Selective regulation of bone cell apoptosis by translational isoforms of the glucocorticoid receptor

The Glucocorticoid Receptor: Isoforms, Functions, and Contribution to Glucocorticoid Sensitivity

Glucocorticoids exert pleiotropic effects on all tissues to regulate cellular and metabolic homeostasis. Synthetic forms are used therapeutically in a wide range of conditions for their anti-inflammatory benefits, at the cost of dose and duration-dependent side effects. Significant variability occurs between tissues, disease states, and individuals with regard to both the beneficial and deleterious effects. The glucocorticoid receptor (GR) is the site of action for these hormones and a vast body of work has been conducted understanding its function. Traditionally, it was thought that the anti-inflammatory benefits of glucocorticoids were mediated by transrepression of pro-inflammatory transcription factors, while the adverse metabolic effects resulted from direct transactivation. This canonical understanding of the GR function has been brought into question over the past 2 decades with advances in the resolution of scientific techniques, and the discovery of multiple isoforms of the receptor present in most tissues. Here we review the structure and function of the GR, the nature of the receptor isoforms, and the contribution of the receptor to glucocorticoid sensitivity, or resistance in health and disease.

Impact of Resolvin-E1 and Maresin-1 on Bone Marrow Stem Cell Osteogenesis under Inflammatory Stress

Periodontal disease is characterized by inflammation and bone loss. Central to its pathogenesis is the dysregulated inflammatory response, complicating regenerative therapies. Mesenchymal stem cells (MSCs) hold significant promise in tissue repair and regeneration. This study investigated the effects of specialized pro-resolving mediators (SPMs), Resolvin E1 (RvE1) and Maresin 1 (MaR1), on the osteogenic differentiation of human bone marrow-derived MSCs under inflammatory conditions. The stem cells were treated with SPMs in the presence of lipopolysaccharide (LPS) to simulate an inflammatory environment. Osteogenic differentiation was assessed through alkaline phosphatase activity and alizarin red staining. Proteomic analysis was conducted to characterize the protein expression profile changes, focusing on proteins related to osteogenesis and osteoclastogenesis. Treatment with RvE1 and MaR1, both individually and in combination, significantly enhanced calcified deposit formation. Proteomic analysis revealed the differential expression of proteins associated with osteogenesis and osteoclastogenesis, highlighting the modulatory impact of SPMs on bone metabolism. RvE1 and MaR1 promote osteogenic differentiation of hBMMSCs in an inflammatory environment, with their combined application yielding synergistic effects. This study provides insights into the therapeutic potential of SPMs in enhancing bone regeneration, suggesting a promising avenue for developing regenerative therapies for periodontal disease and other conditions characterized by inflammation-induced bone loss.

International Union of Basic and Clinical Pharmacology CXIII: Nuclear Receptor Superfamily-Update 2023

The NR superfamily comprises 48 transcription factors in humans that control a plethora of gene network programs involved in a wide range of physiologic processes. This review will summarize and discuss recent progress in NR biology and drug development derived from integrating various approaches, including biophysical techniques, structural studies, and translational investigation. We also highlight how defective NR signaling results in various diseases and disorders and how NRs can be targeted for therapeutic intervention via modulation via binding to synthetic lipophilic ligands. Furthermore, we also review recent studies that improved our understanding of NR structure and signaling. SIGNIFICANCE STATEMENT: Nuclear receptors (NRs) are ligand-regulated transcription factors that are critical regulators of myriad physiological processes. NRs serve as receptors for an array of drugs, and in this review, we provide an update on recent research into the roles of these drug targets.

Biased regulation of glucocorticoid receptors signaling

Glucocorticoids (GCs), steroid hormones that depend on glucocorticoid receptor (GR) binding for their action, are essential for regulating numerous homeostatic functions in the body.GR signals are biased, that is, GR signals are various in different tissue cells, disease states and ligands. This biased regulation of GR signaling appears to depend on ligand-induced metameric regulation, protein post-translational modifications, assembly at response elements, context-specific assembly (recruitment of co-regulators) and intercellular differences. Based on the bias regulation of GR, selective GR agonists and modulators (SEGRAMs) were developed to bias therapeutic outcomes toward expected outcomes (e.g., anti-inflammation and immunoregulation) by influencing GR-mediated gene expression. This paper provides a review of the bias regulation and mechanism of GR and the research progress of drugs.

Neuronal and Astroglial Localization of Glucocorticoid Receptor GRα in Adult Zebrafish Brain (Danio rerio)

Glucocorticoid receptor α (GRα), a ligand-regulated transcription factor, mainly activated by cortisol in humans and fish, mediates neural allostatic and homeostatic functions induced by different types of acute and chronic stress, and systemic inflammation. Zebrafish GRα is suggested to have multiple transcriptional effects essential for normal development and survival, similarly to mammals. While sequence alignments of human, monkey, rat, and mouse GRs have shown many GRα isoforms, we questioned the protein expression profile of GRα in the adult zebrafish (Danio rerio) brain using an alternative model for stress-related neuropsychiatric research, by means of Western blot, immunohistochemistry and double immunofluorescence. Our results identified four main GRα-like immunoreactive bands (95 kDa, 60 kDa, 45 kDa and 35 kDa), with the 95 kDa protein showing highest expression in forebrain compared to midbrain and hindbrain. GRα showed a wide distribution throughout the antero-posterior zebrafish brain axis, with the most prominent labeling within the telencephalon, preoptic, hypothalamus, midbrain, brain stem, central grey, locus coeruleus and cerebellum. Double immunofluorescence revealed that GRα is coexpressed in TH+, β₂-AR+ and vGLUT+ neurons, suggesting the potential of GRα influences on adrenergic and glutamatergic transmission. Moreover, GRα was co-localized in midline astroglial cells (GFAP+) within the telencephalon, hypothalamus and hindbrain. Interestingly, GRα expression was evident in the brain regions involved in adaptive stress responses, social behavior, and sensory and motor integration, supporting the evolutionarily conserved features of glucocorticoid receptors in the zebrafish brain.

[Association of the structure of the glucocorticoid receptor and single nucleotide NR3C1 gene polymorphisms with metabolic disorders]

Glucocorticoid therapy is widely used in the treatment of various pathologies. Sensitivity to glucocorticoids  (GC) has a serious impact not only on the effectiveness of their action, but also on the severity of side effects, the formation of risk factors and the development  of cardiovascular diseases (CVD). Variability of sensitivity to GC causes different phenotypes and severity of metabolic disorders underlying  CVD. Among  them, one can distinguish  a decrease in muscle mass and strength, obesity, glucose and lipid metabolism impairment, and others. Glucocorticoids carry out their effects by binding to the glucocorticoid receptor (GR), and therefore this is considered a critical point in their action. This review presents data on the significance of the glucocorticoid  receptor structure, examines the main single nucleotide polymorphisms (SNP) of the NR3C1 gene associated with hypersensitivity  or relative resistance to glucocorticoids  in the context of metabolic disorders and the development of CVD. The association of the four most studied SNP of the GR gene with metabolic risks is described in detail: BclI (rs41423247), N363S (rs56149945), ER22/23EK (rs6189/rs6190), GR-9ß (rs6198). Their determination can contribute to clarifying the prognosis of both the effectiveness of GC and the development of metabolic disorders, and subsequent early correction of CVD risk factors.

