Calcium-channel blockers and asthma

Assessment of In Vitro Airway Smooth Muscle Relaxant Activity of Rhus coriaria L. Fruit Ethanolic Extract and Its Possible Mechanisms

Rhus coriaria L. (Anacardiaceae), also known as Sumac, is commonly used as a spice, flavoring agent, and as a traditional medicinal herb. This includes also the traditional use for treating asthma, catarrh, and common colds. The accumulating evidence supports its cardioprotective, antidiabetic, neuroprotective, anticancer, gastroprotective, antibacterial, anti-inflammatory, antiviral, antioxidant, and respiratory effects. However, there are no previous studies that have shown its effects and mechanism in the airway smooth muscle tone, and therefore, the aim of our study was to investigate the in vitro pharmacological action of R. coriaria L. extract (RCE) on the rat isolated tracheal and bronchial preparations by exploring its relaxant activity and mechanism of action. The direct relaxant effect of RCE (0.1-0.7 mg/mL) was tested in the rat bronchi and trachea rings precontracted by carbachol (CCh). In addition, the pretreatment with RCE (1 mg/mL) was tested on the bronchial and tracheal reactivity induced by CCh, potassium chloride (KCl), or CaCl2. In addition, the cyclooxygenase inhibitor indomethacin and the nitric oxide synthase inhibitor N(G)-nitro-l-arginine methyl ester (L-NAME), respectively, were used for exploring the mechanisms of RCE-induced relaxation and reduction of reactivity. Our findings demonstrated that RCE induced a concentration-dependent relaxation and a significant reduction of reactivity, significantly reduced with either indomethacin or L-NAME. In addition, RCE decreased the responsiveness to KCl and affected the extracellular Ca2+-induced contraction in the tissues with added CCh or KCl in Ca2+-free Krebs-Henseleit solution. In summary, we have shown that RCE displayed relaxant activities in the in vitro airway smooth muscles, and the possible mechanisms seems to involve the prostaglandin, nitric oxide, and Ca2+ pathways. Taken together, our findings indicate the potential role of RCE in the treatment of respiratory diseases with limited airflow, or obstructive respiratory diseases, and could justify its traditional use in the respiratory diseases.

Androgens are effective bronchodilators with anti-inflammatory properties: A potential alternative for asthma therapy

Changes in plasma androgen levels in asthmatic men may be linked to asthma severity, seemingly acting through nongenomic and genomic effects. Nongenomic effects include rapid relaxation of carbachol or antigenic challenge pre-contracted guinea pig airway smooth muscle (ASM) in vitro: testosterone (TES) blocks l-type voltage dependent Ca²⁺ channels, stored operated Ca²⁺ channels, inositol 1,4,5-trisphosphate receptors and promotes prostaglandin E₂ biosynthesis. In ASM at rest, TES lowers basal intracellular Ca²⁺ concentration and tension, maintaining a proper airway patency keeping steady smooth muscle tension and basal intracellular Ca²⁺ concentration at rest. Moreover, the bronchospasm in sensitized guinea-pigs was ablated by dehydroepiandrosterone (DHEA), a precursor of steroids, TES and its metabolites 5α- and 5β-dihydrotestosterone (DHT). On the other hand, genomic effects related to androgens' anti-inflammatory properties in asthma have been recently studied. Briefly, TES negatively regulates type 2 immune response sustained by CD4+ Th2 and group 2 innate lymphoid cells, diminishing allergic airway inflammation in males. Also, novel findings establish that TES decreases interleukin (IL)-17A protein expression produced by CD4+ Th17 cells and therefore neutrophilic airway inflammation. Clearly, DHEA, TES or its 5β-reduced metabolite that possesses minimal androgenic effect, might have potential therapeutic capacities in the treatment of severe asthma via mechanisms distinct from corticosteroid treatment.

Epigenome-wide association study of total serum immunoglobulin E in children: a life course approach

Background

IgE-mediated sensitization may be epigenetically programmed in utero, but early childhood environment may further alter complex traits and disease phenotypes through epigenetic plasticity. However, the epigenomic footprint underpinning IgE-mediated type-I hypersensitivity has not been well-understood, especially under a longitudinal early-childhood life-course framework.

