Loss of the Novel Myelin Protein CMTM5 in Multiple Sclerosis Lesions and Its Involvement in Oligodendroglial Stress Responses

This study comprehensively addresses the involvement of the protein CKLF-like Marvel transmembrane domain-containing family member 5 (CMTM5) in the context of demyelination and cytodegenerative autoimmune diseases, particularly multiple Sclerosis (MS). An observed reduction in CMTM5 expression in post-mortem MS lesions prompted further investigations in both in vitro and in vivo animal models. In the cuprizone animal model, we detected a decrease in CMTM5 expression in oligodendrocytes that is absent in other members of the CMTM protein family. Our findings also confirm these results in the experimental autoimmune encephalomyelitis (EAE) model with decreased CMTM5 expression in both cerebellum and spinal cord white matter. We also examined the effects of a Cmtm5 knockdown in vitro in the oligodendroglial Oli-neu mouse cell line using the CRISPR interference technique. Interestingly, we found no effects on cell response to thapsigargin-induced endoplasmic reticulum (ER) stress as determined by Atf4 activity, an indicator of cellular stress responses. Overall, these results substantiate previous findings suggesting that CMTM5, rather than contributing to myelin biogenesis, is involved in maintaining axonal integrity. Our study further demonstrates that the knockdown of Cmtm5 in vitro does not modulate oligodendroglial responses to ER stress. These results warrant further investigation into the functional role of CMTM5 during axonal degeneration in the context of demyelinating conditions.

[DREAM: a multifunctional transcriptional regulator]

DREAM (downstream regulatory element antagonist modulator), Calsenilin and KChIP3 (potassium channel interacting protein 3) belong to the neuronal calcium sensor (NCS) superfamily, which transduces the intracellular calcium signaling into a variety of activities. They are encoded by the same gene locus, but have distinct subcellular locations. DREAM was first found to interact with DRE (downstream regulatory element) site in the vicinity of the promoter of prodynorphin gene to suppress gene transcription. Calcium can disassemble this interaction by binding reversibly to DREAM protein on its four EF-hand motifs. Apart from having calcium dependent DRE site binding, DREAM can also interact with other transcription factors, such as cAMP responsive element binding protein (CREB), CREB-binding protein (CBP) and cAMP responsive element modulator (CREM), by this concerted actions, DREAM extends the gene pool under its control. DREAM is predominantly expressed in central nervous system with its highest level in cerebellum, and accumulating evidence demonstrated that DREAM might play important roles in pain sensitivity. Novel findings have shown that DREAM is also involved in learning and memory processes, Alzheimer's disease and stroke. This mini-review provides a brief introduction of its discovery history and protein structure properties, focusing on the mechanism of DREAM nuclear translocation and gene transcription regulation functions.

The Unwanted Cell Migration in the Brain: Glioma Metastasis

Cell migration is identified as a highly orchestrated process. It is a fundamental and essential phenomenon underlying tissue morphogenesis, wound healing, and immune response. Under dysregulation, it contributes to cancer metastasis. Brain is considered to be the most complex organ in human body containing many types of neural cells with astrocytes playing crucial roles in monitoring both physiological and pathological functions. Astrocytoma originates from astrocytes and its most malignant type is glioblastoma multiforme (WHO Grade IV astrocytoma), which is capable to infiltrate widely into the neighboring brain tissues making a complete resection of tumors impossible. Very recently, we have reviewed the mechanisms for astrocytes in migration. Given the fact that astrocytoma shares many histological features with astrocytes, we therefore attempt to review the mechanisms for glioma cells in migration and compare them to normal astrocytes, hoping to obtain a better insight into the dysregulation of migratory mechanisms contributing to their metastasis in the brain.

Alendronate Attenuates Spinal Microglial Activation and Neuropathic Pain

Many derivatives of bisphosphonates, which are inhibitors of bone resorption, have been developed as promising agents for painful pathologies in patients with bone resorption-related diseases. The mechanism for pain relief by bisphosphonates remains uncertain. Studies have reported that bisphosphonates could reduce central neurochemical changes involved in the generation and maintenance of bone cancer pain. In this study, we hypothesized that bisphosphonates would inhibit spinal microglial activation and prevent the development of hyperalgesia caused by peripheral tissue injury. We investigated the effects of alendronate (a nitrogen-containing bisphosphonate) on the development of neuropathic pain and its role in modulating microglial activation in vivo and in vitro. Intrathecal and intraperitoneal administration of alendronate relieved neuropathic pain behaviors induced by chronic constriction sciatic nerve injury. Alendronate also significantly attenuated spinal microglial activation and p38 mitogen-activated protein kinase (MAPK) phosphorylation without affecting astrocytes. In vitro, alendronate downregulated phosphorylated p38 and phosphorylated extracellular signal regulated kinase expression in lipopolysaccharide-stimulated primary microglia within 1 hour, and pretreatment with alendronate for 12 and 24 hours decreased the expression of inflammatory cytokines (tumor necrosis factor α, and interleukins 1β and 6). These findings indicate that alendronate could effectively relieve chronic constriction sciatic nerve injury-induced neuropathic pain by at least partially inhibiting the activation of spinal microglia and the p38 MAPK signaling pathway.

