l-Borneol and d-Borneol promote transdifferentiation of astrocytes into neurons in rats by regulating Wnt/Notch pathway to exert neuroprotective effect during recovery from cerebral ischaemia

BACKGROUND

The Chinese medicines Borneolum and l-Borneolum have neuroprotective effects on acute cerebral ischaemia-reperfusion (IR) in rats. Research on their effects during recovery from cerebral IR is lacking. Cerebral ischaemia can activate astrocytes for conversion into neurons. Neurogenesis cannot be achieved without nutritional support from an improved brain microenvironment through the blood circulation.

PURPOSE

The purpose of this study was to determine whether Borneolum and l-Borneolum can promote transdifferentiation of astrocytes into neurons by regulating the Wnt/Notch pathway to exert neuroprotective effects during recovery from cerebral ischaemia.

STUDY DESIGN AND METHODS

A suture crossing the external carotid artery to occlude the middle cerebral artery was used to prepare a model of cerebral IR (Longa et al., 1989). The Longa neurological function score, modified neurological severity score, tape removal test and grid misstep experiment were used to evaluate motor nerve function. Triphenyltetrazolium chloride was used to determine the extent of cerebral infarction. Left/right hemisphere contrast was used to measure brain atrophy. Astrocytes labelled with adeno-associated virus were used to track their fate after transdifferentiation. Laser speckle contrast imaging was used to observe the effects of l-Borneolum and Borneolum on cerebral blood flow. Immunofluorescence and western blotting were used to investigate their mechanisms.

RESULTS

l-Borneolum and Borneolum significantly improved neurological function and limb movement in rats with cerebral ischaemia during recovery and increased cerebral blood flow. l-Borneolum improved forelimb motor coordination more effectively than Borneolum and promoted transdifferentiation of astrocytes to GABAergic neurons in the striatal region. The expression of Wnt3a and Notch-1 was downregulated. The expression of vascular endothelial growth factor was not significantly changed. Borneolum improved forelimb sensitivity and alleviated cerebral infarction and brain atrophy more effectively than l-Borneolum, which promoted transdifferentiation of astrocytes into neurons and nestin expression and neurogenesis in the striatal zone. The expression of glycogen synthase kinase-3β and β-catenin was upregulated. l-Borneolum and Borneolum had no significant neuroprotective effect on the cortex and hippocampus.

CONCLUSIONS

l-Borneolum and Borneolum exerted neuroprotective effects on cerebral ischaemia during recovery by promoting neurogenesis and blood circulation in the striatal and subventricular zones. Their mechanisms may be related to the Wnt3a and Notch-1 pathways.

STORM Super-Resolution Imaging of CB1 Receptors in Tissue Preparations

Single-molecule localization microscopy (SMLM) opened new possibilities to study the spatial arrangement of molecular distribution and disease-associated redistribution at a previously unprecedented resolution that was not achievable with optical microscopy approaches. Recent discoveries based on SMLM techniques uncovered specific nanoscale organizational principles of signaling proteins in several biological systems including the chemical synapses in the brain. Emerging data suggest that the spatial arrangement of the molecular players of the endocannabinoid system is also precisely regulated at the nanoscale level in synapses and in other neuronal and glial subcellular compartments. The precise nanoscale distribution pattern is likely to be important to subserve several specific signaling functions of this important messenger system in a cell-type- and subcellular domain-specific manner.STochastic Optical Reconstruction Microscopy (STORM) is an especially suitable SMLM modality for cell-type-specific nanoscale molecular imaging due to its compatibility with traditional diffraction-limited microscopy approaches and classical staining methods. Here, we describe a detailed protocol for STORM imaging in mouse brain tissue samples with a focus on the CB₁ cannabinoid receptor, one of the most abundant synaptic receptors in the brain. We also summarize important conceptual and methodical details that are essential for the valid interpretation of single-molecule localization microscopy data.

Modification of Müller Glial Cell Fate and Proliferation with the Use of Small Molecules

In recent years, reprogramming Müller glia by overexpressing Ascl1 and other transcription factors has shown promise for the regeneration of postmitotic retinal neurons, primarily bipolar cells, following injury. Müller glial proliferation and efficiency of neuronal differentiation can be modified by the use of small molecules in various systems. The molecules and pathways studied thus far share remarkable consistency with astrocytes. In this mini review, we provide an overview on the modulation of Müller glial proliferation and cell fate using small molecules in injury and reprogramming. We also compare these observations to what has been observed in astrocytes.

SATB1/SLC7A11/HO-1 Axis Ameliorates Ferroptosis in Neuron Cells After Ischemic Stroke by Danhong Injection

Neuronal damage after ischemic stroke (IS) is frequently due to ferroptosis, contributing significantly to ischemic injury. However, the mechanism against ferroptosis in IS remained unclear. The aim of this study was to investigate the potential mechanism of Danhong injection (DHI) and the critical transcription factor SATB1 in preventing neuronal ferroptosis after ischemic stroke in vivo and in vitro. The results showed that DHI treatment significantly reduced the infarct area and associated damage in the brains of the pMCAO mice, and enhanced the viability of OGD-injured neurons. And several characteristic indicators of ferroptosis, such as mitochondrial necrosis and iron accumulation, were regulated by DHI after IS. Importantly, we found that the expression and activity of SATB1 were decreased in the pMCAO mice, especially in neuron cells. Meanwhile, the SATB1/SLC7A11/HO-1 signaling pathway was activated after DHI treatment in ischemic stroke and was found to improve neuronal ferroptosis. Inhibition of SATB1 significantly reduced SLC7A11-HO-1 and significantly attenuated the anti-ferroptosis effects of DHI in the OGD model. These findings indicate that neuronal ferroptosis after IS can be alleviated by DHI through SATB1/SLC7A11/HO-1 pathway, and SATB1 may be an attractive therapeutic target for treating ischemic stroke.

Cells of the Central Nervous System: An Overview of Their Structure and Function

The central nervous system is the last major organ system in the vertebrate body to yield its cellular structure, due to the complexity of its cells and their interactions. The fundamental unit of the nervous system is the neuron, which forms complex circuits that receive and integrate information and generate adaptive responses. Each neuron is composed of an input domain consisting of multiple dendrites along with the cell body, which is also responsible for the majority of macromolecule synthesis for the cell. The output domain is the axon which is a singular extension from the cell body that propagates the action potential to the synapse, where signals pass from one neuron to another. Facilitating these functions are cohorts of supporting cells consisting of astrocytes, oligodendrocytes and microglia along with NG2 cells and ependymal cells. Astrocytes have a dazzling array of functions including physical support, maintenance of homeostasis, development and integration of synaptic activity. Oligodendrocytes form the myelin sheath which surrounds axons and enables rapid conduction of the nerve impulse. Microglia are the resident immune cells, providing immune surveillance and remodeling of neuronal circuits during development and trauma. All these cells function in concert with each other, producing the remarkably diverse functions of the nervous system.

Oxytocin action on components of endoplasmic reticulum in hippocampal neuronal cells

Despite the known importance of the endoplasmic reticulum (ER) in protein synthesis and vesicular transport, it is not clear whether neuropeptide and neuromodulator oxytocin can directly affect components of the ER in neuronal cells. Therefore, in the present study, we hypothesize that incubation of hippocampal neuronal cells in a presence of oxytocin 1) plays a role in the regulation of the expression of selected ER chaperone components and molecules involved in unfolded protein response pathway 2) affects distribution of the intracellular fluorescence signal highly selective for the ER. We found that oxytocin (1 μM) after 60 min significantly decreased the gene expression of oxidoreductase Ero1β, chaperone glucose-regulated proteins (Grp) 78 and Grp94. A significant decrease in GRP78 protein levels in response to oxytocin treatment occurred after 30, 60 and 120 min. We also observed a time-dependent increase in calreticulin protein levels with a statistically significant increase observed after 360 min. We found that the dynamics of the ER network changes significantly within 2 h of incubation under the influence of oxytocin. In conclusion we have shown that ER chaperones, oxidoreductases and trafficking molecules in neuronal cells are changing in response to oxytocin treatment in a short-term scenario potentially relevant for growth of dendrites and axons.

