Histone deacetylase 2-mediated deacetylation of the glucocorticoid receptor enables NF-kappaB suppression

One hormone, two actions: anti- and pro-inflammatory effects of glucocorticoids

Glucocorticoids are essential steroid hormones secreted from the adrenal gland in response to stress. Since their discovery in the 1940s, glucocorticoids have been widely prescribed to treat inflammatory disorders and hematological cancers. In the traditional view, glucocorticoids are regarded as anti-inflammatory molecules; however, emerging evidence suggests that glucocorticoid actions are more complex than previously anticipated. The anti-inflammatory activity of glucocorticoids is attributed to the repression of pro-inflammatory genes through signal transduction by their steroid receptor, the glucocorticoid receptor (GR). The mechanisms modulating the pro-inflammatory effects of glucocorticoids are not well understood. In this review, we discuss recent findings that provide insights into the mechanism by which GR signaling can play a dual role in the regulation of the immune response. We hypothesize that these apparently opposite processes are working together to prepare the immune system to respond to a stressor (pro-inflammatory effects) and subsequently restore homeostasis (anti-inflammatory effects). Finally, we propose that determining the mechanisms which underlie the tissue-specific effects of glucocorticoids will provide an excellent tool to develop more efficient and selective glucocorticoid therapies.

TGF-β1, but not bone morphogenetic proteins, activates Smad1/5 pathway in primary human macrophages and induces expression of proatherogenic genes

Macrophages are responsible for the control of inflammation and healing, and their malfunction results in cardiometabolic disorders. TGF-β is a pleiotropic growth factor with dual (protective and detrimental) roles in atherogenesis. We have previously shown that in human macrophages, TGF-β1 activates Smad2/3 signaling and induces a complex gene expression program. However, activated genes were not limited to known Smad2/3-dependent ones, which prompted us to study TGF-β1-induced signaling in macrophages in detail. Analysis of Id3 regulatory sequences revealed a novel enhancer, located between +4517 and 4662 bp, but the luciferase reporter assay demonstrated that this enhancer is not Smad2/3 dependent. Because Id3 expression is regulated by Smad1/5 in endothelial cells, we analyzed activation of Smad1/5 in macrophages. We demonstrate here for the first time, to our knowledge, that TGF-β1, but not BMPs, activates Smad1/5 in macrophages. We show that an ALK5/ALK1 heterodimer is responsible for the induction of Smad1/5 signaling by TGF-β1 in mature human macrophages. Activation of Smad1/5 by TGF-β1 induces not only Id3, but also HAMP and PLAUR, which contribute to atherosclerotic plaque vulnerability. We suggest that the balance between Smad1/5- and Smad2/3-dependent signaling defines the outcome of the effect of TGF-β on atherosclerosis where Smad1/5 is responsible for proatherogenic effects, whereas Smad2/3 regulate atheroprotective effects of TGF-β.

Inactivation of histone deacetylase 1 (HDAC1) but not HDAC2 is required for the glucocorticoid-dependent CCAAT/enhancer-binding protein α (C/EBPα) expression and preadipocyte differentiation

Several drugs currently used in the management of mood disorders, epilepsy (ie, valproic acid), or the control of inflammation (ie, corticosteroids) have been shown to promote visceral obesity in humans by increasing the number of newly formed adipocytes. Valproic acid is classified as a nonspecific histone deacetylase (HDAC) inhibitor, along with trichostatin A and butyric acid. In vitro experiments have demonstrated that such molecules greatly enhance the rate of preadipocyte differentiation, similarly to the effect of corticosteroids. The glucocorticoid receptor stimulates adipogenesis in part by enhancing the transcription of C/ebpa through the titration, and subsequent degradation, of HDAC1 from the C/ebpα promoter. There is, however, controversy in the literature as to the role of HDACs during adipogenesis. In this study, we sought to demonstrate, using 2 different strategies, the definite role of HDAC1 in adipogenesis. By using small interference RNA-mediated knockdown of HDAC1 and by generating an enzymatically inactive HDAC1D181A by site-directed mutagenesis, we were able to show that HDAC1, but not HDAC2, suppresses glucocorticoid receptor-potentiated preadipocyte differentiation by decreasing CCAAT/enhancer-binding protein (C/ebp)α and Pparγ expression levels at the onset of differentiation. Finally, we demonstrate that HDAC1D181A acts as a dominant negative mutant of HDAC1 during adipogenesis by modulating C/EBPβ transcriptional activity on the C/ebpα promoter.

Epigenetic targets for novel therapies of lung diseases

In spite of substantial advances in defining the immunobiology and function of structural cells in lung diseases there is still insufficient knowledge to develop fundamentally new classes of drugs to treat many lung diseases. For example, there is a compelling need for new therapeutic approaches to address severe persistent asthma that is insensitive to inhaled corticosteroids. Although the prevalence of steroid-resistant asthma is 5-10%, severe asthmatics require a disproportionate level of health care spending and constitute a majority of fatal asthma episodes. None of the established drug therapies including long-acting beta agonists or inhaled corticosteroids reverse established airway remodeling. Obstructive airways remodeling in patients with chronic obstructive pulmonary disease (COPD), restrictive remodeling in idiopathic pulmonary fibrosis (IPF) and occlusive vascular remodeling in pulmonary hypertension are similarly unresponsive to current drug therapy. Therefore, drugs are needed to achieve long-acting suppression and reversal of pathological airway and vascular remodeling. Novel drug classes are emerging from advances in epigenetics. Novel mechanisms are emerging by which cells adapt to environmental cues, which include changes in DNA methylation, histone modifications and regulation of transcription and translation by noncoding RNAs. In this review we will summarize current epigenetic approaches being applied to preclinical drug development addressing important therapeutic challenges in lung diseases. These challenges are being addressed by advances in lung delivery of oligonucleotides and small molecules that modify the histone code, DNA methylation patterns and miRNA function.

25-Hydroxyvitamin D3-deficiency enhances oxidative stress and corticosteroid resistance in severe asthma exacerbation

Oxidative stress plays a significant role in exacerbation of asthma. The role of vitamin D in oxidative stress and asthma exacerbation remains unclear. We aimed to determine the relationship between vitamin D status and oxidative stress in asthma exacerbation. Severe asthma exacerbation patients with 25-hydroxyvitamin D3-deficiency (V-D deficiency) or 25-hydroxyvitamin D-sufficiency (V-D sufficiency) were enrolled. Severe asthma exacerbation with V-D-deficiency showed lower forced expiratory volume in one second (FEV1) compared to that with V-D-sufficiency. V-D-deficiency intensified ROS release and DNA damage and increased TNF-α, OGG1 and NFκB expression and NFκB phosphorylation in severe asthma exacerbation. Supplemental vitamin D3 significantly increased the rates of FEV1 change and decreased ROS and DNA damage in V-D-deficiency. Vitamin D3 inhibited LPS-induced ROS and DNA damage and were associated with a decline in TNF-α and NFκB in epithelial cells. H₂O₂ reduces nuclear translocation of glucocorticoid receptors in airway epithelial cell lines. V-D pretreatment enhanced the dexamethasone-induced nuclear translocation of glucocorticoid receptors in airway epithelial cell lines and monocytes from 25-hydroxyvitamin D3-deficiency asthma patients. These findings indicate that V-D deficiency aggravates oxidative stress and DNA damage, suggesting a possible mechanism for corticosteroid resistance in severe asthma exacerbation.

