Understanding airway wall remodeling in asthma: a basis for improvements in therapy?

Oral exposure to cadmium and mercury alone and in combination causes damage to the lung tissue of Sprague-Dawley rats

Environmental presence and human exposure to heavy metals in air and cigarette smoke has led to a worldwide increase in respiratory disease. The effects of oral exposure to heavy metals in liver and kidney structure and function have been widely investigated and the respiratory system as a target is often overlooked. The aim of the study was to investigate the possible structural changes in the lung tissue of Sprague-Dawley rats after oral exposure for 28 days to cadmium (Cd) and mercury (Hg), alone and in combination at 1000 times the World Health Organization's limit for each metal in drinking water. Following exposure, the general morphology of the bronchiole and lungs as well as collagen and elastin distribution was evaluated using histological techniques and transmission electron microscopy. In the lungs, structural changes to the alveoli included collapsed alveolar spaces, presence of inflammatory cells and thickening of the alveolar walls. In addition, exposure to Cd and Hg caused degeneration of the alveolar structures resulting in confluent alveoli. Changes in bronchiole morphology included an increase in smooth muscle mass with luminal epithelium degeneration, detachment and aggregation. Prominent bronchiole-associated lymphoid tissue was present in the group exposed to Cd and Hg. Ultrastructural examination confirmed the presence of fibrosis where in the Cd exposed group, collagen fibrils arrangement was dense, while in the Hg exposed group, additional prominent elastin was present. This study identified the lungs as target of heavy metals toxicity following oral exposure resulting in cellular damage, inflammation and fibrosis and increased risk of respiratory disease where Hg showed the greatest fibrotic effect, which was further, aggravated in combination with Cd.

Genomic mosaicism: A neglected factor that promotes variability in asthma diagnosis

To elucidate the genetic architecture of asthma continues to be a challenge for molecular biologists and medical researchers. However, powerful genomic technologies are at disposal to help decipher complete human genomes; the genetic variability in asthma hinders the discovery of common molecular markers for this disease. In this context, we purpose to explore genomic mosaicism on asthma cells' biology as a strategy to discover key mechanisms, which can complement or re-define asthma diagnosis. Recent evidences showed that genomic mosaicism could be a normal event. In brains, each neuron may harbor hundreds of genetic alterations, which may contribute to neuronal diversity. Thus, can mosaicism be a natural motor of diversity in asthma? Why this genetic event is little described in scientific literature? To discuss these questions, we perform a critical review about the normality of genomic mosaicism; moreover, we examine the difficulty of current experimental approaches to detect different genotypes in cell populations of one individual.

An anti-asthmatic activity of natural Toll-like receptor-4 antagonist in OVA-LPS-induced asthmatic rats

Toll-like receptor-4 (TLR4) is a key component of the innate immune system and activation of TLR4 signaling has a significant role in the pathogenesis of asthma. Therefore, our objective was to identify the natural TLR4 antagonist and evaluate its activity in experimentally induced asthma. Soya lecithin origin phosphatidylcholine (soya PC) was identified as a natural TLR4 antagonist by computational study. Based on the computational study, TLR4 antagonist activity of soya PC was confirmed in in vitro lipopolysaccharide (LPS)-induced neutrophil adhesion assay. In the in vivo study, rats were sensitized with ovalbumin (OVA) (100 μg/kg, i.p.) on the 7th, 14th and 21st days and challenged intranasally with OVA (100 μg/100 μL) and LPS (10 ng/100 μL), 4 days/wk for 3 weeks. At the end of the experiment, we performed lung function parameters (respiratory rate, tidal volume, airflow rate), inflammatory cytokines (interleukin [IL]-4, IL-5, IL-13), total and differential leukocytes in blood as well as bronchoalveolar lavage fluid (BALf) and histological examinations. The computational study indicated that TLR4 antagonist activity of soya PC is due to linoleic acid (18:2) fatty acid chain. Soya PC significantly suppressed the LPS-induced neutrophil adhesion in a concentration-dependent manner to 1 μg/mL. The treatment of soya PC (5 and 10 mg/kg, 18 days, i.p.) significantly improved the lung function parameters, total and differential leukocyte counts in blood and BALf in asthmatic rats. This efficacy of soya PC was in extent similar to dexamethasone (2.5 mg/kg, 18 days, i.p.). However, soya PC was superior to dexamethasone in terms of benefits. The protective action of soya PC may be due to TLR4 antagonist activity and linoleic acid composition.

Inhibition of airway remodeling and inflammation by isoforskolin in PDGF-induced rat ASMCs and OVA-induced rat asthma model

Isoforskolin (ISOF) has been reported to play an important role in many illnesses including respiratory, cardiovascular and ophthalmologic diseases. In our study, we aimed to investigate how ISOF regulates airway remodeling and inflammation in asthma. Based on SO₂-stimulated mouse cough model, we assessed the role of ISOF in cough and secretion of phlegm. Afterwards, platelet derived growth factor (PDGF)-induced primary rat airway smooth muscle cell (ASMC) model and ovalbumin (OVA)-induced rat asthma model were used to continue our following research. Our results showed that ISOF could prolong the cough latent period, reduce the cough times in two minutes, and increase the excretion of red phenol, which suggested the antitussive and expectorant effects of ISOF. Besides, ISOF pretreatment reversed the hypotonicity and cytoskeleton remodeling in PDGF-induced ASMCs, and reduced mucus hypersecretion and collagen overdeposition in OVA-induced rat asthma model, which indicated its inhibition on airway remodeling in vitro and in vivo. Moreover, ISOF reduced the invasion of inflammatory cells into bronchoalveolar lavage fluid (BALF) and lungs, which revealed its inhibitory role in airway inflammation. The down-regulation of transforming growth factor β1 (TGF-β1) and interleukin-1β (IL-1β) upon ISOF treatment might be responsible for its anti-remodeling and anti-inflammation roles. In conclusion, ISOF can reduce cough and sputum, as well as inhibit airway remodeling and inflammation by regulating the expression of TGF-β1 and IL-1β. These data indicate the potency of ISOF in treating asthma and also provide insights into the development of new anti-asthma agent.

