Long duration and high potency of antiexudative effects of formoterol in guinea-pig tracheobronchial airways

Capsaicin suppresses ciliary function, while inducing permeability in bronchial epithelial cell cultures of COPD patients

Take Home Message: Capsaicin modified inflammatory response and caused toxicity in bronchial epithelial cultures from patients with COPD. More importantly, capsaicin decreased ciliary beat frequency and induced epithelial permeability and these effects were partially prevented by formoterol and roflumilast.

Tear gas is widely used to halt mass demonstrations. Studies have reported its adverse effects on multiple organ systems; however, its effect on individuals with chronic respiratory diseases and the underlying mechanisms of these effects are unclear. For the first time in the literature, we investigated the effects of capsaicin, the active ingredient of tear gas, on bronchial epithelial cell (BEC) cultures obtained from well-characterized groups of nonsmokers, smokers, and patients with chronic obstructive pulmonary disease (COPD). BEC cultures were incubated with 50-500 μM capsaicin in the absence and presence of formoterol (1μM) and roflumilast (0.1 μM) for 24 h. Ciliary beat frequency (CBF) and transepithelial electrical resistance (TEER) were assessed at T1/4, T1/2, T1, T2, T4, T6, and T24 h, whereas the release of granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin (IL)-8, and lactate dehydrogenase (LDH) was measured at T24 h. Capsaicin (250 µM) significantly decreased CBF of all BEC cultures from T1/4 h to T24 h (p<0.05). Formoterol significantly prevented decreases in CBF induced by capsaicin. Higher concentrations of capsaicin (250-500 μM) significantly reduced TEER of BECs from nonsmokers (T2-T24 h), smokers (T24 h) and COPD patients (T2 and T24 h), which was partially prevented by roflumilast. Capsaicin (500 μM) decreased release of IL-8 (p<0.0001) and GM-CSF (p<0.05) while inducing release of LDH in BECs (p<0.05), and this was more prominent in BEC from patients with COPD. In conclusion, our findings demonstrate that capsaicin can suppress ciliary activity and cytokine release from BECs, induce BEC culture permeability and cellular toxicity and that these effects can be partially prevented by formoterol and roflumilast.

Back to the future: re-establishing guinea pig in vivo asthma models

Research using animal models of asthma is currently dominated by mouse models. This has been driven by the comprehensive knowledge on inflammatory and immune reactions in mice, as well as tools to produce genetically modified mice. Many of the identified therapeutic targets influencing airway hyper-responsiveness and inflammation in mouse models, have however been disappointing when tested clinically in asthma. It is therefore a great need for new animal models that more closely resemble human asthma. The guinea pig has for decades been used in asthma research and a comprehensive table of different protocols for asthma models is presented. The studies have primarily been focused on the pharmacological aspects of the disease, where the guinea pig undoubtedly is superior to mice. Further reasons are the anatomical and physiological similarities between human and guinea pig airways compared with that of the mouse, especially with respect to airway branching, neurophysiology, pulmonary circulation and smooth muscle distribution, as well as mast cell localization and mediator secretion. Lack of reagents and specific molecular tools to study inflammatory and immunological reactions in the guinea pig has however greatly diminished its use in asthma research. The aim in this position paper is to review and summarize what we know about different aspects of the use of guinea pig in vivo models for asthma research. The associated aim is to highlight the unmet needs that have to be addressed in the future.

Comparing clinical efficacy of Symbicort versus Pulmicort in reducing asthma symptom and improving its control

Background:

Recently, higher efficacy of the combination of long-acting beta2-adrenoceptor agonist and inhaled corticosteroids on controlling asthma symptoms has been hypothesized. This study aimed to examine the clinical effects of the combination of Budesonide with formoterol (Symbicort) and Budesonide (Pulmicort) alone in persistent asthma.

Materials and Methods:

In a randomized double-blinded clinical trial, 76 patients with definite diagnosis of moderate-to-severe asthma were randomized to receive Pulmicort 180 mcg/inhalation two puffs twice daily, or receive Symbicort 80/4.5 mg/inhalation two puffs twice daily, or receive Symbicort 160/4.5 mg/inhalation two puffs twice daily for 3 months. All participants were initially evaluated by spirometry for assessing respiratory parameters and also the level of asthma control was assessed by Asthma Control Test (ACT).

Results:

More significant improvement in spirometry parameters, including forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC), FEV1/FVC ratio, as well as in peak expiratory flow (PEF) in both groups of Symbicort with the regimens 80/4.5 mg/inhalation or 160/4.5 mg/inhalation 2 puffs twice daily compared with Pulmicort group, ACT score was significantly improved in Symbicort group with the regimens 160/4.5 mg/inhalation compared with both Symbicort groups with lower dosage and Pulmicort group. Response to treatment in PEF parameter and also in ACT level was significantly more in those who received Symbicort with the regimens 160/4.5 mg/inhalation compared with other two interventional groups adjusted for gender and age.

Conclusion:

Symbicort with the regimens 160/4.5 mg/inhalation has higher efficacy in reducing asthma symptom and improving its control compared with low doses of this drug and with Pulmicort.

Receptor-mediated enhancement of beta adrenergic drug activity by ascorbate in vitro and in vivo

Rationale

Previous in vitro research demonstrated that ascorbate enhances potency and duration of activity of agonists binding to alpha 1 adrenergic and histamine receptors.

Objectives

Extending this work to beta 2 adrenergic systems in vitro and in vivo.

Methods

Ultraviolet spectroscopy was used to study ascorbate binding to adrenergic receptor preparations and peptides. Force transduction studies on acetylcholine-contracted trachealis preparations from pigs and guinea pigs measured the effect of ascorbate on relaxation due to submaximal doses of beta adrenergic agonists. The effect of inhaled albuterol with and without ascorbate was tested on horses with heaves and sheep with carbachol-induced bronchoconstriction.

Measurements

Binding constants for ascorbate binding to beta adrenergic receptor were derived from concentration-dependent spectral shifts. Dose- dependence curves were obtained for the relaxation of pre-contracted trachealis preparations due to beta agonists in the presence and absence of varied ascorbate. Tachyphylaxis and fade were also measured. Dose response curves were determined for the effect of albuterol plus-and-minus ascorbate on airway resistance in horses and sheep.

Main Results

Ascorbate binds to the beta 2 adrenergic receptor at physiological concentrations. The receptor recycles dehydroascorbate. Physiological and supra-physiological concentrations of ascorbate enhance submaximal epinephrine and isoproterenol relaxation of trachealis, producing a 3–10-fold increase in sensitivity, preventing tachyphylaxis, and reversing fade. In vivo, ascorbate improves albuterol's effect on heaves and produces a 10-fold enhancement of albuterol activity in “asthmatic” sheep.

Conclusions

Ascorbate enhances beta-adrenergic activity via a novel receptor-mediated mechanism; increases potency and duration of beta adrenergic agonists effective in asthma and COPD; prevents tachyphylaxis; and reverses fade. These novel effects are probably caused by a novel mechanism involving phosphorylation of aminergic receptors and have clinical and drug-development applications.

Budesonide/formoterol dry powder in asthma: an option for control as maintenance and reliever therapy

IMPORTANCE OF THE FIELD

Asthma is a heterogeneous disease with various components that may contribute to symptoms. Obtaining global control of is one of the fundamental parts of the management of this disease.

