Cellular processing of the glucocorticoid receptor gene and protein: new mechanisms for generating tissue-specific actions of glucocorticoids

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.

Therapeutic Effects of Resiniferatoxin Related with Immunological Responses for Intestinal Inflammation in Trichinellosis

The immune response against Trichinella spiralis at the intestinal level depends on the CD4⁺ T cells, which can both suppress or promote the inflammatory response through the synthesis of diverse cytokines. During the intestinal phase, the immune response is mixed (Th1/Th2) with the initial predominance of the Th1 response and the subsequent domination of Th2 response, which favor the development of intestinal pathology. In this context, the glucocorticoids (GC) are the pharmacotherapy for the intestinal inflammatory response in trichinellosis. However, its therapeutic use is limited, since studies have shown that treatment with GC suppresses the host immune system, favoring T. spiralis infection. In the search for novel pharmacological strategies that inhibit the Th1 immune response (proinflammatory) and assist the host against T. spiralis infection, recent studies showed that resiniferatoxin (RTX) had anti-inflammatory activity, which decreased the serum levels of IL-12, INF-γ, IL-1β, TNF-α, NO, and PGE₂, as well the number of eosinophils in the blood, associated with decreased intestinal pathology and muscle parasite burden. These researches demonstrate that RTX is capable to inhibit the production of Th1 cytokines, contributing to the defense against T. spiralis infection, which places it as a new potential drug modulator of the immune response.

Nuclear receptors in neural stem/progenitor cell homeostasis

In the central nervous system, embryonic and adult neural stem/progenitor cells (NSCs) generate the enormous variety and huge numbers of neuronal and glial cells that provide structural and functional support in the brain and spinal cord. Over the last decades, nuclear receptors and their natural ligands have emerged as critical regulators of NSC homeostasis during embryonic development and adult life. Furthermore, substantial progress has been achieved towards elucidating the molecular mechanisms of nuclear receptors action in proliferative and differentiation capacities of NSCs. Aberrant expression or function of nuclear receptors in NSCs also contributes to the pathogenesis of various nervous system diseases. Here, we review recent advances in our understanding of the regulatory roles of steroid, non-steroid, and orphan nuclear receptors in NSC fate decisions. These studies establish nuclear receptors as key therapeutic targets in brain diseases.

Genomic and epigenomic mechanisms of glucocorticoids in the brain

Following the discovery of glucocorticoid receptors in the hippocampus and other brain regions, research has focused on understanding the effects of glucocorticoids in the brain and their role in regulating emotion and cognition. Glucocorticoids are essential for adaptation to stressors (allostasis) and in maladaptation resulting from allostatic load and overload. Allostatic overload, which can occur during chronic stress, can reshape the hypothalamic-pituitary-adrenal axis through epigenetic modification of genes in the hippocampus, hypothalamus and other stress-responsive brain regions. Glucocorticoids exert their effects on the brain through genomic mechanisms that involve both glucocorticoid receptors and mineralocorticoid receptors directly binding to DNA, as well as by non-genomic mechanisms. Furthermore, glucocorticoids synergize both genomically and non-genomically with neurotransmitters, neurotrophic factors, sex hormones and other stress mediators to shape an organism's present and future responses to a stressful environment. Here, we discuss the mechanisms of glucocorticoid action in the brain and review how glucocorticoids interact with stress mediators in the context of allostasis, allostatic load and stress-induced neuroplasticity.

Stress and the HPA Axis: Balancing Homeostasis and Fertility

An organism’s reproductive fitness is sensitive to the environment, integrating cues of resource availability, ecological factors, and hazards within its habitat. Events that challenge the environment of an organism activate the central stress response system, which is primarily mediated by the hypothalamic–pituitary–adrenal (HPA) axis. The regulatory functions of the HPA axis govern the cardiovascular and metabolic system, immune functions, behavior, and reproduction. Activation of the HPA axis by various stressors primarily inhibits reproductive function and is able to alter fetal development, imparting a biological record of stress experienced in utero. Clinical studies and experimental data indicate that stress signaling can mediate these effects through direct actions in the brain, gonads, and embryonic tissues. This review focuses on the mechanisms by which stress activation of the HPA axis impacts fertility and fetal development.

High-fat diet enhances hepatic ischemia-reperfusion injury-induced apoptosis: Role of glucocorticoid receptors

AIMS

The present study was designed to evaluate whether and how glucocorticoids can affect obesity-regulated hepatic ischemia-reperfusion (I/R) injury.

MAIN METHODS

To this end, we first examined whether hydrocortisone (HCT) has protective effects on liver damage induced by hepatic I/R injury in mice receiving high fat diet treatment. We then explored the role of GR expression and phosphorylation in the anti-apoptotic effects of hydrocortisone upon hepatic I/R injury.

