A guinea pig model for cough variant asthma and role of tachykinins.
Nishitsuji Masaru,Fujimura Masaki,Oribe Yoshitaka,Nakao Shinji
Experimental lung research
Cough variant asthma is known as a major cause of chronic cough. Fundamental features of cough variant asthma are prolonged nonproductive cough responding to bronchodilator therapy, no history of wheezing or dyspnea attack, normal cough sensitivity, and slightly increased bronchial responsiveness. Animal model of cough variant asthma has not been reported. The aim of this study was to establish an animal model for studying detailed pathophysiology of cough variant asthma. Bronchial responsiveness to methacholine and cough reflex sensitivity to capsaicin were measured 72 hours after antigen (ovalbumin, OA) inhalation in actively sensitized guinea pigs. Next, cough number and specific airway resistance (sRaw) were measured during 20 minutes following reinhalation of OA solution, which was carried out 72 hours after the first OA inhalation, and then total cell number and cell differentials in bronchoalveolar lavage fluid (BALE) were measured. Bronchial responsiveness to methacholine, but not cough reflex sensitivity to capsaicin, was significantly increased 72 hours after the first inhalation of OA solution. Number of coughs, sRaw and total cell number in BALF increased significantly by the OA reinhalation, and the cough number and the increase in sRaw were significantly suppressed by beta2 agonist, procaterol. FK224, a specific neurokinin (NK) receptor antagonist, did not significantly influence the OA reinhalation-induced cough and increase in sRaw and total cell number in BALF in this model In conclusion, pathophysiologic feature of this animal model is similar to that of clinical cough variant asthma. Tachykinins may not play an important part in antigen-induced cough associated with bronchoconstriction and airway inflammation in cough variant asthma.
Breathtaking TRP channels: TRPA1 and TRPV1 in airway chemosensation and reflex control.
Bessac Bret F,Jordt Sven-Eric
Physiology (Bethesda, Md.)
New studies have revealed an essential role for TRPA1, a sensory neuronal TRP ion channel, in airway chemosensation and inflammation. TRPA1 is activated by chlorine, reactive oxygen species, and noxious constituents of smoke and smog, initiating irritation and airway reflex responses. Together with TRPV1, the capsaicin receptor, TRPA1 may contribute to chemical hypersensitivity, chronic cough, and airway inflammation in asthma, COPD, and reactive airway dysfunction syndrome.
E. coli O124 K72 alters the intestinal barrier and the tight junctions proteins of guinea pig intestine.
Ren Xiaomeng,Zhu Yanyan,Gamallat Yaser,Ma Shenhao,Chiwala Gift,Meyiah Abdo,Xin Yi
Biomedicine & pharmacotherapy = Biomedecine & pharmacotherapie
Our research group previously isolated and identified a strain of pathogenic Escherichia coli from clinical samples called E. coli O124 K72. The present study was aimed at determining the potential effects of E. coli O124 K72 on intestinal barrier functions and structural proteins integrity in guinea pig. Guinea pigs were grouped into three groups; control (CG); E. coli O124 K72 (E. coli); and probiotics Lactobacillus rhamnosus (LGG). Initially, we create intestinal dysbiosis by giving all animals Levofloxacin for 10days, but the control group (CG) received the same volume of saline. Then, the animals received either E. coli O124 K72 (E. coli) or Lactobacillus rhamnosus (LGG) according to their assigned group. E. coli O124 K72 treatment significantly affected colon morphology and distorted intestinal barrier function by up-regulating Claudin2 and down-regulating Occludin. In addition, E. coli upregulated the mRNA expression of MUC1, MUC2, MUC13 and MUC15. Furthermore, suspected tumor was found in the E. coli treated animals. Our results suggested that E. coli O124 K72 strain has adverse effects on intestinal barrier functions and is capable of altering integrity of structural proteins in guinea pig model while at same time it may have a role in colon carcinogenesis.
Transient receptor potential ankyrin receptor 1 is a novel target for pro-tussive agents.
Andrè E,Gatti R,Trevisani M,Preti D,Baraldi P G,Patacchini R,Geppetti P
British journal of pharmacology
BACKGROUND AND PURPOSE:The transient receptor potential ankyrin receptor 1 (TRPA1) is a cation channel, co-expressed with the pro-tussive transient receptor potential vanilloid type 1 (TRPV1) channel in primary sensory neurons. TRPA1 is activated by a series of irritant exogenous and endogenous alpha,beta-unsaturated aldehydes which seem to play a role in airway diseases. We investigated whether TRPA1 agonists provoke cough in guinea pigs and whether TRPA1 antagonists inhibit this response. EXPERIMENTAL APPROACH:Animals were placed in a Perspex box, and cough sounds were recorded and counted by observers unaware of the treatment used. KEY RESULTS:Inhalation of two selective TRPA1 agonists, allyl isothiocyanate and cinnamaldehyde, dose-dependently caused cough in control guinea pigs, but not in those with airway sensory nerves desensitized by capsaicin. Coughs elicited by TRPA1 agonists were reduced by non-selective (camphor and gentamicin) and selective (HC-030031) TRPA1 antagonists, whereas they were unaffected by the TRPV1 antagonist, capsazepine. Acrolein and crotonaldehyde, two alpha,beta-unsaturated aldehydes recently identified as TRPA1 stimulants and contained in cigarette smoke, air pollution or produced endogenously by oxidative stress, caused a remarkable tussive effect, a response that was selectively inhibited by HC-030031. Part of the cough response induced by cigarette smoke inhalation was inhibited by HC-030031, suggesting the involvement of TRPA1. CONCLUSIONS AND IMPLICATIONS:A novel pro-tussive pathway involves the TRPA1 channel, expressed by capsaicin-sensitive airway sensory nerves and is activated by a series of exogenous (cigarette smoke) and endogenous irritants. These results suggest TRPA1 may be a novel target for anti-tussive medicines.
How irritating: the role of TRPA1 in sensing cigarette smoke and aerogenic oxidants in the airways.
Simon Sidney A,Liedtke Wolfgang
The Journal of clinical investigation
Airway irritants cause a variety of lung pathologies. Two separate studies, the first recently reported in the JCI by Bessac et al. and the second reported by Andrè et al. in the current issue of the JCI (see the related article beginning on page 2574), have identified irritants that activate transient receptor potential cation channel, subfamily A, member 1 (TRPA1) receptors in airway sensory neurons, resulting in neurogenic inflammation and respiratory hypersensitivity. The identification of TRPA1 activation by toxicants from cigarette smoke and polluted air, such as crotonaldehyde, acrolein, and oxidizing agents such as hydrogen peroxide, is an important finding. These two studies enhance our understanding of how pollution and cigarette smoke can damage airway function and will hopefully pave the way for the development of rational alternative therapeutics for such airway injury.
