High constitutive NF-kappaB activity mediates resistance to oxidative stress in neuronal cells

Adaptive responses of neuronal cells to chronic endoplasmic reticulum (ER) stress

Accumulation of misfolded proteins or perturbation of calcium homeostasis leads to endoplasmic reticulum (ER) stress and is linked to the pathogenesis of neurodegenerative diseases. Hence, understanding the ability of neuronal cells to cope with chronic ER stress is of fundamental interest. Interestingly, several brain areas uphold functions that enable them to resist challenges associated with neurodegeneration. Here, we established novel clonal mouse hippocampal (HT22) cell lines that are resistant to prolonged (chronic) ER stress induced by thapsigargin (TgR) or tunicamycin (TmR) as in vitro models to study the adaption to ER stress. Morphologically, we observed a significant increase in vesicular und autophagosomal structures in both resistant lines and 'giant lysosomes', especially striking in TgR cells. While autophagic activity increased under ER stress, lysosomal function appeared slightly impaired; in both cell lines, we observed enhanced ER-phagy. However, proteomic analyses revealed that various protein clusters and signaling pathways were differentially regulated in TgR versus TmR cells in response to chronic ER stress. Additionally, bioenergetic analyses in both resistant cell lines showed a shift toward aerobic glycolysis ('Warburg effect') and a defective complex I of the oxidative phosphorylation (OXPHOS) machinery. Furthermore, ER stress-resistant cells differentially activated the unfolded protein response (UPR) comprising IRE1α and ATF6 pathways. These findings display the wide portfolio of adaptive responses of neuronal cells to chronic ER stress. ER stress-resistant neuronal cells could be the basis to uncover molecular modulators of adaptation, resistance, and neuroprotection as potential pharmacological targets for preventing neurodegeneration.

Enhanced autophagic-lysosomal activity and increased BAG3-mediated selective macroautophagy as adaptive response of neuronal cells to chronic oxidative stress

Oxidative stress and a disturbed cellular protein homeostasis (proteostasis) belong to the most important hallmarks of aging and of neurodegenerative disorders. The proteasomal and autophagic-lysosomal degradation pathways are key measures to maintain proteostasis. Here, we report that hippocampal cells selected for full adaptation and resistance to oxidative stress induced by hydrogen peroxide (oxidative stress-resistant cells, OxSR cells) showed a massive increase in the expression of components of the cellular autophagic-lysosomal network and a significantly higher overall autophagic activity. A comparative expression analysis revealed that distinct key regulators of autophagy are upregulated in OxSR cells. The observed adaptive autophagic response was found to be independent of the upstream autophagy regulator mTOR but is accompanied by a significant upregulation of further downstream components of the canonical autophagy network such as Beclin1, WIPI1 and the transmembrane ATG9 proteins. Interestingly, the expression of the HSP70 co-chaperone BAG3, mediator of BAG3-mediated selective macroautophagy and highly relevant for the clearance of aggregated proteins in cells, was found to be increased in OxSR cells that were consequently able to effectively overcome proteotoxic stress. Overexpression of BAG3 in oxidative stress-sensitive HT22 wildtype cells partly established the vesicular phenotype and the enhanced autophagic flux seen in OxSR cells suggesting that BAG3 takes over an important part in the adaptation process. A full proteome analysis demonstrated additional changes in the expression of mitochondrial proteins, metabolic enzymes and different pathway regulators in OxSR cells as consequence of the adaptation to oxidative stress in addition to autophagy-related proteins. Taken together, this analysis revealed a wide variety of pathways and players that act as adaptive response to chronic redox stress in neuronal cells.

Biphasic activation of nuclear factor-κB and expression of p65 and c-Rel following traumatic neuronal injury