Serum cholesterol selectively regulates glucocorticoid sensitivity through activation of JNK

Glucocorticoids (Gc) are potent anti-inflammatory agents with wide clinical application. We have previously shown that increased serum concentration significantly attenuates regulation of a simple Gc-responsive reporter. We now find that glucocorticoid receptor (GR) regulation of some endogenous transactivated but not transrepressed genes is impaired, suggesting template specificity. Serum did not directly affect GR expression, activity or trafficking, implicating GR crosstalk with other signalling pathways. Indeed, a JNK inhibitor completely abolished the serum effect. We identified the Gc modulating serum component as cholesterol. Cholesterol loading mimicked the serum effect, which was readily reversed by JNK inhibition. Chelation of serum cholesterol with methyl-β-cyclodextrin or inhibition of cellular cholesterol synthesis with simvastatin potentiated the Gc response. To explore the effect in vivo we used ApoE(-/-) mice, a model of hypercholesterolaemia. Consistent with our in vitro studies, we find no impact of elevated cholesterol on the expression of GR, or on the hypothalamic-pituitary-adrenal axis, measured by dexamethasone suppression test. Instead we find selective Gc resistance on some hepatic target genes in ApoE(-/-) mice. Therefore, we have discovered an unexpected role for cholesterol as a selective modulator of Gc action in vivo. Taken together these findings reveal a new environmental constraint on Gc action with relevance to both inflammation and cancer.

Glucocorticoids suppress hypoxia-induced COX-2 and hypoxia inducible factor-1α expression through the induction of glucocorticoid-induced leucine zipper

BACKGROUND AND PURPOSE

The COX-2/PGE2 pathway in hypoxic cancer cells has important implications for stimulation of inflammation and tumourigenesis. However, the mechanism by which glucocorticoid receptors (GRs) inhibit COX-2 during hypoxia has not been elucidated. Hence, we explored the mechanisms underlying glucocorticoid-mediated inhibition of hypoxia-induced COX-2 in human distal lung epithelial A549 cells.

EXPERIMENTAL APPROACH

The expressions of COX-2 and glucocorticoid-induced leucine zipper (GILZ) in A549 cells were determined by Western blot and/or quantitative real time-PCR respectively. The anti-invasive effect of GILZ on A549 cells was evaluated using the matrigel invasion assay.

KEY RESULTS

The hypoxia-induced increase in COX-2 protein and mRNA levels and promoter activity were suppressed by dexamethasone, and this effect of dexamethasone was antagonized by the GR antagonist RU486. Overexpression of GILZ in A549 cells also inhibited hypoxia-induced COX-2 expression levels and knockdown of GILZ reduced the glucocorticoid-mediated inhibition of hypoxia-induced COX-2 expression, indicating that the inhibitory effects of dexamethasone on hypoxia-induced COX-2 are mediated by GILZ. GILZ suppressed the expression of hypoxia inducible factor (HIF)-1α at the protein level and affected its signalling pathway. Hypoxia-induced cell invasion was also dramatically reduced by GILZ expression.

CONCLUSION AND IMPLICATIONS

Dexamethasone-induced upregulation of GILZ not only inhibits the hypoxic-evoked induction of COX-2 expression and cell invasion but further blocks the HIF-1 pathway by destabilizing HIF-1α expression. Taken together, these findings suggest that the suppression of hypoxia-induced COX-2 by glucocorticoids is mediated by GILZ. Hence, GILZ is a potential key therapeutic target for suppression of inflammation under hypoxia.

Mechanisms of glucocorticoid action and insensitivity in airways disease

Glucocorticoids are the mainstay for the treatment of chronic inflammatory diseases including asthma and chronic obstructive pulmonary disease (COPD). However, it has been recognized that glucocorticoids do not work well in certain patient populations suggesting reduced sensitivity. The ultimate biologic responses to glucocorticoids are determined by not only the concentration of glucocorticoids but also the differences between individuals in glucocorticoid sensitivity, which is influenced by multiple factors. Studies are emerging to understand these mechanisms in detail, which would help in increasing glucocorticoid sensitivity in patients with chronic airways disease. This review aims to highlight both classical and emerging concepts of the anti-inflammatory mechanisms of glucocorticoids and also review some novel strategies to overcome steroid insensitivity in airways disease.

Comprehensive overview of the structure and regulation of the glucocorticoid receptor

Glucocorticoids are among the most prescribed drugs worldwide for the treatment of numerous immune and inflammatory disorders. They exert their actions by binding to the glucocorticoid receptor (GR), a member of the nuclear receptor superfamily. There are several GR isoforms resulting from alternative RNA splicing and translation initiation of the GR transcript. Additionally, these isoforms are all subject to several transcriptional, post-transcriptional, and post-translational modifications, all of which affect the protein's stability and/or function. In this review, we summarize recent knowledge on the distinct GR isoforms and the processes that generate them. We also review the importance of all known transcriptional, post-transcriptional, and post-translational modifications, including the regulation of GR by microRNAs. Moreover, we discuss the crucial role of the putative GR-bound DNA sequence as an allosteric ligand influencing GR structure and activity. Finally, we describe how the differential composition and distinct regulation at multiple levels of different GR species could account for the wide and diverse effects of glucocorticoids.

Refractory asthma: mechanisms, targets, and therapy

Asthma is a common medical condition affecting 300 million people worldwide. Airway inflammation, smooth muscle bronchoconstriction leading to airflow obstruction, and mucous hypersecretion are clinical hallmarks of asthma. The NHLBI Expert Panel Report 3 recommends inhaled corticosteroids (ICS) for patients with moderate to severe persistent asthma. Inhaled corticosteroids (ICS) target gene transcription through their interactions with the glucocorticoid (GC) receptor (GR) at the glucocorticoid response element (GRE). The GC/GR complex enhances anti-inflammatory but inhibits pro-inflammatory mediator production. Classically, asthma has been described as a Th2-associated eosinophil-predominant disease, but recently alternative models have been described including a Th17-mediated neutrophil-predominant phenotype resulting in patients with more severe disease who may be less responsive to steroids. Additional mechanisms of steroid resistance include increased activity of GR phosphorylating kinases which modify the interactions of GR with transcription factors to inhibit the ability of GR to bind with GRE, leading to an increase in pro-inflammatory gene transcription. Oxidative stress also affects the balance between pro-inflammatory and anti-inflammatory gene transcription through the modification of transcription factors and cofactors (such as PI3K) leading to the inhibition of histone deacetylase 2. Continued investigations into the mechanisms behind glucocorticoid resistance will lead to novel treatments that improve control of severe refractory asthma.

