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Effects of SSRI on L-glutamate uptake activity of cultured astrocytes
Abstracts P1-c20 Relationship between phosphorylation of cofilin and actin remodeling at the leading edge of myelinating oligodendrocytes after estrogen stimulation Yukie Wada (Hirahara) 1 , Ken-ichi Matsuda 1 , Mitsuhiro Kawata 1 , Joan M. Boggs 2 1 Anatomy and Neurobiology, Kyoto Prefectural University of Medicine, Kyoto, Japan; 2 Molecular Structure and Function, Hospital for Sick Children, Toronto, Canada
During myelinating processes, dramatic changes in the cytoskeleton and the morphology of oligodendrocytes (OLs) occur. We recently showed that the estrogen receptors (ER ␣/) was expressed along the cytoskeletal veins of OLs and was involved in rapid signaling and cytoskeleton remodeling via estradiol. To understand the ERs-dependent molecular mechanism of remodeling of the cytoskeleton in myelinating OLs, the effect of estrogen on the cytoskeleton and phosphorylation of cofilin (P-cofilin), a protein which severs actin filaments, was investigated. The structure of the cytoskeletal network in the membrane sheets rapidly changed, and the P-cofilin increased at the membrane leading edges and along the lacy cytoskeletal network. These results indicate a role for P-cofilin at the leading edge that is required for rearrangement of the cytoskeleton in myelinating OLs in response to estrogen stimulation. doi:10.1016/j.neures.2009.09.347
P1-c21 The tumor suppressor APC is essential for the maintenance of Bergmann glial scaffolds Xiaohong Wang 1 , Tetsuya Imura 1 , Tetsuo Noda 2 , Sofroniew Michael 3 , Shinji Fushiki 1 1 Dept. of Pathology & Applied Neurobiology, Kyoto Prefectural University of Medicine, Kyoto, Japan; 2 Department of Cell Biology, Cancer Institute, Tokyo, Japan; 3 Department of Neurobiology, UCLA, Los Angeles, USA
The tumor suppressor Adenomatous polyposis coli (APC) is an important regulator of the Wnt / beta Catenin pathway. To study the roles of APC in postnatal/adult brains, we applied a conditional gene targeting strategy, using mGFAP-Cre mice, to delete the APC gene in glial cells. APC-conditional knockout mice display progressive ataxia in adults. Beta catenin accumulation in Bergmann glia starts in early postnatal periods followed by the retraction of the radial fibers and aberrant location of the cell bodies in the molecular layer. Bergmann glial abnormalities subsequently causes ectopic granule cells in the molecular layer and loss of Purkinje cells. Thus, APC is critical for the structural integrity of cerebellar cortex by maintaining the radial fibers of Bergmann glia. doi:10.1016/j.neures.2009.09.348
P1-c22 Granulocyte-colony stimulating factor protect neurons through the activation of microglia in the mutant superoxide dismutase 1 transgenic ALS model mice Ryo Yamasaki, Masahito Tanaka, Takahisa Tateishi, Mami Fukunaga, Hitoshi Kikuchi, Yasumasa Oyagi, Jun-ichi Kira Kyushu University, Japan G-CSF is known as an anti-apoptotic agent. We studied the neuroprotective effects of G-CSF using G93A-SOD1 transgenic (mSOD1-Tg) ALS model mice. In chronic neural damage, with daily subctaneous injection of G-CSF, the life spans of G-CSFtreated mSOD1-Tg mice were significantly longer (7.6 days) than those of salinetreated ones. This neuroprotective effect of G-CSF was also seen in acute neural damage of the hypoglossal axotomized model; on 40 days after axotomy, the number of hypoglossal neuron of mSOD1-Tg mice was more decreased than that of nontransgenic (NTG) mice. Neuropathologically, microglia in the axotomized mSOD1Tg mice showed poor encirclement of damaged motor neurons in comparison with NTG mice. With G-CSF treatment, survival rate of hypoglossal neurons recovered. Interestingly, the encirclement of neurons by microglia was recuperated, too. We speculated neuroprotective effect of G-CSF is not only the anti-apoptotic effect, but also through the activation of microglial neuroprotection. doi:10.1016/j.neures.2009.09.349
P1-c23 Physiological role of monocarboxylate transporter in the nucleus of the solitary tract Masashi Nagase 1,2 , Takeshi Suzuki 1 , Fusao Kato 2 1
Div. Basic Biol., Fac. Pharm., Keio Univ., Tokyo, Japan; iol., Dept. Neurosci., Jikei Univ. Sch. Med., Tokyo, Japan
2
Lab. Neurophys-
S87
