Stimulation of ionotropic glutamate receptors activates transcription factor NF-kappa B in primary neurons

TNF-α potentiates glutamate-induced spinal cord motoneuron death via NF-κB

Besides glutamate excitotoxicity, the neuroinflammatory response is emerging as a relevant contributor to motoneuron loss in amyotrophic lateral sclerosis (ALS). In this regard, high levels of circulating proinflammatory cytokines such as tumor necrosis factor-alpha (TNF-α) have been shown both in human patients and in animal models of ALS. The aim of this work was to study the effects of TNF-α on glutamate-induced excitotoxicity in spinal cord motoneurons. In rat spinal cord organotypic cultures chronic glutamate excitotoxicity, induced by the glutamate-uptake inhibitor threohydroxyaspartate (THA), resulted in motoneuron loss that was associated with a neuroinflammatory response. In the presence of TNF-α, THA-induced excitotoxic motoneuron death was potentiated. Co-exposure to TNF-α and THA also resulted in down-regulation of the astroglial glutamate transporter 1 (GLT-1) and in increased extracellular glutamate levels, which were prevented by nuclear factor-kappaB (NF-κB) inhibition. Furthermore, TNF-α and THA also cooperated in the induction of oxidative stress in a mechanism involving the NF-κB signalling pathway as well. The inhibition of this pathway abrogated the exacerbation of glutamate-mediated motoneuron death induced by TNF-α. These data link two important pathogenic mechanisms, excitotoxicity and neuroinflammation, suggested to play a role in ALS and, to our knowledge, this is the first time that TNF-α-induced NF-κB activation has been reported to potentiate glutamate excitotoxicity on motononeurons.

Organization of amyloid-beta protein precursor intracellular domain-associated protein-1 in the rat brain

Sustained activity-dependent synaptic modifications require protein synthesis. Although proteins can be synthesized locally in dendrites, long-term changes also require nuclear signaling. Amyloid-beta protein precursor intracellular domain-associated protein-1 (AIDA-1), an abundant component of the biochemical postsynaptic density fraction, contains a nuclear localization sequence, making it a plausible candidate for synapse-to-nucleus signaling. We used immunohistochemistry to study the regional, cellular, and subcellular distribution of AIDA-1. Immunostaining was prominent in the hippocampus, cerebral cortex, and neostriatum. Along with diffuse staining of neuropil, fluorescence microscopy revealed immunostaining of excitatory synapses throughout the forebrain, and immunoreactive puncta within and directly outside the nucleus. Presynaptic staining was conspicuous in hippocampal mossy fibers. Electron microscopic analysis of material processed for postembedding immunogold revealed AIDA-1 label within postsynaptic densities in both hippocampus and cortex. Together with previous work, these data suggest that AIDA-1 serves as a direct signaling link between synapses and the nucleus in adult rat brain.

Calcium signal-initiated early activation of NF-kappaB in neurons is a neuroprotective event in response to kainic acid-induced excitotoxicity

We demonstrate that activation of nuclear factor kappaB (NF-kappaB) in neurons is neuroprotective in response to kainic acid (KA)-induced excitotoxicity. Combination of Western blotting, immunocytochemistry, and electrophoresis mobility shift assay showed that KA exposure induced a fast but transient nuclear translocation of the NF-kappaB p65 subunit and increased DNA-binding activity of NF-kappaB in primary cultured cortical neurons. The transient NF-kappaB activity was associated with upregulation of antiapoptotic Bcl-xL and XIAP gene products revealed by real-time PCR. Knockdown of p65 decreased neuronal viability and antiapoptotic gene expression. In addition, we showed that KA-stimulated DNA-binding activity of NF-kappaB was associated with reactive oxygen species and calcium signals, using AMPA/KA receptor antagonist, calcium chelator, and antioxidant. These results suggest that the fast and transient activation of NF-kappaB initiated by calcium signals is one of the important proximal events in response to KA-induced excitotoxicity, which has neuroprotective effect against KA-induced apoptosis.

Transcriptomic responses in mouse brain exposed to chronic excess of the neurotransmitter glutamate

Background

Increases during aging in extracellular levels of glutamate (Glu), the major excitatory neurotransmitter in the brain, may be linked to chronic neurodegenerative diseases. Little is known about the molecular responses of neurons to chronic, moderate increases in Glu levels. Genome-wide gene expression in brain hippocampus was examined in a unique transgenic (Tg) mouse model that exhibits moderate Glu hyperactivity throughout the lifespan, the neuronal Glutamate dehydrogenase (Glud1) mouse, and littermate 9 month-old wild type mice.

Results

Integrated bioinformatic analyses on transcriptomic data were used to identify bio-functions, pathways and gene networks underlying neuronal responses to increased Glu synaptic release. Bio-functions and pathways up-regulated in Tg mice were those associated with oxidative stress, cell injury, inflammation, nervous system development, neuronal growth, and synaptic transmission. Increased gene expression in these functions and pathways indicated apparent compensatory responses offering protection against stress, promoting growth of neuronal processes (neurites) and re-establishment of synapses. The transcription of a key gene in the neurite growth network, the kinase Ptk2b, was significantly up-regulated in Tg mice as was the activated (phosphorylated) form of the protein. In addition to genes related to neurite growth and synaptic development, those associated with neuronal vesicle trafficking in the Huntington's disease signalling pathway, were also up-regulated.

Conclusions

This is the first study attempting to define neuronal gene expression patterns in response to chronic, endogenous Glu hyperactivity at brain synapses. The patterns observed were characterized by a combination of responses to stress and stimulation of nerve growth, intracellular transport and recovery.

Cocaine causes memory and learning impairments in rats: involvement of nuclear factor kappa B and oxidative stress, and prevention by topiramate

Different mechanisms have been suggested for cocaine toxicity including an increase in oxidative stress but the association between oxidative status in the brain and cocaine induced-behaviour is poorly understood. Nuclear factor kappa B (NFkappaB) is a sensor of oxidative stress and participates in memory formation that could be involved in drug toxicity and addiction mechanisms. Therefore NFkappaB activity, oxidative stress, neuronal nitric oxide synthase (nNOS) activity, spatial learning and memory as well as the effect of topiramate, a previously proposed therapy for cocaine addiction, were evaluated in an experimental model of cocaine administration in rats. NFkappaB activity was decreased in the frontal cortex of cocaine treated rats, as well as GSH concentration and glutathione peroxidase activity in the hippocampus, whereas nNOS activity in the hippocampus was increased. Memory retrieval of experiences acquired prior to cocaine administration was impaired and negatively correlated with NFkappaB activity in the frontal cortex. In contrast, learning of new tasks was enhanced and correlated with the increase of nNOS activity and the decrease of glutathione peroxidase. These results provide evidence for a possible mechanistic role of oxidative and nitrosative stress and NFkappaB in the alterations induced by cocaine. Topiramate prevented all the alterations observed, showing novel neuroprotective properties.

