Chiaki Yokota

Transcriptional and Posttranscriptional Regulation of Cyclooxygenase-2 Expression by Fluid Shear Stress in Vascular Endothelial Cells

Objective—Fluid shear stress induces cyclooxygenase (COX)-2 gene expression in vascular endothelial cells. We investigated the underlying mechanism of this induction. Methods and Results—Exposure of human umbilical vein endothelial cells to laminar shear stress in the physiological range (1 to 30 dyne/cm2) upregulated the expression of COX-2 but not COX-1, a constitutive isozyme of COX. The expression of COX-2 mRNA began to increase within 0.5 hour after the loading of shear stress and reached a maximal level at 4 hours. Roles of the promoter region and the 3′-untranslated region in the human COX-2 gene were evaluated by the transient transfection of luciferase reporter vectors into bovine arterial endothelial cells. Shear stress elevated luciferase activity via the region between −327 and 59 bp. Mutation analysis indicated that cAMP-responsive element (−59/−53 bp) was mainly involved in this response. On the other hand, shear stress selectively stabilized COX-2 mRNA. Moreover, shear stress elevated luciferase activity when a 3′-untranslated region of COX-2 gene containing 17 copies of the AUUUA mRNA instability motif was inserted into the vector. Conclusions—Transcriptional activation and posttranscriptional mRNA stabilization contribute to the rapid and sustained expression of COX-2 in response to shear stress.

Baseline NIH Stroke Scale Score predicting outcome in anterior and posterior circulation strokes

Objective: The NIH Stroke Scale (NIHSS) may not appropriately assess the spectrum of posterior circulation (PC)–related neurologic deficits. We determined the cutoff baseline NIHSS score that predicts independent daily life activity during the chronic stage in anterior circulation (AC) vs PC ischemic strokes. Methods: A total of 310 consecutive patients hospitalized within 3 days after the onset of an ischemic stroke were prospectively enrolled in the study. Patients on thrombolytic therapy were excluded. In all patients, infarcts and vascular lesions were identified primarily using magnetic resonance techniques. A favorable outcome was defined as a modified Rankin Scale score of ≤2 at 3 months poststroke. Results: In 101 patients with PC stroke, the total baseline NIHSS score was lower (p < 0.001), and the subscores of ataxia (p < 0.001) and visual fields (p = 0.043) were higher than in 209 patients with AC stroke. Multivariate-adjusted OR for the favorable outcome in patients with PC vs AC stroke was 2.339 (95% CI 1.331–4.109, p = 0.003). A low baseline NIHSS score was independently predictive of a favorable outcome in both patients with PC (OR 1.547, 95% CI 1.232–1.941) and AC (1.279, 1.188–1.376) stroke. The optimal cutoff scores of the baseline NIHSS for the favorable outcome were ≤5 for patients with PC stroke (sensitivity, 84%; specificity, 81%) and ≤8 for patients with AC stroke (sensitivity, 80%; specificity, 82%). Conclusions: The cutoff score of the baseline NIH Stroke Scale (NIHSS) for a favorable chronic outcome was relatively low in patients with PC stroke compared to patients with AC stroke. The NIHSS appears to have limitations with respect to its use when comparing the neurologic severity of PC and AC stroke.

Effect of Acetazolamide Reactivity and Long-term Outcome in Patients With Major Cerebral Artery Occlusive Diseases

Background and Purpose—It remains unclear whether hemodynamic insufficiency plays a major role in ischemic events. We performed a prospective follow-up study in ischemic stroke patients with occlusive large-artery diseases to determine whether stroke recurrence is related to reduced vasodilatory capacity, judged with single-photon emission CT and acetazolamide (ACZ) challenge. Methods—During the period from 1987 to 1995, we examined cerebral vasodilatory capacity with single-photon emission CT and an ACZ challenge in 105 consecutive stroke patients with severe stenosis (>75% in diameter) or occlusion of the internal carotid artery or the trunk of the middle cerebral artery who had no or minimal infarcts on CT. According to criteria reported earlier, the patients were divided into two groups: normal (negative ACZ, n=50) or reduced ACZ reactivity (positive ACZ, n=55). They were prospectively followed at regular intervals for a median period of 2.7 years. Results—The Kaplan-Meier analysis revealed no differe...

Experimental thromboembolic stroke in cynomolgus monkey

To develop an experimental model of thromboembolic stroke without intracranial surgery, an autologous blood clot was delivered to the middle cerebral artery (MCA) via the internal carotid artery in cynomolgus monkeys. Male cynomolgus monkeys, in which a chronic catheter had been earlier implanted in the left internal carotid artery, were used. The clot was flushed into the internal carotid artery under sevofluorane anesthesia. A neurologic deficit score was assigned after MCA embolization. After 24 h, cerebral infarct size and location were determined by the TTC staining method. Cerebral blood flow (CBF) was measured prior to and after MCA embolization, using positron emission tomography (PET). After embolization, long-lasting and profound extensor hypotonia of the contralateral upper and lower limbs, and mild to severe incoordination were observed. Contralateral hemiplegia was observed over the following 24 h. In gross morphologic observation of the brain, the lesions involved mostly the caudate nucleus, putamen, globus pallidus and insular cortex. CBF was maximally reduced in the left MCA territory, but not in the right MCA territory. This model is relevant to thromboembolic stroke in human in neurologic dysfunction and histopathologic brain damage.

