Malondialdehyde alteration of low density lipoproteins leads to cholesteryl ester accumulation in human monocyte-macrophages

Ribose-induced advanced glycation end products reduce the lifespan in Drosophila melanogaster by changing the redox state and down-regulating the Sirtuin genes

Advanced Glycation End (AGE) products are one such factor that accumulates during aging and age-related diseases. However, how exogenous AGE compounds cause aging is an area that needs to be explored. Specifically, how an organ undergoes aging and aging-related phenomena that need further investigation. The intestine is the most exposed area to food substances. How AGEs affect the intestine in terms of aging need to be explored. Drosophila melanogaster, a well-known model organism, is used to decode aging and age-associated phenomena. In this study, we fed Ribose induced Advanced Glycation End products (Rib-AGE) to D. melanogaster to study the aging mechanism. The Rib-AGE-induced aging was checked in Drosophila. We found a series of changes in Rib-AGE-fed flies. Reactive oxygen species (ROS) and nitric oxide species (NOs) were higher in the Rib-AGE-fed flies, and the antioxidant level was lower. The intestinal permeability was altered. The microorganism load was higher inside the gut. The structural arrangement of the gut's microfilament was found to be damaged, and the nuclear shape was found to be irregular. Cell death within the gut was elevated in comparison to control. The food intake was found to be reduced. The relative mRNA expression of the Sirtuin 2 and Sirtuin 6 gene of D. melanogaster was downregulated in Rib-AGE-fed flies compared to the control. All these findings strongly suggest that Rib-AGE accelerates aging and age-related disorders in D. melanogaster.

Effects of Daily Consumption of Scallop Oil Prepared from Internal Organs of Japanese Giant Scallop (Patinopecten yessoensis) on Serum Lipid Composition and Its Safety: A Randomized, Double-blind, Placebo-controlled, Parallel Group Comparison Study

Scallop oil (SCO) prepared from the internal organs of the Japanese giant scallop (Patinopecten yessoensis) contains eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and phospholipids (PL). It was previously shown that SCO consumption improves cholesterol and triacylglycerols (TG) contents in mice. The present study demonstrated the effects of daily SCO consumption (1.2 g/day, containing 376 mg of EPA, 63 mg of DHA, and 150 mg of PL) for 12 weeks in human subjects. In this randomized, doubleblind, placebo-controlled, parallel group comparison study, 70 Japanese subjects with serum TG levels ≥120 but < 200 mg/dL were recruited and randomly assigned to the SCO or placebo group. All subjects ingested six capsules per day for 12 weeks. We conducted medical interviews, body composition measurements, vital sign examinations, and blood sampling at weeks 0 (baseline), 4, 8, and 12, and measured peripheral blood flow at weeks 0 and 12. In the case of subjects with higher serum TG levels, SCO consumption decreased the changes in serum TG and malondialdehyde-low density lipoprotein (MDA-LDL) levels compared with the placebo group. Safety assessment revealed no medically significant changes due to continuous SCO consumption. The findings indicate that 1.2 g/day of SCO consumption may be beneficial for reducing serum TG and MDA-LDL levels in persons with higher TG levels.

The Role of Natural Low Molecular Weight Dicarbonyls in Atherogenesis and Diabetogenesis

This review summarises the data from long-term experimental studies and literature data on the role of oxidatively modified low-density lipoproteins (LDL) in atherogenesis and diabetogenesis. It was shown that not "oxidized" (lipoperoxide-containing) LDL, but dicarbonyl-modified LDL are atherogenic (actively captured by cultured macrophages with the help of scavenger receptors), and also cause expression of lectin like oxidized low density lipoprotein receptor 1 (LOX-1) and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 1 (NOX-1) genes in endotheliocytes, which stimulate apoptosis and endothelial dysfunction. The obtained data allowed us to justify new approaches to pharmacotherapy of atherosclerosis and diabetes mellitus.

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.

MgCl2 Attenuates ox-LDL-Induced Vascular Smooth Muscle-Derived Foam Cells Pyroptosis by Downregulating the TLR4/NF-κB Signaling Pathway

Pyroptosis is a type of programmed cell death that is generally upregulated during atherosclerosis (AS). Magnesium, an important cation in the body, has exhibited an antiatherosclerotic effect. We collected AS model datasets from the Gene Expression Omnibus (GEO) and explored the correlation between pyroptosis and AS through a series of bioinformatics methods. We next investigated the impact of oxidized low-density lipoprotein (ox-LDL) on primary cultured vascular smooth muscle cells (VSMCs) foaminess and pyroptosis. Finally, foam cells were preconditioned with different concentrations of MgCl2 to explore its influence on ox-LDL-induced VSMCs pyroptosis. NLRP3-mediated pyroptosis plays a core role in regulating AS progression as shown by bioinformatic analysis. Ox-LDL (50/75/100 mg/L) increased CE/TE ratio (> 50%) in VSMCs and prompted VSMC-derived foam cell formation, and (75/100 mg/L) ox-LDL-induced pyroptosis. Compared to 1 mmol/L MgCl2, 10 mmol/L MgCl2 significantly downregulated the expression of pyroptosis related molecules in VSMCs induced by 75 mg/L ox-LDL, including NLRP3, ASC, caspase-1, and GSDMD. The secretion of IL-1β, IL-18, and LDH was also inhibited by MgCl2. According to CCK-8 and Hoechst 33,342/PI staining, the damage to VSMCs viability induced by ox-LDL was ameliorated by MgCl2. In addition, MgCl2 attenuated the upregulation of TLR4, IKKβ, and p65 and the downregulation of IκBα in VSMCs induced by ox-LDL. The present study demonstrated that pyroptosis-related genes were the core genes in AS. We also revealed the effect and underlying mechanism of MgCl2 on ox-LDL-induced VSMCs pyroptosis, suggesting that MgCl2 has promising clinical applications for AS pyroptosis prevention and treatment.

Antibodies against malondialdehyde among 60-year-olds: prediction of cardiovascular disease

Malondialdehyde (MDA) is generated in oxidized LDL. It forms covalent protein adducts, and is recognized by antibodies (anti-MDA). We previously studied IgM anti-MDA, and here we focus on IgG, IgG1 and IgG2 anti-MDA in predicting cardiovascular disease (CVD). We determined, by ELISA, anti-MDA in a 7-year follow-up of 60-year-old men and women from Stockholm County (2039 men, 2193 women). We identified 210 incident CVD cases (defined as new events of myocardial infarction (MI), and hospitalization for angina pectoris) and ischemic stroke, and 620 age- and sex-matched controls. IgG anti-MDA was not associated with CVD. Median values only differed significantly for IgG1 anti-MDA among men, with lower levels among cases than controls (p = 0.039). High IgG1 anti-MDA (above 75th percentile) was inversely associated with CVD risk after adjustment for smoking, body mass index, type 2 diabetes, hyperlipidemia, and hypertension, (OR and 95% CI: 0.59; 0.40-0.89). After stratification by sex, this association emerged in men (OR and 95% CI: 0.46; 0.27-0.77), but not in women. IgG2 anti-MDA were associated with protection in the whole group and among men though weaker than IgG1 anti-MDA. IgG2 anti-MDA above the 75th percentile was associated with an increased risk of MI/angina in women (OR and 95% CI: 2.57; (1.08-6.16)). IgG1 and less so IgG2 anti-MDA are protection markers for CVD and MI/angina in the whole group and among men. However, IgG2 anti-MDA was a risk marker for MI/angina among women. These findings could have implications for both prediction and therapy.

Clearance and Utilization of Dicarbonyl-Modified LDL in Monkeys and Humans

The kinetics of elimination of various dicarbonyl-modified low-density lipoproteins from the bloodstream of Macaca mulatta monkeys were investigated. The low-density lipoproteins (LDL) in the monkey blood plasma were isolated by density gradient ultracentrifugation and labeled in vitro with the fluorescent dye FITC; thereupon, they were modified with different natural low molecular-weight dicarbonyls: malondialdehyde (MDA), glyoxal, or methylglyoxal. The control native FITC-labeled LDL and dicarbonyl-modified FITC-labeled LDL were injected into the monkey's ulnar vein; thereafter, blood samples were taken at fixed time intervals during 24 h. The plasma level of FITC-labeled LDL was determined with spectrofluorimetry. The study established that glyoxal- and monkeysglyoxal-labeled LDL circulated in monkey virtually at the same time as native (non-modified) LDL. In contrast, MDA-modified LDL disappeared from the blood extremely rapidly. Administration of the PCSK9 inhibitor involocumab (which increases LDL utilization) to patients with coronary heart disease (CHD) was found to significantly reduce levels of MDA-modified LDL.

