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

Clinical observations demonstrate an enhanced risk for myocardial infarction in patients with sustained activation of the local and/or systemic renin-angiotensin system, such as a high renin-sodium profile or a heritably enhanced expression of angiotensin converting enzyme. Chronic renin-angiotensin system blockade by angiotensin converting enzyme inhibition in patients with moderate heart failure reduces the rate of myocardial infarction and reinfarction. Preliminary experimental evidence suggests that these clinical observations may be partially explained by a proatherogenic effect of an activated renin-angiotensin system, which can downregulate the endothelial releasability of nitric oxide. Nitric oxide exerts many potentially antiatherogenic effects on endothelium, platelets and low density lipoproteins and indirectly on monocytes and leukocytes. Hypertension-induced chronic distension of elastic arteries upregulates the local renin-angiotensin system in these arteries and thereby downregulates nitric oxide releasability. Enhanced local synthesis of the trophic factor angiotensin-II and reduced releasability of the antitrophic factor nitric oxide appear to cooperate in the trophic adaptation of the distended vessel wall to the enhanced load, but with the disadvantage of enhanced susceptibility for atheroma development due to reduced releasability of nitric oxide. Chronic blockade of the renin angiotensin system by angiotensin converting enzyme inhibitors or by angiotensin receptor type-1 antagonists normalizes a reduced endothelial releasability of nitric oxide in several models, partially by a bradykinin-dependent mechanism. This endothelial protection proved to attenuate the progression of atherosclerosis in experimental models. The antiatherogenic potential of renin angiotensin system blockade in humans is presently under study.
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PMID:Vascular renin-angiotensin-system, endothelial function and atherosclerosis? 794 78

An enhanced risk for myocardial infarction has been observed in humans with sustained activation of the local and/or systemic renin-angiotensin system, such as a high renin-sodium profile or a heritably enhanced expression of angiotensin converting enzyme. Chronic renin-angiotensin system blockade by angiotensin converting enzyme inhibition reduces the rate of myocardial reinfarction in patients with moderate heart failure. Preliminary experimental evidence suggests that these clinical observations may be partially explained by a proatherogenic effect of an activated renin-angiotensin system, which can downregulate the expression of the endothelial nitric oxide synthase III. Nitric oxide exerts many potentially antiatherogenic effects on endothelium, platelets and low density lipoproteins and indirectly on monocytes and leukocytes Hypertension-induced chronic distension of elastic arteries upregulates the local renin-angiotensin system in these arteries and thereby downregulates nitric oxide synthase. Enhanced local synthesis of the trophic factor angiotensin-II and reduced releasability of the antitrophic factor nitric oxide appear to cooperate in the trophic adaptation of the distended vessel wall to the enhanced load, but with the disadvantage of enhanced susceptibility for atheroma development due to reduced availability of nitric oxide. Chronic blockade of the renin-angiotensin system by angiotensin converting enzyme inhibitors or by angiotensin receptor type-1 antagonists normalizes a reduced endothelial nitric oxide availability in several models, partially by a bradykinin-dependent mechanism. This endothelial protection proved to attenuate the progression of atherosclerosis in experimental models. The antiatherogenic potential of renin-angiotensin system blockade in humans is presently under study.
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PMID:The endothelium and the renin-angiotensin system. 818 13

To investigate the mechanism by which angiotensin-converting enzyme (ACE) inhibition attenuates atherogenesis, we have studied the effects of a non-sulfhydryl ACE inhibitor, enalapril, and an angiotensin receptor antagonist, SC-51316, in cholesterol-fed rabbits. After 3 mo of enalapril treatment (10 mg/kg per d, p.o.) the percent plaque areas in the thoracic aortas of treated animals were significantly reduced (controls: 86.8 +/- 3.5%; treated: 31.1 +/- 8%, P < 0.001). Aortic cholesterol content was also reduced (controls: 31.4 +/- 3.2 mg/g tissue; treated: 7.4 +/- 1.8 mg/g, P < 0.001). Enalapril had no significant effect on plasma lipid levels or conscious blood pressure. In a second study, the angiotensin II receptor antagonist SC-51316 was administered at a dose equivalent to enalapril at blocking angiotensin pressor effects in vivo (30 mg/kg per d, p.o.). Evaluation after 3 mo indicated no significant attenuation of aortic atherosclerosis. These results demonstrate that: (a) enalapril attenuates atherogenesis without affecting either blood pressure or plasma lipid levels; (b) antioxidant activity, found with sulfhydryl-containing ACE inhibitors, is not necessary for reducing plaque formation; and (c) the attenuation of atherogenesis by ACE inhibition may not be due to blockade of the renin-angiotensin system. Alternatively, one must consider the multiple effects of ACE inhibition on other hormone systems, such as bradykinin, or the possibility that alternate angiotensin II receptors may be involved in atherosclerosis.
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PMID:Differential effects of renin-angiotensin system blockade on atherogenesis in cholesterol-fed rabbits. 847 94

