Oxidative Modification Of Low-density Lipoprotein Research Articles

Radical Oxygen Species, Oxidized Low-Density Lipoproteins, and Lectin-like Oxidized Low-Density Lipoprotein Receptor 1: A Vicious Circle in Atherosclerotic Process.

Atherosclerosis is a complex condition that involves the accumulation of lipids and subsequent plaque formation in the arterial intima. There are various stimuli, cellular receptors, and pathways involved in this process, but oxidative modifications of low-density lipoprotein (ox-LDL) are particularly important in the onset and progression of atherosclerosis. Ox-LDLs promote foam-cell formation, activate proinflammatory pathways, and induce smooth-muscle-cell migration, apoptosis, and cell death. One of the major receptors for ox-LDL is LOX-1, which is upregulated in several cardiovascular diseases, including atherosclerosis. LOX-1 activation in endothelial cells promotes endothelial dysfunction and induces pro-atherogenic signaling, leading to plaque formation. The binding of ox-LDLs to LOX-1 increases the generation of reactive oxygen species (ROS), which can induce LOX-1 expression and oxidize LDLs, contributing to ox-LDL generation and further upregulating LOX-1 expression. This creates a vicious circle that is amplified in pathological conditions characterized by high plasma levels of LDLs. Although LOX-1 has harmful effects, the clinical significance of inhibiting this protein remains unclear. Further studies both in vitro and in vivo are needed to determine whether LOX-1 inhibition could be a potential therapeutic target to counteract the atherosclerotic process.

Exploring the role of myeloperoxidase in the atherosclerotic process in hypoxic mice based on the MAPK signaling pathway

Atherosclerosis (AS) is the common pathophysiological basis of various cardiovascular diseases and the leading cause of death from cardiovascular disease worldwide. When the body is in a hypoxic environment, enhanced oxidative stress and significant accumulation of reactive oxygen species (ROS) in tissue cells exacerbate the inflammatory response, resulting in increased release of myeloperoxidase (MPO), catalyzing the formation of large quantities of hypochlorous acid (HOCl), further oxidative modification of low-density lipoprotein (LDL), and exacerbating the formation and progression of atherosclerotic plaques. The MAPK signaling pathway is important in oxidative stress-mediated promotion of atherogenesis. MPO -/- mice were used in this study to establish a hypoxia model simulating 5000 m altitude and a Western high-fat diet-induced atherosclerosis model for 12 weeks. Exploring the role of MPO in the atherosclerotic process in hypoxic mice by observing the MAPK signaling pathway to provide a therapeutic target for the prevention and treatment of hypoxic atherosclerotic disease in the plateau. We found that hypoxia promotes the formation of atherosclerosis in mice, and the mechanism may be that increased MPO in vivo promotes an inflammatory response, which plays a crucial role in the formation of atherosclerosis. In addition, hypoxia further exacerbates plaque instability by activating the MAPK signaling pathway to upregulate vascular endothelial growth factor (VEGF) and matrix metalloproteinase-9 (MMP9), which in turn promotes angiogenesis within the plaque. Therefore, a potential target for preventing and treating hypoxic atherosclerotic disease is the inhibition of MPO.

Yerba Mate as a Protectant against Lipoproteins Oxidation.

Oxidative modification of low-density lipoproteins (LDL) and high-density lipoproteins (HDL) are important factors determining cardiovascular risk. This study investigated the antioxidant mechanisms and potential protective effect of a hydroethanolic extract of yerba mate (Ilex paraguaiensis; EHEM) on the in vitro oxidation of LDL and HDL. EHEM was found to possess ferric reducing power, DPPH free radical scavenging capacity, metal chelating activity, and NO radical scavenging activity. In addition, EHEM reduced the lipoperoxidation induced by α,α'-Azodiisobutyramidine dihydrochloride (AAPH) in HDL and LDL at all tested concentrations. In this study, we demonstrate the antioxidant properties of yerba mate and its phytochemical compounds. These properties may effectively prevent the in vitro oxidation of LDL and HDL molecules, a phenomenon linked to the pathogenesis of atherosclerosis.

