Molecular regulation of dendritic spine dynamics and their potential impact on synaptic plasticity and neurological diseases

Characterizing and targeting glioblastoma neuron-tumor networks with retrograde tracing

Glioblastomas are invasive brain tumors with high therapeutic resistance. Neuron-to-glioma synapses have been shown to promote glioblastoma progression. However, a characterization of tumor-connected neurons has been hampered by a lack of technologies. Here, we adapted retrograde tracing using rabies viruses to investigate and manipulate neuron-tumor networks. Glioblastoma rapidly integrated into neural circuits across the brain, engaging in widespread functional communication, with cholinergic neurons driving glioblastoma invasion. We uncovered patient-specific and tumor-cell-state-dependent differences in synaptogenic gene expression associated with neuron-tumor connectivity and subsequent invasiveness. Importantly, radiotherapy enhanced neuron-tumor connectivity by increased neuronal activity. In turn, simultaneous neuronal activity inhibition and radiotherapy showed increased therapeutic effects, indicative of a role for neuron-to-glioma synapses in contributing to therapeutic resistance. Lastly, rabies-mediated genetic ablation of tumor-connected neurons halted glioblastoma progression, offering a viral strategy to tackle glioblastoma. Together, this study provides a framework to comprehensively characterize neuron-tumor networks and target glioblastoma.

Enriched environment rescues bisphenol A induced anxiety-like behavior and cognitive impairment by modulating synaptic plasticity

Bisphenol A (BPA) is an exogenous endocrine disruptor in the environmental context, garnering attention for its harmful effects on the nervous system function and behavior. Research indicates that being exposed to BPA may result in anxiety-like behavior and impairment in cognitive function. Enriched environment (EE) is beneficial to improve cognitive behavior, but whether EE can improve BPA-induced behavioral impairment is still unclear. This research explored the possible pathways through which EE alleviates anxiety-like behavior and cognitive impairment in mice exposed to BPA. Except for the control mice, all mice received BPA treatment. After BPA treatment, some mice were housed normally, some housed with EE, and some were given NMDA and AMPA receptor agonists. Our research revealed that exposure to BPA results in anxiety-like behavior in open field and elevated-plus maze experiments. Additionally, spatial and learning memory cognitive impairments were observed in Y-maze and water maze tests. Furthermore, exposure to BPA led to a decrease in both the density and maturity of dendritic spines, as well as a reduction in neurite length and branch numbers. PSD-95, GluA1, and NR2A expression were down-regulated, and excitatory synaptic transmission was decreased. However, EE treatment increased dendrite spine density and maturity, up-regulated PSD-95, GluA1and NR2A expression, enhanced excitatory synaptic transmission, and relieved anxiety-like behavior and cognitive impairment in BPA mice. Furthermore, administering NMDA or AMPA receptor agonists to BPA mice led to an increase in dendritic spine density and maturity, a rise in mEPSC amplitude, as well as a restoration of anxiety-like behavior and cognitive deficits induced by BPA. The findings of this study provide proof that EE has a neuroprotective effect in reducing anxiety-related behavior and cognitive decline caused by BPA.

Wogonin mitigates microglia-mediated synaptic over-pruning and cognitive impairment following epilepsy

BACKGROUND

Epilepsy, a neurological disorder characterized by recurrent abnormal neuronal discharges, leading to brain dysfunction and imposing significant psychological and economic burdens on patients. Microglia, the resident immune cells within the central nervous system (CNS), play a crucial role in maintaining CNS homeostasis. However, activated microglia can excessively prune synapses, exacerbating neuronal damage and cognitive dysfunction following epilepsy. Wogonin, a flavonoid from Scutellaria Baicalensis, has known neuroprotective effects via anti-inflammatory and antioxidative mechanisms, but its impact on microglial activation and synaptic pruning in neurons post-epilepsy remains unclear.

METHODS

Synaptic density was assessed using presynaptic marker Synaptophysin and postsynaptic marker Psd-95, and microglial phagocytosis was evaluated with fluorescent microspheres. Pilocarpine-induced mouse model of status epilepticus was used to evaluate synaptic density changes of mouse hippocampus following an intraperitoneal injection of wogonin (50 and 100 mg/kg). Memory and cognitive function in mice were subsequently evaluated using the Y-maze, object recognition, and Morris water maze tests. Single-cell sequencing was employed to investigate the underlying causes of microglial state alterations, followed by experimental validation.

RESULTS

Microglia were transitioned to an activated state post-epilepsy, exhibiting significantly enhanced phagocytic capacity. Correspondingly, levels of synaptophysin and Psd-95 were markedly reduced in neurons. Treatment with wogonin (100 mg/kg) significantly increased neuronal synaptic density and improved learning and memory deficits in epileptic mice. Further investigation revealed that wogonin inhibits the release of pro-inflammatory cytokines and synaptic phagocytosis of microglia by activating the AKT/FoxO1 pathway.

CONCLUSIONS

Wogonin could alleviate excessive synaptic pruning of epileptic neurons by microglia and improve cognitive dysfunction of epileptic mice via the AKT/FoxO1 pathway.

JRM-28, a Novel HDAC2 Inhibitor, Upregulates Plasticity-Associated Proteins in Hippocampal Neurons and Enhances Morphological Plasticity via Activation of CREB: Implications for Alzheimer's Disease

Enhancement of neuronal plasticity by small-molecule therapeutics protects cognitive skills and also ameliorates progressive neurodegenerative pathologies like Alzheimer's disease (AD) and dementia. One such compound, a novel histone deacetylase 2 (HDAC2) inhibitor named JRM-28, was shown here to enhance dendritic strength, augment spine density, and upregulate post-synaptic neurotransmission in hippocampal neurons. The molecular basis for this effect correlates with JRM-28-induced upregulation of the transcription of cAMP response element-binding protein(CREB), induction of its transcriptional activity, and subsequent stimulation of expressions of CREB-dependent plasticity-associated genes, such as those encoding N-methyl-D-aspartate (NMDA) receptor subunit NR2A and the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor subunit GluR1. Specifically, JRM-28 stimulated the NMDA- and AMPA-receptor-sensitive ionotropic calcium influx in hippocampal neurons. Interestingly, JRM-28 did not induce NMDA- and AMPA-sensitive calcium influx in hippocampal neurons once the expression of CREB was knocked down by creb siRNA, suggesting the critical role of CREB in JRM-28-mediated upregulation of synaptic plasticity. Finally, JRM-28 upregulated CREB mRNA, CREB-dependent plasticity-associated markers, and ionotropic calcium influx in iPSC-derived AD human neurons, indicating its therapeutic implications in the amelioration of AD pathologies.

Human stem cell-based models to study synaptic dysfunction and cognition in schizophrenia: A narrative review

Cognitive impairment is the strongest predictor of functional outcomes in schizophrenia and is hypothesized to result from synaptic dysfunction. However, targeting synaptic plasticity and cognitive deficits in patients remains a significant clinical challenge. A comprehensive understanding of synaptic plasticity and the molecular basis of learning and memory in a disease context can provide specific targets for the development of novel therapeutics targeting cognitive impairments in schizophrenia. Here, we describe the role of synaptic plasticity in cognition, summarize evidence for synaptic dysfunction in schizophrenia and demonstrate the use of patient derived induced-pluripotent stem cells for studying synaptic plasticity in vitro. Lastly, we discuss current advances and future technologies for bridging basic science research of synaptic dysfunction with clinical and translational research that can be used to predict treatment response and develop novel therapeutics.

The Effects of Appropriate Perioperative Exercise on Perioperative Neurocognitive Disorders: a Narrative Review

Perioperative neurocognitive disorders (PNDs) are now considered the most common neurological complication in older adult patients undergoing surgical procedures. A significant increase exists in the incidence of post-operative disability and mortality in patients with PNDs. However, no specific treatment is still available for PNDs. Recent studies have shown that exercise may improve cognitive dysfunction-related disorders, including PNDs. Neuroinflammation is a key mechanism underlying exercise-induced neuroprotection in PNDs; others include the regulation of gut microbiota and mitochondrial and synaptic function. Maintaining optimal skeletal muscle mass through preoperative exercise is important to prevent the occurrence of PNDs. This review summarizes current clinical and preclinical evidence and proposes potential molecular mechanisms by which perioperative exercise improves PNDs, providing a new direction for exploring exercise-mediated neuroprotective effects on PNDs. In addition, it intends to provide new strategies for the prevention and treatment of PNDs.

