Abstract
Several investigators have reported that inactivation of secretory phospholipase A 2 purified from bee venom with p-bromophenacyl bromide, an irreversible inhibitor, before injection resulted in attenuation of the subsequent inflammatory reaction in the mouse paw edema model. Recently, thielocin A1β, a novel secretory phospholipase A 2 inhibitor from fungi, was found to suppress histamine release from mast cells stimulated with secretory phospholipase A 2. These observations led us to examine the effect of thielocin A1β against secetory phospholipase A 2-induced paw edema. Thielocin A1β inhibited bee venom phospholipase A 2 in a dose-dependent manner (IC 50 = 1.4 μM). In addition, the inhibition of bee venom phospholipase A 2 was noncompetitive ( K i = 0.57 μM) and reversible. Subplantar injection of bee venom phospholipase A 2 produced a rapid but transient edematous response. Coinjection of thielocin A1β (1 μg/paw) with bee venom phospholipase A 2 resulted in a 44.7 ± 4.6% reduction of edema formation. This anti-edema action was not enhanced by cyproheptadine (antihistamine/antiserotonin). These results suggest that thielocin A1β shows edema-reducing activity via inhibition of the phospholipase A 2 activity which participates in histamine release by mast cells.
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