Expression of the IL-4 receptor alpha-subunit is increased in bronchial biopsy specimens from atopic and nonatopic asthmatic subjects

Elarekibep (PRS-060/AZD1402), a new class of inhaled Anticalin medicine targeting IL-4Ra for type 2 endotype asthma

BACKGROUND

Type 2 endotype asthma is driven by IL-4 and IL-13 signaling via IL-4Ra, which is highly expressed on airway epithelium, airway smooth muscle, and immunocytes in the respiratory mucosa, suggesting potential advantages of an inhalable antagonist. Lipocalin 1 (Lcn1), a 16 kDa protein abundant in human periciliary fluid, has a robust drug-like structure well suited to protein engineering, but it has never been used to make an inhaled Anticalin protein therapeutic.

OBJECTIVES

We sought to reengineer Lcn1 into an inhalable IL-4Ra antagonist and assess its pharmacodynamic/kinetic profile.

METHODS

Lcn1 was systematically modified by directed protein mutagenesis yielding a high-affinity, slowly dissociating, long-acting full antagonist of IL-4Ra designated PRS-060 with properties analogous to dupilumab, competitively antagonizing IL-4Ra-dependent cell proliferation, mucus induction, and eotaxin expression in vitro. Because PRS-060 displayed exquisite specificity for human IL-4Ra, with no cross-reactivity to rodents or higher primates, we created a new triple-humanized mouse model substituting human IL-4Ra, IL-4, and IL-13 at their correct syntenic murine loci to model clinical dosing.

RESULTS

Inhaled PRS-060 strongly suppressed acute allergic inflammation indexes in triple-humanized mice with a duration of action longer than its bulk clearance, suggesting that it may act locally in the lung.

CONCLUSION

Lcn1 can be reengineered into the Anticalin antagonist PRS-060 (elarekibep), exemplifying a new class of inhaled topical, long-acting therapeutic drugs with the potential to treat type 2 endotype asthma.

Trained immunity in type 2 immune responses

Immunological memory of innate immune cells, also termed "trained immunity", allows for cross-protection against distinct pathogens, but may also drive chronic inflammation. Recent studies have shown that memory responses associated with type 2 immunity do not solely rely on adaptive immune cells, such as T- and B cells, but also involve the innate immune system and epithelial cells. Memory responses have been described for monocytes, macrophages and airway epithelial cells of asthmatic patients as well as for macrophages and group 2 innate lymphoid cells (ILC2) from allergen-sensitized or helminth-infected mice. The metabolic and epigenetic mechanisms that mediate allergen- or helminth-induced reprogramming of innate immune cells are only beginning to be uncovered. Trained immunity has been implicated in helminth-driven immune regulation and allergen-specific immunotherapy, suggesting its exploitation in future therapies. Here, we discuss recent advances and key remaining questions regarding the mechanisms and functions of trained type 2 immunity in infection and inflammation.

The establishment of humanized IL-4/IL-4RA mouse model by gene editing and efficacy evaluation

Asthma is a common respiratory immune disease in children and adults, and interleukin-4 (IL-4) is one of the key factors for the onset of asthma. Therefore, targeting human IL-4 and IL-4 receptor alpha (IL-4RA) has become one of the strategies for targeted therapy of cytokines. Herein, we established an animal model of asthmatic airway inflammation using double humanized IL-4/IL-4RA (hIL-4/hIL-4RA) mice, where human IL-4 and IL-4RA replaced their murine counterparts, respectively. We successfully identified the phenotype by Southern blotting, ELISA, and flow cytometry. The hIL-4/hIL-4RA mice induced by ovalbumin (OVA) exhibited several important features of asthma, such as inflammatory cell infiltration, IgE release, goblet cell hyperplasia, and Th2 cytokine secretion. Furthermore, treatment of these humanized mice with anti-human IL-4RA antibodies significantly inhibited level of these pathological indicators. Thus, hIL-4/hIL-4RA mice provide a validated preclinical mouse model to interrogate new therapeutic agents targeting this specific cytokine pathway in asthma.

Staphylococcus aureus and its IgE-inducing enterotoxins in asthma: current knowledge

While immunoglobulin (Ig) E is a prominent biomarker for early-onset, its levels are often elevated in non-allergic late-onset asthma. However, the pattern of IgE expression in the latter is mostly polyclonal, with specific IgEs low or below detection level albeit with an increased total IgE. In late-onset severe asthma patients, specific IgE to Staphylococcal enterotoxins (se-IgE) can frequently be detected in serum, and has been associated with asthma, with severe asthma defined by hospitalisations, oral steroid use and decrease in lung function. Recently, se-IgE was demonstrated to even predict the development into severe asthma with exacerbations over the next decade. Staphylococcus aureus manipulates the airway mucosal immunology at various levels via its proteins, including superantigens, serine-protease-like proteins (Spls), or protein A (SpA) and possibly others. Release of IL-33 from respiratory epithelium and activation of innate lymphoid cells (ILCs) via its receptor ST2, type 2 cytokine release from those ILCs and T helper (Th) 2 cells, mast cell degranulation, massive local B-cell activation and IgE formation, and finally eosinophil attraction with consequent release of extracellular traps, adding to the epithelial damage and contributing to disease persistence via formation of Charcot-Leyden crystals are the most prominent hallmarks of the manipulation of the mucosal immunity by S. aureus In summary, S. aureus claims a prominent role in the orchestration of severe airway inflammation and in current and future disease severity. In this review, we discuss current knowledge in this field and outline the needs for future research to fully understand the impact of S. aureus and its proteins on asthma.

Tight junctions in pulmonary epithelia during lung inflammation

Inflammatory lung diseases like asthma bronchiale, chronic obstructive pulmonary disease and allergic airway inflammation are widespread public diseases that constitute an enormous burden to the health systems. Mainly classified as inflammatory diseases, the treatment focuses on strategies interfering with local inflammatory responses by the immune system. Inflammatory lung diseases predispose patients to severe lung failures like alveolar oedema, respiratory distress syndrome and acute lung injury. These life-threatening syndromes are caused by increased permeability of the alveolar and airway epithelium and exudate formation. However, the mechanism underlying epithelium barrier breakdown in the lung during inflammation is elusive. This review emphasises the role of the tight junction of the airway epithelium as the predominating structure conferring epithelial tightness and preventing exudate formation and the impact of inflammatory perturbations on their function.

Omalizumab reduces bronchial mucosal IgE and improves lung function in non-atopic asthma

Omalizumab therapy of non-atopic asthmatics reduces bronchial mucosal IgE and inflammation and preserves/improves lung function when disease is destabilised by staged withdrawal of therapy.

18 symptomatic, non-atopic asthmatics were randomised (1:1) to receive omalizumab or identical placebo treatment in addition to existing therapy for 20 weeks. Bronchial biopsies were collected before and after 12–14 weeks of treatment, then the patients destabilised by substantial, supervised reduction of their regular therapy. Primary outcome measures were changes in bronchial mucosal IgE+ cells at 12–14 weeks, prior to regular therapy reduction, and changes in lung function (forced expiratory volume in 1 s) after destabilisation at 20 weeks. Quality of life was also monitored.

Omalizumab but not placebo therapy significantly reduced median total bronchial mucosal IgE+ cells (p<0.01) but did not significantly alter median total mast cells, plasma cells, B lymphocytes, eosinophils and plasmablasts, although the latter were difficult to enumerate, being distributed as disperse clusters. By 20 weeks, lung function declined in the placebo-treated patients but improved in the omalizumab treated patients, with significant differences in absolute (p=0.04) and % predicted forced expiratory volume in 1 s (p=0.015).

Omalizumab therapy of non-atopic asthmatics reduces bronchial mucosal IgE+ mast cells and improves lung function despite withdrawal of conventional therapy.

