e-6123 and Bronchial-Hyperreactivity

The aim of this study was elucidate the role of lipid mediators in bronchial hyperresponsiveness (BHR) and airway eosinophil accumulation 24 hours after an antigen challenge in guinea pigs. Thromboxane (TX) A2 receptor antagonist, S-1452 (1, 10 mg/kg), cysteinyl leukotriene (cLT) receptor antagonist, ICI-198, 615 (0.5, 5 mg/kg), platelet activating factor (PAF) receptor antagonist, E-6123 (1, 10 micrograms/kg), and each vehicle were intraperitoneally given 1 h before and 11 h after an ovalbumin (OVA) challenge. BHR to inhaled methacholine was measured and then bronchoalveolar lavage (BAL) was performed 24 h after the OVA challenge. The three drugs significantly inhibited BHR to methacholine, dose dependently. S-1452 significantly inhibited total cell counts (TCC). ICI-198, 615 significantly reduced both TCC and eosinophil percentage, but E-6123 did not alter TCC and cell differentiation in BAL fluid. Therefore, these results clearly showed that lipid mediators were involved in antigen-induced BHR and suggested that TXA2 and cLT may contribute to the penetration of inflammatory cells through capillary wall, still more cLT is concerned eosinophil accumulation with cell specificity. PAF dose not take part in the penetration of inflammatory cells.

Topics: Animals; Azepines; Bridged Bicyclo Compounds; Bronchial Hyperreactivity; Bronchial Provocation Tests; Bronchoalveolar Lavage Fluid; Eosinophils; Fatty Acids, Monounsaturated; Guinea Pigs; Indazoles; Leukotriene Antagonists; Male; Membrane Proteins; Platelet Membrane Glycoproteins; Prostaglandin Antagonists; Receptors, Cell Surface; Receptors, G-Protein-Coupled; Receptors, Leukotriene; Receptors, Thromboxane; Triazoles

Acute exposure to cigarette smoke causes airway hyperresponsiveness (AHR) in guinea-pigs, which resolves within a few hours. Repeated exposure may have a different effect on the airways. To address this question, guinea-pigs were repeatedly exposed to cigarette smoke (six cigarettes for 1 h x day(-1)) for 14 consecutive days. Airway responsiveness to inhaled histamine and differential cell counts in bronchoalveolar lavage fluid (BALF) were evaluated 1 day after the last exposure. Significant neutrophilia in BALF was observed after 3 days of smoke exposure. Significant eosinophilia in BALF and AHR were observed after 14 days of smoke exposure, but not after 3 or 7 days of smoke exposure. These changes persisted until 3 days after the last exposure and resolved 7 days afterwards. Histologically, the recruited eosinophils were observed predominantly in the airways, but not in the alveoli. Treatment with E-6123, a specific platelet-activating factor receptor antagonist (1 mg x kg(-1) x day(-1) p.o. during smoke exposure) significantly inhibited the eosinophil influx and AHR. Repeated exposure to cigarette smoke may induce prolonged airway inflammation and airway hyperresponsiveness in guinea-pigs. Platelet-activating factor or platelet-activating factor-like lipids may play a key role in airway hyperresponsiveness, presumably by the induction of eosinophilic airway inflammation.

Topics: Animals; Azepines; Bronchi; Bronchial Hyperreactivity; Bronchoalveolar Lavage Fluid; Guinea Pigs; Male; Nicotiana; Plants, Toxic; Platelet Activating Factor; Pulmonary Eosinophilia; Smoke; Time Factors; Triazoles

The effects of a newly synthesized PAF antagonist E6123, (S)-(+)-6-(2-chlorophenyl)-3-cyclopropanecarbonyl-8,11-dimethyl-2, 3,4,5- tetrahydro-8H-pyrido[4',3':4,5]thieno[3,2-f][1,2,4]triazolo [4,3-a][1,4]diazepine, on in vivo inhaled PAF-induced pulmonary changes were investigated. E6123 inhibited PAF inhalation-induced bronchoconstriction in guinea pigs with an ED50 value (p.o.) of 1.3 micrograms/kg which was lower than those of other PAF-antagonists such as WEB2347 (ED50 = 26 micrograms/kg) and Y-24180 (ED50 = 12 micrograms/kg). E6123 significantly inhibited PAF inhalation-induced eosinophil infiltration into the bronchiole and trachea, and bronchial hyperreactivity in guinea pigs after oral administration at 1 and 10 micrograms/kg, respectively. E6123 inhibited the PAF-induced increase in intracellular free calcium ion concentration ([Ca2+]i) in guinea pig eosinophils with an IC50 value of 14 nM. The present results suggest that E6123 may be beneficial for the treatment of asthma, in which PAF is assumed to be involved.

Topics: Administration, Oral; Analysis of Variance; Animals; Asthma; Azepines; Bronchial Hyperreactivity; Bronchoconstriction; Calcium; Eosinophils; Guinea Pigs; Lung; Male; Platelet Activating Factor; Triazoles