The Synaptic Vesicle Glycoprotein 2: Structure, Function, and Disease Relevance

Presynaptic antiseizure medications - basic mechanisms and clues for their rational combinations

Among clinically highly efficient antiseizure medications (ASMs) there are modifiers of the presynaptic release machinery. Of them, levetiracetam and brivaracetam show a high affinity to the synaptic vesicle protein type 2 A (SV2A), whereas pregabalin and gabapentin are selective ligands for the α2δ1 subunits of the voltage-gated calcium channels. In this paper, we present recent progress in understanding the significance of presynaptic release machinery in the neurochemical mechanisms of epilepsy and ASMs. Furthermore, we discuss whether the knowledge of the basic mechanisms of the presynaptically acting ASMs might help establish a rational polytherapy for drug-resistant epilepsy.

Challenges and rewards of in vivo synaptic density imaging, and its application to the study of depression

The development of novel radiotracers for Positron Emission Tomography (PET) imaging agents targeting the synaptic vesicle glycoprotein 2 A (SV2A), an integral glycoprotein present in the membrane of all synaptic vesicles throughout the central nervous system, provides a method for the in vivo quantification of synaptic density. This is of particular interest in neuropsychiatric disorders given that synaptic alterations appear to underlie disease progression and symptom severity. In this review, we briefly describe the development of these SV2A tracers and the evaluation of quantification methods. Next, we discuss application of SV2A PET imaging to the study of depression, including a review of our findings demonstrating lower SV2A synaptic density in people with significant depressive symptoms and the use of a ketamine drug challenge to examine synaptogenesis in vivo. We then highlight the importance of performing translational PET imaging in animal models in conjunction with clinical imaging. We consider the ongoing challenges, possible solutions, and present preliminary findings from our lab demonstrating the translational benefit and potential of in vivo SV2A imaging in animal models of chronic stress. Finally, we discuss methodological improvements and future directions for SV2A imaging, potentially in conjunction with other neural markers.

The protective effects of repetitive transcranial magnetic stimulation with different high frequencies on motor functions in MPTP/probenecid induced Parkinsonism mouse models

BACKGROUND

High-frequency repeated transcranial magnetic stimulation (rTMS) stimulating the primary motor cortex (M1) is an alternative, adjunctive therapy for improving the motor symptoms of Parkinson's disease (PD). However, whether the high frequency of rTMS positively correlates to the improvement of motor symptoms of PD is still undecided. By controlling for other parameters, a disease animal model may be useful to compare the neuroprotective effects of different high frequencies of rTMS.

OBJECTIVE

The current exploratory study was designed to compare the protective effects of four common high frequencies of rTMS (5, 10, 15, and 20 Hz) and iTBS (a special form of high-frequency rTMS) and explore the optimal high-frequency rTMS on an animal PD model.

METHODS

Following high frequencies of rTMS application (twice a week for 5 weeks) in a MPTP/probenecid-induced chronic PD model, the effects of the five protocols on motor behavior as well as dopaminergic neuron degeneration levels were identified. The underlying molecular mechanisms were further explored.

RESULTS

We found that all the high frequencies of rTMS had protective effects on the motor functions of PD models to varying degrees. Among them, the 10, 15, and 20 Hz rTMS interventions induced comparable preservation of motor function through the protection of nigrostriatal dopamine neurons. The enhancement of brain-derived neurotrophic factor (BDNF), dopamine transporter (DAT), and vesicular monoamine transporter 2 (VMAT-2) and the suppression of TNF-α and IL-1β in the nigrostriatum were involved in the process. The efficacy of iTBS was inferior to that of the above three protocols. The effect of 5 Hz rTMS protocol was weakest.

CONCLUSIONS

Combined with the results of the present study and the possible side effects induced by rTMS, we concluded that 10 Hz might be the optimal stimulation frequency for preserving the motor functions of PD models using rTMS treatment.

Molecular variations to the proteome of zebrafish larvae induced by environmentally relevant copper concentrations

Contaminants are increasingly accumulating in aquatic environments and biota, with potential adverse effects on individual organisms, communities and ecosystems. However, studies that explore the molecular changes in fish caused by environmentally relevant concentrations of metals, such as copper (Cu), are limited. This study uses embryos of the model organism zebrafish (Danio rerio) to investigate effect of Cu on the proteome and amino acid (AA) composition of fish. Wild-type embryos at 24 h post-fertilisation were exposed to Cu (2 µg L-1 to 120 µg L-1) for 96 h and the number of healthy larvae were determined based on larvae that had hatched and did not display loss of equilibrium (LOE). The effect concentrations where Cu caused a 10 % (EC10) or 50 % (EC50) decrease in the number of healthy larvae were calculated as 3.7 µg L-1 and 10.9 µg L-1, respectively. Proteomics analysis of embryos exposed to the EC10 and EC50 concentrations of Cu revealed the proteome to differ more strongly after 48 h than 96 h, suggesting the acclimatisation of some larvae. Exposure to excess Cu caused differentially expressed proteins (DEPs) involved in oxidative stress, mitochondrial respiration, and neural transduction as well as the modulation of the AAs (Proline, Glycine and Alanine). This is the first study to suggest that LOE displayed by Cu-stressed fish may involve the disruption to GABAergic proteins and the calcium-dependent inhibitory neurotransmitter GABA. Moreover, this study highlights that proteomics and AA analysis can be used to identify potential biomarkers for environmental monitoring.

Neurotoxicology of dopamine: Victim or assailant?

Since the identification of dopamine as a neurotransmitter in the mid-20th century, investigators have examined the regulation of dopamine homeostasis at a basic biological level and in human disorders. Genetic animal models that manipulate the expression of proteins involved in dopamine homeostasis have provided key insight into the consequences of dysregulated dopamine. As a result, we have come to understand the potential of dopamine to act as an endogenous neurotoxin through the generation of reactive oxygen species and reactive metabolites that can damage cellular macromolecules. Endogenous factors, such as genetic variation and subcellular processes, and exogenous factors, such as environmental exposures, have been identified as contributors to the dysregulation of dopamine homeostasis. Given the variety of dysregulating factors that impact dopamine homeostasis and the potential for dopamine itself to contribute to further cellular dysfunction, dopamine can be viewed as both the victim and an assailant of neurotoxicity. Parkinson's disease has emerged as the exemplar case study of dopamine dysregulation due to the genetic and environmental factors known to contribute to disease risk, and due to the evidence of dysregulated dopamine as a pathologic and pathogenic feature of the disease. This review, inspired by the talk, "Dopamine in Durham: location, location, location" presented by Dr. Miller for the Jacob Hooisma Memorial Lecture at the International Neurotoxicology Association meeting in 2023, offers a primer on dopamine toxicity covering endogenous and exogenous factors that disrupt dopamine homeostasis and the actions of dopamine as an endogenous neurotoxin.

Focal clusters of peri-synaptic matrix contribute to activity-dependent plasticity and memory in mice

Recent findings show that effective integration of novel information in the brain requires coordinated processes of homo- and heterosynaptic plasticity. In this work, we hypothesize that activity-dependent remodeling of the peri-synaptic extracellular matrix (ECM) contributes to these processes. We show that clusters of the peri-synaptic ECM, recognized by CS56 antibody, emerge in response to sensory stimuli, showing temporal and spatial coincidence with dendritic spine plasticity. Using CS56 co-immunoprecipitation of synaptosomal proteins, we identify several molecules involved in Ca2+ signaling, vesicle cycling, and AMPA-receptor exocytosis, thus suggesting a role in long-term potentiation (LTP). Finally, we show that, in the CA1 hippocampal region, the attenuation of CS56 glycoepitopes, through the depletion of versican as one of its main carriers, impairs LTP and object location memory in mice. These findings show that activity-dependent remodeling of the peri-synaptic ECM regulates the induction and consolidation of LTP, contributing to hippocampal-dependent memory.

Exploring the Interactions between two Ligands, UCB-J and UCB-F, and Synaptic Vesicle Glycoprotein 2 Isoforms

In silico modeling was applied to study the efficiency of two ligands, namely, UCB-J and UCB-F, to bind to isoforms of the synaptic vesicle glycoprotein 2 (SV2) that are involved in the regulation of synaptic function in the nerve terminals, with the ultimate goal to understand the selectivity of the interaction between UCB-J and UCB-F to different isoforms of SV2. Docking and large-scale molecular dynamics simulations were carried out to unravel various binding patterns, types of interactions, and binding free energies, covering hydrogen bonding and nonspecific hydrophobic interactions, water bridge, π-π, and cation-π interactions. The overall preference for bonding types of UCB-J and UCB-F with particular residues in the protein pockets can be disclosed in detail. A unique interaction fingerprint, namely, hydrogen bonding with additional cation-π interaction with the pyridine moiety of UCB-J, could be established as an explanation for its high selectivity over the SV2 isoform A (SV2A). Other molecular details, primarily referring to the presence of π-π interactions and hydrogen bonding, could also be analyzed as sources of selectivity of the UCB-F tracer for the three isoforms. The simulations provide atomic details to support future development of new selective tracers targeting synaptic vesicle glycoproteins and their associated diseases.

