Interleukin-9 receptor expression in asthmatic airways In vivo

Biotherapy and treatment of adult primary chronic rhinosinusitis with nasal polyps: Cellular and molecular bases

The present article reviews the molecular and cellular mechanisms involved in the pathophysiology of chronic rhinosinusitis with nasal polyps (CRSwCRSwNP) and underlying the action mechanisms of biotherapies. Biotherapy uses substances naturally produced by the organism or their specific antagonists targeting a proinflammatory mechanism. CRSwCRSwNP is a form of chronic rhinosinusitis (CRS), which is classically subdivided in to 2 types according to the presence of polyps. In recent years, the concept of endotypes emerged, with a more exhaustive definition of the types of CRS according to inflammatory mechanism, with a view to developing personalized treatments. CRSwNP pathophysiology is poorly understood. Polyps arise from a primary epithelial lesion in a context of chronic local inflammation, mainly type 2 in Europe, implicating eosinophils, IgE, Th2 cytokines (IL-4/IL-13, IL-5) and T and B cells. Biotherapy seems promising in CRSwNP. The present review details the various pathophysiological pathways underlying the action mechanisms of biotherapies, and the various published studies, assessing efficacy and mode of action in the treatment of CRSwNP.

Resolution of allergic asthma

Allergic asthma is an inflammatory disease of the airways characterized by recurrent episodes of wheezing and bronchoconstriction. Chronic inflammation may finally lead to structural damage followed by airway remodeling. Various studies in recent years contributed to unravel important aspects of the immunopathogenesis of asthma and adapted new pharmaceutical developments. Here, I consider some novel insights into the immunopathogenesis of asthma and the protective and pathogenic roles of some innate and adaptive immune cells as well as the function of soluble mediators such as cytokines. Particular attention will be given to new concepts on resolution of chronic airway inflammation for prevention of airway structural damage.

IL-9 signaling as key driver of chronic inflammation in mucosal immunity

Recent studies have highlighted a crucial regulatory role of the cytokine IL-9 in driving immune responses in chronic inflammatory and autoimmune diseases at mucosal surfaces. IL-9 activates various types of immune and non-immune cells carrying the membrane bound IL-9R. IL-9 signaling plays a pivotal role in controlling the differentiation and activation of these cells by inducing the Jak/STAT pathway. In particular, IL-9 induces activation of T helper cells and affects the function of various tissue resident cells such as mast cells and epithelial cells in the mucosa. Importantly, recent findings suggest that blockade of IL-9 signaling is effective in treating experimental models of autoimmune and chronic inflammatory diseases such as inflammatory bowel diseases, allergic disorders such as food allergy and asthma. Thus, blockade of IL-9 and IL-9R signaling emerges as potentially novel approach for therapy of inflammatory diseases in the mucosal immune system.

Effects of interleukin-9 blockade on chronic airway inflammation in murine asthma models

Purpose

Asthma is a chronic inflammatory disease of the airways associated with structural changes and airway remodeling. Interleukin (IL)-9 has pleiotropic effects on both inflammatory cells and airway structural cells, which are involved in asthma pathogenesis. We evaluated the effects of IL-9 blockade on chronic airway inflammation.

Methods

Acute airway inflammation was induced in Balb/c mice using aerosolized ovalbumin (OVA), whereas chronic asthma was induced by OVA exposure for 5 weeks with anti-IL-9 or isotype-matched antibody (Ab) treatment during the OVA challenge. Inflammatory cells in bronchoalveolar lavage fluid (BALF) were counted and lung tissues were stained to detect cellular infiltration, mucus deposition, and collagen accumulation. The levels of interferon (IFN)-γ, IL-4, IL-5, IL-9, IL-17, and immunoglobulin E (IgE) in BALF were measured using enzyme linked immunosorbent assays, and profiles of inflammatory cells and subsets of T helper (Th) cells were analyzed using flow cytometry.

Results

IL-9, IL-17, and IFN-γ levels were significantly increased in the chronic group compared to the acute asthma group. However, the number of IL-9-positive cells was not affected, with a decrease in Th17 cells in OVA-challenged caspase-1 knockout mice. Numbers of eosinophils, neutrophils, B cells, mast cells, and Th17 cells decreased after administration of anti-IL-9 Ab. Total IgE, IL-5, IL-9, and IL-17 levels were also lower in the anti-IL-9 group.