Co-inhalation of roflumilast, rather than formoterol, with fluticasone more effectively improves asthma in asthmatic mice

Roflumilast is approved as an add-on therapy for chronic obstructive pulmonary disease. The inflammation in chronic obstructive pulmonary disease is mainly neutrophilic, while in asthma it is mainly eosinophilic, studies addressing role of roflumilast in eosinophilic inflammation are recommended. Also in severe asthma, the dominant inflammatory cells are neutrophils. Thus, roflumilast has a potential off-label use in the treatment of asthma. This study was designed to evaluate the effects of co-inhalation of roflumilast and fluticasone compared to that of formoterol and fluticasone in ovalbumin-sensitized and-challenged BALB/c mice. Besides normal control group, the ovalbumin-asthmatic mice were randomly divided into seven groups (n = 8): positive control, vehicle-treated, and five drug-treated groups. Treatments (µg/kg) were given as 15 min-inhalation once/day for five days as follows: roflumilast (500), formoterol (50), fluticasone (1000), roflumilast + fluticasone (500 + 1000), and formoterol + fluticasone (50 + 1000). Penh values were measured in conscious unrestrained mice using the single-chamber whole-body plethysmography. Airway hyperreactivity to inhaled methacholine was evaluated. Bronchoalveolar lavage fluid was used for the measurements of levels of IL-4, IL-5, TNF-α, OVA-specific IgE, and total and differential white cells. Lung sections were stained with hematoxylin and eosin and periodic acid-Schiff. The asthmatic mice showed significant increases in airway hyperreactivity which were significantly reversed by the combination treatments. The asthmatic mice showed significant increases in levels of IL-4, IL-5, TNF-α, ovalbumin-specific IgE, and total and differential white cells in bronchoalveolar lavage fluid. All treatments (except formoterol) significantly reversed these changes mainly with roflumilast + fluticasone. The asthmatic mice showed severe inflammatory infiltration and goblet cell hyperplasia which were maximally reversed by roflumilast + fluticasone, while minimally reversed by formoterol. In conclusion, co-inhalation of roflumilast + fluticasone more significantly improved inflammation and histopathological changes than co-inhalation of formoterol + fluticasone in ovalumin-asthmatic mice. Further studies are needed to help confirm the potential off-label add-on use of roflumilast in typical and atypical asthma and asthma-chronic obstructive pulmonary disease overlap syndrome. Impact statement Roflumilast, a selective phosphodiesterase-4 inhibitor, was approved for the treatment of chronic obstructive pulmonary disease (COPD). This study showed that co-inhalation of roflumilast and fluticasone significantly decreased airway hyperresponsiveness in ovalumin-asthmatic mice. Also, it more significantly improved inflammation and histopathological changes than co-inhalation of formoterol and fluticasone. The current results showed that inhaled roflumilast reduced counts of eosinophils, neutrophils, and macrophages in bronchoalveolar lavage fluid. Consequently, inhaled roflumilast might be of potential off-label benefit in treatment of eosinophilic and neutrophilic asthma and asthma-COPD overlap syndrome (ACOS). These results could also support other experimental and clinical studies addressing the same issue.

Functional Effects of WNT1-Inducible Signaling Pathway Protein-1 on Bronchial Smooth Muscle Cell Migration and Proliferation in OVA-Induced Airway Remodeling

Upregulation of WISP1 has been demonstrated in lung remodeling. Moreover, it has been recently found that some signaling components of WNT pathway can activate GSK3β signaling to mediate remodeling of airway smooth muscle (ASM) in asthma. Therefore, we hypothesized that WISP1, a signaling molecule downstream of the WNT signaling pathway, is involved in PI3K/GSK3β signaling to mediate ASM remodeling in asthma. Our results showed that WISP1 depletion partly suppressed OVA-induced ASM hypertrophy in vivo. In vitro, WISP1 could induce hBSMC hypertrophy and proliferation, accompanied by upregulation of levels of PI3K, p-Akt, p-GSK3β, and its own expression. TGF-β treatment could increase expression of PI3K, p-Akt, p-GSK3β, and WISP1. SH-5 treatment could partly suppress TGF-β-induced hypertrophy and proliferation of hBSMC, and depress expression of p-GSK3β and WISP1. In conclusion, WISP1 may be a potential inducer of ASM proliferation and hypertrophy in asthma. The pro-remodeling effect of WISP1 is likely due to be involved in PI3K-GSK3β-dependent noncanonical TGF-β signaling.

Elastosis during airway wall remodeling explains multiple co-existing instability patterns

Living structures can undergo morphological changes in response to growth and alterations in microstructural properties in response to remodeling. From a biological perspective, airway wall inflammation and airway elastosis are classical hallmarks of growth and remodeling during chronic lung disease. From a mechanical point of view, growth and remodeling trigger mechanical instabilities that result in inward folding and airway obstruction. While previous analytical and computational studies have focused on identifying the critical parameters at the onset of folding, few have considered the post-buckling behavior. All prior studies assume constant microstructural properties during the folding process; yet, clinical studies now reveal progressive airway elastosis, the degeneration of elastic fibers associated with a gradual stiffening of the inner layer. Here, we explore the influence of temporally evolving material properties on the post-bifurcation behavior of the airway wall. We show that a growing and stiffening inner layer triggers an additional subsequent bifurcation after the first instability occurs. Evolving material stiffnesses provoke failure modes with multiple co-existing wavelengths, associated with the superposition of larger folds evolving on top of the initial smaller folds. This phenomenon is exclusive to material stiffening and conceptually different from the phenomenon of period doubling observed in constant-stiffness growth. Our study suggests that the clinically observed multiple wavelengths in diseased airways are a result of gradual airway wall stiffening. While our evolving material properties are inspired by the clinical phenomenon of airway elastosis, the underlying concept is broadly applicable to other types of remodeling including aneurysm formation or brain folding.

Ovalbumin-induced allergic inflammation lead to structural alterations in mouse model and protective effects of intranasal curcumin: A comparative study

BACKGROUND

Antigen exposure and persistent inflammation leads to structural changes in the asthmatic airways which are collectively termed as "airway remodelling". Presently available asthma medications ameliorate inflammations but are unable to prevent or reverse the airway remodelling process as most of the treatment strategies are only focused on inflammation instead of remodelling.

METHODS

Curcumin, a phytochemical present in the rhizome of Curcuma longa is well known for its anti-inflammatory activity; however, the main drawback is its poor bioavailability which limits its therapeutic approval. So, the effect of nasal curcumin on acute and chronic asthma has been studied where short exposure to ovalbumin (4 days) represents acute phase whereas repeated exposures for longer (twice per week till 5 weeks) represents chronic asthma. Disodium cromoglycate (DSCG, 50mg/kg, i.p.) and dexamethasone (1mg/kg, i.p.) were used as standard drugs in acute and chronic model of asthma respectively.

RESULTS

OVA-induced airway inflammation initiated in acute stage led to remodelling due to persistent inflammation, epithelial and sub epithelial thickening (smooth muscle thickening), extracellular matrix (ECM) deposition, goblet cell hyperplasia and mucus plug formation. Intranasal curcumin is effective in inhibiting airway inflammation and remodelling both by maintaining the structural integrity of lungs in terms of inflammation, airway wall thickening and mucus production.

CONCLUSION

Our findings suggest that curcumin administered through nasal route might prove therapeutically efficient in inhibiting allergic airway inflammations and maintaining structural integrity in the mouse model of allergic asthma. This may lead to the development of curcumin aerosol in near future.

