Association of glucocorticoid insensitivity with increased expression of glucocorticoid receptor beta

Neural regulation of innate immunity: a coordinated nonspecific host response to pathogens

The central nervous system (CNS) regulates innate immune responses through hormonal and neuronal routes. The neuroendocrine stress response and the sympathetic and parasympathetic nervous systems generally inhibit innate immune responses at systemic and regional levels, whereas the peripheral nervous system tends to amplify local innate immune responses. These systems work together to first activate and amplify local inflammatory responses that contain or eliminate invading pathogens, and subsequently to terminate inflammation and restore host homeostasis. Here, I review these regulatory mechanisms and discuss the evidence indicating that the CNS can be considered as integral to acute-phase inflammatory responses to pathogens as the innate immune system.

Association of glucocorticoid receptor polymorphism A3669G in exon 9beta with reduced central adiposity in women

The glucocorticoid receptor (GR) may be a common link between human obesity/metabolic syndrome and Cushing's syndrome. The effects of glucocorticoids are mediated through the functional isoform, GRalpha. An alternative isoform, GRbeta, behaves as a dominant negative inhibitor of GRalpha and has been implicated as a contributing factor to glucocorticoid resistance. A naturally occurring ATTTA to GTTTA single nucleotide polymorphism (A3669G) located in the 3' end of exon 9beta results in increased stability of GRbeta mRNA and increased GRbeta protein expression. Enhanced GRbeta expression may result in greater inhibition of GRalpha transcriptional activity, resulting in glucocorticoid insensitivity. To test the hypothesis that the 3669G allele would result in a phenotype less likely to express features of glucocorticoid excess, we studied the prevalence of this polymorphism and its relationship with obesity and features of the metabolic syndrome in 322 Europid and 262 South-Asian subjects in northeast England. We report evidence that 3669G allele is associated with reduced central obesity in Europid women and a more favorable lipid profile in Europid men. These data suggest that the 3669G allele may attenuate the undesirable effects of glucocorticoids on fat distribution and lipid metabolism, although its penetrance may vary in different ethnic groups.

Reduced Glucocorticoid Receptor alpha Expression in Mood Disorder Patients and First-Degree Relatives

BACKGROUND

Individuals with mood disorders exhibit altered function of the hypothalamic-pituitary-adrenal (HPA) axis in response to stress. The glucocorticoid receptor (GR) plays an important role in the negative feedback regulation of the HPA axis. There are two protein isoforms of GR, GRalpha and GRbeta, which have distinct biological activity. It has not been examined whether GRalpha messenger RNA (mRNA) and GRbeta mRNA expressions are altered in peripheral blood cells of mood disorder patients.

METHODS

Using quantitative reverse transcription polymerase chain reaction (RT-PCR), GRalpha mRNA and GRbeta mRNA were measured in peripheral blood cells of major depressive disorder patients (depressive n = 18; remissive n = 38), bipolar disorder patients (depressive n = 13; remissive n = 35), normal control subjects (n = 31), and first-degree relatives of major depressive (n = 17) and bipolar (n = 15) disorder patients.

RESULTS

Reduced expression of GRalpha mRNA was shown in both bipolar and major depressive disorder patients in a current depressive state as well as in remission. First-degree relatives of bipolar disorder patients also showed GRalpha mRNA reduction. Altered GRbeta mRNA expression was not found in mood disorder patients.

CONCLUSIONS

Our results suggest that reduced GRalpha mRNA expression might be trait-dependent and associated with the pathophysiology of mood disorders.

Blood neutrophil activation markers in severe asthma: lack of inhibition by prednisolone therapy

Background

Neutrophils are increased in the airways and in induced sputum of severe asthma patients. We determined the expression of activation markers from circulating neutrophils in severe asthma, and their supressibility by corticosteroids.

Methods

We compared blood neutrophils from mild, moderate-to-severe and severe steroid-dependent asthma, and non-asthmatics (n = 10 each). We examined the effect of adding or increasing oral prednisolone (30 mg/day;1 week).

Results

Flow cytometric expression of CD35 and CD11b, but not of CD62L or CD18, was increased in severe asthma. F-met-leu-phe increased CD11b, CD35 and CD18 and decreased CD62L expression in all groups, with a greater CD35 increase in severe asthma. In severe steroid-dependent asthma, an increase in prednisolone dose had no effect on neutrophil markers particularly CD62L, but reduced CD11b and CD62L on eosinophils. Phorbol myristate acetate-stimulated oxidative burst and IL-8 release by IL-1β, lipopolysaccharide and GM-CSF in whole blood from mild but not severe asthmatics were inhibited after prednisolone. There were no differences in myeloperoxidase or neutrophil elastase release from purified neutrophils.

Conclusion

Because blood neutrophils in severe asthma are activated and are not inhibited by oral corticosteroids, they may be important in the pathogenesis of severe asthma.

CD38 expression is insensitive to steroid action in cells treated with tumor necrosis factor-alpha and interferon-gamma by a mechanism involving the up-regulation of the glucocorticoid receptor beta isoform

Evidence shows that the CD38 molecule, recently involved in the two main features of asthma, bronchial hyper-responsiveness and airway inflammation, could represent a new potential therapeutic target for asthma. In this study, we investigated whether glucocorticoid (GC), the most effective treatment for lung diseases, can affect CD38 expression in human airway smooth muscle (ASM) cells treated with different pro-inflammatory cytokines, such as tumor necrosis factor-alpha (TNFalpha) and interferons (IFNs). We found that CD38 expression induced by TNFalpha alone was completely abrogated by fluticasone (100 nM), dexamethasone (1 microM), or budesonide (100 nM). In contrast, the synergistic induction of CD38 by the combination of TNFalpha with IFNgamma or IFNbeta, but not with IL-1beta or IL-13, was completely insensitive to the GC inhibitory effects. We also found that TNFalpha and IFNgamma impaired GC responsiveness by inhibiting steroid induced both 1) GRalpha-DNA binding activity and 2) GC-responsive element-(GRE)-dependent gene transcription. Although levels of the GC receptor (GR) alpha isoform remained unchanged, expression of GRbeta, the dominant-negative GR isoform, was synergistically increased by TNFalpha and IFNgamma with a GRalpha/GRbeta ratio of 1 to 3. More importantly, fluticasone failed to induce GRE-dependent gene transcription and to suppress TNFalpha-induced CD38 expression in ASM cells transfected with constitutively active GRbeta. We conclude that, upon pro-inflammatory cytokine stimulation, CD38 expression becomes insensitive to GC action by a mechanism involving the up-regulation of GRbeta isoform, thus providing a novel in vitro cellular model to dissect GC resistance in primary cells.

Reversing the defective induction of IL-10-secreting regulatory T cells in glucocorticoid-resistant asthma patients

We previously reported that human CD4+ Tregs secrete high levels of IL-10 when stimulated in the presence of dexamethasone and calcitriol (vitamin D3). We now show that following stimulation by allergen, IL-10-secreting Tregs inhibit cytokine secretion by allergen-specific Th2 cells in an IL-10-dependent manner. A proportion of patients with severe asthma fail to demonstrate clinical improvement upon glucocorticoid therapy, and their asthma is characterized as glucocorticoid resistant (SR, abbreviation derived from "steroid resistant"). Dexamethasone does not enhance secretion of IL-10 by their CD4+ T cells. Addition of vitamin D3 with dexamethasone to cultures of SR CD4+ T cells enhanced IL-10 synthesis to levels observed in cells from glucocorticoid-sensitive patients cultured with dexamethasone alone. Furthermore, pretreatment with IL-10 fully restored IL-10 synthesis in these cells in response to dexamethasone. Vitamin D3 significantly overcame the inhibition of glucocorticoid-receptor expression by dexamethasone while IL-10 upregulated glucocorticoid-receptor expression by CD4+ T cells, suggesting potential mechanisms whereby these treatments may overcome poor glucocorticoid responsiveness. We show here that administration of vitamin D3 to healthy individuals and SR asthmatic patients enhanced subsequent responsiveness to dexamethasone for induction of IL-10. This strongly suggests that vitamin D3 could potentially increase the therapeutic response to glucocorticoids in SR patients.

