IL-5 and IL-5 receptor in asthma

Role of IL-5 in asthma and airway remodelling

Asthma is a common and burdensome chronic inflammatory airway disease that affects both children and adults. One of the main concerns with asthma is the manifestation of irreversible tissue remodelling of the airways due to the chronic inflammatory environment that eventually disrupts the whole structure of the airways. Most people with troublesome asthma are treated with inhaled corticosteroids. However, the development of steroid resistance is a commonly encountered issue, necessitating other treatment options for these patients. Biological therapies are a promising therapeutic approach for people with steroid-resistant asthma. Interleukin 5 is recently gaining a lot of attention as a biological target relevant to the tissue remodelling process. Since IL-5-neutralizing monoclonal antibodies (mepolizumab, reslizumab and benralizumab) are currently available for clinical use, this review aims to revisit the role of IL-5 in asthma pathogenesis at large and airway remodelling in particular, in addition to exploring its role as a target for biological treatments.

CPHEN-017: Comprehensive phenotyping of neutrophil extracellular traps (NETs) on peripheral human neutrophils

With the recent discovery of their ability to produce neutrophil extracellular traps (NETs), neutrophils are increasingly appreciated as active participants in infection and inflammation. NETs are characterized as large, web-like networks of DNA and proteins extruded from neutrophils, and there is considerable interest in how these structures drive disease in humans. Advancing research in this field is contingent on developing novel tools for quantifying NETosis. To this end, we have developed a 7-marker flow cytometry panel for analyzing NETosis on human peripheral neutrophils following in vitro stimulation, and in fresh circulating neutrophils under inflammatory conditions. This panel was optimized on neutrophils isolated from whole blood and analyzed fresh or in vitro stimulated with phorbol 12-myristate 13-acetate (PMA) or ionomycin, two known NET-inducing agonists. Neutrophils were identified as SSChighFSChighCD15+CD66b+. Neutrophils positive for amine residues and 7-Aminoactinomycin D (7-AAD), our DNA dye of choice, were deemed necrotic (Zombie-NIR+7-AAD+) and were removed from downstream analysis. Exclusion of Zombie-NIR and positivity for 7-AAD (Zombie-NIRdim7-AAD+) was used here as a marker of neutrophil-appendant DNA, a key feature of NETs. The presence of two NET-associated proteins - myeloperoxidase (MPO) and neutrophil elastase (NE) - were utilized to identify neutrophil-appendant NET events (SSChighFSChighCD15+CD66b+Zombie NIRdim7-AAD+MPO+NE+). We also demonstrate that NETotic neutrophils express citrullinated histone H3 (H3cit), are concentration-dependently induced by in vitro PMA and ionomycin stimulation but are disassembled with DNase treatment, and are present in both chronic and acute inflammation. This 7-color flow cytometry panel provides a novel tool for examining NETosis in humans.

Granular Insights: Neutrophil Predominance and Elastase Release in Severe Asthma Exacerbations in a Pediatric Cohort

The chronic inflammatory component of asthma is propagated by granulocytes, including neutrophils and eosinophils, in the peripheral circulation and airway. Previous studies have suggested that these cells have an altered expression of adhesion-related molecules and a propensity for the release of granule contents that may contribute to tissue damage and enhance inflammatory complications in patients with status asthmaticus. The goal of this prospective cohort study at a tertiary care pediatric hospital with a large population of asthma patients was to assess the role of granulocyte-based inflammation in the development of asthma exacerbation. Subjects were enrolled from two patient populations: those with mild-to-moderate asthma exacerbations seen in the emergency department and those with severe asthma admitted to the intensive care unit (PICU). Clinical data were collected, and blood was drawn. Granulocytes were immediately purified, and the phenotype was assessed, including the expression of cell surface markers, elastase release, and cytokine production. Severe asthmatics admitted to the PICU displayed a significantly higher total neutrophil count when compared with healthy donors. Moreover, little to no eosinophils were found in granulocyte preparations from severe asthmatics. Circulating neutrophils from severe asthmatics admitted to the PICU displayed significantly increased elastase release ex vivo when compared with the PMN from healthy donors. These data suggest that the neutrophil-based activation and release of inflammatory products displayed by severe asthmatics may contribute to the propagation of asthma exacerbations.

Further evidence of a type 2 inflammatory signature in chronic obstructive pulmonary disease or emphysema

BACKGROUND

There is increasing recognition of a type 2 (T2) inflammatory pattern in a subset of patients with chronic obstructive pulmonary disease (COPD) or emphysema, characterized by blood and airway eosinophilia. The mechanism underlying this is not well established. The recognition that CD125 (interleukin [IL]-5 receptor alpha) is expressed on some lung neutrophils and eosinophils in patients with asthma led us to speculate that CD125 may also be expressed on lung neutrophils in patients with COPD or emphysema.

OBJECTIVE

To interrogate the expression of CD125 on lung neutrophils (and, when present, eosinophils) in patients with COPD/emphysema and identify a meaningful biomarker to predict neutrophil CD125 expression, including other markers of T2 inflammation.

METHODS

We obtained blood and bronchoalveolar lavage (BAL) samples from patients with physician-diagnosed COPD/emphysema undergoing a clinically indicated bronchoscopy.

RESULTS

We found that a highly variable percentage of BAL neutrophils indeed expressed surface CD125 (0%-78.7%), with obvious clustering of CD125high and CD125low patterns. No correlation was found with clinical characteristics, blood or BAL eosinophil or neutrophil counts, BAL cytokines, or BAL eosinophil CD125 expression.

CONCLUSION

We conclude that, similar to asthma, lung neutrophils from patients with COPD display interleukin-5 receptor alpha (CD125) on their surface. This along with the frequent presence of IL-4 and IL-5 in airway fluid further suggests a possible role of the T2 pathway in contributing to COPD severity.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT03984799.

STAT6 Blockade Abrogates Aspergillus-Induced Eosinophilic Chronic Rhinosinusitis and Asthma, A Model of Unified Airway Disease

Unified airway disease, including concurrent asthma and chronic rhinosinusitis (CRS), is a common, but poorly understood disorder with no curative treatment options. To establish a murine model of chronic unified eosinophilic airway inflammation, mice were challenged with Aspergillus niger, and sinonasal mucosa and lung tissue were evaluated by immunohistochemistry, flow cytometry, and gene expression. Inhalation of A niger conidia resulted in a Th2-biased lung and sinus inflammation that typifies allergic asthma and CRS. Gene network and pathway analysis correlated with human disease with upregulation of not only the JAK-STAT and helper T-cell pathways, but also less expected pathways governing the spliceosome, osteoclast differentiation, and coagulation pathways. Utilizing a specific inhibitor and gene-deficient mice, we demonstrate that STAT6 is required for mycosis-induced sinus inflammation. These findings confirm the relevance of this new model and portend future studies that further extend our understanding of the immunopathologic basis of airway mycosis and unified airway disease.

Interleukin-5 receptor alpha (CD125) expression on human blood and lung neutrophils

BACKGROUND

Our previous studies revealed the presence of interleukin-5 (IL-5) receptor alpha chain (IL-5Rα, CD125) on neutrophils in a murine model of influenza and in the lung fluid of children with severe asthma.

OBJECTIVE

To further evaluate the functional characteristics and effects of clinical factors and inflammatory variables on neutrophil surface IL-5Rα abundance in lung fluid and blood.

METHODS

IL-5Rα expression was quantified by flow cytometry performed on purified neutrophils from blood and bronchoalveolar lavage fluid samples obtained from healthy controls and individuals with asthma. Expression was further confirmed by immunohistochemistry. Functional signaling through the IL-5Rα was evaluated by measurement of IL-5-inducible modulation of neutrophil surface CD62L and IL-5Rα expression.

