Hypertension-enhanced monocyte adhesion in experimental atherosclerosis

Monocyte Subset Recruitment Marker Profile Is Inversely Associated With Blood ApoA1 Levels

Dyslipidemia promotes development of the atherosclerotic plaques that characterise cardiovascular disease. Plaque progression requires the influx of monocytes into the vessel wall, but whether dyslipidemia is associated with an increased potential of monocytes to extravasate is largely unknown. Here (using flow cytometry) we examined recruitment marker expression on monocytes from generally healthy individuals who differed in lipid profile. Comparisons were made between monocyte subsets, participants and relative to participants’ lipid levels. Monocyte subsets differed significantly in their expression of recruitment markers, with highest expression being on either the classical or non-classical subsets. However, these inter-subset differences were largely overshadowed by considerable inter-participant differences with some participants having higher levels of recruitment markers on all three monocyte subsets. Furthermore, when the expression of one recruitment marker was high, so too was that of most of the other markers, with substantial correlations evident between the markers. The inter-participant differences were explained by lipid levels. Most notably, there was a significant inverse correlation for most markers with ApoA1 levels. Our results indicate that dyslipidemia, in particular low levels of ApoA1, is associated with an increased potential of all monocyte subsets to extravasate, and to do so using a wider repertoire of recruitment markers than currently appreciated.

Macrophage accumulation within coronary arterial wall in diabetic patients with acute coronary syndrome: a study with in-vivo intravascular imaging modalities

Background and aims

Macrophage accumulation in arteriosclerotic plaque of coronary arteries is involved in plaque destabilization. Atherosclerosis has been known to be progressive in patients with type 2 diabetes mellitus (DM). This study compared the features of 3-dimensional (3D) spatial distribution of macrophage accumulation within coronary artery wall between acute coronary syndrome (ACS) patients with DM (n = 20) and those without (non-DM, n = 20) by using intravascular ultrasound (IVUS) and optical coherence tomography (OCT).

Methods

The OCT-derived macrophage accumulation was measured within the proximal left anterior-descending artery. This measurement was performed for the whole vessel segment of interest, higher shear stress region (flow divider side) and lower shear stress region (the opposite side).

Results

Normalized macrophage accumulation per unit length of the whole segment of interest was significantly larger in ACS patients with DM than without. In non-DM patients, macrophage density per IVUS-derived plaque volume was significantly higher in high shear stress region compared to low shear stress region, however, there was no significant difference between the two regions in DM patients. The macrophage density in the low shear stress region was significantly higher in the DM group than in the non-DM group. A multivariate analysis showed that the presence of DM was a major determinant for macrophage distribution.

Conclusions

Macrophage accumulation was more abundant and homogeneous within coronary arterial wall in DM patients with ACS compared to non-DM patients, suggesting that plaque destabilization may occur more widely throughout coronary wall in DM patients.

Effects of high-temperature heat wave and ozone on hypertensive rats

This study aimed to investigate the effects of heat waves and ozone on hypertensive rats. Heat wave and ozone pollution were simulated on the Shanghai Meteorological and Environmental Animal Exposure System. Eighteen hypertensive rats were randomly divided into a control group, an ozone group, and a heat wave plus ozone group. The experimental groups were transferred to the exposure system for exposure to the ozone and heat wave plus ozone. After exposure, blood samples were collected from the abdominal aorta, and the hearts were harvested in all groups. The concentrations of inflammatory factors, vasomotion factors, cardiovascular risk factors, oxidative stress and thrombosis factors and heat stress factors in heart tissue were measured in each rat. Ozone exposure and heat wave plus ozone exposure increased the levels of inflammatory factors, thrombosis factors, vasomotion factors and cardiovascular risk factors, except for HDL-C, which was reduced. Moreover, experimental exposure increased the heat stress factors and oxidative stress, except for SOD, which was decreased. These data demonstrated that both ozone exposure and heat wave plus ozone exposure could adversely affect hypertensive rats, and that heat wave may enhance the toxic effect of ozone exposure.

Impact of physical activity on monocyte subset CCR2 expression and macrophage polarization following moderate intensity exercise

Coronary artery disease (CAD) is an immune-mediated disease in which CCR2 attracts classical, intermediate, and non-classical monocytes to the arterial intima where they differentiate to macrophages. Balance between pro-inflammatory M1 and anti-inflammatory M2 macrophages contributes to CAD prevention. Moderate to vigorous intensity physical activity (MVPA) elicits an immune response and reduces the incidence of CAD, however, the impact of prior MVPA on monocyte subset CCR2 expression and macrophage polarization following acute exercise is unknown.

Purpose

To determine the impact of physical activity status on monocyte subset CCR2 surface expression and macrophage polarization in response to an acute bout of moderate intensity cycle ergometry.

Methods

24 healthy women and men (12 high physically active [HIACT]: ≥1500 METmin/wk MVPA & 12 low physically active [LOACT]: <600 METmin/wk MVPA) underwent an acute moderate intensity (60% VO2peak) bout of cycle ergometry for 30 ​min. Blood samples were collected prior to (PRE), immediately (POST), 1 ​h (1H), and 2 ​h (2H) following exercise. Monocyte CCR2 and macrophage CD86 (M1) and CD206 (M2) were analyzed by flow cytometry.

