研究者詳細 - 寳田　剛志

論文 - 寳田　剛志

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Possible neuroprotective property of nicotinic acetylcholine receptors in association with predominant upregulation of glial cell line-derived neurotrophic factor in astrocytes 査読

Takeshi Takarada, Noritaka Nakamichi, Hirofumi Kawagoe, Masato Ogura, Ryo Fukumori, Ryota Nakazato, Koichi Fujikawa, Miki Kou, Yukio Yoneda

JOURNAL OF NEUROSCIENCE RESEARCH 90 ( 11 ) 2074 - 2085 2012年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：WILEY-BLACKWELL

The underlying mechanisms are still unclear for the neuroprotective properties of nicotine to date, whereas we have shown functional expression of nicotinic acetylcholine receptors (nAChRs) responsible for the influx of extracellular Ca2+ in cultured rat cortical astrocytes. In this study, we investigated the possible involvement of astrocytic nAChRs in the neuroprotection by this agonist. Exposure to nicotine predominantly induced mRNA expression of glial cell line-derived neurotrophic factor (GDNF) among the different neurotrophic factors examined in cultured astrocytes, in a manner sensitive to nAChR antagonists, nifedipine, and aCa2+ chelator. Nicotine significantly increased GDNF in a concentration-dependent manner in cultured astrocytes but not in neurons or neural progenitors even at the highest concentration used. In cultured astrocytes, a transient increase was seen in the expression of mRNA and corresponding protein for GDNF during sustained exposure to nicotine for 24 hr. Cytotoxicity mediated by oxidative, calcium, mitochondrial, or endoplasmic reticulum stress was invariably protected against in cortical neurons cultured with conditioned medium from astrocytes previously exposed to nicotine, and preincubation with the anti-GDNF antibody reduced the neuroprotection by conditioned medium from astrocytes exposed to nicotine. Intraperitoneal administration of nicotine transiently increased the number of cells immunoreactive for both GDNF and glial fibrillary acidic protein in rat cerebral cortex. These results suggest that astrocytic nAChRs play a role in the neuroprotection against different cytotoxins after predominant upregulation of GDNF expression through a mechanism relevant to the acceleration of extracellular Ca2+ influx in rat brain in a particular situation. (c) 2012 Wiley Periodicals, Inc.

DOI： 10.1002/jnr.23101

Promoted Neuronal Differentiation after Activation of Alpha4/Beta2 Nicotinic Acetylcholine Receptors in Undifferentiated Neural Progenitors 査読

Takeshi Takarada, Noritaka Nakamichi, Seiya Kitajima, Ryo Fukumori, Ryota Nakazato, Nguyen Quynh Le, Yeong-Hun Kim, Koichi Fujikawa, Miki Kou, Yukio Yoneda

PLOS ONE 7 ( 10 ) e46177 2012年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PUBLIC LIBRARY SCIENCE

Background: Neural progenitor is a generic term used for undifferentiated cell populations of neural stem, neuronal progenitor and glial progenitor cells with abilities for proliferation and differentiation. We have shown functional expression of ionotropic N-methyl-D-aspartate (NMDA) and gamma-aminobutyrate type-A receptors endowed to positively and negatively regulate subsequent neuronal differentiation in undifferentiated neural progenitors, respectively. In this study, we attempted to evaluate the possible functional expression of nicotinic acetylcholine receptor (nAChR) by undifferentiated neural progenitors prepared from neocortex of embryonic rodent brains.
Methodology/Principal Findings: Reverse transcription polymerase chain reaction analysis revealed mRNA expression of particular nAChR subunits in undifferentiated rat and mouse progenitors prepared before and after the culture with epidermal growth factor under floating conditions. Sustained exposure to nicotine significantly inhibited the formation of neurospheres composed of clustered proliferating cells and 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide reduction activity at a concentration range of 1 mu M to 1 mM without affecting cell survival. In these rodent progenitors previously exposed to nicotine, marked promotion was invariably seen for subsequent differentiation into cells immunoreactive for a neuronal marker protein following the culture of dispersed cells under adherent conditions. Both effects of nicotine were significantly prevented by the heteromeric alpha 4 beta 2 nAChR subtype antagonists dihydro-beta-erythroidine and 4-(5-ethoxy-3-pyridinyl)-N-methyl-(3E)-3-buten-1-amine, but not by the homomeric alpha 7 nAChR subtype antagonist methyllycaconitine, in murine progenitors. Sustained exposure to nicotine preferentially increased the expression of Math1 among different basic helix-loop-helix proneural genes examined. In undifferentiated progenitors from embryonic mice defective of NMDA receptor subunit-1, nicotine was still effective in significantly inhibiting the proliferation.
Conclusions/Significance: Functional alpha 4 beta 2 nAChR subtype would be constitutively expressed to play a role in the mechanism underlying the determination of proliferation and subsequent differentiation fate into a neuronal lineage in association with preferential promotion of Math1 expression in undifferentiated neural progenitors of developing rodent neocortex independently of NMDA receptor activation.

