1-palmitoyl-2-glutaroyl-sn-glycero-3-phosphorylcholine and 1-palmitoyl-2-(5-oxovaleroyl)-sn-glycero-3-phosphorylcholine

Unsaturated membrane phospholipids are susceptible to oxidation, either by reactive oxygen species or enzymatically, to generate a complex mixture of peroxy and hydroxyl species. They can then spontaneously decompose to truncated oxidised phospholipids composed of aldehyde, carboxyl and hydroxyl species of five to nine carbon atoms chain length, many of which exhibit potent biological activities. In addition, aldehydes can form Schiff's base reactions with protein lysines to form oxidised lipid:protein adducts. While a selection of oxidised phospholipids have been characterised in detail by a range of mass spectrometry techniques, including direct infusion and liquid chromatography mass spectrometry, there are relatively few reports of comprehensive analyses of oxidised phospholipids in disease states. Oxidised phospholipid species are widely thought to be central to the pathology of many diseases, but there is relatively little direct evidence to confirm this in vivo. This review provides an overview of the various analytical methodologies and then summarises their application to examples of chronic and acute disease, cardiovascular disease and acute respiratory distress syndrome, respectively. It highlights the gaps in information and indicates directions for future research.

Topics: Aldehydes; Cardiovascular Diseases; Chromatography, Liquid; Humans; Mass Spectrometry; Oxidation-Reduction; Phospholipid Ethers; Phospholipids; Reproducibility of Results; Sensitivity and Specificity

There is considerable evidence to suggest that oxidation of LDL plays an important role in atherogenesis. Polyunsaturated fatty acids, a major oxidative target, are present as phospholipids in the outer core of the lipoprotein particle. Studies from several laboratories have shown an increase in the levels of phospholipid oxidation products in atherosclerotic lesions and of antibodies to oxidized phospholipids in mice and humans with lesions. Significantly, phospholipid oxidation products have been demonstrated (in vitro) to selectively activate processes in vascular wall cells that may contribute to atherogenesis. This review discusses activities, methods for isolation, identification and measurement of bioactive phospholipids. Past studies suggest that defined and relatively simple current technologies allow identification of bioactive phospholipid oxidation products and measurement of their levels in tissue.

Topics: Animals; Arteriosclerosis; Chromatography, High Pressure Liquid; Chromatography, Thin Layer; Fatty Acids, Unsaturated; Gas Chromatography-Mass Spectrometry; Humans; Lipoproteins, LDL; Magnetic Resonance Spectroscopy; Mass Spectrometry; Mice; Oxidation-Reduction; Phospholipid Ethers; Phospholipids

To evaluate the effects of supervised exercise training (SET) on cardiometabolic risk, cardiorespiratory fitness and oxidative stress status in 2 diabetes mellitus (T2DM), twenty male subjects with T2DM were randomly assigned to an intervention group, which performed SET in a hospital-based setting, and to a control group. SET consisted of a 12-month supervised aerobic, resistance and flexibility training. A reference group of ten healthy male subjects was also recruited for baseline evaluation only. Participants underwent medical examination, biochemical analyses and cardiopulmonary exercise testing. Oxidative stress markers (1-palmitoyl-2-[5-oxovaleroyl]-sn-glycero-3-phosphorylcholine [POVPC]; 1-palmitoyl-2-glutaroyl-sn-glycero-3-phosphorylcholine [PGPC]) were measured in plasma and in peripheral blood mononuclear cells. All investigations were carried out at baseline and after 12 months. SET yielded a significant modification (p < 0.05) in the following parameters: V'O₂max (+14.4%), gas exchange threshold (+23.4%), waist circumference (-1.4%), total cholesterol (-14.6%), LDL cholesterol (-20.2%), fasting insulinemia (-48.5%), HOMA-IR (-52.5%), plasma POVPC (-27.9%) and PGPC (-31.6%). After 12 months, the control group presented a V'O₂max and a gas exchange threshold significantly lower than the intervention group. Plasma POVC and PGPC were significantly different from healthy subjects before the intervention, but not after. In conclusion, SET was effective in improving cardiorespiratory fitness, cardiometabolic risk and oxidative stress status in T2DM.

