F. L. Pearce

Mucosal mast cells: III. Effect of quercetin and other flavonoids on antigen-induced histamine secretion from rat intestinal mast cells

Quercetin, a naturally occurring flavonol structurally related to the antiallergic drug disodium cromoglycate inhibits anaphylactic histamine release from MMC isolated from the small bowel LP of the rat previously infected with the nematode Nippostrongylus brasiliensis. This contrasts with our previous observation that cromoglycate is inactive in this system. The present effect is immediate and does not decrease on preincubation with the drug. The flavonoids acacetin , apigenin , chrysin , and phloretin also demonstrate significant activity but are less potent than quercetin. Catechin, flavone, morin, and taxifolin are inactive. These results resemble those previously reported for the human basophil. In contrast, all compounds with the possible exception of taxifolin demonstrate significant activity against rat PMC. Acacetin and chrysin are the most effective inhibitors and are more active than quercetin. Rutin (the glycane of quercetin) and phlorezin (the glycane of phloretin) are inactive in both systems. These results are discussed in terms of the functional heterogeneity of mast cells from different sources and identify a group of compounds other than doxantrazole (reported previously), which inhibit histamine secretion by MMC.

SOME STUDIES ON THE RELEASE OF HISTAMINE FROM MAST-CELLS STIMULATED WITH POLYLYSINE

1 Polylysine is an extremely potent releaser of histamine from rat peritoneal mast cells. Isolated mesenteric mast cells of the rat also respond to the secretagogue but guinea‐pig mesenteric cells are unreactive. 2 The release does not require the presence of extracellular calcium ions but shows some dependence on internal stores of the cation. 3 The effect of polylysine is blocked by extremes of temperature and by metabolic inhibitors. 4 The release is very rapid and is virtually complete within 10 s of adding the inducer. 5 The release is unaffected by the Antiallergic drug, doxantrazole, but is inhibited by theophylline and disodium cromoglycate. The latter compounds are effective in both the presence and absence of added calcium. This result is discussed in terms of the postulated effect of the drugs on calcium transport.

THE EFFECT OF ALKALINE EARTH CATIONS ON THE RELEASE OF HISTAMINE FROM RAT PERITONEAL MAST CELLS TREATED WITH COMPOUND 48/80 AND PEPTIDE 401

1 Extracellular calcium ions have a dual effect on the release of histamine from rat peritoneal mast cells treated with compound 48/80 and peptide 401. The release is either potentiated or inhibited according to the relative concentrations of ion and inducer. 2 Strontium similarly potentiates the release produced by optimal concentrations of inducer but higher concentrations are required than in the case of calcium. Strontium is markedly less inhibitory than calcium. 3 Mast cells may be depleted of intracellular calcium by incubation for short periods with the chelating agent, ethylenediamine tetraacetic acid (EDTA). They thereby become unresponsive to compound 48/80 and peptide 401 unless calcium is reintroduced into the incubation medium. Strontium and barium, but not magnesium, will substitute for calcium in this system. Barium additionally produces a marked release of histamine even in the absence of inducer. Pretreatment with the ionophore A23187 similarly inhibits the subsequent response to peptide 401 in divalent cation‐free medium. This inhibition is reversed on the reintroduction of calcium. 4 Compound 48/80 and peptide 401 release histamine from mast cells incubated in isotonic sucrose in the complete absence of added metal ions. However, the corrected release under these conditions is potentiated by both mono and divalent cations. 5 On the basis of these results, the possible mechanism of action of the basic releasing agents and their usefulness as models for studying histamine secretion is discussed.

Isolation and properties of cardiac and other mast cells from the rat and guinea-pig

A method is described for the enzymic dispersion into their component cells of cardiac tissues from the rat and guinea-pig. The resulting suspensions containca. 1% free mast cells and exhibit a low spontaneous release of histamine. The reactivity of these cells towards a number of defined chemical histamine liberators is compared with that of other connective tissue mast cells from the same animals. The results obtained are discussed in terms of the general functional heterogeneity of mast cells from different locations.

The ability of thapsigargin and thapsigargicin to activate cells involved in the inflammatory response.

