Post-ischemic protein restriction induces sustained neuroprotection, neurological recovery, brain remodeling, and gut microbiota rebalancing.

BACKGROUND: Moderate dietary protein restriction confers neuroprotection when applied before ischemic stroke. How a moderately protein-reduced diet influences stroke recovery when administered after stroke, is a clinically relevant question. This question has not yet been investigated. METHODS: Male C57BL6/J mice were exposed to transient intraluminal middle cerebral artery occlusion. Immediately after the stroke, mice were randomized to two normocaloric diets: a moderately protein-reduced diet containing 8% protein (PRD) or normal diet containing 20% protein (ND). Post-stroke neurological deficits were evaluated by a comprehensive test battery. Antioxidant and neuroinflammatory responses in the brain and liver were evaluated by Western blot and RTqPCR. Stroke-induced brain injury, microvascular integrity, glial responses, and neuroplasticity were assessed by immunohistochemistry. Fecal microbiota analysis was performed using 16S ribosomal RNA amplicon sequencing. RESULTS: We show that PRD reduces brain infarct volume after three days and enhances neurological and, specifically, motor-coordination recovery over six weeks in stroke mice. The recovery-promoting effects of PRD were associated with increased antioxidant responses and reduced neuroinflammation. Histochemical studies revealed that PRD increased long-term neuronal survival, increased peri-infarct microvascular density, reduced microglia/macrophage accumulation, increased contralesional pyramidal tract plasticity, and reduced brain atrophy. Fecal microbiota analysis showed reduced bacterial richness and diversity in ischemic mice on ND starting at 7 dpi. PRD restored bacterial richness and diversity at these time points. CONCLUSION: Moderate dietary protein restriction initiated post-ischemic stroke induces neurological recovery, brain remodeling, and neuroplasticity in mice by mechanisms involving antiinflammation and, in the post-acute phase, commensal gut microbiota rebalancing.

Hypocaloric Diet Initiated Post-Ischemia Provides Long-Term Neuroprotection and Promotes Peri-Infarct Brain Remodeling by Regulating Metabolic and Survival-Promoting Proteins.

Calorie restriction confers post-ischemic neuroprotection, when administered in a defined time window before ischemic stroke. How a hypocaloric diet influences stroke recovery when initiated after stroke has not been investigated. Male C57BL6/j mice were exposed to transient intraluminal middle cerebral artery occlusion. Immediately post-ischemia, mice were randomized to two groups receiving moderately hypocaloric (2286 kcal/kg food) or normocaloric (3518 kcal/kg) diets ad libitum. Animals were sacrificed at 3 or 56 days post-ischemia (dpi). Besides increased low density lipoprotein at 3 days and reduced alanine aminotransferase and increased urea at 56 days, no alterations of plasma markers were found in ischemic mice on hypocaloric diet. Body weight mildly decreased over 56 dpi by 7.4%. Hypocaloric diet reduced infarct volume in the acute stroke phase at 3 dpi and decreased brain atrophy, increased neuronal survival and brain capillary density in peri-infarct striatum and reduced motor coordination impairment in tight rope tests in the post-acute stroke phase over up to 56 dpi. The abundance of brain-derived neurotrophic factor, the NAD-dependent deacetylase and longevity protein sirtuin-1, the anti-oxidant glutathione peroxidase-3, and the ammonium detoxifier glutamine synthetase in the peri-infarct brain tissue was increased by hypocaloric diet. This study shows that a moderately hypocaloric diet that is initiated after stroke confers long-term neuroprotection and promotes peri-infarct brain remodeling.

Compromised Hippocampal Neuroplasticity in the Interferon-α and Toll-like Receptor-3 Activation-Induced Mouse Depression Model.

