Quantification of malondialdehyde and 4-hydroxynonenal adducts to lysine residues in native and oxidized human low-density lipoprotein

Secondary Lipid Oxidation Products as Modulators of Calpain-2 Functionality In Vitro

The objective was to understand the impacts of secondary lipid oxidation products on calpain-2 activity and autolysis and, subsequently, to determine the quantity and localization of modification sites. 2-Hexenal and 4-hydroxynonenal incubation significantly decreased calpain-2 activity and slowed the progression of autolysis, while malondialdehyde had minimal impact on calpain-2 activity and autolysis. Specific modification sites were determined with LC-MS/MS, including distinct malondialdehyde modification sites on the calpain-2 catalytic and regulatory subunits. 2-Hexenal modification sites were observed on the calpain-2 catalytic subunit. Intact protein mass analysis with MALDI-MS revealed that a significant number of modifications on the calpain-2 catalytic and regulatory subunits are likely to exist. These observations confirm that specific lipid oxidation products modify calpain-2 and may affect the calpain-2 functionality. The results of these novel experiments have implications for healthy tissue metabolism, skeletal muscle growth, and post-mortem meat tenderness development.

Building an Understanding of Proteostasis in Reproductive Cells: The Impact of Reactive Carbonyl Species on Protein Fate

Significance: Stringent regulation of protein homeostasis pathways, under both physiological and pathological conditions, is necessary for the maintenance of proteome fidelity and optimal cell functioning. However, when challenged by endogenous or exogenous stressors, these proteostasis pathways can become dysregulated with detrimental consequences for protein fate, cell survival, and overall organism health. Most notably, there are numerous somatic pathologies associated with a loss of proteostatic regulation, including neurodegenerative disorders, type 2 diabetes, and some cancers. Recent Advances: Lipid oxidation-derived reactive carbonyl species (RCS), such as 4-hydroxynonenal (4HNE) and malondialdehyde, are relatively underappreciated purveyors of proteostatic dysregulation, which elicit their effects via the nonenzymatic post-translational modification of proteins. Emerging evidence suggests that a subset of germline proteins can serve as substrates for 4HNE modification. Among these, prevalent targets include succinate dehydrogenase, heat shock protein A2 and A-kinase anchor protein 4, all of which are intrinsically associated with fertility. Critical Issues: Despite growing knowledge in this field, the RCS adductomes of spermatozoa and oocytes are yet to be comprehensively investigated. Furthermore, the manner by which RCS-mediated adduction impacts protein fate and drives cellular responses, such as protein aggregation, requires further examination in the germline. Given that RCS-protein adduction has been attributed a role in infertility, there has been sparked research investment into strategies to prevent lipid peroxidation in germ cells. Future Directions: An increased depth of knowledge regarding the mechanisms and substrates of RCS-mediated protein modification in reproductive cells may reveal important targets for the development of novel therapies to improve fertility and pregnancy outcomes for future generations.

Computational and physicochemical insight into 4-hydroxy-2-nonenal induced structural and functional perturbations in human low-density lipoprotein

Lipid peroxidation (LPO) is a biological process that frequently occurs under physiological conditions. Undue oxidative stress increases the level of LPO; which may further contribute to the development of cancer. 4-Hydroxy-2-nonenal (HNE), one of the principal by-products of LPO, is present in high concentrations in oxidatively stressed cells. HNE rapidly reacts with various biological components, including DNA and proteins; however, the extent of protein degradation by lipid electrophiles is not well understood. The influence of HNE on protein structures will likely have a considerable therapeutic value. This research elucidates the potential of HNE, one of the most researched phospholipid peroxidation products, in modifying low-density lipoprotein (LDL). In this study, we tracked the structural alterations in LDL by HNE using various physicochemical techniques. To comprehend the stability, binding mechanism and conformational dynamics of the HNE-LDL complex, computational investigations were carried out. LDL was altered in vitro by HNE, and the secondary and tertiary structural alterations were examined using spectroscopic methods, such as UV-visible, fluorescence, circular dichroism and fourier transform infrared spectroscopy. Carbonyl content, thiobarbituric acid-reactive-substance (TBARS) and nitroblue tetrazolium (NBT) reduction assays were used to examine changes in the oxidation status of LDL. Thioflavin T (ThT), 1-anilinonaphthalene-8-sulfonic (ANS) binding assay and electron microscopy were used to investigate aggregates formation. According to our research, LDL modified by HNE results in changes in structural dynamics, oxidative stress and the formation of LDL aggregates. The current investigation must characterize HNE's interactions with LDL and comprehend how it can change their physiological or pathological functions.Communicated by Ramaswamy H. Sarma.

Excessive Lipid Peroxidation in Uterine Epithelium Causes Implantation Failure and Pregnancy Loss

The uterine epithelium undergoes a dramatic spatiotemporal transformation to enter a receptive state, involving a complex interaction between ovarian hormones and signals from stromal and epithelial cells. Redox homeostasis is critical for cellular physiological steady state; emerging evidence reveals that excessive lipid peroxides derail redox homeostasis, causing various diseases. However, the role of redox homeostasis in early pregnancy remains largely unknown. It is found that uterine deletion of Glutathione peroxidase 4 (GPX4), a key factor in repairing oxidative damage to lipids, confers defective implantation, leading to infertility. To further pinpoint Gpx4's role in different cell types, uterine epithelial-specific Gpx4 is deleted by a lactotransferrin (Ltf)-Cre driver; the resultant females are infertile, suggesting increased lipid peroxidation levels in uterine epithelium compromises receptivity and implantation. Lipid peroxidation inhibitor administration failed to rescue implantation due to carbonylation of major receptive-related proteins underlying high lipid reactive oxygen species. Intriguingly, superimposition of Acyl-CoA synthetase long-chain family member 4 (ACSL4), an enzyme that promotes biosynthesis of phospholipid hydroperoxides, along with uterine epithelial GPX4 deletion, preserves reproductive capacity. This study reveals the pernicious impact of unbalanced redox signaling on embryo implantation and suggests the obliteration of lipid peroxides as a possible therapeutic approach to prevent implantation defects.

Dicarbonyl-Modified Low-Density Lipoproteins Are Key Inducers of LOX-1 and NOX1 Gene Expression in the Cultured Human Umbilical Vein Endotheliocytes

Expression of LOX-1 and NOX1 genes in the human umbilical vein endotheliocytes (HUVECs) cultured in the presence of low-density lipoproteins (LDL) modified with various natural dicarbonyls was investigated for the first time. It was found that among the investigated dicarbonyl-modified LDLs (malondialdehyde (MDA)-modified LDLs, glyoxal-modified LDLs, and methylglyoxal-modified LDLs), the MDA-modified LDLs caused the greatest induction of the LOX-1 and NOX1 genes, as well as of the genes of antioxidant enzymes and genes of proapoptotic factors in HUVECs. Key role of the dicarbonyl-modified LDLs in the molecular mechanisms of vascular wall damage and endothelial dysfunction is discussed.

