3 research outputs found
Structural Requirements for Activation of the 5-Oxo-6E,8Z, 11Z,14Z-eicosatetraenoic Acid (5-Oxo-ETE) Receptor: Identification of a Mead Acid Metabolite with Potent Agonist Activity
ABSTRACT The 5-lipoxygenase product 5-oxo-6E,8Z,11Z,14Z-eicosatetraenoic acid (5-oxo-ETE) is a potent chemoattractant for neutrophils and eosinophils, and its actions are mediated by the oxoeicosanoid (OXE) receptor, a member of the G proteincoupled receptor family. To define the requirements for activation of the OXE receptor, we have synthesized a series of 5-oxo-6E,8Z-dienoic acids with chain lengths between 12 and 20 carbons, as well as a series of 20-carbon 5-oxo fatty acids, either fully saturated or containing between one and five double bonds. The effects of these compounds on neutrophils (calcium mobilization, CD11b expression, and cell migration) and eosinophils (actin polymerization) were compared with those of 5-oxo-ETE. The C 12 and C 14 analogs were without appreciable activity, whereas the C 16 5-oxo-dienoic acid was a weak partial agonist. In contrast, the corresponding C 18 analog (5-oxo-18:2) was nearly as potent as 5-oxo-ETE. Among the C 20 analogs, the fully saturated compound had virtually no activity, whereas 5-oxo-6E-eicosenoic acid had only weak agonist activity. In contrast, 5-oxo-6E,8Z,11Z-eicosatrienoic acid (5-oxo-20:3) and its 8-trans isomer were approximately equipotent with 5-oxo-ETE in activating granulocytes. Because of the potent effects of 5-oxo-20:3, we investigated its formation from Mead acid (5Z,8Z,11Z-eicosatrienoic acid), which accumulates in dietary essential fatty acid deficiency, by neutrophils. The main Mead acid metabolite identified was 5-hydroxy-6,8,11-eicosatrienoic acid, followed by 5-oxo-20:3 and two 6-trans isomers of leukotriene B 3 . We conclude that optimal activation of the OXE receptor is achieved with 5-oxo-ETE, 5-oxo-18:2, and 5-oxo-20:3, and that the latter compound could potentially be formed under conditions of essential fatty acid deficiency. Metabolism of arachidonic acid by the 5-lipoxygenase (5-LO) pathway leads to the formation of leukotriene (LT) B 4 , LTC 4 , LTD 4 , and 5-HET
Substrate Selectivity of 5-Hydroxyeicosanoid Dehydrogenase and Its Inhibition by 5-Hydroxy-Δ6-Long-Chain Fatty Acids
5-Oxo-6E,8Z,11Z,14Z-eicosatetraenoic
acid (5-oxo-ETE) is a metabolite of the 5-lipoxygenase (5-LO) product
5S-hydroxy-6E,8Z,11Z,14Z-eicosatetraenoic
acid (5-HETE), formed by the microsomal enzyme 5-hydroxyeicosanoid
dehydrogenase (5-HEDH). 5-oxo-ETE is a chemoattractant for neutrophils and
eosinophils, both in vitro and in vivo. To examine the substrate selectivity
of 5-HEDH and to search for potential inhibitors, we prepared a series of
5S-hydroxy fatty acids (C12 to C20 containing
zero to four double bonds) by total chemical synthesis and examined their
metabolism by microsomes from monocytic U937 cells. Although most of these
fatty acids were oxidized to their 5-oxo metabolites by 5-HEDH, 5-HETE seemed
to be the best substrate. However, substrates containing less than 16 carbons,
a methylated α-carboxyl group, or a hydroxyl group at the ω-end of
the molecule were not substantially metabolized. Some of the fatty acids
tested were fairly potent inhibitors of the formation of 5-oxo-ETE by 5-HEDH,
in particular 5-hydroxy-6-octadecenoic acid and 5-hydroxy-6-eicosenoic acid.
Both substances selectively inhibited 5-oxo-ETE formation by human peripheral
blood mononuclear cells incubated with arachidonic acid and calcium ionophore
without affecting the formation of leukotriene B4, 12-HETE, or
12-hydroxy-5,8,10-heptadecatrienoic acid. We conclude that the requirements
for appreciable metabolism by 5-HEDH include a chain length of at least 16
carbons, a free α-carboxyl group, and a hydrophobic group at the
ω-end of the molecule. 5-Hydroxy-Δ6 C18 and
C20 fatty acids selectively inhibit 5-HEDH without inhibiting 5-LO,
leukotriene A4 hydrolase, 12-lipoxygenase, or cyclooxygenase. Such
compounds may be useful in defining the role of 5-oxo-ETE and its mechanism of
synthesis