Oxidized Phospholipids Research Articles

Platelet-activating factor and oxidized phosphatidylcholines do not suppress endotoxin-induced pro-inflammatory signaling among human myeloid and endothelial cells

Platelet-activating factor (PAF) and related phospholipid oxidation products termed oxidized phospholipids (OxPLs) promote inflammation. PAF is made in response to bacterial endotoxin-lipopolysaccharide (LPS) that is recognized by Toll-like receptor-4 (TLR-4) whose activation leads to translocation of transcription factor NF-ΚB to the nucleus—a key regulator of multiple pro-inflammatory genes including COX-2 and IL-8. Paradoxically, PAF and OxPLs are claimed to inhibit LPS-mediated signaling, questioning the very pro-inflammatory roles of PAF and OxPLs and anti-inflammatory nature of PAF-acetylhydrolase (PAF-AH), an enzyme that attenuates both PAF and OxPLs signaling. We investigated the effect of PAF and representative OxPLs: 1-palmitoyl-2-oxovaleroyl-sn-glycero-3-phosphocholine (POVPC), 1-palmitoyl-2-glutaroyl-sn- glycero-3-phosphocholine (PGPC) and 1-alkyl-2-butanoyl-sn-glycero-3-phosphocholine PAF (C4 PAF) on LPS-induced expression of NF-ΚB mediated inflammation in isolated human myeloid cells: polymorphonuclear leukocyte (PMNs), monocytes and human umbilical vein endothelial cells (HUVECs). Using intracellular calcium transients, we show that POVPC and PGPC dose-dependently activate the PAF-receptor (PAF-R) in PMNs, that can beblocked by the PAF-R antagonist WEB-2086 and rPAF-AH pre-treatment. All the three cell types express minute or no detectable COX-2 when stimulated with either PAF (0.1 µM) or OxPLs (0.1 µM) alone. While LPS (100 ng/mL) induced expression of COX-2 in all the cell types, pre-activation of PAF-R with PAF (0.1 µM) or OxPLs (0.1 µM) did not suppress LPS (100 ng/mL)-induced COX-2 expression and in fact we obresved incereased PGE2 levels in an NS-398 sensitive manner. In addition, pre-activation of PAF-R significantly augmented LPS (100 ng/mL)-induced IL-8 production in PMNs. Thus, PAF and OXPLs do not suppress the ability of LPS to exert its pro-inflammatory effects in isolated human vascular cells.

Expression of E06, a natural monoclonal antibody targeted to oxidized phospholipids (OXPL), attenuates the progression of aortic sclerosis in aged hyperlipidemic mice

Expression of E06, a natural monoclonal antibody targeted to oxidized phospholipids (OXPL), attenuates the progression of aortic sclerosis in aged hyperlipidemic mice

On-line high speed lipid extraction for nanoflow liquid chromatography-tandem mass spectrometry

An on-line lipid extraction method is introduced by utilizing a short capillary extraction column using HILIC and C4 particles prior to nanoflow liquid chromatography-tandem mass spectrometry (nLC–MS/MS). The on-line extraction using a urine sample spiked with PL standards showed similar or slightly higher recovery values (86%–96%) of phospholipids (PLs) compared to those obtained by the conventional off-line extraction based on the Folch method with or without using the air-exposed drying process. In this study, we demonstrated that PL oxidation can occur during the air-exposed drying process of lipid extracts in standard liquid–liquid extraction procedures, which was confirmed by the oxidized PL (OxPL) molecules that were generated from an off-line extraction using a few PL standards. Quantitative comparison of these OxPL species between on- and off-line extraction followed by nLC–MS/MS with multiple reaction monitoring (MRM) analysis showed a significant decrease (2–10 fold) in unwanted OxPL species when on-line extraction was employed. While the number of identified PLs from a urine sample was somewhat lower than those by off-line extraction, the number of OxPLs was significantly reduced (from 70 to 22) with on-line extraction. The new method offers high speed (∼5min) automated extraction of PLs with nLC–MS/MS analysis and presents the possibility of handling a biological sample with a very limited amount of lipids.

The regulation of inflammation by oxidized phospholipids.

