Lysophosphatidylcholine stimulates monocyte chemoattractant protein-1 gene expression in rat aortic smooth muscle cells.
Rong James X,Berman Joan W,Taubman Mark B,Fisher Edward A
Arteriosclerosis, thrombosis, and vascular biology
OBJECTIVE:Monocyte chemoattractant protein (MCP)-1 is a proatherogenic factor that is responsible for approximately 60% of plaque macrophages in mouse models of atherosclerosis. We investigated whether lysophosphatidylcholine (LPC), enriched in oxidized low density lipoprotein, can modulate the expression of MCP-1 in arterial wall cells. METHODS AND RESULTS:LPC induced a 3-fold increase in MCP-1 mRNA in rat vascular smooth muscle cells (VSMCs) in a time- and dose-dependent manner. Nuclear runon analysis showed that this increase was attributable to increased MCP-1 gene transcription. There was a 2-fold increase in MCP-1 protein in the conditioned media of cells treated with LPC. LPC-associated increases of MCP-1 mRNA and protein were similar to those produced by platelet-derived growth factor-BB, a known inducer of MCP-1. Analyses of the MCP-1 promoter in transiently transfected VSMCs indicated an LPC-responsive element(s) between base pairs -146 and -261 (relative to transcription initiation). Further studies suggested that LPC-induced MCP-1 expression partially involves mitogen-activated protein kinase/extracellular signal-regulated kinase, a tyrosine kinase(s), and (to a lesser extent) protein kinase C but not the activation of the platelet-derived growth factor receptor. CONCLUSIONS:LPC stimulates MCP-1 expression at the transcriptional level in VSMCs, suggesting a molecular mechanism by which LPC contributes to the atherogenicity of oxidized low density lipoprotein.
A Fluorescence-Labeled Heptapeptide, (FITC)KP6, as an Efficient Probe for the Specific Detection of Oxidized and Minimally Modified Low-Density Lipoprotein.
Sato Akira,Ueda Chiemi,Kimura Ryu,Kobayashi Chisato,Yamazaki Yoji,Ebina Keiichi
Journal of fluorescence
Two oxidized forms of low-density lipoprotein (LDL), oxidized LDL (ox-LDL) and minimally modified LDL (MM-LDL), are believed to play a major role in the pathogenesis of atherosclerosis. Recently, we reported that a heptapeptide (Lys-Trp-Tyr-Lys-Asp-Gly-Asp, KP6) coupled through the ε-amino group of N-terminus Lys to fluorescein isothiocyanate, (FITC)KP6, bound to ox-LDL but not to LDL. In the present study, we investigated whether (FITC)KP6 could be used as a fluorescent probe for the specific detection of MM-LDL and ox-LDL. Results from polyacrylamide gel electrophoresis and surface plasmon resonance proved that (FITC)KP6 could efficiently bind to MM-LDL as well as ox-LDL in a dose-dependent manner and with high affinity (K D = 3.16 and 3.54 ng/mL protein for MM-LDL and ox-LDL, respectively). (FITC) KP6 bound to lysophosphatidylcholine and oxidized phosphatidylcholine, both present abundantly in ox-LDL and MM-LDL, respectively. In vitro, (FITC)KP6 was detected on the surface and/or in the cytosol of human THP-1-derived macrophages incubated with ox-LDL and MM-LDL, but not LDL. These results suggest that (FITC)KP6 could be an efficient fluorescent probe for the specific detection of ox-LDL and MM-LDL and can therefore contribute to the identification, diagnosis, prevention, and treatment of atherosclerosis.
Lp-PLA2: a new kid on the block.