Malondialdehyde as an Important Key Factor of Molecular Mechanisms of Vascular Wall Damage under Heart Diseases Development

This mini review is devoted to a specific issue: the role of malondialdehyde (MDA)-a secondary product of free radical lipid peroxidation-in the molecular mechanisms of the formation of primary atherosclerotic vascular wall lesions. The principal difference between this review and the available literature is that it discusses in detail the important role in atherogenesis not of "oxidized" LDL (i.e., LDL particles containing lipohydroperoxides), but of LDL particles chemically modified by the natural low-molecular weight dicarbonyl MDA. To confirm this, we consider the data obtained by us earlier, indicating that "atherogenic" are not LDL oxidized as a result of free radical lipoperoxidation and containing lipohydroperoxy derivatives of phospholipids in the outer layer of particles, but LDL whose apoprotein B-100 has been modified due to the chemical reaction of terminal lysine residue amino groups of the apoB-100 with the aldehyde groups of the MDA (Maillard reaction). In addition, we present our original data proving that MDA injures endothelial glycocalyx that suppress the ability of the endothelium to control arterial tone according to changes in wall shear stress. In summary, this mini review for the first time exhaustively discloses the key role of MDA in atherogenesis.

Dicarbonyl-Dependent Modification of LDL as a Key Factor of Endothelial Dysfunction and Atherosclerotic Vascular Wall Damage

The review presents evidence that the main damage to the vascular wall occurs not from the action of “oxidized” LDL, which contain hydroperoxy acyls in the phospholipids located in their outer layer, but from the action of LDL particles whose apoprotein B-100 is chemically modified with low molecular weight dicarbonyls, such as malondialdehyde, glyoxal, and methylglyoxal. It has been argued that dicarbonyl-modified LDL, which have the highest cholesterol content, are particularly “atherogenic”. High levels of dicarbonyl-modified LDL have been found to be characteristic of some mutations of apoprotein B-100. Based on the reviewed data, we hypothesized a common molecular mechanism underlying vascular wall damage in atherosclerosis and diabetes mellitus. The important role of oxidatively modified LDL in endothelial dysfunction is discussed in detail. In particular, the role of the interaction of the endothelial receptor LOX-1 with oxidatively modified LDL, which leads to the expression of NADPH oxidase, which in turn generates superoxide anion radical, is discussed. Such hyperproduction of ROS can cause destruction of the glycocalyx, a protective layer of endotheliocytes, and stimulation of apoptosis in these cells. On the whole, the accumulated evidence suggests that carbonyl modification of apoprotein B-100 of LDL is a key factor responsible for vascular wall damage leading to atherogenesis and endothelial dysfunction. Possible ways of pharmacological correction of free radical processes in atherogenesis and diabetogenesis are also discussed.

Preparation of LDL , Oxidation , Methods of Detection, and Applications in Atherosclerosis Research

The concept of lipid peroxidation has been known for a long time. It is now well established that LDL plays a major role in atherosclerosis. Oxidized low-density lipoprotein (Ox-LDL) has been studied for over 35 years. Numerous pro- and anti-atherogenic properties have been attributed to Ox-LDL. Component composition of Ox-LDL is complex due to the influence of various factors, including the source, method of preparation, storage and use. Hence, it is very difficult to clearly define and characterize Ox-LDL. It contains unoxidized and oxidized fatty acid derivatives both in the ester and free forms, their decomposition products, cholesterol and its oxidized products, proteins with oxidized amino acids and cross-links, polypeptides with varying extents of covalent modification with lipid oxidation products and many others. The measurement of lipid oxidation has been a great boon, not only to the understanding of the process but also in providing numerous serendipitous discoveries and methodologies. In this chapter, we outline the methodologies for the preparation and testing of various lipoproteins for oxidation studies.

Curcumin promotes cholesterol efflux by regulating ABCA1 expression through miR-125a-5p/SIRT6 axis in THP-1 macrophage to prevent atherosclerosis

OBJECTIVE

To seek out the effect of curcumin on cholesterol efflux in THP-1 macrophages and clarify its specific mechanism.

METHODS

THP-1 macrophages were cultured with curcumin at different concentrations, followed by detection of the toxicity of curcumin to cells utilizing CCK-8 assay. Following culturing with serum-free ox-LDL, THP-1 macrophages were transfected with mi-miR-125a-5p, or in-miR-125a-5p, or pcDNA3.1-SIRT6, or si-SIRT6 for 24 hr, prior to treatment with curcumin at different concentrations. Oil red O staining was applied to examine the formation rate of foam cells, the kits were used for measuring intracellular lipid content of THP-1 macrophages, and the fluorescence detection kit for observing the cholesterol efflux rate. The expressions of miR-125a-5p, SIRT6, and ABCA1 were assayed by qRT-PCR and Western blot. ELISA was adopted to assess the contents of TNF-α, IL-6, and MCP-1. The interaction between miR-125a-5p and SIRT6 was evaluated by dual-luciferase reporter gene assay.

RESULTS

The optimal dosage of curcumin could reduce foam cell formation and intracellular lipid content, and promote cholesterol efflux in THP-1 macrophages. Meanwhile, curcumin markedly suppressed the expression of miR-125a-5p and upregulated the expression of SIRT6. MiR-125a-5p negatively targeted SIRT6. Overexpression of SIRT6 partially reversed the inhibition role of miR-125a-5p mimic in the biological function of curcumin. Silencing of SIRT6 could partially reverse the effect of the miR-125a-5p inhibitor on the biological function of curcumin.

CONCLUSION

urcumin could promote cholesterol efflux of THP-1 macrophages through miR-125a-5p/SIRT6 axis and regulate the expression of ABCA1.

Atorvastatin Enhances Foam Cell Lipophagy and Promotes Cholesterol Efflux Through the AMP-Activated Protein Kinase/Mammalian Target of Rapamycin Pathway

ABSTRACT

Foam cells are the main pathological components of atherosclerosis. Therapies reducing foam cell formation can effectively prevent atherosclerotic diseases and cardiovascular events. Beyond lowering plasma cholesterol levels, the pleiotropic functions of statins in atherosclerosis have not been fully elucidated. In the present study, atorvastatin reduced cholesterol content and increased cholesterol efflux from foam cells in a concentration-dependent manner. Atorvastatin (10 μM) inhibited foam cell formation within 48 hours. Furthermore, we found that atorvastatin inhibited foam cell formation by promoting lipophagy, which was manifested by increased autophagy-related gene 5 (Atg5) expression, elevated ratio of microtubule-associated protein1 light chain 3 (LC3) II to LC3I, reduced p62 expression, and increased LC3 and lipid droplets colocalization in foam cells treated with atorvastatin. The autophagy inducer, rapamycin (Rap), did not increase the lipophagy enhancement effect of atorvastatin, but the autophagy inhibitor, 3-methyladenine, suppressed the effect of atorvastatin on Atg5 expression and the LC3II/LC3I ratio, as well as the increased p62 expression, suppressed lipophagy, attenuated cholesterol efflux and increased cholesterol content in foam cells. Further analysis revealed that atorvastatin promoted lipophagy by upregulating adenosine 5'-monophosphate-activated protein kinase (AMPK) phosphorylation, and downregulating mammalian target of rapamycin phosphorylation, whereas the AMPK inhibiter, compound C, attenuated these effects. In conclusion, atorvastatin reduced lipid accumulation and promoted cholesterol efflux by enhancing lipophagy in foam cells and thereby inhibited foam cell formation. The enhanced lipophagy of foam cells was exerted through the AMPK/mammalian target of rapamycin signaling pathway.

Effects of lipoproteins on endothelial cells and macrophages function and its possible implications on fetal adverse outcomes associated to maternal hypercholesterolemia during pregnancy

Hypercholesterolemia is one of the main risk factors associated with atherosclerosis and cardiovascular disease, the leading cause of death worldwide. During pregnancy, maternal hypercholesterolemia develops, and it can occur in a physiological (MPH) or supraphysiological (MSPH) manner, where MSPH is associated with endothelial dysfunction and early atherosclerotic lesions in the fetoplacental vasculature. In the pathogenesis of atherosclerosis, endothelial activation and endothelial dysfunction, characterized by an imbalance in the bioavailability of nitric oxide, contribute to the early stages of this disease. Macrophages conversion to foam cells, cholesterol efflux from these cells and its differentiation into a pro- or anti-inflammatory phenotype are also important processes that contribute to atherosclerosis. In adults it has been reported that native and modified HDL and LDL play an important role in endothelial and macrophage function. In this review it is proposed that fetal lipoproteins could be also relevant factors involved in the detrimental vascular effects described in MSPH. Changes in the composition and function of neonatal lipoproteins compared to adults has been reported and, although in MSPH pregnancies the fetal lipid profile does not differ from MPH, differences in the lipidomic profiles of umbilical venous blood have been reported, which could have implications in the vascular function. In this review we summarize the available information regarding the effects of lipoproteins on endothelial and macrophage function, emphasizing its possible implications on fetal adverse outcomes associated to maternal hypercholesterolemia during pregnancy.

