Advancing cough research: Methodological insights into cough challenge in guinea pig models using double chamber vs whole-body plethysmography.

OBJECTIVE: This study compares two methods of citric acid-induced cough in guinea pigs in whole-body plethysmography (WBP) and double chamber plethysmography (DCP) to evaluate their efficacy. METHODS: Sixteen specific pathogen-free (SPF) and sixteen conventionally-bred (CON) animals were exposed to 0.4 M citric acid aerosol. They underwent cough provocation using both DCP and WBP methods. The number of coughs and latency to the first cough were recorded and analysed using statistical methods to determine significant differences between the two techniques. RESULTS: WBP resulted in significantly higher cough counts (WBP vs. DCP: 13±9 vs 2±3 for SPF; 14±8 vs 5±5 for CON; p<0.0001) and shorter latency (WBP vs. DCP: 59±6 s vs 159±14 s for SPF; 77±4 s vs 112±12 s for CON; p<0.0001) compared to DCP in both groups. CONCLUSION: Methodological differences substantially impact cough responses. WBP provides a more reliable and physiologically relevant methodology for cough assessment, suggesting the need for standardized protocols in cough research to enhance translational relevance.

Cough response in specific pathogen-free guinea pig animal model.

Laboratory animal science associations recommend the usage of specific pathogen-free (SPF) animals in experiments to achieve appropriate results. However, their non-natural microbiome might represent an obstacle in the successful translation of obtained results into clinical practice, since the microbiome contributes to the regulation of the host's physiology. Inconsistent results, even in repeated experiments in separate animal groups, irrespective of the season or sex led us to assess the cough response of SPF animal variables and compare it to wild-type animals. The dose-response curves in citric acid and capsaicin cough challenge construction shows significantly increased cough threshold in SPF animals compared to wild-type animals of both sexes. The cause of cough response alteration in SPF animals is not presently known and thus their usage in basic cough research remains questionable. The relationship between airway reflexes and the airway microbiome has never been studied hence we propose that it might be microbiome-related.

Influence of combined voltage-gated sodium channel NaV1.7 and NaV1.8 inhibitors on cough in a guinea pig model.

Pathological excessive cough is a serious clinical problem in many patients. It is no doubt that an increased activation and sensitization of airway vagal C-fibres in disease stems from dysregulation of the neural pathways that control cough. Due to the limited efficacy and unwanted side effects of current antitussives, there is a continual demand for the development of a novel more effective antitussive. Since voltage-gated sodium channels (NaVs) are absolutely required for action potentials initiation and conduction irrespective of the stimulus, NaVs became a promising and attractive neural target. Current studies establish that NaV1.7 and NaV1.8 inhibitors have the potential to suppress cough. In this study, we demonstrated that inhaled aerosol of NaV1.7 inhibitor PF-05089771 (10 µM) and NaV1.8 inhibitor A-803467 (1 mM) mixture inhibited the capsaicin-induced cough by ≈ 60 % and citric acid-induced cough by ≈ 65 % at doses that did not modify respiratory rate. Our previous and present studies indicate that NaV1.7 and NaV1.8 may present promising therapeutic targets for antitussive therapy.

Modification of oestrogen signalling pathways influences cough induced by citric acid but not capsaicin in the animal model of both sexes.

To clarify the role of oestrogen signalling and the role of oestrogen receptor alpha (ERα) in the cough pathways we performed a study in which coughing was observed in both sexes animal models after the treatment by selective ERα degrader fulvestrant (ICI 182-780) and inhibitor of oestrogen synthesis danazol. Degradation of ERα with the normal plasma oestrogen levels induced by fulvestrant, significantly augments the cough response of female but not male guinea pigs. These changes were observed in citric acid-induced cough. Female guinea pigs responded with an increased count of cough expulsions per challenge time and we also detected shorter cough latency. The capsaicin-induced cough did not change. A similar response was observed after danazol treatment, which decreased the plasma oestrogen level. Our results indicate that the transient receptor potential vanilloid-1 (TRPV1) channel-mediated cough is resistant to the hypoestrous state, while the citric acid-mediated cough is oestrogen-dependent and hypersensitive during the hypoestrous state.

The effect of the voltage-gated sodium channel NaV1.7 blocker PF-05089771 on cough in the guinea pig.

