Low doses of dexamethasone can produce a hypocorticosteroid state in the brain

Unpredictable chronic mild stress shows neuronal remodeling in multipolar projection neurons of hippocampal complex in postnatal chicks

The hippocampal complex of birds is a narrow-curved strip of tissue that plays a crucial role in learning, memory, spatial navigation, and emotional and sexual behavior. This study was conducted to evaluate the effect of unpredictable chronic mild stress in multipolar neurons of 3-, 5-, 7-, and 9-week-old chick's hippocampal complex. This study revealed that chronic stress results in neuronal remodeling by causing alterations in dendritic field, axonal length, secondary branching, corrected spine number, and dendritic branching at 25, 50, 75, and 100 µm. Due to stress, the overall dendritic length was significantly retracted in 3-week-old chick, whereas no significant difference was observed in 5- and 7-week-old chick, but again it was significantly retracted in 9-week-old chick along with the axonal length. So, this study indicates that during initial days of stress exposure, the dendritic field shows retraction, but when the stress continues up to a certain level, the neurons undergo structural modifications so that chicks adapt and survive in stressful conditions. The repeated exposure to chronic stress for longer duration leads to the neuronal structural disruption by retraction in the dendritic length as well as axonal length. Another characteristic which leads to structural alterations is the dendritic spines which significantly decreased in all age groups of stressed chicks and eventually leads to less synaptic connections, disturbance in physiology, and neurology, which affects the learning, memory, and coping ability of an individual.

The cortisol switch between vulnerability and resilience

In concert with neuropeptides and transmitters, the end products of the hypothalamus-pituitary-adrenal (HPA) axis, the glucocorticoid hormones cortisol and corticosterone (CORT), promote resilience: i.e., the ability to cope with threats, adversity, and trauma. To exert this protective action, CORT activates mineralocorticoid receptors (MR) and glucocorticoid receptors (GR) that operate in a complementary manner -as an on/off switch- to coordinate circadian events, stress-coping, and adaptation. The evolutionary older limbic MR facilitates contextual memory retrieval and supports an on-switch in the selection of stress-coping styles at a low cost. The rise in circulating CORT concentration after stress subsequently activates a GR-mediated off-switch underlying recovery of homeostasis by providing the energy for restraining the primary stress reactions and promoting cognitive control over emotional reactivity. GR activation facilitates contextual memory storage of the experience to enable future stress-coping. Such complementary MR-GR-mediated actions involve rapid non-genomic and slower gene-mediated mechanisms; they are time-dependent, conditional, and sexually dimorphic, and depend on genetic background and prior experience. If coping fails, GR activation impairs cognitive control and promotes emotional arousal which eventually may compromise resilience. Such breakdown of resilience involves a transition to a chronic stress construct, where information processing is crashed; it leads to an imbalanced MR-GR switch and hence increased vulnerability. Novel MR-GR modulators are becoming available that may reset a dysregulated stress response system to reinstate the cognitive flexibility required for resilience.

Glucocorticoid feedback paradox: a homage to Mary Dallman

As the end product of the hypothalamus-pituitary-adrenal (HPA) axis, the glucocorticoid hormones cortisol and corticosterone coordinate circadian activities, stress-coping, and adaptation to change. For this purpose, the hormone promotes energy metabolism and controls defense reactions in the body and brain. This life-sustaining action exerted by glucocorticoids occurs in concert with the autonomic nervous and immune systems, transmitters, growth factors/cytokines, and neuropeptides. The current contribution will focus on the glucocorticoid feedback paradox in the HPA-axis: the phenomenon that stress responsivity remains resilient if preceded by stress-induced secretion of glucocorticoid hormone, but not if this hormone is previously administered. Furthermore, in animal studies, the mixed progesterone/glucocorticoid antagonist RU486 or mifepristone switches to an apparent partial agonist upon repeated administration. To address these enigmas several interesting phenomena are highlighted. These include the conditional nature of the excitation/inhibition balance in feedback regulation, the role of glucose as a determinant of stress responsivity, and the potential of glucocorticoids in resetting the stress response system. The analysis of the feedback paradox provides also a golden opportunity to review the progress in understanding the role of glucocorticoid hormone in resilience and vulnerability during stress, the science that was burned deeply in Mary Dallman's emotions.

Commentary: Discussing the antidepressant potential of silymarin

The therapeutic potential of diet, dietary supplements, herbal remedies, and nutraceuticals for treatment of depression and anxiety is being increasingly explored. In this commentary, we discuss the recent findings on the antidepressant potential of silymarin (SILY) in mice and present an alternative approach. We highlight the extensive research on another phytochemical, curcumin, for the treatment of depression and anxiety. Finally, we suggest a future application, which investigates the potential synergistic effects of combined treatment with SILY and curcumin for depression.

The response to stressors in adulthood depends on the interaction between prenatal exposure to glucocorticoids and environmental context

Maternal stress during reproduction can influence how offspring respond to stress later in life. Greater lifetime exposure to glucocorticoid hormones released during stress is linked to greater risks of behavioral disorders, disease susceptibility, and mortality. The immense variation in individual's stress responses is explained, in part, by prenatal glucocorticoid exposure. To explore the long-term effects of embryonic glucocorticoid exposure, we injected Japanese quail (Coturnix japonica) eggs with corticosterone. We characterized the endocrine stress response in offspring and measured experienced aggression at three different ages. We found that prenatal glucocorticoid exposure affected (1) the speed at which the stress response was terminated suggesting dysregulated negative feedback, (2) baseline corticosterone levels in a manner dependent on current environmental conditions with higher levels of experienced aggression associated with higher levels of baseline corticosterone, (3) the magnitude of an acute stress response based on baseline concentrations. We finish by proposing a framework that can be used to test these findings in future work. Overall, our findings suggest that the potential adaptive nature of prenatal glucocorticoid exposure is likely dependent on environmental context and may also be tempered by the negative effects of longer exposure to glucocorticoids each time an animal faces a stressor.

The contribution of the neuroendocrine system to adaption after repeated daily ozone exposure in rats

Ozone-induced lung injury/inflammation dissipates despite continued exposure for 3 or more days; however, the mechanisms of adaptation/habituation remain unclear. Since ozone effects are mediated through adrenal-derived stress hormones, which also regulate longevity of centrally-mediated stress response, we hypothesized that ozone-adaptation is linked to diminution of neuroendocrine stress-axes activation and glucocorticoid levels. Male Wistar-Kyoto-rats (12-week-old) were injected with vehicle or a therapeutically-relevant dexamethasone dose (0.01-mg/kg/day; intraperitoneal) for 1-month to determine if suppression of glucocorticoid signaling was linked to adaptation. Vehicle- and dexamethasone-treated rats were exposed to air or 0.8-ppm ozone, 4 h/day × 2 or 4 days to assess the impacts of acute exposure and adaptation, respectively. Dexamethasone reduced thymus and spleen weights, circulating lymphocytes, corticosterone and increased insulin. Ozone increased lavage-fluid protein and neutrophils and decreased circulating lymphocytes at day-2 but not day-4. Ozone-induced hyperglycemia, glucose intolerance and inhibition of beta-cell insulin release occurred at day-1 but not day-3. Ozone depleted circulating prolactin, thyroid-stimulating hormone, and luteinizing-hormone at day-2 but not day-4, suggesting central mediation of adaptation. Adrenal epinephrine biosynthesis gene, Pnmt, was induced after ozone exposure at both timepoints. However, genes involved in glucocorticoid biosynthesis were induced after day-2 but not day-4, suggesting that acute 1- or 2-day ozone-mediated glucocorticoid increase elicits feedback inhibition to dampen hypothalamic stimulation of ACTH release in response to repeated subsequent ozone exposures. Although dexamethasone pretreatment affected circulating insulin, lymphocytes and adrenal genes, it had modest effect on ozone adaptation. In conclusion, ozone adaptation likely involves lack of hypothalamic response due to reduced availability of circulating glucocorticoids.

