Calcium antagonists and histamine secretion from rat peritoneal mast cells

Actions and cross-reactivity of antiallergic agents and a calcium channel antagonist on rat peritoneal mast cells. Difference in the action mechanisms and cross-reactivity among the agents

The actions of the antiallergic agents, disodium chromoglycate (DSCG), tranilast and ketotifen, and of a calcium channel antagonist, nicardipine, and cross-reactivity among the agents were examined by observing the inhibition of 45Ca uptake and histamine release in rat mast cells stimulated by antigen and compound 48/80 (comp. 48/80). 1) All agents inhibited 45Ca uptake and histamine release in mast cells stimulated by antigen. The inhibition of 45Ca uptake by the antiallergic agents paralleled the inhibition of histamine release, while nicardipine inhibition of 45Ca uptake was stronger than its inhibition of histamine release. 2) The action of DSCG on 45Ca uptake and histamine release was significantly decreased in cells stimulated with antigen and phosphatidylserine (PS), while tranilast inhibition of histamine release was not affected by the addition of PS despite a significant decrease in the inhibition of 45Ca uptake. 3) The inhibitory effect of DSCG and tranilast was significantly lower in mast cells stimulated by comp. 48/80 than in the cells stimulated by antigen. 4) Tachyphylaxis was observed in cells re-exposed to DSCG and tranilast following previous exposure to the agents. 5) Cross-reactivity was found between DSCG and tranilast.

Therapy of chronic idiopathic urticaria with nifedipine: demonstration of beneficial effect in a double-blinded, placebo-controlled, crossover trial

The efficacy of nifedipine, a calcium channel antagonist, in the treatment of chronic idiopathic urticaria, was evaluated in a double-blinded, placebo-controlled, crossover trial. Ten patients with chronic urticaria refractory to maximally tolerated doses of H1 and H2 antihistamines and in whom extensive evaluation failed to identify a cause for their urticaria were entered into the study. Patients continued with their prestudy antihistamine regimens. A study drug dosage was titrated in each patient and maintained throughout the trial. Patients were treated with placebo or nifedipine for 4 weeks and then crossed over to the other medication for 4 weeks. One patient withdrew because of unrelated medical illness, two patients withdrew after crossover to placebo because of intolerable urticaria, and seven patients completed the study. A beneficial effect of nifedipine was clearly demonstrated. Hive count, hive index, and itch index were all significantly improved at the end of 4 weeks of nifedipine treatment (p = 0.023, 0.003, and 0.003, respectively) but not placebo treatment (p = 0.194, 0.664, and 0.944, respectively). Additionally, end point hive index and itch index scores with nifedipine compared to corresponding placebo scores were significantly improved (p = 0.010 and 0.008, respectively). Nifedipine was well tolerated. Thus, when nifedipine is used as an adjunct to antihistamines, it appears to be a safe, efficacious drug for the treatment of chronic idiopathic urticaria.

The effect of different calcium antagonists on histamine- and carbachol-induced acid secretion in the isolated mouse stomach

Earlier experiments suggested that the action of muscarinic agonists in gastric acid secretion might be partly mediated by endogenous histamine release. This possibility could be tested by use of various calcium antagonists provided that they show different activity on histamine- and carbachol-induced secretion. In the present work, three calcium antagonists, verapamil, nifedipine and sodium nitroprusside were used on the isolated mouse stomach where acid secretion induced by histamine and by carbachol was measured. Verapamil (100 microM) did not affect either histamine- or carbachol-induced acid secretion. Nifedipine (100 microM) reduced histamine-induced acid secretion, whereas the effect of carbachol remained unchanged. Sodium nitroprusside (10-100 microM) reduced both histamine- and carbachol-induced acid secretion. The differences in action of calcium antagonists in histamine- and carbachol-induced acid secretion could exclude the possibility that the effect of carbachol is partly mediated by histamine release from mast cells present in the mouse stomach.

