Exogenous polyunsaturated fatty acids (PUFAs) promote changes in growth, phospholipid composition, membrane permeability and virulence phenotypes in Escherichia coli

BACKGROUND

The utilization of exogenous fatty acids by Gram-negative bacteria has been linked to many cellular processes, including fatty acid oxidation for metabolic gain, assimilation into membrane phospholipids, and control of phenotypes associated with virulence. The expanded fatty acid handling capabilities have been demonstrated in several bacteria of medical importance; however, a survey of the polyunsaturated fatty acid responses in the model organism Escherichia coli has not been performed. The current study examined the impacts of exogenous fatty acids on E. coli.

RESULTS

All PUFAs elicited higher overall growth, with several fatty acids supporting growth as sole carbon sources. Most PUFAs were incorporated into membrane phospholipids as determined by Ultra performance liquid chromatography-mass spectrometry, whereas membrane permeability was variably affected as measured by two separate dye uptake assays. Biofilm formation, swimming motility and antimicrobial peptide resistance were altered in the presence of PUFAs, with arachidonic and docosahexaenoic acids eliciting strong alteration to these phenotypes.

CONCLUSIONS

The findings herein add E. coli to the growing list of Gram-negative bacteria with broader capabilities for utilizing and responding to exogenous fatty acids. Understanding bacterial responses to PUFAs may lead to microbial behavioral control regimens for disease prevention.

Comparative lipidomic analysis of phospholipids of hydrocorals and corals from tropical and cold-water regions

To expand our knowledge of lipid and fatty acid (FA) biosynthesis in marine cnidarians, polar lipidomes of hydrocorals were studied for the first time and then compared with those of soft corals from tropical and boreal regions. The structure and content of FAs and molecular species of ethanolamine, choline, serine, and inositol glycerophospholipids (PE, PC, PS, and PI, respectively), and ceramide aminoethylphosphonate (CAEP) in tropical hydrocorals (Millepora platyphylla, M. dichotoma) and the cold-water hydrocoral Allopora steinegeri were determined by chromatography and mass spectrometry. All soft corals and cold-water hydrocorals are characterized by a considerable amount of C₂₀ polyunsaturated FAs (PUFAs) elongated into C₂₂ PUFAs. In the Millepora species, the high level of 22:5n-6 and 22:6n-3 against the background of the extremely low level of C₂₀ PUFAs may be explained by a high activity of rare Δ4 desaturase. In contrast to hydrocorals, soft corals are able to elongate and further desaturate C₂₂ PUFAs into C₂₄ PUFAs. Allopora and soft corals use C₂₀ PUFAs mainly for the synthesis of PE and PC. The molecular species of PS of soft corals concentrate C₂₄ PUFAs, while in Allopora and Millepora the PS molecules are mainly based on 22:4n-6 and 22:5n-6 acyl groups, respectively. Short acyl groups (C₁₄) dominate the CAEP molecules of Allopora. In all the animals compared, most molecular species of PE and PC are ether lipids, but diacyl molecular species dominate PI. Hydrocorals and tropical soft corals contain diacyl and ether PS molecules, respectively, whereas cold-water soft corals contain a mixture of these PS forms. The high similarity of the alkyl/acyl compositions indicates a possible biosynthetic relationship between PS and PI in hydrocorals. The data obtained in our study will provide a resource to further investigate the lipid metabolism in marine invertebrates.

Phospholipids of Animal and Marine Origin: Structure, Function, and Anti-Inflammatory Properties

In this review paper, the latest literature on the functional properties of phospholipids in relation to inflammation and inflammation-related disorders has been critically appraised and evaluated. The paper is divided into three sections: Section 1 presents an overview of the relationship between structures and biological activities (pro-inflammatory or anti-inflammatory) of several phospholipids with respect to inflammation. Section 2 and Section 3 are dedicated to the structures, functions, compositions and anti-inflammatory properties of dietary phospholipids from animal and marine sources. Most of the dietary phospholipids of animal origin come from meat, egg and dairy products. To date, there is very limited work published on meat phospholipids, undoubtedly due to the negative perception that meat consumption is an unhealthy option because of its putative associations with several chronic diseases. These assumptions are addressed with respect to the phospholipid composition of meat products. Recent research trends indicate that dairy phospholipids possess anti-inflammatory properties, which has led to an increased interest into their molecular structures and reputed health benefits. Finally, the structural composition of phospholipids of marine origin is discussed. Extensive research has been published in relation to ω-3 polyunsaturated fatty acids (PUFAs) and inflammation, however this research has recently come under scrutiny and has proved to be unreliable and controversial in terms of the therapeutic effects of ω-3 PUFA, which are generally in the form of triglycerides and esters. Therefore, this review focuses on recent publications concerning marine phospholipids and their structural composition and related health benefits. Finally, the strong nutritional value of dietary phospholipids are highlighted with respect to marine and animal origin and avenues for future research are discussed.

Oxidative Phospholipidomics in health and disease: Achievements, challenges and hopes

Phospholipid peroxidation products are recognized as important bioactive lipid mediators playing an active role as modulators in signalling events in inflammation, immunity and infection. The biochemical responses are determined by the oxidation structural features present in oxPL modulating biophysical and biological properties in model membranes and lipoproteins. In spite of the extensive work conducted with model systems over the last 20 years, the study of oxPL in biological systems has virtually stagnated. In fact, very little is known concerning the predominant oxPL in fluids and tissues, their basal levels, and any variations introduced with age, gender and ethnicity in health and disease. In consequence, knowledge on oxPL has not yet translated into clinical diagnostic, in the early and timely diagnosis of "silent" diseases such as atherosclerosis and cardiovascular diseases, or as prognosis tools in disease stratification and particularly useful in the context of multimorbidities. Their use as therapeutic solutions or the development of innovative functional biomaterials remains to be explored. This review summarizes the achievements made in the identification of oxPL revealing an enormous structural diversity. A brief overview of the challenges associated with the analysis of such diverse array of products is given and a critical evaluation on key aspects in the analysis pipeline that need to be addressed. Once these issues are addressed, Oxidative Phospholipidomics will hopefully lead to major breakthrough discoveries in biochemistry, pharmaceutical, and clinical areas for the upcoming 20 years. This article is part of Special Issue entitled 4-Hydroxynonenal and Related Lipid Oxidation Products.

Pleiotropic effects of oxidized phospholipids

Oxidized phospholipids (OxPLs) are increasingly recognized to play a role in a variety of normal and pathological states. OxPLs were implicated in regulation of inflammation, thrombosis, angiogenesis, endothelial barrier function, immune tolerance and other important processes. Rapidly accumulating evidence suggests that OxPLs are biomarkers of atherosclerosis and other pathologies. In addition, successful application of experimental drugs based on structural scaffold of OxPLs in animal models of inflammation was recently reported. This review briefly summarizes current knowledge on generation, methods of quantification and biological activities of OxPLs. Furthermore, receptor and cellular mechanisms of these effects are discussed. The goal of the review is to give a broad overview of this class of lipid mediators inducing pleiotropic biological effects.

Optimal single-embryo mass spectrometry fingerprinting

In pre-implantation embryos, lipids play key roles in determining viability, cryopreservation and implantation properties, but often their analysis is analytically challenging because of the few picograms of analytes present in each of them. Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) allows obtaining individual phospholipid profiles of these microscopic organisms. This technique is sensitive enough to enable analysis of individual intact embryos and monitoring the changes in membrane lipid composition in the early stages of development serving as screening method for studies of biology and biotechnologies of reproduction. This article introduces an improved, more comprehensive MALDI-MS lipid fingerprinting approach that considerably increases the lipid information obtained from a single embryo. Using bovine embryos as a biological model, we have also tested optimal sample storage and handling conditions before the MALDI-MS analysis. Improved information at the molecular level is provided by the use of a binary matrix that enables phosphatidylcholines, sphingomyelins, phosphatidylserines, phosphatidylinositols and phosphoethanolamines to be detected via MALDI(±)-MS in both the positive and negative ion modes. An optimal MALDI-MS protocol for lipidomic monitoring of a single intact embryo is therefore reported with potential applications in human and animal reproduction, cell development and stem cell research.

Marine omega-3 phospholipids: metabolism and biological activities

The biological activities of omega-3 fatty acids (n-3 FAs) have been under extensive study for several decades. However, not much attention has been paid to differences of dietary forms, such as triglycerides (TGs) versus ethyl esters or phospholipids (PLs). New innovative marine raw materials, like krill and fish by-products, present n-3 FAs mainly in the PL form. With their increasing availability, new evidence has emerged on n-3 PL biological activities and differences to n-3 TGs. In this review, we describe the recently discovered nutritional properties of n-3 PLs on different parameters of metabolic syndrome and highlight their different metabolic bioavailability in comparison to other dietary forms of n-3 FAs.

