Early and enduring: Targeting the endothelium for blood-brain barrier protection.

The disruption of the blood-brain barrier marks a pivotal early pathological event in ischemic stroke that significantly contributes to subsequent permanent damage. Here we delve into the ramifications of a study conducted by Xu and colleagues, which underscores the essential role of the protein peroxiredoxin-4 in cerebrovascular endothelial cells. Peroxiredoxin-4 was shown to preserve blood-brain barrier integrity during the early stages after cerebral ischemia and reperfusion, ultimately leading to improved long-term outcomes.

Hematopoietic growth factors Regulate Entry of Monocytes into the Adult Brain via Chemokine Receptor CCR5.

Monocytes are circulating macrophage precursors and are generated from bone marrow hematopoietic stem cells. In the adults, monocytes continuously replenish cerebral border-associated macrophages under a physiological condition. Monocytes also rapidly infiltrate into the brain in the settings of pathological conditions. The mechanisms of recruiting monocyte-derived macrophages into the brain under pathological conditions have been extensively studied. However, it remains unclear how monocytes enter the brain for renewal of border-associated macrophages under the physiological condition. Using both in vitro and in vivo approaches, this study reveals that the combination of two hematopoietic growth factors, stem cell factor (SCF) and granulocyte colony-stimulating factor (G-CSF), complementarily and synergistically enhances adhesion of monocytes to cerebral endothelial cells in a dose dependent manner. Cysteine-cysteine chemokine receptor 5 (CCR5) in brain endothelial cells, but not cell adhesion molecules mediating neuroinflammation-related infiltration of monocyte-derived macrophages, modulates the SCF+G-CSF-enhanced monocyte-endothelial cell adhesion. Blocking CCR5 or genetically deleting CCR5 reduces monocyte-endothelial cell adhesion induced by SCF+G-CSF. SCF+G-CSF-enhanced recruitment of bone marrow-derived monocytes/macrophages in cerebral perivascular space is also reduced in adult CCR5 knockout mice. This study demonstrates the contribution of SCF and G-CSF in regulating the entry of monocytes into the adult brain to replenish perivascular macrophages.

Updates of the role of B-cells in ischemic stroke.

Ischemic stroke is a major disease causing death and disability in the elderly and is one of the major diseases that seriously threaten human health and cause a great economic burden. In the early stage of ischemic stroke, neuronal structure is destroyed, resulting in death or damage, and the release of a variety of damage-associated pattern molecules induces an increase in neuroglial activation, peripheral immune response, and secretion of inflammatory mediators, which further exacerbates the damage to the blood-brain barrier, exacerbates cerebral edema, and microcirculatory impairment, triggering secondary brain injuries. After the acute phase of stroke, various immune cells initiate a protective effect, which is released step by step and contributes to the repair of neuronal cells through phenotypic changes. In addition, ischemic stroke induces Central Nervous System (CNS) immunosuppression, and the interaction between the two influences the outcome of stroke. Therefore, modulating the immune response of the CNS to reduce the inflammatory response and immune damage during stroke is important for the protection of brain function and long-term recovery after stroke, and modulating the immune function of the CNS is expected to be a novel therapeutic strategy. However, there are fewer studies on B-cells in brain function protection, which may play a dual role in the stroke process, and the understanding of this cell is still incomplete. We review the existing studies on the mechanisms of the role of B-cells, inflammatory response, and immune response in the development of ischemic stroke and provide a reference for the development of adjuvant therapeutic drugs for ischemic stroke targeting inflammatory injury.

Lysophospholipids Are Associated With Outcomes in Hospitalized Patients With Mild Traumatic Brain Injury.

