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At least 253 records · Page 14Linked to original sources
PubMed2004

Revisiting antiphospholipid antibodies: from targeting phospholipids to phospholipid binding proteins.

The antiphospholipid syndrome (APS) is a multi-system prothrombotic disorder associated with circulating auto-antibodies directed against various phospholipid-binding proteins. The major clinical manifestations are recurrent arterial or venous thrombosis, but due to its heterogeneity, atypical presentations can obscure the diagnosis. Decisions regarding when to attribute complications to aPL are difficult. The most established tests are lupus anticoagulant (LA) detected by clotting assays and anticardiolipin (aCL) detected by ELISA. Although LA and aCL assays are clinically useful, these tests do not clearly differentiate antibodies with different specificities. Antibodies to beta2GPI are associated with thrombosis in the APS. Although these antibodies are detected by aCL assay (e.g. beta2GPI-dependent aCL), some aCL are not associated with the syndrome (e.g. beta2GPI-independent aCL). Regarding LAs, more studies are needed to determine if it is clinically important to differentiate specificities against beta2GPI or prothrombin. The role of aPLs in the pathogenesis of thrombosis requires further and intensive investigation. If autoantibodies to particular phospholipid binding proteins are shown to be associated with different clinical presentations or to confer different risks, the availability of more accurate diagnostic techniques will be required for the recognition of pathogenic aPLs. By now, clinical judgement, careful exclusion of other etiologies and serial aPL levels are helpful in this regard.

Animals↗
PubMed1987

Interaction of phospholipids, retinoids and PMA with calcium, phospholipid-dependent protein kinase-catalyzed reaction in skin.

Previous investigations suggested that a mechanism independent of cAMP may be associated with the action of some retinoids. An alternative pathway involving calcium, phospholipid-dependent protein kinase (C-kinase), was therefore studied. In order to demonstrate this, C-kinase was partially purified from skin of hairless, Balb/c normal and Balb/c nude mouse. Interaction and effects of various response modifiers such as phospholipids, retinoids and phorbol ester tumor promoters showed both major and minor differences among these enzymes. In general, retinal, retinoic acid, 13-cis-retinoic acid and etretinate stimulated skin enzyme activity in the absence of the natural stimulants, phosphatidyl serine and diacylglycerol (DAG). However in their presence the C-kinases were inhibited by retinoids. Our data further indicated that the active retinoids may compete with DAG for binding sites on the enzyme. However, the high concentrations of retinoids needed to elicit these effects suggested a pharmacological role for retinoid action as a result of hydrophobic interaction with lipid domains on the enzyme. These investigations also revealed some of the complexity associated with retinoid effects on C-kinase. Tumor promoter, phorbol-12-myristate 13-acetate (PMA) interacted with its receptor (C-kinase) from hairless and normal mouse skin and stimulated enzyme activity. However, PMA-dependent stimulation of nude mouse C-kinase was about half of that noted with the other two C-kinases. Furthermore, unlike its effect on hairless and Balb/c normal C-kinases, PMA was unable to potentiate the retinoid-stimulated activity of nude mouse skin enzyme. This behavior suggested that nude mouse C-kinase may be a variant form of the normal enzyme. The presence of this variant C-kinase may, therefore, be responsible for the lack of phorbol ester-induced tumor promotion observed earlier in nude mouse skin by other investigators. Endogenous substrate phosphorylation catalyzed by C-kinase from hairless and Balb/c normal mice resulted in 32P incorporation into four target polypeptides of molecular weights 75-78, 47-50, 25-29 and 14-18 kilodaltons. However, with the nude mouse enzyme, only the 75- to 78-kilodalton protein served as the target supporting the suggestion that this may be a variant C-kinase. Neither retinoic acid (10(-3) M) nor PMA (10(-6) M) seemed to affect the phosphorylation of any of the four polypeptides.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1986

[Changes in the phospholipid-phospholipid ratios and the enzyme activity of antioxidant protection in the rat lung during dehydration].

