Arg123-Tyr166 domain of human ApoA-I is critical for HDL-mediated inhibition of macrophage homing and early atherosclerosis in mice

Cyclodextrin Ameliorates the Progression of Atherosclerosis via Increasing High-Density Lipoprotein Cholesterol Plasma Levels and Anti-inflammatory Effects in Rabbits

To investigate the therapeutic effects of cyclodextrin on the development of atherosclerosis in rabbits, we evaluated the effects of (2-hydroxypropyl)-β-cyclodextrin (HPβCD) therapy on the organ coefficient, lipid profiles, inflammatory cytokines, and atherosclerotic plaques in rabbits fed a high-fat diet. Our results demonstrated that HPβCD therapy reduced plasma triglyceride levels and inflammatory cytokine levels but increased plasma high-density lipoprotein cholesterol levels. HPβCD therapy produced a significant decrease in the atherosclerotic lesion area and reduced macrophage and collagen content in the lesions. The expression levels of inflammatory genes in aortic plaques were significantly reduced by HPβCD treatment, but the expression of ATP-binding cassette (ABC) transporters A1 (ABCA1) and G1 (ABCG1) in aortic plaques and livers increased significantly. HPβCD therapy may produce additional antiatherosclerotic benefits likely via increasing high-density lipoprotein cholesterol levels.

Synergistic epistasis of paraoxonase 1 (rs662 and rs85460) and apolipoprotein E4 genes in pathogenesis of Alzheimer's disease and vascular dementia

Genetic polymorphism and epistasis play a role in etiopathogenesis of Alzheimer's disease (AD) and vascular dementia (VaD). In this case-control study, a total of 241 patients were included in the study to see the effect of paraoxonase 1 (PON1; rs662 and rs85460) and apolipoprotein E (ApoE) genes in altering the odds of having AD and VaD along with serum PON and lipid profile. The presence of at least 1 variant allele of rs662, but not rs85460, increased the risk of having AD by 1.8-fold (95% confidence interval [CI]: 0.97-3.40) and VaD by 3.09-fold (95% CI: 1.4-6.9). The interaction between PON1 genes (rs662 and rs85460) and ApoE genes showed synergistic epistasis in altering the odds of significantly having both AD and VaD. On the other hand, low serum level of high-density lipoprotein and low level of serum PON activity were found associated significantly (P ≤ .001 in both cases) only in patients with VaD as compared to healthy control.

Heterogeneous vascular responses to lifestyle intervention in obese Latino adolescents

BACKGROUND/OBJECTIVES

Among adolescents, obesity may increase the risk for premature cardiovascular disease (CVD). Lifestyle interventions may prevent or delay the onset of CVD through improvements in vascular health. The purpose of this study was to examine the effects of a 12-week lifestyle intervention on markers of vascular health in obese Latino youth.

SUBJECTS/METHODS

Fifteen obese Latino adolescents [body mass index (BMI) percentile=96.3±1.1%, 15.0±1.0 year, 8 females and 7 males] participated in a 12-week lifestyle intervention consisting of nutrition education and physical activity. Markers of vascular health included oxidized low-density lipoprotein (oxLDL), soluble intercellular adhesion molecule-1 (sICAM-1), soluble vascular cell adhesion molecule-1 (sVCAM-1), and soluble endothelial leukocyte adhesion molecule-1 (sE-Selectin).

RESULTS

Relative to baseline data, the intervention resulted in lower oxLDL (-21.8%, P=0.001) and sE-Selectin (-13.3%, P=0.008) concentrations; sICAM-1 and sVCAM-1 did not change significantly. When examining overall responsiveness to change for each marker, oxLDL was reduced in 93.3%, sE-Selectin was reduced in 78.6%, and sICAM-1 was reduced in 71.4% of participants, respectively, whereas sVCAM-1 was reduced in only 42.9% of participants following lifestyle. Using a composite change score (summed change in four markers) for each participant there was an improvement in at least three of four markers among 64% of participants; this was confirmed by principal component analysis.

CONCLUSIONS

Therefore, although improvements in the vascular health of obese youth were observed, the vascular response to lifestyle intervention may be heterogeneous. Further investigation into the mechanisms mediating the heterogeneity in vascular response to lifestyle intervention is warranted.

