Neurotransmitters in the mediation of cerebral ischemic injury

GABAergic system and chloride cotransporters as potential therapeutic targets to mitigate cell death in ischemia

Gamma aminobutyric acid (GABA) is a critical inhibitory neurotransmitter in the central nervous system that plays a vital role in modulating neuronal excitability. Dysregulation of GABAergic signaling, particularly involving the cotransporters NKCC1 and KCC2, has been implicated in various pathologies, including epilepsy, schizophrenia, autism spectrum disorder, Down syndrome, and ischemia. NKCC1 facilitates chloride influx, whereas KCC2 mediates chloride efflux via potassium gradient. Altered expression and function of these cotransporters have been associated with excitotoxicity, inflammation, and cellular death in ischemic events characterized by reduced cerebral blood flow, leading to compromised tissue metabolism and subsequent cell death. NKCC1 inhibition has emerged as a potential therapeutic approach to attenuate intracellular chloride accumulation and mitigate neuronal damage during ischemic events. Similarly, targeting KCC2, which regulates chloride efflux, holds promise for improving outcomes and reducing neuronal damage under ischemic conditions. This review emphasizes the critical roles of GABA, NKCC1, and KCC2 in ischemic pathologies and their potential as therapeutic targets. Inhibiting or modulating the activity of these cotransporters represents a promising strategy for reducing neuronal damage, preventing excitotoxicity, and improving neurological outcomes following ischemic events. Furthermore, exploring the interactions between natural compounds and NKCC1/KCC2 provides additional avenues for potential therapeutic interventions for ischemic injury.

Advanced Nano-Drug Delivery Systems in the Treatment of Ischemic Stroke

In recent years, the frequency of strokes has been on the rise year by year and has become the second leading cause of death around the world, which is characterized by a high mortality rate, high recurrence rate, and high disability rate. Ischemic strokes account for a large percentage of strokes. A reperfusion injury in ischemic strokes is a complex cascade of oxidative stress, neuroinflammation, immune infiltration, and mitochondrial damage. Conventional treatments are ineffective, and the presence of the blood-brain barrier (BBB) leads to inefficient drug delivery utilization, so researchers are turning their attention to nano-drug delivery systems. Functionalized nano-drug delivery systems have been widely studied and applied to the study of cerebral ischemic diseases due to their favorable biocompatibility, high efficiency, strong specificity, and specific targeting ability. In this paper, we briefly describe the pathological process of reperfusion injuries in strokes and focus on the therapeutic research progress of nano-drug delivery systems in ischemic strokes, aiming to provide certain references to understand the progress of research on nano-drug delivery systems (NDDSs).

Folic acid blocks ferroptosis induced by cerebral ischemia and reperfusion through regulating folate hydrolase transcriptional adaptive program

Cerebral ischemia-reperfusion (I/R) injury is notably linked with folic acid (FA) deficiency. The aim of our investigation was to explore the effects and underlying mechanisms by which FA mitigates I/R, specifically through regulating the GCPII transcriptional adaptive program. Initially, we discovered that following cerebral I/R, levels of FA, methionine synthase (MTR), and methylenetetrahydrofolate reductase (MTHFR) were decreased, while GCPII expression was elevated. Secondly, administering FA could mitigate cognitive impairment and neuronal damage induced by I/R. Thirdly, the mechanism of FA supplementation involved suppressing the transcriptional factor Sp1, subsequently inhibiting GCPII transcription, reducing Glu content, obstructing cellular ferroptosis, and alleviating cerebral I/R injury. In summary, our data demonstrate that FA affords protection against cerebral I/R injury by inhibiting the GCPII transcriptional adaptive response. These findings unveil that targeting GCPII might be a viable therapeutic strategy for cerebral I/R.

Expression, Functional Polymorphism, and Diagnostic Values of MIAT rs2331291 and H19 rs217727 Long Non-Coding RNAs in Cerebral Ischemic Stroke Egyptian Patients

Cerebral ischemic stroke (CIS) is a severe cerebral vascular event. This research aimed to evaluate the role of single-nucleotide polymorphisms (SNPs) of the lncRNAs MIAT rs2331291 and H19 rs217727 and epigenetic methylation in the expression patterns of serum lncRNA H19 in CIS Egyptian patients. It included 80 CIS cases and 40 healthy subjects. Serum MIAT expression levels decreased, whereas serum H19 expression levels increased among CIS compared to controls. For MIAT rs2331291, there were significant differences in the genotypic and allelic frequencies between the CIS and healthy subjects at p = 0.02 and p = 0.0001, respectively. Our findings illustrated a significantly increased MIAT T/T genotype frequency in hypertensive CIS compared to non-hypertensive CIS at p = 0.004. However, H19 rs217727 gene frequency C/C was not significantly higher in non-hypertensive CIS than in hypertensive CIS. The methylation of the H19 gene promoter was significantly higher in CIS patients compared to healthy subjects. The level of MIAT was positively correlated with serum H19 in CIS. Receiver operating characteristics (ROC) analysis revealed that serum MIAT and H19 have a high diagnostic potential for distinguishing CIS subjects from healthy ones. In conclusion, the MIAT-rs2331291 polymorphism might serve as a novel potential indicator of CIS.

Neuroprotective-Neurorestorative Effects Induced by Progesterone on Global Cerebral Ischemia: A Narrative Review

Progesterone (P4) is a neuroactive hormone having pleiotropic effects, supporting its pharmacological potential to treat global (cardiac-arrest-related) cerebral ischemia, a condition associated with an elevated risk of dementia. This review examines the current biochemical, morphological, and functional evidence showing the neuroprotective/neurorestorative effects of P4 against global cerebral ischemia (GCI). Experimental findings show that P4 may counteract pathophysiological mechanisms and/or regulate endogenous mechanisms of plasticity induced by GCI. According to this, P4 treatment consistently improves the performance of cognitive functions, such as learning and memory, impaired by GCI. This functional recovery is related to the significant morphological preservation of brain structures vulnerable to ischemia when the hormone is administered before and/or after a moderate ischemic episode; and with long-term adaptive plastic restoration processes of altered brain morphology when treatment is given after an episode of severe ischemia. The insights presented here may be a guide for future basic research, including the study of P4 administration schemes that focus on promoting its post-ischemia neurorestorative effect. Furthermore, considering that functional recovery is a desired endpoint of pharmacological strategies in the clinic, they could support the study of P4 treatment for decreasing dementia in patients who have suffered an episode of GCI.

Experimental Substantiation of the Use of Phenibut Combinations with Salicylic, Nicotinic, and Glutamic Acids in Cerebral Ischemia

BACKGROUND

One of the possible ways to increase the effectiveness of drugs based on gamma-aminobutyric acid derivatives is to introduce biologically active acids into their structure. In this regard, the compositions of phenibut with organic acids, which have a more pronounced psychotropic activity, low toxicity, and good tolerability, are of interest. The purpose of this study is to experimentally substantiate the use of phenibut combinations with organic acids in various forms of cerebral ischemia.

METHODS

The study was performed on 1210 male Wistar rats weighing 180-220 g each. The cerebroprotective activities of phenibut combinations with salicylic acid (2:1, doses of 15, 30, and 45 mg/kg), nicotinic acid (2:1, doses of 25, 50, and 75 mg/kg), and glutamic acid (2:1, doses of 25, 50, and 75 mg/kg) have been studied. The study involved a single prophylactic administration of phenibut combinations with organic acids and a 7 days course of the combination treatment administered at doses that proved the most effective according to the results of a single prophylactic administration. The rate of local cerebral blood flow and the vasodilating function of cerebral endothelium were measured, and the researchers evaluated the effects of the studied phenibut combinations on biochemical parameters in rats with focal ischemia.

RESULTS

Compositions of phenibut with salicylic, nicotinic, and glutamic acids in subtotal and transient cerebral ischemia were found to have the most pronounced cerebroprotective effect in doses of 30, 50 and 50 mg/kg, respectively. Under reversible 10 min occlusion of the common carotid arteries, prophylactic administration of the studied phenibut compositions prevented a decrease in cerebral blood flow during ischemia and reduced the severity of postischemic hypoperfusion and hyperperfusion. At a course of 7 days of therapeutic administration of compounds, their pronounced cerebroprotective effect was observed.

CONCLUSIONS

The data obtained can be considered as promising the pharmacological search in this series of substances for the treatment of patients with cerebrovascular disease.