AREAS COVERED IN THIS REVIEW

The Cochrane trial database, Medline and Embase, were searched systematically, and approximately 20 respiratory journals and conference abstracts were searched manually. The search was limited to publications in English language of last 20 years and which included the keywords 'budesonide', 'formoterol', 'asthma' and 'control'.

WHAT THE READER WILL GAIN

The purposes of this review are: i) to discuss the rationale about possibility of using combination therapy administered with a single inhaler for both daily maintenance and relief as needed of breakthrough symptoms in asthma management; ii) to give readers the current status of clinical pharmacological treatment of asthma; iii) to discuss the evidence on the use of budesonide/formoterol dry powder in one inhaler.

TAKE HOME MESSAGE

Among the various inhalatory drugs, budesonide and formoterol can be conveniently delivered in one dry powder inhaler and simplify treatment by providing immediate step-up when symptoms increase. Alongside the anti-inflammatory component, formoterol provides both short- and long-acting bronchodilator effects with maintenance and reliever properties. The option of using one inhaler simplifies treatment by simultaneously providing bronchodilator and anti-inflammatory activity, thus enhancing compliance. As indicated in guidelines, all these characteristics are essential for optimizing asthma treatment and control.

Effects of topical formoterol alone and in combination with budesonide in a pollen season model of allergic rhinitis

BACKGROUND

beta(2)-Agonists may exert mast cell stabilizing and anti-plasma exudation effects. While available data suggest no or only marginal effects of beta(2)-agonists on symptoms of allergic rhinitis, little is known about whether these drugs may add to the efficacy of anti-rhinitis drugs.

OBJECTIVE

To examine effects of a beta(2)-agonist, alone and in combination with an intranasal glucocorticosteroid, on symptoms and signs of allergic rhinitis.

METHODS

Patients were examined in a pollen season model. Budesonide 64 microg, alone and in combination with formoterol 9 microg, as well as formoterol 9 microg alone was given in a placebo-controlled and crossover design. After 7 days of treatment, the patients received allergen challenges for 7 days. Symptoms and nasal peak inspiratory flow (PIF) were recorded. Nasal lavages with and without histamine were carried out at the end of each challenge series. These lavages were analysed for tryptase, eosinophil cationic protein (ECP), and alpha(2)-macroglobulin as indices of mast cell activity, eosinophil activity, and plasma exudation, respectively.

RESULTS

Budesonide reduced symptoms of allergic rhinitis and improved nasal PIF in the morning, in the evening as well as post allergen challenge. Formoterol alone did not affect symptoms or nasal PIF and did not affect the efficacy of budesonide. Tryptase, ECP, and alpha(2)-macroglobulin were significantly reduced by budesonide. Formoterol alone did not affect these indices and did not affect the anti-inflammatory effect of budesonide.

CONCLUSION

The present dose of formoterol does not affect symptoms and inflammatory signs of allergic rhinitis and does not add to the efficacy of topical budesonide.

Long-acting beta2-agonists in asthma: not so SMART?

Asthma is a worldwide chronic disorder that is characterised by airway inflammation and hyper-responsiveness, which results in intermittent airflow obstruction and subsequent perception of symptoms and exacerbations. Inhaled corticosteroids are a fundamental component in the prevention of the short- and long-term complications associated with inadequately controlled asthma. However, many individuals experience persistent symptoms and exacerbations despite receiving low-to-medium doses of an inhaled corticosteroid (400-800 microg/day of beclometasone or equivalent). In these symptomatic asthmatic patients, guidelines advocate the initiation of a long-acting beta2-adrenoceptor agonist (LABA) as additional second-line controller therapy. The recent SMART (Salmeterol Multi-centre Asthma Research Trial) study was designed to compare the effects of add-on salmeterol 42 microg (ex-actuator) twice daily with placebo over 28 weeks in a randomised, double-blind, parallel-group fashion, with the intention to enrol 60,000 asthmatic patients. However, the study was halted prematurely because preliminary data revealed an increased mortality associated with regular use of salmeterol. Moreover, concerning rates of respiratory-related deaths, asthma-related deaths and life-threatening events were observed among African Americans, who constituted up to 18% of the study population. This in turn prompted the US FDA to announce important safety information regarding inhalers containing LABAs and advise that new labelling be produced outlining the "small but significant risk in asthma-related deaths" associated with their regular use. This evidence-based review discusses the data from SMART and highlights potentially important drawbacks with regular use of LABAs in persistent asthma.

The use of inhaled formoterol in the treatment of asthma

OBJECTIVE

To discuss the clinical efficacy and safety of formoterol when used to relieve symptoms of asthma and prevent exercise-induced bronchoconstriction (EIB).

DATA SOURCES

A PubMed search was performed for articles published between 1997 and 2005 with the keywords formoterol, asthma, and long-acting beta2-adrenergic agonist, with cross-referencing to identify peer-reviewed journal articles.

STUDY SELECTION

Published articles on the clinical use of formoterol for asthma or EIB were included as well as articles detailing the pharmacologic properties of the drug. To present a thorough review of the literature, published studies based on patient number, study design, or other measures of study quality were not excluded.

RESULTS

Formoterol is the only long-acting beta2-adrenergic agonist that combines a rapid onset of action (within 3 minutes) with a long duration of effect (approximately 12 hours). Clinically, as recommended by asthma treatment guidelines, formoterol in conjunction with inhaled corticosteroids (ICSs) is a preferred treatment for moderate to severe persistent asthma. Significant clinical data support the use of formoterol in combination with ICSs for the treatment of asthma, with studies demonstrating improved pulmonary function and symptom scores and decreased need for maintenance ICSs and short-acting beta2-adrenergic agonists (SABAs) as relief medication. Recent studies also demonstrate that use of formoterol as needed as relief medication is associated with a prolonged time to exacerbation, improved pulmonary function, and decreased asthma symptoms. When used as monotherapy, formoterol provides protection against EIB. Clinical data also demonstrate that formoterol is safe and well tolerated even in high doses, with an adverse event profile similar to that of SABAs.

CONCLUSION

Overall, formoterol is safe and effective as adjunct controller therapy for moderate and severe persistent asthma and as monotherapy for EIB.