Increased glucocorticoid receptor beta alters steroid response in glucocorticoid-insensitive asthma

RATIONALE

Glucocorticoids (GCs) are highly effective in the treatment of asthma. However, some individuals have GC-insensitive asthma.

OBJECTIVES

To evaluate the functional response to steroids of bronchoalveolar lavage (BAL) cells from sites of airway inflammation from patients with GC-insensitive versus GC-sensitive asthma. As well, to attempt to define the functional role of glucocorticoid receptor (GCR)beta (a splicing variant, and dominant negative inhibitor of, the classic GCRalpha) in controlling GCRalpha nuclear translocation and transactivation at a molecular level.

METHODS AND MEASUREMENTS

Fiberoptic bronchoscopy with collection of BAL fluid was performed on seven patients with GC-sensitive asthma and eight patients with GC-insensitive asthma. GCRalpha cellular shuttling in response to 10(-6) M dexamethasone treatment and GCRbeta expression were analyzed in BAL cells by immunofluorescence staining. The effects of overexpression and silencing of GCRbeta mRNA on GCRalpha function were assessed.

MAIN RESULTS

Significantly reduced nuclear translocation of GCRalpha in response to steroids was found in BAL cells from patients with GC-insensitive asthma. BAL macrophages from patients with GC-insensitive asthma had significantly increased levels of cytoplasmic and nuclear GCRbeta. It was demonstrated that GCRalpha nuclear translocation and its transactivation properties were proportionately reduced by level of viral transduction of the GCRbeta gene into the DO-11.10 cell line. RNA silencing of GCRbeta mRNA in human BAL macrophages from patients with GC-insensitive asthma resulted in enhanced dexamethasone-induced GCRalpha transactivation.

CONCLUSIONS

GC insensitivity is associated with loss of GCRalpha nuclear translocation in BAL cells and elevated GCRbeta, which may inhibit GCRalpha transactivation in response to steroids.

Glucocorticoid receptor beta in acute and chronic inflammatory conditions: clinical implications

Glucocorticoids (GC) are hormones with a wide variety of actions, including profound anti-inflammatory/immunosuppressive effects. Their actions are mediated by an intracellular receptor called the glucocorticoid receptor (GCR). The classical GCR that mediates the hormone response is called GCR alpha. Recently however, many GCR isotypes have been described. A defective GC action has been proposed as an etio-pathogenic mechanism for the development of inflammatory/autoimmune diseases. Inadequate GC actions may have multiple causes such as: defective hypothalamic-pituitary-adrenal axis function, GC export from cells, hormone metabolization into inactive compounds and modifications of the GC receptor, among others. In 1995, a dominant negative effect of a GC receptor isotype termed beta was described; starting a still unsolved controversy about the role of GCR beta as an inducer of GC resistance in certain pathological conditions. The present article will review the data about a possible role for GCR beta in the development of GC resistance in inflammatory diseases. This review will especially focus on the role of the GCR beta in rheumatoid arthritis and in septic shock as examples of a chronic inflammatory disease and an acute systemic inflammatory condition. Original data supporting possible hyperexpression of GCR beta in both conditions will be shown.

Does pharmacogenetics have the potential to allow the individualisation of immunosuppressive drug dosing in organ transplantation?

The immunosuppressive drugs used in organ transplantation have a narrow therapeutic index, with rejection occurring as a consequence of underdosing and infection, malignancy and a number of drug-specific side effects with excessive dosing. Significant heterogeneity in the dose of drug required to achieve therapeutic blood concentrations adds to the complexity of the problem, which has been partly resolved by therapeutic drug monitoring. Single nucleotide polymorphisms have been identified in genes encoding metabolic enzymes, drug efflux pumps and drug targets for most of the drugs in widespread use. A pharmacogenetic approach to immunosuppressive drug prescribing remains to be tested. Based on current evidence, the most promising strategy would be use of the cytochrome P450 3A5 expressor genotype to guide initial dosing with tacrolimus.

Impact of smoking on asthma therapy: a critical review of clinical evidence

Airway inflammation is central to the pathophysiology of asthma, with treatment directed towards modification of this inflammation and its consequences. The relationship between cigarette smoking and airway inflammation is also well described, but relatively little data are available on the potential influence of smoking on asthmatic airway inflammation and its treatment. While cigarette smoking is common in people with asthma, with prevalence rates similar to the general population, studies in asthma have tended to concentrate on individuals who have never smoked. However, there is recent evidence that smoking may confer a degree of corticosteroid resistance in asthma, and this review examines the relationship between asthma and cigarette smoking, with particular reference to the impact of smoking on the response to treatment of asthma. Smoking has a number of known influences on drug activity and metabolism, but the mechanism underlying corticosteroid resistance in asthmatic smokers is not yet clear, although there are differences in the nature of the airway inflammation in individuals with asthma who smoke compared with nonsmoking asthmatic patients. Encouragingly, there is some evidence that smoking cessation may at least partially restore corticosteroid responsiveness in asthmatic ex-smokers. Smoking cessation measures must be given a high priority in individuals with asthma who smoke.

High levels of glucocorticoid receptors in patients with active Crohn's disease may predict steroid resistance

Up to 20% of Crohn's disease (CD) patients respond poorly to glucocorticoids (GC). A product of an alternative splicing of the glucocorticoid receptor (GR) premRNA, GRbeta, may play a role as a dominant inhibitor of the glucocorticoid response. Increasing evidence suggests that inflammatory cytokines such as interleukin (IL)-18 alternate the splicing of the primary transcript between the two isoforms GRbeta and GRalpha in hGR gene of CD patients. The aim of this study is to assess the expression of GRalpha and GRbeta in patients with CD and to look for a possible correlation between these receptors and the response to glucocorticoid treatment. Forty-two CD patients and 17 healthy volunteers were studied. Quantitative reverse transcription-polymerase chain reaction (RT-PCR) was performed using real-time PCR techniques. Serum IL-18 protein levels were measured by enzyme-linked immunosorbent assay (ELISA). The amount of hGRalpha-mRNA in patients in remission was significantly lower than in controls (P < 0.05). The amount of hGRbeta-mRNA was significantly higher in GC-resistant patients in the active stage of disease compared with all other groups (P < 0.05). Patients in the active stage of the disease had higher levels of IL-18 than patients in remission and both had higher levels than controls (P < 0.05). The amounts of IL-18 were directly correlated with the amount of hGRbeta mRNA in GC-resistant patients with an active disease. High levels of hGRbeta might be connected to GC resistance. IL-18 might participate in the alternative splicing of the hGR preliminary mRNA of CD patients. The results support the theory that augmented hGRbeta mRNA expression level in PBMC is connected with GC-resistance of CD patients.