Semi-Automated Quantitative Evaluation of Neuron Developmental Morphology In Vitro Using the Change-Point Test

Neuron morphology gives rise to distinct axons and dendrites and plays an essential role in neuronal functionality and circuit dynamics. In rat hippocampal neurons, morphological development occurs over roughly one week in vitro. This development has been qualitatively described as occurring in 5 stages. Still, there is a need to quantify cell growth to monitor cell culture health, understand cell responses to sensory cues, and compare experimental results and computational growth model predictions. To address this need, embryonic rat hippocampal neurons were observed in vitro over six days, and their processes were quantified using both standard morphometrics (degree, number of neurites, total length, and tortuosity) and new metrics (distance between change points, relative turning angle, and the number of change points) based on the Change-Point Test to track changes in path trajectories. Of the standard morphometrics, the total length of neurites per cell and the number of endpoints were significantly different between 0.5, 1.5, and 4 days in vitro, which are typically associated with Stages 2-4. Using the Change-Point Test, the number of change points and the average distance between change points per cell were also significantly different between those key time points. This work highlights key quantitative characteristics, both among common and novel morphometrics, that can describe neuron development in vitro and provides a foundation for analyzing directional changes in neurite growth for future studies.

Alternate-day fasting for the protection of cognitive impairment in c57BL/6J mice following whole-brain radiotherapy

NLRP3 inflammasome activation is implicated in irradiation-induced cognitive dysfunction. Alternate-day fasting (ADF) has been demonstrated to improve neuroinflammation as a non-pharmacological intervention. However, the exact mechanism and the anti-inflammatory effect in irradiation-induced cognitive dysfunction still need further in-depth study. The present study examined the effects of eight-week ADF on the cognitive functions of mice as well as inflammasome-mediated hippocampal neuronal loss following irradiation in mouse models of irradiation-induced cognitive deficits using seven-week-old male C57BL/6J mice. The behavioral results of novel place recognition and object recognition tasks revealed that ADF ameliorated cognitive functions in irradiation-induced cognitive dysfunction mice. ADF inhibited the expression of components of the NLRP3 inflammasome (NLRP3, ASC, and Cl.caspase-1), the downstream inflammatory factor (IL-1β and IL-18), and apoptosis-related proteins (caspase-3) via western blotting. Furthermore, an increased number of neurons and activated astrocytes were observed in the hippocampus using immunohistochemistry and Sholl analysis, which was jointly confirmed by western blotting. According to our study, this is the first time we found that ADF improved cognitive dysfunction induced by irradiation, and the anti-inflammatory effect of ADF could be due to inhibition in NLRP3-mediated hippocampal neuronal loss by suppressing astrocyte activation.

Neuron-Microglia Crosstalk in Neuropsychiatric Disorders

Numerous studies have investigated the causes and mechanisms of psychiatric disorders through postmortem examination of patients with a history of a schizophrenia, mood disorder, or neurocognitive disorder. In addition, the search for specific mechanism-based treatments for psychiatric disorders has been intensified through the use of transgenic animal models involving specific genes tightly associated with psychiatric disorders. As a result, many studies with patients or animal models have reported a close association of neuroglia with major psychiatric disorders. Recently, research has focused on the associations between microglia and major psychiatric disorders and on the role of the immune response and abnormal microglia in the onset and symptoms of psychiatric disorders, in particular. Postmortem studies of brain tissue and animal models recapitulating human mental disorders have also confirmed association between psychiatric disorders and quantitative, structural, or functional abnormalities of neuron-microglia crosstalk. This review aims to describe the relationships between microglia and major psychiatric disorders and to specifically examine studies of gene expression and function of microglia in depression, schizophrenia, and Alzheimer's disease.

Delivery-Dependent Shift in Oxytocin-Responsive Cell Population in the Central Amygdala of the Female Rat

INTRODUCTION

Despite its recent reputation as prosocial neurohormone, the most important physiological role of oxytocin (OT) is stimulating uterine contractions. Though it is well known that plasma OT concentrations change drastically during delivery, it remains unexplored whether and how OT receptors in the maternal brain are activated. We examined whether the responses of cells in the central amygdala (CeA), an OT receptor-rich limbic site involved in pain and fear memory regulation, to exogenously applied OT analogue, Thr-Gly-OT (TGOT), vary depending on delivery.

METHODS

Intracellular Ca2+ dynamics of the CeA cells were visualized in brain slices from female rats at virgin (VG), during pregnancy term (PT) days 16-21, within 24 h after delivery (G0), and within 1-3 days after delivery (G3). The Ca2+ responses to 1 µM TGOT, 20 mM KCl (high K), and 300 µM ADP were compared.

RESULTS

We found that fraction of cells responding to TGOT, high K, and ADP differed significantly between the four delivery-associated terms. In particular, the fraction of cells responding to TGOT (TGOT responders) significantly increased from VG and PT at G0 and G3. Furthermore, the significant positive correlation between TGOT and high K response in TGOT and high K responders was reduced at G0, while that between TGOT and ADP responses in TGOT and ADP responders was increased at G0.

CONCLUSION

These results indicate that the responses of CeA cells to an OT receptor agonist markedly change around delivery, which might play a role in controlling the labor-related pain and post-delivery emotional complications.

Neuronal Ganglioside and Glycosphingolipid (GSL) Metabolism and Disease : Cascades of Secondary Metabolic Errors Can Generate Complex Pathologies (in LSDs)

Glycosphingolipids (GSLs) are a diverse group of membrane components occurring mainly on the surfaces of mammalian cells. They and their metabolites have a role in intercellular communication, serving as versatile biochemical signals (Kaltner et al, Biochem J 476(18):2623-2655, 2019) and in many cellular pathways. Anionic GSLs, the sialic acid containing gangliosides (GGs), are essential constituents of neuronal cell surfaces, whereas anionic sulfatides are key components of myelin and myelin forming oligodendrocytes. The stepwise biosynthetic pathways of GSLs occur at and lead along the membranes of organellar surfaces of the secretory pathway. After formation of the hydrophobic ceramide membrane anchor of GSLs at the ER, membrane-spanning glycosyltransferases (GTs) of the Golgi and Trans-Golgi network generate cell type-specific GSL patterns for cellular surfaces. GSLs of the cellular plasma membrane can reach intra-lysosomal, i.e. luminal, vesicles (ILVs) by endocytic pathways for degradation. Soluble glycoproteins, the glycosidases, lipid binding and transfer proteins and acid ceramidase are needed for the lysosomal catabolism of GSLs at ILV-membrane surfaces. Inherited mutations triggering a functional loss of glycosylated lysosomal hydrolases and lipid binding proteins involved in GSL degradation cause a primary lysosomal accumulation of their non-degradable GSL substrates in lysosomal storage diseases (LSDs). Lipid binding proteins, the SAPs, and the various lipids of the ILV-membranes regulate GSL catabolism, but also primary storage compounds such as sphingomyelin (SM), cholesterol (Chol.), or chondroitin sulfate can effectively inhibit catabolic lysosomal pathways of GSLs. This causes cascades of metabolic errors, accumulating secondary lysosomal GSL- and GG- storage that can trigger a complex pathology (Breiden and Sandhoff, Int J Mol Sci 21(7):2566, 2020).

Glycans and Carbohydrate-Binding/Transforming Proteins in Axon Physiology

The mature nervous system relies on the polarized morphology of neurons for a directed flow of information. These highly polarized cells use their somatodendritic domain to receive and integrate input signals while the axon is responsible for the propagation and transmission of the output signal. However, the axon must perform different functions throughout development before being fully functional for the transmission of information in the form of electrical signals. During the development of the nervous system, axons perform environmental sensing functions, which allow them to navigate through other regions until a final target is reached. Some axons must also establish a regulated contact with other cells before reaching maturity, such as with myelinating glial cells in the case of myelinated axons. Mature axons must then acquire the structural and functional characteristics that allow them to perform their role as part of the information processing and transmitting unit that is the neuron. Finally, in the event of an injury to the nervous system, damaged axons must try to reacquire some of their immature characteristics in a regeneration attempt, which is mostly successful in the PNS but fails in the CNS. Throughout all these steps, glycans perform functions of the outermost importance. Glycans expressed by the axon, as well as by their surrounding environment and contacting cells, encode key information, which is fine-tuned by glycan modifying enzymes and decoded by glycan binding proteins so that the development, guidance, myelination, and electrical transmission functions can be reliably performed. In this chapter, we will provide illustrative examples of how glycans and their binding/transforming proteins code and decode instructive information necessary for fundamental processes in axon physiology.

Neuronal Proteins as Antigenic Targets in Membranous Nephropathy

CONTEXT

The discovery of new target antigens in membranous nephropathy (MN) has revealed new disease phenotypes and, in some cases, has suggested mechanisms of disease shared by two concurrent autoimmune diseases. Subject of Review: Several recent reports and an accompanying editorial describe the association of anti-contactin-1 (CNTN1) autoantibodies of the IgG4 subclass with a novel subtype of MN that co-occurs with a form of chronic inflammatory demyelinating polyradiculoneuropathy caused by anti-CNTN1 antibodies. CNTN1, the cellular source of which is still undetermined, is identified as the target antigen in the kidney since it is present within glomerular subepithelial deposits and anti-CNTN1 IgG4 antibodies can be eluted from the corresponding kidney biopsy tissue. Second Opinion: These new reports reinforce recent findings that many proteins targeted in several other types of primary and secondary MN are proteins whose expression is shared by podocytes and neurons. While complement-mediated podocyte damage represents a well-established paradigm in the pathogenesis of MN, interference with the normal functions of these shared proteins by autoantibodies should be considered as another potential mechanism of glomerular injury to be explored in future research.

