Effects of a specific inhibitor of the 5-lipoxygenase pathway on mediator release from human basophils and mast cells.

We have characterized the effect of a specific inhibitor of the 5-lipoxygenase pathway on mediator release from human basophils and lung mast cells. In four experiments with purified basophils the phenothiazine derivative, L651-392, proved to be an effective inhibitor of leukotriene (LT) C4 release in the range 1-10 microM (P less than .005) although the release of histamine was unaffected by the highest doses of the drug. The release of 5-hydroxyeico-satetraenoic acid (5-HETE) from purified basophils (n = 2) was also reduced from 8.6 ng/10(6) basophils to below the limit of detection (1.2 ng/10(6) basophils). Intermediate concentrations of L651-392 (0.5 microM) reduced both the rate at which LTC4 was produced and the final concentration. The release of LTC4 was complete within 20-30 min and was unaffected by increased incubation periods (up to 90 min). HPLC analysis revealed that the drug was not promoting the metabolism of LTC4 to LTD4 or LTE4. Basophils (average purity = 78 +/- 3, n = 3) labeled with 3H-arachidonic acid (AA) were challenged with anti-IgE (0.1 microgram/ml) and the lipid mediators analyzed by HPLC. Control cells released 3H-LTC4, 3H-HETE, unmetabolized 3H-AA, and an unidentified metabolite, whereas those pretreated with L651-392 released only 3H-AA and the unknown metabolite with no detectable 3H-LTC4 or 3H-HETE. The specificity of the drug for the 5-lipoxygenase pathway was confirmed in three experiments with human lung mast cells.(ABSTRACT TRUNCATED AT 250 WORDS)