Modulation of anaphylactic histamine release by calcium channel agonists and antagonists

Calcium antagonists have been reported to exert protective effects in hypersensitivity reactions in man and animals. However, their effect on anaphylactic histamine release is highly variable and controversial. In the present paper we evaluate the effect of calcium entry blockers and BAY K 8644 on the response to specific antigen in isolated hearts taken from actively sensitized guinea-pigs and from isolated rat and guinea-pig mast cells, actively or passively sensitized. Verapamil, diltiazem, nifedipine and prenylamine dose-dependently decreased anaphylactic histamine release in isolated actively sensitized guinea-pig mast cells. BAY K 8644 was found to be ineffective. In isolated, passively sensitized rat mast cells, verapamil showed a highly significant inhibitory effect, while prenylamine (10(-4) M) was able to evoke a histamine releasing effect. In cardiac anaphylaxis verapamil, diltiazem, prenylamine, but not nifedipine, were active in reducing the release of histamine without modifying the antigen-induced arrhythmias and positive chronotropic and inotropic effects.

Studies on the calcium dependence of human NK cell killing

T lymphocytes and NK cells depend on extracellular Ca2+ to mediate cellular cytotoxicity. In the present work, we have used pharmacological tools to analyze the nature of this calcium dependence. Ca2+ channel blockers like nifedipine greater than or equal to diltiazem greater than verapamil greater than cobalt chloride inhibited NK killing but at concentrations higher than those sufficient to block voltage-operated Ca2+ channels. Quercetin and TMB-8 also suppressed killing. Depolarization or NK cells with high K+ concentration resulted in partial inhibition of lysis in contrast to hyperpolarization with K+ ionophore valinomycin which had no effect. Depolarization of hyperpolarization in the presence of a protein kinase C activator (phorbol ester, TPA) did not initiate killing of NK resistant target cells. Of the two K+ channel inhibitors tested, 4-AP and TEA, only 4-AP was inhibitory for NK killing. No release of membrane-bound Ca2+ as judged by chlorotetracycline fluorescence could be detected in the NK cell population during binding to target cells although an influx of 45Ca2+ into the NK cell population was found. Treatment of NK cells with calcium ionophore A23187 did not trigger killing, but lysis could be induced by simultaneous stimulation with A23187 and TPA. The results indicate that NK killing depends on Ca2+ channels that are different from voltage operated channels and that intracellular Ca2+ may act in concert with protein kinase C activation.

Calmodulin antagonism: a pharmacological approach for the inhibition of mediator release from mast cells

Several Ca2+ antagonists with either Ca2+-entry blocking or calmodulin (CaM) antagonistic properties and antiallergic drugs were investigated for their effects on mediator release from mast cells induced by different secretagogues (compound 48/80, concanavalin A, antigen-IgE and Ca2+ ionophore A23187) and for their ability to inhibit the function of CaM or phospholipid/Ca2+-dependent protein kinase (C-kinase). The effects of the different agents--with the only exception of cromolyn sodium--on histamine release elicited by compound 48/80 correlated well with their actions on two CaM-dependent enzymes whereas the activity of C-kinase was far less altered, or not altered at all. CaM antagonism of cloxacepride, picumast, oxatomide, fendiline and bepridil correlated not only with the inhibition of exocytosis evoked by compound 48/80 but also with that induced by A23187, concanavalin A and antigen-IgE. This indicates an action of these substances distal to the generation of the Ca2+ signal since the various secretagogues elevate the intracellular Ca2+ concentration by different mechanisms. However, prenylamine and thioridazine inhibited concanavalin A- and antigen-IgE-induced mediator release more potently and more effectively than that elicited by compound 48/80 or A23187. Therefore inhibition of allergic histamine release by these drugs may in part be dependent on an impairment of the Ca2+ signal. Since for each of two agents inhibition of histamine release (evoked by different releasers) parallels that of serotonin release it may be concluded that these mediators are secreted via the same mechanism. The results obtained with agents exhibiting different pharmacological properties but which share one common property, namely antagonism of CaM, strengthen the view that CaM is involved in exocytosis of mediators from mast cells.

The role of a Ca2+/calmodulin dependent plasma membrane Ca2+ channel during concanavalin A activation of MC9 mast cells

The effects of Con A on free cytoplasmic calcium concentrations in the cloned murine mast cell, MC9, have been measured using the fluorescent calcium indicator quin 2. Con A causes a rapid, small yet sustained rise in free cytosolic calcium (up to 245 nM) followed closely by increased 45calcium uptake and more slowly by histamine release. The increases in 45calcium uptake and histamine release require extracellular calcium. However, the Ca2+ influx blockers, nifedipine and verapamil inhibit these responses only at concentrations significantly higher than those used in smooth muscle to oppose potential-dependent events, and diltiazem is inactive. These observations suggest that, in these mast cells, other types of channels control Ca2+ entry. In contrast, the intracellular Ca2+ blocker, TMB-8, inhibits both the Con A-induced histamine release and the Ca2+ changes. The calmodulin antagonists calmidazolium, trifluoperazine and W-7 are also highly effective inhibitors of both the Ca2+ changes and histamine release in direct proportion to their potency against calmodulin-dependent phosphodiesterase, implicating calmodulin in the regulation of stimulus-secretion in MC9 cells. These data imply that histamine release follows increases in intracellular Ca2+ concentration. Free intracellular Ca2+ results from rapid release from internal stores and is followed by a slower but more sustained influx of extracellular Ca2+.