The co-chaperone FKBP51 modulates HPA axis activity and age-related maladaptation of the stress system in pituitary proopiomelanocortin cells

Glucocorticoid (GC)-mediated negative feedback of the hypothalamic-pituitary-adrenal (HPA) axis, the body's physiological stress response system, is tightly regulated and essential for appropriate termination of this hormonal cascade. Disturbed regulation and maladaptive response of this axis are fundamental components of multiple stress-induced psychiatric and metabolic diseases and aging. The co-chaperone FK506 binding protein 51 (FKBP51) is a negative regulator of the GC receptor (GR), is highly stress responsive, and its polymorphisms have been repeatedly associated with stress-related disorders and dysfunctions in humans and rodents. Proopiomelanocortin (Pomc)-expressing corticotropes in the anterior pituitary gland are one of the key cell populations of this closed-loop GC-dependent negative feedback regulation of the HPA axis in the periphery. However, the cell type-specific role of FKBP51 in anterior pituitary corticotrope POMC cells and its impact on age-related HPA axis disturbances are yet to be elucidated. Here, using a combination of endogenous knockout and viral rescue, we show that male mice lacking FKBP51 in Pomc-expressing cells exhibit enhanced GR-mediated negative feedback and are protected from age-related disruption of their diurnal corticosterone (CORT) rhythm. Our study highlights the complexity of tissue- and cell type-specific, but also cross-tissue effects of FKBP51 in the rodent stress response at different ages and extends our understanding of potential targets for pharmacological intervention in stress- and age-related disorders.

Mineralocorticoid receptor and glucocorticoid receptor work alone and together in cell-type-specific manner: Implications for resilience prediction and targeted therapy

‘You can't roll the clock back and reverse the effects of experiences' Bruce McEwen used to say when explaining how allostasis labels the adaptive process. Here we will for once roll the clock back to the times that the science of the glucocorticoid hormone was honored with a Nobel prize and highlight the discovery of their receptors in the hippocampus as inroad to its current status as master regulator in control of stress coping and adaptation. Glucocorticoids operate in concert with numerous neurotransmitters, neuropeptides, and other hormones with the aim to facilitate processing of information in the neurocircuitry of stress, from anticipation and perception of a novel experience to behavioral adaptation and memory storage. This action, exerted by the glucocorticoids, is guided by two complementary receptor systems, mineralocorticoid receptors (MR) and glucocorticoid receptors (GR), that need to be balanced for a healthy stress response pattern. Here we discuss the cellular, neuroendocrine, and behavioral studies underlying the MR:GR balance concept, highlight the relevance of hypothalamic-pituitary-adrenal (HPA) -axis patterns and note the limited understanding yet of sexual dimorphism in glucocorticoid actions. We conclude with the prospect that (i) genetically and epigenetically regulated receptor variants dictate cell-type-specific transcriptome signatures of stress-related neuropsychiatric symptoms and (ii) selective receptor modulators are becoming available for more targeted treatment. These two new developments may help to ‘restart the clock’ with the prospect to support resilience.

Mineralocorticoid receptor status in the human brain after dexamethasone treatment: a single case study

BACKGROUND

Synthetic glucocorticoids like dexamethasone can cause severe neuropsychiatric effects. They preferentially bind to the glucocorticoid receptor (GR) over the mineralocorticoid receptor (MR). High dosages result in strong GR activation but likely also result in lower MR activation based on GR-mediated negative feedback on cortisol levels. Therefore, reduced MR activity may contribute to dexamethasone-induced neuropsychiatric symptoms.

OBJECTIVE

In this single case study, we evaluate whether dexamethasone leads to reduced MR activation in the human brain. Brain tissue of an 8-year-old brain tumor patient was used, who suffered chronically from dexamethasone-induced neuropsychiatric symptoms and deceased only hours after a high dose of dexamethasone.

MAIN OUTCOME MEASURES

The efficacy of dexamethasone to induce MR activity was determined in HEK293T cells using a reporter construct. Subcellular localization of GR and MR was assessed in paraffin-embedded hippocampal tissue from the patient and two controls. In hippocampal tissue from the patient and eight controls, mRNA of MR/GR target genes was measured.

RESULTS

In vitro, dexamethasone stimulated MR with low efficacy and low potency. Immunofluorescence showed the presence of both GR and MR in the hippocampal cell nuclei after dexamethasone exposure. The putative MR target gene JDP2 was consistently expressed at relatively low levels in the dexamethasone-treated brain samples. Gene expression showed substantial variation in MR/GR target gene expression in two different hippocampus tissue blocks from the same patient.

CONCLUSIONS

Dexamethasone may induce MR nuclear translocation in the human brain. Conclusions on in vivo effects on gene expression in the brain await the availability of more tissue of dexamethasone-treated patients.

Brain Transcriptome Responses to Dexamethasone Depending on Dose and Sex Reveal Factors Contributing to Sex-Specific Vulnerability to Stress-Induced Disorders

BACKGROUND

Glucocorticoid (GC) receptor (GR) signaling in the hypothalamus (Hyp) and in the superordinate limbic structures, such as the hippocampus (Hip), conveys feedback regulation of the neuroendocrine stress response and acts upon other neurobiological functions that ultimately influence mental health. These responses are strongly influenced by sex, but the molecular causes are still largely unexplored.

METHODS

To investigate GR targets and their GC sensitivity in the Hyp and Hip, we treated juvenile male and female piglets with 10 (D10) or 60 (D60) µg/kg dexamethasone (DEX), a selective GR agonist, and analyzed transcriptome responses compared to a saline control group using RNA sequencing.

RESULTS

Both doses influenced similar biological functions, including cellular response to lipid and immune cell-related functions, but the transcriptional response to D10 was considerably weaker, particularly in the Hip. Weighted Gene Co-expression Network Analysis revealed a network of genes coordinately regulated by DEX in both structures, among which the alpha-arrestin ARRDC2 takes a central position. Distinct functional groups of genes were differentially regulated by DEX between sexes depending on the dose; at D10, these included particularly mitochondrial genes, whereas at D60 interferon signaling and lipid homeostasis genes were enriched. The general and sex-specific transcriptional responses to DEX highlight microglia as the prominent target. Several key marker genes of disease-associated microglia were regulated by DEX depending on sex, such as TREM2 and LPL.

CONCLUSION

The discovered expression signatures suggest that DEX induced a dysfunctional state of microglia in males, while in females microglia were primed, which could entail predisposition for different mental disorders.

The DEXA-CORT trial: study protocol of a randomised placebo-controlled trial of hydrocortisone in patients with brain tumour on the prevention of neuropsychiatric adverse effects caused by perioperative dexamethasone

Introduction

The synthetic glucocorticoid dexamethasone can induce serious neuropsychiatric adverse effects. Dexamethasone activates the glucocorticoid receptor (GR) but, unlike endogenous cortisol, not the mineralocorticoid receptor (MR). Moreover, dexamethasone suppresses cortisol production, thereby eliminating its MR binding. Consequently, GR overactivation combined with MR underactivation may contribute to the neuropsychiatric adverse effects of dexamethasone. The DEXA-CORT trial aims to reactivate the MR using cortisol to reduce neuropsychiatric adverse effects of dexamethasone treatment.

Methods and analysis

The DEXA-CORT study is a multicentre, randomised, double-blind, placebo-controlled trial in adult patients who undergo elective brain tumour resection treated perioperatively with high doses of dexamethasone to minimise cerebral oedema. 180 patients are randomised between treatment with either two times per day 10 mg hydrocortisone or placebo during dexamethasone treatment. The primary study outcome is the difference in proportion of patients scoring ≥3 points on at least one of the Brief Psychiatric Rating Scale (BPRS) questions 5 days postoperatively or earlier at discharge. Secondary outcomes are neuropsychiatric symptoms, quality of sleep, health-related quality of life and neurocognitive functioning at several time points postoperatively. Furthermore, neuropsychiatric history, serious adverse events, prescribed (psychiatric) medication and referrals or evaluations of psychiatrist/psychologist and laboratory measurements are assessed.

Ethics and dissemination

The study protocol has been approved by the Medical Research Ethics Committee of the Leiden University Medical Center, and by the Dutch competent authority, and by the Institutional Review Boards of the participating sites. It is an investigator-initiated study with financial support by The Netherlands Organisation for Health Research and Development (ZonMw) and the Dutch Brain Foundation. Results of the study will be submitted for publication in a peer-reviewed journal.

Trial registration number

NL6726 (Netherlands Trial Register); open for patient inclusion. EudraCT number 2017-003705-17.

