Mucociliary transport and cough in humans

The mucus lining of the respiratory tract originates from products of secretory cells interspersed among mucosal cells or within submucosal glands and protects the underlying mucosa from dehydration. Current understanding is that the lining is a two-fluid model in which the upper layer is a viscoelastic gel (mucus, cross-linked glycoproteins) that overlies a sol layer (serous). Thus mucus propelled by ciliary beating, flows above the sol layer and contains sloughed cells and xenobiotic materials that come into contact with it. Sensory stimuli enhance mucus secretion and cause bronchoconstriction; responses that are usually coupled to cough and two-phase gas-liquid clearance of mucus. Airway clearance can be measured by scintigraphy using insoluble radio-labeled markers deposited by aerosol delivery onto the mucus layer. In a healthy airway, lung inflation/deflation reflexes and perhaps shearing forces at the airway surface during high rates of airflow, stimulate mucociliary clearance. During the early stages of smoke-related airway pathology and mucus hypersecretion, mucus layer transport is delayed, and abnormal clearance predominates in the smaller peripheral airways. If high velocity of expiratory airflow is preserved then even with chronic exposure to respiratory irritants and cigarette smoke, mucus clearance remains effective due to cough and two-phase, gas-liquid interactions. However, in patients with advanced airway obstruction and incapable of generating forceful expiratory flows, cough and shearing are ineffective and mucociliary clearance is disparate with markedly slowed mucus layer transport within central airways. Mucolytic therapy for patients with advanced airway obstruction improves ventilation and reduces the frequency of exacerbation.     

Sensitivity of the cough reflex in patients with chronic cough.

Cough may occur in association with excess bronchial secretions and may, therefore, be productive. However, in a proportion of patients the cough is non-productive and a possible association with an enhanced response of the cough reflex has been postulated. Using the irritant capsaicin, the sensitivity of the cough reflex was measured in 363 individuals. A questionnaire was used to divide subjects into three groups: Group A) non-coughing controls; Group B) subjects with non-productive cough; and Group C) subjects with productive cough. The group means (+/- 99% confidence interval (CI)) of the log capsaicin concentration causing two or more coughs (C2) for groups A, B, C were 0.98 (+/- 0.08), 0.64 (+/- 0.09) and 1.04 (+/- 0.23), respectively. The log capsaicin concentration causing five or more coughs (C5) for groups A, B, C were 1.78 (+/- 0.1), 1.16 (+/- 0.12) and 1.54 (+/- 0.25), respectively. Group B was significantly more sensitive to inhaled capsaicin than the other groups (p less than 0.01). No significant difference was observed between groups A and C. Some differences were found when subgroups were examined within groups B and C. In group B, patients with post-nasal drip were found to have a normal sensitivity of the cough reflex and were, therefore, different from the remainder of patients with non-productive cough. In group C, patients with bronchiectasis and current infection showed an increase in the sensitivity of their cough reflex. It is concluded that cough can occur in association with either excess mucus production leading to productive cough or an increase in the sensitivity of the cough reflex, possibly leading to non-productive cough.     

Premature ventricular complex-induced chronic cough and cough syncope.

The present case study reports a case of chronic cough and cough syncope associated with frequent premature ventricular complexes (PVCs). Careful analysis of cough-related symptoms and ECG monitoring led to the suspicion of PVC-induced cough. A coincidence between PVCs and episodes of cough was also documented by a portable multichannel recorder. Moreover, Doppler echocardiography revealed a PVC-induced transient increase in the pulmonary artery blood flow. After exclusion of other possible aetiologies, complete relief of chronic cough and cough syncope was achieved by radiofrequency ablation of the arrhythmogenic focus located in the right ventricular outflow tract. Premature ventricular complexes should be considered as a cause of chronic cough and cough syncope and an interdisciplinary cooperation can lead to successful diagnosis and treatment of this condition.     

Calcitonin gene-related peptide relates to cough sensitivity in children with chronic cough.

Airway neuropeptides, in particular calcitonin gene-related peptide (CGRP), are likely to be important in the pathogenesis of chronic cough. The present authors evaluated the following: 1) the relationship between cough sensitivity and bronchoalveolar lavage (BAL) neuropeptides; and 2) the effect of reflux oesophagitis (RO) on cough, cough sensitivity and BAL neuropeptides in children not selected for cough. It was hypothesised that CGRP would be increased in children with chronic cough and would relate to cough sensitivity. Capsaicin cough sensitivity was performed in children undergoing gastro-duodenal endoscopy. CGRP, substance P and neurokinin A were measured in BAL obtained nonbronchoscopically. Children were defined as "coughers" if chronic cough was present. Coughers (n = 21) had significantly reduced cough sensitivity but were just as likely as noncoughers (n = 19) to have RO. The median CGRP was significantly higher in coughers with oesophagitis than in noncoughers with oesophagitis. CGRP significantly negatively correlated to cough sensitivity in coughers but not in noncoughers. Elevated calcitonin gene-related peptide, but not substance P or neurokinin A, is only associated with chronic cough in children when oesophagitis coexists. Calcitonin gene-related peptide in bronchoalveolar lavage relates to cough sensitivity and is likely to be important in the pathophysiology of chronic cough.     