During inflammation or under conditions of oxidative stress, the polyunsaturated fatty acid side chains of phospholipids in cellular membranes or lipoproteins can be oxidatively modified. This process generates a complex mixture of structurally diverse oxidized phospholipid (OxPL) species, each of which may exert distinct biological effects. The presence of OxPLs has been documented in acute and chronic microbial infections, metabolic disorders, and degenerative diseases. It is now well recognized that OxPLs actively influence biological processes and contribute to the induction and resolution of inflammation. While many pro- and anti-inflammatory effects have been documented for bulk OxPL preparations, we are only beginning to understand the exact molecular mechanisms and signaling events that mediate the individual proinflammatory or anti-inflammatory bioactivities of discrete isolated OxPL species. Here, we review the current knowledge on the regulation of inflammation by OxPLs and summarize recent studies that establish cyclopentenone-containing OxPLs as a category of potent anti-inflammatory lipid mediators.

Novel immune assay for quantification of plasma protective capacity against oxidized phospholipids.

Oxidized phospholipids (OxPL) are the major pathogenic component of oxidized low-density lipoproteins (OxLDL). Endogenous anti-OxPL activity, defined as the ability to neutralize adverse effects of oxidized lipids, may have biomarker potential. Using two anti-OxPL monoclonal antibodies (commercial mAB-E06 and custom mAB-509) we developed a novel ELISA that measures the global capacity of plasma to inactivate OxPL. Preincubation of OxLDL with plasma inhibits its binding of anti-OxPL mABs. This phenomenon ('masking') reflects anti-OxPL plasma activity. A pilot clinical application of the assay revealed reduced anti-OxPL activity in hypertension, coronary artery disease, acute coronary syndrome and diabetes. Inadequate anti-OxPL protection may contribute to cardiovascular disease and have biomarker potential in conditions associated with abnormal lipid peroxidation.

Abstract 417: Control of Adipose Tissue Macrophage Metabolism by Oxidized Phospholipids

Our group has previously shown that oxidized phospholipids (OxPL) induce a unique macrophage (MΦ) phenotype known as “Mox,” distinct from pro- and anti-inflammatory M1 and M2 phenotypes. We have also shown that Mox make up 30% of the MΦs found in atherosclerotic lesions. OxPL induce TLR2-dependent inflammatory gene expression in MΦs. TLR2 activation by peptidoglycan was shown to induce accumulation of ceramides, which can alter bioenergetics by inhibiting the mitochondria. Recently, it has been shown that spleen tyrosine kinase (Syk) is phosphorylated upon TLR2 agonist Pam3CSK stimulation in MΦs. The effect of OxPL on bioenergetics has never before been studied. Here we test the hypothesis that OxPL change MΦ bioenergetics and inflammatory capacity via a TLR2-Syk-Ceramide pathway. Using flow cytometry, we found that in mice fed a high-fat diet, more than 20% of all adipose tissue MΦs can be described as Mox. Concomitantly, using immunohistochemistry and liquid-chromatography mass spectrometry, we measured increased levels of OxPL in the stromal vascular fraction of obese murine adipose tissue, as compared to lean controls. We treated bone marrow-derived MΦs (BMDMs) from WT, TLR2-KO, and Syk-KO mice with OxPL and measured bioenergetics using a Seahorse Flux Analyzer. Our results show that OxPL decrease oxygen consumption rate (OCR), a measure of oxidative phosphorylation, and decrease extracellular acidification rate (ECAR), a measure of glycolytic capacity. These MΦs can be described as quiescent, but they still engage in low-level cytokine production. Moreover, OxPL result in the accumulation of ceramides, as quantified by mass spectrometry. Finally, using Syk-KO MΦs and Syk inhibitors, we show that OxPL-induced inflammatory gene expression and ceramide accumulation are dependent on Syk. In summary, our results demonstrate that OxPL accumulate in obese adipose tissue and induce a change in the inflammatory and metabolic profiles of MΦs, involving a TLR2-ceramide-Syk dependent pathway. These results suggest that OxPL are triggers of adipose tissue inflammation and subsequent development of insulin resistance. Furthermore, we identify Syk as a therapeutic target for inhibiting diet-induced adipose tissue inflammation and insulin resistance.

