UMLS:C0038454 - FACTA Search

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

Stroke patients have increased levels of endothelin-1 (ET-1), a strong vasoconstrictor, in their plasma or cerebrospinal fluid. Previously, we showed high level of ET-1 mRNA expression in astrocytes after hypoxia/ischemia. It is unclear whether the contribution of ET-1 induction in astrocytes is protective or destructive in cerebral ischemia. Here, we generated a transgenic mouse model that overexpress ET-1 in astrocytes (GET-1) using the glial fibrillary acidic protein promoter to examine the role of astrocytic ET-1 in ischemic stroke by challenging these mice with transient middle cerebral artery occlusion (MCAO). Under normal condition, GET-1 mice showed no abnormality in brain morphology, cerebrovasculature, absolute cerebral blood flow, blood-brain barrier (BBB) integrity, and mean arterial blood pressure. Yet, GET-1 mice subjected to transient MCAO showed more severe neurologic deficits and increased infarct, which were partially normalized by administration of ABT-627 (ET(A) antagonist) 5 mins after MCAO. In addition, GET-1 brains exhibited more Evans blue extravasation and showed decreased endothelial occludin expression after MCAO, correlating with higher brain water content and increased cerebral edema. Aquaporin 4 expression was also more pronounced in astrocytic end-feet on blood vessels in GET-1 ipsilateral brains. Our current data suggest that astrocytic ET-1 has deleterious effects on water homeostasis, cerebral edema and BBB integrity, which contribute to more severe ischemic brain injury.
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PMID:Endothelin-1 overexpression leads to further water accumulation and brain edema after middle cerebral artery occlusion via aquaporin 4 expression in astrocytic end-feet. 1581 85

Angiotensin II stimulates and angiotensin-converting enzyme inhibitor decreases endothelin-1 expression. Effects of the angiotensin-type 1 antagonist (angiotensin receptor blocker) on tissue expression of endothelin-1 in hypertension remained unknown. We investigated the effects of angiotensin-type 1 antagonist with and without co-administration of the aldosterone receptor antagonist spironolactone on cardiac expression of endothelin-1 mRNA. Angiotensin receptor blocker (candesartan, 1.0 mg/kg per day) was orally administered to male spontaneously hypertensive stroke-prone rats/Izm from 4 weeks of age for 4 weeks, 12 weeks and 28 weeks (angiotensin receptor blocker group). Lowdose spironolactone (10 mg/kg per day, s.c.), which does not affect blood pressure, was co-administered with angiotensin-type 1 antagonist for 28 weeks (angiotensin-type 1 antagonist + spironolactone group). Cardiac expression of endothelin-1 mRNA was determined. In the angiotensin receptor blocker group, although cardiac expression of endothelin-1 mRNA was significantly decreased after 4 weeks of treatment, it was significantly increased after 12 weeks and 28 weeks of treatment. In the angiotensin receptor blocker + spironolactone group, while systolic blood pressure did not show a further decrease from that in the angiotensin receptor blocker group, cardiac expression of endothelin-1 mRNA was decreased to the level in the untreated group. These results suggest that effects on endothelin-1 expression could modify the cardioprotective effects of angiotensin receptor blocker. Coadministration of angiotensin receptor blocker with low-dose spironolactone is recommended for further cardioprotection via suppression of endothelin-1 expression.
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PMID:Effects of AT1 receptor antagonist and spironolactone on cardiac expression of ET-1 mRNA in SHR-SP/Izm. 1583 51