Development of SV2A Ligands for Epilepsy Treatment: A Review of Levetiracetam, Brivaracetam, and Padsevonil

Epilepsy is a common neurological disorder that is primarily treated with antiseizure medications (ASMs). Although dozens of ASMs are available in the clinic, approximately 30% of epileptic patients have medically refractory seizures; other limitations in most traditional ASMs include poor tolerability and drug-drug interactions. Therefore, there is an urgent need to develop alternative ASMs. Levetiracetam (LEV) is a first-line ASM that is well tolerated, has promising efficacy, and has little drug-drug interaction. Although it is widely accepted that LEV acts through a unique therapeutic target synaptic vesicle protein (SV) 2A, the molecular basis of its action remains unknown. Even so, the next-generation SV2A ligands against epilepsy based on the structure of LEV have achieved clinical success. This review highlights the research and development (R&D) process of LEV and its analogs, brivaracetam and padsevonil, to provide ideas and experience for the R&D of novel ASMs.

Tau pathology is associated with synaptic density and longitudinal synaptic loss in Alzheimer's disease

The associations of synaptic loss with amyloid-β (Aβ) and tau pathology measured by positron emission tomography (PET) and plasma analysis in Alzheimer's disease (AD) patients are unknown. Seventy-five participants, including 26 AD patients, 19 mild cognitive impairment (MCI) patients, and 30 normal controls (NCs), underwent [18F]SynVesT-1 PET/MR scans to assess synaptic density and [18F]florbetapir and [18F]MK6240 PET/CT scans to evaluate Aβ plaques and tau tangles. Among them, 19 AD patients, 12 MCI patients, and 29 NCs had plasma Aβ42/40 and p-tau181 levels measured by the Simoa platform. Twenty-three individuals, 6 AD patients, 4 MCI patients, and 13 NCs, underwent [18F]SynVesT-1 PET/MRI and [18F]MK6240 PET/CT scans during a one-year follow-up assessment. The associations of Aβ and tau pathology with cross-sectional and longitudinal synaptic loss were investigated using Pearson correlation analyses, generalized linear models and mediation analyses. AD patients exhibited lower synaptic density than NCs and MCI patients. In the whole cohort, global Aβ deposition was associated with synaptic loss in the medial (r = -0.431, p < 0.001) and lateral (r = -0.406, p < 0.001) temporal lobes. Synaptic density in almost all regions was related to the corresponding regional tau tangles independent of global Aβ deposition in the whole cohort and stratified groups. Synaptic density in the medial and lateral temporal lobes was correlated with plasma Aβ42/40 (r = 0.300, p = 0.020/r = 0.289, p = 0.025) and plasma p-tau 181 (r = -0.412, p = 0.001/r = -0.529, p < 0.001) levels in the whole cohort. Mediation analyses revealed that tau tangles mediated the relationship between Aβ plaques and synaptic density in the whole cohort. Baseline tau pathology was positively associated with longitudinal synaptic loss. This study suggested that tau burden is strongly linked to synaptic density independent of Aβ plaques, and also can predict longitudinal synaptic loss.

SV2B defines a subpopulation of synaptic vesicles

Synaptic vesicles can undergo several modes of exocytosis, endocytosis, and trafficking within individual synapses, and their fates may be linked to different vesicular protein compositions. Here, we mapped the intrasynaptic distribution of the synaptic vesicle proteins SV2B and SV2A in glutamatergic synapses of the hippocampus using three-dimensional electron microscopy. SV2B was almost completely absent from docked vesicles and a distinct cluster of vesicles found near the active zone. In contrast, SV2A was found in all domains of the synapse and was slightly enriched near the active zone. SV2B and SV2A were found on the membrane in the peri-active zone, suggesting the recycling from both clusters of vesicles. SV2B knockout mice displayed an increased seizure induction threshold only in a model employing high-frequency stimulation. Our data show that glutamatergic synapses generate molecularly distinct populations of synaptic vesicles and are able to maintain them at steep spatial gradients. The almost complete absence of SV2B from vesicles at the active zone of wildtype mice may explain why SV2A has been found more important for vesicle release.

DDT and titanium dioxide nanoparticle coexposure induced neurobehavioral deficits in zebrafish

Both dichlorodiphenyltrichloroethane (DDT) and titanium dioxide nanoparticle (TiO2 NP) have worldwide-scale commercial applications, resulting in their co-pollution in the ecosystems and posing combined health risks. However, there is a lack of toxicity studies for the interactions of DDT and TiO2 NP in the environmental relevant concentrations. In this study, we characterized the coexposures using a zebrafish waterborne exposure approach and evaluated the neurotoxicity response of the treated embryos or adults. Our results showed that DDT/TiO2 NP coexposure enhanced the DDT accumulation in vivo and increased the larval locomotor. The chronic DDT/TiO2 NP coexposure did not affect the overall survival rate, sex ratio and growth. However, DDT/TiO2 NP coexposure severely affected the adult locomotor activity, social contact, shoaling and aggressive behaviors compared to single treatment groups or controls. These adult behavioral deficits were accompanied by changes in neurotransmitter acetylcholine (ACH) level in the brain and muscle tissues, as well as neural development genes expression activation of growth-associated protein 43 (gap43) and synaptic vesicle glycoprotein 2 (sv2) in the brain. The significantly increased ACH level and the activated neural genes expression in the DDT/TiO2 NP co-exposed fish may account for the observed hyperactivity and social deficits.

Reconstruction of Vesicle Assemblies with DNA Nanorulers for Resolving Heterogeneity of Vesicles in Live Cells

Nanoscale vesicles such as synaptic vesicles play a pivotal role in efficient interneuronal communications in vivo. However, the coexistence of single vesicle and vesicle clusters in living cells increases the heterogeneity of vesicle populations, which largely complicates the quantitative analysis of the vesicles. The high spatiotemporal monitoring of vesicle assemblies is currently incompletely resolved. Here, this work uses synthetic vesicles and DNA nanorulers to reconstruct in vitro the vesicle assemblies that mimic vesicle clusters in living cells. DNA nanorulers program the lateral distance of vesicle assemblies from 3 to 10 nm. This work uses the carbon fiber nanoelectrode (CFNE) to amperometric monitor artificial vesicle assemblies with sub-10 nm interspaces, and obtain a larger proportion of complex events. This work resolves the heterogeneity of individual vesicle release kinetics in PC12 cells with the temporal resolution down to ≈0.1 ms. This work further analyzes the aggregation state of intracellular vesicles and the exocytosis of living cells with electrochemical vesicle cytometry. The results indicate that the exocytosis of vesicle clusters is critically dependent on the size of clusters. This technology has the potential as a tool to shed light on the heterogeneity analysis of vesicle populations.

Epilepsy and epileptiform activity in late-onset Alzheimer disease: clinical and pathophysiological advances, gaps and conundrums

A growing body of evidence has demonstrated a link between Alzheimer disease (AD) and epilepsy. Late-onset epilepsy and epileptiform activity can precede cognitive deterioration in AD by years, and its presence has been shown to predict a faster disease course. In animal models of AD, amyloid and tau pathology are linked to cortical network hyperexcitability that precedes the first signs of memory decline. Thus, detection of epileptiform activity in AD has substantial clinical importance as a potential novel modifiable risk factor for dementia. In this Review, we summarize the epidemiological evidence for the complex bidirectional relationship between AD and epilepsy, examine the effect of epileptiform activity and seizures on cognition in people with AD, and discuss the precision medicine treatment strategies based on the latest research in human and animal models. Finally, we outline some of the unresolved questions of the field that should be addressed by rigorous research, including whether particular clinicopathological subtypes of AD have a stronger association with epilepsy, and the sequence of events between epileptiform activity and amyloid and tau pathology.

Measurement of synaptic density in Down syndrome using PET imaging: a pilot study

Down syndrome (DS) is the most prevalent genetic cause of intellectual disability, resulting from trisomy 21. Recently, positron emission tomography (PET) imaging has been used to image synapses in vivo. The motivation for this pilot study was to investigate whether synaptic density in low functioning adults with DS can be evaluated using the PET radiotracer [11C]UCB-J. Data were acquired from low functioning adults with DS (n = 4) and older neurotypical (NT) adults (n = 37). Motion during the scans required the use of a 10-minute acquisition window for the calculation of synaptic density using SUVR50-60,CS which was determined to be a suitable approximation for specific binding in this analysis using dynamic data from the NT group. Of the regions analyzed a large effect was observed when comparing DS and NT hippocampus and cerebral cortex synaptic density as well as hippocampus and cerebellum volumes. In this pilot study, PET imaging of [11C]UCB-J was successfully completed and synaptic density measured in low functioning DS adults. This work provides the basis for studies where synaptic density may be compared between larger groups of NT adults and adults with DS who have varying degrees of baseline cognitive status.

