Expression Of Glucocorticoid Receptor Isoforms Research Articles

Glucocorticoids, their uses, sexual dimorphisms, and diseases: new concepts, mechanisms, and discoveries.

The normal stress response in humans is governed by the hypothalamic-pituitary-adrenal (HPA) axis through heightened mechanisms during stress, raising blood levels of the glucocorticoid hormone cortisol. Glucocorticoids are quintessential compounds that balance the proper functioning of numerous systems in the mammalian body. They are also generated synthetically and are the preeminent therapy for inflammatory diseases. They act by binding to the nuclear receptor transcription factor glucocorticoid receptor (GR), which has two main isoforms (GRα and GRβ). Our classical understanding of glucocorticoid signaling is from the GRα isoform, which binds the hormone, whereas GRβ has no known ligands. With glucocorticoids being involved in many physiological and cellular processes, even small disruptions in their release via the HPA axis, or changes in GR isoform expression, can have dire ramifications on health. Long-term chronic glucocorticoid therapy can lead to a glucocorticoid-resistant state, and we deliberate how this impacts disease treatment. Chronic glucocorticoid treatment can lead to noticeable side effects such as weight gain, adiposity, diabetes, and others that we discuss in detail. There are sexually dimorphic responses to glucocorticoids, and women tend to have a more hyperresponsive HPA axis than men. This review summarizes our understanding of glucocorticoids and critically analyzes the GR isoforms and their beneficial and deleterious mechanisms and the sexual differences that cause a dichotomy in responses. We also discuss the future of glucocorticoid therapy and propose a new concept of dual GR isoform agonist and postulate why activating both isoforms may prevent glucocorticoid resistance.

Restrained expression of canine glucocorticoid receptor splice variants \u03b1 and P prognosticates fatal disease outcome in SIRS

Glucocorticoids play a central role in the inflammatory response and alleviate the symptoms in critically ill patients. The glucocorticoid action relies on the glucocorticoid receptor (GR) which translocates into the nucleus upon ligand-binding and regulates transcription of a battery of genes. Although the GR is encoded by a single gene, dozens of its splice variants have been described in diverse species. The GRα isoform encodes the full, functionally active protein that is composed of a transactivation, a DNA-binding, and a C-terminal ligand-binding domain. The second most highly expressed receptor variant, the GR-P, is formed by an intron retention that introduces an early stop codon and results in a probably dysfunctional protein with truncated ligand-binding domain. We described the canine ortholog of GR-P and showed that this splice variant is highly abundant in the peripheral blood of dogs. The level of cGRα and cGR-P transcripts are elevated in patients of SIRS and the survival rate is increased with elevated cGRα and cGR-P expression. The ratio of cGRα and cGR-P mRNA did not differ between the survivor and non-survivor patients; thus, the total GR expression is more pertinent than the relative expression of GR isoforms in assessment of the disease outcome.

A Pharmacologic Approach Using Pomalidomide and Dexamethasone to Study Stage-Specific Regulation of Erythroid Progenitors

