Masaaki Akagi

Anti-allergic constituents in the culture medium of Ganoderma lucidum. (I) Inhibitory effect of oleic acid on histamine release

The chloroform extract fromGanoderma lucidum broth markedly inhibited histamine release from rat peritoneal mast cells. From the active fractions, palmitic acid, stearic acid, oleic acid and linoleic acid were isolated. Oleic acid dose-dependently inhibited the histamine release and45Ca uptake into mast cells induced by compound 48/80 and A-23187 at concentrations of 5 to 50 μM and 0.5 to 5 μM, respectively. Saturated fatty acids, however, had only a weak inhibitory effect on histamine release. Although linoleic acid and linolenic acid effectively prevented this release, these two compounds caused marked release at concentrations higher than 10 μM and 20 μM, respectively. Oleic acid induces membrane-stabilization in model membrane systems. It was concluded that one of the effective constituents obtainable from the chloroform extract ofG. lucidum-cultured broth is oleic acid.

Inhibitory effects of oxatomide on intracellular Ca mobilization, Ca uptake and histamine release, using rat peritoneal mast cells

Oxatomide at concentrations of 0.01-10 microM inhibited not only an increase in 45Ca uptake but also the intracellular Ca2+ release induced by compound 48/80 in rat peritoneal mast cells. At higher concentrations, ketotifen or other calcium antagonists caused similar inhibitory effects. However, the inhibitory effect of oxatomide on the 45Ca uptake into rat neonatal heart cells was much weaker than that of verapamil. Through image processing of quin 2-stained mast cells, it was revealed that oxatomide inhibited Ca2+ release from the intracellular store. Although oxatomide alone did not affect cAMP and cGMP contents in sensitized guinea pig lung samples, the drug effectively prevented changes in the nucleotide contents evoked by antigen challenge. These results suggest that the inhibitory effect of oxatomide on histamine release may be caused by a combination of prevention of Ca uptake, which is highly selective toward mast cells; inhibition of Ca2+ release from the intracellular Ca store, and elevation of the cAMP content in mast cells.

Antiallergic Effects of Terfenadine on Immediate Type Hypersensitivity Reactions

Terfenadine dose-dependently inhibited rat homologous PCA (2.5-10 mg/kg, p.o.) and experimentally-induced asthma in guinea pigs (0.5-5 mg/kg, p.o.). Similarly, metabolites I and II dose-dependently inhibited experimentally-induced asthma but their respective potencies were approximately 1/2 and 1/15th that of terfenadine. These results suggest that the metabolites contribute to the antiallergic effects of terfenadine. In ex vivo, terfenadine (5-20 mg/kg, p.o.) also inhibited the release of both antigen-induced histamine and SRS-A from sensitized guinea pig lung samples and that of histamine from rat peritoneal mast cells. Terfenadine dose-dependently increased the cAMP content in rat mast cells and in the lungs; in the latter, the augmented cAMP is associated with an increase in adenylate cyclase activity, but not with the inhibition of phosphodiesterase activity. The above evidence indicates that the inhibitory effects of terfenadine on mediator release from mast cells are in some way related to its antiallergic effects, and that an elevated cAMP content may be effective to enhance mediator release inhibition.

Anti-allergic constituents in the culture medium ofGanoderma lucidum. (II) The inhibitory effect of cyclooctasulfur on histamine release

For centuries,Ganoderma lucidum has been used in Oriental medicine for the treatment of chronic bronchitis. Sequential fractions of the culture medium of this plant revealed that one of the active constitutents was cyclooctasulfur. The latter effectively inhibited hsitamine release from rat peritoneal mast cells and impeded45Ca uptake into these cells without affecting the cyclic AMP content. SDS-PAGE analysis indicated that cyclooctasulfur induced some changes in protein bands obtained from the membrane fraction of mast cells, suggesting that this compound interacts with membrane proteins so as to inhibit45Ca uptake, and that this may be the main cause of histamine release inhibition.

Antiallergic Effect of Epinastine (WAL 801 CL) on Immediate Hypersensitivity Reactions: (I) Elucidation of the Mechanism for Histamine Release Inhibition

Epinastine caused an inhibition of histamine release from rat peritoneal mast cells induced by both antigen-antibody reaction and compound 48/80. Epinastine was similarly effective in inhibiting compound 48/80-induced histamine release not only from isolated rat peritoneal mast cells but also from rat mesenterial pieces. Also, histamine release from lung pieces obtained from actively sensitized guinea pigs after exposure to antigen challenge was markedly inhibited by epinastine. The drug was effective in inhibiting not only Ca2+ uptake into lung mast cells in actively sensitized guinea pigs but also Ca2+ release from the intracellular Ca store of rat peritoneal mast cells exposed to both compound 48/80 and substance P. No significant changes were observed in phosphodiesterase activity in rat peritoneal mast cells treated with epinastine, while adenylate cyclase activity was augmented by epinastine. Epinastine has no inhibitory effect on histamine release induced by Ca2+ or IP3 from permeabilized mast cells. However, the drug significantly and dose-dependently suppressed calmodulin activity suggesting that histamine release inhibition due to epinastine may be partly attributable to Ca(2+)-calmodulin dependent process(es). The drug caused no visible changes in thermodynamic behavior of lipids, either in order parameter or in differential scanning calorimetry, indicating that the drug has no influence on membrane fluidity.

