Leukocyte adhesion molecules in atherogenesis

Body fat percentage and CRP correlates with a composite score of vascular risk markers in healthy, young adults - The Lifestyle, Biomarkers, and Atherosclerosis (LBA) study

Background

Identification of early signs of atherosclerosis in young adults have the potential to guide early interventions to prevent later cardiovascular disease. We therefore analyzed measures of vascular structure and function and biomarkers of cardiovascular risk in a sample of young healthy adults.

Methods

Pulse-wave velocity (PWV), carotid-intima media thickness (cIMT) and augmentation index (AIX) were measured in 834 healthy non-smokers (ages 18.0–25.9). Emphasis was put on discriminating between individuals having a vascular structure and function associated with a higher or lower risk, and cluster analysis algorithms were employed to assign the subjects into groups based on these vascular measurements. In addition, a vascular status score (VSS) was calculated by summarizing the results according to quintiles of the vascular measurements. The associations between VSS and cardiovascular biomarkers were examined by regression analyses.

Results

The cluster analyses did not yield sufficiently distinct clustering (groups of individuals that could be categorized unequivocally as having either a vascular structure and function associated with a higher or lower CVD risk). VSS proved a better classificatory variable. The associations between VSS and biomarkers of cardiovascular risk were analyzed by univariable and multivariable regressions. Only body fat percentage and C-reactive protein (CRP) were independently associated with VSS.

Conclusions

A VSS calculation, which integrates PWV, cIMT, and AIX measurements is better suited for cardiovascular risk evaluation in young adults than cluster analyses. The independent associations of VSS with body fat percentage and CRP highlight the decisive role of adiposity and systemic inflammation in early atherosclerotic progression and suggests a subordinate role of insulin and lipid metabolism in this age span.

Contribution of homeostatic chemokines CCL19 and CCL21 and their receptor CCR7 to coronary artery disease

OBJECTIVE

Our aim was to identify the role of the homeostatic chemokines CCL19 and CCL21 and their common receptor CCR7 in atherogenesis and to study the relationships between CCL19, CCL21, and CCR7 gene variants and coronary artery disease in a Chinese Han population.

APPROACH AND RESULTS

Immunohistochemical analysis of samples with atherosclerosis of various stages showed increased CCL19, CCL21, and CCR7 expression in atherosclerotic coronary plaques compared with nonatherosclerotic controls. Expression levels increased in positive correlation with coronary lesion stage. Cell adhesion assays confirmed that CCL19 promoted monocyte adhesion, which was induced by CCR7, to human umbilical vein endothelial cells, an effect partially antagonized by atorvastatin. After the human umbilical vein endothelial cells were treated with CCR7-neutralizing antibody, both CCL19- and CCL21-induced monocyte to human umbilical vein endothelial cell migration and CCL19-induced monocyte to human umbilical vein endothelial cell adhesion were abolished. The associations between genetic variants of CCL19, CCL21, CCR7, and coronary artery disease in a Chinese Han population were determined by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The following single nucleotide polymorphisms were associated with coronary artery disease: CCL19 rs2227302, CCL21 rs2812377, and CCR7 rs588019. Individuals with the CCL19 rs2227302 T allele or CCL21 rs2812377 G allele had higher plasma CCL19 levels than those with C/C genotype and higher CCL21 levels than those with T/T genotype in both case and control subjects.

CONCLUSION

CCL19/CCL21-CCR7 is a novel homeostatic chemokine system that modulates human monocyte adhesion and migration, promoting atherogenesis. It is associated with coronary artery disease risk in Chinese Han individuals. These data suggest that the CCL19/CCL21-CCR7 axis plays an important role in atherosclerosis progression.