Relationship between cough threshold to inhaled tartaric acid and sex, smoking and atopy in humans

It has been reported that angiotensin converting enzyme inhibitor (ACE-I) elicits dry cough more frequently in women than in men. This study was designed to evaluate whether airway cough receptors are more sensitive in women than in men. Cough threshold to inhaled tartaric acid was measured in 33 men and 29 women. In non-atopic and non-smoking subjects, geometric mean value of cough threshold in women was 10.0 (GSEM, 1.29) %, which was significantly (p less than 0.02) lower than that in men, 22.5 (GSEM, 1.30) %. In non-atopic men, the cough threshold was significantly (p less than 0.05) lower in smokers (9.3 (GSEM, 1.57) %) than in non-smokers. In non-smoking women, the cough threshold was significantly (p less than 0.02) lower in atopic subjects (4.2 (GSEM, 1.33) %) than in non-atopic subjects. These results demonstrated that airway cough receptors may be more sensitive in women, smoking men and atopic women.     

Capsaicin-induced cell death in a human gastric adenocarcinoma cell line

AIM: Capsaicin, a pungent ingredient found in red pepper,has long been used in spices, food additives, and drugs.Cell death induced by the binding of capsaicin was examined in a human gastric adenocarcinoma cell line (AGS cells).METHODS: By using XTT-based cytotoxicityassay, flow cytometry using the TUNEL method, and quantitation of DNA fragmentation, both cell death and DNA fragmentation were detected in AGS cells treated with capsaicin. By using Western blotting methods, capsaicin reduced the expression of Bcl-2, the antiapoptotic protein, in AGS cells in a concentration-dependent manner.RESULTS: After incubation of AGS cells with capsaicin for 24 h, cell viability decreased significantly in a dose-dependent manner. After incubation of AGS cells with capsaicin for 24 h, apoptotic bodies also significantly increased, and were again correlated with the dose of capsaicin. When the concentration of capsaicin was 1 mmol/L, the amount of DNA fragments also increased. Similar results werealso in the lower traces.CONCLUSION: These results suggest that capsaicininduced cell death might be via a Bcl-2 sensitive apoptotic pathway. Therefore, capsaicin might induce protection from gastric cancer.     

Capsaicin-induced cell death in a human gastric adenocarcinoma cell line

AIM: Capsaicin, a pungent ingredient found in red pepper, has long been used in spices, food additives, and drugs. Cell death induced by the binding of capsaicin was examined in a human gastric adenocarcinoma cell line (AGS cells). METHODS: By using XTT-based cytotoxicity assay, flow cytometry using the TUNEL method, and quantitation of DNA fragmentation, both cell death and DNA fragmentation were detected in AGS cells treated with capsaicin. By using Western blotting methods, capsaicin reduced the expression of Bcl-2, the antiapoptotic protein, in AGS cells in a concentration-dependent manner. RESULTS: After incubation of AGS cells with capsaicin for 24 h, cell viability decreased significantly in a dose-dependent manner. After incubation of AGS cells with capsaicin for 24 h, apoptotic bodies also significantly increased, and were again correlated with the dose of capsaicin. When the concentration of capsaicin was 1 mmol/L, the amount of DNA fragments also increased. Similar results were also in the lower traces. CONCLUSION: These results suggest that capsaicin-induced cell death might be via a Bcl-2 sensitive apoptotic pathway. Therefore, capsaicin might induce protection from gastric cancer.     

感冒后咳嗽敏感性及气道神经源性炎症改变

目的观察感冒后咳嗽患者(cough post infectious,CPI)的咳嗽敏感性以及气道分泌物神经肽变化,探讨其可能的发病机制。方法以2005年1~6月于广州呼吸疾病研究所慢性咳嗽专科门诊诊断10例CPI患者(CPI组)及10名正常志愿者(正常对照组)为研究对象,通过辣椒素咳嗽激发试验测定气道咳嗽敏感性;观察诱导痰细胞总数以及细胞分类比例;测定痰上清液P物质(SP)、神经肽A(NKA)、神经肽B(NKB)及降钙素基因相关肽(CGRP);检测诱导痰细胞SP、NKA及SP受体(NK-1)的表达,并进行分析比较。结果CPI组咳嗽阈值lgC5为1.16±0.61,明显低于正常对照组(2.64±0.28)(P<0.001)。CPI组诱导痰细胞总数(WBC)及细胞分类比例与正常对照组差异均无显著性意义。CPI组诱导痰上清液SP质量浓度为(516.3±494.2)ng/L,显著高于正常对照组[(141.7±34.5)ng/L,P<0.05];CGRP质量浓度为(141.2±80.8)ng/L,显著高于正常对照组[(74.3±38.2)ng/L,P<0.05];而2组间NKA、NKB的质量浓度差异均无显著性意义。CPI组痰细胞SP、NK-1蛋白的表达分别为1.86±0.81和1.20±0.75,显著高于正常对照组的(0.65±0.44和0.27±0.24)(P<0.01);而2组间NKA蛋白表达差异无显著性意义。结论CPI患者的咳嗽敏感性增高,并伴随气道神经源性炎症,提示其与CPI发病相关。     

Bordetella pertussis and chronic cough in adults.

