Subthreshold Voltage Analysis Demonstrates Neuronal Cell-Surface Sialic Acids Modulate Excitability and Network Integration

SummaryAll neurons are covered in a thick layer of carbohydrates called glycans. Glycans are modified during neurological processes and are thought to play a role in neuronal communication. We develop a voltage imaging platform for analyzing functional connectivity changes using simultaneous voltage recordings in small populations of neurons. We validate this platform using a culture model of development as well as with several pharmacological interventions. Using this platform, we show that ablation of SNA-binding glycans results in loss of functional connectivity in mouse hippocampal neurons, while ablation of MAL II binding glycans minimally perturbs functional connectivity. Altogether, our data reveal that subpopulations of glycans play different roles in maintenance of electrophysiology and provide a platform for modeling changes in functional connectivity with simultaneous voltage recordings.

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Neurotrophic Properties of Silexan, an Essential Oil from the Flowers of Lavender-Preclinical Evidence for Antidepressant-Like Properties

Pharmacopsychiatry ◽

10.1055/a-1293-8585 ◽

2020 ◽

Vol 54 (01) ◽

pp. 37-46

Author(s):

Kristina Friedland ◽

Giacomo Silani ◽

Anita Schuwald ◽

Carola Stockburger ◽

Egon Koch ◽

...

Keyword(s):

Essential Oil ◽

Hippocampal Neurons ◽

Day Treatment ◽

Neuronal Cell ◽

Antidepressant Activity ◽

In Vivo Models ◽

Antidepressant Effects ◽

Primary Hippocampal Neurons

Abstract Background Silexan, a special essential oil from flowering tops of lavandula angustifolia, is used to treat subsyndromal anxiety disorders. In a recent clinical trial, Silexan also showed antidepressant effects in patients suffering from mixed anxiety-depression (ICD-10 F41.2). Since preclinical data explaining antidepressant properties of Silexan are missing, we decided to investigate if Silexan also shows antidepressant-like effects in vitro as well as in vivo models. Methods We used the forced swimming test (FST) in rats as a simple behavioral test indicative of antidepressant activity in vivo. As environmental events and other risk factors contribute to depression through converging molecular and cellular mechanisms that disrupt neuronal function and morphology—resulting in dysfunction of the circuitry that is essential for mood regulation and cognitive function—we investigated the neurotrophic properties of Silexan in neuronal cell lines and primary hippocampal neurons. Results The antidepressant activity of Silexan (30 mg/kg BW) in the FST was comparable to the tricyclic antidepressant imipramine (20 mg/kg BW) after 9-day treatment. Silexan triggered neurite outgrowth and synaptogenesis in 2 different neuronal cell models and led to a significant increase in synaptogenesis in primary hippocampal neurons. Silexan led to a significant phosphorylation of protein kinase A and subsequent CREB phosphorylation. Conclusion Taken together, Silexan demonstrates antidepressant-like effects in cellular as well as animal models for antidepressant activity. Therefore, our data provides preclinical evidence for the clinical antidepressant effects of Silexan in patients with mixed depression and anxiety.

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Inhibition of the p44/42 MAP kinase pathway protects hippocampal neurons in a cell-culture model of seizure activity

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.95.20.11975 ◽

1998 ◽

Vol 95 (20) ◽

pp. 11975-11980 ◽

Cited By ~ 165

Author(s):

B. Murray ◽

A. Alessandrini ◽

A. J. Cole ◽

A. G. Yee ◽

E. J. Furshpan

Keyword(s):

Cell Culture ◽

Map Kinase ◽

Hippocampal Neurons ◽

Seizure Activity ◽

Cell Culture Model ◽

Culture Model ◽

A Cell ◽

Map Kinase Pathway ◽

Kinase Pathway

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TNFα-induced AMPA-receptor trafficking in CNS neurons; relevance to excitotoxicity?