Conclusions

Our results suggest that anti-IL-9 Ab treatment inhibits pulmonary infiltration of inflammatory cells and cytokine production, especially IL-17. These results provide a basis for the use of an anti-IL-9 Ab to combat IL-17-mediated airway inflammation.

Programmed cell death ligand 2 regulates TH9 differentiation and induction of chronic airway hyperreactivity

BACKGROUND

Asthma is defined as a chronic inflammatory disease of the airways; however, the underlying physiologic and immunologic processes are not fully understood.

OBJECTIVE

The aim of this study was to determine whether TH9 cells develop in vivo in a model of chronic airway hyperreactivity (AHR) and what factors control this development.

METHOD

We have developed a novel chronic allergen exposure model using the clinically relevant antigen Aspergillus fumigatus to determine the time kinetics of TH9 development in vivo.

RESULTS

TH9 cells were detectable in the lungs after chronic allergen exposure. The number of TH9 cells directly correlated with the severity of AHR, and anti-IL-9 treatment decreased airway inflammation. Moreover, we have identified programmed cell death ligand (PD-L) 2 as a negative regulator of TH9 cell differentiation. Lack of PD-L2 was associated with significantly increased TGF-β and IL-1α levels in the lungs, enhanced pulmonary TH9 differentiation, and higher morbidity in the sensitized mice.

CONCLUSION

Our findings suggest that PD-L2 plays a pivotal role in the regulation of TH9 cell development in chronic AHR, providing novel strategies for modulating adaptive immunity during chronic allergic responses.

IL-9 induces VEGF secretion from human mast cells and IL-9/IL-9 receptor genes are overexpressed in atopic dermatitis

Interleukin 9 (IL-9) has been implicated in mast cell-related inflammatory diseases, such as asthma, where vascular endothelial growth factor (VEGF) is involved. Here we report that IL-9 (10–20 ng/ml) induces gene expression and secretion of VEGF from human LAD2. IL-9 does not induce mast cell degranulation or the release of other mediators (IL-1, IL-8, or TNF). VEGF production in response to IL-9 involves STAT-3 activation. The effect is inhibited (about 80%) by the STAT-3 inhibitor, Stattic. Gene-expression of IL-9 and IL-9 receptor is significantly increased in lesional skin areas of atopic dermatitis (AD) patients as compared to normal control skin, while serum IL-9 is not different from controls. These results imply that functional interactions between IL-9 and mast cells leading to VEGF release contribute to the initiation/propagation of the pathogenesis of AD, a skin inflammatory disease.

Cytokine pathways in allergic disease

Cytokines are critical in allergic intercellular communication networks, and they contribute to disease pathology through the recruitment and activation of pro-inflammatory leukocytes and in chronic disease to pro-fibrotic/remodeling events. Th2 cytokines predominate primarily in mild to moderate allergic asthma, although clinical trials with inhibitors of IL-4 and IL-5 have not provided the robust efficacy observed in animal models of allergy. These results not only highlight the complexity of allergic disease, but they also point to the importance of other cytokine networks in driving pathology. The heterogeneous nature of the disease is emphasized by the fact that the Th2/Th1/Th17 cytokine balance can be influenced by the initiating allergic trigger. For example, the house dust mite allergen Der p 2 mimics the activity of MD-2 by presenting lipopolysaccharide to Toll-like receptor-4 for the activation of inflammatory genes including innate-type cytokines. Here we discuss the functions of the novel cytokine players, thymic stromal lymphopoetin (TSLP), IL-33, IL-25, and IL-9 and delineate nonredundant roles for IL-4 and IL-13 in allergic disease. Persistent efforts in the characterization of these and other cytokine networks will be essential for understanding the complex pathogenic mechanisms that underpin allergic disease and for guiding targeted therapeutic interventions.