Abstract 361: Oxidized Phospholipids Are Proinflammatory and Proatherogenic

Oxidized phospholipids (OxPL) are ubiquitously generated during inflammation, and found on apoptotic cells, OxLDL, and Lp(a). They facilitate uptake of OxLDL by macrophages (Mac) and mediate cellular inflammatory responses. The E06 natural IgM binds to the PC of OxPL, neutralizing biological effects and inhibiting OxLDL uptake by Mac. To determine the role of OxPL in atherogenesis, we generated transgenic mice expressing a single chain variant (scFv) of E06 in Ldlr background (E06-Tg). E06-scFv was secreted into plasma, bound to OxLDL and had sufficient titer to inhibit OxLDL uptake into Mac. E06-Tg or Ldlr mice were fed 1% Chol diet for 4, 7 or 12 months (n=12-15 mice/group). Plasma Chol was ~ 1600 mg/dL in all mice. Atherosclerosis decreased in E06-Tg mice: En face lesions decreased 57%, 34% and 28%, and aortic root lesions decreased 55%, 41% and 26% at 4, 7 and 12-months, respectively. OxLDL uptake by Macs was decreased: Thus, in E06-Tg mice, the uptake by peritoneal Mac of fluorescently-labeled OxLDL injected ip was decreased ~ 50%, as was peritoneal Mac Chol content. As Macs secrete E06-scFv, we performed BMT from E06-Tg donors into irradiated Ldlr recipients (n=10-12): This also decreased lesions 31% compared to BMT from control donors, even though plasma titers of E06-scFv were ~10% of Tg mice. Overexpression of E06-scFv was anti-inflammatory: Thus, in E06-Tg mice, both peritoneal and aortic wall resident macrophages exhibited decreased inflammatory gene expression, and phenotypic switches from M1 to M2 analyzed by RNAseq and FACS. Further, in E06-Tg mice, plasma SAA levels were reduced 32%, and hepatic steatosis was also decreased (-50% in both TG and Chol), as was hepatic inflammatory gene expression. Finally, E06-scFv attenuated both a progressive increase in aortic valve gradient (via echocardiography) and calcification in aged Ldlr mice. The E06-scFv lacks functional effects of an intact antibody other than the ability to “neutralize” OxPL. Thus, these data demonstrate that OxPL are profoundly proatherogenic and proinflammatory, which E06 counteracts in vivo . Neutralizing OxPL may therefore reduce the progression of atherosclerosis and cardiovascular events and more generally, represents a novel strategy to safely attenuate inflammation.

Abstract 153: Molecular Mimicry Between Malondialdehyde and Group A Streptococcus Contribute to the Natural Selection of Conserved Innate Immune Response

Innate immunity utilizes evolutionarily conserved pattern recognition receptors (PRRs) to provide an early and effective response against Pathogen-Associated Molecular Patterns (PAMPs) on microbial pathogens and/or against Danger Associated Molecular Patterns (DAMPs) on endogenous modified-self structures. Atherosclerosis is a chronic inflammatory disease in which lipid peroxidation is greatly increased leading to the generation of OxLDL, which contains a variety of proinflammatory oxidation-specific neoepitopes (OSE), such as phosphocholine (PC) containing oxidized phospholipids (OxPL). Our group has shown that OSEs are DAMPs, to which has evolved a concerted innate immune response mediated by PRRs. For example, CD36, CRP and IgM E06 all recognize the PC of OxPL, but also the PC on apoptotic cells as well as the PC on the cell wall of S. pneumonia (but not as part of a lipid). Accordingly, we postulated that both endogenous DAMPs and exogenous PAMPs provide natural selection for PPR responses to PC. Malondialdehyde (MDA) is another prominent OSE target of three different PRR’s: SR-A, CFH, and the IgM NAb E014. Thus, we hypothesized that EO14 should also recognize an epitope/mimotope on an infectious pathogen. We screened a pathogen library with E014 and discovered it avidly bound to group A streptococcus (GAS). Because it was known that CFH also bound to GAS, and specifically to protein M, the major virulence factor of GAS, we used GAS with and without protein M to show that E014 specifically bound to protein M. Using a series of recombinant protein M fragments, we identified a 125 aa sequence required for binding. Using a synthetic peptide array to generate 15 aa-length overlapping peptides, we identified a 24 aa mimitope that E014 bound. We subsequently showed immunological cross reactivity between GAS, Protein M, the mimotope, and MDA in vitro and in vivo in mice and humans. Further, compared to immunization of mice with protein M, immunization with MDA-LDL provided partial protection against lethal infection with GAS. These data support the hypothesis that OSE are important targets of innate immunity and both oxidative events and pathogens have contributed to the natural selection of potent, shared innate immune responses to oxidation-specific epitopes.