Pungent general anesthetics activate transient receptor potential-A1 to produce hyperalgesia and neurogenic bronchoconstriction.
Eilers Helge,Cattaruzza Fiore,Nassini Romina,Materazzi Serena,Andre Eunice,Chu Catherine,Cottrell Graeme S,Schumacher Mark,Geppetti Pierangelo,Bunnett Nigel W
BACKGROUND:Volatile anesthetics such as isoflurane and halothane have been in clinical use for many years and represent the group of drugs most commonly used to maintain general anesthesia. However, despite their widespread use, the molecular mechanisms by which these drugs exert their effects are not completely understood. Recently, a seemingly paradoxical effect of general anesthetics has been identified: the activation of peripheral nociceptors by irritant anesthetics. This mechanism may explain the hyperalgesic actions of inhaled anesthetics and their adverse effects in the airways. METHODS:To test the hypothesis that irritant inhaled anesthetics activate the excitatory ion-channel transient receptor potential (TRP)-A1 and thereby contribute to hyperalgesia and irritant airway effects, we used the measurement of intracellular calcium concentration in isolated cells in culture. For our functional experiments, we used models of isolated guinea pig bronchi to measure bronchoconstriction and withdrawal threshold to mechanical stimulation with von Frey filaments in mice. RESULTS:Irritant inhaled anesthetics activate TRPA1 expressed in human embryonic kidney cells and in nociceptive neurons. Isoflurane induces mechanical hyperalgesia in mice by a TRPA1-dependent mechanism. Isoflurane also induces TRPA1-dependent constriction of isolated bronchi. Nonirritant anesthetics do not activate TRPA1 and fail to produce hyperalgesia and bronchial constriction. CONCLUSIONS:General anesthetics induce a reversible loss of consciousness and render the patient unresponsive to painful stimuli. However, they also produce excitatory effects such as airway irritation and they contribute to postoperative pain. Activation of TRPA1 may contribute to these adverse effects, a hypothesis that remains to be tested in the clinical setting.
Relative contributions of TRPA1 and TRPV1 channels in the activation of vagal bronchopulmonary C-fibres by the endogenous autacoid 4-oxononenal.
Taylor-Clark T E,McAlexander M A,Nassenstein C,Sheardown S A,Wilson S,Thornton J,Carr M J,Undem B J
The Journal of physiology
Transient receptor potential (TRP) A1 channels are cation channels found preferentially on nociceptive sensory neurones, including capsaicin-sensitive TRPV1-expressing vagal bronchopulmonary C-fibres, and are activated by electrophilic compounds such as mustard oil and cinnamaldehyde. Oxidative stress, a pathological feature of many respiratory diseases, causes the endogenous formation of a number of reactive electrophilic alkenals via lipid peroxidation. One such alkenal, 4-hydroxynonenal (4HNE), activates TRPA1 in cultured sensory neurones. However, our data demonstrate that 100 microm 4HNE was unable to evoke significant action potential discharge or tachykinin release from bronchopulmonary C-fibre terminals. Instead, another endogenously produced alkenal, 4-oxononenal (4ONE, 10 microm), which is far more electrophilic than 4HNE, caused substantial action potential discharge and tachykinin release from bronchopulmonary C-fibre terminals. The activation of mouse bronchopulmonary C-fibre terminals by 4ONE (10-100 microm) was mediated entirely by TRPA1 channels, based on the absence of responses in C-fibre terminals from TRPA1 knockout mice. Interestingly, although the robust increases in calcium caused by 4ONE (0.1-10 microm) in dissociated vagal neurones were essentially abolished in TRPA1 knockout mice, at 100 microm 4ONE caused a large TRPV1-dependent response. Furthermore, 4ONE (100 microm) was shown to activate TRPV1 channel-expressing HEK cells. In conclusion, the data support the hypothesis that 4-ONE is a relevant endogenous activator of vagal C-fibres via an interaction with TRPA1, and at less relevant concentrations, it may activate nerves via TRPV1.
Transient receptor potential channels mediate the tussive response to prostaglandin E2 and bradykinin.
Grace Megan,Birrell Mark A,Dubuis Eric,Maher Sarah A,Belvisi Maria G
BACKGROUND:Cough is the most frequent reason for consultation with a family doctor, or with a general or respiratory physician. Treatment options are limited and a recent meta-analysis concluded that over-the-counter remedies are ineffective and there is increasing concern about their use in children. Endogenous inflammatory mediators such as prostaglandin E2 (PGE2) and bradykinin (BK), which are often elevated in respiratory disease states, are also known to cause cough by stimulating airway sensory nerves. However, how this occurs is not understood. METHODS:We hypothesised that the transient receptor potential (TRP) channels, TRPA1 and TRPV1, may have a role as 'common effectors' of tussive responses to these agents. We have employed a range of in vitro imaging and isolated tissue assays in human, murine and guinea pig tissue and an in vivo cough model to support this hypothesis. RESULTS:Using calcium imaging we demonstrated that PGE2 and BK activated isolated guinea pig sensory ganglia and evoked depolarisation (activation) of vagal sensory nerves, which was inhibited by TRPA1 and TRPV1 blockers (JNJ17203212 and HC-030031). These data were confirmed in vagal sensory nerves from TRPA1 and TRPV1 gene deleted mice. TRPV1 and TRPA1 blockers partially inhibited the tussive response to PGE2 and BK with a complete inhibition obtained in the presence of both antagonists together in a guinea pig conscious cough model. CONCLUSION:This study identifies TRPA1 and TRPV1 channels as key regulators of tussive responses elicited by endogenous and exogenous agents, making them the most promising targets currently identified in the development of anti-tussive drugs.
Effects of Schisandra chinensis extracts on cough and pulmonary inflammation in a cough hypersensitivity guinea pig model induced by cigarette smoke exposure.
