Mitsuaki Moriyama

Osaka Prefecture University, Sakai, Osaka-fu, Japan

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Publications (40)147.09 Total impact

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    ABSTRACT: Amphotericin B (AmB) is a polyene antifungal drug and is reported to be one of a few reagents having therapeutic effects on prion diseases, that is, a delay in the appearance of clinical signs and prolongation of the survival time in an animal model. In prion diseases, glial cells have been suggested to play important roles; however, the therapeutic mechanism of AmB on prion diseases remains elusive. We have previously reported that AmB changed the expression of neurotrophic factors in microglia and astrocytes (Motoyoshi et al., 2008, Neurochem. Int. 52, 1290-1296; Motoyoshi-Yamashiro et al., 2013, ibid. 63, 93-100). These results suggested that neurotrophic factors derived from glial cells might be involved in the therapeutic mechanism of AmB. In the present study, we examined immunohistochemically the effects of AmB on the expression of neurotrophic factors in the rat brain. We found that direct injection of AmB into the striatum significantly enhanced the expression of glial cell line-derived neurotrophic factor protein. Amphotericin B also increased the expressions of CD11b and glial fibrillary acidic protein, markers of microglia and astrocytes, respectively. Moreover, expressions of the two neurotrophic factors by AmB were co-localized with the expression of CD11b or glial fibrillary acidic protein. These results suggest that AmB in vivo might also activate glial cells and induce the production of neurotrophic factors protecting neurons in prion diseases.
    The Journal of veterinary medical science / the Japanese Society of Veterinary Science. 10/2014;
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    ABSTRACT: Objectives: In peripheral macrophages, tissue-type transglutaminase (TG2) is reported to be involved in phagocytosis of apoptotic cells. However, the contribution of TG2 to microglial phagocytosis has not been investigated. In this study, using a microglial cell line, BV-2, we examined the changes in TG2 expression, phagocytosis and pinocytosis in cells stimulated by lipopolysaccharide (LPS). Methods: Cells of the mouse microglial cell line BV-2 were stimulated by LPS with or without cystamine, an inhibitor of TG enzyme activity, for 24 h. TG2 expression was measured by real-time RT-PCR and Western blotting. TG activity was evaluated using biotinylated pentylamine as a substrate. Pinocytosis was determined by uptake of 1-µm fluorescent microbeads. Phagocytosis was assessed by uptake of dead cells, human neuroblastoma SH-SY5Y cells, which were pretreated with H2O2 for 24 h. Results: Phagocytosis of dead cells and pinocytosis of fluorescent microbeads were up-regulated by LPS stimulation together with TG2 expression. Blockade of TG enzyme activity by cystamine suppressed TG2 expression, phagocytosis and pinocytosis. Conclusions: These results suggested that LPS-induced TG2 was involved in the mechanism of pinocytosis and phagocytosis in microglia. © 2014 S. Karger AG, Basel.
    NeuroImmunoModulation 10/2014; · 1.84 Impact Factor
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    ABSTRACT: Elucidation of the functions of astrocytes is important for understanding of the pathogenic mechanism of various neurodegenerative diseases. Theophylline is a common drug for bronchial asthma and occasionally develops side-effects, such as acute encephalopathy; although the pathogenic mechanism of the side-effects is unknown. The lipopolysaccharide (LPS)-induced nitric oxide (NO) production is generally used for an index of the activation of astrocyte in vitro. In this study, in order to elucidate the effect of theophylline on the astrocytic functions, we examined the LPS-induced NO production and the expression of iNOS in cultured rat cortex astrocytes. Theophylline alone could not induce the NO production; however, NO production induced by LPS was enhanced by theophylline in a dose-dependent manner; and by isobutylmethylxanthine, a phosphodiesterase inhibitor. The theophylline enhancement of LPS-induced NO production was further increased by dibutyryl cyclic AMP, a membrane-permeable cAMP analog; and by forskolin, an adenylate cyclase activator. When the cells were preincubated with Rp-8-Br-cAMP, an inhibitor of protein kinase A, the theophylline enhancement of LPS-induced NO production was decreased. The extent of iNOS protein expression induced by LPS was also enhanced by theophylline. It is likely that phosphodiesterase inhibition is a major action mechanism for the theophylline enhancement of LPS-induced NO production in astrocytes. Theophylline-induced acute encephalopathy might be due to the hyper-activation of astrocytes via cAMP signaling to produce excess amount of NO.