Analgesic and anti-inflammatory activity of 7-substituted purine-2,6-diones

BACKGROUND

In an effort to develop new analgesic and anti-inflammatory agents, we determined a series of 7-substituted purine-2,6-diones.

METHODS

The obtained compounds (1-6) were evaluated pharmacologically in four in vivo models: the writhing syndrome, the formalin tests, the carrageenan-induced edema model and the zymosan-induced peritonitis. The influence of the investigated compounds on the phosphodiesterase (PDE) and PDE4B activity was also determined. In addition, determination of the antioxidant activity was determined by the FRAP assay.

RESULTS

A majority of the tested compounds showed a significant analgesic and anti-inflammatory activity. The strongest analgesic and anti-inflammatory effect was observed for 1 and 2. The active compound 1 was more efficient than theophylline in inhibiting the PDE and more efficient than rolipram in inhibiting the PDE4B activity. The tested compounds did not show significant antioxidant properties.

CONCLUSION

Active compounds (1-6) inhibited the PDE activity, while compound 1 significantly inhibited the PDE4B activity, what may suggest that this mechanism may be involved in their analgesic/anti-inflammatory properties.

Asthma epigenetics

Asthma is the most common chronic disease of childhood, and a growing body of evidence indicates that epigenetic variations may mediate the effects of environmental exposures on the development and natural history of asthma. Epigenetics is the study of mitotically or meiotically heritable changes in gene expression that occur without directly altering the DNA sequence. DNA methylation, histone modifications and microRNAs are major epigenetic variations in humans that are currently being investigated for asthma etiology and natural history. DNA methylation results from addition of a methyl group to the 5 position of a cytosine ring and occurs almost exclusively on a cytosine in a CpG dinucleotide. Histone modifications involve posttranslational modifications such as acetylation, methylation, phosphorylation and ubiquitination on the tails of core histones. MicroRNAs are short ~22 nucleotide long, non-coding, single-stranded RNAs that binds to complementary sequences in the target mRNAs, usually resulting in gene silencing. While many studies have documented relationships of environmental exposures that have been implicated in asthma etiology with epigenetic alterations, to date, few studies have directly linked epigenetic variations with asthma development. There are several methodological challenges in studying the epigenetics of asthma. In this chapter, the influence of epigenetic variations on asthma pathophysiology, methodological concerns in conducting epigenetic research and future direction of asthma epigenetics research are discussed.

Promoter-specific relevance of histone modifications induced by dexamethasone during the regulation of pro-inflammatory mediators

Glucocorticosteroids (GCs) are widely used to treat different kinds of chronic inflammatory and immune diseases through transcriptional regulation of inflammatory genes. Modulation of gene expression by GCs is known to occur through diverse mechanisms of varying relevance to specific classes of genes. Epigenetic modifications are indeed a pivotal regulatory feature of glucocorticoid receptor and other transcription factors. In this study, histone post-translational modifications were investigated for their involvement in the regulation of selected pro-inflammatory genes - expressed in human monocyte-derived macrophages - in response to treatment with synthetic GC dexamethasone (DEX). We show that histone tail acetylation status is modified following DEX administration, through distinct and alternative mechanisms at the promoters of interleukin-8 and interleukin-23. In addition to histone H3 acetylation, our results demonstrate that H3 lysine 4 trimethylation is affected following drug treatment.

Transcriptional regulation of endothelial arginase 2 by histone deacetylase 2

OBJECTIVE

Arginase 2 (Arg2) is a critical target in atherosclerosis because it controls endothelial nitric oxide, proliferation, fibrosis, and inflammation. Regulators of Arg2 transcription in the endothelium have not been characterized. The goal of the current study is to determine the role of specific histone deacetylases (HDACs) in the regulation of endothelial Arg2 transcription and endothelial function.

APPROACH AND RESULTS

The HDAC inhibitor trichostatin A increased levels of Arg2 mRNA, protein, and activity in both human aortic endothelial cells and mouse aortic rings. These changes occurred in both time- and dose-dependent patterns and resulted in Arg2-dependent endothelial dysfunction. Trichostatin A and the atherogenic stimulus oxidized low-density lipoprotein enhanced the activity of common promoter regions of Arg2. HDAC inhibition with trichostatin A also decreased endothelial nitric oxide, and these effects were blunted by arginase inhibition. Nonselective class I HDAC inhibitors enhanced Arg2 expression, whereas the only selective inhibitor that increased Arg2 expression was mocetinostat, a selective inhibitor of HDACs 1 and 2. Additionally, mouse aortic rings preincubated with mocetinostat exhibited dysfunctional relaxation. Overexpression of HDAC2 (but not HDAC 1, 3, or 8) cDNA in human aortic endothelial cells suppressed Arg2 expression in a concentration-dependent manner, and siRNA knockdown of HDAC2 enhanced Arg2 expression. Chromatin immunoprecipitation indicated direct binding of HDAC2 to the Arg2 promoter, and HDAC2 overexpression in human aortic endothelial cells blocked oxidized low-density lipoprotein-mediated activation of the Arg2 promoter. Finally, overexpression of HDAC2 blocked oxidized low-density lipoprotein-mediated vascular dysfunction.

CONCLUSIONS

HDAC2 is a critical regulator of Arg2 expression and thereby endothelial nitric oxide and endothelial function. Overexpression or activation of HDAC2 represents a novel therapy for endothelial dysfunction and atherosclerosis.

Circadian endocrine rhythms: the hypothalamic-pituitary-adrenal axis and its actions

The stress system effectively restores the internal balance--or homeostasis--of living organisms in the face of random external or internal changes, the stressors. This highly complex system helps organisms to provide a series of neuroendocrine responses to stressors--the stress response--through coordinated activation of the hypothalamic-pituitary-adrenal (HPA) axis and the locus coeruleus/norepinephrine autonomic nervous systems. In addition to stressors, life is influenced by daily light/dark changes due to the 24-h rotation of Earth. To adjust to these recurrent day/night cycles, the biological clock system employs the heterodimer of transcription factors circadian locomotor output cycle kaput/brain-muscle-arnt-like protein 1 (CLOCK/BMAL1), along with a set of other transcription factors, to regulate the circadian pattern of gene expression. Interestingly, the stress system, through the HPA axis, communicates with the clock system; therefore, any uncoupling or dysregulation could potentially cause several disorders, such as metabolic, autoimmune, and mood disorders. In this review, we discuss the biological function of the two systems, their interactions, and the clinical implications of their dysregulation or uncoupling.

