Molecular Communication of a Dying Neuron in Stroke. Int J Mol Sci. 2018;19. [PMID: 30235837 PMCID: PMC6164443 DOI: 10.3390/ijms19092834]

Establishing a high throughput drug screening system for cerebral ischemia using zebrafish larvae

We previously generated an ischemic stroke in a zebrafish model using N₂ gas perfusion; however, this model was an unsuitable drug screening system due to low throughput. In this study, we examined a zebrafish ischemic stroke model using an oxygen absorber to assess drug effects. Hypoxic exposure more than 2 h using the oxygen absorber significantly induced cell death in the brain and damage to the neuronal cells. To confirm the utility of the ischemic model induced by the oxygen absorber, we treated zebrafish with neuroprotective agents. MK-801, an N-methyl-d-aspartate (NMDA) receptor antagonist, significantly suppressed cell death in the brain, and edaravone, a free radical scavenger, significantly reduced the number of dead cells. These results suggest that the activation of NMDA receptors and the production of reactive oxygen species induce neuronal cell damage in accordance with previous mammalian reports. We demonstrate the suitability of an ischemic stroke model in zebrafish larvae using the oxygen absorber, enabling a high throughput drug screening.

Decoding the Transcriptional Response to Ischemic Stroke in Young and Aged Mouse Brain

Ischemic stroke is a well-recognized disease of aging, yet it is unclear how the age-dependent vulnerability occurs and what are the underlying mechanisms. To address these issues, we perform a comprehensive RNA-seq analysis of aging, ischemic stroke, and their interaction in 3- and 18-month-old mice. We assess differential gene expression across injury status and age, estimate cell type proportion changes, assay the results against a range of transcriptional signatures from the literature, and perform unsupervised co-expression analysis, identifying modules of genes with varying response to injury. We uncover downregulation of axonal and synaptic maintenance genetic program, and increased activation of type I interferon (IFN-I) signaling following stroke in aged mice. Together, these results paint a picture of ischemic stroke as a complex age-related disease and provide insights into interaction of aging and stroke on cellular and molecular level.

Neuroprotective and Angiogenesis Effects of Levetiracetam Following Ischemic Stroke in Rats

Objective: The present study explored whether levetiracetam (LEV) could protect against experimental brain ischemia and enhance angiogenesis in rats, and investigated the potential mechanisms in vivo and in vitro.

Methods: The middle cerebral artery was occluded for 60 min to induce middle cerebral artery occlusion (MCAO). The Morris water maze was used to measure cognitive ability. The rotation test was used to assess locomotor function. T2-weighted MRI was used to assess infarct volume. The neuronal cells in the cortex area were stained with cresyl purple. The anti-inflammatory effects of LEV on microglia were observed by immunohistochemistry. Enzyme-linked immunosorbent assays (ELISA) were used to measure the production of pro-inflammatory cytokines. Western blotting was used to detect the levels of heat shock protein 70 (HSP70), vascular endothelial growth factor (VEGF), and hypoxia-inducible factor-1α (HIF-1α) in extracts from the ischemic cortex. Flow cytometry was used to observe the effect of LEV on neuronal cell apoptosis.

Results: LEV treatment significantly increased the density of the surviving neurons in the cerebral cortex and reduced the infarct size (17.8 ± 3.3% vs. 12.9 ± 1.4%, p < 0.01) after MCAO. Concurrently, the time required to reach the platform for LEV-treated rats was shorter than that in the saline group on day 11 after MCAO (p < 0.01). LEV treatment prolonged the rotarod retention time on day 14 after MCAO (84.5 ± 6.7 s vs. 59.1 ± 6.2 s on day 14 compared with the saline-treated groups, p < 0.01). It also suppressed the activation of microglia and inhibited TNF-α and Il-1β in the ischemic brain (135.6 ± 5.2 pg/ml vs. 255.3 ± 12.5 pg/ml, 18.5 ± 1.3 pg/ml vs. 38.9 ± 2.3 pg/ml on day 14 compared with the saline-treated groups, p < 0.01). LEV treatment resulted in a significant increase in HIF-1α, VEGF, and HSP70 levels in extracts from the ischemic cerebral cortex. At the same time, LEV reduced neuronal cell cytotoxicity and apoptosis induced by an ischemic stroke (p < 0.01).

Conclusion: LEV treatment promoted angiogenesis and functional recovery after cerebral ischemia in rats. These effects seem to be mediated through anti-inflammatory and antiapoptotic activities, as well as inducing the expression of HSP70, VEGF, and HIF-1α.

Integrative Multi-omics Analysis to Characterize Human Brain Ischemia

Stroke is a major cause of death and disability. A better comprehension of stroke pathophysiology is fundamental to reduce its dramatic outcome. The use of high-throughput unbiased omics approaches and the integration of these data might deepen the knowledge of stroke at the molecular level, depicting the interaction between different molecular units. We aimed to identify protein and gene expression changes in the human brain after ischemia through an integrative approach to join the information of both omics analyses. The translational potential of our results was explored in a pilot study with blood samples from ischemic stroke patients. Proteomics and transcriptomics discovery studies were performed in human brain samples from six deceased stroke patients, comparing the infarct core with the corresponding contralateral brain region, unveiling 128 proteins and 2716 genes significantly dysregulated after stroke. Integrative bioinformatics analyses joining both datasets exposed canonical pathways altered in the ischemic area, highlighting the most influential molecules. Among the molecules with the highest fold-change, 28 genes and 9 proteins were selected to be validated in five independent human brain samples using orthogonal techniques. Our results were confirmed for NCDN, RAB3C, ST4A1, DNM1L, A1AG1, A1AT, JAM3, VTDB, ANXA1, ANXA2, and IL8. Finally, circulating levels of the validated proteins were explored in ischemic stroke patients. Fluctuations of A1AG1 and A1AT, both up-regulated in the ischemic brain, were detected in blood along the first week after onset. In summary, our results expand the knowledge of ischemic stroke pathology, revealing key molecules to be further explored as biomarkers and/or therapeutic targets.

Nanoparticles of resveratrol attenuates oxidative stress and inflammation after ischemic stroke in rats

Resveratrol is a nutraceutical compound that has exciting pharmacological potential in different diseases, including stroke. Due to its low bioavailability, the efficacy of resveratrol is minimal. Hence, the present study is aimed to synthesize and characterize nanoparticles of resveratrol (NR) followed by evaluating the neuroprotective role and elucidate the mechanism of NR in a rat model of middle cerebral artery occlusion (MCAO). Male Wistar rats (280-300 g) were pretreated with various doses (125 µg, 250 µg, and NR 500 µg; once daily, i.p.) of NR or vehicle (nanostructured lipid carriers) for 10 days. MCAO was performed for 2 h followed by reperfusion of 22 h. After 24 h of MCAO, animals were tested for the neurological outcome and were sacrificed for the analysis of infarct volume, oxidative, inflammatory, and apoptotic markers. NR-treated rats showed a substantial reduction in infarction compared to saline controls in parallel with improved motor and cognitive function. Further, NR pretreatment ameliorated oxidative stress markers and attenuated activities of antioxidant enzymes and Na+ K+ ATPase. The enhanced activities of caspases -3 and -9 and cytokines: interleukin-1β, and -6, and tumor necrosis factor-ɑ) in the MCAO group were significantly protected with the treatment of 500 µg of NR. Taken together, these data indicate that inhibition by NR has therapeutic potential in the ischemic stroke model. Further investigations into the therapeutic efficacy and post-treatment protocols are needed to confirm whether NR treatment could be a promising candidate for a stroke.

Dynamic roles of neutrophils in post-stroke neuroinflammation

Clinical trials involving the blockage of peripheral inflammatory leukocyte recruitment into the brain have puzzlingly led to either no significant improvement in stroke outcome, or even worsened outcomes and increased mortality, prompting a re-evaluation of our understanding into the neuroinflammatory processes after stroke. Whilst traditionally understood as simple effectors of the innate immune system, emerging research in vascular disease biology has redefined the neutrophil as a specialized and highly specific cell type with dynamic functional capacity. Indeed, emerging experimental evidence indicates that neutrophils display diverse roles in the acute stages of ischemic stroke with the ability to elicit both pro-inflammatory and anti-inflammatory effects. Currently, there is some uncertainty as to whether neutrophil diversity is beneficial or harmful in stroke as their interactions with the resident cells of the brain, such as microglia and neurons, would potentially elicit heterogeneous outcomes. Current treatments for patients with stroke aim to remove the vascular blockage and to restore blood flow, but there are currently no drug treatments for managing the loss of functional brain tissue nor restoration of microglial and neuronal damage. If these hypothesized wound-healing functions of neutrophils can be validated in a stroke setting, promoting the recruitment of this type of neutrophils into the injured brain tissue may form a promising therapeutic target for the majority of stroke patients currently without treatment. In this review, we will provide an update on recent research that has explored neutrophil heterogeneity in the neuroinflammatory cascade after ischemic stroke.