PERSPECTIVE

Alendronate could relieve neuropathic pain behaviors in animals by inhibiting the activation of spinal cord microglia and the p38 MAPK cell signaling pathway. Therapeutic applications of alendronate may be extended beyond bone metabolism-related disease.

Ischemia preconditioning protects astrocytes from ischemic injury through 14-3-3γ

Stroke is a leading cause of death and disability, and new strategies are required to reduce neuronal injury and improve prognosis. Ischemia preconditioning (IPC) is an intrinsic phenomenon that protects cells from subsequent ischemic injury and might provide promising mechanisms for clinical treatment. In this study, primary astrocytes exhibited significantly less cell death than control when exposed to different durations of IPC (15, 30, 60, or 120 min). A 15-min duration was the most effective IPC to protect astrocytes from 8-hr-ischemia injury. The protective mechanisms of IPC involve the upregulation of protective proteins, including 14-3-3γ, and attenuation of malondialdehyde (MDA) content and ATP depletion. 14-3-3γ is an antiapoptotic intracellular protein that was significantly upregulated for up to 84 hr after IPC. In addition, IPC promoted activation of the c-Jun N-terminal kinase (JNK), extracellular signal-related kinase (ERK)-1/2, p38, and protein kinase B (Akt) signaling pathways. When JNK was specifically inhibited with SP600125, the upregulation of 14-3-3γ induced by IPC was almost completely abolished; however, there was no effect on ATP or MDA levels. This suggests that, even though both energy preservation and 14-3-3γ up-regulation were turned on by IPC, they were controlled by different pathways. The ERK1/2, p38, and Akt signaling pathways were not involved in the 14-3-3γ upregulation and energy preservation. These results indicate that IPC could protect astrocytes from ischemia injury by inducing 14-3-3γ and by alleviating energy depletion through different pathways, suggesting multiple protection of IPC and providing new insights into potential stroke therapies.

Sulforaphane protects rodent retinas against ischemia-reperfusion injury through the activation of the Nrf2/HO-1 antioxidant pathway

Retinal ischemia-reperfusion (I/R) injury induces oxidative stress, leukocyte infiltration, and neuronal cell death. Sulforaphane (SF), which can be obtained in cruciferous vegetables such as broccoli, exerts protective effects in response to oxidative stress in various tissues. These effects can be initiated through nuclear factor E2-related factor 2 (Nrf2)-mediated induction of heme oxygenase-1 (HO-1). This investigation was designed to elucidate the neural protective mechanisms of SF in the retinal I/R rat model. Animals were intraperitoneally (i.p.) injected with SF (12.5 mg/kg) or vehicle (corn oil) once a day for 7 consecutive days. Then, retinal I/R was made by elevating the intraocular pressure (IOP) to 130 mmHg for 1 h. To determine if HO-1 was involved in the Nrf2 antioxidant pathway, rats were subjected to protoporphyrin IX zinc (II) (ZnPP, 30 mg/kg, i.p.) treatments at 24 h before retinal ischemia. The neuroprotective effects of SF were assessed by determining the morphology of the retina, counting the infiltrating inflammatory cells and the surviving retinal ganglion cells (RGCs) and amacrine cells, and measuring apoptosis in the retinal layers. The expression of Nrf2 and HO-1 was studied by immunofluorescence analysis and western blotting. I/R induced a marked increase of ROS generation, caused pronounced inflammation, increased the apoptosis of RGCs and amacrine cells and caused the thinning of the inner retinal layer (IRL), and these effects were diminished or abolished by SF pretreatment. Meanwhile, SF pretreatment significantly elevated the nuclear accumulation of Nrf2 and the level of HO-1 expression in the I/R retinas; however, ZnPP reversed the protective effects of SF on I/R retinas. Together, we offer direct evidence that SF had protective effects on I/R retinas, which could be attributed, at least in part, to the activation of the Nrf2/HO-1 antioxidant pathway.

Astrocytic exportin-7 responds to ischemia through mediating LKB1 translocation from the nucleus to the cytoplasm

The superfamily of importin-β-related proteins is the largest class of nuclear transport receptors and can be generally divided into importins and exportins according to their transport directions. Eleven importins and seven exportins have been identified, and the expression patterns of both classes are important for their functions in nucleocytoplasmic transport activities. This study demonstrates that all of the importins (importin-β; transportin-1, -2, and -3; and importin-4, -5, -7, -8, -9, -11, and -13) and all the exportins (exportin-1, -2, -4, -5, -6, -7, and -t) are differentially expressed in the cerebral cortex, cerebellum, hippocampus, and brainstem and in primary cultures of cerebral cortical astrocytes and neurons. For astrocytes, we observed that different importins and exportins displayed different expression changes during 0-6 hr of ischemia treatment, especially an increase of both the mRNA and the protein of exportin-7. Immunostaining showed that exportin-7 accumulated inside the nucleus and around the nuclear envelope. In addition, we noticed an increased cytoplasmic distribution of one of the cargo proteins of exportin-7, LKB1, an important element in maintaining energy homeostasis. This increased cytoplasmic distribution was accompanied by an increased expression of exportin-7 under ischemia in astrocytes. We demonstrate that exportin-7 responds to ischemia in astrocytes and that this response involves translocation of LKB1, a protein that plays important roles during metabolic stress, from the nucleus to the cytoplasm.