RESULTS

IL-5Rα was consistently present but at a variable magnitude on blood and lung neutrophils. Expression on lung neutrophils was significantly higher than that on blood cells (p"?>P < .001) where their expression was higher in the presence of airway pathogens, especially with respiratory viruses. Increased receptor expression occurred in response to the translocation of preformed receptors from intracellular stores. Receptors were functional as revealed by IL-5-mediated down-regulation of CD62L and the feed-forward up-regulation of reception expression.

CONCLUSION

In addition to the expression on eosinophils and basophils, the IL-5Rα is consistently and abundantly expressed on the surface of blood and especially air space neutrophils. These observations support the concept that some of the efficacy of IL-5/IL-5R-targeting biologics observed in asthma may reflect their ability to target neutrophilic air space inflammation.

Bronchial Vascular Remodeling Is Attenuated by Anti-IL-17 in Asthmatic Responses Exacerbated by LPS

Introduction

Although the major alterations associated with asthma are related to the airways, there is also evidence of the importance of peribronchial vascular inflammation and remodeling in its pathophysiology.

Objectives

To determine the effects of anti-IL-17 therapy on peribronchial vessels of an asthma model exacerbated by lipopolysaccharide.

Methods

We evaluated several factors, including lung function, inflammation, oxidative stress, vascular remodeling, and signaling pathways present in the peribronchial vessels of 66 male BALB/c mice exposed to ovalbumin and treated (or not) treated with anti-IL-17. Twenty-four hours before the end of the experimental protocol, groups of sensitized animals (OVA–LPS and OVA–LPS anti-IL-17) also received LPS.

Results

The OVA–LPS-anti-IL-17 group presented a decrease in several factors [airway resistance and elastance, bronchoalveolar lavage fluid (BALF) cell counts, inflammatory response, eosinophils, TSLP, IL-33, TARC, TNF-α, CD4+, CD8+, IL-4, IL-6, IL-10, IL-17, and VEGF positive cells/10⁴μm², peribronchovascular edema, and angiogenesis], including remodeling (MMP-9, MMP-12, TIMP-1 and TGF-β positive cells and volume fraction of collagen fibers I, collagen fibers III, collagen fibers V, decorin, lumican, actin, biglycan, fibronectin, and integrin), oxidative stress (iNOS positive cells and volume fraction of PGF2α), and signaling pathways (FoxP3), as well as dendritic cells, NF-kB, ROCK-1, ROCK-2, STAT-1, and phosphor-STAT1-positive cells compared to OVA–LPS (p < 0.05).

Conclusions

In this model of LPS-induced asthma exacerbation, IL-17 inhibition represents a promising therapeutic strategy, indicating the potential of bronchial vascular control of Th2 and Th17 responses and the activation of the remodeling and oxidative stress pathways, associated with the control of signaling pathways.

Biological agents for severe asthma: the evolution of the at-home self-injection approach

PURPOSE OF REVIEW

New biological agents, in addition to the well-established omalizumab, have been nowadays introduced into clinical practice for severe asthma. This suggested the possibility of an at-home self-administration, as currently happening for other biological agents for immune-mediated diseases.

RECENT FINDINGS

In the very recent years, there were structured clinical trials investigating the self at home administrations of biologicals for severe asthma, showing with different principles, a possible advantage and convenience for the patient, and a socioeconomic saving.

SUMMARY

The literature analysis currently shows that the at-home self-administration of biologicals for severe asthma is a promising approach to improve the treatment of such disease.

Identification of a novel splice variant for mouse and human interleukin-5

Expression of interleukins and their receptors is often regulated by alternative splicing. Alternative isoform of IL-5 receptor α-chain is well studied; however, no data on functional alternative splice variants of IL-5 has been reported up today. In the present study, we describe a novel splice variant for the mouse and human IL-5. The new form was found during analysis of PCR-products amplified from different mouse lymphoid tissues with a pair of primers designed to clone full-length mIL-5 ORF. A single short isoform of mIL-5 was detected along with the canonical full-length mRNA in ConA-stimulated lymphoid cells isolated from spleen, thymus, lymph nodes and blood. It was 30-40 nt shorter, and less abundant than classical form. The sequence analysis of an additional form of mIL-5 revealed that it lacks exon-2 (δ2). Using RT-PCR with the splice-specific primers we obtained an additional evidence for δ2 form expression. To verify whether mIL-5δ2 transcript is translated into protein, the coding sequences corresponding to full and δ2 forms of mIL-5 were cloned into an expression plasmid. After transfection into the human 293T cell line, we found that the short form of mIL-5 protein is expressed in cells and secreted into the supernatant, but at the reduced level than that detected for full isoform of mIL-5. Fluorescence microscopy examination revealed a partial translocation of mIL-5δ2 into cytoplasm, whereas mIL-5 resided mostly within endoplasmic reticulum. This can explain why the level of δ2 protein expression was reduced. Using a similar set of experimental approaches, we received the evidence that the human IL-5 mRNA has the δ2 splice form (hIL-5δ2) as well. It can be firmly detected by RT-PCR in PHA-activated mononuclear cells isolated from peripheral blood of healthy persons or patients with asthma. Altogether, our results showed that the human and mouse IL-5 have an alternative mRNA splice isoform, which loses exon-2, but nevertheless is expressed at protein level. However, more comprehensive studies will be required for evaluation of IL-5δ2 expression, regulation, biological function and clinical significance.

Asthma biologics: Comparing trial designs, patient cohorts and study results

OBJECTIVE

Five biologic therapies have FDA-approved indications for difficult-to-control asthma. The clinical trials that proved the efficacy and safety of these biologics were often similar in their inclusion criteria, study designs, and endpoints. Many of these trials have been reanalyzed post hoc to identify subsets of subjects considered to be enhanced responders. As a result, keeping up with the literature and deciding on the most appropriate biologic for our patients has become increasingly difficult. This review summarizes and compares trial designs, patient cohorts, and study results of the major trials involving these therapies.

DATA SOURCES

Included are basic science articles, online Food and Drug Administration (FDA) applications, and all the published reports of phase II and phase III clinical trials for FDA-approved asthma biologics.

STUDY SELECTIONS

Included are the major phase II and phase III clinical trials of 5 asthma biologics.

RESULTS

Because of variations in inclusion criteria and natural variations in enrolled cohorts, the baseline clinical traits and severity of study populations in asthma biologic trials differed significantly, which is important because baseline annualized exacerbation rates and blood eosinophilia are both strong predictors of a biologic's success. Notwithstanding, the trial results, when considered together, can help guide care providers in choosing the most appropriate biologic for our patients.

CONCLUSION

Understanding the details and differences in asthma biologic trial designs, patient cohorts, and in study results will help care providers make more informed decisions when choosing a biologic. We are hopeful this review will serve as a reference to care providers for this purpose.

DNA methylation and allergic sensitizations: A genome-scale longitudinal study during adolescence

BACKGROUND

The presence of allergic sensitization has a major influence on the development and course of common childhood conditions such as asthma and rhinitis. The etiology of allergic sensitization is poorly understood, and its underlying biological mechanisms are not well established. Several studies showed that DNA methylation (DNAm) at some CpGs is associated with allergic sensitization. However, no studies have focused on the critical adolescence period.

METHODS

We assessed the association of pre- and postadolescence genome-wide DNAm with allergic sensitization against indoor, outdoor and food allergens, using linear mixed models. We hypothesized that DNAm is associated with sensitization in general, and with poly-sensitization status, and these associations are age- and gender-specific. We tested these hypotheses in the IoW cohort (n = 376) and examined the findings in the BAMSE cohort (n = 267).