Chronic renal allograft dysfunction is often associated with hypertension, but it is unknown to what extent this affects graft structure and function. We investigated the effect of antihypertensive drug treatments on the course and histopathology of chronic renal allograft rejection in a rat model. Recipient animals were treated with a combination of reserpine, hydralazine and hydrochlorothiazide, the angiotensin converting enzyme inhibitor cilazapril, or the angiotensin II receptor blocker L158,809. Systemic blood pressures and tubular stop-flow pressures were measured on day 50 after transplantation; the histopathology was assessed semiquantitatively in kidneys not used for micropuncture studies. Grafts removed from untreated recipients showed inflammation and structural vascular and glomerular lesions consistent with chronic rejection. All treatment regimens decreased the systemic and glomerular capillary pressures and were associated with improved graft survival, decreased proteinuria and a tendency to improved graft function; the histopathology showed a significant amelioration of glomerular mesangiolysis and glomerulosclerosis but no effect was found on the tubulointerstitial lesions; the angiotensin receptor blocker also inhibited graft atherosclerosis. We conclude that hemodynamic and angiotensin II-mediated processes may play a pivotal role in the expression of immune-mediated glomerular lesions of chronic allograft dysfunction.
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PMID:Post-transplant hypertension and chronic renal allograft failure. 858 80

The essential problem of the vicious circle leading to end-stage cardiovascular disease is atherosclerosis. This paper focuses on the functional changes centred on the endothelium that accompany the development of atherosclerosis, examining in particular pathological alterations in the L-arginine/nitric oxide (NO) pathway. Changes in the NO system are associated with altered platelet and monocyte interactions with the vessel wall, abnormal vasoconstriction and altered vascular structure. Diabetes, hyperglycaemia, hypertension and hypercholesterolaemia are all involved in this process. Endothelin is a vasoconstrictor peptide produced by endothelial cells which is upregulated under these conditions. Normalising endothelial function could involve platelet inhibition, lipid-lowering agents to prevent foam cell formation and decrease the lipid load of the blood vessel wall, and agents to interfere with some of the mechanisms involved in vasoconstriction, proliferation and migration, including ACE-inhibitors and angiotensin receptor antagonists, and possibly new tools such as endothelin receptor antagonists.
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PMID:The internist and the vessel wall. 917 1

Two problems in the treatment of hypertension continue to be largely unsolved. The first, and more simple, is our inability to adequately control blood pressure in the majority of hypertensive patients. This not only reflects the difficulty of retaining patients in effective treatment programs, but also of convincing physicians to strive for optimal blood pressure levels. There is a continuing need for new antihypertensive drugs and combinations to help accomplish these goals. The second major problem is that the major clinical endpoints, including coronary events and renal failure, have not been adequately reduced by traditional therapies. Standard regimens, particularly those including diuretics, have protected against strokes and heart failure. Our improved understanding of vascular biology in hypertension has directed interest to the mechanisms in hypertensive patients that might accelerate atherosclerosis and vascular events in these individuals. This involves addressing the concomitant metabolic risk factors that comprise the "Hypertension Syndrome," and, perhaps of equal importance, finding therapies that directly inhibit unwanted types of growth and proliferative activities within the walls of critical arteries. Many substances within the endothelium and the vascular wall may participate as initiators or mediators of pathology, but most information thus far has focused on the renin-angiotensin system. Angiotensin converting enzyme inhibitors (and potentially angiotensin receptor blockers) have provided coronary and renal protection in various cardiovascular conditions, though not yet in formal hypertension trials. Calcium channel blockers have also shown promise, including recent stroke and cardiovascular benefits in patients with isolated systolic hypertension, but, again, definitive coronary data in hypertension are awaited. Unless concomitant conditions mandate the selection of a particular antihypertensive drug class, physicians currently have a dilemma: should they choose drugs from older classes that have not provided full protection? Or, should they prescribe newer agents with exciting potential but with, as yet, unproved endpoint benefits in hypertension? Until currently ongoing prospective trials of antihypertensive therapy are completed, physicians must be guided by their own interpretations of the available data.
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PMID:Translating data on antihypertensive drugs into clinical practice. 965 68