[Study of phospholipid profile of ovarian tumor by high performance liquid chromatography-mass spectrometry]

Ovarian tumor has been paid more and more attention since its influence on women's health and life quality is increasing. Ovarian cancer is one of the three gynecologic cancers, and its mortality is the highest one of them. Phospholipid metabolic profiling method based on high performance liquid chromatography-electrospray mass spectrometry (HPLC/ESI-MS) has been applied in the study of ovarian tumors including benign (B) and malignant (M) ovarian tumors. The data of phospholipid profile collected by HPLC/ESI-MS were transformed and the peak list was obtained with the commercial software automatically. The total differences of phospholipids among M, B and normal (N) groups were found with the orthogonal signal correction and partial least-squares (OSC-PLS). Further, the differential phospholipids were selected according to the S-plot, the variable importance value (VIP > 1) and p (p < 0.05). These phospholipids were plasmalogen phospatidylethanol, phosphatidylcholine, plasmalogen phosphatidylcholine, sphingomyelin and lysophosphatidylcholine. This research provides some new and useful information of what has happened in phospholipids of the women with ovarian tumors.

[Effect of tangshen formula on phospholipids metabolism in diabetic nephropathy patients]

This study was to report the effect of Tangshen Formula on phospholipids metabolism in diabetic nephropathy patients. A normal phase-HPLC-TOF/MS method was used in this study for the determination of seven species of phospholipids in human plasma. Then, the concentration changes of potential phospholipids biomarkers were discussed in diabetic nephropathy phase III and phase IV patients among different groups, including before and 3, 6 months after administration of Tangshen Formula. Significant increases of PE750, PI885, PC792, PC826, PC830, PC854 and PC802 levels were observed 6 months after administration of Tangshen Formula and conventional western medicine, as well as a decrease of LPC540 level, when compared with those before medication. Concentrations of all the potential phospholipids biomarkers showed a tendency towards normal levels; however, both the improvement degree and onset time of these compounds were not same. Additionally, Tangshen Formula treatment based on conventional western medicine treatment was more efficient in adjusting the levels of these compounds when compared with western medicine treatment alone, especially for the phase IV patients. These results indicated that Tangshen Formula was capable in regulating and improving phospholipids metabolism in diabetic nephropathy patients, which may be related with the direct or indirect inhibition of protein kinase C pathway and the corresponding reduction of phospholipase A2 activity. Therefore, Tangshen Formula may be used as an effective drug for diabetic nephropathy therapy, at least as an adjunctive therapeutic drug.

Differences in membrane acyl phospholipid composition between an endothermic mammal and an ectothermic reptile are not limited to any phospholipid class

This study examined questions concerning differences in the acyl composition of membrane phospholipids that have been linked to the faster rates of metabolic processes in endotherms versus ectotherms. In liver, kidney, heart and brain of the ectothermic reptile, Trachydosaurus rugosus, and the endothermic mammal, Rattus norvegicus, previous findings of fewer unsaturates but a greater unsaturation index (UI) in membranes of the mammal versus those of the reptile were confirmed. Moreover, the study showed that the distribution of phospholipid head-group classes was similar in the same tissues of the reptile and mammal and that the differences in acyl composition were present in all phospholipid classes analysed, suggesting a role for the physical over the chemical properties of membranes in determining the faster rates of metabolic processes in endotherms. The most common phosphatidylcholine (PC) molecules present in all tissues (except brain) of the reptile were 16:0/18:1, 16:0/18:2, 18:0/18:2,18:1/18:1 and 18:1/18:2, whereas arachidonic acid (20:4), containing PCs 16:0/20:4, 18:0/20:4, were the common molecules in the mammal. The most abundant phosphatidylethanolamines (PE) used in the tissue of the reptile were 18:0/18:2, 18:0/20:4, 18:1/18:1, 18:1/18:2 and 18:1/20:4, compared to 16:0/18:2, 16:0/20:4, 16:0/22:6, 18:0/20:4, 18:0/22:6 and 18:1/20:4 in the mammal. UI differences were primarily due to arachidonic acid found in both PC and PEs, whereas docosahexaenoic acid (22:6) was a lesser contributor mainly within PEs and essentially absent in the kidney. The phospholipid composition of brain was more similar in the reptile and mammal compared to those of other tissues.

Clinical and MRI correlates of autoreactive antibodies in multiple sclerosis patients

BACKGROUND

Autoreactive antibodies (ARAB) occur more frequently in patients with multiple sclerosis (MS) than in general population and the presence of these antibodies often causes uncertainty regarding the disease course, response to therapy and the diagnosis of MS.

METHODS

Retrospective analyses of the ARAB, clinical and MRI data of a consecutive patient cohort of MS and clinically isolated syndrome (CIS) patients were conducted. The patients were evaluated for an extensive panel that included various subtypes of antiphospholipid antibody (APLA) including anti-phosphatidylethanolamine (APE), anti-phosphatidylserine (APS), anti-beta-2-glycoprotein-1 (ABGP), anti-cardiolipin (ACA), and several other ARAB such as antinuclear antibody (ANA), anti-neutrophilic cytoplasmic antibodies (ANCA), anti-thyroid peroxidase antibodies (ATA), anti-SS-A, and anti-SS-B antibodies. Quantitative MRI analysis was performed in a subgroup of MS patients measuring T2-lesion volume (LV), T1 black hole LV and brain parenchymal fraction (BPF).

RESULTS

A total of 137 patients (mean age 44.7, 84% female) with either MS (n=111; age: mean 46.5+/-S.D. 10.3 years; disease duration: mean 13.0+/-S.D. 10.4 years; EDSS: mean 3.2+/-S.D. 1.9) or CIS (n=26; age: mean 37.7+/-S.D. 7.8 years; disease duration: mean 1.3+/-S.D. 1.1 years; EDSS: mean 1.0+/-S.D. 0.7) were enrolled. Among MS patients, 82 were RRMS, 26 SPMS, and 3 had PPMS. Seventy-seven (69%) of MS patients showed presence of one or more ARAB. The proportion of MS patients with APLA was 55% (61 patients); IgM subtype was most frequent. Co-occurrence of ACA and APE was more frequent in SPMS as compared to RRMS (15.4% vs. 1.2%, p=0.012). The proportion of CIS patients with ARAB was 75% with IgM subtype being the most frequent. However, the ARAB in majority of CIS patients (9 out of 14, 64%) were transient on repeated testing. In a subgroup of 62 MS patients, quantitative MRI analysis showed significantly higher T2-LV in patients with positive APLA (15.1 ml for APLA positive vs. 6.75 ml for APLA negative) after correcting for the disease duration (p=0.048). The patients with ATA also had significantly higher T2-LV after correction for disease duration (19.0 ml vs.8.5, p=0.044).

CONCLUSIONS

ARAB were present in more than two thirds of MS and CIS patients although most of APLA in CIS were transient. The presence of APLA in MS patients was associated with higher T2-LV.

Phospholipid signalling through phospholipase D and phosphatidic acid

Phospholipase D (PLD) hydrolyzes the phosphodiester bond of the predominant membrane phospholipid, phosphatidylcholine producing phosphatidic acid and free choline. This activity can participate in signal transduction pathways and impact on vesicle trafficking for secretion and endocytosis, as well as receptor signalling. Phospholipids can regulate PLD activity directly, through specific intermolecular interactions, or indirectly, through their effect on the localization or activity of PLD's protein effectors. This short review highlights these various phospholipid inputs into the regulation of PLD activity and also reviews potential roles for PLD-generated phosphatidic acid, particularly a mechanism by which the phospholipid may participate in the process of vesicular trafficking.

Ladderane phospholipids in anammox bacteria comprise phosphocholine and phosphoethanolamine headgroups

Anammox bacteria present in wastewater treatment systems and marine environments are capable of anaerobically oxidizing ammonium to dinitrogen gas. This anammox metabolism takes place in the anammoxosome which membrane is composed of lipids with peculiar staircase-like 'ladderane' hydrocarbon chains that comprise three or four linearly concatenated cyclobutane structures. Here, we applied high-performance liquid chromatography coupled to electrospray ionization tandem mass spectrometry and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry to elucidate the full identity of these ladderane lipids. This revealed a wide variety of ladderane lipid species with either a phosphocholine or phosphoethanolamine polar headgroup attached to the glycerol backbone. In addition, in silico analysis of genome data gained insight into the machinery for the biosynthesis of the phosphocholine and phosphoethanolamine phospholipids in anammox bacteria.

[Determination of liposome/water partition coefficients of salmeterol and budesonide and study on their influencing factors]

AIM

The liposome/water partition coefficients of salmeterol and budesonide between aqueous phase and liposomes were determined and the factors that influence their partition coefficients were studied, the mechanism of interaction between the two drugs and phospholipid bilayer was elucidated.

METHODS

The liposome/water partition coefficients of the two drugs were determined by equilibrium dialysis technique. The change of the partition coefficients of the two drugs along with liposome composition and medium was also studied.

RESULTS

The partition coefficients of the two drugs decreased with the increase of cholesterol content and saturation of phospholipid used. The liposome/water partition coefficient of salmeterol increased with the increase of liposome surface negative charge, medium pH and ionic strength, while the liposome surface charge, medium pH and ionic strength had no distinct effect on the liposome/water partition coefficient of budesonide.