The Human Pseudoautosomal Region (PAR): Origin, Function and Future

The pseudoautosomal regions (PAR1 and PAR2) of the human X and Y chromosomes pair and recombine during meiosis. Thus genes in this region are not inherited in a strictly sex-linked fashion. PAR1 is located at the terminal region of the short arms and PAR2 at the tips of the long arms of these chromosomes. To date, 24 genes have been assigned to the PAR1 region. Half of these have a known function. In contrast, so far only 4 genes have been discovered in the PAR2 region. Deletion of the PAR1 region results in failure of pairing and male sterility. The gene SHOX (short stature homeobox-containing) resides in PAR1. SHOX haploinsufficiency contributes to certain features in Turner syndrome as well as the characteristics of Leri-Weill dyschondrosteosis. Only two of the human PAR1 genes have mouse homologues. These do not, however, reside in the mouse PAR1 region but are autosomal. The PAR regions seem to be relics of differential additions, losses, rearrangements and degradation of the X and Y chromosome in different mammalian lineages. Marsupials have three homologues of human PAR1 genes in their autosomes, although, in contrast to mouse, do not have a PAR region at all. The disappearance of PAR from other species seems likely and this region will only be rescued by the addition of genes to both X and Y, as has occurred already in lemmings. The present review summarizes the current understanding of the evolution of PAR and provides up-to-date information about individual genes residing in this region.

A brief history of IL-9

IL-9 was first described in the late 1980s as a member of a growing number of cytokines that had pleiotropic functions in the immune system. Although many biological functions have been attributed to IL-9, it remains an understudied cytokine. A resurgence of interest in IL-9 has been spurred by recent work demonstrating a role for IL-9 in regulating inflammatory immunity and defining the transcription factors that activate the Il9 gene in cells that most efficiently produce IL-9. In this review, we summarize the characterization of IL-9 biological activities, highlight roles for the cytokine that are clearly defined, and outline questions regarding IL-9 functions that still require further exploration.

IL-13 and TH2 cytokine exposure triggers matrix metalloproteinase 7-mediated Fas ligand cleavage from bronchial epithelial cells

BACKGROUND

Bronchial epithelial damage and activation likely contribute to the inflammatory and airway-remodeling events characteristic of severe asthma. Interaction of Fas receptor (CD95) with its ligand (FasL; CD95L) is an important mechanism of cell-mediated apoptosis. Bronchial epithelial FasL expression provides immune barrier protection from immune cell-mediated damage.

OBJECTIVES

Membrane FasL (mFasL) is a cleavage target of matrix metalloproteinases (MMPs). We investigated whether the asthmatic T(H)2 environment might influence disease processes by increasing airway epithelial MMP-mediated cleavage of mFasL into proinflammatory soluble FasL.

METHODS

We used human airway epithelial cell lines and primary cells to model the human airway epithelium in vitro. Airway tissue from healthy subjects and patients with severe asthma was used to investigate MMP expression patterns in diseased airways.

RESULTS

We demonstrate that active MMP-7 is present in the ciliated epithelial cells of normal human airways. In patients with severe asthma, MMP-7 levels are increased in basal epithelial cells. Airway epithelial cell lines (1HAEo(-) and 16HBE14o(-)) in vitro express constitutively high levels of MMP-2 and MMP-9 but relatively low levels of MMP-7. T(H)2 cytokine (IL-4, IL-9, and IL-13) treatment of 1HAEo(-) cells increased MMP-7 mRNA and activity, triggered colocalization of intracellular MMP-7 with FasL, and caused mFasL cleavage with soluble FasL release. Small interfering RNA knockdown shows that cytokine-induced mFasL cleavage is dependent on MMP-7 activity.

CONCLUSIONS

MMPs serve multiple beneficial roles in the lung. However, chronic disordered epithelial expression of MMP-7 in patients with asthma might increase mFasL cleavage and contribute to airway epithelial damage and inflammation.