Precise Modulation of Pericyte Dysfunction by a Multifunctional Nanoprodrug to Ameliorate Alzheimer's Disease

Pericyte dysfunction severely undermines cerebrovascular integrity and exacerbates neurodegeneration in Alzheimer's disease (AD). However, pericyte-targeted therapy is a yet-untapped frontier for AD. Inspired by the elevation of vascular cell adhesion molecule-1 (VCAM-1) and reactive oxygen species (ROS) levels in pericyte lesions, we fabricated a multifunctional nanoprodrug by conjugating the hybrid peptide VLC, a fusion of the VCAM-1 high-affinity peptide VHS and the neuroprotective apolipoprotein mimetic peptide COG1410, to curcumin (Cur) through phenylboronic ester bond (VLC@Cur-NPs) to alleviate complex pericyte-related pathological changes. Importantly, VLC@Cur-NPs effectively homed to pericyte lesions via VLC and released their contents upon ROS stimulation to maximize their regulatory effects. Consequently, VLC@Cur-NPs markedly increased pericyte regeneration to form a positive feedback loop and thus improved neurovascular function and ultimately alleviated memory defects in APP/PS1 transgenic mice. We present a promising therapeutic strategy for AD that can precisely modulate pericytes and has the potential to treat other cerebrovascular diseases.

Rehmanniae Radix Preparata ameliorates behavioral deficits and hippocampal neurodevelopmental abnormalities in ADHD rat model

Objectives

Abnormal hippocampal neurodevelopment, particularly in the dentate gyrus region, may be a key mechanism of attention-deficit/hyperactivity disorder (ADHD). In this study, we investigate the effect of the most commonly used Chinese herb for the treatment of ADHD, Rehmanniae Radix Preparata (RRP), on behavior and hippocampal neurodevelopment in spontaneously hypertensive rats (SHR).

Methods

Behavior tests, including Morris water maze (MWM) test, open field test (OFT) and elevated plus maze (EPM) test were performed to assess the effect of RRP on hyperactive and impulsive behavior. Hippocampal neurodevelopment was characterized by transmission electron microscopy, immunofluorescence, Golgi staining and Nissl staining approaches. Regulatory proteins such as Trkb, CDK5, FGF2/FGFR1 were examined by Western blot analysis.

Results

The results showed that RRP could effectively control the impulsive and spontaneous behavior and improve the spatial learning and memory ability. RRP significantly reduced neuronal loss and increased the number of hippocampal stem cells, and promoted synaptic plasticity. In addition, FGF/FGFR signaling was upregulated after RRP treatment.

Conclusion

RRP can effectively reduce impulsive and spontaneous behavior and ameliorate hippocampal neurodevelopmental abnormalities in ADHD rat model.

Ultrastructural analysis of nigrostriatal dopaminergic terminals in a knockin mouse model of DYT1 dystonia

DYT1 dystonia is associated with decreased striatal dopamine release. In this study, we examined the possibility that ultrastructural changes of nigrostriatal dopamine terminals could contribute to this neurochemical imbalance using a serial block face/scanning electron microscope (SBF/SEM) and three-dimensional reconstruction to analyse striatal tyrosine hydroxylase-immunoreactive (TH-IR) terminals and their synapses in a DYT1(ΔE) knockin (DYT1-KI) mouse model of DYT1 dystonia. Furthermore, to study possible changes in vesicle packaging capacity of dopamine, we used transmission electron microscopy to assess the synaptic vesicle size in striatal dopamine terminals. Quantitative comparative analysis of 80 fully reconstructed TH-IR terminals in the WT and DYT1-KI mice indicate (1) no significant difference in the volume of TH-IR terminals; (2) no major change in the proportion of axo-spinous versus axo-dendritic synapses; (3) no significant change in the post-synaptic density (PSD) area of axo-dendritic synapses, while the PSDs of axo-spinous synapses were significantly smaller in DYT1-KI mice; (4) no significant change in the contact area between TH-IR terminals and dendritic shafts or spines, while the ratio of PSD area/contact area decreased significantly for both axo-dendritic and axo-spinous synapses in DYT1-KI mice; (5) no significant difference in the mitochondria volume; and (6) no significant difference in the synaptic vesicle area between the two groups. Altogether, these findings suggest that abnormal morphometric changes of nigrostriatal dopamine terminals and their post-synaptic targets are unlikely to be a major source of reduced striatal dopamine release in DYT1 dystonia.

Effects of Cardiac Glycoside Digoxin on Dendritic Spines and Motor Learning Performance in Mice

Synapse formation following the generation of postsynaptic dendritic spines is essential for motor learning and functional recovery after brain injury. The C-terminal fragment of agrin cleaved by neurotrypsin induces dendritic spine formation in the adult hippocampus. Since the α3 subunit of sodium-potassium ATPase (Na/K ATPase) is a neuronal receptor for agrin in the central nervous system, cardiac glycosides might facilitate dendritic spine formation and subsequent improvements in learning. This study investigated the effects of cardiac glycoside digoxin on dendritic spine turnover and learning performance in mice. Golgi-Cox staining revealed that intraperitoneal injection of digoxin less than its IC50 in the brain significantly increased the density of long spines (≥2 µm) in the cerebral cortex in wild-type mice and neurotrypsin-knockout (NT-KO) mice showing impairment of activity-dependent spine formation. Although the motor learning performance of NT-KO mice was significantly lower than control wild-type mice under the control condition, low doses of digoxin enhanced performance to a similar degree in both strains. In NT-KO mice, lower digoxin doses equivalent to clinical doses also significantly improved motor learning performance. These data suggest that lower doses of digoxin could modify dendritic spine formation or recycling and facilitate motor learning in compensation for the disruption of neurotrypsin-agrin pathway.

Aegle marmelos (L.) Leaf Extract Improves Symptoms of Memory Loss Induced by Scopolamine in Rats

Alzheimer's disease (AD) is the most common neurodegenerative disease that results in memory impairment. Aegle marmelos (L.) Correa (AM) is used as a traditional medicine. AM leaves have the potential to inhibit acetylcholinesterase activity. This study used scopolamine to induce AD in rats. The aim of this study was to investigate the effects of AM leaf extract using this model. Motor and memory functions were tested by the motor activity and Morris water maze (MWM) tests, respectively. The density of the synaptophysin and dendritic spines in the CA1 were detected by immunofluorescence and Golgi impregnation, respectively. The hippocampal histology was reviewed by H&E staining. After the treatment, the latency times in the MWM tests of the AD groups reduced, while the motor activities showed no difference. The density of the synaptophysin of the AD groups increased after the treatments, and that of the dendritic spines also increased in all AD groups post-treatment. The hippocampal tissue also recovered. AM leaf extract can improve cognitive impairment in AD models by maintaining the presynaptic vesicle proteins and dendritic spines in a dose-dependent manner.

Protective mechanism of Paeonol on central nervous system

Cerebrovascular diseases involve neuronal damage, resulting in degenerative neuropathy and posing a serious threat to human health. The discovery of effective drug components from natural plants and the study of their mechanism are a research idea different from chemical synthetic medicines. Paeonol is the main active component of traditional Chinese medicine Paeonia lactiflora Pall. It widely exists in many medicinal plants and has pharmacological effects such as anti-atherosclerosis, antiplatelet aggregation, anti-oxidation, and anti-inflammatory, which keeps generally used in the treatment of cardiovascular and cerebrovascular diseases. Based on the therapeutic effects of Paeonol for cardiovascular and cerebrovascular diseases, this article reviewed the pharmacological effects of Paeonol in Alzheimer's disease, Parkinson's disease, stroke, epilepsy, diabetes encephalopathy, and other neurological diseases, providing a reference for the research of the mechanism of Paeonol in central nervous system diseases.

Understanding mechanistic aspect of the therapeutic role of herbal agents on neuroplasticity in cerebral ischemic-reperfusion injury

ETHNOPHARMACOLOGICAL RELEVANCE

Stroke is one of the leading causes of death and disability. The only FDA-approved therapy for treating stroke is tissue plasminogen activator (tPA), exhibiting a short therapeutic window. Due to this reason, only a small number of patients can be benefitted in this critical period. In addition, the use of endovascular interventions may reverse vessel occlusion more effectively and thus help further improve outcomes in experimental stroke. During recovery of blood flow after ischemia, patients experience cognitive, behavioral, affective, emotional, and electrophysiological changes. Therefore, it became the need for an hour to discover a novel strategy for managing stroke. The drug discovery process has focused on developing herbal medicines with neuroprotective effects via modulating neuroplasticity.

AIM OF THE STUDY

We gather and highlight the most essential traditional understanding of therapeutic plants and their efficacy in cerebral ischemia-reperfusion injury. In addition, we provide a concise summary and explanation of herbal drugs and their role in improving neuroplasticity. We review the pharmacological activity of polyherbal formulations produced from some of the most frequently referenced botanicals for the treatment of cerebral ischemia damage.