Inhibition of CCR2 attenuates neuroinflammation and neuronal apoptosis after subarachnoid hemorrhage through the PI3K/Akt pathway

BACKGROUND

Neuroinflammation and neuronal apoptosis are closely associated with a poor prognosis in patients with subarachnoid hemorrhage (SAH). We investigated the role of C-C motif chemokine receptor 2 (CCR2) in SAH.

METHODS

Pre-processed RNA-seq transcriptome datasets GSE167110 and GSE79416 from the Gene Expression Omnibus (GEO) database were screened for genes differentially expressed between mice with SAH and control mice, using bioinformatics analysis. The endovascular perforation model was performed to establish SAH. RS504393 (a CCR2 antagonist) and LY294002 (PI3K inhibitor) were administered to explore the mechanism of neuroinflammation after SAH. SAH grading, neurological scoring, brain water content and blood-brain barrier (BBB) permeability determination, enzyme-linked immunosorbent assay (ELISA), western blotting, and immunofluorescence were performed. An in vitro model of SAH was induced in H22 cells by hemin treatment. The protective mechanism of CCR2 inhibition was studied by adding RS504393 and LY294002. Clinical cerebrospinal fluid (CST) samples were detected by ELISA.

RESULTS

Expression of CCR2 was upregulated in both datasets and was identified as a hub gene. CCR2 expression was significantly upregulated in the cytoplasm of neurons after SAH, both in vitro and in vivo. RS significantly reduced the brain water content and blood-brain barrier permeability, alleviated neuroinflammation, and reduced neuronal apoptosis after SAH. Additionally, the protective effects of CCR2 inhibition were abolished by LY treatment. Finally, the levels of CCR2, inflammatory factors, and apoptotic factors were elevated in the CSF of patients with SAH. CCR2 levels were associated with patient outcomes at the 6-month follow-up.

CONCLUSION

CCR2 expression was upregulated in both in vitro and in vivo SAH models. Additionally, inhibition of CCR2, at least partly through the PI3K/AKT pathway, alleviated neuroinflammation and neuronal apoptosis in vivo and in vitro. CCR2 levels in the CSF have a moderate diagnostic value for 6-month outcome prediction in patients with SAH.

Emerging Treatment Strategies for Cerebral Ischemia-Reperfusion Injury

Cerebral ischemia-reperfusion injury (CI/RI) injury is a common feature of ischemic stroke which occurs when the blood supply is restored after a period of ischemia in the brain. Reduced blood-flow to the brain during CI/RI compromises neuronal cell health as a result of mitochondrial dysfunction, oxidative stress, cytokine production, inflammation and tissue damage. Reperfusion therapy during CI/RI can restore the blood flow to ischemic regions of brain which are not yet infarcted. The long-term goal of CI/RI therapy is to reduce stroke-related neuronal cell death, disability and mortality. A range of drug and interventional therapies have emerged that can alleviate CI/RI mediated oxidative stress, inflammation and apoptosis in the brain. Herein, we review recent studies on CI/RI interventions for which a mechanism of action has been described and the potential of these therapeutic modalities for future use in the clinic.

Functions of the tubulin code in the C. elegans nervous system

Due to their elongated and polarized morphology, neurons rely on the microtubule (MT) cytoskeleton for their shape, as well as for efficient intracellular transport that maintains neuronal function, survival, and connectivity. Although all MTs are constructed from α- and β-tubulins that are highly conserved throughout eukaryotes, different MT networks within neurons exhibit different dynamics and functions. For example, molecular motors must be able to differentially recognize the axonal and dendritic MTs to deliver appropriate cargos to sensory endings and synaptic regions. The Tubulin Code hypothesis proposes that MTs can be specialized in form and function by chemical differences in their composition by inclusion of different α- and β-tubulins into the MT lattice, as well as differences in post-translational enzymatic modifications. The chemical differences encode information that allow MTs to regulate interactions with various microtubule-based molecular motors such as kinesins and dyneins as well as with structural microtubule-associated proteins (MAPs), which can, in turn, modify the function or stability of MTs. Here, we review studies involving C. elegans, a model organism with a relatively simple nervous system that is amenable to genetic analysis, that have contributed to our understanding of how the Tubulin Code can specialize neuronal MT networks to establish differences in neuronal morphology and function. Such studies have revealed molecules and mechanisms that are conserved in vertebrates and have the potential to inform our understanding of neurological diseases involving defects in the cytoskeleton and intracellular transport.

LysM-positive neurons drive Tuberous Sclerosis Complex (TSC)-associated brain lesions

Mutations of Tsc1 or Tsc2 can lead to excessive activation of mTORC1 and cause Tuberous Sclerosis Complex (TSC), which is an autosomal dominant genetic disease prominently characterized by seizures, mental retardation and multiorgan hamartoma. In TSC, pathological changes in the central nervous system are the leading cause of death and disability. In decades, series of rodent models have been established by mutating Tsc1 or Tsc2 genes in diverse neural cell lineages to investigate the underlying cellular and molecular mechanisms, however, the cellular origin triggering neural pathological changes in TSC is undetermined. In this study, we generated a novel mouse model involving conditional deletion of Tsc1 in lysozyme 2 (Lyz2)-positive cells which replicated several features of brain lesions including epileptic seizures, megalencephaly, highly enlarged pS6-positive neurons and astrogliosis. In addition, we confirmed that bone marrow-derived myeloid cells including microglia with Tsc1 deficiency are not the decisive lineage in the cerebral pathologies in TSC. These histological assays in our murine model indicate an essential contribution of Lyz2-positive neurons to TSC progression. The Lyz2-positive neural population-specific onset of Tsc1 loss in murine postnatal brain might be the key to pathological phenotypes. Our findings thus provided evidences supporting new insights into the role of Lyz2-positive neurons in TSC events.

Identification and expression profile of novel STAND gene Nwd2 in the mouse central nervous system

In the central nervous system (CNS), neurons need synaptic neurotransmitter release and cellular response for various cellular stress or environmental stimuli. To achieve these highly orchestrated cellular processes, neurons should drive the molecular mechanisms that govern and integrate complex signaling pathways. The signal transduction ATPases with numerous domains (STAND) family of proteins has been shown to play essential roles in diverse signal transduction mechanisms, including apoptosis and innate immunity. However, a comprehensive understanding of STAND genes remains lacking. Previously, we identified the NACHT and WD repeat domain-containing protein 1 (NWD1), a member of STAND family, in the regulation of the assembly of a giant multi-enzyme complex that enables efficient de novo purine biosynthesis during brain development. Here we identified the mouse Nwd2 gene, which is a paralog of Nwd1. A molecular phylogenetic analysis suggested that Nwd1 emerged during the early evolution of the animal kingdom, and that Nwd2 diverged in the process of Nwd1 duplication. RT-PCR and in situ hybridization analyses revealed the unique expression profile of Nwd2 in the developing and adult CNS. Unlike Nwd1, Nwd2 expression was primarily confined to neurons in the medial habenular nucleus, an essential modulating center for diverse psychological states, such as fear, anxiety, and drug addiction. In the adult brain, Nwd2 expression, albeit at a lower level, was also observed in some neuronal populations in the piriform cortex, hippocampus, and substantia nigra pars compacta. NWD2 might play a unique role in the signal transduction required for specific neuronal circuits, especially for cholinergic neurons in the habenula.

Never in Mitosis Kinase 2 regulation of metabolism is required for neural differentiation

Wnt and Hh are known signalling pathways involved in neural differentiation and recent work has shown the cell cycle regulator, Never in Mitosis Kinase 2 (Nek2) is able to regulate both pathways. Despite its known function in pathway regulation, few studies have explored Nek2 within embryonic development. The P19 embryonal carcinoma cell model was used to investigate Nek2 and neural differentiation through CRISPR knockout and overexpression studies. Loss of Nek2 reduced cell proliferation in the undifferentiated state and during directed differentiation, while overexpression increased cell proliferation. Despite these changes in proliferation rates, Nek2 deficient cells maintained pluripotency markers after neural induction while Nek2 overexpressing cells lost these markers in the undifferentiated state. Nek2 deficient cells lost the ability to differentiate into both neurons and astrocytes, although Nek2 overexpressing cells enhanced neuron differentiation at the expense of astrocytes. Hh and Wnt signalling were explored, however there was no clear connection between Nek2 and these pathways causing the observed changes to differentiation phenotypes. Mass spectrometry was also used during wildtype and Nek2 knockout cell differentiation and we identified reduced electron transport chain components in the knockout population. Immunoblotting confirmed the loss of these components and additional studies showed cells lacking Nek2 were exclusively glycolytic. Interestingly, hypoxia inducible factor 1α was stabilized in these Nek2 knockout cells despite culturing them under normoxic conditions. Since neural differentiation requires a metabolic switch from glycolysis to oxidative phosphorylation, we propose a mechanism where Nek2 prevents HIF1α stabilization, thereby allowing cells to use oxidative phosphorylation to facilitate neuron and astrocyte differentiation.