Disrupted neuronal plasticity due to subtle inflammation is considered to play a fundamental role in the pathogenesis of major depressive disorder. Interferon-α (IFN-α) potentiates immune responses against viral pathogens that induce toll-like receptor-3 (TLR3) activation but evokes severe major depressive disorder in humans by mechanisms that remain insufficiently described. By using a previously established mouse model of depression induced by combined delivery of IFN-α and polyinosinic:polycytidylic acid (poly(I:C)), a TLR3 agonist, we provide evidence that IFN-α and poly(I:C) reduce apical dendritic spine density in the hippocampal CA1 area ex vivo via mechanisms involving decreased TrkB signaling. In vitro, IFN-α and poly(I:C) treatments required neuronal activity to reduce dendritic spine density and TrkB signaling. The levels of presynaptic protein vesicular glutamate transporter (VGLUT)-1 and postsynaptic protein postsynaptic density-95 (PSD95) were specifically decreased, whereas the expression of both synaptic and extrasynaptic α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor 1 (AMPAR1) was increased by IFN-α and poly(I:C) delivery. Patch clamp recordings in primary hippocampal neurons revealed that morphological changes at the synapse induced by IFN-α and poly(I:C) costimulation were accompanied by an increased action potential threshold and action potential frequency, indicative of impaired neuronal excitability. Taken together, IFN-α and poly(I:C) delivery leads to structural and functional alterations at the synapse indicating that compromised neuroplasticity may play an integral role in the pathogenesis of immune response-induced depression.

Neuroprotection Induced by Energy and Protein-Energy Undernutrition Is Phase-Dependent After Focal Cerebral Ischemia in Mice.

Malnutrition predisposes to poor stroke outcome. In animal models, undernutrition protected against ischemic injury in some, but not in other studies. In view of diverse stroke models and food restriction paradigms, the consequences of undernutrition are poorly understood. Herein, we exposed mice to energy-reduced and protein-energy-reduced diets for 7-30 days and subsequently induced intraluminal middle cerebral artery occlusion. Undernutrition phase dependently influenced ischemic injury. Short-lasting 7 days of protein-energy undernutrition, but not energy undernutrition, decreased post-ischemic brain leukocyte infiltration and microglial activation and reduced brain Il-1ß mRNA, but did not protect against ischemic injury. Fourteen days of energy and protein-energy undernutrition, on the other hand, reduced ischemic injury despite absence of anti-inflammatory effects. Anti-oxidant genes (Sod-1, Sod-2, and Cat mRNAs) were regulated in the liver and, to a lesser extent, the ischemic brain, indicating an adapted, compensated stage. Conversely, 30 days of energy and protein-energy undernutrition caused progressive animal exhaustion associated with post-ischemic hypoperfusion, rise of metabolic markers (Sirt-1 and Glut-1 mRNAs, Sirt-1 protein) in the ischemic brain, and reregulation of pro- and anti-oxidant markers (now also Nox-4 and Gpx-3 mRNAs) in the liver. In the latter condition, no neuroprotection was noted. Our study suggests an adaptation of metabolic systems that provides neuroprotection in a circumscribed time window.

Moderate Protein Restriction Protects Against Focal Cerebral Ischemia in Mice by Mechanisms Involving Anti-inflammatory and Anti-oxidant Responses.

Food composition influences stroke risk, but its effects on ischemic injury and neurological deficits are poorly examined. While severe reduction of protein content was found to aggravate neurological impairment and brain injury as a consequence of combined energy-protein malnutrition, moderate protein restriction not resulting in energy deprivation was recently suggested to protect against perinatal hypoxia-ischemia. Male C57BL6/j mice were exposed to moderate protein restriction by providing a normocaloric diet containing 8% protein (control: 20% protein) for 7, 14, or 30 days. Intraluminal middle cerebral artery occlusion was then induced. Mice were sacrificed 24 h later. Irrespective of the duration of food modification (that is, 7-30 days), protein restriction reduced neurological impairment of ischemic mice revealed by a global and focal deficit score. Prolonged protein restriction over 30 days also reduced infarct volume, brain edema, and blood-brain barrier permeability and increased the survival of NeuN+ neurons in the core of the stroke (i.e., striatum). Neuroprotection by prolonged protein restriction went along with reduced brain infiltration of CD45+ leukocytes and reduced expression of inducible NO synthase and interleukin-1ß. As potential mechanisms, increased levels of the NAD-dependent deacetylase sirtuin-1 and anti-oxidant glutathione peroxidase-3 were noted in ischemic brain tissue. Irrespective of the protein restriction duration, a shift from pro-oxidant oxidative stress markers (NADPH oxidase-4) to anti-oxidant markers (superoxide dismutase-1/2, glutathione peroxidase-3 and catalase) was found in the liver. Moderate protein restriction protects against ischemia in the adult brain. Accordingly, dietary modifications may be efficacious strategies promoting stroke outcome.

