Phosphatidylcholine hydroperoxide-induced THP-1 cell adhesion to intracellular adhesion molecule-1

Marine Plasmalogens: A Gift from the Sea with Benefits for Age-Associated Diseases

Aging increases oxidative and inflammatory stress caused by a reduction in metabolism and clearance, thus leading to the development of age-associated diseases. The quality of our daily diet and exercise is important for the prevention of these diseases. Marine resources contain various valuable nutrients, and unique glycerophospholipid plasmalogens are found abundantly in some marine invertebrates, including ascidians. One of the major classes, the ethanolamine class (PlsEtn), exists in a high ratio to phospholipids in the brain and blood, while decreased levels have been reported in patients with age-associated diseases, including Alzheimer's disease. Animal studies have shown that the administration of marine PlsEtn prepared from marine invertebrates improved PlsEtn levels in the body and alleviated inflammation. Animal and human studies have reported that marine PlsEtn ameliorates cognitive impairment. In this review, we highlight the biological significance, relationships with age-associated diseases, food functions, and healthcare materials of plasmalogens based on recent knowledge and discuss the contribution of marine plasmalogens to health maintenance in aging.

Lipid hydroperoxides in nutrition, health, and diseases

Research on lipid peroxidation in food degradation, oil and fat nutrition, and age-related diseases has gained significant international attention for the view of improvement of societal health and longevity. In order to promote basic studies on these topics, a chemiluminescence detection-high performance liquid chromatography instrument using a high-sensitivity single photon counter as a detector was developed. This instrument enabled us to selectively detect and quantify lipid hydroperoxides, a primary product of lipid peroxidation reactions, as hydroperoxide groups at the lipid class level. Furthermore, an analytical method using liquid chromatography-tandem mass spectrometry has been established to discriminate the position and stereoisomerization of hydroperoxide groups in lipid hydroperoxides. Using these two methods, the reaction mechanisms of lipid peroxidation in food and in the body have been confirmed.

Determination of triacylglycerol oxidation mechanisms in canola oil using liquid chromatography-tandem mass spectrometry

Triacylglycerol (TG), the main component of edible oil, is oxidized by thermal- or photo- oxidation to form TG hydroperoxide (TGOOH) as the primary oxidation product. Since TGOOH and its subsequent oxidation products cause not only the deterioration of oil quality but also various toxicities, preventing the oxidation of edible oils is essential. Therefore understanding oxidation mechanisms that cause the formation of TGOOH is necessary. Since isomeric information of lipid hydroperoxide provides insights about oil oxidation mechanisms, we focused on dioleoyl-(hydroperoxy octadecadienoyl)-TG (OO-HpODE-TG) isomers, which are the primary oxidation products of the most abundant TG molecular species (dioleoyl-linoleoyl-TG) in canola oil. To secure highly selective and sensitive analysis, authentic OO-HpODE-TG isomer references (i.e., hydroperoxide positional/geometrical isomers) were synthesized and analyzed with HPLC-MS/MS. With the use of the method, photo- or thermal- oxidized edible oils were analyzed. While dioleoyl-(10-hydroperoxy-8E,12Z-octadecadienoyl)-TG (OO-(10-HpODE)-TG) and dioleoyl-(12-hydroperoxy-9Z,13E-octadecadienoyl)-TG (OO-(12-HpODE)-TG) were characteristically detected in photo-oxidized oils, dioleoyl-(9-hydroperoxy-10E,12E-octadecadienoyl)-TG and dioleoyl-(13-hydroperoxy-9E,11E-octadecadienoyl)-TG were found to increase depending on temperature in thermal-oxidized oils. These results prove that our methods not only evaluate oil oxidation in levels that are unquantifiable with peroxide value, but also allows for the determination of oil oxidation mechanisms. From the analysis of marketed canola oils, photo-oxidized products (i.e., OO-(10-HpODE)-TG and OO-(12-HpODE)-TG) were characteristically accumulated compared to the oil analyzed immediately after production. The method described in this paper is valuable in the understanding of oil and food oxidation mechanisms, and may be applied to the development of preventive methods against food deterioration.

