Intrinsic defect in T cell production of interleukin (IL)-13 in the absence of both IL-5 and eotaxin precludes the development of eosinophilia and airways hyperreactivity in experimental asthma

Human airway smooth muscle cells express the high affinity receptor for IgE (Fc epsilon RI): a critical role of Fc epsilon RI in human airway smooth muscle cell function

Several reports suggest that activated airway smooth muscle (ASM) cells are capable of generating various proinflammatory mediators, including cytokines and chemokines. However, little is known about the mechanism involved in this process. In this regard, we have examined the expression and the role of the high affinity IgE receptor (Fc epsilonRI) by ASM cells. Human ASM cells were found to constitutively express transcripts coding for alpha, beta, and gamma subunits of Fc epsilonRI. Flow cytometry and Western blot analysis confirmed the expression of Fc epsilonRI alpha-chain protein. Interestingly, Fc epsilonRI alpha-chain immunoreactivity was also demonstrated in smooth muscle within bronchial biopsies of asthmatic subjects. Cross-linking of Fc epsilonRI induced mobilization of free calcium in ASM cells, one of the critical signals to trigger smooth muscle contraction. Furthermore, cultured ASM cells released IL-4, IL-13, IL-5, and eotaxin but not IFN-gamma, when sensitized with IgE followed by anti-IgE Ab cross-linking. The addition of anti-Fc epsilonRI alpha-chain Abs directed against IgE binding site inhibited this release. Taken together, these results suggest a potential new and important mechanism by which ASM cells may participate in airway inflammation and bronchoconstriction associated with allergic asthma.

The hypereosinophilic syndromes: still more heterogeneity

In 1968, the term hypereosinophilic syndromes (HES) was coined to refer to a spectrum of eosinophil-associated diseases presumed to be caused by an underlying immunological pathology. In the 1990s, the identification of an HES subset with T lymphocyte clonality and production of cytokines, particularly IL-5, validated this concept. Then, in 2002, imatinib mesylate, which was introduced for the treatment of chronic myelogenous leukemia, effectively controlled another subgroup of HES patients. Imatinib's target is a novel constitutively-active kinase. Most imatinib-responsive HES patients show an increased number of bone marrow mast cells and elevated serum tryptase; mast cells, lymphocytes and neutrophils express the novel kinase. This new information critically modifies our view of HES and indicates that several cell lines are altered and likely to contribute to HES pathophysiology.

The role of eosinophils in the pathogenesis of asthma

Two recent papers have addressed the ever-intriguing question of the role of eosinophils in asthma. Both groups used experimental models of airway inflammation in mice that were gene targeted to selectively ablate the eosinophil lineage. One group found that eosinophils were required for both airway hyperresponsiveness and mucus accumulation. The other demonstrated a 'critical role' for the cell in airway remodelling. The results, although largely confirmatory of previous studies both in mice and humans, put the eosinophil firmly back on the asthma stage and strengthen the case for developing effective eosinophil-depleting agents for clinical use.

No audible wheezing: nuggets and conundrums from mouse asthma models

Mouse models of T helper type 2 (Th2) cell–biased pulmonary inflammation have elucidated mechanisms of sensitization, cell traffic, and induced airway hyperresponsiveness (AHR). Nonetheless, most mice lack intrinsic AHR, a central property of human asthma, and disparities persist regarding the contributions of eosinophils and mast cells and the sensitivity to induced AHR in the commonly used mouse strains. We suggest that these discordances, reflecting methodological and genetic differences, may be informative for understanding heterogeneity of human asthma.

Inhibition of allergen-induced eosinophil recruitment by natural tetranortriterpenoids is mediated by the suppression of IL-5, CCL11/eotaxin and NFkappaB activation

The present study reports the anti-allergic activity of a group of six different tetranortriterpenoids (TNTP) isolated from the seeds of Carapa guianensis Aublet: 6a-acetoxygedunin, 7-deacetoxy-7-oxogedunin, andirobin, methyl angolensate, 6a-acetoxyepoxyazadiradione and gedunin. Oral pretreatment with TNTP significantly inhibited total leukocyte and eosinophil accumulation in C57BL/10 mice pleural cavities 24 h after the intrathoracic (i.t.) injection of ovalbumin (OVA), but had no effect on CD4, CD8 or gammadelta T lymphocyte accumulation. Pleural washes recovered from 6 h OVA-stimulated mice (OPW) pretreated with TNTP failed to induce shape change in eosinophil in vitro, indicating the inhibition of eosinophilotactic chemokines by TNTP. In accordance with such results, ELISA assays showed decreased levels of CCL11/eotaxin and IL-5 in OPW recovered from TNTP pretreated mice within 6 h. TNTP oral pretreatment inhibited nuclear factor-kappaB (NFkappaB) translocation into the nucleus in pleural leukocytes recovered from previously sensitized mice after antigenic challenge. In addition, the incubation of splenocytes recovered from previously sensitized mice with TNTP also inhibited NFkappaB activation after OVA stimulation. Taken together, these results indicate that the inhibition of allergic eosinophilia by TNTP is correlated with the inhibition of CCL11/eotaxin and IL-5 generation through NFkappaB signaling pathway impairment in mice.

Asthmatic changes in mice lacking T-bet are mediated by IL-13

Mice with a targeted deletion of the T-bet gene exhibit spontaneous airway hyperresponsiveness (AHR), airway inflammation, enhanced recovery of T(h)2 cytokines from bronchoalveolar lavage fluid, sub-epithelial collagen deposition and myofibroblast transformation. Here we analyze the mechanisms responsible for the chronic airway remodeling observed in these mice. CD4+ T cells isolated from the lung of T-bet-deficient mice were spontaneously activated CD44(high)CD69(high) memory T cells, with a typical T(h)2 cytokine profile. Neutralization of IL-13 but not IL-4 resulted in amelioration of AHR in airways of mice lacking T-bet. IL-13 blockade also led to reduced eosinophilia and decreased vimentin, transforming growth factor beta (TGF-beta) and alpha smooth muscle actin (alphaSMA) levels. T-bet(-/-) lung fibroblasts proliferated very rapidly and released increased amounts of TGF-beta. Interestingly, neutralization of TGF-beta ameliorated aspects of the chronic airway remodeling phenotype but did not reduce AHR. These data highlight a T-bet-directed function for IL-13 in controlling lung remodeling that is both dependent on and independent of its interaction with TGF-beta in the asthmatic airway.