Topics: Adult; Aged; Body Weight; Cholesterol; Cholesterol, LDL; Diabetes Mellitus, Type 2; Exercise Test; Humans; Leukocytes, Mononuclear; Male; Middle Aged; Oxidative Stress; Phospholipid Ethers; Risk Factors

The influence of two bioactive oxidized phospholipids on model bilayer properties, membrane packing, and endothelial cell biomechanics was investigated computationally and experimentally. The truncated tail phospholipids, 1-palmitoyl-2-(5-oxovaleroyl)-sn-glycero-3-phosphocholine (POVPC) and 1-palmitoyl-2-glutaroyl-sn-glycero-3-phosphocholine (PGPC), are two major oxidation products of the unsaturated phospholipid 1-palmitoyl-2-arachidonoyl-sn-glycero-phosphocholine. A combination of coarse-grained molecular dynamics simulations, Laurdan multiphoton imaging, and atomic force microscopy microindentation experiments was used to determine the impact of POVPC and PGPC on the structure of a multicomponent phospholipid bilayer and to assess the consequences of their incorporation on membrane packing and endothelial cell stiffness. Molecular simulations predicted differential bilayer perturbation effects of the two oxidized phospholipids based on the chemical identities of their truncated tails, including decreased bilayer packing, decreased bilayer bending modulus, and increased water penetration. Disruption of lipid order was consistent with Laurdan imaging results indicating that POVPC and PGPC decrease the lipid packing of both ordered and disordered membrane domains. Computational predictions of a larger membrane perturbation effect by PGPC correspond to greater stiffness of PGPC-treated endothelial cells observed by measuring cellular elastic moduli using atomic force microscopy. Our results suggest that disruptions in membrane structure by oxidized phospholipids play a role in the regulation of overall endothelial cell stiffness.

Topics: Animals; Biomechanical Phenomena; Cattle; Cell Membrane; Endothelial Cells; Lipid Bilayers; Mechanical Phenomena; Molecular Conformation; Molecular Dynamics Simulation; Phospholipid Ethers

The oxidized phospholipids (oxPl) 1-palmitoyl-2-glutaroyl-sn-glycero-3-phosphocholine (PGPC) and 1-palmitoyl-2-(5-oxovaleroyl)-sn-glycero-3-phosphocholine (POVPC) are cytotoxic components of oxidized LDL (oxLDL). Sustained exposure to oxLDL or isolated oxPl induces apoptotic signaling in vascular cells, which is a hallmark of the late phase of atherosclerosis. Activation of sphingomyelinase, the coordinate formation of ceramide and activation of caspase 3/7 as well as the activation of stress-associated kinases are causally involved in this process. Here, we provide evidence for a role of PKCδ in oxPl cytotoxicity. Silencing of the enzyme by siRNA significantly reduced caspase 3/7 activation in RAW 264.7 macrophages under the influence of oxPl. Concomitantly, PKCδ was phosphorylated as a consequence of cell exposure to PGPC or POVPC. Single molecule fluorescence microscopy provided direct evidence for oxPl-protein interaction. Both oxPl recruited an RFP-tagged PKCδ to the plasma membrane in a concentration-dependent manner. In addition, two color cross-correlation number and brightness (ccN&B) analysis of the molecular motions revealed that fluorescently labeled PGPC or POVPC analogs co-diffuse and are associated with the fluorescent protein kinase in live cells. The underlying lipid-protein interactions may be due to chemical bonding (imine formation between the phospholipid aldehyde POVPC with protein amino groups) and physical association (with POVPC or PGPC). In summary, our data supports the assumption that PKCδ acts as a proapototic kinase in oxPl-included apoptosis of RAW 264.7 macrophages. The direct association of the bioactive lipids with this enzyme seems to be an important step in the early phase of apoptotic signaling.

