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Query: UMLS:C0038454 (stroke)
 147,016 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Inducible nitric oxide synthase (iNOS) has been implicated as a mediator of cellular toxicity in a variety of neurodegenerative disorders. Nitric oxide, which is generated in high quantities following induction of iNOS, combines with other oxygen radicals to form highly reactive, death-inducing compounds. Given the frequency of neuronal death due to neurodegenerative diseases, cerebral trauma, and stroke, it is important to study the mechanisms of regulation of iNOS in the brain. We demonstrated previously that angiotensin II (Ang II) decreases the expression of iNOS produced by bacterial endotoxin or cytokines in cultured astroglia prepared from adult rat brain. Here, we have addressed the mechanisms by which Ang II negatively modulates iNOS. The inhibitory effects of Ang II on lipopolysaccharide-induced expression of iNOS mRNA and protein and nitrite accumulation were mimicked by the protein kinase C (PKC) activator phorbol 12-myristate 13-acetate. Down-regulation of PKC produced by long-term treatment of astroglia with phorbol 12-myristate 13-acetate abolished the inhibitory effect of Ang II on lipopolysaccharide-stimulated expression of iNOS mRNA and nitrite accumulation. Finally, the reduction of lipopolysaccharide-induced nitrite accumulation by Ang II was attenuated by the selective PKC inhibitor chelerythrine. Collectively, these data indicate a role for PKC in the inhibitory actions of Ang II on iNOS expression in cultured astroglia.
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PMID:Angiotensin II-induced decrease in expression of inducible nitric oxide synthase in rat astroglial cultures: role of protein kinase C. 1064 12

Angiotensin II is considered to have angiogenic properties. Nevertheless, several authors reported an increase in coronary capillary density after treatment with ACE inhibitors. The aim of the present study was to evaluate the effect of treatment with low doses of ACE inhibitor perindopril, low doses of the diuretic indapamide, or a combination of the two on microvascular structure in hearts from stroke-prone spontaneously hypertensive rats (SHR-sp). Young adult male SHR treated with indapamide (0.24 mg/kg/day), perindopril (0.76 mg/kg/day), or both were compared with untreated animals after 8 or 14 weeks of treatment. Survival of SHR-sp was significantly increased after treatment. Only perindopril alone or in combination with indapamide significantly decreased blood pressure and cardiac mass. Treatment also significantly increased capillary and myocyte densities but arteriolar density tended to decrease. External and internal diameters significantly increased in treated animals while arteriolar thickness remained the same. Thus, thickness in vessels of the same size was the greatest in untreated animals, followed by indapamide- and perindopril-treated rats with the thinnest walls in rats with combined treatment, and the treatment resulted in a significant increase in the lumen to wall ratio. Capillary and arteriolar growth responses in treated animals seem to indicate that the two are independently regulated processes. Treatment with indapamide alone at this dosage did not significantly influence most responses but in combination with perindopril it strengthened the effect of perindopril.
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PMID:The effect of treatment with low dose ACE inhibitor and/or diuretic on coronary microvasculature in stroke-prone spontaneously hypertensive rats. 1068 30

A male Wistar rat model of stroke (middle cerebral artery occlusion; MCAO) was used to study the angiotensin II (Ang II) receptor subtype 2 (AT2) gene expression by reverse transcription polymerase chain reaction (RT-PCR) and immunohistochemical staining. After permanent occlusion of the middle cerebral artery (MCA), AT2 receptor gene expression was found to increase in the infarct cortex by 2.7-fold (1 day) and 1.7-fold (3 days), respectively. Positive AT2 immunostaining was also observed in the infarct area of the cerebral cortex. Apoptotic markers were detected in the necrotic area of the stroke cerebral cortex 1 day after MCAO. This demonstrated up-regulation of AT2 receptor may be involved in the apoptosis of tissue repair after stroke.
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PMID:Expression of angiotensin II AT2 receptor in the acute phase of stroke in rats. 1081 89

