Therapeutic Strategy For Stroke Research Articles

Systemic administration of blood-derived exosomes induced by remote ischemic post-conditioning, by delivering a specific cluster of miRNAs, ameliorates ischemic damage and neurological function.

MicroRNAs, contained in exosomes or freely circulating in the plasma, might play a pivotal role in the infarct-sparing effect exerted by remote limb ischemic postconditioning (RLIP). The aims of the present study were: (1) To evaluate the effect of pure exosomes isolated from plasma of animals subjected to RLIP systemically administered to ischemic rats; (2) To finely dissect exosomes content in terms of miRNAs; (3) To select those regulatory miRNAs specifically expressed in protective exosomes and to identify molecular pathways involved in their neurobeneficial effects. Circulating exosomes were isolated from blood of animals exposed to RLIP and administered to animals exposed to tMCAO by intracerebroventricular, intraperitoneal or intranasal routes. Exosomal miRNA signature was evaluated by microarray and FISH analysis. Plasmatic exosomes isolated from plasma of RLIP rats attenuated cerebral ischemia reperfusion injury and improved neurological functions until 3 days after ischemia induction. Interestingly, miR-702-3p and miR-423-5p seem to be mainly involved in exosome protective action by modulating NOD1 and NLRP3, two key triggers of neuroinflammation and neuronal death. Collectively, the results of the present work demonstrated that plasma-released exosomes after RLIP may transfer a neuroprotective signal to the brain of ischemic animals, thus representing a potentially translatable therapeutic strategy in stroke.

Ferroptosis: a potential therapeutic target for stroke.

Ferroptosis is a form of regulated cell death characterized by massive iron accumulation and iron-dependent lipid peroxidation, differing from apoptosis, necroptosis, and autophagy in several aspects. Ferroptosis is regarded as a critical mechanism of a series of pathophysiological reactions after stroke because of iron overload caused by hemoglobin degradation and iron metabolism imbalance. In this review, we discuss ferroptosis-related metabolisms, important molecules directly or indirectly targeting iron metabolism and lipid peroxidation, and transcriptional regulation of ferroptosis, revealing the role of ferroptosis in the progression of stroke. We present updated progress in the intervention of ferroptosis as therapeutic strategies for stroke in vivo and in vitro and summarize the effects of ferroptosis inhibitors on stroke. Our review facilitates further understanding of ferroptosis pathogenesis in stroke, proposes new targets for the treatment of stroke, and suggests that more efforts should be made to investigate the mechanism of ferroptosis in stroke.

SLC26A11 Inhibition Reduces Oncotic Neuronal Death and Attenuates Stroke Reperfusion Injury

Neuronal swelling is a pathological feature of stroke which contributes to the formation of cytotoxic edema. Under hypoxic condition, aberrant accumulation of sodium and chloride ions inside neurons increases osmotic pressure, leading to cell volume increase. Sodium entry pathway in neurons has been studied extensively. Here, we determine whether SLC26A11 is the major chloride entry pathway under hypoxia and could be the target for protection against ischemic stroke. In this study, electrophysiological properties of chloride current in primary cultured neurons were characterized using low chloride solution, 4,4′-diisothiocyano-2,2′-stilbenedisulfonic acid, and SLC26A11-specific siRNA under physiological conditions or ATP-depleted conditions. In vivo effect of SLC26A11 was evaluated on a rat stroke reperfusion model. We found that SLC26A11 mRNA in primary cultured neurons was upregulated as early as 6 h after oxygen glucose deprivation, and later, the protein level was elevated accordingly. Blockade of SLC26A11 activity could reduce chloride entry and attenuate hypoxia-induced neuronal swelling. In the animal stroke model, SLC26A11 upregulation was mainly located in surviving neurons close to the infarct core. SLC26A11 inhibition ameliorates infarct formation and improves functional recovery. These findings demonstrate that SLC26A11 is a major pathway for chloride entry in stroke, contributing to neuronal swelling. Inhibition of SLC26A11 could be a novel therapeutic strategy for stroke.

The Role of DNA Methylation in Stroke Recovery.

