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Background: In asthma and chronic obstructive pulmonary disease (COPD), airway mucus hypersecretion contributes to impaired mucociliary clearance, mucostasis and, potentially, the development of mucus plugging of the airways. Summary: Excess mucus production can be targeted via therapies that focus on inhibition mucin synthesis, via reducing expression of mucin (MUC) genes, and/or inhibition of mucin secretion into the airways. Key Messages: This review discusses a number of therapeutic approaches to reduce airway mucus in asthma and COPD, including the use of synthetic and natural products. In particular, it highlights areas where clinical trials of inhibitors of particular target molecules are lacking. Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors are an example of a targeted therapy that has been researched to reduce mucus synthesis, as have inhibitors of EGFR's downstream signalling pathways, for example, mitogen-activated protein kinase-13 and hypoxia inducible factor-1. However, their efficacy and safety profiles are currently not up to the mark. There is clinical potential in Bio-11006, which reduces mucus secretion via the inhibition of myristoylated alanine-rich C-kinase substrate and is currently in Phase IIb trial.

Airway mucus hypersecretion is a pathophysiological feature of asthma and chronic obstructive pulmonary disease (COPD). The hypersecretion is associated with phenotypic changes in the airways, notably, increases in the number of surface epithelial goblet cells (hyperplasia) and in the size of the submucosal glands (hypertrophy). The hyperplasia and hypertrophy are associated with increased production of mucin, the gel-forming component of mucus. The excess mucus production contributes to morbidity and mortality in many patients, particularly in those with more severe disease. Although current pharmacotherapy is effective in clinical management of patients with stable asthma, severe asthma is poorly treated and there is no current drug treatment for COPD. In neither disease is there specific, effective pharmacotherapy for the hypersecretion. Consequently, identification of potential drug targets for treatment of hypersecretion in asthma and COPD is warranted. The inflammatory mediators and the associated intracellular signaling pathways underlying upregulation of mucin synthesis and development of goblet cell hyperplasia are gradually being elucidated. These include Th2 cytokines (predominantly IL-9 and IL-13), and IL-1 beta, tumor necrosis factor-alpha (TNF-alpha) and cyclooxygenase (COX)-2. IL-9 may act predominantly via calcium-activated chloride channels (CLCA), IL-13 via STAT-6 and FOXA2, TNF-alpha via NF-kappaB, and IL-1 beta via COX-2. Epidermal growth factor receptor (EGF-R) signaling and FOXA2 appear to be convergent intracellular pathways for a number of inflammatory mediators, with EGF-R upregulated in the airways of asthmatic and COPD patients. Thus, preclinical studies have clearly identified a number of intracellular signaling pathways as possible targets for pharmacotherapy of airway mucus hypersecretion in asthma and COPD. Of these, the EGF-R and Th2 cytokine pathways may have the greatest potential for inhibition of excessive mucus production. However, because these targets are so often intimately involved with different aspects of airway (and systemic) homeostasis, there is potential for development of unwanted side effects with drug intervention. Thus, translation of the promising preclinical studies to the clinic will depend on development of drug moieties with low off-target activity. This may be accomplished by maximizing airway selectivity, which may be facilitated by appropriate delivery device design.

Phytoceuticals (non-nutritional but beneficial plant chemicals) merit investigation as pharmacotherapy for asthma and chronic obstructive pulmonary disease (COPD). Although asthma is mostly treated adequately, COPD is not. Thus, there is a need for new drugs with improved therapeutic benefit, especially in COPD. Recent interest in herbal remedies has redirected attention towards plants as sources of improved treatments for lung disease. Phytoceuticals from a variety of plants and plant products, including butterbur, English ivy, apples, chocolate, green tea and red wine, demonstrate broad-spectrum pharmacotherapeutic activities that could be exploited in the clinic. Well-designed clinical trials are required to determine whether these beneficial activities are reproduced in patients, with the prospect that phytoceuticals are the new physic garden for asthma and COPD.

Small airways (SA) are the main site of airflow obstruction in COPD. Neutrophil products, including proteases and oxidants, damage lung tissue and are implicated in COPD pathophysiology. We studied the effects of protease inhibitors or an antioxidant ( N -acetylcysteine, NAC) on COPD neutrophil supernatant-induced SA dysfunction in ex vivo rat precision-cut lung slices (PCLS) using videomicroscopy. fMLP-stimulated neutrophil supernatants were pre-treated with either neutrophil elastase (NE) inhibitor (10μM, Calbiochem 324745) or MMP-9 inhibitor (10μM, Calbiochem 444278), or NAC (1mM) prior to overnight incubation with rat PCLS, and SA contraction to carbachol (CCh, 10nM-10μM) assessed. Compared with untreated (UT) airways, there was a 33% reduction in maximal airway closure in SA incubated with COPD neutrophil supernatants (UT 86±2, n=10; COPD 53±9% closure, n=7), which was attenuated by 24% by NE inhibitor (77±8%, n=7), but with no effect on PCLS viability (COPD 42±15, n=7; COPD+inhibitor 47±16%UT viability, n=7). MMP-9 inhibitor had no effect on maximal airway closure (UT 83±4, n=8; COPD 36±2, n=4, COPD+inhibitor 24±13% closure, n=5) or viability (COPD 59±13, n=4; COPD+MMP-9 inhibitor 48±12 %UT viability, n=4). NAC restored maximal airway closure by 16% in 1mM H 2 O 2 -treated SA (UT 91±4, n=8; H 2 O 2 70±8, n=8; H 2 O 2 +NAC 86±4%closure, n=6), but not in SA treated with COPD neutrophil supernatants (UT 78±6, n=6; COPD 28±7, n=4; COPD+NAC 7±9% closure, n=4). Therefore, NE was involved in COPD neutrophil supernatant-induced rat SA dysfunction. NE inhibition may protect against elastolytic damage, or inhibit tissue mediator release and therefore could be a target for SA dysfunction in COPD.

Topical gene transfer to the airways of cystic fibrosis (CF) patients has been inefficient, partly due to extracellular barriers such as sputum. In an attempt to circumvent these, we assessed whether airway epithelial cells can be transfected by intravenous (i.v.) administration of liposome-complexed or "naked" oligonucleotides (ODNs). The conducting airways are the likely target for CF therapy and are supplied by the bronchial circulation. Consequently, we assessed ODN transfer in the mouse trachea and main bronchi as these are supplied by the bronchial circulation. Liposome-protamine-DNA (LPD) complexes were detected in the bronchial circulation but did not transfect conducting airway epithelial cells, even in the presence of microvascular leakage. In contrast, 'naked' ODNs were delivered to 17% (inter-quartile range (IQR) 10-34%) and 35% (IQR 24-59%) of epithelial cells when injected at 500 microg/animal, without and with microvascular leakage, respectively. Two types of nuclear signal were observed; punctate in cells throughout the airways (3%, IQR 2-6%, and 6%, IQR 4-7%, of cells when delivered without and with microvascular leakage, respectively) and diffuse in a small number of epithelial cells in the proximal trachea. ODNs may be relevant to CF in a variety of ways and these data suggest one way towards implementing their use.

Airway mucus hypersecretion is a key pathophysiological feature in many patients with asthma and chronic obstructive pulmonary disease (COPD). Consequently, it is important to develop drugs that inhibit mucus hypersecretion in these susceptible patients. Conventional therapy (anticholinergics, β2-adrenoceoptor agonists, corticosteroids, mucolytics and macrolide antibiotics) has variable efficacy in inhibiting airway mucus hypersecretion, and is less effective in COPD than in asthma. Novel pharmacotherapeutic targets are being investigated, including inhibitors of nerve activity, tachykinin antagonists, epoxygenase inducers, inhibitors of mucin exocytosis, inhibitors of mucin synthesis and goblet cell hyperplasia, inducers of goblet cell apoptosis, and purinoceptor antagonists and agonists to inhibit or hydrate secretions. However, real and theoretical differences differentiate the mucus hypersecretory phenotype in asthma from that in COPD. More information is required on these differences to identify spec...

