Cough challenge tests involving mechanical stimulation of the cervical trachea in patients with cough as a leading symptom

From bench to bedside: The role of cough hypersensitivity in chronic cough

BACKGROUND

Chronic cough is a burdensome condition characterized by persistent cough lasting longer than 8 weeks. Chronic cough can significantly affect quality of life, physical function and productivity, with many people troubled with a cough that lasts for months or even years. People with chronic cough commonly report a persistent urge to cough with frequent bouts of coughing triggered by innocuous stimuli, which has led to the concept of cough hypersensitivity.

MAIN BODY

Both central and peripheral neural pathways regulate cough, and although mechanisms driving development of cough hypersensitivity are not fully known, sensitization of these neural pathways contributes to excessive cough triggering in cough hypersensitivity. Effective therapies that control chronic cough are currently lacking. Recent therapeutic development has focused on several ion channels and receptors involved in peripheral activation of cough (e.g., transient receptor potential channels, P2 × 3 receptors and voltage-gated sodium channels) or central cough processing (e.g., neurokinin-1 [NK-1] receptors and nicotinic acetylcholine receptors).

CONCLUSION

These targeted therapies provide novel insights into mechanisms underlying cough hypersensitivity and may offer new treatment options for people with chronic cough. In this review, we explore preclinical and clinical studies that have improved our understanding of the mechanisms responsible for chronic cough and discuss the most promising targeted approaches to date, including trials of P2 × 3-receptor antagonists and NK-1-receptor antagonists.

Somatically evoked cough responses help to identify patients with difficult-to-treat chronic cough: a six-month observational cohort study

BACKGROUND

Recently we identified in patients with chronic cough a sensory dysregulation via which the urge-to-cough (UTC) or coughing are evoked mechanically from "somatic points for cough" (SPCs) in the neck and upper trunk. We investigated the prevalence and the clinical relevance of SPCs in an unselected population of patients with chronic cough.

METHODS

From 2018 to 2021, symptoms of 317 consecutive patients with chronic cough (233 females) were collected on four visits (V1-V4) 2 months apart at the Cough Clinic of the University Hospital in Florence (I). Participants rated the disturbance caused by the cough (0-9 modified Borg Scale). We attempted to evoke coughing and/or UTC using mechanical actions in all participants who were subsequently categorised as responsive (somatic point for cough positive, SPC+) or unresponsive (SPC-) to these actions. An association was established between chronic cough and its commonest causes; treatments were administered accordingly.

FINDINGS

169 patients were SPC+ and had a higher baseline cough score (p < 0.01). In most of the patients, the treatments reduced (p < 0.01) cough-associated symptoms. All patients reported a decrease (p < 0.01) in cough score at V2 (from 5.70 ± 1.4 to 3.43 ± 1.9 and from 5.01 ± 1.5 to 2.74 ± 1.7 for SPC+ and SPC- patients respectively). However, whilst in SPC- patients the cough score continued to decrease indicating virtually complete cough disappearance at V4 (0.97 ± 0.8), in SPC+ patients this variable remained close to V2 values during the entire follow-up.

INTERPRETATION

Our study suggests that the assessment of SPCs may identify patients whose cough is unresponsive and are eligible for specific treatments.

FUNDING

This work was funded by an unrestricted grant from Merck (Italy).

Validation of the traditional medicinal use of a Mexican endemic orchid (Prosthechea karwinskii) through UPLC-ESI-qTOF-MS/MS characterization of its bioactive compounds

Ethnopharmacological relevance

The orchid Prosthechea karwinskii is a medicinal orchid in Oaxaca, Mexico, used to treat diabetes, cough, wounds, and burns, prevent miscarriage and assist in labor. Each part of the plant (leaves, pseudobulbs, or flowers) is used by healers for certain treatment conditions, indicating that each part has different biocompounds with specific pharmacological activity.

Aim of the study

To characterize the biocompounds in extracts from leaves, pseudobulbs, and flowers of P. karwinskii and evaluate their ROS inhibition capacity to associate it with medicinal uses.

Materials and methods

The compounds present in extracts from leaves, pseudobulbs, and flowers of P. karwinskii were identified by UPLC-ESI-qTOF-MS/MS. The chemical differentiation of each extract was tested by principal component analysis (PCA) using compound intensity values. For each extract, total phenol and flavonoid contents were quantified. Their antioxidant capacity was evaluated ex vivo by inhibition of ROS with DCFH-DA and in vitro with DPPH radical.