Epigenetic alterations affect the onset of ischemic stroke, brain injury after stroke, and mechanisms of poststroke recovery. In particular, DNA methylation can be dynamically altered by maintaining normal brain function or inducing abnormal brain damage. DNA methylation is regulated by DNA methyltransferase (DNMT), which promotes methylation, DNA demethylase, which removes methyl groups, and methyl-cytosine–phosphate–guanine-binding domain (MBD) protein, which binds methylated DNA and inhibits gene expression. Investigating the effects of modulating DNMT, TET, and MBD protein expression on neuronal cell death and neurorepair in ischemic stroke and elucidating the underlying mechanisms can facilitate the formulation of therapeutic strategies for neuroprotection and promotion of neuronal recovery after stroke. In this review, we summarize the role of DNA methylation in neuroprotection and neuronal recovery after stroke according to the current knowledge regarding the effects of DNA methylation on excitotoxicity, oxidative stress, apoptosis, neuroinflammation, and recovery after ischemic stroke. This review of the literature regarding the role of DNA methylation in neuroprotection and functional recovery after stroke may contribute to the development and application of novel therapeutic strategies for stroke.

Periodontitis is a potential risk factor for transient ischemic attack and minor ischemic stroke in young adults: A nationwide population-based cohort study.

This study aims to determine whether periodontitis is a risk factor for transient ischemic attack (TIA) in young adults. The National Health Insurance (NHI) Research Database in Taiwan was the source of the data used in this retrospective cohort study. Individuals aged 20 to 53 years with periodontitis in 2001 and 2002 (n=792,426) and an age- and sex-matched control group (n=792,426) were selected. All participants were followed up until TIA diagnosis, 55 years of age, removal from the NHI program, death, or December 31, 2016. The incidence density and hazard ratio (HR) of new-onset TIA were compared between individuals with periodontitis and controls. Periodontitis was defined by dentists according to the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes 523.3-5 with concurrent antibiotic prescription or periodontal treatment excluding scaling performed by certified dentists. TIA was defined according to the ICD-9-CM code 435.x at hospital discharge. After adjustment for confounding factors, the risk of developing TIA/minor ischemic stroke was calculated to be higher in participants with periodontitis (HR,1.24; 95% confidence interval, 1.15-1.32; P<0.001) than in those without. The HR was slightly higher among people aged 20 to 40 years than among those aged 40 to 53 years. Periodontitis is associated with an increased risk of developing TIA/minor ischemic stroke. Periodontitis might be a modifiable risk factor for stroke in young adults. Clinicians must devote greater attention to this potential association to develop new preventive and therapeutic strategies for stroke in young adults.

Neuronal extracellular vesicle derived miR-98 prevents salvageable neurons from microglial phagocytosis in acute ischemic stroke

Extracellular vesicles (EVs), as a novel intercellular communication carrier transferring cargo microRNAs (miRNAs), could play important roles in the brain remodeling process after ischemic stroke. However, the detailed mechanisms involved in EVs derived miRNAs-mediated cellular interactions in the brain remain unclear. Several studies indicated that microRNA-98 (miR-98) might participate in the pathogenesis of ischemic stroke. Here, we showed that expression of miR-98 in penumbra field kept up on the first day but dropped sharply on the 3rd day after ischemic stroke in rats, indicating that miR-98 could function as an endogenous protective factor post-ischemia. Overexpression of miR-98 targeted inhibiting platelet activating factor receptor-mediated microglial phagocytosis to attenuate neuronal death. Furthermore, we showed that neurons transferred miR-98 to microglia via EVs secretion after ischemic stroke, to prevent the stress-but-viable neurons from microglial phagocytosis. Therefore, we reveal that EVs derived miR-98 act as an intercellular signal mediating neurons and microglia communication during the brain remodeling after ischemic stroke. The present work provides a novel insight into the roles of EVs in the stroke pathogenesis and a new EVs-miRNAs-based therapeutic strategy for stroke.