Comparison of nifedipine with a new calcium channel blocker, flordipine, in exercise-induced asthma

Four patients with documented exercise-induced asthma (EIA) were pretreated orally in random, double-blind fashion with the calcium channel blockers nifedipine 20 mg and flordipine 25 and 50 mg and placebo, then subjected to exercise challenge on a cycloergometer. Each patient served as his own control, undergoing exercise challenge with the different pretreatments on 4 separate days. No statistically significant protection from EIA was found with either nifedipine or flordipine.

Heterogeneity of calcium channels in mast cells and basophils and the possible relevance to pathophysiology of lung diseases: a review

Calcium plays a critical role in the formation and secretion of a wide variety of chemical mediators. Calcium slow-channel blockers, e.g. nifedipine and verapamil, have been shown to inhibit the synthesis of SRS (SRS-A, leukotrienes) in human and guinea pig lung tissue, thromboxane A2 formation in rat lung and platelet activating factor in human neutrophils. Verapamil and nifedipine also prevent the release of lysosomal enzymes from rabbit and human polymorphonuclear neutrophils. Calcium-channel blockers produce variable inhibitory effects on allergic and nonallergic histamine secretion. Ca++-entry blockers also inhibit the Ca++ uptake (influx) into mast cells. Many of these inhibitory effects of Ca++ antagonists are antagonized by an increased extracellular Ca++ ion concentration. The magnitude of the inhibitory influences of Ca++-channel blockers on allergic and nonallergic release of chemical mediators appears to depend on the cell source, species, nature and the concentration of the secretory stimuli as well as on the composition and pH of buffers and the concentration of Ca++-entry blockers used. The data summarized in this review suggest the existence of a functional heterogeneity of Ca++ channels in leukocytes, mast cells and basophils. Interference with the Ca++-dependent steps involved in the formation and/or release of chemical mediators appears to be the primary mode of action for Ca++-channel blockers in these cells. The differential effects of Ca++ antagonists on Ca++-dependent activation of phospholipase A2,5-lipoxygenase, and calmodulin (or other intracellular Ca++-binding proteins) in different cell types (mast cells, basophils, leukocytes, lung tissue, etc.) may explain the variation of their effectiveness in inhibiting the synthesis/release of chemical mediators and antagonizing bronchoconstriction in response to diverse stimuli. During the process of hypersensitization and in immediate hypersensitivity diseases, Ca++ homeostasis (uptake, mobilization, distribution, relocation, etc.) may be altered in leukocytes (mast cells, basophils) and lung tissues. The altered Ca++ homeostasis could be responsible for the induction of airway hyperreactivity in asthmatics and for hyperreleasability of chemical mediators from leukocytes, mast cells and other cell types.(ABSTRACT TRUNCATED AT 250 WORDS)

IgE-mediated degranulation of mast cells does not require opening of ion channels

Rat peritoneal mast cells respond to antigenic stimulation by releasing histamine through exocytosis. The dynamics of exocytosis can be investigated by dialysing single cells with patch pipettes using the whole-cell recording configuration of the patch-clamp technique. However, dialysed cells fail to respond to external stimuli such as compound 48/80 or antigens, suggesting that essential cytoplasmic components have been washed out. We have developed a new patch-clamp configuration in which the patch under the pipette tip is not disrupted but instead permeabilized, preventing the diffusion of large molecules out of the cell. In this configuration the cell responds to external stimulation, and the capacitance as well as the conductance of the cell membrane can be recorded during degranulation. On antigenic stimulation, the cell capacitance (proportional to plasma membrane area), after an initial delay, increases by a factor of about 3. This increase in capacitance is often preceded by a transient increase in conductance. Agents that block Ca-activated channels inhibit this conductance change without affecting the amplitude and time course of degranulation. We therefore conclude that, in contrast to excitable secretory cells such as chromaffin cells, mast cells do not use ion channels in stimulus-secretion coupling.

