Membrane glucocorticoid receptors are down regulated by glucocorticoids in patients with systemic lupus erythematosus and use a caveolin-1-independent expression pathway

Study on Potential Differentially Expressed Genes in Idiopathic Pulmonary Fibrosis by Bioinformatics and Next-Generation Sequencing Data Analysis

Idiopathic pulmonary fibrosis (IPF) is a chronic progressive lung disease with reduced quality of life and earlier mortality, but its pathogenesis and key genes are still unclear. In this investigation, bioinformatics was used to deeply analyze the pathogenesis of IPF and related key genes, so as to investigate the potential molecular pathogenesis of IPF and provide guidance for clinical treatment. Next-generation sequencing dataset GSE213001 was obtained from Gene Expression Omnibus (GEO), and the differentially expressed genes (DEGs) were identified between IPF and normal control group. The DEGs between IPF and normal control group were screened with the DESeq2 package of R language. The Gene Ontology (GO) and REACTOME pathway enrichment analyses of the DEGs were performed. Using the g:Profiler, the function and pathway enrichment analyses of DEGs were performed. Then, a protein-protein interaction (PPI) network was constructed via the Integrated Interactions Database (IID) database. Cytoscape with Network Analyzer was used to identify the hub genes. miRNet and NetworkAnalyst databaseswereused to construct the targeted microRNAs (miRNAs), transcription factors (TFs), and small drug molecules. Finally, receiver operating characteristic (ROC) curve analysis was used to validate the hub genes. A total of 958 DEGs were screened out in this study, including 479 up regulated genes and 479 down regulated genes. Most of the DEGs were significantly enriched in response to stimulus, GPCR ligand binding, microtubule-based process, and defective GALNT3 causes HFTC. In combination with the results of the PPI network, miRNA-hub gene regulatory network and TF-hub gene regulatory network, hub genes including LRRK2, BMI1, EBP, MNDA, KBTBD7, KRT15, OTX1, TEKT4, SPAG8, and EFHC2 were selected. Cyclothiazide and rotigotinethe are predicted small drug molecules for IPF treatment. Our findings will contribute to identification of potential biomarkers and novel strategies for the treatment of IPF, and provide a novel strategy for clinical therapy.

The Role of Glucocorticoids in Breast Cancer Therapy

Glucocorticoids (GCs) are anti-inflammatory and immunosuppressive steroid molecules secreted by the adrenal gland and regulated by the hypothalamic-pituitary-adrenal (HPA) axis. GCs present a circadian release pattern under normal conditions; they increase their release under stress conditions. Their mechanism of action can be via the receptor-independent or receptor-dependent pathway. The receptor-dependent pathway translocates to the nucleus, where the ligand-receptor complex binds to specific sequences in the DNA to modulate the transcription of specific genes. The glucocorticoid receptor (GR) and its endogenous ligand cortisol (CORT) in humans, and corticosterone in rodents or its exogenous ligand, dexamethasone (DEX), have been extensively studied in breast cancer. Its clinical utility in oncology has mainly focused on using DEX as an antiemetic to prevent chemotherapy-induced nausea and vomiting. In this review, we compile the results reported in the literature in recent years, highlighting current trends and unresolved controversies in this field. Specifically, in breast cancer, GR is considered a marker of poor prognosis, and a therapeutic target for the triple-negative breast cancer (TNBC) subtype, and efforts are being made to develop better GR antagonists with fewer side effects. It is necessary to know the type of breast cancer to differentiate the treatment for estrogen receptor (ER)-positive, ER-negative, and TNBC, to implement therapies that include the use of GCs.

The Anti-Glucocorticoid Receptor Antibody Clone 5E4: Raising Awareness of Unspecific Antibody Binding

Unspecific antibody binding takes a significant toll on researchers in the form of both the economic burden and the disappointed hopes of promising new therapeutic targets. Despite recent initiatives promoting antibody validation, a uniform approach addressing this issue has not yet been developed. Here, we demonstrate that the anti-glucocorticoid receptor (GR) antibody clone 5E4 predominantly targets two different proteins of approximately the same size, namely AMP deaminase 2 (AMPD2) and transcription intermediary factor 1-beta (TRIM28). This paper is intended to generate awareness of unspecific binding of well-established reagents and advocate the use of more rigorous verification methods to improve antibody quality in the future.