Therapeutic effect of Eleutherococcus senticosus (Rupr. & Maxim.) Maxim. leaves on ischemic stroke via the microbiota-gut-brain axis

Eleutherococcus senticosus (Rupr. & Maxim.) Maxim. leaves (ESL) are widely used to treat ischemic stroke (IS); however, the specific mechanism remains unclear. The microbiota-gut-brain axis plays a critical role in IS and has become a potential therapeutic target. This study aimed to reveal and verify the therapeutic effect of ESL on IS through the microbiota-gut-brain axis. Ultra-high-performance liquid chromatography coupled with mass spectrometry-based untargeted/targeted metabolomics combined with 16S rRNA microbiota sequencing strategy were used to investigate the regulatory effect of ESL on the metabolism and intestinal microenvironment after IS. Lactobacillus reuteri and Clostridium butyricum were used to treat rats with IS to verify that elevated levels of probiotics are key factors in the therapeutic effect of ESL. The results showed that IS significantly altered the accumulation of 41 biomarkers, while ESL restored their concentrations back to normal. Moreover, ESL alleviated the dysbiosis of gut microbiota brought on by IS, by reducing the abundance of pathogens and increasing the abundance of probiotics (e.g., Lactobacillus reuteri and Clostridium butyricum); this could reduce post-stroke injury, thereby having a certain protective effect on IS. This study reveals that ESL plays an important role in treating IS through the microbiota-gut-brain axis, maintaining metabolic homeostasis in vivo.

Targeted Energy Metabolomics Combined with Spatial Metabolomics Study on the Efficacy of Guhong Injection Against Cerebral Ischemia Reperfusion

Optimizing the metabolic phenotype to improve cerebral function is critical for treatment of cerebral ischemia-reperfusion (I/R) injury. Guhong injection (GHI), which comprised safflower extract and aceglutamide, is widely prescribed in Chinese medicine for the treatment of cerebrovascular diseases. In this study, a combination of LC-QQQ-MS and MALDI-MSI were utilized to explore tissue-specific metabolic alterations in the brain of I/R, as well as to evaluate the therapeutic effect of GHI. Pharmacological evaluation demonstrated that GHI can significantly improve infarction rate, neurological deficit, cerebral blood flow, and neuronal damage in I/R rats. Based on LC-QQQ-MS, 23 energy metabolites were found to be significantly altered in the I/R group compared to the sham group (P < 0.05). After GHI treatment, 12 metabolites, including G6P, TPP, NAD, citrate, succinate, malate, ATP, GTP, GDP, ADP, NADP, and FMN showed a significant tendency of returning to baseline values (P < 0.05). Based on MALDI-MSI, 4 metabolites in glycolysis and TCA, 4 metabolites in nucleic acid metabolism, 4 amino acid metabolites, and 6 metabolites were discovered and compared between the different groups in the four special regions of cortex, hippocampus, hypothalamus, and striatum. Parts of these were found to have significant changes after I/R in the special brain region, and were regulated by GHI. The study provides comprehensive and detailed information for specific metabolic reprogramming of brain tissue in rats with I/R, and the therapeutic effect of GHI. Schema describing the discovery strategies of integrated LC-MS and MALDI-MSI to identify cerebral ischemia reperfusion metabolic reprogramming and GHI therapeutic effects.

Plasma Amino Acid Neurotransmitters and Ischemic Stroke Prognosis: A Multicenter Prospective Study

BACKGROUND

Plasma amino acid neurotransmitter dysregulation is suggested to be implicated in the development of ischemic stroke, but its prognostic value for ischemic stroke remains controversial.

OBJECTIVE

We aimed to prospectively investigate the associations between plasma amino acid neurotransmitters levels and adverse outcomes after ischemic stroke in a large-scale multicenter cohort study.

METHODS

We measured 4 plasma amino acid neurotransmitters (glutamic acid, aspartic acid, gamma-aminobutyric acid, and glycine) among 3486 patients with ischemic stroke from 26 hospitals across China. The primary outcome is the composite outcome of death or major disability (modified Rankin Scale score ≥3) at 3 mo after ischemic stroke.

RESULTS

After multivariate adjustment, the odds ratios of death or major disability for the highest versus the lowest quartile were 2.04 (95% confidence interval [CI]: 1.60,2.59; P-trend < 0.001) for glutamic acid, 2.03 (95% CI: 1.59, 2.59; P-trend < 0.001) for aspartic acid, 1.35 (95% CI: 1.06, 1.71; P-trend = 0.016) for gamma-aminobutyric acid, and 0.54 (95% CI: 0.42, 0.69; P-trend < 0.001) for glycine. Each standard deviation increment of log-transformed glutamic acid, aspartic acid, gamma-aminobutyric acid, and glycine was associated with a 34%, 34%, and 9% increased risk, and a 23% decreased risk of death or major disability, respectively (all P < 0.05), in a linear fashion as indicated by spline regression analyses (all P for linearity < 0.05). Addition of the 4 plasma amino acid neurotransmitters to conventional risk factors significantly improved the risk reclassification, as evidenced by integrated discrimination improvement and net reclassification improvement (all P < 0.05).

CONCLUSIONS

Increased glutamic acid, aspartic acid, and gamma-aminobutyric acid and decreased glycine in plasma are associated with adverse outcomes after ischemic stroke, suggesting that plasma amino acid neurotransmitters may be potential intervention targets for improving prognosis of ischemic stroke. The CATIS trial was registered at clinicaltrials.gov (registration number: NCT01840072; URL: ===https://clinicaltrials.gov/ct2/show/NCT01840072?cond=NCT01840072&draw=2&rank=1).

Cardiopulmonary Resuscitation May Not Stop Glutamate Release in the Cerebral Cortex

BACKGROUND

Cardiopulmonary resuscitation (CPR) may not be sufficient to halt the progression of brain damage. Using extracellular glutamate concentration as a marker for neuronal damage, we quantitatively evaluated the degree of brain damage during resuscitation without return of spontaneous circulation.

MATERIALS AND METHODS

Extracellular cerebral glutamate concentration was measured with a microdialysis probe every 2 minutes for 40 minutes after electrical stimulation-induced cardiac arrest without return of spontaneous circulation in Sprague-Dawley rats. The rats were divided into 3 groups (7 per group) according to the treatment received during the 40 minutes observation period: mechanical ventilation without chest compression (group V); mechanical ventilation and chest compression (group VC) and; ventilation, chest compression and brain hypothermia (group VCH). Chest compression (20 min) and hypothermia (40 min) were initiated 6 minutes after the onset of cardiac arrest.

RESULTS

Glutamate concentration increased in all groups after cardiac arrest. Although after the onset of chest compression, glutamate concentration showed a significant difference at 2 min and reached the maximum at 6 min (VC group; 284±48 μmol/L vs. V group 398±126 μmol/L, P =0.003), there was no difference toward the end of chest compression (513±61 μmol/L vs. 588±103 μmol/L, P =0.051). In the VCH group, the initial increase in glutamate concentration was suddenly suppressed 2 minutes after the onset of brain hypothermia.

CONCLUSIONS

CPR alone reduced the progression of brain damage for a limited period but CPR in combination with brain cooling strongly suppressed increases in glutamate levels.

Neurotoxic and cytoprotective mechanisms in the ischemic neocortex

Neuronal damage in ischemic stroke occurs due to permanent imbalance between the metabolic needs of the brain and the ability of the blood-vascular system to maintain glucose delivery and adequate gas exchange. Oxidative stress and excitotoxicity trigger complex processes of neuroinflammation, necrosis, and apoptosis of both neurons and glial cells. This review summarizes data on the structural and chemical changes in the neocortex and main cytoprotective effects induced by focal ischemic stroke. We focus on the expression of neurotrophins (NT) and molecular and cellular changes in neurovascular units in ischemic brain. We also discuss how these factors affect the apoptosis of cortical cells. Ischemic damage involves close interaction of a wide range of signaling molecules, each acting as an efficient marker of cell state in both the ischemic core and penumbra. NTs play the main regulatory role in brain tissue recovery after ischemic injury. Heterogeneous distribution of the BDNF, NT-3, and GDNF immunoreactivity is concordant with the selective response of different types of cortical neurons and glia to ischemic injury and allows mapping the position of viable neurons. Astrocytes are the central link in neurovascular coupling in ischemic brain by providing other cells with a wide range of vasotropic factors. The NT expression coincides with the distribution of reactive astrocytes, marking the boundaries of the penumbra. The development of ischemic stroke is accompanied by a dramatic change in the distribution of GDNF reactivity. In early ischemic period, it is mainly observed in cortical neurons, while in late one, the bulk of GDNF-positive cells are various types of glia, in particular, astrocytes. The proportion of GDNF-positive astrocytes increases gradually throughout the ischemic period. Some factors that exert cytoprotective effects in early ischemic period may display neurotoxic and pro-apoptotic effects later on. The number of apoptotic cells in the ischemic brain tissue correlates with the BDNF levels, corroborating its protective effects. Cytoprotection and neuroplasticity are two lines of brain protection and recovery after ischemic stroke. NTs can be considered an important link in these processes. To develop efficient pharmacological therapy for ischemic brain injury, we have to deepen our understanding of neurochemical adaptation of brain tissue to acute stroke.

