Tripchlorolide May Improve Spatial Cognition Dysfunction and Synaptic Plasticity after Chronic Cerebral Hypoperfusion

Olfactory Three-Needle Electroacupuncture Improved Synaptic Plasticity and Gut Microbiota of SAMP8 Mice by Stimulating Olfactory Nerve

OBJECTIVE

To investigate the effects and mechanisms of olfactory three-needle (OTN) electroacupuncture (EA) stimulation of the olfactory system on cognitive dysfunction, synaptic plasticity, and the gut microbiota in senescence-accelerated mouse prone 8 (SAMP8) mice.

METHODS

Thirty-six SAMP8 mice were randomly divided into the SAMP8 (P8), SAMP8+OTN (P8-OT), and SAMP8+nerve transection+OTN (P8-N-OT) groups according to a random number table (n=12 per group), and 12 accelerated senescence-resistant (SAMR1) mice were used as the control (R1) group. EA was performed at the Yintang (GV 29) and bilateral Yingxiang (LI 20) acupoints of SAMP8 mice for 4 weeks. The Morris water maze test, transmission electron microscopy, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) staining, Nissl staining, Golgi staining, Western blot, and 16S rRNA sequencing were performed, respectively.

RESULTS

Compared with the P8 group, OTN improved the cognitive behavior of SAMP8 mice, inhibited neuronal apoptosis, increased neuronal activity, and attenuated hippocampal synaptic dysfunction (P<0.05 or P<0.01). Moreover, the expression levels of synaptic plasticity-related proteins N-methyl-D-aspartate receptor 1 (NMDAR1), NMDAR2B, synaptophysin (SYN), and postsynaptic density protein-95 (PSD95) in hippocampus were increased by OTN treatment (P<0.05 or P<0.01). Furthermore, OTN greatly enhanced the brain-derived neurotrophic factor (BDNF)/cAMP-response element binding (CREB) signaling and phosphatidylinositol 3-kinase/protein kinase B/mammalian target of rapamycin (PI3K/AKT/mTOR) signaling compared with the P8 group (P<0.05 or P<0.01). However, the neuroprotective effect of OTN was attenuated by olfactory nerve truncation. Compared with the P8 group, OTN had a very limited effect on the fecal microbial structure and composition of SAMP8 mice, while specifically increased the genera Oscillospira and Sutterella (P<0.05). Interestingly, the P8-N-OT group showed an abnormal fecal microbiota with higher microbial α-diversity, Firmicutes/Bacteroidetes ratio and pathogenic bacteria (P<0.05 or P<0.01).

CONCLUSIONS

OTN improved cognitive deficits and hippocampal synaptic plasticity by stimulating the olfactory nerve and activating the BDNF/CREB and PI3K/AKT/mTOR signaling pathways. Although the gut microbiota was not the main therapeutic target of OTN for Alzheimer's disease, the olfactory nerve was essential to maintain the homeostasis of gut microbiota.

Potential therapeutic and diagnostic approaches of exosomes in multiple sclerosis pathophysiology

Exosomes are bilayer lipid vesicles that are released by cells and contain proteins, nucleic acids, and lipids. They can be internalized by other cells, inducing inflammatory responses and instigating toxicities in the recipient cells. Exosomes can also serve as therapeutic vehicles by transporting protective cargo to maintain homeostasis. Multiple studies have shown that exosomes can initiate and participate in the regulation of neuroinflammation, improve neurogenesis, and are closely related to the pathogenesis of central nervous system (CNS) diseases, including multiple sclerosis (MS). Exosomes can be secreted by both neurons and glial cells in the CNS, and their contents change with disease occurrence. Due to their ability to penetrate the blood-brain barrier and their stability in peripheral fluids, exosomes are attractive biomarkers of CNS diseases. In recent years, exosomes have emerged as potential therapeutic agents for CNS diseases, including MS. However, the molecular pathways in the pathogenesis of MS are still unknown, and further research is needed to fully understand the role of exosomes in the occurrence or improvement of MS disease. Thereby, in this review, we intend to provide a more complete understanding of the pathways in which exosomes are involved and affect the occurrence or improvement of MS disease.