Regulatory role of the JNK-STAT1/3 signaling in neuronal differentiation of cultured mouse embryonic stem cells

Stem cell transplantation therapy has provided promising hope for the treatment of a variety of neurodegenerative disorders. Among challenges in developing disease-specific stem cell therapies, identification of key regulatory signals for neuronal differentiation is an essential and critical issue that remains to be resolved. Several lines of evidence suggest that JNK, also known as SAPK, is involved in neuronal differentiation and neural plasticity. It may also play a role in neurite outgrowth during neuronal development. In cultured mouse embryonic stem (ES) cells, we test the hypothesis that the JNK pathway is required for neuronal differentiation. After neural induction, the cells were plated and underwent differentiation for up to 5 days. Western blot analysis showed a dramatic increase in phosphorylated JNKs at 1-5 days after plating. The phosphorylation of JNK subsequently induced activation of STAT1 and STAT3 that lead to expressions of GAP-43, neurofilament, βIII-tubulin, and synaptophysin. NeuN-colabelled with DCX, a marker for neuroblast, was enhanced by JNK signaling. Neuronal differentiation of ES cells was attenuated by treatment with SP600125, which inhibited the JNK activation and decreased the activation of STAT1 and STAT3, and consequently suppressed the expressions of GAP-43, neurofilament, βIII-tubulin, and the secretion of VEGF. Data from immunocytochemistry indicated that the nuclear translocation of STAT3 was reduced, and neurites of ES-derived neurons were shorter after treatment with SP600125 compared with control cells. These results suggest that the JNK-STAT3 pathway is a key regulator required for early neuronal differentiation of mouse ES cells. Further investigation on expression of JNK isoforms showed that JNK-3 was significantly upregulated during the differentiation stage, while JNK-1 and JNK-2 levels decreased. Our study provided interesting information on JNK functions during ES cell neuronal differentiation.

Traumatic scratch injury in astrocytes triggers calcium influx to activate the JNK/c-Jun/AP-1 pathway and switch on GFAP expression

Astrocyte activation is a hallmark of central nervous system injuries resulting in glial scar formation (astrogliosis). The activation of astrocytes involves metabolic and morphological changes with complex underlying mechanisms, which should be defined to provide targets for astrogliosis intervention. Astrogliosis is usually accompanied by an upregulation of glial fibrillary acidic protein (GFAP). Using an in vitro scratch injury model, we scratched primary cultures of cerebral cortical astrocytes and observed an influx of calcium in the form of waves spreading away from the wound through gap junctions. Using the calcium blocker BAPTA-AM and the JNK inhibitor SP600125, we demonstrated that the calcium wave triggered the activation of JNK, which then phosphorylated the transcription factor c-Jun to facilitate the binding of AP-1 to the GFAP gene promoter to switch on GFAP upregulation. Blocking calcium mobilization with BAPTA-AM in an in vivo stab wound model reduced GFAP expression and glial scar formation, showing that the calcium signal, and the subsequent regulation of downstream signaling molecules, plays an essential role in brain injury response. Our findings demonstrated that traumatic scratch injury to astrocytes triggered a calcium influx from the extracellular compartment and activated the JNK/c-Jun/AP-1 pathway to switch on GFAP expression, identifying a previously unreported signaling cascade that is important in astrogliosis and the physiological response following brain injury.

AQP5 is differentially regulated in astrocytes during metabolic and traumatic injuries

Water movement plays vital roles in both physiological and pathological conditions in the brain. Astrocytes are responsible for regulating this water movement and are the major contributors to brain edema in pathological conditions. Aquaporins (AQPs) in astrocytes play critical roles in the regulation of water movement in the brain. AQP1, 3, 4, 5, 8, and 9 have been reported in the brain. Compared with AQP1, 4, and 9, AQP3, 5, and 8 are less studied. Among the lesser known AQPs, AQP5, which has multiple functions identified outside the central nervous system, is also indicated to be involved in hypoxia injury in astrocytes. In our study, AQP5 expression could be detected both in primary cultures of astrocytes and neurons, and AQP5 expression in astrocytes was confirmed in 1- to 4-week old primary cultures of astrocytes. AQP5 was localized on the cytoplasmic membrane and in the cytoplasm of astrocytes. AQP5 expression was downregulated during ischemia treatment and upregulated after scratch-wound injury, which was also confirmed in a middle cerebral artery occlusion model and a stab-wound injury model in vivo. The AQP5 increased after scratch injury was polarized to the migrating processes and cytoplasmic membrane of astrocytes in the leading edge of the scratch-wound, and AQP5 over-expression facilitated astrocyte process elongation after scratch injury. Taken together, these results indicate that AQP5 might be an important water channel in astrocytes that is differentially expressed during various brain injuries.

