Effect of a long-acting beta2-agonist over three months on airway wall vascular remodeling in asthma

Airway Remodeling in Asthma: Mechanisms, Diagnosis, Treatment, and Future Directions

Airway remodeling (AR) with chronic inflammation, are key features in asthma pathogenesis. AR characterized by structural changes in the bronchial wall is associated with a specific asthma phenotype with poor clinical outcomes, impaired lung function and reduced treatment response. Most studies focus on the role of inflammation, while understanding the mechanisms driving AR is crucial for developing disease-modifying therapeutic strategies. This review paper summarizes current knowledge on the mechanisms underlying AR, diagnostic tools, and therapeutic approaches. Mechanisms explored include the role of the resident cells and the inflammatory cascade in AR. Diagnostic methods such as bronchial biopsy, lung function testing, imaging, and possible biomarkers are described. The effectiveness on AR of different treatments of asthma including corticosteroids, leukotriene modifiers, bronchodilators, macrolides, biologics, and bronchial thermoplasty is discussed, as well as other possible therapeutic options. AR poses a significant challenge in asthma management, contributing to disease severity and treatment resistance. Current therapeutic approaches target mostly airway inflammation rather than smooth muscle cell dysfunction and showed limited benefits on AR. Future research should focus more on investigating the mechanisms involved in AR to identify novel therapeutic targets and to develop new effective treatments able to prevent irreversible structural changes and improve long-term asthma outcomes.

Bidirectional interaction of airway epithelial remodeling and inflammation in asthma

Asthma is a chronic disease of the airways that has long been viewed predominately as an inflammatory condition. Accordingly, current therapeutic interventions focus primarily on resolving inflammation. However, the mainstay of asthma therapy neither fully improves lung function nor prevents disease exacerbations, suggesting involvement of other factors. An emerging concept now holds that airway remodeling, another major pathological feature of asthma, is as important as inflammation in asthma pathogenesis. Structural changes associated with asthma include disrupted epithelial integrity, subepithelial fibrosis, goblet cell hyperplasia/metaplasia, smooth muscle hypertrophy/hyperplasia, and enhanced vascularity. These alterations are hypothesized to contribute to airway hyperresponsiveness, airway obstruction, airflow limitation, and progressive decline of lung function in asthmatic individuals. Consequently, targeting inflammation alone does not suffice to provide optimal clinical benefits. Here we review asthmatic airway remodeling, focusing on airway epithelium, which is critical to maintaining a healthy respiratory system, and is the primary defense against inhaled irritants. In asthma, airway epithelium is both a mediator and target of inflammation, manifesting remodeling and resulting obstruction among its downstream effects. We also highlight the potential benefits of therapeutically targeting airway structural alterations. Since pathological tissue remodeling is likewise observed in other injury- and inflammation-prone tissues and organs, our discussion may have implications beyond asthma and lung disease.

Asthma Exacerbations Associated with Lung Function Decline in Patients with Severe Eosinophilic Asthma

BACKGROUND

Limited data describe the association between the frequency of asthma exacerbations and the decline in lung function in severe asthma.

OBJECTIVE

To determine whether asthma exacerbations are associated with enhanced decline in lung function.

METHODS

Changes in lung function were analyzed retrospectively using data from the DREAM and MENSA studies of mepolizumab intervention in patients with severe asthma. Patients were either nonsmokers or former smokers. A linear regression model was used to analyze the relationship between the number of exacerbations and decline in FEV₁ across treatment groups.

RESULTS

In a combined post hoc analysis, 57% (n = 572) of patients had no exacerbations and experienced an improvement in postbronchodilator FEV₁ of 143 mL. In contrast, in patients who experienced 3 or more exacerbations, there was a decrease in postbronchodilator FEV₁ of 77 mL in the combined analysis. The linear modeling analysis estimated that for each exacerbation seen during the observational period, there was a decrease of 50 mL in FEV₁ (P < .001).

CONCLUSIONS

A direct relationship between the number of exacerbations in patients with severe eosinophilic asthma and decline in lung function was observed. Repeated exacerbations may be associated with accelerated loss of lung function.

Associations in asthma between quantitative computed tomography and bronchial biopsy-derived airway remodelling

Airway remodelling in asthma remains poorly understood. This study aimed to determine the association of airway remodelling measured on bronchial biopsies with 1) lung function impairment and 2) thoracic quantitative computed tomography (QCT)-derived morphometry and densitometry measures of proximal airway remodelling and air trapping.Subjects were recruited from a single centre. Bronchial biopsy remodelling features that were the strongest predictors of lung function impairment and QCT-derived proximal airway morphometry and air trapping markers were determined by stepwise multiple regression. The best predictor of air trapping was validated in an independent replication group.Airway smooth muscle % was the only predictor of post-bronchodilator forced expiratory volume in 1 s (FEV₁) % pred, while both airway smooth muscle % and vascularity were predictors of FEV₁/forced vital capacity. Epithelial thickness and airway smooth muscle % were predictors of mean segmental bronchial luminal area (R²=0.12; p=0.02 and R²=0.12; p=0.015), whereas epithelial thickness was the only predictor of wall area % (R²=0.13; p=0.018). Vascularity was the only significant predictor of air trapping (R²=0.24; p=0.001), which was validated in the replication group (R²=0.19; p=0.031).In asthma, airway smooth muscle content and vascularity were both associated with airflow obstruction. QCT-derived proximal airway morphometry was most strongly associated with epithelial thickness and airway smooth muscle content, whereas air trapping was related to vascularity.

Enhancing nuclear translocation: perspectives in inhaled corticosteroid therapy

Corticosteroids are widely used in the treatment of asthma and chronic obstructive pulmonary disease (COPD). In contrast to their use in mild-to-moderate asthma, they are less efficacious in improving lung function and controlling the underlying inflammation in COPD. In most clinical trials, corticosteroids have shown little benefit in COPD, but have shown a greater clinical effect in combination with long-acting bronchodilators. Impaired corticosteroid activation of the glucocorticoid receptor (GR) has been reported in corticosteroid-insensitive individuals. Reversal of corticosteroid-insensitivity by enhancing GR nuclear translocation is a potential therapeutic target. Preclinical studies suggest members of the nuclear receptor superfamily may facilitate glucocorticoid receptor nuclear translocation. Unravelling the mechanisms that govern GR nuclear translocation may identify novel therapeutic targets for reversing corticosteroid-insensitivity.

Asthma therapy and its effect on airway remodelling

Asthma remains a major health problem with significant morbidity, mortality and economic costs. In asthma, airway remodelling, which refers to all the microscopic structural changes seen in the airway tissue, has been recognised for many decades and remains one of the defining characteristics of the disease; however, it is still poorly understood. The detrimental pathophysiological consequences of some features of remodelling, like increased airway smooth muscle mass and subepithelial fibrosis, are well documented. However, whether targeting these by therapy would be beneficial is unknown. Although the prevailing thinking is that remodelling is an abnormal response to persistent airway inflammation, recent evidence, especially from studies of remodelling in asthmatic children, suggests that the two processes occur in parallel. The effects of asthma therapy on airway remodelling have not been studied extensively due to the challenges of obtaining airway tissue in the context of clinical trials. Corticosteroids remain the cornerstone of asthma therapy, and their effects on remodelling have been better studied than other drugs. Bronchial thermoplasty is the only asthma therapy to primarily target remodelling, although how it results in the apparent clinical benefits seen is not exactly clear. In this article we discuss the mechanisms of airway remodelling in asthma and review the effects of conventional and novel asthma therapies on the process.

Asthma is not only an airway disease, but also a vascular disease

Multiple studies have identified an expansion and morphological dysregulation of the bronchial vascular network in the airways of asthmatics. Increased number, size and density of blood vessels, as well as vascular leakage and plasma engorgement, have been reported in the airways of patients with all grades of asthma from mild to fatal. This neovascularisation is an increasingly commonly reported feature of airway remodelling; however, the pathophysiological impact of the increased vasculature in the bronchial wall and its significance to pulmonary function in asthma are unrecognised at this time. Multiple factors capable of influencing the development and persistence of the vascular network exist within asthmatic airway tissue. These include structural components of the altered extracellular matrix (ECM), imbalance of proteases and their endogenous inhibitors, release of active matrikines and the dysregulated levels of both soluble and matrix sequestered growth factors. This review will explore the features of the asthmatic airway which influence the development and persistence of the increased vascular network, as well as the effect of enhanced tissue perfusion on chronic inflammation and airway dynamics. The response of cells of the airways to the altered vascular profile and the subsequent influence on the features of airway remodelling will also be highlighted. We will explore the failure of current asthma therapeutics in "normalising" this vascular remodelling. Finally, we will summarize the outcomes of recent clinical trials which provide hope that anti-angiogenic therapies may be a potent asthma-resolving class of drugs and provide a new approach to asthma management in the future.

