LTA(4)-derived 5-oxo-eicosatetraenoic acid: pH-dependent formation and interaction with the LTB(4) receptor of human polymorphonuclear leukocytes.
5-oxo-(7E,9E,11Z,14Z)-eicosatetraenoic acid (5-oxo-ETE) has been identified as a non-enzymatic hydrolysis product of leukotriene A(4) (LTA(4)) in addition to 5,12-dihydroxy-(6E,8E,10E, 14Z)-eicosatetraenoic acids (5,12-diHETEs) and 5,6-dihydroxy-(7E,9E, 11Z,14Z)-eicosatetraenoic acids (5,6-diHETEs). The amount of 5-oxo-ETE detected in the mixture of the hydrolysis products of LTA(4) was found to be pH-dependent. After incubation of LTA(4) in aqueous medium, the ratio of 5-oxo-ETE to 5,12-diHETE was 1:6 at pH 7.5, and 1:1 at pH 9.5. 5-Oxo-ETE was isolated from the alkaline hydrolysis products of LTA(4) in order to evaluate its effects on human polymorphonuclear (PMN) leukocytes. 5-Oxo-ETE induced a rapid and dose-dependent mobilization of calcium in PMN leukocytes with an EC(50) of 250 nM, as compared to values of 3.5 nM for leukotriene B(4) (LTB(4)500 nM for 5(S)-hydroxy-(6E,8Z,11Z,14Z)-eicosatetraenoic acid (5-HETE). Pretreatment of the cells with LTB(4) totally abolished the calcium response induced by 5-oxo-ETE. In contrast, the preincubation with 5-oxo-ETE did not affect the calcium mobilization induced by LTB(4). The calcium response induced by 5-oxo-ETE was totally inhibited by the specific LTB(4) receptor antagonist LY223982. These data demonstrate that 5-oxo-ETE can induce calcium mobilization in PMN leukocyte via the LTB(4) receptor in contrast to the closely related analog 5-oxo-(6E,8Z,11Z, 14Z)-eicosatetraenoic acid which is known to activate human neutrophils by a mechanism independent of the receptor for LTB(4).
Falgueyret
J
J
Department of Biochemistry and Molecular Biology, Merck Frosst Centre for Therapeutic Research, 16,711 TransCanada Highway, Kirkland, Quebec, Canada.
Riendeau
D
D
D001095:Arachidonic Acids / Q000138:chemical synthesis / Q000378:metabolism* / Q000494:pharmacology; D001577:Benzophenones / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D016257:Fura-2; D006801:Humans; D006863:Hydrogen-Ion Concentration; D017572:Leukotriene A4 / Q000737:chemistry; D020024:Leukotriene Antagonists / Q000494:pharmacology; D009504:Neutrophils / Q000187:drug effects / Q000378:metabolism*; D018102:Receptors, Leukotriene B4 / Q000378:metabolism*
D001095:Arachidonic Acids; D001577:Benzophenones; D017572:Leukotriene A4; D020024:Leukotriene Antagonists; D018102:Receptors, Leukotriene B4; C065916:LY 223982; C080828:5-oxo-6,8,11,14-eicosatetraenoic acid; D002118:Calcium; D016257:Fura-2