CONCLUSION

The liposome/water partition coefficient of drug was affected by the type, saturation of phospholipid used in liposome preparation, the cholesterol content and surface charge of liposome, as well as the pH and ionic strength of medium also have effect on the liposome/water partition coefficient of drug. Accordingly, in order to reflect the actual partition of drug in biological membrane, the determination condition including liposome composition and medium should be similar to the biological membrane.

Half-lives of docosahexaenoic acid in rat brain phospholipids are prolonged by 15 weeks of nutritional deprivation of n-3 polyunsaturated fatty acids

Male rat pups (21 days old) were placed on a diet deficient in n-3 polyunsaturated fatty acids (PUFAs) or on an n-3 PUFA adequate diet containing alpha-linolenic acid (alpha-LNA; 18 : 3n-3). After 15 weeks on a diet, [4,5-3H]docosahexaenoic acid (DHA; 22 : 6n-3) was injected into the right lateral cerebral ventricle, and the rats were killed at fixed times over a period of 60 days. Compared with the adequate diet, 15 weeks of n-3 PUFA deprivation reduced plasma DHA by 89% and brain DHA by 37%; these DHA concentrations did not change thereafter. In the n-3 PUFA adequate rats, DHA loss half-lives, calculated by plotting log10 (DHA radioactivity) against time after tracer injection, equaled 33 days in total brain phospholipid, 23 days in phosphatidylcholine, 32 days in phosphatidylethanolamine, 24 days in phosphatidylinositol and 58 days in phosphatidylserine; all had a decay slope significantly greater than 0 (p < 0.05). In the n-3 PUFA deprived rats, these half-lives were prolonged twofold or greater, and calculated rates of DHA loss from brain, Jout, were reduced. Mechanisms must exist in the adult rat brain to minimize DHA metabolic loss, and to do so even more effectively in the face of reduced n-3 PUFA availability for only 15 weeks.

Strategies and data analysis techniques for lipid and phospholipid chemistry elucidation by intact cell MALDI-FTMS

Ions attributed to lipids and phospholipids are directly observed by desorption from whole bacteria using intact cell (IC) matrix-assisted laser desorption-ionization (MALDI) Fourier transform mass spectrometry (FTMS). Saccharomyces cerevisiae are grown in rich media broth, concentrated, and applied directly to the MALDI surface without lysis or chemical treatment. FTMS of MALDI ions gives excellent signal to noise ratios with typical resolving powers of 90,000 and mass precision better than 0.002 Da. Use of accurate mass measurements and a simple set of rules allow assignment of major peaks into one of twelve expected lipid classes. Subsequently, fractional mass versus whole number mass plots are employed to enhance visual interpretation of the high-resolution data and to facilitate detection of related ions such as those representing homologous series or different degrees of unsaturation. This approach, coupled with rules based on bacterial biochemistry, is used to classify ions with m/z up to about 1000. Major spectral peaks in the range m/z 200-1000 are assigned as lipids and phospholipids. In this study, it is assumed that biologically-derived ions with m/z values lower than 1000 are lipids. This is not unreasonable in view of the facts that molecular weights of lipids are almost always less than 1000 Da, that the copy numbers for lipids in a cell are higher than those for any single protein or other component, and that lipids are generally collections of distinct homologous partners, unlike proteins or other cell components. This paper presents a new rapid lipid-profiling method based on IC MALDI-FTMS.

Alternative approaches for the detection of various phospholipid classes by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

The detection of phospholipids (PLs) by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry was demonstrated nearly a decade ago. However, its use as a conventional tool for PL analysis has been hindered by ambiguities in peak assignments caused by spectral overlaps and difficulties in the detection of some PL classes when analytes with positively charged head groups, such as sphingomyelins (SMs) and phosphatidylcholines (PCs) are present. In this work, either a strong cation-exchange resin or CsCl crystals were added directly to the PL samples to reduce spectral complexity and enhance sensitivity. The quantitative exchange resulted in virtually only protonated or Cs+ adducts. To alleviate difficulties in the detection and identification of PL classes with ionization efficiencies lower than those of SMs and PCs, improvements in the sensitivity of negative-ion mass spectra were sought. For this purpose, several neutral and basic matrices were tried. Among them, p-nitroaniline (PNA) proved to be an advantageous alternative to the use of 2,5-dihydroxybenzoic acid (DHB), the most commonly used matrix in PL analysis. Because of its lower acidity, PNA increased the relative amount of deprotonated species and improved the sensitivity of negative-ion mass spectra. It was possible to confirm peak assignments for PL classes that normally give weak signals when DHB is used. Noteworthy is the detection (in both positive and negative modes) and conclusive identification of species in natural mixtures of phosphatidylethanolamines (PEs) and PE plasmalogens (PEps). PNA allowed the identification of PEs and PEps even in mixtures containing SMs and PCs. Although some cations related to PCs and PEs overlapped in positive-ion spectra, these interferences were eliminated in the negative mode as only the deprotonated forms of PEs and PEps were detectable and those of SMs and PCs were absent owing to their neutrality.

Substrate preference of stress-activated phospholipase D in Chlamydomonas and its contribution to PA formation

In response to various environmental stress conditions, plants rapidly form the intracellular lipid second messenger phosphatidic acid (PA). It can be generated by two independent signalling pathways via phospholipase D (PLD) and via phospholipase C (PLC) in combination with diacylglycerol kinase (DGK). In the green alga Chlamydomonas, the phospholipid substrates for these pathways are characterized by specific fatty acid compositions. This allowed us to establish: (i) PLD's in vivo substrate preference; and (ii) PLD's contribution to PA formation during stress signalling. Accordingly, G-protein activation (1 micro m mastoparan), hyperosmotic stress (150 mm NaCl) and membrane depolarization (50 mm KCl) were used to stimulate PLD, as monitored by the accumulation in 5 min of its unique transphosphatidylation product phosphatidylbutanol (PBut). In each case, PBut's fatty acid composition specifically matched that of phosphatidylethanolamine (PE), identifying this lipid as PLD's favoured substrate. This conclusion was substantiated by analysing the molecular species by electrospray ionization-mass spectrometry (ESI-MS/MS), which revealed that PE and NaCl-induced PBut share a unique (18 : 1)2-structure. The fatty acid composition of PA was much more complex, reflecting the different contributions from the PLC/DGK and PLD pathways. During KCl-induced stress, the PA rise was largely accounted for by PLD activity. In contrast, PLD's contribution to hyperosmotic stress-induced PA was less, being approximately 63% of the total increase. This was because the PLC/DGK pathway was activated as well, resulting in phosphoinositide-specific fatty acids and molecular species in PA.

Mechanism of membrane binding by the bovine seminal plasma protein, PDC-109: a surface plasmon resonance study

PDC-109, the major protein of bovine seminal plasma, binds to sperm plasma membranes upon ejaculation and plays a crucial role in the subsequent events leading to fertilization. The binding process is mediated primarily by the specific interaction of PDC-109 with choline-containing phospholipids. In the present study the kinetics and mechanism of the interaction of PDC-109 with phospholipid membranes were investigated by the surface plasmon resonance technique. Binding of PDC-109 to different phospholipid membranes containing 20% cholesterol (wt/wt) indicated that binding occurs by a single-step mechanism. The association rate constant (k(1)) for the binding of PDC-109 to dimyristoylphosphatidylcholine (DMPC) membranes containing cholesterol was estimated to be 5.7 x 10(5) M(-1) s(-1) at 20 degrees C, while the values of k(1) estimated at the same temperature for the binding to membranes of negatively charged phospholipids such as dimyristoylphosphatidylglycerol (DMPG) and dimyristoylphosphatidic acid (DMPA) containing 20% cholesterol (wt/wt) were at least three orders of magnitude lower. The dissociation rate constant (k(-1)) for the DMPC/PDC-109 system was found to be 2.7 x 10(-2) s(-1) whereas the k(-1) values obtained with DMPG and DMPA was about three to four times higher. From the kinetic data, the association constant for the binding of PDC-109 to DMPC was estimated as 2.1 x 10(7) M(-1). The association constants for different phospholipids investigated decrease in the order: DMPC > DMPG > DMPA > DMPE. Thus the higher affinity of PDC-109 for choline phospholipids is reflected in a faster association rate constant and a slower dissociation rate constant for DMPC as compared to the other phospholipids. Binding of PDC-109 to dimyristoylphosphatidylethanolamine and dipalmitoylphosphatidylethanolamine, which are also zwitterionic, was found to be very weak, clearly indicating that the charge on the lipid headgroup is not the determining factor for the binding. Analysis of the activation parameters indicates that the interaction of PDC-109 with DMPC membranes is favored by a strong entropic contribution, whereas negative entropic contribution is primarily responsible for the rather weak interaction of this protein with DMPA and DMPG.