KEY FINDINGS

We found that HCT reduced hepatic necrosis and inflammatory infiltration after hepatic I/R injury in mice that received high fat diet treatment. However, HCT lost the anti-apoptotic effects in high-fat diet treated mice. This phenomenon was associated with increased GRβ expression, decreased basal levels of GR phosphorylation at Ser220 and lack of HCT-induced GR phosphorylation at Ser220 in high-fat diet treated mice. Additionally, basal levels of ERK phosphorylation was increased in high-fat diet treated mice, and I/R injury was associated with robustly increased ERK phosphorylation in high-fat diet treated mice, compared to normal diet treated mice. Furthermore, we demonstrated that high fat diet treated ERK1^-/- mice exhibited robustly reduced apoptosis rate at 24h after reperfusion, compared to high fat diet treated wild-type mice. Importantly, there was a decreased level of GRβ after high fat diet treatment in ERK1^-/- mice.

SIGNIFICANCE

These results together suggested that ERK1 phosphorylation plays a critical role in regulating GRβ expression and HCT-induce GR phosphorylation at Ser220, which is critical for the anti-apoptotic effects HCT on hepatic I/R injury.

Glucocorticosteroid therapy in inflammatory bowel diseases: From clinical practice to molecular biology

Inflammatory bowel diseases (IBDs), such as ulcerative colitis and Crohn’s disease, are chronic pathologies associated with a deregulated immune response in the intestinal mucosa, and they are triggered by environmental factors in genetically susceptible individuals. Exogenous glucocorticoids (GCs) are widely used as anti-inflammatory therapy in IBDs. In the past, patients with moderate or severe states of inflammation received GCs as a first line therapy with an important effectiveness in terms of reduction of the disease activity and the induction of remission. However, this treatment often results in detrimental side effects. This downside drove the development of second generation GCs and more precise (non-systemic) drug-delivery methods. Recent clinical trials show that most of these new treatments have similar effectiveness to first generation GCs with fewer adverse effects. The remaining challenge in successful treatment of IBDs concerns the refractoriness and dependency that some patients encounter during GCs treatment. A deeper understanding of the molecular mechanisms underlying GC response is key to personalizing drug choice for IBDs patients to optimize their response to treatment. In this review, we examine the clinical characteristics of treatment with GCs, followed by an in depth analysis of the proposed molecular mechanisms involved in its resistance and dependence associated with IBDs. This thorough analysis of current clinical and biomedical literature may help guide physicians in determining a course of treatment for IBDs patients and identifies important areas needing further study.

Plasmodium berghei NK65 in Combination with IFN-γ Induces Endothelial Glucocorticoid Resistance via Sustained Activation of p38 and JNK

Malaria-associated acute respiratory distress syndrome (MA-ARDS) is an often lethal complication of malaria. Currently, no adequate therapy for this syndrome exists. Although glucocorticoids (GCs) have been used to improve clinical outcome of ARDS, their therapeutic benefits remain unclear. We previously developed a mouse model of MA-ARDS, in which dexamethasone treatment revealed GC resistance. In the present study, we investigated GC sensitivity of mouse microvascular lung endothelial cells stimulated with interferon-γ (IFN-γ) and Plasmodium berghei NK65 (PbNK65). Upon challenge with IFN-γ alone, dexamethasone inhibited the expression of CCL5 (RANTES) by 90% and both CCL2 (MCP-1) and CXCL10 (IP-10) by 50%. Accordingly, whole transcriptome analysis revealed that dexamethasone differentially affected several gene clusters and in particular inhibited a large cluster of IFN-γ-induced genes, including chemokines. In contrast, combined stimulation with IFN-γ and PbNK65 extract impaired inhibitory actions of GCs on chemokine release, without affecting the capacity of the GC receptor to accumulate in the nucleus. Subsequently, we investigated the effects of GCs on two signaling pathways activated by IFN-γ. Dexamethasone left phosphorylation and protein levels of signal transducer and activator of transcription 1 (STAT1) unhampered. In contrast, dexamethasone inhibited the IFN-γ-induced activation of two mitogen-activated protein kinases (MAPK), JNK, and p38. However, PbNK65 extract abolished the inhibitory effects of GCs on MAPK signaling, inducing GC resistance. These data provide novel insights into the mechanisms of GC actions in endothelial cells and show how malaria may impair the beneficial effects of GCs.

Corticosteroid and long-acting ß-agonist therapy reduces epithelial goblet cell metaplasia

BACKGROUND

Bronchial epithelial goblet cell metaplasia (GCM) with hyperplasia is a prominent feature of asthma, but the effects of treatment with corticosteroids alone or in combination with a long-acting β₂ -adrenergic receptor agonist (LABA) on GCM in the bronchial epithelium are unknown.

OBJECTIVES

To determine whether corticosteroid alone or in combination with a LABA alters protein and gene expression pathways associated with IL-13-induced goblet cell metaplasia.