Mild traumatic brain injury (mTBI) accounts for 70-90% of all TBI cases. Lipid metabolites have important roles in plasma membrane biogenesis, function, and cell signaling. As TBI can compromise plasma membrane integrity and alter brain cell function, we sought to identify circulating phospholipid alterations after mTBI, and determine if these changes were associated with clinical outcomes. Patients with mTBI (Glasgow Coma Score [GCS] ≥13 and loss of consciousness <30 min) were recruited. A total of 84 mTBI subjects were enrolled after admission to a level I trauma center, with the majority having evidence of traumatic intracranial hemorrhage on brain computed tomography (CT). Plasma samples were collected within 24 h of injury with 32 mTBI subjects returning at 3 months after injury for a second plasma sample to be collected. Thirty-five healthy volunteers were enrolled as controls and had a one-time blood draw. Lipid metabolomics was performed on plasma samples from each subject. Fold change of selected lipid metabolites was determined. Multivariable regression models were created to test associations between lipid metabolites and discharge and 6-month Glasgow Outcomes Scale-Extended (GOSE) outcomes (dichotomized between "good" [GOSE ≥7] and "bad" [GOSE ≤6] functional outcomes). Plasma levels of 31 lipid metabolites were significantly associated with discharge GOSE using univariate models; three of these metabolites were significantly increased, while 14 were significantly decreased in subjects with good outcomes compared with subjects with poor outcomes. In multivariable logistic regression models, higher circulating levels of the lysophospholipids (LPL) 1-linoleoyl-glycerophosphocholine (GPC) (18:2), 1-linoleoyl-GPE (18:2), and 1-linolenoyl-GPC (18:3) were associated with both good discharge GOSE (odds ratio [OR] 12.2 [95% CI 3.35, 58.3], p = 5.23 × 10-4; OR 9.43 [95% CI 2.87, 39.6], p = 7.26 × 10-4; and OR 5.26 [95% CI 1.99, 16.7], p = 2.04 × 10-3, respectively) and 6-month (OR 4.67 [95% CI 1.49, 17.7], p = 0.013; OR 2.93 [95% CI 1.11, 8.87], p = 0.039; and OR 2.57 [95% CI 1.08, 7.11], p = 0.046, respectively). Compared with healthy volunteers, circulating levels of these three LPLs were decreased early after injury and had normalized by 3 months after injury. Logistic regression models to predict functional outcomes were created by adding each of the described three LPLs to a baseline model that included age and sex. Including 1-linoleoyl-GPC (18:2) (8.20% improvement, p = 0.009), 1-linoleoyl-GPE (18:2) (8.85% improvement, p = 0.021), or 1-linolenoyl-GPC (18:3) (7.68% improvement, p = 0.012), significantly improved the area under the curve (AUC) for predicting discharge outcomes compared with the baseline model. Models including 1-linoleoyl-GPC (18:2) significantly improved AUC for predicting 6-month outcomes (9.35% improvement, p = 0.034). Models including principal components derived from 25 LPLs significantly improved AUC for prediction of 6-month outcomes (16.0% improvement, p = 0.020). Our results demonstrate that higher plasma levels of LPLs (1-linoleoyl-GPC, 1-linoleoyl-GPE, and 1-linolenoyl-GPC) after mTBI are associated with better functional outcomes at discharge and 6 months after injury. This class of phospholipids may represent a potential therapeutic target.

Role of microRNA-34a in blood-brain barrier permeability and mitochondrial function in ischemic stroke.

Over the past decade, there has been an uptick in the number of studies conducting research on the role of microRNA (miRNA) molecules in stroke. Among these molecules, miR-34a has emerged as a significant player, as its levels have been observed to exhibit a substantial rise following ischemic events. Elevated levels of miR-34a have been found to have multiple effects, including the modulation of inflammatory molecules involved in the post-stroke recovery process, as well as negative effects on the blood-brain barrier (BBB) permeability. Interestingly, the increase of miR-34a appears to increase BBB permeability post stroke, through the negative effect on mitochondrial function. The strength of mitochondrial function is crucial for limiting para-cellular permeability and maintaining the structural integrity of the BBB. Furthermore, the activation of ischemic repair mechanisms and the reduction of ischemic event damage depend on healthy mitochondrial activity. This review aims to emphasize the involvement of miR-34a in ischemic stroke, specifically its interaction with mitochondrial genes in cerebrovascular endothelial cells, the effect on mitochondrial function, and lastly its regulatory role in BBB permeability. A comprehensive understanding of the role of miR-34a in maintaining BBB integrity and its contribution to the pathogenesis of stroke holds significant value in establishing a foundation for the development of future therapeutics and diagnostic markers.