Edible oils become rancid when reacting with oxygen under light or heat, degrading into different products depending on the pathway. Kiyotaka Nakagawa at Tohoku University, Japan, and co-workers used instruments that can separate and identify by weight components in mixtures to study light- and heat-induced oxidation of canola oil. Using authentic samples of possible oxidation products as references, the team found that each process generated two unique species from triacylglycerol, the main ingredient in edible oils. These signature compounds allowed the researchers to reveal that heat-oxidation sped up as temperature increased and that light-oxidized products gradually accumulated in off-the-shelf canola oil after production. This method is more sensitive than conventional protocols and can tell exactly how oils are oxidized, useful for developing techniques for food preservation.

Increase of β2-integrin on adhesion of THP-1 cells to collagen vitrigel membrane

When human monocyte-derived leukemia (THP-1) cells, which are floating cells, are stimulated with lipid peroxides, or Streptococcus suis, these cells adhere to a plastic plate or endothelial cells. However, it is unclear whether or not non-stimulated THP-1 cells adhere to collagen vitrigel membrane (CVM). In this study, firstly, we investigated the rate of adhesion of THP-1 cells to CVM. When THP-1 cells were not stimulated, the rate of adhesion to CVM was high. Then, to identify adhesion molecules involved in adhesion of THP-1 cells to CVM, expressions of various cell adhesion molecules on the surface of THP-1 cells adhering to CVM were measured. β-actin, β-catenin, and β1-integrin expressions did not change in non-stimulated THP-1 cells cultured on CVM compared with those in cells cultured in a flask, but β2-integrin expression markedly increased.

Metabolism and cytotoxic effects of phosphatidylcholine hydroperoxide in human hepatoma HepG2 cells

In this study, we investigated cellular uptake and metabolism of phosphatidylcholine hydroperoxide (PCOOH) in human hepatoma HepG2 cells by high performance liquid chromatography-tandem mass spectrometry, and then evaluated whether PCOOH or its metabolites cause pathophysiological effects such as cytotoxicity and apoptosis. Although we found that most PCOOH was reduced to PC hydroxide in HepG2 cells, the remaining PCOOH caused cytotoxic effects that may be mediated through an unusual apoptosis pathway. These results will enhance our fundamental understanding of how PCOOH, which is present in oxidized low density lipoproteins, is involved in the development of atherosclerosis.

Protein kinase C-δ and -β coordinate flow-induced directionality and deformation of migratory human blood T-lymphocytes

T-lymphocyte migration under flow is critical for immune responses, but the mechanisms by which flow modulates the migratory behaviors of T-lymphocytes remain unclear. Human peripheral blood T-lymphocytes (PBTLs), when stimulated with phorbol 12-myristate 13-acetate (PMA), stretched their cell bodies dramatically and moved along the flow direction. In contrast, stromal cell-derived factor-1α-stimulated PBTLs deformed and migrated in a random manner. Here we elucidated the molecular mechanisms underlying flow-induced directionality and deformation of PMA-stimulated PBTLs. PMA primed PBTLs for polarization under flow, with protein kinase C (PKC)-δ enriched in the leading edge, PKC-βI in the microtubule organizing center, and PKC-βII in the uropod and peripheral region. PKC-δ regulated cell protrusions in the leading edge through Tiam1/Rac1/calmodulin, whereas PKC-β regulated RhoA/Rho-associated kinase activity and microtubule stability to modulate uropod contractility and detachment. Our findings indicate that PKC-δ and -β coordinate in the cell leading edge and uropod, respectively, to modulate the directionality and deformability of migratory T-lymphocytes under flow.

Time course-changes in phosphatidylcholine profile during oxidative modification of low-density lipoprotein

Background

Oxidized phosphatidylcholines (oxPC) and lysophosphatidylcholine (lysoPC) generated during the formation of oxidized low-density lipoprotein (oxLDL) are involved in atherosclerotic lesion development. We investigated the time course-changes in phosphatidylcholine (PC) molecular species during oxidation of LDL to determine how those atherogenic PCs are produced.

Methods

Human and rabbit LDLs were pretreated with or without a selective platelet-activating factor acetylhydrolase (PAF-AH) inhibitor. LDL was oxidized by incubation with copper sulfate, and PC profiles were analyzed by liquid chromatography-tandem mass spectrometry.