Results

Intermediate monocyte CCR2 decreased in response to exercise in the HIACT group (PRE: 11409.0 ​± ​1084.0 vs. POST: 9524.3 ​± ​1062.4; p ​= ​0.034). Macrophage CD206 was lower in the LOACT compared to the HIACT group at 1H (HIACT: 67.2 ​± ​5.6 vs. LOACT: 50.1 ​± ​5.2%; p ​= ​0.040). Macrophage CD206 at 1H was associated with both PRE (r ​= ​0.446, p ​= ​0.043) and POST (r ​= ​0.464, p ​= ​0.034) non-classical monocyte CCR2.

Conclusion

These data suggest that regular moderate to vigorous physical activity positively impacts both monocytes and macrophages following acute moderate intensity exercise and that this impact may contribute to the prevention of coronary artery disease.

Animal models of surgically manipulated flow velocities to study shear stress-induced atherosclerosis

Atherosclerosis is a chronic inflammatory disease of the arterial tree that develops at predisposed sites, coinciding with locations that are exposed to low or oscillating shear stress. Manipulating flow velocity, and concomitantly shear stress, has proven adequate to promote endothelial activation and subsequent plaque formation in animals. In this article, we will give an overview of the animal models that have been designed to study the causal relationship between shear stress and atherosclerosis by surgically manipulating blood flow velocity profiles. These surgically manipulated models include arteriovenous fistulas, vascular grafts, arterial ligation, and perivascular devices. We review these models of manipulated blood flow velocity from an engineering and biological perspective, focusing on the shear stress profiles they induce and the vascular pathology that is observed.

Importance of hemodynamic forces as signals for exercise-induced changes in endothelial cell phenotype

Current evidence indicates that the ability of physical activity to sustain a normal phenotype of arterial endothelial cells (ECs) plays a central role in the beneficial effects of exercise (Ex) on atherosclerotic disease. Here we evaluate the strength of evidence that shear stress (SS) and/or circumferential wall stress (stretch) are the primary signals, produced by bouts of Ex, that signal altered gene expression in arterial ECs, thereby resulting in a less atherogenic EC phenotype. Current literature indicates that SS is a signal for expression of antiatherogenic genes in cultured ECs, in ECs of isolated arteries, and in ECs of arteries in intact animals. Furthermore, SS levels in the arteries of humans during Ex are in the range that produces beneficial changes. In contrast, complex flow profiles within recirculation zones and/or oscillatory flow patterns can cause proatherogenic gene expression in ECs. In vivo evidence indicates that Ex decreases oscillatory flow/SS in some portions of the arterial tree but may increase oscillatory flow in other areas of the arterial tree. Circumferential wall stress can increase expression of some beneficial EC genes as well, but circumferential wall stress also increases production of reactive oxygen species and increases the expression of adhesion factors and other proatherogenic genes. Interactions of arterial pressure and fluid SS play an important role in arterial vascular health and likely contribute to how Ex bouts signal changes in EC gene expression. It is also clear that other local and circulating factors interact with these hemodynamic signals during Ex to produce the healthy arterial EC phenotype. We conclude that available evidence suggests that exercise signals formation of beneficial endothelial cell phenotype at least in part through changes in SS and wall stretch in the arteries.

The potential anti-inflammatory benefits of improving physical fitness in hypertension

Hypertension is associated with an increased risk of stroke and atherosclerosis. In addition to elevated blood pressure, hypertension is characterized by neuroendocrine and immune activation, including elevated levels of C-reactive protein, inflammatory cytokines, and soluble adhesion molecules, which are predictive of morbidity and mortality outcomes. Pharmacological treatment for hypertension reduces blood pressure, but has limited effectiveness in reducing the accompanying inflammation and its associated morbidity and mortality. Exercise and diet interventions regularly show reductions in blood pressure in hypertensive individuals. Similar interventions in other populations show reductions in many inflammatory markers, but these effects have not been routinely examined in hypertensive individuals. The mechanisms through which exercise might exert an anti-inflammatory action include the sympathetic nervous system, the hypothalamic-pituitary-adrenal axis, as well as direct effects of blood pressure. Here, exercise is promoted as a potentially effective treatment for both the elevated blood pressure and chronic inflammation found in hypertension.

