Patients with combined hypercholesterolemia-hypertriglyceridemia show an increased monocyte-endothelial cell adhesion in vitro: triglyceride level as a major determinant

Effect of Apple Extracts on NF-κB Activation in Human Umbilical Vein Endothelial Cells

The mechanisms by which foods, such as fruit, are able to reduce the risk of chronic disease are still unclear. Several fruit products, including apples and apple juice, that are flavonoid-rich are reported to increase antioxidant levels in human subjects. This is supported by the finding from our previous studies that the chronic consumption of apple juice by human subjects reduced ex vivo low-density lipoprotein (LDL) oxidation; we hypothesized that this was due to the flavonoid in the apple juice, which, as we reported earlier, reduced in vitro LDL oxidation. To further explore whether the mixture of flavonoids and other phytochemicals in apples are biologically relevant antioxidants, we tested the effects of this flavonoid-rich apple extract (AE) on oxidant-related pathways in a model of the endothelium: human umbilical vascular endothelial cells (HUVECs). The effects of AE on oxidant-responsive (i.e., tumor necrosis factor [TNF]-α-induced) nuclear factor (NF)-κB signaling in cell culture were assessed in transfected HUVECs by using a construct that expressed luciferase under the control of NF-κB. Incubation of HUVEC for 24 hrs with up to 10 mM (as gallic acid equivalents) of AE demonstrated no cytotoxicity, as determined by lactate dehydrogenase release, caspase 3 activation, and apoptosis marker–based FACS analysis. AE after a 24-hr incubation period at either 200 or 2000 nM showed a complex pattern of decreased basal and TNF-α-stimulated NF-κB signaling (63% maximal decrease) as assessed by luciferase activity in the transfected HUVECs, as well as by reduced levels of IκBα protein phosphorylation detected by Western blot analysis. We suggest that AE downregulates NF-κB signaling and that this is indicative of an antioxidant effect of the flavonoids present in AE.

Plasma Lipid Levels in 10- to 13-year-old Costa Rican Elementary Schoolchildren

An adverse lipid profile is a major risk factor for atherosclerosis. This study evaluated the lipid profiles of 683 schoolchildren aged 10 to 13 years. The prevalence of both high LDL and high total cholesterol levels was significantly (p < . 001) higher in private schoolchildren than in public schoolchildren. There were no significant differences in the prevalence of high triglyceride levels among the schoolchildren. Mean total cholesterol and LDL cholesterol levels were significantly higher in children whose parents had completed over 11 years of schooling. Private schoolchildren were more sedentary and tended to have a more atherogenic diet. Our data suggest that prevention programmes in primary schools are required to decrease the prevalence of cardiovascular risk factors, including abnormal lipid profiles.

Increase of circulating CD11b(+)Gr1(+) cells and recruitment into the synovium in osteoarthritic mice with hyperlipidemia

Although recent studies suggest that hyperlipidemia is a risk factor for osteoarthritis (OA), the link between OA and hyperlipidemia is not fully understood. As the number of activated, circulating myeloid cells is increased during hyperlipidemia, we speculate that myeloid cells contribute to the pathology of OA. Here, we characterized myeloid cells in STR/Ort mice, a murine osteoarthritis model, under hyperlipidemic conditions. Ratios of myeloid cells in bone marrow, the spleen, and peripheral blood were determined by flow cytometry. To examine the influence of the hematopoietic environment, including abnormal stem cells, on the hematopoietic profile of STR/Ort mice, bone marrow transplantations were performed. The relationship between hyperlipidemia and abnormal hematopoiesis was examined by evaluating biochemical parameters and spleen weight of F₂ animals (STR/Ort x C57BL/6J). In STR/Ort mice, the ratio of CD11b⁺Gr1⁺ cells in spleens and peripheral blood was increased, and CD11b⁺Gr1⁺ cells were also present in synovial tissue. Splenomegaly was observed and correlated with the ratio of CD11b⁺Gr1⁺ cells. When bone marrow from GFP-expressing mice was transplanted into STR/Ort mice, no difference in the percentage of CD11b⁺Gr1⁺ cells was observed between transplanted and age-matched STR/Ort mice. Analysis of biochemical parameters in F₂ mice showed that spleen weight correlated with serum total cholesterol. These results suggest that the increase in circulating and splenic CD11b⁺Gr1⁺ cells in STR/Ort mice originates from hypercholesterolemia. Further investigation of the function of CD11b⁺Gr1⁺ cells in synovial tissue may reveal the pathology of OA in STR/Ort mice.