Astrocytes: implications for neuroinflammatory pathogenesis of Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disease with major clinical hallmarks of memory loss, dementia, and cognitive impairment. Neuroinflammation is involved in the onset of several neurodegenerative disorders. Astrocyte is the most abundant type of glial cells in the central nervous system (CNS) and appears to be involved in the induction of neuroinflammation. Under stress and injury, astrocytes become astrogliotic leading to an upregulation of the expression of proinflammatory cytokines and chemokines, which are associated with the pathogenesis of AD. Cytokines and related molecules play roles in both neuroprotection and neurodegeneration in the CNS. During early AD pathogenesis, amyloid beta (Aβ), S100B and IL-1β could bring about a vicious cycle of Aβ generation between astrocytes and neurons leading to chronic, sustained and progressive neuroinflammation. In advanced stages of AD, TRAIL secreted from astrocytes have been shown to bind to death receptor 5 (DR5) on neurons to trigger apoptosis in a caspase-8-dependent manner. Furthermore, astrocytes could be reactivated by TGFβ1 to generate more Aβ and to undergo the aggravating astrogliosis. TGFβ2 was also observed to cooperate with Aβ to cause neuronal demise by destroying the stability of lysosomes in neurons. Inflammatory molecules can be either potential biomarkers for diagnosis or target molecules for therapeutic intervention. Understanding their roles and their relationship with activated astrocytes is particularly important for attenuating neuroinflammation in the early stage of AD. The main purpose of this review is to provide a comprehensive insight into the role of astrocytes in the neuroinflammatory pathogenesis of AD.

Neutrophils may be a vehicle for viral replication and dissemination in human H5N1 avian influenza

The mechanism of systemic spread of H5N1 virus in patients with avian influenza is unknown. Here, H5N1 nucleoprotein and hemagglutinin were identified by immunohistochemistry in the nucleus and cytoplasm of neutrophils in the placental blood of a pregnant woman. Viral RNA was detected in neutrophils by in situ hybridization and enhanced real-time polymerase chain reaction. Therefore, neutrophils may serve as a vehicle for viral replication and transportation in avian influenza.

Astrocyte and neuron intone through glutamate

The unexpected finding of astrocytes to release glutamate as gliotransmitter challenges the traditional concepts on astrocyte being "passive" in CNS communications. Glutamate is the major excitatory transmitter in transferring information between neurons, but is now also known to activate astrocyte through transporters and receptors. Together with the sensitive swelling response, astrocytes could respond directly to glutamate and neuronal activity. Other new functions of astrocytes include modulation of synaptic plasticity and cerebral blood flow (CBF). The classic glutamate deplenishment through glutamine synthesis and CO(2) production does not account for the total glutamate internalized into astrocytes. This leads us to speculate there are many hidden functions of glutamate in neurons and astrocytes waiting to be discovered. In this review, we attempted to reexamine some of these new and older functions of glutamate and to reevaluate the roles of glutamate intoning these two cell types.

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

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.

H5N1 infection of the respiratory tract and beyond: a molecular pathology study

BACKGROUND

Human infection with avian influenza H5N1 is an emerging infectious disease characterised by respiratory symptoms and a high fatality rate. Previous studies have shown that the human infection with avian influenza H5N1 could also target organs apart from the lungs.

METHODS

We studied post-mortem tissues of two adults (one man and one pregnant woman) infected with H5N1 influenza virus, and a fetus carried by the woman. In-situ hybridisation (with sense and antisense probes to haemagglutinin and nucleoprotein) and immunohistochemistry (with monoclonal antibodies to haemagglutinin and nucleoprotein) were done on selected tissues. Reverse-transcriptase (RT) PCR, real-time RT-PCR, strand-specific RT-PCR, and nucleic acid sequence-based amplification (NASBA) detection assays were also undertaken to detect viral RNA in organ tissue samples.

FINDINGS

We detected viral genomic sequences and antigens in type II epithelial cells of the lungs, ciliated and non-ciliated epithelial cells of the trachea, T cells of the lymph node, neurons of the brain, and Hofbauer cells and cytotrophoblasts of the placenta. Viral genomic sequences (but no viral antigens) were detected in the intestinal mucosa. In the fetus, we found viral sequences and antigens in the lungs, circulating mononuclear cells, and macrophages of the liver. The presence of viral sequences in the organs and the fetus was also confirmed by RT-PCR, strand-specific RT-PCR, real-time RT-PCR, and NASBA.

INTERPRETATION

In addition to the lungs, H5N1 influenza virus infects the trachea and disseminates to other organs including the brain. The virus could also be transmitted from mother to fetus across the placenta.

Cytoglobin Up-regulated by Hydrogen Peroxide Plays a Protective Role in Oxidative Stress

Cytoglobin (Cygb) is a recently discovered intracellular respiratory globin, which exists in all types of cells. It has been suggested that Cygb has a role in protecting cells against oxidative stress. In the present study we have tested this hypothesis. The N2a neuroblastoma cells were exposed to various kinds of insults, including hydrogen peroxide (H(2)O(2)), hypoxia, kainic acid, high extracellular CaCl(2), high osmolarity, UV irradiation and heat shock. Among them, only H(2)O(2)-treatment induced a significant up-regulation of cytoglobin mRNA level. We stably transfected N2a cells with Cygb-siRNA vectors and successfully knocked down Cygb. The Cygb-siRNA could exacerbate cell death upon H(2)O(2)-treatment, as demonstrated by MTT cell viability assay. Thus, Cygb in neuronal cells might be specifically induced under oxidative stress to protect them from death.