Enriched Environment Inhibits Neurotoxic Reactive Astrocytes via JAK2-STAT3 to Promote Glutamatergic Synaptogenesis and Cognitive Improvement in Chronic Cerebral Hypoperfusion Rats

Chronic cerebral hypoperfusion (CCH) is a primary contributor to cognitive decline in the elderly. Enriched environment (EE) is proved to improve cognitive function. However, mechanisms involved remain unclear. The purpose of the study was exploring the mechanisms of EE in alleviating cognitive deficit in rats with CCH. To create a rat model of CCH, 2-vessel occlusion (2-VO) surgery was performed. All rats lived in standard or enriched environments for 4 weeks. Cognitive function was assessed using the novel object recognition test and Morris water maze test. The protein levels of glutamatergic synapses, neurotoxic reactive astrocytes, reactive microglia, and JAK2-STAT3 signaling pathway were measured using Western blot. The mRNA levels of synaptic regulatory factors, C1q, TNF-α, and IL-1α were identified using quantitative PCR. Immunofluorescence was used to detect glutamatergic synapses, neurotoxic reactive astrocytes, and reactive microglia, as well as the expression of p-STAT3 in astrocytes in the hippocampus. The results demonstrated that the EE mitigated cognitive impairment in rats with CCH and enhanced glutamatergic synaptogenesis. EE also inhibited the activation of neurotoxic reactive astrocytes. Moreover, EE downregulated microglial activation, levels of C1q, TNF-α and IL-1α and phosphorylation of JAK2 and STAT3. Our results suggest that inhibition of neurotoxic reactive astrocytes may be one of the mechanisms by which EE promotes glutamatergic synaptogenesis and improves cognitive function in rats with CCH. The downregulation of reactive microglia and JAK2-STAT3 signaling pathway may be involved in this process.

Upregulation of RasGRF1 ameliorates spatial cognitive dysfunction in mice after chronic cerebral hypoperfusion

Chronic cerebral hypoperfusion (CCH)-mediated cognitive impairment is a serious problem worldwide. However, given its complexity, the underlying mechanisms by which CCH induces cognitive dysfunction remain unclear, resulting in a lack of effective treatments. In this study, we aimed to determine whether changes in the expression of RasGRF1, an important protein associated with cognition and synaptic plasticity, underlie the associated impairments in cognition after CCH. We found that RasGRF1 levels markedly decreased following CCH. Through prediction and validation studies, we observed that miRNA-323-3p was upregulated after CCH and could bind to the 3'-untranslated region of Rasgrf1 mRNA and regulate its expression in vitro. Moreover, the inhibition of miRNA-323-3p upregulated Rasgrf1 expression in the hippocampus after CCH, which was reversed by Rasgrf1 siRNA. This suggests that miRNA-323-3p is an important regulator of Rasgrf1. The Morris water maze and Y maze tests showed that miRNA-323-3p inhibition and Rasgrf1 upregulation improved spatial learning and memory, and electrophysiological measurements revealed deficits in long-term potentiation after CCH that were reversed by Rasgrf1 upregulation. Dendritic spine density and mature mushroom spine density were also improved after miRNA-323-3p inhibition and Rasgrf1 upregulation. Furthermore, Rasgrf1 upregulation by miRNA-323-3p inhibition improved dendritic spine density and mature mushroom spine density and ameliorated the deterioration of synapses and postsynaptic density. Overall, RasGRF1 regulation attenuated cognitive impairment, helped maintain structural and functional synaptic plasticity, and prevented synapse deterioration after CCH. These results suggest that Rasgrf1 downregulation by miRNA-323-3p plays an important role in cognitive impairment after CCH. Thus, RasGRF1 and miRNA-323-3p may represent potential therapeutic targets for cognitive impairment after CCH.

Chronic exposure to 2.45 GHz microwave radiation improves cognition and synaptic plasticity impairment in vascular dementia model