Cough in chronic respiratory diseases is a common symptom associated with significant comorbidities including visceral pain. Available antitussive therapy still has limited efficacy. Recent advances in the understanding of voltage-gated sodium channels (NaVs) lead to the rational hypothesis that subtype NaV1.7 is involved in initiating cough and thus may present a promising therapeutic target for antitussive therapy. We evaluated the antitussive effect of NaV1.7 blocker PF-05089771 administered systemically and topically in awake guinea pigs using capsaicin cough challenge. Compared to vehicle, peroral or inhaled PF-05089771 administration caused about 50-60 % inhibition of cough at the doses that did not alter respiratory rate. We conclude that the NaV1.7 blocker PF-05089771 inhibits cough in a manner consistent with its electrophysiological effect on airway C-fibre nerve terminals.

Chondroblastoma of the Temporal Bone: A Case Report and Literature Review.

INTRODUCTION: Temporal bone chondroblastoma is a rare, locally aggressive tumour originating from immature cartilage, which recurs to a high degree. Treatment is surgical. Radiotherapy is reserved for recurrence. We describe a case of a 15-year-old-boy choosing a conservative surgical approach with reconstruction of the posterior canal wall. This study aims to report a rare pediatric case. METHODS: A literature review was performed to better understand temporal bone chondroblastomas, to describe their histopathological and radiological characteristics and to establish the optimal surgical and non-surgical treatments. The research of previous published data was done using PubMed with keywords mentioned below. RESULTS: Authors present a case of a 15-year-old boy with hearing impairment and facial nerve palsy. Conservative surgery with reconstruction of the tympanic membrane and posterior wall of the external auditory canal, restoring the hearing has been performed. We did not administer any adjuvant therapies. No sign of recurrence was observed 1 year after primary surgery. Facial nerve function is normal, and hearing is satisfactory. CONCLUSION: Chondroblastomas account for less than 1% of primary bone tumours. Temporal bone chondroblastoma is rare, locally aggressive, with a high prevalence of recurrence. This study describes specific histopathological and radiological findings, the chosen surgical approach and follow-up to improve the management and the prognosis of patients affected with this particular clinical entity.

Animal models of cough.

Cough is a vital airway reflex that keeps the respiratory tract wisely protected. It is also a sign of many diseases of the respiratory system and it may become a disease in its own right. Even though the efficacy of antitussive compounds is extensively studied in animal models with promising results, the treatment of pathological cough in humans is insufficient at the moment. The limited translational potential of animal models used to study cough causes, mechanisms and possible therapeutic targets stems from multiple sources. First of all, cough induced in the laboratory by mechanical or chemical stimuli is far from natural cough present in human disease. The main objective of this review is to provide a comprehensive summary of animal models currently used in cough research and to address their advantages and disadvantages. We also want to encourage cough researchers to call for precision is research by addressing the sex bias which has existed in basic cough research for decades and discuss the role of specific pathogen-free (SPF) animals.

Changes of Motile Ciliary Phenotype in Patients with Primary Ciliopathies.

Primary ciliopathies are a group of disorders associated with abnormal formation and function of primary cilia. Many cilia-associated proteins found in primary cilia are also present in motile cilia. Such proteins are important for the ciliary base, such as the transition zone or basal bodies, and the intraflagellar transport. Their exact role in the respiratory motile cilia is unsettled. In this prospective clinical single-center study, we investigated the hypothesis that these proteins regulate the function of motile cilia. We addressed the issue by defining the motile cilia beat frequency in the respiratory tract of patients with primary ciliopathies accompanied by chronic kidney disease and comparing it in those without kidney involvement. Ciliary beat frequency in the nasal mucosa samples was evaluated by the ciliary analysis software LabVIEW. Both children and their parents with primary ciliopathies and kidney involvement had significantly lower median airway ciliary beat frequencies than those without kidney involvement who have normal ciliary motility. Further, the ciliary beat frequency is inversely associated with the serum creatinine level. These findings strongly suggest that kidney involvement in patients with primary ciliopathy may underlie the development of motile cilia dysfunction in the respiratory tract, potentially increasing respiratory morbidity.

Parkinson's Disease and the Gut: Future Perspectives for Early Diagnosis.

Parkinson's disease (PD) is a neurodegenerative disease characterized by progressive degeneration of dopaminergic neurons, and at the cellular level by the formation of Lewy bodies in the central nervous system (CNS). However, the onset of the disease is believed to be localized to peripheral organs, particularly the gastrointestinal tract (GIT) and the olfactory bulb sooner before neuropathological changes occur in the CNS. Patients already in the pre-motor stage of PD suffer from various digestive problems and/or due to significant changes in the composition of the intestinal microbiome in this early stage of the disease. Detailed analyses of patient biopsies and autopsies as well as animal models of neuropathological changes characteristic of PD provided important information on the pathology or treatment of PD symptoms. However, presently is not clarified (i) the specific tissue in the GIT where the pathological processes associated with PD is initiated; (ii) the mechanism by which these processes are disseminated to the CNS or other tissues within the GIT; and (iii) which neuropathological changes could also serve as a reliable diagnostic marker of the premotor stages of PD, or (iv) which type of GIT tissue would be the most appropriate choice for routine examination of patient biopsies.