Effect of therapeutic interventions on oxidized phospholipids on apolipoprotein B100 and lipoprotein(a)

Oxidized phospholipids (OxPL) on apolipoprotein B-100 (OxPL-apoB) reflect the biological activity of lipoprotein(a) (Lp[a]) and predict cardiovascular disease events. However, studies with statins and low-fat diets show increases in OxPL-apoB and Lp(a). This study evaluated changes in OxPL-apoB and Lp(a) with extended-release niacin (N), ezetimibe/simvastatin (E/S) and combination E/S/N. A systematic literature review of previously published trials, measuring both OxPL-apoB and Lp(a) after therapeutic interventions, was also performed. OxPL-apoB and Lp(a) were measured in 591 patients at baseline and 24weeks after therapy with N, E/S, or E/S/N in a previously completed randomized trial of hypercholesterolemic patients. The literature review included 12 trials and 3896 patients evaluating statins, low-fat diets, antisense to apolipoprotein(a) and lipid apheresis. Niacin decreased OxPL-apoB levels (median [interquartile range]; 3.5 [2.2-9.2] nM to 3.1 [1.8-7.2] nM, P<.01) and Lp(a) (10.9 [4.6-38.4] to 9.3 [3.1-32.9] mg/dL, P<.01). In contrast, E/S and E/S/N significantly increased OxPL-apoB (3.5 [2.1-7.8] to 4.9 [3.0-11.1] nM, P<.01) and (3.3 [1.9-9.3] to 4.3 [2.6-11.2] nM, P<.01), respectively and Lp(a) (11.5 [6.1-36.4] to 14.9 [6.6-54.6] mg/dL, P<.01) and (11.3 [5.4-43.8] to 11.6 [5.9-52.8] mg/dL, P<.01), respectively. The systematic review of statins and diet demonstrated 23.8% and 21.3% mean increases in OxPL-apoB and 10.6% and 19.4% increases in Lp(a), respectively. However 44.1% and 52.0% decreases in OxPL-apoB and Lp(a), respectively, were present with Lp(a)-lowering therapies. This study demonstrates differential changes in OxPL-apoB and Lp(a) with various lipid-lowering approaches. These changes in OxPL-apoB and Lp(a) may provide insights into the results and interpretation of recent cardiovascular disease outcomes trials.

Antisense inhibition of apolipoprotein (a) to lower plasma lipoprotein (a) levels in humans

Epidemiological, genetic association, and Mendelian randomization studies have provided strong evidence that lipoprotein (a) [Lp(a)] is an independent causal risk factor for CVD, including myocardial infarction, stroke, peripheral arterial disease, and calcific aortic valve stenosis. Lp(a) levels >50 mg/dl are highly prevalent (20% of the general population) and are overrepresented in patients with CVD and aortic stenosis. These data support the notion that Lp(a) should be a target of therapy for CVD event reduction and to reduce progression of aortic stenosis. However, effective therapies to specifically reduce plasma Lp(a) levels are lacking. Recent animal and human studies have shown that Lp(a) can be specifically targeted with second generation antisense oligonucleotides (ASOs) that inhibit apo(a) mRNA translation. In apo(a) transgenic mice, an apo(a) ASO reduced plasma apo(a)/Lp(a) levels and their associated oxidized phospholipid (OxPL) levels by 86 and 93%, respectively. In cynomolgus monkeys, a second generation apo(a) ASO, ISIS-APO(a)Rx, significantly reduced hepatic apo(a) mRNA expression and plasma Lp(a) levels by >80%. Finally, in a phase I study in normal volunteers, ISIS-APO(a)Rx ASO reduced Lp(a) levels and their associated OxPL levels up to 89 and 93%, respectively, with minimal effects on other lipoproteins. ISIS-APO(a)Rx represents the first specific and potent drug in clinical development to lower Lp(a) levels and may be beneficial in reducing CVD events and progression of calcific aortic valve stenosis.

