Molecular mechanisms of antiasthma therapy

Repression of transcription by the glucocorticoid receptor: A parsimonious model for the genomics era

Glucocorticoids are potent anti-inflammatory drugs that are used to treat an extraordinary range of human disease, including COVID-19, underscoring the ongoing importance of understanding their molecular mechanisms. Early studies of GR signaling led to broad acceptance of models in which glucocorticoid receptor (GR) monomers tether repressively to inflammatory transcription factors, thus abrogating inflammatory gene expression. However, newer data challenge this core concept and present an exciting opportunity to reframe our understanding of GR signaling. Here, we present an alternate, two-part model for transcriptional repression by glucocorticoids. First, widespread GR-mediated induction of transcription results in rapid, primary repression of inflammatory gene transcription and associated enhancers through competition-based mechanisms. Second, a subset of GR-induced genes, including targets that are regulated in coordination with inflammatory transcription factors such as NF-κB, exerts secondary repressive effects on inflammatory gene expression. Within this framework, emerging data indicate that the gene set regulated through the cooperative convergence of GR and NF-κB signaling is central to the broad clinical effectiveness of glucocorticoids in terminating inflammation and promoting tissue repair.

Pharmacological bronchodilation is partially mediated by reduced airway wall stiffness

BACKGROUND AND PURPOSE

In asthmatic patients, airflow limitation is at least partly reversed by administration of pharmacological bronchodilators, typically β2 -adrenoceptor agonists. In addition to receptor-mediated bronchodilation, the dynamic mechanical environment of the lung itself can reverse bronchoconstriction. We have now explored the possibility that bronchodilators exert a synergistic effect with oscillatory loads by virtue of reducing airway wall stiffness, and therefore, enhancing the bronchodilatory response to breathing manoeuvres.

EXPERIMENTAL APPROACH

Whole porcine bronchial segments in vitro were contracted to carbachol and relaxed to the non-specific β-adrenoceptor agonist, isoprenaline, under static conditions or during simulated breathing manoeuvres.

KEY RESULTS

The bronchodilatory response to isoprenaline was greater during breathing manoeuvres compared with the response under static conditions. As the bronchodilatory response to breathing manoeuvres is dependent upon airway smooth muscle (ASM) strain, and therefore, airway wall stiffness, our findings are likely to be explained by the effect of isoprenaline on reducing airway wall stiffness, which increased ASM strain, producing greater bronchodilation.

CONCLUSIONS AND IMPLICATIONS

A contribution of reduced airway stiffness and increased ASM strain to the bronchodilator action of isoprenaline is shown, suggesting that oscillatory loads act synergistically with pharmacologically mediated bronchodilation. The implications for the treatment of asthma are that reducing airway wall stiffness represents a potential target for novel pharmacological agents.

Add-on salmeterol compared to double dose fluticasone in pediatric asthma: a double-blind, randomized trial (VIAPAED)

RATIONALE

In asthmatic children whose symptoms are uncontrolled on standard doses of inhaled corticosteroids (ICS), guidelines recommend to either increase the ICS dose or to add further controller medication, e.g. a long acting ss2-agonist (LABA). The aim of this study was to compare the efficacy and safety of doubling the dose of ICS (fluticasone proprionate FP 200 microg twice daily) with adding a long-acting beta-2 agonist to the ICS (SFC, salmeterol 50 microg/ FP 100 microg twice daily) in children with uncontrolled asthma.

METHODS

Children between 4 and 16 years of age were eligible for this multicenter, randomized, double blind, double dummy, parallel-group study. During a 14-day run-in phase, all children inhaled FP 100 microg b.i.d. Patients with persistent symptoms on > or =7 of 14 days were randomized to 8 weeks treatment with a Diskus(R) containing either SFC 50 microg/100 microg b.i.d. or FP 200 microg b.i.d.. The primary endpoint was the mean change in morning (a.m.) PEF from baseline. The initial statistical hypothesis of non-inferiority of SFC vs. FP was confirmed in an adaptive interim analysis, so that the study was terminated prematurely.