The transcription factor nuclear factor-κB (NF-κB) has been shown to function as a key regulator of cell death or survival in neuronal cells. Previous studies indicate that the biphasic activation of NF-κB occurs following experimental neonatal hypoxia-ischemia and subarachnoid hemorrhage. However, the comprehensive understanding of NF-κB activity following traumatic brain injury (TBI) is incomplete. In the current study, an in vitro model of TBI was designed to investigate the NF-κB activity and expression of p65 and c-Rel subunits following traumatic neuronal injury. Primary cultured neurons were assigned to control and transected groups. NF-κB activity was detected by electrophoretic mobility shift assay. Western blotting and immunofluorescence were used to investigate the expression and distribution of p65 and c-Rel. Reverse transcription-quantitative polymerase chain reaction was performed to assess the downstream genes of NF-κB. Lactate dehydrogenase (LDH) quantification and trypan blue staining were used to estimate the neuronal injury. Double peaks of elevated NF-κB activity were observed at 1 and 24 h following transection. The expression levels of downstream genes exhibited similar changes. The protein levels of p65 also presented double peaks while c-Rel was elevated significantly in the late stage. The results of the trypan blue staining and LDH leakage assays indicated there was no sustained neuronal injury during the late peak of NF-κB activity. In conclusion, biphasic activation of NF-κB is induced following experimental traumatic neuronal injury. The elevation of p65 and c-Rel levels at different time periods suggests that within a single neuron, NF-κB may participate in different pathophysiological processes.

Light induces translocation of NF-κB p65 to the mitochondria and suppresses expression of cytochrome c oxidase subunit III (COX III) in the rat retina

The transcription factor nuclear factor kappaB (NF-κB) plays various roles in cell survival, apoptosis, and inflammation. In the rat retina, NF-κB activity increases after exposure to damaging light, resulting in degeneration of photoreceptors. Here, we report that in dark-adapted rats exposed for 6 h to bright white light, the p65 subunit of retinal NF-κB translocates to the mitochondria, an event associated with a decrease in expression of cytochrome c oxidase subunit III (COX III). However, sustained exposure for 12 h depleted p65 from the mitochondria, and enhanced COX III expression. Treatment with the protective antioxidant PBN prior to light exposure prevents p65 depletion in the mitochondria and COX III upregulation during prolonged exposure, and apoptosis in photoreceptor cells. These results indicate that COX III expression is sensitive to the abundance of NF-κB p65 in the mitochondria, which, in turn, is affected by exposure to damaging light.

Rutin alleviates prion peptide-induced cell death through inhibiting apoptotic pathway activation in dopaminergic neuronal cells

Prion disorders are progressive neurodegenerative diseases characterized by extensive neuronal loss and accumulation of the abnormal form of the scrapie prion protein (PrP). Rutin is a flavonoid that occurs naturally in plant-derived beverages and foods and is used in traditional and folkloric medicine worldwide. In the present study, we evaluated the protective effects of rutin against PrP fragment (106-126)-induced neuronal cell death. Rutin treatment blocked PrP (106-126)-mediated increases in reactive oxygen species production and nitric oxide release and helped slowing the decrease of neurotrophic factors that results from PrP accumulation. Rutin attenuated PrP (106-126)-associated mitochondrial apoptotic events by inhibiting mitochondrial permeability transition and caspase-3 activity and blocking expression of the apoptotic signals Bax and PARP. Additionally, rutin treatment significantly decreased the expression of the death receptor Fas and its ligand Fas-L. Overall, our results demonstrated that rutin protects against the neurodegenerative effects of prion accumulation by increasing production of neurotropic factors and inhibiting apoptotic pathway activation in neuronal cells. These results suggested that rutin may have clinical benefits for prion diseases and other neurodegenerative disorders.

Enhanced survival of retinal ganglion cells is mediated by Müller glial cell-derived PEDF

The death of retinal ganglion cells (RGC) leads to visual impairment and blindness in ocular neurodegenerative diseases, primarily in glaucoma and diabetic retinopathy; hence, mechanisms that contribute to protecting RGC from ischemia/hypoxia are of great interest. We here address the role of retinal glial (Müller) cells and of pigment-epithelium-derived factor (PEDF), one of the main neuroprotectants released from the glial cells. We show that the hypoxia-induced loss in the viability of cultured purified RGC is due to apoptosis, but that the number of viable RGC increases when co-cultured with Müller glial cells suggesting that glial soluble mediators attenuate the death of RGC. When PEDF was ablated from Müller cells a significantly lower number of RGC survived in RGC-Müller cell co-cultures indicating that PEDF is a major survival factor allowing RGC to escape cell death. We further found that RGC express a PEDF receptor known as patatin-like phospholipase domain-containing protein 2 (PNPLA2) and that PEDF exposure, as well as the presence of Müller cells, leads to an activation of nuclear factor (NF)-κB in RGC. Furthermore, adding an NF-κB inhibitor (SN50) to PEDF-treated RGC cultures reduced the survival of RGC. These findings strongly suggest that NF-κB activation in RGC is critically involved in the pro-survival action of Müller-cell derived PEDF and plays an important role in maintaining neuronal survival.

