The Neuroendocrine Impact of Acute Stress on Synaptic Plasticity

Stress induces changes in nervous system function on different signaling levels, from molecular signaling to synaptic transmission to neural circuits to behavior-and on different time scales, from rapid onset and transient to delayed and long-lasting. The principal effectors of stress plasticity are glucocorticoids, steroid hormones that act with a broad range of signaling competency due to the expression of multiple nuclear and membrane receptor subtypes in virtually every tissue of the organism. Glucocorticoid and mineralocorticoid receptors are localized to each of the cellular compartments of the receptor-expressing cells-the membrane, cytosol, and nucleus. In this review, we cover the neuroendocrine effects of stress, focusing mainly on the rapid actions of acute stress-induced glucocorticoids that effect changes in synaptic transmission and neuronal excitability by modulating synaptic and intrinsic neuronal properties via activation of presumed membrane glucocorticoid and mineralocorticoid receptors. We describe the synaptic plasticity that occurs in 4 stress-associated brain structures, the hypothalamus, hippocampus, amygdala, and prefrontal cortex, in response to single or short-term stress exposure. The rapid transformative impact of glucocorticoids makes this stress signal a particularly potent effector of acute neuronal plasticity.

Corticosteroid Receptors in Cardiac Health and Disease

Nuclear receptors play a central role in both energy metabolism and cardiomyocyte death and survival in the heart. Recent evidence suggests they may also influence cardiomyocyte endowment. Although several members of the nuclear receptor family play key roles in heart maturation (including thyroid hormone receptors) and cardiac metabolism, here, the focus will be on the corticosteroid receptors, the glucocorticoid receptor (GR) and mineralocorticoid receptor (MR). The heart is an important target for the actions of corticosteroids, yet the homeostatic role of GR and MR in the healthy heart has been elusive. However, MR antagonists are important in the treatment of heart failure, a condition associated with mitochondrial dysfunction and energy failure in cardiomyocytes leading to mitochondria-initiated cardiomyocyte death (Ingwall and Weiss, Circ Res 95:135-145, 2014; Ingwall , Cardiovasc Res 81:412-419, 2009; Zhou and Tian , J Clin Invest 128:3716-3726, 2018). In contrast, animal studies suggest GR activation in cardiomyocytes has a cardioprotective role, including in heart failure.

Glucocorticoid Receptor Signaling in Diabetes

Stress and depression increase the risk of Type 2 Diabetes (T2D) development. Evidence demonstrates that the Glucocorticoid (GC) negative feedback is impaired (GC resistance) in T2D patients resulting in Hypothalamic-Pituitary-Adrenal (HPA) axis hyperactivity and hypercortisolism. High GCs, in turn, activate multiple aspects of glucose homeostasis in peripheral tissues leading to hyperglycemia. Elucidation of the underlying molecular mechanisms revealed that Glucocorticoid Receptor (GR) mediates the GC-induced dysregulation of glucose production, uptake and insulin signaling in GC-sensitive peripheral tissues, such as liver, skeletal muscle, adipose tissue, and pancreas. In contrast to increased GR peripheral sensitivity, an impaired GR signaling in Peripheral Blood Mononuclear Cells (PBMCs) of T2D patients, associated with hyperglycemia, hyperlipidemia, and increased inflammation, has been shown. Given that GR changes in immune cells parallel those in brain, the above data implicate that a reduced brain GR function may be the biological link among stress, HPA hyperactivity, hypercortisolism and hyperglycemia. GR polymorphisms have also been associated with metabolic disturbances in T2D while dysregulation of micro-RNAs—known to target GR mRNA—has been described. Collectively, GR has a crucial role in T2D, acting in a cell-type and context-specific manner, leading to either GC sensitivity or GC resistance. Selective modulation of GR signaling in T2D therapy warrants further investigation.

TAZ inhibits glucocorticoid receptor and coordinates hepatic glucose homeostasis in normal physiological states

The elucidation of the mechanisms whereby the liver maintains glucose homeostasis is crucial for the understanding of physiological and pathological states. Here, we show a novel role of hepatic transcriptional co-activator with PDZ-binding motif (TAZ) in the inhibition of glucocorticoid receptor (GR). TAZ is abundantly expressed in pericentral hepatocytes and its expression is markedly reduced by fasting. TAZ interacts via its WW domain with the ligand-binding domain of GR to limit the binding of GR to the GR response element in gluconeogenic gene promoters. Therefore, liver-specific TAZ knockout mice show increases in glucose production and blood glucose concentration. Conversely, the overexpression of TAZ in mouse liver reduces the binding of GR to gluconeogenic gene promoters and glucose production. Thus, our findings demonstrate that hepatic TAZ inhibits GR transactivation of gluconeogenic genes and coordinates gluconeogenesis in response to physiological fasting and feeding.

Corticosterone pattern-dependent glucocorticoid receptor binding and transcriptional regulation within the liver

Ultradian glucocorticoid rhythms are highly conserved across mammalian species, however, their functional significance is not yet fully understood. Here we demonstrate that pulsatile corticosterone replacement in adrenalectomised rats induces a dynamic pattern of glucocorticoid receptor (GR) binding at ~3,000 genomic sites in liver at the pulse peak, subsequently not found during the pulse nadir. In contrast, constant corticosterone replacement induced prolonged binding at the majority of these sites. Additionally, each pattern further induced markedly different transcriptional responses. During pulsatile treatment, intragenic occupancy by active RNA polymerase II exhibited pulsatile dynamics with transient changes in enrichment, either decreased or increased depending on the gene, which mostly returned to baseline during the inter-pulse interval. In contrast, constant corticosterone exposure induced prolonged effects on RNA polymerase II occupancy at the majority of gene targets, thus acting as a sustained regulatory signal for both transactivation and repression of glucocorticoid target genes. The nett effect of these differences were consequently seen in the liver transcriptome as RNA-seq analysis indicated that despite the same overall amount of corticosterone infused, twice the number of transcripts were regulated by constant corticosterone infusion, when compared to pulsatile. Target genes that were found to be differentially regulated in a pattern-dependent manner were enriched in functional pathways including carbohydrate, cholesterol, glucose and fat metabolism as well as inflammation, suggesting a functional role for dysregulated glucocorticoid rhythms in the development of metabolic dysfunction.

Adrenal glucocorticoid hormones are released in a characteristic ultradian rhythm that becomes dysregulated during chronic stress, disease, or synthetic corticosteroid treatment. Metabolic dysfunction is a comorbidity associated with all these conditions, but the role that altered glucocorticoid dynamics play is unknown. As the liver is a major site of glucocorticoid action on metabolic homeostasis regulated by the glucocorticoid receptor, we have assessed how different patterns of hormone replacement in adrenalectomised rats differentially regulate gene pathways involved in type II diabetes, cirrhosis, and fatty liver development, via altering the pattern of glucocorticoid receptor binding to regulatory sites. We believe our findings have important implications for therapies that can reproduce the endogenous glucocorticoid rhythm and thus minimize adverse metabolic side-effects in patients.

Pandemic aspect of dexamethasone: Molecular mechanisms and clinical application

The rapid spread of coronavirus disease (COVID-19) in many countries has caused inconvenience in conducting daily life activities, and even deaths. Dexamethasone is a corticosteroid applied in clinical medicine since 1957, especially in immune therapy fields. Herein, we present the characteristics of Dexamethasone, from molecular mechanisms such as genomic and nongenomic pathways by cellular signal regulations, to clinical applications in various phases of the disease. During COVID-19 pandemic, Dexamethasone given to patients who required oxygen or ventilation therapy showed improved life efficacy.

Prostaglandin E2 stimulates cAMP signaling and resensitizes human leukemia cells to glucocorticoid-induced cell death

Glucocorticoid (GC) resistance remains a clinical challenge in pediatric acute lymphoblastic leukemia where response to GC is a reliable prognostic indicator. To identify GC resistance pathways, we conducted a genome-wide, survival-based, short hairpin RNA screen in murine T-cell acute lymphoblastic leukemia (T-ALL) cells. Genes identified in the screen interfere with cyclic adenosine monophosphate (cAMP) signaling and are underexpressed in GC-resistant or relapsed ALL patients. Silencing of the cAMP-activating Gnas gene interfered with GC-induced gene expression, resulting in dexamethasone resistance in vitro and in vivo. We demonstrate that cAMP signaling synergizes with dexamethasone to enhance cell death in GC-resistant human T-ALL cells. We find the E prostanoid receptor 4 expressed in T-ALL samples and demonstrate that prostaglandin E2 (PGE2) increases intracellular cAMP, potentiates GC-induced gene expression, and sensitizes human T-ALL samples to dexamethasone in vitro and in vivo. These findings identify PGE2 as a target for GC resensitization in relapsed pediatric T-ALL.