RESULTS

We evaluated the effects of fluticasone propionate (FP) and of salmeterol (SM), on the response of well-differentiated cultured bronchial epithelial cells to interleukin-13 (IL-13). Outcome measures included gene expression of SPDEF/FOXa2, gene expression and protein production of MUC5AC/MUC5B and morphologic appearance of cultured epithelial cell sheets. We additionally analysed expression of these genes in bronchial epithelial brushings from healthy, steroid-naïve asthmatic and steroid-treated asthmatic subjects. In cultured airway epithelial cells, FP treatment inhibited IL-13-induced suppression of FOXa2 gene expression and up-regulation of SPDEF, alterations in gene and protein measures of MUC5AC and MUC5B and induction of GCM. The addition of SM synergistically modified the effects of FP modestly-only for gel-forming mucin MUC5AC. In bronchial epithelial cells recovered from asthmatic vs healthy human subjects, we found FOXa2 and MUC5B gene expression to be reduced and SPDEF and MUC5AC gene expression to be increased; these alterations were not observed in bronchial epithelial cells recovered after treatment with inhaled corticosteroids.

CONCLUSION AND CLINICAL RELEVANCE

Corticosteroid treatment inhibits IL-13-induced GCM of the airways in asthma, possibly through its effects on SPDEF and FOXa2 regulation of mucin gene expression. These effects are modestly augmented by the addition of a long-acting ß-agonist. As we found evidence for drug treatment counteracting the effects of IL-13 on the epithelium, we conclude that further exploration into the mechanisms by which corticosteroids and long-acting β₂ -adrenergic agonists confer protection against pathologic airway changes is warranted.

The evolution, structure and function of the ray finned fish (Actinopterygii) glucocorticoid receptors

Basal ray-finned fish (Actinopterygii) possess a single glucocorticoid receptor (GR) and when compared to the lobe-finned vertebrate (Sarcopterygii) GR possess nine additional amino acids between the zinc-finger of the DNA binding domain. A whole genome duplication event which occurred between 320 and 350MYA in the teleost lineage following the split from the basal ray-finned fish resulted in 2 GRs: one GR group, GR1, has retained the 9 amino acids insert whereas the other group, GR2, has not. The exception to this is the zebrafish, that have lost one of the GRs, but they do possess 2 GRs with a splice variant that lacks the C-terminal portion of the GR to form GRβ which acts as a dominant-repressor of the wildtype GR. Another splice variant sees the basal ray-finned GR and teleost GR1 without the 9 amino acids insert. The molecular basis for GRs retention is beginning to be unravelled. In Pantadon buchholzi, rainbow trout, carp, marine and Japanese medaka GR2 is more sensitive to glucocorticoids (GC), thus potentially playing a more significant role in regulating gene expression at basal circulatory GC concentrations. However, this division in GC sensitivity is not seen in other species. The few studies to evaluate the significance of the 9 amino acid insert have shown that it affect maximal transactivational activity the extent to which is dependent on the number of glucocorticoid response elements (GREs) present in the reporter plasmid. The retention of these GRs would suggest there was an evolutionary advantage, which saw the development of a complex regulatory process to mediate the actions of the glucocorticoids.

Ginseng on Nuclear Hormone Receptors

The first record of ginseng use dates back over two millennia, and ginseng is now popular in more than 35 countries. Ginsenosides are the pharmacological constituents responsible for the beneficial effects of ginseng. There is increasing evidence that ginseng and its bioactive ingredients are involved in the regulation of nuclear receptors, molecules that act in response to the specific binding of hormones, which link to a diverse array of signaling pathways, such as the ERK and PI3K/Akt pathways. Knowledge of the mechanism of how ginseng mediates these complexes is essential for the development of multi-target phytomedicine as possible therapy for different diseases. Here, we discuss the literature on the effects of ginseng and its constituents on estrogen, glucocorticoid, peroxisome proliferator-activated, and androgen nuclear hormone receptors, as well as how ginseng and its constituents exert their biological function in the treatment of cancer, obesity, and cardiovascular and neurological disorders. The accumulated results definitely show that the nuclear receptors are cellular targets of ginsenosides, but more rigorous data are required to establish and provide a scientific basis to confirm the suggested efficacy of ginseng or products with ginsenosides.

