Molecular profile of reactive astrocytes--implications for their role in neurologic disease

Delayed treatment with lidocaine reduces mouse microglial cell injury and cytokine production after stimulation with lipopolysaccharide and interferon γ

BACKGROUND

Neuroinflammation is an important pathological process for almost all acquired neurological diseases. Microglial cells play a critical role in neuroinflammation. We determined whether lidocaine, a local anesthetic with anti-inflammatory property, protected microglial cells and attenuated cytokine production from activated microglial cells.

METHODS

Mouse microglial cultures were incubated with or without 1 μg/mL lipopolysaccharide and 10 U/mL interferon γ (IFNγ) for 24 hours in the presence or absence of lidocaine for 1 hour started at 2, 3, or 4 hours after the onset of lipopolysaccharide and IFNγ stimulation. Lactate dehydrogenase release and cytokine production were determined after the cells were stimulated by lipopolysaccharide and IFNγ for 24 hours.

RESULTS

Lidocaine dose-dependently reduced lipopolysaccharide and IFNγ-induced microglial cell injury as measured by lactate dehydrogenase release. This effect was apparent with lidocaine at 2 μg/mL (30.3% ± 5.8% and 23.1% ± 9.7%, respectively, for stimulation alone and the stimulation in the presence of lidocaine, n = 18, P = 0.025). Lidocaine applied at 2, 3, or 4 hours after the onset of lipopolysaccharide and IFNγ stimulation reduced the cell injury. This lidocaine effect was not affected by the mitochondrial K(ATP) channel inhibitor 5-hydroxydecanoate. Similar to lidocaine, QX314, a permanently charged lidocaine analog that usually does not permeate through the plasma membrane, reduced lipopolysaccharide and IFNγ-induced microglial cell injury. QX314 also attenuated the stimulation-induced interleukin-1β production.

CONCLUSIONS

Delayed treatment with lidocaine protects microglial cells and reduces cytokine production from these cells. These effects may involve action site(s) on the cell surface.

An in vitro trauma model to study rodent and human astrocyte reactivity

Protocols are presented describing a unique in vitro injury model and how to culture and mature mouse, rat, and human astrocytes for its use. This injury model produces widespread injury and astrocyte reactivity that enable quantitative measurements of morphological, biochemical, and functional changes in rodent and human reactive astrocytes. To investigate structural and molecular mechanisms of reactivity in vitro, cultured astrocytes need to be purified and then in vitro "matured" to reach a highly differentiated state. This is achieved by culturing astrocytes on deformable collagen-coated membranes in the presence of adult-derived horse serum (HS), followed by its stepwise withdrawal. These in vitro matured, process-bearing, quiescent astrocytes are then subjected to mechanical stretch injury by an abrupt pressure pulse from a pressure control device that briefly deforms the culture well bottom. This inflicts a measured reproducible, widespread strain that induces reactivity and injury in rodent and human astrocytes. Cross-species comparisons are possible because mouse, rat, and human astrocytes are grown using essentially the same in vitro treatment regimen. Human astrocytes from fetal cerebral cortex are compared to those derived from cortical biopsies of epilepsy patients (ages 1-12 years old), with regard to growth, purity, and differentiation. This opens a unique opportunity for future studies on glial biology, maturation, and pathology of human astrocytes. Prototypical astrocyte proteins including GFAP, S100, aquaporin4, glutamate transporters, and tenascin are expressed in mouse, rat, and human in vitro matured astrocyte. Upon pressure-stretching, rodent and human astrocytes undergo dynamic morphological, gene expression, and protein changes that are characteristic for trauma-induced reactive astrogliosis.

Functional duality of astrocytes in myelination

Astrocytes undergo major phenotypic changes in response to injury and disease that directly influence repair in the CNS, but the mechanisms involved are poorly understood. Previously, we have shown that neurosphere-derived rat astrocytes plated on poly-L-lysine (PLL-astrocytes) support myelination in dissociated rat spinal cord cultures (myelinating cultures). It is hypothesized that astrocyte reactivity can affect myelination, so we have exploited this culture system to ascertain how two distinct astrocyte phenotypes influence myelination. Astrocytes plated on tenascin C (TnC-astrocytes), a method to induce quiescence, resulted in less myelinated fibers in the myelinating cultures when compared with PLL-astrocytes. In contrast, treatment of myelinating cultures plated on PLL-astrocytes with ciliary neurotrophic factor (CNTF), a cytokine known to induce an activated astrocyte phenotype, promoted myelination. CNTF could also reverse the effect of quiescent astrocytes on myelination. A combination of microarray gene expression analysis and quantitative real-time PCR identified CXCL10 as a potential candidate for the reduction in myelination in cultures on TnC-astrocytes. The effect of TnC-astrocytes on myelination was eliminated by neutralizing CXCL10 antibodies. Conversely, CXCL10 protein inhibited myelination on PLL-astrocytes. Furthermore, CXCL10 treatment of purified oligodendrocyte precursor cells did not affect proliferation, differentiation, or process extension compared with untreated controls, suggesting a role in glial/axonal ensheathment. These data demonstrate a direct correlation of astrocyte phenotypes with their ability to support myelination. This observation has important implications with respect to the development of therapeutic strategies to promote CNS remyelination in demyelinating diseases.

EFFECT OF SUBSTRATE STIFFNESS ON THE STRUCTURE AND FUNCTION OF CELLS

Most biological tissues are soft viscoelastic materials with elastic moduli ranging from approximately 100 to 100,000 Pa. Recent studies have examined the effect of substrate rigidity on cell structure and function, and many, but not all cell types exhibit a strong response to substrate stiffness. Some blood cells such as platelets and neutrophils have indistinguishable structures on hard and soft materials as long as they are sufficiently adhesive, whereas many cell types, including fibroblasts and endothelial cells spread much more strongly on rigid compared to soft substrates. A few cell types such as neurons appear to extend better on very soft materials. The different response of astrocytes and neurons to the stiffness of their substrate results in preferential growth of neurons on soft gels and astrocytes on hard gels, and suggests that preventing rigidification of damaged central nervous system tissue after injury may have utility in wound healing. How cells sense substrate stiffness is unknown. One candidate protein, filamin A, which responds to externally derived stresses, was tested in melanoma cells. Cells devoid of filamin A retain the ability to sense substrate stiffness, suggesting that other proteins are required for stiffness sensing.

GFAP-independent inflammatory competence and trophic functions of astrocytes generated from murine embryonic stem cells

The directed generation of pure astrocyte cultures from pluripotent stem cells has proven difficult. Generation of defined pluripotent-stem-cell derived astrocytes would allow new approaches to the investigation of plasticity and heterogeneity of astrocytes. We here describe a two-step differentiation scheme resulting in the generation of murine embryonic stem cell (mESC) derived astrocytes (MEDA), as characterized by the upregulation of 19 astrocyte-associated mRNAs, and positive staining of most cells for GFAP (glial fibrillary acidic protein), aquaporin-4 or glutamine synthetase. The MEDA cultures could be cryopreserved, and they neither contained neuronal, nor microglial cells. They also did not react to the microglial stimulus lipopolysaccharide, while inflammatory activation by a complete cytokine mix (CCM) or its individual components (TNF-α, IL1-β, IFN-γ) was readily observed. MEDA, stimulated by CCM, became susceptible to CD95 ligand-induced apoptosis and produced NO and IL-6. This was preceded by NF-kB activation, and up-regulation of relevant mRNAs. Also GFAP-negative astrocytes were fully inflammation-competent. Neurotrophic support by MEDA was found to be independent of GFAP expression. In summary, we described here the generation and functional characterization of microglia-free murine astrocytes, displaying phenotypic heterogeneity as is commonly observed in brain astrocytes.

