Cough In Guinea Pigs Research Articles

Antitussive effects of Musanga cecropioides in animal models

This study investigates the antitussive effects of Musanga cecropioides, a traditional medicinal plant, using animal models. Musanga cecropioides extracts were prepared from the leaves, roots, and root sap, and their effects were evaluated on mucus expectoration and citric acid-induced cough in mice and guinea pigs, respectively. The results indicated that aqueous and methanol extracts of Musanga cecropioides leaves and roots significantly increased mucus secretion and reduced cough frequency, with the highest effectiveness observed in methanol root extract at 100 mg/kg. These findings suggest that Musanga cecropioides possesses promising antitussive properties, supporting its traditional use in treating cough and respiratory ailments. This natural remedy could offer a safer alternative to conventional cough suppressants, warranting further clinical studies to confirm its efficacy and safety in humans.

20S-Ginsenoside Rh2, the major bioactive saponin in Panax notoginseng flowers, ameliorates cough by inhibition of NaV1.7 and TRPV1 channel currents and downregulation of TRPV1 expression

Ethnopharmacological relevancePanax notoginseng flowers, which are the buds of the traditional Chinese medicinal herb Sanqi, are widely used in China for their cough-ameliorating properties, with demonstrated therapeutic effects in the treatment of both acute and chronic coughs. However, both the antitussive mechanism and active compound basis of P. notoginseng flowers remain poorly understood. Aim of the studyWe investigated the antitussive effects of P. notoginseng flowers, identified the bioactive constituents responsible for alleviating cough symptoms, and elucidated the underlying pharmacological mechanisms. Materials and methodsWe analyzed the major chemical constituents of aqueous extracts of P. notoginseng flowers using liquid chromatography–mass spectrometry and quantitatively analyzed the key component, 20S-ginsenoside Rh2, using high-performance liquid chromatography. Using a cough reflex model in healthy mice and an ovalbumin-induced, highly sensitive guinea pig cough model, we verified the suppressive effects of P. notoginseng flowers and their saponin constituents on coughing. Furthermore, we explored the mechanisms of action of the key ion channels, NaV1.7 and TRPV1, using whole-cell patch-clamp techniques and molecular docking. Finally, the therapeutic mechanisms of P. notoginseng flowers on pathological cough were revealed using hematoxylin and eosin staining, immunohistochemistry, and western blotting. ResultsThe active components of P. notoginseng flowers were primarily protopanaxadiol-type saponins, among which 20S-ginsenoside Rh2 had the highest content (51.46 mg/g). In the mouse model, P. notoginseng flowers exhibited antitussive effects comparable to those of pentoxyverine citrate. Although its main saponin component, 20S-ginsenoside Rh2, showed slightly weaker effects, it still demonstrated concentration-dependent inhibition of channel activity. The whole-cell patch-clamp technique and virtual molecular docking showed that Rh2 might exert its effects by directly binding to the NaV1.7 and TRPV1 channels. In the guinea pig model, P. notoginseng flowers and their saponin components not only reduced cough frequency and prolonged the latency period before cough onset, but also significantly inhibited tracheal and pulmonary inflammation and the overexpression of TRPV1. Conclusions20S-Ginsenoside Rh2, the major bioactive saponin in P. notoginseng flowers, exhibits potent antitussive effects. The potential mechanism of action of 20S-Ginsenoside Rh2 in the treatment of cough may involve inhibiting NaV1.7 and TRPV1 channel currents through direct binding to core protein active sites and downregulating TRPV1 expression.

Modified Dingchuan Decoction treats cough-variant asthma by suppressing lung inflammation and regulating the lung microbiota.