Inhibition of airway inflammation and remodeling by sitagliptin in murine chronic asthma

In this study the role of sitagliptin, dipeptidyl peptidase inhibitor, DPP-4, and dexamethasone in ameliorating inflammation and remodeling of chronic asthma in a mouse model were investigated. Mice sensitized to ovalbumin were chronically challenged with aerosolized antigen for 3days a week continued for 8weeks. During this period animals were treated with sitagliptin or dexamethasone daily. Assessment of inflammatory cell, oxidative markers, total nitrate/nitrite (NOx), interleukin (IL)-13, transforming growth factor-beta1 (TGF-β1) in bronchoalveolar lavage (BAL) and/or lung tissue were done. Also histopathological and immuno-histochemical analysis for lung was carried out. Compared with vehicle alone, treatment with sitagliptin or dexamethasone significantly reduced accumulation of eosinophils and chronic inflammatory cells, subepithelial collagenization, and thickening of the airway epithelium. Also both drug reduced goblet cell hyperplasia, oxidative stress, TGF-β1, IL-13 and epithelial cytoplasmic immunoreactivity for nuclear factor κ-B (NFκ-B). These data indicate that sitagliptin like dexamethasone may play a beneficial role reducing airway inflammation and remodeling in chronic murine model of asthma.

The effect of atorvastatin on lung histopathology in a murine model of chronic asthma

INTRODUCTION

Atorvastatin is a statin group medicine that reduces the level of serum cholesterol; thus it is used to treat hypercholesterolaemia. Independent of the cholesterol-lowering property of statins they also have anti-inflammatory and immunomodulating effects. This study aimed to investigate the effect of atorvastatin on histological changes in the lungs in a murine model of chronic asthma.

MATERIALS AND METHODS

Twenty-eight BALB/c mice in Group I, II, III and IV were divided into four groups. All the mice except the control group (Group I) were sensitised with ovalbumin. Intraperitoneal injection with saline, atorvastatin (10mg/kg), dexametazon (1mg/kg) was administered to Group II, Group III, and Group IV respectively for five consecutive days. Mice were sacrificed 24h after the last drug administration. All the histological properties of lung tissue samples from all groups were evaluated with light and electron microscopy. In addition, IL-4 and IL-5 levels of the lung tissue were measured.

RESULTS

When Group II and Group III (atorvastatin) were compared, thicknesses of basement membrane and subepithelial smooth muscle layer, height of epithelium, number of mast and goblet cells were significantly lower in Group III. In comparing Group III (atorvastatin) and Group IV (dexamethasone), all the improvements in histological parameters were similar. In addition, the IL-4 and IL-5 levels of the lung tissue were significantly lower in atorvastatin group (Group III) compared to placebo-treated group.

CONCLUSION

Atorvastatin had a beneficial effect on histological changes in a chronic murine model of asthma.

In vivo micro-CT assessment of airway remodeling in a flexible OVA-sensitized murine model of asthma

Airway remodeling is a major pathological feature of asthma. Up to now, its quantification still requires invasive methods. In this study, we aimed at determining whether in vivo micro-computed tomography (micro-CT) is able to demonstrate allergen-induced airway remodeling in a flexible mouse model of asthma. Sixty Balb/c mice were challenged intranasally with ovalbumin or saline at 3 different endpoints (Days 35, 75, and 110). All mice underwent plethysmography at baseline and just prior to respiratory-gated micro-CT. Mice were then sacrificed to assess bronchoalveolar lavage and lung histology. From micro-CT images (voxel size = 46×46×46 µm), the numerical values of total lung attenuation, peribronchial attenuation (PBA), and PBA normalized by total lung attenuation were extracted. Each parameter was compared between OVA and control mice and correlation coefficients were calculated between micro-CT and histological data. As compared to control animals, ovalbumin-sensitized mice exhibited inflammation alone (Day 35), remodeling alone (Day 110) or both inflammation and remodeling (Day 75). Normalized PBA was significantly greater in mice exhibiting bronchial remodeling either alone or in combination with inflammation. Normalized PBA correlated with various remodeling markers such as bronchial smooth muscle size or peribronchial fibrosis. These findings suggest that micro-CT may help monitor remodeling non-invasively in asthmatic mice when testing new drugs targeting airway remodeling in pre-clinical studies.

Spirometric parameters and levels of interferon gamma and IL-5 in induced sputum from patients with allergic rhinitis or asthma

BACKGROUND

This study was designed to analyze spirometric parameters and cytokine (interferon [IFN] gamma and IL-5) levels in induced sputum from patients with asthma or allergic rhinitis (AR) and nonatopic subjects.

METHODS

Thirty-three subjects aged 18-60 years were enrolled in the present study. Eight patients had asthma without AR symptoms, 16 had AR without asthma symptoms or history, and both groups had positive skin-prick test (SPT) to aeroallergens. The nine remaining subjects were healthy nonatopic subjects with negative SPT to aeroallergens. Spirometry was performed by evaluating the forced vital capacity (FVC), forced expiratory volume in the 1st second (FEV(1)), and forced expiratory flow between 25 and 75% (FEF(25-75)) of FVC before and after bronchodilator use. Induced sputum samples were also collected for measuring cytokine (IFN-gamma and IL-5) levels by enzyme-linked immunosorbent assay.

RESULTS

Significant pre- and postbronchodilator change was observed only for FEV(1) with higher variation values in asthmatic subjects compared with patients with AR (p < 0.05) and nonatopic subjects (p < 0.01). There was no significant difference in pre- and postbronchodilator spirometric parameters among the three groups, although asthmatic patients showed lower prebronchodilator FEF(25-75) values (p = 0.065). IL-5 levels were higher in induced sputum from patients with asthma and AR compared with nonatopic subjects (p = 0.020 and p = 0.032, respectively), but IFN-gamma levels showed no significant difference between the groups.

CONCLUSION

Spirometric measurements were not able to show any occurrence of bronchial constriction in patients with AR, but predominant IL-5 levels in induced sputum from these patients reinforce the role of Th2-type immune response in lower respiratory airways that could contribute to the concept of "one airway, one disease."