Uptake of ox-LDL by binding to LRP6 mediates oxidative stress-induced BMSCs senescence promoting obesity-related bone loss

Obesity has long been thought to be a main cause of hyperlipidemia. As a systemic disease, the impact of obesity on organs, tissues and cells is almost entirely negative. However, the relationship between obesity and bone loss is highly controversial. On the one hand, obesity has long been thought to have a positive effect on bone due to increased mechanical loading on the skeleton, conducive to increasing bone mass to accommodate the extra weight. On the other hand, obesity-related metabolic oxidative modification of low-density lipoprotein (LDL) in vivo causes a gradual increase of oxidized LDL (ox-LDL) in the bone marrow microenvironment. We have reported that low-density lipoprotein receptor-related protein 6 (LRP6) acts as a receptor of ox-LDL and mediates the bone marrow stromal cells (BMSCs) uptake of ox-LDL. We detected elevated serum ox-LDL in obese mice. We found that ox-LDL uptake by LRP6 led to an increase of intracellular reactive oxygen species (ROS) in BMSCs, and N-acetyl-L-cysteine (NAC) alleviated the cellular senescence and impairment of osteogenesis induced by ox-LDL. Moreover, LRP6 is a co-receptor of Wnt signaling. We found that LRP6 preferentially binds to ox-LDL rather than dickkopf-related protein 1 (DKK1), both inhibiting Wnt signaling and promoting BMSCs senescence. Mesoderm development LRP chaperone (MESD) overexpression inhibits ox-LDL binding to LRP6, attenuating oxidative stress and BMSCs senescence, eventually rescuing bone phenotype.

Differences in structural changes and pathophysiologic effects of low-density lipoproteins upon accumulation of acylhydroperoxy derivatives in their outer phospholipid monolayer or upon chemical modification of apoprotein b-100 by natural dicarbonyl

Nanoparticles of the lipid-transporting system of the organism - low-density lipoproteins (LDL) of blood plasma are easily subjected to free radical peroxidation with formation of their main modified forms - oxidized LDL itself (containing hydroperoxy-acyls in phospholipids of the outer layer of particles) and dicarbonyl-modified LDL (apoprotein B-100 of which was chemically modified by the Maillard reaction). Based on the study of free radical oxidation kinetics of LDL, it was found that the existing in the literature designation “oxidized lipoproteins” is incorrect because it does not reveal the nature of oxidative modification of LDL. It is shown that “atherogenic” LDL (particles of which are actively captured by cultured macrophages) are not the oxidized LDL (in which LOOH-derivatives of phospholipids are formed by enzymatic oxidation of of C-15 lipoxygenase of rabbit reticulocytes), but dicarbonyl-modified LDL. The important role of dicarbonyl-modified LDL in the molecular mechanisms of atherogenesis and endothelial dysfunction is discussed.

Increased 12/15-lipoxygenase by disturbed flow promotes endothelial dysfunction and the development of atherosclerosis

Abstract Introduction Atherosclerosis is predisposed at bifurcations, branch points and arterial curvatures where the blood flow is disturbed. Deposition and oxidative modification of low-density lipoprotein (LDL) in the subendothelial intima is an early event in the pathogenesis of atherosclerosis. However, the effect of disturbed flow (d-flow) on LDL oxidation and the underlying mechanisms remain unclear. Purpose In this study, we investigated the role of 12/15-lipoxygenase (LOX) in LDL oxidation in endothelial cells (EC) and the development of atherosclerosis at d-flow sites. Methods En face immunofluorescence was performed to analyze the expression of 12/15-LOX in EC under exposure to different flow patterns. Protein expression and LDL oxidation was studied in vitro by using 2 different flow apparatuses. Animal model of d-flow was established by partial ligation of the carotid artery. Results En face staining exhibited a significant increase in 12/15-LOX protein expression in EC in areas exposed to d-flow than those exposed to steady flow (s-flow). Carotid partial ligation in ApoE knockout mice led to substantially increased deposition of oxidized LDL in the subendothelial intima and formation of atherosclerotic plaques in the carotid artery, whereas these detrimental effects by d-flow were markedly attenuated in ApoE/12/15-LOX double knockout mice. In cultured EC, d-flow generated by a reversal flow pump markedly promoted the expression of 12/15-LOX and translocation of the protein onto the cell membrane. Inhibition of 12/15-LOX in EC, either by knockdown with its specific siRNA or a pharmacological inhibitor, suppressed production of 15s-HETE and LDL oxidation in response to d-flow. Mechanically, we found d-flow induced the expression of 12/15-LOX by activating a specific responsive element in the 12/15-LOX promoter through recruiting a shear stress-sensitive transcriptional factor SREBP2. Chromatin immunoprecipitation further confirmed the interaction of SREBP2 with the promoter of 12/15-LOX upon d-flow exposure. Conclusions These data define an essential role of 12/15-LOX in promoting the pathogenesis of atherosclerosis under d-flow by increasing LDL oxidation in EC through SREBP2 signaling.