Comprehensive analysis of tissue preservation and recording quality from chronic multielectrode implants

Multielectrodes have been used with great success to simultaneously record the activity of neuronal populations in awake, behaving animals. In particular, there is great promise in the use of this technique to allow the control of neuroprosthetic devices by human patients. However, it is crucial to fully characterize the tissue response to the chronic implants in animal models ahead of the initiation of human clinical trials. Here we evaluated the effects of unilateral multielectrode implants on the motor cortex of rats weekly recorded for 1-6 months using several histological methods to assess metabolic markers, inflammatory response, immediate-early gene (IEG) expression, cytoskeletal integrity and apoptotic profiles. We also investigated the correlations between each of these features and firing rates, to estimate the impact of post-implant time on neuronal recordings. Overall, limited neuronal loss and glial activation were observed on the implanted sites. Reactivity to enzymatic metabolic markers and IEG expression were not significantly different between implanted and non-implanted hemispheres. Multielectrode recordings remained viable for up to 6 months after implantation, and firing rates correlated well to the histochemical and immunohistochemical markers. Altogether, our results indicate that chronic tungsten multielectrode implants do not substantially alter the histological and functional integrity of target sites in the cerebral cortex.

Involvement of CLEC16A in activation of astrocytes after LPS treated

CLEC16A, C-type lectin domain family 16, member A was recently found to be associated with inflation process in the autoimmune diseases. In this study, we elucidated the dynamic expression changes and localization of CLEC16A in lipopolysaccharide (LPS)-induced neuroinflammatory processes in adult rats. CLEC16A expression was strongly induced in active astrocytes in inflamed cerebral cortex. In vitro studies indicated that the up-regulation of CLEC16A may be involved in the subsequent astrocyte activation following LPS challenge. And Knock-down of CLEC16A in cultured primary astrocytes by siRNA showed that CLEC16A was required for the activation of astrocytes induced by LPS. Collectively, these results suggested CLEC16A may be important in host defense in astrocyte-mediated immune response. Understanding the cell signal pathway may provide a novel strategy against inflammatory and immune reaction in neuroinflammtion in CNS.

Proliferative reactive gliosis is compatible with glial metabolic support and neuronal function

Background

The response of mammalian glial cells to chronic degeneration and trauma is hypothesized to be incompatible with support of neuronal function in the central nervous system (CNS) and retina. To test this hypothesis, we developed an inducible model of proliferative reactive gliosis in the absence of degenerative stimuli by genetically inactivating the cyclin-dependent kinase inhibitor p27^Kip1 (p27 or Cdkn1b) in the adult mouse and determined the outcome on retinal structure and function.

Results

p27-deficient Müller glia reentered the cell cycle, underwent aberrant migration, and enhanced their expression of intermediate filament proteins, all of which are characteristics of Müller glia in a reactive state. Surprisingly, neuroglial interactions, retinal electrophysiology, and visual acuity were normal.

Conclusion

The benign outcome of proliferative reactive Müller gliosis suggests that reactive glia display context-dependent, graded and dynamic phenotypes and that reactivity in itself is not necessarily detrimental to neuronal function.

A complex of nuclear factor I-X3 and STAT3 regulates astrocyte and glioma migration through the secreted glycoprotein YKL-40

Nuclear factor I-X3 (NFI-X3) is a newly identified splice variant of NFI-X that regulates expression of several astrocyte-specific markers, such as glial fibrillary acidic protein. Here, we identified a set of genes regulated by NFI-X3 that includes a gene encoding a secreted glycoprotein YKL-40. Although YKL-40 expression is up-regulated in glioblastoma multiforme, its regulation and functions in nontransformed cells of the central nervous system are widely unexplored. We find that expression of YKL-40 is activated during brain development and also differentiation of neural progenitors into astrocytes in vitro. Furthermore, YKL-40 is a migration factor for primary astrocytes, and its expression is controlled by both NFI-X3 and STAT3, which are known regulators of gliogenesis. Knockdown of NFI-X3 and STAT3 significantly reduced YKL-40 expression in astrocytes, whereas overexpression of NFI-X3 dramatically enhanced YKL-40 expression in glioma cells. Activation of STAT3 by oncostatin M induced YKL-40 expression in astrocytes, whereas expression of a dominant-negative STAT3 had a suppressive effect. Mechanistically, NFI-X3 and STAT3 form a complex that binds to weak regulatory elements in the YKL-40 promoter and activates transcription. We propose that NFI-X3 and STAT3 control the migration of differentiating astrocytes as well as migration and invasion of glioma cells via regulating YKL-40 expression.

Upregulated vimentin suggests new areas of neurodegeneration in a model of an alcohol use disorder

Excessive alcohol intake, characteristic of an alcohol use disorder (AUD), results in neurodegeneration as well as cognitive deficits that may recover in abstinence. Neurodegeneration in psychiatric disorders such as AUDs is due to various effects on tissue integrity. Several groups report that alcohol-induced neurodegeneration and recovery include a role for adult neurogenesis. Therefore, the initial purpose of this study was to investigate the effect of alcohol on the temporal profile of neural progenitor cells using the radial glia marker, vimentin, in a model of an AUD. However, striking vimentin expression throughout corticolimbic regions led, instead, to the discovery of a significant gliosis response in this model. Adult male rats were subjected to a 4-day binge model of an AUD and brains harvested for immunohistochemistry at 0, 2, 4, 7, 14, and 28 days following the last dose of ethanol. A prominent increase in vimentin immunoreactivity was apparent at 4 and 7 days post binge that returned to control levels by 14 days in the corticolimbic regions examined. Vimentin-positive cells co-labeled with glial fibrillary acidic protein (GFAP), which suggested that cells were reactive astrocytes. A second experiment supported that increased vimentin was not primarily due to alcohol withdrawal seizures and is more likely due to alcohol-induced cell death. As this gliosis was remarkably distinct in regions where cell death had not previously been reported in this model, adjacent tissue sections were processed for FluoroJade B staining for cell death. FluoroJade B-positive cells were evident immediately following the last ethanol dose as expected, but were significantly elevated in the hippocampal dentate gyrus and CA3 regions and corticolimbic regions from 2 to 7 days post binge. Intriguingly, vimentin labeling of astrogliosis is more widespread than FluoroJade B labeling of cell death, which suggests that 4-day binge ethanol consumption is more damaging than originally realized.

