Identifying vagal bronchopulmonary afferents mediating cough response to inhaled sulfur dioxide in mice.

Sulfur dioxide (SO2), a common environmental and industrial air pollutant, possesses a potent effect in eliciting cough reflex, but the primary type of airway sensory receptors involved in its tussive action has not been clearly identified. This study was carried out to determine the relative roles of three major types of vagal bronchopulmonary afferents [slowly adapting receptors (SARs), rapidly adapting receptors (RARs), and C-fibers] in regulating the cough response to inhaled SO2. Our results showed that inhalation of SO2 (300 or 600 ppm for 8 min) evoked an abrupt and intense stimulatory effect on bronchopulmonary C-fibers, which continued for the entire duration of inhalation challenge and returned toward the baseline in 1-2 min after resuming room air-breathing in anesthetized and mechanically ventilated mice. In stark contrast, the same SO2 inhalation challenge generated a distinct and consistent inhibitory effect on both SARs and phasic RARs; their phasic discharges synchronized with respiratory cycles during the baseline (breathing room air) began to decline progressively within 1-3 min after the onset of SO2 inhalation, ceased completely before termination of the 8-min inhalation challenge, and then slowly returned toward the baseline after >40 min. In a parallel study in awake mice, inhalation of SO2 at the same concentration and duration as that in the nerve recording experiments evoked cough responses in a pattern and time course similar to that observed in the C-fiber responses. Based on these results, we concluded that stimulation of vagal bronchopulmonary C-fibers is primarily responsible for triggering the cough response to inhaled SO2.NEW & NOTEWORTHY This study demonstrated that inhalation of a high concentration of sulfur dioxide, an irritant gas and common air pollutant, completely and reversibly inhibited the neural activities of both slowly adapting receptor and rapidly adapting receptor, two major types of mechanoreceptors in the lungs with their activities conducted by myelinated fibers. Furthermore, the results of this study suggested that stimulation of vagal bronchopulmonary C-fibers is primarily responsible for triggering the cough reflex responses to inhaled sulfur dioxide.

Targeted lung denervation in sheep: durability of denervation and long-term histologic effects on bronchial wall and peribronchial structures.

BACKGROUND: Targeted lung denervation (TLD), a novel bronchoscopic procedure which attenuates pulmonary nerve input to the lung to reduce the clinical consequences of neural hyperactivity, may be an important emerging treatment for COPD. While procedural safety and impact on clinical outcomes have recently been reported, the mechanism of action has not been reported. We explored the long-term pathologic and histopathologic effects in a sheep model of ablation of bronchial branches of the vagus nerve using a novel dual-cooled radiofrequency ablation catheter. METHODS: Nineteen sheep underwent circumferential ablation of both main bronchi with simultaneous balloon surface cooling using a targeted lung denervation system (Nuvaira, Inc., USA). Animals were followed over an extended time course (30, 365, and 640 days post procedure). At each time point, lung denervation (axonal staining in bronchial nerves), and effect on peribronchial structures near the treatment site (histopathology of bronchial epithelium, bronchial cartilage, smooth muscle, alveolar parenchyma, and esophagus) were quantified. One way analysis of variance (ANOVA) was performed to reveal differences between group means on normal data. Non-parametric analysis using Kruskal-Wallis Test was employed on non-normal data sets. RESULTS: No adverse clinical effects were observed in any sheep. Nerve axon staining distal to the ablation site was decreased by 60% at 30 days after TLD and efferent axon staining was decreased by >70% at 365 and 640 days. All treated airways exhibited 100% epithelial integrity. Effect on peribronchial structures was strictly limited to lung tissue immediately adjacent to the ablation site. Tissue structure 1 cm proximal and distal to the treatment area remained normal, and the pulmonary veins, pulmonary arteries, and esophagus were unaffected. CONCLUSIONS: The denervation of efferent axons induced by TLD therapy is durable and likely a contributing mechanism through which targeted lung denervation impacts clinical outcomes. Further, long term lung denervation did not alter the anatomy of the bronchioles or lung, as evaluated from both a gross and histologic perspective.

Antimycin A increases bronchopulmonary C-fiber excitability via protein kinase C alpha.