Validation of a stroke model in rat compatible with rt-PA-induced thrombolysis: new hope for successful translation to the clinic

The recent clinical trial (DAWN) suggests that recanalization treatment may be beneficial up to 24 h after stroke onset, thus re-opening avenues for development of new therapeutic strategies. Unfortunately, there is a continuous failure of drugs in clinical trials and one of the major reasons proposed for this translational roadblock is the animal models. Therefore, the purpose of this study was to validate a new thromboembolic stroke rat model that mimics the human pathology, and that can be used for evaluating new strategies to save the brain in conditions compatible with recanalization. Stroke was induced by injection of thrombin into the middle cerebral artery. Recombinant tissue-type plasminogen activator (rt-PA) or saline was administrated at 1 h/4 h after stroke onset, and outcome was evaluated after 24 h. Induced ischemia resulted in reproducible cortical brain injuries causing a decrease in neurological function 24 h after stroke onset. Early rt-PA treatment resulted in recanalization, reduced infarct size and improved neurological functions, while late rt-PA treatment showed no beneficial effects and caused hemorrhagic transformation in 25% of the rats. This validated and established model’s resemblance to human ischemic stroke and high translational potential, makes it an important tool in the development of new therapeutic strategies for stroke.

Abstract TP98: Aging-Related Impairment in Post-Ischemic O-GlcNAcylation Activation Critically Contributes to Stroke Outcome

Introduction: Activity of the unfolded protein response (UPR) declines with age. The most conserved UPR branch is mediated by inositol- requiring enzyme-1 (IRE1). Once activated, IRE1 is converted to an endonuclease that splices X-box binding protein-1 (Xbp1) mRNA, leading to production of a new 54-kDa protein, XBP1s. XBP1s was recently shown to be capable of up-regulating expression of all major hexosamine biosynthetic pathway (HBP) enzymes. HBP generates UDP-GlcNAc, the sugar donor for O-GlcNAc modification (O-GlcNAcylation). These pathways together form the IRE1/XBP1s/HBP/O-GlcNAc axis. Our previous data demonstrated a pivotal role of this axis in stroke outcome, especially in the aged brain. Here, we expanded on our previous findings and further elucidated that aging-related impairment in post-ischemic O-GlcNAcylation activation critically contributes to stroke outcome. Methods: Permanent and transient middle cerebral artery occlusion (MCAO) surgeries were performed on young and aged animals. Conditional XBP1 transgenic (XBP1s-TG) and knockout (Xbp1-cKO) mice were used to determine the role of the XBP1 branch in stroke outcome. Thiamet-G was used to increase O-GlcNAcylation. Short- and long-term stroke studies were conducted. Functional outcome was evaluated by various behavioral tests. Results and Conclusions: In line with our previous data, XBP1s-TG mice exhibited improved stroke outcome, and boosting O-GlcNAcylation with thiamet-G rescued worse stroke outcome observed in Xbp1-cKO mice. Moreover, intervention with thiamet-G to enhance O-GlcNAcylation in the brain improved not only long-term outcome after transient MCAO in young mice, but also long-term functional recovery after permanent MCAO in aged rats, likely due to its rescue effect on impaired O-GlcNAcylation activation in the aged brain. Finally, we discovered that UDP-GlcNAc production under the physiologic state and after ischemia was compromised in the aged brain, which constitutes a potential mechanism responsible for impaired O-GlcNAcylation activation after stroke. Together, the findings strengthen our notion that targeting pro-survival pathways that are activated in the young, but not the aged, ischemic brain is a new promising therapeutic strategy in stroke.

Abstract TP283: Phosphorylation of IRF5/4 by IRAK4/MyD88 Regulates Microglial Inflammatory Responses to Ischemia

