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Query: UMLS:C0004153 (atherosclerosis)
 77,401 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Recently two local hormones, thromboxane A2 (TXA2) and prostacyclin (PGI2) have been discovered. These hormones are labile metabolites of arachidonic acid. TXA2 is generated by blood platelets, while PGI2 is produced by vascular endothelium. TXA2 is a potent vasoconstrictor. It also initiates the release reaction, followed by platelet aggregation. PGI2 is a vasodilator, especially potent in coronary circulation. It also inhibits platelet aggregation by virtue of stimulation of platelet adenyl cyclase. Common precursors for both hormones are cyclic endoperoxides PGG2 and PGH2, being formed by cyclooxygenation of arachidonic acid. This last enzymic reaction is more efficient in platelets than in vascular endothelium, and therefore the generation of PGI2 by vasuclar wall is accelerated by an interaction between platelets and endothelial cells. During this interaction platelets supply the endothelial PGI2 synthetase with their cyclic endoperoxides. The newly formed PGI2 repels the platelets from the intima. When PGI2 synthetase is irreversibly inactivated by low concentration of lipid peroxides, then the platelets are not rejected but stick to the endothelium, generate TXA2 and mature thrombi are formed. A balance between formation and release of PGI2, TXA2 and/or cyclic endoperoxides in circulation is of utmost importance for the control of intra-arterial thrombi formation and possibly plays a role in the pathogenesis of atherosclerosis.
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PMID:A possible role of thromboxane A2 (TXA2) and prostacyclin (PGI2) in circulation. 36 54

Cell surface anionic sites on primary and transformed cultures of human vascular endothelium were studied using cationized ferritin (CF) as an ultrastructural marker. The native distribution of anionic sites on the upper (free) surfaces of cells, fixed in situ with glutaraldehyde, was uniform. Binding of the polycationic ligand, CF, in unfixed cells induced redistribution of anionic sites. Rapid formation of discrete patches of CF particles was followed by reappearance of binding between patches, movement of surface-bound CF into intercellular clefts, and endocytosis, over the next 30 min. Aldehyde-fixed cells, detached from the culture surface, bound CF on both upper and lower surfaces. The distribution and mobility of negatively charged membrane components in vascular endothelium may have relevance for thrombosis, atherogenesis, and vascular permeability.
Atherosclerosis 1979 Jan
PMID:Distribution and movement of anionic cell surface sites in cultured human vascular endothelial cells. 46 14

In the clinical part of the study routine neck PA radiographs taken with the mouth open were compared with soft tissue films with the mouth closed for detection of calcification in the carotid arteries. Only 5.5% of 90 hospitalized patients showed foci of calcification in routine films. But foci of calcification were seen in 22% of the soft tissue radiographs of the whole series. In the autopsy part of the study large foci of calcification were found at the carotid bifurcations in 12 out of 20 cadavers by radiography. In an additional five cases contact radiographs also showed smaller foci of calcification. The vascular endothelium over the calcification was often ulcerated. The significance of the large arterial foci of calcification demonstrated in the neck radiographs as a sign of atherosclerosis and as a source of cerebral thromboembolism is discussed.
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PMID:Calcification in cervical arteries in life and at autopsy. 67 2