Inflammation can increase the excitability of bronchopulmonary C-fibers leading to excessive sensations and reflexes (e.g. wheeze and cough). We have previously shown modulation of peripheral nerve terminal mitochondria by antimycin A causes hyperexcitability in TRPV1-expressing bronchopulmonary C-fibers through the activation of protein kinase C (PKC). Here, we have investigated the PKC isoform responsible for this signaling. We found PKCß1, PKCδ and PKCε were expressed by many vagal neurons, with PKCα and PKCß2 expressed by subsets of vagal neurons. In dissociated vagal neurons, antimycin A caused translocation of PKCα but not the other isoforms, and only in TRPV1-lineage neurons. In bronchopulmonary C-fiber recordings, antimycin A increased the number of action potentials evoked by α,ß-methylene ATP. Selective inhibition of PKCα, PKCß1 and PKCß2 with 50 nM bisindolylmaleimide I prevented the antimycin-induced bronchopulmonary C-fiber hyperexcitability, whereas selective inhibition of only PKCß1 and PKCß2 with 50 nM LY333531 had no effect. We therefore conclude that PKCα is required for antimycin-induced increases in bronchopulmonary C-fiber excitability.

The voltage-gated sodium channel NaV1.8 blocker A-803467 inhibits cough in the guinea pig.

Cough in respiratory diseases is attributed to the activation of airway C-fibers by inflammation. Inflammatory mediators can act on multiple receptors expressed in airway C-fibers, nonetheless, the action potential initiation in C-fibers depends on a limited number of voltage-gated sodium channel (NaV1) subtypes. We have recently demonstrated that NaV1.8 substantially contributes to the action potential initiation in the airway C-fiber subtype implicated in cough. We therefore hypothesized that the NaV1.8 blocker A-803467 inhibits cough. We evaluated the cough evoked by the inhalation of C-fiber activator capsaicin in awake guinea pigs. Compared to vehicle, intraperitoneal or inhaled A-803467 caused 30-50% inhibition of cough at the doses that did not alter respiratory rate. We conclude that the NaV1.8 blocker A-803467 inhibits cough in a manner consistent with its action on the C-fiber nerve terminals in the airways. Targeting voltage-gated sodium channels mediating action potential initiation in airway C-fibers may offer a means of cough inhibition that is independent of the stimulus.

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

Objective This 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. Methods Healthy 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. Results Inhalation 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. Conclusions Repeated 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.

Nerve ablation after bronchial thermoplasty and sustained improvement in severe asthma.

BACKGROUND: Bronchial thermoplasty (BT) is a non-pharmacological intervention for severe asthma whose mechanism of action is not completely explained by a reduction of airway smooth muscle (ASM). In this study we analyzed the effect of BT on nerve fibers and inflammatory components in the bronchial mucosa at 1 year. METHODS: Endobronchial biopsies were obtained from 12 subjects (mean age 47 ± 11.3 years, 50% male) with severe asthma. Biopsies were performed at baseline (T0) and after 1 (T1), 2 (T2) and 12 (T12) months post-BT, and studied with immunocytochemistry and microscopy methods. Clinical data including Asthma Quality of Life Questionnaire (AQLQ) and Asthma Control Questionnaire (ACQ) scores, exacerbations, hospitalizations, oral corticosteroids use were also collected at the same time points. RESULTS: A statistically significant reduction at T1, T2 and T12 of nerve fibers was observed in the submucosa and in ASM compared to T0. Among inflammatory cells, only CD68 showed significant changes at all time points. Improvement of all clinical outcomes was documented and persisted at the end of follow up. CONCLUSIONS: A reduction of nerve fibers in epithelium and in ASM occurs earlier and persists at one year after BT. We propose that nerve ablation may contribute to mediate the beneficial effects of BT in severe asthma. TRIAL REGISTRATION: Registered on April 2, 2013 at ClinicalTrials.gov Identifier: NCT01839591 .

Capsaicin-evoked cough responses in asthmatic patients: Evidence for airway neuronal dysfunction.

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 (Emax) and the capsaicin dose inducing half-maximal response (ED50). 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 Emax and lower ED50 values than healthy volunteers. Emax 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 Emax value than nonatopic asthmatic patients (P = .04). The ED50 value was 65% lower in female patients (P = .0001) and 71% lower in all asthmatic patients (P = .0008). ED50 values were also influenced by asthma control and serum IgE levels, whereas Emax values were related to 24-hour cough frequency. Age, body mass index, FEV1, PC20, 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.