Modified Dingchuan Decoction (MDD) is a Chinese medicine formula containing 11 materials with cough suppression, asthma relief, and anti-inflammatory effects. This study aimed to evaluate the therapeutic effect of MDD on cough-variant asthma (CVA) and to investigate its mechanism of action. The chemical constituents of MDD were analyzed by ultra-performance liquid chromatography-quadrupole/electrostatic field orbitrap high-resolution mass spectrometry (UPLC-Q-Orbitrap HRMS). A guinea pig CVA model was established using an intramuscular injection of ovalbumin (OVA), combined with an intraperitoneal injection of aluminum hydroxide [Al(OH)3] and nebulized OVA. At the beginning of day 18, the low, medium, and high MDD groups were gavaged with 7.23g/kg, 14.46g/kg, and 28.92g/kg of MDD, respectively, and the positive group was gavaged with 5mg/kg of prednisone acetate combined with 1mg/kg of montelukast sodium; the normal and model groups were given an equal volume of distilled water, once a day for 21 days. The cough was induced by 10-3mol/L capsaicin solution 1h after the last administration, and the number of coughs and the latency of coughs were evaluated. Hematoxylin and eosin staining (H&E) was used to observe pathological changes in the lungs and airways. The concentration of inflammatory factors in bronchoalveolar lavage fluid (BALF) was measured by enzyme-linked immunosorbent assay (ELISA). We analyzed the lung microbiota using 16S ribosomal DNA (16S rDNA) high-throughput sequencing. The 38 chemical components were found in MDD, and MDD reduced the number of coughs in guinea pigs with CVA, prolonged cough latency, improved pathological damage to the lungs and airways, regulated inflammatory factor levels in BALF, and modulated the lung microbiota. This study demonstrated that treating CVA with MDD may be related to inhibiting lung inflammation and regulating lung microbiota.

The antitussive effects of Korean red ginseng on citric acid-induced cough in Guinea pigs

The antitussive effects of Korean red ginseng on citric acid-induced cough in Guinea pigs

Research on function of Feilike Mixture in stopping cough, eliminating phlegm and relieving asthma based on animal experiments and network pharmacology

This study observed the pharmacological effects of Feilike Mixture(FLKM) in stopping cough, eliminating phlegm, and relieving asthma through animal experiments, and explored its mechanism using network pharmacology. The antitussive effect was detected by citric acid-induced guinea pig cough model, the expectorant effect by mouse phenol red excretion experiment and lipopolysaccharide-induced mucus hypersecretion rat model, and the antiasthmatic effect by histamine phosphate-induced guinea pig asthma model. The chemical components of FLKM were collected by TCMSP, TCMID, TCMIP, and BATMAN-TCM databases and literature search, and the potential active components were screened through ADMETlab 2.0. The targets of FLKM were obtained by STITCH, SwissTargetPrediction, and TCMSP, and the symptom targets of cough, phlegm, and asthma were acquired through SymMap database. After taking the intersection of FLKM targets and symptom targets, this study used the OECloud tool to perform Gene Ontology(GO) and Kyoto Encyclopedia of Genes and Genomes(KEGG) enrichment analysis. RESULTS:: demonstrated that FLKM 0.43-1.74 g·kg~(-1) reduced the number of coughs in guinea pigs within 3 min(P<0.05, P<0.01), and FLKM 6-12 g·kg~(-1) increased the tracheal phenol red excretion in mice(P<0.01). Moreover, FLKM 2-8 g·kg~(-1) inhibited the number of goblet cells(P<0.05, P<0.01), and FLKM 7-11.2 g·kg~(-1) prolonged the incubation period of asthma(P<0.05). A total of 115 potential active components and 910 targets of FLKM were obtained through network pharmacological analysis. FLKM had 27, 12, and 7 targets for stopping cough, eliminating phlegm, and relieving asthma, respectively. The GO and KEGG enrichment analysis found that there were commonalities and characteristics, among which cytokine-cytokine receptor interaction and infectious disease-related signaling pathway were shared. FLKM has a good effect of stopping cough, eliminating phlegm, and relieving asthma through animal experiments and network pharmacology.

The Effect of Anti-Chemokine Oral Drug XC8 on Cough Triggered by The Agonists of TRPA1 But Not TRPV1 Channels in Guinea Pigs.