Thiolutin attenuates ischemic stroke injury via inhibition of NLRP3 inflammasome: an in vitro and in vivo study

A recent study confirmed that thiolutin is effective in the treatment of nucleotide-binding domain-like receptor protein 3 (NLRP3)-related inflammatory diseases. Nevertheless, whether thiolutin (THL) is involved in the regulation of NLRP3 inflammasome in ischemic stroke is not known. The murine neuronal cell oxygen-glucose deprivation (OGD) model was first established, and then different concentrations (25 nM and 50 nM) of THL were administered for 48 h incubation, respectively. Subsequently, cell viability and toxicity, and the levels of intracellular inflammatory factors interleukin-1β (IL-1β), interleukin-18 (IL-18), oxidative stress factors superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), catalase (CAT) and malondialdehyde (MDA), and NLRP3 inflammasome activation-related proteins pro-caspase, caspase-1, apoptosis-associated speck like-protein (ASC) and NLRP3 were examined, respectively. We further established the mouse middle cerebral artery occlusion (MCAO) model to evaluate the therapeutic effects of THL on cerebral infarction like behaviors in mice and the preventive effects on NLRP3 inflammasome activation in vivo. Cell cytotoxic, and the levels of inflammatory factors and oxidative stress were conspicuously increased, and NLRP3 inflammasome was materially activated in the OGD-induced cell model and MCAO-established mouse model, which were partially countered by THL treatment. Besides, intraperitoneal injection of THL could prominently reduce the cerebral infarct volume and neuromotor deficit scores in MCAO mice. The present study confirmed that THL attenuated neuronal and cerebral inflammatory injury caused by OGD and MCAO models in mice through restraining NLRP3 inflammasome activation in vitro and in vivo.

The role of excitatory amino acid transporter 2 (EAAT2) in epilepsy and other neurological disorders

Glutamate is the major excitatory neurotransmitter in the central nervous system (CNS). Excitatory amino acid transporters (EAATs) have important roles in the uptake of glutamate and termination of glutamatergic transmission. Up to now, five EAAT isoforms (EAAT1-5) have been identified in mammals. The main focus of this review is EAAT2. This protein has an important role in the pathoetiology of epilepsy. De novo dominant mutations, as well as inherited recessive mutation in this gene, have been associated with epilepsy. Moreover, dysregulation of this protein is implicated in a range of neurological diseases, namely amyotrophic lateral sclerosis, alzheimer's disease, parkinson's disease, schizophrenia, epilepsy, and autism. In this review, we summarize the role of EAAT2 in epilepsy and other neurological disorders, then provide an overview of the therapeutic modulation of this protein.

Transcriptional regulation of NRF1 on metabotropic glutamate receptors in a neonatal hypoxic‑ischemic encephalopathy rat model

BACKGROUND

Neonatal hypoxic-ischemic encephalopathy (HIE) is a kind of brain injury that causes severe neurological disorders in newborns. Metabotropic glutamate receptors (mGluRs) and ionotropic glutamate receptors (iGluRs) are significantly associated with HIE and are involved in ischemia-induced excitotoxicity. This study aimed to investigate the upstream mechanisms of mGluRs and the transcriptional regulation by nuclear respiratory factor 1 (NRF1).

METHODS

The rat model of neonatal HIE was created using unilateral carotid artery ligation and in vitro oxygen-glucose deprivation paradigm. We used western blot, immunofluorescence, Nissl staining, and Morris water maze to investigate the impact of NRF1 on brain damage and learning memory deficit by HIE. We performed ChIP and luciferase activities to identify the transcriptional regulation of NRF1 on mGluRs.

RESULTS

The neuronal NRF1 and some glutamatergic genes expression synchronously declined in infarcted tissues. The NRF1 overexpression effectively restored the expression of some glutamatergic genes and improved cognitive performance. NRF1 regulated some members of mGluRs and iGluRs in hypoxic-ischemic neurons. Finally, NRF1 is bound to the promoter regions of Grm1, Grm2, and Grm8 to activate their transcription.

CONCLUSIONS

NRF1 is involved in the pathology of the neonatal HIE rat model, suggesting a novel therapeutic approach to neonatal HIE.

IMPACT

NRF1 and some glutamatergic genes were synchronously downregulated in the infarcted brain of the neonatal HIE rat model. NRF1 overexpression could rescue cognitive impairment caused by the neonatal HIE rat model. NRF1 regulated the expressions of Grm1, Grm2, and Grm8, which activated their transcription by binding to the promoter regions.

Purification, Identification and Neuroprotective Effects of Proteins from Bombyx batryticatus in Glu-Stimulated PC12 Cells

Bombyx batryticatus (BB) is one of the most commonly used Traditional Chinese Medicines (TCMs) in the treatment of convulsions and epilepsy. The antiepileptic effects of total proteins from BB (BBPs) have been proven in our previous research. In this study, BBPs were further purified, the neuroprotective effects were evaluated in Glu-stimulated PC12 cells, and the structure was identified by Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS). Six subfractions (PF-1 to PF-6) were obtained by DEAE-52 Sepharose FF ion-exchange chromatography. It was found that PF-1, PF-2, and PF-3, with similar protein compositions, possessed neuroprotective effects in Glu-stimulated PC12 cells by significantly increasing the GABA level, and decreasing the levels of IL-1β and TNF-α. The most active fraction (PF-2) was further separated by Sephadex G-75 gel filtration chromatography, and an effective protein component named PF-2-2 was obtained. Fluorescein isothiocyanate-labeled PF-2-2 (FITC-PF-2-2) was prepared, and the binding of FITC-F-2-2 to the PC12 cells was directly observed with a confocal microscope. PF-2-2 was found to first bind to the surface of PC12 cells and then internalize into the cells. The main band of PF-2-2 was then analyzed by MALDI-TOF/TOF-MS and searched in the MASCOT database; finally a protein named Low molecular mass 30 kDa lipoprotein 21G1 was identified. In conclusion, PF-2-2 and purified proteins isolated from BBPs have potential application prospects in the treatment of epilepsy.

Group III metabotropic glutamate receptors as promising targets for neuroprotective therapy: Particular emphasis on the role of mGlu4 and mGlu7 receptors

There is still no effective treatment for central nervous system (CNS) pathologies, including cerebral ischemia, neurotrauma, and neurodegenerative diseases in which the Glu/GABA balance is disturbed with associated excitotoxicity. It is thus important to search for new efficacious therapeutic strategies. Preclinical studies on the role of metabotropic glutamate receptors (mGluRs) in neuroprotection conducted over the years show that these receptors may have therapeutic potential in these CNS disorders. However, clinical trials, especially for treating Parkinson's disease, have been unsatisfactory. This review focuses on the specific role of group III mGluRs in neuroprotection in experimental in vitro and in vivo models of excitotoxicity/neurotoxicity using neurotoxins as well as ischemia, traumatic brain injury, and neurodegenerative diseases such as Parkinson's disease, Alzheimer's diseases, and multiple sclerosis. The review highlights recent preclinical studies in which group III mGluR ligands (especially those acting at mGluR4 or mGluR7) were administered after damage, thus emphasizing the importance of the therapeutic time window in the treatment of ischemic stroke and traumatic brain injury. From a clinical standpoint, the review also highlights studies using group III mGluR agonists with favorable neuroprotective efficacy (histological and functional) in experimental ischemic stroke, including healthy normotensive and-hypertensive rats. This review also summarizes possible mechanisms underlying the neuroprotective activity of the group III mGluR ligands, which may be helpful in developing more effective and safe therapeutic strategies. Therefore, to fully assess the role of these receptors in neuroprotection, it is necessary to uncover new selective ligands, primarily those stimulating mGlu4 and mGlu7 receptors.

Excitatory Synaptic Transmission in Ischemic Stroke: A New Outlet for Classical Neuroprotective Strategies

Stroke is one of the leading causes of death and disability in the world, of which ischemia accounts for the majority. There is growing evidence of changes in synaptic connections and neural network functions in the brain of stroke patients. Currently, the studies on these neurobiological alterations mainly focus on the principle of glutamate excitotoxicity, and the corresponding neuroprotective strategies are limited to blocking the overactivation of ionic glutamate receptors. Nevertheless, it is disappointing that these treatments often fail because of the unspecificity and serious side effects of the tested drugs in clinical trials. Thus, in the prevention and treatment of stroke, finding and developing new targets of neuroprotective intervention is still the focus and goal of research in this field. In this review, we focus on the whole processes of glutamatergic synaptic transmission and highlight the pathological changes underlying each link to help develop potential therapeutic strategies for ischemic brain damage. These strategies include: (1) controlling the synaptic or extra-synaptic release of glutamate, (2) selectively blocking the action of the glutamate receptor NMDAR subunit, (3) increasing glutamate metabolism, and reuptake in the brain and blood, and (4) regulating the glutamate system by GABA receptors and the microbiota–gut–brain axis. Based on these latest findings, it is expected to promote a substantial understanding of the complex glutamate signal transduction mechanism, thereby providing excellent neuroprotection research direction for human ischemic stroke (IS).

