Antiallergic effect of ZCR-2060: antihistaminic action

Effects of Bidens pilosa L. var. radiata SCHERFF treated with enzyme on histamine-induced contraction of guinea pig ileum and on histamine release from mast cells

The medical mechanism against type I allergies is to block the release or production of chemical mediators from mast cells or to block the H(1)-receptor signaling. We previously reported that the anti-allergic action of the dry powder from Bidens pilosa L. var. radiata SCHERFF treated with the enzyme cellulosine (eMMBP) was dependent on the inhibition of histamine release from mast cells. Here, we investigate that the effect of fractions in eMMBP on the histamine-induced contraction in guinea pig ileum and on the release of histamine in rat peritoneal mast cells. The histamine-induced contraction in guinea pig ileum is dose-dependently inhibited by ketotifen, an antagonist of H(1)-receptor. Fractions contained caffeic acid, caffeoylquinic acid and fractions contained flavonoids such as hyperin and isoquercitrin in eMMBP inhibit histamine release from mast cells, but only flavonoids such as hyperin, isoquercitrin and rutin suppress the histamine-induced contraction in guinea pig ileum. Moreover, the histamine-induced contraction was not affected by caffeic acid, however, such contraction was significantly inhibited by rutin. These results suggest that the primary antagonists of H(1)- receptor are different from the components in eMMBP that inhibit histamine release, and that these components participate in the anti-allergic activity of eMMBP.

Anti-allergic properties of Mangifera indica L. extract (Vimang) and contribution of its glucosylxanthone mangiferin

Vimang is the brand name of formulations containing an extract of Mangifera indica L., ethnopharmacologically used in Cuba for the treatment of some immunopathological disorders, including bronchial asthma, atopic dermatitis and other allergic diseases. However, the effects of Vimang on allergic response have not been reported until now. In this study, the effects of Vimang and mangiferin, a C-glucosylxanthone isolated from the extract, on different parameters of allergic response are reported. Vimang and mangiferin showed a significant dose-dependent inhibition of IgE production in mice and anaphylaxis reaction in rats, histamine-induced vascular permeability and the histamine release induced by compound 48/80 from rat mast cells, and of lymphocyte proliferative response as evidence of the reduction of the amount of B and T lymphocytes able to contribute to allergic response. In these experiments, ketotifen, promethazine and disodium cromoglicate were used as reference drugs. Furthermore, we demonstrated that Vimang had an effect on an in-vivo model of inflammatory allergy mediated by mast cells. These results constitute the first report of the anti-allergic properties of Vimang on allergic models, as well as suggesting that this natural extract could be successfully used in the treatment of allergic disorders. Mangiferin, the major compound of Vimang, contributes to the anti-allergic effects of the extract.

Comparative anticholinergic activities of 10 histamine H1 receptor antagonists in two functional models

We determined the relative rank orders of anticholinergic potencies of 10 antihistamines in two functional bioassays: (1) an in vitro assay measuring inhibition of carbachol-induced contractions of isolated guinea pig trachealis muscle, (2) an in vivo bioassay comparing systemic hypotensive responses to bolus i.v. injections of acetylcholine before and after infusions of an antihistamine in anaesthetized rats. In vitro, the rank order of anticholinergic potencies of the antihistamines was cyproheptadine>promethazine>desloratadine>diphenhydramine>loratadine>chlorpheniramine>hydroxyzine>pyrilamine. The pA2 values ranged from 8.2+/-0.4 for cyproheptadine to 4.8+/-0.4 for pyrilamine. Fexofenadine and cetirizine (up to 3 x 10(-4) M) were inactive. In vivo, five antihistamines showed anticholinergic activity: cyproheptadine>promethazine>desloratadine>loratadine>diphenhydramine. The remaining antihistamines had no significant effect at i.v. infusion doses up to 50 imol/kg. Cetirizine and fexofenadine did not antagonize cholinergic responses in either model.

Histamine H1 receptor antagonism by cetirizine in isolated guinea pig tissues: influence of receptor reserve and dissociation kinetics

We characterised histamine H(1) receptor antagonism by cetirizine and its enantiomers on isolated guinea pig ileum and trachea. Competitive or mixed (competitive and apparent noncompetitive) antagonism profiles were observed. The order of potency was: chlorpheniramine> or =mepyramine>levocetirizine>cetirizine> or =terfenadine>loratadine>dextrocetirizine. The inhibitory effects of cetirizine, levocetirizine, terfenadine and loratadine were slowly reversible compared to those of dextrocetirizine or mepyramine. Cetirizine and its enantiomers were inactive on L-type Ca(2+) channels. Reduction of the histamine H(1) receptor reserve by dibenamine in the ileum (100-fold higher than in the trachea) showed a gradual change from the competitive profile of dextrocetirizine and mepyramine to a mixed profile. The present results show that cetirizine and levocetirizine are selective competitive but slowly reversible histamine H(1) receptor antagonists. Their mixed antagonism profile observed in the trachea can be explained by the small receptor reserve present in this tissue compared to the ileum and their very slow dissociation rate from the histamine H(1) receptor.

Antiallergic effects of ZCR-2060: effect on allergic cutaneous reactions and rhinitis models in mice and rats

The antiallergic action of 2-[2-[4-(diphenylmethyl)-1-piperadinyl] ethoxy] benzoic acid maleate (ZCR-2060) was investigated on allergic cutaneous reactions and nasal vascular permeability in mice and rats. ZCR-2060 markedly inhibited immediate allergic cutaneous reactions, including passive cutaneous anaphylaxis (PCA) in rats and mice; histamine-, compound 48/80- and calcium ionophore A 23187-induced cutaneous reactions in rats; and biphasic skin reactions mediated by monoclonal IgE antibody and epicutaneous challenge with antigen in mice, but did not affect 5-hydroxytryptamine-induced cutaneous reaction in rats. The antigen-induced nasal vascular permeability increase in actively and passively sensitized rats and histamine-induced nasal vascular permeability increase in rats (allergic rhinitis model) were clearly inhibited in a dose-dependent fashion by ZCR-2060. Moreover, ZCR-2060 significantly inhibited antigen-induced anaphylactic histamine release from rat peritoneal mast cells and carrageenin-induced paw edema in rats. These results suggest that ZCR-2060 has antiallergic effects on allergic cutaneous reactions and experimental rhinitis, probably due to histamine H1-receptor blockage and the inhibition of histamine release.