Spectroscopic studies of rat mast cells, mouse mastocytoma cells, and compound 48/80--III. Evidence for a protein binding site for compound 48/80

Applications of atomic force microscopy in biophysical chemistry of cells

This article addresses the question of what information and new insights atomic force microscopy (AFM) provides that are of importance and relevance to cellular biophysical chemistry research. Three enabling aspects of AFM are discussed: (a) visualization of membrane structural features with nanometer resolution, such as microvilli, ridges, porosomes, lamellapodia, and filopodia; (b) revealing structural evolution associated with cellular signaling pathways by time-dependent and high-resolution imaging of the cellular membrane in correlation with intracellular components from simultaneous optical microscopy; and (c) qualitative and quantitative measurements of single cell mechanics by acquisition of force-deformation profiles and extraction of Young's moduli for the membrane as well as cytoskeleton. A future prospective of AFM is also presented.

Impact of actin rearrangement and degranulation on the membrane structure of primary mast cells: a combined atomic force and laser scanning confocal microscopy investigation

Degranulation of bone marrow-derived mast cells (BMMCs) triggered by antigens (e.g., 2,4-dinitrophenylated bovine serum albumin (DNP-BSA) and secretagogues (e.g., poly-L-lysine) was investigated by combined atomic force microscopy (AFM) and laser scanning confocal microscopy (LSCM). This combination enables the simultaneous visualization and correlation of membrane morphology with cytoskeletal actin arrangement and intracellular granules. Two degranulation mechanisms and detailed membrane structures that directly corresponded to the two stimuli were revealed. In DNP-BSA triggered activation, characteristic membrane ridges formed in accordance with the rearrangement of underlying F-actin networks. Individual granules were visualized after they released their contents, indicating a "kiss-and-run" pathway. In BMMCs stimulated by poly-L-lysine, lamellopodia and filopodia were observed in association with the F-actin assemblies at and near the cell periphery, whereas craters were observed on the central membrane lacking F-actin. These craters represent a new membrane feature resulting from the "kiss-and-merge" granule fusion. This work provides what we believe is important new insight into the local membrane structures in correlation with the cytoskeleton arrangement and detailed degranulation processes.

Paeonol inhibits anaphylactic reaction by regulating histamine and TNF-α

Paeonol, a major phenolic component of Moutan Cortex, was known to have antiaggregatory, antioxidant and antiinflammatory activities. In the present study, we tried to elucidate the effects of paeonol on anaphylactic reaction and its mode of action. Paeonol significantly inhibited histamine release from the rat peritoneal mast cells (RPMCs) treated with compound 48/80, a mast cell degranulator. The release of tumor necrosis factor (TNF)-alpha mast cell activating cytokine was significantly suppressed in RBL-2H3 mast cells pretreated with anti-dinitrophenyl (DNP) immunoglobulin E (IgE) in a dose-dependent manner. Paeonol significantly inhibited IgE production in B cells activated by anti-CD40 mAb, recombinant interleukin-4 (rIL-4) and recombinant histamine releasing factor (rHRF). Paeonol effectively downregulated the expression of IL-4 in the activated B cells by reverse transcription-polymerase chain reaction (RT-PCR). We also confirmed that paeonol effectively inhibited anaphylactic shock in mice by 90% at a dose of 0.5 mg/mouse versus PBS treated control 2 h after the i.p. injection of compound 48/80. These results suggest that paeonol has antianaphylatic activity by regulating histamine and TNF-alpha.

Effect of Cryptotympana atrata extract on compound 48/80-induced anaphylactic reactions

We studied the effect of the aqueous extract of Cryptotympana atrata Fabricius on anaphylactic reactions. Cryptotympana atrata completely inhibited compound 48/80-induced systemic anaphylactic shock at doses of 0.5 and 1.0 g/kg. When Cryptotympana atrata was given as pretreatment at concentrations ranging from 0.025 to 1.0 g/kg, the plasma histamine levels induced by compound 48/80 were reduced in a dose-dependent manner. Cryptotympana atrata also inhibited histamine release from rat peritoneal mast cells (RPMC) by compound 48/80. In addition, when Cryptotympana atrata was added, the level of cAMP in RPMC transiently and significantly increased about 14-fold compared with that of control cells. Our studies provide evidence that Cryptotympana atrata may be beneficial in the treatment of nonspecific anaphylactic reactions.

