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Query: UMLS:C0020538 (hypertension)
 170,190 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The vascular endothelium influences not only the three classically interacting components of hemostasis: the vessel, the blood platelets and the clotting and fibrinolytic systems of plasma, but also the natural sequelae: inflammation and tissue repair. Two principal modes of endothelial behaviour may be differentiated, best defined as an anti- and a prothrombotic state. Under physiological conditions endothelium mediates vascular dilatation (formation of NO, PGI2, adenosine, hyperpolarizing factor), prevents platelet adhesion and activation (production of adenosine, NO and PGI2, removal of ADP), blocks thrombin formation (tissue factor pathway inhibitor, activation of protein C via thrombomodulin, activation of antithrombin III) and mitigates fibrin deposition (t- and scuplasminogen activator production). Adhesion and transmigration of inflammatory leukocytes are attenuated, e.g. by NO and IL-10, and oxygen radicals are efficiently scavenged (urate, NO, glutathione, SOD). When the endothelium is physically disrupted or functionally perturbed by postischemic reperfusion, acute and chronic inflammation, atherosclerosis, diabetes and chronic arterial hypertension, then completely opposing actions pertain. This prothrombotic, proinflammatory state is characterised by vaso-constriction, platelet and leukocyte activation and adhesion (externalization, expression and upregulation of von Willebrand factor, platelet activating factor, P-selectin, ICAM-1, IL-8, MCP-1, TNF alpha, etc.), promotion of thrombin formation, coagulation and fibrin deposition at the vascular wall (expression of tissue factor, PAI-1, phosphatidyl serine, etc.) and, in platelet-leukocyte coaggregates, additional inflammatory interactions via attachment of platelet CD40-ligand to endothelial, monocyte and B-cell CD40. Since thrombin formation and inflammatory stimulation set the stage for later tissue repair, complete abolition of such endothelial responses cannot be the goal of clinical interventions aimed at limiting procoagulatory, prothrombotic actions of a dysfunctional vascular endothelium.
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PMID:Endothelial function and hemostasis. 1079 71

Tissue factor (TF), a main initiator of clotting, is up-regulated in vasculopathy. We tested the hypothesis that chronic in vivo angiotensin (ANG) II receptor AT(1) receptor blockade inhibits TF expression in a model of ANG II-induced cardiac vasculopathy. Furthermore, we explored the mechanisms by examining transcription factor activation and analyzing the TF promoter. Untreated transgenic rats overexpressing the human renin and angiotensinogen genes (dTGR) feature hypertension and severe left ventricular hypertrophy with focal areas of necrosis, and die at age 7 weeks. Plasma and cardiac ANG II was three- to fivefold increased compared to Sprague-Dawley rats. Chronic treatment with valsartan normalized blood pressure and coronary resistance completely, and ameliorated cardiac hypertrophy (P < 0.001). Valsartan prevented monocyte/macrophage infiltration, nuclear factor-kappaB (NF-kappaB) and activator protein-1 (AP-1) activation, and c-fos expression in dTGR hearts. NF-kappaB subunit p65 and TF expression was increased in the endothelium and media of cardiac vessels and markedly reduced by valsartan treatment. To analyze the mechanism of TF transcription, we then transfected human coronary artery smooth muscle cells and Chinese hamster ovary cells overexpressing the AT(1) receptor with plasmids containing the human TF promoter and the luciferase reporter gene. ANG II induced the full-length TF promoter in both transfected cell lines. TF transcription was abolished by AT(1) receptor blockade. Deletion of both AP-1 and NF-kappaB sites reduced ANG II-induced TF gene transcription completely, whereas the deletion of AP-1 sites reduced transcription. Thus, the present study clearly shows an aberrant TF expression in the endothelium and media in rats with ANG II-induced vasculopathy. The beneficial effects of AT(1) receptor blockade in this model are mediated via the inhibition of NF-kappaB and AP-1 activation, thereby preventing TF expression, cardiac vasculopathy, and microinfarctions.
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PMID:Angiotensin II (AT(1)) receptor blockade reduces vascular tissue factor in angiotensin II-induced cardiac vasculopathy. 1088 Mar 68