The effect of cholesterol on the lateral diffusion of phospholipids in oriented bilayers

Pulsed field gradient NMR was utilized to directly determine the lipid lateral diffusion coefficient for the following macroscopically aligned bilayers: dimyristoylphosphatidylcholine (DMPC), sphingomyelin (SM), palmitoyloleoylphosphatidylcholine (POPC), and dioleoylphosphatidylcholine (DOPC) with addition of cholesterol (CHOL) up to approximately 40 mol %. The observed effect of cholesterol on the lipid lateral diffusion is interpreted in terms of the different diffusion coefficients obtained in the liquid ordered (l(o)) and the liquid disordered (l(d)) phases occurring in the phase diagrams. Generally, the lipid lateral diffusion coefficient decreases linearly with increasing CHOL concentration in the l(d) phase for the PC-systems, while it is almost independent of CHOL for the SM-system. In this region the temperature dependence of the diffusion was always of the Arrhenius type with apparent activation energies (E(A)) in the range of 28-40 kJ/mol. The l(o) phase was characterized by smaller diffusion coefficients and weak or no dependence on the CHOL content. The E(A) for this phase was significantly larger (55-65 kJ/mol) than for the l(d) phase. The diffusion coefficients in the two-phase regions were compatible with a fast exchange between the l(d) and l(o) regions in the bilayer on the timescale of the NMR experiment (100 ms). Thus, strong evidence has been obtained that fluid domains (with size of micro m or less) with high molecular ordering are formed within a single lipid bilayer. These domains may play an important role for proteins involved in membrane functioning frequently discussed in the recent literature. The phase diagrams obtained from the analysis of the diffusion data are in qualitative agreement with earlier published ones for the SM/CHOL and DMPC/CHOL systems. For the DOPC/CHOL and the POPC/CHOL systems no two-phase behavior were observed, and the obtained E(A):s indicate that these systems are in the l(d) phase at all CHOL contents for temperatures above 25 degrees C.

Effect of phospholipids and a transmembrane peptide on the stability of the cubic phase of monoolein: implication for protein crystallization from a cubic phase

The cubic phase of monoolein has successfully been used for crystallization of a number of membrane proteins. However, the mechanism of protein crystallization in the cubic phase is still unknown. It was hypothesized, that crystallization occurs at locally formed patches of bilayers. To get insight into the stability of the cubic phase, we investigated the effect of different phospholipids and a model transmembrane peptide on the lipid organization in mixed monoolein systems. Deuterium-labeled 1-oleoyl-rac-[(2)H(5)]-glycerol was used as a selective probe for (2)H NMR. The phase behavior of the phospholipids was followed by (31)P NMR. Upon incorporation of phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, or phosphatidic acid, the cubic phase of monoolein transformed into the L(alpha) or H(II) phase depending on the phase preference of the phospholipid and its concentration. The ability of phospholipids to destabilize the cubic phase was found to be dependent on the phospholipid packing properties. Electrostatic repulsion facilitated the cubic-to-L(alpha) transition. Incorporation of the transmembrane peptide KALP31 induced formation of the L(alpha) phase with tightly packed lipid molecules. In all cases when phase separation occurs, monoolein and phospholipid participate in both phases. The implications of these findings for protein crystallization are discussed.

The administration of pig brain phospholipids versus soybean phospholipids in the diet during the period of brain development in the rat results in greater increments of brain docosahexaenoic acid

Dietary porcine brain phospholipids are much more efficient than soybean phospholipids for ensuring a normal (optimal obtained with lab chow diet) level of docosahexaenoic acid (DHA) in tissues and brain subcellular fractions (brain myelin and nerve endings). Two weeks before mating, rats were divided into two groups (one group was subdivided into subgroups, fed with varying amounts of porcine brain phospholipids; the other group was divided into subgroups fed varying amounts of soybean phospholipids). Pups were killed when 21 days old. DHA (22:6(n-3)) increased up to normal levels in parallel with increasing amounts of (n-3) fatty acids (omega-3 fatty acids) in the diet, up to 60 mg with dietary porcine brain phospholipids and up to 200 mg with soybean phospholipids. Thus a smaller amount of dietary brain phospholipids resulted in the same level of DHA in tissues as a larger amount of dietary soybean phospholipids. In contrast, 22:5(n-6) declined when (n-3) fatty acids in the diet increased. It stabilized at 60 mg of (n-3) fatty acids/100 g diet with brain phospholipids, and approximately 200 mg/100 g diet with soybean phospholipids. As 22:5(n-6) replaced DHA in tissue when (n-3) fatty acids were not sufficient in the diet, this result shows that the recovery of a normal (and minimal) amount of 22:5(n-6) was obtained with lower dietary levels of brain phospholipids compared with soybean phospholipids.

Comparative measurements of multicomponent phospholipid mixtures by electrospray mass spectroscopy: relating ion intensity to concentration

Electrospray mass spectrometry allows direct identification and sensitive detection of multiple phospholipids in non-derivatized cell extracts. However, quantitative analyses are not straightforward, and are confounded by analyte and mass discrimination effects, and non-linear dependence of the ion intensity on concentration. This non-linearity is particularly severe in the negative mode and precludes even comparative measurements of anion concentrations. Herein, we report a general method for relating negative electrospray ion intensity to concentration when analyzing multicomponent phospholipid samples. In this method, the intensity of individual ions is measured at several different concentrations of the total mixture and the slope (n(E)) of the double log plot of sample concentration vs. intensity for each analyte is determined. The n(E) is then used to map intensity data to a quantity proportional to concentration for each analyte. The method allows facile and accurate comparison of negative spectra of complex mixtures containing structurally different anions.

Growth rate-dependent changes in Escherichia coli membrane structure and protein leakage

The phospholipid and fatty acid content of the Escherichia coli membrane were investigated during continuous cultivation. At low growth rates, there was an increase in cardiolipin produced at the expense of phosphatidylethanolamine. Phosphatidylglycerol had a maximum at a growth rate of 0.3 h(-1). The amount of cyclic fatty acids was markedly increased at lower growth rates, while there was an evident minimum at 0.3 h(-1). This was also the case for saturated fatty acids. At this point, the unsaturated fatty acids had a maximum depending mainly on changes in cis-vaccenic acid. The mechanical strength towards sonication and osmotic shock/enzymatic treatment showed that the cells were more rigid at low dilution rates. However, this was accompanied by a higher cell lysis, a reduced capacity for total and specific protein production and a lower yield of cells. The amount of lipid A in the medium (endotoxin) was constant and negligible at all growth rates. The leakage of periplasmic protein to the medium had an optimum at 0.3 h(-1), resulting in a transport of 20% of the total recombinant product. It is argued that this constitutes the point of highest membrane fluidity and thus an increase possibility for protein transport.

Efficacy of antifreeze protein types in protecting liposome membrane integrity depends on phospholipid class

Antifreeze proteins have been reported to be capable of maintaining the membrane integrity of cold sensitive mammalian cells when exposed to hypothermic temperatures. However the mechanism(s) whereby these proteins exert this protective effect is unknown. The present study used liposomes as a model system to examine the nature of the interactions between four antifreeze (glyco)protein types (AFP I, II, III and AFGP) and albumin, with lipid membranes. Fluorescein isothiocyanate labelling indicated that all of the proteins bound to the three liposome types (dielaidoylphosphatidylcholine (DEPC), dielaidoylphosphatidylethanolamine (DEPE) and dielaidoylphosphatidylglycerol (DEPG)). AFGP was found to be highly effective at preventing leakage from all three liposome compositions as they were cooled through their phase transition temperatures. This was not the case for the other proteins. All four antifreeze types prevented zwitterionic DEPC liposomes from leaking as they were cooled through their phase transition temperature. However, albumin was equally as effective, indicating that this capacity was not unique to antifreeze proteins. All of the proteins, except AFGP, induced the negatively charged DEPG liposomes to leak prior to cooling, and were less effective than AFGP in preventing phase transition leakage from DEPE liposomes. It is proposed that many proteins, including antifreeze proteins, can protect zwitterionic liposomes, such as DEPC, by binding to the lipid bilayer thereby maintaining the ordered structure of the membrane during phase transition. However, when the membrane contains a negatively charged polar group, such as with DEPE and DEPG, proteins, although bound to them, may not be able to maintain sufficient membrane organization to prevent leakage during phase transition or, they may gain entry into the lipid bilayer, disrupt the structure and induce leakage. These results imply that the efficacy of antifreeze proteins in the cold protection of mammalian cells will not only depend on protein structure, but also on the lipid composition of the cell membrane.