Single-Nucleotide Polymorphisms in Oxidative Stress-Related Genes and the Risk of a Stroke in a Polish Population-A Preliminary Study

The present preliminary case-control study was undertaken to detect the potential association of six single nucleotide polymorphisms (SNPs) in oxidative stress-related genes: SOD2 (c.47T > C; rs4880), CAT (c.-89A > T; rs7943316), GPX4 (c.660T > A; rs713041), NOS1 (g.117803515C > T; rs1879417) and NOS2 (c.1823C > T; rs2297518 and c.-227G > C; rs10459953) and the occurrence of a stroke. The SNPs were determined using the TaqMan^® Allelic Discrimination Assay in 107 patients with strokes and 107 age- and sex-matched individuals who had not experienced cerebrovascular accidents. The T alleles of the rs4880 were positively correlated with a stroke (bootstrap OR 1.31; 1.07-1.59 95% CI). In the case of the rs713041, an association with the T allele was found (bootstrap OR 1.36; 1.12-1.67). In addition, the occurrence of a stroke was associated with the presence of the C allele of the rs1879417 (bootstrap OR 1.32; 1.09-1.61). We also found that the C/C genotype and C allele of the rs2297518 increased the risk of a stroke (bootstrap ORs 7.00; 4.34-11.29 and 4.96; 3.88-6.34, respectively). Moreover, the C allele of the rs10459953 was associated with an increased occurrence of this disease (bootstrap OR 1.31; 1.08-1.60). These results indicated that genetics variants in the SOD2, GPX4, NOS1 and NOS2 might be associated with susceptibility to strokes in the Polish population.

l-Borneol Exerted the Neuroprotective Effect by Promoting Angiogenesis Coupled With Neurogenesis via Ang1-VEGF-BDNF Pathway

At present, Stroke is still one of the leading causes of population death worldwide and leads to disability. Traditional Chinese medicine plays an important role in the prevention or treatment of stroke. l-borneol, a traditional Chinese medicine, has been used in China to treat stroke for thousands of years. However, its mechanism of action is unclear. After cerebral ischemia, promoting angiogenesis after cerebral ischemia and providing nutrition for the infarct area is an important strategy to improve the damage in the ischemic area, but it is also essential to promote neurogenesis and replenish new neurons. Here, our research shows that l-borneol can significantly improve the neurological deficits of pMCAO model rats, reduce cerebral infarction, and improve the pathological damage of cerebral ischemia. and significantly increase serum level of Ang-1 and VEGF, and significantly decrease level of ACE and Tie2 to promote angiogenesis. PCR and WB showed the same results. Immunohistochemistry also showed that l-borneol can increase the number of CD34 positive cells, further verifying that l-borneol can play a neuroprotective effect by promoting angiogenesis after cerebral ischemia injury. In addition, l-borneol can significantly promote the expression level of VEGF, BDNF and inhibit the expression levels of TGF-β1 and MMP9 to promote neurogenesis. The above suggests that l-borneol can promote angiogenesis coupled neurogenesis by regulating Ang1-VEGF-BDNF to play a neuroprotective effect. Molecular docking also shows that l-borneol has a very high binding rate with the above target, which further confirmed the target of l-borneol to improve cerebral ischemic injury. These results provide strong evidence for the treatment of cerebral ischemia with l-borneol and provide reference for future research.

Wnt/β-Catenin Signaling Promotes Differentiation of Ischemia-Activated Adult Neural Stem/Progenitor Cells to Neuronal Precursors

Modulating endogenous regenerative processes may represent a suitable treatment for central nervous system (CNS) injuries, such as stroke or trauma. Neural stem/progenitor cells (NS/PCs), which naturally reside in the subventricular zone (SVZ) of the adult brain, proliferate and differentiate to other cell types, and therefore may compensate the negative consequences of ischemic injury. The fate of NS/PCs in the developing brain is largely influenced by Wingless/Integrated (Wnt) signaling; however, its role in the differentiation of adult NS/PCs under ischemic conditions is still enigmatic. In our previous study, we identified the Wnt/β-catenin signaling pathway as a factor promoting neurogenesis at the expense of gliogenesis in neonatal mice. In this study, we used adult transgenic mice in order to assess the impact of the canonical Wnt pathway modulation (inhibition or hyper-activation) on NS/PCs derived from the SVZ, and combined it with the middle cerebral artery occlusion (MCAO) to disclose the effect of focal cerebral ischemia (FCI). Based on the electrophysiological properties of cultured cells, we first identified three cell types that represented in vitro differentiated NS/PCs – astrocytes, neuron-like cells, and precursor cells. Following FCI, we detected fewer neuron-like cells after Wnt signaling inhibition. Furthermore, the immunohistochemical analysis revealed an overall higher expression of cell-type-specific proteins after FCI, indicating increased proliferation and differentiation rates of NS/PCs in the SVZ. Remarkably, Wnt signaling hyper-activation increased the abundance of proliferating and neuron-like cells, while Wnt pathway inhibition had the opposite effect. Finally, the expression profiling at the single cell level revealed an increased proportion of neural stem cells and neuroblasts after FCI. These observations indicate that Wnt signaling enhances NS/PCs-based regeneration in the adult mouse brain following FCI, and supports neuronal differentiation in the SVZ.

Astrocyte-induced synapse formation and ischemic stroke

Astrocytes are closely associated with the regulation of synapse formation and function. In addition, astrocytes have been shown to block certain brain impairments, including synaptic damage from stroke and other diseases of the central nervous system (CNS). Although astrocytes do not completely prevent synaptic damage, they appear to be protective and to restore synaptic function following damage. The purpose of this study is to discuss the role of astrocytes in synaptogenesis and synaptic damage in ischemic stroke. I detail the mechanism of action of the multiple factors secreted by astrocytes that are involved in synapse formation. In particular, I describe the characteristics and role in synapse formation of each secreted molecule related to synaptic structure and function. Furthermore, I discuss the effect of astrocytes on synaptogenesis and repair in ischemic stroke and in other CNS diseases. Astrocytes release molecules such as thrombospondin, hevin, secreted protein acidic rich in cysteine, etc., due to activation by ischemia to induce synaptic structure and function, an effect associated with protection of the brain from synaptic damage in ischemic stroke. In conclusion, I show that astrocytes may regulate synaptic transmission while having the potential to block and repair synaptic dysfunction in stroke-associated brain damage.

miR-374 improves cerebral ischemia reperfusion injury by targeting Wnt5a

To date, studies have demonstrated the potential functions of microRNAs in cerebral ischemia reperfusion (IR) injury. Herein, we established a middle cerebral artery occlusion (MCAO) model in rats and then subjected them to reperfusion to explore the role of microRNA-374 (miR-374) in cerebral IR injury. After reperfusion, the endogenous miR-374 level decreased, and the expression of its target gene, Wnt5a, increased in brain tissues. Intracerebral pretreatment of miR-374 agomir attenuated cerebral damage induced by IR, including neurobehavioral deficits, infarction, cerebral edema and blood-brain barrier disruption. Moreover, rats pretreated with miR-374 agomir showed a remarkable decrease in apoptotic neurons, which was further confirmed by reduced BAX expression as well as increased BCL-2 and BCL-XL expression. A dual-luciferase reporter assay substantiated that Wnt5a was the target gene of miR-374. miR-374 might protect against brain injury by downregulating Wnt5a in rats after IR. Thus, our study provided a novel mechanism of cerebral IR injury from the perspective of miRNA regulation.

Brain-Derived Extracellular Vesicles in Health and Disease: A Methodological Perspective

Extracellular vesicles (EVs) are double membrane structures released by presumably all cell types that transport and deliver lipids, proteins, and genetic material to near or distant recipient cells, thereby affecting their phenotype. The basic knowledge of their functions in healthy and diseased brain is still murky and many questions about their biology are unsolved. In neurological diseases, EVs are regarded as attractive biomarkers and as therapeutic tools due to their ability to cross the blood–brain barrier (BBB). EVs have been successfully isolated from conditioned media of primary brain cells and cerebrospinal fluid (CSF), but protocols allowing for the direct study of pathophysiological events mediated or influenced by EVs isolated from brain have only recently been published. This review aims to give a brief overview of the current knowledge of EVs’ functions in the central nervous system (CNS) and the current protocols to isolate brain-derived EVs (BDEVs) used in different publications. By comparing the proteomic analysis of some of these publications, we also assess the influence of the isolation method on the protein content of BDEVs.