A novel specific aptamer targets cerebrovascular endothelial cells after ischemic stroke.

Cell specific-targeted therapy (CSTT) for acute ischemic stroke remains underdeveloped. Cerebrovascular endothelial cells (CECs) are key components of the blood-brain barrier and are the first brain cells affected by ischemic stroke. After stroke, CEC injury causes insufficient energy supply to neurons and leads to cytotoxic and vasogenic brain edema. Aptamers are short single-stranded RNA or DNA molecules that can bind to specific ligands for cell specific delivery. The expression of vascular cell adhesion molecule-1 (VCAM-1) is increased on CECs after stroke. Herein, we report that an RNA-based VCAM-1-aptamer can specifically target CECs in stroke brains following transient middle cerebral artery occlusion in mice. Our data demonstrate the potential of an RNA-based aptamer as an effective delivery platform to target CECs after stroke. We believe this method will allow for the development of CSTT for treatment of patients with stroke.

Peripheral eosinophil trends and clinical outcomes after non-traumatic subarachnoid hemorrhage.

Background/objective: Uncontrolled systemic inflammation after non-traumatic subarachnoid hemorrhage (SAH) is associated with worse outcomes. Changes in the peripheral eosinophil count have been linked to worse clinical outcomes after ischemic stroke, intracerebral hemorrhage, and traumatic brain injury. We aimed to investigate the association of eosinophil counts with clinical outcomes after SAH. Methods: This retrospective observational study included patients with SAH admitted from January 2009 to July 2016. Variables included demographics, modified Fisher scale (mFS), Hunt-Hess Scale (HHS), global cerebral edema (GCE), and the presence of any infection. Peripheral eosinophil counts were examined as part of routine clinical care on admission and daily for 10 days after aneurysmal rupture. Outcome measures included dichotomized discharge mortality, modified Ranked Scale (mRS) score, delayed cerebral ischemia (DCI), vasospasm, and need for ventriculoperitoneal shunt (VPS). Statistical tests included the chi-square test, Student's t-test, and multivariable logistic regression (MLR) model. Results: A total of 451 patients were included. The median age was 54 (IQR 45, 63) years, and 295 (65.4%) were female patients. On admission, 95 patients (21.1%) had a high HHS (>4), and 54 (12.0%) had GCE. A total of 110 (24.4%) patients had angiographic vasospasm, 88 (19.5%) developed DCI, 126 (27.9%) had an infection during hospitalization, and 56 (12.4%) required VPS. Eosinophil counts increased and peaked on days 8-10. Higher eosinophil counts on days 3-5 and day 8 were seen in patients with GCE (p < 0.05). Higher eosinophil counts on days 7-9 (p < 0.05) occurred in patients with poor discharge functional outcomes. In multivariable logistic regression models, higher day 8 eosinophil count was independently associated with worse discharge mRS (OR 6.72 [95% CI 1.27, 40.4], p = 0.03). Conclusion: This study demonstrated that a delayed increase in eosinophils after SAH occurs and may contribute to functional outcomes. The mechanism of this effect and the relationship with SAH pathophysiology merit further investigation.

Early Systemic Glycolytic Shift After Aneurysmal Subarachnoid Hemorrhage is Associated with Functional Outcomes.

