Publisher：Cold Spring Harbor Laboratory  

Summary

The relationships between microglia and macrophages, especially their lineage segregation outside the yolk sac, have been recently explored, providing a model in which a conversion from macrophages seeds microglia during brain development. However, spatiotemporal evidence to support such microglial seeding and to explain how it occurs has not been obtained. By cell tracking via slice culture, intravital imaging, and Flash tag-mediated labeling, we found that a group of intraventricular macrophages belonging to border-associated macrophages (BAMs), which were abundantly observed along the inner surface of the mouse cerebral wall at embryonic day 12, frequently entered the brain wall. Immunohistochemistry of the tracked cells showed that postinfiltrative BAMs acquired microglial properties while losing a macrophage phenotype. We also found that the intraventricular BAMs were supplied transepithelially from the roof plate. Thus, this study demonstrates that the “roof plate→ventricle→cerebral wall” route is an essential path for microglial colonization into the embryonic mouse brain.

DOI： 10.1101/2022.07.27.501563

Language：English   Publishing type：Research paper (scientific journal)  

Chronic pain is a major public health problem that currently lacks effective treatment options. Here, a method that can modulate chronic pain-like behaviour induced by nerve injury in mice is described. By combining a transient nerve block to inhibit noxious afferent input from injured peripheral nerves, with concurrent activation of astrocytes in the somatosensory cortex (S1) by either low intensity transcranial direct current stimulation (tDCS) or via the chemogenetic DREADD system, we could reverse allodynia-like behaviour previously established by partial sciatic nerve ligation (PSL). Such activation of astrocytes initiated spine plasticity to reduce those synapses formed shortly after PSL. This reversal from allodynia-like behaviour persisted well beyond the active treatment period. Thus, our study demonstrates a robust and potentially translational approach for modulating pain, that capitalizes on the interplay between noxious afferents, sensitized central neuronal circuits, and astrocyte-activation induced synaptic plasticity.

DOI： 10.1038/s41467-022-31773-8

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DOI： 10.1016/j.neures.2022.04.007

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Language：English   Publishing type：Research paper (scientific journal)  

Holographic structured illumination combined with optogenetics enables patterned stimulation of neurons and glial cells in an intact living brain. Moreover, in vivo functional imaging of cellular activity with recent advanced microscope technologies allows for visualization of the cellular responses during learning, emotion and cognition. Integrating these techniques can be used to verify the link between cell function and behavior output. However, there are technical limitations to stimulate multiple cells with high spatial and temporal resolution with available techniques of optogenetic stimulation. Here, we summarized a two-photon microscope combined with holographic system to stimulate multiple cells with high spatial and temporal resolution for living mice and their biological application.

DOI： 10.1016/j.neures.2021.10.012

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Society for Clinical Investigation  

Although immobility is a common cause of muscle atrophy, the mechanism underlying this causality is unclear. We here show that Krüppel-like factor 15 (KLF15) and IL-6 are upregulated in skeletal muscle of limb-immobilized mice and that mice with KLF15 deficiency in skeletal muscle or with systemic IL-6 deficiency are protected from immobility-induced muscle atrophy. A newly developed Ca2+ bioimaging revealed that the cytosolic Ca2+ concentration ([Ca2+]i) of skeletal muscle is reduced to below the basal level by immobilization, which is associated with the downregulation of Piezo1. Acute disruption of Piezo1 in skeletal muscle induced Klf15 and Il6 expression as well as muscle atrophy, which was prevented by antibodies against IL-6. A role for the Piezo1/KLF15/IL-6 axis in immobility-induced muscle atrophy was validated in human samples. Our results thus uncover a paradigm for Ca2+ signaling in that a decrease in [Ca2+]i from the basal level triggers a defined biological event.

DOI： 10.1172/JCI154611

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japanese Society of Veterinary Science  

Neonicotinoid pesticides (NNs) cause behavioral abnormalities in mammals, raising concerns about their effects on neural circuit activity. We herein examined the neurological effects of the NN clothianidin (CLO) by in vivo Ca2+ imaging using two-photon microscopy. Mice were fed the no-observed-adverse-effect-level (NOAEL) dose of CLO for 2 weeks and their neuronal activity in the primary somatosensory cortex (S1) was observed weekly for 2 weeks. CLO exposure caused a sustained influx of Ca2+ in neurons in the S1 2/3 layers, indicating hyperactivation of neurons. In addition, microarray gene expression analysis suggested the induction of neuroinflammation and changes in synaptic activity. These results demonstrate that exposure to the NOAEL dose of CLO can overactivate neurons and disrupt neuronal homeostasis.

