Acquired Glucocorticoid Resistance Due to Homologous Glucocorticoid Receptor Downregulation: A Modern Look at an Age-Old Problem

CGG repeats in the human FMR1 gene regulate mRNA localization and cellular stress in developing neurons

The human genome has many short tandem repeats, yet the normal functions of these repeats are unclear. The 5' untranslated region (UTR) of the fragile X messenger ribonucleoprotein 1 (FMR1) gene contains polymorphic CGG repeats, the length of which has differing effects on FMR1 expression and human health, including the neurodevelopmental disorder fragile X syndrome. We deleted the CGG repeats in the FMR1 gene (0CGG) in human stem cells and examined the effects on differentiated neurons. 0CGG neurons have altered subcellular localization of FMR1 mRNA and protein, and differential expression of cellular stress proteins compared with neurons with normal repeats (31CGG). In addition, 0CGG neurons have altered responses to glucocorticoid receptor (GR) activation, including FMR1 mRNA localization, GR chaperone HSP90α expression, GR localization, and cellular stress protein levels. Therefore, the CGG repeats in the FMR1 gene are important for the homeostatic responses of neurons to stress signals.

The Metabolomic Profile of Microscopic Colitis Is Affected by Smoking but Not Histopathological Diagnosis, Clinical Course, Symptoms, or Treatment

Microscopic colitis (MC) is classified as collagenous colitis (CC) and lymphocytic colitis (LC). Genetic associations between CC and human leucocyte antigens (HLAs) have been found, with smoking being a predisposing external factor. Smoking has a great impact on metabolomics. The aim of this explorative study was to analyze global metabolomics in MC and to examine whether the metabolomic profile differed regarding the type and course of MC, the presence of IBS-like symptoms, treatment, and smoking habits. Of the 240 identified women with MC aged ≤73 years, 131 completed the study questionnaire; the Rome III questionnaire; and the Visual Analog Scale for Irritable Bowel Syndrome (VAS-IBS). Blood samples were analyzed by ultra-high-performance liquid chromatograph mass spectrometry (UHLC-MS/UHPLC-MSMS). The women, 63.1 (58.7-67.2) years old, were categorized based on CC (n = 76) and LC (n = 55); one episode or refractory MC; IBS-like symptoms or not; use of corticosteroids or not; and smoking habits. The only metabolomic differences found in the univariate model after adjustment for false discovery rate (FDR) were between smokers and non-smokers. Serotonin was markedly increased in smokers (p < 0.001). No clear patterns appeared when conducting a principal component analysis (PCA). No differences in the metabolomic profile were found depending on the type or clinical course of the disease, neither in the whole MC group nor in the subgroup analysis of CC.

Acetylation-induced proteasomal degradation of the activated glucocorticoid receptor limits hormonal signaling

Glucocorticoid (GC) signaling is essential for mounting a stress response, however, chronic stress or prolonged GC therapy downregulates the GC receptor (GR), leading to GC resistance. Regulatory mechanisms that refine this equilibrium are not well understood. Here, we identify seven lysine acetylation sites in the amino terminal domain of GR, with lysine 154 (Lys154) in the AF-1 region being the dominant acetyl-acceptor. GR-Lys154 acetylation is mediated by p300/CBP in the nucleus in an agonist-dependent manner and correlates with transcriptional activity. Deacetylation by NAD+-dependent SIRT1 facilitates dynamic regulation of this mark. Notably, agonist-binding to both wild-type GR and an acetylation-deficient mutant elicits similar short-term target gene expression. In contrast, upon extended treatment, the polyubiquitination of the acetylation-deficient GR mutant is impaired resulting in higher protein stability, increased chromatin association and prolonged transactivation. Taken together, reversible acetylation fine-tunes duration of the GC response by regulating proteasomal degradation of activated GR.

