The significance of lipid peroxidation in cardiovascular disease

The interaction of human serum components with model membranes containing phospholipids and lipopolysaccharides

Lipoproteins, key mediators of lipid transport, facilitate the bidirectional transfer of lipids such as fatty acids, triglycerides, and cholesterol between soluble particles and cell membranes. High-density lipoproteins (HDL) primarily engage in reverse cholesterol transport, while low-density lipoproteins (LDL) predominantly deposit lipids, affecting cardiovascular health with a well-known role in the formation of the atherosclerotic plaque. In addition, lipoproteins play an important role in neutralizing bacterial lipopolysaccharides (LPS), the major component of Gram-negative bacterial outer membranes, which act as potent TLR4 agonists and can trigger severe immune responses. Lipoproteins bind LPS in plasma, with HDL showing strong binding affinity and LDL contributing to LPS clearance under specific conditions. Here, we explore the interaction of LDL and human serum albumin (HSA), another serum lipid-binding protein, with model lipid bilayers containing either phospholipids or LPS. Using neutron reflectometry and attenuated total reflection infrared spectroscopy, we characterize lipid transfer processes influenced by calcium levels and lipid composition. Calcium plays a key role in receptor-mediated LDL binding, but less is known on its effect on LDL-mediated lipid transfer in the absence of LDL receptors. Our results show that elevated calcium levels enhance stable LDL adsorption onto mammalian phospholipid-cholesterol membranes, promoting lipid cargo deposition despite the absence of specific LDL-receptors. Conversely, LDL showed no stable binding to LPS reconstituted in asymmetric outer membrane models but was able to deposit phospholipids in the membrane. In contrast, HSA removed lipids from mammalian membranes and exhibited minimal interaction with LPS-containing models. The findings elucidate the distinct lipid exchange mechanisms of LDL and HSA and their roles in modulating lipid transfer at membrane interfaces. Receptor-free enhanced LDL lipid deposition in calcium-enriched environments may have implications for cardiovascular disease progression. Conversely, the minimal interaction of LDL with bacterial LPS suggests a limited ability to extract LPS from membrane environments. This study provides structural insights into the interplay between lipoproteins, calcium, and membrane composition, with relevance to atherosclerosis and systemic endotoxemia.

Resveratrol reduced the detrimental effects of malondialdehyde on human endothelial cells

Introduction: According to the statistics, vascular injury occurs during the onset of diabetic changes after the production of several byproducts. Many authorities have focused to find an alternative therapy for diabetic patients. In this study, we investigated the therapeutic effects of natural polyphenol like resveratrol on human endothelial cells exposed to malondialdehyde for 48 hours.

Methods: Human Umbilical Vein Endothelial Cells were randomly classified into four groups;control, malondialdehyde (2.5 mM), resveratrol (100 μM), and cells received the combined regime for 48 hours. Cell viability was determined by 3-(4, 5-dimethyl thiazol-2-yl) 2, 5-diphenyl-tetrazoliumbromide (MTT) assay. Griess reaction was performed to measure the content of Nitric oxide (NO).Apoptosis was studied by using real-time polymerase chain reaction (RT-PCR) and western blotting assays. Levels of receptor tyrosine kinases like VEGFR-1, -2, Tie-1, and -2 were analyzed by enzyme-linked immunosorbent assay(ELISA). The affinity of resveratrol and malondialdehyde to serum albumin was measured by Surface Plasmon Resonance Assay. Any changes in chromatin remodeling were detected by PCR array analysis.

Results: Resveratrol reduced cytotoxicity and NO content inside cells induced by malondialdehyde(MDA) (P < 0.05). Endothelial cell apoptosis was decreased by the reduction of pro-apoptotic factor Bax and increase of Bcl-2 following the incubation with resveratrol (P < 0.05). MDA-induced receptor tyrosine kinases increase was inhibited by resveratrol and reached near-to-normal levels (P < 0.05).Surface Plasmon Resonance revealed a higher affinity of resveratrol to albumin compared to the malondialdehyde-albumin complex. Polymerase chain reaction (PCR) array revealed the potency of resveratrol in chromatin remodeling following the treatment with malondialdehyde (P < 0.05).

Conclusion: Based on our findings, resveratrol has the potential to decrease diabetic vascular injury induced by lipid byproducts such as MDA.