Extracellular matrix composition is modified by β₂-agonists through cAMP in COPD

Long acting β₂-agonists (LABA) have been reported to modify the extracellular matrix (ECM) composition in the airway wall. Based on our earlier studies we here investigated the mechanism underlying the control of ECM modification by LABA in primary human airway smooth muscle cells. Cells were treated with formoterol or salmeterol (30 min) before TGF-β₁ stimulation (2-3 days) Using RT-PCT, immuno-blotting and ELISA the de novo synthesis and deposition of collagen type-I, -III, -IV and fibronectin were determined. Matrix metalloproteinases (MMP)-2 and -9 were analyzed by zymography. Both LABA activated cAMP and its corresponding transcription factor CREB within 60 min and thus partly reduced TGF-β₁-induced gene transcription of collagen type-I, -III, fibronectin and connective tissue growth factor (CTGF). The inhibitory effect of both LABA on collagen type-I and -III deposition involved a cAMP dependent mechanism, while the inhibitory effect of the two drugs on TGF-β1-induced fibronectin deposition and on CTGF secretion was independent of cAMP. Interestingly, none of the two LABA reduced CTGF-induced synthesis of collagen type-I or type-III deposition. In addition, none of the two LABA modified collagen type-IV deposition or the expression and activity of MMP-2 or MMP-9. Our results show that LABA can prevent de novo deposition of specific ECM components through cAMP dependent and independent signaling. However, they do not reduce all ECM components by the same mechanism and they do not reduce existing collagen deposits. This might explain some of the controversial reports on the anti-remodeling effect of LABA in chronic inflammatory lung diseases.

Mechanisms of airway remodeling

Airway remodeling comprises the structural changes of airway walls, induced by repeated injury and repair processes. It is characterized by the changes of tissue, cellular, and molecular composition, affecting airway smooth muscle, epithelium, blood vessels, and extracellular matrix. It occurs in patients with chronic inflammatory airway diseases such as asthma, COPD, bronchiectasis, and cystic fibrosis. Airway remodeling is arguably one of the most intractable problems in these diseases, leading to irreversible loss of lung function. Current therapeutics can ameliorate inflammation, but there is no available therapy proven to prevent or reverse airway remodeling, although reversibility of airway remodeling is suggested by studies in animal models of disease. Airway remodeling is often considered the result of longstanding airway inflammation, but it may be present to an equivalent degree in the airways of children with asthma, raising the necessity for early and specific therapeutic interventions. In this review, we consider the factors that may contribute to airway remodeling and discuss the current and potential therapeutic interventions.

Treating the small airways

The final article in this series evaluates the approaches undertaken to treating the small-airway region of the lungs and the clinical implications of inhaled therapy targeting the periphery in patients with asthma and chronic obstructive pulmonary disease.

Distinctive characteristics of bronchial reticular basement membrane and vessel remodelling in chronic obstructive pulmonary disease (COPD) and in asthma: they are not the same disease

AIMS

This study compared reticular basement membrane (Rbm) and vascular remodelling within the bronchial mucosa of subjects with chronic obstructive pulmonary disease (COPD) with those from patients with asthma, to test the 'Dutch hypothesis' of whether these are essentially the same or different pathological conditions.

METHODS AND RESULTS

Bronchoscopic biopsies were stained with anti-collagen IV antibody; 18 current smoking COPD, 10 symptomatic asthmatics and 13 healthy non-smoking controls were studied. The Rbm in COPD was fragmented, non-homogeneous, variable in thickness and hypervascular, whereas in asthma the Rbm was compact and homogeneous with no evidence of increased vascularity compared to controls. Length of Rbm splitting presented as percentage of Rbm length was used to measure fragmentation; it was greater in COPD than in controls and asthmatics [median (range) 20.7% (0.4-68.5) versus 5.3% (0.0-21.7) versus 1.5% (0.0-15.1), P < 0.001]. The number of Rbm vessels/mm Rbm [median (range) 10.1 (1.6-23.0) versus 4.5 (0.0-26.4) versus 4.4 (0.4-8.1), P < 0.01] and area of Rbm vessels, μm(2) /mm Rbm [median (range) 953 (115-2456) versus 462 (0-3263) versus 426 (32-2216), P < 0.05] was also increased in COPD compared to normal subjects and asthmatics.

CONCLUSIONS

The characteristics of Rbm remodelling are quite different in asthma and COPD.

Reticular Basement Membrane Vessels Are Increased in COPD Bronchial Mucosa by Both Factor VIII and Collagen IV Immunostaining and Are Hyperpermeable

Background and Objective. Using Collagen IV staining, we have previously reported that the reticular basement membrane (Rbm) is hypervascular and the lamina propria (LP) is hypovascular in COPD airways. This study compared Collagen IV staining with vessels marked with anti-Factor VIII and examined vessel permeability in bronchial biopsies from COPD and normal subjects using albumin staining. Results. Anti-Collagen IV antibody detected more vessels in the Rbm (P = 0.002) and larger vessels in both Rbm (P < 0.001) and LP (P = 0.003) compared to Factor VIII. COPD airways had more vessels (with greater permeability) in the Rbm (P = 0.01) and fewer vessels (with normal permeability) in the LP compared to controls with both Collagen IV and Factor VIII antibodies (P = 0.04 and P = 0.01). Conclusion. Rbm vessels were increased in number and were hyperpermeable in COPD airways. Anti-Collagen IV and anti-Factor VIII antibodies did not uniformly detect the same vessel populations; the first is likely to reflect larger and older vessels with the latter reflecting smaller, younger vessels.

Combined Beta-agonists and corticosteroids do not inhibit extracellular matrix protein production in vitro

Background. Persistent asthma is characterized by airway remodeling. Whereas we have previously shown that neither β(2)-agonists nor corticosteroids inhibit extracellular matrix (ECM) protein release from airway smooth muscle (ASM) cells, the effect of their combination is unknown and this forms the rationale for the present study. Methods. ASM cells from people with and without asthma were stimulated with TGFβ1 (1 ng/ml) with or without budesonide (10(-8) M) and formoterol (10(-10) and 10(-8) M), and fibronectin expression and IL-6 release were measured by ELISA. Bronchial rings from nonasthmatic individuals were incubated with TGFβ1 (1 ng/ml) with or without the drugs, and fibronectin expression was measured using immunohistochemistry. Results. Budesonide stimulated fibronectin deposition, in the presence or absence of TGFβ1, and this was partially reversed by formoterol (10(-8) M) in both asthmatic and nonasthmatic cells. Budesonide and formoterol in combination failed to inhibit TGFβ-induced fibronectin in either cell type. A similar pattern of expression of fibronectin was seen in bronchial rings. TGFβ1-induced IL-6 release was inhibited by the combination of drugs. Conclusion. Current combination asthma therapies are unable to prevent or reverse remodeling events regulated by ASM cells.

Mechanisms of remodeling in asthmatic airways

Asthma is a chronic inflammatory airway disorder characterized by airway hyperresponsiveness and reversible airflow obstruction. Subgroups of asthma patients develop airflow obstruction that is irreversible or only partially reversible and experience an accelerated rate of lung function decline. The structural changes in the airways of these patients are referred to as airway remodeling. All elements of the airway wall are involved, and remodeled airway wall thickness is substantially increased compared to normal control airways. Airway remodeling is thought to contribute to the subphenotypes of irreversible airflow obstruction and airway hyperresponsiveness, and it has been associated with increased disease severity. Reversal of remodeling is therefore of paramount therapeutic importance, and mechanisms responsible for airway remodeling are feasible therapeutic targets for asthma treatment. This paper will focus on our current understanding of the mechanisms of airway remodeling in asthma and potential targets for future intervention.