Hemostasis factors may influence the pathophysiology of stroke. The role of brain hemostasis in ischemic hypertensive brain injury is not known. We studied ischemic injury in spontaneously hypertensive rats in relation to cerebrovascular fibrin deposition and activity of different hemostasis factors in brain microcirculation. In spontaneously hypertensive rats subjected to transient middle cerebral artery occlusion versus normotensive Wistar-Kyoto (W-K) rats, infarct and edema volumes were increased by 6.1-fold (P < 0.001) and 5.8-fold (P < 0.001), respectively, the cerebral blood flow (CBF) reduced during middle cerebral artery occlusion (MCAO) by 55% (P < 0.01), motor neurologic score increased by 6.9-fold (P < 0.01), and cerebrovascular fibrin deposition increased by 6.8-fold (P < 0.01). Under basal conditions, brain capillary protein C activation and tissue plasminogen activator activity were reduced in spontaneously hypertensive rats compared with Wistar-Kyoto rats by 11.8-fold (P < 0.001) and 5.1-fold (P < 0.001), respectively, and the plasminogen activator inhibitor-1 antigen and tissue factor activity were increased by 154-fold (P < 0.00001) and 74% (P < 0.01), respectively. We suggest that hypertension reduces antithrombotic mechanisms in brain microcirculation, which may enhance cerebrovascular fibrin deposition and microvascular obstructions during transient focal cerebral ischemia, which results in greater neuronal injury.
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PMID:Brain injury and cerebrovascular fibrin deposition correlate with reduced antithrombotic brain capillary functions in a hypertensive stroke model. 1089 83

Reports on the effectiveness of endothelin receptor blockers in angiotensin (Ang) II-induced end-organ damage are conflicting, and the mechanisms involved are uncertain. We tested the hypothesis that endothelin (ET)(A/B) receptor blockade with bosentan (100 mg/kg by gavage after age 4 weeks) ameliorates cardiac and renal damage by decreasing inflammation in rats harboring both human renin and angiotensinogen genes (dTGR). Furthermore, we elucidated the effect of bosentan on tissue factor (TF), which is a key regulator of the extrinsic coagulation cascade. We compared bosentan with hydralazine (80 mg/L in the drinking water for 3 weeks) as a blood pressure control. Untreated dTGR featured hypertension, focal necrosis in heart and kidney, and a 45% mortality rate (9 of 20) at age 7 weeks. Compared with Sprague-Dawley controls, both systolic blood pressure and 24-hour albuminuria were increased in untreated dTGR (203+/-8 versus 111+/-2 mm Hg and 67.1+/-8.6 versus 0.3+/-0.06 mg/d at week 7, respectively). Bosentan and hydralazine both reduced blood pressure and cardiac hypertrophy. Mortality rate was markedly reduced by bosentan (1/15) and partially by hydralazine (4/15). However, only bosentan decreased albuminuria and renal injury. Untreated and hydralazine-treated dTGR showed increased nuclear factor (NF)-kappaB and AP-1 expression in the kidney and heart; the p65 NF-kappaB subunit was increased in the endothelium, vascular smooth muscles cells, infiltrating cells, glomeruli, and tubules. In the heart and kidney, ET(A/B) receptor blockade inhibited NF-kappaB and AP-1 activation compared with hydralazine treatment. Macrophage infiltration, ICAM-1 expression, and the integrin expression on infiltrating cells were markedly reduced. Renal vasculopathy was accompanied by increased tissue factor expression on macrophages and vessels of untreated and hydralazine-treated dTGR, which was markedly reduced by bosentan. Thus, ET(A/B) receptor blockade inhibits NF-kappaB and AP-1 activation and the NF-kappaB- and/or AP-1-regulated genes ICAM-1, VCAM-1, and TF, independent of blood pressure-related effects. We conclude that Ang II-induced NF-kappaB and AP-1 activation and subsequent inflammation and coagulation involve at least in part the ET(A/B) receptors.
Hypertension 2000 Aug
PMID:Effect of bosentan on NF-kappaB, inflammation, and tissue factor in angiotensin II-induced end-organ damage. 1094 91

Recently published studies suggest that the procoagulant receptor protein tissue factor (TF) is involved in vitro in cell adhesion and migration, via an interaction of its cytoplasmic domain with cytoskeletal proteins. Interestingly, TF is abundantly expressed in myocardium, but not in skeletal muscle. To elucidate the possible roles of TF in the myocardium, this study examined the cellular distribution of TF in relation to cytoskeletal proteins, as well as its relative amounts in different segments of premature, mature, and pathologically altered cardiac muscle. In juvenile and adult hearts, TF was predominantly detectable in the transverse part of the intercalated discs, where it co-localized with cytoskeletal proteins such as desmin and vinculin. The lowest amount of TF was observed in right atrial and the highest in left ventricular myocardium, which correlated with the number of contact sites of cardiomyocytes in these segments of the cardiac muscle. Lower levels of TF were present in structurally altered myocardium from patients with hypertension or ventricular hypertrophy. In addition, TF expression was decreased in human heart during sepsis and transiently decreased in rabbit heart in an endotoxaemia model, which indicates that a reduction in TF may contribute to cardiac failure in sepsis. The microtopography of TF at cardiomyocyte contact sites indicates that TF may play a structural role in the maintenance of cardiac muscle.
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PMID:Functional implications of tissue factor localization to cell-cell contacts in myocardium. 1095 9