Quercetin Sensitizes RBL-2H3 Cells to Polybasic Mast Cell Secretagogues Through Increased Expression of Gi GTP-Binding Proteins Linked to a Phospholipase C Signaling Pathway

Polybasic secretagogues such as mastoparan, compound 48/80, substance P, and somatostatin stimulate secretion in rat peritoneal mast cells through direct activation of the heterotrimeric G protein, Gi-3. Cultured RBL-2H3 mast cells do not normally respond to these secretagogues, but, as reported here, they do so after prolonged exposure to the kinase inhibitor, quercetin. This inhibitor, which causes phenotypic changes in RBL-2H3 cells, induces a substantial increase (more than sevenfold) in the expression of α subunits of the pertussis toxin-sensitive G proteins, Gi-2 and Gi-3. Compound 48/80-induced secretion is associated with transient hydrolysis of phosphoinositides and a transient increase in cytosolic calcium ions. These responses are inhibited by pertussis toxin, and in addition, secretion is blocked by calcium chelation and the protein kinase C inhibitor, Ro31-7549. These results delineate a pathway for compound 48/80-induced secretion in mast cells via Gi protein(s), phospholipase C, calcium, and protein kinase C. The results also imply that phospholipase C, most likely phospholipase Cβ3, can be transiently activated in RBL-2H3 cells by subunits of Gi proteins to induce cellular responses.

G protein activation: a receptor-independent mode of action for cationic amphiphilic neuropeptides and venom peptides

The neuropeptide substance P, the venom peptide mastoparan and the synthetic polyamine compound 48/80 activate rat peritoneal mast cells, leading to rapid histamine release by exocytosis. Although these effects are inhibited by pertussis toxin and involve a transient increase in IP3, no selective membrane receptors have been identified. However, it has recently been shown that these compounds activate G proteins in vitro. Here Yves Landry and colleagues discuss the proposal that direct activation of G protein is the physiological mechanism of action of substance P on rat peritoneal mast cells, this mechanism being mimicked by mastoparan and 48/80, and possibly by other cationic amphiphilic peptides such as kinins. These compounds might be of help in defining the interaction between membrane receptors and G proteins.

Serotonin release from rat brain mast cells in vitro

Mast cells are primarily localized in connective tissues, where they secrete numerous mediators. They have also been identified in the mammalian central nervous system on the basis of their histochemical and morphological properties, but their role there remains unknown. A perfusion system was used to investigate in vitro mediator release from rat brain mast cells. Compound 48/80, the classic mast cell secretagogue of connective tissue mast cells, induced dose-dependent and non-cytotoxic release of serotonin, histamine and beta-hexosaminidase from mast cells in the rat thalamus and hypothalamus, but not in the cerebellum which was used as a negative control. Detailed studies were performed on thalamic mast cells, which were identified on the basis of metachromasia with Toluidine Blue and Safranin-positive staining with the Alcian Blue/Safranin technique. Their secretion was characterized by: (a) parallel release of serotonin, histamine and beta-hexosaminidase; (b) lack of dependence on extracellular calcium; (c) susceptibility to inhibition by disodium cromoglycate; and (d) lack of lactate dehydrogenase release. These results indicate that the morphology and secretory characteristics of thalamic mast cells resemble those of connective tissue mast cells. The ability of brain mast cells to secrete their mediators is discussed in the context of their possible involvement in brain pathophysiology.

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.

