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Phospholipid plasmalogen, a surrogate marker of oxidative stress, is associated with increased cardiovascular mortality in patients on renal replacement therapy.

BACKGROUND: There is a high incidence of premature cardiovascular disease (CVD) in patients with end-stage renal disease (ESRD). Free radical-induced tissue damage is thought to play a major role in the pathogenesis of atherosclerosis, and there are several reports indicating an increased oxidative stress in ESRD. However, it is not well established that increased oxidative stress predicts cardiovascular mortality in ESRD. Plasmalogens, a group of phospholipids with a vinyl ether bond in the sn-1 position, are considered to be sensitive markers of oxidative stress. METHODS: Cardiovascular and non-cardiovascular mortality was recorded (follow-up time 1860+/-94 days) in 105 ESRD patients (mean age 51+/-2 years) in whom the fasting ratio of the erythrocyte levels of plasmalogens (DMA 16/C16:0 and DMA 18/C18:0) had been determined at the start of renal replacement therapy (RRT). The prevalence of malnutrition (subjective global assessment), diabetes mellitus (DM), smoking habits and CVD was also determined. RESULTS: Thirty-eight patients who died of CVD (0.066+/-0.003) had a significantly lower DMA 16/C16:0 ratio than 15 patients who died of non-cardiovascular causes (0.078+/-0.005; P<0.05) and 52 patients alive at follow-up (0.075+/-0.003; P<0.05). A Cox proportional hazard model analysis showed that a low (<median) DMA 16/C16:0 ratio at the start of RRT was associated (relative risk 1.50; confidence interval 1.07-2.16; P<0.05) with CVD mortality independently of age, gender, DM and CVD. CONCLUSION: These results suggest that increased oxidative stress may be a risk factor for cardiovascular mortality in ESRD.

Cardiovascular Diseases↗

Chemical study of the mechanism for conversion of dimethylacetal obtained by methanolysis of plasmalogen to alkenylmethylether.

The mechanism for the conversion of dimethylacetal which was obtained by methanolysis of plasmalogen to alkenylmethylether was studied by IR spectroscopy, TLC, GC-MS, 1H-NMR, and 13C-NMR. Heating dimethylacetal in an evacuated sealed glass tube at 250 degrees C for 15 min quantitatively yielded the corresponding alkenylmethylether. The alkenylmethylether yielded two bands of about equal amounts on TLC due to cis and trans configurations at the C-1 and C-2 position. Both 1H-NMR and 13C-NMR showed that the signals of protons and carbons at O-CH3, C-1, and C-2 positions were shifted downfield due to the formation of a double bond between the C-1 and C-2, and that each signal derived from O-CH3, C-1, or C-2 position was divided into two signals due to the formation of cis and trans isomers of the alkenylmethylether. As the two signals had the same intensities, it was suggested that equivalent amounts of cis and trans isomers of the alkenylmether were formed. Since alkenylmethylether was quantitatively converted from dimethylacetal, it was suggested that the alkenylether of plasmalogen could be analyzed as alkenylmethylether together with the fatty acid methylester at the same time by GLC using a silicone capillary column, OV-101.

Acetals↗

Isolation and characterization of new phosphatidylglycerol acetals of plasmalogens. A family of ether lipids in clostridia.

A new phosphatidylglycerol acetal of cardiolipin plasmalogen has been isolated from Clostridium innocuum. The structure was derived from the results of quantitative group analyses, the identification of the products of acid hydrolysis, alkaline methanolysis, hydrolysis by a cardiolipin-specific phospholipase D and by one- and two-dimensional proton NMR. Two other minor ether phospholipids: the lyso form of the phosphatidylglycerol acetal of cardiolipin plasmalogen, and the phosphatidylglycerol acetal of plasmenylglycerol have been identified in C. innocuum lipid extracts.

Acetals↗

Lipids of Sphaerophorus ridiculosis: plasmalogen composition.

Lipid analyses of the anaerobic bacterium Sphaerophorus ridiculosis revealed that 24.2% of the polar lipids are the alk-1'-enyl glyceryl ether (plasmalogen) form. The major polar lipids, phosphatidylethanolamine (67.5%), phosphatidylglycerol (11.2%), cardiolipin (12.0%), and lyso-phosphatidylethanolamine (9.3%), contained 26.3, 7.8, 5.2, and 13.4% plasmalogen, respectively.

Anaerobiosis↗

Plasmalogen composition of Anaeroplasma.

The polar lipids of Anaeroplasma contained 33.1 percent alk-1'-enyl glyceryl ether (plasmalogen) form. Phosphatidylglycerol was the major polar lipid (55.2 percent) and contained nearly all of the plasmalogen. The alk-1'-enyl glyceryl ether form accounted for 58.3 percent of the phosphatidylglycerol.