Zalewski Andrew,Nelson Jeanenne J,Hegg Lisa,Macphee Colin
BACKGROUND:Atherosclerosis is a systemic disease with focal rupture of vulnerable plaque responsible for major clinical events. Several population-based studies indicate an association between lipoprotein-associated phospholipase A2 (Lp-PLA2) and cardiovascular events. Lp-PLA2 is emerging as a biomarker that may be a potential link between oxidized LDL cholesterol and multifocal plaque vulnerability. CONTENT:Lp-PLA2 is produced by inflammatory cells of myeloid origin, is associated with circulating atherogenic lipoproteins (e.g., LDL), and is highly expressed in vulnerable plaques (de novo expression). Specificity of Lp-PLA2 toward polar phospholipids in oxidized LDL may contribute to the formation of downstream products (e.g., lysophosphatidylcholine and nonesterified fatty acids) that mediate processes intimately involved in plaque vulnerability in situ, including proinflammatory cell phenotype and macrophage death. Recent studies in patients with acute coronary syndrome (ACS) demonstrate that Lp-PLA2 and LDL measurements are not useful to assess the long-term cardiovascular risk shortly after the acute event, most likely because of the acute drop in LDL values that is commonly observed in ACS. However, when measured at later time points, Lp-PLA2 emerges as an independent predictor of the long-term cardiovascular risk, according to multivariate analysis. SUMMARY:Lp-PLA2 is an intriguing marker of cardiovascular risk and may also be a marker of plaque activity/vulnerability. Despite these findings, unanswered questions still exist with respect to this enzyme and its biologic role in atherosclerosis. Addressing these questions will help clarify the clinical utility of measuring Lp-PLA2 in routine clinical practice in the context of other approaches for identifying high-risk patients.
Lysophosphatidylcholine and secretory phospholipase A2 in vascular disease: mediators of endothelial dysfunction and atherosclerosis.
Kougias Panagiotis,Chai Hong,Lin Peter H,Lumsden Alan B,Yao Qizhi,Chen Changyi
Medical science monitor : international medical journal of experimental and clinical research
Lysophosphatidylcholine (LPC) is the major component of oxidized low density lipoprotein (oxLDL) and it has the ability to initiate or amplify several steps in atherogenesis due to its ability to impair endothelium-dependent vasorelaxation, enhance endothelial proliferation and permeability, stimulate adhesion and activation of lymphocytes, initiate chemotaxis of macrophages, impair migration and proliferation in vascular smooth muscle cells (SMCs), and modify platelet aggregation and coagulation pathways. For many of the LPC-induced effects, protein kinase C-dependent pathways have been implicated. In addition, modulation of ion current activity in the cell membrane, binding to a specific oxLDL receptor or to G-protein coupled receptors, as well as amplification of a highly oxidative state have all been postulated as likely mediating mechanisms. Secretory phopholipase A(2)-II (sPLA(2)-II) is one of the enzymes responsible for LPC production. sPLA(2)-II has been recently recognized as an independent risk factor for coronary artery disease. sPLA(2)-II favors the formation of bioactive lipids, stimulates SMC proliferation, activates macrophages enhancing lipid core formation and cytokine secretion, and binds to proteoglycans in the vessel wall matrix promoting lipid fusion and accumulation. The non-catalytic atherogenic effects of sPLA(2)-II are thought to be related to binding to an M-type receptor. Commonly used medications have been shown to decrease sPLA(2)-II activity generating a legitimate interest in the effects of the sPLA(2)-II pharmacologic antagonism. LPC and sPLA(2)-II are two very important mediators in atherosclerosis. Further research is warranted to clarify the cellular and molecular mechanisms that underlie their actions and to correlate in vitro data with clinical observations.
Evidence supporting a key role of Lp-PLA2-generated lysophosphatidylcholine in human atherosclerotic plaque inflammation.
