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Recent studies have implicated chemokines in microglial activation and pathogenesis of neuropathic pain. C-X-C motif chemokine 13 (CXCL13) is a B lymphocyte chemoattractant that activates CXCR5. Using the spinal nerve ligation (SNL) model of neuropathic pain, we found that CXCL13 was persistently upregulated in spinal cord neurons after SNL, resulting in spinal astrocyte activation via CXCR5 in mice. shRNA-mediated inhibition of CXCL13 in the spinal cord persistently attenuated SNL-induced neuropathic pain. Interestingly, CXCL13 expression was suppressed by miR-186-5p, a microRNA that colocalized with CXCL13 and was downregulated after SNL. Spinal overexpression of miR-186-5p decreased CXCL13 expression, alleviating neuropathic pain. Furthermore, SNL induced CXCR5 expression in spinal astrocytes, and neuropathic pain was abrogated in [Cxcr5.sup.-/-] mice. CXCR5 expression induced by SNL was required for the SNL-induced activation of spinal astrocytes and microglia. Intrathecal injection of CXCL13 was sufficient to induce pain hypersensitivity and astrocyte activation via CXCR5 and ERK. Finally, intrathecal injection of CXCL13-activated astrocytes induced mechanical allodynia in naive mice. Collectively, our findings reveal a neuronal/astrocytic interaction in the spinal cord by which neuronally produced CXCL13 activates astrocytes via CXCR5 to facilitate neuropathic pain. Thus, miR-186-5p and CXCL13/CXCR5-mediated astrocyte signaling may be suitable therapeutic targets for neuropathic pain., Introduction Chemokines are a family of small secreted proteins that are well-known regulators of peripheral immune cell trafficking (1). It has become evident that chemokines are also expressed in the [...]

Astrocyte-elevated gene-1 (AEG-1) expression increases in multiple cancers and plays a crucial role in oncogenic transformation and angiogenesis, which are essential components in tumor cell development, growth, and progression to metastasis. Moreover, AEG-1 directly contributes to resistance to chemotherapeutic drugs, another important hallmark of aggressive cancers. In the present study, we document that AEG-1 mediates protective autophagy, an important regulator of cancer survival under metabolic stress and resistance to apoptosis, which may underlie its significant cancer-promoting properties. AEG-1 induces noncanonical autophagy involving an increase in expression of ATG5. AEG-1 decreases the ATP/AMP ratio, resulting in diminished cellular metabolism and activation of AMP kinase, which induces AMPK/mammalian target of rapamycin-dependent autophagy. Inhibition of AMPK by siAMPK or compound C decreases expression of ATG5, ultimately attenuating AEG-1-induced autophagy. AEG-1 protects normal cells from serum starvation-induced death through protective autophagy, and inhibition of AEG-1-induced autophagy results in serum starvation-induced cell death. We also show that AEG-1-mediated chemoresistance is because of protective autophagy and inhibition of AEG-1 results in a decrease in protective autophagy and chemosensitization of cancer cells. In summary, the present study reveals a previously unknown aspect of AEG-1 function by identifying it as a potential regulator of protective autophagy, an important feature of AEG-1 that may contribute to its tumor-promoting properties. AMPK/mTOR | LC3 | doxorubicin doi/ 10.1073/pnas.1009479107

Neurons rely on their metabolic coupling with astrocytes to combat oxidative stress. The transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) appears important for astrocyte-dependent neuroprotection from oxidative insults. Indeed, Nrf2 activators are effective in stroke, Parkinson disease, and Huntington disease models. However, key endogenous signals that initiate adaptive neuroprotective cascades in astrocytes, including activation of Nrf2-mediated gene expression, remain unclear. Hydrogen peroxide ([H.sub.2][O.sub.2]) plays an important role in cell signaling and is an attractive candidate mediator of adaptive responses in astrocytes. Here we determine (i) the significance of [H.sub.2][O.sub.2] in promoting astrocyte-dependent neuroprotection from oxidative stress, and (ii) the relevance of [H.sub.2][O.sub.2] in inducing astrocytic Nrf2 activation. To control the duration and level of cytoplasmic [H.sub.2][O.sub.2] production in astrocytes cocultured with neurons, we heterologously expressed the [H.sub.2][O.sub.2]-producing enzyme Rhodotorula gracilis D-amino acid oxidase (rgDAAO) selectively in astrocytes. Exposure of rgDAAO-astrocytes to D-alanine lead to the concentration-dependent generation of [H.sub.2][O.sub.2], Seven hours of low-level [H.sub.2][O.sub.2] production (~3.7 nmol x min x mg protein) in astrocytes protected neurons from oxidative stress, but higher levels (~130 nmol x min x mg protein) were neurotoxic. Neuroprotection occurred without direct neuronal exposure to astrocyte-derived [H.sub.2][O.sub.2], suggesting a mechanism specific to astrocytic intracellular signaling. Nrf2 activation mimicked the effect of astrocytic [H.sub.2][O.sub.2] yet [H.sub.2][O.sub.2]-induced protection was independent of Nrf2. Astrocytic protein tyrosine phosphatase inhibition also protected neurons from oxidative death, representing a plausible mechanism for [H.sub.2][O.sub.2]-induced neuroprotection. These findings demonstrate the utility of rgDAAO for spatially and temporally controlling intracellular [H.sub.2][O.sub.2] concentrations to uncover unique astrocyte-dependent neuroprotective mechanisms. doi/ 10.1073/pnas.1003996107

