Suppression of GATA-3 nuclear import and phosphorylation: a novel mechanism of corticosteroid action in allergic disease

Suplatast tosilate ameliorates airway hyperreactivity and inflammation through inhibition of the GATA‑3/IL‑5 signaling pathway in asthmatic rats

Airway hyperreactivity and inflammation are important factors in the aggravation of lung function. Suplatast tosilate (IPD) is a novel and unique anti‑asthma clinical compound. However, the mechanisms of IPD action in the inhibition of asthma remain to be elucidated. The present study aimed to investigate the role of the GATA binding protein 3 (GATA‑3)/interleukin (IL)‑5 signaling pathway in IPD‑induced inhibition of asthma. Sprague‑Dawley rats were sensitized by intraperitoneal injection with ovalbumin (OVA) to establish an animal model of asthma. IPD was administered continuously (C‑IPD) or at a later stage (L‑IPD). Budesonide (BUD) was used as a positive control. Airway resistance and the expression of genes at the mRNA and protein levels were measured. Morphological changes in lung tissue and the percentage of eosinophils (EOS) in peripheral blood were observed and correlation analysis was performed. The results revealed that sensitization by OVA significantly increased airway resistance and the percentage of EOS in peripheral blood and induced significant inflammatory changes in lung tissue, as demonstrated by thick epithelium, goblet cell hyperplasia and submucosal cell infiltration. In addition, sensitization by OVA was found to markedly upregulate IL‑5 mRNA and protein expression. Airway resistance was found to positively correlate with the expression of IL‑5 in the rat lung tissues. Sensitization by OVA was also observed to markedly enhance GATA‑3 protein expression and GATA‑3 levels were found to positively correlate with airway resistance and IL‑5 levels. Similar to the effect of BUD, treatment with C‑IPD or L‑IPD was found to significantly attenuate OVA‑induced increases in airway resistance and the percentage of EOS in peripheral blood. Notably, treatment with C‑IPD or L‑IPD markedly reduced the OVA-induced expression of IL‑5 and GATA‑3. In the present study, IPD intervention was demonstrated to ameliorate airway hyperreactivity and inflammation and the mechanisms may involve inhibition of the GATA‑3/IL‑5 signaling pathway.

Hormonal contraception and HIV-1 infection: medroxyprogesterone acetate suppresses innate and adaptive immune mechanisms

Recent observational studies indicate an association between the use of hormonal contraceptives and acquisition and transmission of HIV-1. The biological and immunological mechanisms underlying the observed association are unknown. Depot medroxyprogesterone acetate (DMPA) is a progestin-only injectable contraceptive that is commonly used in regions with high HIV-1 prevalence. Here we show that medroxyprogesterone acetate (MPA) suppresses the production of key regulators of cellular and humoral immunity involved in orchestrating the immune response to invading pathogens. MPA inhibited the production of interferon (IFN)-γ, IL-2, IL-4, IL-6, IL-12, TNFα, macrophage inflammatory protein-1α (MIP-1α), and other cytokines and chemokines by peripheral blood cells and activated T cells and reduced the production of IFNα and TNFα by plasmacytoid dendritic cells in response to Toll-like receptor-7, -8, and -9 ligands. Women using DMPA displayed lower levels of IFNα in plasma and genital secretions compared with controls with no hormonal contraception. In addition, MPA prevented the down-regulation of HIV-1 coreceptors CXCR4 and CCR5 on the surface of T cells after activation and increased HIV-1 replication in activated peripheral blood mononuclear cell cultures. The presented results suggest that MPA suppresses both innate and adaptive arms of the immune system resulting in a reduction of host resistance to invading pathogens.

Interleukin-13 signaling and its role in asthma

Asthma affects nearly 300 million people worldwide. The majority respond to inhaled corticosteroid treatment with or without beta-adrenergic agonists. However, a subset of 5 to 10% with severe asthma do not respond optimally to these medications. Different phenotypes of asthma may explain why current therapies show limited benefits in subgroups of patients. Interleukin-13 is implicated as a central regulator in IgE synthesis, mucus hypersecretion, airway hyperresponsiveness, and fibrosis. Promising research suggests that the interleukin-13 pathway may be an important target in the treatment of the different asthma phenotypes.