Glucocorticoids and inflammation revisited: the state of the art. NIH clinical staff conference

Glucocorticoids have been used in the treatment of inflammatory and autoimmune diseases and to prevent graft rejection for over 50 years. These hormones exert their effects through cytoplasmic, heat shock protein-bound glucocorticoid receptors that translocate into the nucleus, where they regulate the transcriptional activity of responsive genes by binding to specific promoter DNA sequences (transactivation) or by interacting with transcription factors (transrepression). By interacting with different signaling pathways, newly characterized nuclear receptor coregulators enhance or diminish the actions of glucocorticoids, thus explaining the gene-, cell-, tissue- and context-dependent actions of glucocorticoids. Glucocorticoids modulate genes involved in the priming of the innate immune response, while their actions on the adaptive immune response are to suppress cellular [T helper (Th)1-directed] immunity and promote humoral (Th2-directed) immunity and tolerance. The past decade has produced new insights into the mechanisms of glucocorticoid sensitivity and resistance of inflammatory, autoimmune and allergic diseases. Both the quality and severity of the inflammatory stimulus, as well as the genetics and constitution of the patient, play key roles in the glucocorticoid sensitivity, dependency and resistance of these diseases. Although glucocorticoids increase susceptibility to opportunistic infections, they are also highly beneficial in the presence of serious systemic inflammation, such as that observed in septic shock and acute respiratory distress syndrome, when administered in a sustained fashion throughout the course of the disease. Glucocorticoids produce their cardiovascular, metabolic and antigrowth side effects through molecular mechanisms distinct from those involved in immunomodulation. Fortunately, the first generation of tissue- and immune- versus cardiovascular/metabolic effect-selective glucocorticoids is available for study and further improvement. 'Designer' glucocorticoids promise to be a great new advance in the therapy of inflammatory diseases.

Severe Asthma in Adults

Severe asthma remains poorly understood and frustrating to care for, partly because it is a heterogeneous disease. Patients with severe asthma disproportionately consume health care resources related to asthma. Severe asthma may develop over time, or shortly after onset of the disease. The genetic and environmental elements that may be most important in the development of severe disease are poorly understood, but likely include both allergic and nonallergic elements. Physiologically, these patients often have air trapping, airway collapsibility, and a high degree of methacholine hyperresponsiveness. Specific phenotypes of severe asthma are only beginning to be defined. However, describing severe asthma by age at onset (early- vs. late-onset) appears to describe two phenotypes that differ at immunologic, physiologic, epidemiologic, and pathologic levels. In particular, early-onset severe asthma is a more allergic-associated disease than late-onset severe asthma. In addition, patients with severe asthma can be defined on the basis of presence and type of inflammation. Severe asthma with persistent eosinophilia (of either early or late onset) is more symptomatic and has more near-fatal events. However, at least 50% of patients with severe asthma have very little identifiable inflammation. Thus, "steroid resistance" may occur at numerous levels, not all of which are caused by a lack of effect of steroids on inflammation. Treatment remains problematic, with corticosteroids remaining the most effective therapy. However, 5-lipoxygenase inhibitors, anti-IgE, and immunomodulatory drugs are also likely to have a place in treatment. Improving therapy in this disease will require a better understanding of the phenotypes involved.

The influence of smoking on the treatment response in patients with asthma

PURPOSE OF REVIEW

Cigarette smoking and asthma are associated with poor symptom control and impaired therapeutic responses to corticosteroids. We summarize the clinical evidence for corticosteroid resistance, the mechanisms which could be responsible and potential management of this resistance. We also consider the effect smoking has on other drugs commonly used to treat patients with asthma.

RECENT FINDINGS

In most developed countries the prevalence of active smoking in adults with asthma is about 25%. Compared with nonsmokers with asthma, active smokers have more severe asthma symptoms, accelerated decline in lung function and impaired short-term therapeutic responses to corticosteroids. The mechanism of corticosteroid resistance in smokers with asthma is currently unexplained but could be due to alterations in airway inflammatory cell phenotypes, changes in glucocorticoid receptor alpha to beta ratio, and reduced histone deacetylase activity. Cigarette smoking also increases the clearance of drugs such as theophylline by induction of metabolizing enzymes. Alternative or additional treatment to inhaled corticosteroids may be required for individuals with asthma who are unable to stop smoking or who have persistent symptoms following smoking cessation.

SUMMARY

Smokers with chronic asthma have a reduced response to short-term corticosteroid therapy. Every effort should be made to encourage individuals with asthma who smoke to stop. Alternative or additional therapies to inhaled corticosteroids are needed for individuals with asthma who are unable to quit smoking.

Pathophysiological effects of glucocorticoids on nasal polyps: an update

PURPOSE OF REVIEW

The exact mechanisms by which glucocorticoids exert their beneficial effects on nasal polyps are not clearly defined. Nasal polyps, asthma and allergic rhinitis share common features such as mucosal infiltration with eosinophils and mast cells as well as local IgE production. The present review is an update on the pathophysiological mechanisms of glucocorticoids on nasal polyps described during the last 2 years.

RECENT FINDINGS

The reduction of leukocyte numbers in nasal polyps following glucocorticoid treatment depends on several mechanisms, for example altered balance between the two isoforms of the human glucocorticoid receptors, GRalpha and GRbeta. Another explanation may be inhibition of CD4+ T by CD8+ T cells. Increased expression of the antiinflammatory cytokine transforming growth factor beta may contribute to this. A DNA microarray study which examined the expression of some 22 000 genes showed increased expression of several antiinflammatory genes in nasal polyps after treatment with glucocorticoids. The antiinflammatory gene that increased most was uteroglobin (also known as Clara cell protein 16) which is abundantly expressed in airway secretions and thought to have an important role in regulating inflammation.

SUMMARY

Glucocorticoids affect both pro and antiinflammatory pathways in nasal polyps. Upregulation of antiinflammatory genes such as transforming growth factor beta and uteroglobin may play an important role. Elucidation of these mechanisms may help us to understand not only the effects of glucocorticoids on nasal polyps, but also on related disorders such as allergic rhinitis and asthma.

The human glucocorticoid receptor (GR) isoform {beta} differentially suppresses GR{alpha}-induced transactivation stimulated by synthetic glucocorticoids

The beta-isoform of human glucocorticoid receptor beta (hGRbeta) acts as a natural dominant negative inhibitor of hGRalpha-induced transactivation of glucocorticoid-responsive genes. We determined hGRbeta ability to suppress hGRalpha transactivation that was induced by commonly used synthetic glucocorticoids. HepG2/C3A cells were transiently cotransfected with GR cDNA and a glucocorticoid-responsive promoter, luciferase (MMTV-luc). Transfected cells were incubated for 16 h with glucocorticoid and luciferase. For each compound, a dose-response curve was constructed, and half-maximal effective concentrations and maximal transcriptional activities were compared. hGRbeta, at a 1:1 ratio to hGRalpha, differentially suppressed hGRalpha-induced maximal transcriptional activity stimulated by triamcinolone, dexamethasone, hydrocortisone, and betamethasone (by 96, 68, 62, and 49%, respectively) but not by methylprednisolone. The suppressive effect of hGRbeta on hGRalpha-induced transactivation was stronger at lower concentrations of all tested glucocorticoids, whereas it was blunted at higher concentrations. We conclude that the potency of the dominant negative effect of hGRbeta on hGRalpha-induced transactivation depends on both the type and the dose of the synthetic glucocorticoids in use. These results may provide helpful information concerning the selection of synthetic glucocorticoids for treatment of pathological conditions in which hGRbeta modulates the sensitivity of tissues to glucocorticoids.

Increased expression of glucocorticoid receptor beta messenger RNA in patients with ankylosing spondylitis

BACKGROUND

Glucocorticoids have been known to be less effective for treating ankylosing spondylitis (AS) patients than for treating rheumatoid arthritis (RA) patients. To elucidate the mechanisms underlying this phenomenon, we evaluated whether the glucocorticoid receptor (GR) beta expression of the peripheral blood mononuclear cells (PBMCs) in patients with AS is increased compared with patients with RA.