Metabonomics Study of the Hematopoietic Effect of Medicinal Wine Maoji Jiu on a Blood Deficiency Rat Model by Ultra-High-Performance Liquid Chromatography Coupled to Quadrupole Time-of-Flight Mass Spectrometry and a Pattern Recognition Approach

Maoji Jiu (MJ) is a kind of medicinal wine that has been widely used by Chinese people for many years to nourish and promote blood circulation. The purpose of this study was to investigate the hematopoietic effect of MJ on the metabolism of blood deficient rats and to explore the underlying hematopoietic regulation mechanisms. Blood deficiency model rats were induced by subcutaneous injection of N-acetylphenylhydrazine (APH) and intraperitoneal injection of cyclophosphamide (CTX). The plasma metabolic fingerprints of blood deficiency model rats with and without MJ treatment were obtained by using metabonomics based on ultra-high-performance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry (UHPLC-QTOF/MS). Orthogonal partial least squares-discriminant analysis (OPLS-DA) was used to evaluate the hematopoietic effect of MJ and identify potential biomarkers in the plasma of blood deficiency model rats. The levels of white blood cells (WBC), red blood cells (RBC) and hemoglobin (HGB) and the activity of antioxidant capacity showed a recovery trend to the control group after MJ treatment, while the dose of 10 mL/kg showed the best effect. In this study, thirteen potential biomarkers were identified, which were mainly related to seven metabolic pathways, including linoleic acid metabolism, d-glutamine and d-glutamate metabolism, alanine, aspartate and glutamate metabolism, tryptophan metabolism, pyrimidine metabolism, porphyrin and chlorophyll metabolism and arginine biosynthesis. Metabolomics was applied frequently to reflect the physiological and metabolic state of organisms comprehensively, indicating that the rapid plasma metabonomics may be a potentially powerful tool to reveal the efficacy and enriching blood mechanism of MJ.

The Alteration Profiles of m6A-Tagged circRNAs in the Peri-Infarct Cortex After Cerebral Ischemia in Mice

The N6-methyladenosine (m⁶A) modification acts as a dynamic regulatory factor in diseases by regulating the metabolism and function of the transcriptome, especially mRNAs. However, little is known regarding the functional effects of m⁶A modifications on circRNAs. In this research, we established a distal middle cerebral artery occlusion (MCAO) model in adult C57BL/6J mice. The mice were divided into three groups: sham surgery, 3 days after MCAO (3d), and 7 days after MCAO (7d). Reverse transcription quantitative polymerase chain reaction (RT-qPCR) demonstrated that the mRNA expression levels of m⁶A-related methyltransferases (METTL3, METTL14), demethylases (FTO, ALKBH5), and reading proteins (YTHDF1, YTHDF3) altered compared to the sham group. Furthermore, the translation level of ALKBH5 and YTHDF3 was significantly decreased in the 3d group while increased in 7d group. Methylated RNA immunoprecipitation (MeRIP) and circRNA microarray indicated 85 hypermethylated and 1621 hypomethylated circRNAs in the 3d group. In the 7d group, the methylation level increased in 57 and decreased in 66 circRNAs. Subsequently, our results were verified by MeRIP-qPCR. Bioinformatics analysis was performed to analyze the functions of differentially m⁶A-modified circRNAs. We found some m⁶A modified-circRNAs associated with cerebral infarction, providing a new direction for the molecular mechanism of stroke.

Effects of targeted temperature management at 33°C vs. 36°C on comatose patients after cardiac arrest stratified by the severity of encephalopathy

OBJECTIVES

To assess neurological outcome after targeted temperature management (TTM) at 33°C vs. 36°C, stratified by the severity of encephalopathy based on EEG-patterns at 12 and 24h.

DESIGN

Post hoc analysis of prospective cohort study.

SETTING

Five Dutch Intensive Care units.

PATIENTS

479 adult comatose post-cardiac arrest patients.

INTERVENTIONS

TTM at 33°C (n=270) or 36°C (n=209) and continuous EEG monitoring.

MEASUREMENTS AND MAIN RESULTS

Outcome according to the cerebral performance category (CPC) score at 6 months post-cardiac arrest was similar after 33°C and 36°C. However, when stratified by the severity of encephalopathy based on EEG-patterns at 12 and 24h after cardiac arrest, the proportion of good outcome (CPC 1-2) in patients with moderate encephalopathy was significantly larger after TTM at 33°C (66% vs. 45%; Odds Ratios 2.38, 95% CI=1.32-4.30; p=0.004). In contrast, with mild encephalopathy, there was no statistically significant difference in the proportion of patients with good outcome between 33°C and 36°C (88% vs. 81%; OR 1.68, 95% CI=0.65-4.38; p=0.282). Ordinal regression analysis showed a shift towards higher CPC scores when treated with TTM 33°C as compared with 36°C in moderate encephalopathy (cOR 2.39; 95% CI=1.40-4.08; p=0.001), but not in mild encephalopathy (cOR 0.81 95% CI=0.41-1.59; p=0.537). Adjustment for initial cardiac rhythm and cause of arrest did not change this relationship.

CONCLUSIONS

Effects of TTM probably depend on the severity of encephalopathy in comatose patients after cardiac arrest. These results support inclusion of predefined subgroup analyses based on EEG measures of the severity of encephalopathy in future clinical trials.

Prolactin and Its Altered Action in Alzheimer's Disease and Parkinson's Disease

BACKGROUND

Prolactin (PRL) is one of the most diverse pituitary hormones and is known to modulate normal neuronal function and neurodegenerative conditions. Many studies have described the influence that PRL has on the central nervous system and addressed its contribution to neurodegeneration, but little is known about the mechanisms responsible for the effects of PRL on neurodegenerative disorders, especially on Alzheimer's disease (AD) and Parkinson's disease (PD).

SUMMARY

We review and summarize the existing literature and current understanding of the roles of PRL on various PRL aspects of AD and PD.

KEY MESSAGES

In general, PRL is viewed as a promising molecule for the treatment of AD and PD. Modulation of PRL functions and targeting of immune mechanisms are needed to devise preventive or therapeutic strategies.

Application value and challenge of traditional Chinese medicine carried by ZIF-8 in the therapy of ischemic stroke

Stroke is a group of major diseases that cause death or disability in adults, with high incidence and lack of available therapeutic strategies. Although traditional Chinese medicine (TCM) has continuously achieved good effects in the therapy of stroke while there is still not convincing due to the limitation of blood-brain permeability, as well as the individual differences in usage and dosage. With the improvement of nanotechnology, TCM nanopreparation has gradually become a research hotspot in various fields due to its advantages in permeating the blood-brain barrier, targeting delivery, enhancing sustained-release drug delivery, changing the distribution in the body, and improving bioavailability. Zeolitic imidazolate framework-8 (ZIF-8) is an ideal nano-drug delivery system for adsorption, catalysis, and drug loading, which is a biocompatible metal-organic framework framed by 2-methylimidazole and zinc ions. At present, ZIF-8 was wildly used in the treatment of ischemic stroke. However, challenges remain persists for its clinical application, such as preparation technology, detection technology in vivo, targeting specificity, safety and stability, and so forth. Therefore, more efforts need to overcome the above problems to develop the application of TCM nanopreparations in the therapy of ischemia/reperfusion in the future.

Emerging immune and cell death mechanisms in stroke: Saponins as therapeutic candidates

The complexity of the ischemic cascade is based on the integrated crosstalk of every cell type in the neurovascular unit. Depending on the features of the ischemic insult, several cell death mechanisms are triggered, such as apoptosis, necroptosis, ferroptosis/oxytosis, ETosis or pyroptosis, leading to reactive astrogliosis. However, emerging evidence demonstrates a dual role for the immune system in stroke pathophysiology, where it exerts both detrimental and also beneficial functions. In this review, we discuss the relevance of several cell death modalities and the dual role of the immune system in stroke pathophysiology. We also provide an overview of some emerging immunomodulatory therapeutic strategies, amongst which saponins, which are promising candidates that exert multiple pharmacological effects.

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Several cell death mechanisms coexist in stroke pathophysiology.

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Neurons are more vulnerable to necroptosis than glial cells.

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Inhibitors of receptor-interacting protein kinases and of ferroptosis induce neuroprotection.

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Saponins exert modulatory effects on inflammation and neuronal cell death in stroke.

Inhibition of serum and glucocorticoid regulated kinases by GSK650394 reduced infarct size in early cerebral ischemia-reperfusion with decreased BBB disruption

Blood-brain barrier (BBB) disruption is one of the most important pathological changes following cerebral ischemia-reperfusion. We tested whether inhibition of the serum and glucocorticoid regulated kinase 1 (SGK1) would decrease BBB disruption and contribute to decreasing infarct size in the first few hours of cerebral ischemia-reperfusion within the thrombolysis therapy time window. After transient middle cerebral artery occlusion (MCAO), an SGK1 inhibitor GSK650394, or vehicle was administered into the lateral ventricle of rats. After one hour of MCAO and two hours of reperfusion, we determined BBB disruption using the transfer coefficient (K_i) of ¹⁴C-α-aminoisobutyric acid, and also determined infarct size, phosphorylation of NDRG1, and MMP2 protein level. Ischemia-reperfusion increased (+34%, p < 0.05) and GSK650394 decreased (-25%, p < 0.05) the K_i in the ischemic-reperfused cortex. GSK650394 decreased the percentage of cortical infarct (-31%, p < 0.001). At the same time GSK650394 reduced NDRG1 phosphorylation and MMP2 protein level in the ischemic-reperfused cortex suggesting that SGK1 was inhibited by GSK650394 and that lower MMP2 could be one of the mechanisms of decreased BBB disruption. Collectively our data suggest that GSK650394 could be neuroprotective and one of the mechanisms of the neuroprotection could be decreased BBB disruption. SGK1 inhibition within the thrombolysis therapy time window might reduce cerebral ischemia-reperfusion injury.

