Th2 cytokines and asthma. The role of interleukin-5 in allergic eosinophilic disease.

Interleukin-5 is produced by a number of cell types, and is responsible for the maturation and release of eosinophils in the bone marrow. In humans, interleukin-5 is a very selective cytokine as a result of the restricted expression of the interleukin-5 receptor on eosinophils and basophils. Eosinophils are a prominent feature in the pulmonary inflammation that is associated with allergic airway diseases, suggesting that inhibition of interleukin-5 is a viable treatment. The present review addresses the data that relate interleukin-5 to pulmonary inflammation and function in animal models, and the use of neutralizing anti-interleukin-5 monoclonal antibodies for the treatment of asthma in humans.

Synergistic antiallergic activity of combined histamine H1- and cysteinyl leukotriene1-receptor blockade in human bronchus.

Mast cell histamine (HA) and cysteinyl leukotrienes (CysLT) account for most of the early phase bronchospasm in asthma. However, activation of the smooth muscle CysLT1-receptor plays a major role in asthmatic bronchospasms. CysLT-receptor antagonists or CysLT-synthesis inhibitors are efficacious in asthma but do not completely abolish asthmatic bronchospasms. A recent clinical study showed that combined antagonists loratadine (H1) and zafirlukast (CysLT1) were more effective against allergic bronchospasms than either drug alone. We examined the combined efficacy of H1- and CysLT1-receptor antagonists in allergic human bronchus. The H1- and CysLT1-receptor antagonists chlorpheniramine (CTM; 1 microM) and MK-571 (0.03 microM), were tested alone and in combination, against anti-human IgE antibody (Ab)-induced contractions of passively sensitized isolated human bronchus. Ab-induced allergic contractions were reduced 15% and 36% by CTM (1 microM) and MK-571 (0.03 microM), respectively. Combined CTM (1 microM) and MK-571 (0.03 microM) significantly inhibited the Ab response by 87%. Mechanistic investigations in isolated human bronchus and cultured human cord blood mast cells suggest that H1- and CysLT-receptor interactions likely occur at the airway smooth muscle level. CTM and MK-571 synergistically inhibited human allergic bronchospasm in the present in vitro model. The mechanism underlying this synergistic activity requires further investigation.

Nociceptin inhibits cough in the guinea-pig by activation of ORL(1) receptors.

We studied the central and peripheral antitussive effect of ORL(1) receptor activation with nociceptin/orphanin FQ in conscious guinea-pigs. In guinea-pig cough studies, nociceptin/orphanin FQ (10, 30, and 90 microg) given directly into the CNS by an intracerebroventricular (i.c.v.) route inhibited cough elicited by capsaicin exposure by approximately 23, 29 and 52%, respectively. The antitussive activity of nociceptin/orphanin FQ (90 microg, i.c.v.) was blocked by the selective ORL(1) antagonist [Phe(1)gamma(CH(2)-NH)Gly(2)]nociceptin-(1-13)-NH(2) (180 microg, i.c.v.) and J113397 (10 mg kg(-1), i.p.) but not by the opioid antagonist, naltrexone (3 mg kg(-1), i.p.). Furthermore, intravenous (i.v.) nociceptin/orphanin FQ (1.0 and 3.0 mg kg(-1)) also inhibited cough approximately by 25 and 42%, respectively. These findings indicate that selective ORL(1) agonists display the potential to inhibit cough by both a central and peripheral mechanism, and potentially represent a novel therapeutic approach for the treatment of cough.

Dose-ranging study of a new steroid for asthma: mometasone furoate dry powder inhaler.