Logistics of neuronal protein turnover: Numbers and mechanisms

Research in the past twenty years or so has revealed that neurons synthesize and degrade proteins at their synapses to enable synaptic proteome remodelling on demand and in real-time. Here we provide a quantitative overview of the decentralized neuronal protein-turnover logistics. We first analyse the huge neuronal protein turnover demand that arises from subcellular compartments outside the cell body, followed by an overview of key quantities and modulation strategies in neuronal protein turnover logistics. In the end, we briefly review recent progress in neuronal local protein synthesis and summarize diverse protein-degradation mechanisms that are found near synapses.

Excitatory Dysfunction Drives Network and Calcium Handling Deficits in 16p11.2 Duplication Schizophrenia Induced Pluripotent Stem Cell-Derived Neurons

BACKGROUND

Schizophrenia (SCZ) is a debilitating psychiatric disorder with a large genetic contribution; however, its neurodevelopmental substrates remain largely unknown. Modeling pathogenic processes in SCZ using human induced pluripotent stem cell-derived neurons (iNs) has emerged as a promising strategy. Copy number variants confer high genetic risk for SCZ, with duplication of the 16p11.2 locus increasing the risk 14.5-fold.

METHODS

To dissect the contribution of induced excitatory neurons (iENs) versus GABAergic (gamma-aminobutyric acidergic) neurons (iGNs) to SCZ pathophysiology, we induced iNs from CRISPR (clustered regularly interspaced short palindromic repeats)-Cas9 isogenic and SCZ patient-derived induced pluripotent stem cells and analyzed SCZ-related phenotypes in iEN monocultures and iEN/iGN cocultures.

RESULTS

In iEN/iGN cocultures, neuronal firing and synchrony were reduced at later, but not earlier, stages of in vitro development. These were fully recapitulated in iEN monocultures, indicating a primary role for iENs. Moreover, isogenic iENs showed reduced dendrite length and deficits in calcium handling. iENs from 16p11.2 duplication-carrying patients with SCZ displayed overlapping deficits in network synchrony, dendrite outgrowth, and calcium handling. Transcriptomic analysis of both iEN cohorts revealed molecular markers of disease related to the glutamatergic synapse, neuroarchitecture, and calcium regulation.

CONCLUSIONS

Our results indicate the presence of 16p11.2 duplication-dependent alterations in SCZ patient-derived iENs. Transcriptomics and cellular phenotyping reveal overlap between isogenic and patient-derived iENs, suggesting a central role of glutamatergic, morphological, and calcium dysregulation in 16p11.2 duplication-mediated pathogenesis. Moreover, excitatory dysfunction during early neurodevelopment is implicated as the basis of SCZ pathogenesis in 16p11.2 duplication carriers. Our results support network synchrony and calcium handling as outcomes directly linked to this genetic risk variant.

Neuron matters: neuromodulation with electromagnetic stimulation must consider neurons as dynamic identities

Neuromodulation with electromagnetic stimulation is widely used for the control of abnormal neural activity, and has been proven to be a valuable alternative to pharmacological tools for the treatment of many neurological diseases. Tremendous efforts have been focused on the design of the stimulation apparatus (i.e., electrodes and magnetic coils) that delivers the electric current to the neural tissue, and the optimization of the stimulation parameters. Less attention has been given to the complicated, dynamic properties of the neurons, and their context-dependent impact on the stimulation effects. This review focuses on the neuronal factors that influence the outcomes of electromagnetic stimulation in neuromodulation. Evidence from multiple levels (tissue, cellular, and single ion channel) are reviewed. Properties of the neural elements and their dynamic changes play a significant role in the outcome of electromagnetic stimulation. This angle of understanding yields a comprehensive perspective of neural activity during electrical neuromodulation, and provides insights in the design and development of novel stimulation technology.

Correlative nano-imaging of metals and proteins in primary neurons by synchrotron X-ray fluorescence and STED super resolution microscopy: Experimental validation

BACKGROUND

It is becoming increasingly clear that biological metals such as iron, copper or zinc are involved in synaptic functions, and in particular in the mechanisms of synaptogenesis and subsequent plasticity. Understanding the role of metals on synaptic functions is a difficult challenge due to the very low concentration of these elements in neurons and to the submicrometer size of synaptic compartments.

NEW METHOD

To address this challenge we have developed a correlative nano-imaging approach combining metal and protein detection. First, stimulated emission depletion (STED) microscopy, a super resolution optical microscopy technique, is applied to locate fluorescently labeled proteins. Then, synchrotron radiation induced X-ray fluorescence (SXRF) is performed on the same regions of interest, e.g. synaptic compartments.

RESULTS

We present here the principle scheme that allows this correlative nano-imaging and its experimental validation. We applied this correlative nano-imaging to the study of the physiological distribution of metals in synaptic compartments of primary rat hippocampal neurons. We thus compared the nanometric distribution of metals with that of synaptic proteins, such as PSD95 or cytoskeleton proteins.

COMPARISON WITH EXISTING METHOD(S)

Compared to correlative imaging approaches currently used to characterize synaptic structures, such as electron microscopy correlated with optical fluorescence, our approach allows for ultra-sensitive detection of trace metals using highly focused synchrotron radiation beams.

CONCLUSION

We provide proof-of-principle for correlative imaging of metals and proteins at the synaptic scale and discuss the present limitations and future developments in this area.

CDGSH iron sulfur domain 2 mitigates apoptosis, oxidative stress and inflammatory response caused by oxygen-glucose deprivation/reoxygenation in HT22 hippocampal neurons by Akt-Nrf2-activated pathway

CDGSH iron sulfur domain 2 (Cisd2) is known as a key determinant factor in maintaining cellular homeostasis. However, whether Cisd2 contributes to the mediation of neuronal injury during ischemic stroke has not been well stressed. This work focuses on investigating the role of Cisd2 in regulating neuronal injury caused by oxygen-glucose deprivation/reoxygenation (OGD/R). The dramatic down-regulation of Cisd2 was observed in hippocampal neurons suffering from OGD/R injury. In Cisd2-overexpressed neurons, OGD/R-induced neuronal apoptosis, oxidative stress and inflammation were prominently mitigated. Further investigation uncovered that the forced expression of Cisd2 reinforced the activation of nuclear factor erythroid 2-related factor 2 (Nrf2) pathway in OGD/R-exposed neurons. Moreover, the overexpression of Cisd2 enhanced Akt activation, and the restraint of Akt abolished Cisd2-induced Nrf2 activation. Importantly, restraint of Nrf2 reversed Cisd2-conferred neuroprotective effects in OGD/R-exposed neurons. Taken together, our findings indicate that Cisd2 is able to protect neurons from OGD/R-induced injuries by strengthening Nrf2 activation via Akt. Our work identifies Cisd2 as a potential determinant factor for neuronal injury during cerebral ischemia/reperfusion injury.

Protective effect of ginsenoside Rh2 against Toxoplasma gondii infection-induced neuronal injury through binding TgCDPK1 and NLRP3 to inhibit microglial NLRP3 inflammasome signaling pathway

BACKGROUND

Toxoplasma gondii (T. gondii) is a neurotropic obligate intracellular parasite that can activate microglial and promote neuronal apoptosis, leading to central nervous system diseases. The NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome signaling complex plays a key role in inducing neuroinflammation. Our previous studies have found that ginsenoside Rh2 (GRh2) inhibits T. gondii infection-induced microglial activation and neuroinflammation by downregulating the Toll-like receptor 4/nuclear factor-kappa B signaling pathway. However, whether GRh2 reduces T. gondii infection-induced neuronal injury through actions on microglial NLRP3 inflammasome signaling has not yet been clarified.

METHODS

In this study, we employed T. gondii RH strain to establish in vitro and in vivo infection models in BV2 microglia cell line and BALB/c mice. Molecular docking, localized surface plasmon resonance assay, quantitative competitive-PCR, ELISA, western blotting, flow cytometric analysis, and immunofluorescence were performed.