Changes in the Dentate Gyrus Gene Expression Profile Induced by Levetiracetam Treatment in Rats with Mesial Temporal Lobe Epilepsy

Temporal lobe epilepsy (TLE) is one of the most common forms of focal epilepsy. Levetiracetam (LEV) is an antiepileptic drug whose mechanism of action at the genetic level has not been fully described. Therefore, the aim of the present work was to evaluate the relevant gene expression changes in the dentate gyrus (DG) of LEV-treated rats with pilocarpine-induced TLE. Whole-transcriptome microarrays were used to obtain the differential genetic profiles of control (CTRL), epileptic (EPI), and EPI rats treated for one week with LEV (EPI + LEV). Quantitative RT-qPCR was used to evaluate the RNA levels of the genes of interest. According to the results of the EPI vs. CTRL analysis, 685 genes were differentially expressed, 355 of which were underexpressed and 330 of which were overexpressed. According to the analysis of the EPI + LEV vs. EPI groups, 675 genes were differentially expressed, 477 of which were downregulated and 198 of which were upregulated. A total of 94 genes whose expression was altered by epilepsy and modified by LEV were identified. The RT-qPCR confirmed that LEV treatment reversed the increased expression of Hgf mRNA and decreased the expression of the Efcab1, Adam8, Slc24a1, and Serpinb1a genes in the DG. These results indicate that LEV could be involved in nonclassical mechanisms involved in Ca2+ homeostasis and the regulation of the mTOR pathway through Efcab1, Hgf, SLC24a1, Adam8, and Serpinb1a, contributing to reduced hyperexcitability in TLE patients.

Regional differences in synaptic degeneration are linked to alpha-synuclein burden and axonal damage in Parkinson's disease and dementia with Lewy bodies

Regional differences in synaptic degeneration may underlie differences in clinical presentation and neuropathological disease progression in Parkinson's Disease (PD) and Dementia with Lewy bodies (DLB). Here, we mapped and quantified synaptic degeneration in cortical brain regions in PD, PD with dementia (PDD) and DLB, and assessed whether regional differences in synaptic loss are linked to axonal degeneration and neuropathological burden. We included a total of 47 brain donors, 9 PD, 12 PDD, 6 DLB and 20 non-neurological controls. Synaptophysin+ and SV2A+ puncta were quantified in eight cortical regions using a high throughput microscopy approach. Neurofilament light chain (NfL) immunoreactivity, Lewy body (LB) density, phosphorylated-tau and amyloid-β load were also quantified. Group differences in synaptic density, and associations with neuropathological markers and Clinical Dementia Rating (CDR) scores, were investigated using linear mixed models. We found significantly decreased synaptophysin and SV2A densities in the cortex of PD, PDD and DLB cases compared to controls. Specifically, synaptic density was decreased in cortical regions affected at Braak α-synuclein stage 5 in PD (middle temporal gyrus, anterior cingulate and insula), and was additionally decreased in cortical regions affected at Braak α-synuclein stage 4 in PDD and DLB compared to controls (entorhinal cortex, parahippocampal gyrus and fusiform gyrus). Synaptic loss associated with higher NfL immunoreactivity and LB density. Global synaptophysin loss associated with longer disease duration and higher CDR scores. Synaptic neurodegeneration occurred in temporal, cingulate and insular cortices in PD, as well as in parahippocampal regions in PDD and DLB. In addition, synaptic loss was linked to axonal damage and severe α-synuclein burden. These results, together with the association between synaptic loss and disease progression and cognitive impairment, indicate that regional synaptic loss may underlie clinical differences between PD and PDD/DLB. Our results might provide useful information for the interpretation of synaptic biomarkers in vivo.

An Alzheimer's disease risk variant in TTC3 modifies the actin cytoskeleton organization and the PI3K-Akt signaling pathway in iPSC-derived forebrain neurons

A missense variant in the tetratricopeptide repeat domain 3 (TTC3) gene (rs377155188, p.S1038C, NM_003316.4:c 0.3113C>G) was found to segregate with disease in a multigenerational family with late-onset Alzheimer's disease. This variant was introduced into induced pluripotent stem cells (iPSCs) derived from a cognitively intact individual using CRISPR genome editing, and the resulting isogenic pair of iPSC lines was differentiated into cortical neurons. Transcriptome analysis showed an enrichment for genes involved in axon guidance, regulation of actin cytoskeleton, and GABAergic synapse. Functional analysis showed that the TTC3 p.S1038C iPSC-derived neuronal progenitor cells had altered 3-dimensional morphology and increased migration, while the corresponding neurons had longer neurites, increased branch points, and altered expression levels of synaptic proteins. Pharmacological treatment with small molecules that target the actin cytoskeleton could revert many of these cellular phenotypes, suggesting a central role for actin in mediating the cellular phenotypes associated with the TTC3 p.S1038C variant.

Correlation of SV2C rs1423099 single nucleotide polymorphism with sporadic Parkinson's disease in Han population in Southern China

BACKGROUND

The synaptic vesicle glycoprotein 2 (SV2) has been implicated in synaptic function throughout the brain. Accumulating evidence investigated that SV2C contributed to dopamine release and the disrupted expression of SV2C was considered to be a unique feature of PD that may facilitate dopaminergic neuron dysfunction.

OBJECTIVE

This study aimed to examine the relationship between the SV2C rs1423099 single nucleotide polymorphism and sporadic Parkinson's disease (PD) in the Chinese Han population.

MATERIALS AND METHODS

This study enrolled 351 patients with sporadic PD and 240 normal controls in Chinese Han population. Peripheral blood DNA was extracted by DNA extraction kits and the rs1423099 genotype was analyzed by Agena MassARRAY DNA mass spectrometry. The differences in genotype and allele distribution frequencies between PD patients and control groups were compared using chi-squared tests or Fisher's exact tests.

RESULTS

No statistical difference was revealed in age and sex distribution between the cases and control groups, and the distribution of genotype and allele frequencies was consistent with the Hardy-Weinberg equilibrium test. In SV2C rs1423099 dominant model, the frequency of the CC/CT genotype was significantly higher in the PD group compared to the control group (OR = 4.065,95% CI: 2.801-10.870, p = 0.002). Nevertheless, in the recessive model, CC or CT/TT genotypes have no statistical difference in the two groups (p = 0.09). Additionally, in allelic analysis, the C allele was investigated to increase the risk of PD (OR = 1.346, 95% CI: 1.036-1.745, p = 0.026); Furthermore, subgroup analysis suggested that those carrying the C allele in the male subgroup were at a higher risk to afflicted with PD (OR = 1.637, 95% CI: 1.147-2.336, p = 0.006).

CONCLUSION

SV2C rs1423099 single nucleotide polymorphism was associated with sporadic Parkinson's disease in the Chinese Han population, particularly in males.

Spirocyclic Iodonium Ylides for Fluorine-18 Radiolabeling of Non-Activated Arenes: From Concept to Clinical Research

Positron emission tomography (PET) is a powerful imaging tool for drug discovery, clinical diagnosis, and monitoring of disease progression. Fluorine-18 is the most common radionuclide used for PET, but advances in radiotracer development have been limited by the historical lack of methodologies and precursors amenable to radiolabeling with fluorine-18. Radiolabeling of electron-rich (hetero)aromatic rings remains a long-standing challenge in the production of PET radiopharmaceuticals. In this personal account, we discuss the history of spirocyclic iodonium ylide precursors, from inception to applications in clinical research, for the incorporation of fluorine-18 into complex non-activated (hetero)aromatic rings.

Molecular mechanisms of schizophrenia: Insights from human genetics

Schizophrenia is a debilitating psychiatric disorder that affects millions of people worldwide; however, its etiology is poorly understood at the molecular and neurobiological levels. A particularly important advance in recent years is the discovery of rare genetic variants associated with a greatly increased risk of developing schizophrenia. These primarily loss-of-function variants are found in genes that overlap with those implicated by common variants and are involved in the regulation of glutamate signaling, synaptic function, DNA transcription, and chromatin remodeling. Animal models harboring mutations in these large-effect schizophrenia risk genes show promise in providing additional insights into the molecular mechanisms of the disease.