Several pieces of evidence suggest that vascular endothelium may be a site of latent herpetic viral infection, and that activation of such infection might cause or aggravate atherosclerosis. The present studies which utilized HSV-1 infection of cultured endothelial monolayers, provide insights into two phenomena seemingly relevant in considerations of atherosclerosis. Thus, mechanisms are reported by which infected endothelium may be damaged by marginated inflammatory cells, and be transformed from an anticoagulant to a procoagulant tissue. First, granulocytes are attracted to, and avidly bind, endothelium infected for very brief periods. This interaction is associated with denudation of intact cells as well as actual cytolysis through release of PMN proteases and toxic oxygen species. Second, several potentially additive abnormalities of HSV-infected endothelium would seem to foster coagulation. These include: a) its loss of surface heparans and thrombomodulin; b) its inability to synthesize prostacyclin with associated incapacity to deter platelet adhesion; c) its disordered membrane lipid conformation which is likely associated with excessive surface thrombin generation; and d) its unique ability to generate and release tissue factor. We speculate that mechanical abrasion may reactivate latent herpes (HSV or CMV) infection in endothelial cells particularly those exposed to high shear forces--for instance, at vessel bifurcations. This may underlie the endothelial damage, clotting and atheroma formation commonly found at these sites.
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PMID:Herpes virus infection of endothelium: new insights into atherosclerosis. 132 3

Old concepts of an "inert" vascular endothelium have been entirely discredited. It is now known that the vascular endothelium and media form a "functional unit", communicating via both electric and humoral signals. Normal endothelium maintains vascular dilation through release of various dilatory substances, the main one being endothelial relaxing factor (EDRF), which is nitric oxide (NO). EDRF is, for example, released in response to increased shear stress that accompanies high flow rates, and acts by engaging the cyclic GMP system of smooth muscle cells. Even potential vasoconstrictors such as vasopressin, catecholamines and serotonin release EDRF. Endothelial release of prostacyclin supplements the EDRF action. EDRF (and prostacyclin) also inhibit platelet aggregation. In the presence of hypertension and/or atherosclerosis, endothelial function is often impaired and pressor/thrombogenic factors such as endothelin, thromboxane, vasopressin, catecholamines, and serotonin become more dominant. Antihypertensive therapy should, ideally, seek to restore endothelial function to normal.
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PMID:Hypertension and endothelial function--aspects of atheroma protection. 134 64

Results of animal studies suggest that calcium antagonists can inhibit the development of experimentally induced atherosclerosis. Although the biological process underlying this phenomenon has not been fully elucidated, several mechanisms have been proposed. Notably, calcium antagonists may suppress free radical-induced damage of the vascular endothelial cells with the consequent transport of low-density lipoproteins across the vascular endothelium and the accumulation of the lipids in the intima. Studies have shown that calcium antagonists can inhibit the stimulatory effects of epidermal growth factor on intracellular calcium concentrations and DNA synthesis in cultured rat aortic smooth muscle cells, but not those of platelet-derived growth factor or somatomedin C. Further experimental studies have demonstrated that calcium antagonists stimulate prostacyclin production and inhibit 12-hydroxyeicosatetraenoic acid-induced vascular smooth muscle cell migration, therefore preventing platelet aggregation and intimal thickening, respectively. Despite the encouraging results in animals, comparatively few clinical studies have been undertaken to establish the efficacy of calcium antagonists in the prevention of cardiovascular disease in hypertensive patients. This, in part, is due to the technical difficulties associated with measuring coronary artery stenosis, but the recent development of a technique for the video-densitometric analysis of coronary angiograms has enabled stenotic regions to be quantified. Using this approach, a retrospective study has been undertaken of the efficacy of long-term treatment with a calcium antagonist on the progression of coronary atherosclerosis. Results are encouraging and a prospective long-term, multicenter trial is proposed.
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PMID:The role of calcium antagonists in the treatment of atherosclerosis and hypertension. 136 1