A functional IL1RL1 variant regulates corticosteroid-induced sST2 expression in ulcerative colitis

The ST2/IL33 signalling pathway has been associated with ulcerative colitis (UC). ST2, encoded by the IL1RL1 gene, is expressed as both a membrane-anchored receptor (ST2L) activated by IL33 and as a soluble receptor (sST2) with anti-inflammatory properties. In UC patients, sST2 is further increased by corticosteroid treatment; however, the glucocorticoid-mediated molecular regulation remains unknown. We therefore tested whether genetic variants in the IL1RL1 distal promoter are involved in UC and affect glucocorticoid-mediated ST2 expression. Serum ST2 levels and genetic variants in the IL1RL1 distal promoter were examined by ELISA and PCR sequencing in UC patients receiving corticosteroids. Glucocorticoid-mediated ST2 production was evaluated in intestinal mucosa cultures. Molecular regulation of glucocorticoid-mediated ST2 was assessed by RT-qPCR, ChIP assay and luciferase reporter assay. Dexamethasone effect on ST2 transcript expression was analyzed in leukocytes and related to IL1RL1 variants. Sequencing of a distal IL1RL1 promoter region demonstrated that SNPs rs6543115(C) and rs6543116(A) are associated with increased sST2 in UC patients on corticosteroids. Dexamethasone up-regulated sST2 transcription through interaction with the glucocorticoid-response element (GRE) carrying rs6543115(C) variant. Our data indicate that IL1RL1 SNPs rs6543115(C) confer susceptibility to UC and is contained in the GRE, which may modulate glucocorticoid-induced sST2 expression.

The Effect of Glucocorticoid and Glucocorticoid Receptor Interactions on Brain, Spinal Cord, and Glial Cell Plasticity

Stress, injury, and disease trigger glucocorticoid (GC) elevation. Elevated GCs bind to the ubiquitously expressed glucocorticoid receptor (GR). While GRs are in every cell in the nervous system, the expression level varies, suggesting that diverse cell types react differently to GR activation. Stress/GCs induce structural plasticity in neurons, Schwann cells, microglia, oligodendrocytes, and astrocytes as well as affect neurotransmission by changing the release and reuptake of glutamate. While general nervous system plasticity is essential for adaptation and learning and memory, stress-induced plasticity is often maladaptive and contributes to neuropsychiatric disorders and neuropathic pain. In this brief review, we describe the evidence that stress/GCs activate GR to promote cell type-specific changes in cellular plasticity throughout the nervous system.

Impact of aging immune system on neurodegeneration and potential immunotherapies

The interaction between the nervous and immune systems during aging is an area of avid interest, but many aspects remain unclear. This is due, not only to the complexity of the aging process, but also to a mutual dependency and reciprocal causation of alterations and diseases between both the nervous and immune systems. Aging of the brain drives whole body systemic aging, including aging-related changes of the immune system. In turn, the immune system aging, particularly immunosenescence and T cell aging initiated by thymic involution that are sources of chronic inflammation in the elderly (termed inflammaging), potentially induces brain aging and memory loss in a reciprocal manner. Therefore, immunotherapeutics including modulation of inflammation, vaccination, cellular immune therapies and "protective autoimmunity" provide promising approaches to rejuvenate neuroinflammatory disorders and repair brain injury. In this review, we summarize recent discoveries linking the aging immune system with the development of neurodegeneration. Additionally, we discuss potential rejuvenation strategies, focusing aimed at targeting the aging immune system in an effort to prevent acute brain injury and chronic neurodegeneration during aging.

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.

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.

A Quantitative Study of Internal and External Interactions of Homodimeric Glucocorticoid Receptor Using Fluorescence Cross-Correlation Spectroscopy in a Live Cell

Glucocorticoid receptor (GRα) is a well-known ligand-dependent transcription-regulatory protein. The classic view is that unliganded GRα resides in the cytoplasm, relocates to the nucleus after ligand binding, and then associates with a specific DNA sequence, namely a glucocorticoid response element (GRE), to activate a specific gene as a homodimer. It is still a puzzle, however, whether GRα forms the homodimer in the cytoplasm or in the nucleus before DNA binding or after that. To quantify the homodimerization of GRα, we constructed the spectrally different fluorescent protein tagged hGRα and applied fluorescence cross-correlation spectroscopy. First, the dissociation constant (K_d) of mCherry₂-fused hGRα or EGFP-fused hGRα was determined in vitro. Then, K_d of wild-type hGRα was found to be 3.00 μM in the nucleus, which was higher than that in vitro. K_d of a DNA-binding-deficient mutant was 3.51 μM in the nucleus. This similarity indicated that GRα homodimerization was not necessary for DNA binding but could take place on GRE by means of GRE as a scaffold. Moreover, cytoplasmic homodimerization was also observed using GRα mutated in the nuclear localization signal. These findings support the existence of a dynamic monomer pathway and regulation of GRα function both in the cytoplasm and nucleus.

Identification and molecular characterization of cellular factors required for glucocorticoid receptor-mediated mRNA decay

In this study, Park et al. investigated the molecular mechanisms regulating glucocorticoid receptor-mediated mRNA decay (GMD). The authors characterize the molecular details of GMD, identify specific factors required for efficient GMD, and perform RNA sequencing, identifying many endogenous GMD substrates.