Role of glucocorticoid receptor phosphorylation-mediated synaptic plasticity in anxiogenic and depressive behaviors induced by monosodium glutamate

Psychiatric diseases and metabolic disorders frequently cooccur, yet the mechanisms underlying this interaction remain unknown. The aim of this study was to determine the role of glucocorticoid receptor (GR) phosphorylation in the comorbidity of metabolic and psychiatric disorders. Neonatal Sprague-Dawley rats were subcutaneously injected with monosodium glutamate (MSG) every 2 days for 10 days after birth. Metabolic and behavioral tests were performed 12 weeks later. Golgi staining and transmission electron microscopy (TEM) were performed to evaluate synaptic structural plasticity. Changes in GR phosphorylation and the BDNF/TrkB pathway were evaluated by western blotting and immunofluorescence. We found that MSG-treated rats displayed significant metabolic abnormalities accompanied by anxiogenic and depressive behaviors, an altered synaptic ultrastructure and the loss of dendritic spines. The expression of phosphorylated GR was reduced in the brain. Furthermore, a specific agonist of BDNF/TrkB significantly reversed the reduction in GR phosphorylation, as well as the metabolic and behavioral outcomes. These findings indicate that a decrease in BDNF/TrkB pathway-dependent GR phosphorylation is a long-term effect of MSG treatment that may contribute to metabolic and behavioral disturbances.

Hypoxia regulates GR function through multiple mechanisms involving microRNAs 103 and 107

Glucocorticoids (Gcs) potently inhibit inflammation, and regulate liver energy metabolism, often acting in a hypoxic environment. We now show hypoxic conditions open a specific GR cistrome, and prevent access of GR to part of the normoxic GR cistrome. Motif analysis identified enrichment of KLF4 binding sites beneath those peaks of GR binding exclusive to normoxia, implicating KLF4 as a pioneer, or co-factor under these conditions. Hypoxia reduced KLF4 expression, however, knockdown of KLF4 did not impair GR recruitment. KLF4 is a known target of microRNAs 103 and 107, both of which are induced by hypoxia. Expression of mimics to either microRNA103, or microRNA107 inhibited GR transactivation of normoxic target genes, thereby replicating the hypoxic effect. Therefore, studies in hypoxia reveal that microRNAs 103 and 107 are potent regulators of GR function. We have now identified a new pathway linking hypoxia through microRNAs 103 and 107 to regulation of GR function.

Multifaceted Control of GR Signaling and Its Impact on Hepatic Transcriptional Networks and Metabolism

Glucocorticoids (GCs) and the glucocorticoid receptor (GR) are important regulators of development, inflammation, stress response and metabolism, demonstrated in various diseases including Addison's disease, Cushing's syndrome and by the many side effects of prolonged clinical administration of GCs. These conditions include severe metabolic challenges in key metabolic organs like the liver. In the liver, GR is known to regulate the transcription of key enzymes in glucose and lipid metabolism and contribute to the regulation of circadian-expressed genes. Insights to the modes of GR regulation and the underlying functional mechanisms are key for understanding diseases and for the development of improved clinical uses of GCs. The activity and function of GR is regulated at numerous levels including ligand availability, interaction with heat shock protein (HSP) complexes, expression of GR isoforms and posttranslational modifications. Moreover, recent genomics studies show functional interaction with multiple transcription factors (TF) and coregulators in complex transcriptional networks controlling cell type-specific gene expression by GCs. In this review we describe the different regulatory steps important for GR activity and discuss how different TF interaction partners of GR selectively control hepatic gene transcription and metabolism.

Bidirectional crosstalk between Hypoxia-Inducible Factor and glucocorticoid signalling in zebrafish larvae

In the last decades in vitro studies highlighted the potential for crosstalk between Hypoxia-Inducible Factor-(HIF) and glucocorticoid-(GC) signalling pathways. However, how this interplay precisely occurs in vivo is still debated. Here, we use zebrafish larvae (Danio rerio) to elucidate how and to what degree hypoxic signalling affects the endogenous glucocorticoid pathway and vice versa, in vivo. Firstly, our results demonstrate that in the presence of upregulated HIF signalling, both glucocorticoid receptor (Gr) responsiveness and endogenous cortisol levels are repressed in 5 days post fertilisation larvae. In addition, despite HIF activity being low at normoxia, our data show that it already impedes both glucocorticoid activity and levels. Secondly, we further analysed the in vivo contribution of glucocorticoids to HIF activity. Interestingly, our results show that both glucocorticoid receptor (GR) and mineralocorticoid receptor (MR) play a key role in enhancing it. Finally, we found indications that glucocorticoids promote HIF signalling via multiple routes. Cumulatively, our findings allowed us to suggest a model for how this crosstalk occurs in vivo.

Glucocorticoid signalling drives reduced versican levels in the fetal mouse lung

Glucocorticoid (GC) signaling via the glucocorticoid receptor (GR) is essential for lung maturation in mammals. Previous studies using global or conditional mouse model knockouts of the GR gene have established that GR-mediated signaling in the interstitial mesenchyme of the fetal lung is critical for normal lung development. Screens for downstream GC-targets in conditional mesenchymal GR deficient mouse lung (GRmesKO) identified Versican (Vcan), an important extracellular matrix component and cell proliferation regulator, as a potential GR-regulated target. We show that, of the five major VCAN isoforms, the VCAN-V1 isoform containing the GAGβ domain is the predominant VCAN isoform in the fetal mouse lung distal mesenchyme at both E16.5 and E18.5, whereas the GAGα-specific VCAN-V2 isoform was only localized to the smooth muscle surrounding proximal airways. Both Vcan-V1 mRNA and protein levels were strongly overexpressed in the GRmesKO lung at E18.5. Finally, we investigated the GC regulation of the ECM protease ADAMTS 12 and showed that Adamts 12 mRNA levels were markedly reduced at E18.5 in GRmesKO fetal mouse lung and were strongly induced by both cortisol and betamethasone in cultures of primary rat fetal lung fibroblasts. ADAMTS12 protein immunoreactivity was also strongly increased in the distal lung at E18.5, after dexamethasone treatment in utero. In summary, glucocorticoid signaling via GR represses GAGβ domain-containing VCAN isoforms in distal lung mesenchyme in vivo by repressing Vcan gene expression and, in part, by inducing the ECM protease ADAMTS12, thereby contributing to the control of ECM remodelling and lung cell proliferation prior to birth.

Quantitative Evaluation of the Transcriptional Activity of Steroid Hormone Receptor Mutants and Variants Using a Single Vector With Two Reporters and a Receptor Expression Cassette

Although the rapid development of high-throughput sequencing has led to the identification of a large number of truncated or mutated steroid hormone receptor (SHR) variants, their clinical relevance remains to be defined. A platform for functional analysis of these SHR variants in cells would be instrumental for better assessing their impact on normal physiology and SHR-associated diseases. Here we have developed a new reporter system that allows rapid and accurate assessment of the transcriptional activity of SHR variants in cells. The reporter is a single construct containing a firefly luciferase reporter gene, whose expression is under the control of a promoter with multiple steroid hormone responsive elements, and a Renilla luciferase reporter gene, that is constitutively expressed under the control of an internal ribosome entry site (IRES) and is not regulated by steroid hormones. The corresponding SHR (wildtype or mutant/variant) is also expressed from the same construct. Using this improved reporter system, we revealed a large spectrum of transactivation activities within a set of previously identified mutations and variations of the androgen receptor (AR), the estrogen receptor α (ERα) and the glucocorticoid receptor (GR). This novel reporter system enables functional analysis of SHR mutants and variants in physiological and pathological settings, offering valuable preclinical, or diagnostic information for the understanding and treatment of associated diseases.