Synthesis and biological comparison of enantiomers of mepenzolate bromide, a muscarinic receptor antagonist with bronchodilatory and anti-inflammatory activities

Chronic obstructive pulmonary disease (COPD) is characterized by abnormal inflammatory responses and airflow limitations. We recently proposed that the muscarinic antagonist mepenzolate bromide (mepenzolate) would be therapeutically effective against COPD due to its muscarinic receptor-dependent bronchodilatory activity as well as anti-inflammatory properties. Mepenzolate has an asymmetric carbon atom, thus providing us with the opportunity to synthesize both of its enantiomers ((R)- and (S)-mepenzolate) and to examine their biochemical and pharmacological activities. (R)- or (S)-mepenzolate was synthesized by condensation of benzilic acid with (R)- or (S)-alcohol, respectively, followed by quaternization of the tertiary amine. As predicted by computational simulation, a filter-binding assay in vitro revealed that (R)-mepenzolate showed a higher affinity for the muscarinic M3 receptor than (S)-mepenzolate. In vivo, the bronchodilatory activity of (R)-mepenzolate was superior to that of (S)-mepenzolate, whereas anti-inflammatory activity was indistinguishable between the two enantiomers. We confirmed that each mepenzolate maintained its original stereochemistry in the lung when administered intratracheally. These results suggest that (R)-mepenzolate may have superior properties to (S)-mepenzolate as a drug to treat COPD patients given that the former has more potent bronchodilatory activity than the latter.

Passive smoking impairs histone deacetylase-2 in children with severe asthma

Background:

Parental smoking is known to worsen asthma symptoms in children and to make them refractory to asthma treatment, but the molecular mechanism is unclear. Oxidative stress from tobacco smoke has been reported to impair histone deacetylase-2 (HDAC2) via phosphoinositide-3-kinase (PI3K)/Akt activation and, thus, to reduce corticosteroid sensitivity. The aim of this study was to investigate passive smoking-dependent molecular abnormalities in alveolar macrophages (AMs) by comparing passive smoke-exposed children and non-passive smoke-exposed children with uncontrolled severe asthma.

Methods:

BAL fluid (BALF) was obtained from 19 children with uncontrolled severe asthma (10 non-passive smoking-exposed subjects and nine passive smoking-exposed subjects), and HDAC2 expression/activity, Akt/HDAC2 phosphorylation levels, and corticosteroid responsiveness in AMs were evaluated.

Results:

Parental smoking reduced HDAC2 protein expression by 54% and activity by 47%, with concomitant enhancement of phosphorylation of Akt1 and HDAC2. In addition, phosphorylation levels of Akt1 correlated positively with HDAC2 phosphorylation levels and negatively with HDAC2 activity. Furthermore, passive smoke exposure reduced the inhibitory effects of dexamethasone on tumor necrosis factor-α-induced CXCL8 release in AMs. There were relatively higher neutrophil counts and CXCL8 concentrations in BALF and lower Asthma Control Test scores compared with non-passive smoke-exposed children with uncontrolled severe asthma.

Conclusions:

Passive smoking impairs HDAC2 function via PI3K signaling activation, which could contribute to corticosteroid-insensitive inflammation in children with severe asthma. This novel mechanism will be a treatment target in children with severe asthma and stresses the need for a smoke-free environment for asthmatic children.

Pathological changes in the COPD lung mesenchyme--novel lessons learned from in vitro and in vivo studies

Chronic obstructive pulmonary disease (COPD) is currently the fourth leading cause of death worldwide and, in contrast to the trend for cardiovascular diseases, mortality rates still continue to climb. This increase is in part due to an aging population, being expanded by the "Baby boomer" generation who grew up when smoking rates were at their peak and by people in developing countries living longer. Sadly, there has been a disheartening lack of new therapeutic approaches to counteract the progressive decline in lung function associated with the disease that leads to disability and death. COPD is characterized by irreversible chronic airflow limitation that is caused by emphysematous destruction of lung elastic tissue and/or obstruction in the small airways due to occlusion of their lumen by inflammatory mucus exudates, narrowing and obliteration. These lesions are mainly produced by the response of the tissue to the repetitive inhalational injury inflicted by noxious gases, including cigarette smoke, which involves interaction between infiltrating inflammatory immune cells, resident cells (e.g. epithelial cells and fibroblasts) and the extra cellular matrix. This interaction leads to tissue destruction and airway remodeling with changes in elastin and collagen, such that the epithelial-mesenchymal trophic unit is dysregulated in both the disease pathologies. This review focuses on: 1--novel inflammatory and remodeling factors that are altered in COPD; 2--in vitro and in vivo models to understand the mechanism whereby the extra cellular matrix environment in altered in COPD; and 3--COPD in the context of wound-repair tissue responses, with a focus on the regulation of mesenchymal cell fate and phenotype.

Superiority of pulmonary administration of mepenzolate bromide over other routes as treatment for chronic obstructive pulmonary disease

We recently proposed that mepenzolate bromide (mepenzolate) would be therapeutically effective against chronic obstructive pulmonary disease (COPD) due to its both anti-inflammatory and bronchodilatory activities. In this study, we examined the benefits and adverse effects associated with different routes of mepenzolate administration in mice. Oral administration of mepenzolate caused not only bronchodilation but also decreased the severity of elastase-induced pulmonary emphysema; however, compared with the intratracheal route of administration, about 5000 times higher dose was required to achieve this effect. Intravenously or intrarectally administered mepenzolate also showed these pharmacological effects. The intratracheal route of mepenzolate administration, but not other routes, resulted in protective effects against elastase-induced pulmonary damage and bronchodilation at a much lower dose than that which affected defecation and heart rate. These results suggest that the pulmonary route of mepenzolate administration may be superior to other routes (oral, intravenous or intrarectal) to treat COPD patients.

Lung development: orchestrating the generation and regeneration of a complex organ

The respiratory system, which consists of the lungs, trachea and associated vasculature, is essential for terrestrial life. In recent years, extensive progress has been made in defining the temporal progression of lung development, and this has led to exciting discoveries, including the derivation of lung epithelium from pluripotent stem cells and the discovery of developmental pathways that are targets for new therapeutics. These discoveries have also provided new insights into the regenerative capacity of the respiratory system. This Review highlights recent advances in our understanding of lung development and regeneration, which will hopefully lead to better insights into both congenital and acquired lung diseases.

