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Accumulation of N-acyl-ethanolamine phospholipids in rat brains during post-decapitative ischemia: a 31p NMR study.

Phosphorus-31 nuclear magnetic resonance (31P NMR) spectroscopy has been used to study accumulation of N-acyl-ethanolamine phospholipids in rat brains during post-decapitative ischemia. Lipids were extracted from rat brain homogenates and the extracts were thoroughly washed with aq. potassium ethylenediaminetetraacetic acid (EDTA). The lower organic phases were isolated and evaporated to dryness under a stream of nitrogen and the lipids were redissolved in CDCl3-CH3OH-H2O 100.0:29.9:5.2 (v/v/v) for NMR analysis. Increasing the period of post-decapitative ischemia resulted in an accumulation of two signals in the NMR spectra at 0.18 and 0.22 ppm (relative to the chemical shift of 1,2-diacyl-sn-glycero-3-phosphocholine (PCDIACYL) at -0.84 ppm). These signals were identified as originating from 1,2-diacyl-sn-glycero-3-phospho-(N-acyl)-ethanolamine (NAPEDIACYL) and 1-(1'-alkenyl)-2-acyl-sn -glycero-3-phospho-(N-acyl)-ethanolamine (NAPEPLAS), respectively, by spiking with authentic materials. Additionally, the identification was verified by thin-layer chromatography, which also showed the accumulation of N-acyl-ethanolamine phospholipids. The use of K-EDTA instead of the commonly used Cs-EDTA in the preparation of the NMR samples allowed the separation of the chemical shifts of N-acyl-ethanolamine phospholipids from those of the ethanolamine phospholipids. Moreover, the chemical shift of cardiolipin was moved from 0.15 ppm observed with Cs-EDTA to about 0.31 ppm with K-EDTA. The present study demonstrates that it is possible to detect and quantify post-decapitative accumulation of NAPE subclasses (NAPEDIACYL and NAPEPLAS) in rat brains by the use of 31P NMR spectroscopy.

Acylation↗

An experimental study on hepatotoxicity of sclerosant ethanolamine oleate flowed into portal vein.

Although endoscopic injection sclerotherapy has been a main treatment option for gastroesophageal varices, intraportal inflow of the sclerosant, ethanolamine oleate, induce liver damage. The aim of this study was to clarify the liver damage due to intraportal inflow of ethanolamine oleate. Ethanolamine oleate suspension was injected into livers of male Wistar rats via the portal (ileocolic) vein. Degrees of liver damage were evaluated by serum levels of transaminases and by histological examination. Intraportal injection of ethanolamine oleate led to extensive liver necrosis, which was marked 1 day after the injection and recovered by 7 days after injection. Liver necrosis became severe as the dose of the injected sclerosant increased. Histologically, neither portal thrombosis nor embolism was evident. Carbon powder particles of India ink, which were injected together with ethanolamine oleate, reached and deposited in sinusoids of the necrotic portions of the liver. These findings suggested that the liver damage had not developed simply as a result of impairment of portal blood flow. Ethanolamine oleate may itself have direct hepatotoxic effects.

Animals↗

Phospholipids of rat tissues after feeding pure phosphatidyl ethanolamine and lecithin.

Pure phosphatidyl ethanolamine and lecithin from egg yolks were fed to rats in saline or in olive oil and the changes in individual phospholipids in the intestinal wall, liver, and plasma of the animals were studied. Ingestion of olive oil alone produced increased levels of all phospholipid fractions in each of the three tissues. Feeding phosphatidyl ethanolamine in saline resulted in slightly increased plasma phospholipids, but levels of liver total phospholipids were greatly reduced; when phosphatidyl ethanolamine was fed with olive oil, liver phospholipids were again reduced but this reduction was confined to the phosphatidyl ethanolamine and phosphatidic acid fractions. Feeding lecithin alone did not produce significant changes in levels of plasma or tissue phospholipids. The results suggest that liver phospholipid synthesis is depressed by feeding phosphatidyl ethanolamine; in the presence of olive oil, hepatic synthesis of phosphatidyl ethanolamine seems to be more selectively inhibited.