The Human Glucocorticoid Receptor Beta: From Molecular Mechanisms to Clinical Implications

Glucocorticoids play a fundamental role in a plethora of cellular processes and physiologic functions through binding on a ubiquitously expressed receptor, the glucocorticoid receptor (GR), which functions as a ligand-activated transcription factor influencing the transcription rate of numerous genes in a positive or negative fashion. For many years, we believed that the pleiotropic actions of glucocorticoids were mediated by a single GR protein expressed by the NR3C1 gene. Nowadays, we know that the NR3C1 gene encodes 2 main receptor isoforms, the GRα and the GRβ, through alternative splicing of the last exons. Furthermore, the alternative initiation of GR mRNA translation generates 8 distinct GRα and possibly 8 different GRβ receptor isoforms. The tremendous progress of cellular, molecular, and structural biology in association with the data explosion provided by bioinformatics have enabled a deeper understanding of the role of GRβ in cellular homeostasis. In this review article, I will provide an update on the cellular properties and functions of hGRβ and summarize the current knowledge about the evolving role of the beta isoform of glucocorticoid receptor in endocrine physiology, pathophysiology, and beyond.

Stimulation of osteoclast formation and bone resorption by glucocorticoids: Synergistic interactions with the calcium regulating hormones parathyroid hormone and 1,25(OH)2-vitamin D3

Osteoporosis is a significant health problem, with skeletal fractures increasing morbidity and mortality. Excess glucocorticoids (GC) represents the leading cause of secondary osteoporosis. The first phase of glucocorticoid-induced osteoporosis is increased bone resorption. In this Chapter, in vitro studies of the direct glucocorticoid receptor (GR) mediated cellular effects of GC on osteoclasts to affect bone resorption and indirect effects on osteoblast lineage cells to increase the RANKL/OPG ratio and stimulate osteoclastogenesis and bone resorption are reviewed in detail, together with detailed descriptions of in vivo effects of GC in different portions of the skeleton in research animals and humans. Brief sections are devoted to contrasting functions of GC in osteonecrosis, vitamin D formation, in vitro and in vivo bone resorptive actions dependent on vitamin D receptor and vitamin D toxicity, as well as the molecular basis of GR action. Included are also more detailed assessments of the interactions of GC with the major calcium regulating hormones, 1,25(OH)₂-vitamin D3 and parathyroid hormone, describing the in vitro increases in RANKL/OPG ratios, osteoclastogenesis and synergistic bone resorption that occurs when GC is combined with either 1,25(OH)₂-vitamin D3 or parathyroid hormone. Additionally, a molecular basic for the synergistic interaction of GC with 1,25(OH)₂-vitamin D3 is provided along with a suggested molecular basic for the interaction between GC and parathyroid hormone.

Plasma Proteomics in Healthy Subjects with Differences in Tissue Glucocorticoid Sensitivity Identifies A Novel Proteomic Signature

Significant inter-individual variation in terms of susceptibility to several stress-related disorders, such as myocardial infarction and Alzheimer’s disease, and therapeutic response has been observed among healthy subjects. The molecular features responsible for this phenomenon have not been fully elucidated. Proteomics, in association with bioinformatics analysis, offer a comprehensive description of molecular phenotypes with clear links to human disease pathophysiology. The aim of this study was to conduct a comparative plasma proteomics analysis of glucocorticoid resistant and glucocorticoid sensitive healthy subjects and provide clues of the underlying physiological differences. For this purpose, 101 healthy volunteers were given a very low dose (0.25 mg) of dexamethasone at midnight, and were stratified into the 10% most glucocorticoid sensitive (S) (n = 11) and 10% most glucocorticoid resistant (R) (n = 11) according to the 08:00 h serum cortisol concentrations determined the following morning. One month following the very-low dose dexamethasone suppression test, DNA and plasma samples were collected from the 22 selected individuals. Sequencing analysis did not reveal any genetic defects in the human glucocorticoid receptor (NR3C1) gene. To investigate the proteomic profile of plasma samples, we used Liquid Chromatography–Mass Spectrometry (LC-MS/MS) and found 110 up-regulated and 66 down-regulated proteins in the S compared to the R group. The majority of the up-regulated proteins in the S group were implicated in platelet activation. To predict response to cortisol prior to administration, a random forest classifier was developed by using the proteomics data in order to distinguish S from R individuals. Apolipoprotein A4 (APOA4) and gelsolin (GSN) were the most important variables in the classification, and warrant further investigation. Our results indicate that a proteomics signature may differentiate the S from the R healthy subjects, and may be useful in clinical practice. In addition, it may provide clues of the underlying molecular mechanisms of the chronic stress-related diseases, including myocardial infarction and Alzheimer’s disease.

Bad to the Bone: The Effects of Therapeutic Glucocorticoids on Osteoblasts and Osteocytes

Despite the continued development of specialized immunosuppressive therapies in the form of monoclonal antibodies, glucocorticoids remain a mainstay in the treatment of rheumatological and auto-inflammatory disorders. Therapeutic glucocorticoids are unmatched in the breadth of their immunosuppressive properties and deliver their anti-inflammatory effects at unparalleled speed. However, long-term exposure to therapeutic doses of glucocorticoids decreases bone mass and increases the risk of fractures - particularly in the spine - thus limiting their clinical use. Due to the abundant expression of glucocorticoid receptors across all skeletal cell populations and their respective progenitors, therapeutic glucocorticoids affect skeletal quality through a plethora of cellular targets and molecular mechanisms. However, recent evidence from rodent studies, supported by clinical data, highlights the considerable role of cells of the osteoblast lineage in the pathogenesis of glucocorticoid-induced osteoporosis: it is now appreciated that cells of the osteoblast lineage are key targets of therapeutic glucocorticoids and have an outsized role in mediating their undesirable skeletal effects. As part of this article, we review the molecular mechanisms underpinning the detrimental effects of supraphysiological levels of glucocorticoids on cells of the osteoblast lineage including osteocytes and highlight the clinical implications of recent discoveries in the field.

Corticosterone and Glucocorticoid Receptor in the Cortex of Rats during Aging-The Effects of Long-Term Food Restriction

Numerous beneficial effects of food restriction on aging and age-related pathologies are well documented. It is also well-established that both short- and long-term food restriction regimens induce elevated circulating levels of glucocorticoids, stress-induced hormones produced by adrenal glands that can also exert deleterious effects on the brain. In the present study, we examined the effect of long-term food restriction on the glucocorticoid hormone/glucocorticoid receptor (GR) system in the cortex during aging, in 18- and 24-month-old rats. Corticosterone level was increased in the cortex of aged ad libitum-fed rats. Food restriction induced its further increase, accompanied with an increase in the level of 11β-hydroxysteroid dehydrogenase type 1. However, alterations in the level of GR phosphorylated at Ser²³² were not detected in animals on food restriction, in line with unaltered CDK5 level, the decrease of Hsp90, and an increase in a negative regulator of GR function, FKBP51. Moreover, our data revealed that reduced food intake prevented age-related increase in the levels of NFκB, gfap, and bax, confirming its anti-inflammatory and anti-apoptotic effects. Along with an increase in the levels of c-fos, our study provides additional evidences that food restriction affects cortical responsiveness to glucocorticoids during aging.

Glucocorticoid therapy in assisted reproduction

As glucocorticoids are well-known as important regulators of stress and the immune system, their function and clinical use have elicited substantial interest in the field of reproduction. In particular, the effect of glucocorticoid therapy on endometrial receptivity during assisted reproduction, including in vitro fertilization (IVF) cycles, has led to a great deal of interest and controversy. However, previous studies have not been able to provide consistent and reliable evidence due to their small, non-controlled designs and use of different criteria. Considering the potential risk of exposure to glucocorticoids for mothers and fetuses in early pregnancy, the use of glucocorticoids in IVF cycles should be carefully evaluated, including the balance between risk and benefit. To date, there is no conclusive evidence that the use of glucocorticoids improves the pregnancy rate in IVF cycles with unselected subjects, and a further investigation should be considered with a proper study design.