DOI： 10.1292/jvms.22-0013

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

Abstract

Neonicotinoid pesticides are a class of insecticides that reportedly have harmful effects on bees and dragonflies, causing a reduction in their numbers. Neonicotinoids act as neuroreceptor modulators, and some studies have reported their association with neurodevelopmental disorders. However, the precise effect of neonicotinoids on the central nervous system has not yet been identified. Herein, we conducted in vivo Ca²⁺ imaging using a two-photon microscope to detect the abnormal activity of neuronal circuits in the brain after neonicotinoid application. The oral administration of acetamiprid (ACE) (20 mg/kg body weight (BW) in mature mice with a quantity less than the no-observed-adverse-effect level (NOAEL) and a tenth or half of the median lethal dose (LD₅₀) of nicotine (0.33 or 1.65 mg/kg BW, respectively), as a typical nicotinic acetylcholine receptor (nAChR) agonist, increased anxiety-like behavior associated with altered activities of the neuronal population in the somatosensory cortex. Furthermore, we detected ACE and its metabolites in the brain, 1 h after ACE administration. The results suggested that in vivo Ca²⁺ imaging using a two-photon microscope enabled the highly sensitive detection of neurotoxicant-mediated brain disturbance of nerves.

DOI： 10.1038/s41598-022-09038-7

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Other Link： https://www.nature.com/articles/s41598-022-09038-7

Language：Japanese   Publisher：Japanese Pharmacological Society  

<p>Visualization (or &quot;Understanding&quot; or &quot;Researchinto&quot;) of physiological and pathological phenomena has taken a leapforward by recent advanced optical bio imaging technique. Traditionally,physiological phenomena including cell division, cell function, moleculartransport and cell death were detected by biochemical methods. However, thisinformation lacked high resolution spatial and temporal information. Usingrecent optical techniques, both spatial and temporal information can beintegrated across the molecular, cellular and systems levels that allow us tofurther investigate the hierarchical interaction of brain systems thatultimately reveal the pathological mechanism. In this session, we will discussthe current and potential future state of the construction of bio-imagingcenter, and will further discuss by understanding hierarchical physiologicalsystem that leads to the creation of healthy society.</p>

DOI： 10.1254/jpssuppl.95.0_2-s17-2

CiNii Research

Language：Japanese   Publisher：Japanese Pharmacological Society  

<p>Microglia are the sole immune responding cells in the central nervous system. Their role as neuro-immune cells in the pathogenesis of various neurodegenerative and infectious diseases of the brain have been extensively studied. In addition to the pathological function of microglia, recent developments in molecular probes and optical imaging in vivo have revealed that microglia are highly motile cell in the healthy brain, extending and retracting their process that extend from a largely stationary cell soma. We used in vivo two photon microscopy to reveal their physiological and pathological function on synapse and vessels. We particularly showed the functional consequence of microglial contact on synapse and vessels to indicate their role in neurological or psychiatric brain. </p><p>In this session, we will show 1. Microglial regulation of blood brain barrier, 2. Microglial role for cross modal plasticity that indicate their pathological role in schizophrenia. </p><p></p>

DOI： 10.1254/jpssuppl.95.0_3-s31-3

CiNii Research

Language：Japanese   Publisher：公益社団法人 日本薬学会  

アルツハイマー型認知機能障害、自閉スペクトラム症、統合失調症などの多岐にわたる疾患において、神経回路を決定するシナプスの異常を認める。近年の光学技術の発達に伴い、脳の免疫細胞であるミクログリアが、健常時、発達期、病態期の様々な場面で、シナプスと直接の接触を繰り返し、その新生、除去、維持、活動の制御などの多岐にわたる役割を果たすことが解明されてきた。本稿では、ミクログリアとシナプスに関する最新の知見をまとめ、今後の疾患研究への展望について議論する。