Astrocytes and microglia: responses to neuropathological conditions

Activated astrocytes and microglia, hallmark of neurodegenerative diseases release different factors like array of pro and anti-inflammatory cytokines, free radicals, anti-oxidants, and neurotrophic factors during neurodegeneration which further contribute to neuronal death as well as in survival mechanisms. Astrocytes act as double-edged sword exerting both detrimental and neuroprotective effects while microglial cells are attributed more in neurodegenerative mechanisms. The dual and insufficient knowledge about the precise role of glia in neurodegeneration showed the need for further investigations and thorough review of the function of glia in neurodegeneration. In this review, we consolidate and categorize the glia-released factors which contribute in degenerative and protective mechanisms during neuropathological conditions.

The neurobiology of gliomas: from cell biology to the development of therapeutic approaches

Gliomas are the most common type of primary brain tumour and are often fast growing with a poor prognosis for the patient. Their complex cellular composition, diffuse invasiveness and capacity to escape therapies has challenged researchers for decades and hampered progress towards an effective treatment. Recent molecular characterization of tumour cells combined with new insights into cellular diversification that occurs during development, and the modelling of these processes in transgenic animals have enabled a more detailed understanding of the events that underlie gliomagenesis. Combining this enhanced understanding of the relationship between neural stem cell biology and the cell lineage relationships of tumour cells with model systems offers new opportunities to develop specific and effective therapies.

Pre-conditioning induces the precocious differentiation of neonatal astrocytes to enhance their neuroprotective properties

Hypoxic preconditioning reprogrammes the brain's response to subsequent H/I (hypoxia–ischaemia) injury by enhancing neuroprotective mechanisms. Given that astrocytes normally support neuronal survival and function, the purpose of the present study was to test the hypothesis that a hypoxic preconditioning stimulus would activate an adaptive astrocytic response. We analysed several functional parameters 24 h after exposing rat pups to 3 h of systemic hypoxia (8% O₂). Hypoxia increased neocortical astrocyte maturation as evidenced by the loss of GFAP (glial fibrillary acidic protein)-positive cells with radial morphologies and the acquisition of multipolar GFAP-positive cells. Interestingly, many of these astrocytes had nuclear S100B. Accompanying their differentiation, there was increased expression of GFAP, GS (glutamine synthetase), EAAT-1 (excitatory amino acid transporter-1; also known as GLAST), MCT-1 (monocarboxylate transporter-1) and ceruloplasmin. A subsequent H/I insult did not result in any further astrocyte activation. Some responses were cell autonomous, as levels of GS and MCT-1 increased subsequent to hypoxia in cultured forebrain astrocytes. In contrast, the expression of GFAP, GLAST and ceruloplasmin remained unaltered. Additional experiments utilized astrocytes exposed to exogenous dbcAMP (dibutyryl-cAMP), which mimicked several aspects of the preconditioning response, to determine whether activated astrocytes could protect neurons from subsequent excitotoxic injury. dbcAMP treatment increased GS and glutamate transporter expression and function, and as hypothesized, protected neurons from glutamate excitotoxicity. Taken altogether, these results indicate that a preconditioning stimulus causes the precocious differentiation of astrocytes and increases the acquisition of multiple astrocytic functions that will contribute to the neuroprotection conferred by a sublethal preconditioning stress.

Astrocyte phenotypes and their relationship to myelination

Astrocytes are one of the major glial cell types that maintain homeostasis in the undamaged CNS. After injury and disease, astrocytes become reactive and prevent regeneration; however, it has also been suggested that astrocytes can become activated and promote regeneration. Thus, it is hypothesised that astrocytes have an important role in modulating CNS repair. This review will focus on the variable phenotypic state of astrocytes that range from inactive/quiescent to reactive, and relate these to their ability to influence myelination. Using myelinating cultures plated on astrocytes we propose a possible mechanism for oligodendrocyte precursor cell interaction with the axon, leading to myelination. The phenotypic status of astrocytes is an intriguing and widely discussed issue, which is critical for understanding the mechanisms involved in CNS injury and its subsequent repair.

Neuroprotective effects of granulocyte-colony stimulating factor in a novel transgenic mouse model of SCA17

Spinocerebellar ataxia type 17 (SCA17) is an autosomal dominant inherited disorder characterized by degeneration of spinocerebellar tracts and selected brainstem neurons owing to the expansion of a CAG repeat of the human TATA-binding protein (hTBP) gene. To gain insight into the pathogenesis of this hTBP mutation, we generated transgenic mice with the mutant hTBP gene driven by the Purkinje specific protein (Pcp2/L7) gene promoter. Mice with the expanded hTBP allele developed ataxia within 2-5 months. Behavioral analysis of L7-hTBP transgenic mice showed reduced fall latency in a rotarod assay. Purkinje cell degeneration was identified by immunostaining of calbindin and IP3R1. Reactive gliosis and neuroinflammation occurred in the transgenic cerebellum, accompanied by up-regulation of GFAP and Iba1. The L7-hTBP transgenic mice were thus confirmed to recapitulate the SCA17 phenotype and were used as a disease model to explore the potential of granulocyte-colony stimulating factor in SCA17 treatment. Our results suggest that granulocyte-colony stimulating factor has a neuroprotective effect in these transgenic mice, ameliorating their neurological and behavioral deficits. These data indicate that the expression of the mutant hTBP in Purkinje cells is sufficient to produce cell degeneration and an ataxia phenotype, and constitutes a good model for better analysis of the neurodegeneration in SCA17.

Hepatic stellate cells and astrocytes: Stars of scar formation and tissue repair

Scar formation inhibits tissue repair and regeneration in the liver and central nervous system. Activation of hepatic stellate cells (HSCs) after liver injury or of astrocytes after nervous system damage is considered to drive scar formation. HSCs are the fibrotic cells of the liver, as they undergo activation and acquire fibrogenic properties after liver injury. HSC activation has been compared to reactive gliosis of astrocytes, which acquire a reactive phenotype and contribute to scar formation after nervous system injury, much like HSCs after liver injury. It is intriguing that a wide range of neuroglia-related molecules are expressed by HSCs. We identified an unexpected role for the p75 neurotrophin receptor in regulating HSC activation and liver repair. Here we discuss the molecular mechanisms that regulate HSC activation and reactive gliosis and their contributions to scar formation and tissue repair. Juxtaposing key mechanistic and functional similarities in HSC and astrocyte activation might provide novel insight into liver regeneration and nervous system repair.