A qualitative analysis of the impact of canine hypoadrenocorticism on the quality of life of owners

BACKGROUND

Canine hypoadrenocorticism is a rare chronic disease, which demands intense dog-owner interaction, as its treatment requires to be individualised. The aim of this study was a qualitative analysis of the challenges owners face when dealing with the disease, especially regarding its management and how this affects quality of life. By promoting an online discussion between owners, we transcribed and summarised their experiential knowledge in dealing with the disease.

METHODS

Owners were recruited for the online seminars via social media. After a theoretical introduction, participants were free to share experiences and ask questions. The recorded events were retrospectively analysed.

RESULTS

Twenty-four owners of 22 Addisonian dogs took part in four events. Owners felt most "traumatised" when experiencing their dog's acute adrenal crisis. The initial adjustment phase and distinguishing the non-specific symptoms of hypoadrenocorticism from those of other diseases were also challenging. Overall, owners were well informed on the disease and committed to its long-term adjustment.

CONCLUSIONS

Adrenal crisis and the initial adjustment phase may be more burdening to owners than expected. Understanding what their clients' concerns are, can help veterinarians provide better care and reduce the negative impacts of canine hypoadrenocorticism. Promoting peer to peer support, as well as providing a framework for participative communication might also help.

MDM2- an indispensable player in tumorigenesis

Murine double minute 2 (MDM2) is a well-recognized molecule for its oncogenic potential. Since its identification, various cancer-promoting roles of MDM2 such as growth stimulation, sustained angiogenesis, metabolic reprogramming, apoptosis evasion, metastasis, and immunosuppression have been established. Alterations in the expression levels of MDM2 occur in multiple types of cancers resulting in uncontrolled proliferation. The cellular processes are modulated by MDM2 through transcription, post-translational modifications, protein degradation, binding to cofactors, and subcellular localization. In this review, we discuss the precise role of deregulated MDM2 levels in modulating cellular functions to promote cancer growth. Moreover, we also briefly discuss the role of MDM2 in inducing resistance against anti-cancerous therapies thus limiting the benefits of cancerous treatment.

Patient-Level Meta-Analysis of Low-Dose Hydrocortisone in Adults with Septic Shock

BACKGROUND: Trials and study-level meta-analyses have failed to resolve the role of corticosteroids in the management of patients with septic shock. Patient-level meta-analyses may provide more precise estimates of treatment effects, particularly subgroup effects. METHODS: We pooled individual patient data from septic shock trials investigating the adjunctive use of intravenous hydrocortisone. The primary outcome was 90-day all-cause mortality, and it was also analyzed across predefined subgroups. Secondary outcomes included mortality at intensive care unit and hospital discharge, at 28 and 180 days, and vasopressor-, ventilator-, and organ failure–free days. Adverse events included superinfection, muscle weakness, hyperglycemia, hypernatremia, and gastroduodenal bleeding. RESULTS: Of 24 eligible trials (n=8528), 17 (n=7882) provided individual patient data, and 7 (n=5929) provided 90-day mortality. The marginal relative risk (RR) for 90-day mortality of hydrocortisone versus placebo was 0.93 (95% confidence interval [CI], 0.82 to 1.04; P=0.22; moderate certainty). It was 0.86 (95% CI, 0.79 to 0.92) for hydrocortisone with fludrocortisone and 0.96 (95% CI, 0.82 to 1.12) without fludrocortisone. There was no significant differential treatment effect across subgroups. Hydrocortisone was associated with little to no difference in any of the secondary outcomes except vasopressor-free days (mean difference, 1.24 days; 95% CI, 0.74 to 1.73; high certainty). Hydrocortisone may not be associated with an increase in the risk of superinfection (RR, 1.04; 95% CI, 0.95 to 1.15; low certainty), hyperglycemia (RR, 1.05; 95% CI, 0.98 to 1.12; low certainty), or gastroduodenal bleeding (RR, 1.11; 95% CI, 0.83 to 1.48; low certainty). Hydrocortisone may be associated with an increase in the risk of hypernatremia (RR, 2.01; 95% CI, 1.56 to 2.60; low certainty) and muscle weakness (n=2647; RR, 1.73; 95% CI, 1.49 to 1.99; low certainty). CONCLUSIONS: In this patient-level meta-analysis, hydrocortisone compared with placebo was not associated with reduced mortality for patients with septic shock. (Funded by “Programme d’Investissements d’Avenir,” a research Professorship from the National Institute of Health and Care Research, Leadership Fellowships from the National Health and Medical Research Council of Australia, and Emerging Leaders Fellowship from the National Health and Medical Research Council of Australia; PROSPERO registration number, CRD42017062198.)

