application-consistent-massage-like-perturbations-on-mouse-calves

Application of Consistent Massage-Like Perturbations on Mouse Calves and Monitoring the Resulting Intramuscular Pressure Changes

Massage is generally recognized to be beneficial for relieving pain and inflammation. Although previous studies have reported anti-inflammatory effects of ...

application-passive-head-motion-to-generate-defined-accelerations-at

Application of Passive Head Motion to Generate Defined Accelerations at the Heads of Rodents

Exercise is widely recognized as effective for various diseases and physical disorders, including those related to brain dysfunction. However, molecular ...

National Rehabilitation Center for Persons with disabilities

Astrocytes are the most abundant cell type in the mammalian brain and are important for the functions of the central nervous system. Although previous studies have shown that the STAT signaling pathway or its regulators promote the generation of astrocytes from multipotent neural precursor cells (NPCs) in the developing mammalian brain, the molecular mechanisms that regulate the astrocytic fate decision have still remained largely unclear. Here, we show that the high mobility group nucleosome-binding (HMGN) family proteins, HMGN1, 2, and 3, promote astrocyte differentiation of NPCs during brain development. HMGN proteins were expressed in NPCs, Sox9(+) glial progenitors, and GFAP(+) astrocytes in perinatal and adult brains. Forced expression of either HMGN1, 2, or 3 in NPCs in cultures or in the late embryonic neocortex increased the generation of astrocytes at the expense of neurons. Conversely, knockdown of either HMGN1, 2, or 3 in NPCs suppressed astrocyte differentiation and promoted neuronal differentiation. Importantly, overexpression of HMGN proteins did not induce the phosphorylation of STAT3 or activate STAT reporter genes. In addition, HMGN family proteins did not enhance DNA demethylation and acetylation of histone H3 around the STAT-binding site of the gfap promoter. Moreover, knockdown of HMGN family proteins significantly reduced astrocyte differentiation induced by gliogenic signal ciliary neurotrophic factor, which activates the JAK-STAT pathway. Therefore, we propose that HMGN family proteins are novel chromatin regulatory factors that control astrocyte fate decision/differentiation in parallel with or downstream of the JAK-STAT pathway through modulation of the responsiveness to gliogenic signals.

High mobility group nucleosome-binding family proteins promote astrocyte differentiation of neural precursor cells.

Multipotent neural precursor cells (NPCs) generate astrocytes at late stages of mammalian neocortical development. Many signalling pathways that regulate astrocytogenesis directly induce the expression of GFAP, a marker of terminally differentiated astrocytes. However, astrocyte specification occurs before GFAP expression and essential factors for the specification step have remained elusive. Here we show that Zbtb20 regulates astrocyte specification in the mouse neocortex. Zbtb20 is highly expressed in late-stage NPCs and their astrocytic progeny. Overexpression and knockdown of Zbtb20 promote and suppress astrocytogenesis, respectively, although Zbtb20 does not directly activate the Gfap promoter. Astrocyte induction by Zbtb20 is suppressed by knockdown of Sox9 or NFIA. Furthermore, in the astrocyte lineage, Zbtb20 directly represses the expression of Brn2, which encodes a protein necessary for upper-layer neuron specification. Zbtb20 is thus a key determinant of astrocytogenesis, in which it collaborates with Sox9 and NFIA, and acts in part through direct repression of Brn2 expression. 

Zbtb20 promotes astrocytogenesis during neocortical development.

Brain inflammation is a crucial component of demyelinating diseases such as multiple sclerosis. Although the initiation of inflammatory processes by the production of cytokines and chemokines by immune cells is well characterized, the processes of inflammatory aggravation of demyelinating diseases remain obscure. Here, we examined the contribution of Erk2, one of the isoforms of the extracellular signal-regulated kinase, to demyelinating inflammation.

The crucial role of Erk2 in demyelinating inflammation in the central nervous system.

Oligodendrocyte progenitor cells (OPCs) undergo marked morphological changes to become mature oligodendrocytes, but the metabolic resources for this process have not been fully elucidated. Although lactate, a metabolic derivative of glycogen, has been reported to be consumed in oligodendrocytes as a metabolite, and to ameliorate hypomyelination induced by low glucose conditions, it is not clear about the direct contribution of lactate to cell cycling and differentiation of OPCs, and the source of lactate for remyelination. Therefore, we evaluated the effect of 1,4-dideoxy-1,4-imino-d-arabinitol (DAB), an inhibitor of the glycogen catabolic enzyme glycogen phosphorylase, in a mouse cuprizone model. Cuprizone induced demyelination in the corpus callosum and remyelination occurred after cuprizone treatment ceased. This remyelination was inhibited by the administration of DAB. To further examine whether lactate affects proliferation or differentiation of OPCs, we cultured mouse primary OPC-rich cells and analyzed the effect of lactate. Lactate rescued the slowed cell cycling induced by 0.4 mM glucose, as assessed by the BrdU-positive cell ratio. Lactate also promoted OPC differentiation detected by monitoring the mature oligodendrocyte marker myelin basic protein, in the presence of both 36.6 mM and 0.4 mM glucose. Furthermore, these lactate-mediated effects were suppressed by the reported monocarboxylate transporter inhibitor, α-cyano-4-hydroxy-cinnamate. These results suggest that lactate directly promotes the cell cycling rate and differentiation of OPCs, and that glycogen, one of the sources of lactate, contributes to remyelination in vivo. J. Cell. Physiol. 232: 986-995, 2017. © 2016 The Authors. Journal of Cellular Physiology Published by Wiley Periodicals, Inc.

