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Background The expression and functional role of CysLT 2 receptors in asthma have not been clarified. In this study, we evaluated CysLT 2 receptors expression, and effects of CysLT 2 -and CysLT 1/2 -receptor antagonists on antigen-induced bronchoconstriction using isolated lung tissues from both asthma and non-asthma subjects. Methods CysLT 1 and CysLT 2 receptors expression in asthma and non-asthma lung tissue preparations was examined in immunohistochemistry experiments, and their functional roles in antigen-induced bronchoconstriction were assessed using ONO-6950, a dual CysLT 1/2 -receptor antagonist, montelukast, a CysLT 1 receptor antagonist, and BayCysLT 2 RA, a CysLT 2 receptor-specific antagonist. Results CysLT 1 receptors were expressed on the bronchial smooth muscle and epithelium, and on alveolar leukocytes in 5 in 5 non-asthma subjects and 2 in 2 asthma subjects. On the other hand, although degrees of CysLT 2 receptors expression were variable among the 5 non-asthma subjects, the expression in the asthma lung was detected on bronchial smooth muscle, epithelium and alveolar leukocytes in 2 in 2 asthma subjects. In the non-asthma specimens, antagonism of CysLT 2 receptors did not affect antigen-induced bronchial contractions, even after pretreatment with the CysLT 1 -receptor specific antagonist, montelukast. However, in the bronchus isolated from one of the 2 asthma subjects, antagonism of CysLT 2 receptors suppressed contractions, and dual antagonism of CysLT 1 and CysLT 2 receptors resulted in additive inhibitory effect on anaphylactic contractions. Conclusions CysLT 2 receptors were expressed in lung specimens isolated from asthma subjects. Activation of CysLT 2 receptors may contribute to antigen-induced bronchoconstriction in certain asthma population.

Disodium cromoglycate is an anti-asthmatic drug that has mast cell-stabilizing effects and other anti-inflammatory effects. However, the mechanisms of its anti-inflammatory effects are unclear. In this study, we evaluated effects of disodium cromoglycate on eosinophilia, early and late asthmatic responses, and production of arachidonic acid metabolites in guinea pig lungs. Guinea pigs were alternately sensitized and challenged by exposure to mists of ovalbumin+Al(OH) 3 and ovalbumin, respectively. Disodium cromoglycate (0.5–2 mg/0.1 ml/animal) administered intratracheally before the fifth challenge dose-dependently inhibited asthmatic response, but early asthmatic response was not affected. Disodium cromoglycate at 2 mg/animal potently suppressed increases in cysteinyl leukotrienes (CysLTs) and thromboxane A 2 in the lung during late asthmatic response. Eosinophilia was slightly reduced by disodium cromoglycate. The inhibitory effect of disodium cromoglycate on late asthmatic response is apparently due to inhibition of the release of arachidonic acid metabolites, some of which may be derived from eosinophils that infiltrate the lung.

We evaluated roles of kinins in allergen-induced nasal blockage and sneezing, and development of nasal hyperresponsiveness to leukotriene D4 in a Japanese cedar pollen-induced allergic rhinitis model of guinea pigs. Sensitised guinea pigs were repeatedly challenged by pollen inhalation once every week. Neither a bradykinin B1 receptor antagonist, des-Arg9-[Leu8]bradykinin nor a bradykinin B2 receptor antagonist, icatibant suppressed allergen-induced sneezing and nasal blockage. However, development of nasal hyperresponsiveness to leukotriene D4 was significantly suppressed by them. The amount of bradykinin in nasal cavity lavage fluid was immediately increased after the challenge. In non-sensitised animals, hyperresponsiveness to leukotriene D4 was developed by a bradykinin B2 receptor agonist, bradykinin, but not by a bradykinin B1 receptor agonist, des-Arg10-kallidin, while in the sensitised-challenged animal, both agonists developed hyperresponsiveness. In conclusion, the nasal hyperresponsiveness appeared to be induced by kinins produced in response to the antigen challenge through activation of not only bradykinin B2 but also B1 receptors.

