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

The precipitating event leading to stroke, myocardial infarction, and/or sudden death may be related to the formation of mural thrombus at the site of a ruptured or superficially damaged stenotic plaque. The fluid dynamic properties at atherosclerotic plaques that may be implicated in this thrombus formation have been described in a wide variety of model systems in both the process of plaque rupture and the growth of platelet thrombi. In general, the local fluid dynamic conditions are complex and show major variations from flow in well-defined laminar flow systems. However, no studies have attempted to quantify the effect of stenosis-related disturbances on thrombus formation in native human blood and to compare them with the local fluid dynamics. We developed a parallel-plate perfusion chamber device in which thrombus formation is measured at the "apex" of eccentric stenoses and have correlated such measurements with values of the local fluid dynamics obtained by computer simulation. The extent of stenoses (reduction in the cross-sectional area of the blood flow channel) was 60%, 80%, and 89%, corresponding to "apex" wall shear rates of 2600, 10,500, and 32,000 sec-1, respectively. The wall shear rate in the laminar flow region proximal and distal to the stenoses was 420 sec-1. The surface of the stenosis was purified collagen type III fibrils that were exposed to flowing nonanticoagulated human blood drawn directly from an antecubital vein by a pump placed distally to the perfusion chamber. The resulting blood-collagen interactions were quantified by light microscopy by using a morphometric image analysis technique. Under all conditions studied, platelet thrombus formation at the "apex" was extensive.(ABSTRACT TRUNCATED AT 250 WORDS)

Atherosclerotic lesions are composed of a complex mixture of cell types that are engorged with lipid and enveloped in extracellular matrix elements. This manifestation probably results from imbalances in the cellular processing of cholesterol-delivering lipoproteins, changes in extracellular matrix deposition, and growth factor elaboration. One receptor class that could modulate these processes is LDL receptor-related protein/alpha 2-macroglobulin receptors (LRP/alpha 2-MR). Consequently, the presence of LRP/alpha 2-MR was determined on a temporal basis in lesions of distinct morphologies that were developed in cholesterol-fed New Zealand and heterozygous Watanabe heritable hyperlipidemic (WHHL) rabbits. The two strains of rabbits developed similar degrees of hypercholesterolemia in response to 0.5% wt/wt cholesterol in their diet. Lipoprotein-cholesterol distribution was also similar in the two strains. Aortic intimal areas covered by grossly discernible atherosclerotic lesions were extensive and not statistically different between the strains. Despite the similarities in the extent of hypercholesterolemia, lipoprotein distribution, and extent of atherosclerosis, the cellularity of the lesions formed was different in the two groups. Atherosclerotic lesions in cholesterol-fed New Zealand rabbits were uniformly rich in macrophages and deficient in smooth muscle cells, as determined by immunocytochemical staining with the cell-specific monoclonal antibodies RAM-11 and HHF-35. In contrast, atherosclerotic lesions formed in cholesterol-fed heterozygous WHHL rabbits covered a spectrum ranging from macrophage-rich lesions to those predominantly composed of disaggregated smooth muscle cells that were embedded in dense layers of extracellular matrix.(ABSTRACT TRUNCATED AT 250 WORDS)

