Arachidonate-derived Dihomoprostaglandin Production Observed in Endotoxin-stimulated Macrophage-like Cells

Harkewicz, Richard; Fahy, Eoin; Andreyev, Alexander Y.; Dennis, Edward A.

doi:10.1074/jbc.m610067200

Cited by 47 publications

(43 citation statements)

References 29 publications

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“…Methods used for cell stimulation and quantitation (6), eicosanoid analysis (28,29), transcript quantitation, primary macrophage isolation/ex vivo culture (10), and phospholipid extraction/saponification (25) were all described in previous papers, which also established appropriate sample sizes used in this study. RAW264.7 cells were obtained from the American Type Culture Collection (cat.…”

Section: Methodsmentioning

confidence: 99%

Phospholipase A₂regulates eicosanoid class switching during inflammasome activation

Norris¹,

Gosselin

Reichart

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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118

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Initiation and resolution of inflammation are considered to be tightly connected processes. Lipoxins (LX) are proresolution lipid mediators that inhibit phlogistic neutrophil recruitment and promote wound-healing macrophage recruitment in humans via potent and specific signaling through the LXA 4 receptor (ALX). One model of lipoxin biosynthesis involves sequential metabolism of arachidonic acid by two cell types expressing a combined transcellular metabolon. It is currently unclear how lipoxins are efficiently formed from precursors or if they are directly generated after receptor-mediated inflammatory commitment. Here, we provide evidence for a pathway by which lipoxins are generated in macrophages as a consequence of sequential activation of toll-like receptor 4 (TLR4), a receptor for endotoxin, and P2X 7 , a purinergic receptor for extracellular ATP. Initial activation of TLR4 results in accumulation of the cyclooxygenase-2-derived lipoxin precursor 15-hydroxyeicosatetraenoic acid (15-HETE) in esterified form within membrane phospholipids, which can be enhanced by aspirin (ASA) treatment. Subsequent activation of P2X 7 results in efficient hydrolysis of 15-HETE from membrane phospholipids by group IVA cytosolic phospholipase A 2 , and its conversion to bioactive lipoxins by 5-lipoxygenase. Our results demonstrate how a single immune cell can store a proresolving lipid precursor and then release it for bioactive maturation and secretion, conceptually similar to the production and inflammasome-dependent maturation of the proinflammatory IL-1 family cytokines. These findings provide evidence for receptor-specific and combinatorial control of pro-and anti-inflammatory eicosanoid biosynthesis, and potential avenues to modulate inflammatory indices without inhibiting downstream eicosanoid pathways.lipidomics | enzyme coupling | membrane remodeling A complex network of danger-sensing receptors and bioactive peptide and lipid signals, including cytokines and eicosanoids, regulates innate immunity. Toll-like receptor (TLR) priming is suggested as a precautionary step in building a significant inflammatory response by driving production of IL-1 family protokines, which remain inactive until a second stimulus drives them to bioactive maturation and secretion (1). The second step of this process has been most strongly linked to extracellular ATP and specifically to one of its purinergic receptors, P2X 7 (2, 3), particularly in macrophages (4).TLR stimulations also increase prostaglandin synthesis by activating cytosolic phospholipase A 2 (cPLA 2 ) through a Ca 2+ -independent mechanism to release arachidonic acid (AA) from phospholipids, and by increasing expression of cyclooxygenase-2 (COX-2) and microsomal prostaglandin E 2 synthase-1. P2X 7 stimulation activates cPLA 2 through a Ca 2+ -dependent mechanism that couples AA metabolism with 5-lipoxygenase (5-LOX)-activating protein (FLAP), Ca 2+ -activated 5-LOX, and constitutive COX-1 to form leukotrienes (LTs) and prostaglandins (PGs). Short-term (∼1 h) TLR priming of ...

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Section: Methodsmentioning

confidence: 99%

Phospholipase A₂regulates eicosanoid class switching during inflammasome activation

Norris¹,

Gosselin

Reichart

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

118

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“…By coupling a liquid chromatographic separation to the mass spectrometer and employing the MRM mode, the mass spectrometer is utilized as a highly selective and highly sensitive HPLC detector. A similar MRM method was created for FFA analysis, as we previously reported (29).…”

Section: Methodsmentioning

confidence: 99%

Cholesteryl Ester Hydroperoxides Are Biologically Active Components of Minimally Oxidized Low Density Lipoprotein