BACKGROUND: Aneurysmal subarachnoid hemorrhage (aSAH) leads to a robust systemic inflammatory response. We hypothesized that an early systemic glycolytic shift occurs after aSAH, resulting in a unique metabolic signature and affecting systemic inflammation. METHODS: Control patients and patients with aSAH were analyzed. Samples from patients with aSAH were collected within 24 h of aneurysmal rupture. Mass spectrometry-based metabolomics was performed to assess relative abundance of 16 metabolites involved in the tricarboxylic acid cycle, glycolysis, and pentose phosphate pathway. Principal component analysis was used to segregate control patients from patients with aSAH. Dendrograms were developed to depict correlations between metabolites and cytokines. Analytic models predicting functional outcomes were developed, and receiver operating curves were compared. RESULTS: A total of 122 patients with aSAH and 38 control patients were included. Patients with aSAH had higher levels of glycolytic metabolites (3-phosphoglycerate/2-phosphoglycerate, lactate) but lower levels of oxidative metabolites (succinate, malate, fumarate, and oxalate). Patients with higher clinical severity (Hunt-Hess Scale score ≥ 4) had higher levels of glyceraldehyde 3-phosphate and citrate but lower levels of α-ketoglutarate and glutamine. Principal component analysis readily segregated control patients from patients with aSAH. Correlation analysis revealed distinct clusters in control patients that were not observed in patients with aSAH. Higher levels of fumarate were associated with good functional outcomes at discharge (odds ratio [OR] 1.76, 95% confidence interval [CI] 1.15-2.82) in multivariable models, whereas higher levels of citrate were associated with poor functional outcomes at discharge (OR 0.36, 95% CI 0.16-0.73) and at 3 months (OR 0.35, 95% CI 0.14-0.81). No associations were found with delayed cerebral ischemia. Levels of α-ketoglutarate and glutamine correlated with lower levels of interleukin-8, whereas fumarate was associated with lower levels of tumor necrosis factor alpha. CONCLUSIONS: Aneurysmal subarachnoid hemorrhage results in a unique pattern of plasma metabolites, indicating a shift toward glycolysis. Higher levels of fumarate and lower levels of citrate were associated with better functional outcomes. These metabolites may represent targets to improve metabolism after aSAH.

The Mitochondrial mitoNEET Ligand NL-1 Is Protective in a Murine Model of Transient Cerebral Ischemic Stroke.

PURPOSE: Therapeutic strategies to treat ischemic stroke are limited due to the heterogeneity of cerebral ischemic injury and the mechanisms that contribute to the cell death. Since oxidative stress is one of the primary mechanisms that cause brain injury post-stroke, we hypothesized that therapeutic targets that modulate mitochondrial function could protect against reperfusion-injury after cerebral ischemia, with the focus here on a mitochondrial protein, mitoNEET, that modulates cellular bioenergetics. METHOD: In this study, we evaluated the pharmacology of the mitoNEET ligand NL-1 in an in vivo therapeutic role for NL-1 in a C57Bl/6 murine model of ischemic stroke. RESULTS: NL-1 decreased hydrogen peroxide production with an IC50 of 5.95 µM in neuronal cells (N2A). The in vivo activity of NL-1 was evaluated in a murine 1 h transient middle cerebral artery occlusion (t-MCAO) model of ischemic stroke. We found that mice treated with NL-1 (10 mg/kg, i.p.) at time of reperfusion and allowed to recover for 24 h showed a 43% reduction in infarct volume and 68% reduction in edema compared to sham-injured mice. Additionally, we found that when NL-1 was administered 15 min post-t-MCAO, the ischemia volume was reduced by 41%, and stroke-associated edema by 63%. CONCLUSION: As support of our hypothesis, as expected, NL-1 failed to reduce stroke infarct in a permanent photothrombotic occlusion model of stroke. This report demonstrates the potential therapeutic benefits of using mitoNEET ligands like NL-1 as novel mitoceuticals for treating reperfusion-injury with cerebral stroke.

IL-1ß Antibody Protects Brain from Neuropathology of Hypoperfusion.

Chronic brain hypoperfusion is the primary cause of vascular dementia and has been implicated in the development of white matter disease and lacunar infarcts. Cerebral hypoperfusion leads to a chronic state of brain inflammation with immune cell activation and production of pro-inflammatory cytokines, including IL-1ß. In the present study, we induced chronic, progressive brain hypoperfusion in mice using ameroid constrictor, arterial stenosis (ACAS) surgery and tested the efficacy of an IL-1ß antibody on the resulting brain damage. We observed that ACAS surgery causes a reduction in cerebral blood flow (CBF) of about 30% and grey and white matter damage in and around the hippocampus. The IL-1ß antibody treatment did not significantly affect CBF but largely eliminated grey matter damage and reduced white matter damage caused by ACAS surgery. Over the course of hypoperfusion/injury, grip strength, coordination, and memory-related behavior were not significantly affected by ACAS surgery or antibody treatment. We conclude that antibody neutralization of IL-1ß is protective from the brain damage caused by chronic, progressive brain hypoperfusion.

