Synthesis of ethriolophospholipids of acetal type

New analogues of acetal-type phospholipids were obtained on the basis of ethriol (2-hydroxymethyl-2-ethyl-1,3-propanediol). The starting triol originally was condensed with decanal or dodecanal to form acetals, which were then phosphorylated with tetraethyldiamidophosphorous acid chloride. The amidophosphites were further oxidized with iodosobenzene or sulfurized to the corresponding acetal-type phospholipids and their thio analogues.     

Use of phospholipase A to compare phospholipid organization in synaptic membranes,myelin, and liposomes

Summary The pattern of fatty acid release from rat synaptic membranes in the presence of phospholipase A₂ (Vipera russelli) was compared to that from liposomes comprised of phospholipids. Phospholipase A₂ more readily attacked myelin and synaptic membranes than liposomes prepared from total phospholipids derived from myelin. Although hydrolysis of liposomal phospholipids occurred in the absence of added calcium, the presence of 2mm CaCl₂ or 2% bovine serum albumin significantly enhanced the phospholipase attack of liposomes, but not synaptic membranes or myelin. Phospholipase exhibited a marked preference for phospholipids containing docosahexaenoic acid (226) in the synaptic membranes, while with liposomes the pattern of released fatty acid reflected the fatty acid composition in the two-position of the phospholipids. Although either calcium or albumin markedly increased the phospholipase hydrolysis of liposomes, neither affected the hydrolysis of synaptic membranes or the pattern of fatty acid release from liposomes. It was concluded that the nonlipid constituents, particularly the proteins, of biomembranes were responsible for the organization of the phospholipids and accounted for the observed differences between liposomes and synaptic membranes with respect to enzymic accessibility.     

Synthesis of acetal and phosphocyclic methriolipids

The first representatives of acetal and phosphocyclic lipids based on methriol (2-hydroxymethyl-2-methyl-1,3-propanediol) were synthesized. The interaction of the starting triol with higher aldehydes gave the corresponding alkylidene compounds, which were subsequently phosphorylated by derivatives of phosphorous acid. The intermediate amidophosphites were treated without isolation with iodobenzene, sulfur, or selenium to give phosphoacetals and their thio-and selenoanalogues, which are acetal phospholipids. Methriol bicyclophosphite was also used in the lipid synthesis. It was acylated with palmitoyl chloride at one of the bicyclic oxygen atoms. Alcoholysis of acyl polyol chlorophosphite resulted in a phospholipid, which was oxidized with sulfur to give thionphosphate.     

The cardiolipin analogues of Archaea

The present article reviews studies of the structure and functional roles of the cardiolipin analogues of extremely halophilic prokaryotes belonging to the Archaea domain. Analogies and differences between the archaeal bisphosphatidylglycerol and the mitochondrial cardiolipin are presented. Furthermore the structure of archaeal glycophospholipid dimers is illustrated together with the available information on their function. The studies on the function of cardiolipin analogues in archaebacteria point out the tight interaction established by these phospholipids with membrane proteins and their role as bioactive lipids in the adaptation of microorganisms to osmotic stress.     

Effects of Short- and Long-Term Protriptyline Treatment on Phospholipid Metabolism in Rat Brain

Wistar rats were injected intraperitoneally with 10 mg/kg of protriptyline according to one of the following schedules: a single dose or daily for 4 days (short-term), or daily for 2 or 13 weeks (long-term). Total lipid, total phospholipid, and individual phospholipid contents in the brain were determined. Further, the incorporation of 32P into individual phospholipids in vivo and the fatty acid composition of phosphatidylethanolamine in the brains of rats treated with protriptyline for 13 weeks were studied. Three alternative phases of changes of total and individual phospholipid contents in the brain during 13 weeks of experimentation were distinguished. An increase of phospholipid contents after 4 days, a decrease after 2 weeks, and a further increase after 13 weeks of protriptyline administration were found. However, phosphatidylinositol and phosphatidic acid levels after 13 weeks of protriptyline administration were diminished. The decrease of specific radioactivity of phosphatidylethanolamine, phosphatidylcholine, and phosphatidylserine and the increase of phosphatidylinositol, phosphatidic acid, and sphingomyelin in rats treated with the drug for a longer period of time were noted. No greater differences in fatty acid composition of phosphatidylethanolamine in the brains of the same group of rats were observed as compared to control. These results indicate that during long-term treatment with protriptyline the contents of lipids and phospholipids in rat brain are altered. The modification of the biological function of phospholipids in brain cell membranes is suggested.     