RESULTS

441 patients from 39 centers entered the run-in phase, and 64% of these were randomized to treatment (N = 138 to SFC and N = 145 to FP). After 8 weeks, patients on SFC had significantly better results for primary and secondary endpoints: The mean increase in morning PEF was 30.4 +/- 34.1 L/min in the SFC group and 16.7 +/- 35.8 L/min in the fluticasone group, and the mean (95% CI) improvement from baseline a.m. PEF in the ITT group was significantly larger after SFC (+8.6 L/min, CI: [1.3; infinity]). Patients in the SFC group experienced 8.7% (CI: [1.2;16.3]) more days without asthma symptoms and 8.0% (CI: [0.6;15.3]) more days without salbutamol than patients receiving FP. Good asthma control was achieved for a longer period in the SFC (3.4 +/- 2.7 weeks) group than in the FP group (2.7 +/- 2.7, P = 0.02). Both treatments were generally well tolerated. Asthma exacerbations were recorded in 3 and 6 and SAEs in 2 and 1 patients from the SFC and FP groups, respectively.

CONCLUSIONS

In children with persistent asthma inadequately controlled on low dose ICS alone, adding a long acting beta-2-agonist to ICS in a single inhaler was more effective than doubling the ICS dose. These results support recommendations of adding LABA to low-dose ICS as the preferred controller option for children older than 4 years with symptomatic asthma.

p38 and EGF receptor kinase-mediated activation of the phosphatidylinositol 3-kinase/Akt pathway is required for Zn2+-induced cyclooxygenase-2 expression

Cyclooxygenase 2 (COX-2) expression is induced by physiological and inflammatory stimuli. Regulation of COX-2 expression is stimulus and cell type specific. Exposure to Zn2+ has been associated with activation of multiple intracellular signaling pathways as well as the induction of COX-2 expression. This study aims to elucidate the role of intracellular signaling pathways in Zn2+-induced COX-2 expression in human bronchial epithelial cells. Inhibitors of the phosphatidylinositol 3-kinase (PI3K) potently block Zn2+-induced COX-2 mRNA and protein expression. Overexpression of adenoviral constructs encoding dominant-negative Akt kinase downstream of PI3K or wild-type phosphatase and tensin homolog deleted on chromosome 10, an important PI3K phosphatase, suppresses COX-2 mRNA expression induced by Zn2+. Zn2+ exposure induces phosphorylation of the tyrosine kinases, including Src and EGF receptor (EGFR), and the p38 mitogen-activated protein kinase. Blockage of these kinases results in inhibition of Zn2+-induced Akt phosphorylation as well as COX-2 protein expression. Overexpression of dominant negative p38 constructs suppresses Zn2+-induced increase in COX-2 promoter activity. In contrast, the c-Jun NH2-terminal kinase and the extracellular signal-regulated kinases have minimal effect on Akt phosphorylation and COX-2 expression. Inhibition of p38, Src, and EGFR kinases with pharmacological inhibitors markedly reduces Akt phosphorylation induced by Zn2+. However, the PI3K inhibitors do not show inhibitory effects on p38, Src, and EGFR. These data suggest that p38 and EGFR kinase-mediated Akt activation is required for Zn2+-induced COX-2 expression and that the PI3K/Akt signaling pathway plays a central role in this event.

The therapeutic potential of PDE4 inhibitors

Phosphodiesterase enzymes are responsible for the inactivation of cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP). Phosphodiesterase 4 (PDE4) is a cAMP specific phosphodiesterase expressed in inflammatory cells such as eosinophils. Inhibition of PDE4 results in an elevation of cAMP in these cells, which in turn downregulates the inflammatory response. The anti-inflammatory effects of PDE4 inhibitors have been well documented both in vitro and in vivo in a variety of animal models. The potential use of PDE4 inhibitors as anti-inflammatory agents for the treatment of asthma and other inflammatory disorders has received considerable attention from the pharmaceutical industry, but to date, there are no selective PDE4 inhibitors on the market. Early PDE4 inhibitors, typified by rolipram, suffered from dose-limiting side effects, including nausea and emesis, which severely restricted their therapeutic utility. Second generation compounds, including CDP840 and SB207499 (Ariflo), have been identified with reduced side effect liability. Recent evidence suggests a correlation between side effects and the ability of compounds to bind at the so-called high affinity rolipram binding site (HPDE), whilst beneficial effects appear to correlate with binding at the catalytic site. A number of companies are actively pursuing compounds which exhibit improved affinity for the catalytic site and reduced affinity for the HPDE, in the expectation that this will provide compounds with an improved therapeutic index.

