Effects of marmin, a compound isolated from Aegle marmelos Correa, on contraction of the guinea pig-isolated trachea

Marmin or 7-[6', 7'-dihydroxygeranyl-oxy] coumarin is a compound isolated from Aegle marmelos Correa. In the study, we examined the effects of marmin on the contraction of guinea pig-isolated trachea stimulated by several inducers, namely histamine, metacholine, compound 48/80. We also evaluated its action against contraction induced by extracellular or intracellular calcium ion. The possibility of marmin to potentiate the

elaxation effect of isoprenaline was also studied. Marmin added in the organ bath at 10 min prior to the agonist inhibited the contraction elicited by histamine and metacholine in a concentration-dependent manner. Moreover, marmin antagonized the histamine-induced contraction in competitive manner. Marmin mildly potentiated the relaxation effect of isoprenaline. In the study, marmin abrogated the contraction of tracheal smooth muscle induced by compound 48/80, an inducer of histamine release. Besides, marmin successfully inhibited CaCl[2-]-induced contraction in Ca[2+] -free Krebs solution. Marmin also inhibited two phases of contraction which were consecutively induced by metacholine and CaCl[2] in Ca[2+]-free Krebs solution. Based on the results we concluded that marmin could inhibit contraction of the guinea-pig tracheal smooth muscle, especially by interfering histamine receptor, inhibiting the histamine release from mast, inhibiting intracellular Ca[2+] release from the intracellular store and the Ca[2+] influx through voltage-dependent Ca[2+] channels

Evaluation of anti-allergic activity of gossypin and suramin in mast cell-mediated allergy model.

The mast cell-mediated allergic reactions are involved in many allergic diseases, such as asthma, allergic rhinitis and sinusitis. Stimulation of mast cells initiates the process of degranulation, resulting in the release of mediators such as histamine and an array of inflammatory cytokines. In this report, we investigated the effect of gossypin (a biflavonoid) and suramin (a synthetic polysulphonated naphtylurea) on the mast cell-mediated allergy model, and studied the possible mechanism of their action. Both gossypin and suramin inhibited (P<0.001) compound 48/80-induced systemic anaphylaxis reactions, antiprurities (P<0.001) and reduced the histamine release in rats. Further, both showed significant (P<0.001) protection against rat peritoneal mast cells activated by compound 48/80. Thus, our findings provide evidence that gossypin and suramin inhibit mast cell-derived allergic reactions.

Evaluation of E-721B, an indigenous herbal combination in experimental models of immediate hypersensitivity.

E-721B, an indigenous herbal combination was investigated for its usefulness in immediate hypersensitivity using different animal models. The drug inhibited the mast cell degranulation induced both by antigen and compound 48/80, the Schultz-Dale response in sensitized guinea pig ileum smooth muscle preparation and the production of precipitating antibodies in 50% of tested rats. It also inhibited the mast cell degranulation in passively sensitized rats indicating its suppressive action on production of reaginic antibody (IgE). However, the drug did not inhibit the 48 hours passive cutaneous anaphylaxis reaction in rats, indicating that a single dose of the drug does not have cromoglycate like properties. All the above results indicate the inhibitory effect of E-721B on immediate hypersensitive reactions such as asthma.

Comparative functional characterization of mouse bone marrow-derived mast cells and peritoneal mast cells in response to non-immunological stimuli.

The cultured mouse mast cells that are dependent on spleen-derived factor for their proliferation and maintenance and have been shown to be similar to mucosal mast cells in terms of their T-cell dependence and histochemical staining characteristics. Mast cell heterogeneity has been confirmed by functional characterization of mouse bone marrow-derived mast cells (MBMMC) and mouse peritoneal mast cells (MPMCs). MPMCs released around 30% of histamine when stimulated with compound 48/80 whereas MBMMC were almost unresponsive to the same stimulus. Calcium Ionophore A23187 on the other hand, released histamine in dose-dependent manner from MBMMC. The study was undertaken to investigate the effect of antiallergic drug, disodium cromoglycate (DSCG), a synthetic cromone and quercetin, a plant-derived flavonoid on Ca ionophore A23187 induced histamine release from MBMMC. MBMMCs were almost unresponsive to DSCG whereas Ca Ionophore induced histamine release was blocked by Quercetin. The results indicate that response of mast cells at one anatomic site to a given stimulus does not necessarily predict the response of mast cells at a different anatomic location to the same stimulus. It shows functional heterogeneity within a single species. So, it cannot be assumed that antiallergic compounds stabilizing mast cells in one tissue site or organ will be equally efficacious against mast cells in other sites.

Evaluation of antiallergic activity (type I hypersensitivity) of Inula racemosa in rats.