A new formulation of mometasone furoate (MF) for administration by dry powder inhaler (DPI) was evaluated for the treatment of asthma. A 12-week, double-blind, placebo-controlled dose-ranging study compared the efficacy and safety of three doses of MF DPI (100, 200 and 400 mcg b.i.d) with beclomethasone dipropionate (BDP) 168 mcg b.i.d. administered by metered dose inhaler in 365 adult or adolescent patients being treated with inhaled glucocorticoids. The mean change from baseline to endpoint (last treatment visit) for forced expiratory volume in 1 sec (FEV1) was the primary efficacy variable. Secondary efficacy variables included other objective measures of pulmonary function [forced vital capacity (FVC), forced expiratory flow 25-75% (FEV25-75%.) and peak expiratory flow rate (PEFR)] as well as subjective measures of therapeutic response (patients' daily evaluation of asthma symptoms and physicians' evaluation). At endpoint, all four active treatments were significantly more effective than placebo (P < 0.01) in improving FEV1 (MF DPI 5 to 7%, BDP 3%, placebo -6.6%) and all other measures of pulmonary function (FVC: MF DPI 4 to 5%, BDP 2%, placebo -4.7%; FEF25-75%: MF DPI 6 to 18%, BDP 7.5%, placebo -9.5%; PEFR (AM): MF DPI 5 to 10%, BDP 5.7%, placebo -7%). A consistent trend was observed for better improvement in patients treated with MF DPI 200 mcg b.i.d. than with MF DPI 100 mcg b.i.d., with no apparent additional benefit of MF DPI 400 mcg b.i.d. Results for the MF DPI 100 mcg b.i.d. and BDP 168 mcg b.i.d. treatment groups were similar. Patients' and physicians' subjective evaluations of symptoms found similar improvement in the MF DPI 200 and 400 mcg b.i.d. treatment groups, which were slightly better than that in the MF DPI 100 mcg b.i.d. group. Symptoms tended to worsen in the placebo group. MF DPI was well tolerated at all dose levels and the most frequently reported treatment-related adverse effects were headache, pharyngitis and oral candidiasis. No evidence of HPA-axis suppression was detected in any treatment group. In summary, all doses of MF DPI were well tolerated and significantly improved lung function and MF DPI 400 mcg (200 mcg b.i.d.) was the optimal dose in this study of patients with moderate persistent asthma.

Beyond the histamine receptor: effect of antihistamines on mast cells.

Many antihistamines exhibit inhibition of mediator release from mast cells and basophils, in in vitro studies in addition to H1 antagonism. The underlying mechanism is unclear but is unrelated to H1-receptor antagonism. Clinical studies of antihistamins in antigen challenge and seasonal allergy demonstrate reduction of mast cell mediators in nasal lavage. It is not known what mechanism(s) underly these observations, although the concentrations required in in vitro studies suggests that a direct effect on mast cells is unlikely. Furthermore, the therapeutic contribution of this effect is difficult to assess because of concomitant clinically significant H1 antagonism. This and other potential anti-allergic effects may enhance the therapeutic benefit of antihistamines and long-term studies are underway to explore this possibility.

Cardiovascular profile of loratadine.

The extremely low reporting rate of cardiovascular adverse events for loratadine, the possible preferential use of loratadine in patients with pre-existing cardiovascular disorders, and the impressive lack of cardiovascular effects at extremely high concentrations in clinical and preclinical studies demonstrate the very safe cardiovascular profile of loratadine.

A comparison of double-strength beclomethasone dipropionate (84 microg) MDI with beclomethasone dipropionate (42 microg) MDI in the treatment of asthma.