Role of Inhaled Steroids in Vascular Airway Remodelling in Asthma and COPD

In chronic obstructive airway diseases, such as asthma and chronic obstructive pulmonary disease (COPD), changes in bronchial microvasculature are present in response to inflammatory stimuli. Vascular changes may significantly contribute to airway wall remodelling. Angiogenesis and vascular leakage are prevalent in asthma, while vasodilation and vascular leakage dominate in COPD. An endothelial dysfunction may be present both in asthma and in COPD. Vascular changes may occur simultaneously with the thickening of the airway wall and the narrowing of the bronchial lumen. Consequently, pharmacological control of bronchial vascular remodelling may be crucial for symptom control in asthma and COPD. In asthmatic airways, inhaled steroids can downregulate vascular remodelling by acting on proangiogenic factors. Additionally, studies on combination therapy with long-acting β2-agonists and inhaled steroids have provided evidence of a possible synergistic action on components of vascular remodelling in asthma. In COPD, there is less experimental evidence on the effect of inhaled steroids on airway microvascular changes. Importantly, vascular endothelial growth factor (VEGF), the most specific growth factor for vascular endothelium, is crucially involved in the pathophysiology of airway vascular remodelling, both in asthma and COPD. The inhibition of VEGF and its receptor may be useful in the treatment of the vascular changes in the airway wall.

Inactivation of capsaicin-sensitive nerves reduces pulmonary remodeling in guinea pigs with chronic allergic pulmonary inflammation

Pulmonary remodeling is an important feature of asthma physiopathology that can contribute to irreversible changes in lung function. Although neurokinins influence lung inflammation, their exact role in the extracellular matrix (ECM) remodeling remains to be determined. Our objective was to investigate whether inactivation of capsaicin-sensitive nerves modulates pulmonary ECM remodeling in animals with chronic lung inflammation. After 14 days of capsaicin (50 mg/kg, sc) or vehicle administration, male Hartley guinea pigs weighing 250-300 g were submitted to seven inhalations of increasing doses of ovalbumin (1, 2.5, and 5 mg/mL) or saline for 4 weeks. Seventy-two hours after the seventh inhalation, animals were anesthetized and mechanically ventilated and the lung mechanics and collagen and elastic fiber content in the airways, vessels and lung parenchyma were evaluated. Ovalbumin-exposed animals presented increasing collagen and elastic fiber content, respectively, in the airways (9.2 ± 0.9; 13.8 ± 1.2), vessels (19.8 ± 0.8; 13.4 ± 0.5) and lung parenchyma (9.2 ± 0.9; 13.8 ± 1.2) compared to control (P < 0.05). Capsaicin treatment reduced collagen and elastic fibers, respectively, in airways (1.7 ± 1.1; 7.9 ± 1.5), vessels (2.8 ± 1.1; 4.4 ± 1.1) and lung tissue (2.8 ± 1.1; 4.4 ± 1.1) of ovalbumin-exposed animals (P < 0.05). These findings were positively correlated with lung mechanical responses to antigenic challenge (P < 0.05). In conclusion, inactivation of capsaicin-sensitive nerve fibers reduces pulmonary remodeling, particularly collagen and elastic fibers, which contributes to the attenuation of pulmonary functional parameters.

The role of the bronchial microvasculature in the airway remodelling in asthma and COPD

In recent years, there has been increased interest in the vascular component of airway remodelling in chronic bronchial inflammation, such as asthma and COPD, and in its role in the progression of disease. In particular, the bronchial mucosa in asthmatics is more vascularised, showing a higher number and dimension of vessels and vascular area. Recently, insight has been obtained regarding the pivotal role of vascular endothelial growth factor (VEGF) in promoting vascular remodelling and angiogenesis. Many studies, conducted on biopsies, induced sputum or BAL, have shown the involvement of VEGF and its receptors in the vascular remodelling processes. Presumably, the vascular component of airway remodelling is a complex multi-step phenomenon involving several mediators. Among the common asthma and COPD medications, only inhaled corticosteroids have demonstrated a real ability to reverse all aspects of vascular remodelling. The aim of this review was to analyze the morphological aspects of the vascular component of airway remodelling and the possible mechanisms involved in asthma and COPD. We also focused on the functional and therapeutic implications of the bronchial microvascular changes in asthma and COPD.

Persisting remodeling and less airway wall eosinophil activation in complete remission of asthma

RATIONALE

Individuals with asthma may outgrow symptoms despite not using treatment, whereas others reach complete remission (CoR) with absence of airway obstruction and bronchial hyperresponsiveness. It is uncertain whether this associates with remission of all inflammatory and remodeling asthma features.

OBJECTIVES

To compare the pathologic phenotype of individuals with asthma with CoR and clinical remission (ClinR) and those with active asthma, with and without the use of inhaled corticosteroids (ICS).

METHODS

We investigated 165 individuals known with active asthma, on reexamination having CoR (n = 18), ClinR (n = 44), and current asthma (CuA, n = 103, 64 with and 39 without ICS). MEASUREMENTS MAIN RESULTS: Inflammatory cells were measured in blood, induced sputum, and bronchial biopsies; histamine and ECP in sputum; and eosinophilic peroxidase (EPX) immunopositivity and remodeling (epithelial changes, E-cadherin expression, basement membrane [BM] thickening, collagen deposition) in bronchial biopsies. Median (range) blood eosinophils from CoR were significantly lower than those from CuA (0.10 [0.04-0.24] vs. 0.18 [0.02-1.16] × 10⁹/L). Bronchial EPX immunopositivity was lower in CoR than in both ClinR and CuA (67 [0.5-462] vs. 95 [8-5329] and 172 [6-5313] pixels). Other inflammatory findings were comparable. BM thickness was lowest in CuA, caused by lower BM thickness in those using ICS (CoR, 6.3 [4.7-8.4]; ClinR, 6.5 [3.8-11.7]; CuA, 5.7 [2.8-12.6]; and ICS using CuA, 5.3 [2.8-8.2] μm).

CONCLUSIONS

CoR is still accompanied by airway abnormalities because BM thickness is similar in individuals with asthma with CoR, ClinR, and CuA without ICS. Airway eosinophilic activation best differentiates these three groups, signifying their importance in the clinical expression and severity of bronchial hyperresponsiveness in asthma.

Montelukast added to fluticasone propionate does not alter inflammation or outcomes

BACKGROUND

Airway inflammation is a key pathological feature of asthma which underlies its clinical presentation.

OBJECTIVES

To examine whether adding a leukotriene modifier to an inhaled corticosteroid produces further clinical and/or anti-inflammatory benefits in patients symptomatic on short-acting beta(2)-agonists.

METHODS

Patients uncontrolled on short-acting beta(2)-agonists were treated for 12 weeks with either fluticasone propionate (100mcg BD) or fluticasone propionate (100mcg BD) and montelukast (10mg QD) in a randomized, double-blind, parallel group study. Bronchoscopy with endobronchial biopsy and bronchoalveolar lavage (BAL) was performed before and after treatment to compare effects on airway inflammation.

RESULTS

Of 103 subjects enrolled, 89 subjects completed treatment and 82 subjects had matched pair biopsy samples. Submucosal eosinophil counts, the primary endpoint, and asthma control improved to similar extents after both treatments (p<or=0.008). Both treatments significantly reduced submucosal mast cell, CD3+, CD4+, CD8+ and CD25+ cell counts. Submucosal mast cell reduction was greater in the fluticasone propionate plus montelukast group. There were no differences between treatments in BAL markers of inflammation or thickness of sub-epithelial collagen.

CONCLUSIONS

Low-dose fluticasone propionate significantly improves clinical disease control and reduces airway inflammation in asthma patients uncontrolled with short-acting beta(2)-agonists without further improvement when montelukast is added to low-dose fluticasone propionate.

Angiogenesis and lymphangiogenesis in bronchial asthma

Neovascularization plays a prominent role in inflammation and tissue remodeling in several chronic inflammatory disorders. Vessel number and size, vascular surface area and vascular leakage are all increased in biopsies from patients with asthma. High levels of VEGF and other angiogenic factors have been detected in tissues and biological samples of patients with asthma and correlate with disease activity and inversely with airway hyper-responsiveness. Inflammation in the lung stimulates the growth of new blood vessels and these contribute to the airway obstruction or airway hyper-responsiveness, or both. Effector cells of inflammation (human lung mast cells, basophils, eosinophils, macrophages, etc.) are major sources of a vast array of angiogenic and lymphangiogenic factors. Inhaled corticosteroids reduce vascularity and growth factor expression and might modulate bronchial vascular remodeling in asthma. Specific antagonists to VEGF and other angiogenic factors and their receptors might help to control chronic airway inflammation and vascular remodeling and offer a novel approach for the treatment of chronic inflammatory lung disorders.