Activation of ganglioside GM3 biosynthesis in human blood mononuclear cells in atherosclerosis

Using blood monocytes and lymphocytes from atherosclerotic patients and healthy subjects we have investigated activity of GM3 synthase, cellular levels of ganglioside GM3 and its role in monocyte adhesion to cultured human umbilical vein endothelial cells (HUVEC). The results showed that activity of GM3 synthase and cellular levels of ganglioside GM3 in blood mononuclear cells from atherosclerotic patients were several-fold higher than those from healthy subjects. In monocytes the activity of GM3 synthase was one an order of magnitude higher than in lymphocytes from both groups studied; this suggests the major contribution of monocytes to enhanced biosynthesis and levels of GM3 in mononuclear cells in atherosclerosis. Enrichment of monocytes from healthy subjects with ganglioside GM3 by incubation in medium containing this ganglioside increased adherence of these monocytes to HUVEC up to the values typical for monocytes from atherosclerotic patients. In addition, an increase in CD11b integrin expression was observed that was comparable to that seen in lipopolysaccharide-activated monocytes. It is suggested that in atherosclerosis the enhanced cellular levels of GM3 in monocytes and lymphocytes may be an important element of cell activation that facilitates their adhesion to endothelial cells and penetration into intima.

Nutritional status among women with pre-eclampsia and healthy pregnant and non-pregnant women in a Latin American country

AIMS

Pre-eclampsia (PE) is one of the leading causes of maternal and perinatal morbidity and mortality worldwide. It has been proposed that, among other risk factors, the nutritional status of women can lead to the endothelial dysfunction that characterizes this entity. The aim of the present study was to compare the nutritional status of women with PE with healthy pregnant and non-pregnant women.

MATERIAL AND METHODS

A multicenter case-control study was carried out. Between September 2006 and July 2009, 201 women with PE were compared with 201 pregnant, and 201 non-pregnant aged-matched women without cardiovascular or endocrine diseases. A clinical history and physical examination was performed. Fasting blood samples were drawn to measure serum glucose and lipid profile. The nutritional status of participants was assessed using a food frequency questionnaire.

RESULTS

The average age of women was 26.6 ± 7.2 years. Compared to healthy pregnant controls, women with PE had a higher body mass index, higher fasting blood glucose levels, higher triglycerides, and lower high-density lipoprotein cholesterol levels. Women with PE had a higher intake of carbohydrates, energy intake and cereal compared to healthy pregnant and non-pregnant controls. A conditional logistic regression demonstrated that carbohydrate and sodium intake are associated with PE development.

CONCLUSIONS

Diets of women with PE were characterized by higher energy and carbohydrate intake compared to normal pregnant and non-pregnant women. This suggests that higher carbohydrate and sodium intake increases the risk of PE among women in Colombia.

Validation of the circulating monocyte being representative of the cholesterol-loaded macrophage: biomediator activity

CONTEXT

Inflammation is pivotal to atherosclerosis. The monocyte-macrophage, a crucial cell in atherogenesis, is present during all stages of atherosclerosis. However, there is a paucity of data comparing circulating monocytes to cholesterol-laden macrophages (foam cells), with regard to their atherogenic properties, especially in subjects with established risk factors such as hyperlipidemia.

OBJECTIVE

To determine whether the circulating blood monocyte is representative of the cholesterol-loaded macrophage with regard to its proatherogenicity in healthy controls and hyperlipidemic patients.

DESIGN

Fasting blood was drawn from 32 subjects (n = 16 controls and n = 16 hyperlipidemic patients), and peripheral blood monocytes were obtained. Also, macrophages were cultured and loaded with acetyl low-density lipoprotein on day 10. Day 1 peripheral blood monocytes and day 11 cholesterol-loaded macrophages were assessed for release of superoxide anion and cytokines (interleukin 1, interleukin 6, tumor necrosis factor alpha); surface expression of CD11b, VLA-4, and CD40; and adhesion to human endothelium.

RESULTS

Monocyte and cholesterol-loaded macrophage superoxide anion release, cytokines, and adhesion of monocytes to human endothelium were significantly increased in hyperlipidemic patients compared with controls. Furthermore, following cholesterol loading, there were no significant differences in monocyte versus cholesterol-loaded macrophage activity (P = .71). Also, CD14 and CD11b surface expression on monocytes was significantly increased in hyperlipidemic patients as compared with controls. The magnitude of change in the monocytes versus cholesterol-loaded macrophages was similar.