Topics: Animals; Apoptosis; Caspase 3; Caspase 7; Dose-Response Relationship, Drug; Enzyme Activation; Gene Expression Regulation, Enzymologic; Genes, Reporter; Macrophages; Mice; Oxidation-Reduction; Phospholipid Ethers; Phosphorylation; Protein Kinase C-delta; RAW 264.7 Cells; RNA Interference; Signal Transduction; Time Factors; Transfection

We previously developed a single-molecule microscopy method termed TOCCSL (thinning out clusters while conserving stoichiometry of labeling), which allows for direct imaging of stable nanoscopic platforms with raft-like properties diffusing in the plasma membrane. As a consensus raft marker, we chose monomeric GFP linked via a glycosylphosphatidylinositol (GPI) anchor to the cell membrane (mGFP-GPI). With this probe, we previously observed cholesterol-dependent homo-association to nanoplatforms diffusing in the plasma membrane of live CHO cells. Here, we report the release of this homo-association upon addition of 1-palmitoyl-2-(5-oxovaleroyl)-sn-glycero-3-phosphocholine (POVPC) or 1-palmitoyl-2-glutaroyl-sn-glycero-3-phosphocholine, two oxidized phospholipids (oxPLs) that are typically present in oxidatively modified low-density lipoprotein. We found a dose-response relationship for mGFP-GPI nanoplatform disintegration upon addition of POVPC, correlating with the signal of the apoptosis marker Annexin V-Cy3. Similar concentrations of lysolipid showed no effect, indicating that the observed phenomena were not linked to properties of the lipid bilayer itself. Inhibition of acid sphingomyelinase by NB-19 before addition of POVPC completely abolished nanoplatform disintegration by oxPLs. In conclusion, we were able to determine how oxidized lipid species disrupt mGFP-GPI nanoplatforms in the plasma membrane. Our results favor an indirect mechanism involving acid sphingomyelinase activity rather than a direct interaction of oxPLs with nanoplatform constituents.

Topics: Animals; Apoptosis; Cell Membrane; CHO Cells; Cholesterol; Cricetinae; Cricetulus; Glycosylphosphatidylinositols; Humans; Microscopy; Nanotechnology; Oxidation-Reduction; Phospholipid Ethers

The oxidized phospholipids (oxPL) 1-palmitoyl-2-glutaroyl-sn-glycero-3-phosphocholine (PGPC) and 1-palmitoyl-2-(5-oxovaleroyl)-sn-glycero-3-phosphocholine (POVPC) are generated from 1-palmitoyl-2-arachidonoyl-phosphatidylcholine under conditions of oxidative stress. These oxPL are components of oxidized low density lipoprotein. They are cytotoxic in cells of the arterial wall thus playing an important role in the development and progression of atherosclerosis. The toxic lipid effects include inflammation and under sustained exposure apoptosis. The aim of this study was to find out whether such toxic effects, especially apoptosis, are also elicited by oxPL in melanocytic cells in order to assess their potential for therapeutic intervention. FACS analysis after staining with fluorescent markers was performed to identify the mode of lipid-induced cell death. Activation of sphingomyelinase which generates apoptotic ceramide was measured using an established fluorescence assay. Ceramide profiles were determined by mass spectrometry. We found that 50μM POVPC induce cell death in human melanoma cells isolated from different stages of tumor progression but affect primary human melanocytes to a much lesser extent. In contrast, 50μM PGPC was only apoptotic in two out of four cell lines used in this study. The toxicity of both compounds was associated with efficient lipid uptake into the tumor cells and activation of acid sphingomyelinase. In several but not all melanoma cell lines used in this study, activation of the sphingomyelin degrading enzyme correlated with an increase in the concentration of the apoptotic mediator ceramide. The individual patterns of the newly formed ceramide species were also cell line-specific. PGPC and POVPC may be considered potential drug candidates for topical skin cancer treatment. They are toxic in malignant cells. The respective oxidized phospholipids are naturally formed in the body and resistance to these compounds is not likely to occur.