Adaptive Changes in Detoxification Metabolism and Transmembrane Transport of Bombyx mori Malpighian Tubules to Artificial Diet

The high adaptability of insects to food sources has contributed to their ranking among the most abundant and diverse species on Earth. However, the molecular mechanisms underlying the rapid adaptation of insects to different foods remain unclear. We explored the changes in gene expression and metabolic composition of the Malpighian tubules as an important metabolic excretion and detoxification organ in silkworms (Bombyx mori) fed mulberry leaf and artificial diets. A total of 2436 differentially expressed genes (DEGs) and 245 differential metabolites were identified between groups, with the majority of DEGs associated with metabolic detoxification, transmembrane transport, and mitochondrial function. Detoxification enzymes, such as cytochrome P450 (CYP), glutathione-S-transferase (GST), and UDP-glycosyltransferase, and ABC and SLC transporters of endogenous and exogenous solutes were more abundant in the artificial diet group. Enzyme activity assays confirmed increased CYP and GST activity in the Malpighian tubules of the artificial diet-fed group. Metabolome analysis showed increased contents of secondary metabolites, terpenoids, flavonoids, alkaloids, organic acids, lipids, and food additives in the artificial diet group. Our findings highlight the important role of the Malpighian tubules in adaptation to different foods and provide guidance for further optimization of artificial diets to improve silkworm breeding.

Mapping new pharmacological interventions for cognitive function in Alzheimer's disease: a systematic review of randomized clinical trials

Background and Objective: Alzheimer's disease (AD) is a progressive neurodegenerative disorder, that is, characterized by cognitive decline. To date, there are no effective treatments for AD. Therefore, the objective of this study was to map new perspectives on the effects of pharmacological treatment on cognitive function and the overall psychological state in patients with AD. Methods: Two independent researchers searched for randomized clinical trials (RCTs) exploring new pharmacological approaches related to cognition in Alzheimer's disease in adults from 2018 to 2023 in PubMed, Web of Science, Scopus, and Cochrane Library databases. A total of 17 RCTs were included in this review. Results: The results show that in recent years, new drugs have been tested in patients with Alzheimer's disease, including masitinib, methylphenidate, levetiracetam, Jiannao Yizhi, and Huannao Yicong formulas. Most studies have been conducted in populations with mild to moderate Alzheimer's disease. Conclusion: Although some of the drugs found suggested improvement in cognitive function, the scarcity of available studies highlights the need for further research in this area. Systematic review registration: [www.crd.york.ac.uk/prospero], identifier [CRD42023409986].

An Alzheimer's disease risk variant in TTC3 modifies the actin cytoskeleton organization and the PI3K-Akt signaling pathway in iPSC-derived forebrain neurons

A missense variant in the tetratricopeptide repeat domain 3 ( TTC3 ) gene (rs377155188, p.S1038C, NM_003316.4:c.3113C>G) was found to segregate with disease in a multigenerational family with late onset Alzheimer's disease. This variant was introduced into induced pluripotent stem cells (iPSCs) derived from a cognitively intact individual using CRISPR genome editing and the resulting isogenic pair of iPSC lines were differentiated into cortical neurons. Transcriptome analysis showed an enrichment for genes involved in axon guidance, regulation of actin cytoskeleton, and GABAergic synapse. Functional analysis showed that the TTC3 p.S1038C iPSC-derived neuronal progenitor cells had altered 3D morphology and increased migration, while the corresponding neurons had longer neurites, increased branch points, and altered expression levels of synaptic proteins. Pharmacological treatment with small molecules that target the actin cytoskeleton could revert many of these cellular phenotypes, suggesting a central role for actin in mediating the cellular phenotypes associated with the TTC3 p.S1038C variant.

Highlights

The AD risk variant TTC3 p.S1038C reduces the expression levels of TTC3 The variant modifies the expression of AD specific genes BACE1 , INPP5F , and UNC5C Neurons with the variant are enriched for genes in the PI3K-Akt pathwayiPSC-derived neurons with the alteration have increased neurite length and branchingThe variant interferes with actin cytoskeleton and is ameliorated by Cytochalasin D.

An integrated multi-level analysis reveals learning-memory deficits and synaptic dysfunction in the rat model exposure to austere environment

Austere environment existing in tank, submarine and vessel has many risk factors including high temperature and humidity, confinement, noise, hypoxia, and high level of carbon dioxide, which may cause depression and cognitive impairment. However, the underlying mechanism is not fully understood yet. We attempt to investigate the effects of austere environment (AE) on emotion and cognitive function in a rodent model. After 21 days of AE stress, the rats exhibit depressive-like behavior and cognitive impairment. Compared with control group, the glucose metabolic level of the hippocampus is significantly decreased using whole-brain positron emission tomography (PET) imaging, and the density of dendritic spines of the hippocampus is remarkably reduced in AE group. Then, we employ a label-free quantitative proteomics strategy to investigate the differentially abundant proteins in rats' hippocampus. It is striking that the differentially abundant proteins annotated by KEGG enrich in oxidative phosphorylation pathway, synaptic vesicle cycle pathway and glutamatergic synapses pathway. The synaptic vesicle transport related proteins (Syntaxin-1A, Synaptogyrin-1 and SV-2) are down-regulated, resulting in the accumulation of intracellular glutamate. Furthermore, the concentration of hydrogen peroxide and malondialdehyde is increased while the activity of superoxide dismutase and complex I and IV of mitochondria is decreased, indicating that oxidative damage to hippocampal synapses is associated with the cognitive decline. The results of this study offer direct evidence, for the first time, that austere environment can substantially cause learning and memory deficits and synaptic dysfunction in a rodent model via behavioral assessments, PET imaging, label-free proteomics, and oxidative stress tests. SIGNIFICANCE: The incidence of depression and cognitive decline in military occupations (for example, tanker and submariner) is significantly higher than that of global population. In the present study, we first established novel model to simulate the coexisting risk factors in the austere environment. The results of this study offer the direct evidences, for the first time, that the austere environment can substantially cause learning and memory deficits by altering plasticity of the synaptic transmission in a rodent model via proteomic strategy, PET imaging, oxidative stress and behavioral assessments. These findings provide valuable information to better understand the mechanisms of cognitive impairment.

Morphological and Physiological Aspects of Mutable Collagenous Tissue at the Autotomy Plane of the Starfish Asterias rubens L. (Echinodermata, Asteroidea): An Echinoderm Paradigm

The mutable collagenous tissue (MCT) of echinoderms has the capacity to undergo changes in its tensile properties within a timescale of seconds under the control of the nervous system. All echinoderm autotomy (defensive self-detachment) mechanisms depend on the extreme destabilisation of mutable collagenous structures at the plane of separation. This review illustrates the role of MCT in autotomy by bringing together previously published and new information on the basal arm autotomy plane of the starfish Asterias rubens L. It focuses on the MCT components of breakage zones in the dorsolateral and ambulacral regions of the body wall, and details data on their structural organisation and physiology. Information is also provided on the extrinsic stomach retractor apparatus whose involvement in autotomy has not been previously recognised. We show that the arm autotomy plane of A. rubens is a tractable model system for addressing outstanding problems in MCT biology. It is amenable to in vitro pharmacological investigations using isolated preparations and provides an opportunity for the application of comparative proteomic analysis and other “-omics” methods which are aimed at the molecular profiling of different mechanical states and characterising effector cell functions.

Nicotine-Mediated Rescue of α-Synuclein Toxicity Requires Synaptic Vesicle Glycoprotein 2 in Drosophila

BACKGROUND

Parkinson's disease (PD) is characterized by α-synuclein aggregation and loss of dopamine neurons. Risk of PD arises due to a combination of genetic and environmental factors, which may interact, termed gene-environment (G×E) interactions. An inverse association between smoking and the risk of PD is well established, and a previous genome-wide G×E interaction study identified genetic variation in the synaptic-vesicle glycoprotein 2C (SV2C) locus as an important mediator of the degree to which smoking is inversely associated with PD.

OBJECTIVE

We sought to determine the mechanism of the smoking-SV2C interaction in a Drosophila model of PD.

METHODS

Flies expressing human α-synuclein in all neurons develop the hallmarks of PD, including motor dysfunction, loss of dopaminergic (DA) neurons, and formation of α-synuclein inclusions. We assessed the effects of increasing doses of nicotine on these parameters of neurodegeneration, in the presence or absence of knockdown of two Drosophila orthologues of SV2, hereafter referred to as SV2L1 and SV2L2.

RESULTS

The α-synuclein-expressing flies treated with nicotine had improved locomotion, DA neuron counts, and α-synuclein aggregation. However, in α-synuclein-expressing flies in which SV2L1 and SV2L2 were knocked down, nicotine failed to rescue neurodegeneration.