Local IgE in non-allergic rhinitis

Local allergic rhinitis (LAR) is characterized by the presence of a nasal Th2 inflammatory response with local production of specific IgE antibodies and a positive response to a nasal allergen provocation test (NAPT) without evidence of systemic atopy. The prevalence has been shown to be up to 25% in subjects affected with rhinitis with persistence, comorbidity and evolution similar to allergic rhinitis. LAR is a consistent entity that does not evolve to allergic rhinitis with systemic atopy over time although patients have significant impairment in quality of life and increase in the severity of nasal symptoms over time. Lower airways can be also involved. The diagnosis of LAR is based mostly on demonstration of positive response to NAPT and/or local synthesis of specific IgE. Allergens involved include seasonal or perennial such as house dusts mites, pollens, animal epithelia, moulds (alternaria) and others. Basophils from peripheral blood may be activated by the involved allergens suggesting the spill over of locally synthesized specific IgE to the circulation. LAR patients will benefit from the same treatment as allergic patients using antihistamines, inhaled corticosteroids and IgE antagonists. Studies on immunotherapy are ongoing and will determine its efficacy in LAR in terms of symptoms improvement and evolution of the natural course of the disease.

Targeting IL4/IL4R for the treatment of epithelial cancer metastasis

While progress has been made in treating primary epithelial tumors, metastatic tumors remain largely incurable and still account for 85-90 % of all cancer-related deaths. Interleukin-4 (IL4), a Th2 cytokine, and the IL4/IL4 receptor (IL4R) interaction have well defined roles in the immune system. Yet, IL4 receptors are over-expressed by many epithelial cancers and could be a promising target for metastatic tumor therapy. The IL4/IL4R signaling axis is a strong promoter of pro-metastatic phenotypes in epithelial cancer cells including enhanced migration, invasion, survival, and proliferation. The promotion of breast cancer growth specifically is also supported in part by IL4-induced glutamine metabolism, and we have shown that IL4 is also capable of inducing glucose metabolism in breast cancer cells. Importantly, there are several types of FDA approved medications for use in asthma patients that inhibit the IL4/IL4R signaling axis. However, these approved medications inhibit both the type I IL4 receptor found on immune cells, and the type II IL4 receptor that is predominantly expressed by some non-hematopoietic cells including epithelial cancer cells. This article reviews existing therapies targeting IL4, IL4R, or IL4/IL4R signaling, and recent findings guiding the creation of novel therapies that specifically inhibit the type II IL4R, while taking into consideration effects on immune cells within the tumor microenvironment. Some of these therapies are currently in clinical trials for cancer patients, and may be exploitable for the treatment of metastatic disease.

Regulation of IL-4 receptor signaling by STUB1 in lung inflammation

RATIONALE

IL-4Rα, the common receptor component for IL-4 and IL-13, plays a critical role in IL-4- and IL-13-mediated signaling pathways that regulate airway inflammation and remodeling. However, the regulatory mechanisms underlying IL-4Rα turnover and its signal termination remain elusive.

OBJECTIVES

To evaluate the role of STUB1 (STIP1 homology and U-Box containing protein 1) in regulating IL-4R signaling in airway inflammation.

METHODS

The roles of STUB1 in IL-4Rα degradation and its signaling were investigated by immunoblot, immunoprecipitation, and flow cytometry. The involvement of STUB1 in airway inflammation was determined in vivo by measuring lung inflammatory cells infiltration, mucus production, serum lgE levels, and alveolar macrophage M2 activation in STUB1(-/-) mice. STUB1 expression was evaluated in airway epithelium of patients with asthma and lung tissues of subjects with chronic obstructive pulmonary disease.

MEASUREMENTS AND MAIN RESULTS

STUB1 interacted with IL-4Rα and targeted it for ubiquitination-mediated proteasomal degradation, terminating IL-4 or IL-13 signaling. STUB1 knockout cells showed increased levels of IL-4Rα and sustained STAT6 activation, whereas STUB1 overexpression reduced IL-4Rα levels. Mice deficient in STUB1 had spontaneous airway inflammation, alternative M2 activation of alveolar macrophage, and increased serum IgE. STUB1 levels were increased in airways of subjects with asthma or chronic obstructive pulmonary disease, suggesting that up-regulation of STUB1 might be an important feedback mechanism to dampen IL-4R signaling in airway inflammation.

CONCLUSIONS

Our study identified a previously uncharacterized role for STUB1 in regulating IL-4R signaling, which might provide a new strategy for attenuating airway inflammation.

Association between interleukin-4 receptor α chain (IL4RA) I50V and Q551R polymorphisms and asthma risk: an update meta-analysis

BACKGROUND

The associations between the interleukin-4 receptor α chain (IL4RA) I50V and Q551R polymorphisms and asthma risk remained controversial.

METHODS

We searched the Pubmed, Embase, Chinese National Knowledge Infrastructure (CNKI) and Wanfang databases for studies published before February 2013. The strengths of the associations were calculated using odds ratios (ORs) with 95% confidence intervals (CIs).

RESULTS

A total of 50 studies were included in this meta-analysis. There was a significant association between the IL4RA I50V polymorphism and asthma risk in a dominant genetic model (OR = 1.13, 95% CI 1.04-1.23, P = 0.005). The IL4RA Q551R polymorphism was associated with a significantly elevated asthma risk in a recessive genetic model (OR = 1.46, 95% CI 1.22-1.75, P<0.0001). Subgroup analyses found that the IL4RA I50V polymorphism was significantly associated with asthma risk in Asians (OR = 1.72, 95% CI 1.31-2.25, P<0.0001), pediatric asthma risk (OR = 1.50, 95% CI 1.13-1.99, P = 0.005), and atopic asthma risk (OR = 1.88, 95% CI 1.27-2.79, P = 0.002).

CONCLUSIONS

The results of this meta-analysis suggested that the IL4RA I50V and Q551R polymorphisms may be risk factors for developing asthma.

STAT6 and lung inflammation

Lung inflammation has many etiologies, including diseases of Th2-type immunity, such as asthma and anti-parasitic responses. Inflammatory diseases of the lung involve complex interactions among structural cells (airway epithelium, smooth muscle, and fibroblasts) and immune cells (B and T cells, macrophages, dendritic cells, and innate lymphoid cells). Signal transducer and activator of transcription 6 (STAT6) has been demonstrated to regulate many pathologic features of lung inflammatory responses in animal models including airway eosinophilia, epithelial mucus production, smooth muscle changes, Th2 cell differentiation, and IgE production from B cells. Cytokines IL-4 and IL-13 that are upstream of STAT6 are found elevated in human asthma and clinical trials are underway to therapeutically target the IL-4/IL-13/STAT6 pathway. Additionally, recent work suggests that STAT6 may also regulate lung anti-viral responses and contribute to pulmonary fibrosis. This review will focus on the role of STAT6 in lung diseases and mechanisms by which STAT6 controls immune and structural lung cell function.

Targeting interleukin-4 in asthma: lost in translation?

The first discovery that interleukin-4 (IL-4) is crucial in the development of allergic airway inflammation originates from the early 1990s. Whereas initial studies in experimental animal models provided the community with the optimistic view that targeting IL-4 would be the ultimate solution for treating asthma, the translation of these findings to the clinic has not been evident and has not yet fulfilled the expectations. Many technical challenges have been encountered in the attempts to modulate IL-4 expression or activity and in transferring knowledge of preclinical studies to clinical trials. Moreover, biological redundancies between IL-4 and IL-13 have compelled a simultaneous blockade of both cytokines. A number of phase I/II studies are now providing us with clinical evidence that targeting IL-4/IL-13 may provide some clinical benefit. However, the initial view that asthma is a purely Th2-mediated disease had to be revised. Currently, different asthma phenotypes have been described, implying that blocking specifically Th2 cytokines, such as IL-4, IL-5, and IL-13, should be targeted to only a specific subset of patients. Taking this into consideration, IL-4 (together with IL-13) deserves attention as subject of further investigations to treat asthma. In this review, we will address the role of IL-4 in asthma, describe IL-4 signaling, and give an overview of preclinical and clinical studies targeting the IL-4 Receptor pathway.