Zhong Shan,Nie Yi-chu,Gan Zhen-yong,Liu Xiao-dong,Fang Zhang-fu,Zhong Bo-nian,Tian Jin,Huang Chu-qin,Lai Ke-fang,Zhong Nan-shan
Journal of ethnopharmacology
Schisandra chinensis (S. chinensis) is a traditional Chinese medicine commonly used in prescription medications for the treatment of chronic cough. However, the material basis of S. chinensis in relieving cough has not been completely elucidated yet. This study established a guinea pig model of cough hypersensitivity induced by 14 days of cigarette smoke (CS) exposure, to evaluate the antitussive, antioxidant, and anti-inflammatory effects of three S. chinensis extracts. And then the function of four lignans in reducing expression of TRPV1 and TRPA1 was examined using A549 cells induced by cigarette smoke extract (CSE). The results demonstrated that both ethanol extract (EE) and ethanol-water extract (EWE) of S. chinensis, but not water extract (WE), significantly reduced the cough frequency enhanced by 0.4M citric acid solution in these cough hypersensitivity guinea pigs. Meanwhile, pretreatment with EE and EWE both significantly attenuated the CS-induced increase in infiltration of pulmonary neutrophils and total inflammatory cells, as well as pulmonary MDA, TNF-α, and IL-8, while remarkably increased activities of pulmonary SOD and GSH. According to H&E and immunofluorescence staining assays, airway epithelium hyperplasia, smooth muscle thickening, inflammatory cells infiltration, as well as expression of TRPV1 and TRPA1, were significantly attenuated in animals pretreatment with 1g/kg EE. Moreover, four lignans of EE, including schizandrin, schisantherin A, deoxyschizandrin and γ-schisandrin, significantly inhibited CSE-induced expression of TRPV1, TRPA1 and NOS3, as well as NO release in A549 cells. In conclusion, S. chinensis reduces cough frequency and pulmonary inflammation in the CS-induced cough hypersensitivity guinea pigs. Lignans may be the active components.
Withdrawn: The novel TRPA1 antagonist BI01305834 inhibits ovalbumin-induced bronchoconstriction in guinea pigs.
van den Berg Mariska,Nijboer-Brinksma Susan,Bos Sophie,van den Berge Maarten,Lamb David,van Faassen Martijn,Kema Ido,Gosens Reinoud,Kistemaker Loes
British journal of pharmacology
The above article from the British Journal of Pharmacology, published online on May 20, 2020 in Wiley Online Library (http://wileyonlinelibrary.com) has been withdrawn due to a lack of full disclosure of the chemical structure of the novel TRPA1 antagonist BI01305834, by agreement between the Editor-in-Chief and John Wiley & Sons Inc on behalf of The British Pharmacology Society.
Crude Turmeric Extract Improves the Suppressive Effects of GG on Allergic Inflammation in a Murine Model of House Dust Mite-Induced Asthma.
Ghiamati Yazdi Fariba,Zakeri Amin,van Ark Ingrid,Leusink-Muis Thea,Braber Saskia,Soleimanian-Zad Sabihe,Folkerts Gert
Frontiers in immunology
There is a strong correlation between dysregulation of the gastrointestinal microbiota and development of allergic diseases. The most prevalent therapies for relieving asthma symptoms are associated with serious side effects, and therefore novel approaches are needed. Our objective was to elucidate whether oral administration of GG (LGG) as a probiotic or turmeric powder (TP) as a prebiotic or both as a synbiotic mitigate allergic inflammation including lung function, airway inflammatory cell infiltration, Th2 cytokines/chemokine in a murine model of house dust mite (HDM)-induced asthma. BALB/c mice were intranasally sensitized and challenged with HDM received TP (20 mg/Kg mouse), or/and LGG (10 or 10 cfu/ml), or both orally. Interestingly, the synbiotic intervention (HDM-TP-LGG E7) specifically suppress the developement of airway hyperresponsiveness in response to methacholine. Besides, our synbiotic, TP, and LGG strongly down-regulated eosinophilia, IL-5, CCL17, IL-13. In terms of T cell response, CD4 Th2 cells and CD4 Th17 population were reduced in the splenocytes of the treatment groups compared to control. The synbiotic group not only elevated CD25Foxp3Treg frequency compared to asthmatic group, but also increased T reg cells compared to the probiotic group. The synbiotic also indicated the superior effect in suppressing Th2 cells compared to probiotic. Although, TP and LGG alone displayed suppressive effects, this study showed that the combination therapy consisting of TP and LGG (synbiotic) is more effective in some of the parameters than either of the treatments alone. This novel synbiotic, might be considered as a potential food-based drug for translational medicine and can possibly be used along with corticosteroid treatment.
Effects of immunomodulatory supplementation with Lactobacillus rhamnosus on airway inflammation in a mouse asthma model.
Wu Chia-Ta,Chen Peng-Jung,Lee Yu-Tzu,Ko Jiunn-Liang,Lue Ko-Haung
Journal of microbiology, immunology, and infection = Wei mian yu gan ran za zhi
BACKGROUND:Asthma is a common allergic disease. In previous studies, probiotics improved the balance of intestinal microbes, reduced inflammation, and promoted mucosal tolerance. This study investigated whether oral administrations of Lactobacillus rhamnosus GG (LGG) inhibited allergen (ovalbumin or OVA)-induced airway inflammation in a mouse asthma model. METHODS:The allergy/asthma animal model in this study was sensitization with OVA. After intranasal challenge with OVA, the airway inflammation and hyper-responsiveness were determined by a Buxco system, bronchoalveolar lavage fluid analysis with Liu stain, and enzyme-linked immunosorbent assay. Histopathologic changes in the lung were detected by hematoxylin and eosin staining and immunohistochemistry staining. RESULTS:Both pre- and post-treatment with LGG suppressed the airway hyper-responsiveness to methacholine and significantly decreased the number of infiltrating inflammatory cells and Th2 cytokines in bronchoalveolar lavage fluid and serum compared with the OVA-sensitized mice. In addition, LGG reduced OVA-specific IgE levels in serum. Oral LGG decreased matrix metalloproteinase 9 expression in lung tissue and inhibited inflammatory cell infiltration. CONCLUSION:LGG had an anti-inflammatory effect on OVA-induced airway inflammation and might be an additional or supplementary therapy for allergic airway diseases.
Effect of Lactobacillus rhamnosus GG immunopathologic changes in chronic mouse asthma model.