The past decade has witnessed enormous progress in our understanding of the nature of this process. The development of an atherosclerotic plaque is a complex process which begins with endothelial dysfunction, the trigger for which are factors such as hypercholesterolemia, smoking, hypertension, hyperhomocysteinemia and impaired glucose metabolism. This dysfunction includes increased endothelial permeability to lipoproteins and other plasma constituents, which is mediated by NO, PDGF, prostacyclin, angiotensin II and endothelin; up-regulation of endothelial adhesion molecules including VCAM-1, ICAM-1, and selectins and migration of leukocytes and monocytes-macrophages in the subendothelial space mediated by oxidized LDL, MCP-1, PDGF and MCSF. The next step includes smooth-muscle cells migration (stimulated by PDGF and TGF-beta), T-cell activation (mediated by TNF-alpha and IL-2), formation of foam-cells from macrophages (mediated by oxidized LDL, MCSF, TNF-alpha and IL-1) and platelet adherence and aggregation (stimulated by thromboxane A2, tissue factor etc). The smooth muscle cells form a fibrous cap which confers mechanical stability of the plaque and separates the lipid rich thrombogenic core from the lumen and circulating blood. Whether a plaque will remain intact and therefore stable or rupture and lead to thrombosis causing an acute coronary syndrome (MI, unstable angina pectoris) depends upon a number of factors, the most important of which is its composition. Plaque size plays only a minor role in determining risk of an acute coronary syndrome. Rupture of the fibrous cap occurs due to thinning of the cap caused by an influx and activation of macrophages which release metalloproteinases and other proteolytic enzymes (stimulated by inflammatory cells, particularly T-lymphocytes). These enzymes cause degradation of the fibrous tissue of the cap which can result in thrombous formation and occlusion of the artery. Stable plaques have a thick fibrous cap, a small lipid core, and few inflammatory cells. In contrast, vulnerable plaques have a high lipid content, numerous inflammatory cells, and a thin fibrous cap with reduced collagen and vascular smooth muscle cells in it. Although vulnerable plaques are believed to account for only a small number of all coronary atheromas, they are responsible for most acute coronary events.
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PMID:[New information on the pathophysiology of atherosclerosis]. 1137 94

Increased LDL oxidation is associated with coronary artery disease. The predictive value of circulating oxidized LDL is additive to the Global Risk Assessment Score for cardiovascular risk prediction based on age, gender, total and HDL cholesterol, diabetes, hypertension, and smoking. Circulating oxidized LDL does not originate from extensive metal ion-induced oxidation in the blood but from mild oxidation in the arterial wall by cell-associated lipoxygenase and/or myeloperoxidase. Oxidized LDL induces atherosclerosis by stimulating monocyte infiltration and smooth muscle cell migration and proliferation. It contributes to atherothrombosis by inducing endothelial cell apoptosis, and thus plaque erosion, by impairing the anticoagulant balance in endothelium, stimulating tissue factor production by smooth muscle cells, and inducing apoptosis in macrophages. HDL cholesterol levels are inversely related to risk of coronary artery disease. HDL prevents atherosclerosis by reverting the stimulatory effect of oxidized LDL on monocyte infiltration. The HDL-associated enzyme paraoxonase inhibits the oxidation of LDL. PAF-acetyl hydrolase, which circulates in association with HDL and is produced in the arterial wall by macrophages, degrades bioactive oxidized phospholipids. Both enzymes actively protect hypercholesterolemic mice against atherosclerosis. Oxidized LDL inhibits these enzymes. Thus, oxidized LDL and HDL are indeed antagonists in the development of cardiovascular disease.
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PMID:Oxidized LDL and HDL: antagonists in atherothrombosis. 1164 Dec 34