Circulating adhesion molecules in obstructive sleep apnea and cardiovascular disease

Over 20 years of evidence indicates a strong association between obstructive sleep apnea (OSA) and cardiovascular disease. Although inflammatory processes have been heavily implicated as an important link between the two, the mechanism for this has not been conclusively established. Atherosclerosis may be one of the mechanisms linking OSA to cardiovascular morbidity. This review addresses the role of circulating adhesion molecules in patients with OSA, and how these may be part of the link between cardiovascular disease and OSA. There is evidence for the role of adhesion molecules in cardiovascular disease risk. Some studies, albeit with small sample sizes, also show higher levels of adhesion molecules in patients with OSA compared to controls. There are also studies that show that levels of adhesion molecules diminish with continuous positive airway pressure therapy. Limitations of these studies include small sample sizes, cross-sectional sampling, and inconsistent control for confounding variables known to influence adhesion molecule levels. There are potential novel therapies to reduce circulating adhesion molecules in patients with OSA to diminish cardiovascular disease. Understanding the role of cell adhesion molecules generated in OSA will help elucidate one mechanistic link to cardiovascular disease in patients with OSA.

Peptide inhibitor of NF-κB translocation ameliorates experimental atherosclerosis

Atherosclerosis is a chronic inflammatory disease of the arterial wall. NF-κB is a major regulator of inflammation that controls the expression of many genes involved in atherogenesis. Activated NF-κB was detected in human atherosclerotic plaques, and modulation of NF-κB inflammatory activity limits disease progression in mice. Herein, we investigate the anti-inflammatory and atheroprotective effects of a cell-permeable peptide containing the NF-κB nuclear localization sequence (NLS). In vascular smooth muscle cells and macrophages, NLS peptide specifically blocked the importin α-mediated nuclear import of NF-κB and prevented lipopolysaccharide-induced pro-inflammatory gene expression, cell migration, and oxidative stress. In experimental atherosclerosis (apolipoprotein E-knockout mice fed a high-fat diet), i.p., 0.13 μmol/day NLS peptide administration for 5 weeks attenuated NF-κB activation in atherosclerotic plaques. NLS peptide significantly inhibited lesion development at both early (age 10 weeks) and advanced (age 28 weeks) stages of atherosclerosis in mice, without affecting serum lipid levels. Plaques from NLS-treated mice contained fewer macrophages of pro-inflammatory M1 subtype than those from respective untreated controls. By contrast, the relative smooth muscle cell and collagen content was increased, indicating a more stable plaque phenotype. NLS peptide also attenuated pro-inflammatory gene expression and oxidative stress in aortic lesions. Our study demonstrates that targeting NF-κB nuclear translocation hampers inflammation and atherosclerosis development and identifies cell-permeable NLS peptide as a potential anti-atherosclerotic agent.

Statins suppress apolipoprotein CIII-induced vascular endothelial cell activation and monocyte adhesion

Aims

Activation of vascular endothelial cells (ECs) contributes importantly to inflammation and atherogenesis. We previously reported that apolipoprotein CIII (apoCIII), found abundantly on circulating triglyceride-rich lipoproteins, enhances adhesion of human monocytes to ECs in vitro. Statins may exert lipid-independent anti-inflammatory effects. The present study examined whether statins suppress apoCIII-induced EC activation in vitro and in vivo.

Methods and results

Physiologically relevant concentrations of purified human apoCIII enhanced attachment of the monocyte-like cell line THP-1 to human saphenous vein ECs (HSVECs) or human coronary artery ECs (HCAECs) under both static and laminar shear stress conditions. This process mainly depends on vascular cell adhesion molecule-1 (VCAM-1), as a blocking VCAM-1 antibody abolished apoCIII-induced monocyte adhesion. ApoCIII significantly increased VCAM-1 expression in HSVECs and HCAECs. Pre-treatment with statins suppressed apoCIII-induced VCAM-1 expression and monocyte adhesion, with two lipophilic statins (pitavastatin and atorvastatin) exhibiting inhibitory effects at lower concentration than those of hydrophilic pravastatin. Nuclear factor κB (NF-κB) mediated apoCIII-induced VCAM-1 expression, as demonstrated via loss-of-function experiments, and pitavastatin treatment suppressed NF-κB activation. Furthermore, in the aorta of hypercholesterolaemic Ldlr^−/− mice, pitavastatin administration in vivo suppressed VCAM-1 mRNA and protein, induced by apoCIII bolus injection. Similarly, in a subcutaneous dorsal air pouch mouse model of leucocyte recruitment, apoCIII injection induced F4/80+ monocyte and macrophage accumulation, whereas pitavastatin administration reduced this effect.

