Non-IgE-mediated mast cell stimulation

The effect of a variety of non IgE-mediated stimuli on histamine release from mast cells from different locations is described. Sensory neuropeptides are shown to resemble other polycationic compounds in preferentially activating mast cells from the rat while having a limited effect on human mast cells, except possibly those from skin. Similar results were obtained with the putative non-adrenergic, non-cholinergic neurotransmitter ATP, thereby questioning the role of neuronal mast cell activation in allergy and inflammation. Bradykinin also acted selectively against rat cells while complement-derived and formylmethionyl peptides were effective against human basophils and cutaneous mast cells. The latter results may indicate a role for the skin cell in local inflammatory responses involving complement activation and in host resistance to bacterial infection. Rat mast cells and human basophils were most responsive to hyperosmolar challenge but significant effects were obtained from human pulmonary mast cells obtained by bronchoalveolar lavage. The latter cells may thus be implicated in exercise-induced asthma. The plasma substitute dextran was a specific secretagogue for the rat while morphine sulphate largely induced histamine release from human cutaneous mast cells. The latter result may account for anaphylactoid reactions to the opiate. In total these data emphasize the functional heterogeneity of mast cells from different locations and highlight the particular pharmacological properties of the skin mast cell in man.

Role of nitric oxide in histamine release from human basophils and rat peritoneal mast cells

The effects of a range of nitric oxide (NO)-related compounds on histamine release from human basophils and rat peritoneal mast cells were studied. Basal and immunologic histamine releases from human basophils were not affected by N(omega)-nitro-L-arginine, N(omega)-nitro-L-arginine methyl ester, aminoguanidine or methylene blue (all inhibitors of NO production), sodium nitroprusside (an NO donor), L-arginine (a substrate for NO synthase) or D-arginine (the inactive enantiomer of L-arginine). In rat peritoneal mast cells, NO donors such as sodium nitroprusside, sodium nitrite and sodium nitrate, and lipopolysaccharide (an inducer of NO synthase) had little effect on basal histamine release, while 3-morpholino-sydnonimine (SIN-1, an NO donor), L-arginine and D-arginine increased this release by up to threefold. None of the inhibitors of NO production had any striking effect on histamine release induced by anti-rat immunoglobulin E (IgE), compound 48/80, sodium fluoride, phospholipase C, 1,2-dioctanoyl-sn-glycerol or ionophore A23187. However, haemoglobin was found to inhibit histamine release by anti-rat IgE or A23187 by ca. 40%. Alone of the NO donors, low concentrations of L-arginine produced a mild inhibition of histamine release induced by anti-IgE, compound 48/80 and A23187, but not other ligands, while sodium nitroprusside dose-dependently inhibited (by a maximum of ca. 30%) histamine release by anti-rat IgE, sodium fluoride or A23187. Stimulation with a variety of secretagogues or treatment with L-arginine, D-arginine, lipopolysaccharide, SIN-1 or sodium nitroprusside had no effect on NO production. Similarly, L-arginine, D-arginine or sodium nitroprusside did not change intracellular cGMP levels. On the basis of these results, it is suggested that NO does not play a significant role in the modulation of histamine release from human basophils or rat peritoneal mast cells. The effects of L-arginine, D-arginine and sodium nitroprusside may involve mechanisms unrelated to NO.

Role of serine esterases in mast cell activation

1. A variety of chymotryptic substrates and inhibitors prevented the release of histamine and prostaglandin D2 from rat peritoneal mast cells stimulated with anti-IgE but not the calcium ionophore A23187 or a variety of polyamines. 2. The activity of the compounds was strikingly increased in cells reversibly permeabilized with ATP, indicating the importance of their effective incorporation into the cytosol. 3. The compounds produced a comparable inhibition of immunological, but not pharmacological, histamine release from human mast cells and basophils. 4. Treatment of rat mast cells with anti-IgE led to a marked increase in the total chymotryptic activity expressed by the cells. 5. Immunological, but not pharmacological, stimulation of permeabilized rat mast cells loaded with a fluorescent chymotryptic substrate led to a pronounced and rapid increase in fluorescence, indicating activation of the enzyme and hydrolysis of the substrate. These changes were attenuated by chymotryptic inhibitors. 6. In total, these data provide compelling evidence for the direct involvement of a serine protease in IgE-mediated histamine release from mast cells.