Natural products: The role and mechanism in low-density lipoprotein oxidation and atherosclerosis

Atherosclerosis is a chronic inflammatory, metabolic, and epigenetic disease, which leads to the life-threatening coronary artery disease. Emerging studies from bench to bedside have demonstrated the pivotal role of low-density lipoprotein (LDL) oxidation in the initiation and progression of atherosclerosis. This article hereby reviews oxidation mechanism of LDL, and the pro-atherogenic and biomarker role of oxidized LDL in atherosclerosis. We also review the pharmacological effects of several representative natural products (vitamin E, resveratrol, quercetin, probucol, tanshinone IIA, epigallocatechin gallate, and Lycopene) in protecting against LDL oxidation and atherosclerosis. Clinical and basic research supports the beneficial effects of these natural products in inhibiting LDL oxidation and preventing atherosclerosis, but the data are still controversial. This may be related to factors such as the population and the dosage and time of taking natural products involved in different studies. Understanding the mechanism of LDL oxidation and effect of oxidized LDL help researchers to find novel therapies against atherosclerosis.

Uncoupling Protein 2 as genetic risk factor for systemic lupus erythematosus: association with malondialdehyde levels and intima media thickness

BACKGROUND

Increased oxidative stress potentially leads to accelerated atherosclerosis and, consequently, cardiovascular diseases, the main cause of death in systemic lupus erythematous (SLE). To gain insight into these mechanisms, we studied the association of uncoupling protein (UCP) 2 genetic variants, gene involved in the mitochondrial production of reactive oxygen species, and oxidative stress with SLE and the presence of atherosclerosis.

METHODS

Genetic analysis of the UCP2 -866G/A and UCP2 Ins/Del polymorphisms was performed in 45 SLE patients and 36 healthy controls by RFLP-PCR. Oxidation status was determined by measuring malondialdehyde (MDA) levels. Presence of subclinical atherosclerosis was investigated by evaluation of intima-media thickness using echo-color-Doppler carotid ultrasound examination.

RESULTS

Allelic and genotypic frequencies of the SNPs analysed were evaluated by gene count. Significant association was found between UCP2-866A allele and susceptibility for SLE (P=0.001). Higher levels of MDA were found significantly increased in SLE patients (MDA, 5.05±3.36 µmol/L) compared to normal controls (MDA, 2.79±0.89 µmol/L) (P<0.0001).

CONCLUSIONS

Our results suggest that -866G/A UCP2 polymorphism is associated with SLE causing increased ROS production that, in turn, results in increased MDA levels responsible of accelerated atherosclerosis.

USP10 deletion inhibits macrophage-derived foam cell formation and cellular-oxidized low density lipoprotein uptake by promoting the degradation of CD36

Foam cell formation process is involved in the pathogenesis of atherosclerosis (AS). Activation of this biological process depends on lipid uptake by scavenger receptors, such as CD36, SR-A and SR-B1. Among these receptors, CD36 is the principal one because it dominates roughly 50% lipid uptake in monocytes. In this study, our western blotting and RT-qPCR assays revealed that USP10 inhibition promotes the degradation of CD36 protein but does not change its mRNA level. In addition, Co-IP results showed that USP10 interacts with CD36 and stabilizes CD36 protein by cleaving poly-ubiquitin on CD36. Significantly, USP10 promotes foam cell formation. Immunofluorescence and Oil red O staining assays show that inhibition or knockdown of USP10 suppresses lipid uptake and foam cell formation by macrophages. In conclusion, USP10 promotes the development and progression of atherosclerosis through stabilizing CD36 protein expression. The regulation of USP10-CD36 may provide a significant therapeutic scheme in atherosclerosis.

Albumin-based nanoparticles as contrast medium for MRI: vascular imaging, tissue and cell interactions, and pharmacokinetics of second-generation nanoparticles

This multidisciplinary study examined the pharmacokinetics of nanoparticles based on albumin-DTPA-gadolinium chelates, testing the hypothesis that these nanoparticles create a stronger vessel signal than conventional gadolinium-based contrast agents and exploring if they are safe for clinical use. Nanoparticles based on human serum albumin, bearing gadolinium and designed for use in magnetic resonance imaging, were used to generate magnet resonance images (MRI) of the vascular system in rats ("blood pool imaging"). At the low nanoparticle doses used for radionuclide imaging, nanoparticle-associated metals were cleared from the blood into the liver during the first 4 h after nanoparticle application. At the higher doses required for MRI, the liver became saturated and kidney and spleen acted as additional sinks for the metals, and accounted for most processing of the nanoparticles. The multiple components of the nanoparticles were cleared independently of one another. Albumin was detected in liver, spleen, and kidneys for up to 2 days after intravenous injection. Gadolinium was retained in the liver, kidneys, and spleen in significant concentrations for much longer. Gadolinium was present as significant fractions of initial dose for longer than 2 weeks after application, and gadolinium clearance was only complete after 6 weeks. Our analysis could not account quantitatively for the full dose of gadolinium that was applied, but numerous organs were found to contain gadolinium in the collagen of their connective tissues. Multiple lines of evidence indicated intracellular processing opening the DTPA chelates and leading to gadolinium long-term storage, in particular inside lysosomes. Turnover of the stored gadolinium was found to occur in soluble form in the kidneys, the liver, and the colon for up to 3 weeks after application. Gadolinium overload poses a significant hazard due to the high toxicity of free gadolinium ions. We discuss the relevance of our findings to gadolinium-deposition diseases.

IgM antibodies against malondialdehyde and phosphorylcholine in different systemic rheumatic diseases

IgM antibodies against phosphorylcholine (anti-PC) and malondialdehyde (anti-MDA) may have protective properties in cardiovascular and rheumatic diseases. We here compare these antibodies in systemic rheumatic conditions and study their properties. Anti-PC and anti-MDA was measured using ELISA in patients with SLE (374), RA (354), Mixed connective tissue disease (MCTD, 77), Systemic sclerosis (SSc, 331), Sjögren's syndrome (SjS, 324), primary antiphospholipid syndrome (PAPs, 65), undifferentiated connective tissue disease (UCTD, 118) and 515 matched healthy controls (HC). Cardiovascular score (CV) was broadly defined based on clinical disease symptoms. Anti-PC and anti-MDA peptide/protein characterization were compared using a proteomics de novo sequencing approach. anti-MDA and anti-PC were extracted from total IgM. The proportion of Treg cells was determined by flow cytometry. The maximal difference between cases and controls was shown for MCTD: significantly lower IgM Anti-PC but not anti-MDA among patients (median 49.3RU/ml vs 70.4 in healthy controls, p(t-test) = 0.0037). IgM low levels were more prevalent in MCTD, SLE, SjS, SSc and UCTD. IgM anti-PC variable region profiles were different from and more homologous than anti-MDA. Anti-PC but not anti-MDA were significantly negatively correlated with CV in the whole patient group. In contrast to IgM anti-PC, anti-MDA did not promote polarization of Tregs. Taken together, Anti-PC is decreased in MCTD and also in SLE, SjS and SSc but not in other studied diseases. Anti-PC may thus differentiate between these. In contrast, anti-MDA did not show these differences between diseases studied. Anti-PC level is negatively correlated with CV in the patient group cohort. In contrast to anti-PC, anti-MDA did not promote Treg polarization. These findings could have both diagnostic and therapeutic implications, one possibility being active or passive immunization with PC in some rheumatic conditions.

