Mouse Astrocytes (mouse + astrocyte)

Distribution by Scientific Domains


Selected Abstracts


Smad3-dependent signaling underlies the TGF-,1-mediated enhancement in astrocytic iNOS expression

GLIA, Issue 11 2010
Mary E. Hamby
Abstract We previously demonstrated that transforming growth factor-,1 (TGF-,1), while having no effect alone, enhances nitric oxide (NO) production in primary, purified mouse astrocytes induced by lipopolysaccharide (LPS) plus interferon-, (IFN-,), by recruiting a latent population of astrocytes to respond, thereby enhancing the total number of cells that express Nos2. In this investigation, we evaluated the molecular signaling pathway by which this occurs. We found that purified murine primary astrocytes express mRNA for TGF,RII as well as the TGF,RI subunit activin-like kinase 5 (ALK5), but not ALK1. Immunofluorescence microscopy confirmed the expression of TGF,RII and ALK5 protein in astrocytes. Consistent with ALK5 signaling, Smad3 accumulated in the nucleus of astrocytes as early as 30 min after TGF-,1 (3 ng/mL) treatment and persisted upto 32 hr after TGF-,1 administration. Addition of ALK5 inhibitors prevented TGF-,1-mediated Smad3 nuclear accumulation and NO production when given prior to the Nos2 induction stimuli, but not after. Finally, astrocyte cultures derived from Smad3 null mutant mice did not exhibit a TGF-,1-mediated increase in iNOS expression. Overall, this data suggests that ALK5 signaling and Smad3 nuclear accumulation is required for optimal enhancement of LPS plus IFN,-induced NO production in astrocytes by TGF-,1. © 2010 Wiley-Liss, Inc. [source]


Transplanted astrocytes internalize deposited ,-amyloid peptides in a transgenic mouse model of Alzheimer's disease

GLIA, Issue 2 2008
Rea Pihlaja
Abstract Alzheimer's disease (AD) is one of the most devastating neurodegenerative disorders. The neuropathological hallmarks include extracellular senile plaques consisting of deposited ,-amyloid (A,) peptides and intraneuronal neurofibrillary tangles. Neuroinflammation and activation of astrocytes are also well-established features of AD neuropathology; however, the relationships between astrocytes and A, deposition remain unclear. Previous studies have shown that adult mouse astrocytes internalize and degrade A, deposits in brain sections prepared from human amyloid precursor protein (APP) transgenic mice. In the present study, we demonstrate that cultured adult, but not neonatal mouse astrocytes, respond morphologically and degrade A, deposits present in human AD brain. We also transplanted astrocytes isolated from enhanced green fluorescent protein expressing adult and neonatal mice into the hippocampi of human A, plaque-bearing transgenic APPSwe+PS1dE9 (APdE9) mice and their wild-type littermates and followed the migration and localization of these astrocytes by confocal microscopy upto 7 days after transplantation. Posttransplantation the astrocytes localized as aggregates or thin strings of many cells within the hippocampi of APdE9 and wild-type mice and showed limited migration from the injection site. Interestingly, most of the transplanted astrocytes were found near A, deposits in the hippocampi of APdE9 mice. In contrast to findings in ex vivo degradation assay, confocal microscopy revealed that both adult and neonatal transplanted astrocytes internalized human A, immunoreactive material in vivo. These results support the role of astrocytes as active A, clearing cells in the CNS that may have important implications for future development of therapeutic strategies for AD. © 2007 Wiley-Liss, Inc. [source]


Epo protects SOD2-deficient mouse astrocytes from damage by oxidative stress

GLIA, Issue 4 2006
Jing Liu
Abstract Erythropoietin (Epo) expression, which regulates erythropoiesis, has been shown in rat and mouse brain after hypoxia. A previous study from our laboratory showed that astrocytes from manganese-superoxide dismutase (SOD2) homozygous knockout (SOD2,/,) mice can survive under 5% O2, but not under normal aerobic conditions. However, the mechanism involved is not clear. Our preliminary study using reverse transcriptase-polymerase chain reaction showed increased Epo mRNA expression in astrocytes cultured with 5% hypoxia compared with astrocytes under normal conditions. After administration of anti-sense Epo, protection decreased with time. Dose-dependent administration of Epo to SOD2,/, mouse astrocytes improved their survivability under normal conditions. Survivability of heterozygous SOD2,/+ mutant and wild-type mouse astrocyte cultures was the same under normal conditions but, after administration of 2 mM of paraquat, a reactive oxygen species generator, survivability of the SOD2,/+ astrocytes decreased remarkably compared with the wild-type cells. Epo administration 24 h before exposure to paraquat significantly improved the survivability of the SOD2,/+ astrocytes. Western blot studies suggest that Jak-Stat signal transduction pathways are involved in this process. Our study demonstrates an important role for Epo in the protection of astrocytes from reactive oxygen species. We suggest that Epo can compensate in part for the antioxidant properties of mitochondrial SOD2 deficiency. © 2005 Wiley-Liss, Inc. [source]