Glucocorticoid (GC) receptor (GR) has been shown recently to bind a subset of mRNAs and elicit rapid mRNA degradation. However, the molecular details of GR-mediated mRNA decay (GMD) remain unclear. Here, we demonstrate that GMD triggers rapid degradation of target mRNAs in a translation-independent and exon junction complex-independent manner, confirming that GMD is mechanistically distinct from nonsense-mediated mRNA decay (NMD). Efficient GMD requires PNRC2 (proline-rich nuclear receptor coregulatory protein 2) binding, helicase ability, and ATM-mediated phosphorylation of UPF1 (upstream frameshift 1). We also identify two GMD-specific factors: an RNA-binding protein, YBX1 (Y-box-binding protein 1), and an endoribonuclease, HRSP12 (heat-responsive protein 12). In particular, using HRSP12 variants, which are known to disrupt trimerization of HRSP12, we show that HRSP12 plays an essential role in the formation of a functionally active GMD complex. Moreover, we determine the hierarchical recruitment of GMD factors to target mRNAs. Finally, our genome-wide analysis shows that GMD targets a variety of transcripts, implicating roles in a wide range of cellular processes, including immune responses.

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.

Adipose stem cells from obese patients show specific differences in the metabolic regulators vitamin D and Gas5

Adipose tissue is a significant source of mesenchymal stem cells for regenerative therapies; however, caution should be taken as their environmental niche can affect their functional properties. We have previously demonstrated the negative impact of obesity on the function of adipose-derived stem cells (ASCs). Here we have evaluated other possible properties and targets that are altered by obesity such as the recently described long non-coding molecule Gas5, which is involved in glucocorticoid resistance. Using ASCs isolated from obese (oASCs) and control subjects (cASCs), we have analyzed additional metabolic and inflammatory conditions that could be related with their impaired therapeutic potential and consequently their possible usefulness in the clinic.

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Altered genetic and metabolic targets by obesity in adipose stem cells population

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Gas5 involved in glucocorticoid resistance such as altered target

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Additional metabolic and inflammation conditions on obese adipose stem cells

Mechanisms of Brain Glucocorticoid Resistance in Stress-Induced Psychopathologies

Exposure to stress activates the hypothalamic-pituitary-adrenal axis and leads to increased levels of glucocorticoid (GC) hormones. Prolonged elevation of GC levels causes neuronal dysfunction, decreases the density of synapses, and impairs neuronal plasticity. Decreased sensitivity to glucocorticoids (glucocorticoid resistance) that develops as a result of chronic stress is one of the characteristic features of stress-induced psychopathologies. In this article, we reviewed the published data on proposed molecular mechanisms that contribute to the development of glucocorticoid resistance in brain, including changes in the expression of the glucocorticoid receptor (GR) gene, biosynthesis of GR isoforms, and GR posttranslational modifications. We also present data on alterations in the expression of the FKBP5 gene encoding the main component of cell ultra-short negative feedback loop of GC signaling regulation. Recent discoveries on stress- and GR-induced changes in epigenetic modification patterns as well as normalizing action of antidepressants are discussed. GR and FKBP5 gene polymorphisms associated with stress-induced psychopathologies are described, and their role in glucocorticoid resistance is discussed.

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.

Understanding Physiology in the Continuum: Integration of Information from Multiple -Omics Levels

In this paper, we discuss approaches for integrating biological information reflecting diverse physiologic levels. In particular, we explore statistical and model-based methods for integrating transcriptomic, proteomic and metabolomics data. Our case studies reflect responses to a systemic inflammatory stimulus and in response to an anti-inflammatory treatment. Our paper serves partly as a review of existing methods and partly as a means to demonstrate, using case studies related to human endotoxemia and response to methylprednisolone (MPL) treatment, how specific questions may require specific methods, thus emphasizing the non-uniqueness of the approaches. Finally, we explore novel ways for integrating -omics information with PKPD models, toward the development of more integrated pharmacology models.

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.

Steroid-induced ocular hypertension/glaucoma: Focus on pharmacogenomics and implications for precision medicine

Elevation of intraocular pressure (IOP) due to therapeutic use of glucocorticoids is called steroid-induced ocular hypertension (SIOH); this can lead to steroid-induced glaucoma (SIG). Glucocorticoids initiate signaling cascades ultimately affecting expression of hundreds of genes; this provides the potential for a highly personalized pharmacological response. Studies attempting to define genetic risk factors were undertaken early in the history of glucocorticoid use, however scientific tools available at that time were limited and progress stalled. In contrast, significant advances were made over the ensuing years in defining disease pathophysiology. As the genomics age emerged, it appeared the time was right to renew investigation into genetics. Pharmacogenomics is an unbiased discovery approach, not requiring an underlying hypothesis, and provides a way to pinpoint clinically significant genes and pathways that could not have been discovered any other way. Results of the first genome-wide association study to identify polymorphisms associated with SIOH, and follow-up on two novel genes linked to the disorder, GPR158 and HCG22, is discussed in the second half of the article. However, knowledge of genetic variants determining response to steroids in the eye also has value in its own right as a predictive and diagnostic tool. This article concludes with a discussion of how the Precision Medicine Initiative®, announced by U.S. President Obama in his 2015 State of the Union address, is beginning to touch the practice of ophthalmology. It is argued that SIOH/SIG may provide one of the next opportunities for effective application of precision medicine.