Fc epsilon RI-mediated chloride uptake by rat mast cells: modulation by chloride transport inhibitors in relation to histamine secretion

1. We have examined the role of extracellular chloride in the mast cell secretion process. The immunologically-directed ligand, antibody to IgE (anti-IgE) required extracellular chloride ions for optimum secretion from rat peritoneal mast cells. In contrast, replacement of extracellular chloride did not alter the mast cell secretory response to compound 48/80, calcium ionophore A23187 or substance P. 2. Anti-IgE-stimulation of mast cells evoked a significant uptake of chloride ions compared to non-stimulated cells. The magnitude of chloride uptake correlated with the magnitude of stimulated histamine secretion. 3. Compound 48/80, substance P and A23187 did not alter the rate of chloride ion uptake, although these agents caused significant histamine secretion. 4. The Na+/K+/2Cl- cotransport inhibitor, furosemide, reduced the rate of anti-IgE-stimulated chloride uptake at a relatively high concentration (700 microM). However, the more potent Na+/K+/2Cl- cotransport inhibitors, bumetanide (100 microM) and piretanide (100 microM) had no effect on the stimulated chloride uptake. 5. Furosemide inhibited anti-IgE-induced histamine secretion, bumetanide potentiated the response and piretanide had no effect. This suggests that their respective action on histamine secretion are unrelated to inhibition of the Na+/K+/2Cl- carrier. 6. The chloride channel blocker, 5-nitro-2-((3-phenylpropyl)-amino)-benzoic acid (NPPB), reduced both anti-IgE-stimulated chloride uptake and the corresponding histamine secretion in a dose-dependent manner. The magnitude of the inhibitory action of the drug on these two cellular processes was comparable, implying that chloride channel activity is related to the mechanism of histamine secretion. 7. It is concluded that chloride uptake has a role in the control of Fc epsilon RI-mediated histamine secretion from rodent mast cells.

Human lung mast cells release small amounts of interleukin-4 and tumour necrosis factor-alpha in response to stimulation by anti-IgE and stem cell factor

Recent reports have suggested that mast cells are capable of producing and releasing a number of pro-inflammatory cytokines. However, these studies have mainly been carried out using murine tissue culture derived mast cells and it is known that these cells differ markedly in their functional properties from isolated human mast cells. It was therefore essential to study the release of cytokines from the latter cell type. On immunological stimulation with anti-immunoglobulin E (anti-IgE) or stem cell factor (SCF), purified human lung mast cells released, within 2-10 min, small amounts of tumour necrosis factor-alpha (10.5 +/- 2.9 pg/10(6) mast cells and 17.9 +/- 7.9 pg/10(6) mast cells, respectively) and interleukin-4 (5.3 +/- 2.5 pg/10(6) mast cells and 8.0 +/- 3.2 pg/10(6) mast cells, respectively). After longer periods of activation (30 min-4 h). the amounts of cytokines released from stimulated cells decreased to levels which were below those of the unstimulated cells. This possible degradation of cytokines by mast cells could not be prevented by the addition of protease inhibitors.

The effect of recombinant stem cell factor on human skin and lung mast cells and basophil leukocytes

Recombinant human stem cell factor (rhSCF) induced histamine release from human skin and lung mast cells but had no effect on human basophil leukocytes. More importantly, rhSCF enhanced the release of histamine in response to IgE-crosslinking of human mast cells. This potentiation was observed at rhSCF concentrations which induced histamine release, and also at lower concentrations of the ligand which by themselves produced no effect. Very limited potentiation was observed with human basophil leukocytes. The enhancing effect of SCF was unique to IgE-dependent stimulation and when SCF was incubated with the neurotransmitter substance P and the calcium ionophore A23187, no augmentation of histamine release was observed with any of the cell types tested. These findings suggest that endogenous SCF may contribute to the regulation of mast cell function and may hence play a role in diverse allergic and inflammatory reactions.

Extracellular guanosine 3',5'-cyclic monophosphate and disodium cromoglycate share a similar spectrum of activity in the inhibition of histamine release from isolated mast cells and basophils

In comparison to adenosine 3',5'-cyclic monophosphate (cAMP), surprisingly little is known regarding the role of guanosine 3',5'-cyclic monophosphate (cGMP) in the functional modulation of mast cells and basophils. In the present study, the ability of cGMP, cAMP, and a range of related compounds, to inhibit immunologically induced histamine release from these cells was investigated and compared to the anti-asthmatic drug disodium cromoglycate (DSCG). Exogenously applied cGMP produced a potent inhibition of histamine release from rat peritoneal mast cells, but cAMP had a negligible effect. The attenuation noted with cGMP was markedly reduced if cells were pretreated with the nucleotide before stimulation. Similar results were obtained with DSCG. The inhibitory and tachyphylactic effects noted with cGMP were mimicked by direct derivatives of the compound but not by a range of other cyclic or guanosine nucleotides. The time courses of the induced tachyphylaxis seen with cGMP and DSCG were similar, and cross-tachyphylaxis between the two compounds was observed. In addition, both cGMP and DSCG showed a comparable spectrum of activity against mast cells isolated from the mouse, guinea pig, and human. The parallel effects of the two agents suggests that they may inhibit mediator release from mast cells through similar mechanisms.