High Pressure Promotes Monocyte Adhesion to the Vascular Wall

Hypertension is a known risk factor for the development of atherosclerosis. To assess how mechanical factors contribute to this process, mouse carotid arteries were maintained in organ culture at normal (80 mm Hg) or high (150 mm Hg) intraluminal pressure for 1, 6, 12, or 24 hours. Thereafter, fluorescent human monocytic cells (U937) were injected intraluminally and allowed to adhere for 30 minutes before washout. U937 adhesion was increased in vessels kept at 150 mm Hg 12 hours (23.5+/-5.7 versus 9.9+/-2.2 cells/mm at 80 mm Hg; P<0.05) or 24 hours (26.7+/-5.7 versus 8.8+/-1.5 cells/mm; P<0.05). At 24 hours, high pressure was associated with increased mRNA expression of monocyte chemoattractant protein-1, interleukin-6, keratinocyte-derived chemokine, and vascular cell adhesion molecule-1 (6.9+/-2.1, 4.4+/-0.1, 9.8+/-2.8, and 2.4+/-0.1-fold respectively; P<0.05), as assessed by quantitative RT-PCR and corroborated by immunohistochemistry, which also revealed an increase in intracellular adhesion molecule-1 expression. Nuclear factor kappaB inhibition using SN50 peptide abolished the overexpression of chemokines and adhesion molecules and reduced U937 adhesion in vessels at 150 mm Hg. Moreover, treatment of vessels and cells with specific neutralizing antibodies established that monocyte chemoattractant protein-1, interleukin-6, and keratinocyte-derived chemokine released from vessels at 150 mm Hg primed the monocytes, increasing their adhesion to vascular cell adhesion molecule-1 but not intracellular adhesion molecule-1 via alpha4beta1 integrins. The additive effect of chemokines on the adhesion of U937 cells to vascular cell adhesion molecule-1 was confirmed by in vitro assay. Finally, pressure-dependent U937 adhesion was blunted in arteries from mice overexpressing endothelial NO synthase. Hence, high intraluminal pressure induces cytokine and adhesion molecule expression via nuclear factor kappaB, leading to monocytic cell adhesion. These results indicate that hypertension may directly contribute to the development of atherosclerosis through nuclear factor kappaB induction.

Alteration of Leukocyte–Endothelial Cell Interaction During Aging in Retinal Microcirculation of Hypertensive Rats

PURPOSE

Hypertension, one of the more common chronic diseases affecting the elderly, has been reported to influence leukocyte-endothelial cell interaction. The leukocyte-mediated inflammatory process contributes to age-related changes in vessels. This study was designed to evaluate age-related changes in leukocyte-endothelial cell interaction in the hypertensive rat retina.

METHODS

Male spontaneous hypertensive rats (SHR; 1.5, 3, 6, 12, and 20 months of age) and age-matched Wistar-Kyoto rats (WKY) were used. The number of accumulated leukocytes was counted in sections of flat-mounted retinal tissue. The expression of intercellular adhesion molecule-1 (ICAM-1) and CD18 (the common beta-chain of ICAM-1 ligands) was evaluated. Retinal thickness was evaluated histologically.

RESULTS

The number of accumulated leukocytes and the expression of ICAM-1 and CD18 increased in the aged retina. The number of leukocytes that accumulated and the expression of CD 18 were significantly higher in the SHR group than in the WKY group (P < 0.01). In addition, retinal thickness decreased with age.

CONCLUSION

Leukocyte-endothelial cell interaction increased in the aged retina and these changes were more severe in SHR retina than in WKY retina. This increased interaction was first observed at 3 months, a relatively young age.

Human urotensin II as a link between hypertension and coronary artery disease

Hypertension is a well-known risk factor for atherosclerosis, but the molecular mechanisms that link elevated blood pressure to the progression of atherosclerosis remain unclear. Human urotensin II (U-II), the most potent endogenous vasoconstrictor peptide identified to date, and its receptor (UT receptor) are involved in the etiology of essential hypertension. In patients with essential hypertension, U-II infused into the forearm brachial artery has been shown to induce vasoconstriction. Recent studies have demonstrated elevated plasma U-II concentrations in patients with essential hypertension, diabetes mellitus, atherosclerosis, and coronary artery disease. U-II is expressed in endothelial cells, macrophages, macrophage-derived foam cells, and myointimal and medial vascular smooth muscle cells (VSMCs) of atherosclerotic human coronary arteries. UT receptors are present in VSMCs of human coronary arteries, the thoracic aorta and cardiac myocytes. Lymphocytes are the most active producers of U-II, whereas monocytes and macrophages are the major cell types expressing UT receptors, with relatively little receptor expression in foam cells, lymphocytes, and platelets. U-II accelerates foam cell formation by up-regulation of acyl-coenzyme A:cholesterol acyltransferase-1 in human monocyte-derived macrophages. In human endothelial cells, U-II promotes cell proliferation and up-regulates type 1 collagen expression. U-II also activates nicotinamide adenine dinucleotide phosphate (NADPH) oxidase and plasminogen activator inhibitor-1 in human VSMCs, and stimulates VSMC proliferation with synergistic effects observed when combined with oxidized low-density lipoprotein, lysophosphatidylcholine, reactive oxygen species or serotonin. These findings suggest that U-II plays key roles in accelerating the development of atherosclerosis, thereby leading to coronary artery disease.

Significance of Plaque Disruption Sites in Acute Coronary Syndrome

Coronary plaque disruption and subsequent thrombosis occur in both unstable angina (UA) and acute myocardial infarction (AMI). However, it is unclear why UA and AMI have different clinical courses. The purpose of this angiographic study was to examine whether the longitudinal plaque disruption site is a factor that can be used to distinguish these two conditions. Seventy-two patients with AMI or UA in whom ischemia- or infarct-related arteries and plaque disruption sites could be determined were enrolled. The plaque disruption sites were classified as upstream type or downstream type. The upstream type and downstream type were defined as plaque rupture site located proximal and distal, respectively, to the maximum stenosis on angiography. The frequency of the upstream type was significantly higher in patients with AMI (60.0%) than in patients with UA (18.5%). On the other hand, the frequency of the downstream type was higher in patients with UA (81.5%) in patients with AMI (40.0%; p<0.01). The longitudinal plaque disruption site may thus be a factor that can be used to distinguish these two diseases.

