Neural stem cells promote neuroplasticity: a promising therapeutic strategy for the treatment of Alzheimer’s disease

Recent studies have demonstrated that neuroplasticity,such as synaptic plasticity and neurogenesis,exists throughout the normal lifespan but declines with age and is significantly impaired in individuals with Alzheimer’s disease.Hence,promoting neuroplasticity may represent an effective strategy with which Alzheimer’s disease can be alleviated.Due to their significant ability to self-renew,differentiate,and migrate,neural stem cells play an essential role in reversing synaptic and neuronal damage,reducing the pathology of Alzheimer’s disease,including amyloid-β,tau protein,and neuroinflammation,and secreting neurotrophic factors and growth factors that are related to plasticity.These events can promote synaptic plasticity and neurogenesis to repair the microenvironment of the mammalian brain.Consequently,neural stem cells are considered to represent a potential regenerative therapy with which to improve Alzheimer’s disease and other neurodegenerative diseases.In this review,we discuss how neural stem cells regulate neuroplasticity and optimize their effects to enhance their potential for treating Alzheimer’s disease in the clinic.

Repetitive transcranial magnetic stimulation in Alzheimer’s disease:effects on neural and synaptic rehabilitation

Alzheimer’s disease is a neurodegenerative disease resulting from deficits in synaptic transmission and homeostasis.The Alzheimer’s disease brain tends to be hyperexcitable and hypersynchronized,thereby causing neurodegeneration and ultimately disrupting the operational abilities in daily life,leaving patients incapacitated.Repetitive transcranial magnetic stimulation is a cost-effective,neuro-modulatory technique used for multiple neurological conditions.Over the past two decades,it has been widely used to predict cognitive decline;identify pathophysiological markers;promote neuroplasticity;and assess brain excitability,plasticity,and connectivity.It has also been applied to patients with dementia,because it can yield facilitatory effects on cognition and promote brain recovery after a neurological insult.However,its therapeutic effectiveness at the molecular and synaptic levels has not been elucidated because of a limited number of studies.This study aimed to characterize the neurobiological changes following repetitive transcranial magnetic stimulation treatment,evaluate its effects on synaptic plasticity,and identify the associated mechanisms.This review essentially focuses on changes in the pathology,amyloidogenesis,and clearance pathways,given that amyloid deposition is a major hypothesis in the pathogenesis of Alzheimer’s disease.Apoptotic mechanisms associated with repetitive transcranial magnetic stimulation procedures and different pathways mediating gene transcription,which are closely related to the neural regeneration process,are also highlighted.Finally,we discuss the outcomes of animal studies in which neuroplasticity is modulated and assessed at the structural and functional levels by using repetitive transcranial magnetic stimulation,with the aim to highlight future directions for better clinical translations.

Inverse stochastic resonance in modular neural network with synaptic plasticity

This work explores the inverse stochastic resonance(ISR) induced by bounded noise and the multiple inverse stochastic resonance induced by time delay by constructing a modular neural network, where the modified Oja’s synaptic learning rule is employed to characterize synaptic plasticity in this network. Meanwhile, the effects of synaptic plasticity on the ISR dynamics are investigated. Through numerical simulations, it is found that the mean firing rate curve under the influence of bounded noise has an inverted bell-like shape, which implies the appearance of ISR. Moreover, synaptic plasticity with smaller learning rate strengthens this ISR phenomenon, while synaptic plasticity with larger learning rate weakens or even destroys it. On the other hand, the mean firing rate curve under the influence of time delay is found to exhibit a decaying oscillatory process, which represents the emergence of multiple ISR. However, the multiple ISR phenomenon gradually weakens until it disappears with increasing noise amplitude. On the same time, synaptic plasticity with smaller learning rate also weakens this multiple ISR phenomenon, while synaptic plasticity with larger learning rate strengthens it. Furthermore, we find that changes of synaptic learning rate can induce the emergence of ISR phenomenon. We hope these obtained results would provide new insights into the study of ISR in neuroscience.

Cytokines,synaptic plasticity and network dynamics:a matter of balance

The modern view of the immune system as a sensitizing and modulating machinery of the central nervous system is now well recognized.However,the specific mechanisms underlying this fine crosstalk have yet to be fully disentangled.To control cognitive function and behavior,the two systems are engaged in a subtle interacting act.In this scenario,a dual action of pro-inflammatory cytokines in the modulation of brain network connections is emerging.Pro-inflammatory cytokines are indeed required to express physiological plasticity in the hippocampal network while being detrimental when over-expressed during uncontrolled inflammatory processes.In this dynamic equilibrium,synaptic functioning and the performance of neural networks are ensured by maintaining an appropriate balance between pro-and anti-inflammatory molecules in the central nervous system microenvironment.