Primary Generalized Glucocorticoid Resistance and Hypersensitivity Syndromes: A 2021 Update

Glucocorticoids are the final products of the neuroendocrine hypothalamic-pituitary-adrenal axis, and play an important role in the stress response to re-establish homeostasis when it is threatened, or perceived as threatened. These steroid hormones have pleiotropic actions through binding to their cognate receptor, the human glucocorticoid receptor, which functions as a ligand-bound transcription factor inducing or repressing the expression of a large number of target genes. To achieve homeostasis, glucocorticoid signaling should have an optimal effect on all tissues. Indeed, any inappropriate glucocorticoid effect in terms of quantity or quality has been associated with pathologic conditions, which are characterized by short-term or long-lasting detrimental effects. Two such conditions, the primary generalized glucocorticoid resistance and hypersensitivity syndromes, are discussed in this review article. Undoubtedly, the tremendous progress of structural, molecular, and cellular biology, in association with the continued progress of biotechnology, has led to a better and more in-depth understanding of these rare endocrinologic conditions, as well as more effective therapeutic management.

Prednisolone Suppresses the Extracellular Release of HMGB-1 and Associated Inflammatory Pathways in Kawasaki Disease

Innate immune activity plays an essential role in the development of Kawasaki disease (KD) vasculitis. Extracellular release of high mobility group box-1 (HMGB-1), an endogenous damage-associated molecular pattern protein that can activate the innate immune system and drive host inflammatory responses, may contribute to the development of coronary artery abnormalities in KD. Prednisolone (PSL) added to intravenous immunoglobulin treatment for acute KD may reduce such abnormalities. Here, we evaluate the dynamics of HMGB-1 and therapeutic effects of PSL on HMGB-1-mediated inflammatory pathways on KD vasculitis in vitro. Serum samples were collected prior to initial treatment from patients with KD, systemic juvenile idiopathic arthritis (sJIA), and from healthy controls (VH), then incubated with human coronary artery endothelial cells (HCAECs). Following treatment of KD serum-activated HCAECs with PSL or PBS as a control, effects on the HMGB-1 signaling pathway were evaluated. Compared to that from VH and sJIA, KD serum activation induced HCAEC cytotoxicity and triggered extracellular release of HMGB-1. KD serum-activated HCAECs up-regulated extracellular signal-regulated kinase (ERK)1/2, c-Jun N-terminal kinase (JNK) and, p38 phosphorylation in the cytoplasm and nuclear factor kappa B (NF-κB) phosphorylation in the nucleus and increased interleukin (IL)-1β and tumor necrosis factor (TNF)-α production. PSL treatment of KD serum-activated HCAECs inhibited extracellular release of HMGB-1, down-regulated ERK1/2, JNK, p38, and NF-κB signaling pathways, and decreased IL-1β and TNF-α production. Our findings suggest that extracellular HMGB-1 plays an important role in mediating KD pathogenesis and that PSL treatment during the acute phase of KD may ameliorate HMGB-1-mediated inflammatory responses in KD vasculitis.

Association of TLR4 gene polymorphisms with sepsis after a burn injury: findings of the functional role of rs2737190 SNP

Sepsis is a life-threatening organ dysfunction condition caused by a dysregulated response to an infection that is common among patients with moderate to severe burn injury. Previously, genomic variants in Toll-like receptor 4 (TLR4), a key innate immunity receptor, have been associated with sepsis and infection susceptibility. In this study, the association of six TLR4 SNPs with sepsis after burn injury was tested in the Mexican mestizo population. We found that the rs2737190 polymorphism is associated with sepsis after burn trauma. Interestingly, the G allele and GG genotype were associated with a lower risk of developing sepsis. Since the rs2737190 SNP is in the promoter region of the TLR4 gene, we analyzed the possibility that this polymorphism regulates the TLR4 pathway. We cultured peripheral blood mononuclear cells from different genotype carriers and found, after stimulation with LPS, that carriers of the GG genotype showed a higher expression of TLR4, IL6, and TNFα than AA genotype carriers. The results suggest that the GG genotype produces an increase in the TLR4 expression, and therefore an improvement in the immune response. We conclude that the rs2737190 polymorphism may become a useful marker for genetic studies of sepsis in patients after a burn injury.

Identification of human glucocorticoid response markers using integrated multi-omic analysis from a randomized crossover trial

Background:

Glucocorticoids are among the most commonly prescribed drugs, but there is no biomarker that can quantify their action. The aim of the study was to identify and validate circulating biomarkers of glucocorticoid action.

Methods:

In a randomized, crossover, single-blind, discovery study, 10 subjects with primary adrenal insufficiency (and no other endocrinopathies) were admitted at the in-patient clinic and studied during physiological glucocorticoid exposure and withdrawal. A randomization plan before the first intervention was used. Besides mild physical and/or mental fatigue and salt craving, no serious adverse events were observed. The transcriptome in peripheral blood mononuclear cells and adipose tissue, plasma miRNAomic, and serum metabolomics were compared between the interventions using integrated multi-omic analysis.

Results:

We identified a transcriptomic profile derived from two tissues and a multi-omic cluster, both predictive of glucocorticoid exposure. A microRNA (miR-122-5p) that was correlated with genes and metabolites regulated by glucocorticoid exposure was identified (p=0.009) and replicated in independent studies with varying glucocorticoid exposure (0.01 ≤ p≤0.05).

Conclusions:

We have generated results that construct the basis for successful discovery of biomarker(s) to measure effects of glucocorticoids, allowing strategies to individualize and optimize glucocorticoid therapy, and shedding light on disease etiology related to unphysiological glucocorticoid exposure, such as in cardiovascular disease and obesity.

Funding:

The Swedish Research Council (Grant 2015-02561 and 2019-01112); The Swedish federal government under the LUA/ALF agreement (Grant ALFGBG-719531); The Swedish Endocrinology Association; The Gothenburg Medical Society; Wellcome Trust; The Medical Research Council, UK; The Chief Scientist Office, UK; The Eva Madura’s Foundation; The Research Foundation of Copenhagen University Hospital; and The Danish Rheumatism Association.

Clinical trial number:

NCT02152553.

Several diseases, including asthma, arthritis, some skin conditions, and cancer, are treated with medications called glucocorticoids, which are synthetic versions of human hormones. These drugs are also used to treat people with a condition call adrenal insufficiency who do not produce enough of an important hormone called cortisol. Use of glucocorticoids is very common, the proportion of people in a given country taking them can range from 0.5% to 21% of the population depending on the duration of the treatment. But, like any medication, glucocorticoids have both benefits and risks: people who take glucocorticoids for a long time have an increased risk of diabetes, obesity, cardiovascular disease, and death.

Because of the risks associated with taking glucocorticoids, it is very important for physicians to tailor the dose to each patient’s needs. Doing this can be tricky, because the levels of glucocorticoids in a patient’s blood are not a good indicator of the medication’s activity in the body. A test that can accurately measure the glucocorticoid activity could help physicians personalize treatment and reduce harmful side effects.

As a first step towards developing such a test, Chantzichristos et al. identified a potential way to measure glucocorticoid activity in patient’s blood. In the experiments, blood samples were collected from ten patients with adrenal insufficiency both when they were on no medication, and when they were taking a glucocorticoid to replace their missing hormones. Next, the blood samples were analyzed to determine which genes were turned on and off in each patient with and without the medication. They also compared small molecules in the blood called metabolites and tiny pieces of genetic material called microRNAs that turn genes on and off.

The experiments revealed networks of genes, metabolites, and microRNAs that are associated with glucocorticoid activity, and one microRNA called miR-122-5p stood out as a potential way to measure glucocorticoid activity. To verify this microRNA’s usefulness, Chantzichristos et al. looked at levels of miR-122-5p in people participating in three other studies and confirmed that it was a good indicator of the glucocorticoid activity.

More research is needed to confirm Chantzichristos et al.’s findings and to develop a test that can be used by physicians to measure glucocorticoid activity. The microRNA identified, miR-122-5p, has been previously linked to diabetes, so studying it further may also help scientists understand how taking glucocorticoids may increase the risk of developing diabetes and related diseases.

