• Archives of Pharmacal Research
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• 제28권7호
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• pp.810-815
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• 2005

Previously, we have shown that astrocytes deprived of glucose became highly vulnerable to peroxynitrite, and adenosine and its metabolites attenuated the gliotoxicity via the preservation of cellular ATP level. Here, we found that adenosine and related metabolites prevented the disruption of mitochondrial transmembrane potential (MTP) in glucose-deprived rat primary astrocytes exposed to 3-morpholinosydnonimine (SIN-1), a peroxynitrite releasing agent. Exposure to glucose deprivation and SIN-1(2h) significantly disrupted MTP in astrocytes, and adenosine prevented it in dose-dependent manner with an $EC_{50}\;of\;5.08{\mu}M$. Adenosine also partially prevented the cell death by myxothiazol, a well-known inhibitor of mitochondrial respiration. Blockade of adenosine deamination or intracellular transport with erythro-9-(-hydroxy-3-nonyl)adenosine (EHNA) or S-(4-nitrobenzyl)-6-thioinosine (NBTI), respectively, completely reversed the protective effect of adenosine. Other purine nucleos(t)ides including inosine, guanosine, ATP, ADP, AMP, ITP, and GTP also showed similar protective effects. This study indicates that adenosine and related purine nucleos(t)ides may protect astrocytes from peroxynitrite-induced mitochondrial dysfunction.

• Genomics & Informatics
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• 제2권1호
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• pp.36-44
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• 2004

Astrocytes play supportive roles for neurons in the brain. Recently, they have been accepted to have various functions in the vascular system as well as in the nervous system. We investigated the differential gene expression in rat astrocytes according to the oxygen tension, which is a crucial factor for angiogenesis. A cDNA microarray was performed to find the genes whose expression was sensitive to oxygen tension. We found 26 genes in the astrocyte were found and classified into 4 groups. In order to show the genes' relevancy to angiogenesis, seven of the 26 genes were investigated to see whether they have capabilities of interaction with angiogenesis­related factors in AngioDB. Through this investigation, we found interactions of three proteins with angiogenesis-related factors. These genes were further investigated with a new focus on the vascular endothelial growth factor (VEGF) expression in an astrocyte based on our hypothesis that astrocytes can have effects on endothelial angiogenesis via the release of VEGF. Collectively, we identified several genes whose expressions were dependent on the oxygen concentration of the astrocyte. Furthermore, the relevancy of astrocytes to angiogenesis was investigated using preexisting information of AngioDB, and suggested a possible signaling pathway for VEGF expression in the aspects of brain endothelial angiogenesis by astrocytes.

• Biomolecules & Therapeutics
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• 제27권3호
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• pp.283-289
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• 2019

Brain aging induces neuropsychological changes, such as decreased memory capacity, language ability, and attention; and is also associated with neurodegenerative diseases. However, most of the studies on brain aging are focused on neurons, while senescence in astrocytes has received less attention. Astrocytes constitute the majority of cell types in the brain and perform various functions in the brain such as supporting brain structures, regulating blood-brain barrier permeability, transmitter uptake and regulation, and immunity modulation. Recent studies have shown that SIRT1 and SIRT2 play certain roles in cellular senescence in peripheral systems. Both SIRT1 and SIRT2 inhibitors delay tumor growth in vivo without significant general toxicity. In this study, we investigated the role of tenovin-1, an inhibitor of SIRT1 and SIRT2, on rat primary astrocytes where we observed senescence and other functional changes. Cellular senescence usually is characterized by irreversible cell cycle arrest and induces senescence- associated ${\beta}$-galactosidase (SA-${\beta}$-gal) activity. Tenovin-1-treated astrocytes showed increased SA-${\beta}$-gal-positive cell number, senescence-associated secretory phenotypes, including IL-6 and IL-$1{\beta}$, and cell cycle-related proteins like phospho-histone H3 and CDK2. Along with the molecular changes, tenovin-1 impaired the wound-healing activity of cultured primary astrocytes. These data suggest that tenovin-1 can induce cellular senescence in astrocytes possibly by inhibiting SIRT1 and SIRT2, which may play particular roles in brain aging and neurodegenerative conditions.

