As a sequel of brain ischemia, selective neuronal loss (SNL)-as opposed to pannecrosis (i.e. infarction)-is attracting growing interest, particularly because it is now detectable in vivo. In acute stroke, SNL may affect the salvaged penumbra and hamper functional recovery following reperfusion. Rodent occlusion models can generate SNL predominantly in the striatum or cortex, showing that it can affect behavior for weeks despite normal magnetic resonance imaging. In humans, SNL in the salvaged penumbra has been documented in vivo mainly using positron emission tomography and 11 C-flumazenil, a neuronal tracer validated against immunohistochemistry in rodent stroke models. Cortical SNL has also been documented using this approach in chronic carotid disease in association with misery perfusion and behavioral deficits, suggesting that it can result from chronic or unstable hemodynamic compromise. Given these consequences, SNL may constitute a novel therapeutic target. Selective neuronal loss may also develop at sites remote from infarcts, representing secondary 'exofocal' phenomena akin to degeneration, potentially related to poststroke behavioral or mood impairments again amenable to therapy. Further work should aim to better characterize the time course, behavioral consequences-including the impact on neurological recovery and contribution to vascular cognitive impairment-association with possible causal processes such as microglial activation, and preventability of SNL.

Brief focal ischemia leading to temporary neurological deficits induces delayed hyperintensity on T1-weighted magnetic resonance imaging (MRI) in the striatum of humans and rats. The T1 hyperintensity may stem from biochemical alterations including manganese (Mn) accumulation after ischemia. To clarify the significance of this MRI modification, we investigated the changes in the dorsolateral striatum of rats from 4 hours through 16 weeks after a 15-minute period of middle cerebral artery occlusion (MCAO), for MRI changes, Mn concentration, neuronal number, reactivities of astrocytes and microglia/macrophages, mitochondrial Mn-superoxide dismutase (Mn-SOD), glutamine synthetase (GS), and amyloid precursor protein. The cognitive and behavioral studies were performed in patients and rats and compared with striatal T1 hyperintensity to show whether alteration in brain function correlated with MRI and histological changes. The T1-weighted MRI signal intensity of the dorsolateral striatum increased from 5 days to 4 weeks after 15-minute MCAO, and subsequently decreased until 16 weeks. The Mn concentration of the dorsolateral striatum increased after ischemia in concert with induction of Mn-SOD and GS in reactive astrocytes. The neuronal survival ratio in the dorsolateral striatum decreased significantly from 4 hours through 16 weeks, accompanied by extracellular amyloid precursor protein accumulation and chronic glial/inflammatory responses. The patients and rats with neuroradiological striatal degeneration had late-onset cognitive and/or behavioral declines after brief focal ischemia. This study suggests that (1) the hyperintensity on T1-weighted MRI after mild ischemia may involve tissue Mn accumulation accompanied by Mn-SOD and GS induction in reactive astrocytes, (2) the MRI changes correspond to striatal neurodegeneration with a chronic inflammatory response and signs of oxidative stress, and (3) the subjects with these MRI changes are at risk for showing a late impairment of brain function even though the transient ischemia is followed by total neurological recovery.

Repeated MR images revealed specific lesions in the bilateral basal ganglia, cerebral cortex, substantia nigra, and hippocampus, which suggests the particular vulnerability of these areas to hypoglycemia in the human brain. We speculate that the localized lesions represent tissue degeneration, including some combination of selective neuronal death, proliferation of astrocytic glial cells, paramagnetic substance deposition, and/or lipid accumulation. The absence of localized hemorrhages on MR images in hypoglycemic encephalopathy is in marked contrast to the presence of regional minor hemorrhages in postischemic-anoxic encephalopathy.