Positive interaction of the beta2-agonist CHF 4226.01 with budesonide in the control of bronchoconstriction induced by acetaldehyde in the guinea-pigs

Pretreatment of anaesthetized guinea-pigs with either CHF 4226.01 (8-hydroxy-5-[(1R)-1-hydroxy-2-[N-[(1R)-2-(p-methoxyphenyl)-1-methylethyl]amino]ethyl] carbostyril hydrochloride), formoterol or budesonide reduced acetaldehyde (AcCHO)-evoked responses in the lungs with a rank order of potency CHF 4226.01 (ED(50) values, from 1.88 to 3.31 pmol) > formoterol (ED(50) values, from 3.03 to 5.51 pmol) >> budesonide (ED(50) values, from 335 to 458 nmol). The duration of action of CHF 4226.01 in antagonizing the airway obstruction elicited by AcCHO was also substantially longer than formoterol (area under the curve) at 10 pmol, 763+/-58 and 480+/-34, respectively; P<0.01). Continuous infusion of a subthreshold dose of AcCHO enhanced the intratracheal pressure (ITP) increases caused by subsequent challenges with substance P (from 9.7+/-0.8 to 27.5+/-1.6 cm H(2)O as a peak, P<0.001). Pretreatment with either CHF 4226.01 or formoterol prevented the sensitizing effect of AcCHO on substance P responses (ED(50) values, 2.85 and 6.11 pmol, respectively; P<0.01). The ED(50) value of budesonide (396 nmol) in preventing AcCHO-evoked ITP increase was reduced when this glucocorticoid was combined with 0.1 pmol CHF 4226.01 (ED(50) 76 nmol; P<0.001). CHF 4226.01/budesonide was two-fold more effective (P<0.01) than the formoterol/budesonide combination. These results suggest that CHF 4226.01/budesonide, by optimizing each other's beneficial potential in the control of pulmonary changes caused by AcCHO in the guinea-pigs, may represent a new fixed combination in asthma.

Long-acting beta2-agonists: comparative pharmacology and clinical outcomes

Salmeterol and formoterol are both long-acting beta(2)-adrenoceptor agonists (beta(2)-agonists). They both provide excellent bronchodilating and bronchoprotective effects in patients with asthma but their are some differences between these two long-acting beta(2)-agonists in vitro and in vivo. Formoterol has a greater potency and intrinsic activity than salmeterol, which can become especially apparent at higher doses than that clinically recommended, and in contracted bronchi. Long-term use of long-acting beta(2)-agonists can induce tolerance, which can be partially reversed with corticosteroids. Long-acting beta(2)-agonists have some anti-inflammatory effects in vitro, but data in vivo are less convincing. Compared with doubling the dose of inhaled corticosteroids, the addition of inhaled long-acting beta(2)-agonists to inhaled corticosteroids improves symptom control in patients with asthma and reduces both the exacerbation rate of asthma and hospital admission rate. No enhanced airway responsiveness or loss of perception of dyspnea has been observed with the use of inhaled long-acting beta(2)-agonists. Monotherapy with long-acting beta(2)-agonists is not recommended.

Effects of dual therapy with corticosteroids plus long acting beta2-agonists in asthma

Asthma is a common condition characterised by inflammation, airway hyperresponsiveness and reversible airflow obstruction. Effective pharmacotherapy must therefore be aimed at attenuating these underlying hallmark features. Despite the use of regular low-to-moderate doses of inhaled corticosteroids, many patients remain symptomatic and require further 2nd line controller therapy. The addition of a concomitant long acting beta2-agonist provides an effective means in which to alleviate symptoms and reduce exacerbation frequency. Moreover, both agents can be combined in a single inhaler, and provide patients with a more convenient and effective way in which to deliver treatment to the endobronchial tree. This evidenced-based review article discusses the effects of such combination inhalers upon a variety of outcome parameters and their effects upon asthmatics across a range of severities.

Acute allergic responses induce a prompt luminal entry of airway tissue eosinophils

Traditionally, traffic and activation of eosinophils in asthmatic airways are thought to take place during the late-phase allergic reaction. The present study tests the hypothesis that when eosinophils are present in the tissue before allergen exposure, as in chronically inflamed asthmatic airways, acute anaphylactic reactions initiate an eosinophil response. Using a guinea-pig allergic model, where eosinophilia is present at baseline conditions, the traffic of resident eosinophils was examined in vivo immediately after allergen challenge. By 2 min after challenge, eosinophils had moved up to apical epithelial positions. Within 10 min, a marked migration of eosinophils into the airway lumen was demonstrated. Along with the allergen-induced egression of eosinophils, acute luminal entry of plasma proteins and eotaxin occurred. Eosinophil egression was effectively inhibited by the antiexudative drug formoterol, whereas the proexudative drug bradykinin could in naive animals evoke a prompt luminal entry of eosinophils. In conclusion, the present study demonstrates that acute allergic reactions initiate a prompt transepithelial migration of resident eosinophils. Our data further suggest that this response in part is initiated by the plasma exudation response, which may alter the transepithelial gradient of eosinophil chemoattractants including eotaxin. We propose that prompt eosinophil response is a significant component of the acute phase of allergic reactions when occurring in airways where these cells are already present in the mucosa.

The effects of regular inhaled formoterol and budesonide on preformed Th-2 cytokines in mild asthmatics

In a recent placebo-controlled study in mild atopic asthmatics, we observed a significant decrease in eosinophils in the bronchial submucosa, after 2 months oftreatment with inhaled formoterol and budesonide. Biopsy material from each treatment group; formoterol (24 microg bid), budesonide (400 microg b. i. d.) and placebo has been further assessed to investigatethe role of Th-2 cytokines by immunohistochemistry using Mabs to eosinophils as an index of inflammation, IL-4 and IL-5. Treatment with formoterol significantly reduced the number of eosinophils (EG2+) in the submucosa and epithelium, but this was not paralleled by changes in cytokine immunoreactivity In contrast, treatment with budesonide significantly reduced both the number of eosinophils (EG2+) and immunoreactivity for IL-4 and IL-5 in the submucosa. Thus, while budesonide has effects on cytokines involved in eosinophil recruitmentthis explanation does not apply tothe eosinopaenia observed with the long-acting beta2 adrenoreceptor agonist formoterol.

Inhibition by fenoterol of human eosinophil functions including beta2-adrenoceptor-independent actions

Agonists at beta2 adrenoceptors are used widely as bronchodilators in treating bronchial asthma. These agents also may have important anti-inflammatory effects on eosinophils in asthma. We examined whether widely prescribed beta2-adrenoceptor agonists differ in ability to suppress stimulus-induced eosinophil effector functions such as superoxide anion (O2-) generation and degranulation. To examine involvement of cellular adhesion in such responses, we also investigated effects of beta2 agonists on cellular adhesion and on CD11b expression by human eosinophils. O2- was measured using chemiluminescence. Eosinophil degranulation and adhesion were assessed by a radioimmunoassay for eosinophil protein X (EPX). CD11b expression was measured by flow cytometry. Fenoterol inhibited platelet-activating factor (PAF)-induced O2- generation by eosinophils significantly more than salbutamol or procaterol. Fenoterol partially inhibited PAF-induced degranulation by eosinophils similarly to salbutamol or procaterol. Fenoterol inhibited phorbol myristate acetate (PMA)-induced O2- generation and degranulation by eosinophils, while salbutamol or procaterol did not. Fenoterol inhibition of PMA-induced O2- generation was not reversed by ICI-118551, a selective beta2-adrenoceptor antagonist. Fenoterol, but not salbutamol or procaterol, significantly inhibited PAF-induced eosinophil adhesion. Fenoterol inhibited O2- generation and degranulation more effectively than salbutamol or procaterol; these effects may include a component involving cellular adhesion. Inhibition also might include a component not mediated via beta2 adrenoceptors.