The therapeutic potential of agents acting via purine receptors

A host of physiological processes associated with the cardiovascular (CV) system, central nervous system (CNS), and a variety of other organ systems and tissues are regulated by agents, primarily adenosine (ado) and adenosine triphosphate (ATP), that act via cell-surface purine receptors. These receptors have therefore been the focus of a variety of programmes directed at the discovery and development of new therapeutic agents, most notably for the treatment of disorders of the CV system. Currently, only a handful of agents, including ado, theophylline, dipyridamole, and ticlopidine, are approved for clinical use. A variety of new agents intended for use in CV disease, disorders of the CNS, such as Parkinson's disease, treatment of pain, inflammatory disorders, and diverse other pathophysiological conditions are in clinical development. Historically, ado receptors have been the primary target. Recent research efforts have begun to examine alternative strategies including agents that modulate endogenous levels of extracellular ado and agents that act via P(2) receptors.

Smoking status-dependent association of the 27-bp repeat polymorphism in intron 4 of endothelial nitric oxide synthase gene with plasma nitric oxide concentrations

BACKGROUND

Both positive and negative associations between a rare allele of 27-bp repeat polymorphism (eNOS4b/a polymorphism) in intron 4 of endothelial nitric oxide synthase and plasma nitric oxide (NO) concentrations were previously reported. Although these conflicting results were suggested to be partly accounted for smoking status of subjects, no further studies have been accomplished.

METHODS

We analyzed eNOS4b/a polymorphism in a group of 393 healthy Korean subjects and measured their plasma nitrite and nitrate (NO(x)) concentrations. NO(x) concentrations were measured by the Griess method and the genotypes of eNOS4b/a polymorphism determined by the banding pattern on gel electrophoresis.

RESULTS

The frequency of eNOS4a allele in this study was 11.6%. The plasma NO(x) concentrations (in micromol/l) in subjects with eNOS4a allele was found to be significantly higher relative to those in eNOS4b allele (49.68 +/- 18.62 and 55.25 +/- 20.87, respectively, P < 0.05), which was valid only in smokers. Multiple regression analysis revealed that the most predictive contributing factor for plasma NO(x) concentrations was eNOS4a allele (P < 0.01), followed by smoking (P < 0.05), total cholesterol (P < 0.05), and triglycerides (P < 0.05).

CONCLUSION

Our data indicate that there is substantial effect of eNOS4b/a polymorphism on the variance of plasma NO(x) concentrations in Korean population and that this effect is dependent on smoking status.

Lack of evidence for contribution of Glu298Asp (G894T) polymorphism of endothelial nitric oxide synthase gene to plasma nitric oxide levels

INTRODUCTION

Both positive and negative associations between a rare allele of 27-bp repeat polymorphism in intron 4 of endothelial nitric oxide synthase and plasma nitric oxide (NO) levels were previously reported, and further, these conflicting results were suggested to be partly accounted for smoking status of subjects. However, the genetic contribution of Glu298Asp (G894T) polymorphism to plasma NO levels with respect to smoking status has not been published.

METHODS

In a group of 411 healthy Korean subjects aged 19-81 years, the end product of NO (NO(x): nitrite plus nitrate) as an index of plasma NO levels was measured by the Griess method. The genotypes of G894T polymorphism were determined by the banding patterns on gel electrophoresis after restriction enzyme digestion.

RESULTS

Comparison of plasma NO(x) levels revealed no significant differences across the genotypes and alleles of G894T polymorphism, which is independently of smoking status. However, significant differences in plasma NO(x) levels between nonsmokers and smokers were observed (P = 0.0040). Furthermore, only the common G allele was found to be responsible for these differences. Multiple regression analysis showed that the most independent contributing factor for plasma NO(x) levels was smoking (P = 0.0119) and followed by triglycerides (P = 0.0384).

