摘要:

To elucidate the role of oxygen free radicals and lipid peroxidation in the pathogenesis of early hypertension and atherosclerosis, we studied the native distribution of three primary arterial antioxidant enzymes (AEs). Specific immunohistochemical localization of superoxide dismutase (Cu-Zn SOD), glutathione peroxidase (GSH-Px), and catalase (CAT) was examined in the arterial wall of New Zealand White rabbits: six sham-operated normotensive/normolipidemics (NT/NL), seven coarctation-induced hypertensive/normolipidemics (HT/NL), eight normotensive diet-induced hyperlipidemics (NT/HL), and six hypertensive/hyperlipidemics (HT/HL). All three AEs were confined primarily to the endothelium in NT/NL rabbit aortas. However, in HT and HL rabbits a greater proportion of the arterial wall, including the endothelium, inner media, and middle media, displayed immunolocalization of three AEs. Multiple linear-regression analysis revealed that more than 70% of the total variability in the depth of immunolocalization of arterial AEs could be explained by changes in blood pressure and/or total cholesterol. Also, levels of plasma and arterial cholesterol oxides were significantly different (p<0.05) in HT and HL rabbits compared with controls, with twofold increases in NT/HLs, threefold increases in HT/NLs, and fourfold increases in HT/HLs. We conclude that intense free-radical activity in the arterial wall of HT and HL animals is one possibility and that this occurs despite the presence of abundant AEs.

ISSN:1049-8834    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

The Bronx Aging Study is a 10-year prospective investigation of very elderly volunteers (mean age at study entry, 79 years; range, 75-85 years) designed to assess risk factors for dementia and coronary and cerebrovascular (stroke) diseases. Entry criteria included the absence of terminal illness and dementia. All subjects (n=350) included in this report had at least two lipid and Iipoprotein determinations. Overall, more than one third of subjects showed at least a 10% change in lipid and Iipoprotein levels between the initial and final measurements. Moreover, mean levels for women were consistently different than those for men, and because of this finding subjects were classified into potential-risk categories based on the changes observed by using their sex-specific lipid and Iipoprotein distributions. The incidences of cardiovascular disease, dementia, and death were compared between risk groups. Proportional-hazards analysis showed that in men a consistently low high density Iipoprotein cholesterol level (530 mg/dl) was independently associated with the development of myocardial infarction (p=0.006), cardiovascular disease (p=0.002), or death (p=0.002). For women, however, a consistently elevated low density Iipoprotein cholesterol level (ges;171 mg/dl) was associated with myocardial infarction (p=0.032). Thus, low high density Iipoprotein cholesterol remains a powerful predictor of coronary heart disease risk for men even into old age, while elevated low density Iipoprotein cholesterol continues to play a role in the development of myocardial infarction in women. The findings suggest that an unfavorable Iipoprotein profile increases the risk of cardiovascular morbidity and mortality even at advanced ages for both men and women.

ISSN:1049-8834    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Samples of human plasma having lipoprotein(a) (Lp[a]) protein levels between 5 and 15 mg/dl and a single apolipoprotein(a) (apo[a]) isoform were incubated in vitro at pH 7.7 with various concentrations (1–20 mM) of iV-acetylcysteine, homocysteine, 2-mercaptoethanol (2ME), and dithiothreitol (DTT) for 1 hour at 37°C under a nitrogen atmosphere. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by immunoblot analyses using a polyclonal antibody specific for apo(a) showed a progressive decrease In apo(a) immunoreactivity as a function of reductant concentration. This decrease of apo(a) immunoreactlvity was corroborated by enzyme-linked Immunosorbent assay (ELJSA) using anti-apo(a) as the capture antibody and either anti-apo B or anti-apo(a) as the developing antibody. In turn, there was no significant decrease in the immunoreactivity of apo B-100, as assessed by ELJSA using anti-apo B as both the capture and the detecting antibody. In the case of high concentrations of DTT the plasma samples had to be diluted to prevent gel formation on addition of the reductant. A progressive drop in immunoreactivity as a function of reagent concentration was also observed in pure preparations of Lp(a) incubated with the reducing agents at pH 7.7. At equivalent stoichiometries the changes were more marked than those observed with whole plasma, suggesting a quenching effect by the plasma proteins on the activity of the reductants. The changes in immunoreactivity were attended by dissociation of apo(a) from Lp(a) as assessed by Western blotting. This dissociation, which we interpret as the result of cleavage of the interchain disulfide bond(s), was complete at 5 mM DTT and 100 mM 2ME. In both cases the displaced apo(a) band exhibited a markedly reduced immunoreactivity. It is concluded that in vitro thiols and cysteine-containing compounds affect the immunoreactivity of apo(a), probably as a consequence of the cleavage of the intrakringle dlsulfides, and that at high reductant concentrations the immunologically altered apo(a) dissociates from Lp(a). These observations must be kept in mind when measuring Lp(a) in subjects with high plasma levels of cysteine-containing compounds and when examining apo(a) polymorphism by gel electrophoresis in the presence of the commonly used reagents such as DTT or 2ME.