Latest perspectives on glucocorticoid-induced apoptosis and resistance in lymphoid malignancies

Glucocorticoids are essential drugs in the treatment protocols of lymphoid malignancies. These steroidal hormones trigger apoptosis of the malignant cells by binding to the glucocorticoid receptor (GR), which is a member of the nuclear receptor superfamily. Long term glucocorticoid treatment is limited by two major problems: the development of glucocorticoid-related side effects, which hampers patient quality of life, and the emergence of glucocorticoid resistance, which is a gradual process that is inevitable in many patients. This emphasizes the need to reevaluate and optimize the widespread use of glucocorticoids in lymphoid malignancies. To achieve this goal, a deep understanding of the mechanisms governing glucocorticoid responsiveness is required, yet, a recent comprehensive overview is currently lacking. In this review, we examine how glucocorticoids mediate apoptosis by detailing GR's genomic and non-genomic action mechanisms in lymphoid malignancies. We continue with a discussion of the glucocorticoid-related problems and how these are intertwined with one another. We further zoom in on glucocorticoid resistance by critically analyzing the plethora of proposed mechanisms and highlighting therapeutic opportunities that emerge from these studies. In conclusion, early detection of glucocorticoid resistance in patients remains an important challenge as this would result in a timelier treatment reorientation and reduced glucocorticoid-instigated side effects.

Glucocorticoid receptor modulates dendritic cell function in ulcerative colitis

Ulcerative colitis (UC) is a serious form of inflammatory bowel disease (IBD) occurring worldwide. Although anti-TNF therapy is found to be effective in over 70% of patients with UC, nearly one-third are still deprived of effective treatment. Because glucocorticoids (GC) can effectively inhibit granulocyte-recruitment into the mucosa, cytokine secretion and T cell activation, they are used widely in the treatment of UC. However, remission is observed in only 55% of the patients after one year of steroid use due to a condition known as steroid response. Additionally, it has been noted that 20%-40% of the patients with UC do not respond to GC treatment. Researchers have revealed that the number of dendritic cells (DCs) in patients with UC tends to increase in the colonic mucosa. Many studies have determined that the removal of peripheral DCs through the adsorption and separation of granulocytes and monocytes could improve tolerance of the intestine to its symbiotic flora. Based on these results, further insights regarding the beneficial effects of Adacolumn apheresis in patients subjected to this treatment could be revealed. GC can effectively inhibit the activation of DCs by reducing the levels of major histocompatibility complex class II (MHC II) molecules, which is critical for controlling the recruitment of granulocytes. Therefore, alternative biological and new individualized therapies based on these approaches need to be evaluated to counter UC. In this review, progress in research associated with the regulatory effect of glucocorticoid receptors on DCs under conditions of UC is discussed, thus providing insights and identifying potential targets which could be employed in the treatment strategies against UC.

Progestins Inhibit Interleukin-1β-Induced Matrix Metalloproteinase 1 and Interleukin 8 Expression via the Glucocorticoid Receptor in Primary Human Amnion Mesenchymal Cells

Preterm premature rupture of membranes is a leading cause of preterm births. Cytokine induced matrix metalloproteinase1 and interleukin 8 production from amnion mesenchymal cells may contribute to fetal membrane weakening and rupture. Progestins inhibit inflammation induced fetal membrane weakening but their effect on the inflammatory response of amnion mesenchymal cells is unknown. This study was designed to determine the role of progesterone receptor membrane component 1 and the glucocorticoid receptor in mediating the effects of progestins on interleukin-1β induced matrix metalloproteinase 1 and interleukin-8 expression in human amnion mesenchymal cells. Primary amnion mesenchymal cells harvested from human fetal membranes were passaged once and treated with vehicle, progesterone or medroxyprogesterone acetate at 10-6 M for 1 h followed by stimulation with interleukin-1β at 1 ng/ml for 24 h. Medroxyprogesterone acetate but not progesterone inhibited interleukin-1β-induced interlukin-8 and matrix metalloproteinase 1 mRNA expression. In subsequent dose response studies, medroxyprogesterone acetate, but not progesterone, at doses of 10-6-10-8 M inhibited interleukin-1β induced interleukin-8 and matrix metalloproteinase 1 mRNA expression. We further demonstrated that inhibition of glucocorticoid receptor expression, but not progesterone receptor membrane component 1 knockdown with small interfering RNA transfection, resulted in a reversal in medroxyprogesterone acetate's (10-7 M) inhibition of interleukin-1β- induced matrix metalloproteinase 1 mRNA expression and interleukin-8 mRNA expression and protein expression. Our findings demonstrate that medroxyprogesterone acetate exerts its anti-inflammatory effect primarily through the glucocorticoid receptor in human amnion mesenchymal cells. Modulation of glucocorticoid receptor signaling pathways maybe a useful therapeutic strategy for preventing inflammation induced fetal membrane weakening leading to preterm premature rupture of membranes.

Integrative Analysis for Elucidating Transcriptomics Landscapes of Glucocorticoid-Induced Osteoporosis

Osteoporosis is the most common bone metabolic disease, characterized by bone mass loss and bone microstructure changes due to unbalanced bone conversion, which increases bone fragility and fracture risk. Glucocorticoids are clinically used to treat a variety of diseases, including inflammation, cancer and autoimmune diseases. However, excess glucocorticoids can cause osteoporosis. Herein we performed an integrated analysis of two glucocorticoid-related microarray datasets. The WGCNA analysis identified 3 and 4 glucocorticoid-related gene modules, respectively. Differential expression analysis revealed 1047 and 844 differentially expressed genes in the two datasets. After integrating differentially expressed glucocorticoid-related genes, we found that most of the robust differentially expressed genes were up-regulated. Through protein-protein interaction analysis, we obtained 158 glucocorticoid-related candidate genes. Enrichment analysis showed that these genes are significantly enriched in the osteoporosis related pathways. Our results provided new insights into glucocorticoid-induced osteoporosis and potential candidate markers of osteoporosis.

Glucocorticoid receptor isoforms and effects of glucocorticoids in ovulated mouse oocytes and preimplantation embryos†

To investigate possible involvement of glucocorticoid receptor (GR) in mediating effects of maternal stress or therapeutically administered glucocorticoids on early embryo, we analyzed the expression of GR subtypes in ovulated mouse oocytes and preimplantation embryos. RT-PCR analysis results showed that GRα and GRγ transcripts are relatively highly expressed in mouse oocytes, and both transcripts are present at lower amounts in preimplantation embryos. We also detected low expression of two other splice variants, GRβ and a transcript orthologous to the human GR-P subtype, mainly at the blastocyst stage. Using western blot analysis, we detected several GR protein bands that differed in size between oocytes and preimplantation embryos. To compare the effects of corticosterone (a major endogenous glucocorticoid in rodents) and dexamethasone (a synthetic glucocorticoid) on early embryos, we cultured mouse preimplantation embryos in the presence of these glucocorticoids. Corticosterone showed a strong inhibitory effect on embryo development (starting from a 50 μM concentration), without a significant influence on apoptosis incidence. On the other hand, dexamethasone induced apoptosis in early embryo cells (starting from a 1.5 μM concentration), and its effect on embryo development was less detrimental than that found with the same dose of corticosterone. In summary, our results showed that different GR subtypes are expressed in ovulated mouse oocytes and preimplantation embryos and that the composition of GR subtypes changes during early embryo development. Moreover, we found significant differences in the effects of the two glucocorticoids on early embryo development, which might be associated with activation of different GR subtypes.