Airway remodelling in asthma: from benchside to clinical practice

Airway remodelling refers to the structural changes that occur in both large and small airways relevant to miscellaneous diseases including asthma. In asthma, airway structural changes include subepithelial fibrosis, increased smooth muscle mass, gland enlargement, neovascularization and epithelial alterations. Although controversial, airway remodelling is commonly attributed to an underlying chronic inflammatory process. These remodelling changes contribute to thickening of airway walls and, consequently, lead to airway narrowing, bronchial hyper-responsiveness, airway edema and mucous hypersecretion. Airway remodelling is associated with poor clinical outcomes among asthmatic patients. Early diagnosis and prevention of airway remodelling has the potential to decrease disease severity, improve control and prevent disease expression. The relationship between structural changes and clinical and functional abnormalities clearly deserves further investigation. The present review briefly describes the characteristic features of airway remodelling observed in asthma, its clinical consequences and relevance for physicians, and its modulation by therapeutic approaches used in the treatment of asthmatic patients.

Effect of salmeterol/fluticasone propionate combination on airway hyper-responsiveness in patients with well-controlled asthma

BACKGROUND

The hypothesis that regular treatment aimed at achieving and maintaining asthma control is accompanied by reduced airway hyper-responsiveness (AHR) was investigated.

METHODS

Adult patients (PC(20) methacholine <8 mg/ml, FEV(1)% predicted >or=70%) received salmeterol/fluticasone propionate combination 50/250 microg bd (SFC250) for a 12-week run-in; those achieving well-controlled (WC) asthma were randomised to SFC250 (n = 88) or SFC50/500 microg bd (SFC500) (n = 90) for 24 weeks. AHR (PC(20) methacholine), asthma control, lung function, symptoms, exacerbations and safety were assessed.

RESULTS

During the 12 week run-in (SFC250), a greater than 1 doubling dose increase in PC(20) was observed. During randomised treatment, the increase in AHR was similar, and less than 1 doubling dose, for both groups (adjusted geometric mean PC(20) (mg/mL) at 24 weeks: SFC250: 2.796, SFC500: 2.802; p = 0.992). Compared with SFC250, patients receiving SFC500 had a more rapid improvement in AHR (adjusted mean ratio to baseline respectively at week 4: 1.193 vs. 1.386; week 12: 1.395 vs. 1.672; p = non-significant for both) and showed a greater response to treatment in patients with a low baseline PC(20). Patients maintaining WC asthma were 72 (84%) and 64 (74%) in the SFC250 and SFC500 groups respectively. Both doses of SFC were well tolerated; only four exacerbations were reported, all in the SFC500 group.

CONCLUSION

Regular treatment with SFC resulted in continuous improvement in AHR with maintenance of asthma control in the majority of patients. SFC500 showed a trend for a more rapid improvement in AHR and resulted in greater improvements in patients with a lower baseline PC(20).

Angiogenesis in asthma

Asthma is a chronic inflammatory disease of the airways characterized by infiltration and activation of inflammatory cells and by structural changes, including subepithelial fibrosis, smooth muscle cells hypertrophy/hyperplasia, epithelial cell metaplasia and angiogenesis. These structural changes are thought to correlate with asthma severity and to account for the development of progressive lung function deterioration. The mechanism underlying airway angiogenesis in asthma and its precise clinical relevance have not yet been completely elucidated. This review provides recent data showing the contribution of allergic inflammation in increased airway vascularity and potential therapeutical approaches in asthma treatment by acting on bronchial microvascular changes.

Addition of long-acting beta2-agonists to inhaled steroids versus higher dose inhaled steroids in adults and children with persistent asthma

BACKGROUND

In asthmatic patients inadequately controlled on inhaled corticosteroids and/or those with moderate persistent asthma, two main options are recommended: the combination of a long-acting inhaled ss2 agonist (LABA) with inhaled corticosteroids (ICS) or use of a higher dose of inhaled corticosteroids.

OBJECTIVES

To determine the effect of the combination of long-acting ss(2) agonists and inhaled corticosteroids compared to a higher dose of inhaled corticosteroids on the risk of asthma exacerbations, pulmonary function and on other measures of asthma control, and to look for characteristics associated with greater benefit for either treatment option.

SEARCH STRATEGY

We identified randomised controlled trials (RCTs) through electronic database searches (MEDLINE, EMBASE and CINAHL), bibliographies of RCTs, clinical trial registries and correspondence with manufacturers until May 2008.

SELECTION CRITERIA

RCTs that compared the combination of inhaled LABA and ICS to a higher dose of inhaled corticosteroids, in children and adults with asthma.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed methodological quality and extracted data. We obtained confirmation from the trialists when possible. The primary endpoint was the number of patients experiencing one or more asthma exacerbations requiring oral corticosteroids.

MAIN RESULTS

This review included 48 studies (15,155 participants including 1155 children and 14,000 adults). Participants were inadequately controlled on their current ICS regimen, experiencing ongoing symptoms and with generally moderate (FEV1 60% to 79% of predicted) airway obstruction. The studies tested the combination of salmeterol or formoterol with a median dose of 400 mcg/day of beclomethasone or equivalent (BDP-eq) compared to a median of 1000 mcg/day of BDP-eq, usually for 24 weeks or less. There was a statistically significantly lower risk of exacerbations requiring systemic corticosteroids in patients treated with LABA and ICS (RR 0.88, 95% CI 0.78 to 0.98, 27 studies, N = 10,578) from 11.45% to 10%, with a number needed to treat of 73 (median study duration: 12 weeks). The study results were dominated by adult studies; trial data from three paediatric studies showed a trend towards increased risk of rescue oral steroids (RR 1.24, 95% CI 0.58 to 2.66) and hospital admission (RR 2.21, 95% CI 0.74 to 6.64) associated with combination therapy. Overall, there was no statistically significant difference in the risk ratios for either hospital admission (RR 1.02, 95% CI 0.67 to 1.56) or serious adverse events (RR 1.12, 95% CI 0.91 to 1.37). The combination of LABA and ICS resulted in significantly greater but modest improvement from baseline in lung function, symptoms and rescue medication use than with higher ICS dose. Despite no significant group difference in the risk of overall adverse events (RR 0.99, 95% CI 0.95 to 1.03), there was an increase in the risk of tremor (RR 1.84, 95% CI 1.20 to 2.82) and a lower risk of oral thrush (RR 0.58, 95% CI 0.40 to 0.86)) in the LABA and ICS compared to the higher ICS group. There was no significant difference in hoarseness or headache between the treatment groups. The rate of withdrawals due to poor asthma control favoured the combination of LABA and ICS (RR 0.65, 95% CI 0.51 to 0.83).

AUTHORS' CONCLUSIONS

In adolescents and adults with sub-optimal control on low dose ICS monotherapy, the combination of LABA and ICS is modestly more effective in reducing the risk of exacerbations requiring oral corticosteroids than a higher dose of ICS. Combination therapy also led to modestly greater improvement in lung function, symptoms and use of rescue ss(2) agonists and to fewer withdrawals due to poor asthma control than with a higher dose of inhaled corticosteroids. Apart from an increased rate of tremor and less oral candidiasis with combination therapy, the two options appear relatively safe in adults although adverse effects associated with long-term ICS treatment were seldom monitored. In children, combination therapy did not lead to a significant reduction, but rather a trend towards an increased risk, of oral steroid-treated exacerbations and hospital admissions. These trends raised concern about the safety of combination therapy in view of modest improvement in children under the age of 12 years.

Dispensing of fluticasone propionate/salmeterol combination in the summer and asthma-related outcomes in the fall

BACKGROUND

Asthma exacerbations occur year-round; however, peak asthma-related events occur in the fall and are frequently associated with viral respiratory infections.

OBJECTIVE

To compare the rates of asthma-related emergency department (ED) visits and hospitalizations in the fall (September, October, November) between users and nonusers of fluticasone propionate plus salmeterol in a single inhaler (FSC) in the preceding summer.

METHODS

This was a retrospective, observational study using health care claims from a large managed care database. Patients age 4 to 55 years with both a medical claim for asthma and a pharmacy claim for FSC were categorized into 3 age groups: children (4-11 years), adolescents (12-18 years), and adults (19-55 years).

RESULTS

There were 201,973 observations of FSC dispensings and 184,143 observations without FSC. Across all age groups, summertime dispensings of FSC were associated with a significantly lower (P < .001) risk of an asthma-related ED visit (4-11 years: adjusted odds ratio [OR], 0.54, 95% CI, 0.49-0.60; 12-18 years: OR, 0.59, 95% CI, 0.54-0.64; 19-55 years: OR, 0.53, 95% CI, 0.51-0.55) or hospitalization (4-11 years: OR, 0.43, 95% CI, 0.35-0.54; 12-18 years: OR, 0.49, 95% CI, 0.40-0.60; 19-55 years: OR, 0.61, 95% CI, 0.57-0.65) in the subsequent fall. This protective effect persisted even for patients with fall dispensings of FSC. The risk of oral corticosteroid dispensing in the fall was also significantly reduced in all age groups.