Selective suppression of leukocyte recruitment in allergic inflammation

Allergic diseases result in a considerable socioeconomic burden. The incidence of allergic diseases, notably allergic asthma, has risen to high levels for reasons that are not entirely understood. With an increasing knowledge of underlying mechanisms, there is now more potential to target the inflammatory process rather than the overt symptoms. This focuses attention on the role of leukocytes especially Th2 lymphocytes that regulate allergic inflammation and effector cells where eosinophils have received much attention. Eosinophils are thought to be important based on the high numbers that are recruited to sites of allergic inflammation and the potential of these cells to effect both tissue injury and remodelling. It is hoped that future therapy will be directed towards specific leukocyte types, without overtly compromising essential host defence responses. One obvious target is leukocyte recruitment. This necessitates a detailed understanding of underlying mechanisms, particularly those involving soluble chemoattractants signals and cell-cell adhesion molecules.

Leukotriene D4 induces production of transforming growth factor-beta1 by eosinophils

Eosinophils may play an important role in the pathogenesis of airway remodeling in asthma through the production of various fibrogenic cytokines such as transforming growth factor-beta1 (TGF-beta1). Cysteinyl leukotrienes are also suggested to be involved in remodeling with their potential to induce proliferation of airway smooth muscle cells. Since massive eosinophil infiltration and the release of cysteinyl leukotrienes in airway secretions are often seen in asthma, we hypothesized that cysteinyl leukotrienes may be involved in airway remodeling through induction of TGF-beta1 from eosinophils. Peripheral blood eosinophils were cultured with leukotriene D(4) (LTD(4)) and/or interleukin-5 (IL-5) or granulocyte colony-stimulating factor (GM-CSF) for 16 h and gene expression of TGF-beta1 was quantified with real-time PCR. A combination of LTD(4) and IL-5 or LTD(4) and GM-CSF synergistically induced TGF-beta1 expression in eosinophils although stimulation with single factor, LTD(4), IL-5 or GM-CSF did not induce the gene expression. LTD(4) also induced significant gene expression in eosinophils cultured in an intercellular adhesion molecule-1-coated plate. The results suggested that CysLTs stimulate eosinophils to induce TGF-beta1 production in allergic inflammation where IL-5 and GM-CSF are abundant and may be involved in the pathogenesis of airway remodeling.

Nasal IL-12p70 DNA Prevents and Treats Intestinal Allergic Diarrhea

OVA-induced allergic diarrhea occurs as a consequence of over-expression of Th1 inhibitory IL-12p40 monomers and homodimers in the large intestine, establishing a dominant Th2-type environment. In this study, we demonstrate that intranasally administered murine IL-12p70 naked DNA expression plasmids resulted in the synthesis of corresponding cytokine in the large intestinal CD11c(+) dendritic cells, leading to the inhibition of Ag-specific Th2-type response for the prevention of allergic diarrhea and the suppression of clinical symptoms including OVA-specific IgE Ab synthesis. The nasal IL-12p70 DNA treatment proved effective even after the establishment of allergic diarrhea. These results suggest that the mucosal administration of naked IL-12p70 DNA plasmid should be considered as a possible preventive and therapeutic treatment for Th2 cell-mediated food allergic diseases in the intestinal tract.

IL-13 R130Q, a common variant associated with allergy and asthma, enhances effector mechanisms essential for human allergic inflammation

Genetic factors are known to strongly influence susceptibility to allergic inflammation. The Th2 cytokine IL-13 is a central mediator of allergy and asthma, and common single-nucleotide polymorphisms in IL13 are associated with allergic phenotypes in several ethnically diverse populations. In particular, IL13+2044GA is expected to result in the nonconservative replacement of arginine 130 (R130) with glutamine (Q). We examined the impact of IL13+2044GA on the functional properties of IL-13 by directly comparing the activity of WT IL-13 and IL-13 R130Q on primary human cells involved in the effector mechanisms of allergic inflammation. Our results show that IL-13 R130Q was significantly more active than WT IL-13 in inducing STAT6 phosphorylation and CD23 expression in monocytes and hydrocortisone-dependent IgE switching in B cells. Notably, IL-13 R130Q was neutralized less effectively than WT IL-13 by an IL-13R2 decoy. Decreased neutralization of the minor variant could contribute to its enhanced in vivo activity. Neither IL-13 variant was able to engage T cells, which suggests that increased allergic inflammation in carriers of IL13+2044A depends on enhanced IL-13-mediated Th2 effector functions rather than increased Th2 differentiation. Collectively, our data indicate that natural variation in the coding region of IL13 may be an important genetic determinant of susceptibility to allergy.

Discovery of CC chemokine receptor-3 (CCR3) antagonists with picomolar potency

Starting with our previously described(20) class of CC chemokine receptor-3 (CCR3) antagonist, we improved the potency by replacing the phenyl linker of 1 with a cyclohexyl linker and by replacing the 4-benzylpiperidine with a 3-benzylpiperidine. The resulting compound, 32, is a potent and selective antagonist of CCR3. SAR studies showed that the 3-acetylphenyl urea of 32 could be replaced with heterocyclic ureas or heterocyclic-substituted phenyl ureas and still maintain the potency (inhibition of eotaxin-induced chemotaxis) of this class of compounds in the low-picomolar range (IC(50) = 10-60 pM), representing some of the most potent CCR3 antagonists reported to date. The potency of 32 for mouse CCR3 (chemotaxis IC(50) = 41 nM) and its oral bioavailability in mice (20% F ) were adequate to assess the efficacy in animal models of allergic airway inflammation. Oral administration of 32 reduced eosinophil recruitment into the lungs in a dose-dependent manner in these animal models. On the basis of its overall potency, selectivity, efficacy, and safety profile, the benzenesulfonate salt of 32, designated DPC168, entered phase I clinical trials.