NF-kappaB in the nervous system

The transcription factor NF-kappaB has diverse functions in the nervous system, depending on the cellular context. NF-kappaB is constitutively activated in glutamatergic neurons. Knockout of p65 or inhibition of neuronal NF-kappaB by super-repressor IkappaB resulted in the loss of neuroprotection and defects in learning and memory. Similarly, p50-/- mice have a lower learning ability and are sensitive to neurotoxins. Activated NF-kappaB can be transported retrogradely from activated synapses to the nucleus to translate short-term processes to long-term changes such as axon growth, which is important for long-term memory. In glia, NF-kappaB is inducible and regulates inflammatory processes that exacerbate diseases such as autoimmune encephalomyelitis, ischemia, and Alzheimer's disease. In summary, inhibition of NF-kappaB in glia might ameliorate disease, whereas activation in neurons might enhance memory. This review focuses on results produced by the analysis of genetic models.

Transcriptional targeting to brain cells: Engineering cell type-specific promoter containing cassettes for enhanced transgene expression

Transcriptional targeting using a mammalian cellular promoter to restrict transgene expression to target cells is often desirable for gene therapy. This strategy is, however, hindered by relatively weak activity of some cellular promoters, which may lead to low levels of gene expression, thus declining therapeutic efficacy. Here we outline the advances accomplished in the area of transcriptional targeting to brain cells, with a particular focus on engineering gene cassettes to augment cell type-specific expression. Among the effective approaches that improve gene expression while retaining promoter specificity are promoter engineering to change authentic sequences of a cellular promoter and the combined use of a native cellular promoter and other cis-acting elements. Success in achieving high level and sustained transgene expression only in the cell types of interest would be of importance in allowing gene therapy to have its impact on patient treatment.

CD8+ T cells and neuronal damage: direct and collateral mechanisms of cytotoxicity and impaired electrical excitability

Cytotoxic CD8(+) T cells are increasingly recognized as key players in various inflammatory and degenerative central nervous system (CNS) disorders. CD8(+) T cells are believed to actively contribute to neural damage in these CNS conditions. Conceptually, one can separate two possible ways that CD8(+) T cells harm neuronal function or integrity: CD8(+) T cells either directly target neurons and their neurites in an antigen- or contact-dependent fashion, or exert their action via "collateral" mechanisms of neuronal damage that might follow destruction of the myelin sheath or glial cells in both the CNS gray and white matter. After introducing clinical examples, in which the putative relevance CD8(+) T cells has been demonstrated, we summarize knowledge on the sequence of initiation and execution of CD8(+) T-cell responses in the CNS. This includes the initial antigen cross-presentation and priming of naive CD8(+) T cells, followed by the invasion, migration, and target-cell recognition of CD8(+) effector T cells in the CNS parenchyma. Moreover, we discuss mechanisms of impaired electrical signaling and cell death of neurons as direct and collateral targets of CD8(+) T cells in the CNS.

NESCA: a new NEMO/IKKgamma and TRAF6 interacting protein

NEMO/IKKgamma is the essential regulatory subunit of the IkB Kinase (IKK) complex, required for the activation of Nuclear Factor kB (NF-kB) in many physiological processes such as inflammation, immunity, apoptosis, or development. NEMO works at a converging point of the NF-kB pathway as it interacts with upstream signaling molecules to orchestrate its activation. Here we report on the identification of a novel NEMO-interacting protein, NESCA, an adapter molecule previously shown to be involved in the NGF-pathway via the TrkA receptor. We demonstrated that NESCA and NEMO interact by their N-terminal region. Beside to NEMO, we revealed that NESCA directly associates to the E3 ubiquitin ligase TRAF6, which in turn catalyzes NESCA polyubiquitination. Finally, we demonstrated that NESCA overexpression strongly inhibits TRAF6-mediated polyubiquitination of NEMO. In summary, our results highlight that NESCA represents a novel missing link in the NEMO-mediated NF-kB activation pathway.

Nucleocytoplasmic protein shuttling: the direct route in synapse-to-nucleus signaling

In neurons multiple signaling pathways converge in the nucleus to regulate the expression of genes associated with long-term structural changes of synapto-dendritic input. Of pivotal importance for this type of transcriptional regulation is synapse-to-nucleus communication. Several studies suggest that the nuclear transport of proteins from synapses is involved in this signaling process, including evidence that synapses contain proteins with nuclear localization sequences and components of the nuclear import machinery. Here, we review the evidence for synapse-to-nucleus signaling by means of retrograde transport of proteins from distal processes. We discuss the mechanisms involved in their translocation and their role in the control of nuclear gene expression. Finally, we summarize the current thinking regarding the functional implications of nuclear signaling and address open questions in this evolving area of neuroscience.

Unique aspects of transcriptional regulation in neurons--nuances in NFkappaB and Sp1-related factors

The unique physiology and function of neurons create differences in their cellular physiology, including their regulation of gene expression. We began several years ago exploring the relationships between the NFκB transcription factor, neuronal survival, and glutamate receptor activation in telencephalic neurons. These studies led us to conclude that this population of cells is nearly incapable of activating the NFκB that is nonetheless expressed at reasonable levels. A subset of the κB cis elements are instead bound by members of the Sp1 family in neurons. Also surprising was our discovery that Sp1 itself, typically described as ubiquitous, is severely restricted in expression within forebrain neurons; Sp4 seems to be substituted during neuronal differentiation. These findings and their implications for neuronal differentiation – as well as potential dedifferentiation during degenerative processes – are discussed here.

Molecular mechanisms of neuroprotection by two natural antioxidant polyphenols

Excessive activation of glutamate receptors, or excitotoxicity, contributes to acute and chronic neurological disorders including stroke. We previously showed that two natural polyphenol antioxidants, mangiferin and morin, are neuroprotective in a model of ischemic brain damage. In this study, we analyzed the molecular mechanisms underlying neuroprotection by mangiferin and morin in an in vitro model of excitotoxic neuronal death involving NMDA receptor overactivation. We observed that both polyphenols reduce the formation of reactive oxygen species, activate the enzymatic antioxidant system, and restore the mitochondrial membrane potential. Moreover, both antioxidants inhibit glutamate-induced activation of calpains, normalize the levels of phosphorylated Akt kinase and Erk1/2, as well as of cytosolic Bax, inhibit AIF release from mitochondria, and regulate the nuclear translocation of NF-kappaB. Each of these effects contributes to the substantial reduction of apoptotic neuronal death induced by glutamate. These results demonstrate that mangiferin and morin exhibit excellent antioxidant and antiapoptotic properties, supporting their clinical application as trial neuroprotectors in pathologies involving excitotoxic neuronal death.