Minireview: The versatile roles of lysine deacetylases in steroid receptor signaling

Lysine deacetylases have been known to regulate nuclear receptor function for many years. In the unliganded state, nuclear receptors that form heterodimers with retinoid X receptors, such as the retinoic acid and thyroid hormone receptors, associate with deacetylases to repress target genes. In the case of steroid receptors, binding of an antagonist ligand was initially reported to induce association of deacetylases to prevent activation of target genes. Since then, deacetylases have been shown to have diverse functions in steroid receptor signaling, from regulating interactions with molecular chaperones to facilitating their ability to activate transcription. The purpose of this review is to summarize recent studies on the role of deacetylases in steroid receptor signaling, which show deacetylases to be highly versatile regulators of steroid receptor function.

Histone modifications contribute to cellular replicative and hydrogen peroxide-induced premature senescence in human embryonic lung fibroblasts

Histone modifications are major post-translational mechanisms responsible for regulation of gene transcription involved in cellular senescence. By using immunofluorescence and Western blot, we showed that the global acetylated levels of histone H3 and H4 were significantly reduced in both replicative and premature senescence of human embryonic lung fibroblasts. However the whole trimethylated level of histone H4 lysine 20 was higher in senescent cells. The alterations in the mRNA and protein levels of histone acetyltransferases (HATs), histone methyltransferase (HMT), and histone deacetylases (HDACs) indicate that differential expression exists between replicative and premature senescent cells. Meanwhile, the reduced activity of HDACs was accompanied by cellular senescence. By employing the quantitative chromatin immunoprecipitation assay in detecting specific histone modifications in senescence-related genes including p53 and p16, it was demonstrated that the mRNA expression of p53 was associated with increased H4 acetylation in replicative senescence and increased H4 acetylation and trimethylation of histone H3 at lysine 4 (H3K4me3) in premature senescence. Both acetylation and trimethylation of H3 were involved in replicative senescence, while the acetylation of histone H3 and H4 was predominant in premature senescence, contributing to the mRNA expression of p16. In summary, the global hypoacetylation of histone H3 and H4 and the hypertrimethylation of histone H4 lysine 20 account for epigenetic characteristics in senescence, controlled by HATs, HMT, and HDACs differentially between replicative and premature senescence. Taken together, these findings suggest that the specific histone modifications are involved in regulating the expression of genes related to senescence of human embryonic lung fibroblasts.

Lipopolysaccharide induces up-regulation of TGF-α through HDAC2 in a rat model of bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is characterized by alveolar simplification with decreased alveolar number and increased airspace. Previous studies suggested that transforming growth factor-α (TGF-α) may contribute to arrested alveolar development in BPD. Histone deacetylases (HDACs) control cellular signaling and gene expression. HDAC2 is crucial for suppression of inflammatory gene expression. Here we investigated whether HDAC2 was involved in the arrest of alveolarization, as well as the ability of HDAC2 to regulate TGF-α expression in a rat model of BPD induced by intra-amniotic injection of lipopolysaccharide (LPS). Results showed that LPS exposure led to a suppression of both HDAC1 and HDAC2 expression and activity, induced TGF-α expression, and disrupted alveolar morphology. Mechanistic studies showed that overexpression of HDAC2, but not HDAC1, suppressed LPS-induced TGF-α expression. Moreover, the HDAC inhibitor TSA or downregulation of HDAC2 by siRNA both significantly increased TGF-α expression in cultured myofibroblasts. Finally, preservation of HDAC activity by theophylline treatment improved alveolar development and attenuated TGF-α release. Together, these findings indicate that attenuation of TGF-α-mediated effects in the lung by enhancing HDAC2 may have a therapeutic effect on treating BPD.

Regulation of acetylation of histone deacetylase 2 by p300/CBP-associated factor/histone deacetylase 5 in the development of cardiac hypertrophy

RATIONALE

Histone deacetylases (HDACs) are closely involved in cardiac reprogramming. Although the functional roles of class I and class IIa HDACs are well established, the significance of interclass crosstalk in the development of cardiac hypertrophy remains unclear.

OBJECTIVE

Recently, we suggested that casein kinase 2α1-dependent phosphorylation of HDAC2 leads to enzymatic activation, which in turn induces cardiac hypertrophy. Here we report an alternative post-translational activation mechanism of HDAC2 that involves acetylation of HDAC2 mediated by p300/CBP-associated factor/HDAC5.

METHODS AND RESULTS

Hdac2 was acetylated in response to hypertrophic stresses in both cardiomyocytes and a mouse model. Acetylation was reduced by a histone acetyltransferase inhibitor but was increased by a nonspecific HDAC inhibitor. The enzymatic activity of Hdac2 was positively correlated with its acetylation status. p300/CBP-associated factor bound to Hdac2 and induced acetylation. The HDAC2 K75 residue was responsible for hypertrophic stress-induced acetylation. The acetylation-resistant Hdac2 K75R showed a significant decrease in phosphorylation on S394, which led to the loss of intrinsic activity. Hdac5, one of class IIa HDACs, directly deacetylated Hdac2. Acetylation of Hdac2 was increased in Hdac5-null mice. When an acetylation-mimicking mutant of Hdac2 was infected into cardiomyocytes, the antihypertrophic effect of either nuclear tethering of Hdac5 with leptomycin B or Hdac5 overexpression was reduced.

CONCLUSIONS

Taken together, our results suggest a novel mechanism by which the balance of HDAC2 acetylation is regulated by p300/CBP-associated factor and HDAC5 in the development of cardiac hypertrophy.

The methyltransferase WBSCR22/Merm1 enhances glucocorticoid receptor function and is regulated in lung inflammation and cancer

Glucocorticoids (GC) regulate cell fate and immune function. We identified the metastasis-promoting methyltransferase, metastasis-related methyltransferase 1 (WBSCR22/Merm1) as a novel glucocorticoid receptor (GR) regulator relevant to human disease. Merm1 binds the GR co-activator GRIP1 but not GR. Loss of Merm1 impaired both GR transactivation and transrepression by reducing GR recruitment to its binding sites. This was accompanied by loss of GR-dependent H3K4Me3 at a well characterized promoter. Inflammation promotes GC resistance, in part through the actions of TNFα and IFNγ. These cytokines suppressed Merm1 protein expression by driving ubiquitination of two conserved lysine residues. Restoration of Merm1 expression rescued GR transactivation. Cytokine suppression of Merm1 and of GR function was also seen in human lung explants. In addition, striking loss of Merm1 protein was observed in both inflammatory and neoplastic human lung pathologies. In conclusion, Merm1 is a novel regulator of chromatin structure affecting GR recruitment and function, contributing to loss of GC sensitivity in inflammation, with suppressed expression in pulmonary disease.