CONCLUSIONS

From these studies, we can conclude that the monocyte, which is readily accessible, is an appropriate cell to study for modulation of proatherogenic activity, especially with regard to genomic and proteomic analyses/ microarrays.

Lipaemia, Inflammation and Atherosclerosis

Atherosclerosis is the major cause of death in the world. Fasting and postprandial hyperlipidaemia are important risk factors for coronary heart disease (CHD). Recent developments have undoubtedly indicated that inflammation is pathophysiologically closely linked to atherogenesis and its clinical consequences. Inflammatory markers such as C-reactive protein (CRP), leucocyte count and complement component 3 (C3) have been linked to CHD and to hyperlipidaemia and several other CHD risk factors. Increases in these markers may result from activation of endothelial cells (CRP, leucocytes, C3), disturbances in adipose tissue fatty acid metabolism (CRP, C3), or from direct effects of CHD risk factors (leucocytes). It has been shown that lipoproteins, triglycerides, fatty acids and glucose can activate endothelial cells, most probably as a result of the production of reactive oxygen species. Similar mechanisms may also lead to leucocyte activation. Increases in triglycerides, fatty acids and glucose are common disturbances in the metabolic syndrome and are most prominent in the postprandial phase. People are in a postprandial state most of the day, and this phase is proatherogenic. Inhibition of the activation of leucocytes, endothelial cells, or both, is an interesting target for intervention, as activation is obligatory for adherence of leucocytes to the endothelium, thereby initiating atherogenesis. Potential interventions include the use of unsaturated long-chain fatty acids, polyphenols, antioxidants, angiotensin converting enzyme inhibitors and high-dose aspirin, which have direct anti-inflammatory and antiatherogenic effects. Furthermore, peroxisome proliferator activating receptor gamma (PPARgamma) agonists and statins have similar properties, which are in part independent of their lipid-lowering effects.

Hyperlipidemia coincides with reversible growth impairment of cultured human autologous endothelial cells

Patient-related risk factors for the growth of autologous endothelial cells were assessed in a clinical series of 100 consecutive recipients of in vitro endothelialized prosthetic vascular grafts. For all patients, the indication for bypass operation was arteriosclerotic occlusive disease of the distal arteries. Endothelial cells were harvested from a small piece of subdermal vein and cultured in medium containing 20% of autologous serum. Growth was continually monitored. In cultures that failed to grow, the autologous serum supplement to the culture medium was replaced by pooled homologous serum from young healthy donors. The comparison of a multitude of serum parameters between patients whose endothelial cells failed to grow and those showing normal growth revealed a significant difference in serum lipid content: triglycerides: 4.76 +/- 3.36 versus 2.83 +/- 2.28 mmol/L (p = .001); cholesterol: 6.78 +/- 1.69 versus 5.69 +/- 1.32 mmol/L (p = .003); and lipoprotein (a): 35.9 +/- 28.3 versus 22.2 +/- 26.6 mg/dl (p = .04). Following serum exchange with low-lipid pool serum that contained 1.74 mmol/L triglycerides, 4.86 mmol/L cholesterol, 5 mg/dl lipoprotein (a), and 5.79 mmol/L glucose, a remarkable recovery occurred in 85% of these cultures, resulting in fully restored proliferative capacity. As a consequence, population doubling time did not differ between the two groups at any point in time and mass cultures sufficient for confluent graft endothelialization were obtained with hardly any delay. The authors conclude that hyperlipidemia may lead to growth impairment of cultured human endothelial cells. This growth inhibition is reversible if the supplemented autologous serum is replaced by pooled serum with low lipid content.