There is growing evidence that inflammatory processes may be involved in the development of atherosclerosis and its complications. Viral and bacterial pathogens have been implicated as possible causative factors in the pathogenesis of coronary artery disease (CAD) and restenosis after angioplasty. Antibiotic trials are now in progress to examine whether treatment of infection can prevent the complications of CAD. Atherosclerosis, the primary pathologic process in coronary artery disease (CAD), carotid artery disease, abdominal aortic aneurysm, and peripheral vascular disease, is no longer considered to be an obscure, slowly progressive, degenerative disease. Indeed, recent molecular studies on the atherosclerotic plaque have shown that the initiation, progression, and acute sequelae of atherosclerosis can be explained in part by a low-grade inflammatory process. Studies show that mediators of inflammation can be found at all stages of the life cycle of the atherosclerotic plaque. These include activated macrophages and lymphocytes, cytokines, growth factors, matrix degenerating proteinases, and tissue factor. It is hypothesized that risk factors such as hypertension, smoking, or elevated levels of low-density lipoprotein (LDL) cholesterol result in injury to the endothelial cell of the artery, and this injury initiates the inflammatory process. However, many patients with vascular disease do not have these established risk factors, and this observation has galvanized efforts to find new risk factors. Because inflammation is now considered to be an operative paradigm for atherosclerosis, it is not a major leap to the hypothesis that infectious agents, such as viral or bacterial, may play a role. Certainly this is not a new concept, and with the recent discovery that peptic ulcer disease, heretofore considered a disease of excess acid and reduced mucosal resistance, is caused by the ubiquitous bacterium Helicobacter pylori, interest in finding an infectious etiology for atherosclerosis has increased. Accordingly, the purpose of this discussion is to review in a historical manner the evidence that infectious agents-including herpes simplex virus (HSV), cytomegalovirus (CMV), Epstein-Barr virus (EBV), Enterovirus (adenovirus, Coxsackie virus), Chlamydia pneumoniae, and H. pylori-may play a role in atherosclerosis and its manifestations, especially as they relate to CAD.
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PMID:The role of infection in atherosclerosis and coronary artery disease: a new therapeutic target. 1172 77

Reduced activity of endothelial nitric oxide (NO) may be involved in thrombus formation on atherosclerotic plaques, a major cause of acute coronary syndrome. However, mechanisms of such increase in arterial thrombogenecity have not been fully understood. We previously reported that long-term inhibition of NO synthesis by administration of N(G)-nitro-L-arginine methyl ester (L-NAME) causes hypertension and activates vascular tissue angiotensin-converting enzyme (ACE) activity. We used this model to investigate the mechanism by which long-term impairment of NO activity increases arterial thrombogenecity. We observed cyclic flow variations (CFVs), a reliable marker of platelet thrombi, after the production of stenosis of the carotid artery in rats treated with L-NAME for 4 wk. The thrombin antagonist argatroban suppressed the CFVs. The CFVs were detected in rats receiving L-NAME plus hydralazine but not in rats receiving L-NAME plus an ACE inhibitor (imidapril). Treatment with the ACE inhibitor imidapril, but not with hydralazine, prevented L-NAME-induced increases in carotid arterial ACE activity and attenuated tissue factor expression. These results suggest that long-term inhibition of endothelial NO synthesis may increase arterial thrombogenecity at least in part through angiotensin II-induced induction of tissue factor and the resultant thrombin generation. These data provide a new insight as to how endothelial NO exhibits antithrombogenic properties of the endothelium.
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PMID:Long-term inhibition of nitric oxide synthesis increases arterial thrombogenecity in rat carotid artery. 1189 85

Endothelin-1 (ET-1) and nitric oxide (NO) have been suggested to have a focal role in the regulation of placental and fetal growth. Cyclosporine A (CsA) has been shown to strongly modulate ET-1 and NO synthesis and thus has the potential to affect fetal growth and maternal state. Eleven CsA-treated female kidney transplant recipients were recruited. Fourteen healthy pregnant women served as controls. Placental expression of ET-1 and tissue factor (TF) was evaluated by in situ hybridization, and NO synthase (NOS) was evaluated by staining with the reduced form of nicotinamide-adenine dinucleotide phosphate (NADPH)-diaphorase and in situ hybridization. Kidney transplant recipients showed a marked reduction in NADPH-diaphorase staining, as well as endothelial constitutive NOS (ecNOS) messenger RNA, whereas inducible NOS expression was unchanged. Normal placenta showed a strong positive ET-1 signal along the endothelium of uteroplacental arteries within the basal plate, which increased markedly in decidua of transplant recipients. Thus, transplant recipients showed a remarkable alteration in ET-1/ecNOS balance without alteration in fetal growth or maternal renal function. Next, we explored the state of placental endothelial cell activation downstream from vasoactive factors by evaluating TF gene expression. Transplant recipients did not show modification of TF transcript compared with healthy pregnant women. CsA potently affected the placental ET-1/ecNOS vasoactive balance. Nevertheless, newborns from transplant recipient mothers were appropriate for gestational age, and transplant recipients did not show systemic hypertension or impending renal damage. It is suggested that CsA may blunt the activation of endothelial cells and priming of endothelial-derived substances, which possibly lie downstream from the cited vasoactive agents.
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PMID:Placental imbalance of vasoactive factors does not affect pregnancy outcome in patients treated with Cyclosporine A after transplantation. 1192 Mar 44


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