Purpose: In this study, we evaluated the effects of 2.45 GHz microwave radiation on cognitive dysfunction induced by vascular dementia (VaD).Methods: The VaD was induced by bilateral-common carotid occlusion (2-VO). The rats were divided into 4 groups including: control (n = 6), sham (n = 6), 2-VO (n = 8), and 2-VO + Wi-Fi (n = 10) groups. Wi-Fi modem centrally located at the distance of 25 cm from the animal's cages and the animals were continuously exposed to Wi-Fi signal while they freely moved in the cage (2 h/day for forty-five days). Therefore, the power density (PD) and specific absorption rate value (SAR) decreased at a distance of 25 to 60 cm (PD = 0.018 to 0.0032 mW/cm², SAR = 0.0346 to 0.0060 W/Kg). The learning, memory, and hippocampal synaptic-plasticity were evaluated by radial arm maze (RAM), passive avoidance (PA), and field-potential recording respectively. The number of hippocampal CA1 cells was also assessed by giemsa staining.Results: Our results showed that VaD model led to impairment in the spatial learning and memory performance in RAM and PA that were associated with long-term potentiation (LTP) impairment, decrease of basal-synaptic transmission (BST), increase of GABA transmission, and decline of neurotransmitter release-probability as well as hippocampal cell loss. Notably, chronic Wi-Fi exposure significantly recovered the learning-memory performance, LTP induction, and cell loss without any effect on BST.Conclusions: The LTP recovery by Wi-Fi in the 2-VO rats was probably related to significant increases in the hippocampal CA1 neuronal density, partial recovery of neurotransmitter release probability, and reduction of GABA transmissiSon as evident by rescue of paired-pulse ratio 10 ms.

Berberine Ameliorates Cognitive Impairment by Regulating Microglial Polarization and Increasing Expression of Anti-inflammatory Factors following Permanent Bilateral Common Carotid Artery Occlusion in Rats

BACKGROUND

Chronic cerebral hypoperfusion is associated with vascular cognitive impairment, and there are no specific therapeutic agents for use in clinical practice. Berberine has demonstrated good neuroprotective effects in models of acute cerebral ischemia; however, whether it can alleviate cognitive impairment caused by chronic cerebral hypoperfusion has rarely been investigated.

OBJECTIVE

The present study aimed to explore the mechanism by which berberine alleviates cognitive impairment resulting from chronic cerebral hypoperfusion.

METHODS

Forty-two male Sprague-Dawley rats were randomly divided into three groups: sham, model, and berberine. The models of chronic cerebral hypoperfusion were established via permanent bilateral common carotid artery occlusion (BCCAO). Cognitive function was evaluated using the Morris water maze, while neuronal damage and microglial activation and polarization were evaluated using western blotting and immunofluorescence, respectively. Enzyme-linked immunosorbent assays were used to detect the expression of anti-inflammatory factors including interleukin- 4 (IL-4) and interleukin-10 (IL-10).

RESULTS

Rats exhibited cognitive dysfunction after BCCAO, which was significantly attenuated following the berberine intervention. Levels of synaptophysin and NeuN were decreased in states of chronic cerebral hypoperfusion, during which microglial activation and a transition from the M2 to M1 phenotype were observed. Berberine treatment also significantly reversed these features. Moreover, levels of IL-4 and IL-10 expression increased significantly after berberine treatment.

CONCLUSION

Berberine may mitigate vascular cognitive dysfunction by promoting neuronal plasticity, inhibiting microglial activation, promoting transformation from an M1 to an M2 phenotype, and increasing levels of IL-4 and IL-10 expression.

Treatment With an Angiopoietin-1 Mimetic Peptide Improves Cognitive Outcome in Rats With Vascular Dementia

Background and Purpose

Vascular dementia (VaD) is a complex neurodegenerative disease affecting cognition and memory. There is a lack of approved pharmacological treatments specifically for VaD. In this study, we investigate the therapeutic effects of AV-001, a Tie2 receptor agonist, in middle-aged rats subjected to a multiple microinfarct (MMI) model of VaD.

Methods

Male, 10-12 month-old, Wistar rats were employed. The following experimental groups were used: Sham, MMI, MMI+1 μg/Kg AV-001, MMI+3 μg/Kg AV-001, MMI+6 μg/Kg AV-001. AV-001 treatment was initiated at 1 day after MMI and administered once daily via intraperitoneal injection. An investigator blinded to the experimental groups conducted a battery of neuro-cognitive tests including modified neurological severity score (mNSS) test, novel object recognition test, novel odor recognition test, three chamber social interaction test, and Morris water maze test. Rats were sacrificed at 6 weeks after MMI.