Alcoholic extract of root of Inula racemosa, was studied for its antiallergic effect in experimental models of type I hypersensitivity, viz. egg albumin induced passive cutaneous anaphylaxis (PCA) and mast cell degranulation in albino rats. The alcoholic extract was prepared by the process of continuous heat extraction. LD50 of this extract was found to be 2100 +/- 60 mg/kg, i.p. Assessment of protection against egg albumin induced passive cutaneous anaphylaxix by different doses of Inula racemosa was done by giving drug intraperitoneally or orally for seven days or once only. Mast cell degranulation studies were done by using compound 48/80 as degranulation agent with same dosage schedule. Inula racemosa (i.p. as well as p.o.) showed significant protection against egg albumin induced PCA. Protection against compound 48/80 induced mast cell degranulation by alcoholic extract of Inula racemosa (single dose) was similar to that of disodium cromoglycate. The seven days drug treatment schedule showed greater protection than disodium cromoglycate intraperitoneally. The results suggest that Inula racemosa possesses potent antiallergic properties in rats.

The role of H1- and H2-receptors in the effect of compound 48/80 in the asphyxiation and body temperature of mice

Contribution of histamine H1- and H2-receptors to the effect of compound 48/80, a potent histamine releaser, upon asphyxiation and body temperature in mice was investigated in the present experiments. Compound 48/80 showed an apparent protective potency against hypoxia and significantly prolonged the latencies for convulsions and death in a dose-dependent manner. Compound 48/80 also decreased the body temperature, which was in relation with the antihypoxic effect. Both the H1-receptor antagonist, dimethindene, and the H2-receptor antagonist, ranitidine, attenuated the hypothermic effect of compound 48/80, indicating the involvement of central histamine through both the H1- and H2-receptors. Ranitidine had no effect on the protective effect of compound 48/80 against hypoxia-induced lethality, whereas dimethindene completely antagonized it. These results suggest that the protective effect of compound 48/80 against hypoxia is mediated through histamine H1-receptors and is not related to its ability to induce hypothermia.

Comparative effects of mast cell degranulators on perfused systemic blood vessels of Bufo melanostictus and Rana tigrina.

Three agents known to induce release of mast cell constituents, viz. polymyxin, compound 48/80 and polysorbate-80, were evaluated for effect on perfused blood vessels of R. tigrina and B. melanostictus. The mast cell degranulators caused vasoconstriction in frog and toad, except that for P-80 whose responses in toad were equivocal. Toads showed a general low responsiveness in comparison to frogs. Pharmacologic intervention with pheniramine, metergoline, hydergine, atropine and mecamylamine, respectively ruled out role of histamine, 5-HT, catecholamine or acetylcholine or even autonomic mechanisms in the above phenomena. The observations are suggestive of phylogenetic differences in biochemical profile of mast cells in amphibian species.

Effect of histamine on wound healing.

Using incision, excision and dead space wound models in rats, a study was conducted on the effect of histamine on wound healing. Exogenous histamine given either ip or locally was without any effect. Semicarbazide as (histamine synthesis inhibitor) suppressed healing process (breaking strength of skin incision wound), decreased breaking strength and hydroxyproline content of granulation tissue and delay in period of epithelization. On the other hand compound 48/80 (a promoter of histamine forming capacity) was found to promote wound healing. Exogenous histamine (topical) reversed the anti-healing effect of semicarbazide on incision and excision wounds.

Central lesion abolishes the beneficial effect of hypertonic saline on circulatory shock produced by compound 48/80 in rats

The purpose of the presente study was to examine the protective action of a 7.5% hypertonic NaCl solution (HS) on the ciruclatory shock produced by compound 48/80 (48/80) in rats and to determine the effect of the AV3V lesion on the protective action of HS. Intravenous injection of 48/80 into sham-operated rats resulted in an innediate drop of mean arterial pressure (In sham-operated rats, intravenous inection of HS prevented the drop of MAP produced by 48/80, but HS was ineffective in AV3V-lesioned rats. These results show that HS had a protective action on the circularory shock produced by 48/80 and that the AV3V region plaus an important role in this protective action

Bioflavonoids and vasoactive mediator release from mast cells.

5-hydroxy and 7-hydroxy flavones significantly attenuated the carrageenin-induced pedal inflammation in rats; however, the anti-inflammatory effect declined at higher doses. These compounds produced positive inotropic effect on frog atria, which exhibited tachyphylaxis and was selectively abolished by indomethacin pretreatment. Studies on the rat mesenteric mast cells revealed that both the compounds, administered either in vitro or in vivo, induced a significant degree of mast cell degranulation in higher concentrations/doses. The mast cell degranulation induced by compound 48/80 was, however, prevented by lower, but not higher, concentrations/doses of the flavones. Local injection of 7-hydroxy flavone into the hind paw of rat showed that, in higher doses, the compound produced significant oedema. It was concluded that these compounds have a biphasic action: mast cell stabilisation and degranulation at lower and higher concentrations/doses, respectively.