Effect of 5-trans Isomer of Arachidonic Acid on Model Liposomal Membranes Studied by a Combined Simulation and Experimental Approach

Unsaturated fatty acids are found in humans predominantly in the cis configuration. Fatty acids in the trans configuration are primarily the result of human processing (trans fats), but can also be formed endogenously by radical stress. The cis-trans isomerization of fatty acids by free radicals could be connected to several pathologies. Trans fats have been linked to an increased risk of coronary artery disease; however, the reasons for the resulting pathogenesis remain unclear. Here, we investigate the effect of a mono-trans isomer of arachidonic acid (C20:4-5trans, 8cis, 11cis, 14cis) produced by free radicals in physiological concentration on a model erythrocyte membrane using a combined experimental and theoretical approach. Molecular Dynamics (MD) simulations of two model lipid bilayers containing arachidonic acid and its 5-trans isomer in 3 mol% were carried out for this purpose. The 5-trans isomer formation in the phospholipids was catalyzed by HOCH₂CH₂S· radicals, generated from the corresponding thiol by γ-irradiation, in multilamellar vesicles of SAPC. Large unilamellar vesicles were made by the extrusion method (LUVET) as a biomimetic model for cis-trans isomerization. Atomic Force Microscopy and Dynamic Light Scattering were used to measure the average size, morphology, and the z-potential of the liposomes. Both results from MD simulations and experiments are in agreement and indicate that the two model membranes display different physicochemical properties in that the bilayers containing the trans fatty acids were more ordered and more rigid than those containing solely the cis arachidonic acid. Correspondingly, the average size of the liposomes containing trans isomers was smaller than the ones without.

Lipoprotein binding to anionic biopolyelectrolytes and the effect of glucose on nanoplaque formation in arteriosclerosis and Alzheimer's disease

Arteriosclerosis with its clinical sequelae (cardiac infarction, stroke, peripheral arterial occlusive disease) and vascular/Alzheimer dementia not only result in far more than half of all deaths but also represent dramatic economic problems. The reason is, among others, that diabetes mellitus is an independent risk factor for both disorders, and the number of diabetics strongly increases worldwide. More than one-half of infants in the first 6months of life have already small collections of macrophages and macrophages filled with lipid droplets in susceptible segments of the coronary arteries. On the other hand, the authors of the Bogalusa Heart Study found a strong increase in the prevalence of obesity in childhood that is paralleled by an increase in blood pressure, blood lipid concentration, and type 2 diabetes mellitus. Thus, there is a clear linkage between arteriosclerosis/Alzheimer's disease on the one hand and diabetes mellitus on the other hand. Furthermore, it has been demonstrated that distinct apoE isoforms on the blood lipids further both arteriosclerotic and Alzheimer nanoplaque formation and therefore impair flow-mediated vascular reactivity as well. Nanoplaque build-up seems to be the starting point for arteriosclerosis and Alzheimer's disease in their later full clinical manifestation. In earlier work, we could portray the anionic biopolyelectrolytes syndecan/perlecan as blood flow sensors and lipoprotein receptors in cell membrane and vascular matrix. We described extensively molecular composition, conformation, form and function of the macromolecule heparan sulfate proteoglycan (HS-PG). In two supplementary experimental settings (ellipsometry, myography), we utilized isolated HS-PG for in vitro nanoplaque investigations and isolated human coronary artery segments for in vivo tension measurements. With the ellipsometry-based approach, we were successful in establishing a direct connection on a molecular level between diabetes mellitus on the one side and arteriosclerosis/Alzheimer's disease on the other side. Application of glucose at a concentration representative for diabetics and leading to glycation of proteins and lipids, entailed a significant increase in arteriosclerotic and Alzheimer nanoplaque formation. IDLapoE4/E4 was by far superior to IDLapoE3/E3 in plaque build-up, both in diabetic and non-diabetic patients. Recording vascular tension of flow-dependent reactivity in blood substitute solution and under application of different IDLapoE isoforms showed an impaired vasorelaxation for pooled IDL and IDLapoE4/E4, thus confirming the ellipsometric investigations. Incubation in IDLapoE0/E0 (apoE "knockout man"), however, resulted in a massive flow-mediated contraction, also complemented by strongly aggregated nanoplaques. In contrast, HDL was shown to present a powerful protection against nanoplaque formation on principle, both in the in vitro model and the in vivo scenario on the endothelial cell membrane. The competitive interplay with LDL is highlighted through the flow experiment, where flow-mediated, HDL-induced vasodilatation remains untouched by additional incubation with LDL. This is due to the four times higher affinity for the proteoglycan receptor of HDL as compared to LDL. Taken together, the studies demonstrate that while simplistic, the ellipsometry approach and the endothelial-mimicking proteoglycan-modified surfaces provide information on the initial steps of lipoprotein-related plaque formation, which correlates with findings on endothelial cells and blood vessels, and afford insight into the role of lipoprotein deposition and exchange phenomena at the onset of these pathophysiologies.