Results

There was no mortality observed after 1, 3, or 6 μg/Kg AV-001 treatment in middle-aged rats subjected to MMI. AV-001 treatment (1, 3, or 6 μg/Kg) does not significantly alter blood pressure or heart rate at 6 weeks after MMI compared to baseline values or the MMI control group. Treatment of MMI with 1 or 3 μg/Kg AV-001 treatment does not significantly alter body weight compared to Sham or MMI control group. While 6 μg/Kg AV-001 treated group exhibit significantly lower body weight compared to Sham and MMI control group, the weight loss is evident starting at 1 day after MMI when treatment was initiated and is not significantly different compared to its baseline values at day 0 or day 1 after MMI. AV-001 treatment significantly decreases serum alanine aminotransferase, serum creatinine, and serum troponin I levels compared to the MMI control group; however, all values are within normal range. MMI induces mild neurological deficits in middle-aged rats indicated by low mNSS scores (<6 on a scale of 0-18). Compared to control MMI group, 1 μg/Kg AV-001 treatment group did not exhibit significantly different mNSS scores, while 3 and 6 μg/Kg AV-001 treatment induced significantly worse mNSS scores on days 21-42 and 14-42 after MMI, respectively. MMI in middle-aged rats induces significant cognitive impairment including short-term memory loss, long-term memory loss, reduced preference for social novelty and impaired spatial learning and memory compared to sham control rats. Rats treated with 1 μg/Kg AV-001 exhibit significantly improved short-term and long-term memory, increased preference for social novelty, and improved spatial learning and memory compared to MMI rats. Treatment with 3 μg/Kg AV-001 improves short-term memory and preference for social novelty but does not improve long-term memory or spatial learning and memory compared to MMI rats. Treatment with 6 μg/Kg AV-001 improves only long-term memory compared to MMI rats. Thus, 1 μg/Kg AV-001 treatment was selected as an optimal dose. Treatment of middle-aged rats subjected to MMI with 1 μg/Kg AV-001 significantly increases axon density, myelin density and myelin thickness in the corpus callosum, as well as increases synaptic protein expression, neuronal branching and dendritic spine density in the cortex, oligodendrocytes and oligodendrocyte progenitor cell number in the cortex and striatum and promotes neurogenesis in the subventricular zone compared to control MMI rats.

Conclusions

In this study, we present AV-001 as a novel therapeutic agent to improve cognitive function and reduce white matter injury in middle aged-rats subjected to a MMI model of VaD. Treatment of MMI with 1 μg/Kg AV-001 significantly improves cognitive function, and increases axon density, remyelination and neuroplasticity in the brain of middle-aged rats.

Human ESC-derived immunity- and matrix- regulatory cells ameliorated white matter damage and vascular cognitive impairment in rats subjected to chronic cerebral hypoperfusion

OBJECTIVES

This study investigated the ability of immunity- and matrix- regulatory cells (IMRCs) to improve cognitive function in a rat model of vascular cognitive impairment.

MATERIALS AND METHODS

A chronic cerebral hypoperfusion (CCH) model was established in rats via permanent bilateral occlusion of the common carotid arteries (two-vessel occlusion, 2VO). The rats then received intravenous injections of IMRCs or saline. A single injection of different doses of IMRCs (1 × 106  cells/rat, 2 × 106  cells/rat, or 4 × 106  cells/rat) was administered via tail vein 72 h after establishment of the model. To evaluate functional recovery, the rats were subjected to behavioural tests after 30 days of CCH. Imaging, western blotting, immunofluorescence staining, and quantitative real-time PCR were used to analyse neuroinflammation and white matter injury after 14 and 40 days of CCH. RNA sequencing (RNA-seq) was used to profile gene expression changes in copine 1 (CPNE1) in response to IMRCs treatment.

RESULTS

Intravenous injection of 4 × 106 IMRCs alleviated white matter damage and ameliorated cognitive deficits in rats subjected to CCH. Immunofluorescence staining suggested that activation of microglia and astrocytes was reduced, and RNA sequencing showed that CPNE1 expression was significantly elevated following treatment with IMRCs.

CONCLUSIONS

Intravenous injection of IMRCs protected against CCH-induced white matter injury and cognitive impairment inhibition of microglial activation and regulation of microglia polarization.