Abstract 13109: Empagliflozin Reverses Oxidized LDL-Induced RECK Suppression, MMP Activation, and Human Aortic Smooth Muscle Cell Proliferation and Migration

Empagliflozin, an FDA-approved anti-hyperglycemic agent, is a potent and highly selective inhibitor of sodium glucose co-transporter-2 (SGLT-2) in renal proximal tubule epithelial cells. It blocks glucose reabsorption and promotes glucose excretion via urine. Intriguingly, several clinical trials have reported the pleiotropic beneficial effects of SGLT-2 inhibitors in cardiovascular diseases, including antioxidant and anti-inflammatory effects. Here we investigated whether empagliflozin reverses oxidatively modified LDL (OxLDL)-induced matrix metalloproteinase activation and smooth muscle cell (SMC) migration and proliferation. Quiesced human aortic SMCs (Lonza) were treated with empagliflozin (1 uM) followed by human medium OxLDL (40 ug/mL; Kalen Biomedical). OxLDL stimulated SMC migration (1.8-fold, P<0.05, n=4) and proliferation (1.5-fold, P<0.05, n=4), and empagliflozin attenuated both by 67% (P<0.05, n=4) and 61% (P<0.05, n=4), respectively. Increased migration and proliferation by OxLDL were accompanied by elevated MMP-2 (3.2-fold, P<0.05, n=5) and 9 (3.1-fold, P<0.05, n=5) activities, which were also suppressed by empagliflozin by 65% and 67%, respectively (both P<0.05, n=5). RECK (reversion inducing cysteine rich protein with Kazal motifs) is a membrane anchored MMP inhibitor, and we found that OxLDL dose-dependently downregulated RECK in SMCs (by 60%, P<0.05, n=3) via NF-kB-dependent miR-30b induction. Intriguingly, empagliflozin restored the OxLDL downregulation of RECK to 88% of the control (n=3), as it inhibited miR-30b induction (by 49%, P<0.05, n=5). Consistent with RECK-mediated effects of empagliflozin, adenoviral overexpression of RECK inhibited OxLDL-induced SMC migration (by 67%, P<0.05, n=5) and proliferation (by 50%, P<0.05, n=5). Together, these results suggest that the vasculoprotective effects of empagliflozin are at least in part mediated by restoring RECK, thereby attenuating SMC migration and proliferation under elevated oxidative stress condition. Our results also suggest therapeutic potential of empagliflozin or RECK overexpression in vascular proliferative diseases.

Differences in Structural Changes and Pathophysiological Effects of Low-Density Lipoprotein Particles upon Accumulation of Acylhydroperoxy Derivatives in Their Outer Phospholipid Monolayer or upon Modification of Apoprotein B-100 by Natural Dicarbonyls.

Nanoparticles of the lipid-transporting system of the organism, low-density lipoproteins (LDL) of blood plasma, are prone to free radical peroxidation with formation of their main modified forms - oxidized LDL itself (containing hydroperoxy-acyls in phospholipids of the outer layer of particles) and dicarbonyl-modified LDL (apoprotein B-100 in which chemically modified via the Maillard reaction). Based on the study of free radical oxidation kinetics of LDLs, it was found that the existing in the literature designation of "oxidized lipoproteins" is incorrect because it does not reveal the nature of oxidative modification of LDLs. It was shown in this study that the "atherogenic" LDLs (particles of which are actively captured by the cultured macrophages) are not the oxidized LDL (in which LOOH-derivatives of phospholipids are formed by enzymatic oxidation by C-15 lipoxygenase of rabbit reticulocytes), but dicarbonyl-modified LDLs. Important role of the dicarbonyl-modified LDLs in the molecular mechanisms of atherogenesis and endothelial dysfunction is discussed.