It was established that water deprivation during 3, 6, 9 days caused a distinct decrease in phospholipid level and disturbances of phospholipid composition in the rat lung tissue. It was accompanied by alterations in the activity of antioxidant defense system enzymes (superoxide dismutase, glutathione peroxidase, glutathione reductase, catalase, glucose-6-phosphate dehydrogenase). These data are indicative of lipid peroxidation intensification in the rat lungs during water deprivation.

Animals↗
PubMed1986

Reconstitution of Saccharomyces cerevisiae phosphatidylserine synthase into phospholipid vesicles. Modulation of activity by phospholipids.

Membrane-associated phosphatidylserine synthase was purified from Saccharomyces cerevisiae (Bae-Lee, M., and Carman, G. M. (1984) J. Biol. Chem. 259, 10857-10862) and reconstituted into phospholipid vesicles containing phosphatidylcholine/phosphatidylethanolamine/ phosphatidylinositol/phosphatidylserine. Reconstitution was performed by removing detergent from an octyl glucoside/phospholipid/Triton X-100/enzyme mixed micelle by Sephadex G-50 super-fine chromatography. The average diameter of the vesicles was 90 nm, and the enzyme was reconstituted asymmetrically with the active site facing outward. The enzymological properties of reconstituted phosphatidylserine synthase were determined in the absence of detergent. The enzyme was reconstituted into vesicles with phospholipid compositions approximating those of wild type and mutant strains of S. cerevisiae. Reconstituted activity was modulated by the phosphatidylinositol/phosphatidylserine ratio in the vesicles. The modulation of activity observed in the vesicles is enough to account for some of the fluctuations in the phosphatidylserine content in vivo.

Binding Sites↗
PubMed1988

Behavior of human apolipoprotein A-I: phospholipid and apoHDL:phospholipid complexes in vitro and after injection into rabbits.

Apolipoprotein A-I was purified from human high density lipoprotein and complexed with polyunsaturated phosphatidylcholine (PC) in deoxycholate (Lipostabil); the bile salt was removed subsequently by dialysis. The behavior of the resultant apoA-I/PC complexes was compared with that of Lipostabil in vitro and after injection into rabbits. In vivo apoA-I/PC complexes had the density of HDL throughout but had both alpha and pre beta electrophoretic mobility, the latter probably reflecting dissociation of apoA-I from PC. Lipostabil initially behaved like LDL but gradually acquired the density of HDL after incubation with plasma and in vivo. Both preparations increased plasma total phospholipids in normolipidemic rabbits to a similar extent, but, increments in HDL phospholipid were greater after apoA-I/PC complexes were injected. ApoHDL/PC complexes, prepared in a similar manner, appeared to promote efflux of cholesterol from perfused rabbit aortas in the presence of lecithin:cholesterol acyltransferase (LCAT) activity, consistent with a stimulatory effect on cholesterol mobilization. Injection of apoHDL/PC complexes into hyperlipidemic rabbits decreased plasma cholesterol but increased HDL cholesterol, whereas Lipostabil decreased both. These findings suggest that human apoA-I/PC complexes resemble HDL in their behavior more closely than does Lipostabil, and show that both types of liposome undergo modification upon interaction with plasma. It remains to be shown whether they possess any therapeutic potential.

Animals↗
PubMed1987

Synthesis of phospholipids and nucleoside-phospholipid conjugates via hydrogenphosphonate intermediates.

Chemical synthesis of nucleoside-phospholipid conjugates based on hydrogenphosphonate chemistry has been achieved via coupling of 1,2-dipalmitoylglycero-3-H-phosphonate with suitable protected nucleosides or via coupling of nucleoside H-phosphonates with 1,2-dipalmitoylglycerol. It was also found that 1,2-dipalmitoylglycero-3-H-phosphonate, which is a stable compound, can serve as a convenient intermediate in the synthesis of various phospholipids.

Indicators and Reagents↗
PubMedDate not supplied

[Changes in the phospholipid-phospholipid ratio and lipid peroxidation in the heart muscle in experimental myocardial infarction before and after combined antioxidant therapy].