Methods

We used epigenome-wide DNA methylation (IlluminaHumanMethylation450 BeadChip) in cord blood and mid-childhood peripheral blood to investigate pre- and post-natal methylation marks associated with mid-childhood (age 6.7-10.2) total serum IgE levels in 217 mother-child pairs in Project Viva-a prospective longitudinal pre-birth cohort in eastern Massachusetts, USA. We identified methylation sites associated with IgE using covariate-adjusted robust linear regressions.

Results

Nineteen methylation marks in cord blood were associated with IgE in mid-childhood (FDR < 0.05) in genes implicated in cell signaling, growth, and development. Among these, two methylation sites (C7orf50, ZAR1) remained robust after the adjustment for the change in DNA methylation from birth to mid-childhood (FDR < 0.05). An analysis of the change in methylation between cord blood and mid-childhood DNA (Δ-DNAm) identified 395 methylation marks in 272 genes associated with mid-childhood IgE (FDR < 0.05), with multiple sites located within ACOT7 (4 sites), EPX (5 sites), EVL (3 sites), KSR1 (4 sites), ZFPM1 (3 sites), and ZNF862 (3 sites). Several of these methylation loci were previously associated with asthma (ADAM19, EPX, IL4, IL5RA, and PRG2).

Conclusion

This study identified fetally programmed and mid-childhood methylation signals associated with mid-childhood IgE. Epigenetic priming during fetal development and early childhood likely plays an important role in IgE-mediated type-I hypersensitivity.

Tumor Necrosis Factor Alpha Inhibits L-Type Ca(2+) Channels in Sensitized Guinea Pig Airway Smooth Muscle through ERK 1/2 Pathway

Tumor necrosis factor alpha (TNF-α) is a potent proinflammatory cytokine that plays a significant role in the pathogenesis of asthma by inducing hyperresponsiveness and airway remodeling. TNF-α diminishes the L-type voltage dependent Ca²⁺ channel (L-VDCC) current in cardiac myocytes, an observation that seems paradoxical. In guinea pig sensitized tracheas KCl responses were lower than in control tissues. Serum from sensitized animals (Ser-S) induced the same phenomenon. In tracheal myocytes from nonsensitized (NS) and sensitized (S) guinea pigs, an L-VDCC current (ICa) was observed and diminished by Ser-S. The same decrease was detected in NS myocytes incubated with TNF-α, pointing out that this cytokine might be present in Ser-S. We observed that a small-molecule inhibitor of TNF-α (SMI-TNF) and a TNF-α receptor 1 (TNFR1) antagonist (WP9QY) reversed ICa decrease induced by Ser-S in NS myocytes, confirming the former hypothesis. U0126 (a blocker of ERK 1/2 kinase) also reverted the decrease in ICa. Neither cycloheximide (a protein synthesis inhibitor) nor actinomycin D (a transcription inhibitor) showed any effect on the TNF-α-induced ICa reduction. We found that Ca_V1.2 and Ca_V1.3 mRNA and proteins were expressed in tracheal myocytes and that sensitization did not modify them. In cardiac myocytes, ERK 1/2 phosphorylates two sites of the L-VDCC, augmenting or decreasing ICa; we postulate that, in guinea pig tracheal smooth muscle, TNF-α diminishes ICa probably by phosphorylating the L-VDCC site that reduces its activity through the ERK1/2 MAP kinase pathway.

Some extracardiac effects of diltiazem and other calcium entry blockers

Calcium entry blockers have a well documented relaxing effect of smooth muscle, vascular as well as non-vascular. Mainly as a consequence of this action, the drugs have been used for treatment of several non-cardiac disorders where hyperactivity of smooth muscle is considered to have an important role in the pathogenesis. In this short review some of these extracardiac effects of calcium entry blockers are discussed and also their clinical application.

Calcium, calcium channel blockade and airways function

This review will highlight recent advances in understanding the physiological role of calcium and effects of calcium channel blockers on pathogenetic factors in asthma, including airway smooth muscle contraction, mast cell degranulation and mucus secretion. A review of clinical studies with calcium channel blockers in asthma will also be presented.