Intermittent Lipopolysaccharide Exposure Significantly Increases Cortical Infarct Size and Impairs Autophagy.

Globally, stroke is a leading cause of death and disability. Traditional risk factors like hypertension, diabetes, and obesity do not fully account for all stroke cases. Recent infection is regarded as changes in systemic immune signaling, which can increase thrombosis formation and other stroke risk factors. We have previously shown that administration of lipopolysaccharide (LPS) 30-minutes prior to stroke increases in infarct volume. In the current study, we found that animals intermittently exposed to LPS have larger cortical infarcts when compared to saline controls. To elucidate the mechanism behind this phenomenon, several avenues were investigated. We observed significant upregulation of tumor necrosis factor-alpha (TNF-α) mRNA, especially in the ipsilateral hemisphere of both saline and LPS exposed groups compared to sham surgery animals. We also observed significant reductions in expression of genes involved in autophagy in the ipsilateral hemisphere of LPS stroke animals. In addition, we assessed DNA methylation of autophagy genes and observed a significant increase in the ipsilateral hemisphere of LPS stroke animals. Intermittent exposure to LPS increases cortical infarct volume, downregulates autophagy genes, and induces hypermethylation of the corresponding CpG islands. These data suggest that intermittent immune activation may deregulate epigenetic mechanisms and promote neuropathological outcomes after stroke.

Blood substitution therapy rescues the brain of mice from ischemic damage.

Acute stroke causes complex, pathological, and systemic responses that have not been treatable by any single medication. In this study, using a murine transient middle cerebral artery occlusion stroke model, a novel therapeutic strategy is proposed, where blood replacement (BR) robustly reduces infarctions and improves neurological deficits in mice. Our analyses of immune cell subsets suggest that BR therapy substantially decreases neutrophils in blood following a stroke. Electrochemiluminescence detection demonstrates that BR therapy reduces cytokine storm in plasma and ELISA demonstrates reduced levels of matrix metalloproteinase-9 (MMP-9) in the plasma and brains at different time points post-stroke. Further, we have demonstrated that the addition of MMP-9 to the blood diminishes the protective effect of the BR therapy. Our study is the first to show that BR therapy leads to profoundly improved stroke outcomes in mice and that the improved outcomes are mediated via MMP-9. These results offer new insights into the mechanisms of stroke damage.

The Incidence and Predictors of Postoperative Delirium After Brain Tumor Resection in Adults: A Cross-Sectional Survey.

BACKGROUND: Postoperative delirium (POD) describes a multifactorial disease process occurring after surgery. However, few studies have focused on patients undergoing brain tumor resection, and its influencing factors are unclear. METHODS: We performed a 1-year, single-center, cross-sectional, retrospective survey at Huashan Hospital. Patients were screened using the Confusion Assessment Method for the Intensive Care Unit (CAM-ICU), Confusion Assessment Method, and Richmond Agitation Sedation Scale by trained bedside nurses. Perioperative data were collected using demographic and disease-related questionnaires. The primary outcome measures were the incidence of POD and subtype of POD. Independent predictors of POD were estimated from multivariate logistic regression models, and receiver operating characteristic analysis was used to compare the predictive performance of the models. RESULTS: Of the 916 patients included in the study, 893 were analyzed. The overall incidence was 14.78%, 67 had hyperactive delirium (50.76%), 55 had hypoactive delirium (41.67%), and 10 had mixed delirium (7.57%). Age, sex, working status, tobacco use history, comorbidities, physical restraint, axillary temperature (>38.5°C), electrolyte disturbances, duration of anesthesia, pathologic diagnosis, tumor site, length of disease, and duration of operation were risk factors for POD. Conversely, saddle area mass was a protective factor. Age, tobacco use history, electrolyte disturbances, physical restraint, and duration of operation were included in the model. CONCLUSIONS: POD is harmful to patients undergoing brain tumor resection, increasing length of stay in the intensive care unit and hospitalization costs. Intraoperative factors and postoperative factors, in addition to older age and tobacco use history, are associated with POD.

Mechanisms in blood-brain barrier opening and metabolism-challenged cerebrovascular ischemia with emphasis on ischemic stroke.

