Severe asthma in adults: what are the important questions?

Anti-inflammatory effects of the neurotransmitter agonist Honokiol in a mouse model of allergic asthma

Chronic airway inflammation is a hallmark of asthma, an immune-based disease with great societal impact. Honokiol (HNK), a phenolic neurotransmitter receptor (γ-aminobutyric acid type A) agonist purified from magnolia, has anti-inflammatory properties, including stabilization of inflammation in experimentally induced arthritis. The present study tested the prediction that HNK could inhibit the chronic inflammatory component of allergic asthma. C57BL/6 mice sensitized to and challenged with OVA had increased airway hyperresponsiveness to methacholine challenge and eosinophilia compared with naive controls. HNK-treated mice showed a reduction in airway hyperresponsiveness as well as a significant decrease in lung eosinophilia. Histopathology studies revealed a marked drop in lung inflammation, goblet cell hyperplasia, and collagen deposition with HNK treatment. Ag recall responses from HNK-treated mice showed decreased proinflammatory cytokines in response to OVA, including TNF-α-, IL-6-, Th1-, and Th17-type cytokines, despite an increase in Th2-type cytokines. Regulatory cytokines IL-10 and TGF-β were also increased. Assessment of lung homogenates revealed a similar pattern of cytokines, with a noted increase in the number of FoxP3(+) cells in the lung. HNK was able to alter B and T lymphocyte cytokine secretion in a γ-aminobutyric acid type A-dependent manner. These results indicate that symptoms and pathology of asthma can be alleviated even in the presence of increased Th2 cytokines and that neurotransmitter agonists such as HNK have promise as a novel class of anti-inflammatory agents in the treatment of chronic asthma.

Severe asthma and adherence to peak flow monitoring: longitudinal assessment of psychological aspects

BACKGROUND

Adherence in severe asthma is a difficult health problem. Although psychosocial factors may be responsible for non-adherence, few longitudinal studies have investigated their link with adherence, with most studies having focused on pharmacology.

METHODS

Sixty patients with severe asthma were recruited. Adherence was electronically monitored using peak flow measurements at entry and after 1 year of follow-up. Eysenck's Personality Inventory, Rotter's Locus of Control (LOC), and health control beliefs were all studied. Multiple logistic regression (MLR) was used for risk calculations.

RESULTS

Initially, subjects with poor adherence had an external LOC (P=.001) and a high extraversion score (P=.003) compared to those with good adherence. The lie score was high in all patients. Nocturnal awakenings were highly significantly correlated with poor adherence (P=.006). After 1 year, patient adherence, extraversion, and neuroticism remained unchanged. The LOC changed in subjects with poor adherence, showing a less "external" orientation (P=.007). The health parameters were better at the end of the study. By MLR analysis, externality, extraversion, and low social desirability were associated with poor adherence. Patients with poor adherence had a greater probability of nocturnal symptoms.

CONCLUSION

No specific personality type was associated with lack of adherence in the present study, but a high extraversion score, a low social desirability score, and a high level of externality were all predictors of poor adherence.

Nontuberculous mycobacterial infection as a cause of difficult-to-control asthma: a case-control study

BACKGROUND

Symptomatic disease due to nontuberculous mycobacteria (NTM) is known to occur commonly in the presence of structural lung disease, but is not described in association with asthma.

METHODS

This was a case-control study nested in a cohort. We identified 22 patients with difficult asthma referred to a tertiary academic referral center and subsequently found to have infection with NTM. We matched each case with two control subjects (next two consecutive patients referred for asthma management).

RESULTS

It took on average 2.1 years from the onset of new or worsening symptoms to NTM diagnosis. The most common symptoms were worsening cough (77%), sputum production (40.9%), and frequent exacerbations (31.8%). Mycobacterium avium complex accounted for 63.6% of the infections, Mycobacterium xenopi the balance. Case subjects were older (59.8 ± 8.9 vs 42.6 ± 18 years; P < .001) and had more severe airflow obstruction (FEV(1), 57% [40%-74%] vs 89.5% [80%-98%]; P < .001). There was no difference between case and control subjects in the proportion using inhaled corticosteroids (ICS) or the average daily dose at the time of presentation, but case subjects had used ICS for a longer period (17 [6.2-20] vs 4 [0.75-6.0] years; P=.002). Six subjects with NTM were being treated with daily oral steroids, whereas none of the control subjects was. Of the 22 cases, 10 were treated with antibiotics for NTM, seven demonstrating clinical improvement or resolution of the presenting symptoms.

CONCLUSIONS

NTM infection can be associated with asthma and should be considered in difficult-to-treat disease, especially in older individuals with more severe airflow obstruction and greater exposure to inhaled or systemic corticosteroids.

Omalizumab-induced decrease of FcξRI expression in patients with severe allergic asthma

BACKGROUND

It is documented that omalizumab treatment reduces the cell surface expression of immunoglobulin E high-affinity receptor (FcɛRI) on several cell types. This has not been investigated in patients with uncontrolled severe persistent allergic asthma.

METHODS

In a double-blind, randomized, placebo-controlled study, patients with severe allergic asthma uncontrolled by high dose inhaled corticosteroids and long-acting β(2)-agonist received either omalizumab (n = 20) or placebo (n = 11) over 16 weeks at appropriate doses and frequencies. Baseline and end of study (week 16) FcɛRI expression on basophils and plasmacytoid dendritic cells was determined by flow cytometry for the primary endpoint. Secondary efficacy endpoints included asthma control and lung function as part of an initial investigation into the use of FcɛRI expression as a marker of response.

RESULTS

In the omalizumab group, and with respect to placebo, FcɛRI expression was significantly reduced at end of study on basophils (-82.6%, p < 0.01) and plasmacytoid dendritic cells (-44.2%, p = 0.029). FcɛRI expression reduction was not found to be correlated with clinical response.

CONCLUSIONS

Long-term omalizumab treatment induced reduction of FcɛRI expression on circulating basophils and plasmacytoid dendritic cells. These changes were not associated with those of clinical features related to severe asthma, which does not support further investigation into its use as a predictive marker of response.

TRIAL REGISTRATION

The study was registered with ClinicalTrials.gov (identifier: NCT00454051) and the European Clinical Trials Database, EudraCT (identifier: 2006-003591-35).

Predicting intermediate phenotypes in asthma using bronchoalveolar lavage-derived cytokines

An important problem in realizing personalized medicine is the development of methods for identifying disease subtypes using quantitative proteomics. Recently we found that bronchoalveolar lavage (BAL) cytokine patterns contain information about dynamic lung responsiveness. In this study, we examined physiological data from 1,048 subjects enrolled in the US Severe Asthma Research Program (SARP) to identify four largely separable, quantitative intermediate phenotypes. Upper extremes in the study population were identified for eosinophil- or neutrophil-predominant inflammation, bronchodilation in response to albuterol treatment, or methacholine sensitivity. We evaluated four different statistical ("machine") learning methods to predict each intermediate phenotype using BAL A-cytokine measurements on a 76 subject subset. Comparison of these models using area under the ROC curve and overall classification accuracy indicated that logistic regression and multivariate adaptive regression splines produced the most accurate methods to predict intermediate asthma phenotypes. These robust classification methods will aid future translational studies in asthma targeted at specific intermediate phenotypes.