Effects of light on phospholipid metabolism in DunaUella salina

Dunalliella salina (Teodoresco) is a unicellular, wall-less, halotolerant green alga. Previous work has shown that levels of inositol phospholipiils in whole cells of D. salina fluctuate in response to hyper- and hypo-osmotic shock. In this paper, we report the effects of changes in the light environment on levels of phospholipids, including inositol phospholipids, in D. scilina. Utilizing both short-term and long-term labeling of phospholipids with ³²PO₄, we were able to compare both immediate and long-term changes in lipid metabolism during changes in the light environment. Relative to the other phospholipids. phosphotidic acid and the inositol phospholipids phosphatidylinositol, phosphatidylinositol 4-phosphate and phosphatidylinositol 4,5-bisphosphate were rapidly labeled, even in the dark, suggesting that the metabolism of these compounds is more active than that of the bulk cellular phospholipids. There was little change in inositol phospholipid metabolism when cells were illuminated following a 1 h dark adaptation period, Furthermore, the inositol phospholipid signal transduction pathway did not respond to severe photoinhibition treatment. Apparently this plasma-membrane-based signal transduction pathway, which responds to changes in the external environment, is relatively insensitive to major changes in chloroplast metabolism.     

磷脂酰丝氨酸外翻和磷脂氧化在凋亡细胞被吞噬细胞清除过程中的协作效应

为探讨磷脂酰丝氨酸(phosphatidylserine,PS)外翻和磷脂氧化在凋亡细胞被吞噬细胞清除中的作用,用脂质体整合的方法将不同的磷脂整合到红细胞上或用N-乙酰马来酰胺(N-ethylmaleimide,NEM)预处理红细胞然后整合磷脂,制备含不同凋亡信号的红细胞模型,测定巨噬细胞对整合不同磷脂信号红细胞的结合率和吞噬率。结果表明,单独整合PS或用NEM处理造成PS外翻,可显著性提高巨噬细胞对红细胞的结合率,但对吞噬率没有影响;同时整合PS和氧化磷脂(氧化PS或氧化磷脂酰胆碱(phosphatidylcholine,PC)),或用NEM处理造成PS外翻后再整合氧化PS或氧化PC,不仅可显著提高巨噬细胞对红细胞的结合率,而且可显著性提高吞噬率。这些结果提示PS外翻可能参与了巨噬细胞对凋亡细胞的结合,而磷脂氧化可能启动了巨噬细胞对凋亡细胞的吞噬,二者协作才可能完成巨噬细胞对凋亡细胞的清除。     

Comparison of linoleate,palmitate and acetate metabolism in rat ventral prostate

Rat ventral prostate incorporated (1-¹⁴C)acetate, (1-¹⁴C)palmitate and (1-¹⁴C)linoleate into different phospholipids in a time-dependent process. The rate of incorporation into total phospholipids was higher with linoleate (10.0 nmol/g) than with either palmitate (5.8 nmol/g) or acetate (4.7 nmol/g). Predominant labelling with all the radioactive substrates assayed was found in choline glycerophospholipids (PC). The radioactive profiles for linoleate in the other ventral prostate phospholipids differed from those obtained with palmitate and acetate. Specifically linoleate was incorporated into inositol glycerophospholipids plus lysoethanolamine glycerophospholipids (PI+LPE) and not into sphingomyelin (SM), while palmitate and acetate incorporated into SM but not into PI+LPE. Acetate showed the highest oxidation to CO₂ whereas no differences were observed in the radioactivity incorporated into CO₂ from a saturated (palmitate) or an essential unsaturated fatty acid (linoleate). These studies also show zinc-dependence by the acetate to CO₂ oxidation.Abbreviations PL total phospholipids - PC choline glycerophospholipids - PE ethanolamine glycerophospholipids - PI+LPE inositol glycerophospholipids plus lysoethanolamine glycerophospholipids - PS serine glycerophospholipids - SM sphingomyelin     

Head group-independent interaction of phospholipids with bile salts. A fluorescence and EPR study

