Eosinophilic inflammation assessed by induced sputum in corticosteroid-dependent asthma

Current and future biomarkers in allergic asthma

Diagnosis early in life, sensitization, asthma endotypes, monitoring of disease and treatment progression are key motivations for the exploration of biomarkers for allergic rhinitis and allergic asthma. The number of genes related to allergic rhinitis and allergic asthma increases steadily; however, prognostic genes have not yet entered clinical application. We hypothesize that the combination of multiple genes may generate biomarkers with prognostic potential. The current review attempts to group more than 161 different potential biomarkers involved in respiratory inflammation to pave the way for future classifiers. The potential biomarkers are categorized into either epithelial or infiltrate-derived or mixed origin, epithelial biomarkers. Furthermore, surface markers were grouped into cell-type-specific categories. The current literature provides multiple biomarkers for potential asthma endotypes that are related to T-cell phenotypes such as Th1, Th2, Th9, Th17, Th22 and Tregs and their lead cytokines. Eosinophilic and neutrophilic asthma endotypes are also classified by epithelium-derived CCL-26 and osteopontin, respectively. There are currently about 20 epithelium-derived biomarkers exclusively derived from epithelium, which are likely to innovate biomarker panels as they are easy to sample. This article systematically reviews and categorizes genes and collects current evidence that may promote these biomarkers to become part of allergic rhinitis or allergic asthma classifiers with high prognostic value.

Primary lysis of eosinophils in severe desquamative asthma

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

Association between eosinophilic airway inflammation and persistent airflow limitation

OBJECTIVE

We aimed to evaluate the association between eosinophilic inflammation in induced sputum and pulmonary function and persistent airflow limitation in children.

METHODS

A total of 92 asthmatic children and 72 controls were enrolled in this study. Eosinophil count (%) and eosinophil cationic protein (ECP) levels were measured in induced sputum. We performed spirometry and a methacholine challenge test, and measured total eosinophil count, total serum IgE, and serum ECP in all subjects.

RESULTS

Asthmatic children had significantly higher levels of sputum eosinophils (9% vs. 0%; P < 0.001) and sputum ECP (2.3 ± 0.7 vs. 1.6 ± 0.6 log µg/L, p < .001) than controls. Sputum ECP levels showed a significant negative correlation with post-bronchodilator (post-BD) FEV(1) (r = -0.307; p = .001) and post-BD FEV(1)/FVC (r = -0.286; p = .002), whereas sputum eosinophils showed no correlation with post-BD FEV(1) and post-BD FEV(1)/FVC. However, no significant differences in sputum ECP and sputum eosinophil counts were observed in asthmatic children with and without persistent airflow limitation.

CONCLUSIONS

Our findings suggest that sputum eosinophilic inflammation, especially ECP, is associated with pulmonary function and persistent airflow limitation, which is manifested by low post-BD FEV(1)/FVC.

Analysing the eosinophil cationic protein--a clue to the function of the eosinophil granulocyte

Eosinophil granulocytes reside in respiratory mucosa including lungs, in the gastro-intestinal tract, and in lymphocyte associated organs, the thymus, lymph nodes and the spleen. In parasitic infections, atopic diseases such as atopic dermatitis and asthma, the numbers of the circulating eosinophils are frequently elevated. In conditions such as Hypereosinophilic Syndrome (HES) circulating eosinophil levels are even further raised. Although, eosinophils were identified more than hundred years ago, their roles in homeostasis and in disease still remain unclear. The most prominent feature of the eosinophils are their large secondary granules, each containing four basic proteins, the best known being the eosinophil cationic protein (ECP). This protein has been developed as a marker for eosinophilic disease and quantified in biological fluids including serum, bronchoalveolar lavage and nasal secretions. Elevated ECP levels are found in T helper lymphocyte type 2 (atopic) diseases such as allergic asthma and allergic rhinitis but also occasionally in other diseases such as bacterial sinusitis. ECP is a ribonuclease which has been attributed with cytotoxic, neurotoxic, fibrosis promoting and immune-regulatory functions. ECP regulates mucosal and immune cells and may directly act against helminth, bacterial and viral infections. The levels of ECP measured in disease in combination with the catalogue of known functions of the protein and its polymorphisms presented here will build a foundation for further speculations of the role of ECP, and ultimately the role of the eosinophil.

