The effect of beta-adrenoceptor blocking drugs on histamine liberation, prostaglandin synthesis and phospholipid turnover in isolated mast cells stimulated with concanavalin A.

Exaprolol, metipranolol and propranolol decreased significantly histamine liberation, degranulation, 45Ca uptake and thromboxane B2 formation in isolated rat mast cells stimulated with concanavalin A and phosphatidylserine. Moreover, exaprolol and metipranolol decreased 32P incorporation into membrane phospholipids and metipranolol and propranolol reduced the liberation of arachidonic acid from membrane phospholipids of stimulated mast cells. Exaprolol significantly increased the arachidonic acid liberation from these cells. Possible mechanisms of interaction of beta-adrenoceptor blocking drugs with isolated mast cells are discussed.     

Effect of chloroquine on isolated mast cells.

Chloroquine liberated a relatively low amount of histamine from isolated rat mast cells. In a dose-dependent way, this drug inhibited histamine liberation from mast cells stimulated with compound 48/80, A23187, concanavalin A plus phosphatidylserine (Con A + PS) and abolished histamine liberation induced by exaprolol. The degranulation was decreased in cells stimulated with 48/80, Con A + PS and exaprolol. Chloroquine significantly inhibited the formation of thromboxane B2 in mast cells stimulated with 48/80, Con A + PS and A23187. We assume that chloroquine interferes with mast cells at a plasmic membrane site as well as intracellularly.     

On the interaction of beta-adrenoceptor-blocking drugs with isolated mast cells

The interaction of beta-adrenoceptor blocking drugs (BAB drugs) with isolated mast cells resulted, according to the compound, in either a liberation of biogenic amines or an inhibition of stimulated amine release. The liberatory drugs exaprolol and K? 1124 decreased the level of cAMP, stimulated the activity of cyclic nucleotide-phosphodiesterase, decreased the incorporation of orthophosphate into membrane phospholipids and rapidly displaced calcium from binding sites in mast cells. The inhibitory drugs alprenolol, metipranolol, oxprenolol, practolol and propranolol, possessing lower liposolubility, produced opposite effects. Drugs from both groups displaced histamine from binding sites in isolated mast cell granules. The interaction of BAB drugs with mast cells is a result of non-specific rather than specific receptor interactions. Inhibitory drugs interfere with mast cells at membrane sites while liberatory drugs penetrate the membrane, thus acting both at the level of membrane and intracellularly.     

Effect of beta-adrenoceptor blocking drugs on 32P incorporation into and arachidonic acid liberation from phospholipids in stimulated rat mast cells

The lipophilic beta-adrenoceptor blocking (BAB) drugs metipranolol, propranolol and exaprolol significantly decreased 48/80- and A23187-induced 32P incorporation into rat mast cell phospholipids. Exaprolol was the most active, followed by propranolol and metipranolol. Atenolol and metipranolol significantly decreased the 48/80-stimulated, and metipranolol and exaprolol the A23187-stimulated 3H-arachidonic acid liberation from isolated mast cells.     

Membrane perturbing activity of beta-adrenoceptor blocking drugs in isolated rat mast cells

Beta-adrenoceptor blocking (BAB) drugs perturb the membranes of isolated rat mast cells. Membrane fluidisation was temperature dependent and was determined by the liposolubility of the BAB drugs. The secretory index, evaluated as the ratio between histamine liberation and degranulation, correlated with the membrane order parameter of the mast cell membranes. The rank order of potency for mast cell activation and membrane fluidisation was: exaprolol greater than propranolol greater than metipranolol greater than atenolol.     

On the relationship between incorporation of 32P into phospholipids and binding of beta-adrenoceptor blocking drugs to isolated mast cells

The lipophilic beta-adrenoceptor blocking drugs exaprolol and propranolol significantly decreased the incorporation of 32P into phosphatidylethanolamine, phosphatidylcholine and phosphatidylinositol of isolated rat mast cells. In contrast, the hydrophilic drugs metipranolol, practolol and atenolol increased the incorporation of 32P into phosphatidylethanolamine, phosphatidylserine and phosphatidylinositol. The inhibition of 32P incorporation by lipophilic drugs correlated with the high binding of these drugs to mast cells.     

Analysis of the adverse effects of drugs at the cellular and subcellular levels]

A release of histamine after the lipophilic betablockers exaprolol and propranolol correlates with their capability of displacing the bound membrane Ca2+ and increasing the disorder of phospholipidic membranes of the isolated mast cells. Electron microscopy confirmed intracellular displacement of histamine from granules of mast cells after exaprolol without marked structural changes on the plasmatic membrane. Hydrophilic and selective atenolol, which does not possess a histamine-liberating effect, decreases spontaneous transfer of the intracellular calcium, decreases the disorder of the mast-cell membranes, and together with exaprolol and propranolol inhibits, in dose-dependence way, the gain of extracellular histamine in cells. The inhibitory effect of EDTA, tetrodotoxine and suramine on histamine release after exaprolol explains the non-receptor mechanism of exaprolol effect, which confirms a possibility of induction of adverse effects of blockers of the beta-adrenergic receptor in the development of a bronchospasm.     