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.

Overexpression of Interleukin-8 Promotes the Progression of Fatty Liver to Nonalcoholic Steatohepatitis in Mice

Nonalcoholic steatohepatitis (NASH) is an advanced stage of fatty liver disease characterized by liver damage, inflammation, and fibrosis. Although neutrophil infiltration is consistently observed in the livers of patients with NASH, the precise role of neutrophil-recruiting chemokines and infiltrating neutrophils in NASH pathogenesis remains poorly understood. Here, we aimed to elucidate the role of neutrophil infiltration in the transition from fatty liver to NASH by examining hepatic overexpression of interleukin-8 (IL8), a major chemokine responsible for neutrophil recruitment in humans. Mice fed a high-fat diet (HFD) for 3 months developed fatty liver without concurrent liver damage, inflammation, and fibrosis. Subsequent infection with an adenovirus overexpressing human IL8 for an additional 2 weeks increased IL8 levels, neutrophil infiltration, and liver injury in mice. Mechanistically, IL8-induced liver injury was associated with the upregulation of components of the NADPH oxidase 2 complex, which participate in neutrophil oxidative burst. IL8-driven neutrophil infiltration promoted macrophage aggregate formation and upregulated the expression of chemokines and inflammatory cytokines. Notably, IL8 overexpression amplified factors associated with fibrosis, including collagen deposition and hepatic stellate cell activation, in HFD-fed mice. Collectively, hepatic overexpression of human IL8 promotes neutrophil infiltration and fatty liver progression to NASH in HFD-fed mice.

Binding properties of recombinant LDL receptor and LOX-1 receptor to LDL measured using bio-layer interferometry and atomic force microscopy

Oxidation of low-density lipoproteins (LDLs) triggers a recognition by scavenger receptors such as lectin-like oxidized LDL receptor-1 (LOX-1) and is related to inflammation and cardiovascular diseases. Although LDLs that are recognized by LOX-1 can be risk-related LDLs, conventional LDL detection methods using commercially available recombinant receptors remain undeveloped. Using a bio-layer interferometry (BLI), we investigated the binding of recombinant LOX-1 (reLOX-1) and LDL receptors to the oxidized LDLs. The recombinant LDL receptor preferably bound minimally modified LDLs, while the reLOX-1 recognized extensively oxidized LDLs. An inversed response of the BLI was observed during the binding in the case of reLOX-1. AFM study showed that the extensively oxidized LDLs and aggregates of LDLs were observed on the surface, supporting the results. Altogether, a combined use of these recombinant receptors and the BLI method is useful in detecting high-risk LDLs such as oxidized LDLs and modified LDLs.

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.

Lipid Peroxidation Has Major Impact on Malondialdehyde-Derived but Only Minor Influence on Glyoxal and Methylglyoxal-Derived Protein Modifications in Carbohydrate-Rich Foods

In the present work, the contribution of lipid peroxidation on modifications of lysine and arginine residues of proteins was investigated. Lipid peroxidation had a major impact on malondialdehyde-derived protein modifications; however, the influence on glyoxal and methylglyoxal-derived modifications in flat wafers was negligible. Therefore, vegetable oils (either linseed oil, sunflower oil, or coconut oil) were added to respective batters, and flat wafers were baked (150 °C, 3-10 min). Analysis of malondialdehyde indicated oxidation in linseed wafers, which was supported by the direct quantitation of three malondialdehyde protein adducts in the range of 0.09-23.5 mg/kg after enzymatic hydrolysis. In contrast, levels of free glyoxal and methylglyoxal were independent of the type of oil added, which was in line with the analysis of 13 advanced glycation end products. Comprehensive incubations of 40 mM N²-t-Boc-lysine (100 mM phosphate buffer, pH 7.4) with either 10% oil or an equimolar concentration of carbohydrates led to magnitudes higher (10³-10⁵) amounts of N⁶-carboxymethyl lysine, N⁶-glycolyl lysine, and N⁶-carboxyethyl lysine in the latter. Furthermore, malondialdehyde exceeded glyoxal and methylglyoxal in incubations of pure oils at 150 °C by factors of 30 and 100, respectively.

Effect of Malondialdehyde on the Digestibility of Beef Myofibrillar Protein: Potential Mechanisms from Structure to Modification Site

Lipid oxidation and protein oxidation occur side by side in meat. Here, the effect of malondialdehyde (MDA), the major product of lipid oxidation, on the digestibility of beef myofibrillar proteins (MP) was studied. MP samples were incubated with 0, 0.1, 0.3, 0.5, and 0.7 mM MDA at 4 °C for 12 h and then subjected to in vitro gastrointestinal digestion. The result showed that MDA remarkably reduced the digestibility of MP (p < 0.05). MDA treatments significantly increased carbonyl and Schiff base contents in MP (p < 0.05). The microstructure observed by atomic force microscopy showed that MDA treatments resulted in the aggregation of MP. Non-reducing and reducing electrophoresis suggested the aggregation was mainly caused by covalent bonds including disulfide bond and carbonyl−amine bond. Proteomics analysis proved that the myosin tail was the main target of MDA attack, meanwhile, lysine residues were the major modification sites. Taken together, the above results imply that MDA induces protein oxidation, aggregation, and blockage of hydrolysis sites, consequently leading to the decrease in both gastric and gastrointestinal digestibility of MP.

Ozone-Microbubble-Washing with Domestic Equipment: Effects on the Microstructure, and Lipid and Protein Oxidation of Muscle Foods

This study aimed to compare ozone-microbubble-washing (OM) performed by domestic equipment with conventional water-washing (CW) regarding resultant quality attributes of muscle foods. For this purpose, muscle microstructure and lipid and protein oxidation were evaluated in pork and fish samples after OM and CW treatments. The assessment of muscle microstructure showed that OM treatment did not damage the microstructure of muscle fibers in both pork and fish samples. Thiobarbituric acid reactive substances (TBARS) values were not detected in both treatment groups, and they were substantially below the generally acceptable threshold (1 mg MDA/kg). The methylglyoxal (MGO) level of OM-treated fish samples was significantly higher than that of CW-treated fish samples. However, glyoxal (GO) and MGO levels of OM-treated pork samples were significantly lower than that of CW-treated pork samples. Similar types and sites of oxidative modification and similar numbers of modified peptides, as well as no significant difference in the concentration of total and most of the free amino acids (FAA) between treatment groups, indicated that OM treatment did not accelerate protein oxidation.

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.