DOI： 10.1371/journal.pone.0046177

Clock Genes Influence Gene Expression in Growth Plate and Endochondral Ossification in Mice 査読

Takeshi Takarada, Ayumi Kodama, Shogo Hotta, Michihiro Mieda, Shigeki Shimba, Eiichi Hinoi, Yukio Yoneda

JOURNAL OF BIOLOGICAL CHEMISTRY 287 ( 43 ) 36081 - 36095 2012年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC

We have previously shown transient promotion by parathyroid hormone of Period-1 (Per1) expression in cultured chondrocytes. Here we show the modulation by clock genes of chondrogenic differentiation through gene transactivation of the master regulator of chondrogenesis Indian hedgehog (IHH) in chondrocytes of the growth plate. Several clock genes were expressed with oscillatory rhythmicity in cultured chondrocytes and rib growth plate in mice, whereas chondrogenesis was markedly inhibited in stable transfectants of Per1 in chondrocytic ATDC5 cells and in rib growth plate chondrocytes from mice deficient of brain and muscle aryl hydrocarbon receptor nuclear translocator-like (BMAL1). Ihh promoter activity was regulated by different clock gene products, with clear circadian rhythmicity in expression profiles of Ihh in the growth plate. In BMAL1-null mice, a predominant decrease was seen in Ihh expression in the growth plate with a smaller body size than in wild-type mice. BMAL1 deficit led to disruption of the rhythmic expression profiles of both Per1 and Ihh in the growth plate. A clear rhythmicity was seen with Ihh expression in ATDC5 cells exposed to dexamethasone. In young mice defective of BMAL1 exclusively in chondrocytes, similar abnormalities were found in bone growth and Ihh expression. These results suggest that endochondral ossification is under the regulation of particular clock gene products expressed in chondrocytes during postnatal skeletogenesis through a mechanism relevant to the rhythmic Ihh expression.

DOI： 10.1074/jbc.M112.408963

Promotion of Both Proliferation and Neuronal Differentiation in Pluripotent P19 Cells with Stable Overexpression of the Glutamine Transporter slc38a1 査読

Masato Ogura, Takami Kakuda, Takeshi Takarada, Noritaka Nakamichi, Ryo Fukumori, Yeong-Hun Kim, Eiichi Hinoi, Yukio Yoneda

PLOS ONE 7 ( 10 ) e48270 2012年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PUBLIC LIBRARY SCIENCE

Background: We previously demonstrated the functional expression in newborn rat neocortical astrocytes of glutamine transporter (GlnT = slc38a1) believed to predominate in neurons over astroglia in the brain. In order to evaluate the possible role of this transporter in neurogenesis, we attempted to establish stable transfectants of GlnT in mouse embryonal carcinoma P19 cells endowed to proliferate for self-renewal and differentiate into progeny cells such as neurons and astroglia, in addition to in vitro pharmacological profiling of the green tea ingredient theanine, which is shown to be a potent inhibitor of glutamine transport mediated by GlnT in cultured neurons and astroglia.
Methodology/Principal Findings: The full-length coding region of rat GlnT was inserted into a vector for gene transfection along with selection by G418, followed by culture with all-trans retinoic acid under floating conditions and subsequent dispersion for spontaneous differentiation under adherent conditions. Stable overexpression of GlnT led to marked increases in the size of round spheres formed during the culture for 4 days and 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2Htetrazolium bromide reduction, with concomitant promotion of subsequent differentiation into cells immunoreactive for a neuronal marker protein. In these stable GlnT transfectants before differentiation, drastic upregulation was seen for mRNA expression of several proneural genes with a basic helix-loop-helix domain such as NeuroD1. Although a drastic increase was seen in NeuroD1 promoter activity in stable GlnT transfectants, theanine doubled NeuroD1 promoter activity in stable transfectants of empty vector (EV), without affecting the promoter activity already elevated in GlnT transfectants. Similarly, theanine promoted cellular proliferation and neuronal differentiation in stable EV transfectants, but failed to further stimulate the acceleration of both proliferation and neuronal differentiation found in stable GlnT transfectants.
Conclusions/Significance: GlnT would promote both proliferation and neuronal differentiation through a mechanism relevant to the upregulation of particular proneural genes in undifferentiated P19 cells.