RESULTS

Our results showed that GRh2 alleviated neuropathological damage and neuronal apoptosis in cortical tissue of T. gondii-infected mice. GRh2 and CY-09 (an inhibitor of NLRP3) exhibited potent anti-T. gondii effects through binding T. gondii calcium-dependent protein kinase 1 (TgCDPK1). GRh2 decreased Iba-1 (a specific microglial marker) and NLRP3 inflammasome signaling pathway-related protein expression by binding NLRP3. Co-culture of microglia/primary cortical neurons revealed that T. gondii-induced microglial activation caused neuronal apoptosis, but GRh2 reduced this effect, consistent with the effects of CY-09.

CONCLUSION

Taken together, our results show that GRh2 has a protective effect against T. gondii infection-induced neuronal injury by binding TgCDPK1 and NLRP3 to inhibit NLRP3 inflammasome signaling pathway in microglia.

Seeing Is Perceiving (Believing)

Our perception of distinct structures in brain cells and understanding of their function has been revised and updated overtime. Past approaches combined with current powerful technologies provide a more complete picture of the brain's organization, from how the neurons connect with each other to finer details of every corner inside the neurons.

Prenatal exposure to Cannabis smoke induces early and lasting damage to the brain

Cannabis is the most widely used illegal drug during pregnancy, however, the effects of gestational exposure to Cannabis smoke (CS) on the central nervous system development remain uncharacterised. This study investigates the effects of maternal CS inhalation on brain function in the offspring. Pregnant mice were exposed daily to 5 min of CS during gestational days (GD) 5.5-17.5. On GD 18.5 half of the dams were euthanized for foetus removal. The offspring from the remaining dams were euthanized on postnatal days (PND) 20 and 60 for evaluation. Brain volume, cortex cell number, SOX2, histone-H3, parvalbumin, NeuN, and BDNF immunoreactivity were assessed in all groups. In addition, levels of NeuN, CB1 receptor, and BDNF expression were assessed and cortical primary neurons from rats were treated with Cannabis smoke extract (CSE) for assessment of cell viability. We found that male foetuses from the CS exposed group had decreased brain volume, whereas mice at PND 60 from the exposed group presented with increased brain volume. Olfactory bulb and diencephalon volume were found lower in foetuses exposed to CS. Mice at PND 60 from the exposed group had a smaller volume in the thalamus and hypothalamus while the cerebellum presented with a greater volume. Also, there was an increase in cortical BDNF immunoreactivity in CS exposed mice at PND 60. Protein expression analysis showed an increase in pro-BDNF in foetus brains exposed to CS. Mice at PND 60 presented an increase in mature BDNF in the prefrontal cortex (PFC) in the exposed group and a higher CB1 receptor expression in the PFC. Moreover, hippocampal NeuN expression was higher in adult animals from the exposed group. Lastly, treatment of cortical primary neurons with doses of CSE resulted in decreased cell viability. These findings highlight the potential negative neurodevelopmental outcomes induced by gestational CS exposure.

Redox biology in neurodegenerative disorders

Oxidative stress and alteration of redox signaling is shown to be involved in the mechanism of neuronal loss in the most of neurodegenerative diseases. This Special Issue features seven review articles that cover major aspects of the changes of redox biology in the mechanism of pathology of neurodegenerative diseases and discusses possible ways for prevention.

Glial-neuron crosstalk in health and disease: A focus on metabolism, obesity, and cognitive impairment

Dementia is a complex set of disorders affecting normal cognitive function. Recently, several clinical studies have shown that diabetes, obesity, and components of the metabolic syndrome (MetS) are associated with cognitive impairment, including dementias such as Alzheimer's disease. Maintaining normal cognitive function is an intricate process involving coordination of neuron function with multiple brain glia. Well-orchestrated bioenergetics is a central requirement of neurons, which need large amounts of energy but lack significant energy storage capacity. Thus, one of the most important glial functions is to provide metabolic support and ensure an adequate energy supply for neurons. Obesity and metabolic disease dysregulate glial function, leading to a failure to respond to neuron energy demands, which results in neuronal damage. In this review, we outline evidence for links between diabetes, obesity, and MetS components to cognitive impairment. Next, we focus on the metabolic crosstalk between the three major glial cell types, oligodendrocytes, astrocytes, and microglia, with neurons under physiological conditions. Finally, we outline how diabetes, obesity, and MetS components can disrupt glial function, and how this disruption might impair glia-neuron metabolic crosstalk and ultimately promote cognitive impairment.

Decoding transcriptional signatures of the association between free water and macroscale organizations in healthy adolescents

We leveraged a novel index of diffusion MRI to investigate the relationships among cortical free water, macro-organizations and gene expression in healthy adults. Few research has been conducted to investigate the role of free water in the healthy adults due to it can easily be affected also by aging diseases. High quality data of 350 subjects from Human Connectome Project were used in our study. Cortical free water was estimated by using a bi-tensor model. The free water was high in the limbic, insular and somatosensory cortex, while being lower in motor and association cortex. The negative correlation between the free water and cortical thickness has been consistently identified in almost all the cortical regions. Negative correlation between the cortical free water and structural covariance (rho=-0.38, p_spin=0.005) revealed the free water was sensitive to cortical heterogeneity. Using human gene expression dataset, we found the gene expression pattern of the relationship between the free water and cortical thickness spatially coupled with primary gradient of structural covariance network (rho=0.40, p_spin=0.004). Our findings indicated the free water was sensitive to the cortical cellular status. The relationship between free water and macroscale organization also reflected hierarchal structures of cerebral cortex.

Combination Therapy Using Nanomaterials and Stem Cells to Treat Spinal Cord Injuries

As a part of the central nervous system, the spinal cord (SC) provides most of the communications between the brain and other parts of the body. Any damage to SC interrupts this communication, leading to serious problems, which may remain for the rest of their life. Due to its significant impact on patients' quality of life and its exorbitant medical costs, SC injury (SCI) is known as one of the most challengeable diseases in the world. Thus, it is critical to introduce highly translatable therapeutic platforms for SCI treatment. So far, different strategies have been introduced, among which utilizing various types of stem cells is one of the most interesting ones. The capability of stem cells to differentiate into several types of cell lines makes them promising candidates for the regeneration of injured tissues. One of the other interesting and novel strategies for SCI treatment is the application of nanomaterials, which could appear as a carrier for therapeutic agents or as a platform for culturing the cells. Combining these two approaches, stem cells and nanomaterials, could provide promising therapeutic strategies for SCI management. Accordingly, in this review we have summarized some of the recent advancements in which the applications of different types of stem cells and nanomaterials, alone and in combination forms, were evaluated for SCI treatment.

Correlative imaging to resolve molecular structures in individual cells: Substrate validation study for super-resolution infrared microspectroscopy

Light microscopy has been a favorite tool of biological studies for almost a century, recently producing detailed images with exquisite molecular specificity achieving spatial resolution at nanoscale. However, light microscopy is insufficient to provide chemical information as a standalone technique. An increasing amount of evidence demonstrates that optical photothermal infrared microspectroscopy (O-PTIR) is a valuable imaging tool that can extract chemical information to locate molecular structures at submicron resolution. To further investigate the applicability of sub-micron infrared microspectroscopy for biomedical applications, we analyzed the contribution of substrate chemistry to the infrared spectra acquired from individual neurons grown on various imaging substrates. To provide an example of correlative immunofluorescence/O-PTIR imaging, we used immunofluorescence to locate specific organelles for O-PTIR measurement, thus capturing molecular structures at the sub-cellular level directly in cells, which is not possible using traditional infrared microspectroscopy or immunofluorescence microscopy alone.