Spontaneously hypertensive stroke-prone rats (SHR-SP) suffer spontaneous stroke in part as a result of abnormal cerebrovascular development. Reduction of regional cerebral blood flow in this model has already been demonstrated. This model has three distinct stages of hypertension: pre-hypertensive, typical hypertensive and malignant hypertensive. We investigated the level of endothelin-1 and its receptor expression in the frontal cortex of SHR-SP at the malignant hypertensive stage (35-40 weeks of age), during which time the rats suffer strokes. The cerebral endothelin-1 level, as determined by enzyme-linked immunosorbent assay, was highly increased at this severely hypertensive stage compared to their genetic control, normotensive Wistar-Kyoto rats. This upregulation was associated with an increased expression of endothelin-A receptor, however, another endothelin-1 receptor, endothelin-B, was downregulated. The regional cerebral blood flow in the frontal cortex was reduced by 60% in 40-week-old malignantly SHR-SP as compared to age-matched Wistar-Kyoto rats. Thus, cerebral endothelin-1 expression increased in malignant hypertension in SHR-SP. The enhanced endothelin-1 may activate the endothelin-A receptor, which would, in turn, result in reduced cerebral blood flow. Downregulation of the endothelin-B receptor may cause suppression of endothelium-derived relaxing factors in the brain of SHR-SP and be an underlying factor in their stroke susceptibility.
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PMID:Altered expression of endothelin and its receptors in the brain of SHR-SP at malignant hypertensive stage. 1583 56

Increased levels of endothelin-1 have been demonstrated in the ischemic brain, and endothelin receptor antagonism has been shown to improve the outcome of cerebral ischemia. However, it remains unknown what the relative receptor distribution in the brain of the spontaneously hypertensive stroke-prone rat (SHR-SP) is and whether it is changed by endothelin antagonism. The present study aimed to investigate the expression of the two endothelin receptors in the frontal cortex of SHR-SP after 12 weeks of treatment with an endothelin-A/endothelin-B dual receptor antagonist, SB209670, or saline (vehicle) starting from the prehypertensive stage (6 weeks old). A 50% increase in the endothelin-A receptor was found in the vehicle-treated brain of SHR-SP compared with that of the age-matched Wistar-Kyoto control, but endothelin antagonism reversed this upregulation completely. A 20% decrease in endothelin-B receptor was found in the vehicle-treated brain of SHR-SP compared with Wistar-Kyoto and was recovered by endothelin antagonism. This is the first study to explore the relative endothelin receptor distribution in the frontal cortex of SHR-SP at the typical hypertensive stage and changes resulting from long-term endothelin antagonism starting from the prehypertensive stage.
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PMID:Expression of endothelin receptors in the brain of SHR-SP and effects of an endothelin blocker. 1583 68

Previously, we have demonstrated that mRNA expression of endothelin-1 (ET-1), a potent vasoconstrictor, is induced in astrocytes and endothelial cells after ischemic conditions, suggesting that both of these cells synthesize ET-1 under this stress condition. Furthermore, ET-1 protected primary cultured astrocytes from ischemic stress. In order to further investigate the role of endothelial ET-1 in cerebral ischemic injury, transgenic mouse lines (TET) with a transgene that included ET cDNA with SV40 polyA under tyrosine kinase with immunoglobulin and epidermal growth factor homology domain (Tie-1) promoter were used. TET mouse lines were further characterized for ET-1 over-expression in the brain. The reverse transcription-polymerase chain reaction (RT-PCR) analysis using the primers specific for transgene ET-1 showed that transgene ET-1 is only expressed in the brain from TET mice. Total expression of ET- 1 mRNA was also increased in the transgenic brain compared with the non-transgenic brain by semi-quantitative RT-PCR. In situ hybridization and immunocytochemical analyses showed that the increased ET-1 mRNA and peptide expressions were detected in endothelial cells of cerebral vessels of TET mice. Under normal conditions, the TET mice that have a slightly increased blood pressure compared with that of non-transgenic mice showed no gross morphological abnormalities in the brain. However, after transient middle cerebral artery occlusion, TET mice showed a more severe neurological deficit, and larger infarct size and volume, suggesting that over-expressing ET-1 in endothelial cells is deleterious to neuronal survival under ischemic conditions. Our present TET model will serve as an ideal model for studying the role of endothelial ET- 1 in the pathogenesis of ischemic stroke.
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PMID:Endothelial cell-specific over-expression of endothelin-1 leads to more severe cerebral damage following transient middle cerebral artery occlusion. 1583 4