Identification of contact and respiratory sensitizers according to IL-4 receptor α expression and IL-2 production

Identification of allergenic chemicals is an important occupational safety issue. While several methods exist to identify contact sensitizers, there is currently no validated model to predict the potential of chemicals to act as respiratory sensitizers. Previously, we reported that cytometry analysis of the local immune responses induced in mice dermally exposed to the respiratory sensitizer trimellitic anhydride (TMA 10%) and contact sensitizer dinitrochlorobenzene (DNCB 1%) could identify divergent expression of several immune parameters. The present study confirms, first, that IgE-positive B cells, MHC class II molecules, interleukin (IL)-2, IL-4 and IL-4Rα can differentiate the allergic reactions caused by high doses of strong respiratory (TMA, phthalic anhydride and toluene diisocyanate) and contact sensitizers (DNCB, dinitrofluorobenzene and oxazolone). The second part of the study was designed to test the robustness of these markers when classing the weakly immunogenic chemicals most often encountered. Six respiratory allergens, including TMA (2.5%), five contact allergens, including DNCB (0.25%), and two irritants were compared at doses of equivalent immunogenicity. The results indicated that IL-4Rα and IL-2 can be reliably used to discriminate sensitizers. Respiratory sensitizers induced markedly higher IL-4Rα levels than contact allergens, while irritants had no effect on this parameter. Inversely, contact allergens tended to induce higher percentages of IL-2⁺CD8⁺ cells than respiratory allergens. In contrast, the markers MHC-II, IgE and IL-4 were not able to classify chemicals with low immunogenic potential. In conclusion, IL-4Rα and IL-2 have the potential to be used in classifying a variety of chemical allergens.

Expression of IL-4/IL-13 receptors in differentiating human airway epithelial cells

IL-4 and IL-13 elicit several important responses in airway epithelium including chemokine secretion and mucous secretion that may contribute to airway inflammation, cell migration, and differentiation. These cytokines have overlapping but not identical effector profiles likely due to shared subunits in their receptor complexes. These receptors are variably described in epithelial cells, and the relative expression, localization, and function of these receptors in differentiated and repairing epithelial cells are not clear. We examined IL-4/IL-13 receptor expression and localization in primary airway epithelial cells collected from normal human lungs and grown under conditions yielding both undifferentiated and differentiated cells inclusive of basal, goblet, and ciliated cell phenotypes. Gene expression of the IL-4Rα, IL-2Rγc, IL-13Rα1, and IL-13Rα2 receptor subunits increased with differentiation, but different patterns of localization and protein abundance were seen for each subunit based on both differentiation and the cell subtypes present. Increased expression of receptor subunits observed in more differentiated cells was associated with more substantial functional responses to IL-4 stimulation including increased eotaxin-3 expression and accelerated migration after injury. We demonstrate substantial differences in IL-4/IL-13 receptor subunit expression and responsiveness to IL-4 based on the extent of airway epithelial cell differentiation and suggest that these differences may have functional consequences in airway inflammation.

Immunotherapy for allergies and asthma: present and future

Allergen immunotherapy (IT) is a proven approach for treating allergic rhinitis and allergic asthma that has been practiced since 1911 and has undergone significant development in the past two decades. As currently practiced, IT involves subcutaneous or sublingual administration of allergens, both methods of which have been extensively investigated. In addition to allergen IT, a number of additional nonspecific IT approaches are being used or are in phase II/phase III clinical trials, which may be available in clinics within the next one to three years. Such therapies include anti-IgE antibodies and the soluble IL-4 receptor. Other experimental IT approaches are at the preclinical research stage and may proceed to clinical trials and the clinic within the next five to ten years. This review discusses the pros and cons of recent developments in both currently practiced and experimental IT approaches.

Cytokines in idiopathic inflammatory myopathies

Recent findings suggest cytokines as important key molecules in the pathogenic mechanisms of idiopathic inflammatory myopathies, myositis. In this review, we focus on cytokines with a potential role in disease mechanisms in myositis and present some general information on individual cytokines and an updated summary from the literature concerning cytokines in these disorders. The idiopathic inflammatory myopathies is a heterogeneous group of disorders clinically characterized by symmetric proximal muscle weakness and by certain defined histolopathological findings, including inflammatory infiltrates in muscle tissue. Other prominent findings in the target tissue of these patients are defined molecular changes of blood vessels and muscle fibers, including reformation to high endothelial venule (HEV)-like blood vessels and intensive MHC class I expression in muscle fibers. The predominant clinical symptoms of muscle weakness and decreased muscle endurance are shared by all subsets of inflammatory myopathies and indicate that some pathogenic mechanisms related to muscle function may be shared by the different disease groups. Studies on cytokine gene, RNA and protein expression in muscle tissue from patients with various forms of the disease also indicate similar profiles, despite different phenotypes of the inflammatory cells present in muscle tissue from the different subsets of myositis. There is a pronounced expression of various cytokines in muscle tissue, among which the proinflammatory cytokines TNF-alpha and IL-1 are most widely explored in the inflammatory myopathies, which has made them into potential therapeutic targets. The use of targeted cytokine therapy has been successful in several other chronic inflammatory diseases and although the exact role of cytokines in chronic idiopathic inflammatory myopathies remains to be delineated their potential role as targets for new therapies in this disorder will be discussed in this review.

IL-4 is proangiogenic in the lung under hypoxic conditions

IL-4-mediated proangiogenic and proinflammatory vascular responses have been implicated in the pathogenesis of chronic lung diseases such as asthma. Although it is well known that hypoxia induces pulmonary angiogenesis and vascular alterations, the underlying mechanism of IL-4 on the pulmonary vasculature under hypoxic conditions remains unknown. In this context, we designed the present study to determine the functional importance of IL-4 for pulmonary angiogenesis under hypoxic conditions using IL-4 knockout (KO) animals. Our results show that hypoxia significantly increased IL-4R alpha expression in wild-type (WT) control lungs. Even though hypoxia significantly up-regulated vascular endothelial growth factor (VEGF) receptor expression in the lungs of both genotypes, hypoxia-induced VEGF, VCAM-1, HIF-1alpha, and ERK phosphorylation were significantly diminished in IL-4 KO lungs as compared with WT control lungs. In addition, hypoxia-induced pulmonary angiogenesis and proliferating activities in the airway and pulmonary artery were significantly suppressed in IL-4 KO lungs as compared with WT control lungs. We also isolated primary lung fibroblasts from these genotypes and stimulated these cells with hypoxia. Hypoxia-induced VEGF production was significantly suppressed in lung fibroblasts from IL-4 KO mice. These in vitro results are in accordance with the in vivo data. Furthermore, we observed a significant increase of hypoxia-induced pulmonary angiogenesis in STAT6 KO mice similar to that in WT controls. In conclusion, IL-4 has proangiogenic properties in the lung under hypoxic conditions via the VEGF pathway, and this is independent of the STAT6 pathway.

Effect of suplatast tosilate on goblet cell metaplasia in patients with asthma

BACKGROUND

Goblet cell metaplasia is a pathologic characteristic of asthma, associated with excess mucus secretion. Interleukin (IL)-4 and IL-13 plays an important role in mucus hypersecretion. Suplatast tosilate (suplatast), an antiallergic agent, is a Th2 cytokine inhibitor that suppresses the synthesis of IL-4, IL-5, IL-13, and eosinophilic airway inflammation.