Corticosteroids: still at the frontline in asthma treatment?

Inhaled corticosteroids (ICS) have led to improved asthma control and reduced asthma mortality in the Western world. ICS are effective in combating T-helper type 2-driven inflammation featuring mast cell and eosinophilic airway infiltration. Their effect on innate immunity-driven neutrophilic inflammation is poor and their ability to prevent airway remodeling and accelerated lung decline is controversial. Although ICS remain pivotal drugs in asthma management, research is needed to find drugs complementary to the combination ICS/long-acting β2-agonist in refractory asthma and perhaps a new class of drugs as a first-line treatment in mild to moderate noneosinophilic asthma.

DUSPs, to MAP kinases and beyond

Phosphatases are important regulators of intracellular signaling events, and their functions have been implicated in many biological processes. Dual-specificity phosphatases (DUSPs), whose family currently contains 25 members, are phosphatases that can dephosphorylate both tyrosine and serine/threonine residues of their substrates. The archetypical DUSP, DUSP1/MKP1, was initially discovered to regulate the activities of MAP kinases by dephosphorylating the TXY motif in the kinase domain. However, although DUSPs were discovered more than a decade ago, only in the past few years have their various functions begun to be described. DUSPs can be categorized based on the presence or absence of a MAP kinase-interacting domain into typical DUSPs and atypical DUSPs, respectively. In this review, we discuss the current understanding of how the activities of typical DUSPs are regulated and how typical DUSPs can regulate the functions of their targets. We also summarize recent findings from several in vivo DUSP-deficient mouse models that studied the involvement of DUSPs during the development and functioning of T cells. Finally, we discuss briefly the potential roles of DUSPs in the regulation of non-MAP kinase targets, as well as in the modulation of tumorigenesis.

Severe asthma: advances in current management and future therapy

Effective treatment of severe asthma is a major unmet need because patients' symptoms are not controlled on maximum treatment with inhaled therapy. Asthma symptoms can be poorly controlled because of poor adherence to controller therapy, and this might be addressed by using combination inhalers that contain a corticosteroid and long-acting β(2)-agonist as reliever therapy in addition to maintenance treatment. New bronchodilators with a longer duration of action are in development, and recent studies have demonstrated the benefit of a long-acting anticholinergic bronchodilator in addition to β(2)-agonists in patients with severe asthma. Anti-IgE therapy is beneficial in selected patients with severe asthma. Several new blockers of specific mediators, including prostaglandin D(2), IL-5, IL-9, and IL-13, are also in clinical trials and might benefit patients with subtypes of severe asthma. Several broad-spectrum anti-inflammatory therapies that target neutrophilic inflammation are in clinical development for the treatment of severe asthma, but adverse effects after oral administration might necessitate inhaled delivery. Macrolides might benefit some patients with infection by atypical bacteria, but recent results are not encouraging, although there could be an effect in patients with predominant neutrophilic asthma. Corticosteroid resistance is a major problem in patients with severe asthma, and several molecular mechanisms have been described that might lead to novel therapeutic approaches, including drugs that could reverse this resistance, such as theophylline and nortriptyline. In selected patients with severe asthma, bronchial thermoplasty might be beneficial, but thus far, clinical studies have not been encouraging. Finally, several subtypes of severe asthma are now recognized, and in the future, it will be necessary to find biomarkers that predict responses to specific forms of therapy.

Asthma phenotypes: the evolution from clinical to molecular approaches

Although asthma has been considered as a single disease for years, recent studies have increasingly focused on its heterogeneity. The characterization of this heterogeneity has promoted the concept that asthma consists of multiple phenotypes or consistent groupings of characteristics. Asthma phenotypes were initially focused on combinations of clinical characteristics, but they are now evolving to link biology to phenotype, often through a statistically based process. Ongoing studies of large-scale, molecularly and genetically focused and extensively clinically characterized cohorts of asthma should enhance our ability to molecularly understand these phenotypes and lead to more targeted and personalized approaches to asthma therapy.