Long-Term Prognosis, by Stroke Subtypes, after a First-Ever Stroke: A Hospital-Based Study over a 20-Year Period

Background and Purpose: The influence of stroke subtype on recurrence, and determinants of recurrence-free survival after a first-ever stroke are not fully understood. We aimed to clarify the long-term prognosis by stroke subtypes and to identify determinants for recurrence and death after a first-ever stroke. Methods: We enrolled 1,732 consecutive patients (men/women = 1,134/598, mean age of 65 years) with a first-ever acute stroke who were admitted to our Stroke Care Unit during a period of 20 years. Stroke subtypes were classified as atherothrombotic brain infarction, lacunar infarction, cardioembolic infarction, other type of infarction, and brain hemorrhage. The prognosis was assessed by stroke subtypes. Results: During the hospital stay (mean 61 days), 99 patients died: 73 died directly from stroke. A total of 198 patients had recurrent strokes, and 286 died within 3 years after the index stroke. The overall recurrence rate within the first year was 6.5%, which was different among stroke subtypes. Patients with cardioembolic infarction (9.0%) as well as other type of infarction (9.1%) had more recurrent strokes within the initial year compared with the other subtypes. A history of transient ischemic attack (relative risk = 1.38), atrial fibrillation (1.52), ischemic heart disease (1.40), and disability at discharge (2.64) were independent predictors for the recurrence and death within 3 years after the first-ever stroke. Conclusions: The recurrence rate was different among stroke subtypes within 1 year after the index stroke. Atrial fibrillation, ischemic heart disease, history of transient ischemic attack, and disability at discharge were important determinants for stroke recurrence and death.

Aggravation of hemorrhagic transformation by early intraarterial infusion of low-dose vascular endothelial growth factor after transient focal cerebral ischemia in rats

Vascular endothelial growth factor (VEGF) is a unique growth factor associated with angiogenesis, vascular permeability, and neuroprotection. The aim of this study was to observe the effects of early intraarterial infusion of low-dose VEGF on ischemia/reperfusion injury after transient focal cerebral ischemia in rats. Male Sprague-Dawley rats were subjected to 2 h of focal ischemia by middle cerebral artery occlusion. After the 2 h ischemia, the rats were infused with 0.3 microg/kg of VEGF (n = 15), or the vehicle as a control (n = 15), via the reperfused internal carotid artery. The brains were collected after a 1 h, 6 h, or 72 h reperfused period. Severity of ischemic cellular injury, serum extravasation, hemorrhagic transformation, and matrix metalloproteinase (MMP)-2 and -9 expressions were compared between the VEGF-treated and control groups. No significant difference in the extent of ischemic cellular injury and serum extravasation was observed between the two groups. However, vessel numbers with hemorrhagic transformation were significantly greater in the VEGF-treated group than in the control group after the 72 h reperfusion (9.4 +/- 1.6 versus 2.6 +/- 1.5; P = 0.028). The severity of hemorrhagic transformation was not correlated with the extent of ischemic cellular injury or serum extravasation. MMP-2 and -9 expressions were not enhanced in the VEGF-treated group compared with the control group. These results suggest that exogenous VEGF administered intravascularly at a very early point in reperfusion aggravates hemorrhagic transformation. The aggravated hemorrhagic transformation does not seem to depend on the enlargement of ischemic cellular injury, serum extravasation, or overexpressions of MMP-2 and -9.

Gadolinium-enhanced magnetic resonance imaging in acute myocardial infarction

To investigate the clinical application of gadolinium diethylenetriaminepentaacetic acid (Gd-DTPA)-enhanced magnetic resonance imaging (MRI) in the management of acute myocardial infarction (AMI), we examined 44 patients with AMI within 1 month after onset. Enhanced images were classified into 4 types: nontransmural (type 1), transmural and homogeneous (type 2), transmural and marginal (type 3), and no enhancement (type 4). Each enhancement pattern was correlated with angiographic and thallium-201 imaging results. The redistribution images of thallium were graded on a 4-point scale from 0 (normal) to 3 (markedly reduced or absent activity). The percentage of the perimeter affected by asynergy was obtained from the left ventriculogram. Peak creatine kinase and the percentage of asynergic perimeter were significantly higher in type 3 than in other type patients. End-diastolic volume index was significantly higher in type 3 than in type 2 patients. Left ventricular ejection fraction was lowest, and end-systolic volume index, thallium-201 score, and incidence of wall thinning on MRI were highest in type 3 patients. Therefore, the transmural and marginal enhancement pattern (type 3) was compatible with extensive myocardial infarction with infarct expansion and less viable myocardium. In the other types, the infarction was small to moderate in size and left ventricular function was well preserved. Thus, Gd-DTPA-enhanced MRI may be useful in the evaluation of left ventricular function and myocardial viability of the infarct region after AMI.