To evaluate Bordetella pertussis as a cause of persistent cough in adults, we examined 201 patients who had a cough for 2-12 weeks and no pulmonary disease. We obtained the following at presentation: medical history, chest radiograph, respiratory function measurement, nasopharyngeal aspirate for polymerase chain reaction (PCR), nasopharyngeal swab specimen for culture, and a blood sample (acute serum). Four weeks later a second blood sample (convalescent serum) was obtained. Control sera were obtained from 164 age-matched healthy blood donors with no history of cough during the previous 12 weeks. Four patients were B. pertussis culture-positive; 11 (including the culture-positive patients) were B. pertussis PCR-positive; and 33, including 10 of the 11 PCR-positive patients, had serological evidence of recent B. pertussis infection. Pertussis-positive and -negative patients could not be discriminated by a history of cough. We conclude that B. pertussis infection is a common cause of persistent cough in adults. This is of concern, because these patients may be B. pertussis reservoirs from which transmission may occur to infants, in whom the disease can be devastating.     

Chronic cough and phlegm in young adults.

The Global Initiative for Chronic Obstructive Lung Disease (GOLD) guidelines underline that the presence of chronic cough and sputum production before airflow obstruction offers a unique opportunity to identify subjects at risk of chronic obstructive pulmonary disease for an early intervention. Current epidemiological data on these subjects are scant. Between 1998-2000, the authors evaluated the prevalence and characteristics of these symptoms by a multicentre cross-sectional survey of Italian people aged between 20-44 yrs from the general population (Italian Study on Asthma in Young Adults (ISAYA)). Besides the questions on asthma, more than 18,000 subjects answered the question: "Have you had cough and phlegm on most days for as much as 3 months per year and for at least two successive years?" The adjusted prevalence of subjects with chronic cough and phlegm was 11.9%, being 11.8% in males and 12.0% in females. From these subjects approximately 20% reported coexisting asthma and approximately 30%, predominately females, were nonsmokers. The survey showed that sex (female), smoking and low socioeconomic status were significantly and independently associated with chronic cough and phlegm, current smoking playing the major role. The prevalence of subjects with chronic cough and phlegm is startlingly high among young adults. Further follow-up studies are needed to establish how many of them will go on to develop chronic obstructive pulmonary disease.     

Mechanism of pacemaker induced cough.

Single chamber ventricular pacing (VVI) may be associated with a group of adverse symptoms known as the pacemaker syndrome. Cough is an unusual but recognised feature of the pacemaker syndrome. A patient with a VVI permanent pacemaker experienced a disturbing cough during VVI pacing. There were no other symptoms associated with the pacemaker syndrome. The effects of short-term ventricular pacing on the cough were examined while the subject was standing and lying. After control recordings, the pulse generator was programmed to either VVI 50 beats/min or 90 beats/min and recordings made over 60 seconds. There was an interval of 60s between recordings. Overall, five recording periods at VVI of 50 beats/min and VVI of 90 beats/min were made in random order. The patient was blinded to the order of programming. The recordings were repeated with the subject lying. Cough was not found during normal sinus rhythm. During VVI pacing the patient experienced a tickling sensation in the throat associated with intermittent coughing. The number of coughs decreased during each successive recording period. The pacing cough reflex was enhanced when the patient was lying down. The mechanism of cough during VVI pacing is uncertain. The findings suggest a possible role for afferent vagal receptors from the airways.     

A rare cause of cough.

A patient receiving amiodarone for longstanding ventricular dysrhythmias presented with idiopathic chylothorax. During drainage of chylothorax for pleurodesis, serial plasma amiodarone concentrations declined while pleural fluid concentrations remained stable. Chylous transport of amiodarone and other lipid-bound drugs should be recognized to avert complications during chylothorax drainage.     

Differential diagnosis of chronic cough.

Coughing that lasts >3 weeks is generally considered chronic. The causes of chronic cough are many. Most often, chronic cough is due to postnasal drainage, asthma, and/or gastroesophageal disease. However, other causes such as laryngopharyngeal reflux, vocal cord dysfunction, occult sinusitis, pertussis, and angiotensin-converting enzyme inhibitor should be considered. Even rarer entities will be discussed as well as some of the pathophysiology associated with the cough reflex.