Some studies on the effects of alpha-chymotrypsin on mast cells from the rat and other species

We have examined the effect of alpha-chymotrypsin on isolated mast cells from different sources. The enzyme induced a dose-dependent secretion of histamine from purified and non-purified populations of rat peritoneal mast cells. The release was non-cytotoxic and was inhibited by metabolic blockers and extremes of temperature. The process was relatively slow, being essentially complete within 20 min, and was unaffected by phosphatidylserine. A substantial component of the secretion persisted in the absence of extracellular Ca2+. The release was suppressed by extremes of pH and a variety of anti-allergic compounds and serine esterase inhibitors. In addition to the secretion of preformed mediators, alpha-chymotrypsin also induced the metabolism of arachidonic acid, resulting in the release of prostaglandin D2 in a dose-related manner from purified rat peritoneal mast cells. alpha-Chymotrypsin exhibited a marked tissue and species selectivity in its action and tissue mast cells of the rat, guinea pig and human were generally resistant to the enzyme except at cytotoxic concentrations. On the basis of these results, the possible role of endogenous serine esterases in mast cell activation is discussed.

Involvement of a serine protease in mast cell activation

To examine the putative role of an endogenous serine esterase in mast cell activation, we have investigated the effect of inhibitors of, and substrates for, alpha-chymotrypsin in normal and permeabilized rat mast cells. These agents effectively blocked histamine release induced by anti-IgE, with an enhanced potency in permeabilized cells, but were ineffective against secretion evoked by compound 48/80. Activation of a chymotryptic enzyme, as evidenced by hydrolysis of a fluorescent substrate, was directly demonstrated following immunologic stimulation of permeabilized mast cells. No such activation was observed with compound 48/80. Immunologic stimulation also led to a significant increase in the total chymotryptic activity recoverable from the cells.

Does the mast cell have an intrinsic role in the pathogenesis of interstitial cystitis?

In order to examine the role of mast cells in the inflammatory bladder disease interstitial cystitis, mast cells isolated from the human bladder of normal and diseased tissue were challenged with a range of secretagogues. Calcium ionophore A23187 and anti-IgE caused histamine release from all bladder mast cells in a dose-related manner. Mast cells from the diseased tissue were far more responsive than those from the normal tissue. Mast cells from the muscle of normal bladder were responsive towards substance P and compound 48/80. However, mast cells from interstitial cystitis bladder did not release significant amounts of histamine with these two secretagogues.

Effect of loop diuretics on rat peritoneal and human lung mast cells

The effects of furosemide and bumetanide on immunologically stimulated rat peritoneal and human lung mast cells were compared. Furosemide and bumetanide had different modulatory actions on the rat peritoneal mast cell. Furosemide inhibited anti-IgE-induced histamine release. Preincubation of the cells with the drug, prior to anti-IgE stimulation, significantly reduced furosemide's inhibitory effect. In contrast, bumetanide potentiated anti-IgE-induced histamine secretion from the rat peritoneal mast cell. Both diuretics were modest inhibitors of anti-IgE-mediated histamine release from human lung mast cells. For furosemide, inhibition decreased with preincubation, while preincubation increased bumetanide's inhibitory action.

Effects of the H2-antagonists famotidine and nizatidine and the cytoprotectant misoprostol on human colonic and rat peritoneal mast cells

The H2-antagonists famotidine and nizatidine produced a dose-dependent inhibition of histamine release from human colonic mucosal and muscle mast cells stimulated with anti-IgE. The IC30 values were in the range 0.5-10 microM and the maximum inhibition approached 50%. The compounds showed similar efficacy against rat peritoneal mast cells but were more potent. The cytoprotectant misoprostol had a striking effect on the human colonic mast cells, producing more than 50% inhibition at concentrations of 0.1-1 nM, but was much less active against the rat cells.