Synaptic plasticity and neural regeneration

Totally three articles focusing on ＂effects of electromagnetic radiation on synaptic structures in the CA1 region of rat hippocampus effects of transcranial magnetic stimulation and rehabilitation training on synaptic structure on the unaffected side of sensorimotor cortex, and effects of environmental enrichment on hippocampal synapses in adolescent offspring of mothers exposed to prenatal stress＂ are published in three issues. We hope that our readers find these papers useful to their research.

Glutamate receptor delocalization in postsynaptic membrane and reduced hippocampal synaptic plasticity in the early stage of Alzheimer's disease

Mounting evidence suggests that synaptic plasticity provides the cellular biological basis of learning and memory, and plasticity deficits play a key role in dementia caused by Alzheimer's disease. However, the mechanisms by which synaptic dysfunction contributes to the pathogenesis of Alzheimer's disease remain unclear. In the present study, Alzheimer's disease transgenic mice were used to determine the relationship between decreased hippocampal synaptic plasticity and pathological changes and cognitive-behavioral deterioration, as well as possible mechanisms underlying decreased synaptic plasticity in the early stages of Alzheimer's disease-like diseases. APP/PS1 double transgenic(5 XFAD; Jackson Laboratory) mice and their littermates(wild-type, controls) were used in this study. Additional 6-weekold and 10-week-old 5 XFAD mice and wild-type mice were used for electrophysiological recording of hippocampal dentate gyrus. For10-week-old 5 XFAD mice and wild-type mice, the left hippocampus was used for electrophysiological recording, and the right hippocampus was used for biochemical experiments or immunohistochemical staining to observe synaptophysin levels and amyloid beta deposition levels. The results revealed that, compared with wild-type mice, 6-week-old 5 XFAD mice exhibited unaltered long-term potentiation in the hippocampal dentate gyrus. Another set of 5 XFAD mice began to show attenuation at the age of 10 weeks, and a large quantity of amyloid beta protein was accumulated in hippocampal cells. The location of α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor and N-methyl-D-aspartic acid receptor subunits in synaptosomes was decreased. These findings indicate that the delocalization of postsynaptic glutamate receptors and an associated decline in synaptic plasticity may be key mechanisms in the early onset of Alzheimer's disease. The use and care of animals were in strict accordance with the ethical standards of the Animal Ethics Committee of Capital Medical University,China on December 17, 2015(approval No. AEEI-2015-182).

An enriched environment promotes synaptic plasticity and cognitive recovery after permanent middle cerebral artery occlusion in mice

Cerebral ischemia activates an endogenous repair program that induces plastic changes in neurons. In this study, we investigated the effects of environmental enrichment on spatial learning and memory as well as on synaptic remodeling in a mouse model of chronic cerebral ischemia, produced by subjecting adult male C57 BL/6 mice to permanent left middle cerebral artery occlusion. Three days postoperatively, mice were randomly assigned to the environmental enrichment and standard housing groups. Mice in the standard housing group were housed and fed a standard diet. Mice in the environmental enrichment group were housed in a cage with various toys and fed a standard diet. Then, 28 days postoperatively, spatial learning and memory were tested using the Morris water maze. The expression levels of growth-associated protein 43, synaptophysin and postsynaptic density protein 95 in the hippocampus were analyzed by western blot assay. The number of synapses was evaluated by electron microscopy. In the water maze test, mice in the environmental enrichment group had a shorter escape latency, traveled markedly longer distances, spent more time in the correct quadrant(northeast zone), and had a higher frequency of crossings compared with the standard housing group. The expression levels of growth-associated protein 43, synaptophysin and postsynaptic density protein 95 were substantially upregulated in the hippocampus in the environmental enrichment group compared with the standard housing group. Furthermore, electron microscopy revealed that environmental enrichment increased the number of synapses in the hippocampal CA1 region. Collectively, these findings suggest that environmental enrichment ameliorates the spatial learning and memory impairment induced by permanent middle cerebral artery occlusion. Environmental enrichment in mice with cerebral ischemia likely promotes cognitive recovery by inducing plastic changes in synapses.