Curcumin affects ox-LDL-induced IL-6, TNF-α, MCP-1 secretion and cholesterol efflux in THP-1 cells by suppressing the TLR4/NF-κB/miR33a signaling pathway

The aim of the present study was to study the molecular mechanism of how curcumin decreases the formation of ox-LDL induced human monocyte macrophage foam cells, promotes the efflux of cholesterol and reduces the secretion of inflammatory cytokines. In vitro cultured THP-1 cells were induced to become macrophages using phorbol-12-myristate-13-acetate. The cells were then pre-treated with curcumin before inducing the foam cell model by addition of oxidized low-density lipoprotein (ox-LDL). Western blot assays were used to detect expression levels of toll-like receptor (TLR)4, nuclear factor κB (NF-κB), NF-κB inhibitor α (IκBα), phosphorylated-IκBα and ATP binding cassette transporter (ABC)A1. Reverse transcription-quantitative PCR was employed to examine mRNA levels of TLR4, microRNA (miR)33a and ABCA1. ELISAs were used to detect inflammatory factors, including tumor necrosis factor (TNF)-α, monocyte chemotactic protein (MCP)-1 and interleukin (IL)-6. ox-LDL successfully induced the foam cell model, promoted phosphorylation of IκBα, promoted nuclear translocation of NF-κB, promoted the expression of TLR4 and miR33a, and promoted the secretion of TNF-α, MCP-1 and Il-6. Additionally, ox-LDL reduced the expression of ABCA1 and cholesterol efflux. However, pretreatment with curcumin increased the expression of ABCA1 and cholesterol efflux and suppressed secretion of TNF-α, MCP-1 and Il-6. TLR4 antibodies, the NF-κB blocker, PDTC, and the miR33a inhibitor also reduced the abnormal transformations induced by ox-LDL. Curcumin promoted cholesterol efflux by suppressing the TLR4/NF-κB/miR33a signaling pathway, and reduced the formation of foam cells and the secretion of inflammatory factors.

Signaling Pathways Potentially Responsible for Foam Cell Formation: Cholesterol Accumulation or Inflammatory Response-What is First?

Accumulation of lipid-laden (foam) cells in the arterial wall is known to be the earliest step in the pathogenesis of atherosclerosis. There is almost no doubt that atherogenic modified low-density lipoproteins (LDL) are the main sources of accumulating lipids in foam cells. Atherogenic modified LDL are taken up by arterial cells, such as macrophages, pericytes, and smooth muscle cells in an unregulated manner bypassing the LDL receptor. The present study was conducted to reveal possible common mechanisms in the interaction of macrophages with associates of modified LDL and non-lipid latex particles of a similar size. To determine regulatory pathways that are potentially responsible for cholesterol accumulation in human macrophages after the exposure to naturally occurring atherogenic or artificially modified LDL, we used transcriptome analysis. Previous studies of our group demonstrated that any type of LDL modification facilitates the self-association of lipoprotein particles. The size of such self-associates hinders their interaction with a specific LDL receptor. As a result, self-associates are taken up by nonspecific phagocytosis bypassing the LDL receptor. That is why we used latex beads as a stimulator of macrophage phagocytotic activity. We revealed at least 12 signaling pathways that were regulated by the interaction of macrophages with the multiple-modified atherogenic naturally occurring LDL and with latex beads in a similar manner. Therefore, modified LDL was shown to stimulate phagocytosis through the upregulation of certain genes. We have identified at least three genes (F2RL1, EIF2AK3, and IL15) encoding inflammatory molecules and associated with signaling pathways that were upregulated in response to the interaction of modified LDL with macrophages. Knockdown of two of these genes, EIF2AK3 and IL15, completely suppressed cholesterol accumulation in macrophages. Correspondingly, the upregulation of EIF2AK3 and IL15 promoted cholesterol accumulation. These data confirmed our hypothesis of the following chain of events in atherosclerosis: LDL particles undergo atherogenic modification; this is accompanied by the formation of self-associates; large LDL associates stimulate phagocytosis; as a result of phagocytosis stimulation, pro-inflammatory molecules are secreted; these molecules cause or at least contribute to the accumulation of intracellular cholesterol. This chain of events may explain the relationship between cholesterol accumulation and inflammation. The primary sequence of events in this chain is related to inflammatory response rather than cholesterol accumulation.

The Role of Halogenative Stress in Atherogenic Modification of Low-Density Lipoproteins

This review discusses formation of reactive halogen species (RHS) catalyzed by myeloperoxidase (MPO), an enzyme mostly present in leukocytes. An imbalance between the RHS production and body's ability to remove or neutralize them leads to the development of halogenative stress. RHS reactions with proteins, lipids, carbohydrates, and antioxidants in the content of low-density lipoproteins (LDLs) of the human blood are described. MPO binds site-specifically to the LDL surface and modifies LDL properties and structural organization, which leads to the LDL conversion into proatherogenic forms captured by monocytes/macrophages, which causes accumulation of cholesterol and its esters in these cells and their transformation into foam cells, the basis of atherosclerotic plaques. The review describes the biomarkers of MPO enzymatic activity and halogenative stress, as well as the involvement of the latter in the development of atherosclerosis.

Lipid Perxidtion and Antioxidants in Continuous Ambulatory Dialysis Patients

Objective

Oxidative cell damage due to the production of free radical species has been implicated in the pathogenesis of cardiovascular disease for which dialysis patients are at increased risk. Plasma lipid peroxides (malon-dialdehyde), the antioxidants plasma albumin thiol, and red cell superoxide dismutase (SOD) were therefore measured in 18 patients undergoing continuous ambulatory peritoneal dialysis (CAPD), 20 hemodialysis patients, and 30 normal controls.

Setting

Renal dialysis unit.

Results

Malondialdehyde(MDA)concentrationswere significantly higher in dialysis patients compared to controls (p<0.001 ) and were significantly higher in CAPD patients compared to hemodialysis patients, p<0.001 (CAPD, median and range: 11.25 (8.4–15.5) nmol/mL; hemodialysis: 8.75 (7.0–12.6) nmol/mL; controls: 6.65 (5.2–9.6) nmol/mL). Plasma thiol and red cell SOD were significantly lower in dialysis patients compared to controls, but there was no significant difference between CAPD and hemodialysis patients (CAPD thiol: 333.5 (282480) μmol/L; hemodialysis thiol: 344 (203–468) μmol/L; control thiol: 421.5 (351 -504) μmol/L; CAPD SOD: 78.2 (42.4 -112.8) u//2 mL red cells; hemodialysis SOD: 89.4 (44.6–121.1) u//2 mL red cells; control SOD: 96.8 (66.8153.4) u//2 mL red cells). Red cell SOD was significantly negatively correlated with duration of dialysis in CAPD patients (r=-0.683, p<0.01 ).

Conclusion

In dialysis patients there is indirect evidence for increased free radical activity, which may be further influenced by the mode of dialysis.

Inhibition of USP14 suppresses the formation of foam cell by promoting CD36 degradation

Atherosclerosis is regarded as a chronic progressive inflammatory disease and is a basic pathophysiological process in coronary artery disease which is life threatening in clinic. The formation of foam cell plays a key role in the pathogenesis of atherosclerosis. OxLDL is a significant factor in progression of coronary artery disease. Our studies have demonstrated that USP14 promotes cancer development and mediates progression of cardiac hypertrophy and LPS‐induced inflammation. However, the underlying mechanism of USP14 is unknown. In this study, we found that the inhibition of USP14 significantly suppressed the oxLDL uptake, subsequently decreased the foam cell formation. Surprisingly, USP14 has an effect on the expression of CD36 but not SR‐A, ABCA1, Lox‐1, ABCG1 and SR‐Bl. Furthermore, USP14 stabilizes CD36 protein via cleaving the ubiquitin chain on CD36. Blocking CD36 activation using antibody‐dependent blocking assay remarkably attenuated the function of USP14 on the formation of foam cell. In summary, our results suggested that the inhibition of USP14 decreases foam cell formation by down‐regulating CD36‐mediated lipid uptake and provides a potential therapeutic target for atherosclerosis.

Isolevuglandins as mediators of disease and the development of dicarbonyl scavengers as pharmaceutical interventions

Products of lipid peroxidation include a number of reactive lipid aldehydes such as malondialdehyde, 4-hydroxy-nonenal, 4-oxo-nonenal, and isolevuglandins (IsoLGs). Although these all contribute to disease processes, the most reactive are the IsoLGs, which rapidly adduct to lysine and other cellular primary amines, leading to changes in protein function, cross-linking and immunogenicity. Their rapid reactivity means that only IsoLG adducts, and not the unreacted aldehyde, can be readily measured. This high reactivity also makes it challenging for standard cellular defense mechanisms such as aldehyde reductases and oxidases to dispose of them before they react with proteins and other cellular amines. This led us to seek small molecule primary amines that might trap and inactivate IsoLGs before they could modify cellular proteins or other endogenous cellular amines such as phosphatidylethanolamines to cause disease. Our studies identified 2-aminomethylphenols including 2-hydroxybenzylamine as IsoLG scavengers. Subsequent studies showed that they also trap other lipid dicarbonyls that react with primary amines such as 4-oxo-nonenal and malondialdehyde, but not hydroxyalkenals like 4-hydroxy-nonenal that preferentially react with soft nucleophiles. This review describes the use of these 2-aminomethylphenols as dicarbonyl scavengers to assess the contribution of IsoLGs and other amine-reactive lipid dicarbonyls to disease and as therapeutic agents.

