Fatty acids negatively regulate platelet function through formation of noncanonical 15-lipoxygenase-derived eicosanoids.

The antiplatelet effect of polyunsaturated fatty acids is primarily attributed to its metabolism to bioactive metabolites by oxygenases, such as lipoxygenases (LOX). Platelets have demonstrated the ability to generate 15-LOX-derived metabolites (15-oxylipins); however, whether 15-LOX is in the platelet or is required for the formation of 15-oxylipins remains unclear. This study seeks to elucidate whether 15-LOX is required for the formation of 15-oxylipins in the platelet and determine their mechanistic effects on platelet reactivity.

DHA 12-LOX-derived oxylipins regulate platelet activation and thrombus formation through a PKA-dependent signaling pathway.

Background: The effects of docosahexaenoic acid (DHA) on cardiovascular disease are controversial and a mechanistic understanding of how this omega-3 polyunsaturated fatty acid (ω-3 PUFA) regulates platelet reactivity and the subsequent risk of a thrombotic event is warranted. In platelets, DHA is oxidized by 12-lipoxygenase (12-LOX) producing the oxidized lipids (oxylipins) 11-HDHA and 14-HDHA. We hypothesized that 12-LOX DHA-oxylipins may be involved in the beneficial effects observed in dietary supplemental treatment with ω-3 PUFAs or DHA itself.

Omega-6 DPA and its 12-lipoxygenase-oxidized lipids regulate platelet reactivity in a nongenomic PPARα-dependent manner.

Arterial thrombosis is the underlying cause for a number of cardiovascular-related events. Although dietary supplementation that includes polyunsaturated fatty acids (PUFAs) has been proposed to elicit cardiovascular protection, a mechanism for antithrombotic protection has not been well established. The current study sought to investigate whether an omega-6 essential fatty acid, docosapentaenoic acid (DPAn-6), and its oxidized lipid metabolites (oxylipins) provide direct cardiovascular protection through inhibition of platelet reactivity.

Biosynthesis of the Maresin Intermediate, 13S,14S-Epoxy-DHA, by Human 15-Lipoxygenase and 12-Lipoxygenase and Its Regulation through Negative Allosteric Modulators.

Human reticulocyte 15-lipoxygenase-1 (h15-LOX-1 or ALOX15) and platelet 12-lipoxygenase (h12-LOX or ALOX12) catalysis of docosahexaenoic acid (DHA) and the maresin precursor, 14S-hydroperoxy-4Z,7Z,10Z,12E,16Z,19Z-docosahexaenoic acid (14S-HpDHA), were investigated to determine their product profiles and relative rates in the biosynthesis of the key maresin intermediate, 13S,14S-epoxy-4Z,7Z,9E,11E,16Z,19Z-docosahexaenoic acid (13S,14S-epoxy-DHA). Both enzymes converted DHA to 14S-HpDHA, with h12-LOX having a 39-fold greater / value (14.0 ± 0.

5 S,15 S-Dihydroperoxyeicosatetraenoic Acid (5,15-diHpETE) as a Lipoxin Intermediate: Reactivity and Kinetics with Human Leukocyte 5-Lipoxygenase, Platelet 12-Lipoxygenase, and Reticulocyte 15-Lipoxygenase-1.

The reaction of 5 S,15 S-dihydroperoxyeicosatetraenoic acid (5,15-diHpETE) with human 5-lipoxygenase (LOX), human platelet 12-LOX, and human reticulocyte 15-LOX-1 was investigated to determine the reactivity and relative rates of producing lipoxins (LXs). 5-LOX does not react with 5,15-diHpETE, although it can produce LXA when 15-HpETE is the substrate. In contrast, both 12-LOX and 15-LOX-1 react with 5,15-diHpETE, forming specifically LXB.

Pseudomonas aeruginosa utilizes host polyunsaturated phosphatidylethanolamines to trigger theft-ferroptosis in bronchial epithelium.