Stroke is the leading cause of disability among adults as well as the 2nd leading cause of death globally. Ischemic stroke accounts for about 85% of strokes, and currently, tissue plasminogen activator (tPA), whose therapeutic window is limited to up to 4.5 h for the appropriate population, is the only FDA approved drug in practice and medicine. After a stroke, a cascade of pathophysiological events results in the opening of the blood-brain barrier (BBB) through which further complications, disabilities, and mortality are likely to threaten the patient's health. Strikingly, tPA administration in eligible patients might cause hemorrhagic transformation and sustained damage to BBB integrity. One must, therefore, delineate upon stroke onset which cellular and molecular factors mediate BBB permeability as well as what key roles BBB rupture plays in the pathophysiology of stroke. In this review article, given our past findings of mechanisms underlying BBB opening in stroke animal models, we elucidate cellular, subcellular, and molecular factors involved in BBB permeability after ischemic stroke. The contribution of each factor to stroke severity and outcome is further discussed. Determinant factors in BBB permeability and stroke include mitochondria, miRNAs, matrix metalloproteinases (MMPs), immune cells, cytokines, chemokines, and adhesion proteins. Once these factors are interrogated and their roles in the pathophysiology of stroke are determined, novel targets for drug discovery and development can be uncovered in addition to novel therapeutic avenues for human stroke management.

MiR-34a Interacts with Cytochrome c and Shapes Stroke Outcomes.

Blood-brain barrier (BBB) dysfunction occurs in cerebrovascular diseases and neurodegenerative disorders such as stroke. Opening of the BBB during a stroke has a negative impact on acute outcomes. We have recently demonstrated that miR-34a regulates the BBB by targeting cytochrome c (CYC) in vitro. To investigate the role of miR-34a in a stroke, we purified primary cerebrovascular endothelial cells (pCECs) from mouse brains following 1 h transient middle cerebral artery occlusion (tMCAO) and measured real-time PCR to detect miR-34a levels. We demonstrate that the miR-34a levels are elevated in pCECs from tMCAO mice at the time point of BBB opening following 1 h tMCAO and reperfusion. Interestingly, knockout of miR-34a significantly reduces BBB permeability, alleviates disruption of tight junctions, and improves stroke outcomes compared to wild-type (WT) controls. CYC is decreased in the ischemic hemispheres and pCECs from WT but not in miR-34a-/- mice following stroke reperfusion. We further confirmed CYC is a target of miR-34a by a dural luciferase reporter gene assay in vitro. Our study provides the first description of miR-34a affecting stroke outcomes and may lead to discovery of new mechanisms and treatments for cerebrovascular and neurodegenerative diseases such as stroke.

Ischemic stroke alters immune cell niche and chemokine profile in mice independent of spontaneous bacterial infection.

INTRODUCTION: Stroke-associated pneumonia (SAP) is a major cause of mortality in patients who have suffered from severe ischemic stroke. Although multifactorial in nature, stroke-induced immunosuppression plays a key role in the development of SAP. Previous studies using a murine model of transient middle cerebral artery occlusion (tMCAO) have shown that focal ischemic stroke induction results in functional defects of lymphocytes in the spleen, thymus, and peripheral blood, leading to spontaneous bacterial infection in the lungs without inoculation. However, how ischemic stroke alters immune cell niche and the expression of cytokines and chemokines in the lungs has not been fully characterized. METHODS: Ischemic stroke was induced in mice by tMCAO. Immune cell profiles in the brain and the lungs at 24- and 72-hour time points were compared by flow cytometric analysis. Cytokine and chemokine expression in the lungs were determined by multiplex bead arrays. Tissue damage and bacterial burden in the lungs following tMCAO were evaluated. RESULTS: Ischemic stroke increases the percentage of alveolar macrophages, neutrophils, and CD11b+ dendritic cells, but reduces the percentage of CD4+ T cells, CD8+ T cells, B cells, natural killer cells, and eosinophils in the lungs. The alteration of immune cell niche in the lungs coincides with a significant reduction in the levels of multiple chemokines in the lungs, including CCL3, CCL4, CCL5, CCL17, CCL20, CCL22, CXCL5, CXCL9, and CXCL10. Spontaneous bacterial infection and tissue damage following tMCAO, however, were not observed. CONCLUSION: This is the first report to demonstrate a significant reduction of lymphocytes and multiple proinflammatory chemokines in the lungs following ischemic stroke in mice. These findings suggest that ischemic stroke directly impacts pulmonary immunity.