[ROLE OF MAST CELLS IN BRONCHIAL CONTRACTION IN NONALLERGIC OBSTRUCTIVE LUNG PATHOLOGY].

In model of chronic obstructive pulmonary disease induced in rats by 60-day intermittent exposure to nitrogen dioxide mast cells participation in the mechanism of bronchial smooth muscle contractile activity patterns was evaluated. Since the 31st day, one group of rats was inhaled with sodium cromoglycate every day before the nitrogen dioxide exposure to stabilize the mast cell membrane. The other group (control) hasn't been treated. Isometric contraction of the bronchial isolated preparations in response to nerve or smooth muscle stimulation were determined. Inhibition of mast cell degranulation and the release of endogenous histamine by stabilizing cell membranes prevented the development of bronchial smooth muscle hyperactivity caused by prolonged inhalation of nitrogen dioxide. It is believed that a mechanism to increase the contractile activity of the bronchial wall smooth muscles is mediated by activation of the transmembrane adenosine receptor in resident mast cells, leading to their partial degranulation with release of histamine, acting on the histamine Hl-receptors with the launch of reflex pathways through intramural ganglion neurons.

Respiratory disease and the oesophagus: reflux, reflexes and microaspiration.

Gastro-oesophageal reflux is associated with a wide range of respiratory disorders, including asthma, isolated chronic cough, idiopathic pulmonary fibrosis, chronic obstructive pulmonary disease and cystic fibrosis. Reflux can be substantial and reach the proximal margins of the oesophagus in some individuals with specific pulmonary diseases, suggesting that this association is more than a coincidence. Proximal oesophageal reflux in particular has led to concern that microaspiration might have an important, possibly even causal, role in respiratory disease. Interestingly, reflux is not always accompanied by typical reflux symptoms, such as heartburn and/or regurgitation, leading many clinicians to empirically treat for possible gastro-oesophageal reflux. Indeed, costs associated with use of acid suppressants in pulmonary disease far outweigh those in typical GERD, despite little evidence of therapeutic benefit in clinical trials. This Review comprehensively examines the possible mechanisms that might link pulmonary disease and oesophageal reflux, highlighting the gaps in current knowledge and limitations of previous research, and helping to shed light on the frequent failure of antireflux treatments in pulmonary disease.

[THE INFLUENCE OF HISTAMINE ON THE EFFECTOR NEURONS OF INTRAMURAL GANGLIA OF THE TRACHEA AND BRONCHI].

We considered the influence of the neurons of intramural ganglia in the reaction of the smooth muscle trachea and bronchi caused by electric field stimulation, by the action of histamine. We studied the effect of neurons of intramural ganglia in the activity of the smooth muscle trachea and bronchi in the action of low doses of histamine (0,1 and 10 µg/ml), L-NAME and hexamethonium. It was shown the blockade of neuronal transmission decreased the contraction of the smooth muscles trachea and bronchi by stimulation of the afferent nerve structures. The smooth muscle relaxation under the influence of hexamethonium was also reduced. Histamine and hexamethonium increased contractile activity and increased the amplitude of the relaxation of the trachea and bronchi. The inhibition of NO- synthesis did not affect on the contraction, but reduced the relaxation of the trachea and bronchi. Histamine and L-NAME enhanced contractile activity, but not modified smooth muscle relaxation. Concluded that the neurons of intramural ganglia have an inhibitory effect on the smooth muscle of the trachea and bronchi and may have a modulating effect on contraction and dilatation of the smooth muscles of the airways.

Role of calcium ions in the positive interaction between TRPA1 and TRPV1 channels in bronchopulmonary sensory neurons.