Angiogenic activation of valvular endothelial cells in aortic valve stenosis

Here, we demonstrate the angiogenic response of valvular endothelial cells to aortic valve (AV) stenosis using a new ex vivo model of aortic leaflets. Histological analysis revealed neovascularization within the cusps of stenotic but not of non-stenotic aortic valves. Correspondingly, the number of capillary-like outgrowth in 3D collagen gel was significantly higher in stenotic than in non-stenotic valves. Capillary-like sprouting was developed significantly faster in stenotic than in non-stenotic valves. New capillary sprouts from stenotic aortic valves exhibited the endothelial cell markers CD31, CD34 and von-Willebrand factor (vWF) as well as carcinoembryonic antigen cell adhesion molecule-1 (CEACAM1), Tie-2 and angiogenesis inhibitor endostatin. Western blot analyses revealed a significant increase of CEACAM1 and endostatin in stenotic aortic valve tissue. Electron microscopic examinations demonstrate that these capillary-like tubes are formed by endothelial cells containing Weibel-Palade bodies. Remarkably, inter-endothelial junctions are established and basement membrane material is partially deposited on the basal side of the endothelial tubes. Our data demonstrate the capillary-like sprout formation from aortic valves and suggest a role of angiogenesis in the pathogenesis of aortic valve stenosis. These data provide new insights into the mechanisms of valvular disorders and open new perspectives for prevention and early treatment of calcified aortic stenosis.

Changes in plasma levels of adhesion molecules after percutaneous mitral balloon valvuloplasty

BACKGROUND

Adhesion molecules are expressed on vascular endothelium and on immune and inflammatory cells. Recently increased levels of adhesion molecules have been shown in patients with rheumatic mitral stenosis. This study examined the serum levels of the adhesion molecules intercellular adhesion molecule 1 (ICAM-1), vascular cell adhesion molecule 1 (VCAM-1), and E-selectin in patients with rheumatic mitral stenosis and the effects of percutaneous mitral balloon valvuloplasty (PMBV) on these adhesion molecules.

MATERIALS AND METHODS

Thirty five patients (3 men, 32 women, mean age 39+/-5 years) with severe rheumatic mitral stenosis who underwent percutaneous balloon mitral valvuloplasty, and 35 age and sex matched healthy control subjects were included in the study. Serum levels of ICAM-1, VCAM-1, and E-selectin were measured in all patients who underwent PMBV and in all control subjects. Blood samples were taken for measurement of adhesion molecules immediately before and 24 h after the mitral balloon valvuloplasty.

RESULTS

The plasma levels of soluble adhesion molecules E-selectin, ICAM-1 and VCAM-1 were significantly elevated in patients with mitral stenosis compared to control subjects: E-selectin, 97+/-59 vs. 45+/-24 ng/ml (P=.001), sICAM-1, 874+/-301 ng/ml vs. 238+/-82 ng/ml (P<.0001); sVCAM-1, 3056+/-763 ng/ml vs. 985+/-298 ng/ml (P<.0001). Plasma levels of VCAM-1 significantly increased 24 h after the valvuloplasty procedure (3056+/-763 ng/ml vs. 3570+/-1225 ng/ml P=.013). Plasma levels of E-selectin showed a significant decrease after PMBV (97+/-59 vs. 70+/-58 ng/ml, P=.043) and plasma levels of ICAM-1 did not show any change after PMBV (874+/-301 vs. 944+/-377 ng/ml, P=.356).

CONCLUSION

Cellular adhesion molecules, sICAM-1, E-selectin, sVCAM-1 have shown changes in different directions in response to PMBV. These results necessitate further studies to clarify the mechanism underlying the association between adhesion molecules and PMBV as well as rheumatic mitral stenosis.

Mechanotransduction of endothelial oxidative stress induced by cyclic strain

Atherosclerotic lesions display a nonuniform distribution throughout the vascular tree. Mechanical forces produced by local alterations in blood flow may play an important role in the localization of atherosclerosis. One such force, cyclic strain, has been hypothesized to promote atherogenesis by inducing oxidative stress in endothelial cells, resulting in enhanced endothelial adhesiveness for monocytes. To investigate the signal transduction systems involved, human aortic endothelial cells were plated on flexible silicone strips that were either non-coated or adsorbed with poly-L-lysine, vitronectin, fibronectin, or collagen I. Cells were then subjected to uniform sinusoidal stretch (10%) for 6 h. Endothelial superoxide anion production was increased in cells exposed to cyclic strain compared to static conditions. Furthermore, endothelial oxidative response to stretch was matrix protein-dependent, whereas cells grown on fibronectin and collagen I produced significantly more superoxide. The oxidative response to cyclic strain was reduced by coincubation with RGD peptides, blocking antibodies to alpha2- and beta-integrins antibodies, as well as inhibitors of protein kinase C. To investigate the effect of oxidative stress on gene transcription, endothelial cells grown on collagen I were transfected with an NFkappaB-sensitive luciferase construct. Cells that underwent cyclic strain displayed a tenfold induction of NFkappaB activation compared to static controls. Strain-induced luciferase activity was blunted by coincubation with RGD peptides or calphostin C. Thus, exposure of endothelial cells to cyclic strain led to integrin activation of a PKC-sensitive pathway that results in increased superoxide anion production and mobilization of NFkappaB.