Ciliary dysfunction and ultrastructural abnormalities are features of severe asthma

BACKGROUND

Epithelial dysfunction has been implicated in asthma pathophysiology, but no studies have directly assessed ciliary function in asthma.

OBJECTIVE

To study the ciliary function and epithelial ultrastructure of patients with asthma and healthy controls.

METHODS

We studied ciliary beat frequency and beat pattern by using digital high-speed video imaging and ultrastructure by transmission electron microscopy of bronchial epithelial strips from 7 subjects with mild, 7 with moderate, and 19 with severe asthma and 9 healthy controls.

RESULTS

The median (interquartile range) ciliary beat frequency was decreased in moderate (6.5 [4.4-8.5] Hz) and severe asthma (6.7 [6.1-7.6] Hz) compared with controls (10.5 [9.7-11.8] Hz; P < .01). Dyskinesia and immotility indices were higher in severe asthma (65% [43%-75%]; 6.3% [1%-9.5%], respectively) compared with controls (4% [0%-6.7%; 0%, respectively; P < .01). These abnormalities were related to disease severity (ciliary beat frequency, r(s) = -0.68; dyskinesia index, r(s) = 0.86; immotility index, r(s) = 0.65; P < .0001). The ultrastructure of the epithelium was abnormal in severe asthma with a reduction in ciliated cells, an increase in dead cells, and ciliary disorientation compared with all other groups (P < .05). Compared with patients with mild asthma and healthy controls, patients with severe asthma showed increased ciliary depletion, microtubular defects, mitochondrial damage, and cytoplasmic blebbing (P < .01). All of these changes were related to disease severity.

CONCLUSION

Ciliary dysfunction and ultrastructural abnormalities are closely related to asthma severity. Ciliary dysfunction is a feature of moderate to severe asthma, and profound ultrastructural abnormalities are restricted to severe disease. Whether these changes contribute to the development of severe asthma phenotype remains to be determined.

Expression and activation of the oxytocin receptor in airway smooth muscle cells: Regulation by TNFalpha and IL-13

Background

During pregnancy asthma may remain stable, improve or worsen. The factors underlying the deleterious effect of pregnancy on asthma remain unknown. Oxytocin is a neurohypophyseal protein that regulates a number of central and peripheral responses such as uterine contractions and milk ejection. Additional evidence suggests that oxytocin regulates inflammatory processes in other tissues given the ubiquitous expression of the oxytocin receptor. The purpose of this study was to define the role of oxytocin in modulating human airway smooth muscle (HASMCs) function in the presence and absence of IL-13 and TNFα, cytokines known to be important in asthma.

Method

Expression of oxytocin receptor in cultured HASMCs was performed by real time PCR and flow cytomery assays. Responses to oxytocin was assessed by fluorimetry to detect calcium signals while isolated tracheal rings and precision cut lung slices (PCLS) were used to measure contractile responses. Finally, ELISA was used to compare oxytocin levels in the bronchoalveloar lavage (BAL) samples from healthy subjects and those with asthma.

Results

PCR analysis demonstrates that OXTR is expressed in HASMCs under basal conditions and that both interleukin (IL)-13 and tumor necrosis factor (TNFα) stimulate a time-dependent increase in OXTR expression at 6 and 18 hr. Additionally, oxytocin increases cytosolic calcium levels in fura-2-loaded HASMCs that were enhanced in cells treated for 24 hr with IL-13. Interestingly, TNFα had little effect on oxytocin-induced calcium response despite increasing receptor expression. Using isolated murine tracheal rings and PCLS, oxytocin also promoted force generation and airway narrowing. Further, oxytocin levels are detectable in bronchoalveolar lavage (BAL) fluid derived from healthy subjects as well as from those with asthma.

Conclusion

Taken together, we show that cytokines modulate the expression of functional oxytocin receptors in HASMCs suggesting a potential role for inflammation-induced changes in oxytocin receptor signaling in the regulation of airway hyper-responsiveness in asthma.

The efficacy of tiotropium as a steroid-sparing agent in severe asthma

People with severe asthma account for 5% to 10% of all asthmatic patients; however, this small group uses the majority of health care resources. Novel methods are needed to cope with the burden that this minority of patients places on the health care system. A severe asthma clinic patient, who was monitored through the University of Alberta's Virtual Asthma Clinic (Edmonton, Alberta) is presented. Despite optimization of his disease and individualized asthma education (provided by a certified asthma educator), the patient remained on oral glucocorticosteroids (OGS) to control his disease. Following optimization and stabilization, a further reduction in the dose of his OGS by the addition of the long-acting anticholinergic agent tiotropium bromide, was demonstrated. The role of tiotropium as a potential 'steroid-sparing agent' in severe refractory asthma is discussed, noting that if patients who are on OGS are not monitored for active inflammation, they may overuse the amount of prescribed systemic steroids, which can result in long-term steroid-related sequelae.

Recommendation for optimal management of severe refractory asthma

Patients whose asthma is not adequately controlled despite treatment with a combination of high dose inhaled corticosteroids and long-acting bronchodilators pose a major clinical challenge and an important health care problem. Patients with severe refractory disease often require regular oral corticosteroid use with an increased risk of steroid-related adverse events. Alternatively, immunomodulatory and biologic therapies may be considered, but they show wide variation in efficacy across studies thus limiting their generalizability. Managing asthma that is refractory to standard treatment requires a systematic approach to evaluate adherence, ensure a correct diagnosis, and identify coexisting disorders and trigger factors. In future, phenotyping of patients with severe refractory asthma will also become an important element of this systematic approach, because it could be of help in guiding and tailoring treatments. Here, we propose a pragmatic management approach in diagnosing and treating this challenging subset of asthmatic patients.

An integrative systems biology approach to understanding pulmonary diseases

Chronic inflammatory pulmonary diseases such as COPD and asthma are highly prevalent and associated with a major health burden worldwide. Despite a wealth of biologic and clinical information on normal and pathologic airway structure and function, the primary causes and mechanisms of disease remain to a large extent unknown, preventing the development of more efficient diagnosis and treatment. We propose to overcome these limitations through an integrative systems biology research strategy designed to identify the functional and regulatory pathways that play central roles in respiratory pathophysiology, starting with severe asthma. This approach relies on global genome, transcriptome, proteome, and metabolome data sets collected in cross-sectional patient cohorts with high-throughput measurement platforms and integrated with biologic and clinical data to inform predictive multiscale models ranging from the molecular to the organ levels. Working hypotheses formulated on the mechanisms and pathways involved in various disease states are tested through perturbation experiments using model simulation combined with targeted and global technologies in cellular and animal models. The responses observed are compared with those predicted by the initial models, which are refined to account better for the results. Novel perturbation experiments are designed and tested both computationally and experimentally to arbitrate between competing hypotheses. The process is iterated until the derived knowledge allows a better classification and subphenotyping of severe asthma using complex biomarkers, which will facilitate the development of novel diagnostic and therapeutic interventions targeting multiple components of the molecular and cellular pathways involved. This can be tested and validated in prospective clinical trials.

Cytokine production from sputum cells and blood leukocytes in asthmatics according to disease severity

BACKGROUND

Although mild to moderate asthma is known to be Th2 driven, cytokines produced in refractory asthma might not fit the classical Th2 pattern.