CONCLUSIONS

Our results indicate no substantial effect of G894T polymorphism on the variance of plasma NO(x) levels in healthy Korean population.

Drug therapy approaches in the treatment of acute severe asthma in hospitalised children

Acute severe paediatric asthma remains a serious and debilitating disease throughout the world. The incidence and mortality from asthma continue to increase. Early, effective and aggressive outpatient therapy is essential in reducing symptoms and preventing life-threatening progression. When complications occur or when the disease progresses to incipient respiratory failure, these children need to be managed in a continuous care facility where aggressive and potentially dangerous interventions can be safely instituted to reverse persistent bronchospasm. The primary drugs for acute severe asthma include oxygen, corticosteroids, salbutamol (albuterol) and anticholinergics. Second-line drugs include heliox, magnesium sulfate, ketamine and inhalational anaesthetics. Future therapies may include furosemide, leukotriene modifiers, antihistamines and phosphodiesterase inhibitors. This review attempts to explore the multitude of medications available with emphasis on pharmacology and pathophysiology.

Tumor necrosis factor has positive and negative self regulatory feed back cycles centered around cAMP

This paper reviews data that allow recognition of, (1) two opposing intracellular chains of events occurring subsequent to an increase in tumor necrosis factor, TNF, and (2) that these two chains have opposing effects on intracellular cyclic adenosine monophosphate, cAMP. The two chains - attenuation cycle, where TNF results in prostaglandin E mediated increased cAMP and, consequent to this, suppression of TNF levels; and an amplification cycle, where increased TNF increases intracellular cyclic adenosine phosphodiesterase, lowering cAMP, thereby raising TNF levels further. TNF is a central mediator in several inflammatory diseases. Understanding TNF control systems will allow better delineation of pathophysiology and clinical care.

Steroid-refractory neonatal eosinophilic pneumonia responsive to cyclosporin A

Idiopathic neonatal eosinophilic pneumonia is extremely rare. We report an infant who presented with tachypnea and interstitial infiltrates on chest radiograph at age 2 wk. Lung biopsy revealed perivascular and interstitial eosinophils. Despite initial improvement, the patient's condition became resistant to corticosteroids, cromolyn, and intravenous gamma globulin. After treatment with cyclosporin A his symptoms resolved.

Effects of systemic steroid treatment in chronic polypoid rhinosinusitis evaluated with magnetic resonance imaging

BACKGROUND

The aim of this prospective study was to evaluate the efficacy of a combined (local and systemic) steroid therapy on the extent of chronic polypoid rhinosinusitis and patient symptoms.

METHODS AND PATIENTS

Subjects of this study were 20 patients with severe chronic polypoid rhinosinusitis with total or subtotal narrowing of the all sinuses. A nasal budesonide spray (2 x 0.1 mg/day) and an oral fluocortolone medication with a daily reduction during a 12-day period (total dose: 560 mg = group 1) and a 20-day period (total dose: 715 mg = group 2), respectively, were administered. Before and after the steroid treatment we evaluated the extent of the sinusitis with MRI and patient symptoms with symptom-related questionnaires.

RESULTS

A significant reduction (> 30%) of the chronic polypoid rhinosinusitis was observed in 50% of MRI findings. The steroid effect on polypoid masses was heterogeneous in different anatomic areas (maxillary sinus 40%, anterior ethmoid 19%, posterior ethmoid 33%, sphenoidal sinus 61%, frontal sinus 46%). Most sinusitis-related symptoms were distinctly diminished in most patients (80%). No major side effects were observed.

CONCLUSIONS

A combined short-term steroid therapy is highly effective in chronic polypoid rhinosinusitis, reducing the mucosal inflammation mainly in the large sinuses and reducing the incidence of symptoms significantly. However, this therapy was insufficient in the anterior ethmoid and cannot replace the current surgical treatment concept of the osteomeatal complex in CPR. The indication for such a short-term steroid therapy is the preoperative treatment. It facilitates functional endoscopic sinus surgery by reducing the extent of surgical procedures, the time, and thereby the risks of sinus surgery.