Separation and quantitation of phospholipids and their ether analogues by high-performance liquid chromatography

The common mobile phase hexane/isopropanol/water used for separation of phospholipids on high-performance liquid chromatography silica columns poses several problems, such as incomplete separation and rapid column deterioration. By inclusion of 5 mM ammonium sulfate in the aqueous phase, we were able to substantially improve the chromatographic resolution and obtain complete separation of phosphatidylcholine, phosphatidylethanolamine, lysophosphatidylcholine, lysophosphatidylethanolamine, phosphatidylserine, phosphatidylinositol, cardiolipin, phosphatidylglycerol, and sphingomyelin. In addition, ammonium sulfate prevented column degeneration and greatly improved reproducibility. A new quantitation method for alkenylacyl, alkylacyl, and diacyl forms of phospholipids was also developed based on derivatization with [(3)H]acetic anhydride. Separation and quantitation of the radioactive acetyl diradylglycerols were performed by straight-phase HPLC coupled to a radioactive flow detector and enabled detection of the various ether analogues at the picomole level with high reproducibility. The described methods are mild and nondestructive and can therefore be easily combined with analysis of either molecular species or fatty acid and aldehyde composition of the individual phospholipids.

Sterol Carrier Protein-2 Expression Alters Plasma Membrane Lipid Distribution and Cholesterol Dynamics

Although sterol carrier protein-2 (SCP-2) binds, transfers, and/or enhances the metabolism of many membrane lipid species (fatty acids, cholesterol, phospholipids), it is not known if SCP-2 expression actually alters the membrane distribution of lipids in living cells or tissues. As shown herein for the first time, expression of SCP-2 in transfected L-cell fibroblasts reduced the plasma membrane levels of lipid species known to traffic through the HDL-receptor-mediated efflux pathway: cholesterol, cholesteryl esters, and phospholipids. While the ratio of cholesterol/phospholipid in plasma membranes of intact cells was not changed by SCP-2 expression, phosphatidylinositol, a molecule important to intracellular signaling and vesicular trafficking, and anionic phospholipids were selectively retained. Only modest alterations in plasma membrane phospholipid percent fatty acid composition but no overall change in the proportion of saturated, unsaturated, monounsaturated, or polyunsaturated fatty acids were observed. The reduced plasma membrane content of cholesterol was not due to SCP-2 inhibition of sterol transfer from the lysosomes to the plasma membranes. SCP-2 dramatically enhanced sterol transfer from isolated lysosomal membranes to plasma membranes by eliciting detectable sterol transfer within 30 s, decreasing the t(1/2) for sterol transfer 364-fold from >4 days to 7-15 min, and inducing formation of rapidly transferable sterol domains. In summary, data obtained with intact transfected cells and in vitro sterol transfer assays showed that SCP-2 expression (i) selectively modulated plasma membrane lipid composition and (ii) decreased the plasma membrane content cholesterol, an effect potentially due to more rapid SCP-2-mediated cholesterol transfer from versus to the plasma membrane.

Quantitative determination of phospholipid compositions by ESI-MS: effects of acyl chain length, unsaturation, and lipid concentration on instrument response

Electrospray ionization-mass spectrometry (ESI-MS) is a very promising tool for the analysis of phospholipid compositions, but is hampered by the fact that not all molecular species are detected with equal efficiency. We studied this and other issues that need to be taken into account to obtain truly quantitative compositional data. The key findings were as follows: First, the instrument response for both saturated and unsaturated phospholipid species decreased with increasing acyl chain length. This effect became increasingly prominent with increasing overall lipid concentration. Second, the degree of acyl chain unsaturation also had a significant effect on instrument response. At the highest concentration studied (10 pmol/microl), polyunsaturated species gave 40% higher intensity than the fully saturated ones. The effect of unsaturation diminished and nearly disappeared with progressive dilution. Third, the instrument response for the different head group classes varied markedly depending on the infusion solvent used. Notably, inclusion of ammonia in the infusion solvent eliminated sodium adduct formation in the positive ion mode, thus greatly simplifying the interpretation of the spectra. The fact that instrument response is dependent on many structural features, overall lipid concentration, solvent composition, and instrument settings makes it necessary to include several internal standards for each phospholipid class to obtain accurate data. Preferably, both unsaturated and saturated standards should be used. Finally, we quantified the major phospholipid classes of BHK cells using ESI-MS. The data agreed closely with those obtained with thin-layer chromatography and phosphorus analysis. This study indicates that quantitative compositional data can be obtained with ESI-MS, provided that proper attention is paid to experimental details, particularly the choice of internal standards.

Serum fatty acid imbalance in bone loss: example with periodontal disease

Among the numerous factors of bone remodelling, the local action of arachidonic acid metabolites together with cytokines, is particularly important, especially that of prostaglandin PGE2. It has been suggested that the alveolar bone destruction in periodontal disease and osteoporosis can be treated by reducing the ratio of arachidonic acid in phospholipids, which would diminish prostaglandin production. The aim of this study was to evaluate the main serum polyunsaturated fatty acids and a possible alteration in the level of arachidonic acid in patients suffering from periodontal bone loss. Of the 105 patients who participated the study, 78 were suffering from periodontal bone loss and 27 served as a control group. The fatty acids were measured in serum by gas-chromatography. The results showed that the level of fatty acids of the n-6 pathway was higher in our patients with bone loss than in the control group, whereas the reverse was observed with fatty acids of the n-3 pathway. In conclusion, our patients' bone losses are linked with an imbalance between n-6 and n-3 fatty acids, which seems to justify a diet increase in 20- and 22-carbon fatty acids.

Role of phospholipase A2 in cholesterol gallstone formation is associated with biliary phospholipid species selection at the site of hepatic excretion: indirect evidence

Phospholipase A2 plays a role in cholesterol gallstone development by hydrolyzing bile phospholipids into lysolecithin and free fatty acids. Lysolecithin and polyunsaturated free fatty acids are known to stimulate the synthesis and/or secretion of gallbladder mucin via a prostanoid pathway, leading to enhancing cholesterol crystal nucleation and growth, and therefore, the action of phospholipase A2 is associated, in part, with bile phospholipid fatty acid. To clarify this hypothesis, we evaluated the effect on bile lipid metastability in vitro of replacing phospholipids with lysolecithin and various free fatty acids. Supersaturated model biles were created with an identical composition (cholesterol saturation index, 1.8; egg yolk lecithin, 34 mM; taurocholate, 120 mM; cholesterol, 25 mM) except for 5%, 10%, or 20% replacement of egg yolk lecithin with a combination of palmitoyl-lysolecithin and a free fatty acid (palmitate, stearate, oleate, linoleate, or arachidonate), followed by time-sequentially monitoring of vesicles and cholesterol crystals using spectrophotometer and video-enhanced differential contrast microscopy. Replacement with hydrophilic fatty acids (linoleate and arachidonate) reduced vesicle formation and promoted cholesterol crystallization, whereas an enhanced cholesterol-holding capacity was evident after replacement with hydrophobic fatty acids (palmitate and stearate). These results indicate that the effect of phospholipase A2 on bile lithogenecity is modulated by the fatty acid species in bile phospholipids, and therefore, that the role of phospholipase A2 in cholesterol gallstone formation is dependent, in part, on biliary phospholipid species selection at the site of hepatic excretion.

Hyperreactive onchocerciasis exhibits reduced arachidonate and linoleate levels in serum triglycerides

The mechanism by which the minority of patients with onchocerciasis exhibiting the hyperreactive (sowda) form of the disease may be able to kill the microfilariae of Onchocerca volvulus is still poorly understood. In this study, the relative amounts of arachidonate and linoleate in serum phospholipids and triglycerides were investigated by gas chromatography both in patients infected with O. volvulus who exhibited either a hyperreactive or a generalized form of onchocerciasis and in persons with no filarial infections. Remarkable differences were observed in the serum triglycerides but not in the phospholipids. In comparison to persons without any filarial infection, significantly lower relative amounts of arachidonate--indicated by elevated triene-tetraene ratios--and of linoleate--indicated by lower diene + tetraene - triene values--were detected in patients with hyperreactive onchocerciasis, and less pronounced differences were found in persons with generalized onchocerciasis. The relationship between reduced amounts of arachidonate and linoleate in serum triglycerides and possible implications on the eicosanoid production in the host-parasite relationship leading to parasite elimination are discussed.

Sterol carrier protein-2 expression alters phospholipid content and fatty acyl composition in L-cell fibroblasts

The effects sterol carrier protein-2 (SCP-2) expression on L-cell phospholipid levels and fatty acyl composition was assessed using L-cells transfected with the murine cDNA encoding for either the 15 kDa proSCP-2 or 13.2 kDa SCP-2. Expression of these proteins reduced total phospholipid mass (nmol/mg protein) by 24% and reduced the cholesterol to phospholipid ratio 60 and 28%, respectively. In 15 kDa proSCP-2 expressing cells, individual phospholipid class masses, excluding sphingomyelin (CerPCho), were reduced as follows: phosphatidylinositol (PtdIns) and phosphatidylserine (PtdSer) >> ethanolamine glycerophospholipid (EtnGpl) > choline glycerophospholipid (ChoGpl). Furthermore, ethanolamine plasmalogen mass was decreased 25%, while choline plasmalogen mass was elevated 30% in 15 kDa proSCP-2 expressing cells. In 13.2 kDa SCP-2 expressing cells, phospholipid class mass was decreased as follows: PtdIns and PtdSer >> ChoGpl. These changes in phospholipid mass resulted in altered cellular phospholipid composition. Expression of either protein differentially altered the type of fatty acid esterified onto the phospholipids. These effects included a greater proportion of polyunsaturated fatty acids and a reduction in saturated fatty acids, although 15 kDa proSCP-2 expression had a more robust effect on these parameters than did 13.2 kDa SCP-2 expression. In summary, expression of SCP-2 reduced individual phospholipid class mass, except for CerPCho, and altered the fatty acid composition of each phospholipid class examined. These results clearly demonstrate that SCP-2 expression altered basal phospholipid levels, suggesting that SCP-2 can alter the function of endoplasmic reticulum phospholipid synthetic enzymes.