The Glucocorticoid Receptor in Cardiovascular Health and Disease

The glucocorticoid receptor is a member of the nuclear receptor family that controls many distinct gene networks, governing various aspects of development, metabolism, inflammation, and the stress response, as well as other key biological processes in the cardiovascular system. Recently, research in both animal models and humans has begun to unravel the profound complexity of glucocorticoid signaling and convincingly demonstrates that the glucocorticoid receptor has direct effects on the heart and vessels in vivo and in vitro. This research has contributed directly to improving therapeutic strategies in human disease. The glucocorticoid receptor is activated either by the endogenous steroid hormone cortisol or by exogenous glucocorticoids and acts within the cardiovascular system via both genomic and non-genomic pathways. Polymorphisms of the glucocorticoid receptor are also reported to influence the progress and prognosis of cardiovascular disease. In this review, we provide an update on glucocorticoid signaling and highlight the critical role of this signaling in both physiological and pathological conditions of the cardiovascular system. With increasing in-depth understanding of glucocorticoid signaling, the future is promising for the development of targeted glucocorticoid treatments and improved clinical outcomes.

A General Introduction to Glucocorticoid Biology

Glucocorticoids (GCs) are steroid hormones widely used for the treatment of inflammation, autoimmune diseases, and cancer. To exert their broad physiological and therapeutic effects, GCs bind to the GC receptor (GR) which belongs to the nuclear receptor superfamily of transcription factors. Despite their success, GCs are hindered by the occurrence of side effects and glucocorticoid resistance (GCR). Increased knowledge on GC and GR biology together with a better understanding of the molecular mechanisms underlying the GC side effects and GCR are necessary for improved GC therapy development. We here provide a general overview on the current insights in GC biology with a focus on GC synthesis, regulation and physiology, role in inflammation inhibition, and on GR function and plasticity. Furthermore, novel and selective therapeutic strategies are proposed based on recently recognized distinct molecular mechanisms of the GR. We will explain the SEDIGRAM concept, which was launched based on our research results.

Placental glucocorticoid receptor isoforms in a sheep model of maternal allergic asthma

Maternal asthma increases the risk of adverse pregnancy outcomes and may affect fetal growth and placental function by differential effects on the expression of glucocorticoid receptor (GR) isoforms, leading to altered glucocorticoid signalling. Our aim was to examine the effect of maternal asthma on placental GR profiles using a pregnant sheep model of asthma. Nine known GR isoforms were detected. There was a significant increase in the expression of placental GR isoforms that are known to have low trans-activational activity in other species including GR A, GR P and GRγ which may result in a pro-inflammatory environment in the presence of allergic asthma.

Molecular mechanisms of enzalutamide resistance in prostate cancer

An estimated 30,000 men in the United States will die of metastatic prostate cancer (PCa) each year due to the development of therapy resistance, most notably resistance to second-generation antiandrogen enzalutamide. The vast majority of PCa is driven by the androgen receptor (AR). Enzalutamide is an AR antagonist, which extends patient survival and is widely used in the clinic for the treatment of castration-resistant prostate cancer (CRPC); however, many patients will have primary or develop acquired resistance and continue to progress. Characterization of the molecular mechanisms of enzalutamide resistance provides insight into potentially efficacious therapies for enzalutamide-resistant CRPC (ER-CRPC). Understanding these mechanisms is critical for the identification of biomarkers predictive of therapy resistance and the development of therapeutic strategies to target ER-CRPC.

Molecular changes during TGFβ-mediated lung fibroblast-myofibroblast differentiation: implication for glucocorticoid resistance

Airway remodeling is an important process in response to repetitive inflammatory-mediated airway wall injuries. This is characterized by profound changes and reorganizations at the cellular and molecular levels of the lung tissue. It is of particular importance to understand the mechanisms involved in airway remodeling, as this is strongly associated with severe asthma leading to devastating airway dysfunction. In this study, we have investigated the transforming growth factor-β (TGFβ, a proinflammatory mediator)-activated fibroblast to myofibroblast transdifferentiation pathway, which plays a key role in asthma-related airway remodeling. We show that TGFβ induces fibroblast to myofibroblast transdifferentiation by the expression of αSMA, a specific myofibroblast marker. Furthermore, Smad2/Smad3 gene and protein expression patterns are different between fibroblasts and myofibroblasts. Such a change in expression patterns reveals an important role of these proteins in the cellular phenotype as well as their regulation by TGFβ during cellular transdifferentiation. Interestingly, our data show a myofibroblastic TGFβ-mediated increase in glucocorticoid receptor (GR) expression and a preferential localization of GR in the nucleus, compared to in fibroblasts. Furthermore, the GRβ (nonfunctional GR isoform) is increased relative to GRα (functional isoform) in myofibroblasts. These results are interesting as they support the idea of a GRβ-mediated glucocorticoid resistance observed in the severe asthmatic population. All together, we provide evidence that key players are involved in the TGFβ-mediated fibroblast to myofibroblast transdifferentiation pathway in a human lung fibroblast cell line. These players could be the targets of new treatments to limit airway remodeling and reverse glucocorticoid resistance in severe asthma.

Progesterone-Related Immune Modulation of Pregnancy and Labor

Pregnancy involves a complex interplay between maternal neuroendocrine and immunological systems in order to establish and sustain a growing fetus. It is thought that the uterus at pregnancy transitions from quiescent to laboring state in response to interactions between maternal and fetal systems at least partly via altered neuroendocrine signaling. Progesterone (P4) is a vital hormone in maternal reproductive tissues and immune cells during pregnancy. As such, P4 is widely used in clinical interventions to improve the chance of embryo implantation, as well as reduce the risk of miscarriage and premature labor. Here we review research to date that focus on the pathways through which P4 mediates its actions on both the maternal reproductive and immune system. We will dissect the role of P4 as a modulator of inflammation, both systemic and intrinsic to the uterus, during human pregnancy and labor.

Immune regulation by glucocorticoids can be linked to cell type-dependent transcriptional responses

A functional genomics approach uncovers previously undescribed cell type–dependent responses that can be linked to the immunoregulatory actions of glucocorticoids in humans.

Glucocorticoids remain the most widely used immunosuppressive and anti-inflammatory drugs, yet substantial gaps exist in our understanding of glucocorticoid-mediated immunoregulation. To address this, we generated a pathway-level map of the transcriptional effects of glucocorticoids on nine primary human cell types. This analysis revealed that the response to glucocorticoids is highly cell type dependent, in terms of the individual genes and pathways affected, as well as the magnitude and direction of transcriptional regulation. Based on these data and given their importance in autoimmunity, we conducted functional studies with B cells. We found that glucocorticoids impair upstream B cell receptor and Toll-like receptor 7 signaling, reduce transcriptional output from the three immunoglobulin loci, and promote significant up-regulation of the genes encoding the immunomodulatory cytokine IL-10 and the terminal-differentiation factor BLIMP-1. These findings provide new mechanistic understanding of glucocorticoid action and emphasize the multifactorial, cell-specific effects of these drugs, with potential implications for designing more selective immunoregulatory therapies.

Glucocorticoid signaling and osteoarthritis

Glucocorticoids are steroid hormones synthesized and released by the adrenal cortex. Their main function is to maintain cell homeostasis through a variety of signaling pathways, responding to changes in an organism's environment or developmental status. Mimicking the actions of natural glucocorticoids, synthetic glucocorticoids have been recruited to treat many diseases that implicate glucocorticoid receptor signaling such as osteoarthritis. In osteoarthritis, synthetic glucocorticoids aim to alleviate inflammation and pain. The variation of patients' response and the possibility of complications associated with their long-term use have led to a need for a better understanding of glucocorticoid receptor signaling in osteoarthritis. In this review, we performed a literature search in the molecular pathways that link the osteoarthritic joint to the glucocorticoid receptor signaling. We hope that this information will advance research in the field and propose new molecular targets for the development of more optimized therapies for osteoarthritis.

Glucocorticoid Resistance

Primary generalized glucocorticoid resistance or Chrousos syndrome is a rare disorder, which affects all tissues expressing the human glucocorticoid receptor. It is characterized by generalized, partial tissue insensitivity to glucocorticoids caused by genetic defects in the NR3C1 gene. We and others have applied standard methods of molecular and structural biology to investigate the molecular mechanisms and conformational alterations through which the mutant glucocorticoid receptors lead to the broad spectrum of clinical manifestations of Chrousos syndrome. The ever-increasing application of novel technologies, including the next-generation sequencing, will enhance our knowledge in factors that influence the glucocorticoid signal transduction in a positive or negative fashion.