Results

When human LDL was oxidized, the peak areas for polyunsaturated fatty acid (PUFA)-containing PC species dramatically decreased after a short lag period, concomitantly lysoPC species increased sharply. Although a variety of oxPC species containing oxidized fatty acyl groups or cleaved acyl chains are formed during LDL oxidation, only a few oxPC products accumulated in oxLDL: 1-palmitoyl-2-(9-oxo-nonanoyl) PC and long-chain oxPC with two double bonds. Pretreatment of LDL with the PAF-AH inhibitor greatly reduced lysoPC production while it had no effect on lipid peroxidation reactions and oxPC profiles. Rabbit LDL, which has a different composition of PC molecular species and needs a longer time to reach achieve full oxidation than human LDL, also accumulated lysoPC during oxidation. The increase in lysoPC in rabbit oxLDL was suppressed by pretreatment with the PAF-AH inhibitor. The major oxPC species formed in rabbit oxLDL were almost the same as human oxLDL.

Conclusions

These results suggest that lysoPC species are the major products and PAF-AH activity is crucial for lysoPC generation during oxidation of LDL. The oxPC species accumulated are limited when LDL is oxidized with copper ion in vitro.

The hydrophobic substituent in aminophospholipids affects the formation kinetics of their Schiff bases

Schiff bases (SBs) are the initial products of non-enzymatic glycation reactions, which are associated to some diabetes-related diseases. In this work, we used physiological pH and temperature conditions to study the formation kinetics of the SBs of 1,2-dihexanoyl-sn-glycero-3-phosphoethanolamine (DPHE) and 1,2-dihexanoyl-sn-glycero-3-phospho-l-serine (DHPS) with various glycating compounds and with pyridoxal 5'-phosphate (an effective glycation inhibitor). Based on the obtained results, the hydrophobic environment simultaneously decreases the nucleophilic character of the amino group (k1) and increases its pKa, thereby increasing the formation rate of SB (kobs). Therefore, the presence of hydrophobic chains in aminophospholipids facilitates the formation and stabilization of SBs, and also, in a biological environment, their glycation. Additionally, the results confirm the inhibitory action of B6 vitamers on aminophospholipid glycation.

Platelets and platelet-like particles mediate intercellular RNA transfer

The role of platelets in hemostasis and thrombosis is clearly established; however, the mechanisms by which platelets mediate inflammatory and immune pathways are less well understood. Platelets interact and modulate the function of blood and vascular cells by releasing bioactive molecules. Although the platelet is anucleate, it contains transcripts that may mirror disease. Platelet mRNA is only associated with low-level protein translation; however, platelets have a unique membrane structure allowing for the passage of small molecules, leading to the possibility that its cytoplasmic RNA may be passed to nucleated cells. To examine this question, platelet-like particles with labeled RNA were cocultured with vascular cells. Coculture of platelet-like particles with activated THP-1, monocytic, and endothelial cells led to visual and functional RNA transfer. Posttransfer microarray gene expression analysis of THP-1 cells showed an increase in HBG1/HBG2 and HBA1/HBA2 expression that was directly related to the transfer. Infusion of wild-type platelets into a TLR2-deficient mouse model established in vivo confirmation of select platelet RNA transfer to leukocytes. By specifically transferring green fluorescent protein, we also observed external RNA was functional in the recipient cells. The observation that platelets possess the capacity to transfer cytosolic RNA suggests a new function for platelets in the regulation of vascular homeostasis.

Inflammation-related gene expression by lipid oxidation-derived products in the progression of atherosclerosis

Vascular areas of atherosclerotic development persist in a state of inflammation, and any further inflammatory stimulus in the subintimal area elicits a proatherogenic response; this alters the behavior of the artery wall cells and recruits further inflammatory cells. In association with the inflammatory response, oxidative events are also involved in the development of atherosclerotic plaques. It is now unanimously recognized that lipid oxidation-derived products are key players in the initiation and progression of atherosclerotic lesions. Oxidized lipids, derived from oxidatively modified low-density lipoproteins (LDLs), which accumulate in the intima, strongly modulate inflammation-related gene expression, through involvement of various signaling pathways. In addition, considerable evidence supports a proatherogenic role of a large group of potent bioactive lipids called eicosanoids, which derive from oxidation of arachidonic acid, a component of membrane phospholipids. Of note, LDL lipid oxidation products might regulate eicosanoid production, modulating the enzymatic degradation of arachidonic acid by cyclooxygenases and lipoxygenases; these enzymes might also directly contribute to LDL oxidation. This review provides a comprehensive overview of current knowledge on signal transduction pathways and inflammatory gene expression, modulated by lipid oxidation-derived products, in the progression of atherosclerosis.