Cordycepin Ameliorates Synaptic Dysfunction and Dendrite Morphology Damage of Hippocampal CA1 via A1R in Cerebral Ischemia

Cordycepin exerted significant neuroprotective effects and protected against cerebral ischemic damage. Learning and memory impairments after cerebral ischemia are common. Cordycepin has been proved to improve memory impairments induced by cerebral ischemia, but its underlying mechanism has not been revealed yet. The plasticity of synaptic structure and function is considered to be one of the neural mechanisms of learning and memory. Therefore, we investigated how cordycepin benefits dendritic morphology and synaptic transmission after cerebral ischemia and traced the related molecular mechanisms. The effects of cordycepin on the protection against ischemia were studied by using global cerebral ischemia (GCI) and oxygen-glucose deprivation (OGD) models. Behavioral long-term potentiation (LTP) and synaptic transmission were observed with electrophysiological recordings. The dendritic morphology and histological assessment were assessed by Golgi staining and hematoxylin-eosin (HE) staining, respectively. Adenosine A1 receptors (A1R) and adenosine A2A receptors (A2AR) were evaluated with western blotting. The results showed that cordycepin reduced the GCI-induced dendritic morphology scathing and behavioral LTP impairment in the hippocampal CA1 area, improved the learning and memory abilities, and up-regulated the level of A1R but not A2AR. In the in vitro experiments, cordycepin pre-perfusion could alleviate the hippocampal slices injury and synaptic transmission cripple induced by OGD, accompanied by increased adenosine content. In addition, the protective effect of cordycepin on OGD-induced synaptic transmission damage was eliminated by using an A1R antagonist instead of A2AR. These findings revealed that cordycepin alleviated synaptic dysfunction and dendritic injury in ischemic models by modulating A1R, which provides new insights into the pharmacological mechanisms of cordycepin for ameliorating cognitive impairment induced by cerebral ischemia.

Enriched environment remedies cognitive dysfunctions and synaptic plasticity through NMDAR-Ca2+-Activin A circuit in chronic cerebral hypoperfusion rats

Chronic cerebral ischemia (CCI) is one of the critical factors in the occurrence and development of vascular cognitive impairment (VCI). Apoptosis of nerve cells and changes in synaptic activity after CCI are the key factors to induce VCI. Synaptic stimulation up-regulates intraneuronal Ca2+ level through N-methyl-D-aspartic acid receptor (NMDAR) via induction of the activity-regulated inhibitor of death (AID) expression to produce active-dependent neuroprotection. Moreover, the regulation of synaptic plasticity could improve cognition and learning ability. Activin A (ActA), an exocrine protein of AID, can promote NMDAR phosphorylation and participate in the regulation of synaptic plasticity. We previously found that exogenous ActA can improve the cognitive function of rats with chronic cerebral ischemia and enhance the oxygenated glucose deprivation of intracellular Ca2+ level. In addition to NMDAR, the Wnt pathway is critical in the positive regulation of LTP through activation or inhibition. It plays an essential role in synaptic transmission and activity-dependent synaptic plasticity. The enriched environment can increase ActA expression during CCI injury. We speculated that the NMDAR-Ca2+-ActA signal pathway has a loop-acting mode, and the environmental enrichment could improve chronic cerebral ischemia cognitive impairment via NMDAR-Ca2+-ActA, Wnt/β-catenin pathway is involved in this process. For the hypothesis verification, this study intends to establish chronic cerebral hypoperfusion (CCH) rat model, explore the improvement effect of enriched environment on VCI, detect the changes in plasticity of synaptic morphology and investigate the regulatory mechanism NMDAR-Ca2+-ActA-Wnt/β-catenin signaling loop, providing a therapeutic method for the treatment of CCH.

Dimethyl fumarate improves cognitive deficits in chronic cerebral hypoperfusion rats by alleviating inflammation, oxidative stress, and ferroptosis via NRF2/ARE/NF-κB signal pathway