Novel insights into the neuroendocrine control of inflammation: the role of GR and PARP1

Inflammatory responses are elicited after injury, involving release of inflammatory mediators that ultimately lead, at the molecular level, to the activation of specific transcription factors (TFs; mainly activator protein 1 and nuclear factor-κB). These TFs propagate inflammation by inducing the expression of cytokines and chemokines. The neuroendocrine system has a determinant role in the maintenance of homeostasis, to avoid exacerbated inflammatory responses. Glucocorticoids (GCs) are the key neuroendocrine regulators of the inflammatory response. In this study, we describe the molecular mechanisms involved in the interplay between inflammatory cytokines, the neuroendocrine axis and GCs necessary for the control of inflammation. Targeting and modulation of the glucocorticoid receptor (GR) and its activity is a common therapeutic strategy to reduce pathological signaling. Poly (ADP-ribose) polymerase 1 (PARP1) is an enzyme that catalyzes the addition of PAR on target proteins, a post-translational modification termed PARylation. PARP1 has a central role in transcriptional regulation of inflammatory mediators, both in neuroendocrine tumors and in CNS cells. It is also involved in modulation of several nuclear receptors. Therefore, PARP1 and GR share common inflammatory pathways with antagonic roles in the control of inflammatory processes, which are crucial for the effective maintenance of homeostasis.

Prothymosin α overexpression contributes to the development of pulmonary emphysema

Emphysema is one of the disease conditions that comprise chronic obstructive pulmonary disease. Prothymosin α transgenic mice exhibit an emphysema phenotype, but the pathophysiological role of prothymosin α in emphysema remains unclear. Here we show that prothymosin α contributes to the pathogenesis of emphysema by increasing acetylation of histones and nuclear factor-kappaB, particularly upon cigarette smoke exposure. We find a positive correlation between prothymosin α levels and the severity of emphysema in prothymosin α transgenic mice and emphysema patients. Prothymosin α overexpression increases susceptibility to cigarette smoke-induced emphysema, and cigarette smoke exposure further enhances prothymosin α expression. We show that prothymosin α inhibits the association of histone deacetylases with histones and nuclear factor-kappaB, and that prothymosin α overexpression increases expression of nuclear factor-kappaB-dependent matrix metalloproteinase 2 and matrix metalloproteinase 9, which are found in the lungs of patients with chronic obstructive pulmonary disease. These results demonstrate the clinical relevance of prothymosin α in regulating acetylation events during the pathogenesis of emphysema.

Pulmonary emphysema obstruct airflow in the lung and often develop in smokers. Here Su et al. show that prothymosin α contributes to emphysema development through alterations in the acetylation of histones and the transcription factor NF-κB, and that exposure to cigarette smoke increases prothymosin α expression.

Histone deacetylase isoforms regulate innate immune responses by deacetylating mitogen-activated protein kinase phosphatase-1

The MAPK pathway mediates TLR signaling during innate immune responses. We discovered previously that MKP-1 is acetylated, enhancing its interaction with its MAPK substrates and deactivating TLR signaling. As HDACs modulate inflammation by deacetylating histone and nonhistone proteins, we hypothesized that HDACs may regulate LPS-induced inflammation by deacetylating MKP-1. We found that mouse macrophages expressed a subset of HDAC isoforms (HDAC1, HDAC2, and HDAC3), which all interacted with MKP-1. Genetic silencing or pharmacologic inhibition of HDAC1, −2, and −3 increased MKP-1 acetylation in cells. Furthermore, knockdown or pharmacologic inhibition of HDAC1, −2, and −3 decreased LPS-induced phosphorylation of the MAPK member p38. Also, pharmacologic inhibition of HDAC did not decrease MAPK signaling in MKP-1 null cells. Finally, inhibition of HDAC1, −2, and −3 decreased LPS-induced expression of TNF-α, IL-1β, iNOS (NOS2), and nitrite synthesis. Taken together, our results show that HDAC1, −2, and −3 deacetylate MKP-1 and that this post-translational modification increases MAPK signaling and innate immune signaling. Thus, HDAC1, −2, and −3 isoforms are potential therapeutic targets in inflammatory diseases.

Low-level laser therapy suppresses the oxidative stress-induced glucocorticoids resistance in U937 cells: relevance to cytokine secretion and histone deacetylase in alveolar macrophages

Oxidative stress is present in severe asthma and contributes to the low response to corticoids through the downregulation of histone deacetylase (HDAC) and the increase of cytokines. Low-level laser therapy (LLLT) has been proven to be an anti-inflammatory. Thus, we investigated the laser effect on lipopolysaccharide (LPS)-induced cytokine secretion and HDAC activity in U937 cells under oxidative stress. U937 cells activated with oxidative stress were treated with dexamethasone (dexa) or laser. Cytokines and phosphoinositide 3-kinase (PI3K) were measured by ELISA whilst the HDAC was detected through colorimetric assay. LPS activated- U937 cells cytokines secretion increased with H2O2 (hydrogen peroxide) as well as with TSA (trichostatin). The HDAC activity in activated U937 cells was decreased. LLLT and dexa inhibited the LPS-stimulated U937 cells cytokines, but dexa effect disappeared with H2O2. With TSA, the LLLT was less effective on H2O2/LPS stimulated- U937 cells cytokines. Dexa failed on H2O2/LPS- induced HDAC, while LLLT restored the HDAC and the dexa effect. LLLT plus prostaglandin E2 (PGE2) increased cyclic adenosine monophosphate (cAMP) and potentiated the laser action on oxidative stress-induced cytokine. LLLT reduced the PI3K and its effects on cytokine and HDAC was suppressed with LY294002. In situations of corticoid resistance, LLLT acts decreasing the cytokines and HDAC through the activation of the protein kinase A via the inhibition of PI3K.

Dominance of the strongest: inflammatory cytokines versus glucocorticoids

Pro-inflammatory cytokines are involved in the pathogenesis of many inflammatory diseases, and the excessive expression of many of them is normally counteracted by glucocorticoids (GCs), which are steroids that bind to the glucocorticoid receptor (GR). Hence, GCs are potent inhibitors of inflammation, and they are widely used to treat inflammatory diseases, such as asthma, rheumatoid arthritis and inflammatory bowel disease. However, despite the success of GC therapy, many patients show some degree of GC unresponsiveness, called GC resistance (GCR). This is a serious problem because it limits the full therapeutic exploitation of the anti-inflammatory power of GCs. Patients with reduced GC responses often have higher cytokine levels, and there is a complex interplay between GCs and cytokines: GCs downregulate pro-inflammatory cytokines while cytokines limit GC action. Treatment of inflammatory diseases with GCs is successful when GCs dominate. But when cytokines overrule the anti-inflammatory actions of GCs, patients become GC insensitive. New insights into the molecular mechanisms of GR-mediated actions and GCR are needed for the design of more effective GC-based therapies.