Conclusions

These findings further establish the direct role of apoCIII in atherogenesis and suggest that anti-inflammatory effects of statins could improve vascular disease in the population with elevated plasma apoCIII.

Mouse models of atherosclerosis

Genetically altered mice carrying mutations of genes encoding crucial components of the immune system and lipid metabolism have been widely used to study the role of immune responses and inflammation in atherosclerosis. These mice are often fed a diet, with a high content of cholesterol and saturated fat in order to induce hypercholesterolemia and arterial lesions. We review the different mouse models of atherosclerosis, type of diets, and techniques to measure lipid deposition and lesion size in the arterial walls. Moreover, the methods used to determine the presence of the immune cells in atherosclerotic lesions are also described here.

The macrophage at the intersection of immunity and metabolism in obesity

Obesity is a worldwide pandemic representing one of the major challenges that societies face around the globe. Identifying the mechanisms involved in its development and propagation will help the development of preventative and therapeutic strategies that may help control its rising rates.Obesity is associated with chronic low-grade inflammation, and this is believed to be one of the major contributors to the development of insulin resistance, which is an early event in obesity and leads to type 2 diabetes when the pancreas fails to keep up with increased demand for insulin. In this review, we discuss the role of macrophages in mediation of inflammation in obesity in metabolic organs including adipose tissue, skeletal muscle and liver. The presence of immune cells at the interface with metabolic organs modulates both metabolic function and inflammatory responses in these organs, and may provide a potential therapeutic target to modulate metabolic function in obesity.

The effect of different doses of aerobic exercise training on endothelial function in postmenopausal women with elevated blood pressure: results from the DREW study

OBJECTIVES

The aim of this study was to examine the effect of three different doses of aerobic exercise training (corresponding to approximately 50%, 100% and 150% of the National Institutes of Health consensus guidelines) on endothelial function in sedentary obese postmenopausal women with elevated blood pressure. Aerobic exercise training improves endothelial function in individuals with cardiovascular risk; however, it is unknown whether these adaptations occur in a dose-dependent manner.

METHODS

Obese postmenopausal women (n=155) with elevated blood pressure (systolic blood pressure between 120 and 159.0 mm Hg) were randomly assigned to one of four groups: 4, 8 or 12 kilocalories per kilogram of energy expenditure per week (kcal/kg/week) or a non-exercise control group for 6 months. Endothelial function was assessed via flow-mediated dilation (FMD) at baseline and post-intervention.

RESULTS

After exercise training, there was a similar improvement (1.02-1.5%) in FMD in all three exercise groups (p<0.05) compared with control (-0.5%). Change in FMD after exercise training was significantly correlated with FMD at baseline (r= -0.35, p<0.001). Post hoc analyses found a significant improvement in FMD in exercisers (all exercise groups combined) with endothelial dysfunction (FMD < 5.5%) at baseline (1.8%, 95% CI: 1.17 to 2.38; p<0.001) compared with exercisers with normal endothelial function (FMD ≥ 5.5%) (-1.2%; 95% CI: -1.17 to 0.69; p=0.60).

CONCLUSIONS

Aerobic exercise training was associated with improved FMD in postmenopausal women with elevated blood pressure. In addition, exercise training may be more efficacious in improving endothelial function in postmenopausal women with endothelial dysfunction than individuals with normal endothelial function at baseline.

Dynamic changes in regulatory T cells are linked to levels of diet-induced hypercholesterolemia

BACKGROUND

Regulatory T cells (Treg) are present in atherosclerotic lesions and can modulate disease. In this study we characterized changes in Treg responses associated with prolonged hypercholesterolemia and lesion progression.

METHODS AND RESULTS

Low-density lipoprotein receptor null mice in which Treg express green fluorescent protein were fed a control or cholesterol-rich diet, and green fluorescent protein-positive cells were enumerated in lymphoid tissues and in aorta. Splenic Treg numbers increased after 4, 8, and 20 weeks in cholesterol-diet-fed mice. However, the number of circulating and lesional Treg peaked at 4 weeks and decreased significantly at 8 and 20 weeks, concomitant with increased numbers of CD4(+) effector T cells and increased lesion size over this period. Treg expression of selectin ligands and their ability to bind to aortic endothelium decreased after prolonged hypercholesterolemia, and apoptosis of lesional Treg increased. After 4 weeks of cholesterol-rich diet, a switch to a control diet for 4 weeks reduced serum cholesterol and stopped lesion growth, and the high aortic Treg content was maintained, compared with mice fed a cholesterol diet for 8 weeks. After the diet reversal, the splenic Treg retained the phenotype of Treg after 4 weeks of cholesterol diet.