Cholesterol attenuates linoleic acid-induced endothelial cell activation

Vascular endothelial cell activation and dysfunction are critical early events in atherosclerosis. Even though very low or high levels of cholesterol can compromise cellular functions, cholesterol is a critical membrane component and may protect the vascular endothelium from oxidative stress and polyunsaturated fatty acid-mediated inflammatory responses. We have previously shown that the parent omega-6 fatty acid linoleic acid can markedly activate vascular endothelial cells. We now propose that membrane cholesterol can modify and inhibit linoleic acid-mediated endothelial cell dysfunction. To test this hypothesis, pulmonary artery endothelial cells were incubated with cholesterol (0 to 100 micromol/L) for 24 hours and then treated with 90 micromol/L of linoleic acid (18:2n-6) for 6 to 24 hours. In control cells, treatment with linoleic acid reduced intracellular glutathione levels and induced the DNA binding activity of nuclear factor-kappaB (NF-kappaB) leading to the upregulation of interleukin-6 (IL-6). In addition, the expression of endothelial nitric oxide synthase (eNOS) was altered, with linoleic acid increasing eNOS activity. In contrast, enrichment with cholesterol enhanced glutathione levels and reduced the linoleic acid-induced activation of NF-kappaBand the production of IL-6. Prior exposure to 50 micromol/L cholesterol also prevented the fatty acid-induced increase in eNOS activation. Cholesterol loading activated peroxisome proliferator-activated receptor-gamma (PPAR-gamma), a nuclear receptor that can decrease inflammatory responses. Furthermore, the PPAR-gamma agonist thiazolidinedione markedly downregulated the NF-kappaB activation mediated by linoleic acid. Our data suggest that signaling pathways linked to endothelial cell activation by prooxidant and proinflammatory insults may be influenced by cellular cholesterol levels.

Induction of Atherosclerosis by Human Chylomicron Remnants: A Hypothesis

Epidemiologic studies have provided support for the association between delayed remnant removal and premature atherosclerosis. Triglyceride-rich particles such as chylomicrons and chylomicron remnants that carry dietary derived fats, may play a role in the early stages of developing arteriosclerosis. Currently research focuses on these lipoprotein classes seeking distinguishing factors that causes some lipoproteins to be atherogenic while others are not. Such lipoproteins could be involved in atherogenesis directly or indirectly. Direct involvement occurs by interaction of triglyceride-rich particles with the arterial wall, possibly affecting the artery wall by oxidative stress, direct endothelial toxicity by constituents such as lysophosphatidylcholine or oxysterols, induction of prothrombotic changes, stimulation of endothelial expression of cell adhesion molecules and direct interaction with circulating blood cells. Indirect involvement refers to the influence of triglyceride-rich lipoproteins on other lipoproteins on the composition of low density lipoprotein (LDL) and high density lipoprotein (HDL) particles. We propose that in individuals with delayed removal of chylomicron remnants, the prolonged exposure of areas of endothelium that have been partially activated by turbulent flow, to specific components of the remnants, results in the endothelial cells becoming further activated and able to bind monocytes. During or shortly after the transcytosis to the intima and transformation of monocytes to macrophages, the macrophages become engorged with remnant derived lipids and form the nidus of a fatty streak.

High-Energy Diets, Fatty Acids and Endothelial Cell Function: Implications for Atherosclerosis

Diets high in fat and/or calories can lead to hypertriglyceridemia and postprandial lipemia and thus are considered a risk factor for the development of atherosclerosis. Plasma chylomicron levels are elevated in humans after consuming a high-fat meal, and hepatic synthesis of VLDL is increased when caloric intake is in excess of body needs. High lipoprotein lipase activity and subsequent hydrolysis of triglyceride-rich lipoproteins may be an important source of elevated concentrations of fatty acid anions in the proximity to the endothelium and hence a major risk factor for atherosclerosis. We have shown that selected fatty acids, as well as lipoprotein lipase-derived remnants of lipoproteins isolated from hypertriglyceridemic subjects, can activate vascular endothelial cells and disrupt endothelial integrity. Our studies suggest that omega-6 fatty acids, and especially linoleic acid, cause endothelial cell dysfunction most markedly as well as can potentiate TNF-mediated endothelial cell injury. We propose that high-energy diets, and especially diets rich in linoleic acid, are atherogenic by contributing to an imbalance in cellular oxidative stress/antioxidant status of the endothelium, which can lead to activation of oxidative stress-responsive transcription factors, inflammatory cytokine production and the expression of adhesion molecules. Our data also suggest that nutrients, which have antioxidant and/or membrane stabilizing properties, can protect endothelial cells. These findings contribute to the understanding of the interactive role of high fat/calorie diets and subsequent hypertriglyceridemia with inflammatory components and nutrients that exhibit antiatherogenic properties in the development of atherosclerosis. Moreover, results from our research further support the concept that high-fat/calorie diets and associated postprandial hypertriglyceridemia are significant risk factors for atherosclerosis.

Impaired endothelium-dependent vasodilatation in renal failure in humans

BACKGROUND

The main causes of death in patients with chronic renal failure (CRF) are cardiovascular complications. The aim of the present study was to compare endothelium-dependent vasodilatation (EDV) in patients with chronic renal failure with a control population controlling for hypertension, diabetes mellitus and hypercholesterolaemia.