Possible role of NF-κB in Bcl-XLprotection against hydrogen peroxide-induced PC12 cell death

Bcl-X(L), a mitochondrial membrane protein, blocks apoptosis induced by a wide array of death signals. In spite of extensive research, the molecular milieu that characterizes the anti-apoptotic function of Bcl-X(L) is complex and not fully clarified. In the present work, we have investigated the role of Bcl-X(L) in protecting against oxidative death induced by H(2)O(2) in cultured rat pheochromocytoma (PC12) cells. PC12 cells exposed to H(2)O(2) underwent apoptotic cell death as determined by internucleosomal DNA fragmentation and an increased pro-apoptotic Bax to anti-apoptotic Bcl-X(L) ratio. Moreover, stable transfection with the bcl-X(L) gene rescued PC12 cells from apoptotic death caused by H(2)O(2). PC12 cells overexpressing bcl-X(L) exhibited relatively high constitutive transcriptional as well as DNA binding activities of NF-kappaB, compared with the vector-transfected control cells. Addition of NF-kappaB inhibitors, such as parthenolide and N-tosyl-L-phenylalanine chloromethyl ketone, to the media aggravated H(2)O(2)-induced oxidative cell death. PC12 cells transfected with bcl-X(L) exhibited higher levels of the heme oxygenase-1, which may confer these cells protection against oxidative stress. These results suggest that the redox-sensitive transcription factor NF-kappaB may play a role in bcl-X(L)-mediated protection against oxidative cell death.

Influence of the dopaminergic system, CREB, and transcription factor-κB on cocaine neurotoxicity

Cocaine is a widely used drug and its abuse is associated with physical, psychiatric and social problems. Abnormalities in newborns have been demonstrated to be due to the toxic effects of cocaine during fetal development. The mechanism by which cocaine causes neurological damage is complex and involves interactions of the drug with several neurotransmitter systems, such as the increase of extracellular levels of dopamine and free radicals, and modulation of transcription factors. The aim of this review was to evaluate the importance of the dopaminergic system and the participation of inflammatory signaling in cocaine neurotoxicity. Our study showed that cocaine activates the transcription factors NF-κB and CREB, which regulate genes involved in cellular death. GBR 12909 (an inhibitor of dopamine reuptake), lidocaine (a local anesthetic), and dopamine did not activate NF-κB in the same way as cocaine. However, the attenuation of NF-κB activity after the pretreatment of the cells with SCH 23390, a D1 receptor antagonist, suggests that the activation of NF-κB by cocaine is, at least partially, due to activation of D1 receptors. NF-κB seems to have a protective role in these cells because its inhibition increased cellular death caused by cocaine. The increase in BDNF (brain-derived neurotrophic factor) mRNA can also be related to the protective role of both CREB and NF-κB transcription factors. An understanding of the mechanisms by which cocaine induces cell death in the brain will contribute to the development of new therapies for drug abusers, which can help to slow down the progress of degenerative processes.

Involvement of NF kappa B in potentiated effect of Mn-containing dithiocarbamates on MPP(+) induced cell death

Humans are exposed to various chemical mixtures daily. The toxic response to a mixture of chemicals could be potentiated or suppressed. This study demonstrates that non-toxic doses of pesticides can induce cellular changes that increase cell sensitivity to other toxins or stress. Pesticide exposure is an environmental risk factor for Parkinson's disease. Manganese (Mn) is essential but high dose exposure may results in neurological dysfunction. Mn-containing dithiocarbamates, maneb (MB) and mancozeb (MZ), are primarily used as pesticides. Studies have shown that MB can augment dopaminergic damage triggered by sub-toxic doses of Parkinsonian mimetic MPTP. However, the mechanism underlying this effect is not clear. Activation of nuclear factor kappa B (NF-κB) has been implicated in MPTP toxicity. Mn stimulates the activation of NF-κB and subsequently induces neuronal injury via an NF-κB dependent mechanism. We speculate that MB and MZ enhance MPTP active metabolite (methyl-4-phenylpyridine ion, MPP(+)) toxicity by activating NF-κB. The activation of NF-κB was observed using Western blot analysis and NF-κB response element driven Luciferase reporter assay. Western blot data demonstrated the nuclear translocation of NF-κB p65 and the degradation of IkBα after MB and MZ 4-h treatments. Results of NF-κB response element luciferase reporter assay confirmed that MB and MZ activated NF-κB. The NF-κB inhibitor (SN50) was also shown to alleviate cytotoxicity induced by co-treatment of MB or MZ and MPP(+). This study demonstrates that activation of NF-κB is responsible for the potentiated toxic effect of MB and MZ on MPP(+) induced cytotoxicity.