Gαi2 is the essential Gαi protein in immune complex-induced lung disease

Heterotrimeric G proteins of the Gα(i) family have been implicated in signaling pathways regulating cell migration in immune diseases. The Gα(i)-protein-coupled C5a receptor is a critical regulator of IgG FcR function in experimental models of immune complex (IC)-induced inflammation. By using mice deficient for Gα(i2) or Gα(i3), we show that Gα(i2) is necessary for neutrophil influx in skin and lung Arthus reactions and agonist-induced neutrophilia in the peritoneum, whereas Gα(i3) plays a less critical but variable role. Detailed analyses of the pulmonary IC-induced inflammatory response revealed several shared functions of Gα(i2) and Gα(i3), including mediating C5a anaphylatoxin receptor-induced activation of macrophages, involvement in alveolar production of chemokines, transition of neutrophils from bone marrow into blood, and modulation of CD11b and CD62L expression that account for neutrophil adhesion to endothelial cells. Interestingly, C5a-stimulated endothelial polymorphonuclear neutrophil transmigration, but not chemotaxis, is enhanced versus reduced in the absence of neutrophil Gα(i3) or Gα(i2), respectively, and knockdown of endothelial Gα(i2) caused decreased transmigration of wild-type neutrophils. These data demonstrate that Gα(i2) and Gα(i3) contribute to inflammation by redundant, overlapping, and Gα(i)-isoform-specific mechanisms, with Gα(i2) exhibiting unique functions in both neutrophils and endothelial cells that appear essential for polymorphonuclear neutrophil recruitment in IC disease.

Epigenetic manifestation of metabolic syndrome and dietary management

SIGNIFICANCE

Metabolic syndrome constitutes a group of disorders such as insulin resistance, hypertension, and hypertriglyceridemia, predisposing an individual to risk factors such as cardiovascular disease, diabetes, obesity, and dyslipidemia. A majority of these diseases are influenced by the environmental factors, nutrient uptake, and genetic profile of an individual that together dysregulate gene function. These genetic and nongenetic factors are reported to introduce epigenetic cues that modulate the gene function which is inherited by the offspring.

RECENT ADVANCES

Considering the epigenetic modulation of the metabolic disorders, nutrigenomics has been distinctly categorized as a branch that deals with modulatory effect of nutrients on metabolic disorders and disease progression by supplementing the individuals with key nutrient-enriched diets which are derived from plant and animal sources.

CRITICAL ISSUES

Nutritional components of the diet regulate the metabolic health of an individual either by controlling the expression of some key genes related to metabolic pathways or by modulating the epigenetic events on such genes. The present article discusses various metabolic disorders in detail and the effect of nutrients on the specific genes causing those disorders. We also highlight the molecular mechanisms of some metabolic disorders through epigenetic modifications and possible therapeutic interventions.

FUTURE DIRECTIONS

With the advent of high-throughput technologies and epigenetic modulation of the metabolic disorders, an altered epigenetic code that is programmed due to improper nutrients can be reverted back by supplementing the diet with various plant-derived compounds. The implication of small molecular drugs is also of utmost significance for challenging the metabolic disorders.

Oxidative stress and lectin-like ox-LDL-receptor LOX-1 in atherogenesis and tumorigenesis

Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) has been identified as a major receptor for oxidized low-density lipoprotein (ox-LDL) in endothelial cells, monocytes, platelets, cardiomyocytes, and vascular smooth muscle cells. Its expression is minimal under physiological conditions but can be induced under pathological conditions. The upregulation of LOX-1 by ox-LDL appears to be important for physiologic processes, such as endothelial cell proliferation, apoptosis, and endothelium remodeling. Pathophysiologic effects of ox-LDL in atherogenesis have also been firmly established, including endothelial cell dysfunction, smooth muscle cell growth and migration, monocyte transformation into macrophages, and finally platelet aggregation-seen in atherogenesis. Recent studies show a positive correlation between increased serum ox-LDL levels and an increased risk of colon, breast, and ovarian cancer. As in atherosclerosis, ox-LDL and its receptor LOX-1 activate the inflammatory pathway through nuclear factor-kappa B, leading to cell transformation. LOX-1 is important for maintaining the transformed state in developmentally diverse cancer cell lines and for tumor growth, suggesting a molecular connection between atherogenesis and tumorigenesis.

