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•No infarct was detected in mice without SD during experimental ischemia.•The infarct size tended to be larger in repeated SD-occurred mice.•The specific blood flow response depending ...on ischemic level were summarized.•Ischemia-induced SD may trigger infarct formation and/or exacerbate the damage.
Clinical and experimental evidence suggests that spreading depolarizations (SD) usually occur in patients with ischemic or hemorrhagic stroke when the gray matter of the brain is affected. In this study, we evaluated spatiotemporal changes of cerebral blood flow (CBF) during middle cerebral artery (MCA) occlusion and examined the relationship between SD occurrence and cerebral infarct development. In male isoflurane-anesthetized C57BL/6J mice, CBF changes over the ipsilateral parietal bone were recorded by laser speckle flowgraphy during and after transient (45 min, n = 22) or permanent occlusion (n = 22) of the distal MCA. Infarct volume was evaluated 24 hr after the operation. Upon MCA occlusion, CBF decreased by −55.6 ± 8.5 % in the lowest CBF and linearly recovered with increasing distance from the region. At 1–10 min after onset of occlusion, SD occurred and concentrically propagated from the core region, showing a decrease of CBF in the whole observed area along with a transient hyperemia and oligemia in the normal region. SD spontaneously re-occurred and propagated around the ischemic area in 37 % of mice, accompanied with a marked decrease of CBF in the core or a marked increase of CBF in the normal region. The CBF response to SDs gradually changed from the core to the normal area, depending upon the distance from the core region. Infarction was not observed in transiently (n = 2) or permanently (n = 4) occluded mice without SD. The infarct area tended to be larger with increasing number of SDs in transiently occluded mice. In conclusion, our findings suggest that the occurrence of SD during ischemia might elicit infarct formation and/or influence infarct development.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Goreisan, a traditional Japanese Kampo medicine, is often used to treat headaches, including migraines; however, the underlying mechanisms remain unknown. Therefore, we investigated whether chronic ...treatment with Goreisan affects cortical spreading depolarization (CSD) in migraines. CSD susceptibility was assessed in male and female C57BL/6 mice by comparing CSD threshold, propagation velocity, and CSD frequency between animals treated with Goreisan for approximately 3 weeks and the corresponding controls with a potassium-induced CSD model. No significant differences were observed in CSD susceptibility between mice that were chronically treated with Goreisan and the control mice. Additionally, no significant differences were observed in other physiological parameters, including body weight, blood gases, and blood pressure. CSD susceptibility was not affected by chronic treatment with Goreisan, which suggests that the drug treats headaches via mechanisms that do not involve CSD modulation.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Stroke-like episodes (SLEs) in mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) with m.3243A > G mutation usually develop in the cerebral cortex. Few reports ...have documented SLEs in the cerebellum. The clinical neuroimaging features of cerebellar SLEs have not been fully investigated. We report distinctive features of cerebellar stroke-like lesions (SLLs) in a case of MELAS with m.3243A > G mutation.
A 47-year-old Japanese man with type-2 diabetes presented to our hospital with acute onset of aphasia. A brain MRI obtained on admission (day 1) showed increased diffusion-weighted imaging (DWI)/fluid-attenuated inversion recovery (FLAIR) signal in the left anterolateral temporal lobe, which subsequently spread along the cortex posteriorly accompanied by a new lesion in the right anterior temporal lobe. The patient was initially treated with acyclovir and subsequently with immunotherapy. However, on day 45, cerebellar ataxia developed. The brain MRI showed extensive increased DWI/FLAIR signals in the cerebellum along the folia without involvement of deep cerebellar nucleus or cerebellar peduncle; SLLs were incongruent with a vascular territory, similarly to classic cerebral SLLs. Apparent diffusion coefficient (ADC) map did not show reduction in ADC values in the affected folia. Genomic analysis revealed m.3243A > G mutation (heteroplasmy in leukocytes, 17%), confirming the diagnosis of MELAS. After the treatment with taurine (12,000 mg/day), L-arginine (12,000 mg/day), vitamin B1 (100 mg/day), and carnitine (3000 mg/day), the patient became able to follow simple commands, and he was transferred to a rehabilitation center on day 146. The follow-up MRI showed diffuse brain atrophy, including the cerebellum.