Ocular allergy and mast cell stabilizers

The role of the mast cell in ocular allergy is becoming understood. As a result, the therapeutic effects of agents that stabilize the mast cell have been evaluated in the treatment of seasonal allergic conjunctivitis, vernal keratoconjunctivitis, atopic keratoconjunctivitis, and giant papillary conjunctivitis. At present, cromolyn sodium is the only available mast cell stabilizer of known effectiveness. Clinical and laboratory investigations of the effectiveness of cromolyn sodium in the treatment of ocular allergy are reviewed in the present article.

Comparative effects of various calcium entry blockers and anti-asthmatic compounds on antigen-induced bronchoconstriction in rat and histamine release from rat mast cells

The effects of four calcium entry blockers (diltiazem, nifedipine, mesudipine and verapamil) were studied on antigen-induced bronchoconstriction in sensitized rats and histamine release from rat mast cells, in comparison with compounds frequently used in atopic patients (theophylline, isoproterenol, disodium cromoglycate, ketotifen and clemastine). The four Ca2+ entry blockers produced a dose-related inhibition of the IgE-dependent bronchoconstriction in rat whereas the other drugs exhibited a weak effect or even were inactive. 48/80-induced histamine release was antagonized by nifedipine, verapamil and ketotifen. On the contrary, diltiazem, mesudipine, theophylline, isoproterenol, disodium cromoglycate and clemastine were not able to interfere with this release process. These data may suggest an important role of both extra- and intracellular calcium in such phenomena.

Calcium antagonists and asthma

Calcium ions participate in the pathogenesis of asthma. Increased cytosolic concentrations of free Ca2+ must develop to trigger smooth muscle contraction, mast cell mediator release, mucous gland secretion, vagal nerve activity, and the movement of inflammatory cells into the walls of the airways. Recent interest has centered on the possibility that Ca2+ antagonists might be useful in the treatment of asthma. Evidence now exists that airway smooth muscle contraction and mast cell and basophil mediator release may be inhibited by the calcium channel blockers nifedipine and verapamil. Other experiments indicate that these drugs may interfere with EIA and bronchoconstriction provoked by cold air and methacholine, for example. CaM antagonists may also interfere with smooth muscle contraction and mediator release. It is possible that more specific calcium antagonists, both Ca2+ channel blockers and CaM-active compounds, will be developed and find use as effective antiasthmatic agents.

Plasma membrane fluidity studies by fluorescence polarization in rat mast cells stimulated by compound 48/80

Plasma membrane fluidity measurements were performed on purified living mast cells using a novel non-permeant fluorescence polarization probe TMA-DPH, upon stimulation by compound 48/80. The fluorescence anisotropy increased rapidly after treatment by 48/80 in a dose-dependent way. The effect was found to be specific for mast cells; it was inhibited by the histamine release antagonist FR 7534 in a correlative manner. The role of calcium was examined. The results brought evidence for a plasma membrane fluidity decrease induced by 48/80; a biphasic mechanism was inferred for the histamine release process.

PY 108-068: a calcium antagonist with an unusual pattern of cardiovascular activity

PY 108-068 (PY) is a potent dihydropyridine derived calcium antagonist, which is light-stable enough to allow experiments in vitro to be done under normal daylight. It potently antagonized depolarization-induced contraction of rabbit aorta (EC50: 4 X 10(-9) M) but not receptor-stimulated contraction (EC50 much greater than 10(-5) M). It also decreased the rate of spontaneously beating guinea-pig and rabbit atria very potently (EC25 2.9 and 4.3 X 10(-9) M respectively) but considerably higher concentrations were needed for negative inotropic effects on guinea-pig left atria or rabbit papillary muscles (EC25 1.5 and 1 X 10(-7) M respectively). In open chest dogs PY (10 micrograms/kg i.v.) increased coronary flow and cardiac output, lowered blood pressure, and tended to decrease heart rate while myocardial contractile force was unchanged. Myocardial oxygen consumption, however, was decreased despite the absence of cardiodepression. Similar results with respect to the systemic circulation were observed in cats. The effects of PY on the vascular beds of a large number of organs were investigated using tracer microspheres. PY effected regional vasodilatation in the heart, brain and skeletal muscle. Antivasoconstrictor effects of PY were investigated in similar cat experiments by pretreating the animals with angiotension II infusions. The vasoconstrictor effects of angiotensin II on the vessels of the kidney, stomach and small intestine were antagonized, even though no vasodilatation had been seen in these regions in the previous experiments without the vasoconstrictor pretreatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibitory effects of various drugs on phorbol myristate acetate and n-formyl methionyl leucyl phenylalanine induced O2- production in polymorphonuclear leukocytes