PET/MR Imaging of Malondialdehyde-Acetaldehyde Epitopes With a Human Antibody Detects Clinically Relevant Atherothrombosis

BACKGROUND

Oxidation-specific epitopes (OSEs) are proinflammatory, and elevated levels in plasma predict cardiovascular events.

OBJECTIVES

The purpose of this study was to develop novel positron emission tomography (PET) probes to noninvasively image OSE-rich lesions.

METHODS

An antigen-binding fragment (Fab) antibody library was constructed from human fetal cord blood. After multiple rounds of screening against malondialdehyde-acetaldehyde (MAA) epitopes, the Fab LA25 containing minimal nontemplated insertions in the CDR3 region was identified and characterized. In mice, pharmacokinetics, biodistribution, and plaque specificity studies were performed with Zirconium-89 (⁸⁹Zr)-labeled LA25. In rabbits, ⁸⁹Zr-LA25 was used in combination with an integrated clinical PET/magnetic resonance (MR) system. ¹⁸F-fluorodeoxyglucose PET and dynamic contrast-enhanced MR imaging were used to evaluate vessel wall inflammation and plaque neovascularization, respectively. Extensive ex vivo validation was carried out through a combination of gamma counting, near infrared fluorescence, autoradiography, immunohistochemistry, and immunofluorescence.

RESULTS

LA25 bound specifically to MAA epitopes in advanced and ruptured human atherosclerotic plaques with accompanying thrombi and in debris from distal protection devices. PET/MR imaging 24 h after injection of ⁸⁹Zr-LA25 showed increased uptake in the abdominal aorta of atherosclerotic rabbits compared with nonatherosclerotic control rabbits, confirmed by ex vivo gamma counting and autoradiography. ¹⁸F-fluorodeoxyglucose PET, dynamic contrast-enhanced MR imaging, and near-infrared fluorescence signals were also significantly higher in atherosclerotic rabbit aortas compared with control aortas. Enhanced liver uptake was also noted in atherosclerotic animals, confirmed by the presence of MAA epitopes by immunostaining.

CONCLUSIONS

⁸⁹Zr-LA25 is a novel PET radiotracer that may allow noninvasive phenotyping of high-risk OSE-rich lesions.

Modified and Dysfunctional Lipoproteins in Atherosclerosis: Effectors or Biomarkers?

Atherosclerotic diseases are the leading cause of mortality in industrialized countries. Correspondingly, studying the pathogenesis of atherosclerosis and developing new methods for its diagnostic and treatment remain in the focus of current medicine and health care. This review aims to discuss the mechanistic role of low-density lipoprotein (LDL) and high-density lipoprotein (HDL) in atherogenesis. In particular, the generally accepted hypothesis about the key role of oxidized LDL in atherogenesis is questioned, and an alternative concept of multiple modification of LDL is presented. The fundamental question discussed in this review is whether LDL and HDL are effectors or biomarkers, or both. This is important for understanding whether lipoproteins are a therapeutic target or just diagnostic indicators.

Investigation of Blood and Urine Malondialdehyde Levels in Mice Exposed to Silica Dust

Background and Objectives:

Occupational exposure to silica dust can lead to biochemical damage. Malondialdehyde (MDA) can be considered as a primary marker for measuring the level of oxidative stress in a living organism. This study was conducted in order to evaluate the level of MDA in blood and urine of mice exposed to silica dust.

Material and Methods:

In this experimental study, 72 mice (BALB/c) were randomly allocated to five exposed groups and 1 control group. Exposure of mice to pure 99% silica dust was done in closed containers. Blood sampling was performed from the heart of mice and urine sampling fulfilled by insertion into a metabolic cage. The RAOet al. method was used to measure MDA.

Results:

The highest level of plasma MDA in group 1 in the 4thmonth was 8.4±0.41 nmol/l and the lowest level of MDA was 1.3±0.2 nmol/l in the third sampling in the control group, also the highest amount of urine MDA in the first and second groups and 4 months after exposure was 1.16±0.51 nmol/l, and the lowest in the control group and in the third sampling was 0.48±0.06 nmol/l. A significant difference was found between the levels of MDA in all exposed groups at different times except for the 5thgroup with the lowest concentration (P< 0.05).

Conclusion:

MDA in blood and urine could be proposed as a good biomarker for the evaluation of biochemical damages caused by silica dust. Measuring MDA is also a simple and inexpensive method that does not require complex equipment and can be used as an early detection test for biochemical damages caused by silica.

Lipoxidation in cardiovascular diseases

Lipids can go through lipid peroxidation, an endogenous chain reaction that consists in the oxidative degradation of lipids leading to the generation of a wide variety of highly reactive carbonyl species (RCS), such as short-chain carbonyl derivatives and oxidized truncated phospholipids. RCS exert a wide range of biological effects due to their ability to interact and covalently bind to nucleophilic groups on other macromolecules, such as nucleic acids, phospholipids, and proteins, forming reversible and/or irreversible modifications and generating the so-called advanced lipoxidation end-products (ALEs). Lipoxidation plays a relevant role in the onset of cardiovascular diseases (CVD), mainly in the atherosclerosis-based diseases in which oxidized lipids and their adducts have been extensively characterized and associated with several processes responsible for the onset and development of atherosclerosis, such as endothelial dysfunction and inflammation. Herein we will review the current knowledge on the sources of lipids that undergo oxidation in the context of cardiovascular diseases, both from the bloodstream and tissues, and the methods for detection, characterization, and quantitation of their oxidative products and protein adducts. Moreover, lipoxidation and ALEs have been associated with many oxidative-based diseases, including CVD, not only as potential biomarkers but also as therapeutic targets. Indeed, several therapeutic strategies, acting at different levels of the ALEs cascade, have been proposed, essentially blocking ALEs formation, but also their catabolism or the resulting biological responses they induce. However, a deeper understanding of the mechanisms of formation and targets of ALEs could expand the available therapeutic strategies.

Lipoproteins as targets and markers of lipoxidation

Lipoproteins are essential systemic lipid transport particles, composed of apolipoproteins embedded in a phospholipid and cholesterol monolayer surrounding a cargo of diverse lipid species. Many of the lipids present are susceptible to oxidative damage by lipid peroxidation, giving rise to the formation of reactive lipid peroxidation products (rLPPs). In view of the close proximity of the protein and lipid moieties within lipoproteins, the probability of adduct formation between rLPPs and amino acid residues of the proteins, a process called lipoxidation, is high. There has been interest for many years in the biological effects of such modifications, but the field has been limited to some extent by the availability of methods to determine the sites and exact nature of such modification. More recently, the availability of a wide range of antibodies to lipoxidation products, as well as advances in analytical techniques such as liquid chromatography tandem mass spectrometry (LC-MSMS), have increased our knowledge substantially. While most work has focused on LDL, oxidation of which has long been associated with pro-inflammatory responses and atherosclerosis, some studies on HDL, VLDL and Lipoprotein(a) have also been reported. As the broader topic of LDL oxidation has been reviewed previously, this review focuses on lipoxidative modifications of lipoproteins, from the historical background through to recent advances in the field. We consider the main methods of analysis for detecting rLPP adducts on apolipoproteins, including their advantages and disadvantages, as well as the biological effects of lipoxidized lipoproteins and their potential roles in diseases.

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Lipoproteins can be modified by reactive Lipid Peroxidation Products (rLPPs).

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Lipoprotein lipoxidation is known to occur in several inflammatory diseases.

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Biochemical, immunochemical and mass spectrometry methods can detect rLPP adducts.

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Due to higher information output, MS can facilitate localization of modifications.

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Antibodies against some rLPPs have been used to identify lipoxidation in vivo.

Isolevuglandins and cardiovascular disease

Isolevuglandins are 4-ketoaldehydes formed by peroxidation of arachidonic acid. Isolevuglandins react rapidly with primary amines including the lysyl residues of proteins to form irreversible covalent modifications. This review highlights evidence for the potential role of isolevuglandin modification in the disease processes, especially atherosclerosis, and some of the tools including small molecule dicarbonyl scavengers utilized to assess their contributions to disease.