Airway mucus hypersecretion is now recognized as a key pathophysiological feature in many patients with asthma, chronic obstructive pulmonary disease (COPD) and cystic fibrosis. Consequently, it is important to develop drugs that inhibit mucus hypersecretion in these susceptible patients. Conventional therapies, including anticholinergics, ss2-adrenoceptor agonists, corticosteroids, mucolytics and macrolide antibiotics, have variable efficacy in inhibiting airway mucus hypersecretion, and are less effective in COPD than in asthma. Novel pharmacotherapeutic targets are being investigated, including inhibitors of nerve activity (e.g. large conductance calcium-activated potassium, BKCa, channel activators), tachykinin receptor antagonists, epoxygenase inducers (e.g. benzafibrate), inhibitors of mucin exocytosis (e.g. anti-myristoylated alanine-rich C kinase substrate (MARCKS), peptide and Munc-18B blockers), inhibitors of mucin synthesis and goblet cell hyperplasia (e.g. epidermal growth factor (EGF), receptor tyrosine kinase inhibitors, p38 mitogen-activated protein (MAP), kinase inhibitors, MAP kinase kinase/extracellular signal-regulated kinase (MEK/ERK), inhibitors, human calcium-activated chloride (hCACL2), channel blockers and retinoic acid receptor-a antagonists), inducers of goblet cell apoptosis (e.g. Bax inducers or Bcl-2 inhibitors), and purinoceptor P(2Y2) antagonists to inhibit mucin secretion or P(2Y2) agonists to hydrate secretions. However, real and theoretical differences delineate the mucus hypersecretory phenotype in asthma from that in COPD. More information is required on these differences to identify specific therapeutic targets which, in turn, should lead to rational design of anti-hypersecretory drugs for treatment of airway mucus hypersecretion in asthma and COPD.

Often considered an aggravating but otherwise benign component of chronic obstructive pulmonary disease (COPD), airway mucus hypersecretion is now recognised as a potential risk factor for an accelerated loss of lung function in COPD and is a key pathophysiological feature in many patients, particularly those prone to respiratory tract infection. Consequently, it is important to develop drugs that inhibit mucus hypersecretion in these susceptible patients. Conventional therapy including anticholinergics, beta2-adrenoceoptor agonists, alone or in combination with corticosteroids, mucolytics and macrolide antibiotics are not entirely or consistently effective in inhibiting airway mucus hypersecretion in COPD. Novel pharmacotherapeutic targets are being investigated, including inhibitors of nerve activity (e.g., BK(Ca) channel activators), tachykinin receptor antagonists, epoxygenase inducers (e.g., benzafibrate), inhibitors of mucin exocytosis (e.g., anti-MARCKS peptide and Munc-18B blockers), inhibitors of mucin synthesis and goblet cell hyperplasia (e.g., EGF receptor tyrosine kinase inhibitors, p38 MAP kinase inhibitors, MEK/ERK inhibitors, hCACL2 blockers and retinoic acid receptor-alpha antagonists), inducers of goblet cell apoptosis (e.g., Bax inducers or Bcl-2 inhibitors), and purinoceptor P(2Y2) antagonists to inhibit mucin secretion or P(2Y2) agonists to hydrate secretions. However, real and theoretical differences delineate the mucus hypersecretory phenotype in COPD from that in other hypersecretory diseases of the airways. More information is required on these differences to identify therapeutic targets pertinent to COPD which, in turn, should lead to rational design of anti-hypersecretory drugs for specific treatment of airway mucus hypersecretion in COPD.

Background The pathophysiology of chronic obstructive pulmonary disease (COPD) features pulmonary inflammation with a predominant alveolar macrophage involvement. Bronchoalveolar macrophages from patients with COPD release increased amounts of inflammatory cytokines in vitro, an effect that is not inhibited by the glucocorticosteroid dexamethasone. Resveratrol (3,5,4'-trihydroxystilbene) is a component of red wine extract that has anti-inflammatory and antioxidant properties. A study was undertaken to determine whether or not resveratrol would inhibit cytokine release in vitro by alveolar macrophages from patients with COPD. Methods Alveolar macrophages were isolated from bronchoalveolar lavage (BAL) fluid from cigarette smokers and from patients with COPD (n=15 per group). The macrophages were stimulated with either interleukin (IL)-1beta or cigarette smoke media (CSM) to release IL-8 and granulocyte macrophage-colony stimulating factor (GM-CSF). The effect of resveratrol was examined on both basal and stimulated cytokine release. Results Resveratrol inhibited basal release of IL-8 in smokers and patients with COPD by 94% and 88% respectively, and inhibited GM-CSF release by 79% and 76% respectively. Resveratrol also inhibited stimulated cytokine release. Resveratrol reduced IL-1beta stimulated IL-8 and GM-CSF release in both smokers and COPD patients to below basal levels. In addition, resveratrol inhibited CSM stimulated IL-8 release by 61% and 51% respectively in smokers and COPD patients, and inhibited GM-CSF release by 49% for both subject groups. Conclusions Resveratrol inhibits inflammatory cytokine release from alveolar macrophages in COPD. Resveratrol or similar compounds may be effective pharmacotherapy for macrophage pathophysiology in COPD.

Chronic obstructive pulmonary disease (COPD) is a common, severe inflammatory condition of the respiratory tract for which there is an enormous worldwide pharmaceutical potential. Despite this, current pharmacotherapy for COPD is suboptimal. Consequently, there are legitimate reasons for seeking alternative therapies for COPD. Proteases may contribute to the pathophysiology of COPD, whilst retinoids may be involved in lung repair. Recent patent applications from a variety of pharmaceutical companies disclose an array of different structural classes of protease inhibitors and retinoid compounds that may be of benefit in COPD. The antiprotease compounds comprise inhibitors of matrix metalloproteinases, including hydroxamic and carboxylic acid derivatives, lactams, β-amino acid derivatives and piperidine and piperazine derivatives, inhibitors of serine proteases, including guanidine derivatives, polypeptides and oxadiazole derivatives and inhibitors of cysteine proteases, including amide derivatives and nitr...

Airway mucus hypersecretion is a clinical feature of a number of childhood diseases, including asthma and bronchitis-associated conditions. However, compared with adults, there is relatively scarce information concerning mucus pathophysiology in respiratory diseases in children. The available evidence indicates many similarities between adult and childhood respiratory hypersecretory conditions, including goblet-cell hyperplasia and submucosal gland hypertrophy, and airway mucus plugging in asthma. Consequently, it is likely that treatments that are effective in adults would be effective in children. Numerous therapeutic targets are linked to the pathophysiology of airway mucus hypersecretion in experimental models and adults with respiratory disease. Whether or not these same targets are relevant in children is for the most part unclear. These targets include the inflammatory cells mediating the inflammatory response that generates the hypersecretory phenotype, and highly specific cellular elements such as epidermal growth factor receptor tyrosine kinase and calcium-activated chloride (CACL) channels. Identification of these factors is linked with the development of different classes of pharmacotherapeutic molecules directed at these targets. Compounds with a broader spectrum of anti-inflammatory activity are likely to be more effective than compounds with restricted activity. However, certain highly specific targets, such as human CACL1 channels, appear to be strongly associated with the development of an airway hypersecretory phenotype. Data from current clinical trials in adults with blockers of these specific targets are awaited with great interest. The hope is that, if effective, pediatric trials with these compounds could be initiated with a view to alleviation of the clinical impact of airway mucus hypersecretion in children. A significant challenge to the therapeutic progression of these new compounds is effective delivery to the airways in children, with the research effort into development of new compounds matched by advances in inhaler design.

Chronic obstructive pulmonary disease (COPD) is a common, smoking-related, severe respiratory condition characterised by progressive, irreversible airflow limitation. Current treatment of COPD is symptomatic, with no drugs capable of halting the relentless progression of airflow obstruction. Better understanding of the airway inflammation, oxidative stress and alveolar destruction that characterise COPD has delineated new disease targets, with consequent identification of novel compounds with therapeutic potential. These new drugs include aids to smoking cessation (e.g. bupropion) and improvements to existing therapies, for example long-acting rather than short-acting bronchodilators, as well as combination therapy. New antiproteases include acyl-enzyme and transition state inhibitors of neutrophil elastase (e.g. sivelestat and ONO-6818), matrix metalloprotease inhibitors (e.g. batimastat), cathepsin inhibitors and peptide protease inhibitors (e.g. DX-890 [EPI-HNE-4] and trappin-2). New antioxidants include superoxide dismutase mimetics (e.g. AEOL-10113) and spin trap compounds (e.g. N-tert-butyl-alpha-phenylnitrone). New anti-inflammatory interventions include phosphodiesterase-4 inhibitors (e.g. cilomilast), inhibitors of tumour necrosis factor-alpha (e.g. humanised monoclonal antibodies), adenosine A(2a) receptor agonists (e.g. CGS-21680), adhesion molecule inhibitors (e.g. bimosiamose [TBC1269]), inhibitors of nuclear factor-kappaB (e.g. the naturally occurring compounds hypoestoxide and (-)-epigallocatechin-3-gallate) and activators of histone deacetylase (e.g. theophylline). There are also selective inhibitors of specific extracellular mediators such as chemokines (e.g. CXCR2 and CCR2 antagonists) and leukotriene B(4) (e.g. SB201146), and of intracellular signal transduction molecules such as p38 mitogen activated protein kinase (e.g. RWJ67657) and phosphoinositide 3-kinase. Retinoids may be one of the few potential treatments capable of reversing alveolar destruction in COPD, and a number of compounds are in clinical trial (e.g. all-trans-retinoic acid). Talniflumate (MSI-1995), an inhibitor of human calcium-activated chloride channels, has been developed to treat mucous hypersecretion. In addition, the purinoceptor P2Y(2) receptor agonist diquafosol (INS365) is undergoing clinical trials to increase mucus clearance. The challenge to transferral of these new compounds from preclinical research to disease management is the design of effective clinical trials. The current scarcity of well characterised surrogate markers predicts that long-term studies in large numbers of patients will be needed to monitor changes in disease progression.