Alteration of PON1 activity in adult and childhood obesity and its relation to adipokine levels

Obesity as a pathogenic disorder is a predisposing factor for cardiovascular diseases and shows an increasing incidence in the industrialized countries. Adipokines such as leptin, adiponectin and resistin have a great impact on the development of atherosclerosis in obesity. Elevated levels of leptin have been found to be atherogenic whereas decreased levels of adiponectin have been proved to be anti-atherogenic in recent studies. The exact role of resistin in the process of atherosclerosis has so far remained uncertain and controversial. In our recent work, we studied the alteration in human paraoxonase-1 (PON1) activity and adipokine levels; furthermore, we also aimed at identifying the potential correlation between these parameters in this metabolic disorder. We investigated the above-mentioned parameters both in adults and in children, with regard to the emerging role of childhood obesity and to get a clearer view of these factors during a whole lifetime. Investigating the adult population with a broad range of body mass index (BMI) we found significantly increased leptin and significantly decreased adiponectin and resistin levels and PON1 activity in the obese group compared to the lean controls. Adiponectin and resistin levels showed significantly positive correlation, while leptin and BMI showed significantly negative correlation with PON1 activity. Our findings were similar in childhood obesity: leptin showed significantly negative correlation, while adiponectin showed significantly positive correlation with PON1 activity. We found gender differences in the univariate correlations of leptin and adiponectin levels with PON1 activity in the adult population. In multiple regression analysis, adiponectin proved to be an independent factor of PON1 activity both in childhood and adult obesity, furthermore thiobarbituric acid-reactive substances (TBARS) also proved to be an independent predictor of the enzyme in adults, reflecting the important role of oxidative stress in obesity. Investigating PON 192 Q/R polymorphism by phenotypic distribution (A/B isoenzyme) in obese children, we found a significant correlation of PON1 arylesterase activity with leptin and adiponectin levels, and of body fat percentage with PON1 192 B isoenzyme. According to our studies, these metabolic changes in obesity predispose to the early development of atherosclerosis throughout our whole lifetime. Decreased activity of PON1 and alterations in adipokine levels in childhood obesity could contribute to an early commencement of this process, detected only later in adulthood by increased cardiovascular morbidity and mortality. Changed levels of leptin, adiponectin, resistin and PON1 activity at all ages, just like 192 Q/R polymorphism determined by phenotypic distribution, may be useful markers beside the general risk factors.

Biomarkers of inflammation and oxidative stress in atherosclerosis

Increasing evidence has highlighted the roles of oxidative stress and inflammation in the promotion of atherosclerotic cardiovascular disease. Recent pathological studies have elucidated specific mediators that appear to link these pathways to the progression and rupture of atherosclerotic plaque in the artery wall. The ability to measure levels of these mediators in the systemic circulation has provoked interest in their development as biomarkers for potential use in risk assessment and in evaluation of the response to the use of preventive therapies. The discovery of these pathological mediators and their potential translation to the clinical arena will be reviewed.

Aging-related nicotinamide adenine dinucleotide oxidase response to dietary supplementation: the French paradox revisited

Aging-related cell-surface NADH oxidase (arNOX)-specific activities increase with age between age 30 and ages 50-65. The protein is shed and circulates. Activity correlates with a number of aging-related disorders including low-density lipoprotein (LDL) oxidation as a precondition to atherosclerosis as well as oxidation of collagen and elastin as a major contributor to skin aging. arNOX inhibitors formulated for sustained release are capable of maintaining circulating arNOX at low levels with regular use as food supplements formulated with natural compounds. Among the best sources are certain culinary seasonings, all of which are ingredients used extensively in the French kitchen. Their regular use may contribute to an understanding of the nutritional basis for the French Paradox.