Phosphatidylcholine hydroperoxide promotes VEGF-induced angiogenesis in endothelial cells and rat aorta ring cultures

BACKGROUND

Phosphatidylcholine hydroperoxide (PCOOH) is a primary oxidation product of PC, and is markedly accumulated in blood plasma and arterial walls in atherosclerotic animals and humans. The role of PCOOH in the induction of angiogenesis is unknown.

METHODS

In this study, we investigated whether PCOOH stimulated angiogenic responses (e.g., vascular endothelial growth factor (VEGF)-induced cell proliferation, migration, and tube formation, and angiogenesis-related gene/protein expression) in human umbilical vein endothelial cells (HUVEC) and in an ex vivo rat aorta model.

RESULTS

VEGF induced proliferation, migration, and tube formation of HUVEC, and these angiogenic responses were all enhanced by PCOOH but not by native (nonoxidized) PC. The angiogenic effects of PCOOH are considered to be mediated via generation of reactive oxygen species and activation of both PI3K/AKT and MAPK pathways. The angiogenic activities of PCOOH were also confirmed by the rat aortic ring assay.

CONCLUSIONS

These results indicate that PCOOH can elicit several angiogenic responses.

GENERAL SIGNIFICANCE

The present study implies an important role of PCOOH in atherosclerosis progression and plaque instability.

Hyperketonemia increases monocyte adhesion to endothelial cells and is mediated by LFA-1 expression in monocytes and ICAM-1 expression in endothelial cells

Frequent episodes of hyperketonemia are associated with a higher incidence of vascular disease. The objective of this study was to examine the hypothesis that hyperketonemia increases monocyte-endothelial cell (EC) adhesion and the development of vascular disease in diabetes. Human U937 and THP-1 monocyte cell lines and human umbilical vein endothelial cells (HUVECs) were cultured with acetoacetate (AA) (0-10 mM) or β-hydroxybutyrate (BHB) (0-10 mM) for 24 h prior to evaluating adhesion and adhesion molecule expression. The results demonstrate a significant (P < 0.01) increase in both U937 and THP-1 adhesion to HUVEC monolayers treated with 4 mM AA compared with control. Equal concentrations of BHB resulted in similar increases in monocyte-EC adhesion. Similarly, treatments of AA or BHB to isolated monocytes from human blood also show increases in adhesion to endothelial cells. intercellular adhesion molecule-1 (ICAM-1) was significantly increased on the surface of HUVECs and an increase in total protein expression with AA treatment compared with control. The expression level of lymphocyte function-associated antigen-1 (LFA-1) was increased in monocytes treated with AA, and LFA-1 affinity was altered from low to high affinity following treatment with both AA and BHB. Monocyte adhesion could be blocked when cells were preincubated with an antibody to ICAM-1 or LFA-1. Results also show a significant increase in IL-8 and MCP-1 secretion in monocytes and HUVECs treated with 0-10 mM AA. These results suggest that hyperketonemia can induce monocyte adhesion to endothelial cells and that it is mediated via increased ICAM-1 expression in endothelial cells and increased expression and affinity of LFA-1 in monocytes.

αVβ3-integrin expression through ERK activation mediates cell attachment and is necessary for production of tumor necrosis factor alpha in monocytic THP-1 cells stimulated by phorbol myristate acetate

Macrophages play a key role in inflammation. Activated macrophages express adhesion molecules and produce tumor necrosis factor alpha (TNFα). Integrins are the main adhesion molecules that mediate binding to the extracellular matrix and they are involved in intracellular pathways. In the present study, human monocytic THP-1 cell adhesion to uncoated plastic plate was examined to investigate the regulatory mechanism of TNFα secretion. Addition of phorbol myristate acetate (PMA) for THP-1 cell activation induced cell adhesion in parallel with TNFα production. Among the mitogen-activated protein kinase pathways, the protein kinase C (PKC)-extracellular signal-regulated kinase (ERK) pathway was involved in αVβ3-integrin expression and PMA-induced cell adhesion. Flow cytometry and reverse transcription - quantitative polymerase chain reaction analysis revealed increased expression of matrix-binding integrins including integrin-αVβ3. Blockade of αVβ3-integrin by a specific antibody suppressed cell adhesion and TNFα production. These findings indicate that TNFα production from THP-1 cells is PKC-ERK, αVβ3-integrin and adhesion-dependent and its related pathway could be a target for TNFα-related diseases.