The two principal features of airway goblet cells are rapid secretion of mucin onto the airway surface and increase in number (hyperplasia) with chronic inhaled 'insult'. The first is associated with homeostasis, the latter with pathophysiology. Myristoylated alanine-rich C kinase (MARCKS) is a key molecule regulating mucin exocytosis, a process also involving cooperative interaction between protein kinase (PK) C and PKG. The epidermal growth factor (EGF) cascade and calcium activated chloride channels (CLCA) are key signalling molecules involved in development of goblet cell hyperplasia, with Bcl-2, an inhibitor of apoptosis, involved in maintenance of hyperplasia. Goblet cell hyperplasia and associated mucus hypersecretion is a pathophysiological feature of asthma and chronic obstructive pulmonary disease (COPD). Novel therapeutic strategies to prevent or reverse goblet cell hyperplasia include inhibitors of EGF receptor tyrosine kinase and CLCA, of which viable pharmaceutical molecules are now available for clinical trial in hypersecretory conditions of the airways.

Chronic obstructive pulmonary disease (COPD) is characterized by inflammation of the respiratory tract in which macrophages are the predominant inflammatory cell and for which the efficacy of treatment with corticosteroids is controversial. We investigated the effect of dexamethasone on basal and interleukin (IL)-1beta or cigarette smoke media (CSM)-stimulated release of IL-8 and granulocyte macrophage-colony stimulating factor (GM-CSF) by bronchoalveolar lavage macrophages from cigarette smokers and patients with COPD (n = 15). Basal release of IL-8 was approximately fivefold greater in patients with COPD than smokers, whereas GM-CSF was similar for each group. IL-1beta and CSM increased IL-8 and GM-CSF release by macrophages from both smokers and patients with COPD. Dexamethasone did not inhibit basal or stimulated IL-8 release from macrophages from patients with COPD but inhibited release in smokers. In contrast, basal and IL-1beta-stimulated GM-CSF release, but not CSM-stimulated release, was inhibited by dexamethasone. We conclude that the lack of efficacy of corticosteroids in COPD might be due to the relative steroid insensitivity of macrophages in the respiratory tract.

Background: In cystic fibrosis (CF), genetic mutations in the CF transmembrane conductance regulator (CFTR) gene cause reduced chloride efflux from ciliated airway epithelial cells. This results in a reduction in periciliary liquid (PCL) depth of the airway surface liquid due to associated reduced water efflux. PCL layer dehydration reduces mucociliary clearance (MCC), leading to airway obstruction (reduced airflow and inflammation due to pathogen invasion) with mucus plug formation. Summary: Rehydrating mucus increases MCC. Mucus hydration can be achieved by direct hydration (administering osmotic agents to set up an osmotic gradient), using CFTR modulators to correct dysfunctional CFTR, or it can be achieved pharmacologically (targeting other ion channels on airway epithelial cells). Key Messages: The molecular mechanisms of several therapies are discussed in the context of pre-clinical and clinical trial studies. Currently, only the osmotic agent 7% hypertonic saline and the CFTR ‘potentiator' VX-770 (ivacaftor) are used clinically to hydrate mucus. Emerging therapies include the osmotic agent mannitol (Bronchitol), the intracellular Ca2+-raising agent Moli1901/lancovutide, the CFTR potentiator sildenafil [phosphodiesterase type 5 (PDE5) inhibitor] and the CFTR ‘corrector' VX-809 (lumacaftor). Other CFTR correctors (e.g. ‘chemical chaperones') are also showing pre-clinical promise.

Chronic obstructive pulmonary disease (COPD) is characterized by a neutrophilic airway inflammation that can be demonstrated by examination of induced sputum. Theophylline has antiinflammatory effects in asthma, and in the present study we investigated whether a similar effect occurs in COPD patients treated with low doses of theophylline. Twenty-five patients with COPD were treated with theophylline (plasma level of 9-11 mg/L) for 4 weeks in a placebo-controlled, randomized, double-blind crossover study. Theophylline was well tolerated. Induced sputum inflammatory cells, neutrophils, interleukin-8, myeloperoxidase, and lactoferrin were all significantly reduced by about 22% by theophylline. Neutrophils from subjects treated with theophylline showed reduced chemotaxis to N-formyl-met-leu-phe (approximately 28%) and interleukin-8 (approximately 60%). Neutrophils from a healthy donor showed reduced chemotaxis (approximately 30%) to induced sputum samples obtained during theophylline treatment. These results suggest that theophylline has antiinflammatory properties that may be useful in the long-term treatment of COPD.

Asthma and chronic obstructive pulmonary disease (COPD) are common, severe inflammatory diseases of the respiratory tract for which there is an enormous pharmaceutical market. Current therapy for asthma is for the most part effective and comprises bronchodilators and anti-inflammatory glucocorticosteroids. In contrast, pharmacotherapy of COPD is much less effective. In addition, there are potentially undesirable side effects of current treatment of both conditions. Consequently, there are legitimate reasons for seeking alternative or additional therapies for asthma and COPD. There are theoretical reasons, supported by experimental evidence in animals, that sensory-efferent nerves and tachykinins, principally substance P and neurokinin A, contribute to the pathophysiology of asthma and COPD. In contrast, clinical studies to date using tachykinin receptor antagonists do not support a role for tachykinins in these conditions, most particularly asthma. However, confounding influences hinder adequate interpret...

Activation of nerves increases airway mucus secretion. The mucus derives from submucosal glands and epithelial goblet cells. Depending upon species and airway level, innervation comprises parasympathetic (cholinergic), sympathetic (adrenergic) and 'sensory-efferent' pathways. In all species studied, cholinergic mechanisms predominate, particularly in human airways. Muscarinic M3 receptors on the secretory cells mediate the cholinergic response. Tachykinins (substance P and neurokinin A) mediate the sensory-efferent response, acting via tachykinin NK1 receptors. Endogenous mechanisms regulate the magnitude of neurogenic secretion, including enzymes (degrade neurotransmitters), nitric oxide (NO) and vasoactive intestinal peptide (VIP) (regulate stimulated secretion), and muscarinic M2 autoreceptors (inhibit acetylcholine release). Exogenous opioids also inhibit neurogenic secretion prejunctionally. Both VIP and opioids act by opening large conductance, calcium-activated potassium (BK(Ca)) channels. Present understanding of neural control of mucus secretion in animal airways requires translation into human data. This information should lead to rational development of drugs for bronchial diseases in which neurogenic mucus hypersecretion contributes to pathophysiology, including chronic bronchitis and asthma.