Correlation between nuclear expression of heat shock protein 90 in dermis and glucocorticoid resistance in bullous dermatosis

BACKGROUND

bullous dermatosis is a group of skin diseases that occur on the skin and mucous membrane, with blister and bulla as basic damage, mainly including pemphigus and bullous pemphigoid. Glucocorticoid (GC) is still the preferred drug for its treatment, but some patients respond poorly to GC and even develop glucocorticoid resistance (GCR). However, at present about the disease the understanding of the mechanisms for GCR is limited.

OBJECTIVE

This study attempted to investigate the molecular mechanism of GCR in bullous dermatosis with heat shock proteins 90 (HSP90) and glucocorticoid receptor (GR) as molecular targets.

METHODS

In this study, flow cytometry was used to measure and analyze the expression of HSP90 and GR in the lesions of patients with glucocorticoid-resistant bullosa dermatosis. Immunohistochemistry and immunofluorescence were used to observe the expression distribution and cell localization of HSP90 and GR.

RESULTS

The expression of HSP90 in skin lesions of GCR group was significantly higher than that of glucocorticoid-sensitive (GCS) group, while the expression level of GR was lower than that of GCS group. In the epidermis, the expression and distribution of HSP90 were not different between the GCR group and the GCS group. And in the dermis, HSP90 and GR were more likely to be expressed in the nucleus in the GCR group.

CONCLUSION

The overexpression and nuclear distribution of HSP90 may be related to the occurrence of GCR in patients with bullous dermatosis. And this correlation is more likely to occur in the dermis than in the epidermis.

Dexamethasone Is Not Sufficient to Facilitate Tenogenic Differentiation of Dermal Fibroblasts in a 3D Organoid Model

Self-assembling three-dimensional organoids that do not rely on an exogenous scaffold but maintain their native cell-to-cell and cell-to-matrix interactions represent a promising model in the field of tendon tissue engineering. We have identified dermal fibroblasts (DFs) as a potential cell type for generating functional tendon-like tissue. The glucocorticoid dexamethasone (DEX) has been shown to regulate cell proliferation and facilitate differentiation towards other mesenchymal lineages. Therefore, we hypothesized that the administration of DEX could reduce excessive DF proliferation and thus, facilitate the tenogenic differentiation of DFs using a previously established 3D organoid model combined with dose-dependent application of DEX. Interestingly, the results demonstrated that DEX, in all tested concentrations, was not sufficient to notably induce the tenogenic differentiation of human DFs and DEX-treated organoids did not have clear advantages over untreated control organoids. Moreover, high concentrations of DEX exerted a negative impact on the organoid phenotype. Nevertheless, the expression profile of tendon-related genes of untreated and 10 nM DEX-treated DF organoids was largely comparable to organoids formed by tendon-derived cells, which is encouraging for further investigations on utilizing DFs for tendon tissue engineering.

Molecular mechanisms of glucocorticoid resistance

BACKGROUND

As a powerful anti-inflammatory, immunosuppressive, and antiproliferative drug, glucocorticoid (GC) plays an important role in the treatment of various diseases. However, some patients may experience glucocorticoid resistance (GCR) in clinical, and its molecular mechanism have not been determined.