SLLs develop in the cerebellum in MELAS with m.3243A > G mutation. The neuroimaging similarities to cerebral SLLs suggest the presence of the common pathophysiological mechanisms underlying both SLEs, which include microangiopathy and increased susceptibility of the cortex to metabolic derangements.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Acutely following focal cerebral ischemia disruption of the microvessel blood–brain barrier allows transit of plasma proteins into the neuropil as edema formation that coincides with loss of ...microvessel endothelial β1-integrins. We extend previous findings to show that interference with endothelial β1-integrin–matrix adhesion by the monoclonal IgM Ha2/5 increases the permeability of primary cerebral microvascular endothelial cell monolayers through reorganization of claudin-5, occludin, and zonula occludens-1 (ZO-1) from inter-endothelial borders. Interference with β1-integrin–matrix adhesion initiates F-actin conformational changes that coincide with claudin-5 redistribution. β1-integrin–matrix interference simultaneously increases phosphorylation of myosin light chain (MLC), while inhibition of MLC kinase (MLCK) and Rho kinase (ROCK) abolishes the Ha2/5-dependent increased endothelial permeability by 6 h after β1-integrin–matrix interference. These observations are supported by concordant observations in the cortex of a high-quality murine conditional β1-integrin deletion construct. Together they support the hypothesis that detachment of β1-integrins from abluminal matrix ligands increases vascular endothelial permeability through reorganization of tight junction (TJ) proteins via altered F-actin conformation, and indicate that the β1-integrin–MLC signaling pathway is engaged when β1-integrin detachment occurs. These findings provide a novel approach to the research and treatment of cerebral disorders where the breakdown of the blood–brain barrier accounts for their progression and complication.
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NUK, OILJ, SAZU, UKNU, UL, UM, UPUK
Cerebral venous thrombosis (CVT) is challenging to diagnose, as it presents with variable symptoms. We encountered a complicated case of CVT that mimicked limbic encephalitis due to sensory aphasia. ...Based on the characteristic magnetic resonance imaging findings, this 72-year-old Japanese man was later confirmed to have CVT, the cause of which was periodontitis due to Eikenella corrodens, a Gram-negative facultative anaerobic that is part of the mouth's normal flora. The symptoms improved without sequelae following anticoagulation treatment and antibiotics. Clinicians should consider CVT as a differential diagnosis when unexplainable neurological symptoms suggesting limbic encephalitis are observed.
Toll-like receptor 4 (TLR4) plays a pivotal role in the pathophysiology of stroke-induced inflammation. Both astroglia and microglia express TLR4, and endogenous ligands produced in the ischemic ...brain induce inflammatory responses. Reactive oxygen species (ROS), nitric oxide (NO), and inflammatory cytokines produced by TLR4 activation play harmful roles in neuronal damage after stroke. Although astroglia exhibit pro-inflammatory responses upon TLR4 stimulation by lipopolysaccharide (LPS), they may also play cytoprotective roles via the activation of the pentose phosphate pathway (PPP), reducing oxidative stress by glutathione peroxidase. We investigated the mechanisms by which astroglia reduce oxidative stress via the activation of PPP, using TLR4 stimulation and hypoxia in concert with microglia.
In vitro experiments were performed using cells prepared from Sprague-Dawley rats. Coexisting microglia in the astroglial culture were chemically eliminated using L-leucine methyl ester (LME). Cells were exposed to LPS (0.01 μg/mL) or hypoxia (1 % O2) for 12-15 h. PPP activity was measured using 1-(14)Cglucose and 6-(14)Cglucose. ROS and NO production were measured using 2',7'-dichlorodihydrofluorescein diacetate and diaminofluorescein-FM diacetate, respectively. The involvement of nuclear factor-erythroid-2-related factor 2 (Nrf2), a cardinal transcriptional factor under stress conditions that regulates glucose 6-phosphate dehydrogenase, the rate-limiting enzyme of PPP, was evaluated using immunohistochemistry.
Cultured astroglia exposed to LPS elicited 20 % increases in PPP flux, and these actions of astroglia appeared to involve Nrf2. However, the chemical depletion of coexisting microglia eliminated both increases in PPP and astroglial nuclear translocation of Nrf2. LPS induced ROS and NO production in the astroglial culture containing microglia but not in the microglia-depleted astroglial culture. LPS enhanced astroglial ROS production after glutathione depletion. U0126, an upstream inhibitor of mitogen-activated protein kinase, eliminated LPS-induced NO production, whereas ROS production was unaffected. U0126 also eliminated LPS-induced PPP activation in astroglial-microglial culture, indicating that microglia-derived NO mediated astroglial PPP activation. Hypoxia induced astroglial PPP activation independent of the microglia-NO pathway. Elimination of ROS and NO production by sulforaphane, a natural Nrf2 activator, confirmed the astroglial protective mechanism.