Beta-adrenoceptor agonists and asthma--100 years of development

Inhaled beta(2)-adrenoceptor agonists are by far the most effective and safe bronchodilators currently available. They have not been surpassed by any other bronchodilating principle. The way to this position has been long and started with the first successful treatment of acute, severe asthma with s.c. injections of adrenaline 100 years ago. Over the years, synthetic congeners of adrenaline have been produced and tested for their pharmacological properties. During the first decades, little attention was given airway smooth muscle. The discovery of isoprenaline in 1940 was the first major step towards selective bronchodilation. This compound became a key tool for the classification of adrenoceptors into alpha and beta. Salbutamol and terbutaline were the first to show a significant attenuation of the cardiostimulant effect and confirmed the subdivision of beta-adrenoceptors into beta(1) and beta(2). Much effort was made to eliminate the next dose-limiting side effect, skeletal muscle tremor but in vain. Prolonged duration of action was achieved in three ways: with bambuterol, an orally active carbamate ester prodrug of terbutaline, salmeterol, an inhaled beta(2)-adrenoceptor agonist emerging from a purposeful research project, and formoterol which was found, accidentally, to have a long duration of action when inhaled. Throughout the 20th century, beta-adrenoceptor agonists have been developed and marketed as racemates. The pharmacological activity usually resides in the (R)-enantiomer. Despite claims for the opposite, there is so far no compelling evidence that the presence of the less active (S)-enantiomer is of any harm to the patient. One hundred years of experience of structural modifications of adrenaline has shown that the possibilities to modify the properties of this endogenous prototype appear to be unlimited.

Fenoterol inhibits superoxide anion generation by human polymorphonuclear leukocytes via beta-adrenoceptor-dependent and -independent mechanisms

BACKGROUND

Beta2-adrenoceptor agonists, used widely as bronchodilator in treating bronchial asthma, may have anti-inflammatory activity.

OBJECTIVE

We examined whether various widely prescribed beta2-adrenoceptor agonists differ in anti-inflammatory mechanisms.

METHODS

We investigated effects of these drugs on superoxide anion generation by stimulated human polymorphonuclear leukocytes in vitro using chemiluminescence.

RESULTS

At high concentrations, fenoterol significantly inhibited both N-formylmethionyl-leucyl-phenylalanine- and phorbol myristate acetate-induced superoxide generation by neutrophils. In contrast, salbutamol or procaterol partially inhibited generation with the former stimulus but not the latter. Inhibition by salbutamol or procaterol was completely reversed by either propranolol, a nonselective beta-adrenoceptor antagonist, or ICI-118551, a beta2-adrenoceptor-selective antagonist. In contrast, the effect of fenoterol at concentrations exceeding 10(-6) M against superoxide generation with the former stimulus was only partially reversed by antagonists, and the effect of high concentrations of fenoterol against generation with the latter stimulus was not reversed. No drugs scavenged superoxide at the highest concentration used (10(-5) M).

CONCLUSIONS

Fenoterol at high concentrations has an inhibitory effect on superoxide generation that includes a component not mediated via beta2-adrenoceptors. Direct inhibition at or downstream from protein kinase C may be involved.

Comparison of formoterol and terbutaline for as-needed treatment of asthma: a randomised trial

BACKGROUND

Asthma guidelines recommend that long-acting inhaled beta-agonists should be used as maintenance therapy for patients with asthma inadequately controlled on an inhaled corticosteroid. We studied the safety and efficacy of the long-acting beta-agonist formoterol compared with terbutaline, each taken as needed, in patients with moderate to severe asthma.

METHODS

Patients were taking an inhaled corticosteroid (mean dose 870 microg daily) and had a forced expiratory volume in 1 s (FEV1) of at least 50% predicted (mean 74%). Those requiring an inhaled beta-agonist three to eight times a day during the study run-in period (362 of 621 who started) were randomly assigned formoterol 4.5 microg or terbutaline 0.5 mg as needed by Turbuhaler in daily doses up to 54 microg and 6 mg, respectively, for 12 weeks in a double-blind, parallel-group study. Analyses were by intention to treat.

FINDINGS

The 362 randomised patients (157 men, 205 women) had a mean age of 47 years. Patients taking formoterol had a longer time to their first severe asthma exacerbation (relative-risk ratio 0.55 [95% CI 0.34-0.89]), took fewer inhalations of study drug, and had larger increases in FEV1 (5%) and morning and evening peak expiratory flow (mean difference in increase 11 L/min and 8 L/min) than those taking terbutaline. No safety issues were identified.

INTERPRETATION

When taken as needed, formoterol 4.5 microg provided better asthma control than terbutaline 0.5 mg in patients requiring moderate doses of relief medication despite inhaled corticosteroid treatment. Safety studies should be extended to a wider population of patients with asthma.

The pathobiologic implications for treatment. Old and new strategies in the treatment of chronic asthma

An increased understanding of the pathobiology of asthma has led to improved treatment for chronic asthma. This article discusses the old and new strategies of asthma therapy based on a pathobiologic approach. Therapeutic agents discussed include beta-adrenergic agonists, methylxanthines, corticosteroids, cromolyn, nedocromil, leukotriene modifiers, and new investigational agents.

Ligand-independent activation of the glucocorticoid receptor by beta2-adrenergic receptor agonists in primary human lung fibroblasts and vascular smooth muscle cells

The glucocorticoid receptor (GR) is a ubiquitously expressed transcription factor present in most cell types. Upon ligand binding, the GR is activated and translocates into the nucleus where it transmits the anti-inflammatory actions of glucocorticoids. Here, we describe the ligand-independent activation of GR by the beta2-adrenergic receptor (beta2-AR) agonists, salbutamol and salmeterol, in primary human lung fibroblasts and vascular smooth muscle cells. Immunohistochemistry demonstrated expression of GR and the beta2-AR by fibroblasts and vascular smooth muscle cells. Treatment of the cells with the beta2-AR agonists, salbutamol or salmeterol, resulted in translocation of GR into the nucleus beginning at 30 min, as shown by immunohistochemistry and Western blotting of cytosolic and nuclear cell extracts. In comparison, activation of GR induced by the corticosteroids dexamethasone and fluticasone occurred at the same time after treatment (30 min) but resulted in a more complete depletion of GR from the cytosolic compartment. Electrophoretic mobility shift assays confirmed that nuclear GR, activated by both beta2-AR agonists and glucocorticoids, actively bound to the GR consensus sequence (GR element). Functional activation of the GR was confirmed by a Luciferase reporter gene assay, using a GR driven promoter fragment from the p21((WAF1/CIP1)) gene. The effects of the beta2-AR agonists, salbutamol and salmeterol, were dependent upon binding to the beta2-AR, because blocking of beta2-AR with propranolol abrogated GR activation. GR activation appeared to involve cAMP. In summary, these data show that beta2-AR agonists are potent activators of GR. Ligand-independent activation of GR by beta2-AR agonists may substantially mediate the anti-inflammatory actions of these drugs observed in vitro and in vivo.

Effects of formoterol on histamine induced plasma exudation in induced sputum from normal subjects

BACKGROUND

A number of studies have shown that beta 2 agonists, including formoterol, inhibit plasma exudation induced by the inflammatory stimulus in animal airways. Whether clinical doses of beta 2 agonists inhibit plasma exudation in human bronchial airways is unknown.