CONCLUSIONS

This work confirms a G×E interaction between nicotine and SV2, defines a role for this interaction in α-synuclein proteostasis, and suggests that future clinical trials on nicotine should consider genetic variation in SV2C. Furthermore, this provides proof of concept that our model can be used for the mechanistic study of G×E, paving the way for the investigation of additional G×E interactions or the identification of novel G×E. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

A Comprehensive Structural Analysis of Clostridium botulinum Neurotoxin A Cell-Binding Domain from Different Subtypes

Botulinum neurotoxins (BoNTs) cause flaccid neuromuscular paralysis by cleaving one of the SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) complex proteins. BoNTs display high affinity and specificity for neuromuscular junctions, making them one of the most potent neurotoxins known to date. There are seven serologically distinct BoNTs (serotypes BoNT/A to BoNT/G) which can be further divided into subtypes (e.g., BoNT/A1, BoNT/A2…) based on small changes in their amino acid sequence. Of these, BoNT/A1 and BoNT/B1 have been utilised to treat various diseases associated with spasticity and hypersecretion. There are potentially many more BoNT variants with differing toxicological profiles that may display other therapeutic benefits. This review is focused on the structural analysis of the cell-binding domain from BoNT/A1 to BoNT/A6 subtypes (H_C/A1 to H_C/A6), including features such as a ganglioside binding site (GBS), a dynamic loop, a synaptic vesicle glycoprotein 2 (SV2) binding site, a possible Lys-Cys/Cys-Cys bridge, and a hinge motion between the H_CN and H_CC subdomains. Characterising structural features across subtypes provides a better understanding of how the cell-binding domain functions and may aid the development of novel therapeutics.

Longitudinal Synaptic Density PET with 11 C-UCB-J 6 Months After Ischemic Stroke

OBJECTIVE

The purpose of this study was to explore longitudinal changes in synaptic density after ischemic stroke in vivo with synaptic vesicle protein 2A (SV2A) positron emission tomography (PET).

METHODS

We recruited patients with an ischemic stroke to undergo ¹¹ C-UCB-J PET/MR within the first month and 6 months after the stroke. We investigated longitudinal changes of partial volume corrected ¹¹ C-UCB-J standardized uptake value ratio (SUVR; relative to centrum semiovale) within the ischemic lesion, peri-ischemic area and unaffected ipsilesional and contralesional grey matter. We also explored crossed cerebellar diaschisis at 6 months. Additionally, we defined brain regions potentially influencing upper limb motor recovery after stroke and studied ¹¹ C-UCB-J SUVR evolution in comparison to baseline.

RESULTS

In 13 patients (age = 67 ± 15 years) we observed decreasing ¹¹ C-UCB-J SUVR in the ischemic lesion (ΔSUVR = -1.0, p = 0.001) and peri-ischemic area (ΔSUVR = -0.31, p = 0.02) at 6 months after stroke compared to baseline. Crossed cerebellar diaschisis as measured with ¹¹ C-UCB-J SUVR was present in 11 of 13 (85%) patients at 6 months. The ¹¹ C-UCB-J SUVR did not augment in ipsilesional or contralesional brain regions associated with motor recovery. On the contrary, there was an overall trend of declining ¹¹ C-UCB-J SUVR in these brain regions, reaching statistical significance only in the nonlesioned part of the ipsilesional supplementary motor area (ΔSUVR = -0.83, p = 0.046).

INTERPRETATION

At 6 months after stroke, synaptic density further declined in the ischemic lesion and peri-ischemic area compared to baseline. Brain regions previously demonstrated to be associated with motor recovery after stroke did not show increases in synaptic density. ANN NEUROL 2023.

Transcriptomic Analysis Reveals That Retinal Neuromodulation Is a Relevant Mechanism in the Neuroprotective Effect of Sitagliptin in an Experimental Model of Diabetic Retinopathy

Synaptic dysfunction and neuronal damage have been extensively associated with diabetic retinopathy (DR). Our group evidenced that chronic hyperglycemia reduces the retinal expression of presynaptic proteins, which are crucial for proper synaptic function. The aim of the study was to explore the effect of topically administered sitagliptin, an inhibitor of the enzyme dipeptidyl peptidase-4, on the retinal expression patterns of an experimental model of DR. Transcriptome analysis was performed, comparing the retinas of 10 diabetic (db/db) mice randomly treated with sitagliptin eye drops (10 mg/mL) twice daily and the retinas of 10 additional db/db mice that received vehicle eye drops. Ten non-diabetic mice (db/+) were used as a control group. The Gene Ontology (GO) and Reactome databases were used to perform the gene set enrichment analysis (GSEA) in order to explore the most enriched biological pathways among the groups. The most differentiated genes of these pathways were validated through quantitative RT-PCR. Transcriptome analysis revealed that sitagliptin eye drops have a significant effect on retinal expression patterns and that neurotransmission is the most enriched biological process. Our study evidenced enriched pathways that contain genes involved in membrane trafficking, transmission across chemical synapses, vesicle-mediated transport, neurotransmitter receptors and postsynaptic signal transmission with negative regulation of signaling as a consequence of neuroprotector treatment with sitagliptin. This improves the modulation of the macromolecule biosynthetic process with positive regulation of cell communication, which provides beneficial effects for the neuronal metabolism. This study suggests that topical administration of sitagliptin ameliorates the abnormalities on presynaptic and postsynaptic signal transmission during experimental DR and that this improvement is one of the main mechanisms behind the previously demonstrated beneficial effects.

Perinatal hypoxia and thalamus brain region: increased efficiency of antiepileptic drug levetiracetam to inhibit GABA release from nerve terminals

Levetiracetam (LV), 2S-(2-oxo-1-pyrrolidiny1) butanamide, is an antiepileptic drug. The exact mechanisms of anticonvulsant effects of LV remain unclear. In this study, rats (Wistar strain) underwent hypoxia and seizures at the age of 10–12 postnatal days (pd). [3H]GABA release was analysed in isolated from thalamus nerve terminals (synaptosomes) during development at the age of pd 17–19 and pd 24–26 (infantile stage), pd 38–40 (puberty) and pd 66–73 (young adults) in control and after perinatal hypoxia. The extracellular level of [3H]GABA in the preparation of thalamic synaptosomes increased during development at the age of pd 38–40 and pd 66–73 as compared to earlier ones. LV did not influence the extracellular level of [3H]GABA in control and after perinatal hypoxia at all studied ages. Exocytotic [3H]GABA release in control increased at the age of pd 24–26 as compared to pd 17–19. After hypoxia, exocytotic [3H]GABA release from synaptosomes also increased during development. LV elevated [3H]GABA release from thalamic synaptosomes at the age of pd 66–73 after hypoxia and during blockage of GABA uptake by NO-711 only. LV realizes its antiepileptic effects at the presynaptic site through an increase in exocytotic release of [3H]GABA in thalamic synaptosomes after perinatal hypoxia at pd 66–73. LV exhibited a more significant effect in thalamic synaptosomes after perinatal hypoxia than in control ones. The action of LV is age-dependent, and the drug was inert at the infantile stage that can be useful for an LV application strategy in child epilepsy therapy. Keywords: brain development, exocytosis, GABA, levetiracetam, perinatal hypoxia, thalamic synaptosomes

Proper modulation of AHR signaling is necessary for establishing neural connectivity and oligodendrocyte precursor cell development in the embryonic zebrafish brain

2,3,7,8-tetrachlorodibenzo-[p]-dioxin (TCDD) is a persistent global pollutant that exhibits a high affinity for the aryl hydrocarbon receptor (AHR), a ligand activated transcription factor. Epidemiological studies have associated AHR agonist exposure with multiple human neuropathologies. Consistent with the human data, research studies using laboratory models have linked pollutant-induced AHR activation to disruptions in learning and memory as well as motor impairments. Our understanding of endogenous AHR functions in brain development is limited and, correspondingly, scientists are still determining which cell types and brain regions are sensitive to AHR modulation. To identify novel phenotypes resulting from pollutant-induced AHR activation and ahr2 loss of function, we utilized the optically transparent zebrafish model. Early embryonic TCDD exposure impaired embryonic brain morphogenesis, resulted in ventriculomegaly, and disrupted neural connectivity in the optic tectum, habenula, cerebellum, and olfactory bulb. Altered neural network formation was accompanied by reduced expression of synaptic vesicle 2. Loss of ahr2 function also impaired nascent network development, but did not affect gross brain or ventricular morphology. To determine whether neural AHR activation was sufficient to disrupt connectivity, we used the Gal4/UAS system to express a constitutively active AHR specifically in differentiated neurons and observed disruptions only in the cerebellum; thus, suggesting that the phenotypes resulting from global AHR activation likely involve multiple cell types. Consistent with this hypothesis, we found that TCDD exposure reduced the number of oligodendrocyte precursor cells and their derivatives. Together, our findings indicate that proper modulation of AHR signaling is necessary for the growth and maturation of the embryonic zebrafish brain.