Post-ischemic brain damage: NF-kappaB dimer heterogeneity as a molecular determinant of neuron vulnerability

Nuclear factor-kappaB (NF-kappaB) has been proposed to serve a dual function as a regulator of neuron survival in pathological conditions associated with neurodegeneration. NF-kappaB is a transcription family of factors comprising five different proteins, namely p50, RelA/p65, c-Rel, RelB and p52, which can combine differently to form active dimers in response to external stimuli. Recent research shows that diverse NF-kappaB dimers lead to cell death or cell survival in neurons exposed to ischemic injury. While the p50/p65 dimer participates in the pathogenesis of post-ischemic injury by inducing pro-apoptotic gene expression, c-Rel-containing dimers increase neuron resistance to ischemia by inducing anti-apoptotic gene transcription. We present, in this report, the latest findings and consider the therapeutic potential of targeting different NF-kappaB dimers to limit ischemia-associated neurodegeneration.

Glutamate-induced NFkappaB activation in the retina

PURPOSE

To determine the distribution and glutamate-mediated activation of nuclear factor (NF) kappaB members in the retina and pan-purified retinal ganglion cells (RGCs) and to characterize steps in the signal transduction events that lead to NFkappaB activation.

METHODS

Retinal expression patterns and RGCs were evaluated for five NFkappaB proteins with the aid of immunohistochemistry. Retinal explants or RGCs were treated with glutamate with or without the presence of the NDMA receptor antagonist memantine, the calcium chelator EGTA, or a specific inhibitor for calcium/calmodulin-dependent protein kinase-II (CaMKII). Characterizations of NFkappaB activation were performed with the aid of electrophoretic mobility shift assays and supershift assays.

RESULTS

All five NFkappaB proteins were present in the retina and in the pan-purified RGCs. In response to a glutamate stimulus, all NFkappaB proteins except c-Rel were activated. P65 was unique in that it was not constitutively active but showed a glutamate-inducible activation in the retina and in the cultured RGCs. Memantine, EGTA, or autocamtide-2-related inhibitory peptide (AIP) inhibited NFkappaB activation in the retina. Furthermore, AIP significantly reduced the level of glutamate-induced degradation of IkappaBs.

CONCLUSIONS

These data indicate that glutamate activates distinct NFkappaB proteins in the retina. P65 activation may be especially important with regard to RGC responses to glutamate given that its activity is induced by conditions known to lead to the death of these cells. The NMDA receptor-Ca(2+)-CaMKII signaling pathway is involved in glutamate-induced NFkappaB activation. Because AIP blocks the degradation of IkappaB, its regulation is clearly downstream of CaMKII.

Receptor for advanced glycation end products (RAGE) mediates neuronal differentiation and neurite outgrowth

The receptor for advanced glycation end products (RAGE) plays a crucial role in several disease processes, such as diabetes, inflammation, and neurodegeneration. In this article we report multiple roles of RAGE in neuronal differentiation and neurite outgrowth. In retinoic-induced P19 embryonic carcinoma stem cells, silencing the expression of RAGE by RNA interference (RNAi) blocked differentiation of the P19 cells into neuronal cells and enhanced the formation of vimentin-positive fibroblast-like cells. RAGE knockdown inhibited retinoic acid-induced activation and blocked nuclear translocation of NF-kappaB, suggesting RAGE regulates activation of NF-kappaB. RAGE was also shown to be involved in survival of P19 cells during retinoic acid differentiation. Additionally, knockdown of RAGE strongly inhibited neurite outgrowth in retinoic acid-differentiated P19 cells, indicating that RAGE is required for neurite outgrowth of differentiated P19 cells. Retinoic acid-treated P19 cells activated GTPases, Rac1, and Cdc42. This activation of the GTPases was inhibited in RAGE-knockdown cells. In primary cerebellar granule neurons, the knockdown of RAGE also inhibited neurite outgrowth. In these cells, overexpression of dominant-negative forms of Rac1 and Cdc42 inhibited neurite outgrowth, whereas overexpression of constitutively active forms of Rac1 and Cdc42 in RAGE-deficient neurons restored neurite outgrowth, indicating that RAGE mediated neurite outgrowth through the Rac1/Cdc42 pathway. This is the first report on the role of RAGE in cell lines and primary neurons, as determined by RNAi knockdown.

Dual roles of NF-kappaB in cell survival and implications of NF-kappaB inhibitors in neuroprotective therapy

NF-kappaB is a well-characterized transcription factor with multiple physiological and pathological functions. NF-kappaB plays important roles in the development and maturation of lymphoids, regulation of immune and inflammatory response, and cell death and survival. The influence of NF-kappaB on cell survival could be protective or destructive, depending on types, developmental stages of cells, and pathological conditions. The complexity of NF-kappaB in cell death and survival derives from its multiple roles in regulating the expression of a broad array of genes involved in promoting cell death and survival. The activation of NF-kappaB has been found in many neurological disorders, but its actual roles in pathogenesis are still being debated. Many compounds with neuroprotective actions are strongly associated with the inhibition of NF-kappaB, leading to speculation that blocking the pathological activation of NF-kappaB could offer neuroprotective effects in certain neurodegenerative conditions. This paper reviews the recent developments in understanding the dual roles of NF-kappaB in cell death and survival and explores its possible usefulness in treating neurological diseases. This paper will summarize the genes regulated by NF-kappaB that are involved in cell death and survival to elucidate why NF-kappaB promotes cell survival in some conditions while facilitating cell death in other conditions. This paper will also focus on the effects of various NF-kappaB inhibitors on neuroprotection in certain pathological conditions to speculate if NF-kappaB is a potential target for neuroprotective therapy.