Sphingosine 1-phosphate levels in plasma and HDL are altered in coronary artery disease

High-density lipoproteins (HDL) are the major plasma carriers for sphingosine 1-phosphate (S1P) in healthy individuals, but their S1P content is unknown for patients with coronary artery disease (CAD). The aim of the study was to determine whether the S1P levels in plasma and HDL are altered in coronary artery disease. S1P was determined in plasma and HDL isolated by ultracentrifugation from patients with myocardial infarction (MI, n = 83), stable CAD (sCAD, n = 95), and controls (n = 85). In our study, total plasma S1P levels were lower in sCAD than in controls (305 vs. 350 pmol/mL). However, normalization to HDL-cholesterol (a known determinant of plasma S1P) revealed higher normalized plasma S1P levels in sCAD than in controls (725 vs. 542 pmol/mg) and even higher ones in MI (902 pmol/mg). The S1P amount contained in isolated HDL from these individuals was lower in sCAD than in controls (S1P per protein in HDL: 132 vs. 153 pmol/mg). The amount of total plasma S1P bound to HDL was lower in sCAD and MI than in controls (sCAD: 204, MI: 222, controls: 335 pmol/mL), while the non-HDL-bound S1P was, accordingly, higher (sCAD: 84, MI: 81, controls: 10 pmol/mL). HDL-bound plasma S1P was dependent on the plasma HDL-C in all groups, but normalization to HDL-C still yielded lower HDL-bound plasma S1P in patients with sCAD than in controls (465 vs. 523 pmol/mg). The ratio of non-HDL-bound plasma S1P to HDL-C-normalized HDL-bound S1P was also higher in both sCAD (0.18 mg/mL) and MI (0.15 mg/mL) than in controls (0.02 mg/mL). Remarkably, levels of non-HDL-bound plasma S1P correlated with the severity of CAD symptoms as graded by Canadian Cardiovascular Score, and discriminated patients with MI and sCAD from controls. Furthermore, a negative association was present between non-HDL-bound plasma S1P and the S1P content of isolated HDL in controls, but was absent in sCAD and MI. Finally, MI patients with symptom duration of less than 12 h had the highest levels of total and normalized plasma S1P, as well as the highest levels of S1P in isolated HDL. The HDL-C-normalized plasma level of S1P is increased in sCAD and even further in MI. This may be caused by an uptake defect of HDL for plasma S1P in CAD, and may represent a novel marker of HDL dysfunction.

The role of lipoprotein-associated phospholipase A2 in atherosclerosis may depend on its lipoprotein carrier in plasma

Platelet-activating factor (PAF) acetylhydrolase exhibits a Ca(2+)-independent phospholipase A2 activity and degrades PAFas well as oxidized phospholipids (oxPL). Such phospholipids are accumulated in the artery wall and may play key roles in vascular inflammation and atherosclerosis. PAF-acetylhydrolase in plasma is complexed to lipoproteins; thus it is also referred to as lipoprotein-associated phospholipase A2 (Lp-PLA2). Lp-PLA2 is primarily associated with low-density lipoprotein (LDL), whereas a small proportion of circulating enzyme activity is also associated with high-density lipoprotein (HDL). The majority of the LDL-associated Lp-PLA2 (LDL-Lp-PLA2) activity is bound to atherogenic small-dense LDL particles and it is a potential marker of these particles in plasma. The distribution of Lp-PLA2 between LDL and HDL is altered in various types of dyslipidemias. It can be also influenced by the presence of lipoprotein (a) [Lp(a)] when plasma levels of this lipoprotein exceed 30 mg/dl. Several lines of evidence suggest that the role of plasma Lp-PLA2 in atherosclerosis may depend on the type of lipoprotein particle with which this enzyme is associated. In this regard, data from large Caucasian population studies have shown an independent association between the plasma Lp-PLA2 levels (which are mainly influenced by the levels of LDL-Lp-PLA2) and the risk of future cardiovascular events. On the contrary, several lines of evidence suggest that HDL-associated Lp-PLA2 may substantially contribute to the HDL antiatherogenic activities. Recent studies have provided evidence that oxPL are preferentially sequestered on Lp(a) thus subjected to degradation by the Lp(a)-associated Lp-PLA2. These data suggest that Lp(a) may be a potential scavenger of oxPL and provide new insights into the functional role of Lp(a) and the Lp(a)-associated Lp-PLA2 in normal physiology as well as in inflammation and atherosclerosis. The present review is focused on recent advances concerning the Lp-PLA2 structural characteristics, the molecular basis of the enzyme association with distinct lipoprotein subspecies, as well as the potential role of Lp-PLA2 associated with different lipoprotein classes in atherosclerosis and cardiovascular disease.