AICAR Protects Vascular Endothelial Cells from Oxidative Injury Induced by the Long-Term Palmitate Excess

Hyperlipidemia manifested by high blood levels of free fatty acids (FFA) and lipoprotein triglycerides is critical for the progression of type 2 diabetes (T2D) and its cardiovascular complications via vascular endothelial dysfunction. However, attempts to assess high FFA effects in endothelial culture often result in early cell apoptosis that poorly recapitulates a much slower pace of vascular deterioration in vivo and does not provide for the longer-term studies of endothelial lipotoxicity in vitro. Here, we report that palmitate (PA), a typical FFA, does not impair, by itself, endothelial barrier and insulin signaling in human umbilical vein endothelial cells (HUVEC), but increases NO release, reactive oxygen species (ROS) generation, and protein labeling by malondialdehyde (MDA) hallmarking oxidative stress and increased lipid peroxidation. This PA-induced stress eventually resulted in the loss of cell viability coincident with loss of insulin signaling. Supplementation with 5-aminoimidazole-4-carboxamide-riboside (AICAR) increased endothelial AMP-activated protein kinase (AMPK) activity, supported insulin signaling, and prevented the PA-induced increases in NO, ROS, and MDA, thus allowing to maintain HUVEC viability and barrier, and providing the means to study the long-term effects of high FFA levels in endothelial cultures. An upgraded cell-based model reproduces FFA-induced insulin resistance by demonstrating decreased NO production by vascular endothelium.

Oxidized LDLs as Signaling Molecules

Levels of oxidized low-density lipoproteins (oxLDLs) are usually low in vivo but can increase whenever the balance between formation and scavenging of free radicals is impaired. Under normal conditions, uptake and degradation represent the physiological cellular response to oxLDL exposure. The uptake of oxLDLs is mediated by cell surface scavenger receptors that may also act as signaling molecules. Under conditions of atherosclerosis, monocytes/macrophages and vascular smooth muscle cells highly exposed to oxLDLs tend to convert to foam cells due to the intracellular accumulation of lipids. Moreover, the atherogenic process is accelerated by the increased expression of the scavenger receptors CD36, SR-BI, LOX-1, and SRA in response to high levels of oxLDL and oxidized lipids. In some respects, the effects of oxLDLs, involving cell proliferation, inflammation, apoptosis, adhesion, migration, senescence, and gene expression, can be seen as an adaptive response to the rise of free radicals in the vascular system. Unlike highly reactive radicals, circulating oxLDLs may signal to cells at more distant sites and possibly trigger a systemic antioxidant defense, thus elevating the role of oxLDLs to that of signaling molecules with physiological relevance.

Protein oxidation - Formation mechanisms, detection and relevance as biomarkers in human diseases

Generation of reactive oxygen species and related oxidants is an inevitable consequence of life. Proteins are major targets for oxidation reactions, because of their rapid reaction rates with oxidants and their high abundance in cells, extracellular tissues, and body fluids. Additionally, oxidative stress is able to degrade lipids and carbohydrates to highly reactive intermediates, which eventually attack proteins at various functional sites. Consequently, a wide variety of distinct posttranslational protein modifications is formed by protein oxidation, glycoxidation, and lipoxidation. Reversible modifications are relevant in physiological processes and constitute signaling mechanisms ("redox signaling"), while non-reversible modifications may contribute to pathological situations and several diseases. A rising number of publications provide evidence for their involvement in the onset and progression of diseases as well as aging processes. Certain protein oxidation products are chemically stable and formed in large quantity, which makes them promising candidates to become biomarkers of oxidative damage. Moreover, progress in the development of detection and quantification methods facilitates analysis time and effort and contributes to their future applicability in clinical routine. The present review outlines the most important classes and selected examples of oxidative protein modifications, elucidates the chemistry beyond their formation and discusses available methods for detection and analysis. Furthermore, the relevance and potential of protein modifications as biomarkers in the context of disease and aging is summarized.

Efficacy of metal oxide nanoparticles as novel antimicrobial agents against multi-drug and multi-virulent Staphylococcus aureus isolates from retail raw chicken meat and giblets

Staphylococcus aureus is among the most common zoonotic pathogens originating from animals consumed as food, especially raw chicken meat (RCM). As far as we know, this might be the first report that explores the efficacy of metal oxide nanoparticles (MONPs), such as zinc peroxide nanoparticles (ZnO₂-NPs), zinc oxide nanoparticles (ZnO-NPs), and titanium dioxide nanoparticles (TiO₂-NPs) against multidrug resistant (MDR) and/or pandrug resistant (PDR) S. aureus strains with a strong biofilm-producing ability isolated from RCM and giblets. The overall prevalence of coagulase-positive staphylococci was 21%, with a contamination level range between 10² and 10⁴ CFU/g. The incidence of virulence genes See (21/36), pvl (16/36), clfA (15/36), sec (12/36), tst (12/36), and sea (11/36) among S. aureus strains were relatively higher those of seb, sed, fnbA, and fnbB. For antimicrobial resistance gene distribution, most strains harbored the blaZ gene (25/36), aacA-aphD gene (24/36), mecA gene (22/36), vanA gene (20/36), and apmA gene (20/36) confirmed the prevalence of MDR among S. aureus of RCM products. However, cfr (11/36), spc (9/36), and aadE (7/36) showed a relatively lower existence. The data of antibiogram resistance profiles was noticeably heterogeneous (25 patterns) with 32 MDR and four PDR S. aureus strains. All tested strains had a very high MAR index value (>0.2) except the P11 pattern (GEN, MXF, PMB), which showed a MAR index of 0.19. Among the strong biofilm-producing ability (BPA), 14 (70%) strains were isolated from wet markets, while only six strong BPA strains were isolated from supermarkets. The mean values of BPA ranged from 2.613 ± 0.04 to 11.013 ± 0.05. Clearly, ZnO₂-NPs show significant inhibitory activity against S. aureus strains compared with those produced by the action of ZnO-NPs and TiO₂-NPs. The results of anti-inflammatory activity suggest ZnO₂-NPs as a lead compound for designing an alternative antimicrobial agent against drug-resistant and strong biofilm-producing S. aureus isolates from retail RCM and giblets.