NF-kB/NOS cross-talk induced by mitochondrial complex II inhibition: implications for Huntington's disease

Nuclear factor-kB (NF-kB) is a family of DNA-binding proteins that are important regulators involved in immune and inflammatory responses, as well as in cell survival and apoptosis. In the nervous system NF-kB is activated under physiological and pathological conditions including learning and memory mechanisms and neurodegenerative diseases. NF-kB is activated in neurons in response to excitotoxic, metabolic and oxidative stress and there is a body of evidence to suggest that glutamate induces NF-kB by the main ionotropic glutamate receptors. In the present study, 3 nitroproprionic acid (3NP), an irreversible inhibitor of succinate dehydrogenase (SD, complex II) has been employed to provide an experimental model of Huntington's disease (HD). Specifically, we described 3NP-induced activation of NF-kB and of iNOS and nNOS genes in striatal treated slices. To aim to better understand the relationship between these identified dysregulated genes and mitochondrial dysfunction, we investigated in SK-N-MC human neuroblastoma cells following 3NP treatment, whether NF-kB nuclear translocation and activation might be involved in the mechanisms by which 3NP leads to transcriptional activation of NOS genes. These results are relevant to more precisely define the role of NF-kB in neuronal cells and better understand its putative involvement in neurodegeneration.

Transcription factor NF-kappaB is transported to the nucleus via cytoplasmic dynein/dynactin motor complex in hippocampal neurons

Background

Long-term changes in synaptic plasticity require gene transcription, indicating that signals generated at the synapse must be transported to the nucleus. Synaptic activation of hippocampal neurons is known to trigger retrograde transport of transcription factor NF-κB. Transcription factors of the NF-κB family are widely expressed in the nervous system and regulate expression of several genes involved in neuroplasticity, cell survival, learning and memory.

Principal Findings

In this study, we examine the role of the dynein/dynactin motor complex in the cellular mechanism targeting and transporting activated NF-κB to the nucleus in response to synaptic stimulation. We demonstrate that overexpression of dynamitin, which is known to dissociate dynein from microtubules, and treatment with microtubule-disrupting drugs inhibits nuclear accumulation of NF-κB p65 and reduces NF-κB-dependent transcription activity. In this line, we show that p65 is associated with components of the dynein/dynactin complex in vivo and in vitro and that the nuclear localization sequence (NLS) within NF-κB p65 is essential for this binding.

Conclusion

This study shows the molecular mechanism for the retrograde transport of activated NF-κB from distant synaptic sites towards the nucleus.

Alteration of NF-kappaB activity leads to mitochondrial apoptosis after infection with pathological prion protein

Nuclear factor kappa B (NF-kappaB) is a key regulator of the immune response, but in almost the same manner it is involved in induction of inflammation, proliferation and regulation of apoptosis. In the central nervous system activated NF-kappaB plays a neuroprotective role. While in some neurodegenerative disorders the role of NF-kappaB is well characterized, there is poor knowledge on the role of NF-kappaB in prion disease. We found binding but no transcriptional activity of the transcription factor in vitro. Characterizing the mechanism of cell death after infection with pathological prion protein increased caspase-9 and caspase-3 activity was detected and the lack of NF-kappaB activity resulted in the inability to activate target genes that usually play an important role in neuroprotection. Additionally, we investigated the role of NF-kappaB after prion infection of Nfkb1(-/-), Nfkb2(-/-) and Bcl3(-/-) mice and central nervous system-specific p65-deleted mice revealing an accelerated prion disease in NF-kappaB2- and Bcl-3-deficient mice, which is in line with a reduced neuroprotective activity in prion infection. Based on our findings, we propose a model whereby the alteration of NF-kappaB activity at the early stages of infection with pathological prion protein leads to neuronal cell death mediated by mitochondrial apoptosis.

Regulation of CNS synapses by neuronal MHC class I

Until recently, neurons in the healthy brain were considered immune-privileged because they did not appear to express MHC class I (MHCI). However, MHCI mRNA was found to be regulated by neural activity in the developing visual system and has been detected in other regions of the uninjured brain. Here we show that MHCI regulates aspects of synaptic function in response to activity. MHCI protein is colocalized postsynaptically with PSD-95 in dendrites of hippocampal neurons. In vitro, whole-cell recordings of hippocampal neurons from beta2m/TAP1 knockout (KO) mice, which have reduced MHCI surface levels, indicate a 40% increase in mini-EPSC (mEPSC) frequency. mEPSC frequency is also increased 100% in layer 4 cortical neurons. Similarly, in KO hippocampal cultures, there is a modest increase in the size of presynaptic boutons relative to WT, whereas postsynaptic parameters (PSD-95 puncta size and mEPSC amplitude) are normal. In EM of intact hippocampus, KO synapses show a corresponding increase in vesicles number. Finally, KO neurons in vitro fail to respond normally to TTX treatment by scaling up synaptic parameters. Together, these results suggest that postsynaptically localized MHCl acts in homeostatic regulation of synaptic function and morphology during development and in response to activity blockade. The results also imply that MHCI acts retrogradely across the synapse to translate activity into lasting change in structure.

Transcriptional regulation of intronic calcium-activated potassium channel SK2 promoters by nuclear factor-kappa B and glucocorticoids

Small-conductance Ca(2+)-activated K(+) channels (SK) of the SK2 subtype are widely expressed in the central nervous system where they contribute to the control of neuronal excitability. Two SK2 isoforms, SK2-S and SK2-L, the latter representing an N-terminally extended protein of SK2-S, are expressed in similar patterns in the brain. However, our understanding of mechanisms by which the expression of SK2 is regulated is limited. We identified one functional glucocorticoid response element (GRE) at position -2248 bp and two functional nuclear factor-kappB (NF-kappaB) response elements at positions -1652 and -1586 bp in the SK2-S promoter. An increase in SK2-S promoter activity was observed in PC12 cells transiently transfected with a wild-type SK2-S promoter-luciferase reporter gene construct and treated with aldosterone or dexamethasone. The mineralocorticoid receptor (MR) antagonist spironolactone or the glucocorticoid receptor (GR) antagonist mifepristone fully inhibited aldosterone or dexamethasone activation of the SK2-S promoter, respectively. SK2-S promoter activity was also induced by the cell-permeable ceramide analog, N-acetylsphingosine (C2-ceramide). Antisense oligonucleotides directed to NF-kappaB p65 or p50 suppressed SK2-S transcription induced by C2-ceramide. Deletion studies showed that only the -1586 bp NF-kappaB binding site was necessary for maximum C2-ceramide response. Finally, we showed that activation of GRs but not of MRs repressed the NF-kappaB-mediated induction of SK2-S transcription. These findings suggest a possible transcriptional cross talk between GRs and NF-kappaB in the intronic promoter regulation of SK2-S channel gene transcription.