A novel prostacyclin agonist protects against airway hyperresponsiveness and remodeling in mice

Airway remodeling in bronchial asthma results from chronic, persistent airway inflammation. The effects of the reversal of airway remodeling by drug interventions remain to be elucidated. We investigated the effects of ONO-1301, a novel prostacyclin agonist with thromboxane inhibitory activity, on the prevention and reversibility of airway remodeling in an experimental chronic asthma model. Mice sensitized and challenged to ovalbumin (OVA) three times a week for 5 consecutive weeks were administered ONO-1301 or vehicle twice a day from the fourth week of OVA challenges. Twenty-four hours after the final OVA challenge, airway hyperresponsiveness (AHR) was assessed, and bronchoalveolar lavage was performed. Lung specimens were excised for staining to detect goblet-cell metaplasia, airway smooth muscle, and submucosal fibrosis. Mice administered ONO-1301 showed limited increases in AHR compared with mice administered the vehicle. The histological findings of airway remodeling were improved in ONO-1301-treated mice compared with vehicle-treated mice. Presumably, these therapeutic effects of ONO-1301 are attributable to the up-regulation of production of hepatocyte growth factor (HGF) in lung tissue, because the neutralization of HGF by antibodies prevented the effects of ONO-1301 on AHR and airway remodeling. Mice administered ONO-1301 showed similar levels of AHR and airway remodeling as mice administered montelukast, a cysteinyl-leukotriene-1 receptor antagonist, and lower levels were observed in mice administered dexamethasone. These data suggest that ONO-1301 exerts the effect of reversing airway remodeling, at least in part through an elevation of HGF in the lungs, and may be effective as an anti-remodeling drug in the treatment of asthma.

Beneficial effects of erythropoietin on airway histology in a murine model of chronic asthma

BACKGROUND

Erythropoietin (EPO) is originally defined as a haematopoietic growth factor, but also has anti-inflammatory effects through cytokine modulation. This anti-inflammatory and cytokine modulating effect has not been investigated for the treatment of asthma. We aimed to determine the beneficial effects of erythropoietin on lung histology of murine model of chronic asthma.

METHODS

Thirty-five BALB/c mice were divided into five groups: I; II; III; IV; and control group. All groups except control group were sensitised and challenged with ovalbumin. Mice with experimentally induced asthma in Group I received saline; Group II EPO 500IU/kg; Group III EPO 1000IU/kg; and Group IV dexamethasone 1mg/kg intraperitoneally once a day in the last five days of the challenge period. Animals were sacrificed 24h after the last administration of study drugs. Histological findings of airways were evaluated by light and electron microscopic examination.

RESULTS

All histological parameters of asthma in the group treated with a high dose of EPO (Group III) were significantly ameliorated when compared with the group treated with saline (Group I). In comparison to the group treated with low dose of EPO (Group II) and the group treated with saline (Group I), basement membrane thicknesses and number of mast cells were significantly lower in the group treated with low dose of EPO (Group II). All histological parameters were similar between the group treated with high dose of EPO (Group III) and the group treated with dexamethasone (Group IV) except higher number of mast cells in the group treated with high dose of EPO (Group III). Additionally, the results of all histological parameters in the group treated with high dose of EPO (Group III) were significantly better when compared with the group treated with low dose of EPO (Group II).

CONCLUSIONS

We found that EPO ameliorated histological changes of chronic murine model of asthma. Further studies are needed to evaluate the efficacy of EPO in the treatment of asthma.

Treatment of asthma and food allergy with herbal interventions from traditional chinese medicine

Prevalence of asthma and allergy has increased over the past 2-3 decades in Westernized countries. Despite increased understanding of the pathogenesis of asthma and allergic diseases, control of severe asthma is still difficult. Asthma is also associated with a high prevalence of anxiety, particularly in adolescents. There is no effective treatment for food allergy. Food allergy is often associated with severe and recalcitrant eczema. Novel approaches for treatment of asthma and food allergy and comorbid conditions are urgently needed. Traditional Chinese medicine, used in Asia for centuries, is beginning to play a role in Western healthcare. There is increasing scientific evidence supporting the use of traditional Chinese medicine for asthma treatment. Since 2005, several controlled clinical studies of "antiasthma" herbal remedies have been published. Among the herbal medicines, antiasthma herbal medicine intervention is the only antiasthma traditional Chinese medicine product that is a Food and Drug Administration investigational new drug that has entered clinical trials in the United States. Research into the effects and mechanisms of action of antiasthma herbal medicine intervention in animal models is actively being pursued. Research on traditional Chinese medicine herbal medicines for treating food allergy is rare. The herbal intervention Food Allergy Herbal Formula-2 is the only Food and Drug Administration botanical investigational new drug under investigation as a multiple food allergy therapy. This review article discusses promising traditional Chinese medicine interventions for asthma, food allergy, and comorbid conditions, and explores their possible mechanisms of action.

Anti-asthmatic and anti-anaphylactic activities of Blatta orientalis mother tincture

OBJECTIVES

To study the anti-asthmatic and anti-anaphylactic activities of Blatta orientalis mother tincture (B. orientalis MT), a homeopathic medicine, in experimental animal models.

METHODS

The anti-asthmatic activity of B. orientalis MT was studied in the bronchial hyperactivity models, acetylcholine and histamine induced bronchospasm, in guinea pigs. Anti-anaphylactic activity was tested by active and passive anaphylaxis models in rats, anti-eosinophilic activity was tested by milk-induced eosinophilia in mice.

RESULTS

Significant protection against acetylcholine and histamine aerosol-induced bronchospasm in B. orientalis MT treated guinea pigs was seen. In active and passive anaphylaxis albino rat models significant reduction in mesenteric mast cells degranulation, serum IgE level and eosinophil cell count was observed in the B. orientalis MT treated rat group when compared with the sensitized control rat group.

CONCLUSION

These results reveal broad activity of B. orientalis MT. It may have nonselective anti-asthmatic activity. The anti-anaphylactic activity of B. orientalis MT may be due to mast cell stabilization, suppression of IgE and eosinophil cell count.

Developing a tissue-engineered model of the human bronchiole

Scientists are always looking for new tools to better mimic human anatomy and physiology, especially to study chronic respiratory disease. Airway remodelling is a predominant feature in asthma and occurs in conjunction with chronic airway inflammation. Both the inflammatory and repair processes alter the airway wall which is marked by anatomical, physiological and functional changes. A tissue-engineered model of bronchiole remodelling presents a novel approach to investigating the initiation and progression of airway remodelling. By developing a unique bioreactor system, cylindrical-shaped bronchioles constructed from well-characterized human lung primary cells have been engineered and examined with a much greater control over experimental variables. We have grown human bronchioles composed of fibroblasts, airway smooth muscle cells, small airway epithelial cells and extracellular matrices. The various cell types are in close proximity to one another for cell-cell signalling and matrix interactions. The cylindrical geometry of the tissue applies radial distension for mechanotransduction and the air interface provides a natural environment for the epithelial cells. Optimal cell density, extracellular matrix concentration and media composition were determined. Immunohistochemistry verified bronchiole phenotypic stability. Quiescence was gauged by protein expression which verified a change in phenotype after the initial fabrication stage and implementation of the air interface. A fabrication timeline was devised for repeatable bronchiole fabrication and to understand tissue contraction and cell-seeding duration. The stability of the bronchiole structures and their cellular composition lends these bronchioles to study cell-cell interactions and remodelling events while maintaining in vivo geometrical dimensions and relationships.