CONCLUSIONS

Prolonged hypercholesterolemia impairs Treg but not effector T cell accumulation in lesions, but reversal of hypercholesterolemia can prevent loss of lesional Treg. Therefore, cholesterol-lowering therapies may induce dynamic and beneficial changes in Treg:effector T cell ratios in atherosclerotic lesions.

The changes in the endothelial expression of cell adhesion molecules and iNOS in the vessel wall after the short-term administration of simvastatin in rabbit model of atherosclerosis

Cell adhesion molecules P-selectin, VCAM-1 and ICAM-1 play an important role in the pathogenesis of atherosclerosis. High levels of nitric oxide (NO) produced by inducible NO synthase (iNOS) have been associated with atherosclerotic processes. Simvastatin is an HMG-CoA reductase inhibitor responsible for many clinical benefits. The aim of this study was to detect and quantify changes in endothelial expression of P-selectin, VCAM-1, ICAM-1 and iNOS in the vessel wall after the short-term administration of simvastatin in a rabbit model of atherosclerosis. Eighteen New Zealand White rabbits were randomly divided into three groups (n = 6). In the cholesterol group, rabbits consumed an atherogenic diet (0.4% cholesterol) for eight weeks. In the simvastatin group, rabbits consumed an atherogenic diet for six weeks and then consumed an atherogenic diet supplemented with simvastatin (10 mg kg−1) for two weeks. Biochemical analysis showed that administration of simvastatin led to an almost two-fold lowering of the total serum cholesterol, VLDL, LDL and HDL, but not triglycerides, compared with the cholesterol-fed rabbits only. Stereological analysis of the immuno-histochemical staining revealed that administration of simvastatin (10 mg kg−1 daily) in an atherogenic diet decreased the endothelial expression of P-selectin, ICAM-1 and iNOS in both aortic arch and carotid artery compared with the cholesterol fed-rabbits only. We conclude that simvastatin has beneficial effects on endothelial function by decreasing expression of P-selectin, ICAM-1 and iNOS in endothelial cells in the very early stages of atherogenesis.

Quantum dot mediated imaging of atherosclerosis

The progression of atherosclerosis is associated with leukocyte infiltration within lesions. We describe a technique for the ex vivo imaging of cellular recruitment in atherogenesis which utilizes quantum dots (QD) to color-code different cell types within lesion areas. Spectrally distinct QD were coated with the cell-penetrating peptide maurocalcine to fluorescently-label immunomagnetically isolated monocyte/macrophages and T lymphocytes. QD-maurocalcine bioconjugates labeled both cell types with a high efficiency, preserved cell viability, and did not perturb native leukocyte function in cytokine release and endothelial adhesion assays. QD-labeled monocyte/macrophages and T lymphocytes were reinfused in an ApoE(-/-) mouse model of atherosclerosis and age-matched controls and tracked for up to four weeks to investigate the incorporation of cells within aortic lesion areas, as determined by oil red O (ORO) and immunofluorescence ex vivo staining. QD-labeled cells were visible in atherosclerotic plaques within two days of injection, and the two cell types colocalized within areas of subsequent ORO staining. Our method for tracking leukocytes in lesions enables high signal-to-noise ratio imaging of multiple cell types and biomarkers simultaneously within the same specimen. It also has great utility in studies aimed at investigating the role of distinct circulating leukocyte subsets in plaque development and progression.

