T cells and eosinophils in bronchial smooth muscle cell death in asthma

Background Bronchial smooth muscle cells (SMC) proliferate, express adhesion molecules, secrete cytokines and thus efficiently contribute to the pathogenesis of asthma.
Objective The aim of the study was to investigate whether, and by which mechanism, T cells and eosinophils can cause death of airway SMC.
Methods The T cell- and eosinophil-induced cell death was analysed in primary human bronchial SMC cultures as well as in bronchial biopsy specimens from non-asthmatic and asthmatic individuals.
Results Bronchial SMC death showed characteristic morphological features of apoptosis in 3–6 days cultures with inflammatory cytokines (IFN-γ, TNF-α), soluble death ligands [sFasL, TNF-related apoptosis-inducing ligand (TRAIL)] and activated T-helper type 1 (Th1) and Th2 cell supernatants. The recombinant eosinophil cationic protein induced SMC necrosis within 1 h. Resting SMC expressed the death receptors TNFR1, TNFR2, Fas, TRAILR1, TRAILR2 and membrane FasL as a death-inducing ligand. IFN-γ and TNF-α up-regulated TNFR1, TNFR2, Fas and membrane FasL on SMC. TNF-α up-regulated TRAILR1 and TRAILR2; sFasL up-regulated TNFR2. The intracellular caspase-3 activation in SMC was significantly increased by IFN-γ, sFasL, TRAIL, Th1 and Th2 cell supernatants. Increased expression of TRAIL in asthmatics, but not in non-asthmatic individuals was demonstrated in situ . The apoptosis receptors TRAILR1 and TRAILR2 were expressed in SMC and epithelial cells both in healthy and asthmatic biopsies. Prominent apoptosis of SMC was observed in fatal asthma, but not intermittent asthma biopses.
Conclusion The demonstration of bronchial SMC death both by apoptosis and necrosis indicates the essential role of T cells and eosinophils in the bronchial tissue injury particularly in the severe asthma.     

Apoptosis and loss of adhesion of bronchial epithelial cells in asthma

BACKGROUND: Asthma is an inflammatory airway disease associated with infiltration of T cells and eosinophils, increased levels of pro-inflammatory cytokines, and shedding of bronchial epithelial cells (EC). We have recently shown that T cells and eosinophils cooperate in inducing bronchial EC apoptosis in asthma through secretion of IFN-gamma and TNF-alpha. Since EC shedding is a histologic hallmark of asthma, the intercellular junction of EC may be a target of pro-inflammatory cytokines. METHODS: Bronchial EC, cultured and exposed to IFN-gamma and TNF-alpha, were studied for the expression of adhesion molecules and apoptosis. In addition, the epithelial layer of bronchial biopsies from asthma patients was evaluated for apoptosis, shedding, and expression of adhesion molecules. RESULTS: We demonstrate that the induction of EC apoptosis is accompanied by loss of E-cadherin. In situ examination of E-cadherin in asthma revealed a reduction in its expression on EC membranes. In contrast, the in vitro and in vivo expression of beta1-integrins and intercellular adhesion molecule-1 (ICAM-1) increased on EC during asthmatic airway inflammation. CONCLUSIONS: Loss of cadherin-mediated intercellular adhesion and apoptosis could account for fragility and shedding of EC in asthma, especially since this occurs between columnar and basal EC.     

Effects of suplatast tosilate on allergic eosinophilic airway inflammation in patients with mild asthma

