Collisionally induced dissociation of epoxyeicosatrienoic acids and epoxyeicosatrienoic acid-phospholipid molecular species

Bernström, Kerstin; Kayganich, Kathleen; Murphy, Robert C.

doi:10.1016/0003-2697(91)90530-7

Cited by 49 publications

(28 citation statements)

References 16 publications

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“…Electrospray ionization tandem mass spectrometry analysis (18,(21)(22)(23)(24)(25) of PC species labeled with specific deuterated precursors allowed us to distinguish the PC species synthesized from the CDP-choline pathway and the PE methylation pathway (Fig. 1A).…”

Section: Resultsmentioning

confidence: 99%

Molecular Distinction of Phosphatidylcholine Synthesis between the CDP-Choline Pathway and Phosphatidylethanolamine Methylation Pathway

DeLong

Shen

Thomas

et al. 1999

Journal of Biological Chemistry

354

271

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In addition to the CDP-choline pathway for phosphatidylcholine (PC) synthesis, the liver has a unique phosphatidylethanolamine (PE) methyltransferase activity for PC synthesis via three methylations of the ethanolamine moiety of PE. Previous studies indicate that the two pathways are functionally different and not interchangeable even though PC is the common product of both pathways. This study was designed to test the hypothesis that these two pathways produce different profiles of PC species. The PC species from these two pathways were labeled with specific stable isotope precursors, D9-choline and D4-ethanolamine, and analyzed by electrospray tandem mass spectrometry. Our studies revealed a profound distinction in PC profiles between the CDP-choline pathway and the PE methylation pathway. PC molecules produced from the CDP-choline pathway were mainly comprised of medium chain, saturated (e.g. 16:0/18:0) species. On the other hand, PC molecules from the PE methylation pathway were much more diverse and were comprised of significantly more long chain, polyunsaturated (e.g. 18:0/20:4) species. PC species from the methylation pathway contained a higher percentage of arachidonate and were more diverse than those from the CDP-choline pathway. This profound distinction of PC profiles may contribute to the different functions of these two pathways in the liver.Phosphatidylcholine (PC) 1 is a major group of phospholipid in all mammalian cells (1). PC is comprised of hydrocarbon chains attached to glycerophosphocholine via acyl, alkyl, or alkenyl linkages. The molecular diversity of PC and other phospholipids is dictated by the combination of different lengths, number of double bonds, and types of linkages of hydrocarbon chains. As a result, a single mammalian cell contains at least a thousand species of phospholipids (2). In most mammalian cells, PC is synthesized mainly via the CDPcholine pathway (3). This pathway uses choline as an initial substrate and is catalyzed by three enzymes: choline kinase, CTP:phosphocholine cytidylyltransferase (CT), and cholinephosphate transferase, with CT as the rate-limiting enzyme (1). Hepatocytes are unique because they also possess a high activity of phosphatidylethanolamine methyltransferase (PEMT) that converts PE to PC via three sequential steps of methylation (4) in addition to a high level of CDP-choline pathway activity. The significance of the PEMT pathway is not completely understood (5).The PEMT pathway seems redundant because its product, PC, is also synthesized by the CDP-choline pathway in hepatocytes. Therefore, the PEMT pathway is traditionally considered a backup pathway for PC synthesis in hepatocytes (3). However, recent studies indicate that these two pathways apparently have opposite effects on proliferative characteristics of the liver and liver-derived cell lines (6 -10). These studies suggest that the higher activity of the CDP-choline pathway favors the faster proliferation of hepatocytes. Conversely, expression of PEMT strongly inhibits the growth of hepatom...

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Section: Resultsmentioning

confidence: 99%

Molecular Distinction of Phosphatidylcholine Synthesis between the CDP-Choline Pathway and Phosphatidylethanolamine Methylation Pathway

DeLong

Shen

Thomas

et al. 1999

Journal of Biological Chemistry

354

271

View full text Add to dashboard Cite

show abstract

“…The fragment ion of m/z 257, which is of lesser importance, could be the result of loss of water and either loss of CO 2 or loss of a neutral alkene and H 2 via charge remote fragmentation (31). The identity of the compound, which appeared to be 14,15-EET based on HPLC retention time (Fig.…”