Delayed Treatment with Human Dental Pulp Stem Cells Accelerates Functional Recovery and Modifies Responses of Peri-Infarct Astrocytes Following Photothrombotic Stroke in Rats

Dental pulp contains multipotent mesenchymal stem cells that improve outcomes when administered early after temporary middle cerebral artery occlusion in rats. To further assess the therapeutic potential of these cells, we tested whether functional recovery following stroke induced by photothrombosis could be modified by a delayed treatment that was initiated after the infarct attained maximal volume. Photothrombosis induces permanent focal ischemia resulting in tissue changes that better reflect key aspects of the many human strokes in which early restoration of blood flow does not occur. Human dental pulp stem cells (approximately 400 × 10³ viable cells) or vehicle were injected into the infarct and adjacent brain tissue of Sprague-Dawley rats at 3 days after the induction of unilateral photothrombotic stroke in the sensorimotor cortex. Forepaw function was tested up to 28 days after stroke. Cellular changes in peri-infarct tissue at 28 days were assessed using immunohistochemistry. Rats treated with the stem cells showed faster recovery compared with vehicle-treated animals in a test of forelimb placing in response to vibrissae stimulation and in first attempt success in a skilled forelimb reaching test. Total success in the skilled reaching test and forepaw use during exploration in a Perspex cylinder were not significantly different between the 2 groups. At 28 days after stroke, rats treated with the stem cells showed decreased immunolabeling for glial fibrillary acidic protein in tissue up to 1 mm from the infarct, suggesting decreased reactive astrogliosis. Synaptophysin, a marker of synapses, and collagen IV, a marker of capillaries, were not significantly altered at this time by the stem-cell treatment. These results indicate that dental pulp stem cells can accelerate recovery without modifying initial infarct formation. Decreases in reactive astrogliosis in peri-infarct tissue could have contributed to the change by promoting adaptive responses in neighboring neurons.

Cellular and Molecular Mechanisms of R/S-Roscovitine and CDKs Related Inhibition under Both Focal and Global Cerebral Ischemia: A Focus on Neurovascular Unit and Immune Cells

Ischemic stroke is the second leading cause of death worldwide. Following ischemic stroke, Neurovascular Unit (NVU) inflammation and peripheral leucocytes infiltration are major contributors to the extension of brain lesions. For a long time restricted to neurons, the 10 past years have shown the emergence of an increasing number of studies focusing on the role of Cyclin-Dependent Kinases (CDKs) on the other cells of NVU, as well as on the leucocytes. The most widely used CDKs inhibitor, (R)-roscovitine, and its (S) isomer both decreased brain lesions in models of global and focal cerebral ischemia. We previously showed that (S)-roscovitine acted, at least, by modulating NVU response to ischemia. Interestingly, roscovitine was shown to decrease leucocytes-mediated inflammation in several inflammatory models. Specific inhibition of roscovitine majors target CDK 1, 2, 5, 7, and 9 showed that these CDKs played key roles in inflammatory processes of NVU cells and leucocytes after brain lesions, including ischemic stroke. The data summarized here support the investigation of roscovitine as a potential therapeutic agent for the treatment of ischemic stroke, and provide an overview of CDK 1, 2, 5, 7, and 9 functions in brain cells and leucocytes during cerebral ischemia.

Effects of Thrombin on the Neurovascular Unit in Cerebral Ischemia

Cerebral ischemia is a cerebrovascular disease with high morbidity and mortality that poses a significant burden on society and the economy. About 60% of cerebral ischemia is caused by thrombus, and the formation of thrombus proceeds from insoluble fibrin, following its transformation from liquid fibrinogen. In thrombus-induced ischemia, increased permeability of the blood-brain barrier (BBB), followed by the extravasation of blood components into the brain results in an altered brain microenvironment. Changes in the brain microenvironment affect brain function and the neurovascular unit (NVU), the working unit of the brain. Recent studies have reported that coagulation factors interact with the NVU and its components, but the specific function of this interaction is highly speculative and warrants further investigations. In this article, we reviewed the role of coagulation factors in cerebral ischemia and the role of coagulation factors in thrombosis. Additionally, the influence of thrombin on the NVU is introduced, as well as in the function of NVU, which may help to explore part of brain injury mechanism during ischemia. Lastly, we propose some novel therapeutic approaches on ischemic stroke by reducing the risk of coagulation.

Physiopathology of ischemic stroke and its modulation using memantine: evidence from preclinical stroke

Ischemic stroke is the most common type of cerebrovascular disease and is caused by an interruption of blood flow in the brain. In this disease, two different damage areas are identifying: the lesion core, in which cells quickly die; and the penumbra (surrounding the lesion core), in which cells are functionally weakened but may recover and restore their functions. The currently approved treatments for ischemic stroke are the recombinant tissue plasminogen activator and endovascular thrombectomy, but they have a short therapeutic window (4.5 and 6 hours after stroke onset, respectively) and a low percentage of stroke patients actually receive these treatments. Memantine is an approved drug for the treatment of Alzheimer’s disease. Memantine is a noncompetitive, low affinity and use-dependent antagonist of N-methyl-D-aspartate glutamate receptor. Memantine has several advantages over developing a new drug to treat focal ischemic stroke, but the most important is that it has sufficient safe probes in preclinical models and humans, and if the preclinical studies provide more evidence about pharmacological actions in tissue protection and repair, this could help to increase the number of clinical trials. The present review summarizes the physiopathology of isquemic stroke and the pharmacological actions in neuroprotection and neuroplasticity of memantine in the post stroke stage of preclinical stroke models, to illustrate their potential to improve functional recovery in human patients.

Post-ischemic stroke systemic inflammation: Immunomodulation by progesterone and vitamin D hormone

Post-stroke systemic inflammation, due to the injury itself and exacerbated by in-hospital infections, can increase morbidity and mortality in stroke patients. In this study, we examined the immunomodulatory effects of progesterone (P4) alone and in combination with vitamin D hormone (VDH) on acute phase post-stroke peripheral immune dysfunction and functional/behavioral deficits. Adult rats underwent transient middle cerebral artery occlusion/reperfusion (tMCAO) and delayed systemic inflammation was induced by injections of lipopolysaccharide (LPS) beginning 24 h post-stroke. Animals were tested for behavioral outcomes and immune function at day 4 post-stroke. We also measured infarction volume and markers of neuronal inflammation (GFAP, IL-6) and apoptosis (cleaved caspase-3) in brain post-stroke. We observed the worst stroke outcomes in the stroke + systemic inflammation group compared to the stroke-alone group. Flow cytometric analysis of different subsets of immune cells in blood, spleen and thymus revealed peripheral immune dysfunction which was restored by both P4 and VDH monotherapy. P4 monotherapy reduced infarction volume, behavioral/functional deficits, peripheral immune dysfunction, neuronal inflammation, and apoptosis induced by post-stroke systemic inflammation. Combination treatment with P4+VDH improved outcomes better than monotherapy. Our findings can be taken to suggest that the current standard of care for stroke and post-stroke infection can be substantially improved by P4 and VDH combination therapy.

Role of HMGB1/TLR4 Axis in Ischemia/Reperfusion-Impaired Extracellular Glutamate Clearance in Primary Astrocytes

(1) Background: Abnormal accumulation of extracellular glutamate can occur as dysfunction of astrocytic glutamate transporters, which has been linked to ischemic brain injury. Excessive extracellular glutamate-induced abnormal excitotoxicity is the major cause of secondary neuronal damage after cerebral ischemia/reperfusion. However, the definite mechanism of impaired astrocytic glutamate reuptake remains unclear. (2) Methods: We investigated the mechanism of the HMGB1/TLR4 axis in extracellular glutamate clearance in primary astrocytes exposed to ischemia/reperfusion by using OGD/R (oxygen-glucose deprivation/reoxygenation) model. (3) Results: OGD/R insult activated the HMGB1/TLR4 axis for reducing the activity of glutamate clearance by inhibiting GLAST (glutamate aspartate transporter) expression in primary astrocytes. Interestingly, OGD/R-untreated astrocytes showed impairment of glutamate clearance after exposure to exogenous HMGB1 or conditioned medium from OGD/R-treated astrocytes culture. Inhibition of HMGB1 or TLR4 effectively prevented impaired glutamate clearance, which was induced by OGD/R, exogenous HMGB1, or conditioned medium from OGD/R-treated astrocytes. Furthermore, glycyrrhizic acid attenuated OGD/R-induced impairment of astrocytic glutamate clearance mediated by the HMGB1-TLR4 axis. (4) Conclusion: The HMGB1/TLR4 axis is a potential target for the treatment of post-ischemic excitotoxicity caused by GLAST dysfunction in astrocytes.

Biochemical and structural magnetic resonance imaging in chronic stroke and the relationship with upper extremity motor function

Background

Recovery of upper extremity (UE) motor function after stroke is variable from one to another due to heterogeneity of stroke pathology. Structural and biochemical magnetic resonance imaging of the primary motor cortex (M1) have been used to document reorganization of neural activity after stroke.

Objective

To assess cortical biochemical and structural causes of delayed recovery of UE motor function impairment in chronic subcortical ischemic stroke patients.

Methodology

A cross-sectional study with fifty patients were enrolled: thirty patients with chronic (> 6 months) subcortical ischemic stroke suffering from persistent UE motor function impairment (not improved group) and twenty patients with chronic subcortical ischemic stroke and improved UE motor function (improved group). We recruited a group of (16) age-matched healthy subjects. Single voxel proton magnetic resonance spectroscopy (1H-MRS) was performed to measure n-acetylaspartate (NAA) and glutamate+glutamine (Glx) ratios relative to creatine (Cr) in the precentral gyrus which represent M1of hand area in both ipsilesional and contralesional hemispheres. Brain magnetic resonance imaging (MRI) to measure precentral gyral thickness is representing the M1of hand area. UE motor function assessment is using the Fugl Meyer Assessment (FMA-UE) Scale.