IntroductionChronic cough heavily affects patients’ quality of life, and there are no effective licensed therapies available. Cough is a complication of severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2) infection, asthma, and other diseases. Patients with various diseases have a different profile of tussive responses to diverse cough triggers, thereby suggesting sundry mechanisms of neuronal dysfunctions. Previously, we demonstrated that the small molecule drug XC8 shows a clinical anti-asthmatic effect. The objective of the present study was to investigate the effect of XC8 on cough.MethodsWe studied the antitussive effect of XC8 on cough induced by agonists activating human transient receptor potential (TRP) cation channels TRPA1 or TRPV1 in guinea pigs. We checked the agonistic/antagonistic activity of XC8 on the human cation channels TRPA1, TRPV1, TRPM8, P2X purinoceptor 2 (P2X2), and human acid sensing ion channel 3 (hASIC3) in Fluorescent Imaging Plate Reader (FLIPR) assay.ResultsXC8 demonstrated clear antitussive activity and dose-dependently inhibited cough in guinea pigs induced by citric acid alone (up to 67.1%) or in combination with IFN-γ (up to 76.4%). XC8 suppressed cough reflexes induced by the repeated inhalation of citric acid (up to 80%) or by cinnamaldehyde (up to 60%). No activity of XC8 against cough evoked by capsaicin was revealed. No direct agonistic/antagonistic activity of XC8 on human TRPA1, TRPV1, TRPM8, P2X2, or hASIC3 was detected.ConclusionsXC8 acts against cough evoked by the activation of TRPA1 (citric acid/cinnamaldehyde) but not TRPV1 (capsaicin) channels. XC8 inhibits the cough reflex and suppresses the cough potentiation by IFN-γ. XC8 might be of significant therapeutic value for patients suffering from chronic cough associated with inflammation.

Evidence for Alpha7 Nicotinic Receptor Activation During the Cough Suppressing Effects Induced by Nicotine and Identification of ATA-101 as a Potential Novel Therapy for the Treatment of Chronic Cough.

Studies performed in healthy smokers have documented a diminished responsiveness to tussive challenges, and several lines of experimental evidence implicate nicotine as an antitussive component in both cigarette smoke and the vapors generated by electronic cigarettes (eCigs). We set out to identify the nicotinic receptor subtype involved in the antitussive actions of nicotine and to further evaluate the potential of nicotinic receptor-selective agonists as cough-suppressing therapeutics. We confirmed an antitussive effect of nicotine in guinea pigs. We additionally observed that the alpha-4 beta-2 (α 4 β 2)-selective agonist Tc-6683 was without effect on evoked cough responses in guinea pigs, while the α 7-selective agonist PHA 543613 dose-dependently inhibited evoked coughing. We subsequently describe the preclinical evidence in support of ATA-101, a potent and highly selective (α 7) selective nicotinic receptor agonist, as a potential candidate for antitussive therapy in humans. ATA-101, formerly known as Tc-5619, was orally bioavailable and moderately central nervous system (CNS) penetrant and dose-dependently inhibited coughing in guinea pigs evoked by citric acid and bradykinin. Comparing the effects of airway targeted administration versus systemic dosing and the effects of repeated dosing at various times prior to tussive challenge, our data suggest that the antitussive actions of ATA-101 require continued engagement of α 7 nicotinic receptors, likely in the CNS. Collectively, the data provide the preclinical rationale for α 7 nicotinic receptor engagement as a novel therapeutic strategy for cough suppression. The data also suggest that α 7 nicotinic acetylcholine receptor (nAChR) activation by nicotine may be permissive to nicotine delivery in a way that may promote addiction. SIGNIFICANCE STATEMENT: This study documents the antitussive actions of nicotine and identifies the α7 nicotinic receptor subtype as the target for nicotine during cough suppression described in humans. We additionally present evidence suggesting that ATA-101 and other α7 nicotinic receptor-selective agonists may be promising candidates for the treatment of chronic refractory cough.

Development and Characterization of Treprostinil Palmitil Inhalation Aerosol for the Investigational Treatment of Pulmonary Arterial Hypertension.

Treprostinil palmitil (TP) is a prodrug of treprostinil (TRE), a pulmonary vasodilator that has been previously formulated for inhaled administration via a nebulizer. TP demonstrates a sustained presence in the lungs with reduced systemic exposure and prolonged inhibition of hypoxia-induced pulmonary vasoconstriction in vivo. Here, we report on re-formulation efforts to develop a more convenient solution-based metered-dose inhaler (MDI) formulation of TP, a treprostinil palmitil inhalation aerosol (TPIA) that matches the pharmacokinetic (PK) and efficacy profile of a nebulized TP formulation, treprostinil palmitil inhalation suspension (TPIS). MDI canisters were manufactured using a two-stage filling method. Aerosol performance, formulation solubility, and chemical stability assays were utilized for in vitro evaluation. For in vivo studies, TPIA formulations were delivered to rodents using an inhalation tower modified for MDI delivery. Using an iterative process involving evaluation of formulation performance in vitro (TP and excipient solubility, chemical stability, physical stability, and aerosol properties) and confirmatory testing in vivo (rat PK and efficacy, guinea pig cough), a promising formulation was identified. The optimized formulation, TPIA-W, demonstrates uniform in vitro drug delivery, a PK profile suitable for a once-daily administration, efficacy lasting at least 12 h in a hypoxic challenge model, and a significantly higher cough threshold than the parent drug treprostinil.