High-resolution B-mode ultrasonography of the carotid arteries is used to investigate the signs of early atherosclerotic vessel wall disease. To assess whether carotid artery findings reflect atherosclerosis elsewhere, we studied the association between common carotid intima-media thickness and lower extremity arterial atherosclerosis among the first 1000 participants of the Rotterdam Study. The Rotterdam Study is a single-center population-based prospective follow-up study of 7983 subjects, > or = 55 years old. Baseline measurements include ultrasound imaging of intima-media thickness of the distal common carotid artery and determination of the ankle-to-arm systolic blood pressure index. Lower extremity arterial disease was defined as an ankle-arm index < 0.90 in at least one leg. An increase of 0.1 mm in common carotid artery intima-media thickness was associated with an age- and sex-adjusted reduction of the ankle-arm index of 0.026 (95% confidence interval [CI]: 0.018 to 0.034). The age- and sex-adjusted odds ratio of lower extremity arterial disease for subjects with an intima-media thickness > or = 0.89 mm (upper quintile) to that of subjects with an intima-media thickness < 0.89 mm was 3.4 (95% CI: 2.2 to 5.2). Analysis among subjects free from symptomatic cardiovascular disease yielded a reduction in ankle-arm index per 0.1 mm increase in intima-media thickness of 0.018 (95% CI: 0.008 to 0.28) and an odds ratio for lower extremity arterial disease of 3.0 (95% CI: 1.7 to 5.1). Adjustments for differences in serum lipids, hypertension, and current smoking status only slightly attenuated the results.(ABSTRACT TRUNCATED AT 250 WORDS)

The Wisconsin Hypoalpha Mutant (WHAM) chicken has a sex-linked mutation associated with a 90% reduction in high-density lipoprotein (HDL) cholesterol and apolipoprotein A-I (apoA-I). In the present studies, we did not detect a defect in apoA-I synthesis or secretion in liver or intestine. We tested the hypothesis that apoA-I is not binding properly to lipoprotein particles and is undergoing hypercatabolism. We therefore studied the in vivo turnover of lipid-free 125I-apoA-I. Its turnover was fourfold faster in WHAM chickens than in normal chickens. The 125I-apoA-I equilibrated more slowly with HDL in the WHAM chickens, and these animals had a much larger steady-state pool of lipid-free apoA-I than did control chickens. To determine the tissue sites of degradation of apoA- I, the tissue distribution of 125I-tyramine cellobiose apoA-I was assessed. The liver and kidneys were the major sites of apoA-I degradation, but in the WHAM chickens, the kidney made a twofold larger contribution to apoA-I degradation than in normal chickens. Total plasma phospholipid levels are reduced by 44% to 78% in the WHAM chickens. A phospholipid deficit might explain the elevated lipid-free apoA-I pool and, secondarily, the HDL deficiency of the WHAM chickens.

Proliferation of bovine aortic smooth muscle cells (SMCs) induced by thrombin, basic fibroblast growth factor, or serum is inhibited by anionic, nonsulfated aromatic compounds that mimic many of the effects of heparin. Among these compounds are aurintricarboxylic acid (ATA) and a newly synthesized polymer of 4-hydroxyphenoxy acetic acid (compound RG-13577). Iodinated- or 14C-labeled compound RG-13577 binds to cultured SMCs in a highly specific and saturable manner. Scatchard analysis of the binding data revealed the presence of an estimated 1 x 10(7) binding sites per cell with an apparent dissociation constant of 3 x 10(-6) mol/L. Binding of radiolabeled RG-13577 was efficiently competed for by related aromatic anionic compounds and by apolipoprotein E, but not by heparin, heparan sulfate, suramin, or various purified growth factors and extracellular matrix proteins. Receptor cross-linking of SMC-bound 125I-RG-13577 revealed a single species of high M(r) (approximately 280 kD) cell surface receptors detected in the absence but not the presence of excess unlabeled compound RG-13577. Binding was susceptible to downregulation and restoration of receptor levels in a manner similar to that of hormone and growth factor receptors. We suggest that the antiproliferative activity of compound RG-13577 and related compounds is initiated by binding to specific growth-inhibiting cell surface receptors. Heparin-mimicking compounds may be applied to inhibit SMC proliferation associated with atherosclerosis and restenosis.