The erythroid progenitors, burst forming unit-erythroid (BFU-E) and colony forming unit-erythroid (CFU-E), control red cell production through the integration of a variety of self-renewal and differentiation signals. The identification of these signals and their effects on erythroid progenitor populations are of therapeutic interest for human disorders characterized by decreased red cell production such as Diamond Blackfan Anemia (DBA). We have previously documented that pomalidomide acts at the BFU-E stage and dexamethasone at the CFU-E stage in in vitro models of human erythropoiesis. Therefore, these two agents represent potential pharmacologic interventions for the treatment of human diseases with disordered erythropoiesis. Here, we studied the mechanisms by which pomalidomide and dexamethasone enhance erythroid progenitor numbers in cord blood and adult bone marrow-derived CD34+ hematopoietic stem and progenitor cells (HSPC).Pomalidomide increased adult and fetal BFU-E numbers in both serum-free and serum-containing in vitro erythroid culture systems. CFU-E numbers and terminal erythroblasts were also transiently attenuated suggesting that pomalidomide mediates increased BFU-E in part through delayed progression to erythropoietin-sensitive progenitors and precursor stages. Transforming growth factor-β (TGF-β) has previously been shown to regulate the transition from BFU-E to CFU-E, and therefore, we investigated whether pomalidomide modulates TGF-β signaling. We noted accelerated differentiation as assessed by glycophorin A (GPA) expression of CD34+ HSPCs treated with TGF-β1, and the addition of pomalidomide completely abrogated TGF-β1 mediated differentiation. This effect was not due to inhibition of TGF-β1 receptors or kinases as treatment of NIH 3T3 cells with TGF-β1 ± pomalidomide failed to prevent SMAD2 phosphorylation. Only CD34+ HSPCs differentiated in the presence of pomalidomide exhibited reduced sensitivity to TGF-β1. These results suggest that pomalidomide alters erythroid and/or earlier hematopoietic progenitor differentiation to enrich a population of TGF-β1 insensitive cells and/or affects the activity of downstream TGF-β1 effectors.Dexamethasone, in contrast to pomalidomide, was found to specifically increase the number of CFU-E progenitors. Elevated CFU-E self-renewal was associated with an accumulation of cells in G0/G1 of the cell cycle, which suggests that alterations to cell cycle progression may contribute to the regulation of self-renewal genes in CFU-E. In contrast to adult-derived CFU-E, dexamethasone failed to affect CFU-E numbers or cell cycle status in cord blood derived CFU-Es. We investigated the expression of glucocorticoid receptor isoforms (GRα and GRβ) in erythroid progenitors, which revealed that BFU-E and CFU-E differentially express GR isoforms. BFU-E expressed comparable levels of GRα and the hypothesized dominant-negative GRβ, where as only GRα transcript was measured in CFU-E. These expression patterns were similar between adult and cord blood-derived progenitors. Despite similar GR levels, adult-derived erythroid progenitors, but not cord blood derived progenitors, were shown to translocate GRα to the nucleus after a 24hr pulse of dexamethasone suggesting that post-translational mechanisms may govern dexamethasone response in erythroid progenitors.These findings strongly indicate that pharmacologic modulation of the TGF-β and glucocorticoid-signaling pathways can effectively stimulate erythroid progenitor self-renewal. We are currently elucidating specific targets for pomalidomide and dexamethasone in BFU-E and CFU-E, respectively, through proteomics and transcriptome approaches, and investigating the efficacy of mono- and combination therapies using peripheral blood-derived CD34+ HSPCs from DBA patients to study their therapeutic efficacy. DisclosuresNo relevant conflicts of interest to declare.

Multifaceted Control of GR Signaling and Its Impact on Hepatic Transcriptional Networks and Metabolism.

Glucocorticoids (GCs) and the glucocorticoid receptor (GR) are important regulators of development, inflammation, stress response and metabolism, demonstrated in various diseases including Addison's disease, Cushing's syndrome and by the many side effects of prolonged clinical administration of GCs. These conditions include severe metabolic challenges in key metabolic organs like the liver. In the liver, GR is known to regulate the transcription of key enzymes in glucose and lipid metabolism and contribute to the regulation of circadian-expressed genes. Insights to the modes of GR regulation and the underlying functional mechanisms are key for understanding diseases and for the development of improved clinical uses of GCs. The activity and function of GR is regulated at numerous levels including ligand availability, interaction with heat shock protein (HSP) complexes, expression of GR isoforms and posttranslational modifications. Moreover, recent genomics studies show functional interaction with multiple transcription factors (TF) and coregulators in complex transcriptional networks controlling cell type-specific gene expression by GCs. In this review we describe the different regulatory steps important for GR activity and discuss how different TF interaction partners of GR selectively control hepatic gene transcription and metabolism.