The Interface of Nuclear and Membrane Steroid Signaling

Steroid hormones bind receptors in the cell nucleus and in the cell membrane. The most widely studied class of steroid hormone receptors are the nuclear receptors, named for their function as ligand-dependent transcription factors in the cell nucleus. Nuclear receptors, such as estrogen receptor alpha, can also be anchored to the plasma membrane, where they respond to steroids by activating signaling pathways independent of their function as transcription factors. Steroids can also bind integral membrane proteins, such as the G protein-coupled estrogen receptor. Membrane estrogen and progestin receptors have been cloned and characterized in vitro and influence the development and function of many organ systems. Membrane androgen receptors were cloned and characterized in vitro, but their function as androgen receptors in vivo is unresolved. We review the identity and function of membrane proteins that bind estrogens, progestins, and androgens. We discuss evidence that membrane glucocorticoid and mineralocorticoid receptors exist, and whether glucocorticoid and mineralocorticoid nuclear receptors act at the cell membrane. In many cases, integral membrane steroid receptors act independently of nuclear steroid receptors, even though they may share a ligand.

Revisiting steroidogenesis and its role in immune regulation with the advanced tools and technologies

Historically tools and technologies facilitated scientific discoveries. Steroid hormone research is not an exception. Unfortunately, the dramatic advancement of the field faded this research area and flagged it as a solved topic. However, it should have been the opposite. The area should glitter with its strong foundation and attract next-generation scientists. Over the past century, a myriad of new facts on biochemistry, molecular biology, cell biology, physiology and pathology of the steroid hormones was discovered. Several innovations were made and translated into life-saving treatment strategies such as synthetic steroids, and inhibitors of steroidogenesis and steroid signaling. Steroid molecules exhibit their diverse effects on cell metabolism, salt and water balance, development and function of the reproductive system, pregnancy, and immune-cell function. Despite vigorous research, the molecular basis of the immunomodulatory effect of steroids is still mysterious. The recent excitement on local extra-glandular steroidogenesis in regulating inflammation and immunity is revitalizing the topic with a new perspective. Therefore, here we review the role of steroidogenesis in regulating inflammation and immunity, discuss the unresolved questions, and how this area can bring another golden age of steroid hormone research with the development of new tools and technologies and advancement of the scientific methods.

Glucose Metabolism in Burns-What Happens?

Severe burns represent an important challenge for patients and medical teams. They lead to profound metabolic alterations, trigger a systemic inflammatory response, crush the immune defense, impair the function of the heart, lungs, kidneys, liver, etc. The metabolism is shifted towards a hypermetabolic state, and this situation might persist for years after the burn, having deleterious consequences for the patient's health. Severely burned patients lack energy substrates and react in order to produce and maintain augmented levels of glucose, which is the fuel "ready to use" by cells. In this paper, we discuss biological substances that induce a hyperglycemic response, concur to insulin resistance, and determine cell disturbance after a severe burn. We also focus on the most effective agents that provide pharmacological modulations of the changes in glucose metabolism.

More Than Suppression: Glucocorticoid Action on Monocytes and Macrophages

Uncontrolled inflammation is a leading cause of many clinically relevant diseases. Current therapeutic strategies focus mainly on immunosuppression rather than on the mechanisms of inflammatory resolution. Glucocorticoids (GCs) are still the most widely used anti-inflammatory drugs. GCs affect most immune cells but there is growing evidence for cell type specific mechanisms. Different subtypes of monocytes and macrophages play a pivotal role both in generation as well as resolution of inflammation. Activation of these cells by microbial products or endogenous danger signals results in production of pro-inflammatory mediators and initiation of an inflammatory response. GCs efficiently inhibit these processes by down-regulating pro-inflammatory mediators from macrophages and monocytes. On the other hand, GCs act on “naïve” monocytes and macrophages and induce anti-inflammatory mediators and differentiation of anti-inflammatory phenotypes. GC-induced anti-inflammatory monocytes have an increased ability to migrate toward inflammatory stimuli. They remove endo- and exogenous danger signals by an increased phagocytic capacity, produce anti-inflammatory mediators and limit T-cell activation. Thus, GCs limit amplification of inflammation by repressing pro-inflammatory macrophage activation and additionally induce anti-inflammatory monocyte and macrophage populations actively promoting resolution of inflammation. Further investigation of these mechanisms should lead to the development of novel therapeutic strategies to modulate undesirable inflammation with fewer side effects via induction of inflammatory resolution rather than non-specific immunosuppression.

