Eosinophilic bronchitis is an important cause of chronic cough

Non-astmatic Eosinophilic Bronchitis

Non-asthmatic eosinophilic bronchitis (NAEB) is eosinophilic inflammation of the respiratory tract, without any bronchospasm. In this article, we want to draw attention to the NAEB. It should also be considered in differential diagnosis of chronic cough. Eosinophilia is present in all induced or spontaneous sputum samples of NAEB patients. NAEB patients and asthmatic patients have similar airway inflammation. Remarkably, NAEB mainly occurs in the lower airways. Unlike asthma, mast cells in NAEB are active in the bronchial epithelium. Diagnosis is based on the clinical, radiological, and spirometric measurements of other causes of chronic cough (Post-nasal discharge syndrome, asthma, gastroesophageal reflux etc.) and the assessment of inflammation in the lower respiratory tract. Airway inflammation can be assessed by sputum induction. The main treatment is anti-inflammatory therapy with inhaled corticosteroids and taking protective measures if inflammation is due to occupational exposure or allergen inhalation. If NAEB is untreated, it may be transient, episodic, or persistent; rarely, long-term oral steroid treatment may be required in patients. There is a requirement for studies that investigate the role of non-invasive markers of chronic inflammation associated with NAEB and the effectiveness of other treatments.

Eotaxin and IL-4 levels are increased in induced sputum and correlate with sputum eosinophils in patients with nonasthmatic eosinophilic bronchitis

Nonasthmatic eosinophilic bronchitis (NAEB) is characterized by chronic cough and airway eosinophilic inflammation. Airway and systemic inflammation cytokine profile have not been comprehensively described in patients with NAEB.The aim of the study was to identify the cytokine profile in sputum and serum of NAEB patients. Furthermore, the relationship between cytokines and clinical features would be evaluated.Induced sputum and serum were collected from untreated NAEB patients and healthy subjects. The cytokine profile in sputum and serum was analyzed by a bead-based multiplex cytokine assay including 21 cytokines.The levels of EGF, eotaxin, GM-CSF, GRO, IFN-γ, IL-1β, IL-4, IL-6, IL-17A, IP-10, MIP-1α, and TNF-α in sputum were significantly higher in NAEB patients than that in healthy subjects (all P < 0.05). Values of area under the receiver operating characteristic curve (AUROC) of these cytokines were all above 0.750. The concentrations of eotaxin and IL-4 were positively correlated with sputum eosinophil percentage (r = 0.726, P = 0.002; r = 0.511, P = 0.043; respectively). No significant correlations between other cytokines (EGF, GM-CSF, GRO, IFN-γ, IL-1β, IL-6, IL-17A, IP-10, MIP-1α, and TNF-α) in sputum and sputum eosinophil percentage were found. The level of IL-4 in serum was slightly higher in NAEB patients than in healthy subjects. However, there was no correlation between serum IL-4 levels and sputum eosinophil percentage.We identified the cytokine profile in sputum and serum from NAEB patients. Sputum eotaxin and IL-4 could have the potential to become the biomarkers for NAEB and might be useful to assist in the diagnosis of NAEB.

A Longitudinal Study of Association between Heavy Metals and Itchy Eyes, Coughing in Chronic Cough Patients: Related with Non-Immunoglobulin E Mediated Mechanism

The association between heavy metals exposure and respiratory diseases or allergic sensitization showing high serum immunoglobulin E (IgE) has been suggested. However, previous findings have been inconsistent and the mechanisms responsible remain unclear. We evaluated heavy metal exposure and its association with coughing, itchy eyes in chronic cough patients with different IgE levels. Ninety outpatients in Kanazawa University Hospital were recruited between January-June 2011. Subjects whose total IgE measured by radioimmunosorbent test were asked to record their daily symptoms. We collected daily total suspended particles (TSP) from which concentrations of calcium (Ca), cadmium (Cd), chromium (Cr), iron (Fe), manganese (Mn), nickel (Ni), and lead (Pb) were determined then divided into high and low level groups. Generalized estimating equations were applied to compute the relationship between concentrations of these metals and symptoms. All metals at high levels were significantly associated with itchy eyes compared with low levels, with exception of Ca, the six others were significant in patients with IgE < 250 IU/mL. Cd, Fe, Mn had association with coughing (odds ratio-OR (95% confidence interval-CI): 1.13 (1.03, 1.24), 1.22 (1.05, 1.42), and 1.13 (1.01, 1.27), respectively), this relationship remained significant for Cd (OR (95% CI): 1.14 (1.03, 1.27)) and Mn (OR (95% CI): 1.15 (1.00, 1.31)) in patients with lower IgE. Our findings demonstrate the relationship between aerial heavy metals and itchy eyes, coughing in chronic cough patients, suggesting these symptoms may be due to a non-IgE mediated mechanism.