Retrospective Study of Factors Potentially Influencing Occurrence of Cough in Slovak Patients with Sarcoidosis.

Introduction: Sarcoidosis is a multisystem granulomatous disease of unknown aetiology, commonly involving the lungs.  Cough is a frequent and troublesome symptom of sarcoidosis that reduces patients' quality of life. Aim: Retrospective analysis of different factors-smoking history, Scadding stage, results of lung function testing, calcium metabolism, endobronchial finding, CD4+/CD8+ T-cell ratio in bronchoalveolar lavage fluid (BALF), and other sarcoidosis symptoms in relationship to presence/absence of cough in sarcoidosis patients. Methods: We retrospectively studied sarcoidosis patients diagnosed at the Clinic of Pneumology and Phthisiology of Martin University Hospital between 1998 and 2018. Patients with a history of cough-relevant comorbidities were excluded from the study. GraphPad Prism 7.0 software was used to perform statistical analysis. Results: 101 sarcoidosis patients were included to the study: 65 patients reporting from cough and 36 without cough. The cough was slightly more frequent in nonsmokers (p=0.166) and in women (p=0.688). Cough was associated with dyspnoea (p=0.0007), fever (p=0.0324), and chest pain (p=0.0206) and did not associate with arthralgia (p=0.317) and erythema nodosum (p=0.505). Patients with cough had significantly a lower average value of calciuria (p=0.0014) and lower MEF25 (p=0.0304), MEF50 (p=0.0061), FEV1 (p=0.0025), and FVC (p=0.0025) in % of predicted values, and more often positive endobronchial finding (p=0.0206), compared to patients without cough. Calcemia, FEV1/FVC, DLCO, and CD4+/CD8+ T-cell ratio in BALF and occurrence of cough did not differ between different stages of the disease. Conclusions: We found significant differences between sarcoidosis patients with/without cough regarding symptoms, results of lung function tests, endobronchial finding, and calcium metabolism. Further research is needed to understand the etiopathogenesis of cough in sarcoidosis patients.

Lidocaine, a Non-selective Inhibitor of Voltage-Gated Sodium Channels, Blocks Chemically-Induced Cough in Awake Naïve Guinea Pigs.

Pathological cough is an unwanted and debilitating symptom of a range of chronic respiratory diseases. Currently used antitussive therapies are ineffective and act largely through the central nervous system, having a number of dangerous adverse effects. There is an urgent need for new, better peripherally acting antitussive drugs with minimal adverse effects. Significant progress has recently been achieved in the understanding of voltage-gated sodium channels (NaVs), which points to the biological plausibility that blocking specific NaV sybtypes (NaV1.1 - NaV1.9) in the airway sensory nerves may lead to the inhibition of pathological coughing. In this study we investigated the effect of lidocaine, a non-selective NaVs blocker, on citric acid- and capsaicin-induced cough in the awake naïve guinea pig experimental model. We found that pre-inhalation followed by continuous inhalation of nebulized lidocaine (10 mM) during citric acid (0.8 M) cough challenge was effective in suppressing the cough response (number of coughs, median [IQR]) - (5 [3.8-6.3] pre-lidocaine vs. 1 [0.3-3.8] post-lidocaine; p = 0.002, n = 11). Likewise, lidocaine during capsaicin (50 µM) cough challenge reduced the number of coughs (6 [4.1-7.9] pre-lidocaine vs. 1 [0.5-1.5] post-lidocaine; p = 0.0005, n = 12). We conclude that nebulized lidocaine effectively blocks chemically induced cough. These findings lend support to the notion that NaVs may become a novel neural target in antitussive treatment.

Cough in sarcoidosis patients.

Sarcoidosis is a multi-system disease of unknown aetiology characterized by presence of non-caseating granulomatous inflammation. Cough is a common and significant symptom in sarcoidosis, reducing quality of life. Objective 24 h cough monitoring proved that sarcoidosis patients have significantly higher cough frequency compared to controls and their cough has diurnal variation, it is gender-specific and shows racial differences. It correlates with the presence of inflammation in the airways, but is not influenced by the X-ray staging of the disease, nor the degree of airway obstruction. Subjects with sarcoidosis have heightened cough reflex sensitivity, which is a result of interaction between the airway cough sensors and consequences of pathological process, detailed pathogenesis of cough in this demographic is unclear. The airway hyperresponsiveness, sarcoidosis of the upper airways and sensitivity to biomechanical forces play a role. More studies should be performed to understand pathogenesis of cough in sarcoidosis patients to improve the management of this troublesome symptom.