Glucocorticoids inhibit lipopolysaccharide-mediated inflammatory response by downregulating microRNA-155: a novel anti-inflammation mechanism

Glucocorticoids (GCs) are among the most widely used and effective therapies for many chronic inflammatory diseases. Although attempts have been made to identify important protein-coding genes and pathways involved in the anti-inflammatory effect of GCs, knowledge of genomic aberrations associated with noncoding genes, such as micro-RNAs (miRNAs), and their contributions is relatively limited. In this study, a systematic screening of the miRNA expression profile by microarray showed that GCs inhibited the expression of miR-155 in lipopolysaccharide (LPS)-induced macrophage inflammatory responses. Overexpression of miR-155 markedly reversed the suppressive action of GCs, whereas inhibition of miR-155 exhibited an effect similar to that of GCs on LPS-treated RAW264.7 cells, indicating miR-155 to be a functional regulator in the anti-inflammatory effect of GCs. Furthermore, GCs inhibited miR-155 expression in a GC receptor- and NF-κB-dependent manner. Bioinformatics analysis and luciferase assay revealed that the NF-κB binding site located in the promoter region of the B-cell integration cluster was important in mediating the GC-driven suppression of miR-155 in response to LPS stimulation. In addition, the combination of treatment with GCs and inhibition of miR-155 enhanced the anti-inflammatory effect of GCs on LPS-stimulated RAW264.7 cells. Therefore, we identify miR-155 to be a novel target through which GCs exert their anti-inflammatory effect on the LPS-induced macrophage inflammatory response. These findings may provide a basic rationale for new approaches in the effort to develop anti-inflammatory therapeutics.

Compound A, a dissociated glucocorticoid receptor modulator, inhibits T-bet (Th1) and induces GATA-3 (Th2) activity in immune cells

Background

Compound A (CpdA) is a dissociating non-steroidal glucocorticoid receptor (GR) ligand which has anti-inflammatory properties exerted by down-modulating proinflammatory gene expression. By favouring GR monomer formation, CpdA does not enhance glucocorticoid (GC) response element-driven gene expression, resulting in a reduced side effect profile as compared to GCs. Considering the importance of Th1/Th2 balance in the final outcome of immune and inflammatory responses, we analyzed how selective GR modulation differentially regulates the activity of T-bet and GATA-3, master drivers of Th1 and Th2 differentiation, respectively.

Results

Using Western analysis and reporter gene assays, we show in murine T cells that, similar to GCs, CpdA inhibits T-bet activity via a transrepressive mechanism. Different from GCs, CpdA induces GATA-3 activity by p38 MAPK-induction of GATA-3 phosphorylation and nuclear translocation. CpdA effects are reversed by the GR antagonist RU38486, proving the involvement of GR in these actions. ELISA assays demonstrate that modulation of T-bet and GATA-3 impacts on cytokine production shown by a decrease in IFN-γ and an increase in IL-5 production, respectively.

Conclusions

Taken together, through their effect favoring Th2 over Th1 responses, particular dissociated GR ligands, for which CpdA represents a paradigm, hold potential for the application in Th1-mediated immune disorders.

A dissociated glucocorticoid receptor modulator reduces airway hyperresponsiveness and inflammation in a mouse model of asthma

The glucocorticoid receptor (GR) is a transcription factor able to support either target gene activation via direct binding to DNA or gene repression via interfering with the activity of various proinflammatory transcription factors. An improved therapeutic profile for combating chronic inflammatory diseases has been reported through selectively modulating the GR by only triggering its transrepression function. We have studied in this paper the activity of Compound A (CpdA), a dissociated GR modulator favoring GR monomer formation, in a predominantly Th2-driven asthma model. CpdA acted similarly to the glucocorticoid dexamethasone (DEX) in counteracting OVA-induced airway hyperresponsiveness, recruitment of eosinophils, dendritic cells, neutrophils, B and T cells, and macrophages in bronchoalveolar lavage fluid, lung Th2, Tc2, Th17, Tc17, and mast cell infiltration, collagen deposition, and goblet cell metaplasia. Both CpdA and DEX inhibited Th2 cytokine production in bronchoalveolar lavage as well as nuclear translocation of NF-κB and its subsequent recruitment onto the IκBα promoter in the lung. By contrast, DEX but not CpdA induces expression of the GR-dependent model gene MAPK phosphatase 1 in the lung, confirming the dissociative action of CpdA. Mechanistically, we demonstrate that CpdA inhibited IL-4-induced STAT6 translocation and that GR is essential for CpdA to mediate chemokine repression. In conclusion, we clearly show in this study the anti-inflammatory effect of CpdA in a Th2-driven asthma model in the absence of transactivation, suggesting a potential therapeutic benefit of this strategy.