MATERIALS AND METHODS

A systematic literature review of bentham, scopus, pubmed, medline, and embase (elsevier) databases was carried out with the help of the keywords like neuroplasticity, herbal drugs, neural progenitor cells, neuroprotection, stem cells. The review was conducted using the above keywords to understand the therapeutic and mechanistic role of herbal neuroprotective agents on neuroplasticity in cerebral ischemic-reperfusion injury.

RESULTS

Neuroplasticity emerged as an alternative to improve recovery and management after cerebral ischemic reperfusion injury. Neuroplasticity is a physiological process throughout one's life in response to any stimuli and environment. Traditional herbal medicines have been established as an adjuvant to stroke therapy since they were used from ancient times and provided promising effects as an adjuvant to experimental stroke. The plants and phytochemicals such as Curcuma longa L., Moringa oliefera Lam, Panax ginseng C.A. Mey., and Rehmannia glutinosa (Gaertn.) DC., etc., have shown promising effects in improving neuroplasticity after experimental stroke. Such effects occur by modulation of various molecular signalling pathways, including PI3K/Akt, BDNF/CREB, JAK/STAT, HIF-1α/VEGF, etc. CONCLUSIONS: Here, we gave a perspective on plant species that have shown neuroprotective effects and can show promising results in promoting neuroplasticity with specific targets after cerebral ischemic reperfusion injury. In this review, we provide the complete detail of studies conducted on the role of herbal drugs in improving neuroplasticity and the signaling pathway involved in the recovery and management of experimental stroke.

Machine learning identifies phenotypic profile alterations of human dopaminergic neurons exposed to bisphenols and perfluoroalkyls

Parkinson's disease (PD) is the second most common neurodegenerative disease and is characterized by the loss of midbrain dopaminergic neurons. Endocrine disrupting chemicals (EDCs) are active substances that interfere with hormonal signaling. Among EDCs, bisphenols (BPs) and perfluoroalkyls (PFs) are chemicals leached from plastics and other household products, and humans are unavoidably exposed to these xenobiotics. Data from animal studies suggest that EDCs exposure may play a role in PD, but data about the effect of BPs and PFs on human models of the nervous system are lacking. Previous studies demonstrated that machine learning (ML) applied to microscopy data can classify different cell phenotypes based on image features. In this study, the effect of BPs and PFs at different concentrations within the real-life exposure range (0.01, 0.1, 1, and 2 µM) on the phenotypic profile of human stem cell-derived midbrain dopaminergic neurons (mDANs) was analyzed. Cells exposed for 72 h to the xenobiotics were stained with neuronal markers and evaluated using high content microscopy yielding 126 different phenotypic features. Three different ML models (LDA, XGBoost and LightGBM) were trained to classify EDC-treated versus control mDANs. EDC treated mDANs were identified with high accuracies (0.88-0.96). Assessment of the phenotypic feature contribution to the classification showed that EDCs induced a significant increase of alpha-synuclein (αSyn) and tyrosine hydroxylase (TH) staining intensity within the neurons. Moreover, microtubule-associated protein 2 (MAP2) neurite length and branching were significantly diminished in treated neurons. Our study shows that human mDANs are adversely impacted by exposure to EDCs, causing their phenotype to shift and exhibit more characteristics of PD. Importantly, ML-supported high-content imaging can identify concrete but subtle subcellular phenotypic changes that can be easily overlooked by visual inspection alone and that define EDCs effects in mDANs, thus enabling further pathological characterization in the future.

Overlap in synaptic neurological condition susceptibility pathways and the neural pannexin 1 interactome revealed by bioinformatics analyses

Many neurological conditions exhibit synaptic impairments, suggesting mechanistic convergence. Additionally, the pannexin 1 (PANX1) channel and signaling scaffold is linked to several of these neurological conditions and is an emerging regulator of synaptic development and plasticity; however, its synaptic pathogenic contributions are relatively unexplored. To this end, we explored connections between synaptic neurodevelopmental disorder and neurodegenerative disease susceptibility genes discovered by genome-wide association studies (GWASs), and the neural PANX1 interactome (483 proteins) identified from mouse Neuro2a (N2a) cells. To identify shared susceptibility genes, we compared synaptic suggestive GWAS candidate genes amongst autism spectrum disorders, schizophrenia, Parkinson's disease, and Alzheimer's disease. To further probe PANX1 signaling pathways at the synapse, we used bioinformatics tools to identify PANX1 interactome signaling pathways and protein-protein interaction clusters. To shed light on synaptic disease mechanisms potentially linking PANX1 and these four neurological conditions, we performed additional cross-analyses between gene ontologies enriched for the PANX1 synaptic and disease-susceptibility gene sets. Finally, to explore the regional specificity of synaptic PANX1-neurological condition connections, we identified brain region-specific elevations of synaptic PANX1 interactome and GWAS candidate gene set transcripts. Our results confirm considerable overlap in risk genes for autism spectrum disorders and schizophrenia and identify potential commonalities in genetic susceptibility for neurodevelopmental disorders and neurodegenerative diseases. Our findings also pinpointed novel putative PANX1 links to synaptic disease-associated pathways, such as regulation of vesicular trafficking and proteostasis, warranting further validation.

BMECs Ameliorate High Glucose-Induced Morphological Aberrations and Synaptic Dysfunction via VEGF-Mediated Modulation of Glucose Uptake in Cortical Neurons

It has been demonstrated that diabetes cause neurite degeneration in the brain and cognitive impairment and neurovascular interactions are crucial for maintaining brain function. However, the role of vascular endothelial cells in neurite outgrowth and synaptic formation in diabetic brain is still unclear. Therefore, present study investigated effects of brain microvascular endothelial cells (BMECs) on high glucose (HG)-induced neuritic dystrophy using a coculture model of BMECs with neurons. Multiple immunofluorescence labelling and western blot analysis were used to detect neurite outgrowth and synapsis formation, and living cell imaging was used to detect uptake function of neuronal glucose transporters. We found cocultured with BMECs significantly reduced HG-induced inhibition of neurites outgrowth (including length and branch formation) and delayed presynaptic and postsynaptic development, as well as reduction of neuronal glucose uptake capacity, which was prevented by pre-treatment with SU1498, a vascular endothelial growth factor (VEGF) receptor antagonist. To analyse the possible mechanism, we collected BMECs cultured condition medium (B-CM) to treat the neurons under HG culture condition. The results showed that B-CM showed the same effects as BMEC on HG-treated neurons. Furthermore, we observed VEGF administration could ameliorate HG-induced neuronal morphology aberrations. Putting together, present results suggest that cerebral microvascular endothelial cells protect against hyperglycaemia-induced neuritic dystrophy and restorate neuronal glucose uptake capacity by activation of VEGF receptors and endothelial VEGF release. This result help us to understand important roles of neurovascular coupling in pathogenesis of diabetic brain, providing a new strategy to study therapy or prevention for diabetic dementia. Hyperglycaemia induced inhibition of neuronal glucose uptake and impaired to neuritic outgrowth and synaptogenesis. Cocultured with BMECs/B-CM and VEGF treatment protected HG-induced inhibition of glucose uptake and neuritic outgrowth and synaptogenesis, which was antagonized by blockade of VEGF receptors. Reduction of glucose uptake may further deteriorate impairment of neurites outgrowth and synaptogenesis.

Co-exposure to low-dose lead, cadmium, and mercury promotes memory deficits in rats: Insights from the dynamics of dendritic spine pruning in brain development

Lead (Pb), cadmium (Cd), and mercury (Hg) are environmentally toxic heavy metals that can be simultaneously detected at low levels in the blood of the general population. Although our previous studies have demonstrated neurodevelopmental toxicity upon co-exposure to these heavy metals at these low levels, the precise mechanisms remain largely unknown. Dendritic spines are the structural foundation of memory and undergo significant dynamic changes during development. This study focused on the dynamics of dendritic spines during brain development following Pb, Cd, and Hg co-exposure-induced memory impairment. First, the dynamic characteristics of dendritic spines in the prefrontal cortex were observed throughout the life cycle of normal rats. We observed that dendritic spines increased rapidly from birth to their peak value at weaning, followed by significant pruning and a decrease during adolescence. Dendritic spines tended to be stable until their loss in old age. Subsequently, a rat model of low-dose Pb, Cd, and Hg co-exposure from embryo to adolescence was established. The results showed that exposure to low doses of heavy metals equivalent to those detected in the blood of the general population impaired spatial memory and altered the dynamics of dendritic spine pruning from weaning to adolescence. Proteomic analysis of brain and blood samples suggested that differentially expressed proteins upon heavy metal exposure were enriched in dendritic spine-related cytoskeletal regulation and axon guidance signaling pathways and that cofilin was enriched in both of these pathways. Further experiments confirmed that heavy metal exposure altered actin cytoskeleton dynamics and disturbed the dendritic spine pruning-related LIM domain kinase 1-cofilin pathway in the rat prefrontal cortex. Our findings demonstrate that low-dose Pb, Cd, and Hg co-exposure may promote memory impairment by perturbing dendritic spine dynamics through dendritic spine pruning-related signaling pathways.