Postacute Delivery of GABAA α5 Antagonist Promotes Postischemic Neurological Recovery and Peri-infarct Brain Remodeling.

Background and Purpose- Poststroke, neuronal excitability is tonically reduced in peri-infarct tissue via inhibitory influences of extrasynaptic GABAA receptors. We hypothesized that GABAA α5 blockade by the competitive antagonist S44819 enhances postischemic neurological recovery, brain remodeling, and neuroplasticity. Methods- In an explorative study followed by a confirmation study, male C57Bl6/j mice were exposed to transient intraluminal middle cerebral artery occlusion. Starting 72 hours poststroke, vehicle or S44819 (3 or 10 mg/kg, BID) was delivered orally for 28 days. Neurological recovery, perilesional tissue remodeling, and contralesional pyramidal tract plasticity were evaluated for 42 days, that is, 14 days after completion of S44819 delivery. Results- S44819, delivered at 10 but not 3 mg/kg, persistently improved motor coordination and spatial memory in both studies. Striatal atrophy was reduced by 10 mg/kg S44819 at 42 days post-treatment onset, and neuronal long-term survival in the peri-infarct striatum was increased. Delayed neuroprotection was associated with reduced peri-infarct astrogliosis, increased peri-infarct brain capillary density, and increased neural precursor cell proliferation and differentiation in proximity to the ipsilesional subventricular zone. Contralesional pyramidal tract plasticity, evaluated by anterograde tract tracing at the level of the red nucleus, was not influenced by S44819. Concentrations of neurotrophic (brain-derived neurotrophic factor and glial cell line-derived neurotrophic factor) and angiogenic (vascular endothelial growth factor and basic fibroblast growth factor) growth factors were elevated by 10 mg/kg S44819 in peri-infarct but not contralesional brain tissue. Conclusions- Our data demonstrate that S44819 enhances neurological recovery and peri-infarct brain remodeling in the postacute stroke phase.

Vesicular glutamate transporters play a role in neuronal differentiation of cultured SVZ-derived neural precursor cells.

The role of glutamate in the regulation of neurogenesis is well-established, but the role of vesicular glutamate transporters (VGLUTs) and excitatory amino acid transporters (EAATs) in controlling adult neurogenesis is unknown. Here we investigated the implication of VGLUTs in the differentiation of subventricular zone (SVZ)-derived neural precursor cells (NPCs). Our results show that NPCs express VGLUT1-3 and EAAT1-3 both at the mRNA and protein level. Their expression increases during differentiation closely associated with the expression of marker genes. In expression analyses we show that VGLUT1 and VGLUT2 are preferentially expressed by cultured SVZ-derived doublecortin+ neuroblasts, while VGLUT3 is found on GFAP+ glial cells. In cultured NPCs, inhibition of VGLUT by Evans Blue increased the mRNA level of neuronal markers doublecortin, B3T and MAP2, elevated the number of NPCs expressing doublecortin protein and promoted the number of cells with morphological appearance of branched neurons, suggesting that VGLUT function prevents neuronal differentiation of NPCs. This survival- and differentiation-promoting effect of Evans blue was corroborated by increased AKT phosphorylation and reduced MAPK phosphorylation. Thus, under physiological conditions, VGLUT1-3 inhibition, and thus decreased glutamate exocytosis, may promote neuronal differentiation of NPCs.

3D visualization and quantification of microvessels in the whole ischemic mouse brain using solvent-based clearing and light sheet microscopy.

The visualization of cerebral microvessels is essential for understanding brain remodeling after stroke. Injection of dyes allows for the evaluation of perfused vessels, but has limitations related either to incomplete microvascular filling or leakage. In conventional histochemistry, the analysis of microvessels is limited to 2D structures, with apparent limitations regarding the interpretation of vascular circuits. Herein, we developed a straight-forward technique to visualize microvessels in the whole ischemic mouse brain, combining the injection of a fluorescent-labeled low viscosity hydrogel conjugate with 3D solvent clearing followed by automated light sheet microscopy. We performed transient middle cerebral artery occlusion in C57Bl/6j mice and acquired detailed 3D vasculature images from whole brains. Subsequent image processing, rendering and fitting of blood vessels to a filament model was employed to calculate vessel length density, resulting in 0.922 ± 0.176 m/mm3 in healthy tissue and 0.329 ± 0.131 m/mm3 in ischemic tissue. This analysis showed a marked loss of capillaries with a diameter ≤ 10 µm and a more moderate loss of microvessels in the range > 10 and ≤ 20 µm, whereas vessels > 20 µm were unaffected by focal cerebral ischemia. We propose that this protocol is highly suitable for studying microvascular injury and remodeling post-stroke.

