Arteriosclerosis and thrombosis : a journal of vascular biology最新文献

The species difference in the turnover rates of the cholesteryl ester (CE) cycle in macrophage foam cells (MFC) was examined in mice and rats. MFC were induced by acetyl-LDL and pulsed with [3H]oleate, followed by a chase with [14C]oleate. The replacement of the initial amount of cholesteryl [3H]oleate by cholesteryl [14C]oleate within 24 hours was 63% in mouse MFC, whereas it was 33% in rat MFC. The corresponding replacement in rabbit MFC was < 10%. In addition, HDL removed 41% of the CE mass from mouse MFC but only 22% from rat MFC. HDL-induced CE reduction from mouse MFC was enhanced by 40% by the inhibitor for acyl-coenzyme A:cholesterol acyltransferase (58-035), whereas the enhancing effect was not observed with rat MFC. These results indicate that the rate of CE turnover may serve as a critical factor to determine the capacity of MFC to respond to HDL-induced CE reduction, suggesting the possibility that the species difference in the turnover rates of the CE cycle in MFC might explain, in part, the species difference in susceptibility to experimental atherosclerosis.

The mechanisms by which dietary fatty acids can modulate atherogenesis and inflammation are poorly understood. Induction in endothelial cells of adhesion molecules for circulating leukocytes and of inflammatory mediators by cytokines probably contributes to the early phases of atherogenesis and inflammation. We report here that incorporation into cellular lipids of docosahexaenoic acid (DHA), a specific fatty acid of the omega 3 family, decreases cytokine-induced expression of endothelial leukocyte adhesion molecules, secretion of inflammatory mediators, and leukocyte adhesion to cultured endothelial cells. DHA, but not eicosapentaenoic acid, decreased in a dose- and time-dependent fashion the expression of vascular cell adhesion molecule 1 (VCAM-1) induced by interleukin (IL)-1, tumor necrosis factor (TNF), IL-4, or bacterial lipopolysaccharide, with half-maximum inhibition at < 10 mumol/L. This reduction required prolonged (24- to 96-hour) exposure of endothelial cells to DHA and correlated with the degree of DHA incorporation into cellular lipids. DHA also limited cytokine-stimulated endothelial cell expression of E-selectin and intercellular adhesion molecule 1 and the secretion of IL-6 and IL-8 into the medium but not the surface expression of constitutive surface molecules. Cyclooxygenase inhibition did not block the effect of DHA on VCAM-1. In parallel with reduced surface VCAM-1 protein expression, DHA reduced VCAM-1 mRNA induction by IL-1 or TNF. DHA treatment also reduced the adhesion of human monocytes and of monocytic U937 cells to cytokine-stimulated endothelial cells. These properties of DHA may contribute to antiatherogenic and anti-inflammatory effects of omega 3 fatty acids.

We used the single-strand conformational polymorphism method to screen 311 patients with familial hypercholesterolemia from London lipid clinics and Southampton and South West Hampshire health district for mutations in the 3' part of exon 4 of the low-density lipoprotein (LDL) receptor gene. This part of the gene codes for repeat 5 of the binding domain of the LDL receptor, which is known to be critical for the receptor-mediated removal of both triglyceride-rich lipoprotein remnants and LDL. Six previously described mutations were identified in 29 apparently unrelated individuals (9.3%), with the mutations all lying within a 50-bp fragment of the gene. Three of the mutations are null alleles producing no protein, and the other three lead to production of a defective protein. The effect of the different gene mutations on lipid levels was examined, after the data were combined with information on previously reported mutations in this patient group. Mean LDL cholesterol levels were highest in those individuals with a mutation creating a null allele (9.54 mmol/L) and were similar to levels in those individuals with a mutation affecting repeat 5 that resulted in the production of a defective protein (9.37 mmol/L). In this sample, previously identified patients with a defective protein mutation outside repeat 5 had lower mean levels of LDL cholesterol (7.78 mmol/L), which were similar to levels seen in patients in whom the specific mutation had not been identified (7.31 mmol/L). Overall, these differences were highly statistically significant (P < .001).(ABSTRACT TRUNCATED AT 250 WORDS)

The plasma level of factor VII activity was a risk factor for the development of ischemic heart disease (IHD) in a prospective epidemiological study of hemostatic factors. We have previously reported significant correlations between factor VII clotting activity or antigen and lipid fractions in a group of 132 young men (< 30 years old) at low risk for IHD and concluded that control of the plasma factor VII level may be linked to lipid metabolism in normal male physiology. Because factor VII is one of four vitamin K-dependent procoagulant proteins, we hypothesized that plasma levels of all these proteins would be similarly controlled in normal physiology. In an extension of this study, we have measured two additional vitamin K-dependent clotting factors (prothrombin [factor II] and factor X activity), as well as factor VII activity and antigen and fasting serum lipid fractions in healthy young men and women (< 30 years old) at low risk for IHD. In the women, we found significant positive correlations of factor VII antigen with total or HDL cholesterol and of prothrombin or factor X with total or LDL cholesterol. In the men, factor VII activity or antigen correlated with total cholesterol, triglycerides, HDL cholesterol, or LDL cholesterol; prothrombin or factor X correlated with total cholesterol, triglycerides, or LDL cholesterol. In contrast, we found no significant correlations of fibrinogen with any of the lipid fractions in our groups of men or women. Our data support the hypothesis that control of the levels of the vitamin K-dependent procoagulant proteins is linked to lipid metabolism in the normal physiology of both men and women.