Glyphosate Suppresses the Ability of PON1 to Hydrolyse Oxidized-LDL in the Exposed Farm Workers in Pahang, Malaysia

INTRODUCTION: Paraoxonase 1 (PON1) is a high-density lipoprotein (HDL)-associated enzyme which is known to hydrolyse most pesticides including organophosphates (OPs) and prevent atherosclerosis by inhibiting oxidative modification of low-density lipoprotein (LDL). Glyphosate is one of the common organophosphate pesticides used in agriculture in many developing countries including Malaysia. The aim of this study to is to assess the PON1 ability to hydrolyse oxidized LDL in glyphosate exposed farm workers. MATERIALS AND METHODS: In this cross-sectional comparative study, a total of 103 subjects (53 Glyphosate-exposed and 50 non-exposed) were recruited. Fasting serum samples were analysed for PON1 activities towards substrates paraoxon, phenylacetate, and diazoxon, as well as for lipid profiles and oxidized-LDL (ox-LDL). RESULTS: The results showed lower basal paraoxonase activity [156.96 (58.87) vs 177.06 (66.78)], arylesterase activity [90.06 (17.14) vs 96.92 (23.87)] and diazoxonase activity [850.93 (206.75) vs 990.48 (248.73)] in glyphosate-exposed compared to non-exposed, however, only diazoxonase activity was statistically significant (p<0.05). PON1 activity is not significantly different with different length of period of exposure except for arylesterase. There was also significantly higher (p<0.05) ox-LDL in the exposed group but no significant differences in lipid profiles (p>0.05) between the two groups. The PON1 to ox-LDL ratio which probably reflects the ability of PON1 to hydrolyse ox-LDL were also significantly lower (p<0.05) among the glyphosate-exposed group. CONCLUSION: The results suggested that the decreased PON1 activity in glyphosate-exposed individuals could predispose them to the development of atherosclerosis and coronary artery disease through decreased PON1 ability to hydrolyse ox-LDL.

HDL Function and Atherosclerosis: Reactive Dicarbonyls as Promising Targets of Therapy.

Epidemiologic studies detected an inverse relationship between HDL (high-density lipoprotein) cholesterol (HDL-C) levels and atherosclerotic cardiovascular disease (ASCVD), identifying HDL-C as a major risk factor for ASCVD and suggesting atheroprotective functions of HDL. However, the role of HDL-C as a mediator of risk for ASCVD has been called into question by the failure of HDL-C-raising drugs to reduce cardiovascular events in clinical trials. Progress in understanding the heterogeneous nature of HDL particles in terms of their protein, lipid, and small RNA composition has contributed to the realization that HDL-C levels do not necessarily reflect HDL function. The most examined atheroprotective function of HDL is reverse cholesterol transport, whereby HDL removes cholesterol from plaque macrophage foam cells and delivers it to the liver for processing and excretion into bile. Indeed, in several studies, HDL has shown inverse associations between HDL cholesterol efflux capacity and ASCVD in humans. Inflammation plays a key role in the pathogenesis of atherosclerosis and vulnerable plaque formation, and a fundamental function of HDL is suppression of inflammatory signaling in macrophages and other cells. Oxidation is also a critical process to ASCVD in promoting atherogenic oxidative modifications of LDL (low-density lipoprotein) and cellular inflammation. HDL and its proteins including apoAI (apolipoprotein AI) and PON1 (paraoxonase 1) prevent cellular oxidative stress and LDL modifications. Importantly, HDL in humans with ASCVD is oxidatively modified rendering HDL dysfunctional and proinflammatory. Modification of HDL with reactive carbonyl species, such as malondialdehyde and isolevuglandins, dramatically impairs the antiatherogenic functions of HDL. Importantly, treatment of murine models of atherosclerosis with scavengers of reactive dicarbonyls improves HDL function and reduces systemic inflammation, atherosclerosis development, and features of plaque instability. Here, we discuss the HDL antiatherogenic functions in relation to oxidative modifications and the potential of reactive dicarbonyl scavengers as a therapeutic approach for ASCVD.

