The effect of stimulation and unloading of baroreceptors on cough in experimental conditions.

Cough, the main airway defensive process, is modulated by multiple sensory inputs from the respiratory system and outside of it. This modulation is one of the mechanisms that contributes to the sensitization of cough pathways at the peripheral and/or central level via neuroplasticity and it manifests most often as augmented coughing. Cardiorespiratory coupling is an important mechanism responsible for a match between oxygenation and cardiac output and bidirectional relationships exist between respiration and cardiovascular function. While the impact of cough with the robust swings of the intrathoracic pressure on haemodynamic parameters and heart electrophysiology are well characterized, little is known about the modulation of cough by haemodynamic parameters - mainly the blood pressure. Some circumstantial findings from older animal studies and more recent sophisticated analysis confirm that baroreceptor stimulation and unloading alters coughing evoked in experiments. Clinical relevance of such findings is not presently known.

Legacy of Prof. Juraj Korpás: International Impact of Slovak School of Experimental Respirology.

Human health is the main role of medical research. Scientists were always intrigued by disease prevention, their diagnostics and proper treatment. In fact, research in medicine is always directed towards the improvement of the health care and improvement of the quality of life of the target population. Nowadays, physiological research, which is the base stone for clinical research, progresses fast forward, providing new information about body functions in health and diseases. This obvious progress is associated with modern methods, such as neuronal tracing, patch-clamp methods, electrophysiology, molecular biology and many more, which supported by comprehensive information technology guarantees high quality and complex data. Our younger colleagues, young scientists, post-docs or PhD students are well-trained and qualified in utilizing these new methods.

Cough as a Cause and Consequence of Heart Dysfunction - Current State of Art.

The cough reflex is an airway defensive process that can be modulated by afferent inputs from organs located also out of the respiratory system. A bidirectional relationship between cough and heart dysfunctions are presented in the article, with the special insights into an arrhythmia-triggered cough. Albeit rare, cough induced by cardiac pathologies (mainly arrhythmias) seems to be an interesting and underestimated phenomenon. This condition is usually associated with the presence of abnormal heart rhythms and ceases with successful treatment of arrhythmia either by pharmacotherapy or by radiofrequency ablation of arrhythmogenic substrate. The two main hypotheses on cough-heart relationships - reflex and hemodynamic - are discussed in the review, including the authors' perspective based on the experiences with an arrhythmia-triggered cough.

Exhaled and Nasal Nitric Oxide - Impact for Allergic Rhinitis.

FeNO measurement is a validated non-invasive technique, which is used for diagnosis and monitoring of asthma. It would be desirable to find a reliable method to monitor allergic rhinitis (AR) via measurement of FeNO, and/or nasal nitric oxide (nNO). The aim of our study was the assessment of the efficacy of FeNO and nNO as markers in AR treatment. FeNO and nNO were measured with the portable NO analyser (NIOX MINO®) in healthy participants and in patients with AR. The patients were examined during the pollen season and out of it. The effect of local corticosteroids and antihistamine therapy was observed in patients with AR during pollen season after three weeks of therapy. There are significant differences between FeNO and nNO in patients with AR compared to healthy controls at all set points of measurements. While FeNO responded well to the treatment with both antihistamines and combined therapy, nNO decreased only after combined therapy with antihistamines and nasal corticosteroids. nNO monitoring alone is not a suitable method to monitor inflammation of the upper airways in AR and its suppression by anti-allergic treatment and should be correlated with other markers as FeNO or symptom scores.

Female Guinea Pig Model for Cough Studies and Its Response to Most Common Tussive Substances.

Laboratory research of cough reflex utilizes almost exclusively male guinea pigs - a practice that represents a significant obstacle in the successful translation of results into clinical practice. Chronic hypersensitivity cough syndrome affects mostly postmenopausal women and it represents significant decrease in patient's quality of life. No cause for such exaggerated cough can be found, therefore this condition cannot be treated appropriately. One of the reasons leading to the lack of relevant data about mechanisms responsible for hypersensitivity of cough related pathways is nowadays widely discussed gender bias, which is present in nearly all branches of biomedical research. Since gender differences in cough reflex physiology do exist in humans, it would be reasonable to study cough-related phenomena on both sexes of laboratory animals. In this study, we focused on detailed characterization of cough response of female guinea pigs to aerosols of commonly used tussive agents (capsaicin, distilled water, allyl isothiocyanate, cinnamaldehyde, citric acid). In pooled data from multiple challenges we found no statistical difference in number of cough and cough latency between sexes. Based on our results we conclude that the utilization of female guinea pigs model does not lead to messy data and can be used in basic cough research.