Several unfavorable cardiovascular events show a well-defined pattern in their occurrence throughout the day. Myocardial infarction and ischemia, sudden cardiac death and stroke occur with greater frequency in the morning hours after awakening. Multiple biologic functions such as blood pressure, heart rate, sympathetic neurotransmission, vascular tone, platelet aggregability, and coagulation parameters also show a diurnal variation and appear to contribute to adverse cardiac outcomes. Recent studies have emphasized the importance of 24 h control in decreasing cardiovascular risk. The renin-angiotensin system (RAS), through the important effector peptide, angiotensin II (Ang II), has potent effects on blood pressure, salt and water homeostasis, and target-organ damage. Inhibiting the RAS consequently becomes an important therapeutic avenue for treating hypertension and target-organ damage. Ang II receptor antagonists selectively compete with the binding of Ang II to the Ang II type 1 receptor and, by inhibiting the multiple activities mediated by Ang II at this receptor, may confer cardiovascular benefits additional to that of blood pressure control. Ang II receptor antagonists with an intrinsically long duration of action that produce smooth, sustained antihypertensive activity over the dosing period provide a similar 24 h benefit of Ang II inhibition.
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PMID:Factors affecting circadian variability. 1090 36

A considerable amount of data have implicated angiotensin receptors (AT receptors) in the development and maintenance of essential hypertension and renovascular hypertension as well as in progressive renal pathologies. Inhibition of angiotensin II (Ang II) action by blocking Ang II formation through angiotensin-converting enzyme (ACE) inhibitors, or by blocking AT1 receptors directly using subtype-selective nonpeptide antagonists, has been found to attenuate the proteinuria, microalbuminuria, glomerulosclerosis, and nephrosclerosis in a variety of experimental models and in clinical trials. This review will first broadly discuss AT receptor subtypes in terms of their structure, function, tissue distribution and signaling. Secondly, the mechanistic differences between ACE inhibition and AT1 receptor blockade will be examined because these pharmaceutical agents are widely used tools to investigate the role of AT receptors in renal disease. Lastly, experimental models of essential hypertension, renovascular hypertension and progressive renal disease will be presented, which include the Fawn-hooded rat, the stroke prone spontaneously hypertensive rat, renal mass ablation and the 2K1C and 1K1C animal models. The overall goal of this review is to critically evaluate the data regarding the role of AT receptors in the pathophysiology of renal disease.
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PMID:Kidney angiotensin receptors and their role in renal pathophysiology. 1102 92

It is unclear whether the previous in vitro evidence of a link between angiotensin II (Ang II) and growth factor receptors can apply to the in vivo situation. In this study, we examined vascular platelet-derived growth factor (PDGF) and epidermal growth factor (EGF) receptor activation in stroke-prone spontaneously hypertensive rats (SHRSP) and the role of Ang II. Tyrosyl phosphorylation of the growth factor receptors was determined by Western blot analysis coupled with immunoprecipitation. Tyrosyl phosphorylation of the aortic PDGF beta-receptor, but not the EGF receptor, was chronically increased in SHRSP with hypertension, compared with normotensive rats, being accompanied by increased extracellular signal-regulated kinase (ERK) activity. Treatment of SHRSP with ACE inhibitors (perindopril or enalapril) significantly reduced aortic PDGF beta-receptor tyrosyl phosphorylation and ERK activity, whereas treatment with hydralazine failed to reduce these activities. Therefore, these aortic changes in SHRSP were mediated by Ang II in response to vascular ACE. Ang II was infused into rats to examine the effects on aortic growth factor receptors. Chronic Ang II infusion, via the angiotensin type 1 receptor, significantly increased activation of the aortic PDGF beta-receptor but not the EGF receptor. Thus, the aortic PDGF beta-receptor, activated by ACE-mediated Ang II, seems to be responsible for vascular remodeling in hypertensive rats.
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PMID:In vivo activation of rat aortic platelet-derived growth factor and epidermal growth factor receptors by angiotensin II and hypertension. 1111 50

Multiple factors are involved in thrombus formation and require complex and highly therapeutic strategies. Platelet activation plays a critical role in the genesis of acute coronary syndromes involving not only platelets but also endothelial cells, leucocytes and erythrocytes. Angiotensin II (Ang II) is a vasoconstrictor that could participate in the thrombotic process. Platelets also express Ang II AT1 type receptors on their surface. Losartan is a non-peptidic inhibitor of AT1 receptors. It has been demonstrated that losartan reduced platelet aggregation induced by the thromboxane A2 (TXA2) analogue U46619. This effect was not observed with the losartan metabolite EXP 3174. The effect of losartan was assessed in binding studies in which losartan competitively inhibited the binding of [3H]U46619 to platelets in a dose-dependent manner. Irbesartan also inhibits the TXA2 receptor in platelets, an effect that was not obtained with the active form of candesartan, CV11974, and with valsartan. These results suggest that the structural requirements necessary to antagonize the TXA2/PGH2 platelet receptor may be different from those involved in AT1 receptor antagonism. The in vivo relevance of the in vitro findings has been confirmed by the fact that in vivo administration of losartan decreases P-selectin expression in platelets obtained from stroke-prone spontaneously hypertensive rats.
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PMID:Angiotensin II AT(1) receptor antagonists and platelet activation. 1136 20