METHODS

The authors performed a review of the literature on GCR focusing on mutations in the NR3C1 gene and impaired glucocorticoid receptor (GR) signalling, using METSTR (2000 through May 2022) to identify original articles and reviews on this topic. The search terms included 'glucocorticoid resistance/insensitive', 'steroid resistance/insensitive', 'NR3C1', and 'glucocorticoid receptor'.

RESULTS

Primary GCR is mainly caused by NR3C1 gene mutation, and 31 NR3C1 gene mutations have been reported so far. Secondary GCR is caused by impaired GC signalling pathways, including decreased expression of GR, impaired nuclear translocation of GR, and impaired binding of GR to GC and GR to target genes. However, the current research is more on the expression level of GR, and there are relatively few studies on other mechanisms. In addition, methods for improving GC sensitivity are rarely reported.

CONCLUSION

The molecular mechanisms of GCR are complex and may differ in different diseases or different patients. In future studies, when exploring the mechanism of GCR, methods to improve GC sensitivity should also be investigated.

The mineralocorticoid receptor modulates timing and location of genomic binding by glucocorticoid receptor in response to synthetic glucocorticoids in keratinocytes

Glucocorticoids (GCs) exert potent antiproliferative and anti-inflammatory properties, explaining their therapeutic efficacy for skin diseases. GCs act by binding to the GC receptor (GR) and the mineralocorticoid receptor (MR), co-expressed in classical and non-classical targets including keratinocytes. Using knockout mice, we previously demonstrated that GR and MR exert essential nonoverlapping functions in skin homeostasis. These closely related receptors may homo- or heterodimerize to regulate transcription, and theoretically bind identical GC-response elements (GRE). We assessed the contribution of MR to GR genomic binding and the transcriptional response to the synthetic GC dexamethasone (Dex) using control (CO) and MR knockout (MR^EKO ) keratinocytes. GR chromatin immunoprecipitation (ChIP)-seq identified peaks common and unique to both genotypes upon Dex treatment (1 h). GREs, AP-1, TEAD, and p53 motifs were enriched in CO and MR^EKO peaks. However, GR genomic binding was 35% reduced in MR^EKO , with significantly decreased GRE enrichment, and reduced nuclear GR. Surface plasmon resonance determined steady state affinity constants, suggesting preferred dimer formation as MR-MR > GR-MR ~ GR-GR; however, kinetic studies demonstrated that GR-containing dimers had the longest lifetimes. Despite GR-binding differences, RNA-seq identified largely similar subsets of differentially expressed genes in both genotypes upon Dex treatment (3 h). However, time-course experiments showed gene-dependent differences in the magnitude of expression, which correlated with earlier and more pronounced GR binding to GRE sites unique to CO including near Nr3c1. Our data show that endogenous MR has an impact on the kinetics and differential genomic binding of GR, affecting the time-course, specificity, and magnitude of GC transcriptional responses in keratinocytes.

Immune Modulations by Glucocorticoids: From Molecular Biology to Clinical Research

Due to their potent anti-inflammatory and immune-suppressive actions, glucocorticoids have been used in the treatment of inflammatory and autoimmune disease for more than 70 years [...].

Novel assays monitoring direct glucocorticoid receptor protein activity exhibit high predictive power for ligand activity on endogenous gene targets

Exogenous glucocorticoids are widely used in the clinic for the treatment of inflammatory disorders and auto-immune diseases. Unfortunately, their use is hampered by many side effects and therapy resistance. Efforts to find more selective glucocorticoid receptor (GR) agonists and modulators (called SEGRAMs) that are able to separate anti-inflammatory effects via gene repression from metabolic effects via gene activation, have been unsuccessful so far. In this study, we characterized a set of functionally diverse GR ligands in A549 cells, first using a panel of luciferase-based reporter gene assays evaluating GR-driven gene activation and gene repression. We expanded this minimal assay set with novel luciferase-based read-outs monitoring GR protein levels, GR dimerization and GR Serine 211 (Ser211) phosphorylation status and compared their outcomes with compound effects on the mRNA levels of known GR target genes in A549 cells and primary hepatocytes. We found that luciferase reporters evaluating GR-driven gene activation and gene repression were not always reliable predictors for effects on endogenous target genes. Remarkably, our novel assay monitoring GR Ser211 phosphorylation levels proved to be the most reliable predictor for compound effects on almost all tested endogenous GR targets, both driven by gene activation and repression. The integration of this novel assay in existing screening platforms running both in academia and industry may therefore boost chances to find novel GR ligands with an actual improved therapeutic benefit.