MiR-34a and stroke: Assessment of non-modifiable biological risk factors in cerebral ischemia.

Aging of the nervous system, and the occurrence of age-related brain diseases such as stroke, are associated with changes to a variety of cellular processes controlled by many distinct genes. MicroRNAs (miRNAs), short non-coding functional RNAs that can induce translational repression or site-specific cleavage of numerous target mRNAs, have recently emerged as important regulators of cellular senescence, aging, and the response to neurological insult. Here, we focused on the assessment of the role of miR-34a in stroke. We noted increases in miR-34a expression in the blood of stroke patients as well as in blood and brain of mice subjected to experimental stroke. Our methodical genetic manipulation of miR-34a expression substantially impacted stroke-associated preclinical outcomes and we have in vitro evidence that these changes may be driven at least in part by disruptions to blood brain barrier integrity and mitochondrial oxidative phosphorylation in endothelial cells. Finally, aging, independent of brain injury, appears to be associated with shifts in circulating miRNA profiles. Taken together, these data support a role for miRNAs, and specifically miR-34a, in brain aging and the physiological response to age-related neurological insult, and lay the groundwork for future investigation of this novel therapeutic target.

Gradual common carotid artery occlusion as a novel model for cerebrovascular Hypoperfusion.

Chronic cerebrovascular hypoperfusion results in vascular dementia and increases predisposition to lacunar infarcts. However, there are no suitable animal models. In this study, we developed a novel model for chronic irreversible cerebral hypoperfusion in mice. Briefly, an ameroid constrictor was placed on the right carotid artery to gradually occlude the vessel, while a microcoil was placed on the left carotid artery to prevent compensation of the blood flow. This procedure resulted in a gradual hypoperfusion developing over a period of 34 days with no cerebral blood flow recovery. Histological analysis of the brain revealed neuronal and axonal degeneration as well as necrotic lesions. The most severely affected regions were located in the hippocampus and the corpus callosum. Overall, our paradigm is a viable model to study brain pathology resulting from gradual cerebrovascular hypoperfusion.

Uncoupling of the Electron Transport Chain Compromises Mitochondrial Oxidative Phosphorylation and Exacerbates Stroke Outcomes.

OBJECTIVE: Mitochondrial dysfunction is known to be implicated in stroke, but the complex mechanisms of stroke have led to few stroke therapies. The present study to disrupted mitochondrial oxidative phosphorylation through a known electron transport chain (ETC) uncoupler, Carbonyl cyanide-4 (trifluoromethoxy) phenylhydrazone (FCCP). Analyzing the resulting neurological deficits as well as infarct volume could help determine the role of mitochondria in stroke outcome and determine whether uncoupling the ETC could potentially be a strategy for new stroke therapies. The objective of this study was to determine the effects of uncoupling electron flow on mitochondrial oxidative phosphorylation and stroke infarction. METHODS: Cerebral endovascular cells (CECs) were treated with various concentrations of FCCP, and bioenergetics were measured. For the stroke mouse model, FCCP (1 mg/kg, i.p) or vehicle was administered followed by 1-hour transient middle cerebral artery occlusion (tMCAO). Infarct volume was measured after a 23-hour reperfusion, and triphenyl tetrazolium chloride (TTC) staining was used to assess infarct volume. RESULTS: FCCP significantly decreased basal respiration, ATP turnover, maximal respiration, and spare capacity when the concentration of FCCP was greater than 1000 nM. The mice pretreated with FCCP had a significantly increased infarct volume within the cortex, striatum, and total hemisphere. Mice receiving FCCP had a significantly increased neurological deficit score compared to the vehicle. CONCLUSIONS: FCCP compromised mitochondrial oxidative phosphorylation in CECs in a dose-dependent manner. Uncoupling the electron transport chain with FCCP prior to tMCAO exacerbated stroke infarction in mice.