Neuron Glia Biology ◽

10.1017/s1740925x05000608 ◽

2004 ◽

Vol 1 (3) ◽

pp. 263-273 ◽

Cited By ~ 41

Author(s):

DMITRI LEONOUDAKIS ◽

STEVEN P. BRAITHWAITE ◽

MICHAEL S. BEATTIE ◽

ERIC C. BEATTIE

Keyword(s):

Cell Death ◽

Inflammatory Response ◽

Hippocampal Neurons ◽

Neuronal Damage ◽

Neuronal Cell Death ◽

Neuronal Cell ◽

Cell Types ◽

Synaptic Function ◽

Ampar Trafficking ◽

Novel Target

Injury and disease in the CNS increases the amount of tumor necrosis factor α (TNFα) that neurons are exposed to. This cytokine is central to the inflammatory response that occurs after injury and during prolonged CNS disease, and contributes to the process of neuronal cell death. Previous studies have addressed how long-term apoptotic-signaling pathways that are initiated by TNFα might influence these processes, but the effects of inflammation on neurons and synaptic function in the timescale of minutes after exposure are largely unexplored. Our published studies examining the effect of TNFα on trafficking of AMPA-type glutamate receptors (AMPARs) in hippocampal neurons demonstrate that glial-derived TNFα causes a rapid (<15 minute) increase in the number of neuronal, surface-localized, synaptic AMPARs leading to an increase in synaptic strength. This indicates that TNFα-signal transduction acts to facilitate increased surface localization of AMPARs from internal postsynaptic stores. Importantly, an excess of surface localized AMPARs might predispose the neuron to glutamate-mediated excitotoxicity and excessive intracellular calcium concentrations, leading to cell death. This suggests a new mechanism for excitotoxic TNFα-induced neuronal death that is initiated minutes after neurons are exposed to the products of the inflammatory response.Here we review the importance of AMPAR trafficking in normal neuronal function and how abnormalities that are mediated by glial-derived cytokines such as TNFα can be central in causing neuronal disorders. We have further investigated the effects of TNFα on different neuronal cell types and present new data from cortical and hippocampal neurons in culture. Finally, we have expanded our investigation of the temporal profile of the action of this cytokine relevant to neuronal damage. We conclude that TNFα-mediated effects on AMPAR trafficking are common in diverse neuronal cell types and very rapid in their onset. The abnormal AMPAR trafficking elicited by TNFα might present a novel target to aid the development of new neuroprotective drugs.

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Selective increase of functional network connectivity in Arc-positive neuronal engrams after long-term potentiation

10.1101/2020.12.07.415109 ◽

2020 ◽

Author(s):

Yuheng Jiang ◽

Antonius M.J. VanDongen

Keyword(s):

Functional Connectivity ◽

Hippocampal Neurons ◽

Network Effects ◽

Network Connectivity ◽

Long Term Potentiation ◽

Early Gene ◽

Memory Traces ◽

Term Potentiation ◽

Memory Engram

ABSTRACTNew tools in optogenetics and molecular biology have culminated in recent studies which mark immediate-early gene (IEG)-expressing neurons as memory traces or engrams. Although the activity-dependent expression of IEGs has been successfully utilised to label memory traces, their roles in engram specification is incompletely understood. Outstanding questions remain as to whether expression of IEGs can interplay with network properties such as functional connectivity and also if neurons expressing different IEGs are functionally distinct. We investigated the expression of Arc and c-Fos, two commonly utilised IEGs in memory engram specification, in cultured hippocampal neurons. After pharmacological induction of long-term potentiation (LTP) in the network, we noted an emergent network property of refinement in functional connectivity between neurons, characterized by a global down-regulation of network connectivity, together with strengthening of specific connections. Subsequently, we show that Arc expression correlates with the effects of network refinement, with Arc-positive neurons being selectively strengthened. Arc positive neurons were also found to be located in closer physical proximity to each other in the network. While the expression pattern of IEGs c-Fos and Arc strongly overlaps, Arc was more selectively expressed than c-Fos. These IEGs also act together in coding information about connection strength pruning. These results demonstrate important links between IEG expression and network connectivity, which serve to bridge the gap between cellular correlates and network effects in learning and memory.