Huntington disease (HD) is an inherited neurological disorder caused by a polyglutamine expansion in the protein huntingtin and is characterized by selective neurodegeneration that preferentially occurs in striatal medium spiny neurons. Because the medium spiny neurons are innervated abundantly by glutamatergic axons from cortical neurons, the preferential degeneration in the striatal neurons supports the glutamate excitotoxicity theory for HD pathogenesis. Thus, glutamate uptake by gila may be particularly important for preventing glutamate excitotoxicity in HD. Although mutant huntingtin is expressed ubiquitously in various types of cells, it accumulates and forms aggregates in fewer glial cells than in neuronal cells. It remains largely unknown whether and how mutant huntingtin in gila can contribute to the neurological symptoms of HD. We generated transgenic mice that express N-terminal mutant huntingtin in astrocytes, a major type of glial cell that remove extracellular glutamate in the brain. Although transgenic mutant huntingtin in astrocytes is expressed below the endogenous level, it can cause age-dependent neurological phenotypes in transgenic mice. Mice expressing mutant huntingtin show body weight loss, have motor function deficits, and die earlier than wild-type or control transgenic mice. We also found that mutant huntingtin in astrocytes decreases the expression of glutamate transporter by increasing its binding to Sp1 and reducing the association of Sp1 with the promoter of glutamate transporter. These results imply an important role for glial mutant huntingtin in HD pathology and suggest possibilities for treatment. excitotoxicity | glia | neurodegeneration | polyglutamine | glutamate doi/10.1073/pnas.0911503106

There is a growing appreciation that endogenously produced mediators may actively promote the resolution of inflammation. Lipoxins (LX) are a group of recently discovered lipid mediators that have been shown to exert anti-inflammatory and proresolution effects on cells of myeloid and nonmyeloid origin. LXs mediate a number of processes, including regression of pro-inflammatory cytokine production, inhibition of cell proliferation, and stimulation of phagocytosis of apoptotic leukocytes by macrophages. Lipoxin [A.sub.4] ([LXA.sub.4]) is one of the principal LXs formed by mammalian cells. Recently, a G protein-coupled receptor that binds [LXA.sub.4]. the lipoxin [A.sub.4] receptor, was identified in astrocytes and microglia, suggesting that these cells may be a target for LX action in the brain. In this study, we have investigated the potential of [LXA.sub.4] to modify inflammatory responses of astrocytes, using the 1321N1 human astrocytoma cell line as a model system. As shown by quantitative RT-PCR, [LXA.sub.4] (10 nM) significantly inhibited (P < 0.05) the IL-1[beta]-induced stimulation of IL-8 and ICAM-1 expression in these cells. Furthermore, [LXA.sub.4] (10 nM) decreased the expression of IL-1[beta]-induced IL-8 protein levels (P < 0.05). [LXA.sub.4] (10 nM) was found to inhibit IL-1[beta]-induced degradation of I[kappa]B[alpha] (P < 0.05), and the activation of an NF[kappa]B regulated reporter gene construct (P < 0.05). Overall, these data suggest that [LXA.sub.4] exerts anti-inflammatory effects in 1321N1 astrocytoma cells at least in part via an NF[kappa]B-dependent mechanism. It is concluded that [LXA.sub.4] may represent a potentially novel therapeutic approach to acute or chronic inflammation in the brain. neuroinflammation; formyl-peptide receptor like-1; alxr