Co-culture models of endothelial cells, macrophages, and vascular smooth muscle cells for the study of the natural history of atherosclerosis.

This work aims to present a fast, affordable, and reproducible three-cell co-culture system that could represent the different cellular mechanisms of atherosclerosis, extending from atherogenesis to pathological intimal thickening. We built four culture models: (i) Culture model #1 (representing normal arterial intima), where human coronary artery endothelial cells were added on top of Matrigel-coated collagen type I matrix, (ii) Culture model #2 (representing atherogenesis), which demonstrated the subendothelial accumulation and oxidative modification of low-density lipoproteins (LDL), (iii) Culture model #3 (representing intimal xanthomas), which demonstrated the monocyte adhesion to the endothelial cell monolayer, transmigration into the subendothelial space, and transformation to lipid-laden macrophages, (iv) Culture model #4 (representing pathological intimal thickening), which incorporated multiple layers of human coronary artery smooth muscle cells within the matrix. Coupling this model with different shear stress conditions revealed the effect of low shear stress on the oxidative modification of LDL and the upregulation of pro-inflammatory molecules and matrix-degrading enzymes. Using electron microscopy, immunofluorescence confocal microscopy, protein and mRNA quantification assays, we showed that the behaviors exhibited by the endothelial cells, macrophages and vascular smooth muscle cells in these models were very similar to those exhibited by these cell types in nascent and intermediate atherosclerotic plaques in humans. The preparation time of the cultures was 24 hours. We present three-cell co-culture models of human atherosclerosis. These models have the potential to allow cost- and time-effective investigations of the mechanobiology of atherosclerosis and new anti-atherosclerotic drug therapies.

Apolipoproteins as potential communicators play an essential role in the pathogenesis and treatment of early atherosclerosis.

Atherosclerosis as the leading cause of the cardiovascular disease is closely related to cholesterol deposition within subendothelial areas of the arteries. Significantly, early atherosclerosis intervention is the critical phase for its reversal. As atherosclerosis progresses, early foam cells formation may evolve into fibrous plaques and atheromatous plaque, ulteriorly rupture of atheromatous plaque increases risks of myocardial infarction and ischemic stroke, resulting in high morbidity and mortality worldwide. Notably, amphiphilic apolipoproteins (Apos) can concomitantly combine with lipids to form soluble lipoproteins that have been demonstrated to associate with atherosclerosis. Apos act as crucial communicators of lipoproteins, which not only can mediate lipids metabolism, but also can involve in pro-atherogenic and anti-atherogenic processes of atherosclerosis via affecting subendothelial retention and aggregation of low-density lipoprotein (LDL), oxidative modification of LDL, foam cells formation and reverse cholesterol transport (RCT) in macrophage cells. Correspondingly, Apos can be used as endogenous and/or exogenous targeting agents to effectively attenuate the development of atherosclerosis. The article reviews the classification, structure, and relationship between Apos and lipids, how Apos serve as communicators of lipoproteins to participate in the pathogenesis progression of early atherosclerosis, as well as how Apos as the meaningful targeting mass is used in early atherosclerosis treatment.

Methods for Measurements of Oxidized LDL, Homocysteine and Nitric Oxide as Clinical Parameters of Oxidative Stress and Endothelial Dysfunction