Results

Based on the PCA, it was observed that some compounds were completely separated from others according to the correlation that they presented. The compounds common to all three plant parts were quinic, malic, succinic, azelaic, and pinellic acids. Among the compounds identified, two were exclusive to leaves, four to pseudobulbs, and ten to flowers. Some of the identified compounds have well-known antioxidant activity. The leaves had the highest content of total phenols and flavonoids, and the highest in vitro and ex vivo antioxidant capacity. A strong correlation was observed between phenol and flavonoid contents, and antioxidant capacity ex vivo and in vitro.

Conclusions

It was found that the bioactive compounds and antioxidant capacity of each part of the plant were associated with its traditional medicinal use. A pharmacological potential was also found in P. karwinskii for further biological studies because of the type of compounds it contained.

•

Compounds common and specific to each plant part were identified by UPLC-ESI-qTOF-MS/MS.

•

The biological activities reported for the identified compounds validate the traditional medicinal use of P. karwinskii.

•

Embelin (inflammation) is exclusive to leaves, phloridzin (diabetes) to pseudobulbs, and abscisic acid (in labor) to flowers.

•

In the literature, the antioxidant compounds are rutin, kaempferol-3-O-rutinoside, embelin, guanosine, and azelaic acid.

•

Pearson's correlation coefficients indicate that a higher content of phenols and flavonoids has a higher antioxidant capacity.

Evaluation methods and influencing factors of cough sensitivity

Increased cough sensitivity is an important mechanism of chronic cough, and the evaluation of cough sensitivity helps understand the mechanism of cough and explore better methods to reduce cough. Evaluation methods may be direct or indirect. Direct methods include mechanical stimulation and chemical stimulation, and indirect methods include laryngeal reflex test, questionnaires, and brain functional magnetic resonance imaging (fMRI). Chemical stimulation is the most common method, while the capsaicin cough challenge test is proven and widely used. In this article, we will compare evaluation methods and explore influencing factors of cough sensitivity.

Methods for assessing cough sensitivity

Cough sensitivity can be described as the reaction intensity of the cough reflex to different stimuli which activate chemically and mechanically sensitive vagal afferent nerves innervating airways and lungs. Measurement of cough reflex sensitivity plays an important role in revealing the underlying mechanisms of cough and evaluating the effects of pharmacological interventions. Besides, different responses to cough suppression therapies indicate the existence of cough hypersensitivity. In consideration of these factors stated above, cough sensitivity should therefore be assessed with a variety of cough challenge tests. Based on the neuroanatomical characteristics of the cough reflex, chemical challenge tests have been developed to objectively assess cough sensitivity. In cough inhalation challenges, capsaicin and citric acid are commonly used as the tussive agents to induce cough, which are validated for describing a profile of cough sensitivity to chemical irritants. Recently, mechanical methodologies have also been tried to measure the mechanical sensitivity of the cough reflex. Methodological consideration and selection are necessary for the reasonable assessment of cough sensitivity while employing cough challenges in clinical trials. Thus, in this review, we will focus on describing various methodologies of cough sensitivity measurement and, detailing some factors influencing on the accuracy of outcomes in the experimentally induced cough.

Prosthechea karwinskii, an orchid used as traditional medicine, exerts anti-inflammatory activity and inhibits ROS

ETHNOPHARMACOLOGICAL RELEVANCE

Prosthechea karwinskii (Mart.) J.M.H. Shaw is a Mexican orchid used in traditional medicine by some indigenous communities to treat issues related to inflammation (cough, wounds, burns, and diabetes). Pharmacological research of this orchid could validate its therapeutic uses and demonstrate its potential for treating other health conditions of high prevalence in Mexico, including those associated with oxidative stress such as diabetes, cancer, atherosclerosis, and hypertension as well as inflammation.

AIM OF THE STUDY

The leaf extract from P. karwinskii was examined to identify its compounds and elucidate its inhibitory effect on reactive oxygen species as well as its anti-inflammatory activity and gastroprotective effects in an animal model.