T(H)2 cytokines modulate the IL-9R expression on human neutrophils

Interleukin (IL)-9 is associated with key pathological features of asthma such as airway hyperresponsiveness, bronchoconstriction and mucus production. Inflammatory responses mediated by IL-9 rely on the expression of the IL-9R which has been reported on lung epithelial cells, T lymphocytes and recently on airway granulocyte infiltrates. In this study, we assessed the regulatory and constitutive cell surface expression of the IL-9Ralpha in unfractionated and purified human neutrophils from atopic asthmatics, atopic non-asthmatics and healthy normal controls. We demonstrate that T(H)2 cytokines (IL-4 or IL-13) and granulocyte macrophage-colony stimulating factor (GM-CSF) up-regulated mRNA and cell surface expression levels of the IL-9Ralpha in primary human and HL-60 differentiated neutrophils. Pharmacological inhibition of NF-kappaB did not affect T(H)2-mediated IL-9Ralpha expression in human neutrophils although IFN-gamma and IL-10 down-regulated IL-9Ralpha expression when co-incubated with IL-4, IL-13 or GM-CSF. Collectively, our results reveal a regulatory function for IFN-gamma and IL-10 on modulating the inducible IL-9Ralpha expression levels on peripheral blood neutrophils by T(H)2 cytokines.

Agents against cytokine synthesis or receptors

Various cytokines play a critical role in pathophysiology of chronic inflammatory lung diseases including asthma and chronic obstructive pulmonary disease (COPD). The increasing evidence of the involvement of these cytokines in the development of airway inflammation raises the possibility that these cytokines may become the novel promising therapeutic targets. Studies concerning the inhibition of interleukin (IL)-4 have been discontinued despite promising early results in asthma. Although blocking antibody against IL-5 markedly reduces the infiltration of eosinophils in peripheral blood and airway, it does not seem to be effective in symptomatic asthma, while blocking IL-13 might be more effective. On the contrary, anti-inflammatory cytokines themselves such as IL-10, IL-12, IL-18, IL-23 and interferon-gamma may have a therapeutic potential. Inhibition of TNF-alpha may also be useful in severe asthma or COPD. Many chemokines are also involved in the inflammatory response of asthma and COPD through the recruitment of inflammatory cells. Several small molecule inhibitors of chemokine receptors are now in development for the treatment of asthma and COPD. Antibodies that block IL-8 reduce neutrophilic inflammation. Chemokine CC3 receptor antagonists, which block eosinophil chemotaxis, are now in clinical development for asthma therapy. As many cytokines are involved in the pathophysiology of inflammatory lung diseases, inhibitory agents of the synthesis of multiple cytokines may be more useful tools. Several such agents are now in clinical development.

Targeting memory Th2 cells for the treatment of allergic asthma

Th2 memory cells play an important role in the pathogenesis of allergic asthma. Evidence from patients and experimental models indicates that memory Th2 cells reside in the lungs during disease remission and, upon allergen exposure, become activated effectors involved in disease exacerbation. The inhibition of memory Th2 cells or their effector functions in allergic asthma influence disease progression, suggesting their importance as therapeutic targets. They are allergen specific and can potentially be suppressed or eliminated using this specificity. They have distinct activation, differentiation, cell surface phenotype, migration capacity, and effector functions that can be targeted singularly or in combination. Furthermore, memory Th2 cells residing in the lungs can be treated locally. Capitalizing on these unique attributes is important for drug development for allergic asthma. The aim of this review is to present an overview of therapeutic strategies targeting Th2 memory cells in allergic asthma, emphasizing Th2 generation, differentiation, activation, migration, effector function, and survival.

Airway allergen exposure stimulates bone marrow eosinophilia partly via IL-9

Background

Interleukin (IL)-9 is a Th2-derived cytokine with pleiotropic biological effects, which recently has been proposed as a candidate gene for asthma and allergy. We aimed to evaluate the therapeutic effect of a neutralizing anti-IL-9 antibody in a mouse model of airway eosinophilic inflammation and compared any such effect with anti-IL-5 treatment.

Methods

OVA-sensitized Balb/c mice were intraperitoneally pretreated with a single dose (100 μg) of an anti-mouse IL-9 monoclonal antibody (clone D9302C12) or its vehicle. A third group was given 50 μg of a monoclonal anti-mouse IL-5 antibody (TRFK-5) or its vehicle. Animals were subsequently exposed to OVA on five days via airways. Newly produced eosinophils were labelled using 5-bromo-2'-deoxyuridine (BrdU). BrdU⁺ eosinophils and CD34⁺ cell numbers were examined by immunocytochemistry. After culture and stimulation with OVA or PMA+IC, intracellular staining of IL-9 in bone marrow cells from OVA-exposed animals was measured by Flow Cytometry. The Mann-Whitney U-test was used to determine significant differences between groups.

