Influence of acyl and plasmalogenic analogs of platelet activating factor on chemotaxis of human leukocytes in vitro and their inflammatory and antiinflammatory activity in vivo

The effects of platelet activating factor (PAF) and its cell analogs 1-O-alk-1;-enyl-2-acetyl-sn-glycero-3-phosphocholine (1-alkenyl-PAF) and 1-acyl-2-acetyl-sn-glycero-3-phosphocholine (1-acyl-PAF) on chemotaxis of human leukocytes in vitro and their inflammatory and antiinflammatory activities in vivo were studied. Both analogs stimulated chemotaxis of human leukocytes in agarose gel. PAF and 1-alkenyl-PAF induced rat paw edema in the range of doses 0.1-10 and 10-100 micro g per paw, respectively. Paw edema induced by 1-acyl-PAF (10-100 micro g per paw) was more pronounced than that induced by PAF or 1-alkenyl-PAF. The latter also exhibited significant antiinflammatory effect by inhibiting PAF- or carrageenan-induced rat paw edema, and this effect exceeded that of dexamethasone. In these models of inflammation 1-acyl-PAF did not exhibit any antiinflammatory activity. The data suggest that PAF is not the only cell phospholipid mediating inflammation--its cell analogs, 1-acyl-PAF and 1-alkenyl-PAF, may also be involved into the inflammatory response. Possible interrelationships between cellular synthesis of 1-acyl-PAF, its formation in oxidized LDL, biological effects of lysolecithin, and penetration of LDL into the arterial wall are discussed.

Conformational studies of a novel cationic glycolipid, glyceroplasmalopsychosine, from bovine brain by NMR spectroscopy

A novel glycosphingolipid containing a long chain aldehyde conjugated to galactose and glycerol, Gro1(3)-O-CH((CH(2))(n)CH(3))-O-6Galbeta-sphingosine (glyceroplasmalopsychosine) has been studied by NMR spectroscopy (Hikita et al. J. Biol. Chem. 2001, 276, 23084-23091). We further report here on the conformation showing the galactose and the glycerol at the end of two parallel hydrophobic chains, i.e. the sphingosine and the fatty aldehyde. This is proposed based on the interproton distances derived from ROESY experiments and 3 J (H,H) coupling constants. The absence of any intraresidual NOEs between protons in the glycerol residue suggested that the C-C-2 and C-C-3 bonds in the glycerol may be rotating freely, supporting the proposed conformation in which the unique terminal glycerol is in an environment with a minimal steric hindrance. The present study proposes a conformation of glyceroplasmalopsychosine greatly different from the two conventional plasmalopsychosines possessing a fatty aldehyde chain oriented in an opposite direction to the sphingosine.

Differential effects of n-3 fatty acid deficiency on phospholipid molecular species composition in the rat hippocampus

In this study, we have examined the effects of n-3 fatty acid deficient diets on the phospholipids (PL) molecular species composition in the hippocampus. Female rats were raised for two generations on diets containing linoleic acid (18:2n-6), with or without supplementation of alpha-linolenic acid (18:3n-3) or 18:3n-3 plus docosahexaenoic acid (22:6n-3). At 84 days of age, the hippocampal phospholipids were analyzed by reversed phase HPLC-electrospray ionization mass spectrometry. Depleting n-3 fatty acids from the diet led to a reduction of 22:6n-3 molecular species in phosphatidylcholine (PC), phosphatidylethanolamine (PE), PE-plasmalogens (PLE), and phosphatidylserine (PS) by 70-80%. In general, 22:6n-3 was replaced with 22:5n-6 but the replacement at the molecular species level did not always occur in a reciprocal manner, especially in PC and PLE. In PC, the 16:0,22:6n-3 species was replaced by 16:0,22:5n-6 and 18:0,22:5n-6. In PLE, substantial increases of both 22:5n-6 and 22:4n-6 species compensated for the decreases in 22:6n-3 species in n-3 fatty acid deficient groups. While the total PL content was not affected by n-3 deficiency, the relative distribution of PS decreased by 28% with a concomitant increase in PC. The observed decrease of 22:6n-3 species along with PS reduction may represent key biochemical changes underlying losses in brain-hippocampal function associated with n-3 deficiency.