ISSN:1049-8834    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Clopidogrel, like the homologous thienopyridine derivative tidopidine, selectively inhibits platelet aggregation induced by ADP. We have previously described two nucleotide-binding sites on platelets related to ADP- mediated platelet responses. The first is a high-affinity binding she for 2-methylthio-ADP (2-MeSADP) that is linked to the inhibition of stimulated adenylate cyclase. The second is the 100-kd exofacial membrane protein aggregin, which is labeled by the reactive ADP analogue 5′-p-fluorosulfonyibenzoyl adenosine (FSBA) that is related to shape change and aggregation. We set out to determine if either of these sites is blocked in vivo by clopidogrel or its active metabolite. Six subjects were given clopidogrel (75 mg/day for 10 days) in a double-blind crossover experiment All of the subjects developed prolonged bleeding times while taking the drug. The rate of onset of the effect on bleeding time varied among subjects. Platelet aggregation induced by ADP or thrombin was significantly impaired by the drug treatment, but no effect was detected on shape change. The incorporation of [3H]FSBA into aggregin was also unaffected. Inhibition of adenylate cyclase by ADP or by 2-MeSADP was greatly reduced in all subjects, and in the case of 2-MeSADP, there was evidence for a noncompetitive effect Inhibition of adenylate cyclase by epinephrine was unaffected. In the three subjects for whom binding measurements were made, the number of binding sites for [32P]2-MeSADP was reduced from 534±44 molecules per platelet during control and placebo periods (11 determinations) to 199±78 molecules per platelet during drug treatment (three determinations). There was no consistent change in the binding affinity. The inhibition of platelet function by clopidogrel is associated with a selective reduction in the number of functional receptors mediating the inhibition of stimulated adenylate cyclase activity by ADP.

ISSN:1049-8834    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

The effects of ethanol on platelets from rabbits with two different types of hypercholesterolemia, diet-induced and genetically determined, were investigated. There were no differences between the hypercholesterolemic groups and their controls in the extent of (primary) ADP-induced aggregation of washed platelets, and this aggregation was not inhibited by ethanol. Platelets from cholesterol-fed rabbits were more sensitive to aggregation and secretion induced by collagen, whereas platelets from Watanabe heritable hyperlipidemic (WHHL) rabbits were less sensitive. Ethanol inhibited collagen-induced responses of platelets from both hypercholesterolemic groups, but the extent of inhibition of aggregation was not different compared with controls. Because ethanol did not affect U46619-induced responses of aspirin-treated platelets, ethanol does not inhibit aggregation and secretion stimulated by collagen via an effect on thromboxane A2(TxA2)-induced responses. Platelets from cholesterol-fed rabbits were more sensitive to thrombin even when TA2formation was blocked by aspirin, and inhibition of aggregation by ethanol was less in cholesterol-fed rabbits than in controls. However, neither the extent of thrombininduced responses nor the inhibitory effect of ethanol was different in platelets from WHHL rabbits compared with controls. Thus, different etiologies of hypercholesterolemla produce different changes in platelet function, and ethanol has different effects on the platelets from cholesterol-fed rabbits compared with the platelets from WHHL rabbits. The inhibitory effect of ethanol on the thrombin-induced aggregation of platelets from cholesterol-fed rabbits is attenuated compared with controls, and this finding contrasts with the reported greater inhibitory effect of ethanol on platelets enriched with saturated fats.