METHODS

PBMCs were isolated from the subjects of 3 study groups: the healthy controls (n=25), the RA patients (n=25), and the AS patients (n=25). All the subjects had never taken corticosteroids and the patients with RA or AS were newly diagnosed. The expression of GR beta messenger RNA (mRNA) was determined by reverse transcription of the total RNA, and this was followed by semi-quantitative polymerase chain reaction analysis (RT-PCR).

RESULTS

The level of GR alpha mRNA expression was not different among three groups. GR beta mRNA expression of the AS patients (2.02 [range: 0.99-7.21], median [25th-75th percentiles]) was enhanced compared with that of the controls (0.78 [range: 0.43-1.62]) and the RA patients (0.98 [range: 0.79-1.18]). The level of GR beta mRNA expression was not related to the inflammatory markers or the disease activity score 28 for the RA patients, and it was not related to the Bath ankylosing spondylitis disease activity index for the AS patients.

CONCLUSION

The expression of GR beta mRNA, which is a dominant negative regulator for the glucocorticoid response, was increased in AS patients. The results suggest that the increased expression of GR beta mRNA may be related to the ineffectiveness of glucocorticoids for the treatment of AS.

Repeated intraarticular injections of triamcinolone acetonide alter cartilage matrix metabolism measured by biomarkers in synovial fluid

Although intraarticular (IA) corticosteroids are frequently used to treat joint disease, the effects of their repeated use on articular cartilage remains controversial. The aim of our study was to determine the effects of a clinically recommended dose of IA triamcinolone acetonide (TA), on synovial fluid (SF) biomarkers of cartilage metabolism. Ten adult horses, free of osteoarthritis (OA) in their radiocarpal joints, were studied. One radiocarpal joint of each horse was randomly chosen for treatment and the contralateral anatomically paired joint acted as the control. Aseptic arthrocentesis was performed weekly on both joints for 13 weeks. The initial results from the first 3 weeks of the experimental period established baseline untreated control marker levels for each joint, each being its own control. On weeks 3, 5, and 7, a sterile suspension of 12 mg of TA was injected into the treated joint and an equivalent volume of sterile saline solution (0.9%) was injected into the control joint. SF was immunoassayed for biomarkers of aggrecan turnover (CS 846 & KS), types I and II collagen cleavage (C1,2C) and type II collagen synthesis (CPII). In treated joints, there was a significant increase in CS 846, KS, C1,2C and CPII epitope concentrations following IA TA injections when compared to baseline levels. There was also a significant increase in C1,2C and CPII epitope concentrations in the contralateral control joints following IA TA injections in the treated joint. Significant differences were observed between treated and control joints for all markers except CPII. These findings indicate that TA alters articular cartilage and collagen metabolism in treated and, interestingly, also in control joints, suggesting a systemic effect of the drug. Though intuitively the observed findings would favor the hypothesis that long-term IA TA treatment changes joint metabolism and this may have detrimental effects; further studies would be necessary to confirm this.

Asthma and COPD: differences and similarities. With special reference to the usefulness of budesonide/formoterol in a single inhaler (Symbicort) in both diseases

Asthma and chronic obstructive pulmonary disease (COPD) both have a high prevalence worldwide and yet each condition remains underdiagnosed. Despite a number of common features, these inflammatory respiratory syndromes have distinct clinical outcomes. COPD represents a greater economic burden than asthma because it has a less favourable prognosis and is associated with greater morbidity and mortality. Therefore, it is important to distinguish between these two diseases at an early stage, so that appropriate therapy can be prescribed to prevent deterioration. However, effective treatments that may be used in both conditions can minimise the effects of misdiagnosis and maximise the impact of treatment without the associated complexity when both conditions occur together. The current review summarises the differences and similarities of asthma and COPD, in terms of risk factors, pathophysiology, symptoms and diagnosis, to provide greater understanding of the role of budesonide/formoterol in a single inhaler in both diseases.

Significance of glucocorticoid receptor expression in colonic mucosal cells of patients with ulcerative colitis

AIM: Glucocorticoid (GC) resistant ulcerative colitis (UC) remains a serious disease and is difficult to manage. Although the molecular basis of GC insensitivity is still unknown, GC receptors (GRα and GRβ) may play an important role in it. This study was aimed to investigate the relationship between the expression of GRα and GRβ in colonic mucosal cells of patients with UC, the efficacy of GC therapy and the intensity of inflammation.

METHODS: Twenty-five cases of UC were classified into: GC sensitive (n = 16) and GC resistant (n = 9) cases. Patients consisted of mild (n = 6), moderate (n = 8) and severe (n = 11) cases. GRα and GRβ expression in colonic mucosal specimens were investigated by immunohistochemistry, and compared between GC resistant and sensitive groups, and also among various degrees of inflammation.

RESULTS: All cases were positive for GRα and GRβ expression. Both positive association between GRα expression and the response of UC to GC and strong negative association between GRβ expression and the response of UC to GC were identified. There was no significant association between GRα/GRβ expression and the degree of inflammation of UC.

CONCLUSION: These findings suggest that both GRα and GRβ may play an important role in the action of GC, and that GRβ functions as a dominant negative inhibitor of GRα. Expression of GRα and GRβ in colonic mucosal cells of patients with UC may serve as predictors of glucocorticoid response, but can not function as markers of inflammatory intensity.

Oral corticosteroids decrease eosinophil and CC chemokine expression but increase neutrophil, IL-8, and IFN-gamma-inducible protein 10 expression in asthmatic airway mucosa

BACKGROUND

Cytokines and chemokines have been implicated in the pathogenesis of asthma. Inhaled corticosteroids have been shown to decrease the number of eosinophils and to downregulate T H 2 cytokines but to increase neutrophils. The effect of corticosteroids on chemokine expression in asthma has not yet been investigated.

OBJECTIVE

We sought to investigate the effect of a 2-week course of oral corticosteroid (methylprednisolone, 40 mg/d) on the expression of CXC chemokines (IL-8 and IFN-gamma-inducible protein 10 [IP-10]) and CC chemokines (eotaxin and monocyte chemotactic proteins [MCPs] 1-4) in endoscopic biopsy specimens of 13 patients with moderate-to-severe asthma.

METHODS

CD3, major basic protein, and elastase immunoreactivities were monitored before and after treatment by using immunocytochemistry. Eotaxin, IL-8, IP-10, MCP-1, MCP-2, MCP-3, and MCP-4 mRNA expression in epithelium and submucosa were studied by using in situ hybridization.

RESULTS

Corticosteroids reduced the number of CD3-positive T cells and major basic protein-positive eosinophils ( P < .05), whereas the number of neutrophils were increased ( P < .05). Corticosteroids also reduced the number of eotaxin ( P < .05), MCP-3, and MCP-4 mRNA-positive cells ( P < .001) in the epithelium and subepithelium. However, corticosteroids caused a significant increase in the epithelial expression of IL-8 ( P < .001), IP-10 ( P < .05), and MCP-2 mRNAs ( P < .01). Corticosteroids had no effects on MCP-1 mRNA expression.

CONCLUSION

Our results demonstrate the dual nature of corticosteroids. Although corticosteroids can downregulate the expression of some asthma-associated chemokines, such as eotaxin, MCP-3, and MCP-4, they can also upregulate the expression of other chemokines, including IL-8, IP-10, and MCP-2. The failure of oral corticosteroids to inhibit IL-8 mRNA expression might contribute to persistent airway neutrophilia observed in patients with moderate-to-severe asthma, despite treatment with corticosteroids.