Studies of angiotensin-converting enzyme inhibitor-induced cough have involved extensive use of experimental models in which guinea pigs are exposed to an inhaled stimulus such as capsaicin or citric acid. In the present study, we examined enalapril-induced potentiation of spontaneous cough in guinea pigs, without an inhaled stimulus. Daily oral administration of enalapril (3 mg/kg) for 20 to 30 days enhanced spontaneous cough. This enhancement of cough was inhibited by the bradykinin B 1 receptor antagonist des-Arg 10 -[Leu 9 ]kallidin, but not by the bradykinin B 2 receptor antagonist icatibant. The amount of the bradykinin B 1 receptor agonist [ 3 H]des-Arg 10 -kallidin specifically bound to membrane fractions from the trachea and larynx was increased by prolongation of the enalapril treatment, and positively correlated well with coughing frequency. In conclusion, the present results indicate that enalapril-induced cough is mediated by up-regulation of bradykinin B 1 receptors.

We examined whether nasal hyperresponsiveness to leukotriene (LT) D4 is seen in our allergic rhinitis model, which showed sneezing and biphasic nasal blockage by repeated antigen inhalation challenge, and whether a dilatation of mucosal blood vessels contributes to this hyperresponsiveness. Nasal blockage [increase of specific airway resistance (sRaw)] was indexed as nasal (hyper)responsiveness. The sensitized - challenged guinea pig showed a remarkable dose-dependent increase in sRaw by intranasal instillation of LTD4 (10 μl/nostril) at 10−10 to 10−6 M 10 h and 2 days but not 7 days after the challenge. The increase in sRaw induced by LTD4 was largely blocked by pranlukast or naphazoline, and this was dose-dependently suppressed by Nω-nitro- L -arginine methyl ester. Sodium nitroprusside induced an elevation of sRaw in the sensitized - challenged animal in the hyperresponsiveness state, but the degree did not differ from that in the non-sensitized - non-challenged group. The amount of NO2− and NO3− in nasal cavity lavage fluid after LTD4 instillation in the sensitized - challenged animal in the hyperresponsiveness state was significantly greater than that before the instillation. These results demonstrate that the hyperresponsiveness to LTD4 acquired by repeated antigen challenge is mainly due to dilatation of nasal blood vessels, which can be related to hyperproduction of nitric oxide through cysteinyl LTi-receptor activation.

We have developed an allergic rhinitis model in guinea pigs using Japanese cedar pollen as antigen. In the present study, we examined whether provocation by pollen induces similar magnitudes of rhinitis symptoms in passively and actively sensitized guinea pigs. One group of animals was actively sensitized by intranasal application of pollen extract, and another was passively sensitized by intraperitoneal injection with anti-pollen serum. Actively and passively sensitized groups were then challenged by repeated and a single pollen inhalation, respectively. In both groups, sneeze was induced immediately after the challenge. The actively sensitized animals developed not only early but also late nasal blockage, whereas the passively sensitized animals showed only early nasal blockage. In both groups, an H1 antagonist, mepyramine, inhibited the occurrence of sneezing but did not inhibit nasal blockage. Nasal hyperresponsiveness to intranasal instillation of leukotriene D4 was obvious only in the actively sensitized animals. We thus conclude that although early nasal blockage is induced by a single antigen-antibody reaction, repetitive anaphylactic reaction is required for occurrence of late nasal blockage and hyperresponsiveness to stimuli. Furthermore, histamine plays a central role in induction of sneezing but not in nasal blockage, irrespective of whether animals are actively or passively sensitized.

Substance P causes histamine release from rat peritoneal mast cells probably through direct activation of a specific G protein at micromolar concentrations. We found that peritoneal mast cells of a substrain of Wistar rats (Std:Wistar) responds to nanomolar concentrations of substance P by releasing histamine in a concentration-dependent manner. In addition, potent histamine release from peritoneal mast cells of the substrain rats was also induced by neurokinin A in a concentration-dependent fashion. Histamine release induced by low concentrations of substance P was significantly blocked by a tachykinin NK1 receptor antagonist, CP-96345 [(2S,3S)-cis-2-(diphenylmethyl)-N-[(2-methoxyphenyl)-methyl]-1-aza bicyclo[2.2.2]octan-3-amine dihydrochloride], whereas that induced by concentrations as high as 10 microM appeared resistant to the antagonist. The concentration-histamine release curve for neurokinin A was parallel-shifted to the right by the drug. A tachykinin NK2 receptor antagonist, SR-48968 [(S)-N-methyl-N[4-(4-acetylamino-4-phenyl piperadino)-2-(3,4-dichlorophenyl)butyl]benzamide], did not influence release stimulated by substance P and neurokinin A. On the other hand, peritoneal mast cells of Sprague-Dawley and other Wistar rats did not respond to neurokinin A. At over 1 microM but not at nanomolar concentrations, substance P caused modest histamine release from peritoneal mast cells of these rats. The results suggest that neurokinin A and nanomolar, but not micromolar concentrations of substance P stimulate tachykinin NK receptors on the peritoneal mast cells of Std:Wistar rat to release histamine.