We investigated the effect of MEN 11467 ((1R,2S)-2-N[1(H)indol-3-yl-carbonyl]-1-N-{Nα(p-tolylacetyl)-Nα(methyl)-D-3-(2-naphthyl)alanyl}diaminocyclohexane) on tachykinin-induced mucus secretion in ferret trachea in vitro and determined its effect on secretion by tracheae from allergic ferrets in response to allergen challenge. Repeated administration of [Sar9,Met(O2)11]-substance P ([Sar9]SP, 1 μM) maintained mucus output above control values for at least 1.75 h. MEN 11467 inhibited secretion in a concentration-dependent manner with maximal inhibition at 10 μM and an approximate IC50 of 0.3 μM. Inhibition by MEN 11467 (0.1 – 10 μM) was maintained, to varying degree, for at least 1.75 h after washout in the continued presence of [Sar9]SP. In electrically stimulated tracheae, tachykininergic neural secretion was virtually abolished by 1 μM MEN 11467. In tracheae from ovalbumin-sensitised animals, repeated administration of ovalbumin maintained mucus output above controls for 1.5 h. MEN 11467 inhibited ovalbumin-induced secretion in a concentration-dependent manner, with complete inhibition at 1 μM. Inhibition by MEN 11467 (1 and 10 μM) was maintained, to varying degree, after drug washout for the 1.5 h of ovalbumin stimulation. MEN 11467 1 μM did not affect secretion induced by either acetylcholine or histamine, whereas 10 μM MEN 11467 did inhibit agonist-induced secretion. We conclude that, in ferret trachea in vitro, MEN 11467 at concentrations of 0.1 – 1 μM is a long acting and selective inhibitor of tachykininergic-induced mucus secretion, and may have therapeutic potential for bronchial hypersecretion associated with allergic conditions, for example in asthma. Keywords: Airway, allergy, asthma, mucin, mucus, MEN 11467, respiratory tract, sensitisation, tachykinin receptor, tachykinin receptor antagonist Introduction Mucus secretion is a vital component of airway homeostasis, providing the ‘front-line' barrier to inhaled irritants. The rate of secretion is controlled by both humoral and neuronal mechanisms. In mammalian airways, the dominant neural control is cholinergic (Rogers, 2000a). Adrenergic neural mechanisms contribute little to control, particularly in human airways. Capsaicin-sensitive ‘sensory-efferent' nerves also control secretion, although their relative contribution varies with species (Rogers, 2000a). Asthma and chronic obstructive pulmonary disease (COPD) are two severe respiratory conditions that are associated with airway mucus hypersecretion (Liu et al., 1998a; Rogers, 2000b). In both conditions, abnormalities in neural control are implicated in pathophysiology. Consequently, investigation of the neural control of airway secretion is linked to design of therapeutic drugs for bronchial mucus hypersecretion. Preclinical test systems have, therefore, been developed to assess compounds with potential to inhibit neurogenic secretion. One such system is the in vitro ferret trachea. Neurogenic secretion in ferret trachea is mediated via cholinergic nerves and capsaicin-sensitive ‘sensory-efferent' nerves (Rogers, 2000a). Tachykinin receptor agonist studies (Geppetti et al., 1993; Meini et al., 1993) and tachykinin receptor antagonist studies using a range of peptide and non-peptide compounds (Ramarine et al., 1994; Khawaja et al., 1999) show that the sensory-efferent secretory response is mediated exclusively via tachykinin NK1 receptors. Thus, mucus secretion from the in vitro ferret trachea is a useful experimental system for investigating drugs acting at tachykinin NK1 receptors. Allergy is one component of asthma. Consequently, antigen-sensitized animals are commonly employed as models of allergic asthma (Chung, 1995). In guinea-pigs, the later-phase of antigen-induced tracheal plasma exudation is mediated via tachykinin interaction with tachykinin NK1 receptors (Bertrand et al., 1993a). The involvement of tachykininergic pathways in antigen-induced airway mucus secretion is not reported. In the present study, we used the pseudopeptide tachykinin NK1 receptor antagonist, MEN 11467 ((1R,2S)-2-N[1(H)indol-3-yl-carbonyl]-1-N-{Nα(p-tolylacetyl)-Nα (methyl)-D-3-(2-naphthyl) alanyl}diaminocyclohexane) (Cirillo et al., 1998), to study tachykininergic involvement in antigen-induced mucus secretion in ferret trachea in vitro. We used this antagonist because its long duration of action was required if antigen-induced neurogenic secretory responses were late in onset (Bertrand et al., 1993a). Firstly, we determined the inhibitory profile and duration of action of MEN 11467 against secretion induced by the selective tachykinin NK1 receptor agonist [Sar9,Met(O2)11]-substance P ([Sar9]SP). Secondly, we examined inhibition by MEN 11467 of electrically stimulated tissue in the presence of adrenoceptor and cholinoceptor blockade (i.e. tachykininergic neural secretion). Thirdly, we assessed the inhibitory profile and duration of action of MEN 11467 in tracheae from ovalbumin-sensitised animals challenged with ovalbumin (‘allergic' secretion). Finally, the selectivity of MEN 11467 for tachykininergic-induced mucus secretion was assessed using acetylcholine and histamine to induce secretion. We used 35SO4 as a mucus marker because it localises to secretory structures and is released upon stimulation (Gashi et al., 1987), and the released material has a molecular weight and buoyant density characteristic of a mucus glycoprotein (Davies et al., 1990).

Chronic obstructive pulmonary disease (COPD) is a severe chronic respiratory condition characterised by progressive, irreversible airflow limitation. It is common, affecting more than 16 million people in the United States and is the fourth highest cause of death. The worldwide incidence of COPD is increasing and, in parallel, the economic and social burden the disease incurs. The treatment of COPD is symptomatic, with no drugs currently available to halt the relentless progression of airflow obstruction. However, with a better understanding of the pathological features of the airway inflammation and alveolar destruction that characterises COPD, new therapeutic strategies are being developed. This article provides a critical evaluation of current pharmacotherapy in COPD, essentially bronchodilators (anticholinergics, beta 2-adrenoceptor agonists and theophylline) and corticosteroids, and an overview of international recommendations for their use.

Inhalation of ozone in normal subjects causes a neutrophilic inflammatory response in the airways. Pretreatment with inhaled corticosteroids reduces the inflammatory response to inhaled ozone in dogs. We undertook a double-blind, randomized, placebo-controlled, crossover study to investigate the effects of 2 wk of treatment with inhaled budesonide 800 microg twice daily or placebo prior to ozone exposure in humans. Fifteen (six male; mean age, 31.1 +/- 2.1 yr) healthy nonsmokers were exposed to 400 parts per billion (ppb) ozone for 2 h with intermittent exercise. Spirometry, exhaled carbon monoxide (CO) and nitric oxide (NO) levels, measurement of methacholine reactivity, and collection of exhaled air condensate and induced sputum samples were performed at baseline, preexposure, and at intervals up to 24 h postexposure. Ozone exposure led to significant decreases in spirometry and increased methacholine reactivity and sputum neutrophils and myeloperoxidase (MPO). There were no changes in exhaled NO and CO levels, or exhaled breath nitrite after ozone exposure. There were no differences in any of the parameters after treatment with budesonide compared with placebo, and no differences in the response to ozone between treatment groups. We conclude that a high dose of inhaled corticosteroid does not protect against the effects of ozone exposure in normal subjects.

We investigated whether vasoactive intestinal peptide (VIP) and its related peptides, pituitary adenylate cyclase activating peptide (PACAP) and secretin, regulate cholinergic neural mucus secretion in ferret trachea in vitro, using 35SO4 as a mucus marker. We also studied the interaction between VIP and secretin on cholinergic mucus output. VIP (1 and 10 μM) increased secretion, whereas neither PACAP1–27, PACAP1–38 nor secretin (up to 10 μM) increased mucus output. In contrast, VIP, PACAP1–27 and PACAP1–38 concentration-dependently inhibited cholinergic neural secretion, with an order of potency of VIP>PACAP 1–38>PACAP1–27. Neither PACAP1–27 nor PACAP1–38 altered the secretion induced by acetylcholine (ACh). Secretin increased cholinergic neural secretion with a maximal increase of 190% at 1 μM. This potentiation was blocked by VIP or atropine. Similarly, secretin (1 μM) potentiated VIP (1 μM)-induced mucus output by 160%. Secretin did not alter exogenous ACh-induced secretion. VIP vs secretin competition curves suggested these two peptides were competing reversibly for the same receptor. We conclude that, in ferret trachea in vitro, VIP and PACAPs inhibit cholinergic neural secretion via pre-junctional modulation of cholinergic neurotransmission. VIP and secretin compete for the same receptor, possibly a VIP1 receptor, at which secretin may be a receptor antagonist. British Journal of Pharmacology (1999) 128, 1353–1359; doi:10.1038/sj.bjp.0702942

Short-acting beta2-agonists provide greater protection against bronchoconstriction induced by adenosine 5'-monophosphate (AMP) than by direct-acting bronchoconstrictors such as histamine and methacholine. AMP is thought to cause bronchoconstriction via release of mediators from mast cells, which suggests that these drugs stabilize mast cells in vivo. This in vivo property has not yet been demonstrated for long-acting beta2-agonists. We undertook a double-blind, randomized, placebo-controlled, cross-over study to investigate the effects of a single dose of formoterol inhaled via Turbuhaler (12 micrograms) and of albuterol inhaled via Turbuhaler (200 micrograms) on airway responsiveness to AMP and histamine in 16 subjects with mild atopic asthma. Albuterol reduced airway responsiveness to AMP and histamine by 4.1 +/- 0.5 and 3.5 +/- 0.4 doubling doses, respectively. In contrast, formoterol caused a greater protective effect against AMP than against histamine challenge, decreasing airway responsiveness by 6.0 +/- 0.8 and 4.2 +/- 0.4 doubling doses, respectively (p0.05). Thus, the long-acting beta2-agonist formoterol appears to have a mast cell-stabilizing effect in vivo in mild asthma.