STUDY OBJECTIVE: To compare the efficacy and safety of a double-strength formulation of beclomethasone dipropionate (BDP 84) metered-dose inhaler (MDI) with that of beclomethasone dipropionate (BDP 42) MDI in the treatment of chronic asthma. DESIGN: A 28-day, randomized, double-blind, double-dummy, placebo-controlled, multicenter study. SETTING: Outpatient. PATIENTS: A total of 423 patients aged 12 to 65 years (mean range, 34 to 36 years) with moderate asthma (FEV1, 50 to 80% of predicted) who required long-term inhaled corticosteroids were enrolled. INTERVENTIONS: Patients were randomized to receive BDP 84, two oral inhalations bid (336 microg/d), BDP 42, four oral inhalations bid (336 microg/d), or placebo. A fourth treatment arm administering BDP 84, eight oral inhalations bid (HD BDP 84; 1,344 microg/d) was also included to determine whether a dose-response relationship could be demonstrated. MEASUREMENTS: Spirometry, clinical observations. RESULTS: The three active treatments were significantly more effective (p < or = 0.01) than placebo at all time points in improving FEV1, the primary efficacy parameter; BDP 42 and BDP 84 were comparable to each other at every time point. Secondary pulmonary function tests (FVC, forced expiratory flow at 25 to 75% of FVC, and peak expiratory flow rate) showed similar results. All three active treatments were well tolerated. A dose response between 336 microg/d and 1,344 microg/d was demonstrated. CONCLUSION: In this well-controlled 28-day study, BDP 42 and BDP 84 were shown to be comparable in efficacy and safety on a microgram-for-microgram basis.

Dose ranging study of mometasone furoate (Nasonex) in seasonal allergic rhinitis.

BACKGROUND: Topical nasal corticosteroids are rapidly gaining acceptance as first-line therapy for seasonal allergic rhinitis, but there is a desire for effective corticosteroids with an improved safety profile over existing products. OBJECTIVE: A multicenter, double-blind dose ranging study was conducted to compare the activity and tolerance of four doses of mometasone furoate nasal spray (tradename Nasonex) and placebo in adult patients with seasonal allergic rhinitis. METHODS: Four hundred eighty patients with seasonal allergic rhinitis were enrolled and randomized to receive mometasone furoate nasal spray 50 micrograms (n = 96), 100 micrograms (n = 95), 200 micrograms (n = 98) or 800 micrograms (n = 95), or placebo vehicle (n = 95) once daily for 28 days. RESULTS: All of the doses of mometasone furoate nasal spray showed activity in reducing the severity of rhinitis. The 200-microgram dose reduced total nasal symptom scores and total symptom scores throughout the study (P < .05 versus placebo vehicle). The 50-microgram dose and the 100-microgram dose showed less consistent activity at early timepoints (days 3 and 7), while the 800 microgram dose did not provide significant additional benefits over the 200-microgram dose. All dose levels were well tolerated CONCLUSION: The results of this trial indicate that 200 micrograms once daily is the optimum dose of mometasone furoate nasal spray for the treatment of seasonal allergic rhinitis.

Antihistamine activity, central nervous system and cardiovascular profiles of histamine H1 antagonists: comparative studies with loratadine, terfenadine and sedating antihistamines in guinea-pigs.

BACKGROUND: Sedation limits the clinical utility of classical H1 antihistamines, while newer antihistamines such as loratadine and terfenadine are non-sedating. However, clinical use of the terfenadine has been associated with rare but severe cardiac arrhythmias, in particular torsades de pointes. OBJECTIVE: To establish a quantitative experimental model for assessing the sedating and cardiotoxicity potential of non-sedating and sedating antihistamines. METHODS: Drugs were administered intravenously and the integrated amplitude of the cortical electroencephalogram (EEG) signal was recorded. The threshold dose that depressed EEG activity was compared with the dose required to inhibit by 50% the peripheral bronchospasm elicited by 10 micrograms/kg i.v., of histamine. In separate studies, the electrocardiogram (ECG) and cardiovascular effects of loratadine (30 and 100 mg/kg, i.v.), terfenadine (10 mg/kg, i.v.), promethazine (5 mg/kg, i.v.) and diphenhydramine (20 mg/kg, i.v.) were evaluated. RESULTS: The sedating antihistamines, diphenhydramine and promethazine, depressed the integrated EEG at doses between 0.6 and 2.0 times their peripheral antihistamine doses. Loratadine had no EEG depressant activity at 100 mg/kg, i.v., a dose more than 170 times its ED50 (0.58 mg/kg, i.v.) against histamine bronchospasm. We were unable to evaluate the EEG effects of terfenadine, because it produced cardiovascular collapse at 10 mg/kg, i.v. Loratadine and promethazine did not produce adverse cardiovascular effects, nor did they alter normal ECG activity. Diphenhydramine produced bradycardia followed by a transient hypertensive phase without affecting the QTc interval. In contrast, terfenadine elicited hypotension, bradycardia and significant arrhythmogenic activity, causing a prolongation of the QTc interval and a torsades de pointes--like ventricular arrhythmia. Pharmacokinetic studies after i.v. administration of loratadine (30 and 100 mg/kg) demonstrated plasma levels of loratadine and its major metabolite descarboethoxyloratadine to be several orders of magnitude greater than levels found in humans at the clinical dose of 10 mg. CONCLUSION: The CNS depressant effects of H1 antihistamines are promethazine approximately diphenhydramine >> loratadine = placebo. Of the non-sedating antihistamines, loratadine was devoid of adverse cardiovascular effects whereas terfenadine caused a pronounced disruption of the normal ECG, characterized by a torsades de pointes-like effect.