CONCLUSION

Summertime dispensings of FSC were associated with a decreased risk of serious asthma-related outcomes in the subsequent fall. Continuous use of FSC before seasonal viral exposure may decrease seasonally related exacerbations.

Increased vascular permeability precedes cellular inflammation as asthma control deteriorates

BACKGROUND

Airway microcirculation is abnormal in asthma but the role of vascular changes in asthma deteriorations remains poorly defined. We prospectively assessed the vascular changes accompanying worsening of asthma control by using an inhaled corticosteroid (ICS) dose-reduction model.

OBJECTIVES

To evaluate airway vascularity, vascular permeability and expression of vascular endothelial growth factor (VEGF) in early asthma deterioration induced by ICS back-titration.

METHODS

Twenty mild-to-moderate persistent symptomatic asthmatics on low-to-moderate ICS were recruited and treated with 4 weeks of high-dose fluticasone propionate (1000 microg/day) to achieve symptom control. This was followed by dose reduction to half of the pre-study doses for 4-8 weeks until the symptoms began to return. Endobronchial biopsy and bronchoalveolar lavage (BAL) samples were obtained after both treatment periods.

RESULTS

Vascularity as measured by the number and size of blood vessels, as well as VEGF expression did not change following ICS reduction. Even on high-dose ICS, perivascular albumin staining and BAL microalbumin levels in asthmatic subjects, as markers of permeability, were elevated when compared with normal subjects and both further increased significantly after ICS reduction. There was a significant association between changes in vascular leakiness and clinical deterioration. Increases in airway albumin correlated with previously reported increases in airway wall infiltration with T lymphocytes.

CONCLUSIONS

Our results suggest that airway vascular leakage is a major pathophysiologic feature of early asthma deterioration, occurring before recrudescence of cellular inflammation.

Addition of inhaled long-acting beta2-agonists to inhaled steroids as first line therapy for persistent asthma in steroid-naive adults and children

BACKGROUND

Consensus statements recommend the addition of long-acting inhaled ss2-agonists (LABA) only in asthmatic patients who are inadequately controlled on inhaled corticosteroids (ICS). It is not uncommon for some patients to be commenced on ICS and LABA together as initial therapy.

OBJECTIVES

To compare the efficacy of combining inhaled corticosteroids with long-acting ss2-agonists (ICS+LABA) with inhaled corticosteroids alone (ICS alone) in steroid-naive children and adults with persistent asthma. We assessed two protocols: (1) LABA + ICS versus a similar dose of ICS (comparison 1) and (2) LABA + ICS versus a higher dose of ICS (comparison 2).

SEARCH STRATEGY

We identified randomised controlled trials through electronic database searches (May 2008).

SELECTION CRITERIA

Randomised trials comparing ICS + LABA with ICS alone in children and adults with asthma who had no inhaled corticosteroids in the preceding 28 days prior to enrolment.

DATA COLLECTION AND ANALYSIS

Each author assessed studies independently for risk of bias and extracted data. We obtained confirmation from the trialists when possible. The primary endpoint was rate of patients with one or more asthma exacerbations requiring rescue systemic corticosteroids. Results are expressed as relative risks (RR) for dichotomous data and as mean differences (MD) or standardised mean differences (SMD) for continuous data.

MAIN RESULTS

Twenty-eight study comparisons drawn from 27 trials (22 adult; five paediatric) met the review entry criteria (8050 participants). Baseline data from the studies indicated that trial populations had moderate or mild airway obstruction (FEV1>/=65% predicted), and that they were symptomatic prior to randomisation. In comparison 1, the combination of ICS and LABA was not associated with a significantly lower risk of patients with exacerbations requiring oral corticosteroids (RR 1.04; 95% confidence interval (CI) 0.73 to 1.47) or requiring hospital admissions (RR 0.38; 95% CI 0.09 to 1.65) compared to a similar dose of ICS alone. The combination of LABA and ICS led to a significantly greater improvement from baseline in FEV1 (0.12 L/sec; 95% CI 0.07 to 0.17), in symptoms (SMD -0.26; 95% CI -0.37 to -0.14) and in rescue ss2-agonist use (-0.41 puffs/day; 95% CI -0.73 to -0.09) compared with a similar dose of ICS alone. There was no significant group difference in the risk of serious adverse events (RR 1.15; 95% CI 0.64 to 2.09), any adverse events (RR 1.02; 95% CI 0.96 to 1.09), study withdrawals (RR 0.95; 95% CI 0.82 to 1.11), or withdrawals due to poor asthma control (RR 0.94; 95% CI 0.63 to 1.41).In comparison 2, the combination of LABA and ICS was associated with a higher risk of patients requiring oral corticosteroids (RR 1.24; 95% CI 1 to 1.53) and study withdrawal (RR 1.31; 95% CI 1.07 to 1.59) than a higher dose of ICS alone. For every 100 patients treated over 43 weeks, nine patients using a higher dose ICS compared to 11 (95% CI 9 to 14) on LABA and ICS suffered one or more exacerbations requiring rescue oral corticosteroids. There was a high level of statistical heterogeneity for FEV1 and morning peak flow. There was no statistically significant group difference in the risk of serious adverse events. Due to insufficient data we could not aggregate results for hospital admission, symptoms and other outcomes.

AUTHORS' CONCLUSIONS

In steroid-naive patients with mild to moderate airway obstruction, the combination of ICS and LABA does not significantly reduce the risk of patients with exacerbations requiring rescue oral corticosteroids over that achieved with a similar dose of ICS alone. However, it significantly improves lung function, reduces symptoms and marginally decreases rescue ss2-agonist use. Initiation of a higher dose of ICS is more effective at reducing the risk of exacerbations requiring rescue systemic corticosteroids, and of withdrawals, than combination therapy. Although children appeared to respond similarly to adults, no firm conclusions can be drawn regarding combination therapy in steroid-naive children, given the small number of children contributing data.

Budesonide and formoterol inhibit inflammatory mediator production by bronchial epithelial cells infected with rhinovirus

BACKGROUND

Rhinoviruses (RVs) are responsible for the majority of acute asthma and chronic obstructive pulmonary disease (COPD) exacerbations. RVs infect the lower airways and induce the production of pro-inflammatory and remodelling-associated mediators. Budesonide (BUD) and formoterol (FORM) synergize in controlling asthma and COPD exacerbations; however, their effects on virus-induced inflammation and remodelling are less known.

OBJECTIVE

We investigated whether BUD and FORM synergize in suppressing RV-induced inflammation and remodelling in the airways.

METHODS

In vitro models of RV infection of BEAS-2B and primary normal human bronchial epithelial (NHBE) cells were used. We assessed the effects of individual and combined drugs administered post-infection, at a clinically relevant concentration range (10(-6)-10(-10) m), on the production of CCL5, CXCL10, CXCL8, IL-6 and the remodelling-associated VEGF and bFGF, using ELISA and RT-PCR.

RESULTS

BUD effectively suppressed RV-mediated induction of all mediators studied, in a concentration-dependent manner. FORM alone suppressed the production of CXCL8 and bFGF. The combination of BUD and FORM had concentration-dependent, additive or synergistic effects in the suppression of RV-induced CCL5, CXCL8 and CXCL10 in both cell types as well as VEGF in NHBE only. Combination treatment also resulted in an enhanced suppression of RV-induced IL-6, and CCL5 at the mRNA level as compared with BUD or FORM alone.

CONCLUSION

BUD and FORM suppress RV-induced chemokines and growth factors in bronchial epithelial cells in a concentration-dependent, synergistic or additive manner. These data further support the combined use of BUD and FORM in asthma and COPD and intensification of this therapy during exacerbations.