Aldehydes↗

Activation of myocardial protein kinase C by plasmalogenic diglycerides.

Recently, we have demonstrated that myocardial sarcolemma is predominantly comprised of plasmalogen molecular species and that the plasmalogen metabolite 1-O-alk-1'-enyl-2-acyl-sn-glycerol (AAG) accumulates during myocardial ischemia despite substantial decreases in 1,2-diacyl-sn-glycerol (DAG) content. To elucidate the physiological significance of AAG accumulation during myocardial ischemia, rabbit myocardial protein kinase C was partially purified by DE-52 and high-performance hydroxylapatite chromatographies, and the potency of AAG as an activator of myocardial protein kinase C was assessed. Both AAG and 1-O-alkyl-2-acyl-sn-glycerol are potent activators of myocardial protein kinase C with obligatory requirements for physiological increments in free Ca2+ concentration. In contrast, a substantial amount of myocardial protein kinase C activity elicited by DAG was calcium independent. Concentration dependence of ATP for protein kinase C-mediated phosphorylation was identical utilizing either ether-linked diglycerides or DAG as activators, with maximal phosphorylation manifest at ATP concentrations two orders of magnitude less than those found in ischemic myocardium. Thus accumulation of AAG in ischemic myocardium in conjunction with increases in intracellular free Ca2+ concentration may synergistically activate protein kinase C and therefore modulate phosphorylation of proteins in specific subcellular loci.

Adenosine Triphosphate↗

Selective hydrolysis of plasmalogen phospholipids by Ca2+-independent PLA2 in hypoxic ventricular myocytes.

Accelerated phospholipid catabolism occurs early after the onset of myocardial ischemia and is likely to be mediated by the activation of one or more phospholipases in ischemic tissue. We hypothesized that hypoxia increases phospholipase A2 (PLA2) activity in isolated ventricular myocytes, resulting in increased lysophospholipid and arachidonic acid production, contributing to arrhythmogenesis in ischemic heart disease. The majority of ventricular myocyte arachidonic acid was found in plasmalogen phospholipids. Hypoxia increased membrane-associated, Ca2+-independent, plasmalogen-selective PLA2 activity, resulting in increased arachidonic acid release and lysoplasmenylcholine production. Pretreatment with the specific Ca2+-independent PLA2 inhibitor bromoenol lactone blocked hypoxia-induced increases in PLA2 activity, arachidonic acid release, and lysoplasmenylcholine production. Lysoplasmenylcholine produced action potential derangements, including shortening of action potential duration, and induced early and delayed afterdepolarizations in normoxic myocytes. The electrophysiological alterations induced by lysoplasmenylcholine would likely contribute to the initiation of arrhythmogenesis in the ischemic heart.

Action Potentials↗

Selective plasmalogen substrate utilization by thrombin-stimulated Ca(2+)-independent PLA(2) in cardiomyocytes.

Thrombin stimulation of rabbit ventricular myocytes activates a membrane-associated, Ca(2+)-independent phospholipase A(2) (PLA(2)) capable of hydrolyzing plasmenylcholine (choline plasmalogen), plasmanylcholine (alkylacyl choline phospholipid), and phosphatidylcholine substrates. To identify the endogenous phospholipid substrates, we quantified the effects of thrombin stimulation on diradyl phospholipid mass and arachidonic acid and lysophospholipid production. Thrombin stimulation resulted in a selective decrease in arachidonylated plasmenylcholine, with no change in arachidonylated phosphatidylcholine. The decrease in arachidonylated plasmenylcholine was accompanied by an increase in plasmenylcholine species containing linoleic and linolenic acids at the sn-2 position. A decrease in arachidonylated plasmenylethanolamine was also observed after thrombin stimulation, with no concomitant change in arachidonylated phosphatidylethanolamine. Thrombin stimulation resulted in the selective production of lysoplasmenylcholine, with no increase in lysophosphatidylcholine content. There was no evidence for significant acetylation of lysophospholipids to form platelet-activating factor. Arachidonic acid released after thrombin stimulation was rapidly oxidized to prostacyclin. Thus thrombin-stimulated Ca(2+)-independent PLA(2) selectively hydrolyzes arachidonylated plasmalogen substrates, resulting in production of lysoplasmalogens and prostacyclin as the principal bioactive products.

Animals↗

Bioactive amide of prostaglandin E1 and ethanolamine plasmalogen analog of platelet-activating factor inhibits several pathways of human platelet aggregation.