It is already well known that alteration of angiotensin II (Ang II) receptors results in cardiac remodeling in different pathological states, and it is believed that Ang II stimulates the release of endothelin-1 (ET-1). The present study aimed at investigating the interaction between ET-1 and different Ang II receptors in the heart of stroke-prone spontaneously hypertensive rats (SHR-SP). These were treated for 3 months with SB209670, an endothelin-A/endothelin-B dual receptor antagonist, or saline (vehicle) starting from the prehypertensive stage (6 weeks of age). Blood pressure, body weight, heart weight and left ventricular weight were sufficiently decreased after treatment of SHR-SP with SB209670. Ang II type 1 receptor was significantly upregulated in the heart of vehicle-treated SHR-SP compared with the age-matched control, Wistar-Kyoto rat. After endothelin antagonism with SB209670, Ang II type 1 receptor in SHR-SP heart was markedly suppressed. On the other hand, Ang II type 2 receptor was approximately 45% downregulated in the heart of vehicle-treated SHR-SP compared with that of the control, and recovered after endothelin antagonism. The present study demonstrates for the first time the effects of endothelin antagonism on the differential expression and regulation of Ang II receptors in the malignant hypertensive model, SHR-SP, and suggests that the endothelin system may be able to function on the upstream of Ang II signaling.
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PMID:Effects of endothelin receptor antagonist on expression of AT1 and AT2 receptors in the heart of SHR-SP. 1583 60

Neuroprotective therapies and tissue plasminogen activator (t-PA) have limited application for most stroke patients and thus rehabilitation is the primary treatment option for improving recovery of function. Following brain injury, environmental enrichment, pharmacological and rehabilitative treatments can markedly alter neuronal plasticity and behavioral recovery even when delayed by several weeks after the insult. Fluoxetine has been given to stroke patients to combat depression but its effects on recovery of function are not known. Functional magnetic resonance imaging reveals that fluoxetine alters brain activity and modulates motor performance in stroke patients in a use-dependent fashion. Several antidepressants, including fluoxetine, increase growth factors and other proteins associated with plasticity, such as brain-derived neurotrophic factor (BDNF). In this study, we examined whether chronic administration of fluoxetine combined with rehabilitation affected recovery of function on 3 separate tests of forelimb reaching, preference and limb coordination after focal ischemia in rats. Ischemia was induced in male Long-Evans rats by intracortical and striatal injections of endothelin-1. Fluoxetine (10 mg/kg/day) combined with rehabilitation therapy (6 h/day) for 4 weeks did not alter the degree or rate of recovery of function compared to non-treated animals. Despite the ability of fluoxetine to alter brain activity and increase growth factors, it does not appear to be an effective pharmacological adjunct to functional recovery after ischemia in rats.
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PMID:Fluoxetine and recovery of motor function after focal ischemia in rats. 1586 86

Insulin resistance (IR) impairs endothelium-mediated vasodilation in cerebral arteries as well as K+ channel function in vascular smooth muscle. Peripheral arteries also show an impaired endothelium-dependent vasodilation in IR and concomitantly show an enhanced contractile response to endothelin-1 (ET-1). However, the contractile responses of the cerebral arteries in IR have not been examined systematically. This study examined the contractile responses of pressurized isolated middle cerebral arteries (MCAs) in fructose-fed IR and control rats. IR MCAs showed no difference in pressure-mediated (80 mmHg) vasoconstriction compared to controls, either in time to develop spontaneous tone (control: 61+/-3 min, n=30; IR: 63+/-2 min, n=26) or in the degree of that tone (control: 60 min: 33+/-2%, n=22 vs. IR 60 min: 34+/-3%, n=17). MCAs treated with ET-1 (10(-8.5) M) constrict similarly in control (53+/-3%, n=14) and IR (53+/-3%, n=14) arteries. Constrictor responses to U46619 (10(-6) M) are also similar in control (48+/-9%, n=8) and IR (42+/-5%, n=6) MCAs as are responses to extraluminal uridine 5'-triphosphate (UTP; 10(-4.5) M) (control: 35+/-7%, n=11 vs. IR: 38+/-3%, n=10). These findings demonstrate that constrictor responses remain intact in IR despite a selective impairment of dilator responses and endothelial and vascular smooth muscle K+ channel function in cerebral arteries. Thus, it appears that the increased susceptibility to cerebrovascular abnormalities associated with IR and diabetes (including cerebral ischemia, stroke, vertebrobasilar transient ischemic attacks) is not due to an enhanced vasoreactivity to constrictor agents.
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PMID:Insulin resistance does not impair contractile responses of cerebral arteries. 1595 70