The purpose of this study was to determine whether an angiotensin converting enzyme (ACE) inhibitor, benazepril, and an angiotensin receptor antagonist, valsartan, would decrease atherosclerotic severity in cholesterol-fed rabbits. Male rabbits were fed either: (a) normal rabbit chow; (b) 2% cholesterol diet; (c) 2% cholesterol diet supplemented by benazepril (3 mg/kg per day, subcutaneous injection); or (d) 2% cholesterol diet supplemented by valsartan (1 mg/kg per day, subcutaneous injection). After 12 weeks, the arteries were harvested for histomorphometry and immunohistochemistry. We observed that decreases in serum triglyceride (TG) and total cholesterol (TC) and ACE activity with benazepril-treatment were more than 60, 30, and 84%, respectively, in comparison with the cholesterol group; with valsartan-treatment, TG levels were 53% lower than in the cholesterol group, however, there was no significant difference in TC and ACE activity. The percentage of aortic surface atherosclerotic area, intimal thickness and the ratio of aortic intimal area to medial area were about 40% lower in the benazepril-treated group in comparison with those of the cholesterol group; the difference was more than 60% in the thoracic aorta. The valsartan-treated group had 23% less atherosclerotic area, less effective than benazepril treatment. The percent of PCNA-positive cells and the number of intimal proliferative cells/mm2 were significantly less in the benazepril-treated group compared with the cholesterol group (by 55 and 63%); these parameters were 35 and 17% lower, respectively, with valsartan. The ratio of proliferating macrophages to smooth muscle cells (SMCs) was 3:1 in the cholesterol group, 1:1 in the benazepril and 2:1 in the valsartan-treated group. These results indicate that benazepril could reduce atherosclerotic progression by decreasing macrophage proliferation and accumulation in the arterial wall. The mechanisms for reducing atherosclerotic progression by benazepril and valsartan may be related to reduction of TG and blockade of the angiotensin II action.
Atherosclerosis 1999 Apr
PMID:Antiatherogenic effect of angiotensin converting enzyme inhibitor (benazepril) and angiotensin II receptor antagonist (valsartan) in the cholesterol-fed rabbits. 1021 60

A growing body of evidence supports the notion that angiotensin II (Ang II), the central product of the renin-angiotensin system, may play a central role not only in the etiology of hypertension but also in the pathophysiology of cardiovascular and renal diseases in humans. In this review, we focus on the role of Ang II in cardiovascular and renal diseases at the molecular and cellular levels and discuss up-to-date evidence concerning the in vitro and in vivo actions of Ang II and the pharmacological effects of angiotensin receptor antagonists in comparison with angiotensin-converting enzyme inhibitors. Ang II, via AT(1) receptor, directly causes cellular phenotypic changes and cell growth, regulates the gene expression of various bioactive substances (vasoactive hormones, growth factors, extracellular matrix components, cytokines, etc.), and activates multiple intracellular signaling cascades (mitogen-activated protein kinase cascades, tyrosine kinases, various transcription factors, etc.) in cardiac myocytes and fibroblasts, vascular endothelial and smooth muscle cells, and renal mesangial cells. These actions are supposed to participate in the pathophysiology of cardiac hypertrophy and remodeling, heart failure, vascular thickening, atherosclerosis, and glomerulosclerosis. Furthermore, in vivo recent evidence suggest that the activation of mitogen-activated protein kinases and activator protein-1 by Ang II may play the key role in cardiovascular and renal diseases. However, there are still unresolved questions and controversies on the mechanism of Ang II-mediated cardiovascular and renal diseases.
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PMID:Molecular and cellular mechanisms of angiotensin II-mediated cardiovascular and renal diseases. 1069 53