Prioritization of human well-being spectrum related GWAS-SNVs using ENCODE-based web-tools predict interplay between PSMC3, ITIH4, and SERPINC1 genes in modulating well-being

Several traits related to positive and negative affect show a high genetic as well as phenotypic correlation with well-being in humans, and are therefore collectively termed as "Well-being spectrum". Genome-Wide Association studies (GWA studies) on "well-being measurement" have led to identification of several genomic variants (Single Nucleotide Variants - SNVs), but very little has been explained with respect to their functionality and mode of alteration of well-being. Utilizing a pool of 1258 GWA studies based SNVs on "well-being measurement", we prioritized the SNVs and tried to annotate well-being related functionality through several bioinformatic tools to predict whether a protein sequence variation affects protein function, as well as experimentally validated datasets available in ENCODE based web-tools namely rSNPBase, RegulomeDB, Haploreg, along with GTEx Portal and STRING based protein interaction networks. Prioritization yielded three key SNVs; rs3781627-A, rs13072536-T and 5877-C potentially regulating three genes, PSMC3, ITIH4 and SERPINC1, respectively. Interestingly, the genes showed well clustered protein-protein interaction (maximum combined confidence score >0.4) with other well-being candidate genes, namely TNF and CRP genes suggesting their important role in modulation of well-being. PSMC3 and ITIH4 genes are also involved in driving acute phase responses signifying a probable cross-talk between well-being and psychoneuroimmunological system. To best of our knowledge this study is the first of its kind where the well-being associated GWA studies-SNVs were prioritized and functionally annotated, majorly based on functional data available in public domain, which revealed PSMC3, ITIH4 and SERPINC1 genes as probable candidates in regulation of well-being spectrum.

MMP9 mRNA is a potential diagnostic and treatment monitoring marker for PTSD: Evidence from mice and humans

Although matrix metalloproteinase 9 (MMP9) has been found associated with various psychiatric disorders and with threat memories in humans, its role in post-traumatic stress disorder (PTSD) and related animal models is understudied. Thus, we analyzed MMP9 mRNA expression kinetics during two different stress experiments, i.e., the Trier Social Stress Test and the dexamethasone suppression test (DST), in whole blood of two independent cohorts of PTSD patients vs. non-traumatized healthy controls (HC) and, moreover, in a mouse model of PTSD and in dexamethasone-treated mice. Besides MMP9, we quantified mRNA levels of four of its regulators, i.e., interleukin (IL)-1 receptor 1 and 2 (IL1R1, IL1R2), IL-6 receptor and tumor necrosis factor receptor 1 (TNFR1) in 10 patients exposed to the DST before vs. after successful PTSD psychotherapy vs. 13 HC and, except from Il6r, also in different brain regions of the PTSD mouse model. We are the first to show that blood MMP9 mRNA concentrations were elevated after acute dexamethasone in PTSD patients, improved upon partial remission of PTSD and were, furthermore, also elevated, together with its regulator Tnfr1, in the prefrontal cortex of PTSD-like mice. In contrast, blood TNFR1 and IL1R2 were markedly underexpressed in PTSD patients. In conclusion, we found translational evidence supporting that, I, TNFR1 and MMP9 mRNA expression might be involved in PTSD pathobiology, II, might constitute potential diagnostic blood biomarkers for PTSD and, importantly, III, post-dexamethasone blood MMP9 hyperexpression, which speculatively results from post-dexamethasone underexpression of IL1R2, might serve also as potential treatment monitoring biomarker for PTSD.

The co-chaperone Fkbp5 shapes the acute stress response in the paraventricular nucleus of the hypothalamus of male mice

Disturbed activation or regulation of the stress response through the hypothalamic-pituitary-adrenal (HPA) axis is a fundamental component of multiple stress-related diseases, including psychiatric, metabolic, and immune disorders. The FK506 binding protein 51 (FKBP5) is a negative regulator of the glucocorticoid receptor (GR), the main driver of HPA axis regulation, and FKBP5 polymorphisms have been repeatedly linked to stress-related disorders in humans. However, the specific role of Fkbp5 in the paraventricular nucleus of the hypothalamus (PVN) in shaping HPA axis (re)activity remains to be elucidated. We here demonstrate that the deletion of Fkbp5 in Sim1+ neurons dampens the acute stress response and increases GR sensitivity. In contrast, Fkbp5 overexpression in the PVN results in a chronic HPA axis over-activation, and a PVN-specific rescue of Fkbp5 expression in full Fkbp5 KO mice normalizes the HPA axis phenotype. Single-cell RNA sequencing revealed the cell-type-specific expression pattern of Fkbp5 in the PVN and showed that Fkbp5 expression is specifically upregulated in Crh+ neurons after stress. Finally, Crh-specific Fkbp5 overexpression alters Crh neuron activity, but only partially recapitulates the PVN-specific Fkbp5 overexpression phenotype. Together, the data establish the central and cell-type-specific importance of Fkbp5 in the PVN in shaping HPA axis regulation and the acute stress response.

Glucocorticoids, metabolism and brain activity

The review integrates different experimental approaches including biochemistry, c-Fos expression, microdialysis (glutamate, GABA, noradrenaline and serotonin), electrophysiology and fMRI to better understand the effect of elevated level of glucocorticoids on the brain activity and metabolism. The available data indicate that glucocorticoids alter the dynamics of neuronal activity leading to context-specific changes including both excitation and inhibition and these effects are expected to support the task-related responses. Glucocorticoids also lead to diversification of available sources of energy due to elevated levels of glucose, lactate, pyruvate, mannose and hydroxybutyrate (ketone bodies), which can be used to fuel brain, and facilitate storage and utilization of brain carbohydrate reserves formed by glycogen. However, the mismatch between carbohydrate supply and utilization that is most likely to occur in situations not requiring energy-consuming activities lead to metabolic stress due to elevated brain levels of glucose. Excessive doses of glucocorticoids also impair the production of energy (ATP) and mitochondrial oxidation. Therefore, glucocorticoids have both adaptive and maladaptive effects consistently with the concept of allostatic load and overload.

Glucocorticoids and the Brain after Critical Illness

Treatment for critical illness typically focuses on a patient's short-term physical recovery; however, recent work has broadened our understanding of the long-term implications of illness and treatment strategies. In particular, survivors of critical illness have significantly elevated risk of developing lasting cognitive impairment and psychiatric disorders. In this review, we examine the role of endogenous and exogenous glucocorticoids in neuropsychiatric outcomes following critical illness. Illness is marked by acute elevation of free cortisol and adrenocorticotropic hormone suppression, which typically normalize after recovery; however, prolonged dysregulation can sometimes occur. High glucocorticoid levels can cause lasting alterations to the plasticity and structural integrity of the hippocampus and prefrontal cortex, and this mechanism may plausibly contribute to impaired memory and cognition in critical illness survivors, though specific evidence is lacking. Glucocorticoids may also exacerbate inflammation-associated neural damage. Conversely, current evidence indicates that glucocorticoids during illness may protect against the development of post-traumatic stress disorder. We propose future directions for research in this field, including determining the role of persistent glucocorticoid elevations after illness in neuropsychiatric outcomes, the role of systemic vs neuroinflammation, and probing unexplored lines of investigation on the role of mineralocorticoid receptors and the gut-brain axis. Progress toward personalized medicine in this area has the potential to produce tangible improvements to the lives patients after a critical illness, including Coronavirus Disease 2019.

Experience and activity-dependent control of glucocorticoid receptors during the stress response in large-scale brain networks

The diversity of actions of the glucocorticoid stress hormones among individuals and within organs, tissues and cells is shaped by age, gender, genetics, metabolism, and the quantity of exposure. However, such factors cannot explain the heterogeneity of responses in the brain within cells of the same lineage, or similar tissue environment, or in the same individual. Here, we argue that the stress response is continuously updated by synchronized neural activity on large-scale brain networks. This occurs at the molecular, cellular and behavioral levels by crosstalk communication between activity-dependent and glucocorticoid signaling pathways, which updates the diversity of responses based on prior experience. Such a Bayesian process determines adaptation to the demands of the body and external world. We propose a framework for understanding how the diversity of glucocorticoid actions throughout brain networks is essential for supporting optimal health, while its disruption may contribute to the pathophysiology of stress-related disorders, such as major depression, and resistance to therapeutic treatments.

The effects of suppressing the biological stress systems on social threat-assessment following acute stress

RATIONALE

Stress is associated with increased sensitivity to threat. Previous investigations examining how stress affects threat processing have largely focused on biomarker responses associated with either the sympathetic-nervous-system (SNS) or the hypothalamus-pituitary-adrenal (HPA) axis.

OBJECTIVES

We pharmacologically suppressed activations of SNS, HPA, or both, prior to stress and investigated how each stress system modulates social threat assessment.