[Elimination kinetics of carbonyl-modified low density lipoproteins from bloodstream]

The elimination kinetics of carbonyl-modified low density lipoproteins (LDL) from rabbit bloodstream was studied using isolated LDL of rabbits and humans after preliminary biotinylation or labeling with FITZ. LDL from rabbit or human blood plasma were isolated using differential ultracentrifugation in a density gradient, and then LDL were labeled using biotinylation or FITZ, after which they were modified with various low molecular weight natural dicarbonyls: malondialdehyde (MDA), glyoxal or methylglyoxal. Native and dicarbonyl-modified biotinylated or FITZ-labeled LDL were injected into the ear vein of rabbits and blood samples were taken at certain intervals. To determine the content of biotinylated LDL in blood plasma, an enzyme immunoassay was performed; FITZ-labeled LDL were determined by spectra fluorescence. It is shown that glyoxal- and methylglyoxal-modified LDL in rabbits and humans circulated in the bloodstream for almost the same time as native (unmodified) LDL. At the same time, MDA-modified rabbit and human LDL were extremely quickly eliminated from the rabbit bloodstream. Dicarbonyl-modified LDL from the donors blood plasma were not associated with the red blood cells and endothelial cells. It has been shown that using the kits Oxidized LDL ELISA ("Mercodia", Sweden), it is possible to identify mainly MDA-modified LDL. The level of MDA-modified LDL in the blood plasma of CHD patients sharply decreases during therapy with the hypocholesterolemic drug the PCSK9 inhibitor (evulokumab), which activates LDL reutilization in the liver cells. These results explain the extreme drop in the level of MDA-modified LDL by their increased utilization in hepatocytes. The results obtained indicate a high atherogenicity of glyoxal- and methylglyoxal-modified LDL, long-term circulating in the bloodstream.

Molecular mechanisms of the disturbance caused by malondialdehyde on probiotic Lactobacillus reuteri PL503

This study aimed to provide insight into the molecular and genetic mechanisms implicated in the responses of Lactobacillus reuteri against the oxidative stress induced by malondialdehyde (MDA) by analysing protein oxidation and assessing the uspA and the dhaT genes. Four experimental groups were evaluated depending on the concentration of MDA added in Man, Rogosa and Sharpe (MRS) broth: Control (L. reuteri), 5 µM (L. reuteri + 5 µM MDA), 25 µM (L. reuteri + 25 µM MDA) and 100 µM (L. reuteri + 100 µM MDA). Three replicates were incubated at 37 °C for 24 h in microaerophilic conditions and sampled at 12, 16, 20 and 24 h. The upregulation of the uspA gene by L. reuteri indicates the recognition of MDA as a potential DNA‐damaging agent. The dhaT gene, encoding a NADH‐dependent‐oxidoreductase, was also upregulated at the highest MDA concentrations. This gene was proposed to play a role in the antioxidant response of L. reuteri. The incubation of L. reuteri with MDA increased the production of ROS and caused thiol depletion and protein carbonylation. L. reuteri is proposed to detoxify pro‐oxidative species while the underlying mechanism requires further elucidation.

Method To Characterize and Monitor Covalent Interactions of Flavor Compounds with β-Lactoglobulin Using Mass Spectrometry and Proteomics

This study develops a method to measure the covalent bonds formed between the side chains and terminal amino acids of β-lactoglobulin (BLG) and selected flavor molecules (benzaldehyde, citral, or allyl isothiocyanate) using electrospray ionization mass spectrometry (ESI/MS) and tandem mass spectrometry (MS/MS). This technique made it possible to measure increases in molecular weight of BLG as the reaction takes place (BLG + flavor compound). The observed mass shifts on the reaction corresponded to either Schiff base or Michael addition reactions between the chosen flavor compounds and BLG. In the case of citral, sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis revealed that these reactions lead to protein cross-linking. A proteomic approach using MS/MS to identify the sites of post-translational modification between benzaldehyde and BLG revealed that the lysine groups were the reaction sites. Interestingly, benzaldehyde was found to react with several different lysine groups but never more than one of them per BLG molecule (BLG contains 15 lysine groups/molecule). Furthermore, adducts with benzaldehyde were not observed at two lysine groups. Allyl isothiocyanate was found to react with several sites on each BLG molecule. The ESI/MS methodology in tandem with proteomics yields a detailed view of flavor/BLG interactions that may offer insights on minimizing these undesirable reactions in the future.

The Advanced Lipoxidation End-Product Malondialdehyde-Lysine in Aging and Longevity

The nonenzymatic adduction of malondialdehyde (MDA) to the protein amino groups leads to the formation of malondialdehyde-lysine (MDALys). The degree of unsaturation of biological membranes and the intracellular oxidative conditions are the main factors that modulate MDALys formation. The low concentration of this modification in the different cellular components, found in a wide diversity of tissues and animal species, is indicative of the presence of a complex network of cellular protection mechanisms that avoid its cytotoxic effects. In this review, we will focus on the chemistry of this lipoxidation-derived protein modification, the specificity of MDALys formation in proteins, the methodology used for its detection and quantification, the MDA-lipoxidized proteome, the metabolism of MDA-modified proteins, and the detrimental effects of this protein modification. We also propose that MDALys is an indicator of the rate of aging based on findings which demonstrate that (i) MDALys accumulates in tissues with age, (ii) the lower the concentration of MDALys the greater the longevity of the animal species, and (iii) its concentration is attenuated by anti-aging nutritional and pharmacological interventions.

D-4F, an ApoA-I mimetic peptide ameliorating TRPA1-mediated nocifensive behaviour in a model of neurogenic inflammation

Background

High doses of capsaicin are recommended for the treatment of neuropathic pain. However, low doses evoke mechanical hypersensitivity. Activation of the capsaicin chemosensor transient receptor potential vanilloid 1 (TRPV1) induces neurogenic inflammation. In addition to the release of pro-inflammatory mediators, reactive oxygen species are produced. These highly reactive molecules generate oxidised phospholipids and 4-hydroxynonenal (4-HNE) which then directly activate TRP ankyrin 1 (TRPA1). The apolipoprotein A-I mimetic peptide D-4F neutralises oxidised phospholipids. Here, we asked whether D-4F ameliorates neurogenic hypersensitivity in rodents by targeting reactive oxygen species and 4-HNE in the capsaicin-evoked pain model.

Results

Co-application of D-4F ameliorated capsaicin-induced mechanical hypersensitivity and allodynia as well as persistent heat hypersensitivity measured by Randell–Selitto, von Frey and Hargreaves test, respectively. In addition, mechanical hypersensitivity was blocked after co-injection of D-4F with the reactive oxygen species analogue H₂O₂ or 4-HNE. In vitro studies on dorsal root ganglion neurons and stably transfected cell lines revealed a TRPA1-dependent inhibition of the calcium influx when agonists were pre-incubated with D-4F. The capsaicin-induced calcium influx in TRPV1-expressing cell lines and dorsal root ganglion neurons sustained in the presence of D-4F.

Conclusions

D-4F is a promising compound to ameliorate TRPA1-dependent hypersensitivity during neurogenic inflammation.

