摘要:

We previously reported that cell membrane components and lipoproteins were able to induce the growth of murine peritoneal macrophages. The aim of the present study was to examine whether macrophage growth could also be induced by chemically modified lipoproteins, such as acetylated low density lipoprotein (acetyl-LDL) or oxidized LDL, ligands known to be endocytosed by the macrophage scavenger receptors. When murine peritoneal exudate macrophages were cultured in vitro with 25-100 ju.g/mL acetyl-LDL or oxidized LDL, significant growth was induced. On comparing the dose—response curves of these LDLs, a more potent effect was seen with oxidized LDL than acetyl-LDL, especially on resident macrophages. On the other hand, growth of these cells was not stimulated by native (unmodified) LDL or high density lipoprotein. These in vitro data revealed a new function of chemically modified LDLs as effective inducers of macrophage cell growth. This aspect may be physiologically relevant to the growth of macrophage foam cells in situ in the development of atherosclerosis.

ISSN:1049-8834    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

The effects of native and acetylated low density lipoproteins (LDLs and acetyl-LDLs, respectively) on the release of plasminogen activator inhibitor type 1 (PAI-1) by cultured human umbilical vein endothelial cells (ECs) were evaluated. LDL and acetyl-LDL incubated with ECs for 16-18 hours increased the PAI-1 antigen levels in conditioned medium. At a concentration of 100 /tg/mL, LDL and acetyl-LDL increased PAI-1 by 10.8 and 12.0 ng/mL, respectively (p<0.05 andp<0.01 versus control). The increases in PAI-1 antigen levels exerted by the lipoproteins paralleled the changes in PAI-1 activity. The effect of LDL and acetyl-LDL was concentration dependent and specific for PAI-1 because tissue-type plasminogen activator and expression of procoagulant activity were not affected by either lipoprotein. In addition, total protein synthesis evaluated in [35S] methionine-labeled ECs was not affected, and studies with cycloheximide showed that the effect of LDL and acetyl-LDL on PAI-1 release was due to de novo protein synthesis. Experiments using the C7 monoclonal antibody against the LDL receptor and binding-defective LDL indicated that the effect of LDL on the synthesis of PAI-1 was not dependent on the interaction of the LDLs with their specific receptors. Finally, extensive oxidation of LDL prevented and even reversed the effect of LDL on PAI-1 release by ECs. It is concluded that LDL specifically increases the synthesis of PAI-1 by ECs with mechanisms that are not receptor mediated.

ISSN:1049-8834    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

Morphological techniques (histology and electron microscopy), as well as immunofluorescence assays, were applied to the study of the localization and smooth muscle cell (SMC) composition of atherosclerotic lesions in Watanabe heritable hyperlipidemic (WHHL) rabbits during a 4.5-month period. Vascular segments from different arteries (carotid, coronary, and iliac arteries) or from the same vessel at different levels (aorta) of animals at days 7,15, 30, 40, 60, 90, and 135 showed that the atherosclerotic lesion first became visible at the level of the aortic arch in 60-day-old WHHL animals. Histological examination of serial cryosections from this vascular region indicated that the vascular lesion arose from a cavity in the media layer, located anatomically at the level of the juncture of the ligamentum arteriosum with the aortic arch. This aortic arch cavity is formed during the postnatal closure of the ductus arteriosus and is characterized by the presence of a thickened intima, which was absent in the other vascular regions examined. Immunofluorescence comparison of normal and atherosclerotic tissues from the aortic arch cavity wall with the use of monoclonal antibodies specific for smooth muscle and nonmuscle myosin isoforms revealed the existence of distinct SMC populations. SMCs in the thickened intima showed a myosin isoform pattern peculiar to cells with a degree of maturation intermediate between the fully differentiated and the developing (fetal) aortic SMCs. By contrast, SMCs present in atherosclerotic lesions displayed a predominant fetal-type pattern of myosin isoform expression. The achievement of this myosin isoform content seems to be correlated with the accumulation of lipids in the intima. In the media subjacent to the intimal thickening or atherosclerotic lesion, SMCs primarily displayed an intermediate degree of maturation. In older WHHL animals and at this aortic level, the SMC composition of the atherosclerotic lesion did not change, whereas in the subjacent media, the cells of intermediate type almost disappeared. In the vascular regions in which the atherosclerotic lesion appeared at later stages, such as near the aortic bifurcation, the distribution of fetal and intermediate cell types in the atherosclerotic wall was similar to that taken at the aortic arch level. These results indicate that there is 1) a preferential anatomic site from which atherogenesis initiates in WHHL rabbits; 2) a time correlation between the accumulation of lipids in the wall and the phenotypic change of SMCs toward a poorly differentiated cell type; and 3) the tendency for SMCs to follow the same differentiation pattern in early atherosclerotic lesions, irrespective of the site and time at which they develop.