Chronic Ethanol Consumption Alters Glucocorticoid Receptor Isoform Expression in Stress Neurocircuits and Mesocorticolimbic Brain Regions of Alcohol-Preferring Rats

Evidence suggests the hypothalamic–pituitary–adrenal (HPA) axis is involved in Alcohol Use Disorders (AUDs), which might be mediated by an imbalance of glucocorticoid receptor (GR), GRα and GRβ, activity. GRβ antagonizes the GRα isoform to cause glucocorticoid (GC) resistance. In the present study, we aimed to investigate the effects of chronic continuous free-choice access to ethanol on GR isoform expression in subregions of the mesocorticolimbic reward circuit. Adult male alcohol-preferring (P) rats had concurrent access to 15% and 30% ethanol solutions, with ad lib access to lab chow and water, for six weeks. Quantitative Real-time PCR (RT-PCR) analysis showed that chronic ethanol consumption reduced GRα expression in the nucleus accumbens shell (NAcsh) and hippocampus, whereas ethanol drinking reduced GRβ in the nucleus accumbens core (NAcc), prefrontal cortex (PFC), and hippocampus. An inhibitor of GRα, microRNA-124-3p (miR124-3p) was significantly higher in the NAcsh, and GC-induced gene, GILZ, as a measure of GC-responsiveness, was significantly lower. These were not changed in the NAcc. Likewise, genes associated with HPA axis activity were not significantly changed by ethanol drinking [i.e., corticotrophin-releasing hormone (Crh), adrenocorticotrophic hormone (Acth), and proopiomelanocortin (Pomc)] in these brain regions. Serum corticosterone levels were not changed by ethanol drinking. These data indicate that the expression of GRα and GRβ isoforms are differentially affected by ethanol drinking despite HPA-associated peptides remaining unchanged, at least at the time of tissue harvesting. Moreover, the results suggest that GR changes may stem from ethanol-induced GC-resistance in the NAcsh. These findings confirm a role for stress in high ethanol drinking, with GRα and GRβ implicated as targets for the treatment of AUDs.

Glucocorticoid Receptor-α and MKP-1 as Candidate Biomarkers for Treatment Response and Disease Activity in Vogt-Koyanagi-Harada Disease

To investigate the potential of utilizing the expression of genes for glucocorticoid receptor (GR) and mitogen-activated protein kinase phosphatase-1 (MKP-1) as biomarkers of corticosteroid (CS) refractoriness and disease activity in patients with Vogt-Koyanagi-Harada (VKH) disease. Prospective cohort study. Twenty VKH patients receiving their first cycle of CS treatment in the absence of additional systemic immunosuppressive therapy and a control group of fifteen healthy volunteers were recruited from the University of Chile (Santiago, Chile) and US National Institutes of Health (Bethesda, United States). Intraocular inflammation was clinically quantified at enrolment and all follow-up visits. CS refractoriness was defined as an ocular reactivation of VKH upon CS withdrawal at a daily oral prednisone dose of 10mg or more. Quantitative Reverse transcription polymerase chain reaction (qRT-PCR) was performed to measure the mRNA levels of the alpha (α) and beta (β) isoforms of GR and MKP-1 in peripheral blood mononuclear cells (PBMC) after invitro stimulation with either anti-CD3/anti-CD28 antibodies, lipopolysaccharide (LPS), or phytohemagglutinin (PHA), in the presence or absence of dexamethasone (Dex). After 6 hours of stimulation in the presence of Dex, PBMC from CS-refractory VKH patients had an impaired elevation in GRα expression (P= .03). Furthermore, inactive patients showed a significant Dex-induced upregulation of MKP-1 (P= .005). In this pilot study, the expression of GR isoforms and MKP-1 corresponded with patients' clinical response to systemic CS treatment and disease activity, respectively. Hence, these candidate biomarkers have potential clinical utility in the early identification of CS refractoriness and subclinical inflammation in patients with VKH disease.

Glucocorticoid receptor isoform expression in peripheral blood mononuclear leukocytes of patients with chronic rhinosinusitis.