Calcium dependence of the contraction produced by endothelin (ET-1) in isolated guinea-pig trachea

Endothelin (ET-1, 1 pM to 0.1 microM) produced a concentration-dependent contraction of isolated guinea-pig trachea. BAY K 8644 (1 microM) did not significantly alter the concentration-response curve for ET-1. Incubation with nicardipine (10 microM) partly inhibited responses to low concentrations (10 pM to 1 nM) of ET-1 while verapamil (10 microM) and diltiazem (10 microM) were ineffective. La3+ (10 microM) and Cd2+ (10 microM) preferentially depressed the responses evoked by high concentrations (30 nM-0.1 microM) of ET-1 without affecting the responses evoked by low concentrations of the peptide. Incubation in Ca2(+)-free (with EDTA, 1 mM) medium resulted in suppression of the responses elicited by low concentrations of ET-1 and partial inhibition of the responses elicited by high concentrations of the peptide. It is concluded that responses to ET-1 are dependent on extracellular Ca2+. The promotion of Ca2+ entry by ET-1 is not confined to a particular class of Ca2+ channel. An intracellular source of Ca2+ is also mobilized by high concentrations (greater than 10(-9) M) of ET-1.

The clinical performance of nicardipine in elderly hypertensive patients with concomitant diseases

The efficacy and tolerance of nicardipine were evaluated in 2184 ambulatory hypertensive patients with or without concomitant diseases in a 24-week Italian multicenter study. Of the total patient group 1083 had one or more concomitant diseases (diabetes mellitus, coronary heart disease, cardiac failure, mild renal failure, chronic cerebrovascular disease, obstructive lung disease, and peripheral vascular disease); of these patients, 419 were aged over 65 years. Patients were seen on an outpatient basis and after a 2- to 4-week washout period were admitted to the study. The initial nicardipine dose of 20 mg three times a day was titrated in subsequent weeks; thereafter a second antihypertensive drug was added if seated diastolic blood pressure was not reduced below 90 mm Hg. The nicardipine-based therapy significantly lowered seated blood pressure in the whole population (mean 185/102 to 152/86 mm Hg) without clinically and statistically significant differences between the patient subgroups with concomitant diseases. There were no changes in either symptoms, or biochemical and instrumental tests of the concomitant diseases. The incidence of side effects was low; in particular, there was no orthostatic hypotension. Nicardipine-based treatment is therefore effective, safe, and well tolerated in elderly hypertensive patients with concomitant disease.

Different ability of trifluoperazine to inhibit agonist-induced contraction of lung parenchyma strips from control and sensitized guinea-pigs

There is increasing interest in the therapeutic potential of calcium antagonists in asthma. Among them the use of calmodulin antagonists deserves consideration. In the present work the effect of trifluoperazine on contractions generated by different mechanisms (CaCl2, KCl, acetylcholine, histamine and 5-hydroxytryptamine) in lung parenchyma strip isolated from control and actively sensitized guinea-pigs has been studied. Trifluoperazine produced both in unsensitized and sensitized lung strips, a concentration-dependent, right, downward displacement of the concentration-response curves to the agonists used, although the sensitization procedure resulted in a potentiation in the ability of trifluoperazine to inhibit agonist-induced contractions. The basis for this greater potency of trifluoperazine in sensitized tissues remains to be elucidated but raises attention to the future use of selective calmodulin antagonists in the management of asthma.

Sodium-calcium exchange in sarcolemmal vesicles from tracheal smooth muscle

Sarcolemmal vesicles prepared by a new procedure from bovine tracheal smooth muscle were found to have a Na-Ca exchange activity that is significantly higher than that reported for different preparations from other types of smooth muscle. The exchange process system co-purified with 5'-nucleotidase, a plasma membrane marker enzyme, and was significantly enriched (over 100-fold) compared to mitochondria (cytochrome-c oxidase) but only slightly enriched (4-fold) compared to sarcoplasmic reticulum (NADPH-cytochrome-c reductase). The Na+ dependence of Ca2+ transport was demonstrated through both uptake and efflux procedures. The uptake profile with respect to Ca2+ was monotonic with a linear vo VS. vo.S-1 plot. The resultant Km of Ca2+ from the airway sarcolemmal vesicles (20 microM) was similar in magnitude to the Km of cardiac sarcolemmal vesicles (30 microM). Tracheal vesicles demonstrated a Vmax of 0.3-0.5 nmol.mg-1.s-1 which is significantly higher than that reported in preparations from other smooth muscle types. Furthermore, two processes found to stimulate cardiac Na-Ca exchange, pretreatment with either a mixture of dithiothreitol and Fe2+ or with chymotrypsin, were ineffective on the tracheal smooth muscle. Thus, the Na-Ca exchanger identified in tracheal smooth muscle appears to be different from that observed in cardiac muscle, implying that regulation of this activity may also be different.