DOI： 10.14894/faruawpsj.58.9_858

CiNii Research

Language：Japanese   Publishing type：Research paper (scientific journal)  

The central nervous system (CNS) is an immune-privileged area. The blood-brain barrier (BBB) is thought to separate the CNS from any systemic inflammatory states to maintain homeostasis within this specialized, vulnerable organ. However, accumulating studies have challenged this concept by demonstrating systemic inflammatory effects on brain. Moreover, the coronavirus disease pandemic caused by severe acute respiratory syndrome coronavirus 2 in 2019 has rapidly evoked attention toward the BBB as the systemic-CNS immunological interface. In this review, we focus on microglia, the sole immune cells in the CNS, and briefly introduce our new findings regarding microglial BBB regulation in systemic inflammation. With a close eye on associated literature, we carefully rethink the traditional immune system in the CNS and suggest a new possible mechanism of systemic-CNS immune cell interaction, while an understanding of the BBB develops.

DOI： 10.11477/mf.1416201861

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CiNii Research

Language：Japanese   Publishing type：Research paper (scientific journal)  

The pathophysiology of mental disorders remains unknown. This causes many gaps in pathophysiology, diagnosis, and treatment of mental disorders. To close these gaps, a new perspective, which is not bound by the existing diagnostic classifications or pathological hypotheses for mental disorders, is required. Recently, it has been reported that glial cells play active roles in normal brain function and circuit formation, and their disruption results in the onset of mental disorders. Here, we discuss mental disorders from the perspective of glial cell-related pathophysiology, along with our current efforts and research.

DOI： 10.11477/mf.1416201836

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CiNii Research

Language：Japanese   Publishing type：Research paper (scientific journal)  

Oligodendrocytes, which form the myelin sheaths that insulate axons, regulate conduction velocity. Myelinated axons make up the brain's white matter and contribute to the efficiency of information processing by regulating the timing of neural activity. Traditionally, it has been thought that myelin is a static, inactive insulator around the axon. However, recent studies in humans using magnetic resonance imaging have shown that structural changes in the white matter occur during learning and training, suggesting that 1) white matter change depends on neural activity and 2) activity-dependent changes in white matter are essential for learning and behavior. Furthermore, suppression of oligodendrocytes and their progenitor cells leads to deficits in motor learning and remote fear memory consolidation, suggesting a causal relationship between glial function and the learning process. However, for technical reasons, it remains unclear how myelin-generating glia modulate neural circuitry and what underlying mechanisms they employ to affect learning and behavior. Recent advances in optical and genetic techniques have helped elucidate this mechanism. In this review, we highlight evidence that neural activities regulated by myelin plasticity play a pivotal role in learning and behavior and provide further insight into possible therapeutic targets for treating diseases accompanied by myelin impairment.

DOI： 10.1016/j.neures.2020.12.005

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：American Association for the Advancement of Science (AAAS)  

Sustained neuropathic pain from injury or inflammation remains a major burden for society. Rodent pain models have informed some cellular mechanisms increasing neuronal excitability within the spinal cord and primary somatosensory cortex (S1), but how activity patterns within these circuits change during pain remains unclear. We have applied multiphoton in vivo imaging and holographic stimulation to examine single S1 neuron activity patterns and connectivity during sustained pain. Following pain induction, there is an increase in synchronized neuronal activity and connectivity within S1, indicating the formation of pain circuits. Artificially increasing neuronal activity and synchrony using DREADDs reduced pain thresholds. The expression of N-type voltage-dependent Ca²⁺ channel subunits in S1 was increased after pain induction, and locally blocking these channels reduced both the synchrony and allodynia associated with inflammatory pain. Targeting these S1 pain circuits, via inhibiting N-type Ca²⁺ channels or other approaches, may provide ways to reduce inflammatory pain.