DOI： 10.1371/journal.pone.0048270

Osteoclastogenesis is negatively regulated by D-serine produced by osteoblasts 査読

Takeshi Takarada, Mika Takarada-Iemata, Yoshifumi Takahata, Daisuke Yamada, Tomomi Yamamoto, Yukari Nakamura, Eiichi Hinoi, Yukio Yoneda

JOURNAL OF CELLULAR PHYSIOLOGY 227 ( 10 ) 3477 - 3487 2012年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：WILEY-BLACKWELL

We have shown the functional expression by chondrocytes of serine racemase (SR) which is responsible for the synthesis of D-serine (Ser) from L-Ser in cartilage. In this study, we evaluated the possible functional expression of SR by bone-forming osteoblasts and bone-resorbing osteoclasts. Expression of SR mRNA was seen in osteoblasts localized at the cancellous bone surface in neonatal rat tibial sections and in cultured rat calvarial osteoblasts endowed to release D-Ser into extracellular medium, but not in cultured osteoclasts differentiated from murine bone marrow progenitor cells. Sustained exposure to D-Ser failed to significantly affect alkaline phosphatase activity and Ca2+ accumulation in cultured osteoblasts, but significantly inhibited differentiation and maturation in a concentration-dependent manner at a concentration range of 0.11?mM without affecting cellular survival in cultured osteoclasts. By contrast, L-Ser promoted osteoclastic differentiation in a manner sensitive to the inhibition by D-Ser. Matured osteoclasts expressed mRNA for the amino acid transporter B0,+ (ATB0,+) and the system alanine, serine, and cysteine amino acid transporter-2 (ASCT2), which are individually capable of similarly incorporating extracellular L- and D-Ser. Knockdown of these transporters by siRNA prevented both the promotion by L-Ser and the inhibition by D-Ser of osteoclastic differentiation in pre-osteoclastic RAW264.7 cells. These results suggest that D-Ser may play a pivotal role in osteoclastogenesis through a mechanism related to the incorporation mediated by both ATB0,+ and ASCT2 of serine enantiomers in osteoclasts after the synthesis and subsequent release from adjacent osteoblasts. J. Cell. Physiol. 227: 34773487, 2012. (C) 2012 Wiley Periodicals, Inc.

DOI： 10.1002/jcp.24048

Signaling Factors in a Variety of Cells Derived from Mesenchymal Stem Cells 査読

Takeshi Takarada

YAKUGAKU ZASSHI-JOURNAL OF THE PHARMACEUTICAL SOCIETY OF JAPAN 132 ( 10 ) 1145 - 1149 2012年10月

記述言語：日本語出版者・発行元：PHARMACEUTICAL SOC JAPAN

L-Glutamate (Glu) and gamma-aminobutyric acid (GABA) has been thought to be an excitatory/inhibitory amino acid neurotransmitter in the mammalian central nervous system (CNS). Limited information is available in the literature with regard to an extracellular transmitter role of Glu and GABA in peripheral neuronal and non-neuronal tissues, whereas recent molecular biological analyses including ours give rise to a novel function for Glu and GABA as an autocrine and/or paracrine factor in a variety of cells derived from mesenchymal stem cells, in addition to other peripheral tissues including pancreas, adrenal, and pituitary glands. Emerging evidence suggests that Glu and GABA could play a dual role in mechanisms underlying maintenance of cellular homeostasis as a neurotransmitter in the CNS and as an extracellular signal mediator in peripheral autocrine and/or paracrine tissues. In this review, therefore, we summarized the possible signaling by Glu and GABA as an extracellular signal mediator in mechanisms underlying maintenance of cellular homeostasis in mesenchymal stem cells, osteoblasts and chondrocytes.