Effects of genistein on oxidative injury in endothelial cells

The aim of this study was to test the hypothesis that genistein protects vascular endothelial cells against the pro-atherosclerotic stressor, oxidized low-density lipoprotein (ox-LDL), by inducing antioxidant enzymes and preventing apoptosis. Human umbilical cord-derived endothelial cells (ECV 304) were incubated with genistein (10-100 micromol/L), the radical scavenging antioxidant vitamin E (alpha-tocopherol, 50 micromol/L), or vehicle for 24 h and then were incubated with ox-LDL for an additional 24 h. Subsequently, antioxidant enzyme activities, lipid peroxidation, adhesion to monocytes, cell morphology, viability and apoptotic index were assessed. Ox-LDL decreased superoxide dismutase and glutathione peroxidase activities in endothelial cells and caused lipid peroxidation, adhesion to monocytes, morphological injury and apoptosis (p<0.05). These effects were prevented by vitamin E and dose-dependently by genistein (p<0.05). Further, this effect of genistein is associated with maintenance of antioxidant enzyme activities and inhibition of lipid peroxidation.

Circulating oxidized low-density lipoprotein: a biomarker of atherosclerosis and cardiovascular risk?

Low-density lipoproteins (LDLs) are susceptible to structural modifications by oxidation, particularly the small dense LDL particles. The formation of lipid peroxidation derivates, such as thiobarbituric reactive substances, conjugated dienes, lipid hydroperoxides, and aldehydes, is associated with changes in apolipoprotein conformation and affects the functional properties of LDLs. Oxidized LDL (oxLDL) formation in the subendothelial space of the arterial wall is a key initiating step in atherosclerosis because it contributes to foam cell generation, endothelial dysfunction, and inflammatory processes. In the last decade, immunoassays were developed using monoclonal antibodies against oxidation-dependent epitopes of LDL which made it possible to directly measure oxLDL in the circulation. Increased circulating oxLDL concentrations have been related to cardiovascular disease in some studies, although not always independently after adjustment of classical lipid markers. The Asklepios Study, investigating 2524 healthy middle-aged subjects, showed that circulating oxLDL is affected by many biological and lifestyle factors, as well as (generalized) subclinical atherosclerosis.

Clin Chem Lab Med 2009;47:128–37.

Lipid and lipoprotein profile in women with polycystic ovary syndromeThis article is one of a selection of papers published in the special issue Bridging the Gap: Where Progress in Cardiovascular and Neurophysiologic Research Meet

Polycystic ovary syndrome (PCOS) is a common endocrine disorder characterized by obesity-related risk factors for cardiovascular disease. The objective of our study was to determine values of key lipid and lipoprotein fractions in PCOS, and their possible relation to insulin resistance. A total of 75 women with PCOS (aged 23.1 ± 5.1 years, BMI 24.9 ± 4.7 kg/m2), and 56 age- and BMI-matched controls were investigated. In all subjects, basal glucose, cholesterol (total, HDL, and LDL), oxidized LDL (OxLDL), triglycerides, apolipoprotein (apo)A1, apoB, and apoE, nonesterified fatty acids, insulin, testosterone, sex hormone-binding globulin, homeostasis model assessment (HOMA) index, and free androgen index were determined in the follicular phase of the cycle. PCOS patients compared with controls had increased indices of insulin resistance, basal insulin (p < 0.001), and HOMA index (p < 0.001), and worsened insulin resistance-related dyslipidemia with decreased HDL cholesterol (p < 0.01), elevated triglycerides (p = 0.010), and pronounced LDL oxidation (p < 0.001). In conclusion, characteristic dyslipidemia of insulin resistance and unfavorable proatherogenic lipoprotein ratios were present only in women with PCOS and not in controls. Elevated OxLDL and the relation of apoE and nonesterified fatty acids with insulin resistance suggest that women with PCOS are at increased risk for premature atherosclerosis.