Fighting the Fire: Mechanisms of Inflammatory Gene Regulation by the Glucocorticoid Receptor

For many decades, glucocorticoids have been widely used as the gold standard treatment for inflammatory conditions. Unfortunately, their clinical use is limited by severe adverse effects such as insulin resistance, cardiometabolic diseases, muscle and skin atrophies, osteoporosis, and depression. Glucocorticoids exert their effects by binding to the Glucocorticoid Receptor (GR), a ligand-activated transcription factor which both positively, and negatively regulates gene expression. Extensive research during the past several years has uncovered novel mechanisms by which the GR activates and represses its target genes. Genome-wide studies and mouse models have provided valuable insight into the molecular mechanisms of inflammatory gene regulation by GR. This review focusses on newly identified target genes and GR co-regulators that are important for its anti-inflammatory effects in innate immune cells, as well as mutations within the GR itself that shed light on its transcriptional activity. This research progress will hopefully serve as the basis for the development of safer immune suppressants with reduced side effect profiles.

Glucocorticoids pharmacology and their application in the treatment of childhood-onset systemic lupus erythematosus

Glucocorticoids are potent anti-inflammatory and immunosuppressant medications and remain the mainstay of systemic lupus erythematosus (SLE) therapy. The potency of a specific glucocorticoid, i.e., the dose of glucocorticoid that is required to produce a specific effect, is dependent on its pharmacokinetic (PK) and pharmacodynamic (PD) properties. In this review, we summarize the PK/PD properties of commonly used glucocorticoids in an attempt to better delineate their role in the management of children with childhood-onset SLE (cSLE). We also address glucocorticoid side effects as these play a major role when deciding on the dose, frequency, and duration of use. A better understanding of the pharmacology of glucocorticoids appears useful to achieve improved outcomes in the management of cSLE.

Non-genomic Effects of Glucocorticoids: An Updated View

Glucocorticoid (GC) anti-inflammatory effects generally require a prolonged onset of action and involve genomic processes. Because of the rapidity of some of the GC effects, however, the concept that non-genomic actions may contribute to GC mechanisms of action has arisen. While the mechanisms have not been completely elucidated, the non-genomic effects may play a role in the management of inflammatory diseases. For instance, we recently reported that GCs 'rapidly' enhanced the effects of bronchodilators, agents used in the treatment of allergic asthma. In this review article, we discuss (i) the non-genomic effects of GCs on pathways relevant to the pathogenesis of inflammatory diseases and (ii) the putative role of the membrane GC receptor. Since GC side effects are often considered to be generated through its genomic actions, understanding GC non-genomic effects will help design GCs with a better therapeutic index.

The risk benefit ratio of glucocorticoids in SLE: have things changed over the past 40 years?

PURPOSE OF REVIEW

Glucocorticoids have been the mainstay of treatment in systemic lupus erythematosus for more than half a century. Despite advancements in knowledge concerning the pathophysiology of systemic lupus, the genomic/non-genomic actions of glucocorticoids, and the use of novel therapeutic agents in SLE, the burden of toxicity from glucocorticoid use remains unchanged.

RECENT FINDINGS

SLE patients receiving long-term prednisone therapy are at significant risk of morbidity due to permanent organ damage and prednisone daily dosages above 6 mg have been shown to increase the risk of future organ damage by 50%. Glucocorticoid use carries a higher risk of opportunistic infections, iatrogenic osteoporosis and avascular necrosis, an increase in risk of cardiovascular events, cataracts and glaucoma, as well as psychiatric adverse effects like psychosis and manic episodes. There are limited data regarding the relative efficacy of the different glucocorticoid formulations or dosing regimens.

SUMMARY

The use and dosing of glucocorticoids in SLE remains more art than science, although our knowledge regarding their complex genomic and non-genomic effects, as well as the resultant adverse effects, has greatly expanded over the past half a century.