Expression profile of synaptic vesicle glycoprotein 2A, B, and C paralogues in temporal neocortex tissue from patients with temporal lobe epilepsy (TLE)

Synaptic vesicle glycoprotein-2 (SV2) is a family of proteins consisting of SV2A, SV2B, and SV2C. This protein family has attracted attention in recent years after SV2A was shown to be an epileptic drug target and a perhaps a biomarker of synaptic density. So far, the anatomical localization of these proteins in the rodent and human brain have been reported, but co-expression of SV2 genes on a cellular level, their expressions in the human brain, comparison to radioligand binding, any possible regulation in epilepsy are not known. We have here analyzed the expression of SV2 genes in neuronal subtypes in the temporal neocortex in selected specimens by using single nucleus-RNA sequencing, and performed quantitative PCR in populations of temporal lobe epilepsy (TLE) patients and healthy controls. [3H]-UCB-J autoradiography was performed to analyze the correlation between the mRNA transcript and binding capacity to SV2A. Our data showed that the SV2A transcript is expressed in all glutamatergic and GABAergic cortical subtypes, while SV2B expression is restricted to only the glutamatergic neurons and SV2C has very limited expression in a small subgroup of GABAergic interneurons. The level of [3H]-UCB-J binding and the concentration of SV2A mRNA is strongly correlated in each patient, and the expression is lower in the TLE patients. There is no relationship between SV2A expression and age, sex, seizure frequency, duration of epilepsy, or whether patients were recently treated with levetiracetam or not. Collectively, these findings point out a neuronal subtype-specific distribution of the expression of the three SV2 genes, and the lower levels of both radioligand binding and expression further emphasize the significance of these proteins in this disease.

Brivaracetam and Levetiracetam Suppress Astroglial L-Glutamate Release through Hemichannel via Inhibition of Synaptic Vesicle Protein

To explore the pathophysiological mechanisms of antiseizure and adverse behavioural/psychiatric effects of brivaracetam and levetiracetam, in the present study, we determined the effects of brivaracetam and levetiracetam on astroglial L-glutamate release induced by artificial high-frequency oscillation (HFO) bursts using ultra-high-performance liquid chromatography. Additionally, the effects of brivaracetam and levetiracetam on protein expressions of connexin43 (Cx43) and synaptic vesicle protein 2A (SV2A) in the plasma membrane of primary cultured rat astrocytes were determined using a capillary immunoblotting system. Acutely artificial fast-ripple HFO (500 Hz) burst stimulation use-dependently increased L-glutamate release through Cx43-containing hemichannels without affecting the expression of Cx43 or SV2A in the plasma membrane, whereas acute physiological ripple HFO (200 Hz) stimulation did not affect astroglial L-glutamate release or expression of Cx43 or SV2A. Contrarily, subchronic ripple HFO and acute pathological fast-ripple HFO (500 Hz) stimulations use-dependently increased L-glutamate release through Cx43-containing hemichannels and Cx43 expression in the plasma membrane. Subchronic fast-ripple HFO-evoked stimulation produced ectopic expression of SV2A in the plasma membrane, but subchronic ripple HFO stimulation did not generate ectopic SV2A. Subchronic administration of brivaracetam and levetiracetam concentration-dependently suppressed fast-ripple HFO-induced astroglial L-glutamate release and expression of Cx43 and SV2A in the plasma membrane. In contrast, subchronic ripple HFO-evoked stimulation induced astroglial L-glutamate release, and Cx43 expression in the plasma membrane was inhibited by subchronic levetiracetam administration, but was not affected by brivaracetam. These results suggest that brivaracetam and levetiracetam inhibit epileptogenic fast-ripple HFO-induced activated astroglial transmission associated with hemichannels. In contrast, the inhibitory effect of therapeutic-relevant concentrations of levetiracetam on physiological ripple HFO-induced astroglial responses probably contributes to the adverse behavioural/psychiatric effects of levetiracetam.

Levetiracetam Mechanisms of Action: From Molecules to Systems

Epilepsy is a chronic disease that affects millions of people worldwide. Antiepileptic drugs (AEDs) are used to control seizures. Even though parts of their mechanisms of action are known, there are still components that need to be studied. Therefore, the search for novel drugs, new molecular targets, and a better understanding of the mechanisms of action of existing drugs is still crucial. Levetiracetam (LEV) is an AED that has been shown to be effective in seizure control and is well-tolerable, with a novel mechanism of action through an interaction with the synaptic vesicle protein 2A (SV2A). Moreover, LEV has other molecular targets that involve calcium homeostasis, the GABAergic system, and AMPA receptors among others, that might be integrated into a single mechanism of action that could explain the antiepileptogenic, anti-inflammatory, neuroprotective, and antioxidant properties of LEV. This puts it as a possible multitarget drug with clinical applications other than for epilepsy. According to the above, the objective of this work was to carry out a comprehensive and integrative review of LEV in relation to its clinical uses, structural properties, therapeutical targets, and different molecular, genetic, and systemic action mechanisms in order to consider LEV as a candidate for drug repurposing.

Neuron-recognizable characteristics of peptides recombined using a neuronal binding domain of botulinum neurotoxin

Recombinant peptides were designed using the C-terminal domain (receptor binding domain, RBD) and its subdomain (peptide A2) of a heavy chain of botulinum neurotoxin A-type 1 (BoNT/A1), which can bind to the luminal domain of synaptic vesicle glycoprotein 2C (SV2C-LD). Peptide A2- or RBD-containing recombinant peptides linked to an enhanced green fluorescence protein (EGFP) were prepared by expression in Escherichia coli. A pull-down assay using SV2C-LD-covered resins showed that the recombinant peptides for CDC297 BoNT/A1, referred to EGFP-A2' and EGFP-RBD', exhibited ≥ 2.0-times stronger binding affinity to SV2C-LD than those for the wild-type BoNT/A1. Using bio-layer interferometry, an equilibrium dissociation rate constant (K_D) of EGFP-RBD' to SV2C-LD was determined to be 5.45 μM, which is 33.87- and 15.67-times smaller than the K_D values for EGFP and EGFP-A2', respectively. Based on confocal laser fluorescence micrometric analysis, the adsorption/absorption of EGFP-RBD' to/in differentiated PC-12 cells was 2.49- and 1.29-times faster than those of EGFP and EGFP-A2', respectively. Consequently, the recombinant peptides acquired reasonable neuron-specific binding/internalizing ability through the recruitment of RBD'. In conclusion, RBDs of BoNTs are versatile protein domains that can be used to mark neural systems and treat a range of disorders in neural systems.

Integrated Multi-Omics Analysis Reveals the Effect of Maternal Gestational Diabetes on Fetal Mouse Hippocampi

Growing evidence suggests that adverse intrauterine environments could affect the long-term health of offspring. Recent evidence indicates that gestational diabetes mellitus (GDM) is associated with neurocognitive changes in offspring. However, the mechanism remains unclear. Using a GDM mouse model, we collected hippocampi, the structure critical to cognitive processes, for electron microscopy, methylome and transcriptome analyses. Reduced representation bisulfite sequencing (RRBS) and RNA-seq in the GDM fetal hippocampi showed altered methylated modification and differentially expressed genes enriched in common pathways involved in neural synapse organization and signal transmission. We further collected fetal mice brains for metabolome analysis and found that in GDM fetal brains, the metabolites displayed significant changes, in addition to directly inducing cognitive dysfunction, some of which are important to methylation status such as betaine, fumaric acid, L-methionine, succinic acid, 5-methyltetrahydrofolic acid, and S-adenosylmethionine (SAM). These results suggest that GDM affects metabolites in fetal mice brains and further affects hippocampal DNA methylation and gene regulation involved in cognition, which is a potential mechanism for the adverse neurocognitive effects of GDM in offspring.

Acute social isolation and regrouping cause short- and long-term molecular changes in the rat medial amygdala

Social isolation poses a severe mental and physiological burden on humans. Most animal models that investigate this effect are based on prolonged isolation, which does not mimic the milder conditions experienced by people in the real world. We show that in adult male rats, acute social isolation causes social memory loss. This memory loss is accompanied by significant changes in the expression of specific mRNAs and proteins in the medial amygdala, a brain structure that is crucial for social memory. These changes particularly involve the neurotrophic signaling and axon guidance pathways that are associated with neuronal network remodeling. Upon regrouping, memory returns, and most molecular changes are reversed within hours. However, the expression of some genes, especially those associated with neurodegenerative diseases remain modified for at least a day longer. These results suggest that acute social isolation and rapid resocialization, as experienced by millions during the COVID-19 pandemic, are sufficient to induce significant changes to neuronal networks, some of which may be pathological.