Interleukin-13 in asthma pathogenesis

Bronchial asthma is a complex disorder that is thought to arise as a result of aberrant T-lymphocyte responses to noninfectious environmental antigens. In particular, the symptoms of asthma are closely associated with the presence of activated T-helper 2 cell (Th2) cytokine-producing cells [interleukin (IL)-4, IL-5, IL-9, and IL-13] in the airway wall. Although each of the Th2 cytokines likely contributes to the overall immune response directed against environmental antigens, a substantial body of evidence points to a singular role for IL-13 in the regulation of the allergic diathesis. Initial studies in animal models of disease provided compelling evidence that IL-13, independently of other Th2 cytokines, was both necessary and sufficient to induce all features of allergic asthma. The importance of IL-13 in allergic disorders in humans is supported by consistent associations between tissue IL-13 levels and genetic variants in the IL-13 gene with asthma and related traits. With the preponderance of evidence continuing to support a pivotal role for IL-13 in allergic disorders, attention is now turned toward understanding the mechanisms by which this cytokine may mediate the pathophysiological features of allergic disease. The emerging paradigm is that IL-13 induces features of the allergic response via a complex array of actions on resident airway cells rather than through traditional effector pathways involving eosinophils and immunoglobulin E-mediated events. In light of these recent developments, this review explores our current understanding of the singular role of IL-13 in the pathogenesis of asthma, with a particular focus on new insights into the mechanisms by which IL-13 mediates various features of asthma.

IL-13 may mediate allergen-induced hyperresponsiveness independently of IL-5 or eotaxin by effects on airway smooth muscle

IL-13 is a mediator of allergen-induced airway hyperresponsiveness (AHR). The aim of this study was to evaluate whether eotaxin and IL-5 were implicated in the effects of IL-13 on allergen-induced AHR or whether IL-13 may exert its effects through direct actions on airway smooth muscle (ASM). To study this question airway inflammation and AHR were induced in mice by sensitization and subsequent challenge on three successive days with ovalbumin. A monoclonal anti-IL-13 antibody administered before each challenge significantly reduced AHR without affecting airway eosinophilia. No changes of mRNA in BAL and lung tissues or protein levels in BAL of IL-5 or eotaxin were found following anti-IL-13 treatment. Combined injection of monoclonal anti-IL-5 and antieotaxin antibodies before each antigen challenge blocked airway eosinophilia but failed to reduce AHR. IL-13 induced calcium transients in cultured murine ASM cells and augmented the calcium and contractile responses of these cells to leukotriene D4. These results suggest that IL-13 plays an important role in allergen-induced AHR and is important in the early phases of the inflammatory process. Its effects on AHR are mediated independently of IL-5 and eotaxin and may involve a direct effect on ASM to augment its responsiveness.

The role of human mast cell-derived cytokines in eosinophil biology

Eosinophil-mediated diseases, such as allergic asthma, eosinophilic fasciitis, and certain hypersensitivity pulmonary disorders, are characterized by eosinophil infiltration and tissue injury. Mast cells and T cells often colocalize to these areas. Recent data suggest that mast cells can contribute to eosinophil-mediated inflammatory responses. Activation of mast cells can occur by antigen and immunoglobulin E (IgE) via the high-affinity receptor (FcepsilonRI) for IgE. The liberation of proteases, leukotrienes, lipid mediators, and histamine can contribute to tissue inflammation and allow recruitment of eosinophils to tissue. In addition, the synthesis and expression of a plethora of cytokines and chemokines (such as granulocyte-macrophage colony-stimulating factor [GM-CSF], interleukin-1 [IL-1], IL-3, IL-5, tumor necrosis factor-alpha [TNF-alpha], and the chemokines IL-8, regulated upon activation normal T cell expressed and secreted [RANTES], monocyte chemotactic protein-1 [MCP-1], and eotaxin) by mast cells can influence eosinophil biology. Stem cell factor (SCF)-c-kit, cytokine-cytokine receptor, and chemokine-chemokine receptor (CCR3) interactions leading to nuclear factor kappaB (NF-kappaB), mitogen-activated protein kinase (MAPK) expression, and other signaling pathways can modulate eosinophil function. Eosinophil hematopoiesis, activation, survival, and elaboration of mediators can all be regulated thus by mast cells in tissue. Moreover, because eosinophils can secrete SCF, eosinophils can regulate mast cell function in a paracrine manner. This two-way interaction between eosinophils and mast cells can pave the way for chronic inflammatory responses in a variety of human diseases. This review summarizes this pivotal interaction between human mast cells and eosinophils.

Adenovirus expressing Fas ligand gene decreases airway hyper-responsiveness and eosinophilia in a murine model of asthma

Allergic asthma is characterized by airway hyper-responsiveness (AHR) and cellular infiltration of the airway with predominantly eosinophils and Th2 cells. The normal resolution of inflammation in the lung occurs through the regulated removal of unneeded cells by Fas-Fas ligand-mediated apoptosis. Fas ligand (FasL) is a member of the tumor necrosis factor family, and when bound to Fas, it induces apoptosis of the cells. To examine the effect of the FasL gene on airway inflammation and immune effector cells in allergic asthma, recombinant adenovirus expressing murine FasL (Ad-FasL) was delivered intratracheally into ovalbumin (OVA)-immunized mice. We found that a single administration of Ad-FasL in OVA-immunized mice significantly alleviated AHR and eosinophilia by inducing the apoptosis of eosinophils and/or reducing eosinophil attractant factors, such as IL-5 and eotaxin levels. The number of infiltrated lymphocytes and Th2 cytokines, including IL-5 and IL-13, decreased in OVA-immunized mice by administration of Ad-FasL. KC and TNF-alpha production also decreased in Ad-FasL-treated OVA-immunized mice. These findings indicated that the administration of Ad-FasL to OVA-sensitized mice significantly suppressed pulmonary allergic responses. Although more studies are needed, these results suggested that Ad-FasL might be applied as an alternative therapy for allergic asthma.