Wu Chia-Ta,Lin Fei-Hung,Lee Yu-Tzu,Ku Min-Sho,Lue Ko-Haung
Journal of microbiology, immunology, and infection = Wei mian yu gan ran za zhi
BACKGROUND:Asthma is a heterogeneous inflammatory disorder of the airway. A Th2 response usually contributes to high levels of allergen-specific IgE and eosinophilic airway inflammation. Several findings have demonstrated that neutrophils, not eosinophils, are the major inflammatory cells in chronic asthma patients with steroid-resistance. Lactobacillus rhammosus GG (LGG) exhibits anti-inflammatory properties on OVA-induced acute airway inflammation. OBJECTIVE:We hypothesized that orally administrated LGG should reduce airway remodeling in chronic experimental models. METHODS:Female Balb/c mice were sensitized with OVA. LGG was used to investigate whether oral administrations of LGG inhibited OVA-induced airway inflammation in a chronic asthma model and the different intervention times between LGG pre-treatment and post-treatment groups. BALF was analyzed with Liu's stain and ELISA assay. Lung histopathology was assayed with HE, IHC and Masson's trichrome staining. Lung tissues were assayed with PCR (T-bet, GATA3, RORrt and Foxp3). Many cytokines were detected in the serum and BALF. RESULTS:LGG significantly decreased the number of infiltrating inflammatory cells. We also found that the oral LGG group suppressed not only Th2 cytokine, but also IL-17, TNF-α and HMGB1 in the BALF levels. However, GATA3 and RORrt decreased significantly in the RNA level in the LGG groups, but the T-bet and Foxp3 increased in the RNA level. CONCLUSIONS:LGG not only had anti-inflammatory effects on OVA-induced airway inflammation, but also improved airway remodeling and collagen expression in the chronic asthma mouse model. Moreover, LGG might be an additional or supplementary therapy for allergic airway diseases.
Intranasal administration of probiotic Lactobacillus rhamnosus GG prevents birch pollen-induced allergic asthma in a murine model.
Spacova I,Petrova M I,Fremau A,Pollaris L,Vanoirbeek J,Ceuppens J L,Seys S,Lebeer S
BACKGROUND:There is an increasing interest in targeted application of probiotic bacteria for prevention and treatment of airway diseases, including allergies. Here, we investigated the beneficial effects of preventive intranasal treatment with probiotics Lactobacillus rhamnosus GG and L. rhamnosus GR-1 in a mouse model of allergic asthma. METHODS:Lactobacillus rhamnosus was administered intranasally eight times on days 1-4 and 8-11 at 5 × 10 CFU/dose, followed by a 2-week asthma induction protocol with birch pollen extract on alternating days. Effects of preventive treatment were analyzed based on serum antibody levels, bronchoalveolar lavage cell counts, lung histology, lung cytokine levels, and airway hyperreactivity. Colonization and translocation of L. rhamnosus were assessed by bacterial cell counts in nasal mucosa, fecal samples, cervical lymph nodes, and blood. Binding of fluorescent L. rhamnosus to fixed murine nasal mucosal cells and airway macrophages was visualized by fluorescence microscopy. RESULTS:Transient colonization of the murine upper airways by L. rhamnosus GG was demonstrated and was approximately ten times higher compared to L. rhamnosus GR-1. Marked binding of fluorescent L. rhamnosus GG to murine nasal mucosal cells and airway macrophages was visualized. Preventive treatment with L. rhamnosus GG (but not L. rhamnosus GR-1) resulted in a significant decrease in bronchoalveolar lavage eosinophil counts, lung interleukin-13 and interleukin-5 levels, and airway hyperreactivity. A tendency toward a decrease in serum Bet v 1-specific immunoglobulin G1 was likewise observed. CONCLUSION:Intranasally administered L. rhamnosus GG prevents the development of cardinal features of birch pollen-induced allergic asthma in a strain-specific manner.
A role for ATP in bronchoconstriction-induced activation of guinea pig vagal intrapulmonary C-fibres.
Weigand Letitia A,Ford Anthony P,Undem Bradley J
The Journal of physiology
Activation of vagal afferent sensory C-fibres in the lungs leads to reflex responses that produce many of the symptoms associated with airway allergy. There are two subtypes of respiratory C-fibres whose cell bodies reside within two distinct ganglia, the nodose and jugular, and whose properties allow for differing responses to stimuli. We here used extracellular recording of action potentials in an ex vivo isolated, perfused lung-nerve preparation to study the electrical activity of nodose C-fibres in response to bronchoconstriction. We found that treatment with both histamine and methacholine caused strong increases in tracheal perfusion pressure that were accompanied by action potential discharge in nodose, but not in jugular C-fibres. Both the increase in tracheal perfusion pressure and action potential discharge in response to histamine were significantly reduced by functionally antagonizing the smooth muscle contraction with isoproterenol, or by blocking myosin light chain kinase with ML-7. We further found that pretreatment with AF-353 or 2',3'-O-(2,4,6-Trinitrophenyl)-adenosine-5'-triphosphate (TNP-ATP), structurally distinct P2X3 and P2X2/3 purinoceptor antagonists, blocked the bronchoconstriction-induced nodose C-fibre discharge. Likewise, treatment with the ATPase apyrase, in the presence of the adenosine A1 and A2 receptor antagonists 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) and SCH 58261, blocked the C-fibre response to histamine, without inhibiting the bronchoconstriction. These results suggest that ATP released within the tissues in response to bronchoconstriction plays a pivotal role in the mechanical activation of nodose C-fibres.
Chronic cough in adults.
Spanevello Antonio,Beghé Bianca,Visca Dina,Fabbri Leonardo M,Papi Alberto
European journal of internal medicine
Cough, a defense mechanism for clearing the airways of secretions, exudate, or foreign bodies, may become a troublesome symptom. Chronic cough, one of the most frequent symptoms requiring medical attention, is often not due to identifiable causes in adults. Chronic productive cough defines chronic bronchitis, and thus is present in 100% of these patients, and frequently in patients with bronchiectasis, cystic fibrosis, and chronic infectious respiratory diseases. However, chronic cough is most frequently dry. Thus, chronic cough in adults is a difficult syndrome requiring multidisciplinary approaches, particularly to diagnose and treat the most frequent identifiable causes, but also to decide which patients may benefit by treating the central cough hypersensitivity by neuromodulatory therapy and/or non-pharmacologic treatment (speech pathology therapy). Recent guidelines provide algorithms for diagnosis and assessment of cough severity; particularly chronic cough in adults. After excluding life-threatening diseases, chronic cough due to identifiable causes (triggers and/or diseases), particularly smoking and/or the most frequent diseases (asthma, chronic bronchitis, chronic obstructive pulmonary disease, eosinophilic bronchitis, and adverse reactions to drugs [angiotensin-converting enzyme inhibitors and sitagliptin]) should be treated by avoiding triggers and/or according to guidelines for each underlying disease. In patients with troublesome chronic cough due to unknown causes or persisting even after adequate avoidance of triggers, and/or treatment of the underlying disease(s), a symptomatic approach with neuromodulators and/or speech pathology therapy should be considered. Additional novel promising neuromodulatory agents in clinical development (e.g., P2X3 inhibitors) will hopefully become available in the near future.
A novel formulation of inhaled sodium cromoglicate (PA101) in idiopathic pulmonary fibrosis and chronic cough: a randomised, double-blind, proof-of-concept, phase 2 trial.