Abstract 11339: Relationship of LPA Single Nucleotide Polymorphisms With Apolipoprotein (a) Isoforms and Biomarkers of Oxidized Lipoproteins in African-Americans, Caucasians and Hispanics: Results From the DALLAS Heart Study

Background: Oxidized phospholipids (OxPL) measured on apolipoprotein B-100 particles (OxPL-apoB) are a measure of the pro-inflammatory activity of Lp(a). Lp(a) in plasma is genetically determined by variability in kringle IV (KIV) repeats and single nucleotide polymorphisms (SNPs) in the LPA gene, is causally related to cardiovascular disease (CVD) and has become a target of therapy. Methods and Results: OxPL-apoB IgG and IgM autoantibodies to oxidized LDL and apoB-immune complexes, KIV repeats of the major apolipoprotein (a) isoform, LPA snps rs3798220, rs10455872 and rs9457951 were measured in 3454 subjects (1798 African-Americans, 1032 Caucasian and 576 Hispanic) subjects enrolled in the Dallas Heart Study (Table). All 3 snps were highly correlated with the number of KIV repeats in African-Americans but only rs3798220 and rs10455872 were correlated with KIV repeats in Caucasians or Hispanics. rs3798220 and rs10455872 demonstrated strong correlations with Lp(a) and OxPL-apoB levels in subjects with low numbers of KIV repeats, whereas rs9457951 showed similar associations only in African-Americans. None of the LPA snps correlated with the other biomarkers of oxidation. Conclusion: Significant racial differences exist among LPA SNPs and their relationship to Lp(a), apolipoprotein (a) isoforms and OxPL-apoB. These findings may provide insights into the clinical variability of Lp(a)-mediated risk in different racial groups and suggests novel avenues of investigation and therapeutic potential in mitigating the CVD risk of Lp(a) and OxPL-apoB.

Circulating levels of plasminogen and oxidized phospholipids bound to plasminogen distinguish between atherothrombotic and non-atherothrombotic myocardial infarction.

Oxidized phospholipids (OxPL) are abundant in atherosclerotic plaques. They are also bound to circulating plasminogen after myocardial infarction (MI), and their binding to plasminogen may accentuate fibrinolysis. We sought to assess whether circulating levels of plasminogen and OxPL bound to plasminogen (OxPL-PLG) increase following acute MI and whether this increase differs between atherothrombotic (Type 1) and non-atherothrombotic (Type 2) MI. We measured circulating levels of plasminogen and OxPL-PLG at 0, 6, 24, 48h, and >3months (stable state) following acute MI and following an angiogram for stable coronary artery disease (CAD). Forty-nine subjects met the criteria for acute MI, of whom 34 had clearly defined atherothrombotic (n=22) or non-atherothrombotic (n=12) MI; 15 patients met the criteria for stable CAD. Mean baseline levels of plasminogen and OxPL-PLG were lower in the acute MI group than in the stable CAD group (9.75 vs 20.2, p<0.0001 for plasminogen and 165.5 vs 275.1, p=0.0002 for OxPL-PLG) and did not change over time or between time points, including the 3-month follow-up. Mean baseline levels of plasminogen and OxPL-PLG were also lower in atherothrombotic (Type 1) than in non-atherothrombotic (Type 2) MI subjects (8.65 vs 12.1, p<0.03 for plasminogen and 164.5 vs 245.7, p=0.02 for OxPL-PLG), and this relationship did not change over time or between time points. Plasminogen and OxPL-PLG were lower in patients presenting with an acute MI than in those with stable CAD and also in those with atherothrombotic MI (Type 1) vs. those with non-atherothrombotic MI (Type 2). These findings persisted at a median follow-up of 3months post-MI. The association of plasminogen and OxPL-PLG with acute MI, particularly atherothrombotic MI (Type 1), could reflect a reduced fibrinolytic capacity, associated with an increased risk of atherothrombotic events differentiating stable CAD from unstable CAD and atherothrombotic MI (Type 1) from non-atherothrombotic MI (Type 2). Additional study with a larger sample size is warranted.