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.

Nebulised sodium cromoglycate and verapamil in methacholine induced asthma

Fifteen children with asthma underwent challenges with methacholine on separate days after double blind administration by nebuliser of either verapamil (5 mg), cromoglycate (20 mg), or saline (placebo). The provocation doses that produced a 20% fall in forced expiratory volume in one second (PD20) were analysed. There was variation in the protective effects of verapamil and cromoglycate among the patients. Although cromoglycate produced an increase in PD20 in 53% of the children tested, the protection was not significant when compared with the placebo. Verapamil was partially protective, however, in 80% of children and achieved significantly better results than the placebo. We suggest that this is likely to be due to a direct effect on bronchial smooth muscle.

Nitrendipine. A review of its pharmacodynamic and pharmacokinetic properties, and therapeutic efficacy in the treatment of hypertension

Nitrendipine is a calcium entry blocker shown to inhibit the movement of calcium through the 'slow channel' of cardiac and vascular smooth muscle, thus inducing peripheral vasodilation with consequent reductions in elevated blood pressure. As evidenced by clinical trials, nitrendipine promptly lowers blood pressure in patients with mild to moderate hypertension, and sustains this effect during long term administration. Combining nitrendipine with other antihypertensive agents such as diuretics or beta-blockers often results in successful treatment in patients unresponsive to nitrendipine monotherapy. Headache, oedema, flushing and palpitations commonly occurring during treatment with nitrendipine are generally mild, usually subsiding with continued therapy. Thus, although additional long term studies are required to properly assess the relative merits of the drug compared with other antihypertensives, by providing the clinician with an effective and safe alternative to traditional therapies, nitrendipine represents a step forward in the treatment of mild to moderate hypertension.

Receptor pharmacology of calcium entry blocking agents

The mechanism of action of calcium channel modulators, a class of drugs that includes 3 chemical groups--1,4-dihydropyridines, phenylalkylamines and benzothiazepines--has been extensively reviewed. The best known representatives of these 3 groups are nifedipine, verapamil and diltiazem, respectively. These drugs bind reversibly, stereospecifically and with high affinity to both the membrane-bound and the purified receptor complex. Non-dihydropyridines allosterically regulate dihydropyridine binding. This has been shown by using (-) [3H]202-791 and (+) [3H]PN200-110 as labeled ligands. The purified receptor complex that possesses binding sites for all 3 chemical groups is likely to be related to the voltage-dependent calcium channel. As the result of a drug-receptor interaction, voltage-dependent calcium channels are either activated or inactivated. The drugs that activate channels act by promoting long-lasting channel openings. The drugs that inhibit calcium channels, the calcium entry-blocking agents, act by preventing channel openings upon membrane depolarization. A complex pharmacologic, electrophysiologic, biochemical, immunologic and molecular genetic approach is required to determine the molecular mechanism of action of calcium channel modulators. Clinically, calcium entry-blocking agents are recommended for the treatment of angina pectoris, hypertension, posthemorrhagic cerebral vasospasm, supraventricular tachycardia, migraine and asthma and the protection of the ischemic myocardium.

Influence of nimodipine and nifedipine on intrapulmonary shunting--a comparison to other vasoactive drugs

This study was assigned to investigate the influence of calcium channel blockers (nimodipine and nifedipine) in comparison to other vasoactive drugs (nitroglycerin, dopamine) on pulmonary shunting (Qs/Qt). Fifty anesthetised patients scheduled for aortocoronary bypass operation were randomly allocated to 5 groups receiving one of the following drugs: nimodipine 1.0 microgram X kg-1 X min-1; nifedipine 0.7 microgram X kg-1 X min-1; nitroglycerin (TNG) 0.5 microgram X kg-1 X min-1; dopamine; micrograms X kg-1 X min-1; placebo (0.9% NaCl). Nimodipine as well as nifedipine led to a significant increase in cardiac output (+44%; +39%), pulmonary vascular resistance simultaneously decreased (-25%; -28%). PaO2 increased significantly (+16%; +13%), too, whereas Qs/Qt remained almost unchanged. In contrast, the increase in cardiac output induced by dopamine (+27%) was accompanied by a significant increase in shunting (+34%). TNG application did not alter Qs/Qt, but pulmonary artery pressure (PAP) decreased markedly (-19%).