Potential genetic influences on the response to asthma treatment

Genetic factors play a key role in determining the widely heterogeneous response to pharmacological treatment detectable among asthmatics. In particular, polymorphisms of the genes encoding relevant anti-asthma drug targets contribute significantly to such a variability. Therefore, it is very important to characterize asthmatic patient's genotypes and the related phenotypic patterns, in order to predict the individual therapeutic outcome. This pharmacogenetic approach will eventually help clinicians to optimize and personalize anti-asthma treatment, and will also provide useful information with regard to pre- and post-marketing evaluation of both effectiveness and side effects of newly introduced drugs.

Can we alter the natural history of Crohn disease in children?

The natural history of Crohn disease is characterized by recurrent bouts of active disease, the consequences of which can severely impair sufferers' physical and social functioning. Not only does the illness cause day-to-day morbidity for children but the consequence of the chronic inflammatory process also commonly results in the need for major intestinal surgery. The present challenge facing physicians treating children with Crohn disease is to alleviate symptoms and prolong periods of remission via the use of specifically targeted therapies while minimizing toxicity and promoting normal growth and development. Although systemic corticosteroids are effective in inducing clinical remission, they are of little or no benefit in maintaining remission and can contribute to linear growth retardation. Immunomodulating drugs such as azathioprine, 6-mercaptopurine and methotrexate have proved effective for inducing and maintaining remission of active Crohn disease. These agents are now commonly prescribed in children at diagnosis, after a severe attack or after surgery or in those who become corticosteroid-dependent or corticosteroid-resistant. Their use is not without potential adverse effects and not all patients respond well to these agents. With the introduction of biologic agents, notably the tumor necrosis factor-alpha monoclonal antibody infliximab, progress has been made in targeting specific pathogenetic mechanisms of Crohn disease and potentially altering the underlying disease process. Published experience in children is currently limited, but infliximab has been shown to improve symptoms and achieve corticosteroid independence in this age group. Unresolved issues with infliximab and other emerging biologic agents, including long-term safety, necessitate a degree of caution in selecting appropriate patients for treatment and with careful monitoring of their effects. The collection of contemporary natural history data is crucial to facilitate the better integration of current and emerging therapies in an attempt to alter the natural history of Crohn disease in children.

Anti-interleukin-4 therapy

Interleukin 4 (IL-4) mediates important pro-inflammatory functions in asthma, including T helper cell type 2 lymphocyte differentiation, induction of IgE production, up-regulation of IgE receptors, expression of vascular cell-adhesion molecule 1, promotion of eosinophil transmigration into the lungs, inhibition of T-lymphocyte apoptosis, and mucus hypersecretion. The role of IL-4 in the pathogenesis of asthma is supported by identification of polymorphisms linked to asthma in the IL-4 gene promoter and proteins involved in IL-4 signaling. Several approaches to IL-4 antagonism are or have been in clinical development. This article examines IL-4 and the antagonists that have been developed. Early trial results and the future of anti-IL-4 therapy are discussed.

Dexamethasone resistance in B-cell precursor childhood acute lymphoblastic leukemia occurs downstream of ligand-induced nuclear translocation of the glucocorticoid receptor

Glucocorticoids are among the most effective agents used in the treatment of childhood acute lymphoblastic leukemia (ALL), and patient response to treatment is an important determinant of long-term outcome. Despite its clinical significance, the molecular basis of glucocorticoid resistance in lymphoid malignancies is still poorly understood. We have recently developed a highly clinically relevant experimental model of childhood ALL, in which primary childhood ALL biopsies were established as xenografts in nonobese diabetic/severe combined immunodeficient (NOD/SCID) mice. The in vivo and in vitro responses of a panel of these xenografts to the glucocorticoid, dexamethasone, reflected the outcome of the patients from whom they were derived. In this report we show that glucocorticoid resistance in B-cell precursor (BCP) ALL xenografts was not due to down-regulation of the glucocorticoid receptor (GR) nor to defective ligand binding of the GR. Moreover, dexamethasone-induced GR translocation from the cytoplasm to the nucleus was comparable in all xenografts. However, glucocorticoid resistance was associated with profoundly attenuated induction of the BH3-only proapoptotic protein, Bim, when xenograft cells were exposed to dexamethasone. These results show that dexamethasone resistance in BCP ALL xenografts occurs downstream of ligand-induced nuclear translocation of the GR, but upstream of Bim induction.

Mechanisms of glucocorticoid receptor signaling during inflammation

Glucocorticoids are among the most widely prescribed anti-inflammatory drugs. They act by binding to the glucocorticoid receptor (GR) that, upon activation, translocates to the nucleus and either stimulates or inhibits gene expression. GR inhibition of many proinflammatory response genes occurs through induction of the synthesis of anti-inflammatory proteins as well as through repression of proinflammatory transcription factors, such as nuclear factor-kappaB (NF-kappaB) or activator protein-1 (AP-1). In this review, we discuss the molecular mechanisms underlying GR inhibition of inflammatory responses, with an emphasis on repression of NF-kappaB and AP-1 and their respective signaling pathways.

Glucocorticoid receptors in human airways

Inhaled and intranasal glucocorticoids are the most common and effective drugs for controlling symptoms and airway inflammation in respiratory diseases such as asthma, allergic rhinitis, and nasal polyposis. The last few years have seen a growing understanding of the mechanisms of glucocorticoid action and, in particular, the receptor that mediates glucocorticoid actions, the glucocorticoid receptor (GR). In this revision we present an update on the GR gene, the expression and regulation of its gene products, namely GRalpha and GRbeta, as well as their alterations in pathological states. GRalpha is responsible for the induction and repression of target genes, it is expressed in virtually all human cells and tissues, and its expression is known to be downregulated by glucocorticoids. GRbeta has been found to act as a dominant negative inhibitor of GRalpha-mediated transactivation in in vitro studies with transfected cells, but it does not appear to have a significant inhibitory effect on GRalpha-mediated transrepression. In addition, for most tissues the expression of GRbeta, at least at the mRNA level, is extremely low compared with that of GRalpha. Some pro-inflammatory cytokines appear to upregulate the expression of GRbeta, and increased GRbeta expression has been reported in diseases associated with glucocorticoid resistance or insensitivity, such as bronchial asthma, nasal polyposis, and ulcerative colitis. However, the possible role of GRbeta in modulating glucocorticoid sensitivity and/or resistance in vivo has been highly debated and it is not yet clear.

Expression of glucocorticoid receptors alpha and beta in steroid sensitive and steroid insensitive interstitial lung diseases

BACKGROUND

Sensitivity to glucocorticoids may be related to the concentration of glucocorticoid receptors alpha (GRalpha) and beta (GRbeta). A study was undertaken to assess GRalpha and GRbeta expression in steroid insensitive interstitial lung disease (idiopathic pulmonary fibrosis (IPF)) and steroid sensitive interstitial lung diseases (sarcoidosis and cryptogenic organising pneumonia (COP)).

METHODS

Lung tissue was obtained from control subjects and from patients with IPF, sarcoidosis, and COP. Pulmonary function tests were carried out at the time of lung biopsy and every 3 months. GRalpha and GRbeta expression was evaluated by both competitive RT-PCR and immunohistochemistry. Data are presented as median and 25-75th percentile.

RESULTS

GRalpha mRNA expression (10(5) cDNA copies/ micro g total RNA) was higher in patients with steroid sensitive interstitial lung diseases (10.0; 7.8-14.9; n = 11) than in patients with IPF (4.4; 3.2-6.6; n = 19; p<0.001). GRbeta expression was at least 1000 times lower than that of GRalpha and did not differ between the three groups. A negative correlation was found between GRalpha mRNA levels and the fibrotic pathology score of the tissue (r = -0.484, p<0.01) and a positive correlation was found between GRalpha mRNA levels and improvement in forced vital capacity (r = 0.633; p<0.01) after treatment of patients with glucocorticoids. Immunoreactivity for GR protein was also higher in patients with sarcoidosis and COP than in those with IPF.