To clarify the mechanisms of O2- formation by polymorphonuclear leukocytes (PMNs), the effects of clinically employed drugs on PMNs were investigated by measuring changes in membrane potential and rates of O2- production. These variables were effectively diminished with antihistaminic agents, adrenergic beta-antagonists, and antiarrhythmic drugs when guinea pig peritoneal PMNs were stimulated by either phorbol myristate acetate (PMA) or n-formyl-methionyl-leucyl-phenylalanine (FMLP). The order of potency of the inhibitory effects of these chemicals on the PMA-induced O2- formation was as follows: azelastine (IC50 = 4.1 microM) less than clemastine less than dl-propranolol less than chlorpheniramine maleate less than dichlorisoproterenol less than quinidine less than diphenhydramine less than indomethacin (IC50 greater than 400 microM). Similar phenomena were observed when FMLP was employed instead of PMA, but the FMLP-stimulated O2- production was effectively inhibited by indomethacin. Changes in membrane potential, using the cyanin dye method, also indicated that most of these drugs cancelled functional changes of plasma membrane of PMNs. From these observations, it was demonstrated that changes in membrane potential by the stimuli were essential for the initiation of O2- generation from plasma membrane of PMNs, although the initiation mechanisms were not identical for the two stimuli.

Role of calcium in arachidonic acid-induced contractions of guinea pig airways

We have previously shown that arachidonic acid (AA)-induced contractions of indomethacin-pretreated guinea pig trachea and parenchyma are due to the synthesis of leukotrienes C4 and D4. The present experiments were designed to investigate the role of calcium (Ca2+) in the above. AA (66 microM)-induced contractions of trachea, but not parenchyma, were reduced in Ca2+-free Krebs-Henseleit solution ( KHS ). However the contractions of both trachea and parenchyma were abolished in Ca2+-free KHS with either lanthanum chloride (1 mM) or EDTA (300 microM). The Ca2+ antagonists, verapamil (100 microM), nitrendipine (100 microM), and TMB-8 (100 microM), reduced AA-induced contractions of both trachea and parenchyma. Re-addition of Ca2+ (2.2 mM) to trachea and parenchyma in Ca2+-free KHS in the presence of lanthanum restored the AA-induced contractions. This effect of Ca2+ was reduced by verapamil (100 microM) or nitrendipine (100 microM). LTC4-induced contractions of trachea and parenchyma were unaffected by nitrendipine (100 microM), whereas tracheal contractions were reduced in Ca2+-free KHS . Both tracheal and parenchymal contractions to LTC4 were reduced in Ca2+-free KHS in the presence of lanthanum chloride (1 mM). We conclude that superficially bound pools of Ca2+ are important in AA-induced contractions of the airways. Furthermore, nitrendipine reduces AA-induced contractions by inhibiting AA metabolism and not by inhibiting airway smooth muscle contraction induced by released leukotrienes.

Recognition of the 'calcium paradox' and the effects of verapamil and gallopamil in human adenoidal mast cells

Human mast cells from adenoids show when resuspended in medium containing 10(-3) M CaCl2 after their temporary exposure to Ca2+-free saline for about 20 min an irreversible reduction of responsiveness to a variety of stimuli: The histamine release induced by concanavalin A or ionophore A 23187 is only 30-50% of the one obtained in cells which were kept in 10(-3) M Ca2+ throughout the experiment. This phenomenon called 'calcium paradox' can be almost entirely avoided if the cells are temporarily exposed to 10(-4) M Ca2+ instead of Ca2+-free saline. Number yields, average histamine contents of mast cells and the rate of the spontaneous histamine release are not affected by the transitory lack of Ca2+, nor is the histamine release enhancing effect of adenosine. At 10(-3) M Ca2+ concentration the calcium antagonists verapamil or gallopamil cause a significant inhibition of the Con A-induced histamine release only at concentrations much higher (10(-4) M than those effective in smooth muscle preparations. The actions of both calcium antagonists were not affected by the presence of added extracellular adenosine.

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.