    Neurochemical Research 11/2013; · 2.13 Impact Factor
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    ABSTRACT: Amphotericin B (AmB) is a polyene antibiotic and reported to be one of a few reagents having therapeutic effects on prion diseases, such as the delay in the appearing of the clinical signs and the prolongation of the survival time. In prion diseases, glial cells have been suggested to play important roles by proliferating and producing various factors such as nitric oxide, proinflammatory cytokines, and neurotrophic factors. However, the therapeutic mechanism of AmB on prion diseases remains elusive. We have previously reported that AmB changed the expression of neurotoxic and neurotrophic factors in microglia (Motoyoshi et al., 2008, Neurochem. Int. 52, 1290-1296). In the present study, we examined the effects of AmB on cellular functions of rat cultured astrocytes. We found that AmB could activate astrocytes to produce nitric oxide via inducible nitric oxide synthase induction. AmB also induced mRNA expression of interleukin-1β and tumor necrosis factor-α, and productions of their proteins in astrocytes. Moreover, AmB changed levels of neurotrophic factor mRNAs and proteins. Among three neurotrophic factors examined here, neurotrophin-3 mRNA expression and its protein production in the cells were down-regulated by AmB stimulation. On the other hand, AmB significantly enhanced the amounts of glial cell line-derived neurotrophic factor and brain-derived neurotrophic factor proteins in the cells and the medium. These results suggest that AmB might show therapeutic effects on prion diseases by controlling the expression and production of such mediators in astrocytes.
    Neurochemistry International 05/2013; · 2.66 Impact Factor
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    ABSTRACT: Depression is one of the most prevalent and livelihood-threatening forms of mental illnesses and the neural circuitry underlying depression remains incompletely understood. Recent studies suggest that the neuronal plasticity involved with brain-derived neurotrophic factor (BDNF) plays an important role in the recovery from depression. Some antidepressants are reported to induce BDNF expression in vivo; however, the mechanisms have been considered solely in neurons and not fully elucidated. In the present study, we evaluated the effects of imipramine, a classic tricyclic antidepressant drug, on BDNF expression in cultured rat brain astrocytes. Imipramine dose-dependently increased BDNF mRNA expression in astrocytes. The imipramine-induced BDNF increase was suppressed with inhibitors for protein kinase A (PKA) or MEK/ERK. Moreover, imipramine exposure activated transcription factor cAMP response element binding protein (CREB) in a dose-dependent manner. These results suggested that imipramine induced BDNF expression through CREB activation via PKA and/or ERK pathways. Imipramine treatment in depression might exert antidepressant action through BDNF production from astrocytes, and glial BDNF expression might be a target of developing novel antidepressants.
    Journal of Pharmacological Sciences 10/2012; · 2.15 Impact Factor
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    ABSTRACT: Under some pathological conditions in brain, a large amount of superoxide anion (O(2) (-)) is produced, causing various cellular damages. Among three isozymes of superoxide dismutase (SOD), extracellular (EC)-SOD should play a role to detoxify O(2) (-) in extracellular space; however, a little is known about EC-SOD in brain. Although dopamine (DA) stored in the synaptic vesicle is stable, the excess leaked DA is spontaneously oxidized to yield O(2) (-) and reactive DA quinones, causing damages of dopaminergic neurons. In the present study, we examined the effects of DA on SOD expression in cultured rat cortical astrocytes. By means of RT-PCR, all mRNA of three isozymes of SOD could be detected; however, only EC-SOD was increased by DA exposure for 24 h, dose-dependently. The expression of EC-SOD protein and the cell-surface SOD activity in astrocytes also increased with 100 μM DA exposure. The increase of EC-SOD mRNA by DA was inhibited by a DA transporter inhibitor, GBR12909, whereas it was not changed by DA receptor antagonists, SKF-83566 (D1) and haloperidol (D2). Furthermore, a monoamine oxidase inhibitor, pargyline, and antioxidants, N-acetyl-L-cysteine and glutathione, also did not affect the DA-induced expression of EC-SOD mRNA. On the other hand, an inhibitor of nuclear factor kappaB (NF-κB), ammonium pyrrolidine-1-carbodithioate, suppressed the DA-induced expression of EC-SOD mRNA. These results suggest that DA incorporated into the cells caused the induction of EC-SOD mRNA followed by the enhancements of EC-SOD protein level and the enzyme activity, and that NF-κB activation is involved in the mechanisms of the EC-SOD induction. The regulation of EC-SOD in astrocytes surrounding dopaminergic neurons may contribute to the defensive mechanism against oxidative stress in brain.