Lithium-induced neuroprotection in stroke involves increased miR-124 expression, reduced RE1-silencing transcription factor abundance and decreased protein deubiquitination by GSK3ß inhibition-independent pathways.

Lithium promotes acute poststroke neuronal survival, which includes mechanisms that are not limited to GSK3ß inhibition. However, whether lithium induces long-term neuroprotection and enhanced brain remodeling is unclear. Therefore, mice were exposed to transient middle cerebral artery occlusion and lithium (1 mg/kg bolus followed by 2 mg/kg/day over up to 7 days) was intraperitoneally administered starting 0-9 h after reperfusion onset. Delivery of lithium no later than 6 h reduced infarct volume on day 2 and decreased brain edema, leukocyte infiltration, and microglial activation, as shown by histochemistry and flow cytometry. Lithium-induced neuroprotection persisted throughout the observation period of 56 days and was associated with enhanced neurological recovery. Poststroke angioneurogenesis and axonal plasticity were also enhanced by lithium. On the molecular level, lithium increased miR-124 expression, reduced RE1-silencing transcription factor abundance, and decreased protein deubiquitination in cultivated cortical neurons exposed to oxygen-glucose deprivation and in brains of mice exposed to cerebral ischemia. Notably, this effect was not mimicked by pharmacological GSK3ß inhibition. This study for the first time provides efficacy data for lithium in the postacute ischemic phase, reporting a novel mechanism of action, i.e. increased miR-124 expression facilitating REST degradation by which lithium promotes postischemic neuroplasticity and angiogenesis.

Post-acute delivery of memantine promotes post-ischemic neurological recovery, peri-infarct tissue remodeling, and contralesional brain plasticity.

The NMDA antagonist memantine preferentially inhibits extrasynaptic NMDA receptors, which are overactivated upon stroke and thought to disturb neuroplasticity. We hypothesized that memantine enhances post-ischemic neurological recovery, brain remodeling, and plasticity. C57BL6/j mice were exposed to intraluminal middle cerebral artery occlusion. Starting 72 hours post-stroke, vehicle or memantine (4 or 20 mg/kg/day) were subcutaneously delivered over 28 days. Neurological recovery, perilesional tissue remodeling and contralesional pyramidal tract plasticity were evaluated over 49 days. Memantine, delivered at 20 but not 4 mg/kg/day, persistently improved motor-coordination and spatial memory. Secondary striatal atrophy was reduced by memantine. This delayed neuroprotection was associated with reduced astrogliosis and increased capillary formation around the infarct rim. Concentrations of BDNF, GDNF, and VEGF were bilaterally elevated by memantine in striatum and cortex. Anterograde tract tracing studies revealed that memantine increased contralesional corticorubral sprouting across the midline in direction to the ipsilesional red nucleus. In the contralesional motor cortex, the NMDA receptor subunit GluN2B, which is predominantly expressed in extrasynaptic NMDA receptors, was transiently reduced by memantine after 14 days, whereas GluN2A and PSD-95, which preferentially co-localize with synaptic NMDA receptors, were increased after 28 days. Our data suggest the utility of memantine for enhancing post-acute stroke recovery.

Neonatal Administration of Memantine Enhances Social Cognition in Adult Rats Subjected to Early Maternal Deprivation.

Schizophrenia is considered a neurodevelopmental disorder; however, all the available treatment options are used when the disease becomes clinically significant in adolescence or early adulthood. Using a developmental rat model of schizophrenia, we examined whether neonatal treatment with memantine, an NMDA receptor modulator, can improve schizophrenic-like symptoms in adulthood. Early maternal deprivation in rats produces deficits in social interaction behaviors in adulthood. In contrast, memantine administrated in neonatal rats subjected to early maternal deprivation significantly reduces deficits in social interaction behaviors in adulthood. These results raise the possibility that pharmacological treatment with memantine at the early developmental stage helps people with a risk to develop schizophrenic-like symptoms.