(1) Cerebral ischemia and reperfusion induce several changes on the endothelial cells at the microcirculatory level. (2) Vasogenic brain edema due to compromised blood-brain barrier, transformation of the endothelial cell surface from an anticoagulant to a procoagulant surface are important factors in the pathogenesis of ischemic stroke. (3) Release of prostaglandins, endothelin-1, complement proteins, and matrix metalloproteinase-9 by microvascular endothelial cells are other components in the complex mechanism of brain ischemia/hypoxia. (4) Ultrastructural studies documented the opened paracellular avenues in the course of vasogenic edema in different experimental models (5) Tight junctions of endothelial cells have been characterized with freeze fracture electron microscopy, and the process of transvesiculation was analyzed using rapid freeze and freeze substitution procedure before electron microscopy studies (6) In endothelial cell-culture experiments, we used rodent and later human brains. (7) Endothelial cells co-cultured with astroglia resulted in an elaborate tight junctional complex. (8) This co-culture technique becomes the basis of in vitro blood-brain barrier studies On endothelial cells of human brain origin, different regulatory factors found to be responsible for the complex mechanism of ischemic stroke.
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PMID:Human cerebral microvessel endothelial cell culture as a model system to study the blood-brain interface in ischemic/hypoxic conditions. 1596 14

The effects of endothelin-1 (ET-1) on systemic and pulmonary circulation were investigated in anaesthetised freshwater turtles (Trachemys scripta) instrumented with arterial catheters and blood flow probes. Bolus intra-arterial injections of ET-1 (0.4-400 pmol kg(-1)) caused a dose-dependent systemic vasodilatation that was associated with a decrease in systemic pressure (P(sys)) and a rise in systemic blood flow (Q(sys)), causing systemic conductance (G(sys)) to increase. ET-1 had no significant effects on the pulmonary vasculature, heart rate (fh) or total stroke volume (Vs(tot)). This response differs markedly from mammals, where ET-1 causes an initial vasodilatation that is followed by a pronounced pressor response. In mammals, the initial dilatation is caused by stimulation of ET(B)-receptors, while the subsequent constriction is mediated by ET(A)-receptors. In the turtles, infusion of the ET(B)-receptor agonist BQ-3020 (150 pmol kg(-1)) elicited haemodynamic changes that were similar to those of ET-1, and the effects of ET-1 were not affected by the ET(A)-antagonist BQ-610 (0.15 micromol kg(-1)). Conversely, all effects of ET-1 were virtually abolished after specific ET(B)-receptor blockade with the ET(B)-antagonist BQ-788 (0.15 micromol kg(-1)). The subsequent treatment with the general ET-receptor antagonist tezosentan (15.4 micromol kg(-1)) did not produce effects that differed from the treatment with ET(B)-antagonist, and the blockade of ET-1 responses persisted. This present study indicates, therefore, that ET(B)-receptors are responsible for the majority of the cardiovascular responses to ET-1 in Trachemys.
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PMID:Endothelin-1 causes systemic vasodilatation in anaesthetised turtles (Trachemys scripta) through activation of ETB-receptors. 1616 51

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