Behavior of Malondialdehyde and Its Whey Protein Adducts during In Vitro Simulated Gastrointestinal Digestion

The behavior of malondialdehyde and its whey protein adducts in aqueous buffer and fully hydrogenated coconut oil-in-water emulsions stabilized by Tween 20 or by whey protein was studied during in vitro gastrointestinal digestion. The malondialdehyde levels during in vitro digestion depended upon the kind of sample, the location of the whey protein, and the extent of adduct formation before digestion. During gastric digestion, degradation of acid-labile malondialdehyde-whey protein adducts as well as formation of new malondialdehyde adducts with hydrolyzed whey protein was suggested to occur, in addition to the earlier described equilibria with respect to the aldol self-condensation of malondialdehyde and its hydrolytic cleavage. After in vitro digestion, both malondialdehyde and its adducts were present in the digest with malondialdehyde recoveries varying between 55 and 86% depending upon the model system studied. To conclude, the reactivity of malondialdehyde toward (hydrolyzed) proteins does not stop at the point of ingestion.

The Use of Biomarkers as Alternatives to Current Animal Tests on Food Chemicals

Recent developments in biomarkers relating to the interrelationship of diet, disease and health were surveyed. Most emphasis was placed on biomarkers of deleterious effects, since these are of greatest relevance to the subject of this review. The area of greatest activity was found to be that relating to biomarkers of mutagenic, genotoxic and carcinogenic effects. This is also one of the major areas of concern in considerations of the beneficial and deleterious effects of dietary components, and also the area in which regulatory testing requires studies of the longest duration. A degree of progress has also been made in the identification and development of biomarkers relating to certain classes of target organ toxicity. Biomarkers for other types of toxicity, such as immunotoxicity, neurotoxicity, reproductive toxicity and developmental toxicity, are less developed, and further investigation in these areas is required before a comprehensive biomarker strategy can be established. A criticism that recurs constantly in the biomarker literature is the lack of standardisation in the methods used, and the lack of reference standards for the purposes of validation and quality control. It is encouraging to note the growing acknowledgement of the need for validation of biomarkers and biomarker assays. Some validation studies have already been initiated. This review puts forward proposals for criteria to be used in biomarker validation. More discussion on this subject is required. It is concluded that the use of biomarkers can, in some cases, facilitate the implementation of the Three Rs with respect to the testing of food chemicals and studies on the effects of diet on health. The greatest potential is seen to be in the refinement of animal testing, in which biomarkers could serve as early and sensitive endpoints, in order to reduce the duration of the studies and also reduce the number of animals required. Biomarkers could also contribute to establishing a mechanistic basis for in vitro test systems and to facilitating their validation and acceptance. Finally, the increased information that could result from the incorporation of biomarker determinations into population studies could reduce the need for supplementary animal studies. This review makes a number of recommendations concerning the prioritisation of future activities on dietary biomarkers in relation to the Three Rs. It is emphasised, however, that further discussions will be required among toxicologists, epidemiologists and others researching the relationship between diet and health.

Potential Adverse Public Health Effects Afforded by the Ingestion of Dietary Lipid Oxidation Product Toxins: Significance of Fried Food Sources

Exposure of polyunsaturated fatty acid (PUFA)-rich culinary oils (COs) to high temperature frying practices generates high concentrations of cytotoxic and genotoxic lipid oxidation products (LOPs) via oxygen-fueled, recycling peroxidative bursts. These toxins, including aldehydes and epoxy-fatty acids, readily penetrate into fried foods and hence are available for human consumption; therefore, they may pose substantial health hazards. Although previous reports have claimed health benefits offered by the use of PUFA-laden COs for frying purposes, these may be erroneous in view of their failure to consider the negating adverse public health threats presented by food-transferable LOPs therein. When absorbed from the gastrointestinal (GI) system into the systemic circulation, such LOPs may significantly contribute to enhanced risks of chronic non-communicable diseases (NCDs), e.g. cancer, along with cardiovascular and neurological diseases. Herein, we provide a comprehensive rationale relating to the public health threats posed by the dietary ingestion of LOPs in fried foods. We begin with an introduction to sequential lipid peroxidation processes, describing the noxious effects of LOP toxins generated therefrom. We continue to discuss GI system interactions, the metabolism and biotransformation of primary lipid hydroperoxide LOPs and their secondary products, and the toxicological properties of these agents, prior to providing a narrative on chemically-reactive, secondary aldehydic LOPs available for human ingestion. In view of a range of previous studies focused on their deleterious health effects in animal and cellular model systems, some emphasis is placed on the physiological fate of the more prevalent and toxic α,β-unsaturated aldehydes. We conclude with a description of targeted nutritional and interventional strategies, whilst highlighting the urgent and unmet clinical need for nutritional and epidemiological trials probing relationships between the incidence of NCDs, and the frequency and estimated quantities of dietary LOP intake.

Intensification of serum albumin amyloidogenesis by a glycation-peroxidation loop (GPL)

The interaction of reducing sugars with proteins leads to the formation of advanced glycation end products (AGE) and reactive oxidative species (ROS). ROS peroxidise free or membrane included unsaturated fatty acids, leading to generate reactive aldehydes as advanced lipid peroxidation end products (ALE). Aldehydes from lipid peroxidation (LPO) react with proteins to cause alteration of protein structure to exacerbate complication of diseases. Here we studied serum albumin glycation in the presence and absence of liposomes as a bio-membrane model to investigate protein structural changes using various techniques including intrinsic and extrinsic fluorescence spectroscopies and electron microscopy analysis. Accordingly, serum albumin glycation and fibrillation were accelerated and intensified in the presence of liposomes through a hypothesized glycation-peroxidation loop (GPL). Together, our results shed light on the necessity of reconsidering diabetic protein glycation to make it close to physiological conditions mimicry, more importantly, proteins structural change due to diabetic glycation is intensified in the proximity of cell membranes which probably potentiates programmed cell death distinct from apoptosis.

Oxidative Stress in Poultry: Lessons from the Viral Infections

Reactive species (RS), generally known as reactive oxygen species (ROS) and reactive nitrogen species (RNS), are produced during regular metabolism in the host and are required for many cellular processes such as cytokine transcription, immunomodulation, ion transport, and apoptosis. Intriguingly, both RNS and ROS are commonly triggered by the pathogenic viruses and are famous for their dual roles in the clearance of viruses and pathological implications. Uncontrolled production of reactive species results in oxidative stress and causes damage in proteins, lipids, DNA, and cellular structures. In this review, we describe the production of RS, their detoxification by a cellular antioxidant system, and how these RS damage the proteins, lipids, and DNA. Given the widespread importance of RS in avian viral diseases, oxidative stress pathways are of utmost importance for targeted therapeutics. Therefore, a special focus is provided on avian virus-mediated oxidative stresses. Finally, future research perspectives are discussed on the exploitation of these pathways to treat viral diseases of poultry.

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.