In several inflammatory disorders, altered peripheral blood mononuclear leukocyte (PBML) glucocorticoid (GC) receptor isoform expression has been associated with GC resistance and disease severity. However, it is unclear if PBML GC receptor isoforms are expressed differentially and are associated with worsened disease severity in chronic rhinosinusitis (CRS). PBMLs were isolated from control (n = 8), CRS without nasal polyps (CRSsNP) (n = 8), atopic CRS with nasal polyps (CRSwNP) (n = 8), non-atopic CRSwNP (n = 8), and allergic fungal rhinosinusitis (AFRS) (n = 8) patients. Demographics, atopic status, asthmatic status, 22-item Sino-Nasal Outcome Test (SNOT-22) scores, Lund-Kennedy nasal endoscopy scores, Lund-Mackay sinus computed tomography (CT) scores, Kennedy Osteitis scores, and GC utilization 6 months postoperatively were collected. Intracellular immunostaining was then performed for functional GC receptor α (GCRα) and nonfunctional GC receptor β (GCRβ), followed by flow cytometry analysis of geometric mean fluorescent intensity (MFI) and the percentage of cells expressing each GC receptor isoform. Compared to controls, each CRS subtype had decreased PBML GCRα and GCRα:GCRβ MFI expression, but no difference in GCRβ expression. Decreasing PBML GCRα in AFRS was associated with increasing Lund-Mackay sinus CT scores (r = -0.880, p =0.004). No significant associations were found between GC receptor isoform expression and other clinical measures. CRS patients have reduced functional PBML GCRα expression and decreased GCRα:GCRβ compared to controls. Reductions in GCRα in AFRS are associated with worsening Lund-Mackay sinus CT scores. The clinical implications of decreased functional GC receptor expression merits further investigation.

LPS regulates the expression of glucocorticoid receptor \u03b1 and \u03b2 isoforms and induces a selective glucocorticoid resistance in vitro

BackgroundThis study was aimed to evaluate the effect of LPS in glucocorticoid receptor (GR) isoforms expression on different cell lines and PBMC from healthy donors in vitro and glucocorticoid sensitivity of PBMC in vitro.MethodsU-2 OS cell lines expressing GR isoforms, different cell lines (CEM, RAJI, K562 and HeLa) or PBMC from healthy donors, were cultured or not with LPS. The expression of GRα and GRβ was evaluated by Western blot. Glucocorticoid sensitivity was evaluated in PBMC treated with LPS, testing genes which are transactivated or transrepressed by glucocorticoid. For transactivated genes (MKP1, FKBP5) PBMC were treated with Dexamethasone 100 nM for 6 h. The mRNA expression was measured by RT-PCR. For transrepressed genes (IL-8, GM-CSF), PBMC were cultured in Dexamethasone 100 nM and LPS 10 μg/ml for 6 h and protein expression was measure by ELISA.ResultsGR isoforms were induced in U-2 OS cells with a greater effect on GRα expression. Both isoforms were also induced in CEM cells with a tendency to a greater effect on GRβ. LPS induced only the expression of GRα in Raji and HeLa cells, and in PBMC, with no effect in K562 cells. LPS induced a loss of glucocorticoid inhibitory effect only on the secretion of GM-CSF.ConclusionLPS in vitro differentially modulates the expression of GR isoforms in a cell specific manner. In PBMC from healthy donors LPS induces an approximately two times increase in the expression of GRα and a loss of the glucocorticoid inhibitory effect on the secretion of GM-CSF, without affecting other glucocorticoid responses evaluated.

Evaluation of the Glucocorticoid Receptor as a Biomarker of Treatment Response in Vogt-Koyanagi-Harada Disease.