Crosstalk between C/EBP homologous protein (CHOP) and glucocorticoid receptor in lung cancer

Loss of homeostasis triggers the endoplasmic reticulum (ER) stress response and activates the unfolded protein response (UPR) resulting in the induction of the CCAAT/enhancer binding protein (C/EBP) homologous protein (CHOP). Glucocorticoids (GCs), via the glucocorticoid receptor (GR), regulate numerous physiological processes in an effort to maintain homeostasis. Previous studies demonstrated that glucocorticoids suppress ER stress by enhancing correct folding of secreted proteins and degradation of misfolded proteins. Here, we describe a novel crosstalk between ER-stress and the glucocorticoid receptor signaling. We showed that treatment of wild type mice with Tunicamycin (inducer of ER-stress) increased GR protein levels in the lungs. Treatment of A549 cells (human lung cancer cells) with ER stress inducers modulated the Dexamethasone-induced subcellular localization of GR and the phosphorylated forms of GR (pGRSer211 and pGRSer203) with concomitant changes in the expression of primary GR-target genes. We demonstrated a significant protein-protein interaction between GR and CHOP, (GR-CHOP heterocomplex formation) under ER stress conditions. The functional consequences of ER stress- GR signaling crosstalk were assessed and demonstrated that long time exposure (24-48 h) of A549 cells to dexamethasone (10(-6) M) reversed the Tunicamycin-induced cell death, a phenomenon associated with parallel increases in GR protein content, increases in cell survival parameters and decreases in cell apoptosis-related parameters. Our study provides evidence that there is a cross talk between ER-stress and GR signaling, this being associated with mutual functional antagonism between CHOP and GR-mediated pathways in lung cells with important implications in lung cell function.

The Non-Conventional Effects of Glucocorticoids in Cancer

Synthetic corticosteroids are widely used for the treatment of a variety of diseases, including pre-malignant and malignant conditions. In striking contrast, recent evidence suggests that corticosteroids can bear tumor-promoting effects in solid tumors of epithelial origin. We have recently shown that epithelial tissues, including the mucosa of the oral cavity and the skin, are able to modulate the local concentration of active corticosteroids and to produce steroids de novo. This has important clinical and physiopathological implications, because tissue-specific regulation of glucocorticoids plays a key role in the overall effect of these molecules. In the present review of the current English literature, performed using MEDLINE/PubMed/Ovid databases, we collected published evidence to demonstrate that corticosteroids induce effects that are more complex and controversial than previously acknowledged. Published studies clearly demonstrate that this class of molecules influences pathophysiological processes that are strictly related to malignancy, providing the rationale for further investigation. J. Cell. Physiol. 231: 2368-2373, 2016. © 2016 Wiley Periodicals, Inc.

Glucocorticoid therapy and ocular hypertension

The projected number of people who will develop age-related macular degeneration in estimated at 2020 is 196 million and is expected to reach 288 million in 2040. Also, the number of people with Diabetic retinopathy will grow from 126.6 million in 2010 to 191.0 million by 2030. In addition, it is estimated that there are 2.3 million people suffering from uveitis worldwide. Because of the anti-inflammatory properties of glucocorticoids (GCs), they are often used topically and/or intravitreally to treat ocular inflammation conditions or edema associated with macular degeneration and diabetic retinopathy. Unfortunately, ocular GC therapy can lead to severe side effects. Serious and sometimes irreversible eye damage can occur as a result of the development of GC-induced ocular hypertension causing secondary open-angle glaucoma. According to the world health organization, glaucoma is the second leading cause of blindness in the world and it is estimated that 80 million will suffer from glaucoma by 2020. In the current review, mechanisms of GC-induced damage in ocular tissue, GC-resistance, and enhancing GC therapy will be discussed.

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.