Chronic Cough as a Female Gender Issue

Cough accompanying acute respiratory tract disorders is a self-limiting phenomenon, and it usually does not require sophisticated management. Chronic cough, in contrast, is a bothersome problem, considerably influencing the quality of life of affected individuals. Specialized cough clinics report that substantial proportion of their patients are middle aged-to-postmenopausal females who cough for years in response to otherwise non-tussigenic stimuli, without a clear underlying disease reason. A newly established entity - 'cough hypersensitivity syndrome' explains pathogenesis of this problem. However, the syndrome has not been generally accepted, and the guidelines regarding the diagnostic protocols and treatment are not yet available. The reason why females cough more than males do is unclear, but the analysis of literature and experience with the chronic cough patients allows selecting three main targets of hormonal background which can contribute to the enhanced coughing in females. They are as follows: increased activity of transient receptor potential (TRP) channels expressed on vagal C-fibers mediating cough, laryngeal hypersensitivity and laryngeal dysfunction with paradoxical vocal cord movement, and mast cells which are known to express receptors for female sexual hormones and are frequently found in the bronchoalveolar lavage in chronic cough patients. In this review we analyze the potential contribution of the factors above outlined to excessive cough in female subjects.

Future directions in treating cough

Cough is a common and troublesome symptom that can be difficult to treat. New therapeutic options that are safe and more effective than those currently available are needed. In this article, the authors offer opinion on future directions in the treatment of cough, with a particular emphasis on the clinical syndrome associated with cough reflex hypersensitivity. In addition, the article provides an overview of some of the diagnostic technologies and promising drug targets likely to emerge from current clinical and scientific endeavor.

Association of genetic variations in neurokinin-2 receptor with enhanced cough sensitivity to capsaicin in chronic cough

BACKGROUND

Chronic cough is associated with increased sensitivity to inhaled capsaicin, and both tachykinins and their receptors play important roles in the cough reflex. However, associations between polymorphisms of the tachykinin receptor genes and cough sensitivity in patients with non-productive chronic cough have not been reported.

METHODS

Direct sequencing was used to identify single nucleotide polymorphisms (SNPs) in the genes for the neurokinin-1 and neurokinin-2 receptors (NK-1R and NK-2R, respectively). Informative non-synonymous SNPs were scored using the single base extension method for 312 patients with chronic cough and for 100 age matched healthy controls. The cough response to capsaicin was recorded for 312 patients with chronic cough, and the potential genetic association between cough sensitivity to capsaicin and the NK-1R and NK-2R genotypes was evaluated.

RESULTS

Two informative SNPs were identified in NK-2R (Gly231Glu and Arg375His), whereas no informative SNP was found in NK-1R. After adjusting for atopy, sex, age, and smoking, the prevalence of enhanced cough sensitivity to capsaicin was higher in the chronic cough patients with the 231Glu allele (p = 0.004; OR 1.69 (95% CI 1.18 to 2.42)) and the 231Glu_375Arg haplotype (p = 0.003; OR 1.71 (95% CI 1.20 to 2.24)). Moreover, the lowest capsaicin concentration to cause five consecutive coughs (C5) was significantly lower in patients with 231Glu (mean (SD) 44.1 (53.2) v 60.9 (55.8) microM/l, p = 0.04) and those with 231Glu_375Arg (43.2 (52.7) v 69.6 (52.0) microM/l, p = 0.03).

CONCLUSIONS

The results of this study suggest that NK-2R gene polymorphisms are involved in the enhanced cough sensitivity to capsaicin of patients with chronic cough.

Comparison of atopic cough with cough variant asthma: is atopic cough a precursor of asthma?

BACKGROUND

We have described a group of patients who present with isolated chronic bronchodilator resistant non-productive cough with an atopic constitution, eosinophilic tracheobronchitis, and airway cough receptor hypersensitivity without bronchial hyperresponsiveness, which we have termed "atopic cough". Although cough variant asthma (in which the cough responds to bronchodilators) is recognised as a precursor of typical asthma, it is not known whether atopic cough is also a precursor of asthma.

METHODS

Eighty two patients with atopic cough were retrospectively examined for onset of typical asthma and compared with 55 patients with cough variant asthma (20 untreated patients and 35 treated with long term inhaled beclomethasone dipropionate (BDP), 218-467 micro g/day). The median follow up period for patients with atopic cough and cough variant asthma was 4.8 (1-11.5) years and 3.7 (1-12.4) years, respectively.

RESULTS

Onset of typical asthma occurred in only one of the patients with atopic cough. In patients with cough variant asthma, typical asthma developed in two of 35 patients taking BDP and six of 20 untreated patients (difference 24.3%, 95% CI 2.8 to 45.8, p<0.02).

CONCLUSIONS

These findings suggest that cough variant asthma is a precursor of typical asthma but that atopic cough is not. Treatment with inhaled steroids may prevent the transformation of cough variant asthma into typical asthma.