AUTOTAXIN ENHANCES AORTIC VALVE MINERALIZATION THROUGH A NF-κB / IL-6 / BMP-2 DEPENDENT INFLAMMATORY PATHWAY

Calcific aortic valve disease (CAVD) is characterized by a progressive mineralization of the aortic valve. Recent studies of Mendelian randomization have revealed an association between lipoprotein (a) [Lp (a)] and CAVD. However, the mechanism by which the Lp (a) causes aortic valve interstitial cells (VICs) calcification remains unknown. Lp (a) carries oxidized phospholipids (OxPLs) with a high content in lysophosphatidylcholine (LPC). The enzyme autotaxin (ATX) converts LPC into lysophosphatidic acid (LysoPA). We investigated whether ATX-produced LysoPA could induce mineralisation. We documented the expression of ATX in control and CAVD valves. We investigated in vitro the mechanisms by which ATX promotes inflammation and mineralization of VICs. These results were then validated in a mouse model of CAVD. In CAVD, immunohistochemical stainings revealed the expression of ATX by VICs and ATX co-distributed with Lp (a). Moreover, ATX-specific enzyme activity confirmed the expression of ATX in CAVD. An interaction between ATX and Lp (a) was revealed by 'proximity ligation assay'. Also, we have detected a high level of ATX activity in Lp (a) purified fractions. On the other hand, we showed that ATX promotes inflammation and mineralization of the aortic valve by the activation of a NF-kB / IL-6 / BMP-2 dependent pathway. LysoPA injections, in mice LDLR - / - / ApoB 100/100 / IGFII fed with a HFHS diet, accelerated the development of CAVD compared with HFHS diet alone. Echocardiographic analyzes of these mice showed a two fold increase in the delta velocity in comparison with control mice. ATX is transported in the aortic valve by Lp (a) and is secreted by VICs. ATX and LysoPA promote inflammation and mineralization of the aortic valve and could therefore represent new therapeutic targets in CAVD.

Oxidized Phospholipids, Lipoprotein(a), and Progression of Calcific Aortic Valve Stenosis

BackgroundElevated lipoprotein(a) (Lp[a]) is associated with aortic stenosis (AS). Oxidized phospholipids (OxPL) are key mediators of calcification in valvular cells and are carried by Lp(a). ObjectivesThis study sought to determine whether Lp(a) and OxPL are associated with hemodynamic progression of AS and AS-related events. MethodsOxPL on apolipoprotein B-100 (OxPL-apoB), which reflects the biological activity of Lp(a), and Lp(a) levels were measured in 220 patients with mild-to-moderate AS. The primary endpoint was the progression rate of AS, measured by the annualized increase in peak aortic jet velocity in m/s/year by Doppler echocardiography; the secondary endpoint was need for aortic valve replacement and cardiac death during 3.5 ± 1.2 years of follow-up. ResultsAS progression was faster in patients in the top tertiles of Lp(a) (peak aortic jet velocity: +0.26 ± 0.26 vs. +0.17 ± 0.21 m/s/year; p = 0.005) and OxPL-apoB (+0.26 ± 0.26 m/s/year vs. +0.17 ± 0.21 m/s/year; p = 0.01). After multivariable adjustment, elevated Lp(a) or OxPL-apoB levels remained independent predictors of faster AS progression. After adjustment for age, sex, and baseline AS severity, patients in the top tertile of Lp(a) or OxPL-apoB had increased risk of aortic valve replacement and cardiac death. ConclusionsElevated Lp(a) and OxPL-apoB levels are associated with faster AS progression and need for aortic valve replacement. These findings support the hypothesis that Lp(a) mediates AS progression through its associated OxPL and provide a rationale for randomized trials of Lp(a)-lowering and OxPL-apoB-lowering therapies in AS. (Aortic Stenosis Progression Observation: Measuring Effects of Rosuvastatin [ASTRONOMER]; NCT00800800)

Heritability of Biomarkers of Oxidized Lipoproteins: Twin Pair Study.