Detection of four polymorphisms in 5' upstream region of PNPLA2 gene and their associations with economic traits in pigs

As an important triglyceride hydrolase in mammalian cells, patatin-like phospholipase domain-containing 2 (PNPLA2) predominantly performs the first step in triglyceride hydrolysis. The objective of this study was to detect and evaluate the effects of mutations in the 5' upstream region of porcine PNPLA2 gene with fat deposition and carcass traits. Four single nuclear polymorphisms were identified, including g.161969 T>C, g.161962 A>G, g.161953 C>G and g.161904 G>T, and subsequently genotyped in five pure breeds. Three haplotypes were constructed, including H1(CGGT), H2(TACG) and H3(CACT), which were the most abundant haplotypes in Duroc (0.75), Landrace (0.78) and Chinese indigenous breeds (>0.73), respectively. Duroc individuals with the H1H1 diplotype always exhibited the lowest feed conversion ratio (FCR) (P < 0.05), while H2H2 had the thickest backfat thickness (P < 0.05). Landrace individuals with H2H3 had lower backfat thickness (P < 0.05), higher muscle thickness (P < 0.05) and estimated lean meat percentage (P < 0.05) than those with diplotype H2H2 and H3H3. Luciferase assay indicated pGL3-basic-H2 had the highest activity and pGL3-basic-H1 had the lowest activity in driving reporter gene transcription in HEK293 cells in vitro. In H1 haplotype, two GR binding sites and an ERα binding site were predicted to be introduced. While in H2 and H3, there were other transcriptional factor binding sites predicted in H2 and H3, such as Sp1, AP-2 and CAC-binding proteins, which were broadly expressed transcription factors and capable of contributing to basal promoter activity. The reduced basal promoter activity of H1 may be due to the lack of inducement for GR and ERα binding sites in HEK293 cells. The identified functional polymorphisms provide new evidence of PNPLA2 as an important candidate gene for fat deposition and carcass traits in pigs.

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.

Glucocorticoid-independent modulation of GR activity: Implications for immunotherapy

Pharmacological doses of glucocorticoids (GCs), acting via the glucocorticoid receptor (GR) to repress inflammation and immune function, remain the most effective therapy in the treatment of inflammatory and immune diseases. Since many patients on GC therapy exhibit GC resistance and severe side-effects, much research is focused on developing more selective GCs and combination therapies, with greater anti-inflammatory potency. GCs mediate their classical genomic transcriptional effects by binding to the cytoplasmic GR, followed by nuclear translocation and modulation of transcription of target genes by direct DNA binding of the GR or its tethering to other transcription factors. Recent evidence suggests, however, that the responses mediated by the GR are much more complex and involve multiple parallel mechanisms integrating simultaneous signals from other receptors, both in the absence and presence of GCs, to shift the sensitivity of a target cell to GCs. The level of cellular stress, immune activation status, or the cell cycle phase may be crucial for determining GC sensitivity and GC responsiveness as well as subcellular localization of the GR and GR levels. Central to the development of new drugs that target GR signaling alone or as add-on therapies, is an in-depth understanding of the molecular mechanisms of GC-independent GR desensitization, priming and activation of the unliganded GR, as well as synergy and cross-talk with other signaling pathways. This review will discuss the information currently available on these topics and their relevance to immunotherapy, as well as identify unanswered questions and future areas of research.

Diagnostic and therapeutic strategies for management of autoimmune encephalopathies

INTRODUCTION

The understanding of the etio-pathogenesis of autoimmune encephalopathy syndromes has grown significantly in recent years. These are potentially reversible conditions, with variable clinical presentation and potential dramatic response to immunotherapy.

AREAS COVERED

In this article we review various diagnostic techniques and therapeutic options for management of autoimmune encephalopathy. We also review medication adverse effects and monitoring strategies. Expert commentary: Early diagnosis and immunomodulatory treatment remains the cornerstone of management, to halt the underlying neuro-inflammatory process and prevent permanent neuronal injury. The availability of serological testing and various imaging modalities has further improved detection of these immune-mediated neurological disorders. Understanding the mechanisms and potential adverse effects of immunomodulatory therapies will help physicians to choose the most favorable therapeutic strategy for each patient.

The Interactome of the Glucocorticoid Receptor and Its Influence on the Actions of Glucocorticoids in Combatting Inflammatory and Infectious Diseases

Glucocorticoids (GCs) have been widely used for decades as a first-line treatment for inflammatory and autoimmune diseases. However, their use is often hampered by the onset of adverse effects or resistance. GCs mediate their effects via binding to glucocorticoid receptor (GR), a transcription factor belonging to the family of nuclear receptors. An important aspect of GR's actions, including its anti-inflammatory capacity, involves its interactions with various proteins, such as transcription factors, cofactors, and modifying enzymes, which codetermine receptor functionality. In this review, we provide a state-of-the-art overview of the protein-protein interactions (PPIs) of GR that positively or negatively affect its anti-inflammatory properties, along with mechanistic insights, if known. Emphasis is placed on the interactions that affect its anti-inflammatory effects in the presence of inflammatory and microbial diseases.