Protective effect of Bajijiasu against β-amyloid-induced neurotoxicity in PC12 cells

Beta-amyloid peptide (Aβ), a major protein component of senile plaques associated with Alzheimer's disease (AD), is also directly neurotoxic. Mitigation of Aβ-induced neurotoxicity is thus a possible therapeutic approach to delay or prevent onset and progression of AD. This study evaluated the protective effect of Bajijiasu (β- D-fructofuranosyl (2-2) β- D-fructofuranosyl), a dimeric fructose isolated from the Chinese herb Radix Morinda officinalis, on Aβ-induced neurotoxicity in pheochromocytoma (PC12) cells. Bajijiasu alone had no endogenous neurotoxicity up to 200 μM. Brief pretreatment with 10-40 μM Bajijiasu (2 h) significantly reversed the reduction in cell viability induced by subsequent 24 h exposure to Aβ25-35 (21 μM) as measured by MTT and LDH assays, and reduced Aβ25-35-induced apoptosis as indicated by reduced annexin V-EGFP staining. Bajijiasu also decreased the accumulation of intracellular reactive oxygen species and the lipid peroxidation product malondialdehyde in PC12 cells, upregulated expression of glutathione reductase and superoxide dismutase, prevented depolarization of the mitochondrial membrane potential (Ψm), and blocked Aβ25-35-induced increases in [Ca(2+)] i . Furthermore, Bajijiasu reversed Aβ25-35-induced changes in the expression levels of p21, CDK4, E2F1, Bax, NF-κB p65, and caspase-3. Bajijiasu is neuroprotective against Aβ25-35-induced neurotoxicity in PC12 cells, likely by protecting against oxidative stress and ensuing apoptosis.

Minimal NF-κB activity in neurons

Nuclear factor-kappa B (NF-κB) is a ubiquitous transcription factor that regulates immune and cell-survival signaling pathways. NF-κB has been reported to be present in neurons wherein it reportedly responds to immune and toxic stimuli, glutamate, and synaptic activity. However, because the brain contains many cell types, assays specifically measuring neuronal NF-κB activity are difficult to perform and interpret. To address this, we compared NF-κB activity in cultures of primary neocortical neurons, mixed brain cells, and liver cells, employing Western blot of NF-κB subunits, electrophoretic mobility shift assay (EMSA) of nuclear κB DNA binding, reporter assay of κB DNA binding, immunofluorescence of the NF-κB subunit protein p65, quantitative real-time polymerase chain reaction (PCR) of NF-κB-regulated gene expression, and enzyme-linked immunosorbent assay (ELISA) of produced proteins. Assay of p65 showed its constitutive presence in cytoplasm and nucleus of neurons at levels significantly lower than in mixed brain or liver cells. EMSA and reporter assays showed that constitutive NF-κB activity was nearly absent in neurons. Induced activity was minimal--many fold lower than in other cell types, as measured by phosphorylation and degradation of the inhibitor IκBα, nuclear accumulation of p65, binding to κB DNA consensus sites, NF-κB reporting, or induction of NF-κB-responsive genes. The most efficacious activating stimuli for neurons were the pro-inflammatory cytokines tumor necrosis factor α (TNFα) and interleukin-beta (IL-β). Neuronal NF-κB was not responsive to glutamate in most assays, and it was also unresponsive to hydrogen peroxide, lipopolysaccharide, norepinephrine, ATP, phorbol ester, and nerve growth factor. The chemokine gene transcripts CCL2, CXCL1, and CXCL10 were strongly induced via NF-κB activation by TNFα in neurons, but many candidate responsive genes were not, including the neuroprotective genes SOD2 and Bcl-xL. Importantly, the level of induced neuronal NF-κB activity in response to TNFα or any other stimulus was lower than the level of constitutive activity in non-neuronal cells, calling into question the functional significance of neuronal NF-κB activity.