Gonçalves Isabel,Edsfeldt Andreas,Ko Na Young,Grufman Helena,Berg Katarina,Björkbacka Harry,Nitulescu Mihaela,Persson Ana,Nilsson Marie,Prehn Cornelia,Adamski Jerzy,Nilsson Jan
Arteriosclerosis, thrombosis, and vascular biology
OBJECTIVE:To determine whether the level of lysophosphatidylcholine (lysoPC) generated by lipoprotein-associated phospholipase A2 (Lp-PLA2) is associated with severity of inflammation in human atherosclerotic plaques. Elevated plasma Lp-PLA2 is associated with increased cardiovascular risk. Lp-PLA2 inhibition reduces atherosclerosis. Lp-PLA2 hydrolyzes low-density lipoprotein-oxidized phospholipids generating lysoPCs. According to in vitro studies, lysoPCs are proinflammatory but the association between their generation and plaque inflammation remains unknown. METHODS AND RESULTS:Inflammatory activity in carotid plaques (162 patients) was determined immunohistochemically and by analyzing cytokines in homogenates (multiplex immunoassay). LysoPCs were quantified using mass spectrometry and Lp-PLA2 and the lysoPC metabolite lysophosphatidic acid (LPA) by ELISA. There was a strong correlation among lysoPC 16:0, 18:0, 18:1, LPA, and Lp-PLA2 in plaques. LysoPC 16:0, 18:0, 18:1, LPA, and Lp-PLA2 correlated with interleukin-1β, interleukin-6, monocyte chemoattractant protein-1, macrophage inflammatory protein-1β, regulated on activation normal T-cell expressed and secreted, and tumor necrosis factor-α in plaques. High lysoPC and Lp-PLA2 correlated with increased plaque macrophages and lipids and with low content of smooth muscle cells, whereas LPA only correlated with plaque macrophages. Lp-PLA2, lysoPC 16:0, 18:0, and 18:1, but not LPA were higher in symptomatic than in asymptomatic plaques. CONCLUSIONS:The associations among Lp-PLA2, lysoPCs, LPA, and proinflammatory cytokines in human plaques suggest that lysoPCs play a key role in plaque inflammation and vulnerability. Our findings support Lp-PLA2 inhibition as a possible strategy for the prevention of cardiovascular disease.
[Does Lp-PLA2 determination help predict atherosclerosis and cardiocerebrovascular disease?].
Sertić Jadranka,Skorić Bosko,Lovrić Jasna,Bozina Tamara,Reiner Zeljko
Acta medica Croatica : casopis Hravatske akademije medicinskih znanosti
Thorough control of risk factors is pivotal for cardiocerebrovascular diseases. As classic risk assessment accounts for only 50% of risk variability and due to the role of inflammatory processes in endothelial dysfunction and atherosclerotic plaque rupture, it is necessary to identify new biomarkers for risk prediction. In addition to the inflammatory marker high sensibility C-reactive protein (hs-CRP), lipoprotein associated phospholipase A2 (Lp-PLA2) is gaining increasing significance, since it is directly involved in the pathogenesis of atherosclerotic plaque progression. Lp-PLA2 is highly specific for vascular inflammation, has low biological variability, and plays a causative role in atherosclerotic plaque inflammation. It belongs to the group of intracellular and secretory phospholipase enzymes that can hydrolyze sn-2 phospholipid ester bond of cellular membranes and lipoproteins. Lp-PLA2 enzyme is formed by macrophages and foam cells in atherosclerotic plaque, and is associated primarily with LDL particles in blood. Lp-PLA2 that is bound to LDL is the sole enzyme responsible for hydrolysis of oxidized phospholipids (oxPL) on LDL particles. Lp-PLA2 hydrolyzes oxPL at the surface of lipoproteins, but has weak activity against non-oxPL. Lp-PLA2 is also the enzyme that hydrolyzes oxPL on HDL particles, where it may have a role in the antioxidative function of HDL. The distribution of Lp-PLA2 between LDL and HDL particles depends on the extent of Lp-PLA2 glycosylation, which may affect the activity of Lp-PLA2 in plasma. Stable atherosclerotic plaques contain few inflammatory cells and a small amount of Lp-PLA2. In contrast, unstable plaques most often do not have significant impact on arterial lumen but may be detected by its thin connective tissue cap, low collagen and high lipid content. A distinguishing factor between stable and unstable atherosclerotic plaque may also be the presence of activated inflammatory cells and increased Lp-PLA2 concentration in unstable plaque. These new insights indicate that