Journal Article↗

Changes in the composition of fatty chains of diacyl, alkylacyl and alkenylacyl ethanolamine and choline phosphoglycerides during the development of chick heart ventricular cells. High accumulation of 22-carbon fatty acid in ether phospholipids.

The phospholipids of embryonic chick ventricular cells were analysed at various developmental stages with respect to the composition of alkylacyl, alkenylacyl and diacyl ethanolamine and choline phosphoglycerides and for the fatty chain composition of these lipid classes. The percentage of alkylacyl and alkenylacyl choline phosphoglycerides increased in the course of the development. The fatty chain composition of ether-linked phosphoglycerides was significantly different from that of the diacyl compound. In general, both ether choline and ethanolamine phosphoglycerides consisted of a significantly higher percentage of 22-carbon fatty chains, such as 22:4, 22:5 and 22:6, compared to that of the diacyl compounds, throughout the earlier stage of development. During development, there was a dramatic increase of 20:4 and a decrease of 22:6, mainly in total ethanolamine phosphoglycerides but also in choline phosphoglycerides. A particularly significant decrease of 22:6 was found with diacyl ethanolamine phosphoglycerides. When 14C-labeled 22:4 and 3H-labeled 20:4 were incorporated into the ethanolamine and choline phosphoglycerides of ventricles in vitro, it was observed that 22:4 was mainly associated with ether phospholipids, especially the ethanolamine alkyl ether phospholipids, suggesting that there is a high selectivity of 22-carbon fatty acid to ether phospholipids during the synthesis of these compounds.

Aging↗

Studies on the embryopathic effects of ethanolamine in Long-Evans rats: preferential embryopathy in pups contiguous with male siblings in utero.

The embryopathic effects of high doses of ethanolamine were evaluated in pregnant Long-Evans rats during the "critical period" or organogenesis. Ethanolamine was given by gavage at levels of 0, 500, 300, or 50 mg/kg/day (24%, 14.4%, or 2.4% of the LD50 value). Ethanolamine caused dose-dependent increases in intrauterine deaths, malformations, and intrauterine growth retardation. Embryolethality caused by 500 mg/kg of ethanolamine was not random: male pups contiguous to two male siblings (designated mMm) were almost quantitatively replaced by resorptions that were contiguous to two live male pups (designated mRm) (mMm pups constituted 6.7% of control implants and decreased to only 0.9% of group II implants while mRm resorptions increased from 0.3% in controls to 5.6% in group II dams). Intrauterine growth retardation and increases in gross structural anomalies (considered indicative of depressed fetal growth) more severely affected male than female offspring at all dose levels. Pups of either sex who were contiguous to male siblings were more adversely affected than those offspring contiguous to one or more female siblings. As ethanolamine was given prior to the period of greatest fetal growth and fetal sex steroidogenesis, it is suggested that intrauterine levels of female sex steroids (estradiol) enhance fetal repair of cellular damage while testosterone inhibits fetal repair or exacerbates previous embryonic damage by some unknown mechanism. Such interaction furthers the concept that intrauterine position affects the endpoints of developmental toxicity, as expressed at parturition.

Animals↗

Incorporation of [3H]ethanolamine into a single cytosolic protein in a cell free system: ethanolaminylation of EF-1 alpha in vitro.

Ethanolamine containing modifications of cytosolic proteins have only been described for elongation factor 1 alpha (EF-1 alpha) which contains two ethanolamine-phosphoglycerol moieties at Glu 301 and 374 (Whiteheart et al. (1989) J. Biol. Chem. 264, 14334-14341 and Dever et al. (1989) J. Biol. Chem. 264, 20518-20525). In this report, we describe a cell-free, cytosolic extract which specifically incorporates [3H]ethanolamine into a single cytosolic protein with properties identical to EF-1 alpha. The incorporation reaction is dependent on time and extract and is independent of any membrane-bound components. The single in vitro-radiolabeled protein is modified on two sites and chromatographic analysis of pronase-digested peptides is consistent with the addition of an unmodified ethanolamine. Ethanolaminylation does not require divalent cations or ATP but is inhibited by N-ethylmaleimide and stimulated by reducing agents (beta-mercaptoethanol and dithiothreitol), indicating the requirement for free sulfhydryls. The nucleophile, hydroxylamine, at low concentrations, greatly inhibits the incorporation reaction, indicating the importance of an electrophilic center. This cytosolic extract appears to be able to carry out only the initial step in the addition of the ethanolamine-phosphoglycerol moieties to EF-1 alpha, and subsequent addition of the phosphoglycerol moiety appears to require membrane components.