Lasting Impact of Chronic Adolescent Stress and Glucocorticoid Receptor Selective Modulation in Male and Female Rats

Adolescent animals are vulnerable to the effects of stress on brain development. We hypothesized that long-term effects of adolescent chronic stress are mediated by glucocorticoid receptor (GR) signaling. We used a specific GR modulator (CORT108297) to pharmacologically disrupt GR signaling in adolescent rats during exposure to chronic variable stress (CVS). Male and female rats received 30 mg/kg of drug during a 2-week CVS protocol starting at PND46. Emotional reactivity (open field) and coping behaviors (forced swim test (FST)) were then tested in adulthood, 5 weeks after the end of the CVS protocol. Blood samples were collected two days before FST and serial samples after the onset of the swim test to determine baseline and stress response levels of HPA hormones respectively. Our results support differential behavioral, physiological and stress circuit reactivity to adolescent chronic stress exposure in males and females, with variable involvement of GR signaling. In response to adolescent stress, males had heightened reactivity to novelty and exhibited marked reduction in neuronal excitation following swim stress in adulthood, whereas females developed a passive coping strategy in the FST and enhanced HPA axis stress reactivity. Only the latter effect was attenuated by treatment with the GR modulator C108297. In summary, our data suggest that adolescent stress differentially affects emotional behavior and circuit development in males and females, and that GR manipulation during stress can reverse at least some of these effects.

The impact of steroids on the injured podocytes in nephrotic syndrome

Nephrotic syndrome (NS), a common chronic kidney disease, embraces a variety of kidney disorders. Though Glucocorticoids (GCs) are generally used in the treatment of NS, their mechanism of action is poorly understood. A plethora of evidence indicates that podocytes are considered as the main target cells for the therapeutic strategies to prevent NS. GCs regulate the transactivation and transrepression of genes in podocytes that affect their morphological and cytoskeletal features, motility, apoptosis and survival rate. Moreover, they prevent protein leakage through the glomerular barrier membrane by affecting the synthesis, trafficking and posttranslational modifications of slit diaphragms components, podocytes' intercellular junctions. The response to the treatment is variable among different ethnics and populations and resistance to the steroids is detected in almost 50% of adult patients. Not only do pharmacokinetics and pharmacogenetics of steroids play a role in GC resistance but also the genetic variations in one or more podocyte related genes are connected with the steroid resistance in cases with NS. The focus of this review is to explain the underlying cellular and molecular mechanisms of GCs in podocytes. Understanding the mechanisms by which the GCs and GCs receptors in podocytes regulate the gene expression network and crosstalk with other molecular pathways would guarantee an optimum therapeutic benefit of steroid treatment.

General Adaptation in Critical Illness: Glucocorticoid Receptor-alpha Master Regulator of Homeostatic Corrections

In critical illness, homeostatic corrections representing the culmination of hundreds of millions of years of evolution, are modulated by the activated glucocorticoid receptor alpha (GRα) and are associated with an enormous bioenergetic and metabolic cost. Appreciation of how homeostatic corrections work and how they evolved provides a conceptual framework to understand the complex pathobiology of critical illness. Emerging literature place the activated GRα at the center of all phases of disease development and resolution, including activation and re-enforcement of innate immunity, downregulation of pro-inflammatory transcription factors, and restoration of anatomy and function. By the time critically ill patients necessitate vital organ support for survival, they have reached near exhaustion or exhaustion of neuroendocrine homeostatic compensation, cell bio-energetic and adaptation functions, and reserves of vital micronutrients. We review how critical illness-related corticosteroid insufficiency, mitochondrial dysfunction/damage, and hypovitaminosis collectively interact to accelerate an anti-homeostatic active process of natural selection. Importantly, the allostatic overload imposed by these homeostatic corrections impacts negatively on both acute and long-term morbidity and mortality. Since the bioenergetic and metabolic reserves to support homeostatic corrections are time-limited, early interventions should be directed at increasing GRα and mitochondria number and function. Present understanding of the activated GC-GRα's role in immunomodulation and disease resolution should be taken into account when re-evaluating how to administer glucocorticoid treatment and co-interventions to improve cellular responsiveness. The activated GRα interdependence with functional mitochondria and three vitamin reserves (B1, C, and D) provides a rationale for co-interventions that include prolonged glucocorticoid treatment in association with rapid correction of hypovitaminosis.

Role of Hepatic Glucocorticoid Receptor in Metabolism in Models of 5αR1 Deficiency in Male Mice

Inhibition of 5α-reductases impairs androgen and glucocorticoid metabolism and induces insulin resistance in humans and rodents. The contribution of hepatic glucocorticoids to these adverse metabolic changes was assessed using a liver-selective glucocorticoid receptor (GR) antagonist, A-348441. Mice lacking 5α-reductase 1 (5αR1-KO) and their littermate controls were studied during consumption of a high-fat diet, with or without A-348441(120 mg/kg/d). Male C57BL/6 mice (age, 12 weeks) receiving dutasteride (1.8 mg/kg/d)) or vehicle with consumption of a high-fat diet, with or without A-348441, were also studied. In the 5αR1-KO mice, hepatic GR antagonism improved diet-induced insulin resistance but not more than that of the controls. Liver steatosis was not affected by hepatic GR antagonism in either 5αR1KO mice or littermate controls. In a second model of 5α-reductase inhibition using dutasteride and hepatic GR antagonism with A-348441 attenuated the excess weight gain resulting from dutasteride (mean ± SEM, 7.03 ± 0.5 vs 2.13 ± 0.4 g; dutasteride vs dutasteride plus A-348441; P < 0.05) and normalized the associated hyperinsulinemia after glucose challenge (area under the curve, 235.9 ± 17 vs 329.3 ± 16 vs 198.4 ± 25 ng/mL/min; high fat vs high fat plus dutasteride vs high fat plus dutasteride plus A-348441, respectively; P < 0.05). However, A-348441 again did not reverse dutasteride-induced liver steatosis. Thus, overall hepatic GR antagonism improved the insulin resistance but not the steatosis induced by a high-fat diet. Moreover, it attenuated the excessive insulin resistance caused by pharmacological inhibition of 5α-reductases but not genetic disruption of 5αR1. The use of dutasteride might increase the risk of type 2 diabetes mellitus and reduced exposure to glucocorticoids might be beneficial.

Identification of Betamethasone-Regulated Target Genes and Cell Pathways in Fetal Rat Lung Mesenchymal Fibroblasts

Preterm birth is characterized by severe lung immaturity that is frequently treated antenatally or postnatally with the synthetic steroid betamethasone. The underlying cellular targets and pathways stimulated by betamethasone in the fetal lung are poorly defined. In this study, betamethasone was compared with corticosterone in steroid-treated primary cultures of fetal rat lung fibroblasts stimulated for 6 hours and analyzed by whole-cell transcriptome sequencing and glucocorticoid (GC) receptor (GR) chromatin immunoprecipitation sequencing (ChIP-Seq) analysis. Strikingly, betamethasone stimulated a much stronger transcriptional response compared with corticosterone for both induced and repressed genes. A total of 483 genes were significantly stimulated by betamethasone or corticosterone, with 476 stimulated by both steroids, indicating a strong overlap in regulation. Changes in mRNA levels were confirmed by quantitative PCR for eight induced and repressed target genes. Pathway analysis identified cell proliferation and cytoskeletal/cell matrix remodeling pathways as key processes regulated by both steroids. One target, transglutaminase 2 (Tgm2), was localized to fetal lung mesenchymal cells. Tgm2 mRNA and protein levels were strongly increased in fibroblasts by both steroids. Whole-genome GR ChIP-Seq analysis with betamethasone identified GC response element-binding sites close to the previously characterized GR target genes Per1, Dusp1, Fkbp5, and Sgk1 and near the genes identified by transcriptome sequencing encoding Crispld2, Tgm2, Hif3α, and Kdr, defining direct genomic induction of expression in fetal lung fibroblasts via the GR. These results demonstrate that betamethasone stimulates specific genes and cellular pathways controlling cell proliferation and extracellular matrix remodeling in lung mesenchymal fibroblasts, providing a basis for betamethasone's treatment efficacy in preterm birth.