Monocarboxylate transporters (MCTs) are key molecules in fueling the neurons by astrocytes through trans-cellular transfer of lactate. Lines of evidence indicate, however, neurons use lactate only in energy deprivation, leaving the physiological role of energy of astrocyte origin in maintaining neuronal activities equivocal. Here we analyzed effects of inhibiting MCT with alpha-cyano-4-hydroxycinnamic acid (CHCA) on neuronal activities in the nucleus of the solitary tract (NTS) in the presence of 10 mM glucose and 95% oxygen in rat brainstem slices. CHCA (1 mM, 15 min) slightly decreased the action potential amplitude and hyperpolarized the cells. In contrast, the amplitude of EPSCs and AMPA-induced currents was significantly decreased by CHCA without change in the paired-pulse ratio; the amplitude of IPSCs was also decreased but to a lesser extent than that of EPSCs. These results suggest that a major part of glutamatergic responses in the NTS requires MCT-dependent energy supply under conditions where the neurons can produce enough energy. doi:10.1016/j.neures.2009.09.350
P1-c24 Effects of SSRI on L-glutamate uptake activity of cultured astrocytes Junpei Takaki 1 , Jun-Ichi Kuriwaki 2 , Kaoru Sato 2 , Takeshi Suzuki 1 1
Division of Basic Biological Sciences Faculty of Pharmacy Keio University, Japan; 2 Division of Pharmacology National Institute of Health Sciences, Japan Astrocyte L-glutamate (glu) transporters are membrane proteins that reuptake glu, the major excitatory neurotransmitter, and play an important role for the maintenance of low extracellular glu concentration. A growing body of evidence from human postmortem and animal studies suggests that deficits in glial cells (particularly astrocytes), in limbic region, contribute to the etiology of depressive disorders. We therefore investigated effects of SSRI on glu uptake activity of cultured astrocytes. SSRI did not show any effects just after 24 h treatment. However, some SSRIs increased the glu uptake 72 h after the SSRI treatment. These observations indicate that the effects of SSRI are due to the protein induction (e.g. glial glu transporter etc.). Taking that the clinical effects of SSRI take 2–4 weeks to become apparent into consideration, the effects on L-glu uptake may be correlated with the antidepressive effects of SSRI. doi:10.1016/j.neures.2009.09.351
P1-c25 ZNRF1 regulates glutamine synthetase protein levels in Schwann cells by the ubiquitin-proteasome pathway Toshiyuki Araki, Fuminori Saito National Institute of Neurology and Psychiatry, Japan Phenotypic changes of Schwann cells, glial cells in the peripheral nervous system, are controlled by a series of transcriptional regulation events. We previously indentified ZNRF1, an E3 ubiquitin ligase containing a RING finger motif, whose expression is up-regulated in Schwann cells after nerve injury. This suggested that the involvement of post-translational regulation of protein expression in Schwann cells by proteasomal degradation is controlling the Schwann cell phenotype. We demonstrated here that the expression of glutamine synthetase (GS), a substrate for E3 activity of ZNRF1 in Schwann cells, promotes myelination. Among substrates and products of GS, increased glutamate concentration inhibited myelination and promoted Schwann cell proliferation, suggesting that GS exerts its effect on Schwann cell differentiation via regulation of the glutamate concentration. These results suggest that the ZNRF1-GS system may play an important role in associating metabolism with differentiation of Schwann cells. doi:10.1016/j.neures.2009.09.352
P1-c26 Appearance of phagocytic microglia in facial nuclei after nerve avulsion in presymptomatic ALS model rats Tomomi Sanagi 1 , Shigeki Yuasa 2 , Yasuko Nakamura 1 , Masashi Aoki 3 , Hitoshi Warita 3 , Yasuto Itoyama 3 , Shinichi Kohsaka 1 , Keiko Ohsawa 1 1
Dept. Neurochem., Natl. Inst. Neurosci., Japan; 2 Dept. Ultrastructural Res., Natl. Inst. Neurosci., Japan; 3 Dept. Neurol., Tohoku Univ. Grad. Sch. Med., Japan Microglial activation occurs early in the pathogenesis of amyotrophic lateral sclerosis (ALS) and seems to influence the disease promotion. It has been reported that neuronal damage after facial nerve avulsion is exacerbated in presymptomatic mutant SOD1 (H46R) transgenic (Tg) rats compared with wild type (WT) rats. However, it is unclear which functions of microglia contribute the motoneuron death. In this study, we investigated the microglial response after facial nerve avulsion in 39-day-old Tg rats. At 3 days and 2 weeks after avulsion, the number of microglial
