Cough Is an Airway Itch?

Divergent sensory pathways of sneezing and coughing

Sneezing and coughing are primary symptoms of many respiratory viral infections and allergies. It is generally assumed that sneezing and coughing involve common sensory receptors and molecular neurotransmission mechanisms. Here, we show that the nasal mucosa is innervated by several discrete populations of sensory neurons, but only one population (MrgprC11+MrgprA3-) mediates sneezing responses to a multitude of nasal irritants, allergens, and viruses. Although this population also innervates the trachea, it does not mediate coughing, as revealed by our newly established cough model. Instead, a distinct sensory population (somatostatin [SST+]) mediates coughing but not sneezing, unraveling an unforeseen sensory difference between sneezing and coughing. At the circuit level, sneeze and cough signals are transmitted and modulated by divergent neuropathways. Together, our study reveals the difference in sensory receptors and neurotransmission/modulation mechanisms between sneezing and coughing, offering neuronal drug targets for symptom management in respiratory viral infections and allergies.

The 5-HT1A receptor agonist, 8-OH-DPAT, attenuates long-lasting pain in imiquimod-induced psoriasis in mice

Psoriasis pain is a common symptom underestimated and rarely evaluated in psoriasis clinical trials. This work aimed to investigate whether the development of secondary chronic allodynia and hyperalgesia in the imiquimod (IMQ)-induced psoriasis mice model could be modulated by anti-inflammatory agents and compound 48/80 (C48/80) and to determine whether the activation of 5-HT_1A receptor modulates these nociceptive behaviours. C57BL/6 male mice were treated with 5% IMQ for 7 days. The paw withdrawal responses to von Frey filaments (10 and 250 mN) were used to assess the allodynia and hyperalgesia. Nociceptive behaviours were also evaluated using ketorolac 15 mg/kg s.c., adalimumab 10 mg/kg s.c. and C48/80 10 mg/kg i.p. Then, the serum serotonin and the impact of 8-OH-DPAT (1 mg/kg s.c), a 5-HT_1A receptor agonist, on long-lasting pain were examined. Mice receiving IMQ showed enhanced nociception, which decreased with all tested compounds. The serum serotonin in the IMQ group showed a significant decrease (947.042 ng/ml) regarding the control group (1143.68 ng/ml). The pretreatment with 8-OH-DPAT alleviated pain-related behaviours. These results suggest that the long-lasting pain resulting from psoriasis inflammation is also associated with the serotonergic system. The 5-HT1A receptor should be further explored as a potential therapeutic target for psoriasis pain modulation.

Itch and pain differences and commonalities

Pain and itch are generally regarded antagonistic as painful stimuli such as scratching suppresses itch. Moreover, inhibition of pain processing by opioids generates itch further supporting their opposing role. Separate specific pathways for itch and pain processing have been uncovered, and several molecular markers have been established in mice that identify neurons involved in the processing of histaminergic and non-histaminergic itch on primary afferent and spinal level. These results are in agreement with the specificity theory for itch and might suggest that pain and itch should be investigated separately on the level of neurons, mediators, and mechanisms. However, in addition to broadly overlapping mediators of itch and pain, there is also evidence for overlapping functions in primary afferents: nociceptive primary afferents can provoke itch when activated very locally in the epidermis, and sensitization of both nociceptors and pruriceptors has been found following local nerve growth factor application in volunteers. Thus, also mechanisms that underlie the development of chronic itch and pain including spontaneous activity and sensitization of primary afferents as well as spinal cord sensitization may well overlap to a great extent. Rather than separating itch and pain, research concepts should therefore address the common mechanisms. Such an approach appears most appropriate for clinical conditions of neuropathic itch and pain and also chronic inflammatory conditions. While itch researchers can benefit from the large body of information of the pain field, pain researchers will find behavioral readouts of spontaneous itch much simpler than those for spontaneous pain in animals and the skin as source of the pruritic activity much more accessible even in patients.

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.

Implementing lessons learned from previous bronchial biopsy trials in a new randomized controlled COPD biopsy trial with roflumilast

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is a chronic inflammatory disease mediated by an array of inflammatory cells and mediators, but above all, CD8+ T-lymphocytes, macrophages and neutrophils are important players in disease pathogenesis. Roflumilast, a first-in-class, potent and selective phosphodiesterase 4 (PDE4) inhibitor, reduces the rate of exacerbations in patients with a high risk of future exacerbations and has been shown to reduce inflammatory cells and mediators in induced sputum, a surrogate of airway inflammation. However, these anti-inflammatory effects are yet to be confirmed in another robust study directly assessing inflammatory markers in bronchial sub-mucosa.