Results

The current study found that ipslesional cortical thickness was significantly lower than contralesional cortical thickness among all stroke patients. Our study found that ipsilesional NAA/Cr ratio was lower than contralesional NAA/Cr among stroke patients. UE and hand motor function by FMA-UE showed highly statistically significant correlation with ipsilesional cortical thickness and ipsilesional NAA/Cr ratio, more powerful with NAA/Cr ratio.

Conclusion

We concluded that persistent motor impairment in individuals with chronic subcortical stroke may be at least in part related to ipsilesional structural and biochemical changes in motor areas remote from infarction in form of decreased cortical thickness and NAA/Cr ratio which had the strongest relationship with that impairment.

Silencing PAQR3 protects against oxygen-glucose deprivation/reperfusion-induced neuronal apoptosis via activation of PI3K/AKT signaling in PC12 cells

AIMS

Neuronal apoptosis acts as the pivotal pathogenesis of cerebral ischemia/reperfusion (I/R) injury after ischemic stroke. PAQR3 (progestin and adipoQ receptor family member 3) is a crucial player who participates in the regulation of cell death. We aim to explore the specific function and the underlying mechanism of PAQR3 in cerebral I/R induced neuronal injury.

MAIN METHODS

We established a mouse middle cerebral artery occlusion/reperfusion (MCAO/R) model and rat adrenal pheochromocytoma (PC12) cell oxygen-glucose deprivation/reperfusion (OGD/R) model to detect the expression and of PAQR3 after I/R treatment in vivo and in vitro. We used lentivirus to knockdown PAQR3 and investigated the function of PAQR3 in I/R induced neuronal apoptosis.

KEY FINDINGS

PAQR3 expression is markedly increased in the ischemic hemisphere of C57BL/6 mice and PC12 cells after I/R stimulation. Knockdown PAQR3 can attenuate neuronal apoptosis induced by I/R in PC12 cells and exerts neuroprotective effects. PAQR3 deficiency can significantly raise cell viability and suppress LDH leakage under I/R treatment. Silencing PAQR3 attenuates neuronal apoptosis remarkably with fewer TUNEL-positive cells and lower apoptosis rate under I/R treatment. Mechanistically, knockdown of PAQR3 can inhibit the apoptosis pathway through inducing anti-apoptotic proteins and inhibiting pro-apoptotic proteins. Besides, PI3K/AKT signaling suppression with LY294002 abolished the neuroprotective functions induced by silencing PAQR3.

SIGNIFICANCE

Our results elucidate that silencing PAQR3 can protect PC12 from OGD/R injury via activating PI3K/AKT pathway. And therefore, provide a novel therapeutic target for the prevention of cerebral I/R injury.

Metal-containing taurine compounds protect rat’s brain in reperfusion-induced injury

Introduction: The study aim was to explore a neuroprotective action of magnesium (LKhT-317) and zinc (LKhT-318) taurine salts on experimental models of reperfusion brain damage in rats and cell culture.

Materials and methods: The study was performed on male Sprague Dawley rats, and rat’s hippocampal mixed neuroglial cell culture. Magnesium- (LKhT-317) and zinc-containing (LKhT-318) derivatives of taurine were studied. Reperfusion brain damage was induced 30 min after intraluminal cerebral middle artery occlusion. Severity of the injury was assessed by local blood flowmetry, neurological symptoms scaling and brain tissue staining. Levels of IL-1b, IL-10 and TNF-alpha in tissue were determined by qualitative ELISA. Caspase-3 and Bcl-2 expressions were detected by IHC. Neurons survival was assessed by cytochemistry. Cellular calcium responses were detected by fluorescent microscopy of Fura-2-containig cells.

Results and discussion: Metal-containing taurine derivatives – LKhT-317 and LKhT-318 – demonstrated a sufficient neuroprotective property in rats with a reperfusion-induced brain injury. Both derivatives effectively prevented severity of the animals’ brain damage, motor deficiency, reduction of microvascular perfusion, and proinflammatory cytokines production. Magnesium-containing compound LKhT-317 was comparatively more effective than zinc-containing one. LKhT-317 possessed an anti-apoptotic action in vivo, and protected neurons from OGD-mediated cell death in mixed hippocampal culture. The aforementioned actions may be associated with an LKhT-317 inhibitory effect on NMDA-induced cellular Ca2+ response and, therefore, the anti-excitotoxic property of the compound.

Conclusion: Magnesium- and zinc-containing taurine derivatives may be considered as promising neuroprotectors in the reperfusion-induced brain injury.

Intravenous injection of apelin-13 improves sensory-motor balance deficits caused by cerebral ischemic reperfusion injury in male wistar rats via restoration of nitric oxide

It has been reported that apelin-13 possesses neuroprotective effects against cerebral ischemia/reperfusion injury (IRI). Disabilities in sense, movement and balance are the major stroke complications which, result in a high rate of mortality. Here, effects of intravenous (IV) injection of apelin-13 on the severity of neural death, infarct volume, neurological defects and its association with nitric oxide (NO) were investigated. A rat model of cerebral IRI was created by middle cerebral artery occlusion (MCAO) for 60 min and restoration of blood flow for 23 h. Animals were randomly assigned into six groups: sham, ischemia (MCAO), vehicle (MCAO + PBS) and three treatment groups (MCAO + apelin-13 in 10, 20, 40 μg/kg doses, IV). All injections were carried out via tail vein injection 5 min before reperfusion. Neural loss and infarct volume were evaluated by Nissl and 2,3,5-triphenyltetrazolium chloride (TTC) staining, respectively. Neurological defects were scored by standard modified criteria. Serum NO was measured by colorimetric method. Apelin-13 in doses of 20 and 40 μg/kg significantly reduced neural death, infarct volume and disturbance of sensory-motor balance compared to control and vehicle groups (p < 0.05). Serum NO levels reduced in MCAO groups compared to sham. Apelin-13 restored serum NO levels at 20 μg/kg dose (p < 0.05). Our data showed beneficial effect of IV injection of apelin-13 on sensory-motor balance defects by reducing neural death and restoration of serum NO levels. The present study shows the validity of apelin-13 in treatment of ischemic stroke in different administration methods.

Collagen Nanoparticle-Mediated Brain Silymarin Delivery: An Approach for Treating Cerebral Ischemia and Reperfusion-Induced Brain Injury

Silymarin is a bioactive constituent isolated from milk thistle (Silybum marinum). Since its discovery, silymarin has been considered a gold standard drug in treating ailments related to the liver, resulting from alcohol consumption and viral hepatitis. This hepatoprotective nature of silymarin arises out of antioxidative and tissue-regenerating properties of silymarin. However, several recent studies have established the neuroprotective link of silymarin, too. Thus, the current investigation was aimed at exploring the neuroprotective effect of nanosilymarin (silymarin encapsulated inside collagen-based polymeric nanoparticulate drug delivery system). The study aimed at bringing out the role of nanoparticles in enhancing the therapeutic effect of silymarin against neuronal injury, originating out of oxidative-stress-related brain damages in focal cerebral ischemia. Collagen-based micellar nanoparticles were prepared and stabilized using 3-ethyl carbodiimide-hydrochloride (EDC-Hcl) and malondialdehyde (MDA) as crosslinkers. Nanoparticles were characterized using dynamic light scattering (DLS), transmission electron microscopy (TEM), and Fourier transform infrared (FT-IR) spectroscopy techniques, and the size of nanoparticles was found to be around 48 nm. Male albino Wistar rats were pretreated with three different doses of nanosilymarin of 10, 100, and 1,000 μg/kg b.wt and a dose of free silymarin of 100 mg/kg b.wt intraperitoneally (i.p.) for 7 days. Focal cerebral ischemia was induced using the middle cerebral artery occlusion (MCAO) model on the eighth day for 1 h followed by 24 h reperfusion. The animals were then evaluated for neurobehavioral, infarct analysis, biochemical, histopathological, and immunohistochemical studies. All the above parameters showed remarkable improvement in nanosilymarin-treated groups in comparison to the silymarin-treated group. Nanoparticle encapsulation of drug enhanced neuroprotection by increasing drug bioavailability and targeting. Thus, the present study concluded with satisfactory results, showing the critical role played by nanoparticles in improving the neuroprotection at very low drug doses.

A20-Binding Inhibitor of NF-κB 1 Ameliorates Neuroinflammation and Mediates Antineuroinflammatory Effect of Electroacupuncture in Cerebral Ischemia/Reperfusion Rats

A20-binding inhibitor of NF-κB 1 (ABIN1) is an inhibitor of NF-κB and exerts anti-inflammatory effect. Electroacupuncture (EA) is considered as a neuroprotective strategy by inhibiting neuroinflammatory damage after cerebral ischemia. This study was performed to explore the role of ABIN1 and investigate whether the ABIN1 is involved in the mechanism of EA in cerebral ischemia/reperfusion (I/R) rats. Male Sprague-Dawley (SD) rats were subjected to middle cerebral artery occlusion/reperfusion (MCAO/R) and received EA after reperfusion once a day. Lentivirus-mediated ABIN1 gene knockdown was used to detect the role of ABIN1 in neuroinflammation after I/R. ABIN1 expression, proinflammatory cytokine levels, microglial activation, neurological function, infarct volumes, and NF-κB activation were assessed. ABIN1 expression was elevated in the peri-infarct cortex and was further upregulated by EA. ABIN1 knockdown increased the levels of proinflammatory cytokines and activation of microglia, worsened neurological deficits, and enlarged the infarct volume. Moreover, ABIN1 was blocked to partially reverse the neuroprotective effect of EA, and this treatment weakened the ability of EA to suppress NF-κB activity. Based on these findings, ABIN1 is a potential suppressor of neuroinflammation and ABIN1 mediates the antineuroinflammatory effect of EA in cerebral I/R rats.