    Neurochemical Research 09/2012; · 2.13 Impact Factor
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    ABSTRACT: Under pathological conditions such as ischemia/reperfusion, a large amount of superoxide anion (O(2) (-)) is produced and released in brain. Among three isozymes of superoxide dismutase (SOD), extracellular (EC)-SOD, known to be excreted outside cells and bound to extracellular matrix, should play a role to detoxify O(2) (-) in extracellular space; however, a little is known about EC-SOD in brain. In order to evaluate the SOD activity in extracellular space of CNS as direct as possible, we attempted to measure the cell-surface SOD activity on primary cultured rat brain cells by the inhibition of color development of a water-soluble tetrazolium due to O(2) (-) generation by xanthine oxidase/hypoxanthine added into extracellular medium of intact cells. The cell-surface SOD activity on cultured neuron and microglia was below the detection limit; however, that on cultured astrocyte was high enough to measure. By means of RT-PCR, all mRNA of three isozymes of SOD could be detected in the three types of the cells examined; however, the semi-quantitative analysis revealed that the level of EC-SOD mRNA in astrocytes was significantly higher than that in neurons and microglia. When astrocytes were stimulated with lipopolysaccharide (LPS) for 12-24 h, the cell-surface SOD activity decreased to a half, whereas the activity recovered after 36-48 h. The decrease in the activity was dependent on the LPS concentration. On the other hand, the SOD activity in the medium increased by the LPS-stimulation in a dose dependent manner; suggesting that the SOD protein localized on cell-surface, probably EC-SOD, was released into the medium. These results suggest that EC-SOD of astrocyte play a role for detoxification of extracellular O(2) (-) and the regulation of EC-SOD in astrocytes may contribute to the defensive mechanism against oxidative stress in brain.
    Neurochemical Research 06/2012; 37(10):2108-16. · 2.13 Impact Factor
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    ABSTRACT: Activation of glia has been observed in various neurodegenerative diseases. Excessive production of nitric oxide (NO), as a consequence of increased inducible nitric oxide synthase (iNOS) in glia, contributes to the neurodegeneration. The enhancement of intracellular stresses such as oxidative stress and endoplasmic reticulum (ER) stress has been also implicated in several neurodegenerative disorders. During a search for compounds that regulate ER stress, a dibenzoylmethane derivative, 2,2′-dimethoxydibenzoylmethane (DBM 14-26), was identified as a novel neuroprotective agent (Takano et al. [2007] Am. J. Physiol. Cell Physiol. 293:C1884–C1894). In the present study, we found that DBM 14-26 protected cultured astrocytes from H2O2-induced cytotoxicity at lower concentrations than antioxidants, GSH and N-acetyl cysteine. DBM 14-26 prevented the productionof reactive oxygen species in the cells exposed to H2O2 as evaluated by fluorescent intensity of dichlorofluorescein. Further examination revealed that DBM 14-26 inhibited lipopolysaccharide (LPS)-induced iNOS expression and NO production. DBM 14-26 suppressed LPS-stimulated nuclear factor-κB (NF-κB) activation evaluated by p65 immunostaining and gel retardation electrophoresis. These results indicate thatDBM 14-26 protects astrocytes from oxidative stress and suppresses astrocytes activation via inhibition of NF-κB activation. Functional regulation of astrocytes by DBM 14-26 could be a therapeutic candidate for the treatment of neurodegenerative diseases. © 2011 Wiley-Liss, Inc.