Rapalink-1 Increased Infarct Size in Early Cerebral Ischemia-Reperfusion With Increased Blood-Brain Barrier Disruption

It has been reported that the mechanistic target of rapamycin (mTOR) pathway is involved in cerebral ischemia–reperfusion injury. One of the important pathological changes during reperfusion after cerebral ischemia is disruption of blood–brain barrier (BBB). Rapamycin, a first-generation mTOR inhibitor, produces divergent effects on neuronal survival and alteration in BBB disruption. In this study, we investigated how Rapalink-1, a third-generation mTOR inhibitor, would affect neuronal survival and BBB disruption in the very early stage of cerebral ischemia–reperfusion that is within the time window of thrombolysis therapy. The middle cerebral artery occlusion (MCAO) was performed in rats under isoflurane anesthesia with controlled ventilation. Of note, 2 mg/kg of Rapalink-1 or vehicle was administered intraperitoneally 10 min after MCAO. After 1 h of MCAO and 2 h of reperfusion, the transfer coefficient (K_i) of ¹⁴C-α-aminoisobutyric acid (104 Da) and the volume of ³H-dextran (70,000 Da) distribution were determined to assess the degree of BBB disruption. At the same time points, phosphorylated S6 (Ser240/244) and Akt (Ser473) as well as matrix metalloproteinase-2 (MMP2) protein level were determined by Western blot along with the infarct size using tetrazolium stain. Rapalink-1 increased the K_i in the ischemic-reperfused cortex (IR-C, +23%, p < 0.05) without a significant change in the volume of dextran distribution. Rapalink-1 increased the percentage of cortical infarct out of the total cortical area (+41%, p < 0.005). Rapalink-1 significantly decreased phosphorylated S6 and Akt to half the level of the control rats in the IR-C, which suggests that both of the mechanistic target of rapamycin complex 1 and 2 (mTORC1 and mTORC2) were inhibited. The MMP2 level was increased suggesting that BBB disruption could be aggravated by Rapalink-1. Taken together, our data suggest that inhibiting both mTORC1 and mTORC2 by Rapalink-1 could worsen the neuronal damage in the early stage of cerebral ischemia–reperfusion and that the aggravation of BBB disruption could be one of the contributing factors.

Roles and Mechanisms of Axon-Guidance Molecules in Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disease that is characterized by progressive memory decline and cognitive dysfunctions. Although the causes of AD have not yet been established, many mechanisms have been proposed. Axon-guidance molecules play the roles in the occurrence and development of AD by participating in different mechanisms. Therefore, what roles do axon-guidance molecules play in AD? This study aimed at elucidating how axon-guidance molecules Netrins, Slits, Semaphorins, and Ephrins regulate the levels of Aβ, hyperphosphorylation of tau protein, Reelin, and other ways through different signaling pathways, in order to show the roles of axon-guidance molecules in the occurrence and development of AD. And it is hoped that this study can provide a theoretical basis and new perspectives in the search for new therapeutic targets for AD.

Mass spectrometry-based serum lipidomics strategy to explore the mechanism of Eleutherococcus senticosus (Rupr. & Maxim.) Maxim. leaves in the treatment of ischemic stroke

Eleutherococcus senticosus (Rupr. & Maxim.) Maxim. leaves (ESL) were reported to have neuroprotective function and are also used to treat cranial and cerebral traumas as a traditional Chinese medicine and food herbage plant. However, there has been no previous study on ESL treatment for stroke at the level of lipid disorders. To clarify the mechanism of ESL in treating ischemic stroke, this study was carried out from 3 aspects, namely, the regulation of lipid disorders, protection of the nervous system, as well as anti-inflammatory and antioxidant actions. This study established a lipidomics research strategy that was developed by UPLC-Q-TOF/MS analysis. The quantification of neurotransmitters in the serum and brain tissue of rats was performed using UPLC-TQ/MS. Also, we quantified the oxidative stress and inflammatory reaction by measuring the contents of SOD, MDA, TNF-α, IL-6, and IL-10 via the ELISA kits for serum and brain tissue. According to UPLC-Q-TOF/MS-based lipidomics analysis, 27 lipidomics biomarkers were identified in this study, including PC, PE, SM, and TG, which were distributed in various lipid metabolic pathways, including glycerophospholipid, linoleic acid, alpha-linolenic acid, glycerolipid, sphingolipid, and arachidonic acid metabolism pathways. By reversing the changes in the lipid content caused by the disease, ESL has a therapeutic effect on ischemic stroke. Furthermore, quantitative results of neurotransmitters indicated that they can be regulated by ESL. Finally, the results of ELISA showed that ESL can treat ischemic stroke to a certain extent by reducing the oxidative and inflammatory damage. Therefore, ESL may play a therapeutic role in the treatment of ischemic stroke in different ways. This research preliminarily revealed the mechanism of ESL in the treatment of ischemic stroke and provided support for the further application of ESL.

GABA synaptopathy promotes the elevation of caspases 3 and 9 as pro-apoptotic markers in Egyptian patients with autism spectrum disorder

Autism spectrum disorder (ASD) is classified as a neurodevelopmental disorder characterized by reduced social communication as well as repetitive behaviors. Many studies have proved that defective synapses in ASD influence how neurons in the brain connect and communicate with each other. Synaptopathies arise from alterations that affecting the integrity and/or functionality of synapses and can contribute to synaptic pathologies. This study investigated the GABA levels in plasma being an inhibitory neurotransmitter, caspase 3 and 9 as pro-apoptotic proteins in 20 ASD children and 20 neurotypical controls using the ELISA technique. Analysis of receiver-operating characteristic (ROC) of the data that was obtained to evaluate the diagnostic value of the aforementioned evaluated biomarkers. Pearson's correlations and multiple regressions between the measured variables were also done. While GABA level was reduced in ASD patients, levels of caspases 3 and 9 were significantly higher when compared to neurotypical control participants. ROC and predictiveness curves showed that caspases 3, caspases 9, and GABA might be utilized as predictive markers in autism diagnosis. The present study indicates that the presence of GABAergic dysfunction promotes apoptosis in Egyptian ASD children. The obtained GABA synaptopathies and their connection with apoptosis can both relate to neuronal excitation, and imbalance of the inhibition system, which can be used as reliable predictive biomarkers for ASD.

Caffeine and Its Neuroprotective Role in Ischemic Events: A Mechanism Dependent on Adenosine Receptors

Ischemia is characterized by a transient, insufficient, or permanent interruption of blood flow to a tissue, which leads to an inadequate glucose and oxygen supply. The nervous tissue is highly active, and it closely depends on glucose and oxygen to satisfy its metabolic demand. Therefore, ischemic conditions promote cell death and lead to a secondary wave of cell damage that progressively spreads to the neighborhood areas, called penumbra. Brain ischemia is one of the main causes of deaths and summed with retinal ischemia comprises one of the principal reasons of disability. Although several studies have been performed to investigate the mechanisms of damage to find protective/preventive interventions, an effective treatment does not exist yet. Adenosine is a well-described neuromodulator in the central nervous system (CNS), and acts through four subtypes of G-protein-coupled receptors. Adenosine receptors, especially A₁ and A_2A receptors, are the main targets of caffeine in daily consumption doses. Accordingly, caffeine has been greatly studied in the context of CNS pathologies. In fact, adenosine system, as well as caffeine, is involved in neuroprotection effects in different pathological situations. Therefore, the present review focuses on the role of adenosine/caffeine in CNS, brain and retina, ischemic events.