Injury to the vascular endothelium and the subsequent inflammatory response are considered prerequisites for the development of atherosclerosis. Platelet-derived growth factor (PDGF) production by and monocyte adhesion to aortic endothelial cells (EC) may participate in this inflammatory process and therefore are two potential targets for control by anti-inflammatory agents. Our previous studies have demonstrated that monocyte adhesion and PDGF production are stimulated by thrombin in EC. Here, we provide evidence that treatment of EC with the anti-inflammatory agent 3-deazaadenosine (c3Ado) effectively abolished thrombin-stimulated PDGF production and monocyte adhesion. c3Ado had no significant effect on either basal monocyte adhesion or constitutive PDGF production. c3Ado was also effective in negating monocyte adhesion induced by other agonists, such as interleukin-1, phorbol 12-myristate 13-acetate (PMA), and lipopolysaccharide. Northern analysis demonstrated that c3Ado significantly reduced thrombin- and PMA-stimulated steady-state levels of PDGF-A chain, PDGF-B chain, and endothelial-leukocyte adhesion molecule-1 (ELAM-1) mRNAs. Nuclear run-on studies demonstrated that a marked transcriptional activation of these genes by thrombin and PMA was abrogated by c3Ado treatment. The transcriptional rate of the alpha-tubulin gene was unaffected by the drug. Antibody binding studies with an anti-ELAM-1 monoclonal antibody 7A9 revealed that thrombin-stimulated EC expression of ELAM-1 was abolished by c3Ado, indicating that the suppression of ELAM-1 expression on EC surface may be a mechanism by which c3Ado interferes with monocyte adhesion. Experiments with the nucleoside transport inhibitor nitrobenzylthioinosine suggested that the transport of c3Ado into EC was required for its inhibitory activity. In addition, L-homocysteine thiolactone was found to potentiate the inhibitory activity of c3Ado, suggesting that the accumulation of intracellular c3Ado homocysteine may be the underlying mechanism by which c3Ado inhibits thrombin-induced EC function. Taken together, these results indicate that c3Ado may prove effective against vascular injury and inflammation through its ability to inhibit induction of both monocyte adhesion and PDGF production.
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PMID:3-Deazaadenosine inhibits thrombin-stimulated platelet-derived growth factor production and endothelial-leukocyte adhesion molecule-1-mediated monocytic cell adhesion in human aortic endothelial cells. 137 93

Remnants, resulting from the lipolysis of triglyceride-rich lipoproteins, injured cultured endothelial cells and resulted in decreased barrier function of the vascular endothelium. Endothelial cells were cultured on micropore filters. Albumin transfer across endothelial cell monolayers was measured after a 24-h exposure to media enriched with control or in vitro-lipolyzed samples of various hypertriglyceridemic (HTG) sera and its isolated lipoprotein (VLDL, LDL and HDL) and serum free protein (d greater than 1.21 g/ml) fractions. Compared with control cultures, neither control HTG serum nor its isolated lipoprotein and serum-free protein fractions had any effect on albumin transfer. In contrast, lipolyzed HTG (L-HTG) serum and all of its isolated lipoprotein fractions (L-VLDL, L-IDL, L-LDL and L-HDL) caused a marked decrease in endothelial barrier function, evidenced by a significant increase in albumin transfer across endothelial monolayers. The L-IDL and L-HDL fractions were more effective in increasing albumin transfer than the L-VLDL and L-LDL fractions. The extent of the L-IDL and L-HDL mediated increases in albumin transfer was concentration dependent. An exposure of 12 h was required for L-HDL to increase albumin transfer. The L-HDL mediated increase in albumin transfer was reversible only after a 12-h exposure at low concentrations. The free protein fraction from L-HTG serum had no significant effect on the barrier function of endothelial cells. The presence of normolipidemic HDL in culture medium prevented disruption of the endothelial barrier induced by L-IDL but not by L-HDL. The decrease in endothelial barrier function induced by lipolyzed samples of HTG serum or lipoproteins appeared to be correlated with the level of free fatty acids contained in lipolytic remnants. Enrichment of LDL, and in particular HDL, with fatty acid significantly increased albumin transfer. Compared with lipolyzed samples, sera/lipoproteins oxidized in vitro by Cu2+ ions had little effect on endothelial barrier function, which did not correlate with their respective thiobarbituric acid-reacting substance (TBARS) values. TBARS remained within normal range after L-HDL incubation with endothelial cells for up to 48 h. At most concentrations tested, exposure to lipolyzed but not oxidized lipoproteins resulted in morphological perturbations of cell monolayers. These data suggest that lipolytic remnants of triglyceride-rich lipoproteins may play an important role in the development of atherosclerosis by decreasing the barrier function of the vascular endothelium. The remnant-induced injury of the arterial wall may permit the entry of cholesterol-rich lipolytic remnants as well as LDL into the arterial wall.
Atherosclerosis 1992 Aug
PMID:Disruption of endothelial barrier function by lipolytic remnants of triglyceride-rich lipoproteins. 141 97