METHODS

Fifty-six patients with moderate CRF (mean creatinine clearance 29.4 ml/min/1.73 m(2)) underwent evaluation of EDV and endothelium-independent vasodilatation (EIDV) by means of forearm blood flow (FBF) measurements with venous occlusion plethysmography during local intra-arterial infusions of methacholine (Mch, 2 and 4 microg/min evaluating EDV) and sodium nitroprusside (SNP, 5 and 10 microg/min evaluating EIDV). Fifty-six control subjects without renal impairment underwent the same investigation.

RESULTS

Infusion of Mch increased FBF significantly less in patients with renal failure than in controls (198 vs 374%, P<0.001), whereas no significant difference was seen regarding the vasodilatation induced by SNP (278 vs 269%). The differences in EDV between the groups were still significant after controlling for hypertension, blood glucose, and serum cholesterol in multiple regression analysis (P<0.001). EDV was related to serum creatinine (r=-0.37, P<0.01), creatinine clearance (r=0.45, P<0.005) and to serum triglyceride levels (r=-0.29, P<0.005) in the CRF group.

CONCLUSIONS

Patients with moderate CRF have an impaired EDV even after correction for traditional cardiovascular risk factors and this impairment is related to the degree of renal failure.

Genomewide scan for familial combined hyperlipidemia genes in finnish families, suggesting multiple susceptibility loci influencing triglyceride, cholesterol, and apolipoprotein B levels

Familial combined hyperlipidemia (FCHL) is a common dyslipidemia predisposing to premature coronary heart disease (CHD). The disease is characterized by increased levels of serum total cholesterol (TC), triglycerides (TGs), or both. We recently localized the first locus for FCHL, on chromosome 1q21-q23. In the present study, a genomewide screen for additional FCHL loci was performed. In stage 1, we genotyped 368 polymorphic markers in 35 carefully characterized Finnish FCHL families. We identified six chromosomal regions with markers showing LOD score (Z) values >1.0, by using a dominant mode of inheritance for the FCHL trait. In addition, two more regions emerged showing Z>2.0 with a TG trait. In stage 2, we genotyped 26 more markers and seven additional FCHL families for these interesting regions. Two chromosomal regions revealed Z>2.0 in the linkage analysis: 10p11.2, Z=3.20 (theta=.00), with the TG trait; and 21q21, Z=2.24 (theta=.10), with the apoB trait. Furthermore, two more chromosomal regions produced Z>2.0 in the affected-sib-pair analysis: 10q11.2-10qter produced Z=2.59 with the TC trait and Z=2.29 with FCHL, and 2q31 produced Z=2.25 with the TG trait. Our results suggest additional putative loci influencing FCHL in Finnish families, some potentially affecting TG levels and some potentially affecting TC or apoB levels.

Effect of hyperketonemia on blood monocytes in type-I diabetic patients and apoptosis in cultured U937 monocytes

Recent studies have proposed a role for a reduced number of circulating monocytes in the development of atherosclerosis and circulatory diseases in diabetes. Ketosis is frequently encountered in type-I diabetics. This study was undertaken to test the hypothesis that hyperketonemia can lower blood monocyte count in type-I diabetic patients. Blood monocyte count was significantly lower (p < 0.05) in diabetics (n = 27) compared with age-matched normal siblings (n = 22). Blood levels of acetoacetate (AA) and triglycerides were significantly higher in diabetics compared with normals. To examine whether hyperketonemia can directly alter the monocyte count in diabetics, we studied the effect of ketone bodies AA and beta-hydroxybutyrate (BHB) on U937 cells, a human-derived promonocytic cell line as an in vitro model. The cell culture studies showed a dose-dependent growth inhibition and induction of apoptosis as a result of treatment with AA in U937 cells. Furthermore, there was a significant decrease in GSH and increase in lipid peroxidation products in AA-treated U937 cells. Taken together, this study suggests that elevated levels of ketone body AA can result in oxidative damage, accelerated apoptosis, and inhibition of cell growth in monocytes, which in turn can lower monocyte count in the blood of type-I diabetic patients.