Bone Marrow Mesenchymal Stem Cells and Electroacupuncture Downregulate the Inhibitor Molecules and Promote the Axonal Regeneration in the Transected Spinal Cord of Rats

Our previous study has reported that electroacupuncture (EA) promotes survival, differentiation of bone marrow mesenchymal stem cells (MSCs), and functional improvement in spinal cord-transected rats. In this study, we further investigated the structural bases of this functional improvement and the potential mechanisms of axonal regeneration in injured spinal cord after MSCs and EA treatment. Five experimental groups, 1) sham control (Sham-control); 2) operated control (Op-control); 3) electroacupuncture treatment (EA); 4) MSCs transplantation (MSCs), and 5) MSCs transplantation combined with electroacupuncture (MSCs + EA), were designed for this study. Western blots and immunohistochemical staining were used to assess the fibrillary acidic protein (GFAP) and chondroitin sulfate proteoglycans (CSPGs) proteins expression. Basso, Beattie, Bresnahan (BBB) locomotion test, cortical motor evoked potentials (MEPs), and anterograde and retrograde tracing were utilized to assess cortical-spinal neuronal projection regeneration and functional recovery. In the MSCs + EA group, increased labeling descending corticospinal tract (CST) projections into the lesion site showed significantly improved BBB scales and enhanced motor evoked potentials after 10 weeks of MSCs transplant and EA treatment. The structural and functional recovery after MSCs + EA treatment may be due to downregulated GFAP and CSPGs protein expression, which prevented axonal degeneration as well as improved axonal regeneration.

Immunohistochemical analysis of TIMP-2 and collagen types I and IV in experimental spinal cord ischemia-reperfusion injury in rats

BACKGROUND

Thoracic and thoracoabdominal aortic intervention carries a significant risk of spinal cord ischemia. The pathophysiologic mechanisms that cause hypoxic/ischemic injury to the spinal cord have not been totally explained. In normal spinal cord, neurons and glial cells do not express type IV collagen. Type IV collagen produced by reactive astrocytes is reported to participate in glial scar formation. Tissue inhibitors of metalloproteinases (TIMPs) are endogenous inhibitors that regulate the activity of the matrix metalloproteinases (MMPs). TIMP-2 binds strongly with MMP-2, facilitating activation by membrane-type MMP. Imbalance between TIMPs and MMPs can lead to excessive degradation of matrix components. Type IV collagen involved in the blood-brain barrier disruption and glial scar formation, TIMP-2 influences MMP-2 that controls degradation of collagen I and IV.

OBJECTIVE

To examine the immunohistochemical analysis of TIMP-2 and collagen types I-IV in experimental spinal cord ischemia-reperfusion in rats.

METHODS

Thirty-two male Wistar rats weighing 250-300 g were divided into four groups: group S: sham group (n = 8); group 0P: 30-minute occlusion without perfusion (n = 8); group 3P: 30-minute occlusion and 3-hour perfusion (n = 8); and group 24P: 30-minute occlusion and 24-hour perfusion (n = 8). Infrarenal aorta was cross-clamped at two sites by using two aneurysm clips for 30 minutes. Reperfusion was provided after removal of the clips. Lumbar spinal cord segments were removed for immunohistochemical analysis.

RESULTS

TIMP-2 and collagen staining in 3-hour perfused (3P) group were nearly the same with sham group (S). TIMP-2 and collagen staining increased in the 24-hour perfused group.

CONCLUSION

Alterations in collagen levels may relate to the biphasic breakdown of the blood-brain barrier and collagen staining in new cell types with relation to glial scar formation. Our results demonstrate that 3-hour perfusion after occlusion in hypoxic/ischemic spinal cord injury seems to be the critical reversible period.

Physiological unfolded protein response regulated by OASIS family members, transmembrane bZIP transcription factors

The endoplasmic reticulum (ER) plays role in the maintenance of numerous aspects of cellular and organismal homeostasis by folding, modifying, and exporting nascent secretory and transmembrane proteins. Failure of the ER's adaptive capacity results in accumulation of unfolded or malfolded proteins in the ER lumen (ER stress). To avoid cellular damage, mammalian cells activate the specific signals from the ER to the cytosol or nucleus to enhance the capacity for protein folding, attenuate the synthesis of proteins, and degrade unfolded proteins. These signaling pathways are collectively known as the unfolded protein response (UPR). The canonical branches of the UPR are mediated by three ER membrane-bound proteins, PERK, IRE1, and ATF6. These ER stress transducers basically play important roles in cell survival after ER stress. Recently, novel types of ER stress transducers, OASIS family members that share a region of high sequence similarity with ATF6 have been identified. They have a transmembrane domain, which allows them to associate with the ER, and possess a transcription-activation domain and a bZIP domain. OASIS family proteins include OASIS, BBF2H7, CREBH, AIbZIP, and Luman. Despite the structural similarities among OASIS family proteins and ATF6, differences in activating stimuli, tissue distribution, and response element binding indicate specialized functions of each member on regulating the UPR in the specific organs and tissues. Here, we summarize our current understanding of biochemical characteristics and in vivo functions of OASIS family proteins, particularly focusing on OASIS and BBF2H7. A growing body of new works suggests that the UPR branches regulated by OASIS family members play essential roles in cell differentiation and maturation or maintenance of basal cellular homeostasis in mammals.

Acetate supplementation attenuates lipopolysaccharide-induced neuroinflammation

Glyceryl triacetate (GTA), a compound effective at increasing circulating and tissue levels of acetate was used to treat rats subjected to a continual 28 day intra-ventricular infusion of bacterial lipopolysaccharide (LPS). This model produces a neuroinflammatory injury characterized by global neuroglial activation and a decrease in choline acetyltransferase immunoreactivity in the basal forebrain. During the LPS infusion, rats were given a daily treatment of either water or GTA at a dose of 6 g/kg by oral gavage. In parallel experiments, free-CoA and acetyl-CoA levels were measured in microwave fixed brains and flash frozen heart, liver, kidney and muscle following a single oral dose of GTA. We found that a single oral dose of GTA significantly increased plasma acetate levels by 15 min and remained elevated for up to 4 h. At 30 min the acetyl-CoA levels in microwave-fixed brain and flash frozen heart and liver were increased at least 2.2-fold. The concentrations of brain acetyl-CoA was significantly increased between 30 and 45 min following treatment and remained elevated for up to 4 h. The concentration of free-CoA in brain was significantly decreased compared to controls at 240 min. Immunohistochemical and morphological analysis demonstrated that a daily treatment with GTA significantly reduced the percentage of reactive glial fibrillary acidic protein-positive astrocytes and activated CD11b-positive microglia by 40-50% in rats subjected to LPS-induced neuroinflammation. Further, in rats subjected to neuroinflammation, GTA significantly increased the number of choline acetyltransferase (ChAT)-positive cells by 40% in the basal forebrain compared to untreated controls. These data suggest that acetate supplementation increases intermediary short chain acetyl-CoA metabolism and that treatment is potentially anti-inflammatory and neuroprotective with regards to attenuating neuroglial activation and increasing ChAT immunoreactivity in this model.