DOI： 10.1248/yakushi.12-00191

Possible involvement of mitochondrial uncoupling protein-2 in cytotoxicity mediated by acquired N-methyl-D-aspartate receptor channels 査読

Ryo Fukumori, Takeshi Takarada, Yuki Kambe, Ryota Nakazato, Koichi Fujikawa, Yukio Yoneda

NEUROCHEMISTRY INTERNATIONAL 61 ( 4 ) 498 - 505 2012年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD

We have previously shown the possible involvement of mitochondrial membrane potential disruption in the mechanisms underlying the neurotoxicity seen after activation of N-methyl-D-aspartate (NMDA) receptors (NMDAR) in primary cultured rat hippocampal neurons. In this study, we attempted to demonstrate a pivotal role of mitochondrial uncoupling protein-2 (UCP2) as a determinant of the NMDA neurotoxicity by using acquired NMDAR channels artificially orchestrated in HEK293 cells. In cells with overexpression of UCP2, immunoreactive UCP2 was exclusively detected at intracellular locations stained with the mitochondrial marker MitoTracker. In cells with acquired NMDAR channels, exposure to either NMDA or the calcium ionophore A23187 similarly led to a significant increase in cytosolic Ca2+ levels determined by Fluo-3 imaging irrespective of the overexpression of UCP2. By contrast, NMDA, but not A23187, was significantly more effective in increasing mitochondrial Ca2+ levels determined by Rhod-2 fluorescence imaging in cells transfected with NMDAR subunit and UCP2 expression vectors than in those without UCP2 overexpression. Overexpression of UCP2 significantly increased the number of cells stained with propidium iodide in cultures with acquired NMDAR channels, but failed to significantly affect that in cells exposed to A23187. Immunocytochemical and immunoprecipitation analyses similarly revealed the possible interaction between GluN1 subunit and UCP2 in HEK293 cells with acquired NMDAR channels and UCP2 overexpression. These results suggest that UCP2 could play a role as a determinant of the neurotoxicity mediated by NMDAR through a mechanism related to the unidentified interaction with the essential GluN1 subunit toward modulation of mitochondrial Ca2+ levels in neurons. (C) 2012 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.neuint.2012.03.019

Positive regulation by γ-aminobutyric acid B receptor subunit-1 of chondrogenesis through acceleration of nuclear translocation of activating transcription factor-4. 査読

Takahata Y, Hinoi E, Takarada T, Nakamura Y, Ogawa S, Yoneda Y

The Journal of biological chemistry 287 ( 40 ) 33293 - 33303 2012年9月

Delayed Mitochondrial Membrane Potential Disruption by ATP in Cultured Rat Hippocampal Neurons Exposed to N-Methyl-D-Aspartate 査読

Koichi Fujikawa, Noritaka Nakamichi, Shunsuke Kato, Ryo Fukumori, Miho Hida, Takeshi Takarada, Yukio Yoneda

JOURNAL OF PHARMACOLOGICAL SCIENCES 119 ( 1 ) 20 - 29 2012年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：JAPANESE PHARMACOLOGICAL SOC

Necrotic damage leads to a massive leakage from injured cells of different intracellular constituents such as glutamate (Glu) and ATP, which are believed to play a role in the neuronal survival in the brain. In this study, we evaluated pharmacological properties of ATP, which is shown to be an endogenous inhibitor of N-methyl-D-aspartate (NMDA) receptors, on the neurotoxicity relevant to mitochondrial membrane potential disruption in cultured rat hippocampal neurons. Exposure to Glu or NMDA significantly inhibited cellular viability determined 24 and 48 h later, while simultaneous addition of 1 mM ATP significantly ameliorated the decreased viability in neurons exposed to Glu and NMDA, but not in those exposed to other cytotoxins. Both Glu and NMDA markedly increased intracellular free Ca2+ levels in a manner sensitive to blockade by the exposure to ATP, but not by that to adenosine. Exposure to ATP significantly delayed the rate of mitochondrial membrane potential disruption induced by Glu and NMDA. These results suggest that extracellular ATP would play a role as an endogenous antagonist endowed to protect rat hippocampal neurons from the excitotoxicity mediated by NMDA receptors in association with the delayed mitochondrial membrane potential disruption after the liberation from adjacent cells under necrotic death.

