Correlation between glucocorticoid receptor binding parameters, blood pressure, and body mass index in a healthy human population

Central intracrine DHEA synthesis in ageing-related neuroinflammation and neurodegeneration: therapeutic potential?

It is a well-known fact that DHEA declines on ageing and that it is linked to ageing-related neurodegeneration, which is characterised by gradual cognitive decline. Although DHEA is also associated with inflammation in the periphery, the link between DHEA and neuroinflammation in this context is less clear. This review drew from different bodies of literature to provide a more comprehensive picture of peripheral vs central endocrine shifts with advanced age—specifically in terms of DHEA. From this, we have formulated the hypothesis that DHEA decline is also linked to neuroinflammation and that increased localised availability of DHEA may have both therapeutic and preventative benefit to limit neurodegeneration. We provide a comprehensive discussion of literature on the potential for extragonadal DHEA synthesis by neuroglial cells and reflect on the feasibility of therapeutic manipulation of localised, central DHEA synthesis.

Lymphocyte glucocorticoid receptor expression level and hormone-binding properties differ between war trauma-exposed men with and without PTSD

OBJECTIVE

Posttraumatic stress disorder (PTSD) has been shown to be associated with altered glucocorticoid receptor (GR) activity. We studied the expression and functional properties of the receptor in peripheral blood mononuclear cells (PBMCs) from non-traumatized healthy individuals (healthy controls; n=85), and war trauma-exposed individuals with current PTSD (n=113), with life-time PTSD (n=61) and without PTSD (trauma controls; n=88). The aim of the study was to distinguish the receptor alterations related to PTSD from those related to trauma itself or to resilience to PTSD.

METHODS

Functional status of the receptor was assessed by radioligand binding and lysozyme synthesis inhibition assays. The level of GR gene expression was measured by quantitative PCR and immunoblotting.

RESULTS

Current PTSD patients had the lowest, while trauma controls had the highest number of glucocorticoid binding sites (Bmax) in PBMCs. Hormone-binding potential (Bmax/KD ratio) of the receptor was diminished in the current PTSD group in comparison to all other study groups. Correlation between Bmax and KD that normally exists in healthy individuals was decreased in the current PTSD group. Contrasting Bmax data, GR protein level was lower in trauma controls than in participants with current or life-time PTSD.

CONCLUSIONS

Current PTSD is characterized by reduced lymphocyte GR hormone-binding potential and by disturbed compensation between Bmax and hormone-binding affinity. Resilience to PTSD is associated with enlarged fraction of the receptor molecules capable of hormone binding, within the total receptor molecule population in PBMCs.

Impact of glucocorticoid receptor density on ligand-independent dimerization, cooperative ligand-binding and basal priming of transactivation: a cell culture model

Glucocorticoid receptor (GR) levels vary between tissues and individuals and are altered by physiological and pharmacological effectors. However, the effects and implications of differences in GR concentration have not been fully elucidated. Using three statistically different GR concentrations in transiently transfected COS-1 cells, we demonstrate, using co-immunoprecipitation (CoIP) and fluorescent resonance energy transfer (FRET), that high levels of wild type GR (wtGR), but not of dimerization deficient GR (GRdim), display ligand-independent dimerization. Whole-cell saturation ligand-binding experiments furthermore establish that positive cooperative ligand-binding, with a concomitant increased ligand-binding affinity, is facilitated by ligand-independent dimerization at high concentrations of wtGR, but not GRdim. The down-stream consequences of ligand-independent dimerization at high concentrations of wtGR, but not GRdim, are shown to include basal priming of the system as witnessed by ligand-independent transactivation of both a GRE-containing promoter-reporter and the endogenous glucocorticoid (GC)-responsive gene, GILZ, as well as ligand-independent loading of GR onto the GILZ promoter. Pursuant to the basal priming of the system, addition of ligand results in a significantly greater modulation of transactivation potency than would be expected solely from the increase in ligand-binding affinity. Thus ligand-independent dimerization of the GR at high concentrations primes the system, through ligand-independent DNA loading and transactivation, which together with positive cooperative ligand-binding increases the potency of GR agonists and shifts the bio-character of partial GR agonists. Clearly GR-levels are a major factor in determining the sensitivity to GCs and a critical factor regulating transcriptional programs.

Glucocorticoid receptor concentration and the ability to dimerize influence nuclear translocation and distribution

Glucocorticoid receptor (GR) concentrations and the ability of the GR to dimerize are factors which influence sensitivity to glucocorticoids. Upon glucocorticoid binding, the GR is actively transported into the nucleus, a crucial step in determining GR function. We examined the effects of GR concentration and the ability to dimerize on GR nuclear import, export and nuclear distribution using both live cell microscopy of GFP-tagged GR and immunofluorescence of untagged GR, with both wild type GR (GRwt) and dimerization deficient GR (GRdim). We found that the observed rate of GR nuclear import increases significantly at higher GR concentrations, at saturating concentrations of dexamethasone (10(-6) M) using GFP-tagged GR, while with untagged GR it is only discernable at sub-saturating ligand concentrations (10(-10)-10(-9) M). Loss of dimerization results in a slower observed rate of nuclear import (2.5- to 3.3-fold decrease for GFP-GRdim) as well as a decreased extent of GR nuclear localization (18-27% decrease for untagged GRdim). These results were linked to an increased rate of GR export at low GR concentrations (1.4- to 1.6-fold increase for untagged GR) and where GR dimerization is abrogated (1.5- to 1.7-fold increase for GFP-GRdim). Furthermore, GR dimerization was shown to be required for the appearance of discrete GC-dependent GR nuclear foci, the loss of which may explain the increased rate of GR export for the GRdim. The reduction in the observed rate of nuclear import and increased rate of nuclear export displayed at low GR concentrations and by the GRdim could explain the lowered glucocorticoid response under these conditions.