CONCLUSION

The variable response of some interstitial lung diseases to steroid treatment may be the result of differences in the expression of GRalpha.

Glucocorticoid Receptor Isoforms α and β inin VitroCytokine-induced Glucocorticoid Insensitivity

We stimulated peripheral blood mononuclear cells from 14 healthy subjects, 14 patients with stable asthma, and 13 patients with unstable asthma with interleukin (IL)-2 and IL-4 to induce glucocorticoid insensitivity and we examined the relationship between insensitivity and the expression of glucocorticoid receptor (GR) isoforms. Results are expressed as IC(50) (nanomolar) values (means +/- SD) in proliferation assays and as 10(3) cDNA molecules per microgram of total RNA (means +/- SD) in real-time polymerase chain reaction analysis. Cells from patients with unstable asthma were less sensitive (316 +/- 7 nM) to dexamethasone antiproliferative effects than those from healthy control subjects (102 +/- 4 nM, p < 0.05) and patients with stable asthma (107 +/- 2 nM, p < 0.05). Coincubation with IL-2 and IL-4 repressed the inhibitory effect of dexamethasone on proliferation in all groups (unstable: 851 +/- 47 nM, p < 0.01; stable: 912 +/- 52 nM, p = 0.001; control subjects: 537 +/- 45 nM, p = 0.001). GR-alpha mRNA baseline expression was higher in patients with unstable asthma [(1.95 +/- 0.40) x 10(3) cDNA molecules/microg total RNA, p < 0.05] than in patients with stable asthma [(1.46 +/- 0.35) x 10(3) cDNA molecules/microg total RNA] and healthy subjects [(1.35 +/- 0.25) x 10(3) cDNA molecules/microg total RNA]. GR-beta mRNA was 600 times lower than GR-alpha in the three groups. Coincubation with IL-2 and IL-4 significantly increased GR-alpha mRNA expression in the three groups (p < 0.01), but caused no significant change in GR-beta mRNA. GR-alpha, but not GR-beta, protein was detected at baseline and after cytokine exposure. Our data do not support the hypothesis that increased GR-beta expression can contribute to cytokine-induced glucocorticoid insensitivity.

Familial/sporadic glucocorticoid resistance: clinical phenotype and molecular mechanisms

Glucocorticoids regulate a variety of biologic processes and exert profound influences on many physiologic functions. Their actions are mediated by the glucocorticoid receptor (GR), which belongs to the nuclear receptor family of ligand-dependent transcription factors. Alterations in tissue sensitivity to glucocorticoids may manifest as states of resistance or hypersensitivity. Glucocorticoid resistance is a rare, familial or sporadic, condition characterized by generalized, partial target-tissue resistance to glucocorticoids. Compensatory elevations in circulating adrenocorticotropic hormone (ACTH) concentrations lead to increased production of adrenal steroids with mineralocorticoid and/or androgenic activity and their corresponding clinical manifestations, as well as increased urinary free-cortisol excretion in the absence of symptomatology suggestive of hypercortisolism. The molecular basis of the condition has been ascribed to mutations in the GR gene, which impair normal glucocorticoid signal transduction, altering tissue sensitivity to glucocorticoids. The present review focuses on the mechanisms of GR action and the clinical manifestations and molecular mechanisms of familial/sporadic glucocorticoid resistance.

Novel repression of the glucocorticoid receptor by anthrax lethal toxin

Death from anthrax has been reported to occur from systemic shock. The lethal toxin (LeTx) is the major effector of anthrax mortality. Although the mechanism of entry of this toxin into cells is well understood, its actions once inside the cell are not as well understood. LeTx is known to cleave and inactivate MAPKKs. We have recently shown that LeTx represses the glucocorticoid receptor (GR) both in vitro and in vivo. This repression is partial and specific, repressing the glucocorticoid, progesterone, and estrogen receptor alpha, but not the mineralocorticoid or estrogen receptor beta. This toxin does not affect GR ligand or DNA binding, and we have suggested that it may function by removing/inactivating one or more of the many cofactors involved in nuclear hormone receptor signaling. Although the precise involvement of this nuclear hormone receptor repression in LeTx toxicity is unknown, examples of blunted HPA axis and glucocorticoid signaling in numerous autoimmune/inflammatory diseases suggest that such repression of critically important receptors could have deleterious effects on health.

Microbial superantigens induce glucocorticoid receptor beta and steroid resistance in a nasal explant model

OBJECTIVE

To study the role of superantigen (SAg) in inducing glucocorticoid (GC) receptor beta and steroid resistance in an explant model of nasal tissue.

METHODS

Nasal tissue was obtained from inferior turbinates of controls and ragweed (RW)-sensitive patients. Tissue samples were incubated with SAg of staphylococcal enterotoxin B. In addition, tissue samples from RW-sensitive patients were incubated with RW allergen in the presence and absence of both SAg and dexamethasone (DEX). The expression of GC receptor beta was assessed by immunocytochemistry. The expression of interleukin (IL)-2 and IL-4 mRNA was assessed by in situ hybridization.

RESULTS

SAg induced an increase in the expression of GC receptor beta in atopic tissue and to a lesser extent in nonatopic tissue. The most significant induction of GC receptor beta was observed in response to SAg and RW in atopic tissue. Stimulation of atopic tissue with RW alone and SAg alone induced IL-4 and IL-2 mRNA, respectively. Incubation of atopic tissue with both SAg and RW induced both IL-2 and IL-4 mRNA. The increase in IL-4 mRNA expression was blunted by the addition of DEX to atopic tissue stimulated with RW alone but not to tissue stimulated by both RW and SAg.

CONCLUSION

Our results demonstrate that SAgs induce steroid resistance in atopic nasal explant tissue by up-regulating the expression of GC receptor beta. Furthermore, we have shown that the up-regulation of GC receptor beta is a local event that is associated with the coexpression of IL-2 and IL-4 mRNA.

Phenotype-specific treatment of difficult asthma in children

Most children with asthma can be treated successfully with low-to-moderate doses of inhaled corticosteroid and long-acting beta-2 agonist. Those that fail to respond are a heterogeneous group. We propose that the nature and type of any steroid-resistant inflammation, the extent of any persistent airflow limitation and the extent of bronchial hyper-reactivity should be determined separately to allow a rational treatment approach to these children, rather than the haphazard advice of many current guidelines. Reasons for persistent difficult asthma include persistent eosinophilic inflammation, non-eosinophilic inflammation, airway reactivity without residual inflammation and persistent airflow limitation. We propose a protocol that uses non-invasive and invasive (bronchoscopic) methods to document the response to systemic steroids (depot triamcinolone). The aim of the protocol is to determine an individualised treatment plan; for example, cyclosporin for persistent eosinophilic inflammation, azithromycin for persistent neutrophilic inflammation and continuous subcutaneous terbutaline if there is airway reactivity without residual inflammation. Multi-centre studies are required to test the utility of this approach.

Mechanisms of severe asthma

The mechanisms behind the development of severe asthma are poorly understood. However, these patients disproportionately consume healthcare resources related to asthma. Severe asthma may develop over time, or may develop shortly after onset of the disease. The genetic and environmental elements that may be most important in the development of severe disease are poorly understood. Physiologically, these patients often have air trapping and airway collapsibility. The pathology demonstrates a heterogeneity of findings, including continued eosinophilic inflammation, an apparently different pathology, structural changes likely to be remodelling related, and predominant distal disease. Treatment remains problematic and likely will remain so until a better understanding of this disease develops.