    Journal of Neuroscience Research 03/2011; 89(6):955-65. · 2.97 Impact Factor
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    ABSTRACT: Brain edema and associated increased intracranial pressure are major consequences of traumatic brain injury (TBI). An important early component of the edema associated with TBI is astrocyte swelling (cytotoxic edema). Mechanisms for such swelling, however, are poorly understood. Ion channels/transporters/exchangers play a major role in cell volume regulation, and a disturbance in one or more of these systems may result in cell swelling. To examine potential mechanisms in TBI-mediated brain edema, we employed a fluid percussion model of in vitro barotrauma and examined the role of the ion transporter Na(+)-K(+)-2Cl(-)-cotransporter 1 (NKCC1) in trauma-induced astrocyte swelling as this transporter has been strongly implicated in the mechanism of cell swelling in various neurological conditions. Cultures exposed to trauma (3, 4, 5 atm pressure) caused a significant increase in NKCC1 activity (21%, 42%, 110%, respectively) at 3 h. At 5 atm pressure, trauma significantly increased NKCC1 activity at 1 h and it remained increased for up to 3 h. Trauma also increased the phosphorylation (activation) of NKCC1 at 1 and 3 h. Inhibition of MAPKs and oxidative/nitrosative stress diminished the trauma-induced NKCC1 phosphorylation as well as its activity. Bumetanide, an inhibitor of NKCC1, significantly reduced the trauma-induced astrocyte swelling (61%). Silencing NKCC1 with siRNA led to a reduction in trauma-induced NKCC1 activity as well as in cell swelling. These findings demonstrate the critical involvement of NKCC1 in the astrocyte swelling following in vitro trauma, and suggest that blocking NKCC1 activity may represent a useful therapeutic strategy for the cytotoxic brain edema associated with the early phase of TBI.
    Journal of Neurochemistry 02/2011; 117(3):437-48. · 3.97 Impact Factor
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    ABSTRACT: Cytotoxic brain edema, usually a consequence of astrocyte swelling, is an important complication of stroke, traumatic brain injury, hepatic encephalopathy, and other neurological disorders. Although mechanisms underlying astrocyte swelling are not fully understood, oxidative stress (OS) has generally been considered an important factor in its pathogenesis. To better understand the mechanism(s) by which OS causes cell swelling, we examined the potential involvement of mitogen-activated protein kinases (MAPKs) in this process. Cultures exposed to theoxidant H2O2 (10, 25, 50 μM) for different time periods (1–24 hr) significantly increased cell swelling in a triphasic manner. Swelling was initially observed at 10 min (peaking at 30 min), which was followed by cell shrinkage at 1 hr. A subsequent increase in cell volume occurred at approximately 6 hr, and the rise lasted for at least 24 hr. Cultures exposed to H2O2 caused the activation of MAPKs (ERK1/2, JNK and p38-MAPK), whereas inhibition of MAPKs diminished cell swelling induced by 10 and 25 μM H2O2. These findings suggest that activation of MAPKs is an important factor in the mediation of astrocyte swelling following oxidative stress. © 2010 Wiley-Liss, Inc.
    Journal of Neuroscience Research 08/2010; 88(11):2450 - 2458. · 2.97 Impact Factor
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    ABSTRACT: Brain edema and the consequent increase in intracranial pressure and brain herniation are major complications of acute liver failure (fulminant hepatic failure) and a major cause of death in this condition. Ammonia has been strongly implicated as an important factor, and astrocyte swelling appears to be primarily responsible for the edema. Ammonia is known to cause cell swelling in cultured astrocytes, although the means by which this occurs has not been fully elucidated. A disturbance in one or more of these systems may result in loss of ion homeostasis and cell swelling. In particular, activation of the Na-K-Cl cotransporter (NKCC1) has been shown to be involved in cell swelling in several neurological disorders. We therefore examined the effect of ammonia on NKCC activity and its potential role in the swelling of astrocytes. Cultured astrocytes were exposed to ammonia (NH(4)Cl; 5 mm), and NKCC activity was measured. Ammonia increased NKCC activity at 24 h. Inhibition of this activity by bumetanide diminished ammonia-induced astrocyte swelling. Ammonia also increased total as well as phosphorylated NKCC1. Treatment with cyclohexamide, a potent inhibitor of protein synthesis, diminished NKCC1 protein expression and NKCC activity. Since ammonia is known to induce oxidative/nitrosative stress, and antioxidants and nitric-oxide synthase inhibition diminish astrocyte swelling, we also examined whether ammonia caused oxidation and/or nitration of NKCC1. Cultures exposed to ammonia increased the state of oxidation and nitration of NKCC1, whereas the antioxidants N-nitro-l-arginine methyl ester and uric acid all significantly diminished NKCC activity. These agents also reduced phosphorylated NKCC1 expression. These results suggest that activation of NKCC1 is an important factor in the mediation of astrocyte swelling by ammonia and that such activation appears to be mediated by NKCC1 abundance as well as by its oxidation/nitration and phosphorylation.