BACKGROUND: Bronchial asthma is a chronic inflammatory disease characterized mainly by infiltration of the airway mucosa by various inflammatory cells, notably eosinophils. T(H)2-type cytokines are suggested to be deeply involved in the pathogenesis of asthma. OBJECTIVE: We sought to determine the suppressive effects of suplatast tosilate, an inhibitor of T(H)2-type cytokines, on eosinophilic inflammation of the bronchial mucosa in patients with mild asthma. METHODS: Airway hyperresponsiveness tests, pulmonary function tests, eosinophil measurements in induced sputum, and bronchial mucosa biopsies were performed before and after treatment with suplatast tosilate for 6 weeks in 15 patients with mild asthma and in 13 control patients with mild asthma not receiving suplatast tosilate. This study was performed as a case-controlled open study. RESULTS: In the treatment group a significant improvement in the provocation concentration of histamine was observed (P <.05). Improvements in peak expiratory flow (P <.01) and in symptom score (P <.05) were also noted in the suplatast tosilate-treated group. Moreover, the average number of infiltrating eosinophils and EG2(+) cells significantly decreased (both P <.05), as did the ratios of eosinophils and EG2(+) cells in sputum (both P <.01). The average number of CD4(+) and CD25(+) T lymphocytes also decreased (both P <.05). CONCLUSION: Suplatast tosilate appears to inhibit allergic airway inflammation mediated by T(H)2-type cytokine and to improve clinical symptoms in patients with mild asthma.     

Primary lysis of eosinophils in severe desquamative asthma

Primary lysis of eosinophils liberates free eosinophil granules (FEGs) releasing toxic proteins in association with bronchial epithelial injury repair. Eosinophil lysis may be significantly pathogenic. Bronchial mucosal FEGs are associated with uncontrolled asthma, severe asthma, aspirin‐sensitive asthma, and lethal asthma. FEGs in the bronchial wall may characterize severe asthma without sputum eosinophilia. Excessive numbers of sputum FEGs occur in severe exacerbations of asthma and are reduced along with clinical improvement. Occurrence of FEGs affects interpretation of other sputum biomarkers including numbers of eosinophils, ECP, and eosinophil‐stained macrophages. Thus, eosinophil lysis produces FEGs as bronchial biomarkers of severe asthma. Blood eosinophils in severe asthma seem primed exhibiting a propensity to lyse that is greater the more severe the asthma. Proclivity of blood eosinophils to lyse also distinguished three levels of severity among children with exacerbations of asthma. Numerous FEGs releasing toxic proteins occur in association with grave derangement and shedding of epithelium in severe asthma. Subepithelial FEGs correlate negatively with intact bronchial epithelium in clinically uncontrolled asthma. Significant correlations between sputum ECP, Creola bodies, and severity of asthma exacerbations have also been demonstrated. Hence, eosinophil lysis apparently causes epithelial desquamation in severe asthma. Exaggerated epithelial repair in turn would contribute to inflammatory and remodelling features of severe asthma. Perseverance of FEGs together with maintained disease activity, despite treatment with ‘eosinophil‐depleting’ steroids and anti‐IL5 biologicals, agrees with the possibility that eosinophil lysis is worthy target for novel anti‐asthma drugs. Priming and lysis of eosinophils, and protein release from FEGs, are regulated and can be targeted. Eosinophil lysis and FEGs belong to the disease picture of severe asthma and need consideration in asthma studies concerned with phenotypes, biomarkers, roles of epithelial injury/repair, and targeting novel drugs.     

IL‐5‐induced airway eosinophilia – the key to asthma?

Summary: Bronchial asthma is a chronic inflammatory airway disease defined by reversible airway obstruction and non-specific airway hyper-responsiveness (AHR). Although profound insights have been made into the pathophysiology of asthma, the exact mechanisms inducing and regulating the disease are still not fully understood. Yet, it is generally accepted that the pathological changes in asthma are induced by a chronic inflammatory process which is characterized by infiltration of the bronchial mucosa with lymphocytes and eosinophils, increased mucus production and submucosal edema. There is increasing evidence that an imbalance in the T-helper (Th) cell response of genetically predisposed individuals to common environmental antigens plays a pivotal role in the pathogenesis of allergic bronchial asthma and other atopic disorders. Following allergic sensitization, T cells from atopic patients tend to produce elevated levels of Th2-type cytokines, especially interleukin (IL)-4, IL-13, IL-5 and IL-6, which induce and regulate IgE production and eosinophil airway infiltration. In this review, the role of Th2-type cytokines, IgE and airway eosinophils in the induction of airway inflammation and AHR is discussed, and animal studies of asthma and AHR, mainly in rodents will be considered. A better understanding of the underlying mechanisms leading to asthma pathology may yield more specific immunological strategies for the treatment of this disease which is increasing worldwide.
I thank the many colleagues in the laboratory of Dr. E. W. Gelfand, National Jewish Research Center, Denver CO, USA, for continuous support and encouragement. E.H. is a fellow of the Deutsche Forschungsgemeinschaft (DFG Ha 2162/1-1 and 2-1).     