Synthesis and structure-activity relationships of long-acting beta2 adrenergic receptor agonists incorporating arylsulfonamide groups

A series of saligenin alkoxyalkylphenylsulfonamide beta(2) adrenoceptor agonists were prepared by reacting a protected saligenin oxazolidinone with alkynyloxyalkyl bromides, followed by Sonogashira reaction, hydrogenation, and deprotection. The meta-substituted primary sulfonamide was more potent than the para- and the ortho-analogues. Primary sulfonamides were more potent than the secondary and tertiary analogues. The onset and duration of action in vitro of selected compounds was assessed on isolated superfused guinea pig trachea. Sulfonamide 29b had the best profile of potency, selectivity, onset, and duration of action on both guinea pig trachea and human bronchus. Furthermore, 29b was found to have low oral bioavailability in rat and dog and also to have long duration of action in an in vivo model of bronchodilation. Crystalline salts of 29b were identified that had suitable properties for inhaled administration. A proposed binding mode for 29b to the beta(2)-receptor is presented.

Antiinflammatory effects of long-acting beta2-agonists in patients with asthma: a systematic review and metaanalysis

BACKGROUND

Long-acting beta(2)-agonists (LABAs) are recommended as add-on therapy to antiinflammatory treatment in patients with chronic persistent asthma. Results from individual studies evaluating the in vivo antiinflammatory effect of LABAs are conflicting. The purpose of this metaanalysis was to determine whether LABAs have an in vivo antiinflammatory effect compared to placebo and whether the addition of a LABA to therapy with inhaled corticosteroids (ICSs) has a synergistic or additive antiinflammatory effect.

METHODS

A systematic search was performed of online databases for randomized controlled trials evaluating the antiinflammatory effects of the following: (1) LABAs compared to placebo; and (2) a LABA plus ICS vs ICS alone in adults and children with asthma. Inflammatory outcome measures included cell counts and markers of cell activation in sputum, BAL fluid, bronchial biopsy specimens, serum, and exhaled nitric oxide (ENO). Data were independently extracted by two study investigators and analyzed to generate standardized mean differences using either a fixed or random-effects metaanalysis depending on the degree of heterogeneity.

RESULTS

Thirty-two studies (n = 1,105 participants) met the inclusion criteria. The mean number of participants and mean number of studies for each inflammatory outcome in the metaanalysis was 113.1 (SD, 46.2) and 3.5 (SD, 1.3), respectively. There was no effect of LABA therapy on sputum, BAL fluid, or mucosal inflammatory cells in adults or in children. LABA therapy decreased ENO levels and BAL fluid albumin levels in adults. In children, LABA therapy was associated with a small decrease in serum eosinophils and interleukin-4.

CONCLUSION

LABA therapy does not appear to have any clinically important antiinflammatory or proinflammatory effect. LABA therapy decreases BAL fluid albumin levels, suggesting a possible modulating effect on microvascular leakage.

Therapeutic perspectives in bronchial vascular remodeling in COPD

COPD may be characterized by significant changes in airway mucosal blood vessels, which may contribute to bronchial airway remodeling. The airway wall is more vascularized in COPD patients than in healthy subjects, though this phenomenon is less evident than in asthmatic patients. The vascular mucosal changes in the airways of patients with COPD are strictly linked to the inflammatory processes. The cellular mechanisms responsible for the microvascular changes are still unclear, however, pro-angiogenic factors, such as VEGF, TGF-beta, FGF, and proteolytic enzymes such as MMPs, may play a role. Up to now, the clinical and functional consequences of this phenomenon and the therapeutic approach have been scarcely investigated. Inhaled corticosteroids seem to have positive effects, by reducing the vascular area and growth factor expression. Specific antagonists to VEGF, TGF- beta, FGF, and MMPs could beneficially control chronic airway inflammation and vascular remodeling in COPD as well as slow down the progression of the disease. Several of these growth factor antagonists are being evaluated and some seem to be effective in reducing vascularity, however further studies are required to ascertain whether or not these antagonists may play a role in COPD therapy.

Vascular endothelial growth factor overexpression in induced sputum of children with bronchial asthma

Vascular endothelial growth factor (VEGF) induces angiogenesis and increases vascular permeability participating in narrowing of the airway lumen that follows lung injury. We sought to investigate the expression of VEGF in induced sputum during and after recovery from acute episodes of bronchial asthma in children. Eighteen asthmatic children with acute attacks of varying severity were subjected to VEGF estimation by an enzymatic immunoassay in induced sputum. They were followed up till complete remission of symptoms and signs and were then retested. VEGF was also estimated in sputum induced from age 34 and sex-matched healthy children enrolled as a control group. The sputum VEGF levels during acute asthma [median = 71 ng/ml; mean (s.d.) = 114.6 (121.8) ng/ml] were significantly higher than the levels estimated during remission [median = 50 ng/ml; mean (s.d.) = 45.7 (24.2) ng/ml] and both were higher than the corresponding levels of the control group [median = 36 ng/ml; mean (s.d.) = 31.3 (17.2) ng/ml]. VEGF levels during asthmatic episodes correlated positively to the recovery levels (r = 0.6, p = 0.009). The patients' VEGF expression did not vary with asthma severity, serum total IgE concentration, peripheral blood eosinophil count, or erythrocyte sedimentation rate of patients. Children on corticosteroids inhalation therapy at enrollment had sputum VEGF levels that were comparable to those on other therapies. The increased expression of sputum VEGF in asthmatic children reinforces the concept that it might have a pathogenetic role in bronchial asthma and may represent a biomarker of airway inflammation.

Clinical significance of plasma and serum vascular endothelial growth factor in asthma

BACKGROUND

Vascular endothelial growth factor (VEGF) is a mediator of airway inflammation and remodeling in asthma.

PURPOSE

We investigated whether VEGF levels are elevated in plasma and serum obtained from patients with asthma and evaluated whether levels of plasma VEGF correlated with those of serum VEGF.

METHODS

We measured levels of plasma and serum VEGF in patients with stable asthma or with acute asthma and examined the correlation between plasma and serum VEGF concentration with initial forced expiratory volume in 1 second (FEV(1)).

RESULTS

We found that levels of VEGF in plasma or in serum were significantly increased in stable asthmatic patients and even higher in acute asthmatic patients compared with the levels in healthy control subjects. The levels of serum VEGF correlated significantly with those of plasma VEGF. Additionally, the circulating VEGF levels were significantly inversely correlated with the percent predicted FEV(1).

CONCLUSION

These results suggest that the overproduction of VEGF is implicated in asthma exacerbation and that measurement of either plasma or serum VEGF level can be a valid index in asthmatic patients. Therefore, the changes in the VEGF levels in peripheral blood of asthmatic patients can be used as a measure for progression of asthma during treatment.

Asp-Tyr-Leu-Lys tetrapeptide inhibits airway inflammation in toluene-2,4-diisocyanate-induced asthma mice

BACKGROUND

Airway inflammation and remodelling contribute to chronic airway obstruction of asthma. Currently, no medication effectively controls airway remodelling and related vascular changes. Therefore, new strategies need to be developed. The kringle 5 domain has anti-angiogenic activity resulting from the tetrapeptide Lys-Leu-Tyr-Asp (KLYD).

OBJECTIVE

To investigate the therapeutic effect of KLYD and its inverse form Asp-Tyr-Leu-Lys (DYLK) on the inflammation and remodelling of toluene-2,4-diisocyanate (TDI)-sensitization/challenged mice.

METHODS

Cell numbers were measured in the presence of various concentrations of KLYD and DYLK using in vitro endothelial cell proliferation assay. The changes of cell number and the level of vascular endothelial growth factor (VEGF) in bronchoalveolar lavage (BAL) fluid and response to methacholine (MCh) were measured using the in vivo TDI-sensitized/challenged mice model. Muc5ac, smooth muscle actin (SMA) and proliferating cell nuclear antigen (PCNA) protein expression was analysed on trachea and intrapulmonary bronchi using immunohistochemical stain.

RESULTS

Compared with KLYD, DYLK had a greater inhibitory effect on endothelial cell proliferation (P<0.05). Pre-treatment of DYLK showed dose-dependent reduction in the response to MCh (P<0.05) and numbers of inflammatory cells in BAL fluids of TDI-sensitized/challenged mice. TDI induced increases in Muc5ac, SMA and PCNA protein expression and VEGF levels, which were also abolished by DYLK treatment.

CONCLUSIONS

Local administration of DYLK effectively inhibits the airway inflammation and airway remodelling of TDI-sensitized/challenged mice via down-regulation of VEGF. These findings suggest that anti-angiogenic peptide therapies, such as local administration of DYLK, are an effective strategy for the treatment of remodelling in asthma.