A Multifunctional Nanocarrier System for Highly Efficient and Targeted Delivery of Ketamine to NMDAR Sites for Improved Treatment of Depression

Ketamine (KA), commonly used as an anesthetic, is now widely studied as an antidepressant for the treatment of depression. However, due to its side effects, such as addiction and cognitive impairment, the dosage and frequency of (S)-ketamine approved by the FDA for the treatment of refractory depression is very low, which limits its efficacy. Here, a new multifunctional nanocarrier system (AC-RM@HA-MS) with specific targeting capabilities is developed to improve the efficacy of KA treatment. KA-loaded NPs (AC-RM@HA-MS-KA) are constructed with a multilayer core-shell structure. KA-loaded mesoporous silica NPs are prepared, conjugated with hyaluronic acid (HA) as pore gatekeepers, and sheathed with an RBC-membrane (RM) for camouflage. Finally, the surface is tagged with bifunctional peptides (Ang-2-Con-G, AC) to achieve specific targeting. One peptide (Ang-2) is acted as a guide to facilitate the crossing of the blood-brain barrier (BBB), while the other (Con-G) is functioned as a ligand for the targeted delivery of KA to the N-methyl-D-aspartate receptor sites. Animal experiments reveal that AC-RM@HA-MS-KA NPs effectively cross the BBB and directionally accumulate in the curing areas, thereby alleviating the depressive symptoms and improving the cognitive functions of depressed mice. After treatment, the depressed mice almost completely return to normal without obvious symptoms of addiction.

The Function of Spag6 to Repair Brain Edema Damage After Cerebral Ischemic Stroke-reperfusion

Sperm associated antigen 6 (Spag6) is the PF16 homolog of Chlamydomonas and participates in the regulation of cilia movement. Studies have shown that Spag6 is expressed in the brain, and its loss will lead to cerebral edema caused by a defect in motor cilium function in ependymal cells. However, it has not been reported whether the limited or extensive cerebral edema resulting from ischemic strokes is related to the expression regulation of Spag6. Therefore, this study aimed to investigate the effect and related mechanism of Spag6 in alleviating Cerebral Ischemic stroke-reperfusion (CIS/R) damage. Our experimental results showed that Spag6 overexpression alleviated CIS/R-mediated motor cilia structural disorder, improved cerebral edema, inhibited nerve injuries in rats with cerebral ischemia, and alleviated synaptic and dendritic spinal injuries by regulating the expressions of synaptic-related proteins such as CaMKII, PSD95, and CREB. Based on significant changes in PI3K/AKT-mTOR signaling pathway activity after CIS/R determination, we determined that Spag6 regulates the abnormal expression of CIS/R-induced inflammatory factors NF-κB, NLRP3, IL-10, and the autophagy-related proteins Beclin-1, LC3, and P62 by activating the PI3K/AKT-mTOR signaling pathway. This inhibits inflammation and autophagy in the brain tissue. In summary, this study revealed that Spag6 alleviates brain edema damage after CIS/R by maintaining the structural function of the motor cilium, regulating the PI3K/AKT-mTOR signaling pathway, and inhibiting inflammation and autophagy reaction.

SpineTool is an open-source software for analysis of morphology of dendritic spines

Dendritic spines form most excitatory synaptic inputs in neurons and these spines are altered in many neurodevelopmental and neurodegenerative disorders. Reliable methods to assess and quantify dendritic spines morphology are needed, but most existing methods are subjective and labor intensive. To solve this problem, we developed an open-source software that allows segmentation of dendritic spines from 3D images, extraction of their key morphological features, and their classification and clustering. Instead of commonly used spine descriptors based on numerical metrics we used chord length distribution histogram (CLDH) approach. CLDH method depends on distribution of lengths of chords randomly generated within dendritic spines volume. To achieve less biased analysis, we developed a classification procedure that uses machine-learning algorithm based on experts' consensus and machine-guided clustering tool. These approaches to unbiased and automated measurements, classification and clustering of synaptic spines that we developed should provide a useful resource for a variety of neuroscience and neurodegenerative research applications.

Biocytin-Labeling in Whole-Cell Recording: Electrophysiological and Morphological Properties of Pyramidal Neurons in CYLD-Deficient Mice

Biocytin, a chemical compound that is an amide formed from the vitamin biotin and the amino acid L-lysine, has been used as a histological dye to stain nerve cells. Electrophysiological activity and morphology are two key characteristics of neurons, but revealing both the electrophysiological and morphological properties of the same neuron is challenging. This article introduces a detailed and easy-to-operate procedure for single-cell labeling in combination with whole-cell patch-clamp recording. Using a recording electrode filled with a biocytin-containing internal solution, we demonstrate the electrophysiological and morphological characteristics of pyramidal (PNs), medial spiny (MSNs) and parvalbumin neurons (PVs) in brain slices, where the electrophysiological and morphological properties of the same individual cell are elucidated. We first introduce a protocol for whole-cell patch-clamp recording in various neurons, coupled with the intracellular diffusion of biocytin delivered by the glass capillary of the recording electrode, followed by a post hoc procedure to reveal the architecture and morphology of biocytin-labeled neurons. An analysis of action potentials (APs) and neuronal morphology, including the dendritic length, number of intersections, and spine density of biocytin-labeled neurons, were performed using ClampFit and Fiji Image (ImageJ), respectively. Next, to take advantage of the techniques introduced above, we uncovered defects in the APs and the dendritic spines of PNs in the primary motor cortex (M1) of deubiquitinase cylindromatosis (CYLD) knock-out (Cyld^-/-) mice. In summary, this article provides a detailed methodology for revealing the morphology as well as the electrophysiological activity of a single neuron that will have many applications in neurobiology.

Neuromodulatory effect of 4-(methylthio)butyl isothiocyanate against 3-nitropropionic acid induced oxidative impairments in human dopaminergic SH-SY5Y cells via BDNF/CREB/TrkB pathway

Mitochondrial impairment, energetic crisis and elevated oxidative stress have been demonstrated to play a pivotal role in the pathological processes of Huntington's disease (HD). 3-Nitropropionic acid (3-NPA) is a natural neurotoxin that mimics the neurological dysfunctions, mitochondrial impairments and oxidative imbalance of HD. The current investigation was undertaken to demonstrate the neuroprotective effect of 4-(methylthio)butyl isothiocyanate (4-MTBITC) against the 3-NPA induced neurotoxicity in human dopaminergic SH-SY5Y cells. The experimental evidence of oxidative DNA damage by 3-NPA was elucidated by pBR322 DNA nicking assay. In contrast, the 4-MTBITC considerably attenuated the DNA damage, suggesting its free radical scavenging action against 3-NPA and Fenton's reagent. The dose and time-dependent increase of 3-NPA revealed its neurotoxic dose as 0.5 mM after 24 h of treatment of SH-SY5Y cells in MTT assay. In order to determine the optimal dose at which 4-MTBITC protects cell death, the 3-NPA (IC₅₀) induced cells were pretreated with different concentrations of 4-MTBITC for 1 h. The neuroprotective dose of 4-MTBITC against 3-NPA was found to be 0.25 μM. Additionally, the elevated GSH levels in cells treated with 4-MTBITC indicate its propensity to eliminate reactive species generated as a result of 3-NPA-induced mitochondrial dysfunction. Likewise, it was determined through microscopic and flow cytometric experiments that 3-NPA's induced overproduction of reactive species and a decline in mitochondrial membrane potential (MMP) could be efficiently prevented by pre-treating cells with 4-MTBITC. To elucidate the underlying molecular mechanism, the RT-qPCR analysis revealed that the pre-treatment of 4-MTBITC effectively protected neuronal cells against 3-NPA-induced cell death by preventing Caspase-3 activation, Brain-derived neurotrophic factor (BDNF) upregulation, activation of cAMP response element-binding protein (CREB) and Nrf2 induction. Together, our findings lend credence to the idea that pre-treatment with 4-MTBITC reduced 3-NPA-induced neurotoxicity by lowering redox impairment, apoptotic state, and mitochondrial dysfunction. The present work, in conclusion, presented the first proof that the phytoconstituent 4-MTBITC supports the antioxidant system, BDNF/TrkB/CREB signaling, and neuronal survival in dopaminergic SH-SY5Y cells against 3-NPA-induced oxidative deficits.