Let-7f promotes the differentiation of neural stem cells in rats

Hypoxic-ischemic brain damage (HIBD) is the major recognized perinatal cause of neurological morbidity in full-term new borns. Neural stem cells (NSCs) have been extensively studied because of their clinical applications in treating neuro degenerative diseases and brain injuries, including HIBD, while microRNAs (miRNAs) are deemed critical regulators of the proliferation and differentiation of NSCs. However, the role of let-7f in NSC differentiation remains unknown. Our study aims to investigate the role of let-7f in the differentiation of NSCs and brain development in rats and hence to explore the therapeutic potential of let-7f in the treatment of HIBD. The quantitative real-time polymerase chain reaction (qRT-PCR) was applied to assess the expressions of let-7f, and western blot was performed to detect GFAP, Tuj1 and Nestin in rat brains at postnatal day 1, 8 and 14 (n=12 per time point). The NSCs isolated from the brains of rat fetuses at gestational day 15 were transduced with lenti virus expressing let-7f or let-7f inhibitor so as to observe altered expressions of let-7f, GFAP, Tuj1 and Nestin. A gradually-increasing expression of let-7f was detected by qRT-PCR in rat brain tissues during postnatal brain development. Increased levels of GFAP and Tuj1, while a decreased level of Nestin, were detected by western blot in let-7f-overexpressing NSCs. In contrast, the cells expressing the let-7f inhibitor exhibited lower levels of GFAP and Tuj1, while a higher level of Nestin, compared with control cells. Therefore, let-7f is involved in brain development and promotes the differentiation of NSCs in rats.

Transcriptional block of AMPK-induced autophagy promotes glutamate excitotoxicity in nutrient-deprived SH-SY5Y neuroblastoma cells

We investigated the role of autophagy, a controlled lysosomal degradation of cellular macromolecules and organelles, in glutamate excitotoxicity during nutrient deprivation in vitro. The incubation in low-glucose serum/amino acid-free cell culture medium synergized with glutamate in increasing AMP/ATP ratio and causing excitotoxic necrosis in SH-SY5Y human neuroblastoma cells. Glutamate suppressed starvation-triggered autophagy, as confirmed by diminished intracellular acidification, lower LC3 punctuation and LC3-I conversion to autophagosome-associated LC3-II, reduced expression of proautophagic beclin-1 and ATG5, increase of the selective autophagic target NBR1, and decreased number of autophagic vesicles. Similar results were observed in PC12 rat pheochromocytoma cells. Both glutamate-mediated excitotoxicity and autophagy inhibition in starved SH-SY5Y cells were reverted by NMDA antagonist memantine and mimicked by NMDA agonists D-aspartate and ibotenate. Glutamate reduced starvation-triggered phosphorylation of the energy sensor AMP-activated protein kinase (AMPK) without affecting the activity of mammalian target of rapamycin complex 1, a major negative regulator of autophagy. This was associated with reduced mRNA levels of autophagy transcriptional activators (FOXO3, ATF4) and molecules involved in autophagy initiation (ULK1, ATG13, FIP200), autophagosome nucleation/elongation (ATG14, beclin-1, ATG5), and autophagic cargo delivery to autophagosomes (SQSTM1). Glutamate-mediated transcriptional repression of autophagy was alleviated by overexpression of constitutively active AMPK. Genetic or pharmacological AMPK activation by AMPK overexpression or metformin, as well as genetic or pharmacological autophagy induction by TFEB overexpression or lithium chloride, reduced the sensitivity of nutrient-deprived SH-SY5Y cells to glutamate excitotoxicity. These data indicate that transcriptional inhibition of AMPK-dependent cytoprotective autophagy is involved in glutamate-mediated excitotoxicity during nutrient deprivation in vitro.

Characterization of brain-derived extracellular vesicles reveals changes in cellular origin after stroke and enrichment of the prion protein with a potential role in cellular uptake

Extracellular vesicles (EVs) are important means of intercellular communication and a potent tool for regenerative therapy. In ischaemic stroke, transient blockage of a brain artery leads to a lack of glucose and oxygen in the affected brain tissue, provoking neuronal death by necrosis in the core of the ischaemic region. The fate of neurons in the surrounding penumbra region depends on the stimuli, including EVs, received during the following hours. A detailed characterization of such stimuli is crucial not only for understanding stroke pathophysiology but also for new therapeutic interventions. In the present study, we characterize the EVs in mouse brain under physiological conditions and 24 h after induction of transient ischaemia in mice. We show that, in steady-state conditions, microglia are the main source of small EVs (sEVs), whereas after ischaemia the main sEV population originates from astrocytes. Brain sEVs presented high amounts of the prion protein (PrP), which were further increased after stroke. Moreover, EVs were enriched in a proteolytically truncated PrP fragment (PrP-C1). Because of similarities between PrP-C1 and certain viral surface proteins, we studied the cellular uptake of brain-derived sEVs from mice lacking (PrP-KO) or expressing PrP (WT). We show that PrP-KO-sEVs are taken up significantly faster and more efficiently than WT-EVs by primary neurons. Furthermore, microglia and astrocytes engulf PrP-KO-sEVs more readily than WT-sEVs. Our results provide novel information on the relative contribution of brain cell types to the sEV pool in murine brain and indicate that increased release of sEVs by astrocytes together with elevated levels of PrP in sEVs may play a role in intercellular communication at early stages after stroke. In addition, amounts of PrP (and probably PrP-C1) in brain sEVs seem to contribute to regulating their cellular uptake.

Mixed Lineage Leukemia 1 Promoted Neuron Apoptosis in Ischemic Penumbra via Regulating ASK-1/TNF-α Complex

Neuron apoptosis in ischemic penumbra was proved to be involved in ischemic stroke (IS) development and contributed to the poor prognosis of IS. Recent studies showed that aberrant trimethylation of histone H3 lysine 4 (H3K4me3) level was associated with cell apoptosis. This study aimed to explore the underlying mechanism of neuron apoptosis in ischemic penumbra via histone methyltransferase (HMT) mixed lineage leukemia 1 (MLL1) mediated epigenetic pathway. Mouse IS model was established by middle cerebral artery occlusion (MCAO). Mouse primary cortical mixed cells were cultured and treated with oxygen–glucose deprivation (OGD) to simulate IS process. The expressions of apoptosis signal regulating kinase-1 (ASK-1), pASK-1, cleaved caspase-3, ASK-1/serine–threonine kinase receptor-associated protein (STRAP)/14-3-3 complex, ASK-1/tumor necrosis factor-α (TNF-α) complex, and MLL1 in mouse brain tissue and mouse primary cortical mixed cells were analyzed. The function of MLL1 was investigated using small interfering RNA (siRNA) targeting MLL1 and vector overexpressing MLL1. In vivo inhibition of MLL1 was conducted to explore its value as a therapeutic target. The prognostic value of MLL1 was investigated in IS patients. Results showed that the expressions of ASK-1, pASK-1, cleaved caspase-3, ASK-1/TNF-α complex, and MLL1 increased significantly in ischemic penumbra compared to brain tissue from the control group (P < 0.05). MCAO and OGD significantly upregulated the H3K4me3 level in ASK-1 promoter region and promoted the recruitment of MLL1 to this region (P < 0.05). siMLL1 significantly reversed the proapoptosis effects of OGD in primary cortical mixed cells, while MLL1 overexpression induced apoptosis of cells (P < 0.05). In vivo inhibition of MLL1 significantly reduced the infarct volume and the neurological score of MCAO mice (P < 0.05). Serum MLL1 level had a positive association with that in ischemic core and penumbra in mouse model and was positively correlated with the infarct volume and neurological score (P < 0.05). Besides, serum MLL1 level was also significantly correlated with the severity of IS (P < 0.05), and high serum MLL1 level indicated poor prognosis of IS patients (P < 0.05). These results revealed that MLL1 contributed to neuron cell apoptosis in ischemic penumbra after IS onset by promoting the formation of ASK-1/TNF-α complex, and its serum level was associated with poor prognosis of IS.