Results

Anti-IL-9 significantly reduced bone marrow eosinophilia, primarily by decrease of newly produced (BrdU⁺) and mature eosinophils. Anti-IL-9 treatment also reduced blood neutrophil counts, but did not affect BAL neutrophils. Anti-IL-5 was able to reduce eosinophil numbers in all tissue compartments, as well as BrdU⁺ eosinophils and CD34⁺ progenitor cells, and in all instances to a greater extent than anti-IL-9. Also, FACS analysis showed that IL-9 is over-expressed in bone marrow CD4⁺ cells after allergen exposure.

Conclusions

Our data shows that a single dose of a neutralizing IL-9 antibody is not sufficient to reduce allergen-induced influx of newly produced cells from bone marrow to airways. However, in response to allergen, bone marrow cells over-express IL-9. This data suggest that IL-9 may participate in the regulation of granulocytopoiesis in allergic inflammation.

Interleukin 9 production in the lungs of infants with severe respiratory syncytial virus bronchiolitis

BACKGROUND

Respiratory syncytial virus (RSV) bronchiolitis is the most prevalent acute wheezing disorder in infants and is associated with recurrent wheeze and asthma in childhood. Interleukin 9, a type 2 cytokine has been proposed as a key cytokine in susceptibility to asthma. We aimed to investigate whether interleukin 9 was produced in the lungs of infants with severe RSV disease and if found, from which cells it originated.

METHODS

We did 150 non-bronchoscopic bronchoalveolar lavages during the course of ventilation in 24 term infants and 21 preterm infants ventilated for RSV bronchiolitis. We also did 10 bronchoalveolar lavages on the day of intubation in 10 control infants ventilated for non-respiratory causes. We measured pulmonary interleukin 9 mRNA and protein in samples from all groups. We used immunostaining to identify the cells that produce interleukin 9.

FINDINGS

Interleukin 9 mRNA expression, which persisted over the course of ventilation, was noted in all infants with bronchiolitis. Three of the control group also showed interleukin 9 mRNA expression. Median interleukin 9 protein concentration on day 1 (1.9 microg/L [range 0.1-36.2]) was significantly greater in term infants with bronchiolitis than either preterm infants (0.4 microg/L [0.1-2.9]; p<0.05) or the control group (0.7 microg/L [0.4-2.5]; p<0.05). There was a trend for interleukin 9 protein concentrations in term, but not preterm infants to decrease over time. Immunostained cell smears showed that most interleukin 9 expression in bronchoalveolar lavage was by neutrophils.

INTERPRETATION

In term infants with RSV bronchiolitis, we noted large amounts of interleukin 9 mRNA and interleukin 9 protein. Neutrophils seem to be the main source of this type 2 cytokine. Interleukin 9 production by neutrophils may contribute to the pathogenesis of RSV disease. These findings may be relevant to other disease processes in the lung where neutrophils are the predominant inflammatory cell type.

Cytokine-directed therapies for the treatment of chronic airway diseases

Multiple cytokines play a critical role in orchestrating and perpetuating inflammation in asthma and chronic obstructive pulmonary disease (COPD) and several specific cytokine and chemokine inhibitors now in development as future therapy for these diseases. Anti-IL-5 antibody markedly reduces peripheral blood and airway eosinophils, but does not appear to be effective in symptomatic asthma. Inhibition of IL-4 despite promising early results in asthma has been discontinued and blocking IL-13 might be more effective. Inhibitory cytokines, such as IL-10, interferons and IL-12 are less promising, as systemic delivery produces side effects. Inhibition of TNF-alpha may be useful in severe asthma and for treating severe COPD with systemic features. Many chemokines are involved in the inflammatory response of asthma and COPD and several small molecule inhibitors of chemokine receptors (CCR) are in development. CCR3 antagonists (which block eosinophil chemotaxis) and CXCR2 antagonists (which block neutrophil and monocyte chemotaxis) are in clinical development for asthma and COPD, respectively. Because so many cytokines are involved in asthma, drugs that inhibit the synthesis of multiple cytokines may prove to be more useful; several such classes of drug are now in clinical development and any risk of side effects with these non-specific inhibitors may be reduced by the inhaled route.