METHODS

One hundred sixty-one healthy men and women were randomized in a between-subject design, to one of four pharmacological or placebo conditions: dexamethasone-placebo, placebo-propranolol, dexamethasone-propranolol, or placebo-placebo. Participants provided threat assessments for angry and neutral human faces on a baseline day, and immediately after stress induction on a testing day.

RESULTS

With both systems responding normally to stress (placebo-placebo), threat assessment was higher for neutral faces compared with angry. Compared with placebo, SNS suppression resulted in increased threat assessment for angry faces. HPA suppression resulted in decreased threat assessment for neutral and angry faces. When both systems were suppressed, there was an increase in threat assessment for angry faces, and no difference from placebo for neutral.

CONCLUSION

Our findings demonstrated that when intact, the biological stress systems adaptively support organisms during stress by focusing attention towards specific stimuli that are relevant to the threat. Dysregulations of the stress systems result in important system specific consequences on threat evaluation, such that suppression of either stress system alone resulted in reduced threat assessment for contextually relevant threatening stimuli, whereas when both systems were suppressed, individuals appear indiscriminately attentive to all potential threats in the environment, resulting in increased threat processing of both contextually relevant and irrelevant stimuli. Given that stress-related psychopathologies have been associated with dysregulations of the stress systems and biased responses to social threat, a systematic understanding of the mechanisms that underlie how stress systems modulate social threat assessment is needed, and can provide important insights into the cognitive processes that are involved in the development and maintenance of stress-related psychopathologies.

The effects of psychosocial stress on dopaminergic function and the acute stress response

Chronic psychosocial adversity induces vulnerability to mental illnesses. Animal studies demonstrate that this may be mediated by dopaminergic dysfunction. We therefore investigated whether long-term exposure to psychosocial adversity was associated with dopamine dysfunction and its relationship to psychological and physiological responses to acute stress. Using 3,4-dihydroxy-6-[¹⁸F]-fluoro-l-phenylalanine ([¹⁸F]-DOPA) positron emission tomography (PET), we compared dopamine synthesis capacity in n = 17 human participants with high cumulative exposure to psychosocial adversity with n = 17 age- and sex-matched participants with low cumulative exposure. The PET scan took place 2 hr after the induction of acute psychosocial stress using the Montréal Imaging Stress Task to induce acute psychosocial stress. We found that dopamine synthesis correlated with subjective threat and physiological response to acute psychosocial stress in the low exposure group. Long-term exposure to psychosocial adversity was associated with dampened striatal dopaminergic function (p=0.03, d = 0.80) and that psychosocial adversity blunted physiological yet potentiated subjective responses to acute psychosocial stress. Future studies should investigate the roles of these changes in vulnerability to mental illnesses.

Dexamethasone affects day/night development and function of thymus-derived T regulatory cells

Thymus-derived T regulatory (tTregs) cells play a crucial role in the maintenance of tolerance and immune homeostasis. Mechanisms and factors regulating tTreg development and function are widely investigated, but to a large degree still remain unclear. Our previous findings demonstrated that, in physiological conditions, the development and suppressive function of tTregs demonstrated day/night rhythmicity, which correlated with the concentration of plasma corticosterone and the expression of glucocorticoid receptors. In this study we ask whether synthetic glucocorticoids commonly used to inhibit excessive activity of the immune system, can modulate the development and suppressive function of tTregs in vivo depending on the time of administration. Young C57BL/6 male and female mice were injected intraperitoneally with a single dose of dexamethasone at two time points of the day: 7.00-8.00 a.m. and 7.00-8.00 p.m. The experimental can be used to indicate on the potentially expected positive or adverse side effects and can constitute also a good model for the assessment of the effects of long-term therapy. The results of our studies demonstrated the increase of the percentage of tTregs at both time points in male mice, but only in the evening in females. The suppressive activity of tTregs increased independently on the day time of in female mice, but in the morning only in males. We concluded that in the condition of dexamethasone supplementation, the elevated suppressive potential of tTregs is balanced by the induction apoptosis in order to prevent excessive suppression.

Resetting the Stress System with a Mifepristone Challenge

Psychotic depression is characterized by elevated circulating cortisol, and high daily doses of the glucocorticoid/progesterone antagonist mifepristone for 1 week are required for significant improvement. Using a rodent model, we find that such high doses of mifepristone are needed because the antagonist is rapidly degraded and poorly penetrates the blood–brain barrier, but seems to facilitate the entry of cortisol. We also report that in male C57BL/6J mice, after a 7-day treatment with a high dose of mifepristone, basal blood corticosterone levels were similar to that of vehicle controls. This is surprising because after the first mifepristone challenge, corticosterone remained elevated for about 16 h, and then decreased towards vehicle control levels at 24 h. At that time, stress-induced corticosterone levels of the 1xMIF were sevenfold higher than the 7xMIF group, the latter response being twofold lower than controls. The 1xMIF mice showed behavioral hyperactivity during exploration of the circular hole board, while the 7xMIF mice rather engaged in serial search patterns. To explain this rapid reset of corticosterone secretion upon recurrent mifepristone administration, we suggest the following: (i) A rebound glucocorticoid feedback after cessation of mifepristone treatment. (ii) Glucocorticoid agonism in transrepression and recruitment of cell-specific coregulator cocktails. (iii) A more prominent role of brain MR function in control of stress circuit activity. An overview table of neuroendocrine MIF effects is provided. The data are of interest for understanding the mechanistic underpinning of stress system reset as treatment strategy for stress-related diseases.

Importance of the brain corticosteroid receptor balance in metaplasticity, cognitive performance and neuro-inflammation

Bruce McEwen's discovery of receptors for corticosterone in the rat hippocampus introduced higher brain circuits in the neuroendocrinology of stress. Subsequently, these receptors were identified as mineralocorticoid receptors (MRs) that are involved in appraisal processes, choice of coping style, encoding and retrieval. The MR-mediated actions on cognition are complemented by slower actions via glucocorticoid receptors (GRs) on contextualization, rationalization and memory storage of the experience. These sequential phases in cognitive performance depend on synaptic metaplasticity that is regulated by coordinate MR- and GR activation. The receptor activation includes recruitment of coregulators and transcription factors as determinants of context-dependent specificity in steroid action; they can be modulated by genetic variation and (early) experience. Interestingly, inflammatory responses to damage seem to be governed by a similarly balanced MR:GR-mediated action as the initiating, terminating and priming mechanisms involved in stress-adaptation. We conclude with five questions challenging the MR:GR balance hypothesis.

30 YEARS OF THE MINERALOCORTICOID RECEPTOR: The brain mineralocorticoid receptor: a saga in three episodes

In 1968, Bruce McEwen discovered that ³H-corticosterone administered to adrenalectomised rats is retained in neurons of hippocampus rather than those of hypothalamus. This discovery signalled the expansion of endocrinology into the science of higher brain regions. With this in mind, our contribution highlights the saga of the brain mineralocorticoid receptor (MR) in three episodes. First, the precloning era dominated by the conundrum of two types of corticosterone-binding receptors in the brain, which led to the identification of the high-affinity corticosterone receptor as the 'promiscuous' MR cloned in 1987 by Jeff Arriza and Ron Evans in addition to the classical glucocorticoid receptor (GR). Then, the post-cloning period aimed to disentangle the function of the brain MR from that of the closely related GR on different levels of biological complexity. Finally, the synthesis section that highlights the two faces of brain MR: Salt and Stress. 'Salt' refers to the regulation of salt appetite, and reciprocal arousal, motivation and reward, by a network of aldosterone-selective MR-expressing neurons projecting from nucleus tractus solitarii (NTS) and circumventricular organs. 'Stress' is about the limbic-forebrain nuclear and membrane MRs, which act as a switch in the selection of the best response to cope with a stressor. For this purpose, activation of the limbic MR promotes selective attention, memory retrieval and the appraisal process, while driving emotional expressions of fear and aggression. Subsequently, rising glucocorticoid concentrations activate GRs in limbic-forebrain circuitry underlying executive functions and memory storage, which contribute in balance with MR-mediated actions to homeostasis, excitability and behavioural adaptation.