Cerebrovascular disease and its risk factors cause persistent decrease of cerebral blood flow, chronic cerebral hypoperfusion (CCH) is the major foundation of vascular cognitive impairment (VCI). The hippocampus is extremely vulnerable to cerebral ischemia and hypoxia. Oxidative stress and neuroinflammation injury are important pathophysiological mechanisms of this process, which is closely related to hippocampal neurons damage and loss. Dimethyl fumarate (DMF), an FDA-approved therapeutic for multiple sclerosis (MS), plays a protective role in multiple neurological disorders. Studies have shown that DMF exerts anti-inflammatory and antioxidant effects via the NRF2/ARE/NF-κB signaling pathway. Thus, this study aimed to evaluate the neuroprotective effect of DMF in the CCH rat model. Ferroptosis, a novel defined iron-dependent cell death form, were found to be strongly associated with the pathophysiology of CCH. Emerging evidences have shown that inhibition of ferroptosis by targeting NRF2 exerted neuroprotective effect in neurodegeneration diseases. We also investigated whether DMF can alleviate cognitive deficits through inhibition of ferroptosis by the NRF2 signaling pathway in this study. DMF was intragastric for consecutive five weeks (100 mg/kg/day). Then behavior test and histological, molecular, and biochemical analysis were performed. We found that DMF treatment significantly improved cognitive deficits and partially reversed hippocampus neuronal damage and loss caused by CCH. And DMF treatment decreased hippocampus IL-1β, TNF-α, and IL-6 pro-inflammatory cytokines concentration, and mediated the NF-κB signaling pathway. And DMF also alleviated hippocampus oxidative stress through reducing MDA, and increasing GSH and SOD levels, which are also closely associated with ferroptosis. Besides, DMF treatment reduced the expression of PTGS2, and increased the expression of FTH1 and xCT, and the iron content is also reduced, which were the important features related to ferroptosis. Furthermore, DMF activated the NRF2/ARE signaling pathway and upregulated the expression of HO-1, NQO1 and GPX4. These outcomes indicated that DMF can improve cognitive impairment in rats with CCH, possibly through alleviating neuroinflammation, oxidative stress damage and inhibiting ferroptosis of hippocampal neurons. Overall, our results provide new evidence for the neuroprotective role of DMF.

Tectorigenin attenuates cognitive impairments in mice with chronic cerebral ischemia by inhibiting the TLR4/NF-κB signaling pathway

This study aims to explore the effect of Tectorigenin in chronic cerebral ischemia (CCI)-induced cognitive impairment mice model. Cognitive impairment, hippocampal tissue histopathology, and myelin density in CCI mice were detected. HT22 cells were used to induce oxygen-glucose deprivation/reperfusion (OGD/R) injury. Cell viability and apoptosis of transfected HT22 cells and toll-like receptor-4 (TLR4)/nuclear factor-kappaB (NF-κB) pathway-related factor levels in hippocampal tissue and OGD/R models were detected. CCI caused cognitive impairment, hippocampal damage, and decreased myelin density in mice while promoting interleukin-1β, tumor necrosis factor-alpha, TLR4, myeloid differentiation primary response gene 88, p-p65, NLRP3, and ASC levels. Tectorigenin reversed the effects of CCI in mice and reversed the promoting effects of OGD/R on apoptosis and TLR4/NF-κB pathway-related factors levels, while overexpressed TLR4 reversed the effects of Tectorigenin in OGD/R-induced HT-22 cells. Tectorigenin alleviated cognitive impairment in CCI mice by inhibiting the TLR4/NF-κB signaling pathway.

EGB761 ameliorates chronic cerebral hypoperfusion-induced cognitive dysfunction and synaptic plasticity impairment

Chronic cerebral hypoperfusion (CCH) may lead to the cognitive dysfunction, but the underlying mechanisms are unclear. EGB761, extracted from Ginkgo biloba and as a phytomedicine widely used in the world, has been showed to have various neuroprotective roles and mechanisms, and therapeutic effects in Alzheimer’s disease and other cognitive dysfunctions. However, improvements in cognitive function after CCH, following treatment with EGB761, have not been ascertained yet. In this study, we used the behavior test, electrophysiology, neurobiochemistry, and immunohistochemistry to investigate the EGB761’s effect on CCH-induced cognitive dysfunction and identify its underlying mechanisms. The results showed that EGB761 ameliorates spatial cognitive dysfunction occurring after CCH. It may also improve impairment of the long-term potentiation, field excitable potential, synaptic transmission, and the transmission synchronization of neural circuit signals between the entorhinal cortex and hippocampal CA1. EGB761 may also reverse the inhibition of neural activity and the degeneration of dendritic spines and synaptic structure after CCH; it also prevents the downregulation of synaptic proteins molecules and pathways related to the formation and stability of dendritic spines structures. EGB761 may inhibit axon demyelination and ameliorate the inhibition of the mTOR signaling pathway after CCH to improve protein synthesis. In conclusion, EGB761 treatment after CCH may improve spatial cognitive function by ameliorating synaptic plasticity impairment, synapse degeneration, and axon demyelination by rectifying the inhibition of the mTOR signaling pathway.