Phosphodiesterase expression in human epithelial cells

Epithelial cells play a critical role in airway inflammation and have the capacity to produce many inflammatory mediators, including bioactive lipids and proinflammatory cytokines. Intracellular levels of cAMP and cGMP are important in the control of inflammatory cell function. These cyclic nucleotides are inactivated via a family of phosphodiesterase (PDE) enzymes, providing a possible site for drug intervention in chronic inflammatory conditions. We studied the expression of PDE activity in an epithelial cell line (A549) and in primary human airway epithelial cells (HAECs). We measured PDE function using specific inhibitors to identify the PDE families present and used RT-PCR to elucidate the expression of PDE isogenes. Both A549 cells and HAECs predominantly expressed PDE4 activity, with lesser PDE1, PDE3, and PDE5 activity. RT-PCR identified HSPDE4A5 and HSPDE4D3 together with HSPDE7. Inhibition of PDE4 and PDE3 reduced secretion by these cells. Epithelial PDE may be an important target for PDE4 inhibitors in the development of the control of asthmatic inflammation, particularly when delivered via the inhaled route.

Cyclooxygenase isoenzyme localization and mRNA expression in rat lungs

Prostanoid generation may proceed via both isoforms of cyclooxygenase, Cox-1 and Cox-2. Cox-1 is thought to be ubiquitously expressed, whereas Cox-2 is mostly assumed to be dynamically regulated, responding to inflammatory stimuli. The cellular localization of Cox-1 and Cox-2 in the lung, an organ with high cyclooxygenase activity, is not known. In normal rat lungs the expression and localization of Cox-1 and Cox-2 were examined with immunogold-silver staining and the RT-PCR technique. Quantitative image analysis of the staining intensity was performed by measuring mean gray values of digitized epipolarization images. Expression of both Cox-1 and Cox-2 was readily detectable in rat lungs. Cox-1 immunoreactivity localized predominantly to bronchial epithelial cells, smooth muscle cells of large hilum veins, and (with lower expression) to alveolar macrophages and pulmonary artery endothelial cells. The most intense Cox-2 staining was noted in macrophage- and mast cell-like cells, detected in close vicinity to the bronchial epithelium and in the connective tissue surrounding the vessels. In addition, strong Cox-2 expression was found in smooth muscle cells of partially muscular vessels and large veins of the hilum. Bronchial epithelial cells displayed Cox-2 immunoreactivity with limited intensity. Alveolar macrophages and alveolar septal cells were only occasionally stained with anti-Cox-2 antibodies. Both Cox-1 and Cox-2 are constitutively expressed in several cell types of normal rat lung, but display clearly different patterns of cellular localization. Cox-2 may not be related only to lung inflammation, but is suggested to be implicated in regulatory processes under physiological conditions as well.

Aerosol therapy in the equine species

Inhalation therapy plays an increasing role in the management of equine respiratory disorders. This alternative to systematic treatment permits a high concentration of medication to act locally while minimizing side effects and residues. In human medicine, literature in this field is prolific and continuously renewed, whereas in veterinary medicine, applications of aerosol therapy are less extensive. This review considers the principles of action of the different types of devices used for inhalation, i.e., nebulization, metered-dose inhalation and dry powder inhalation, describes the technical and practical requirements for their use in the equine species and considers the advantages and disadvantages of each inhalation device. The pharmacological agents currently administered to horses by inhalation are also discussed. Perspectives of aerosol therapy in the equine species, including aerosols already used in human medicine and their potential applications for horses are described.

Nuclear factor-kappa B repression in antiinflammation and immunosuppression by glucocorticoids

The transcription factor nuclear factor-kappaB (NF-kappaB) directs transcription of a large number of key molecules in immunological and inflammatory responses. The recently discovered inhibition of transcriptional activity of this factor by the activated glucocorticoid receptor (GR) provides a molecular basis for the potent antiinflammatory and immunosuppressive properties of glucocorticoids. This repressive activity of the GR can function independently of transcriptional activity. Because it has been shown that certain steroid receptor ligands can differentially address transactivation and transrepression functions, it may be possible to develop ligands that specifically suppress NF-kappaB activity and, as a result, are more efficient in treatment of a variety of important chronic inflammatory diseases with less severe side effects than those of currently available drugs.