Effect of IL-17 on ICAM-1 expression of human bronchial epithelial cells, NCI-H 292]

Bronchial asthma is characterized as a chronic inflammation of the airway infiltrated by eosinophils, lymphocytes, and neutrophils. ICAM-1 expression on airway epithelium facilitates adhesion between these inflammatory cells and bronchial epithelial cells, and induces the activation of inflammatory cells. ICAM-1 expression was affected by various cytokines, such as IL-17. IL-17 is a novel cytokine released by CD4+ activated memory T cells. In this study, we examined the effect of IL-17 on ICAM-1 expression by RT-PCR and flow cytometry. Human bronchial epithelial cells, NCI-H 292 cells, were stimulated with IL-17 (100 ng/ml) and/or IFN-gamma (100 U/ml). ICAM-1 was expressed constitutively. IL-17 alone did not enhance ICAM-1 expression on NCI-H 292 cells. However, IL-17 synergistically enhanced ICAM-1 expression induced by IFN-gamma. These results suggest that IL-17 has an effect on ICAM-1 expression of bronchial epithelial cells in airway inflammation.     

Effects of ketotifen on symptoms and on bronchial mucosa in patients with atopic asthma

Ketotifen is marketed throughout the world as an antiallergy drug, but whether it affects infiltration of inflammatory cells into airway mucosa is not known. We studied the effects of ketotifen on symptoms, pulmonary function, and airway inflammation in 25 patients with atopic asthma. Patients took ketotifen (1 mg twice daily) or a matching placebo for 8 weeks in a double-blind, parallel-group study. Data recorded on diary cards were used for 2 weeks before treatment began, and they were used for the last 2 weeks of treatment to study asthma symptoms, use of β2–agonists, and peak expiratory flow (PEF). Pulmonary function tests, bronchial responsiveness to methacholine, and fiberoptic bronchoscopy were performed before and after treatment. Biopsy specimens were obtained by bronchoscopy. Specimens were stained immunohistochemically with monoclonal antibodies against stored eosinophil cationic protein (EG1), the secreted form of eosinophil cationic protein (EG2), mast-cell tryptase (AA1), neutrophil elastase (NP57), CD3, CD4, CD8, and CD25. The numbers of positively stained cells in the lamina propria were counted. Compared with the placebo, the ketotifen-treated group exhibited significant improvement of asthma symptoms ( P <0.05) and bronchial responsiveness (P<0.05). This was accompanied by a reduction of EG2+ eosinophils ( P <0.05), CD3+ T cells ( P <0.001), CD4+ T cells (P<0.01), and CD25+ activated T cells ( P <0.01) in the bronchial mucosa. These results suggested that the beneficial effects of ketotifen in bronchial asthma may result from consequent inhibition of activated eosinophils and T-cell recruitment into the airway. Moreover, ketotifen may relieve allergic inflammation in bronchial asthma.     