Pathophysiology of Glucocorticoid Signaling

Glucocorticoids (GC), such as cortisol or dexamethasone, control various physiological functions, notably those involved in development, metabolism, inflammatory processes and stress, and exert most of their effects upon binding to the glucocorticoid receptor (GR, encoded by NR3C1 gene). GC signaling follows several consecutive steps leading to target gene transactivation, including ligand binding, nuclear translocation of ligand-activated GR complexes, DNA binding, coactivator interaction and recruitment of functional transcriptional machinery. Any step may be impaired and may account for altered GC signaling. Partial or generalized glucocorticoid resistance syndrome may result in a reduced level of functional GR, a decreased hormone affinity and binding, a defect in nuclear GR translocation, a decrease or lack of DNA binding and/or post-transcriptional GR modifications. To date, 26 loss-of-function NR3C1 mutations have been reported in the context of hypertension, hirsutism, adrenal hyperplasia or metabolic disorders. These clinical signs are generally associated with biological features including hypercortisolism without negative regulatory feedback loop on the hypothalamic-pituitary-adrenal axis. Patients had often low plasma aldosterone and renin levels despite hypertension. Only one GR gain-of-function mutation has been described associating Cushing's syndrome phenotype with normal urinary-free cortisol. Some GR polymorphisms (ER22/23EK, GR-9β) have been linked to glucocorticoid resistance and a healthier metabolic profile whereas some others seemed to be associated with GC hypersensitivity (N363S, BclI), increasing cardiovascular risk (diabetes type 2, visceral obesity). This review focuses on the earlier findings on the pathophysiology of GR signaling and presents criteria facilitating identification of novel NR3C1 mutations in selected patients.

Glucocorticoid receptor isoform-specific regulation of development, circadian rhythm, and inflammation in mice

Glucocorticoids are primary stress hormones, and their synthetic derivatives are widely used clinically. The therapeutic efficacy of these steroids is limited by side effects and glucocorticoid resistance. Multiple glucocorticoid receptor (GR) isoforms are produced from a single gene by alternative translation initiation; however, the role individual isoforms play in tissue-specific responses to glucocorticoids is unknown. We have generated knockin mice that exclusively express the most active receptor isoform, GR-C3. GR-C3 knockin mice die at birth due to respiratory distress. Microarray analysis of fibroblasts from wild-type and GR-C3 mice indicated that most genes regulated by GR-C3 were unique to this isoform. Antenatal glucocorticoid administration rescued GR-C3 knockin mice from neonatal death. Dual-energy X-ray absorptiometry revealed no major alterations in body composition for rescued knockin mice. Rescued female, but not male, GR-C3 mice exhibited increased wheel running activity in the light portion of the day. LPS administration induced premature mortality in rescued GR-C3 knockin mice, and gene expression studies revealed a deficiency in the ability of GR-C3 to repress a large cohort of immune and inflammatory response genes. These findings demonstrate that specific GR translational isoforms can influence development, circadian rhythm, and inflammation through the regulation of distinct gene networks.-Oakley, R. H., Ramamoorthy, S., Foley, J. F., Busada, J. T., Lu, N. Z., Cidlowski, J. A. Glucocorticoid receptor isoform-specific regulation of development, circadian rhythm, and inflammation in mice.

Vertebral fractures assessed with dual-energy X-ray absorptiometry in patients with Addison's disease on glucocorticoid and mineralocorticoid replacement therapy

PURPOSE

to assess bone damage and metabolic abnormalities in patients with Addison's disease given replacement doses of glucocorticoids and mineralocorticoids.

METHODS

A total of 87 patients and 81 age-matched and sex-matched healthy controls were studied. The following parameters were measured: urinary cortisol, serum calcium, phosphorus, creatinine, 24-h urinary calcium excretion, bone alkaline phosphatase, parathyroid hormone, serum CrossLaps, 25 hydroxyvitamin D, and 1,25 dihydroxyvitamin D. Clear vertebral images were obtained with dual-energy X-ray absorptiometry in 61 Addison's disease patients and 47 controls and assessed using Genant's classification.

RESULTS

Nineteen Addison's disease patients (31.1%) had at least one morphometric vertebral fracture, as opposed to six controls (12.8%, odds ratio 3.09, 95% confidence interval 1.12-8.52). There were no significant differences in bone mineral density parameters at any site between patients and controls. In Addison's disease patients, there was a positive correlation between urinary cortisol and urinary calcium excretion. Patients with fractures had a longer history of disease than those without fractures. Patients taking fludrocortisone had a higher bone mineral density than untreated patients at all sites except the lumbar spine.

CONCLUSIONS

Addison's disease patients have more fragile bones irrespective of any decrease in bone mineral density. Supra-physiological doses of glucocorticoids and longer-standing disease (with a consequently higher glucocorticoid intake) might be the main causes behind patients' increased bone fragility. Associated mineralocorticoid treatment seems to have a protective effect on bone mineral density.

Regulatory and Mechanistic Actions of Glucocorticoids on T and Inflammatory Cells

Glucocorticoids (GCs) play an important role in regulating the inflammatory and immune response and have been used since decades to treat various inflammatory and autoimmune disorders. Fine-tuning the glucocorticoid receptor (GR) activity is instrumental in the search for novel therapeutic strategies aimed to reduce pathological signaling and restoring homeostasis. Despite the primary anti-inflammatory actions of GCs, there are studies suggesting that under certain conditions GCs may also exert pro-inflammatory responses. For these reasons the understanding of the GR basic mechanisms of action on different immune cells in the periphery (e.g., macrophages, dendritic cells, neutrophils, and T cells) and in the brain (microglia) contexts, that we review in this chapter, is a continuous matter of interest and may reveal novel therapeutic targets for the treatment of immune and inflammatory response.

Endocannabinoids: Effectors of glucocorticoid signaling

For decades, there has been speculation regarding the interaction of cannabinoids with glucocorticoid systems. Given the functional redundancy between many of the physiological effects of glucocorticoids and cannabinoids, it was originally speculated that the biological mechanisms of cannabinoids were mediated by direct interactions with glucocorticoid systems. With the discovery of the endocannabinoid system, additional research demonstrated that it was actually the opposite; glucocorticoids recruit endocannabinoid signaling, and that the engagement of endocannabinoid signaling mediated many of the neurobiological and physiological effects of glucocorticoids. With the development of advances in pharmacology and genetics, significant advances in this area have been made, and it is now clear that functional interactions between these systems are critical for a wide array of physiological processes. The current review acts a comprehensive summary of the contemporary state of knowledge regarding the biological interactions between glucocorticoids and endocannabinoids, and their potential role in health and disease.

Identification of novel regulatory GRE-binding elements in the porcine IP3R1 gene promoter and their transcriptional activation under glucocorticoid stimulation

Inositol 1,4,5-trisphosphate receptor 1 (IP3R1) is a type of ligand-gated calcium channel that is expressed predominantly in mammalian skeletal muscle, where it acts as a key regulator of calcium homeostasis. In meat, calcium disequilibrium is accompanied by the deterioration of meat quality. Here we show that serum cortisol concentration was higher and the IP3R1 gene expression level increased markedly in pigs exposed to high stress. In porcine primary muscle cells, dexamethasone (DEX, a synthetic glucocorticoid) increased the protein levels of porcine IP3R1 and GRα, and cell apoptosis, and the specific GRα inhibitor RU486 attenuated these effects. DEX also increased the expression of IP3R1 at both the gene and protein levels, and this expression was attenuated by RU486, siRNA against GRα, and the transcriptional inhibitor actinomycin D. DEX significantly reduced cell viability and increased the intracellular calcium concentration, and these effects were attenuated by siRNA against GRα. Bioinformatics analyses predicted a potential glucocorticoid response element (GRE) located in the region -326 to -309 upstream of the IP3R1 promoter and highly conserved in pigs and other mammalian species. Promoter analysis showed that this region containing the GRE was critical for transcriptional activity of porcine IP3R1 under DEX stimulation. This was confirmed by deletion and site-mutation methods. EMSA and ChIP assays showed that this potential GRE bound specifically to GRα and this complex activated the transcription of the IP3R1 gene. Taken together, these data suggest that DEX-mediated induction of IP3R1 influences porcine muscle cells through the transcriptional activation of a mechanism involving interactions between GRα and a GRE present in the proximal IP3R1 promoter. This process can lead to an imbalance in intracellular calcium concentration, which may subsequently activate the apoptosis signal and decrease cell activity, and cause deterioration of meat quality.