Glucocorticoid receptors in lung cancer: new perspectives

Proper expression of the glucocorticoid receptor (GR) plays an essential role in the development of the lung. GR expression and signalling in the lung is manipulated by administration of synthetic glucocorticoids (Gcs) for the treatment of neonatal, childhood and adult lung diseases. In lung cancers, Gcs are also commonly used as co-treatment during chemotherapy. This review summarises the effect of Gc monotherapy and co-therapy on lung cancers in vitro, in mouse models of lung cancer, in xenograft, ex vivo and in vivo The disparity between the effects of pre-clinical and in vivo Gc therapy is commented on in light of the recent discovery of GR as a novel tumour suppressor gene.

Pomalidomide in combination with dexamethasone results in synergistic anti-tumour responses in pre-clinical models of lenalidomide-resistant multiple myeloma

Pomalidomide is an IMiD(®) immunomodulatory agent, which has shown clinically significant benefits in relapsed and/or refractory multiple myeloma (rrMM) patients when combined with dexamethasone, regardless of refractory status to lenalidomide or bortezomib. (Schey et al, ; San Miguel et al, 2013; Richardson et al, 2014; Scott, ) In this work, we present preclinical data showing that the combination of pomalidomide with dexamethasone (PomDex) demonstrates potent anti-proliferative and pro-apoptotic activity in both lenalidomide-sensitive and lenalidomide-resistant MM cell lines. PomDex also synergistically inhibited tumour growth compared with single-agent treatment in xenografts of lenalidomide-resistant H929 R10-1 cells. Typical hallmarks of IMiD compound activity, including IKZF3 (Aiolos) degradation, and the downregulation of interferon regulatory factor (IRF) 4 and MYC, seen in lenalidomide-sensitive H929 MM cell lines, were also observed in PomDex-treated lenalidomide-resistant H929 MM cells. Remarkably, this resulted in strong, synergistic effects on the induction of apoptosis in both lenalidomide-sensitive and resistant MM cells. Furthermore, gene expression profiling revealed a unique differential gene expression pattern in PomDex-treated samples, highlighted by the modulation of pro-apoptotic pathways in lenalidomide-resistant cells. These results provide key insights into molecular mechanisms of PomDex in the lenalidomide-resistant setting.

Biased signalling from the glucocorticoid receptor: Renewed opportunity for tailoring glucocorticoid activity

Recent landmark studies applying analytical pharmacology approaches to the glucocorticoid receptor (GR) have demonstrated that different ligands can cause differential activation of distinct GR-regulated genes. Drawing on concepts of signalling bias from the field of G protein-coupled receptor (GPCR) biology, we speculate that ligand-dependent differences in GR signalling can be considered analogous to GPCR biased signalling, and thus can be quantitatively analysed in a similar way. This type of approach opens up the possibility of using rational structure-based drug optimisation strategies to improve the therapeutic selectivity of glucocorticoid drugs to maximise their efficacy and minimise adverse effects.

The glucocorticoid receptor: cause of or cure for obesity?

Glucocorticoid hormones (GCs) are important regulators of lipid metabolism, promoting lipolysis with acute treatment but lipogenesis with chronic exposure. Conventional wisdom posits that these disparate outcomes are mediated by the classical glucocorticoid receptor GRα. There is insufficient knowledge of the GC receptors (GRα and GRβ) in metabolic conditions such as obesity and diabetes. We present acute models of GC exposure that induce lipolysis, such as exercise, as well as chronic-excess models that cause obesity and lipid accumulation in the liver, such as hepatic steatosis. Alternative mechanisms are then proposed for the lipogenic actions of GCs, including induction of GC resistance by the GRβ isoform, and promotion of lipogenesis by GC activation of the mineralocorticoid receptor (MR). Finally, the potential involvement of chaperone proteins in the regulation of adipogenesis is considered. This reevaluation may prove useful to future studies on the steroidal basis of adipogenesis and obesity.

Glucocorticoid-induced changes in glucocorticoid receptor mRNA and protein expression in the human placenta as a potential factor for altering fetal growth and development

Glucocorticoids (GCs) control essential metabolic processes in virtually every cell in the body and play a vital role in the development of fetal tissues and organ systems. The biological actions of GCs are mediated via glucocorticoid receptors (GRs), the cytoplasmic transcription factors that regulate the transcription of genes involved in placental and fetal growth and development. Several experimental studies have demonstrated that fetal exposure to high maternal GC levels early in gestation is associated with adverse fetal outcomes, including low birthweight, intrauterine growth restriction and anatomical and structural abnormalities that may increase the risk of cardiovascular, metabolic and neuroendocrine disorders in adulthood. The response of the fetus to GCs is dependent on gender, with female fetuses becoming hypersensitive to changes in GC levels whereas male fetuses develop GC resistance in the environment of high maternal GCs. In this paper we review GR function and the physiological and pathological effects of GCs on fetal development. We propose that GC-induced changes in the placental structure and function, including alterations in the expression of GR mRNA and protein levels, may play role in inhibiting in utero fetal growth.