The tuberculous tickle

Biomedicine Tuberculosis is caused by Mycobacterium tuberculosis (Mtb) and often manifests with a persistent cough. This cough is concerning not only for the patient but also because it provides a mechanism for onward transmission. Coughing often results from the activation of nociceptive neurons in the lungs. Ruhl et al. wanted to know how Mtb infection induces cough in patients. They isolated extracts from the bacterium and applied them to nociceptive neurons in vitro. A specific glycolipid, sulfolipid-1 (SL-1), activated the neurons and induced cough in guinea pigs, but Mtb mutants that did not synthesize SL-1 failed to induce cough in these animals. Thus, this bacterial molecule appears to specifically enhance transmissibility of Mtb. Cell 181 , 293 (2020).

Protective Effect of GHX02 Extract on Particulate Matter-Induced Lung Injury.

Industrial development, along with the rapid growth of the economy, has greatly improved the quality of life in humans. Moreover, advancements in medical technology have increased life expectancy. Small particles increase airway inflammation when they penetrate the alveoli. We observed that GHX02 decreased the frequency and delayed the onset time of citric acid-induced coughing in guinea pigs. A phenol red secretion assay indicated that the GHX02 extract exhibits potent expectorant activity. The GHX02 extract also greatly reduced leukocyte levels. Our results indicate that GHX02 inhibits airway inflammation, reduces sputum production, and relieves cough. The GHX02 extract suppressed histamine release from mast cells resulting from compound 48/80-induced degranulation. The extract exhibited antimicrobial activity against Streptococcus pneumoniae and significantly inhibited the formation of LTC4. At high concentrations, the GHX02 extract suppressed the formation of PGE2 (prostaglandin E2). Interleukin (IL)-4 and IL-13 levels decreased with an increasing dosage of GHX02. Oral administration of the GHX02 extract suppressed PM10D-induced inflammatory symptoms in the lung, including increased alveolar wall thickness, accumulation of collagen fibers, and cytokine release. Treatment with the GHX02 extract also resulted in lower levels of inflammatory cells, in bronchoalveolar lavage fluid and lung tissue. Our results indicate that GHX02 may be a useful therapeutic agent for treatment of respiratory diseases.

Fructus mume Protects Against Cigarette Smoke Induced Chronic Cough Guinea Pig.

Fructus mume was recorded in the Chinese Pharmacopoeia and traditional Chinese medical books for chronic cough, but the effect and related constituents are still unknown. Thus, we investigated the protect effects and the relevant constituents of F. mume in a guinea pig model with chronic cough induced by cigarette smoke (CS). The organic acids and polysaccharides in F. mume were detected by high performance liquid chromatography, gel permeation chromatography, and gas chromatography-mass spectrometry. The guinea pigs were orally administrated with vehicle or the water extract of Fructus mume (FW) during the 14 days of CS exposure. Citric acid induced coughs were automatically measured by Buxco system. The differential cells in bronchoalveolar lavage fluid (BALF) and histopathological changes in lung tissue were assessed by hematoxylin and eosin staining. The tumor necrosis factor alpha (TNF-α) and interleukin-8 (IL-8) levels in lung tissue were detected via enzyme-linked immunosorbent assay. The mucus productions in tracheas were determined with Alcian blue-periodic acid Schiff staining. The results suggested relatively high concentration of citric acid, chlorogenic acid, and neochlorogenic acid in F. mume, and high proportion of galactose and glucose and lower molecular weight of polysaccharides. Administration of FW significantly reduced the cough frequency, decreased inflammatory cells in BALF and lung tissue, and attenuated the thickening of airway epithelium and submucosa compared with CS-exposure group. Moreover, the overproduction of TNF-α and IL-8 in lung tissues, and mucus in central airways of CS-induced guinea pigs was markedly inhibited by FW. The extract could also protect against CS exposure-induced chronic cough in guinea pigs by reducing coughs, airways inflammation, and mucus overproduction.