DOI： 10.1126/sciadv.abd8261

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Language：Japanese   Publisher：The Japanese Society of Toxicology  

<p>Neonicotionoid pesticides are insecticides which have been thought to be one of the causes of Colony Collapse Disorder. They were considered to be less toxic to mammals than insects, but some of the recent studies suggested their association with disruption of higher brain fuction in mammals. Nevertheless, it is still unclear how neonicotionoids affect on the central nervous system. Here, we propose the use of in vivo Ca²⁺ imaging with two-photon microscope to detect abnormal activity of neuronal circuits in brain with the application of neonicotionoids.</p><p>In this study, a less than the no-observed-adverse-effect level (NOAEL) of acetamiprid (20 mg/kg bw); and a tenth or half of the median lethal doses of nicotine (0.33 or 1.65 mg/kg bw respectively) were orally administered to mice. They were subjected to elevated plus maze test and Ca²⁺ imaging by two-photon microscope in the somatosensory cortex. We further detected acetamiprid and metabolites in brain and blood an hour after the administration.</p><p>Mice exposed to acetamiprid or nicotine exhibited an increase in anxiety-like behavior that associated with the altered activities of the neuronal population in the somatosensory cortex. Although the dose of acetamiprid used in the current study was below the NOAEL, both acetamiprid and nicotine affected the behavior and the neuronal activity in the somatosensory cortex. The results suggested that in vivo Ca²⁺ imaging using two-photon microscope enabled highly sensitive detection of brain neurodisruption by neurotoxicants.</p>

DOI： 10.14869/toxpt.48.1.0_p-37e

CiNii Research

Publishing type：Research paper (international conference proceedings)  

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Language：Japanese   Publishing type：Research paper (scientific journal)  

Maternal infection or inflammation causes abnormalities in brain development associated with subsequent cognitive impairment and in an increased susceptibility to schizophrenia and autism spectrum disorders. Maternal immune activation (MIA) and increases in serum cytokine levels mediates this association via effects on the fetal brain, and microglia can respond to maternal immune status, but consensus on how microglia may respond is lacking and no-one has yet examined if microglial process motility is impaired. In this study we investigated how MIA induced at two different gestational ages affected microglial properties at different developmental stages. Immune activation in mid-pregnancy increased IL-6 expression in embryonic microglia, but failed to cause any marked changes in morphology either at E18 or postnatally. In contrast MIA, particularly when induced earlier (at E12), caused sustained alterations in the patterns of microglial process motility and behavioral deficits. Our research has identified an important microglial property that is altered by MIA and which may contribute to the underlying pathophysiological mechanisms linking maternal immune status to subsequent risks for cognitive disease.

DOI： 10.1038/s41598-020-78294-2

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Language：Japanese   Publishing type：Research paper (scientific journal)  

Microglia, the brain's resident macrophages, help to regulate brain function by removing dying neurons, pruning non-functional synapses, and producing ligands that support neuronal survival1. Here we show that microglia are also critical modulators of neuronal activity and associated behavioural responses in mice. Microglia respond to neuronal activation by suppressing neuronal activity, and ablation of microglia amplifies and synchronizes the activity of neurons, leading to seizures. Suppression of neuronal activation by microglia occurs in a highly region-specific fashion and depends on the ability of microglia to sense and catabolize extracellular ATP, which is released upon neuronal activation by neurons and astrocytes. ATP triggers the recruitment of microglial protrusions and is converted by the microglial ATP/ADP hydrolysing ectoenzyme CD39 into AMP; AMP is then converted into adenosine by CD73, which is expressed on microglia as well as other brain cells. Microglial sensing of ATP, the ensuing microglia-dependent production of adenosine, and the adenosine-mediated suppression of neuronal responses via the adenosine receptor A1R are essential for the regulation of neuronal activity and animal behaviour. Our findings suggest that this microglia-driven negative feedback mechanism operates similarly to inhibitory neurons and is essential for protecting the brain from excessive activation in health and disease.

DOI： 10.1038/s41586-020-2777-8

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Language：Japanese   Publisher：(一社)日本毒性学会  

Language：Japanese   Publishing type：Research paper (scientific journal)  

In the developing cortex, postmigratory neurons accumulate in the cortical plate (CP) to properly differentiate consolidating subtype identities. Microglia, despite their extensive surveying activity, temporarily disappear from the midembryonic CP. However, the mechanism and significance of this absence are unknown. Here, we show that microglia bidirectionally migrate via attraction by CXCL12 released from the meninges and subventricular zone and thereby exit the midembryonic CP. Upon nonphysiological excessive exposure to microglia in vivo or in vitro, young postmigratory and in vitro-grown CP neurons showed abnormal differentiation with disturbed expression of the subtype-associated transcription factors and genes implicated in functional neuronal maturation. Notably, this effect is primarily attributed to interleukin 6 and type I interferon secreted by microglia. These results suggest that "sanctuarization" from microglia in the midembryonic CP is required for neurons to appropriately fine-tune the expression of molecules needed for proper differentiation, thus securing the establishment of functional cortical circuit.