The presence of active Cdk5 associated with p35 in astrocytes and its important role in process elongation of scratched astrocyte

Cyclin-dependent kinase 5 (Cdk5) is a unique member of the Cdk family; its kinase activity requires association with its activator, p35 or p39. p35 is the strongest and best characterized activator. Previous studies showed that p35 is a neuron-specific protein that restricts Cdk5 activity in neurons. However, a high expression level of Cdk5 is found in astrocytes, which raises the possibility that astrocytic Cdk5 is functional. Here we show the presence of functional Cdk5 associated with p35 in astrocytes and demonstrate its important role in process elongation of scratched astrocytes. We found that p35 and glial fibrillary acidic protein (GFAP) were co-localized in primary cultured and acute isolated brain cells. Cdk5 could form an immunocomplex with p35 and its activity was shown in pure primary cultured astrocytes. p35 was upregulated in astrocytes injured by scratching, concomitantly with upregulation of Cdk5 kinase activity. Pretreatment of the scratched astrocytes with a Cdk5 inhibitor, roscovitine, could delay wound healing by inhibiting the reorganization of tubulin, GFAP, and the extension of hypertrophic processes. Moreover, overexpression of dominant negative Cdk5 could shorten the length of extending protrusion of reactive astrocytes. Thus, our findings demonstrated that functional Cdk5, associated with p35, was expressed in astrocytes and its activity could be upregulated in reactive astrocytes, a new role of Cdk5 that has never been reported in the nervous system. The present study may provide new insight for understanding the multifunctional protein complex Cdk5/p35 in the nervous system.

14-3-3γ affects dynamics and integrity of glial filaments by binding to phosphorylated GFAP

Recent findings indicated a protective role of GFAP in ischemic brain, injured spinal cord, and in neurodegenerative disease. We previously demonstrated that 14-3-3γ, once thought to be neuronal specific, was up-regulated by ischemia in astrocytes and may play a specific protective role in astrocytes. Here we report that 14-3-3γ associates with both soluble and filamentous GFAP in a phosphorylation- and cell-cycle-dependent manner in primary cultured astrocytes. The amount of association increases during G2/M phase due to more phosphorylated GFAP. Moreover, this interaction is independent of vimentin, another type III intermediate filament protein in astrocytes which forms glial filaments with GFAP. A series of domain deletion mutants and substitution mutations at phosphorylation sites (from serine to alanine) on GFAP demonstrated that serine 8 in the head domain is essential for the direct association of GFAP to 14-3-3γ. Overexpression of 14-3-3γ destroyed the integrity and affected the movement of GFAP intermediate filaments. This data demonstrates that 14-3-3γ contributes to the regulation of dynamics of GFAP filaments, which may contribute to the stability of the cytoskeleton and the mechanisms of central nervous system neurodegenerative disease.

Detection of Newcastle disease virus using nucleic acid sequence-based amplification

Newcastle disease (ND) is a contagious and widespread avian disease affecting most species of birds. ND virus (NDV) is the only member of the avian paramyxovirus serotype 1 (APMV1) causing ND outbreak in bird flocks. The technique of nucleic acid sequence-based amplification (NASBA) is a potential method to rapidly and reliably detect NDV isolates. Here, we describe an effective and unprecedented method for detecting NDV strains of all pathotypes. A conserved region of the fusion protein gene was used for designing oligonucleotides specific to all NDV pathotypes. The dynamic range of this NDV NASBA detection method is comparable to virus culture and therefore the NDV NASBA method is a potential alternative for NDV screening and surveillance.

The novel neurotrophin-regulated neuronal development-associated protein, NDAP, mediates apoptosis

We identified a novel gene and named it, "neuronal development-associated protein (NDAP)". We detected NDAP mRNA presence in most tissues including the brain where it was present in the area from the external granular layer to the multiform layer in the cerebral cortex, and in CA1, CA2, CA3 and the dentate gyrus in the hippocampus. Its expression increased transiently in primary cultures of 2-4 day neurons and 1-2 week astrocytes and was significantly reduced in older cultures. Treatment by the neurotrophin, NT-3, significantly attenuated the decline of NDAP in neurons from days 2 to 10, whereas growth factors such as GDNF and insulin, and high potassium levels did not. To elucidate the effects of neurotrophins, we treated day 5 neurons with NT-3, BDNF or NGF for 48 h. NT-3 and BDNF both inhibited downregulation of NDAP mRNA levels but NGF slightly enhanced the already present downregulation; this effect of NGF was significant when examined in day 3 neurons. To investigate the potential function of NDAP, we over-expressed an NDAP-EGFP fusion protein in 4-week-old astrocytes. The newly expressed NDAP gradually aggregated into membrane-bound structures and eventually led to cell death through apoptosis by 24 h. Significant levels of cell death were also observed in NDAP-EGFP transfected HEK293 cells. Thus maintenance of high NDAP levels may cause apoptosis. The different regulations of NDAP expression by neurotrophins indicate that the expression of NDAP might be a checkpoint for apoptosis during neuronal development.