Topics: Apoptosis; Boron Compounds; Cell Line, Tumor; Ceramides; Chromatography, High Pressure Liquid; Chromatography, Reverse-Phase; Humans; Lipoproteins, LDL; Melanoma; Microscopy, Fluorescence; Oxidation-Reduction; Phosphatidylcholines; Phospholipid Ethers; Sphingomyelin Phosphodiesterase

Oxidized phospholipids (oxPLs) are components of oxidized LDL (oxLDL). It is known that oxLDL activates expression of a series of atherogenic genes and their oxPLs contribute to their biological activities. In this study we present the effects of 1-palmitoyl-2-glutaroyl-sn-glycero-3-phosphocholine (PGPC) and 1-palmitoyl-2-(5-oxovaleroyl)-sn-glycero-3-phosphocholine (POVPC) on gene expression in RAW 264.7 macrophages using cDNA microarrays. PGPC affected the regulation of 146 genes, whereas POVPC showed only very minor effects. PGPC preferentially influenced expression of genes related to cell death, angiogenesis, cholesterol efflux, procoagulant mechanisms, atherogenesis, inflammation, and cell cycle. Many of these effects are known from studies with oxLDL or oxidized 1-hexadecanoyl-2-eicosatetra-5',8',11',14'-enoyl-sn-glycero-3-phosphocholine (oxPAPC), containing PGPC in addition to other oxPL species. It is known that POVPC efficiently reacts with proteins by Schiff base formation, whereas PGPC only physically interacts with its biological targets. POVPC seems to affect cell physiology to a great extent on the protein level, whereas PGPC gives rise to both the modulation of protein function and regulation on the transcriptional level.

Topics: Animals; Apoptosis; Cell Cycle Checkpoints; Cell Line; Cholesterol; Down-Regulation; Macrophages; Mice; Neovascularization, Physiologic; Oligonucleotide Array Sequence Analysis; Phospholipid Ethers; Schiff Bases; Time Factors; Up-Regulation

Oxidized phospholipids (OxPLs), including 1-palmitoyl-2-glutaroyl-sn-glycero-3-phosphocholine (PGPC) and 1-palmitoyl-2-oxovaleroyl-sn-glycero-3-phosphocholine (POVPC) are among several biologically active derivatives that are generated during oxidation of low-density lipoproteins (LDLs). These OxPLs are factors contributing to pro-atherogenic effects of oxidized LDLs (OxLDLs), including inflammation, proliferation and death of vascular cells. OxLDL also elicits formation of the lipid messenger ceramide (Cer) which plays a pivotal role in apoptotic signaling pathways. Here we report that both PGPC and POVPC are cytotoxic to cultured macrophages and induce apoptosis in these cells which is associated with increased cellular ceramide levels after several hours. In addition, exposure of RAW 264.7 cells to POVPC and PGPC under the same conditions resulted in a significant increase in ceramide synthase activity, whereas, acid or neutral sphingomyelinase activities were not affected. PGPC is not only more toxic than POVPC, but also a more potent inducer of ceramide formation by activating a limited subset of CerS isoforms. The stimulated CerS activities are in line with the C16-, C22-, and C24:0-Cer species that are generated under the influence of the OxPL. Fumonisin B1, a specific inhibitor of CerS, suppressed OxPL-induced ceramide generation, demonstrating that OxPL-induced CerS activity in macrophages is responsible for the accumulation of ceramide. OxLDL elicits the same cellular ceramide and CerS effects. Thus, it is concluded that PGPC and POVPC are active components that contribute to the capacity of this lipoprotein to elevate ceramide levels in macrophages.

Topics: Animals; Apoptosis; Cell Line; Cell Survival; Ceramides; Enzyme Activation; Flow Cytometry; Gene Expression Regulation, Enzymologic; Isoenzymes; Lipoproteins, LDL; Macrophages; Mice; Oxidation-Reduction; Oxidoreductases; Phospholipid Ethers; Phospholipids; Reverse Transcriptase Polymerase Chain Reaction