Section: Determination Of Epoxidementioning

confidence: 99%

“…Identification of EET Metabolites-A Hewlett-Packard 1100 MSD LC/MS system was used to separate and identify the metabolites (31). HPLC was carried out on a Supelco C 18 5 m 4.6 ϫ 150 mm Discovery TM column with mobile phase solvents consisting of water/formic acid (100: 0.03 v/v) (solvent A) and acetonitrile (solvent B) at a flow rate of 0.7 ml/min.…”

Section: Synthesis Of [mentioning

confidence: 99%

“…The mass spectrum of 14,15-EET contains a (M Ϫ H) Ϫ ion of m/z 319, an ion of m/z 301 due to loss of one water molecule, and an ion of m/z 219 from fragmentation of the carbon chain through the oxirane ring (31,33). The fragment ion of m/z 257, which is of lesser importance, could be the result of loss of water and either loss of CO 2 or loss of a neutral alkene and H 2 via charge remote fragmentation (31).…”

Section: Determination Of Epoxidementioning

confidence: 99%

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Pathways of Epoxyeicosatrienoic Acid Metabolism in Endothelial Cells

Fang

Kaduce

Weintraub

et al. 2001

Journal of Biological Chemistry

177

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“…As EETs are incorporated into cellular phospholipids (13) and bind to fatty acid-binding proteins (14), EETs may have long lasting effects subject to release from phospholipids in response to hormonal activation (15). EET phospholipids have been identified in human red blood cells by Nakamura et al (16) who proposed that erythrocytes serve "as a reservoir from which EETs can be released."…”

mentioning

confidence: 99%

Identification of 5,6-trans-Epoxyeicosatrienoic Acid in the Phospholipids of Red Blood Cells

Jiang

McGiff

Quilley

et al. 2004

Journal of Biological Chemistry

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A novel eicosanoid, 5,6-trans-epoxy-8Z,11Z,14Z-eicosatrienoic acid (5,6-trans-EET), was identified in rat red blood cells. Characterization of 5,6-trans-EET in the sn-2 position of the phospholipids was accomplished by hydrolysis with phospholipase A 2 followed by gas chromatography/mass spectrometry as well as electrospray ionization-tandem mass spectrometry analyses. The electron ionization spectrum of 5,6-erythro-dihydroxyeicosatrienoic acid (5,6-erythro-DHET), converted from 5,6-trans-EET in the samples, matches that of the authentic standard. Hydrogenation of the extracted 5,6-erythro-DHET with platinum(IV) oxide/hydrogen resulted in an increase of the molecular mass by 6 daltons and the same retention time shift as an authentic standard in gas chromatography, suggesting the existence of three olefins as well as the 5,6-erythro-dihydroxyl structure in the metabolite. Match of retention times by chromatography indicated identity of the stereochemistry of the red blood cell 5,6-erythro-DHET vis à vis the synthetic standard. High pressure liquid chromatographyelectrospray ionization-tandem mass spectrometry analysis of the phospholipase A 2 -hydrolyzed lipid extracts from red blood cells revealed match of the mass spectrum and retention time of the compound with the authentic 5,6-trans-EET standard, providing direct evidence of the existence of 5,6-trans-EET in red blood cells. The presence of other trans-EETs was also demonstrated. The ability of both 5,6-trans-EET and its product 5,6-erythro-DHET to relax preconstricted renal interlobar arteries was significantly greater than that of 5,6-cis-EET. In contrast, 5,6-cis-EET and 5,6-trans-EET were equipotent in their capacity to inhibit collageninduced rat platelet aggregation, whereas 5,6-erythro-DHET was without effect. We propose that the red blood cells serve as a reservoir for epoxides which on release may act in a vasoregulatory capacity.

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Collisionally induced dissociation of epoxyeicosatrienoic acids and epoxyeicosatrienoic acid-phospholipid molecular species

Cited by 49 publications

References 16 publications

Molecular Distinction of Phosphatidylcholine Synthesis between the CDP-Choline Pathway and Phosphatidylethanolamine Methylation Pathway

Molecular Distinction of Phosphatidylcholine Synthesis between the CDP-Choline Pathway and Phosphatidylethanolamine Methylation Pathway

Pathways of Epoxyeicosatrienoic Acid Metabolism in Endothelial Cells

Identification of 5,6-trans-Epoxyeicosatrienoic Acid in the Phospholipids of Red Blood Cells

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