Reactive brominating species produced by myeloperoxidase target the vinyl ether bond of plasmalogens: disparate utilization of sodium halides in the production of alpha-halo fatty aldehydes

Plasmalogens are a phospholipid molecular subclass that are enriched in the plasma membrane of many mammalian cells. The present study demonstrates that reactive brominating species produced by myeloperoxidase, as well as activated neutrophils, attack the vinyl ether bond of plasmalogens. Reactive brominating species produced by myeloperoxidase target the vinyl ether bond of plasmalogens, resulting in the production of a neutral lipid and lysophosphatidylcholine. Gas chromatography-mass spectrometry and proton NMR analyses of this neutral lipid demonstrated that it was 2-bromohexadecanal (2-BrHDA). In comparison to myeloperoxidase-generated reactive chlorinating species, reactive brominating species attacked the plasmalogen vinyl ether bond at neutral pH. In the presence of a 20-fold molar excess of NaCl compared with NaBr, myeloperoxidase-derived reactive halogenating species favored the production of 2-BrHDA over that of 2-chlorohexadecanal. Additionally, 2-BrHDA was preferentially produced from plasmalogen treated with hypochlorous acid in the presence of NaBr. The potential physiological significance of this pathway was suggested by the demonstration that both 2-BrHDA and 2-bromooctadecanal were produced by PMA-stimulated neutrophils. Taken together, the present studies demonstrate the targeting of the vinyl ether bond of plasmalogens by the reactive brominating species produced by myeloperoxidase and by activated neutrophils, resulting in the production of novel brominated fatty aldehydes.

Effect of cholesterol and surfactant protein B on the viscosity of phospholipid mixtures

Low viscosity of the surface of alveolar fluid is mandatory for undisturbed surfactant function. Based on the known reduction of the viscosity of surfactant-like phospholipid (PL-) mixtures by plasmalogens, the effect of cholesterol and surfactant protein (SP-) B on surface viscosity of these lipid mixtures has been studied. Surface viscosity at the corresponding surface tension was measured with the oscillating drop surfactometer. We found that the viscosity was lowest in cholesterol-, followed by plasmalogen- and SP-B containing samples. Addition of SP-B to a plasmalogen-containing PL-mixture caused a further decrease in viscosity. However, in cholesterol containing mixtures, addition of SP-B led to a significant increase in viscosity, and the effect was reversed by further addition of plasmalogens. We conclude that SP-B, plasmalogens and cholesterol all affect the surface viscosity, thus synergistically regulate monolayer stability. This suggests that they are all needed in vivo for fine tuning of surface properties of pulmonary surfactant.

Chloroaluminum phthalocyanine tetrasulfonate delivered via acid-labile diplasmenylcholine-folate liposomes: intracellular localization and synergistic phototoxicity

Folate-diplasmenylcholine (1,2-di-O-(Z-1'-hexadecenyl)-sn-glycero-3-phosphocholine; DPPlsC) liposomes have been shown to greatly enhance the potency of water-soluble antitumor agents via a selective folate-mediated uptake and acid-catalyzed endosomal escape mechanism (Rui et al. J. Am. Chem. Soc., 1998; 120:11213--18). This study describes an adaptation of this strategy for the delivery of chloroaluminum phthalocyanine tetrasulfonate ([AlPcS(4)](4-)), a water-soluble sensitizer used in photodynamic therapy, in a binary targeting scheme designed to enhance both its tumor selectivity and phototoxicity. [AlPcS(4)](4-)/DPPlsC:folate liposomes (9.8 microM bulk concentration, 2.5 mM intraliposomal concentration) were substantially more phototoxic to folate-deficient KB cells than 12.5 microM free [AlPcS(4)](4-) after a 30 min irradiation (630-910 nm). Considerable differences in phototoxicity were observed, however, between the commercially-available AlPcS(4)(4-) and an HPLC purified sample of [AlPcS(4)](4-) due to an increased tendency for the latter to aggregate. Experiments with [AlPcS(4)](4-)/DPPC:folate and folate-free [AlPcS(4)](4-)/DPPlsC liposomes (acid-insensitive and non-targeted controls, respectively) showed significantly reduced phototoxicities under the same illumination conditions. Our results imply that higher concentrations of water-soluble sensitizers can be delivered to target cells using the folate receptor-mediated pathway, which can change both the biodistribution and intracellular localization of the sensitizer when acid-labile DPPlsC liposomes are used as the delivery vehicle. Potential advantages of this approach include the use of lower bulk [AlPcS(4)](4-) concentrations, rapid plasma clearance of free [AlPcS(4)](4-), and better phototoxic responses, due to higher intracellular [AlPcS(4)](4-) concentrations combined with reduced collateral photodamage arising from misguided sensitizer accumulation, thereby enhancing the selective phototoxicity of PDT treatments.