The influence of an amide of prostaglandin E1 and ethanolamine plasmalogen platelet-activating factor analog 1-O-alk-1;-enyl-2-acetyl-sn-glycero-3-phospho-(N-11alpha, 15alpha-dioxy-9-keto-13-prostenoyl)ethanolamine (PGE1-PPAF) on platelet-activating factor (PAF)-, ADP-, and thrombin-induced human platelet aggregation has been studied. It was found that PGE1-PPAF inhibits the PAF-, ADP-, and thrombin-induced platelet aggregation in platelet-rich plasma. 1-O-alk-1;-enyl-2-acetyl-sn-glycero-3-phosphoethanolamine inhibited PAF-induced aggregation up to 50% but had no influence on platelet aggregation induced by ADP or thrombin. The ethanolamine plasmalogen analog of PAF 1-O-alk-1;-enyl-2-acetyl-sn-glycero-3-phospho-(N-palmitoyl)ethanolami ne, having a palmitoyl residue instead of PGE1, did not inhibit platelet aggregation induced by PAF, ADP, or thrombin. We propose that inhibition of human platelet aggregation by PGE1-PPAF is mediated by its action on platelet PAF-receptors and the adenylate cyclase system.

Alprostadil↗

Serum plasmalogens in ischemic cerebrovascular disease.

Plasmalogens, a subclass of glycerophospholipids are ubiquitous constituents of cellular membranes and serum lipoproteins. Comparing concentrations of plasmalogens in sera from patients suffering from ischemic cerebrovascular disease with serum levels in a normal population significantly lower values were found for patient sera.

Aged↗

[Plasmalogen distribution in the subcellular fractions of the vertebrate brain].

Studies have been made on plasmalogen and diacylic forms of phospholipids, i. e. phosphatidylethanolamine and phosphatidylcholine (their relative content and ratio), in subcellular fractions isolated from the brain of the trout Salmo trideus, frog Rana temporaria, pigeon Columba livia, tortoise Testudo horsfieldi, and rabbit. Investigation was carried out on 5 subcellular fractions (myelin, nuclei, microsomes, mitochondria, synaptosomes) as well as on brain homogenates. In all the fractions, relative content of plasmalogens is the lowest in the trout, increasing in parallel with the increase in the complexity of the nervous system and reaching the highest values in pigeons and rabbits.

Animals↗

Identification of neutral active phospholipase C which hydrolyzes choline glycerophospholipids and plasmalogen selective phospholipase A2 in canine myocardium.

Two novel phospholipase activities have been identified in the cytosolic fraction of canine myocardium. Neutral active phospholipase C activity was partially purified by anion exchange, hydroxylapatite, chromatofocusing, and gel filtration chromatographies. The partially purified enzyme had similar maximum velocities (237 versus 241 nmol/mg X h) and apparent Michaelis constants (20 versus 14 microM) utilizing either plasmenylcholine or phosphatidylcholine as substrate. Myocardial phospholipase C had a pH optimum between 7 and 8, required divalent cations for maximal activity, and did not hydrolyze phosphatidylinositol or sphingomyelin. Myocardial cytosol contained a potent inhibitor of phospholipase C which masked enzymic activity until it was removed during the purification procedure. A plasmalogen selective phospholipase A2 activity was also identified in the cytosolic fraction of canine myocardium. The protein catalyzing this activity was partially purified by DEAE-Sephacel-hydroxylapatite tandem chromatography and exhibited a maximum velocity of 5 nmol/mg X h for plasmenylcholine but only 1 nmol/mg X h for phosphatidylcholine, had a pH optimum between 6 and 7 for both substrates, and did not require calcium ion for activity. These results constitute the first demonstration of a neutral active phospholipase C specific for choline and ethanolamine glycerophospholipids and a plasmalogen selective phospholipase A2 in mammalian tissue.

Animals↗

Chromatographic separation of plasmalogenic, alkyl-acyl, and diacyl forms of ethanolamine glycerophosphatides.

The plasmalogenic, alkyl-acyl, and diacyl forms of ethanolamine glycerophosphatides were completely separated from each other as methylated dinitrophenyl derivatives by thin-layer chromatography on Silica Gel G. The relatively high resolving power needed was obtained by multiple unidimensional development with solvents that give very low mobility to the lipids. Under these conditions the plasmalogens moved fastest, the alkyl-acyl lipids were intermediate, and the diacyl lipids were the slowest. The presence of all these forms of lipids in the ethanolamine phosphatides of hen's eggs, ox brain, and human blood plasma could be directly demonstrated with the new method.

Animals↗

Reactivity of plasmalogens: kinetics of acid-catalyzed hydrolysis.

The acid-catalyzed hydrolysis of the alpha,-unsaturated ether group of two plasmalogens, lysophosphatidal choline and lysophosphatidal ethanolamine, and several model compounds (isobutyl vinyl ether, 1-butenyl ethyl ether, and dihydropyran) was studied by determining the true second-order rate constants. The results indicate that the chemical reactivity of the substituted vinyl ether group in plasmalogens is not appreciably affected by the presence of a bulky substituent on the -carbon. Activation energies, enthalpies, and entropies were also determined (from measurements of the rate constants at different temperatures).

