level of 5HT and 5HIAA in both the hypothalamus and in the hippocampus. In conclusion, prenatal morphine exposure produces long-lasting alterations in brain serotonin transmission and in the sympathoadrenal responsiveness to an acute systemic stress.

Stress and glucocorticoid inhibit apical GLUT2-trafficking and intestinal glucose absorption in rat small intestine

We have proposed a new model of rat intestinal sugar absorption in which high glucose concentrations promote rapid insertion of GLUT2 into the apical membrane, so that absorptive capacity is precisely regulated to match dietary intake. Construction and building work during expansion and refurbishment of our department permitted opportunistic experiments on the effects of building-induced stress on the GLUT2 component of absorption. In fed rats perfused with 75 mM glucose in vivo, stress rapidly inhibited glucose absorption 36.4 +/- 3.0% compared with control rats. Selective inhibition of the GLUT2 component with phloretin demonstrated that stress inhibited the GLUT2 component by 42.8 +/- 3.8%, which correlated with a corresponding diminution in apical GLUT2 levels: the SGLT1 component and its level were unaltered by stress. Effects of stress were reversed by the administration in drinking water of metyrapone, which inhibits 11-beta-hydroxylase. Injection of dexamethasone into control rats 60 min before perfusion resulted in absorption and transporter properties indistinguishable from stressed rats. Our data are consistent with the view that stress activates the hypothalamus-pituitary-adrenal (HPA) axis, causing release of glucocorticoid. The ensuing inhibition of GLUT2 trafficking and absorption seems necessary to prevent enhanced intestinal delivery of glucose to the circulation from antagonizing the essential stress response of glucorticoid in mobilizing peripheral energy stores for emergency purposes.