METHODS/DESIGN

An international, 16-week, randomized, double-blind, placebo-controlled, parallel-group study investigating the effects of roflumilast 500 μg once-daily versus placebo on inflammatory parameters in bronchial biopsy tissue specimens, sputum and blood serum. One hundred and fifty patients with COPD and chronic bronchitis for at least 12 months will be recruited into the study and randomized in a 1:1 ratio to receive either roflumilast or placebo. The primary endpoint will be the number of CD8+ cells (cell counts per mm2) in bronchial biopsy tissue specimens (sub-mucosa) and the key secondary endpoint will be the number of CD68+ cells (cell counts per mm2), assessed by indirect immunohistochemistry.

DISCUSSION

It is hypothesized that treatment with roflumilast reduces the characteristic inflammation found in the airways of patients with moderate-to-severe COPD, compared with placebo. The design of the present study has built on the work of previous bronchial biopsy studies available in the literature. It is hoped that it will reveal the cellular mechanisms underlying the anti-inflammatory effects of roflumilast and identify potentially important biomarkers and other surrogate endpoints in patients with COPD. The design and rationale for this trial are described herein.

Cough in asthma is due to eosinophilic airway inflammation: a pro/con debate

Multiple prospective studies have demonstrated that asthma is among the most common etiologies of chronic cough, along with upper-airway cough syndrome (formerly known as postnasal drip syndrome) and gastroesophageal reflux disease. More recently, the entity of nonasthmatic eosinophilic bronchitis has been appreciated as a significant cause of chronic cough worldwide. Chronic cough associated with both of these conditions typically responds well to therapy with systemic or inhaled corticosteroids, thus leading to a general assumption that the suppression of eosinophilic airway inflammation explains the improvement in cough. However, some recent studies challenge a causal relationship between eosinophilic airway inflammation and cough in asthmatics. The 4th American Cough Conference, held in New York in June 2013, provided an ideal forum for discussion and debate of this issue between two internationally recognized experts in the field of asthma and chronic cough.

What's the place of immunotherapy in malignant mesothelioma treatments?

Malignant pleural mesothelioma (MPM) is a rare malignancy of the pleura with a very poor prognosis. Treatments evaluated for malignant mesothelioma, including chemotherapy, radiotherapy and surgery are of limited efficacy. However, the fact that the tumors of some patients with MPM regress spontaneously or respond to immunotherapy suggests that the immune system may respond to MPM under some circumstances. In this respect, animal studies have demonstrated immunoreactivity of MPM to different immunotherapies. In the case of MPM, several clinical studies have demonstrated a correlation between the presence of a lymphocyte infiltrate and a better prognosis and humoral response directed against specific antigens related to tumor. Thus, MPM immunotherapy is undoubtedly a highly promising but also very challenging approach to the treatment of this disease that has slipped through the defense lines of the immune system. This article reviews past and recent developments of the clinical strategies that concern immunotherapy of mesothelioma.

Bronchial thermoplasty for the treatment of asthma

Asthma is an increasingly prevalent disease, particularly in industrialized countries. With modern treatment, many patients can expect good asthma control; however, a significant minority continue to have excessive symptoms. Bronchial thermoplasty is a novel approach to treating asthma in which the hypertrophied airway smooth muscle present in the asthmatic airway is specifically targeted and depleted using thermal energy. In this article, we review the early animal and human development of the technique, summarize the randomized trials carried out in patients to date, discuss proposed mechanisms of action, and suggest directions for future work.