DOI： 10.1038/s41467-020-15409-3

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media {LLC}  

Despite the promising clinical efficacy of the second-generation anaplastic lymphoma kinase (ALK) inhibitor alectinib in patients with ALK-rearranged lung cancer, some tumor cells survive and eventually relapse, which may be an obstacle to achieving a cure. Limited information is currently available on the mechanisms underlying the initial survival of tumor cells against alectinib. Using patient-derived cell line models, we herein demonstrate that cancer cells survive a treatment with alectinib by activating Yes-associated protein 1 (YAP1), which mediates the expression of the anti-apoptosis factors Mcl-1 and Bcl-xL, and combinatorial inhibition against both YAP1 and ALK provides a longer tumor remission in ALK-rearranged xenografts when compared with alectinib monotherapy. These results suggest that the inhibition of YAP1 is a candidate for combinatorial therapy with ALK inhibitors to achieve complete remission in patients with ALK-rearranged lung cancer.

DOI： 10.1038/s41467-019-13771-5

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Language：English   Publishing type：Research paper (scientific journal)  

Myelination increases the conduction velocity in long-range axons and is prerequisite for many brain functions. Impaired myelin regulation or impairment of myelin itself is frequently associated with deficits in learning and cognition in neurological and psychiatric disorders. However, it has not been revealed what perturbation of neural activity induced by myelin impairment causes learning deficits. Here, we measured neural activity in the motor cortex during motor learning in transgenic mice with a subtle impairment of their myelin. This deficit in myelin impaired motor learning, and was accompanied by a decrease in the amplitude of movement-related activity and an increase in the frequency of spontaneous activity. Thalamocortical axons showed variability in axonal conduction with a large spread in the timing of postsynaptic cortical responses. Repetitive pairing of forelimb movements with optogenetic stimulation of thalamocortical axon terminals restored motor learning. Thus, myelin regulation helps to maintain the synchrony of cortical spike-time arrivals through long-range axons, facilitating the propagation of the information required for learning. Our results revealed the pathological neuronal circuit activity with impaired myelin and suggest the possibility that pairing of noninvasive brain stimulation with relevant behaviors may ameliorate cognitive and behavioral abnormalities in diseases with impaired myelination.

DOI： 10.1002/glia.23713

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Language：Japanese   Publisher：The Japanese Society of Toxicology  

<p> By acting on receptors in the brain, some chemicals exhibit "signal toxicity" that disrupts intracellular and intercellular signaling, causing unexpected effects. In particular, in brain function, a complex signal network between neurons and glial cells is formed, and disruption of this network can be a critical endpoint of signal toxicity. However, “disruption of brain function” due to signal toxicity is often not accompanied by cell death and accompanying brain tissue degeneration, and cannot be detected by current neurotoxicity test methods. In this study, we used neonicotinoids (NNs) and nicotine, which are agonists of the nicotinic acetylcholine receptor (nAChR), as model compounds, and detected changes in neuronal activity in the somatosensory cortex using a two-photon microscope. The aim was to detect disruption of brain function associated with signal toxicity.</p><p> C57BL/6N were orally administered ACE at 20 mg/kg (with reference to LOAEL in general pharmacology test of the central nervous system) and their blood was collected over time. It was analyzed quantitatively using LC-MS/MS. Then, we exposed mice to ACE at 20 mg/kg or 7.1 mg/kg (with reference to NOAEL to rats), and their behavior was observed using openfield (OF) test 1 hour after the administration at the former concentration, and using elevated plus maze (EPM) test 1 hour after the administration at the latter concentration. In addition, C57BL/6J were administered ACE at 30 mg/kg (with reference to NOAEL in the subacute toxicity test) and Nicotine, which is the typical agonist of nAChR, at 1.6 mg/kg (with reference to 1/2 LD50), and the neuronal activity in somatosensory cortex was observed over time by using two-photon microscope. </p><p> As a result, ACE absorbed quickly and the Tmax of ACE was around 25 minutes after administration. In comparison, dm-ACE, which is one of its major metabolites, absorbed a bit slower and the Tmax was around 150 minutes. An hour after the administration, the activity of mice decreased, and the anxiety-like behavior increased. In the somatosensory cortex, the firing frequency of nerve cells decreased, and the synchronous firing increased, 1 hour and 2.5 hour after ACE administration. Similarly, the firing frequency tended to decrease, and the synchronous firing increased, 5 minutes and 30 minutes after the administration of Nicotine. This suggest that changes in neuronal activity after administration of ACE are the result of ACE acting as a ligand for nAChR because we can see the same trends between ACE and Nicotine. In summary, it was observed that administration of ACE at a concentration that is originally non-toxic, such as NOAEL, affects the behavior and neural activities. This suggests that cranial nerve activity is responsible for changes in behavior.</p>