Interleukin-9 influences chemokine release in airway smooth muscle: role of ERK

Interleukin (IL)-9 is a pleiotropic cytokine that has been proposed as a candidate gene for asthma. As IL-9 expression is correlated with airway hyperresponsiveness in animals, we examined the effects of IL-9 on cultured human airway smooth muscle (HASM) cells. IL-9 alone had no effect on IL-8 release, but at concentrations of > or =30 ng/ml, IL-9 significantly increased IL-8 release induced by TNF-alpha. IL-9 increased phosphorylation of extracellular signal-regulated protein kinase (ERK, p42 and p44) in a concentration- and time-dependent fashion, and U-0126 (10 micro M), which inhibits ERK phosphorylation, abolished the synergism between TNF-alpha and IL-9 on IL-8 release. IL-9 alone had no effect on eotaxin release into HASM cell supernatants but at concentrations of > or =10 ng/ml caused an approximately 50% increase in release of eotaxin evoked by IL-13 (10 ng/ml). U-0126 blocked the synergism between IL-9 and IL-13 on eotaxin release. IL-9 had no effect on cyclooxygenase-2 (COX-2) expression or PGE(2) release and did not augment the COX-2 expression that was induced by IL-1beta. Our results indicate that airway smooth muscle is a target for IL-9 and that IL-9 amplifies the potential for these cells to recruit eosinophils and neutrophils into the airways by a mechanism involving ERK.

Segmental allergen challenge in patients with atopic asthma leads to increased IL-9 expression in bronchoalveolar lavage fluid lymphocytes

BACKGROUND

IL-9 is a T(H)2 cell-derived cytokine that might be involved in the pathophysiology of allergic diseases. Little is known about its expression and release during the allergic response in the human lung.

OBJECTIVE

The expression of IL-9 was measured in 10 atopic subjects with mild asthma and 5 nonatopic healthy control subjects at baseline and 24 hours after segmental sham and allergen challenge.

METHODS

IL-9 protein was measured in bronchoalveolar lavage (BAL) fluid by means of ELISA and detected within the BAL cells by means of immunocytochemistry. Furthermore, IL9 mRNA expression of BAL cells was detected by means of real-time PCR.

RESULTS

Although only low or undetectable amounts of IL9 mRNA and IL-9 protein were present in nonatopic control subjects and atopic asthmatic patients at baseline, there was an increase after segmental allergen challenge in the atopic subjects. Lymphocytes were identified as major cellular sources of IL-9 production by means of immunocytochemistry. Furthermore, IL-9 protein and IL9 mRNA expression correlated with eosinophil numbers in BAL fluid.

CONCLUSIONS

These findings demonstrate that IL-9 is specifically upregulated after local allergen challenge in the lungs of atopic asthmatic patients. Lymphocytes are the major cellular source of IL-9. The increased expression and its correlation with eosinophil numbers suggest a potential role for IL-9 in the late phase of the allergic response.

Interleukin-9 induces goblet cell hyperplasia during repair of human airway epithelia

Asthma is characterized by airway inflammation, smooth muscle hyperreactivity, and airway remodeling with excessive mucus production. The effect cytokines like interleukin (IL)-9 have on airway epithelia has been addressed using murine models of asthma, as well as transgenic and knockout mice. Though highly informative, differences exist between mouse and human airway epithelia, including cellular composition (e.g., Clara cells) and stem cell/plasticity capabilities. Therefore, to address cytokine effects on human airway epithelia, we have used a primary model system to ask whether IL-9 can alter cell fates of human airway epithelia. Here, we show that IL-9 has little effect on fully differentiated ciliated human airway epithelia. However, in the setting of airway injury repair, IL-9 results in goblet cell hyperplasia. A similar response was observed when the epithelium was exposed to IL-9 before it became fully differentiated. Moreover, exposure to IL-9 resulted in increased lysozyme and mucus production by the epithelia. Thus, a combination of IL-9 and mechanical injury can explain, in part, goblet cell hyperplasia that is evident in the lungs of individuals with asthma. These data suggest that interventions that limit airway epithelial damage, block IL-9, or modulate the repair process should result in decreased airway remodeling and prevent the chronic manifestations of this disease.