Activity-dependent AIDA-1 nuclear signaling regulates nucleolar numbers and protein synthesis in neurons

Neuronal development, plasticity and survival require activity-dependent synapse-to-nucleus signaling. Most studies implicate an activity-dependent regulation of gene expression in this phenomenon. However, little is known about other nuclear functions that are regulated by synaptic activity. Here we show that a newly identified component of rat postsynaptic densities (PSDs), AIDA-1d, can regulate global protein synthesis by altering nucleolar numbers. AIDA-1d binds to the first two postsynaptic density-95/Discs large/zona occludens-1 (PDZ) domains of the scaffolding protein PSD-95 via its C-terminal three amino acids. Stimulation of NMDA receptors (NMDARs), which are also bound to PSD-95, results in a Ca2+-independent translocation of AIDA-1d to the nucleus, where it couples to Cajal bodies and induces Cajal body-nucleolar association. Long-term neuronal stimulation results in an AIDA-1-dependent increase in nucleolar numbers and protein synthesis. We propose that AIDA-1d mediates a link between synaptic activity and control of protein biosynthetic capacity by regulating nucleolar assembly.

NF-kappaB activation by depolarization of skeletal muscle cells depends on ryanodine and IP3 receptor-mediated calcium signals

Depolarization of skeletal muscle cells by either high external K(+) or repetitive extracellular field potential pulses induces calcium release from internal stores. The two components of this release are mediated by either ryanodine receptors or inositol 1,4,5-trisphosphate (IP(3)) receptors and show differences in kinetics, amplitude, and subcellular localization. We have reported that the transcriptional regulators including ERKs, cAMP/Ca(2+)-response element binding protein, c-fos, c-jun, and egr-1 are activated by K(+)-induced depolarization and that their activation requires IP(3)-dependent calcium release. We presently describe the activation of the nuclear transcription factor NF-kappaB in response to depolarization by either high K(+) (chronic) or electrical pulses (fluctuating). Calcium transients of relative short duration activate an NF-kappaB reporter gene to an intermediate level, whereas long-lasting calcium increases obtained by prolonged electrical stimulation protocols of various frequencies induce maximal activation of NF-kappaB. This activation is independent of extracellular calcium, whereas calcium release mediated by either ryanodine or IP(3) receptors contribute in all conditions tested. NF-kappaB activation is mediated by IkappaBalpha degradation and p65 translocation to the nucleus. Partial blockade by N-acetyl-l-cysteine, a general antioxidant, suggests the participation of reactive oxygen species. Calcium-dependent signaling pathways such as those linked to calcineurin and PKC also contribute to NF-kappaB activation by depolarization, as assessed by blockade through pharmacological agents. These results suggest that NF-kappaB activation in skeletal muscle cells is linked to membrane depolarization and depends on the duration of elevated intracellular calcium. It can be regulated by sequential activation of calcium release mediated by the ryanodine and by IP(3) receptors.

Microtubules are required for NF-kappaB nuclear translocation in neuroblastoma IMR-32 cells: modulation by zinc

The relevance of a functional cytoskeleton for Nuclear Factor-kappaB (NF-kappaB) nuclear translocation was investigated in neuronal cells, using conditions that led to a disruption of the cytoskeleton [inhibition of tubulin (vinblastine, colchicine), or actin (cytochalasin D) polymerization and zinc deficiency]. We present evidence that an impairment in tubulin polymerization can inhibit the formation of the complex tubulin-dynein-karyopherin alpha-p50 that is required for neuronal retrograde and nuclear NF-kappaB transport. Cells treated with vinblastine, colchicine or cytochalasin D, and zinc deficient cells, all showed a low nuclear NF-kappaB binding activity, and low nuclear concentrations of RelA and p50. The altered nuclear translocation was reflected by a decreased transactivation of NF-kappaB-driven genes. The immunocytochemical characterization of cellular RelA showed that cytoskeleton disruption can lead to an altered distribution of RelA resulting in the formation of peripheral accumuli. These results support the concept that cytoskeleton integrity is necessary for the transport and translocation of NF-kappaB required for synapse to nuclei communication. We suggest that during development, as well as in the adult brain, conditions such as zinc deficiency, that affect the normal structure and function of the cytoskeleton can affect neuronal proliferation, differentiation, and survival by altering NF-kappaB nuclear translocation and subsequent impairment of NF-kappaB-dependent gene regulation.

NF-kappaB/Rel regulates inhibitory and excitatory neuronal function and synaptic plasticity

Changes in synaptic plasticity required for memory formation are dynamically regulated through opposing excitatory and inhibitory neurotransmissions. To explore the potential contribution of NF-kappaB/Rel to these processes, we generated transgenic mice conditionally expressing a potent NF-kappaB/Rel inhibitor termed IkappaBalpha superrepressor (IkappaBalpha-SR). Using the prion promoter-enhancer, IkappaBalpha-SR is robustly expressed in inhibitory GABAergic interneurons and, at lower levels, in excitatory neurons but not in glia. This neuronal pattern of IkappaBalpha-SR expression leads to decreased expression of glutamate decarboxylase 65 (GAD65), the enzyme required for synthesis of the major inhibitory neurotransmitter, gamma-aminobutyric acid (GABA) in GABAergic interneurons. IkappaBalpha-SR expression also results in diminished basal GluR1 levels and impaired synaptic strength (input/output function), both of which are fully restored following activity-based task learning. Consistent with diminished GAD65-derived inhibitory tone and enhanced excitatory firing, IkappaBalpha-SR+ mice exhibit increased late-phase long-term potentiation, hyperactivity, seizures, increased exploratory activity, and enhanced spatial learning and memory. IkappaBalpha-SR+ neurons also express higher levels of the activity-regulated, cytoskeleton-associated (Arc) protein, consistent with neuronal hyperexcitability. These findings suggest that NF-kappaB/Rel transcription factors act as pivotal regulators of activity-dependent inhibitory and excitatory neuronal function regulating synaptic plasticity and memory.

Inhibition of nuclear factor κB is associated with neuroprotective effects of glycyrrhizic acid on glutamate-induced excitotoxicity in primary neurons

Glycyrrhizic acid is an herbal drug with a broad spectrum of antiviral activities and pharmacological effects and multiple sites of action. We investigated whether glycyrrhizic acid protects against glutamate-induced excitotoxicity and the underlying mechanisms. We found that glycyrrhizic acid protected against neurotoxicity in rat primary neuronal cultures and hippocampal slices by suppression of the glutamate-induced apoptosis. Glycyrrhizic acid conferred neuroprotective properties in a concentration-dependent manner, as determined by cell survival, apoptosis, and Ca(2+) influx. Glycyrrhizic acid selectively inhibited the Ca(2+) influx activated through N-methyl-D-aspartate (NMDA) receptor by glutamate, but not through membrane depolarization elicited by high K(+) induction. Glycyrrhizic acid treatment also diminished glutamate-induced DNA fragmentation and cleavage of poly (ADP-ribose) polymerase (PARP). Electrophoretic mobility shift assay (EMSA) indicated that glycyrrhizic acid inhibited the binding activity of nuclear factor kappaB (NF-kappaB) to its target elements. Western blot analysis of NF-kappaB inhibitor (IkappaBalpha) protein revealed that the inhibitory effect of glycyrrhizic acid on glutamate-induced activation of NF-kappaB activity was attributable to the inhibition of IkappaB kinase activity. Thus, the site of action of glycyrrhizic acid could be a downstream consequence of Ca(2+)entry through NMDA receptors and that NF-kappaB may be one downstream target in this process. These observations suggest that glycyrrhizic acid may be of therapeutic value for the prevention of cerebral damage elicited by the glutamate.