ISSN:1049-8834    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Previous studies have suggested that greater arterial concentrations of undegraded low density lipoprotein (LDL) and/or greater arterial rates of LDL degradation may play role(s) in determining regional differences in arterial susceptibility to atherosclerosis in rabbits (Schwenke and Carew, Arteriosclerosis 1989;9:895-918). The White Carneau (WC) pigeon is also useful for investigating potential mechanism(s) that might account for regional variation in arterial susceptibility to atherosclerosis because atherosclerosis develops predictably in the aorta at the level of the cellac bifurcation (atherosclerosis-susceptible celiac site). In this study we sought to determine whether the123I-tyramine cellobiose (125I-TC) content 1 day after injecting '"I-TC-LDL ("I-TC-LDL accumulation") would be greater in the celiac site in arteries of WC pigeons and whether I-TC-LDL accumulation would be exaggerated by cholesterol feeding. Because '"I-TC remains trapped in cells after cellular degradation, arterial sites that either degrade LDL at higher rates or contain higher concentrations of undegraded LDL or both will demonstrate greater "'I-TC-LDL accumulation. Young WC pigeons were studied while consuming a cholesterol-free diet and after consuming a cholesterol-containing diet for 1,2, 4, and 8 weeks. In pigeons fed a cholesterol-free diet, "I-TC-LDL accumulation in the celiac site was equivalent to 0.24 ±0.02 u% LDL cholesterol/cm2aortic surface/day compared with only 0.14±0.02 /ig LDL cholesterol/cm1/day for the adjacent aorta, which is resistant to atherosclerosis (atherosclerosis-resistant site) (p<0.025). In atherosclerotic lesions excised from the celiac site,115I-TC-LDL accumulation was equivalent to 21±10 fig LDL cholesterol/cm1aortic surface/day compared with 0.66±0.17 fig LDL cholesterol/cm1/day for the adjacent atherosclerosis-resistant site (p<0.001). During cholesterol feeding,I25I-TC-LDL cholesterol accumulation in the celiac site as a whole increased 30-fold compared with a fivefold increase in plasma LDL cholesterol. In comparison, '"I-TC-LDL cholesterol accumulation in the adjacent atherosclerosis-resistant arterial site increased at the same rate as the plasma LDL cholesterol, while125I-TC-LDL cholesterol accumulation in two other relatively atherosclerosis-resistant arterial sites that we studied increased relatively little during cholesterol feeding. The results of this study suggest that differences in arterial '"I-TC-LDL accumulation, both those present in normal animals and those induced by cholesterol feeding, may contribute to the characteristic regional variation in arterial susceptibility to atherosclerosis in WC pigeons. Additional studies will be needed to determine whether this difference reflects differences in arterial permeability to LDL, retention of undegraded LDL within the arterial extracellular matrix, or the cellular metabolism of LDL.

ISSN:1049-8834    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Oxidation and scavenger receptor-mediated uptake of low density lipoprotein (LDL) in intimal macrophages are believed to be key events in the development of atherosclerosis. We report here that oxidized LDL increases DNA synthesis, expression of HLA-DR, and interleukin-2 receptors in T cells. The stimulatory effect of oxidized LDL was not due to a direct effect on T cells but required the presence of monocytes. Oxidized LDL also stimulated the release of interleukin-10 from monocytes. The maximal effect of oxidized LDL on T-cell activation and interleukin-1/3 release occurred at a concentration of 1figjml.Native LDL also had the capacity to activate T cells, although only at higher concentrations. The stimulatory effect of both native and oxidized LDL was inhibited by superoxide dismutase. Monocytes as well as T cells were found to have the ability to oxidize LDL, suggesting that the stimulatory effect of native LDL may arise as a result of LDL oxidation during incubation with monocytes and T cells. The results suggest that oxidized LDL may activate T ceils in atherosclerotic lesions.

ISSN:1049-8834    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

The solubilization and delivery of lipids in plasma rely on both forms of apolipoprotein B (apo B): apo B-100 and apo B-48. Apo B-48 is the translational product of apo B-100 mRNA that undergoes peritranscriptional conversion of C±U, replacing codon CAA (glntamine 2,153) with the infirame stop codon (UAA). We examined mRNA editing activity in the human and the rat by reverse transcriptionpolymerase chain reaction primer-extension analysis of intestine and liver total RNA. In rat intestine the percentage of apo B transcripts that undergo editing increases dramatically the day before birth (from &#151;1% to 80%), whereas the rat liver acquires an adult level of editing activity during the third postnatal week (rising from &#151;8% to 30%), when weaning is completed, bile acid composition matures, and plasma thyroid hormone levels peak. In contrast to the rat, the human intestine acquires adult levels of apo B mRNA editing relatively early in fetal development, rising from 10% at 10 weeks to &#151;80% by the end of the second trimester. Our results establish that apo B mRNA editing is 1) developmentally regulated in a tissueand species-specific manner; 2) fully developed prenatally in both human and rat intestine, suggesting a crucial role of apo B-48 in mammalian fetal adaptation to extrauterine life; and 3) acquired early in human fetal intestine, implying a potential role for apo B-48 in prenatal lipid metabolism.