T-cell-mediated inflammation does not contribute to the maintenance of airway dysfunction in mice

T-cell-mediated airway inflammation is considered to be critical in the pathogenesis of airway hyperresponsiveness (AHR). We have described a mouse model in which chronic allergen exposure results in sustained AHR and aspects of airway remodeling and here sought to determine whether eliminating CD4+ and CD8+ cells, at a time when airway remodeling had occurred, would attenuate this sustained AHR. Sensitized BALB/c mice were subjected to either brief or chronic periods of allergen exposure and studied 24 h after brief or 4 wk after chronic allergen exposure. In both models, mice received three treatments with anti-CD4 and -CD8 monoclonal antibodies during the 10 days before outcome measurements. Outcomes included in vivo airway responsiveness to intravenous methacholine, CD4+ and CD8+ cell counts of lung and spleen using flow cytometric analysis, and airway morphometry using a computer-based image analysis system. Compared with saline control mice, brief allergen challenge resulted in AHR, which was eliminated by antibody treatment. Chronic allergen challenge resulted in sustained AHR and indexes of airway remodeling. This sustained AHR was not reversed by antibody treatment, even though CD4+ and CD8+ cells were absent in lung and spleen. These results indicate that T-cell-mediated inflammation is critical for development of AHR associated with brief allergen exposure, but is not necessary to maintain sustained AHR.

Chemokine receptor antagonists: a novel therapeutic approach in allergic diseases

The aim of this review is to give an overview of the role of chemokines, particularly ligands of the CC chemokine receptor CCR3, in allergic diseases and to show the new concept in the treatment of allergies using chemokine receptor antagonists. Allergic diseases such as allergic asthma, allergic rhinitis and atopic dermatitis are characterized by a complex interaction of different cell types and mediators. Among this, Th2 cells, mast cells, basophils and eosinophils are found in the inflamed tissue due to the attraction of chemokines. Of all the known chemokine receptors, the chemokine receptor CCR3 seems to play the major role in allergic diseases which is supported by the detection of this receptor on the cell types mentioned above. Therefore, academic and industrial research focus on compounds to block this receptor. To date, certain chemokine receptor antagonists derived from peptides and small molecules exist to block the chemokine receptor CCR3. However, the in vivo data about these compounds and the mechanisms of receptor interaction are poorly understood, as yet. For the development of additional chemokine receptor antagonists, more details about the interaction between the ligands and their receptors are required. Therefore, additional studies will lead to the identification of novel CCR3 chemokine receptor antagonists, which can be therapeutically used in allergic asthma, allergic rhinitis, and atopic dermatitis.

Interleukin-13 in asthma pathogenesis

Numerous studies have clearly shown that the Th2 cytokine, interleukin (IL)-13, is the central regulator of the allergic diathesis. Initial studies in animal models of disease provided compelling evidence that IL-13, independent of other Th2 cytokines, was both necessary and sufficient to induce all features of allergic asthma. The importance of IL-13 in allergic disorders in humans is supported by consistent associations between tissue IL-13 levels and genetic variants in the IL-13 gene with asthma and related traits. With the preponderance of evidence continuing to support the importance of IL-13 in allergic disorders, attention is now turned toward understanding the mechanisms by which this cytokine might mediate the pathophysiologic features of allergic disease. The emerging paradigm is that IL-13 induces features of the allergic response via its actions on epithelial cells and smooth muscle cells, not through traditional effector pathways involving eosinophils and IgE-mediated events. In light of these recent developments, in this review our current understanding of the role of IL-13 in the pathogenesis of asthma is explored, with a particular focus on new insights into the mechanisms by which IL-13 induces the features of asthma.

Eosinophil function in allergic inflammation: from bone marrow to tissue response

The role of the eosinophil in the pathophysiology of allergy and asthma has been the focus of intense interest during the past two decades. Although the presence of eosinophils in humans with allergy and asthma is well established, the precise role of this cell in human and animal tissue response is still unclear. However, recent developments in research on many organ systems have provided novel insights into the possible underlying role of the eosinophil in both allergic and nonallergic inflammation. In this review, we examine the pathways associated with eosinophil recruitment and activation, and discuss these findings with reference to clinically defined categories.

Current and emerging nonsteroidal anti-inflammatory therapies targeting specific mechanisms in asthma and allergy

Today inhaled corticosteroids (ICS) are regarded as the first-line controller anti-inflammatory treatment in the management of asthma. However, there is an increasing awareness of the risk of long-term adverse effects of ICS and that asthma is not only an organ-specific disease but also a systemic and small airway disease. This thinking has called for systemic treatment alternatives to treat asthma targeting more disease-specific mechanisms without influencing normal physiologic functions. Blocking of disease-specific mediators is a mechanism utilized by anti-leukotrienes and anti-immunoglobulin E treatment, each proven to be effective in both asthma and allergic rhinitis.Different cytokine-modifying strategies have been tested in clinical trials with variable results, some disappointing and some encouraging. Anti-interleukin (IL)-5 monoclonal antibody treatment effectively reduces the number of eosinophils locally in the airways and in peripheral blood in asthmatic patients. Unfortunately, this marked effect on eosinophils was not associated with an improvement in bronchial hyperresponsiveness and/or symptoms. Clinical trials with a recombinant soluble IL-4 receptor have been somewhat more successful at improving asthma control and allowing reduction of ICS therapy in asthma. Treatment with recombinant IL-12 had an effect on bronchial hyperresponsiveness and eosinophilic response, but was associated with unacceptable adverse effects. Other interesting cytokine-modulating treatments include those targeting IL-9, IL-10, IL-12 and IL-13.Immune-modulating treatment with bacterial antigens represents another strategy, originating from the hypothesis that some bacterial infections guide the immune system towards a T helper (Th) type 1 immune response. Mycobacterium vaccae, Bacille Calmette-Guerin (BCG) and immunostimulatory DNA sequences have all been tested in clinical trials, with encouraging results. Future asthma and allergy treatment will probably include not only one but also two or more disease-modifying agents administered to the same patient.

Defining a link with asthma in mice congenitally deficient in eosinophils

Eosinophils are often dominant inflammatory cells present in the lungs of asthma patients. Nonetheless, the role of these leukocytes remains poorly understood. We have created a transgenic line of mice (PHIL) that are specifically devoid of eosinophils, but otherwise have a full complement of hematopoietically derived cells. Allergen challenge of PHIL mice demonstrated that eosinophils were required for pulmonary mucus accumulation and the airway hyperresponsiveness associated with asthma. The development of an eosinophil-less mouse now permits an unambiguous assessment of a number of human diseases that have been linked to this granulocyte, including allergic diseases, parasite infections, and tumorigenesis.