Abstract: Timely and accurate evaluation of clinical parameters associated with endothelial dysfunction is critical in diagnosing and treating atherosclerosis, which represents a severe health problem, accounting for at least 30% of deaths globally. A critical early event in the pathogenesis of atherosclerosis is the oxidative modification of low-density lipoprotein [LDL]. Oxidized LDL [OxLDL] represents numerous changes in lipid and apolipoprotein B [apo B] fractions of LDLs generated by lipid peroxidation. Another critical indicator of perturbed vascular homeostasis is homocysteine [Hcy], an amino acid containing sulfhydryl-group, an intermediate methionine and cysteine biosynthesis product. The total level of Hcy in plasma correlates better than cholesterol with the risk of cardiovascular disease. In addition, nitric oxide [NO] plays an essential role in regulating vascular physiological homeostasis due to its involvement in intravascular free radical and oxidant reactions. Reduced NO decreases oxidative stress in the vascular wall, which reduces the rate of LDL oxidation and the expression of redox-sensitive genes involved in atherogenesis. Endothelial dysfunction is typically associated with increased levels of OxLDL, decreased nitric oxide [NO], and hyperhomocysteinemia. Thus, OxLDL, Hcy, and NO are representative parameters of oxidative stress and endothelial dysfunction. Considering the important role of oxLDL, Hcy and NO in oxidative stress, atherogenesis and accompanying endothelial dysfunction, the challenge of the present work was to systematically present available methods for reliable measurement of these parameters and assess their potential for the use in the clinical setting. Here we present a comprehensive overview of analytical methods for measuring OxLDL, HCy, and NO in biological samples and discuss their advantages and potential problems regarding their application in clinical settings.

Lipidomics Revealed Plasma Phospholipid Profile Differences between Deceased and Recovered COVID-19 Patients.

Thorough understanding of metabolic changes, including lipidome alteration, associated with the development of COVID-19 appears to be crucial, as new types of coronaviruses are still reported. In this study, we analyzed the differences in the plasma phospholipid profiles of the deceased COVID-19 patients, those who recovered and healthy people. Due to identified abnormalities in plasma phospholipid profiles, deceased patients were further divided into two subgroups (D1 and D2). Increased levels of phosphatidylethanolamines (PE), phosphatidylcholines (PC) and phosphatidylserines (PS) were found in the plasma of recovered patients and the majority of deceased patients (first subgroup D1) compared to the control group. However, abundances of all relevant PE, PC and PS species decreased dramatically in the plasma of the second subgroup (D2) of five deceased patients. These patients also had significantly decreased plasma COX-2 activity when compared to the control, in contrast to unchanged and increased COX-2 activity in the plasma of the other deceased patients and recovered patients, respectively. Moreover, these five deceased patients were characterized by abnormally low CRP levels and tremendous increase in LDH levels, which may be the result of other pathophysiological disorders, including disorders of the immune system, liver damage and haemolytic anemia. In addition, an observed trend to decrease the autoantibodies against oxidative modifications of low-density lipoprotein (oLAb) titer in all, especially in deceased patients, indicate systemic oxidative stress and altered immune system that may have prognostic value in COVID-19.

Correlation of Oxidised LDL with Oxidant and Antioxidant enzymes in subjects with Elevated LDL levels

Mortality due to atherosclerosis is very common and the oxidative modification of low-density lipoprotein (LDL) is responsible for the progression of atherosclerosis. Estimation of oxidized LDL (Ox-LDL), myeloperoxidase (MPO), and paraoxonase (PON1) in subjects with elevated LDL and correlation of oxidized LDL with MPO and PON1 was the main objective. Ox-LDL was determined by ELISA. Activity of Myeloperoxidase and Paraoxonase was estimated by spectrophotometric method. LDL and HDL estimations were carried out in the autoanalyser. Significant increase in the myeloperoxidase and Ox-LDL with the significant decrease in the paraoxonase levels were obseved (p<0.001). No significant change in the HDL levels was seen. LDL showed a positive association with MPO and a negative association with Basal Paraoxonase (BPON) in both cases and controls. Ox-LDL also showed a positive association with MPO and a negative association with BPON only in cases, while no significant association was seen in controls. Ox-LDL seems to be a more sensitive indicator of cardiovascular disease risk than either HDL or LDL cholesterol. Measurement of Ox-LDL, /Myeloperoxidase and Paraoxonase may provide additional details in cardiovascular disease risk prediction.

Effect of Dialyzer Reuse on the Activity of Paraoxonase 1 in Patients on Hemodialysis.