• Archives of Pharmacal Research
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• 제28권8호
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• pp.942-947
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• 2005

Peroxynitrite is a potent neurotoxic molecule produced from a reaction between NO and super-oxide and induces NO-mediated inflammation under neuropathological conditions. Previously, we reported that glucose deprivation induced ATP depletion and cell death in immunostimulated astrocytes, which was mainly due to peroxynitrite. In this study, the role of MAPKs (ERK1/2, p38MAPK, and JNK/SAPK) signal pathway in the SIN-1/glucose deprivation-induced death of astrocytes was examined. A combined treatment with glucose deprivation and $50 {\mu}M$ SIN-1, an endogenous peroxynitrite generator, rapidly and markedly increased the death in rat primary astrocytes. Also, SIN-1/glucose deprivation resulted in the activation of MAPKs, which was significantly blocked by the treatment with $20{\mu}M$ MAPKs inhibitors (ERK1/2, PD98059; p38MAPK, SB203580; JNK/SAPK, SP600125). Interestingly, SIN-1/glucose deprivation caused the loss of intracellular ATP level, which was significantly reversed by MAPKs inhibitors. These results suggest that the activation of MAPKs plays an important role in SIN-1/glucose deprivation-induced cell death by regulating the intracellular ATP level.

• Animal cells and systems
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• 제10권2호
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• pp.79-83
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• 2006

Tissue plasminogen activator (tPA) is used to lyse clots and reperfuse brain in ischemic stroke. However, sideeffects of intracerebral hemorrhage (ICH) and edema limit their clinical application. In part, these phenomena has been linked with elevations in matrix metalloproteinase-9 (MMP-9) in neurovascular unit. However little is known about their regulatory signaling pathways in brain cells. Here, I examine the role of MAP kinase pathways in tPA-induced MMP-9 regulation in rat cortical astrocytes. tPA $(1-10\;{\mu}g/ml)$ induced dose-dependent elevations in MMP-9 and MMP-2 in conditioned media. Although tPA increased phosphorylation in two MAP kinases (ERK, JNK), only inhibition of the JNK pathway by the JNK inhibitor SP600126 significantly reduced MMP-9 upregulation. Neither ERK inhibition with U0126 nor p38 inhibition with SB203580 had any significant effects. Taken together, these results suggest that c-jun N-terminal kinase (JNK) plays an essential role for tPA-induced MMP-9 upregulation.

• BMB Reports
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• 제56권2호
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• pp.90-95
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• 2023

Mitochondria are important organelles that regulate adenosine triphosphate production, intracellular calcium buffering, cell survival, and apoptosis. They play therapeutic roles in injured cells via transcellular transfer through extracellular vesicles, gap junctions, and tunneling nanotubes. Astrocytes can secrete numerous factors known to promote neuronal survival, synaptic formation, and plasticity. Recent studies have demonstrated that astrocytes can transfer mitochondria to damaged neurons to enhance their viability and recovery. In this study, we observed that treatment with mitochondria isolated from rat primary astrocytes enhanced cell viability and ameliorated hydrogen peroxide-damaged neurons. Interestingly, isolated astrocytic mitochondria increased the number of cells under damaged neuronal conditions, but not under normal conditions, although the mitochondrial transfer efficiency did not differ between the two conditions. This effect was also observed after transplanting astrocytic mitochondria in a rat middle cerebral artery occlusion model. These findings suggest that mitochondria transfer therapy can be used to treat acute ischemic stroke and other diseases.

• BMB Reports
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• 제29권6호
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• pp.530-534
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• 1996

Astrocyte are the major glial cell type in the central nervous system (CNS), and analogous to macrophage, mediates the number of immune responses such as production of cytokines including tumor necrosis factor alpha ($TNF-{\alpha}$) upon activation. $TNF-{\alpha}$ has been implicated in neuroimmunological disorders through killing oligodendrocytes and thus causing demyelination. It has been previously demonstrated that mitogen-activated T cells synthesized a 26 kDa precursor form of $TNF-{\alpha}$ which is bound to the surface of a membrane, and is later secreted as a 17 kDa mature version. In order to examine whether astrocytes would produce the transmembrane form of $TNF-{\alpha}$, astrocytes were stimulated with biological stimuli and the membrane form of $TNF-{\alpha}$ was analyzed by Western blot and FACS analysis. When astrocytes are stimulated with lipopolysaccharide (LPS), $IFN-{\gamma}/LPS$, or $IFN-{\gamma}/IL-1{\beta}$, they were able to express a membrane-anchored $TNF-{\alpha}$ of approximately 26 kDa protein which was immunoreactive to an $anti-TNF-{\alpha}$ antibody, whereas unstimulated astrocytes or astrocytes treated with $IFN-{\gamma}$ or $IL-1{\beta}$ alone was not. Our FACS data were also consistent with the immunoblot analysis. Our result suggests that the membrane form of $TNF-{\alpha}$ expressed by activated astrocytes may cause local damage to oligodendrocytes by direct cell-cell contact and contribute to demyelination observed in multiple sclerosis (MS) and experimental allergic encephalomyelitis (EAE).