Animals↗

Rat lens choline and ethanolamine kinases: independent kinetics in intact tissue-competition in homogenates.

In the committed step of phosphatidylcholine and phosphatidylethanolamine synthesis, choline and ethanolamine are phosphorylated to form phosphocholine and phosphoethanolamine. Studies of rat tissues in several laboratories attribute these two kinase activities to a single enzyme for which choline and ethanolamine are competing alternative substrates. However, in this study of intact cultured lenses, choline and ethanolamine were phosphorylated independently, and neither compound inhibited phosphorylation of the other, even at high lenticular concentrations. In contrast, choline kinase in lens homogenates was competitively inhibited by ethanolamine (Ki = 2.3 mM), and choline strongly inhibited ethanolamine kinase activity. The results suggest a fragile metabolic compartmentation or organization of kinase enzyme(s) or substrates within the intact, physiologically integrated lens which results in striking changes in kinetic characteristics when the biological organization of the lens is disrupted.

Animals↗

Clofibrate and other peroxisomal proliferating agents relatively specifically inhibit synthesis of ethanolamine phosphoglycerides in cultured human fibroblasts.

Effects of several classes of peroxisomal proliferators on peroxisomal functions, hepatomegaly, hepatocarcinogenesis and lipid metabolism have been extensively investigated in rodents. Less is known about influences of these agents, some used as hypolipidemic drugs, on various metabolic parameters in humans. We examined effects of clofibrate, di(2-ethyl-hexyl)phthalate (DEHP) and pirinixic acid (WY-14,643) on phospholipid metabolism in human fibroblasts in culture. Clofibrate inhibited incorporation of [1-14C]hexadecanol and [1-14C]linolenic acid into ethanolamine phosphoglycerides in a time- and concentration-dependent manner; labeling of plasmalogens and non-plasmalogen ethanolamine phosphoglycerides was reduced by 40-80% compared to a generalized 10-30% inhibition of labeling of other phospholipids, including phosphatidylcholine. In pulse and pulse-chase experiments, selective inhibition of incorporation of [1,2-14C]ethanolamine, compared to [methyl-3H]choline, confirmed relative specificity of inhibition of ethanolamine phosphoglycerides. Similar concentration dependence and specificity for inhibition of phospholipid turnover was observed for DEHP and WY-14,643, in both control and mutant (Zellweger and adrenoleukodystrophy) fibroblasts, in the absence of major effects on peroxisomal markers. These observations that peroxisomal proliferators specifically inhibit ethanolamine phosphoglyceride turnover in human fibroblasts should be considered when assessing the efficacy and safety of such agents as hypolipidemic drugs or when evaluating mechanisms of proliferator action at the cellular level.

Cells, Cultured↗

Ethanolamine mimics insulin effects in vitro.

The comparative effects of insulin and ethanolamine on 14CO2 production and lipid synthesis from [U-14C]-D-glucose in isolated rat adipocytes were studied. Ethanolamine (10 mM) increased 14CO2 production (glucose oxidation) about 5-fold and lipogenesis about 3-fold as compared to the control. Ethanolamine was more efficient than 25 microU/ml insulin regarding both parameters, but it was less efficient than 200 microU/ml insulin in glucose oxidation, and equally potent in lipogenesis. The combination of ethanolamine and insulin was more active than insulin alone. The mechanisms of ethanolamine action include facilitation of glucose transport and increase of pyruvate dehydrogenase activity.

Adipose Tissue↗

In vitro effects of ethanolamine on insulin secretion.

