1-palmitoyl-2-oleoylphosphatidylcholine and 1-palmitoyl-2-linoleoylphosphatidylcholine

The secondary process of lipid peroxidation produces some toxic aldehydes. Since this process takes place via free radical reaction in lipophilic circumstances, α-tocopherol would suppress the formation of such aldehydes by trapping free-radical intermediates. This study reports the effect of α-tocopherol on the hemin-catalyzed decomposition of 1-palmitoyl-2-linoleoyl-3-sn-phosphatidylcholine 13-hydroperoxide (PLPC-OOH) in micelles and liposomes. PLPC-OOH and α-tocopherol were reacted with hemin in micelles, and the reaction products were characterized to be 1-palmitoyl-2-(α-tocopheroxy-12,13-epoxyoctadecenoyl)-3-sn-phosphatidylcholines (T-epoxyPLPC) and known compounds, 1-palmitoyl-2-[(8a-dioxy-α-tocopherone)-12,13-epoxyoctadecenoyl]-3-sn-phosphatidylcholines (TOO-epoxyPLPC) and α-tocopherol dimer. The hemin-catalyzed decomposition of PLPC-OOH in micelles produced hexanal as one of secondary aldehydic products. α-Tocopherol suppressed the formation of hexanal, and α-tocopherylquinone, α-tocopherol dimer, TOO-epoxyPLPC, and T-epoxyPLPC were detected during the reaction. In liposomes, α-tocopherol could partially suppress the formation of hexanal, and the main products were TOO-epoxyPLPC and α-tocopherol dimer. The results indicate that α-tocopherol may suppress the formation of hexanal by trapping the epoxyperoxyl and epoxyalkyl radicals derived from PLPC-OOH.

Topics: alpha-Tocopherol; Catalysis; Chromatography, High Pressure Liquid; Chromatography, Reverse-Phase; Hemin; Lipid Peroxides; Liposomes; Magnetic Resonance Spectroscopy; Micelles; Phosphatidylcholines

Saturated phospholipids (PCs), particularly dipalmitoylphosphatidylcholine (DPPC), predominate in surfactant lining the alveoli, although little is known about the relationship between saturated and unsaturated PCs on the outer surface of the lung, the pleura. Seven healthy cats were anesthetized and a bronchoalveolar lavage (BAL) was performed, immediately followed by a pleural lavage (PL). Lipid was extracted from lavage fluid and then analyzed for saturated, primarily dipalmitoylphosphatidylcholine (DPPC), and unsaturated PC species using high-performance liquid chromatography (HPLC) with combined fluorescence and ultraviolet detection. Dilution of epithelial lining fluid (ELF) in lavage fluids was corrected for using the urea method. The concentration of DPPC in BAL fluid (85.3+/-15.7 microg/mL) was significantly higher (P=0.021) than unsaturated PCs ( approximately 40 microg/mL). However, unsaturated PCs ( approximately 34 microg/mL), particularly stearoyl-linoleoyl-phosphatidylcholine (SLPC; 17.4+/-6.8), were significantly higher (P=0.021) than DPPC (4.3+/-1.8 microg/mL) in PL fluid. These results show that unsaturated PCs appear functionally more important in the pleural cavity, which may have implications for surfactant replenishment following pleural disease or thoracic surgery.

Topics: 1,2-Dipalmitoylphosphatidylcholine; Animals; Body Fluids; Bronchoalveolar Lavage Fluid; Cats; Female; Leukocytes; Male; Phosphatidylcholines; Phospholipids; Pleura; Pleural Cavity; Pulmonary Surfactants