Various aspects of sex and gender bias in biomedical research.

The main role of research in medicine is to provide relevant knowledge which, after successful translation to clinical practice, improves the quality of healthcare. The sex bias which is still present in the majority of research disciplines prefers male subjects despite legislation changes in the US grant agencies and European research programme Horizon 2020. Male subjects (cells, animals) still dominate in preclinical research and it has detrimental consequences for women's health and the quality of science. Opposite bias exists for data obtained mainly in animal models utilizing female subjects (e.g. research in multiple sclerosis, osteoporosis) with skewed outcomes for men affected by these diseases. Either way, scientists are producing results which compromise half of the population. Assumptions that females as cohorts are more variable and another assumption that the oestrous cycle should be tracked in case the females are enrolled in preclinical studies were proven wrong. Variability of male versus female cohorts are comparable and do not only stem from hormonal levels. The widespread prevalence of sex differences in human diseases ultimately requires detailed experiments performed on both sexes, unless the studies are specifically addressing reproduction or sex-related behaviors.

Physiology of nitric oxide in the respiratory system.

Nitric oxide (NO) is an important endogenous neurotransmitter and mediator. It participates in regulation of physiological processes in different organ systems including airways. Therefore, it is important to clarify its role in the regulation of both airway and vascular smooth muscle, neurotransmission and neurotoxicity, mucus transport, lung development and in the. surfactant production. The bioactivity of NO is highly variable and depends on many factors: the presence and activity of NO-producing enzymes, activity of competitive enzymes (e.g. arginase), the amount of substrate for the NO production, the presence of reactive oxygen species and others. All of these can change NO primary physiological role into potentially harmful. The borderline between them is very fragile and in many cases not entirely clear. For this reason, the research focuses on a comprehensive understanding of NO synthesis and its metabolic pathways, genetic polymorphisms of NO synthesizing enzymes and related effects. Research is also motivated by frequent use of exhaled NO monitoring in the clinical manifestations of respiratory diseases. The review focuses on the latest knowledge about the production and function of this mediator and understanding the basic physiological processes in the airways.

Nasal nitric oxide in healthy adults - reference values and affecting factors.

Nitric oxide (NO) is an important endogenous mediator with significant role in the respiratory system. Many endogenous and exogenous factors influence the synthesis of NO and its level is significantly changed during the inflammation. Analysis of nasal nitric oxide (nNO) is not validated so far as the diagnostic method. There is a lack of reference values with possible identification of factors modulating the nNO levels. In healthy adult volunteers (n=141) we studied nasal NO values by NIOX MINO® (Aerocrine, Sweden) according to the recommendations of the ATS & ERS. Gender, age, height, body weight, waist-to-hip ratio, FEV1/FVC, PEF and numbers of leukocytes, eosinophils, basophils and monocytes were studied as potential variables influencing the levels of nNO. The complexity of the results allowed us to create a homogenous group for nasal NO monitoring and these data can be used further as the reference data for given variables. Because of significant correlation between nNO and exhaled NO, our results support the "one airway - one disease" concept. Reference values of nasal NO and emphasis of the individual parameters of tested young healthy population may serve as a starting point in the non-invasive monitoring of the upper airway inflammation.

Sex differences in cough reflex.

Majority of patients visiting cough clinics are postmenopausal women, who are affected by intractable cough for years. Why the cough reflex becomes exaggerated in women is not known. Basic research excludes females from the studies contributing to the sex bias which may be responsible for lack of understanding of "hypersensitive" cough in women. Biological and behavioural differences between women and men are the factors affecting cough physiology. Gender also shapes the patterns of behaviour and determines the character of environmental exposures which differs between sexes. The article offers an insight into the physiology of the cough, differences in the maturation of it and biological, social and behavioural factors contributing to the sex differences in cough.