Budesonide/formoterol decreases expression of vascular endothelial growth factor (VEGF) and VEGF receptor 1 within airway remodelling in asthma

INTRODUCTION

Angiogenesis and microvascular remodelling may play a vital role in the chronic inflammatory process within asthma. One of the most important factors involved in angiogenesis is vascular endothelial growth factor (VEGF). In this study we hypothesised that an increased expression of VEGF may be involved in airway remodelling in asthma patients. To this end, we compared the histology and expression levels of VEGF and one of its receptors (VEGFR1) in bronchial tissues of patients with asthma compared with control patients. We also investigated the effect of treatment with budesonide/formoterol (Symbicort; AstraZeneca, Lund, Sweden) in the relationship between VEGF and airway remodelling.

METHODS

Bronchial tissues were obtained from patients attending the West China Hospital from April to November 2006. Thirteen patients were diagnosed with moderate asthma and 10 others were treated as control. Histological and immunohistochemical comparisons between asthmatic and control patients were made at baseline, and (for asthmatic subjects) following 6 months of treatment with budesonide/formoterol.

RESULTS

Compared with control patients, asthmatic patients had significantly decreased respiratory parameters, including forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV(1)) (% predictive). Furthermore, patients with asthma had submucosal gland hyperplasia, increased smooth muscle mass, increased subepithelial fibrosis and neovascularisation. Asthmatic patients also exhibited increased expression of VEGF and VEGFR1 within epithelial cells. The increased expression of VEGF and its receptor correlated well with airway remodelling, airflow obstruction and airway hyper-responsiveness. After treatment with budesonide/formoterol for 6 months, the expression of VEGF and VEGFR1 was decreased, with correlatory decreased airway remodelling in patients with asthma.

CONCLUSION

The increased expression of VEGF and VEGFR(1) in asthmatic patients is accompanied by an increased number and size of blood vessels in asthmatic airways, as well as airway remodelling. Budesonide/formoterol therapy for 6 months can decrease the expression of VEGF and VEGFR(1) alongside airway remodelling in asthma. The inhibition of VEGF and its receptor may be a good therapeutic strategy for asthma.

Angiogenesis: a potentially critical part of remodelling in chronic airway diseases?

Angiogenesis is a prominent feature of the structural tissue remodelling that occurs in the chronic airway diseases of asthma, Bronchiolitis Obliterans Syndrome (BOS, post-lung transplantation), and in smoking-related Chronic Obstructive Pulmonary Disease (COPD). For each, we have explored the relationship between angiogenesis and underlying chronic inflammatory processes--are the hypervascular changes secondary to inflammation, or do they occur in parallel? What are the likely growth factors which stimulate the angiogenic process? We discuss the relationships that have been studied between angiogenesis and the physiological impairment of airflow obstruction. The pattern that emerges is complex and variable. In asthma, there is strong evidence to suggest that Vascular Endothelial Growth Factor (VEGF) and its receptor system is upregulated in the airway. Local production of VEGF has also been implicated as a major driver of angiogenesis in the airway component of COPD, though paradoxically emphysema seems to be due to lack of VEGF in the lung parenchyma. In BOS, the evidence suggests that VEGF is lacking in the airway: other mediators and especially C-X-C chemokines such as Interleukin (IL)-8, are likely to be more important in angiogenesis. The physiological consequences of angiogenesis are likely to be important in asthma (especially during acute episodes of deterioration), and probably also in COPD, although data is equivocal. In BOS, increased airway vascularity appears to occur early, but is not progressive. In terms of therapy, evidence for anti-angiogenic effectiveness is strongest for Inhaled Corticosteroid (ICS) and Long Acting Beta-Agonists (LABA) in asthma.

Asthma therapy and airway remodeling

Asthma is characterized by variable degrees of chronic inflammation and structural alterations in the airways. The most prominent abnormalities include epithelial denudation, goblet cell metaplasia, subepithelial thickening, increased airway smooth muscle mass, bronchial gland enlargement, angiogenesis, and alterations in extracellular matrix components, involving large and small airways. Chronic inflammation is thought to initiate and perpetuate cycles of tissue injury and repair in asthma, although remodeling may also occur in parallel with inflammation. In the absence of definite evidence on how different remodeling features affect lung function in asthma, the working hypothesis should be that structural alterations can lead to the development of persistent airway hyperresponsiveness and fixed airway obstruction. It is still unanswered whether and when to begin treating patients with asthma to prevent or reverse deleterious remodeling, which components of remodeling to target, and how to monitor remodeling. Consequently, efforts are being made to understand better the effects of conventional anti-inflammatory therapies, such as glucocorticosteroids, on airway structural changes. Animal models, in vitro studies, and some clinical studies have advanced present knowledge on the cellular and molecular pathways involved in airway remodeling. This has encouraged the development of biologicals aimed to target various components of airway remodeling. Progress in this area requires the explicit linking of modern structure-function analysis with innovative biopharmaceutical approaches.

Synergistic effects of fluticasone propionate and salmeterol on inhibiting rhinovirus-induced epithelial production of remodelling-associated growth factors

BACKGROUND

Rhinoviruses (RV), the major trigger of acute asthma exacerbations, are able to infect bronchial epithelium and induce production of pro-inflammatory, but also angiogenic and pro-fibrotic mediators. Fluticasone propionate (FP) and salmeterol (S) are clinically effective and act synergistically in controlling persistent asthma; however, their effect on virus-associated asthma is less clear.

AIM

The aim of this study was to assess the individual and combined effects of FP and S on RV-induced epithelial production of vascular endothelial growth factor (VEGF) and fibroblast growth factor-2 (FGF-2).

METHODS

Bronchial epithelial cells (BEAS-2B) were exposed in vitro to RV and were subsequently treated with FP and S, at physiologically relevant concentrations, alone or in combination. VEGF and FGF-2 were measured in the supernatants of these cultures using ELISA.

RESULTS

FP was able to reduce RV-induced VEGF production in a dose-dependent manner. S also induced a smaller reduction; addition of both factors inhibited VEGF synergistically. FGF-2 production was not inhibited by either FP or S alone, but was significantly reduced when both substances were present in the culture.

CONCLUSION

This study demonstrates that FP and S may synergistically inhibit the production of angiogenic and/or pro-fibrotic factors that are induced after RV infection of BEAS-2B and are implicated in airway remodelling, suggesting that this combination may represent an important therapeutic option on virus-induced asthma.

Opposite effect of corticosteroids and long-acting beta(2)-agonists on serum- and TGF-beta(1)-induced extracellular matrix deposition by primary human lung fibroblasts

Asthma and chronic obstructive pulmonary disease (COPD) are characterized by chronic airway inflammation and major structural lung tissue changes including increased extracellular matrix (ECM) deposition. Inhaled corticosteroids and long-acting beta(2)-agonists (LABA) are the basic treatment for both diseases, but their effect on airway remodeling remains unclear. In this study, we investigated the effect of corticosteroids and LABA, alone or in combination, on total ECM and collagen deposition, gene expression, cell proliferation, and IL-6, IL-8, and TGF-beta(1) levels by primary human lung fibroblasts. In our model, fibroblasts in 0.3% albumin represented a non-inflammatory condition and stimulation with 5% FCS and/or TGF-beta(1) mimicked an inflammatory environment with activation of tissue repair. FCS (5%) increased total ECM, collagen deposition, cell proliferation, and IL-6, IL-8, and TGF-beta(1) levels. In 0.3% albumin, corticosteroids reduced total ECM and collagen deposition, involving the glucocorticoid receptor (GR) and downregulation of collagen, heat shock protein 47 (Hsp47), and Fli1 mRNA expression. In 5% FCS, corticosteroids increased ECM deposition, involving upregulation of COL4A1 and CTGF mRNA expression. LABA reduced total ECM and collagen deposition under all conditions partly via the beta(2)-adrenergic receptor. In combination, the drugs had an additive effect in the presence or absence of TGF-beta(1) further decreasing ECM deposition in 0.3% albumin whereas counteracting each other in 5% FCS. These data suggest that the effect of corticosteroids, but not of LABA, on ECM deposition by fibroblasts is altered by serum. These findings imply that as soon as airway inflammation is resolved, long-term treatment with combined drugs may beneficially reduce pathological tissue remodeling.

Long-acting beta2-agonists in asthma: not so SMART?