Management of chronic cough

Cough that remains unexplained after basic clinical assessment is a common reason for referral to secondary care. Much of the evidence about management of isolated chronic cough is derived from case series; this evidence suggests that isolated chronic cough is usually due to asthma, gastro-oesophageal reflux disease, and upper airway conditions, and that it can be cured in most people by treatment of these conditions. However, there is increasing recognition that satisfactory control of chronic cough is not achieved in a substantial number of patients seen in secondary care. Moreover, there is a concern that perpetuation of the belief that chronic cough is solely due to the effects of comorbid conditions is inhibiting research into the pathophysiology of an abnormally heightened cough reflex, and jeopardising development of improved treatments. We advocate a change in emphasis, which makes a clear distinction between cough due to corticosteroid-responsive eosinophilic airway diseases and corticosteroid-resistant non-eosinophilic cough. We recommend that some factors with weak evidence of an association with cough are best viewed as potential aggravating factors of an intrinsic abnormality of the cough reflex, rather than the cause. We call for more research into the basic mechanisms and pharmacological control of an abnormally heightened cough reflex, and recommend ways to assess the effects of potentially antitussive treatments.

Are pruritus and scratching the cough of the skin?

Pruritus is not the equivalent of the cough of the skin, but itch and scratch can certainly be defined as such. In physiological conditions, they share the same function: to exclude a foreign body. Itch/scratching and cough could be selective responses for the same diseases, mainly atopic diseases, and their pathophysiology is similar (role of C fibers and mast cells; role of histamine, substance P and tachykinins). This is an intriguing analogy rather than a pathophysiological identity. It may be inappropriate for many disease settings. Itch and cough can be triggered or enhanced by stress. This similarity is very interesting because it could give rise to many new research ideas.

The role of sensory dysfunction in the development of voice disorders, chronic cough and paradoxical vocal fold movement

Sensory function may be important in the pathogenesis of Chronic Cough (CC) and Paradoxical Vocal Fold Movement (PVFM). This paper aims to explore sensory issues related to the pathogenesis, classification, assessment and management of these conditions. Sensory disruption of the vagus nerve can occur through neural plasticity whereby a change occurs in the way a central neuron reacts to an incoming stimulus. Such disruption can be demonstrated through assessment of cough reflex sensitivity and extrathoracic airway hyperresponsiveness both of which may be increased in CC and PVFM. In addition, sensory function may be determined by measuring the laryngeal adductor reflex, however this phenomenon is yet to be explored in CC and PVFM. The similarity in sensory dysfunction between CC and PVFM provides support for a link between the two conditions. There are also similarities in underlying medical conditions and symptom profiles between CC/PVFM and voice disorders such as muscle tension dysphonia. Although coughing and throat clearing may be contributing factors in the development and maintenance of voice disorders, they may occur in response to extrathoracic airway hyperresponsiveness. Dysphonia can occur in CC/PVFM and may improve following behavioural treatment of CC.

Perceptual Voice Characteristics in Chronic Cough and Paradoxical Vocal Fold Movement

Voice problems have been reported in chronic cough (CC) and paradoxical vocal fold movement (PVFM), however, there is a lack of a systematic description of voice characteristics in these conditions. This study examined the perceptual voice characteristics of 56 individuals with CC, 8 with PVFM and 55 with both CC and PVFM, compared to 25 people with muscle tension dysphonia (MTD) and 27 healthy controls. There was a high prevalence of abnormal voice quality in the CC and PVFM groups compared with healthy controls. More than one third of participants with CC and PVFM demonstrated strained, rough and/or breathy voices to a moderate or severe degree. The perceptual features in CC and PVFM were similar to those in MTD with greater severity evident in MTD. Possible mechanisms for abnormalities in voice quality include the presence of muscle tension and the frequency of coughing. These results have implications for the identification and management of voice disorders in CC and PVFM and suggest that clinicians should be alert to the incidence of voice abnormalities in these populations.

A potent human anti-eotaxin1 antibody, CAT-213: isolation by phage display and in vitro and in vivo efficacy

The CC chemokine, eotaxin1 (CCL11) is an important regulator of eosinophil function. A marked accumulation of eosinophils in tissues has been correlated with the up-regulation of eotaxin1 expression in several diseases. The potential therapeutic value of neutralizing the effects of eotaxin1 in inflammatory conditions (including asthma) is under investigation. A human single-chain fragment variable antibody that neutralizes human eotaxin1 (CAT-212) was produced using antibody phage display and converted to whole antibody IgG4 format (CAT-213). A novel approach to lead optimization in which the length of the variable heavy chain complementarity-determining region 3 was reduced by one amino acid resulted in an increase in potency of >1000-fold compared with the parent anti-eotaxin1 antibody. The optimized antibody binds eotaxin1 with high affinity (80.4 pM) and specificity. CAT-213 and CAT-212 do not bind or neutralize a range of other human proteins including human monocyte chemoattractant protein-1, a structurally similar chemokine. CAT-213 neutralizes the ability of eotaxin1 to cause an increase in intracellular calcium signaling (with an IC(50) value of 2.86 nM), migration of CCR3-expressing L1.2 cells (with an IC(50) value of 0.48 nM), and inhibition of the eotaxin1-evoked shape change of human eosinophils in vitro (with an IC(50) of 0.71 nM). Local administration of CAT-213 to mice (1-100 microg kg(-1)) attenuates dermal eosinophilia induced by human eotaxin1, achieving >90% inhibition of eosinophil influx. CAT-213 may therefore be of therapeutic value in inhibiting diseases in which eotaxin1 and eosinophils play a major role, for example, severe asthma.