The Guinea Pig Sensitized by House Dust Mite: A Model of Experimental Cough Studies.

The guinea pig sensitized by ovalbumin is the most widely used model to study cough experimentally, as the neurophysiology of the vagus nerve in the guinea pig is closest to humans. Nonetheless, the choice of the antigen remains questionable, which influences the translation of results into clinical medicine. The present study seeks to develop an alternative model of cough study using house dust mite sensitization (HDM). Thirty guinea pigs were divided into the HDM group, ovalbumin (OVA) group, and control group based on their cough response to 0.4 M citric acid. In the HDM group animals were sensitized by 0.25 %HDM aerosol, which they inhaled for 5 min over 5 days, followed by inhalation of 0.5 %HDM in the same protocol. Sensitization was confirmed by a skin test. Symptoms of allergic rhinitis were induced by intranasal application of 15 µl 0.5 %HDM and cough challenges with citric acid were performed. Airway resistance was measured in vivo by Pennock's method. We found that both HDM and OVA-sensitized groups showed a significantly enhanced nasal reactivity and cough response compared with controls. The airway resistance data did not show significant differences. We conclude that the HDM cough model replicates functional aspects of the OVA model, which may make it an alternative to the latter. However, the superiority of the HDM model for experimental cough studies remains to be further explored.

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.

Histamine, histamine intoxication and intolerance.

Excessive accumulation of histamine in the body leads to miscellaneous symptoms mediated by its bond to corresponding receptors (H1-H4). Increased concentration of histamine in blood can occur in healthy individuals after ingestion of foods with high contents of histamine, leading to histamine intoxication. In individuals with histamine intolerance (HIT) ingestion of food with normal contents of histamine causes histamine-mediated symptoms. HIT is a pathological process, in which the enzymatic activity of histamine-degrading enzymes is decreased or inhibited and they are insufficient to inactivate histamine from food and to prevent its passage to blood-stream. Diagnosis of HIT is difficult. Multi-faced, non-specific clinical symptoms provoked by certain kinds of foods, beverages and drugs are often attributed to different diseases, such as allergy and food intolerance, mastocytosis, psychosomatic diseases, anorexia nervosa or adverse drug reactions. Correct diagnosis of HIT followed by therapy based on histamine-free diet and supplementation of diamine oxidase can improve patient's quality of life.

The effect of selective antagonist of H4 receptor JNJ7777120 on nasal symptoms, cough, airway reactivity and inflammation in guinea pigs.

The efficacy of H4R antagonist JNJ7777120 on nasal symptoms, cough, airway resistance (Raw), inflammatory cell count in bronchoalveolar lavage (BAL) and blood in ovalbumin (OVA) induced allergic rhinitis (AR) was studied in guinea pigs. Animals (n=8) were sensitized by i.p. OVA and were repeatedly challenged with nasal OVA to induce rhinitis, seven animals were not sensitized. Animals were pre-treated with JNJ7777120 2.5 and 5mg/kg i.p. 30 min prior OVA. Cough was induced by inhalation of citric acid, Raw was measured in vivo by Pennock's method as baseline, during AR and after JNJ7777120 treatment. Leucocyte count in BAL and blood was analyzed. JNJ7777120 (5mg/kg) significantly suppressed nasal symptoms and the number of coughs. This compound significantly inhibited airway reactivity to histamine, but not methacholine. Pre-treatment with JNJ7777120 5mg/kg did not influence significantly the leucocyte count in BAL and blood except for a significant decrease in monocyte count in blood compared to the control group (p<0.05). We conclude that the antitussive action of JNJ7777120 is peripheral. The primary effect of the compound is anti-inflammatory, and the suppression of cough is a consequence of reduced airway inflammation.

The effects of nasal irritant induced responses on breathing and cough in anaesthetized and conscious animal models.