Harkewicz

Hartvigsen

Almazan

et al. 2008

Journal of Biological Chemistry

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111

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Oxidation of low density lipoprotein (LDL) occurs in vivo and significantly contributes to the development of atherosclerosis. An important mechanism of LDL oxidation in vivo is its modification with 12/15-lipoxygenase (LO). We have developed a model of minimally oxidized LDL (mmLDL) in which native LDL is modified by cells expressing 12/15LO. This mmLDL activates macrophages inducing membrane ruffling and cell spreading, activation of ERK1/2 and Akt signaling, and secretion of proinflammatory cytokines. In this study, we found that many of the biological activities of mmLDL were associated with cholesteryl ester (CE) hydroperoxides and were diminished by ebselen, a reducing agent. Liquid chromatography coupled with mass spectroscopy demonstrated the presence of many monoand polyoxygenated CE species in mmLDL but not in native LDL. Nonpolar lipid extracts of mmLDL activated macrophages, although to a lesser degree than intact mmLDL. The macrophage responses were also induced by LDL directly modified with immobilized 12/15LO, and the nonpolar lipids extracted from 12/15LO-modified LDL contained a similar set of oxidized CE. Cholesteryl arachidonate modified with 12/15LO also activated macrophages and contained a similar collection of oxidized CE molecules. Remarkably, many of these oxidized CE were found in the extracts of atherosclerotic lesions isolated from hyperlipidemic apoE ؊/؊ mice. These results suggest that CE hydroperoxides constitute a class of biologically active components of mmLDL that may be relevant to proinflammatory activation of macrophages in atherosclerotic lesions.

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“…Several adrenic acids and elongated prostaglandins were found (27). Analysis of the phospholipid content of macrophage cell types (i.e.…”

Section: Sterols and Prenols-over A 24mentioning

confidence: 99%

A Mouse Macrophage Lipidome

Dennis

Deems

Harkewicz

et al. 2010

Journal of Biological Chemistry

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271

282

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We report the lipidomic response of the murine macrophage RAW cell line to Kdo 2 -lipid A, the active component of an inflammatory lipopolysaccharide functioning as a selective TLR4 agonist and compactin, a statin inhibitor of cholesterol biosynthesis. Analyses of lipid molecular species by dynamic quantitative mass spectrometry and concomitant transcriptomic measurements define the lipidome and demonstrate immediate responses in fatty acid metabolism represented by increases in eicosanoid synthesis and delayed responses characterized by sphingolipid and sterol biosynthesis. Lipid remodeling of glycerolipids, glycerophospholipids, and prenols also take place, indicating that activation of the innate immune system by inflammatory mediators leads to alterations in a majority of mammalian lipid categories, including unanticipated effects of a statin drug. Our studies provide a systems-level view of lipid metabolism and reveal significant connections between lipid and cell signaling and biochemical pathways that contribute to innate immune responses and to pharmacological perturbations.The "omics" revolution has provided significant insight into the genes, mRNAs, and proteins of mammalian cells, biological systems, and disease (1-3). An important function of these macromolecular classes is the production of metabolites that in turn are used by cells for replication and function. Lipids comprise major structural and metabolic components of cells and have essential functions in the formation of membranes, energy production, and intracellular signaling. Despite the central role of lipids in mammalian cell function, there has been no systematic effort to define the lipid "parts list" of a mammalian cell or the changes in these lipids associated with cellular function and disease. Many biochemical pathways leading to the synthesis and degradation of major lipid categories are known, but how these pathways interact under normal and pathological conditions remains unexplored. Recent advances in mass spectrometry have made it possible to qualitatively and quantitatively analyze a majority of cellular lipids (4 -8). We report here a comprehensive systems-level analysis of a mammalian cell lipidome through temporal measurements.We characterized lipidomic responses of RAW264.7 (RAW) macrophages to a highly specific ligand for Toll-like receptor 4 (TLR4) 4 that mimics aspects of bacterial infection. This model is of particular interest because of the essential roles that alterations in macrophage lipid metabolism play in innate and adaptive immune responses and the development of chronic inflammatory and cardiovascular diseases. Recent studies further suggest that TLR signaling in macrophages is not only required for innate immunity against viral and bacterial pathogens but also contributes to the pathogenesis of atherosclerosis, diabetes, arthritis, and other inflammatory diseases (9). Although TLR4 signaling is known to exert profound effects on the macrophage transcriptome (10), proteome (11), and selected lipid species that...

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Arachidonate-derived Dihomoprostaglandin Production Observed in Endotoxin-stimulated Macrophage-like Cells

Cited by 47 publications

References 29 publications

Phospholipase A₂regulates eicosanoid class switching during inflammasome activation

Phospholipase A₂regulates eicosanoid class switching during inflammasome activation

Cholesteryl Ester Hydroperoxides Are Biologically Active Components of Minimally Oxidized Low Density Lipoprotein

A Mouse Macrophage Lipidome

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Arachidonate-derived Dihomoprostaglandin Production Observed in Endotoxin-stimulated Macrophage-like Cells

Cited by 47 publications

References 29 publications

Phospholipase A2regulates eicosanoid class switching during inflammasome activation

Phospholipase A2regulates eicosanoid class switching during inflammasome activation

Cholesteryl Ester Hydroperoxides Are Biologically Active Components of Minimally Oxidized Low Density Lipoprotein

A Mouse Macrophage Lipidome

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Phospholipase A₂regulates eicosanoid class switching during inflammasome activation

Phospholipase A₂regulates eicosanoid class switching during inflammasome activation