Hiroshi Sugimori

Pivotal role of cerebral interleukin-17|[ndash]|producing |[gamma]||[delta]|T cells in the delayed phase of ischemic brain injury

Lymphocyte recruitment and activation have been implicated in the progression of cerebral ischemia-reperfusion (I/R) injury, but the roles of specific lymphocyte subpopulations and cytokines during stroke remain to be clarified. Here we demonstrate that the infiltration of T cells into the brain, as well as the cytokines interleukin-23 (IL-23) and IL-17, have pivotal roles in the evolution of brain infarction and accompanying neurological deficits. Blockade of T cell infiltration into the brain by the immunosuppressant FTY720 reduced I/R-induced brain damage. The expression of IL-23, which was derived mostly from infiltrated macrophages, increased on day 1 after I/R, whereas IL-17 levels were elevated after day 3, and this induction of IL-17 was dependent on IL-23. These data, together with analysis of mice genetically disrupted for IL-17 and IL-23, suggest that IL-23 functions in the immediate stage of I/R brain injury, whereas IL-17 has an important role in the delayed phase of I/R injury during which apoptotic neuronal death occurs in the penumbra. Intracellular cytokine staining revealed that γδT lymphocytes, but not CD4+ helper T cells, were a major source of IL-17. Moreover, depletion of γδT lymphocytes ameliorated the I/R injury. We propose that T lymphocytes, including γδT lymphocytes, could be a therapeutic target for mitigating the inflammatory events that amplify the initial damage in cerebral ischemia.

Postischemic Gene Transfer of Interleukin-10 Protects Against Both Focal and Global Brain Ischemia

Background—Gene therapy may be a promising approach for treatment of brain ischemia, although the efficiency of postischemic gene therapy is not established. Our goal in this study was to examine the effects of gene transfer of interleukin-10 (IL-10), an antiinflammatory cytokine, after induction of brain ischemia. Methods and Results—Brain ischemia was produced by either photochemical occlusion of distal middle cerebral artery for focal ischemia or bilateral carotid occlusion for global ischemia in spontaneously hypertensive rats. Adenoviral vectors encoding human IL-10 (AdIL10) or &bgr;-galactosidase (control) were injected into the lateral ventricle 90 or 60 minutes after focal or global ischemia. Five days after ischemia, IL-10, IL-1&bgr;, or tissue necrosis factor-&agr; in the cerebrospinal fluid, infarct volume, infiltrations of leukocytes/macrophages in the infarct area, or hippocampal neuronal damages were determined. The transduced IL-10 was released to the cerebrospinal fluid from the ventricular wall and increased to 7623±2965 pg/mL 5 days after AdIL10 transfection. Cerebral blood flow during ischemia was not different between treatments in either focal or global ischemia. Brain infarction of the AdIL10 group was significantly smaller and infiltrations of leukocytes and macrophages were fewer in the IL-10 treatment than control. Hippocampal neurons after global ischemia were more preserved, and the terminal deoxynucleotidyl transferase–mediated dUTP-biotin in situ nick end labeling–positive cells were diminished by the IL-10 gene transfer with attenuated IL-1&bgr; and augmented tissue necrosis factor-&agr;. Conclusions—Postischemic gene transfer of IL-10 into the lateral ventricle attenuated brain infarction and hippocampal damages, suggesting the promise for treatment of brain ischemia.

Proteinuria and clinical outcomes after ischemic stroke

Objectives: The impact of chronic kidney disease (CKD) on clinical outcomes after acute ischemic stroke is still not fully understood. The aim of the present study was to elucidate how CKD and its components, proteinuria and low estimated glomerular filtration rate (eGFR), affect the clinical outcomes after ischemic stroke. Methods: The study subjects consisted of 3,778 patients with first-ever ischemic stroke within 24 hours of onset from the Fukuoka Stroke Registry. CKD was defined as proteinuria or low eGFR (<60 mL/min/m2) or both. The study outcomes were neurologic deterioration (≥2-point increase in the NIH Stroke Scale during hospitalization), in-hospital mortality, and poor functional outcome (modified Rankin Scale score at discharge of 2 to 6). The effects of CKD, proteinuria, and eGFR on these outcomes were evaluated using a multiple logistic regression analysis. Results: CKD was diagnosed in 1,320 patients (34.9%). In the multivariate analyses after adjusting for confounding factors, patients with CKD had significantly higher risks of neurologic deterioration, in-hospital mortality, and poor functional outcome (p <0.001 for all). Among the CKD components, a higher urinary protein level was associated with an elevated risk of each outcome (p for trend < 0.001 for all), but no clear relationship between the eGFR level and each outcome was found. Conclusions: CKD is an important predictor of poor clinical outcomes after acute ischemic stroke. Proteinuria independently contributes to the increased risks of neurologic deterioration, mortality, and poor functional outcome, but the eGFR may not be relevant to these outcomes.