To determine whether biomarkers of oxidized lipoproteins are genetically determined. Lipoprotein(a) (Lp[a]) is a heritable risk factor and carrier of oxidized phospholipids (OxPL). We measured oxidized phospholipids on apolipoprotein B-containing lipoproteins (OxPL-apoB), Lp(a), IgG, and IgM autoantibodies to malondialdehyde-modified low-density lipoprotein, copper oxidized low-density lipoprotein, and apoB-immune complexes in 386 monozygotic and dizygotic twins to estimate trait heritability (h(2)) and determine specific genetic effects among traits. A genome-wide linkage study followed by genetic association was performed. The h(2) (scale: 0-1) for Lp(a) was 0.91±0.01 and for OxPL-apoB 0.87±0.02, which were higher than physiological, inflammatory, or lipid traits. h(2) of IgM malondialdehyde-modified low-density lipoprotein, copper oxidized low-density lipoprotein, and apoB-immune complexes were 0.69±0.04, 0.67±0.05, and 0.80±0.03, respectively, and for IgG malondialdehyde-modified low-density lipoprotein, copper oxidized low-density lipoprotein, and apoB-immune complexes 0.62±0.05, 0.52±0.06, and 0.53±0.06, respectively. There was an inverse correlation between the major apo(a) isoform and OxPL-apoB (R=-0.49; P<0.001) and Lp(a) (R=-0.48; P<0.001) and OxPL-apoB was modestly correlated with Lp(a) (ρ=0.57; P<0.0001). The correlation in major apo(a) isoform size was concordant (R=1.0; P<0.001) among monozygotic twins but not dizygotic twins (R=0.40; P=0.055). Lp(a) and OxPL-apoB shared genetic codetermination (genetic covariance, ρG=0.774±0.032; P=1.09×10(-38)), although not environmental determination (environmental covariance, ρE=0.081±0.15; P=0.15). In contrast, Lp(a) shared environmental but not genetic codetermination with autoantibodies to malondialdehyde-modified low-density lipoprotein and copper oxidized low-density lipoprotein, and apoB-immune complexes. Sib-pair genetic linkage of the Lp(a) trait revealed that single nucleotide polymorphism rs10455872 was significantly associated with OxPL-apoB after adjusting for Lp(a). OxPL-apoB and other biomarkers of oxidized lipoproteins are highly heritable cardiovascular risk factors that suggest novel genetic origins of atherothrombosis.

Abstract 399: Oxidized Phospholipids Regulate Inflammatory Gene Transcription via Bromodomain Containing 4 (BRD4) In Vascular Endothelial Cells

Objective: Atherosclerosis is a chronic inflammatory disease initiated by monocyte infiltration into the vessel wall. Oxidized phospholipids (Ox-PL) that accumulate in the subendothelial space during hyperlipidemia elicit changes in inflammatory gene transcription and endothelial cell function. Bromodomain-containing 4 (BRD4) reads histone acetyl epigenetic modification and regulates inflammatory gene transcription controlled by the modification in the endothelial cells. In this study, we tested whether oxidized phospholipids regulates inflammatory gene transcription via histone acetyl epigenetic modification and its reader BRD4 in vascular endothelial cells. Methods and Results: A representative Ox-PL, Ox-PAPC (oxidized 1-palmitoyl-2-arachidonoyl-sn-glycerol-3-phosphatidylcholine), regulates over 1,500 transcripts in human aortic endothelial cells (HAECs) including inflammatory IL-8 and monocyte chemoattractant protein 1 (MCP1). Gene silencing of histone acetyl transferases (HATs) p300 and CBP also inhibited transcription of inflammatory genes in endothelial cells, suggesting that the histone acetyl epigenetic modification are involved in inflammatory gene transcription by Ox-PAPC. Small molecule inhibitors of BRD4 or BRD4 gene silencing potently and selectively repressed inflammatory gene transcription by Ox-PAPC. Microarray analysis revealed that the inhibitor downregulated hundreds of genes involved in inflammation and apoptosis. The administration of the BRD4 inhibitor JQ1(+) in LDLR null mouse showed a significant inhibition of the inflammatory responses induced by hyperlipidemia in the vascular system. Conclusion: Histone acetyl epigenetic modification and the reader BRD4 mediates inflammatory gene transcription by oxidized phospholipids in the endothelial cells. Targeting of BRD4 may be an efficient approach to prevent hyperlipidemia-induced inflammation and atherosclerosis.

Monocyte subset distribution in patients with stable atherosclerosis and elevated levels of lipoprotein(a)

BackgroundLipoprotein(a) (Lp(a)) is a proatherogenic plasma lipoprotein currently established as an independent risk factor for the development of atherosclerotic disease and as a predictor for acute thrombotic complications. In addition, Lp(a) is the major carrier of proinflammatory oxidized phospholipids (OxPL). Today, atherosclerosis is considered to be an inflammatory disease of the vessel wall in which monocytes and monocyte-derived macrophages are crucially involved. Circulating monocytes can be divided according to their surface expression pattern of CD14 and CD16 into at least 3 subsets with distinct inflammatory and atherogenic potential.ObjectiveThe aim of this study was to examine whether elevated levels of Lp(a) and OxPL on apolipoprotein B-100–containing lipoproteins (OxPL/apoB) are associated with changes in monocyte subset distribution.MethodsWe included 90 patients with stable coronary artery disease. Lp(a) and OxPL/apoB were measured, and monocyte subsets were identified as classical monocytes (CMs; CD14++CD16−), intermediate monocytes (IMs; CD14++CD16+), and nonclassical monocytes (NCMs; CD14+CD16++) by flow cytometry.ResultsIn patients with elevated levels of Lp(a) (>50 mg/dL), monocyte subset distribution was skewed toward an increase in the proportion of IM (7.0 ± 3.8% vs 5.2 ± 3.0%; P = .026), whereas CM (82.6 ± 6.5% vs 82.0 ± 6.8%; P = .73) and NCM (10.5 ± 5.3 vs 12.8 ± 6.0; P = .10) were not significantly different. This association was independent of clinical risk factors, choice of statin treatment regime, and inflammatory markers. In addition, OxPL/apoB was higher in patients with elevated Lp(a) and correlated with IM but not CM and NCM.ConclusionsIn conclusion, we provide a potential link between elevated levels of Lp(a) and a proatherogenic distribution of monocyte subtypes in patients with stable atherosclerotic disease.

