Leukotriene C4 synthase polymorphisms and responsiveness to leukotriene antagonists in asthma

AIM: Cysteinyl leukotrienes are important pro-inflammatory mediators in the pathogenesis of asthma, while leukotriene C4 synthase is a key enzyme in their biosynthesis. Our aim is to evaluate whether responsiveness to leukotriene receptor antagonists was determined by expression of the variant (C) or wild-type (A) polymorphism of this enzyme. METHODS: We carried out a retrospective analysis of 8 randomised, placebo-controlled trials performed in our department in mild-to-moderate asthmatics. In all trials, effect of leukotriene receptor antagonist was compared to placebo, where the primary outcome was bronchial hyperresponsiveness to adenosine monophosphate or methacholine. Secondary outcomes were forced expiratory volume in 1 second, exhaled nitric oxide and peripheral blood eosinophils. RESULTS: For the primary outcome of attenuation of bronchial hyperresponsiveness by leukotriene receptor antagonist vs placebo, there were significant effects within each genotype on adenosine monophosphate (AMP) (n = 78): 2.21 and 2.07-fold improvements for AA and AC/CC, respectively; while for methacholine (n = 81) there were 1.39 and 1.36-fold improvements, respectively. There were no significant differences between genotypes (i.e. AA vs AC/CC): geometric mean fold-differences of 1.07 (95%CI 0.63-1.81) and 1.02 (95%CI 0.70-1.50) for AMP and methacholine, respectively. There were also no differences between genotypes for all secondary outcomes. CONCLUSION: Polymorphisms of leukotriene C4 synthase did not determine responsiveness, in terms of attenuation of bronchial hyperresponsiveness, to leukotriene receptor antagonists in mild-to-moderate asthmatics. Further prospective large pharmacogenetic studies are required in more severe patients, where there may be greater improvements in pharmacodynamic outcome measures such as bronchial hyperresponsiveness and exhaled nitric oxide.     

Comparison of the Bronchodilator Effect of Inhaled Short- and Long-Acting beta(2)-Agonists in Children with Bronchial Asthma: A Randomised Trial

OBJECTIVE: This study compared the bronchodilator effects of short-acting (salbutamol and procaterol) and long-acting (salmeterol and formoterol) beta(2)-agonists in children with bronchial asthma. PATIENTS: Twenty-seven (18 male, 9 female) children with bronchial asthma were enrolled in the study. Drugs were administered randomly in the morning for 5 days as follows: 1 single dose of two short-acting beta(2)-agonists, salbutamol 200microg and procaterol 20microg, and two long-acting beta(2)-agonists salmeterol 50microg and formoterol 24microg, and placebo. RESULTS: All beta(2)-agonists demonstrated a significantly higher bronchodilator effect than that observed with placebo. This effect appeared to be due to the forced expiratory flows. Formoterol produced a higher bronchodilator effect than salbutamol, and salmeterol showed a bronchodilator effect comparable with salbutamol at 30 minutes but higher than salbutamol after 3 hours. CONCLUSION: Our study confirmed the efficacy of the bronchodilator effects of the beta(2)-agonists. Salmeterol and formoterol, in particular, produced an improvement in respiratory function with a significant increase in forced expiratory flows in children with bronchial asthma.     

Roflumilast: a selective phosphodiesterase 4 inhibitor

Roflumilast is a selective phosphodiesterase (PDE) 4 inhibitor with a range of anti-inflammatory properties and potential for treatment of inflammatory disease. The therapeutic effects of roflumilast are thought to be mediated via increased levels of cellular 3',5'-cyclic adenosine monophosphate (cAMP) and include inhibition of microvascular leakage, inhibition of trafficking, release of cytokines and chemokines from inflammatory cells, and bronchodilation. The anti-inflammatory and bronchodilator properties of roflumilast have resulted in clinical studies to investigate the effects of roflumilast in inflammatory airway diseases such as asthma and chronic obstructive pulmonary disease. In asthma, roflumilast taken as a once-daily oral dose of 500 ug has been shown to improve clinical symptoms and airway function, reduce exercise-induced asthma and decrease bronchial airway hyperresponsiveness. In chronic obstructive pulmonary disease, roflumilast taken as a once-daily oral dose of 500 ug has been shown to reduce the frequency of exacerbations with small effects on improving lung function. Side effects of roflumilast appear to be mild and short lasting. It is likely that this new class of selective PDE4 inhibitor may provide a therapeutic option for patients with inflammatory airway disease.     