Introduction: Interferon Regulatory Factors 5 and 4 (IRF5/4) have been suggested to play a determinant role in regulating pro-inflammatory (M1) or anti-inflammatory (M2) microglia/macrophage response. However, how IRF5/4 signaling are activated in these phagocytes has not been well understood. Our previous study has shown an increased level of phosphorylated-IRF4 in both the cytosolic and nuclear fraction of cultured microglial homogenates after ischemia, suggesting phosphorylation is important for IRF4 activation. Interleukin-1 receptor associated kinase 4 (IRAK4) and the adaptor protein MyD88 are the upstream signals of IRF5. In the present study we hypothesized that IRAK4/MyD88 phosphorylate IRF5/4 in ischemic microglia and trigger the translocation of IRF5/4 from the cytoplasm to the nucleus, to promote expression of inflammatory mediators. Methods: Spontaneously Immortalized (SIM)-A9 or primary microglia from C57BL/6 mice were cultured and exposed to oxygen-glucose deprivation (OGD) for 4 hours; after OGD the cells were reperfused overnight with glucose-containing medium in room air. Phosphorylation of IRF5/4 by IRAK4 was determined with IRAK4 inhibitor (ND-2158). The interaction between IRAK4/MyD88 with IRF5/4 and the nuclear translocation of phosphorylated-IRF5/4 were examined by immunocytochemistry (ICC) and co-immunoprecipitation (Co-IP)/Western Blots (WB). Production of inflammatory cytokines was measured by ELISA in the culture medium. Results: WB showed more robust nuclear p-IRF5 signals; ELISA found increased level of TNFα, IL-1β, and IL6 in OGD vs. normoxic microglia. A similar pattern was observed for p-IRF4 nuclear translocation but with moderately increased anti-inflammatory cytokine (IL-4 and IL-10) levels with OGD. Co-IP revealed a higher ratio of p-IRF5/4 over total IRF5/4 in the nuclear vs. cytosol fraction, and interactions of IRAK4/MyD88 with both IRFs. ND-2158 treatment led to decreased phosphorylation of IRF5/4 after OGD compared to the vehicle group. Conclusion: IRAK4/MyD88 complex phosphorylates microglial IRF5/4 which subsequently mediates the production of inflammatory cytokines after ischemia. Manipulation of IRF5/4 signaling potentially represents a novel therapeutic strategy for stroke.

Abstract WP307: Molecular Mechanisms, Temporal and Spatial Dynamics of Inflammasome Activation in Ischemic Stroke

Background: Multiple sensors, executors and products are involved in inflammasome activation. Inflammasome activation has been found in several immune cells after stroke. However, the molecular mechanisms, the temporal and spatial dynamics of inflammasome activation in stroke remain elusive. Therapeutic value of modifying inflammasome activation in stroke is still debatable. Methods: Inflammasome markers of NLRP3 and IL-1β in stroke patients and healthy control were evaluated with flow cytometry. Correlation of NLRP3/IL-1β expression with stroke outcomes of patients was assessed. Ischemic stroke was induced in mice with transient middle cerebral artery occlusion (tMCAO, 1h). Expression dynamics of inflammasome components, location and cellular target of inflammasome activation in tMCAO models were analyzed. Therapeutic effects of inhibiting inflammasome activation on stroke outcomes were evaluated. Results: Rapid increase of inflammasome markers NLRP3 and IL-1β was detected at 1d after disease onset in stroke patients, which was positively correlated with patients’ infarct volume and NIHSS score. The sensors of NLRP3 and NLRC4 were involved in post stroke inflammasome activation, which increased at 1-3d after stroke and peaked at 3-5d in tMCAO models. Similar dynamics of the executors cleaved Caspase-1/11, as well as the products IL-1β, IL-18 and GSDMD were detected. AIM2 and Caspase-8 seemed not to take any part in post-stroke inflammasome activation. Macrophage was demonstrated as the main cell in which inflammasome was formed in both patients and mice, while microglia, dendritic cells and neutrophil also had inflammasome formation. Inflammasome activation of macrophage was mostly detected in stroke lesion. The executors of Caspase-1 and -11 were the key factors in inflammasome activation in stroke. Preventing inflammasome activation by inhibiting Caspase-1/11 signalings showed promising therapeutic efficacy. Conclusion: The impact of inflammasome activation is detrimental to ischemic stroke. Inhibiting Caspase-1/11 signalings is a promising therapeutic strategy for stroke.

Measurement of cerebrovascular reserve by multimodal imaging for cerebral arterial occlusion or stenosis patients: protocol of a prospective, randomized, controlled clinical study