Atorvastatin Improves Mitochondrial Function and Prevents Oxidative Stress in Hippocampus Following Amyloid-β1-40 Intracerebroventricular Administration in Mice

Amyloid-β (Aβ) peptides play a significant role in the pathogenesis of Alzheimer's disease (AD). Neurotoxic effects promoted by Aβ peptides involve glutamate transmission impairment, decrease of neurotrophic factors, mitochondrial dysfunction, oxidative stress, synaptotoxicity, and neuronal degeneration. Here, we assessed the early events evoked by Aβ_1-40 on the hippocampus. Additionally, we sought to unravel the molecular mechanisms of atorvastatin preventive effect on Aβ-induced hippocampal damage. Mice were treated orally (p.o.) with atorvastatin 10 mg/kg/day during 7 consecutive days before the intracerebroventricular (i.c.v.) infusion of Aβ_1-40 (400 pmol/site). Twenty-four hours after Aβ_1-40 infusion, a reduced content of mature BDNF/proBDNF ratio was observed in Aβ-treated mice. However, there is no alteration in synaptophysin, PSD-95, and doublecortin immunocontent in the hippocampus. Aβ_1-40 promoted an increase in reactive oxygen species (ROS) and nitric oxide (NO) generation in hippocampal slices, and atorvastatin prevented this oxidative burst. Mitochondrial OXPHOS was measured by high-resolution respirometry. At this time point, Aβ_1-40 did not alter the O₂ consumption rates (OCR) related to phosphorylating state associated with complexes I and II, and the maximal OCR. However, atorvastatin increased OCR of phosphorylating state associated with complex I and complexes I and II, maximal OCR of complexes I and II, and OCR associated with mitochondrial spare capacity. Atorvastatin treatment improved mitochondrial function in the rodent hippocampus, even after Aβ infusion, pointing to a promising effect of improving brain mitochondria bioenergetics. Therefore, atorvastatin could act as an adjuvant in battling the symptoms of AD to preventing or delaying the disease progression.

Show Me Your Friends and I Tell You Who You Are: The Many Facets of Prion Protein in Stroke

Ischemic stroke belongs to the leading causes of mortality and disability worldwide. Although treatments for the acute phase of stroke are available, not all patients are eligible. There is a need to search for therapeutic options to promote neurological recovery after stroke. The cellular prion protein (PrPC) has been consistently linked to a neuroprotective role after ischemic damage: it is upregulated in the penumbra area following stroke in humans, and animal models of stroke have shown that lack of PrPC aggravates the ischemic damage and lessens the functional outcome. Mechanistically, these effects can be linked to numerous functions attributed to PrPC: (1) as a signaling partner of the PI3K/Akt and MAPK pathways, (2) as a regulator of glutamate receptors, and (3) promoting stem cell homing mechanisms, leading to angio- and neurogenesis. PrPC can be cleaved at different sites and the proteolytic fragments can account for the manifold functions. Moreover, PrPC is present on extracellular vesicles (EVs), released membrane particles originating from all types of cells that have drawn attention as potential therapeutic tools in stroke and many other diseases. Thus, identification of the many mechanisms underlying PrPC-induced neuroprotection will not only provide further understanding of the physiological functions of PrPC but also new ideas for possible treatment options after ischemic stroke.

Apoptosis regulation in the penumbra after ischemic stroke: expression of pro- and antiapoptotic proteins

Ischemic stroke is the leading cause of human disability and mortality in the world. The main problem in stroke therapy is the search of efficient neuroprotector capable to rescue neurons in the potentially salvageable transition zone (penumbra), which is expanding after brain damage. The data on molecular mechanisms of penumbra formation and expression of diverse signaling proteins in the penumbra during first 24 h after ischemic stroke are discussed. Two basic features of cell death regulation in the ischemic penumbra were observed: (1) both apoptotic and anti-apoptotic proteins are simultaneously over-expressed in the penumbra, so that the fate of individual cells is determined by the balance between these opposite tendencies. (2) Similtaneous and concerted up-regulation in the ischemic penumbra of proteins that execute apoptosis (caspases 3, 6, 7; Bcl-10, SMAC/DIABLO, AIF, PSR), signaling proteins that regulate different apoptosis pathways (p38, JNK, DYRK1A, neurotrophin receptor p75); transcription factors that control expression of various apoptosis regulation proteins (E2F1, p53, c-Myc, GADD153); and proteins, which are normally involved in diverse cellular functions, but stimulate apoptosis in specific situations (NMDAR2a, Par4, GAD65/67, caspase 11). Hence, diverse apoptosis initiation and regulation pathways are induced simultaneously in penumbra from very different initial positions. Similarly, various anti-apoptotic proteins (Bcl-x, p21/WAF-1, MDM2, p63, PKBα, ERK1, RAF1, ERK5, MAKAPK2, protein phosphatases 1α and MKP-1, estrogen and EGF receptors, calmodulin, CaMKII, CaMKIV) are upregulated. These data provide an integral view of neurodegeneration and neuroprotection in penumbra. Some discussed proteins may serve as potential targets for anti-stroke therapy.

Metformin preferentially provides neuroprotection following cardiac ischemia/reperfusion in non-diabetic rats

Following acute myocardial infarction, re-establishment of coronary perfusion aggravates further injuries in the heart and remote organs including the brain as a consequence of ischemia/reperfusion (I/R) injury. Since pretreatment with metformin attenuated both cardiac and cerebral I/R injury via AMP-activated protein kinase (AMPK) pathways, we hypothesized that metformin given after ischemia mitigates both cardiac and brain pathologies following cardiac I/R. Male Wistar rats were subjected to either cardiac I/R (30 min-ischemia/120 min-reperfusion; n = 30) or sham operation (n = 5). Metformin 200 mg/kg was given intravenously to the cardiac I/R group (n = 10/group), either during ischemia (D-MET) or at the onset of reperfusion (R-MET). Left ventricular ejection fraction (LVEF) and arrhythmia scores were determined. The heart and brain tissues were collected to determine the extent of injury, mitochondrial function, and apoptosis. Additionally, microglial morphology, Alzheimer's proteins, and dendritic spine density were determined in the brain. Cardiac I/R led to not only reduced LVEF, cardiac mitochondrial dysfunction, and arrhythmias, but also brain mitochondrial dysfunction, apoptosis, Alzheimer's protein aggregation, microglial activation, and dendritic spine loss. A single dose of metformin did not alter p-AMPK/AMPK in both organs. In the heart, impaired LVEF, arrhythmias, infarct size expansion, mitochondrial dysfunction, and apoptosis were not alleviated. On the contrary, metformin attenuated brain mitochondrial dysfunction, apoptosis, and Alzheimer's protein levels. Microglial morphology and dendritic spine density were additionally preserved in D-MET group. In conclusion, metformin given during ischemia preferentially provides neuroprotection against brain mitochondrial dysfunction, apoptosis, microglial activation, and dendritic spine loss in an AMPK-independent manner following cardiac I/R injury.

Metabolomics coupled with integrative pharmacology reveals the therapeutic effect of l-borneolum against cerebral ischaemia in rats

Objectives

This study aimed to investigate metabolic biomarker changes and related metabolic pathways before and after treatment with l-borneolum in cerebral ischaemic rats.

Methods

Rats were subjected to pMCAO surgery. The Zea-Longa scoring method was used to evaluate neurological deficits. TTC staining was used to observe cerebral infarction. HE staining was used to observe the pathological changes in brain tissue. The metabolomics method was used to analyse the changes in metabolism.

Results

The pharmacology changes of the H-B group were significantly different from those of the vehicle group. Moreover, according to the metabolomics method, identification of potential biomarkers in cerebral ischaemia treatment showed that the levels of l-valine and l-arginine were increased while the levels of N-succinyl-L,L-2,6-diaminopimelate and LysoPC (18 : 1(9Z)) were reduced, which were related to energy metabolism. Simultaneously, thermogenesis and bile secretion levels were inhibited by l-borneolum. Furthermore, elevated level of methotrexate might be related to an anti-inflammatory effect.

Conclusions

The therapeutic effect of l-borneolum on cerebral ischaemia might be associated with the regulation of energy metabolism, thermogenesis and bile secretion. These metabolic changes and the core target changes, as well as the metabolic-target pathway network, help to elucidate the mechanisms governing the effect of l-borneolum on cerebral ischaemia.

Systems Pharmacology-Dissection of the Molecular Mechanisms of Dragon's Blood in Improving Ischemic Stroke Prognosis

Materials and Methods

(1) Based on system-pharmacology platform, the potential active compounds of DB are screened out according to ADME. (2) The ischemic stroke-related targets are predicted by utilizing these active compounds as probes, mapping the targets to the CTD database to establish a molecular-target-disease network. (3) To analyze the mechanism of DB treatment for the prognosis of ischemic stroke, we used the Metascape and DAVID databases to construct "ischemic stroke pathways". (4) PC12 cells were used to explore the protective effect of loureirin B on oxygen-glucose deprivation/reperfusion (OGD/R) injury, and BV-2 cells were used to determine the anti-inflammation effect of 4',7-dihydroxyflavone.

Results

Finally, we obtained 38 active compounds and 58 stroke-related targets. Network and pathway analysis indicate that DB is effective in the treatment of ischemic stroke by enhancing cell survival and inhibiting inflammatory and antiplatelet activation. In in vitro experiments, the main component loureirin B promoted the expression of HO-1 and Bcl-2 via positive regulation of PI3K/AKT/CREB and Nrf2 signaling pathways in PC12 cells against OGD/R damage. And the anti-inflammatory activity of 4',7-dihydroxyflavone was related to the inhibition of COX-2, TNF-α, and IL-6 in LPS-induced BV-2 cells.