Use of omalizumab in a severe asthma clinic

There is an urgent need to define new treatment strategies for severe persistent asthma. Using a severe asthma clinic model, it is possible to systematically assess diagnosis, self-management skills, and treatment efficacy. The addition of single-patient trials of therapy is useful to detect individual responders to drugs where use is limited because of access, cost, or toxicity. Omalizumab is effective in severe asthma, however access is restricted by cost and availability. We conducted single patient efficacy trials of omalizumab in 12 subjects with severe refractory asthma. There were 2 definite and 6 partial responders. Patients with difficult/therapy resistant or refractory asthma can respond to omalizumab, and this response can be detected in individual patients using a single patient controlled trial conducted in the setting of a severe asthma clinic.

Eosinophil cationic protein: is it useful in asthma? A systematic review

INTRODUCTION

Eosinophil cationic protein (ECP) has been widely investigated as a potential biomarker of airway inflammation.

METHOD

A systematic review was performed using Medline with key terms eosinophil cationic protein and asthma, limiting the search to titles or abstracts. Out of 688 potential papers found, abstracts were reviewed based on the following criteria: (1) ECP was used as a biological marker, (2) asthma was the index disease studied, (3) it was a controlled clinical study and (4) ECP was assessed as a diagnostic, assessment or management tool. One hundred and sixty-nine articles satisfied the selection criteria and their full-text versions were reviewed. Only 53 papers were found to provide clinically useful information.

RESULTS

ECP has been measured in serum, plasma, sputum, saliva and broncho-alveolar lavage fluids but serum and sputum are the most established. Levels of ECP in normal and asthmatic subjects in various body fluids were identified. ECP correlates well with airway inflammation but not airway hyper-responsiveness. It is raised in other atopic diseases and hence is not diagnostic for asthma. However, it has been shown to be useful in assessing asthma severity, compliance with anti-inflammatory asthma therapy and as a guide to tailing down inhaled corticosteroid therapy. Although there is some evidence that ECP levels are affected by age, smoking, circadian rhythm and seasonal variation, only smoking appears to be of clinical significance.

DISCUSSION

Despite its limitations, ECP remains potentially useful in asthma management. Future research on ECP should focus on using serial measurements and combining it with other markers of asthma which may increase its clinical usefulness.

Leukotriene modifier vs inhaled corticosteroid in mild-to-moderate asthma: clinical and anti-inflammatory effects

STUDY OBJECTIVE

Evidence for the anti-inflammatory activity of leukotriene receptor antagonists in humans is somewhat limited. There are also no data comparing the anti-inflammatory effects of leukotriene receptor antagonists with those of inhaled corticosteroids. This study was designed to assess the clinical efficacy and anti-inflammatory effects of leukotriene receptor antagonist plus low-dose inhaled corticosteroids compared to those of a high-dose inhaled corticosteroid in patients with mild-to-moderate asthma.

METHODS

Forty-nine patients with newly diagnosed asthma were recruited. They were randomly assigned to groups that received, for a 6-week period, either (1) budesonide, 600 microg bid (1,200 microg/d) or (2) budesonide, 200 microg (400 microg/d), and zafirlukast, 20 mg bid. The variables of asthma control were recorded daily. Sputum induction and methacholine provocation tests were performed.

RESULTS

The results indicated that the administration of a low-dose inhaled corticosteroid plus zafirlukast was as effective as that of a high-dose inhaled corticosteroid regarding clinical improvement and anti-inflammatory effects (ie, eosinophil percentage, and eosinophilic cationic protein [ECP] and cysteinyl leukotriene C4 levels in induced sputum). Nineteen (group 1, 8 patients; group 2, 11 patients) of 49 patients (38.8%) had returned to normal airway responsiveness after treatment. Among these patients, 16 patients (84.2%) had normal ECP levels and 10 patients (52.6%) had normal percentages of eosinophils. ECP level, but not the eosinophil percentage, was significantly associated with symptom scores. The peak expiratory flow rate (PEFR) showed a significant correlation with the provocative concentration of methacholine causing a 20% fall in FEV1 (PC20) instead of with symptom scores.

CONCLUSIONS

The addition of a leukotriene modifier to treatment with low-dose inhaled corticosteroids is equivalent to treatment with high-dose inhaled corticosteroids in patients with newly diagnosed mild-to-moderate asthma. In addition to symptoms and PEFR, the monitoring of ECP and PC20 may be of great value in achieving optimal control of asthma.

Eosinophils and eosinophilic cationic protein in induced sputum and blood: effects of budesonide and terbutaline treatment

BACKGROUND

There is a need for easily measurable markers of airway inflammation to guide the use of anti-inflammatory treatment in asthma. Eosinophilic cationic protein (ECP) levels in sputum and blood correlate with clinical severity, and serial measurements of ECP have been proposed as a suitable candidate.