Could administration of bacille Calmette-Guérin vaccination at birth protect from the development of asthma and allergic diseases in the western world? Has this question been adequately investigated?

Asthma and allergic diseases are disorders with a predominant Th2 immune response and there is some evidence of an inverse correlation between incidence of tuberculosis and prevalence of allergic diseases. Skewing the immune response towards a Th1 phenotype has been shown to suppress allergic inflammation. One of the ways this could be achieved is by administration of BCG vaccination early in life. Unfortunately, studies examining the protective role of BCG vaccination early in life against development of allergic diseases have shown some conflicting results and this article critically discusses the pitfalls in the currently available data. We propose that well controlled double blind placebo-controlled multi-centre study is carried out to address this important question and if this study shows a favourable outcome simple measures such as offering BCG vaccination early in life could help reduce prevalence of allergic diseases.

Role of cytokines and chemokines in bronchial hyperresponsiveness and airway inflammation

Over the last decade there has been an intense interest in the potential role of cytokines and chemokines as important mediators in various atopic diseases, including asthma and the mechanisms by which these mediators regulate airway inflammation and bronchial hyperresponsiveness. This research effort has recently culminated in the publication of clinical studies that have assessed the role of interleukin (IL)-4 [Borish et al., Am J Respir Crit Care Med 160, 1816-1823 (1999)], IL-5 [Leckie et al., Lancet 356, 2144-2148 (2000)], and IL-12 [Bryan et al., Lancet 356, 2149-2153 (2000)] in allergic asthma, and the results have been disappointing. This is not surprising given the pleiotropic role cytokines play in the allergic response confirmed by numerous animal studies providing evidence of functional redundancy. The alternative view is that our current concepts in asthma pathogenesis need significant revision. This review will summarise the evidence for the role of cytokines and chemokines in various aspects of asthma pathophysiology; namely, bronchial hyperresponsiveness, eosinophil recruitment to the airways, mucus secretion, and airway remodelling.

Cytokine expression profiling in human leukocytes after exposure to hypertonic and isotonic fluids

BACKGROUND

Resuscitation from hemorrhagic shock causes profound immunologic changes. The tonicity of fluids used for resuscitation clearly influences the immune response. Our study was designed to determine whether isotonic and hypertonic fluids exert their differential effects on immune response by altering the cytokine gene profile of human leukocytes. The cDNA array method was used to profile transcriptional responses after exposure to hypertonic and isotonic fluids.

METHODS

Blood from seven healthy volunteers was incubated for 30 minutes with isotonic (10% dextran-40 and lactated Ringer's [LR] solution) and hypertonic (7.5% hypertonic saline and hypertonic dextran [HTD]) fluids. The volumes of isotonic fluids used were equal to the volume of blood, whereas the volumes of hypertonic fluids were adjusted to keep the salt load identical to the LR group. The cDNA array technique was used to measure the gene expression of 23 common cytokines.

RESULTS

Increased gene transcription of proinflammatory cytokines (interleukin [IL]-1alpha, IL-6, IL-10, and tumor necrosis factor-alpha) as well as others (IL-5, IL-7, and IL-16) was found after incubation with resuscitation fluids. Variances were noted depending on the type of fluid: HTD and LR solution did not induce expression of IL-5, and HTD also did not induce IL-1beta expression. Genes encoding IL-1alpha, IL-6, IL-9, and tumor necrosis factor-alpha had low level baseline expression in leukocytes isolated from unstimulated blood, and their expression increased markedly after exposure to resuscitation fluids. The inducible transcripts included IL-1beta, IL-7, IL-10, and IL-16. However, there was no difference in cytokine expression profile between isotonic and hypertonic fluids.

CONCLUSION

Exposure of human leukocytes to resuscitation fluids causes an increase in cytokine gene expressions compared with undiluted blood. This expression profile is largely independent of the type of fluid used.