The truncated phospholipids 1-palmitoyl-2-(5-oxovaleroyl)-sn-glycero-3-phosphocholine (POVPC) and 1-palmitoyl-2-glutaroyl-sn-glycero-3-phosphocholine (PGPC) are oxidation products of 1-palmitoyl-2-arachidonoyl phosphatidylcholine. Depending on concentration and the extent of modification, these compounds induce growth and death, differentiation and inflammation of vascular cells thus playing a role in the development of atherosclerosis. Here we describe the import of fluorescent POVPC and PGPC analogs into cultured RAW 264.7 macrophages and the identification of their primary protein targets. We found that the fluorescent oxidized phospholipids were rapidly taken up by the cells. The cellular target sites depended on the chemical reactivity of these compounds but not on the donor (aqueous lipid suspension, albumin or LDL). The great differences in cellular uptake of PGPC and POVPC are a direct consequence of the subtle structural differences between both molecules. The former compound (carboxyl lipid) can only physically interact with the molecules in its immediate vicinity. In contrast, the aldehydo-lipid covalently reacts with free amino groups of proteins by forming covalent Schiff bases, and thus becomes trapped in the cell surface. Despite covalent binding, POVPC is exchangeable between (lipo)proteins and cells, since imines are subject to proton-catalyzed base exchange. Protein targeting by POVPC is a selective process since only a limited subfraction of the total proteome was labeled by the fluorescent aldehydo-phospholipid. Chemically stabilized lipid-protein conjugates were identified by MS/MS. The respective proteins are involved in apoptosis, stress response, lipid metabolism and transport. The identified target proteins may be considered primary signaling platforms of the oxidized phospholipid.

Topics: Animals; Boron Compounds; Cattle; Cell Line; Electrophoresis, Gel, Two-Dimensional; Electrophoresis, Polyacrylamide Gel; Fluorescent Dyes; Humans; Lipoproteins, LDL; Macrophages; Membrane Proteins; Mice; Microscopy, Fluorescence; Models, Chemical; Molecular Structure; Oxidation-Reduction; Phosphatidylcholines; Phospholipid Ethers; Protein Binding; Proteins; Serum Albumin, Bovine; Tandem Mass Spectrometry

To determine whether calcium-permeable channels are targets for the oxidized phospholipids: 1-palmitoyl-2-glutaroyl-phosphatidylcholine (PGPC) and 1-palmitoyl-2-oxovaleroyl-phosphatidylcholine (POVPC).. Oxidized phospholipids are key factors in inflammation and associated diseases, including atherosclerosis; however, the initial reception mechanisms for cellular responses to the factors are poorly understood. Low micromolar concentrations of PGPC and POVPC evoked increases in intracellular calcium in human embryonic kidney 293 cells that overexpressed human transient receptor potential canonical 5 (TRPC5) but not human TRP melastatin (TRPM) 2 or 3. The results of electrophysiological experiments confirmed stimulation of TRPC5. To investigate relevance to endogenous channels, we studied proliferating vascular smooth muscle cells from patients undergoing coronary artery bypass surgery. PGPC and POVPC elicited calcium entry that was inhibited by anti-TRPC5 or anti-TRPC1 antibodies or dominant-negative mutant TRPC5. Calcium release did not occur. The effect was functionally relevant because it enhanced cell migration. The actions of PGPC and POVPC depended on G(i/o) proteins but not on previously identified G protein-coupled receptors for oxidized phospholipids.. Stimulation of calcium-permeable TRPC5-containing channels may be an early event in cellular responses to oxidized phospholipids that couples to cell migration and requires an unidentified G protein-coupled receptor.

Topics: Calcium Signaling; Cell Line; Cell Movement; Cell Proliferation; GTP-Binding Protein alpha Subunits, Gi-Go; Humans; Membrane Potentials; Muscle, Smooth, Vascular; Mutation; Myocytes, Smooth Muscle; Oxidation-Reduction; Phospholipid Ethers; Time Factors; Transfection; TRPC Cation Channels; TRPM Cation Channels