Identification and characterization of BATF3 as a context-specific coactivator of the glucocorticoid receptor

The ability of the glucocorticoid receptor (GR) to regulate the transcriptional output of genes relies on its interactions with transcriptional coregulators. However, which coregulators are required for GR-dependent activation is context-dependent and can be influenced by the sequence of the DNA bound by GR and by the nature of the GR isoform responsible for the regulation of a gene. Here, we screened for GR-interacting proteins for which the interaction signal differed between two GR isoforms GRα and GRγ. These isoforms diverge by a single amino acid insertion in a domain, the lever arm, which adopts DNA sequence-specific conformations. We identify Basic Leucine Zipper ATF-Like Transcription Factor 3 (BATF3), an AP-1 family transcription factor, as a GR coregulator whose interaction with GR is modulated by the lever arm. Further, a combination of experiments uncovered that BATF3 acts as a gene-specific coactivator of GR whose coactivator potency is influenced by the sequence of the GR binding site. Together, our findings suggest that GR isoform and the sequence of GR binding site influence the interaction of GR with BATF3, which might direct the assembly of gene-specific regulatory complexes to fine-tune the expression of individual GR target genes.

nr3c1 null mutant zebrafish are viable and reveal DNA-binding-independent activities of the glucocorticoid receptor

Glucocorticoids (GCs) play important roles in developmental and physiological processes through the transcriptional activity of their cognate receptor (Gr). Using CRISPR/Cas9 technology, we established a zebrafish null Gr mutant line and compared its phenotypes with wild type and a zebrafish line with partially silenced gr (gr^s357/s357). Homozygous gr^−/− larvae are morphologically inconspicuous and, in contrast to GR^−/− knockout mice, viable through adulthood, although with reduced fitness and early life survival. Mutants gr^−/− are fertile, but their reproductive capabilities fall at around 10 months of age, when, together with cardiac and intestinal abnormalities already visible at earlier stages, increased fat deposits are also observed. Mutants show higher levels of whole-body cortisol associated with overstimulated basal levels of crh and pomca transcripts along the HPI axis, which is unresponsive to a mechanical stressor. Transcriptional activity linked to immune response is also hampered in the gr^−/− line: after intestinal damage by dextran sodium sulphate exposure, there are neither inflammatory nor anti-inflammatory cytokine gene responses, substantiating the hypothesis of a dual-action of the GC-GR complex on the immune system. Hence, the zebrafish gr mutant line appears as a useful tool to investigate Gr functions in an integrated in vivo model.

Glucocorticoids and Reproduction: Traffic Control on the Road to Reproduction

Glucocorticoids are steroid hormones that regulate diverse cellular functions and are essential to facilitate normal physiology. However, stress-induced levels of glucocorticoids result in several pathologies including profound reproductive dysfunction. Compelling new evidence indicates that glucocorticoids are crucial to the establishment and maintenance of reproductive function. The fertility-promoting or -inhibiting activity of glucocorticoids depends on timing, dose, and glucocorticoid responsiveness within a given tissue, which is mediated by the glucocorticoid receptor (GR). The GR gene and protein are subject to cellular processing, contributing to signaling diversity and providing a mechanism by which both physiological and stress-induced levels of glucocorticoids function in a cell-specific manner. Understanding how glucocorticoids regulate fertility and infertility may lead to novel approaches to the regulation of reproductive function.

Glucocorticoid receptors: finding the middle ground

Glucocorticoids (GCs; referred to clinically as corticosteroids) are steroid hormones with potent anti-inflammatory and immune modulatory profiles. Depending on the context, these hormones can also mediate pro-inflammatory activities, thereby serving as primers of the immune system. Their target receptor, the GC receptor (GR), is a multi-tasking transcription factor, changing its role and function depending on cellular and organismal needs. To get a clearer idea of how to improve the safety profile of GCs, recent studies have investigated the complex mechanisms underlying GR functions. One of the key findings includes both pro- and anti-inflammatory roles of GR, and a future challenge will be to understand how such paradoxical findings can be reconciled and how GR ultimately shifts the balance to a net anti-inflammatory profile. As such, there is consensus that GR deserves a second life as a drug target, with either refined classic GCs or a novel generation of nonsteroidal GR-targeting molecules, to meet the increasing clinical needs of today to treat inflammation and cancer.

Disruption of Endothelial Cell Homeostasis Plays a Key Role in the Early Pathogenesis of Coronary Artery Abnormalities in Kawasaki Disease

Disruption of endothelial cell homeostasis may be associated with the pathogenesis of coronary artery abnormalities (CAA) in Kawasaki disease (KD). We sought to clarify the poorly understood pathogenic role of endothelial cell survival and death in KD vasculitis. Human umbilical vein endothelial cells (HUVECs) stimulated with sera from KD patients, compared with sera from patients with bacterial infections, exhibited significant increases in cytotoxicity, high mobility group box protein 1 (HMGB-1), and caspase-3/7 and a decrease in phosphorylated Akt/Akt (pAkt/Akt) ratios. HUVECs stimulated with sera from KD patients treated with immunoglobulin (IG) showed significantly decreased cytotoxicity, HMGB-1, and caspase-3/7 levels and increased pAkt/Akt ratios, as compared with results for untreated HUVECs (P < 0.001, P = 0.008, P = 0.040, and P < 0.001, respectively). In HUVECs stimulated with sera from KD patients, the increased cytotoxicity levels and the suppression of increased pAkt/Akt ratios after subsequent IG treatment were closely related to the development of CAA (P = 0.002 and P = 0.035). Our data reveal that shifting the balance toward cell death rather than survival appears to perturb endothelial cell homeostasis and is closely related to the development of CAA. The cytoprotective effects of IG treatment appear to ameliorate endothelial cell homeostasis.

Cross-talk between the glucocorticoid receptor and MyoD family inhibitor domain-containing protein provides a new mechanism for generating tissue-specific responses to glucocorticoids

Glucocorticoids are primary stress hormones that regulate many physiological processes, and synthetic derivatives of these molecules are widely used in the clinic. The molecular factors that govern tissue specificity of glucocorticoids, however, are poorly understood. The actions of glucocorticoids are mediated by the glucocorticoid receptor (GR). To discover new proteins that interact with GR and modulate its function, we performed a yeast two-hybrid assay. The MyoD family inhibitor domain-containing protein (MDFIC) was identified as a binding partner for GR. MDFIC associated with GR in the cytoplasm of cells, and treatment with glucocorticoids resulted in the dissociation of the GR-MDFIC complex. To investigate the function of the GR-MDFIC interaction, we performed a genome-wide microarray in intact and MDFIC-deficient A549 cells that were treated with glucocorticoids. A large cohort of genes was differentially regulated by GR depending on the presence or absence of MDFIC. These gene changes were strongly associated with inflammation, and glucocorticoid regulation of the inflammatory response was altered in MDFIC-deficient cells. At a molecular level, the interaction of MDFIC with GR altered the phosphorylation status of the receptor. We demonstrate in COS-1 cells that changes in receptor phosphorylation underlie the ability of MDFIC to regulate the transcriptional activity of GR. Finally, we show that GR directly represses the MDFIC gene, revealing a negative feedback loop by which glucocorticoids limit MDFIC activity. These findings identify a new binding partner for cytoplasmic GR that modulates the receptor transcriptome and contributes to the tissue-specific actions of glucocorticoids.