Nucleoside transporter expression and function in cultured mouse astrocytes

GLIA, Issue 1 2005
Liang Peng
Abstract Uptake of purine and pyrimidine nucleosides in astrocytes is important for several reasons: (1) uptake of nucleosides contributes to nucleic acid synthesis; (2) astrocytes synthesize AMP, ADP, and ATP from adenosine and GTP from guanosine; and (3) adenosine and guanosine function as neuromodulators, whose effects are partly terminated by cellular uptake. It has previously been shown that adenosine is rapidly accumulated by active uptake in astrocytes (Hertz and Matz, Neurochem Res 14:755,760, 1989), but the ratio between active uptake and metabolism-driven uptake of adenosine is unknown, as are uptake characteristics for guanosine. The present study therefore aims at providing detailed information of nucleoside transport and transporters in primary cultures of mouse astrocytes. Reverse transcription-polymerase chain reaction identified the two equilibrative nucleoside transporters, ENT1 and ENT2, together with the concentrative nucleoside transporter CNT2, whereas CNT3 was absent, and CNT1 expression could not be investigated. Uptake studies of tritiated thymidine, formycin B, guanosine, and adenosine (3-s uptakes at 1,4°C to study diffusional uptake and 1,60-min uptakes at 37°C to study concentrative uptake) demonstrated a fast diffusional uptake of all four nucleosides, a small, Na+ -independent and probably metabolism-driven uptake of thymidine (consistent with DNA synthesis), larger metabolism-driven uptakes of guanosine (consistent with synthesis of DNA, RNA, and GTP) and especially of adenosine (consistent with rapid nucleotide synthesis), and Na+ -dependent uptakes of adenosine (consistent with its concentrative uptake) and guanosine, rendering neuromodulator uptake independent of nucleoside metabolism. Astrocytes are accordingly well suited for both intense nucleoside metabolism and metabolism-independent uptake to terminate neuromodulator effects of adenosine and guanosine. © 2005 Wiley-Liss, Inc. [source]


RANTES stimulates inflammatory cascades and receptor modulation in murine astrocytes

GLIA, Issue 1 2002
Yi Luo
Abstract Cultured mouse astrocytes respond to the CC chemokine RANTES by production of chemokine and cytokine transcripts. Stimulation of astrocytes with 1 nM RANTES or 3,10 nM of the structurally related chemokines (eotaxin, macrophage inflammatory protein-1, and -, [MIP-1,, MIP-1,]) induced transcripts for KC, monocyte chemoattractant protein-1 (MCP-1), tumor necrosis factor-, (TNF-,), MIP-1,, MIP-2, and RANTES in a chemokine and cell-specific fashion. Synthesis of chemokine (KC and MCP-1) and cytokine (TNF-,) proteins was also demonstrated. RANTES-mediated chemokine synthesis was specifically inhibited by pertussis toxin, indicating that G-protein-coupled chemokine receptors participated in astrocyte signaling. Astrocytes expressed CCR1 and CCR5 (the redundant RANTES receptors). Astrocytes derived from mice with targeted mutations of either CCR1 or CCR5 respond after RANTES stimulation, suggesting multiple chemokine receptors may separately mediate RANTES responsiveness in astrocytes. Preliminary data suggest activation of the MAP kinase pathway is also critical for RANTES-mediated signaling in astrocytes. Treatment with RANTES specifically modulated astrocyte receptors upregulating intercellular adhesion molecule 1 (ICAM-1) and downregulating CX3CR1 expression. Thus, after chemokine treatment, astrocytes release proinflammatory mediators and reprogram their surface molecules. The combined effects of RANTES may serve to amplify inflammatory responses within the central nervous system. GLIA 39:19,30, 2002. © 2002 Wiley-Liss, Inc. [source]