MATERIALS AND METHODS

Compounds were identified via ultra-high-performance liquid chromatography coupled with electrospray ionization with quadrupole time of flight-mass spectrometry. Inhibition of reactive oxygen species was determined ex vivo in peripheral blood mononuclear cells with 2',7'-dichlorodihydrofluorescein diacetate. The anti-inflammatory activity was assessed using a carrageenan-induced paw edema model in Wistar rats; nitric oxide and tumor necrosis factor alpha levels were quantified. The gastroprotective effect was evaluated in Wistar rats with indomethacin-induced gastric injury.

RESULTS

Nine compounds were identified in the P. karwinskii leaf extract. Most compounds, such as quinic acid, malic acid, neochlorogenic acid, chlorogenic acid, rutin, embelin, pinellic acid, and azelaic acid, were reported to exhibit antioxidant and/or anti-inflammatory activity. The extract was also found to inhibit reactive oxygen species in the ex vivo model. Unlike other anti-inflammatory drugs, the extract exerted a dual effect: anti-inflammatory activity and protection of the gastric mucosa. The results showed that the extract could significantly inhibit the release of nitric oxide without a dose-response relationship.

CONCLUSION

P. karwinskii leaf extract inhibited reactive oxygen species and exerted an anti-inflammatory effect. Moreover, this extract did not induce gastric damage in the animals. The bioactivity of the species was found to support its use in traditional medicine. This orchid could be used to treat inflammatory diseases without causing the side effects associated with nonsteroidal anti-inflammatory drugs. It can also be employed to treat other pathological conditions associated with oxidative stress. The findings herein form the basis for the future discovery of natural products that may serve as safe alternative therapies for inflammatory disorders.

Mild tracheal compression by aberrant innominate artery and chronic dry cough in children

BACKGROUND

In children with aberrant innominate artery (AIA) one of the most prevalent respiratory symptom is dry cough. How frequently this mediastinal vessels anomaly, that can induce tracheal compression (TC) of different degree, may be detected in children with chronic dry cough is not known.

METHODS

In a 3-year retrospective study, the occurrence of mediastinal vessels abnormalities and the presence and degree of TC was evaluated in children with recurrent/chronic dry cough.

RESULTS

Vascular anomalies were detected in 68 out of the 209 children evaluated. A significant TC was detected in 54 children with AIA, in eight with right aortic arch, in four with double aortic arch but not in two with aberrant right subclavian artery. In AIA patients, TC evaluated on computed tomography scans, was mild in 47, moderate in six and severe in one. During bronchoscopy TC increased in expiration or during cough, but this finding was more pronounced in children with right aortic arch and double aortic arch in which a concomitant tracheomalacia was more evident. Comorbidities were detected in 21 AIA patients, including atopy, reversible bronchial obstruction and gastroesophageal reflux. Aortopexy was performed in eight AIA patients, while the remaining AIA patients were managed medically and showed progressive improvement with time.

CONCLUSION

Mild TC induced by AIA can be detected in a sizeable proportion of children with recurrent/chronic dry cough. The identification of this anomaly, that may at least partially explain the origin of their symptom, may avoid further unnecessary diagnostic examinations and ineffective chronic treatments.

Inhibitory effect of cervical trachea and chest wall vibrations on cough reflex sensitivity and perception of urge-to-cough in healthy male never-smokers

BACKGROUND

Non-pharmacological options for symptomatic management of cough are desired. Although chest wall mechanical vibration is known to ameliorate cough reflex sensitivity, the effect of mechanical vibrations on perceptions of urge-to-cough has not been studied. Therefore, we investigated the effect of mechanical vibration of cervical trachea, chest wall and femoral muscle on cough reflex sensitivity, perceptions of urge-to-cough as well as dyspnea.

METHODS

Twenty-four healthy male never-smokers were investigated for cough reflex sensitivity, perceptions of the urge-to-cough and dyspnea with or without mechanical vibration. Cough reflex sensitivity and urge-to-cough were evaluated by the inhalation of citric acid. The perception of dyspnea was evaluated by Borg scores during applications of external inspiratory resistive loads. Mechanical vibration was applied by placing a vibrating tuning fork on the skin surface of cervical trachea, chest wall and femoral muscle.

RESULTS

Cervical trachea vibration significantly increased cough reflex threshold, as expressed by the lowest concentration of citric acid that elicited five or more coughs (C5), and urge-to-cough threshold, as expressed by the lowest concentration of citric acid that elicited urge-to-cough (Cu), but did not significantly affect dypnea sensation during inspiratory resistive loading. On the other hand, the chest wall vibration not only significantly increased C5 and Cu but also significantly ameliorated the load-response curve of dyspnea sensation.