Asthma is a worldwide chronic disorder that is characterised by airway inflammation and hyper-responsiveness, which results in intermittent airflow obstruction and subsequent perception of symptoms and exacerbations. Inhaled corticosteroids are a fundamental component in the prevention of the short- and long-term complications associated with inadequately controlled asthma. However, many individuals experience persistent symptoms and exacerbations despite receiving low-to-medium doses of an inhaled corticosteroid (400-800 microg/day of beclometasone or equivalent). In these symptomatic asthmatic patients, guidelines advocate the initiation of a long-acting beta2-adrenoceptor agonist (LABA) as additional second-line controller therapy. The recent SMART (Salmeterol Multi-centre Asthma Research Trial) study was designed to compare the effects of add-on salmeterol 42 microg (ex-actuator) twice daily with placebo over 28 weeks in a randomised, double-blind, parallel-group fashion, with the intention to enrol 60,000 asthmatic patients. However, the study was halted prematurely because preliminary data revealed an increased mortality associated with regular use of salmeterol. Moreover, concerning rates of respiratory-related deaths, asthma-related deaths and life-threatening events were observed among African Americans, who constituted up to 18% of the study population. This in turn prompted the US FDA to announce important safety information regarding inhalers containing LABAs and advise that new labelling be produced outlining the "small but significant risk in asthma-related deaths" associated with their regular use. This evidence-based review discusses the data from SMART and highlights potentially important drawbacks with regular use of LABAs in persistent asthma.

Effects of inhaled fluticasone on angiogenesis and vascular endothelial growth factor in asthma

BACKGROUND

Subepithelial hypervascularity and angiogenesis in the airways are part of structural remodelling of the airway wall in asthma, but the effects of inhaled corticosteroids (ICS) on these have not been explored. Increased vascularity in asthma may contribute to a number of functional abnormalities. A study was undertaken to explore angiogenic modulation by ICS and its likely regulation via vascular endothelial growth factor (VEGF), its receptors and the angiopoietins.

METHODS

A placebo-controlled intervention study with ICS in asthma was performed, examining vascularity, VEGF, its receptors (VEGFR1 and VEGFR2), and angiopoietin-1 (Ang1) to assess which of these factors were changed in the asthmatic airways after ICS treatment. Airway wall biopsy specimens, lavage fluid and cells were obtained from 35 patients with mild asthma randomised to receive ICS or placebo for 3 months, after which bronchoscopic examination and sample collection were repeated. Immunohistochemistry and image analysis were used to obtain quantitative measures of vessels, angiogenic sprouts, VEGF, VEGFR1, VEGFR2 and Ang1 staining in airway biopsy specimens. ELISA was used to assess VEGF concentrations in the lavage fluid.

RESULTS

Vessel, VEGF and sprout staining were decreased after 3 months of ICS treatment. VEGF levels remained unchanged. VEGF receptors and Ang1 staining were not reduced after treatment.

CONCLUSIONS

The findings of this study support an effect of ICS in downregulating angiogenic remodelling in the airways in asthma, associated with decreasing VEGF activity within the airway wall. The environment of the airways after treatment with ICS, with changes in the balance between VEGF, its receptors, Ang1 and sprouts, appears to be less angiogenic than in untreated asthma.

The importance of the airway microvasculature in asthma

PURPOSE OF REVIEW

The microvasculature in asthma has been known to contribute to airway-wall thickening and oedema from early post-mortem series. Current concepts of airway inflammation in asthma highlight the importance of the role of the Th2 lymphocyte in the atopic response to aeroallergens, the importance of mast-cell mediators in airway remodelling, potential actions of the vascular response in determining airway thickness and mechanisms of angiogenesis involving endogenous as well as homing progenitor cells with angioblastic potential.

RECENT FINDINGS

The development of animal models of asthmatic airway inflammation and remodelling have given new insight into mechanisms of angiogenesis in asthma. The central role of vascular endothelial growth factor in angiogenesis, vessel leakage and vascular homeostasis is now recognized. A more recent finding is the influence of this factor in enhancing the Th2 response in airway inflammation. The ability of bone marrow-derived angioblasts to migrate to sites of inflammation and contribute to angiogenesis indicates a pivotal role of stem cells in this process.

SUMMARY

These findings now provide logical links between the inflammatory response, stem-cell mobilization, angiogenesis and airflow obstruction in the remodelled airway of asthma. Future studies examining airway-wall thickness will be able to account for the contribution of the vasculature and airway-wall oedema. Therapies aimed at vascular mechanisms may be useful adjuncts to current treatments and the recognition of stem cells as key players in airway remodelling may provide strategies to reduce fixed airflow obstruction in severe disease.

Vascular Endothelial Growth Factor Modulates Matrix Metalloproteinase-9 Expression in Asthma

RATIONALE

Vascular endothelial growth factor (VEGF) and matrix metalloproteinase-9 (MMP-9) are mediators of airway inflammation and remodeling in asthma.

OBJECTIVES

This study investigates a potential relationship between VEGF and MMP-9, and the mechanisms by which VEGF signaling regulates MMP-9 expression in asthma.

METHODS

We evaluated whether levels of VEGF correlated with levels of MMP-9 in the sputum of asthma patients, and the effect of VEGF receptor inhibitors on MMP-9 expression in murine model of asthma.

MEASUREMENTS AND MAIN RESULTS

We have found that levels of VEGF and MMP-9 are significantly higher in the sputum of patients with asthma than in healthy control subjects, and a significant correlation is found between the levels of VEGF and MMP-9. This study with the ovalbumin-induced model of asthma revealed the following typical pathophysiologic features of asthma in the lungs: increased numbers of inflammatory cells of the airways, airway hyperresponsiveness, increased vascular permeability, and increased levels of MMP-9 and VEGF. Administration of VEGF receptor inhibitors reduced the pathophysiologic signs of asthma and decreased the increased expression of MMP-9 after ovalbumin inhalation.

CONCLUSIONS

These results indicate that there is a close relationship between VEGF and MMP-9 expression and that inhibition of VEGF receptor down-regulates the expression of MMP-9. These findings suggest that VEGF signaling regulates MMP-9 expression and plays a critical role in initiation and maintenance of asthma.

Airway remodelling in asthma: current understanding and implications for future therapies

Airway remodelling refers to the structural changes that occur in the airway wall in asthma. These include epithelial hyperplasia and metaplasia, subepithelial fibrosis, muscle cell hyperplasia and angiogenesis. These structural changes result in thickening of the airway wall, airway hyperresponsiveness (AHR), and a progressive irreversible loss of lung function. The precise sequence of events that take place during the remodelling process and the mechanisms regulating these changes remain poorly understood. It is thought that airway remodelling is initiated and promoted by repeated episodes of allergic inflammation that damage the surface epithelium of the airway. However, other mechanisms are also likely to contribute to this process. Moreover, the interrelationship between airway remodelling, inflammation and AHR has not been clearly defined. Currently, there are no effective treatments that halt or reverse the changes of airway remodelling and its effects on lung function. Glucocorticoids have been unable to eliminate the progression of remodelling changes and there is limited evidence of a beneficial effect from other available therapies. The search for novel therapies that can directly target individual components of the remodelling process should be made a priority. In this review, we describe the current understanding of the airway remodelling process and the mechanisms regulating its development. The impact of currently available asthma therapies on airway remodelling is also discussed.

Phosphatase and tensin homolog deleted on chromosome 10 (PTEN) reduces vascular endothelial growth factor expression in allergen-induced airway inflammation

Vascular endothelial growth factor (VEGF) plays a pivotal role in the pathogenesis of bronchial asthma. Phosphatase and tensin homolog deleted on chromosome 10 (PTEN) has been implicated in regulating cell survival signaling through the phosphoinositide 3-kinase (PI3K)/Akt pathway. The key role of PI3K in VEGF-mediated signal transduction is established. However, the effects of PTEN on VEGF-mediated signaling in asthma are unknown. This study aimed to determine the effect of PI3K inhibitors and PTEN on VEGF expression in allergen-induced airway inflammation. We have used a female C57BL/6 mouse model for asthma to determine the role of PTEN in allergen-induced airway inflammation, specifically in the expression of VEGF. Allergen-induced airway inflammation leads to increased activity of PI3K in lung tissue. These mice develop the following typical pathophysiological features of asthma in the lungs: increased numbers of inflammatory cells of the airways; airway hyper-responsiveness; increased expression of interleukin (IL)-4, IL-5, IL-13, intercellular adhesion molecule 1, vascular cell adhesion molecule 1, regulated on activation normal T cell expressed and secreted (RANTES), and eotaxin; increased vascular permeability; and increased levels of VEGF. Administration of PI3K inhibitors or adenoviruses carrying PTEN cDNA reduced the symptoms of asthma and decreased the increased levels of plasma extravasation and VEGF in allergen-induced asthmatic lungs. These results indicate that PTEN reduces VEGF expression in allergen-induced airway inflammation.