1. We investigated the inhibitory effects of the cysteinyl leukotriene (CysLT1) receptor antagonists, pranlukast and zafirlukast, on 35SO4 labelled mucus output, in vitro, in guinea-pig trachea, induced by leukotriene D4 (LTD4) or by antigen challenge of sensitized animals. Agonists and antagonists were administered mucosally, except in selected comparative experiments where drugs were administered both mucosally and serosally to assess the influence of the epithelium on evoked-secretion. 2. LTD4 increased 35SO4 output in a concentration-related manner with a maximal increase of 23 fold above controls at 100 microM and an approximate EC50 of 2 microM. Combined mucosal and serosal addition of LTD4 did not significantly affect the secretory response compared with mucosal addition alone. Neither LTC4 nor LTE4 (10 microM each) affected 35SO4 output. Pranlukast or zafirlukast significantly inhibited 10 microM LTD4-evoked 35SO4 output in a concentration-dependent fashion, with maximal inhibitions of 83% at 10 microM pranlukast and 78% at 10 microM zafirlukast, and IC50 values of 0.3 microM for pranlukast and 0.6 microM for zafirlukast. Combined mucosal and serosal administration of the antagonists (5 microM each) gave degrees of inhibition of mucosal-serosal 10 microM LTD4-evoked 35SO4 output similar to those of the drugs given mucosally. Pranlukast (0.5 microM) caused a parallel rightward shift of the LTD4 concentration-response curve with a pKB of 7. Pranlukast did not inhibit ATP-induced 35SO4 output. 3. Ovalbumin (10-500 microg ml(-1) challenge of tracheae from guinea-pigs actively sensitized with ovalbumin caused a concentration-related increase in 35SO4 output with a maximal increase of 20 fold above vehicle controls at 200 microg ml(-1). The combination of the antihistamines pyrilamine and cimetidine (0.1 mM each) did not inhibit ovalbumin-induced 35SO4 output in sensitized guinea-pigs. Neither mucosal (10 microM or 100 microM) nor mucosal-serosal (100 microM) histamine had any significant effect on 35SO4 output. 4. Pranlukast or zafirlukast (5 microM each) significantly suppressed ovalbumin-induced secretion in tracheae from sensitized guinea-pigs by 70% and 65%, respectively. 5 We conclude that LTD4 or ovalbumin challenge of sensitized animals provokes mucus secretion from guinea-pig trachea in vitro and this effect is inhibited by the CysLT1 receptor antagonists pranlukast and zafirlukast. These antagonists may be beneficial in the treatment of allergic airway diseases in which mucus hypersecretion is a clinical symptom, for example asthma and allergic rhinitis.

This report is based on a conference held at the National Heart & Lung Institute, London, UK (15–17 September 1997) entitled Conquering Airway Inflammation in the 21st Century. We are indebted to the following national and international speakers for their support and for allowing us to discuss data that are not yet published: Dr T. J. Torphy (SmithKline-Beecham, Philadelphia, USA), Dr A. Greening (University of Edinburgh, Edinburgh, UK), Dr A. J. Coyle (Millennium Pharmaceuticals, Boston, USA), Dr A. J. Lewis (Signal Pharmaceuticals, San Diego, USA), Dr C. Bertrand (Roche Biosciences, Palo Alto, USA), Dr C. J. Corrigan (Charing Cross Hospital, London, UK), Dr C-C. Chan (Merck Frosst Centre for Therapeutic Research, Montreal, Canada), Dr D. Cavalla (Napp Laboratories, Cambridge, UK), Dr D. W. P. Hay (SmithKline-Beecham, Philadelphia, USA), Dr H. Kankaanranta (University of Tampere, Tampere, Finland), Dr I. P. Hall (University of Nottingham, Nottingham, UK), Dr J. A. Mitchell (Royal Brompton Hospital, London, UK), Dr J. E. Souness (Rhone-Poulenc Rorer, Dagenham, UK), Dr J. W. Nyce (EpiGenesis Pharmaceuticals, Greenville, USA), Dr K. H. Banner (King's College, London, UK), Dr M. Johnson (Glaxo-Wellcome, Stockley Park, UK), Dr P. Ind (Royal Post-Graduate Medical School, London, UK), Dr P. Young (SmithKline-Beecham, Philadelphia, USA), Dr P. G. Hellewell [National Heart & Lung Institute (NHLI), London, UK], Dr R. Egan (Schering-Plough, Kenilworth, USA), Dr R. A. Coleman (Pharmagene, Hertfordshire, UK), Dr S. Green (University of Cincinnati, Cincinnati, USA), Dr S. Manzini (Menarini, Florence, Italy), Dr T. Wells (Glaxo Institute of Molecular Biology, Geneva, Switzerland), Dr V. Cohan (Pfizer, Groton, USA), Dr W. Cookson (John Radcliffe Hospital, Headington, Oxford, UK), Dr A. J. Knox (City Hospital, Nottingham, UK), Dr B. J. O'Connor (King's College Hospital, London, UK), Professor A. B. Kay (NHLI, London, UK), Professor J. Westwick (University of Bath, Bath, UK), Professor P. J. Barnes (NHLI, London, UK), Professor S. T. Holgate (Southampton General Hospital, UK) and Professor T. J. Williams (NHLI, London, UK). We apologize to those whose work was not cited owing to space limitation. The second meeting will be held on 14–16 September 1998. More information is available from http://www.nhli.ic.ac.uk/mtgs.htm#dg

1. Opioid agonists inhibit neurogenic mucus secretion in the airways. The mechanism of the inhibition is unknown but may be via opening of potassium (K+) channels. We studied the effect on neurogenic secretion in ferret trachea in vitro of the OP1 receptor (formerly known as delta opioid receptor) agonist [D-Pen2,5]enkephalin (DPDPE), the OP2 receptor (formely kappa) agonist U-50,488H, the OP3 receptor (formerly micro) agonist [D-Ala2, N-Me-Phe, Gly-ol5]enkephalin (DAMGO), the ATP-sensitive K+ (K(ATP)) channel inhibitor glibenclamide, the large conductance calcium activated K+ (BK(Ca)) channel blocker iberiotoxin, the small conductance K(Ca) (SK(Ca)) channel blocker apamin, the K(ATP) channel opener levcromakalim, a putative K(ATP) channel opener RS 91309, and the BK(Ca) channel opener NS 1619. Secretion was quantified by use of 35SO4 as a mucus marker. 2. Electrical stimulation increased tracheal secretion by up to 40 fold above sham-stimulated levels. DAMGO or DPDPE (10 microm each) significantly inhibited neurogenic secretion by 85% and 77%, respectively, effects which were reversed by naloxone. U-50,488H had no significant inhibitory effect on neurogenic secretion, and none of the opioids had any effect on ACh-induced or [Sar9]substance P-induced secretion. 3. Inhibition of neurogenic secretion by DAMGO or DPDPE was reversed by iberiotoxin (3 microM) but not by either glibenclamide or apamin (0.1 microM each). Iberiotoxin alone did not affect the neurogenic secretory response. 4. Levcromakalim, RS 91309 or NS 1619 (3 nM-3 microM) inhibited neurogenic secretion with maximal inhibitions at 3 microM of 68%, 72% and 96%, respectively. Neither levcromakalim nor RS 91309 at any concentration tested significantly inhibited acetylcholine (ACh)-induced secretion, whereas inhibition (60%) was achieved at the highest concentration of NS 1619, a response which was blocked by iberiotoxin. 5. Inhibition of neurogenic secretion by levcromakalim (3 microM) or RS 91309 (30 nM) was inhibited by glibenclamide but not by iberiotoxin. In contrast, inhibition by NS 1619 (30 nM and 3 microM) was blocked by iberiotoxin but not by glibenclamide. 6. We conclude that, in ferret trachea in vitro, OP1 or OP3 opioid receptors inhibit neurogenic mucus secretion at a prejunctional site and that the mechanism of the inhibition is via opening of BK(Ca) channels. Direct opening of BK(Ca) channels or K(ATP) channels also inhibits neurogenic mucus secretion. In addition, opening of BK(Ca) channels inhibits ACh-evoked secretion of mucus. Drugs which open BK(Ca) channels may have therapeutic anti-secretory activity in bronchial diseases in which neurogenic mechanisms and mucus hypersecretion are implicated in pathophysiology, for example asthma and chronic bronchitis.

There is a continuing need for development of new treatments for lung disease. Basic scientific investigations are identifying novel targets for the development of new approaches to therapy of a range of respiratory conditions. Coupled with the advances in technology being harnessed by the pharmaceutical and biotechnological industries, there is now an impressive range of potential treatments including gene therapy, not just for cystic fibrosis but also for a range of inflammatory lung conditions, anti-cytokine and anti-adhesion molecule approaches, and targeting of intracellular signal transduction pathways including cyclic AMP metabolism, tyrosine kinases and MAP kinases. "Old" molecules such as heparin and secretory leukoprotease inhibitor (SLPI) are demonstrating new beneficial activities. Simple molecules such as nitric oxide (NO) gas may be involved in the pathophysiology of different airway conditions. It is an exciting time for respiratory science and a time for optimism for those seeking new approaches to the treatment of lung diseases.