Dental caries status and salivary properties of asthmatic children and adolescents

AIMS

This study aimed to investigate the dental caries status and salivary properties in 3- to 15-year-old children/adolescents.

METHODS

The sample was split in two groups: asthma group (AG), composed of 65 patients who attended Public Health Service; asthma-free group (AFG), composed of 65 nonasthmatic children/adolescents recruited in two public schools. Stimulated salivary samples were collected for 3 min. Buffering capacity and pH were ascertained in each salivary sample. A single trained and calibrated examiner (kappa = 0.98) performed the dental caries examination according to WHO criteria.

RESULTS

The AFG showed salivary flow rate (1.10 ± 0.63 mL/min) higher (P = 0.002) than AG (0.80 ± 0.50 mL/min). An inverse relationship was observed between asthma severity and salivary flow rate (Phi coefficient, rφ: 0.79, P = 0.0001). Children with moderate or severe asthma showed an increased risk for reduced salivary flow rate (OR: 17.15, P < 0.001). No association was observed between drug use frequency (P > 0.05) and drug type (P > 0.05) with salivary flow rate. Buffering capacity was similar in both groups. No significant differences were encountered in dental caries experience between AFG and AG groups.

CONCLUSIONS

Although asthma can cause reduction in flow rate, the illness did not seem to influence dental caries experience in children with access to proper dental care.

Mesenchymal stem cells ameliorate the histopathological changes in a murine model of chronic asthma

Asthma therapies are effective in reducing inflammation but airway remodeling is poorly responsive to these agents. New therapeutic options that have fewer side effects and reverse chronic changes in the lungs are essential. Mesenchymal stem cells (MSCs) are promising for the development of novel therapies in regenerative medicine. This study aimed to examine the efficacy of MSCs on lung histopathology in a murine model of chronic asthma. BALB/c mice were divided into four groups: Group 1 (control group, n=6), Group 2 (ovalbumin induced asthma only, n=10), Group 3 (ovalbumin induced asthma + MSCs, n=10), and Group 4 (MSCs only, n=10). Histological findings (basement membrane, epithelium, subepithelial smooth muscle thickness, numbers of goblet and mast cells) of the airways and MSC migration were evaluated by light, electron, and confocal microscopes. In Group 3, all early histopathological changes except epithelial thickness and all of the chronic changes were significantly ameliorated when compared with Group 2. Evaluation with confocal microscopy showed that no noteworthy amount of MSCs were present in the lung tissues of Group 4 while significant amount of MSCs was detected in Group 3. Serum NO levels in Group 3, were significantly lower than Group 2. The results of this study revealed that MSCs migrated to lung tissue and ameliorated bronchial asthma in murine model. Further studies are needed to evaluate the efficacy of MSCs for the treatment of asthma.

Analysis of body posture in children with mild to moderate asthma

The mechanical alterations related to the excessive use of accessory respiratory muscles and the mouth breathing observed in children with asthma may lead to the development of alterations in head posture, shoulders, thoracic region and, consequently, in alterations of body posture. The purpose of this study was to assess body posture changes of children with asthma compared to a non-asthmatic control group matched for gender, age, weight, and height. Thirty children with asthma and 30 non-asthmatic children aged 7 to 12 years were enrolled in this study. Digital photographic records were obtained for analysis of the body posture of the children by computed photogrammetry. The intraclass correlation coefficient and Student's t test (p < 0.05) were used for statistical analysis. There were no significant differences between groups for the angles analyzed, except for the knee flexor angle. These results demonstrate that children with asthma did not present postural alterations compared to non-asthmatic controls since the only angle for which there was a significant difference between groups showed weak reproducibility. The findings of this study do not support the notion that children with asthma present alterations in body posture.

Interleukin-13 acts as an apoptotic effector on lung epithelial cells and induces pro-fibrotic gene expression in lung fibroblasts

BACKGROUND

IL-13 promotes acute allergic asthma and is discussed to play a role in late asthmatic features such as fibrotic processes and airway remodelling. The contributions of IL-13-mediated mechanisms to subepithelial events related to fibrosis are not yet settled.

OBJECTIVE

We investigated the impact of IL-13 on lung epithelial cells as apoptotic effector and on lung fibroblasts as inducer of pro-fibrotic gene expression.

METHODS

Using the two lung epithelial cell lines A549 and BEAS-2B as well as primary lung epithelial cells, we investigated the capability of IL-13 to induce apoptosis by both flow-cytometry and ELISA. The ability of IL-13 to increase the expression of pro-fibrotic genes and to exert influence on the expression of its own receptor was investigated by real-time quantitative PCR measurement of mRNAs encoding collagen I, collagen III, basic fibroblast growth factor (bFGF), alpha-smooth muscle actin (alpha-SMA) and the IL-13 receptor alpha1 (IL-13Ralpha1) chain in human primary lung fibroblasts. The specificity of IL-13-mediated cellular responses was confirmed by means of an inhibitory monoclonal antibody directed to the IL-13 receptor.

RESULTS

IL-13 induces apoptosis in lung epithelial cell lines as well as in primary lung epithelial cells. Furthermore, IL-13 increases the expression of mRNA for alpha-SMA and collagen III, but not for bFGF in human primary lung fibroblasts. The susceptibility of lung fibroblasts to IL-13-induced up-regulation of pro-fibrotic genes is associated with the regulation of IL-13 receptor expression. IL-13-dependent fibrosis-associated effects could be inhibited by antibody-mediated blockade of the IL-13Ralpha1 subunit.

CONCLUSION

Our findings indicate a function of IL-13 as a mediator in fibrotic processes leading to loss of functional airway tissue in asthma. They also highlight the therapeutic potential of specifically targeting the interaction between IL-13 and its receptor.

Understanding the mechanisms of viral induced asthma: new therapeutic directions

Asthma is a common and debilitating disease that has substantially increased in prevalence in Western Societies in the last 2 decades. Respiratory tract infections by respiratory syncytial virus (RSV) and rhinovirus (RV) are widely implicated as common causes of the induction and exacerbation of asthma. These infections in early life are associated with the induction of wheeze that may progress to the development of asthma. Infections may also promote airway inflammation and enhance T helper type 2 lymphocyte (Th2 cell) responses that result in exacerbations of established asthma. The mechanisms of how RSV and RV induce and exacerbate asthma are currently being elucidated by clinical studies, in vitro work with human cells and animal models of disease. This research has led to many potential therapeutic strategies and, although none are yet part of clinical practise, they show much promise for the prevention and treatment of viral disease and subsequent asthma.

