Calcium ionophore A23187 as a secretagogue for rat mast cells: does it bypass inhibition by calcium flux blockers?

An overview on marine anti-allergic active substances for alleviating food-induced allergy

Food provides energy and various nutrients and is the most important substance for the survival of living beings. However, for allergic people, certain foods cause strong reactions, and sometimes even cause shock or death. Food allergy has been recognized by the World Health Organization (WHO) as a major global food safety issue which affect the quality of life of nearly 5% of adults and 8% of children, and the incidence continues to rise but there is no effective cure. Drug alleviation methods for food allergies often have shortcomings such as side effects, poor safety, and high cost. At present, domestic and foreign scientists have turned to research and develop various new, safe and efficient natural sources of hypoallergenic or anti-allergic drugs or foods. There are many kinds of anti-allergic substances obtained from the plants and animals have been reported. Besides, probiotics and bifidobacteria also have certain anti-allergic effects. Of all the sources of anti-allergic substances, the ocean is rich in effective active substances due to its remarkable biodiversity and extremely complex living environment, and plays a huge role in the field of anti-food allergy. In this paper, the anti-food allergic bioactive substances isolated from marine organisms encompassing marine microbial, plant, animal sources and their mechanism were reviewed and the possible targets of anti-allergic substances exerting effects are illustrated by drawing. In addition, the development prospects of marine anti-allergic market are discussed and forecasted, which can provide reference for future research on anti-allergic substances.

IgE receptor-mediated arachidonic acid release by rat basophilic leukemia (RBL-2H3) cells: possible role in activating degranulation

Aggregation of the IgE receptor on rat basophilic leukemia (RBL-2H3) cells triggers increased hydrolysis of polyphosphoinositides (PI), secretion of arachidonic acid (AA) and its metabolites, and degranulation to release 5-hydroxytryptamine. Despite the documented involvement of second messengers produced by the PI pathway in RBL cell exocytosis, recent evidence has suggested that additional signalling events are also necessary. We have, therefore, examined PLA2 activation and AA metabolite production by these cells in response to Ag stimulation, and evaluated the potential role of these in activating degranulation. The time course and antigen dose dependence for release of AA and its metabolites were comparable to those for degranulation and production of inositol phosphates (InsPs) when examined in parallel. Stimulated fatty acid release was highly selective for AA (compared with oleic or linoleic acids) and appeared to result predominantly from PLA2 activation. AA released upon antigen stimulation is rapidly metabolized to produce prostaglandin and leukotrienes. These are not required for activating degranulation, since BW755c completely inhibited AA metabolite production without affecting AA release, degranulation or InsP production. In contrast, the PLA2 inhibitors quinacrine and quercetin inhibited both AA release and degranulation in parallel, without significantly affecting levels of InsP production, and this inhibition could be partially reversed by exogenous addition of AA and lysophospholipid. These results demonstrate that activation of IgE-receptor mediated exocytosis of RBL cells does not require AA metabolites, and strongly suggest that PLA2 activation and release of AA and lysophospholipid may be involved in triggering this response.

Effect of inhibitors on histamine release from mast cells recovered by bronchoalveolar lavage in basenji-greyhound and mongrel dogs

Studies of rodent mast cells have demonstrated that subpopulations differ in regard to their response to inhibitors of histamine release. To determine whether such compounds have different effects on mast cells from Basenji-Greyhound (BG) dogs with airway hyperreactivity and from mongrel dogs, we investigated the effect of cromolyn sodium, nedocromil sodium, theophylline, and quercetin on calcium ionophore A23187-induced histamine release from mast cells recovered by bronchoalveolar lavage. Mast cells recovered from BG and mongrel dogs were similar in respect to morphology and spontaneous and calcium ionophore-induce histamine release. Histamine release from mast cells from both BG and mongrel dogs was inhibited by quercetin (10(-4) M) and nedocromil sodium (5 x 10(-5) M). In contrast, only the histamine release from mast cells recovered from mongrel dogs was inhibited by cromolyn sodium (10(-4) M) and theophylline (5 x 10(-3) M). Thus, mast cells that are similar in regard to morphology and response to histamine liberators may differ in their response to inhibitors of histamine release.