The purposes of this study were to compare fibrinolytic responses to moderate intensity exercise in physically active and inactive men and during morning and evening exercise. Fourteen physically inactive men (mean age, 34.7 +/- 4.0 years) and 12 regularly active men (34.8 +/- 4.0 years) performed two exercise sessions, morning and evening, at 50% of maximal oxygen consumption. Tissue plasminogen activator (TPA) and plasminogen activator inhibitor-1 (PAI-1) activity were measured before and after exercise. Data were analyzed using a three-way ANOVA with repeated measures. TPA activity increased with exercise in both groups, although the active group demonstrated greater increases than the inactive group. Postexercise TPA activity was greater with evening than morning exercise. The inactive group exhibited greater PAI-1 activity than the active group. PAI-1 activity was higher during the morning than evening but did not change with exercise for either group. We conclude that moderate intensity exercise increases TPA activity in physically active and inactive men, with greater increases seen in active men, particularly during evening exercise. Moderate intensity exercise does not appear to affect PAI-1 activity. The lower PAI-1 activity in active men may be one mechanism whereby regular physical activity lowers the risk for coronary artery disease.

The presence of a silicone elastomer collar around one carotid artery of a rabbit induces thickening of the tunica intima. We used immunoblotting to study quantitatively changes in the isoforms of caldesmon, a protein implicated in the regulation of contractility in smooth muscle, while also monitoring the histological changes during 28 days after collaring. Control rabbit carotid arteries (n = 28) contained 245 +/- 6.4 nmol/g protein of the larger isoform of caldesmon (CDh) and 68.3 +/- 3.6 nmol/g protein of the smaller isoform (CD1). Four days after collaring, intimal thickening was slight, but 44% of arterial CDh had been lost; this loss of CDh was therefore from the tunica media. At 10 days, CDh fell to 37% of the control level. Immunofluorescence using CDh-specific antibodies showed that the CDh level was diminished but remained uniform across the wall of collared arteries. At 14 days, when intimal thickening was maximal, there was 30% more CD1 than in controls. At 28 days, the neointima had thinned, and CD1 had fallen to below control levels. Thus, CD1 levels reflected the development and regression of neointima. Changes in caldesmon isoforms showed that smooth muscle cell phenotypic changes occurred throughout the arterial wall.