Polydopamine-assisted deposition of heparin for selective adsorption of low-density lipoprotein

Low-density lipoprotein (LDL) is the main carrier of blood cholesterol, with elevated levels of LDL increasing the risk of atherosclerosis.

Combined lowering of low grade systemic inflammation and insulin resistance in metabolic syndrome patients treated with Ginkgo biloba

In a clinical pilot study with eleven metabolic syndrome patients, a simultaneous decrease in hs-CRP from 8.85 ± 4.09 to 4.92 ± 2.51 mg/L (-44.4%) (p < 0.0436) and HOMA-IR from 3.07 ± 0.63 to 2.60 ± 0.51 mU/L × mg/dL (-15.3%) (p < 0.0120) as well as a beneficial change of arteriosclerotic, inflammatory and oxidative stress biomarkers were detected after 2-month treatment with Ginkgo biloba. Furthermore, both IL-6 (-12.9%, p < 0.0407) and nanoplaque formation (-14.3%, p < 0.0077) were additionally reduced. According to a large clinical trial elucidating the importance of insulin resistance and low-grade systemic inflammation for cardiovascular disease and overall mortality risk, these data might indicate a CVD/total mortality risk reduction.

Cardiovascular disease detection using bio-sensing techniques

Universally, cardiovascular disease (CVD) is recognised as the prime cause of death with estimates exceeding 20 million by 2015 due to heart disease and stroke. Facts regarding the disease, its classification and diagnosis are still lacking. Hence, understanding the issues involved in its initiation, its symptoms and early detection will reduce the high risk of sudden death associated with it. Biosensors developed to be used as rapid screening tools to detect disease biomarkers at the earliest stage and able to classify the condition are revolutionising CVD diagnosis and prognosis. Advances in interdisciplinary research areas have made biosensors faster, highly accurate, portable and environmentally friendly diagnostic devices. The recent advances in microfluidics and the advent of nanotechnology have resulted in the development of improved diagnostics through reduction of analysis time and integration of several clinical assays into a single, portable device as lab-on-a-chip (LOC). The development of such affinity based systems is a major drive of the rapidly growing nanotechnology industry which involves a multidisciplinary research effort encompassing nanofluidics, microelectronics and analytical chemistry. This review summarised the classification of CVD, the biomarkers used for its diagnosis, biosensors and their application including the latest developments in the field of heart-disease detection.

Optical aptasensors for quantitative detection of small biomolecules: a review

Aptasensors are aptamer-based biosensors with excellent recognition capability towards a wide range of targets. Specially, there have been ever-growing interests in the development of aptasensors for the detection of small molecules. This phenomenon is contributed to two reasons. On one hand, small biomolecules play an important role in living organisms with many kinds of biological function, such as antiarrhythmic effect and vasodilator activity of adenosine. On the other hand, the concentration of small molecules can be an indicator for disease diagnosis, for example, the concentration of ATP is closely associated with cell injury and cell viability. As a potential analysis tool in the construction of aptasensors, optical analysis has attracted much more interest of researchers due to its high sensitivity, quick response and simple operation. Besides, it promises the promotion of aptasensors in performance toward a new level. Review the development of optical aptasensors for small biomolecules will give readers an overall understanding of its progress and provide some theoretical guidelines for its future development. Hence, we give a mini-review on the advance of optical aptasensors for small biomolecules. This review focuses on recent achievements in the design of various optical aptasensors for small biomolecules, containing fluorescence aptasensors, colorimetric aptasensors, chemiluminescence aptasensors and other optical aptasensors.