Insights into the pathogenesis of asthma utilizing murine models

Asthma is a common syndrome in children and adults. Despite the increasing prevalence and socioeconomic burden, the underlying pathophysiology remains poorly defined in a large percentage of asthmatics. Animal models and, in particular, murine models of allergic airway disease have helped to reveal some of the potential underlying mechanisms and have played an important role in identifying the importance of T cells and TH2 cytokines in development of allergen-induced inflammation and airway hyperresponsiveness. In addition, other cell types including mast cells and eosinophils have been implicated in the development of some aspects of the disease. To further understand this complex syndrome, the development of animal models which mimic elements of this chronic airway disease is essential.

Effects of anticytokine therapy in a mouse model of chronic asthma

The relative contribution of Th2 and Th1 cytokines to the pathogenesis of lesions of chronic asthma remains poorly understood. To date, therapeutic inhibition of Th2 cytokines has proved disappointing. We used a clinically relevant model of chronic allergic asthma in mice to compare the effects of administering neutralizing antibodies to interleukin (IL)-13, IL-5, and interferon-gamma (IFN-gamma) to animals with established disease. As has been observed in clinical studies, anti-IL-5 inhibited both inflammation and remodeling but had no effect on airway responsiveness to methacholine. Anti-IL-13 effectively suppressed eosinophil recruitment and accumulation of chronic inflammatory cells in the airways. This treatment also partially suppressed changes of airway wall remodeling, including goblet cell hyperplasia/metaplasia and subepithelial fibrosis, but had limited ability to inhibit airway hyperreactivity (AHR). In contrast, treatment with anti-IFN-gamma markedly suppressed AHR. This antibody inhibited accumulation of chronic inflammatory cells but did not affect eosinophil recruitment or changes of remodeling. We conclude that inhibition of IL-5 is beneficial and that inhibition of IL-13 has considerable potential as a therapeutic strategy in chronic asthma, that IFN-gamma may play an important role in the pathogenesis of AHR, and that co-operative interaction between Th2 and Th1 cytokines contributes to the pathogenesis of the lesions of chronic asthma.

Platelet-activating factor receptor develops airway hyperresponsiveness independently of airway inflammation in a murine asthma model

Lipid mediators play an important role in modulating inflammatory responses. Platelet-activating factor (PAF) is a potent proinflammatory phospholipid with eosinophil chemotactic activity in vitro and in vivo. We show in this study that mice deficient in PAF receptor exhibited significantly reduced airway hyperresponsiveness to muscarinic cholinergic stimulation in an asthma model. However, PAF receptor-deficient mice developed an eosinophilic inflammatory response at a comparable level to that of wild-type mice. These results indicate an important role for PAF receptor, downstream of the eosinophilic inflammatory cascade, in regulating airway responsiveness after sensitization and aeroallergen challenge.

Asthma: mechanisms of disease persistence and progression

When asthma is diagnosed, eosinophilic inflammation and airway remodeling are established in the bronchial airways and can no longer be separated as cause and effect because both processes contribute to persistence and progression of disease, despite anti-inflammatory therapy. Th2 cells are continually active in the airways, even when disease is quiescent. IL-13 is the key effector cytokine in asthma and stimulates airway fibrosis through the action of matrix metalloproteinases on TGF-beta and promotes epithelial damage, mucus production, and eosinophilia. The production of IL-13 and other Th2 cytokines by non-T cells augments the inflammatory response. Inflammation is amplified by local responses of the epithelium, smooth muscle, and fibroblasts through the production of chemokines, cytokines, and proteases. Injured cells produce adenosine that enhances IL-13 production. We review human and animal data detailing the cellular and molecular interactions in established allergic asthma that promote persistent disease, amplify inflammation, and, in turn, cause disease progression.

Is interleukin-13 critical in maintaining airway hyperresponsiveness in allergen-challenged mice?

Interleukin (IL)-13 is regarded as being a central effector in the pathophysiology of airway hyperresponsiveness. We have described a mouse model in which chronic allergen exposure results in sustained airway hyperresponsiveness and aspects of airway remodeling, and here sought to demonstrate that this component of airway hyperresponsiveness is independent of biologically active IL-13. Sensitized mice were subjected to either brief or chronic periods of allergen exposure and studied 24 hours after brief or 4 weeks after chronic allergen inhalation. A soluble murine anti-IL-13 receptor fusion protein that specifically binds to and neutralizes IL-13 was given daily during the 4 days before the day of outcome measurements in both protocols. Outcome measurements included airway responses to intravenous methacholine, bronchoalveolar lavage fluid cell counts, and airway morphometry. Compared with the saline control, brief allergen challenge resulted in airway hyperresponsiveness, which was prevented by anti-IL-13 treatment. Chronic allergen challenge resulted in sustained airway hyperresponsiveness and indices of airway remodeling; IL-13 blockade failed to reverse this sustained airway hyperresponsiveness. These results confirm that IL-13 is critical for the development of airway hyperresponsiveness associated with brief allergen exposure, but is not necessary to maintain the sustained airway hyperresponsiveness associated with airway remodeling.

T helper-2 immunity regulates bronchial hyperresponsiveness in eosinophil-associated gastrointestinal disease in mice

BACKGROUND & AIMS

Eosinophil-associated gastrointestinal diseases are frequently associated with extraintestinal features, including bronchopulmonary manifestations. The factors predisposing to bronchial hyperresponsiveness in eosinophil-associated gastrointestinal diseases are unknown. To elucidate the mechanistic link between eosinophil-associated gastrointestinal diseases and bronchial hyperresponsiveness, we used murine models of eosinophil-associated gastrointestinal diseases and eotaxin-1/transgene-induced eosinophil-associated gastrointestinal diseases.

METHODS

Mice were sensitized and orally challenged with ovalbumin-coated encapsulated particles to induce eosinophil-associated gastrointestinal disease, and bronchial responsiveness was examined. Furthermore, transgenic mice expressing eotaxin in the intestine (with the rat fatty acid-binding promoter) were used to specifically elucidate the contribution of this chemokine in eosinophil-associated gastrointestinal disease-associated bronchial hyperresponsiveness.