During myelinating processes, dramatic changes in the cytoskeleton and the morphology of oligodendrocytes (OLs) occur. We recently showed that the estrogen receptors (ER ␣/) was expressed along the cytoskeletal veins of OLs and was involved in rapid signaling and cytoskeleton remodeling via estradiol. To understand the ERs-dependent molecular mechanism of remodeling of the cytoskeleton in myelinating OLs, the effect of estrogen on the cytoskeleton and phosphorylation of cofilin (P-cofilin), a protein which severs actin filaments, was investigated. The structure of the cytoskeletal network in the membrane sheets rapidly changed, and the P-cofilin increased at the membrane leading edges and along the lacy cytoskeletal network. These results indicate a role for P-cofilin at the leading edge that is required for rearrangement of the cytoskeleton in myelinating OLs in response to estrogen stimulation. doi:10.1016/j.neures.2009.09.347
P1-c21 The tumor suppressor APC is essential for the maintenance of Bergmann glial scaffolds Xiaohong Wang 1 , Tetsuya Imura 1 , Tetsuo Noda 2 , Sofroniew Michael 3 , Shinji Fushiki 1 1 Dept. of Pathology & Applied Neurobiology, Kyoto Prefectural University of Medicine, Kyoto, Japan; 2 Department of Cell Biology, Cancer Institute, Tokyo, Japan; 3 Department of Neurobiology, UCLA, Los Angeles, USA
The tumor suppressor Adenomatous polyposis coli (APC) is an important regulator of the Wnt / beta Catenin pathway. To study the roles of APC in postnatal/adult brains, we applied a conditional gene targeting strategy, using mGFAP-Cre mice, to delete the APC gene in glial cells. APC-conditional knockout mice display progressive ataxia in adults. Beta catenin accumulation in Bergmann glia starts in early postnatal periods followed by the retraction of the radial fibers and aberrant location of the cell bodies in the molecular layer. Bergmann glial abnormalities subsequently causes ectopic granule cells in the molecular layer and loss of Purkinje cells. Thus, APC is critical for the structural integrity of cerebellar cortex by maintaining the radial fibers of Bergmann glia. doi:10.1016/j.neures.2009.09.348
P1-c22 Granulocyte-colony stimulating factor protect neurons through the activation of microglia in the mutant superoxide dismutase 1 transgenic ALS model mice Ryo Yamasaki, Masahito Tanaka, Takahisa Tateishi, Mami Fukunaga, Hitoshi Kikuchi, Yasumasa Oyagi, Jun-ichi Kira Kyushu University, Japan G-CSF is known as an anti-apoptotic agent. We studied the neuroprotective effects of G-CSF using G93A-SOD1 transgenic (mSOD1-Tg) ALS model mice. In chronic neural damage, with daily subctaneous injection of G-CSF, the life spans of G-CSFtreated mSOD1-Tg mice were significantly longer (7.6 days) than those of salinetreated ones. This neuroprotective effect of G-CSF was also seen in acute neural damage of the hypoglossal axotomized model; on 40 days after axotomy, the number of hypoglossal neuron of mSOD1-Tg mice was more decreased than that of nontransgenic (NTG) mice. Neuropathologically, microglia in the axotomized mSOD1Tg mice showed poor encirclement of damaged motor neurons in comparison with NTG mice. With G-CSF treatment, survival rate of hypoglossal neurons recovered. Interestingly, the encirclement of neurons by microglia was recuperated, too. We speculated neuroprotective effect of G-CSF is not only the anti-apoptotic effect, but also through the activation of microglial neuroprotection. doi:10.1016/j.neures.2009.09.349
P1-c23 Physiological role of monocarboxylate transporter in the nucleus of the solitary tract Masashi Nagase 1,2 , Takeshi Suzuki 1 , Fusao Kato 2 1
Div. Basic Biol., Fac. Pharm., Keio Univ., Tokyo, Japan; iol., Dept. Neurosci., Jikei Univ. Sch. Med., Tokyo, Japan
2
Lab. Neurophys-
S87