METHODS

The aim of our study was to assess the cytokine production by sputum and blood cells from 15 refractory asthmatics (American Thoracic Society Criteria) compared to 15 mild untreated and 17 moderate treated asthmatics and 22 healthy subjects. Spontaneous production of interleukin (IL)-4, IL-6, IL-10, interferon-gamma, and tumor necrosis factor alpha was measured by immunotrapping after 24 h sputum or blood cell culture.

RESULTS

Moderate and refractory asthmatics were both characterized by a lower production of IL-6 from their airway cells compared to healthy subjects. However, the difference was no longer significant when expressing the results per gram of sputum. No significant difference between the three groups was found regarding other cytokines. As for cytokine production from blood, the three groups of asthmatics exhibited raised production of IL-4 when compared to healthy subjects, and this was true when results were expressed per blood volume or after normalization for total leukocyte cell count. Moderate asthmatics exhibited greater production of IL-10 when compared to refractory asthmatics and healthy subjects when results were normalized for total leukocyte cell count.

CONCLUSIONS

Sputum cells from moderate and refractory asthmatics release less IL-6. While the systemic overproduction of IL-4 was observed through the all spectrum of asthma severity, moderate asthmatics exhibited greater systemic IL-10 production compared to refractory asthmatics.

Expression of the T helper 17-associated cytokines IL-17A and IL-17F in asthma and COPD

Background:

Asthma and COPD are characterized by airway dysfunction and inflammation. Neutrophilic airway inflammation is a common feature of COPD and is recognized in asthma, particularly in severe disease. The T helper (Th) 17 cytokines IL-17A and IL-17F have been implicated in the development of neutrophilic airway inflammation, but their expression in asthma and COPD is uncertain.

Methods:

We assessed IL-17A and IL-17F expression in the bronchial submucosa from 30 subjects with asthma, 10 ex-smokers with mild to moderate COPD, and 27 nonsmoking and 14 smoking control subjects. Sputum IL-17 concentration was measured in 165 subjects with asthma and 27 with COPD.

Results:

The median (interquartile range) IL-17A cells/mm² submucosa was increased in mild to moderate asthma (2.1 [2.4]) compared with healthy control subjects (0.4 [2.8]) but not in severe asthma (P = .04). In COPD, IL-17A⁺ cells/mm² submucosa were increased (0.5 [3.7]) compared with nonsmoking control subjects (0 [0]) but not compared with smoking control subjects (P = .046). IL-17F⁺ cells/mm² submucosa were increased in severe asthma (2.7 [3.6]) and mild to moderate asthma (1.6 [1.0]) compared with healthy controls subjects (0.7 [1.4]) (P = .001) but was not increased in subjects with COPD. IL-17A and IL-17F were not associated with increased neutrophilic inflammation, but IL-17F was correlated with the submucosal eosinophil count (rs = 0.5, P = .005). The sputum IL-17 concentration in COPD was increased compared with asthma (2 [0-7] pg/mL vs 0 [0-2] pg/mL, P < .0001) and was correlated with post-bronchodilator FEV₁% predicted (r = −0.5, P = .008) and FEV₁/FVC (r = −0.4, P = .04).

Conclusions:

Our findings support a potential role for the Th17 cytokines IL-17A and IL-17F in asthma and COPD, but do not demonstrate a relationship with neutrophilic inflammation.

Perceptions about self-management among people with severe asthma

AIM

The purpose of this study was to explore the perceptions about self-management among people who were being followed up in a severe asthma clinic by asthma specialists for confirmed, overall severe asthma. Such insight informs how best to tailor programs for this difficult to treat patient population.

METHOD

In-depth tape-recorded interviews of eight adults with severe asthma were transcribed and analyzed for salient themes using content analysis.

RESULTS

To self-manage their illness, over time participants sought asthma information from a variety of sources that they often viewed as inadequate due to lack of scope and or plain language. The most valued sources of asthma information were encountered after referral to an asthma specialist and were health professionals and a pulmonary rehabilitation program.

CONCLUSION

There is a need to examine the content of asthma information sources for their relevance to and influence on the behavior of patients with severe asthma.

[Factors associated with asthma control in primary care patients: the CHAS study]

BACKGROUND

Asthma control is inadequate in all populations studied to date, leading to a major part of the cost of the disease. The aim of our study was to evaluate the prevalence of uncontrolled asthma in primary care patients and identify the associated factors.

METHODS

We carried out a cross-sectional study of the population of primary care asthmatic patients over 18 years old in Spain (n=2159). Asthma control was measured with the Asthma Control Questionnaire (ACQ). The sociodemographic variables and treatment compliance were measured using a questionnaire. We built logistic-regression models using Asthma control, a dichotomous variable generated from ACQ score.

RESULTS

The prevalence of uncontrolled asthma was 63.9%. Treatment with oral corticosteroids (OCS) (OR=6.55), greater asthma severity (OR=3.11), presence of a distressing event (OR=2.44), lower significance given to treatment compliance (OR=1.66) and living in a rural area (OR=1.29) are associated with uncontrolled asthma. On the contrary, sex, age, obesity, smoking, alcohol intake and educational level had no effect on asthma control.

CONCLUSIONS

In Spain asthma is still uncontrolled and some factors leading to this situation appear to be modifiable by the health system.

S100A8/A9: a mediator of severe asthma pathogenesis and morbidity?

Nearly 12% of children and 6% of adults in Canada have been diagnosed with asthma. Although in most patients symptoms are controlled by inhaled steroids, a subpopulation (approximately 10%) characterized by excessive airway neutrophilia, is refractory to treatment; these patients exhibit severe disease, and account for more than 50% of asthma health care costs. These numbers underscore the need to better understand the biology of severe asthma and identify pro-asthma mediators released by cells, such as neutrophils, that are unresponsive to common steroid therapy. This review focuses on a unique protein complex consisting of S100A8 and S100A9. These subunits belong to the large Ca2+-binding S100 protein family and are some of the most abundant proteins in neutrophils and macrophages. S100A8/A9 is a damage-associated molecular pattern (DAMP) protein complex released in abundance in rheumatoid arthritis, inflammatory bowel disease, and cancer, but there are no definitive studies on its role in inflammation and obstructive airways disease. Two receptors for S100A8/A9, the multiligand receptor for advanced glycation end products (RAGE) and Toll-like receptor 4 (TLR4), are expressed in lung. TLR4 is linked with innate immunity that programs local airway inflammation, and RAGE participates in mediating fibroproliferative remodeling in idiopathic pulmonary fibrosis. S100A8/A9 can induce cell proliferation, or apoptosis, inflammation, collagen synthesis, and cell migration. We hypothesize that this capacity suggests S100A8/A9 could underpin chronic airway inflammation and airway remodeling in asthma by inducing effector responses of resident and infiltrating airway cells. This review highlights some key issues related to this hypothesis and provides a template for future research.

Exhaled nitric oxide and exhaled breath condensate pH in severe refractory asthma

BACKGROUND

Distinct inflammatory cellular phenotypes of severe refractory asthma (SRA) have been reported. Fractional exhaled nitric oxide (FeNO) primarily is related to eosinophilic inflammation. Exhaled breath condensate (EBC) pH has been suggested as a noninvasive tool in the assessment of patients with asthma. We sought to determine whether FeNO and EBC pH could identify the presence and type of the underlying cellular inflammation in patients with SRA.

METHODS

Twenty-nine patients with SRA, 27 patients with moderate asthma, and 17 healthy subjects underwent FeNO measurement, EBC collection for pH measurement, and sputum induction for cell count identification.