• 약학회지
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• 제50권2호
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• pp.124-128
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• 2006

Astrocyte has emerged as an active regulator of brain function, which connects between blood vessels and neurons as well as is a structural component of the blood-brain barrier, From its structural characteristics, astrocyte seems to sensitively respond to oxygen tension, and, in turn, generate diverse cellular cascades. Therefore, to reveal astrocytlc events by oxygen change, we screened genes whose expressions are upregulated under reoxygenation after hypoxic stress using cDNA representational difference analysis (RDA) technique. Meteorin that regulates glial differentiation was isolated from primary cultured rat astrocytes as a hypoxia/reoxygenation regulatory factor. We cloned rat version of Meteorin (rMe-teorin) and determined full-size sequences of rMeteorin. In addition, RT-PCR analysis revealed that Meteorin was increased under reoxygenation in astrocytes and highly expressed in the developing brain. Collectively, these results suggest that Meteorin may regulate astrocyte-mediated effects in response to the change of oxygen tension in the pathophysiological states.

• The Korean Journal of Physiology and Pharmacology
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• 제3권2호
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• pp.127-135
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• 1999

As part of a study on the effects of dexamethasone and dehydroepiandrosterone (DHEA) on the biological roles of astrocytes in brain injury, this study evaluated the effects of dexamethasone and DHEA on the responses of primary cultured rat cortical astrocytes to lipopolysaccharide (LPS) and antimycin A. Dexamethasone decreased spontaneous release of LDH from astrocytes, and the dexamethasone effect was inhibited by DHEA. However, the inhibitory effect of DHEA on the dexamethasone-induced decrease of LDH release was not shown in astrocytes treated with LPS, and antimycin A-induced LDH release was not affected by dexamethasone or DHEA. Unlike dexamethasone, DHEA increased MTT value of astrocytes and also attenuated the antimycin A-induced decrease of MTT value. Glutamine synthetase activity of astrocytes was not affected by DHEA or LPS but increased by dexamethasone, and the dexamethasone- dependent increase was attenuated by DHEA. However, antimycin A markedly decreased glutamine synthetase activity, and the antimycin A effect was not affected by dexamethasone or DHEA. Basal release of $[^3H]arachidonic$ acid from astrocytes was moderately increased by LPS and markedly by antimycin A. Dexamethasone inhibited the basal and LPS-dependent releases of $[^3H]arachidonic$ acid, but neither dexamethasone nor DHEA affected antimycin A-induced $[^3H]arachidonic$ acid release. Basal IL-6 release from astrocytes was not affected by dexamethasone or DHEA but markedly increased by LPS and antimycin A. LPS-induced IL-6 release was attenuated by dexamethasone but was little affected by DHEA, and antimycin A-induced IL-6 release was attenuated by DHEA as well as dexamethasone. At the concentration of dexamethasone and DHEA which does not affect basal NO release from astrocytes, they moderately inhibited LPS-induced NO release but little affected antimycin A-induced decrease of NO release. Taken together, these results suggest that dexamethasone and DHEA, in somewhat different manners, modulate the astrocyte reactivity in brain injuries inhibitorily.

• Biomolecules & Therapeutics
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• 제27권6호
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• pp.530-539
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• 2019

Brain aging is an inevitable process characterized by structural and functional changes and is a major risk factor for neurodegenerative diseases. Most brain aging studies are focused on neurons and less on astrocytes which are the most abundant cells in the brain known to be in charge of various functions including the maintenance of brain physical formation, ion homeostasis, and secretion of various extracellular matrix proteins. Altered mitochondrial dynamics, defective mitophagy or mitochondrial damages are causative factors of mitochondrial dysfunction, which is linked to age-related disorders. Etoposide is an anti-cancer reagent which can induce DNA stress and cellular senescence of cancer cell lines. In this study, we investigated whether etoposide induces senescence and functional alterations in cultured rat astrocytes. Senescence-associated ${\beta}$-galactosidase (SA-${\beta}$-gal) activity was used as a cellular senescence marker. The results indicated that etoposide-treated astrocytes showed cellular senescence phenotypes including increased SA-${\beta}$-gal-positive cells number, increased nuclear size and increased senescence-associated secretory phenotypes (SASP) such as IL-6. We also observed a decreased expression of cell cycle markers, including PhosphoHistone H3/Histone H3 and CDK2, and dysregulation of cellular functions based on wound-healing, neuronal protection, and phagocytosis assays. Finally, mitochondrial dysfunction was noted through the determination of mitochondrial membrane potential using tetramethylrhodamine methyl ester (TMRM) and the measurement of mitochondrial oxygen consumption rate (OCR). These data suggest that etoposide can induce cellular senescence and mitochondrial dysfunction in astrocytes which may have implications in brain aging and neurodegenerative conditions.