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Remote Corticospinal Tract Degeneration After Cortical Stroke in Rats May Not Preclude Spontaneous Sensorimotor Recovery

Neurorehabilitation and Neural Repair ◽

10.1177/15459683211041318 ◽

2021 ◽

pp. 154596832110413

Author(s):

Michel R. T. Sinke ◽

Geralda A. F. van Tilborg ◽

Anu E. Meerwaldt ◽

Caroline L. van Heijningen ◽

Annette van der Toorn ◽

...

Keyword(s):

Functional Connectivity ◽

Corticospinal Tract ◽

Sprague Dawley ◽

Post Stroke ◽

Neuronal Communication ◽

Cortical Stroke ◽

Magnetic Resonance Imaging Mri ◽

And Behavior ◽

Sensorimotor Recovery

Background. Recovery of motor function after stroke appears to be related to the integrity of axonal connections in the corticospinal tract (CST) and corpus callosum, which may both be affected after cortical stroke. Objective. In the present study, we aimed to elucidate the relationship of changes in measures of the CST and transcallosal tract integrity, with the interhemispheric functional connectivity and sensorimotor performance after experimental cortical stroke. Methods. We conducted in vivo diffusion magnetic resonance imaging (MRI), resting-state functional MRI, and behavior testing in twenty-five male Sprague Dawley rats recovering from unilateral photothrombotic stroke in the sensorimotor cortex. Twenty-three healthy rats served as controls. Results. A reduction in the number of reconstructed fibers, a lower fractional anisotropy, and higher radial diffusivity in the ipsilesional but intact CST, reflected remote white matter degeneration. In contrast, transcallosal tract integrity remained preserved. Functional connectivity between the ipsi- and contralesional forelimb regions of the primary somatosensory cortex significantly reduced at week 8 post-stroke. Comparably, usage of the stroke-affected forelimb was normal at week 28, following significant initial impairment between day 1 and week 8 post-stroke. Conclusions. Our study shows that post-stroke motor recovery is possible despite degeneration in the CST and may be supported by intact neuronal communication between hemispheres.

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Inhibition of Src family kinases improves cognitive function after intraventricular hemorrhage or intraventricular thrombin

Journal of Cerebral Blood Flow & Metabolism ◽

10.1177/0271678x16666291 ◽

2016 ◽

Vol 37 (7) ◽

pp. 2359-2367 ◽

Cited By ~ 11

Author(s):

Da Zhi Liu ◽

Ben Waldau ◽

Bradley P Ander ◽

Xinhua Zhan ◽

Boryana Stamova ◽

...

Keyword(s):

Spatial Memory ◽

Hippocampal Neurons ◽

Intraventricular Hemorrhage ◽

Memory Loss ◽

Neuronal Cell ◽

Memory Deficits ◽

Src Family Kinases ◽

Intraventricular Injection ◽

Src Family Kinase ◽

Autologous Whole Blood

Intraventricular hemorrhage causes spatial memory loss, but the mechanism remains unknown. Our recent studies demonstrated that traumatic brain injury activates Src family kinases, which cause spatial memory loss. To test whether the spatial memory loss was due to blood in the ventricles, which activated Src family kinases, we infused autologous whole blood or thrombin into the lateral ventricles of adult rats to model non-traumatic intraventricular hemorrhage. Hippocampal neuron loss was examined 1 day to 5 weeks later. Spatial memory function was assessed 29 to 33 days later using the Morris water maze. Five weeks after the ventricular injections of blood or thrombin, there was death of most hippocampal neurons and significant memory deficits compared with sham operated controls. These data show that intraventricular thrombin is sufficient to kill hippocampal neurons and produce spatial memory loss. In addition, systemic administration of the non-specific Src family kinase inhibitor PP2 or intraventricular injection of siRNA-Fyn, a Src family kinase family member, prevented hippocampal neuronal loss and spatial memory deficits following intraventricular hemorrhage. The data support the conclusions that thrombin mediates the hippocampal neuronal cell death and spatial memory deficits produced by intraventricular blood and that these can be blocked by non-specific inhibition of Src family kinases or by inhibiting Fyn.