Chemokine concentrations and mast cell chemotactic activity in BAL fluid in patients with eosinophilic bronchitis and asthma, and in normal control subjects

BACKGROUND

Asthma and eosinophilic bronchitis share many immunopathologic features including increased numbers of eosinophils and mast cells in the superficial airway. The mast cell chemotactic activity of airway secretions has not been assessed in patients with eosinophilic bronchitis.

OBJECTIVES

To investigate the concentration of chemokines in bronchial wash samples and BAL fluid, and the mast cell chemotactic activity in BAL fluid from subjects with asthma and eosinophilic bronchitis, and from healthy control subjects.

METHODS

We measured the concentrations of CCL11, CXCL8, and CXCL10 in bronchial wash samples and BAL fluid from 14 subjects with eosinophilic bronchitis, 14 subjects with asthma, and 15 healthy control subjects. Mast cell chemotaxis to BAL fluid from these subjects was examined using the human mast cell line HMC-1.

RESULTS

The bronchial wash sample and BAL fluid concentrations of CXCL10 and CXCL8 was increased in subjects with eosinophilic bronchitis compared to those in subjects with asthma and healthy control subjects (p < 0.05). The CCL11 concentration was below the limit of detection in most subjects. BAL fluid from subjects with eosinophilic bronchitis was chemotactic for mast cells (1.4-fold migration compared to a control, 95% confidence interval, 1.1 to 1.9; p = 0.04) and was inhibited by blocking CXCR1 (45% inhibition; p = 0.002), CXCR3 (38% inhibition; p = 0.034), or both (65% inhibition; p = 0.01). BAL fluid from the subjects with asthma and healthy control subjects was not chemotactic for mast cells. Mast cell migration to BAL fluid was correlated with the concentration of CXCL8 (r = 0.42; p = 0.031) and CXCL10 (r = 0.52; p = 0.007).

CONCLUSION

In subjects with eosinophilic bronchitis, CXCL8 and CXCL10 concentrations were elevated in airway secretions. These chemokines may play a key role in mast cell recruitment to the superficial airway in this condition.

Interpreting the histopathology of chronic cough: a prospective, controlled, comparative study

HYPOTHESIS

Trauma from chronic coughing produces airway inflammation similar to diseases causing cough.

DESIGN

Prospective, cross-sectional, controlled, clinicopathologic correlation study in four groups: group 1, cough from intrapulmonary diseases; group 2, cough from extrapulmonary diseases; group 3, cough that was unexplained; and group 4, nonsmoking, asymptomatic control subjects.

METHODS

Patients with chronic cough underwent a standardized workup including endobronchial biopsies before treatment. Causes were determined by a favorable response to therapy. Bronchial biopsy samples from control subjects were obtained from surgical specimens.

RESULTS

There were 24 adult subjects (13 women and 11 men) with mean cough duration of 8.6 +/- 7.4 years (+/- SD). Thirteen patients had cough due to a specific disease: intrapulmonary diseases in 5 patients, and extrapulmonary diseases in 8 patients. Eleven patients had unexplained cough. Compared to control subjects, there was minimal-to-moderate chronic inflammation in all coughers (p < or = 0.0004), in group 1 (p < or = 0.039), group 2 (p = 0.061), and group 3 (p < or = 0.025) diseases that were not correlated with cough duration. There was no difference in type of inflammation, cough duration, or smoking history between groups, nor were there histologic differences between subjects with explained causes of cough compared with unexplained cough.