Effect of multiple applications of compound 48/80 on mast cells of rat conjunctiva

We sought to determine the effect on rat conjunctival mast cells of chronic exposure to a degranulating agent. Compound 48/80 (250 micrograms in 10 microliter) was applied daily to the ocular surface of rats for a total of 13 treatments administered in 17 days. A single application of compound 48/80 was given to rats for comparison. Four groups of animals (6 in each group) were evaluated 1 or 48 h after the last application of compound 48/80 in both chronic exposure and single exposure studies. Although a single exposure to compound 48/80 induced significant degranulation of mast cells in animals observed 1 h after treatment, no significant degranulation of mast cells was observed 1 h after the last dose of compound 48/80 was given to rats whose conjunctiva had been chronically exposed to this degranulating agent. Thus, multiple applications of compound 48/80 attenuated the mast cell response to compound 48/80. This acquired tolerance to compound 48/80 was reflected in the lessened clinical signs in rats receiving repeated applications compared with those given a single application.

Binding of active components of compound 48/80 to rat peritoneal mast cells

The binding characteristics of compound 48/80 were examined using rat mast cells and fractionated 14C-labeled compound 48/80 components at 4 degrees C in vitro where no degranulation of the cells occurred. The binding potencies of these components in the presence of Ca2+ generally paralleled their histamine releasing activities, except in the case of fractions G (decamer) and H (nonamer), both Ca2+-independent releasers, for the binding of which Ca2+ was inhibitory. Scatchard analyses and displacement studies indicated that the mast cells had two types of binding sites with high and low affinities for fractions D (tridecamer, Ca2+-dependent releaser, Kd = 3.41 X 10(-8) M and 3.35 X 10(-6) M) and H (Ca2+-independent releaser, Kd = 1.11 X 10(-7) M and 9.11 X 10(-6) M), respectively. These sites partially overlapped each other, and also the fraction D site partially overlapped the IgE site and the fraction H site overlapped the neurotensin or substance P site.

Inhibition of bone resorption in vitro by compound 48/80

The mechanisms that control cycles of bone formation and bone resorption are not well understood. In this report we provide evidence that compound 48/80 is a potent inhibitor of bone resorption in vitro. Resorption was assessed by the release of calcium-45 from pre-labelled newborn mouse calvaria that were treated with compound 48/80 and/or parathyroid hormone (PTH) in organ culture. Our results demonstrate that co-incubation of calvaria with PTH plus compound 48/80 (concentrations 1-10 mcg/ml) produces a marked reduction of calcium-45 release compared to PTH alone. Furthermore, pre-incubation of calvaria with compound 48/80, for as little as three hours, inhibits resorption by subsequent treatment with PTH alone. Measurement of lactate dehydrogenase (LDH) released into the culture medium indicated that treatment with compound 48/80, at the doses and time periods studied, was not cytotoxic. This novel effect of compound 48/80 may provide a useful tool for studying the cellular mechanisms involved in the bone resorption process.

Effects of polyamines upon capacitation and fertilization in the guinea pig

The effects of polyamines upon the ability of guinea pig spermatozoa to undergo the acrosome reaction and upon sperm-egg fusion were investigated. All of the polyamines (polyarginines and compound 48/80) stimulated the occurrence of the acrosome reaction, although differences in the duration of the preincubation period required were noted. The stimulatory effect of the polyarginines could not be reversed by washing, while that of 48/80 was abolished by its removal prior to induction of the acrosome reaction. Polyarginine-treated spermatozoa were fully capable of fertilizing intact guinea pig eggs. In contrast, 48/80 completely blocked sperm-egg fusion at only 5-10 micrograms/ml. This inhibition was reversible by washing either treated gamete. The ability of polyamines which may also be present at the time and site of fertilization, in vivo, to inhibit or stimulate gamete functions or interactions is discussed.

Permeability increase in black lipid membrane induced by compound 48/80

When compound 48/80, a potent histamine liberator, was added in the aqueous phase facing the black lipid membrane, the conductivity of the membrane was remarkably increased. Although valinomycin displayed a distinct selectivity for K+ movement, such selection for ionic permeability was not observed in the case of compound 48/80.