Hepatocellular carcinoma (HCC) is a highly aggressive vascular cancer characterized by diverse etiology, activation of multiple signal transduction pathways, and various gene mutations. Here, we have determined a specific role for astrocyte elevated gene-1 (AEG1) in HCC pathogenesis. Expression of AEG1 was extremely low in human hepatocytes, but its levels were significantly increased in human HCC. Stable overexpression of AEG1 converted nontumorigenic human HCC cells into highly aggressive vascular tumors, and inhibition of AEG1 abrogated tumorigenesis by aggressive HCC cells in a xenograft model of nude mice. In human HCC, AEG1 overexpression was associated with elevated copy numbers. Microarray analysis revealed that AEG1 modulated the expression of genes associated with invasion, metastasis, chemoresistance, angiogenesis, and senescence. AEG1 also was found to activate Wnt/[beta]-catenin signaling via ERK42/44 activation and upregulated lymphoid-enhancing factor 1/T cell factor 1 (LEF1/TCF1), the ultimate executor of the Wnt pathway, important for HCC progression. Inhibition studies further demonstrated that activation of Wnt signaling played a key role in mediating AEG1 function. AEG1 also activated the NF-[kappa]B pathway, which may play a role in the chronic inflammatory changes preceding HCC development. These data indicate that AEG1 plays a central role in regulating diverse aspects of HCC pathogenesis. Targeted inhibition of AEG1 might lead to the shutdown of key elemental characteristics of HCC and could lead to an effective therapeutic strategy for HCC., Introduction Hepatocellular carcinoma (HCC) is one of the 5 most common cancers worldwide (1). HCC has a high prevalence in Asian countries because of endemic HBV infection, and the incidence [...]

Influx of [Ca.sup.2+] ions through [alpha]-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptors contributes to neuronal damage in stroke, epilepsy, and neurodegenerative disorders such as ALS. The [Ca.sup.2+] permeability of AMPA receptors is largely determined by the glutamate receptor 2 (GluR2) subunit, receptors lacking GluR2 being permeable to [Ca.sup.2+] ions. We identified a difference in GluR2 expression in motor neurons from two rat strains, resulting in a difference in vulnerability to AMPA receptor-mediated excitotoxicity both in vitro and in vivo. Astrocytes from the ventral spinal cord were found to mediate this difference in GluR2 expression in motor neurons. The presence of ALS-causing mutant superoxide dismutase 1 in astrocytes abolished their GluR2-regulating capacity and thus affected motor neuron vulnerability to AMPA receptor-mediated excitotoxicity. These results reveal a mechanism through which astrocytes influence neuronal functioning in health and disease. amyotrophic lateral sclerosis | [alpha]-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor | neurodegeneration | mutant superoxide dismutase 1

Research has been conducted on the oligodendrocyte lineage genes Olig1 and Olig2 encoding bHLH proteins. Results indicate that oligodendrocytes and astrocytes are produced from a glial-restricted precursor.

Rat cortical astrocytes in pure culture are functionally coupled to neighboring cells via connexin (Cx) 43 gap junctions under ordinary conditions. Small fluorescent molecules such as Lucifer yellow (LY) pass between cell interiors via gap junctions, but do not enter the cells when externally applied. Subjecting rat and mouse cortical astrocytes to 'chemical ischemia' by inhibition of glycolytic and oxidative metabolism induced permeabilization of cells to Lucifer yellow and ethidium bromide before loss of membrane integrity determined by dextran uptake and lactate dehydrogenase release. The gap junction blockers octanol and 18[alpha]-glycyrrhetinic acid markedly reduced dye uptake, suggesting that uptake was mediated by opening of unapposed hemichannels. Extracellular [La.sup.3+] also reduced dye uptake and delayed cell death. The purinergic blocker, oxidized ATP, was ineffective. Astrocytes isolated from mice with targeted deletion of the Cx43 coding DNA exhibited greatly reduced dye coupling and ischemia-induced dye uptake, evidence that dye uptake is mediated by Cx43 hemichannels. Dye coupling was reduced but not blocked by metabolic inhibition. Blockade of lipoxygenases or treatment with free radical scavengers reduced dye uptake by rat astrocytes, suggesting a role for arachidonic acid byproducts in hemichannel opening. Furthermore, permeabilization was accompanied by reduction in ATP levels and dephosphorylation of Cx43. Although hemichannel opening would tend to collapse electrochemical and metabolic gradients across the plasma membrane of dying cells, healthy cells might rescue dying cells by transfer of ions and essential metabolites via Cx43 gap junctions. Alternatively, dying astrocytes might compromise the health of neighboring cells via Cx43 gap junctions, thereby promoting the propagation of cell death. astroglia | dye uptake | dye coupling | Cx43 | phosphorylation

Research has been conducted on the bHLH transcription factor neurogenin (Ngn1) inhibiting neural stem cell differentiation into astrocytes. Results indicate that Ngn1 effectively inhibits astrocyte differentiation, and the Ngn1 glial-specific gene-transcription repression mechanisms have been identified.