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Proline-rich transmembrane protein 2 (PRRT2) regulates the actin cytoskeleton during synaptogenesis

Cell Death and Disease ◽

10.1038/s41419-020-03073-w ◽

2020 ◽

Vol 11 (10) ◽

Author(s):

Elisa Savino ◽

Romina Inès Cervigni ◽

Miriana Povolo ◽

Alessandra Stefanetti ◽

Daniele Ferrante ◽

...

Keyword(s):

Actin Cytoskeleton ◽

Neurotransmitter Release ◽

Hippocampal Neurons ◽

Neuronal Excitability ◽

Transmembrane Protein ◽

Neuronal Cell ◽

Cell Aggregation ◽

Actin Dynamics ◽

Actin Binding ◽

Filamentous Actin

Abstract Mutations in proline-rich transmembrane protein 2 (PRRT2) have been recently identified as the leading cause of a clinically heterogeneous group of neurological disorders sharing a paroxysmal nature, including paroxysmal kinesigenic dyskinesia and benign familial infantile seizures. To date, studies aimed at understanding its physiological functions in neurons have mainly focused on its ability to regulate neurotransmitter release and neuronal excitability. Here, we show that PRRT2 expression in non-neuronal cell lines inhibits cell motility and focal adhesion turnover, increases cell aggregation propensity, and promotes the protrusion of filopodia, all processes impinging on the actin cytoskeleton. In primary hippocampal neurons, PRRT2 silencing affects the synaptic content of filamentous actin and perturbs actin dynamics. This is accompanied by defects in the density and maturation of dendritic spines. We identified cofilin, an actin-binding protein abundantly expressed at the synaptic level, as the ultimate effector of PRRT2. Indeed, PRRT2 silencing unbalances cofilin activity leading to the formation of cofilin-actin rods along neurites. The expression of a cofilin phospho-mimetic mutant (cof-S3E) is able to rescue PRRT2-dependent defects in synapse density, spine number and morphology, but not the alterations observed in neurotransmitter release. Our data support a novel function of PRRT2 in the regulation of the synaptic actin cytoskeleton and in the formation of synaptic contacts.

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Dynamic Interhemispheric Desynchronization in Marmosets and Humans With Disorders of the Corpus Callosum

Frontiers in Neural Circuits ◽

10.3389/fncir.2020.612595 ◽

2020 ◽

Vol 14 ◽

Author(s):

Diego Szczupak ◽

Cecil C. Yen ◽

Cirong Liu ◽

Xiaoguang Tian ◽

Roberto Lent ◽

...

Keyword(s):