DOI： 10.1254/jphs.12034FP

Possible Modulation of Process Extension by N-Methyl-D-aspartate Receptor Expressed in Osteocytic MLO-Y4 Cells 査読

Hiroyuki Fujita, Eiichi Hinoi, Eri Nakatani, Tomomi Yamamoto, Takeshi Takarada, Yukio Yoneda

JOURNAL OF PHARMACOLOGICAL SCIENCES 119 ( 1 ) 112 - 116 2012年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：JAPANESE PHARMACOLOGICAL SOC

In contrast to osteoblasts, little attention has been paid to expression profiles of different glutamatergic signaling machineries in osteocytes, which are the most abundant cells with a possible role as a mechanical sensor in bone. Here, we show that N-methyl-D-aspartate receptor (NMDAR) is expressed by osteocytic cells in five-weeks-old mouse tibiae in vivo as well as by osteocytic MLO-Y4 cells in vitro. Sustained exposure to the NMDAR antagonist dizocilpine significantly increased the number of cells with processes in cultured MLO-Y4 cells. These results suggest that NMDAR would be expressed by osteocytes with an unidentified role in the process extension.

DOI： 10.1254/jphs.12068SC

Transferrin receptor-1 suppresses neurite outgrowth in neuroblastoma Neuro2A cells 査読

Yukary Nakamura, Noritaka Nakamichi, Takeshi Takarada, Kiyokazu Ogita, Yukio Yoneda

NEUROCHEMISTRY INTERNATIONAL 60 ( 5 ) 448 - 457 2012年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD

Transferrin receptor-1 (TfR1) is a cell membrane-associated glycoprotein responsible for incorporation of the iron bound to transferrin through an endocytotic process from the circulating blood. Iron is believed to play a dual role as an active center of the electron transfer system in mitochondria and as an endogenous cytotoxin through promoted generation of reactive oxygen species in different eukaryotic cells. In this study, we evaluated expression profiles of different genes related to iron mobilization across plasma membranes in neuronal cells. Marked mRNA expression was seen for various iron-related genes such as TfR1 in cultured mouse neocortical neurons, while TfR1 mRNA levels were more than doubled during culture from 3 to 6 days. In mouse embryonal carcinoma P19 cells endowed to differentiate into neuronal and astroglial lineages, a transient increase was seen in both mRNA and corresponding protein for TfR1 in association with neuronal marker expression during culture with all-trans retinoic acid (ATRA). In neuronal Neuro2A cells cultured with ATRA, moreover, neurite was elongated together with increased expression of both mRNA and protein for TfR1. Overexpression of TfR1 significantly decreased the length of neurite elongated, however, while significant promotion was invariably seen in the neurite elongation in Neuro2A cells transfected with TfR1 siRNA as well as in Neuro2A cells cultured with an iron chelator. These results suggest that TfR1 would be highly expressed by neurons rather than astroglia to play a negative role in the neurite outgrowth after the incorporation of circulating transferrin in the brain. (C) 2011 Published by Elsevier B.V.

DOI： 10.1016/j.neuint.2011.08.018

Positive Regulation of Osteoclastic Differentiation by Growth Differentiation Factor 15 Upregulated in Osteocytic Cells Under Hypoxia 査読

Eiichi Hinoi, Hiroki Ochi, Takeshi Takarada, Eri Nakatani, Takashi Iezaki, Hiroko Nakajima, Hiroyuki Fujita, Yoshifumi Takahata, Shinya Hidano, Takashi Kobayashi, Shu Takeda, Yukio Yoneda

JOURNAL OF BONE AND MINERAL RESEARCH 27 ( 4 ) 938 - 949 2012年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：WILEY-BLACKWELL

Osteocytes are thought to play a role as a mechanical sensor through their communication network in bone. Although osteocytes are the most abundant cells in bone, little attention has been paid to their physiological and pathological functions in skeletogenesis. Here, we have attempted to delineate the pivotal functional role of osteocytes in regulation of bone remodeling under pathological conditions. We first found markedly increased osteoclastic differentiation by conditioned media (CM) from osteocytic MLO-Y4 cells previously exposed to hypoxia in vitro. Using microarray and real-time PCR analyses, we identified growth differentiation factor 15 (GDF15) as a key candidate factor secreted from osteocytes under hypoxia. Recombinant GDF15 significantly promoted osteoclastic differentiation in a concentration-dependent manner, with concomitant facilitation of phosphorylation of both p65 and inhibitory-kappa B in the presence of receptor activator of nuclear factor-kappa B ligand. To examine the possible functional significance of GDF15 in vivo, mice were subjected to ligation of the right femoral artery as a hypoxic model. A significant increase in GDF15 expression was specifically observed in tibias of the ligated limb but not in tibias of the normally perfused limb. Under these experimental conditions, in cancellous bone of proximal tibias in the ligated limb, a significant reduction was observed in bone volume, whereas a significant increase was seen in the extent of osteoclast surface/bone surface when determined by bone histomorphometric analysis. Finally, the anti-GDF15 antibody prevented bone loss through inhibiting osteoclastic activation in tibias from mice with femoral artery ligation in vivo, in addition to suppressing osteoclastic activity enhanced by CM from osteocytes exposed to hypoxia in vitro. These findings suggest that GDF15 could play a pivotal role in the pathogenesis of bone loss relevant to hypoxia through promotion of osteoclastogenesis after secretion from adjacent osteocytes during disuse and/or ischemia in bone. (c) 2012 American Society for Bone and Mineral Research.