OBJECTIVE

We examined the effects of suplatast on mucus production in bronchial biopsy specimens taken from asthmatic subjects.

METHODS

Oral suplatast 300 mg daily, or placebo was administered for 3 months in a double-blind, parallel-group study in 25 patients with asthma. Biopsy specimens were evaluated at before and after treatment for alcian blue/period acid-Schiff (AB/PAS), MUC5AC staining in bronchial epithelium and IL-4+, IL-13+ cells as well as inflammatory cells in lamina propria.

RESULTS

There were significant decreases in the percentage of AB/PAS (P < 0.01) and MUC5AC (P < 0.01) stained area in the suplatast group. These changes were accompanied by significant decreases in IL-4+ and IL-13+ cells in suplatast-treated subjects. Additionally, we have observed that the number of infiltrating eosinophils and CD4+ T cells significantly decreased.

CONCLUSIONS

These findings suggest that suplatast prevents goblet cell metaplasia through modulation of Th2 cytokine production and the recruitment of eosinophils and CD4+ T cells in the asthmatic airways.

CD8+ T cell contributions to allergen induced pulmonary inflammation and airway hyperreactivity

The pathogenesis of asthma has been linked to the production of type 2 cytokines, which can be expressed by several cell types in the lung. These studies investigated CD8(+) T cell responses in a murine cockroach antigen (CRA) model of asthma. The results from these present studies show that depletion of CD8(+) T cells after allergen sensitization to CRA significantly reduces airway hyperreactivity, airway eosinophilia and pulmonary type 2 cytokine levels. The data demonstrate that CD8(+) T cells from CRA-sensitized mice can produce type 2 cytokines IL-4, IL-5 and IL-13 upon antigen challenge, and that the transfer of these cells into naive mice will cause airway hyperreactivity when exposed to CRA. We found that the transferred airway response is dependent on both IL-4 and IL-13 from CD8(+) T cells using cytokine knockout mice. Compared to CD4(+) T cells, CD8(+) T cells were not as numerous in the lungs of sensitized and challenged mice, but were as efficacious in the transfer of airway disease. The most severe airway response was observed when both CD4(+) and CD8(+) T cells were transferred at the same time. Altogether, these studies highlight a role for CD8(+) T lymphocytes in the development of allergen-induced airway responses.

How frequent is altered gene expression among susceptibility genes to human complex disorders?

It is regularly thought that human complex disorder susceptibility genes show differences in gene expression between normal and pathologic tissues. Thus, differences of transcript amounts could be indicative of complex disorder susceptibility loci and, therefore, be used for the discovery or the validation of human susceptibility genes to complex disorders/traits. Whether human complex disorder susceptibility genes effectively display differences in transcript amounts was tested by meta-analysis of the published literature comparing transcript amounts of well-validated human susceptibility genes to complex traits/disorders. A total of 94 gene-disease associations, which were studied in at least three independent studies and showed strong evidence of positive association, were analyzed. For 23 out of these 94 well-validated gene-disease associations, 120 gene expression studies comparing normal and pathologic human tissues were found. For 60 out of these 120 gene expression studies, the difference of level expression between normal and pathologic human tissues was statistically significant. This result was highly significant, as only 6 significant results were expected randomly under the null hypothesis (P < 10(-112)). A large excess of replication studies were also found, which were in agreement with the original report (P = 6 x 10(-4)). However, the overall level of expression change between normal and pathologic human tissues was relatively moderate, because only 36 (60%) and 19 (31.6%) out of the 62 statistically significant gene expression studies reached 2- or 3-fold changes in expression level, respectively. The present meta-analysis confirms statistical differences of expression levels between normal and pathologic human tissues for human susceptibility genes to complex traits/disorders. However, the levels of differences in transcript amounts appear to be relatively weak. These findings rationalize the use of gene expression for the discovery/validation of human susceptibility genes, but the weak differences of expression typically found should be taken into account for the design of such studies.

Epsilon germ-line and IL-4 transcripts are expressed in human intestinal mucosa and enhanced in patients with food allergy

BACKGROUND

The mechanisms of gastrointestinal (GI) food allergy (FA) are poorly understood. Immunoglobulin E (IgE) is increased in stools from patients with FA, as well as the number of cells carrying IgE in intestinal mucosa, but the origin of IgE production remains unknown. To investigate a local production of IgE in intestine, we analysed the levels of transcripts for epsilon germ-line (epsilonGT), and potential regulators of IgE production, IL-4, IL-13, IFN-gamma, IL-4Ralpha, STAT6 and FcepsilonRIalpha in intestinal mucosa of adult patients with FA.

METHODS

Endoscopic biopsies were obtained from the caecum of 25 patients with FA and 14 control patients. The levels of epsilonGT, IL-4, IL-13, IFN-gamma, IL-4Ralpha, STAT6 and FcepsilonRIalpha mRNA were analysed by real-time RT-PCR and compared with unpaired nonparametric Mann-Whitney test.

RESULTS

The mean epsilonGT transcript level in caecum was increased in FA patients compared with control patients (P < 0.05). IL-4 mRNA expression was also increased in FA patients (P < 0.05), whereas mRNA expression for IL-13, IFN-gamma, IL-4Ralpha, STAT6 and FcepsilonRIalpha mRNA expression was not altered. However, the ratio of IL-4 mRNA/IFN-gamma mRNA was significantly increased in FA patients (P < 0.05). No correlation was observed between epsilonGT transcripts expression in intestinal mucosa and total IgE levels in serum.

CONCLUSIONS

This study shows that (i) epsilonGT transcripts are expressed in human intestinal mucosa; (ii) epsilonGT and IL-4 transcripts are increased in caecal mucosa from patients with FA. These results suggest local production of IgE in intestine that might be of importance for inflammatory reactions in the GI tract.

Effect of inhaled corticosteroid on an immunoreactive thymus and activation-regulated chemokine expression in the bronchial biopsies from asthmatics

BACKGROUND

Bronchial asthma is characterized by airway inflammation, notably because of eosinophils and T cells. Thymus and activation-regulated chemokine (TARC) is known to selectively attract Th2 cells, and is increased in response to interleukin (IL)-4 and IL-13, which share a common receptor, IL-4 receptor alpha (IL-4Ralpha). While corticosteroids have proven, very effective in modifying airway inflammation, the effect of corticosteroids on TARC in asthmatics has been little studied.

OBJECTIVE

We examined the effects of inhaled budesonide (BUD) on the expression of TARC and the number of inflammatory cells in bronchial biopsy specimens taken from asthma patients.

METHODS

Inhaled BUD 800 mug daily, or placebo was administered for 3 months in a double-blind, parallel-group study, and bronchial biopsies were performed before and after treatment. Biopsy specimens were examined by immunocytochemistry.

RESULTS

We observed a significant decrease in the epithelial expression of TARC (P < 0.01) in the BUD group compared with the placebo group. This was accompanied by decreases in the number of eosinophils (P < 0.01), CD3(+) T cells (P < 0.05), and CD4(+) T cells (P < 0.01). A significant correlation was found between changes in epithelial TARC and in IL-4Ralpha immunoreactivity (r(s) = 0.66, P < 0.01).

CONCLUSIONS

These findings suggest that corticosteroid asthma treatment can reduce infiltration of the airway by inflammatory cells, an effect modulated by down-regulation of bronchial epithelial TARC expression.