Dynamics of quantitative relations between neutral and acid phospholipids in rabbit myocardium was studied with simultaneous registration of lipid free radical oxidation (estimated by malonic dialdehyde content) in NADP-dependent system of oxidation within various periods after simulation of myocardial infarction in the animals treated with alpha-tocopherol and sodium nucleinate 2 and 25 mg/kg of body mass, respectively) and did not receiving the drugs. The complex treatment led to normalization of qualitative and quantitative relations between phospholipids in the impaired myocardium and to decrease the lipid peroxidation in myocardium infarction.

Animals↗
PubMedDate not supplied

[Phospholipid-phospholipid relations and changes of free radical lipid oxidation in biological membranes during alloxan diabetes].

Quantitative and qualitative composition of phospholipids as well as lipid peroxidation were studied in outer and inner mitochondrial membranes and microsomal fraction from rat liver tissue under conditions of alloxane diabetes. In the diabetes amount of phospholipids, mainly cardiolipins and phosphatidylethanolamines, was increased in the inner and decreased in the outer mitochondrial membranes. Phosphatidylcholines and phosphatidylserines were increased in microsomal fraction. At the same time, lipid peroxidation was activated both in ascorbate- and NADPH-dependent systems of oxidation. These data suggest that lipid peroxidation affects the composition of mitochondrial membranes either by means of removing of the substances from membranes or via their redistribution between the subcellular fractions.

Animals↗
PubMed1981

Studies on thermal adaptation in Tetrahymena membrane lipids. Changes in positional distribution of fatty acids in diacyl-phospholipids and alkyl-acyl-phospholipids during temperature acclimation.

The positioning of acyl chains in both 1-O-alkyl-2-acyl- and 1,2-diacyl-phospholipids was analyzed at various time intervals for a thermotolerant strain (NT-1) of Tetrahymena pyriformis cells during cold acclimation. During the 10 h period of adaptation, cells were not able to grow but maintained the ability to divide. The content of palmitate (16 : 0) in phosphatidylcholine and phosphatidylethanolamine was decreased after temperature-shift, with a concurrent increase of palmitoleate (16 : 1 delta 9) and gamma-linolenate (18 : 3 delta 6,9,12). An increase in gamma-linolenate at the 1-position and linoleate at the 2-position was observed in diacyl-phospholipids (phosphatidylethanolamine, phosphatidylcholine and 2-aminoethylphosphonolipid). The 2-position of 1-O-alkyl-2-acyl-phosphatidylcholine and 1-O-alkyl-2-acyl-(2-aminoethyl)phosphonolipid was occupied mainly by gamma-linolenate together with cilienate (18 : 2 delta 6,11) and linoleate (18 : 2 delta 9,12). Cilienate and gamma-linolenate at the 2-position of 1-O-alkyl-2-acyl-phosphatidylcholine were increased after temperature shift, with a small decrease of linoleate. There are little significant changes in alkyl ether lipid content of phosphatidylcholine and 2-aminoethylphosphonolipid after temperature shift. The results indicate that phosphatidylethanolamine, which is most abundant and present only in the diacyl form, would play a crucial role in thermal adaptation of membrane lipids, by replacing palmitate with gamma-linolenate at its 1-position, and also that hexadecyl/gamma-linolenoyl phosphatidylcholine would be an important molecular species in the acclimation.

Animals↗
PubMed1999

Ultrasound interaction with large unilamellar vesicles at the phospholipid phase transition: perturbation by phospholipid side chain substitution with deuterium.

The ultrasonic absorption, alpha lambda, as a function of temperature and frequency was determined in large unilamellar vesicles (LUVs) in which specific phospholipid side chains were deuterated. Deuteration significantly altered the temperature and frequency dependence of alpha lambda. The frequency change was especially marked, with decreased frequency and broadening of the ultrasound relaxation, even with only minor changes in the phase transition temperature. Deuteration decreased the Tm and enthalpy of the lipid phase transition, as shown by differential scanning calorimetry, whereas electron spin resonance showed that at and above the lipid phase transition, no differences in the mobility as a function of temperature were observed. These results show that the observed increase in ultrasonic absorption in LUVs at the phospholipid phase transition arises from the interaction of ultrasound with the hydrophobic side chains, probably coupling with structural reorganization of small domains of molecules, a process which is maximized at the phase transition temperature.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1981

Interaction of cytochrome c with phospholipid monolayers. Orientation and penetration of protein as functions of the packing density of film, nature of the phospholipids, and ionic content of the aqueous phase.

