Determination of lipid ester ozonides and core aldehydes by high-performance liquid chromatography with on-line mass spectrometry

Unsaturated triacylglycerols (TG) and choline (PC) and ethanolamine (PE) phosphatides of known structure were subjected to ozonization and reduction with triphenylphosphine to yield the corresponding lipid ester core aldehydes. Mono- and di-C₉ aldehyde palmitoylglycerols were prepared from oleoyldipalmitoyl and oleoyllinoleoylpalmitoyl glycerols, respectively, while egg yolk PC and PE provided the mono-C₅ and mono-C₉ aldehydes of palmitoyl-and stearoyl glycerophospholipids. The aldehydes were isolated in the free form and as the dinitrophenylhydrazone (DNPH) derivatives by thin-layer chromatography (TLC). The intermediate ozonides, free aldehydes and hydrazones were identified by reversed phase high performance liquid chromatography (HPLC) with on-line negative ion thermospray and normal phase HPLC with on-line positive ion electrospray mass spectrometry (LC-MS). The synthetic aldehydes were used as carriers during isolation from natural sources and as reference compounds in quantitative analyses     

Structure and Function of Membrane-Lytic Peptides

This article reviews the membrane interactions of a variety of peptides including alamethicin, melittin, cecropins, magainins, and defensins. The biological activities of the peptides are discussed and correlated to results from biophysical and structural studies. A picture emerges that allows one to understand the mechanisms of lysis and the regulation of the peptides' activities. Specific peptide–lipid interactions are particularly important in the case of antibiotic peptides, which affect the functionality of bacterial membranes, fungal membranes, or both but leave the bilayers of higher organisms, including those of the host cells, intact. Several models are presented and discussed in view of the ensemble of experimental data. These include the barrel stave, the wormhole, the carpet, and the detergent-like model.     

Cardiolipin of Chlamydomonas reinhardtii 137

The fatty acids of cardiolipin from the phototrophic green alga Chlamydomonas reinhardtii 137⁺ have been quantitatively analysed. Comparison is made at the molecular level between the cardiolipin of Chlamydomonas and that of higher plant tissue.     

Interactions of drought and low temperature stress on lipid and fatty acid composition of cucumber genotypes differing in growth response at suboptimal temperature

The effects of drought stress and/or low temperature stress on total lipid and phospholipid content and fatty acid composition of leaves of cucumber ( Cucumis sativus L.) genotypes differing in growth response at suboptimal temperature were studied. Both drought and low temperature resulted in reduced growth, especially in cv. Farbio, the genotype least tolerant to low temperature. Drought resulted in an increase in total lipid and phospholipid per g fresh weight. On a lipid basis no change in phospholipids or fatty acid content was observed. The fatty acid composition was changed by drought and low temperature, resulting in an increase in the degree of unsaturation. The genotype-specific reaction to treatment for total lipid content and the degree of unsaturation point to the possibility of a genetic origin for drought-induced lipid changes, which may be used in a breeding program for improved growth at suboptimal temperature.     

Liposomes from polymerizable phospholipids

The synthesis and characterization of a great variety of single and double chain phospholipids containing the diacetylene and butadiene moiety is described. These substances can be dispersed in water by ultrasonication and the resulting vesicles can be photopolymerized with the retention of their original structure. Absorption spectra of the polymerized diacetylenic lipids show significant differences depending on the molecular structure of the monomers. By the polymerization reaction, the gel to liquid crystalline phase transition is suppressed, which does not correspond to the properties of biological membranes. Evidence for enhanced stability of polymerized vesicles is given by treatment with ethanol and detergents showing that trapped markers are released to a much smaller extent than in the case of unpolymerized vesicles. Diacetylenic lipids show a pronounced hysteresis of the phase transition. If the membrane of supercooled vesicles crystallizes, all trapped marker is released within seconds. Possibilities for overcoming this extreme rigidity of the membranes are discussed.     

Cholesteryl hemiazelate identified in CVD patients causes in vitro and in vivo inflammation

Oxidation of PUFAs in LDLs trapped in the arterial intima plays a critical role in atherosclerosis. Though there have been many studies on the atherogenicity of oxidized derivatives of PUFA-esters of cholesterol, the effects of cholesteryl hemiesters (ChEs), the oxidation end products of these esters, have not been studied. Through lipidomics analyses, we identified and quantified two ChE types in the plasma of CVD patients and identified four ChE types in human endarterectomy specimens. Cholesteryl hemiazelate (ChA), the ChE of azelaic acid (n-nonane-1,9-dioic acid), was the most prevalent ChE identified in both cases. Importantly, human monocytes, monocyte-derived macrophages, and neutrophils exhibit inflammatory features when exposed to subtoxic concentrations of ChA in vitro. ChA increases the secretion of proinflammatory cytokines such as interleukin-1β and interleukin-6 and modulates the surface-marker profile of monocytes and monocyte-derived macrophage. In vivo, when zebrafish larvae were fed with a ChA-enriched diet, they exhibited neutrophil and macrophage accumulation in the vasculature in a caspase 1- and cathepsin B-dependent manner. ChA also triggered lipid accumulation at the bifurcation sites of the vasculature of the zebrafish larvae and negatively impacted their life expectancy. We conclude that ChA behaves as an endogenous damage-associated molecular pattern with inflammatory and proatherogenic properties.     