Elevated resting-state connectivity in the medial temporal lobe and the prefrontal cortex among patients with Cushing's syndrome in remission

Objective Cushing's syndrome is associated with long-term cognitive deficits and affective symptoms such as depression and anxiety. The alterations in brain function underlying these deficits after Cushing's syndrome are unclear and therefore we aimed to explore alterations in resting-state functional connectivity in patients with Cushing's syndrome in remission. Design Cross-sectional case-control study. Methods Nineteen women with Cushing's syndrome in remission for a median time of 7 years (IQR: 6-10) and a mean age of 45 years were included at three university clinics. These patients and 38 age-matched female controls underwent brain imaging at a single center. The main outcome measure was functional connectivity at rest, measured with functional magnetic resonance imaging. Results The medial temporal lobe (MTL) and prefrontal cortex networks, exhibited elevated functional connectivity among patients compared to controls. The degree of elevated functional connectivity in the MTL was negatively associated with time in remission. Conclusions Resting-state functional connectivity within glucocorticoid receptor-rich regions, particularly the MTL and medial prefrontal cortex, was increased in patients. These differences in connectivity may provide a neural basis for the cognitive deficits and affective symptoms commonly experienced by patients with Cushing's syndrome in remission.

Top-down and bottom-up control of stress-coping

In this 30th anniversary issue review, we focus on the glucocorticoid modulation of limbic-prefrontocortical circuitry during stress-coping. This action of the stress hormone is mediated by mineralocorticoid receptors (MRs) and glucocorticoid receptors (GRs) that are co-expressed abundantly in these higher brain regions. Via both receptor types, the glucocorticoids demonstrate, in various contexts, rapid nongenomic and slower genomic actions that coordinate consecutive stages of information processing. MR-mediated action optimises stress-coping, whereas, in a complementary fashion, the memory storage of the selected coping strategy is promoted via GR. We highlight the involvement of adipose tissue in the allocation of energy resources to central regulation of stress reactions, point to still poorly understood neuronal ensembles in the prefrontal cortex that underlie cognitive flexibility critical for effective coping, and evaluate the role of cortisol as a pleiotropic regulator in vulnerability to, and treatment of, trauma-related psychiatric disorders.

Glucocorticoid receptor in stromal cells is essential for glucocorticoid-mediated suppression of inflammation in arthritis

BACKGROUND

Glucocorticoid (GC) therapy is frequently used to treat rheumatoid arthritis due to potent anti-inflammatory actions of GCs. Direct actions of GCs on immune cells were suggested to suppress inflammation.

OBJECTIVES

Define the role of the glucocorticoid receptor (GR) in stromal cells for suppression of inflammatory arthritis.

METHODS

Bone marrow chimeric mice lacking the GR in the hematopoietic or stromal compartment, respectively, and mice with impaired GR dimerisation (GRdim) were analysed for their response to dexamethasone (DEX, 1 mg/kg) treatment in serum transfer-induced arthritis (STIA). Joint swelling, cell infiltration (histology), cytokines, cell composition (flow cytometry) and gene expression were analysed and RNASeq of wild type and GRdim primary murine fibroblast-like synoviocytes (FLS) was performed.

RESULTS

GR deficiency in immune cells did not impair GC-mediated suppression of STIA. In contrast, mice with GR-deficient or GR dimerisation-impaired stromal cells were resistant to GC treatment, despite efficient suppression of cytokines. Intriguingly, in mice with impaired GR function in the stromal compartment, GCs failed to stimulate non-classical, non-activated macrophages (Ly6Cneg, MHCIIneg) and associated anti-inflammatory markers CD163, CD36, AnxA1, MerTK and Axl. Mice with GR deficiency in FLS were partially resistant to GC-induced suppression of STIA. Accordingly, RNASeq analysis of DEX-treated GRdim FLS revealed a distinct gene signature indicating enhanced activity and a failure to reduce macrophage inflammatory protein (Mip)-1α and Mip-1β.

CONCLUSION

We report a novel anti-inflammatory mechanism of GC action that involves GR dimerisation-dependent gene regulation in non-immune stromal cells, presumably FLS. FLS control non-classical, anti-inflammatory polarisation of macrophages that contributes to suppression of inflammation in arthritis.

HIV and symptoms of depression are independently associated with impaired glucocorticoid signaling

Chronic inflammation caused by HIV infection may lead to deficient glucocorticoid (GC) signaling predisposing people living with HIV to depression and other psychiatric disorders linked to GC resistance. We hypothesized that comorbid HIV and depressive symptoms in women would synergistically associate with deficits in GC signaling. This cross-sectional study used samples obtained from the Women's Interagency HIV Study (WIHS). The Centers for Epidemiological Studies (CES-D) was used to define depression in four groups of women from the Women's Interagency HIV Study (WIHS): 1) HIV-negative, non-depressed (n = 37); 2) HIV-negative, depressed (n = 34); 3) HIV-positive, non-depressed (n = 38); and 4) HIV-positive, depressed (n = 38). To assess changes in GC signaling from peripheral blood mononuclear cells (PBMCs), we examined baseline and dexamethasone (Dex)-stimulated changes in the expression of the GC receptor (GR, gene: Nr3c1) and its negative regulator Fkbp5 via quantitative RT-PCR. GR sensitivity was evaluated in vitro by assessing the Dex inhibition of lipopolysaccharide (LPS)-stimulated IL-6 and TNF-α levels. Depressive symptoms and HIV serostatus were independently associated with elevated baseline expression of Fkbp5 and Nr3c1. Depressive symptoms, but not HIV status, was independently associated with reduced LPS-induced release of IL-6. Counter to predictions, there was no interactive association of depressive symptoms and HIV on any outcome. Comorbid depressive symptoms with HIV infection were associated with a gene expression and cytokine profile similar to that of healthy control women, a finding that may indicate further disruptions in disease adaptation.

Corticosteroids and the brain

The brain is continuously exposed to varying levels of adrenal corticosteroid hormones such as corticosterone in rodents and cortisol in humans. Natural fluctuations occur due to ultradian and circadian variations or are caused by exposure to stressful situations. Brain cells express two types of corticosteroid receptors, i.e. mineralocorticoid and glucocorticoid receptors, which differ in distribution and affinity. These receptors can mediate both rapid non-genomic and slow gene-mediated neuronal actions. As a consequence of these factors, natural (e.g. stress-induced) shifts in corticosteroid level are associated with a complex mosaic of time- and region-dependent changes in neuronal activity. A series of experiments in humans and rodents have revealed that these time- and region-dependent cellular characteristics are also reflected in distinct cognitive patterns after stress. Thus, directly after a peak of corticosteroids, attention and vigilance are increased, and areas involved in emotional responses and simple behavioral strategies show enhanced activity. In the aftermath of stress, areas involved in higher cognitive functions become activated allowing individuals to link stressful events to the specific context and to store information for future use. Both phases of the brain's response to stress are important to face a continuously changing environment, promoting adaptation at the short as well as long term. We argue that a balanced response during the two phases is essential for resilience. This balance may become compromised after repeated stress exposure, particularly in genetically vulnerable individuals and aggravate disease manifestation. This not only applies to psychiatric disorders but also to neurological diseases such as epilepsy.