Intensive treadmill training promotes cognitive recovery after cerebral ischemia-reperfusion in juvenile rats

Rehabilitation training is routine for children who experience stroke, but its protective mechanism remains unclear. To study the effect of treadmill training intensity on hippocampal synaptic plasticity after cerebral ischemia, a model of middle cerebral artery occlusion (MCAO)/reperfusion was established in young rats to simulate childhood ischemic stroke. The rats were randomly allocated into five groups: sham operation, MCAO, low-intensity exercise and MCAO (5 m/min), medium-intensity exercise and MCAO (10 m/min), and high-intensity exercise and MCAO (15 m/min). Intervention was continued for 14 days, and a series of experimental tests were conducted. After MCAO, the juvenile rats exhibited a series of morphological and functional alterations, including changes in their neurobehavior and cerebral infarct volumes. Compared with control rats, MCAO rats had a longer escape latency and crossed fewer platforms in the water maze test and exhibited decreased hippocampal neuron density and Synapsin I and PSD95 expression. Furthermore, MCAO rats exhibited synapse morphology changes and abnormal serum levels of lactic acid and corticosterone. Treadmill training effectively reduced the neurobehavioral scores and cerebral infarction volumes, with medium-intensity training showing the best effect. Treadmill training shortened the escape latency, increased the number of platform crossings, and improved the spatial cognitive abilities of the rats, with the medium intensity training having the best effect on spatial learning/memory efficiency. Treadmill training increased the neuron density in the hippocampus, with the medium-intensity training resulting in the highest density. Treadmill training had a positive effect on the expression of Synapsin I and PSD95, with the medium-intensity training showing the strongest effect. Treadmill training improved the sub-microstructure synapse morphology, with the medium-intensity training demonstrating the best effect. Treadmill training increased the plasma levels of lactic acid and corticosterone, with the high-intensity training having the most obvious effect. Treadmill training can provide neuroprotection by promoting hippocampal synaptic plasticity, with medium-intensity training showing the most optimal effects.

Identification of a hippocampal lncRNA-regulating network in cognitive dysfunction caused by chronic cerebral hypoperfusion

Cognitive dysfunction caused by chronic cerebral hypoperfusion is a common underlying cause of many cognition-related neurodegenerative diseases. The mechanisms of cognitive dysfunction caused by CCH are not clear. Long non-coding RNA is involved in synaptic plasticity and cognitive function, but whether lncRNA is involved in cognitive dysfunction caused by CCH has not yet been reported. In the present study, we identified the altered lncRNAs and mRNAs by deep RNA sequencing. A total of 128 mRNAs and 91 lncRNAs were up-regulated, and 108 mRNAs and 98 lncRNAs were down-regulated. Real-time reverse transcription-polymerase chain reaction verified the reliability of the lncRNA and mRNA sequencing. Gene Ontology and KEGG pathway analyses showed that differentially-expressed mRNAs were related to peptide antigen binding, the extracellular space, the monocarboxylic acid transport, and tryptophan metabolism. The co-expression analysis showed that 161 differentially expressed lncRNAs were correlated with DE mRNAs. By predicting the miRNA in which both DE lncRNAs and DE mRNAs bind together, we constructed a competitive endogenous RNA network. In this lncRNAs-miRNAs-mRNAs network, 559 lncRNA-miRNA-mRNA targeted pairs were identified, including 83 lncRNAs, 67 miRNAs, and 108 mRNAs. Through GO and KEGG pathway analysis, we further analyzed and predicted the regulatory function and potential mechanism of ceRNA network regulation. Our results are helpful for understanding the pathogenesis of cognitive dysfunction caused by CCH and provide direction for further research.

Tropisetron But Not Granisetron Ameliorates Spatial Memory Impairment Induced by Chronic Cerebral Hypoperfusion