Lp-PLA2 may be a risk factor, which is important for the formation of atherosclerotic plaque but also for its rupture. The purpose of applying markers of inflammation is to improve stratification of patients at risk, so that treatment intensity may be adjusted to the risk level. Lp-PLA2 inhibition is associated with decreased cytokines. Lipid-affecting drugs stabilize atherosclerotic plaque by reducing the central lipid core, decreasing macrophage infiltration, and thickening of the connective tissue cap. These drugs reduce Lp-PLA2 concentration and the frequency of cardiocerebrovascular events as well. Besides acting as a specific marker of atherosclerotic plaque inflammation, Lp-PLA2 has a significant prognostic value because of its direct role in the formation of rupture-prone atherosclerotic plaque, unlike classic risk factors, for example lipid measurement or vascular imaging, which do not directly estimate acute ischemic potential in the arterial wall. Studies have demonstrated correlation between increased Lp-PLA2 concentrations and enhanced risk of cardiocerebrovascular events, even after multivariate adjustment to classic risk factors. In addition to its high specificity for vascular inflammation, Lp-PLA2 concentration is stable in terms of time, unlike, for instance, CRP levels. Lp-PLA2 has been confirmed as an independent risk predictor, which is complementary to hsCRP. It could be used in clinical practice for improved risk assessment in patients with transient cardiocerebrovascular risk, particularly in those with metabolic syndrome (obese patients with mixed dyslipidemia, hyperglycemia, insulin resistance, and arterial hypertension). Lp-PLA2 levels allow for further risk stratification of high-risk patients into a very high risk group where more aggressive therapy is recommended, as well as the achievement of LDL-cholesterol levels < 2.5 or, even better, < 2.0 mmol/L as a feasible therapeutic target. Similar to hsCRP, the levels of Lp-PLA2 are reduced by lipid-affecting drugs, while its low concentrations are associated with a very low risk of cardiocerebrovascular events both in low- and high-risk population. According to recent American guidelines for assessing the risk of cardiovascular disease, Lp-PLA2 determination is recommended as an additional marker to the classic risk assessment in patients with moderate and high risk.
Role of phospholipid oxidation products in atherosclerosis.
Lee Sangderk,Birukov Konstantin G,Romanoski Casey E,Springstead James R,Lusis Aldons J,Berliner Judith A
There is increasing clinical evidence that phospholipid oxidation products (Ox-PL) play a role in atherosclerosis. This review focuses on the mechanisms by which Ox-PL interact with endothelial cells, monocyte/macrophages, platelets, smooth muscle cells, and HDL to promote atherogenesis. In the past few years major progress has been made in identifying these mechanisms. It has been recognized that Ox-PL promote phenotypic changes in these cell types that have long-term consequences for the vessel wall. Individual Ox-PL responsible for specific cellular effects have been identified. A model of the configuration of bioactive truncated Ox-PL within membranes has been developed that demonstrates that the oxidized fatty acid moiety protrudes into the aqueous phase, rendering it accessible for receptor recognition. Receptors and signaling pathways for individual Ox-PL species are now determined and receptor independent signaling pathways identified. The effects of Ox-PL are mediated both by gene regulation and transcription independent processes. It has now become apparent that Ox-PL affects multiple genes and pathways, some of which are proatherogenic and some are protective. However, at concentrations that are likely present in the vessel wall in atherosclerotic lesions, the effects promote atherogenesis. There have also been new insights on enzymes that metabolize Ox-PL and the significance of these enzymes for atherosclerosis. With the knowledge we now have of the regulation and effects of Ox-PL in different vascular cell types, it should be possible to design experiments to test the role of specific Ox-PL on the development of atherosclerosis.
Caspase-11-Gasdermin D-Mediated Pyroptosis Is Involved in the Pathogenesis of Atherosclerosis.
