A Bradykinin Antagonist Modifies Allergen-induced Mediator Release and Late Bronchial Responses in Sheep

Abstract

We assessed the role of bradykinin (BK) in allergen-induced early and late bronchial responses, airway inflammation, mediator release, and antigen-induced airway hyperresponsiveness in allergic sheep by studying the effects of the BK B2 receptor antagonist, NPC-567 (D-Arg-[Hyp3, D-Phe7]-BK), on these parameters. Antigen challenge was performed on two occasions greater than 3 wk apart, once with placebo (control) and once after high-dose (10 mg/ml) and low-dose (5 mg/ml) treatments with aerosol NPC-567. In the control trials (n = 14) antigen challenge resulted in an early and late increase in specific lung resistance (SRL). The early response was associated with increases (p less than 0.05) in prostaglandin (PG) D2, immunoreactive kinin, tosyl-L-arginine methyl ester (TAME)-esterase, and PGE2 in bronchoalveolar lavage (BAL) fluid. The late response was associated with increases (p less than 0.05) in leukotrienes (LT) B4 and C4, thromboxane (TX) B2, 6-keto-PGF10, and PGE2. There was a significant influx of neutrophils in the BAL fluid during the late response, and airway hyperresponsiveness to carbachol aerosol was apparent 4 h after challenge. In six sheep the high-dose NPC-567 treatment (given before, during, and 4 h after antigen challenge) did not attenuate the early bronchoconstrictor response or the early release of mediators but caused a significant reduction in the late response (p less than 0.05). This protective effect was accompanied by reductions (p less than 0.05) in both the concentrations of all the mediators associated with the late response and the severity of the BAL neutrophilia. High-dose NPC-567 did not attenuate the airway hyperresponsiveness or the cellular inflammatory response seen 24 h after challenge. In eight sheep treated with the low dose of NPC-567 (given before, during, and 4, 8, and 24 h after challenge) the early response was not blocked but the late response was again inhibited, as were the mediators associated with the late response. At the low dose the drug did not prevent the airway inflammation at 8 or 24 h. The additional treatments did, however, prevent the 24 h hyperresponsiveness. These data suggest that kinin generation during antigen-induced airway anaphylaxis may be important for controlling the release of arachidonic acid metabolites from airway inflammatory cells that contribute to the development of the late response in the allergic sheep model.

Alpha 4-integrins mediate antigen-induced late bronchial responses and prolonged airway hyperresponsiveness in sheep.

“…That the eosinophil may be more prominent in mediating the late response and airway hyperresponsiveness is not surprising considering the differences in the biochemical pathways of the two cell types. The neutrophil does not produce sulfidopeptide leukotrienes (47,48), i.e., leukotrienes C4, D4, and E4) major mediators ofthe late response (38,(49)(50)(51) ), whereas the eosinophil, is a potent source of these spasmogens. In addition, eosinophils release major basic protein which damages respiratory epithelium (52,53) and can provoke airway hyperresponsiveness (54,55 Previous studies in Ascaris suum-sensitive monkeys suggest that selective endothelial adhesion proteins regulate specific pathophysiological events that follow antigen challenge.…”

“…Plates were blocked with 1% BSA in PBS for 1 h at room temperature, washed once with RPMI 1640 containing 10% FBS (RPMI/ 10), and adhesion assays with sheep peripheral blood mononuclear leukocytes were performed with inverted centrifugation as described ( 11,32). Blood leukocyte adhesion was quantified by fluorescence as described (33 (36)(37)(38). Pleural pressure was estimated with the esophageal balloon catheter (filled with I ml of air), which was positioned 5-10 cm from the gastroesophageal junction.…”

“…The solenoid valve was activated for one second at the beginning ofthe inspiratory cycle ofthe respirator. Aerosols were delivered at a tidal volume of 500 ml and a rate of 20 breaths per minute as previously described (36,38).…”

“…The distal tip of a specially designed 80-cm fiberoptic bronchoscope was wedged into a randomly selected subsegmental bronchus. Lung lavage was performed by slow infusion and gentle aspiration of 3 X 30-ml aliquots of PBS (pH 7.4) at 39°C, using 30-ml syringes attached to the working channel of the bronchoscope (38). The effluent collected was strained through gauze to remove mucus and then centrifuged at 420 g for 15 min.…”

“…30 min after treatment, SRL was remeasured and then the animals were challenged with antigen. SRL was remeasured immediately after, hourly from 1 to 6 h after and half-hourly from 6.5 to 8 h after antigen challenge as previously described (35,38). Postchallenge determinations of airway responsiveness (PC4w) were made at 24 and 48 h, and 1 and 2 wk after antigen challenge.…”