RESULTS

The induction of allergen-induced eosinophil-associated gastrointestinal disease was directly correlated with the development of bronchial hyperresponsiveness. The development of bronchial hyperresponsiveness in mice with allergen-induced eosinophil-associated gastrointestinal disease was dependent on eotaxin expression in the gastrointestinal tract. Expression of eotaxin in the gastrointestinal tract of transgenic mice was sufficient to promote bronchial hyperresponsiveness. Bronchial hyperresponsiveness was shown to be directly linked to the aberrant CD4(+) T helper 2 lymphocyte production of interleukin-13. It is interesting to note that transgenic expression of eotaxin was linked with enhanced T helper 2 lymphocyte/cytokine synthesis (interleukin-4, -5, and -13) and the production of mucosal immunoglobulin G1 in the gastrointestinal lumen. We also showed that eotaxin treatment of CD4(+) T cells enhanced interleukin-13 production in vitro.

CONCLUSIONS

These studies suggest that increased expression of eotaxin in the gastrointestinal compartment can lead to increased CD4(+) T cell-derived T helper 2 lymphocyte-cytokine production that drives aberrant immunophysiological responses in distant noninflamed mucosal tissue (the lung). These results provide a possible explanation for the altered lung function seen in some patients with inflammatory gastrointestinal disorders.

Inhibition of airway remodeling in IL-5-deficient mice

To determine the role of IL-5 in airway remodeling, IL-5-deficient and WT mice were sensitized to OVA and challenged by repetitive administration of OVA for 3 months. IL-5-deficient mice had significantly less peribronchial fibrosis (total lung collagen content, peribronchial collagens III and V) and significantly less peribronchial smooth muscle (thickness of peribronchial smooth muscle layer, alpha-smooth muscle actin immunostaining) compared with WT mice challenged with OVA. WT mice had a significant increase in the number of peribronchial cells staining positive for major basic protein and TGF-beta. In contrast, IL-5-deficient mice had a significant reduction in the number of peribronchial cells staining positive for major basic protein, which was paralleled by a similar reduction in the number of cells staining positive for TGF-beta, suggesting that eosinophils are a significant source of TGF-beta in the remodeled airway. OVA challenge induced significantly higher levels of airway epithelial alphaVbeta6 integrin expression, as well as significantly higher levels of bioactive lung TGF-beta in WT compared with IL-5-deficient mice. Increased airway epithelial expression of alphaVbeta6 integrin may contribute to the increased activation of latent TGF-beta. These results suggest an important role for IL-5, eosinophils, alphaVbeta6, and TGF-beta in airway remodeling.

The eosinophil enigma

Eosinophils accumulate in high numbers in the lungs of asthmatic patients. These cells have the ability to induce tissue damage, a capacity that relates to their traditional role in host defense against parasitic worms. On the other hand, eosinophils produce growth factors associated with tissue repair and remodeling, notably TGF-beta1. The relationship of these activities to lung dysfunction in asthma is highly controversial, but recent observations in humans and in animal models add spice to the debate.

Interleukin-18 enhances the production of interferon-gamma (IFN-γ) by allergen-specific and unspecific stimulated cord blood mononuclear cells

BACKGROUND

IL-18 is a pleiotropic cytokine involved in the polarisation of T-cell response. This study was performed to determine whether or not IL-18 is detectable in phytohemagglutinin (PHA) or betalactoglobulin (BLG) stimulated supernatants of cord blood mononuclear cells (CBMC) and to study the in vitro effect of IL-18 on the interferon (IFN)-gaamma and IL-13 release of CBMC of healthy neonates.

METHODS

CBMC of neonates were isolated by Ficoll density centrifugation. The cytokines IFN-gamma, IL-13 and IL-18 in the cell culture supernatants were measured using the ELISA technique following stimulation with a unspecific (PHA 20 microg/ml) and an allergen-specific stimulus (BLG 25 microg/ml). In order to study the in vitro effect of IL-18, CBMC were stimulated either with medium alone or with IL-18, IL-18 + PHA and IL-18 + BLG.

RESULTS

IL-18 levels in supernatants of CBMC were low and did not vary significantly between unstimulated and PHA or BLG stimulated cell cultures (median 21.4; 23.5 and 15.5 pg/ml, respectively). IFN-gamma and IL-13 levels were significantly higher in response to PHA and BLG (PHA: IFN-gamma, 6154; IL-13, 4357; BLG: IFN-gamma, 801; IL-13, 249 pg/ml) compared to unstimulated cell cultures. The addition of IL-18 to PHA or BLG stimulated CBMC significantly enhanced the IFN-gamma release (PHA: 6154; PHA + IL-18: 13474, p = 0.0001; BLG: 801; BLG + IL-18: 1077, p = 0.008). In comparison to incubation without IL-18, the release of IL-13 was invariable or even reduced, when CBMC were stimulated with PHA + IL-18 (4026, p = 0.16) or BLG + IL-18 (124, p = 0.0001) compared to stimulation of CBMC with PHA (4357 pg/ml) or BLG (249 pg/ml) alone.

CONCLUSIONS

IL-18 is detectable in supernatants of CBMC. We observed a significant effect of IL-18 + PHA as well as IL-18 + BLG on IFN-gamma release in vitro. Based on our findings we conclude that IL-18 could act as a strong TH1-inducing factor on stimulated CBMC also in vivo.

Eotaxin-2 and IL-5 cooperate in the lung to regulate IL-13 production and airway eosinophilia and hyperreactivity

BACKGROUND

Eotaxin-2 is a member of the eotaxin subfamily of CC chemokines that display eosinophil-specific, chemotactic properties and has been associated with allergic disorders. However, the contribution of eotaxin-2 to the development of defined pathogenic features of allergic disease remains to be defined.

OBJECTIVE

We sought to determine whether eotaxin-2 was a cofactor with IL-5 for the regulation of pulmonary eosinophilia and to identify the combined role of these molecules in the induction of phenotypic characteristics of allergic lung disease.

METHODS

We instilled recombinant eotaxin-2 into the airways of wild-type mice that had been treated systemically with IL-5 or into IL-5-transgenic mice and characterized pulmonary eosinophil numbers, IL-13 production, and airway hyperreactivity (AHR) to methacholine. Mice deficient in the IL-4 receptor alpha-chain, IL-13, and signal transducers and activators of transcription 6 or mice treated with anti-CCR3 monoclonal antibody were also used.