Effects of adenosine A2a receptor agonist and antagonist on hippocampal nuclear factor-kB expression preceded by MDMA toxicity

There is an abundance of evidence showing that repeated use of 3,4-methlylenedioxymethamphetamine (MDMA; ecstasy) is associated with brain dysfunction, memory disturbance, locomotor hyperactivity, and hyperthermia. MDMA is toxic to both the serotonergic neurons and dopaminergic system. Adenosine is an endogenous purine nucleoside with a neuromodulatory function in the central nervous system. Nuclear factor kappa-B (NF-kB) plays a pivotal role in the initiation and perpetuation of an immune response by triggering the expression of major inflammatory mediators such as cytokines, chemokines, and adhesion molecules. Here, we investigated the effects of the A2a adenosine receptor (A2a-R) agonist (CGS) and antagonist (SCH) on NF-kB expression after MDMA administration. Male Sprague-Dawley rats were injected to MDMA (10 mg/kg) followed by intraperitoneal injection of either CGS or SCH (0.03 mg/kg each) to animals. The hippocampi were then removed for western blot and RT- PCR analyses. MDMA significantly elevated NF-kB expression. Our results show that administration of CGS following MDMA significantly elevated the NF-kB expression both at mRNA and protein levels. By contrast, administration of the A2a-R antagonist SCH resulted in a decrease in the NF-kB levels. Taken together, these results indicate that, co-administration of A2a agonist (CGS) can protect against MDMA neurotoxic effects by increasing NF-kB expression levels; suggesting a potential application for protection against the neurotoxic effects observed in MDMA users.

Apoptosis induced by trimethyltin chloride in human neuroblastoma cells SY5Y is regulated by a balance and cross-talk between NF-κB and MAPKs signaling pathways

Trimethyltin chloride (TMT) has been known as a classic neurotoxicant which can cause serious neuronal degeneration diseases. Nuclear factor κB (NF-κB) and mitogen-activated protein kinases (MAPKs) signaling pathways play pivotal role in the central nerves system. In the present study, the intracellular pathways involved in TMT-induced apoptosis on human neuroblastoma cells SY5Y (SH-SY5Y) were investigated. We observed high level of nuclear NF-κB p65 submit, activated JNK, ERK, and p38 by TMT exposure. In contrast, low level of Bcl-2 and XIAP (two known NF-κB-regulated endogenous anti-apoptotic molecules) was present. To further investigate the role of these pathways and the relationship between them, specific inhibitors were used and the alteration of each pathway was evaluated. Pretreatment with MG132, an inhibitor of proteasome activity, and BAY11-7082, an inhibitor of IκBα phosphorylation, both inhibited NF-κB p65 translocation and significantly promoted apoptosis. NF-κB inhibition also induced down-expression of Bcl-2 and XIAP, exaggerated JNK phosphorylation, and ERK inhibition. SP600125 and U0126, by blocking the phosphorylation of c-Jun and MEK1/2, inhibited JNK and ERK phosphorylation, respectively, and attenuated apoptosis significantly. JNK and ERK inhibition also induced IκBα degradation and NF-κB p65 translocation, leading to expression of Bcl-2 and XIAP. The detrimental role of MG132 and BAY11-7082 appears related to the exaggerated JNK phosphorylation. The SP600125 and U0126 neuroprotection appears related to NF-κB-regulated transcriptional control of Bcl-2 and XIAP. These results suggest that the cross-talk and a balance between NF-κB and MAPKs may be involved in TMT-induced apoptosis on SH-SY5Y cells.

NF-κB drives the synthesis of melatonin in RAW 264.7 macrophages by inducing the transcription of the arylalkylamine-N-acetyltransferase (AA-NAT) gene

We demonstrate that during inflammatory responses the nuclear factor kappa B (NF-κB) induces the synthesis of melatonin by macrophages and that macrophage-synthesized melatonin modulates the function of these professional phagocytes in an autocrine manner. Expression of a DsRed2 fluorescent reporter driven by regions of the aa-nat promoter, that encodes the key enzyme involved in melatonin synthesis (arylalkylamine-N-acetyltransferase), containing one or two upstream κB binding sites in RAW 264.7 macrophage cell lines was repressed when NF-κB activity was inhibited by blocking its nuclear translocation or its DNA binding activity or by silencing the transcription of the RelA or c-Rel NF-κB subunits. Therefore, transcription of aa-nat driven by NF-κB dimers containing RelA or c-Rel subunits mediates pathogen-associated molecular patterns (PAMPs) or pro-inflammatory cytokine-induced melatonin synthesis in macrophages. Furthermore, melatonin acts in an autocrine manner to potentiate macrophage phagocytic activity, whereas luzindole, a competitive antagonist of melatonin receptors, decreases macrophage phagocytic activity. The opposing functions of NF-κB in the modulation of AA-NAT expression in pinealocytes and macrophages may represent the key mechanism for the switch in the source of melatonin from the pineal gland to immune-competent cells during the development of an inflammatory response.