972. A Mycobacterium tuberculosis Secreted Lipid Triggers Cough Through a Neuronal Cough Receptor

BackgroundA hallmark symptom of active pulmonary tuberculosis vital for disease transmission is cough. The current paradigm for tuberculosis-related cough is that it results from airway damage or irritation. However, there is limited experimental data to support this theory, and whether Mycobacterium tuberculosis (Mtb) induces cough to facilitate its own transmission has not been explored. The cough reflex is a complex and coordinated event involving both the nervous and musculoskeletal systems initiated by particulate or chemical molecules activating nociceptive neurons, which sense pain or irritation. This activation induces a signaling cascade ultimately resulting in a cough. Respiratory nociceptive neurons innervate the airway of humans and most mammals and thus are poised to respond to noxious molecules to help protect the lung from damage. Because Mtb is a lung pathogen, cough is a primary mechanism of Mtb transmission, and respiratory nociceptive neurons activate cough, we hypothesized that Mtb produces molecules that stimulate cough thereby facilitating its spread from infected to uninfected individuals. We previously identified a cough molecule produced by Mtb, and in this work characterize its neuronal receptor using genetics, biochemistry, and pharmacology.MethodsWe used an in vitro neuronal activation bioassay to study Mtb cough-inducing molecules. We also used a biochemical assay to identify the cough receptor. Finally, we used gene silencing, biochemistry, and pharmacologic inhibition to validate and characterize the activity of the newly discovered cough receptor.ResultsWe isolated a complex lipid produced by Mtb that activates nociceptive neurons. Both an organic Mtb extract and the purified molecule alone were sufficient to induce cough in a conscious guinea pig cough model and guinea pigs infected with wild-type Mtb cough much more frequently than guinea pigs infected with Mtb strains unable to produce nociceptive molecules. Using genetics, biochemistry, and pharmacology techniques, we identified and validated a cough receptor for the Mtb lipid expressed on nociceptive neurons.ConclusionWe conclude that Mtb produces a molecule that activates nociceptive neurons and induces cough through a specific neuronal receptor. These findings have significant implications for our understanding of Mtb transmission.Disclosures All Authors: No reported Disclosures.

BLU-5937: A selective P2X3 antagonist with potent anti-tussive effect and no taste alteration

BLU-5937 is a small molecule that was shown to be a potent, selective and non-competitive P2X3 homotrimeric receptor antagonist. P2X3 receptors are ATP ion-gated channels located on primary afferent neurons. ATP released from damaged or inflamed tissues in the airways acts on P2X3 receptors of primary afferent neurons, triggering depolarization and action potentials that are transmitted centrally and interpreted as urge to cough. There are strong preclinical and clinical evidence supporting the role of P2X3 receptors in hypersensitization of the cough reflex, leading to chronic cough. By inhibiting P2X3 receptors on the primary sensory neurons, BLU-5937 would inhibit the hypersensitization of the cough reflex and, hence, the exaggerated cough experienced in chronic cough patients. BLU-5937 is being developed for the treatment of unexplained, refractory chronic cough.The high potency and selectivity of BLU-5937 for P2X3 homotrimeric receptors was demonstrated in vitro by inhibiting αβ-meATP-evoked P2X3 or P2X2/3 receptor activity in cloned human hP2X3 and hP2X2/3 channels expressed in mammalian cells. The IC50 of BLU-5937 for hP2X3 homotrimeric and hP2X2/3 heterotrimeric receptors was established at 25 nM and >24 μM, respectively. Furthermore, BLU-5937 (500 nM) was able to block αβ-meATP-induced sensitization and firing activity of isolated primary nociceptors in rat dorsal root ganglions (DRGs), through P2X3 homotrimeric receptor antagonism.In a guinea pig cough model, BLU-5937 (0.3, 3 and 30 mg/kg, oral) significantly reduced, in a dose-dependent fashion, the histamine-induced enhancement in the number of citric acid-induced coughs. BLU-5937 (3 and 30 mg/kg, oral) was also shown to reduce significantly and dose-dependently the ATP-induced enhancement of citric acid-induced coughs in the guinea pig. These anti-tussive effects were obtained at a plasma concentration known to block P2X3 homotrimeric receptors, but at concentration 50-fold lower than that required to block P2X2/3 heterotrimeric receptors. These results indicate that the anti-tussive effect of BLU-5937 is primarily mediated through the inhibition of P2X3 homotrimeric receptors.In a rat behavioral taste model, BLU-5937 (10–20 mg/kg, IP) did not alter taste perception as compared to control animals. In the same experiment, N-00588 (10–20 mg/kg, IP), a weakly selective antagonist for P2X3 versus P2X2/3 receptors, had a significant inhibitory effect on taste perception. Pharmacokinetic analysis of drug plasma concentrations showed that BLU-5937 did not affect taste function at concentrations up to 30 times the IC50 for P2X3. These results suggest that N-00588 achieved systemic concentration that blocked P2X3 and P2X2/3 receptors expressed on gustatory nerve ending innervating taste buds. The lack of effect of BLU-5937, even at high doses, on taste perception may be attributed to its higher selectivity for the P2X3 versus P2X2/3 receptors on the taste buds.The safety, tolerability and pharmacokinetic profile of BLU-5937 was assessed in a battery of preclinical studies and have revealed that BLU-5937 exhibits excellent drug-like characteristics, including good oral bioavailability, low predicted clearance in human, no blood-brain barrier permeability and high safety margin versus human predicted efficacious exposure. BLU-5937 is currently in clinical phase I development stage.In conclusion, BLU-5937 was selected as a drug candidate for the treatment of chronic cough due to its high potency and selectivity for P2X3 homotrimeric receptors, strong anti-tussive effects, excellent tolerability and predicted pharmacokinetic properties in humans.