DOI： 10.14869/toxpt.47.1.0_p-4s

CiNii Research

Language：Japanese   Publishing type：Research paper (scientific journal)  

Microglia survey brain parenchyma, responding to injury and infections. Microglia also respond to systemic disease, but the role of blood-brain barrier (BBB) integrity in this process remains unclear. Using simultaneous in vivo imaging, we demonstrated that systemic inflammation induces CCR5-dependent migration of brain resident microglia to the cerebral vasculature. Vessel-associated microglia initially maintain BBB integrity via expression of the tight-junction protein Claudin-5 and make physical contact with endothelial cells. During sustained inflammation, microglia phagocytose astrocytic end-feet and impair BBB function. Our results show microglia play a dual role in maintaining BBB integrity with implications for elucidating how systemic immune-activation impacts neural functions.

DOI： 10.1038/s41467-019-13812-z

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1002/mds.27819

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DOI： 10.1073/pnas.1908361116

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Microglia, the sole immune cells in the brain, are the key player for synaptic regulation required for our brain function in both developing and adult brain. They have highly motile processes to detect synaptic functions. Recent accumulated studies have unveiled the mechanism underlying synapse detection and pruning / formation by microglia. In this review, we summarize the current knowledge of various microglial machinery recruited in synaptic modulation in the different life stages and contexts.

DOI： 10.1111/neup.12560

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Oligodendrocyte form myelin around the axons to regulate the conduction velocity. Myelinated axons are composed of white matter to act as cables to connect distinct brain regions. Recent human MRI studies showed that the signal from white matter change in the people with special skills such as taxi driver, piano player, and juggling. The change of the white matter suggested that (1) The plasticity of myelination depends on neuronal activity (activity-dependent myelination) and (2) White matter plasticity is essential for brain functions. In this session, we discussed that how the un-electrical components, oligodendrocytes, and its precursor cells receive the signal from electrically active neurons and differentiate, proliferate, and myelinate the axons to modulate the activity of neuronal circuits, ultimately affect on their behaviors. In this review, we highlight the physiological functions of oligodendrocyte and their neuronal activity-dependent functions and thus show new insight for their contribution to brain functions.

DOI： 10.1007/978-981-32-9636-7_4

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Microglia are traditionally known as immune sentinels of the brain and as key player in the pathogenesis of neurodegenerative diseases such as Alzheimer's disease, Parkinson disease, or amyotrophic lateral sclerosis. Recently, they were also identified as synaptic organizer, promoting formation and maturation of synapses as well as modifying synaptic activity. Interestingly, microglia-mediated synaptic pruning and microglia-mediated changes in synaptic plasticity were observed both during brain development and in neurodegenerative diseases, stressing the key role of microglia-synapse interaction in these processes. Here we descried a technique for noninvasive in vivo monitoring of microglia-synapse interactions by means of two-photon microscopy.