BACKGROUND: Sputum induction is becoming more commonly used to assess airway inflammation. Since it is a relatively non-invasive procedure it may be useful for repeated measurements over a short period of time. METHODS: To assess the repeatability of the method over a 24 hour period, eight healthy, non-smoking, non-atopic subjects (four men) of mean age 30 years underwent sputum induction, repeated at eight hours and 24 hours. Sputum was induced by inhalation of 3.5% saline. Absolute and differential counts of inflammatory cells were performed on the whole sputum after dilution in Hank's balanced salt solution containing 1% dithiothreitol to solubilise the mucus content of the samples. RESULTS: There was a significant rise in the percentage of neutrophils in the eight hour sample compared with the baseline (57%, range 25-94% at eight hours compared with 28%, range 19-60%: median difference 26%). The median baseline percentage of macrophages was 55% (range 26-69%) which fell to 38% (range 3-56%: median difference 22%) at eight hours and 19% (range 14-59%: median difference 25%) at 24 hours. There was no significant change in the differential counts of eosinophils, lymphocytes or columnar epithelial cells, nor in any of the absolute cell counts, at any time point. CONCLUSIONS: Sputum induction may have limited utility in serial assessment of neutrophilic airway inflammation in normal subjects within a 24 hour period.

1. We investigated the effect of acute inhalation of cigarette smoke on subsequent non-adrenergic, non-cholinergic (NANC) neural bronchoconstriction in anaesthetized guinea-pigs in vivo by use of pulmonary insufflation pressure (PIP) as an index of airway tone. The contribution of endogenous nitric oxide (NO) was investigated with the NO synthase inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME). The contribution of plasma exudation to the response was investigated with Evans blue dye as a plasma marker. 2. Inhalation of 50 tidal volumes of cigarette smoke or air had no significant effect on baseline PIP. In the presence of propranolol and atropine (1 mg kg(-1) each), electrical stimulation of the vagus nerves in animals given air 30 min previously induced a frequency-dependent increase in PIP above sham stimulated controls (16 fold increase at 2.5 Hz, 24 fold increase at 10 Hz). In contrast, in smoke-exposed animals, the increase in subsequent vagally-induced PIP was markedly less than in the air controls (90% less at 2.5 Hz, 76% less at 10 Hz). 3. L-NAME (10 mg kg[-1]), given 10 min before air or smoke, potentiated subsequent vagally-induced (2.5 Hz) NANC bronchoconstriction by 338% in smoke-exposed animals, but had no significant effect in air-exposed animals. The inactive enantiomer D-NAME (10 mg kg[-1]) had no effect, and the potentiation by L-NAME was partially reversed by the NO-precursor L-arginine (100 mg kg[-1]). Vagal stimulation did not affect the magnitude of vagally-induced bronchoconstriction 30 min later. 4. Cigarette smoke exposure reduced the magnitude of subsequent bronchoconstriction induced by neurokinin A (NKA) by 37% compared with the effect of NKA in air-exposed animals. L-NAME had no significant effect on the smoke-induced inhibition of NKA-induced bronchoconstriction. 5. Vagally-induced plasma exudation in the main bronchi was greater in smoke-exposed animals compared with air-exposed animals (120% greater at 2.5 Hz, 82% greater at 10 Hz). 6. We conclude that cigarette smoke-induced inhibition of subsequent NANC neurogenic bronchoconstriction is not associated with inhibition of airway plasma exudation and is mediated in part via exogenous smoke-derived NO, or another bronchoprotective molecule, and by endogenous NO.

1. Muscarinic receptor subtypes mediating neurogenic mucus secretion in ferret trachea were characterized in vitro and in vivo using 35SO4 as a label for secreted mucus, and the muscarinic receptor antagonists telenzepine for the M1 receptor subtype, methoctramine for the M2 subtype and 4-diphenylacetoxy-N-methylpiperidine methobromide (4-DAMP) for the M3 receptor. We also performed receptor binding and mapping studies. 2. Each muscarinic antagonist displaced [N-methyl-3H]scopolamine binding with high-affinity binding constant (KH) values of 1.9, 2.7 and 5.0 nM for telenzepine, methoctramine and 4-DAMP, respectively. Muscarinic M1 and M3 receptors localized to submucosal glands, whereas M2 receptors did not. 3. In vitro, electrical stimulation (50 V, 10 Hz, 0.5 ms for 5 min) increased 35SO4 output by 160%. Telenzepine did not inhibit the neurogenic secretory response at concentrations two-or twentyfold its KH value, nor did it inhibit secretion induced by acetylcholine (ACh). 4-DAMP inhibited neurogenic secretion by 80 and 95%, respectively, at concentrations two-and twentyfold its KH value, and also inhibited ACh-induced secretion. Methoctramine potentiated neurogenic secretion induced at 2.5 Hz (50 V, 0.5 ms for 5 min) in a dose-related (5.4-100 nM) manner with increases of 33-451% above electrically stimulated values. Methoctramine did not potentiate secretion induced at 10 Hz and did not have any effect on ACh-induced secretion. 4. In vivo, vagal stimulation (10 V, 10 Hz, 2 ms for 8 min) increased output of 35SO4 by approximately 120%. Telenzepine had no significant effect on neurogenic secretion. Methoctramine approximately doubled the stimulated response, whereas 4-DAMP abolished the stimulated secretory response. 5. We conclude that in ferret trachea, cholinergic nerve stimulation increases mucus secretion via muscarinic M3 receptors on the submucosal glands. The magnitude of the secretory response is regulated by neuronal M2 muscarinic receptors. The muscarinic M1 receptors localized to the submucosal glands do not appear to be involved with mucus secretion.

1. Cigarette smoke induces plasma exudation in the airways of rodents by activation of capsaicin-sensitive 'sensory-efferent' nerves. The response is mediated predominantly by substance P (SP) and the magnitude of exudation is regulated by neutral endopeptidase (NEP). The component(s) of the smoke responsible for the activation of the nerves may be reactive oxygen radicals. We investigated the effect of the hydroxyl radical scavenger dimethylthiourea (DMTU), a regulator of superoxide anion, superoxide dismutase (SOD), and a regulator of hydrogen peroxide, catalase, on plasma exudation (measured using Evans blue dye) induced by cigarette smoke in guinea-pig main bronchi in vivo. The effect of DMTU on plasma exudation and non-cholinergic bronchoconstriction (measured as pulmonary insufflation pressure, PIP) induced by electrical stimulation of the vagus nerves was also assessed. Interaction between hydroxyl radicals and NEP was assessed with the NEP inhibitor phosphoramidon. 2. In each of the experiments, cigarette smoke increased plasma exudation by approximately 200% above air-exposed controls. Acute administration of DMTU (1.5 g kg-1, i.v. for 20 min) significantly reduced cigarette smoke-induced plasma exudation by 69%. In contrast, neither SOD (240,000 u kg-1, i.v.) nor catalase (400,000 u kg-1, i.v.) significantly affected the exudative response. 3. Chronic pretreatment with DMTU (1.25 g kg-1 over 4 days) significantly reduced bronchial plasma exudation induced by cigarette smoke by 72%. Phosphoramidon (1.5 mg kg-1, i.v.) completely reversed the inhibition by DMTU of cigarette smoke-induced plasma exudation. 4. Vagal stimulation increased plasma exudation by approximately 200% and PIP by approximately 250%. Acute treatment with DMTU had no significant inhibitory effect on these responses, whereas chronic pretreatment inhibited them by approximately 80%. Phosphoramidon reversed the inhibition by chronic DMTU. 5. SP (1 nmol kg-1) increased plasma exudation by approximately 250%, a response which was not inhibited by either acute or chronic DMTU. 6. We conclude that hydroxyl radicals, rather than superoxide anion or hydrogen peroxide, are involved in the induction of neurogenic plasma exudation and bronchoconstriction induced by cigarette smoke or by electrical stimulation of the vagus nerves. These radicals also affect the activity of NEP. Acute DMTU may affect directly the neural actions of hydroxyl radicals contained in the cigarette smoke. Chronic pretreatment with DMTU may inhibit the neurogenic airway responses by effects on tachykinin biosynthesis and/or axonal transport.