G2A deficiency in mice promotes macrophage activation and atherosclerosis

G2A is a stress-inducible G protein-coupled receptor that is expressed on several cell types within atherosclerotic lesions. We demonstrated previously that G2A deficiency in mice increased aortic monocyte recruitment and increased monocyte:endothelial interactions. To investigate the impact of G2A deficiency in macrophages, we isolated peritoneal macrophages from G2A(+/+)ApoE(-/-) and G2A(-/-)ApoE(-/-) mice. G2A(-/-)ApoE(-/-) macrophages had significantly lower apoptosis than control macrophages. The prosurvival genes BCL-2, BCL-xL, and cFLIP were increased in G2A(-/-)ApoE(-/-) macrophages. Macrophages from G2A(-/-)ApoE(-/-) mice also had increased proinflammatory status that was indicative of a M1 macrophage phenotype. This was indicated by significantly increased nuclear translocation of nuclear factor kappaB, as well as production of interleukin-12p40, tumor necrosis factor alpha, and interleukin-6, and reduced expression of arginase-I. Moreover, G2A(-/-)ApoE(-/-) macrophages had reduced ability to engulf apoptotic cells in vitro. We examined atherosclerosis in mice fed a Western diet for 10 weeks and found that G2A deficiency increased lesion size in the aortic root by 50%. Plasma lipid levels were not changed in G2A(-/-)ApoE(-/-) mice. However, we found that absence of G2A increased the number of aortic macrophages and attenuated apoptosis in this cell type. Moreover, bone marrow transplantation studies indicated that deficiency of G2A in marrow-derived cells significantly contributed to atherosclerosis development. In the absence of G2A, increased macrophage activation and decreased apoptosis is associated with accumulation of macrophages in the aorta and increased atherosclerosis.

Real-time imaging of mechanically injured femoral artery in mice reveals a biphasic pattern of leukocyte accumulation

Wire injury of an artery has been recognized as a standard model of vascular inflammation and atherosclerosis; however, the mechanism of leukocyte recruitment has not been studied in this model. In this study, we documented the recruitment of leukocytes to the murine femoral artery after a wire injury. A transluminal mechanical injury was generated by insertion of a wire into the femoral artery of male C57BL/6J mice. The mice were anesthetized and ventilated after tracheotomy and protected from hypothermia by a warming lamp. Body temperature and blood pH did not significantly change during the experiment. The interaction between rhodamine 6G-labeled leukocytes and the injured femoral artery was monitored using an epifluorescent microscope, and the images were evaluated using a computer-assisted image analysis program. In the absence of injury, virtually no leukocyte adhesion was observed. In contrast, the number of adherent leukocytes increased 4 and 24 h after injury and declined 72 h after injury. The rolling flux of leukocytes increased 4 h after injury and remained high up to 7 days, but it was faster 72 h after injury. We identified another peak of leukocyte adhesion 7 days after injury. Injection of anti-P-selectin antibody significantly reduced leukocyte adhesion at the early and later phases. In conclusion, we have established a novel experimental system for direct observation of leukocyte recruitment to the injured femoral artery. Our system revealed a previously undetected, unique profile of leukocyte recruitment during vascular injury.

Antiatherogenic effects of S-nitroso-N-acetylcysteine in hypercholesterolemic LDL receptor knockout mice

BACKGROUND

The pathophysiology of the NO/NO synthase system and dysfunctional changes in the endothelium in the early phases of the atherogenic process are incompletely understood. In this study, we investigated the effects of the nitrosothiol NO donor S-nitroso-N-acetylcysteine (SNAC) in the early prevention of plaque development in the hypercholesterolemic LDLr-/- mice as well as the changes in endothelium-dependent relaxation and NO synthase expression.

METHODS AND RESULTS

LDLr-/- mice were fed a 1.25% cholesterol-enriched diet for 15 days. Plasma cholesterol/triglyceride levels increased and this increase was accompanied by the development of aortic root lesions. Aortic vasorelaxation to acetylcholine was increased, although endothelium-independent relaxation in response to sodium nitroprusside did not change, which suggest stimulated NO release enhanced. This dysfunction was associated with enhanced aortic superoxide production and with increased levels of constitutive NOS isoform expression, particularly neuronal NOS. SNAC (S-nitroso-N-acetylcysteine) administration (0.51 micromol/kg/day i.p. for 15 days) decreased the extent of the plaque by 55% in hypercholesterolemic mice, but had no effects on vasomotor changes. It did, however, lead to a decrease in constitutive NOS expression. The SNAC induced only minor changes in plasma lipid profile.