Local effect of lung contusion on lung surfactant composition in multiple trauma patients

OBJECTIVE

The aim of this study was to investigate the direct influence of lung contusion on pulmonary surfactant in multiple trauma patients.

DESIGN

Prospective, nonrandomized study.

SETTING

University hospital, trauma intensive care unit.

PATIENTS

Eighteen multiple trauma patients with unilateral lung contusions and Injury Severity Scores >19 were studied prospectively.

INTERVENTIONS

Bronchoalveolar lavage was performed daily until either day 7 or extubation. Samples from the side of lung contusion (n = 62) and the contralateral, uninjured side (n = 62) were obtained at the same time in 14 patients. Total phospholipids, total phospholipid classes, and surfactant apoprotein A were quantified. Additionally, surfactant function was measured with a pulsating bubble surfactometer in four patients. All data are presented as mean +/- SEM. Statistical analyses were performed using programs of SPSS for Windows 6.1.3 (SPSS Inc., Chicago, IL) (Student's t-test; p < .05).

MEASUREMENTS AND MAIN RESULTS

Total phospholipids were significantly increased on the side of lung contusion (contusion side, 40+/-7 microg/mL; contralateral side, 21+/-3 microg/mL; p = .004). The percentage contents of phosphatidylcholine (contusion side, 87.1%+/-1.0%; contralateral side, 84.3%+/-1.0%; p = .04) and sphingomyelin (contusion side, 2.9%+/-0.3%; contralateral side, 1.9%+/-0.2%; p = .004) were significantly higher. In contrast, the percentage content of phosphatidylglycerol was significantly decreased (contusion side, 4.1%+/-0.1%; contralateral side, 6.9%+/-0.6%; p = .001). No alterations were found for the relative contents of phosphatidylethanolamine (contusion side, 2.4%+/-0.2%; contralateral side, 2.2%+/-0.2%; p = .47), phosphatidylinositol (contusion side, 3.5%+/-0.4%; contralateral side, 4.6%+/-0.5%; p = .06), and surfactant apoprotein A (contusion side, 7177+/-1404 ng/mL; contralateral side, 4513+/-787 ng/mL, p = .10). There was no statistical difference for minimal surface tension measured with the pulsating bubble surfactometer after 5 mins of oscillation (contusion side, 29.5+/-2.3 mN/m; contralateral side, 23.7+/-2.1 mN/m; p = .08).

CONCLUSIONS

Direct damage of lung parenchyma by lung contusion alters the composition of surfactant. No additional changes in surfactant function were observed that would argue in favor of functional compensation.

Quantitative analysis of phospholipids in functionally important membrane domains from RBL-2H3 mast cells using tandem high-resolution mass spectrometry

We recently showed that ligand-mediated cross-linking of FcepsilonRI, the high-affinity receptor for immunoglobulin E, on RBL-2H3 mast cells results in its co-isolation with detergent-resistant membranes (DRM) and its consequent tyrosine phosphorylation by the co-localized tyrosine kinase Lyn that is a critical early event in signaling by this receptor [Field et al. (1997) J. Biol. Chem. 272, 4276-4280]. As part of efforts to determine the structural bases for these interactions, we examined the phospholipid composition of DRM vesicles isolated from RBL-2H3 cells under conditions that preserve FcepsilonRI association. We used positive and negative mode electrospray Fourier transform ion cyclotron resonance mass spectrometry to compare quantitatively the phospholipid composition of isolated DRM to that of total cell lipids and to a plasma membrane preparation. From these analyses, over 90 different phospholipid species were spectrally resolved and unambiguously identified; more than two-thirds of these were determined with a precision of +/-0.5% (absolute) or less. Quantitative characterization of lipid profiles shows that isolated DRM are substantially enriched in sphingomyelin and in glycerophospholipids with a higher degree of saturation as compared to total cellular lipids. Plasma membrane vesicles isolated from RBL-2H3 cells by chemically induced blebbing exhibit a degree of phospholipid saturation that is intermediate between DRM and total cellular lipids, and significant differences in the headgroup distribution between DRM and plasma membranes vesicles are observed. DRM from cells with cross-linked FcepsilonRI exhibit a larger ratio of polyunsaturated to saturated and monounsaturated phospholipids than those from unstimulated cells. Our results support and strengthen results from previous studies suggesting that DRM have a lipid composition that promotes liquid-ordered structure. Furthermore, they demonstrate the potential of mass spectrometry for examining the role of membrane structure in receptor signaling and other cellular processes.

Diazepam treatment in rats induces changes in the concentrations of different phospholipid classes in liver and liver mitochondria

Liver phospholipid concentrations were determined in rats after the administration of diazepam (5 mg/Kg/day), for a period of two months. Increased concentrations of total phospholipids (P < 0.05), phosphatidylcholine (P < 0.05) and phosphatidylinositol (P < 0.05) were found in the rats taking diazepam. In contrast, a decreased concentration of phosphatidylserine (P < 0.01) was observed in the same group of animals. In addition, changes in the concentration of rat liver mitochondrial phospholipids after the administration of diazepam during the same period of time were determined. Increased concentrations of total phospholipids (P < 0.01), phosphatidylcholine (P < 0.001) and diphosphatidylglycerol (P < 0.001) were found in the rats treated with diazepam. In contrast, decreased phosphatidylserine (P < 0.001) and phosphatidylinositol (P < 0.01) concentrations were observed in the same group of animals. The considerable changes observed in liver phospholipids and individual classes of liver mitochondrial phospholipids induced by long-term administration of diazepam, possibly suggest a stimulation of liver phospholipid biosynthesis. This effect may be related to enzymatic systems which are involved in phospholipid pathways, and are linked to benzodiazepinergic binding sites.

Apolipoprotein A-I promotes cholesterol release and apolipoprotein E recruitment from THP-1 macrophage-like foam cells

Apolipoprotein E (apoE) is synthesized and secreted by arterial macrophages while apolipoprotein A-I (apoA-I) is present in surrounding interstitial fluids. Both apolipoproteins play important roles in macrophage cholesterol homeostasis by forming lipid complexes (nascent-HDL) with cellular phospholipids (PL) and cholesterol (UC) thereby promoting cholesterol efflux. In this study, we evaluated the relative contributions of apoA-I and endogenously produced apoE in mediating the recruitment of cellular cholesterol. THP-1 human monocytes were differentiated (300 nm phorbol dibutyrate) into macrophages and macrophage-foam cells were generated by cholesterol loading with acetylated LDL (50 microg protein/ml). ApoA-I (10 microg/ml) depleted macrophage-foam cell cholesteryl esters by 50% in 24 h. This reduction was accompanied by a significant increase in the UC/PL mole ratio of nascent HDL (UC/PL = 0.80 +/- 0.15) in the medium compared to complexes isolated from macrophages (UC/PL = 0.59 +/- 0.08). Significantly more (70%) nascent-HDL were formed in incubations of apoA-I with macrophage-foam cells than with macrophages. Medium apoE accumulation paralleled the assembly of apoA-I containing nascent HDL where 2- and 4-fold increases were observed with macrophages and macrophage-foam cells, respectively, compared to incubations in the absence of apoA-I. Despite the increase in medium apoE accumulation, a majority (85%) of particles (11, 9, and 7.4 nm in diameter) from macrophages and macrophage-foam cells possessed apoA-I without apoE. ApoA-I plus apoE particles (13-16 nm) were also formed along with a small quantity of apoE-only particles (19-20 nm). The predominance of apoA-I only particles indicates, however, that the assembly of apoA-I-containing nascent-HDL represents a major metabolic pathway of cellular cholesterol recruitment compared to the endogenous production of apoE.

Fatty acid composition of phospholipids in epithelium and stroma of human benign prostatic hyperplasia

BACKGROUND

Although it is well known that prostatic 5alpha-reductase is active only in its membrane-bound form, rather limited information is available concerning the composition of cellular lipids in human BPH. Therefore, in the present study, the phospholipid fatty acid composition and content in epithelium and stroma of human BPH have been investigated for the first time.

METHODS

Phospholipids separated on TLC plates were methylated and fatty acid methyl esters were analyzed by capillary gas chromatography.

RESULTS

The fatty acid composition of total phospholipids was significantly different between epithelium and stroma. In particular, the percentage of oleic acid was significantly higher in epithelium as compared with stroma, whereas that of arachidonic acid was significantly lower in epithelium than in stroma. In addition, significant differences between epithelium and stroma were found in regard to the fatty acid composition of the main phospholipid subclasses. Another remarkable finding were the age-dependent changes of the fatty acid composition in human BPH.