Suppressing the endocrine and autonomic stress systems does not impact the emotional stress experience after psychosocial stress

Acute psychosocial stress activates the physiological and endocrine stress systems and increases the subjective emotional experience of stress. While considerable efforts have been made to link changes in the activity of the biological stress systems with changes in the subjective emotional experience of stress, results so far have been mixed, at best. To investigate this association in a study employing experimental manipulation, we pharmacologically suppressed both the autonomic and the endocrine stress responses, and investigated the effects of acute psychosocial stress on the emotional stress experience. 22 healthy men and women received dexamethasone (2mg) the day before, and propranolol (80mg) one hour before psychosocial stress induction. A control group (n=24) received placebo pills on each occasion. Salivary cortisol, alpha-amylase and heart-rate responses to stress were assessed before, during and after stress induction. Subjective stress, mood, and state self-esteem assessments were made before and after stress. In the pharmacological manipulation group, subjects demonstrated no increase in autonomic or endocrine stress response, after exposure to psychosocial stress. Despite these effects, the emotional stress experience was intact in this group and identical to the control group. Participants in the experimental group showed an increase in subjective stress, greater mood dysregulation, and lower state self-esteem following stress exposure, with the response magnitude comparable to the control group. Our findings suggest that at least acutely, the physiological stress arousal systems and the emotional experience of stress are dissociated. This raises important questions about the efficacy of our measurement of subjective stress, and the unique contributions of the autonomic and endocrine responses in the subjective stress experience.

A Refill for the Brain Mineralocorticoid Receptor: The Benefit of Cortisol Add-On to Dexamethasone Therapy

Some serious medical conditions require life-saving treatment with high doses of synthetic glucocorticoids such as dexamethasone. A substantial number of patients subjected to this treatment develops psychosis, mood disturbances, or sleep problems. A recent clinical trial demonstrated that dexamethasone therapy for young patients with acute lymphoblastic leukemia caused severe adverse psychological effects and sleep disturbances in about 30% of these patients. These side effects were ameliorated by coadministration of a low dose of the naturally occurring glucocorticoid hormone cortisol. This paradoxical finding was predicted by the idea that the synthetic glucocorticoid targets the glucocorticoid receptor, causing suppression of cortisol secretion and, thus, depletion of the brain mineralocorticoid receptor (MR) of its endogenous ligand. The refill of the unoccupied brain MR with physiological amounts of cortisol ameliorates the dexamethasone-induced psychological side effects. In the present report, we discuss the mechanistic underpinning of the MR refill concept in glucocorticoid therapy.

The Functional and Clinical Significance of the 24-Hour Rhythm of Circulating Glucocorticoids

Adrenal glucocorticoids are major modulators of multiple functions, including energy metabolism, stress responses, immunity, and cognition. The endogenous secretion of glucocorticoids is normally characterized by a prominent and robust circadian (around 24 hours) oscillation, with a daily peak around the time of the habitual sleep-wake transition and minimal levels in the evening and early part of the night. It has long been recognized that this 24-hour rhythm partly reflects the activity of a master circadian pacemaker located in the suprachiasmatic nucleus of the hypothalamus. In the past decade, secondary circadian clocks based on the same molecular machinery as the central master pacemaker were found in other brain areas as well as in most peripheral tissues, including the adrenal glands. Evidence is rapidly accumulating to indicate that misalignment between central and peripheral clocks has a host of adverse effects. The robust rhythm in circulating glucocorticoid levels has been recognized as a major internal synchronizer of the circadian system. The present review examines the scientific foundation of these novel advances and their implications for health and disease prevention and treatment.

Brain mineralocorticoid receptor function in control of salt balance and stress-adaptation

We will highlight in honor of Randall Sakai the peculiar characteristics of the brain mineralocorticoid receptor (MR) in its response pattern to the classical mineralocorticoid aldosterone and the naturally occurring glucocorticoids corticosterone and cortisol. Neurons in the nucleus tractus solitarii (NTS) and circumventricular organs express MR, which mediate selectively the action of aldosterone on salt appetite, sympathetic outflow and volume regulation. The MR-containing NTS neurons innervate limbic-forebrain circuits enabling aldosterone to also modulate reciprocally arousal, motivation, fear and reward. MR expressed in abundance in this limbic-forebrain circuitry, is target of cortisol and corticosterone in modulation of appraisal processes, memory performance and selection of coping strategy. Complementary to this role of limbic MR is the action mediated by the lower affinity glucocorticoid receptors (GR), which promote subsequently memory storage of the experience and facilitate behavioral adaptation. Current evidence supports the hypothesis that an imbalance between MR- and GR-mediated actions compromises resilience and adaptation to stress.

A users guide to HPA axis research

Glucocorticoid hormones (cortisol and corticosterone - CORT) are the effector hormones of the hypothalamic-pituitary-adrenal (HPA) axis neuroendocrine system. CORT is a systemic intercellular signal whose level predictably varies with time of day and dynamically increases with environmental and psychological stressors. This hormonal signal is utilized by virtually every cell and physiological system of the body to optimize performance according to circadian, environmental and physiological demands. Disturbances in normal HPA axis activity profiles are associated with a wide variety of physiological and mental health disorders. Despite numerous studies to date that have identified molecular, cellular and systems-level glucocorticoid actions, new glucocorticoid actions and clinical status associations continue to be revealed at a brisk pace in the scientific literature. However, the breadth of investigators working in this area poses distinct challenges in ensuring common practices across investigators, and a full appreciation for the complexity of a system that is often reduced to a single dependent measure. This Users Guide is intended to provide a fundamental overview of conceptual, technical and practical knowledge that will assist individuals who engage in and evaluate HPA axis research. We begin with examination of the anatomical and hormonal components of the HPA axis and their physiological range of operation. We then examine strategies and best practices for systematic manipulation and accurate measurement of HPA axis activity. We feature use of experimental methods that will assist with better understanding of CORT's physiological actions, especially as those actions impact subsequent brain function. This research approach is instrumental for determining the mechanisms by which alterations of HPA axis function may contribute to pathophysiology.

Pathogenetic and Therapeutic Applications of Tumor Necrosis Factor-α (TNF-α) in Major Depressive Disorder: A Systematic Review

Major depressive disorder (MDD) is characterized by mood, vegetative, cognitive, and even psychotic symptoms and signs that can cause substantial impairments in quality of life and functioning. Up to now, the exact pathogenesis of MDD remains poorly understood. Recent research has begun to reveal that the pro-inflammatory cytokines, particularly, tumor necrosis factor-α (TNF-α), play an integral role in the pathophysiology of depressive disorders and the mechanism of antidepressant treatment. On the base of several observations: it is found that subsets of MDD patients have enhanced plasma levels TNF-α; antidepressant treatments had linked with the decline of TNF-α; central administration of TNF-α gives rise to sickness behavior which shares features with depression; and a blockade of it can ameliorate depressive symptomatology in animal models and clinical trials. In this review article, we focus on recent evidence linking TNF-α and MDD looking at data from animal and clinical studies, illustrating the pathophysiological role, susceptibility and its therapeutic application in depression. We conclude by discussing future directions for research, in particular the opportunities for the development of novel therapeutics that target TNF-α. This will be very important for designing preventative strategies and for the identification of new drug targets and preventative strategies.

Limiting glucocorticoid secretion increases the anorexigenic property of Exendin-4

Objective

Glucagon-like peptide-1 (GLP-1) analogs are attractive options for the treatment of type II diabetes and obesity because of their incretin and anorexigenic effects. Peripheral administration of the GLP-1R agonist Exendin-4 (Ex-4) also increases glucocorticoid secretion in rodents and humans, but whether the released glucocorticoids interact with Ex-4's anorexigenic effect remains unclear.

Methods

To test this, we used two experimental approaches that suppress corticosterone secretion and then assessed Ex-4 effects on eating in adult male rats. First, we combined acute and chronic low dose dexamethasone treatment with Ex-4. Second, we ablated hindbrain catecholamine neurons projecting to the hypothalamus with anti-dopamine-β-hydroxylase-saporin (DSAP) to block Ex-4-induced corticosterone secretion.

Results

Combining dexamethasone and Ex-4 produced a larger acute anorexigenic effect than Ex-4 alone. Likewise, chronic dexamethasone and Ex-4 co-treatment produced a synergistic effect on eating and greater body weight loss in diet-induced obese rats than Ex-4 alone. DSAP lesions not only blunted Ex-4's ability to increase corticosterone secretion, but potentiated the anorexigenic effect of Ex-4, indicating that Ex-4-dependent corticosterone secretion opposes Ex-4's actions. Consistent with the enhancement of Ex-4's anorexigenic effect, DSAP lesion altered Ex-4-dependent changes in neuropeptide Y, preproglucagon, and corticotropin releasing hormone gene expression involved in glucocorticoid feedback.