DOI： 10.1002/jbmr.1538

Artificial orchestration of functional NMDAR channels in HEK293 cells 査読

Takaya Katsurayama, Ryo Fukumori, Takeshi Takarada, Yukio Yoneda

Japanese Journal of Neuropsychopharmacology 32 ( 2 ) 113 - 114 2012年4月

NR2-reactive antibody decreases cell viability through augmentation of Ca2+ influx in systemic lupus erythematosus 査読

Takahisa Gono, Takeshi Takarada, Ryo Fukumori, Yasushi Kawaguchi, Hirotaka Kaneko, Masanori Hanaoka, Yasuhiro Katsumata, Yukio Yoneda, Hisashi Yamanaka

ARTHRITIS AND RHEUMATISM 63 ( 12 ) 3952 - 3959 2011年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：WILEY-BLACKWELL

Objective AntiN-methyl-D-aspartate (anti-NMDA) receptor subunit NR2-reactive antibody may play a crucial role in neuronal manifestations of systemic lupus erythematosus (SLE). However, how NR2-reactive antibody acts as a critical modulator of the NMDA receptor is unknown. This study was undertaken to investigate the biologic function of NR2-reactive antibody in patients with SLE.
Methods. The study included 14 patients with SLE, 9 of whom had NR2-reactive antibody. We analyzed the effects of NR2-reactive antibody on cell viability and intracellular Ca2+ level. We also investigated the efficacy of zinc as a modulator of the intracellular Ca2+ level in the presence of NR2-reactive antibody.
Results. There was a significant inverse correlation between the NR2-reactive antibody titer and cell viability (R-2 = 0.67, P < 0.0001; n = 23), and there was a significant association between the NR2-reactive antibody titer and the intracellular Ca2+ level in NR1/NR2a-transfected HEK 293 cells (R-2 = 0.69, P < 0.0001). Intracellular Ca2+ levels were significantly higher in cells incubated with IgG derived from NR2reactive antibody-positive SLE patients than in those incubated with IgG derived from NR2-reactive antibody-negative SLE patients (P = 0.0002). The addition of zinc decreased the intracellular Ca2+ level in a dose-dependent manner. NR2-reactive antibodypositive SLE IgG weakened the efficacy of zinc as a negative modulator of the intracellular Ca2+ level.
Conclusion. Our findings indicate that NR2-reactive antibody decreases cell viability by Ca2+ influx in SLE through inhibition of the binding capacity of zinc.

DOI： 10.1002/art.30616

Negative Regulation of Osteoblastogenesis Through Downregulation of Runt-Related Transcription Factor-2 in Osteoblastic MC3T3-E1 Cells with Stable Overexpression of the Cystine/Glutamate Antiporter xCT Subunit 査読

Kyosuke Uno, Takeshi Takarada, Mika Takarada-Iemata, Yukari Nakamura, Hiroyuki Fujita, Eiichi Hinoi, Yukio Yoneda

JOURNAL OF CELLULAR PHYSIOLOGY 226 ( 11 ) 2953 - 2964 2011年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：WILEY-BLACKWELL