Vitamin E inhibits low-density lipoprotein-induced adhesion of monocytes to human aortic endothelial cells in vitro

Monocyte adhesion to human aortic endothelial cells (ECs) is one of the early events in the development of atherogenesis. ECs were used to investigate the role of vitamin E in human monocyte adhesion to ECs in vitro. ECs incubated with 40 to 193 mg/dL of low-density lipoprotein cholesterol (LDL) for 22 hours exhibited increasing dose-dependent adherence for untreated, isolated human monocytes (P < .05). ECs exposed to the highest dose of LDL (193 mg/dL) but pretreated with 19 mumol/L alpha-tocopherol for 24 hours showed a trend to lower adherence for monocytes compared with non-treated ECs (4.4 +/- 1.2% versus 7.6 +/- 1.9%; P = .09). This effect of vitamin E became more significant (P < .05) when ECs were exposed to a lower level of LDL (40 mg/dL) or were pretreated with a higher level of alpha-tocopherol (42 mumol/L) and then exposed to 80 mg/dL LDL. Presupplementation of ECs with 15, 19, and 37 mumol/L alpha-tocopherol significantly (P < .05) reduced monocyte adhesion by 6 +/- 1%, 37 +/- 6%, and 69 +/- 17%, respectively. Levels of soluble intercellular adhesion molecule-1 (sICAM-1), one of the adhesion molecules for monocytes, increased after incubation of ECs with LDL 80 mg/dL (4.7 +/- 0.7 versus 6.4 +/- 1.2 ng/mL, respectively; P < .05). Treatment of ECs with alpha-tocopherol (42 mumol/L) significantly reduced induction of sICAM-1 by LDL to 2.2 +/- 2.3 ng/mL. After exposure to LDL, prostaglandin I2 production by ECs was diminished, whereas presupplementation of ECs with alpha-tocopherol partially reversed the LDL effect. Production of interleukin-1 beta was not detectable when ECs were treated with alpha-tocopherol, LDL, or alpha-tocopherol followed by LDL. Our findings indicate that vitamin E has an inhibitory effect on LDL-induced production of adhesion molecules and adhesion of monocytes to ECs via its antioxidant function and/or its direct regulatory effect on sICAM-1 expression.

Hypertension-enhanced monocyte adhesion in experimental atherosclerosis

PURPOSE

Hypertension is a known clinical risk factor for atherosclerosis. In experimental atherosclerosis, monocyte adhesion to the endothelial surface is enhanced and is considered to be an important early stage in plaque formation. We tested the hypothesis that hypertension enhances monocyte adhesion in experimental atherosclerosis.

METHODS

Twenty-two New Zealand White rabbits were fed an atherogenic diet for 3 weeks to induce plaque formation. Aortic coarctation was created in eight rabbits by wrapping a Dacron band around the midportion of the descending thoracic aorta (stenosis group), whereas six rabbits underwent banding without aortic constriction (no stenosis group). Eight rabbits served as nonoperated controls. Monocyte binding to the aortic endothelial surface was counted with epifluorescent microscopy on standard aortic segments proximal and distal to the band. Immunohistochemistry was performed for the following antibodies: VCAM-1, RAM11, CD11b, and factor VIII.

RESULTS

Mean blood pressure was 89 +/- 3 mm Hg in the aorta proximal to the stenosis, compared with 64 +/- 4 mm Hg in the no stenosis group and 74 +/- 3 mm Hg in the control group (p < 0.01). The mean aortic blood pressure gradient across the stenosis was 16 +/- 2 mm Hg in the stenosis group, whereas the aortic blood pressure gradient was 0.2 +/- 0.6 mm Hg in the no stenosis group and -0.3 +/- 0.4 mm Hg in the control group (p < 0.001). Monocyte adhesion to the aortic endothelial surface proximal to the stenosis was increased twofold compared with adhesion to the aorta distal to the stenosis and compared with the proximal aorta in the control group (p < 0.02). The proximal-to-distal aortic ratio of monocyte binding was enhanced in the stenosis group (2.2) compared with the no stenosis (0.76) and control (0.83) groups (p < 0.01). The intima area of the aorta proximal to the stenosis was significantly increased compared with the proximal aortas in the no stenosis and control groups (p < 0.01). RAM11, CD11b, and endothelial VCAM-1 expression were enhanced in the hypertensive region proximal to the stenosis.

CONCLUSIONS

In the hypertensive region in the aorta proximal to the stenosis, monocyte adhesion and endothelial VCAM-1 expression were increased, with intimal thickening and accumulation of macrophages. These findings suggest that hypertension may promote atherosclerotic plaque formation by enhancing monocyte adhesion.