Electroacupuncture Ameliorates Cerebral Ischemic Injury by Inhibiting Ferroptosis

Background: Our previous study found that electroacupuncture (EA) can promote the recovery of neurological functions, reduce the volume of cerebral infarction, and protect the neurovascular unit in middle cerebral artery occlusion (MCAO) rats. Some studies have shown that ferroptosis is closely related to ischemic stroke; however, whether EA plays a protective role by regulating ferroptosis is unknown. Objective: We aimed to investigate the inhibitory effects of EA on ferroptosis in MCAO rats. Methods: We used 36 adult male Sprague-Dawley rats in this study. MCAO rats were established according to the Zea method and treated with EA at a continuous wave of 2/100 Hz and ~2-4 V for 30 min for 7 consecutive days. We analyzed the coordinated motor deficit and volume of cerebral infarction in vivo through 9.4-tesla magnetic resonance imaging. Then, the ischemic brain tissue was isolated and the levels of malondialdehyde (MDA), superoxide dismutase (SOD), glutathione (GSH), and iron were determined. Western blotting and real-time quantitative PCR were performed to evaluate the expression of glutathione peroxidase 4 (GPX4), transferrin (Tf), transferrin receptor 1 (TfR1), and ferritin heavy chain 1 (FTH1). To confirm the results, we used a transmission electron microscope to observe the mitochondrial morphology. Results: EA intervention significantly decreased the oxidative stress level and inhibited ferroptosis. EA significantly improved coordinated motor deficit (P < 0.01) and decreased cerebral infarct volume (P < 0.01) in the EA + MCAO group, compared with the MCAO group. EA downregulated the level of MDA (P < 0.01) and total iron (P < 0.01) and upregulated the level of SOD (P < 0.01) and GSH (P < 0.01) in the EA + MCAO group, compared with the MCAO group. EA increased the levels of GPX4 and GPX4 mRNA (P < 0.01) and FTH1 and FTH1 mRNA (P < 0.05, P < 0.01), whereas it decreased the levels of Tf and Tf mRNA (P < 0.05, P < 0.01) and TfR1 and TfR1 mRNA (P < 0.01) in the EA + MCAO group, compared with the MCAO group. EA also promoted the recovery of mitochondrial morphology according to the mitochondrial classification system for the ischemic cerebral tissue. Conclusion: Our results indicate that EA can inhibit ferroptosis by regulating oxidative stress and iron-related proteins, thus conferring protection against MCAO in a rat model.

Neuroprotective Treatment of Postanoxic Encephalopathy: A Review of Clinical Evidence

Postanoxic encephalopathy is the key determinant of death or disability after successful cardiopulmonary resuscitation. Animal studies have provided proof-of-principle evidence of efficacy of divergent classes of neuroprotective treatments to promote brain recovery. However, apart from targeted temperature management (TTM), neuroprotective treatments are not included in current care of patients with postanoxic encephalopathy after cardiac arrest. We aimed to review the clinical evidence of efficacy of neuroprotective strategies to improve recovery of comatose patients after cardiac arrest and to propose future directions. We performed a systematic search of the literature to identify prospective, comparative clinical trials on interventions to improve neurological outcome of comatose patients after cardiac arrest. We included 53 studies on 21 interventions. None showed unequivocal benefit. TTM at 33 or 36°C and adrenaline (epinephrine) are studied most, followed by xenon, erythropoietin, and calcium antagonists. Lack of efficacy is associated with heterogeneity of patient groups and limited specificity of outcome measures. Ongoing and future trials will benefit from systematic collection of measures of baseline encephalopathy and sufficiently powered predefined subgroup analyses. Outcome measurement should include comprehensive neuropsychological follow-up, to show treatment effects that are not detectable by gross measures of functional recovery. To enhance translation from animal models to patients, studies under experimental conditions should adhere to strict methodological and publication guidelines.

Uric acid inhibits HMGB1-TLR4-NF-κB signaling to alleviate oxygen-glucose deprivation/reoxygenation injury of microglia

Mounting evidence has implicated inflammation in ischemia-reperfusion injury following acute ischemic stroke (AIS). Microglia remain the primary initiator and participant of brain inflammation. Emerging evidence has indicated that uric acid has promise for the treatment of AIS, but its explicit mechanisms remain elusive. Here, we observed that uric acid reduced the severity of cerebral infarction and attenuated the activation of microglia in the cerebral cortex in a mouse middle cerebral-artery occlusion/reperfusion model. Thus, we speculated that uric acid may play a role by directly interfering with the inflammatory response of microglia. First, we investigated whether the HMGB1-TLR4-NF-κB signaling plays a role in oxygen glucose deprivation and reperfusion (OGD/R) injury of BV2 cells. Inhibition of the signaling significantly reduced the release of the proinflammatory cytokines tumor necrosis factor α (TNF-α), interleukin 1β (IL1β), and IL6 caused by OGD/R in BV2 cells. Second, uric acid weakened the decreased cell viability and lactate dehydrogenase release induced by OGD/R in BV2 cells. Finally, uric acid reduced the release of the proinflammatory cytokines TNF-α, IL1β, and IL6 caused by OGD/R in BV2 cells by dampening HMGB1-TLR4-NF-κB signaling, which was reversed by probenecid treatment, an inhibitor of the uric acid channel. Hence, uric acid halted the release of inflammatory factors and the decreased cell viability induced by ODG/R via inhibiting the microglia HMGB1-TLR4-NF-κB signaling, thereby alleviating the damage to microglia. This may be part of the molecular mechanisms by which uric acid protects mice against the brain damage of middle cerebral-artery occlusion/reperfusion.

Targeting the WNK-SPAK/OSR1 Pathway and Cation-Chloride Cotransporters for the Therapy of Stroke

Stroke is one of the major culprits responsible for morbidity and mortality worldwide, and the currently available pharmacological strategies to combat this global disease are scanty. Cation-chloride cotransporters (CCCs) are expressed in several tissues (including neurons) and extensively contribute to the maintenance of numerous physiological functions including chloride homeostasis. Previous studies have implicated two CCCs, the Na+-K+-Cl- and K+-Cl- cotransporters (NKCCs and KCCs) in stroke episodes along with their upstream regulators, the with-no-lysine kinase (WNKs) family and STE20/SPS1-related proline/alanine rich kinase (SPAK) or oxidative stress response kinase (OSR1) via a signaling pathway. As the WNK-SPAK/OSR1 pathway reciprocally regulates NKCC and KCC, a growing body of evidence implicates over-activation and altered expression of NKCC1 in stroke pathology whilst stimulation of KCC3 during and even after a stroke event is neuroprotective. Both inhibition of NKCC1 and activation of KCC3 exert neuroprotection through reduction in intracellular chloride levels and thus could be a novel therapeutic strategy. Hence, this review summarizes the current understanding of functional regulations of the CCCs implicated in stroke with particular focus on NKCC1, KCC3, and WNK-SPAK/OSR1 signaling and discusses the current and potential pharmacological treatments for stroke.

GABAB receptor antagonist promotes hippocampal neurogenesis and facilitates cognitive function recovery following acute cerebral ischemia in mice

PURPOSE AND BACKGROUND

Previous studies have suggested that promoting endogenous neurogenesis has great significance for the recovery of cognitive dysfunction caused by cerebral ischemia (CI). Pharmacological inhibition of GABA_B receptor can enhance neurogenesis in adult healthy and depressed mice. In the study, we intended to investigate the effects of GABA_B receptor antagonists on cognitive function and hippocampal neurogenesis in mice following CI.

METHODS

Adult mice were subjected to bilateral common carotid artery occlusion (BCCAO) for 20 min to induce CI and treated with CGP52432 (antagonist of GABA_B receptor, CGP, 10 mg/kg intraperitoneal injection) starting 24 h after CI. The Morris water maze test was performed to test spatial learning and memory at day 28. Immunofluorescence was applied to detect neurogenesis in the DG region at day 14 and 28. In in vitro experiments, cell proliferation was detected by CCK8 and immunofluorescence, and the expression of cAMP/CREB signaling pathway-related proteins was detected by ELISA assay and Western blot.

RESULTS

CGP significantly improved spatial learning and memory disorders caused by CI, and it enhanced the proliferation of neural stem cells (NSCs), the number of immature neurons, and the differentiation from newborn cells to neurons. In vitro experiments further confirmed that CGP dose-dependently enhanced the cell viability of NSCs, and immunofluorescence staining showed that CGP promoted the proliferation of NSCs. In addition, treatment with CGP increased the expression of cAMP, PKA, and pCREB in cultured NSCs.

CONCLUSION

Inhibition of GABA_B receptor can effectively promote hippocampal neurogenesis and improve spatial learning and memory in adult mice following CI.

23-Hydroxytormentic acid reduces cerebral ischemia/reperfusion damage in rats through anti-apoptotic, antioxidant, and anti-inflammatory mechanisms

23-Hydroxytormentic acid (23-HTA) is an important herbal medicine purified from immature fruits of African Rubus aceae (Rosaceae). This study was carried out to examine the protection properties and potential mechanisms of 23-HTA against cerebral ischemia/reperfusion (I/R) damage. Rats underwent middle cerebral artery occlusion/reperfusion (MCAO/R) 2/24 h. All animals were euthanized 24 h after reperfusion. Rats were injected with various concentrations of 23-HTA intraperitoneally. Evaluations of infarct volumes, neurological deficit, and brain water contents were carried out to assess the outcome of 23-HTA treatment. The results showed that 23-HTA reduced infarct volumes, brain water content, and neurological deficit in a dosage-dependent manner. 23-HTA can also significantly reduce the numbers of TUNEL-positive cells, the expression levels of Bax, caspase-3, lipid peroxidation, Sod 1, Sod 2, catalase, and pro-inflammatory cytokines TNF and IL-1β and increase the expression levels of Bcl-2 and p-Akt. 23-HTA has a neuroprotective effect due to its anti-apoptotic, antioxidant, and anti-inflammatory effects.