Downregulation of caveolin-1 contributes to the synaptic plasticity deficit in the hippocampus of aged rats

Caveolin-1 is involved in the regulation of synaptic plasticity, but the relationship between its ex-pression and cognitive function during aging remains controversial. To explore the relationship be-tween synaptic plasticity in the aging process and changes in learning and memory, we examined caveolin-1 expression in the hippocampus, cortex and cerebellum of rats at different ages. We also examined the relationship between the expression of caveolin-1 and synaptophysin, a marker of synaptic plasticity. Hippocampal caveolin-1 and synaptophysin expression in aged （22-24 month old） rats was significantly lower than that in young （1 month old） and adult （4 months old） rats. Ex- pression levels of both proteins were significantly greater in the cortex of aged rats than in that of young or adult rats, and levels were similar between the three age groups in the cerebellum. Linear regression analysis revealed that hippocampal expression of synaptophysin was associated with memory and learning abilities. Moreover, synaptophysin expression correlated positively with caveolin-1 expression in the hippocampus, cortex and cerebellum. These results confirm that caveolin-1 has a regulatory effect on synaptic plasticity, and suggest that the downregulation of hippocampal caveolin-1 expression causes a decrease in synaptic plasticity during physiological aging.

Paired associative stimulation improves synaptic plasticity and functional outcomes after cerebral ischemia

Paired associative stimulation is a relatively new non-invasive brain stimulation technique that combines transcranial magnetic stimulation and peripheral nerve stimulation. The effects of paired associative stimulation on the excitability of the cerebral cortex can vary according to the time interval between the transcranial magnetic stimulation and peripheral nerve stimulation. We established a model of cerebral ischemia in rats via transient middle cerebral artery occlusion. We administered paired associative stimulation with a frequency of 0.05 Hz 90 times over 4 weeks. We then evaluated spatial learning and memory using the Morris water maze. Changes in the cerebral ultra-structure and synaptic plasticity were assessed via transmission electron microscopy and a 64-channel multi-electrode array. We measured mRNA and protein expression levels of brain-derived neurotrophic factor and N-methyl-D-aspartate receptor 1 in the hippocampus using a real-time polymerase chain reaction and western blot assay. Paired associative stimulation treatment significantly improved learning and memory in rats subjected to cerebral ischemia. The ultra-structures of synapses in the CA1 area of the hippocampus in rats subjected to cerebral ischemia were restored by paired associative stimulation. Long-term potentiation at synapses in the CA3 and CA1 regions of the hippocampus was enhanced as well. The protein and mRNA expression of brain-derived neurotrophic factor and N-methyl-D-aspartate receptor 1 increased after paired associative stimulation treatment. These data indicate that paired associative stimulation can protect cog-nition after cerebral ischemia. The observed effect may be mediated by increases in the mRNA and protein expression of brain-derived neurotrophic factor and N-methyl-D-aspartate receptor 1, and by enhanced synaptic plasticity in the CA1 area of the hippocampus. The animal experiments were approved by the Animal Ethics Committee of Tongji Medical College, Huazhong University of Science & Technology, China(approval No. TJ-A20151102) on July 11, 2015.

Correlation between the cumulative analgesic effect of electroacupuncture intervention and synaptic plasticity of hypothalamic paraventricular nucleus neurons in rats with sciatica

In the present study, a rat model of chronic neuropathic pain was established by ligation of the sciatic nerve and a model of learning and memory impairment was established by ovariectomy to investigate the analgesic effect of repeated electroacupuncture stimulation at bilateral Zusanfi （ST36） and Yanglingquan （GB34）. In addition, associated synaptic changes in neurons in the paraventricular nucleus of the hypothalamus were examined. Results indicate that the thermal pain threshold （paw withdrawal latency） was significantly increased in rats subjected to 2-week electroacupuncture intervention compared with 2-day electroacupuncture, but the analgesic effect was weakened remarkably in ovariectomized rats with chronic constrictive injury. 2-week electroacupuncture intervention substantially reversed the chronic constrictive injury-induced increase in the synaptic cleft width and thinning of the postsynaptic density. These findings indicate that repeated electroacupuncture at bilateral Zusanfi and Yanglingquan has a cumulative analgesic effect and can effectively relieve chronic neuropathic pain by remodeling the synaptic structure of the hypothalamic paraventricular nucleus.

Protective effect of tetrahydroxy stilbene glucoside on learning and memory by regulating synaptic plasticity

Damage to synaptic plasticity induced by neurotoxicity of amyloid-beta is regarded to be one of the pathological mechanisms of learning and memory disabilities in Alzheimer＇s disease patients. This study assumed that the damage of amyloid-beta to learning and memory abilities was strongly associated with the changes in the Fyn/N-methyl-D-aspartate receptor 2B （NR2B） expression. An APP695V7171 transgenic mouse model of Alzheimer＇s disease was used and treatment with tetrahydroxy-stilbene glucoside was administered intragas- trically. Results showed that intragastric administration of tetrahydroxy-stilbene glucoside improved the learning and memory abilities of the transgenic mice through increasing NR2B receptors and Fyn expression. It also reversed parameters for synaptic interface structure of gray type I. These findings indicate that tetrahydroxy stilbene glucoside has protective effects on the brain, and has prospects for its clinical application to improve the learning and memory abilities and treat Alzheimer＇s disease.