Phenotypic switching of vascular smooth muscle cells (VSMCs) is known to play a critical role in the development of atherosclerosis. However, the factors present within lesions that mediate VSMC phenotypic switching are unclear. Oxidized phospholipids (OxPLs), including 1-palmitoyl-2-(5-oxovaleroyl)-sn-glycero-3-phosphorylcholine (POVPC), are active components of minimally modified low density lipoprotein and have been previously shown to induce multiple proatherogenic events in endothelial cells and macrophages, but their effects on VSMCs have been largely unexplored until recently. We previously showed that OxPLs induced phenotypic switching of VSMCs, including suppression of SMC differentiation marker genes. The goal of the present studies was to test the hypothesis that OxPLs alter extracellular matrix production and VSMC migration. Results showed that POVPC activated expression of several extracellular matrix proteins in VSMC. POVPC increased expression of type VIII collagen alpha1 chain (Col8a1) mRNA in cultured VSMCs and in vivo in rat carotid arteries by 9-fold and 4-fold, respectively. POVPC-induced activation of Col8a1 gene expression was reduced by small interfering RNA-mediated suppression of Krüppel-like factor 4 (Klf4) and Sp1, and was abolished in Klf4-knockout VSMCs. POVPC increased Klf4 binding to the Col8a1 gene promoter both in vivo in rat carotid arteries and in cultured VSMCs based on chromatin immunoprecipitation assays. Moreover, POVPC-induced VSMC migration was markedly reduced in Klf4- or type VIII collagen-knockout VSMCs. Given evidence that OxPLs are present within atherosclerotic lesions, it is interesting to suggest that OxPL-induced changes in VSMC phenotype may contribute to the pathogenesis of atherosclerosis at least in part through changes in extracellular matrix composition.

Topics: Animals; Aorta; Apolipoproteins E; Carotid Arteries; Cell Movement; Cells, Cultured; Collagen Type VIII; Kruppel-Like Factor 4; Kruppel-Like Transcription Factors; Lipoproteins, LDL; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Muscle, Smooth, Vascular; Myocytes, Smooth Muscle; Oxidation-Reduction; Phenotype; Phosphatidylcholines; Phospholipid Ethers; Phospholipids; Promoter Regions, Genetic; Rats; RNA Interference; RNA, Messenger; RNA, Small Interfering; Sp1 Transcription Factor; Time Factors; Transfection; Up-Regulation

Regulation of both the expression and function of connexins in the vascular wall is important during atherosclerosis. Progression of the disease state is marked by vascular smooth muscle cell (VSMC) proliferation, which coincides with the reduced expression levels of connexin 43 (Cx43). However, nothing is currently known about the factors that regulate post-translational modifications of Cx43 in atherogenesis, which could be of particular importance, due to the association between site-specific Cx43 phosphorylation and cellular proliferation. We compared the effects of direct carotid applications of two oxidized phospholipid derivatives, 1-palmitoyl-2-oxovaleroyl-sn-glycero-3-phosphorylcholine (POVPC) and 1-palmitoyl-2-glutaroyl-sn-glycero-3-phosphorylcholine (PGPC), on Cx43 expression and phosphorylation, and on cell proliferation. Since both POVPC and PGPC have been shown to act through different intracellular pathways, we hypothesized that each oxidized phospholipid species could induce differential Cx43 phosphorylation events in the cytoplasmically located carboxyl-terminal region of the protein, which could potentially enhance cell proliferation. Application of POVPC caused a reduction in VSMC Cx43 levels, enhanced its phosphorylation at serine (pS) 279/282, and increased VSMC proliferation both in vivo and in vitro. Treatment with PGPC enhanced VSMC pS368 levels with no associated change in proliferation. These oxidized phospholipid-induced Cx43 post-translational changes in VSMCs were consistent with those identified in ApoE(-/-) mice. Taken together, these results demonstrate that post-translational phosphorylation of Cx43 could be a key factor in the pathogenesis of atherosclerosis.