Cloned Th cells confer eosinophilic inflammation and bronchial hyperresponsiveness

BACKGROUND: The essential role of Th cells and T cell cytokines in eosinophilic inflammation has been established. METHODS: To determine whether Th cells are sufficient for the development of airway eosinophilic inflammation, ovalbumin-reactive murine Th clones were established and infused into unprimed mice. RESULTS: Eosinophilic infiltration into the lung was induced upon antigen inhalation in parallel with the rise in bronchoalveolar lavage fluid (BALF) eosinophil peroxidase activity. Neither IgG, IgA, nor IgE antibodies were present in this model. Pathological examination showed swelling and desquamation of epithelial cells, mucous plugs, and goblet cell hyperplasia, all of which well resemble human asthma. Fluorescent probe labeled Th clones migrated into the lung prior to the eosinophil accumulation. Bronchial hyperresponsiveness (BHR) was clearly induced upon antigen inhalation. Anti-IL-5 monoclonal antibody abrogated the responses. Dexamethasone and cyclosporin A suppressed cytokine production by Th cells both in vitro and in vivo, BALF eosinophilia, and BHR. The number of eosinophils recovered in the BALF correlated with the intensity of BHR. CONCLUSION: The results clearly indicated that monoclonal Th cells are sufficient for the development of both airway eosinophilia and BHR. Agents capable of downregulating IL-5 production seem promising for the treatment of bronchial asthma.     

Involvement of IL-9 in the bronchial phenotype of patients with nasal polyposis

BACKGROUND: Nasal polyposis (NP) is frequently associated with asthma. In this disease, asymptomatic bronchial hyperresponsiveness (BHR) is thought to precede the development of asthma. IL-9 and its receptor have been reported as candidate genes for asthma and to be associated with BHR. OBJECTIVE: The objective of this study was to assess the contribution of 11-9 to the pathogenesis of BHR in NP by comparing the expression of IL-9 and its receptor in bronchial biopsy specimens from three groups of patients with NP: NP without BHR, NP with asymptomatic BHR, and NP with BHR and asthma. METHODS: Bronchial biopsy specimens were examined in terms of cellular infiltration and in terms of expression of IL-9 protein and mRNA as well as of its receptor by using immunohistochemistry and in situ hybridization. RESULTS: Patients with NP with asthma as compared with the two other groups exhibited an increased bronchial infiltration of basophils, eosinophils, and T cells that correlated with the asthma score. The two groups of patients with NP with BHR showed an increased expression in IL-9 protein and mRNA as well as an increase in the expression of IL-9R mRNA at the epithelial level. These modifications were inversely correlated with the airway responsiveness to methacholine, producing a 20% fall in FEV1. There was a close association between IL-9+ cells, IL-5 mRNA expression, and eosinophil infiltration that correlated with each other. CONCLUSIONS: These results suggest an important role for IL-9 in the pathogenesis of BHR and a causal relation between IL-9 and the development of bronchial eosinophilia in asthma.     

An immunohistochemical study on cellular infiltration of bronchial walls in bronchial asthma]

Inflammatory cell reactions in bronchial asthma have been considered to contribute directly to asthmatic attacks. Therefore, attention has been focused on the role of inflammatory cells in the airway wall. In this study, we investigated inflammatory cells in the airway wall of bronchial asthma histologically and immunohistologically using 20 autopsy cases who died of the asthma attacks (Group A) and 11 autopsy cases who died of other causes (Group B). Six autopsy cases were treated as controls (Group C). A significantly larger number of eosinophils in the bronchi and bronchioles were found in Group A. The majority of eosinophils were found to be stained with EG2. Parts of the bronchial epithelium with marked infiltration of EG2 positive eosinophils were detached from the basal layer. Immunoelectron microscopically, the matrix of EG2 positive areas within the eosinophils corresponded to that of eosinophil granules. A significantly larger number of lymphocytes in the bronchi and bronchioles was observed in Groups A and B. Almost all of these lymphocytes were determined to be activated T lymphocytes. There were significantly more IgE positive cells in cases with bronchial asthma, especially in Group A. The majority of IgE positive cells were determined to be mast cells. These results suggest that eosinophils, lymphocytes and mast cells play an important role in the pathogenesis of bronchial asthma.     