Immature Brain Cortical Neurons Have Low Transcriptional Competence to Activate Antiviral Defences and Control RNA Virus Infections

Virus infections of the central nervous system (CNS) cause important diseases of humans and animals. As in other tissues, innate antiviral responses mediated by type I interferons (IFNs) are crucially important in controlling CNS virus infections. The maturity of neuronal populations is an established critical factor determining the outcome of CNS virus infection. Using primary cultures of mouse cortical neurons, we investigated the relationships between neuronal maturation, type I IFN responses, and the outcome of Semliki Forest virus infection. The virus replicated better, infected more cells, and produced higher titres of infectious viruses in immature neurons. Complete transcriptome analysis demonstrated that resting immature neurons have low transcriptional competence to mount antiviral responses. They had no detectable transcription of the genes Ddx58 and Ifih1, which encode key RNA virus cytoplasmic sensors RIG-I and MDA5, and very low expression of genes encoding key regulators of associated signalling pathways. Upon infection, immature neurons failed to mount an antiviral response as evidenced by their failure to produce chemokines, IFNs, and other cytokines. Treatment of immature neurons with exogenous IFNβ prior to infection resulted in antiviral responses and lower levels of virus replication and infectious virus production. In contrast, resting mature neurons generated a robust antiviral response. This was augmented by pretreatment with IFNβ. Infection of mature neurons derived from IFNAR-/- mice did not make an antiviral response and replicated virus to high levels.

miR-451a Regulates Neuronal Apoptosis by Modulating 14-3-3ζ-JNK Axis upon Flaviviral Infection

Japanese Encephalitis Virus (JEV)/West Nile Virus (WNV)-induced encephalitis, although observed in selective cases, is associated with fatal consequences ranging from decline in cognitive abilities among recovered patients to coma/death. Loss of neuronal cells following viral infection-induced neuronal death imposes significant challenge to the central nervous system (CNS) homeostasis eventually resulting in loss of CNS tissue integrity and poor disease outcome in patients. In our present study, we aim to evaluate the role played by miRNA in modulating neuronal death upon neurotropic flaviviral infections. Infection of neuronal cell line resulted in upregulation of miR-451a abundance. Upon its upregulation, miR-451a has been demonstrated to target 3′-UTR of 14-3-3ζ transcript culminating into downregulation of 14-3-3ζ at the protein level. In response to 14-3-3ζ protein depletion in the cytosol upon flavivirus infection, increased phosphorylation of JNK protein has been shown to take place thus paving way for the cell to undergo apoptosis. Reversal of virus-induced miR-451a-upregulation helped abrogate neuronal apoptosis which is accompanied by a restoration of 14-3-3ζ protein and phosphorylated-JNK abundance to its normal level. Our findings hence provide a possible therapeutic target for preventing JEV/WNV-induced neuronal apoptosis thus improving disease outcome in flaviviral infection-associated encephalitis.

IMPORTANCE Neuronal infection by JEV/WNV culminates into neuronal cell death thus contributing to signs and symptoms exhibited by patients that suffer from and that have recovered from JEV/WNV-induced encephalitis. In the present study we have evaluated the role of miRNA in promoting flavivirus-induced neuronal apoptosis. miR-451a has been demonstrated to promote neuronal cell death by targeting 14-3-3ζ protein function. The function of miR-451a in modulating neuronal physiology toward self-destruction has been shown to be independent of its effect upon the virus infection life cycle. The 14-3-3ζ transcript upon being targeted by miR-451a promotes JNK phosphorylation hence culminating into neuronal death by activation of apoptotic machinery. Inhibition of miR-451a upon neuronal infection by JEV/WNV helped reduce apoptotic machinery activation hence providing us with possible future therapeutic strategy in ameliorating flavivirus-induced neurological manifestations and overall disease burden in terms of morbidity.

Ferroptosis participates in neuron damage in experimental cerebral malaria and is partially induced by activated CD8+ T cells

Cerebral malaria is the most serious complication of malaria infection, with 26% of surviving children having neurological sequelae, which may be caused by neuron damage, but the mechanism is not clear. Ferroptosis has been reported to play an important role in neuron damage in several nervous system diseases. However, the occurrence of ferroptosis in experimental cerebral malaria (ECM) pathogenesis is still unknown. In this study, we firstly detected increased levels of malondialdehyde (MDA) and iron, which are indicators of ferroptosis, in the cerebrum of ECM mice. Some important regulators of ferroptosis, including upregulated expression of transferrin receptor 1 (TfR1) and acyl-CoA synthetase long-chain family member 4 (ACSL4), and downregulation of glutathione peroxidase 4 (GPX4) levels, were also confirmed in ECM mice. Consistently, neuron damage, which was detected in the cerebrum of ECM mice, was positively correlated with reduced GPX4 expression and furtherly rescued by administration of the ferroptosis inhibitor ferrostatin-1 (Fer-1). In addition, primary neurons were damaged by activated CD8⁺ T cells, an effect that was also partially rescued by Fer-1 on amyloid precursor protein expression and mitochondrial membrane potential levels in vitro. Activated CD8⁺ T cells were also shown to infiltrate the cerebrum of ECM mice and upregulate TfR1 expression in primary neurons, which may be an important event for inducing ferroptosis in ECM. Altogether, we show that ferroptosis contributes to neuron damage in ECM pathogenesis, and activated CD8⁺ T cells may be important inducers of neuronal ferroptosis. Hence, targeting ferroptosis may be a promising adjuvant therapeutic strategy for neurological sequelae in patients with cerebral malaria.

Neurological sequela and disruption of neuron-glia homeostasis in SARS-CoV-2 infection

The coronavirus disease 2019 (COVID-19) pandemic is responsible for 267 million infections and over 5 million deaths globally. COVID-19 is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a single-stranded RNA beta-coronavirus, which causes a systemic inflammatory response, multi-organ damage, and respiratory failure requiring intubation in serious cases. SARS-CoV-2 can also trigger neurological conditions and syndromes, which can be long-lasting and potentially irreversible. Since COVID-19 infections continue to mount, the burden of SARS-CoV-2-induced neurologic sequalae will rise in parallel. Therefore, understanding the spectrum of neurological clinical presentations in SARS-CoV-2 is needed to manage COVID-19 patients, facilitate diagnosis, and expedite earlier treatment to improve outcomes. Furthermore, a deeper knowledge of the neurological SARS-CoV-2 pathomechanisms could uncover potential therapeutic targets to prevent or mitigate neurologic damage secondary to COVID-19 infection. Evidence indicates a multifaceted pathology involving viral neurotropism and direct neuroinvasion along with cytokine storm and neuroinflammation leading to nerve injury. Importantly, pathological processes in neural tissue are non-cell autonomous and occur through a concerted breakdown in neuron-glia homeostasis, spanning neuron axonal damage, astrogliosis, microgliosis, and impaired neuron-glia communication. A clearer mechanistic and molecular picture of neurological pathology in SARS-CoV-2 may lead to effective therapies that prevent or mitigate neural damage in patients contracting and developing severe COVID-19 infection.

Genome-wide translation control analysis of developing human neurons

During neuronal differentiation, neuroprogenitor cells become polarized, change shape, extend axons, and form complex dendritic trees. While growing, axons are guided by molecular cues to their final destination, where they establish synaptic connections with other neuronal cells. Several layers of regulation are integrated to control neuronal development properly. Although control of mRNA translation plays an essential role in mammalian gene expression, how it contributes temporarily to the modulation of later stages of neuronal differentiation remains poorly understood. Here, we investigated how translation control affects pathways and processes essential for neuronal maturation, using H9-derived human neuro progenitor cells differentiated into neurons as a model. Through Ribosome Profiling (Riboseq) combined with RNA sequencing (RNAseq) analysis, we found that translation control regulates the expression of critical hub genes. Fundamental synaptic vesicle secretion genes belonging to SNARE complex, Rab family members, and vesicle acidification ATPases are strongly translationally regulated in developing neurons. Translational control also participates in neuronal metabolism modulation, particularly affecting genes involved in the TCA cycle and glutamate synthesis/catabolism. Importantly, we found translation regulation of several critical genes with fundamental roles regulating actin and microtubule cytoskeleton pathways, critical to neurite generation, spine formation, axon guidance, and circuit formation. Our results show that translational control dynamically integrates important signals in neurons, regulating several aspects of its development and biology.

Dipeptidylamino-tripeptidylcarboxypeptidase NEMP3 and DPP3 (DPP III) are the same protein

Earlier it was shown that a group of extracellular low-specific metallopeptidases is present in the mammalian brain Kropotova and Mosevitsky (2016) [1]. These enzymes are weakly connected to the axonal ends of neurons. They were named Neuron bound Extracellular MetalloPeptidases (NEMP). The enzyme named NEMP3 turned out to be a unique exopeptidase that exhibits two activities: it removes the dipeptide from the N-end of the peptide, and it can also remove the tripeptide from the C-end of the peptide. Therefore, NEMP3 possesses the activities of dipeptidylaminopeptidase and of tripeptidylcarboxypeptidase. Mass spectrometry has revealed a homology of NEMP3 with DPP3 (DPP III, EC3.4.14.4), known as cytosolic dipeptidylaminopeptidase. We isolated DPP3 from rat and bovine liver and brain by the procedures used for this purpose by other authors. The effect of DPP3 on test peptides is the same as that of NEMP3. In particular, all DPP3 samples delete the tripeptide (AKF) from the C-end of the test peptide blocked at the N-end. The data obtained show that NEMP3 and DPP3 are the same protein (enzyme). Thus, DPP3 has two exopeptidase activities: the previously known activity of dipeptidylaminopeptidase and the activity of tripeptidylcarboxypeptidase discovered in this study. Another discovery is the extracellular activity of DPP 3 in the mammalian brain near synapses, which controls neuropeptides. DPP3 is involved in various processes, but in many cases its role remains to be clarified. The results obtained in this study will be useful for solving these questions.