Peripheral blood mononuclear cell CD62L and CD11a expression and soluble interstitial cell adhesion molecule-1 levels following infused isoproterenol in hypertension

OBJECTIVES

Increasingly, studies indicate that alterations in leukocyte and endothelial cell adhesion molecules may enhance atherosclerotic processes in human hypertension. beta-adrenergic receptor activation has long been implicated in the aetiology and/or maintenance of hypertension and also has significant effects on leukocyte and endothelial adhesion molecules. This study therefore examined the effects of hypertension on peripheral blood mononuclear cell CD62L and CD11a expression and circulating soluble interstitial cell adhesion molecule (ICAM)-1 (sCD54) levels following infusion of the non-specific beta-adrenergic agonist isoproterenol.

DESIGN

In the setting of a General Clinical Research Center, 15 hypertensive and 20 normotensive subjects underwent an infusion of isoproterenol consisting of two sequential 15 min fixed-order doses of 20 and 40 ng/kg per min. Flow cytometry was used to quantify lymphocyte and monocyte populations and adhesion molecules, and ELISA was used to quantify sCD54 levels.

RESULTS

As expected, isoproterenol led to a significant increase in the number of circulating lymphocytes (P < 0.001) and monocytes (P < 0.01). The number of circulating CD3+CD8+CD62Llow T cytotoxic cells increased following isoproterenol (P < 0.001) and this increase was greater in hypertensives than in normotensives (P < 0.05). Isoproterenol led to a decrease in surface density of CD62L (P < 0.001) and an increase in surface density of CD11a (P < 0.001) in all subjects. Hypertensives had a significantly lower CD62L density (P = 0.01) and higher CD11a density on lymphocytes (P = 0.002) compared to normotensives. sCD54 levels were unchanged following isoproterenol but were elevated in hypertensives (P < 0.05).

CONCLUSIONS

A beta-adrenergic-induced environment of increased CD62Llow/CD11ahigh leukocytes, coupled with existing endothelial CD54 activation, could support basic atherosclerotic processes of increased peripheral blood mononuclear cell-endothelial adhesion in hypertension.

Arterial changes in paediatric haemodialysis patients undergoing renal transplantation

BACKGROUND

The relationship between primary renal disease and arterial wall changes in paediatric haemodialysis patients has been little studied. The aim of the present work was to determine the influence of primary renal disease on arterial wall pathology in uraemic paediatric patients.

METHODS

Twelve paediatric haemodialysis patients (seven girls, five boys) aged 11-17 years were included in the study. The primary renal diseases were urinary malformations in six patients (uropathy group) and acquired glomerular diseases (glomerulopathy group) in six patients. Age, sex distribution, duration of chronic renal failure, duration of haemodialysis, blood pressure, serum glucose, triglycerides, cholesterol, fibrinogen, calcium, phosphorus and parathyroid hormone levels were compared. Internal iliac artery samples were obtained at the time of related-donor renal transplantation. Artery samples were fixed in formaldehyde and sections were stained separately with haematoxylin and eosin, Orcein, Verhoef-van Gieson, and Masson trichrome.

RESULTS

Five arteries had fibrous or fibroelastic intimal thickening, medial mucoid ground substance and disruption of the internal elastic lamella. Two of these had microcalcification in the intimal layer; another two demonstrated atheromatous plaques; the remaining five were normal. These pathological changes were found in the arteries of all six patients with uropathy, whereas of the six patients with glomerulopathy only one had arterial changes (P<0.001). The duration of chronic renal failure was 4.8+/-1.9 years in the uropathy group and 2.2+/-1.2 in the glomerulopathy group (P<0.05). The two groups were comparable in terms of serum glucose, triglycerides, cholesterol, fibrinogen, calcium, and parathyroid hormone levels, presence of hypertension, sex distribution, and duration of haemodialysis. Plasma phosphorus and the calcium x phosphate product were higher in the uropathy group than in the glomerulopathy group (P<0.05).

CONCLUSIONS

This study demonstrated that pathological changes are common in the arteries of uraemic paediatric patients, and that calcification and atherosclerosis are integral to this disease process. In our study, these alterations were more common in the patients with uropathy. We speculate that the patients with uropathy are more prone to these alterations due to slower progression and a longer duration of renal insufficiency.