CONCLUSIONS

This study shows that the fatty acid composition of phospholipids is significantly different between epithelium and stroma of human BPH. Furthermore, age-dependent alterations of the fatty acid composition were found. Further studies are needed to determine whether the endogenous hormonal milieu in the prostate modulates the fatty acid composition of the prostatic cells, as well as what impact such modulation could have on the properties of membrane proteins, i.e., enzymes like the 5alpha-reductase and receptors, which are thought to be affected by alterations in membrane fluidity or composition, or both.

Phospholipid composition of the granular amebocyte from the horseshoe crab, Limulus polyphemus

The phospholipid composition was determined for the amebocyte of the primitive arthropod Limulus polyphemus. The total fatty acid composition of the cells' lipids was analyzed by gas chromatography/mass spectrometry (GC/MS) of fatty acid methyl esters (FAME). The FAME analysis revealed high levels of 20-carbon polyunsaturated fatty acids (PUFA), especially arachidonic (20:4n-6) and eicosapentaenoic (20:5n-3) acids. Almost 20% of the total lipid profile was comprised of dimethyl acetals of 16- to 20-carbon chain lengths, indicative of plasmalogens in the phospholipid pool. Phospholipids, analyzed by high-pressure liquid chromatography, included phosphatidylethanolamine (PE), phosphatidylcholine (PC), phosphatidylserine (PS), phosphatidylinositol (PI), sphingomyelin (SPH), and cardiolipin (CL). PE and PC levels predominated at 42.2 and 36.3%, respectively. Smaller amounts of PS (9.0%) and PI (6.2%) were present, as well as low levels of SPH (4.6%), CL (1.6%), and trace amounts of lysophosphatidylcholine. The major phospholipid species, PE, PC, PS and PI, were collected and their molecular species were examined by electrospray-ionization mass spectrometry. The molecular species within the phospholipid classes reflected the high levels of PUFA seen in the total lipid profile. PI was mainly composed of 18:0a/20:4. Over half of the PS consisted of 18:0a/18:1 and 18:0a/20:4. The major PE species were 20:1p/20:5, 20:1p/20:4, 18:0p/20:5, and 18:0p/20:4. PC had the largest distribution of molecular species, and its most abundant species were 16:0e/20:5, 16:0e/20:4, and 16:0p/20:4. The presence of 16:0e/20:4 is the first documentation of a specific precursor to platelet-activating factor in an invertebrate hemocyte. Note: at the sn-1 position: [a=1=O-acyl, e = 1-O-alkylether, and p = 1-O-alk-1'-enyl (plasmalogen)].

Diacylglycerol molecular species in plasma membrane and microsomes change transiently with endothelin-1 treatment of glioma cells

Agonist-induced intracellular signal transduction often involves activation of protein kinase C by diacylglycerol (DAG) released from membrane phospholipids by phospholipases. Using either DAG kinase or HPLC assays to quantitatively determine DAG mass, we observed a time-dependent increase in DAG accumulation upon incubation of rat C6 glioma cells with 200 nM endothelin-1 (ET-1). Total cell DAG rapidly increased by 25-35% from a basal level of 4.5 +/- 0.3 nmol/mg protein during one min of ET-1 treatment and remained constant or slightly decreased between 1 and 2 min. Thereafter, DAG increased to a maximum (1.6-fold above basal) by 5-10 min. and remained elevated to 30 min. Resolution of DAG molecular species by HPLC after incubation of cells with ET-1 revealed that accumulation of DAG species differed in total cell lysate and subcellular compartments. In plasma membrane, major DAG species increased at 1 min. followed by a decrease at 10 min. whereas in microsomes DAG species did not change at 1 min. and decreased at 10 min. Although phospholipid sources of DAG species were not identified specifically, there was preferential hydrolysis of molecular species of phospholipid for DAG production. We propose that molecular species of DAG produced at the plasma membrane may be transferred to the endoplasmic reticulum so that phospholipid resynthesis can replenish molecular species initially utilized in signal transduction.

Phospholipid subclass specific alterations in the passive ion permeability of membrane bilayers: separation of enthalpic and entropic contributions to transbilayer ion flux

Alterations in phospholipid class, subclass, and individual molecular species contribute to the diversity of biologic membranes, but their effects on membrane passive ion permeability have not been systematically studied. Herein, we developed a simple and efficient fluorescence technique based upon the loss of valinomycin-inducible membrane potential to characterize the passive flux of ions across phospholipid bilayers. Detailed kinetic characterization of ion flux across membrane bilayers composed of discrete chemical entities demonstrated that the class, subclass, and individual molecular species of each phospholipid have substantive effects on membrane passive ion permeability properties. Increasing the degree of unsaturation in either the sn-1 or sn-2 aliphatic chains in phosphatidylcholine markedly enhanced transmembrane ion flux, with over 10-fold differences in the first-order rate constant manifested in molecular species containing four double bonds in comparison to those possessing three double bonds (e.g., kapp = 0.0014 min-1 for 1-octadec-9'-enoyl-2-octadec-9', 12'-dienoyl-sn-glycero-3-phosphocholine (18:1-18:2 phosphatidylcholine) while kapp = 0.021 min-1 for 1,2-dioctadec-9', 12'-dienoyl-sn-glycero-3-phosphocholine (18:2-18:2 phosphatidylcholine)). Moreover, although the apparent first-order rate constants for transmembrane ion flux in vesicles composed of phosphatidylcholine or plasmanylcholine containing palmitate at the sn-1 position and arachidonate at the sn-2 position were similar (kapp = 0.04 min-1 at 22 degreesC for both), the kapp for corresponding vesicles composed of plasmenylcholine was 20-fold less (kapp = 0.002 min-1 at 22 degreesC). Examination of the temperature dependence of passive membrane ion permeability demonstrated that altered ion flux across membranes composed of choline glycerophospholipids was primarily due to entropic effects without substantial changes in the activation energy for ion translocation. For example, Ea = 19.7 +/- 0.5 and 20.7 +/- 0.6 kcal.mol-1 for 1-hexadecanoyl-2-eicosa-5',8',11', 14'-tetraenoyl-sn-glycero-3-phosphocholine (16:0-20:4 phosphatidylcholine) and 1-O-(Z)-hexadec-1'-enyl-2-eicosa-5',8',11', 14'-tetraenoyl-sn-glycero-3-phosphocholine (16:0-20:4 plasmenylcholine), respectively, while their difference in the entropies of activation (DeltaS) was 4.3 +/- 0.5 cal.mol-1.K-1. Collectively, these results identify substantial differences in the membrane passive ion permeability properties of phospholipid classes, subclasses, and molecular species present in biologic membranes of eukaryotic cells and identify entropic alterations as an important contributor to these differences.

Effects of intravenously infused fish oil on platelet fatty acid phospholipid composition and on platelet function in postoperative trauma

BACKGROUND

The aim of this study was to assess the short-term effect of IV infusion of fish oil emulsion on the fatty acid profiles of platelet phosphatidylcholine and phosphatidylethanolamine and on platelet function in postoperative patients.

METHODS

Over a 7-day period, 10 patients received a 20% soybean fat emulsion with an added 10% marine fish oil emulsion, whereas 9 controls received only 20% soybean fat emulsion.

RESULTS

By comparison with controls, in patients receiving fish oil, (1) a large increase in eicosapentaenoic acid (20:5n-3) was observed in both platelet phosphatidylcholine (1.55% +/- 0.17% vs 0.38% +/- 0.06% by weight, p < .01) and phosphatidylethanolamine 2.21% +/- 0.18% vs 0.66% +/- 0.08% by weight, p < .01); (2) eicosapentaenoic acid (20:5n-3)/arachidonic acid (20:4n-6) ratios doubled in both platelet phosphatidylcholine (p < .01) and phosphatidylethanolamine (p < .05); (3) with collagen as aggregating factor, maximal reaction speed decreased (p < .02) and latency increased (p < .002); and (4) no toxic effect, in particular no increase of postoperative bleeding and no perturbation of hepatic and renal function, was observed during the fish oil infusion.

CONCLUSIONS

A short-term IV infusion of fish oil clearly modifies the platelet composition and changes some parameters of platelet function.

