title: Endogenous hydroxyeicosatetraenoic acids stimulate the human polymorphonuclear leukocyte 15-lipoxygenase pathway.
abstract: Arachidonic acid metabolism in ionophore A23187-activated human polymorphonuclear leukocytes (PMNs) proceeds predominantly via the 5-lipoxygenase pathway in comparison to metabolism by the 15-lipoxygenase route. Products of both lipoxygenase pathways appear to be involved in the mediation of inflammatory reactions. Pretreatment of polymorphonuclear leukocytes with micromolar amounts of the platelet-derived 12-lipoxygenase product 12-hydroxy-5,8,10,14- eicosatetraenoic acid (12-HETE) prior to the addition of A23187 and [14C]arachidonic acid resulted in the unexpected dose-dependent stimulation of the 15-lipoxygenase pathway, as evidenced by the formation of [14C]15-HETE. A concomitant inhibition of the 5-lipoxygenase pathway was also observed. The structural identity of 15-HETE was confirmed by retention times on straight-phase and reverse-phase high pressure liquid chromatography in comparison with an authentic standard, radioimmunoassay, and chemical derivatization. When other isomeric HETEs were tested, the order of stimulatory potencies was 15-HETE greater than 12-HETE greater than 5-HETE. When arachidonic acid metabolism via the 5-lipoxygenase route was inhibited by nordihydroguaiaretic acid, previously ineffective concentrations of exogenous 12-HETE were now able to stimulate the polymorphonuclear leukocyte 15-lipoxygenase. Thus, blockade of the 5-lipoxygenase pathway appeared to be a prerequisite for the activation of the 15-lipoxygenase. The HETE-induced activation of the 15-lipoxygenase occurred within 1-2 min, was a reversible process, and was enhanced in the presence of A23187. In nine donors tested, up to 14-fold stimulation of [14C]15-HETE production was observed. Our results indicate that endogenous HETEs can have a dual role in the post-phospholipase regulation of arachidonic acid metabolism since they can act as physiological stimulators of the 15-lipoxygenase as well as inhibitors of the 5-lipoxygenase.
mesh_terms: D019377:12-Hydroxy-5,8,10,14-eicosatetraenoic Acid; D001091:Arachidonate Lipoxygenases; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000378:metabolism; D000001:Calcimycin / Q000494:pharmacology; D002851:Chromatography, High Pressure Liquid; D002855:Chromatography, Thin Layer; D006801:Humans; D006893:Hydroxyeicosatetraenoic Acids / Q000494:pharmacology*; D008084:Lipoxygenase / Q000378:metabolism*; D008956:Models, Chemical; D009504:Neutrophils / Q000187:drug effects / Q000201:enzymology*; D013997:Time Factors
chemical_list: D001095:Arachidonic Acids; D006893:Hydroxyeicosatetraenoic Acids; D016718:Arachidonic Acid; D000001:Calcimycin; C022022:5-hydroxy-6,8,11,14-eicosatetraenoic acid; D019377:12-Hydroxy-5,8,10,14-eicosatetraenoic Acid; C025984:15-hydroxy-5,8,11,13-eicosatetraenoic acid; D001091:Arachidonate Lipoxygenases; D008084:Lipoxygenase