Birring Surinder S,Wijsenbeek Marlies S,Agrawal Sanjay,van den Berg Jan W K,Stone Helen,Maher Toby M,Tutuncu Ahmet,Morice Alyn H
The Lancet. Respiratory medicine
BACKGROUND:Cough can be a debilitating symptom of idiopathic pulmonary fibrosis (IPF) and is difficult to treat. PA101 is a novel formulation of sodium cromoglicate delivered via a high-efficiency eFlow nebuliser that achieves significantly higher drug deposition in the lung compared with the existing formulations. We aimed to test the efficacy and safety of inhaled PA101 in patients with IPF and chronic cough and, to explore the antitussive mechanism of PA101, patients with chronic idiopathic cough (CIC) were also studied. METHODS:This pilot, proof-of-concept study consisted of a randomised, double-blind, placebo-controlled trial in patients with IPF and chronic cough and a parallel study of similar design in patients with CIC. Participants with IPF and chronic cough recruited from seven centres in the UK and the Netherlands were randomly assigned (1:1, using a computer-generated randomisation schedule) by site staff to receive PA101 (40 mg) or matching placebo three times a day via oral inhalation for 2 weeks, followed by a 2 week washout, and then crossed over to the other arm. Study participants, investigators, study staff, and the sponsor were masked to group assignment until all participants had completed the study. The primary efficacy endpoint was change from baseline in objective daytime cough frequency (from 24 h acoustic recording, Leicester Cough Monitor). The primary efficacy analysis included all participants who received at least one dose of study drug and had at least one post-baseline efficacy measurement. Safety analysis included all those who took at least one dose of study drug. In the second cohort, participants with CIC were randomly assigned in a study across four centres with similar design and endpoints. The study was registered with ClinicalTrials.gov (NCT02412020) and the EU Clinical Trials Register (EudraCT Number 2014-004025-40) and both cohorts are closed to new participants. FINDINGS:Between Feb 13, 2015, and Feb 2, 2016, 24 participants with IPF were randomly assigned to treatment groups. 28 participants with CIC were enrolled during the same period and 27 received study treatment. In patients with IPF, PA101 reduced daytime cough frequency by 31·1% at day 14 compared with placebo; daytime cough frequency decreased from a mean 55 (SD 55) coughs per h at baseline to 39 (29) coughs per h at day 14 following treatment with PA101, versus 51 (37) coughs per h at baseline to 52 (40) cough per h following placebo treatment (ratio of least-squares [LS] means 0·67, 95% CI 0·48-0·94, p=0·0241). By contrast, no treatment benefit for PA101 was observed in the CIC cohort; mean reduction of daytime cough frequency at day 14 for PA101 adjusted for placebo was 6·2% (ratio of LS means 1·27, 0·78-2·06, p=0·31). PA101 was well tolerated in both cohorts. The incidence of adverse events was similar between PA101 and placebo treatments, most adverse events were mild in severity, and no severe adverse events or serious adverse events were reported. INTERPRETATION:This study suggests that the mechanism of cough in IPF might be disease specific. Inhaled PA101 could be a treatment option for chronic cough in patients with IPF and warrants further investigation. FUNDING:Patara Pharma.
Role of reactive oxygen species and TRP channels in the cough reflex.
Taylor-Clark Thomas E
The cough reflex is evoked by noxious stimuli in the airways. Although this reflex is essential for health, it can be triggered chronically in inflammatory and infectious airway disease. Neuronal transient receptor potential (TRP) channels such as ankyrin 1 (TRPA1) and vanilloid 1 (TRPV1) are polymodal receptors expressed on airway nociceptive afferent nerves. Reactive oxygen species (ROS) and other reactive compounds are associated with inflammation, from either NADPH oxidase or mitochondria. These reactive compounds cause activation and hyperexcitability of nociceptive afferents innervating the airways, and evidence suggests key contributions of TRPA1 and TRPV1.
TRPA1 agonists evoke coughing in guinea pig and human volunteers.
Birrell Mark A,Belvisi Maria G,Grace Megan,Sadofsky Laura,Faruqi Shoaib,Hele David J,Maher Sarah A,Freund-Michel Véronique,Morice Alyn H
American journal of respiratory and critical care medicine
RATIONALE:Cough is the most frequent reason for consultation with a family doctor, or with a general or respiratory physician. Treatment options are limited and one meta-analysis concluded that over-the-counter remedies are ineffective. There is also increasing concern about their use in children. Environmental irritants such as air pollution and cigarette smoke are thought to evoke cough by stimulating airway sensory nerves; however, how this occurs is not fully understood. OBJECTIVES:We hypothesized that the TRPA1 (transient receptor potential cation channel, subfamily A, member 1) receptor may have a role as a novel target for tussive agents given that many potential irritants have been shown to activate this channel. METHODS:We investigated the effect of TRPA1 ligands on vagal sensory nerve activity in vitro and in guinea pig and human tussive challenge models. MEASUREMENTS AND MAIN RESULTS:We demonstrated that TRPA1 agonists such as acrolein activate cloned human TRPA1 channels in HEK293 cells and also vagal sensory nerves in murine, guinea pig, and human tissues. A role for TRPA1 was confirmed, using specific inhibitors and tissue from Trpa1(-/-) gene-deleted animals. Finally, TRPA1 ligands evoked reproducible tussive responses in both a guinea pig model and normal volunteers. CONCLUSIONS:This study identifies the TRPA1 receptor as a promiscuous receptor, activated by a wide range of stimuli, making it a perfect target for triggering cough and as such one of the most promising targets currently identified for the development of antitussive drugs.
TRPA1 receptors in cough.
Grace Megan S,Belvisi Maria G
Pulmonary pharmacology & therapeutics
In the early 1990's ion channels of the Transient Receptor Potential (TRP) class were implicated in the afferent sensory loop of the cough reflex and in the heightened cough sensitivity seen in disease. Agonists of the TRPV1 capsaicin receptor such as vanilloids and protons were demonstrated to be amongst the most potent chemical stimuli which cause cough. However, more recently, the TRPA1 receptor (not activated by capsaicin) has become of interest in the cough field because it is known to be activated by ligands such as acrolein which is present in air pollution and the acrid smoke from organic material. TRPA1 is a Ca(2+)-permeant non-selective cation channel with 14 ankyrin repeats in its amino terminus which belongs to the larger TRP family. TRPA1 has been characterised as a thermoreceptor which is activated by cold temperature, environmental irritants and reactive electrophilic molecules which can be generated by oxidant stress and inflammation. TRPA1 is primarily expressed in small diameter, nociceptive neurons where its activation probably contributes to the perception of noxious stimuli and the phenomena known as inflammatory hyperalgesia and neurogenic inflammation. The respiratory tract is innervated by primary sensory afferent nerves which are activated by mechanical and chemical stimuli. Activation of these vagal sensory afferents leads to central reflexes including dyspnoea, changes in breathing pattern and cough. Recently, it has been demonstrated that stimulating TRPA1 channels activates vagal bronchopulmonary C-fibres in the guinea pig and rodent lung, and recent data have shown that TRPA1 ligands cause cough in both animal models and normal volunteers. In summary, due to their activation by a wide range of irritant and chemical substances, either by exogenous agents, endogenously produced mediators during inflammation or by oxidant stress, we suggest TRPA1 channels should be considered as one of the most promising targets currently identified for the development of novel anti-tussive drugs.