A glucocorticoid receptor antagonist reduces sign-tracking behavior in male Japanese quail

Addiction is characterized as a chronic debilitating disease. One devastating feature of addiction is the susceptibility of relapse (40-60%) after stretches of abstinence. One theory that may account for relapse suggests that drug cues (e.g., paraphernalia) may increase stress hormones, and this may prompt relapse. Repeatedly pairing a neutral cue with a reward is commonly utilized to measure what subjects learn about a cue that is predictive of reward. Research has shown that animals that attend to a cue more than to the reward (sign trackers) may be more vulnerable to drug addiction. Additionally, research has shown that sign tracking is associated with an increase in corticosterone, a primary stress hormone. PT150 is a novel glucocorticoid receptor antagonist that moderates the release of corticosterone. In the current experiment, it was hypothesized that subjects given repeated administration of PT150 would reduce sign tracking compared to subjects given placebo. Time spent (in seconds) near a cue that predicts reward (conditional stimulus) served as a measure of sign tracking, and PT150 or placebo was administered following sign tracking. An independent-samples t test revealed that subjects that received PT150 had reduced time spent near the conditioned stimulus compared to controls. Given the devastating effects of drug addiction, identification of a potential pharmacological intervention in the reduction of relapse would be of great value. Therefore, future research is needed to validate the use of PT150 in reducing behaviors associated with drug addiction. (PsycINFO Database Record

Common genes associated with antidepressant response in mouse and man identify key role of glucocorticoid receptor sensitivity

Response to antidepressant treatment in major depressive disorder (MDD) cannot be predicted currently, leading to uncertainty in medication selection, increasing costs, and prolonged suffering for many patients. Despite tremendous efforts in identifying response-associated genes in large genome-wide association studies, the results have been fairly modest, underlining the need to establish conceptually novel strategies. For the identification of transcriptome signatures that can distinguish between treatment responders and nonresponders, we herein submit a novel animal experimental approach focusing on extreme phenotypes. We utilized the large variance in response to antidepressant treatment occurring in DBA/2J mice, enabling sample stratification into subpopulations of good and poor treatment responders to delineate response-associated signature transcript profiles in peripheral blood samples. As a proof of concept, we translated our murine data to the transcriptome data of a clinically relevant human cohort. A cluster of 259 differentially regulated genes was identified when peripheral transcriptome profiles of good and poor treatment responders were compared in the murine model. Differences in expression profiles from baseline to week 12 of the human orthologues selected on the basis of the murine transcript signature allowed prediction of response status with an accuracy of 76% in the patient population. Finally, we show that glucocorticoid receptor (GR)-regulated genes are significantly enriched in this cluster of antidepressant-response genes. Our findings point to the involvement of GR sensitivity as a potential key mechanism shaping response to antidepressant treatment and support the hypothesis that antidepressants could stimulate resilience-promoting molecular mechanisms. Our data highlight the suitability of an appropriate animal experimental approach for the discovery of treatment response-associated pathways across species.

Major depression is the second leading cause of disability worldwide. However, only one-third of patients with depression benefit from the first antidepressant compound they are prescribed. It is a fundamental problem that the outcomes of individual antidepressant treatments are still highly unpredictable. In clinical studies, discovery of biomarkers for antidepressant response is hampered by confounding factors such as the heterogeneity of the disease phenotype and additional environmental factors, e.g., previous life events and different schedules of psychopharmacological treatment, which reduce the power to detect true response biomarkers. To overcome some of these limitations, we have established a conceptually novel approach that allows the selection of extreme phenotypes in an antidepressant-responsive mouse strain. In the first step, we identify signatures in the transcriptome of peripheral blood associated with responses following stratification into good and poor treatment responders. As proof of concept, we translate the murine data to a population of depressed patients. We show that differences in expression profiles from baseline to week 12 of the human orthologues predict response status in patients. We finally provide evidence that sensitivity of the glucocorticoid receptor could be a potential key mechanism shaping response to antidepressant treatment.

Pioneer Factors FOXA1 and FOXA2 Assist Selective Glucocorticoid Receptor Signaling in Human Endometrial Cells

Successful pregnancy relies on dynamic control of cell signaling to achieve uterine receptivity and the necessary biological changes required for endometrial decidualization, embryo implantation, and fetal development. Glucocorticoids are master regulators of intracellular signaling and can directly regulate embryo implantation and endometrial remodeling during murine pregnancy. In immortalized human uterine cells, we have shown that glucocorticoids and estradiol (E2) coregulate thousands of genes. Recently, glucocorticoids and E2 were shown to coregulate the expression of Left-right determination factor 1 (LEFTY1), previously implicated in the regulation of decidualization. To elucidate the molecular mechanism by which glucocorticoids and E2 regulate the expression of LEFTY1, immortalized and primary human endometrial cells were evaluated for gene expression and receptor recruitment to regulatory regions of the LEFTY1 gene. Glucocorticoid administration induced expression of LEFTY1 messenger RNA and protein and recruitment of the glucocorticoid receptor (GR) and activated polymerase 2 to the promoter of LEFTY1. Glucocorticoid-mediated recruitment of GR was dependent on pioneer factors FOXA1 and FOXA2. E2 was found to antagonize glucocorticoid-mediated induction of LEFTY1 by reducing recruitment of GR, FOXA1, FOXA2, and activated polymerase 2 to the LEFTY1 promoter. Gene expression analysis identified several genes whose glucocorticoid-dependent induction required FOXA1 and FOXA2 in endometrial cells. These results suggest a molecular mechanism by which E2 antagonizes GR-dependent induction of specific genes by preventing the recruitment of the pioneer factors FOXA1 and FOXA2 in a physiologically relevant model.

Nuclear Receptor Function through Genomics: Lessons from the Glucocorticoid Receptor

Unlocking the therapeutic potential of the glucocorticoid receptor (GR) has motivated a search for small molecules that selectively modulate its ability to activate or repress gene transcription. Recently, breakthrough studies in the field of genomics have reinvigorated debate over longstanding transcriptional models explaining how GR controls tissue-specific gene expression. Here, we highlight these genomic studies with the dual goals of advancing understanding of nuclear receptor-mediated transcription and stimulating thought on the development of anti-inflammatory and immunosuppressive ligands for GR that have reduced harmful effects on metabolism.

Glucocorticoid receptor signalling activates YAP in breast cancer

The Hippo pathway is an oncosuppressor signalling cascade that plays a major role in the control of cell growth, tissue homoeostasis and organ size. Dysregulation of the Hippo pathway leads to aberrant activation of the transcription co-activator YAP (Yes-associated protein) that contributes to tumorigenesis in several tissues. Here we identify glucocorticoids (GCs) as hormonal activators of YAP. Stimulation of glucocorticoid receptor (GR) leads to increase of YAP protein levels, nuclear accumulation and transcriptional activity in vitro and in vivo. Mechanistically, we find that GCs increase expression and deposition of fibronectin leading to the focal adhesion-Src pathway stimulation, cytoskeleton-dependent YAP activation and expansion of chemoresistant cancer stem cells. GR activation correlates with YAP activity in human breast cancer and predicts bad prognosis in the basal-like subtype. Our results unveil a novel mechanism of YAP activation in cancer and open the possibility to target GR to prevent cancer stem cells self-renewal and chemoresistance.

Environmental enrichment protects against stress-induced anxiety: Role of glucocorticoid receptor, ERK, and CREB signaling in the basolateral amygdala

Environmental enrichment (EE) is an experimental animal model that enhances an animal's opportunity to interact with sensory, motor, and social stimuli, compared to standard laboratory conditions. A prominent benefit of EE is the reduction of stress-induced anxiety. The relationship between stress and the onset of anxiety-like behavior has been widely investigated in experimental research, showing a clear correlation with structural changes in the hippocampus and basolateral amygdala (BLA). However, the mechanisms by which EE exerts its protective roles in stress and anxiety remain unclear, and it is not known whether EE reduces the effects of acute stress on animal behavior shortly following the cessation of stress. We found that EE can prevent the emergence of anxiety-like symptoms in rats measured immediately after acute restraint stress (1 h) and this effect is not due to changes in systemic release of corticosterone. Rather, we found that stress promotes a rapid increase in the nuclear translocation of glucocorticoid receptor (GR) in the BLA, an effect prevented by previous EE exposure. Furthermore, we observed a reduction of ERK (a MAPK protein) and CREB activity in the BLA promoted by both EE and acute stress. Finally, we found that EE decreases the expression of the immediate-early gene EGR-1 in the BLA, indicating a possible reduction of neuronal activity in this region. Hyperactivity of BLA neurons has been reported to accompany anxiety-like behavior and changes in this process may be one of the mechanism by which EE exerts its protective effects against stress-induced anxiety.

The Effects of Chorioamnionitis and Betamethasone on 11β, Hydroxysteroid Dehydrogenase Types 1 and 2 and the Glucocorticoid Receptor in Preterm Human Placenta

OBJECTIVE

Preterm birth is one of the major problems faced in perinatal medicine and is often associated with underlying clinical infection. Treatment with maternal betamethasone has helped to improve neonatal morbidity and mortality. We hypothesized that betamethasone treatment and chorioamnionitis would alter the bioavailability of placental glucocorticoids through the regulation of the 11beta hydroxysteroid dehydrogenase (11beta HSD) isozymes and the glucocorticoid receptor (GR).