Cigarette smoking and hypertension influence nitric oxide release and plasma levels of adhesion molecules

Progression of atherosclerosis is currently believed to involve interactions between leukocytes and vascular endothelium. Epidemiological risk factors for atherosclerosis such as hypertension and smoking are known to cause endothelial dysfunction, which is an early event in the atherosclerotic process; they also may be considered in the light of their effects on adhesion molecule expression and release. Little is known about the additive effect between these two risk factors on endothelial adhesion molecule expression and nitric oxide release. Soluble adhesion molecules and the nitric oxide were quantified in smoking hypertensive patients in comparison to those from patients with hypertension alone. Cotinine, a stable metabolite of nicotine, has been used to identify smokers. One hundred and three hypertensive patients were selected: 51 smokers (plasma cotinine levels >25 ng/ml) and 52 non-smokers. Plasma concentrations of soluble intercellular cell adhesion molecule-1 (sICAM-1), soluble endothelial leukocyte adhesion molecule-1 (sELAM-1) and soluble vascular cell adhesion molecule-1 (sVCAM-I) were quantified with ELISA methods. Plasma concentration of nitric oxide metabolites was measured by HPLC, whilst plasma concentration of cotinine was measured by RIA. Significant increases of sICAM-1 and sVCAM-1 were demonstrated in smokers (p<0.001 and p<0.05, respectively). In the same patients, a positive significant correlation between sVCAM-1 and plasma cotinine levels was observed (p<0.002). Nitric oxide metabolites were reduced significantly (p<0.04) in smokers. In conclusion, our data show that the two risk factors, smoking and hypertension, are additive risk factors in generating endothelial dysfunction and vascular damage, which plays a key role in atherogenesis.

Upregulated Expression of Rat Heart Intercellular Adhesion Molecule-1 in Angiotensin II- but Not Phenylephrine- Induced Hypertension

-Intercellular adhesion molecule-1 (ICAM-1), part of an immunoglobulin-like superfamily of adhesion molecules, is involved in several cardiovascular diseases. We investigated whether in vivo angiotensin II (Ang II) increases ICAM-1 in rats. Sprague-Dawley rats were infused with vehicle or Ang II (750 µg. kg(-1). d(-1) SC) for 7 days. The contribution of Ang II receptors to ICAM-1 expression was investigated with a nonpeptide Ang II type 1 (AT(1)) receptor antagonist losartan (30 mg. kg(-1). d(-1) in drinking water). Systolic blood pressure was elevated in Ang II-treated animals compared with sham-treated controls, and losartan blocked this increase. Tumor necrosis factor (TNF)-alpha (5 µg/kg IP bolus), a prototype inducer of ICAM-1, was administered as a positive control for ICAM-1 expression. After treatment, hearts were frozen in liquid nitrogen; homogenates were subjected to SDS-PAGE and immunoblotted with an anti-rat ICAM-1 monoclonal antibody. We detected a predominantly high-molecular-weight band in homogenates from non-TNF-alpha-treated rats, which was enhanced by 80+/-5% in TNF-alpha-treated rats. This band measured approximately 200 kDa, which is the molecular weight of ICAM-1 in its native dimer form. The same band was detected in homogenates from sham and Ang II-treated rats, with the latter showing a 150+/-10% increase in ICAM-1 versus sham controls. Immunoprecipitation of rat heart homogenates with anti-rat ICAM-1 antibody resulted in a dominant band of the same molecular weight as samples not treated with antibody. Losartan prevented enhanced expression of ICAM-1 in the presence of Ang II but had no effect on basal ICAM-1 expression. Phenylephrine, an alpha-agonist (3 mg. kg(-1). d(-1) ), was infused for 1 week but had no effect on ICAM-1 expression, even though systolic blood pressure was elevated to the same level as in rats treated with Ang II. Thus, heart ICAM-1 expression is enhanced via AT(1) receptor activation independent of hypertension. Ang II-induced ICAM-1 expression was time and dose dependent, with maximal expression occurring within 5 to 7 days at 100 to 750 µg/kg Ang II. Immunohistochemical staining demonstrated markedly increased ICAM-1 levels in the perivascular area in Ang II-infused rats. Monocyte/macrophage accumulation was significantly greater in Ang II-treated rat hearts than in sham-treated hearts (10+/-1; P:<0.001; n=5). Thus during inflammation, overexpression of ICAM-1 may contribute to cardiovascular damage in diseases characterized by increased activity of the renin-angiotensin system.

Peripheral blood mononuclear cell-endothelial adhesion in human hypertension following exercise

OBJECTIVE

To determine the effects of hypertension and exercise on interleukin-6 (IL-6) levels and mononuclear cell adhesion to endothelial cells.

DESIGN

Twelve hypertensive and 33 normotensive volunteers were studied prior to and following exhaustive exercise. End points were stimulated IL-6 levels and peripheral blood mononuclear cell (PBMC) CD11a (LFA-1) expression and in vitro PBMC adhesion to human umbilical venous endothelial cells (HUVEC).

RESULTS

In response to exercise, all subjects showed a significant increase in lymphocyte CD11a a density and in IL-6 levels (P < 0.001). Compared to normotensives, hypertensives showed significantly greater mean density of CD11a on lymphocytes (P< 0.05) and on monocytes (P < 0.05). In response to exercise, hypertensive subjects showed a twofold greater increase in IL-6 as compared to normotensives (+ 240 pg/ml versus + 123 pg/ml, respectively; P< 0.05). PBMC adhesion to HUVEC was increased in hypertensives but decreased in normotensives following exercise (P< 0.03).