Different IL-5 and IFN-gamma production from peripheral blood T-cell subsets in atopic and nonatopic asthmatic children

Defective Th1 and enhanced Th2-type cytokine responses have been implicated in the development of atopic disease. However, the immunopathology of nonatopic asthma, especially in children, remains unclear, and there have been few studies to compare the cytokine profile in peripheral blood T-cell subsets between atopic and nonatopic asthmatic children. To document whether atopic asthmatic children have a cytokine imbalance and to compare the cytokine profile between atopic and nonatopic asthmatic children, we investigated the interleukin (IL)-5-producing and interferon (IFN)-gamma-producing T-cell subsets from peripheral blood mononuclear cells (PBMC). The percentages of IFN-gamma-producing CD4+ and CD8+ T cells from atopic asthmatic children were decreased, but those in nonatopic asthmatic children were not decreased. In both groups of asthmatic children, the percentages of IFN-gamma-producing CD4+ T cells were inversely correlated with the peripheral blood eosinophils and had a significant correlation with airway responsiveness (PC20). Thus, we found that the mechanism underlying allergic inflammation of nonatopic asthma is not simple a Th1/Th2 cytokine imbalance. Considering the inverse relationship between IFN-gamma-producing CD4+ T cells and eosinophilia or airway hyperresponsiveness, IFN-gamma from CD4+ T cells may play an important role in allergic inflammation and airway hyperresponsiveness in asthmatic children.

Gene-gene interaction between interleukin-4 and interleukin-4 receptor alpha in Korean children with asthma

BACKGROUND

Interleukin-4 receptor alpha (IL-4Ralpha), which binds IL-4 and IL-13, is involved in signal transduction of those cytokines that lead to IgE production, and is also a key functional component of the Th2 lymphocyte phenotype.

OBJECTIVE

To determine whether IL-4 and IL-4Ralpha polymorphisms are associated with susceptibility to asthma and whether there are gene-gene interactions between IL-4 and IL-4Ralpha polymorphisms.

METHODS

We genotyped three groups of Korean children, consisting of 196 atopic asthmatics, 60 non-atopic asthmatics, and 100 healthy children, for an IL-4 promoter polymorphism (C-590T) and three IL-4Ralpha polymorphisms (Ile50Val, Pro478Ser, and Arg551Gln) using PCR-RFLP (restriction fragment length polymorphism) assays.

RESULTS

The allele frequencies of the IL-4 (C/T) polymorphism and the Ile50Val and Pro478Ser polymorphisms of IL-4Ralpha did not differ statistically among the three groups of children. For the Arg551Gln polymorphism, the combined genotype frequency of the Arg/Gln heterozygote and the Arg/Arg homozygote was significantly higher in atopic asthmatics (27.6%) than in healthy children (16.0%) (odds ratio (OR) = 1.97, 95% CI (confidence interval) = 1.07-3.71). The eosinophil fraction (%) and bronchial responsiveness were higher in children with the Arg/Gln and Arg/Arg genotype than in those with the Gln/Gln genotype (P = 0.036 and 0.024, respectively). In asthmatic children, combinations of the IL-4 CT/TT genotype and the IL-4Ralpha Arg/Gln and Arg/Arg genotypes were associated with significantly increased risk for development of asthma (OR = 3.70, 95% CI = 1.07-12.78, P = 0.038).

CONCLUSIONS

In Korean children, the IL-4Ralpha Arg551 allele may play a role in susceptibility to atopic asthma and correlate with markers of asthma pathogenesis, including increased eosinophil fraction and enhanced bronchial hyper-responsiveness. In addition, a significant gene-gene interaction between the IL-4-590C and the IL-4Ralpha Arg551 allele significantly increases an individual's susceptibility to asthma.

Mechanisms of intrinsic asthma

PURPOSE OF REVIEW

The phenomenon of intrinsic or nonatopic asthma continues to raise questions about the possible role of IgE-mediated mechanisms in asthma pathogenesis. With the current availability of anti-IgE therapy for asthma, clarification of this issue has never been more timely and relevant.

RECENT FINDINGS

This article summarizes recent studies for and against the proposition that IgE-mediated mechanisms play a critical role in asthma pathogenesis. These data comprise epidemiological studies and recent molecular studies, suggesting that IgE synthesis may take place in the bronchial mucosa of patients with nonatopic asthma, despite the fact that allergen-specific IgE is not detectable in the periphery by standard skin prick testing.

SUMMARY

At present, available data do not allow a firm conclusion to be made as to whether or not IgE-mediated mechanisms play an obligatory role in asthma pathogenesis. Implications for the future therapy of nonatopic asthma in either case are discussed, as well as some suggestions for further research.

Immunopathogenesis of allergic bronchopulmonary aspergillosis in cystic fibrosis

Allergic bronchopulmonary aspergillosis (ABPA) is a hypersensitivity lung disease mediated by an allergic late-phase inflammatory response to Aspergillus fumigatus antigens. ABPA is characterized by markedly elevated Aspergillus-specific and total IgE levels and eosinophilia, and manifested by wheezing, pulmonary infiltrates, and bronchiectasis and fibrosis, which afflict asthmatic and cystic fibrosis (CF) patients. We propose that ABPA develops in genetically susceptible CF patients due to HLA-DR2 and DR5 restriction, increased sensitivity to IL-4 stimulation, and increased A. fumigatus allergen-specific Th2 CD4+ T-cell-mediated responses. In addition, A. fumigatus proteases play a role in facilitation of antigen transport across the epithelial cell layer by damaging the epithelial integrity and by a direct interaction with epithelial cell surface receptors, resulting in pro-inflammatory cytokine production and corresponding inflammatory responses.

Increased sensitivity to IL-4 in cystic fibrosis patients with allergic bronchopulmonary aspergillosis

BACKGROUND

Allergic bronchopulmonary aspergillosis (ABPA) is characterized by a heightened Th2 CD4+ T-cell response to Aspergillus fumigatus allergens and a hyper-immunoglobulin (Ig)E state compared with cystic fibrosis patients without ABPA. We hypothesize that one reason for this response is increased sensitivity to interleukin (IL)-4 in ABPA resulting in increased expression of CD23 and CD86 and leading to a positive amplification mechanism that increases Th2 CD4+ T cell responses.

METHODS

Peripheral blood mononuclear cells (PBMC) were isolated from seven ABPA CF and 19 non-ABPA CF patients and 16 nonatopic controls and stimulated with rIL-4 (range 0.1-10 ng/ml) and rIL-13 (range 1-10 ng/ml) for 48 h. The number of CD23 molecules and percentages of CD23+ B cells were quantified by flow cytometry. Both phorbol 12-myristate 13-acetate (PMA)/ionomycin (IO) and antigen stimulated, toxoid and Asp f2/f3/f4, PBMC were examined for cytoplasmic cytokine synthesis enumerated by cytokine staining using flow cytometry to measure Th2 and Th1 CD3+ T cells.

RESULTS

The numbers of CD23 molecules on B-cells were significantly elevated at time 0 in ABPA CF patients compared with both non-ABPA CF patients and nonatopic controls. Following IL-4 stimulation in vitro, the numbers and percentages of CD23 expression on B cells were significantly up-regulated in ABPA CF patients compared with non-ABPA CF patients and controls. The IL-13 stimulation up-regulated CD23 expression; however, there was no significant difference in ABPA CF patients compared with non-ABPA CF patients and controls. The percentages of interferon (IFN)-gamma+ CD3+T cells following PMA/IO stimulation were significantly decreased in both ABPA and non-ABPA CF patients compared with controls. There were no significant differences of IL-4+ and IL-13+ CD3+ T cells between ABPA and non-ABPA CF patients. When tetanus toxoid stimulated T cells were examined, both ABPA and non-ABPA CF patients had significantly decreased IFN-gamma+ CD3+ T cells compared with controls. In Asp f2/f3/f4 stimulated T cells, ABPA CF patients had significantly increased IL-4+ CD3+ T cells compared with non-ABPA CF patients and controls.