Bile salts are essential for phospholipid secretion into the bile. To study the relevance of the structure of phospholipids for their interaction with bile salts, we used spin-labeled or fluorescent phospholipid analogues of different head groups and acyl chain length. Those analogues form micelles in aqueous suspension. Their solubilization by bile salts resulting in the formation of mixed micelles was followed by the decrease of spin-spin interaction of spin-labeled analogues or by the relief of fluorescence self-quenching of (7-nitro-2-1,3-benzooxadiazol (NBD))-labeled analogues. Solubilization of analogue micelles occurred at and above the critical micellar concentration (CMC) of the bile salts. As revealed by stopped-flow technique, solubilization of NBD-analogues was very rapid with half times as low as 0.1 sec above the CMC of taurocholate. Both kinetics and extent of solubilization were independent of the phospholipid head group, but were significantly affected by the fatty acid chain length. Furthermore, using vesicles with varying phospholipid composition and different types of analogues in self-quenching concentrations, we could show that bile salt-mediated vesicle solubilization depended on the fatty acid chain length of phospholipids. In contrast, neither for phospholipids nor for analogues could an influence of the lipid head group on the solubilization process be observed. These findings support a head group-independent mechanism of bile salt-mediated enrichment of specific phospholipids in the bile fluid.     

Fatty acid composition and the hydrophilic properties of phospholipids in seedlings of spring and winter wheat growing at 20°C and 2°C

The work of adhesion between water and a heptane solution of phospholipids extracted from spring (cv. Jara) and winter (cv. Grana) wheat ( Triticum aestivum L.) grown at 2°C and 20°C was measured in order to determine the effect of changes in the composition of fatty acids on the hydrophilic properties of the lipid bilayer of membranes. The work of adhesion water/phospholipids was positively correlated with the contents of the oleic and linoleic acids (18:1 and 18:2, respectively) and negatively correlated with the content of linolenic acid (18:3) in the phospholipids. The sensitivity of the work of adhesion to changes in the particular fatty acids decreased with increasing number of double bonds. In addition, it depended on the genotype and on the temperature of growth of the seedlings.     

Chronic valproate treatment decreases the in vivo turnover of arachidonic acid in brain phospholipids: a possible common effect of mood stabilizers

Both (Li(+)) and valproic acid (VPA) are effective in treating bipolar disorder, but the pathway by which either works, and whether it is common to both drugs, is not agreed upon. We recently reported, using an in vivo fatty acid model, that Li(+) reduces the turnover rate of the second messenger arachidonic acid (AA) by 80% in brain phospholipids of the awake rat, without changing turnover rates of docosahexaenoic or palmitic acid. Reduced AA turnover was accompanied by down-regulation of gene expression and protein levels of an AA-specific cytosolic phospholipase A(2) (cPLA(2)). To see if VPA had the same effect on AA turnover, we used our in vivo fatty acid model in rats chronically administered VPA (200 mg/kg, i.p. for 30 days). Like Li(+), VPA treatment significantly decreased AA turnover within brain phospholipids (by 28-33%), although it had no effect on cPLA(2) protein levels. Thus, both mood stabilizers, Li(+) and VPA have a common action in reducing AA turnover in brain phospholipids, albeit by different mechanisms.     

Circadian Rhythm of the Liver of Male Rats Pre-Treated with Phenobarbital—ii. Hexobarbital Sleeping Time and Lipids Content in Liver and Serum

The circadian rhythm of hexobarbital sleeping time and lipids content in liver and serum were studied in 226 male Sprague-Dawley rats pretreated daily at 0800-0900 with 70 mg/kg (study 1 or 3) or 50 mg/kg (study 2) phenobarbital (PB) orally for 7 days. Thereafter, eight (study 1) or five (study 2 and 3) rats each were studied at 4-hr intervals at 1000, 1400, 1800, 2200, 0200, 0600 and 1000 through the following day. The lighting schedule in the colony was 12:12 ± light:dark (light from 0600 to 1800). The hexobarbital sleeping times of PB-pretreated rats were generally shortened compared to the controls and no circadian rhythm was observed. PB-treatment increased slightly the liver content of cholesterol, and significantly that of triglycerides and phospholipids. Liver cholesterol and phospholipids showed circadian rhythms with peaks during the dark phase. No circadian rhythm of liver triglycerides existed. In serum, levels of triglycerides and phospholipids were slightly lowered by PB-treatment, while levels of cholesterol and beta-lipoprotein were not influenced. Serum values did not exhibit circadian rhythms.     