Cellular and molecular mechanisms of chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease is associated with chronic inflammation affecting predominantly lung parenchyma and peripheral airways and results in largely irreversible and progressive airflow limitation. This inflammation is characterized by increased numbers of alveolar macrophages, neutrophils, and T lymphocytes, which are recruited from the circulation. Oxidative stress plays a key role in driving this inflammation. The pulmonary inflammation may enhance the development and growth of lung cancer. The peripheral inflammation extends into the circulation, resulting in systemic inflammation with the same inflammatory proteins. Systemic inflammation may worsen comorbidities. Treatment of pulmonary inflammation may therefore have beneficial effects.

Nuclear receptors in inflammation control: repression by GR and beyond

Inflammation is a protective response of organisms to pathogens, irritation or injury. Primary inflammatory sensors activate an array of signaling pathways that ultimately converge upon a few transcription factors such as AP1, NFκB and STATs that in turn stimulate expression of inflammatory genes to ultimately eradicate infection and repair the damage. A disturbed balance between activation and inhibition of inflammatory pathways can set the stage for chronic inflammation which is increasingly recognized as a key pathogenic component of autoimmune, metabolic, cardiovascular and neurodegenerative disorders. Nuclear receptors (NRs) are a large family of transcription factors many of which are known for their potent anti-inflammatory actions. Activated by small lipophilic ligands, NRs interact with a wide range of transcription factors, cofactors and chromatin-modifying enzymes, assembling numerous cell- and tissue-specific DNA-protein transcriptional regulatory complexes with diverse activities. Here we discuss established and emerging roles and mechanisms by which NRs and, in particular, the glucocorticoid receptor (GR) repress genes encoding cytokines, chemokines and other pro-inflammatory mediators.

How glucocorticoid receptors modulate the activity of other transcription factors: a scope beyond tethering

The activity of the glucocorticoid receptor (GR), a nuclear receptor transcription factor belonging to subclass 3C of the steroid/thyroid hormone receptor superfamily, is typically triggered by glucocorticoid hormones. Apart from driving gene transcription via binding onto glucocorticoid response elements in regulatory regions of particular target genes, GR can also inhibit gene expression via transrepression, a mechanism largely based on protein:protein interactions. Hereby GR can influence the activity of other transcription factors, without contacting DNA itself. GR is known to inhibit the activity of a growing list of immune-regulating transcription factors. Hence, GCs still rule the clinic for treatments of inflammatory disorders, notwithstanding concomitant deleterious side effects. Although patience is a virtue when it comes to deciphering the many mechanisms GR uses to influence various signaling pathways, the current review is testimony of the fact that groundbreaking mechanistic work has been accumulating over the past years and steadily continues to grow.

A polymorphism in the histone deacetylase 1 gene is associated with the response to corticosteroids in asthmatics

BACKGROUND/AIMS

Recent investigations suggest that histone deacetylase 1 (HDAC1) and HDAC2 may be target molecules to predict therapeutic responses to corticosteroids. We evaluated the effects of variation in HDAC1 and HDAC2 on the response to corticosteroids in asthmatics.

METHODS

Two single nucleotide polymorphisms (SNPs) were selected after resequencing HDAC1 and HDAC2. For the first analysis, we evaluated the association between those SNPs and asthma severity in 477 asthmatics. For the second analysis, we evaluated the effects of these SNPs on lung function improvements in response to corticosteroid treatment in 35 independent adult asthmatics and 70 childhood asthmatics.

RESULTS

We found that one SNP in HDAC1 (rs1741981) was significantly related to asthma severity in a recessive model (corrected p = 0.036). Adult asthmatics who were homozygous for the minor allele of rs1741981 showed significantly lower % forced expiratory volume in 1 second (%FEV1) increases in response to systemic corticosteroids treatment compared with the heterozygotes or those homozygous for the major allele (12.7% ± 7.2% vs. 37.4% ± 33.7%, p = 0.018). Similarly, childhood asthmatics who were homozygous for the minor allele of rs1741981 showed significantly lower %FEV1 increases in response to inhaled corticosteroid treatment compared with the heterozygotes or those homozygous for the major allele (14.1% ± 5.9% vs. 19.4% ± 8.9%, p = 0.035).

CONCLUSIONS

The present study demonstrated that rs1741981 in HDAC1 was significantly associated with the response to corticosteroid treatment in asthmatics.

Comparative cytoprotective effects of carbocysteine and fluticasone propionate in cigarette smoke extract-stimulated bronchial epithelial cells

Cigarette smoke extracts (CSE) induce oxidative stress, an important feature in chronic obstructive pulmonary disease (COPD), and oxidative stress contributes to the poor clinical efficacy of corticosteroids in COPD patients. Carbocysteine, an antioxidant and mucolytic agent, is effective in reducing the severity and the rate of exacerbations in COPD patients. The effects of carbocysteine on CSE-induced oxidative stress in bronchial epithelial cells as well as the comparison of these antioxidant effects of carbocysteine with those of fluticasone propionate are unknown. The present study was aimed to assess the effects of carbocysteine (10(-4) M) in cell survival and intracellular reactive oxygen species (ROS) production (by flow cytometry) as well as total glutathione (GSH), heme oxygenase-1 (HO-1), nuclear-related factor 2 (Nrf2) expression and histone deacetylase 2 (HDAC-2) expression/activation in CSE-stimulated bronchial epithelial cells (16-HBE) and to compare these effects with those of fluticasone propionate (10(-8) M). CSE, carbocysteine or fluticasone propionate did not induce cell necrosis (propidium positive cells) or cell apoptosis (annexin V-positive/propidium-negative cells) in 16-HBE. CSE increased ROS production, nuclear Nrf2 and HO-1 in 16-HBE. Fluticasone propionate did not modify intracellular ROS production, GSH and HDCA-2 but reduced Nrf2 and HO-1 in CSE-stimulated 16-HBE. Carbocysteine reduced ROS production and increased GSH, HO-1, Nrf2 and HDAC-2 nuclear expression/activity in CSE-stimulated cells and was more effective than fluticasone propionate in modulating the CSE-mediated effects. In conclusion, the present study provides compelling evidences that the use of carbocysteine may be considered a promising strategy in diseases associated with corticosteroid resistance.