Lipid rafts in membrane-cytoskeleton interactions and control of cellular biomechanics: actions of oxLDL

Membrane-cytoskeleton coupling is known to play major roles in a plethora of cellular responses, such as cell growth, differentiation, polarization, motility, and others. In this review, the authors discuss the growing amount of evidence indicating that membrane-cytoskeleton interactions are regulated by the lipid composition of the plasma membrane, suggesting that cholesterol-rich membrane domains (lipid rafts), including caveolae, are essential for membrane-cytoskeleton coupling. Several models for raft-cytoskeleton interactions are discussed. Also described is the evidence suggesting that raft-cytoskeleton interactions play key roles in several cytoskeleton-dependent processes, particularly in the regulation of cellular biomechanical properties. To address further the physiological significance of raft-cytoskeleton coupling, the authors focus on the impact of oxidized low density lipoproteins, one of the major cholesterol carriers and proatherogenic factors, on the integrity of lipid rafts/caveolae, and on the organization of the cytoskeleton. Finally, the authors review the recent studies showing that oxLDL and cholesterol depletion have similar impacts on the biomechanical properties of vascular endothelial cells, which in turn affect endothelial angiogenic potential.

Plasma PAF-acetylhydrolase: an unfulfilled promise?

Plasma Platelet-activating-Factor (PAF)-acetylhydrolase (PAF-AH also named lipoprotein-PLA(2) or PLA(2)G7 gene) is secreted by macrophages, it degrades PAF and oxidation products of phosphatidylcholine produced upon LDL oxidation and/or oxidative stress, and thus is considered as a potentially anti-inflammatory enzyme. Cloning of PAF-AH has sustained tremendous promises towards the use of PAF-AH recombinant protein in clinical situations. The reason for that stems from the numerous animal models of inflammation, atherosclerosis or sepsis, where raising the levels of circulating PAF-AH either through recombinant protein infusion or through the adenoviral gene transfer showed to be beneficial. Unfortunately, neither in human asthma nor in sepsis the recombinant PAF-AH showed sufficient efficacy. One of the most challenging questions nowadays is as to whether PAF-AH is pro- or anti-atherogenic in humans, as PAF-AH may possess a dual pro- and anti-inflammatory role, depending on the concentration and the availability of potential substrates. It is equally possible that the plasma level of PAF-AH is a diagnostic marker of ongoing atherosclerosis.

Oxidized phospholipids, Lp(a) lipoprotein, and coronary artery disease

BACKGROUND

Lp(a) lipoprotein binds proinflammatory oxidized phospholipids. We investigated whether levels of oxidized low-density lipoprotein (LDL) measured with use of monoclonal antibody E06 reflect the presence and extent of obstructive coronary artery disease, defined as a stenosis of more than 50 percent of the luminal diameter.

METHODS

Levels of oxidized LDL and Lp(a) lipoprotein were measured in a total of 504 patients immediately before coronary angiography. Levels of oxidized LDL are reported as the oxidized phospholipid content per particle of apolipoprotein B-100 (oxidized phospholipid:apo B-100 ratio).

RESULTS

Measurements of the oxidized phospholipid:apo B-100 ratio and Lp(a) lipoprotein levels were skewed toward lower values, and the values for the oxidized phospholipid:apo B-100 ratio correlated strongly with those for Lp(a) lipoprotein (r=0.83, P<0.001). In the entire cohort, the oxidized phospholipid:apo B-100 ratio and Lp(a) lipoprotein levels showed a strong and graded association with the presence and extent of coronary artery disease (i.e., the number of vessels with a stenosis of more than 50 percent of the luminal diameter) (P<0.001). Among patients 60 years of age or younger, those in the highest quartiles for the oxidized phospholipid:apo B-100 ratio and Lp(a) lipoprotein levels had odds ratios for coronary artery disease of 3.12 (P<0.001) and 3.64 (P<0.001), respectively, as compared with patients in the lowest quartile. The combined effect of hypercholesterolemia and being in the highest quartiles of the oxidized phospholipid:apo B-100 ratio (odds ratio, 16.8; P<0.001) and Lp(a) lipoprotein levels (odds ratio, 14.2; P<0.001) significantly increased the probability of coronary artery disease among patients 60 years of age or younger. In the entire study group, the association of the oxidized phospholipid:apo B-100 ratio with obstructive coronary artery disease was independent of all clinical and lipid measures except one, Lp(a) lipoprotein. However, among patients 60 years of age or younger, the oxidized phospholipid:apo B-100 ratio remained an independent predictor of coronary artery disease.