Both transient receptor potential ankyrin 1 (TRPA1) and vanilloid 1 (TRPV1) receptors are abundantly expressed in bronchopulmonary C-fiber sensory nerves and can be activated by a number of endogenous inflammatory mediators. A recent study has reported a synergistic effect of simultaneous TRPA1 and TRPV1 activations in vagal pulmonary C-fiber afferents in anesthetized rats, but its underlying mechanism was not known. This study aimed to characterize a possible interaction between these two TRP channels and to investigate the potential role of Ca(2+) as a mediator of this interaction in isolated rat vagal pulmonary sensory neurons. Using the perforated patch-clamp recording technique, our study demonstrated a distinct positive interaction occurring abruptly between TRPA1 and TRPV1 when they were activated simultaneously by their respective agonists, capsaicin (Cap) and allyl isothiocyanate (AITC), at near-threshold concentrations in these neurons. AITC at this low concentration evoked only minimal or undetectable responses, but it markedly amplified the Cap-evoked current in the same neurons. This potentiating effect was eliminated when either AITC or Cap was replaced by non-TRPA1 and non-TRPV1 chemical activators of these neurons, demonstrating the selectivity of the interaction between these two TRP channels. Furthermore, when Ca(2+) was removed from the extracellular solution, the synergistic effect of Cap and AITC on pulmonary sensory neurons was completely abrogated, clearly indicating a critical role of Ca(2+) in mediating the action. These results suggest that this TRPA1-TRPV1 interaction may play a part in regulating the sensitivity of pulmonary sensory neurons during airway inflammatory reaction.

Morphologic Characterization of Nerves in Whole-Mount Airway Biopsies.

RATIONALE: Neuroplasticity of bronchopulmonary afferent neurons that respond to mechanical and chemical stimuli may sensitize the cough reflex. Afferent drive in cough is carried by the vagus nerve, and vagal afferent nerve terminals have been well defined in animals. Yet, both unmyelinated C fibers and particularly the morphologically distinct, myelinated, nodose-derived mechanoreceptors described in animals are poorly characterized in humans. To date there are no distinctive molecular markers or detailed morphologies available for human bronchopulmonary afferent nerves. OBJECTIVES: Morphologic and neuromolecular characterization of the afferent nerves that are potentially involved in cough in humans. METHODS: A whole-mount immunofluorescence approach, rarely used in human lung tissue, was used with antibodies specific to protein gene product 9.5 (PGP9.5) and, for the first time in human lung tissue, 200-kD neurofilament subunit. MEASUREMENTS AND MAIN RESULTS: We have developed a robust technique to visualize fibers consistent with autonomic and C fibers and pulmonary neuroendocrine cells. A group of morphologically distinct, 200-kD neurofilament-immunopositive myelinated afferent fibers, a subpopulation of which did not express PGP9.5, was also identified. CONCLUSIONS: PGP9.5-immunonegative nerves are strikingly similar to myelinated airway afferents, the cough receptor, and smooth muscle-associated airway receptors described in rodents. These have never been described in humans. Full description of human airway nerves is critical to the translation of animal studies to the clinical setting.

Protease-activated receptor-2 inhibits BK channel activity in bronchopulmonary sensory neurons.

Activation of protease-activated receptor-2 (PAR2) contributes to airway inflammation and airway hypersensitivity, the hallmark features of allergic asthma; and a neurogenic mechanism involving hypersensitivity of bronchopulmonary sensory nerves has been indicated. Large-conductance Ca(2+)-activated potassium (BK) channels are known to play an important role in shaping neuronal excitability. The aim of this study was to investigate the potential regulation of BK channel activities by PAR2 activation in vagal bronchopulmonary sensory neurons. Our results showed that pretreatment with PAR2-activating peptide (PAR2-AP; 100µM, 120s), but not its control peptide PAR2-RP, significantly reduced BK current density in these neurons. Inhibition of phospholipase C, PKC, PKA or MEK/ERK signaling pathway did not prevent the suppression of BK current by PAR2 activation; whereas intracellular application of Ca(2+) chelator BAPTA-AM completely abolished the PAR2 regulation of BK current. In addition, our results demonstrated that activation of PAR2 increased excitability of bronchopulmonary sensory neurons, in a similar manner as displayed by a direct BK channel blockade. In summary, our data suggest that suppression of BK channel activity contributes to PAR2 activation-induced hyperexcitability of vagal bronchopulmonary sensory neurons.

Medicinas tradicionales andinas y su despenalización: entrevista con Walter Álvarez Quispe / Decriminalizing traditional Andean medicine: an interview with Walter Álvarez Quispe

Walter Álvarez Quispe, terapeuta kallawaya y biomédico especializado en cirugía general y ginecología, presenta la lucha de los terapeutas tradicionales y alternativos por la depenalización de estos sistemas médicos andinos realizada entre 1960 y 1990. Bolivia se torna el primer país en América Latina y el Caribe en despenalizar la medicina tradicional antes de los planteamientos de la Conferencia Internacional sobre Atención Primaria de Salud (Alma-Ata, 1978). Los datos aportados por el entrevistado aseguran que los logros alcanzados, principalmente por los kallawayas, responden a un proyecto propio y autónomo. Estas conquistas no se deben a las políticas oficiales de interculturalidad en salud, aunque busquen atribuirse para sí los logros alcanzados.