Induction of airway remodeling and persistent cough by repeated citric acid exposure in a guinea pig cough model

BackgroundA previous study involving guinea pigs showed that repeated cough could increase peripheral airway smooth muscle area, which can also aggravate cough. The airway pathologic changes produced by prolonged cough are still unknown. ObjectiveTo study the airway pathologic changes in prolonged cough models of guinea pigs. MethodsGuinea pigs were assigned to three treatment groups: citric acid inhalation (CA) alone, citric acid inhalation with codeine pretreatment (COD), or saline solution inhalation (SA). Animals were challenged with citric acid or saline solution three times weekly. The intervention period was 22 or 43 days. Animals were challenged with citric acid on the first and last days of exposure. Lung specimens were obtained for pathologic analysis 72 h after the last exposure. ResultsCompared with the other two groups, the CA group had increased frequency of cough on both 22 and 43 days of exposure. Tracheal basement membrane (BM) thickness was increased after 43 days of exposure, correlating with the frequency of cough. The area of airway smooth muscles (ASM index) in small airways increased in the CA group after both 22 and 43 days of exposure, compared with the SA group. Compared with the COD group, the ASM index in small airways increased in the CA group after 22 days of exposure instead of 43 days of exposure. ConclusionsAn increase in peripheral smooth muscle area by repeated cough was confirmed. Moreover, this is the first study to show that tracheal BM thickness increased after prolonged exposure (43 days). Repeated cough may lead to airway remodeling, which was also associated with an increased frequency of cough.