CONCLUSION

The present study has shown that, in early stages of plaque development in LDLr-/- mice, specific changes in NO/NO synthase system develop, that are characterized by increased endothelium-dependent vasorelaxation and increased constitutive NOS expression. Since the development of plaque and the indicator of endothelial cell dysfunction were prevented by SNAC, such treatment may constitute a novel strategy for the halting of progression of early plaque.

Application of stereological methods for the quantification of VCAM-1 and ICAM-1 expression in early stages of rabbit atherogenesis

Early stages of atherogenesis are characterized by the overexpression of cell adhesion molecules with the subsequent accumulation of macrophages, smooth muscle cells and proliferation of extracellular matrix in arterial intima. The quantification of atherogenic changes is necessary for the objective evaluation of the atherogenic process. The purpose of this study was to introduce stereological methods that may be used for the quantification of immunohistochemical staining, namely intercellular cell adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1). Twenty-four New Zealand White rabbits were subdivided into the three groups. Eighteen rabbits received a 0.4% cholesterol diet for 1, 2 and 3 months, respectively. Stereological principles of the systematic uniform random sampling and the point-counting method were applied for the quantification. Stereological analysis showed that VCAM-1 and ICAM-1 were upregulated during the consumption of high cholesterol diet and that VCAM-1, but not ICAM-1, has a considerable role in the formation of early atherosclerotic lesions. Stereological methods proved to be useful for the quantification of immunohistochemistry and can be used for an objective characterization of atherogenic changes in atherosclerosis.

Aortic recruitment of blood lymphocytes is most pronounced in early stages of lesion formation in apolipoprotein-E-deficient mice

Lymphocyte accumulation in the arterial intima affects development of atherosclerotic lesions. We studied the kinetics of lymphocyte accumulation in the arterial wall by injecting lymphocytes from male LacZ transgenic mice into female apolipoprotein-E-deficient mice. Recipient mouse aortas were removed and separated into lesioned and non-lesioned parts 2, 24, 48, or 72 h later. The accumulation of donor lymphocytes was quantified with real-time PCR of donor lymphocyte-specific genes. The accumulation of lymphocytes in the lesioned parts of aorta decreased with increasing lesion severity (r=-0.74, P=0.0005, n=18). Moreover, the accumulation of lymphocytes in the lesioned part of aorta was larger (392+/-108%, P=0.016) compared with the accumulation in the non-lesioned part in mice with mild atherosclerosis, whereas it was smaller (58+/-19%, P<0.01) compared with the accumulation in the non-lesioned part in mice with severe atherosclerosis. The results suggest that aortic recruitment of blood lymphocytes is most pronounced in early stages of lesion formation.

Influence of interferon-gamma on the extent and phenotype of diet-induced atherosclerosis in the LDLR-deficient mouse

OBJECTIVE

The aim of this study was to investigate the influence of interferon-gamma (IFN-gamma) on atherosclerosis in low density lipoprotein receptor (LDLR)-null mice.

METHODS AND RESULTS

We cross-bred IFN-gamma-deficient mice with LDLR-null mice and analyzed lipoprotein profiles and atherosclerosis in the compound mutant progeny after 8 and 20 weeks on a cholesterol-enriched diet. IFN-gamma deficiency did not affect serum cholesterol levels or lipoprotein profiles, but it did affect the extent and phenotype of atherosclerosis. Atherosclerotic lesions in IFN-gamma-deficient mice were reduced by 75% in the aortic arch and by 46% in the descending aorta compared with control mice after 8 weeks on the diet. After 20 weeks, arch lesions were reduced by 43%, and descending aorta lesions were reduced by 65% in IFN-gamma-deficient mice compared with controls. At 8 weeks, percent lesional macrophage and smooth muscle content was significantly less in the IFN-gamma-deficient mice, but not at 20 weeks. Although there were fewer class II major histocompatibility complex-positive cells in the lesions of IFN-gamma-deficient animals compared with controls, class II major histocompatibility complex expression on endothelial cells overlying lesions persisted in the absence of IFN-gamma.

CONCLUSIONS

These data provide direct evidence that IFN-gamma influences atherosclerosis development and phenotype in the LDLR-deficient mouse, independent of changes in blood lipoprotein profiles.