There is little evidence to support the down-regulation of coughing from the nose. The cough response to citric acid (CA) was studied in anesthetized and conscious guinea pigs after nasal pretreatment with saline, 1% DMSO, allylisothiocyanate (TRPA1 agonist) and allylisothiocyanate +AP-18 (TRPA1 antagonist). Cough was induced by adding citric acid (CA) to the tracheal perfusion in anaesthetized animals, or by inhaling 0.4M CA in conscious animals. The cough response was counted from the dose response curves, airflow traces and cough sound analysis. In conscious animals, nasal allylisothiocyanate induced reproducible, dose dependent nasal symptoms and a significant drop in respiratory rate. Cough induced by CA was suppressed after nasal allylisothiocyanate (p<0.05), and this effect was prevented by AP-18 (1mM). In anaesthetized animals, nasal allylisothiocyanate induced a significant drop in respiratory rate. Cough induced subsequently by CA was suppressed when compared to baseline and vehicle responses (p<0.05). The reasons for the suppression of CA induced cough by TRPA1 agonist applied to the nose are not clear and remain to be elucidated.

[Histamine intolerance]. / Histamínová intolerancia.

Histamine intolerance (HIT) is a pathological process that results from a disbalance between levels of released histamine and the ability of the body to metabolize it. Accumulated histamine leads to the onset of "histamine mediated" reactions which are usually excessive and decrease quality of life. Although we have a lot of knowledge about histamine intolerance, HIT is still vastly underestimated, because it manifests via the diversity of clinical symptoms, that are often misinterpreted by the patient and sometimes even by a physician. Clinical symptoms and their provocation by certain kinds of food, beverages and drugs are often attributed to the different diseases, such as food allergy and intolerance of sulfites, or other biogenic amines (eg. tyramine), mastocytosis, psychosomatic diseases or adverse drug reactions in general. Proper diagnosis of HIT followed by therapy based on histamine--free diet and supplementation of diaminooxidase can considerably improve patient's quality of life.

The role of trigeminal nasal TRPM8-expressing afferent neurons in the antitussive effects of menthol.

The cold-sensitive cation channel TRPM8 is a target for menthol, which is used routinely as a cough suppressant and as an additive to tobacco and food products. Given that cold temperatures and menthol activate neurons through gating of TRPM8, it is unclear how menthol actively suppresses cough. In this study we describe the antitussive effects of (-)-menthol in conscious and anesthetized guinea pigs. In anesthetized guinea pigs, cough evoked by citric acid applied topically to the tracheal mucosa was suppressed by menthol only when it was selectively administered as vapors to the upper airways. Menthol applied topically to the tracheal mucosa prior to and during citric acid application or administered continuously as vapors or as an aerosol to the lower airways was without effect on cough. These actions of upper airway menthol treatment were mimicked by cold air delivered to the upper airways but not by (+)-menthol, the inactive isomer of menthol, or by the TRPM8/TRPA1 agonist icilin administered directly to the trachea. Subsequent molecular analyses confirmed the expression of TRPM8 in a subset of nasal trigeminal afferent neurons that do not coincidently express TRPA1 or TRPV1. We conclude that menthol suppresses cough evoked in the lower airways primarily through a reflex initiated from the nose.

Antitussive effects of nasal thymol challenges in healthy volunteers.

Eighteen healthy volunteers with normal lung function were tested for cough. Before and after nasal administration of thymol (0.025 ml, 10(-3) M) into both nostrils, urge-to-cough, cough threshold, cumulative and total count of coughs per provocation were estimated during standardized and validated capsaicin cough challenge. Nasal thymol challenges induced pleasant olfactory sensation and in 6 out of the 18 subjects also mild cooling sensation. Cough threshold was not influenced when compared with intranasal saline and vehicle challenges (12.5 vs. 13.2 vs. 10.2 µM of capsaicin to induce two or more coughs (C2), respectively), but the total count of coughs after nasal thymol challenge was significantly lower than that obtained after saline or vehicle (19 vs. 20 vs. 14 coughs/provocation, respectively; p<0.05). Importantly, subjects did not report the urge to cough, which appeared to correspond to C2. We conclude that the modulation of cough by thymol is mostly of olfactory origin.

Intranasal TRPV1 agonist capsaicin challenge and its effect on c-fos expression in the guinea pig brainstem.