Preconditioning and neurotrophins: a model for brain adaptation to seizures, ischemia and other stressful stimuli

The amino acid glutamate, the major excitatory neurotransmitter in the central nervous system, activates receptors coupled to calcium influx. Excessive activation of glutamate receptors in conditions such as severe epileptic seizures or stroke can kill neurons in a process called excitotoxicity. However, subtoxic levels of activation of the N-methyl-D-aspartate (NMDA) type of glutamate receptor elicit adaptive responses in neurons that enhance their ability to withstand more severe stress. A variety of stimuli induce adaptive responses to protect neurons. For example, sublethal ischemic episodes or a mild epileptic insult can protect neurons in a process referred to as tolerance. The molecular mechanisms that protect neurons by these different stressful stimuli are largely unknown but they share common features such as the transcription factor, nuclear factor kappa B (NF-kappaB), which is activated by ischemic and epileptic preconditioning as well as exposure to subtoxic NMDA concentrations. In this article, we describe stress-induced neuroprotective mechanisms highlighting the role of brain-derived neurotrophic factor (BDNF), a protein that plays a crucial role in neuronal survival and maintenance, neurogenesis and learning and memory.

NF-kappaB functions in the nervous system: from development to disease

The transcription factor nuclear factor-kappaB (NF-kappaB) is an ubiquitously expressed dimeric molecule with post-translationally regulated activity. Its role in the immune system and host defense has been well characterized over the last two decades. In contrast, our understanding of the function of this transcription factor in the nervous system (NS) is only emerging. Given their cytoplasmic retention and nuclear translocation upon stimulus, NF-kappaB members are likely to exert an important role in transduction of signals from synaptic terminals to nucleus, to initiate transcriptional responses. This report describes recent findings deciphering the diverse functions of NF-kappaB in NS development and activity, which range from the control of cell growth, survival and inflammatory response to synaptic plasticity, behavior and cognition. Particular attention is given to the specific roles of NF-kappaB in the various cells of the NS, e.g. neurons and glia. Current knowledge of the contribution of NF-kappaB to several neurodegenerative disorders, such as Alzheimer's, Parkinson's and Huntington's diseases is also summarized.

Roles for NF-kappaB in nerve cell survival, plasticity, and disease

Here we review evidence of roles for NF-kappaB in the regulation of developmental and synaptic plasticity, and cell survival in physiological and pathological settings. Signaling pathways modulating NF-kappaB activity include those engaged by neurotrophic factors, neurotransmitters, electrical activity, cytokines, and oxidative stress. Emerging findings support a pivotal role for NF-kappaB as a mediator of transcription-dependent enduring changes in the structure and function of neuronal circuits. Distinct subunits of NF-kappaB may uniquely affect cognition and behavior by regulating specific target genes. NF-kappaB activation can prevent the death of neurons by inducing the production of antiapoptotic proteins such as Bcl-2, IAPs and manganese superoxide dismutase (Mn-SOD). Recent findings indicate that NF-kappaB plays important roles in disorders such as epilepsy, stroke, Alzheimer's and Parkinson's diseases, as well as oncogenesis. Molecular pathways upstream and downstream of NF-kappaB in neurons are being elucidated and may provide novel targets for therapeutic intervention in various neurological disorders.

GAL4-NF-kappaB fusion protein augments transgene expression from neuronal promoters in the rat brain

Targeted gene expression mediated by a mammalian cellular promoter is desirable for gene therapy in the brain, where there are a variety of different neuronal phenotypes, several types of supportive cells, and blood vessels. However, this approach can be hampered by weak activity of some cellular promoters. In view of the potency of the transcription factor NF-kappaB in regulating neuronal gene expression, we have assessed whether it can be used to enhance the strength of neuron-specific promoters. Our approach was to use a neuronal promoter to drive expression of a chimeric transactivator, which consisted of a part of the transcriptional activation domain of the NF-kappaB p65 protein fused to the DNA-binding domain of GAL4 protein from yeast. The second copy of the neuronal promoter was modified by introducing the unique GAL4 binding sequences at its 5' end and used to drive the expression of a transgene. Binding of the chimeric transcriptional activator upstream of the second promoter was expected to potentiate its transcriptional activity. In this study, the approach was applied to the platelet-derived growth factor beta chain and synapsin-1 neuron-specific promoters and tested in vitro and in vivo using plasmid, lentiviral, and baculoviral vectors. We observed up to a 100-fold improvement in reporter gene expression in cultured neurons and 20-fold improvement in the rat brain in vivo. Moreover, the cell-type specificity of the two tested promoters was well preserved and restricted to neurons. Finally, the expression driven by the new lentiviral vectors with the p65-potentiated synapsin-1 promoter showed no signs of decline or cell damage 4 weeks after injection. This approach should be suitable for constructing powerful and stable gene expression systems based on weak cell-specific promoters in neuronal phenotypes.

ROS-production-mediated activation of AP-1 but not NFkappaB inhibits glutamate-induced HT4 neuronal cell death

Aside from their deleterious effect, reactive oxygen species (ROS) can function as small messenger molecules during physiologic processes. ROS have been shown to activate the transcription nuclear factor kappa B (NFkappaB) and activator protein 1 (AP-1). Exposure of HT4 neuronal cells to 10 mM glutamate results in cell death after 12 h. Here we show that glutamate treatment leads to an increase in ROS production and activation of AP-1, but not NFkappaB. 12-O-Tetradecanoylphorbol 13-acetate (TPA), an activator of protein kinase C and an inducer of NFkappaB and AP-1, protected the cells. This protective effect was preceded by increased production of ROS compared with glutamate alone, which was accompanied by a synergistic increase in AP-1, but not NFkappaB activity. We used all-trans-retinoic acid (ATRA), overexpression of retinoic acid receptor alpha (RARalpha) and a decoy oligonucleotide inclusion assay to suppress AP-1 activity. NFkappaB was inhibited by using a super suppressor (IkappaBalphaDeltaN-transfected cells). Inhibition of AP-1, but not NFkappaB resulted in increased cellular vulnerability to glutamate. Inhibition of AP-1 activity was coincident with a decrease in ROS production. Thus, although ROS are significant to the cell-death effect induced by glutamate, they also activate protective pathways mediated by increasing AP-1 activity, and not that of NFkappaB.