    Journal of Biological Chemistry 11/2008; 283(49):33874-82. · 4.65 Impact Factor
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    ABSTRACT: Astrocyte swelling and brain edema are major neuropathological findings in the acute form of hepatic encephalopathy (fulminant hepatic failure), and substantial evidence supports the view that elevated brain ammonia level is an important etiological factor in this condition. Although the mechanism by which ammonia brings about astrocyte swelling remains to be determined, oxidative/nitrosative stress and mitogen-activated protein kinases (MAPKs) have been considered as important elements in this process. One factor known to be activated by both oxidative stress and MAPKs is nuclear factor kappaB (NFkappaB), a transcription factor that activates many genes, including inducible nitric oxide synthase (iNOS). As the product of iNOS, nitric oxide (NO), is known to cause astrocyte swelling, we examined the potential involvement of NFkappaB in ammonia-induced astrocyte swelling. Western blot analysis of cultured astrocytes showed a significant increase in NFkappaB nuclear translocation (a measure of NFkappaB activation) from 12 h to 2 days after treatment with NH(4)Cl (5 mM). Cultures treated with anti-oxidants, including superoxide dismutase, catalase, and vitamin E as well as the MAPKs inhibitors, SB239063 (an inhibitor of p38-MAPK) and SP600125 (an inhibitor of c-Jun N-terminal kinase), significantly diminished NFkappaB activation by ammonia, supporting a role of oxidative stress and MAPKs in NFkappaB activation. The activation of NFkappaB was associated with increased iNOS protein expression and NO generation, and these changes were blocked by BAY 11-7082, an inhibitor of NFkappaB. Additionally, ammonia-induced astrocyte swelling was inhibited by the NFkappaB inhibitors, BAY 11-7082 and SN-50, thereby implicating NFkappaB in the mechanism of astrocyte swelling. Our studies indicate that cultured astrocytes exposed to ammonia display NFkappaB activation, which is likely to be a consequence of oxidative stress and activation of MAPKs. NFkappaB activation appears to contribute to the mechanism of ammonia-induced astrocyte swelling, apparently through its up-regulation of iNOS protein expression and the subsequent generation of NO.
    Journal of Neurochemistry 08/2008; 106(6):2302-11. · 3.97 Impact Factor
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    ABSTRACT: Amphotericin B (AmB) is a polyene antibiotic and reported to have therapeutic effects on prion diseases, in which the microglial activation has been suggested to play important roles by proliferating and producing various factors such as nitric oxide, proinflammatory cytokines, and so on. However, the therapeutic mechanism of AmB on prion diseases remains elusive. In the present study, we investigated the effects of AmB on cellular functions of rat primary cultured microglia. We found that AmB, similarly as lipopolysaccharide (LPS), could activate microglia to produce nitric oxide via inducible nitric oxide synthase. Both AmB and LPS also induced mRNA expressions of interleukin-1beta, interleukin-6, and tumor necrosis factor-alpha in microglia. AmB also changed the expression levels of neurotrophic factors mRNAs. AmB and LPS significantly down-regulated the level of ciliary neurotrophic factor mRNA. However, AmB, but not LPS, significantly up-regulated the level of glial cell-line derived neurotrophic factor mRNA in microglia. In addition, brain-derived neurotrophic factor mRNA expression level was tending upward by treatment with AmB, but not with LPS. Taken together, these results suggest that AmB regulates the microglial activation in different manner from LPS and that microglia may participate in the therapeutic effects of AmB on prion diseases by controlling the expression and production of such mediators.