Does nifedipine affect the diurnal variation of asthma in children?

Diurnal variations in airway caliber and in bronchial reactivity have been described. The mechanisms underlying these variations are not known. The hypothesis that these variations can be diminished by calcium channel blockers was tested by giving 22 asthmatic children 10 mg of nifedipine or identical placebo three times a day for 4 weeks in a double-blind, randomized, crossover-designed study. Treatment with nifedipine did not diminish the diurnal variations in airway caliber, judged from peak expiratory flow rates, or in bronchial reactivity, judged from bronchodilator responsiveness. Group mean amplitude of the diurnal variation in airway caliber was 10.5% on nifedipine and 10.6% on placebo. Group mean amplitude of the diurnal variation in bronchodilator responsiveness was 75.4% on nifedipine and 69.5% on placebo. There were no differences in mean peak expiratory flow rate between nifedipine and placebo periods. This study did not find any evidence to support the hypothesis that the diurnal variations in airway caliber and in bronchial reactivity can be diminished by calcium channel blockers.

Further studies on the mechanism of action of leukotrienes and histamine on guinea pig lung parenchyma. Role of calcium, phospholipase and methyltransferase

The contractile activity of leukotriene B4 (LTB4), leukotriene D4 (LTD4) and histamine on strips of guinea pig lung parenchyma was shown to be dependent on the calcium concentrations of the Krebs solution. The calcium channel blocker verapamil (2.0 to 15 microM) had an additive effect on the inhibitory activity of low calcium (0.1 mM) on contractions of guinea pig parenchyma to leukotrienes and histamine. Cobalt chloride, a divalent cation, also produced dose-dependent reductions of the myotropic activities of LTB4, LTD4 and histamine. An antagonist of calmodulin, trifluoperazine (1-200 microM), dose-dependently inhibited the contractile activity of the three agonists on the parenchyma strip. The IC50 of this compound for inhibition of histamine was much lower (2-3 microM) than the IC50 for inhibition of leukotrienes (75 microM). Valinomycin, a potassium ionophore, also interfere with the contractile activities of leukotrienes and histamine whereas a blocker of sodium channel, tetrodotoxin, had no effect on the activity of these agonists. Furthermore, an inhibitor of methyltransferase, 3-deazaadenosine, significantly diminished the responses of the parenchyma to leukotrienes and histamine. These results confirmed the important role of extracellular and intracellular calcium in the myotropic activity of leukotrienes and histamine in guinea pig lungs and showed that compounds which interfere either directly or indirectly with calcium mobilization into the lung smooth muscles, decreased the tissue responsiveness.

Pharmacological characterization of the effects of verapamil and nifedipine on isolated guinea-pig lung parenchymal strip

Verapamil and nifedipine elicited dose-related relaxations and produced a right downward shift of the concentration-response curves to CaCl2, KCl, acetylcholine and histamine in the isolated guinea-pig lung parenchymal strip. These Ca-entry blockers had greater inhibitory effects on contractions evoked by CaCl2 and KCl than against those elicited by acetylcholine and histamine.

Relative activities of three calcium channel antagonists on histamine, acetylcholine and antigen-induced contractions of guinea pig ileum

The molar concentrations of verapamil, diltiazem, nifedipine, tripelennamine and atropine necessary to block histamine, acetylcholine (ACH) and ovalbumin-induced contractions of the isolated guinea pig ileum were compared. The calcium blockers inhibited ovalbumin contractions in previously sensitized ilea at lower concentrations than those required to block the phasic component of histamine and ACH contractions. These compounds were, however, more active in blocking the tonic phase of histamine and ACH concentrations than ovalbumin contractions. Tripelennamine was almost as active against ovalbumin contractions as it was against histamine concentrations, while atropine was inactive against ovalbumin. The results are interpreted as being supportive of continued efforts to develop calcium channel antagonists which selectively block the smooth muscle effects of inflammatory mediators.