Elevation of N-acetyltransferase 10 in hippocampal neurons mediates depression- and anxiety-like behaviors

Major depressive disorder (MDD) is one of the most debilitating and severe mental diseases globally. Increasing evidence has shown that epigenetics is critical for understanding brain function and brain disorders, including MDD. N-acetyltransferase 10 (NAT10), acting on histones, mRNA and other substrates, has been reported to be involved in epigenetic events, including histone acetylation and mRNA modifications. NAT10 is highly expressed in the brain. However, the potential effects of NAT10 on MDD are still unknown. Here, we exploited chronic mild stress (CMS) to induce anxiety- and depression-like behaviors in mice and found that the expression of NAT10 in the mouse hippocampus was upregulated after CMS treatment. Inhibition of NAT10 by pharmacological methods produced anxiolytic- and antidepressant-like effects. Neuron-specific overexpression of NAT10 in the hippocampus resulted in anxiety- and depression-like behaviors, accompanied by higher SIRT1 protein levels, and lower dendritic spine densities. Overall, it was found that elevation of NAT10 in hippocampal neurons is involved in the occurrence of anxiety- and depression-like behaviors, suggesting that NAT10 could be a potential new target for developing anxiolytics and antidepressants.

Improvement of synaptic plasticity by nanoparticles and the related mechanisms: Applications and prospects

Synaptic plasticity is an important basis of learning and memory and participates in brain network remodelling after different types of brain injury (such as that caused by neurodegenerative diseases, cerebral ischaemic injury, posttraumatic stress disorder (PTSD), and psychiatric disorders). Therefore, improving synaptic plasticity is particularly important for the treatment of nervous system-related diseases. With the rapid development of nanotechnology, increasing evidence has shown that nanoparticles (NPs) can cross the blood-brain barrier (BBB) in different ways, directly or indirectly act on nerve cells, regulate synaptic plasticity, and ultimately improve nerve function. Therefore, to better elucidate the effect of NPs on synaptic plasticity, we review evidence showing that NPs can improve synaptic plasticity by regulating different influencing factors, such as neurotransmitters, receptors, presynaptic membrane proteins and postsynaptic membrane proteins, and further discuss the possible mechanism by which NPs improve synaptic plasticity. We conclude that NPs can improve synaptic plasticity and restore the function of damaged nerves by inhibiting neuroinflammation and oxidative stress, inducing autophagy, and regulating ion channels on the cell membrane. By reviewing the mechanism by which NPs regulate synaptic plasticity and the applications of NPs for the treatment of neurological diseases, we also propose directions for future research in this field and provide an important reference for follow-up research.

Neuronal miR-29a protects from obesity in adult mice

Objective

Obesity, a growing threat to the modern society, represents an imbalance of metabolic queues that normally signal to the arcuate hypothalamic nucleus, a critical brain region sensing and regulating energy homeostasis. This is achieved by various neurons many of which developmentally originate from the proopiomelanocortin (POMC)-expressing lineage. Within the mature neurons originating from this lineage, we aimed to identify non-coding genes in control of metabolic function in the adulthood.

Methods

In this work, we used microRNA mimic delivery and POMC^Cre-dependent CRISPR-Cas9 knock-out strategies in young or aged mice. Importantly, we also used CRISPR guides directing suicide cleavage of Cas9 to limit the off-target effects.

Results

Here we found that mature neurons originating from the POMC lineage employ miR-29a to protect against insulin resistance obesity, hyperphagia, decreased energy expenditure and obesity. Moreover, we validated the miR-29 family as a prominent regulator of the PI3K-Akt-mTOR pathway. Within the latter, we identified a direct target of miR-29a-3p, Nras, which was up-regulated in those and only those mature POMC^CreCas9 neurons that were effectively transduced by anti-miR-29 CRISPR-equipped construct. Moreover, POMC^Cre-dependent co-deletion of Nras in mature neurons attenuated miR-29 depletion-induced obesity.

Conclusions

Thus, the first to our knowledge case of in situ Cre-dependent CRISPR-Cas9-mediated knock-out of microRNAs in a specific hypothalamic neuronal population helped us to decipher a critical metabolic circuit in adult mice. This work significantly extends our understanding about the involvement of neuronal microRNAs in homeostatic regulation.

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Delivery of miR-29a-3p to the arcuate hypothalamic nucleus attenuates obesity.

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Knock-out of genes in mature neurons by Cre-dependent CRISPR/Cas9 technique involving Cas9-cleaving sgRNAs to limit off-target effects.

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Deletion of miR-29a in mature Pomc^Cre neurons leads to early-onset insulin resistance and later to hyperphagia and decreased energy expenditure.

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POMC^Cre-restricted deletion of miR-29a causes cell-autonomous Nras up-regulation leading to obesity.

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POMC^Cre-restricted knock-out of Nras, a direct target of miR-29a-3p, attenuates obesity in mice.

Failed regeneration and inflammation in schizophrenia: two sides of the same coin?

More than 100 years after its conceptual definition as 'Dementia Praecox' by Emil Kraepelin, which was changed to schizophrenia by Eugen Bleuler, this is still a serious and debilitating psychiatric illness. The neurodevelopmental hypothesis of schizophrenia, introduced more than 30 years ago, states that schizophrenia is a consequence of failed neurodevelopmental processes leading to a dysfunctional neuronal network forming the basis for a psychosis proneness. Subsequently, significant research efforts were made to prove the neurodevelopmental or the neurodegenerative perspective. This review summarizes key arguments speaking for or against the two hypotheses leading to a concept with both aspects position side by side.

Vitamin D3 suppresses astrocyte activation and ameliorates coal dust-induced mood disorders in mice

BACKGROUND

Pneumoconiosis patients exhibit significantly more anxiety and depression than healthy individuals. However, the mechanism of coal dust-induced anxiety and depression remains unclear.

METHODS

A pneumoconiosis mouse model with anxiety- and depression-like behaviors were established after 28 days of exposure to coal dust. Vitamin D3 treatment (1200 IU/kg/week) was administered intraperitoneally for 3 months starting from the first coal exposure. Tail suspension test (TST), open field test (OFT), and elevated plus-maze (EPM) test were used to assess anxiety- and depression-like behaviors. Theserum concentration of 25(OH)D₃ and fibrillary acid protein (GFAP) expression were determined. In addition, the morphology and distribution of GFAP and neurogenic differentiation factor1 expression (NeuroD1) in different cerebral hippocampus were observed.

RESULTS

In coal dust-exposed mice, immobility time decreased in OFT and increased in TST,and the frequency of entering the open arm decreased in the EPM compared with the control mice. Coal dust increased hippocampal GFAP expression and astrocyte activation and reduced neurogenic differentiation factor1 expression (NeuroD1). In addition, Vitamin D3 significantly alleviated anxiety- and depressive-like behaviors in TST and EPM test, decreased GFAP expression level, modified hippocampal astrocyte activation pattern, and advanced brain-derived neurotrophic factor (BDNF) distribution and expression in CA1 and CA3 of the hippocampus.

CONCLUSIONS

Taken together, our results suggest that, by inhibiting the over-activation of astrocytes and increasing BDNF and neuron protection, vitamin D treatment ameliorates coal-dust-induced depressive and anxiety-like behavior, which is the first evidence that vitamin D may be a new approach for treating mood disorders caused by particulate matter.

Morphological and electrophysiological evidences of synaptic switching in vestibular nerve of land snail Helix lucorum L

It is well known that the initiation of the reflex arcs of the vertebrate vestibular system occurs in the receptors of the labyrinthine organs which transmit the sensory signals via the ribbon synapses to the vestibular nerve afferents (an interneuron). In invertebrate species, and in particular, the statocyst of pulmonate mollusks, it is thought that the receptors send their axons out of the statocyst in the vestibular connective and establish the first synapse onto cerebral ganglia neurons, thereby bypassing the interneuron in the reflex arc. Morphological and electrophysiological techniques were used in this study to identify the first synapse in the vestibular arc of the mollusk Helix is actually within the vestibular connective on its way from the statocyst to cerebral ganglia. Cerebral interneurons were found that sent their neurites to the vestibular nerve, and thus have the potential to respond to the statocyst output or send efferent input to the statocyst.