METHODS

In order to explore the microvascular permeability and its potential inhibition by beta 2 agonists in human bronchial airways a dual induction method was developed: plasma exudation induced by histamine inhalation followed by sputum induction by hypertonic saline (4.5%) inhalation. Sixteen healthy subjects received formoterol (18 micrograms) in a placebo controlled, double blind, crossover study. Sputum was induced on five occasions: once at baseline and four times after histamine challenge (30 minutes and eight hours after both formoterol and placebo treatments). Sputum levels of alpha 2-macroglobulin were determined to indicate microvascular-epithelial exudation of bulk plasma.

RESULTS

Histamine induced plasma exudation 30 minutes after placebo was considerably greater than at baseline (median difference 11.3 micrograms/ml (95% confidence interval 0.9 to 90.0)). At 30 minutes after formoterol the effect of histamine was reduced by 5.1 (0.9 to 61.9) micrograms/ml compared with placebo. At eight hours histamine produced less exudation and inhibition by formoterol was not demonstrated.

CONCLUSION

This study shows for the first time an anti-exudative effect of a beta 2 agonist in healthy human bronchial airways. Through its physical and biological effects, plasma exudation is of multipotential pathogenic importance in asthma. If the present findings translate to disease conditions, it suggests that an anti-exudative effect may contribute to the anti-asthmatic activity of formoterol.

Allergen challenge-induced extravasation of plasma in mouse airways

BACKGROUND

Mouse models are extensively used to study genetic and immunological mechanisms of potential importance to inflammatory airway diseases, e.g. asthma. However, the airway pathophysiology in allergic mice has received less attention. For example, plasma extravasation and the ensuing tissue-deposition of plasma proteins, which is a hallmark of inflammation, has not been examined in allergic mice.

OBJECTIVE

This study aims to examine the vascular permeability and the distribution of plasma proteins in mouse airways following exposure to allergen and serotonin.

METHODS

Extravasated plasma was quantified by a dual isotop technique using intravascular (131I-albumin) and extrasvascular (125I-albumin) plasma tracers. Histological visualization of fibrinogen and colloidal gold revealed the tissue distribution of extravasated plasma.

RESULTS

Allergen aerosol exposure (3% OVA, 15min) of sensitized animals resulted in a marked plasma extravasation response in the trachea (P < 0.01) and the bronchi but not in the lung parenchyma. A similar extravasation response was induced by serotonin (P<0.001). Extravasating vessels (assessed by Monastral blue dye) were identified as intercartilaginous venules. Extravasated plasma abounded in the subepithelial tissue but was absent in the epithelium and airway lumen. The allergen-induced response was dose-dependently inhibited by iv administration of formoterol (P < 0.001), a vascular antipermeability agent.

CONCLUSION

The present study demonstrates that serotonin and allergen challenge of sensitized mice increase airway venular permeability to cause transient extravasation and lamina propria distribution of plasma in the large airways. We suggest that the extravasation response is a useful measure of the intensity and the distribution of active inflammation

Intranasal salmeterol inhibits allergen-induced vascular permeability but not mast cell activation or cellular infiltration

BACKGROUND

Salmeterol is a long-acting beta2-adrenergic agonist that is widely used in the treatment of asthma. It has been suggested that non-bronchodilator actions of salmeterol may contribute to its efficacy.

OBJECTIVE

To further evaluate the potential non-bronchodilator actions of salmeterol in vivo, using a model of nasal challenge with allergen.

METHODS

Twelve asymptomatic subjects with seasonal allergic rhinitis participated in a randomized, double-blind, placebo-controlled crossover trial of the effects of a single dose of 100 microg of salmeterol on the response to allergen challenge. Sneezing and symptom scores, and levels of histamine and albumin in nasal lavages, were measured throughout the protocol. Concentrations of tryptase, prostaglandin D2 and lysozyme were measured during the acute allergic response, while levels of IL-3, IL-5 and IL-8 were measured at later time points. Numbers of eosinophils and of total white blood cells were also recorded.

RESULTS

Salmeterol did not affect sneezing or symptom scores at any point. During the immediate response to allergen challenge, mast cell activation, reflected by concentrations of histamine, tryptase and prostaglandin D2, and serous glandular secretion, assessed by measurements of lysozyme, were unaffected by salmeterol treatment but vascular permeability, reflected by concentrations of albumin in nasal lavages, was significantly reduced. At later time points, salmeterol had no effect on levels of histamine or albumin and did not affect cellular infiltration. Concentrations of IL-3, IL-5 and IL-8 were not increased by allergen challenge in these subjects, so the effects of salmeterol could not be evaluated.

CONCLUSIONS

Treatment with a single dose of salmeterol had no effect on activation of mast cells or cellular infiltration but inhibited vascular permeability. The ability of salmeterol to inhibit antigen-induced vascular permeability may contribute to its therapeutic efficacy in asthma.

Contribution of plasma-derived molecules to mucosal immune defence, disease and repair in the airways

This review discusses recent observations, in health and disease, on the release and distribution of plasma-derived molecules in the airway mucosa. Briefly, the new data on airway mucosal exudation mechanisms suggest that the protein systems of plasma contribute significantly to the mucosal biology, not only in injured airways but also in such mildly inflamed airways that lack oedema and exhibit no sign of epithelial derangement. Plasma as a source of pluripotent growth factor, adhesive, leucocyte-activating, etc., molecules may deserve a prominent position in schemes that claim to illustrate immunological and inflammatory mechanisms of the airway mucosa in vivo.

Long-acting inhaled beta2-agonists in asthma therapy

OBJECTIVE

To review the pharmacology of the long-acting inhaled beta2-agonists, salmeterol and formoterol, summarize results of their clinical trials, evaluate their safety records, and discuss their roles in the treatment of asthma.

DATA SOURCES

Preclinical and clinical studies involving salmeterol or formoterol were identified by a MEDLINE search, weekly computerized literature updates, and manual searches. Studies of satisfactory quality were chosen for review.

DATA SYNTHESIS

Salmeterol and formoterol are potent and selective beta2-adrenoceptor agonists with durations of action >12 h. Their major differences are that formoterol has a rapid onset of action and is a partial agonist of high intrinsic efficacy, whereas salmeterol has a delayed onset and is a partial agonist of low intrinsic efficacy. Twice daily use of either drug results in improved lung function, reduced symptoms, and a better quality of life. These agents protect against exercise-induced asthma for 12 h and eliminate nighttime awakening in most patients. Limited tolerance develops, especially to their bronchoprotective effects, but their improvement of lung function is sustained.

CONCLUSIONS

Regular use of salmeterol or formoterol provides subjective and objective amelioration of asthma in patients experiencing excessive symptoms or physiologic impairment despite the regular administration of low doses of inhaled corticosteroids (equivalent to approximately 500 microg/d of beclomethasone). Intermittent use of either long-acting beta2-agonist can provide prolonged protection against exercise-induced asthma or nighttime symptoms. Patients should be instructed to continue taking inhaled steroids when long-acting beta2-agonists are administered on a regular schedule and to not take long-acting beta2-agonists between regularly scheduled doses. Used properly, they are effective and safe adjunctive agents in the treatment of asthma.

Effect of inhaled formoterol and budesonide on exacerbations of asthma. Formoterol and Corticosteroids Establishing Therapy (FACET) International Study Group

BACKGROUND

The role of long-acting, inhaled beta2-agonists in treating asthma is uncertain. In a double-blind study, we evaluated the effects of adding inhaled formoterol to both lower and higher doses of the inhaled glucocorticoid budesonide.