Comparison of TRPA1-versus TRPV1-mediated cough in guinea pigs.
Brozmanova Mariana,Mazurova Lenka,Ru Fei,Tatar Milos,Kollarik Marian
European journal of pharmacology
TRPA1 receptor is activated by endogenous inflammatory mediators and exogenous pollutant molecules relevant to respiratory diseases. Previous studies have implicated TRPA1 as a drug target for antitussive therapy. Here we evaluated the relative efficacy of TRPA1 activation to evoke cough. In conscious guinea pigs the TRPA1 agonist allyl-isothiocyanate (AITC) evoked cough with a maximally effective concentration of 10mM that was abolished by the selective TRPA1 antagonist AP-18. AITC (10mM) was approximately 3-times less effective in inducing cough than capsaicin (50 μM). Ex vivo single fiber extracellular recordings revealed that, similarly to capsaicin, AITC evoked activation in airway jugular C-fibers, but not in airway nodose Aδ-fibers. Consistent with the cough studies, AITC was approximately 3-times less effective than capsaicin in evoking sustained activation of the jugular C-fibers. Another TRPA1 agonist, cinnamaldehyde, was approximately twofold more effective than AITC in inducing cough. However, the cinnamaldehyde (10mM)-induced cough was only partially inhibited by the TRPA1 antagonist AP-18, and was abolished by combination of AP-18 and the TRPV1 antagonist I-RTX. We conclude that in naïve guinea pigs, TRPA1 activation initiates cough that is relatively modest compared to the cough initiated by TRPV1, likely due to lower efficacy of TRPA1 stimulation to induce sustained activation of airway C-fibers.
Increased expression of lung TRPV1/TRPA1 in a cough model of bleomycin-induced pulmonary fibrosis in Guinea pigs.
Guo Yali,Ying Sun,Zhao Xuehui,Liu Jian,Wang Yuguang
BMC pulmonary medicine
BACKGROUND:Chronic cough is a difficult-to-treat comorbidity of idiopathic pulmonary fibrosis (IPF), and significantly impacts on the quality of life of patients with IPF. Transient receptor potential (TRP) channel proteins may play an important role in chronic cough. However, expression of these proteins in lung of IPF is largely unknown. METHODS:Guinea pig model of pulmonary fibrosis was established by single intratracheal delivery of bleomycin. Respiratory ungated micro-CT scans were performed on days 7, 14, 21 and 28 to assess progression of pulmonary fibrosis. Cough sensitivity to capsaicin was evaluated in conscious animals on days 13 and 27. Real-time PCR (qPCR) and immunohistochemistry were employed to measure expression of TRPV1 and TRPA1 in lung tissue. RESULTS:Micro-CT showed that lung consolidation was detectable from day 7 distributing mainly in the middle and lower lung fields, which was significantly correlated to Ashcroft fibrosis score (r = 0.7993, p < 0.001). Cough sensitivity to capsaicin in bleomycin-treated animals was significantly increased on days 13 and 27. qPCR showed that expression of TRPV1 and TRPA1 was positively correlated each other and significantly upregulated in lung tissues of model group compared with that of controls, which was further supported by immunohistochemistry. Furthermore, immunoreactivity for TRPV1 and TRPA1 was negatively correlated with Ashcroft fibrosis score. CONCLUSION:Expression of TRPV1/TRPA1 was upregulated in the chronic cough related to bleomycin induced pulmonary fibrosis in guinea pigs, which provided new insights into the mechanism of IPF-associated cough hypersensitivity. Micro-CT is very helpful methodology to access pulmonary fibrosis progression in small animal models.
Bradykinin sensitizes the cough reflex via a B receptor dependent activation of TRPV1 and TRPA1 channels through metabolites of cyclooxygenase and 12-lipoxygenase.
Al-Shamlan Fajer,El-Hashim Ahmed Z
BACKGROUND:Inhaled bradykinin (BK) has been reported to both sensitize and induce cough but whether BK can centrally sensitize the cough reflex is not fully established. In this study, using a conscious guinea-pig model of cough, we investigated the role of BK in the central sensitization of the cough reflex and in airway obstruction. METHODS:Drugs were administered, to guinea pigs, by the intracerebroventricular (i.c.v.) route. Aerosolized citric acid (0.2 M) was used to induce cough in a whole-body plethysmograph box, following i.c.v. infusion of drugs. An automated analyser recorded both cough and airway obstruction simultaneously. RESULTS:BK, administered by the i.c.v. route, dose-dependently enhanced the citric acid-induced cough and airway obstruction. This effect was inhibited following i.c.v. pretreatment with a B receptor antagonist, TRPV1 and TRPA1 channels antagonists and cyclooxygenase (COX) and 12-lipoxygenase (12-LOX) inhibitors. Furthermore, co-administration of submaximal doses of the TRPV1 and TRPA1 antagonists or the COX and 12-LOX inhibitors resulted in a greater inhibition of both cough reflex and airway obstruction. CONCLUSIONS:Our findings show that central BK administration sensitizes cough and enhances airway obstruction via a B receptor/TRPV1 and/or TRPA1 channels which are coupled via metabolites of COX and/or 12-LOX enzymes. In addition, combined blockade of TRPV1 and TRPA1 or COX and 12-LOX resulted in a greater inhibitory effect of both cough and airway obstruction. These results indicate that central B receptors, TRPV1/TRPA1 channels and COX/12-LOX enzymes may represent potential therapeutic targets for the treatment of cough hypersensitivity.
Heterogeneity of cough hypersensitivity mediated by TRPV1 and TRPA1 in patients with chronic refractory cough.