Redox Signaling by Reactive Electrophiles and Oxidants

The concept of cell signaling in the context of nonenzyme-assisted protein modifications by reactive electrophilic and oxidative species, broadly known as redox signaling, is a uniquely complex topic that has been approached from numerous different and multidisciplinary angles. Our Review reflects on five aspects critical for understanding how nature harnesses these noncanonical post-translational modifications to coordinate distinct cellular activities: (1) specific players and their generation, (2) physicochemical properties, (3) mechanisms of action, (4) methods of interrogation, and (5) functional roles in health and disease. Emphasis is primarily placed on the latest progress in the field, but several aspects of classical work likely forgotten/lost are also recollected. For researchers with interests in getting into the field, our Review is anticipated to function as a primer. For the expert, we aim to stimulate thought and discussion about fundamentals of redox signaling mechanisms and nuances of specificity/selectivity and timing in this sophisticated yet fascinating arena at the crossroads of chemistry and biology.

A Novel Mechanism for Atherosclerotic Calcification: Potential Resolution of the Oxidation Paradox

AIM

In this study, we tested the hypothesis that lipid peroxide-derived dicarboxylic acids (DCAs), by virtue of their ability to bind to calcium (Ca), might be involved in atherosclerotic calcification. We determined the ability of azelaic acid (AzA) to promote calcification in human aortic smooth muscle cells (HASMCs), identified AzA in human calcified atherosclerotic lesions, and compared its levels with control and noncalcified atherosclerotic lesions.

RESULTS

HASMCs efficiently converted 9-oxononanoic acid (ONA), a lipid peroxide-derived monocarboxylic aldehyde, to AzA. In vitro incubations of AzA micelles with HASMC resulted in the formation of Ca deposits, which contained AzA. Liquid chromatography-mass spectrometry analysis of human control uninvolved artery, noncalcified, and calcified lesions showed significant increase of AzA in calcified lesions compared with noncalcified and control tissues. Calcified mouse atherosclerotic lesions also showed substantial presence of AzA in Ca complexes.

INNOVATION

This study identifies a DCA, AzA, as an integral part of the Ca complex. The study also demonstrates the conversion of a lipid peroxidation product, ONA, as a potential source of AzA, and establishes the presence of AzA in calcified materials isolated from human and mouse lesions.

CONCLUSION

The presence of AzA as a Ca sequestering agent in atherosclerotic lesions (i) might indicate participation of oxidized low-density lipoprotein (Ox-LDL) derived products in calcification, (ii) explain the potential correlation between calcification and overall plaque burden (as Ox-LDL has been suggested to be involved in atherogenesis), (iii) could contribute to plaque stabilization via its anti-inflammatory actions, and (iv) might explain why antioxidants failed to affect atherosclerosis in clinical studies. Antioxid. Redox Signal. 29, 471-483.

Impact of Atherosclerosis- and Diabetes-Related Dicarbonyls on Vascular Endothelial Permeability: A Comparative Assessment

Background

Malondialdehyde (MDA), glyoxal (GO), and methylglyoxal (MGO) levels increase in atherosclerosis and diabetes patients. Recent reports demonstrate that GO and MGO cause vascular endothelial barrier dysfunction whereas no evidence is available for MDA.

Methods

To compare the effects of MDA, GO, or MGO on endothelial permeability, we used human EA.hy926 endothelial cells as a standard model. To study cortical cytoplasm motility and cytoskeletal organization in endothelial cells, we utilized time-lapse microscopy and fluorescent microscopy. To compare dicarbonyl-modified protein band profiles in these cells, we applied Western blotting with antibodies against MDA- or MGO-labelled proteins.

Results

MDA (150–250 μM) irreversibly suppressed the endothelial cell barrier, reduced lamellipodial activity, and prevented intercellular contact formation. The motile deficiency of MDA-challenged cells was accompanied by alterations in microtubule and microfilament organization. These detrimental effects were not observed after GO or MGO (250 μM) administration regardless of confirmed modification of cellular proteins by MGO.

Conclusions

Our comparative study demonstrates that MDA is more damaging to the endothelial barrier than GO or MGO. Considering that MDA endogenous levels exceed those of GO or MGO and tend to increase further during lipoperoxidation, it appears important to reduce oxidative stress and, in particular, MDA levels in order to prevent sustained vascular hyperpermeability in atherosclerosis and diabetes patients.

3-n-Butylphthalide reduces the oxidative damage of muscles in an experimental autoimmune myositis animal model

3-n-Butylphthalide (NBP) protects the mitochondria and reduces apoptosis in multiple disease models. However, it remains to be determined whether NBP can protect muscle cells from oxidative stress, lipid peroxidation and apoptosis in myositis. In the present study, a myosin immunization protocol was applied to induce experimental autoimmune myositis (EAM) in guinea pigs. After 4 weeks, a low- or high-dose NBP solution was injected intraperitoneally into the guinea pigs, with saline solution serving as the negative control. After 10 days, the guinea pigs were sacrificed and muscle cells were isolated for analysis. The results revealed that NBP increased the superoxide dismutase and catalase activity, and reduced malondialdehyde activity in the EAM model. Furthermore, NBP enhanced ATPase activity in muscle mitochondrial membranes and muscle fiber membranes, reduced the number of apoptotic cells, and differentially regulated the Bcl-2, Bax and BAD mRNA and protein expression levels in muscle tissues and sera. NBP directly protects muscle mitochondria and muscle cells from oxidative damage. Notably, NBP reduced muscle cell apoptosis. Thus, it is speculated that, as an antioxidant treatment, NBP may benefit individuals with myopathy.

Dicarbonyls and Advanced Glycation End-Products in the Development of Diabetic Complications and Targets for Intervention

Advanced glycation end-products (AGEs) are non-enzymatic protein and amino acid adducts as well as DNA adducts which form from dicarbonyls and glucose. AGE formation is enhanced in diabetes and is associated with the development of diabetic complications. In the current review, we discuss mechanisms that lead to enhanced AGE levels in the context of diabetes and diabetic complications. The methylglyoxal-detoxifying glyoxalase system as well as alternative pathways of AGE detoxification are summarized. Therapeutic approaches to interfere with different pathways of AGE formation are presented.

Reaction Mechanism of Covalent Modification of Phosphatidylethanolamine Lipids by Reactive Aldehydes 4-Hydroxy-2-nonenal and 4-Oxo-2-nonenal

4-Hydroxy-2-nonenal (HNE) and 4-oxo-2-nonenal (ONE) are biologically important reactive aldehydes formed during oxidative stress in phospholipid bilayers. They are highly reactive species due to presence of several reaction centers and can react with amino acids in peptides and proteins, as well as phosphoethanolamine (PE) lipids, thus modifying their biological activity. The aim of this work is to study in a molecular detail the reactivity of HNE and ONE toward PE lipids in a simplified system containing only lipids and reactive aldehydes in dichloromethane as an inert solvent. We use a combination of quantum chemical calculations, ¹H NMR measurements, FT-IR spectroscopy, and mass spectrometry experiments and show that for both reactive aldehydes two types of chemical reactions are possible: formation of Michael adducts and Schiff bases. In the case of HNE, an initially formed Michael adduct can also undergo an additional cyclization step to a hemiacetal derivative, whereas no cyclization occurs in the case of ONE and a Michael adduct is identified. A Schiff base product initially formed when HNE is added to PE lipid can also further cyclize to a pyrrole derivative in contrast to ONE, where only a Schiff base product is isolated. The suggested reaction mechanism by quantum-chemical calculations is in a qualitative agreement with experimental yields of isolated products and is also additionally investigated by ¹H NMR measurements, FT-IR spectroscopy, and mass spectrometry experiments.