sVCAM-1 levels after segmental antigen challenge correlate with eosinophil influx, IL-4 and IL-5 production, and the late phase response.

Evidence from in vitro studies suggests a potential role for vascular cell adhesion molecule-1 (VCAM-1) in eosinophil trafficking. We hypothesized that induction of VCAM-1 occurs in the lung during IgE-mediated airway inflammation in humans. The technique of segmental antigen provocation followed by bronchoalveolar lavage (BAL) at 24 h was used to study 27 ragweed-allergic asthmatics (AA) and 18 atopic nonasthmatics (ANA). Total and differential cell counts were performed, and IL-4, IL-5, and soluble (VCAM) (sVCAM) levels in concentrated BAL fluid were measured by ELISA. A large increase in sVCAM levels after segmental challenge in both AA and ANA (1.79 +/- 0.31 to 139.39 +/- 68.58 ng/ml, p < 0.0005 and 2.85 +/- 0.80 to 98.25 +/- 77.35 ng/ml, p < 0.05, respectively) was observed. BAL IL-4 and IL-5 also increased after challenge (IL-4: 51.7 +/- 17.72 to 150.1 +/- 58.82 pg/ml, 0.05 < p < 0.10, n = 20 for AA, and 36.6 +/- 9.05 to 116.8 +/- 51.5 pg/ml, 0.05 < p < 0.10, n = 15 for ANA; IL-5: 0 to 2.67 +/- 1.62 ng/ml, p < 0.01, n = 16 for AA, and 0 to 2.87 +/- 2.16 ng/ml, 0.05 < p < 0.10, n = 10 for ANA). In both groups, the majority of the increase in sVCAM, IL-4, and IL-5 was accounted for by subjects who displayed a dual phase response after whole-lung antigen inhalation. This fact, plus the strong correlation observed between postchallenge sVCAM, IL-4, and IL-5 levels and eosinophil influx, suggests that VCAM, IL-4, and IL-5 play important roles in the recruitment of eosinophils to the lung of humans after antigen challenge.

Ventilatory effects of substance P, vasoactive intestinal peptide, and nitroprusside in humans.

Animal studies suggest that the neuropeptides, substance P and vasoactive intestinal peptide (VIP), may influence carotid body chemoreceptor activity and that substance P may take part in the carotid body response to hypoxia. The effects of these peptides on resting ventilation and on ventilatory responses to hypoxia and to hypercapnia have been investigated in six normal humans. Infusions of substance P (1 pmol.kg-1.min-1) and of VIP (6 pmol.kg-1.min-1) were compared with placebo and with nitroprusside (5 micrograms.kg-1.min-1) as a control for the hypotensive action of the peptides. Both peptides caused significantly less hypotension than nitroprusside. Substance P and nitroprusside caused significantly greater increases in ventilation and in the hypoxic ventilatory response than VIP. No changes were seen in hypercapnic sensitivity. The stimulation of ventilation and the differential effects on ventilatory chemosensitivity that accompanied hypotension are consistent either with stimulation of carotid body chemoreceptor activity or with an interaction with peripheral chemoreceptor input to the respiratory center, as is seen in animals. The similar cardiovascular but different ventilatory effects of the peptides suggest that substance P may also stimulate the carotid body in a manner independent of the effect of hypotension. This is consistent with a role of substance P in the hypoxic ventilatory response in humans.