CONCLUSIONS

Both cervical and trachea vibrations significantly inhibited cough reflex sensitivity and perception of urge-to-cough. These vibration techniques might be options for symptomatic cough management.

Superiority of nebulized corticosteroids over dry powder inhalers in certain patients with cough variant asthma or cough-predominant asthma

BACKGROUND

The particle distribution might differ between nebulizer therapy and metered-dose inhaler (MDI) or dry powder inhaler (DPI) therapy because the particles repeatedly enter/re-enter the airways with the nebulizer. Inhaled corticosteroids (ICS) were administered with a nebulizer to assess the benefit of changes in the distribution of particles in patients with cough variant asthma (CVA) and cough-predominant asthma (CPA).

METHODS

Patients whose symptoms were not controlled by their current therapy were enrolled. In patients receiving high-dose ICS by MDI or DPI (ICS-MDI/DPI), steroid therapy was switched to 1,320μg/day of nebulized dexamethasone (1,600μg as dexamethasone sodium phosphate) (chronic steroid-independent group). In patients receiving systemic steroids regardless of their ICS-MDI/DPI therapy, nebulized dexamethasone was added and any concurrent ICS-MDI/DPI therapy was halted to detect a steroid-sparing effect (chronic steroid-dependent group). In patients with acute exacerbation of CVA or CPA and persistent symptoms despite systemic corticosteroids, nebulized dexamethasone was added to assess its effect (acute group).

RESULTS

Superior symptom control was achieved in 10 out of 12 steroid-independent patients, 3 out of 6 steroid-dependent patients, and all 7 acute patients.

CONCLUSIONS

Delivery of ICS via a nebulizer has advantages over ICS-MDI/DPI in some patients with CVA or CPA.

Cough hypersensitivity syndrome is an important clinical concept: a pro/con debate

The major etiologies of chronic cough are generally accepted to consist of upper airway cough syndrome (formerly postnasal drip syndrome), eosinophilic airway inflammation (asthma, nonasthmatic eosinophilic bronchitis), and gastroesophageal reflux disease (GERD). However, only a small percentage of patients with these very common conditions suffers from chronic cough. Furthermore, acute cough due to viral upper respiratory tract infection (URI) is almost always a transient, self-limited condition, yet in a small subgroup of patients, URI heralds the onset of chronic, refractory cough. The cough hypersensitivity syndrome has been proposed to explain the occurrence of chronic cough in a subgroup of patients exposed to the same putative triggers as the vast majority of the population in whom chronic cough does not result. Although conceptually the cough hypersensitivity syndrome may be intellectually satisfying, differences of opinion remain as to whether this newly recognized entity is of clinical significance, i.e., useful for the treatment of patients suffering from chronic cough. The Third American Cough Conference, held in New York in June 2011, provided an ideal forum for the debate of this issue between two internationally recognized authorities in the field of cough.

Iontophoresis-facilitated delivery of prednisolone through throat skin to the trachea after topical application of its succinate salt

PURPOSE

The possibility of direct delivery of steroids through the skin to the trachea and the effect of iontophoresis on delivery efficacy were evaluated after the application of an ionic steroidal prodrug, prednisolone sodium succinate (PS-Na), to the throat skin.

METHODS

Fluorescein sodium salt (FL-Na) and PS-Na were applied as model compounds at a concentration of 1% in pH 7.4 phosphate-buffered saline to the throat skin of hairless rats, and constant current-cathodal iontophoresis (0.4 mA/cm(2)) was performed for 8 or 10 h.

RESULTS

In vitro permeation experiment involving cathodal iontophoresis through excised hairless rat abdominal skin revealed 30- and 10-times higher levels of skin permeation of PS and its active drug, prednisolone (P), than those induced without iontophoresis. In vivo iontophoresis treatment of the rat's throat skin produced 2.6-, 1.6- and 12-times higher FL, PS and P concentrations, respectively, in the trachea than those observed without iontophoresis.

CONCLUSION

The present results suggest the usefulness of topical application of the ionic steroidal prodrugs onto throat skin followed by iontophoresis treatment for directly delivering the steroid to the trachea.