Immune regulation by glucocorticoids

Endogenous glucocorticoids are crucial to various physiological processes, including metabolism, development and inflammation. Since 1948, synthetic glucocorticoids have been used to treat various immune-related disorders. The mechanisms that underlie the immunosuppressive properties of these hormones have been intensely scrutinized, and it is widely appreciated that glucocorticoids have pleiotropic effects on the immune system. However, a clear picture of the cellular and molecular basis of glucocorticoid action has remained elusive. In this Review, we distil several decades of intense (and often conflicting) research that defines the interface between the endocrine stress response and the immune system.

Mechanisms of Glucocorticoid Action During Development

Glucocorticoids are primary stress hormones produced by the adrenal cortex. The concentration of serum glucocorticoids in the fetus is low throughout most of gestation but surge in the weeks prior to birth. While their most well-known function is to stimulate differentiation and functional development of the lungs, glucocorticoids also play crucial roles in the development of several other organ systems. Mothers at risk of preterm delivery are administered glucocorticoids to accelerate fetal lung development and prevent respiratory distress. Conversely, excessive glucocorticoid signaling is detrimental for fetal development; slowing fetal and placental growth and programming the individual for disease later in adult life. This review explores the mechanisms that control glucocorticoid signaling during pregnancy and provides an overview of the impact of glucocorticoid signaling on fetal development.

Corticosteroids: Mechanisms of Action in Health and Disease

Glucocorticoids are primary stress hormones that regulate a variety of physiologic processes and are essential for life. The actions of glucocorticoids are predominantly mediated through the classic glucocorticoid receptor (GR). GRs are expressed throughout the body, but there is considerable heterogeneity in glucocorticoid sensitivity and biologic responses across tissues. The conventional belief that glucocorticoids act through a single GR protein has changed dramatically with the discovery of a diverse collection of receptor isoforms. This article provides an overview of the molecular mechanisms that regulate glucocorticoid actions, highlights the dynamic nature of hormone signaling, and discusses the molecular properties of the GR isoforms.

Molecular Actions of Glucocorticoids in Cartilage and Bone During Health, Disease, and Steroid Therapy

Cartilage and bone are severely affected by glucocorticoids (GCs), steroid hormones that are frequently used to treat inflammatory diseases. Major complications associated with long-term steroid therapy include impairment of cartilaginous bone growth and GC-induced osteoporosis. Particularly in arthritis, GC application can increase joint and bone damage. Contrarily, endogenous GC release supports cartilage and bone integrity. In the last decade, substantial progress in the understanding of the molecular mechanisms of GC action has been gained through genome-wide binding studies of the GC receptor. These genomic approaches have revolutionized our understanding of gene regulation by ligand-induced transcription factors in general. Furthermore, specific inactivation of GC signaling and the GC receptor in bone and cartilage cells of rodent models has enabled the cell-specific effects of GCs in normal tissue homeostasis, inflammatory bone diseases, and GC-induced osteoporosis to be dissected. In this review, we summarize the current view of GC action in cartilage and bone. We further discuss future research directions in the context of new concepts for optimized steroid therapies with less detrimental effects on bone.

Rapid Eye Movement Sleep Deprivation Produces Long-Term Detrimental Effects in Spatial Memory and Modifies the Cellular Composition of the Subgranular Zone

Sleep deprivation (SD) affects spatial memory and proliferation in the dentate gyrus. It is unknown whether these deleterious effects persist in the long run. The aim of this study was to evaluate the proliferation, differentiation and maturation of neural progenitors as well as spatial memory 21 days after suffering SD. Sixty-day old male Balb/C mice were exposed to 72-h REM-SD. Spatial memory, cell fate, apoptosis and expression levels of insulin-like growth factor 1 receptor (IGF-1R) were evaluated in the hippocampus at 0, 14, and 21 days after SD or control conditions. After 21-days recovery period, memory performance was assessed with the Barnes maze, we found a significant memory impairment in SD mice vs. control (94.0 ± 10.2 s vs. 25.2 ± 4.5 s; p < 0.001). The number of BrdU+ cells was significantly decreased in the SD groups at day 14 (controls = 1.6 ± 0.1 vs. SD mice = 1.2 ± 0.1 cells/field; p = 0.001) and at day 21 (controls = 0.2 ± 0.03 vs. SD mice = 0.1 ± 0.02 cells/field; p < 0.001). A statistically significant decrease was observed in neuronal differentiation (1.4 ± 0.1 cells/field vs. 0.9 ± 0.1 cells/field, p = 0.003). Apoptosis was significantly increased at day 14 after SD (0.53 ± 0.06 TUNEL+ cells/field) compared to controls (0.19 ± 0.03 TUNEL+ cells/field p < 0.001) and at 21-days after SD (SD mice 0.53 ± 0.15 TUNEL+ cells/field; p = 0.035). At day 0, IGF-1R expression showed a statistically significant reduction in SD animals (64.6 ± 12.2 units) when compared to the control group (102.0 ± 9.8 units; p = 0.043). However, no statistically significant differences were found at days 14 and 21 after SD. In conclusion, a single exposition to SD for 72-h can induce deleterious effects that persist for at least 3 weeks. These changes are characterized by spatial memory impairment, reduction in the number of hippocampal BrdU+ cells and persistent apoptosis rate. In contrast, changes IGF-1R expression appears to be a transient event. Highlight Sleep deprivation affects spatial memory and proliferation in the dentate gyrus. To date it is unknown whether these deleterious effects are persistent over a long period of time. We analyzed the effects of sleep deprivation in the hippocampus after 21 days of recovery sleep. Our findings indicate that after sleep recovery, the detrimental effects of SD can be observed for at least 2 weeks, as shown by a reduction in memory performance, changes in the hippocampal cellular composition and higher apoptotic rate over a long period of time.

Comprehensive RNA profiling of villous trophoblast and decidua basalis in pregnancies complicated by preterm birth following intra-amniotic infection

INTRODUCTION

We performed RNA sequencing with the primary goal of discovering key placental villous trophoblast (VT) and decidua basalis (DB) transcripts differentially expressed in intra-amniotic infection (IAI)-induced preterm birth (PTB).

METHODS

RNA was extracted from 15 paired VT and DB specimens delivered of women with: 1) spontaneous PTB in the setting of amniocentesis-proven IAI and histological chorioamnionitis (n = 5); 2) spontaneous idiopathic PTB (iPTB, n = 5); and 3) physiologic term pregnancy (n = 5). RNA sequencing was performed using the Illumina HiSeq 2500 platform, and a spectrum of computational tools was used for gene prioritization and pathway analyses.

RESULTS

In the VT specimens, 128 unique long transcripts and 7 mature microRNAs differed significantly between pregnancies complicated by IAI relative to iPTB (FDR<0.1). The up-regulated transcripts included many characteristic of myeloblast-derived cells, and bioinformatic analyses revealed enrichment for multiple pathways associated with acute inflammation. In an expanded cohort including additional IAI and iPTB specimens, the expression of three proteins (cathepsin S, lysozyme, and hexokinase 3) and two microRNAs (miR-133a and miR-223) was validated using immunohistochemistry and quantitative PCR, respectively. In the DB specimens, only 11 long transcripts and no microRNAs differed significantly between IAI cases and iPTB controls (FDR<0.1). Comparison of the VT and DB specimens in each clinical scenario revealed signatures distinguishing these placental regions.

DISCUSSION

IAI is associated with a transcriptional signature consistent with acute inflammation in the villous trophoblast. The present findings illuminate novel signaling pathways involved in IAI, and suggest putative therapeutic targets and potential biomarkers associated with this condition.