We have previously demonstrated that glutamate (Glu) suppresses cellular proliferation toward self-renewal through amechanism associated with intracellularGSHdepletionmediated by the bidirectional cystine/Glu antiporter in osteoblasticMC3T3-E1 cells cultured in the absence of differentiation inducers. To further evaluate the possible role of the antiporter in osteoblastogenesis, in this study, we have established stable transfectants of the xCT subunit of the antiporter in MC3T3-E1 cells. Stable overexpression led to a significant facilitation of cellular proliferation determined by different indices with increased GSH levels and decreased ROS generation in addition to promoted [(14)C] cystine incorporation, while Glu failed to significantly inhibit cellular proliferation in stable xCT transfectants. In stable transfectants cultured under differentiation conditions, drastic decreases were invariably seen in Ca(2+) accumulation, alkaline phosphatase activity and several osteoblastic marker gene expressions, in addition to downregulation ofmRNA and corresponding protein for runt-related transcription factor-2 (Runx2). Runx2 promoter activitywas significantly promoted by the introduction ofRunx2 expression vector in amanner sensitive to the prevention by the co-introduction of xCT expression vector in MC3T3-E1 cells. In both MC3T3-E1 cells and murine calvarial osteoblasts cultured with differentiation inducers, transient transfection with xCT siRNA significantly increased Runx2 protein expression alongwith decreases in xCT mRNA expression and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide reduction. These results suggest that the cystine/ Glu antiporter plays a pivotal role in cellular differentiation through a mechanismrelated to the regulation of transactivation of Runx2 essential for osteoblastogenesis toward maturation in osteoblastic cells. J. Cell. Physiol. 226: 2953-2964, 2011. (C) 2011 Wiley-Liss, Inc.

DOI： 10.1002/jcp.22642

Osteoblastic γ-aminobutyric acid, type B receptors negatively regulate osteoblastogenesis toward disturbance of osteoclastogenesis mediated by receptor activator of nuclear factor κB ligand in mouse bone. 査読

Takahata Y, Takarada T, Hinoi E, Nakamura Y, Fujita H, Yoneda Y

The Journal of biological chemistry 286 ( 38 ) 32906 - 32917 2011年9月

A possible pivotal role of mitochondrial free calcium in neurotoxicity mediated by N-methyl-D-aspartate receptors in cultured rat hippocampal neurons 査読

Yuki Kambe, Noritaka Nakamichi, Takeshi Takarada, Ryo Fukumori, Ryota Nakazato, Eiichi Hinoi, Yukio Yoneda

NEUROCHEMISTRY INTERNATIONAL 59 ( 1 ) 10 - 20 2011年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD

We have previously shown that mitochondrial membrane potential disruption is involved in mechanisms underlying differential vulnerabilities to the excitotoxicity mediated by N-methyl-D-aspartate (NMDA) receptors between primary cultured neurons prepared from rat cortex and hippocampus. To further elucidate the role of mitochondria in the excitotoxicity after activation of NMDA receptors, neurons were loaded with the fluorescent dye calcein diffusible in the cytoplasm and organelles for determination of the activity of mitochondrial permeability transition pore (mPTP) responsible for the leakage of different mitochondrial molecules. The addition of CoCl2 similarly quenched the intracellular fluorescence except mitochondria in both cultured neurons, while further addition of NMDA led to a leakage of the dye into the cytoplasm in hippocampal neurons only. An mPTP inhibitor prevented the NMDA-induced loss of viability in hippocampal neurons, while an activator of mPTP induced a similarly potent loss of viability in cortical and hippocampal neurons. Although NMDA was more effective in increasing rhodamine-2 fluorescence as a mitochondrial calcium indicator in hippocampal than cortical neurons, a mitochondrial calcium uniporter inhibitor significantly prevented the NMDA-induced loss of viability in hippocampal neurons. Expression of mRNA was significantly higher for the putative uniporter uncoupling protein-2 in hippocampal than cortical neurons. These results suggest that mitochondrial calcium uniporter would be at least in part responsible for the NMDA neurotoxicity through a mechanism relevant to promotion of mPTP orchestration in hippocampal neurons. (C) 2011 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.neuint.2011.03.018

Selective Upregulation of Pen1 mRNA Expression by ATP Through Activation of P2X7 Purinergic Receptors Expressed in Microglial Cells 査読

Ryota Nakazato, Takeshi Takarada, Tomomi Yamamoto, Shogo Hotta, Eiichi Hinoi, Yukio Yoneda

JOURNAL OF PHARMACOLOGICAL SCIENCES 116 ( 4 ) 350 - 361 2011年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：JAPANESE PHARMACOLOGICAL SOC