CONCLUSIONS

Our findings suggest that airway inflammation associated with chronic cough, assessed on morphologic appearance and inflammatory cell counting in hematoxylin-eosin-prepared samples, may be due to the trauma of coughing, and the inflammation may be similar to that seen with diseases putatively thought to cause chronic cough. Investigators must be cautious when attributing pathogenic importance to observed inflammatory changes in airways of coughing subjects.

Involuntary Glottal Closure during Inspiration in Muscle Tension Dysphonia

OBJECTIVE/HYPOTHESIS

The purpose of this study was to examine respiratory function in a group of patients with muscle tension dysphonia (MTD) DESIGN: Cross-sectional analytical study.

METHODS

Participants included 15 people with a diagnosis of MTD referred to speech pathology for management of their voice disorder, fiberoptic evidence of glottal or supraglottic constriction during phonation with or without posterior chink, or bowing combined and deviation in perceptual voice quality. A second group of 15 participants with no history of voice disorder served as healthy controls. Baseline pulmonary function test measures included forced expiratory volume in the first second (FEV1), FVC, FEF25 to 75, FIF50, FEV1/FVC, ratio and FEF50/FIF50 ratio. Hypertonic saline challenge test measures included FEV1 and FIF50 after provocation, dose response slope, and provocation dose.

RESULTS

Compared with healthy controls, participants with MTD demonstrated a higher prevalence of glottal constriction during inspiration after provocation with nebulized hypertonic saline as demonstrated by a reduction in FIF50 after the hypertonic saline challenge. There was no significant difference between the MTD and healthy control groups in baseline pulmonary function testing. Participants with MTD demonstrated a higher prevalence than healthy controls of abnormal glottic closure during inspiration similar to paradoxical vocal fold movement (PVFM). This suggests that they either had previously undiagnosed coexisting PVFM or that the condition of MTD could be expanded to include descriptions of aberrant glottic function during respiration. This study enhances the understanding of PVFM and MTD by combining research advances made in the fields of otolaryngology and respiratory medicine.

Airway inflammation and remodelling changes in patients with chronic cough: do they tell us about the cause of cough?

Airway mucosal changes have been reported in chronic cough. In cough variant asthma and in eosinophilic bronchitis, there is evidence of eosinophil infiltration and sub-basement membrane thickening. In non-asthmatic cough, an increase of bronchoalveolar mast cells, mucosal mononuclear cells, and epithelial shedding have been reported. In a more recent study, evidence of airway wall remodelling has been observed in both asthmatic and non-asthmatic cough, such as an increase in sub-basement membrane thickness, goblet cell area, vascularity and vessel size. Smooth muscle area was increased in non-asthmatic coughers. Heightened cough sensitivity in non-asthmatic coughers was related to the degree of goblet cell hyperplasia and epithelial shedding. Cough reflex may be heightened by increased production of growth factors that might be further enhanced by the physical effects of cough on the airways. Mast cells may participate in the cough pathophysiology through release of growth factors as well as tussive mediators. Changes in the airway wall mucosa and epithelium may be important in the pathogenesis of cough receptor sensitization.

In vivo evaluation of the effectiveness of bronchial thermoplasty with computed tomography

A recent study has reported that the application of thermal energy delivered through a bronchoscope (bronchial thermoplasty) impairs the ability of airway smooth muscle to shorten in response to methacholine (MCh)(Danek CJ, Lombard CM, Dungworth DL, Cox PG, Miller JD, Biggs MJ, Keast TM, Loomas BE, Wizeman WJ, Hogg JC, and Leff AR. J Appl Physiol 97: 1946-1953, 2004). If such a technique is successful, it has the potential to serve as a therapy to attenuate airway narrowing in asthmatic subjects regardless of the initiating cause that stimulates the smooth muscle. In the present study, we have applied high-resolution computed tomography to accurately quantify the changes in airway area before and after a standard MCh aerosol challenge in airways treated with bronchial thermoplasty. We studied a total of 193 airways ranging from 2 to 15 mm in six dogs. These were divided into treated and control populations. The MCh dose-response curves in untreated airways and soon-to-be-treated airways were superimposable. In contrast, the dose-response curves in treated airways were shifted upward at all points, showing a significantly decreased sensitivity to MCh at both 2 and 4 wk posttreatment. These results thus show that treated airways have significantly increased luminal area at any dose of inhaled MCh compared with untreated airways. The work in this study thus supports the underlying concept that impairing the smooth muscle may be an effective treatment for asthma.