Background Exacerbations of chronic bronchitis or chronic obstructive pulmonary disease (COPD) are a significant health burden. A substantial component of these exacerbations in many patients is mucus-hypersecretion. Mucolytics, drugs that ‘thin’ mucus, have potential efficacy in these patients. Currently, erdosteine is the only mucolytic in the British National Formulary (BNF) indicated for “symptomatic treatment of acute exacerbations of chronic bronchitis”, while other BNF mucolytics (carbocisteine, mecysteine and N-acetylcysteine) have had more general or non-respiratory indications, e.g. “reduction in sputum viscosity”. It is theorised that there is clinical evidence that erdosteine is useful in treatment of acute exacerbations of chronic bronchitis, unlike any of the other aforementioned mucolytics. Methods In this narrative systematic review, databases utilised included: Medline, Embase and PubMed. Studies for inclusion had to be Randomised Controlled Trials (RCTs) primarily investigating the effect of erdosteine in exacerbations of chronic bronchitis or COPD. For comparison, RCTs were also included if they investigated carbocisteine, mecysteine and N-acetylcysteine’s effects in exacerbations. A secondary outcome was to investigate the use of these mucolytics in improving COPD signs and symptoms. Once selected, a two-stage publication elimination process was devised by the author to assess the quality of the trials. Results Very few trials of adequate quality assessed the efficacy of mucolytics in chronic bronchitis or COPD. Of the 5,560 search results, only 62 trials investigated the aforementioned mucolytics use in chronic bronchitis or COPD, 41 were RCTs. Of the 41 RCTs only 13 were found to be of adequate quality; erdosteine (1 RCT), carbocisteine (3 RCTs), mecysteine (0 RCTs) and N-acetylcysteine (9 RCTs). There was no evidence that erdosteine is useful in treating exacerbations, and very limited, weak evidence for some efficacy in exacerbation prevention. In contrast, carbocisteine showed some strong evidence of efficacy in preventing exacerbations, especially in Asian populations. N-acetylcysteine trial results were variable, and evenly distributed between positive and no effects, with one study showing adverse effects. There were no trials of adequate quality investigating mecysteine. Conclusion There is little evidence that erdosteine is useful in treating chronic bronchitis exacerbations, whereas, overall carbocisteine seems to be more efficacious in exacerbation prevention.

La secretion de mucus peut etre induite dans les voies aeriennes par l'activation des nerfs. Le mecanisme du processus induisant la secretion neurogene de mucus est cholinergique. Toutefois, il subsiste une reponse secretrice faible mais significative apres un blocage des adrenorecepteurs et des cholinorecepteurs. Ce mecanisme neural non adrenergique, non cholinergique (NANC) n'est pas clair, mais on sait qu'il comporte une voie orthodromique et une voie « efferente sensitive » (ou « effectrice locale ») sensible a la capsaicine. La voie orthodromique est constituee de nerfs cholinergiques (et a un degre beaucoup plus faible de nerfs adrenergiques) dont les neuropeptides, incluant le peptide intestinal vasoactif (VIP) et le neuropeptide tyrosine (NPY), sont localises et co-liberes avec le neurotransmetteur classique. L'etude de la contribution de la voie neurale orthodromique a la secretion neurogene necessite l'elaboration d'antagonistes de recepteurs specifiques pour le VIP et le NPY. Le peptide lie au gene de la calcitonine et les tachykinines substance P et neurokinine A sont des neurotransmetteurs de la voie neurale efferente sensitive. L'ordre de puissance des tachykinines naturelles et des agonistes synthetiques selectifs des recepteurs de tachykinines indique que le recepteur NK 1 de la tachykinine est ubiquiste pour les processus secreteurs des voies aeriennes, incluant la secretion de mucus et le transport d'ions. Les etudes sur les antagonistes montrent que la reponse secretrice muqueuse neurale NANC est induite en tres grande partie via les recepteurs NK 1 et peu ou pas via les recepteurs NK 2 . On ne sait encore quelle attention accorder au role physiologique de la voie neurale efferente sensitive ; cependant, il pourrait prendre de l'importance dans les maladies inflammatoires chroniques associees a l'hypersecretion des muqueuses, par exemple, dans l'asthme et la bronchite chronique, ou l'activite neurale efferente sensible semble augmenter.

We characterized plasma exudation induced by direct inhalation of cigarette smoke in anesthetized, artificially ventilated guinea pigs, using Evans blue dye as a plasma marker, and investigated the neurogenic mechanisms underlying the response. Cigarette smoke increased plasma exudation in the lower trachea, main bronchi, and proximal intrapulmonary airways in a dose-related manner. Exudation was rapid in onset and was maintained for 0.5 to 2 h, depending upon airway level. Exudation was not reduced after removal of the particular phase of the smoke, nor by atropine, phentolamine, propranolol, hexamethonium, antihistamines, or bilateral vagotomy. Nicotine, at a dose calculated to approximate that in the plasma of cigarette-exposed animals, did not increase airway plasma exudation. Cigarette smoke-induced exudation was blocked by capaicinization or by a substance P antagonist and was potentiated by phosphoramidon but not by captopril. Nedocromil sodium or morphine (0.1 mg/kg each intravenously) partially inhibited cigarette smoke-induced exudation but had no effect on the response to substance P. Inhibition by morphine, but not that by nedocromil sodium, was reversed by naloxone. Thus, direct inhalation of cigarette smoke induces a dose-related, long-lasting increase in airway plasma exudation that is due to vapor-phase activation of sensory-efferent nerves, release of sensory neuropeptides that mediate the exudative response via interaction with substance P receptors, and regulation by neutral endopeptidase. The inhibitory effect of nedocromil and morphine on cigarette smoke-induced airway plasma exudation occurs through inhibition of neurotransmission. Lei Y-H, Barnes PJ, Rogers DF. Mechanisms and modulation of airway plasma exudation after direct inhalation of cigarette smoke. Am J Respir Crit Care Med 1995 ;151 :1752-62.

Trimellitic anhydride is a cause of occupational asthma in humans. We have previously found that tracheal instillation of trimellitic anhydride conjugated to guinea pig serum albumin induces acute bronchoconstriction and airway plasma exudation in sensitised animals, responses mediated primarily via histamine release. In the present study, neural mechanisms mediating bronchoconstriction and goblet cell secretion were determined in trimellitic anhydride-sensitised guinea pigs using the ganglionic blocker hexamethonium to eliminate efferent reflex mechanisms, pretreatment with capsaicin to eliminate afferent mechanisms, or cimetidine and mepyramine to eliminate histamine-mediated mechanisms. The magnitude of secretion of intracellular mucus from tracheal goblet cells was quantified morphometrically as a mucus score which is inversely related to the degree of discharge. Guinea pigs were injected intradermally either with 0.1 ml 0.3% trimellitic anhydride in corn oil or with corn oil alone as control. Fourteen to eighteen days later all sensitised animals had developed specific immunoglobulin (Ig) G1 antibodies whereas the controls had not. Tracheal instillation of conjugated trimellitic anhydride in anaesthitised animals significantly increased airway lung resistance ( R L ) 24-fold in sensitised guinea pigs (34.3 ± 7.9 cm H 2 O · ml −1 · s) compared with controls (1.4 ± 0.1 cm H 2 O · ml −1 · s). Mucus score was significantly reduced by 51% (indicating goblet cell secretion) in sensitised guinea pigs (183 ± 22 mucus score units) compared with controls (372 ± 41 mucus score units). The antihistamines significantly inhibited conjugated trimellitic anhydride-induced bronchoconstriction by 89%, but did not significantly affect goblet cell discharge. Hexamethonium alone did not significantly affect conjugated trimellitic anhydride-induced bronchoconstriction or goblet cell secretion. Capsaicin pretreatment (in combination with hexamethonium) significantly inhibited golet cell discharge (by 80%) but had no significant effect on bronchoconstriction. We conclude that conjugated trimellitic anhydride challenge of trimellitic anhydride-sensitised guinea pigs induces goblet cell discharge and bronchoconstriction via different mechanisms with activation of capsaicin-sensitive sensory nerves responsible for secretion and histamine release responsible for airway constriction. The guinea pig model of trimellitic anhydride-induced occupational asthma may prove useful in examination of mechanisms of goblet cell secretion in allergic diseases.

Background Therapeutic intervention in the pathophysiology of airway mucus hypersecretion is clinically important. Several types of drugs are available with different possible modes of action. We examined the effects of guaifenesin (GGE), N-acetylcysteine (NAC) and ambroxol (Amb) on differentiated human airway epithelial cells stimulated with IL-13 to produce additional MUC5AC. Methods After IL-13 pre-treatment (3 days), the cultures were treated with GGE, NAC or Amb (10–300 μM) in the continued presence of IL-13. Cellular and secreted MUC5AC, mucociliary transport rates (MTR), mucus rheology at several time points, and the antioxidant capacity of the drugs were assessed. Results IL-13 increased MUC5AC content (~25%) and secretion (~2-fold) and decreased MTR, but only slightly affected the G’ (elastic) or G” (viscous) moduli of the secretions. GGE significantly inhibited MUC5AC secretion and content in the IL-13-treated cells in a concentration-dependent manner (IC50s at 24 hr ~100 and 150 μM, respectively). NAC or Amb were less effective. All drugs increased MTR and decreased G’ and G” relative to IL-13 alone. Cell viability was not affected and only NAC exhibited antioxidant capacity. Conclusions Thus, GGE effectively reduces cellular content and secretion of MUC5AC, increases MTR, and alters mucus rheology, and may therefore be useful in treating airway mucus hypersecretion and mucostasis in airway diseases.