Risk factors related to fixed airway obstruction in patients with asthma after antiasthma treatment

BACKGROUND

There are many unanswered questions about the role of airway remodeling in asthma.

OBJECTIVE

To evaluate the physiologic factors related to airway remodeling after antiasthma drug treatment for 1 year.

METHODS

We gave 582 patients with asthma long-term control medication for 1 year according to the severity of their asthma. Airway remodeling was defined using forced expiratory volume in 1 second/forced vital capacity and a predicted forced expiratory volume in 1 second of less than 75% after antiasthma treatment.

RESULTS

Of the 582 patients, 49 (8.4%) had airway remodeling. Severe asthma resulted in more airway remodeling than mild-to-moderate asthma. Asthmatic patients with airway remodeling were significantly older and had a longer duration of asthma. Asthmatic patients with airway remodeling had more emphysema on high-resolution computed tomography, a higher rate of near-fatal asthma attacks, a lower percentage of sputum eosinophils, a lower atopy frequency, a greater response to short-acting bronchodilators, and a lower body mass index (BMI) than those without airway remodeling. Age, asthma duration, and BMI were important discriminators of airway remodeling.

CONCLUSION

Nonatopy, asthma duration, emphysema on high-resolution computed tomography, sputum eosinophils, age, and BMI before antiasthma treatment are important factors related to airway remodeling in patients with asthma.

Brown Norway rat asthma model of diphenylmethane-4,4'-diisocyanate (MDI): impact of vehicle for topical induction

The development of this Brown Norway (BN) rat asthma model was focused on the duplication of at least some hallmarks of human diisocyanate asthma using the skin as the initial priming route of exposure. Equal total doses of polymeric diphenylmethane-diisocyanate (MDI) were applied to similar surface areas either dissolved in di-n-octyl sebacic acid ester (20%) (SEBA), in acetone:olive oil (20%) (AOO) or undiluted. The elicitation of respiratory allergy utilized four repeated nose-only inhalation challenges of 30 min with 39 mg/m(3) MDI-aerosol approximately every 2 weeks. Emphasis was directed towards the analysis of respiratory responses delayed in onset. Endpoints suggestive of an allergic inflammatory response were examined by bronchoalveolar lavage (BAL) 1 day after the last inhalation challenge and comprised protein, LDH, cytodifferentiation of BAL cells, MCP-1, and some Th1 and Th2 cytokines. MCP-1 and cytokines were comparatively determined in three compartments: BAL fluid, BAL cells, and lung-associated lymph nodes (LALN). In all groups sensitized topically to MDI typical delayed-onset respiratory responses occurred. The lung and LALN weights, BAL-protein and -LDH were significantly increased as compared to the naïve control group challenged identically. There was compelling evidence of a neutrophilic rather than an eosinophilic inflammatory response. The patterns of interleukin (IL) IL-1alpha, TNF-alpha, IFN-gamma, GM-CSF, and IL-4 differed appreciably from one compartment to another and were essentially maximal in BAL cells. In contrast, MCP-1 was increased to the same extent in all compartments measured. Collectively, changes were slightly, although consistently more pronounced when using SEBA as vehicle when compared with the vehicle AOO or undiluted MDI. Notable was a discordance of cytokine profiles and respiratory responses. In conclusion, the priming potency of topically administered MDI and subsequent asthma-like responses following repeated inhalation exposures appear to be dependent on multiple factors, one of them appears to be associated with the type of matrix used to dissolve MDI. This animal model provides a versatile and robust experimental tool to evaluate and assess at least some features of MDI-related asthma.

Angiogenesis is induced by airway smooth muscle strain

Angiogenesis is an important feature of airway remodeling in both chronic asthma and chronic obstructive pulmonary disease (COPD). Airways in those conditions are exposed to excessive mechanical strain during periods of acute exacerbations. We recently reported that mechanical strain of human airway smooth muscle (HASM) led to an increase in their proliferation and migration. Sustained growth in airway smooth muscle in vivo requires an increase in the nutritional supply to these muscles, hence angiogenesis. In this study, we examined the hypothesis that cyclic mechanical strain of HASM produces factors promoting angiogenic events in the surrounding vascular endothelial cells. Our results show: 1) a significant increase in human lung microvascular endothelial cell (HMVEC-L) proliferation, migration, and tube formation following incubation in conditioned media (CM) from HASM cells exposed to mechanical strain; 2) mechanical strain of HASM cells induced VEGF expression and release; 3) VEGF neutralizing antibodies inhibited the proliferation, migration, and tube formations of HMVEC-L induced by the strained airway smooth muscle CM; 4) mechanical strain of HASM induced a significant increase in hypoxia-inducible factor-1alpha (HIF-1alpha) mRNA and protein, a transcription factor required for VEGF gene transcription; and 5) mechanical strain of HASM induced HIF-1alpha/VEGF through dual phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) and ERK pathways. In conclusion, exposing HASM cells to mechanical strain induces signal transduction pathway through PI3K/Akt/mTOR and ERK pathways that lead to an increase in HIF-1alpha, a transcription factor required for VEGF expression. VEGF release by mechanical strain of HASM may contribute to the angiogenesis seen with repeated exacerbation of asthma and COPD.

Extracellular matrix remodeling by dynamic strain in a three-dimensional tissue-engineered human airway wall model

Airway wall remodeling is a hallmark of asthma, characterized by subepithelial thickening and extracellular matrix (ECM) remodeling. Mechanical stress due to hyperresponsive smooth muscle cells may contribute to this remodeling, but its relevance in a three-dimensional environment (where the ECM plays an important role in modulating stresses felt by cells) is unclear. To characterize the effects of dynamic compression in ECM remodeling in a physiologically relevant three-dimensional environment, a tissue-engineered human airway wall model with differentiated bronchial epithelial cells atop a collagen gel containing lung fibroblasts was used. Lateral compressive strain of 10 or 30% at 1 or 60 cycles per hour was applied using a novel straining device. ECM remodeling was assessed by immunohistochemistry and zymography. Dynamic strain, particularly at the lower magnitude, induced airway wall remodeling, as indicated by increased deposition of types III and IV collagen and increased secretion of matrix metalloproteinase-2 and -9. These changes paralleled increased myofibroblast differentiation and were fibroblast-dependent. Furthermore, the spatial pattern of type III collagen deposition correlated with that of myofibroblasts; both were concentrated near the epithelium and decreased diffusely away from the surface, indicating some epithelial control of the remodeling response. Thus, in a physiologically relevant three-dimensional model of the bronchial wall, dynamic compressive strain induced tissue remodeling that mimics many features of remodeling seen in asthma, in the absence of inflammation and dependent on epithelial-fibroblast signaling.