Lipid peroxidation process has attracted much attention due to the growing evidence of its involvement in the pathogenesis of age-related diseases. The monitoring of the lipid peroxidation products in phospholipids, formed under oxidative stress conditions, may provide new markers for oxidative stress signaling and for disease states, giving new insights in the pathogenesis process. Reversed-phase liquid chromatographic method coupled to mass spectrometry was developed for the separation of oxidized glycero-phosphatidylcholine (GPC) peroxidation products formed by the Fenton reaction that mimic in vivo oxidative stress conditions. The LC-MS conditions were applied for the separation of peroxidation products of oleoyl- (POPC), lineloyl- (PLPC) and arachidonoyl-palmitoyl phosphatidylcholine (PAPC). The peroxidation products separated included products resulting from the insertion of oxygen atoms in the sn-2 chain (long-chain), and products with the sn-2 chain shortened resulting from cleavage of oxygen-centered radicals (short-chain). Among long-chain products were the keto, hydroxy, hydroperoxide and poly-hydroxy derivatives, while short-chain products included dicarboxylic acids, aldehydes and hydroxy-aldehydes. Separation of long-chain products formed in each phosphatidylcholine was observed, and the reconstructed ion chromatogram of each ion showed an increase in the number of peaks with the increase in the number of oxygen atoms inserted into the phospholipid. Separation of short-chain products took place according to the functional group present at the sn-2 moiety that allowed the elution of dicarboxylic acids distinct from aldehydes. Separation between isomeric structures that were present in short- and long-chain products was also achieved.

Topics: Chromatography, High Pressure Liquid; Lipid Peroxidation; Oxidative Stress; Phosphatidylcholines; Spectrometry, Mass, Electrospray Ionization

The importance of unsaturated, and especially polyunsaturated phosphatidylcholine molecules for the functional properties of biological membranes is widely accepted. Here, the effects of unsaturation on the nanosecond-scale structural and dynamic properties of the phosphatidylcholine bilayer were elucidated by performance of multinanosecond molecular dynamics simulations of all-atom bilayer models. Bilayers of dipalmitoylphosphatidylcholine and its mono-, di-, and tetraunsaturated counterparts were simulated, containing, respectively, oleoyl, linoleoyl, or arachidonoyl chains in the sn-2 position. Analysis of the simulations focused on comparison of the structural properties, especially the ordering of the chains in the membranes. Although the results suggest some problems in the CHARMM force field of the lipids when applied in a constant pressure ensemble, the features appearing in the ordering of the unsaturated chains are consistent with the behaviour known from (2)H NMR experiments. The rigidity of the double bonds is compensated by the flexibility of skew state single bonds juxtaposed with double bonds. The presence of double bonds in the sn-2 chains considerably reduces the order parameters of the CH bonds. Moreover, the double bond region of tetraunsaturated chains is shown to span all the way from the bilayer centre to the head group region.

Topics: 1,2-Dipalmitoylphosphatidylcholine; Carbon; Computer Simulation; Glycerol; Lipid Bilayers; Lipids; Macromolecular Substances; Magnetic Resonance Spectroscopy; Models, Chemical; Models, Molecular; Models, Statistical; Models, Theoretical; Molecular Conformation; Oxygen; Phosphatidylcholines; Phospholipids; Pressure; Protein Binding; Protein Conformation; Software; Static Electricity; Time Factors