Lower synaptic density is associated with psychiatric and cognitive alterations in obesity

Obesity is a serious medical condition that often co-occurs with stress-related psychiatric disorders. It is recognized that the brain plays a key role in the (patho)physiology of obesity and that there is a bidirectional relationship between obesity and psychopathology, yet molecular mechanisms altered in obesity have not been fully elucidated. Thus, we investigated relationships between obesity and synaptic density in vivo using the radioligand [11C]UCB-J (which binds to synaptic glycoprotein SV2A) and positron emission tomography in individuals with obesity, and with or without stress-related psychiatric disorders. Regions of interest were the dorsolateral prefrontal cortex, orbitofrontal cortex, ventromedial, amygdala, hippocampus, and cerebellum. Forty individuals with a body mass index (BMI) ≥ 25 kg/m2 (overweight/obese), with (n = 28) or without (n = 12) psychiatric diagnosis, were compared to 30 age- and sex-matched normal weight individuals (BMI < 25), with (n = 14) or without (n = 16) psychiatric diagnosis. Overall, significantly lower synaptic density was observed in overweight/obese relative to normal weight participants (ηp2 = 0.193, F = 2.35, p = 0.042). Importantly, in participants with stress-related psychiatric diagnoses, we found BMI to be negatively correlated with synaptic density in all regions of interest (p ≤ 0.03), but no such relationship observed for mentally healthy controls (p ≥ 0.68). In the stress-related psychiatric groups, dorsolateral prefrontal cortex synaptic density was negatively associated with measures of worry (r = -0.46, p = 0.01), tension/anxiety (r = -0.38, p = 0.04), fatigue (r = -0.44, p = 0.02), and attentional difficulties (r = -0.44, p = 0.02). In summary, the findings of this novel in vivo experiment suggest compounding effects of obesity and stress-related psychopathology on the brain and the associated symptomatology that may impact functioning. This offers a novel biological mechanism for the relationship between overweight/obesity and stress-related psychiatric disorders that may guide future intervention development efforts.

Emerging roles of N-linked glycosylation in brain physiology and disorders

N-linked glycosylation is a complex, co- and post-translational series of events that connects metabolism to signaling in almost all cells. Metabolic assembly of N-linked glycans spans multiple cellular compartments, and early N-linked glycan biosynthesis is a central mediator of protein folding and the unfolded protein response (UPR). In the brain, N-linked glycosylated proteins participate in a myriad of processes, from electrical gradients to neurotransmission. However, it is less clear how perturbations in N-linked glycosylation impact and even potentially drive aspects of neurological disorders. In this review, we discuss our current understanding of the metabolic origins of N-linked glycans in the brain, their role in modulating neuronal function, and how aberrant N-linked glycosylation can drive neurological disorders.

Lipidomics Reveals Dysregulated Glycerophospholipid Metabolism in the Corpus Striatum of Mice Treated with Cefepime

Cefepime exhibits a broad spectrum of antimicrobial activity and thus is a widely used treatment for severe bacterial infections. Adverse effects on the central nervous system (CNS) have been reported in patients treated with cefepime. Current explanation for the adverse neurobehavioral effect of cefepime is mainly attributed to its ability to cross the blood-brain barrier and competitively bind to the GABAergic receptor; however, the underlying mechanism is largely unknown. In this study, mice were intraperitoneally administered 80 mg/kg cefepime for different periods, followed by neurobehavioral tests and a brain lipidomic analysis. LC/MS-MS-based metabolomics was used to investigate the effect of cefepime on the brain lipidomic profile and metabolic pathways. Repeated cefepime treatment time-dependently caused anxiety-like behaviors, which were accompanied by reduced locomotor activity in the open field test. Cefepime profoundly altered the lipid profile, acyl chain length, and unsaturation of fatty acids in the corpus striatum, and glycerophospholipids accounted for a large proportion of those significantly modified lipids. In addition, cefepime treatment caused obvious alteration in the lipid-enriched membrane structure, neurites, mitochondria, and synaptic vesicles of primary cultured striatal neurons; moreover, the spontaneous electrical activity of striatal neurons was significantly reduced. Collectively, cefepime reprograms glycerophospholipid metabolism in the corpus striatum, which may interfere with neuronal structure and activity, eventually leading to aberrant neurobehaviors in mice.

Reduced Levels of miR-342-5p in Plasma Are Associated With Worse Cognitive Evolution in Patients With Mild Alzheimer's Disease

Background

Progressive cognitive decline is the most relevant clinical symptom of Alzheimer’s disease (AD). However, the rate of cognitive decline is highly variable between patients. Synaptic deficits are the neuropathological event most correlated with cognitive impairment in AD. Considering the important role of microRNAs (miRNAs) in regulating synaptic plasticity, our objective was to identify the plasma miRNAs associated with the rate of cognitive decline in patients with mild AD.

Methods

We analyzed 754 plasma miRNAs from 19 women diagnosed with mild AD using TaqMan low-density array cards. The patients were grouped based on the rate of decline in the MMSE score after 2 years [<4 points (N = 11) and ≥4 points (N = 8)]. The differentially expressed miRNAs between the two groups were validated in an independent cohort of men and women (N = 53) with mild AD using RT-qPCR.

Results

In the discovery cohort, 17 miRNAs were differentially expressed according to the fold change between patients with faster declines in cognition and those with slower declines. miR-342-5p demonstrated differential expression between the groups and a good correlation with the rate of cognitive decline in the validation cohort (r = −0.28; p = 0.026). This miRNA had a lower expression level in patients who suffered from more severe decline than in those who were cognitively more stable after 2 years (p = 0.049).

Conclusion

Lower levels of miR-342-5p in plasma were associated with faster cognitive decline in patients with mild AD after 2 years of follow-up.

Transcriptional Profiles of Diploid Mutant Apis mellifera Embryos after Knockout of csd by CRISPR/Cas9

Simple Summary

In honey bees, males are haploid while females are diploid, leading to a fundamental difference in genetic materials between the sexes. In order to better control the comparison of gene expression between males and females, diploid mutant males were generated by knocking out the sex-determining gene, complementary sex determiner (csd), in fertilized embryos. The diploid mutant drones had male external morphological features, as well as male gonads. RNA sequencing was performed on the diploid mutant embryos and one-day-old larvae. The transcriptome analysis showed that several female-biased genes, such as worker-enriched antennal (Wat), vitellogenin (Vg), and some venom-related genes, were down-regulated in the diploid mutant males. In contrast, some male-biased genes, like takeout and apolipophorin-III-like protein (A4), were up-regulated. Moreover, the co-expression gene networks suggested that csd might interact very closely with fruitless (fru), feminizer (fem) might have connections with hexamerin 70c (hex70c), and transformer-2 (tra2) might play roles with troponin T (TpnT). Foundational information about the differences in the gene expression caused by sex differentiation was provided in this study. It is believed that this study will pave the ground for further research on the different mechanisms between males and females in honey bees.

Abstract

In honey bees, complementary sex determiner (csd) is the primary signal of sex determination. Its allelic composition is heterozygous in females, and hemizygous or homozygous in males. To explore the transcriptome differences after sex differentiation between males and females, with genetic differences excluded, csd in fertilized embryos was knocked out by CRISPR/Cas9. The diploid mutant males at 24 h, 48 h, 72 h, and 96 h after egg laying (AEL) and the mock-treated females derived from the same fertilized queen were investigated through RNA-seq. Mutations were detected in the target sequence in diploid mutants. The diploid mutant drones had typical male morphological characteristics and gonads. Transcriptome analysis showed that several female-biased genes, such as worker-enriched antennal (Wat), vitellogenin (Vg), and some venom-related genes, were down-regulated in the diploid mutant males. In contrast, some male-biased genes, such as takeout and apolipophorin-III-like protein (A4), had higher expressions in the diploid mutant males. Weighted gene co-expression network analysis (WGCNA) indicated that there might be interactions between csd and fruitless (fru), feminizer (fem) and hexamerin 70c (hex70c), transformer-2 (tra2) and troponin T (TpnT). The information provided by this study will benefit further research on the sex dimorphism and development of honey bees and other insects in Hymenoptera.