Beta-adrenoceptor blocking drugs and calcium transport in isolated rat mast cells

The beta-adrenoceptor blocking (BAB) drugs exaprolol (EXA), metipranolol (MET) and propranolol (PRO) inhibited histamine liberation and degranulation from isolated rat mast cells stimulated with the calcium ionophore A23187. MET was the most and EXA the least active. Atenolol (ATE) had no effect. Inhibition by BAB drugs of secretion induced with A23187 was not accompanied by any change in 45Ca uptake. On the other hand, EXA, MET and PRO significantly decreased 45Ca uptake by mast cells stimulated with 48/80. The effect of BAB drugs on inhibition of A23187-induced secretion from isolated mast cells was dependent on the lipid solubility of the studied drugs.     

Evidence for intracellular histamine liberation in isolated rat mast cells

The beta-adrenoceptor blocking drug exaprolol liberated histamine from isolated rat mast cells in a dose- and time-dependent way. Histamine was liberated within seconds and was not followed by a parallel granule liberation. The inhibition of histamine liberation was induced with low temperature, low pH, high concentration of Ca2+, TTD, suramin and EDTA. Subcellular distribution of 3H-exaprolol demonstrated a quantitative relationship between histamine depletion against exaprolol uptake in isolated rat mast cell granules. A nonspecific mechanism of action in the effect of exaprolol on mast cells is discussed. It is proposed that the drug acts on mast cells due to the direct and indirect ion exchange mechanism resulted in disproportion between histamine and granule liberation.     

Effect of stobadine on stimulated isolated mast cells

Stobadine, an antiarrhythmic drug with antihistaminic properties, did not liberate histamine from mast cells in vitro. Compound 48/80-stimulated histamine liberation and degranulation was decreased in the presence of stobadine in a dose-dependent way. The spontaneous as well as stimulated calcium displacement in mast cells was significantly decreased by stobadine. Stobadine most probably possesses a membrane-stabilizing effect on isolated rat mast cells.     

Histamine liberation as a result of nonreceptor interaction.

The highly lipophilic drug exaprolol liberates histamine from isolated mast cells and decreases the uptake of extracellular histamine in a dose-dependent manner. Intracellular histamine depletion was confirmed by electron microscopy and was accompanied by calcium displacement from intracellular storage sites. The significant decrease in membrane fluidity due to exaprolol was temperature-dependent and was most probably a result of its high membrane affinity and intracellular penetration. Membrane perturbation by exaprolol may account for this nonreceptor interaction. This could contribute to the understanding of adverse reactions to beta-adrenoceptor blocking drugs.     

The role of membrane bound sialic acid of rat mast cells in histamine release induced by compound 48/80 and derivatives as well as calcium

Histamine release induced by compound 48/80 from rat mast cells is not dependent on extracellular Ca2+. Preincubation of mast cells with trypsin has only little effects on histamine release induced by this polycation. This work also demonstrates that histamine release induced by compound 48/80 and its analogues in the absence of extracellular Ca2+ depends on membrane bound sialic acid of the mast cell. Neuraminidase treatment of the cells in the presence of extracellular Ca2+ leads to histamine liberation. These findings suggest that sialic acid residues of the mast cell membrane constitute the site at which polycations exert their stimulatory actions of histamine liberation.     

Amine transport in isolated rat mast cells treated with betaadrenoceptor blocking drugs

Histamine and serotonin uptake in isolated rat mast cells is decreased in the presence of betaadrenoceptor blocking (BAB) drugs. Such inhibition is dose-dependent and is evidently higher for the inhibition of serotonin uptake. The most potent drugs were the highly lipophilic compounds K? 1124 and propranolol. No difference was found among the various BAB drugs in their ability to decrease histamine uptake. It is evident from the ratio between histamine and serotonin liberation on one side, to the uptake of both amines in mast cells on the other side, that with the exception of K? 1124, all investigated BAB drugs possesses higher inhibition of extracellular amine uptake in comparison with histamine and serotonin liberation. Such an effect might be a result of a primary interaction of BAB drugs with mast cells at the plasma membrane.     

Comparison of the effect of eleven beta-adrenoceptor blocking drugs in perturbing lipid membrane: an ESR spectroscopy study

The perturbation effect of the beta-adrenoceptor blocking drugs atenolol, propranolol, practolol, oxprenolol, doberol, pronethanol, metipranolol, alprenolol, K?-1124, pindolol, and exaprolol on rat brain lipid membrane was investigated by ESR spectroscopy using the spin probe method. Using stearic acids spin labeled at the 5th, 12th, and 16th positions, it was found that lipophilic drugs disorder the membrane and their effect is about 5-10 times higher at the 16th carbon membrane depth than at the 5th depth. Exaprolol induced nonlamellar phases in the bovine brain lipid membrane as detected by 31P NMR spectroscopy. The relative potencies of the drugs at 10 mmol/liter concentration to disorder the lipid membrane at the 16th carbon depth were in the order: exaprolol greater than alprenolol approximately equal to propranolol greater than metipranolol approximately equal to doberol greater than control sample greater than pindolol approximately equal to practolol approximately equal to atenolol. This order qualitatively corresponds with some of their nonspecific biological membrane activities but is not related to their beta-adrenoceptor blocking potencies. The inequality of the membrane perturbation propensities of the drugs indicates that they perturb the lipid membrane in a structure-dependent manner, i.e., that each induces a specific rather than a nonspecific membrane perturbation.     