Patients with insulin-dependent diabetes mellitus (IDDM) have proatherogenic disturbances in cholesteryl ester transfer (CET) despite intensive subcutaneous insulin therapy (ISC). Since CET is activated by insulin-sensitive lipoprotein lipase (LPL), which normally increases postprandially, we queried whether iatrogenic hyperinsulinism from ISC stimulated LPL and CET by studying well-controlled IDDM patients after ISC and then 6 months after lowering systemic insulin levels by intraperitoneal (IP) insulin delivery. Although glycemic control (HbA1c IDDM, 6.9 +/- 1.7%; control, 4.5% to 8%) was excellent during ISC, CET was accelerated (P < .001) and both systemic insulin levels and LPL specific activity were increased (P < .05). Following IP, basal systemic insulin levels declined by more than one half (ISC, 8.22 +/- 6.5 versus IP, 2.77 +/- 2.4 microU/mL; mean +/- SD; P < .025), and both LPL and CET activities returned to normal. Plasma triglyceride, cholesterol, high-density lipoprotein-2 (HDL2) cholesterol, HDL3 cholesterol, cholesteryl ester transfer protein mass, and glycemic control (HbA1c, 6.3 +/- 0.8%) were unchanged and remained normal. These findings indicate that ISC is associated with high levels of basal CET and LPL. These alterations both appear to be closely linked to iatrogenic hyperinsulinemia resulting from ISC. The fact that they are both reversed when systemic insulin levels are reduced by IP suggests that insulin, acting through LPL, influences the nature of the interaction of the lipoproteins engaged in CET.(ABSTRACT TRUNCATED AT 250 WORDS)

To establish whether lovastatin, an inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase, exhibits a specific effect on apolipoprotein (apo) A- and apoB-containing lipoproteins, 63 subjects, a subset of the 270 Monitored Atherosclerosis Regression Study (MARS) patients with hypercholesterolemia (190 to 295 mg/dL) and documented coronary artery disease, were randomized into either lovastatin 40 mg twice daily or matching placebo tablets twice daily. Both groups consumed a diet containing 27% calories as fat (polyunsaturated fat/saturated fat ratio, 2.85) and a daily cholesterol intake of less than 250 mg. The plasma lipid and apolipoprotein profiles were determined at the time of randomization and after 2 years of treatment, and the levels of apoA- and apoB-containing lipoprotein families were measured after 2 years of treatment. After this treatment period, the drug group was characterized in comparison with the placebo group by significantly reduced levels of total cholesterol (33%), triglycerides (30%), very-low-density lipoprotein cholesterol (36%), low-density lipoprotein cholesterol (43%), apoB (36%), apoC-III (18%), and apoE (17%) and slightly but insignificantly increased levels of high-density lipoprotein cholesterol (6%) and apoA-I (1%). The 2-year levels of lipoprotein containing apoA-I but no apoA-II (LpA-I) and lipoprotein containing both apoA-I and apoA-II (LpA-I/A-II) particles separated by immunoaffinity chromatography on an anti-apoA-II immunosorber did not differ between the two treatment groups. However, the apoB-containing lipoprotein (Lp) families defined by apolipoprotein composition and separated by immunoaffinity chromatography on anti-apoA-II and anti-apoC-III immunosorbers were affected in a selective manner.(ABSTRACT TRUNCATED AT 250 WORDS)

