Datura stramonium agglutinin released histamine from rat peritoneal mast cells that was inhibited by pertussis toxin, haptenic sugar and N-acetylglucosamine-specific lectins: involvement of glycoproteins with N-acetylglucosamine residues.

The N-acetyl glucosamine (GlcNAc)-specific lectin Datura stramonium agglutinin (DSA) rapidly and sugar-specifically released histamine from rat peritoneal mast cells, and pertussis toxin (IAP) inhibited it, suggesting that DSA activated mast cells via an IAP-sensitive G protein pathway. The additive effects of DSA and basic secretagogues such as compound 48/80 that activate IAP-sensitive G protein directly suggest that they shared the same mechanism of action including involvement of the IAP-sensitive G protein. Using lectin-blotting, blots of the corresponding glycoproteins detected by DSA diminished by haptenic sugar or pretreatment of the cells with N-glycosidase F, suggesting that the binding of DSA was responsible for the mast cell activation. The other GlcNAc-specific lectins such as Phytolacca americana mitogen, Solanum tuberosum agglutinin and wheat germ agglutinin (WGA) inhibited the histamine release induced by DSA, suggesting that these lectins were antagonists, but DSA was an agonist. Sialic acid-specific Macckia amurensis mitogen (MAM) inhibited the histamine release, and neuraminidase-treatment decreased mast cell activation induced by DSA. At least four mast cell glycoproteins that have affinity to DSA, WGA and MAM and are sensitive to neuraminidase-treatment were detected by lectin-blotting. Some of them may be binding sites coupled to histamine release including the IAP-sensitive G protein pathway. DSA is a useful tool for studying signal transduction of mast cells including the involvement of the IAP-sensitive G protein.

An initial signal of activation of rat peritoneal mast cells stimulated by Datura stramonium agglutinin: a confocal fluorescence microscopic analysis of intracellular calcium ion and cytoskeletal assembly.

A confocal fluorescence microscope using fluo-3 and 9-(dicyanovinyl)- julolidine (DCVJ) was used to study the mast cell activation by the N-acetyl glucosamine oligomer specific lectin Datura stramonium agglutinin (DSA) and inhibition by antagonist lectins having affinity to N-acetyl glucosamine (GlcNAc). DSA induced a transient increase in intracellular free calcium concentration ([Ca2+]i) followed by cytoskeletal disassembly and reassembly in rat peritoneal mast cells. These changes induced by DSA resulted in histamine release. The time course of fluorescence intensity in mast cells loaded with fluo-3- or DCVJ and activated by DSA resembled those activated by the basic polymer compound 48/80. Inhibition of [Ca2+]i rise by antagonist lectins was responsible for the inhibition of cytoskeletal assembly and the consequent histamine release induced by DSA. At the level of the individual cell, a mast cell stimulated by DSA responds in an all-or-none fashion. DSA possible induced intracellular calcium mobilization and cytoskeletal change by recognizing the GlcNAc-oligomer residues of specific glycoproteins of mast cells.

Calcium antagonist-like actions of coumarins isolated from "Qian-Hu" on anaphylactic mediator release from mast cell induced by concanavalin A.

The effects of coumarins on anaphylactic mediator release from rat mast cells were investigated. Since Pd-Ia (3'-angeloyloxy-4'-acetoxy-3',4'-dihydroseselin) causes relaxation of smooth muscle by inhibiting calcium influx, and since mediator release is a calcium-dependent process, studies were made on whether coumarins block calcium influx into rat mast cells stimulated by concanavalin A. Pd-Ia isolated from Peucedanum praeruptorum Dunn and related compounds, named Pd-C-II, Pd-C-III and Pd-C-IV, from Peucedanum decursivum Maxim., (Angelica decursiva Fr. et Sav.) inhibited anaphylactic mediator release from purified mast cells induced by concanavalin A with phosphatidylserine; their IC50 values were 79, 100, 102 and 73 microM, respectively. Pd-III, decursidin and water-soluble analogues of Pd-Ia (Pd-Ia-OH, Pd-Ia-OCH2CH3) did not inhibit the release. Thus the inhibitory actions of coumarins on calcium influx seemed to depend on the chemical structures of these compounds; an acetoxyl residue at position 3' or 4' on the seselin or xanthyletin skeleton might be essential for an inhibitory effect. Furthermore, Pd-Ia and Pd-C-III caused more than 40% reduction in 45Ca uptake induced by concanavalin A, whereas decursidin had little effect on it. Therefore, the inhibitions of mediator release of mast cells by some of coumarins from "Qian-Hu" seem to depend on their effects in blocking calcium influx.