Correlates of Post-Stroke Brain Plasticity, Relationship to Pathophysiological Settings and Implications for Human Proof-of-Concept Studies.

The promotion of neurological recovery by enhancing neuroplasticity has recently obtained strong attention in the stroke field. Experimental studies support the hypothesis that stroke recovery can be improved by therapeutic interventions that augment neuronal sprouting. However plasticity responses of neurons are highly complex, involving the growth and differentiation of axons, dendrites, dendritic spines and synapses, which depend on the pathophysiological setting and are tightly controlled by extracellular and intracellular signals. Thorough mechanistic insights are needed into how neuronal plasticity is influenced by plasticity-promoting therapies in order not to risk the success of future clinical proof-of-concept studies.

Kallikrein-8 inhibition attenuates Alzheimer's disease pathology in mice.

INTRODUCTION: Memory loss and increased anxiety are clinical hallmarks of Alzheimer's disease (AD). Kallikrein-8 is a protease implicated in memory acquisition and anxiety, and its mRNA is known to be up-regulated in AD-affected human hippocampus. Therefore, an involvement of Kallikrein-8 in Alzheimer's pathogenesis is conceivable but remains to be proved. METHODS: We determined the cerebral expression of Kallikrein-8 mRNA and protein during the course of AD in patients and in transgenic mice and tested the impact of Kallikrein-8 inhibition on AD-related pathology in mice and in primary glial cells. RESULTS: Kallikrein-8 mRNA and protein were up-regulated in both species at incipient stages of AD. Kallikrein-8 inhibition impeded amyloidogenic amyloid-precursor-protein processing, facilitated amyloid ß (Aß) clearance across the blood-brain-barrier, boosted autophagy, reduced Aß load and tau pathology, enhanced neuroplasticity, reversed molecular signatures of anxiety, and ultimately improved memory and reduced fear. DISCUSSION: Kallikrein-8 is a promising new therapeutic target against AD.

Characterization of Seeding Conditions for Studies on Differentiation Patterns of Subventricular Zone Derived Neurospheres.

Stem cell research depends on extensive in vitro research. Poly-D-lysine (PDL) and polyornithine (PornT) are chemically synthesized amino acid chains promoting cell adhesion to solid substrates. Although, PDL and PornT are extensively used, there is no common agreement regarding the most optimal substance and its concentration. We therefore aimed at testing the effect of increasing concentrations (10, 50, and 100 µg/ml) for each compound and their corresponding mixtures (5+5 and 10+10 µg/ml) on the differentiation patterns of subventricular zone derived neurospheres. The latter were cultured for 24 h for protein and morphological analysis or for 8 h for migration analysis. No significant differences were found between increasing concentrations of PDL and PornT alone and the 10+10 condition in Western blots and immunocytochemistry. However, the mixed condition of 5+5 showed decreased glial fibrillary acidic protein and nestin expression with no changes in Akt, pAkt, GSK-3-beta, and pGSK-3-beta expression patterns. The various coating conditions also had no influence on migration of cells emerging from the neurosphere. Nevertheless, stimulation with recombinant human Erythropoietin (rhEpo) reduced migration by 20% regardless of the coating condition. We therefore conclude that a minimal concentration of 10 µg/ml of either compound should be used to produce reliable results with no alterations in protein levels as found for the 5+5 groups, and that the coating has no effect on the response of cells to chemical interventions. As such, a concentration of 10 µg/ml for either substance is sufficient when studying cellular processes of neurospheres in an in vitro or ex vivo environment.

Implantation of Miniosmotic Pumps and Delivery of Tract Tracers to Study Brain Reorganization in Pathophysiological Conditions.