Sensitivity of airway cough-related afferents is influenced by female sex hormones.

Chronic hypersensitivity cough syndrome affects mainly postmenopausal women; however, the pathogenesis of cough hypersensitivity in this demographic is not entirely understood. The role of sex hormones in cough has never been studied in detail; however, sex hormones seem to play an important role in the lung health of women. Our study was aimed to analyse the effect of female sex hormones (oestrogen - E2 and progesterone - Pg) on cough sensitivity measured by inhalation of capsaicin in follicular and luteal phases of menstrual cycle, characterized by significantly different concentrations of sex hormones. These data were compared with a matched group of women taking oral contraceptives. Cough sensitivity to capsaicin increased in luteal phase in subjects with normal menstrual cycle, and this functional change was not present in group with contraceptive pills. The cough sensitivity correlates with the Pg/E2 ratio, and relative lack of oestrogen in luteal phase is associated with higher cough sensitivity to capsaicin.

Role of gender in basic cough research.

Cough hypersensitivity affects mainly postmenopausal women. Pathogenesis remains unknown in their case; therefore, an optimal treatment is unavailable. Only male guinea pigs are used in basic cough research and exclusion of females leads to gender bias. Nowadays, the efforts of grant agencies aim to support projects which take gender into account and involve both sexes to reduce gender bias. The aim of our pilot study is to assess the suitability of female guinea pig model in cough research. Cough response to citric acid (0.4M) was obtained in female and male guinea pigs (n=12 each). Reproducibility of cough response was tested four times a week apart. The cough was detected from the airflow traces and cough sound analysis. Our initial results show that cough response of female guinea pigs is higher than in males. Variability of females is also higher than in males. Further investigations are necessary to validate this model in different conditions to achieve gender equality in cough studies.

TRPV4 antagonist GSK2193874 does not modulate cough response to osmotic stimuli.

Osmolarity changes of airway superficial fluid are associated with cough and are used in research. TRPV4 is calcium channel initially described as osmosensor. In the airways, it can play role in increasing cough reflex sensitivity. The aim of our study was to test whether cough to osmotic stimuli is mediated via TRPV4 channel. Cough response was measured in 12 male guinea pigs by inhalation of saline, distilled water, hypertonic solution and citric acid for 10min in whole-body plethysmograph. Data were obtained in naïve animals and after pre-treatment with selective TRPV4 antagonist GSK2193874 in doses 300µg/kg (GSK300) and 900µg/kg (GSK900). Cough response to all tested aerosols was significantly higher than to saline. Pre-treatment with GSK300 did not influence response to osmotic stimuli - only reduced cough to citric acid. GSK900 reduced cough response to hypotonic stimuli and citric acid. TRPV4 mediated activation of airway afferents does not seem to be the exclusive mechanism responsible for cough to osmotic stimuli.

Modulation of cough response by sensory inputs from the nose - role of trigeminal TRPA1 versus TRPM8 channels.

BACKGROUND: Cough, the most important airways defensive mechanism is modulated by many afferent inputs either from respiratory tussigenic areas, but also by afferent drive from other organs. In animal models, modulation of cough by nasal afferent inputs can either facilitate or inhibit the cough response, depending on the type of trigeminal afferents stimulated. METHODS: In this study we addressed the question of possible bidirectional modulation of cough response in human healthy volunteers by nasal challenges with TRPA1 and TRPM8 agonists respectively. After nasal challenges with isocyanate (AITC), cinnamaldehyde, (-) menthol and (+) menthol (all 10-3 M) nasal symptom score, cough threshold (C2), urge to cough (Cu) and cumulative cough response were measured). RESULTS: Nasal challenges with TRPA1 relevant agonists induced considerable nasal symptoms, significantly enhanced urge to cough (p<0.05) but no statistically significant modulation of the C2 and cumulative cough response. In contrast, both TRPM8 agonists administered to the nose significantly modulated all parameters including C2 (p<0.05), Cu (p<0.01) and cumulative cough response (p <0.01) documenting strong anti irritating potential of menthol isomers. CONCLUSIONS: In addition to trigeminal afferents expressing TRP channels, olfactory nerve endings, trigemino - olfactoric relationships, the smell perception process and other supramedullar influences should be considered as potential modulators of the cough response in humans.