Binding of Crotoxin, a Presynaptic Phospholipase A2Neurotoxin, to Negatively Charged Phospholipid Vesicles

Crotoxin, isolated from the venom of Crotalus durissus terrificus, is a potent neurotoxin consisting of a basic and weakly toxic phospholipase A2 subunit (component B) and an acidic nonenzymatic subunit (component A). The nontoxic component A enhances the toxicity of the phospholipase subunit by preventing its nonspecific adsorption. The binding of crotoxin and of its subunits to small unilamellar phospholipid vesicles was examined under experimental conditions that prevented any phospholipid hydrolysis. Isolated component B rapidly bound with a low affinity (Kapp in the millimolar range) to zwitterionic phospholipid vesicles and with a high affinity (Kapp of less than 1 microM) to negatively charged phospholipid vesicles. On the other hand, the crotoxin complex did not interact with zwitterionic phospholipid vesicles but dissociated in the presence of negatively charged phospholipid vesicles; the noncatalytic component A was released into solution, whereas component B remained tightly bound to lipid vesicles, with apparent affinity constants from 100 to less than 1 microM, according to the chemical composition of the phospholipids. On binding, crotoxin or its component B caused the leakage of a dye entrapped in vesicles of negatively charged but not of zwitterionic phospholipids. The selective binding of crotoxin suggests that negatively charged phospholipids may constitute a component of the acceptor site of crotoxin on the presynaptic plasma membrane.     

Lipid Hydroperoxides Inhibit Reacylation of Phospholipids in Neuronal Membranes

The unsaturated fatty acids that rapidly accumulate during ischemia are thought to participate in inducing irreversible brain injury, especially because they are highly susceptible to peroxidation when the tissue is reoxygenated. Our hypothesis was that peroxidation products of unsaturated fatty acids interfere with the reacylation of synaptic phospholipids, a process essential to membrane repair. To test this hypothesis, we have examined the effect of fatty acid hydroperoxides on incorporation of [1-14C]arachidonic acid into synaptosomal phospholipids. Rat forebrain synaptosomes were incubated with arachidonic or linoleic acid hydroperoxides and [14C]arachidonate, and then lipids were extracted and separated by TLC. Both hydroperoxides inhibited [14C]arachidonate incorporation into phospholipids in a concentration-dependent manner, with 50% inhibition occurring at less than 25 microM hydroperoxide, in both the absence and presence of exogenous lysophospholipids. The inhibition was of the non-competitive type. It is concluded that (a) low levels of fatty acid hydroperoxides inhibit the reacylation of synaptosomal phospholipids, and (b) this inhibition may constitute an important mechanism whereby peroxidative processes contribute to irreversible brain damage.     

The Synthesis of Thio- and Selenoanalogues of Phospholipids on the Basis of 2-Butyl-2-Hydroxymethyl-1,3-Propanediol

New analogues of nonglycerol polyol phospholipids were prepared on the basis of 1,1,1-trimethylolpenthane. Amidophosphites and cyclophosphites of the isopropylidene derivative of this polyol were intermediates in the syntheses. They were treated with sulfur or selenium. Phosphoacetals were converted into lipids by direct acylation with higher fatty acid chlorides. The triol bicyclophosphite was also used in the lipid syntheses. It was directly acylated at the oxygen atom, and the resulting acylpolyol of chlorophosphite was then converted into phospholipids by alcoholysis and subsequent treatment with sulfur.__________Translated from Bioorganicheskaya Khimiya, Vol. 31, No. 4, 2005, pp. 414–419.Original Russian Text Copyright © 2005 by Savin, Kutsemako.     

Biosynthesis of N-acylethanolamine phospholipids by dog brain preparations

Abstract: Dog brain homogenates and subcellular preparations incubated in the presence of Ca²⁺ produced a new phospholipid that was isolated and identified by its infrared spectrum and by chemical degradation as a mixture of 1, 2-diacyl, alkenylacyl, and alkylacyl sn -glycero-3-phospho ( N -acyl)ethanolamines, 50, 45, and 5%, respectively. The N -acyl groups consisted almost exclusively of 16:0, 18:0, and 18:1 fatty acids. Formation of N -acylethanolamine phospholipids from endogenous substrates was linear for about 90 min at approximately 4.5 nmol/h/mg protein and exhibited a pH optimum of 10. Biosynthetic activity was associated with particulate fractions, primarily microsomes, synaptosomes, and mitochondria, but not with myelin. In each case, small amounts (∼0.5 nmol/h/mg protein) of long-chain N -acylethanolamines were also produced. Incubation of dog brain microsomes with 1,2-di[1'-¹⁴C]palmitoyl glycero-phosphocholine yielded N -acylethanolamine phospholipids labeled at both N -acyl (55%) and O -acyl (45%) moieties. It appears that dog brain organelles may contain a phosphatidylethanolamine N -acyl transferase (transacylase) analogous to that recently demonstrated in the myocardial tissue.     