Pharmacological treatment in animal models of cerebral disease imposes the problem of repeated injection protocols that may induce stress in animals and result in impermanent tissue levels of the drug. Additionally, drug delivery to the brain is delicate due to the blood brain barrier (BBB), thus significantly reducing intracerebral concentrations of selective drugs after systemic administration. Therefore, a system that allows both constant drug delivery without peak levels and circumvention of the BBB is in order to achieve sufficiently high intracerebral concentrations of drugs that are impermeable to the BBB. In this context, miniosmotic pumps represent an ideal system for constant drug delivery at a fixed known rate that eludes the problem of daily injection stress in animals and that may also be used for direct brain delivery of drugs. Here, we describe a method for miniosmotic pump implantation and post operatory care that should be given to animals in order to successfully apply this technique. We embed the aforementioned experimental paradigm in standard procedures that are used for studying neuroplasticity within the brain of C57BL6 mice. Thus, we exposed animals to 30 min brain infarct and implanted with miniosmotic pumps connected to the skull via a cannula in order to deliver a pro-plasticity drug. Behavioral testing was done during 30 days of treatment. After removal the animals received injections of anterograde tract tracers to analyze neuronal plasticity in the chronic phase of recovery. Results indicated that neuroprotection by the delivered drug was accompanied with increase in motor fibers crossing the midline of the brain at target structures. The results affirm the value of these techniques for drug administration and brain plasticity studies in modern neuroscience.

Methods for the analysis of neuronal plasticity and brain connectivity during neurological recovery.

The study of neuronal plasticity under pathological conditions is now a major point of focus on the field of neurological recovery. After the repeated failure of acute neuroprotection strategies for stroke treatment, the design of studies aimed at promoting the reconstruction of neuronal networks has become essential. Methods for the delivery of therapeutic agents on a steady dosage, thus preventing pharmacological peaks or excessive manipulation of experimental animals, are thus required. Additionally, methods that allow the visualization of neurological remodeling processes are fundamental to the understanding of how a therapeutic agent exerts its function. Here we describe how the use of miniosmotic pumps for the steady delivery of such agents, together with tract tracer injections, can be combined to unveil important information on how the brain changes after stroke and how therapeutic agents promote brain remodeling recovery.

Post-stroke transplantation of adult subventricular zone derived neural progenitor cells--A comprehensive analysis of cell delivery routes and their underlying mechanisms.

With neuroprotective approaches having failed until recently, current focus on experimental stroke research has switched towards manipulation of post-ischemic neuroregeneration. Transplantation of subventricular zone (SVZ) derived neural progenitor cells (NPCs) is a promising strategy for promotion of neurological recovery. Yet, fundamental questions including the optimal cell delivery route still have to be addressed. Consequently, male C57BL6 mice were exposed to transient focal cerebral ischemia and allowed to survive for as long as 84 days post-stroke. At 6h post-stroke, NPCs were grafted using six different cell delivery routes, i.e., intravenous, intraarterial, ipsilateral intrastriatal, contralateral intrastriatal, ipsilateral intraventricular and ipsilateral intracortical injection. Control mice received PBS only using the aforementioned delivery routes. Intralesional numbers of GFP(+) NPCs were high only after ipsilateral intrastriatal transplantation, whereas other injection paradigms only yielded comparatively small numbers of grafted cells. However, acute neuroprotection and improved functional outcome were observed after both systemic (i.e., intraarterial and intravenous) and ipsilateral intrastriatal transplantation only. Whereas systemic cell delivery induced acute and long-term neuroprotection, reduction of brain injury after ipsilateral intrastriatal cell grafting was only temporary, in line with the loss of transplanted NPCs in the brain. Both systemic and ipsilateral intrastriatal NPC delivery reduced microglial activation and leukocyte invasion, thus reducing free radical formation within the ischemic brain. On the contrary, only systemic NPC administration stabilized the blood-brain-barrier and reduced leukocytosis in the blood. Although intraarterial NPC transplantation was as effective as intravenous cell grafting, mortality of stroke mice was high using the intraarterial delivery route. Consequently, intravenous delivery of native NPCs in our experimental model is an attractive and effective strategy for stroke therapy that deserves further proof-of-concept studies.

[Brain repair after ischemic stroke: role of neurotransmitters in post-ischemic neurogenesis]. / Neurorrestauración tras la isquemia cerebral: papel de los neurotransmisores en la neurogénesis postisquémica.