Mitogen-activated protein kinase phosphatase (MKP)-1 in immunology, physiology, and disease

Mitogen-activated protein kinases (MAPKs) are key regulators of cellular physiology and immune responses, and abnormalities in MAPKs are implicated in many diseases. MAPKs are activated by MAPK kinases through phosphorylation of the threonine and tyrosine residues in the conserved Thr-Xaa-Tyr domain, where Xaa represents amino acid residues characteristic of distinct MAPK subfamilies. Since MAPKs play a crucial role in a variety of cellular processes, a delicate regulatory network has evolved to control their activities. Over the past two decades, a group of dual specificity MAPK phosphatases (MKPs) has been identified that deactivates MAPKs. Since MAPKs can enhance MKP activities, MKPs are considered as an important feedback control mechanism that limits the MAPK cascades. This review outlines the role of MKP-1, a prototypical MKP family member, in physiology and disease. We will first discuss the basic biochemistry and regulation of MKP-1. Next, we will present the current consensus on the immunological and physiological functions of MKP-1 in infectious, inflammatory, metabolic, and nervous system diseases as revealed by studies using animal models. We will also discuss the emerging evidence implicating MKP-1 in human disorders. Finally, we will conclude with a discussion of the potential for pharmacomodulation of MKP-1 expression.

Coordinated regulation of IL-4 and IL-13 expression in human T cells: 3C analysis for DNA looping

Asthma is a chronic allergic disorder characterised by chronic inflammation. The balance of type I and type II (CD4+) T helper cells is of critical importance. In asthma there is an overexpression of T(H)2 cytokines, such as IL-4, IL-5 and IL-13. The genes encoding these cytokines are located together the same chromosomal region, 5q31.1 in humans. Here we confirm a central role for the transcription factors NFAT and GATA3 in the regulation of human IL-4 and IL-13. Chromatin Conformation Capture (3C) demonstrated the formation of specific ligation products containing spliced IL-4 and IL-13 DNA sequences in human T(H)2 polarised HuT-78 cells. This suggests that co-ordinate expression of T(H)2 cytokines, under the control of GATA3 and NFAT1 is due to the formation of a chromatin hub by DNA looping.

Microenvironments dictating tumor cell dormancy

The mechanisms driving dormancy of disseminated tumor cells (DTCs) remain largely unknown. Here, we discuss experimental evidence and theoretical frameworks that support three potential scenarios contributing to tumor cell dormancy. The first scenario proposes that DTCs from invasive cancers activate stress signals in response to the dissemination process and/or a growth suppressive target organ microenvironment inducing dormancy. The second scenario asks whether therapy and/or micro-environmental stress conditions (e.g. hypoxia) acting on primary tumor cells carrying specific gene signatures prime new DTCs to enter dormancy in a matching target organ microenvironment that can also control the timing of DTC dormancy. The third and final scenario proposes that early dissemination contributes a population of DTCs that are unfit for immediate expansion and survive mostly in an arrested state well after primary tumor surgery, until genetic and/or epigenetic mechanisms activate their proliferation. We propose that DTC dormancy is ultimately a survival strategy that when targeted will eradicate dormant DTCs preventing metastasis. For these non-mutually exclusive scenarios we review experimental and clinical evidence in their support.