Histamine release inhibition and prevention of the decrease in membrane fluidity induced by certain anti-allergic drugs: Analysis of the inhibitory mechanisms of NCO-650

NCO-650 exerted a dose-dependent inhibition of histamine release from isolated rat mast cells without affecting the Ca-uptake and intracellular cAMP levels. When the membrane stabilizing action of NCO-650 was investigated with the liposomes prepared by various phospholipids with or without cholesterol, it became clear that compound 48/80 decreases the order parameter of liposomes and NCO-650 inhibits the decrease of order parameter. Histamine release from histamine-containing liposomes was brought about by compound 48/80 at concentrations higher than 0.5 μg/ml, and pretreatment of the liposomes with NCO-650 inhibited histamine release due to compound 48/80. The incorporation of NCO-650 in the liposomes was effective in abolishing the phase transition of the lipid bilayer membranes from crystalline gel to liquid crystalline phases, and decreased the phase transition temperature. Those changes in the lipid bilayer membranes correspond to those displayed by incorporation of cholesterol in the liposomes. An increase of permeability of lipid membrane by compound 48/80 may be due to partial loosening of the lipid order; NCO-650 rigidifled the liposome membrane and as a result of this, it decreased histamine release.

Properties of hydrogen peroxide-induced histamine release from rat mast cells.

Incubation of rat peritoneal mast cells with hydrogen peroxide results in a marked release of histamine. Maximal release is observed with 0.05-0.1 mM H(2)O(2), but higher concentrations of H(2)O(2) instead suppresses the release. Histamine release starts after about 2 min of lag time and reaches a plateau in about 10 min. Hydrogen peroxide-induced release does not exceed 50-60 per cent of total histamine if the incubations are prolonged or additional H(2)O(2) is given at 10 min. This would be explained by the fact that H(2)O(2) causes impairment of the histamine releasing system of mast cells simultaneously with the release of histamine. Hydrogen peroxide-induced release is not due to nonspecific lysis of the cells because lactate dehydrogenase, a cytoplasmic enzyme, is not liberated during the reaction. The reaction requires the presence of Ca(2+), is enhanced by D(2)O and suppressed by colchicine. It is not, however, affected by dibutyryl cAMP or dibutyryl cGMP. No significant alteration of intracellular levels of cyclic AMP and cyclic GMP is observed during the incubation of mast cells with 0.1 mM H(2)O(2). These results indicate that microtubular functions would be involved in the releasing reaction although they are not under the control of cyclic nucleotides. Microscopic observation shows that H(2)O(2)-induced release is accompanied by degranulation.

Role of Microfilaments in the Exocytosis of Rat Peritoneal Mast Cells

When rat peritoneal mast cells were treated with the potent histamine releaser compound 48/80 in the presence of tetramethylrhodamine-labeled G-actin, the fluorescent G-actin particles were bound to the surface of extruded granules and to the cell surface. When rhodamine-phalloidin was incorporated into permeabilized rat mast cells in a Ca2+-free medium, rhodamine fluorescence was observed on the cell surface accompanied by serpentine ridges which appeared in the resting state. After perfusion with a cytosol-like solution containing Ca2+, rhodamine fluorescence appeared on the cell surface as a distinct network formation. In some cases, circular fluorescences which appeared to surround the extruded pores were observed in the cell membrane. These findings indicate the existence of actin filaments in the cell membrane and/or subplasmalemmal network. In whole-mount preparations, the granules were surrounded very densely with microfilaments of various widths. After exposure to compound 48/80, granules protruding through the cell membrane were wrapped in many filaments. The extruded granules located in the periphery of the cells were connected by many filamentous structures and disruptions in the middle of these connections were occasionally observed. In some cases, circular configurations of microfilaments were observed at the bottom of the extruded granules and in others dense gatherings of microfilaments were seen just beneath the granules, as if the latter were being pushed up and out of the cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Distribution of actin filaments in rat mast cells and its role in histamine release.

The distribution of action filaments was confirmed by immunofluorescence microscopy and immuno-electron microscopy in nonsecreting and secreting rat peritoneal mast cells. In a resting cell, immunofluorescence of the actin showed up as a net-like formation surrounding each granule. After stimulation with compound 48/80 or A-23187, the distribution of the actin filaments became very irregular and disordered, disappearing completely in some areas within the cell and expanding in conjunction with the swelling of the granules. Similar changes are seen in a passively sensitized mast cell exposed to antigen. When cells were pretreated with cytochalasin B or colchicine, the distribution of actin filaments was not greatly affected by stimulation. The results clearly show that actin filaments exist in mast cells.

Effect of N-methylation of phosphatidylethanolamine on the fluidity of phospholipid bilayers

The effect of N-methylphosphatidylethanolamine on phase transition and the fluidity of the liposomes made of dipalmitoylphosphatidylcholine or phosphatidylethanolamine was studied by the steady-state fluorescence polarization method and differential scanning calorimetry. N-methylation of phosphatidylethanolamine caused a decrease of fluidity of liposomes made of dipalmitoylphosphatidylcholine, but had little effect on dipalmitoylphosphatidylethanolamine. The liposomes prepared with both phosphatidylcholine and N-methylphosphatidylethanolamine and also phosphatidylethanolamine and N-methylphosphatidylethanolamine could be composed of solid solution and exhibited symmetric phase diagram.