METHODS

After a four-week run-in period of treatment with budesonide (800 microg twice daily), 852 patients being treated with glucocorticoids were randomly assigned to one of four treatments given twice daily by means of a dry-powder inhaler (Turbuhaler): 100 microg of budesonide plus placebo, 100 microg of budesonide plus 12 microg of formoterol, 400 microg of budesonide plus placebo, or 400 microg of budesonide plus 12 microg of formoterol. Terbutaline was permitted as needed. Treatment continued for one year; we compared the frequency of exacerbations of asthma, symptoms, and lung function in the four groups. A severe exacerbation was defined by the need for oral glucocorticoids or a decrease in the peak flow to more than 30 percent below the base-line value on two consecutive days.

RESULTS

The rates of severe and mild exacerbations were reduced by 26 percent and 40 percent, respectively, when formoterol was added to the lower dose of budesonide. The higher dose of budesonide alone reduced the rates of severe and mild exacerbations by 49 percent and 37 percent, respectively. Patients treated with formoterol and the higher dose of budesonide had the greatest reductions -- 63 percent and 62 percent, respectively. Symptoms of asthma and lung function improved with both formoterol and the higher dose of budesonide, but the improvements with formoterol were greater.

CONCLUSIONS

In patients who have persistent symptoms of asthma despite treatment with inhaled glucocorticoids, the addition of formoterol to budesonide therapy or the use of a higher dose of budesonide may be beneficial. The addition of formoterol to budesonide therapy improves symptoms and lung function without lessening the control of asthma.

Effect of beta 2-agonists on histamine-induced airway microvascular leakage in ozone-exposed guinea pigs

beta 2-adrenergic agonists exhibit antipermeability effects in the airways. However, it is not known whether beta 2-agonists have this beneficial effect in airway mucosa that is already inflamed. We evaluated the effects of two inhaled beta 2-agonists, salbutamol and formoterol, on the histamine-induced bronchoconstriction and plasma extravasation in the airways of guinea pigs with or without ozone exposure. Total pulmonary resistance (RL) was measured before and after histamine inhalation in anesthetized animals that were pretreated with inhaled salbutamol, formoterol, or saline. Plasma extravasation in the airways was measured using Evans blue dye. In the control animals not exposed to ozone, salbutamol and formoterol each significantly reduced both the histamine-induced bronchoconstriction and the plasma extravasation in the trachea and main bronchi. In the ozone-exposed animals, the increase in RL after histamine was greater than that in control animals. Salbutamol and formoterol each significantly reduced histamine-induced bronchoconstriction, even in the ozone-exposed animals. Salbutamol did not affect the histamine-induced plasma extravasation, whereas formoterol reduced the plasma extravasation in the main bronchi, but not in the trachea, of the animals exposed to ozone. These results suggest that the anti-inflammatory properties of formoterol in inflamed airways may contribute to the beneficial effects in the treatment of airway inflammation.

Some pharmacodynamic aspects on long-acting beta-adrenoceptor agonists

1. Formoterol and salmeterol are the first members of a new generation of long-acting beta(2)-adrenoceptor agonists for inhalation. The discovery of the long effect duration of formoterol was made by chance, while the development of salmeterol appeared to follow a purposeful research strategy. 2. Preclinical evaluation predictive of the clinical duration of effect of long-acting bronchodilators is not straightforward. Experiments in vitro may give false positive results, while experiments in vivo may show false negative results. 3. Once the principle of a long duration of effect was established, a number of novel long-acting beta(2)-adrenoceptor agonists of various chemical structure have emerged. 4. There are two alternative models for the explanation of the long duration of effect: the exosite binding explaining the mode of action of salmeterol, and the more general diffusion microkinetic model applicable for both formoterol and salmeterol. 5. Long-acting beta-adrenoceptor agonists with a relatively low efficacy like salmeterol may, under certain circumstances, inhibit competitively the relaxing effect of agonists with higher efficacy like formoterol and salbutamol. 6. Like all other beta(2)-adrenoceptor agonists in current clinical use, formoterol and salmeterol comprise racemic mixtures. Only the RR- and R-enantiomers are pharmacologically active. The experimental compounds TA-2005 and picumeterol have been developed as pure RR- and R-enantiomers, respectively.

Anti-inflammatory, membrane-stabilizing interactions of salmeterol with human neutrophils in vitro

1. We have investigated the effects of salmeterol (0.3-50 microM) on several pro-inflammatory activities of human neutrophils in vitro. 2. Oxidant production by FMLP- and calcium ionophore (A23187)-activated neutrophils was particularly sensitive to inhibition by low concentrations (0.3-3 microM) of salmeterol, while the responses of phorbol myristate acetate- and opsonised zymosan-stimulated cells were affected only by higher concentrations (3-50 microM) of the drug. At these concentrations salmeterol is not cytotoxic, nor does it act as a scavenger of superoxide. 3. These anti-oxidative interactions of salmeterol with neutrophils were insensitive to propranolol but could be eliminated by washing the cells, or by pretreatment with low concentrations (1-2 microM) of the pro-oxidative, membrane-destabilizing phospholipids, lysophosphatidylcholine (LPC), platelet activating factor (PAF) and lysoPAF (LPAF). 4. At concentrations of 6.25-50 microM salmeterol interfered with several other activities of stimulated neutrophils, including intracellular calcium fluxes, phospholipase A2 activity and synthesis of PAF. 5. In an assay of membrane-stabilizing activity, salmeterol (25 and 50 microM) neutralized the haemolytic action of LPC, PAF and LPAF. 6. Of the other commonly used beta 2-adrenoceptor agonists, fenoterol, and formoterol, but not salbutamol, caused moderate inhibition of neutrophil oxidant generation by a superoxide-scavenging mechanism. However, unlike salmeterol, these agents possessed only weak membrane stabilizing properties. 7. We conclude that salmeterol antagonizes the pro-inflammatory, pro-oxidative activity of several bioactive lipids implicated in the pathogenesis of bronchial asthma, by a mechanism related to the membrane-stabilizing, rather than to the beta 2-agonist properties of this agent.