Association of IL-13 polymorphisms with leukotriene receptor antagonist drug responsiveness in Korean children with exercise-induced bronchoconstriction

BACKGROUND: IL-13 is a pivotal cytokine in allergic inflammation and bronchial hyperresponsiveness, and is known to influence leukotriene levels. OBJECTIVE: We investigated whether IL-13 polymorphisms may be associated with clinical phenotypes and drug responsiveness to the leukotriene receptor antagonist (LTRA) in Korean asthmatic children with exercise-induced bronchoconstriction (EIB). METHODS: We enrolled 242 normal controls and 374 patients with asthma. Of the asthmatic patients, 100 performed exercise challenge tests before and after receiving montelukast (5 mg/day) for 8 weeks and included 80 subjects in drug responsiveness analysis. We assessed IL-13 polymorphisms (-1512A/C, -1112C/T, +2044G/A) through PCR-restriction fragment length polymorphism analysis. RESULTS: Significantly higher total IgE levels and maximum percent fall in forced expiratory volume in 1 s (FEV1) (%) after exercise challenge test were found in asthmatic patients carrying one or two copies of the IL-13 +2044A versus those homozygous for +2044G (P=0.011 and 0.040, respectively). We further noted a correlation of total IgE with maximum percent fall in FEV1 (%) in asthmatic patients, as well as a reverse correlation with improvement of maximum percent fall in FEV1 (%) after exercise challenge tests. Finally, we observed a significant association between responsiveness to montelukast and IL-13 -1112C/T polymorphism and the haplotype of IL-13 polymorphisms. CONCLUSION: The IL-13 +2044G/A polymorphism may be associated with atopy and EIB severity in Korean children with EIB, and thus could potentially be considered as a disease-modifying gene. Moreover, the IL-13 -1112C/T polymorphism and the haplotype of IL-13 polymorphisms seem to be associated with LTRA drug responsiveness, and thus might prove useful as a target for modulation of LTRA drug responsiveness.     

Synergistic effects of pranlukast and leukotriene B4 receptor antagonist on antigen-induced pulmonary reaction.

We now attempted to differentiate effects of cysteinyl-leukotrienes and leukotriene B4 on antigen-induced pulmonary reaction by using a selective leukotriene D4/E4 (CysLT1) receptor antagonist and a selective LTB4 (BLT) receptor antagonist in rats. An intratracheal challenge with ovalbumin to Brown-Norway rats actively sensitized with ovalbumin produced two phases of airway responses which were estimated based on airway resistance, the immediate-type airway response within 30 min, and the delayed-type airway response beginning from 4 to 6 h after the challenge. Pretreatment of the rats with a CysLT1 receptor antagonist (pranlukast) failed to reduce the elevation of airway resistance, and pretreatment with a BLT receptor antagonist (ONO-4057; 5-[2-(2-carboxyethyl)-3-[6-(4-methoxyphenyl)-5E-hexenyl]- oxyphenoxy] valeric acid) also produced no decrease. In contrast, combined pretreatment of the rats with pranlukast and ONO-4057 did not reduce the amplitude of the immediate-type airway response, but did allow the elevated airway resistance to return to its baseline level and also significantly inhibited the delayed-type airway response. Histological examination at 6 h after ovalbumin challenge showed infiltration of inflammatory cells with a predominance of neutrophils and scattered eosinophils in the bronchial submucosa. While pretreatment with neither pranlukast nor with ONO-4057 inhibited the infiltration of inflammatory cells in the bronchial submucosa, pretreatment with the two antagonists combined significantly inhibited the infiltration of granulocytes into the bronchial submucosa. On the contrary, intratracheal administration of either leukotriene D4 or leukotriene B4 up to 10 microg resulted in the infiltration of granulocytes into the bronchial submucosa, but no synergism for the infiltration of granulocytes was observed after combined administration. These results suggest that leukotriene B4 appears to play a significant role in the antigen-induced pulmonary reaction in association with cysteinyl-leukotrienes. Accordingly, the combined antagonism at the CysLT1 receptor and BLT receptor may be a useful intervention for the treatment of bronchial asthma.     