Comparison of the action of calcium antagonists on basophil histamine release

The inhibitory capacity of calcium antagonists on basophil histamine release was examined in allergic patients and in controls. All dihydropyridines tested (nifedipine, nimodipine, nitrendipine, nicardipine, felodipine) dose-dependently inhibited anti-IgE- and A23187-induced release with an order of potency of felodipine greater than nicardipine greater than nifedipine = nimodipine = nitrendipine. Only the inhibition induced by felodipine and nicardipine on anti-IgE-induced release could be counteracted by increasing extracellular calcium. Diltiazem, not belonging to the dihydropyridines, was a weak inhibitor. A combination of felodipine and verapamil in low concentrations exerted a synergistic inhibitory effect on histamine release, whereas this was not the case with other combinations of antagonists. The results suggest differences in the mode of action of the 1.4-dihydropyridines. This might be of significance in the search for calcium antagonists suitable in the treatment of allergic diseases.

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)

Inhibition of rat mast cell degranulation by verapamil

Calcium antagonists, e.g. verapamil, prevent exercise-induced asthma. This protective effect may proceed from inhibition of contraction of bronchial smooth muscle, release of mediators by primary effector cells, e.g. mast cells, or both. Therefore, we studied the inhibitory effect of increasing concentrations of verapamil on both in vitro antigen-induced degranulation and ionophore A23187-induced release of labelled serotonin by rat peritoneal mast cells. There was a dose-dependent inhibition by verapamil of both ovalbumin-induced degranulation of mast cells passively sensitized by incubation with mice IgE-rich serum and ionophore-induced release of tritiated serotonin by mast cells previously incubated with (3H)-5HT; the 50% inhibiting concentration was 1.4 X 10(-4) mol I-1 and 5.2 X 10(-5) mol I-1, respectively. An attractive explanation of our results is that verapamil inhibits the antigen-induced release of mediators by mast cells through its calcium antagonist effect. Our results also suggest that the preventing effect of calcium antagonists on asthma may be multi-factorial since other authors have clearly shown that these drugs inhibit contraction of guinea-pig tracheal smooth muscle in vitro.

Role of calcium in airway smooth muscle contraction and mast cell secretion

The principal pathological features of asthma, including tracheobronchial smooth muscle contraction and mast cell mediator synthesis and release, are calcium-dependent processes. Calcium plays an integral role in transmitting signals at the cell surface to the enzymatic machinery of the cell interior; its role as the agent for "excitation-contraction coupling" of airway smooth muscle and for "stimulus-secretion coupling" of mast cells is reviewed. A rise in intracellular calcium ion concentration triggers cellular activation. In smooth muscle, calcium bound to calmodulin stimulates the myosin light chain kinase which is important in the regulation of actin-myosin interaction. In mast cells, calcium may bind to calmodulin or to a calmodulinlike regulatory protein, and it also stimulates enzymes important in the synthesis of newly generated mediators including prostaglandins and leukotrienes. The regulatory role of cyclic AMP in both cell systems is discussed, especially as it pertains to calcium metabolism. By interfering with transmembrane calcium fluxes, the calcium channel blocking drugs have the potential for significantly modifying bronchoconstriction and airway inflammation in asthma and related bronchospastic disorders. Some of the in vitro studies of calcium channel blockers in these two cell systems are reviewed. Finally a speculation about the role of abnormal sensitivity to calcium in airway smooth muscle as a potential cause of airway hyperreactivity is entertained.

A microtiter plate assay using cellulose acetate filters for measuring cellular [3H]serotonin release

An assay system for measuring the release of tritium-labeled serotonin that accompanies cellular degranulation is described. The assay is carried out with [3H]serotonin loaded rat basophilic leukemia (RBL) cells that have been sensitized with IgE, and aliquots of these are combined with dilutions of specific antigen in the wells of a microtiter plate together with appropriate control samples. The released activity in all of the wells is harvested simultaneously and quickly using commercial cellulose acetate filters which are counted following addition of scintillation fluor. In many applications this plate assay is faster and more convenient than the conventional test tube assay, and the results obtained are shown to be comparable. For the plate assay, the effect of cell concentration and some other conditions are shown. In general it is found that greatly improved results can be obtained if the cells are cultured overnight during the [3H]serotonin incorporation. With this assay it is shown that RBL cells also release incorporated 51Cr specifically during degranulation.