A novel non genomic glucocorticoid signaling mediated by a membrane palmitoylated glucocorticoid receptor cross talks with GnRH in gonadotrope cells

Glucocorticoid hormones (GC) are the main stress mediators associated with reproductive disorders. GC exert their effects through activation of the glucocorticoid receptor (GR) principally acting as a transcription factor. Beside well-established GR-mediated genomic actions, several lines of evidence suggest a role for rapid membrane-initiated GC signaling in gonadotrope cells triggered by a membrane-associated GR. Herein, we demonstrate the existence of a specific membrane-initiated GC signaling in LβT2 gonadotrope cells involving two related phosphoproteins: Ca²⁺/Calmodulin-dependent protein kinase II (CaMKII) and synapsin-I. Within 5 min, LβT2 cells treated with stress range of 10⁻⁷ M Corticosterone or a membrane impermeable-GC, BSA-conjugated corticosterone, exhibited a 2-fold increase in levels of phospho-CaMKII and phospho-synapsin-I. Biochemical approaches revealed that this rapid signaling is promoted by a palmitoylated GR. Importantly, GC significantly alter GnRH-induced CaMKII phosphorylation, consistent with a novel cross-talk between the GnRH receptor and GC. This negative effect of GC on GnRH signaling was further observed on LH release by mouse pituitary explants. Altogether, our work provides new findings in GC field by bringing novel understanding on how GR integrates plasma membrane, allowing GC membrane-initiated signaling that differs in presence of GnRH to disrupt GnRH-dependent signaling and LH secretion.

Unraveling the functions of the membrane-bound glucocorticoid receptors: first clues on origin and functional activity

Glucocorticoids (GCs) are routinely used to treat a wide range of rheumatic and other inflammatory diseases. GCs are steroidal drugs that exert their strong anti-inflammatory and immunosuppressive effects via genomic mechanisms, primarily by signaling through the cytosolic glucocorticoid receptor. In addition, rapid, nongenomic responses following GC treatment have been reported to involve signaling via the membrane-bound glucocorticoid receptor (mGR). Since an important clinical role of this receptor has been proposed, investigations regarding the origin and function of the mGR are currently performed in order to understand rapid GC signaling and to optimize treatment strategies with GCs. Here, we summarize the current knowledge on the mGR and compare these findings to results obtained for other membrane-bound receptors, such as membrane forms of the estrogen and progesterone receptors.

Optimized glucocorticoid therapy: teaching old drugs new tricks

Glucocorticoids (GCs) are commonly used in the treatment of a wide range of rheumatic and other inflammatory diseases. They exert their potent anti-inflammatory and immunosuppressive effects primarily via so called genomic mechanisms, mediated by the cytosolic glucocorticoid receptor (cGR). This mechanism of GC action can be divided into the transactivation and the transrepression processes. However, also rapid effects of GCs exist which are mediated by specific and unspecific non-genomic mechanisms. A clinical relevance of this mode of GC action is assumed for effects mediated by membrane-bound glucocorticoid receptors, but detailed knowledge on the underlying mechanisms is still missing. Great efforts have been made in the past to diminish GC-induced adverse effects, thus improving the benefit/risk ratio of the drugs. Besides approaches to improve the treatment with conventional glucocorticoids currently available to clinicians, new innovative GCs or GC receptor ligands are also being developed.

Membrane glucocorticoid receptor activation induces proteomic changes aligning with classical glucocorticoid effects

Glucocorticoids exert rapid nongenomic effects by several mechanisms including the activation of a membrane-bound glucocorticoid receptor (mGR). Here, we report the first proteomic study on the effects of mGR activation by BSA-conjugated cortisol (Cort-BSA). A subset of target proteins in the proteomic data set was validated by Western blot and we found them responding to mGR activation by BSA-conjugated cortisol in three additional cell lines, indicating a conserved effect in cells originating from different tissues. Changes in the proteome of BSA-conjugated cortisol treated CCRF-CEM leukemia cells were associated with early and rapid pro-apoptotic, immune-modulatory and metabolic effects aligning with and possibly "priming" classical activities of the cytosolic glucocorticoid receptor (cGR). PCR arrays investigating target genes of the major signaling pathways indicated that the mGR does not exert its effects through the transcriptional activity of any of the most common kinases in these leukemic cells, but RhoA signaling emerged from our pathway analysis. All cell lines tested displayed very low levels of mGR on their surface. Highly sensitive and specific in situ proximity ligation assay visualized low numbers of mGR even in cells previously thought to be mGR negative. We obtained similar results when using three distinct anti-GR monoclonal antibodies directed against the N-terminal half of the cGR. This strongly suggests that the mGR and the cGR have a high sequence homology and most probably originate from the same gene. Furthermore, the mGR appears to reside in caveolae and its association with caveolin-1 (Cav-1) was clearly detected in two of the four cell lines investigated using double recognition proximity ligation assay. Our results indicate however that Cav-1 is not necessary for membrane localization of the GR since CCRF-CEM and Jurkat cells have a functional mGR, but did not express this caveolar protein. However, if expressed, this membrane protein dimerizes with the mGR modulating its function.

