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

Topical ophthalmic beta blockers may cause release of histamine through cytotoxic effects on inflammatory cells

AIM

To evaluate the effects of beta blockers used in ophthalmology on the release of histamine from mixed cell preparations containing human leucocytes and basophils.

METHODS

A mixed leucocyte and basophil preparation was obtained from venous blood of healthy non-atopic volunteers. Cell preparations were then incubated with betaxolol, metipranolol, timolol, or carteolol. After incubation for 1 hour the histamine content of the supernatant was analysed by automated fluorometric analysis. Cell viability was tested by measuring lactate dehydrogenase (LDH) concentrations.

RESULTS

Betaxolol and metipranolol in concentrations between 10(-2) M and 10(-3) M liberated histamine from human blood cells in a dose dependent manner. Carteolol and timolol had no effect on histamine at these concentrations. At the same concentrations LDH was also detected in the supernatants of cell suspensions incubated with metipranolol or betaxolol.

CONCLUSIONS

Betaxolol and metipranolol induce substantial histamine release from human leucocytes, probably as a result of their cytotoxic effect.

The role of intracellular calcium in A-23187 stimulated and beta-adrenoceptor blocking drug treated blood platelets

A significant concentration-dependent difference was found between beta-adrenoceptor blocking drugs in their ability to inhibit A23187-induced isolated platelet aggregation. In the absence of extracellular calcium ions the following rank order of potency to inhibit calcium ionophore stimulated platelet aggregation was shown: propranolol > bevantolol > alprenolol > metipranolol > oxprenolol > atenolol > pindolol > metoprolol approximately sotalol approximately practolol. The interruption of induced aggregation, as well as inhibition of aggregation, in the absence of extracellular calcium ions indicated interference of inhibitory beta-adrenoceptor blocking drugs with intramembrane or intraplatelet calcium pools activated with A23187. This suggestion was supported by the reversal of the inhibitory effect of beta-adrenoceptor blocking drugs in the presence of extracellular calcium ions. The effect was dose dependent and occurred within 30 sec after calcium administration. The results indicated that inhibitory beta-adrenoceptor blocking drugs, possessing a cationic amphiphilic structure, suppressed calcium mobilization in A23187-stimulated platelets, most probably after entering platelets. This explains why lipophilic drugs are more effective than hydrophilic ones in calcium ionophore A23187-stimulated platelets.

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.

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.

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.

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.

Role of mast cells in anaphylaxis. Evidence for the importance of mast cells in the cardiopulmonary alterations and death induced by anti-IgE in mice

We used genetically mast cell-deficient WBB6F1-W/Wv and WCB6F1-S1/S1d mice and the congenic normal (+/+) mice to investigate the effects of intravenous infusion of goat antimouse IgE on heart rate (HR), pulmonary dynamic compliance (Cdyn), pulmonary conductance (GL), and survival. In WBB6F1-+/+ and WCB6F1-+/+ mice, anti-IgE induced extensive degranulation of tracheobronchial mast cells, as well as significant elevation of HR, significant reductions in Cdyn and GL and, in some cases, death. In contrast, W/Wv and S1/S1d mice exhibited little or no pathophysiological responses and no mortality after challenge with anti-IgE. In W/Wv mice reconstituted with mast cells by intravenous administration of bone marrow cells derived from congenic +/+ mice (+/+ BM----W/Wv mice), anti-IgE induced extensive mast cell degranulation, as well as pathophysiological responses and mortality similar to those observed in WBB6F1-+/+ mice. These findings suggest a critical role for mast cells in the development of the cardiopulmonary changes and mortality associated with anti-IgE-induced anaphylaxis.

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.

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.

Histamine liberation and aggregation of rabbit blood platelets treated with beta-adrenoceptor blocking drugs

The liberation of histamine from rabbit blood platelets during aggregation as well as the effect of propranolol and atenolol on this process was investigated. Thrombin, but not ADP, liberated histamine from platelets in a dose-dependent manner. This liberation was influenced by beta-adrenoceptor blocking drugs and some modes of action are discussed.

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.

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.

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 Kö 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 Kö 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.