CONCLUSIONS

Circulating levels of oxidized LDL are strongly associated with angiographically documented coronary artery disease, particularly in patients 60 years of age or younger. These data suggest that the atherogenicity of Lp(a) lipoprotein may be mediated in part by associated proinflammatory oxidized phospholipids.

Herpes Simplex Virus 1 Induced LOX-1 Expression in an Endothelial Cell Line, ECV 304

Infections, such as by Chlamydophilia pneumoniae, cytomegalovirus, herpes simplex virus, and Helicobacter pylori, have been shown to be involved in atherogenesis. Herpes simplex virus I (HSV-1) could infect vascular endothelial cells, and it has been shown that, when endothelial cells were activated with oxidized LDL (oxLDL), a number of cellular events are occurred, leading to endothelial cell dysfunction. Since LOX-1 is a major receptor for oxLDL on endothelial cells and its expression was increased in atherosclerosis, we investigated whether HSV1 infection can lead to the increase expression of LOX-1 in endothelial cells. LOX-1 mRNA expression determined by RT-PCR and LOX-1 promoter activity measured by luciferase assay were increased in endothelial cells following HSV-1 infection. This suggests that one of the mechanisms by which HSV-1 is involved in atherogenesis maybe the enhanced uptake of oxLDL via the increased expression of LOX-1 in endothelial cells.

Apolipoprotein A-I-stimulated apolipoprotein E secretion from human macrophages is independent of cholesterol efflux

Apolipoprotein A-I (apoA-I)-mediated cholesterol efflux involves the binding of apoA-I to the plasma membrane via its C terminus and requires cellular ATP-binding cassette transporter (ABCA1) activity. ApoA-I also stimulates secretion of apolipoprotein E (apoE) from macrophage foam cells, although the mechanism of this process is not understood. In this study, we demonstrate that apoA-I stimulates secretion of apoE independently of both ABCA1-mediated cholesterol efflux and of lipid binding by its C terminus. Pulse-chase experiments using (35)S-labeled cellular apoE demonstrate that macrophage apoE exists in both relatively mobile (E(m)) and stable (E(s)) pools, that apoA-I diverts apoE from degradation to secretion, and that only a small proportion of apoA-I-mobilized apoE is derived from the cell surface. The structural requirements for induction of apoE secretion and cholesterol efflux are clearly dissociated, as C-terminal deletions in recombinant apoA-I reduce cholesterol efflux but increase apoE secretion, and deletion of central helices 5 and 6 decreases apoE secretion without perturbing cholesterol efflux. Moreover, a range of 11- and 22-mer alpha-helical peptides representing amphipathic alpha-helical segments of apoA-I stimulate apoE secretion whereas only the C-terminal alpha-helix (domains 220-241) stimulates cholesterol efflux. Other alpha-helix-containing apolipoproteins (apoA-II, apoA-IV, apoE2, apoE3, apoE4) also stimulate apoE secretion, implying a positive feedback autocrine loop for apoE secretion, although apoE4 is less effective. Finally, apoA-I stimulates apoE secretion normally from macrophages of two unrelated subjects with genetically confirmed Tangier Disease (mutations C733R and c.5220-5222delTCT; and mutations A1046D and c.4629-4630insA), despite severely inhibited cholesterol efflux. We conclude that apoA-I stimulates secretion of apoE independently of cholesterol efflux, and that this represents a novel, ABCA-1-independent, positive feedback pathway for stimulation of potentially anti-atherogenic apoE secretion by alpha-helix-containing molecules including apoA-I and apoE.