Cytokine modulators as novel therapies for asthma

Cytokines play a critical role in orchestrating and perpetuating inflammation in asthmatic airways and several specific cytokine and chemokine inhibitors are now in development for the treatment of asthma. Inhibition of IL-4 with soluble IL-4 receptors has shown promising early results in asthma. Anti-IL-5 antibody is very effective at inhibiting peripheral blood and airway eosinophils but does not appear to be effective in symptomatic asthma. Inhibitory cytokines, such as IL-10, interferons, and IL-12 are less promising because systemic delivery produces intolerable side effects. Inhibition of TNF-alpha may be useful in severe asthma. Many chemokines are involved in the inflammatory response of asthma, and small-molecule inhibitors of chemokine receptors are in development. CCR3 antagonists are now in clinical development for the treatment of asthma. Because so many cytokines are involved in asthma, drugs that inhibit the synthesis of multiple cytokines may prove to be more useful. Several such classes of drug are now in clinical development, and the risk of side effects with these nonspecific inhibitors may be reduced by the inhaled route of delivery.

Cytokine modulators for allergic diseases

Cytokines play a critical role in orchestrating and perpetuating inflammation in allergic diseases and several specific cytokine inhibitors now in development for the treatment of asthma and other allergic diseases. The effects of inhibiting the T helper 2 cytokines interleukin-5, interleukin-13 and interleukin-9 are discussed, together with inhibition of tumor necrosis factor-alpha. Inhibitory cytokines, such as interleukin-10, interferons and interleukin-12, are also being considered in the treatment of allergic diseases.

A novel method of gene transcript profiling in airway biopsy homogenates reveals increased expression of a Na+-K+-Cl- cotransporter (NKCC1) in asthmatic subjects

Comprehensive and systematic analysis of airway gene expression represents a strategy for addressing the multiple, complex, and largely untested hypotheses that exist for disease mechanisms, including asthma. Here, we report a novel real-time PCR-based method specifically designed for quantification of multiple low-abundance transcripts using as little as 2.5 fg of total RNA per gene. This method of gene expression profiling has the same specificity and sensitivity as RT-PCR and a throughput level comparable to low-density DNA microarray hybridization. In this two-step method, multiplex RT-PCR is successfully combined with individual gene quantification via real-time PCR on generated cDNA product. Using this method, we measured the expression of 75 genes in bronchial biopsies from asthmatic versus healthy subjects and found expected increases in expression levels of Th2 cytokines and their receptors in asthma. Surprisingly, we also found increased gene expression of NKCC1--a Na+-K+-Cl- cotransporter. Using immunohistochemical method, we confirmed increased protein expression for NKCC1 in the asthmatic subject with restricted localization to goblet cells. These data validate the new transcriptional profiling method and implicate NKCC1 in the pathophysiology of mucus hypersecretion in asthma. Potential applications for this method include transcriptional profiling in limited numbers of laser captured cells and validation of DNA microarray data in clinical specimens.

Il-9 stimulates release of chemotactic factors from human bronchial epithelial cells

Interleukin (IL)-9 is a T helper 2 cytokine implicated as a candidate gene and contributor to human asthma. We hypothesized that the inflammatory potential of bronchial epithelium is affected by its local environment and explored this hypothesis with respect to the effect of IL-9 on bronchial epithelium. We investigated the response of primary and immortalized human bronchial epithelial cells to IL-9 stimulation with respect to the release of T-cell chemoattractant factors. In response to IL-9, the HBE4-E6/E7 cell line, but not BEAS-2B cells, released the T-cell chemoattractants IL-16 and regulated on activation, normal T cells expressed and secreted (RANTES) in a dose-dependent fashion. We found a similar dose response to IL-9 in primary cells from bronchial brushings of healthy subjects and that nearly all of the T-cell chemoattraction was attributable to IL-16 and RANTES. Reverse transcriptase/polymerase chain reaction of BEAS-2B, HBE4-E6/E7, and primary cells from two subjects revealed messenger RNA for IL-9 receptor (IL-9R) alpha but not in BEAS-2B cells. Fluorescence-activated cell sorter analysis of HBE4-E6/E7 and primary cells confirmed surface expression of the IL-9 receptor. Costimulation of both cell types with IL-9 and antibody to either gamma-common chain or IL-9Ralpha completely blocked the release of T-cell chemoattractant activity, confirming the primary role of a functioning IL-9 receptor for IL-9 signaling in HBE4-E6/E7 and primary bronchial epithelial cells. We conclude that IL-9 is a stimulus for airway epithelial cell release of T-cell chemoattractant factors, which in turn may modulate the immune response in allergic airway inflammation.