RESULTS

Eotaxin-2 and IL-5 cooperatively promoted eosinophil accumulation, IL-13 production, and AHR to methacholine. Neither eotaxin-2 nor IL-5 alone induced these features of allergic disease. IL-13 production was critically dependent on eotaxin-2- and IL-5-regulated eosinophilia, which predisposed to the development of AHR. AHR was dependent on IL-13 and signaling through the IL-4R alpha-chain and signal transducers and activators of transcription 6 pathways and the presence of eosinophils in the lung.

CONCLUSION

These investigations demonstrate important cooperativity between eotaxin-2, IL-5, and IL-13 signaling systems and eosinophils for the development of hallmark features of allergic disease of the lung.

Gene microarray analysis reveals interleukin-5-dependent transcriptional targets in mouse bone marrow

Interleukin-5 (IL-5) is a hematopoietic differentiation factor that promotes the development of mature eosinophils from progenitors in bone marrow. We present a multifactorial microarray study documenting the transcriptional events in bone marrow of wild-type and IL-5-deficient mice at baseline and in response to infection with Schistosoma mansoni. The microarray data were analyzed by a 4-way subtractive algorithm that eliminated confounding non-IL-5-related sequelae of schistosome infection as well as alterations in gene expression among uninfected mice. Among the most prominent findings, we observed 7- to 40-fold increased expression of transcripts encoding the classic eosinophil granule proteins (eosinophil peroxidase, major basic protein, the ribonucleases) together with arachidonate-15-lipoxygenase and protease inhibitor plasminogen activator inhibitor 2 (PAI-2), in the IL-5-producing, infected wild-type mice only. This was accompanied by increased transcription of genes involved in secretory protein biosynthesis and granule-vesicle formation. Interestingly, we did not detect increased expression of genes encoding eosinophil-related chemokine receptors (CCR1, CCR3) or members of the GATA or CCAAT/enhancer binding protein (C/EBP) transcription factor families. These data suggest that the IL-5-responsive progenitors in the mouse bone marrow are already significantly committed to the eosinophil lineage and that IL-5 promotes differentiation of these committed progenitors into cells with recognizable and characteristic cytoplasmic granules and granule proteins.

IL-13 effector functions

IL-13 was first recognized for its effects on B cells and monocytes, where it upregulated class II expression, promoted IgE class switching and inhibited inflammatory cytokine production. It was also thought to be functionally redundant with IL-4. However, studies conducted with knockout mice, neutralizing antibodies, and novel antagonists demonstrate that IL-13 possesses several unique effector functions that distinguish it from IL-4. Resistance to most gastrointestinal nematodes is mediated by type-2 cytokine responses, in which IL-13 plays a dominant role. By regulating cell-mediated immunity, IL-13 modulates resistance to intracellular organisms including Leishmania major, Leishmania mexicana, and Listeria monocytogenes. In the lung, IL-13 is the central mediator of allergic asthma, where it regulates eosinophilic inflammation, mucus secretion, and airway hyperresponsiveness. Manipulation of IL-13 effector function may also prove useful in the treatment of some cancers like B-cell chronic lymphocytic leukemia and Hodgkin's disease, where IL-13 modulates apoptosis or tumor cell growth. IL-13 can also inhibit tumor immunosurveillance. As such, inhibitors of IL-13 might be effective as cancer immunotherapeutics by boosting type-1-associated anti-tumor defenses. Finally, IL-13 was revealed as a potent mediator of tissue fibrosis in both schistosomiasis and asthma, which indicates that it is a key regulator of the extracellular matrix. The mechanisms that regulate IL-13 production and/or function have also been investigated, and IL-4, IL-12, IL-18, IFN-gamma, IL-10, TGF-beta, TNF-alpha, and the IL-4/IL-13 receptor complex play important roles. This review highlights the effector functions of IL-13 and describes multiple pathways for modulating its activity in vivo.

Peroxisome proliferator-activated receptors alpha and gamma down-regulate allergic inflammation and eosinophil activation

Allergic asthma is characterized by airway hyperresponsiveness, eosinophilia, and mucus accumulation and is associated with increased IgE concentrations. We demonstrate here that peroxisome proliferator-activated receptors (PPARs), PPAR-alpha and PPAR-gamma, which have been shown recently to be involved in the regulation of various cell types within the immune system, decrease antigen-induced airway hyperresponsiveness, lung inflammation, eosinophilia, cytokine production, and GATA-3 expression as well as serum levels of antigen-specific IgE in a murine model of human asthma. In addition, we demonstrate that PPAR-alpha and -gamma are expressed in eosinophils and their activation inhibits in vitro chemotaxis and antibody-dependent cellular cytotoxicity. Thus, PPAR-alpha and -gamma (co)agonists might be of therapeutic interest for the regulation of allergic or inflammatory reactions by targeting both regulatory and effector cells involved in the immune response.

Interleukin-5 transgene expression and eosinophilia are associated with retarded mammary gland development in mice

Eosinophils are prevalent in the female reproductive tract, where they may contribute to regulation of development and maintenance of epithelial integrity. The present study examined the effects of constitutive interleukin-5 (IL-5) expression and overabundance of eosinophils on the development and function of the mammary gland, uterus, and ovary in mice. Eosinophils were up to 13-fold and 4-fold more abundant in the uterus and mammary gland, respectively, in female IL-5 transgenic (IL-5Tg) mice than in wild-type (Wt) animals. Eosinophils were present in large numbers in regressing corpora lutea in IL-5Tg mice but not in ovaries from Wt mice. Postpubertal mammary gland development was retarded in IL-5Tg mice, with impaired terminal end bud formation and an altered pattern of epithelial cell proliferation across the mammary fat pad coincident with disrupted ductal branching and extension. By 10 wk of age, the ductal tree was complete in both genotypes. Onset of first estrus was also delayed in IL-5Tg mice, but once IL-5Tg mice reached puberty, serum estrogen content across the cycle and estrous cycle duration were normal. The histology of uterine tissue and epithelial cell turnover were unchanged. Capacity to mate and achieve pregnancy was not affected by maternal IL-5 transgene expression, although at Day 18 of gestation, a modest decrease in the fetal:placental weight ratio was observed. Furthermore, parturition and ability to lactate and nurture postnatal pup development were not compromised. These data demonstrate an effect of IL-5 overexpression on ductal morphogenesis during postpubertal mammary gland development that is consistent with a direct regulatory role for eosinophils in these events, but these data also show that eosinophil excess does not have long-term consequences for adult reproductive function.