The initial plasma acceptor of unesterified cholesterol and phospholipids from peripheral cells has been identified as pre-beta migrating, lipid-free, or lipid-poor apolipoprotein (apo) A-I (pre-beta apoA-I). Pre-beta apoA-I is formed when plasma factors, such as cholesteryl ester transfer protein (CETP), remodel high-density lipoproteins (HDL). The aim of this study is to determine how phospholipids influence pre-beta apoA-I formation during the CETP-mediated remodeling of HDL. Reconstituted HDL (rHDL) containing either 1-palmitoyl-2-oleoyl phosphatidylcholine (POPC), 1-palmitoyl-2-linoleoyl phosphatidylcholine (PLPC), 1-palmitoyl-2-arachidonyl phosphatidylcholine (PAPC), or 1-palmitoyl-2-docosahexanoyl phosphatidylcholine (PDPC) as the only phospholipid were prepared. The rHDL were comparable in size and core lipid/protein molar ratio and contained only cholesteryl esters in their core and apoA-I as the sole apolipoprotein. The (POPC)rHDL, (PLPC)rHDL, (PAPC)rHDL, and (PDPC)rHDL were respectively incubated for 0-24 h with CETP and microemulsions containing triolein and either POPC, PLPC, PAPC, or PDPC. The rate at which the rHDL were depleted of core lipids and remodeled to small particles varied widely with (POPC)rHDL < (PLPC)rHDL < (PDPC)rHDL approximately (PAPC)rHDL. Pre-beta apoA-I was not formed in the (POPC)rHDL incubations. Pre-beta apoA-I was apparent by 24 h in the (PLPC)rHDL incubations and by 12 h in the (PAPC)rHDL and (PDPC)rHDL incubations. The enhanced formation of pre-beta apoA-I in the (PAPC)rHDL and (PDPC)rHDL incubations reflected the increased core lipid depletion of the particles combined with the destabilization and progressive exclusion of apoA-I from the particle surface. In conclusion, these results show that phospholipids play a key role in the CETP-mediated remodeling of rHDL and pre-beta apoA-I formation.

Topics: Apolipoprotein A-I; Carrier Proteins; Cholesterol Ester Transfer Proteins; Cholesterol Esters; Electrophoresis, Polyacrylamide Gel; Emulsions; Glycoproteins; High-Density Lipoproteins, Pre-beta; Humans; Lipoproteins, HDL; Phosphatidylcholines; Phospholipid Ethers; Phospholipids; Surface Plasmon Resonance

Effects of hypochlorous acid and of the myeloperoxidase-hydrogen peroxide-chloride system on mono- and polyunsaturated phosphatidylcholines were analyzed by means of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Chlorohydrins and glycols were detected as main products according to the characteristic shift of molecular masses. Mainly mono-chlorohydrins result upon the incubation of HOCl/(-)OCl with 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine, whereas only traces of mono-glycols were detected. 1-Palmitoyl-2-linoleoyl-sn-glycero-3-phosphocholine yielded a complex mixture of products. Mono-chlorohydrins and glycols dominated only at short incubation, while bis-chlorohydrins as well as products containing one chlorohydrin and one glycol moiety appeared after longer incubation. Similarly, a complex product mixture resulted upon incubation of 1-stearoyl-2-arachidonoyl-sn-glycero-3-phosphocholine with hypochlorous acid. Additionally, tris-chlorohydrins, products with two chlorohydrin and one glycol moiety, as well as lysophosphatidylcholines and fragmentation products of the arachidonoyl side chain were detectable. Mono-chlorohydrins of 1-stearoyl-2-oleoyl-sn-glycero-3-phosphocholine were detected after the incubation of the latter phospholipid with the myeloperoxidase-hydrogen peroxide-chloride system at pH 6.0. These chlorohydrins were not observed in the absence of chloride, hydrogen peroxide, or myeloperoxidase as well as in the presence of methionine, taurine, or sodium azide. Thus, mono-chlorohydrins in 1-stearoyl-2-oleoyl-sn-glycero-3-phosphocholine produced by hypochlorous acid from the myeloperoxidase-hydrogen peroxide-chloride system can also be detected by means of MALDI-TOF MS.

Topics: Chlorides; Chlorohydrins; Fatty Acids, Unsaturated; Glycols; Hydrogen Peroxide; Hypochlorous Acid; Peroxidase; Phosphatidylcholines; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization

The ability of different phosphatidylcholine (PC) species to inhibit cytokine-induced expression of vascular cell adhesion molecule 1 (VCAM-1) in human umbilical vein endothelial cells (HUVECs) was investigated. PC species containing palmitoyl- in the sn-1 position and palmitoyl- (DPPC), arachidonyl- (PAPC), linoleoyl- (PLPC) or oleoyl- (POPC) in the sn-2 position were compared. These PC species were studied as components of reconstituted high density lipoproteins (rHDL) (containing apolipoprotein A-I [apoA-I] as the sole protein) or as small unilamellar vesicles (SUVs). The rHDL containing PLPC and PAPC inhibited VCAM-1 expression in activated HUVECs by 95 and 70%, respectively, at an apoA-I concentration of 16 micrometer. At this concentration of apoA-I, POPC rHDL inhibited by only 16% and DPPC rHDL did not inhibit at all. These differences could not be explained by differential binding of the rHDL to HUVECs. The same hierarchy of inhibitory activity was observed when these PC species were presented to the cells as SUVs but only when the SUVs also contained an antioxidant. It was concluded that rHDL PC is responsible for their inhibitory activity and that this varies widely with different PC species.