Lipid glycation and protein glycation in diabetes and atherosclerosis

Recent instrumental analyses using a hybrid quadrupole/linear ion trap spectrometer in LC-MS/MS have demonstrated that the Maillard reaction progresses not only on proteins but also on amino residues of membrane lipids such as phosphatidylethanolamine (PE), thus forming Amadori-PE (deoxy-D: -fructosyl PE) as the principal products. The plasma Amadori-PE level is 0.08 mol% of the total PE in healthy subjects and 0.15-0.29 mol% in diabetic patients. Pyridoxal 5'-phosphate and pyridoxal are the most effective lipid glycation inhibitors, and the PE-pyridoxal 5'-phosphate adduct is detectable in human red blood cells. These findings are beneficial for developing a potential clinical marker for glycemic control as well as potential compounds to prevent the pathogenesis of diabetic complications and atherosclerosis. Glucose and other aldehydes, such as glyoxal, methylglyoxal, and glycolaldehyde, react with the amino residues of proteins to form Amadori products and Heynes rearrangement products. Because several advanced glycation end-product (AGE) inhibitors such as pyridoxamine and benfotiamine inhibit the development of retinopathy and neuropathy in streptozotocin (STZ)-induced diabetic rats, AGEs may play a role in the development of diabetic complications. In the present review, we describe the recent progress and future applications of the Maillard reaction research regarding lipid and protein modifications in diabetes and atherosclerosis.

Temperature modulation of integrin-mediated cell adhesion

In response to external stimuli, cells modulate their adhesive state by regulating the number and intrinsic affinity of receptor/ligand bonds. A number of studies have shown that cell adhesion is dramatically reduced at room or lower temperatures as compared with physiological temperature. However, the underlying mechanism that modulates adhesion is still unclear. Here, we investigated the adhesion of the monocytic cell line THP-1 to a surface coated with intercellular adhesion molecule-1 (ICAM-1) as a function of temperature. THP-1 cells express the integrin lymphocyte function-associated antigen-1 (LFA-1), a receptor for ICAM-1. Direct force measurements of cell adhesion and cell elasticity were carried out by atomic force microscopy. Force measurements revealed an increase of the work of de-adhesion with temperature that was coupled to a gradual decrease in cellular stiffness. Of interest, single-molecule measurements revealed that the rupture force of the LFA-1/ICAM-1 complex decreased with temperature. A detailed analysis of the force curves indicated that temperature-modulated cell adhesion was mainly due to the enhanced ability of cells to deform and to form a greater number of longer membrane tethers at physiological temperatures. Together, these results emphasize the importance of cell mechanics and membrane-cytoskeleton interaction on the modulation of cell adhesion.

Generation and biological activities of oxidized phospholipids

Glycerophospholipids represent a common class of lipids critically important for integrity of cellular membranes. Oxidation of esterified unsaturated fatty acids dramatically changes biological activities of phospholipids. Apart from impairment of their structural function, oxidation makes oxidized phospholipids (OxPLs) markers of "modified-self" type that are recognized by soluble and cell-associated receptors of innate immunity, including scavenger receptors, natural (germ line-encoded) antibodies, and C-reactive protein, thus directing removal of senescent and apoptotic cells or oxidized lipoproteins. In addition, OxPLs acquire novel biological activities not characteristic of their unoxidized precursors, including the ability to regulate innate and adaptive immune responses. Effects of OxPLs described in vitro and in vivo suggest their potential relevance in different pathologies, including atherosclerosis, acute inflammation, lung injury, and many other conditions. This review summarizes current knowledge on the mechanisms of formation, structures, and biological activities of OxPLs. Furthermore, potential applications of OxPLs as disease biomarkers, as well as experimental therapies targeting OxPLs, are described, providing a broad overview of an emerging class of lipid mediators.