In hypercholesterolemia, lower peripheral monocyte count is unique among the major predictors of atherosclerosis

Many studies have shown that enhanced monocyte adherence is an important factor in the initiation of atherosclerosis. Because the relationships between circulating monocyte count and atherosclerosis or its major predictors have received little attention, we conducted this study with the aim of clarifying these relationships. The study included 409 men and women who underwent a carotid artery duplex study and white blood cell analysis (Sysmex Cell Counter) during a 2-day health check at our hospital in 1994. We found no correlation between preexisting carotid atherosclerosis and monocyte count. After adjustment for age and sex, hypercholesterolemia, among the major predictors of atherosclerosis, showed a unique correlation with both lower monocyte count and percentage (P < .001, P < .0001, respectively), whereas smoking was correlated with a higher monocyte count (P < .001). There was a slight but nonsignificant increase in monocyte count in hypertension, diabetes, and hypertriglyceridemia. Our results imply that: (1) hypercholesterolemia has a strong, peripheral monocyte-reducing effect, probably due to direct enhancement of monocyte adhesion to the endothelium, which subsequently initiates the atherosclerotic process, and (2) the mechanisms of other predictor(s)-induced atherosclerosis may be quite different from that of hypercholesterolemia. Another possible explanation for the inverse correlation between monocyte count and serum cholesterol level is that decreased monocyte levels might lead to hypercholesterolemia because of decreased uptake of cholesterol from the plasma by less monocyte-derived macrophages. The reasons why preexisting carotid atherosclerosis did not correlate with monocyte count are also discussed.

Increased transcapillary escape rate of albumin in elderly subjects due to long-term smoking habits

Transcapillary escape rate of albumin (TER) expressed as percentage decrease in specific activity of plasma albumin per hour was measured in 44 healthy male subjects, 10 young non-smokers (median age 24.0 years, range 21-33), 10 young smokers (30.5 years, range 27-36), 10 elderly non-smokers (64.0 years, range 51-75) and 14 elderly smokers (61.5 years, range 54-69). In addition urinary albumin excretion rates were measured in 15 of the elderly subjects. The subjects were investigated after overnight fasting and abstention from tobacco. Median TER was 7.33% (interquartile range 5.82-9.90) in the elderly smoking subjects. This value was significantly elevated as compared to elderly non-smokers, 4.47% (2.93-5.83), young non-smokers, 3.70% (2.24-6.30) and young smokers, 4.25% (2.80-4.44). A statistically non-significant (P = 0.064) tendency of a higher urinary albumin excretion rate was observed in elderly smokers. This agrees with other investigations showing slightly increased albuminuria in smokers compared with non-smokers. The differences were not related to differences in blood pressure, plasma cholesterol, weight, or abuse of alcohol in the elderly subjects. Diabetic subjects with an increased TER to levels comparable with levels in long-term smokers have increased urinary albumin excretion rates, which seems to be greater than in long-term smoking subjects. It is suggested that increased TER in long-term smokers may indicate a vascular dysfunction affecting either capillary permeability or endothelial surface area.

Monocytes from patients with combined hypercholesterolemia-hypertriglyceridemia and isolated hypercholesterolemia show an increased adhesion to endothelial cells in vitro: II. Influence of intrinsic and extrinsic factors on monocyte binding

One of the primary risk factors for atherosclerosis is hypercholesterolemia. Patients with isolated hypercholesterolemia or combined hypercholesterolemia-hypertriglyceridemia are at risk to develop premature atherosclerosis. Diet-induced hypercholesterolemia in animals leads to an increased adhesion of monocytes to and transmigration through the intact endothelium of the vessel wall. In the present study, we investigated in vitro binding of freshly isolated monocytes from patients and healthy controls to a monolayer of endothelial cells obtained from human umbilical vein. All four diagnosed patient groups with isolated or combined hypercholesterolemia showed a significant increase in monocyte binding as compared with the control group (familial hypercholesterolemia [FH], +41%; polygenic hypercholesterolemia [PH] +35%; familial combined hypercholesterolemia [FCH], +47%; nonfamilial combined hypercholesterolemia-hypertriglyceridemia [CHH], +67%). In a longitudinal study it was observed that diet or medication induced a decrease in cholesterol and triglycerides; however, these therapeutic conditions did not diminish in vitro monocyte binding in the patient groups. There was no correlation between monocyte binding and plasma cholesterol, low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, triglycerides, or lipoprotein(a) within hyperlipidemic patient groups. The presence of heart and vessel disease in hyperlipidemic patients was not associated with a change in monocyte binding. The adhesion to endothelial cells of monocytes from smoking patients with combined hypercholesterolemia (27%) was significantly higher (+23%) than that of monocytes from nonsmoking patients. Cytofluorimetric analysis of monocytes from FCH and CHH patients for specific monocyte differentiation markers and integrins did not show differences as compared with monocytes from healthy controls.