Influence of rat substrain and growth conditions on the characteristics of primary cultures of adult rat spinal cord astrocytes

Primary astrocyte cell cultures have become a valuable tool for studies of signaling pathways that regulate astrocyte physiology, reactivity, and function; however, differences in culture preparation affect data reproducibility. The aim of this work was to define optimal conditions for obtaining primary astrocytes from adult rat spinal cord with an expression profile most similar to adult human spinal cord astrocytes. Hence, we examined whether different Sprague-Dawley substrains and culture conditions affect astrocyte culture quality. Medium supplemented with fetal bovine serum from three sources (Sigma, Gibco, Hyclone) or a medium with defined composition (AM medium) was used to culture astrocytes isolated from spinal cords of adult Harlan and Charles River Spraque-Dawley rats. Purity was significantly different between cultures established in media with different sera. No microglia were detected in AM or Hyclone cultures. Gene expression was also affected, with AM cultures expressing the highest level of glutamine synthetase, connexin-43, and glutamate transporter-1. Interestingly, cell response to starvation was substrain dependent. Charles River-derived cultures responded the least, while astrocytes derived from Harlan rats showed a greater decrease in Gfap and glutamine synthetase, suggesting a more quiescent phenotype. Human and Harlan astrocytes cultured in AM media responded similarly to starvation. Taken together, this study shows that rat substrain and growth medium composition affect purity, expression profile and response to starvation of primary astrocytes suggesting that cultures of Harlan rats in AM media have optimal astrocyte characteristics, purity, and similarity to human astrocytes.

FOXO3a inhibits TNF-α- and IL-1β-induced astrocyte proliferation:Implication for reactive astrogliosis

Reactive astrogliosis is one of the pathological hallmarks of neurodegenerative diseases. Inflammatory cytokines, such as TNF-α and IL-1β, have been shown to mediate the reactive astrogliosis in neurodegenerative diseases; however, the molecular mechanism remains unclear. In this study, we investigated the role of transcription factor FOXO3a on astrocyte proliferation, one primary aspect of severe reactive astrogliosis. Our results confirmed that TNF-α and IL-1β increased astrocyte proliferation, as determined by Ki67 and BrdU immunostaining. Furthermore, we found that cytokine-mediated astrocyte proliferation was accompanied by an increase of the phosphorylation and reduced nuclear expression of FOXO3a. Intracranial injection of TNF-α and IL-1β induced astrocyte proliferation and hypertrophy, which was associated with reduced nuclear expression of Foxo3a in astrocytes. To determine the function of FOXO3a in astrocyte proliferation, wild type FOXO3a was overexpressed with adenovirus, which subsequently upregulated p27Kip1 and Gadd45α, and significantly inhibited cytokine-induced astrocyte proliferation. In contrast, overexpression of dominant negative FOXO3a decreased p27Kip1, upregulated cyclin D1 and promoted astrocyte proliferation. Along the same line, astrocytes isolated from Foxo3a-null mice have higher proliferative potential. In response to intracranial injection of cytokines, Foxo3a-null mice manifested severe astrogliosis in vivo. In conclusion, FOXO3a is important in restraining astrocyte proliferation during proinflammatory cytokine stimulation and loss of function of FOXO3a may be responsible for the proliferation of astrocytes in the severe form of reactive astrogliosis. Understanding the key regulatory role of FOXO3a in reactive astrogliosis may provide a novel therapeutic target during neuroinflammation.

Evidence for cellular injury in the midbrain of rats following chronic constriction injury of the sciatic nerve

Complex behavioural disabilities, as well as pain, characterise neuropathic pain conditions for which clinical treatment is sought. In rats, chronic constriction injury (CCI) of the sciatic nerve evokes, allodynia and hyperalgesia as well as three distinct patterns of disability, characterised by changes in social and sleep-wake behaviours: (i) Pain & Disability; (ii) Pain & Transient Disability and (iii) Pain alone. Importantly, the degree of allodynia and hyperalgesia is identical for each of these groups. Social-interactions and sleep-wake behaviours are regulated by neural networks, which converge on the periaqueductal grey (PAG). Rats with Pain & Disability show astrocyte activation restricted to the lateral and ventrolateral PAG. Reactive astrocytes are a hallmark of cell death (apoptosis and necrosis). Quantitative real-time RT-PCR for the mRNAs encoding Bax, Bcl-2, heat shock protein 60 (HSP60), mitogen activated kinase kinase (MEK2) and iNOS was performed on the dorsal midbrains of individual, disability characterised rats, extending our earlier Gene-Chip data, showing a select up-regulation of Bax and MEK2 mRNA, and a down-regulation of HSP60 mRNA, in Pain & Disability rats. The anatomical location of TUNEL and cleaved-caspase-3 immunoreactive profiles in the midbrain was also identified. Rats with Pain & Disability showed: (i) pro-apoptotic ratios of Bax:Bcl-2 mRNAs; (ii) decreased HSP60 mRNA; (iii) increased iNOS and MEK2 mRNAs; (iv) TUNEL-positive profiles in the lateral and ventrolateral PAG; and (v) caspase-3 immunoreactive neurons in the mesencephalic nucleus of the trigeminal nerve. Cell death in these specific midbrain regions may underlie the disabilities characterising this subgroup of nerve-injured rats.

HPMA-RGD hydrogels seeded with mesenchymal stem cells improve functional outcome in chronic spinal cord injury

Chronic spinal cord injury (SCI) is characterized by tissue loss and a stable functional deficit. While several experimental therapies have proven to be partly successful for the treatment of acute SCI, treatment of chronic SCI is still challenging. We studied whether we can bridge a chronic spinal cord lesion by implantation of our newly developed hydrogel based on 2-hydroxypropyl methacrylamide, either alone or seeded with mesenchymal stem cells (MSCs), and whether this treatment leads to functional improvement. A balloon-induced compression lesion was performed in adult 2-month-old male Wistar rats. Five weeks after injury, HPMA-RGD hydrogels [N-(2-hydroxypropyl)-methacrylamide with attached amino acid sequences--Arg-Gly-Asp] were implanted into the lesion, either with or without seeded MSCs. Animals with chronic SCI served as controls. The animals were behaviorally tested using the Basso–Beattie-Breshnahan (BBB) (motor) and plantar (sensory) tests once a week for 6 months. Behavioral analysis showed a statistically significant improvement in rats with combined treatment, hydrogel and MSCs, compared with the control group (P < 0.05). Although a tendency toward improvement was found in rats treated with hydrogel only, this was not significant. Subsequently, the animals were sacrificed 6 months after SCI, and the spinal cord lesions evaluated histologically. The combined therapy (hydrogel with MSCs) prevented tissue atrophy (P < 0.05), and the hydrogels were infiltrated with axons myelinated with Schwann cells. Blood vessels and astrocytes also grew inside the implant. MSCs were present in the hydrogels even 5 months after implantation. We conclude that 5 weeks after injury, HPMA-RGD hydrogels seeded with MSCs can successfully bridge a spinal cord cavity and provide a scaffold for tissue regeneration. This treatment leads to functional improvement even in chronic SCI.

Non-invasive quantification of brain tumor-induced astrogliosis

Background

CNS injury including stroke, infection, and tumor growth lead to astrogliosis, a process that involves upregulation of glial fibrillary acidic protein (GFAP) in astrocytes. However, the kinetics of astrogliosis that is related to these insults (i.e. tumor) is largely unknown.