RESULTS

Via linear mixed models, we identified 35 CpGs in IoW associated with allergic sensitization (at false discovery rate of 0.05), of which 33 were available in BAMSE and replicated with respect to the direction of associations with allergic sensitization. At the 35 CpGs except for cg19210306 on C13orf27, a reduction in methylation among atopic subjects was observed, most notably for cg21220721 and cg11699125 (ACOT7). DNAm at cg10159529 was strongly correlated with expression of IL5RA in peripheral blood (P-value = 6.76 × 10^-20 ). Three CpGs (cg14121142, cg23842695, and cg26496795) were identified in IoW with age-specific association between DNAm and allergic sensitization.

CONCLUSION

In adolescence, the status of allergic sensitization was associated with DNAm differentiation and at some CpGs the association is likely to be age-specific.

Human eosinophils and mast cells: Birds of a feather flock together

While the origin of the phrase "birds of a feather flock together" is unclear, it has been in use for centuries and is typically employed to describe the phenomenon that people with similar tastes or interests tend to seek each other out and congregate together. In this review, we have co-opted this phrase to compare innate immune cells of related origin, the eosinophil and mast cell, because they very often accumulate together in tissue sites under both homeostatic and inflammatory conditions. To highlight overlapping yet distinct features, their hematopoietic development, cell surface phenotype, mediator release profiles and roles in diseases have been compared and contrasted. What emerges is a sense that these two cell types often interact with each other and their tissue environment to provide synergistic contributions to a variety of normal and pathologic immune responses.

Overexpression of microRNA-375 impedes platelet-derived growth factor-induced proliferation and migration of human fetal airway smooth muscle cells by targeting Janus kinase 2

The abnormal proliferation and migration of airway smooth muscle (ASM) cells play a critical role in airway remodeling during the development of asthma. MicroRNAs (miRNAs) have emerged as critical regulators of ASM cell proliferation and migration in airway remodeling. In this study, we aimed to investigate the potential role of miR-375 in the regulation of platelet-derived growth factor (PDGF)-induced fetal ASM cell proliferation and migration. Our results showed that miR-375 expression was significantly decreased in fetal ASM cells that were treated with PDGF. Functional data showed that overexpression of miR-375 inhibited the proliferation and migration of fetal ASM cells, whereas inhibition of miR-375 enhanced the proliferation and migration of fetal ASM cells. The results of bioinformatics analysis and a dual-luciferase reporter assay showed that miR-375 binds directly to the 3'-untranslated region of Janus kinase 2 (JAK2). Further data confirmed that miR-375 negatively regulates the expression of JAK2 in fetal ASM cells. Moreover, miR-375 also impeded the PDGF-induced activation of signal transducer and activator of transcription 3 (STAT3) in fetal ASM cells. However, restoration of JAK2 expression partially reversed the inhibitory effect of miR-375 on fetal ASM cell proliferation and migration. Overall, our results demonstrate that miR-375 inhibits fetal ASM cell proliferation and migration by targeting JAK2/STAT3 signaling. Our study provides a potential therapeutic target for the development of novel treatment strategies for pediatric asthma.

Chloride Channel 3 Channels in the Activation and Migration of Human Blood Eosinophils in Allergic Asthma

Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase is responsible for respiratory burst in immune cells. Chloride channel 3 (CLC3) has been linked to the respiratory burst in eosinophils and neutrophils. The effect of cytokines and the involvement of CLC3 in the regulation of NADPH-dependent oxidative stress and on cytokine-mediated migration of eosinophils are not known. Human peripheral blood eosinophils were isolated from healthy individuals and from individuals with asthma by negative selection. Real-time PCR was used to detect the expression of NADPH oxidases in eosinophils. Intracellular reactive oxygen species (ROS) measurement was done with flow cytometry. Superoxide generation was measured with transforming growth factor (TGF)-β, eotaxin, and CLC3 blockers. CLC3 dependence of eosinophils in TGF-β- and eotaxin-induced migration was also examined. The messenger RNA (mRNA) transcripts of NADPH oxidase (NOX) 2, dual oxidase (DUOX) 1, and DUOX2 were detected in blood eosinophils, with very low expression of NOX1, NOX3, and NOX5 and no NOX4 mRNA. The level of NOX2 mRNA transcripts increased with disease severity in the eosinophils of subjects with asthma compared with healthy nonatopic volunteers. Change in granularity and size in eosinophils, but no change in intracellular ROS, was observed with phorbol myristate acetate (PMA). PMA, TGF-β, and eotaxin used the CLC3-dependent pathway to increase superoxide radicals. TGF-β and eotaxin induced CLC3-dependent chemotaxis of eosinophils. These findings support the requirement of CLC3 in the activation and migration of human blood eosinophils and may provide a potential novel therapeutic target to regulate eosinophil hyperactivity in allergic airway inflammation in asthma.

Splicing Regulation of Pro-Inflammatory Cytokines and Chemokines: At the Interface of the Neuroendocrine and Immune Systems

Alternative splicing plays a key role in posttranscriptional regulation of gene expression, allowing a single gene to encode multiple protein isoforms. As such, alternative splicing amplifies the coding capacity of the genome enormously, generates protein diversity, and alters protein function. More than 90% of human genes undergo alternative splicing, and alternative splicing is especially prevalent in the nervous and immune systems, tissues where cells need to react swiftly and adapt to changes in the environment through carefully regulated mechanisms of cell differentiation, migration, targeting, and activation. Given its prevalence and complexity, this highly regulated mode of gene expression is prone to be affected by disease. In the following review, we look at how alternative splicing of signaling molecules—cytokines and their receptors—changes in different pathological conditions, from chronic inflammation to neurologic disorders, providing means of functional interaction between the immune and neuroendocrine systems. Switches in alternative splicing patterns can be very dynamic and can produce signaling molecules with distinct or antagonistic functions and localization to different subcellular compartments. This newly discovered link expands our understanding of the biology of immune and neuroendocrine cells, and has the potential to open new windows of opportunity for treatment of neurodegenerative disorders.

Functional activity of peripheral blood eosinophils in allergen-induced late-phase airway inflammation in asthma patients

OBJECTIVE

We aimed to investigate peripheral blood eosinophil chemotaxis, generation of spontaneous reactive oxygen species (ROS), and apoptosis in patients with allergic asthma after bronchial allergen challenge.

MATERIAL AND METHODS

A total of 18 patients with allergic asthma (AA), 14 with allergic rhinitis (AR), and 10 healthy subjects (HS) underwent bronchial challenge with a specific allergen extract. Eosinophils from peripheral blood were isolated 24 h before as well as 7 and 24 h after bronchial allergen challenge. Chemotaxis, spontaneous ROS production in eosinophils, and apoptosis were analyzed by flow cytometry. Serum and induced sputum IL-5 levels were measured by ELISA; the cell count in sputum was analyzed by the May-Grünwald-Giemsa method.

RESULTS

Before bronchial allergen challenge, peripheral blood eosinophil chemotaxis, spontaneous ROS production was enhanced and eosinophil apoptosis was reduced in the patients with AA as compared with AR patients and HS (P < 0.05). Meanwhile, eosinophil chemotaxis and ROS generation markedly increased in the patients with AA 7 h and 24 h after challenge compared with other groups and baseline values (P < 0.05). The percentage of apoptotic eosinophils in the patients with AA decreased at 7 h as well as 24 h after challenge when compared with other groups and the baseline values (P < 0.05). There was a significant correlation between the migrated peripheral blood eosinophil count and the sputum eosinophil count (Rs = 0.89, P < 0.0001) and the sputum IL-5 level (Rs = 0.68, P = 0.002) at 24 h after bronchial challenge only in the patients with AA. Furthermore, the percentage of peripheral blood apoptotic eosinophils significantly correlated with eosinophil count in sputum (Rs = -0.53, P = 0.02), and ROS production correlated with the serum IL-5 levels (Rs = 0.71, P = 0.01).