Astroglia in concert with microglia may play a cytoprotective role for countering oxidative stress in stroke.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
ROS (reactive oxygen species) play an essential role in the pathophysiology of diabetes, stroke and neurodegenerative disorders. Hyperglycaemia associated with diabetes enhances ROS production and ...causes oxidative stress in vascular endothelial cells, but adverse effects of either acute or chronic high-glucose environments on brain parenchymal cells remain unclear. The PPP (pentose phosphate pathway) and GSH participate in a major defence mechanism against ROS in brain, and we explored the role and regulation of the astroglial PPP in response to acute and chronic high-glucose environments. PPP activity was measured in cultured neurons and astroglia by determining the difference in rate of 14CO2 production from 1-14Cglucose and 6-14Cglucose. ROS production, mainly H2O2, and GSH were also assessed. Acutely elevated glucose concentrations in the culture media increased PPP activity and GSH level in astroglia, decreasing ROS production. Chronically elevated glucose environments also induced PPP activation. Immunohistochemical analyses revealed that chronic high-glucose environments induced ER (endoplasmic reticulum) stress (presumably through increased hexosamine biosynthetic pathway flux). Nuclear translocation of Nrf2 (nuclear factor-erythroid 2 p45 subunit-related factor 2), which regulates G6PDH (glyceraldehyde-6-phosphate dehydrogenase) by enhancing transcription, was also observed in association with BiP (immunoglobulin heavy-chain-binding protein) expression. Acute and chronic high-glucose environments activated the PPP in astroglia, preventing ROS elevation. Therefore a rapid decrease in glucose level seems to enhance ROS toxicity, perhaps contributing to neural damage when insulin levels given to diabetic patients are not properly calibrated and plasma glucose levels are not adequately maintained. These findings may also explain the lack of evidence for clinical benefits from strict glycaemic control during the acute phase of stroke.
To clarify the clinical features of moyamoya disease in Japan, 941 patients with definite moyamoya disease were analyzed from the databases constructed by the Research Committee on Moyamoya Disease, ...established by the Ministry of Health, Labour and Welfare. Moyamoya disease occurs much more frequently among women than men, with a female-to-male ratio of 1.98. A family history of the disease was observed in 14.9%. The age at onset was characterized by two peaks: one at 5-9 years and another lower peak at around 40 years. Initial clinical features were transient ischemic attack in 46%, infarction in 20%, hemorrhage in 21%, headache in 6%, and epilepsy in 4%. The distribution of the age at onset showed one peak at around 40 years in patients with hemorrhage but two peaks in patients with ischemia.
Oxidative stress plays an important role in the onset and progression of Parkinson disease. Although released dopamine at the synaptic terminal is mostly reabsorbed by dopaminergic neurons, some ...dopamine is presumably taken up by astroglia. This study examined the dopamine-induced astroglial protective function through the activation of the pentose-phosphate pathway (PPP) to reduce reactive oxygen species (ROS). In vitro experiments were performed using striatal neurons and cortical or striatal astroglia prepared from Sprague-Dawley rats or C57BL/6 mice. The rates of glucose phosphorylation in astroglia were evaluated using the 14Cdeoxyglucose method. PPP activity was measured using 1-14Cglucose and 6-14Cglucose after acute (60 min) or chronic (15 hr) exposure to dopamine. ROS production was measured using 2′,7′-dichlorodihydrofluorescein diacetate. The involvement of the Kelch-like ECH-associated protein 1 (Keap1) or nuclear factor-erythroid-2-related factor 2 (Nrf2) system was evaluated using Nrf2 gene knockout mice, immunohistochemistry, and quantitative reverse transcription polymerase chain reaction analysis for heme oxygenase-1. Acute exposure to dopamine elicited increases in astroglial glucose consumption with lactate release. PPP activity in astroglia was robustly enhanced independently of Na+-dependent monoamine transporters. In contrast, chronic exposure to dopamine induced moderate increases in PPP activity via the Keap1/Nrf2 system. ROS production from dopamine increased gradually over 12 hr. Dopamine induced neuronal cell damage that was prevented by coculturing with astroglia but not with Nrf2-deficient astroglia. Dopamine-enhanced astroglial PPP activity in both acute and chronic manners may possibly reduce neuronal oxidative stress.
Atrial fibrillation (AF) increases the risk and severity of thromboembolic stroke. Generally, antithrombotic agents increase the hemorrhagic risk of thromboembolic stroke. However, significant ...reductions in thromboembolism and intracerebral hemorrhage have been shown with the antithrombin dabigatran compared with warfarin. As thrombin has been implicated in microvessel injury during cerebral ischemia, we hypothesized that dabigatran decreases the risk of intracerebral hemorrhage by direct inhibition of the thrombin-mediated increase in cerebral endothelial cell permeability. Primary murine brain endothelial cells (mBECs) were exposed to murine thrombin before measuring permeability to 4-kDa fluorescein isothiocyanate-dextran. Thrombin increased mBEC permeability in a concentration-dependent manner, without significant endothelial cell death. Pretreatment of mBECs with dabigatran completely abrogated the effect of thrombin on permeability. Neither the expressions of the endothelial cell β1-integrins nor the tight junction protein claudin-5 were affected by thrombin exposure. Oxygen-glucose deprivation (OGD) also increased permeability; this effect was abrogated by treatment with dabigatran, as was the additive effect of thrombin and OGD on permeability. Taken together, these results indicate that dabigatran could contribute to a lower risk of intracerebral hemorrhage during embolism-associated ischemia from AF by protection of the microvessel permeability barrier from local thrombin challenge.
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NUK, OILJ, SAZU, UKNU, UL, UM, UPUK
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