Hepatitis E Virus Induces Hepatocyte Apoptosis via Mitochondrial Pathway in Mongolian Gerbils

Previous studies demonstrated that Mongolian gerbils can be infected by hepatitis E virus (HEV), which induces the hepatic injury. Here, the mitochondria in hepatocytes from HEV-infected gerbils were considerably swollen, thin cristae. After HEV infection, the activity of superoxide dismutase significantly decreased (p < 0.01), while malondialdehyde concentrations significantly increased, compared with those in the control group (p < 0.01). Adenosine triphosphatase levels decreased significantly in the hepatocyte of the inoculated groups, compared with those in control group (p < 0.05) at days 21, 28, 42 post-inoculation (dpi) as well. Furthermore, the levels of ATP synthetase ATP5A1 significantly decreased during HEV infection, compared with those in the control group (p < 0.05). According to the TdT mediated dUTP nick end labeling (TUNEL) detection, TUNEL positive hepatocytes increased in the inoculated group, compared with that in the control group (p < 0.05). Up-regulation of the mitochondrion-mediated apoptosis regulating proteins, Bax and Bcl-2, in the HEV-infected gerbils (p < 0.05) was observed. However, cytochrome c levels in mitochondria decreased, while this molecule was detected in the cytoplasm of the infected animals, in contrast to that in the control group. Apaf-1, and active caspase-9 and -3 levels were shown to be significantly higher in the inoculated group compared with those in the control group (p < 0.05). Taken together, our results demonstrated that HEV infection induces hepatocyte injuries and activity of the mitochondrial apoptotic pathway, which trigger the hepatocyte apoptosis in Mongolian gerbils.

Oxidative Stress in Human Atherothrombosis: Sources, Markers and Therapeutic Targets

Atherothrombosis remains one of the main causes of morbidity and mortality worldwide. The underlying pathology is a chronic pathological vascular remodeling of the arterial wall involving several pathways, including oxidative stress. Cellular and animal studies have provided compelling evidence of the direct role of oxidative stress in atherothrombosis, but such a relationship is not clearly established in humans and, to date, clinical trials on the possible beneficial effects of antioxidant therapy have provided equivocal results. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase is one of the main sources of reactive oxygen species (ROS) in human atherothrombosis. Moreover, leukocyte-derived myeloperoxidase (MPO) and red blood cell-derived iron could be involved in the oxidative modification of lipids/lipoproteins (LDL/HDL) in the arterial wall. Interestingly, oxidized lipoproteins, and antioxidants, have been analyzed as potential markers of oxidative stress in the plasma of patients with atherothrombosis. In this review, we will revise sources of ROS, focusing on NADPH oxidase, but also on MPO and iron. We will also discuss the impact of these oxidative systems on LDL and HDL, as well as the value of these modified lipoproteins as circulating markers of oxidative stress in atherothrombosis. We will finish by reviewing some antioxidant systems and compounds as therapeutic strategies to prevent pathological vascular remodeling.

Proatherogenic effects of 4-hydroxynonenal

4-hydroxy-2-nonenal (HNE) is a α,β-unsaturated hydroxyalkenal generated by peroxidation of n-6 polyunsaturated fatty acid. This reactive carbonyl compound exhibits a huge number of biological properties that result mainly from the formation of HNE-adducts on free amino groups and thiol groups in proteins. In the vascular system, HNE adduct accumulation progressively leads to cellular dysfunction and tissue damages that are involved in the progression of atherosclerosis and related diseases. HNE contributes to the atherogenicity of oxidized LDL, by forming HNE-apoB adducts that deviate the LDL metabolism to the scavenger receptor pathway of macrophagic cells, and lead to the formation of foam cells. HNE activates transcription factors (Nrf2, NF-kappaB) that (dys)regulate various cellular responses ranging from hormetic and survival signaling at very low concentrations, to inflammatory and apoptotic effects at higher concentrations. Among a variety of cellular targets, HNE can modify signaling proteins involved in atherosclerotic plaque remodeling, particularly growth factor receptors (PDGFR, EGFR), cell cycle proteins, mitochondrial and endoplasmic reticulum components or extracellular matrix proteins, which progressively alters smooth muscle cell proliferation, angiogenesis and induces apoptosis. HNE adducts accumulate in the lipidic necrotic core of advanced atherosclerotic lesions, and may locally contribute to macrophage and smooth muscle cell apoptosis, which may induce plaque destabilization and rupture, thereby increasing the risk of athero-thrombotic events.

Dual signaling evoked by oxidized LDLs in vascular cells

The oxidative theory of atherosclerosis relies on the modification of low density lipoproteins (LDLs) in the vascular wall by reactive oxygen species. Modified LDLs, such as oxidized LDLs, are thought to participate in the formation of early atherosclerotic lesions (accumulation of foam cells and fatty streaks), whereas their role in advanced lesions and atherothrombotic events is more debated, because antioxidant supplementation failed to prevent coronary disease events and mortality in intervention randomized trials. As oxidized LDLs and oxidized lipids are present in atherosclerotic lesions and are able to trigger cell signaling on cultured vascular cells and macrophages, it has been proposed that they could play a role in atherogenesis and atherosclerotic vascular remodeling. Oxidized LDLs exhibit dual biological effects, which are dependent on extent of lipid peroxidation, nature of oxidized lipids (oxidized phospholipids, oxysterols, malondialdehyde, α,β-unsaturated hydroxyalkenals), concentration of oxidized LDLs and uptake by scavenger receptors (e.g. CD36, LOX-1, SRA) that signal through different transduction pathways. Moderate concentrations of mildly oxidized LDLs are proinflammatory and trigger cell migration and proliferation, whereas higher concentrations induce cell growth arrest and apoptosis. The balance between survival and apoptotic responses evoked by oxidized LDLs depends on cellular systems that regulate the cell fate, such as ceramide/sphingosine-1-phosphate rheostat, endoplasmic reticulum stress, autophagy and expression of pro/antiapoptotic proteins. In vivo, the intimal concentration of oxidized LDLs depends on the influx (hypercholesterolemia, endothelial permeability), residence time and lipid composition of LDLs, oxidative stress intensity, induction of defense mechanisms (antioxidant systems, heat shock proteins). As a consequence, the local cellular responses to oxidized LDLs may stimulate inflammatory or anti-inflammatory pathways, angiogenic or antiangiogenic responses, survival or apoptosis, thereby contributing to plaque growth, instability, complication (intraplaque hemorrhage, proteolysis, calcification, apoptosis) and rupture. Finally, these dual properties suggest that oxLDLs could be implicated at each step of atherosclerosis development, from early fatty streaks to advanced lesions, depending on the nature and concentration of their oxidized lipid content.

Aldehyde Oxidase 4 Plays a Critical Role in Delaying Silique Senescence by Catalyzing Aldehyde Detoxification

The Arabidopsis (Arabidopsis thaliana) aldehyde oxidases are a multigene family of four oxidases (AAO1-AAO4) that oxidize a variety of aldehydes, among them abscisic aldehyde, which is oxidized to the phytohormone abscisic acid. Toxic aldehydes are generated in plants both under normal conditions and in response to stress. The detoxification of such aldehydes by oxidation is attributed to aldehyde dehydrogenases but never to aldehyde oxidases. The feasibility of the detoxification of aldehydes in siliques via oxidation by AAO4 was demonstrated, first, by its ability to efficiently oxidize an array of aromatic and aliphatic aldehydes, including the reactive carbonyl species (RCS) acrolein, hydroxyl-2-nonenal, and malondialdehyde. Next, exogenous application of several aldehydes to siliques in AAO4 knockout (KO) Arabidopsis plants induced severe tissue damage and enhanced malondialdehyde levels and senescence symptoms, but not in wild-type siliques. Furthermore, abiotic stresses such as dark and ultraviolet C irradiation caused an increase in endogenous RCS and higher expression levels of senescence marker genes, leading to premature senescence of KO siliques, whereas RCS and senescence marker levels in wild-type siliques were hardly affected. Finally, in naturally senesced KO siliques, higher endogenous RCS levels were associated with enhanced senescence molecular markers, chlorophyll degradation, and earlier seed shattering compared with the wild type. The aldehyde-dependent differential generation of superoxide and hydrogen peroxide by AAO4 and the induction of AAO4 expression by hydrogen peroxide shown here suggest a self-amplification mechanism for detoxifying additional reactive aldehydes produced during stress. Taken together, our results indicate that AAO4 plays a critical role in delaying senescence in siliques by catalyzing aldehyde detoxification.