Inhibition by adenosine of histamine and leukotriene release from human basophils

Adenosine inhibited the release of histamine and leukotriene C4 (LTC4) from immunologically-activated basophils in a dose-dependent manner. Structural congeners of adenosine also attenuated the elaboration of these two mediators from stimulated basophils and a rank order of potency for the inhibition was observed following the sequence 2-chloroadenosine greater than or equal to N-ethylcarboxamidoadenosine (NECA) greater than adenosine greater than or equal to R-phenylisopropyladenosine (R-PIA) greater than or equal to S-PIA. These same nucleosides modulated the generation of LTC4 more potently than the release of histamine. A number of methylxanthines, which are antagonists of cell surface adenosine receptors, reversed the inhibition by adenosine and its congeners of the release of both histamine and LTC4 to varying extents. Dipyridamole and nitrobenzylthioinosine (NBTI), agents that block the intracellular uptake of adenosine, antagonized the inhibition of histamine release by adenosine (and 2-chloroadenosine) but failed to reverse the attenuation of LTC4 generation by the nucleoside. These same uptake blockers were unable to antagonize the inhibitory effects of NECA on either histamine or LTC4 release. In purified basophils, NECA and R-PIA, and in that order of decreasing reactivity, increased total cell cyclic adenosine monophosphate (cAMP) levels and inhibited the stimulated release of mediators. In total, these results suggest that the basophil possesses a cell surface adenosine receptor which, on the basis of both pharmacological and biochemical criteria, most closely conforms to an A2/Ra-like receptor. However, in addition to an interaction at the cell surface, studies with agents that block the intracellular uptake of adenosine suggest that the nucleoside may also exert intracellular effects when countering the release of histamine (but not LTC4).     

Tiotropium bromide, a new, once-daily inhaled anticholinergic bronchodilator for chronic-obstructive pulmonary disease

Tiotropium bromide is a quaternary ammonium compound structurally related to ipratropium and has recently been approved in the US for the long-term, once-daily, maintenance treatment of bronchospasm associated with chronic-obstructive pulmonary disease (COPD). It is available in a dry powder form, where 18 microg [corrected] of the drug is inhaled once-daily through a device, the HandiHaler). The potency and long duration of effect of this anticholinergic bronchodilator result primarily from a prolonged blockade of the M1 and M3 muscarinic receptors in the airways and a relatively more rapid dissociation from the M2 receptor (which provides inhibitory feedback). Multiple studies of up to a duration of 1 year have demonstrated its effectiveness as a bronchodilator for COPD, with a trough increase (measured approximately 24 h after administration of the drug) in forced expiratory volume in 1 s of approximately 0.12 l and a peak increase of approximately 0.25 l. Tiotropium inhalation also leads to a significant reduction in static lung volumes in hyperinflated patients with COPD; this probably contributes to the reduction in dyspnoea that is associated with long-term use of this maintenance bronchodilator. Regular use of the drug was associated with clinically meaningful increases in the Transitional Dyspnoea Index, which indicate reductions in dyspnoea associated with daily activities. Improvement in the respiratory-specific health status questionnaire, the St George's Respiratory Questionnaire component and total scores was also documented. Finally, pooled data from two 1-year studies and two 6-month studies documented 20 and 28% reductions in the number of exacerbations per patient per year. Side effects have been relatively minimal, with dry mouth the most common symptom, ranging 6 - 16% of patients and rarely leading to discontinuation of the study drug. Limited comparisons of efficacy with other bronchodilators are available. Once-daily tiotropium has been demonstrated to be clearly superior to ipratropium four times daily as a bronchodilator for COPD. Combined results from two studies comparing once-daily tiotropium to twice-daily inhalation of standard doses of salmeterol, indicate a magnitude of the bronchodilator response similar in the two drugs early in the study. However, by 6 months, the bronchodilator effect of tiotropium was somewhat greater than that of the long-acting beta-agonist. Preliminary data suggest that combining tiotropium with long-acting beta-agonists may produce additional bronchodilator action in COPD.     

Characterization of the leukotriene D4 receptor in hyperreactive rat lung.