Topics: Animals; Apolipoproteins E; Atherosclerosis; Carotid Arteries; Cell Proliferation; Connexin 43; Mice; Mice, Inbred C57BL; Muscle, Smooth, Vascular; Myocytes, Smooth Muscle; Oxidation-Reduction; Phospholipid Ethers; Phospholipids; Phosphorylation; Protein Processing, Post-Translational

Lipids are key regulators of immune responses. In this study we investigated the direct impact of oxidized phospholipids (ox-PL) on T cell activation and function. We could demonstrate that ox-PL strongly inhibit proliferation of purified human T cells induced with anti-CD3/CD28 or anti-CD3/CD63 mAb, whereas proliferation of naive T cells from human cord blood was not affected by ox-PL. Unoxidized phospholipids showed no such effect. Inhibition of T cell proliferation by ox-PL was not due to cell death. Moreover, T cell proliferation triggered by PMA/ionomycin activation was not diminished by ox-PL. T cells activated in the presence of ox-PL produced and released low amounts of IFN-gamma and IL-2, whereas IL-4 was only slightly diminished. Ox-PL prevented the expression of de novo synthesized activation markers (CD25, MHC class II) but not expression of CD63 or CD69. We further observed that T cells stimulated in the presence of ox-PL are poorly cytotoxic T cells. Most importantly, T cells activated in the presence of ox-PL failed to proliferate in response to restimulation. This hypo-proliferative state was accompanied with an up-regulation of early growth response gene 3 and Casitas B-lineage lymphoma protein B. Taken together, our results demonstrate that ox-PL are potent and specific regulators of T cell activation and function.

Topics: Antibodies, Monoclonal; Antigens, Differentiation, T-Lymphocyte; CD3 Complex; Cell Differentiation; Cell Proliferation; Cells, Cultured; Clonal Anergy; Cytokines; Cytotoxicity, Immunologic; Early Growth Response Protein 3; Gene Expression; Histocompatibility Antigens Class II; Humans; Lymphocyte Activation; Oxidation-Reduction; Phosphatidylglycerols; Phosphatidylserines; Phospholipid Ethers; Phospholipids; Proto-Oncogene Proteins c-cbl; T-Lymphocytes; T-Lymphocytes, Cytotoxic

Lipid oxidation is now thought to be an initiating and sustaining event in atherogenesis. Oxidatively fragmented phospholipids, namely 1-palmitoyl-2-glutaroyl-sn-glycero-3-phosphocholine (PGPC) and 1-palmitoyl-2-(5-oxovaleroyl)-sn-glycero-3-phosphocholine (POVPC), present in minimally modified LDL and atherosclerotic lesions, have been reported to elicit a wide range of pathophysiological responses in the cells of the vascular wall. Nevertheless, the question of their potential sites of action and their primary molecular targets remains open. To address this issue, a series of fluorescently labeled analogs, which differ with regard to structure and binding site of the fluorophore, were synthesized and used as tools for studying the uptake, intracellular stability, and distribution of PGPC and POVPC in vascular smooth muscle cells (VSMCs). We demonstrate that in accordance with their lysophospholipid-like structure, these highly similar molecules transferred rapidly either from aqueous phospholipid dispersions or preloaded native LDL into VSMCs, producing disparate fluorescence patterns irrespective of the attached fluorophore. PGPC derivatives were translocated to the lysosomes. In sharp contrast, POVPC analogs were initially captured in the plasma membrane, most likely in consequence of the formation of covalent adducts with free amino and sulfhydryl groups of proteins and phospholipids. LDL internalization is not required for cellular lipid uptake. Collectively, our data provide evidence that oxidized phospholipids, owing to their high exchangeability between lipoproteins and cell membranes, may act within a short time on different cellular sites in VSMCs and affect various lipid and protein components through physical or chemical interactions, which might then serve as starting points for intracellular signaling.

Topics: Animals; Cells, Cultured; Electrophoresis, Gel, Two-Dimensional; Fluorescence; Lipoproteins, LDL; Microscopy, Fluorescence; Molecular Structure; Muscle, Smooth, Vascular; Myocytes, Smooth Muscle; Oxidation-Reduction; Phospholipid Ethers; Phospholipids; Rats; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization

Oxidized phospholipids, including 1-palmitoyl-2-(5-oxovaleroyl)-sn-glycero-3-phosphocholine (POVPC) and 1-palmitoyl-2-glutaroyl-sn-glycero-3-phosphocholine (PGPC) are typically present in oxidatively modified low density lipoprotein (oxLDL) and have been found in atherosclerotic lesions. These compounds are gaining increasing importance as inducers of different cellular responses like inflammation, proliferation, or cell death. The aim of this study was to elicit the type and outcome of the cellular response of vascular smooth muscle cells (VSMC) upon treatment with POVPC and PGPC. Both oxidized phospholipids led to inhibition of cell proliferation and showed cytotoxic effects in VSMC. Several morphological criteria, the presence of typical DNA fragments, and a phosphatidylserine shift towards the outer leaflet of the cell membrane revealed that apoptosis was the predominant mode of cell death. In all experiments, POVPC was found to be a more potent inducer of apoptosis than PGPC. Interestingly, in the presence of high levels of serum in the growth media the proapoptotic but not the antiproliferative effects of both oxidized phospholipids were abolished. Thus, we conclude that under low serum conditions both intact POVPC and PGPC are proapoptotic mediators. Under high serum conditions, these lipids are hydrolyzed and the resultant lipid mixture containing the degradation products is no longer apoptotic but antiproliferative. Thus, the direct and indirect effects of POVPC and PGPC on cell viability may account for the detrimental actions of oxLDL on VSMC.

Topics: Animals; Aorta, Thoracic; Apoptosis; Cell Line; Cell Proliferation; Fetal Blood; Lipid Peroxidation; Lipoproteins, LDL; Myocytes, Smooth Muscle; Oxidation-Reduction; Phosphatidylserines; Phospholipid Ethers; Rats; Serum

We previously described 3 bioactive oxidation products of 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphorylcholine (PAPC) containing oxovaleroyl (POVPC), glutaroyl (PGPC), and epoxyisoprostane (PEIPC) groups at the sn-2 position that were increased in minimally modified/oxidized low density lipoprotein (MM-LDL) and rabbit atherosclerotic lesions. We demonstrated specific and contrasting effects of POVPC and PGPC on leukocyte-endothelial interactions and described an effect of PEIPC on monocyte binding. The major purpose of the present study was to determine the effects of structural changes on the bioactivities of these 3 lipids. We demonstrate herein that the group at the sn-2 position determines the specific bioactivity and that the substitution of stearoyl for palmitoyl at the sn-1 position or ethanolamine for choline at the sn-3 position of the phospholipid did not alter bioactivity. Oxidized PAPC, oxidized 1-stearoyl-2-arachidonoyl-sn-glycero-3-phosphorylcholine, and oxidized 1-stearoyl-2-arachidonoyl-sn-glycero-3-phosphorylethanolamine stimulated monocyte binding and inhibited lipopolysaccharide-induced expression of the neutrophil-binding molecule E-selectin. Furthermore, all oxovaleroyl phospholipids but not the glutaroyl phospholipids induced monocyte binding without an increase in vascular cell adhesion molecule-1 (VCAM-1) expression and inhibited lipopolysaccharide-induced E-selectin expression. In contrast, glutaroyl phospholipids but not oxovaleroyl phospholipids stimulated E-selectin and VCAM-1 expression. We further demonstrate that all parts of the phospholipid molecules are required for these bioactivities. Hydrolysis with phospholipase (PL) A(1), PLA(2), and PLC strongly reduced the bioactivities of POVPC, PGPC, and mixed isomers of PEIPC. PLD had a smaller but still significant effect. The effects of POVPC and PEIPC could be abolished by sodium borohydride treatment, indicating the importance of the reducible groups (carbonyl and epoxide) in these molecules. In summary, these studies identify 6 new bioactive, oxidized phospholipids that are increased in MM-LDL and, where measured, in atherosclerotic lesions. They thus suggest that a family of phospholipid oxidation products containing oxovaleroyl, glutaroyl, and epoxyisoprostane at the sn-2 position play an important role in the regulation of leukocyte-endothelial interactions, bioactivity being in part controlled by several types of phospholipid hydrolases.

Topics: Animals; Aorta; Arteriosclerosis; Borohydrides; Diet, Atherogenic; E-Selectin; Lipopolysaccharides; Lipoproteins, LDL; Molecular Structure; Monocytes; Oxidation-Reduction; Phospholipases; Phospholipid Ethers; Rabbits; Stereoisomerism; Vascular Cell Adhesion Molecule-1