Transgenic mice expressing apolipoprotein (apo) E(Cys 142), a human defective variant of apo E, have elevated levels of plasma cholesterol, triglycerides, and very-low-density lipoproteins (VLDL); beta-VLDL, the biochemical hallmark of the human genetic disease type III hyperlipoproteinemia (HLP), is also present in these mice. This study was designed to determine whether these type III HLP mice have an increased susceptibility to spontaneous or diet-induced atherosclerosis. Three 4-month-old male transgenic mice and three male nontransgenic littermates were assessed for the presence of atherosclerotic lesions in the proximal aorta. No lipid-stained microscopic lesions were visible in the aortas of nontransgenic mice, whereas minimal lesions were observed on the aortic valve stumps of transgenic mice. To magnify the effect of the mutant apo E on the susceptibility of the transgenic animals to atherosclerosis, 8 transgenic and 8 nontransgenic mice were fed a synthetic diet containing 1% cholesterol, 16% fat, and 0.5% cholic acid for 3 months. The diet induced an increase in plasma cholesterol level in both transgenic and nontransgenic mice. However, the increase in plasma cholesterol level in the transgenic mice was all in the VLDL fraction, whereas in nontransgenic mice it was due to increases in both VLDL and high-density lipoprotein (HDL) fractions. Plasma triglyceride levels fell in both groups of mice. After 3 months on the diet, there were compositional changes in the VLDL of both groups, characterized mainly by higher cholesteryl ester content, that resulted in beta-migration on agarose gel electrophoresis. Despite similar VLDL lipid compositions, the extent of atherosclerosis differed markedly in the two groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Study subjects (6 women and 5 men) over the age of 40 years with fasting low-density lipoprotein cholesterol concentrations > 130 mg/dL were studied during three 5-week diet phases and one 10-week phase: baseline (36% fat: 13% saturated fatty acids [SFA], 12% monounsaturated fatty acids [MUFA], 8% polyunsaturated fatty acids [PUFA], and 128 mg cholesterol/1000 kcal); reduced fat (29% fat: 7% SFA, 9% MUFA, 11% PUFA, and 85 mg cholesterol/1000 kcal); and two low fat (15% fat: 5% SFA, 5% MUFA, 3% PUFA, and 73 mg cholesterol/1000 kcal). Body weight was maintained during the first three 5-week phases (baseline, reduced fat, and low fat [-->energy]) and decreased during the last 10-week phase when the low-fat diet was provided such that the subjects determined, in part, their caloric intake (low fat [decreases energy]). Mean body weight declined by 0.62 +/- 0.47 kg/wk during the first 5 weeks and 0.43 +/- 0.43 kg/wk during the second 5 weeks of the 10-week low-fat (decreases energy) period. Relative to the baseline diet, plasma cholesterol concentrations decreased from 226 +/- 33 to 195 +/- 19 (-13%), 208 +/- 22 (-7%), and 190 +/- 19 (-15%) mg/dL when the subjects consumed the reduced-fat, low-fat (--> energy), and low-fat (decreases energy) diets, respectively. Low-density lipoprotein cholesterol concentrations decreased from 158 +/- 28 to 128 +/- 16 (-18%), 134 +/- 17 (-14%), and 119 +/- 15 (-23%) mg/dL when the subjects consumed the reduced-fat, low-fat (--> energy), and low-fat (decreases energy) diets, respectively. High-density lipoprotein cholesterol concentrations decreased from 48 +/- 11 to 42 +/- 9 (-10%), 35 +/- 7 (-25%), and 38 +/- 8 (-18%) mg/dL when the subjects consumed the reduced-fat, low-fat (--> energy), and low-fat (decreases energy) diets, respectively. Triglyceride concentrations increased from 110 +/- 32 to 115 +/- 31 (8%), 188 +/- 76 (75%), and 130 +/- 32 (22%) mg/dL when the subjects consumed the reduced-fat, low-fat (--> energy), and low-fat (decreases energy) diets, respectively. Maximal changes in plasma lipid concentrations were observed after the first 5 weeks of the low-fat (decreases energy) diet phase despite continued weight loss throughout the entire 10-week diet period.(ABSTRACT TRUNCATED AT 400 WORDS)

Endothelial cells grown on filters developed junctional complexes that reduced diffusional transport and increased electrical resistance over the cell layer. Induction of tissue factor by recombinant interleukin-1 beta led to a highly polarized tissue factor expression on the apical cell surface only. After prolonged growth to allow deposition of matrix, removal of the endothelial cells by collagenase or by 0.1 mol/L NH4OH left behind some cellular material as well as tissue factor, which was only detectable in the upper compartment. A human bladder carcinoma cell line, which does not form tight junctions and expresses tissue factor constitutively, showed essentially no polarity. Endothelial cell secretory compounds like von Willebrand factor, tissue plasminogen activator, and plasminogen activator inhibitor-1 were constitutively released to both sides. The added secretion due to recombinant interleukin-1 beta stimulation of the endothelial cells observed for von Willebrand factor and tissue plasminogen activator was, however, localized to the apical surface. The availability of tissue factor on the luminal surface of endothelial cells, ie, allowing contact with factor VII in the flowing blood, has potentially very significant pathophysiological consequences.

The blocker of receptor-mediated calcium entry SK&F 96365 was used to evaluate the contribution of calcium influx to the formation of biologically active endothelial prostanoids and endothelium-derived relaxing factor (EDRF). SK&F 96365 inhibited histamine-stimulated calcium entry into human umbilical vein endothelial cells but not its discharge from intracellular stores as determined spectrofluorometrically by changes of intracellular calcium concentration in fura-2-loaded cells. Concordantly, SK&F 96365 inhibited histamine-induced endothelial synthesis of 6-keto-prostaglandin F1 alpha and thromboxane B2 in a dose-dependent manner. To assess the functional significance of endothelial formation of prostacyclin and EDRF to platelets, the cAMP- and cGMP-dependent phosphorylation of two platelet proteins, rap1B and a 50-kD vasodilator-stimulated phosphoprotein (VASP), was analyzed in coincubation experiments of endothelial cells with platelets. Autacoids released by histamine-stimulated endothelial cells caused the phosphorylation of rap1B and VASP in platelets, which was only partly inhibited by either indomethacin or NG-monomethyl-L-arginine but was almost completely suppressed by SK&F 96365. The concomitant endothelial release of thromboxane A2 had no effect on protein kinase C- and calcium-dependent phosphorylation of platelet proteins. The results demonstrate that blockade of receptor-mediated calcium entry by SK&F 96365 markedly reduced the release of biologically active prostacyclin and EDRF from endothelial cells. Thus, calcium influx but not calcium release from intracellular stores plays a critical role in the receptor-stimulated formation and liberation of prostacyclin and EDRF in endothelial cells.