Effects of dietary gamma-linolenic acid-rich borage oil combined with marine fish oils on tissue phospholipid fatty acid composition and production of prostaglandins E and F of the 1-, 2- and 3-series in a marine fish deficient in delta5 fatty acyl desaturase

The effects of gamma-linolenic acid-rich borage oil (BO), in combination with different marine oils, namely an eicosapentaenoic acid (EPA) rich oil (MO) or a DHA-rich oil (TO), on tissue fatty acid composition and prostaglandin production were investigated in turbot, a species which lacks appreciable delta5 fatty acyl desaturase activity. The juvenile turbot grew well on the experimental diets and there were no significant differences in final weights between dietary treatments. Irrespective of the marine oil component, both the BO-containing diets increased tissue phospholipid levels of 18:2n-6 and 18:3n-6, and their respective elongation products, 20:2n-6 and 20:3n-6, compared to fish fed a control diet containing a standard Northern hemisphere fish oil. Both the BO-containing diets increased the production of 1-series prostaglandins (PG), this being observed across all tissues investigated with PGF and especially PGE. The BO/MO diet also reduced 20:4n-6 in tissue phospholipids without affecting 20:5n-3, whereas the BO/TO combination decreased 20:5n-3 but increased 20:4n-6. The production of 2-series and 3-series PGs was also altered by the dietary treatments but the changes were less dependent upon the tissue levels of their respective precursor fatty acids, 20:4n-6 and 20:5n-3. The BO-containing diets had very significant effects on gross fatty acid compositions of the phospholipids including increased proportions of saturated fatty acids and n-6 polyunsaturated fatty acids (PUFA) and decreased proportions of monounsaturated fatty acids and n-3 PUFA. Overall, this study shows that eicosanoid production in turbot tissues can be influenced by dietary fatty acids, not only by changes in the absolute and relative levels of specific eicosanoid precursor PUFA in tissue phospholipids, but also by general effects on membrane composition, structure and function induced by gross fatty acid compositional changes.

The membrane lipids of the marine ciliated protozoan Parauronema acutum

The membrane lipid composition of the marine ciliated protozoan Parauronema acutum was characterized. Phospholipids of P. acutum comprised 75% of the total lipids and consisted of phosphatidyl ethanolamine (33%), phosphatidyl choline and its phosphono analog (24%), phosphatidyl inositol (12%), phosphatidyl serine (8%), an unidentified phosphonolipid (18%) and small amounts of sphingomyelin, phosphatidic acid and lysophospholipid. Neutral sphingolipids comprised 15% of the total ciliate lipids and consisted of two major glycosphingolipids and six minor glycosphingolipids. These contained two kinds of long chain bases, one of which was sphingosine and either glucose or galactose or mixtures of both. The fatty acids of the total lipids of P. acutum consisted primarily of palmitic acid (13%), oleic acid (6%), linoleic acid (25%), alpha-linolenic aid (12%) plus highly unsaturated fatty acids of the omega - 3 family including all-cis 6,9,12,15-octatetraenoic acid (9%), all-cis 5,8,11,14,17-eicosapentaenoic acid (10%) and all-cis 4,7,10,13,16,19,22-docosa-hexaenoic acid (5%). Individual lipids had their own specific fatty acid patterns.

Incorporation of [U-14C]palmitate into rat brain: effect of an inhibitor of beta-oxidation

We examined the effect of a clinically therapeutic dose of methyl 2-tetradecylglycidate (McN-3716, methyl palmoxirate, MEP) (2.5 mg/kg), an inhibitor of beta-oxidation of fatty acids, on incorporation of radiolabeled palmitic acid ([U-14C]PAM) from plasma into brain lipids of awake rats. Four hour pretreatment with 2.5 mg/kg MEP significantly increased the incorporation of [U-14C]PAM into brain lipids and substantially decreased aqueous radiolabeled metabolites in brain that can constitute unwanted background signal when analyzed by quantitative autoradiography. MEP treatment increased the lipid to aqueous background radioactivity from 0.8 to 3.0. Net rate of incorporation, k*, was significantly increased (60%) by MEP and was attributed to incorporation of [U-14C]PAM into phospholipid and triglyceride brain compartments. MEP treatment did not affect the size of the fatty acyl-CoA pool or the distribution of the various molecular acyl-CoA species. These results indicate that MEP, at a dose of 2.5 mg/kg (per os), can be used to increase incorporation of [1-(11C)]PAM for studying brain lipid metabolism in humans by positron emission tomography (PET).

Effects of growth temperature on the fatty acid composition of the free-living nematode Caenorhabditis elegans

The effects of growth temperature on the fatty acid compositions of the phosphatidylcholine (PC), phosphatidylethanolamine (PE), and total lipid (TL) fractions of the free-living nematode Caenorhabditis elegans were investigated. A reduction in growth temperature from 25 to 15 degrees C caused the proportions of eicosapentaenoic acid (20:5n-3) to increase from 23.6 to 32.5% in the PC, from 7.4 to 10.8% in the PE, and from 12.9 to 19.9% in the TL fractions. Conversely, the levels of dihomo-gamma-linolenic acid (20:3n-6) and arachidonic acid (20:4n-6) in these phospholipid fractions and the TL fraction both decreased with decreasing growth temperature. Analysis of the positional distribution of fatty acids in the PC fraction revealed that the change in the composition of C20 polyunsaturated fatty acid was obvious in position sn-2. Lowering the growth temperature induced an increase in the level of the diacyl subclass of PE from 58% at 25 degrees C to 71% at 15 degrees C, with a concomitant decrease in the levels of the alkylacyl and alkenylacyl subclass of PE of C. elegans. These changes observed in the phospholipids of C. elegans might be one mechanism for adaptation to low temperature.

Quantitative 31P nuclear magnetic resonance analysis of the phospholipids of erythrocyte membranes using detergent

31P Nuclear magnetic resonance (NMR) spectra of human erythrocyte lysates dissolved in sodium cholate were acquired. The narrow resonances of phospholipids were mostly well resolved, allowing identification and accurate quantitative analysis of phospholipid classes of the erythrocyte membranes. The ether-linked phosphatidylethanolamine components of the erythrocyte membranes were identified, based on the removal of plasmalogens by acidolysis and of diacyl phospholipid species by degradation using phospholipase A1. It was also shown that the introduction of double bonds on the acyl chains of phosphatidylcholine shifted the 31P NMR resonances to lower frequencies. Quantitative analyses of phospholipids from the spectra were based on their apparent molar concentrations. The recoveries of phospholipids from erythrocytes were significantly higher than those using conventional extraction procedures.

Differential labelings suggest two specific phospholipid subclass hydrolysis promoted by PDGF-BB in vascular smooth muscle cells

We have used differential phospholipid subclass labelings performed with [3H]lyso PAF and [3H] myristic acid into vascular smooth muscle cells (vSMC) to characterize the subclasses of phospholipid substrates upon different stimulation times with platelet-derived growth factor (PDGF-BB). In cells labeled with [3H]lyso PAF, PDGF-BB induced a sustained hydrolysis of alkyl-PE. In contrast, in [3H]myristic acid-labeled cells, PDGF-BB promoted a rapid and transitory hydrolysis of diacyl-PC. This hydrolysis was concomitant with an synthesis of diglyceride (DG) and phosphatidic acid (PA). Thus, both diacyl-PC and alkyl-PE appear to be major targets in PDGF-BB stimulation of SMC. These results suggest that agonists could induce the hydrolysis of precise phospholipid subclasses leading to a new specificity into the signal transduction cascade.

Diradylglycerol formation in cholecystokinin-stimulated rabbit pancreatic acini. Assessment of precursor phospholipids by means of molecular species analysis

The aim of the present study was to assess the origin of the 1,2-diradylglycerols produced during prolonged hormonal stimulation of rabbit pancreatic acini by comparison of their relative molecular species composition with that of the major acinar phospholipids. Both phosphatidylcholine (PtdCho) and phosphatidylethanolamine (PtdEtn) consisted of 1,2-diacyl as well as 1-alk-1-2-acyl species. In contrast, phosphatidylinositol (PtdIns), phosphatidylserine and phosphatidic acid existed only in the 1,2-diacyl form. Acinar cells did not contain detectable amounts of 1-alkyl-2-acyl phospholipids. Similarly, the acinar 1,2-diradylglycerol fraction consisted of 1,2-diacylglycerols and 1-alk-1-enyl-2-acylglycerols. Mass 1,2-diradylglycerol measurements revealed that prolonged stimulation with cholecystokinin resulted in a marked and sustained increase in acinar 1,2-diradylglycerol content. Based on the relative amounts of the 1,2-diacyl species present in both the 1,2-diradylglycerol fraction and the individual phospholipids, it is calculated that under control conditions 60% of the 1,2-diacylglycerols originate from PtdCho and 40% from PtdIns, whereas under stimulatory conditions 53% is calculated to be derived from PtdCho, 46% from PtdIns and 1% from PtdEtn. Likewise, it is calculated that in control as well as stimulated acini 100% of the 1-alk-l-enyl-2-acylglycerols originate from plasmenylcholine. Further evidence in favour of the idea that at least a considerable part of the 1,2-diacylglycerols produced during prolonged hormonal stimulation originate from inositolphospholipids is provided by the observation that labeling of phosphatidylinositol 4,5-bisphosphate with inorganic phosphate reached isotopic equilibrium markedly faster under stimulatory conditions as compared to the control situation, which is in agreement with an elevated turnover rate. The data presented support the idea that PtdCho and inositolphospholipids are the major precursors in basal and stimulated 1,2-diradylglycerol production in rabbit pancreatic acini.