    Neurochemistry International 06/2008; 52(6):1290-6. · 2.66 Impact Factor
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    ABSTRACT: Brain edema and associated increased intracranial pressure are major consequences of traumatic brain injury that account for most early deaths after traumatic brain injury. An important component of brain edema after traumatic brain injury is astrocyte swelling (cytotoxic edema). To examine the pathophysiologic mechanisms of trauma-induced astrocyte swelling, we used an in vitro fluid percussion trauma model. Exposure of cultured rat astrocytes to 5 atm of pressure resulted in significant cell swelling at 1 to 24 hours posttrauma that was maximal at 3 hours. Because oxidative/nitrosative stress, mitochondrial permeability transition (mPT), and mitogen-activated protein kinases (MAPKs) have been implicated in astrocyte swelling in other neurologic conditions, we examined their potential roles in this model. We previously showed increased free radical generation after in vitro trauma and show here that trauma to astrocytes increased the production of nitric oxide. Trauma also induced mPT and increased phosphorylation (activation) of MAPKs (extracellular signal-regulated kinase 1/2, c-Jun-N-terminal kinase, and p38-MAPK); these changes were diminished by antioxidants and the nitric oxide synthase inhibitor N-nitro-l-arginine methyl ester. Antioxidants, N-nitro-l-arginine methyl ester, the mPT inhibitor cyclosporin A, and inhibitors of MAPKs all significantly diminished trauma-induced astrocyte swelling. These findings demonstrate that direct mechanical injury to cultured astrocytes brings about cell swelling, and that blockade of oxidative/nitrosative stress, mPT, and MAPKs significantly reduce such swelling.
    Journal of Neuropathology and Experimental Neurology 06/2008; 67(5):417-27. · 4.35 Impact Factor
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    ABSTRACT: To determine the role played by lymphocytes and cytokines in the growth of sympathetic neurons in vivo, the innervation and cytokine levels were examined in the spleens of SCID mice that lack T and B cells. Splenic noradrenaline, nerve growth factor (NGF), and IL-1beta levels were elevated in SCID mice. Immunohistochemical examination revealed that the density of tyrosine hydroxylase-positive (TH(+)) fibers of splenic central arteries in SCID mice was increased compared with wild-type C.B-17 mice, while SCID mice had significantly fewer TH(+) fibers in their periarteriolar lymphatic sheaths (PALS). Two weeks after SCID mice were injected with C.B-17 splenic T cells, their TH(+) fiber staining increased in the PALS. IL-3 levels increased significantly in SCID mice following T cell reconstitution, and the administration of anti-IL-3 Ab blocked the above T cell-induced increase in innervation in the PALS. Anti-IL-3 treatment also inhibited the regeneration of splenic sympathetic neurons in C.B-17 mice after they were chemically sympathetomized with 6-hydroxydopamine. Depletion of NK cells by anti-asialo GM1 promoted the splenic innervation in SCID mice, while there were no significant changes in the innervation between CD8(+) T cell-deficient beta(2)-microglobulin knockout mice and their wild type. Our results suggest that T cells (probably CD4(+) Th cells but not CD8(+) CTLs) play a role in regulating the sympathetic innervation of the spleen; this effect appeared to be mediated, at least in part, by IL-3. On the contrary, NK cells may exert an inhibitory effect on the sympathetic innervation.
    The Journal of Immunology 04/2008; 180(6):4227-34. · 5.52 Impact Factor
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    ABSTRACT: Citrin is the liver-type mitochondrial aspartate-glutamate carrier that participates in urea, protein, and nucleotide biosynthetic pathways by supplying aspartate from mitochondria to the cytosol. Citrin also plays a role in transporting cytosolic NADH reducing equivalents into mitochondria as a component of the malate-aspartate shuttle. In humans, loss-of-function mutations in the SLC25A13 gene encoding citrin cause both adult-onset type II citrullinemia and neonatal intrahepatic cholestasis, collectively referred to as human citrin deficiency. Citrin knock-out mice fail to display features of human citrin deficiency. Based on the hypothesis that an enhanced glycerol phosphate shuttle activity may be compensating for the loss of citrin function in the mouse, we have generated mice with a combined disruption of the genes for citrin and mitochondrial glycerol 3-phosphate dehydrogenase. The resulting double knock-out mice demonstrated citrullinemia, hyperammonemia that was further elevated by oral sucrose administration, hypoglycemia, and a fatty liver, all features of human citrin deficiency. An increased hepatic lactate/pyruvate ratio in the double knock-out mice compared with controls was also further elevated by the oral sucrose administration, suggesting that an altered cytosolic NADH/NAD(+) ratio is closely associated with the hyperammonemia observed. Microarray analyses identified over 100 genes that were differentially expressed in the double knock-out mice compared with wild-type controls, revealing genes potentially involved in compensatory or downstream effects of the combined mutations. Together, our data indicate that the more severe phenotype present in the citrin/mitochondrial glycerol-3-phosphate dehydrogenase double knock-out mice represents a more accurate model of human citrin deficiency than citrin knock-out mice.