Jiang Mengqing,Sun Xuejing,Liu Suzhen,Tang Yan,Shi Yunming,Bai Yuanyuan,Wang Yujie,Yang Qiong,Yang Qize,Jiang Weihong,Yuan Hong,Jiang Qixia,Cai Jingjing
Frontiers in pharmacology
Pyroptosis is a form of cell death triggered by proinflammatory signals. Recent studies have reported that oxidized phospholipids function as caspase-11 agonists to induce noncanonical inflammasome activation in immune cells. As the levels of oxidized phospholipids derived from ox-LDL are largely elevated in atherosclerotic lesions, this study sought to determine whether oxidized lipids trigger pyroptosis and subsequent inflammation in the pathogenesis of atherosclerosis. In our current study, after integrating transcriptomic data available from the Gene Expression Omnibus with data from hyperlipidemic mice and ox-LDL-treated peritoneal macrophages, we discovered that caspase-4/11-gasdermin D-associated inflammatory signaling was significantly activated. Consistently, the mRNA expression of caspase-4 and gasdermin D was upregulated in peripheral blood mononuclear cells from patients with coronary heart disease. In particular, the expression of caspase-4 was closely associated with the severity of lesions in the coronary arteries. An study showed that caspase-11-gasdermin D activation occurred in response to a high-fat/high-cholesterol (HFHC) diet in ApoE mice, while caspase-11 deletion largely attenuated the volume and macrophage infiltration of atherosclerotic lesions. An mechanistic study showed that caspase-11-mediated inflammation occurred partly via gasdermin D-mediated pyroptosis in macrophages. Suppressing gasdermin D in HFHC-fed ApoE mice via delivery of an adeno-associated virus markedly decreased lesion volume and infiltrating macrophage numbers. Caspase-11-gasdermin D-mediated pyroptosis and the subsequent proinflammatory response in macrophages are involved in the pathogenesis of atherosclerosis. Therefore, targeting the caspase 11-gasdermin D may serve as an alternative strategy for the treatment of atherosclerosis.
Lysophosphatidylcholine induces expression of genes involved in cholesterol biosynthesis in THP-1 derived macrophages.
Cha Min Ho,Lee So Min,Jung Jeeyoun
Lysophosphatidylcholine (LPC), a major component of oxidized low-density lipoprotein, is associated with atherosclerosis, obesity, stroke, and cancer. However, the direction and mechanism of this relationship remains unclear. In this study, we conducted RNA profiling in THP-1 derived macrophages treated with LPC and uncovered a relationship between LPC and the cholesterol biosynthesis pathway. Principal component analysis (PCA) of RNA profiling showed that untreated THP-1 cells and those treated with 10, 20, or 40 µM LPC were distinctly distributed. Functional annotation revealed that LPC affected the expression of genes involved in cytokine-cytokine receptor interaction, TNF signaling, and MAPK signaling. Interestingly, LPC also altered the expression of 11 genes involved in cholesterol synthesis such as those in terpenoid backbone biosynthesis and steroid biosynthesis pathways. This increased gene expression occurred in a dose-dependent manner in response to LPC treatment. Especially, LPC with saturated acyl groups enhanced the expression of these genes compared to LPC with unsaturated acyl groups, and similar results were shown in response to saturated and unsaturated free fatty acids. Our findings demonstrate that LPCs with saturated acyl groups induce the expression of genes involved in cholesterol biosynthesis and may have implications for cholesterol related diseases.
Lysophosphatidylserine has Bilateral Effects on Macrophages in the Pathogenesis of Atherosclerosis.
Nishikawa Masako,Kurano Makoto,Ikeda Hitoshi,Aoki Junken,Yatomi Yutaka
Journal of atherosclerosis and thrombosis
AIM:Lysophospholipids, particularly sphingosine 1-phosphate and lysophosphatidic acid, are known to be involved in the pathogenesis of atherosclerosis; however, the role of lysophosphatidylserine (LysoPS) in the onset of atherosclerotic diseases remains uncertain. METHODS:We investigated the effects of LysoPS on the uptake of oxidized low-density lipoprotein (oxLDL) and the modulation of inflammatory mediators and ER stress utilizing RAW264.7 cells and mouse peritoneal macrophages (MPMs). RESULTS:We found that LysoPS augmented cholesterol accumulation in both models. Consistent with these findings, LysoPS increased the expression of scavenger receptors (CD36, MSR1, LOX1 and TLR4). Regarding the involvement of these lipids in inflammation, LysoPS significantly decreased the expression of inflammatory mediators in lipopolysaccharide (LPS)-treated RAW264.7 cells and MPMs. LysoPS also attenuated ER stress in LPS-untreated RAW264.7 cells. The expression patterns of LysoPS receptors differed considerably among the LPS-untreated RAW264.7 cells, LPS-treated RAW264.7 cells and MPMs. CONCLUSIONS:LysoPS may have proatherosclerotic properties in the setting of foam cell formation as well as antiatherosclerotic effects on inflammation in macrophages.