Labelling of the inner side of granules membrane during exocytosis. A method to differentiate secretion processes

A fluorescence method to monitor quantitatively exocytosis phenomena in suspensions of intact cells was investigated, on the basis of the particular incorporation properties of a specific plasma membrane fluorescent label trimethylammonium-diphenylhexatriene (TMA-DPH). The method was tested with purified peritoneal mast cells stimulated by compound 48/80. Kinetics and dose-dependent response to compound 48/80 could be described accurately by the TMA-DPH fluorescence increase accompanying the exocytosis phenomenon, as controlled by conventional titrations of the released histamine. TMA-DPH bound to the outer side of the plasma membrane of resting cells and additively to the inner side of granules connected by pores to the exterior of stimulated mast cells.     

On the interaction of local anesthetics with mast cells

The carbanilate local anesthetics carbisocaine, hepatacaine and pentacaine liberate histamine from isolated rat mast cells. Procaine, carticaine, trimecaine, cocaine and butanilicaine were ineffective. Histamine liberation was dose-dependent, followed by calcium displacement from membrane binding sites and occurred without concomitant degranulation. Low temperature and pH-dependent inhibition of histamine liberation indicated a non-specific, membrane perturbing effect of highly liposoluble carbanilate local anesthetics. Conformational changes in the sodium channel on the mast cell membrane induced by carbanilate anesthetics might result in histamine exchange occurring intracellularly.     

Histamine liberation and membrane fluidisation of mast cells exposed to the beta-adrenoceptor blocking drug propranolol

Propranolol liberates histamine from isolated mast cells and decreases the uptake of extracellular histamine in a dose-dependent way. Histamine liberation due to propranolol is accompanied by calcium displacement from intracellular storage sites. The significant increase in membrane fluidity due to propranolol is temperature dependent. The perturbation of membranes is most probably the explanation of propranolol's interaction with isolated rat mast cells which results in altered histamine transportation.     

The effect of beta-adrenergic blocking drugs and inhibitors of phosphodiestease on histamine release from isolated mast cells.

Differences in the histamine liberation from isolated rat mast cells after beta-adrenergic blocking drugs were demonstrated. In equimolar concentrations histamine release was induced by K? 1124, K? 1500, K? 1560, K? 1561 and propranolol. Alprenolol, oxprenolol, propranolol, and trimepranol significantly decreased thehistamine release induced by compound 48-80. The release of granules from cells was inhibited quantitatively more than the release of histamine. This enabled us to surmise the selective effect of beta-adrenergic blocking drugs on cell membranes of mast cells. The possible mechanisms of release reaction are discussed.     

Biscoclaurine alkaloids inhibit receptor-mediated phospholipase A2 activation probably through uncoupling of a GTP-binding protein from the enzyme in rat peritoneal mast cells.

The mechanism underlying the inhibitory effect of biscoclaurine (bisbenzylisoquinoline) alkaloids on phospholipase A2 activation in the signalling system of stimulated rat peritoneal mast cells was studied. Cepharanthine, berbamine and isotetrandrine inhibited antigen- and compound 48/80-induced arachidonic acid liberation, but not diacylglycerol formation or histamine release. They had no effect on A23187-induced arachidonic acid liberation, which was prevented by p-bromophenacyl bromide, a known phospholipase A2 inhibitor, and also did not affect phospholipase A2 activity in a cell-free system including an exogenous phospholipid substrate. Each alkaloid also inhibited arachidonic acid liberation induced by guanosine 5'-O-(3-thiotriphosphate) in saponin-permeabilized mast cells, and by mastoparan or NaF plus AlCl3 intact cells. Furthermore, each alkaloid abolished the inhibitory effect of islet-activating protein on the compound 48/80-induced arachidonic acid liberation. These data suggest that these alkaloids suppress the receptor-mediated phospholipase A2 activation through, at least in part, uncoupling of a GTP-binding protein from the enzyme, rather than by affecting the enzyme directly.     

Inhibitory effects of natural flavonoids on secretion from mast cells and neutrophils

30 natural flavonoids were tested for their inhibitory action on stimulated secretion from rat mast cells and rabbit neutrophils in vitro. There was no correlation between the degrees of inhibitory activity of the flavonoids on the two cell types, or upon the inhibition of the Ca2+ transporting ATPase from sarcoplasmic reticulum. The inhibitory action of flavonoids on mast cells is believed to be at the level of the receptor directed Ca2+ channels in the plasma membrane. For neutrophils it is demonstrated that inhibitory flavonoids do not significantly alter Ca2+ movements across the plasma membrane; nor do they reduce the extent of ligand binding to its receptor. This evidence suggests that flavonoids do not have a common mode of inhibition on these cell types. Rather, the flavonoids must have more specific effects on the different systems examined.