Tropisetron and Granisetorn are 5-HT3 antagonists with antiemetic effects. Tropisetron also has a partial agonistic effect on alpha-7 nicotinic acetylcholine receptors (α7 nAChRs). On the other hand, chronic cerebral hypoperfusion (CCH) attenuates cerebral blood flow and impairs cognitive functions. The goal of this study was to investigate the effect of Tropisetron and Granisetron on CCH-induced spatial memory impairment in rats. Forty-eight male Wistar rats were used in this study. 2-VO surgery was done to induce CCH and Radial Eight Arm Maz apparatus was used to evaluate spatial memory (working and reference memory). Tropisetron was injected intraperitoneally at the doses of 1 and 5 mg/kg, and Granisetron was injected intraperitoneally at the dose of 3 mg/kg. Dorsal hippocampal (CA1) neurons count, Interleukin 6 (IL-6) serum level, and serotonin-reuptake transporter (SERT) gene expression were also evaluated. The results showed, CCH impaired working and reference memory, increased IL-6 serum level, and decreased CA1 neurons and SERT expression. Tropisetron at the dose of 5 mg/kg restored all the effects of CCH. However, Granisetron did not restore CCH-induced memory impairment. Furthermore, Granisetron had no effect on IL-6. While, it increased SERT expression and CA1 neurons. In conclusion, Tropisetron but not Granisetron, ameliorated spatial memory impairment induced by CCH. We suggested conducting more detailed studies investigating the role of serotonergic system (5-HT3 receptors and serotonin transporters) and also α7 nAChRs in the effects of Tropisetron.

MicroRNA-153 impairs presynaptic plasticity by blocking vesicle release following chronic brain hypoperfusion

Background

Chronic brain hypoperfusion (CBH) is closely related to Alzheimer’s disease (AD) and vascular dementia (VaD). Meanwhile, synaptic pathology plays a prominent role in the initial stage of AD and VaD. However, whether and how CBH impairs presynaptic plasticity is currently unclear.

Methods

In the present study, we performed a battery of techniques, including primary neuronal culture, patch clamp, stereotaxic injection of the lentiviral vectors, morris water maze (MWM), dual luciferase reporter assay, FM1–43 fluorescence dye evaluation, qRT-PCR and western blot, to investigate the regulatory effect of miR-153 on hippocampal synaptic vesicle release both in vivo and in vitro. The CBH rat model was generated by bilateral common carotid artery ligation (2VO).

Results

Compared to sham rats, 2VO rats presented decreased field excitatory postsynaptic potential (fEPSP) amplitude and increased paired-pulse ratios (PPRs) in the CA3-CA1 pathway, as well as significantly decreased expression of multiple vesicle fusion-related proteins, including SNAP-25, VAMP-2, syntaxin-1A and synaptotagmin-1, in the hippocampi. The levels of microRNA-153 (miR-153) were upregulated in the hippocampi of rats following 2VO surgery, and in the plasma of dementia patients. The expression of the vesicle fusion-related proteins affected by 2VO was inhibited by miR-153, elevated by miR-153 inhibition, and unchanged by binding-site mutation or miR masks. FM1–43 fluorescence images showed that miR-153 blunted vesicle exocytosis, but this effect was prevented by either 2′-O-methyl antisense oligoribonucleotides to miR-153 (AMO-153) and miR-masking of the miR-153 binding site in the 3′ untranslated region (3’UTR) of the Snap25, Vamp2, Stx1a and Syt1 genes. Overexpression of miR-153 by lentiviral vector-mediated miR-153 mimics (lenti-pre-miR-153) decreased the fEPSP amplitude and elevated the PPR in the rat hippocampus, whereas overexpression of the antisense molecule (lenti-AMO-153) reversed these changes triggered by 2VO. Furthermore, lenti-AMO-153 attenuated the cognitive decline of 2VO rats.

Conclusions

Overexpression of miR-153 controls CBH-induced presynaptic vesicle release impairment by posttranscriptionally regulating the expression of four vesicle release-related proteins by targeting the 3’UTRs of the Stx1a, Snap25, Vamp2 and Syt1 genes. These findings identify a novel mechanism of presynaptic plasticity impairment during CBH, which may be a new drug target for prevention or treatment of AD and VaD.

Aluminum-Induced Synaptic Plasticity Impairment via PI3K-Akt-mTOR Signaling Pathway

Aluminum (Al) is an environmental neurotoxin with extensive exposure by humans, but the molecular mechanism of its toxicity is still unclear. Several studies have indicated that exposure to aluminum can impair learning and memory function. The purpose of this study was to investigate the mechanism of LTP injury and the effect of aluminum exposure on related signal pathways. The results showed that the axonal dendrites of neurons in the hippocampal CA1 area of rats exposed to maltol aluminum showed neuritic beading and the dendritic spines were reduced. This resulted in dose-dependent LTP inhibition and led to impaired learning and memory function in rats. The PI3K-Akt-mTOR pathway may play a crucial role in this process.