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Vol. 287, Issue 1, 150-156, October 1998
Department of Pediatrics, Division of Basic Sciences, National
Jewish Medical and Research Center, Denver, Colorado
The effect of exogenous leukotriene B4 (LTB4)
on opsonized zymosan-stimulated human neutrophil formation of
5-lipoxygenase products and arachidonic acid release was directly
assessed using reverse-phase HPLC/tandem mass spectrometric methods for
quantitation. Stable isotopically labeled LTB4,
[1,2-13C2]LTB4, caused a
dose-dependent inhibition of LTB4 production in isolated
human neutrophils with significant inhibition (60 ± 7% of
control levels) when 0.12 nM
[13C2]LTB4 was present.
Production of 5-hydroxy-6,8,11,14-eicosatetraenoic acid and
release of free arachidonic acid were also dose-dependently inhibited
by exogenous LTB4. Metabolites of LTB4,
20-hydroxy-LTB4 and 3(S)-hydroxy-LTB4, also
significantly reduced LTB4 production to levels as low as
10 ± 6% and 10 ± 7% of control levels, respectively, when
present exogenously at 10 nM. Exogenous
5-hydroxy-6,8,11,14-eicosatetraenoic acid at concentrations as high as
10 nM produced no significant reduction in LTB4
biosynthesis during zymosan-stimulated human neutrophil production of
LTB4. The inhibitory effect of LTB4 could be
partially reversed by the LTB4 receptor antagonist U 75302. Furthermore, an alternative stimulus,
N-formyl-methionyl-leucyl-phenylalanine (100 nM), did not inhibit the
production of LTB4 in opsonized zymosan-stimulated human
neutrophils. These results suggest that activation of the
LTB4 receptor on the human neutrophil during phagocytosis
limits the ultimate biosynthesis of LTB4. This autocrine effect is opposite to that observed when neutrophils have much of the
signal transduction pathways bypassed when stimulated with calcium
ionophore A23187 or treated with exogenous free arachidonic acid.
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