Monocarboxylate transporters (MCTs) are key molecules in fueling the neurons by astrocytes through trans-cellular transfer of lactate. Lines of evidence indicate, however, neurons use lactate only in energy deprivation, leaving the physiological role of energy of astrocyte origin in maintaining neuronal activities equivocal. Here we analyzed effects of inhibiting MCT with alpha-cyano-4-hydroxycinnamic acid (CHCA) on neuronal activities in the nucleus of the solitary tract (NTS) in the presence of 10 mM glucose and 95% oxygen in rat brainstem slices. CHCA (1 mM, 15 min) slightly decreased the action potential amplitude and hyperpolarized the cells. In contrast, the amplitude of EPSCs and AMPA-induced currents was significantly decreased by CHCA without change in the paired-pulse ratio; the amplitude of IPSCs was also decreased but to a lesser extent than that of EPSCs. These results suggest that a major part of glutamatergic responses in the NTS requires MCT-dependent energy supply under conditions where the neurons can produce enough energy. doi:10.1016/j.neures.2009.09.350
P1-c24 Effects of SSRI on L-glutamate uptake activity of cultured astrocytes Junpei Takaki 1 , Jun-Ichi Kuriwaki 2 , Kaoru Sato 2 , Takeshi Suzuki 1 1
Division of Basic Biological Sciences Faculty of Pharmacy Keio University, Japan; 2 Division of Pharmacology National Institute of Health Sciences, Japan Astrocyte L-glutamate (glu) transporters are membrane proteins that reuptake glu, the major excitatory neurotransmitter, and play an important role for the maintenance of low extracellular glu concentration. A growing body of evidence from human postmortem and animal studies suggests that deficits in glial cells (particularly astrocytes), in limbic region, contribute to the etiology of depressive disorders. We therefore investigated effects of SSRI on glu uptake activity of cultured astrocytes. SSRI did not show any effects just after 24 h treatment. However, some SSRIs increased the glu uptake 72 h after the SSRI treatment. These observations indicate that the effects of SSRI are due to the protein induction (e.g. glial glu transporter etc.). Taking that the clinical effects of SSRI take 2–4 weeks to become apparent into consideration, the effects on L-glu uptake may be correlated with the antidepressive effects of SSRI. doi:10.1016/j.neures.2009.09.351
P1-c25 ZNRF1 regulates glutamine synthetase protein levels in Schwann cells by the ubiquitin-proteasome pathway Toshiyuki Araki, Fuminori Saito National Institute of Neurology and Psychiatry, Japan Phenotypic changes of Schwann cells, glial cells in the peripheral nervous system, are controlled by a series of transcriptional regulation events. We previously indentified ZNRF1, an E3 ubiquitin ligase containing a RING finger motif, whose expression is up-regulated in Schwann cells after nerve injury. This suggested that the involvement of post-translational regulation of protein expression in Schwann cells by proteasomal degradation is controlling the Schwann cell phenotype. We demonstrated here that the expression of glutamine synthetase (GS), a substrate for E3 activity of ZNRF1 in Schwann cells, promotes myelination. Among substrates and products of GS, increased glutamate concentration inhibited myelination and promoted Schwann cell proliferation, suggesting that GS exerts its effect on Schwann cell differentiation via regulation of the glutamate concentration. These results suggest that the ZNRF1-GS system may play an important role in associating metabolism with differentiation of Schwann cells. doi:10.1016/j.neures.2009.09.352
P1-c26 Appearance of phagocytic microglia in facial nuclei after nerve avulsion in presymptomatic ALS model rats Tomomi Sanagi 1 , Shigeki Yuasa 2 , Yasuko Nakamura 1 , Masashi Aoki 3 , Hitoshi Warita 3 , Yasuto Itoyama 3 , Shinichi Kohsaka 1 , Keiko Ohsawa 1 1
Dept. Neurochem., Natl. Inst. Neurosci., Japan; 2 Dept. Ultrastructural Res., Natl. Inst. Neurosci., Japan; 3 Dept. Neurol., Tohoku Univ. Grad. Sch. Med., Japan Microglial activation occurs early in the pathogenesis of amyotrophic lateral sclerosis (ALS) and seems to influence the disease promotion. It has been reported that neuronal damage after facial nerve avulsion is exacerbated in presymptomatic mutant SOD1 (H46R) transgenic (Tg) rats compared with wild type (WT) rats. However, it is unclear which functions of microglia contribute the motoneuron death. In this study, we investigated the microglial response after facial nerve avulsion in 39-day-old Tg rats. At 3 days and 2 weeks after avulsion, the number of microglial