Serial Changes in Cerebral Blood Flow and Flow—Metabolism Uncoupling in Primates with Acute Thromboembolic Stroke

The authors recently developed a primate thromboembolic stroke model. To characterize the primate model, the authors determined serial changes in cerebral blood flow (CBF) and the relation between CBF and cerebral metabolic rate of glucose (CMRglc) using high-resolution positron emission tomography. Thromboembolic stroke was produced in male cynomolgus monkeys (n = 4). Acute obstruction of the left middle cerebral artery was achieved by injecting an autologous blood clot into the left internal carotid artery. Cerebral blood flow was measured with [15O]H2O before and 1, 2, 4, 6, and 24 hours after embolization. CMRglc was measured with 2-[18F]fluoro-2-deoxy-D-glucose ([18F]FDG) 24 hours after embolization. Lesion size and location 24 hours after embolization was determined by the 2,3,5-triphenyltetrazolium chloride (TTC) staining method. The results are summarized as follows: (1) 1 hour after embolization, CBF in the temporal cortex and the basal ganglia decreased to < 40% of the contralateral values. In these regions, regarded as an ischemic core, CBF decreased further with time and CMRglc at 24 hours also decreased. Infarcted lesions as indicated by being unstained with TTC were consistently observed in these regions. (2) In the parietal cortex and several regions surrounding the ischemic core, CBF was >40% of the contralateral values 1 hour after embolization and recovered gradually with time (ischemic penumbra). In these regions, CMRglc at 24 hours increased compared with that in the contralateral regions, indicating an uncoupling of CBF and CMRglc. No obvious TTC-unstained lesions were detected in these regions. The authors demonstrated a gradual recovery of reduced CBF, an elevated CMRglc and a CBF-CMRglc uncoupling in the penumbra regions of the primate model. Positron emission tomography investigations using this model will provide better understanding of the pathophysiology of thromboembolic stroke in humans.

Temporal and topographic profiles of cyclooxygenase-2 expression during 24 h of focal brain ischemia in rats

Substantial increases in cyclooxygenase-2 (COX-2) mRNA and protein levels were demonstrated in the peri-infarct and focal ischemic areas after 3-24 and 12-24 h, respectively, in rats. In the ischemic core, significant increases in COX-2 mRNA followed 6 h of ischemia, though the peak level was about one-third of that in the peri-infarct area. Increases in COX-2 protein in the ischemic core were not observed during ischemic periods. Diffuse, neuronal COX-2 staining was found in peri-infarct areas as well as in discrete, immunoreactive neurons in the ischemic core. Robust increases in prostaglandin E2 levels in the peri-infarct area were demonstrated following 24 h of ischemia. Prostaglandin production as well as COX-2 expression in ischemic tissues depended on the degree and duration of the reduction in cerebral blood flow.

Effects of 24-Hour Blood Pressure and Heart Rate Recorded With Ambulatory Blood Pressure Monitoring on Recovery From Acute Ischemic Stroke

Background and Purpose— This study used ambulatory blood pressure (BP) monitoring to generate BP and heart rate (HR) profiles soon after stroke onset and evaluated the association between determined values and 3-month stroke outcomes. Methods— We analyzed 24-hour ambulatory BP monitoring records from 104 patients with acute ischemic stroke. Ambulatory BP monitoring was attached at the second and eighth hospitalization days (Days 1 and 7). Both BP and HR were characterized using baseline, mean, maximum, and minimum values and coefficient of variation during 24-hour recording periods. Outcomes at 3 months were assessed as independence according to a modified Rankin Scale score of ⩽2 and poor according to the score of ≥5. Results— Sixty-six (63%) patients achieved independence and 12 (11%) had poor outcomes. Mean ambulatory BP monitoring values changed from 150.5±19.5/85.7±11.3 mm Hg on Day 1 to 139.6±19.3/80.0±11.7 mm Hg on Day 7. After multivariate adjustment, mean values of systolic BP (OR, 0.63; 95% CI, 0.45–0.85), diastolic BP (0.61; 0.37–0.98), pulse pressure (0.55; 0.33–0.85), and HR (0.61; 0.37–0.98) recorded on Day 1 as well as mean HR on Day 7 (0.47; 0.23–0.87) were inversely associated with independence and mean values of systolic BP (1.92; 1.15–3.68), diastolic BP (5.28; 1.92–22.85), and HR (4.07; 1.83–11.88) on Day 1 as well as mean HR on Day 7 (4.92; 1.36–36.99) were positively associated with a poor outcome. Conclusions— All of systolic BP, diastolic BP, pulse pressure, and HR on Day 1 and HR on Day 7 assessed using ambulatory BP monitoring were associated with outcomes of patients with stroke at 3 months.