Distinct roles of diverse nuclear factor-kappaB complexes in neuropathological mechanisms

The nuclear transcription factors kappaB (NF-kappaB) function as key regulators of physiological processes in the central nervous system. Aberrant regulation of NF-kappaB can underlie neurological disorders associated with neurodegeneration. A large number of studies have reported a dual role of NF-kappaB in regulating neuron survival in pathological conditions. A recent progress in understanding the mechanisms responsible for opposite effects elicited by NF-kappaB in brain dysfunctions arises from the identification of diverse NF-kappaB complexes specifically involved in the mechanism of neuronal cell death or cell survival. We here discuss the latest findings and consider the therapeutic potential of targeting distinct NF-kappaB complexes for the treatment of neurodegenerative disorders and memory dysfunctions.

Regulation of nuclear factor kappaB in the hippocampus by group I metabotropic glutamate receptors

An increasing amount of evidence suggests that the family of nuclear factor kappaB (NF-kappaB) transcription factors plays an important role in synaptic plasticity and long-term memory formation. The present study investigated the regulation of NF-kappaB family members p50, p65/RelA, and c-Rel in the hippocampus in response to metabotropic glutamate receptor (mGluR) signaling. Activation of group I metabotropic glutamate receptors (GpI-mGluRs) with the agonist (S)-3,5-dihydroxyphenylglycine (DHPG) resulted in a time-dependent increase in DNA binding activity of p50, p65, and c-Rel in area CA1 of the hippocampus. An antagonist of mGluR5, 2-Methyl-6-(phenylethynyl)pyridine, inhibited the DHPG-induced activation of NF-kappaB, whereas an antagonist of mGluR1, (S)-(+)-alpha-amino-4-carboxy-2-methylbenzeneacetic acid, did not. Using a series of inhibitors, we investigated the signaling pathways necessary for DHPG-induced activation of NF-kappaB and found that they included the phosphatidyl inositol 3-kinase, protein kinase C, mitogen-activated protein kinase kinase, and p38-mitogen-activated protein kinase pathways. To determine the functional significance of mGluR-induced regulation of NF-kappaB, we measured long-term depression (LTD) of Schaffer-collateral synapses in the hippocampus of c-Rel knock-out mice. Early phase LTD was normal in c-rel(-/-) mice. However, late-phase LTD (>90 min) was impaired in c-rel(-/-) mice. The observations of this deficit in hippocampal synaptic plasticity prompted us to further investigate long-term memory formation in c-rel(-/-) mice. c-rel(-/-) mice exhibited impaired performance in a long-term passive avoidance task, providing additional evidence for c-Rel in long-term memory formation. These results demonstrate that the NF-kappaB transcription factor family is regulated by GpI-mGluRs in the hippocampus and that the c-Rel transcription factor is necessary for long-term maintenance of LTD and formation of long-term memory.

NF-kappaB regulates spatial memory formation and synaptic plasticity through protein kinase A/CREB signaling

Synaptic activity-dependent de novo gene transcription is crucial for long-lasting neuronal plasticity and long-term memory. In a forebrain neuronal conditional NF-kappaB-deficient mouse model, we demonstrate here that the transcription factor NF-kappaB regulates spatial memory formation, synaptic transmission, and plasticity. Gene profiling experiments and analysis of regulatory regions identified the alpha catalytic subunit of protein kinase A (PKA), an essential memory regulator, as a new NF-kappaB target gene. Consequently, NF-kappaB inhibition led to a decrease in forskolin-induced CREB phosphorylation. Collectively, these results disclose a novel hierarchical transcriptional network involving NF-kappaB, PKA, and CREB that leads to concerted nuclear transduction of synaptic signals in neurons, accounting for the critical function of NF-kappaB in learning and memory.

Effects of noradrenaline on neuronal NOS2 expression and viability

The authors previously showed that conditioned media (CM) from activated microglia increased inducible nitric oxide synthase (NOS2) in cortical neurons. Here they examined the ability of noradrenaline (NA) to reduce neuronal NOS2 or cell death. Primary mouse cortical neurons were activated using CM from microglia incubated with lipopolysaccharide (LPS). Neuronal NOS2 was assessed by increases in nitrite accumulation, and increases in NOS2 mRNA levels and fluorescence of the NO-sensitive probe DAF-2 DA. NOS2 induction was associated with an increase in neuronal LDH release. When NA was added during microglial activation, neuronal NOS2 was significantly reduced (by approximately 70%); in contrast if NA was added to the neurons along with CM, there was less reduction (about 35% decrease) in NOS2 expression. NA added to either microglia or to neurons reduced neuronal LDH release comparably. Pretreatment of CM with blocking antibody to TNFalpha, alone or with IL1-receptor antagonist, partially reduced neuronal cell death and NOS2. Incubation of neurons with NA increased IkBalpha, which could reduce NOS2. These results demonstrate that NA modulates neuronal NOS2 expression and damage, and that these effects are primarily due to inhibition of microglia released factors. Perturbations of NA could exacerbate neuronal damage by allowing for increased inflammatory responses.

Chronic unpredictable stress exacerbates lipopolysaccharide-induced activation of nuclear factor-kappaB in the frontal cortex and hippocampus via glucocorticoid secretion

Although the anti-inflammatory actions of glucocorticoids (GCs) are well established in the periphery, these stress hormones can increase inflammation under some circumstances in the brain. The transcription factor nuclear factor-kappaB (NF-kappaB), which is inhibited by GCs, regulates numerous genes central to inflammation. In this study, the effects of stress, GCs, and NMDA receptors on lipopolysaccharide (LPS)-induced activation of NF-kappaB in the brain were investigated. One day after chronic unpredictable stress (CUS), nonstressed and CUS rats were treated with saline or LPS and killed 2 h later. CUS potentiated the increase in LPS-induced activation of NF-kappaB in frontal cortex and hippocampus but not in the hypothalamus. This stress effect was blocked by pretreatment of rats with RU-486, an antagonist of the GC receptor. MK-801 [(+)-5-methyl-10,11-dihydro-5H-dibenzo [a,d] cyclohepten-5,10-imine maleate], an NMDA receptor antagonist, also reduced the effect of LPS in all three brain regions. However, the combined antagonism of both GC and NMDA receptors produced no further reduction in NF-kappaB activation when compared with the effect of each treatment alone. Our results indicate that stress, via GC secretion, can increase LPS-induced NF-kappaB activation in the frontal cortex and hippocampus, agreeing with a growing literature demonstrating proinflammatory effects of GCs.