Ischemic long-term-potentiation(iLTP): perspectives to set the threshold of neural plasticity toward therapy

The precise role of neural plasticity under pathological conditions remains not well understood. It appears to be well accepted, however, that changes in the ability of neurons to express plasticity accompany neurological diseases. Here, we discuss recent experimental evidence, which suggests that synaptic plasticity induced by a pathological stimulus, i.e., ischemic long-term-potentiation（i LTP） of excitatory synapses, could play an important role for post-stroke recovery by influencing the post-lesional reorganization of surviving neuronal networks.

Double-target neural circuit-magnetic stimulation improves motor function in spinal cord injury by attenuating astrocyte activation

Multi-target neural circuit-magnetic stimulation has been clinically shown to improve rehabilitation of lower limb motor function after spinal cord injury. However, the precise underlying mechanism remains unclear. In this study, we performed double-target neural circuit-magnetic stimulation on the left motor cortex and bilateral L5 nerve root for 3 successive weeks in a rat model of incomplete spinal cord injury caused by compression at T10. Results showed that in the injured spinal cord, the expression of the astrocyte marker glial fibrillary acidic protein and inflammatory factors interleukin 1β, interleukin-6, and tumor necrosis factor-α had decreased, whereas that of neuronal survival marker microtubule-associated protein 2 and synaptic plasticity markers postsynaptic densification protein 95 and synaptophysin protein had increased. Additionally, neural signaling of the descending corticospinal tract was markedly improved and rat locomotor function recovered significantly. These findings suggest that double-target neural circuit-magnetic stimulation improves rat motor function by attenuating astrocyte activation, thus providing a theoretical basis for application of double-target neural circuit-magnetic stimulation in the clinical treatment of spinal cord injury.

Synaptic plasticity effects on FeCl_2-induced post-traumatic epilepsy onset in the rat

Studies have confirmed that iron induces epilepsy onset, and iron ion-induced epilepsy in anima models closely resembles the clinical situation. Models of post-traumatic epilepsy （PTE） were established by intracortical injection of FeCl2 using stereotactic techniques. Electron microscopy revealed neuronal degeneration, with shrinkage of the neuronal soma, hyperplasia of rough endoplasmic reticulum, ribosomal detachment from the endoplasmic reticulum, and vacuolar degeneration of glial cells in the right frontal lobe of FeCl2-induced PTE rats. With prolonged time injuries became more severe and neuronal apoptosis was observed. Synapses in the hippocampal neuropil significantly increased （primarily type I/excitatory synapses） at day 14 following injury. Type II synapses （inhibitory synapse） were observed in the rat hippocampus at day 30. Cortical neuronal degeneration, apoptosis, glial cell proliferation, and ultrastructural hippocampal changes, in particular changes in type of neuronal synapse, play an important role in PTE onset.

高压氧治疗抑郁症的效果及机制研究进展

目前,高压氧疗法因副作用少且操作方便的特点,可作为治疗抑郁症的潜在方法。本文通过综述高压氧治疗抑郁症的临床应用现状和作用机制,以期为抑郁症治疗新策略的制定提供参考。高压氧疗法现已被作为抑郁症患者的有效疗法,可通过调节下丘脑-垂体-肾上腺轴、抑制神经炎症以及增强突触可塑性,进而改善抑郁症患者的临床症状。高压氧疗法作为抗抑郁药物的联合治疗方法,在一定程度上有助于改善治疗效果。