Enhanced endothelial adhesiveness in hypercholesterolemia is attenuated by L-arginine

BACKGROUND

We have shown that chronic administration of the nitric oxide (NO) precursor L-arginine normalizes NO-dependent vasodilation and markedly inhibits atherogenesis in a hypercholesterolemic rabbit model. We hypothesized that this antiatherogenic effect is due to modulation of endothelial adhesiveness by endothelium-derived NO.

METHODS AND RESULTS

New Zealand White rabbits were fed normal chow (Cont), a high-cholesterol diet (Chol), a high-cholesterol diet supplemented with L-arginine (Arg), or a normal diet supplemented with the NO synthase antagonist L-nitroarginine (L-NA) for 2 weeks. In additional studies, some animals receiving L-NA were also treated with hydralazine to normalize blood pressure. After 2 weeks, thoracic aortas were harvested, opened longitudinally, and placed in a culture dish with the endothelial surface exposed to medium containing WEHI 78/24 cells, a monocytoid cell line. After incubation with the monocytoid cells for 30 minutes on a rocking platform, the aortic segments were washed repeatedly to remove nonadherent cells and adherent cells counted by epifluorescent microscopy. Monocytoid cell binding to aortic endothelium was significantly increased in Chol (P < .001 versus Cont); binding was markedly reduced in arginine-fed hypercholesterolemic animals (P < .05, Arg versus Chol). Monocytoid cell binding to aortic endothelium was also significantly increased in L-NA (P < .05); hydralazine normalized blood pressure but did not reduce monocytoid cell binding. To confirm that alterations in NO activity modulate endothelial cell-monocyte interaction, the release of nitrogen oxides (NOx) by thoracic aortas was assessed by a chemiluminescent technique. The concentration of NOx in the conditioned medium from segments of Arg thoracic aortas was significantly greater than that from Cont aortas, whereas that from L-NA aortas was significantly less.

CONCLUSIONS

Hypercholesterolemia enhances the adhesiveness of aortic endothelium for monocytes; this effect is attenuated by dietary L-arginine. Conversely, inhibition of NO synthesis enhances monocyte binding. The results suggest that endothelium-derived NO plays an important role in regulating the endothelial adhesiveness for monocytes. Alterations in NO activity may play a critical role in atherogenesis.

Probucol inhibits mononuclear cell adhesion to vascular endothelium in the cholesterol-fed rabbit

Mononuclear cells, isolated from the blood of hyperlipidaemic patients, are hyper-reactive and possess an increased propensity to adhere to vascular endothelial cells. Hyperlipidaemia is also associated with a dysfunctional endothelium, to which mononuclear cells stick with greater avidity. In order to assess the importance of lipid peroxidation and free-radical generation in these processes, we have investigated the effects of probucol on mononuclear cell adhesion to vascular endothelial cells in vivo and in vitro in the cholesterol-fed rabbit. New Zealand White rabbits were fed either: (i) control chow (n = 15), (ii) 2% cholesterol (n = 11), or (iii) 2% cholesterol with 1% probucol (n = 11). Mononuclear cell adherence to endothelium in the common carotid artery was assessed 5 weeks after the start of the experimental diet using the Hoechst 33342 staining technique. The 2% cholesterol diet caused a more than 6-fold increase in mean mononuclear cell adherence (P < 0.001). Concurrent probucol therapy abrogated the effects of cholesterol feeding, and in animals in this group, in vivo mononuclear cell adherence did not differ significantly from control animals. In vivo mononuclear cell adherence was directly related to serum cholesterol levels (r = 0.68, P < 0.0001) and inversely related to serum probucol concentrations (r = -0.63, P < 0.002). Concurrent probucol therapy also reduced the in vitro binding of mononuclear cells, isolated from hypercholesterolaemic animals, to endothelial cell monolayers (P < 0.01). These data suggest that the increased binding of mononuclear cells to vascular endothelium of cholesterol-fed rabbits may be a free radical mediated process that is inhibited by antioxidants.