CONCLUSION

The findings suggest that exercise leads to increased mononuclear cell adhesion to endothelial cells in patients with hypertension, possibly through cytokine-induced activation of mononuclear cell CD11a. These findings, coupled with prior data indicating increased endothelial activation in hypertension, may be relevant to the increased risk of atherosclerosis in human hypertension.

Reduction of aortic wall motion inhibits hypertension-mediated experimental atherosclerosis

Hypertension is a well-known risk factor for coronary artery disease and carotid and lower extremity occlusive disease. Surgically induced hypertension in hypercholesterolemic animals results in increased aortic wall motion and increased plaque formation. We tested the hypothesis that reduction in aortic wall motion, despite continued hypertension, could reduce plaque formation. New Zealand White rabbits (n=26) underwent thoracic aortic banding to induce hypertension and were fed an atherogenic diet for 3 weeks. In 13 rabbits, a segment of aorta proximal to an aortic band was externally wrapped to reduce wall motion. All animals were fed an atherogenic diet for 3 weeks. Four groups were studied: 1, coarctation control (no wrap, n=7); 2, coarctation with loose wrap (n=6); 3, coarctation with firm wrap (n=7); and 4, control (noncoarcted, n=6). Wall motion, blood pressure, and pulse pressure were measured at standard reference sites proximal and distal to the coarctation by use of intravascular ultrasound. Quantitative morphometry was used to measure intimal plaque. Mean arterial pressure and cyclic aortic wall motion were equally increased proximal to the aortic coarctation in all 3 coarcted rabbit groups compared with the control group (P:<0.001). Wall motion in the segment of aorta under the loose and firm wraps was no different from the control value. The external wrap significantly reduced intimal thickening in the 4 groups by the following amounts: group 1, 0.30+/-0.03 mm(2); group 2, 0.06+/-0.02 mm(2); group 3, 0. 04+/-0.02 mm(2); and group 4, 0.01+/-0.01 mm(2) (P:<0.001). Localized inhibition of aortic wall motion in the lesion-prone hypertensive aorta resulted in significant reduction in intimal plaque formation. These data suggest that arterial wall cyclic motion may stimulate cellular proliferation and lipid uptake in experimental atherosclerosis.

Plasma concentrations of VCAM-1 and ICAM-1 are elevated in patients with Type 1 diabetes mellitus with microalbuminuria and overt nephropathy

AIMS

Elevated urinary albumin excretion is associated with macrovascular atherosclerotic complications in Type 1 diabetes mellitus. Adhesion molecules mediate leucocyte adhesion to the endothelium early in the atherosclerotic process. The present study tests the hypothesis that microalbuminuria and diabetic nephropathy are associated with elevated plasma concentrations of soluble vascular adhesion molecule (sVCAM)-1, soluble intercellular adhesion molecule (sICAM)-1, and soluble E-selectin (sE-selectin) aiming to illustrate factors of potential pathogenetic relevance for the excess cardiovascular disease in diabetic patients with renal complications.

METHODS

Soluble adhesion molecule concentrations were measured by enzyme-linked immunosorbent assays (ELISA) in healthy controls (n = 16) and in 59 Type 1 diabetic patients: group 1-patients with normoalbuminuria (n = 16); group 2-patients with microalbuminuria (n = 15); group 3-patients with macroalbuminuria and normal serum creatinine (n = 15), group 4-patients with macroalbuminuria and moderately elevated serum creatinine (n = 13).

RESULTS

Plasma concentrations of sVCAM-1 and sICAM-1 were similar in healthy controls and normoalbuminuric Type 1 diabetic patients, but the concentrations were increased by the presence of microalbuminuria and overt nephropathy (P < 0.001 and P < 0.0001, ANOVA). Concentrations of sE-selectin did not differ between diabetic patients and controls.

CONCLUSIONS

Plasma concentration of sICAM-1 is elevated in Type 1 diabetic patients with microalbuminuria and the concentrations of sICAM-1 as well as sVCAM-1 are elevated in patients with macroalbuminuria and normal s-creatinine. The elevated plasma concentrations of these soluble adhesion molecule concentrations in patients with renal complication can be of pathogenetic importance for the development of atherosclerosis and plasma soluble adhesion molecule concentrations may provide additional information on cardiovascular risk.

Expression of endothelial cell adhesion molecules on heart valves: up-regulation in degeneration as well as acute endocarditis

Inflammatory cytokines such as interleukin-1 (IL-1) and tumour necrosis factor-alpha (TNF-alpha), as well as shear stress, cause endothelial cells (ECs), to undergo not only functional alterations but also structural reorganizations, which contribute to vascular leakage. Like ECs of the human aorta, ECs on heart valves are exposed to extreme shear stress. However, while ECs expression of cell adhesion molecules (CAMs) in large vessels has been widely studied, it seems that there are no such studies on ECs of heart valves, although this knowledge might be important for our understanding of the aetiological aspects of local inflammatory responses. Using immunohistochemistry, this study characterized the CAM expression of ECs on degenerative, mostly calcified heart valves and on heart valves with florid endocarditis. As expected, the constitutively expressed molecules (ICAM-1, CD34, CD31) were found both on degenerative and on inflamed valves. Furthermore, marked expression of E-selectin and VCAM-1 was found not only on inflamed valves, but also on larger portions of the degenerative valves with no morphological evidence of inflammation. This striking finding might help to explain why patients with fibrotic heart valves are susceptible to recurrent endocarditis. Why the endothelial activation markers E-selectin and VCAM-1 are expressed on degenerative heart valves requires further investigation.