METHODS

Placental samples were obtained from three groups of women who delivered prematurely: (1) those who delivered in the absence of infection, (2) those who received betamethasone treatment before delivering without infection, and (3) those who had pregnancies complicated with chorioamnionitis. Western blotting was used to determine 11beta HSD-1, 11beta HSD-2, GRT, and GRalpha expression, and 11beta HSD-2 activity was determined in each group. JEG-3 cells were used to study the regulation of the 11beta HSD isozymes.

RESULTS

In cases of chorioamnionitis where mothers had not been treated with betamethasone, placental 32-kd 11beta HSD-1 protein expression was increased. In cases of chorioamnionitis regardless of betamethasone treatment, placental 11beta HSD-2 expression and activity was decreased compared to controls. In these placental samples, the expression of GRT and GRalpha did not change significantly. In JEG-3 cells, 11beta HSD-1 32-kd expression was increased with interleukin (IL)-1beta and tumor necrosis factor alpha (TNF-alpha), while 11beta HSD-2 expression was unaffected.

CONCLUSION

These data suggest that there could be an increased fetal exposure to maternal glucocorticoids in cases of chorioamnionitis as a result of changes in the expression and activity of the placental 11beta HSD isozymes.

Stress and Depression: a Crucial Role of the Mineralocorticoid Receptor

Cortisol and corticosterone act on the appraisal process, which comprises the selection of an appropriate coping style and the encoding of the experience for storage in the memory. This action exerted by the stress hormones is mediated by mineralocorticoid receptors (MRs), which are expressed abundantly in the limbic circuitry, particularly in the hippocampus. Limbic MR is down-regulated by chronic stress and during depression but induced by antidepressants. Increased MR activity inhibits hypothalamic-pituitary-adrenal axis activity, promotes slow wave sleep, reduces anxiety and switches circuit connectivity to support coping. Cortisol and emotion-cognition are affected by MR gene haplotypes based on rs5522 and rs2070951. Haplotype 1 (GA) moderates the effects of (early) life stressors, reproductive cycle and oral contraceptives. MR haplotype 2 (CA) is a gain of function variant that protects females against depression by association with an optimistic, resilient phenotype. Activation of MR therefore may offer a target for alleviating depression and cognitive dysfunction. Accordingly, the MR agonist fludrocortisone was found to enhance the efficacy of antidepressants and to improve memory and executive functions in young depressed patients. In conclusion, CORT coordinates via MR the networks underlying how an individual copes with stress, and this action is complemented by the widely distributed lower affinity glucocorticoid receptor (GR) involved in the subsequent management of stress adaptation. In this MR:GR regulation, the MR is an important target for promoting resilience.

Maternal betaine supplementation during gestation modifies hippocampal expression of GR and its regulatory miRNAs in neonatal piglets

Methyl donor nutrients are critical for embryonic development of brain. Hippocampus is the most susceptible brain region to various factors including prenatal supply of methyl donors. Glucocorticoid receptor (GR) expressed in hippocampus is involved in the regulation of energy homeostasis and stress sensitivity. Hippocampal GR expression is highly susceptible to epigenetic regulation, yet the effect of maternal methyl donor supplementation on epigenetic regulation of GR transcription in offspring hippocampus remains unclear. In this study, we fed sows with betaine (3 g/kg) throughout the gestation and analyzed the hippocampal expression of GR mRNA and its variants, as well as the CpG methylation status of the promoter and the microRNAs predicted to target 3' UTR of porcine GR gene in neonatal piglets. Total GR mRNA (P<0.01) and its variants GR 1-4 (P<0.05) and 1-9,10 (P<0.01), were significantly higher in the hippocampus of betaine-treated piglets, while the content of GR protein was not significantly changed. The CpGs located in the -1650 ~ -1515 segment of GR gene were hypermethylated (P<0.05). The hippocampal expression of miR-130b (P<0.05), miR-181a (P<0.05) and miR-181d (P<0.01) was significantly up-regulated. The targeting efficacy of miR-130b and miR-181d was validated in vitro using dual-luciferase reporter assay system. Our results demonstrate that maternal betaine supplementation during gestation enhances GR mRNA expression in offspring hippocampus, which involves alterations in miRNAs expression.

[Research progress on the effect of glucocorticoid receptor signaling pathways in bladder cancer]

Glucocorticoid receptor (GR) is identified as a member of nuclear receptor family. To exert its biological action, the ligand bound GR is translocated from the cytoplasm into the nucleus by regulating transcriptional signals of related genes. In clinical practice, the effects of glucocorticoid are often mediated by GR signaling pathways. An increasing number of studies have indicated that GR signaling pathways play an essential role in the proliferation, invasion and prognosis of bladder cancer. Meanwhile, the new-generation selective GR activator improves its anti-tumor effects, and at the same time reduces the adverse reactions of hormones, which probably raises the prospect for the treatment of bladder cancer.

Coping with the Forced Swim Stressor: Towards Understanding an Adaptive Mechanism

In the forced swim test (FST) rodents progressively show increased episodes of immobility if immersed in a beaker with water from where escape is not possible. In this test, a compound qualifies as a potential antidepressant if it prevents or delays the transition to this passive (energy conserving) behavioural style. In the past decade however the switch from active to passive "coping" was used increasingly to describe the phenotype of an animal that has been exposed to a stressful history and/or genetic modification. A PubMed analysis revealed that in a rapidly increasing number of papers (currently more than 2,000) stress-related immobility in the FST is labeled as a depression-like phenotype. In this contribution we will examine the different phases of information processing during coping with the forced swim stressor. For this purpose we focus on the action of corticosterone that is mediated by the closely related mineralocorticoid receptors (MR) and glucocorticoid receptors (GR) in the limbic brain. The evidence available suggests a model in which we propose that the limbic MR-mediated response selection operates in complementary fashion with dopaminergic accumbens/prefrontal executive functions to regulate the transition between active and passive coping styles. Upon rescue from the beaker the preferred, mostly passive, coping style is stored in the memory via a GR-dependent action in the hippocampal dentate gyrus. It is concluded that the rodent's behavioural response to a forced swim stressor does not reflect depression. Rather the forced swim experience provides a unique paradigm to investigate the mechanistic underpinning of stress coping and adaptation.

Glucocorticoids enhance muscle endurance and ameliorate Duchenne muscular dystrophy through a defined metabolic program

Classic physiology studies dating to the 1930s demonstrate that moderate or transient glucocorticoid (GC) exposure improves muscle performance. The ergogenic properties of GCs are further evidenced by their surreptitious use as doping agents by endurance athletes and poorly understood efficacy in Duchenne muscular dystrophy (DMD), a genetic muscle-wasting disease. A defined molecular basis underlying these performance-enhancing properties of GCs in skeletal muscle remains obscure. Here, we demonstrate that ergogenic effects of GCs are mediated by direct induction of the metabolic transcription factor KLF15, defining a downstream pathway distinct from that resulting in GC-related muscle atrophy. Furthermore, we establish that KLF15 deficiency exacerbates dystrophic severity and muscle GC-KLF15 signaling mediates salutary therapeutic effects in the mdx mouse model of DMD. Thus, although glucocorticoid receptor (GR)-mediated transactivation is often associated with muscle atrophy and other adverse effects of pharmacologic GC administration, our data define a distinct GR-induced gene regulatory pathway that contributes to therapeutic effects of GCs in DMD through proergogenic metabolic programming.

Glucocorticoid receptor and Klf4 co-regulate anti-inflammatory genes in keratinocytes

The glucocorticoid (GC) receptor (GR) and Kruppel-like factor Klf4 are transcription factors that play major roles in skin homeostasis. However, whether these transcription factors cooperate in binding genomic regulatory regions in epidermal keratinocytes was not known. Here, we show that in dexamethasone-treated keratinocytes GR and Klf4 are recruited to genomic regions containing adjacent GR and KLF binding motifs to control transcription of the anti-inflammatory genes Tsc22d3 and Zfp36. GR- and Klf4 loss of function experiments showed total GR but partial Klf4 requirement for full gene induction in response to dexamethasone. In wild type keratinocytes induced to differentiate, GR and Klf4 protein expression increased concomitant with Tsc22d3 and Zfp36 up-regulation. In contrast, GR-deficient cells failed to differentiate or fully induce Klf4, Tsc22d3 and Zfp36 correlating with increased expression of the epithelium-specific Trp63, a known transcriptional repressor of Klf4. The identified transcriptional cooperation between GR and Klf4 may determine cell-type specific regulation and have implications for developing therapies for skin diseases.