The effects of ethanolamine on insulin secretion by the perfused rat pancreas were examined. During the second phase of glucose-induced insulin secretion 5-minute perfusions of ethanolamine at final concentrations of 0.1, 1 and 10 mM inhibited insulin release in a dose-related manner. When given throughout the experiment the highest dose of ethanolamine markedly suppressed both phases of glucose-induced insulin release. The inhibitory effect of ethanolamine was blunted in the presence of phentolamine. It is concluded that ethanolamine inhibits glucose-induced insulin secretion by the perfused rat pancreas and that alpha-adrenergic receptors play a role in its actions on insulin output.

Animals↗

Lipid metabolism in T47D human breast cancer cells: 31P and 13C-NMR studies of choline and ethanolamine uptake.

31P and 13C-NMR were used to determine the kinetics of choline and ethanolamine incorporation in T47D clone 11 human breast cancer cells grown as small (150 microns) spheroids. Spheroids were perfused inside the spectrometer with 1,2-13C-labeled choline or 1,2-13C-labeled ethanolamine (0.028 mM) and the buildup of labeled phosphoryl-choline (PC) or phosphorylethanolamine (PE) was monitored. Alternatively the PC and GPC pools were prelabeled with 13C and the reduction of label was monitored. 31P spectra were recorded from which the overall energetic status as well as total pool sizes could be determined. The ATP content was 8 +/- 1 fmol/cell, and the total PC and PE pool sizes were 16 and 14 fmol/cell, respectively. PC either increased by 50% over 24 h or remained constant, while PE remained constant in medium without added ethanolamine but increased 2-fold within 30 h in medium containing ethanolamine, indicating a dependence on precursor concentration in the medium. The 31P and 13C data yielded similar kinetic results: the rate of the enzymes phosphocholine kinase and phosphoethanolamine kinase were both on the order of 1.0 fmol/cell per h, and the rate constants for CTP:phosphocholine cytidyltransferase and CTP:phosphoethanolamine kinase were 0.06 h-1 for both enzymes. The kinetics of choline incorporation did not alter in the presence of 0.028 mM ethanolamine indicating that they have non-competing pathways.

Breast Neoplasms↗

Characterization of [3H]palmitate- and [3H]ethanolamine-labelled proteins in the multicellular parasitic trematode Schistosoma mansoni.

Biosynthetic labelling experiments with cercariae and schistosomula of the multicellular parasitic trematode Schistosoma mansoni were performed to determine whether [3H]palmitate or [3H]ethanolamine was incorporated into proteins. Parasites incorporated [3H]palmitate into numerous proteins, as judged by SDS/polyacrylamide-gel electrophoresis and fluorography. The radiolabel was resistant to extraction with chloroform, but sensitive to alkaline hydrolysis, indicating the presence of an ester bond. Further investigation of the major 22 kDa [3H]palmitate-labelled species showed that the label could be recovered in a Pronase fragment which bound detergent and had an apparent molecular mass of 1200 Da as determined by gel filtration on Sephadex LH-20. Schistosomula incubated with [3H]ethanolamine for up to 24 h incorporated this precursor into several proteins; labelled Pronase fragments recovered from the three most intensely labelled proteins were hydrophilic and had a molecular mass of approx. 200 Da. Furthermore, reductive methylation of such fragments showed that the [3H]ethanolamine bears a free amino group, indicating the lack of an amide linkage. We also evaluated the effect of phosphatidylinositol-specific phospholipase C from Staphylococcus aureus: [3H]palmitate-labelled proteins of schistosomula and surface-iodinated proteins were resistant to hydrolysis with this enzyme. In conclusion, [3H]palmitate and [3H]ethanolamine are incorporated into distinct proteins of cercariae and schistosomula which do not bear glycophospholipid anchors. The [3H]ethanolamine-labelled proteins represent a novel variety of protein modification.

Amino Acids↗

Interrelationships between the enzymes of ethanolamine metabolism in Escherichia coli.