Topics: Cells, Cultured; Endothelium, Vascular; Humans; Interleukin-1; Lipoproteins, HDL; Liposomes; Phosphatidylcholines; Phospholipids; Structure-Activity Relationship; Tumor Necrosis Factor-alpha; Umbilical Veins; Vascular Cell Adhesion Molecule-1

The enzyme CTP:phosphocholine cytidylyltransferase (CT) binds reversibly to membranes and is active only in its membrane-bound form. Membrane lipid composition influences the equilibrium between its soluble and membrane-bound forms. Whereas the enzyme is not activated by phosphatidylcholine (PC) vesicles, it is activated by PC vesicles that have been oxidized with HClO(4) [Drobnies, A. E., et al. (1998) Biochim. Biophys. Acta 1393, 90-98]. Here we explore the mechanism of activation of CT by a PC oxidized with lipoxidase. Multilamellar vesicles (MLVs) containing > or =5 mol % oxidized 1-palmitoyl-2-arachidonoylPC (PAPC) progressively activated the enzyme, which was fully activated by 25 mol % oxidized PC. The effect of oxidized PAPC on lipid order was investigated by (2)H NMR, using MLVs containing PAPC perdeuterated on the palmitoyl chain. Spectral depaking generated order parameter profiles along the sn-1 chain. The average order parameter (S(CD)) in the plateau region at 37 degrees C decreased from 0.18 to 0.15 with increasing percent of oxidized PAPC (0-25%). The change in S(CD) was even greater near the end of the palmitoyl chain. CT activation was inversely related to lipid order. The major component of the lipoxidase-oxidized PAPC was purified and characterized by mass spectrometry and NMR. This component, 1-palmitoyl-2-(11,15-dihydroxy)eicosatrienoylPC (dihydroxyPAPC), incorporated into PAPC MLVs, also stimulated CT activity and reduced the lipid order parameter. Both effects were reversed by egg sphingomyelin. We propose that CT activation by oxidized PAPC is mediated by effects on lipid packing perturbations. This is the first study to report the effects of a purified oxidized PC on the orientational order along the acyl chain and to correlate the lipid disordering of the oxidized PC with the activation of a membrane-associated regulatory enzyme.

Topics: Catalysis; Choline-Phosphate Cytidylyltransferase; Deuterium; Enzyme Activation; Glycine max; Lipid Bilayers; Lipoproteins, LDL; Lipoxygenase; Nuclear Magnetic Resonance, Biomolecular; Oxidation-Reduction; Phosphatidylcholines; Phospholipid Ethers; Sphingomyelins

Kinetics of the consumption of hypochlorous acid in its reaction with double bonds of unsaturated phospholipids and fatty acids were measured using luminol chemiluminescence. Stoichiometry ratios between the consumption of HOCl/OCl- and the loss of double bonds vary from 2:1 to 1:1. Highest values were found in DMPC liposomes containing 5 mol% oleic acid or OPPC. With increasing content of double bonds or higher numbers of double bonds in a fatty acid acyl chain due to incorporated unsaturated fatty acids or phospholipids in DMPC liposomes the stoichiometry ratio falls continuously to 1:1. A ratio of about 1:1 was observed in multilamellar and unilamellar liposomes composed of egg yolk phosphatidylcholine. Products of the reaction of oleic acid with hypochlorous acid were analyses by 1H-NMR spectroscopy. Chlorohydrins were formed in both DMPC liposomes containing 5 or 40 mol% oleic acid.