Prestroke Glycemic Control Is Associated With the Functional Outcome in Acute Ischemic Stroke The Fukuoka Stroke Registry

Background and Purpose— Diabetes mellitus is an established risk factor for stroke. However, it is uncertain whether prestroke glycemic control (PSGC) status affects clinical outcomes of acute ischemic stroke. The aim of this study was to elucidate the association between PSGC status and neurological or functional outcomes in patients with acute ischemic stroke. Methods— From the Fukuoka Stroke Registry (FSR), a multicenter stroke registry in Japan, 3627 patients with first-ever ischemic stroke within 24 hours after onset were included in the present analysis. The patients were categorized into 4 groups based on their PSGC status: excellent (hemoglobin [Hb] A1c on admission <6.2%), good (6.2–6.8%), fair (6.9–8.3%) and poor (≥8.4%). Study outcomes were neurological improvement (≥4 points decrease in the National Institutes of Health Stroke Scale [NIHSS] score during hospitalization or 0 points on NIHSS score at discharge), neurological deterioration (≥1 point increase in NIHSS score) and poor functional outcome (death or dependency at discharge, modified Rankin Scale 2–6). Results— The age- and sex-adjusted ORs for neurological improvement were lower, and those for neurological deterioration and a poor functional outcome were higher in patients with poorer PSGC status. After adjusting for multiple confounding factors, these trends were unchanged (all probability values for trends were <0.002). These findings were comparable in patients with noncardioembolic and cardioembolic infarctions. Conclusions— In ischemic stroke patients, HbA1c on admission was an independent significant predictor for neurological and functional outcomes.

Can Transcranial Doppler Really Detect Reduced Cerebral Perfusion States

BACKGROUND AND PURPOSE This study was designed to determine whether transcranial Doppler ultrasonography (TCD) may detect reduced perfusion states of the brain in patients with hypertension or diabetes mellitus with suspected cerebral atherosclerosis and arteriolosclerosis. METHODS We determined blood flow velocity with TCD in the middle cerebral artery and cerebrovascular vasodilator responses to carbon dioxide in 22 patients with or without carotid artery occlusive disease and minor stroke; we compared the results with the measurements of cerebral blood flow and oxygen metabolism by positron emission tomography (PET). RESULTS Blood flow velocity measured by TCD correlated with ipsilateral cerebral blood flow measured by PET in frontal, temporal, and striatal regions and throughout the entire hemisphere (P < .05 to P < .005). Relative changes in blood flow velocity and calculated cerebrovascular resistance tested by carbon dioxide inhalation both correlated closely with regional mean transit time (calculated as the ratio of cerebral blood volume divided by cerebral blood flow) in frontal, striatal, temporal, parietal, and occipital regions and also in the entire hemisphere (P < .05 to P < .0001). TCD variables did not correlate with hemispheric measurements of oxygen metabolism by PET. CONCLUSIONS Although TCD is not useful in assessing impairments of cerebral metabolism, it is useful for detecting abnormalities of cerebral hemodynamics among patients with risk factors for cerebrovascular disease.