Anionic biopolyelectrolytes of the syndecan/perlecan superfamily: physicochemical properties and medical significance

In the review article presented here, we demonstrate that the connective tissue is more than just a matrix for cells and a passive scaffold to provide physical support. The extracellular matrix can be subdivided into proteins (collagen, elastin), glycoconjugates (structural glycoproteins, proteoglycans) and glycosaminoglycans (hyaluronan). Our main focus rests on the anionic biopolyelectrolytes of the perlecan/syndecan superfamily which belongs to extracellular matrix and cell membrane integral proteoglycans. Though the extracellular domain of the syndecans may well be performing a structural role within the extracellular matrix, a key function of this class of membrane intercalated proteoglycans may be to act as signal transducers across the plasma membrane and thus be more appropriately included in the group of cell surface receptors. Nevertheless, there is a continuum in functions of syndecans and perlecans, especially with respect to their structural role and biomedical significance. HS/CS proteoglycans are receptor sites for lipoprotein binding thus intervening directly in lipid metabolism. We could show that among all lipoproteins, HDL has the highest affinity to these proteoglycans and thus instals a feedforward forechecking loop against atherogenic apoB100 lipoprotein deposition on surface membranes and in subendothelial spaces. Therefore, HDL is not only responsible for VLDL/IDL/LDL cholesterol exit but also controls thoroughly the entry. This way, it inhibits arteriosclerotic nanoplaque formation. The ternary complex 'lipoprotein receptor (HS/CS-PG) - lipoprotein (LDL, oxLDL, Lp(a)) - calcium' may be interpreted as arteriosclerotic nanoplaque build-up on the molecular level before any cellular reactivity, possibly representing the arteriosclerotic primary lesion combined with endothelial dysfunction. With laser-based ellipsometry we could demonstrate that nanoplaque formation is a Ca(2+)-driven process. In an in vitro biosensor application of HS-PG coated silica surfaces we tested nanoplaque formation and size in clinical trials with cardiovascular high-risk patients who underwent treatment with ginkgo or fluvastatin. While ginkgo reduced nanoplaque formation (size) by 14.3% (23.4%) in the isolated apoB100 lipid fraction at a normal blood Ca(2+) concentration, the effect of the statin with a reduction of 44.1% (25.4%) was more pronounced. In addition, ginkgo showed beneficial effects on several biomarkers of oxidative stress and inflammation. Besides acting as peripheral lipoprotein binding receptor, HS/CS-PG is crucially implicated in blood flow sensing. A sensor molecule has to fulfil certain mechanochemical and mechanoelectrical requirements. It should possess viscoelastic and cation binding properties capable of undergoing conformational changes caused both mechanically and electrostatically. Moreover, the latter should be ion-specific. Under no-flow conditions, the viscoelastic polyelectrolyte at the endothelium - blood interface assumes a random coil form. Blood flow causes a conformational change from the random coil state to the directed filament structure state. This conformational transition effects a protein unfurling and molecular elongation of the GAG side chains like in a 'stretched' spring. This configuration is therefore combined with an increase in binding sites for Na(+) ions. Counterion migration of Na(+) along the polysaccharide chain is followed by transmembrane Na(+) influx into the endothelial cell and by endothelial cell membrane depolarization. The simultaneous Ca(2+) influx releases NO and PGI2, vasodilatation is the consequence. Decrease in flow reverses the process. Binding of Ca(2+) and/or apoB100 lipoproteins (nanoplaque formation) impairs the flow sensor function. The physicochemical and functional properties of proteoglycans are due to their amphiphilicity and anionic polyelectrolyte character. Thus, they potently interact with cations, albeit in a rather complex manner. Utilizing (23)Na(+) and (39)K(+) NMR techniques, we could show that, both in HS-PG solutions and in native vascular connective tissue, the mode of interaction for monovalent cations is competition. Mg(2+) and Ca(2+) ions, however, induced a conformational change leading to an increased allosteric, cooperative K(+) and Na(+) binding, respectively. Since extracellular matrices and basement membranes form a tight-fitting sheath around the cell membrane of muscle and Schwann cells, in particular around sinus node cells of the heart, and underlie all epithelial and endothelial cell sheets and tubes, a release of cations from or an adsorption to these polyanionic macromolecules can transiently lead to fast and drastic activity changes in these tiny extracellular tissue compartments. The ionic currents underlying pacemaker and action potential of sinus node cells are fundamentally modulated. Therefore, these polyelectrolytic ion binding characteristics directly contribute to and intervene into heart rhythm.