A novel plasmal conjugate to glycerol and psychosine ("glyceroplasmalopsychosine"): isolation and characterization from bovine brain white matter

A novel plasmal conjugate of glycosphingolipid having cationic lipid properties was isolated from the white matter of bovine brain. Linkage analysis of galactosyl residue by methylation, liquid secondary ion, and electrospray ionization mass spectrometry of intact and methylated derivatives, and by (1)H- and (13)C-NMR spectroscopy, identified the structure unambiguously as an O-acetal conjugate of plasmal to the primary hydroxyl group of glycerol and to the 6-hydroxyl group of galactosyl residue of beta-galactosyl 1-->1 sphingosine (psychosine). This novel compound is hereby termed "glyceroplasmalopsychosine"; its structure is shown below (see text).

Plasmalogens: workhorse lipids of membranes in normal and injured neurons and glia

Plasmalogens are unique glycerophospholipids because they have an enol ether double bond at the sn-1 position of the glycerol backbone. They are found in all mammalian tissues, with ethanolamine plasmalogens 10-fold higher than choline plasmalogens except in muscles. The enol ether double bond at the sn-1 position makes plasmalogens more susceptible to oxidative stress than the corresponding ester-bonded glycerophospholipids. Plasmalogens are not only structural membrane components and a reservoir for second messengers but may also be involved in membrane fusion, ion transport, and cholesterol efflux. Plasmalogens may also act as antioxidants, thus protecting cells from oxidative stress. Receptor-mediated degradation of plasmalogens by plasmalogen-selective phospholipase A2 results in the generation of arachidonic acid, eicosanoids, and platelet activating factor. Low levels of these metabolites have trophic effects, but at high concentration they are cytotoxic and may be involved in allergic response, inflammation, and trauma. Levels of plasmalogens are decreased in several neurological disorders including Alzheimer's disease, ischemia, and spinal cord trauma. This may be due to the stimulation of plasmalogen-selective phospholipase A2. A deficiency of plasmalogens in peroxisomal disorders and Niemann-Pick type C disease indicates that this deficiency may be due to the decreased activity of plasmalogen synthesizing enzymes that occur in peroxisomes.

Microsomal fatty aldehyde dehydrogenase catalyzes the oxidation of aliphatic aldehyde derived from ether glycerolipid catabolism: implications for Sjögren-Larsson syndrome

The enzyme that catalyzes the oxidation of fatty aldehyde derived from ether glycerolipid catabolism has not been identified. To determine whether microsomal fatty aldehyde dehydrogenase (FALDH) is responsible, we investigated the metabolism of 1-O-[9, 10-(3)H-octadecyl]-glycerol ([(3)H]OG) in FALDH-deficient cultured cells from patients with Sjögren-Larsson syndrome (SLS) and in mutant Chinese hamster ovary (CHO) cells. Intact fibroblasts from SLS patients incubated with [(3)H]OG showed a selective deficiency (38+/-7% of normal) in the incorporation of radioactivity into fatty acid, but no decrease in incorporation of radioactivity into fatty alcohol, total lipids and phosphatidylethanolamine (PE). Consistent with fatty aldehyde accumulation, incorporation of radioactivity into N-alkyl-phosphatidylethanolamine, which is derived from Schiff base formation of free aldehyde with PE, was 4-fold higher in SLS fibroblasts compared to normal controls. Similar results were seen with SLS keratinocytes, whereas FALDH-deficient CHO cells showed a more profound reduction in radioactive fatty acid to 12+/-2% of normal. These results implicate FALDH in the oxidation of ether-derived fatty aldehyde in human and rodent cells. Metabolism of ether glycerolipids is a previously unrecognized source of fatty aldehyde that may contribute to the pathogenesis of SLS.

Effect of ethanol amine plasmalogens on Fe-induced peroxidation of arachidonic acid in dipalmitoylphosphatidylcholine vesicles

We have investigated the influence of ethanolamine plasmalogens on iron-induced oxidation of arachidonic acid in dipalmitoylphosphatidylcholine (DPPC) vesicles. Lipoperoxidation was induced by the addition of 50 microM FeSO4 and studied above (50 degrees C) and below (15 degrees C) the gel-to liquid transition temperature of the vesicles, at two different pH values (7.4 or 6.4). The extent of peroxidation was measured as thiobarbituric reactive product formed and the influence exerted by ethanolamine plasmalogens (PEPL) in this process was compared to that of dipalmitoylphosphatidylethanolamine (DPPE) and diacylphosphatidylethanolamines (DAPE). The extent of peroxidation of arachidonic acid embedded in DPPC vesicles was similar at the two temperatures and greater at 50 degrees C under acidic conditions. However, the peroxidative process was significantly decreased at 50 degrees C in the presence of PEPL, but not of DPPE or DAPE and the inhibitory effect was enhanced at pH 6.4. The possibility that a different phase distribution of the phospholipids, namely a transition from a lamellar to a hexagonal phase, may play a role in the scavenger effect of ethanolamine plasmalogens is discussed.