Differential mechanisms underlying the modulation of delayed-rectifier K+ channel in mouse neocortical neurons by nitric oxide

The modulatory effects of nitric oxide (NO) on voltage-dependent K+ channels are intricate. In our present study, the augmentation and reduction of K+ currents by NO donor S-nitro-N-acetylpenicillamine (SNAP) and pure dissolved NO was observed in dissociated neurons from mice neocortex with both whole cell and cell-attached patch clamp. By using a specific electrochemical sensor, the critical concentrations of NO that increased or reduced the channel activities were accurately quantified. Low concentrations of SNAP (20 microM) or NO solution (0.1 microM) enhanced whole cell delayed rectifier K+ -current (IK) and left the fast inactivating A current (IA) unchanged. However, high concentrations of SNAP (100 microM) and NO (0.5 microM) reduced both IK and IA currents. In cell-attached experiments, a significant increase in channel open probability (NP0) was observed when using low concentrations of SNAP or NO. High concentrations of SNAP or NO dramatically decreased NP0. The increase in channel activities by low concentrations of SNAP was abolished in the presence of either inhibitors of soluble guaylate cyclase or inhibitors of cGMP-dependent protein kinase G, suggesting a link to the NO-cGMP signaling cascade. The reduction of channel activities by high concentrations of SNAP was reversed by the reducing agent dithiothreitol, implying a redox reaction mechanism. Thus both NO-cGMP signaling and a redox mechanism are involved in the modulation of IK channel activity for neuron excitability.

Detection of animal viruses using nucleic acid sequence-based amplification (NASBA)

As seen in recent avian influenza outbreaks in Asia, prevention is the key to fighting infectious disease successfully. Efficient disease surveillance systems on the basis of molecular diagnostics will help monitor the emergence of viruses in the early stage and thus prompt containment measures can be in place to minimize disease spread. Here we describe and review molecular diagnostics focusing on nucleic acid sequence-based amplification (NASBA) technology in detecting viruses causing animal diseases, such as avian influenza, foot-and-mouth disease, and Newcastle disease. NASBA offers high sensitivity, specificity, accuracy, and speed of availability of results, and NASBA would be the most applicable molecular diagnostics for disease surveillance and control.

Association of 14-3-3gamma and phosphorylated bad attenuates injury in ischemic astrocytes

Our recent findings indicate an induced upregulation of 14-3-3gamma mRNA and protein in ischemic cortical astrocytes. Despite being brain-specific, the functional role of 14-3-3gamma in the brain still remains largely unknown. In this study, we show that among all the 14-3-3 isoforms, only the gamma isoform is inducible under ischemia in astrocytes. Furthermore, this upregulation of 14-3-3gamma may play a specific protective role in astrocytes under ischemia. Overexpression experiments and antisense treatment show that an elevation of 14-3-3gamma protein in astrocytes promotes survival, while a decrease in 14-3-3gamma enhances apoptosis in astrocytes under ischemia. Under ischemia, endogenous 14-3-3gamma binds p-Bad, thus preventing Bad from entering mitochondria to initiate apoptosis. Therefore, 14-3-3gamma is selectively induced during ischemia to protect astrocytes from apoptosis through p-Bad-related signaling.

Inactivation of bad by site-specific phosphorylation: The checkpoint for ischemic astrocytes to initiate or resist apoptosis

Bcl-2-associated death protein (Bad), a member of the Bcl family, directs astrocytes in primary cultures to enter or resist apoptosis during ischemia in vitro. Under ischemia, Bad was the only Bcl family member whose expression was upregulated significantly during the early stages of an ischemic insult. Increased endogenous Bad was translocated from the cytoplasm to mitochondria to induce apoptosis in astrocytes. Concurrently, ischemia also induced Bad phosphorylation specifically on Ser112 to promote survival. This site-specific phosphorylation of Bad was mediated by an early activation of the mitogen-activated protein kinase/extracellular signal-regulated protein kinase (MAPK/ERK) intracellular signaling pathway. This study demonstrates that ischemia-induced Bad plays a dual role in determining whether astrocytes enter or resist apoptosis after an ischemic insult.

A Model to Induce Low Temperature Trauma for in vitro Astrogliosis Study

Astrogliosis is an inevitable and rapid response of astrocytes to physical, chemical and pathological injuries. To study astrogliosis, we developed a reproducible in vitro model in which low temperature injury to cultured astrocytes could be induced by placing the culture dish onto a copper pipe pre-cooled by liquid nitrogen. Using this model, the relationship between the temperature decline and the severity of cellular damage was analyzed. An increase in the expression of some known injury-related proteins, such as glial fibrillary acidic protein (GFAP), immediate early response genes (IEGs), and heat shock proteins 70 (HSP70), was demonstrated in astrocytes after low temperature trauma. With the use of this low temperature trauma model, the flexibility in the temperature control and injury area may allow researchers to evaluate cryotherapy and cryosurgery, which could be applicable to future development of quality health care.