Simplified Model of Krypton LaserInduced Thrombotic Distal Middle Cerebral Artery Occlusion in Spontaneously Hypertensive Rats

BACKGROUND AND PURPOSE The effects of thrombotic occlusion of the middle cerebral artery on compromised ischemic tissue may be different from and more severe than those of cerebral ischemia induced by mechanical occlusion of the artery. Photothrombosis, which is based on photochemical damage to the endothelium and subsequent platelet aggregation, is an efficient method to induce thrombosis in vivo. This study aimed to improve and simplify this unique method for an ischemia model of middle cerebral artery occlusion in rats. METHODS Male spontaneously hypertensive rats (5 to 6 months old, 300 to 450 g) were anesthetized with halothane, endotracheally intubated, and mechanically ventilated. A krypton laser operating at 568 nm was used to irradiate the exposed distal middle cerebral artery with an intact dura above the rhinal fissure. The photosensitizing dye rose bengal (20 mg/kg body wt) was administered intravenously over 90 seconds starting simultaneously with 4 minutes of laser irradiation at a power of 20 mW to cause thrombotic occlusion of this artery. RESULTS The irradiated middle cerebral artery was completely occluded by intraluminal thrombi within 3 minutes after simultaneous laser irradiation and rose bengal infusion. Thrombosed materials were not stained by phosphotungstic acid-hematoxylin stain (ie, aggregated platelets lacked apparent fibrin). The mean volume of 3-day-old infarction, indicated by the lack of staining with 2,3,5-triphenyltetrazolium chloride, was 84.8 +/- 17.4 mm3 (mean +/- SD, n = 6). CONCLUSIONS We demonstrated a reproducible and minimally traumatic model of brain infarction induced by the thrombotic distal middle cerebral artery occlusion in rats.

PDGF Receptor β Signaling in Pericytes Following Ischemic Brain Injury

Platelet derived growth factor (PDGF)-B plays a neuroprotective role in brain damages, including ischemic stroke. It has been suggested recently that PDGF receptor β (PDGFRβ) expressed in brain pericytes as well as in neurons and astrocytes may mediate the neuroprotective role of PDGF-B. The aims of this study were to elucidate the roles of PDGFRβ signaling in brain pericytes after ischemic stroke. In a rat middle cerebral artery occlusion (MCAO) model, PDGFRβ expression was induced specifically in the pericytes in peri-infarct areas and its level was gradually increased. PDGF-B induced marked phosphorylation of Akt in cultured brain pericytes. Consistently, PDGF-B was upregulated in endothelial cells in per-infarct areas and Akt was strongly phosphorylated in the PDGFRβ-expressing pericytes in periinfarct areas after MCAO. In the cultured pericytes, PDGF-B induced cell growth and anti-apoptotic responses through Akt. Furthermore, PDGF-B significantly increased the expression of nerve growth factor (NGF) and neurotrophin-3 (NT-3) through Akt in the pericytes. Thus, the PDGFRβ-Akt signaling in brain pericytes may play various important roles leading to neuroprotection after ischemic stroke.

Hemodialysis causes severe orthostatic reduction in cerebral blood flow velocity in diabetic patients

Orthostatic hypotension is a serious problem in patients with diabetes mellitus (DM) undergoing hemodialysis (HD). To evaluate cerebral circulation during orthostasis in patients with DM, we examined changes in mean blood flow velocity in the middle cerebral artery (VMCA) during 60 degrees head-up tilt for 5 minutes in patients with DM (six men, two women; age, 57 +/- 3 years [mean +/- SEM]; HD duration, 47 +/- 27 months) before and after bicarbonate HD by using transcranial Doppler sonography. The findings were compared with those in HD patients without diabetes (non-DM; 12 men, 5 women; age, 47 +/- 3 years; HD duration, 82 +/- 23 months). Mean blood pressure (MBP) in the supine position, hematocrit (Hct), plasma fibrinogen, and volume of fluid removed by HD were not significantly different between the two groups (MBP, 106 +/- 6 versus 103 +/- 4 mm Hg; Hct, 26% +/- 1% versus 28% +/- 1%; fibrinogen, 355 +/- 37 versus 357 +/- 27 mg/dL; fluid, 2.5 +/- 0.2 versus 2.3 +/- 0.2 L). Percentage of change in VMCA (% VMCA) during tilt was compared between the groups before and after HD. Before HD, MBP decreased significantly to 93 +/- 5 mm Hg during tilt only in patients with DM. The degree of MBP reduction was -13 +/- 2 mm Hg in DM and -2 +/- 2 mm Hg in non-DM patients (P < 0.01). % VMCA equally decreased during tilt; DM, -12% +/- 3%, and non-DM, -12% +/- 2%. After HD; MBP decreased by 36 +/- 7 mm Hg in patients with DM, which was significantly greater than before HD. VMCA also decreased in both groups after HD, and % VMCA in DM (-32% +/- 5%) was significantly greater than before HD (P < 0.01) and in non-DM patients (-13% +/- 2%; P < 0.01). % VMCA positively correlated with the percentage of change ratio of MBP during tilt in both groups after HD (DM, r = 0. 87, P < 0.01; non-DM, r = 0.61, P < 0.01). Our results showed a significant decrease in cerebral blood flow velocity during tilt of equal magnitude in both groups before HD despite differences in the level of hypotension, whereas reduction in cerebral blood flow velocity and decrease in MBP were more marked in DM after HD. Orthostasis could thus cause hemodynamically mediated brain damage after HD, especially in patients with DM.

