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

Thrombin is involved in the pathogenesis of venous and arterial thrombosis. This study addressed the question of the relative importance of thrombin in the early and late phases of thrombogenesis. The effect of Ro 46-6240 (1.43 mg/kg bolus and 0.1 mg/kg per minute i.v.), a novel, selective thrombin inhibitor on thrombogenesis induced by rabbit aorta subendothelium, was measured ex vivo in a perfusion chamber model after a short (5-minute) and long (30-minute) exposure time to rabbit native blood. The role of the perfusion time was assessed at shear rates of 100/s, 650/s, and 2600/s. These shear rates mimic blood flow conditions found in veins, arteries, and small or stenosed arteries, respectively. Fibrin deposition and platelet thrombus formation on subendothelium were evaluated by microscopic morphometry. In the presence of Ro 46-6240, fibrin deposition was abolished at both perfusion times and at all shear rates. In the 5-minute experiments, thrombus height was reduced by Ro 46-6240 at shear rates of 100/s (85%) and 650/s (35%) but not at a shear rate of 2600/s, whereas thrombus area was not affected at any shear rate. In contrast, both thrombus height and thrombus area were reduced (60% to 90%) by Ro 46-6240 in the 30-minute perfusion groups at all wall shear rates. The antithrombotic effect of Ro 46-6240 after 30-minute perfusion was confirmed by the minimal increase in the pressure difference between the entrance and the exit of the perfusion chamber compared with the control groups.(ABSTRACT TRUNCATED AT 250 WORDS)

To test the hypothesis that hepatic cholesteryl ester is involved in the regulation of apolipoprotein (apo) B secretion into plasma, apoB kinetic studies were performed in six control miniature pigs and in six pigs after a 21-day administration of the acyl coenzyme A:cholesterol acyltransferase (ACAT) inhibitor DuP 128 (2.2 mg.kg-1.d-1 i.v.). Pigs were fed low-fat, cholesterol-free diets. Total plasma cholesterol, triglyceride, very-low-density lipoprotein (VLDL) triglyceride, and low-density lipoprotein (LDL) cholesterol decreased 18%, 29%, 40%, and 26% respectively (P < .03). 131I-VLDL and 125I-LDL were injected simultaneously into each animal, and apoB kinetics were analyzed by using multi-compartmental analysis (SAAM30). VLDL apoB pool size decreased significantly by 60% (0.32 versus 0.84 mg/kg), which was due to a 65% reduction in the VLDL apoB production or secretion rate (1.03 versus 2.94 mg.kg-1.h-1). The fractional catabolic rate was unchanged. LDL apoB pool size decreased nonsignificantly by 18% (5.61 versus 6.90 mg/kg) due entirely to a 24% decrease in production rate (0.26 versus 0.34 mg.kg-1.h-1). At necropsy, hepatic microsomal ACAT activity decreased by 68% (0.28 versus 0.88 nmol.min-1.mg-1; P < .0002). Although an increase in hepatic free cholesterol leading to a decreased LDL receptor expression might be expected, this did not occur. The concentration of hepatic cholesterol and the LDL apoB fractional catabolic rate were unaffected by DuP 128. In addition, the concentration of hepatic triglyceride and the activity of diacylglycerol acyltransferase were not altered by DuP 128, indicating a lack of effect of DuP 128 on hepatic triglyceride metabolism. We conclude that inhibition of hepatic cholesteryl ester synthesis in vivo decreases apoB secretion into plasma.

Low-density lipoprotein receptor-related protein/alpha 2-macroglobulin receptor (LRP/alpha 2-MR) is a multifunctional cell-surface receptor that is responsible for the clearance of lipoprotein remnants, proteases, or cytokines/growth factors in complex with alpha 2-macroglobulin as well as of plasminogen activators complexed with inhibitors. We investigated the expression of LRP/alpha 2-MR in healthy and atherosclerotic human arteries by in situ hybridization using an LRP/alpha 2-MR mRNA-specific riboprobe and immunocytochemistry using specific monoclonal antibodies. The cell types expressing LRP/alpha 2-MR were identified by immunolabeling of antigens specific for endothelial cells, smooth muscle cells, and macrophages. In normal arteries, LRP/alpha 2-MR mRNA and protein were found in smooth muscle cells of the media and vasa vasorum and in adventitial fibroblasts. Endothelial cells were negative for LRP/alpha 2-MR protein but positive for its mRNA. Atherosclerotic arteries exhibited a strong labeling for LRP/alpha 2-MR mRNA and protein that was observed in intimal smooth muscle cells exhibiting normal or foam cell characteristics and in lipid-laden cells positive for macrophage markers. A particularly high expression was detected in macrophages located in the cap of the lipid-rich necrotic core. These results suggest that cellular components of the atherosclerotic plaque express LRP/alpha 2-MR. This receptor may play an important local scavenger role for lipoprotein remnants, for growth factors/cytokines, and for extracellular protease-inhibitor complexes.