AIMS AND METHODS

Our aim was to confirm that sputum and serum ECP measurements would provide a more sensitive indicator of responses to asthma treatment than eosinophil counts per se, in a randomized, placebo-controlled, crossover study of terbutaline, budesonide, and their combination in patients with chronic persistent asthma. We compared the changes in eosinophil counts and ECP in induced sputum and blood during each treatment period.

RESULTS

Budesonide and combined treatment caused a significant reduction in sputum eosinophils (-2.7% and -2.3%, respectively, P < 0.05). Sputum eosinophils increased with terbutaline (+3.9%, P = 0.049). In contrast, the changes for sputum ECP were not significant. There was a similar treatment effect on blood eosinophils, but not for serum ECP. Correlations between sputum and blood eosinophils were significant with and without budesonide, but were nonsignificant between sputum and blood ECP during the active treatments. Correlations between sputum eosinophils and ECP, and between blood eosinophils and serum ECP were greatest during treatment with placebo or terbutaline alone: budesonide weakened or abolished these relationships.

CONCLUSIONS

Compared with eosinophil counts, ECP measurements in either induced sputum or serum failed to reflect treatment-related changes in chronic asthma. We conclude that ECP is not a sensitive or reliable means of evaluating airway inflammation, and can not be recommended for assessing responses to anti-inflammatory therapy.

Non-eosinophilic asthma: importance and possible mechanisms

There is increasing evidence that inflammatory mechanisms other than eosinophilic inflammation may be involved in producing the final common pathway of enhanced bronchial reactivity and reversible airflow obstruction that characterises asthma. A review of the literature has shown that, at most, only 50% of asthma cases are attributable to eosinophilic airway inflammation. It is hypothesised that a major proportion of asthma is based on neutrophilic airway inflammation, possibly triggered by environmental exposure to bacterial endotoxin, particulate air pollution, and ozone, as well as viral infections. If there are indeed two (or more) subtypes of asthma, and if non-eosinophilic (neutrophil mediated) asthma is relatively common, this would have major consequences for the treatment and prevention of asthma since most treatment and prevention strategies are now almost entirely focused on allergic/eosinophilic asthma and allergen avoidance measures, respectively. It is therefore important to study the aetiology of asthma further, including the underlying inflammatory profiles.

Lipoxins are potential endogenous antiinflammatory mediators in asthma

Lipoxins, endogenous eicosanoids biosynthetized in vivo at inflammation sites, are potential antiinflammatory mediators. Subjects with severe asthma present chronic inflammation of the airways despite long-term treatment with oral glucocorticoids. Therefore it is of interest to investigate the potential antiinflammatory effects of lipoxin A4 (LXA4) and lipoxin B4 (LXB4) that could attenuate chronic inflammation. In a first time, we detected interleukin (IL)-8 and LXA4 in supernatants of induced sputum. IL-8 was heightened in severe asthma (p = 0.001), whereas high concentrations of lipoxin A4 were present in mild asthma (p = 0.001). We then studied the effects of LXA4 on IL-8 released in vitro. Nanomolar concentrations of LXA4 and LXB4 inhibited the IL-8 released by peripheral blood mononuclear cells from the two groups of patients with asthma: a maximal inhibition of 29.4% (p < 0.01) was observed for patients with mild asthma, and 41.5% inhibition (p < 0.001) for patients with severe asthma at 1 nM and 100 nM LXA4 concentrations, respectively. Polymerase chain reaction analysis indicated that peripheral blood mononuclear cells from patients with asthma expressed the LXA4 receptor mRNA. Moreover, pertussis toxin reversed LXA4- and LXB4-inhibited IL-8 release. These findings suggest that lipoxins have potential antiinflammatory action in asthma.

Sputum eosinophilia in Churg-Strauss syndrome

Sputum induction (IS) can be used to study airway inflammation in asthmatics and other lung diseases. However, no data are available for patients with Churg-Strauss syndrome (CSS). A study was carried out to evaluate eosinophil counts and eosinophil cationic protein (ECP) levels in induced sputum during the follow-up of three patients with CSS. Induced sputum was carried out in 10 patients with corticosteroid-dependent asthma (used as a control group). Patients with CSS had significantly higher eosinophils percentages and ECP levels in sputum than those with stable corticosteroid-dependent asthma. During the follow-up, patients with CSS presented increased ECP levels sputum and eosinophils in sputum as well as increased blood eosinophils, despite their oral corticosteroid and immunosuppressive treatment. Eosinophil percentage in sputum and the total number of eosinophils in peripheral blood were more predictive of exacerbations of CSS than sputum ECP.