Metal oxide nanoparticles as antimicrobial agents: a promise for the future

Microbial infectious diseases are a global threat to human health. Excess and improper use of antibiotics has created antimicrobial-resistant microbes that can defy clinical treatment. The hunt for safe and alternate antimicrobial agents is on in order to overcome such resistant micro-organisms, and the birth of nanotechnology offers promise to combat infectious organisms. Over the past two decades, metal oxide nanoparticles (MeO-NPs) have become an attractive alternative source to combat microbes that are highly resistant to various classes of antibiotics. Their vast array of physicochemical properties enables MeO-NPs to act as antimicrobial agents through various mechanisms. Apart from exhibiting antimicrobial properties, MeO-NPs also serve as carriers of drugs, thus barely providing a chance for micro-organisms to develop resistance. These immense multiple properties exhibited by MeO-NPs will have an impact on the treatment of deadly infectious diseases. This review discusses the mechanisms of action of MeO-NPs against micro-organisms, safety concerns, challenges and future perspectives.

The Role of Oxidative Stress in Diabetic Neuropathy: Generation of Free Radical Species in the Glycation Reaction and Gene Polymorphisms Encoding Antioxidant Enzymes to Genetic Susceptibility to Diabetic Neuropathy in Population of Type I Diabetic Patients

Diabetic neuropathy (DN) represents the main cause of morbidity and mortality among diabetic patients. Clinical data support the conclusion that the severity of DN is related to the frequency and duration of hyperglycemic periods. The presented experimental and clinical evidences propose that changes in cellular function resulting in oxidative stress act as a leading factor in the development and progression of DN. Hyperglycemia- and dyslipidemia-driven oxidative stress is a major contributor, enhanced by advanced glycation end product (AGE) formation and polyol pathway activation. There are several polymorphous pathways that lead to oxidative stress in the peripheral nervous system in chronic hyperglycemia. This article demonstrates the origin of oxidative stress derived from glycation reactions and genetic variations within the antioxidant genes which could be implicated in the pathogenesis of DN. In the diabetic state, unchecked superoxide accumulation and resultant increases in polyol pathway activity, AGEs accumulation, protein kinase C activity, and hexosamine flux trigger a feed-forward system of progressive cellular dysfunction. In nerve, this confluence of metabolic and vascular disturbances leads to impaired neural function and loss of neurotrophic support, and over the long term, can mediate apoptosis of neurons and Schwann cells, the glial cells of the peripheral nervous system. In this article, we consider AGE-mediated reactive oxygen species (ROS) generation as a pathogenesis factor in the development of DN. It is likely that oxidative modification of proteins and other biomolecules might be the consequence of local generation of superoxide on the interaction of the residues of L-lysine (and probably other amino acids) with α-ketoaldehydes. This phenomenon of non-enzymatic superoxide generation might be an element of autocatalytic intensification of pathophysiological action of carbonyl stress. Glyoxal and methylglyoxal formed during metabolic pathway are detoxified by the glyoxalase system with reduced glutathione as co-factor. The concentration of reduced glutathione may be decreased by oxidative stress and by decreased in situ glutathione reductase activity in diabetes mellitus. Genetic variations within the antioxidant genes therefore could be implicated in the pathogenesis of DN. In this work, the supporting data about the association between the -262T > C polymorphism of the catalase (CAT) gene and DN were shown. The -262TT genotype of the CAT gene was significantly associated with higher erythrocyte catalase activity in blood of DN patients compared to the -262CC genotype (17.8 ± 2.7 × 10(4) IU/g Hb vs. 13.5 ± 3.2 × 10(4) IU/g Hb, P = 0.0022). The role of these factors in the development of diabetic complications and the prospective prevention of DN by supplementation in formulations of transglycating imidazole-containing peptide-based antioxidants (non-hydrolyzed carnosine, carcinine, n-acetylcarcinine) scavenging ROS in the glycation reaction, modifying the activity of enzymic and non-enzymic antioxidant defenses that participate in metabolic processes with ability of controlling at transcriptional levels the differential expression of several genes encoding antioxidant enzymes inherent to DN in Type I Diabetic patients, now deserve investigation.

A Clinical Trial about a Food Supplement Containing α-Lipoic Acid on Oxidative Stress Markers in Type 2 Diabetic Patients

The aim of this study was to evaluate the effect of a food supplement containing α-lipoic acid and of a placebo on glyco-metabolic control and on oxidative stress markers in type 2 diabetics. We randomized 105 diabetics to either a supplementation containing 600 mg of α-lipoic acid, 165 mg of L-carnosin, 7.5 mg of zinc, and vitamins of group B, or a placebo, for three months. We evaluated body mass index, fasting plasma glucose (FPG), post-prandial-glucose (PPG), glycated hemoglobin (HbA_1c), fasting plasma insulin (FPI), HOMA-index (HOMA-IR), lipid profile, high sensitivity C-reactive protein (Hs-CRP), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), malondialdehyde (MDA). There was a reduction of FPG, PPG, and HbA_1c with the food supplement containing α-lipoic acid compared with a baseline, and with the placebo. Concerning lipid profile, we observed a reduction of LDL-C, and Tg with the food supplement, compared with both the baseline, and the placebo. There was a reduction of Hs-CRP with the food supplement containing α-lipoic acid, both compared with the baseline and the placebo. An increase of SOD, and GSH-Px, and a decrease of MDA were reached by the food supplement containing α-lipoic acid, both compared with the baseline and the placebo. We can conclude that the food supplement containing α-lipoic acid, L-carnosin, zinc, and vitamins of group B improved glycemic control, lipid profile, and anti-oxidative stress markers.

Impact of Malondialdehyde-Modified Low-Density Lipoprotein on Tissue Characteristics in Patients With Stable Coronary Artery Disease - Integrated Backscatter-Intravascular Ultrasound Study

BACKGROUND

Malondialdehyde-modified low-density lipoprotein (MDA-LDL) is considered to play an essential role in plaque destabilization. We aimed to investigate the association between the tissue characteristics of culprit plaque assessed by integrated backscatter (IB)-intravascular ultrasound (IVUS) and the serum MDA-LDL levels in patients with stable coronary artery disease.