DXplorer: A Unified Visualization Framework for Interactive Dendritic Spine Analysis Using 3D Morphological Features

Dendritic spines are dynamic, submicron-scale protrusions on neuronal dendrites that receive neuronal inputs. Morphological changes in the dendritic spine often reflect alterations in physiological conditions and are indicators of various neuropsychiatric conditions. However, owing to the highly dynamic and heterogeneous nature of spines, accurate measurement and objective analysis of spine morphology are major challenges in neuroscience research. Most conventional approaches for analyzing dendritic spines are based on two-dimensional (2D) images, which barely reflect the actual three-dimensional (3D) shapes. Although some recent studies have attempted to analyze spines with various 3D-based features, it is still difficult to objectively categorize and analyze spines based on 3D morphology. Here, we propose a unified visualization framework for an interactive 3D dendritic spine analysis system, DXplorer, that displays 3D rendering of spines and plots the high-dimensional features extracted from the 3D mesh of spines. With this system, users can perform the clustering of spines interactively and explore and analyze dendritic spines based on high-dimensional features. We propose a series of high-dimensional morphological features extracted from a 3D mesh of dendritic spines. In addition, an interactive machine learning classifier with visual exploration and user feedback using an interactive 3D mesh grid view ensures a more precise classification based on the spine phenotype. A user study and two case studies were conducted to quantitatively verify the performance and usability of the DXplorer. We demonstrate that the system performs the entire analytic process effectively and provides high-quality, accurate, and objective analysis.

Neural mechanism underlies CYLD modulation of morphology and synaptic function of medium spiny neurons in dorsolateral striatum

Although the deubiquitinase cylindromatosis (CYLD), an abundant protein in the postsynaptic density fraction, plays a crucial role in mediating the synaptic activity of the striatum, the precise molecular mechanism remains largely unclear. Here, using a Cyld-knockout mouse model, we demonstrate that CYLD regulates dorsolateral striatum (DLS) neuronal morphology, firing activity, excitatory synaptic transmission, and plasticity of striatal medium spiny neurons via, likely, interaction with glutamate receptor 1 (GluA1) and glutamate receptor 2 (GluA2), two key subunits of alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptors (AMPARs). CYLD deficiency reduces levels of GluA1 and GluA2 surface protein and increases K63-linked ubiquitination, resulting in functional impairments both in AMPAR-mediated excitatory postsynaptic currents and in AMPAR-dependent long-term depression. The results demonstrate a functional association of CYLD with AMPAR activity, which strengthens our understanding of the role of CYLD in striatal neuronal activity.

Morphological Features of Human Dendritic Spines

Dendritic spine features in human neurons follow the up-to-date knowledge presented in the previous chapters of this book. Human dendrites are notable for their heterogeneity in branching patterns and spatial distribution. These data relate to circuits and specialized functions. Spines enhance neuronal connectivity, modulate and integrate synaptic inputs, and provide additional plastic functions to microcircuits and large-scale networks. Spines present a continuum of shapes and sizes, whose number and distribution along the dendritic length are diverse in neurons and different areas. Indeed, human neurons vary from aspiny or "relatively aspiny" cells to neurons covered with a high density of intermingled pleomorphic spines on very long dendrites. In this chapter, we discuss the phylogenetic and ontogenetic development of human spines and describe the heterogeneous features of human spiny neurons along the spinal cord, brainstem, cerebellum, thalamus, basal ganglia, amygdala, hippocampal regions, and neocortical areas. Three-dimensional reconstructions of Golgi-impregnated dendritic spines and data from fluorescence microscopy are reviewed with ultrastructural findings to address the complex possibilities for synaptic processing and integration in humans. Pathological changes are also presented, for example, in Alzheimer's disease and schizophrenia. Basic morphological data can be linked to current techniques, and perspectives in this research field include the characterization of spines in human neurons with specific transcriptome features, molecular classification of cellular diversity, and electrophysiological identification of coexisting subpopulations of cells. These data would enlighten how cellular attributes determine neuron type-specific connectivity and brain wiring for our diverse aptitudes and behavior.

c-Abl kinase at the crossroads of healthy synaptic remodeling and synaptic dysfunction in neurodegenerative diseases

Our ability to learn and remember depends on the active formation, remodeling, and elimination of synapses. Thus, the development and growth of synapses as well as their weakening and elimination are essential for neuronal rewiring. The structural reorganization of synaptic complexes, changes in actin cytoskeleton and organelle dynamics, as well as modulation of gene expression, determine synaptic plasticity. It has been proposed that dysregulation of these key synaptic homeostatic processes underlies the synaptic dysfunction observed in many neurodegenerative diseases. Much is known about downstream signaling of activated N-methyl-D-aspartate and α-amino-3-hydroxy-5-methyl-4-isoazolepropionate receptors; however, other signaling pathways can also contribute to synaptic plasticity and long-lasting changes in learning and memory. The non-receptor tyrosine kinase c-Abl (ABL1) is a key signal transducer of intra and extracellular signals, and it shuttles between the cytoplasm and the nucleus. This review focuses on c-Abl and its synaptic and neuronal functions. Here, we discuss the evidence showing that the activation of c-Abl can be detrimental to neurons, promoting the development of neurodegenerative diseases. Nevertheless, c-Abl activity seems to be in a pivotal balance between healthy synaptic plasticity, regulating dendritic spines remodeling and gene expression after cognitive training, and synaptic dysfunction and loss in neurodegenerative diseases. Thus, c-Abl genetic ablation not only improves learning and memory and modulates the brain genetic program of trained mice, but its absence provides dendritic spines resiliency against damage. Therefore, the present review has been designed to elucidate the common links between c-Abl regulation of structural changes that involve the actin cytoskeleton and organelles dynamics, and the transcriptional program activated during synaptic plasticity. By summarizing the recent discoveries on c-Abl functions, we aim to provide an overview of how its inhibition could be a potentially fruitful treatment to improve degenerative outcomes and delay memory loss.

Introduction: What Are Dendritic Spines?

Dendritic spines are cellular specializations that greatly increase the connectivity of neurons and modulate the "weight" of most postsynaptic excitatory potentials. Spines are found in very diverse animal species providing neural networks with a high integrative and computational possibility and plasticity, enabling the perception of sensorial stimuli and the elaboration of a myriad of behavioral displays, including emotional processing, memory, and learning. Humans have trillions of spines in the cerebral cortex, and these spines in a continuum of shapes and sizes can integrate the features that differ our brain from other species. In this chapter, we describe (1) the discovery of these small neuronal protrusions and the search for the biological meaning of dendritic spines; (2) the heterogeneity of shapes and sizes of spines, whose structure and composition are associated with the fine-tuning of synaptic processing in each nervous area, as well as the findings that support the role of dendritic spines in increasing the wiring of neural circuits and their functions; and (3) within the intraspine microenvironment, the integration and activation of signaling biochemical pathways, the compartmentalization of molecules or their spreading outside the spine, and the biophysical properties that can affect parent dendrites. We also provide (4) examples of plasticity involving dendritic spines and neural circuits relevant to species survival and comment on (5) current research advancements and challenges in this exciting research field.

Pentylenetetrazol-induced seizures are followed by a reduction in the multiunitary activity of hippocampal CA1 pyramidal neurons in adult rats

Pentylenetetrazol (PTZ) blocks the inhibitory action of GABA, triggering a Glu-mediated hyperexcitation of the dendritic spines in hippocampal CA1 pyramidal neurons that leads to the generation of epileptiform seizures. The aim of this work was to determine the effect of PTZ on the electrical activity of the hippocampal pyramidal neurons in male rats. Bipolar electrodes were implanted stereotaxically in the right and left hippocampal CA1 fields of adults, and PTZ (65 mg/kg) was administered i.p. Simultaneous recordings of the field activity and the firing rate (multiunitary activity, MUA) were analyzed at 10, 20, and 30 min post-administration of PTZ. Only rats that presented tonic-clonic seizures during the first 1-5 min after PTZ treatment were included in the study. The recordings of the field activity were analyzed in 4 frequency bands. In both the right and left hippocampal CA1 fields, the relative power corresponding to the slow waves (4-7 Hz) increased, while in the bands 13-30 Hz and 31-50 Hz, it decreased at 10, 20, and 30 min post-PTZ. MUA recordings were analyzed at four levels. The highest levels corresponded to larger amplitudes of the action potentials in the pyramidal neurons. The firing rates of the PTZ-treated rats did not differ from baseline but presented a significant decrement at 10, 20, and 30 min post-PTZ. The decreased firing rate of the hippocampal CA1 pyramidal neurons after PTZ treatment could be associated with plastic changes of dendritic spines along with some microenvironmental adaptations at synaptic level, after neuronal PTZ-mediated hyperexcitation.