Functional Connectivity ◽

Corpus Callosum ◽

Resting State ◽

Human Subjects ◽

Healthy Controls ◽

Resting State Functional Connectivity ◽

Periodic Patterns ◽

Lower Strength ◽

Neuronal Communication ◽

Clear Explanation

The corpus callosum, the principal structural avenue for interhemispheric neuronal communication, controls the brain’s lateralization. Developmental malformations of the corpus callosum (CCD) can lead to learning and intellectual disabilities. Currently, there is no clear explanation for these symptoms. Here, we used resting-state functional MRI (rsfMRI) to evaluate the dynamic resting-state functional connectivity (rsFC) in both the cingulate cortex (CG) and the sensory areas (S1, S2, A1) in three marmosets (Callithrix jacchus) with spontaneous CCD. We also performed rsfMRI in 10 CCD human subjects (six hypoplasic and four agenesic). We observed no differences in the strength of rsFC between homotopic CG and sensory areas in both species when comparing them to healthy controls. However, in CCD marmosets, we found lower strength of quasi-periodic patterns (QPP) correlation in the posterior interhemispheric sensory areas. We also found a significant lag of interhemispheric communication in the medial CG, suggesting asynchrony between the two hemispheres. Correspondingly, in human subjects, we found that the CG of acallosal subjects had a higher QPP correlation than controls. In comparison, hypoplasic subjects had a lower QPP correlation and a delay of 1.6 s in the sensory regions. These results show that CCD affects the interhemispheric synchrony of both CG and sensory areas and that, in both species, its impact on cortical communication varies along the CC development gradient. Our study shines a light on how CCD misconnects homotopic regions and opens a line of research to explain the causes of the symptoms exhibited by CCD patients and how to mitigate them.

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TMIC-46. GLIOMA-INDUCED SYNAPTOGENESIS IS ENRICHED WITHIN FUNCTIONAL CONNECTIVITY NETWORK HUBS AND INFLUENCES LANGUAGE PROCESSING IN ADULT IDH WT GLIOBLASTOMA

Neuro-Oncology ◽

10.1093/neuonc/noz175.1080 ◽

2019 ◽

Vol 21 (Supplement_6) ◽

pp. vi257-vi258

Author(s):

Saritha Krishna ◽

Sofia Kakaizada ◽

Claudia Valdivia ◽

Kyounghee Seo ◽

David Raleigh ◽

...

Keyword(s):

Neural Networks ◽

Functional Connectivity ◽

Task Performance ◽

Language Processing ◽

Hippocampal Neurons ◽

Neuronal Excitability ◽

Glioma Cells ◽

Network Connectivity ◽

Marker Expression ◽

Neuron Interactions

Abstract INTRODUCTION Little is known about the mechanisms by which gliomas integrate into functional neural networks and influence complex cognitive processes such as language. Glioma-neuron interactions are bidirectional, with increased neuronal activity promoting tumor growth and the latter in turn influencing neuronal excitability and synaptic connections. It remains unknown whether glioma-neuron interactions play a role in maintaining long-range neural networks subserving cognition in humans. We test the hypothesis that glioma-neuron interactions (“synaptogenic glioma cells”) are enriched within intratumoral high functional connectivity (FC) network hubs, thereby influencing language processing via release of synaptogenic factors into the tumor microenvironment. METHODS We employed magnetoencephalography imaginary coherence measures to identify intratumoral high (HFC) and low (LFC) functional connectivity network hubs in newly diagnosed glioblastoma patients. Primary patient samples and cultures from HFC and LFC sites were assessed for pre and post-synaptic marker expression (IF), cocultured with murine hippocampal neurons, and induced neuron organoids. ECOG Field recordings were performed on HFC/LFC tumors. Secreted proteins were measured from patient serum and LFC/HFC culture supernatant. Language assessments were performed to correlate task performance with FC measures. RESULTS Primary patient samples from HFC regions are enriched for glioblastoma cells with a synaptogenic profile as characterized by pre- and post-synaptic marker expression at both tissue and cellular level (coculture with mouse hippocampal neuron and organoid models). RNA sequencing and proteomic analyses from HFC samples revealed a neurogenic signature including thrombospondin 1 (TSP1). Overexpression of TSP1 in LFC primary patient cultures rescues the synaptogenic and proliferative phenotype. Importantly, we found a linear relationship between intratumoral HFC with patient serum TSP1 (ELISA) with a further correlation with language task performance. CONCLUSION An enriched population of synaptogenic glioma cells are organized within intratumoral high network connectivity regions. Glioma-induced neuronal synaptogenesis contributes to the microenvironment in support of network connectivity through secretion of TSP1.

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