Platelet activating factor: effects on bronchomotor tone and bronchial responsiveness in human beings.

Platelet-activating factor (PAF) is a newly discovered lipid mediator of inflammation. When inhaled by normal volunteers, it induces bronchoconstriction associated with facial flushing and with a transient fall in circulating neutrophils. Of greater interest is its ability to induce prolonged increases in bronchial responsiveness to methacholine. These observations support an important role for PAF in asthama; the availability of specific PAF antagonists will allow us to test this hypothesis.

Is choice of drug delivery as important as choice of drug in childhood asthma?

Inhalation of aerosols from a metered dose inhaler is a rational, convenient and well-liked method of administration of anti-asthmatic medication in adults but, in children, this method may be neither practical nor desirable. A number of devices such as spacers and dry powder inhalers have been developed and are particularly useful where children are too young to coordinate inspiration with actuation of the aerosol canister. In infants, administration of drug suspensions or solutions from a jet nebuliser via a face mask, or syrups by mouth, may be the only means of delivering anti-asthmatic medication.

Airway smooth muscle and disease workshop: epithelial mediators.

The bronchial epithelium has a number of mechanical functions including mucociliary clearance and protection against noxious agents. However, there is increasing evidence that it is a metabolically active tissue that may modulate the function of the underlying smooth muscle by metabolism and regulation of mediators and the production of relaxant, constrictor, or chemotactic factors. It is therefore possible that the epithelial abnormalities observed in asthmatics may lead, via several different mechanisms, to increased bronchial hyperresponsiveness (figure 2), which is a fundamental feature of asthma. However, it may not be necessary to invoke structural damage to explain derangement of epithelial function. It is possible that functional biochemical abnormalities may be present in epithelial cells, thereby producing bronchial hyperresponsiveness in the absence of histologic abnormalities. Further studies with bronchial epithelium, similar to those with vascular endothelium, are needed to clarify its role in the pathogenesis of asthma.

Breakdown of phosphoinositides in airway smooth muscle: lack of influence of anti-asthmatic drugs.

Hydrolysis of membrane inositol phospholipids during agonist-induced contraction in bronchial smooth muscle leads to formation of inositol phosphates. Inositol phosphates are associated with intracellular Ca++ mobilization, which in smooth muscle leads to contraction. We have investigated the effects of inhibitors of the contraction, theophylline, isoproterenol (isoprenaline), and verapamil, on contraction due to carbachol and histamine in bovine airway smooth muscle, and on the formation of inositol phosphates in the same preparation. Since phospholipase C and A2 are involved in the formation of inositol phosphates, we have also studied the effect of inhibitors of phospholipases, dexamethasone and mepacrine, on the accumulation of inositol phosphates. Theophylline, isoproterenol and verapamil elicited a concentration-dependent relaxation of pre-contracted smooth muscle, with the following order of potency: Isoproterenol greater than verapamil greater than theophylline. The relaxant effect was more effective on histamine than on carbachol-induced contraction and depended on the initial airway tone. However, neither theophylline, isoproterenol or verapamil, nor dexamethasone or mepacrine changed the basal level of inositol phosphates or affected the rise due to agonists. We conclude that the smooth muscle effects of theophylline, isoproterenol, verapamil, dexamethasone and mepacrine are not mediated by interference with membrane phosphoinositide breakdown.

Calcitonin gene-related peptide is localised to human airway nerves and potently constricts human airway smooth muscle.

