Respirable antisense oligonucleotides: a new, third drug class targeting respiratory disease

What is new in the management of childhood asthma?

The prevalence of asthma has increased in developed countries. The efficacy of available drugs in those with severe persistent disease is limited. This has led to a renewed search for the reasons for failures of the existing treatment and for novel concepts. Treatment with inhaled corticosteroids, and to a much lesser extent theophylline, can reduce the survival of inflammatory cells including eosinophils. Emerging trends in treatments for asthma could include strategies to alter the cytokine/chemokine balance. It is evident that the current ICS are already very efficient and safe, it will be difficult to introduce further improved formulations. Perhaps the most fruitful effort shall be in developing patient friendly easy to use targeted delivery systems. The newer therapies are planned for the several upstream targets and may have potential to prevent the disease. Various potential therapies are being worked upon like-targeting prevention of T cell activation, modulation of Th-1/Th-2 differentiation, inhibition of Th-2 related cytokines, Th-1/Th-2 modulation, inhibition of downstream mediators etc. The new strategy shall perhaps lie with matching the patients and their disease with the most suitable therapy.

Therapeutic approaches for control of transcription factors in allergic disease

The inflammatory response observed in allergic disease involves multiple cell types but is orchestrated in part by the T(H)2 cytokines IL-4, IL-5, and IL-13. In recent years, the transcription factors that control the expression and function of these cytokines have been elucidated, including signal transducer and activator of transcription 6, GATA3, nuclear factor of activated T cells, and nuclear factor kappaB. These molecules are attractive targets for therapeutic intervention because they regulate the expression of numerous effector molecules and functions simultaneously. For instance, the immunosuppressive agents glucocorticoids and cyclosporin A both function by repressing the activity of transcription factors through a variety of mechanisms. In this review we examine the role of each transcription factor in allergic disease and discuss approaches that have been taken to therapeutically interfere with transcription factor function in allergic disease.

Effective prevention and therapy of experimental allergic asthma using a GATA-3-specific DNAzyme

BACKGROUND

Allergic bronchial asthma is a chronic inflammatory disease of the airways. The transcription factor GATA-3 was shown to play an important role in TH2 cell activation, but also in the regulation of other cell types involved in bronchial asthma including mast cells, eosinophils, and epithelial cells. DNAzymes represent a new class of antisense molecules that combines the specificity of DNA base pairing with an inherent RNA-cleaving enzymatic activity.

OBJECTIVE

To develop a GATA-3 mRNA-specific DNAzyme and analyze its allergy-preventing activity in murine models of experimental allergic asthma.

METHODS

The most active DNAzyme (termed gd21) was selected by in vitro cleavage assays. Allergic airway inflammation was assessed by inflammatory cell and cytokine analysis within bronchoalveolar lavage. Lung histology, including goblet cell hyperplasia and lung function, was analyzed using head-out body-plethysmography.

RESULTS

Intranasal administration of gd21 prevented airway inflammation and mucus production and inhibited development of airway hyperresponsiveness to methacholine in models of acute allergic airway inflammation. Similar effects were also detected in a model of chronic experimental asthma. Interestingly, gd21 was at least as effective as other antisense molecules, and off-target effects were not detected. Further experiments indicated that pulmonary surfactant may facilitate the cellular uptake of gd21 by acting as an endogenous transfectant.

CONCLUSION

These results indicate that topical application of the GATA-3-specific DNAzyme is a promising novel approach for the treatment of allergic bronchial asthma.

Role of adenosine receptors in the treatment of asthma and chronic obstructive pulmonary disease: recent developments

Adenosine is a naturally occurring purine nucleoside with a ubiquitous presence in human tissue, where it plays a key role in many biological processes such as energy generation and protein metabolism. It has been shown that adenosine induces bronchoconstriction in asthmatic and chronic obstructive pulmonary disease (COPD) patients, but not in normal airways. Four different G-protein-coupled adenosine receptors have been described, namely adenosine A(1), A(2A), A(2B) and A(3) receptors. The main mechanism of adenosine-induced bronchoconstriction appears to involve the release of inflammatory mediators from mast cells via activation of the A(2B) receptor. However, adenosine can also act on A(1), A(2A) and A(3) receptors. In recent years there has been an increasing interest in the role of adenosine receptors in asthma and COPD, since it is now clear that they play an important role in the pathophysiology of asthma and COPD. Adenosine receptors are involved in the production and release of a variety of mediators from inflammatory and structural cells. A therapeutic potential for adenosine receptor modulation has even been anticipated. This review focuses on the role of adenosine and adenosine receptors in the treatment of asthma and COPD.

Anti-TNF-alpha and Th1 cytokine-directed therapies for the treatment of asthma

PURPOSE OF REVIEW

This article examines recent work about the role of TNF-alpha and of selected Th1-related cytokines in asthma with particular emphasis on the therapeutic potential of blocking the biological activity of these mediators.