Phospholipid composition in late infantile neuronal ceroid lipofuscinosis

BACKGROUND

Neuronal ceroid lipofuscinosis (NCL) is a relatively common group of inherited neurodegenerative disorders characterised by the accumulation of autofluorescent lipopigments (ceroid) similar to lipofuscin. Because of this property, studies have concentrated on fatty acid metabolism and lipid peroxidation.

METHODS

In the present study, the fatty acid composition of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) and the molecular species compositions of diacylglycerophosphocholine (diacyl GPC), diacylglycerophosphoethanolamine (diacyl GPE) and alkenylacyl GPE (plasmalogens) were investigated in cultured skin fibroblasts from three patients with a confirmed diagnosis of the late infantile form of the disease (LINCL, CLN2) and three healthy age-matched controls.

RESULTS

Relatively minor differences in the fatty acid compositions of PC and PE were observed between patients and controls. However, dimethyl acetals of plasmalogens were found to be 40% higher in the patients compared to in the controls. Control and LINCL fibroblasts displayed only slight differences in the molecular compositions of diacyl GPE and diacyl GPC. In contrast, compared with normal cells, LINCL fibroblasts had higher levels of alkenylacyl GPE species containing both 18 : 1 and polyunsaturated fatty acids, but lower levels of species with 16 : 0 or 18 : 0 in the sn-1 position.

CONCLUSION

The molecular composition of PC and PE subclasses in skin fibroblasts of healthy subjects and patients suffering from LINCL is here described for the first time. While few differences are noticeable in the fatty acid composition of PC and PE and the molecular species distribution of diacylGPC and diacylGPE, the alkenylacyl GPE (or ethanolamine plasmalogens) were found to differ significantly between patients and healthy controls.

Chemical composition of the lipophylic extract from the tunicate Botryllus schlosseri

Eighteen sterols were identified in Botryllus schlosseri, stanols being the main sterols. The sterol composition is in agreement with our recent paper on taxonomic separation of tunicates into three groups. Again we found in invertebrates of the Black Sea sterols with a (22Z)-double bond. This confirms the presence of such sterols in nature. The composition of the phospholipids appeared to be complex, and twelve groups of them were identified in Botryllus schlosseri. The main representatives of phospholipids appeared to be phosphatidylcholine and phosphatidylethanolamine. Only four volatile compounds were identified, which is unusual for marine invertebrates.

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.

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.

Structural characterization of oxidized phospholipid products derived from arachidonate-containing plasmenyl glycerophosphocholine

Plasmenyl phospholipids are a structurally unique class of lipids that contain a vinyl ether substituent at the sn-1 position of the glycerol backbone, imparting unique susceptibility to oxidative reactions that may take place at the cell membrane lipid bilayer. Several studies have supported the hypothesis that plasmalogens may be antioxidant molecules that protect cells from oxidative stress. Because the molecular mechanism for the antioxidant properties of plasmenyl phospholipids is not fully understood, the oxidation of arachidonate-containing plasmalogen-glycerophosphocholine (GPC) was studied using electrospray tandem mass spectrometry after exposure to the free radical initiator 2, 2'-azobis(2-amidinopropane)hydrochloride (AAPH). Various oxidized GPC products involving the sn-1 position alone (1-formyl-2-arachidonyl lipids and lysophospholipid), oxidation products involving the sn-2 position alone (chain-shortened omega-aldehyde radyl substituents at sn-2) as well as products oxidized both at the sn-1 and sn-2 positions were observed and structurally identified. The results of these experiments suggest that oxidation of plasmenyl phospholipids esterified with polyunsaturated fatty acid groups at sn-2 likely undergo unique and specific free radical oxidation at the 1'-alkenyl position as well as oxidation of the double bond closest to the ester moiety at sn-2.