Rapid Nongenomic Glucocorticoid Actions in Male Mouse Hypothalamic Neuroendocrine Cells Are Dependent on the Nuclear Glucocorticoid Receptor

Corticosteroids act classically via cognate nuclear receptors to regulate gene transcription; however, increasing evidence supports rapid, nontranscriptional corticosteroid actions via activation of membrane receptors. Using whole-cell patch clamp recordings in hypothalamic slices from male mouse genetic models, we tested for nongenomic glucocorticoid actions at glutamate and gamma aminobutyric acid (GABA) synapses in hypothalamic neuroendocrine cells, and for their dependence on the nuclear glucocorticoid receptor (GR). In enhanced green fluorescent protein-expressing CRH neurons of the paraventricular nucleus (PVN) and in magnocellular neurons of the PVN and supraoptic nucleus (SON), dexamethasone activated postsynaptic membrane-associated receptors and G protein signaling to elicit a rapid suppression of excitatory postsynaptic inputs, which was blocked by genetic deletion of type I cannabinoid receptors and a type I cannabinoid receptor antagonist. In magnocellular neurons, dexamethasone also elicited a rapid nitric oxide-dependent increase in inhibitory postsynaptic inputs. These data indicate a rapid, synapse-specific glucocorticoid-induced retrograde endocannabinoid signaling at glutamate synapses and nitric oxide signaling at GABA synapses. Unexpectedly, the rapid glucocorticoid effects on both excitatory and inhibitory synaptic transmission were lost with conditional deletion of GR in the PVN and SON in slices from a single minded-1-cre-directed conditional GR knockout mouse. Thus, the nongenomic glucocorticoid actions at glutamate and GABA synapses on PVN and SON neuroendocrine cells are dependent on the nuclear GR. The nuclear GR, therefore, is responsible for transducing the rapid steroid response at the membrane, or is either a critical component in the signaling cascade or regulates a critical component of the signaling cascade of a distinct membrane GR.

Novel aspects of glucocorticoid actions

Normal hypothalamic-pituitary-adrenal (HPA) axis activity leading to the rhythmic and episodic release of adrenal glucocorticoids (GCs) is essential for body homeostasis and survival during stress. Acting through specific intracellular receptors in the brain and periphery, GCs regulate behaviour, as well as metabolic, cardiovascular, immune and neuroendocrine activities. By contrast to chronic elevated levels, circadian and acute stress-induced increases in GCs are necessary for hippocampal neuronal survival and memory acquisition and consolidation, as a result of the inhibition of apoptosis, the facilitation of glutamatergic neurotransmission and the formation of excitatory synapses, and the induction of immediate early genes and dendritic spine formation. In addition to metabolic actions leading to increased energy availability, GCs have profound effects on feeding behaviour, mainly via the modulation of orexigenic and anorixegenic neuropeptides. Evidence is also emerging that, in addition to the recognised immune suppressive actions of GCs by counteracting adrenergic pro-inflammatory actions, circadian elevations have priming effects in the immune system, potentiating acute defensive responses. In addition, negative-feedback by GCs involves multiple mechanisms leading to limited HPA axis activation and prevention of the deleterious effects of excessive GC production. Adequate GC secretion to meet body demands is tightly regulated by a complex neural circuitry controlling hypothalamic corticotrophin-releasing hormone (CRH) and vasopressin secretion, which are the main regulators of pituitary adrenocorticotrophic hormone (ACTH). Rapid feedback mechanisms, likely involving nongenomic actions of GCs, mediate the immediate inhibition of hypothalamic CRH and ACTH secretion, whereas intermediate and delayed mechanisms mediated by genomic actions involve the modulation of limbic circuitry and peripheral metabolic messengers. Consistent with their key adaptive roles, HPA axis components are evolutionarily conserved, being present in the earliest vertebrates. An understanding of these basic mechanisms may lead to novel approaches for the development of diagnostic and therapeutic tools for disorders related to stress and alterations of GC secretion.

Glucocorticoid receptor in prostate epithelia is not required for corticosteroid-induced epithelial hyperproliferation in the mouse prostate

BACKGROUND

Glucocorticoids are used as a last resort treatment for prostate cancer but the cell-specific glucocorticoid receptor (GR) mediated actions and the role of endogenous glucocorticoids in prostate are not understood.

METHODS

We evaluated the influence of prostate epithelial GR mediated actions of glucocorticoids in prostate structural development by comparing the intact wild-type (WT) and prostate epithelia selective GR knockout (peGRKO) males at 8, 20, and 35 weeks of age. We also determined the cell-specific role of GR on corticosterone treatment induced prostate abnormalities by treating peGRKO and WT male mice with corticosterone depot pellets or placebo for 4 weeks.

RESULTS

GR was not expressed in the epithelial cells of peGRKO prostate unlike WT but was expressed in stromal of both peGRKO and WT mice. Nevertheless, prostate weights, histological appearance, and secretory protein probasin expression in peGRKO were no different from WT. Despite lacking epithelial GR, the peGRKO prostate demonstrated corticosterone treatment induced hyperplasia similar to WT suggesting that stromal rather than epithelial GR mediates the hyperproliferative mouse prostate response to corticosterone. As circulating androgen levels were not affected by corticosterone treatment, this effect is likely to be mediated directly via prostate GR.

CONCLUSIONS

Sustained administration of corticosterone induces prostate hyperplasia, which is mediated via GR expressed predominantly in the stroma. Thus GR mediated actions in the prostate may have significant cell-specific effects that could be utilized for more rational therapeutic approaches in prostate cancer treatment. This also illustrates the paracrine hormonal mechanisms in prostate pathophysiology.

A kinase-independent activity of Cdk9 modulates glucocorticoid receptor-mediated gene induction

A gene induction competition assay has recently uncovered new inhibitory activities of two transcriptional cofactors, NELF-A and NELF-B, in glucocorticoid-regulated transactivation. NELF-A and -B are also components of the NELF complex, which participates in RNA polymerase II pausing shortly after the initiation of gene transcription. We therefore asked if cofactors (Cdk9 and ELL) best known to affect paused polymerase could reverse the effects of NELF-A and -B. Unexpectedly, Cdk9 and ELL augmented, rather than prevented, the effects of NELF-A and -B. Furthermore, Cdk9 actions are not blocked either by Ckd9 inhibitors (DRB or flavopiridol) or by two Cdk9 mutants defective in kinase activity. The mode and site of action of NELF-A and -B mutants with an altered NELF domain are similarly affected by wild-type and kinase-dead Cdk9. We conclude that Cdk9 is a new modulator of GR action, that Ckd9 and ELL have novel activities in GR-regulated gene expression, that NELF-A and -B can act separately from the NELF complex, and that Cdk9 possesses activities that are independent of Cdk9 kinase activity. Finally, the competition assay has succeeded in ordering the site of action of several cofactors of GR transactivation. Extension of this methodology should be helpful in determining the site and mode of action of numerous additional cofactors and in reducing unwanted side effects.

In vivo actions of the Sertoli cell glucocorticoid receptor

We determined the functional role of the Sertoli cell glucocorticoid receptor (GR) in vivo using a transgenic Cre-loxP approach to conditionally disrupt GR expression. Sertoli cell GR knockout (SCGRKO) was shown by absent Sertoli cell-specific GR immunolocalization and reduced levels of glucocorticoid-responsive Stc1 and Tsc22d3 mRNA in SCGRKO relative to control testes. Adult SCGRKO testes exhibited distinct morphological changes, including reduced seminiferous tubular lumen formation, decreased total Sertoli cell numbers, and parallel reductions in meiotic spermatocyte and postmeiotic spermatid numbers. Conversely, tubular diameter was increased and testis size was normal in SCGRKO males. Decreased serum FSH and testicular Fshr mRNA levels were consistent with reduced Sertoli cell number. Adult SCGRKO testes also displayed atypical germ cells and interstitial focal accumulations of hypertrophic lipid-laden, immature-like Leydig cells. Circulating LH, and testicular Lhr mRNA, testosterone, dihydrotestosterone, and 3α/3β-diol levels were all reduced in mature SCGRKO mice, whereas serum testosterone and dihydrotestosterone levels remained normal. Moreover, Sertoli cell GR disruption caused differential changes to steroidogenic enzyme transcripts, with down-regulated testicular Cyp11a1 contrasting with up-regulated Hsd17b3 expression. Reduced SCGRKO testicular expression of Hsd11b2, encoding an enzyme for corticosterone inactivation, supports a dynamic coupling between Hsd11b and androgen production. Our novel SCGRKO model has revealed that Sertoli cell-mediated GR actions support normal testicular function. Sertoli cell GR is required to maintain normal testicular Sertoli/germ cell numbers and circulating gonadotropin levels, as well as optimal Leydig cell maturation and steroidogenesis, providing new insight into gluocorticoid-mediated impact on male reproduction.