Stress Affects Central Compensation of Neural Responses to Cochlear Synaptopathy in a cGMP-Dependent Way

In light of the increasing evidence supporting a link between hearing loss and dementia, it is critical to gain a better understanding of the nature of this relationship. We have previously observed that following cochlear synaptopathy, the temporal auditory processing (e.g., auditory steady state responses, ASSRs), is sustained when reduced auditory input is centrally compensated. This central compensation process was linked to elevated hippocampal long-term potentiation (LTP). We further observed that, independently of age, central responsiveness to cochlear synaptopathy can differ, resulting in either a low or high capacity to compensate for the reduced auditory input. Lower central compensation resulted in poorer temporal auditory processing, reduced hippocampal LTP, and decreased recruitment of activity-dependent brain-derived neurotrophic factor (BDNF) expression in hippocampal regions (low compensators). Higher central compensation capacity resulted in better temporal auditory processing, higher LTP responses, and increased activity-dependent BDNF expression in hippocampal regions. Here, we aimed to identify modifying factors that are potentially responsible for these different central responses. Strikingly, a poorer central compensation capacity was linked to lower corticosterone levels in comparison to those of high compensators. High compensators responded to repeated placebo injections with elevated blood corticosterone levels, reduced auditory brainstem response (ABR) wave I amplitude, reduced inner hair cell (IHC) ribbon number, diminished temporal processing, reduced LTP responses, and decreased activity-dependent hippocampal BDNF expression. In contrast, the same stress exposure through injection did not elevate blood corticosterone levels in low compensators, nor did it reduce IHC ribbons, ABR wave I amplitude, ASSR, LTP, or BDNF expression as seen in high compensators. Interestingly, in high compensators, the stress-induced responses, such as a decline in ABR wave I amplitude, ASSR, LTP, and BDNF could be restored through the “memory-enhancing” drug phosphodiesterase 9A inhibitor (PDE9i). In contrast, the same treatment did not improve these aspects in low compensators. Thus, central compensation of age-dependent cochlear synaptopathy is a glucocorticoid and cyclic guanosine-monophosphate (cGMP)-dependent neuronal mechanism that fails upon a blunted stress response.

GR-α and GR-β mRNA levels in peripheral blood mononuclear cells of acute myelitis patients can assist in the identification of glucocorticoid sensitivity and are correlated with glucocorticoid therapeutic effect

Acute myelitis (AM) is a rare neuro-immune spinal cord disease. This study sought to explore the transcription level of glucocorticoid (GC) receptors α and β (GR-α/GR-β) in peripheral blood mononuclear cells (PBMCs) and their correlation with GC efficacy and sensitivity in AM patients. AM patients were grouped into the GC-sensitive group (N = 80) and GC-refractory group (N = 67). The GR-α and GR-β mRNA levels in PBMCs were detected. The differentiating value of GR-α, GR-β, and GR-α + GR-β on GC sensitivity and resistance in AM patients was assessed. The independent correlation between GR-α and GR-β mRNA levels and GC sensitivity in AM patients,t and the correlation between GR-α and GR-β mRNA levels and spinal function after GC treatment were analyzed. GR-α mRNA level in PBMCs of GC-refractory patients was lower than that of GC-sensitive patients, while GR-β mRNA level was higher than that of GC-sensitive patients. GR-α + GR-β mRNA had a high diagnostic value for GC sensitivity and resistance in AM patients (area under the ROC curve = 0.881, sensitivity = 79.1%, specificity = 85.0%). GR-α and GR-β mRNA levels were independently correlated with GC sensitivity. GR-α and GR-β mRNA levels were correlated with the spinal function of AM patients after GC treatment. Overall, GR-α and GR-β mRNA levels in PBMCs of AM patients can assist in the identification of GC sensitivity and are correlated with GC efficacy.