Combined DiI and Antibody Labeling Reveals Complex Dysgenesis of Hippocampal Dendritic Spines in a Mouse Model of Fragile X Syndrome

Structural, functional, and molecular alterations in excitatory spines are a common hallmark of many neurodevelopmental disorders including intellectual disability and autism. Here, we describe an optimized methodology, based on combined use of DiI and immunofluorescence, for rapid and sensitive characterization of the structure and composition of spines in native brain tissue. We successfully demonstrate the applicability of this approach by examining the properties of hippocampal spines in juvenile Fmr1 KO mice, a mouse model of Fragile X Syndrome. We find that mutant mice display pervasive dysgenesis of spines evidenced by an overabundance of both abnormally elongated thin spines and cup-shaped spines, in combination with reduced density of mushroom spines. We further find that mushroom spines expressing the actin-binding protein Synaptopodin-a marker for spine apparatus-are more prevalent in mutant mice. Previous work identified spines with Synaptopodin/spine apparatus as the locus of mGluR-LTD, which is abnormally elevated in Fmr1 KO mice. Altogether, our data suggest this enhancement may be linked to the preponderance of this subset of spines in the mutant. Overall, these findings demonstrate the sensitivity and versatility of the optimized methodology by uncovering a novel facet of spine dysgenesis in Fmr1 KO mice.

Evaluation of Neurotoxicity in BALB/c Mice following Chronic Exposure to Polystyrene Microplastics

BACKGROUND

The toxicity of microplastics (MPs) has attracted wide attention from researchers. Previous studies have indicated that MPs produce toxic effects on a variety of organs in aquatic organisms and mammals. However, the exact neurotoxicity of MPs in mammals is still unclear.

OBJECTIVES

We aimed to confirm the neurotoxicity of chronic exposure to polystyrene MPs (PS-MPs) at environmental pollution concentrations.

METHODS

In the present study, mice were provided drinking water containing 100μg/L and 1,000μg/L PS-MPs with diameters of 0.5, 4, and 10μm for 180 consecutive days. After the exposure period, the mice were anesthetized to gain brain tissues. The accumulation of PS-MPs in brain tissues, integrity of the blood-brain barrier, inflammation, and spine density were detected. We evaluated learning and memory ability by the Morris water maze and novel object recognition tests.

RESULTS

We observed the accumulation of PS-MPs with various particle diameters (0.5, 4, and 10μm) in the brains of exposed mice. Meanwhile, exposed mice also exhibited disruption of the blood-brain barrier, higher level of dendritic spine density, and an inflammatory response in the hippocampus. In addition, exposed mice exhibited cognitive and memory deficits compared with control mice as determined using the Morris water maze and novel object recognition tests, respectively. There was a concentration-dependent trend, but no particle size-dependent differences were seen in the neurotoxicity of MPs.

CONCLUSIONS

Collectively, our results suggested that PS-MPs exposure can lead to learning and memory dysfunctions and induce neurotoxic effects in mice, findings which have wide-ranging implications for the public regarding the potential risks of MPs. https://doi.org/10.1289/EHP10255.

Brain circuit pathology in Down syndrome: from neurons to neural networks

Down syndrome (DS), a genetic pathology caused by triplication of chromosome 21, is characterized by brain hypotrophy and impairment of cognition starting from infancy. While studies in mouse models of DS have elucidated the major neuroanatomical and neurochemical defects of DS, comparatively fewer investigations have focused on the electrophysiology of the DS brain. Electrical activity is at the basis of brain functioning. Therefore, knowledge of the way in which brain circuits operate in DS is fundamental to understand the causes of behavioral impairment and devise targeted interventions. This review summarizes the state of the art regarding the electrical properties of the DS brain, starting from individual neurons and culminating in signal processing in whole neuronal networks. The reported evidence derives from mouse models of DS and from brain tissues and neurons derived from individuals with DS. EEG data recorded in individuals with DS are also provided as a key tool to understand the impact of brain circuit alterations on global brain activity.

PI3K/AKT/mTOR signalling inhibitor chrysophanol ameliorates neurobehavioural and neurochemical defects in propionic acid-induced experimental model of autism in adult rats

Autism spectrum disorder (ASD) is a complex neurodevelopmental disorder marked by social and communication deficits as well as repetitive behaviour. Several studies have found that overactivation of the PI3K/AKT/mTOR signalling pathways during brain development plays a significant role in autism pathogenesis. Overexpression of the PI3K/AKT/mTOR signalling pathway causes neurological disorders by increasing cell death, neuroinflammation, and oxidative stress. Chrysophanol, also known as chrysophanic acid, is a naturally occurring chemical obtained from the plant Rheum palmatum. This study aimed to examine the neuroprotective effect of CPH on neurobehavioral, molecular, neurochemical, and gross pathological alterations in ICV-PPA induced experimental model of autism in adult rats. The effects of ICV-PPA on PI3K/AKT/mTOR downregulation in the brain were studied in autism-like rats. Furthermore, we investigated how CPH affected myelin basic protein (MBP) levels in rat brain homogenate and apoptotic biomarkers such as caspase-3, Bax, and Bcl-2 levels in rat brain homogenate and blood plasma samples. Rats were tested for behavioural abnormalities such as neuromuscular dysfunction using an actophotometer, motor coordination using a beam crossing task (BCT), depressive behaviour using a forced swim test (FST), cognitive deficiency, and memory consolidation using a Morris water maze (MWM) task. In PPA-treated rats, prolonged oral CPH administration from day 12 to day 44 of the experimental schedule reduces autistic-like symptoms. Furthermore, in rat brain homogenates, blood plasma, and CSF samples, cellular, molecular, and cell death markers, neuroinflammatory cytokines, neurotransmitter levels, and oxidative stress indicators were investigated. The recent findings imply that CPH also restores abnormal neurochemical levels and may prevent autism-like gross pathological alterations, such as demyelination volume, in the rat brain.

Methylphenidate Restores Behavioral and Neuroplasticity Impairments in the Prenatal Nicotine Exposure Mouse Model of ADHD: Evidence for Involvement of AMPA Receptor Subunit Composition and Synaptic Spine Morphology in the Hippocampus

In ADHD treatment, methylphenidate (MPH) is the most frequently used medication. The present work provides evidence that MPH restored behavioral impairments and neuroplasticity due to changes in AMPAR subunit composition and distribution, as well as maturation of dendritic spines, in a prenatal nicotine exposure (PNE) ADHD mouse model. PNE animals and controls were given a single oral dose of MPH (1 mg/kg), and their behavior was tested for attention, hyperactivity, and working memory. Long-term potentiation (LTP) was induced and analyzed at the CA3/CA1 synapse in hippocampal slices taken from the same animals tested behaviorally, measuring fEPSPs and whole-cell patch-clamp EPSCs. By applying crosslinking and Western blots, we estimated the LTP effects on AMPAR subunit composition and distribution. The density and types of dendritic spines were quantified by using the Golgi staining method. MPH completely restored the behavioral impairments of PNE mice. Reduced LTP and AMPA-receptor-mediated EPSCs were also restored. EPSC amplitudes were tightly correlated with numbers of GluA1/GluA1 AMPA receptors at the cell surface. Finally, we found a lower density of dendritic spines in hippocampal pyramidal neurons in PNE mice, with a higher fraction of thin-type immature spines and a lower fraction of mushroom mature spines; the latter effect was also reversed by MPH.

Single-Vesicle Electrochemistry Following Repetitive Stimulation Reveals a Mechanism for Plasticity Changes with Iron Deficiency

Deficiency of iron, the most abundant transition metal in the brain and important for neuronal activity, is known to affect synaptic plasticity, causing learning and memory deficits. How iron deficiency impacts plasticity by altering neurotransmission at the cellular level is not fully understood. We used electrochemical methods to study the effect of iron deficiency on plasticity with repetitive stimulation. We show that during iron deficiency, repetitive stimulation causes significant decrease in exocytotic release without changing vesicular content. This results in a lower fraction of release, opposite to the control group, upon repetitive stimulation. These changes were partially reversible by iron repletion. This finding suggests that iron deficiency has a negative effect on plasticity by decreasing the fraction of vesicular release in response to repetitive stimulation. This provides a putative mechanism for how iron deficiency modulates plasticity.