Elevated plasma homocysteine enhances the risk of thrombosis and premature arteriosclerosis. We have assessed the activity of the 3 prime enzymes of homocysteine metabolism in cultured human venous endothelial cells, in a study of their possible protective roles. In cells from 4 individuals, cultured in Dulbecco's modified Eagle medium, the mean activity +/- S.D. of cystathionine beta-synthase (nmol of product/h per mg of cell protein, at 37 degrees C) was 3.58 +/- 3.11 at pH 8.6. The assay used was our newly developed amino acid analyser-based procedure. The activity of 5-methyltetrahydrofolate:homocysteine methyltransferase at pH 7.4 was 4.12 +/- 1.25 and betaine:homocysteine methyltransferase (BHMT) was undetectable (< 1.4 nmol/h per mg protein). Cells were also cultured in a medium aimed at stimulating methionine biosynthesis, containing methionine-deficient Dulbecco's modified Eagle medium to which L-homocystine (100 mumol/l) and methylcobalamin (1 mumol/l) had been added. In these cells 5-methyltetrahydrofolate:homocysteine methyltransferase activity increased to 7.95 +/- 1.45, P < 0.001, there was a non-significant decrease in cystathionine beta-synthase activity to 2.16 +/- 1.52 and BHMT activity was still undetectable. These cells were more resistant to in vitro homocysteine-induced detachment than were cells from the same line cultured in Dulbecco's modified Eagle medium alone. Our findings establish that human endothelial cells express 2 of the 3 primary enzymes of homocysteine catabolism. They suggest that persons who are deficient in cystathionine beta-synthase or 5-methyltetrahydrofolate:homocysteine methyltransferase activity may not only develop homocysteinemia, but also have vascular endothelium which is more susceptible to damage by homocysteine than persons with normal enzyme levels.
Atherosclerosis 1992 Nov
PMID:Homocysteine catabolism: levels of 3 enzymes in cultured human vascular endothelium and their relevance to vascular disease. 144 98

Human atherosclerosis requires decades to develop spontaneously, and its development customarily is not monitored by serial biopsies. Atherosclerosis in allografts develops within months, and biopsy specimens are usually obtained from the grafts. We have used immunocytochemical techniques to study biopsy specimens of cardiac and renal allografts for parameters of vascular changes. The antibodies used in this investigation were specific for T lymphocytes, macrophages, IgM, and complement, and detailed studies were done with the use of antibodies specific for components of the hemostatic, fibrinolytic, and natural anticoagulant pathways. The results indicated a lack of association between the appearance of cellular infiltrates and measurable alterations in vascular endothelium and smooth-muscle cells. Although infiltrating macrophages and lymphocytes were identified in biopsy specimens with vascular change, such changes were also observed in biopsy specimens that were devoid of cellular infiltrates. The most prominent vascular changes in endothelium and smooth-muscle cells were accelerated hemostasis, depressed fibrinolysis, and deranged anticoagulant pathways. A negative association between the presence of IgM and fibrin on endothelial cells was also identified. Whether vascular changes are due to immunologically mediated reactions or to as yet undefined metabolic stresses of the graft-host relationship remains to be determined. This study provides a model for the study of vascular changes in atheroma development as viewed through the window of transplant-induced atherosclerosis.
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PMID:Vascular immunopathology and atheroma development in human allografted organs. 145 81


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