Binding of a spin label analogue of compound 48/80 to rat peritoneal mast cells: correlation of binding properties with surface topography

A spin label analogue of compound 48/80 has been synthesized and its binding to purified rat peritoneal mast cells has been studied by electron spin resonance spectroscopy. The spin label analogue (SL-48/80) had almost identical biological activity to unlabeled compound 48/80. SL-48/80 was used to estimate the number of binding sites per cell on normal mast cells (7.25 X 10(10)), on mast cells deactivated by sodium azide and 2-deoxyglucose or by heating to 46 degrees for 30 min (1 X 10(10)) and cells from animals actively-sensitized to ovalbumin (5.2 X 10(10)). SL-48/80 was also shown to bind to isolated mast cell granules. Differences in the binding properties of mast cells after the different treatments are related to their surface topography as seen by scanning electron microscopy, and the contribution of the granules to the number of binding sites is discussed.

Compound 48/80-induced permeability change in liposomal membrane

The action of compound 48/80 (a mixture of condensation products of p-methoxy-N-methylphenethylamine with formaldehyde) on liposomal membranes was studied by means of K+-loaded liposomes and a K+ ion-selective electrode. Prompt efflux of K+ was detected when 48/80 was added to the negatively charged liposome suspension, while the monomer of 48/80, p-methoxy-N-methylphenethylamine, did not release K+ from the same liposomes. The mechanism for the action of 48/80 is discussed in comparison with that of a polymyxin, well known as an antibiotic acting on bacterial membranes.

Mastocytosis and the mast cell

Mastocytosis is a disease in which the mast cell population is increased in various tissues. Although the mechanism for the increased density of mast cells is not understood, recent research into mast cell structure and function has improved our understanding of the symptomatology and prompted newer and better approaches to treatment. To be discussed, and of particular interest to the dermatologist, is the management of, and evaluation for, systemic disease in a patient presenting with cutaneous findings.

Inhibition by calcium antagonists of histamine release and calcium influx of rat mast cells: difference between induction of histamine release by concanavalin A and compound 48/80

The relation between calcium influx and histamine release from rat mast cells was investigated. When purified mast cells pretreated with a calcium antagonist (MnCl2 or methoxyverapamil (D-600)) were exposed to concanavalin A or compound 48/80 in Tyrode solution (pH 7.4) at 37 degrees C, the calcium antagonists inhibited the extracellular calcium-dependent component of concanavalin A-induced histamine release. MnCl2 also inhibited the extracellular calcium-dependent component of compound 48/80-induced histamine release, whereas D-600 did not inhibit the release. D-600 inhibited the 45Ca uptake induced by concanavalin A, but did not inhibit the 45Ca uptake induced by compound 48/80. It was found that the inhibitory action of calcium antagonists depended on the uptake of extracellular calcium. These observations suggest that concanavalin A and compound 48/80 stimulate different mechanisms of calcium influx. Studies on inactivation of the mechanisms of calcium influx showed that calcium influx into cells activated by concanavalin A stopped when concanavalin A was washed out, whereas the influx activated by compound 48/80 was still operative after compound 48/80 had been washed out.

Inhibition of lymphocyte DNA-synthetic responses by spermine-derived polycations

The polyamines putrescine, spermidine, and spermine are oxidized by the enzyme diamine oxidase to form the corresponding aldehyde derivatives. These aldehydes have been shown to undergo a variety of spontaneous reactions, some of which result in polycationic addition compounds. We have chemically synthesized some spermine-derived polycations by reaction with the dialdehyde glutaraldehyde followed by reduction of te resulting Schiff base with sodium borohydride. Their migration on ion exchange and gel filtration columns was consistent with the formation of polycations with properties similar to those reported for the spontaneous reaction products. When added to cultures of alloantigen or mitogen stimulated lymphocytes, these polycations were potent inhibitors of the incorporation of tritiated thymidine and blast cell formation. This inhibition was reversible, non-cytotoxic, and only apparent if the polycation was added early in the culture period. The concentration of polycation necessary to achieve 50% inhibition of the lymphocyte response decreased as the cationic nature relative to spermine increased.