Mineralocorticoid and glucocorticoid receptors at the neuronal membrane, regulators of nongenomic corticosteroid signalling

The balance between corticosteroid actions induced via activation of the mineralocorticoid receptor (MR) and the glucocorticoid receptor (GR) determines the brain's response to stress. While both receptors are best known for their delayed genomic role, it has become increasingly evident that they can also associate with the plasma membrane and act as mediators of rapid, nongenomic signalling. Nongenomic corticosteroid actions in the brain are required for the coordination of a rapid adaptive response to stress; membrane-associated MRs and GRs play a major role herein. However, many questions regarding the underlying mechanism are still unresolved. How do MR and GR translocate to the membrane and what are their downstream signalling partners? In this review we discuss these issues based on insights obtained from related receptors, most notably the estrogen receptor α.

Glucocorticoid receptor-mediated transcriptional activation of S100P gene coding for cancer-related calcium-binding protein

S100P is a member of the S100 family of calcium-binding proteins involved in calcium sensing and signal transduction. Its abnormal expression and biological activities are linked to tumor phenotype, namely to increased survival, proliferation, invasion and metastatic propensity of tumor cells. Association of S100P with outcome of tumor treatment and preliminary data from S100P promoter analysis prompted us to study regulation of S100P expression by glucocorticoids, which are implicated in tumor response to chemotherapy. We showed that dexamethasone (DX), a representative glucocorticoid, was capable to induce activity of S100P promoter by means of increased expression, nuclear translocation, and transactivation properties of the glucocorticoid receptor (GR). Moreover, DX treatment led to decreased phosphorylation of ERK1/2, reduced transcriptional activity of AP1, and modulated activity of some additional transcription factors. We identified a promoter region responsible for DX-mediated transactivation and proved GR binding to S100P promoter. We found that the effect of DX was enhanced by partial but not complete inhibition of the MAPK/ERK pathway, supporting an active crosstalk between GR and MAPK/ERK signal transduction in control of S100P expression. On the other hand, suppression of GR mRNA level by transient siRNA expression resulted in reduced S100P transcription. The role of GR activation in S100P regulation was supported by co-expression of GR with S100P in cells treated with DX. These data suggest that S100P is a direct transcriptional target of glucocorticoid-mediated signaling in tumor cells that is activated through the interplay of GR and MAPK pathways.

Glucocorticoid receptor: implications for rheumatic diseases

The glucocorticoid receptor (GR), a member of the nuclear receptor superfamily, mediates most of the known biologic effects of glucocorticoids. The human GR gene consists of 9 exons and expresses 2 alternative splicing isoforms, the GRα and GRβ. GRα is the classic receptor that binds to glucocorticoids and mediates most of the known actions of glucocorticoids, while GRβ does not bind to these hormones and exerts a dominant negative effect upon the GRα-induced transcriptional activity. Each of the two GR splice isoforms has 8 translational variants with specific transcriptional activity and tissue distribution. GRα consists of three subdomains, translocates from the cytoplasm into the nucleus upon binding to glucocorticoids, and regulates the transcriptional activity of numerous glucocorticoid-responsive genes either by binding to its cognate DNA sequences or by interacting with other transcription factors. In addition to these genomic actions, the GR also exerts rapid, non-genomic effects, which are possibly mediated by membrane-localised receptors or by translocation into the mitochondria. All these actions of the GR appear to play an important role in the regulation of the immune system. Specifically, the splicing variant GRβ may be involved in the pathogenesis of rheumatic diseases, while the circadian regulation of the GR activity via acetylation by the Clock transcription factor may have therapeutic implications for the preferential timing of glucocorticoid administration in autoimmune inflammatory disorders.