Long Li,Yao Hongmei,Tian Jing,Luo Wei,Yu Xinxin,Yi Fang,Chen Qiaoli,Xie Jiaxing,Zhong Nanshan,Chung Kian Fan,Lai Kefang
BACKGROUND:The differential sensitivity of cough to antitussive therapies implies the existence of heterogeneity in cough hypersensitivity, but how such heterogeneity is expressed across individual patients is poorly understood. We investigated the phenotypes of cough hypersensitivity by examining transient receptor potential ankyrin 1 (TRPA1)- and transient receptor potential vanilloid 1 (TRPV1)-mediated cough sensitivity in patients with chronic refractory cough. METHODS:Using a selective TRPA1 agonist, allyl isothiocyanate (AITC), we established an AITC cough challenge as a measure of TRPA1-mediated cough sensitivity. The AITC cough challenge and the widely used capsaicin (a selective TRPV1 agonist) cough challenge were performed with 250 patients with chronic refractory cough and 56 healthy subjects. The concentration of AITC or capsaicin solution causing at least two (C2) and five coughs (C5) was recorded. Cough sensitivity was expressed as the mean (95% confidence interval) of log C5, and cough hypersensitivity was defined as a log C5 value lower than that of healthy subjects. RESULTS:A distinct concentration-response effect of inhaled AITC was identified both in patients with chronic refractory cough and in healthy subjects. Cough sensitivity to AITC and capsaicin was significantly higher in patients than in healthy subjects (AITC: 2.42 [2.37-2.48] vs 2.72 [2.66-2.78] mM, p = 0.001; capsaicin: 1.87 [1.75-1.98] vs 2.53 [2.36-2.70] μM, p = 0.001) and was higher in females than in males for both healthy subjects and patients (all p < 0.05). Among the 234 patients who completed both challenges, 25 (10.7%) exhibited hypersensitivity to both AITC and capsaicin, 44 (18.8%) showed hypersensitivity to AITC only, 28 (11.9%) showed hypersensitivity to capsaicin only, and 137 (58.6%) exhibited hypersensitivity to neither. Those with TRPA1- and/or TRPV1-mediated hypersensitivity were predominantly female, while those without TRPA1- and TRPV1-mediated hypersensitivity were mainly male. CONCLUSIONS:Four phenotypes of cough hypersensitivity were identified by the activation of TRPV1 and TRPA1 channels, which supports the existence of heterogeneity in cough pathways and provides a new direction for personalized management of chronic refractory cough. TRIAL REGISTRATION:ClinicalTrials.gov NCT02591550 .
Transient receptor potential ankyrin 1 (TRPA1) antagonists: a patent review (2015-2019).
Chen Huifen,Terrett Jack A
Expert opinion on therapeutic patents
INTRODUCTION:TRPA1 is a non-selective cation channel predominantly expressed in sensory neurons, and functions as an irritant sensor for a plethora of noxious external stimuli and endogenous ligands. Due to its involvement in pain, itch, and respiratory syndromes, TRPA1 has been pursued as a promising drug target. AREAS COVERED:In this review, the small molecule patent literature of TRPA1 antagonists from 2015-2019 was surveyed. The patent applications are described with a focus on chemical structures, biochemical/pharmacological activities, and potential clinical applications. The development of TRPA1 antagonists in clinical trials has been highlighted. EXPERT OPINION:During 2015-2019, significant progress was made toward the discovery of new TRPA1 antagonists. A total of 14 organizations published 28 patent applications disclosing several distinct classes of chemical matter and potential uses. During this period, three new molecules entered the clinic (ODM-108, HX-100, and GDC-0334) bringing the total number of TRPA1 antagonists to reach clinical trials to five (including earlier molecules CB-625 and GRC 17536); however, to our knowledge, development of all five molecules have been discontinued. Further clinical trials of recent TRPA1 antagonists with good pharmacokinetics would be needed to help understand TRPA1 involvement in human diseases and its potential as a therapeutic target.
Capsaicin-evoked cough responses in asthmatic patients: Evidence for airway neuronal dysfunction.
Satia Imran,Tsamandouras Nikolaos,Holt Kimberley,Badri Huda,Woodhead Mark,Ogungbenro Kayode,Felton Timothy W,O'Byrne Paul M,Fowler Stephen J,Smith Jaclyn A
The Journal of allergy and clinical immunology
BACKGROUND:Cough in asthmatic patients is a common and troublesome symptom. It is generally assumed coughing occurs as a consequence of bronchial hyperresponsiveness and inflammation, but the possibility that airway nerves are dysfunctional has not been fully explored. OBJECTIVES:We sought to investigate capsaicin-evoked cough responses in a group of patients with well-characterized mild-to-moderate asthma compared with healthy volunteers and assess the influences of sex, atopy, lung physiology, inflammation, and asthma control on these responses. METHODS:Capsaicin inhalational challenge was performed, and cough responses were analyzed by using nonlinear mixed-effects modeling to estimate the maximum cough response evoked by any concentration of capsaicin (E) and the capsaicin dose inducing half-maximal response (ED). RESULTS:Ninety-seven patients with stable asthma (median age, 23 years [interquartile range, 21-27 years]; 60% female) and 47 healthy volunteers (median age, 38 years [interquartile range, 29-47 years]; 64% female) were recruited. Asthmatic patients had higher E and lower ED values than healthy volunteers. E values were 27% higher in female subjects (P = .006) and 46% higher in patients with nonatopic asthma (P = .003) compared with healthy volunteers. Also, patients with atopic asthma had a 21% lower E value than nonatopic asthmatic patients (P = .04). The ED value was 65% lower in female patients (P = .0001) and 71% lower in all asthmatic patients (P = .0008). ED values were also influenced by asthma control and serum IgE levels, whereas E values were related to 24-hour cough frequency. Age, body mass index, FEV, PC, fraction of exhaled nitric oxide, blood eosinophil counts, and inhaled steroid treatment did not influence cough parameters. CONCLUSION:Patients with stable asthma exhibited exaggerated capsaicin-evoked cough responses consistent with neuronal dysfunction. Nonatopic asthmatic patients had the highest cough responses, suggesting this mechanism might be most important in type 2-low asthma phenotypes.
TRPA1 activation in a human sensory neuronal model: relevance to cough hypersensitivity?