Cardiovascular disease is the major cause of mortality in patients undergoing chronic hemodialysis treatment. The oxidative modification of low-density lipoprotein is a crucial step in the pathogenesis of atherosclerosis. Paraoxonase 1 (PON1) is the protein responsible for most of the antioxidant activity of high-density lipoprotein, and its reduced levels are associated with more cardiovascular events in several populations. In hemodialysis patients, reduced PON1 activity has been shown to be associated with increased cardiovascular mortality. Studies have shown that after the hemodialysis session, the activity of PON1 increases. The influence of dialyzer reuse on the activity of PON1 is unknown. We aimed to evaluate the effect of the reuse of two types of dialyzers (polynephron and polyethersulfone) on the PON1 activity of hemodialysis patients. A total of 30 patients on hemodialysis were included. Pre- and post-dialysis blood samples were collected to analyze the activity of PON1 in thefirst use of the dialyzer and in the hemodialysis session of its sixth reuse. This process was carried out with polynephron (bisphenol-free) and polyethersulfone dialyzers. We found that post-dialysis PON1 activity was significantly higher than pre-dialysis activity in both thefirst use and sixth reuse (P < 0.001). The practice of reusing the dialyzer did not interfere with the improvement of PON1 activity after the hemodialysis session.

Curcumin Alleviates Palmitic Acid-Induced LOX-1 Upregulation by Suppressing Endoplasmic Reticulum Stress in HUVECs.

Excessive free fatty acid- (FFA-) induced endothelial lipotoxicity is involved in the pathogenesis of atherosclerosis. Endoplasmic reticulum (ER) stress is mechanistically related to endothelial lipotoxicity. Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) is the major oxidatively modified low-density lipoprotein (OxLDL) receptor in endothelial cells and is highly abundant in atherosclerotic lesions. Curcumin reduces the LOX-1 expression; however, the mechanism underlying this effect remains unknown. In the current study, we explored whether curcumin ameliorates palmitic acid- (PA-) induced endothelial lipotoxicity and LOX-1 upregulation by reducing ER stress in human umbilical vein endothelial cells (HUVECs). We built endothelial lipotoxicity in vitro and found that LOX-1 was upregulated after PA stimulation, during which ER stress played an important role. Next, we observed that curcumin substantially alleviated PA-induced lipotoxicity by restoring cell viability, increasing angiogenesis, and decreasing lipid deposition. Furthermore, LOX-1 upregulation in HUVECs was blocked by curcumin, possibly via ER stress suppression. Overall, our findings demonstrated that curcumin alleviates endothelial lipotoxicity and LOX-1 upregulation, and ER stress inhibition may play a critical role in this effect.

Ferryl Hemoglobin and Heme Induce A1-Microglobulin in Hemorrhaged Atherosclerotic Lesions with Inhibitory Function against Hemoglobin and Lipid Oxidation.

Infiltration of red blood cells into atheromatous plaques and oxidation of hemoglobin (Hb) and lipoproteins are implicated in the pathogenesis of atherosclerosis. α1-microglobulin (A1M) is a radical-scavenging and heme-binding protein. In this work, we examined the origin and role of A1M in human atherosclerotic lesions. Using immunohistochemistry, we observed a significant A1M immunoreactivity in atheromas and hemorrhaged plaques of carotid arteries in smooth muscle cells (SMCs) and macrophages. The most prominent expression was detected in macrophages of organized hemorrhage. To reveal a possible inducer of A1M expression in ruptured lesions, we exposed aortic endothelial cells (ECs), SMCs and macrophages to heme, Oxy- and FerrylHb. Both heme and FerrylHb, but not OxyHb, upregulated A1M mRNA expression in all cell types. Importantly, only FerrylHb induced A1M protein secretion in aortic ECs, SMCs and macrophages. To assess the possible function of A1M in ruptured lesions, we analyzed Hb oxidation and heme-catalyzed lipid peroxidation in the presence of A1M. We showed that recombinant A1M markedly inhibited Hb oxidation and heme-driven oxidative modification of low-density lipoproteins as well plaque lipids derived from atheromas. These results demonstrate the presence of A1M in atherosclerotic plaques and suggest its induction by heme and FerrylHb in the resident cells.