Allergic inflammation and its pharmacological modulation in asthma

While most asthma occurs in association with atopy, the relationship of this to clinical expression of the disease is not clearly understood. Allergen provocation causes an immediate bronchoconstriction (early asthmatic reaction) due to the release of mast-cell-derived histamine, prostaglandin D2 and leukotriene C4. The late reaction and attendent increase in bronchial responsiveness are associated with eosinophil influx, activation and mediator secretion, resulting in mucosal swelling in addition to smooth muscle contraction. Endobronchial biopsy and broncho-alveolar lavage have provided compelling evidence that both mast cells and eosinophils contribute to disordered airway function in 'clinical' asthma and that these cells are under the control of T lymphocytes. Topical corticosteroids which produce beneficial clinical effects probably do so by inhibiting those factors that maintain mast cell and eosinophil populations and their enhanced activation. The most likely contenders for these regulatory functions are the cytokines, particularly interleukin-3, -4 and -5.     

Nasal allergen provocation induces adhesion molecule expression and tissue eosinophilia in upper and lower airways

BACKGROUND: Allergic rhinitis (AR) and asthma are characterized by means of a similar inflammatory process in which eosinophils are important effector cells. The migration of eosinophils from the blood into the tissues is dependent on adhesion molecules. OBJECTIVE: To analyze the aspects of nasobronchial cross-talk, we studied the expression of adhesion molecules in nasal and bronchial mucosa after nasal allergen provocation (NP). METHODS: Nine nonasthmatic subjects with seasonal AR and 9 healthy control subjects underwent NP out of season. Bronchial and nasal biopsy specimens were taken before (T(0)) and 24 hours after NP (T(24)). Mucosal sections were analyzed for the presence of eosinophils, IL-5, eotaxin, intercellular adhesion molecule 1 (ICAM-1), vascular cell adhesion molecule 1 (VCAM-1), E-selectin, and human endothelium (CD31). RESULTS: At T(24), an influx of eosinophils was detected in nasal epithelium (P =.01) and lamina propria (P <.01), as well as in bronchial epithelium (P =.05) and lamina propria (P <.05), of the patients with AR. At T(24), increased expression of ICAM-1, as well as increased percentages of ICAM-1+, VCAM-1+, and E-selectin+ vessels, were seen in nasal and bronchial tissue of patients with AR. The number of mucosal eosinophils correlated with the local expression of ICAM-1, E-selectin, and VCAM-1 in patients with AR. CONCLUSION: This study shows that NP in patients with AR results in generalized airway inflammation through upregulation of adhesion molecules.     

Human airway submucosal glands augment eosinophil chemotaxis during rhinovirus infection

BACKGROUND: Asthma exacerbations are frequently associated with rhinovirus (RV) infections. However, the contribution of airway submucosal gland (SMG) to exacerbations of asthma in RV respiratory infection has not been studied. OBJECTIVE: This study was undertaken to examine whether RV-infected human respiratory SMG cells produce pro-inflammatory cytokines and chemokines for eosinophils, and augment eosinophil transmigration across human airway epithelium. METHODS: We infected cultured human tracheal SMG cells with RV14, collected culture media at 1, 3, and 5 days after infection, and measured the chemotactic activity for eosinophils in the culture supernatant using a 48-well microchemotaxis chamber and a (51)Cr-labelled eosinophil transmigration assay. RESULTS: Exposing a confluent human tracheal SMG cell monolayer to RV14 consistently led to infection. Human SMG cells with RV infection secreted soluble factors activating human eosinophil chemotaxis into the culture supernatant in a time-dependent manner, and the culture supernatant significantly augmented the transmigration of (51)Cr-labelled eosinophils through human airway epithelial cell layers from the basal to mucosal side. These effects were completely abolished by a mixture of a monoclonal antibody regulated on activation, normal T cells expressed and secreted (RANTES) and an antibody to granulocyte macrophage-colony stimulating factor (GM-CSF). CONCLUSION: These results suggest that human respiratory SMG cells may augment eosinophil transmigration across the airway epithelium through the secretion of RANTES and GM-CSF after RV infection, and may contribute to exacerbations of asthma.     