Cause or consequence? Understanding the role of cortisol in the increased inflammation observed in depression

Glucocorticoids such as cortisol are a class of steroid hormones that play an important role in co-ordinating the body's response to stress. Elevated cortisol levels and increased inflammation have frequently been reported in patients with depression. The currently accepted "glucocorticoid resistance" model posits this increased inflammation as a consequence of reduced sensitivity to cortisol's putative anti-inflammatory action. However, opposing evidence has accumulated that supports a more recent model, which instead proposes that cortisol possesses immune potentiating properties and may thus directly cause the increased inflammation seen in depression. Despite all of this, a clear explanation of the neuroendocrine mechanism that contributes to the development of depression is still lacking and thus requires further investigation in improved future studies.

Corticosteroid Treatment-Resistance in Myasthenia Gravis

Chronic, high-dose, oral prednisone has been the mainstay of myasthenia gravis treatment for decades and has proven to be highly beneficial in many, toxic in some way to all, and not effective in a significant minority. No patient characteristics or biomarkers are predictive of treatment response leading to many patients suffering adverse effects with no benefit. Presently, measurements of treatment response, whether taken from clinician or patient perspective, are appreciated to be limited by lack of good correlation, which then complicates correlation to biological measures. Treatment response may be limited because disease mechanisms are not influenced by corticosteroids, limits on dosage because of adverse effects, or individual differences in corticosteroids. This review evaluates potential mechanisms that underlie lack of response to glucocorticoids in patients with myasthenia gravis.

Relative contribution of molecular mechanisms to cumulative ligand-mediated downregulation of GRα

Central to the pharmacological use of glucocorticoids (GCs) is the availability of the glucocorticoid receptor alpha (GRα). However, chronic GC therapy often results in the ligand-mediated downregulation of the GRα, and the subsequent development of an acquired GC resistance. While studies have demonstrated the dimerization-dependent downregulation of GRα, as well as the molecular mechanisms through which ligand-mediated downregulation occurs, little is known regarding the relative contribution of these molecular mechanisms to the cumulative ligand-mediated downregulation of the receptor, especially within an endogenous system. Thus, to probe this, the current study evaluates the conformational-dependent regulation of GRα protein using mouse embryonic fibroblast (MEF) cells containing either wild type GRα (MEFwt) or the dimerization deficient GRα mutant (MEFdim) and inhibitors of transcription, translation, and proteasomal degradation. Results show that the promotion of GRα dimerization increases the downregulation of the receptor via two main mechanisms, proteasomal degradation of the receptor protein, and downregulation of GRwt mRNA transcripts. In contrast, when receptor dimerization is restricted these two mechanisms play a lesser role and results suggest that stabilization of GRα protein by non-coding RNAs may potentially be the major regulatory mechanism. Together, these findings clarify the relative contribution of the molecular mechanisms involved in ligand-mediated downregulation of GRα and provides pharmacological targets for the development of GRα ligands with a more favourable therapeutic index.

Mechanisms behind context-dependent role of glucocorticoids in breast cancer progression