Human IgM Antibodies to Malondialdehyde Conjugated With Albumin Are Negatively Associated With Cardiovascular Disease Among 60-Year-Olds

Background

Malondialdehyde (MDA) is generated during lipid peroxidation as in oxidized low‐density lipoprotein, but antibodies against oxidized low‐density lipoprotein show variable results in clinical studies. We therefore studied the risk of cardiovascular disease (CVD) associated with IgM antibodies against MDA conjugated with human albumin (anti‐MDA).

Methods and Results

In a 5‐ to 7‐year follow‐up of 60‐year‐old men and women from Stockholm County previously screened for cardiovascular risk factors (2039 men, 2193 women), 209 incident CVD cases (defined as new events of coronary heart disease, fatal and nonfatal myocardial infarction, ischemic stroke, and hospitalization for angina pectoris) and 620 age‐ and sex‐matched controls were tested for IgM anti‐MDA by ELISA. Antibody peptide/protein characterization was done using a proteomics de novo sequencing approach. After adjustment for smoking, body‐mass index, type 2 diabetes mellitus, hyperlipidemia, and hypertension, an increased CVD risk was observed in the low IgM anti‐MDA percentiles (below 10th and 25th) (odds ratio and 95% CI: 2.0; 1.19–3.36 and 1.67; 1.16–2.41, respectively). Anti‐MDA above the 66th percentile was associated with a decreased CVD risk (odds ratio 0.68; CI: 0.48–0.98). After stratification by sex, associations were only present among men. IgM anti‐MDA levels were lower among cases (median [interquartile range]: 141.0 [112.7–164.3] versus 147.4 [123.5–169.6]; P=0.0177), even more so among men (130.6 [107.7–155.3] versus 143.0 [120.1–165.2]; P=0.001). The IgM anti‐MDA variable region profiles are distinctly different and also more homologous in their content (correlates strongly with fewer peptides) than control antibodies (not binding MDA).

Conclusions

IgM anti‐MDA is a protection marker for CVD. This finding could have diagnostic and therapeutic implications.

Activated Platelet and Oxidized LDL Induce Endothelial Membrane Vesiculation: Clinical Significance of Endothelial Cell-Derived Microparticles in Patients With Type 2 Diabetes

Endothelial cells, platelets, and oxidized LDL could play very important roles in the development of atherosclerosis in diabetes patients. The levels of plasma endothelial cell-derived microparticles (EDMP), platelet-derived microparticles (PDMP), platelet-P-selectin (plt-PS), soluble CD40 ligand (sCD40L), and anti-oxidized LDL antibody were measured and compared to develop a better understanding of their potential contribution to diabetic vascular complications. The concentrations of EDMP, PDMP, plt-PS, and sCD40L in diabetic patients were significantly higher than those in normal subjects. The number of EDMPs in patients with diabetes complicated by nephropathy was significantly higher than that in those without complications. Levels of anti-oxidized LDL antibody were also higher in type 2 diabetic patients than in control subjects. In addition, anti-oxidized LDL antibody levels correlated with EDMP, PDMP, plt-PS, and sCD40L levels in nephropathy patients. In the nephropathy group treated with sarpogrelate hydrochrolide, a 5-HT2A receptor antagonist, EDMP, PDMP, plt-PS, and sCD40L levels were decreased significantly. Oxidized LDL increased expression of plt-PS, and also promoted shedding of PDMP. Furthermore, oxidized LDL promoted a dose-dependent release of 5-hydroxytriptamine. On the other hand, activated platelets and PDMP promoted endothelial cells and THP-1 (monocytic cell line) interaction, and membrane vesiculation occurred in the presence of oxidized LDL. These findings suggest that activated platelets and oxidized LDL induce EDMP generation, and that elevated EDMPs may be a sign of vascular complications in type 2 diabetic patients, particularly those who suffer from diabetes-associated nephropathy

Malondialdehyde epitopes as mediators of sterile inflammation

Enhanced lipid peroxidation occurs during oxidative stress and results in the generation of lipid peroxidation end products such as malondialdehyde (MDA), which can attach to autologous biomolecules, thereby generating neo-self epitopes capable of inducing potentially undesired biological responses. Therefore, the immune system has developed mechanisms to protect from MDA epitopes by binding and neutralizing them through both cellular and soluble effectors. Here, we briefly discuss innate immune responses targeting MDA epitopes and their pro-inflammatory properties, followed by a review of physiological carriers of MDA epitopes that are relevant in homeostasis and disease. Then we discuss in detail the evidence for cellular responses towards MDA epitopes mainly in lung, liver and the circulation as well as signal transduction mechanisms and receptors implicated in the response to MDA epitopes. Last, we hypothesize on the role of MDA epitopes as mediators of inflammation in diseases and speculate on their contribution to disease pathogenesis. This article is part of a Special Issue entitled: Lipid modification and lipid peroxidation products in innate immunity and inflammation edited by Christoph J. Binder.

IgM antibodies against malondialdehyde and phosphorylcholine are together strong protection markers for atherosclerosis in systemic lupus erythematosus: Regulation and underlying mechanisms

OBJECTIVES

Phosphorylcholine (PC) and malondialdehyde (MDA) are generated during lipid peroxidation and form adducts with proteins as albumin as studied herein. Atherosclerosis and cardiovascular disease (CVD) are increased in systemic lupus erythematosus (SLE). We here investigate the role and regulation of IgM antibodies against PC (anti-PC) and MDA (anti-MDA).

METHODS

IgM anti-PC and anti-MDA in SLE patients (n=114) were compared with age- and sex-matched population-based controls (n=108). Common carotid intima-media thickness (IMT) and plaque occurrence were determined by B-mode ultrasound. Plaques were graded according to echogenicity (potentially vulnerability). Production of IgM anti-PC and anti-MDA by B cells was determined by ELISA and ELISPOT. The effect of anti-PC and anti-MDA on macrophage uptake of apoptotic cells and oxidative stress was studied by flow cytometry.

RESULTS

Above 66rd percentile together, IgM anti-PC and anti-MDA were striking protection markers for plaque prevalence and echolucency in SLE (OR: 0.08, CI: 0.01-0.46 and OR: 0.10, CI: 0.01-0.82), respectively, and risk markers for plaque prevalence when below 33rd percentile: OR: 3.79, CI: (1.10-13.00). In vitro, IgM anti-PC and anti-MDA were much higher when B cells were co-cultured with CD3 T cells. Anti-HLA-, anti-CD40 antibody or CD40 silencing abolished these effects. Uptake of apoptotic cells was increased by IgM anti-PC and anti-MDA. MDA induced increased oxidative stress, which was inhibited by IgM anti-MDA.

CONCLUSIONS

Unexpectedly, both IgM anti-MDA and IgM anti-PC are T-cell dependent and especially together, are strong protection markers for atherosclerosis in SLE. Underlying mechanisms include increased phagocytosis of apoptotic cells and decrease of oxidative stress.

Malondialdehyde Epitopes as Targets of Immunity and the Implications for Atherosclerosis

Accumulating evidence suggests that oxidation-specific epitopes (OSEs) constitute a novel class of damage-associated molecular patterns (DAMPs) generated during high oxidative stress but also in the physiological process of apoptosis. To deal with the potentially harmful consequences of such epitopes, the immune system has developed several mechanisms to protect from OSEs and to orchestrate their clearance, including IgM natural antibodies and both cellular- and membrane-bound receptors. Here, we focus on malondialdehyde (MDA) epitopes as prominent examples of OSEs that trigger both innate and adaptive immune responses. First, we review the mechanisms of MDA generation, the different types of adducts on various biomolecules and provide relevant examples for physiological carriers of MDA such as apoptotic cells, microvesicles, or oxidized low-density lipoproteins. Based on recent insights, we argue that MDA epitopes contribute to the maintenance of homeostatic functions by acting as markers of elevated oxidative stress and tissue damage. We discuss multiple lines of evidence that MDA epitopes are proinflammatory and thus important targets of innate and adaptive immune responses. Finally, we illustrate the relevance of MDA epitopes in human pathologies by describing their capacity to drive inflammatory processes in atherosclerosis and highlighting protective mechanisms of immunity that could be exploited for therapeutic purposes.