Conclusions

Our findings demonstrate that limiting glucocorticoid secretion and actions with low dose dexamethasone or DSAP lesion increases Ex-4's ability to reduce food intake and body weight. Novel glucocorticoid receptor based mechanisms, therefore, may help enhance GLP-1-based obesity therapies.

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Blocking HPA axis by low dose dexamethasone increased the anorexigenic property of Ex-4.

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Dexamethasone/Ex-4 co-treatment reduced food intake and body weight in diet-induced obese rats more than Ex-4 alone.

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A brain lesion model identified a potential central interaction between glucocorticoids and GLP-1 in food intake control.

Behavioral effects of glucocorticoids during the first exposures to the forced swim stress

RATIONALE

Glucocorticoids facilitate coping with stress, but their high levels have been also implicated in mood disorders. Due to this duality, the role of glucocorticoid signaling in the development of the first episodes of stress-induced depression remains unclear.

OBJECTIVES

To address this issue, effects of the glucocorticoid signal modulation on depressive-like behavior during pretest and test Porsolt swim sessions were examined.

METHODS

Metyrapone (MET; 150 mg/kg, i.p.) was injected 3 h before pretest to block stress-induced increase in corticosterone levels. Dexamethasone (DEX; 0.2 mg/kg, s.c.) was applied to MET-treated rats 1 h before both pretest and test sessions. In addition to behavior during these sessions, glucocorticoid receptor (GR) expression was analyzed by immunohistochemistry 2 h after the second swim.

RESULTS

In pretest, MET-treated rats exhibited increased latency to immobility and shortened immobility. DEX reversed the behavioral effects of MET in the pretest. In the test, animals from MET + DEX group unexpectedly exhibited an antidepressant-like behavior. Swim stress increased GR expression in the frontal cortex irrespective of the pharmacological treatment. A significant elevation in GR expression was found in the prefrontal cortex (PFC) of stressed MET + DEX-treated rats and in the PFC of unstressed rats 6 h after injection of DEX alone.

CONCLUSION

The data suggest that the increase in glucocorticoid levels under swim stress during pretest directly contributes to the development of the immobility response. Transition of DEX effect from prodepressant in the pretest to an antidepressant in the test was associated with the elevation in the PFC GR expression.

Is Dysregulation of the HPA-Axis a Core Pathophysiology Mediating Co-Morbid Depression in Neurodegenerative Diseases?

There is increasing evidence of prodromal manifestation of neuropsychiatric symptoms in a variety of neurodegenerative diseases such as Parkinson's disease (PD) and Huntington's disease (HD). These affective symptoms may be observed many years before the core diagnostic symptoms of the neurological condition. It is becoming more apparent that depression is a significant modifying factor of the trajectory of disease progression and even treatment outcomes. It is therefore crucial that we understand the potential pathophysiologies related to the primary condition, which could contribute to the development of depression. The hypothalamic-pituitary-adrenal (HPA)-axis is a key neuroendocrine signaling system involved in physiological homeostasis and stress response. Disturbances of this system lead to severe hormonal imbalances, and the majority of such patients also present with behavioral deficits and/or mood disorders. Dysregulation of the HPA-axis is also strongly implicated in the pathology of major depressive disorder. Consistent with this, antidepressant drugs, such as the selective serotonin reuptake inhibitors have been shown to alter HPA-axis activity. In this review, we will summarize the current state of knowledge regarding HPA-axis pathology in Alzheimer's, PD and HD, differentiating between prodromal and later stages of disease progression when evidence is available. Both clinical and preclinical evidence will be examined, but we highlight animal model studies as being particularly useful for uncovering novel mechanisms of pathology related to co-morbid mood disorders. Finally, we purpose utilizing the preclinical evidence to better inform prospective, intervention studies.

Glucocorticoid Mechanisms of Functional Connectivity Changes in Stress-Related Neuropsychiatric Disorders

Stress—especially chronic, uncontrollable stress—is an important risk factor for many neuropsychiatric disorders. The underlying mechanisms are complex and multifactorial, but they involve correlated changes in structural and functional measures of neuronal connectivity within cortical microcircuits and across neuroanatomically distributed brain networks. Here, we review evidence from animal models and human neuroimaging studies implicating stress-associated changes in functional connectivity in the pathogenesis of PTSD, depression, and other neuropsychiatric conditions. Changes in fMRI measures of corticocortical connectivity across distributed networks may be caused by specific structural alterations that have been observed in the prefrontal cortex, hippocampus, and other vulnerable brain regions. These effects are mediated in part by glucocorticoids, which are released from the adrenal gland in response to a stressor and also oscillate in synchrony with diurnal rhythms. Recent work indicates that circadian glucocorticoid oscillations act to balance synapse formation and pruning after learning and during development, and chronic stress disrupts this balance. We conclude by considering how disrupted glucocorticoid oscillations may contribute to the pathophysiology of depression and PTSD in vulnerable individuals, and how circadian rhythm disturbances may affect non-psychiatric populations, including frequent travelers, shift workers, and patients undergoing treatment for autoimmune disorders.

Impact of Adiposity and Fat Distribution on the Dynamics of Adrenocorticotropin and Cortisol Rhythms

Obesity impacts many hormonal systems, including pituitary hormones, as well as insulin and leptin. In this review we discuss articles which investigate the influence of obesity on the hypothalamic-pituitary-adrenal (HPA) axis. Different techniques have been used to assess the function of the HPA-axis in obesity, including measuring fasting and/or late evening levels of adrenocorticotropic hormone (ACTH) and (free) cortisol in plasma and saliva, studying feedback with dexamethasone or cortisol, and evaluating responsiveness of the system to corticotropin-releasing hormone (CRH) and arginine vasopressin (AVP) or ACTH 1-29. In addition, more elaborate studies investigated 24-h secretion patterns, analyzed with deconvolution techniques to quantitate pulsatile secretion rates of cortisol and less often ACTH. Other investigators used timed infusions of labeled cortisol for the estimation of the 24-h secretion rate, clearance rate and distribution volume. Many studies relied on the 24-h urinary excretion of free cortisol, but for quantitation of the 24-h secretion, measurement of all cortisol-derived metabolites is required. Several studies have applied modern liquid chromatography-tandem-mass spectrometry techniques to measure these metabolites. The picture emerging from all these studies is that, first, ACTH secretion is amplified, likely via enhanced forward drive; and, second, serum cortisol levels are normal or even low, associated with a normal 24-h cortisol secretion per liter distribution volume determined by deconvolution, but enhanced when based on the increased total distribution volume associated with obesity. Increased cortisol secretion was also established by isotope dilution studies and reports based on the measurement of all urinary cortisol metabolites. The responsiveness of the adrenal gland to ACTH is diminished. The studies do not address quantitative aspects of cortisol-cortisone metabolism on individual organs, including liver, central and peripheral fat, intestine, skin, and muscle.

Upregulation of nucleoside triphosphate diphosphohydrolase-1 and ecto-5'-nucleotidase in rat hippocampus after repeated low-dose dexamethasone administration

Although dexamethasone (DEX), a synthetic glucocorticoid receptor (GR) analog with profound effects on energy metabolism, immune system, and hypothalamic-pituitary-adrenal axis, is widely used therapeutically, its impact on the brain is poorly understood. The aim of the present study was to explore the effect of repeated low-dose DEX administration on the activity and expression of the ectonucleotidase enzymes which hydrolyze and therefore control extracellular ATP and adenosine concentrations in the synaptic cleft. Ectonucleotidases tested were ectonucleoside triphosphate diphosphohydrolase 1-3 (NTPDase1-3) and ecto-5'-nucleotidase (eN), whereas the effects were evaluated in two brain areas that show different sensitivity to glucocorticoid action, hippocampus, and cerebral cortex. In the hippocampus, but not in cerebral cortex, modest level of neurodegenerative changes as well as increase in ATP, ADP, and AMP hydrolysis and upregulation of NTPDase1 and eN mRNA expression ensued under the influence of DEX. The observed pattern of ectonucleotidase activation, which creates tissue volume with enhanced capacity for adenosine formation, is the hallmark of the response after different insults to the brain.