The effects of formoterol on plasma exudation produced by a localized acute inflammatory response to bradykinin in the tracheal mucosa of rats in vivo

1. The effects of formoterol, a beta 2-adrenoceptor agonist, on plasma protein exudation and microvascular permeability induced by topical, i.e. applied onto the tracheal mucosal surface, bradykinin (10 nmol; 20 microM, 5 min, 0.1 ml min-1) were studied in a perfused segment of trachea prepared in situ in anaesthetized rats. 2. Bradykinin increased the amount of plasma (fluorimetric assay for protein) in the perfusate (response; 10.98 +/- 0.357 microliters, n = 69; total increase in plasma over basal during 45 min after start of bradykinin application) and 2 responses at a 90 min interval were reproducible. Carbon labelling was seen in tracheal sections from animals that received i.v. colloidal carbon, indicating that bradykinin caused tracheal microvessels to leak (increase in microvascular permeability). 3. Five minutes after topical formoterol, 5 or 30 nmol (10 or 60 microM perfused for 5 min), the bradykinin response was significantly reduced. The effects of formoterol were not dose-related, i.e. were maximal at 5 nmol. The bradykinin response was at control levels 30 min after 5 nmol formoterol. After 30 nmol formoterol, the response was still reduced 120 min later. The bradykinin response was significantly reduced 60 min after systemic formoterol (i.p., 0.029 to 870 nmol kg-1) and, for 290 nmol kg-1 i.p. formoterol, this reduction was shown to last at least 150 min. 4 The bradykinin response was not prevented by supramaximal doses of topical (30 nmol) or i.p.(870 nmol kg-1) formoterol and carbon-labelled microvessels were seen in tracheal sections from all animals that received formoterol, although these were less in number and less densely labelled than in the absence of formoterol. There was a correlation between the plasma exudation response (ul) and the number of carbon-labelled vessels (Spearman's correlation coefficient 0.415, P<0.001).5 In animals pretreated with propranolol (3 pmol kg-1, i.v.), 29 nmol kg-1 formoterol, i.p., did not reduce the bradykinin response. However, propranolol itself markedly potentiated the bradykinin response which confounded the interpretation of its effects on formoterol.6 The study has shown, in a preparation of rat trachea in situ, that supramaximal doses of the beta2-adrenoceptor agonist, formoterol (a) produced a sustained, but incomplete, inhibition of plasma exudation (induced by topical bradykinin), and (b) did not prevent bradykinin-induced leaky microvessels. The data support the view that, at least in rodent airways, beta2-adrenoceptor agonists attenuate, but do not abolish, the microvascular permeability effects of bradykinin, a putative asthma mediator.

Ability of inhaled procaterol, a beta 2 adrenoceptor agonist, to attenuate eicosanoid-induced airflow obstruction and airway microvascular leakage

Beta-2 adrenoceptor agonists are widely used as bronchodilators in the treatment of asthma mainly via inhalation. In the present study, we evaluated the ability of inhaled procaterol, a beta 2 adrenoceptor agonist, to reduce eicosanoid-induced airway microvascular leakage, and compared the ability with its inhibitory effect against bronchoconstriction. Tracheostomized guinea-pigs were given aerosolized procaterol (10 or 100 micrograms/ml) for 10 min under spontaneous breathing. Immediately after the end of inhalation, the animals were mechanically ventilated. Fourteen minutes after the end of inhalation, Evans blue dye (20 mg/kg) was given i.v. One minute later, 2 nmol/kg leukotriene D4 (LTD4), 50 nmol/kg U-46619, a thromboxane A2 mimetic, or vehicle was administered i.v. LTD4- or U-46619-induced increase in lung resistance was measured for 6 min. After removing the lungs, the amount of extravasated Evans Blue due in the lower airways was examined as an index of microvascular leakage. Inhaled procaterol significantly attenuated increases in both lung resistance and Evans Blue dye extravasation caused by these eicosanoids. The degree of inhibition was almost complete for lung resistance (approximately 90%), but it was only partial (range 18.5-61.2%) for the dye extravasation. No significant changes in mean systemic blood pressure and in heart rate was observed after an inhalation of 10 micrograms/ml procaterol. These results suggest that inhaled beta 2 adrenoceptor agonists may reduce airway microvascular leakage caused by inflammatory mediators such as eicosanoids without affecting systemic circulation.

Formoterol and salmeterol are both long acting compared to terbutaline in the isolated perfused and ventilated guinea-pig lung

An isolated, perfused and ventilated guinea-pig lung was used to compare the duration of effect of the bronchodilating beta 2-adrenoceptor agonists formoterol, salmeterol and terbutaline. Lung conductance was measured real time with the aid of a computer. Bronchoconstriction was induced in the preparation every 10 min by bolus injections of acetylcholine into the pulmonary artery. Lung conductance was reduced by about 70% after acetylcholine. The test compounds or the vehicle was administered for 1 min as aerosols generated from solutions: formoterol (10 mumol/l), salmeterol (100 mumol/l) and terbutaline (1000 mumol/l). This treatment inhibited the response to acetylcholine by 50-60% within the first 10 min for all three test compounds. The onset of action appeared to be slower for salmeterol than for formoterol and terbutaline. The inhibitory effect of terbutaline disappeared completely during the next 20 min of continuous perfusion (single pass), while both formoterol and salmeterol displayed a significant inhibitory effect 40 min after their administration. Formoterol, when inhaled at a higher dose (100 mumol/l), caused a 90% inhibition of the response to acetylcholine. This effect was completely reversed by 0.1 mumol/l propranolol in the perfusion medium. There were in general no major changes in the basal conductance measured between the acetylcholine provocations.

Comparison of the anti-inflammatory properties of formoterol, salbutamol and salmeterol in guinea-pig skin and lung

1. We have compared some anti-inflammatory properties of formoterol, salbutamol and salmeterol in guinea-pig skin and lung. 2. Intradermal formoterol (1 x 10(-10) to 1 x 10(-8) mol/site), salbutamol (1 x 10(-8) and 1 x 10(-7) mol/site) and salmeterol (1 x 10(-8) and 1 x 10(-7) mol/site) inhibited bradykinin-induced plasma protein extravasation (PPE) in guinea-pig skin. A maximally effective dose of formoterol (1 x 10(-9) mol/site) and salbutamol (1 x 10(-8) mol/site) inhibited PPE in guinea-pig skin for 2-4 h and 1-2 h respectively, whereas salmeterol (1 x 10(-8) mol/site) was effective for > 6 h. 3. Inhaled formoterol (nebuliser concentration 0.1 to 100 micrograms ml-1 inhibited histamine-induced plasma protein extravasation (PPE) in guinea-pig lung, with significant inhibition being observed at 10 and 100 micrograms ml-1. Formoterol (100 micrograms ml-1) inhibited PPE in guinea-pig lung for 2-4 h, a duration of action intermediate between that previously obtained for salbutamol (1 h) and salmeterol (> 6 h). 4. Formoterol, like salbutamol, had no effect on neutrophil accumulation or granulocyte-dependent PPE (zymosan-induced) in guinea-pig skin. Formoterol inhibited neutrophil accumulation (lipopolysaccharide-induced) in guinea-pig lung but at doses greater than those required to inhibit granulocyte-independent PPE (histamine-induced). In contrast, salmeterol inhibited neutrophil accumulation and granulocyte-dependent PPE in guinea-pig skin and inhibited neutrophil accumulation in guinea-pig lung at doses which inhibit granulocyte-independent PPE. 5. Inhaled formoterol (nebuliser concentration 100 microg ml-1) and salmeterol (100 microg ml-1) both inhibited PAF-induced eosinophil accumulation in guinea-pig lung. However, unlike salmeterol, this effect of formoterol was observed only at suprabronchodilator doses.6. We conclude that to inhibit neutrophil accumulation, at doses which inhibit granulocyte-independent PPE, agonists acting at beta-adrenoceptors on vascular endothelium require a duration of action greater than that of salbutamol and formoterol. However, we speculate that the mechanism of inhibition of eosinophil accumulation in guinea-pig lung by beta2-adrenoceptor agonists may involve an action on beta2-adrenoceptors on a cell type other than the endothelial cell.