Conclusions

In our study, the results illustrated that DB in improving ischemic stroke prognosis may involve enhancing cell survival and antioxidant, anti-inflammation, and antiplatelet activities.

Toll-Like Receptor 4 Signaling in Focal Cerebral Ischemia: a Focus on the Neurovascular Unit

A robust innate immune activation leads to downstream expression of inflammatory mediators that amplify tissue damage and consequently increase the morbidity after stroke. The Toll-like receptor 4 (TLR4) pathway is a major innate immune pathway activated acutely and chronically after stroke. Hence, understanding the intricacies of the temporal profile, specific control points, and cellular specificity of TLR4 activation is crucial for the development of any novel therapeutics targeting the endogenous innate immune response after focal cerebral ischemia. The goal of this review is to summarize the current findings related to TLR4 signaling after stroke with a specific focus on the components of the neurovascular unit such as astrocytes, neurons, endothelial cells, and pericytes. In addition, this review will examine the effects of focal cerebral ischemia on interaction of these neurovascular unit components.

Ischemia-Triggered Glutamate Excitotoxicity From the Perspective of Glial Cells

A plethora of neurological disorders shares a final common deadly pathway known as excitotoxicity. Among these disorders, ischemic injury is a prominent cause of death and disability worldwide. Brain ischemia stems from cardiac arrest or stroke, both responsible for insufficient blood supply to the brain parenchyma. Glucose and oxygen deficiency disrupts oxidative phosphorylation, which results in energy depletion and ionic imbalance, followed by cell membrane depolarization, calcium (Ca²⁺) overload, and extracellular accumulation of excitatory amino acid glutamate. If tight physiological regulation fails to clear the surplus of this neurotransmitter, subsequent prolonged activation of glutamate receptors forms a vicious circle between elevated concentrations of intracellular Ca²⁺ ions and aberrant glutamate release, aggravating the effect of this ischemic pathway. The activation of downstream Ca²⁺-dependent enzymes has a catastrophic impact on nervous tissue leading to cell death, accompanied by the formation of free radicals, edema, and inflammation. After decades of “neuron-centric” approaches, recent research has also finally shed some light on the role of glial cells in neurological diseases. It is becoming more and more evident that neurons and glia depend on each other. Neuronal cells, astrocytes, microglia, NG2 glia, and oligodendrocytes all have their roles in what is known as glutamate excitotoxicity. However, who is the main contributor to the ischemic pathway, and who is the unsuspecting victim? In this review article, we summarize the so-far-revealed roles of cells in the central nervous system, with particular attention to glial cells in ischemia-induced glutamate excitotoxicity, its origins, and consequences.

Xanthohumol protects neuron from cerebral ischemia injury in experimental stroke

Treatment of antioxidants is necessary to protect ischemic stroke associated neuronal damage. Xanthohumol (XN), a natural flavonoid extracted from hops, has been reported to have potential function as an antioxidant and can be used for neuro protection. However, the role of XN in ischemic stroke remains unclear. Here, we studied the neuroprotective effects of XN through experimental stroke models. Middle cerebral artery occlusion (MCAO) and oxygen-glucose deprivation (OGD) was used as in vivo and in vitro model, respectively. We found that the treatment of XN improved MCAO-induced brain injury by reducing infarct size, improving neurological deficits, reversing neuronal damage, reducing oxidative stress injury and cell apoptosis. Further experimental studies showed that XN could revive neuronal apoptosis induced by OGD by preventing oxidative stress injury. In addition, our study suggested that these effects were related to the inhibition of phosphorylation of p38-MAPK and the mediation of nuclear Nrf2 activation. In conclusion, the neuroprotective effects of XN showed in this study make XN a promising supplement for ischemic stroke protection.

Treadmill exercise improves neurological function by inhibiting autophagy and the binding of HMGB1 to Beclin1 in MCAO juvenile rats

AIMS

Treadmill exercise is a beneficial treatment following childhood stroke. Thus, studies focusing on the neuroprotective mechanism of exercise training during postischemic treatment in children with ischemic stroke are urgently needed. We evaluated the effects of treadmill exercise on autophagy after cerebral ischemia in young rats.

MAIN METHODS

Rats (23-25 days old) underwent cerebral ischemia-reperfusion (CI/R) surgery. The experimental animals were divided into 5 groups, and some groups received either treadmill exercise, a rapamycin (RAPA) injection or combination therapy for 3 or 7 days. We performed a series of experimental tests including neurological scoring, hematoxylin-eosin staining (H&E), Nissl staining, triphenyl tetrazolium chloride (TTC) staining, Western blot analysis (WB), immunofluorescence (IF), enzyme-linked immunosorbent assay (ELISA), transmission electron microscopy (TEM) and Terminal deoxynucleotidyl transferase-mediated dUTP-digoxigenin nick end labeling (TUNEL) fluorescence.

KEY FINDINGS

The experimental data indicated that treadmill exercise inhibited autophagy in the ischemic penumbra, inhibited high mobility group box 1 (HMGB1) translocation and binding to Beclin1, reduced apoptosis, reduced infarct volumes, and aided in functional recovery. However, RAPA promoted the opposite effects of treadmill exercise.

SIGNIFICANCE

We found that treadmill exercise improves the neurological deficits induced by CI/R by inhibiting autophagy and HMGB1 binding to Beclin1.

Quantitative Proteomics Reveals the Beneficial Effects of Low Glucose on Neuronal Cell Survival in an in vitro Ischemic Penumbral Model

Understanding proteomic changes in the ischemic penumbra are crucial to rescue those salvageable cells and reduce the damage of an ischemic stroke. Since the penumbra region is dynamic with heterogeneous cells/tissues, tissue sampling from animal models of stroke for the molecular study is a challenge. In this study, cultured hippocampal HT22 cells under hypoxia treatment for 17.5 h with 0.69 mM low glucose (H+LG) could mimic ischemic penumbral cells since they had much higher cell viability and viable cell number compared to hypoxia without glucose (H-G) treatment. To validate established cell-based ischemic penumbral model and understand the beneficial effects of low glucose (LG), quantitative proteomics analysis was performed on H+LG, H-G, and normoxia with normal 22 mM glucose (N+G) treated cells. We identified 427 differentially abundant proteins (DAPs) between H-G and N+G and further identified 105 DAPs between H+LG and H-G. Analysis of 105 DAPs revealed that LG promotes cell survival by activating HIF1α to enhance glycolysis; preventing the dysregulations of extracellular matrix remodeling, cell cycle and division, and antioxidant and detoxification; as well as attenuating inflammatory reaction response, protein synthesis and neurotransmission activity. Our results demonstrated that this established cell-based system could mimic penumbral conditions and can be used for molecular studies.

Monitoring maturation of neural stem cell grafts within a host microenvironment

Neural stem cells (NSC) act as a versatile tool for neuronal cell replacement strategies to treat neurodegenerative disorders in which functional neurorestorative mechanisms are limited. While the beneficial effects of such cell-based therapy have already been documented in terms of neurodegeneration of various origins, a neurophysiological basis for improvement in the recovery of neurological function is still not completely understood. This overview briefly describes the cumulative evidence from electrophysiological studies of NSC-derived neurons, aimed at establishing the maturation of differentiated neurons within a host microenvironment, and their integration into the host circuits, with a particular focus on the neurogenesis of NSC grafts within the post-ischemic milieu. Overwhelming evidence demonstrates that the host microenvironment largely regulates the lineage of NSC grafts. This regulatory role, as yet underestimated, raises possibilities for the favoured maturation of a subset of neural phenotypes in order to gain timely remodelling of the impaired brain tissue and amplify the therapeutic effects of NSC-based therapy for recovery of neurological function.

Stanniocalcin-1 ameliorates cerebral ischemia by decrease oxidative stress and blood brain barrier permeability

Blood brain barrier (BBB) permeability and oxidative stress have been reported to be important mechanisms for brain damage following ischemic stroke and stanniocalcin-1 (STC-1), a neuroprotective protein, has anti-inflammatory and anti-oxidative stress properties. Herein, we report the effect of STC-1 on BBB permeability and brain oxidative stress after stroke in an animal model. Male Wistar received an intracerebroventricularly injection of human recombinant STC-1 (100 ng/kg) or saline and were subjected to sham procedure or global cerebral ischemia/reperfusion (I/R) model. Six and 24 h after I/R, neurological evaluation was performed; at 24 h brain water content was evaluated in the total brain, and BBB permeability, nitrite/nitrate (N/N) concentration, lipid peroxidation, protein carbonyls formation, superoxide dismutase (SOD) and catalase (CAT) activity were determined in the hippocampus, cortex, prefrontal cortex, striatum and cerebellum. Rats exhibited neurological deficit at 6 and 24 h after I/R and STC-1 reduction at 24 h. After I/R there were an increase of brain water content, BBB permeability in the hippocampus, cortex and pre-frontal cortex and N/N in the hippocampus, and STC-1 decreased this level only in the hippocampus. STC-1 decreased lipid peroxidation in the hippocampus, cortex and prefrontal cortex and protein oxidative damage in the hippocampus and cortex. SOD activity decreased in the hippocampus, cortex and prefrontal cortex after I/R and STC-1 reestablished these levels in the hippocampus and cortex. CAT activity decreased only in the hippocampus and cortex and STC-1 increased the CAT activity in the hippocampus. Our data provide the first experimental demonstration that STC-1 reduced brain dysfunction associated with cerebral I/R in rats, by decreasing BBB permeability and oxidative stress parameters.