Characterization of a mouse model of allergy to a major occupational latex glove allergen Hev b 5

Allergen-specific immunotherapy is a clinically proven effective treatment for many allergic diseases, including asthma; however, it is not currently available for latex allergy because of the high risk of anaphylaxis. There is, therefore, a crucial need for an animal model of latex allergy in which to develop effective immunotherapy. Previous mouse models of latex allergy either did not characterize the allergic pulmonary immune response or used crude latex extracts, making it difficult to quantify the contribution of individual proteins and limiting their usefulness for developing specific immunotherapy. We immunized mice with recombinant Hev b 5, a defined major latex allergen, or latex glove protein extract, representing the range of occupationally encountered processed latex allergens. The immune response was compared with that seen in ovalbumin-immunized mice. Immunization with Hev b 5 or glove extract elicits hallmarks of allergic pulmonary Th2-type immune responses, comparable to those for ovalbumin, including (1) serum antigen-specific IgE, (2) an eosinophilic inflammatory infiltrate in the lung, (3) increased interleukin-5 in lung bronchoalveolar lavage fluid, and (4) mucus hypersecretion by epithelial cells in the lung airways. This mouse model will aid the development of potentially curative treatments for latex-sensitized individuals, including those with occupational asthma.

A small molecule very late antigen-4 antagonist can inhibit ovalbumin-induced lung inflammation

A nonpeptidyl small molecule antagonist, compound A, to nonactivated very late antigen-4 (VLA4) was examined in lung inflammation induced by a single dose of ovalbumin challenge. Compound A presented a good pharmacokinetic property, when given intratracheally, and the blood cells from such pharmacokinetic study showed good receptor occupancy of the compound for approximately 8 hours. Compound A was then tested in an ovalbumin-induced airway inflammation model by intranasal or intravenous route of administration. There was a dose-dependent inhibition of eosinophilia in the bronchiolar lavage fluid, when compound A was given intranasally but not when it was given intravenously. For comparison, antibody to VLA4 and another compound, BIO1211, which reacts only with activated VLA4, were examined in this system. Immunohistochemical analyses of the lung tissue substantiated the findings in the bronchiolar lavage fluid. Specific staining of the major basic protein of eosinophils showed peribronchiolar infiltration of eosinophils. Some of these eosinophils were also positive for nitrotyrosine, suggesting activation of eosinophils in the lung interstitium. There was deposition of major basic protein and nitrotyrosine at the base of the perivascular endothelium, indicative of degranulation of eosinophils in the area. After intranasal treatment with compound A, eosinophils in the lungs and their activation products were substantially decreased, documenting its effectiveness in inhibiting lung inflammation.

Inhibition of allergic airways inflammation and airway hyperresponsiveness in mice by dexamethasone: role of eosinophils, IL-5, eotaxin, and IL-13

BACKGROUND

Glucocorticoids inhibit allergen-induced airway eosinophilia and airway hyperresponsiveness (AHR). Whether glucocorticoids mediate their effects on AHR by inhibiting eotaxin and IL-5, 2 of the principal mediators of eosinophilia, or through IL-13, an important mediator of AHR, has not been established.

OBJECTIVE

We sought to investigate the effects of glucocorticoids on airway eosinophilia and the expression of IL-5, eotaxin, and IL-13 in relation to the induction of AHR in a murine model of allergic asthma.

METHODS

Dexamethasone (4 mg/kg) and mAbs against eotaxin (80 micro g/kg) and IL-5 (100 micro g/kg) singly and in combination were administered to immunized mice before antigen challenge. Airway responsiveness to methacholine was measured in anesthetized and mechanically ventilated animals. Eotaxin, IL-5, and IL-13 in bronchoalveolar lavage fluid (BALF), lung homogenates, or both were measured by means of ELISA.

RESULTS

A single antigen challenge induced AHR that lasted at least 10 days. Eotaxin protein and mRNA levels increased in lung tissue but not in BALF after challenge. IL-5 protein and mRNA levels increased both in BALF and in lung tissue. Dexamethasone reduced airway eosinophilia, AHR, and protein and mRNA for eotaxin and IL-5. Anti-murine eotaxin and anti-IL-5 antibodies alone and in combination reduced the ovalbumin-induced airway eosinophilia significantly but failed to inhibit AHR. Both dexa-methasone and anti-IL-5/anti-eotaxin inhibited the increases in lung IL-13 levels after ovalbumin challenge to a similar extent.

CONCLUSION

These findings suggest that the inhibition of AHR by the glucocorticoid dexamethasone does not appear to be explained by effects on eosinophilia, eotaxin, IL-5, or IL-13.

A causative relationship exists between eosinophils and the development of allergic pulmonary pathologies in the mouse

Asthma and mouse models of allergic respiratory inflammation are invariably associated with a pulmonary eosinophilia; however, this association has remained correlative. In this report, a causative relationship between eosinophils and allergen-provoked pathologies was established using eosinophil adoptive transfer. Eosinophils were transferred directly into the lungs of either naive or OVA-treated IL-5(-/-) mice. This strategy resulted in a pulmonary eosinophilia equivalent to that observed in OVA-treated wild-type animals. A concomitant consequence of this eosinophil transfer was an increase in Th2 bronchoalveolar lavage cytokine levels and the restoration of intracellular epithelial mucus in OVA-treated IL-5(-/-) mice equivalent to OVA-treated wild-type levels. Moreover, the transfer also resulted in the development of airway hyperresponsiveness. These pulmonary changes did not occur when eosinophils were transferred into naive IL-5(-/-) mice, eliminating nonspecific consequences of the eosinophil transfer as a possible explanation. Significantly, administration of OVA-treated IL-5(-/-) mice with GK1.5 (anti-CD4) Abs abolished the increases in mucus accumulation and airway hyperresponsiveness following adoptive transfer of eosinophils. Thus, CD4(+) T cell-mediated inflammatory signals as well as signals derived from eosinophils are each necessary, yet alone insufficient, for the development of allergic pulmonary pathology. These data support an expanded view of T cell and eosinophil activities and suggest that eosinophil effector functions impinge directly on lung function.