INTRODUCTION: Brain ischemia and reperfusion produce alterations in the microenvironment of the parenchyma, including ATP depletion, ionic homeostasis alterations, inflammation, release of multiple cytokines and abnormal release of neurotransmitters. As a consequence, the induction of proliferation and migration of neural stem cells towards the peri-infarct region occurs. DEVELOPMENT: The success of new neurorestorative treatments for damaged brain implies the need to know, with greater accuracy, the mechanisms in charge of regulating adult neurogenesis, both under physiological and pathological conditions. Recent evidence demonstrates that many neurotransmitters, glutamate in particular, control the subventricular zone, thus being part of the complex signalling network that influences the production of new neurons. CONCLUSION: Neurotransmitters provide a link between brain activity and subventricular zone neurogenesis. Therefore, a deeper knowledge of the role of neurotransmitters systems, such as glutamate and its transporters, in adult neurogenesis, may provide a valuable tool to be used as a neurorestorative therapy in this pathology.

Neurorrestauración tras la isquemia cerebral: papel de los neurotransmisores en la neurogénesis postisquémica / Brain repair after ischemic stroke: role of neurotransmitters in post-ischemic neurogenesis

Introducción. La isquemia cerebral y la reperfusión producen alteraciones en el microambiente del parénquima, que incluyen la depleción de adenosín trifosfato, alteración de la homeostasis iónica, inflamación, liberación de múltiples citocinas y factores de crecimiento, y liberación anormal de neurotransmisores. Como consecuencia, se induce la proliferación y migración de las células precursoras neurales hacia las regiones del periinfarto. Desarrollo. El éxito de los nuevos tratamientos neurorrestauradores para el cerebro dañado implica la necesidad de conocercon mayor precisión los mecanismos que regulan la neurogénesis de adulto, tanto en condiciones fisiológicas como patológicas. Evidencias recientes demuestran que muchos neurotransmisores, en especial el glutamato, afectan la zona subventricular, formando parte, por lo tanto, de la compleja red de señales que influencian la producción de nuevas neuronas. Conclusiones. Los neurotransmisores proporcionan una conexión entre la actividad cerebral y la neurogénesis de la zona subventricular. Por ello, un conocimiento más profundo de la participación de los sistemas de neurotransmisores, como el glutamato y sus transportadores vesiculares y de membrana, en la neurogénesis del adulto puede proporcionar una herramienta valiosa que se podría utilizar como terapia neurorreparadora en esta patología (AU)

Introduction. Brain ischemia and reperfusion produce alterations in the microenvironment of the parenchyma, including ATP depletion, ionic homeostasis alterations, inflammation, release of multiple cytokines and abnormal release of neurotransmitters. As a consequence, the induction of proliferation and migration of neural stem cells towards the peri-infarct region occurs. Development. The success of new neurorestorative treatments for damaged brain implies the need to know, with greater accuracy, the mechanisms in charge of regulating adult neurogenesis, both under physiological and pathological conditions. Recent evidence demonstrates that many neurotransmitters, glutamate in particular, control the subventricular zone, thus being part of the complex signalling network that influences the production of new neurons. Conclusion. Neurotransmitters provide a link between brain activity and subventricular zone neurogenesis. Therefore, a deeper knowledge of the role of neurotransmitters systems, such as glutamate and its transporters, in adult neurogenesis, may provide a valuable tool to be used as a neurorestorative therapy in this pathology (AU)

Transient focal cerebral ischemia significantly alters not only EAATs but also VGLUTs expression in rats: relevance of changes in reactive astroglia.

The involvement of plasma membrane glutamate transporters (EAATs - excitatory aminoacid transporters) in the pathophysiology of ischemia has been widely studied, but little is known about the role of vesicular glutamate transporters (VGLUTs) in the ischemic process. We analyzed the expression of VGLUT1-3 in the cortex and caudate-putamen of rats subjected to transient middle cerebral artery occlusion. Western blot and immunohistochemistry revealed an increase of VGLUT1 signal in cortex and caudate-putamen until 3 days of reperfusion followed by a reduction 7 days after the ischemic insult. By contrast, VGLUT2 and 3 were drastically reduced. Confocal microscopy revealed an increase in VGLUT2 and 3 immunolabelling in the reactive astrocytes of the ischemic corpus callosum and cortex. Changes in VGLUTs and EAATs expression were differently correlated to neurological deficits. Interestingly, changes in VGLUT1 and EAAT2 expression showed a significant positive correlation in caudate-putamen. Taken together, these results suggest a contribution of VGLUTs to glutamate release in these structures, which could promote neuroblast migration and neurogenesis during ischemic recovery, and a possible interplay with EAATs in the regulation of glutamate levels, at least in the first stages of ischemic recovery.