In vitro glucocorticoid sensitivity is associated with clinical glucocorticoid therapy outcome in rheumatoid arthritis

Introduction

Genetic and disease-related factors give rise to a wide spectrum of glucocorticoid (GC) sensitivity in rheumatoid arthritis (RA). In clinical practice, GC treatment is not adapted to these differences in GC sensitivity. In vitro assessment of GC sensitivity before the start of therapy could allow more individualized GC therapy. The aim of the study was to investigate the association between in vitro and in vivo GC sensitivity in RA.

Methods

Thirty-eight early and 37 established RA patients were prospectively studied. In vitro GC sensitivity was assessed with dexamethasone-induced effects on interleukin-2 (IL-2) and glucocorticoid-induced leucine zipper (GILZ) messenger RNA expression in peripheral blood mononuclear cells (PBMCs). A whole-cell dexamethasone-binding assay was used to measure number and affinity (1/K_D) of glucocorticoid receptors (GRs).

In vivo GC sensitivity was determined by measuring the disease activity score (DAS) and health assessment questionnaire disability index (HAQ-DI) score before and after 2 weeks of standardized GC treatment.

Results

GR number was positively correlated with improvement in DAS. IL-2-EC₅₀ and GILZ-EC₅₀ values both had weak near-significant correlations with clinical improvement in DAS in intramuscularly treated patients only. HAQ responders had lower GILZ-EC₅₀ values and higher GR number and K_D.

Conclusions

Baseline cellular in vitro glucocorticoid sensitivity is modestly associated with in vivo improvement in DAS and HAQ-DI score after GC bridging therapy in RA. Further studies are needed to evaluate whether in vitro GC sensitivity may support the development of tailor-made GC therapy in RA.

Age, body mass index, and serum level of DHEA-S can predict glucocorticoid receptor function in women with polycystic ovary syndrome

Glucocorticoid receptor (GR) transduces the glucocorticoid (GC) signal that could lead to metabolic derangements depending on the tissue responsiveness to GC. We aimed to investigate possible causative relation of the GR functional properties in peripheral blood mononuclear cells of women with polycystic ovary syndrome (PCOS), with their clinical and biochemical characteristics. Thirty women with PCOS [mean age: 26.5 ± 5.1 years, mean body mass index (BMI) 24.5 ± 5 kg/m(2)], and thirty respective controls were analyzed for the number of GR sites per cell (B (max)), apparent equilibrium dissociation constant (K (d)), and binding potency (GR potency). A strong association between B (max) and K (d) (r = 0.70, P < 0.0001), and GR potency with age (r = 0.49, P = 0.009) was observed in PCOS women. The multiple regression analyses within the PCOS group revealed that independent predictors for K (d) were BMI, total cholesterol, and dehydroepiandrosterone-sulfate (DHEA-S) (r = 0.58, P = 0.038), while for GR potency (r = 0.687, P = 0.013) were age, BMI, DHEA-S, and basal cortisol concentration. The results suggest that PCOS pathophysiology may be related to alterations of a cross stalk between glucocorticoid signaling, age, and metabolic parameters. These findings should be further explored in studies on the role of GR in PCOS-related metabolic derangements.

Glucocorticoid Receptor in Health and Disease

Glucocorticoid hormones are essential for life, have a vital place in the treatment of inflammatory and autoimmune diseases and are increasingly implicated in the pathogenesis of a number of common disorders. Their action is mediated by an intracellular receptor protein, the glucocorticoid receptor (GR), functioning as a ligand-inducible transcription factor. Multiple synthetic glucocorticoids are used as potent antiinflammatory and immunosuppressive agents, but their therapeutic usefulness is limited by a wide range and severity of side-effects. One of the most important pharmaceutical goals has been to design steroidal and non-steroidal GR ligands with profound therapeutic efficacy and reduced unwanted effects. The therapeutic benefit of glucocorticoid agonists is frequently compromised by resistance to glucocorticoids, which may depend on: access of the hormones to target cells, steroid metabolism, expression level and isoform composition of the GR protein, mutations and polymorphisms in the GR gene and association of the receptor with chaperone proteins. The major breakthrough into the critical role of glucocorticoid signaling in the maintenance of homeostasis and pathogenesis of diseases, as well as into the molecular mechanisms underlying the therapeutic usefulness of antiinflammatory drugs acting through the GR is expected to result from the current progress in large-scale gene expression profiling technologies and computational biology.