Clarke Rebecca,Monaghan Kevin,About Imad,Griffin Caoimhin S,Sergeant Gerard P,El Karim Ikhlas,McGeown J Graham,Cosby S Louise,Curtis Timothy M,McGarvey Lorcan P,Lundy Fionnuala T
The European respiratory journal
The cough reflex becomes hyperresponsive in acute and chronic respiratory diseases, but understanding the underlying mechanism is hampered by difficulty accessing human tissue containing both nerve endings and neuronal cell bodies. We refined an adult stem cell sensory neuronal model to overcome the limited availability of human neurones and applied the model to study transient receptor potential ankyrin 1 (TRPA1) channel expression and activation.Human dental pulp stem cells (hDPSCs) were differentiated towards a neuronal phenotype, termed peripheral neuronal equivalents (PNEs). Using molecular and immunohistochemical techniques, together with Ca microfluorimetry and whole cell patch clamping, we investigated roles for nerve growth factor (NGF) and the viral mimic poly I:C in TRPA1 activation.PNEs exhibited morphological, molecular and functional characteristics of sensory neurons and expressed functional TRPA1 channels. PNE treatment with NGF for 20 min generated significantly larger inward and outward currents compared to untreated PNEs in response to the TRPA1 agonist cinnamaldehyde (p<0.05). PNE treatment with poly I:C caused similar transient heightened responses to TRPA1 activation compared to untreated cells.Using the PNE neuronal model we observed both NGF and poly I:C mediated sensory neuronal hyperresponsiveness, representing potential neuro-inflammatory mechanisms associated with heightened nociceptive responses recognised in cough hypersensitivity syndrome.
XEN-D0501, a Novel Transient Receptor Potential Vanilloid 1 Antagonist, Does Not Reduce Cough in Patients with Refractory Cough.
Belvisi Maria G,Birrell Mark A,Wortley Michael A,Maher Sarah A,Satia Imran,Badri Huda,Holt Kimberley,Round Patrick,McGarvey Lorcan,Ford John,Smith Jaclyn A
American journal of respiratory and critical care medicine
RATIONALE:Heightened cough responses to inhaled capsaicin, a transient receptor potential vanilloid 1 (TRPV1) agonist, are characteristic of patients with chronic cough. However, previously, a TRPV1 antagonist (SB-705498) failed to improve spontaneous cough frequency in these patients, despite small reductions in capsaicin-evoked cough. OBJECTIVES:XEN-D0501 (a potent TRPV1 antagonist) was compared with SB-705498 in preclinical studies to establish whether an improved efficacy profile would support a further clinical trial of XEN-D0501 in refractory chronic cough. METHODS:XEN-D0501 and SB-705498 were profiled against capsaicin in a sensory nerve activation assay and in vivo potency established against capsaicin-induced cough in the guinea pig. Twenty patients with refractory chronic cough participated in a double-blind, randomized, placebo-controlled crossover study evaluating the effect of 14 days of XEN-D0501 (oral, 4 mg twice daily) versus placebo on awake cough frequency (primary outcome), capsaicin-evoked cough, and patient-reported outcomes. MEASUREMENTS AND MAIN RESULTS:XEN-D0501 was more efficacious and 1,000-fold more potent than SB-705498 at inhibiting capsaicin-induced depolarization of guinea pig and human isolated vagus nerve. In vivo XEN-D0501 completely inhibited capsaicin-induced cough, whereas 100 times more SB-705498 was required to achieve the same effect. In patients, XEN-D0501 substantially reduced maximal cough responses to capsaicin (mean change from baseline, XEN-D0501, -19.3 ± 16.4) coughs; placebo, -1.8 ± 5.8 coughs; P < 0.0001), but not spontaneous awake cough frequency (mean change from baseline, XEN-D0501, 6.7 ± 16.9 coughs/h; placebo, 0.4 ± 13.7 coughs/h; P = 0.41). CONCLUSIONS:XEN-D0501 demonstrated superior efficacy and potency in preclinical and clinical capsaicin challenge studies; despite this improved pharmacodynamic profile, spontaneous cough frequency did not improve, ruling out TRPV1 as an effective therapeutic target for refractory cough. Clinical trial registered with www.clinicaltrialsregister.eu (2014-000306-36).
IFN-γ Enhances the Cough Reflex Sensitivity via Calcium Influx in Vagal Sensory Neurons.
Deng Zheng,Zhou Wenliang,Sun Jiayang,Li Chenhui,Zhong Bonian,Lai Kefang
American journal of respiratory and critical care medicine
RATIONALE:Cough hypersensitivity syndrome is often triggered by a viral infection. The viral infection might trigger cough hypersensitivity via increasing the release of IFN-γ from T lymphocytes in the lung. OBJECTIVES:To investigate effects of IFN-γ on the vagal sensory neurons and the cough reflex. METHODS:Effects of IFN-γ on the cough reflex were investigated in guinea pigs. Cellular immunofluorescence imaging, calcium imaging, and patch clamp techniques were used to study effects of IFN-γ in primary cultured rat vagal sensory neurons. MEASUREMENTS AND MAIN RESULTS:Intratracheal instillation of IFN-γ enhanced the cough response to citric acid in vivo. IFN-γ significantly increased levels of phosphorylated signal transducer and activator of transcription-1 but not phosphorylated transient receptor potential vanilloid 1 in vitro. Not only did IFN-γ enhance the response of neurons to capsaicin and electric stimulation, but also it directly induced Ca influx, membrane depolarization, and action potentials in neurons via the Janus kinase, protein kinase A, and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid pathways. However, IFN-γ did not elicit Ca release from the endoplasmic reticulum via the phospholipase C pathway. Although IFN-γ-induced action potentials were suppressed by Ca influx inhibitors, IFN-γ-induced Ca influx was not altered by an inhibitor of rapid sodium channels. CONCLUSIONS:The membrane potential in vagal sensory neurons may be depolarized by IFN-γ-induced Ca influx. The depolarization of membrane potentials may enhance the cough reflex sensitivity and cause action potentials. IFN-γ may be a new target for treating cough hypersensitivity syndrome and postviral cough.
Translational review: Neuroimmune mechanisms in cough and emerging therapeutic targets.
McGovern Alice E,Short Kirsty R,Kywe Moe Aung Aung,Mazzone Stuart B
The Journal of allergy and clinical immunology
Cough is an essential defensive behavior for maintaining airway patency and to protect the lungs from potentially harmful agents. However, inflammatory pathologies can sensitize and activate the neural pathways regulating cough, leading to excessive and nonproductive coughing that serves little protective utility. Problematic cough continues to be one of the most common reasons for seeking medical advice, yet for many patients, it can be refractory to disease-specific treatments and currently available antitussive therapies. The effect of inflammation on cough neural processing occurs not only at the level of the bronchopulmonary sensory nerve terminals but also within the nervous system at multiple peripheral and central sites. Sensory nerves also actively regulate inflammation, and it is therefore a complex interplay between the immune and nervous systems that contributes to chronic cough and the associated sensory hypersensitivities. In this review we provide a brief overview of cough neurobiology in health and disease and then explore the peripheral and central nervous system sites at which neuroimmune interactions can occur. We present advancements in the development of effective antitussive therapies and suggest novel targets for future consideration.