This study is aimed to investigate the role of glucocorticoid receptor (GR) isoforms in peripheral blood mononuclear cells (PBMC) as biomarkers of glucocorticoid (GC) resistance and to validate a set of clinical predictive factors in patients with Vogt-Koyanagi-Harada (VKH) disease. This was a prospective cohort study that included a total of 21 patients with VKH. A complete ophthalmologic evaluation was carried out at baseline that recorded the presence of any clinical predictive factors (visual acuity ≤ 20/200, tinnitus, chronic disease, and fundus depigmentation). Real-time quantitative PCR was performed to measure the mRNA levels of GR alpha (GRα) and beta (GRβ) isoforms at baseline and at 2 weeks after prednisone therapy initiation. There were no differences between GRα and GRβ levels in GC-sensitive and GC-resistant patients at baseline before treatment initiation. After 2 weeks of prednisone treatment, GC-sensitive patients had a median 5.5-fold increase in levels of GRα, whereas GC-resistant patients had a median 0.7-fold decrease in levels of this isoform (P = 0.003). Similarly, GRβ increased in GC-sensitive patients, in comparison with GR-resistant patients (6.49-fold versus 1.01 fold, respectively, I = 0.04). The mRNA levels of GR isoforms were independent of disease activity. Fundus depigmentation and chronic disease at diagnosis were associated with GC resistance (P = 0.03, odds ratio = 21.0; and P = 0.008, odds ratio = 37.8, respectively). However, associations with visual acuity or tinnitus were not confirmed in this study. The evaluation of clinical predictive factors and determination of the change in expression of GR isoforms as potential biomarkers can contribute to the early identification of GC-resistant patients with VKH.

Maternal dexamethasone exposure in the mouse causes sex specific alterations in the pattern of glucocorticoid receptor isoform expression

Maternal dexamethasone exposure in the mouse causes sex specific alterations in the pattern of glucocorticoid receptor isoform expression

Relationship between expression of glucocorticoid receptor isoforms and glucocorticoid resistance in immune thrombocytopenia

Background: Glucocorticoids (GCs) play an important role in the treatment of several hematological malignancies, such as immune thrombocytopenia (ITP). The glucocorticoid receptor (GR) mediates the effects of GCs. Five isoforms of GR mRNA were described: GRα, GRβ, GRγ, GRP, and GRA. GR levels are regulated by alternative splicing of GR mRNA. Several studies demonstrated that a lower GR expression was associated with poor GC response.Purpose: This study investigated the expression of GR isoforms and the relationship between GC resistance in ITP.Methods: This study determined GRα/β/γ/P mRNA and GRα/β protein expression levels using SYBR Green Real-time PCR and Western blot, respectively, in 49 newly diagnosed ITP patients and 31 controls.Results: The expression of GR isoform mRNA in ITP and controls showed the following trend: GRα > GRP > GRγ > GRβ. The expression of GRα, β mRNA and the total frequency of the four GR isoforms in ITP was significantly higher than in controls (P < 0.05). The expression of GRα mRNA and protein in the GC-resistant group was significantly lower than that in the GC-sensitive group and controls (P < 0.05). GRβ could not be detected at the protein level in our experimental conditions.Conclusion: GRα and GRP were the main GR isoforms responsible for the effects of GC, and GRα and GRP exhibited synergistic effects. The down-regulation of GRα levels may play an important role in GC resistance in ITP. The effects of GCs in ITP were not associated with changes in GRβ and GRγ.

Identification of Eight Different Isoforms of the Glucocorticoid Receptor in Guinea Pig Placenta: Relationship to Preterm Delivery, Sex and Betamethasone Exposure.

The placental glucocorticoid receptor (GR) is central to glucocorticoid signalling and for mediating steroid effects on pathways associated with fetal growth and lung maturation but the GR has not been examined in the guinea pig placenta even though this animal is regularly used as a model of preterm birth and excess glucocorticoid exposure. Guinea pig dams received subcutaneous injections of either vehicle or betamethasone at 24 and 12 hours prior to preterm or term caesarean-section delivery. At delivery pup and organ weights were recorded. Placentae were dissected, weighed and analysed using Western blot to examine GR isoform expression in nuclear and cytoplasmic extracts. A comparative examination of the guinea pig GR gene identified it is capable of producing seven of the eight translational GR isoforms which include GRα-A, C1, C2, C3, D1, D2, and D3. GRα-B is not produced in the Guinea Pig. Total GR antibody identified 10 specific bands from term (n = 29) and preterm pregnancies (n = 27). Known isoforms included GRγ, GRα A, GRβ, GRP, GRA and GRα D1-3. There were sex and gestational age differences in placental GR isoform expression. Placental GRα A was detected in the cytoplasm of all groups but was significantly increased in the cytoplasm and nucleus of preterm males and females exposed to betamethasone and untreated term males (KW-ANOVA, P = 0.0001, P = 0.001). Cytoplasmic expression of GRβ was increased in female preterm placentae and preterm and term male placentae exposed to betamethasone (P = 0.01). Nuclear expression of GRβ was increased in all placentae exposed to betamethasone (P = 0.0001). GRα D2 and GRα D3 were increased in male preterm placentae when exposed to betamethasone (P = 0.01, P = 0.02). The current data suggests the sex-specific placental response to maternal betamethasone may be dependent on the expression of a combination of GR isoforms.