ISSN:1049-8834    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

We have observed that NPC-1S669, a leucine derivative with anti-inflammatory activity, reduced the proliferation of human aortic smooth muscle cells (HASMCs) in culture. We used a colorimetric assay and tritiated thymidine to measure the cell density and proliferation of HASMC cultures treated with this agent. We also studied the effect of NPC-15669 on the proliferation and migration of human aortic endothelial cells (HAECs). Subconfluent HASMC cultures were growth arrested for 2 days. On the third day, growth was stimulated with either growth media (medium Ml99 containing 10% fetal bovine serum [FBS]), human platelet-derived growth factor (hPDGF), or fibroblast growth factor (FGF) in the absence or presence of NPC-15669 (0.1-50fiM).Regardless of the stimulating agent for HASMCs (FBS, hPDGF, or FGF), NPC-15669 at concentrations of 10-25/xMcaused a significant reduction in thymidine incorporation (36.7% and 77.2% in 10pMand 25fiM, respectively;p<0.005) and cell density (25–87%,p<0.001) compared with control. NPC-15669 did not, however, have an effect on the rate of proliferation or migration of HAECs, even at concentrations up to 50fiM.Two other anti-inflammatory agents, aspirin and dexamethasone, caused substantially and significantly less inhibition, even at high concentrations (50 and 25/iM, respectively). This study demonstrates that in vitro, NPC-15669 significantly inhibits HASMC proliferation but has no effect on proliferation or migration of HAECs.

ISSN:1049-8834    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

Plasma glucose and insulin responses to oral glucose and mixed meals and the ability of insulin to stimulate glucose disposal were quantified in normal volunteer subjects and patients with types II A, IIB, and IV hyperlipoproteinemia (HLP). The results indicated that patients with either type IIB or IV HLP had higher plasma glucose (p<0.05-<0.001) and insulin (p<0.001) responses to both oral glucose and mixed meals compared with the normal subjects and patients with type IIA HLP. Steady-state plasma glucose concentrations (mmol/L) were also higher (p<0.001) in patients with types IIB (13.3±0.6) and IV (12.8±1.2) HLP during a continuous infusion of somatostatin, glucose, and insulin than either the control group (volunteer subjects) (6.2±0.9) or patients with type IIA HLP (5.6±1.0). Because the steady-state plasma insulin concentrations were similar in all four groups, patients with either type IIB or IV HLP were resistant to insulin-mediated glucose uptake. These data indicate that patients with hypertriglyceridemia are insulin resistant, glucose intolerant, and hyperinsulinemic, irrespective of the plasma cholesterol concentration. The results further demonstrate that hypercholesterolemic patients with normal triglyceride concentrations do not have any abnormalities of glucose and insulin metabolism.