Control of Synapse Structure and Function by Actin and Its Regulators

Neurons transmit and receive information at specialized junctions called synapses. Excitatory synapses form at the junction between a presynaptic axon terminal and a postsynaptic dendritic spine. Supporting the shape and function of these junctions is a complex network of actin filaments and its regulators. Advances in microscopic techniques have enabled studies of the organization of actin at synapses and its dynamic regulation. In addition to highlighting recent advances in the field, we will provide a brief historical perspective of the understanding of synaptic actin at the synapse. We will also highlight key neuronal functions regulated by actin, including organization of proteins in the pre- and post- synaptic compartments and endocytosis of ion channels. We review the evidence that synapses contain distinct actin pools that differ in their localization and dynamic behaviors and discuss key functions for these actin pools. Finally, whole exome sequencing of humans with neurodevelopmental and psychiatric disorders has identified synaptic actin regulators as key disease risk genes. We briefly summarize how genetic variants in these genes impact neurotransmission via their impact on synaptic actin.

Impact of Pharmacological and Non-Pharmacological Modulators on Dendritic Spines Structure and Functions in Brain

Dendritic spines are small, thin, hair-like protrusions found on the dendritic processes of neurons. They serve as independent compartments providing large amplitudes of Ca2+ signals to achieve synaptic plasticity, provide sites for newer synapses, facilitate learning and memory. One of the common and severe complication of neurodegenerative disease is cognitive impairment, which is said to be closely associated with spine pathologies viz., decreased in spine density, spine length, spine volume, spine size etc. Many treatments targeting neurological diseases have shown to improve the spine structure and distribution. However, concise data on the various modulators of dendritic spines are imperative and a need of the hour. Hence, in this review we made an attempt to consolidate the effects of various pharmacological (cholinergic, glutamatergic, GABAergic, serotonergic, adrenergic, and dopaminergic agents) and non-pharmacological modulators (dietary interventions, enriched environment, yoga and meditation) on dendritic spines structure and functions. These data suggest that both the pharmacological and non-pharmacological modulators produced significant improvement in dendritic spine structure and functions and in turn reversing the pathologies underlying neurodegeneration. Intriguingly, the non-pharmacological approaches have shown to improve intellectual performances both in preclinical and clinical platforms, but still more technology-based evidence needs to be studied. Thus, we conclude that a combination of pharmacological and non-pharmacological intervention may restore cognitive performance synergistically via improving dendritic spine number and functions in various neurological disorders.

A multimodal electrochemical approach to measure the effect of zinc on vesicular content and exocytosis in a single cell model of ischemia

Zinc ion is essential for normal brain function that modulates synaptic activity and neuronal plasticity and it is associated with memory formation. Zinc is considered to be a contributing factor to the pathogenesis of ischemia, but the association between zinc and ischemia on vesicular exocytosis is unclear. In this study, we used a combination of chemical analysis methods and a cell model of ischemia/reperfusion to investigate exocytotic release and vesicular content, as well as the effect of zinc alteration on vesicular exocytosis. Oxygen–glucose deprivation and reperfusion (OGDR) was used as an in vitro model of ischemia in a model cell line. Exocytotic release and vesicular storage of catecholamine content were increased following OGDR, resulting in a higher fraction of release during exocytosis. However, zinc eliminated these increases following OGDR and the fraction of release remained unchanged. Understanding the consequences of zinc accumulation on vesicular exocytosis at the early stage of OGDR should aid in the development of therapeutic strategies to reduce ischemic brain injury. As the fraction released has been suggested to be related to presynaptic plasticity, insights are gained towards deciphering ischemia related memory impairment.

Changes in the Number and Morphology of Dendritic Spines in the Hippocampus and Prefrontal Cortex of the C58/J Mouse Model of Autism

Autism spectrum disorder (ASD) has a broad range of neurobiological characteristics, including alterations in dendritic spines, where approximately 90% of excitatory synapses occur. Therefore, changes in their number or morphology would be related to atypical brain communication. The C58/J inbred mouse strain displays low sociability, impaired communication, and stereotyped behavior; hence, it is considered among the animal models suitable for the study of idiopathic autism. Thus, this study aimed to evaluate the dendritic spine differences in the hippocampus and the prefrontal cortex of C58/J mice. We found changes in the number of spines and morphology in a brain region-dependent manner: a subtle decrease in spine density in the prefrontal cortex, higher frequency of immature phenotype spines characterized by filopodia-like length or small morphology, and a lower number of mature phenotype spines with mushroom-like or wide heads in the hippocampus. Moreover, an in silico analysis showed single nucleotide polymorphisms (SNPs) at genes collectively involved in regulating structural plasticity with a likely association with ASD, including MAP1A (Microtubule-Associated Protein 1A), GRM7 (Metabotropic Glutamate Receptor, 7), ANKRD11 (Ankyrin Repeat Domain 11), and SLC6A4 (Solute Carrier Family 6, member 4), which might support the relationship between the C58/J strain genome, an autistic-like behavior, and the observed anomalies in the dendritic spines.

Association of CaMK2A and MeCP2 signaling pathways with cognitive ability in adolescents

The glutamatergic signaling pathway is involved in molecular learning and human cognitive ability. Specific single variants (SNVs, formerly single-nucleotide polymorphisms) in the genes encoding N-methyl-d-aspartate receptor subunits have been associated with neuropsychiatric disorders by altering glutamate transmission. However, these variants associated with cognition and mental activity have rarely been explored in healthy adolescents. In this study, we screened for SNVs in the glutamatergic signaling pathway to identify genetic variants associated with cognitive ability. We found that SNVs in the subunits of ionotropic glutamate receptors, including GRIA1, GRIN1, GRIN2B, GRIN2C, GRIN3A, GRIN3B, and calcium/calmodulin-dependent protein kinase IIα (CaMK2A) are associated with cognitive function. Plasma CaMK2A level was correlated positively with the cognitive ability of Taiwanese senior high school students. We demonstrated that elevating CaMK2A increased its autophosphorylation at T286 and increased the expression of its downstream targets, including GluA1 and phosphor- GluA1 in vivo. Additionally, methyl-CpG binding protein 2 (MeCP2), a downstream target of CaMK2A, was found to activate the expression of CaMK2A, suggesting that MeCP2 and CaMK2A can form a positive feedback loop. In summary, two members of the glutamatergic signaling pathway, CaMK2A and MeCP2, are implicated in the cognitive ability of adolescents; thus, altering the expression of CaMK2A may affect cognitive ability in youth.

Estradiol attenuates chronic restraint stress-induced dendrite and dendritic spine loss and cofilin1 activation in ovariectomized mice

Ovarian hormone deprivation is associated with mood disorders, such as depression, and estradiol therapy is significantly more effective than placebos in treating major depression associated with menopause onset. However, the effect of estradiol on neuronal plasticity and its mechanisms remain to be further elucidated. In this study, behavioral assessments were used to examine the antidepressant effect of estradiol in ovariectomized (OVX) B6.Cg-TgN (Thy-YFP-H)-2Jrs transgenic mice on chronic restraint stress (CRS)-induced dendrite and dendritic spine loss; Yellow fluorescent protein (YFP) is characteristically expressed in excitatory neurons in transgenic mice, and its three-dimensional images were used to evaluate the effect of estradiol on the density of different types of dendritic spines. Quantification and distribution of cofilin1 and p-cofilin1 were determined by qPCR, Western blots, and immunohistochemistry, respectively. The results revealed that treatment with estradiol or clomipramine significantly improved depression-like behaviors. Estradiol treatment also significantly upregulated the dendritic density in all areas examined and increased the density of filopodia-type, thin-type and mushroom-type spines in the hippocampal CA1 and elevated the thin-type and mushroom-type spine density in the PFC. Consistent with these changes, estradiol treatment significantly increased the density of p-cofilin1 immunopositive dendritic spines. Thus, these data reveal a possible estradiol antidepressant mechanism, in that estradiol promoted the phosphorylation of cofilin1 and reduced the loss of dendrites and dendritic spines, which of these dendritic spines include not only immature spines such as filopodia-type, but also mature spines such as mushroom-type, and attenuated the depression-like behavior.