DOI： 10.1007/978-1-4939-9658-2_20

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Microglia are the sole immune responding cells in the central nervous system. Their role as neuroimmune cells in the pathogenesis of various neurodegenerative and infectious diseases of the brain have been extensively studied. Upon brain disease and infection, they adopt an activated phenotype associated with the release of cytokines and neurotrophic factors and resulting in neuroprotective or neurotoxic outcomes. However, microglia are resident also in the healthy or physiological brain, but much less is known about their role(s) in the healthy brain, partly due to technical limitations regarding investigation of these highly reactive cells in the intact brain. Recent developments in molecular probes and in vivo optical imaging techniques has now helped to characterize microglia in the physiological or healthy brain. In vivo two-photon imaging of fluorescently labeled microglia have revealed that they are highly motile cells in the healthy brain, extending and retracting their processes that extend from a largely stationary cell soma. In this chapter, we briefly summarize some of the physiological functions of microglia in the uninjured brain, with a focus on interactions they have with synapses.

DOI： 10.1007/978-1-4939-9658-2_6

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The speed of impulse transmission is critical for optimal neural circuit function, but it is unclear how the appropriate conduction velocity is established in individual axons. The velocity of impulse transmission is influenced by the thickness of the myelin sheath and the morphology of electrogenic nodes of Ranvier along axons. Here we show that myelin thickness and nodal gap length are reversibly altered by astrocytes, glial cells that contact nodes of Ranvier. Thrombin-dependent proteolysis of a cell adhesion molecule that attaches myelin to the axon (neurofascin 155) is inhibited by vesicular release of thrombin protease inhibitors from perinodal astrocytes. Transgenic mice expressing a dominant-negative fragment of VAMP2 in astrocytes, to reduce exocytosis by 50%, exhibited detachment of adjacent paranodal loops of myelin from the axon, increased nodal gap length, and thinning of the myelin sheath in the optic nerve. These morphological changes alter the passive cable properties of axons to reduce conduction velocity and spike-time arrival in the CNS in parallel with a decrease in visual acuity. All effects were reversed by the thrombin inhibitor Fondaparinux. Similar results were obtained by viral transfection of tetanus toxin into astrocytes of rat corpus callosum. Previously, it was unknown how the myelin sheath could be thinned and the functions of perinodal astrocytes were not well understood. These findings describe a form of nervous system plasticity in which myelin structure and conduction velocity are adjusted by astrocytes. The thrombin-dependent cleavage of neurofascin 155 may also have relevance to myelin disruption and repair.

DOI： 10.1073/pnas.1811013115

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A new type of functional optical microscope system called three-dimensional (3D) stimulation and imaging-based functional optical microscopy (SIFOM) is proposed, to the best of our knowledge. SIFOM can precisely stimulate user-defined targeted biological cells and can simultaneously record the volumetric fluorescence distribution in a single acquisition. Precise and simultaneous stimulation of fluorescent-labeled biological cells is achieved by multiple 3D spots generated by digital holograms displayed on a phase-mode spatial light modulator. Single-shot 3D acquisition of the fluorescence distribution is accomplished by common-path off-axis incoherent digital holographic microscopy in which a diffraction grating with a focusing lens is displayed on another phase-mode spatial light modulator. The effectiveness of the proposed functional microscope system was verified in experiments using fluorescent microbeads and human lung cancer cells located at various defocused positions. The system can be used for manipulating the states of cells in optogenetics.

DOI： 10.1364/OL.43.005447

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Excitotoxicity is well known in the neuronal death in the brain and is also linked to neuronal damages in the retina. Recent accumulating evidence show that microglia greatly affect excitotoxicity in the brain, but their roles in retina have received only limited attention. Here, we report that retinal excitotoxicity is mediated by microglia. To this end, we employed three discrete methods, that is, pharmacological inhibition of microglia by minocycline, pharmacological ablation by an antagonist for colony stimulating factor 1 receptor (PLX5622), and genetic ablation of microglia using Iba1-tTA::DTAtetO/tetO mice. Intravitreal injection of NMDA increased the number of apoptotic retinal ganglion cells (RGCs) followed by reduction in the number of RGCs. Although microglia did not respond to NMDA directly, they became reactive earlier than RGC damages. Inhibition or ablation of microglia protected RGCs against NMDA. We found up-regulation of proinflammatory cytokine genes including Il1b, Il6 and Tnfa, among which Tnfa was selectively blocked by minocycline. PLX5622 also suppressed Tnfa expression. Tumor necrosis factor α (TNFα) signals were restricted in microglia at very early followed by spreading into other cell types. TNFα up-regulation in microglia and other cells were significantly attenuated by minocycline and PLX5622, suggesting a central role of microglia for TNFα induction. Both inhibition of TNFα and knockdown of TNF receptor type 1 by siRNA protected RGCs against NMDA. Taken together, our data demonstrate that a phenotypic change of microglia into a neurotoxic one is a critical event for the NMDA-induced degeneration of RGCs, suggesting an importance of non-cell-autonomous mechanism in the retinal neuronal excitotoxicity.