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

BACKGROUND: Bronchial asthma is characterized by airway inflammation, notably because of eosinophils and T cells. Thymus and activation-regulated chemokine (TARC) is known to selectively attract Th2 cells, and is increased in response to interleukin (IL)-4 and IL-13, which share a common receptor, IL-4 receptor alpha (IL-4Ralpha). While corticosteroids have proven, very effective in modifying airway inflammation, the effect of corticosteroids on TARC in asthmatics has been little studied. OBJECTIVE: We examined the effects of inhaled budesonide (BUD) on the expression of TARC and the number of inflammatory cells in bronchial biopsy specimens taken from asthma patients. METHODS: Inhaled BUD 800 mug daily, or placebo was administered for 3 months in a double-blind, parallel-group study, and bronchial biopsies were performed before and after treatment. Biopsy specimens were examined by immunocytochemistry. RESULTS: We observed a significant decrease in the epithelial expression of TARC (P < 0.01) in the BUD group compared with the placebo group. This was accompanied by decreases in the number of eosinophils (P < 0.01), CD3(+) T cells (P < 0.05), and CD4(+) T cells (P < 0.01). A significant correlation was found between changes in epithelial TARC and in IL-4Ralpha immunoreactivity (r(s) = 0.66, P < 0.01). CONCLUSIONS: These findings suggest that corticosteroid asthma treatment can reduce infiltration of the airway by inflammatory cells, an effect modulated by down-regulation of bronchial epithelial TARC expression.     

Eosinophils in asthma.

Eosinophils, a prominent feature of asthma, are found in increased numbers in the circulation and sputum, usually in relation to the severity of asthma. As a consequence of these clinical observations, investigators now speculate that the eosinophil has a central role in the pathogenesis of asthma. Recent evidence has begun to confirm these speculations. The allergic reaction of the airway to antigen and the development of the late asthmatic reaction have provided a clinical model to study asthma and the contribution of eosinophils to bronchial reactivity. In the late asthmatic reaction, airway eosinophilia occurs. Through a series of independent observations, the following eosinophil-related events have been noted with the development of late asthmatic reactions. With either laboratory or natural exposure to antigen, eosinophilic chemotactic factors are released. Although the sources of eosinophil chemotaxis are multicellular, this is an early step in the attraction of eosinophils to the airway. As this process is initiated, a series of events occurs to cause eosinophils to arrive in the airway and promote obstruction, injury, and bronchial hyperresponsiveness. These steps include eosinophil migration through the vascular endothelium, upregulation of eosinophils (characterized by a change in cell density), adhesion of eosinophils to airway epithelium, and release of eosinophil toxic products. This presentation will review some of the eosinophil-dependent factors that can cause asthma. Furthermore, the eosinophil may be a good target for future therapeutic interventions.     

High-resolution computed tomography scan and airway remodeling in children with severe asthma

BACKGROUND: Children with severe asthma have a significantly higher bronchial wall thickness (BWT) on high-resolution computed tomography scan than control children. OBJECTIVE: We sought to determine whether a BWT score correlates with markers of airway remodeling and inflammation. METHODS: In 37 children with severe asthma, we determined reticular basement membrane thickness; number of intraepithelial neutrophils and eosinophils on bronchial biopsy; IFN-gamma, IL-4, IL-5, and eosinophil cationic protein levels and IFN-gamma/IL-4 ratio on bronchoalveolar lavage specimen; and alveolar nitric oxide (NO) concentration and the maximum airway wall NO flux. RESULTS: The BWT score significantly correlated with reticular basement membrane thickening (r = 0.34; P = .04) and NO production by the airway wall (r = 0.45; P = .02). The correlation with the eosinophil cationic protein level was just significant (r = 0.40; P = .05), whereas there was no correlation with IFN-gamma/IL-4 ratio (r = -0.31; P = .08). The BWT score did not correlate with FEV(1) or forced expiratory flow at 25% to 75% of forced vital capacity. CONCLUSION: High-resolution computed tomography scan is a noninvasive technique that might be valuable for quantifying airway remodeling in children with severe asthma. The new generations of multislice computed tomography scanners will allow higher definition and lower radiation exposure and probably give a better assessment of airway remodeling and efficacy of treatment in children with asthma.     