Suppressive effect of verproside isolated from Pseudolysimachion longifolium on airway inflammation in a mouse model of allergic asthma

Allergic inflammation of the airways has a critical role in asthma development. We investigated a suppressive effect of verproside (3,4-dihydroxy catalpol) isolated from the extract of Pseudolysimachion longifolium on asthmatic parameters--such as immunoglobulin E (IgE) level, cytokine release, eosinophilia, airway hyperresponsiveness and mucus hypersecretion--in an OVA-sensitized/challenged mouse model. Verproside significantly inhibited the increase of total IgE and the cytokines IL-4 and IL-13 in plasma and bronchoalveolar lavage fluid, and also effectively suppressed airway hyperresponsiveness, eosinophilia and mucus hypersecretion in OVA-induced asthmatic mice. The efficacy of verproside was comparable to montelukast, an anti-asthmatic drug that is currently available. These results suggest that verproside could be a major marker in herbal medicines that are used for asthma treatment, and could also act as a lead for anti-asthmatic drugs.

Enhanced expression of urocortin in lung tissues of rats with allergic asthma

Bronchial asthma is defined as a chronic airway inflammatory disease characterized by sustained activation of many inflammatory cells including mast cells. Urocortin (UCN) is synthesized and secreted by human mast cells and activated mast cells release more UCN. On the other hand, UCN can induce mast cell degranulation and generation of many proinflammatory factors. The purpose of this study was to examine the expression profile of UCN in rat lung with allergic asthma. Twenty-four male Sprague-Dawley rats were allocated to normal control, asthma model, and dexamethasone group, respectively. Animals were actively sensitized by subcutaneous injection of ovalbumin (OVA) and challenged by an aerosol of 1% OVA 2 weeks after sensitization. Both UCN mRNA and peptide were expressed in normal rat lungs. Rats in asthma model group developed severe infiltration of inflammatory cells and inflammation in airway, together with a significantly up-regulated expression of urocortin mRNA detected by semi-quantitative reverse transcriptase-polymerase chain reaction and peptide measured both by immunohistochemistry and Western blot analysis. In contrast, treatment with dexamethasone resulted in markedly ameliorated airway inflammation and alleviated airway inflammatory cell infiltration, coupled with a significantly decreased urocortin expression. Regression analysis revealed a positive correlation between urocortin expression and the number of inflammatory cells in bronchoalveolar lavage fluid (P<0.01). In the present study, we first demonstrated that UCN was locally produced in rat lungs and expressed more pronouncedly in inflammatory airway of asthmatic rats. Glucocorticoid treatment markedly reduced the production of UCN in asthmatic lung tissues. Peripherally produced UCN in lung may act as a possible local autocrine and paracrine immune-inflammatory mediator in inflammatory airway of allergic asthma rats.

Antagonistic effects of nobiletin, a polymethoxyflavonoid, on eosinophilic airway inflammation of asthmatic rats and relevant mechanisms

Eosinophils are known to be the important effector cells in asthmatic airway inflammation. The purpose of this study was to investigate the effects of nobiletin, a polymethoxyflavonoid, on eosinophilic airway inflammation of asthmatic rats, and explore its possible mechanisms. Animals were actively sensitized by subcutaneous injection of ovalbumin (OVA). The inflammation in lung tissues of asthmatic rats was observed by hematoxylin and eosin (HE) staining. The eosinophils in blood and BALF were separated by Percoll density gradient centrifugation and counted under microscope. The level of Eotaxin was detected by enzyme-linked immunosorbent assay (ELISA). In addition, the apoptosis of eosinophils was labeled by TdT-mediated dUTP nick end labeling (TUNEL) technique, the semi-quantitative detection for Fas mRNA expression of eosinophils was performed by reverse transcription-polymerase chain reaction (RT-PCR). The airway inflammation of asthmatic rats pretreated with nobiletin was obviously alleviated. Nobiletin (1.5 and 5.0 mg/kg given intraperitoneally) significantly reduced OVA-induced increases in eosinophils, remarkably lowered the level of Eotaxin in blood and broncho-alveolar lavage fluid (BALF) of asthmatic rats. On the other hand, semi-quantitative RT-PCR analysis for Fas of eosinophils from OVA aerosol-challenged sensitized rats showed that Fas mRNA expression of eosinophils was obviously enhanced by nobiletin. Meanwhile, the apoptosis index of cultured eosinophils was significantly elevated after treatment with different doses of nobiletin. These results indicated that nobiletin could inhibit the eosinophilic airway inflammation. Lowering the levels of Eotaxin, relieving airway infiltration of eosinophils and promoting apoptosis of eosinophils by enhancing expression of Fas mRNA may be important mechanisms for nobiletin to antagonize eosinophilic airway inflammation of asthmatic rats.

Anti-IL-13 monoclonal antibody inhibits airway hyperresponsiveness, inflammation and airway remodeling

Asthma is a chronic inflammatory disease characterized by reversible bronchial constriction, pulmonary inflammation and airway remodeling. Current standard therapies for asthma provide symptomatic control but fail to target the underlying disease pathology. Furthermore, no therapeutic agent is effective in preventing airway remodeling. Interleukin 13 (IL-13) is a pleiotropic cytokine produced mainly by T cells. A substantial amount of evidence suggests that IL-13 plays a critical role in the pathogenesis of asthma. Therefore, a neutralizing anti-IL-13 monoclonal antibody could provide therapeutic benefits to asthmatic patients. To test the concept we have generated a neutralizing rat anti-mouse IL-13 monoclonal antibody, and evaluated its effects in a chronic mouse model of asthma. Chronic asthma-like response was induced in ovalbumin (OVA) sensitized mice by repeated intranasal OVA challenges. After weeks of challenge, mice developed airway hyperresponsiveness (AHR) to methacholine stimulation, severe airway inflammation, hyper mucus production, and subepithelial fibrosis. When given at the time of each intranasal OVA challenge, anti-IL-13 antibody significantly suppressed AHR, eosinophil infiltration, proinflammatory cytokine/chemokine production, serum IgE, and most interestingly, airway remodeling. Taken together, these results strongly suggest that a neutralizing anti-human IL-13 monoclonal antibody could be an effective therapeutic agent for asthma.

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.

Expression of growth factors by airway epithelial cells in a model of chronic asthma: regulation and relationship to subepithelial fibrosis

BACKGROUND

Growth factors produced by airway epithelial cells may be important in the pathogenesis of subepithelial fibrosis, a distinctive lesion of chronic human asthma.

OBJECTIVE

To examine the relationship between the development of subepithelial fibrosis and the expression of transforming growth factor-beta 1 (TGF-beta 1) and ligands for the epidermal growth factor receptor.

METHODS

BALB/c mice sensitized to ovalbumin were chronically challenged by inhalation of low levels of antigen, leading to development of subepithelial fibrosis and other changes of airway wall remodelling. Growth factor expression was assessed by immunohistochemistry and enzyme immunoassay.