Glucocorticoid receptors GRα and GRβ are expressed in inflammatory dermatoses

Glucocorticoids (GC) are the most commonly used anti-inflammatory drugs in dermatology. The actions of GCs are mediated by the glucocorticoid receptor (GR). Alternative splicing of GR mRNA gives rise to different isoforms, GRα and GRβ being the most important. GRβ antagonizes the activity of GRα and its up-regulation has been associated with glucocorticoid insensitivity in several non-cutaneous inflammatory diseases. Using immunohistochemical stainings, we analyzed the expression of GRα and GRβ in lesional skin samples of patients with atopic dermatitis, lichen ruber planus, eczema nummulare and lichen simplex chronicus. We also conducted a study of 13 severe atopic patients to investigate the effect of prednisolone treatment on the expression of GR isoforms using quantitative PCR, western blot and immunohistochemical analysis. GRα and GRβ were expressed in atopic dermatitis, lichen ruber planus, eczema nummulare and lichen simplex chronicus. Our novel finding was that GRβ is abundant in keratinocytes and cutaneous neutrophils. Nuclear staining of both GRα and GRβ was strongest in keratinocytes of patients with lichen ruber planus, whereas the least nuclear positivity was detected in keratinocytes of patients with atopic dermatitis. In severe atopic dermatitis GRα and GRβ were expressed in both peripheral blood mononuclear cells and the skin. The expression of GRα and GRβ varied during prednisolone therapy but the changes were not related to treatment response or GC insensitivity. GRα and GRβ are expressed in inflammatory dermatoses. In severe atopic dermatitis the increased expression of GRβ mRNA is not connected to insensitivity against prednisolone treatment.

Expression of eight glucocorticoid receptor isoforms in the human preterm placenta vary with fetal sex and birthweight

IntroductionAdministration of betamethasone to women at risk of preterm delivery is known to be associated with reduced fetal growth via alterations in placental function and possibly direct effects on the fetus. The placental glucocorticoid receptor (GR) is central to this response and recent evidence suggests there are numerous isoforms for GR in term placentae. In this study we have questioned whether GR isoform expression varies in preterm placentae in relation to betamethasone exposure, fetal sex and birthweight. MethodsPreterm (24–36 completed weeks of gestation, n = 55) and term placentae (>37 completed weeks of gestation, n = 56) were collected at delivery. Placental GR expression was examined using Western Blot and analysed in relation to gestational age at delivery, fetal sex, birthweight and betamethasone exposure. Data was analysed using non-parametric tests. ResultsEight known isoforms of the GR were detected in the preterm placenta and include GRα (94 kDa), GRβ (91 kDa), GRα C (81 kDa) GR P (74 kDa) GR A (65 kDa), GRα D1–3 (50–55 kDa). Expression varied between preterm and term placentae with a greater expression of GRα C in preterm placentae relative to term placentae. The only sex differences in preterm placentae was that GRα D2 expression was higher in males than females. There were no alterations in preterm placental GR expression in association with betamethasone exposure. DiscussionGRα C is the isoform involved in glucocorticoid induced apoptosis and suggests that its predominance in preterm placentae may contribute to the pathophysiology of preterm birth.