ISSN:1049-8834    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

We have previously demonstrated that the acetylated low density lipoprotein (LDL), or scavenger, receptor expressed by rabbit smooth muscle cells (SMCs) is regulated. Phorbol ester treatment of the cells increased the number of scavenger receptors expressed and the metabolism of acetoacetylated (AcAc) LDL. The current studies examined the interaction of oxidized (Ox) LDL with the rabbit scavenger receptor. The internalization and degradation of both Ox-LDL and AcAc-LDL were increased to a similar extent by phorbol ester treatment of the SMCs. In cross-competition experiments, both Ox-LDL and AcAc-LDL competed equally for the degradation of125I-Ox-LDL, suggesting that there is no independent receptor for Ox-LDL on these cells. In contrast, only AcAc-LDL competed totally for the degradation of125I-AcAc-LDL. Similar results were obtained in cross-competition experiments with rabbit macrophages. To determine whether these data were consistent with the binding of both ligands to a single receptor, competition studies were conducted in Chinese hamster ovary fibroblasts transfected with the bovine scavenger receptor. After transfection, the metabolism of both AcAc-LDL and Ox-LDL was increased, in agreement with the previous data from other investigators, and cross-competition studies yielded essentially identical results to those obtained in the SMCs and macrophages. Northern blot analysis with an antisense rabbit scavenger receptor probe detected the same mRNA species in total RNA from rabbit macrophages and SMCs and showed that scavenger receptor mRNA increased dramatically after phorbol ester treatment of SMCs. The probe also detected bovine scavenger receptor mRNA. A mixture of bovine scavenger receptor antipeptide antibodies detected a scavenger receptor of &#151;260 kD among membrane proteins of both SMCs and macrophages. This 260-kD protein bound acetyl-LDL in ligand blots. The data demonstrate that the scavenger receptor expressed by rabbit SMCs and macrophages binds both Ox-LDL and chemically modified LDL and that the rabbit receptor is related to the bovine scavenger receptor.

ISSN:1049-8834    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

Atherosclerosis is a common feature of autogenous vein bypass grafts resulting in their long-term failure. Arterial pressure-induced distension is thought to play a major role in the wall thickening of vein grafts, which may in turn favor atherosclerotic complications. In this study, we evaluated the influence of vein distension on the development of atherosclerotic lesions in jugular vein grafts interposed into the common carotid arteries of rabbits. The proximal half of each vein graft was wrapped with a 4-mm-diameter polytetrafluoroethylene graft that reduced the vein graft diameter by 46 ±5%. Fourteen animals were fed a 1% cholesterol-rich diet for 8 weeks, and five animals were fed a normal diet. In normocholesterolemic and hypercholesterolemic animals, the wall thickness and the total cross-sectional area were significantly reduced in wrapped compared with unwrapped segments. Foam cells were never observed in normocholesterolemic animals. In hypercholesterolemic rabbits, the sudanophilic lesions covered 62 ±4% of the luminal surface in unwrapped segments and 31 ±7% in wrapped segments (p<0.0001). In transverse sections, the surface areas of foam cells were also markedly reduced in wrapped compared with unwrapped segments. Reduction of the wall distension using a rigid external support protected the vein grafts from atherosclerosis, possibly as a result of the decrease in wall thickening that occurred in response to arterialization.