METHODS AND RESULTS

The study group consisted of 179 patients undergoing IB-IVUS during elective percutaneous coronary intervention. Patients were classified into 2 groups based on serum MDA-LDL level: low MDA-LDL group (<102 U/L, n=88) and high MDA-LDL group (≥102 U/L, n=91). Plaques in the high MDA-LDL group had higher %lipid (45.2±12.5% vs. 54.9±14.5%, P<0.001) and lower %fibrosis (43.0±9.1% vs. 36.4±11.4%, P<0.001) than did plaques in the low MDA-LDL group. Lipid-rich plaque (%lipid >60% or %fibrosis <30%) was significantly more frequently found in the high MDA-LDL group than in the low MDA-LDL group (14.3% vs. 39.8%, P<0.001). The incidence of MACE (cardiac death, myocardial infarction and/or hospitalization for heart failure) during 3 years was significantly higher in the high MDA-LDL group than in the low MDA-LDL group (6.6% vs. 15.9%, P=0.02).

CONCLUSIONS

Higher MDA-LDL might be associated with greater lipid and lower fibrous content, contributing to coronary plaque vulnerability. (Circ J 2016; 80: 2173-2182).

Oxidative injury in multiple sclerosis cerebellar grey matter

Cerebellar dysfunction is a significant contributor to disability in multiple sclerosis (MS). Both white matter (WM) and grey matter (GM) injury occurs within MS cerebellum and, within GM, demyelination, inflammatory cell infiltration and neuronal injury contribute to on-going pathology. The precise nature of cerebellar GM injury is, however, unknown. Oxidative stress pathways with ultimate lipid peroxidation and cell membrane injury occur extensively in MS and the purpose of this study was to investigate these processes in MS cerebellar GM. Post-mortem human cerebellar GM from MS and control subjects was analysed immunohistochemically, followed by semi-quantitative analysis of markers of cellular injury, lipid peroxidation and anti-oxidant enzyme expression. We have shown evidence for reduction in myelin and neuronal markers in MS GM, coupled to an increase in expression of a microglial marker. We also show that the lipid peroxidation product 4-hydroxynonenal co-localises with myelin and its levels negatively correlate to myelin basic protein levels. Furthermore, superoxide dismutase (SOD1 and 2) enzymes, localised within cerebellar neurons, are up-regulated, yet the activation of subsequent enzymes responsible for the detoxification of hydrogen peroxide, catalase and glutathione peroxidase are relatively deficient. These studies provide evidence for oxidative injury in MS cerebellar GM and further help define disease mechanisms within the MS brain.

An experimentally robust model of monomeric apolipoprotein A-I created from a chimera of two X-ray structures and molecular dynamics simulations

High-density lipoprotein (HDL) retards atherosclerosis by accepting cholesterol from the artery wall. However, the structure of the proposed acceptor, monomeric apolipoprotein A-I (apoA-I), the major protein of HDL, is poorly understood. Two published models for monomeric apoA-I used cross-linking distance constraints to derive best fit conformations. This approach has limitations. (i) Cross-linked peptides provide no information about secondary structure. (ii) A protein chain can be folded in multiple ways to create a best fit. (iii) Ad hoc folding of a secondary structure is unlikely to produce a stable orientation of hydrophobic and hydrophilic residues. To address these limitations, we used a different approach. We first noted that the dimeric apoA-I crystal structure, (Δ185-243)apoA-I, is topologically identical to a monomer in which helix 5 forms a helical hairpin, a monomer with a hydrophobic cleft running the length of the molecule. We then realized that a second crystal structure, (Δ1-43)apoA-I, contains a C-terminal structure that fits snuggly via aromatic and hydrophobic interactions into the hydrophobic cleft. Consequently, we combined these crystal structures into an initial model that was subjected to molecular dynamics simulations. We tested the initial and simulated models and the two previously published models in three ways: against two published data sets (domains predicted to be helical by H/D exchange and six spin-coupled residues) and against our own experimentally determined cross-linking distance constraints. We note that the best fit simulation model, superior by all tests to previously published models, has dynamic features of a molten globule with interesting implications for the functions of apoA-I.

Malonyldialdehyde and glyoxal act differently on low-density lipoproteins and endotheliocytes

Under some pathological conditions, the natural dicarbonyl compounds can accumulate in the blood. The examples are malonyldialdehyde (MDA) formed as a secondary product of lipid peroxidation of unsaturated fatty acids during atherosclerosis, and glyoxal (GOX), a homolog of MDA, which accumulates during glucose autoxidation in patients with diabetes mellitus. This study compared the influence of both dicarbonyl compounds on low-density lipoproteins (LDL) and the membrane of endotheliocytes. In comparison with GOX, MDA induced more pronounced changes in physical and chemical properties of LDL particles. On the other hand, GOX-modified LDL particles were more prone to oxidation and aggregation than MDA-modified LDL. Incubation of endotheliocytes with MDA increased cell mechanical stiffness in contrast to incubation with GOX, which decreased it.

The initiation of free radical peroxidation of low-density lipoproteins by glucose and its metabolite methylglyoxal: a common molecular mechanism of vascular wall injure in atherosclerosis and diabetes

It was found that glucose in the range of concentrations 12.5-100 mM stimulated Cu(2+)-mediated free radical peroxidation of low-density lipoproteins (LDL) from human blood plasma. Considering the kinetic parameters of LDL peroxidation we proposed that intensification of this process may be caused by formation of free radical intermediates of glucose auto-oxidation. Addition of SOD to the medium inhibited LDL oxidation, indicating the formation of superoxide anion-radicals under autoxidation of glucose. Similarly, SOD inhibited free radical peroxidation of liposomes from egg lecithin in the presence of glucose that confirms the generation of superoxide radicals under co-oxidation of unsaturated lipids and glucose. Normalization of glucose level in the blood of patients with type 2 diabetes mellitus during therapy was accompanied by a significant decrease in LDL oxidation in vivo (the decrease in primary and secondary lipoperoxidation products). The formation of superoxide anion-radicals was observed during interaction of aminoacid L-lysine with a product of glucose oxidative metabolism-methylglyoxal, but not with a product of lipoperoxidation malonyldialdehyde. In accordance with the foregoing the administration of sugar-lowering drug metformin, which binds and utilizes methylglyoxal, caused a stronger inhibition of LDL peroxidation in the blood of patients with diabetes mellitus, probably due to decrease in methylglyoxal-dependent generation of superoxide anion-radicals. Based on the results we set out the hypothesis about autocatalytic mechanism of free radical reactions involving natural dicarbonyls and suppose the common molecular mechanism of vascular wall injury in atherosclerosis and diabetes.