RESULTS

FeNO was significantly higher and pH significantly lower in patients with SRA than in the other groups. In SRA, FeNO levels of > 19 parts per billion were associated with a sensitivity of 0.78 and a specificity of 0.73 for sputum eosinophilia, whereas FeNO levels of < 19 parts per billion were associated with a sensitivity of 0.63 and a specificity of 0.9 for sputum neutrophilia irrespective of the presence of eosinophils. The pH failed to predict the cellular profile in SRA, but a cutoff value of < 7.37 could predict sputum eosinophilia in moderate asthma.

CONCLUSIONS

In patients with SRA, different FeNO threshold values can identify those with predominant eosinophilia as well as those with neutrophilia. FeNO levels were reduced in patients with predominant neutrophilia regardless of the concomitant presence of eosinophilia. Although pH could not identify the cellular profile in SRA, it seemed to be a better index for predicting eosinophilia in moderate asthma.

Use of exhaled nitric oxide measurement to identify a reactive, at-risk phenotype among patients with asthma

RATIONALE

Exhaled nitric oxide (Fe(NO)) is a biomarker of airway inflammation in mild to moderate asthma. However, whether Fe(NO) levels are informative regarding airway inflammation in patients with severe asthma, who are refractory to conventional treatment, is unknown. Here, we hypothesized that classification of severe asthma based on airway inflammation as defined by Fe(NO) levels would identify a more reactive, at-risk asthma phenotype.

METHODS

Fe(NO) and major features of asthma, including airway inflammation, airflow limitation, hyperinflation, hyperresponsiveness, and atopy, were determined in 446 individuals with various degrees of asthma severity (175 severe, 271 non-severe) and 49 healthy subjects enrolled in the Severe Asthma Research Program.

MEASUREMENTS AND MAIN RESULTS

Fe(NO) levels were similar among patients with severe and non-severe asthma. The proportion of individuals with high Fe(NO) levels (>35 ppb) was the same (40%) among groups despite greater corticosteroid therapy in severe asthma. All patients with asthma and high Fe(NO) had more airway reactivity (maximal reversal in response to bronchodilator administration and by methacholine challenge), more evidence of allergic airway inflammation (sputum eosinophils), more evidence of atopy (positive skin tests, higher serum IgE and blood eosinophils), and more hyperinflation, but decreased awareness of their symptoms. High Fe(NO) identified those patients with severe asthma characterized by the greatest airflow obstruction and hyperinflation and most frequent use of emergency care.

CONCLUSIONS

Grouping of asthma by Fe(NO) provides an independent classification of asthma severity, and among patients with severe asthma identifies the most reactive and worrisome asthma phenotype.

Variable expression of cysteinyl leukotriene type I receptor splice variants in asthmatic females with different promoter haplotypes

BACKGROUND

Cysteinyl leukotrienes are potent inflammatory mediators implicated in the pathogenesis of asthma. Human cysteinyl leukotriene receptor 1 (CYSLTR1) gene contains five exons that are variably spliced. Within its promoter few polymorphisms were described. To date, there has been no evidence about the expression of different splice variants of CysLT1 in asthma and their association with CYSLTR1 promoter polymorphisms.The goal of our study was to investigate CysLT1 alternative transcripts expression in asthmatic patients with different CYSLTR1 promoter haplotypes.The study groups consisted of 44 patients with asthma, diagnosed according to GINA 2008 criteria and 18 healthy subjects. Genomic DNA and total RNA was extracted from peripheral blood mononuclear cells. Real-time PCR was performed with specific primers for transcript I [GenBank:DQ131799] and II [GenBank:DQ131800]. Fragments of the CYSLTR1 promoter were amplified by PCR and sequenced directly to identify four single nucleotide polymorphisms: C/T [SNP:rs321029], A/C [SNP:rs2637204], A/G [SNP:rs2806489] and C/T [SNP:rs7066737].

RESULTS

The expression of CysLT1 transcript I and II in asthma did not differ from its expression in healthy control group. However, in major alleles homozygotic CAAC/CAAC women with asthma we found significantly higher expression of transcript I as compared to heterozygous CAAC/TCGC women in that loci. CysLT1 transcript I expression tended to negative correlation with episodes of acute respiratory infection in our asthmatic population. Moreover, expression of CysLT1 transcript II in CAAC/CAAC homozygotic women with asthma was significantly lower than in CAAC/CAAC healthy control females.

CONCLUSIONS

Genetic variants of CYSLTR1 promoter might be associated with gender specific expression of CysLT1 alternative transcripts in patients with asthma. CysLT1 splice variants expression might also correlate with the susceptibility to infection in asthmatic population.

Effects of glucocorticoids on the neutrophil count: a cohort study among hospitalized patients

BACKGROUND

Systemic glucocorticoids are often used in clinical practice for a large variety of indications. Clinical observations have shown that patients using glucocorticoids often have higher neutrophil counts. Debate remains whether this observed neutrophilia is associated with glucocorticoid use or that other factors, like disease and severity of disease, should be considered. The objective of this study was to investigate the effect of systemic glucocorticoids on the absolute neutrophil count in hospitalized patients.

METHODS

A cohort study was conducted using data from the Utrecht Patient Oriented Database which comprises clinical data of patients of the University Medical Center Utrecht. We identified all adult patients, hospitalized in 2005 with at least two blood samples for hematological testing during admission and compared in-hospital glucocorticoid use with non-use.

RESULTS

A total of 809 glucocorticoid users and 2658 non-users were included in the study with comparable neutrophil counts at admission (8.2.10(9)/l for glucocorticoid users and 8.0.10(9)/l for non-users). Overall analysis showed a slight association between glucocorticoid use and an increase in neutrophil count (RR 1.3; 95% CI 1.1-1.5). However, within diagnostic subgroups there was no increase in neutrophil count in glucocorticoid users. Furthermore, among all no dose response relationship, no effect of time between the two samples, and no effect of anti-inflammatory/sodium retaining potency was found.

CONCLUSION

Observed neutrophilia in users of systemic glucocorticoids is probably associated with underlying disease, rather than glucocorticoid use itself.

Cytokine and anti-cytokine therapy in asthma: ready for the clinic?

Asthma is a common disease with an increasing prevalence worldwide. Up to 10% of these patients have asthma that is refractory to current therapy. This group have a disproportionate use of health care resources attributed to asthma, have significant morbidity and mortality and therefore represent an unmet clinical need. Asthma is a complex heterogeneous condition that is characterized by typical symptoms and disordered airway physiology set against a background of airway inflammation and remodelling. The inflammatory process underlying asthma is co-ordinated by a cytokine network. Modulating this network with biological therapy presents a new paradigm for asthma treatment. Clinical trials undertaken to date have underscored the complexity of the inflammatory profile and its relationship to the clinical features of the disease and have raised the importance of safety considerations related to these novel therapies. T helper type 2 cytokine blockade remains the most promising strategy, with anti-interleukin-5 reducing asthma exacerbations. Although anti-cytokine therapy is not yet ready for the clinic, the long-awaited possibility of new treatments for severe asthma is moving ever closer.