Walter Álvarez Quispe, a Kallawaya healer and biomedical practitioner specializing in general surgery and gynecology, presents the struggle of traditional and alternative healers to get their Andean medical systems depenalized between 1960 and 1990. Bolivia was the first country in Latin America and the Caribbean to decriminalize traditional medicine before the proposals of the International Conference on Primary Health Care (Alma-Ata, 1978). The data provided by the interviewee show that the successes achieved, mainly by the Kallawayas, stem from their own independent initiative. These victories are not the result of official policies of interculturality in healthcare, although the successes achieved tend to be ascribed to them.

Differential regulation of ASICs and TRPV1 by zinc in rat bronchopulmonary sensory neurons.

PURPOSE: Zinc has been known to act as a signaling molecule that regulates a variety of neuronal functions. In this study, we aimed to study the effect of zinc on two populations of acid-sensitive ion channels, acid-sensing ion channels (ASICs), and transient receptor potential vanilloid receptor-1 (TRPV1), in vagal bronchopulmonary sensory neurons. METHODS: Rat vagal sensory neurons innervating lungs and airways were retrogradely labeled with a fluorescent tracer. Whole-cell perforated patch-clamp recordings were carried out in primarily cultured bronchopulmonary sensory neurons. The acid-evoked ASIC and TRPV1 currents were measured and compared between before and after the zinc pretreatment. RESULTS: ASIC currents were induced by a pH drop from 7.4 to 6.8 or 6.5 in the presence of capsazepine (10 µM), a specific TRPV1 antagonist. Pretreatment with zinc (50 or 300 µM, 2 min) displayed different effects on the two distinct phenotypes of ASIC currents: a marked potentiation on ASIC channels with fast kinetics of activation and inactivation or no significant effect on ASIC currents with slow activation and inactivation. On the other hand, pretreatment with zinc significantly inhibited the acid (pH 5.5 or 5.3)-induced TRPV1 currents. The inhibition was abolished by intracellular chelation of zinc by TPEN (25 µM), indicating that intracellular accumulation of zinc was likely required for its inhibitory effect on TRPV1 channels. CONCLUSIONS: Our study showed that zinc differentially regulates the activities of ASICs and TRPV1 channels in rat vagal bronchopulmonary sensory neurons.

Sensory nerve terminal mitochondrial dysfunction induces hyperexcitability in airway nociceptors via protein kinase C.

Airway sensory nerve excitability is a key determinant of respiratory disease-associated reflexes and sensations such as cough and dyspnea. Inflammatory signaling modulates mitochondrial function and produces reactive oxygen species (ROS). Peripheral terminals of sensory nerves are densely packed with mitochondria; thus, we hypothesized that mitochondrial modulation would alter neuronal excitability. We recorded action potential firing from the terminals of individual bronchopulmonary C-fibers using a mouse ex vivo lung-vagal ganglia preparation. C-fibers were characterized as nociceptors or non-nociceptors based upon conduction velocity and response to transient receptor potential (TRP) channel agonists. Antimycin A (mitochondrial complex III Qi site inhibitor) had no effect on the excitability of non-nociceptors. However, antimycin A increased excitability in nociceptive C-fibers, decreasing the mechanical threshold by 50% and increasing the action potential firing elicited by a P2X2/3 agonist to 270% of control. Antimycin A-induced nociceptor hyperexcitability was independent of TRP ankyrin 1 or TRP vanilloid 1 channels. Blocking mitochondrial ATP production with oligomycin or myxothiazol had no effect on excitability. Antimycin A-induced hyperexcitability was dependent on mitochondrial ROS and was blocked by intracellular antioxidants. ROS are known to activate protein kinase C (PKC). Antimycin A-induced hyperexcitability was inhibited by the PKC inhibitor bisindolylmaleimide (BIM) I, but not by its inactive analog BIM V. In dissociated vagal neurons, antimycin A caused ROS-dependent PKC translocation to the membrane. Finally, H2O2 also induced PKC-dependent nociceptive C-fiber hyperexcitability and PKC translocation. In conclusion, ROS evoked by mitochondrial dysfunction caused nociceptor hyperexcitability via the translocation and activation of PKC.