1 The ability of thapsigargin and thapsigargicin to activate mast cells and leukocytes has been investigated. 2 The thapsigargin‐induced histamine release from rat peritoneal mast cells was found to be dependent on the concentration of thapsigargin, the purity of the mast cell preparations, and the number of mast cells in suspension. 3 Thapsigargin induced histamine release from human basophil leukocytes. 4 Thapsigargin induced β‐glucuronidase and lysozyme release from human neutrophil leukocytes. 5 Thapsigargin caused a release of histamine from mesentery, lung, and heart mast cells of the rat, but only to a minor extent from the corresponding guinea‐pig cells. 6 Thapsigargicin induced histamine release from mesentery, lung, and heart mast cells of the rat at concentrations from 0.1 μM but provoked only a release from the corresponding guinea‐pig cells in the concentration‐range 0.16 to 1.6 μM. 7 Thapsigargin increased the cytoplasmic free calcium level in intact human blood platelets at concentrations from 3.0 nM

Role of intra- and extracellular calcium in histamine release from rat peritoneal mast cells

The present study provides evidence for a number of calcium pools important in histamine secretion from the mast cell. Firstly, calcium loosely bound to the cell membrane, and in rapid equilibrium with the extracellular environment, may be utilized for histamine release induced by most secretagogues. Secondly, all inducers are able to mobilize deeply buried or internal stores of calcium to initiate exocytosis. Finally, calcium bound to regulatory sites in the membrane may modulate the secretory process. Removal of calcium from the latter sites by brief treatment with chelating agents markedly enhances the secretory response in the absence of extracellular calcium, probably by facilitating the mobilization of bound stores of the ion. Saturation of these sites in the presence of excess calcium inhibits the release process and may restrict influx of the cation.

Comparison of the Histamine-Releasing Action of Substance P on Mast Cells and Basophils from Different Species and Tissues

The action of the neuropeptide substance P as a histamine-releasing agent has been compared in histamine-containing cells from a variety of different tissues and species. Peritoneal mast cells from rat, mouse and hamster but not human cells gave a concentration-dependent release of histamine in response to substance P. Release was greater in the absence than in the presence of calcium in the extracellular medium. Mast cells from rat mesentery, lung and heart released histamine in response to substance P, but heart mast cells responded only weakly. All guinea-pig mast cells and histamine-containing cells from human tissues did not give any substantial substance-P-induced release of histamine. The data provides further evidence for the functional heterogeneity of histamine-containing cells.

Calcium Pools Involved in Histamine Release from Rat Mast Cells

Basic secretagogues, antigen, concanavalin A, the ionophore A23187 and, to a lesser extent, anti-rat IgE produce a significant release of histamine from rat peritoneal mast cells in the absence of extracellular calcium. This release is due to the mobilization of intracellular reservoirs of calcium. The release is abolished by prolonged exposure to chelating agents, but is potentiated by brief exposure to these substances. It is suggested that the latter treatment removes calcium from a superficial, regulatory site and thus facilitates the mobilization of more internal pools of the ion. By analogy with smooth muscle, these regulatory sites may also modulate calcium influx into the cell. On the basis of these and other results, the possible calcium pools important in histamine secretion are discussed.

ISOLATION AND SOME PROPERTIES OF MAST-CELLS FROM THE MESENTERY OF THE RAT AND GUINEA-PIG

A number of enzymes were screened for their ability to dissociate mesenteric tissues from the rat and guinea pig into their component cells. The bacterial enzyme collagenase was found to be the most satisfactory agent and a procedure based on the use of this protease was developed. The resulting suspensions contained 1–2% free mast cells and exhibited a low (ca. 5%) spontaneous release of histamine. The tissue cells contained less histamine than rat peritoneal mast cells and the guinea pig cells were smaller in size. Cells obtained from actively sensitized animals responded to antigenic challenge more strongly than the chopped tissue indicating that they were functionally intact. Rat mesenteric cells could be passively sensitized with homologous reaginic antibody and also responded to anti-rat IgE. The immunologically induced releases from rat mesenteric and peritoneal cells showed differing sensitivities to potentiation by phosphatidyl serine but the responses were directly comparable in the absence of this effect. Rat mesenteric cells also responded, but less effectively than the peritoneal cells, to the ionophore A23187, concanavalin A, ATP and basic secretagogues. They were, however, essentially refractory to the action of dextran. In contrast, guinea pig mast cells responded strongly only to the ionophore and weakly or not at all to the other agents. These results indicate marked inter-and intra-species differences in the reactivity of mast cells and suggest that rat peritoneal cells should not be used as the sole model for studying histamine secretion.

Differential reactivity of isolated mast cells from the rat and guinea pig

The effects of various chemical histamine liberators on isolated rat peritoneal, rat mesenteric and guinea-pig mesenteric mast cells were examined. All three cell types responded, but to different degrees, to calcium ionophores and surface active agents. The rat mesenteric cells also reponded, but less effectively than the peritoneal cells, to compound 48/80, peptide 401 from bee venom and ATP. Rat mesenteric cells were essentially refractory to the action of dextran and guinea-pig cells were almost totally unresponsive to the named secretagogues. These results show that there are marked functional differences between the mast cells examined and suggest that isolated tissue cells may usefuly complement rat peritoneal cells in the study of anaphylactic and anaphylactoid reactions.