KIF4 Motor Regulates Activity-Dependent Neuronal Survival by Suppressing PARP-1 Enzymatic Activity

In brain development, apoptosis is a physiological process that controls the final numbers of neurons. Here, we report that the activity-dependent prevention of apoptosis in juvenile neurons is regulated by kinesin superfamily protein 4 (KIF4), a microtubule-based molecular motor. The C-terminal domain of KIF4 is a module that suppresses the activity of poly (ADP-ribose) polymerase-1 (PARP-1), a nuclear enzyme known to maintain cell homeostasis by repairing DNA and serving as a transcriptional regulator. When neurons are stimulated by membrane depolarization, calcium signaling mediated by CaMKII induces dissociation of KIF4 from PARP-1, resulting in upregulation of PARP-1 activity, which supports neuron survival. After dissociation from PARP-1, KIF4 enters into the cytoplasm from the nucleus and moves to the distal part of neurites in a microtubule-dependent manner. We suggested that KIF4 controls the activity-dependent survival of postmitotic neurons by regulating PARP-1 activity in brain development.

NFkappaB in neurons? The uncertainty principle in neurobiology

Nuclear factor kappaB (NFkappaB) is a dynamically modulated transcription factor with an extensive literature pertaining to widespread actions across species, cell types and developmental stages. Analysis of NFkappaB in a complex environment such as neural tissue suffers from a difficulty in simultaneously establishing both activity and location. Much of the available data indicate a profound recalcitrance of NFkappaB activation in neurons, as compared with most other cell types. Few studies to date have sought to distinguish between the various combinatorial dimers of NFkappaB family members. Recent research has illuminated the importance of these problems, as well as opportunities to move past them to the nuances manifest through variable activation pathways, subunit complexity and target sequence preferences.

Potential role of NF-kappaB in adult neural stem cells: the underrated steersman?

Neural stem cells are precursors of neurons and glial cells. During brain development, these cells proliferate, migrate and differentiate into specific lineages. Recently neural stem cells within the adult central nervous system were identified. Informations are now emerging about regulation of stem cell proliferation, migration and differentiation by numerous soluble factors such as chemokines and cytokines. However, the signal transduction mechanisms downstream of these factors are less clear. Here, we review potential evidences for a novel central role of the transcription factor nuclear factor kappa B (NF-kappaB) in these crucial signal transduction processes. NF-kappaB is an inducible transcription factor detected in neurons, glia and neural stem cells. NF-kappaB was discovered by David Baltimore's laboratory as a transcription factor in lymphocytes. NF-kappaB is involved in many biological processes such as inflammation and innate immunity, development, apoptosis and anti-apoptosis. It has been recently shown that members of the NF-kappaB family are widely expressed by neurons, glia and neural stem cells. In the nervous system, NF-kappaB plays a crucial role in neuronal plasticity, learning, memory consolidation, neuroprotection and neurodegeneration. Recent data suggest an important role of NF-kappaB on proliferation, migration and differentiation of neural stem cells. NF-kappaB is composed of three subunits: two DNA-binding and one inhibitory subunit. Activation of NF-kappaB takes place in the cytoplasm and results in degradation of the inhibitory subunit, thus enabling the nuclear import of the DNA-binding subunits. Within the nucleus, several target genes could be activated. In this review, we suggest a model explaining the multiple action of NF-kappaB on neural stem cells. Furthermore, we discuss the potential role of NF-kappaB within the so-called brain cancer stem cells.

The role of CaMKII in BDNF-mediated neuroprotection of retinal ganglion cells (RGC-5)

The purpose of the study is to determine if expression or secretion of brain-derived neurotrophic factor (BDNF) in retinal ganglion cells (RGC-5) is mediated by NFkappaB or Ca2+/calmodulin-dependent protein kinase II (CaMKII). RGC-5 cells were exposed to 1 mM glutamate for various periods of time, in the presence or absence of prospective regulatory molecules. BDNF mRNA and protein expression were assessed with the aid of real-time PCR and immunoblots, respectively, and BDNF secretion was determined by ELISA. The NFkappaB inhibitor (TLCK and PTD-p65), or a specific CaMKII inhibitor (m-AIP), was used to study association of NFkappaB or CaMKII with BDNF expression/secretion in RGC-5 cells. Glutamate stimulated a transient increase in BDNF mRNA and protein in RGC-5 cells, and also stimulated an early release of BDNF into the culture media. Neutralizing the BDNF or blocking the TrkB receptor enhanced the glutamate-induced cytotoxicity. NFkappaB nuclear translocation was revealed in response to glutamate treatment. Application of TLCK or PTD-p65 inhibited the glutamate-induced BDNF expression and secretion. Inhibition of CaMKII by m-AIP did not affect expression but significantly enhanced the release of BDNF from glutamate challenged cells. Our data suggest that glutamate treatment may stimulate expression of BDNF in RGC-5 cells through NFkappaB activation. A novel mechanism for neuroprotection is proposed for the CaMKII inhibitor, AIP, which appears to protect RGC-5 cells from cytotoxicity by enhancing the release of BDNF from glutamate challenged cells.

Signaling via NF-κB in the nervous system

Nuclear factor kappa B (NF-kappaB) is an inducible transcription factor present in neurons and glia. Recent genetic models identified a role for NF-kappaB in neuroprotection against various neurotoxins. Furthermore, genetic evidence for a role in learning and memory is now emerging. This review highlights our current understanding of neuronal NF-kappaB in response to synaptic transmission and summarizes potential physiological functions of NF-kappaB in the nervous system. This article contains a listing of NF-kappaB activators and inhibitors in the nervous system, furthermore specific target genes are discussed. Synaptic NF-kappaB activated by glutamate and Ca2+ will be presented in the context of retrograde signaling. A controversial role of NF-kappaB in neurodegenerative diseases will be discussed. A model is proposed explaining this paradox as deregulated physiological NF-kappaB activity, where novel results are integrated, showing that p65 could be turned from an activator to a repressor of anti-apoptotic genes.

Ischemic tolerance in the brain

Endogenous tolerance to cerebral ischemia is nature's strategy for neuroprotection. Exploring the physiologic and molecular mechanism of this phenomenon may give us new means of protection against ischemia and other degenerative disorders. This article reviews the currently available experimental methods to induce ischemic tolerance in the brain and gives a brief summary of the potential mode of action.