A [3H]leukotriene D4 radioreceptor binding assay has been established in rat lung and has been used to fully characterize the leukotriene D4 receptor in lung membranes from an inbred strain of rats displaying non-specific bronchial hyperreactivity. [3H]leukotriene D4 specific binding in this tissue is of high affinity (KD 0.12 nM), saturable (Bmax 42 fmol/mg protein), inhibited by both guanine nucleotide analogues and sodium ions and increased by divalent cations. In addition, Ki values show that agonists, but not antagonists, compete for [3H]leukotriene D4 binding in rat lung with the same potency as they compete for [3H]leukotriene D4 binding in guinea-pig lung, the classical tissue for leukotriene D4 receptor studies. Finally, [3H]leukotriene D4 binding in hyperreactive rat lung has been compared with [3H]leukotriene D4 binding in lung tissue from Fischer rats, which are a less responsive strain.     

Reducing electrostatic charge on spacer devices and bronchodilator response

AIMS: Plastic spacers are widely used with pressurized metered dose inhalers (pMDI). Reducing electrostatic charge by washing spacers with detergent has been shown to greatly improve in vitro and in vivo drug delivery. We assessed whether this finding is associated with an improved bronchodilator response in adult asthmatics. METHODS: Twenty subjects (age 18-65 years) with a known bronchodilator response inhaled in random order salbutamol from a pMDI (Ventolin) through an untreated new spacer (Volumatic) and through a detergent washed spacer. Patients received the following doses of salbutamol via pMDI at 20 min intervals: 100 microg, 100 microg, 200 microg, 400 microg, 800 microg. Spirometry, heart rate and blood pressure were checked prior to each dose and 20 min after the last dose. RESULTS: There were no differences between baseline forced expiratory volume in 1 s (FEV1) using either spacer (2.61+/-0.56 and 2.52+/-0.45 l, untreated and treated with detergent, respectively; mean +/- s.d.). The provocation dose required to cause a clinically significant improvement of 10% in FEV1 (PD10) was significantly lower when the detergent treated spacer was used (1505 +/-1335 and 430+/-732 microg, untreated and treated, respectively, P<0.002). CONCLUSIONS: We have demonstrated an improvement in bronchodilator response, in adult asthmatics, after reducing the electrostatic charge in a spacer device by washing it with ordinary household detergent. This finding stresses the importance of an optimal choice of delivery device for asthma medication.     

Effects of transdermal scopolamine on pulmonary function, symptoms and bronchial hyperresponsiveness to methacholine

This study is a result of two consecutive double-blind, placebo-controlled, cross-over studies. In the first study, we evaluated therapeutic effects of a single transdermal scopolamine patch (Scopoderm® TTS, size 2.5 cm², Ciba Geigy) on forced expiratory volume in one second (FEV₁), reversibility, peak expiratory flow (PEF) and symptoms in ten patients with reversible airways disease (ΔFEV₁9% predicted). During the study, blood and urine samples were taken from the patients and analysed for scopolamine levels. The drug was adequately taken up from the patch into the systemic circulation. However, no significant clinical effects, nor correlations between the scopolamine levels and the outcome parameters were observed. Because of the possibility of sub-therapeutic doses in the first study, a second study with two transdermal scopolamine patches was performed in ten patients with bronchial hyperresponsiveness to methacholine. The blood and urine concentrations of free scopolamine were doubled compared to the first study. There were still no statistically significant effects on FEV₁, PEF, symptoms, and bronchial hyperresponsiveness, yet most of the patients now reported adverse side effects. We conclude that transdermal administration of scopolamine is not clinically useful in asthma and chronic obstructive pulmonary disease. Even application of two patches does not result in therapeutically effective levels at the muscarinic receptors in the lung, yet causes several side effects.     

Tiotropium bromide,a new,once-daily inhaled anticholinergic bronchodilator for chronic-obstructive pulmonary disease