Natural killer T cells and the regulation of asthma

A crucial role has been suggested for invariant natural killer T cells (iNKT) in regulating the development of asthma, a complex and heterogeneous disease characterized by airway inflammation and airway hyperreactivity (AHR). iNKT cells constitute a unique subset of T cells responding to endogenous and exogenous lipid antigens, rapidly secreting a large amount of cytokines, which amplify both innate and adaptive immunity. Herein, we review recent studies showing a requirement for iNKT cells in various models of asthma in mice and monkeys as well as studies in human patients. Surprisingly, in several different murine models of asthma, distinct subsets of iNKT cells were required, suggesting that iNKT cells serve as a common critical pathogenic element for many different forms of asthma. The importance of iNKT cells in both allergic and non-allergic forms of asthma, which are independent of adaptive immunity and associated with airway neutrophils, may explain situations previously found to be incompatible with the Th2 paradigm of asthma.

The soluble tumor necrosis factor-alpha receptor suppresses airway inflammation in a murine model of acute asthma

PURPOSE

Tumor necrosis factor-alpha (TNF-alpha) is a proinflammatory cytokine that has been implicated in many aspects of the airway pathology in asthma. TNF-alpha blocking strategies are now being tried in asthma patients. This study investigated whether TNF-alpha blocking therapy inhibits airway inflammation and airway hyperresponsiveness (AHR) in a mouse model of asthma. We also evaluated the effect of TNF-alpha blocking therapy on cytokine production and adhesion molecule expression.

MATERIALS AND METHODS

Ovalbumin (OVA) sensitized BALB/c female mice were exposed to intranasal OVA administration on days 31, 33, 35, and 37. Mice were treated intraperitoneally with soluble TNF-alpha receptor (sTNFR) during the OVA challenge.

RESULTS

There were statistically significant decreases in the numbers of total cell and eosinophil in bronchoalveolar lavage fluid (BALF) in the sTNFR treated group compared with the OVA group. However, sTNFR-treatment did not significantly decrease AHR. Anti-inflammatory effect of sTNFR was accompanied with reduction of T helper 2 cytokine levels including interleukin (IL)-4, IL-5 and IL-13 in BALF and vascular cell adhesion molecule 1 expression in lung tissue.

CONCLUSION

These results suggest that sTNFR treatment can suppress the airway inflammation via regulation of Th2 cytokine production and adhesion molecule expression in bronchial asthma.

Masitinib, a c-kit/PDGF receptor tyrosine kinase inhibitor, improves disease control in severe corticosteroid-dependent asthmatics

BACKGROUND

Masitinib is a tyrosine kinase inhibitor targeting stem cell factor receptor (c-kit) and platelet-derived growth factor (PDGF) receptor, which are expressed on several cell types including mast cells and bronchial structural cells, respectively. We hypothesized that c-kit and PDGF receptor inhibition may decrease bronchial inflammation and interfere with airway remodeling, which are crucial features of severe asthma.

OBJECTIVES

The primary endpoint was the percent change from baseline in oral corticosteroids after 16 weeks of treatment. Change in asthma control (asthma control questionnaire), exacerbation rate, pulmonary function tests, rescue medication requirement and safety were secondary endpoints.

METHODS

A 16-week randomized, dose-ranging (3, 4.5, and 6 mg/kg/day), placebo-controlled study was undertaken in 44 patients with severe corticosteroid-dependent asthma who remained poorly controlled despite optimal asthma management.

RESULTS

At 16 weeks of treatment, a comparable reduction in oral corticosteroids was achieved with masitinib and placebo (median reduction of -78% and -57% in the masitinib and placebo arms, respectively). Despite this similar reduction, the Asthma Control Questionnaire score was significantly better in the masitinib arm as compared to placebo with a reduction by 0.99 unit at week 16 (P < 0.001) vs 0.43 unit in the placebo arm. Masitinib therapy was associated with more transient skin rash and edema.

CONCLUSIONS

Masitinib, a c-kit and PDGF-receptor tyrosine kinase inhibitor, may represent an innovative avenue of treatment in corticosteroid-dependent asthma. These preliminary results warrant further long-term clinical studies in severe asthma

15-Lipoxygenase-1 induces expression and release of chemokines in cultured human lung epithelial cells

15-Lipoxygenase-1 (15-LOX-1) has been proposed to be involved in various physiological and pathophysiological activities such as inflammation, atherosclerosis, cell maturation, and tumorigenesis. Asthma and chronic obstructive pulmonary disease are associated with increased expression of 15-LOX-1 in bronchial epithelial cells, but the potential functions of 15-LOX-1 in airway epithelial cells have not been well clarified. To study the function of 15-LOX-1 in bronchial epithelial cells, we ectopically expressed 15-LOX-1 in the human lung epithelial cell line A549. We found that overexpression of 15-LOX-1 in A549 cells leads to increased release of the chemokines MIP-1α, RANTES, and IP-10, and thereby to increased recruitment of immature dendritic cells, mast cells, and activated T cells. These results suggest that an increased expression and activity of 15-LOX-1 in lung epithelial cells is a proinflammatory event in the pathogenesis of asthma and other inflammatory lung disorders.

[Complexity in asthma: inflammation and scale-free networks]

Our understanding of asthma has traditionally been based on linear deterministic relationships of the type stimulus-bronchial hyperresponsiveness-obstruction-symptoms. This notion however neglects the fact that nonlinear relationships may be present. To better define the disease, some authors therefore suggest that we should think in terms of complex systems with a scale-free topology. The idea of multiple inflammatory hits proposed by the group of Pavord is in its broadest sense a further contribution to this line of thought. According to this theory, the coexistence of additional inflammatory stimuli, which may or may not be localized to the lungs, are responsible for deteriorating lung function. The effects of these stimuli may be additive or act in synergy with the underlying inflammation of asthma itself. In addition to the practical implications, this hypothesis serves as a reminder that the body is made up of interconnected parts and that the pathogenesis of asthma includes distinct elements linked together. If this hypothesis proves valid, future approaches should start to look for the hubs in this network that constitutes asthma, and attempt to integrate information from genomics, proteomics, and metabolomics.

Etanercept prevents airway hyperresponsiveness by protecting neuronal M2 muscarinic receptors in antigen-challenged guinea pigs

BACKGROUND AND PURPOSE

Increased tumour necrosis factor-alpha (TNF-alpha) is associated with airway hyperreactivity in antigen-challenged animals. In human asthmatics, TNF-alpha is increased and blocking it prevents airway hyperreactivity in some asthmatic patients. However, the mechanisms by which TNF-alpha mediates hyperreactivity are unknown. Airway hyperreactivity can be caused by dysfunction of neuronal M(2) muscarinic receptors that normally limit acetylcholine release from parasympathetic nerves. Here we test whether blocking TNF-alpha receptors with etanercept prevents M(2) receptor dysfunction and airway hyperreactivity in antigen-challenged guinea pigs.

EXPERIMENTAL APPROACH

Ovalbumin-sensitized guinea pigs were challenged by inhalation of antigen. Some animals received etanercept (3 mg kg(-1) i.p.) 3 h before challenge. 24 h after challenge, airway hyperreactivity and M(2) receptor function were tested. Inflammatory cells in bronchoalveolar lavage, blood and lung were counted. TNF-alpha and its receptors were detected by real-time RT-PCR and immunocytochemistry in parasympathetic nerves from humans and guinea pigs and in human neuroblastoma cells.

KEY RESULTS

Antigen-challenged animals were hyperreactive to vagal stimulation and neuronal M(2) receptors were dysfunctional. Both M(2) receptor dysfunction and airway hyperreactivity were prevented by etanercept. Etanercept reduced eosinophils around airway nerves, and in blood, bronchoalveolar lavage and airway smooth muscle. Also, TNF-alpha decreased M(2) receptor mRNA in human and guinea pig parasympathetic neurons.