Human basophil degranulation is not triggered by very dilute antiserum against human IgE

We have attempted to reproduce the findings of Benveniste and co-workers, who reported in 1988 that degranulation of human basophil leukocytes is triggered by very dilute (10(2)-10(120)) antiserum against IgE. The results were contrary to conventional scientific theory and were not satisfactorily explained. Following as closely as possible the methods of the original study, we can find no evidence for any periodic or polynomial change of degranulation as a function of anti-IgE dilution. Our results contain a source of variation for which we cannot account, but no aspect of the data is consistent with the previously published claims.

Some characteristics of the ATP-induced histamine release from and permeabilization of rat mast cells

Extracellular adenosine 5'-triphosphate (ATP) induced a characteristic, dose-dependent release of histamine and prostaglandin D2 (PGD2) from rat peritoneal mast cells. The process was relatively slow, non-cytotoxic, maximal at physiological pH and dependent on external calcium. Strontium and barium ions were able to substitute for calcium, although higher concentrations were required for maximal release. Cells stimulated in the absence of calcium progressively lost the ability to respond to subsequent reintroduction of the cation. The secretion of histamine induced by ATP was largely unaffected by the anti-asthmatic drugs disodium cromoglycate and nedocromil sodium but was inhibited by structurally related flavonoids and by cAMP-active drugs. Importantly, the non-hydrolysable guanosine 5'-triphosphate (GTP) analogue, GTP-gamma-S, elicited a dose-dependent release of histamine when introduced into mast cells permeabilized with ATP in the absence of external calcium. ATP thus appears to be a useful cell permeabilizing tool with which to study the biochemical processes involved in mast cell activation.

Effect of nedocromil sodium on mediator release from mast cells

Bronchial asthma is a complex inflammatory disorder that involves activation of, and mediator release by, a variety of cells including mast cells. Nedocromil sodium can inhibit the activity of a range of inflammatory cells including mast cells, as has been demonstrated in several studies. In human beings nedocromil sodium inhibited histamine secretion from mast cells obtained by bronchoalveolar lavage and from dispersed lung mast cells. Tachyphylaxis was noted with the latter cells only. Because the bronchoalveolar lavage mast cells would come into direct contact with inhaled drugs, these cells may be a major target for the action of nedocromil sodium. The inhibitory effects of nedocromil sodium on mast cell activation and secretion are one way the drug may be effective in controlling airway obstruction.

Basophil mediator release in atopic dermatitis

Basophils have been implicated as a source of histamine and pro-inflammatory eicosanoids in atopic dermatitis. However, mechanisms regulating basophil mediator release are not understood. An H3 receptor involved in the control of histamine synthesis and release has been identified in nervous tissue. In this study we have investigated 1) release of histamine, leukotriene C4, and prostaglandin D2 from anti-immunoglobulin E (IgE)-stimulated basophils of adults with atopic dermatitis and unaffected individuals and 2) specific H3 receptor-dependent basophil mediator release, using an H3 receptor agonist and antagonist. Basophil-rich leukocyte fractions were prepared by dextran sedimentation of venous blood from 19 patients with atopic dermatitis (five male, 14 female, mean age 30.6 years, range 19-59 years) and 15 unaffected individuals (five male, 10 female, mean age 27.6 years, range 19-50 years). Anti-IgE (0.78-78.0 micrograms/ml) stimulation of basophils induced a concentration-dependent release of histamine and leukotriene C4, but not prostaglandin D2. Histamine release was maximally induced by 7.8 micrograms/ml anti-IgE with no significant (Mann-Whitney U test) difference between atopic basophils (n = 17; 43.65 +/- 4.16% mean +/- SEM) and normal basophils (n = 13; 52.23 +/- 4.39%). LTC4 release was maximal from atopic basophils incubated with 2.6 micrograms/ml anti-IgE (n = 5; 0.99 +/- 0.29 pg/10(6) cells) and from normal basophils incubated with 0.78 microgram/ml anti-IgE (n = 5; 25.38 +/- 5.79 pg/10(6) cells). Anti-IgE-stimulated release of leukotriene C4 from atopic basophils was significantly less than from normal basophils at all concentrations (p < 0.05). Basophils were co-incubated with anti-IgE (2.6 and 7.8 micrograms/ml) and either the H3 receptor agonist, (R)alpha-methylhistamine (10(-8) and 10(-7) M), or the H3 receptor antagonist thioperamide (10(-6) and 10(-5) M). Neither drug modulated anti-IgE-induced release of histamine (atopics, n = 10; normals, n = 8). These results indicate 1) that basophils from adults with atopic dermatitis release the same amount of histamine as, but less leukotriene C4 than, basophils of unaffected adults and 2) that H3 receptors are not involved in anti-IgE release of histamine from basophils. These data do not support a role for increased basophil release of histamine as a mediator in the itch and erythema of atopic dermatitis in adults.