Identification of a distinct glucocorticosteroid-insensitive pulmonary macrophage phenotype in patients with chronic obstructive pulmonary disease

BACKGROUND

In patients with chronic obstructive pulmonary disease (COPD), pulmonary macrophages increase in number, release increased levels of inflammatory mediators, and respond poorly to glucocorticosteroids. Whether this is due to a change in macrophage phenotype or localized activation is unknown.

OBJECTIVE

We sought to investigate whether macrophages from patients with COPD are a distinct phenotype.

METHODS

Macrophage populations were isolated from human lung tissue from nonsmokers, smokers, and patients with COPD by using Percoll density gradients. Five macrophage populations were isolated on the basis of density (1.011-1.023, 1.023-1.036, 1.036-1.048, 1.048-1.061, and 1.061-1.073 g/mL), and cell-surface expression of CD14, CD16, CD163, CD40, and CD206 was assessed by using flow cytometry. Release of active matrix metalloproteinase 9, TNF-α, CXCL8, and IL-10 was measured by using ELISA.

RESULTS

The 2 least dense fractions were more than 90% apoptotic/necrotic, with the remaining fractions greater than 70% viable. Macrophages from nonsmokers and smokers were CD163(+), CD206(+), CD14(+), and CD40(-), whereas macrophages from patients with COPD were less defined, showing significantly lower expression of all receptors. There were no differences in receptor expression associated with density. Macrophages from patients with COPD of a density of 1.036 to 1.048 g/mL released higher levels of active matrix metalloproteinase 9 compared with cells from nonsmokers, with no difference between the remaining fractions. This population of macrophages from patients with COPD was less responsive to budesonide compared with those from nonsmokers and smokers when stimulated with LPS. Glucocorticosteroid insensitivity was selective for proinflammatory cytokines because budesonide inhibition of LPS-stimulated IL-10 release was similar for all macrophages.

CONCLUSIONS

This study identifies a specific macrophage phenotype in the lungs of patients with COPD who are glucocorticosteroid insensitive with a density of 1.036 to 1.048 g/mL but do not correspond to the current concept of macrophage phenotypes.

Novel therapeutic strategies for lung disorders associated with airway remodelling and fibrosis

Inflammatory cell infiltration, cytokine release, epithelial damage, airway/lung remodelling and fibrosis are central features of inflammatory lung disorders, which include asthma, chronic obstructive pulmonary disease, acute respiratory distress syndrome and idiopathic pulmonary fibrosis. Although the lung has some ability to repair itself from acute injury, in the presence of ongoing pathological stimuli and/or insults that lead to chronic disease, it no longer retains the capacity to heal, resulting in fibrosis, the final common pathway that causes an irreversible loss of lung function. Despite inflammation, genetic predisposition/factors, epithelial-mesenchymal transition and mechanotransduction being able to independently contribute to airway remodelling and fibrosis, current therapies for inflammatory lung diseases are limited by their ability to only target the inflammatory component of the disease without having any marked effects on remodelling (epithelial damage and fibrosis) that can cause lung dysfunction independently of inflammation. Furthermore, as subsets of patients suffering from these diseases are resistant to currently available therapies (such as corticosteroids), novel therapeutic approaches are required to combat all aspects of disease pathology. This review discusses emerging therapeutic approaches, such as trefoil factors, relaxin, histone deacetylase inhibitors and stem cells, amongst others that have been able to target airway inflammation and airway remodelling while improving related lung dysfunction. A better understanding of the mode of action of these therapies and their possible combined effects may lead to the identification of their clinical potential in the setting of lung disease, either as adjunct or alternative therapies to currently available treatments.

Resveratrol attenuates the release of inflammatory cytokines from human bronchial smooth muscle cells exposed to lipoteichoic acid in chronic obstructive pulmonary disease

During bacterial infections, pathogen-associated molecular patterns (PAMPs) induce cytokine/chemokine release in immunoactive cells. This increases corticosteroid-resistant airway inflammation in chronic obstructive pulmonary disease (COPD) and leads to exacerbations. Anti-inflammatory therapies other than corticosteroids are required and resveratrol is currently under discussion. Resveratrol is an activator of sirtuins, which are class III histone deacetylases (HDACs). We suggested that human airway smooth muscle cells (HASMCs) release COPD-associated cytokines/chemokines in response to lipoteichoic acid (LTA), a major PAMP of gram-positive bacteria and that resveratrol is superior to the corticosteroid dexamethasone in suppressing these cytokines/chemokines. Cultivated HASMCs of patients with COPD were pre-incubated with resveratrol or dexamethasone before stimulation with LTA. CCL2, GM-CSF, IL-6 and IL-8 were analysed in culture supernatants by enzyme-linked immunosorbent assay. Drug effects were investigated in the absence and presence of trichostatin A (TSA), an inhibitor of class I/II HDACs, and EX527, an inhibitor of the sirtuin SIRT1. LTA induced robust cytokine/chemokine release. Resveratrol was superior to dexamethasone in reducing CCL-2, IL-6 and IL-8 in LTA-exposed HASMCs of patients with COPD. Both drugs were equally effective in reducing GM-CSF. Resveratrol effects were partially reversed by EX527 but not by TSA. Dexamethasone effects were partially reversed by TSA but not by EX527. We conclude that HASMCs contribute to the increase in airway inflammation in COPD exacerbations caused by gram-positive bacterial infections. Our data suggest resveratrol as an alternative anti-inflammatory therapy in infection-induced COPD exacerbations. Resveratrol and corticosteroids suppress cytokine/chemokine expression through activation of SIRT1 or interaction with class I/II HDACs, respectively, in HASMCs.

The biology of the glucocorticoid receptor: new signaling mechanisms in health and disease

Glucocorticoids are primary stress hormones necessary for life that regulate numerous physiologic processes in an effort to maintain homeostasis. Synthetic derivatives of these hormones have been mainstays in the clinic for treating inflammatory diseases, autoimmune disorders, and hematologic cancers. The physiologic and pharmacologic actions of glucocorticoids are mediated by the glucocorticoid receptor (GR), a member of the nuclear receptor superfamily of ligand-dependent transcription factors. Ligand-occupied GR induces or represses the transcription of thousands of genes through direct binding to DNA response elements, physically associating with other transcription factors, or both. The traditional view that glucocorticoids act through a single GR protein has changed dramatically with the discovery of a large cohort of receptor isoforms with unique expression, gene-regulatory, and functional profiles. These GR subtypes are derived from a single gene by means of alternative splicing and alternative translation initiation mechanisms. Posttranslational modification of these GR isoforms further expands the diversity of glucocorticoid responses. Here we discuss the origin and molecular properties of the GR isoforms and their contribution to the specificity and sensitivity of glucocorticoid signaling in healthy and diseased tissues.