Pathophysiology of allergic inflammation

Allergic inflammation is due to a complex interplay between several inflammatory cells, including mast cells, basophils, lymphocytes, dendritic cells, eosinophils, and sometimes neutrophils. These cells produce multiple inflammatory mediators, including lipids, purines, cytokines, chemokines, and reactive oxygen species. Allergic inflammation affects target cells, such as epithelial cells, fibroblasts, vascular cells, and airway smooth muscle cells, which become an important source of inflammatory mediators. Sensory nerves are sensitized and activated during allergic inflammation and produce symptoms. Allergic inflammatory responses are orchestrated by several transcription factors, particularly NF-κB and GATA3. Inflammatory genes are also regulated by epigenetic mechanisms, including DNA methylation and histone modifications. There are several endogenous anti-inflammatory mechanisms, including anti-inflammatory lipids and cytokines, which may be defective in allergic disease, thus amplifying and perpetuating the inflammation. Better understanding of the pathophysiology of allergic inflammation has identified new therapeutic targets but developing effective novel therapies has been challenging. Corticosteroids are highly effective with a broad spectrum of anti-inflammatory effects, including epigenetic modulation of the inflammatory response and suppression of GATA3.

Medroxyprogesterone acetate alters Mycobacterium bovis BCG-induced cytokine production in peripheral blood mononuclear cells of contraceptive users

Most individuals latently infected with Mycobacterium tuberculosis (M.tb) contain the infection by a balance of effector and regulatory immune responses. This balance can be influenced by steroid hormones such as glucocorticoids. The widely used contraceptive medroxyprogesterone acetate (MPA) possesses glucocorticoid activity. We investigated the effect of this hormone on immune responses to BCG in household contacts of active TB patients. Multiplex bead array analysis revealed that MPA demonstrated both glucocorticoid and progestogenic properties at saturating and pharmacological concentrations in peripheral blood mononuclear cells (PBMCs) and suppressed antigen specific cytokine production. Furthermore we showed that PBMCs from women using MPA produced significantly lower levels of IL-1α, IL-12p40, IL-10, IL-13 and G-CSF in response to BCG which corresponded with lower numbers of circulating monocytes observed in these women. Our research study is the first to show that MPA impacts on infections outside the genital tract due to a systemic effect on immune function. Therefore MPA use could alter susceptibility to TB, TB disease severity as well as change the efficacy of new BCG-based vaccines, especially prime-boost vaccine strategies which may be administered to adult or adolescent women in the future.

Biochemical basis of asthma therapy

Current therapy for asthma is highly effective. β(2)-Adrenergic receptor (β(2)AR) agonists are the most effective bronchodilators and relax airway smooth muscle cells through increased cAMP concentrations and directly opening large conductance Ca(2+) channels. β(2)AR may also activate alternative signaling pathways that may have detrimental effects in asthma. Glucocorticoids are the most effective anti-inflammatory treatments and switch off multiple activated inflammatory genes through recruitment of histone deacetylase-2, activating anti-inflammatory genes, and through increasing mRNA stability of inflammatory genes. There are beneficial molecular interactions between β(2)AR and glucocorticoid-activated pathways. Understanding these signaling pathways may lead to even more effective therapies in the future.

Glucocorticosteroids: current and future directions

Glucocorticoids are the most effective anti-inflammatory therapy for asthma yet are relatively ineffective in chronic obstructive pulmonary disease. Glucocorticoids suppress inflammation via several molecular mechanisms. Glucocorticoids suppress the multiple inflammatory genes that are activated in chronic inflammatory diseases, such as asthma, by reversing histone acetylation of activated inflammatory genes through binding of ligand-bound glucocorticoid receptors (GR) to co-activator molecules and recruitment of histone deacetylase-2 to the activated inflammatory gene transcription complex (trans-repression). At higher concentrations of glucocorticoids GR homodimers interact with DNA recognition sites to activate transcription through increased histone acetylation of anti-inflammatory genes and transcription of several genes linked to glucocorticoid side effects (trans-activation). Glucocorticoids also have post-transcriptional effects and decrease stability of some pro-inflammatory mRNA species. Decreased glucocorticoid responsiveness is found in patients with severe asthma and asthmatics who smoke, as well as in all patients with chronic obstructive pulmonary disease. Several molecular mechanisms of glucocorticoid resistance have now been identified which involve post-translational modifications of GR. Histone deacetylase-2 is markedly reduced in activity and expression as a result of oxidative/nitrative stress so that inflammation becomes resistant to the anti-inflammatory actions of glucocorticoids. Dissociated glucocorticoids and selective GR modulators which show improved trans-repression over trans-activation effects have been developed to reduce side effects, but so far it has been difficult to dissociate anti-inflammatory effects from adverse effects. In patients with glucocorticoid resistance alternative anti-inflammatory treatments are being investigated as well as drugs that may reverse the molecular mechanisms of glucocorticoid resistance.