From receptor balance to rational glucocorticoid therapy

Corticosteroids secreted as end product of the hypothalamic-pituitary-adrenal axis act like a double-edged sword in the brain. The hormones coordinate appraisal processes and decision making during the initial phase of a stressful experience and promote subsequently cognitive performance underlying the management of stress adaptation. This action exerted by the steroids on the initiation and termination of the stress response is mediated by 2 related receptor systems: mineralocorticoid receptors (MRs) and glucocorticoid receptors (GRs). The receptor types are unevenly distributed but colocalized in abundance in neurons of the limbic brain to enable these complementary hormone actions. This contribution starts from a historical perspective with the observation that phasic occupancy of GR during ultradian rhythmicity is needed to maintain responsiveness to corticosteroids. Then, during stress, initially MR activation enhances excitability of limbic networks that are engaged in appraisal and emotion regulation. Next, the rising hormone concentration occupies GR, resulting in reallocation of energy to limbic-cortical circuits with a role in behavioral adaptation and memory storage. Upon MR:GR imbalance, dysregulation of the hypothalamic-pituitary-adrenal axis occurs, which can enhance an individual's vulnerability. Imbalance is characteristic for chronic stress experience and depression but also occurs during exposure to synthetic glucocorticoids. Hence, glucocorticoid psychopathology may develop in susceptible individuals because of suppression of ultradian/circadian rhythmicity and depletion of endogenous corticosterone from brain MR. This knowledge generated from testing the balance hypothesis can be translated to a rational glucocorticoid therapy.

Early experience of a novel-environment in isolation primes a fearful phenotype characterized by persistent amygdala activation

Prolonged maternal separation (MS) activates the neonate's hypothalamus-pituitary-adrenal axis causing elevated basal and stress-induced corticosterone levels that may initiate amygdala-dependent fear learning. Here we test the hypothesis that the adult fearful phenotype is programmed by the pup's stressful experience during prolonged MS rather than by prolonged maternal absence per se. For this purpose, Wistar rat pups were exposed, on postnatal-day (pnd) 3, to: (i) repeated-MS in home-environment (HOME-SEP), 8h-MS daily for three days with the pups remaining together in the home-cage; (ii) repeated-MS in a novel-environment (NOVEL-SEP), with the same separation procedure, but now the pups were individually housed in a novel-environment during the 8h dam's absence; (iii) repeated handling, which consisted of daily brief (15 min instead of 8h) MS in the home-altogether or in a novel-environment individually (HOME-HAN and NOVEL-HAN, respectively); (iv) no-separation/no-handling (NON-SEP/NON-HAN) control condition, in which pups were left undisturbed in their home-cage. Compared to HOME-SEP rats, the NOVEL-SEP rats showed one day after the last MS enhanced stress-induced amygdala c-Fos expression and ACTH-release, despite of reduced adrenal corticosterone secretion. The higher amygdala c-Fos expression, ACTH-release and reduced corticosterone output observed postnatally, persisted into adulthood of the NOVEL-SEP animals. Behaviorally, NOVEL-SEP juvenile rats displayed deficits in social play, had intact spatial memory in the peri-pubertal period and showed more contextual fear memory compared to HOME-SEP in adulthood. Finally, NOVEL-HAN, compared to HOME-HAN, displayed increased stress-induced corticosterone output, no deficits in social play and reduced contextual fear. In conclusion, programming of an adult fearful phenotype linked to amygdala priming develops if pups are repeatedly isolated from peers in a novel-environment, while away from the dam for a prolonged period of time.

Context modulates outcome of perinatal glucocorticoid action in the brain

Prematurely born infants may be at risk, because of inadequate maturation of tissues. If there are signs of preterm birth, it has become common practice therefore to treat either antenatally the mother or postnatally the infant with glucocorticoids to accelerate tissue development, particularly of the lung. However, this life-saving early glucocorticoid treatment was found to increase the risk of adverse outcome in later life. In one animal study, the authors reported a 25% shorter lifespan of rats treated as newborns with the synthetic glucocorticoid dexamethasone, but so far this finding has not been replicated. After a brief clinical introduction, we discuss studies in rodents designed to examine how perinatal glucocorticoid action affects the developing brain. It appears that the perinatal action of the glucocorticoid depends on the context and the timing as well as the type of administered steroid. The type of steroid is important because the endogenous glucocorticoids cortisol and corticosterone bind to two distinct receptor populations, i.e., mineralocorticoid and glucocorticoid receptors (GR), while synthetic glucocorticoids predominantly bind to the GR. In addition, if given antenatally hydrocortisone is inactivated in the placenta by 11β-HSD type 2, and dexamethasone is not. With respect to timing, the outcome of glucocorticoid effects is different in early vs. late phases of brain development. The context refers to the environmental input that can affect the susceptibility to glucocorticoid action in the newborn rodent brain; early handling of pups and maternal care obliterate effects of post-natal dexamethasone treatment. Context also refers to coping with environmental conditions in later life, for which the individual may have been programed epigenetically by early-life experience. This knowledge of determinants affecting the outcome of perinatal glucocorticoid exposure may have clinical implications for the treatment of prematurely born infants.

Lifetime achievement from a brain-adrenal perspective: on the CRF-urocortin-glucocorticoid balance

This contribution dedicated to Wylie Vale is focused on the action of the glucocorticoid hormone aimed to counterbalance the stress response orchestrated by the corticotrophin releasing factor (CRF) and urocortin (Ucn) family of peptides. It appears that the release and action of these stress hormones themselves are subjected to intrinsic self-regulatory feedback loops that operate as checks and balances in stress adaptation. One of these feedback loops is operated by the mineralocorticoid (MR) and glucocorticoid receptors (GR) that mediate in complementary fashion the action of endogenous cortisol/corticosterone in brain circuits underlying the onset and termination of the stress response. By affecting appraisal processes MR has an important role in coordinating emotional expression and cognitive flexibility with the onset of the stress response, while GR's role is prominent in the management of behavioral and physiological adaptations during the recovery phase. Genetic variation in interaction with environmental input and experience-related factors can modulate this balance between susceptibility and recovery governed by a balanced MR:GR signaling. Thanks to the Wylie Vale School of scientists a parallel balanced regulation between the CRF/CRF-1 and Ucn/CRF-2 receptor systems is being uncovered, leading inexorably to the question: how do the CRF/Ucn and glucocorticoid systems interact in multiple brain sites to maintain homeostasis and health?

Low-dose dexamethasone treatment promotes the pro-survival signalling pathway in the adult rat prefrontal cortex

Synthetic glucocorticoid dexamethasone (DEX), a highly potent anti-inflammatory and immunosuppressive agent, is widely used in the treatment of brain cancer, as well as for inflammatory and autoimmune diseases. The present study aimed to determine whether low-dose subchronic DEX treatment (100 μg/kg for eight consecutive days) exerts long-term effects on apoptosis in the adult rat prefrontal cortex (PFC) by examining the expression of cell death-promoting molecules [poly(ADP-ribose) polymerase (PARP), p53, procaspase 3, cleaved caspase 3, Bax] and cell-survival molecules (AKT, Bcl-2). The results obtained revealed that body, thymus and adrenal gland weights, as well corticosterone levels, in the serum and PFC were reduced 1 day after the last DEX injection. In the PFC, DEX caused activation of AKT, augmentation of pro-survival Bcl-2 protein and an enhanced Bcl-2/Bax protein ratio, as well Bcl-2 translocation to the mitochondria. An unaltered profile with respect to the protein expression of apoptotic molecules PARP, procaspase 3 and Bax was detected, whereas p53 protein was decreased. Reverse transcriptase -polymerase chain reaction analysis showed a decrease of p53 mRNA levels and no significant difference in Bcl-2 and Bax mRNA expression in DEX-treated rats. Finally, a DNA fragmentation assay and Fluoro-Jade staining demonstrated no considerable changes in apoptosis in the rat PFC. Our findings support the concept that low-dose DEX creates a hypocorticoid state in the brain and also indicate that subchronic DEX treatment activates the pro-survival signalling pathway but does not change apoptotic markers in the rat PFC. This mechanism might be relevant for the DEX-induced apoptosis resistance observed during and after chemotherapy of patients with brain tumours.