Spectrum of acute hemodynamic effects of nifedipine in severe congestive heart failure

The acute hemodynamic effects of 20 to 50 mg of orally administered nifedipine were evaluated in 31 patients with severe chronic congestive heart failure (CHF) and the results were analyzed according to the response of the cardiac index (CI). Although the group mean value of CI increased significantly after nifedipine treatment (from 2.1 +/- 0.5 to 2.4 +/- 0.8 liters/min/m2, p less than 0.001), the individual response was variable. Twenty of the patients had 15% or greater increase in CI (group A) and 11 patients had less than a 15% increase or a decrease in CI (group B). Marked differences were also noted in the effects of nifedipine on other hemodynamic variables. Stroke volume increased 29 +/- 14% in group A and decreased 11 +/- 18% in group B (p less than 0.001). Systemic vascular resistance decreased 34 +/- 11% in group A (p less than 0.001) and increased slightly, 2 +/- 28%, in group B. Left ventricular (LV) stroke work index increased 11 +/- 19% in group A (p less than 0.001) and decreased markedly in Group B (21 +/- 20%). Six group B patients had a substantial worsening (20% or more) of one or more hemodynamic measurements, including CI, stroke volume index, LV stroke work index and mean pulmonary artery wedge pressure. A comparison of control hemodynamic values at rest, LV ejection fraction, associated coronary artery disease, nifedipine dose, and concomitant diuretic therapy revealed no significant differences between the 2 groups. This study confirms, in a large group of patients with severe CHF, the variable hemodynamic effects of nifedipine therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibition of histamine release from dispersed human lung and tonsillar mast cells by nicardipine and nifedipine

Calcium entry blocking drugs attenuate antigen-induced bronchoconstriction in asthma which is mast cell mediated. We have investigated the effects of two calcium uptake blockers, nicardipine and nifedipine on histamine secretion from human mast cells dispersed from lung and tonsillar tissue. Mast cells were activated for secretion with anti-human IgE or calcium ionophore, A23187. Nicardipine and nifedipine caused a concentration-related inhibition of IgE-dependent histamine release from both lung (IC30 10 microM and 4.4 microM) and tonsillar (IC30 21 microM and 47 microM) mast cells. Nicardipine and nifedipine also inhibited mast cell histamine release induced by A23187 with IC30 values of 14 microM and 67 microM for lung and 15 microM and 30 microM for tonsillar mast cells. In the absence of drugs, increasing the extracellular calcium concentrations from 0.2 to 5 mM caused a concentration related increase in IgE-dependent histamine release from tonsillar mast cells. Both nicardipine and nifedipine (50 microM) displaced the concentration-effect curve to the right. Nicardipine (0.01-100 microM) caused a concentration related inhibition of rat kidney histamine methyltransferase activity used in the radioenzymatic assay of histamine (ki of 7.5-12 microM) whereas nifedipine was only a weak inhibitor. Nicardipine also interfered with the spectrofluorimetric assay after exposure to ultraviolet light. These observations demonstrate that nicardipine and nifedipine inhibit IgE-dependent and ionophore stimulated mediator secretion from human mast cells. The lack of stimulus-related specificity and the high drug concentrations required suggest that classical calcium channel blockade is not responsible for inhibition of mast cell mediator release. Furthermore, we suggest that inhibition of mast cell mediator release is unlikely to be the mechanism by which these drugs alleviate asthma.

Use of inhaled calcium channel blocking agents in the treatment of asthma

The inhalation of drugs that are active in the respiratory tract offers the ideal route of administration, since it results in the rapid delivery of appropriate concentrations with a much reduced risk of systemic adverse effects: Problems with regard to poor absorption from the gastrointestinal tract (sodium cromoglycate) or substantial effect on liver metabolism (verapamil) can be avoided. Certain drugs such as antihistamines and ketotifen may be more effective administered by inhalation since high concentrations with reduced unwanted effects can be achieved on the bronchial surface where, in allergic asthma, the critical initial interaction between sensitized mast cells (mucosal?) and allergen with subsequent mediator release occurs. Indeed inhaled verapamil has been shown to be effective in animal models of asthma but not in man. Systemically administered nifedipine gives partial and variable protection against induced asthma in man and its efficacy (with reduced cardiovascular effects) may well be improved by inhalation.