Of the population in the United States 65 years of age or older, more than half have high blood pressure. The benefits of treatment are well established, with decreased morbidity and mortality from stroke and MI. Antihypertensive therapy available for the elderly now includes losartan, the prototype of a new class of drugs, the angiotensin II-receptor blockers. The likelihood of even fewer side effects with the angiotensin II-receptor blockers than with ACE inhibitors promises to make them an important new therapy for elderly patients. Angiotensin II is the primary vasoactive component of the renin-angiotensin system, which is implicated in the pathophysiology of hypertension. Influencing this system pharmacologically has, therefore, important consequences for high blood pressure treatment. The ACE inhibitors have had success as antihypertensive agents, but they act early in the renin-angiotensin cascade, possibly leading to unwanted effects. The angiotensin II-receptor blockers act directly at the receptor level, thus avoiding the complications of interrupting the metabolic pathway early and disrupting other hormonal systems. These agents represent a new treatment option for hypertension in the elderly. Other clinical indications, such as heart failure and post-MI, are being investigated.
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PMID:Angiotensin II-Receptor Blockers: Profile of a New Drug Class for Antihypertensive Therapy. 1141 98

In order to investigate the role of Angiotensin II (AII) for the vasogenic cerebral edema, the AT1 receptor antagonist (TCV-116) was administered to 19-week-old stroke-prone spontaneously hypertensive rats (SHRSP) for 2 weeks at a dosage which did not decrease the blood pressure. Although no remarkable changes were found in blood pressure after treatment, the average brain weight of the treated group was relatively lower as compared to that of control SHRSP and no edematous changes were found in any brains. The immunohistochemical expression of intercellular adhesion molecule-1 (ICAM-1) was less and the glucose transporter-1 (GLUT-1) expression was much more intense in the endothelial cells of the micro vessels in the cerebral cortex of the treated group. Fibrinogen expression around micro-vessels was also remarkably reduced in the treated group. A decreased expression of ICAM-1 in the treated group was confirmed by RT-PCR analysis. These results indicate that the AT1 receptor blockade ameliorates hypertensive cerebral injury in a blood pressure-independent manner and suggest that AII may have an important role for endothelial injury in severe hypertension.
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PMID:AT1 receptor antagonist prevents brain edema without lowering blood pressure. 1144 94

Uncontrolled hypertension leads to an increased risk of cardiovascular disease and stroke. Hypertensive patients with concomitant type 2 diabetes are at even greater risk of cardiovascular complications; also, this high-risk patient population is at increased risk of renal disease and, ultimately, renal failure. Prospective morbidity and mortality trials have demonstrated that tight blood pressure control improves the cardiovascular prognosis and provides target organ protection. Current treatment guidelines recommend a target blood pressure of < 130/85 mm Hg for patients with hypertension and diabetes. Angiotensin II (A-II), a major component of the renin-angiotensin system, plays an essential role in the pathophysiology of hypertension and diabetes-related renal disease. Currently, the treatment of choice for hypertensive patients with diabetes is angiotensin-converting enzyme (ACE) inhibition, but most of the data are limited to patients with type 1 diabetes. Although ACE inhibition is clearly a mechanism for blocking A-II formation, inhibition at this site may not be complete, as alternate pathways exist for A-II formation. Thus, for interrupting the renin-angiotensin system, A-II receptor antagonists theoretically provide advantages over ACE inhibitors in that they directly inhibit A-II by binding to the AT(1) receptor subtype. The objectives of this review are to: 1) provide an overview of the associated risk of cardiovascular complications with concomitant hypertension and diabetes; 2) demonstrate the cardiovascular benefits of effective blood pressure control in this patient population; 3) review the current treatment guidelines for managing high-risk hypertensive patients; and 4) discuss major, ongoing clinical studies with A-II receptor antagonists in patients with concomitant hypertension, type 2 diabetes, and renal disease. (c)2001 Le Jacq Communications, Inc.
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PMID:Management of high-risk hypertensive patients with diabetes: potential role of angiotensin II receptor antagonists. 1149 50


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