Energy-transfer fluorescence quenching has been used to observe the binding of cytochrome c to a lipid assembly. The probe (donor), dansylphosphatidylethanolamine, was dispersed either in dipalmitoylphosphatidylcholine, in phosphatidic acid, or in a mixture of the two lipids. The heme of the protein was the acceptor. When the phospholipids were spread in monolayer at the air-water interface, orientation and penetration parameters of the protein relative to the membrane were obtained. The cytochrome is bound with an orientation such that its heme crevice is fully accessible to the aqueous space. It penetration in the lipid layer is dependent on the ionic content of the subphase and the initial packing of the film. The perturbation induced in the lipid matrix by the binding appear very localized. The same results were obtained with lipid microvesicles. The type of binding of cytochrome c to phospholipids observed here implies that there are specific areas on the protein which appear to be different from those involved in its interaction with cytochrome oxidase and other cytochromes. These conclusions are relevant to the existence of different classes of binding sites for cytochrome c in the mitochondrial membrane.

Cytochrome c Group↗
PubMed1990

Evidence that the inositol phospholipids are necessary for exocytosis. Loss of inositol phospholipids and inhibition of secretion in permeabilized cells caused by a bacterial phospholipase C and removal of ATP.

We directly manipulated the levels of PtdIns, PtdInsP and PtdInsP2 in digitonin-treated adrenal chromaffin cells with a bacterial phospholipase C (PLC) from Bacillus thuringiensis and by removal of ATP. The PtdIns-PLC acted intracellularly to cause a large decrease in [3H]inositol- or [32P]phosphate-labelled PtdIns, but did not directly hydrolyse PtdInsP or PtdInsP2. [3H]PtdInsP and [3H]PtdInsP2 levels declined markedly, probably because of the action of phosphatases in the absence of synthesis. Removal of ATP also caused marked decreases in [3H]PtdInsP and [3H]PtdInsP2. The decrease in polyphosphoinositide levels by PtdIns-PLC treatment or ATP removal was reflected by the inhibition of the production of inositol phosphates upon subsequent activation of the endogenous PLC by Ca2(+)-dependent catecholamine secretion from permeabilized cells was strongly inhibited by PtdIns-PLC treatment and by ATP removal. Ca2(+)-dependent secretion was similarly correlated with the sum of PtdInsP and PtdInsP2 when the level of these lipids was changed by either manipulation. PtdIns-PLC inhibited only the ATP-dependent component of secretion and did not affect ATP-dependent secretion. Both PtdIns-PLC and ATP removal inhibited the late slow phase of secretion, but had little effect on the initial rapid phase. Although we found a tight correlation between polyphosphoinositide levels and secretion, endogenous phospholipase C activity (stimulated by Ca2+, guanine nucleotides and related agents) was not correlated with secretion. Additional experiments indicated that neither the products of the PtdIns-PLC reaction (diacylglycerol and InsP1) nor the inability to generate products by subsequent activation of the endogenous PLC is likely to account for the inhibition of secretion. Incubation of permeabilized cells with neomycin in the absence of ATP maintained the level of polyphosphoinositides and more than doubled subsequent Ca2(+)-dependent secretion. The data suggest that: (1) Ca2(+)-dependent secretion has a requirement for the presence of inositol phospholipids; (2) the enhancement of secretion by ATP results in part from increased polyphosphoinositide levels; and (3) the role for inositol phospholipids in secretion revealed in these experiments is independent of their being substrates for the generation of diacylglycerol and InsP3.

Adenosine Triphosphate↗
PubMed1985

Interaction of the sperm adhesive protein, bindin, with phospholipid vesicles. I. Specific association of bindin with gel-phase phospholipid vesicles.