Cycloheximide and actinomycin D delay death and affect bcl-2, bax, and Ice gene expression in astrocytes under in vitro ischemia

An in vitro ischemia model was established and the effect of the metabolic inhibitors cycloheximide (CHX) and actinomycin D (ActD) on apoptosis in astrocytes under ischemia studied. CHX decreased by 75% the number of cells dying after 6 hr of ischemia compared with control cultures. TdT-mediated dUTP nick end labelling (TUNEL) staining of comparable cultures was reduced by 40%. ActD decreased cell death by 60% compared with controls. The number of TUNEL-positive cells was reduced by 38%. The nuclear shrinkage in TUNEL-positive astrocytes in control cultures did not occur in ActD-treated astrocytes, indicating that nuclear shrinkage and DNA fragmentation during apoptosis are two unrelated processes. Expression of bcl-2 (alpha and beta), bax, and Ice in astrocytes under similar ischemic conditions, as measured by quantitative reverse transcription-polymerase chain reaction, indicated that ischemia down-regulated bcl-2 (alpha and beta) and bax. Ice was initially down-regulated from 0 to 4 hr, before returning to control levels after 8 hr of ischemia. ActD decreased the expression of these genes. CHX reduced the expression of bcl-2 (alpha and beta) but increased bax and Ice expression. It is hypothesized that the balance of proapoptotic (Bad, Bax) and antiapoptotic (Bcl-2, Bcl-Xl) proteins determines apoptosis. The data suggest that the ratio of Bcl-2/Bad in astrocytes following ActD and CHX treatment does not decrease as much in untreated cells during ischemia. Our data indicate that it is the ratio of Bcl-2 family members that plays a critical role in determining ischemia-induced apoptosis. It is also important to note that ischemia-induced apoptosis involves the regulation of RNA and protein synthesis.

Apoptosis and activation of Erkl/2 and Akt in astrocytes postischemia

We have shown previously that in vitro ischemia could induce apoptosis in primary culture of astrocytes. In this paper we demonstrate that astrocytes in culture could undergo apoptosis during in vitro incubation postischemia. We also measured the changes of phosphorylated Erk1/2 (p-Erk1/2) and phosphorylated Akt (p-Akt) in order to determine whether these two pathways play a role in apoptosis. After 4 h in vitro ischemic incubation of cultured astrocytes, a limited amount of nuclear condensation was demonstrated by Hoechst 33342 staining. When ischemic incubation was halted and the cultures transferred to standard normoxic incubation (postischemia) conditions, DNA fragmentation and apoptosis were demonstrated by TUNEL and DNA laddering analysis. TUNEL-positive astrocytes began to appear at 6 h postischemia and increased in number from 12 h postischemia. Western blot analysis showed that both p-Erk1/2 and p-Akt were elevated in astrocytes subjected to 4 h of ischemia. Elevated p-Erk1/2 levels were sustained during the postischemia incubation for 12 h and decreased significantly afterward, but did not return to the levels in the control cultures that did not experience ischemic insult. In contrast, the p-Akt level continued to increase at 6 and 12 h postischemia before declining significantly. The changes in p-Erk1/2 and p-Akt correlated well with the appearance of apoptotic astrocytes in the culture.

14-3-3gamma is upregulated by in vitro ischemia and binds to protein kinase Raf in primary cultures of astrocytes

The 14-3-3 protein family comprises critical regulatory molecules involved in signaling during cell division, proliferation, and apoptosis. Despite extensive study, the functions of the 14-3-3 proteins in brain remain unclear. 14-3-3gamma, a subtype of the 14-3-3 family of proteins, was thought to be brain- and neuron-specific. Using RNA arbitrarily primed PCR, we identified an upregulated cDNA fragment of the 14-3-3gamma gene in primary cultures of astrocytes. Using Northern blot analysis, we confirmed this fragment was brain-specific. In cultures of astrocytes, 14-3-3gamma genes and proteins were differentially expressed at different ages and the proteins were distributed only in the cytoplasm. These results indicated that 14-3-3gamma was not neuron-specific but also expressed in astrocytes. The function of this protein in brain is unclear. Northern and Western blot analyses demonstrated that 14-3-3gamma mRNA and protein were upregulated in cultured astrocytes in an anaerobic chamber-induced ischemia model. The induction of 14-3-3gamma proteins was neither suppressed by an MAP kinase inhibitor (U0126) nor a PI-3 kinase inhibitor (LY294002). These data indicated that induction of 14-3-3gamma might not involve PI-3 and MAP kinase-dependent pathways. Using coimmunoprecipitation, we demonstrated that endogenous 14-3-3gamma bound to c-Raf-1 and p-Raf 259. As Raf is one of the critical serine/threonine kinases controlling cell growth, differentiation, and death, the binding of 14-3-3gamma to Raf indicates the critical role of this protein in ischemia-induced apoptosis and the changes in signal transduction in astrocytes in culture.