RESULTS

Allergic sensitization directly correlated with airway epithelial expression of both the cleaved, potentially biologically active form of TGF-beta 1 and of amphiregulin in response to allergen challenge. Accumulation of TGF-beta 1 was related to remodelling of the airway wall in chronic asthma, whereas expression of amphiregulin did not exhibit a similar relationship. Production of epithelial cell-derived TGF-beta 1 appeared to be regulated by IL-13, while both IL-13 and CD4(+) T cells regulated accumulation of TGF-beta 1. In contrast to results reported in high-level exposure models of airway fibrosis, eosinophils did not appear to be a significant source of TGF-beta 1.

CONCLUSION

Airway epithelial cell-derived TGF-beta 1 has a potentially crucial role in the development of airway wall remodelling in asthma. Immunological mechanisms may regulate the release and accumulation of TGF-beta 1.

Inhibition of inflammation and remodeling by roflumilast and dexamethasone in murine chronic asthma

Phosphodiesterase (PDE) inhibitors have potential as alternatives or adjuncts to glucocorticoid therapy in asthma. We compared roflumilast (a selective PDE4 inhibitor) with pentoxifylline (a nonselective inhibitor) and dexamethasone in ameliorating the lesions of chronic asthma in a mouse model. BALB/c mice sensitized to ovalbumin were chronically challenged with aerosolized antigen for 6 weeks. During weeks 5 and 6, groups of animals were treated with roflumilast or dexamethasone by daily gavage or with pentoxifylline by daily intraperitoneal injection. Airway hyper-reactivity (AHR) was evaluated by whole-body plethysmography and airway lesions by histomorphometry and immunohistochemistry. Compared with vehicle alone, treatment with roflumilast or dexamethasone significantly reduced accumulation of eosinophils and chronic inflammatory cells, subepithelial collagenization, and thickening of the airway epithelium. Dexamethasone also reduced goblet cell hyperplasia/metaplasia, subepithelial accumulation of transforming growth factor-beta1, and epithelial cytoplasmic immunoreactivity for nuclear factor-kappaB. Treatment with pentoxifylline inhibited only eosinophil recruitment and epithelial thickening. Roflumilast and dexamethasone slightly decreased AHR, whereas this was significantly reduced by pentoxifylline. Thus, in this model of chronic asthma, both roflumilast and dexamethasone were potent inhibitors of airway inflammation and remodeling. Roflumilast did not diminish accumulation of transforming growth factor-beta1, suggesting that it might affect remodeling by mechanisms distinct from glucocorticoids.

Dissociation of T helper type 2 cytokine-dependent airway lesions from signal transducer and activator of transcription 6 signalling in experimental chronic asthma

BACKGROUND

Type 2 T helper lymphocytes (Th2 cells) and their cytokine products are important in the pathogenesis of asthma.

OBJECTIVE

To examine the contribution of the signal transducer and activator of transcription (STAT) 6 pathway, involved in Th2 cytokine signalling, to the development of lesions of chronic asthma.

METHODS

BALB/c mice sensitized to ovalbumin were chronically challenged by inhalational of low mass concentrations of antigen for 6 weeks. Airway lesions in wild-type mice were compared with those in STAT6-deficient mice and in IL-4/13 double-deficient mice by histomorphometry and immunohistochemistry. Airway responses to methacholine were evaluated by whole-body plethysmography. Cytokine production by peribronchial lymph node cells was quantified by enzyme immunoassay.

RESULTS

STAT6-/- mice developed a variety of airway lesions that were at least equivalent to those in wild-type mice, including accumulation of intraepithelial eosinophils and of chronic inflammatory cells in the lamina propria, subepithelial fibrosis and epithelial thickening. In addition, STAT6-/- mice exhibited exaggerated airway hyper-reactivity (AHR) compared to wild-type animals. This was despite a shift from a Th2 to a Th1 pattern of immunoglobulin production by plasma cells in the inflammatory infiltrate and diminished mucous cell hyperplasia/metaplasia, together with increased production of IFN-gamma by peribronchial lymph node cells, consistent with absence of signalling via the STAT6 pathway. In contrast, gene-targeted IL-4/13-/- mice exhibited markedly diminished eosinophil recruitment and airway remodelling, as well as absence of AHR.

CONCLUSIONS

In this model, the effects of STAT6 deficiency were in marked contrast to the suppression of inflammation and AHR described in models of allergic bronchopulmonary inflammation. These results, which provide evidence of STAT6-independent AHR in an inhalational challenge model of chronic asthma, emphasize the critical effector roles of IL-4 and IL-13, as well as the need to use appropriate models to understand cytokine signalling pathways that may be potential therapeutic targets in asthma.

Antiinflammatory effects of genistein, a tyrosine kinase inhibitor, on a guinea pig model of asthma

Protein tyrosine kinase signaling cascade plays a pivotal role in the activation of inflammatory cells. The purpose of this study was to investigate the effects of genistein, a broad-spectrum protein tyrosine kinase inhibitor, on airway inflammation in an in vivo guinea pig model of asthma. Guinea pigs were actively sensitized by intraperitoneal injections of ovalbumin. Aerosolized ovalbumin induced acute bronchoconstriction in conscious animals in a dose-dependent manner. Genistein (15 mg/kg given intraperitoneally) markedly inhibited ovalbumin-induced, but not histamine- and methacholine-induced, acute bronchoconstriction. In addition, genistein significantly reduced ovalbumin-induced increases in total cell counts and eosinophils recovered in bronchoalveolar lavage fluid, airway eosinophilia, and eosinophil peroxidase activity in cell-free bronchoalveolar lavage fluid and markedly attenuated ovalbumin-induced airway hyperresponsiveness to inhaled methacholine. Immunoblot analysis of lung lysates isolated from genistein-pretreated animals showed that epidermal growth factor-induced tyrosine phosphorylation in lung tissues was inhibited by genistein. These results implicate that inhibition of tyrosine kinase signaling cascade may have therapeutic potential for allergic airway inflammation.

New asthma targets: recent clinical and preclinical advances

Current asthma therapy is directed at the relief of chronic inflammation or improving lung function through bronchodilation. These approaches treat the overt symptoms of asthma but do not approach underlying causes of the disease. Such therapies have limited efficacy and for a number of patients the disease remains poorly controlled. The short-term future of asthma therapy will probably focus on the treatment of multiple symptoms to provide improved lung function. Long-term approaches to asthma will have to focus on modulation of the mechanisms that are the underlying causes of the various asthmatic pathophysiologies. These targets include a number of TH2-type T-cell-generated cytokines and chemokines, G-protein-coupled receptors, TH2-related transcription factors, neurotrophins and adhesion molecules. Additional new targets and understanding of asthma may also arise from genetic analysis.