Comparative analyses of transcriptional responses of Dectes texanus LeConte (Coleoptera: Cerambycidae) larvae fed on three different host plants and artificial diet

Dectes texanus is an important coleopteran pest of soybeans and cultivated sunflowers in the Midwestern United States that causes yield losses by girdling stems of their host plants. Although sunflower and giant ragweed are primary hosts of D. texanus, they began colonizing soybeans approximately 50 years ago and no reliable management method has been established to prevent or reduce losses by this pest. To identify genes putatively involved when feeding soybean, we compared gene expression of D. texanus third-instar larvae fed soybean to those fed sunflower, giant ragweed, or artificial diet. Dectes texanus larvae differentially expressed 514 unigenes when fed on soybean compared to those fed the other diet treatments. Enrichment analyses of gene ontology terms from up-regulated unigenes in soybean-fed larvae compared to those fed both primary hosts highlighted unigenes involved in oxidoreductase and polygalacturonase activities. Cytochrome P450s, carboxylesterases, major facilitator superfamily transporters, lipocalins, apolipoproteins, glycoside hydrolases 1 and 28, and lytic monooxygenases were among the most commonly up-regulated unigenes in soybean-fed larvae compared to those fed their primary hosts. These results suggest that D. texanus larvae differentially expressed unigenes involved in biotransformation of allelochemicals, digestion of plant cell walls and transport of small solutes and lipids when feeding in soybean.

Effects of chronic exposure to haloperidol, olanzapine or lithium on SV2A and NLGN synaptic puncta in the rat frontal cortex

Positron emission tomography studies using the synaptic vesicle glycoprotein 2A (SV2A) radioligand [11C]-UCB-J provide in vivo evidence for synaptic dysfunction and/or loss in the cingulate and frontal cortex of patients with schizophrenia. In exploring potential confounding effects of antipsychotic medication, we previously demonstrated that chronic (28-day) exposure to clinically relevant doses of haloperidol does not affect [3H]-UCB-J radioligand binding in the cingulate and frontal cortex of male rats. Furthermore, neither chronic haloperidol nor olanzapine exposure had any effect on SV2A protein levels in these brain regions. These data do not exclude the possibility, however, that more subtle changes in SV2A may occur at pre-synaptic terminals, or the post-synaptic density, following chronic antipsychotic drug exposure. Moreover, relatively little is known about the potential effects of psychotropic drugs other than antipsychotics on SV2A. To address these questions directly, we herein used immunostaining and confocal microscopy to explore the effect of chronic (28-day) exposure to clinically relevant doses of haloperidol, olanzapine or the mood stabilizer lithium on presynaptic SV2A, postsynaptic Neuroligin (NLGN) puncta and their overlap as a measure of total synaptic density in the rat prefrontal and anterior cingulate cortex. We found that, under the conditions tested here, exposure to antipsychotics had no effect on SV2A, NLGN, or overall synaptic puncta count. In contrast, chronic lithium exposure significantly increased NLGN puncta density relative to vehicle, with no effect on either SV2A or total synaptic puncta. Future studies are required to understand the functional consequences of these changes.

Bioinformatics analysis of potential core genes for glioblastoma

Background: Glioblastoma (GBM) has a high degree of malignancy, aggressiveness and recurrence rate. However, there are limited options available for the treatment of GBM, and they often result in poor prognosis and unsatisfactory outcomes.

Materials and methods: In order to identify potential core genes in GBM that may provide new therapeutic insights, we analyzed three gene chips (GSE2223, GSE4290 and GSE50161) screened from the GEO database. Differentially expressed genes (DEG) from the tissues of GBM and normal brain were screened using GEO2R. To determine the functional annotation and pathway of DEG, Gene Ontology (GO) and KEGG pathway enrichment analysis were conducted using DAVID database. Protein interactions of DEG were visualized using PPI network on Cytoscape software. Next, 10 Hub nodes were screened from the differentially expressed network using MCC algorithm on CytoHubba software and subsequently identified as Hub genes. Finally, the relationship between Hub genes and the prognosis of GBM patients was described using GEPIA2 survival analysis web tool.

Results: A total of 37 up-regulated and 187 down-regulated genes were identified through microarray analysis. Amongst the 10 Hub genes selected, SV2B appeared to be the only gene associated with poor prognosis in glioblastoma based on the survival analysis.

Conclusion: Our study suggests that high expression of SV2B is associated with poor prognosis in GBM patients. Whether SV2B can be used as a new therapeutic target for GBM requires further validation.

miR-96 Inhibits SV2C to Promote Depression-Like Behavior and Memory Disorders in Mice

Accumulating evidence continues to emphasize the role of microRNAs as significant contributors to depression-like behavior and memory disorders. The current study aimed to investigate the mechanism by which miR-96 influences depression-like behavior and memory deficit in mice. A depression-like behavior and memory disorder mouse model was initially established by means of intraperitoneal injection with lipopolysaccharide. Memory deficits in the mice were evaluated using the Novel Object Recognition Test and Morris water maze experiments, whereas the Sucrose Preference Experiment and forced swimming experiments were performed to identify depression-like behavior in mice. The levels of tumor necrosis factor-α, malondialdehyde, superoxide dismutase, glutathione, and the monoamine transmitters 5-hydroxytryptamine and dopamine were subsequently detected in the serum. Reverse transcription-quantitative polymerase chain reaction and Western blot analysis evaluated the expression of miR-96 and SV2C expression in the CA1 hippocampal region of the mice. Finally, the relationship of miR-96 and SV2C was verified by dual-luciferase reporter gene assay. Our data indicated that the expression of miR-96 was increased, whereas that of SV2C was decreased in the CA1 region of mice exhibiting depression-like behavior and memory impairment. When miR-96 was downregulated or SV2C was overexpressed via intra-cerebroventricular injection with a miR-96 antagonist (miR-96 antagomir) or overexpression of SV2C vector, the Novel Object Recognition Test and sucrose preference index were increased, whereas the escape latency, the number of water maze platform crossings, and the immobility time of the mice were decreased. The serum levels of tumor necrosis factor-α, interleukin-1β, and malondialdehyde in the mouse CA1 region of mice were reduced, whereas the levels of superoxide dismutase and glutathione were elevated after the downregulation of miR-96 or overexpression of SV2C. Collectively, our study demonstrates that miR-96 negatively regulates the expression of SV2C, which consequently leads to depression-like behavior and memory impairment in mice. Our findings highlight the potential of miR-96-targeted therapeutics.

Brivaracetam prevents astroglial l-glutamate release associated with hemichannel through modulation of synaptic vesicle protein

The antiepileptic/anticonvulsive action of brivaracetam is considered to occur via modulation of synaptic vesicle protein 2A (SV2A); however, the pharmacological mechanisms of action have not been fully characterised. To explore the antiepileptic/anticonvulsive mechanism of brivaracetam associated with SV2A modulation, this study determined concentration-dependent effects of brivaracetam on astroglial L-glutamate release associated with connexin43 (Cx43), tumour-necrosis factor-α (TNFα) and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/glutamate receptor of rat primary cultured astrocytes using ultra-high-performance liquid chromatography. Furthermore, interaction among TNFα, elevated extracellular K⁺ and brivaracetam on expression of SV2A and Cx43 was determined using capillary immunoblotting. TNFα and elevated extracellular K⁺ predominantly enhanced astroglial L-glutamate release associated with respective AMPA/glutamate receptor and hemichannel. These effects were enhanced by a synergistic effect of TNFα and elevated extracellular K⁺ in combination. The activation of astroglial L-glutamate release, and expression of SV2A and Cx43 in the plasma membrane was suppressed by subchronic brivaracetam administration but were unaffected by acute administration. These results suggest that migration of SV2A to the astroglial plasma membrane by hyperexcitability activates astroglial glutamatergic transmission, perhaps via hemichannel activation. Subchronic brivaracetam administration suppressed TNFα-induced activation of AMPA/glutamate receptor and hemichannel via inhibition of ectopic SV2A. These findings suggest that combined inhibition of vesicular and ectopic SV2A functions contribute to the antiepileptic/anticonvulsive mechanism of brivaracetam action.

Acetylcholinesterase inhibitors for the treatment of Alzheimer's disease - a patent review (2016-present)

Introduction - AD, the most common form of dementia, has a multifactorial etiology, and the current therapy (AChEIs and memantine) is unable to interrupt its progress and fatal outcome. This is reflected in the research programs that are oriented toward the development of new therapeutics able to operate on multiple targets involved in the disease progression.Areas covered - The patents from 2016 to present regarding the use of AChEIs in AD, concerns the development of new AChEIs, multitarget or multifunctional ligands, or the associations of currently used AChEIs with other compounds acting on different targets involved in the AD.Expert opinion - The development of new multitarget AChEIs promises to identify compounds with great therapeutic potential but requires more time and effort in order to obtain drugs with the optimal pharmacodynamic profile. Otherwise, the research on new combinations of existing drugs, with known pharmacodynamic and ADME profile, could shorten the time and reduce the costs to develop a new therapeutic treatment for AD. From the analyzed data, it seems more likely that a response to the urgent need to develop effective treatments for AD therapy could come more quickly from studies on drug combinations than from the development of new AChEIs.