CONCLUSIONS

ABPA CF patients have increased sensitivity to IL-4 but not to IL-13 up-regulation of CD23 molecules compared with non-ABPA CF patients. There were decreased percentages of IFN-gamma+ and IL-2+ Th1 T cells in CF patients compared with nonatopic controls but similar percentages of IL-4+ Th2 T cells in all three groups. However, ABPA CF patients had increased frequency of Aspergillus-stimulated Th2 T cells. This indicated that there is skewing of Th2 T cells in ABPA CF patients. Thus, in CF ABPA patients there is increased Th2 T cells and increased sensitivity to IL-4.

Regulation of procollagen I (alpha1) by interleukin-4 in human bronchial fibroblasts: a possible role in airway remodelling in asthma

BACKGROUND

In bronchial mucosa, T cells are in close association with fibroblasts. This cell contact raises the possibility of cross-talk between the two cell types through cytokines, such as interleukin-4 (IL-4).

OBJECTIVE

We postulated that IL-4 may modulate collagen synthesis and degradation in the fibroblasts of asthmatics.

METHODS

Bronchial fibroblasts from asthmatics (BAF) and normal controls (BNF) were stimulated with IL-4. Procollagen I gene expression and protein production were measured by real-time PCR, RT-PCR, and radioimmunoassay. The effect of IL-4 on the regulation of procollagen I (alpha1) promoter was studied through transient cell transfections. The implication of Sp1 and AP-1 in regulating IL-4-induced procollagen I (alpha1) production was determined. The effect of IL-4 on metalloproteinase-2 (MMP-2) and tissue inhibitor of metalloproteinase-2 (TIMP-2) production and gene expression was evaluated.

RESULTS

Following IL-4 stimulation, there was a significant increase in the expression of mRNA of procollagen I (alpha1) by human bronchial fibroblasts of asthmatics and controls. IL-4 has a dose-response effect on mRNA, with a maximal effect at 5 ng/mL, as determined by real-time PCR. The maximal increase in procollagen I (alpha1) was observed at 6 h after IL-4 stimulation in both BNF and BAF. BAFs have a greater increase in the procollagen I (alpha1)/beta2 microglobulin ratio after 6 h of IL-4 stimulation (4.1 x 10-2+/-0.03 to 20.8 x 10-2+/-0.1) compared with BNF (2.9 x 10-2+/-0.006 to 9.2 x 10-2+/-0.08) (P=0.001). In transient transfection experiments, IL-4 increased promoter activity by threefold in BAF and BNF. Sp1 was up-regulated after IL-4 stimulation and AP-1 was down-regulated as shown by electrophoretic mobility shift assay. IL-4 decreased MMP-2 protein and mRNA levels, and did not alter TIMP-2 production.

CONCLUSIONS

IL-4 positively regulates procollagen I (alpha1) transcription by direct promoter activation and increases the TIMP-2/MMP-2 ratio, thereby supporting the profibrotic effect of this cytokine. Thus, this study emphasizes that IL-4 may be considered as a link between inflammation and collagen deposition observed in asthmatic airways.

T helper type 2 cytokine receptors and associated transcription factors GATA-3, c-MAF, and signal transducer and activator of transcription factor-6 in induced sputum of atopic asthmatic patients

BACKGROUND

It is well-known that the expression of T helper (Th) type 2 cytokines such as interleukin (IL)-4 and IL-5, and their receptors, is up-regulated within the airways of allergic asthmatic patients. Furthermore, higher numbers of cells producing GATA-3, c-MAF, and signal transducer and activator of transcription factor (STAT)-6, which are transcription factors (TFs) that are implicated in the regulation and signaling of the Th2 cytokines, have been observed in bronchial biopsy specimens from asthmatic patients but not in those of healthy control subjects.

METHODS

We examined whether these mediators also can be detected in induced sputum. Immunoreactivity for IL-4Ralpha, IL-5Ralpha, GATA-3, c-MAF, and STAT-6 was investigated in samples of induced sputum from asthmatic patients (n = 8) and healthy control subjects (n = 8).

RESULTS

Our results showed that the numbers of cells expressing IL-4 receptor alpha (Ralpha) and IL-5Ralpha were higher in samples from asthmatic patients compared to those of control subjects (p < 0.01). More cells exhibiting GATA-3, c-MAF, and STAT-6 immunoreactivity also were found in asthmatic patients vs those in control subjects (p < 0.005). Furthermore, the expression of STAT-6 and IL-4Ralpha, GATA-3 and IL-5Ralpha, and c-MAF with both IL-4Ralpha and IL-5Ralpha was correlated (p < 0.05).

CONCLUSIONS

This study demonstrated that induced sputum provides sufficient sensitivity for examining the pathways of cytokine signaling, cytokine receptor signaling, and intracellular signaling. Furthermore, these data show correlations between the expression of Th2 cytokine receptors and associated TFs in the human lung, which has not been documented previously.

Interleukin-4 and interleukin-4 soluble receptor alpha levels in bronchoalveolar lavage from children with asthma

BACKGROUND

In asthma there is increased expression of the Th2-type cytokine interleukin-4 (IL-4). IL-4 is important in immunoglobulin isotype switching to immunoglobulin E and adhesion of eosinophils to endothelium.

OBJECTIVE

We hypothesized that levels of IL-4 in bronchoalveolar lavage (BAL) fluid would be increased in stable, atopic asthmatic children compared with controls and that levels of its physiologic inhibitor IL-4 soluble receptor alpha (IL-4sR alpha) would be correspondingly decreased.

METHODS

One hundred sixteen children attending a children's hospital for elective surgery were recruited. A nonbronchoscopic BAL was performed, and IL-4 and IL-4sR alpha were measured in the BAL supernatants.

RESULTS

There was no significant difference in IL-4 concentrations between atopic asthmatic children, atopic normal controls, and nonatopic normal controls [0.13 pg/mL (0.13 to 0.87) vs 0.13 pg/mL (0.13 to 0.41) vs 0.13 pg/mL (0.13 to 0.5), P = 0.65]. IL-4sR alpha levels were significantly increased in asthmatic patients compared with atopic controls [6.4 pg/mL (5.0 to 25.5) vs 5.0 pg/mL (5.0 to 9.9), P = 0.018], but not when compared with the nonatopic controls [5.2 pg/mL (5.0 to 10.6), P = 0.19].

CONCLUSIONS

Contrary to expectation, IL-4sR alpha levels are increased in BAL from stable asthmatic children compared with nonatopic controls, and we speculate that IL-4sR alpha is released by inflammatory cells in the airways to limit the proinflammatory effects of IL-4.

Gene therapy for asthma

The accessibility of the airway epithelium and the limitations of current treatments for asthma make the disease a logical target for gene therapy. Study of the immunopathology of chronic airway inflammation has recently identified several pathways that lead to the maladaptive, antigen-induced polarization of CD4+ T cells to a type-2 phenotype. This polarization is thought to lead to IgE production and eosinophil recruitment and activation that is associated with epithelial cell injury and airway hyper-reactivity. Gene transfer to the bronchial epithelium has been used in experimental models to redirect these pathways toward a less injurious, type-1 phenotype. This mini-review highlights recent mechanism-based immunomodulatory and supportive gene transfer approaches to treat animal models of asthma. Although substantial hurdles to airway gene transfer remain, gene transfer offers the possibility of interrupting the pathophysiology of airway inflammation. Doing so can be expected to yield long-lasting protection from bronchospastic challenge and reduced dependence on inhaled and oral medications.