Gene expression profiles in a rabbit model of systemic lupus erythematosus autoantibody production

We previously reported the establishment of a rabbit (Oryctolagus cuniculus) model in which peptide immunization led to production of lupus-like autoantibodies including anti-Sm, -RNP, -SS-A, -SS-B, and -dsDNA characteristic of those produced in systemic lupus erythematosus (SLE) patients. Some neurologic symptoms in the form of seizures and nystagmus were observed. The animals used in the previous and in the current study were from a National Institute of Allergy and Infectious Diseases colony of rabbits that were pedigreed, Ig-allotype defined, but not inbred. Their genetic heterogeneity may correspond to that found among patients of a given ethnicity. We extended the information about this rabbit model by microarray-based expression profiling. We first demonstrated that human expression arrays could be used with rabbit RNA to yield information on molecular pathways. We then designed a study evaluating gene expression profiles in eight groups of control and treated rabbits (47 rabbits in total). Genes significantly upregulated in treated rabbits were associated with NK cytotoxicity, Ag presentation, leukocyte migration, cytokine activity, protein kinases, RNA spliceosomal ribonucleoproteins, intracellular signaling cascades, and glutamate receptor activity. These results link increased immune activation with upregulation of components associated with neurologic and anti-RNP responses, demonstrating the utility of the rabbit model to uncover biological pathways related to SLE-induced clinical symptoms, including neuropsychiatric lupus. Our finding of distinct gene expression patterns in rabbits that made anti-dsDNA compared with those that only made other anti-nuclear Abs should be further investigated in subsets of SLE patients with different autoantibody profiles.

Emerging pathways of non-genomic glucocorticoid (GC) signalling in T cells

In the last decade new glucocorticoid (GC)-signalling mechanisms have emerged. The evolving field of non-genomic GC actions was precipitated from two major directions: (i) some rapid/acute clinical GC applications could not be explained based on the relatively slowly appearing genomic GC action and (ii) accumulating evidence came to light about the discrepancy in the apoptosis sensitivity and GR expression of thymocytes and other lymphoid cell types. Herein, we attempt to sample the latest information in the field of non-genomic GC signalling in T cells, and correlate it with results from our laboratory. We discuss some aspects of the regulation of thymocyte apoptosis by GCs, paying special interest to the potential role(s) of mitochondrial GR signalling. The interplay between the T cell receptor (TcR) and glucocorticoid receptor (GR) signalling pathways is described in more detail, focusing on ZAP-70, which is a novel target of rapid GC action.

Glucocorticoids and neuro- and behavioural development

Epidemiological evidence links exposure to stress hormones during fetal or early postnatal development with lifetime prevalence of cardiac, metabolic, auto-immune, neurological and psychiatric disorders. This has led to the concept of 'developmental programming through stress'. Importantly, these effects (specifically, hypertension, hyperglycaemia and neurodevelopmental and behavioural abnormalities) can be reproduced by exposure to high glucocorticoid levels, indicating a crucial role of glucocorticoids in their causation. However, there can be important differences in outcome, depending on the exact time of exposure, as well as duration and receptor selectivity of the glucocorticoid applied. The mechanisms underlying programming by stress are still unclear but it appears that these environmental perturbations exploit epigenetic modifications of DNA and/or histones to induce stable modifications of gene expression. Programming of neuro- and behavioural development by glucocorticoids and stress are important determinants of lifetime health and should be a consideration when choosing treatments in obstetric and neonatal medicine.

[Glucocorticoids in rheumatology]

Glucocorticoids (GC) are effective drugs which are often used in rheumatology. However, they have a considerable potential for frequent and sometimes serious side effects that restrict their use. Their mechanisms of action are either receptor dependent (specific) or independent (unspecific) on the genomic as well as the non-genomic level. Many adverse effects are predominantly caused by transactivation while the desired effects are mostly mediated by transrepression. Treatment strategies are sub-classified into low, medium, high, very high dose and pulse therapy based on criteria such as dose, indication, duration of treatment and potential risk of adverse events. The musculoskeletal, gastrointestinal, neuro-endocrino-immunological, opthalmological and neuropsychiatric systems are examples where adverse effects may occur.