Central neuronal interaction seems to play a role in pathogenesis of upper airway cough syndrome. In the guinea pig model we used the method c-fos expression to identify neurons involved in processing of nociceptive nasal stimuli and their contribution to enhancement of cough. 21 spontaneously breathing, urethane anaesthetized animals were used. The controls received intranasal saline, stimulation group received capsaicin (15 microl, 50 microM), and not-treated group was free of nasal challenge. After 2 h animals were deeply anaesthetized, exsanguinated and transcardially perfused with saline and paraformaldehyde. The brainstems were removed, post-fixed, and slices were processed immunohistochemically for c-fos. In capsaicin group the FLI was detected in the nTs 0.5 mm caudal, 1.5 mm lateral to the obex, the area postrema, LRN and VRG. Intensive FLI was identified in trigeminal nuclear complex. Mean number of FOS positive neurons per section was significantly higher in capsaicin group than that in no-treatment controls or saline controls at the level of obex (p<0.01). Neurons of nTs and VRG clearly activated after nasal provocation may participate in enhancement of cough.

Convergence of nasal and tracheal neural pathways in modulating the cough response in guinea pigs.

In the present study we investigated the possibility of central convergence of neural pathways coming from distant anatomical regions in modulating the cough response. We addressed this issue by inducing cough from the tracheo-bronchial region on the background of capsaicin-stimulated and mesocain-blocked nasal mucosa in 14 anesthetized guinea pigs. The control group consisted of 6 guinea pigs in which the active agents, capsaicin and mesocain, were substituted for by inert physiological saline. All animals were tracheostomized, and the larynx was disconnected from the proximal part of the trachea with preserved innervations, and all were subjected to the same protocol. Cough, induced by mechanical irritation of the tracheo-bronchial mucosa, was elicited three times: in the control condition, after intranasal capsaicin challenge, and after another capsaicin challenge preceded by intranasal instillation of a local anesthetic, mesocain. The main finding of the study was that the number of cough efforts per bout, assessed from positive deflections on the intrapleural pressure recordings, was significantly enhanced by intranasal capsaicin challenge and this effect was reversed by intranasal pretreatment with the anesthetic mesocain [2.1 +/-0.2 (control) vs. 3.5 +/-0.4 (capsaicin) vs. 2.2 +/-0.2 (capsaicin after mesocain) (P<0.01)], with no appreciable changes in the magnitude of cough efforts. The cough response in the control group remained unchanged. We conclude that tracheo-bronchial cough may be modified by neural sensory input to the brain coming from nasal mucosa. Therefore, cough reflex is subject to central convergence of peripheral neural pathways originating at distant anatomical locations.

Influence of stimulation of nasal afferents on expiration reflex evoked from vocal folds.

Cough and sneezing are upregulated during the upper airway diseases, most likely to enhance airway defense. The aim of this study was to assess the expiration reflex (ER), another expulsive defensive airway reflex, during allergic rhinitis (AR) and intranasal (i.n.) capsaicin challenge. Thirty male guinea pigs, sensitized to ovalbumin were used in the study. They were divided into 3 groups of 10 animals each: AR group (i.n. ovalbumin), capsaicin group (i.n. capsaicin 50 microM, 15 microl), and controls without any challenge. The animals were anesthetized with urethane (1.1 mg/kg) and allowed to breath spontaneously via tracheostomy. Metal canula was introduced into the right hemithorax to assess intrapleural pressure. ER was elicited by mechanical stimulation of the vocal folds using a thin nylon loop introduced upwards via tracheostomy. Maximal expiratory effort of ER (MEE) and the count of post-ER laryngeal coughs were evaluated. Mechanical stimulation of the vocal folds in controls produced isolated ER. They were followed by post-ER cough only in 11% of provocations. AR and capsaicin challenge increased MEE compared with that in controls (P<0.05). In these two groups of animals, the ER was followed by post ER-cough in 75% of provocations. The count of post-ER coughs in the group order control/AR/capsaicin was 0-2/2-4/1-3, respectively; P<0.05). The ER from the vocal folds is upregulated in a similar manner as is cough and sneeze. The central neuronal mechanisms are proposed to mediate this effect, but the spread of inflammation from upper airways to the larynx, verified histologically in the present study, may contribute as well.