Rapid and sensitive detection of avian influenza virus subtype H7 using NASBA

Nucleic acid sequence-based amplification with electrochemiluminescent detection (NASBA/ECL) is an isothermal technique allowing rapid amplification and detection of specific regions of nucleic acid from a diverse range of sources. It is especially suitable for amplifying RNA. A NASBA/ECL technique has been developed allowing the detection of RNA from avian influenza virus subtype H7 derived from allantoic fluid harvested from inoculated chick embryos and from cell cultures. Degenerate amplification primers and amplicon capture probes were designed enabling the detection of low and highly pathogenic avian influenza of the H7 subtype from the Eurasian and North American lineages and the Australian sub-lineage. The NASBA/ECL technique is specific for subtype H7 and does not cross-react with other influenza subtypes or with viruses containing haemagglutinin-like genes. The assay is 10- to 100-fold more sensitive than a commercially available antigen capture immunoassay system. The NASBA/ECL assay could be used in high throughput poultry screening programmes.

Changes of ATP and ADP in cultured astrocytes under and after in vitro ischemia

A very large body of evidence from in vivo studies has been accumulated on a link between the change of energy and cell survival/apoptosis. Using an in vitro ischemia model, we have previously shown that ischemia could induce apoptosis in astrocytes. In this study, we utilized the same in vitro model to investigate changes in ATP and ADP levels in cultured astrocytes and attempted to demonstrate an energy-cell death linkage. Astrocytes remained unaltered after 2 hr of ischemia but were moderately or severely damaged after 4 or 6-8 hr, respectively. The astrocytes that survived various lengths of in vitro ischemic incubation retained their ability to produce ATP after ischemia. Both ATP and ADP levels were increased in astrocytes that remained alive under in vitro ischemia for over 6 hr. The largest decline in the percent of viable astrocytes during ischemia corresponded well to the reduction in ATP and ADP levels in these cultures.

The association of 14-3-3gamma and actin plays a role in cell division and apoptosis in astrocytes

The 14-3-3 protein family plays critical regulatory roles in signaling pathways in cell division and apoptosis. 14-3-3gamma is mainly expressed in brain. Using primary cultures of cerebral cortical astrocytes, we investigated the relationships between 14-3-3gamma proteins and actin in astrocytes in cell division and under ischemia. Our results showed that endogenous 14-3-3gamma proteins in immature astrocytes appeared filamentous and co-localized with filamentous actin (F-actin). During certain stages of mitosis, 14-3-3gamma proteins first aggregated and then formed a ring-like structure that surrounded the daughter nuclei and enclosed the F-actin. In 4-week-old cultures of astrocytes, 14-3-3gamma proteins appeared as punctate aggregates in the cytoplasm. Under ischemia, 14-3-3gamma proteins formed filamentous structures and were closely associated with F-actin in surviving astrocytes. However, in apoptotic astrocytes, the intensity of immunostaining of 14-3-3gamma proteins in the cytoplasm decreased. The proteins aggregated around the nucleus and dissociated from the actin filaments. Reciprocal co-immunoprecipitations demonstrated that endogenous 14-3-3gamma proteins bound to detergent-soluble actin and the level of binding increased after 4h of ischemia. As actin is a critical structural protein heavily involved in cell division and apoptotic death, our findings suggest that 14-3-3gamma proteins play a role in cytoskeletal function during the process of cell division and apoptosis in astrocytes in association with actin.

Activation of Erk1/2 and Akt in astrocytes under ischemia

Substantial evidence has shown that extracellular signal-regulated kinases 1 and 2 (Erk1/2) and serine/threonine kinase (Akt) play important roles in regulating cell survival. We examined the activities of these kinases in astrocytes under ischemia in an anaerobic chamber. The level of phosphorylated Erk1/2 in astrocytes began to increase after 1 h ischemia, reached a maximum after 4 h ischemia, before decreasing from 5 to 6 h. Akt was activated later than Erk1/2. It was significantly increased after 4 h ischemia before declining steadily afterwards. Lactate dehydrogenase (LDH) assay and Hoechst nucleic staining indicated that U0126, which inhibits Erk1/2 phosphorylation, enhanced ischemia-induced cell death, whereas LY294002, which inhibits Akt phosphorylation, delayed cell death. These effects were dose-dependent. At 4 and 6 h ischemia, U0126-treated astrocytes expressed a lower level of Bcl-2 than controls. In contrast, LY294002-treated astrocytes expressed a higher level of Bcl-2 than controls as shown by Western blots. Bcl-x(L) expression level was not affected by either treatment. These data suggest that activation of the MAPK/Erk1/2 pathway might protect astrocytes from ischemic injury, but activation of the PI3-K/Akt pathway does not. The effect may involve Bcl-2 but not Bcl-x(L) expression.

Detection of highly pathogenic and low pathogenic avian influenza subtype H5 (Eurasian lineage) using NASBA

Nucleic acid sequence-based amplification (NASBA) is a technique that allows the rapid amplification of specific regions of nucleic acid obtained from a diverse range of sources. It is especially suitable for amplifying RNA sequences. A NASBA technique has been developed that allows the detection of avian influenza A subtype H5 from allantoic fluid harvested from inoculated chick embryos. The amplified viral RNA is detected by electrochemiluminescence. The NASBA technique described below is rapid and specific for the identification of influenza A subtype H5 viruses of the Eurasian lineage. More importantly, it can be used to distinguish highly pathogenic and low pathogenic strains of the H5 subtype.