Contribution of glucocorticoids and glucocorticoid receptors to the regulation of neurodegenerative processes

Isolation of glucocorticoids (GCs) from adrenal glands followed by synthesis led rapidly to their first clinical application, about 70 years ago, for treatment of rheumatoid arthritis. To this day GCs are used in diseases that have an inflammatory component. However, their use is carefully monitored because of harmful side effects. GCs are also synonymous with stress and adaptation. In CNS, GC binds and activates high affinity mineralocorticoid receptor (MR) and low affinity glucocorticoid receptor (GR). GR, whose expression is ubiquitous, is only activated when GC levels rise as during circadian peak and in response to stress. Numerous recent studies have yielded important and new insights on the mechanisms concerning pulsatile secretory pattern of GCs as well as various processes that tightly control their synthesis via hypothalamic-pituitary-adrenal (HPA) axis involving regulated release of corticotropin-releasing hormone (CRH) and adrenocorticotropic hormone (ACTH) from hypothalamus and pituitary, respectively. GR modulates neuronal functions and viability through both genomic and non-genomic actions, and importantly its transcriptional regulatory activity is tightly locked with GC secretory pattern. There is increasing evidence pointing to involvement of GC-GR in neurodegenerative disorders. Patients with Alzheimer's or Parkinson's or Huntington's disease show chronically high cortisol levels suggesting changes occurring in controls of HPA axis. In experimental models of these diseases, chronic stress or GC treatment was found to exacerbate both the clinical symptoms and neurodegenerative processes. However, recent evidence also shows that GC-GR can exert neuroprotective effects. Thus, for any potential therapeutic strategies in these neurodegenerative diseases we need to understand the precise modifications both in HPA axis and in GR activity and find ways to harness their protective actions.

Mifepristone treatment affects the response to repeated amphetamine injections, but does not attenuate the expression of sensitization

Rationale Glucocorticoid hormones facilitate sensitization to repeated administration of psychostimulants, an effect that is mediated by glucocorticoid receptors (GRs). It is still unclear, however, at which stage of psychomotor sensitization are stress and GR-mediated effects involved.

OBJECTIVES

In the present study, we have tested the hypothesis that GR-mediated effects during the phase of repeated amphetamine injections play a crucial role in the long-term expression of sensitization. For this purpose, we used DBA/2 mice, an inbred strain commonly used for the study of stress effects on psychostimulant sensitization.

METHODS

Animals were treated with the GR antagonist mifepristone (200 mg/kg) at 2.5 h before each daily injection of amphetamine (2.5 mg/kg) or saline in a 5-day protocol. The amphetamine or saline injections were given in the home or a novel context. This was followed by a 2.5-week withdrawal period, without any drug delivery. Following the withdrawal period, two low-dose amphetamine challenges (1.25 mg/kg) were given subsequently, without additional mifepristone.

RESULTS

The animals receiving amphetamine in the novel context showed a higher expression of sensitization at challenge as compared to those in the home condition. Mifepristone treatment influenced locomotor response to repeated amphetamine injections, but this effect during the initial phase did not affect the expression of sensitization after a withdrawal period.

CONCLUSION

Our results indicate that GR-related processes during the initial phase of sensitization are involved in, but not crucial for, the development of long-term sensitization.

Complex genomic interactions in the dynamic regulation of transcription by the glucocorticoid receptor

The glucocorticoid receptor regulates transcriptional output through complex interactions with the genome. These events require continuous remodeling of chromatin, interactions of the glucocorticoid receptor with chaperones and other accessory factors, and recycling of the receptor by the proteasome. Therefore, the cohort of factors expressed in a particular cell type can determine the physiological outcome upon treatment with glucocorticoid hormones. In addition, circadian and ultradian cycling of hormones can also affect GR response. Here we will discuss revision of the classical static model of GR binding to response elements to incorporate recent findings from single cell and genome-wide analyses of GR regulation. We will highlight how these studies have changed our views on the dynamics of GR recruitment and its modulation of gene expression.

Molecular determinants of glucocorticoid actions in inflammatory joint diseases

Since their discovery in 1948, glucocorticoids have been widely used clinically to treat inflammatory disorders like rheumatoid arthritis. However, their usefulness, especially in rheumatoid arthritis therapy, is hampered by severe side effects on bone leading to glucocorticoid-induced osteoporosis. The molecular and cellular mechanisms mediating the beneficial and adverse effects remain poorly understood. Nevertheless, advanced molecular biological analyses and in vivo approaches using conditional mutant mice have helped to unravel in part the underlying mechanisms of immunosuppression and side effects of glucocorticoid therapy in arthritis, thereby contributing to an improved understanding of these therapeutically important hormones.

Chromatin architecture defines the glucocorticoid response

The glucocorticoid receptor (GR) functions to regulate a wide group of physiological processes through hormone inducible interaction with genomic loci and subsequent manipulation of the transcriptional output of target genes. Despite expression in a wide variety of tissues, the GR has diverse roles that are regulated tightly in a cell type specific manner. With the advent of whole genome approaches, the details of that diversity and the mechanisms regulating them are beginning to be elucidated. This review aims describe the recent advances detailing the role chromatin structure plays in dictating GR specificity.

Metabolic control through glucocorticoid hormones: an update

In the past decades, glucocorticoid (GC) hormones and their cognate, intracellular receptor, the glucocorticoid receptor (GR), have been well established as critical checkpoints in mammalian energy homeostasis. Whereas many aspects in healthy nutrient metabolism require physiological levels and/or action of GC, aberrant GC/GR signalling has been linked to severe metabolic dysfunction, including obesity, insulin resistance and type 2 diabetes. Consequently, studies of the molecular mechanisms within the GC signalling axis have become a major focus in biomedical research, up-to-date particularly focusing on systemic glucose and lipid handling. However, with the availability of novel high throughput technologies and more sophisticated metabolic phenotyping capabilities, as-yet non-appreciated, metabolic functions of GC have been recently discovered, including regulatory roles of the GC/GR axis in protein and bile acid homeostasis as well as metabolic inter-organ communication. Therefore, this review summarises recent advances in GC/GR biology, and summarises findings relevant for basic and translational metabolic research.

Metabolic functions of glucocorticoid receptor in skeletal muscle

Glucocorticoids (GCs) exert key metabolic influences on skeletal muscle. GCs increase protein degradation and decrease protein synthesis. The released amino acids are mobilized from skeletal muscle to liver, where they serve as substrates for hepatic gluconeogenesis. This metabolic response is critical for mammals' survival under stressful conditions, such as fasting and starvation. GCs suppress insulin-stimulated glucose uptake and utilization and glycogen synthesis, and play a permissive role for catecholamine-induced glycogenolysis, thus preserving the level of circulating glucose, the major energy source for the brain. However, chronic or excess exposure of GCs can induce muscle atrophy and insulin resistance. GCs convey their signal mainly through the intracellular glucocorticoid receptor (GR). While GR can act through different mechanisms, one of its major actions is to regulate the transcription of its primary target genes through genomic glucocorticoid response elements (GREs) by directly binding to DNA or tethering onto other DNA-binding transcription factors. These GR primary targets trigger physiological and pathological responses of GCs. Much progress has been made to understand how GCs regulate protein and glucose metabolism. In this review, we will discuss how GR primary target genes confer metabolic functions of GCs, and the mechanisms governing the transcriptional regulation of these targets. Comprehending these processes not only contributes to the fundamental understanding of mammalian physiology, but also will provide invaluable insight for improved GC therapeutics.