Results

Using transgenic mice expressing firefly luciferase under the regulation of the GFAP promoter (GFAP-luc), we developed a model system to monitor astrogliosis upon tumor growth in a rapid, non-invasive manner. A biphasic induction of astrogliosis was observed in our xenograft model in which an early phase of activation of GFAP was associated with inflammatory response followed by a secondary, long-term upregulation of GFAP. These animals reveal GFAP activation with kinetics that is in parallel with tumor growth. Furthermore, a strong correlation between astrogliosis and tumor size was observed.

Conclusions

Our results suggest that non-invasive, quantitative bioluminescent imaging using GFAP-luc reporter animal is a useful tool to monitor temporal-spatial kinetics of host-mediated astrogliosis that is associated with glioma and metastatic brain tumor growth.

The role of propriospinal interneurons in recovery from spinal cord injury

Over one hundred years ago, Sir Charles Sherrington described a population of spinal cord interneurons (INs) that connect multiple spinal cord segments and participate in complex or 'long' motor reflexes. These neurons were subsequently termed propriospinal neurons (PNs) and are known to play a crucial role in motor control and sensory processing. Recent work has shown that PNs may also be an important substrate for recovery from spinal cord injury (SCI) as they contribute to plastic reorganisation of spinal circuits. The location, inter-segmental projection pattern and sheer number of PNs mean that after SCI, a significant number of them are capable of 'bridging' an incomplete spinal cord lesion. When these properties are combined with the capacity of PNs to activate and coordinate locomotor central pattern generators (CPGs), it is clear they are ideally placed to assist locomotor recovery. Here we summarise the anatomy, organisation and function of PNs in the uninjured spinal cord, briefly outline the pathophysiology of SCI, describe how PNs contribute to recovery of motor function, and finally, we discuss the mechanisms that underlie PN plasticity. We propose there are two major challenges for PN research. The first is to learn more about ways we can promote PN plasticity and manipulate the 'hostile' micro-environment that limits regeneration in the damaged spinal cord. The second is to study the cellular/intrinsic properties of PNs to better understand their function in both the normal and injured spinal cord. This article is part of a Special Issue entitled 'Synaptic Plasticity & Interneurons'.

The neuroprotective effects of cyclooxygenase-2 inhibition in a mouse model of aneurysmal subarachnoid hemorrhage

The CNS inflammatory reaction occurring after aneurysmal subarachnoid hemorrhage (SAH) involves the upregulation of numerous cytokines and prostaglandins. Cyclooxygenase (COX) inhibition is a well-established pharmacological anti-inflammatory agent. Previous studies have shown marked increases in COX-2 expression in neurons, astrocytes, microglia, and endothelial cells following brain injury. COX-2 inhibition has been shown to be beneficial following various types of brain injury. This experiment investigates the role of COX-2 activity in early brain injury following SAH. CD-1 mice were subjected to an endovascular perforation model of SAH or SHAM surgery. Following experimental SAH animals were treated with the specific COX-2 inhibitor, NS398, in dosages of either 10 or 30 mg/kg. Neurological performance and brain edema were evaluated 24 and 72 h after SAH. NS398 at 30 mg/kg significantly reduced SAH-induced neurological deterioration. NS 398 at 30 mg/kg resulted in a trend toward the reduction of SAH-induced cerebral edema. Treatment had no effect on mortality. This experiment provides preliminary evidence that COX-2 inhibition is an effective pharmacological intervention for the prevention of brain edema and the preservation of neurological function following SAH.

Structure and functions of aquaporin-4-based orthogonal arrays of particles

Orthogonal arrays or assemblies of intramembranous particles (OAPs) are structures in the membrane of diverse cells which were initially discovered by means of the freeze-fracturing technique. This technique, developed in the 1960s, was important for the acceptance of the fluid mosaic model of the biological membrane. OAPs were first described in liver cells, and then in parietal cells of the stomach, and most importantly, in the astrocytes of the brain. Since the discovery of the structure of OAPs and the identification of OAPs as the morphological equivalent of the water channel protein aquaporin-4 (AQP4) in the 1990s, a plethora of morphological work on OAPs in different cells was published. Now, we feel a need to balance new and old data on OAPs and AQP4 to elucidate the interrelationship of both structures and molecules. In this review, the identity of OAPs as AQP4-based structures in a diversity of cells will be described. At the same time, arguments are offered that under pathological or experimental circumstances, AQP4 can also be expressed in a non-OAP form. Thus, we attempt to project classical work on OAPs onto the molecular biology of AQP4. In particular, astrocytes and glioma cells will play the major part in this review, not only due to our own work but also due to the fact that most studies on structure and function of AQP4 were done in the nervous system.

Down-regulation of glutamine synthetase enhances migration of rat astrocytes after in vitro injury

Astrocytes undergo reactive transformation in response to physical injury (reactive gliosis) that may impede neural repair. Glutamine synthetase (GS) is highly expressed by astrocytes, and serves a neuroprotective function by converting cytotoxic glutamate and ammonia into glutamine. Glutamine synthetase was down-regulated in reactive astrocytes at the site of mechanical spinal cord injury (SCI) and in cultured astrocytes at the margins of a scratch wound, suggesting that GS may modulate reactive transformation and glial scar development. We evaluated this potential function of GS using siRNA-mediated GS knock-down. Suppression of astrocytic GS by GS siRNA increased cell migration into the scratch wound zone and decreased substrate adhesion as indicated by the number of focal adhesions expressing the adaptor protein paxillin. Migration was enhanced by glutamine and suppressed by glutamate, in contrast to the result expected if enhanced migration was due solely to changes in glutamine and glutamate concomitant with reduced GS activity. The membrane type 1-matrix metalloproteinase (MT1-MMP) was up-regulated in GS siRNA-treated astrocytes, while a broad-spectrum MMP antagonist inhibited migration in both wild type and GS knock-down astrocytes. In addition, GS siRNA inhibited expression of integrin β1, while antibody-mediated inhibition of integrin β1 impaired direction-specific protrusion and motility. Thus, GS may modulate motility and substrate adhesion through transmembrane integrin β1 signaling to the cytoskeleton and by MMT-mediated proteolysis of the extracellular matrix.

Role of glial cells in neurotoxin-induced animal models of Parkinson's disease

Dopaminergic neurons are selectively vulnerable to oxidative stress and inflammatory attack. The neuronal cell loss in the substantia nigra is associated with a glial response composed markedly of activated microglia and, to a lesser extent, of reactive astrocytes although these glial responses may be the source of neurotrophic factors and can protect against oxidative stress such as reactive oxygen species and reactive nitrogen species. However, the glial response can also mediate a variety of deleterious events related to the production of pro-inflammatory, pro-oxidant reactive species, prostaglandins, cytokines, and so on. In this review, we discuss the possible protective and deleterious effects of glial cells in the neurodegenerative diseases and examine how these factors may contribute to the pathogenesis of Parkinson's disease. This review suggests that further investigation concerning glial reaction in Parkinson's disease may lead to disease-modifying therapeutic approaches and may contribute to the pathogenesis of this disease.