Human apolipoprotein (apo) E, a polymorphic protein with three common alleles, epsilon 2, epsilon 3, and epsilon 4, plays an important role in lipoprotein metabolism. This article describes the association of this polymorphism with lipids, apolipoproteins, and lipoproteins with a particular regard to lipoprotein particles, as defined by their apolipoprotein content, as well as the risk of myocardial infarction in a multicenter population-based case-control study (ECTIM study). In the ECTIM study, 574 male patients aged 25 to 64 were examined 3 to 9 months after myocardial infarction in four regions participating in the World Health Organization MONICA project: Belfast (Northern Ireland) and Lille, Strasbourg, and Toulouse (France). Control subjects (n = 722) were randomly selected from the regional populations. The distribution of apoE phenotypes was significantly different across the four control samples (P = .04), with a higher frequency of the epsilon 4 allele in Belfast (14.3%) than in Toulouse (8.2%). The association of apoE polymorphism with biological measurements was studied in the control groups (n = 640) after men with coronary heart disease or those taking hypolipidemic drugs were omitted, with the apoE3/3 phenotype as a reference after adjustment for concomitant factors. Individuals carrying the epsilon 2 allele had lower levels of plasma cholesterol, low-density lipoprotein cholesterol (LDL-C), and apoB and higher levels of triglycerides, very-low-density lipoprotein cholesterol (VLDL-C), apoC-III, apoE, lipoprotein (Lp) C-III:B, and Lp E:B. However, the effect of the epsilon 2 allele on triglyceride, VLDL-C, apoE, and Lp E:B parameters was heterogeneous across the populations.(ABSTRACT TRUNCATED AT 250 WORDS)

During inflammation, serum amyloid A (SAA) protein increases up to 1000-fold and can become a major component of high-density lipoprotein (HDL). We have identified a new apolipoprotein molecule (SAA5) as a distinct member of the SAA family. It differs from the inflammatory isotypes (SAA1, SAA2, and SAA3) not only in structure but in the fact that it is constitutive on normal HDL where it accounts for more than 90% of total SAA. Whereas all members of the SAA family, including SAA5, responded to endotoxin administration, SAA5 contrasted with other SAAs in its resistance to induction either by a high-fat, high-cholesterol atherogenic diet or the injection of mildly oxidized LDL (MM-LDL). These data provide further evidence that the induction of inflammatory molecules by oxidized lipids is selective. In atherosclerosis-susceptible C57BL/6 mice and atherosclerosis-resistant C3H/HeJ mice, the inflammatory SAA isotypes (SAA1, SAA2, and SAA3) responded in a strain-specific manner to oxidized lipids either generated with feeding of the atherogenic diet or introduced by MM-LDL injection. We hypothesize that the constitutive SAA5 molecules on normal HDL may contribute to its normal physiological role and that the dramatic induction of the inflammatory SAA subfamily equips the particle for an altered yet related functional role appropriate to the inflammatory state.

Recent data suggest that proinsulin is associated with cardiovascular risk factors in nondiabetic and diabetic subjects. Since most conventional insulin assays cross-react with proinsulin, it has been suggested that the associations of insulin concentrations with dyslipidemia and hypertension could actually reflect associations with proinsulin. We examined these associations by using both a conventional immunoreactive insulin assay and a specific Linco insulin assay that does not cross-react with proinsulin in 623 nondiabetic and in 180 non-insulin-dependent diabetic subjects who participated in the San Antonio Heart Study, a population-based study of diabetes and cardiovascular disease. Both the immunoreactive insulin assay and the specific Linco insulin assay were equally correlated with cardiovascular risk factors in nondiabetic subjects. Insulin concentrations were moderately correlated with high triglyceride and low high-density lipoprotein cholesterol levels and were weakly correlated with increased blood pressure. In diabetic subjects there were only weak associations between insulin and cardiovascular risk factors using either assay. We conclude that the association of insulin concentrations with cardiovascular risk factors is not a function of using insulin assays that cross-react with proinsulin and that for epidemiological studies of cardiovascular risk factors, conventional immunoreactive insulin assays are as good as the newer specific insulin assays.