BackgroundCerebrovascular reactivity (CVR) is the change in cerebral blood flow in response to a vaso-active stimulus, and may assist the treatment strategy of ischemic stroke. However, previous studies reported that a therapeutic strategy for stroke mainly depends on the degree of vascular stenosis with steady-state vascular parameters (e.g., cerebral blood flow and CVR). Hence, measurement of CVR by multimodal imaging techniques may improve the treatment of ischemic stroke.Methods/designThis is a prospective, randomized, controlled clinical trial that aimed to examine the capability of multimodal imaging techniques for the evaluation of CVR to improve treatment of patients with ischemic stroke. A total of 66 eligible patients will be recruited from Renji Hospital, Shanghai Jiaotong University School of Medicine. The patients will be categorized based on CVR into two subgroups as follows: CVR > 10% group and CVR < 10% group. The patients will be randomly assigned to medical management, percutaneous transluminal angioplasty and stenting, and intracranial and extra-cranial bypass groups in a 1:1:1 ratio. The primary endpoint is all adverse events and ipsilateral stroke recurrence at 6, 12, and 24 months after management. The secondary outcomes include the CVR, the National Institute of Health stroke scale and the Modified Rankin Scale at 6, 12, and 24 months.DiscussionMeasurement of cerebrovascular reserve by multimodal image is recommended by most recent studies to guide the treatment of ischemic stroke, and thus its efficacy and evaluation accuracy need to be established in randomized controlled settings. This prospective, parallel, randomized, controlled registry study, together with other ongoing studies, should present more evidence for optimal individualized accurate treatment of ischemic stroke.Trial registrationChinese Clinical Trial Registry, ID: ChiCTR-IOR-16009635; Registered on 16 October 2016.All items are from the World Health Organization Trial Registration Data Set and registration in the Chinese Clinical Trial Registry: ChiCTR-IOR-16009635.

Revealing sex-specific molecular changes in hypoxia-ischemia induced neural damage and subsequent recovery using zebrafish model

Functional recovery from hypoxia-ischemia depends on an individual’s response to the ischemic damage and recovery. Many of the neurological disorders, including cerebral stroke have sex-specific characteristics. Deciphering the differential molecular mechanisms of sex-specific recovery from hypoxic-ischemic insult can improve medical practice in the treatment of cerebral stroke. In the present study, we describe the establishment of a sex-specific global hypoxia-ischemia neural damage and repair model in zebrafish. During hypoxic exposure a delayed behavioural response was observed in female fish that resumed normal swimming pattern earlier than their male counterparts. Moreover, female appeared more affected as they showed restricted locomotor and exploratory behaviour in novel tank test, reduced mitochondrial enzyme activity, enhanced DNA damage, and cell death after hypoxia insult. However, they showed a faster recovery as compared to male. Analysis of mRNA and protein expression levels of some characteristic hypoxic-ischemic markers showed notable sex-specific differences. Using zebrafish model, we have uncovered cellular and molecular differences in sex-specific systemic responses during the post-hypoxia recovery. This insight might help in devising better therapeutic strategy for stroke in female patients.

Urban Versus Rural Egypt: Stroke Risk Factors and Clinical Profile: Cross-Sectional Observational Study

Background: Egypt is a densely populated country with living habits and health care services that differ from urban to rural regions. We aimed to study how characteristics of stroke vary among these regions. Methods: This is a cross-sectional observational study of ischemic stroke, thus hemorrhagic and venous strokes were excluded. A total of 1475 ischemic stroke patients were recruited for analysis from a tertiary hospital in Cairo representing urban area and from a secondary care hospital in Suhag representing rural region. Results: Analysis was done for 1143 ischemic stroke patients from urban and 332 from rural area. Onset to door was shorter in urban. Urban patients showed an older age and higher prevalence of hypertension and diabetes (65.9%, 48.6% respectively), while rural patients were characterized by female preponderance (51.5%), more dyslipidemia, smoking 44.6%, stroke in young 20.5%, atrial fibrillation 23.8% % and recurrent stroke 44.3%. Rural cases showed a severer deficit at onset and poorer outcome. Conclusion: Vascular risk factors, stroke type, and presentation tend to differ in Egypt according to the geographic distribution whether urban or rural. Studying patterns of such difference may aid in planning specific targeted preventive and therapeutic strategies for stroke in urban and rural Egypt.

Inhibition of miRNA-27b enhances neurogenesis via AMPK activation in a mouse ischemic stroke model.