Abstract 15019: Differential Effects of Omega-3 Fatty Acid Combinations on the Inhibition of Oxidation Of Human Low-density Lipoproteins in vitro

Background: Omega-3 fatty acids (O3FAs) reduce levels of triglyceride but may also have additional atheroprotective benefits. Randomized trials have suggested potential clinical outcome differences among O3FAs formulations. Oxidative modification of low-density lipoproteins (LDL) contributes to endothelial dysfunction, inflammation, and other aspects of atherogenesis. Individual O3FAs have been shown to inhibit LDL oxidation to varying degrees, but the antioxidant effects of combining O3FAs is unknown. Objective: To compare the dose- and time-dependent antioxidant effects of eicosapentaenoic acid (EPA, 20:5) alone and in combination with either docosapentaenoic acid (DPA, 22:5) or docosahexaenoic acid (DHA, 22:6) in human LDL in vitro . Methods: Human LDL was isolated from healthy subjects and adjusted to a final ApoB concentration of 100 μg/mL in physiologic buffer (PBS) before being incubated with O3FAs at 37°C. The EPA levels in the combinations were fixed at either 2.0, 3.0, or 4.5 μM, while the DPA or DHA levels were set at 0, 0.5, 1.0, and 2.0 μM. Oxidation was initiated by copper sulfate (10 μM) and measured over time by formation of malondialdehyde (MDA), a lipid oxidation product. Results: When combined with EPA, both DPA and DHA increased inhibition of oxidation in a dose- and time-dependent manner, with DPA showing a greater effect and more prolonged inhibition. At high levels of EPA (4.5 μM), DPA showed significantly greater antioxidant activity than equimolar DHA; these differences were more apparent with time. After 8 hours, adding 1.0 μM DPA reduced MDA formation by 61% versus vehicle (3.10 ± 0.42 vs. 7.98 ± 0.56, p &lt;0.001), while adding 1.0 μM DHA only reduced MDA formation by 20% (6.40 ± 1.23, p &lt;0.05). When 2 μM DPA or DHA were added, after 10 hours only DPA still had a significant degree of inhibition versus vehicle (37%; 6.65 ± 0.95 vs. 8.21 ± 0.53, p &lt;0.05). Similar trends were observed in combinations containing 2.0 and 3.0 μM EPA. Conclusion: Adding DPA or DHA to EPA provide dose-dependent incremental antioxidant effects, with DPA providing a larger degree and a longer duration of inhibition. These observations highlight potential differences among O3FAs (and their combinations) in novel mechanisms of atheroprotection.

Genetic associations and serum paraoxonase levels with atherosclerosis in western Iranian patients.

The oxidative modification of low-density lipoprotein (LDL) in the arterial wall plays a pivotal role in the initiation and progression of atherosclerosis which is a complex and progressive disorder. Paraoxonase1 (PON1), which is required for lipid metabolism, is believed to protect LDL from oxidation. The relationship between PON1 gene Leusin55Methionin (L55M) and Glutamine192Arginine (Q192R) polymorphisms in western Iranians with atherosclerosis and its association with enzyme activity and oxidized low-density lipoprotein (oxLDL) were examined in the present study. In this study, blood specimens were collected from 145 healthy individuals and 154 patients with atherosclerosis proven by angiography referred to Shahid Madani Hospital, Khorramabad, Iran. Genomic deoxy ribonucleic acid (DNA) was extracted from whole blood. For all the subjects, restriction fragment length polymorphism-polymerase chain reaction (RFLP-PCR) was carried out for the detection of L55M and Q192R polymorphisms. PON1 enzyme activity and the level of oxLDL were also evaluated. There was a 3.114-fold increase in the risk of developing atherosclerosis in the subjects presenting the PON1L55M, MM genotype compared to those with the LL genotype (OR 3.114; 95% CI 1.412-6.870). PON1Q192R polymorphism in the PON1 gene was not associated with atherosclerosis. Patients with atherosclerosis had significantly higher oxLDL and reduced PON1 enzyme activity (P < 0.05) compared to the controls. There was no association between the type of genotype, enzyme activity, and oxLDL level. It has been concluded that PON1L55M polymorphism and MM genotype are associated with an increased risk of coronary artery disease (CAD) in Iranian patients with atherosclerosis. We did not find any relationship between PON1Q192R polymorphism and atherosclerosis.