Oligodendrocyte Progenitor Cells Directly Utilize Lactate for Promoting Cell Cycling and Differentiation.

In an embryonic developmental stage of the peripheral nervous system (PNS), Schwann cell precursors migrate along neuronal axons to their final destinations. After birth, they eventually wrap around individual axons to form myelin sheaths, which insulate axons to increase the nerve conduction velocity. Some growth factors and adhesion molecules are known to control these developmental stages from in the fish to in the mammal. Neuregulin-1 (NRG1), which is composed of many alternative splicing variants, is such a growth factor. Among these variants, the type III isoform of NRG1, interacting with ErbB2 and ErbB3 receptors on Schwann cells, plays an essential role in myelination in the fish and the mammal. NRG1 type III is also known to promote migration of fish Schwann cell precursors; however, it still remains to be clarified whether mammalian type III isoform does it. We have therefore generated type III isoform-specific knockout mice in inbred strain. The mice result in delayed migration of the precursors from the dorsal to ventral root via a peripheral ganglion, comparing littermate controls. Similar results are observed in an in vitro migration assay using reaggregated Schwann cell precursors. Furthermore, the knockout mice exhibit reduced myelin thickness, consistent with the established role of NRG1 type III in myelination. These results indicate that in mice, NRG1 type III plays a key role not only in myelination but also in migration.

Neuregulin-1 type III knockout mice exhibit delayed migration of Schwann cell precursors.

Oligodendrocyte precursor cells (OPCs) act as a reservoir of new oligodendrocytes (OLs) in homeostatic and pathological conditions. OPCs are activated in response to injury to generate myelinating OLs, but the underlying mechanisms remain poorly understood. Here, we show that chromodomain helicase DNA binding protein 7 (Chd7) regulates OPC activation after spinal cord injury (SCI). Chd7 is expressed in OPCs in the adult spinal cord and its expression is upregulated with a concomitant increase in Sox2 expression after SCI. OPC-specific ablation of Chd7 in injured mice leads to reduced OPC proliferation, the loss of OPC identity, and impaired OPC differentiation. Ablation of Chd7 or Sox2 in cultured OPCs shows similar phenotypes to those observed in  knock-out mice. Chd7 and Sox2 form a complex in OPCs and bind to the promoters or enhancers of the  () and θ (θ) genes, thereby inducing their expression. The expression of Rgcc and PKCθ is reduced in the OPCs of the injured  knock-out mice. In cultured OPCs, overexpression and knock-down of Rgcc or PKCθ promote and suppress OPC proliferation, respectively. Furthermore, overexpression of both Rgcc and PKCθ rescues the Chd7 deletion phenotypes. Chd7 is thus a key regulator of OPC activation, in which it cooperates with Sox2 and acts via direct induction of Rgcc and PKCθ expression. Spinal cord injury (SCI) leads to oligodendrocyte (OL) loss and demyelination, along with neuronal death, resulting in impairment of motor or sensory functions. Oligodendrocyte precursor cells (OPCs) activated in response to injury are potential sources of OL replacement and are thought to contribute to remyelination and functional recovery after SCI. However, the molecular mechanisms underlying OPC activation, especially its epigenetic regulation, remain largely unclear. We demonstrate here that the chromatin remodeler chromodomain helicase DNA binding protein 7 (Chd7) regulates the proliferation and identity of OPCs after SCI. We have further identified regulator of cell cycle (Rgcc) and protein kinase Cθ (PKCθ) as novel targets of Chd7 for OPC activation.

Chd7 Collaborates with Sox2 to Regulate Activation of Oligodendrocyte Precursor Cells after Spinal Cord Injury.

Physical inactivity gives rise to numerous diseases and organismal dysfunctions, particularly those related to aging. Musculoskeletal disorders including muscle atrophy, which can result from a sedentary lifestyle, aggravate locomotive malfunction and evoke a vicious circle leading to severe functional disruptions of vital organs such as the brain and cardiovascular system. Although the significance of physical activity is evident, molecular mechanisms behind its beneficial effects are poorly understood. Here, we show that massage-like mechanical interventions modulate immobilization-induced pro-inflammatory responses of macrophages  and alleviate muscle atrophy. Local cyclical compression (LCC) on mouse calves, which generates intramuscular pressure waves with amplitude of 50 mmHg, partially restores the myofiber thickness and contracting forces of calf muscles that are decreased by hindlimb immobilization. LCC tempers the increase in the number of cells expressing pro-inflammatory proteins, tumor necrosis factor-α and monocyte chemoattractant protein-1 (MCP-1), including macrophages  The reversing effect of LCC on immobilization-induced thinning of myofibers is almost completely nullified when macrophages recruited from circulating blood are depleted by administration of clodronate liposomes. Furthermore, application of pulsatile fluid shear stress, but not hydrostatic pressure, reduces the expression of MCP-1 in macrophages  Together with the LCC-induced movement of intramuscular interstitial fluid detected by µCT analysis, these results suggest that mechanical modulation of macrophage function is involved in physical inactivity-induced muscle atrophy and inflammation. Our findings uncover the implication of mechanosensory function of macrophages in disuse muscle atrophy, thereby opening a new path to develop a novel therapeutic strategy utilizing mechanical interventions.