Brain aging and late-onset Alzheimer's disease: many open questions

Despite decades of research in the field of Alzheimer's disease (AD), a real understanding of its molecular pathophysiology and treatments relevant to the day-to-day lives of patients remain out of reach. Research has, with good reason, focused on certain key pathways and potential mechanisms, but sometimes this has been at the expense of work on other theories, which may be slowing down progress in this field. Interesting theories at present include oxidative stress and caloric restriction. Work on the Aβ cascade should continue but with a shift in focus to its intracellular effects and an awareness that additional pathogenetic factors and processes must be involved--most importantly, brain aging. Hyperphosphorylation of tau, for instance, provides another interesting pathway, with one old drug showing promise in this regard. Moreover, work in epigenetics and on protein homeostasis has produced interesting findings and both lines of investigation may reveal suitable targets for future intervention. Taken together, analysis of the biochemistry of aged neurons and the interplay with pathways of neurodegeneration may lead to a better understanding of AD and how to treat and prevent this condition.

UCP4 is a target effector of the NF-κB c-Rel prosurvival pathway against oxidative stress

Mitochondrial uncoupling protein-4 (UCP4) enhances neuronal survival in 1-methyl-4-phenylpyridinium (MPP(+)) toxicity by suppressing oxidative stress and preserving intracellular ATP and mitochondrial membrane potential (MMP). NF-κB regulates neuronal viability via its complexes, p65 mediating cell death and c-Rel promoting cell survival. We reported previously that NF-κB mediates UCP4 neuroprotection against MPP(+) toxicity. Here, we investigated its link with the NF-κB c-Rel prosurvival pathway in alleviating mitochondrial dysfunction and oxidative stress. We overexpressed a c-Rel-encoding plasmid in SH-SY5Y cells and showed that c-Rel overexpression induced NF-κB activity without affecting p65 level. Overexpression of c-Rel increased UCP4 promoter activity and protein expression. Electrophoretic mobility shift assay showed that H(2)O(2) increased NF-κB binding to the UCP4 promoter and that NF-κB complexes were composed of p50/p50 and p50/c-Rel dimers. Under H(2)O(2)-induced oxidative stress, UCP4 knockdown significantly increased superoxide levels, decreased reduced glutathione (GSH) levels, and increased oxidized glutathione levels, compared to controls. UCP4 expression induced by c-Rel overexpression significantly decreased superoxide levels and preserved GSH levels and MMP under similar stress. These protective effects of c-Rel overexpression in H(2)O(2)-induced oxidative stress were significantly reduced after UCP4 knockdown, indicating that UCP4 is a target effector gene of the NF-κB c-Rel prosurvival pathway to mitigate the effects of oxidative stress.

Impairment of the ubiquitin-proteasome pathway by methyl N-(6-phenylsulfanyl-1H-benzimidazol-2-yl)carbamate leads to a potent cytotoxic effect in tumor cells: a novel antiproliferative agent with a potential therapeutic implication

In recent years, there has been a great deal of interest in proteasome inhibitors as a novel class of anticancer drugs. We report that fenbendazole (FZ) (methyl N-(6-phenylsulfanyl-1H-benzimidazol-2-yl)carbamate) exhibits a potent growth-inhibitory activity against cancer cell lines but not normal cells. We show here, using fluorogenic substrates, that FZ treatment leads to the inhibition of proteasomal activity in the cells. Succinyl-Leu-Leu-Val-Tyr-methylcoumarinamide (MCA), benzyloxycarbonyl-Leu-Leu-Glu-7-amido-4-MCA, and t-butoxycarbonyl-Gln-Ala-Arg-7-amido-4-MCA fluorescent derivatives were used to assess chymotrypsin-like, post-glutamyl peptidyl-hydrolyzing, and trypsin-like protease activities, respectively. Non-small cell lung cancer cells transiently transfected with an expression plasmid encoding pd1EGFP and treated with FZ showed an accumulation of the green fluorescent protein in the cells due to an increase in its half-life. A number of apoptosis regulatory proteins that are normally degraded by the ubiquitin-proteasome pathway like cyclins, p53, and IκBα were found to be accumulated in FZ-treated cells. In addition, FZ induced distinct ER stress-associated genes like GRP78, GADD153, ATF3, IRE1α, and NOXA in these cells. Thus, treatment of human NSCLC cells with fenbendazole induced endoplasmic reticulum stress, reactive oxygen species production, decreased mitochondrial membrane potential, and cytochrome c release that eventually led to cancer cell death. This is the first report to demonstrate the inhibition of proteasome function and induction of endoplasmic reticulum stress/reactive oxygen species-dependent apoptosis in human lung cancer cell lines by fenbendazole, which may represent a new class of anticancer agents showing selective toxicity against cancer cells.