CONCLUSION

During allergen-induced late-phase airway inflammation, peripheral blood eosinophils demonstrated further alterations of their functional activity manifested by enhanced spontaneous ROS production, increased chemotaxis, and diminished apoptosis in patients with AA.

Abr, a negative regulator of Rac, attenuates cockroach allergen-induced asthma in a mouse model

Abr deactivates Ras-related C3 botulinum toxin substrate (Rac), a master molecular switch that positively regulates many immune cell functions, by converting it to its GDP-bound conformation. In this article, we report that, in the absence of Abr function, cockroach allergen (CRA)-immunized mice experienced a fatal asthma attack when challenged with CRA. The asthma in abr(-/-) mice was characterized by increased pulmonary mucus production, elevated serum IgE, and leukocyte airway infiltration. Decreased pulmonary compliance was further documented by increased airway resistance upon methacholine challenge. Peribronchial and bronchoalveolar lavage eosinophils, key cells associated with allergic asthma, were increased in abr(-/-) mice, but adoptive transfer of this cell type from immunized mice to naive controls, followed by CRA challenge, showed that eosinophils are not primarily responsible for differences in airway resistance between controls and abr-null mutants. CD4(+) T cell numbers in the airways of CRA-challenged abr(-/-) mice also were significantly increased compared with controls, as were the Th2 T cell-secreted cytokines IL-4 and IL-5 in total lung. Interestingly, when control and abr(-/-) CD4(+) T cells from CRA-immunized mice were transferred to wild-type animals, airway resistance upon challenge with CRA was significantly higher in mice transplanted with T cells lacking Abr function. CD4(+) T cells from CRA-immunized and challenged abr(-/-) mice contained elevated levels of activated GTP-bound Rac compared with wild-type controls. Functionally, abr(-/-) CD4(+) T cells from CRA-exposed mice showed significantly enhanced chemotaxis toward CCL21. These results identify Abr-regulated CD4(+) T cell migration as an important component of severe CRA-evoked allergic asthma in mice.

The involvement of the JAK-STAT signaling pathway in chronic inflammatory skin disease atopic dermatitis

Atopic dermatitis (AD), a common chronic inflammatory skin disease, is characterized by inflammatory cell skin infiltration. The JAK-STAT pathway has been shown to play an essential role in the dysregulation of immune responses in AD, including the exaggeration of Th2 cell response, the activation of eosinophils, the maturation of B cells, and the suppression of regulatory T cells (Tregs). In addition, the JAK-STAT pathway, activated by IL-4, also plays a critical role in the pathogenesis of AD by upregulating epidermal chemokines, pro-inflammatroy cytokines, and pro-angiogenic factors as well as by downregulating antimicrobial peptides (AMPs) and factors responsible for skin barrier function. In this review, we will highlight the recent advances in our understanding of the JAK-STAT pathway in the pathogenesis of AD.

A genetic effect of IL-5 receptor α polymorphism in patients with aspirin-exacerbated respiratory disease

Persistent eosinophil activation in both the upper and lower airway mucosa is a central feature of aspirin-exacerbated respiratory disease (AERD). Eosinophil activation and survival are profoundly influenced by interleukin 5 (IL-5) and its receptor, IL-5R. In patients susceptible to allergic disorders, IL-5 receptor α (IL5RA) polymorphisms have been reported; however, an association with AERD remains unclear. We hypothesize that IL5RA polymorphisms may contribute to eosinophil activation in AERD patients. We recruited 139 AERD patients, 171 aspirin-tolerant asthma patients and 160 normal controls. IL5RA polymorphisms (−5993G>A, −5567C>G and −5091G>A) were genotyped and functional activity of polymorphism was assessed by luciferase reporter assay and electrophoretic mobility shift assay (EMSA). There was no significant difference in the genotype frequency of the three polymorphisms among the three groups. AERD patients carrying the AA genotype at −5993G>A had a significantly higher presence of serum-specific immunoglobulin E (IgE) to staphylococcal enterotoxin A (P=0.008) than those with the GG/GA genotype. In vitro, the −5993A allele had a higher promoter activity compared with the −5993G allele in human mast cell (HMC-1; P=0.030) and human promyelocytic leukemia (HL-60; P=0.013) cells. In EMSA, a −5993A probe produced a specific shifted band than the −5993G had. These findings suggest that a functional polymorphism in IL5RA may contribute to eosinophil and mast cell activation along with specific IgE responses to staphylococcal enterotoxin A in AERD patients.

Eosinophils in fungus-associated allergic pulmonary disease

Asthma is frequently caused and/or exacerbated by sensitization to fungal allergens, which are ubiquitous in many indoor and outdoor environments. Severe asthma with fungal sensitization is characterized by airway hyperresponsiveness and bronchial constriction in response to an inhaled allergen that is worsened by environmental exposure to airborne fungi and which leads to a disease course that is often very difficult to treat with standard asthma therapies. As a result of complex interactions among inflammatory cells, structural cells, and the intercellular matrix of the allergic lung, patients with sensitization to fungal allergens may experience a greater degree of airway wall remodeling and progressive, accumulated pulmonary dysfunction as part of the disease sequela. From their development in the bone marrow to their recruitment to the lung via chemokine and cytokine networks, eosinophils form an important component of the inflammatory milieu that is associated with this syndrome. Eosinophils are recognized as complex multi-factorial leukocytes with diverse functions in the context of allergic fungal asthma. In this review, we will consider recent advances in our understanding of the molecular mechanisms that are associated with eosinophil development and migration to the allergic lung in response to fungal inhalation, along with the eosinophil’s function in the immune response to and the immunopathology attributed to fungus-associated allergic pulmonary disease.

A retrospective cross-sectional study of risk factors and clinical spectrum of children admitted to hospital with pandemic H1N1 influenza as compared to influenza A

OBJECTIVE

To compare risk factors for severe disease as measured by admission to hospital and intensive care unit (ICU) and other clinical outcomes in children with pandemic H1N1 (pH1N1) versus those with seasonal influenza.

DESIGN

Retrospective analysis of children admitted to hospital with pH1N1 versus seasonal influenza A.

SETTING

Canadian tertiary referral children's hospital.

PARTICIPANTS

All laboratory-identified cases of pH1N1 in children younger than 18 years admitted to hospital in 2009 (n=176) and all seasonal influenza A cases admitted to hospital from influenza seasons 2004-2005 to 2008-2009 (n=200). Children with onset of symptoms more than 3 days after admission were excluded.

PRIMARY AND SECONDARY OUTCOME MEASURES

Primary outcomes include admission to hospital and ICU and need for mechanical ventilation. Secondary outcomes include length of stay in hospital and duration of supplemental oxygen requirement.

RESULTS

Children admitted with pH1N1 were older than seasonal influenza A admissions (hospital admission: 6.5 vs 3.3 years, p<0.01; ICU admission: 7.3 vs 3.6 years, p=0.02). Children hospitalised with pH1N1 were more likely to have a pre-existing diagnosis of asthma (15% vs 5%, p<0.01); however, there was no difference in the severity of pre-existing asthma between the two groups. After controlling for obesity, asthma (OR 4.59, 95% CI 1.42 to 14.81) and age ≥5 years (OR 2.87, 95% CI 1.60 to 5.16) were more common risk factors in admitted children with pH1N1. Asthma was a significant predictor of the need for intensive care in patients with pH1N1 (OR 4.56, 95% CI 1.16 to 17.89) but not in patients with seasonal influenza A.