Anaphylactic histamine release from isolated rat peritoneal mast cells was concentration-dependently blocked by a 5-min treatment with exogenous histamine at 0.9 and 9 microM and enhanced by a 20- to 30-min treatment with thioperamide (H3-antagonist) at 3 microM with significance, but little affected by mepyramine (H1-antagonist) and cimetidine (H2-antagonist) at the cell concentration of 10(6) mast cells/ml. At a low concentration of mast cells (10(4) mast cells/ml), (R)-alpha-methylhistamine (alpha-MH), an H3-agonist, at 0.9-90 microM also inhibited the release in a concentration-dependent fashion. Thioperamide, but neither mepyramine nor cimetidine, significantly restored the decreased release by alpha-MH. However, the complete restoration by thioperamide could not be achieved because the drug itself slightly but concentration-dependently inhibited anaphylactic histamine release. On the other hand, not only betahistine and dimaprit but also alpha-MH did not suppress histamine release from the mast cells induced by compound 48/80. In rat plasma, considerable levels of histamine were detected. From these results, it is strongly suggested that histamine H3-like receptors are largely responsible for the negative feedback regulation of the anaphylactic histamine release from rat peritoneal mast cells.

Whether anaphylactic histamine release from rat peritoneal mast cells is influenced by betahistine, a histamine H1-receptor agonist/H3-antagonist, and dimaprit, an H2-agonist, was examined. Treatment with dimaprit at 6 and 60 microM for 20 min significantly inhibited the anaphylactic histamine release, whereas betahistine at up to 80 microM under the same conditions did not affect it. Treatment with dimaprit at 6 and 60 microM for 1 to 20 min and for 5 to 20 min, respectively, caused a time-dependent inhibition of the release, but up to 30 min treatment with 8 and 80 microM betahistine had no effect. The decreased histamine release induced by dimaprit was recovered by neither mepyramine nor cimetidine. However, thioperamide, an H3-selective antagonist, dose-dependently restored the diminished release. From these results, the inhibition of anaphylactic histamine release by dimaprit is not produced by the stimulation of H2-receptors, but involves the stimulation of H3-like receptors or H3-subtype receptors, which are distinct from the H3-receptors located in brain, and suggests that the receptor plays an important role in the negative feedback regulation of histamine release.

A Ca ionophore, A23187 has been thought to induce the chemical mediator release from a variety of cells by directly transporting Ca++ into the related cells. Our previous experiments on the release of histamine and slow reacting substance(SRS) from guinea pig lung fragments have suggested that A23187 activates cells prior to Ca++ influx for the release. In this report, we further examined the mode of action of A23187 in the release. The results obtained were as follows: 1) The release of histamine and SRS by A23187 was gradually increased with incubation time, reaching the maximum at 60 to 100min, as previously reported(whole stage). Under the same conditions without Ca++ & Mg++(lst stage), a small amount of both mediators was detected. 2) After 60min incubation at the 1st stage, an addition of Ca++(2nd stage) followed by 40min incubation induced the marked release of both mediators, but Mg++ did not lead to the release. The release by an addition of Ca++ at the 2nd stage was clearly different from that of the whole stage in terms of the very rapid and marked(1.5-fold in histamine & 2-fold in SRS at the whole stage) release. 3) An addition of bovine serum albumin which effectively binds with A23187, during the whole stage, caused surplus histamine and SRS release. 4) Both histamine and SRS release were dose-dependently inhibited by the treatment with diisopropyl-fluorophosphate. From the above results, it was further suggested that A23187 activates the cells prior to Ca++ influx.