Differential functions of IL-4 receptor types I and II for dendritic cell maturation and IL-12 production and their dependency on GM-CSF

Little is known about the distinct roles of the two types of IL-4R on DC. Here we report that IL-4 and IL-13 are able to promote DC maturation, as evaluated by up-regulation of MHC class II and costimulatory molecules, when the concentration of GM-CSF is relatively lower than the dose of IL-4 or IL-13. In addition, under these conditions both cytokines enable DC to respond to maturation stimuli such as bacterial products or proinflammatory cytokines. Both IL-4 and IL-13 act synergistically with weak maturation stimuli such as TNF-alpha or CD40. The IL-4R signaling for DC maturation requires the IL-4R alpha-chain and STAT6, but not Janus kinase 3, indicating that IL-4R type II signaling is preferentially responsible for these effects. In contrast, the production of IL-12 p70, but not IL-10 and TNF, induced by microbial products was enhanced only by IL-4, not by IL-13 or Y119D, a selective type II IL-4R agonist, in vitro and in vivo. This enhancement was dependent on the presence of Janus kinase 3, indicating that this function is exclusively mediated by the type I IL-4R. In short, we discerned the individual roles of the two IL-4R types on DC function, showing that IL-4R type I promotes IL-12 secretion independently of GM-CSF concentration, while IL-4R type II promotes the up-regulation of MHC class II and costimulatory surface markers in a GM-CSF concentration-dependent manner.

Interleukin-13 induces goblet cell differentiation in primary cell culture from Guinea pig tracheal epithelium

The Th2 cytokines, interleukin (IL)-4 and IL-13, bind to IL-4Ralpha, and cause goblet cell metaplasia/hyperplasia with increased mucin expression in vivo. However, there is not enough evidence that these cytokines directly induce mucin production in vitro. In this study, primary epithelial cells from guinea pig trachea were cultured at an air-liquid interface, and immediately after achieving confluence at Day 7 they were treated with human recombinant IL-4 or IL-13 for 14 d. IL-13-treated cells consisted of a large number of fully mature goblet cells with a smaller number of ciliated cells. Secretory granules of the goblet cells were positive for both periodic acid-Schiff and toluidine blue, and showed exocytosis. By contrast, IL-4 failed to induce goblet cell differentiation. The electric resistances of IL-13-treated cells were lower than those of IL-4-treated cells and nontreated cells, suggesting leaky epithelia. MUC5AC protein level in cell lysates measured by ELISA was several-fold higher in IL-13-treated cells than in nontreated cells, whereas the level in IL-4-treated cells was not changed. These data suggest that human recombinant IL-13, but not IL-4, can induce differentiation into mature goblet cells that produce MUC5AC protein in guinea pig tracheal epithelial cells in vitro.

Biochemical and functional characterization of human transmembrane tryptase (TMT)/tryptase gamma. TMT is an exocytosed mast cell protease that induces airway hyperresponsiveness in vivo via an interleukin-13/interleukin-4 receptor alpha/signal transducer and activator of transcription (STAT) 6-dependent pathway

Transmembrane tryptase (TMT)/tryptase gamma is a membrane-bound serine protease stored in the secretory granules of human and mouse lung mast cells (MCs). We now show that TMT reaches the external face of the plasma membrane when MCs are induced to degranulate. Analysis of purified recombinant TMT revealed that it is a two-chain neutral protease. Thus, TMT is the only MC protease identified so far which retains its 18-residue propeptide when proteolytically activated. The genes that encode TMT and tryptase betaI reside on human chromosome 16p13.3. However, substrate specificity studies revealed that TMT and tryptase betaI are functionally distinct even though they are approximately 50% identical. Although TMT is rapidly inactivated by the human plasma serpin alpha(1)-antitrypsin in vitro, administration of recombinant TMT (but not recombinant tryptase betaI) into the trachea of mice leads to airway hyperresponsiveness (AHR) and increased expression of interleukin (IL) 13. T cells also increase their expression of IL-13 mRNA when exposed to TMT in vitro. TMT is therefore a novel exocytosed surface mediator that can stimulate those cell types that are in close proximity. TMT induces AHR in normal mice but not in transgenic mice that lack signal transducer and activator of transcription (STAT) 6 or the alpha-chain of the cytokine receptor that recognizes both IL-4 and IL-13. Based on these data, we conclude that TMT is an exocytosed MC neutral protease that induces AHR in lungs primarily by activating an IL-13/IL-4Ralpha/STAT6-dependent pathway.

Genetics of IL-13 and functional relevance of IL-13 variants

Studies in both humans and mice clearly show that interleukin (IL)-13 is a central regulator of allergic inflammation. Numerous single nucleotide polymorphisms have been recently identified in the IL-13 gene and have been found to be associated with allergic and/or asthmatic phenotypes in different populations throughout the world. Furthermore, functional genomics studies are highlighting mechanistic pathways that may link genetic variation in IL-13 and disease. IL-13 is therefore an ideal model to study the impact of genetic variation on the regulation of gene expression and function in complex diseases.

Mycoplasma pneumoniae-induced activation and cytokine production in rodent mast cells

BACKGROUND

Mycoplasma pneumoniae is a respiratory tract pathogen that has been associated with severe exacerbations in patients with chronic asthma. Murine models of infection have recently been established, with disease manifestations similar to those observed in human subjects. Previous studies have suggested that this organism is capable of producing activation of a wide range of immunologic cell types.

OBJECTIVE

We sought to determine whether M pneumoniae can induce mast cell activation in the rodent mast cell line RBL-2H3.

RESULTS

After 4 hours of coculture, morphologic changes indicative of activation were observed by means of electron microscopy, and M pneumoniae was identified, by means of immunoelectron microscopy, adhering to mast cell membranes. Coculture of rat basophilic leukemia cells with viable M pneumoniae for 4 hours resulted in net release of beta-hexosaminidase and serotonin into the supernatant. Live, but not heat-killed, organisms induced the release of IL-4 protein into the culture supernatant, with a peak at 4 hours. During coculture with M pneumoniae, production of mRNA for IL-4, IL-6, and TNF-alpha was upregulated after 2 hours and had returned to near baseline by 24 hours after infection.

CONCLUSIONS

We conclude that viable M pneumoniae induces activation of mast cells with release of granule contents, as well as cytokine production.

Signal transducer and activator of transcription 6 (STAT-6) expression and function in asthmatic bronchial epithelium

BACKGROUND

Asthma is associated with increased production of IL-4 and IL-13.

OBJECTIVE

Because many of the effects of these cytokines are mediated by activation of signal transducer and activator of transcription 6 (STAT-6), we investigated expression and function of this transcription factor in the airways.

METHODS

STAT-6 expression was investigated through use of immunohistochemistry or RT-PCR applied to bronchial biopsy specimens or brushings from normal control or asthmatic subjects. STAT-6 function was investigated by means of Western blotting and ELISA applied to primary epithelial cell cultures.

RESULTS

Immunohistochemistry revealed that the bronchial epithelium was the major site of STAT-6 expression, both cytoplasmic and nuclear staining being observed. The level of STAT-6 expression in subjects with mild asthma (median [range] percent epithelial staining, 3.4% [0% to 16.0%]; n = 14) did not differ significantly from that in normal controls (4.7% [0.0% to 20.0%]; n = 11); however, in subjects with severe asthma, epithelial STAT-6 expression (13.7% [4.8% to 25.7%]; n = 9) was increased in comparison with subjects with mild asthma and normal controls (P < .05). RT-PCR analysis showed that epithelial STAT-6 expression was heterogeneous and comprised both full-length STAT-6 and the dominant-negative variant that lacks the SH2 domain. Treatment of primary cultures of bronchial epithelial cells with IL-4 resulted in STAT-6 phosphorylation and stimulation of IL-8 secretion; however, no difference in the responses of epithelial cells was observed between normal (n = 12) and asthmatic (n = 14) donors.