Tissue factor regulation and cytokine expression in monocyte-endothelial cell co-cultures: effects of a statin, an ACE-inhibitor and a low-molecular-weight heparin

INTRODUCTION

Mounting evidence implies beneficial properties of statins and angiotensin converting enzyme (ACE)-inhibitors beyond those of their original indications in the treatment of coronary artery disease (CAD). Less is known of the mechanisms by which low-molecular-weight (LMW) heparin, also used in unstable CAD, affects the cellular micro-environment. The effects of these drugs in monocyte-endothelial cell co-culture systems have so far been sparsely investigated.

MATERIALS AND METHODS

We studied the expression of tissue factor (TF) and the cytokines tumour necrosis factor (TNF)-alpha, interleukin (IL)-6 and IL-10 in a co-culture model with monocytic, vitamin D(3)(vitD(3))-differentiated U-937 cells and human coronary artery endothelial cells (HCAEC), and the effects of the above-mentioned drugs in this system. Cells were co-cultured for 18 h, with or without pre-stimulation of the HCAEC with interferon (IFN)-gamma, and in the presence or absence of simvastatin, enalapril or dalteparin. Analyses of surface tissue factor and intracellular cytokines were done by flow cytometry.

RESULTS

Co-culture with activated HCAEC induced tissue factor expression in U-937 cells but not in the endothelial cells. All three drugs significantly reduced tissue factor up-regulation (p<0.001 for each). Co-culture also induced IL-6 expression in U-937 cells and an increase in IL-10 production by HCAEC, none of which was affected by drugs. When cultured separately, both cell types expressed TNF-alpha. This was attenuated in U-937 cells by all three drugs (p<0.001 for each), whereas only enalapril reduced the TNF-alpha content of activated HCAEC (p=0.02). Enalapril also down-regulated the basal expression of IL-6 (p=0.01) and IL-10 (p<0.01) in HCAEC, which simvastatin and dalteparin failed to do.

CONCLUSIONS

In this study, we demonstrated for the first time that a statin, an ACE-inhibitor and an LMW-heparin all suppress tissue factor up-regulation in monocyte-endothelial cell co-cultures, thus adding new information regarding the cellular effects of these drugs that may be of importance in the treatment of CAD.

Erythrocyte damage and leukocyte activation in ischemic stroke

BACKGROUND

The traditional lipid risk factors can only predict some of the cardiovascular events. Our work has focused on new potential biological markers of risk, namely leukocyte activation and erythrocyte membrane damage, in ischemic stroke cases.

METHODS

Besides the traditional lipid profile, we evaluated the plasma levels of elastase and lactoferrin as markers of leukocyte activation, and membrane band 3 protein profile and membrane bound hemoglobin as markers of erythrocyte damage. Total and differential leukocyte counts and erythrocyte counts, hematocrit and hemoglobin concentrations were also evaluated. The lipid study included the evaluation of triglycerides, total cholesterol, high-density lipoprotein cholesterol (HDLc), low-density lipoprotein cholesterol (LDLc), apolipoprotein AI (Apo AI) and B (Apo B), and lipoprotein (a) (Lp(a)). The work was performed in a control group (n=29) with no history of cardiovascular events, presenting normal hematological and lipid values, and in a pathologic group (n=21) of ischemic stroke cases diagnosed by computed tomographic imaging.

RESULTS

We found that ischemic stroke was associated with significantly higher values of leukocytes, which seem to be activated, as shown by significant higher levels of elastase and lactoferrin. This activation seems to impose erythrocyte damage, as suggested by a significant increase in membrane bound hemoglobin and by a different band 3 profile.

CONCLUSIONS

Our data suggest that plasma levels of elastase and lactoferrin, together with levels of erythrocyte membrane bound hemoglobin and band 3 profile, could be used as powerful new markers of risk for cardiovascular events.