NF-κB and epigenetic mechanisms as integrative regulators of brain resilience to anoxic stress

Brain cells display an amazing ability to respond to several different types of environmental stimuli and integrate this response physiologically. Some of these responses can outlive the original stimulus by days, weeks or even longer. Long-lasting changes in both physiological and pathological conditions occurring in response to external stimuli are almost always mediated by changes in gene expression. To effect these changes, cells have developed an impressive repertoire of signaling systems designed to modulate the activity of numerous transcription factors and epigenetic mechanisms affecting the chromatin structure. Since its initial characterization in the nervous system, NF-κB has shown to respond to multiple signals and elicit pleiotropic activities suggesting that it may play a pivotal role in integration of different types of information within the brain. Ample evidence demonstrates that NF-κB factors are engaged in and necessary for neuronal development and synaptic plasticity, but they also regulate brain response to environmental noxae. By focusing on the complexity of NF-κB transcriptional activity in neuronal cell death, it emerged that the composition of NF-κB active dimers finely tunes the neuronal vulnerability to brain ischemia. Even though we are only beginning to understand the contribution of distinct NF-κB family members to the regulation of gene transcription in the brain, an additional level of regulation of NF-κB activity has emerged as operated by the epigenetic mechanisms modulating histone acetylation. We will discuss NF-κB and epigenetic mechanisms as integrative regulators of brain resilience to anoxic stress and useful drug targets for restoration of brain function. This article is part of a Special Issue entitled: Brain Integration.

Rutin prevents cognitive impairments by ameliorating oxidative stress and neuroinflammation in rat model of sporadic dementia of Alzheimer type

The objective of the present study was to assess the neuroprotective role of rutin (vitamin P) and delineate the mechanism of action. Recent evidence indicates that rutin exhibits antioxidant potential and protects the brain against various oxidative stressors. More precisely, the aim of the present study was to examine the modulating impacts of rutin against cognitive deficits and oxidative damage in intracerebroventricular-streptozotocin (ICV-STZ)-infused rats. Rats were injected bilaterally with ICV-STZ (3 mg/kg), whereas sham rats received the same volume of vehicle. After 2 weeks of streptozotocin (STZ) infusion, rats were tested for cognitive performance using Morris water maze tasks and thereafter euthanized for further biochemical, histopathological, and immunohistochemical studies. Rutin pretreatment (25 mg/kg, orally, once daily for 3 weeks) significantly attenuated thiobarbituric acid reactive substances (TBARS), activity of poly ADP-ribosyl polymerase, and nitrite level and decreased level of reduced glutathione (GSH) and activities of its dependent enzymes (glutathione peroxidase [GPx] and glutathione reductase [GR]) and catalase in the hippocampus of ICV-STZ rats. ICV-STZ rats showed significant cognitive deficits, which was improved significantly by rutin supplementation. The results indicate that rutin attenuates STZ-induced inflammation by reducing the expression of cyclooxygenase-2 (COX-2), glial fibrillary acidic protein (GFAP), interleukin-8 (IL-8), inducible nitric oxide synthase (iNOS), nuclear factor-kB, and preventing the morphological changes in hippocampus. The study thereby suggests the effectiveness of rutin in preventing cognitive deficits and might be beneficial for the treatment of sporadic dementia of Alzheimer type (SDAT).