Interleukin-1β regulates the expression of glucocorticoid receptor isoforms in nasal polyps in vitro via p38 MAPK and JNK signal transduction pathways.

BackgroundTo explore the upstream signal transduction mechanisms responsible for the imbalanced expression of glucocorticoid receptor (GR) isoforms in chronic rhinosinusitis (CRS) mucosa.MethodsAn in vitro model of Glucocorticoid resistance was established by inducing nasal polyp tissue with IL-1β. Changes in the protein and mRNA expression of GRα, GRβ and the key enzymes in the p38 MAPK and JNK signal pathways were measured, respectively, before and after being induced with different doses of IL-1β and specific inhibitors of p38 MAPK, JNK, ERK, PI3K and PKC. The Glucocorticoid sensitivity was measured using in vitro Glucocorticoid binding assay. Analysis of variance (ANOVA) was used to analyze the data.ResultsThe mRNA and protein expression levels of GRα, GRβ and key enzymes of the p38 MAPK and JNK pathways increased both in time- and concentration-dependent manners in IL-1β-induced nasal polyp tissue. The expression of GRβ increased more significantly than that of GRα, and the GRα/GRβ ratio decreased in time- and concentration-dependent manners. Statistically significant differences were found in the GRα/GRβ ratio and the mRNA expression of phospho-p38 MAPK and phospho-JNK between the IL-1β-induced groups and the control groups (P < 0.05). Either a specific inhibitor of the p38 MAPK pathway or a specific inhibitor of the JNK pathway increased the GRα/GRβ ratio and the Glucocorticoid affinity. None of the specific inhibitors of ERK, PI3K or PKC had any influence on the expression of GR isoforms.ConclusionOur results demonstrated that the imbalanced expression of GR isoforms in nasal polyp tissue induced by IL-1β in vitro is mediated through the p38 MAPK and JNK signal pathways.

Expression of Glucocorticoid Receptor Isoforms (a, β, γ, and p) in Egyptian Primary Immune Thrombocytopenia Patients

Expression of Glucocorticoid Receptor Isoforms (a, β, γ, and p) in Egyptian Primary Immune Thrombocytopenia Patients

The prognostic value of glucocorticoid receptors for adult acute lymphoblastic leukemia.

BackgroundTherapeutic protocols used in adult acute lymphoblastic leukemia (ALL) are widely variable, and glucocorticoids (GCs) are essential components in ALL treatment. Therefore, this study aimed to evaluate the distribution of prominent glucocorticoid receptor (GR) gene polymorphic variants among adult ALL patients. We also investigated the association between GR messenger ribonucleic acid (mRNA) isoform expressions and the response to chemotherapy.MethodsFifty-two newly diagnosed Philadelphia-negative adult ALL patients and 30 healthy control subjects were enrolled in this study. Genotyping was carried out using a polymerase chain reaction (PCR)-restriction fragment length polymorphism analysis. GR mRNA isoform expressions were assayed by quantitative real-time PCR.ResultsALL patients in this study had a median age of 34 years (range, 18-75). GRα expression was associated with complete remission (P=0.03), while GRγ mRNA expression was significantly higher in GC resistant patients (P=0.032) and in non-responders (P=0.019). However, there were no significant associations with GC resistance. The BclI polymorphic variant of the GR gene was the most frequent in adult ALL patients and was not associated with the GC response. Both higher GRα expression and lower GRγ expression were associated with achievement of complete remission, while higher GRγ expression was associated with GC-resistance.ConclusionOur data suggest that the level of GR isoform expression may be useful in predicting GC response, achievement of complete remission, and better event-free survival in ALL patients. However, further evaluation with a larger cohort of patients is warranted.