Punicic acid production in Brassica napus

Punicic acid (PuA; 18:3Δ^{9cis,11trans,13cis}), a conjugated linolenic acid isomer bearing three conjugated double bonds, is associated with various health benefits and has potential for industrial use. The major nature source of this unusual fatty acid is pomegranate (Punica granatum) seed oil, which contains up to 80% (w/w) of its fatty acids as PuA. Pomegranate seed oil, however, is low yielding with unstable production and thus limits the supply of PuA. Metabolic engineering of established temperate oil crops for PuA production, therefore, has the potential to be a feasible strategy to overcome the limitations associated with sourcing PuA from pomegranate. In this study, the cDNAs encoding a pomegranate fatty acid conjugase and a pomegranate oleate desaturase were co-expressed in canola-type Brassica napus. Transgenic B. napus lines accumulated up to 11% (w/w) of the total fatty acids as PuA in the seed oil, which is the highest level of PuA reported in metabolically engineered oilseed crops so far. Levels of seed oil PuA were stable over two generations and had no negative effects on seed germination. The transgenic B. napus lines with the highest PuA levels contained multiple transgene insertions and the PuA content of B. napus seed oil was correlated with efficiency of oleic acid desaturation and linoleic acid conjugation. In addition, PuA accumulated at lower levels in polar lipids (5.0–6.9%) than triacylglycerol (7.5–10.6%), and more than 60% of triacylglycerol-associated PuA was present at the sn-2 position. This study provides the basis for the commercial production of PuA in transgenic oilseed crops and thus would open new prospects for the application of this unusual fatty acid in health and industry.     

The presence of odd-chain fatty acids in Drosophila phospholipids

ABSTRACT

Most fatty acids in phospholipids and other lipid species carry an even number of carbon atoms. Also odd-chain fatty acids (OCFAs), such as C15:0 and C17:0, are widespread throughout the living organism. However, the qualitative and quantitative profiles of OCFAs-containing lipids in living organisms remain unclear. Here, we show that OCFAs are present in Drosophila phosphatidylcholine (PC) and phosphatidylethanolamine (PE) and that their level increases in accordance with progression of growth. Furthermore, we found that food-derived propionic acid/propanoic acid (C3:0) is utilized for production of OCFA-containing PC and PE. This study provides the basis for understanding in vivo function of OCFA-containing phospholipids in development and lipid homeostasis.     

Loss of membrane phospholipid asymmetry during activation of blood platelets and sickled red cells; mechanisms and physiological significance

Membrane phospholipid asymmetry is considered to be a general property of biological membranes. Detailed information is presently available on the non-random orientation of phospholipids in red cell- and platelet membranes. The outer leaflet of the lipid bilayer membrane is rich in choline-phospholipids, whereas amino-phospholipids are abundant in the inner leaflet. Studies with blood platelets have shown that these asymmetries are not maintained when the cells are activated in various ways. Undoing the normal asymmetry of membrane phospholipids in activated blood cells is presumably mediated by increased transbilayer movement of phospholipids. This process, which leads to increased exposure of negatively charged phosphatidylserine at the outer surface, plays an important physiological role in local blood clotting reactions. A similar phenomenon occurs in sickled red cells. Phospholipid vesicles breaking off from reversibly sickled cells contribute similarly to intravascular clotting in the crisis phase of sickle cell disease.The loss of membrane phospholipid asymmetry in activated platelets seems to be strictly correlated with degradation of cytoskeletal proteins by endogenous calpain. It is remarkable that membrane phospholipid asymmetry can be (partly) restored when activated platelets are treated with reducing agents. This leads to disappearance of phosphatidylserine from the outer leaflet where it was previously exposed during cell activation. These observations will be discussed in relation to two mechanisms which have been recognized to play a role in the regulation of membrane phospholipid asymmetry; i.e. the interaction of aminophospholipids to cytoskeletal proteins, and the involvement of a phospholipid-translocase catalyzing outward-inward transbilayer movement of amino-phospholipids.