Bindin is a 30,000-mol-wt protein of sea urchin sperm that is responsible for the specific adhesion of the sperm acrosomal process to the vitelline layer covering the egg plasma membrane during fertilization. Sulfated glycoconjugates are believed to be the egg surface receptors for bindin, but the mechanism by which bindin associates with the sperm acrosomal membrane is unknown. Here I report that bindin specifically associates with phospholipid vesicles in vitro. Interaction of the bindin polypeptide with liposomes was found to cause an increase in the density of the liposomes and induce the aggregation of the vesicles. A novel property of this association of bindin with membranes was that it required phospholipids in a gel phase. The interaction of bindin with liposomes was greatly reduced at temperatures above the phase transition temperature. The interaction of bindin with gel-phase vesicles appeared to be reversible, since the aggregated vesicles dissaggregated as the temperature was raised above the phase transition temperature. Association of bindin with the bilayer did not alter the accessibility of the polypeptide to cleavage by trypsin, which suggests that most of the polypeptide chain remains exposed at the surface of the membrane.

Animals↗
PubMed1987

Reconstitution of purified chicken gizzard 5'-nucleotidase in phospholipid vesicles. Evidence for its transmembraneous character and the existence of functional domains on both sides of the phospholipid bilayer.

5'-Nucleotidase, purified to homogeneity from chicken gizzard using published procedures [Dieckhoff, J., Knebel, H., Heidemann, M. and Mannherz, H. G. (1985) Eur. J. Biochem. 151, 377-383] was incorporated into artificial phospholipid vesicles after prolonged dialysis against detergent-free buffer or by a gel filtration procedure. After dialysis the obtained liposomes exhibit a mean diameter of 80 nm and contain 5'-nucleotidase at random orientation, demonstrated by finding up to 50% of the total liposome-incorporated AMPase activity to be cryptic, i.e. could only be measured after their permeabilization by addition of detergent. By affinity chromatography a phospholipid vesicle fraction could be obtained containing almost exclusively cryptic AMPase activity, thus representing the inside-out orientation of 5'-nucleotidase. Comparative analysis of physiochemical and enzymatic properties of 5'-nucleotidase reveals differences between the detergent-solubilized and the liposome-incorporated 5'-nucleotidase including a changed accessibility of the enzyme to polyclonal and monoclonal antibodies. Binding and AMPase inhibition studies with different polyclonal antibodies strongly indicate to the existence of a cytoplasmic domain of chicken gizzard 5'-nucleotidase. F-actin appears preferentially to interact with the cytoplasmic domain of liposome-incorporated 5'-nucleotidase.

5'-Nucleotidase↗
PubMed2003

Reactivity profiles of autoantibodies to different phospholipids and the phospholipid-binding protein beta2-glycoprotein I in patients with clinical symptoms related to thromboembolic and/or vasculopathic events with or without connective tissue diseases.

To study the antigenic and epitope specificities of anti-phospholipid Ab in detail, we investigated 177 patients without (62 with APS-related systemic clinical symptoms, 115 with microangiopathies) and 164 patients with connective tissue diseases (CTD). Ab associated with primary APS (pAPS) seem to show a restricted specificity (phospholipid/beta2-GPI-complexes), whereas those in secondary APS (sAPS) react additionaly with pure beta2-GPI. Simultaneously, beta2-GPI-independent Ab were also frequently present in both conditions (50% of all Ab-positive sera). In CTD patients, the reactivity profile "pure beta2-GPI + phospholipid/beta2-GPI-complexes" is significantly associated with clinically manifest sAPS. Comparing cardiolipin and phosphatidylserine as antigenic target, the overall concordance (crossreactivity?) between both assays was lower than expected (52%), being highest in pAPS (87%) and sAPS (65%). Based on these results, a two-step procedure for reliable serological diagnosis of APS could be recommended: Ab-screening using a mix of phospholipids complexed with beta2-GPI (sensitivity > 90% for Ab concentrations above 20 U/ml) followed by an assay allowing the simultaneous detection of all relevant antigenic and epitope specificities.

