Activation of the human neutrophil 5‐lipoxygenase by leukotriene B4

Abstract

In the present study, we demonstrate that leukotriene B4 (LTB4) has the ability to activate the human neutrophil 5‐lipoxygenase (5‐LO). Stimulation of neutrophils with 30 nm 14,15‐dideuterio‐LTB4 (D2‐LTB4) failed to induce the synthesis of LTB4 from endogenous arachidonic acid (AA), but stimulated the formation of LTB4 from 3.3 μm exogenous AA, as determined by GC‐MS analysis. The stimulatory effect of LTB4 on 5‐LO activity was further examined with an alternative substrate; LTB4 time‐ and dose‐dependently stimulated the 5‐LO‐mediated conversion of exogenous 15(S)‐hydroperoxy‐5,8,11,13‐(Z,Z,Z,E)‐eicosatetraenoate (15‐HpETE) into 5(S), 15(S)‐dihydroxy‐6,8,11,13,‐(E,Z,Z,E)‐eicosatetraenoate (5,15‐DiHETE), with a threshold effect at 300 pm. The ability of LTB4 to activate the 5‐LO showed structural specificity, since LTB4 was found to be 100 times more potent than ω‐hydroxy‐LTB4, and 300 times more potent than its Δ6‐trans‐12‐epi‐ isomer. The LTB4‐induced 5‐LO activation was effectively inhibited by MK‐886 (an inhibitor of 5‐LO translocation), by pertussis toxin, and by the LTB4 receptor antagonist, LY‐223982. 6 These results demonstrate that the binding of LTB4 to its cell‐surface receptor results in 5‐LO activation in a process mediated by pertussis toxin‐sensitive guanine nucleotide‐binding proteins. Our data also suggest that the underlying mechanism involves a translocation of the 5‐LO to the membrane. These findings raise the possibility that LTB4 produced by phagocytes may positively feedback on its own synthesis. 1992 British Pharmacological Society