Mechanisms of high-density lipoprotein cholesterol effects on the endothelial function in hyperlipemia

High-density lipoprotein-cholesterol (HDL-c) has a favorable influence on the endothelial function, but the mechanisms of this protective action are not fully understood. We studied lipid parameters, soluble adhesion molecules (vascular cell adhesion molecule-1 [VCAM-1], intercellular adhesion molecule [ICAM-1], E-selectin) oxidized low-density lipoproteins (LDL), and brachial-artery flow-mediated vasodilation (FMV) in 184 hyperlipemic patients (90 men, age 54 +/- 10 years, waist/hip circumference ratio 0.89 +/- 0.07, LDL-cholesterol [LDL-c] 4.9 +/- 1.3 mmol/L, triglycerides 1.8 +/- 0.9 mmol/L, HDL-c 1.3 +/- 0.5 mmol/L) after excluding those with current smoking, diabetes, hypertension, and vascular diseases. Patients were divided into 2 groups on the basis of HDL-c levels: < 1.03 mmol/L (n = 53) v >or= 1.03 mmol/L (n = 131). Patients with low HDL-c showed significantly lower LDL-c (P <.05), higher triglycerides (P <.001), higher body mass index (P <.02), lower FMV (3.7% +/- 2.0% v 4.9% +/- 3.4%, P <.002), higher VCAM-1 (1,195 +/- 395 ng/mL v 984 +/- 303 ng/mL, P <.01), and higher ICAM-1 (406 +/- 78 ng/mL v 364 +/- 68 ng/mL, P <.01). E-selectin and oxidized LDL showed no significant differences. In a multivariate age, oxidized LDL and brachial artery diameter predicted a lower FMV, while HDL-c was an independent predictor of a greater FMV (P =.003). Increasing levels of VCAM-1 and ICAM-1 were predicted by lower HDL-c, while higher oxidized LDL predicted higher VCAM-1 (P <.05). Our data suggest that in hyperlipemic subjects free of cardiovascular disease low HDL-c negatively modulates endothelial function through a lack of oxidation inhibition and a concomitant overexpression of adhesion molecules.

Structure-guided protein engineering modulates helix bundle exchangeable apolipoprotein properties

Apolipoprotein (apo) E plays a major role in lipid metabolism by mediating cellular uptake of lipoprotein particles through interaction with members of the low density lipoprotein (LDL) receptor family. The primary region of apoE responsible for receptor binding has been limited to a cluster of basic amino acids between residues 134 and 150, located in the fourth helix of the N-terminal domain globular helix bundle structure. To investigate structural and functional requirements of this "receptor binding region" we engineered an apolipoprotein chimera wherein residues 131-151 of human apoE were substituted for residues 146-166 (helix 5) of Manduca sexta apolipophorin III (apoLp-III). Recombinant hybrid apolipoprotein was expressed in Escherichia coli, isolated, and characterized. Hybrid apolipoprotein and apoE3-N-terminal, but not apoLp-III, bound to heparin-Sepharose. Far UV circular dichroism spectroscopy revealed the presence of predominantly alpha-helix secondary structure, and stability studies revealed a urea denaturation midpoint of 1.05 m, similar to wild-type apoLp-III. Hybrid apolipoprotein-induced dimyristoylphosphatidylcholine (DMPC) bilayer vesicle solubilization activity was significantly enhanced compared with either parent protein, consistent with detection of solvent-exposed hydrophobic regions on the protein in fluorescent dye binding experiments. Unlike wild-type apoLp-III.DMPC complexes, disc particles bearing the hybrid apolipoprotein competed with 125ILDL for binding to the LDL receptor on cultured human skin fibroblasts. We conclude that a hybrid apolipoprotein containing a key receptor recognition element of apoE preserves the structural integrity of the parent protein while conferring a new biological activity, illustrating the potential of helix swapping to introduce desirable biological properties into unrelated or engineered apolipoproteins.

Role of oxidized low-density lipoprotein in renal disease

Accelerated atherosclerosis is often observed in patients with chronic renal failure. In the present review we summarize and discuss the recent literature on the pathogenic role of low-density lipoproteins modified by oxidative processes in atherosclerosis and the possible role in renal diseases. Pathogenetically, the oxidation of low-density lipoproteins is considered to be a key event in the development of atherosclerosis, in part by causing enhanced uptake of lipids by macrophages. In addition, oxidation of low-density lipoproteins exerts cytotoxic, proinflammatory and immunogenic properties, all of which could potentially contribute to the development and progression of atherosclerosis.