CONCLUSION

While most pH1N1 cases presented with classic influenza-like symptoms, risk factors for severe pH1N1 disease differed from seasonal influenza A. Older age and asthma were associated with increased admission to hospital and ICU for children with pH1N1.

Benralizumab--a humanized mAb to IL-5Rα with enhanced antibody-dependent cell-mediated cytotoxicity--a novel approach for the treatment of asthma

INTRODUCTION

Benralizumab is a monoclonal antibody that binds the α subunit of the receptor to IL-5. As IL-5 is implicated in disease states that are mediated by eosinophils, benralizumab is an attractive option for use in the management of asthma. As a result of enhanced antibody-directed cell cytotoxicity, it has enhanced eosinophil-depleting activity as compared with neutralizing monoclonal antibody directed against IL-5.

AREAS COVERED

This review presents the available data on benralizumab, including pharmacodynamics, pharmacokinetics, preclinical data and relevant clinical studies.

EXPERT OPINION

Our review indicates that although further investigation is necessary to demonstrate clinical benefit, benralizumab remains a promising treatment modality.

Eosinophilic bronchitis, eosinophilia associated genetic variants, and notch signaling in asthma

While much has indeed been learned about the biology and role of eosinophils, the paradigm of eosinophils has the pros and cons in development of asthma. To answer the questions in the black box, this review firstly discusses the biological and morphological differences between asthma and eosinophilic bronchitis (EB). EB is an interesting clinical manifestation of eosinophilic airway disease that does not involve airway hyperresponsiveness (AHR), demonstrating that airway eosinophilia alone is insufficient to merit a diagnosis of asthma. Secondly, I will describe and discuss the effect(s) of single-nucleotide polymorphisms (SNPs) in the genes CCR3, IL-5 RECEPTOR ALPHA (IL5RA), and IL1RL1, and finally the in vitro and in vivo effects of Notch inhibition on both eosinophil differentiation and experimental asthma. Eosinophilic airway inflammation is not as important in the pathogenesis and maintenance of asthma as had previously been thought. However, the role of eosinophils in other asthma subphenotypes, including refractory or severely remodeled asthma, needs to be evaluated further. High-throughput methodologies such as genomics will facilitate the discovery of new markers of inflammation; these, in turn, will aid in the evaluation of the role of eosinophils in asthma and its various subphenotypes.

Genetic effect of CCR3 and IL5RA gene polymorphisms on eosinophilia in asthmatic patients

BACKGROUND

Eosinophilic infiltration and peripheral blood eosinophilia in asthma require the cooperation of eosinophil-specific cytokines and chemokines and their receptors.

OBJECTIVE

We investigated the association of polymorphisms in CCR3 and IL5RA with asthma susceptibility or peripheral blood eosinophilia and the effects of the polymorphisms on receptor expression.

METHODS

Polymorphisms in CCR3 and IL5RA were identified and genotyped in 576 asthmatic patients and 180 healthy control subjects. CCR3 and IL-5 receptor alpha (IL-5R alpha) protein expression on eosinophils was measured by means of flow cytometry.

RESULTS

Although polymorphisms in CCR3 were not associated with asthma susceptibility, the CCR3 haplotype ht2 showed a negative gene dose effect on the eosinophil count (P = .003-.009). IL5RA c.-5091G>A was weakly associated with eosinophil count. The effects of ht2 were greater when paired with IL5RA c.-5091A (P = .001-.002). CCR3 protein expression was higher on eosinophils of asthmatic patients without ht2 than in those with ht2. Asthmatic patients with the IL5RA c.-5091A allele showed higher IL-5R alpha expression than those who were homozygous for the G allele.

CONCLUSION

The genetic association between CCR3 polymorphisms and the number of circulating eosinophils was revealed as a novel finding. These associations were more pronounced when the CCR3 polymorphisms were paired with polymorphisms in IL5RA. The protein expression levels of CCR3 and IL-5R alpha on peripheral blood eosinophils are associated with the polymorphisms on their own genes.

CLINICAL IMPLICATIONS

The identification of single nucleotide polymorphisms and haplotypes of CCR3 and IL5RA might be useful in developing markers for intermediate phenotypes of eosinophil number and in designing strategies to control diseases related to hypereosinophilia.

Roles of integrin activation in eosinophil function and the eosinophilic inflammation of asthma

Eosinophilic inflammation is a characteristic feature of asthma. Integrins are highly versatile cellular receptors that regulate extravasation of eosinophils from the postcapillary segment of the bronchial circulation to the airway wall and airspace. Such movement into the asthmatic lung is described as a sequential, multistep paradigm, whereby integrins on circulating eosinophils become activated, eosinophils tether in flow and roll on bronchial endothelial cells, integrins on rolling eosinophils become further activated as a result of exposure to cytokines, eosinophils arrest firmly to adhesive ligands on activated endothelium, and eosinophils transmigrate to the airway in response to chemoattractants. Eosinophils express seven integrin heterodimeric adhesion molecules: alpha 4 beta 1 (CD49d/29), alpha 6 beta 1 (CD49f/29), alpha M beta 2 (CD11b/18), alpha L beta 2 (CD11a/18), alpha X beta 2 (CD11c/18), alpha D beta2 (CD11d/18), and alpha 4 beta 7 (CD49d/beta 7). The role of these integrins in eosinophil recruitment has been elucidated by major advances in the understanding of integrin structure, integrin function, and modulators of integrins. Such findings have been facilitated by cellular experiments of eosinophils in vitro, studies of allergic asthma in humans and animal models in vivo, and crystal structures of integrins. Here, we elaborate on how integrins cooperate to mediate eosinophil movement to the asthmatic airway. Antagonists that target integrins represent potentially promising therapies in the treatment of asthma.

Expression of IL-12 and T helper cell 1 cytokines in the fluid of paranasal sinus mucoceles

OBJECTIVE

The objective of this study was to assess the expression of regulatory cytokines and T helper cell (Th)1/Th2 cytokines in paranasal sinus mucoceles.

MATERIALS AND METHODS

Fluid samples of 12 paranasal sinus mucoceles were assessed by enzyme-linked immunosorbent assay for concentrations of regulatory cytokines (interleukin [IL]-10 and IL-12), Th1 cytokines (IL-2 and interferon gamma), and Th2 cytokines (IL-4 and IL-5).

RESULTS

IL-12 was detected in all samples, whereas IL-10 was detected in only one case. The concentration of IL-12 tended to correlate with that of interferon gamma and was significantly and positively correlated with that of IL-2.

CONCLUSIONS

Th1 cytokines and the Th1 regulatory cytokine IL-12, but not IL-10, potentially play a key role in the pathogenesis of paranasal sinus mucoceles. Together with our recent report showing that lipopolysaccharide is highly detected in mucocele fluid, the data from this study suggest that the Th1 response induced by lipopolysaccharide may affect the immunological inflammation in the epithelium of paranasal sinus mucoceles.