Cerebral hemodynamics in hypertensive patients compared with normotensive volunteers. A transcranial Doppler study.

Background and Purpose The present study was designed to examine cerebral hemodynamics in early and chronic stages of hypertension using transcranial Doppler sonography. Methods Our study population consisted of 16 chronic hypertensive patients with chronic and small deep brain infarction, 10 young early‐stage hypertensive subjects, and 16 young normotensive healthy volunteers. Using three‐dimensional mapping techniques, we identified the M1 portion of the middle cerebral arteries and measured mean blood flow velocity, and we calculated the Gosling pulsatility index (PI), Fourier PI of the first harmonic (Fourier PI1), and cerebrovascular resistance. Results Mean blood flow velocity in the young hypertensive group was statistically higher (71.7±11.7 cm/s [mean±SD]) than among chronic hypertensive subjects (56.9±21.4 cm/s, P<.01) and normotensive subjects (63.2±11.8 cm/s, P<.05). Gosling PI presented a mirror image of mean blood flow velocity in both hypertensive and normotensive subjects. Chronic hypertensive subjects showed significantly higher Fourier PI1 (0.32±0.05) and cerebrovascular resistance (2.08±0.82 mm Hg/cm per second) than normotensive subjects (0.25±0.03 and 1.31±0.23 mm Hg/cm per second [P<.005], respectively) or early‐stage hypertensive subjects (0.25±0.04 and 1.44±0.26 mm Hg/cm per second [P<.02], respectively). Conclusions Early‐stage hypertensive subjects demonstrated higher velocity, normal Fourier PI1, and near normal vascular resistance, whereas chronic hypertensive subjects showed near normal velocity, higher Fourier PI1, and greater vascular resistance. Results may indicate different degrees of cerebral arteriopathy and arteriolopathy between early and late stages of hypertension. (Stroke. 1994;25:1384‐1389.)

Photothrombotic Middle Cerebral Artery Occlusion and Reperfusion Laser System in Spontaneously Hypertensive Rats

Background and Purpose— To establish a less invasive and reproducible focal ischemia model in the rat, we adopted a 2-laser system (ie, photothrombosis and YAG laser–induced reperfusion). Methods— The distal middle cerebral artery (MCA) of spontaneously hypertensive rats was occluded by 568-nm krypton laser and intravenous infusion of the photosensitizing dye rose bengal and was recanalized by 355-nm ultraviolet laser irradiation. Cerebral blood flow was determined by laser-Doppler flowmetry at the penumbral cortex. Infarct volume was determined at 3 days after distal MCA occlusion. Results— Brain temperature determined with infrared thermography was maintained within an acceptable range of approximately 1°C upper shift of the center of brain temperature distribution during krypton or YAG laser irradiation. The average of the values (23 experiments; n=163) of coefficient of variation of infarct volume was 21±6%, indicating high reproducibility of this model. After distal MCA occlusion, cerebral blood flow was decreased to 32±16% of the control values and was increased to 98±21% after YAG laser–induced reperfusion. Infarct volume in these rats was 61±18 mm3 (coefficient of variation=30%; n=6). Conclusions— We have characterized a highly reproducible focal ischemia model utilizing a 2-laser system, one to induce thrombotic MCA occlusion and the other to facilitate reperfusion.