Reperfusion after brain ischemia causes thrombus formation and microcirculatory disturbances, which are dependent on the platelet glycoprotein Ib-von Willebrand factor (VWF) axis. Because ADAMTS13 cleaves VWF and limits platelet-dependent thrombus growth, ADAMTS13 may ameliorate ischemic brain damage in acute stroke. We investigated the effects of ADAMTS13 on ischemia-reperfusion injury using a 30-minute middle cerebral artery occlusion model in Adamts13 ؊/؊ and wild-type mice. After reperfusion for 0.5 hours, the regional cerebral blood flow in the ischemic cortex was decreased markedly in Adamts13 ؊/؊ mice compared with wild-type mice (P < .05), which also resulted in a larger infarct volume after 24 hours for Adamts13 ؊/؊ compared with wild-type mice (P < .01). Thus, Adamts13 gene deletion aggravated ischemic brain damage, suggesting that ADAMTS13 may protect the brain from ischemia by regulating VWF-platelet interactions after reperfusion. These results indicate that ADAMTS13 may be a useful therapeutic agent for stroke. (Blood. 2010; 115:1650-1653) Introductionvon Willebrand factor (VWF) is a large multimeric protein that plays a key role in thrombus formation by tethering platelets at sites of vascular injury. 1 Smaller VWF multimers are less active, and the potent thrombogenic activity of ultra-large VWF (ULVWF) secreted from endothelium is regulated in vivo through cleavage by ADAMTS13. 2,3 The importance of this mechanism for normal hemostasis is supported by evidence that patients with deficiency of ADAMTS13 function, diagnosed with thrombotic thrombocytopenic purpura, have ULVWF in circulating blood and VWFdependent microvascular thrombosis. 2 Recently, we demonstrated that ADAMTS13 cleaves VWF on the surface of platelet thrombi in a shear force-dependent manner, which limits thrombus growth in vitro. 4 These data suggest that ADAMTS13 is a key molecule that maintains a physiologic balance between hemostasis and thrombosis through regulation of VWF function in vivo.ADAMTS13 function is crucial for preventing thrombosis in the cerebral microvasculature, as indicated by the occurrence of neurologic deficits in thrombotic thrombocytopenic purpura, but the role of ADMTS13 in the pathogenesis of reperfusion injury after arterial thrombosis has not been established. To address this issue, we investigated the role of ADAMTS13 in a transient middle cerebral arterial occlusion (MCAO) model of ischemia-reperfusion injury in the mouse brain 5 using Adamts Ϫ/Ϫ mice. 6 Because brain ischemia-reperfusion injury is dependent on the platelet glycoprotein Ib-VWF axis 7 and platelet thrombosis adversely affects the postischemic cerebral microcirculation 8-11 leading to secondary brain damage, 10 ADAMTS13 may reduce platelet thrombus growth and thereby ameliorate ischemic brain injury by improving the postischemic no-reflow phenomenon. 12 Here we demonstrate that Adamts13 gene deletion aggravates postischemic cerebral blood reflow, resulting in larger infarct volume. This result suggests that ADAMTS13 may indeed supp...

Background and Purpose-Minocycline, a semisynthetic tetracycline antibiotic, has been reported to ameliorate brain injury and inhibit microglial activation after focal cerebral ischemia. However, the cerebroprotective mechanism of minocycline remains unclear. In the present study, we investigated that mechanism of minocycline in a murine model of 4-hour middle cerebral artery (MCA) occlusion. Methods-One day after 4-hour MCA occlusion, minocycline was administered intraperitoneally for 14 days. Neurologic scores were measured 1, 7, and 14 days after cerebral ischemia. Motor coordination was evaluated at 14 days by the rota-rod test at 10 rpm. Activated microglia and high-mobility group box1 (HMGB1), a cytokine-like mediator, were also evaluated by immunostaining and Western blotting. In addition, terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling immunostaining was carried out 14 days after cerebral ischemia. Results-Repeated treatment with minocycline (1, 5, and 10 mg/kg) for 14 days improved neurologic score, motor coordination on the rota-rod test, and survival in a dose-dependent manner. Minocycline decreased the expression of Iba1, a marker of activated microglia, as assessed by both immunostaining and Western blotting. Moreover, minocycline decreased the activation of microglia expressing HMGB1 within the brain and also decreased both brain and plasma HMGB1 levels. Additionally, minocycline significantly decreased the number of terminal deoxynucleotidyl transferasemediated dUTP nick end-labeling-positive cells and prevented ischemic brain atrophy 14 days after cerebral ischemia. Conclusions-Our