Differential engagement of modules 1 and 4 of vascular cell adhesion molecule-1 (CD106) by integrins alpha4beta1 (CD49d/29) and alphaMbeta2 (CD11b/18) of eosinophils

We have studied adhesion of eosinophils to various forms of vascular cell adhesion molecule 1 (VCAM-1, CD106), an integrin counter-receptor implicated in eosinophil recruitment to the airway in asthma. Full-length 7d-VCAM-1, with seven immunoglobulin-like modules, contains integrin-binding sites in modules 1 and 4. The alternatively spliced six-module protein, 6d-VCAM-1, lacks module 4. In static assays, unactivated purified human blood eosinophils adhered similarly to recombinant soluble human 6d-VCAM-1 and 7d-VCAM-1 coated onto polystyrene microtiter wells. Further experiments, however, revealed differences in recognition of modules 1 and 4. Antibody blocking indicated that eosinophil adhesion to 6d-VCAM-1 or a VCAM-1 construct containing only modules 1-3, 1-3VCAM-1, is mediated by alpha4beta1 (CD49d/29), whereas adhesion to a construct containing modules 4-7, 4-7VCAM-1, is mediated by bothalpha4beta1 andalphaMbeta2 (CD11b/18). Inhibitors of phosphoinositide 3-kinase, which block adhesion of eosinophils mediated by alphaMbeta2, blocked adhesion to 4-7VCAM-1 but had no effect on adhesion to 6d-VCAM-1. Consistent with the antibody and pharmacological blocking experiments, eosinophilic leukemic cell lines lacking alphaMbeta2 did not adhere to 4-7VCAM-1 but did adhere to 6d-VCAM-1 or 1-3VCAM-1. Activation of eosinophils by interleukin (IL)-5 enhanced static adhesion to 6d-VCAM-1, 7d-VCAM-1, or 4-7VCAM-1; IL-5-enhanced adhesion to all 3 constructs was blocked by anti-alphaMbeta2. Adhesion of unstimulated eosinophils to 7d-VCAM-1 under flow conditions was inhibited by anti-alpha4 or anti-alphaM. IL-5 treatment decreased eosinophil adhesion to 7d-VCAM-1 under flow, and anti-alphaM had the paradoxical effect of increasing adhesion. These results demonstrate that alphaMbeta2 modulatesalpha4beta1-mediated eosinophil adhesion to VCAM-1 under both static and flow conditions.

Interleukin-5 does not influence differential transcription of transmembrane and soluble isoforms of IL-5R alpha in vivo

Interleukin-5 (IL-5) promotes signal transduction and expansion of eosinophil colonies in bone marrow via interactions with its heterodimeric receptor (IL-5R). Two variants encoding soluble forms of the alpha subunit (sIL-5R alpha) have been described, although the signals promoting and/or limiting differential transcription remain to be clarified.

OBJECTIVES

Our intent was to explore the role of IL-5 in regulating differential transcription of these splice variants in vivo.

METHODS

We have designed a quantitative reverse transcriptase-polymerase chain reaction assay to detect transcripts encoding the transmembrane, soluble 1 and 2 forms of IL-5R alpha in two strains of wild-type (BALB/c and C57BL/6) and corresponding IL-5 gene-deleted mice. Wild-type mice respond to S. mansoni infection with a gradual increase in serum IL-5 and eosinophilia, which is not observed in IL-5 gene-deleted mice.

RESULTS AND CONCLUSIONS

We find that IL-5 is not necessary for differential splicing to occur in vivo, as all three forms of the IL-5R alpha are detected in both strains of IL-5 gene-deleted mice, with ratios of transcript expression (transmembrane : soluble 1 : soluble 2) that were indistinguishable from their wild-type counterparts. Differential splicing does vary markedly between strains, potentially because of local effects of strain-specific polymorphisms.

Effect of mitomycin C on the secretion of granulocyte macrophages colonies stimulating factor and interleukin-5 in eosinophilic nasal polyps stromal culture

The research involving tissue factors, such as granulocyte macrophage colonies stimulating factor (GM-CSF) and interleukin 5 (IL-5), leads to the mechanisms involved in the maintenance of eosinophilia, which is essential for the pathogenesis on eosinophilic nasal polyps. Mitomycin C has been successfully used in otolaryngology. Aim: The objective of this study was to evaluate the effect of mitomycin C in secretion of GM-CSF and IL-5 on eosinophilic nasal polyps. Study design: case-control. Material and Method: This is a comparative and auto-matched experimental study, performed with fragments of polyps which had been obtained from biopsy of patients with eosinophilic nasosinusal polyposis. The fragments of the experimental group were treated with mitomycin C (400 microg/ml) for 5 minutes and then washed in RPMI substrate. At time zero, 12 and 24 hours, the surface material was taken to determination of its GM-CSF levels in 22 patients and of IL-5 levels in 19 patients, by ELISA method. Results: Reduction in GM-CSF expression on the experimental group at time 24 h (p<= 0.05). The treated group presented significant GM-CSF expression between zero time and 12 h time (p=0.013) showing the culture viability such as in the non-treated group. Tendency to decreasing IL-5 levels on the treated groups at 24 hours. Conclusion: This study showed that mitomycin C was efficient in inhibiting GM-CSF synthesis with reduction of IL-5 secretion, but this fact needs complementary studies.

Association analysis of interleukin 5 receptor alpha subunit (IL5RA) polymorphisms and asthma

The alpha subunit of interleukin 5 receptor (IL5RA) on chromosome 3p26-p24 is known to regulate the development and function of eosinophils. In an effort to discover additional polymorphism(s) in genes whose variant(s) have been implicated in asthma, we investigated the genetic polymorphisms in IL5RA to evaluate the gene as a potential candidate for a host genetic study of asthma. By direct DNA sequencing in 24 individuals, we identified 22 sequence variants within exons and flanking regions including a 1.5-kb promoter region of IL5RA; 10 common polymorphic sites were selected for genotyping in our asthma cohort (n = 587). Two haplotype blocks were identified in a Korean population. Statistical analysis revealed that one promoter SNP, c.-5993A > G, and one ins/del polymorphism in intron 3, c.-480_482insdelGTT, showed significant association with the risk of asthma development. The genetic effects of c.-5993A>G and c.-480_482insdelGTT on asthma were more apparent among atopic subjects. Our findings suggest that polymorphisms in IL5RA might be among the genetic risk factors for asthma development, especially in atopic populations. IL5RA variant/haplotype information identified in this study will provide valuable information for strategies for the control of asthma.

Consequences of regulated pre-mRNA splicing in the immune system

Alternative splicing is widely recognized to be a ubiquitous and crucial mechanism for generating protein diversity and regulating protein expression. Numerous immunologically relevant genes have been found to undergo alternative splicing; however, there has been little effort to develop a coherent picture of how alternative splicing might be used as a general mechanism to regulate the function of the immune system. In this review, I summarize the mechanisms by which splicing is controlled in T cells, and discuss the role of alternative splicing and alternative isoform expression in the regulation of T-cell activation and function.

Cytokines in Mycoplasma pneumoniae infections

Mycoplasma pneumoniae (M. pneumoniae) is one of the smallest free-living bacteria known. Along with other unique characteristics of this genus, it lacks the typical peptidoglycan cell wall of most eubacteria. Best known for causing tracheobronchitis and atypical pneumonia in humans, this pathogen also causes a number of extrapulmonary syndromes such as meningitis/encephalitis and arthritis. Recent studies also suggest that infection may be associated with chronic conditions such as asthma. Although the mechanisms of M. pneumoniae pathogenesis remain to be elucidated, one important component of M. pneumoniae infections is the induction of proinflammatory and other cytokines in both acute and chronic conditions. In this review, we survey the induction of cytokines by M. pneumoniae in different model systems, and we discuss the possible role of induced cytokines in M. pneumoniae pathogenesis.

Therapeutic potential of antisense oligonucleotides as modulators of alternative splicing

An estimated 60% of all human genes undergo alternative splicing, a highly regulated process that produces splice variants with different functions. Such variants have been linked to a variety of cancers, and genetic diseases such as thalassemia and cystic fibrosis. This Perspective describes a promising approach to RNA repair based on the use of antisense oligonucleotides to modulate alternative splicing and engender the production of therapeutic gene products.

