Platelet-activating factor (PAF-acether) induced leukotriene C₄ formation and luminol dependent chemiluminescence by human eosinophils

Human eosinophils are capable of synthesizing almost exclusively the strongly spasmogenic compound LTC4 when stimulated with either the calcium ionophore A 23187 or opsonized zymosan (OZ). Although PAF-acether in concentrations ranging from 10 nM to 1 μM is hardly capable of inducing significant LTC4 synthesis itself, it significantly enhances the OZ-induced LTC4 formation at a concentration of 1 μM. However, at a concentration of 10 μM, PAF-acether itself is capable of inducing LTC4 formation comparable with that induced by OZ. PAF-acether, at a concentration of 10 μM (and not at a concentration of 1 μM) is also capable of inducing a luminol dependent chemiluminescent response by eosinophils. The PAF-acether antagonist BN 52021 at a concentration of 0.1 mM not only partially inhibited the PAF-acether induced LTC4 formation but also the OZ induced LTC4 formation. Since an equal inhibition is found the inhibitory mode of action of BN 52021 is most likely directed towards a common pathway. Taken together, these results suggest that eosinophils may be triggered by high locally reached concentrations of PAF-acether to release inflammatory and bronchoconstrictive mediators. This may be of importance for the pathogenesis of the allergen induced late phase asthmatic reaction.