The activities of the enzymes ethanolamine ammonia-lyase, CoA-dependent and CoA-independent aldehyde dehydrogenases, and isocitrate lyase were assayed in Escherichia coli which had been grown on various sources of carbon and nitrogen. Induction of ethanolamine ammonia-lyase and of maximal levels of both aldehyde dehydrogenases required the concerted effects of ethanolamine and vitamin (or coenzyme) B12. Molecular exclusion chromatography revealed that, in the absence of one or both co-inducers, two repressible isoenzymes of CoA-dependent aldehyde dehydrogenase (mol. wts 900000 and 120000) were produced, these being replaced by two inducible isoenzymes (mol. wts 520000 and 370000) in the presence of both co-inducers. A similar inducible repressible series of isoenzymes was also observed for CoA-independent aldehyde dehydrogenase. No evidence was found for structural relationships between ethanolamine ammonia-lyase, CoA-dependent aldehyde dehydrogenase and CoA-independent aldehyde dehydrogenase, but mutant and physiological studies demonstrated that the induction of the first two enzymes is under common control. Evidence is presented for the operation of a previously unreported pathway of ethanolamine metabolism in E. coli.

Aldehyde Dehydrogenase↗

Release of ethanolamine, but not of serine or choline, in rat pontine nuclei on stimulation of afferents from the cortex, in vivo.

Release of ethanolamine, serine, and choline in rat pontine nuclei on electrical stimulation of afferents from the cortex was investigated using in vivo push-pull cannula techniques. Ethanolamine was determined by using gas chromatographic techniques; serine was measured with a HPLC system; and choline was assayed with a luminescence method. Resting elution rates of ethanolamine, serine, and choline were 50.8 +/- 8.4, 34.8 +/- 12.6, and 1.16 +/- 0.20 pmol/5 min, respectively. Stimulation of the cortico-pontine tract evoked a highly significant 3.4-fold increase in release of ethanolamine, whereas serine and choline release was unaffected. Reactions in membrane phospholipids are most likely involved in the stimulation-dependent release of ethanolamine and special consideration was given to base-exchange reactions. Alternatively, a release from intracellular, possibly synaptic stores cannot be excluded.

Afferent Pathways↗

Incorporation of glycerol and ethanolamine into glycerophospholipid in rat brain areas during bicuculline-induced convulsive seizures.

The effect of bicuculline-induced convulsive seizures on lipid metabolism has been studied in four brain areas (cerebellum, cerebral cortex, hippocampus, and brainstem) using [2-3H]glycerol and [1,2-14C]ethanolamine as radioactive lipid precursors administered simultaneously with bicuculline. Twelve minutes after the administration, the uptake of radioactivity depended both on brain area and treatment, being generally higher in convulsing rats. The uptake of glycerol was influenced to a larger extent than that of ethanolamine and increased during convulsions, but its incorporation into lipids did not. In contrast, the amount of ethanolamine incorporated into lipids increased during bicuculline-induced seizures. The difference in behavior of glycerol and of ethanolamine is also indicated by the decrease of the 3H/14C ratio of phosphatidyl-ethanolamine in various brain areas during convulsions. It is, therefore, evident that the metabolism of the two precursors is affected differently by seizures.

Animals↗

Use of radioactive ethanolamine incorporation into phospholipids to assess in vitro antimalarial activity by the semiautomated microdilution technique.

Phospholipid biosynthetic activity is intense in the erythrocytic stage of Plasmodium falciparum because of the parasite's own enzymatic machinery. The incorporation of various labeled phospholipid precursors in comparison with the incorporation of nucleic acid and protein precursors was tested to evaluate P. falciparum growth in vitro. These precursors, namely, [3H]ethanolamine, [3H]hypoxanthine, [3H]palmitate, [14C]serine, [3H]choline, [3H]inositol, and [3H]isoleucine, were all accurate indicators of parasite growth. However, because of its high level of incorporation, [3H]ethanolamine proved to be the best tool for assessing parasite viability. When culture parameters were carefully controlled, [3H]ethanolamine incorporation into phospholipids was proportional to pulse time, precursor concentration, and initial parasitemia and was sensitive to the number of uninfected erythrocytes (hematocrit). It can be used for a wide range of infected erythrocytes, from 2 x 10(4) to 5 x 10(5). The use of [3H]ethanolamine for in vitro antimalarial drug screening is a good alternative to the method of Desjardins et al. (R. E. Desjardins, C. J. Canfield, J. D. Haynes, and J. D. Chulay, Antimicrob. Agents. Chemother. 16:710-718, 1979). The major advantage is that the culture medium can be supplemented with hypoxanthine, which results in better parasite growth. [3H]ethanolamine is also an ideal tool when compounds that interfere with DNA and/or RNA metabolism are to be investigated for their effect on Plasmodium growth.