ISSN:1049-8834    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

The plasma level of high density lipoprotein cholesterol (HDL-C) has been reported to be inversely correlated with the level of triglycerides (TGs) and the magnitude of postprandial lipemia because subjects with low HDL-C accompanying high TG levels often have an increased postprandial response to a fat load. However, information is limited regarding the postprandial response to a fat load in subjects with low HDL-C and normal fasting TG values (hypoalphalipoproteinemia [hypoalpha]). We administered an oral fat load (70 g/m2of body surface area) to six subjects with hypoalpha and six aged-matched control subjects. Plasma levels of lipids and lipoproteins and the mass of triglyceride-rich lipoproteins (TRLs: S, >100 and Sf20-100) were measured every 2 hours for 8 hours. The mass and chemical composition of Sr>100 or Sr20-100 TRLs were not different between the fasting groups; postprandial Sr> 100 but not Sr20-100 TRLs (mean±SD) was significantly lower in subjects with hypoalpha (200.4 ±64.8 mg/dL versus 110.6±50.9 mg/dL; analysis of variance,Ftest, p=0.04). In the hypoalpha subjects, the compositions of postprandial Sr> 100 TRLs were TG poor and cholesterol and phospholipid enriched (p<0.001) while the Sf20-100 TRLs were enriched in cholesterol and phospholipid but relatively protein depleted (p=0.002). When the hypoalpha subjects received gemfibrozil, the masses of both fasting (p=0.014) and postprandial (p=0.0004) Sf20-100 TRLs were lower compared with baseline, a response that was accompanied by partial normalization of composition in postprandial hypoalpha Sf20-100 TRLs. Our results indicate that in contrast to subjects with low plasma HDL-C and high TG levels, hypoalpha subjects with normal TG values did not display an increased postprandial response to fat feeding. Rather, the phenotype of hypoalpha appears to have a distinct metabolic component characterized by a reduced number of postprandial Sf> 100 TRLs of abnormal composition. Gemfibrozil reduced the mass and altered the composition of Sf20-100 TRLs in hypoalpha subjects.

ISSN:1049-8834    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

Shear-induced platelet aggregation is important in physiological hemostasis and in the pathogenesis of arterial thrombosis. It requires extracellular Ca2+, platelet membrane glycoproteins Ib/IX and Ilb/IIIa, von Willebrand factor (vWF), and ADP. We studied the effects of desmopressin (DDAVP), which increases plasma vWF levels and shortens the bleeding time, and of ticlopidine, which inhibits platelet responses to ADP, on shear-induced platelet aggregation. Eleven healthy volunteers were given oral ticlopidine (250 mg b.i.d.) for 7 days. The same subjects were infused intravenously with DDAVP (03jug/kg body wt) before the first and after the last doses of ticlopidine. The degree of platelet aggregation induced by shear stress at 25, 50, 75, and 100 dyne/cm2in a cone-and-plate viscometer, plasma vWF levels, and the bleeding time were measured before and after each DDAVP infusion. Plasma vWF levels and the extent of shear-induced platelet aggregation increased after DDAVP and were correlated. Ticlopidine partially inhibited shearinduced platelet aggregation both before and after DDAVP infusion. The bleeding time, prolonged by ticlopidine, was shortened by DDAVP. Potentiation by DDAVP of shear-induced platelet aggregation may be one mechanism by which the drug shortens the prolonged bleeding time. Since shear-induced platelet aggregation can cause thrombotic occlusions in stenotic arterial vessels, our findings may explain the therapeutic efficacy of ticlopidine in arterial thrombosis.

ISSN:1049-8834    

出版商:OVID    

年代:1993

数据来源: OVID

摘要:

We have recently shown that von Willebrand factor (vWF) binds to endothelial and fibroblastic extracellular matrixes (ECM) in a dose-dependent, specific, and saturable way. To localize the domain on the vWF subunit responsible for this interaction, purified proteolytic fragments of vWF were compared for their ability to inhibit125I-vWF binding to ECM. A tryptic dimeric fragment of 116 kD (T116), extending from amino acid (aa) residues 449 to 728, produced a significant inhibition of125I-vWF binding to the ECM. In contrast, P34 (aa 1-272), Spl (aa 911-1,365), and SpII (aa 1,366-2,050) had no significant effect on125I-vWF binding to the ECM. Using an immunoHuorescence technique, we identified type VI collagen and heparan sulfate in the endothelial ECM.125I-vWF was found to bind specifically to purified type VI collagen. Unlabeled vWF and Spill were able to completely inhibit125I-vWF binding to type VI collagen. T116 and Spl appeared as competitors of this interaction, whereas P34 and SpII were not. Our data suggest that vWF binds to the endothelial ECM through the T116 fragment and that T116 and Spl each contain a binding site for type VI collagen. Heparin is known to be a vWF ligand, but did not appear as a competitor of vWF binding to the ECM, nor did heparan sulfate.

ISSN:1049-8834    

出版商:OVID    

年代:1993

数据来源: OVID