Stroke is a leading cause of death and disability, but treatment options remain limited. Recent studies have suggested that cerebral ischemia‐induced neurogenesis plays a vital role in post‐stroke repair. Overactivation of AMP‐activated protein kinase (AMPK), a master sensor of energy balance, has been reported to exacerbate neuron apoptosis, but the role of chronic AMPK stimulus in post‐stroke recovery remains unclear. MicroRNAs have emerged as regulators of neurogenesis and have been reported to be involved in neurological function. In this study, we verified that miR‐27b directly targets AMPK and inhibits AMPK expression. In cultured neural stem cells, miR‐27b inhibitor improved proliferation and differentiation via the AMPK signaling pathway, but did not have an obvious effect on cell viability under oxygen and glucose deprivation conditions. In a mouse middle cerebral artery occlusion model, administration of miR‐27b inhibitor significantly enhanced behavioral function recovery and spatial memory. Up‐regulation of neurogenesis was observed both in the subventricular zone and in the hippocampal dentate gyrus. Collectively, our data suggest that miR‐27b inhibition promotes recovery after ischemic stroke by regulating AMPK activity. These findings may facilitate the development of novel therapeutic strategies for stroke.

Transplanting Mesenchymal Stem Cells for Treatment of Ischemic Stroke

Stroke is a major disease that leads to high mortality and morbidity. Given the ageing population and the potential risk factors, the prevalence of stroke and socioeconomic burden associated with stroke are expected to increase. During the past decade, both prophylactic and therapeutic strategies for stroke have made significant progress. However, current therapies still cannot adequately improve the outcomes of stroke and may not apply to all patients. One of the significant advances in modern medicine is cell-derived neurovascular regeneration and neuronal repair. Progress in stem cell biology has greatly contributed to ameliorating stroke-related brain injuries in preclinical studies and demonstrated clinical potential in stroke treatment. Mesenchymal stem cells (MSCs) have the differentiating potential of chondrocytes, adipocytes, and osteoblasts, and they have the ability to transdifferentiate into endothelial cells, glial cells, and neurons. Due to their great plasticity, MSCs have drawn much attention from the scientific community. This review will focus on MSCs, stem cells widely utilized in current medical research, and evaluate their effect and potential of improving outcomes in ischemic stroke.

Multifaceted Effects of Delta Opioid Receptors and DADLE in Diseases of the Nervous System.

The opioid system is considered a potential therapeutic target in a variety of neurological disorders. Delta opioid receptors (DORs) are broadly expressed in the brain, and their activation protects cells from hypoxic/ischemic insults by counteracting disruptions of ionic homeostasis and initiating neuroprotective pathways. The DOR agonist D-Ala2-D-Leu2-Enkephalin (DADLE) promotes neuronal survival, mitigates apoptotic pathways, and protects neurons and glial cells from ischemia-induced cell death, thus making DADLE a promising therapeutic option for stroke. The significant amount of research regarding DORs and DADLE in the last decades also suggests their potential in treating other neurological disorders. This review compiled relevant literature detailing the role of DORs and agonists in central nervous system function and neuropathologies. Several studies demonstrate potential mechanisms implicating a key interaction between DORs and DADLE in conferring neuroprotective benefits. A better understanding of DOR function in disease-specific contexts is critical to transitioning DOR agonists into the clinic as a therapy for stroke and other neurological diseases. Evidence-based studies support the potential of the delta-opioid family of receptors and its ligands in developing novel therapeutic strategies for stroke and other brain disorders.

Extracellular vesicles in mesenchymal stromal cells: A novel therapeutic strategy for stroke.

A stroke is a focal cerebral insult that frequently causes severe neurological deficit and mortality. Recent studies have demonstrated that multipotent mesenchymal stromal cells (MSCs) hold great promise for neurovascular remodeling and neurological function recovery following a stroke. Rather than a direct replacement of parenchymal brain cells, the therapeutic mechanism of MSCs is suggested to be the secretion of soluble factors. Specifically, emerging data described MSCs as being able to release extracellular vesicles (EVs), which contain a variety of cargo including proteins, lipids, DNA and various RNA species. The released EVs can target neurocytes and vascular cells and modify the cell's functions by delivering the cargo, which are considered to mediate the neural restoration effects of MSCs. Therefore, EVs may be developed as a novel cell-free therapy for neurological disorders. In the present review, the current advances regarding the components, functions and therapeutic potential of EVs are summarized and the use of MSC-derived EVs as a promising approach in the treatment of stroke are highlighted.