Tiotropium modulates transient receptor potential V1 (TRPV1) in airway sensory nerves: A beneficial off-target effect?

BACKGROUND: Recent studies have suggested that the long-acting muscarinic receptor antagonist tiotropium, a drug widely prescribed for its bronchodilator activity in patients with chronic obstructive pulmonary disease and asthma, improves symptoms and attenuates cough in preclinical and clinical tussive agent challenge studies. The mechanism by which tiotropium modifies tussive responses is not clear, but an inhibition of vagal tone and a consequent reduction in mucus production from submucosal glands and bronchodilation have been proposed. OBJECTIVE: The aim of this study was to investigate whether tiotropium can directly modulate airway sensory nerve activity and thereby the cough reflex. METHODS: We used a conscious cough model in guinea pigs, isolated vagal sensory nerve and isolated airway neuron tissue- and cell-based assays, and in vivo single-fiber recording electrophysiologic techniques. RESULTS: Inhaled tiotropium blocked cough and single C-fiber firing in the guinea pig to the transient receptor potential (TRP) V1 agonist capsaicin, a clinically relevant tussive stimulant. Tiotropium and ipratropium, a structurally similar muscarinic antagonist, inhibited capsaicin responses in isolated guinea pig vagal tissue, but glycopyrrolate and atropine did not. Tiotropium failed to modulate other TRP channel-mediated responses. Complementary data were generated in airway-specific primary ganglion neurons, demonstrating that tiotropium inhibited capsaicin-induced, but not TRPA1-induced, calcium movement and voltage changes. CONCLUSION: For the first time, we have shown that tiotropium inhibits neuronal TRPV1-mediated effects through a mechanism unrelated to its anticholinergic activity. We speculate that some of the clinical benefit associated with taking tiotropium (eg, in symptom control) could be explained through this proposed mechanism of action.

[Efferent innervation of pulmonary blood vessels and bronchi in rat (an immunohistochemical study)].

In this investigation the peculiarities of innervation of bronchi and blood vessels of the lung were studied in 20 rats using immunohistochemical demonstration of synaptophysin and alpha-actin. The results obtained have showen that the densest innervation is typical for bronchial walls, particularly, for the muscular lamina. Synaptophysin-immunoreactive terminals (SFIT) were detected in the bronchi in close association with both circular bundles of smooth muscle cells and microganglia. Dense network of SFIT was found in the pulmonary vein--in its middle tunic formed by cardiomyocytes. In contrast to the bronchi and pulmonary vein, large branches of the pulmonary artery contained no SFIT. We briefly discuss the problem of the origin of the nerve fibers described and their functions and suggest that SFIT are formed by efferent fibers (axons) of neurons arising from either the intrapulmonary parasympathetic ganglia.

Pathways underlying afferent signaling of bronchopulmonary immune activation to the central nervous system.

Bronchopulmonary inflammation, such as that associated with asthma, activates afferent neural pathways. We recently demonstrated that localized inflammation in the lungs, induced by intratracheal administration of ovalbumin in ovalbumin-preimmunized mice (an animal model of asthma) results in activation of the dorsolateral part of the nucleus of the solitary tract, a major target of vagal afferent fibers innervating the lungs and airways. Activation of the nucleus of the solitary tract was evident in the absence of activation of the area postrema, a circumventricular organ, consistent with the hypothesis that localized inflammation in the bronchopulmonary system can signal to the central nervous system via specific neural pathways, in the absence of circulating proinflammatory mediators. The pattern of brain activation in ovalbumin-challenged mice differs from the pattern of activation in mice challenged with heat-killed Mycobacterium vaccae, suggesting that qualitative aspects of bronchopulmonary inflammation determine the overall pattern of brain activation. The mechanisms through which localized bronchopulmonary inflammation signals to the central nervous system is poorly understood, but appears to involve both vagal and spinal afferent pathways. In this chapter, we review our current understanding of the anatomical pathways through which localized inflammation in the bronchopulmonary system influences central nervous system function.