Visualising the cytoskeletal machinery in neuronal growth cones using cryo-electron tomography

Neurons extend axons to form the complex circuitry of the mature brain. This depends on the coordinated response and continuous remodelling of the microtubule and F-actin networks in the axonal growth cone. Growth cone architecture remains poorly understood at nanoscales. We therefore investigated mouse hippocampal neuron growth cones using cryo-electron tomography to directly visualise their three-dimensional subcellular architecture with molecular detail. Our data showed that the hexagonal arrays of actin bundles that form filopodia penetrate and terminate deep within the growth cone interior. We directly observed the modulation of these and other growth cone actin bundles by alteration of individual F-actin helical structures. Microtubules with blunt, slightly flared or gently curved ends predominated in the growth cone, frequently contained lumenal particles and exhibited lattice defects. Investigation of the effect of absence of doublecortin, a neurodevelopmental cytoskeleton regulator, on growth cone cytoskeleton showed no major anomalies in overall growth cone organisation or in F-actin subpopulations. However, our data suggested that microtubules sustained more structural defects, highlighting the importance of microtubule integrity during growth cone migration.

Summary: Cryo-electron tomographic reconstruction of neuronal growth cone subdomains reveals distinctive F-actin and microtubule cytoskeleton architectures and modulation at molecular detail.

In Times of Adversity: A Neuroscience Perspective on Stress, Health, and Implications for Society Post-pandemic

The relationship between chronic stress and chronic disease (including mental illness) is well established: HPA-axis hyperactivity leads to hormonal dysregulation of primary mediators (eg, glucocorticoids, cytokines, etc.), allostatic overload, and neurological degradation, followed by clinical manifestations of disease. Amid the largest public health crisis of the century lay a myriad of challenges pushing people beyond their limit. From experiencing loss of connection or dealing with loss of life to financial shocks of COVID-19 lockdowns or infection by the SARS-CoV-2 virus, stress is at an all-time high, threatening both brain and mental health at scale. Fortunately, there is a way forward: the neuroscience of resilience teaches us that it is possible to resist, recover, and redirect the brain from trauma to re-establish balance in the body and improve well-being. At the same time, health follows a social gradient: adverse and protective psychosocial factors are shaped by wider social and economic determinants of health. This paper argues the neurobiology of stress is not separate from health disparities linked to adverse factors (ie, stress) created by complex social and economic contexts. Therefore, the field of neuroscience is challenged to inform multi-context and multi-level approaches and engage with decision-makers to enact policies and interventions aimed at promoting the resilient element in a wider population health context. Undoubtedly, achieving such a goal for current and future generations to benefit and lead healthier lives requires a heroic effort from all key stakeholders. The cost of willful neglect to resolve these issues is too expensive.

Chronic microglial inflammation promotes neuronal lactate supply but impairs its utilization in primary rat astrocyte-neuron co-cultures

Neuronal activity is closely associated with energy metabolism. In addition to glucose, astrocyte-derived lactate serves as an energy source for neurons. Chronic inflammation is a common pathological event that is associated with aging and neurodegenerative diseases. However, the mechanisms underlying inflammation-induced neuronal injury are not fully understood. Both microglia and astrocytes participate in the regulation of neuronal functions; therefore, we used astrocyte-neuron co-cultures to investigate the effects of chronic microglial activation on neuronal lactate metabolism. Chronic low-grade inflammation was induced by repeated stimulation of primary rat microglia with low-dose lipopolysaccharide (LPS, 10 ng/mL). The medium from the LPS-activated microglia was collected and used to mimic the inflammatory environment in primary cultures. In monocultures exposed to an inflammatory environment, intracellular lactate decreased in neurons but increased in astrocytes. However, astrocyte-neuron co-cultures exhibited increased lactate levels in neurons and decreased lactate levels in astrocytes when exposed to an inflammatory environment. Inhibition of lactate transporters expressed on neurons or astrocytes reduced the intracellular lactate in co-cultured neurons exposed to inflammation, but not in those exposed to physiological conditions. Adenosine triphosphate (ATP) production was reduced in both mono-cultured and co-cultured neurons. These results indicate that a chronic inflammatory environment increases neuronal lactate supply by promoting the astrocyte-neuron lactate shuttle, but it impairs lactate oxidation in neurons. Additionally, chronic inflammation disrupts the neuronal cytoskeleton. This study highlights the importance of glial cells in regulating neuroenergetics and neuronal function and provides a comprehensive explanation for the neurotoxic effects of neuroinflammation.

Protective effect of Celastrus paniculatus on cognitive function in glutamate induced brain injured mice by reducing the intracellular influx of Ca. Int J Dev Neurosci 2022;82:331-338. [PMID: 35338672 DOI: 10.1002/jdn.10182] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Present investigation evaluates the protective effect of Celastrus paniculatus (CP) on the cognitive function in neuronal injured mice. Neuronal injury was induced by oral administration of monosodium glutamate (MSG) at a dose of 1.66 g/kg/day for 30 days. Mice in the CP treated group receives CP 30 mg/kg i.p. and CP+GGA treated group received CP 30 mg/kg i.p. and glutamic acid (GGA, 1.5 mg/kg, i.p.) 30 min prior to the administration of MSG for 30 days. Assessment of cognitive function was done using Morris water maze. Level of inflammatory cytokines and production of reactive oxygen species (ROS) was estimated in the brain tissue of brain injured mice. Moreover, intracellular concentration of Ca⁺ ion was estimated in the brain tissue and expression of Bcl-2, Bax and caspase-3 protein was estimated in the brain tissue by western blot assay. Cognitive function was attenuated in CP treated glutamate injured mice. Data of the study suggest that treatment with CP reduces the level of inflammatory cytokines and production of ROS in the brain tissue compared to negative control group. There was reduction in the concentration of Ca⁺ ion in the neuronal cells in CP treated group than negative control group of mice. Treatment with CP ameliorates the expression of Bax, Bcl-2 and caspase-3 in the brain tissue of glutamate induced brain injured mice. In conclusion, data of the study suggest that treatment with CP attenuates the cognitive function and neuronal apoptosis in glutamate induced neuronal injury by reducing the concentration of intracellular Ca⁺ ion.

Microwave radiation induces neuronal autophagy through miR-30a-5p/AMPKα2 signal pathway

The potential health hazards of microwaves have attracted much more attention. Our previous study found that 2856 MHz microwave radiation damaged synaptic plasticity and activated autophagy in neurons. However, the mechanisms underlying microwave-induced autophagy were still unclear. In the present study, we established neuronal damage models by exposing rat hippocampal neurons and rat adrenal pheochromocytoma (PC12) cell-derived neuron-like cells to 30 mW/cm² microwaves, which resulted in miR-30a-5p (‘miR-30a’ for short) down-regulation and autophagy activation in vivo and in vitro. Bioinformatics analysis was conducted, and Beclin1, Prkaa2, Irs1, Pik3r2, Rras2, Ddit4, Gabarapl2 and autophagy-related gene 12 (Atg12) were identified as potential downstream genes of miR-30a involved in regulating autophagy. Based on our previous findings that microwave radiation could lead to abnormal energy metabolism in neurons, Prkaa2, encoding adenosine 5′-monophosphate-activated protein kinase (AMPK) α2 (AMPKα2, an important catalytic subunit of energy sensor AMPK), was selected for further analysis. Dual-luciferase reporter assay results showed that Prkaa2 was a downstream gene of miR-30a. Moreover, microwave radiation increased the expression of AMPKα2 and the phosphorylation of AMPKα (Thr¹⁷²) both in vivo and in vitro. The transfection of PC12 cells with miR-30a mimics increased miR-30a levels, reduced AMPKα2 expression, suppressed AMPKα (Thr¹⁷²) phosphorylation, and inhibited autophagy occurrence in neuron-like cells. Importantly, miR-30a overexpression abolished microwave-activated autophagy and inhibited microwave-induced AMPKα2 up-regulation and AMPKα (Thr¹⁷²) phosphorylation. In conclusion, microwave radiation promoted the occurrence of autophagy in neurons through the miR-30a/AMPKα2 signal pathway.

Innervation in organogenesis

Proper innervation of peripheral organs helps to maintain physiological homeostasis and elicit responses to external stimuli. Disruptions to normal function can result in pathophysiological consequences. The establishment of connections and communication between the central nervous system and the peripheral organs is accomplished through the peripheral nervous system. Neuronal connections with target tissues arise from ganglia partitioned throughout the body. Organ innervation is initiated during development with stimuli being conducted through several types of neurons including sympathetic, parasympathetic, and sensory. While the physiological modulation of mature organs by these nerves is largely understood, their role in mammalian development is only beginning to be uncovered. Interactions with cells in target tissues can affect the development and eventual function of several organs, highlighting their significance. This chapter will cover the origin of peripheral neurons, factors mediating organ innervation, and the composition and function of organ-specific nerves during development. This emerging field aims to identify the functional contribution of innervation to development which will inform future investigations of normal and abnormal mammalian organogenesis, as well as contribute to regenerative and organ replacement efforts where nerve-derived signals may have significant implications for the advancement of such studies.