Genomic and nongenomic effects of glucocorticoids

The strong anti-inflammatory and immunosuppressive effects of glucocorticoids are mediated primarily by the cytosolic glucocorticoid receptors. These receptors are members of the steroid hormone receptor family, a superfamily of ligand-inducible transcription factors, and exert genomic effects that can result in increased expression of regulatory-including anti-inflammatory-proteins (transactivation), or decreased production of proinflammatory proteins (transrepression). Transactivation is thought to be responsible for numerous adverse effects of glucocorticoids; transrepression is thought to be responsible for many of the clinically desirable anti-inflammatory and immunosuppressive effects of glucocorticoids. Optimized glucocorticoids, such as selective glucocorticoid receptor agonists, are being developed to try to minimize the adverse effects many patients experience. Glucocorticoids also exert their effects via rapid, nongenomic mechanisms that can be classified as involving nonspecific interactions of glucocorticoids with cellular membranes, nongenomic effects that are mediated by cytosolic glucocorticoid receptors, or specific interactions with membrane-bound glucocorticoid receptors. Increased understanding of these mechanisms of glucocorticoid action could enable the development of novel drugs with which to treat patients with inflammatory and autoimmune disease.

Molecular mechanisms of glucocorticoid action and selective glucocorticoid receptor agonists

Glucocorticoids (GC) are the most common used anti-inflammatory and immunosuppressive drugs in the treatment of rheumatic and other inflammatory diseases. Their therapeutic effects are considered to be mediated by four different mechanisms of action: the classical genomic mechanism of action caused by the cytosolic glucocorticoid receptor (cGCR); secondary non-genomic effects which are also initiated by the cGCR; membrane-bound glucocorticoid receptor (mGCR)-mediated non-genomic effects; non-specific, non-genomic effects caused by interactions with cellular membranes. The classical, genomic mechanism of GC-action can be divided into two processes: "transrepression", which is responsible for a large number of desirable anti-inflammatory and immunomodulating effects, and "transactivation" which is associated with frequently occurring side effects as well as with some immunosuppressive activities [Ehrchen, J., Steinmuller, L., Barczyk, K., Tenbrock, K., Nacken, W., Eisenacher, M., Nordhues, U., Sorg, C., Sunderkotter, C., Roth, J., 2007. Glucocorticoids induce differentiation of a specifically activated, anti-inflammatory subtype of human monocytes. Blood 109, 1265-1274]. Great efforts have been made to diminish glucocorticoid-induced adverse effects, but the improvement of conventional glucocorticoids has almost reached its limits. As a consequence, new variations of the conventional "good old drugs" are being tested and nitro-steroids and long circulating liposomal glucocorticoids indeed show promising results. Nevertheless, crux of the matter should be the design of qualitatively new drugs, such as selective glucocorticoid receptor agonists (SEGRAs). These innovative steroidal or non-steroidal molecules induce transrepression, while transactivation processes are less affected. First reports on two different GCR ligands, A276575 and ZK216348, show promising results. Here, we review the above-mentioned mechanisms of glucocorticoid action and give particular attention to the development of optimized glucocorticoids and SEGRAs.

Immune-neuroendocrine interactions and autoimmune diseases

The relationship between immune-neuroendocrine system is firmly established. The messengers of this connection are hormones, neuropeptides, neurotransmitters and cytokines. The immune-neuroendocrine system have the capacity to synthesize and release these molecules, which, in turn, can stimulate or suppress the activity of immune or neuroendocrine cells by binding to receptors. In fact, hormones, neuropeptides and neurotransmitters participate in innate and adaptive immune response.

Autoimmune rheumatic diseases (ARD) are characterized by aberrant production of pro-inflammatory cytokines, which are a potent activator of the HPA axis. In consequence, high levels of pro-inflammatory hormones such as estrogens and prolactin, and low levels of glucocorticoids, an anti-inflammatory hormone, have been described in the active phase of ARD. In addition, high levels of pro-inflammatory hormones and cytokines have also been frequently detected in organ involvement of patients with ARD, suggesting an abnormal local neuroendocrine immune interaction. There is evidence that hormonal changes may appear before the symptomatic phase of the disease. Therefore, it is possible that a pro-inflammatory hormone favors the rupture of tolerance, which is a key feature of autoimmune diseases. The interactions between the immune-neuroendocrine system have a major impact on our understanding of the pathogenic mechanisms, diagnosis and therapy of ARD.