Effect of beta 2-adrenoceptor agonists against platelet-activating factor-induced airway microvascular leakage and bronchoconstriction in the guinea pig

We have investigated the effect of inhaled formoterol (0.75 mg/ml, 60 breaths) and salbutamol (25 mg/ml, 60 breaths) against airway microvascular leakage and bronchoconstriction induced by inhaled platelet-activating factor (PAF) and histamine in anaesthetized guinea pigs. Lung resistance (RL) was measured for 6 min after challenge, followed by measurement of extravasation of Evans blue dye into airway tissues, used as an index of airway microvascular leakage. PAF (0.1, 0.4 and 1 mM; 30 breaths) caused a significant increase in RL and extravasation of dye, but the responses were smaller than those induced by histamine (5 mM, 30 breaths). Both formoterol and salbutamol caused a small but significant inhibition of extravasation in the distal intrapulmonary airways induced by PAF (0.1 and 0.4 mM for formoterol and 0.1 mM for salbutamol), and only formoterol reduced the increase in RL induced by 1 mM PAF. These drugs also inhibited both airway effects of histamine to a higher degree. In conclusion, formoterol and salbutamol can partly inhibit airway microvascular leakage and bronchoconstriction induced by inhaled PAF and histamine. The inhibitory potency of beta 2-adrenoceptor agonists may be dependent on the inflammatory mediator inducing the airway effects.

Allergen-induced biphasic plasma exudation responses in guinea pig large airways

In this study involving sensitized guinea pigs (anesthetized intramuscularly with a 3:2 mixture of ketamine+xylazine, 1 ml/kg), we applied allergen (ovalbumin) selectively to the tracheobronchial mucosa (sparing the nasal passages and the terminal airways) and examined the occurrence of immediate and late-phase inflammatory exudation of plasma and plasma-derived mediators (bradykinins) into the airway lumen. The experiments were terminated 10 to 480 min after challenge. A selective lavage that sampled the surface liquids of the extrapulmonary bronchi and the lower trachea was performed. The amount of plasma (microliter) was determined by analysis of a plasma tracer, [125I]albumin, in lavage fluid and blood (plasma) samples. Ovalbumin, 3 to 12 pmol, and histamine, 5 and 10 nmol, produced a dose-dependent immediate exudation response (p < 0.001). The effects were nonneurogenic because they were not affected by topical lidocaine given in a dose (3 nmol) that prevented the exudative effect of capsaicin. The 6- and 12-pmol doses of ovalbumin (but not 3 pmol) produced a significant late-phase exudative response at 5 h (p < 0.001), and both the immediate and late phases were associated with increased (p < 0.01 to p < 0.001) levels of bradykinin in the lavage fluids. Histamine, even in doses that produced a greater early response than the allergen, did not produce a late-phase response. A single topical dose of an antiasthma steroid (budesonide, 12 mumol/kg) administered just before ovalbumin (6 pmol) had little effect on the immediate response but inhibited the late-phase response (p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

In vitro effect of beta 2-agonists on bacterial killing and superoxide anion (O2-) release from alveolar macrophages of patients with chronic bronchitis

A new class of long-acting beta 2-adrenoceptor agonists has been studied in the last few years. Apparently, they display an important anti-inflammatory activity with an inhibition of different cellular functions. This study was carried out to compare a long-acting beta 2-agonist, formoterol, with a conventional short-acting one, salbutamol, on the release of superoxide anion (O2-) and bacterial killing by alveolar macrophages obtained with bronchoalveolar lavage (BAL) from 20 patients with chronic bronchitis. The O2- production in basal conditions was not affected by beta 2-agonists. On the contrary, after phagocytosis of opsonized zymosan 10(-5) M formoterol significantly affected the phagocytic index (difference between stimulated and basal O2- release): 7.9 +/- 2.0 nM O2-/10(6) AM/10 min vs 16.8 +/- 2.5, p < 0.0007. Bacterial killing was inhibited by the two drugs in a dose-dependent way, but the effect of formoterol was more evident than that of salbutamol. After blocking beta 2-receptors with propranolol, we observed a prevention of the beta 2-agonist effects on both O2- release and bacterial killing. The inhibition of the alveolar macrophage functions considered in this study is evident for both beta 2-agonists, but it is significantly more pronounced for formoterol. Our data can be interpreted as one possible mechanism of the anti-inflammatory effect described for long-acting beta 2-agonists. On the other hand, also a potential suppression of pulmonary antibacterial defenses must not be overlooked, particularly in chronic bronchitis, a disease characterized by recurrent airways infections. Whether current therapeutic dosages are sufficient to achieve anti-inflammatory or microbicidal suppressive effects of clinical relevance has not been demonstrated so far.

Formoterol: pharmacology, molecular basis of agonism, and mechanism of long duration of a highly potent and selective beta 2-adrenoceptor agonist bronchodilator

Formoterol is an innovative, highly potent, beta 2-adrenoceptor-selective agonist combining the clinical advantages of rapid onset of action with a duration of action in excess of 12 h. In vitro, formoterol is a potent airway smooth muscle relaxant with high efficacy, and very high affinity and selectivity for the beta 2-adrenoceptor. Formoterol appears to be retained in airway smooth muscle for extended periods since its relaxant effect on human airway smooth muscle is resistant to repeated washing and formoterol displays 'reassertion' of relaxation after washout of a beta-adrenoceptor antagonist. A model based on the diffusion microkinetics of formoterol into the plasmalemma lipid bilayer is proposed as a basis for these properties. In addition to the release of pro-inflammatory mediators from cells such as the mast cell, several other disease processes probably occur in asthma. Leukocytes, notably eosinophils, adhere to the vascular endothelium and emigrate into airway tissues, which may be damaged by these cells if they are activated to release mediators or their granular contents. Plasma and its component proteins are extravasated from the bronchial microcirculation. Formoterol has been demonstrated to potently inhibit these cells and processes in experimental test systems. Continuing clinical research involving histological examination of tissue reactions may allow a more complete determination of the effects of formoterol on inflammatory processes in humans and the clinical relevance of any such effects.

The action of beta-receptors on microvascular endothelium or: is airways plasma exudation inhibited by beta-agonists?

The connections between airway inflammation, plasma exudation and a possible anti-exudative action of beta-agonists are discussed. Asthma involves a response to inflammatory mediators which results in increased microvascular leakage with exudation of plasma into the airways. This plasma exudation is a specific inflammatory response and also a general response in the sense that it is independent of the mechanism sustaining the inflammation. Thus, mucosal exudation of plasma may reflect the subepithelial airway inflammatory process, irrespective of its genesis. In addition, the exudate itself contains many substances which may themselves promote inflammation and be major factors in producing and sustaining acute and chronic airway inflammation. This suggests that drug therapies should be aimed at reducing plasma exudation. Studies in guinea pigs have shown that a number of drugs such as xanthines, cromoglycates, glucocorticoids and beta-agonists may inhibit this exudation, but the effect seems to be attenuated in human mucosal tissue. beta-Agonists appear promising in this respect, but if an anti-exudative effect is confirmed for them, it will be necessary to determine whether this is a direct effect or secondary to their effects on cellular inflammatory processes in the airways.

The use of the nose to study the inflammatory response of the respiratory tract

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