Activated T-lymphocytes and eosinophils in the bronchial mucosa in isocyanate-induced asthma.

We have studied the phenotype and activation status of leukocytes in the bronchial mucosa in patients with isocyanate-induced asthma. Fiberoptic bronchial biopsy specimens were obtained from nine subjects with occupational (five toluene- and four methylene diisocyanate-sensitive) asthma, 10 subjects with extrinsic asthma, and 12 nonatopic healthy control subjects. Bronchial biopsy specimens were examined by immunohistology with a panel of monoclonal antibodies and the alkaline phosphatase-antialkaline phosphatase method. There was a significant increase in the number of CD25+ cells (interleukin-2 receptor-bearing cells, presumed "activated" T-lymphocytes; p less than 0.01) in isocyanate-induced asthma compared with that of control subjects. There were also significant increases in major basic protein (BMK-13)-positive (p less than 0.02) and EG2-positive (p less than 0.01) cells that represent total and "activated" eosinophil cationic protein-secreting eosinophils, respectively. In agreement with our previous findings, CD25+ (p less than 0.01), BMK-13 (p less than 0.03), and EG2+ (p less than 0.01) cells were also elevated in extrinsic asthma. No significant differences were observed in the numbers of T-lymphocyte phenotypic markers (CD3, CD4, and CD8) between subjects with asthma (isocyanate-induced and extrinsic) and control subjects. Similarly, no significant differences in immunostaining for neutrophil elastase (neutrophils) or CD68 (macrophages) were observed. The results suggest that isocyanate-induced occupational asthma and atopic (extrinsic) asthma have a similar pattern of inflammatory cell infiltrate. The results support the view that T-lymphocyte activation and eosinophil recruitment may be important in asthma of diverse etiology.     

The role of PTEN in allergic inflammation

Bronchial asthma is a chronic inflammatory disease of the airways, characterized by airway eosinophilia, goblet cell hyperplasia with mucus hyper-secretion, and hyper-responsiveness to inhaled allergens and to non-specific stimuli. Eosinophil accumulation and subsequent activation in bronchial tissues play critical roles in the pathophysiology of bronchial asthma. Many inflammatory mediators attract and activate eosinophils via signal transduction pathways involving an enzyme phosphatidylinositol 3-kinase (PI3-kinase). Studies using wortmannin, a specific inhibitor of PI3-kinase, have revealed the involvement of PI3-kinase in the biochemical transduction of activation signals generated by many inflammatory mediators in eosinophils. Wortmannin prevents the development of airway inflammation, either by inhibiting the eosinophil infiltration of bronchial tissues or their activation on arrival. Phosphatase and tensin homologue deleted on chromosome 10 (PTEN) is part of a complex signaling system that affects a variety of important cell functions. PTEN opposes the action of PI3-kinase by dephosphorylating the signaling lipid phosphatidylinositol 3,4,5-triphosphate. Recently we have demonstrated that PTEN expression is diminished in airway epithelial cells of antigen-sensitized and -challenged mice. Administration of PI3-kinase inhibitors or adenoviruses carrying PTEN complementary DNA remarkably reduces eosinophil levels and inflammation. One likely mechanism for this reduction is PTEN-mediated eosinophil degranulation and suppression of interleukin (IL)-4 and IL-5.These findings indicate that use of PTEN may be a good therapeutic strategy for the management of allergic inflammation.     