RECENT FINDINGS

Current research endeavours suggest that asthma pathogenesis is driven by a mixed Th1/Th2 immune response. The contribution of individual Th1-associated and Th2-associated effector mechanisms to this mixed response profile is highly heterogeneous and variations in response patterns seem to be associated with heterogeneity in clinical phenotypes. In particular, it is now acknowledged that allergen-specific Th1 responses appear to be responsible for the pathogenetic effects seen in patients suffering from the more severe chronic forms of the disease. This is important because usual treatments for asthma appear to have limited effects on the more chronic severe forms of the disease and there is a pressing need for the development of new treatment strategies. The failure of topical corticosteroids to reduce TNF-alpha and Th1-derived cytokines to a significant level in asthmatic airways may explain to a certain extent why these drugs appear to have limited effects in the more severe forms of asthma.

SUMMARY

It is likely that therapies blocking TNF-alpha and interfering with Th1-derived cytokines may be a considerable advance in the management of those asthma patients who are particularly resistant to typical treatment modalities.

Antisense- and RNA interference-based therapeutic strategies in allergy

Modern therapeutic methods for manipulation of gene expression in allergic diseases have been receiving increased attention in the emerging era of functional genomics. With the growing application of gene silencing technologies, pharmacological modulation of translation represents a great advance in molecular therapy for allergy. Several strategies for sequence-specific post-transcriptional inhibition of gene expression can be distinguished: antisense oligonucleotides (AS-ONs), ribozymes (RZs), DNA enzymes (DNAzymes), and RNA interference (RNAi) triggered by small interfering RNAs (siRNAs). Potential anti-mRNA drugs in asthma and other allergic disorders may be targeted to cell surface receptors (adenosine A1 receptor, high-affinity receptor Fc-epsilon RI-alpha, cytokine receptors), adhesion molecules and ligands (ICAM-1, VLA-4), ion channels (calcium-dependent chloride channel-1), cytokines and related factors (IL-4, IL-5, IL-13, SCF, TNF-alpha, TGF-beta1), intracellular signal transduction molecules, such as tyrosine-protein kinases (Syk, Lyn, Btk), serine/ threonine-protein kinases (p38 alpha MAPkinase, Raf-1), non-kinase signaling proteins (RasGRP4), and transcription factors involved in Th2 differentiation and allergic inflammation (STAT-6, GATA-3, NF-kappaB). The challenge to scientists is to determine which of the candidate targets warrants investment of time and resources. New-generation respirable AS-ONs, external guide sequence ribozymes, and RNA interference-based therapies have the potential to satisfy unmet needs in allergy treatment, acting at a more proximal level to a key etiopathogenetic molecular process, represented by abnormal expression of genes. Moreover, antisense and siRNA technologies imply a more rational design of new drugs for allergy.

Newer drugs for asthma

Several new drugs have resulted from innovative pharmacological and immunomodulatory approaches towards treatment of asthma. Diverse therapeutic targets have provided new agents. The new classes of drugs available are newer "on site activated inhaled corticisteroids" and soft steroids, anti IgE compounds, leukotriene inhibitors and single isomer agents which are available for clinical use. Anti interleukin agents and phosphodiesterase inhibitors are in the stage of clinical trials. Antisense therapy and pharmacogenetics are the on horizon for treatment of asthma.

New asthma drugs acting on gene expression

New asthma drugs acting on transcription are transcription factor agonists (dissociated steroids, peroxisome proliferator-activated receptor gamma agonists), transcription factor inhibitors (NF-kappaB / AP-1 inhibitors, STAT6 inhibitors), inhibitors of protein kinases acting on transcription factors (p38 MAP kinase inhibitors), and chromatin modifying agents. Pharmacological approach of translation in asthma includes therapeutic ribozymes and antisense oligonucleotides targeting receptors (adenosine A1 receptor, alpha chain of IL-5 receptor, common beta chain of IL-3/IL-5/GM-CSF receptor), cytokines (IL-4, IL-5, SCF), signal transduction molecules (Syk, Lyn), transcription factors (STAT-6, GATA-3). Some of these drugs acting on gene expression have the potential to improve therapeutic benefits compared with traditional drugs.

Potential new drugs for therapy of chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease is a major health problem with cigarette smoking as its major risk factor. Current therapies are directed against the symptoms (e.g., breathlessness and mucus production) or the chronic airway inflammation. However, the excessive annual decline in lung function and the airway inflammation have not yet been shown to be improved by these strategies. New potential drug therapies are directed against specific components of the inflammation. Novel drugs have been developed for treatment of inflammatory diseases including chronic obstructive pulmonary disease in order to antagonise cytokines and chemokines such as TNF-alpha, CXC chemokine ligand 8 (IL-8) or CC chemokine ligand 2 (monocyte chemoattractant protein 1) that orchestrate the inflammatory process. Some of these drugs are shown to be effective in patients with other chronic inflammatory diseases but still have to prove their efficacy in the treatment of chronic obstructive pulmonary disease.