高龄妊娠对子代大鼠前额叶皮层神经干细胞增殖及突触可塑性的影响

目的探究高龄妊娠对子代大鼠前额叶皮层神经干细胞增殖及突触可塑性的影响。方法选择3月龄与12月龄SD雌性大鼠,均与3月龄SD雄性大鼠合笼。子代鼠出生后,将其分为适龄子代组(Con组)和高龄子代组(AMA组)。取出生后1 d的子代大鼠脑组织,利用HE染色观察前额叶皮层神经元的形态变化;利用qRT-PCR和Western blot方法分别检测前额叶皮层中G蛋白信号调节蛋白2(RGS2)、巢蛋白(Nestin)、突触后致密区蛋白95(PSD95)、脑源性神经营养因子(BDNF)和突触素(SYN)的mRNA及其蛋白质表达变化情况。结果HE染色结果发现,与Con组比较,AMA组前额叶皮层的神经元数目减少,部分神经元发生变性,出现胞体肿胀、空泡化现象。qRT-PCR和Western blot结果发现,与Con组比较,AMA组Nestin、RGS2、PSD95、BDNF、SYN mRNA及蛋白质相对表达水平均显著下降(P<0.05)。结论高龄孕鼠子代前额叶皮层的神经干细胞增殖能力减弱,突触可塑性能力降低,可能是造成子代脑发育障碍和认知功能下降的原因之一。

阿尔茨海默病中小胶质细胞的作用及针刺干预研究概况

阿尔茨海默病是最常见的神经退行性疾病,该病病因病机尚不明确,目前仍缺乏有效的治疗药物和治疗方法。小胶质细胞作为中枢神经系统固有的先天免疫细胞,其介导的神经炎症在阿尔茨海默病发病机制中起着核心作用,而自噬的激活可以减少神经细胞凋亡,抑制神经炎症。针刺对于治疗阿尔茨海默病疗效显著,且对小胶质细胞具有调控作用,能抑制中枢性炎症、激活自噬功能、调节突触可塑性。

Dopamine in the prefrontal cortex plays multiple roles in the executive function of patients with Parkinson's disease

Parkinson’s disease can affect not only motor functions but also cognitive abilities,leading to cognitive impairment.One common issue in Parkinson’s disease with cognitive dysfunction is the difficulty in executive functioning.Executive functions help us plan,organize,and control our actions based on our goals.The brain area responsible for executive functions is called the prefrontal co rtex.It acts as the command center for the brain,especially when it comes to regulating executive functions.The role of the prefrontal cortex in cognitive processes is influenced by a chemical messenger called dopamine.However,little is known about how dopamine affects the cognitive functions of patients with Parkinson’s disease.In this article,the authors review the latest research on this topic.They start by looking at how the dopaminergic syste m,is alte red in Parkinson’s disease with executive dysfunction.Then,they explore how these changes in dopamine impact the synaptic structure,electrical activity,and connection components of the prefrontal cortex.The authors also summarize the relationship between Parkinson’s disease and dopamine-related cognitive issues.This information may offer valuable insights and directions for further research and improvement in the clinical treatment of cognitive impairment in Parkinson’s disease.

microRNA-124在阿尔兹海默症中的作用及针刺干预研究进展

阿尔兹海默症(AD)是老年人常见的神经退行性疾病。目前认为AD的病因大多与大脑中β-淀粉样蛋白(Aβ)的异常沉积、相关蛋白Tau的过度磷酸化以及各种细胞因子、补体的释放有关。microRNA-124在中枢神经系统中高度表达,与许多神经生理和病理过程相关。microRNA-124通过Aβ沉积、Tau蛋白过度磷酸化、神经炎症、氧化应激、神经元兴奋性和神经分化等多种方式在AD中发挥作用。它还可能通过调节细胞凋亡对突触可塑性和轴突生长产生不利影响,进而影响AD。因此,探讨microRNA-124在AD中的表达变化以及靶向治疗至关重要。针刺治疗AD疗效明确,可能与microRNA-124调控相关。文章就AD所具有的几个典型组织病理学特征与microRNA-124的相关性进行综述,包括老年斑中Aβ的积累、Tau过度磷酸化、神经炎症和突触丧失。综述了microRNA-124通过靶向不同的基因与调节下游信号在AD中发挥作用,以及针刺治疗AD的可能干预机制,为未来治疗提供新思路。

星形胶质细胞外囊泡在卒中后认知障碍中的研究进展

卒中后认知障碍(PSCI)是卒中患者的常见并发症,以认知功能障碍为特征,直接影响患者生活质量。既往研究发现,星形胶质细胞在PSCI发病机制中发挥重要作用。此外,细胞外囊泡(EVs)已被公认为细胞间通讯中的重要递质,并通过携带和运输各种货物参与各种病理生理过程。星形胶质细胞外囊泡(ADEVs)可能与其他脑细胞进行交流,通过增强突触可塑性、调控神经炎症、调节血管生成和细胞自噬等过程改善PSCI。本综述阐明了ADEVs对PSCI发展的多方面影响,为研究PSCI的潜在机制提供新的策略,并进一步探讨ADEVs作为新型药物和生物标志物在诊断和治疗PSCI方面的潜在用途。