CONCLUSIONS AND IMPLICATIONS

Tumour necrosis factor-alpha may contribute to M(2) receptor dysfunction and airway hyperreactivity directly by decreasing receptor expression and indirectly by promoting recruitment of eosinophils, containing major basic protein, an M(2) antagonist. This suggests that etanercept may be beneficial in treatment of allergic asthma.

Inhaled corticosteroids for asthma: are they all the same?

OBJECTIVES

To assess similarities and differences among currently available inhaled corticosteroids (ICS) for treatment of asthma, with special emphasis on factors that may affect the relative safety of these medications.

METHODS

PubMed was searched for relevant reviews and original articles. Information from these studies was synthesized and critically assessed.

RESULTS

Differences in corticosteroid formulations and delivery systems can create variations in therapeutic efficacy. Chemical properties of the various corticosteroids may also affect their relative safety. Ciclesonide and beclomethasone dipropionate are administered as prodrugs activated by enzymes present in the lungs but not the oropharynx. Corticosteroid-specific adverse effects in the oropharynx are thus avoided, although formulation-specific effects may remain. Other adverse effects require systemic availability, either via the gastrointestinal tract or the lung. Once they enter the systemic circulation, all ICS are rapidly metabolized by the liver. Oral bioavailability of ICS such as fluticasone, ciclesonide and mometasone is minimal, as a result of their essentially complete first-pass metabolism in the liver. Ciclesonide also undergoes extrahepatic metabolism that eliminates it even more rapidly. Additionally, ciclesonide and mometasone exhibit very high levels of binding to serum proteins that reduces their ability to stimulate glucocorticoid receptors outside the lung.

CONCLUSIONS

Despite acting by similar mechanisms, currently available ICS and their delivery systems differ in ways that can potentially affect both safety and therapeutic effectiveness for individual patients.

Granulocyte-macrophage colony-stimulating factor expression in induced sputum and bronchial mucosa in asthma and COPD

Background:

Granulocyte–macrophage colony-stimulating factor (GM-CSF) has been implicated as an important mediator in the pathogenesis of asthma and chronic obstructive pulmonary disease (COPD). However, the expression of GM-CSF and its receptor in airway samples in asthma and COPD across disease severity needs to be further defined.

Methods:

Sputum GM-CSF was measured in 18 control subjects, 45 subjects with asthma and 47 subjects with COPD. Enumeration of GM-CSF+ cells in the bronchial submucosa and airway smooth muscle bundle was performed in 29 control subjects, 36 subjects with asthma and 10 subjects with COPD.

Results:

The proportion of subjects with measurable GM-CSF in the sputum was raised in those with moderate (7/14) and severe (11/18) asthma, and in those with COPD GOLD (Global Initiative for Chronic Obstructive Lung Disease) stage II (7/16), III (8/17) and IV (7/14) compared with controls (1/18) and those with mild asthma (0/13); p = 0.001. The sputum GM-CSF concentration was correlated with the sputum eosinophilia in subjects with moderate to severe asthma (r_s = 0.41; p = 0.018). The median (interquartile range) GM-CSF+ and GM-CSFR+ cells/mm² of submucosa was increased in severe asthma (1.4 (3.0) and 2.1 (8.4)) compared with those with mild to moderate asthma (0 (2.5) and 1.1 (5)) and healthy controls (0 (0.5) and 0 (1.6)), (p = 0.004 and p = 0.02, respectively).

Conclusions:

The findings support a potential role for GM-CSF in asthma and COPD and suggest that overexpression of GM-CSF in sputum and the bronchial mucosa is a particular feature of severe asthma.

The gender disparity in adult asthma hospitalizations dynamically relates to age

Although it is known that women have a higher prevalence of asthma than men, it is not known whether and/or how gender differences in asthma severity are affected by age. Asthma hospitalization rates were compared for men and women in New York State from 1990 through 2006 between the ages of 20 and 84. Female and male hospitalization rates were calculated and characterized for the different age intervals. The ratio between female to male hospitalization rates were compared for different age groups. While males showed an overall linear increase in hospitalization rates with increasing age, women had a steeper increase in hospitalization rates followed by a slowing beginning at the ages between 40-54. The ratio of the female to male hospitalization rates was maximal in this age interval, with a mean ratio of 2.41 compared to 1.97 in other ages. For each year, this female to male ratio was consistently higher for the age range between 40 to 54 than for other ages, and this difference remained when admissions associated obesity, tobacco dependence, and chronic non-asthmatic pulmonary disease were excluded. Differences between the hospitalization rates for men and women vary by age. The gender gap in hospitalization rates appears to be maximal between the ages of 40 and 54. This may reflect age related asthma prevalence and/or severity differences between men and women.

[Treatment of an asthmatic patient on dialysis and awaiting transplantation with anti-IgE]

INTRODUCTION

Omalizumab, a monoclonal antibody to IgE, is a possible treatment for severe, uncontrolled allergic asthma.

CASE REPORT

A severe asthmatic patient with renal insufficiency and on dialysis was awaiting transplantation. The asthma was uncontrolled with poor respiratory function. He received anti IgE treatment with omazilumab with immediate clinical improvement and his renal transplant was performed satisfactorily.

CONCLUSION

Anti-IgE treatment can improve severe, uncontrolled allergic asthmatic patients allowing, in this case, transplantation without further respiratory problems.

Fibrocyte localization to the airway smooth muscle is a feature of asthma

BACKGROUND

Airway smooth muscle (ASM) hyperplasia is a hallmark of asthma that is associated with disease severity and persistent airflow obstruction.

OBJECTIVES

We sought to investigate whether fibrocytes, a population of peripheral blood mesenchymal progenitors, are recruited to the ASM compartment in asthma.

METHODS

We assessed the number of fibrocytes in bronchial biopsy specimens and peripheral blood from subjects with mild-to-severe refractory asthma versus healthy control subjects. In vitro we investigated potential mechanisms controlling fibrocyte migration toward the ASM bundle.

RESULTS

Fifty-one subjects with asthma and 33 control subjects were studied. In bronchial biopsy specimens, the number of fibrocytes was increased in the lamina propria of subjects with severe refractory asthma (median [interquartile range] number, 1.9/mm(2) [1.7/mm(2)]) versus healthy control subjects (median [interquartile range] number, 0/mm(2) [0.3/mm(2)], P < .0001) and in the ASM bundle of subjects with asthma of all severities (subjects with severe asthma, median [interquartile range] number, 3.8/mm(2) [9.4/mm(2)]; subjects with mild-to-moderate asthma, median [interquartile range] number, 1.1/mm(2) [2.4/mm(2)]); healthy control subjects, (median [interquartile range] number, 0/mm(2) [0/mm(2)]); P = .0004). In the peripheral blood the fibrocyte number was also increased in subjects with severe refractory asthma (median [interquartile range] number, 1.4 x 10(4)/mL [2.6 x 10(4)/mL]) versus healthy control subjects (median [interquartile range] number, 0.4 x 10(4)/mL [1.0 x 10(4)/mL], P = .002). We identified that in vitro ASM promotes fibrocyte chemotaxis and chemokinesis (distance of migration after 4.5 hours, 31 microm [2.9 microm] vs 17 microm [2.4 microm], P = .0001), which was in part mediated by platelet-derived growth factor (mean inhibition by neutralizing antibody, 16% [95% CI, 2% to 32%], P = .03) but not by activation of chemokine receptors.