Topics: Chemical Phenomena; Chemistry, Physical; Dimyristoylphosphatidylcholine; Hypochlorous Acid; Linoleic Acid; Linoleic Acids; Liposomes; Luminescent Measurements; Magnetic Resonance Spectroscopy; Oleic Acid; Oleic Acids; Phosphatidylcholines

An equation of state for lipid monolayers at the air-water interface is presented, which takes into account the effects of the conformation and the number and position of double bonds of the hydrocarbon chains. The total Hamiltonian of the monolayer is assumed to consist of three terms. Two of them are calculated exactly within the limitations of the formulation. These are the two-dimensional entropy of mixing of the lipid and water molecules at the surface and the conformational entropy of the chains using a model available from the literature. These two terms give rise to positive surface pressure. The third term, which includes all energies that are not amenable to calculation, was obtained as the difference between the sum of the two calculated terms and experimental data and is found to represent an approximately area-independent tension. The effects of chain unsaturation on the equation of state were modeled in the present theory in two ways; the chain bend caused by cis double bonds increases the minimal molecular area, and the double bond linkage on a chain decreases the degrees of freedom of the chain. Calculations revealed that the former is highly significant whereas the latter is negligible. The deduced equation of state reproduces experimental data with appropriate values for three parameters, which represent the collapse area, the overlap of adjacent chains, and the combined effects of the intra- and intermolecular interactions other than the surface mixing entropy and the chain conformational energy.

Topics: 1,2-Dipalmitoylphosphatidylcholine; Air; Biophysical Phenomena; Biophysics; In Vitro Techniques; Lipids; Models, Chemical; Molecular Conformation; Molecular Structure; Phosphatidylcholines; Phosphatidylethanolamines; Thermodynamics; Water

The rate of phospholipid turnover in erythrocyte membranes in vivo has been studied using a recently developed procedure (Kuypers, F.A., Easton, E.W., van den Hoven, R., Wensing, T., Roelofsen, B., Op den Kamp, J.A.F. and van Deenen, L.L.M. (1985) Biochim. Biophys. Acta 819, 170-178). The technique is based on the application of phospholipid transfer proteins in order to introduce trace amounts of radiolabelled phospholipids in the membrane of isolated erythrocytes, followed by re-injection of the erythrocytes into the bloodstream of the animal. The most abundant species of the phosphatidylcholine (PC) class, 1-palmitoyl,2-linoleoyl PC, has, on the basis of loss of the radioactivity in its fatty acyl part, a relatively high turnover with a half-time value of 1.5 days. Other PC species studied exhibit more moderate turnover rates of about 5 days for 1-palmitoyl,2-oleoyl PC and 1-stearoyl,2-arachidonoyl PC. Dipalmitoyl PC, labelled in the polar headgroup, turns over at a slow rate with a half-time value of 9 days. From these data and the relative abundance of the various species, it can be calculated that, on a daily basis in vivo, about one third of the total PC pool in rabbit erythrocyte membranes is replaced and/or modified by de-/reacylation. The only phosphatidylethanolamine (PE) species studied so far, 1-palmitoyl,2-arachidonoyl PE, appeared to be renewed at a relatively low rate with a half-time value of 12 days. The data demonstrate that the in vivo turnover values of phospholipids in the erythrocyte membrane may depend on their polar head group structure, their localization in the membrane and, to a large extent, on their fatty acid composition.

Topics: Animals; Carrier Proteins; Erythrocyte Membrane; Fatty Acids; Female; Half-Life; Membrane Proteins; Phosphatidylcholines; Phospholipid Transfer Proteins; Phospholipids; Rabbits

Topics: Cholesterol; Chromatography, Thin Layer; Fatty Acids, Unsaturated; Gas Chromatography-Mass Spectrometry; Humans; Hydrogen Peroxide; Hypochlorous Acid; Micelles; Models, Biological; Neutrophils; Peroxidase; Phosphatidylcholines