    Journal of Biological Chemistry 09/2007; 282(34):25041-52. · 4.65 Impact Factor
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    ABSTRACT: Mutations in SLC25A13, encoding the mitochondrial aspartate-glutamate carrier citrin, cause adult-onset type II citrullinemia (CTLN2) in humans. We have previously reported that although citrin-knockout (Ctrn-/-) mice fail to display symptoms of CTLN2, liver perfusion revealed a deficit in ureogenesis from ammonia accompanied by an increase in the perfusate lactate-to-pyruvate (L/P) ratio. The present study explores the effects of pyruvate, aspartate and citrate on improving the abnormalities observed in the Ctrn-/- liver. We measured the rate of ureogenesis from ammonium chloride using the liver-perfusion system. Pyruvate infusion lowered the L/P ratio and corrected the deficit in ureogenesis in the Ctrn-/- liver. This effect was found to be dose-dependent in both instances. Phenazine methosulfate, a cytosolic oxidant, also improved the rate of ureogenesis in the Ctrn-/- liver and led to a fall in the L/P ratio. The addition of aspartate or citrate did not change either the rate of ureogenesis or the L/P ratio in the Ctrn-/- liver. Citrin deficiency disturbs urea synthesis primarily as a result of an elevated cytosolic NADH/NAD+ ratio owing to limited reoxidation of reducing equivalents. Clinically, pyruvate may have a therapeutic benefit for CTLN2 patients.
    Journal of Hepatology 06/2006; 44(5):930-8. · 9.86 Impact Factor
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    ABSTRACT: Uptake of K+ is an important role of astrocytes to maintain physiological lower extracellular K+ concentration in the CNS. In this study, the effect of high K+ concentration was examined on the cellular function of astrocytes from embryonic rat brain in primary culture. Nitric oxide (NO) production induced by lipopolysaccharide (LPS) was measured as an index of cellular function of astrocytes. Increasing KCl concentration to about 40 mM did not directly evoke NO production, but doubled the level of LPS (1 ng/ml)-induced NO production. K-gluconate showed a similar enhancing effect although the degree of enhancement was about half of that of KCl. Neither NaCl nor Na-gluconate showed any effect. The K(+)-channel blocker, 4-aminopyridine, but not tetraethylammonium or apamin, inhibited the enhancing effect of KCl. The LPS-induced iNOS protein expression determined by immunoblotting analysis was enhanced by high K+ treatment. The level of iNOS mRNA determined by real-time RT-PCR technique was also augmented by the presence of 40 mM KCl. These results indicate that the elevation of extracellular K+ concentration regulates astrocytic cell functions through a mechanism involving K(A)-type K(+)-channels and that potentiation of NO production by high K+ is due to the augmentation of iNOS mRNA and iNOS protein levels.