Spontaneous combined hyperlipidemia, coronary heart disease and decreased survival in Dahl salt-sensitive hypertensive rats transgenic for human cholesteryl ester transfer protein

The acceleration of atherosclerosis by polygenic (essential) hypertension is well-characterized in humans; however, the lack of an animal model that simulates human disease hinders the elucidation of pathogenic mechanisms. We report here a transgenic atherosclerosis-polygenic hypertension model in Dahl salt-sensitive hypertensive rats that overexpress the human cholesteryl ester transfer protein (Tg[hCETP]DS). Male Tg[hCETP]DS rats fed regular rat chow showed age-dependent severe combined hyperlipidemia, atherosclerotic lesions, myocardial infarctions and decreased survival. These findings differ from various mouse atherosclerosis models, demonstrating the necessity of complex disease modeling in different species. The data demonstrate that cholesteryl ester transfer protein can be proatherogenic. The interaction of polygenic hypertension and hyperlipidemia in the pathogenesis of atherosclerosis in Tg[hCETP]DS rats substantiates epidemiological observations in humans.

Mononuclear cell adherence to cultured endothelium is enhanced by hypertension and insulin resistance in healthy nondiabetic volunteers

BACKGROUND

This study was initiated to compare the adherence to cultured endothelial cells of mononuclear cells isolated from normotensive and hypertensive individuals.

METHODS AND RESULTS

Mononuclear cell binding to endothelium was greater in patients with hypertension (32+/-1 versus 25+/-2; P<0.001) than in normal volunteers. There was a significant relationship (r=0.42, P<0. 01) between mononuclear cell binding and mean arterial pressure, independent of differences in age, sex, and body mass index. A significant relationship also existed between insulin resistance (estimated by the steady-state plasma glucose concentration during the insulin suppression test) and mononuclear cell binding in both the normotensive (r=0.86, P<0.001) and hypertensive (r=0.74, P<0. 001) groups. Furthermore, multiple regression analysis demonstrated an independent relationship (P<0.001) between mononuclear cell binding and both steady-state plasma glucose and hypertensive status.

CONCLUSIONS

These results indicate that both hypertension and insulin resistance lead to changes in mononuclear cells that increase their adherence to cultured endothelial cells.

The role of adhesion molecules in atherosclerosis

The progression of atherosclerosis is currently believed to involve the interaction of monocytes with the vascular endothelium. Within the last decade, the cell-surface proteins thought to control these interactions have been investigated. This review seeks to describe the nature of these interactions through what are known as adhesion molecules and their role in atherogenesis. It begins with the stages of atherogenesis from the movement of the monocyte to the endothelium, followed by the migration of smooth muscle cells from the media to the intima, and subsequently to the later stages of fibrofatty plaque formation and potential complications due to thrombosis and/or plaque fissure and embolism. The different structural classifications of the adhesion molecules, such as integrins, cadherins, selectins, and members of the immunoglobulin gene superfamily, are outlined, and interaction of binding domains are highlighted. The vascular endothelium and the basic role of adhesion molecules in dysfunction are considered. Discussion of the role of adhesion molecules in atherogenesis focuses on interactions of the endothelium, monocytes, and leukocytes, as well as the influences of cytokines, oxidized low-density lipoproteins, and genetic determinants. Finally, epidemiological risk factors associated with atherosclerosis such as hypertension and dyslipidemia are considered in light of their effects on adhesion molecule expression.

Distribution of inflammatory cells in atherosclerotic plaques relates to the direction of flow

BACKGROUND

The distribution of macrophages and smooth muscle cells (SMCs) within atherosclerotic plaques is highly variable. This is clinically relevant because these cell types have opposite effects on the stability of atherosclerotic plaques. The present study was designed to investigate whether local variations in arterial flow over the plaque surface could relate to differences in the distribution of SMCs and macrophages in plaques.

METHODS AND RESULTS

Thirty-three entire carotid plaques were collected at autopsy and marked at their proximal (in relation to the direction of the blood flow) ends, and the cell composition of upstream parts (where high flow and high shear prevail) was compared with that of downstream parts (low flow and low shear stress). Seventy percent of plaques showed more SMCs in their downstream part, and 67% of plaques contained more macrophages in the upstream part. Immunostained macrophage areas were larger in upstream parts (P=0. 011). Immunostained SMC areas were larger in downstream parts (P=0. 031). Rupture sites of 6 of 9 ruptured plaques were in the upstream part.

CONCLUSIONS

Significant differences in cell composition between upstream and downstream parts of plaques indicate a role for arterial flow in the distribution of different cell types. The low-flow/low-shear downstream areas of plaques contain significantly more SMCs, which could provide the background for slowly progressive growth at distal ends of plaques. The significantly high number of macrophages in the upstream areas suggests a relationship between high flow/high shear and plaque instability.