The glucocorticoid receptor and the orphan nuclear receptor chicken ovalbumin upstream promoter-transcription factor II interact with and mutually affect each other's transcriptional activities: implications for intermediary metabolism

Glucocorticoids exert their metabolic effect via their intracellular receptor, the glucocorticoid receptor (GR). In a yeast two-hybrid screening, we found the chicken ovalbumin upstream promoter transcription factor II (COUP-TFII), an orphan nuclear receptor that plays important roles in glucose, cholesterol, and xenobiotic metabolism, as a partner of GR. In an in vitro glutathione-S-transferase pull-down assay, COUP-TFII interacted via its DNA-binding domain with the hinge regions of both GRalpha and its splicing variant GRbeta, whereas COUP-TFII formed a complex with GRalpha, but not with GRbeta, in an in vivo chromatin immunoprecipitation and a regular immunoprecipitation assay. Accordingly, GRalpha, but not GRbeta, enhanced COUP-TFII-induced transactivation of the simple COUP-TFII-responsive 7alpha-hydroxylase promoter through the transcriptional activity of its activation function-1 domain, whereas COUP-TFII repressed GRalpha-induced transactivation of the glucocorticoid-responsive promoter by attracting the silencing mediator for retinoid and thyroid hormone receptors. Importantly, mutual protein-protein interaction of GRalpha and COUP-TFII was necessary for glucocorticoid-induced enhancement of the promoter activity and the endogenous mRNA expression of the COUP-TFII-responsive phosphoenolpyruvate carboxykinase, the rate-limiting enzyme of hepatic gluconeogenesis. We suggest that COUP-TFII may participate in some of the metabolic effects of glucocorticoids through direct interactions with GRalpha. These interactions influence the transcription of both COUP-TFII- and GRalpha-responsive target genes, seem to be promoter specific, and can be in either a positive or negative direction.

Glucocorticoid receptor alpha, beta and gamma expression vs in vitro glucocorticod resistance in childhood leukemia

Alternative splicing of the primary glucocorticoid receptor (GR) transcript, resulting in glucocorticoid receptor alpha GRalpha, glucocorticoid receptor beta GRbeta and glucocorticoid receptor gamma GRgamma, may influence glucocorticoid (GC) resistance in childhood leukemia. To test this hypothesis, we determined GRalpha/beta protein and GRalpha/beta/gamma mRNA expression levels in 43 initial acute lymphoblastic leukemia (iALL), 10 initial myeloid leukemia (iAML), 11 relapsed ALL (rALL) samples and one rAML sample. The results were correlated with in vitro GC resistance. GRalpha mRNA correlated with protein expression (rho=0.39-0.56, P<0.05), but the protein to mRNA ratio was median 2.2-fold lower in rALL than in iALL (P<0.05). GRbeta mRNA was median 137-fold lower than GRalpha mRNA and correlated with GRalpha mRNA expression (rho=0.71, P<0.0001). GRbeta could not be detected at the protein level. GRgamma accounted for a median of 2.8% (range 0.95-7.4%) of all GR transcripts. GRalpha (protein and mRNA) and GRbeta (mRNA) expressions or GRalpha/GRbeta ratios did not correlate with in vitro GC resistance in iALL, but GRgamma (mRNA) did (rho=0.52, P=0.007). These results suggest that GRbeta is not involved in GC resistance in childhood leukemia. The association between GRgamma expression and in vitro GC resistance in iALL and the decreased protein/mRNA ratio in rALL, a subgroup resistant to GCs, warrants further exploration.

Molecular immunology and immunotherapy for chronic sinusitis

The development of chronic sinusitis is a complex multifactorial process characterized by inflammation of nasal and sinus mucosa. Many studies have shown that the composition of the inflammatory substrate in chronic sinusitis is similar to that seen in allergic rhinitis and in the late-phase response to antigen challenge. Mononuclear cells, consisting of T and B lymphocytes and activated eosinophils, are prominent in the sinus mucosa of patients with chronic sinusitis, especially in atopic patients. Cellular recruitment and activation of the inflammatory infiltrate have been largely attributed to the effects of T(H)2 cytokines (namely interleukin -4, IL-5, IL-13, and granulocyte-macrophage colony-stimulating factor). Current treatment of allergic chronic sinusitis consists of nasal corticosteroids and immunotherapy. A subgroup of steroid-insensitive patients demonstrates an overexpression of a variant of the glucocorticoid receptor (GR). Despite these advances, the management and treatment of chronic sinusitis is often fraught with failures and remains a frustrating task for both physician and patient.

Identification of a novel glucocorticoid receptor mutation in budesonide-resistant human bronchial epithelial cells

We developed a molecular genetic model to investigate glucocorticoid receptor (GR) signaling in human bronchial epithelial cells in response to the therapeutic steroid budesonide. Based on a genetic selection scheme using the human Chago K1 cell line and integrated copies of a glucocorticoid-responsive herpes simplex virus thymidine kinase gene and a green fluorescent protein gene, we isolated five Chago K1 variants that grew in media containing budesonide and ganciclovir. Three spontaneous budesonide-resistant subclones were found to express low levels of GR, whereas two mutants isolated from ethylmethane sulfonate-treated cultures contained normal levels of GR protein. Analysis of the GR coding sequence in the budesonide-resistant subclone Ch-BdE5 identified a novel Val to Met mutation at amino acid position 575 (GRV575M) which caused an 80% decrease in transcriptional regulatory functions with only a minimal effect on ligand binding activity. Homology modeling of the GR structure in this region of the hormone binding domain and molecular dynamic simulations suggested that the GRV575M mutation would have a decreased affinity for the LXXLL motif of p160 coactivators. To test this prediction, we performed transactivation and glutathione-S-transferase pull-down assays using the p160 coactivator glucocorticoid interacting protein 1 (GRIP1)/transcriptional intermediary factor 2 and found that GRV575M transcriptional activity was not enhanced by GRIP1 in transfected cells nor was it able to bind GRIP1 in vitro. Identification of the novel GRV575M variant in human bronchial epithelial cells using a molecular genetic selection scheme suggests that functional assays performed in relevant cell types could identify subtle defects in GR signaling that contribute to reduced steroid sensitivities in vivo.

Neural immune pathways and their connection to inflammatory diseases

Inflammation and inflammatory responses are modulated by a bidirectional communication between the neuroendocrine and immune system. Many lines of research have established the numerous routes by which the immune system and the central nervous system (CNS) communicate. The CNS signals the immune system through hormonal pathways, including the hypothalamic-pituitary-adrenal axis and the hormones of the neuroendocrine stress response, and through neuronal pathways, including the autonomic nervous system. The hypothalamic-pituitary-gonadal axis and sex hormones also have an important immunoregulatory role. The immune system signals the CNS through immune mediators and cytokines that can cross the blood-brain barrier, or signal indirectly through the vagus nerve or second messengers. Neuroendocrine regulation of immune function is essential for survival during stress or infection and to modulate immune responses in inflammatory disease. This review discusses neuroimmune interactions and evidence for the role of such neural immune regulation of inflammation, rather than a discussion of the individual inflammatory mediators, in rheumatoid arthritis.