A novel free radical scavenger, NSP-116, ameliorated the brain injury in both ischemic and hemorrhagic stroke models

Reperfusion injury is a serious problem in ischemic stroke therapy, which leads to neuronal damage and intracranial hemorrhage (ICH). A novel free radical scavenger, NSP-116, has anti-oxidative effect and may ameliorate reperfusion injury. The purpose of this study was to investigate the effects of NSP-116 on both ischemic and hemorrhagic stroke models. First, we assessed whether NSP-116 has protective effects in vitro. Pre-treatment of NSP-116 decreased neuronal cell damage induced by H₂O₂ or LPS. Moreover, NSP-116 also suppressed mitochondria damage and apoptosis in H₂O₂-induced neuronal injury model. Based on these results, we used a middle cerebral artery occlusion (MCAO)-induced ischemic stroke model or a collagenase-induced ICH model. Using the MCAO model, we evaluated the cerebral blood flow (CBF), neurological deficit, and infarct volume. Hematoma volume was assessed at 3 days after ICH. In the MCAO model, oral administration of NSP-116 at 30 mg/kg attenuated the reduction of CBF, neurological deficits, and infarct formation. Interestingly, NSP-116 also ameliorated hematoma expansion and neurological deficits in the ICH model. Additionally, pre-treatment of NSP-116 suppressed the brain microvascular endothelial cell death induced by collagenase treatment. Collectively, our findings indicated that oral administration of NSP-116 attenuates both ischemic and hemorrhagic brain injuries after stroke.

Roles of glial ion transporters in brain diseases

Glial ion transporters are important in regulation of ionic homeostasis, cell volume, and cellular signal transduction under physiological conditions of the central nervous system (CNS). In response to acute or chronic brain injuries, these ion transporters can be activated and differentially regulate glial functions, which has subsequent impact on brain injury or tissue repair and functional recovery. In this review, we summarized the current knowledge about major glial ion transporters, including Na⁺ /H⁺ exchangers (NHE), Na⁺ /Ca²⁺ exchangers (NCX), Na⁺ -K⁺ -Cl^- cotransporters (NKCC), and Na⁺ -HCO₃ ^- cotransporters (NBC). In acute neurological diseases, such as ischemic stroke and traumatic brain injury (TBI), these ion transporters are rapidly activated and play significant roles in regulation of the intra- and extracellular pH, Na⁺ , K⁺ , and Ca²⁺ homeostasis, synaptic plasticity, and myelin formation. However, overstimulation of these ion transporters can contribute to glial apoptosis, demyelination, inflammation, and excitotoxicity. In chronic brain diseases, such as glioma, Alzheimer's disease (AD), Parkinson's disease (PD), and multiple sclerosis (MS), glial ion transporters are involved in the glioma Warburg effect, glial activation, neuroinflammation, and neuronal damages. These findings suggest that glial ion transporters are involved in tissue structural and functional restoration, or brain injury and neurological disease development and progression. A better understanding of these ion transporters in acute and chronic neurological diseases will provide insights for their potential as therapeutic targets.

Modes of Calcium Regulation in Ischemic Neuron

Calcium (Ca2+) dysregulation is a major catalytic event. Ca2+ dysregulation leads to neuronal cell death and brain damage result in cerebral ischemia. Neurons are unable in maintaining calcium homeostasis. Ca2+ homeostasis imbalance results in increased calcium influx and impaired calcium extrusion across the plasma membrane. Ca2+ dysregulation is mediated by different cellular and biochemical mechanism, which leads to neuronal loss resulting stroke/cerebral ischemia. A better understanding of the Ca2+ dysregulation might help in the development of new treatments in order to reduce ischemic brain injury. An optimal concentration of Ca2+ does not lead to neurotoxicity in the ischemic neuron. Intracellular Ca2+ act as a trigger for acute neurotoxicity and this cause induction of long-lasting processes leading to necrotic and/or apoptotic post-ischemic delayed neuronal death or of compensatory, neuroprotective mechanisms has increased considerably. Moreover, routes of ischemic Ca2+ influx to neurons, involvement of intracellular Ca2+ stores and Ca2+ buffers, spatial and temporal relations between ischemia-induced increases in intracellular Ca2+ concentration and neurotoxicity will further increase our understanding about underlying mechanism and they can act as a target for the development of drugs. Here, in our article we are trying to provide a brief overview of various Ca2+ influx pathways involve in ischemic neuron and how ischemic neuron attempts to counterbalance this calcium overload.

Tooth loss causes spatial cognitive impairment in rats through decreased cerebral blood flow and increased glutamate

OBJECTIVE

The loss of teeth not only causes damage to oral function but also is associated with cognitive impairment. Previous studies have reported that chewing can increase CBF, and CBF plays an important role in cognitive function. Whether the loss of teeth can lead to cognitive impairment by reducing CBF is unclear. This study aimed to investigate the changes in CBF, glutamate concentration, the expression of neuronal apoptosis-relatedBax/Bcl-2 and Caspase-3 mRNA and pyramidal cells in the hippocampus, as well as behavioral changes after tooth loss in rats.

DESIGN

Twelve weeks after the extraction of all maxillary molars in rats, their spatial learning and memory were tested by the Morris water maze, the CBF was detected by ASL-MRI and glutamate concentration was detected by HPLC; the expression of neuronal apoptosis-related Bax/Bcl-2 and Caspase-3 mRNA and the number of pyramidal cells in the CA1 region were also measured.

RESULTS

Rats with tooth loss exhibited spatial cognitive impairment in the Morris water maze, decreased CBF, increased glutamate levels andBax/Bcl-2 and Caspase-3 mRNA expression in the hippocampus; the number of pyramidal cells in the CA1 region were also reduced.

CONCLUSIONS

These findings suggest that the loss of teeth causes spatial cognitive impairment in rats and that the underlying mechanism might be associated with a decrease in CBF and an increase in the glutamate level in the hippocampus.

MicroRNAs in Neuroinflammation: Implications in Disease Pathogenesis, Biomarker Discovery and Therapeutic Applications

The central nervous system can respond to threat via the induction of an inflammatory response. Under normal circumstances this response is tightly controlled, however uncontrolled neuroinflammation is a hallmark of many neurological disorders. MicroRNAs are small non-coding RNA molecules that are important for regulating many cellular processes. The ability of microRNAs to modulate inflammatory signaling is an area of ongoing research, which has gained much attention in recent years. MicroRNAs may either promote or restrict inflammatory signaling, and either exacerbate or ameliorate the pathological consequences of excessive neuroinflammation. The aim of this review is to summarize the mode of regulation for several important and well-studied microRNAs in the context of neuroinflammation, including miR-155, miR-146a, miR-124, miR-21 and let-7. Furthermore, the pathological consequences of miRNA deregulation during disorders that feature neuroinflammation are discussed, including Multiple Sclerosis, Alzheimer’s disease, Parkinson’s disease, Prion diseases, Japanese encephalitis, Herpes encephalitis, ischemic stroke and traumatic brain injury. There has also been considerable interest in the use of altered microRNA signatures as biomarkers for these disorders. The ability to modulate microRNA expression may even serve as the basis for future therapeutic strategies to help treat pathological neuroinflammation.

Hypoxia Induces Astrocyte-Derived Lipocalin-2 in Ischemic Stroke

Ischemic stroke causes rapid hypoxic damage to the core neural tissue which is followed by graded chronological tissue degeneration in the peri-infarct zone. The latter process is mainly triggered by neuroinflammation, activation of inflammasomes, proinflammatory cytokines, and pyroptosis. Besides microglia, astrocytes play an important role in the fine-tuning of the inflammatory network in the brain. Lipocalin-2 (LCN2) is involved in the control of innate immune responses, regulation of excess iron, and reactive oxygen production. In this study, we analyzed LCN2 expression in hypoxic rat brain tissue after ischemic stroke and in astrocyte cell cultures receiving standardized hypoxic treatment. Whereas no LCN2-positive cells were seen in sham animals, the number of LCN2-positive cells (mainly astrocytes) was significantly increased after stroke. In vitro studies with hypoxic cultured astroglia revealed that LCN2 expression is significantly increased after only 2 h, then further increased, followed by a stepwise decline. The expression pattern of several proinflammatory cytokines mainly followed that profile in wild type (WT) but not in cultured LCN2-deficient astrocytes. Our data revealed that astrocytes are an important source of LCN2 in the peri-infarct region under hypoxic conditions. However, we must also stress that brain-intrinsic LCN2 after the initial hypoxia period might come from other sources such as invaded immune cells and peripheral organs via blood circulation. In any case, secreted LCN2 might have an influence on peripheral organ functions and the innate immune system during brain hypoxia.