165. Mycobacterium tuberculosis Produces Molecules That Trigger Nociceptive Neurons to Activate Cough

BackgroundA hallmark symptom of active pulmonary tuberculosis vital for disease transmission is cough. The current paradigm for tuberculosis-related cough is that it results from airway damage or irritation. However, there is limited experimental data to support this theory, and whether Mycobacterium tuberculosis (Mtb) induces cough to facilitate its own transmission has not been explored. The cough reflex is a complex and coordinated event involving both the nervous and musculoskeletal systems initiated by particulate or chemical molecules activating nociceptive neurons, which sense pain or irritation. This activation induces a signaling cascade ultimately resulting in a cough. Respiratory nociceptive neurons innervate the airway of humans and most mammals, and thus are poised to respond to noxious molecules to help protect the lung from damage. Because Mtb is a lung pathogen, cough is a primary mechanism of Mtb transmission, and respiratory nociceptive neurons activate cough, we hypothesized that Mtb produces molecules that stimulate cough, thereby facilitating its spread from infected to uninfected individuals.MethodsWe used an in vitro neuronal activation bioassay to fractionate, identify, and characterize Mtb cough-inducing molecules. We also measured cough in vivo in response to pure Mtb-derived cough molecules and during Mtb infection using a guinea pig model.ResultsWe found that an acellular organic extract of Mtb triggers and activates nociceptive neurons in vitro with a neuronal response that is as robust as the response to capsaicin, an established nociceptive and cough-inducing molecule. Using analytical chemistry and our neuronal bioassay, we then isolated 2 molecules produced by Mtb that activate nociceptive neurons. Both the organic Mtb extract and purified molecules alone were sufficient to induce cough in a conscious guinea pig cough model. Finally guinea pigs infected with wild-type Mtb cough much more frequently than guinea pigs infected with Mtb strains unable to produce nociceptive molecules.ConclusionWe conclude that Mtb produces molecules that activate nociceptive neurons and induce cough. These findings have significant implications for our understanding of Mtb transmission.Disclosures All authors: No reported disclosures.

Association of cough hypersensitivity with tracheal TRPV1 activation and neurogenic inflammation in a novel guinea pig model of citric acid-induced chronic cough.

ObjectiveThis study was performed to establish a novel model of citric acid-induced chronic cough in guinea pigs and to investigate the pathogenesis of cough hypersensitivity.MethodsHealthy conscious guinea pigs inhaled citric acid (0.4 M) for 3 minutes twice daily for 25 days. Cough reactivity was evaluated, substance P (SP) and calcitonin gene-related peptide (CGRP) in bronchoalveolar lavage fluid were detected, and transient receptor potential cation channel subfamily V member 1 (TRPV1) protein expression in the trachea and bronchus was determined. Tracheal and bronchial tissues were examined for TRPV1.ResultsInhalation of 0.4 M citric acid increased coughing in a time-dependent manner: coughing peaked at 15 days and reached the lowest level at 25 days. This was accompanied by similar changes in SP, CGRP, and TRPV1 protein expression. TRPV1 was mainly observed in the mucosal and submucosal layer of the trachea and bronchi. The areas of TRPV1 positivity in the trachea and bronchi of citric acid-treated animals were significantly larger than in the control group.ConclusionsRepeated inhalation of citric acid can be employed to establish a chronic cough model in guinea pigs. Cough hypersensitivity in this model is related to tracheal TRPV1 activation and neurogenic inflammation.

A Physicochemical Assessment of Acid-induced Post-inhalation Cough in a Guinea Pig Animal Model

A study was conducted with a Guinea Pig (GP) cough model to demonstrate that post-inhalation (PI) cough can be correlated and predicted with the acidity constant of the chemical stimulant. The test animals were exposed to nebulized solutions of citric acid and maleic acid. Cough responses were measured by audio, video, and respiratory flow signals via whole-body plethysmography. Nonparametric one-way ANOVA (Kruskal-Wallis) of cough counts showed statistically significant dose dependence for both citric acid (p<0.0001) and maleic acid (p<0.0001). For citric acid, post-hoc Dunn’s test indicated elevated cough response at the higher concentrations (p ≤ 0.0001 for 200 mM, and 300 mM) compared to control, i.e., isotonic saline (SL). The cough count at 100 mM citric acid was not significantly different from SL (p>0.05). Similar results were obtained for maleic acid exposures, with cough response at the higher concentrations significantly different compared to SL (p=0.0039 for 50 mM, p<0.0001 for 100 mM), while cough counts at 30 mM were not different compared to SL. The GP model is able to differentiate the cough response of maleic acid vs. citric acid, and the threshold of cough (1-2 coughs in 2 min) for maleic acid (~30 mM) is lower than that for citric acid (~100 mM). The lower threshold of cough for maleic acid as compared to citric acid is consistent with the mechanism of action mediated by protons, in a dose dependent way. A prediction of the cough response from citric acid to maleic acid was confirmed by this study. Experiments with nebulized acids confirmed expectations that the threshold of cough for citric acid in GP is at 100 mM and for maleic acid at 10- 30 mM. The lower cough threshold for maleic vs. citric acid is consistent with proton-mediated mechanism of action.