Clock genes are believed to play a pivotal role in the generation and oscillation of circadian rhythm as a central clock in the hypothalamic suprachiasmatic nucleus in the mammalian brain. In this study, mRNA expression was for the first time demonstrated with clock genes in both cultured murine microglia and microglial cell line BV-2 cells. Exposure to ATP transiently increased Period-1 (Per1) mRNA expression without affecting that of other clock genes in BV-2 cells, while a similarly transient increase was shown in Per1 mRNA expression in a manner sensitive to P2X7 purinergic receptor antagonists in cultured microglia exposed to ATP. In BV-2 cells transfected with a Per1 promoter luciferase reporter plasmid, ATP significantly increased luciferase activity in a manner sensitive to a P2X7-receptor antagonist. In both microglia and BV-2 cells, a significant increase by ATP was seen in the immunocytochemical fluorescence intensity of cells expressing Per1 protein, with mRNA expression of different P2 receptors including P2X7. Per1 siRNA significantly decreased the number of cells with processes in BV-2 cells exposed to ATP. These results suggest that ATP selectively promotes Per1 expression through gene transactivation after stimulation of P2X7 purinergic receptors in microglial cells.

DOI： 10.1254/jphs.11069FP

Selective downregulation of N-methyl-D-aspartate receptor (NMDAR) rather than non-NMDAR subunits in ipsilateral cerebral hemispheres in rats with middle cerebral artery occlusion 査読

Takeshi Takarada, Tomoya Hara, Shiho Konishi, Ryota Nakazato, Yukio Yoneda

Japanese Journal of Neuropsychopharmacology 31 ( 4 ) 187 - 194 2011年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：4

Ischemic brain damage is believed to involve the drastic increase in extracellular glutamate levels after reperfusion and subsequent overactivation of both N-methyl-D-aspartate (NMDA) receptor (NMDAR) and non-NMDAR channels for delayed neuronal cell death mediated by Ca 2+ overload. In this study, we evaluated expression profiles of mRNA and corresponding proteins for different subunits of NMDAR and non-NMDAR in brains of rats with transient middle cerebral artery occlusion (MCAO). Cellular vitality was markedly reduced in proportion to increasing durations of MCAO for 1 to 8 h when determined 1 day after reperfusion. Within 7 days after reperfusion, MCAO for 2 h led to a gradual decrease in the neuronal marker microtubules-associated protein-2 (MAP2) level in the ipsilateral cerebral hemisphere, in addition to inducing a transient increase in the microglial marker CD11b expression without affecting the astroglial marker protein levels. MCAO for 2 h significantly decreased the expression of both mRNA and corresponding proteins for NR1, NR2A and NR2B subunits of NMDAR, but not for non-NMDAR subunits, in the ipsilateral hemisphere. These results suggest that NMDAR may be preferentially down-regulated in response to ischemic signal inputs amongst three different subtypes of ionotropic glutamate receptors in rats with MCAO.

Positive Regulation by GABA(B)R1 Subunit of Leptin Expression through Gene Transactivation in Adipocytes 査読

Yukari Nakamura, Eiichi Hinoi, Takeshi Takarada, Yoshifumi Takahata, Tomomi Yamamoto, Hiroyuki Fujita, Saya Takada, Syota Hashizume, Yukio Yoneda

PLOS ONE 6 ( 5 ) e20167 2011年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PUBLIC LIBRARY SCIENCE

Background: The view that gamma-aminobutyric acid (GABA) plays a functional role in non-neuronal tissues, in addition to an inhibitory neurotransmitter role in the mammalian central nervous system, is prevailing, while little attention has been paid to GABAergic signaling machineries expressed by adipocytes to date. In this study, we attempted to demonstrate the possible functional expression of GABAergic signaling machineries by adipocytes.
Methodology/Principal Findings: GABA(B) receptor 1 (GABA(B)R1) subunit was constitutively expressed by mouse embryonic fibroblasts differentiated into adipocytes and adipocytic 3T3-L1 cells in culture, as well as mouse white adipose tissue, with no responsiveness to GABA(B)R ligands. However, no prominent expression was seen with mRNA for GABA(B)R2 subunit required for heteromeric orchestration of the functional GABA(B)R by any adipocytic cells and tissues. Leptin mRNA expression was significantly and selectively decreased in adipose tissue and embryonic fibroblasts, along with drastically reduced plasma leptin levels, in GABA(B)R1-null mice than in wild-type mice. Knockdown by siRNA of GABA(B)R1 subunit led to significant decreases in leptin promoter activity and leptin mRNA levels in 3T3-L1 cells.
Conclusions/Significance: Our results indicate that GABA(B)R1 subunit is constitutively expressed by adipocytes to primarily regulate leptin expression at the transcriptional level through a mechanism not relevant to the function as a partner of heterodimeric assembly to the functional GABA(B)R.

DOI： 10.1371/journal.pone.0020167

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