Animals↗

Secretion of VLDL, but not HDL, by rat hepatocytes is inhibited by the ethanolamine analogue N-monomethylethanolamine.

The role of phospholipids in the assembly and secretion of very low density lipoproteins (VLDL) has been investigated by incubation of monolayer cultures of rat hepatocytes with monomethylethanolamine, an analogue of ethanolamine and choline. The cellular concentration of phosphatidylmonomethylethanolamine was increased 17-fold in response to treatment of hepatocytes with monomethylethanolamine. The secretion of phosphatidylcholine, triacylglycerol, and the apolipoproteins BH, BL, and E into VLDL was inhibited by approximately 50% in hepatocytes incubated with monomethylethanolamine, compared to untreated cells. Cell viability was unaffected by treatment with the ethanolamine analogue, as was cellular protein synthesis. The mechanism by which monomethylethanolamine reduced VLDL secretion was examined. Since monomethylethanolamine is a structural analogue of ethanolamine and choline, an obvious hypothesis for explanation of the effect on VLDL secretion was that phosphatidylcholine biosynthesis, which is required for VLDL secretion (Z. Yao and D. E. Vance. 1988. J. Biol. Chem. 263: 2998-3004) was inhibited. However, the biosynthesis of phosphatidylcholine from [3H]choline or from [3H]glycerol was not significantly reduced in the analogue-treated, compared with the untreated, hepatocytes. Nor was the incorporation of [3H]glycerol into cellular triacylglycerol altered in the monomethylethanolamine-treated cells. Furthermore, addition of monomethylethanolamine to hepatocytes did not reduce the rate of biosynthesis of phosphatidylethanolamine either from CDP-ethanolamine or from phosphatidylserine, nor was phosphatidylserine biosynthesis from [3-3H]serine affected. The 50% inhibition of VLDL secretion elicited by monomethylethanolamine was apparently specific for VLDL because there was no difference in secretion of HDL (lipid or apoprotein moieties) or albumin by cells incubated with or without the ethanolamine analogue. The experiments showed that inhibition of VLDL secretion by monomethylethanolamine was not the result of decreased biosynthesis of phospholipids, triacylglycerols, or cholesteryl esters. More subtle effects of the ethanolamine/choline analogue, for example interference by the increased amount of phosphatidylmonomethylethanolamine, in the process of assembly of lipids with apoB remain a possibility.

Animals↗

Studies of rat brain choline ethanolamine phosphotransferases using labeled alkylacylglycerol as substrate with evidence for reversibility of the reactions.

Cholinephosphotransferase activity in brain microsomes may be assayed with labeled alkylacylglycerols or with CDP-choline with label in the phosphocholine with nearly identical results. The direct linear plot method was used for evaluation of Michaelis-Menten kinetic parameters. Most of the cholinephosphotransferase activity is in microsomes and a stimulatory factor seems to be present in the cytosol. Incubation of microsomes with labeled alkylacylglycerols and CDP-choline, in the initial absence of CDP-ethanolamine, produced labeled ethanolamine glycerophospholipids as well as labeled choline glycerophospholipids. Since the labeling of ethanolamine glycerophospholipids was increased by the addition of CMP, the labeling was probably due to the reversal of ethanolamine phosphotransferase to yield CDP-ethanolamine produced by the choline phosphotransferase reaction. Cholinephosphotransferase was reversed more readily than ethanolaminephosphotransferase in brain as it is in liver (Kanok and Ohno, 1973). Only trace quantities of plasmalogens were formed with labeled alkylacylglycerols. Previous results of plasmalogen labeling from labeled CDP-nucleotides were apparently due to reversal of phosphotransferase reactions. Alkylacylglycerophospholipids are not good substrates for plasmalogen formation, even when they are incorporated into microsomes.

Animals↗