A Transcriptome Community-and-Module Approach of the Human Mesoconnectome

Graph analysis allows exploring transcriptome compartments such as communities and modules for brain mesostructures. In this work, we proposed a bottom-up model of a gene regulatory network to brain-wise connectome workflow. We estimated the gene communities across all brain regions from the Allen Brain Atlas transcriptome database. We selected the communities method to yield the highest number of functional mesostructures in the network hierarchy organization, which allowed us to identify specific brain cell functions (e.g., neuroplasticity, axonogenesis and dendritogenesis communities). With these communities, we built brain-wise region modules that represent the connectome. Our findings match with previously described anatomical and functional brain circuits, such the default mode network and the default visual network, supporting the notion that the brain dynamics that carry out low- and higher-order functions originate from the modular composition of a GRN complex network.

Connecting the Neurobiology of Developmental Brain Injury: Neuronal Arborisation as a Regulator of Dysfunction and Potential Therapeutic Target

Neurodevelopmental disorders can derive from a complex combination of genetic variation and environmental pressures on key developmental processes. Despite this complex aetiology, and the equally complex array of syndromes and conditions diagnosed under the heading of neurodevelopmental disorder, there are parallels in the neuropathology of these conditions that suggest overlapping mechanisms of cellular injury and dysfunction. Neuronal arborisation is a process of dendrite and axon extension that is essential for the connectivity between neurons that underlies normal brain function. Disrupted arborisation and synapse formation are commonly reported in neurodevelopmental disorders. Here, we summarise the evidence for disrupted neuronal arborisation in these conditions, focusing primarily on the cortex and hippocampus. In addition, we explore the developmentally specific mechanisms by which neuronal arborisation is regulated. Finally, we discuss key regulators of neuronal arborisation that could link to neurodevelopmental disease and the potential for pharmacological modification of arborisation and the formation of synaptic connections that may provide therapeutic benefit in the future.

Synaptic modifications in learning and memory - A dendritic spine story

Synapses are specialized sites where neurons connect and communicate with each other. Activity-dependent modification of synaptic structure and function provides a mechanism for learning and memory. The advent of high-resolution time-lapse imaging in conjunction with fluorescent biosensors and actuators enables researchers to monitor and manipulate the structure and function of synapses both in vitro and in vivo. This review focuses on recent imaging studies on the synaptic modification underlying learning and memory.

The p75 neurotrophin receptor as a novel intermediate in L-dopa-induced dyskinesia in experimental Parkinson's disease

In Parkinson's disease (PD), long-term administration of L-dopa often leads to L-dopa-induced dyskinesia (LID), a debilitating motor complication. The p75 neurotrophin receptor (p75NTR) is likely to play a critical role in the regulation of dendritic spine density and morphology and appears to be associated with neuroinflammation, which previously has been identified as a crucial mechanism in LID. While aberrant modifications of p75NTR in neurological diseases have been extensively documented, only a few studies report p75NTR dysfunction in PD, and no data are available in LID. Here, we explored the functional role of p75NTR in LID. In LID rats, we identified that p75NTR was significantly increased in the lesioned striatum. In 6-hydroxydopamine (6-OHDA)-hemilesioned rats, specific knockdown of striatal p75NTR levels achieved by viral vector injection into the striatum prevented the development of LID and increased striatal structural plasticity. By contrast, we found that in 6-OHDA-hemilesioned rats, striatal p75NTR overexpression exacerbated LID and facilitated striatal dendritic spine losses. Moreover, we observed that the immunomodulatory drug fingolimod attenuated LID without lessening the therapeutic efficacy of L-dopa and normalized p75NTR levels. Together, these data demonstrate for the first time that p75NTR plays a pivotal role in the development of LID and that p75NTR may act as a potential novel target for the management of LID.

Ghrelin treatment leads to dendritic spine remodeling in hippocampal neurons and increases the expression of specific BDNF-mRNA species

Ghrelin (Gr) is an orexigenic peptide that acts via its specific receptor, GHSR-1a distributed throughout the brain, being mainly enriched in pituitary, cortex and hippocampus (Hp) modulating a variety of brain functions. Behavioral, electrophysiological and biochemical evidence indicated that Gr modulates the excitability and the synaptic plasticity in Hp. The present experiments were designed in order to extend the knowledge about the Gr effect upon structural synaptic plasticity since morphological and quantitative changes in spine density after Gr administration were analyzed "in vitro" and "in vivo". The results show that Gr administered to hippocampal cultures or stereotactically injected in vivo to Thy-1 mice increases the density of dendritic spines (DS) being the mushroom type highly increased in secondary and tertiary extensions. Spines classified as thin type were increased particularly in primary extensions. Furthermore, we show that Gr enhances selectively the expression of BDNF-mRNA species.

Preservation of dendritic spine morphology and postsynaptic signaling markers after treatment with solid lipid curcumin particles in the 5xFAD mouse model of Alzheimer's amyloidosis

BACKGROUND

Synaptic failure is one of the principal events associated with cognitive dysfunction in Alzheimer's disease (AD). Preservation of existing synapses and prevention of synaptic loss are promising strategies to preserve cognitive function in AD patients. As a potent natural anti-oxidant, anti-amyloid, and anti-inflammatory polyphenol, curcumin (Cur) shows great promise as a therapy for AD. However, hydrophobicity of natural Cur limits its solubility, stability, bioavailability, and clinical utility for AD therapy. We have demonstrated that solid lipid curcumin particles (SLCP) have greater therapeutic potential than natural Cur in vitro and in vivo models of AD. In the present study, we have investigated whether SLCP has any preservative role on affected dendritic spines and synaptic markers in 5xFAD mice.

METHODS

Six- and 12-month-old 5xFAD and age-matched wild-type mice received oral administration of SLCP (100 mg/kg body weight) or equivalent amounts of vehicle for 2 months. Neuronal morphology, neurodegeneration, and amyloid plaque load were investigated from prefrontal cortex (PFC), entorhinal cortex (EC), CA1, CA3, and the subicular complex (SC). In addition, the dendritic spine density from apical and basal branches was studied by Golgi-Cox stain. Further, synaptic markers, such as synaptophysin, PSD95, Shank, Homer, Drebrin, Kalirin-7, CREB, and phosphorylated CREB (pCREB) were studied using Western blots. Finally, cognitive and motor functions were assessed using open-field, novel object recognition (NOR) and Morris water maze (MWM) tasks after treatment with SLCP.

RESULTS

We observed an increased number of pyknotic and degenerated cells in all these brain areas in 5xFAD mice and SLCP treatment partially protected against those losses. Decrease in dendritic arborization and dendritic spine density from primary, secondary, and tertiary apical and basal branches were observed in PFC, EC, CA1, and CA3 in both 6- and 12-month-old 5xFAD mice, and SLCP treatments partially preserved the normal morphology of these dendritic spines. In addition, pre- and postsynaptic protein markers were also restored by SLCP treatment. Furthermore, SLCP treatment improved NOR and cognitive function in 5xFAD mice.

CONCLUSIONS

Overall, these findings indicate that use of SLCP exerts neuroprotective properties by decreasing amyloid plaque burden, preventing neuronal death, and preserving dendritic spine density and synaptic markers in the 5xFAD mice.

Early appearance of developmental alterations in the dendritic tree of the hippocampal granule cells in the Ts65Dn model of Down syndrome

Down syndrome (DS), a genetic condition caused by triplication of chromosome 21, is characterized by alterations in various cognitive domains, including hippocampus-dependent memory functions, starting from early life stages. The major causes of intellectual disability in DS are prenatal neurogenesis alterations followed by impairment of dendritic development in early infancy. While there is evidence that the Ts65Dn mouse, the most widely used model of DS, exhibits dendritic alterations in adulthood, no studies are available regarding the onset of dendritic pathology. The goal of the current study was to establish whether this model exhibits early dendritic alterations in the hippocampus, a region whose function is severely damaged in DS. To this purpose, in Golgi-stained brains, we evaluated the dendritic arborization and dendritic spines of the granule cells of the hippocampal dentate gyrus in Ts65Dn mice aged 8 (P8) and 15 (P15) days. While P15 Ts65Dn mice exhibited a notably hypotrophic dendritic arbor and a reduced spine density, P8 mice exhibited a moderate reduction in the number of dendritic ramifications and no differences in spine density in comparison with their euploid counterparts. Both in P8 and P15 mice, spines were longer and had a longer neck, suggesting possible alterations in synaptic function. Moreover, P8 and P15 Ts65Dn mice had more thin spines and fewer stubby spines in comparison with euploid mice. Our study provides novel evidence on the onset of dendritic pathology, one of the causes of intellectual disability in DS, showing that it is already detectable in the dentate gyrus of Ts65Dn pups. This evidence strengthens the suitability of this model of DS as a tool to study dendritic pathology in DS and to test the efficacy of early therapeutic interventions aimed at ameliorating hippocampal development and, therefore, memory functions in children with DS.