Decreased expression of membrane IL-5 receptor alpha on human eosinophils: I. Loss of membrane IL-5 receptor alpha on airway eosinophils and increased soluble IL-5 receptor alpha in the airway after allergen challenge

IL-5 is a key cytokine for eosinophil maturation, recruitment, activation, and possibly the development of inflammation in asthma. High concentrations of IL-5 are present in the airway after Ag challenge, but the responsiveness of airway eosinophils to IL-5 is not well characterized. The objectives of this study were to establish, following airway Ag challenge: 1) the expression of membrane (m)IL-5Ralpha on bronchoalveolar lavage (BAL) eosinophils; 2) the responsiveness of these cells to exogenous IL-5; and 3) the presence of soluble (s)IL-5Ralpha in BAL fluid. To accomplish these goals, blood and BAL eosinophils were obtained from atopic subjects 48 h after segmental bronchoprovocation with Ag. There was a striking reduction in mIL-5Ralpha on airway eosinophils compared with circulating cells. Furthermore, sIL-5Ralpha concentrations were elevated in BAL fluid, but steady state levels of sIL-5Ralpha mRNA were not increased in BAL compared with blood eosinophils. Finally, BAL eosinophils were refractory to IL-5 for ex vivo degranulation, suggesting that the reduction in mIL-5Ralpha on BAL eosinophils may regulate IL-5-mediated eosinophil functions. Together, the loss of mIL-5Ralpha, the presence of sIL-5Ralpha, and the blunted functional response (degranulation) of eosinophils to IL-5 suggest that when eosinophils are recruited to the airway, regulation of their functions becomes IL-5 independent. These observations provide a potential explanation for the inability of anti-IL-5 therapy to suppress airway hyperresponsiveness to inhaled Ag, despite a reduction in eosinophil recruitment.

Decreased expression of membrane IL-5 receptor alpha on human eosinophils: II. IL-5 down-modulates its receptor via a proteinase-mediated process

In the accompanying study, we demonstrated that following Ag challenge, membrane (m)IL-5Ralpha expression is attenuated on bronchoalveolar lavage eosinophils, soluble (s)IL-5Ralpha is detectable in BAL fluid in the absence of increased steady state levels of sIL-5Ralpha mRNA, and BAL eosinophils become refractory to IL-5 for ex vivo degranulation. We hypothesized that IL-5 regulates its receptor through proteolytic release of mIL-5Ralpha, which in turn contributes to the presence of sIL-5Ralpha. Purified human peripheral blood eosinophils were incubated with IL-5 under various conditions and in the presence of different pharmacological agents. A dose-dependent decrease in mIL-5Ralpha was accompanied by an increase in sIL-5Ralpha in the supernatant. IL-5 had no ligand-specific effect on mIL-5Ralpha or sIL-5Ralpha mRNA levels. The matrix metalloproteinase-specific inhibitors BB-94 and GM6001 and tissue inhibitor of metalloproteinase-3 partially inhibited IL-5-mediated loss of mIL-5Ralpha, suggesting that sIL-5Ralpha may be produced by proteolytic cleavage of mIL-5Ralpha. IL-5 transiently reduced surface expression of beta-chain, but had no effect on the expression of GM-CSFRalpha. Pretreatment of eosinophils with a dose of IL-5 that down-modulated mIL-5Ralpha rendered these cells unable to degranulate in response to further IL-5 stimulation, but they were fully responsive to GM-CSF. These findings suggest that IL-5-activated eosinophils may lose mIL-5Ralpha and release sIL-5Ralpha in vivo, which may limit IL-5-dependent inflammatory events in diseases such as asthma.

T lymphocyte-mediated changes in airway smooth muscle responsiveness are attributed to induced autocrine release and actions of IL-5 and IL-1beta

BACKGROUND

Bidirectional stimulatory cross-talk was recently found to exist between activated T cells and airway smooth muscle (ASM) cells, a process that involves coligation of specific cellular adhesion-costimulatory molecules that results in the induction of proasthmatic-like changes in ASM responsiveness.

OBJECTIVE

The present study examined whether the cooperative intercellular signaling between activated T cells and ASM cells is coupled to the induced expression and actions of IL-5 and IL-1beta.

METHODS

Agonist-induced constrictor and relaxant responses were examined in rabbit ASM segments exposed to resting and anti-CD3-activated T cells in the absence and presence of either an anti-IL-5 receptor mAb or the recombinant human IL-1 receptor antagonist. In addition, mRNA and protein expression of IL-5 and IL-1beta were assayed under control and anti-CD3-stimulated conditions.

RESULTS

Relative to inactive T cells, incubation of ASM tissues with anti-CD3-activated T cells induced proasthmatic-like changes in agonist-mediated ASM responsiveness. This T cell-induced perturbation in ASM responsiveness was ablated by pretreating the tissues with either an anti-IL-5 receptor mAb or IL-1 receptor antagonist. Moreover, exposure of ASM cells to anti-CD3-activated T cells elicited an initial increased mRNA expression and release of IL-5, followed by an enhanced expression and release of IL-1beta, and the induced release of these cytokines was prevented in ASM cells that were pretreated with an anti-IL-5 receptor mAb.

CONCLUSION

Collectively, these observations provide new evidence demonstrating that exposure of naive ASM cells to activated T cells induces the sequential release of IL-5 and IL-1beta from the ASM cells and that the latter cytokines act in an autocrine manner to elicit the proasthmatic phenotype of altered ASM responsiveness.

Pathogenesis of asthma

There is now strong evidence that airway inflammation is a predominant underlying problem in patients with asthma, and it has been suggested that ongoing inflammation may lead to airway injury and remodeling. There is also recent evidence that longstanding asthma could be associated with loss of elastic recoil, which can enhance airway obstruction and worsen asthma control [82,83]. Therefore, the use of anti-inflammatory therapy has been advocated in all guidelines, including the National Asthma Education and Prevention Program (NAEPP) Expert Panel Report [84] and its recent update [85] that recommended inhaled steroids as a first mode of therapy for patients with mild, moderate, or severe, persistent asthma. There is preliminary evidence that early institution of anti-inflammatory therapy might lead to disease modification and limit the progression of subepithelial fibrosis and airway remodeling. The pathogenesis of asthma clearly involves many cells and mediators, although the contribution of each individual factor is probably different from patient to patient depending on the setting and stimulus. Although currently available therapies are highly effective in controlling asthma symptoms and limiting exacerbations in the majority of patients, there is still a subset of patients that proceed to develop severe asthma with decreased lung function, lack of responsiveness to therapy, or frequent exacerbations. It is hoped that rapid progress in the area of asthma genetics and pharmacogenetics will yield a more precise and patient-specific understanding of asthma pathogenesis and allow practitioners to prescribe therapies that are designed for a particular patient or exacerbation. That will undoubtedly help to improve the care of asthma, limit its morbidity, and reduce the side effect of medications.

T(H)2 cytokine expression in atopic children with otitis media with effusion

BACKGROUND

Otitis media with effusion (OME) is more common in atopic children. Few studies have looked for the presence of inflammatory mediators in the middle-ear effusions of this population.

OBJECTIVE

We hypothesize that atopic children with OME have a different inflammatory cell and cytokine profile than nonatopic patients with the disease.

METHODS

Twenty-six patients with OME undergoing myringotomy and ventilation tube placement were recruited at the McGill University Hospital Center. The atopic status was determined for each patient by using standard skin testing. By means of immunocytochemistry, fluid specimens were assessed for T lymphocytes (CD3), eosinophils (major basic protein), neutrophils (elastase), mast cells (tryptase), and basophils (BB1). By using in situ hybridization, the expression of IL-4, IL-5, and IFN-gamma was assessed.