Evaluation of apoptosis of eosinophils, macrophages, and T lymphocytes in mucosal biopsy specimens of patients with asthma and chronic bronchitis

BACKGROUND: Apoptosis regulates inflammatory cell survival, and its reduction contributes to the chronicity of an inflammatory process. Apoptosis is controlled by suppressing or inducing genes, such as bcl-2 and p53, respectively. OBJECTIVE: We sought to assess apoptosis of eosinophils, macrophages, and T lymphocytes in bronchial biopsy specimens from asthmatic subjects and to examine its regulation by evaluating the expression of B-cell lymphoma leukemia-2 (Bcl-2) and P53 proteins. We also sought to explore the relationships between cell apoptosis and GM-CSF, a cytokine able to increase eosinophil and macrophage survival. METHODS: Apoptosis in eosinophils, macrophages, and T lymphocytes was evaluated in bronchial biopsy specimens obtained from 30 asthmatic subjects, 26 subjects with chronic bronchitis, and 15 control subjects by combining the terminal deoxynucleotidyl transferase-mediated dNTP nick end-labeling technique and immunohistochemistry. The expression of P53, Bcl-2, and GM-CSF was studied through immunohistochemistry by using specific mAbs. RESULTS: The number of apoptotic eosinophils and macrophages was lower in subjects with asthma than in those with chronic bronchitis (P <.007 and P <.001, respectively) and inversely correlated with the clinical severity of asthma (P <.001 and P <.002, respectively). Few T lymphocytes were apoptotic in all groups studied. In asthma GM-CSF+ cells correlated with the number of nonapoptotic eosinophils and macrophages (P =.0001) and with the severity of the disease (P <.003). In asthma Bcl-2+ cells were higher than in control subjects and subjects with chronic bronchitis (P <.002 and P <.015, respectively), they outnumbered P53+ cells, and they correlated with the number of T lymphocytes (P <.001) and with the severity of the disease (P <.003). CONCLUSION: Airway inflammation in asthma is associated with an enhanced survival of different cell types caused by reduced apoptosis.     

Interleukin-5 enhances eosinophil adhesion to bronchial epithelial cells

BACKGROUND: Eosinophil-bronchial epithelial cell interactions are thought to be central to the pathogenesis of asthma, both in terms of the epithelium as a source of pro-inflammatory mediators and as a target for eosinophil-mediated damage. We have therefore investigated adhesion interactions between these two cell types. OBJECTIVES: To determine the role of eosinophil and epithelial activation on eosinophil adhesion to bronchial epithelium and to characterize the adhesion receptors mediating eosinophil adhesion. METHODS: Eosinophils were purified from human peripheral blood by immunomagnetic selection and adhesion to confluent cultures of the airway epithelial cell lines A549 and BEAS-2B was studied. RESULTS: Stimulation of A549 cells with TNFalpha, IFNgamma or a combination of 50 ng/mL of TNFalpha, IFNgamma and IL-1 (cytomix) did not effect eosinophil binding despite an increase in ICAM-1 expression. Similarly stimulation of eosinophils with PAF or IL-5 had no effect on eosinophil binding to medium- or cytokine-treated A549 cells. In contrast stimulation of BEAS-2B cells with cytomix caused a significant increase in eosinophil adhesion. This was associated with an increase in expression of ICAM-1 and induced expression of VCAM-1. Treatment of eosinophils with Mn2+ and IL-5 but not eotaxin, RANTES or PAF also significantly enhanced eosinophil adhesion to medium-treated BEAS-2B cells. Using blocking mAbs we were able to demonstrate that the increased adhesion resulting from stimulation of eosinophils or BEAS-2B cells was in both cases mediated by a combination of CD18 and alpha4 integrins. CONCLUSIONS: This study demonstrates a selective role for IL-5 in mediating integrin-dependent eosinophil adhesion to airway epithelium and once again emphasizes the importance of this cytokine in controlling eosinophil activation in diseases such as asthma.