CONCLUSION

These data demonstrate expression and activation of STAT-6 in normal and asthmatic bronchial epithelium. The activity of this transcription factor is likely to play a key role in mediating the responses of the bronchial epithelium to T(H)2 cytokines that are characteristic of the asthmatic phenotype.

TH2 cytokine-associated transcription factors in atopic and nonatopic asthma: evidence for differential signal transducer and activator of transcription 6 expression

BACKGROUND

The expression of IL-4 and IL-5 is increased in patients with atopic asthma compared with control subjects and correlates with indices of pulmonary function. In nonatopic asthma the expression of IL-4, unlike IL-5, fails to correlate with pulmonary function, and compared with their atopic counterparts, these patients have fewer cells expressing IL-4 receptor (IL-4R). As such, a deficiency in the IL-4 signaling pathway may be implicated in nonatopic asthma. The transcription factors GATA-3 and cMAF mediate IL-4 and IL-5 synthesis, whereas signal transducer and activator of transcription 6 (STAT-6) is critical for IL-4R signaling.

OBJECTIVE

This study examines the expression profile of these transcription factors in asthma, according to atopic status.

METHODS

With immunocytochemistry, the expression of GATA-3, cMAF, and STAT-6 protein was determined in sections of bronchial biopsy specimens from patients with atopic asthma (n = 7), patients with nonatopic asthma (n = 8), and control subjects (n = 8).

RESULTS

Higher numbers of cells expressing GATA-3 and cMAF were observed in patients with atopic and those with nonatopic asthma than in control subjects and patients with tuberculosis (P <.001). There were also more STAT-6-immunoreactive cells in patients with atopic and those with nonatopic asthma than in control subjects (P <.0001, P <.05). Notably, however, fewer cells expressing STAT-6 protein were observed in nonatopic versus atopic asthma (P <.0001).

CONCLUSIONS

These results demonstrate the upregulation of GATA-3 and cMAF in both variants of asthma and indicate that reduced IL-4R signaling, because of lower STAT-6 expression, may be a feature of nonatopic asthma.

New anti-asthma therapies: suppression of the effect of interleukin (IL)-4 and IL-5

Asthma is currently defined as a chronic inflammatory disorder of the airways. The central role of allergen-specific Th2 cells in the regulation of this mucosal airway inflammation has been highlighted. Hence, there is large interest in the therapeutic potential of an anti-Th2 cell approach. One of the strategies which has been developed, is to inhibit the effect of interleukin (IL)-4 or IL-5, two main Th2 cell derived cytokines. Interleukin-4 is pivotal in the pathogenesis of allergic disorders through its wide range of effects. An important observation, especially during secondary antigen exposure, is the possible redundancy with IL-13. Both cytokines share common elements in their receptor and intracellular signalling pathway. As a result, compounds can be developed that selectively inhibit the effect of either IL-4 or IL-13, or alternatively, by interfering with the common pathway, inhibit the effect of both cytokines. Eosinophils are generally seen as a particularly harmful element in the allergic inflammation. The importance of IL-5 on eosinophil biology has clearly been established. Conversely, in man, the biological effects of IL-5 are largely limited to eosinophil function. Therefore, IL-5 antagonists offer the unique opportunity of selectively neutralizing the effect of eosinophils. Several strategies have now been developed that successfully inhibit the biological effect of interleukin-4 or interleukin-5. Some of these compounds have proven to be biologically active in man. The challenge now is to establish their therapeutic role in asthma.

Regulation of allergic airways inflammation by cytokines and glucocorticoids

Cytokines mediate the allergic inflammatory response of the airways, and glucocorticosteroids ameliorate allergy symptoms by regulating cytokine expression. Recent studies provide insight into the manner by which cytokines work together to mediate allergic airway disease. Real progress has also been gained in our understanding of subcellular mechanisms of allergic inflammation, particularly the role of transcription factors in regulating the expression of specific cytokine profiles and the differentiation of the TH2 subset. This article provides an update of recently reported findings in this field and highlights emerging concepts of allergic inflammation.

Association between airway hyperreactivity and bronchial macrophage dysfunction in individuals with mild asthma

Little is known about the functional capabilities of bronchial macrophages (BMs) and their relationship to airway disease such as asthma. We hypothesize that BMs from asthmatics may be modulated in their function compared with similar cells from healthy individuals. BMs obtained by induced sputum from mild asthmatics (n = 20) and healthy individuals (n = 20) were analyzed using flow cytometry for CD16, CD64, CD11b, CD14, and human leukocyte antigen-DR expression, phagocytosis of IgG opsonized yeast, and oxidant production. Asthma status was assessed by lung function [percent predicted forced vital capacity and forced expiratory volume in 1 s (FEV(1))], percent sputum eosinophils, and nonspecific airway responsiveness [provocative concentration that produces a 20% fall in FEV(1) (PC(20,FEV1))]. Asthmatics with >5% airway eosinophils (AEo+) had decreased BM CD64 expression and phagocytosis compared with asthmatics with <5% eosinophils (AEo-). Among asthmatics, a significant correlation was found between CD64 expression and BM phagocytosis (R = 0.7, P < 0.009). Phagocytosis was also correlated with PC(20,FEV1) (R = 0.6, P < 0.007), lung function (%predicted FEV(1), R = 0.7, P < 0.002) and percent eosinophils (R = -0.6, P < 0.01). In conclusion, BM from asthmatics are functionally modulated, possibly by Th2 cytokines involved in asthma pathology.

The pathology of chronic asthma

Our understanding of the pathophysiology of asthma has undergone great advances in the past decade, particularly with the recognition of cytokines and the roles they may take in orchestrating the local immune response. With this information, it has been possible to target new therapeutic entities such as cytokine or chemokine receptors. Eosinophils and T lymphocytes have a special place in the inflammatory and structural alterations contributing to the asthmatic diathesis. It is possible that phenotype subsets of these cells exist and they hold the key to perpetuation of immunologic and physiologic abnormalities in asthma.

Soluble IL-4 receptor inhibits airway inflammation following allergen challenge in a mouse model of asthma

In vitro and in vivo studies, in both animal models and human asthmatics, have implicated IL-4 as an important inflammatory mediator in asthma. In a murine asthma model, we examined the anti-inflammatory activities of soluble IL-4R (sIL-4R). In this model, mice sensitized to OVA by i.p. and intranasal (i.n.) routes are challenged with the allergen by i.n. administration. The OVA challenge elicits an eosinophil infiltration into the lungs, with widespread mucus occlusion of the airways, and results in bronchial hyperreactivity. sIL-4R (0.1-100 microgram) was administered by either i.n. or i.p. routes before OVA challenge in OVA-sensitized mice. Both blood and bronchoalveolar lavage fluid levels of sIL-4R were significantly elevated compared with controls by i.n. delivery of 100 microgram sIL-4R; i.p. delivery of 100 microgram sIL-4R only raised blood levels of sIL-4R. The i.n. administration of 100 microgram sIL-4R before allergen challenge significantly reduced late phase pulmonary inflammation, blocking airway eosinophil infiltration, VCAM-1 expression, and mucus hypersecretion. In contrast, i.p. delivery of 100 microgram sIL-4R inhibited only the influx of eosinophils into the lungs, but not airway mucus release. Furthermore, sIL-4R treatment by either i.n. or i.p. routes did not reduce airway hyperreactivity in response to methacholine challenge. Thus, elevating airway levels of sIL-4R through the administration of exogenous sIL-4R is effective in blocking the late phase pulmonary inflammation that occurs in this murine allergen-challenge asthma model. These results suggest that sIL-4R may have beneficial anti-inflammatory effects in asthmatic patients.