Glial cell line-derived neurotrophic factor protects astrocytes from staurosporine- and ischemia- induced apoptosis

JOURNAL OF NEUROSCIENCE RESEARCH, Issue 15 2007
Albert Cheung Hoi Yu
Abstract Glial cell line-derived neurotrophic factor (GDNF) promotes the survival and functions of neurons. It has been shown to be a promising candidate in the treatment of ischemia and other neurodegenerative diseases. We transfected mouse astrocytes in primary cultures with a human GDNF gene and found that their conditioned medium could not only support the growth and survival of cultured dopaminergic neurons but also protect astrocytes from staurosporine- and ischemia-induced apoptosis. This indicated that these transfected astrocytes could release GDNF. A similar protective effect on astrocytes against apoptosis was evident when recombinant human GDNF was used. Moreover, GDNF reduced caspase-3 activity but not that of caspase-1 in cultured astrocytes after ischemia treatment. Thus, GDNF protects astrocytes from apoptosis by inhibiting the activation of caspase-3. © 2007 Wiley-Liss, Inc. [source]


Neudesin, a novel secreted protein with a unique primary structure and neurotrophic activity

JOURNAL OF NEUROSCIENCE RESEARCH, Issue 3 2005
Ikuo Kimura
Abstract We identified a novel secreted protein and named it neudesin. Mouse neudesin of 171 amino acids is unique with no primary structural similarity to any known proteins. The neudesin protein produced in cultured cells was secreted efficiently into the culture medium. Mouse neudesin mRNA was expressed abundantly in the developing brain and spinal cord in embryos, but was expressed widely in postnatal tissues including brain, heart, lung, and kidney. Mouse neudesin mRNA was expressed in neurons but not glial cells of the brain. The protein exhibited significant neurotrophic activity in primary cultured mouse neurons but not mitogenic activity in primary cultured mouse astrocytes. Neudesin activated the mitogen-activated protein (MAP) and phosphatidylinositol-3 (PI-3) kinase pathways. The activity of neudesin was inhibited by the inhibitor pertussis toxin for Gi/Go-protein but not by inhibitors for receptor tyrosine kinases. These results indicated that the activity was mediated via the activation of the MAP and PI-3 kinase pathways, potentially by the activation of a Gi/Go-protein-coupled receptor. Human neudesin of 172 amino acids with high similarity (,91% identity) to mouse neudesin was also identified. The human neudesin gene was mapped to chromosome 1p33. The identification of neudesin, a novel secreted protein with a unique primary structure and neurotrophic activity, will provide new insights into the development and maintenance of neurons. © 2004 Wiley-Liss, Inc. [source]


Visualization of localized store-operated calcium entry in mouse astrocytes.

THE JOURNAL OF PHYSIOLOGY, Issue 3 2005
Close proximity to the endoplasmic reticulum
Unloading of endoplasmic reticulum (ER) Ca2+ stores activates influx of extracellular Ca2+ through ,store-operated' Ca2+ channels (SOCs) in the plasma membrane (PM) of most cells, including astrocytes. A key unresolved issue concerning SOC function is their spatial relationship to ER Ca2+ stores. Here, using high resolution imaging with the membrane-associated Ca2+ indicator, FFP-18, it is shown that store-operated Ca2+ entry (SOCE) in primary cultured mouse cortical astrocytes occurs at plasma membrane,ER junctions. In the absence of extracellular Ca2+, depletion of ER Ca2+ stores using cyclopiazonic acid, an ER Ca2+ -ATPase inhibitor, and caffeine transiently increases the sub-plasma-membrane Ca2+ concentration ([Ca2+]SPM) within a restricted space between the plasma membrane and adjacent ER. Restoration of extracellular Ca2+ causes localized Ca2+ influx that first increases [Ca2+]SPM in the same restricted regions and then, with a delay, in ER-free regions. Antisense knockdown of the TRPC1 gene, proposed to encode endogenous SOCs, markedly reduces SOCE measured with Fura-2. High resolution immunocytochemistry with anti-TRPC1 antibody reveals that these TRPC-encoded SOCs are confined to the PM microdomains adjacent to the underlying ,junctional' ER. Thus, Ca2+ entry through TRPC-encoded SOCs is closely linked, not only functionally, but also structurally, to the ER Ca2+ stores. [source]