Mechanisms and functions of p38 MAPK signalling

The p38 MAPK (mitogen-activated protein kinase) signalling pathway allows cells to interpret a wide range of external signals and respond appropriately by generating a plethora of different biological effects. The diversity and specificity in cellular outcomes is achieved with an apparently simple linear architecture of the pathway, consisting of a core of three protein kinases acting sequentially. In the present review, we dissect the molecular mechanisms underlying p38 MAPK functions, with special emphasis on the activation and regulation of the core kinases, the interplay with other signalling pathways and the nature of p38 MAPK substrates as a source of functional diversity. Finally, we discuss how genetic mouse models are facilitating the identification of physiological functions for p38 MAPKs, which may impinge on their eventual use as therapeutic targets.

New therapies for asthma: is there any progress?

Current therapy for asthma with inhaled corticosteroids and long-acting inhaled beta(2)-agonists is highly effective, safe and relatively inexpensive, but for many patients, their disease remains poorly controlled. Most advances in asthma therapy have occurred through improving these drug classes, and a major developmental hurdle is to improve existing drug classes. The major unmet needs include better treatment of severe asthma, and curative therapies for mild to moderate asthma. Many new treatments are specific, targeting a single mediator or receptor, and are unlikely to have a major clinical effect, although they might be effective in specific asthma phenotypes. Drugs with more widespread effects, such as kinase inhibitors, might be more effective but have a greater risk of side effects. New treatments targeting the underlying allergic/immune process would treat concomitant allergic diseases. Improved immunotherapy approaches have the prospect of disease modification, although prospects for a cure are currently remote. The most promising therapeutic developments for asthma are discussed in this review.

The role of the glucocorticoid receptor in inflammation and immunity

Glucocorticoids are potent immunosuppressive agents with complex actions on immune cells evoking the following effects: inducing apoptosis, changing differentiation fate, inhibition of cytokine release, inhibition of migration and other features. Distinct molecular mechanisms of the glucocorticoid receptor (GR) contribute to different anti-inflammatory effects. Recently inflammatory models have been investigated using conditional knockout and function selective mice shedding light on critical cell types and molecular mechanisms of endogenous and therapeutic GC actions. Here we review the multiple effects of GCs on major immune cells, dendritic cells, myeloid cells and B- and T-lymphocytes and give a summary of studies using conditional GR knockout mice.

GATA3 in development and cancer differentiation: cells GATA have it!

There is increasing evidence that the numerous mechanisms that regulate cell differentiation during normal development are also involved in tumorigenesis. In breast cancer, differentiation markers expressed by the primary tumor are routinely profiled to guide clinical decisions. Indeed, numerous studies have shown that the differentiation profile correlates with the metastatic potential of tumors. The transcription factor GATA3 has emerged recently as a strong predictor of clinical outcome in human luminal breast cancer. In the mammary gland, GATA3 is required for luminal epithelial cell differentiation and commitment, and its expression is progressively lost during luminal breast cancer progression as cancer cells acquire a stem cell-like phenotype. Importantly, expression of GATA3 in GATA3-negative, undifferentiated breast carcinoma cells is sufficient to induce tumor differentiation and inhibits tumor dissemination in a mouse model. These findings demonstrate the exquisite ability of a differentiation factor to affect malignant properties, and raise the possibility that GATA3 or its downstream genes could be used in treating luminal breast cancer. This review highlights our recent understanding of GATA3 in both normal mammary development and tumor differentiation.