CONCLUSION

This study provides the first evidence that fibrocytes are present in the ASM compartment in asthma and that ASM can augment fibrocyte migration. The importance of fibrocytes in the development of ASM hyperplasia and airway dysfunction in asthma remains to be determined.

Control of persistent asthma in Spain: associated factors

INTRODUCTION

The main objective of asthma treatment is tailored control for each patient. However, despite the excellent therapeutic arsenal currently available, many patients remain unable to achieve adequate control of this disease.

OBJECTIVE

The main objective this study was to evaluate the degree of control and the determinants of asthma in patients with persistent asthma in Spain in usual clinical practice.

MATERIALS AND METHODS

This was a cross-sectional epidemiological study. The patients enrolled were 18 years of age or over, with a 6-month history of diagnosed persistent asthma, who were followed up by primary care physicians in Spain between the months of June and December 2006. Demographic and socioeconomic data were collected, as were anthropometric data and different clinical variables. The control of asthma was evaluated using the Asthma Control Questionnaire (ACQ).

RESULTS

The study included 6,824 patients, of whom 306 were excluded; therefore the final number of patients analyzed was 6,518 (95.5%). According to severity, 41.4% of patients had mild persistent asthma, 51.2% had moderate persistent asthma, and the remainder severe persistent asthma. The mean score in the ACQ was 1.4 +/- 1.0, distributed as follows: in 28.4% of cases, the score was below 0.75; in 31.6%, it was between 0.75 and 1.5; and in 39.7% it was above 1.5. Multiple regression analysis showed that the factor that most affected the degree of control of the disease was classification by severity. Other associated factors were sex, race, body mass index, smoking, level of education, habitual activity, years since diagnosis of asthma, number of exacerbations and admissions to hospital during the last year, and basic treatment of the disease.

CONCLUSIONS

The number of patients with poorly controlled persistent asthma in Spain is high (71.6%). There are demographic, socioeconomic, anthropometric, and clinical variables that affect the level of control of this disease.

Assessment of the lung microstructure in patients with asthma using hyperpolarized 3He diffusion MRI at two time scales: comparison with healthy subjects and patients with COPD

PURPOSE

To investigate short- and long-time-scale (3)He diffusion in asthma.

MATERIALS AND METHODS

A hybrid MRI sequence was developed to obtain co-registered short- and long-time-scale apparent diffusion coefficient (ADC) maps during a single breath-hold. The study groups were: asthma (n = 14); healthy (n = 14); chronic obstructive pulmonary disease (COPD) (n = 9). Correlations were made between mean-ADC and %ADC-abn (abnormal) (%pixels with ADC > mean +2 SD of healthy) at both time scales and spirometry. Sensitivities were determined using receiver operating characteristic (ROC) analysis.

RESULTS

For asthmatics, the short- and long-time-scale group-mean ADCs were 0.254 +/- 0.032 cm(2)/s and 0.0237 +/- 0.0055 cm(2)/s, respectively, representing a 9% and 27% (P = 0.038 and P = 0.005) increase compared to the healthy group. The group-mean %ADC-abn were 6.4% +/- 3.7% and 17.5% +/- 14.2%, representing a 107% and 272% (P = 0.004 and P = 0.006) increase. For COPD much greater elevations were observed. %ADC-abn provided better discrimination than mean-ADC between asthmatic and healthy subjects. In asthmatics ADC did not correlate with spirometry.

CONCLUSION

With long-time scale (3)He diffusion magnetic resonance imaging (MRI) changes in lung microstructure were detected in asthma that more conspicuous regionally than at the short time scale. The hybrid diffusion method is a novel means of identifying small airway disease.

Endotyping asthma: new insights into key pathogenic mechanisms in a complex, heterogeneous disease

Clinical asthma is very widely assumed to be the net result of excessive inflammation driven by aberrant T-helper-2 (Th2) immunity that leads to inflamed, remodelled airways and then functional derangement that, in turn, causes symptoms. This notion of disease is actually poorly supported by data, and there are substantial discrepancies and very poor correlation between inflammation, damage, functional impairment, and degree of symptoms. Furthermore, this problem is compounded by the poor understanding of the heterogeneity of clinical disease. Failure to recognise and discover the underlying mechanisms of these major variants or endotypes of asthma is, arguably, the major intellectual limitation to progress at present. Fortunately, both clinical research and animal models are very well suited to dissecting the cellular and molecular basis of disease endotypes. This approach is already suggesting entirely novel pathways to disease-eg, alternative macrophage specification, steroid refractory innate immunity, the interleukin-17-regulatory T-cell axis, epidermal growth factor receptor co-amplification, and Th2-mimicking but non-T-cell, interleukins 18 and 33 dependent processes that can offer unexpected therapeutic opportunities for specific patient endotypes.

Alterations of the arginine metabolome in asthma

RATIONALE

As the sole nitrogen donor in nitric oxide (NO) synthesis and key intermediate in the urea cycle, arginine and its metabolic pathways are integrally linked to cellular respiration, metabolism, and inflammation.

OBJECTIVES

We hypothesized that arginine (Arg) bioavailability would be associated with airflow abnormalities and inflammation in subjects with asthma, and would be informative for asthma severity.

METHODS

Arg bioavailability was assessed in subjects with severe and nonsevere asthma and healthy control subjects by determination of plasma Arg relative to its metabolic products, ornithine and citrulline, and relative to methylarginine inhibitors of NO synthases, and by serum arginase activity. Inflammatory parameters, including fraction of exhaled NO (Fe(NO)), IgE, skin test positivity to allergens, bronchoalveolar lavage, and blood eosinophils, were also evaluated.

MEASUREMENTS AND MAIN RESULTS

Subjects with asthma had greater Arg bioavailability, but also increased Arg catabolism compared with healthy control subjects, as evidenced by higher levels of Fe(NO) and serum arginase activity. However, Arg bioavailability was positively associated with Fe(NO) only in healthy control subjects; Arg bioavailability was unrelated to Fe(NO) or other inflammatory parameters in severe or nonsevere asthma. Inflammatory parameters were related to airflow obstruction and reactivity in nonsevere asthma, but not in severe asthma. Conversely, Arg bioavailability was related to airflow obstruction in severe asthma, but not in nonsevere asthma. Modeling confirmed that measures of Arg bioavailabilty predict airflow obstruction only in severe asthma.

CONCLUSIONS

Unlike Fe(NO), Arg bioavailability is not a surrogate measure of inflammation; however, Arg bioavailability is strongly associated with airflow abnormalities in severe asthma.

Airway lipoxin A4 generation and lipoxin A4 receptor expression are decreased in severe asthma

RATIONALE

Airway inflammation is common in severe asthma despite antiinflammatory therapy with corticosteroids. Lipoxin A(4) (LXA(4)) is an arachidonic acid-derived mediator that serves as an agonist for resolution of inflammation.

OBJECTIVES

Airway levels of LXA(4), as well as the expression of lipoxin biosynthetic genes and receptors, in severe asthma.

METHODS

Samples of bronchoalveolar lavage fluid were obtained from subjects with asthma and levels of LXA(4) and related eicosanoids were measured. Expression of lipoxin biosynthetic genes was determined in whole blood, bronchoalveolar lavage cells, and endobronchial biopsies by quantitative polymerase chain reaction, and leukocyte LXA(4) receptors were monitored by flow cytometry.