Tiotropium bromide is a quaternary ammonium compound structurally related to ipratropium and has recently been approved in the US for the long-term, once-daily, maintenance treatment of bronchospasm associated with chronic-obstructive pulmonary disease (COPD). It is available in a dry powder form, where 18 mg of the drug is inhaled once-daily through a device, the HandiHaler^®. The potency and long duration of effect of this anticholinergic bronchodilator result primarily from a prolonged blockade of the M₁ and M₃ muscarinic receptors in the airways and a relatively more rapid dissociation from the M₂ receptor (which provides inhibitory feedback). Multiple studies of up to a duration of 1 year have demonstrated its effectiveness as a bronchodilator for COPD, with a trough increase (measured ～ 24 h after administration of the drug) in forced expiratory volume in 1 s of ～ 0.12 l and a peak increase of ～ 0.25 l. Tiotropium inhalation also leads to a significant reduction in static lung volumes in hyperinflated patients with COPD; this probably contributes to the reduction in dyspnoea that is associated with long-term use of this maintenance bronchodilator. Regular use of the drug was associated with clinically meaningful increases in the Transitional Dyspnoea Index, which indicate reductions in dyspnoea associated with daily activities. Improvement in the respiratory-specific health status questionnaire, the St George’s Respiratory Questionnaire component and total scores was also documented. Finally, pooled data from two 1-year studies and two 6-month studies documented 20 and 28% reductions in the number of exacerbations per patient per year. Side effects have been relatively minimal, with dry mouth the most common symptom, ranging 6 – 16% of patients and rarely leading to discontinuation of the study drug. Limited comparisons of efficacy with other bronchodilators are available. Once-daily tiotropium has been demonstrated to be clearly superior to ipratropium four times daily as a bronchodilator for COPD. Combined results from two studies comparing once-daily tiotropium to twice-daily inhalation of standard doses of salmeterol, indicate a magnitude of the bronchodilator response similar in the two drugs early in the study. However, by 6 months, the bronchodilator effect of tiotropium was somewhat greater than that of the long-acting β-agonist. Preliminary data suggest that combining tiotropium with long-acting β-agonists may produce additional bronchodilator action in COPD.     

Effect of clenbuterol on peripheral airway obstruction in bronchial asthma

A study was carried out in 6 patients with bronchial asthma to investigate the effects of clenbuterol, a beta 2-sympathomimetic bronchodilator, on peripheral airway obstruction. The basal lung functions of the patients were almost within normal range in both vital capacity (VC) and forced expiratory volume in 1 second (FEV1), but their maximal flow rates were lower in effort-independent phase of both maximal expiratory flow volume (MEFV) curve and partial expiratory flow volume (PEFV) curve. Furthermore, they demonstrated marked basal frequency dependence of dynamic compliance [CL,dyn]. Oral administration of clenbuterol (40 micrograms) produced a significant increase in the maximal flow in effort-independent phase of both MEFV and PEFV curves, and markedly decreased frequency dependence of CL,dyn in comparison with the baseline values, while it improved both VC and FEV1 to a lesser extent. These results suggest that clenbuterol preferentially reduced the peripheral airway obstruction in bronchial asthma.     

Antileukotriene drugs in childhood asthma: what is their place in therapy?

Leukotriene antagonists are a new class of anti-inflammatory drugs which have shown clinical efficacy in the management of asthma. However, their role in paediatric asthma is still unclear. In essence, while there are theoretical reasons as to why leukotriene antagonists would be of use in the management of childhood asthma, there is little clinical data on their use in this patient group. Studies with leukotriene antagonists to date have been performed in children with chronic 'undertreated' asthma which, under current recommendations, should be treated with inhaled corticosteroids. Furthermore, the magnitude of effect of leukotriene antagonists on lung function (forced expiratory volume in one second of less than 5% better than placebo) and daily symptoms (0.23 puffs per day of B2 agonist less than placebo), while reaching statistical significance, is unlikely to be of clinical significance in children with chronic undertreated asthma. There is, however, good evidence for leukotriene antagonist use in exercise induced asthma in children. We conclude that although leukotriene antagonists may play an important role in the management of childhood asthma in the future, particularly as corticosteroid sparing agents and in exercise induced asthma, clinical data in paediatric asthma is poor.     

Comparative trough effects of formoterol and salmeterol on lymphocyte β2-adrenoceptor – regulation and bronchodilatation