Local cyclical compression modulates macrophage function  and alleviates immobilization-induced muscle atrophy.

Mechanical forces are known to be involved in various biological processes. However, it remains unclear whether brain functions are mechanically regulated under physiological conditions. Here, we demonstrate that treadmill running and passive head motion (PHM), both of which produce mechanical impact on the head, have similar effects on the hallucinogenic 5-hydroxytryptamine (5-HT) receptor subtype 2A (5-HT) signaling in the prefrontal cortex (PFC) of rodents. PHM generates interstitial fluid movement that is estimated to exert shear stress of a few pascals on cells in the PFC. Fluid shear stress of a relevant magnitude on cultured neuronal cells induces ligand-independent internalization of 5-HT receptor, which is observed in mouse PFC neurons after treadmill running or PHM. Furthermore, inhibition of interstitial fluid movement by introducing polyethylene glycol hydrogel eliminates the effect of PHM on 5-HT receptor signaling in the PFC. Our findings indicate that neuronal cell function can be physiologically regulated by mechanical forces in the brain.

Mechanical Regulation Underlies Effects of Exercise on Serotonin-Induced Signaling in the Prefrontal Cortex Neurons.

In the majority of spinal cord injury (SCI) patients, spasticity develops in the subacute phase and chronically persists with muscle hypertonia. Among various pathological conditions underlying spasticity, upregulated expression of 5-HT receptors (5-HTR) on the spinal motor neurons due to 5-HT denervation is considered one of crucial factors for hyperexcitability of the spinal circuit. As a 5-HT signal modulator, selective serotonin re-uptake inhibitors (SSRIs) are ordinarily prescribed for diseases associated with 5-HT in the CNS, and are known for their ability to increase 5-HT levels as well as to desensitize 5-HTR. Here, we hypothesized that early SSRI administration as a preemptive treatment strategy would effectively prevent the onset of spasticity. We used a rat model of contusive SCI and administered escitalopram during the first 4 weeks after injury, which is the period required for spasticity development in rodent models. We performed a swimming test to quantify spastic behaviors and conducted the Hoffman reflex test as well as histological analyses for 5-HTR and KCC2 expressions. Four weeks of escitalopram administration suppressed spastic behaviors during the swimming test and reduced the population of spasticity-strong rats. Moreover, the treatment resulted in decreased immunoreactivity of 5-HTR in the spinal motor neurons. Result of the H-reflex test and membrane expression of KCC2 were not significantly altered. In summary, early escitalopram administration could prevent the onset of spastic behaviors via regulation of 5-HT system after SCI, but could not modulate exaggerated spinal reflex. Our results suggest a novel application of SSRIs for preventative treatment of spasticity.

ArticleTotal : 2	Year
Publication title Cited by 5	2019
Publication title Cited by 1	2022

Article	Year
High mobility group nucleosome-binding family proteins promote astrocyte differentiation of neural precursor cells. Stem cells (Dayton, Ohio)\| PubMed ID: 25069414	2014
Zbtb20 promotes astrocytogenesis during neocortical development. Nature communications\| PubMed ID: 27000654	2016
The crucial role of Erk2 in demyelinating inflammation in the central nervous system. Journal of neuroinflammation\| PubMed ID: 27596241	2016
Oligodendrocyte Progenitor Cells Directly Utilize Lactate for Promoting Cell Cycling and Differentiation. Journal of cellular physiology\| PubMed ID: 27861886	2017
Neuregulin-1 type III knockout mice exhibit delayed migration of Schwann cell precursors. Biochemical and biophysical research communications\| PubMed ID: 28322798	2017
Chd7 Collaborates with Sox2 to Regulate Activation of Oligodendrocyte Precursor Cells after Spinal Cord Injury. The Journal of neuroscience : the official journal of the Society for Neuroscience\| PubMed ID: 28931573	2017
Local cyclical compression modulates macrophage function and alleviates immobilization-induced muscle atrophy. Clinical science (London, England : 1979)\| PubMed ID: 30209036	2018
Mechanical Regulation Underlies Effects of Exercise on Serotonin-Induced Signaling in the Prefrontal Cortex Neurons. iScience\| PubMed ID: 32062453	2020
Early escitalopram administration as a preemptive treatment strategy against spasticity after contusive spinal cord injury in rats. Scientific reports\| PubMed ID: 33782426	2021

Motoshi Nagao

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