Lipid Mediators in Lung Anaphylaxis: Kinetics of Their Release and Modulation by Selected Drugs

Abstract

Various arachidonic acid metabolites are released from the lungs during hypersensitivity reactions such as anaphylaxis or asthma. Thromboxane A2 and leukotrienes were shown to play a key role in the bronchoconstriction associated with these conditions. In our experiments, Reverse Phase High Performance Liquid Chromatography (RP-HPLC) and Enzyme Immunoassay (EIA) techniques were use (a) to study the profile of cyclooxygenase and lipoxygenase products released during guinea pig anaphylaxis, (b) to characterize their time-course of release, and (c) to investigate the complex interactions regulating their synthesis. The lungs of guinea pigs sensitized to ovalbumin (100 mg intraperitonealy and 100 mg subcutaneously) were perfused with Krebs solution. Anaphylaxis was induced by specific challenge (ovalbumin, 100 ug/ml) and the effluent was collected at 1 min intervals for the measure of prostaglandin E2 (PGE2), thromboxane B2 (TxB2), leukotrienes B4 (LTB4) and D4 (LTD4). In a set of experiments, the 12-hydroxyheptadecatrienoic acid (HHT) and 12-keto heptadecatrienoic acid (12-keto-HT) were analysed. Our results showed that the time-course of release of all the arachidonic acid metabolites were maximal approximately 5–6 min following the onset of the challenge. Leukotriene D4 and to a higher extent LTB4 were the major lipoxygenase products detected during anaphylaxis. Perfusion of the lungs with aspirin and indomethacin decreased the formation of PGE2 and TxB2 but did not modify the release of leukotrienes. On the contrary, BW755C and eicosatetraynoic acid (ETYA) reduced the release of all icosanoids from the lungs. FPL-55712, a selective leukotriene antagonist, significantly reduced the release of PGE2, TxB2, LTB4 and LTD4 at the high concentration (20 uM). In summary, this study made use of novel techniques to quantify arachidonic acid metabolites in the effluent of perfused lungs. New metabolites were described. Our study also stresses the possible significance of LTB4 as a mediator of anaphylaxis and asthma.