The role of prolactin in central nervous system inflammation

Prolactin has been shown to favor both the activation and suppression of the microglia and astrocytes, as well as the release of inflammatory and anti-inflammatory cytokines. Prolactin has also been associated with neuronal damage in diseases such as multiple sclerosis, epilepsy, and in experimental models of these diseases. However, studies show that prolactin has neuroprotective effects in conditions of neuronal damage and inflammation and may be used as neuroprotector factor. In this review, we first discuss general information about prolactin, then we summarize recent findings of prolactin function in inflammatory and anti-inflammatory processes and factors involved in the possible dual role of prolactin are described. Finally, we review the function of prolactin specifically in the central nervous system and how it promotes a neuroprotective effect, or that of neuronal damage, particularly in experimental autoimmune encephalomyelitis and during excitotoxicity. The overall studies indicated that prolactin may be a promising molecule for the treatment of some neurological diseases.

Changes in the metabolic profiles of the serum and putamen in Parkinson's disease patients - In vitro and in vivo NMR spectroscopy studies

The aim of this study was to investigate the relationship between serum metabolomic biomarkers and brain in vivo magnetic resonance spectroscopy (MRS) biomarkers in patients with Parkinson's disease (PD) as well as to investigate compound concentration changes by comparing the results with healthy control subjects. Univariate statistical analysis of the serum showed significant differences in the levels of phenylalanine, tyrosine, lysine, glutamine, glutamate, acetone, acetate, 3-hydroxybutyrate, and 1-monoacylglycerol (1-MAG) between the PD patient group and the control group. Orthogonal partial least squares discriminant analysis showed significantly different compound concentrations of acetate, 3-hydroxybutyrate, glutamine, tyrosine, 1-MAG and testosterone. In vivo MRS of the putamen showed significantly higher concentrations of glutamine/glutamate complex and glutamine in patients with PD in comparison to control subjects. Following disrupted metabolic pathways in patients with PD were identified: dopamine synthesis, steroid hormone biosynthesis, fatty acid biosynthesis, the synthesis and degradation of ketone bodies, the metabolism of pyruvate, arginine, proline, alanine, aspartate, glutamate, tyrosine and phenylalanine. The obtained results may indicate changes in neurotransmission, disturbances in energy production and an altered cell membrane structure.

The study of neuroprotective effects and underlying mechanism of Naoshuantong capsule on ischemia stroke mice

Background

Naoshuantong capsule (NSTC) is an oral Chinese medicine formula composed of Typhae Pollen, Radix Paeoniae Rubra, Curcumae Radix, Gastrodiae Rhizoma and Radix Rhapontici. It has been widely used at the acute and recovery stage of ischemic stroke since 2001. Comparing with its wide clinical application, there are only few studies emphasize on investigating its pharmacological effects.

Methods

To more generally elucidate the underlying mechanisms in this study, we identified active ingredients in NSTC by a network pharmacology approach based on transcriptomics analysis and pharmacological experiments. Modified neurological severity scores and morphometric analysis using Nissl staining were employed to evaluate the neuroprotective effects of NSTC on ischemia stroke in mice.

Results

The results showed that NSTC had preventive and protective effects on ischemia stroke, featuring repair of brain tissue during the sub-acute stage of stroke. This may attribute to the underlying mechanisms including anti-inflammatory, antioxidant, and anti-apoptotic activities, as well as an attenuation of excitatory amino acids (EAAs) toxicity of the active ingredients, especially the most active apigenin, from NSTC. Specifically, naringenin, calycosin, gastrodin, caffeic acid, paeoniflorin, and β-elemene seem to be also pharmacological active substances responsible for the anti-inflammatory effects. Meanwhile, 13-hydroxygemone, gastrodin, and p-hydroxybenzyl alcohol contributed to the attenuation of EAAs toxicity Furthermore, apigenin, naringenin, calycosin, gastrodin, and β-elemene accelerated the repair of brain ischemic tissue by up-regulating the expression of TGF-β1 levels.

Conclusions

The present study identifies the active ingredients of NSTC and illustrates the underlying mechanism using a combination of network pharmacology, transcriptomics analysis, and pharmacological experiments.

Ischemic Postconditioning Reduces NMDA Receptor Currents Through the Opening of the Mitochondrial Permeability Transition Pore and KATP Channel in Mouse Neurons

Ischemic postconditioning (PostC) is known to reduce cerebral ischemia/reperfusion (I/R) injury; however, whether the opening of mitochondrial ATP-dependent potassium (mito-K_ATP) channels and mitochondrial permeability transition pore (mPTP) cause the depolarization of the mitochondrial membrane that remains unknown. We examined the involvement of the mito-K_ATP channel and the mPTP in the PostC mechanism. Ischemic PostC consisted of three cycles of 15 s reperfusion and 15 s re-ischemia, and was started 30 s after the 7.5 min ischemic load. We recorded N-methyl-D-aspartate receptors (NMDAR)-mediated currents and measured cytosolic Ca²⁺ concentrations, and mitochondrial membrane potentials in mouse hippocampal pyramidal neurons. Both ischemic PostC and the application of a mito-K_ATP channel opener, diazoxide, reduced NMDAR-mediated currents, and suppressed cytosolic Ca²⁺ elevations during the early reperfusion period. An mPTP blocker, cyclosporine A, abolished the reducing effect of PostC on NMDAR currents. Furthermore, both ischemic PostC and the application of diazoxide potentiated the depolarization of the mitochondrial membrane potential. These results indicate that ischemic PostC suppresses Ca²⁺ influx into the cytoplasm by reducing NMDAR-mediated currents through mPTP opening. The present study suggests that depolarization of the mitochondrial membrane potential by opening of the mito-K_ATP channel is essential to the mechanism of PostC in neuroprotection against anoxic injury.

Propofol exerts neuroprotective functions by down-regulating microRNA-19a in glutamic acid-induced PC12 cells

BACKGROUND

Propofol, a kind of intravenous sedative drug, is certified that exerts anti-inflammation and antitumor functions. However, the influence of propofol in cerebral injury and the corresponding mechanism remains unexplained, that our article focuses on.

METHODS

PC12 cells were treated with propofol and exposed in glutamic acid (Glu) solutions. Cell viability, apoptotic potential, apoptosis-related and autophagy-linked proteins were tested via CCK-8, flow cytometry, and western blot assays. Reverse transcription-quantitative real-time PCR was utilized to test miR-19a expression in Glu-stimulated cells. Next, miR-19a mimic transfection was used to assess the effects of miR-19a on cell apoptosis and autophagy in Glu or propofol treated cells. Finally, western blot was performed to test AMPK and mTOR pathways.

RESULTS

Glu exposure promoted cell apoptosis and autophagy of PC12 cells, while propofol attenuated cell apoptosis and autophagy triggered by Glu. Additionally, propofol decreased the miR-19a expression in Glu-stimulated PC12 cells. Meanwhile, over-expression of miR-19a reversed the effects of propofol on Glu-induced cell apoptosis and autophagy. Moreover, propofol potentiated AMPK and mTOR pathways in Glu-stimulated PC12 cells via impeding miR-19a expression.

CONCLUSIONS

These finding revealed that propofol relieved Glu-triggered apoptosis and autophagy of PC12, and activated AMPK and mTOR pathways by suppressing miR-19a expression.

CGA ameliorates cognitive decline by regulating the PI3K/AKT signaling pathway and neurotransmitter systems in rats with multi-infarct dementia

Multi infarct dementia (MID) is a form of dementia that is preventable and treatable. However, at present, the drugs used in MID treatment were developed for Alzheimer's disease. While only a limited range of drugs is available, the incidence of MID is increasing year on year. The present study aimed to investigate the effect and underlying mechanisms of a combination of ginsenosides and astragalosides (CGA) on cognitive decline in rats with MID. A rat model of MID was established using micro-thromboembolism, and the behavioral changes in the rats were evaluated using the Morris water maze and open field tests at 60 days post-CGA intervention. The pathological morphology of the hippocampal CA1 area was observed using hematoxylin and eosin staining. The contents of ATP, ADP and AMP were determined using high-performance liquid chromatography. Mitochondrial swelling and changes in the membrane potential in the hippocampus were detected using flow cytometry, and the changes in insulin, glutamate and γ-aminobutyric acid (GABA) content were detected using ELISA. Additionally, the expression of PI3K and AKT proteins was detected using western blot analysis. In a rat model of MID, CGA shortened the escape latency, increased the frequency of platform crossing, improved the disordered vertebral cell arrangement and reduced the cell number in the hippocampal CA1 area. CGA also reduced the degree of mitochondrial swelling, increased the mitochondrial membrane potential, and elevated the energy load and ATP content in the brain of rats with MID. Furthermore, CGA increased the insulin content and upregulated the expression of PI3K and AKT in the brain of rats with MID. In addition, in the rat model of MID, CGA also enhanced the movement time and the frequency of standing, and decreased the concentration of glutamate and GABA in the brain tissue. Amelioration of the cognitive decline in rats with MID by CGA was associated with its regulatory effect on the PI3K/AKT signaling pathway and neurotransmitter systems.