A mouse model has been generated for medulloblastoma, one of the most common types of malignancies in children. Cre-LoxP-mediated inactivation of Rb and p53 tumor suppressor genes was carried out in the external granular layer (EGL) cells of the cerebellum. Loss of function of RB seems to be essential for medulloblastoma development in the mouse. It is hypothesized that medulloblastomas come from multipotent precursor cells in the EGL.

The promoter region regulating the proliferation of astrocytes through the mediation of basic fibroblast growth factor (bFGF) was identified. Astrocytes that were induced to multiply in cultures showed a constant level of expression of bFGF luciferase. However, there was a higher incidence of the luciferase binding to the promoter region from denser cell cultures. This is in contrast with glioma cells, in which proliferation does not require cell contact.

The CD44 adhesion molecule expression in astrocytes was studied to determine CD44 molecule role in interactions between astrocytes and lymphocytes. Primary cultures of astrocytes from the brain of a new-born mouse revealed that transcript levels and surface expression of total CD44 are up-regulated, after being reacted with tumor-inducing agent PMA or alpha-TNF plus gamma-IFN. An in vitro model for adhesion of T cells and astrocytes was revealed a relationship between the activity and adhesion capability of the cells.

A study was done on the activation of expression of genes coding for extracellular matrix proteins in Tat-producing glioblastoma cells. It was shown that the presence of HIV-1 regulatory protein in Tat is associated with a significant induction in the expression of certain protein components of the extracellular matrix in glial-derived cells. The induction is also seen at the level of protein synthesis and the presence of Tat results in increased transcription of fibronectin and alpha1 type 1 collagen promoters.

The tailless (Tlx) gene is exclusively expressed in astrocyte-like B cells in the subventricular zone (SVZ) of the adult brain and is necessary for the transformation from radial glial cells to astrocyte-like neural stem cells. The significant role of Tlx in the generation and maintenance of neural stem cells (NSCs) in the adult SVZ in vivo is demonstrated.

A study on whether re-expression of activated ErbB2 can induce mature astrocytes to revert to a radial glial progenitor phenotype in the adult cerebral cortex is presented. The results indicate a positive response and raise the possibility that reinduced radial glia in the mature brain can be manipulated to generate and guide new neurons.

Research has been conducted on transcription factor Sox9. The authors describe the study of the mice spinal cord development where Sox9 has been ablated from neural stem cells by the CRE/loxP recombination system.

Fischer, Silvia, Maria Wobben, Jan Kleinstuck, Dieter Renz, and Wolfgang Schaper. Effect of astroglial cells on hypoxia-induced permeability in PBMEC cells. Am J Physiol Cell Physiol 279: C935-C944, 2000.--An in vitro model of the blood-brain barrier (BBB), consisting of porcine brain-derived microvascular endothelial cells (PBMEC), was used to evaluate the effect of astrocytes in the BBB disruption during hypoxia. Hypoxia-induced hyperpermeability was decreased significantly in a coculture model of astroglia cells, either astrocytes or C6 glioma cells, with PBMEC and, to the same extent, when glia cell-conditioned medium was used. Corresponding to effects on hypoxia-induced hyperpermeability, astrocyte- and C6 cell-conditioned medium diminished hypoxia-induced vascular endothelial growth factor (VEGF) mRNA and protein expression, which recently was shown to be responsible for hypoxia-induced permeability changes in vitro. The effect on hypoxia-induced hyperpermeability and VEGF expression was specific for astroglia cells because conditioned medium from bovine smooth muscle cells (BSMC) did not show any effect. Immunocytochemistry revealed that 24 h of hypoxia disrupted the continuity of the tight junction protein, zonula occludens-1 (ZO-1), which lines the cytoplasmic face of intact tight junctions. These changes were prevented when hypoxia was performed in glia cell-conditioned medium. Results suggest that astrocytes protect the BBB from hypoxia-induced paracellular permeability changes by decreasing hypoxia-induced VEGF expression in microvascular endothelial cells. porcine brain microvascular endothelial cells; vascular endothelial growth factor; astrocytes

Foust, K.D. et al. Nat. Biotechnol. published online, doi:10.1038/nbt.1515 (21 December 2008) Researchers have achieved the difficult task of delivering genes across the blood-brain barrier to the brain and spinal [...]