ISSN:1049-8834    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Tissue factor (TF) is a transmembrane glycoprotein that mediates cellular initiation of the coagulation serine protease cascades. Moreover, expression of TF in human atherosclerotic plaques is likely to play a significant role in the thrombotic complications associated with plaque rupture. In this study the complete murine TF gene,Cf-3, was isolated from mouse NIH 3T3 cells and was found to consist of six exons spanning about 11 kilobase pairs (kbp) of DNA. A major transcriptional start site was located 24 bp downstream of a TATA box.Cf-3was mapped to chromosome 3 by analysis of an intersubspecies test cross. Conserved transcription factor-binding sites were identified by comparison of 5′ flanking regions of the murine and human TF genes. A region of the TF promoter required for constitutive expression exhibited 85% identity in DNA sequence and included two conserved binding sites for Spl. Furthermore, two AP-1 sites and an NF-KB site were conserved in a 56-bp region necessary for transcriptional activation in response to bacterial lipoporysaccharide. These highly conserved regions of the TF promoter, which contain several binding sites for well-characterized transcription factors, are likely to be functionally important in the complex pattern of TF gene expression observed in a variety of cell types.

ISSN:1049-8834    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Macrophages, unlike most other cells, possess both low density lipoprotein (LDL) and scavenger receptors. The scavenger receptor has been shown to mediate the uptake of oxidized LDL (ox-LDL), which ultimately leads to cholesterol loading of the macrophages. The present study was undertaken to define epitopes on ox-LDL that are important for lipoprotein binding to macrophages and to ascertain whether ox-LDL can bind to the LDL receptor. Monoclonal antibodies (Mabs) directed against several epitopes along the apolipoprotein B-100 (apo B-100) molecule were used. LDL (300 /tg/ml) was oxidized by incubation with 10 jtM CuSO, for 24 hours. Ox-LDL, as opposed to acetylated LDL (ac-LDL), reacted with Mabs directed against the LDL receptor-binding domains (Mabs B1B6 and B1B3). Similarly, uptake of ox-LDL but not ac-LDL by a murine J774 macrophage&#151;like cell line was inhibited by as much as 40% after using Mab B1B6. The anti-LDL receptor antibody IgG-C7 also inhibited '"I-ox-LDL uptake by macrophages by 60%. Chromatography on heparin-Sepharose columns of LDL that was partially oxidized for only 3 hours resulted in two fractions: an unbound traction with characteristics similar to those of ox-LDL and a bound fraction similar to native LDL. Macrophage degradation of the unbound fraction was inhibited by Mab IgG-C7 and Mab B1B6, whkh are directed toward the LDL receptor and the LDL receptor-binding domains on apo B-100, respectively. When incubated with three types of macrophages, J774 macrophage cells, mouse peritoneal macrophages, and human monocyte-derived macrophages, excess amounts of unlabeled ox-LDL, like native LDL but unlike ac-LDL, substantially suppressed the uptake and degradation ofl25l-labekd LDL. Similar studies with fibroblasts, however, revealed that unlabeled LDL but not unlabeled ox-LDL or ac-LDL competed with ""I-LDL for cellular uptake and degradation. Mab directed against epitopes on the amino terminus domain of apo B-100 (C14) demonstrates a similar immunoreactivity with ox-LDL and native LDL but a much lower reactivity with ac-LDL. Mab C14 inhibited macrophage degradation of ox-LDL by 34% but had no inhibitory effect on the uptake of native LDL or ac-LDL. Thus, the ac-LDL and LDL receptor-binding domains as well as a unique epitope on the ammo terminus of apo B-100 may be involved in macrophage binding of ox-LDL. We conclude that 1) ox-LDL contains epitopes that are also present in native LDL, although considerable changes in these epitopes are suggested and 2) these epitopes are involved in the uptake of ox-LDL by macrophages.

ISSN:1049-8834    

出版商:OVID    

年代:1992

数据来源: OVID