ANTITUSSIVE ACTIVITY ASSAYOF SAGE (LANTANA CAMARA L.)LEAVES BASED ON THE BREATHING PATTERN OF MALE GUINEA PIGS USING ADOBE AUDITION 1.5 PROGRAM

Objective: The present study was aimed to assay antitussive activity of Sage (Lantana camara L.)leavesMethods: Antitussive Assay was conducted based on The Breathing Pattern of Male Guinea Pigs Using Adobe Audition 1.5 Program.Results: Comparison of the frequency of breathing patterns guinea pig groups sage (Lantana camara L.)Â leaves water fraction at a dose of 4.58 mg/kg bw dose of 9.17 mg/kg bw and doses of 18.35 mg/kg bw statistically significantly different results (p&lt;0.05), as well as the ratio of intensity of the breathing pattern of the guinea pig. As for the water extract, significant differences in the frequency comparison guinea pig respiratory pattern is only shown at a dose of 18.35 mg/kg bw on the other side for its intensity did not show significant differences (p&lt;0.05).Conclusion: Ethanol extract of sage leaves in the form of three fractionation (ethyl acetate, n-hexane, and water) can improve the breathing pattern guinea pig cough, especially at a dose of 18.35 mg/kg bw.Â

Targeting fatty acid amide hydrolase as a therapeutic strategy for antitussive therapy.

Cough is the most common reason to visit a primary care physician, yet it remains an unmet medical need. Fatty acid amide hydrolase (FAAH) is an enzyme that breaks down endocannabinoids, and inhibition of FAAH produces analgesic and anti-inflammatory effects. Cannabinoids inhibit vagal sensory nerve activation and the cough reflex, so it was hypothesised that FAAH inhibition would produce antitussive activity via elevation of endocannabinoids.Primary vagal ganglia neurons, tissue bioassay, in vivo electrophysiology and a conscious guinea pig cough model were utilised to investigate a role for fatty acid amides in modulating sensory nerve activation in vagal afferents.FAAH inhibition produced antitussive activity in guinea pigs with concomitant plasma elevation of the fatty acid amides N-arachidonoylethanolamide (anandamide), palmitoylethanolamide, N-oleoylethanolamide and linoleoylethanolamide. Palmitoylethanolamide inhibited tussive stimulus-induced activation of guinea pig airway innervating vagal ganglia neurons, depolarisation of guinea pig and human vagus, and firing of C-fibre afferents. These effects were mediated via a cannabinoid CB2/Gi/o-coupled pathway and activation of protein phosphatase 2A, resulting in increased calcium sensitivity of calcium-activated potassium channels.These findings identify FAAH inhibition as a target for the development of novel, antitussive agents without the undesirable side-effects of direct cannabinoid receptor agonists.

Neurophenotypes in Airway Diseases. Insights from Translational Cough Studies.

Most airway diseases, including chronic obstructive pulmonary disease (COPD), are associated with excessive coughing. The extent to which this may be a consequence of increased activation of vagal afferents by pathology in the airways (e.g., inflammatory mediators, excessive mucus) or an altered neuronal phenotype is unknown. Understanding whether respiratory diseases are associated with dysfunction of airway sensory nerves has the potential to identify novel therapeutic targets. To assess the changes in cough responses to a range of inhaled irritants in COPD and model these in animals to investigate the underlying mechanisms. Cough responses to inhaled stimuli in patients with COPD, healthy smokers, refractory chronic cough, asthma, and healthy volunteers were assessed and compared with vagus/airway nerve and cough responses in a cigarette smoke (CS) exposure guinea pig model. Patients with COPD had heightened cough responses to capsaicin but reduced responses to prostaglandin E2 compared with healthy volunteers. Furthermore, the different patient groups all exhibited different patterns of modulation of cough responses. Consistent with these findings, capsaicin caused a greater number of coughs in CS-exposed guinea pigs than in control animals; similar increased responses were observed in ex vivo vagus nerve and neuron cell bodies in the vagal ganglia. However, responses to prostaglandin E2 were decreased by CS exposure. CS exposure is capable of inducing responses consistent with phenotypic switching in airway sensory nerves comparable with the cough responses observed in patients with COPD. Moreover, the differing profiles of cough responses support the concept of disease-specific neurophenotypes in airway disease. Clinical trial registered with www.clinicaltrials.gov (NCT 01297790).