Oxidation of low-density lipoprotein (LDL) in the artery wall is probably determined by several factors, some of which may include physiological oxidants such as heme and hydrogen peroxide, blood serum components, and the interaction of the lipoprotein with glycosaminoglycans. Glycosaminoglycans form complexes with LDL that increase its susceptibility to oxidation in vitro. To examine the effect of these factors on oxidation of LDL from serum by using heparin and oxidized the resolubilized lipoprotein (Hep-LDL) with hemin and hydrogen peroxide in the presence of apolipoprotein B lipoprotein-deficient serum (BLPDS). Low levels (2.1%) of BLPDS stimulated the oxidation of Hep-LDL by approximately fivefold, and increasing concentrations reduced oxidation to baseline rates. By comparison, the oxidation of native LDL was stimulated to a similar extent at lower concentrations of BLPDS (0.83%) and returned to baseline more rapidly with increasing levels of the serum fraction. Oxidation rates did not change significantly with increasing concentrations of BLPDS alone. Human serum albumin (HSA) at comparable levels produced changes in the oxidation of Hep-LDL similar to those seen with BLPDS. Degradation of heme was accelerated by low levels of BLPDS or HSA in the presence of hydrogen peroxide but not by higher levels, and maximal degradation rates were inhibited by comparatively low levels of butylated hydroxytoluene (35 mumol/L). This antioxidant also effectively inhibited oxidation of Hep-LDL maximally stimulated by BLPDS. The data suggest that serum components, particularly HSA, modulate the peroxidation of both glycosaminoglycan-treated LDL and native LDL by hemin and hydrogen peroxide via mechanisms that may involve oxidative interactions between heme and HSA. This phenomenon may influence oxidation of LDL in vivo, where levels of HSA in regions of the artery wall are comparable with levels that stimulate the oxidation of Hep-LDL in vitro.

We sought to evaluate the mechanisms by which mechanical perturbation elevates intracellular calcium in endothelial cells. We report that the transient elevation in intracellular calcium in cultured bovine aortic endothelial cells (BAEC) in response to gentle perturbation with the side of a micropipette was not blocked by depolarization (external K+, 130 mmol/L), nifedipine (10 mumol/L), or Bay K 8644 R(+) (10 mumol/L). Thus, voltage-dependent calcium channels were not involved in the response. Also, amiloride (10 mumol/L) and tetraethylammonium (1 mmol/L) had no effect on calcium mobilization, indicating that Na+ and K+ transporters were not involved. Pretreatment of the cells with the phospholipase C and phospholipase A2 inhibitor manoalide (10 mumol/L) for 10 minutes at 37 degrees C completely abolished the calcium response, as did a 10-minute pretreatment with the inhibitor of actin polymerization, cytochalasin B (1 mumol/L). We observed an inhibitory effect of the phospholipase A2 and phospholipase C inhibitor 4-bromophenacyl bromide (10 mumol/L) on the mechanical response of BAEC that was not as potent as that observed with manoalide. To examine the role of arachidonic acid (AA) and subsequent metabolites that may be released after a putatively mechanical activation of phospholipase A2, we exposed BAEC to exogenous AA. We found that continued exposure of BAEC for 5 minutes to 10 nmol/L to 10 mumol/L AA caused no elevation of intracellular calcium. If mechanical stimulation activates phospholipase A2, the liberated AA and subsequent metabolites do not appear to have much effect on BAEC intracellular calcium.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma factor VII activity (factor VIIc) is one of the independent risk factors for coronary artery disease and is controlled by both genetic and environmental factors. Several studies in healthy Caucasian subjects have revealed an association of a common genetic polymorphism at residue 353 (Arg-->Gln) of the factor VII gene with plasma factor VIIc. We have investigated the influence of this polymorphism (factor VII Arg/Gln353) on fasting plasma factor VIIc and antigen (factor VIIag) levels and its interaction with triglyceride levels in 185 healthy Dravidian Indians of both sexes (128 men, 57 women). The frequency of Gln353 has been found to be significantly higher in Dravidian Indians (0.29; confidence interval, 0.27 to 0.30) than in Caucasians (0.10). The distribution of factor VII Arg/Gln353 genotypes was at Hardy-Weinberg equilibrium. The carriers of the Gln353 allele had significantly lower plasma factor VIIc and factor VIIag in men (P < .05). The factor VII Arg/Gln353 polymorphism explained 13% and 11% of the total variance of plasma factor VIIc and factor VIIag, respectively, in men (P < .001) and 6% and 9% in women (P > .1). The genotype-specific correlation of factor VIIc and factor VIIag with triglyceride levels was stronger in carriers of the Gln353 allele (r = .38 and .41; P < .001) than in Arg353 homozygotes (r = .09 and .27; P = .19 and .005, respectively).