Ischemia-induced Neuronal Cell Death Is Mediated by Chemokine Receptor CX3CR1

The chemokine fractalkine (CX3CL1) and its receptor CX3CR1 play a fundamental role in the pathophysiology of stroke. Previous studies have focused on a paracrine interaction between neurons that produce fractalkine and microglia that express CX3CR1 receptors in the central nervous system. Recent findings have demonstrated the functional expression of CX3CR1 receptors by hippocampal neurons, suggesting their involvement in neuroprotective and neurodegenerative actions. To elucidate the roles of neuronal CX3CR1 in neurodegeneration induced by ischemic stroke, a mouse model of permanent middle cerebral artery occlusion (pMCAO) was employed. In the pMCAO mice, increased CX3CR1 levels, apoptosis-associated morphological changes, and Caspase 3-positive neuronal cells were observed in the striatum and in the hippocampus 24 hours after occlusion. Upregulation of CX3CR1 in ischemic neurons is associated with neuronal apoptotic cell death. In contrast, ischemia-induced apoptotic neuronal cell death was decreased in CX3CR1 deficient mice. Cultured primary hippocampal neurons obtained from CX3CR1 deficient mice were more resistant to glutamate-induced excitotoxicity by blocking calcium influx than those from wild-type mice. For the first time, we reported that neuronal CXCR1 mediates neuronal apoptotic cell death in ischemia. Our results suggest that modulating CXCR1 activity offers a novel therapeutic strategy for stroke.

Human Neural Stem Cells for Ischemic Stroke Treatment.

Ischemic stroke is the second most common cause of death worldwide and a major cause of disability. It takes place when the brain does not receive sufficient blood supply due to the blood clot in the vessels or narrowing of vessels' inner space due to accumulation of fat products. Apart from thrombolysis (dissolving of blood clot) and thrombectomy (surgical removal of blood clot or widening of vessel inner area) during the first hours after an ischemic stroke, no effective treatment to improve functional recovery exists in the post-ischemic phase. Due to their narrow therapeutic time window, thrombolysis and thrombectomy are unavailable to more than 80% of stroke patients.Many experimental studies carried out in animal models of stroke have demonstrated that stem cell transplantation may become a new therapeutic strategy in stroke. Transplantation of stem cells of different origin and stage of development has been shown to lead to improvement in experimental models of stroke through several mechanisms including neuronal replacement, modulation of cellular and synaptic plasticity and inflammation, neuroprotection and stimulation of angiogenesis. Several clinical studies and trials based on stem cell delivery in stroke patients are in progress with goal of improvements of functional recovery through mechanisms other than neuronal replacement. These approaches may provide therapeutic benefit, but generation of specific neurons for reconstruction of stroke-injured neural circuitry remains ultimate challenge. For this purpose, neural stem cells could be developed from multiple sources and fated to adopt required neuronal phenotype.

Improving Cerebral Blood Flow after Arterial Recanalization: A Novel Therapeutic Strategy in Stroke.

Ischemic stroke is caused by a disruption in blood supply to a region of the brain. It induces dysfunction of brain cells and networks, resulting in sudden neurological deficits. The cause of stroke is vascular, but the consequences are neurological. Decades of research have focused on finding new strategies to reduce the neural damage after cerebral ischemia. However, despite the incredibly huge investment, all strategies targeting neuroprotection have failed to demonstrate clinical efficacy. Today, treatment for stroke consists of dealing with the cause, attempting to remove the occluding blood clot and recanalize the vessel. However, clinical evidence suggests that the beneficial effect of post-stroke recanalization may be hampered by the occurrence of microvascular reperfusion failure. In short: recanalization is not synonymous with reperfusion. Today, clinicians are confronted with several challenges in acute stroke therapy, even after successful recanalization: (1) induce reperfusion, (2) avoid hemorrhagic transformation (HT), and (3) avoid early or late vascular reocclusion. All these parameters impact the restoration of cerebral blood flow after stroke. Recent advances in understanding the molecular consequences of recanalization and reperfusion may lead to innovative therapeutic strategies for improving reperfusion after stroke. In this review, we will highlight the importance of restoring normal cerebral blood flow after stroke and outline molecular mechanisms involved in blood flow regulation.