Phospholipid oxidation generates potent anti-inflammatory lipid mediators that mimic structurally related pro-resolving eicosanoids by activating Nrf2.

Exposure of biological membranes to reactive oxygen species creates a complex mixture of distinct oxidized phospholipid (OxPL) species, which contribute to the development of chronic inflammatory diseases and metabolic disorders. While the ability of OxPL to modulate biological processes is increasingly recognized, the nature of the biologically active OxPL species and the molecular mechanisms underlying their signaling remain largely unknown. We have employed a combination of mass spectrometry, synthetic chemistry, and immunobiology approaches to characterize the OxPL generated from the abundant phospholipid 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphocholine (PAPC) and investigated their bioactivities and signaling pathways in vitro and in vivo. Our study defines epoxycyclopentenones as potent anti-inflammatory lipid mediators that mimic the signaling of endogenous, pro-resolving prostanoids by activating the transcription factor nuclear factor E2-related factor 2 (Nrf2). Using a library of OxPL variants, we identified a synthetic OxPL derivative, which alleviated endotoxin-induced lung injury and inhibited development of pro-inflammatory T helper (Th) 1 cells. These findings provide a molecular basis for the negative regulation of inflammation by lipid peroxidation products and propose a novel class of highly bioactive compounds for the treatment of inflammatory diseases.

NIACIN REDUCES OXIDIZED PHOSPHOLIPIDS ON APOLIPOPROTEIN-B-100 (OXPL/APOB) CONTAINING LIPOPROTEINS

Oxidized phospholipids (OxPL), present on OxLDL and Lp(a), are mediators of inflammation and cardiovascular disease (CVD) and are particularly enriched in vulnerable lesions. OxPL/apoB is an established biomarker that predicts anatomical CVD and events. Among lipoproteins, OxPL are primarily carried

Profiling of oxidized phospholipids in lipoproteins from patients with coronary artery disease by hollow fiber flow field-flow fractionation and nanoflow liquid chromatography-tandem mass spectrometry.

Oxidized phospholipids (Ox-PLs) are oxidatively modified PLs that are produced during the oxidation of lipoproteins; oxidation of low density lipoproteins especially is known to be associated with the development of coronary artery disease (CAD). In this study, different lipoprotein classes (high density, low density, and very low density lipoproteins) from pooled plasma of CAD patients and pooled plasma from healthy controls were size-sorted on a semipreparative scale by multiplexed hollow fiber flow field-flow fractionation (MxHF5), and Ox-PLs that were extracted from each lipoprotein fraction were quantified by nanoflow liquid chromatography-tandem mass spectrometry (nLC-ESI-MS/MS). The present study showed that oxidation of lipoproteins occurred throughout all classes of lipoproteins with more Ox-PLs identified from CAD patient lipoproteins: molecular structures of 283 unique PL species (including 123 Ox-PLs) from controls and 315 (including 169 Ox-PLs) from patients were identified by data-dependent collision-induced dissociation experiments. It was shown that oxidation of PLs occurred primarily with hydroxylation of PL; in particular, a saturated acyl chain such as 16:0, 18:0, or even 18:1 at the sn-1 location of the glycerol backbone along with sn-2 acyl chains with at least two double bonds were identified. The acyl chain combinations commonly found for hydroxylated Ox-PLs in the lipoproteins of CAD patients were 16:0/18:2, 16:0/20:4, 18:0/18:2, and 18:0/20:4.