Role of the Alternatively Spliced Glucocorticoid Receptor Isoform GRβ in Steroid Responsiveness and Glaucoma

Glucocorticoid (GC)-induced ocular hypertension (OHT) is a serious side effect of GC therapy in susceptible individuals. This OHT is due to increased aqueous humor (AH) outflow resistance in the trabecular meshwork (TM) caused by GC-mediated changes in TM structure and function. GCs may also play a role in the development of primary open-angle glaucoma (POAG). Elevated cortisol levels in the AH or enhanced GC sensitivity may be one of the reasons for elevated intraocular pressure in POAG patients. The GC OHT responder population is at greater risk of developing POAG compared with non-responders. We recently have gained insight into the molecular mechanisms responsible for this differential GC responsiveness, which is attributed to differences in GC receptor isoform expression in the TM. This article summarizes current knowledge on alternative GC receptor splicing to generate GC receptor alpha (GRα) and GRβ and their roles in the regulation of GC responsiveness in normal and glaucoma TM.

Heterogenous Nuclear Ribonucleoprotein L Regulates The Selective Expression Of Glucocorticoid Receptor Translational Isoforms In HL-60 Cells

Selective glucocorticoid receptor (GR) translational isoforms, i.e. the GR-D isoforms, mediate glucocorticoid protection of neutrophils from spontaneous apoptosis. HL-60 cells, like neutrophils, have predominantly the GR-D isoform. We determined whether the translation factor heterogenous nuclear ribonucleoprotein L (hnRNPL) plays a role in selective expression of the GR isoforms in HL-60 cells. Knockdown using hnRNPL shRNA in HL-60 cells was performed using retroviral transduction. Empty vector was used as controls. Western blot analyses were used to determine the level of hnRNPL and GR isoforms. The expression of GR target genes in cells treated with vehicle or dexamethasone (DEX, 100 nM, 6h) were measured using realtime RT-PCR. Knockdown using hnRNPL shRNA reduced the level of hnRNPL to background level. After hnRNPL knockdown, the GR-D isoform in HL-60 cells decreased significantly and the GR-A isoform increased significantly. Reflecting the switch of the GR isoforms, GR function was altered. DEX increased the expression of IkappaB in control cells but not in cells expressing hnRNPL shRNA. In contrast, DEX increased the expression of GILZ in both control and shRNA expressing cells. In addition, TNF and retinoic acid both decreased the level of hnRNPL and switched the GR-D to the GR-A isoform. The translation factor hnRNPL regulates the selective expression of the GR-D isoforms in HL-60 cells. Selective expression of GR isoforms underlies gene-specific glucocorticoid responses in HL-60 cells.

Low expression of glucocorticoid receptor alpha isoform in adult immune thrombocytopenia correlates with glucocorticoid resistance

The expression of glucocorticoid receptor (GR) isoforms has been linked to glucocorticoid (GC) resistance in various diseases treated with GC. However, existing data are conflicting in these diseases, and little information is available regarding immune thrombocytopenia (ITP). To further investigate the role of GR isoforms in GC resistance in adult ITP patients, we measured the mRNA expression of GR isoforms (GRα, GRβ, GRγ, GRp) in peripheral blood mononuclear cells (PBMC) from 54 newly diagnosed ITP patients, including GC-sensitive (GCS) and GC-resistant (GCR) patients and 35 healthy volunteers. The GRα and GRβ proteins in PBMC, nuclear factor-κB (NF-κB), and activator protein-1 (AP-1) in the nucleus were detected by Western blotting. Compared to normal subjects, both GRα and GRβ mRNAs were significantly increased in ITP patients (p < 0.05), while there was no significant difference in the mRNA expression of GRγ and GRp. Compared to GCR patients, the expressions of GRα mRNA and GRα protein were significantly higher in GCS patients (p < 0.05). Moreover, no significant difference in the mRNA expression of the GRβ, GRγ, and GRp isoforms was observed between GCS and GCR patients and the GRβ protein could not be detected. Compared to GCS group, the expression of p65/NF-κB was significantly higher in the GCR group (p < 0.05). Overall, we did not find differences in c-Jun/AP-1 protein expression between GCS and GCR patients. In summary, GC resistance in adult ITP patients is associated with a reduced expression of GRα, which may be related with increased NF-κB. GRβ was very low and may not be involved in GC resistance in adult ITP, warranting further exploration.