Elevated Levels of Plasma IgA Autoantibodies against Oxidized LDL Found in Proliferative Diabetic Retinopathy but Not in Nonproliferative Retinopathy

Aims. This study investigated the association of autoantibodies binding to oxidized low-density lipoproteins (oxLDL) in diabetic retinopathy (DR). Methods. Plasma from 229 types 1 and 2 patients with DR including diabetic macular edema (DME) and proliferative diabetic retinopathy (PDR) was analysed with ELISA-based assay to determine IgA, IgG, and IgM autoantibody levels binding to oxLDL. The controls were 106 diabetic patients without retinopathy (NoDR) and 139 nondiabetic controls (C). Results. PDR group had significantly higher IgA autoantibody levels than DME or NoDR: mean 94.9 (SD 54.7) for PDR, 75.5 (41.8) for DME (p = 0.001), and 76.1 (48.2) for NoDR (p = 0.008). There were no differences in IgG, IgM, or IgA that would be specific for DR or for DME. Type 2 diabetic patients had higher levels of IgA autoantibodies than type 1 diabetic patients (86.0 and 65.5, resp., p = 0.004) and the highest levels in IgA were found in type 2 diabetic patients with PDR (119.1, p > 0.001). Conclusions. IgA autoantibodies were increased in PDR, especially in type 2 diabetes. The high levels of IgA in PDR, and especially in type 2 PDR patients, reflect the inflammatory process and enlighten the role of oxLDL and its autoantibodies in PDR.

Oxidative theory of atherosclerosis and antioxidants

Atherosclerosis is a multifactorial process that begins early in infancy and affects all the humans. Early steps of atherogenesis and the evolution towards complex atherosclerotic plaques are briefly described. After a brief history of the 'Lipid theory of atherosclerosis', we report the most prominent discoveries on lipoproteins, their receptors and metabolism, and their role in atherogenesis. The main focus is the 'oxidative theory of atherosclerosis', with emphasis on free radicals and reactive oxygen species, lipid peroxidation and LDL oxidation, biological properties of oxidized LDL and their potential role in atherogenesis. Then, we report the properties of antioxidants and antioxidant systems and their effects in vitro, on cultured cells, in animal models and in humans. The surprising discrepancy between the efficacy of antioxidants in vitro and in animal models of atherosclerosis and the lack of protective effect against cardiovascular events and death in epidemiological study and clinical trials are discussed. In contrast, epidemiological studies seem to indicate that the Mediterranean diet may protect (in part) against atherosclerosis complications (myocardial infarction and cardiovascular death).

N-acetylcysteine inhibits in vivo oxidation of native low-density lipoprotein

Low-density lipoprotein (LDL) is non-atherogenic, while oxidized LDL (ox-LDL) is critical to atherosclerosis. N-acetylcysteine (NAC) has anti-atherosclerotic effect with largely unknown mechanisms. The present study aimed to determine if NAC could attenuate in vivo LDL oxidation and inhibit atherosclerosis. A single dose of human native LDL was injected intravenously into male C57BL/6 mice with and without NAC treatment. Serum human ox-LDL was detected 30 min after injection, reached the peak in 3 hours, and became undetectable in 12 hours. NAC treatment significantly reduced serum ox-LDL level without detectable serum ox-LDL 6 hours after LDL injection. No difference in ox-LDL clearance was observed in NAC-treated animals. NAC treatment also significantly decreased serum ox-LDL level in patients with coronary artery diseases and hyperlipidemia without effect on LDL level. Intracellular and extracellular reactive oxidative species (ROS) production was significantly increased in the animals treated with native LDL, or ox-LDL and in hyperlipidemic LDL receptor knockout (LDLR(-/-)) mice that was effectively prevented with NAC treatment. NAC also significantly reduced atherosclerotic plaque formation in hyperlipidemic LDLR(-/-) mice. NAC attenuated in vivo oxidation of native LDL and ROS formation from ox-LDL associated with decreased atherosclerotic plaque formation in hyperlipidemia.

A model of chlorpyrifos distribution and its biochemical effects on the liver and kidneys of rats

This study investigated the main target sites of chlorpyrifos (CPF), its effect on biochemical indices, and the pathological changes observed in rat liver and kidney function using gas chromatography/mass spectrometry. Adult female Wistar rats (n = 12) were randomly assigned into two groups (one control and one test group; n = 6 each). The test group received CPF via oral gavage for 21 days at 5 mg/kg daily. The distribution of CPF was determined in various organs (liver, brain, heart, lung, kidney, ovary, adipose tissue, and skeletal muscle), urine and stool samples using GCMS. Approximately 6.18% of CPF was distributed in the body tissues, and the highest CPF concentration (3.80%) was found in adipose tissue. CPF also accumulated in the liver (0.29%), brain (0.22%), kidney (0.10%), and ovary (0.03%). Approximately 83.60% of CPF was detected in the urine. CPF exposure resulted in a significant increase in plasma transaminases, alkaline phosphatase, and total bilirubin levels, a significant reduction in total protein levels and an altered lipid profile. Oxidative stress due to CPF administration was also evidenced by a significant increase in liver malondialdehyde levels. The detrimental effects of CPF on kidney function consisted of a significant increase in plasma urea and creatinine levels. Liver and kidney histology confirmed the observed biochemical changes. In conclusion, CPF bioaccumulates over time and exerts toxic effects on animals.

Molecular mechanism of a new Laminaria japonica polysaccharide on the suppression of macrophage foam cell formation via regulating cellular lipid metabolism and suppressing cellular inflammation

SCOPE

Laminaria japonica is an important marine vegetable with great health benefits for preventing atherosclerosis. Since the foam cell formation is an important hallmark for the initiation of atherosclerosis, we examined the effect and underlying mechanism of a purified L. japonica polysaccharide (LJP61A) on the suppression of macrophage foam cell formation in this study. The chemical structure was further characterized.

METHODS AND RESULTS

Using oxidized low-density lipoprotein (ox-LDL)-induced foam cell model, we found that the cellular lipid accumulation was significantly attenuated by 25 μg/mL LJP61A. Meanwhile, LJP61A caused a remarkable decrease in mRNA expression of peroxisome proliferator-activated receptor γ that was accompanied by the reduction of CD36 and Acyl coenzyme A: cholesterol acyltransferase-1 mRNA levels, and the enhancement of ATP-binding cassette transporters A1 and scavenger receptor B1 mRNA levels. Besides these, the ox-LDL-induced cellular inflammation was also restricted by LJP61A treatment via mammalian target of rapamycin-mediated Toll-like receptor 2/4-Mitogen-activated protein kinases/nuclear factor kappa-B pathways. The structure of LJP61A was characterized as a repeating unit consisting of →3,6)-α-d-Manp-(1→, →4)-α-d-Manp-(1→, →4)-2-O-acetyl-β-d-Glcp-(1→, →4)-β-d-Glcp-(1→, →6)-4-O-SO3 -β-d-Galp-(1→, →6)-β-d-Galp-(1→, →3)-β-d-Galp-(1→, and a terminal residue of α-d-Glcp-(1→.

CONCLUSION

Our findings suggest that LJP61A inhibits the conversion of macrophage into foam cell via regulating cellular lipid metabolism and suppressing cellular inflammation.

Quercetin protects RAW264.7 macrophages from glucosamine-induced apoptosis and lipid accumulation via the endoplasmic reticulum stress pathway

It is increasingly recognized that macrophages are a key cell in the development of atherosclerosis. Glucosamine, the product of the hexosamine biosynthetic pathway in diabetes mellitus, can disturb lipid metabolism, induce apoptosis and accelerate atherosclerosis via endoplasmic reticulum (ER) stress in various types of cells. Previous studies have indicated that quercetin possesses antidiabetic, anti‑oxidative, anti‑inflammatory and anti‑apoptotic activities as a flavonoid. Studies have also demonstrated its novel pharmacological properties for inhibiting ER stress. The present study focussed on the effects of quercetin on cell injury and ER stress in glucosamine‑induced macrophages. RAW264.7 macrophages were cultured with 15 mM glucosamine, following which the levels of apoptosis, intracellular total and free cholesterol, and apoptosis‑ and ER stress‑associated proteins were measured in the macrophages treated with or without quercetin. Additionally, the ratio of cholestryl ester/total cholesterol was calculated to observe the formation of foam cells. The results demonstrated that apoptosis and abnormal lipid accumulation in the RAW264.7 cells, which was induced by glucosamine, were significantly reversed by quercetin. In addition, quercetin treatment suppressed the increase of C/EBP homologous protein, and inhibited the activation of JNK and caspase‑12, which was induced by glucosamine. Quercetin also increased the expression level of full length activating transcriptional factor 6 and decreased the expression of glucose regulated protein 78. Of note, the beneficial effects of quercetin on the glucosamine‑induced RAW264.7 cells were reversed by treatment with tunicamycin. These findings suggest that quercetin may have properties to prevent glucosamine‑induced apoptosis and lipid accumulation via the ER stress pathway in RAW264.7 macrophages.