Ferroptosis is a death program executed via selective oxidation of arachidonic acid-phosphatidylethanolamines (AA-PE) by 15-lipoxygenases. In mammalian cells and tissues, ferroptosis has been pathogenically associated with brain, kidney, and liver injury/diseases. We discovered that a prokaryotic bacterium, Pseudomonas aeruginosa, that does not contain AA-PE can express lipoxygenase (pLoxA), oxidize host AA-PE to 15-hydroperoxy-AA-PE (15-HOO-AA-PE), and trigger ferroptosis in human bronchial epithelial cells.

12-HETrE inhibits platelet reactivity and thrombosis in part through the prostacyclin receptor.

The dihomo-γ-linolenic acid (DGLA)-derived metabolite of 12-lipoxygenase, 12-hydroxy-eicosatrienoic acid (12-HETrE), was recently shown to potently inhibit thrombus formation without prolonging bleeding in murine models. Although 12-HETrE was found to inhibit platelet activation via the Gα signaling pathway, the Gα-coupled receptor by which 12-HETrE mediates its antiplatelet effects has yet to be identified. Defining the receptor by which 12-HETrE exerts its effects is key to determining its therapeutic potential as an antiplatelet drug.

Human 15-LOX-1 active site mutations alter inhibitor binding and decrease potency.

Human 15-lipoxygenase-1 (h15-LOX-1 or h12/15-LOX) reacts with polyunsaturated fatty acids and produces bioactive lipid derivatives that are implicated in many important human diseases. One such disease is stroke, which is the fifth leading cause of death and the first leading cause of disability in America. The discovery of h15-LOX-1 inhibitors could potentially lead to novel therapeutics in the treatment of stroke, however, little is known about the inhibitor/active site interaction.

12(S)-HETrE, a 12-Lipoxygenase Oxylipin of Dihomo-γ-Linolenic Acid, Inhibits Thrombosis via Gαs Signaling in Platelets.

Objective: Dietary supplementation with polyunsaturated fatty acids has been widely used for primary and secondary prevention of cardiovascular disease in individuals at risk; however, the cardioprotective benefits of polyunsaturated fatty acids remain controversial because of lack of mechanistic and in vivo evidence. We present direct evidence that an omega-6 polyunsaturated fatty acid, dihomo-γ-linolenic acid (DGLA), exhibits in vivo cardioprotection through 12-lipoxygenase (12-LOX) oxidation of DGLA to its reduced oxidized lipid form, 12(S)-hydroxy-8Z,10E,14Z-eicosatrienoic acid (12(S)-HETrE), inhibiting platelet activation and thrombosis.

Approach And Results: DGLA inhibited ex vivo platelet aggregation and Rap1 activation in wild-type mice, but not in mice lacking 12-LOX expression (12-LOX(-/-)).

Biochemical and Cellular Characterization and Inhibitor Discovery of Pseudomonas aeruginosa 15-Lipoxygenase.

Pseudomonas aeruginosa is an opportunistic pathogen that can cause nosocomial and chronic infections in immunocompromised patients. P. aeruginosa secretes a lipoxygenase, LoxA, but the biological role of this enzyme is currently unknown.

A potent and selective inhibitor targeting human and murine 12/15-LOX.

Human reticulocyte 12/15-lipoxygenase (h12/15-LOX) is a lipid-oxidizing enzyme that can directly oxidize lipid membranes in the absence of a phospholipase, leading to a direct attack on organelles, such as the mitochondria. This cytotoxic activity of h12/15-LOX is up-regulated in neurons and endothelial cells after a stroke and thought to contribute to both neuronal cell death and blood-brain barrier leakage. The discovery of inhibitors that selectively target recombinant h12/15-LOX in vitro, as well as possessing activity against the murine ortholog ex vivo, could potentially support a novel therapeutic strategy for the treatment of stroke.