DOI： 10.1002/glia.23475

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Peripheral nerve injury causes maladaptive plasticity in the central nervous system and induces chronic pain. In addition to the injured limb, abnormal pain sensation can appear in the limb contralateral to the injury, called mirror image pain. Because synaptic remodeling in the primary somatosensory cortex (S1) has critical roles in the induction of chronic pain, cortical reorganization in the S1 ipsilateral to the injured limb may also accompany mirror image pain. To elucidate this, we conducted in vivo 2-photon calcium imaging of neuron and astrocyte activity in the ipsilateral S1 after a peripheral nerve injury. We found that cross-callosal inputs enhanced the activity of both S1 astrocytes and inhibitory neurons, whereas activity of excitatory neurons decreased. When local inhibitory circuits were blocked, astrocyte-dependent spine plasticity and allodynia were revealed. Thus, we propose that cortical astrocytes prime the induction of spine plasticity and mirror image pain after peripheral nerve injury. Moreover, this result suggests that cortical synaptic rewiring could be sufficient to cause allodynia on the uninjured periphery.

DOI： 10.1097/j.pain.0000000000001248

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Electrical activity is essential for brain function. However, neurons, the electrically active cells, are less numerous than the non-electrical glial cells in the central nervous system. The non-electrical components modify the function of neural circuits, depending on the electrical neuronal activity, by wrapping synapses, myelinating axons and phagocytozing the neuronal components. Moreover, recent evidence has suggested that they contribute to neurological and psychiatric disease by regulating neuronal circuits, ultimately affecting their behaviour. In this review, we highlight the physiological functions of glial cells, particularly the electrical activity-dependent processes, to provide further insight into their role in brain function.

DOI： 10.1093/jb/mvy023

Web of Science

Scopus

PubMed

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1523/ENEURO.0088-18.2018

Web of Science

PubMed

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1117/12.2323184

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：SAGE PUBLICATIONS INC  

Mastication is an indispensable oral function related to physical, mental, and social health throughout life. The elderly tend to have a masticatory dysfunction due to tooth loss and fragility in the masticatory muscles with aging, potentially resulting in impaired cognitive function. Masticatory stimulation has influence on the development of the central nervous system (CNS) as well as the growth of maxillofacial tissue in children. Although the relationship between mastication and cognitive function is potentially important in the growth period, the cellular and molecular mechanisms have not been sufficiently elucidated. Here, we show that the reduced mastication resulted in impaired spatial memory and learning function owing to the morphological change and decreased activity in the hippocampus. We used an in vivo model for reduced masticatory stimuli, in which juvenile mice were fed with powder diet and found that masticatory stimulation during the growth period positively regulated long-term spatial memory to promote cognitive function. The functional linkage between mastication and brain was validated by the decrease in neurons, neurogenesis, neuronal activity, and brain-derived neurotrophic factor (BDNF) expression in the hippocampus. These findings taken together provide in vivo evidence for a functional linkage between mastication and cognitive function in the growth period, suggesting a need for novel therapeutic strategies in masticatory function-related cognitive dysfunction.

DOI： 10.1177/0022034517708771

Web of Science

PubMed

© 2019 SPIE. Multispots in three-dimensions generated by phase mode spatial light modulators (SLMs) are very useful in laser processing or light induced biological treatments, such as optogenetics. So far, the intensity of the focus spots varies depending to the distance from optical axis. In order to equalize intensities in all generated spots, simple feedback method was applied. Further, look up table was created by dividing imaging area in sectors. Experiment results show improvement in the random spots at some degree, however, further analyzation is required.

Scopus

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