Structural remodeling of fibrous astrocytes after axonal injury

Reactive astrocytes are a pathological hallmark of many CNS injuries and neurodegenerations. They are characterized by hypertrophy of the soma and processes and an increase in the expression of glial fibrillary acidic protein. Because the cells obscure each other in immunostaining, little is known about the behavior of a single reactive astrocyte, nor how single astrocytes combine to form the glial scar. We have investigated the reaction of fibrous astrocytes to axonal degeneration using a transgenic mouse strain expressing enhanced green fluorescent protein in small subsets of astrocytes. Fibrous astrocytes in the optic nerve and corpus callosum initially react to injury by hypertrophy of the soma and processes. They retract their primary processes, simplifying their shape and dramatically reducing their spatial coverage. At 3 d after crush, quantitative analysis revealed nearly a twofold increase in the thickness of the primary processes, a halving of the number of primary processes leaving the soma and an eightfold reduction in the spatial coverage. In the subsequent week, they partially reextend long processes, returning to a near-normal morphology and an extensive spatial overlap. The resulting glial scar consists of an irregular array of astrocyte processes, contrasting with their original orderly arrangement. These changes are in distinct contrast to those reported for reactive protoplasmic astrocytes of the gray matter, in which the number of processes and branchings increase, but the cells continue to maintain nonoverlapping individual territories throughout their response to injury.

Effect of interleukin-1β on the expression of actin isoforms in cultured mouse astroglia

Cytokines are soluble mediators that are thought to act as communication signals between astroglia and neighboring neural cells. They are both released by, and act on, astroglia. It is hypothesized that it is this effect on astroglia that may be important in widespread phenomena including traumatic brain injury, inflammation, and scar formation. In this article, we examine the effect of mouse recombinant interleukin-1β (IL-1β) on the morphology, organization, and expression of glial fibrillary acidic protein (GFAP) and actin isoforms in cultured mouse astroglia. This study shows that the majority of the astroglia treated with IL-1β acquire long processes. Immunofluorescence staining shows that there are no remarkable changes in the organization of GFAP, F-actin, α-smooth muscle (α-sm) actin, and β-actin isoforms. In fluorescent microplate assay, the short-term treated astroglia (range, 1-2 days) show an increase in the intensity of GFAP and β-actin isoform over the level observed in untreated control, whereas no remarkable changes are observed in the intensity of α-sm actin isoform. In the case of long-term treatment (range, 4-8 days), the intensity of GFAP and α-sm actin isoform progressively decreases below the level of untreated control. In addition, the intensity of β-actin isoform increases above the control level. These results have been confirmed by immunoblotting experiments. The upregulation of β-actin isoform may be important in limiting the noxious effects of an inflammatory reaction. This gives credence to the hypothesis that it might be possible to modulate astroglial effects on neuronal inflammation and scar formation with appropriate therapies.

Phosphoproteomic analysis reveals site-specific changes in GFAP and NDRG2 phosphorylation in frontotemporal lobar degeneration

Frontotemporal lobar degeneration (FTLD) is a progressive neurodegenerative disease characterized by behavioral abnormalities, personality changes, language dysfunction, and can co-occur with the development of motor neuron disease. One major pathological form of FTLD is characterized by intracellular deposition of ubiquitinated and phosphorylated TAR DNA binding protein-43 (TDP-43), suggesting that dysregulation in phosphorylation events may contribute to disease progression. However, to date systematic analysis of the phosphoproteome in FTLD brains has not been reported. In this study, we employed immobilized metal affinity chromatography (IMAC) followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) to identify phosphopeptides from FTLD and age-matched control post-mortem human brain tissue. Using this approach, we identified 786 phosphopeptides in frontal cortex (control and FTLD), in which the population of phosphopeptides represented approximately 50% of the total peptides analyzed. Label-free quantification using spectral counts revealed six proteins with significant changes in the FTLD phosphoproteome. N-myc-Downstream regulated gene 2 (NDRG2) and glial fibrillary acidic protein (GFAP) had an increased number of phosphospectra in FTLD, whereas microtubule associated protein 1A (MAP1A), reticulon 4 (RTN4; also referred to as neurite outgrowth inhibitor (Nogo)), protein kinase C gamma (PRKCG), and heat shock protein 90 kDa alpha, class A member 1(HSP90AA1) had significantly fewer phosphospectra compared to control brain. To validate these differences, we examined NDRG2 phosphorylation in FTLD brain by immunoblot analyses, and using a phosphoserine-13 (pSer13) GFAP monoclonal antibody we show an increase in pSer13 GFAP levels by immunoblot concomitant with increased overall GFAP levels in FTLD cases. These data highlight the utility of combining proteomic and phosphoproteomic strategies to characterize post-mortem human brain tissue.

Astrogliosis in amyotrophic lateral sclerosis: role and therapeutic potential of astrocytes

Amyotrophic lateral sclerosis (ALS) is a fatal disorder characterized by the progressive loss of motor neurons. Although the molecular mechanism underlying motor neuron degeneration remains unknown; non-neuronal cells (including astrocytes) shape motor neuron survival in ALS. Astrocytes closely interact with neurons to provide an optimized environment for neuronal function and respond to all forms of injury in a typical manner known as reactive astrogliosis. A strong reactive astrogliosis surrounds degenerating motor neurons in ALS patients and ALS-animal models. Although reactive astrogliosis in ALS is probably both primary and secondary to motor neuron degeneration; astrocytes are not passive observers and they can influence motor neuron fate. Due to the important functions that astrocytes perform in the central nervous system; it is of key importance to understand how these functions are altered when astrocytes become reactive in ALS. Here; we review the current evidences supporting a potential toxic role of astrocytes and their viability as therapeutic targets to alter motor neuron degeneration in ALS.

Intermediate filaments attenuate stimulation-dependent mobility of endosomes/lysosomes in astrocytes

Intermediate filament (IF) proteins upregulation is a hallmark of astrocyte activation and reactive gliosis, but its pathophysiological implications remain incompletely understood. A recently reported association between IFs and directional mobility of peptidergic vesicles allows us to hypothesize that IFs affect vesicle dynamics and exocytosis-mediated astrocyte communication with neighboring cells. Here, we ask whether the trafficking of recycling vesicles (i.e., those fused to and then retrieved from the plasma membrane) and endosomes/lysosomes depends on IFs. Recycling vesicles were labeled by antibodies against vesicle glutamate transporter 1 (VGLUT1) and atrial natriuretic peptide (ANP), respectively, and by lysotracker, which labels endosomes/lysosomes. Quantitative fluorescence microscopy was used to monitor the mobility of labeled vesicles in astrocytes, derived from either wild-type (WT) mice or mice deficient in glial fibrillary acidic protein and vimentin (GFAP(-/-)Vim(-/-)), the latter lacking astrocyte IFs. Stimulation with ionomycin or ATP enhanced the mobility of VGLUT1-positive vesicles and reduced the mobility of ANP-positive vesicles in WT astrocytes. In GFAP(-/-)Vim(-/-) astrocytes, both vesicle types responded to stimulation, but the relative increase in mobility of VGLUT1-positive vesicles was more prominent compared with nonstimulated cells, whereas the stimulation-dependent attenuation of ANP-positive vesicles mobility was reduced compared with nonstimulated cells. The mobility of endosomes/lysosomes decreased following stimulation in WT astrocytes. However, in GFAP(-/-)Vim(-/-) astrocytes, a small increase in the mobility of endosomes/lysosomes was observed. These findings show that astrocyte IFs differentially affect the stimulation-dependent mobility of vesicles. We propose that upregulation of IFs in pathologic states may alter the function of astrocytes by deregulating vesicle trafficking.