Updating a Strategy for Histone Deacetylases and Its Inhibitors in the Potential Treatment of Cerebral Ischemic Stroke

BACKGROUND

Cerebral ischemic stroke is one of the severe diseases with a pathological condition that leads to nerve cell dysfunction with seldom available therapy options. Currently, there are few proven effective treatments available for improving cerebral ischemic stroke outcome. However, recently, there is increasing evidence that inhibition of histone deacetylase (HDAC) activity exerts a strong protective effect in in vivo and vitro models of ischemic stroke. Review Summary. HDAC is a posttranslational modification that is negatively regulated by histone acetyltransferase (HATS) and histone deacetylase. Based on function and DNA sequence similarity, histone deacetylases (HDACs) are organized into four different subclasses (I-IV). Modifications of histones play a crucial role in cerebral ischemic affair development after translation by modulating disrupted acetylation homeostasis. HDAC inhibitors (HDACi) mainly exert neuroprotective effects by enhancing histone and nonhistone acetylation levels and enhancing gene expression and protein modification functions. This article reviews HDAC and its inhibitors, hoping to find meaningful therapeutic targets.

CONCLUSIONS

HDAC may be a new biological target for cerebral ischemic stroke. Future drug development targeting HDAC may make it a potentially effective anticerebral ischemic stroke drug.

Experimental cortical stroke induces aberrant increase of sharp-wave-associated ripples in the hippocampus and disrupts cortico-hippocampal communication

The functional consequences of ischemic stroke in the remote brain regions are not well characterized. The current study sought to determine changes in hippocampal oscillatory activity that may underlie the cognitive impairment observed following distal middle cerebral artery occlusion (dMCAO) without causing hippocampal structural damage. Local field potentials were recorded from the dorsal hippocampus and cortex in urethane-anesthetized rats with multichannel silicon probes during dMCAO and reperfusion, or mild ischemia induced by bilateral common carotid artery occlusion (CCAO). Bilateral change of brain state was evidenced by reduced theta/delta amplitude ratio and shortened high theta duration following acute dMCAO but not CCAO. An aberrant increase in the occurrence of sharp-wave-associated ripples (150-250 Hz), crucial for memory consolidation, was only detected after dMCAO reperfusion, coinciding with an increased occurrence of high-frequency discharges (250-450 Hz). dMCAO also significantly affected the modulation of gamma amplitude in the cortex coupled to hippocampal theta phase, although both hippocampal theta and gamma power were temporarily decreased during dMCAO. Our results suggest that MCAO may disrupt the balance between excitatory and inhibitory circuits in the hippocampus and alter the function of cortico-hippocampal network, providing a novel insight in how cortical stroke affects function in remote brain regions.

TRPA1 mediates damage of the retina induced by ischemia and reperfusion in mice

Oxidative stress is implicated in retinal cell injury associated with glaucoma and other retinal diseases. However, the mechanism by which oxidative stress leads to retinal damage is not completely understood. Transient receptor potential ankyrin 1 (TRPA1) is a redox-sensitive channel that, by amplifying the oxidative stress signal, promotes inflammation and tissue injury. Here, we investigated the role of TRPA1 in retinal damage evoked by ischemia (1 hour) and reperfusion (I/R) in mice. In wild-type mice, retinal cell numbers and thickness were reduced at both day-2 and day-7 after I/R. By contrast, mice with genetic deletion of TRPA1 were protected from the damage seen in their wild-type littermates. Daily instillation of eye drops containing two different TRPA1 antagonists, an oxidative stress scavenger, or a NADPH oxidase-1 inhibitor also protected the retinas of C57BL/6J mice exposed to I/R. Mice with genetic deletion of the proinflammatory TRP channels, vanilloid 1 (TRPV1) or vanilloid 4 (TRPV4), were not protected from I/R damage. Surprisingly, genetic deletion or pharmacological blockade of TRPA1 also attenuated the increase in the number of infiltrating macrophages and in the levels of the oxidative stress biomarker, 4-hydroxynonenal, and of the apoptosis biomarker, active caspase-3, evoked by I/R. These findings suggest that TRPA1 mediates the oxidative stress burden and inflammation that result in murine retinal cell death. We also found that TRPA1 (both mRNA and protein) is expressed by human retinal cells. Thus, it is possible that inhibition of a TRPA1-dependent pathway could also attenuate glaucoma-related retinal damage.

Neurovascular Unit as a Source of Ischemic Stroke Biomarkers-Limitations of Experimental Studies and Perspectives for Clinical Application

Cerebral stroke, which is one of the most frequent causes of mortality and leading cause of disability in developed countries, often leads to devastating and irreversible brain damage. Neurological and neuroradiological diagnosis of stroke, especially in its acute phase, is frequently uncertain or inconclusive. This results in difficulties in identification of patients with poor prognosis or being at high risk for complications. It also makes difficult identification of these stroke patients who could benefit from more aggressive therapies. In contrary to the cardiovascular disease, no single biomarker is available for the ischemic stroke, addressing the abovementioned issues. This justifies the need for identifying of effective diagnostic measures characterized by high specificity and sensitivity. One of the promising avenues in this area is studies on the panels of biomarkers characteristic for processes which occur in different types and phases of ischemic stroke and represent all morphological constituents of the brains' neurovascular unit (NVU). In this review, we present the current state of knowledge concerning already-used or potentially applicable biomarkers of the ischemic stroke. We also discuss the perspectives for identification of biomarkers representative for different types and phases of the ischemic stroke, as well as for different constituents of NVU, which concentration levels correlate with extent of brain damage and patients' neurological status. Finally, a critical analysis of perspectives on further improvement of the ischemic stroke diagnosis is presented.

Purines: From Diagnostic Biomarkers to Therapeutic Agents in Brain Injury

The purines constitute a family of inter-related compounds that serve a broad range of important intracellular and extracellular biological functions. In particular, adenosine triphosphate (ATP) and its metabolite and precursor, adenosine, regulate a wide variety of cellular and systems-level physiological processes extending from ATP acting as the cellular energy currency, to the adenosine arising from the depletion of cellular ATP and responding to reduce energy demand and hence to preserve ATP during times of metabolic stress. This inter-relationship provides opportunities for both the diagnosis of energy depletion during conditions such as stroke, and the replenishment of ATP after such events. In this review we address these opportunities and the broad potential of purines as diagnostics and restorative agents.

Lysophosphatidic Acid Receptor 5 Plays a Pathogenic Role in Brain Damage after Focal Cerebral Ischemia by Modulating Neuroinflammatory Responses

Receptor-mediated lysophosphatidic acid (LPA) signaling has come to be considered an important event for various diseases. In cerebral ischemia, LPA₁ has recently been identified as a receptor subtype that mediates brain injury, but the roles of other LPA receptor subtypes remain unknown. Here, we investigated the potential role of LPA₅ as a novel pathogenic factor for cerebral ischemia using a mouse model of transient middle cerebral artery occlusion (tMCAO). LPA₅ was upregulated in the ischemic core region after tMCAO challenge, particularly in activated microglia. When TCLPA5, a selective LPA₅ antagonist, was given to tMCAO-challenged mice immediately after reperfusion, brain damage, including brain infarction, functional neurological deficit, and neuronal and non-neuronal apoptosis, was reduced in mice. Similarly, delayed TCLPA5 administration (at three hours after reperfusion) reduced brain infarction and neurological deficit. The histological results demonstrated that TCLPA5 administration attenuated microglial activation, as evidenced by the decreased Iba1 immunoreactivities, the number of amoeboid cells, and proliferation in an injured brain. TCLPA5 administration also attenuated the upregulation of the expression of pro-inflammatory cytokines at mRNA levels in post-ischemic brain, which was also observed in lipopolysaccharide-stimulated BV2 microglia upon LPA₅ knockdown. Overall, this study identifies LPA₅ as a novel pathogenic factor for cerebral ischemia, further implicating it as a promising target for drug development to treat this disease.

γ-Aminobutyric acid transporters as relevant biological target: Their function, structure, inhibitors and role in the therapy of different diseases

γ-Aminobutyric acid (GABA) is a major inhibitory neurotransmitter in the nervous system. It plays a crucial role in many physiological processes. Upon release from the presynaptic element, it is removed from the synaptic cleft by reuptake due to the action of GABA transporters (GATs). GATs belong to a large SLC6 protein family whose characteristic feature is sodium-dependent relocation of neurotransmitters through the cell membrane. GABA transporters are characterized in many contexts, but their spatial structure is not fully known. They are divided into four types, which differ in occurrence and role. Herein, the special attention was paid to these transporting proteins. This comprehensive review presents the current knowledge about GABA transporters. Their distribution in the body, physiological functions and possible utilization in the therapy of different diseases were fully discussed. The important structural features were described based on published data, including sequence analysis, mutagenesis studies, and comparison with known SLC6 transporters for leucine (LeuT), dopamine (DAT) and serotonin (SERT). Moreover, the most important inhibitors of GABA transporters of various basic scaffolds, diverse selectivity and potency were presented.