On the mechanism of action of sodium orthovanadate in inducing histamine release from rat peritoneal mast cells

Sodium orthovanadate produced a dose-dependent release of histamine and prostaglandin D2 from rat peritoneal mast cells. The release of histamine was selectively inhibited by the anion channel blockers SITS and DIDS, and by theophylline and dibutyryl cyclic-AMP, but was unaffected by disodium cromoglycate and lanthanum ions. Unlike IgE-directed ligands, vanadate did not produce any change in the intracellular concentration of cyclic-AMP but did promote a substantial uptake of calcium-45 from the incubation medium. This effect paralleled the release of histamine. These results are discussed in terms of the possible mode of action of vanadate.

Mast cell heterogeneity in man: unique functional properties of skin mast cells in response to a range of polycationic stimuli

Human mast cell heterogeneity was assessed by histochemical and detailed functional criteria using mast cells isolated from foreskin, uterine myometrium and lung parenchyma. The skin mast cells were histochemically distinct from their counterparts in the other two tissues by being predominantly insensitive to blockage of dye-binding following formalin fixation (ca. 80%). Functionally, a wide range of structurally diverse polycationic compounds induced selective histamine release from the skin mast cells (ca. 10% at top concentrations) although these cells were less responsive to immunological ligands and calcium ionophores when compared with the uterine and lung cells. The basic compounds, polyarginine and histone, proved to be more generalised histamine liberators as compared with their structural analogues, polylysine and protamine sulphate, probably by virtue of their high content of arginine residues and hydrophobic nature (histone). Studies with the anaphylatoxin, C3a, and its analogues 21R and C3ades Arg on skin mast cells emphasized the importance of basic amino acids for histamine-liberating peptides. Skin mast cells also proved more susceptible than their uterine counterparts to lysis by the detergents, Triton X-100 and Tween 20, suggesting that fundamental differences in membrane structure and/or fluidity might account for functional heterogeneity within the human mast cell population.

Mast cell heterogeneity: evidence that mast cells isolated from various connective tissue locations in the rat display markedly graded phenotypes

The present study has extended histochemical and functional investigations into rat mast cell heterogeneity using isolated mast cells from four connective tissue locations; the peritoneum, mesentery, lung and skin. On histological examination, mast cells from these locations displayed a range of phenotypes following formalin fixation and staining with Alcian blue/safranin O, suggesting the existence of both chondroitin sulphate and heparin proteoglycans in varying proportions in these cell types. Functional studies using the structurally diverse polycationic secretagogues, compound 48/80, the polyamino acids, polymyxin B, substance P, ACTH1-24, mastoparan, protamine sulphate, histone, d-tubocurarine and ranitidine confirmed the existence of such phenotypic gradation. This investigation highlights the inappropriate usage of the terms CTMC and MMC which represent two phenotypic extremes between which a gradation of phenotypes clearly exists.

The human skin mast cell: a comparison with the human lung cell and a novel mast cell type, the uterine mast cell

The functional and histochemical properties of isolated mast cells from human skin, uterine myometrium and lung parenchyma were compared. The skin cell showed a marked difference in responsiveness to both secretagogues and anti-allergic compounds when compared to mast cells from the uterus and lung. The latter cell types responded more strongly to immunologically-directed ligands and calcium ionophores than the skin cell. However, the skin cell released histamine in response to a wide variety of polycationic compounds whilst the lung and uterine cells were essentially refractory to these agents. The antiallergic drugs, disodium cromoglycate (DSCG) and nedocromil sodium, were weakly inhibitory against the skin cell but were in contrast more effective against the lung and uterine cells.

Mast cells from human gastric mucosa: a comparative study with lung and colonic mast cells

Mast cells isolated from human gastric mucosa released histamine on challenge with IgE-directed ligands and calcium ionophores but were essentially unresponsive to a variety of non-immunological stimuli. Moreover, immunologically induced histamine secretion from these cells was inhibited by a number of anti-allergic agents including anti-asthmatic chromones, beta-adrenoceptor agonists and phosphodiesterase inhibitors. In total, these data indicate that mast cells from the human gastric mucosa are in many respects functionally similar to their lung and colonic counterparts.