High lipoprotein(a) [Lp(a)] plasma concentrations are an independent risk factor for atherosclerosis. In the general population, Lp(a) levels are primarily determined by allelic variation at the apolipoprotein(a) [apo(a)] gene locus. Apo(a) isoforms of various sizes are associated with different Lp(a) concentrations. Patients with end-stage renal disease (ESRD) have elevated plasma concentrations of Lp(a), which are not explained by the size variation at the apo(a) gene locus. To further investigate the origin of the elevated Lp(a) plasma concentrations, we examined Lp(a) concentrations and apo(a) phenotypes in 154 ESRD patients undergoing renal transplantation. In a prospective longitudinal study we observed a rapid normalization of Lp(a) levels from an average concentration of 25.9 +/- 28.7 mg/dL before to 17.9 +/- 25.5 mg/dL 3 weeks after renal transplantation (P < .0001). Only patients with high-molecular-weight phenotypes had a significant decrease in Lp(a) plasma concentrations. This study demonstrates the nongenetic origin of elevated Lp(a) concentrations in ESRD patients, which is obviously caused by the disease. It further confirms a phenotype-associated elevation of Lp(a) concentrations in ESRD.

Several studies have demonstrated that atherosclerotic complications are the major cause of morbidity and mortality in hemodialysis patients. High lipoprotein(a) [Lp(a)] plasma concentrations are an independent risk factor for atherosclerosis. Patients with end-stage renal disease (ESRD) have elevated plasma concentrations of Lp(a), which are not explained by size variation at the apolipoprotein(a) [apo(a)] gene locus. The aim of our study was to investigate whether Lp(a) concentrations and/or apo(a) phenotypes are predictive of the degree of atherosclerosis in the extracranial carotid arteries in ESRD patients. Of 167 patients, 108 showed atherosclerotic plaques (65%). Univariate analysis showed that the plaque-affected group was significantly older and had a higher frequency of angina pectoris, previous myocardial infarction, or cerebrovascular accident. Furthermore, this group included significantly more patients with low-molecular-weight apo(a) isoforms (26.9% versus 8.5%, P < .005) and had significantly higher mean Lp(a) plasma concentrations (29.3 +/- 31.0 versus 19.7 +/- 25.7 mg/dL, P < .05). Lp(a) plasma concentration increased significantly with the number of affected arterial sites, from 19.7 mg/dL in patients without plaques to 40.1 mg/dL in patients with seven or eight affected sites. In patients with low-molecular-weight phenotypes, significantly more arterial sites were affected (3.62 versus 2.08, P < .001). Multivariate regression analysis showed that age, angina pectoris, and the apo(a) phenotype were the only significant predictors of the degree of atherosclerosis. We conclude that, besides age, the apo(a) phenotype is the best predictor of carotid atherosclerosis in ESRD patients and may be used for assessment of general atherosclerosis risk in this patient group.

A prominent metalloproteinase activity with an apparent molecular mass of 80 kD and additional activities at 67 through 70, 50, and 32 kD have been observed on casein, gelatin, and elastin gel zymography in extracts from abdominal aortic aneurysms (AAAs). The forms at 80, 50, and 32 kD were isolated by affinity to recombinant tissue inhibitor of metalloproteinases, and the 80-kD and 50-kD components were shown to be derived from matrix metalloproteinase-9 (MMP-9). The relative electrophoretic mobility of these forms under reducing and nonreducing conditions corresponds to those of MMP-9 generated by MMP-3 (stromelysin-1) cleavage, and the active forms of MMP-3 at 45 and 35 kD were detected in aneurysmal extracts under reducing conditions by using specific antibody. Confirmation that the major proteolytic activity observed at 80 kD is MMP-9 was also demonstrated by immunoprecipitation of the activity with specific antibody. Comparative immunoblots of tissue extracts from 10 typical AAA patients, using specific antibody against MMP-9, revealed bands at 92, 82, 67, 51 through 53, 27, 23, and 20 kD under reducing conditions; six aortic control specimens displayed negligible immunoreactivity. This report is the first to show that known activated forms of MMP-3 and MMP-9 are present in the aneurysmal aortic wall and that they may play a role in the destruction of aortic matrix in AAA disease.