1. We characterized the tachykinin receptor(s) mediating 'sensory-efferent' neural control of release of 35SO4-labelled macromolecules (mucus) from ferret trachea in vitro in Ussing chambers using selective tachykinin antagonists. Secretion was induced by substance P (SP), neurokinin A (NKA), capsaicin, the NK1 tachykinin receptor agonist [Sar9, Met(O2)11]substance P ([Sar9]SP), or acetylcholine (ACh), or by electrical stimulation of nerves. Antagonists used were FK888 and L-668,169, selective for the NK1 receptor, SR 48968, selective for the NK2 receptor, and FK224, a dual antagonist at NK1 and NK2 receptors. The selectivity of FK888 and SR 48968 was examined on NKA-induced contraction of ferret tracheal smooth muscle in vitro. 2. SP (1 microM) increased mucus secretion by 695% above vehicle controls. FK888 (0.1 microM-30 microM) inhibited SP-induced secretion in a dose-dependent manner, with complete inhibition at 10 microM and an IC50 of 1 microM. L-668,169 (1 microM) also completely inhibited SP-induced secretion. 3. NKA (1 microM) significantly increased mucus secretion by 271% above baseline, a response which was completely inhibited by FK888 (10 microM) or L-668,169 (microM). Secretion induced by ACh (10 microM: 317% above baseline) was not inhibited by FK888 but was inhibited by atropine. Capsaicin (10 microM)-induced secretion (456% above vehicle controls) was significantly inhibited by FK888 and by L-668,169 (111% and 103% inhibition respectively). 4. Electrical stimulation (50 V, 10 Hz, 0.5 ms, 5 min) increased mucus output above baseline (increased by 12 to 26 fold), a response blocked by tetrodotoxin (0.1 microM). FK888 (10 microM) inhibited the increase in secretion due to electrical stimulation by 47%. Atropine, propranolol and phentolamine in combination(APP) inhibited the response to electrical stimulation by 48%. The remaining NANC response, i.e. in the presence of APP, was further reduced by 66% with FK888. FK224 (10 microM) inhibited neurally evoked secretion by 73%. SR 48968 (0.1 fLM) had no effect on electrically-stimulated or [Sar9]SP-induced secretion.5. NKA (10nM- 1O microM: in the presence of DMSO control vehicle) induced tracheal smooth muscle contraction in a concentration-dependent manner with a maximal contraction of 30% of the maximal response to ACh (10 mM) and an ECm of 0.3 JAM. SR 48968 (0.1 microM in DMSO) inhibited the NKA induced contraction whereas FK888 did not. Neither antagonist had any inhibitory effect on ACh induced contraction.6. We conclude that 'sensory-efferent' neurogenic mucus secretion in ferret trachea in vitro is mediated via tachykinin NK, receptors with no involvement of NK2 receptors. Potent and selective tachykinin antagonists may have therapeutic potential in bronchial diseases such as asthma and chronic bronchitis in which neurogenic mucus hypersecretion may be aetiologically important.

Baseline and agonist-stimulated secretion of fucose, hexose, and protein (markers of mucus secretion) was investigated in vitro in 45 bronchial segments from 14 patients with cystic fibrosis (CF) (three after heart-lung transplant, the remainder < 4.5 h after autopsy), in 51 segments from 26 patients with carcinoma (24 resection, 2 after autopsy), and in 4 segments from 3 patients with bronchiectasis (resection). Basal rates of secretion of each mucus marker by CF bronchi were not significantly different from those by carcinoma bronchi bronchiectatic bronchi. However, rates of secretion of each marker in response to the cholinomimetic methacholine (10 microM; n = 11-18, depending on marker) and the beta 2-adrenoceptor agonist terbutaline (10 microM; n = 9-11) were significantly (p < .05) increased in carcinoma bronchi (by 50-117% above basal), but not in CF airways (n = 11-14). The secretory response to the sensory neuropeptide substance P (1 nM to 10 microM; n = 5-7) was also reduced in CF compared with carcinoma bronchi. Physiological and morphological data indicated that the reduced response by CF tissue could not be accounted for by inclusion of autopsy tissue in the study. These data suggest a defect in autonomic control of bronchial secretion in CF, not in the basal rate of secretion, but in its response to receptor stimulation.

Gross pathology, histological and ultrastructural observations and analysis of sputum and lavage fluid indicate that plasma exudation from the bronchial microvasculature and the formation of tissue oedema are characteristic features of asthma. Appropriate mediators for the induction of plasma exudation are generated in the blood and airways of asthmatic patients and when administered experimentally will cause plasma leakage and oedema. Plasma exudate may not only contribute directly to the thickened bronchial walls and mucus plugs in the airways of asthmatics, but may also play a role in epithelial shedding, thickening of the basement membrane, hypertrophy of the smooth muscle, inducing mucus secretion and in thickening the secreted mucus. The beneficial effect of corticosteroids in asthma may be due to an anti-leakage action. Development of drugs with a broad spectrum of action against mediator release may have therapeutic advantage over specific receptor antagonist drugs.

Airway mucus hypersecretion is a pathophysiological feature of asthma and, in many patients, contributes to morbidity and mortality. Although current pharmacotherapy is effective in patients with stable disease, severe asthma is poorly treated, and there is no specific treatment for the hypersecretion. Consequently, identification of potential targets for pharmacotherapy of hypersecretion in asthma is warranted. This review identifies intracellular signalling pathways as rational targets for treatment of excessive airway mucus production.The inflammatory mediators and the associated intracellular signalling pathways underlying development of goblet cell hyperplasia, an index of mucus hypersecretion, are becoming ever clearer, and include T-helper type 2 (Th2) cytokines, in particular interleukin (IL)-9 and IL-13, as well as IL-1beta, tumour necrosis factor (TNF)-alpha and cyclooxygenase (COX)-2. IL-9 may act predominantly via calcium-activated chloride channels (CLCAs), IL-13 via STAT-6 and FOXA2, TNF-alpha via nuclear factor (NF)-kappaB, and IL-1beta via COX-2. Epidermal growth factor receptor (EGF-R) and FOXA2 appear to be convergent pathways for a number of mediator signals, with EGF-R up-regulated in the airways of asthmatic patients.Although many potential intracellular signalling pathways have been identified as possible targets for pharmacotherapy of airway mucus hypersecretion in asthma, the EGF-R and Th2 cytokine pathways offer the greatest potential for inhibition of excessive mucus production.

Publisher Summary The chapter addresses the above issues by discussion of similarities and differences in the pulmonary inflammatory “profile” between asthma and chronic obstructive pulmonary disease (COPD) and how these may relate to the generation of the airway mucus hypersecretory state in the two conditions. It begins with consideration of sputum, airway mucus, and mucins, followed by an outline of the characteristics of mucus hypersecretion in asthma and COPD, emphasizing differences between the two conditions and the theoretical requirements for drugs aimed at effectively inhibiting airway mucus hypersecretion. Patients with asthma or COPD invariably exhibit characteristics of airway mucus hypersecretion, comprising sputum production, excessive mucus in the airway lumen, goblet cell hyperplasia, and submucosal gland hypertrophy. The pathophysiological sequelae of mucus hypersecretion are airway obstruction, airflow limitation, ventilation-perfusion mismatch, and impairment of gas exchange. The association of airway mucus hypersecretion with asthma and COPD is not necessarily cause and effect. The excess mucus may merely be a result of the inflammatory processes causing the disease. Consequently, treating the mucus problem will not inevitably treat the disease, especially if the changes that have led to increased mucus production are irreversible. Production of airway mucus is a vital homeostatic mechanism that protects the respiratory tract from a barrage of inhaled insult. However, abnormal production of mucus can contribute to respiratory disease. Airway obstruction by mucus is a common feature of a number of severe respiratory conditions, including asthma and COPD. At present, there is considerable interest in inhibitors of EGF receptor tyrosine kinases, MEK/ERK, and CLCA channels to suppress goblet cell hyperplasia, and in molecules to selectively interfere with mucin exocytosis and thereby inhibit airway mucus hypersecretion.

Most patients with chronic obstructive pulmonary disease (COPD) exhibit characteristics of airway mucus hypersecretion, namely sputum production, increased luminal mucus, submucosal gland hypertrophy and goblet cell hyperplasia. The clinical consequences of hypersecretion are impaired gas exchange and compromised mucociliary clearance, which encourages bacterial colonization and associated exacerbations. However, the extent of the contribution of mucus to pathophysiology of COPD is controversial. Early epidemiological studies found little evidence for the involvement of mucus in the age-related decline in lung function and mortality associated with COPD and concluded that chronic airflow obstruction and mucus hypersecretion were independent processes. Later studies found positive associations between phlegm production and decline in lung function, hospitalization and death. Thus, although not diagnostic for the condition, mucus hypersecretion contributes to morbidity and mortality in certain groups of patients with COPD. This suggests that it is important to develop drugs that inhibit mucus hypersecretion in these patients. Unfortunately, ambiguity in clinical studies of mucoactive drugs means that mucolytics are not recommended in clinical management. Future research should determine whether there is an intrinsic abnormality in mucus in COPD, which will determine development of appropriate inhibitors, which in turn can be used in 'proof of concept' and in treatment.