Antiinflammatory activity of melatonin in central nervous system

Melatonin is mainly produced in the mammalian pineal gland during the dark phase. Its secretion from the pineal gland has been classically associated with circadian and circanual rhythm regulation. However, melatonin production is not confined exclusively to the pineal gland, but other tissues including retina, Harderian glands, gut, ovary, testes, bone marrow and lens also produce it. Several studies have shown that melatonin reduces chronic and acute inflammation. The immunomodulatory properties of melatonin are well known; it acts on the immune system by regulating cytokine production of immunocompetent cells. Experimental and clinical data showing that melatonin reduces adhesion molecules and pro-inflammatory cytokines and modifies serum inflammatory parameters. As a consequence, melatonin improves the clinical course of illnesses which have an inflammatory etiology. Moreover, experimental evidence supports its actions as a direct and indirect antioxidant, scavenging free radicals, stimulating antioxidant enzymes, enhancing the activities of other antioxidants or protecting other antioxidant enzymes from oxidative damage. Several encouraging clinical studies suggest that melatonin is a neuroprotective molecule in neurodegenerative disorders where brain oxidative damage has been implicated as a common link. In this review, the authors examine the effect of melatonin on several neurological diseases with inflammatory components, including dementia, Alzheimer disease, Parkinson disease, multiple sclerosis, stroke, and brain ischemia/reperfusion but also in traumatic CNS injuries (traumatic brain and spinal cord injury).

Astrocytes in the amygdala

The amygdala has received considerable attention because of its established role in specific behaviors and disorders such as anxiety, depression, and autism. Studies have revealed that the amygdala is a complex and dynamic brain region that is highly connected with other areas of the brain. Previous works have focused on neurons, demonstrating that the amygdala in rodents is highly plastic and sexually dimorphic. However, our more recent work explores sex differences in nonneuronal cells, joining a rich literature concerning glia in the amygdala. Prior investigation of glia in the amygdala can generally be divided into disease-related and hormone-related categories, with both areas of research producing interesting findings concerning glia in this important brain region. Despite a wide range of research topics, the collected findings make it clear that glia in the amygdala are sensitive and plastic cells that respond and develop in a highly region specific manner.

Transduction of the inner mouse retina using AAVrh8 and AAVrh10 via intravitreal injection

Adeno-associated virus (AAV) is a proven, safe and effective vector for gene delivery in the retina. There are over 100 serotypes of AAV, and AAV2 through AAV9 have been evaluated in the retina. Each AAV serotype has different cell tropism and transduction efficiency. Intravitreal injections of AAV into the eye tend to transduce cells in the ganglion cell layer (GCL), while subretinal injections tend to transduce retinal pigment epithelium and photoreceptors. Efficient transduction of the inner retina beyond the GCL is not well established with the current methodologies and serotypes used to date. In this study, we compared the cellular tropism of AAVrh8 and AAVrh10 vectors encoding enhanced green fluorescent protein (EGFP) using intravitreal injections. We found that AAVrh8 largely transduced cells in the GCL and also amacrine cells in the inner nuclear layer (INL), as well as Müller and horizontal cells. Inner retinal transduction with AAVrh10 was similar to AAVrh8, but AAVrh10 appeared to also transduce bipolar cells. The transduction efficiency as measured by the intensity of EGFP signal was 3.5 fold higher in horizontal cells transduced with AAVrh10 than AAVrh8. Glial fibrillary accessory protein (GFAP) levels were increased in Müller cells in transduced areas for both serotypes. The results of this study suggest that AAVrh8 and AAVrh10 may be excellent vector candidates to deliver genetic material to the INL, particularly for amacrine and horizontal cells, however they may also cause cellular stress as shown by increased glial GFAP expression.

Activated astroglia during chronic inflammation in Alzheimer's disease--do they neglect their neurosupportive roles?

Alzheimer's disease (AD) is a neurodegenerative disorder, characterized histopathologically by the extracellular deposition of beta-amyloid peptide in senile plaques, as well as intracellular neurofibrillary tangles (NFT) of hyperphosphorylated tau protein, extensive neuronal loss and synaptic changes in the hippocampus and cerebral cortex. In addition, the AD brain shows chronic inflammation characterized by an abundance of reactive astrocytes and activated microglia. In the healthy brain, astrocytes provide essential services for brain homeostasis and neuronal function, including metabolic support for neurons in the form of lactate, glutamate uptake and conversion into glutamine, and synthesis of glutathione and its precursors. In AD, a large body of evidence now suggests that by transforming from a basal to a reactive state, astrocytes neglect their neurosupportive functions, thus rendering neurons vulnerable to neurotoxins including pro-inflammatory cytokines and reactive oxygen species. This review will explain the normal functions of astrocytes, and how these cells might be activated to turn into inflammatory cells, actively contributing to neurodegeneration and neglecting their neurosupportive roles ("neuro-neglect hypothesis"). Furthermore, it is proposed that astrocytes might be promising target of therapeutic intervention for Alzheimer's disease, if these compromised functions can be normalized with pharmacological agents that are specifically designed to return astrocytes to a quiescent phenotype or supplement factors which activated astrocytes lack to produce.

Glial scar and neuroregeneration: histological, functional, and magnetic resonance imaging analysis in chronic spinal cord injury

Object

A glial scar is thought to be responsible for halting neuroregeneration following spinal cord injury (SCI). However, little quantitative evidence has been provided to show the relationship of a glial scar and axonal regrowth after injury.

Methods

In this study performed in rats and dogs, a traumatic SCI model was made using a weight-drop injury device, and tissue sections were stained with H & E for immunohistochemical analysis. The function and behavior of model animals were tested using electrophysiological recording and the Basso-Beattie-Bresnahan Locomotor Rating Scale, respectively. The cavity in the spinal cord after SCI in dogs was observed using MR imaging.

Results

The morphological results showed that the formation of an astroglial scar was defined at 4 weeks after SCI. While regenerative axons reached the vicinity of the lesion site, the glial scar blocked the extension of regrown axons. In agreement with these findings, the electrophysiological, behavioral, and in vivo MR imaging tests showed that functional recovery reached a plateau at 4 weeks after SCI. The thickness of the glial scars in the injured rat spinal cords was also measured. The mean thickness of the glial scar rostral and caudal to the lesion cavity was 107.00 ± 20.12 μm; laterally it was 69.92 ± 15.12 μm.

Conclusions

These results provide comprehensive evidence indicating that the formation of a glial scar inhibits axonal regeneration at 4 weeks after SCI. This study reveals a critical time window of postinjury recovery and a detailed spatial orientation of glial scar, which would provide an important basis for the development of therapeutic strategy for glial scar ablation.