Objectives: The primary aim of the present study was to evaluate comparative trough effects of formoterol and salmeterol on β₂-adrenoceptor regulation and bronchodilator response after regular twice-daily treatment, with a secondary aim to evaluate any possible association with β₂-adrenoceptor polymorphism. Methods: Sixteen asthmatic subjects, with mean (SD) age 33(9) years, all taking inhaled corticosteroids and with a forced expiratory volume in 1 s (FEV₁) of 81(12)% predicted were recruited to take part in a randomised single-blind, three-way cross-over study. The subjects received three treatments each for 1 week, with 1-week washout periods in between: (1) formoterol dry powder, 12 μg twice daily, (2) salmeterol dry powder, 50 μg twice daily, or (3) placebo, twice daily. Spirometry and lymphocyte β₂-adrenoceptor parameters were measured before the first dose and 12 h after the last dose of each treatment, as well as domiciliary peak flow during each treatment. Results: There were no differences in β₂-adrenoceptor density (B_max) between the three treatments prior to the first dose; whereas, after the last dose, B_max was lower with both active treatments than with placebo, but was significant for salmeterol only – a 1.2-fold geometric mean fold difference (95% CI 1- to 1.4-fold), P = 0.04. Compared with placebo, there were n = 9 of 16 subjects with salmeterol and n = 6 of 16 with formoterol who had a greater than 15% fall in B_max. Post-hoc trend analysis of polymorphism showed that the propensity for downregulation appeared to be related to the occurrence of an allelic substitution of glycine at codon 16 – 8 of 13 for salmeterol versus 5 of 13 for formoterol with a greater than 15% fall compared with placebo. There were no significant differences between salmeterol and formoterol in terms of mean or individual values for downregulation. There was evidence of persistent bronchodilator activity with both active treatments compared with placebo; this was significant for forced expiratory flow rate between 25% and 75% of vital capacity (FEF_25–75) – the mean difference versus salmeterol was 0.39 l/s (95% CI 0.06–0.70), P = 0.02, and versus formoterol was 0.35 l/s (95% CI 0.16–0.53), P = 0.001. These effects were mirrored by significant improvements in morning peak flow rate compared with placebo – mean difference versus salmeterol was 24 l/min (95% CI 7–42), P = 0.01, and versus formoterol was 36 l/min (95% CI 25–48), P < 0.0001. Conclusion: There were no differences between regular treatment with formoterol and salmeterol in their effects on lymphocyte β₂-adrenoceptor regulation at the end of a 12-h dosing interval, with both drugs exhibiting a residual degree of bronchodilator activity at the same time point. Further studies to evaluate receptor regulation and bronchodilator response are required in susceptible patients who have the homozygous glycine-16 polymorphism. Received: 15 January 1999 / Accepted in revised form: 19 April 1999     

Effects of non-bronchoconstrictive doses of inhaled propranolol on airway responsiveness to methacholine

OBJECTIVES: The aim of this study was to evaluate the effects of non-bronchoconstrictive doses of propranolol on airway hyperresponsiveness to methacholine. METHODS: Double increasing concentrations (from 0.03 to 64 micrograms/ml) of inhaled propranolol were administered to a study population which included ten patients with mild asthma, ten rhinitics, and ten healthy control subjects. After the baseline bronchial responses to propranolol and methacholine, expressed as the cumulative provocative dose producing a 20% fall in forced expiratory volume in 1 s (PD20FEV1), were assessed, methacholine challenge was repeated after pretreatment with non-bronchoconstrictive doses of propranolol. RESULTS: The pharmacologically induced beta-blockade did not cause any effect in normal individuals, but it worsened airway responsiveness to methacholine in all asthmatics (geometric mean PD20 FEV1: 257 and 87 micrograms, respectively) and some rhinitics (geometric mean PD20 FEV1: 724 and 446 micrograms, respectively). CONCLUSION: Asthmatic patients were extremely sensitive to beta-blockers, whereas we observed a variable response to propranolol within the group of rhinitic subjects. This variability in the latter group is possibly because these individuals had different degrees of airway inflammation, increased parasympathetic activity, and beta-adrenoceptor dysfunction.     

Mediators of adenosine- and ovalbumen-induced bronchoconstriction of sensitized guinea-pig isolated airways

The mediators of bronchoconstriction of isolated lungs and trachea from ovalbumen sensitized guinea-pigs to adenosine and ovalbumen were examined using relevant antagonists. Changes in perfusion pressure and tension of paired lung halves and tracheal spiral strips, respectively, were recorded in response to adenosine (1 mM lung, 300 microM trachea), histamine (10 microM), methacholine (10 microM) and ovalbumen (10 microg). One half was perfused with antagonist while the other received vehicle. Tracheal strips were superfused throughout with the P(1) receptor antagonist 8-phenyltheophylline, to examine 8-phenyltheophylline-resistant responses. The histamine H(1) receptor antagonist, mepyramine (1.5 mM), the cyclooxygenase inhibitors, indomethacin (5 mM) and diclofenac (5 mM), the leukotriene receptor antagonist, zafirlukast (1 mM), and the lipoxygenase inhibitor, zileuton (20 mM), alone failed to inhibit bronchoconstriction by adenosine and ovalbumen of the lung and trachea. When two antagonists were combined, only mepyramine and zafirlukast significantly reduced the lung responses to adenosine and ovalbumen. The tracheal adenosine response was substantially reduced, although not significantly, while ovalbumen was significantly reduced. When mepyramine, indomethacin and zafirlukast were combined, the lung constriction by adenosine and ovalbumen were virtually abolished. Similarly, the combination of mepyramine, diclofenac and zafirlukast significantly attenuated the lung responses to adenosine and ovalbumen. Thus, histamine, cyclooxygenase products and leukotrienes alone are not responsible for the bronchoconstriction of isolated sensitized lung tissues to adenosine or ovalbumen, which appears to be due to the release of all three mediators.     