Biochemical and mass spectrometry recognition of phospholipid–peptide complexes in wheat sprouts extract

Total hydroalcoholic extract of wheat sprouts was treated with 90% cold acetone as a preliminary step directed to separate antioxidant peptides from antioxidant polyphenols. Surprisingly, the addition of acetone causes the formation of a yellow buoyant gelatinous drop that prevailingly contains peptides and phospholipids. In this context, evidences have been presented that support the hypothesis that peptides (and perhaps other active molecules) are complexed with phospholipids. In fact, the MS/MS analysis of some main ions, present in RP HPLC fractions of wheat sprout extract, generates several ions that correspond to molecular weight of phospholipids or phospholipid fragments. Moreover, several ions were detected that correspond to lysophosphatidylcholine or phosphatidylcholine–peptide complexes. The possibility that phospholipids can be complexed with peptides has been discussed in the light of potential involvement in the peptide bioavailability. Copyright © 2011 European Peptide Society and John Wiley & Sons, Ltd.     

Comparative adsorption of natural lung surfactant, extracted phospholipids, and artificial phospholipid mixtures to the air-water interface

Adsorption to the air-water interface of natural lung surfactant obtained by bovine lung lavage is compared and contrasted with the adsorption of mixtures of synthetic phospholipids and of extracted mixed lung lipids containing minimal protein. Surface pressure-time (pi-t) adsorption isotherms are measured at 35 degrees C for the surfactant mixtures as a function of the presence or absence of divalent metal cations (Ca2+ and Mg2+) and of heating to 45 degrees C or 90 degrees C. The effect of aqueous dispersion technique (sonication or mechanical vortexing) on the adsorption process is also studied for the extracted or synthetic phospholipid mixtures. The results imply that the protein component is necessary for the optimal adsorption of natural lung surfactant. However, by taking advantage of different methods available for phospholipid dispersion in an aqueous phase in vitro, it is possible to formulate dispersions of extracted lung phospholipids containing of order 1% protein which adsorb as well as the complete surfactant system. These results suggest that protein concentrations in surfactant mixtures can be minimized for applications such as exogenous lung surfactant replacement for the neonatal Respiratory Distress Syndrome (RDS). However, for situations which may involve alterations in endogenous surfactant function such as in lung injury, effects involving pulmonary surfactant protein and protein-lipid interactions may be of functional significance.     

Effects of analogues of ethanolamine and choline on phospholipid metabolism in rat hepatocytes

1. Analogues of ethanolamine and choline were incubated with different labelled precursors of phospholipids and isolated hepatocytes and the effects on phospholipid synthesis were studied. 2. 2-Aminopropan-1-ol and 2-aminobutan-1-ol were the most efficient inhibitors of [(14)C]ethanolamine incorporation into phospholipids, whereas the incorporation of [(3)H]choline was inhibited most extensively by NN-diethylethanolamine and NN-dimethylethanolamine. 3. When the analogues were incubated with [(3)H]glycerol and hepatocytes, the appearance of (3)H in unnatural phospholipids indicated that they were incorporated, at least in part, via CDP-derivatives. The distribution of [(3)H]glycerol among molecular species of phospholipids containing 2-aminopropan-1-ol and 1-aminopropan-2-ol was the same as in phosphatidylethanolamine. In other phospholipid analogues the distribution of (3)H was more similar to that in phosphatidylcholine. 4. NN-Diethylethanolamine stimulated both the conversion of phosphatidylethanolamine into phosphatidylcholine and the incorporation of [Me-(14)C]methionine into phospholipids. Other N-alkyl- or NN-dialkyl-ethanolamines also stimulated [(14)C]methionine incorporation, but inhibited the conversion of phosphatidylethanolamine into phosphatidylcholine. This indicates that phosphatidyl-NN-diethylethanolamine is a poor methyl acceptor, in contrast with other N-alkylated phosphatidylethanolamines. 5. These results on the regulation of phospholipid metabolism in intact cells are discussed with respect to the possible control points. They also provide guidelines for future experiments on the manipulation of phospholipid polar-headgroup composition in primary cultures of hepatocytes.