Oxidation of plasmalogens produces highly effective modulators of macrophage function

Model derivatives of plasmalogens and chemically synthesized oxidative degradation products as found e.g. during oxidation of low density lipoproteins show strong effects on phagocytosis induced secretion of reactive oxygen species of macrophages which was measured by luminol-enhanced chemiluminescence. Whereas a plasmalogen epoxide showed enhancing effects in submicromolar range, inhibition was found with higher concentrations as well as with alpha-hydroxyaldehydes. The substances showed only little effects on the non-cellular ROS-dependent chemiluminescence of the reaction between hydrogen peroxide and opsonized zymosan and no cytotoxic effects under the assay conditions used. These results show that oxidative modification and degradation of plasmalogens occuring also under pathophysiological situations in vivo produces effective modulators of macrophage function which could be important; e.g. during inflammation or atherogenesis.

Fatty acid composition of choline and ethanolamine glycerophospholipid subclasses in heart tissue of mammals and migratory and demersal fish

The distribution and fatty acid composition of cardiac choline and ethanolamine glycerophospholipids in both migratory and demersal fish and bovine and pig were determined. Phospholipid contents (mg/g heart) were 4.7-9.4 in demersal fish, 14.0-16.5 in migratory fish, and 16.8-20.6 in mammals. Phosphatidylcholine (PC) and phosphatidylethanolamine (PE) were the major components in the phospholipid fraction. Diacyl forms represented 50.2-88.1% of PC in all animals, while plasmalogens comprised 47.0% in bovine, 8.2% in pig and 6.2-7.2% in four species of fish. In PE, plasmalogens varied from 45.0% in bovine and 57.9% in pig to 26.1-29.7% in fish. This glycerophospholipid subclass was identified as containing higher proportions of polyunsaturated fatty acids (PUFAs; 20:4, 20:5, and 22:6) than found in alkylacyl- and diacyl-glycerophospholipids. Qualitative and quantitative differences were found in PE-plasmalogen between land mammals and fish, especially with regard to n-3 fatty acid composition, but no significant difference was noted between migratory and demersal fish.

Decrease and structural modifications of phosphatidylethanolamine plasmalogen in the brain with Alzheimer disease

Several lipid modifications, some of which were attributed to oxidative stress, have been reported in the brains of patients with Alzheimer disease (AD). To evaluate this possibility, all phospholipids and their ether subclasses from the frontal cortex, hippocampus, and the white matter of AD brain were analyzed by high performance liquid chromatography and gas chromatography. The total phospholipid in the frontal cortex and hippocampus decreased on a DNA basis by about 20% and this change was essentially explained by a selective decrease in phosphatidylethanolamine and phosphatidylcholine. The lower content of phosphatidylethanolamine was due to a specific decrease in the plasmalogen subclass. Phosphatidylethanolamine plasmalogen was also the only lipid exhibiting major structural modifications: a significant decrease in polyunsaturated fatty acids and oleic acid as well as a shift of the aldehyde pattern from 18:1 to 18:0. The only modification observed in the other phospholipids was a decrease in oleic acid in diacyl-phosphatidylethanolamine and diacyl-phosphatidylcholine. None of these changes were observed in the white matter. Both the vinyl ether bond of phosphatidylethanolamine plasmalogen and polyunsaturated fatty acids are major targets in oxidative stress; thus, these specific lipid modifications strongly support the involvement of free radicals in the pathogenesis of AD.

Susceptibility of plasmenyl glycerophosphoethanolamine lipids containing arachidonate to oxidative degradation

Plasmenyl phospholipids (1-alk-1'-enyl-2-acyl-3-glycerophospholipids, plasmalogens) are a structurally unique class of lipids that contain an alpha-unsaturated ether substituent at the sn-1 position of the glycerol backbone. Several studies have supported the hypothesis that plasmalogens may be antioxidant molecules that protect cells from oxidative stress. Because the molecular mechanisms responsible for the antioxidant properties of plasmenyl phospholipids are not fully understood, the oxidation of plasmalogens in natural mixtures of phospholipids was studied using electrospray tandem mass spectrometry. Glycerophosphoethanolamine (GPE) lipids from bovine brain were found to contain six major molecular species (16:0p/18:1-, 18:1p/18:1-, 18:0p/20:4-, 16:0p/20:4, 18:0a/20:4-, and 18:0a/22:6-GPE). Oxidation of GPE yielded lyso phospholipid products derived from plasmalogen species containing only monounsaturated sn-2 substituents and diacyl-GPE with oxidized polyunsaturated fatty acyl substituents at sn-2. The only plasmalogen species remaining intact following oxidation contained monounsaturated fatty acyl groups esterified at sn-2. The mechanism responsible for the rapid and specific destruction of plasmalogen GPE may likely involve unique reactivity imparted by a polyunsaturated fatty acyl group esterified at sn-2. This structural feature may play a central role determining the antioxidant properties ascribed to this class of phospholipids.