Inhaled dopamine induces bronchodilatation in patients with bronchial asthma.

OBJECTIVE: To determine the probable bronchodilating effect of dopamine administered by inhalation route in patients with crisis of bronchial asthma and the effect of dopamine on bronchial motor tone. DESIGN AND METHOD: We have studied eighteen (18) patients with crisis of bronchial asthma, ten (10) subjects with bronchial hyperreactivity and ten (10) healthy subjects. Patients with other pulmonary or cardiac disease were excluded. All received by inhalation placebo (0.9% saline solution), dopamine at 0.5 microg/kg/min (controlled by heart rate and arterial pressure with a dynamap), and placebo. Respiratory parameters: forced vital capacity (FVC), forced expiratory volume at the first second (FEV1), forced maximal expiratory flow (FEFmax) and forced expiratory flow at the 50% of vital capacity (FEF50) were measured in each protocol period. Student's paired t test, Wilcoxon and Mann Whitney analysis were performed. RESULTS: After dopamine inhalation, there was an increase of FVC by 23% (p<0.001); an increase of FEV1 by 39% (p<0.0001); an increase of FEF50 by 33% (p<0.001) and an increase of FEFmax by 31% (p<0.001). There were no respiratory parameter changes in both, subjects with bronchial hyperreactivity and normal after dopamine inhalation. CONCLUSIONS: Inhaled dopamine induces bronchodilatation in patients with crisis of bronchial asthma. Inhaled dopamine neither alters basal bronchial tone in healthy subjects nor in subjects with bronchial hyperreactivity.     

Prostanoid DP receptor antagonists suppress symptomatic asthma-like manifestation by distinct actions from a glucocorticoid in rats

While inhaled glucocorticoids are the best treatment for the majority of chronic asthmatics, there is a small group who do not respond to these drugs or whose disease can only be controlled by high doses of oral glucocorticoids with risks of severe side effects. Therefore, a safe novel anti-asthmatic agent which has a different mechanism from that of glucocorticoids is needed for the management of asthma. We have previously shown that an orally active prostanoid DP receptor antagonist, S-5751, had potent anti-inflammatory effects in guinea pig and sheep asthma models. In this study, using a rat asthma like model, we found that lung neutrophilia and proinflammatory cytokine secretion as well as bronchial hyperresponsiveness and lung eosinophilia were induced by repeated antigen-inhalations after antigen-sensitization. These symptoms are similar to the pathogenesis of symptomatic asthma. Orally-administered prostanoid DP receptor antagonists S-5751 and pinagladin significantly suppressed not only bronchial hyperresponsiveness and lung eosinophilia but also neutrophilia and mucus secretion in the lung, while oral prednisolone inhibited only bronchial hyperresponsiveness and eosinophil infiltration. In addition, prostanoid DP receptor antagonists significantly suppressed interleukin (IL)-1β, IL-6 and CXCL1 mRNA in contrast to suppression of IL-4 and CCL11 mRNA by prednisolone. The majority of prostanoid DP receptor-expressing cells in both rat and human asthmatic lungs are infiltrative macrophages and/or monocytes. These results suggest that prostanoid DP receptor antagonists utilize different mechanisms from glucocorticoids, and that they would be a novel alternative and/or combination drug for asthma therapy.     

哮喘患者外周血单个核细胞腺苷受体

目的通过检测哮喘患者外周血单个核细胞（PBMCs）腺苷受体mRNA表达,探讨腺苷受体在哮喘发病中的作用。方法用Ficoll液分离PBMCs,采用逆转录-多聚酶联反应法和图象分析半定量法检测PBMCs腺苷受体mRNA。结果正常人及哮喘患者PBMCs均表达A