In hypercholesterolemia in the presence or absence of atherosclerosis, cardiovascular dysfunction and altered signaling of angiotensin, nitric oxide, or prostanoids are closely related to enhanced oxidant stress. We analyzed the potentially beneficial effects of the specific angiotensin-converting enzyme inhibitor enalapril and the specific angiotensin receptor blocker losartan on cardiac performance, eicosanoid metabolism, and parameters of oxidant stress in hypercholesterolemic animals. Guinea pigs were fed a 1% cholesterol diet for 8 weeks (Chol) with or without equieffective doses of either enalapril (1.5 mg/kg/d; Ena) or losartan (3 mg/kg/d; Los). Hemodynamics were analyzed in Langendorff hearts. Detection of eicosanoids was by enzyme immunoassay. Estimation of plasma xanthine oxidase (XO) activity was determined by spectrophotometry. In hypercholesterolemic guinea pigs, enhanced oxidant stress (e.g., increased plasma XO activities) was associated with profound myocardial and coronary (e.g., endothelial) dysfunction. Both enalapril and losartan lowered plasma cholesterol levels slightly, but only the angiotensin receptor antagonist effectively suppressed the increased plasma XO activities (from 11.4 +/- 0.7 to 7.6 +/- 2.2 U/L), and at the same time decreased the augmented coronary flow (from 26.0 +/- 1.0 to 23.0 +/- 1.0 mL/min/g tissue) observed in hypercholesterolemic animals. Assessment of left ventricular pressure and contractility (e.g., dp/dtmax) as well as the diastolic relaxation parameter (tau) revealed substantial myocardial dysfunction (systolic and diastolic) in Chol that was more substantially (and comparably) improved during administration of losartan (Los) than during enalapril (Ena). Surprisingly, angiotensin signaling blockade by either antagonist further suppressed the diminished coronary dilator responses to bradykinin (BK; not significant for enalapril) or adenosine (Ado) was demonstrated in Chol Langendorff hearts [delta CPPBK/Ado: from 5.0 +/- 0.5/0.9 +/- 0.1 to 4.4 +/- 1.5/0.4 +/- 0.1 (Ena) or to 1.9 +/- 0.5/0.4 +/- 0.1 (Los) cm2 (area under the curve), respectively]. Finally, as expected from control studies using heart preparations from normocholesterolemic guinea pigs, enhanced cardiac release of eicosanoids, prostacyclin, and thromboxane in Chol (0.48 +/- 0.03 and 0.6 +/- 0.1 ng/min/g) was augmented even further by treatment with enalapril (Ena: 1.6 +/- 0.4 and 1.0 +/- 0.1 ng/min/g), but was significantly reduced to or below control levels in losartan-treated animals (Los: 0.4 +/- 0.1 and 0.2 +/- 0.1 ng/min/g). Blockade of angiotensin signaling via angiotensin-converting enzyme inhibition or receptor antagonism--although differentially acting on enhanced cardiac prostanoid metabolism and oxidant stress--efficiently restored proper systolic and diastolic myocardial performance (losartan was more beneficial than enalapril), probably by counterbalancing altered angiotensin II-->angiotensin receptor signaling in the cardiovascular system of hypercholesterolemic animals. Impaired coronary vasodilator capacity seems to be irreversible after 8 weeks of a high-cholesterol diet, as shown by the unexpected lack of a dilator effect with both enalapril and losartan.
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PMID:Blockade of angiotensin signaling improves myocardial function in hypercholesterolemia independent of changes in eicosanoid release. 1093 54

Angiotensin-converting enzyme (ACE) inhibitors appear to possess unique cardioprotective benefits, even when used in patients without high blood pressure or left ventricular dysfunction (the traditional indications for ACE inhibitor therapy). The ACE inhibitors improve endothelial function and regress both left ventricular hypertrophy and arterial mass better than other antihypertensive agents that lower blood pressure equally as well. These agents promote collateral vessel development and improve prognosis in patients who have had a coronary revascularization procedure (i.e., percutaneous transluminal coronary angioplasty and coronary artery bypass graft surgery). Insulin resistance, present not only in type 2 diabetes but also commonly in patients with hypertension or coronary artery disease, or both, sensitizes the vasculature to the trophic effects of angiotensin II and aldosterone. This may partly explain the improvement in prognosis noted when patients who have atherosclerosis or diabetes are treated with an ACE inhibitor. Therapy with ACE inhibitors has also been shown, in two large, randomized trials, to reduce the incidence of new-onset type 2 diabetes through largely unknown mechanisms. The ACE inhibitors are safe, well tolerated and affordable medications. The data suggest that most people with atherosclerosis should be considered candidates for ACE inhibitor therapy, unless they are intolerant to the medication, or have systolic blood pressures consistently <100 mm Hg. Patients who show evidence of insulin resistance (with or without overt type 2 diabetes) should also be considered as candidates for prophylactic ACE inhibitor therapy. Although angiotensin receptor blockers should not be considered equivalent to ACE inhibitors for this indication, they may be a reasonable alternative for patients intolerant of ACE inhibitors.
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PMID:Should an angiotensin-converting enzyme inhibitor be standard therapy for patients with atherosclerotic disease? 1115 22


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