Glial scarring is traditionally thought to be detrimental after stroke. But emerging studies now suggest that reactive astrocytes may also contribute to neurovascular remodeling. Here, we assessed the effects and mechanisms of metabolic inhibition of reactive astrocytes in a mouse model of stroke recovery. Five days after stroke onset, astrocytes were metabolically inhibited with fluorocitrate (FC, 1 nmol). Markers of reactive astrocytes (glial fibrillary acidic protein (GFAP), HMGB1), markers of neurovascular remodeling (CD31, synaptophysin, PSD95), and behavioral outcomes (neuroscore, rotarod latency) were quantified from 1 to 14 days. As expected, focal cerebral ischemia induced significant neurological deficits in mice. But over the course of 14 days after stroke onset, a steady improvement in neuroscore and rotarod latencies were observed as the mice spontaneously recovered. Reactive astrocytes coexpressing GFAP and HMGB1 increased in peri-infarct cortex from 1 to 14 days after cerebral ischemia in parallel with an increase in the neurovascular remodeling markers CD31, synaptophysin, and PSD95. Compared with stroke-only controls, FC-treated mice demonstrated a significant decrease in HMGB1-positive reactive astrocytes and neurovascular remodeling, as well as a corresponding worsening of behavioral recovery. Our results suggest that reactive astrocytes in peri-infarct cortex may promote neurovascular remodeling, and these glial responses may aid functional recovery after stroke.

We examined the neuroprotective mechanism of cannabidiol, non-psychoactive component of marijuana, on the infarction in a 4 h mouse middle cerebral artery (MCA) occlusion model in comparison with D 9 -tetrahydrocannabinol (D 9 -THC). Release of glutamate in the cortex was measured at 2 h after MCA occlusion. Myeloperoxidase (MPO) and cerebral blood flow were measured at 1 h after reperfusion. In addition, infarct size and MPO were determined at 24 and 72 h after MCA occlusion. The neuroprotective effect of cannabidiol was not inhibited by either SR141716 or AM630. Both pre-and postischemic treatment with cannabidiol resulted in potent and long-lasting neuroprotection, whereas only pre-ischemic treatment with D 9 -THC reduced the infarction. Unlike D 9 -THC, cannabidiol did not affect the excess release of glutamate in the cortex after occlusion. Cannabidiol suppressed the decrease in cerebral blood flow by the failure of cerebral microcirculation after reperfusion and inhibited MPO activity in neutrophils. Furthermore, the number of MPO-immunopositive cells was reduced in the ipsilateral hemisphere in cannabidioltreated group. Cannbidiol provides potent and long-lasting neuroprotection through an anti-inflammatory CB 1 receptorindependent mechanism, suggesting that cannabidiol will have a palliative action and open new therapeutic possibilities for treating cerebrovascular disorders. Keywords: cannabidiol, cannabinoid, cerebral blood flow, cerebral ischemia, glutamate, myeloperoxidase. Cannabis contains about 60 different cannabinoids, including the psychoactive component D 9 -tetrahydrocannabinol (D 9 -THC) and other major non-psychoactive components such as cannabidiol, cannabinol, and cannabigerol. D 9 -THC has been demonstrated to produce hypothermia, neuroprotection, and tolerance (Hampson et al. 2000;Rubino et al. 2000;Wiley and Martin 2002;Braida et al. 2003;Leker et al. 2003;Hayakawa et al. 2004;Mishima et al. 2005). These effects are, at least in part, related to binding to the CB 1 receptor. On the other hand, cannabidiol has a very low affinity (in the micromolar range) for CB 1 and CB 2 receptors and has been found to act as an anticonvulsant in animal models of epilepsy and in humans with epilepsy. Moreover, cannabidiol has been shown to have antispasmodic, anxiolytic, anti-nausea, and anti-rheumatoid properties

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