RESULTS

There is a higher percentage of eosinophils and T lymphocytes in atopic patients with OME (n = 8) compared with that seen in nonatopic patients (n = 18, P <.01). There is a higher percentage of neutrophils in nonatopic patients with OME compared with that seen in atopic patients (P <.01). In examining cytokine profiles, there is a higher percentage of cells expressing IL-4 and IL-5 in atopic patients with OME compared with that seen in nonatopic patients (P <.01).

CONCLUSION

The predominance of eosinophils, T lymphocytes, and T(H)2 mediators in the middle-ear effusions of atopic children provides evidence that allergy might play a role in the pathogenesis of OME.

Interleukin-4 and interferon-gamma gene expression in summer pasture-associated obstructive pulmonary disease affected horses

We hypothesised that horses affected with summer pasture-associated obstructive pulmonary disease (SPAOPD) react to an allergen or allergens in their summer environment that is either absent or present at lower levels in their winter environment; and that such allergens stimulate SPAOPD-affected horses to produce a different T helper lymphocyte cytokine profile from that of control horses. The primary objective of this study was to determine the cytokine mRNA profile of T helper lymphocytes obtained from summer pasture-associated obstructive pulmonary disease (SPAOPD) affected horses when 1) the horses were showing signs of disease (summer) and 2) they were in clinical remission (winter). A further objective was to determine the differences between cytokine mRNA T helper lymphocyte profiles of control and affected horses in the summer and winter seasons. Interleukin 4 (IL-4) and interferon-gamma (IFN-gamma) mRNA expression levels were increased in bronchoalveolar lavage fluid (BALF) and peripheral blood mononuclear cell (PBMC) samples of affected horses during disease expression. No significant amounts of IL-5 mRNA were detected in any of the samples. These results suggest that there is an allergic component to SPAOPD of horses and that appropriate manipulation of the immune system could offer hope for treatment and prevention of the disease in the future. Further research studies will be needed to determine the most appropriate treatments to use to alter the antigen-stimulated cytokine profile being expressed by SPAOPD-affected horses or to alter the effects that these cytokines produce.

Evidence for systemic rather than pulmonary effects of interleukin-5 administration in asthma

BACKGROUND

Interleukin 5 (IL-5) has an important role in mobilisation of eosinophils from the bone marrow and in their subsequent terminal differentiation. A study was undertaken to determine whether inhaled and intravenous IL-5 could induce pulmonary eosinophilia and bronchial hyperresponsiveness (BHR) independently of these effects.

METHODS

Nine mild asthmatics received inhaled (15 microg) or intravenous (2 microg) IL-5 or placebo in random order in a double blind, crossover study. Blood samples were taken before and at 0.5, 1, 2, 3, 4, 5, 24, and 72 hours following IL-5 or placebo, and bronchial responsiveness (PC(20) methacholine) and eosinophil counts in induced sputum were determined.

RESULTS

Serum IL-5 levels were markedly increased 30 minutes after intravenous IL-5 (p=0.002), and sputum IL-5 levels increased 4 and 24 hours after inhaled IL-5 (p<0.05). Serum eotaxin was raised 24 hours after intravenous IL-5 but not after inhaled IL-5 or placebo. Blood eosinophils were markedly reduced 0.5-2 hours after intravenous IL-5 (p<0.05), followed by an increase at 3, 4, 5, and 72 hours (p<0.05). Sputum eosinophils rose significantly in all three groups at 24 hours but there were no differences between the groups. Bronchial responsiveness was not affected by IL-5.

CONCLUSION

The effects of IL-5 appear to be mainly in the circulation, inducing peripheral mobilisation of eosinophils to the circulation without any effect on eosinophil mobilisation in the lungs or on bronchial responsiveness.

Autocrine signaling by IL-10 mediates altered responsiveness of atopic sensitized airway smooth muscle

To elucidate the role and mechanism of action of interleukin (IL)-10 in regulating airway smooth muscle (ASM) responsiveness in the atopic asthmatic state, isolated rabbit tracheal ASM segments were passively sensitized with serum from atopic asthmatic patients or nonatopic nonasthmatic (control) subjects in both the absence and presence of an anti-IL-10 receptor blocking antibody (Ab). Relative to control ASM, atopic asthmatic serum-sensitized tissues exhibited enhanced isometric constrictor responses to administered acetylcholine and attenuated the relaxation responses to isoproterenol. These proasthmatic effects were prevented in atopic asthmatic serum-sensitized ASM that was pretreated with anti-IL-10 receptor Ab. In complementary experiments, exposure of cultured human ASM cells to atopic asthmatic serum induced upregulated expression of IL-10 mRNA. Moreover, extended studies demonstrated that 1) exogenous IL-10 administration to naive ASM elicited augmented contractility to acetylcholine and impaired relaxation to isoproterenol, 2) these effects of IL-10 were prevented by pretreating the tissues with an IL-5 receptor Ab, and 3) IL-10 administration induced upregulated mRNA expression and release of IL-5 protein from cultured ASM cells. Collectively, these findings provide new evidence demonstrating that the altered responsiveness of atopic asthmatic serum-sensitized ASM is largely attributed to activation of an intrinsic T helper type 2-type autocrine mechanism involving IL-10-mediated release and the action of IL-5 in the sensitized ASM itself.

Protective role for interleukin-5 during chronic Toxoplasma gondii infection

To investigate the role of interleukin-5 (IL-5) during Toxoplasma gondii infection, IL-5 knockout (KO) mice and C57BL/6 control mice were infected intraperitoneally with ME49 cysts and the course of infection was monitored. The mortality rate during chronic infection was significantly greater in IL-5-deficient animals, and consistent with this finding, the KO mice harbored a greater number of brain cysts and tachyzoites than did their wild-type counterparts. Although the IL-5 KO animals did not succumb until late during infection, increased susceptibility, as measured by accelerated weight loss, was detectable during the acute stages of infection. The amounts of total immunoglobulin (Ig), IgM, and IgG2b were comparable in both strains, while the amount of IgG1 was much smaller in IL-5 KO mice. Spleen cell production of IL-12 in response to T. gondii antigen was approximately threefold lower in the KO strain, and this decrease correlated with a selective loss of B lymphocytes during culture. A link between the presence of B cells and augmented IL-12 production was established by the finding that after removal of B cells with monoclonal antibody and complement, wild-type- and KO-derived cells produced equivalent levels of IL-12 in response to T. gondii antigen. These results demonstrate a protective role of IL-5 against T. gondii infection and suggest that IL-5 may play a role in the production of IL-12.

Linkage and association of atopic asthma to markers on chromosome 13 in the Japanese population

Chromosome 13 contains several candidate genes for asthma and atopy, and markers on this chromosome have been shown to be linked to phenotypes of atopy or asthma in two genome-wide searches. We conducted a linkage study for atopic asthma using markers spanning the whole of chromosome 13 in Japanese families ascertained through asthmatic children and examined associations of atopic asthma with markers where linkage was suggested. Data were analysed using MAPMAKER/SIBS for the multipoint lod score (MLS) analysis and SIB-PAIR for the transmission dis-equilibrium test (TDT). Three peaks which exceeded a lod score of 1.0 were observed (MLS 2.4 between D13S175 and D13S217, MLS 2.0 between D13S153 and D13S156, and MLS 1.4 between D13S285 and D13S293). The global TDT for atopic asthma was significant for the marker D13S153 ( P = 0.0065) and the 96 bp allele of D13S153 was preferentially transmitted to atopic asthma-affected children ( P = 0.0009, Bonferroni correction 5% = 0. 0037, 1% = 0.00072). These findings indicate that genes on chromosome 13 may play an important role in the development of atopy or asthma across various populations.