Adult↗
PubMed1991

[Microsomal phospholipid pattern and liver ultrastructure of aging rats following treatment with essential phospholipids].

The treatment of aging rats with 100 or 300 mg/kg "essential" phospholipids (EPL) for 10 weeks significantly changed the microsomal concentration of phosphatidyl serine plus phosphatidyl inositol. The most marked alterations of the phospholipid fatty acid pattern predominantly observed with unsaturated fatty acids were detectable even 7 days after cessation of EPL application. Ultrastructurally, an enrichment in the hepatocytes with rough endoplasmic reticulum was visible which was more prominent in acinus zone 3. The changes after EPL administration are regarded as the expression of an increased membrane fluidity.

Aging↗
PubMed1980

The occurrence of direct desaturation of phospholipid acyl chain in Tetrahymena pyriformis. Thermal adaptation of membrane phospholipid.

Microsomes from Tetrahymena pyriformis catalyzed the conversion of 1-acyl-2-[1-14C]oleoyl-sn-glycero-3-phosphorylcholine to 1-acyl-2-[1-14C]linoleoyl-sn-glycero-3-phosphorylcholine in the presence of oxygen and NADH or NADPH as cofactors. This desaturation enzyme activity was inhibited by cyanide and increased by 0.05-0.1% Triton X-100. Under optimal conditions desaturation appeared to follow Michaelis-Menten kinetics with a Km value of 6.9 . 10(-4) M. During incubation, no significant cleavage of phospholipid substrate was observed and no desaturation of free fatty acid occurred. The activity of 1-acyl-2-oleoyl-sn-glycero-3-phosphorylcholine desaturase was increased approx. 4-fold when Tetrahymena cells were shifted to a lower growth temperature. These data suggest the existence of a direct phospholipid desaturation system from oleoylphosphatidylcholine to linoleoylphosphatidylcholine. In addition, this desaturation may participate in the control of membrane lipid adaptation to a lower growth temperature in Tetrahymena.

Animals↗
PubMed1982

Transfer properties of the bovine brain phospholipid transfer protein. Effect of charged phospholipids and of phosphatidylcholine fatty acid composition.

The monolayer technique has been used to study the transfer of [14C]phosphatidylinositol from the monolayer to phosphatidylcholine vesicles. An equivalent transfer rate was found for egg phosphatidylcholine, dioleoylphosphatidylcholine, dielaidoylphosphatidylcholine and dipalmitoylphosphatidylcholine. A reduced transfer rate was found for a shorter-chain derivative, dimyristoylphosphatidylcholine, and for species with two polyunsaturated fatty acid chains such as dilinoleoylphosphatidylcholine, diheptadecadienoylphosphatidylcholine, dilinolenoylphosphatidylcholine and diether and dialkyl derivatives. No activity was found for 1,3-dipalmitoylphosphatidylcholine. The presence of up to 5 mol% phosphatidylinositol in egg phosphatidylcholine vesicles had no effect on the transfer rate. Introduction of more than 5 mol% phosphatidylinositol or phosphatidic acid into the phosphatidylcholine vesicles gradually decreased the rate of phosphatidylinositol transfer from the monolayer. 20 mol% acidic phospholipid was nearly completely inhibitory. Transfer experiments between separate monolayers of phosphatidylcholine and phosphatidylinositol showed that the protein-bound phosphatidylcholine is readily exchanged for phosphatidylinositol, but the protein-bound phosphatidylinositol exchange for phosphatidylcholine occurs at a 20-times lower rate. The release of phosphatidylinositol is dependent on the lipid composition and the concentration of charged lipid in the acceptor membrane, but also on the ratio between donor and acceptor membranes. The main transfer protein from bovine brain which transfers phosphatidylinositol and phosphatidylcholine transfers also phosphatidylglycerol, but not phosphatidylserine or phosphatidic acid. The absence of significant changes in the surface pressure indicate that the phosphatidylinositol and phosphatidylcholine transfer is not accompanied by net mass transfer.

Animals↗