Chemical Phenomena↗

Quantitative micro determination and isolation of plasmalogen aldehydes as 2,4-dinitrophenylhydrazones.

A micro spectrophotometric procedure for the quantitative determination of plasmalogen aldehydes is described which utilizes simultaneous methanolysis and formation of 2,4-dinitrophenylhydrazones. After isolation of the hydrazones by thin-layer chromatography, the aldehydes can be regenerated, reduced, acetylated, and then analyzed by gas-liquid chromatography. Identification of the plasmalogen aldehydes obtained from rumen holotrich protozoa is described.

Aldehydes↗

Viscoelasticity of BLM from choline plasmalogen, alkylacyl- and diacyl-glycerophosphocholines.

Mechanical characteristics of bilayer lipid membranes (BLM) composed of alkenylacyl-, alkylacyl-, and diacyl-glycerophosphocholines were studied by measuring modulus of elasticity in the direction normal to BLM plane, E perpendicular, and coefficient of dynamic viscosity eta. Alkenylacyl-glycerophosphocholine (choline plasmalogen) BLM typically show larger values of E perpendicular and eta as compared to their analogs, suggesting a tighter packing of their hydrophobic regions. Increasing cholesterol concentrations are associated with monotonically increasing values of parameters E perpendicular and eta of plasmalogen BLM, whereas a nonmonotonic dependence of these parameters with a maximum around c = 66 mol% cholesterol is typical for the diacyl analog POPC. This may be due to the formation of cholesterol clusters at c > 66 mol%.

Cholesterol↗

Identification and characterization of alkenyl hydrolase (lysoplasmalogenase) in microsomes and identification of a plasmalogen-active phospholipase A2 in cytosol of small intestinal epithelium.

A lysoplasmalogenase (EC 3.3.2.2; EC 3.3.2.5) that liberates free aldehyde from 1-alk-1'-enyl-sn-glycero-3-phospho-ethanolamine or -choline (lysoplasmalogen) was identified and characterized in rat gastrointestinal tract epithelial cells. Glycerophosphoethanolamine was produced in the reaction in equimolar amounts with the free aldehyde. The microsomal membrane associated enzyme was present throughout the length of the small intestines, with the highest activity in the jejunum and proximal ileum. The rate of alkenyl ether bond hydrolysis was dependent on the concentrations of microsomal protein and substrate, and was linear with respect to time. The enzyme hydrolyzed both ethanolamine- and choline-lysoplasmalogens with similar affinities; the Km values were 40 and 66 microM, respectively. The enzyme had no activity with 1-alk-1'-enyl-2-acyl-sn-glycero-3-phospho-ethanolamine or -choline (intact plasmalogen), thus indicating enzyme specificity for a free hydroxyl group at the sn-2 position. The specific activities were 70 nmol/min/mg protein and 57 nmol/min/mg protein, respectively, for ethanolamine- and choline-lysoplasmalogen. The pH optimum was between 6.8 and 7.4. The enzyme required no known cofactors and was not affected by low mM levels of Ca2+, Mg2+, EDTA, or EGTA. The detergents, Triton X-100, deoxycholate, and octyl glucoside inhibited the enzyme. The chemical and physical properties of the lysoplasmalogenase were very similar to those of the enzyme in liver and brain microsomes. In developmental studies the specific activities of the small intestinal and liver enzymes increased markedly, 11.1- and 3.4-fold, respectively, in the first approximately 40 days of postnatal life. A plasmalogen-active phospholipase A2 activity was identified in the cytosol of the small intestines (3.3 nmol/min/mg protein) and liver (0.3 nmol/min/mg protein) using a novel coupled enzyme assay with microsomal lysoplasmalogenase as the coupling enzyme.

Aldehydes↗

THE MAGNESIUM-ION-DEPENDENT CLEAVAGE OF THE VINYL ETHER LINKAGE OF BRAIN ETHANOLAMINE PLASMALOGEN.

1. There was a significant decrease in the amount of endogenous ethanolamine phospholipids when preparations of whole brain were incubated in bicarbonate-Ringer solutions, leading in particular to the hydrolysis of vinyl ether groups. 2. The hydrolysis of ethanolamine phospholipids in such preparations was abolished in the absence of bivalent cations. 3. An enzyme present in extracts of acetone-dried brain powders that cleaved the vinyl ether linkage in ethanolamine plasmalogen maximally at pH 7.4 required Mg(2+) for activity. 4. The cleavage of the vinyl ether linkage of an ethanolamine lysoplasmalogen was enhanced in the presence of Mg(2+) but the requirement was not absolute.

Brain↗