An update on lipid oxidation and inflammation in cardiovascular diseases.
Zhong Shanshan,Li Luxiao,Shen Xia,Li Qiujing,Xu Wenxin,Wang Xiaoping,Tao Yongzhen,Yin Huiyong
Free radical biology & medicine
Cardiovascular diseases (CVD), including ischemic heart diseases and cerebrovascular diseases, are the leading causes of morbidity and mortality worldwide. Atherosclerosis is the major underlying factor for most CVD. It is well-established that oxidative stress and inflammation are two major mechanisms leading to atherosclerosis. Under oxidative stress, polyunsaturated fatty acids (PUFA)-containing phospholipids and cholesterol esters in cellular membrane and lipoproteins can be readily oxidized through a free radical-induced lipid peroxidation (LPO) process to form a complex mixture of oxidation products. Overwhelming evidence demonstrates that these oxidized lipids are actively involved in the inflammatory responses in atherosclerosis by interacting with immune cells (such as macrophages) and endothelial cells. In addition to lipid lowering in the prevention and treatment of atherosclerotic CVD, targeting chronic inflammation has been entering the medical realm. Clinical trials are under way to lower the lipoprotein (a) (Lp(a)) and its associated oxidized phospholipids, which will provide clinical evidence that targeting inflammation caused by oxidized lipids is a viable approach for CVD. In this review, we aim to give an update on our understanding of the free radical oxidation of LPO, analytical technique to analyze the oxidation products, especially the oxidized phospholipids and cholesterol esters in low density lipoproteins (LDL), and focusing on the experimental and clinical evidence on the role of lipid oxidation in the inflammatory responses associated with CVD, including myocardial infarction and calcific aortic valve stenosis. The challenges and future directions in understanding the role of LPO in CVD will also be discussed.
Dooming Phagocyte Responses: Inflammatory Effects of Endogenous Oxidized Phospholipids.
Di Gioia Marco,Zanoni Ivan
Frontiers in endocrinology
Endogenous oxidized phospholipids are produced during tissue stress and are responsible for sustaining inflammatory responses in immune as well as non-immune cells. Their local and systemic production and accumulation is associated with the etiology and progression of several inflammatory diseases, but the molecular mechanisms that underlie the biological activities of these oxidized phospholipids remain elusive. Increasing evidence highlights the ability of these stress mediators to modulate cellular metabolism and pro-inflammatory signaling in phagocytes, such as macrophages and dendritic cells, and to alter the activation and polarization of these cells. Because these immune cells serve a key role in maintaining tissue homeostasis and organ function, understanding how endogenous oxidized lipids reshape phagocyte biology and function is vital for designing clinical tools and interventions for preventing, slowing down, or resolving chronic inflammatory disorders that are driven by phagocyte dysfunction. Here, we discuss the metabolic and signaling processes elicited by endogenous oxidized lipids and outline new hypotheses and models to elucidate the impact of these lipids on phagocytes and inflammation.
[Oxidized phospholipids and atherosclerosis].
Zhao Min,Liu Bo-Yan,Qin Shu-Cun
Sheng li xue bao : [Acta physiologica Sinica]
Phospholipids are important components of biomembrane and lipoproteins. Phospholipids can be oxidized by free radicals/nonradicals and enzymes to form oxidized phospholipids (OxPLs), which can lead to further generation of oxidation products with different biological activities. Clinical evidence shows that OxPLs are constantly generated and transformed during the pathogenesis of atherosclerosis and accumulated at the lesion sites. OxPLs are highly heterogeneous mixtures that can influence the progress of atherosclerosis through a variety of related receptors or signaling pathways. This review summarizes the process of phospholipid oxidation, the related products, the interaction of OxPLs with endothelial cells, monocytes/macrophages, smooth muscle cells, platelets and lipoproteins involved in the pathological process of atherosclerosis, and the progress of the researches using OxPLs as a target to inhibit atherosclerosis in recent years.