In human airways synthetic human sequence calcitonin gene-related peptide (hCGRP), a novel peptide produced by alternative processing of mRNA from the calcitonin gene, caused concentration-dependent contraction of human bronchi (EC50 4.9 X 10(-9) M) and was significantly more potent than substance P or carbachol. The contractile response was unaffected by atropine (2 X 10(-6) M), propranolol (10(-6) M), indomethacin (10(-5) M), tetrodotoxin (3 X 10(-6) M), chlorpheniramine (10(-4) M), cimetidine (10(-5) M), or FPL55712 (10(-4) M) suggesting a direct effect of CGRP on airways smooth muscle. CGRP was detected in human airways by radioimmunoassay with highest concentrations in cartilaginous airways. CGRP was localised by immunocytochemistry to both nerves and ganglia in human airways. CGRP, is a potent constrictor of human airways and may have important effects on airway function and be implicated in the pathogenesis of bronchial hyper-responsiveness and asthma.

Bradykinin-induced bronchoconstriction in humans. Mode of action.

The effect of bradykinin was studied by inhalation in normal and asthmatic human subjects, as well as on human bronchial smooth muscle in vitro. Bradykinin caused cough and retrosternal discomfort in all subjects and bronchoconstriction in asthmatic subjects. Bradykinin was approximately 10 times more potent than histamine and methacholine, and there was a significant correlation between the subjects' sensitivity to histamine and bradykinin. Bradykinin-induced bronchoconstriction was prolonged when compared with that of histamine and the C-fiber stimulant capsaicin. This bronchoconstriction was subject to tachyphylaxis, which was also associated with desensitization of the subjects to inhaled histamine. The provocative dose causing a 35% fall in specific airway conductance (PD35) was unaffected by aspirin (1 g orally). However, ipratropium bromide (0.25 mg by nebulizer) significantly inhibited the effect of bradykinin, the PD35 being 0.8 mumol (range, 0.16 to 3.4) and 0.15 mumol (range, 0.047 to 1.15) after active dose and placebo, respectively (p less than 0.05). Likewise, cromolyn sodium (40 mg dry powder) also significantly reduced response to bradykinin, with a PD35 of 0.04 mumol (range, 0.13 to 0.31) after placebo and 0.39 mumol (range, 0.05 to 4.45) after SCG (p less than 0.05). Bradykinin only weakly constricted human bronchial smooth muscle in vitro. Bradykinin at 10(-4) caused only 21.5 +/- 5.5% of the maximal carbamylcholine contraction in 11 of 18 airways. Captopril did not enhance the effect of bradykinin. Bradykinin is a potent bronchoconstrictor of human airways in vivo, acting in part through cholinergic mechanisms but not because of the formation of prostaglandins.

VIP and PHM and their role in nonadrenergic inhibitory responses in isolated human airways.

There is increasing evidence in many species that vasoactive intestinal peptide (VIP) may be a neurotransmitter in nonadrenergic inhibitory nerves. We have studied the effect of electrical field stimulation (EFS), exogenous VIP, and isoproterenol (Iso) on human airways in vitro. We have also studied a related peptide, peptide histidine methionine (PHM), which coexists with VIP in human airway nerves, and in separate experiments studied fragments of the VIP amino acid sequence (VIP1-10 and VIP16-28) for agonist and antagonist activity. Human airways were obtained at thoracotomy and studied in an organ bath. In bronchi EFS gave an inhibitory response that was unaltered by 10(-6) M propranolol but was blocked by tetrodotoxin, whereas in bronchioles there was little or no nonadrenergic inhibitory response. VIP, PHM, and Iso all caused dose-dependent relaxation of bronchi, VIP and PHM being approximately 50-fold more potent than Iso. VIP, but not Iso, mimicked the time course of nonadrenergic inhibitory nerve stimulation. In contrast bronchioles relaxed to Iso but not to VIP or PHM. Neither propranolol nor indomethacin altered the relaxant effects of VIP or PHM, suggesting a direct effect of these peptides on airway smooth muscle. Neither of the VIP fragments showed either agonist or antagonist activity. We conclude that VIP and PHM are more potent bronchodilators of human bronchi than Iso and that the association between the relaxant effects of these peptides and nonadrenergic inhibitory responses suggests that they may be possible neurotransmitters of nonadrenergic inhibitory nerves in human airways.