Glucocorticoids (GCs), mostly dexamethasone (dex), are routinely administered as adjuvant therapy to manage side effects in breast cancer. However, recently, it has been revealed that dex triggers different effects and correlates with opposite outcomes depending on the breast cancer molecular subtype. This has raised new concerns regarding the generalized use of GC and suggested that the context-dependent effects of GCs can be taken into potential consideration during treatment design. Based on this, attention has recently been drawn to the role of the glucocorticoid receptor (GR) in development and progression of breast cancer. Therefore, in this comprehensive review, we aimed to summarize the different mechanisms behind different context-dependent GC actions in breast cancer by applying a multilevel examination, starting from the association of variants of the GR-encoding gene to expression at the mRNA and protein level of the receptor, and its interactions with other factors influencing GC action in breast cancer. The role of GCs in chemosensitivity and chemoresistance observed during breast cancer therapy is discussed. In addition, experiences using GC targeting therapeutic options (already used and investigated in preclinical and clinical trials), such as classic GC dexamethasone, selective glucocorticoid receptor agonists and modulators, the GC antagonist mifepristone, and GR coregulators, are also summarized. Evidence presented can aid a better understanding of the biology of context-dependent GC action that can lead to further advances in the personalized therapy of breast cancer by the evaluation of GR along with the conventional estrogen receptor (ER) and progesterone receptor (PR) in the routine diagnostic procedure.

Corticosterone induces obesity partly via promoting intestinal cell proliferation and survival

INTRODUCTION

A vicious cycle ensues whereby prolonged exposure to social stress causes increased production of glucocorticoids (GCs), leading to obesity even further. Understanding the role of GCs, the key element in the vicious circle, might be helpful to break the vicious circle. However, the mechanism by which GCs induce obesity remains elusive.

METHODS

Corticosterone (CORT) was administered to mice for 8 weeks. Food and water intake were recorded; obesity was analyzed by body-weight evaluation and magnetic resonance imaging (MRI); intestinal proliferation and survival were evaluated by H&E staining, EdU-progression test, TUNEL assay and immunofluorescence staining of Ki67 and CC3; RNA-seq was performed to analyze transcriptional alterations in small intestines and livers.

RESULTS

Chronic CORT treatment induced obesity, longer small intestines, hepatic steatosis and elevated levels of serum insulin and leptin in mice; CORT-treated mice showed increased cell proliferation and decreased apoptosis of small intestines; RNA-seq results indicate that differentially expressed genes (DEGs) were enriched in several cell growth/death-associated signaling pathways.

DISCUSSION

Herein we find that administration of CORT to mice promotes the proliferation and survival of intestinal cells, which might contribute to the longer small intestines and the elongated intestinal villi, thus leading to increased nutrient absorption and obesity in mice. Understanding CORT-induced alterations in intestines and associated signaling pathways might provide novel therapeutic clues for GCs or stress-associated obesity.

Homeostatic Regulation of Glucocorticoid Receptor Activity by Hypoxia-Inducible Factor 1: From Physiology to Clinic

Glucocorticoids (GCs) represent a well-known class of lipophilic steroid hormones biosynthesised, with a circadian rhythm, by the adrenal glands in humans and by the inter-renal tissue in teleost fish (e.g., zebrafish). GCs play a key role in the regulation of numerous physiological processes, including inflammation, glucose, lipid, protein metabolism and stress response. This is achieved through binding to their cognate receptor, GR, which functions as a ligand-activated transcription factor. Due to their potent anti-inflammatory and immune-suppressive action, synthetic GCs are broadly used for treating pathological disorders that are very often linked to hypoxia (e.g., rheumatoid arthritis, inflammatory, allergic, infectious, and autoimmune diseases, among others) as well as to prevent graft rejections and against immune system malignancies. However, due to the presence of adverse effects and GC resistance their therapeutic benefits are limited in patients chronically treated with steroids. For this reason, understanding how to fine-tune GR activity is crucial in the search for novel therapeutic strategies aimed at reducing GC-related side effects and effectively restoring homeostasis. Recent research has uncovered novel mechanisms that inhibit GR function, thereby causing glucocorticoid resistance, and has produced some surprising new findings. In this review we analyse these mechanisms and focus on the crosstalk between GR and HIF signalling. Indeed, its comprehension may provide new routes to develop novel therapeutic targets for effectively treating immune and inflammatory response and to simultaneously facilitate the development of innovative GCs with a better benefits-risk ratio.