Very low levels of the glucocorticoid receptor beta isoform in the human hippocampus as shown by Taqman RT-PCR and immunocytochemistry

The hippocampus is an important target for glucocorticoid hormones. Glucocorticoid receptor (GR) mediated feedback in this area is important for control of behavioural adaptation. An alternative splice variant, the GRbeta (GRbeta) isoform, does not bind ligand and has been proposed to inhibit classic GRalpha-mediated transactivation of target genes. Hence, an increased ratio of GRbeta to GRalpha may induce relative corticosteroid-resistance, as e.g. presumed to occur in major depression. To investigate whether GRbeta is involved in the human hippocampus, we studied GRalpha and GRbeta expression levels in postmortem hippocampal tissue of control subjects by quantitative PCR (Taqman RT-PCR) and immunocytochemistry. Taqman RT-PCR demonstrated a very low relative abundance of GRbeta in the human hippocampus (GRalpha:GRbeta ratio approximately 14,500:1). Immunohistochemical analysis confirmed the occurrence of isolated profiles indeed displaying nuclear staining in the main hippocampal subregions. Subsequent double immunofluorescent analysis revealed that >98% of these GRbeta positive cells were double positive for leucocyte common antigen, that identifies exclusively blood-derived cells of haematopoietic origin, including microglia. We conclude that GRbeta is present in very low amounts in the control human hippocampus, and that of these low numbers of cells, notably, almost all are derived from blood which is inevitably present in postmortem tissue. A functionally relevant role for the GRbeta in control of the human hippocampus is therefore not very likely. Whether this is altered in disease conditions awaits further research.

Corticosteroid receptors, 11 beta-hydroxysteroid dehydrogenase, and the heart

Mineralocorticoid and glucocorticoid hormones are known as corticosteroid hormones and are synthesized mainly in the adrenal cortex; however, more recently the enzymes involved in their synthesis have been found in a variety of cells and tissues, including the heart. The effects of these hormones are mediated via both cytoplasmic mineralocorticoid receptors (MRs) and glucocorticoid receptors (GRs), which act as ligand-inducible transcription factors. In addition, rapid, nongenomically mediated effects of these steroids can occur that may be via novel corticosteroid receptors. The lipophilic nature of these hormones allows them to pass freely through the cell membrane, although the intracellular concentration of mineralocorticoids and glucocorticoids is dependent on several cellular factors. The main regulators of intracellular glucocorticoid levels are 11 beta-hydroxysteroid dehydrogenase (11 beta HSD) isoforms. 11 beta HSD1 acts predominantly as a reductase in vivo, facilitating glucocorticoid action by converting circulating receptor-inactive 11-ketoglucocorticoids to active glucocorticoids. In contrast, 11 beta HSD 2 acts exclusively as an 11 beta-dehydrogenase and decreases intracellular glucocorticoids by converting them to their receptor-inactive 11-ketometabolites. Furthermore, P-glycoproteins, by actively pumping steroids out of cells, can selectively decrease steroids and local steroid synthesis can increase steroid concentrations. Receptor concentration, receptor modification, and receptor-protein interactions can also significantly impact on the corticosteroid response. This review details the receptors and possible mechanisms involved in both mediating and modulating corticosteroid responses. In addition, direct effects of corticosteroids on the heart are described including a discussion of the corticosteroid receptors and the mechanisms involved in mediating their effects.

Serine-arginine-rich protein p30 directs alternative splicing of glucocorticoid receptor pre-mRNA to glucocorticoid receptor beta in neutrophils

Glucocorticoid (GC) insensitivity is a major clinical challenge in the treatment of many inflammatory diseases. It has been shown previously that GC insensitivity, in several inflammatory cell types, is due to an overabundance of the beta isoform of the glucocorticoid receptor (GCRbeta) relative to the ligand binding isoform, GCRalpha. GCRbeta functions as a dominant inhibitor of GCRalpha action. A number of GCR isoforms are created from the same pre-mRNA transcript via alternative splicing, and the factor or factors that control alternative splicing of GCR pre-mRNA are of great importance. In the current study, we have identified the predominant alternative splicing factor present in human neutrophils, which is known to be exceptionally GC-insensitive. The predominant alternative splicing factor in neutrophils is SRp30c, which is one of several highly conserved serine-arginine-rich (SR) proteins that are involved in both constitutive and alternative splicing in eukaryotic cells. Inhibition of SRp30c expression with antisense oligonucleotide strongly inhibited expression of GCRbeta and stimulated expression of GCRalpha. Antisense molecules targeted to other SR proteins had no effect. Our data indicate that SRp30c is necessary for alternative splicing of the GCR pre-mRNA to create mRNA encoding GCRbeta.

Molecular origins for the dominant negative function of human glucocorticoid receptor beta

This study molecularly elucidates the basis for the dominant negative mechanism of the glucocorticoid receptor (GR) isoform hGRbeta, whose overexpression is associated with human glucocorticoid resistance. Using a series of truncated hGRalpha mutants and sequential mutagenesis to generate a series of hGRalpha/beta hybrids, we find that the absence of helix 12 is neither necessary nor sufficient for the GR dominant negative phenotype. Moreover, we have localized the dominant negative activity of hGRbeta to two residues and found that nuclear localization, in addition to heterodimerization, is a critical feature of the dominant negative activity. Molecular modeling of wild-type and mutant hGRalpha and hGRbeta provides structural insight and a potential physical explanation for the lack of hormone binding and the dominant negative actions of hGRbeta.

11beta-hydroxysteroid dehydrogenases, cell proliferation and malignancy

The enzymes 11beta-hydroxysteroid dehydrogenase type 1 and 2 (11beta-HSD1 and 2) have well-defined roles in the tissue-specific metabolism of glucocorticoids which underpin key endocrine mechanisms such as adipocyte differentiation (11beta-HSD1) and mineralocorticoid action (11beta-HSD2). However, in recent studies we have shown that the effects of 11beta-HSD1 and 2 are not restricted to distinct tissue-specific hormonal functions. Studies of normal fetal and adult tissues, as well as their tumor equivalents, have shown a further dichotomy in 11beta-HSD expression and activity. Specifically, most normal glucocorticoid receptor (GR)-rich tissues such as adipose tissue, bone, and pituitary cells express 11beta-HSD1, whereas their fetal equivalents and tumors express 11beta-HSD2. We have therefore postulated that the ability of 11beta-HSD1 to generate cortisol acts as an autocrine anti-proliferative, pro-differentiation stimulus in normal adult tissues. In contrast, the cortisol-inactivating properties of 11beta-HSD2 lead to pro-proliferative effects, particularly in tumors. This proposal is supported by experiments in vitro which have demonstrated divergent effects of 11beta-HSD1 and 2 on cell proliferation. Current studies are aimed at (1) characterizing the underlying mechanisms for a "switch" in 11beta-HSD isozyme expression in tumors; (2) defining the molecular targets for glucocorticoids as regulators of cell proliferation; (3) evaluating the potential for targeting glucocorticoid metabolism as therapy for some cancers. These and other issues are discussed in the present review.

Glucocorticoids: new mechanisms and future agents

Glucocorticoids are widely used to treat inflammatory and immune diseases. The most common use of glucocorticoids today is in the treatment of asthma. Inhaled glucocorticoids are first-line treatment in adults and children with persistent asthma, the most common chronic airway inflammatory disease. Our knowledge of how glucocorticoids suppress inflammation is based on recent developments in understanding the fundamental mechanisms of gene transcription, namely recruitment of histone-modifying co-factors. The determination of the crystal structure of the ligand-binding domain of the human glucocorticoid receptor (GR) has advanced our understanding of how ligands interact with GR and provide a glimpse of a future of rational drug design based on "space-filling" structures with dissociated properties. This might have important clinical implications, leading to a better understanding of the inflammatory mechanisms of many diseases and might signal the development of new anti-inflammatory treatments in the future.