    Neurochemistry International 02/2006; 48(1):43-9. · 2.66 Impact Factor
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    ABSTRACT: Citrin, encoded by SLC25A13, is a liver-type mitochondrial aspartate-glutamate carrier (AGC), of which deficiency, in autosomal recessive trait, causes neonatal intrahepatic cholestasis (NICCD) and adult-onset type II citrullinemia (CTLN2). NICCD patients have jaundice, hypoproteinemia, hypoglycemia, galactosemia, growth retardation, fatty liver and multiple aminoacidemia including citrulline, methionine, threonine and tyrosine. Some of the neonates who have experienced NICCD suffer from severe CTLN2 more than 10 years or several decades later. In CTLN2, neuropsychotic symptoms such as disorientation, aberrant behavior, coma and death are observed. Laboratory findings reveal hyperammonemia, citrullinemia, fatty liver and liver-specific decrease in a urea cycle enzyme, argininosuccinate synthetase (ASS). In some cases, hyperlipidemia, pancreatitis and hepatoma are accompanied with CTLN2. Citrin as a liver-type AGC plays a role in supplying aspartate to the cytosol for urea, protein and nucleotide synthesis by exchanging mitochondrial aspartate for cytosolic glutamate and proton, and transporting cytosolic NADH reducing equivalent to mitochondria as a member of malate aspartate shuttle essential for aerobic glycolysis. AGC is also important for gluconeogenesis from lactate. Although it is difficult to explain pathogenesis of the symptoms such as cholestasis in NICCD and liver-specific decrease of ASS protein in CTLN2 from the functions of the AGC, some are understandable by the loss of citrin functions. Many CTLN2 patients have been treated with a low protein and high carbohydrate diet and glycerol at the hyperammonemic coma. We argue that those treatments may result in fatty liver, hyperlipidemia, hyperammonemia and even death due to loss of the citrin functions. Loss of citrin first cause deficiency of aspartate in the cytosol, which results in an increase in cytosolic NADH/NAD(+) ratio and then activation of fatty acid synthesis pathway to compensate the aberrant ratio. This follows inhibition of fatty acid oxidation. The peculiar fondness for food of CTLN2 patients who like protein and dislike carbohydrate and sweets may be related to their metabolic requirements.
    Hepatology Research 11/2005; 33(2):181-4. · 2.07 Impact Factor
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    ABSTRACT: Patients with poorly controlled diabetes are at high risk of acquiring bacterial infections. However, conflicting results have been reported on neutrophil function in diabetes. We periodically evaluated neutrophil dysfunction in multiple low-dose streptozotocin (STZ)-induced diabetic mice, and then evaluated the effects of troglitazone and other thiazolidinediones (TZDs) on the decline of neutrophil function. Zymosan was injected intraperitoneally and neutrophil infiltration and phagocytosis were evaluated. While phagocytosis of zymosan by peritoneal neutrophils was consistently reduced in diabetic mice, neutrophil infiltration was decreased on day 30, but increased on day 40 after STZ injection. The in vitro chemotactic and phagocytic activities of blood neutrophils in mice that did not receive zymosan were consistently reduced in diabetic mice. Phorbol myristate acetate (PMA)-stimulated superoxide production by zymosan-induced peritoneal neutrophils and the levels of zymosan-induced tumour necrosis factor (TNF)-alpha and interleukin (IL)-1beta in peritoneal exudate fluids were also reduced in the diabetic mice. Treatment of the diabetic mice with troglitazone beginning 2 weeks after STZ injection did not improve hyperglycaemia but did prevent the decline of zymosan-induced neutrophil infiltration on day 30, and additionally promoted the increased infiltration on day 40. Troglitazone also promoted the chemotactic activity of blood neutrophils isolated from normal mice in vitro. Rosiglitazone but not pioglitazone induced a similar effect. Neutrophil phagocytosis was not enhanced by troglitazone either in vivo or in vitro. Taken together, neutrophil function is impaired by STZ-induced diabetes, but inflammatory infiltration does not always vary with the chemotactic disability or cytokine levels. Furthermore, troglitazone and rosiglitazone were suggested to improve at least neutrophil chemotactic activity in these animals.
    Clinical & Experimental Immunology 09/2004; 137(2):263-71. · 3.41 Impact Factor

Publication Stats

379 Citations
147.09 Total Impact Points

Institutions

  • 1993–2013
    • Osaka Prefecture University
      • • Graduate School of Life and Environmental Sciences
      • • School of Veterinary Science
      Sakai, Osaka-fu, Japan
  • 2008–2011
    • University of Miami Miller School of Medicine
      • Department of Pathology
      Miami, FL, United States
    • Radboud University Nijmegen
      Nymegen, Gelderland, Netherlands
  • 1995–1998
    • Hokkaido University
      • • Graduate School of Veterinary Medicine
      • • Department of Biomedical Sciences
      Sapporo-shi, Hokkaido, Japan