MEASUREMENTS AND MAIN RESULTS

Individuals with severe asthma had significantly less LXA(4) in bronchoalveolar lavage fluids (11.2 +/- 2.1 pg/ml) than did subjects with nonsevere asthma (150.1 +/- 38.5 pg/ml; P < 0.05). In contrast, levels of cysteinyl leukotrienes were increased in both asthma cohorts compared with healthy individuals. In severe asthma, 15-lipoxygenase-1 mean expression was decreased fivefold in bronchoalveolar lavage cells. In contrast, 15-lipoxgenase-1 was increased threefold in endobronchial biopsies, but expression of both 5-lipoxygenase and 15-lipoxygenase-2 in these samples was decreased. Cyclooxygenase-2 expression was decreased in all anatomic compartments sampled in severe asthma. Moreover, LXA(4) receptor gene and protein expression were significantly decreased in severe asthma peripheral blood granulocytes.

CONCLUSIONS

Mechanisms underlying pathological airway responses in severe asthma include lipoxin underproduction with decreased expression of lipoxin biosynthetic enzymes and receptors. Together, these results indicate that severe asthma is characterized, in part, by defective lipoxin counterregulatory signaling circuits.

Steroid resistance in asthma: mechanisms and treatment options

Glucocorticoid insensitivity presents a profound management problem in patients with asthma because conventional therapies are not effective. Glucocorticoids, acting through the glucocorticoid receptor (GR), are able to selectively repress inflammatory gene expression by utilizing several distinct mechanisms targeting nuclear factor-varphiB and activator protein-1 activation complexes and by effects on mitogen-activated protein kinases. Different model systems often activate distinct sets of signaling molecules and different glucocorticoid responsiveness may result from differences in concentrations and timing of steroid treatment of cells, GR expression levels, and the precise inflammatory stimulus used. Thus, abnormal activation of many signaling pathways may affect corticosteroid responsiveness in patients with corticosteroid-resistant asthma. Understanding the molecular mechanisms of GR action and inaction may lead to the development of new anti-inflammatory drugs or enable clinicians to reverse the relative steroid-insensitivity that is characteristic of some patients with severe asthma.

Obesity and asthma: possible mechanisms

Epidemiologic data indicate that obesity increases the prevalence and incidence of asthma and reduces asthma control. Obese mice exhibit innate airway hyperresponsiveness and augmented responses to certain asthma triggers, further supporting a relationship between obesity and asthma. Here I discuss several mechanisms that may explain this relationship. In obesity, lung volume and tidal volume are reduced, events that promote airway narrowing. Obesity also leads to a state of low-grade systemic inflammation that may act on the lung to exacerbate asthma. Obesity-related changes in adipose-derived hormones, including leptin and adiponectin, may participate in these events. Comorbidities of obesity, such as dyslipidemia, gastroesophageal reflux, sleep-disordered breathing, type 2 diabetes, or hypertension may provoke or worsen asthma. Finally, obesity and asthma may share a common etiology, such as common genetics, common in utero conditions, or common predisposing dietary factors. Novel therapeutic strategies for treatment of the obese patient with asthma may result from an increased understanding of the mechanisms underlying this relationship.

Molecular phenotyping of severe asthma using pattern recognition of bronchoalveolar lavage-derived cytokines

BACKGROUND

Asthma is a heterogeneous clinical disorder. Methods for objective identification of disease subtypes will focus on clinical interventions and help identify causative pathways. Few studies have explored phenotypes at a molecular level.

OBJECTIVE

We sought to discriminate asthma phenotypes on the basis of cytokine profiles in bronchoalveolar lavage (BAL) samples from patients with mild-moderate and severe asthma.

METHODS

Twenty-five cytokines were measured in BAL samples of 84 patients (41 severe, 43 mild-moderate) using bead-based multiplex immunoassays. The normalized data were subjected to statistical and informatics analysis.

RESULTS

Four groups of asthmatic profiles could be identified on the basis of unsupervised analysis (hierarchical clustering) that were independent of treatment. One group, enriched in patients with severe asthma, showed differences in BAL cellular content, reductions in baseline pulmonary function, and enhanced response to methacholine provocation. Ten cytokines were identified that accurately predicted this group. Classification methods for predicting methacholine sensitivity were developed. The best model analysis predicted hyperresponders with 88% accuracy in 10 trials by using a 10-fold cross-validation. The cytokines that contributed to this model were IL-2, IL-4, and IL-5. On the basis of this classifier, 3 distinct hyperresponder classes were identified that varied in BAL eosinophil count and PC20 methacholine.

CONCLUSION

Cytokine expression patterns in BAL can be used to identify distinct types of asthma and identify distinct subsets of methacholine hyperresponders. Further biomarker discovery in BAL may be informative.

Physiologic similarities and differences between asthma and chronic obstructive pulmonary disease

PURPOSE OF REVIEW

This review examines the physiologic mechanisms responsible for persistent maximum expiratory airflow limitation in nonsmoking patients with acute and chronic moderate to severe persistent asthma in comparison to chronic obstructive pulmonary disease.

RECENT FINDINGS

The phenomenon of acute but reversible loss of lung elastic recoil during acute asthma is reviewed, although no plausible pathophysiologic explanation has been offered. Nonsmoking adults with stable asthma and persistent maximum expiratory airflow limitation, despite optimal polytherapy, were shown to have unsuspected and unexplained marked loss of lung elastic recoil in the absence of lung computed tomography scored emphysema. This condition resulted in up to 50% reduction in maximum expiratory airflow. Furthermore, these patients remain at high risk for adverse clinical events, including near-fatal asthma. In chronic obstructive pulmonary disease, reduction in maximum expiratory airflow is related to variable extent of loss of lung elastic recoil secondary to emphysema and concurrent intrinsic airway obstruction or obliteration of small airways. There is also an unexplained loss of lung elastic recoil in primary intrinsic small airways disease in the absence of emphysema.

SUMMARY

Nonsmoking patients with moderate-severe persistent asthma and patients with smoking-related chronic obstructive pulmonary disease share similar physiologic mechanisms of expiratory airflow limitation, but probably caused by different anatomic abnormalities.

Targeting TNF-alpha: a novel therapeutic approach for asthma

Approximately 5% to 10% of patients with asthma have severe disease that is refractory or poorly responsive to inhaled corticosteroid therapy. These patients represent an important unmet clinical need because they experience considerable morbidity and mortality and consume a disproportionately large amount of health care resources. TNF-alpha is a proinflammatory cytokine that has been implicated in many aspects of the airway pathology in asthma. Evidence is emerging to suggest that it might play an important role in severe refractory disease. The development of novel TNF-alpha antagonists has allowed us to test the role of this cytokine in vivo. Preliminary studies have demonstrated an improvement in asthma quality of life, lung function, and airway hyperresponsiveness and a reduction in exacerbation frequency in patients treated with anti-TNF-alpha therapy. However, there is marked heterogeneity in response, suggesting that benefit is likely to be reserved to a small subgroup. Importantly, where efficacy is reported, this also needs to be considered in the context of concerns about the safety of anti-TNF-alpha therapies. Therefore the challenge for clinicians is to evaluate the risk/benefit ratio of these therapies in individual patients with asthma.