Circadian glucocorticoid oscillations promote learning-dependent synapse formation and maintenance

Excessive glucocorticoid exposure during chronic stress causes synapse loss and learning impairment. Under normal physiological conditions, glucocorticoid activity oscillates in synchrony with the circadian rhythm. Whether and how endogenous glucocorticoid oscillations modulate synaptic plasticity and learning is unknown. Here we show that circadian glucocorticoid peaks promote postsynaptic dendritic spine formation in the mouse cortex after motor skill learning, whereas troughs are required for stabilizing newly formed spines that are important for long-term memory retention. Conversely, chronic and excessive exposure to glucocorticoids eliminates learning-associated new spines and disrupts previously acquired memories. Furthermore, we show that glucocorticoids promote rapid spine formation through a non-transcriptional mechanism by means of the LIM kinase-cofilin pathway and increase spine elimination through transcriptional mechanisms involving mineralocorticoid receptor activation. Together, these findings indicate that tightly regulated circadian glucocorticoid oscillations are important for learning-dependent synaptic formation and maintenance. They also delineate a new signaling mechanism underlying these effects.

Differential targeting of brain stress circuits with a selective glucocorticoid receptor modulator

Glucocorticoid receptor (GR) antagonism may be of considerable therapeutic value in stress-related psychopathology such as depression. However, blockade of all GR-dependent processes in the brain will lead to unnecessary and even counteractive effects, such as elevated endogenous cortisol levels. Selective GR modulators are ligands that can act both as agonist and as antagonist and may be used to separate beneficial from harmful treatment effects. We have discovered that the high-affinity GR ligand C108297 is a selective modulator in the rat brain. We first demonstrate that C108297 induces a unique interaction profile between GR and its downstream effector molecules, the nuclear receptor coregulators, compared with the full agonist dexamethasone and the antagonist RU486 (mifepristone). C108297 displays partial agonistic activity for the suppression of hypothalamic corticotropin-releasing hormone (CRH) gene expression and potently enhances GR-dependent memory consolidation of training on an inhibitory avoidance task. In contrast, it lacks agonistic effects on the expression of CRH in the central amygdala and antagonizes GR-mediated reduction in hippocampal neurogenesis after chronic corticosterone exposure. Importantly, the compound does not lead to disinhibition of the hypothalamus-pituitary-adrenal axis. Thus, C108297 represents a class of ligands that has the potential to more selectively abrogate pathogenic GR-dependent processes in the brain, while retaining beneficial aspects of GR signaling.

Diminished adrenal sensitivity and ACTH efficacy in obese premenopausal women

BACKGROUND

The ACTH-cortisol axis in women is activated and associated with decreased ACTH potency, estimated by relating ACTH and cortisol pulse masses. Recently, a new accurate method for constructing the endogenous dose-response relationship was introduced, which is based on the relation between ACTH concentrations and associated cortisol secretion rates within cortisol bursts.

HYPOTHESIS

The endogenous dose-response relation between ACTH and cortisol in obesity is changed, leading to diminished responsiveness.

SUBJECTS

Twenty-five obese premenopausal women and 16 normal weight premenopausal women were studied by 10-min blood sampling for 24 h.

OUTCOMES

ACTH and cortisol secretion rates, analytical dose-response estimates of endogenous ACTH efficacy (maximal cortisol secretion), dynamic ACTH potency, and adrenal sensitivity (slope term) from 24-h ACTH-cortisol profiles were quantified.

RESULTS

The initial potency (negative logarithm) was -7.83 ± 0.75 (mean ± s.e.m.) in obese women and -10.14 ± 1.08 in lean women (P=0.10), and the corresponding values for the recovery phase were -26.62 ± 2.21 and -36.67 ± 1.66 (P=0.004). The sensitivity (curve slope) amounted to 0.468 ± 0.05 in obese women and 0.784 ± 0.09 in normal weight women (P=0.004). The efficacy (maximal value) was 17.6 ± 4.9 nmol/l per min in obese women and 26.3 ± 3.8 nmol/l per min in normal weight women (P=0.009). Basal secretion rate, inflection point, and EC(50) values were not different. Bromocriptine or acipimox did not change the dose-response curve.

CONCLUSION

The ACTH-cortisol relation in obesity in women is characterized by decreased sensitivity and efficacy, thus explaining non-elevated serum cortisol concentrations despite increased plasma ACTH levels.

Differential effects to CCK-4-induced panic by dexamethasone and hydrocortisone

OBJECTIVES

Peripheral administration of the cholecystokinin (CCK) receptor agonist CCK-4 generates panic and activates the hypothalamic-pituitary-adrenal (HPA) axis. Direct effects at the pituitary and CCK-HPA interactions at higher regulatory sites have been suggested. According to preliminary data, ACTH response to CCK receptor agonists may differ from its response to exogenous CRH by its resistance to cortisol feedback inhibition. To further explore this resistance and to better characterize CCK-4 sites of action, the effects of different glucocorticoid pretreatments on CCK-4-induced panic were compared.

METHODS

Using a double-blind placebo-controlled design we pretreated healthy males with either dexamethasone (peripheral action) or hydrocortisone (central-peripheral action) each followed by a CCK-4 challenge. Blood levels of ACTH and cortisol were analyzed and panic symptoms were assessed.

RESULTS

We found a blunted response of ACTH release following CCK-4 injection only after hydrocortisone pretreatment. Dexamethasone however did not affect CCK-4-induced ACTH release relative to baseline. In contrast to dexamethasone, hydrocortisone reduced the severity of CCK-4-induced panic as measured by the Acute Panic Inventory on a trend level.

CONCLUSIONS

Findings suggest that CCK-4-induced stress hormone release seems susceptible to cortisol-feedback inhibition and argues for a suprapituitary site of CCK action. Effects on panic anxiety were weak but congruent with studies showing that CCK-4-induced HPA axis inhibition is accompanied by a reduction of anxiety after CCK-4.

Steroid psychosis: a review for neurosurgeons

Steroids are beneficial in neurological illness, but have many serious side effects. Having observed several patients with severe steroid psychoses, which greatly prolonged their hospitalizations, the authors sought to improve understanding of this entity. A literature review was conducted. The incidence of severe psychiatric symptoms was estimated in a meta-analysis of 2,555 patients to be 5.7 % and the incidence of any psychiatric symptoms was 18.6 % in patients receiving >80 mg/day of prednisone (12 mg/day dexamethasone). Dose is not predictive of time of onset, severity, type, or duration of symptoms. Symptoms can develop rapidly following exposure to even low doses and with oral, epidural, or intra-articular administration. Glucocorticoid effects on the brain fall into three categories: genomic, non-genomic, and neurotrophic/neurotoxic and can be permanent. Excessive glucocorticoid exposure may result in decreased production of endogenous neurosteroid molecules, resulting in unopposed glucocorticoid effects. Treatment includes early recognition, steroid withdrawal when appropriate, reduction in stimulation, and medication. Atypical antipsychotics like olanzapine and risperidone may cause fewer dystonic reactions and extrapyramidal symptoms than typical antipsychotics like haloperidol, and therefore, are often recommended as first line treatment. Steroids are powerful medications with many undesirable side effects. They should be used with caution. More research is needed on their effects on the human central nervous system.

The combined dexamethasone/TSST paradigm--a new method for psychoneuroendocrinology

The two main physiological systems involved in the regulation of the stress response are the hypothalamus-pituitary-adrenal (HPA) axis and the sympathetic nervous system (SNS). However, the interaction of these systems on the stress response remains poorly understood. To better understand the cross-regulatory effects of the different systems involved in stress regulation, we developed a new stress paradigm that keeps the activity of the HPA constant when exposing subjects to psychosocial stress. Thirty healthy male participants were recruited and randomly assigned to either a dexamethasone (DEX; n = 15) or placebo (PLC; n = 15) group. All subjects were instructed to take the Dexamethasone (2 mg) or Placebo pill the night before coming to the laboratory to undergo the Trier Social Stress Task (TSST). Salivary cortisol, salivary alpha amylase (sAA), heart rate, blood pressure and subjective stress were assessed throughout the protocol. As expected, the DEX group presented with suppressed cortisol levels. In comparison, their heart rate was elevated by approximately ten base points compared to the PLC group, with increases throughout the protocol and during the TSST. Neither sAA, nor systolic or diastolic blood pressures showed significant group differences. Subjective stress levels significantly increased from baseline, and were found to be higher before and after the TSST after DEX compared to placebo. These results demonstrate a significant interaction between the HPA and the SNS during acute stress. The SNS activity was found to be elevated in the presence of a suppressed HPA axis, with some further effects on subjective levels of stress. The method to suppress the HPA prior to inducing stress was found to completely reliable, without any adverse side effects. Therefore, we propose this paradigm as a new method to investigate the interaction of the two major stress systems in the regulation of the stress response.