Cholesterol enrichment upregulates intercellular adhesion molecule-1 in human vascular endothelial cells

Hypercholesterolemia is a major risk factor for atherosclerosis, but the mechanism by which cholesterol activates the endothelium remains undocumented. The present investigation was undertaken to investigate the role of cholesterol, one of the bioactive moieties of the low-density lipoprotein (LDL) particle, in initiating of intracellular signaling in endothelial cells (ECs) and culminating in increased abundance of the intercellular adhesion molecule-1 (ICAM-1). Cholesterol was delivered to human umbilical vein ECs (HUVECs) via cholesterol-enriched liposomes. In HUVECs, the cellular cholesterol:phospholipid ratio increased after 1 h of exposure to cholesterol. The level of ICAM-1 increased in both mRNA and protein after 24 h of cholesterol exposure. ICAM-1 mRNA half-life was not affected by cholesterol exposure. Promoter studies showed greater than two-fold activation of the ICAM-1 gene expression after cholesterol exposure. Electrophoretic mobility shift assay showed that activator protein-1 (AP-1) activity substantially increased after 2 h of exposure to cholesterol. In contrast, cholesterol did not affect nuclear factor-kappaB (NF-kappaB) activity. Results of trans-reporting assay revealed 2.5-fold increased expression of the AP-1-dependent reporter gene after cholesterol exposure whereas NF-kappaB-dependent expression was not affected. The AP-1/Ets (-891 to -908) site, one of the three AP-1-like sites in the ICAM-1 promoter, was most responsive to cholesterol. These data demonstrate for the first time that cholesterol enrichment phenotypically modulates ECs by transcriptionally upregulating ICAM-1 expression.

Adenovirus-mediated overexpression of dominant-negative mutant of c-Jun prevents intercellular adhesion molecule-1 induction by LDL: a critical role for activator protein-1 in endothelial activation

Low density lipoprotein (LDL) induces intercellular adhesion molecule-1 (ICAM-1) gene expression and leads to endothelial cell (EC) leukocyte adhesion. However, the transcriptional mechanism for LDL-induced EC perturbation remains to be fully explained. Activator protein-1 (AP-1) is induced after the exposure of ECs to LDL. In the present study, a regulated adenovirus expressing a dominant-negative mutant of c-Jun (TAM-67) was used to examine the role of AP-1 in the LDL-induced ICAM-1 activation. Overexpression of TAM-67 specifically inhibited AP-1 activation and prevented the LDL-activated surface expression of ICAM-1 protein in human umbilical vein ECs and human coronary artery ECs. Northern analyses and promoter transactivation assays indicated that this effect of TAM-67 was likely mediated through a suppression of the transcriptional regulation of the ICAM-1 gene. Functionally, TAM-67 attenuated leukocyte adherence to ECs in response to LDL. Furthermore, electrophoresis mobility shift assays and site-directed mutagenesis suggested that an AP-1-like motif in the promoter region of the human ICAM-1 gene was a critical cis element for LDL induction. These results, for the first time, provide evidence suggesting that AP-1 is a major regulatory mechanism leading to endothelial activation.

ICAM-1 deficiency reduces atherosclerotic lesions in double-knockout mice (ApoE(-/-)/ICAM-1(-/-)) fed a fat or a chow diet

Intercellular adhesion molecule (ICAM)-1, a major adhesion molecule, plays a critical role in the homing of leukocytes to sites of atherosclerotic lesions. However, very little is known on the role of ICAM-1 in initiating and perpetuating vascular lesions in ApoE(-/-) mice fed a chow or a fat diet. This study has investigated the mean aortic lesions in mice (C57BL6 background) with a single-knockout (ApoE(-/-)) or double-knockout (DKO; ApoE(-/-), ICAM-1(-/-)) fed a chow or a fat diet over a period of 3, 6, 15, and 20 weeks. A 3-fold reduction in lesion size was observed at all time points in DKO mice fed a chow diet. However, in DKO mice fed a fat diet, a marked reduction in the aortic lesion was observed at 3 and 15 weeks, which did not reach a significant level at 6 and 20 weeks. This study shows in essence that DKO mice are protected from developing significant lesions for up to 6 weeks when fed a chow diet and from 3 to 6 weeks when fed a fat diet. After 6 weeks, the lesion size of the DKO mice follows that of the single-knockout mice when fed a chow diet and gets to the same level in mice fed a fat diet. Plasma cholesterol levels were not altered as a result of ICAM-1 deficiency. These studies show that ICAM-1 is implicated in the formation and progression of atherosclerotic lesions.