Human Schwann cells retain essential phenotype characteristics after immortalization

Schwann cells (SCs) play an important role in the pathogenesis of peripheral nerve diseases and represent a potential target for development of therapies. However, use of primary human SCs (hSCs) for in vitro models is limited because these cells are difficult to prepare and maintain in high yield and purity under common cell culture conditions. To circumvent this obstacle, we immortalized primary human fetal SCs using the SV40 large T-antigen and human telomerase reverse transcriptase expression vectors. After cloning, selection, and purification, we evaluated several immortalized SC lines for their ability to express extracellular matrix (ECM) molecules and myelinate embryonic rat sensory axons. In addition, we established a gene expression profile and explored their sensitivity to oxidative stress in a simple in vitro assay. Immortalized hSC clones expressed common glial markers and a broad variety of growth factors, receptors, and ECM molecules as determined by immunocytochemistry, microarray, and quantitative reverse transcription-polymerase chain reaction. In neuron-SC co-cultures, these cells were able to myelinate rat dorsal root ganglia neurons, although their effectiveness was lower in comparison to primary rat SCs. In toxicity assays, immortalized hSCs remain susceptible to oxidative stress induced by H(2)O(2). This study shows that, using specific immortalization techniques, it is possible to establish hSC lines that retain characteristics of typical primary hSCs. These cells are particularly useful for drug screening and studies aimed at disease mechanisms involving SCs.

Inhibition of extracellular signal-regulated kinases 1/2 provides neuroprotection in spinal cord ischemia/reperfusion injury in rats: relationship with the nuclear factor-kappaB-regulated anti-apoptotic mechanisms

Previously we demonstrated benefits of inhibiting the extracellular signal-regulated kinases 1/2 (ERK1/2) signaling pathway in spinal cord ischemia/reperfusion (I/R) injury. To further identify the underlying mechanisms, we investigated the impact of ERK inhibition on apoptosis and cellular protective mechanisms against cell death. Spinal cord I/R injury induced ERK1/2 phosphorylation, followed by neuronal loss through caspase 3-mediated apoptosis. Pre-treatment with U0126, a specific inhibitor of MAPK/ERK kinases 1/2 (MEK1/2), inhibited ERK1/2 phosphorylation, and significantly attenuated apoptosis and increased neuronal survival. MEK/ERK inhibition also induced I-kappaB phosphorylation and enhanced nuclear factor (NF)-kappaB/DNA binding activity, leading to expression of cellular inhibitors of apoptosis protein 2 (c-IAP2), a known nuclear factor-kappaB (NF-kappaB)-regulated endogenous anti-apoptotic molecule. Pyrrolidine dithiocarbamate, an NF-kappaB inhibitor, by blocking I-kappaB phosphorylation, NF-kappaB activation, and c-IAP2 synthesis, abolished the protective effects of U0126. The MEK/ERK pathway appears to mediate cellular death following I/R injury. The U0126 neuroprotection appears related to NF-kappaB-regulated transcriptional control of c-IAP2. MEK/ERK inhibition at the initial stage of I/R injury may cause changes in c-IAP2 gene expression or c-IAP2/caspase 3 interactions, resulting in long lasting therapeutic effects. Future research should focus on the possible cross-talk between the MEK/ERK pathway and the NF-kappaB transcriptional cascade.

Hydrogen peroxide induces the death of astrocytes through the down-regulation of the constitutive nuclear factor-kappaB activity

Nuclear factor-kappaB (NF-kappaB) has a dual role in the promotion or attenuation of cell death. Here, we demonstrated the role of NF-kappaB in the H(2)O(2)-induced death of astrocytes. H(2)O(2) evoked the release of lactate dehydrogenase (LDH), a marker of cell death, and concomitantly decreased the DNA binding and transcriptional activity of NF-kappaB in cultured astrocytes. H(2)O(2)-induced astrocyte death was markedly increased by the co-treatment with pyrrolidinedithiocarbamate, an NF-kappaB inhibitor. Moreover, the elevation of constitutive NF-kappaB activity by overexpressing p65 NF-kappaB subunit attenuated H(2)O(2) toxicity, whereas NF-kappaB inhibition by overexpressing IkappaB potentiated the toxicity. NF-kappaB activity and H(2)O(2) cytotoxicity was further found to be dependent on cell density. Compared with astrocytes in low cell density, those in high cell density exhibited a higher constitutive NF-kappaB activity and a stronger resistance to H(2)O(2) cytotoxicity. These results indicate that the constitutive activity of NF-kappaB in astrocytes is required for their survival under oxidative stress such as H(2)O(2).

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.

Cocaine induces cell death and activates the transcription nuclear factor kappa-B in PC12 cells

Cocaine is a worldwide used drug and its abuse is associated with physical, psychiatric and social problems. The mechanism by which cocaine causes neurological damage is very complex and involves several neurotransmitter systems. For example, cocaine increases extracellular levels of dopamine and free radicals, and modulates several transcription factors. NF-kappaB is a transcription factor that regulates gene expression involved in cellular death. Our aim was to investigate the toxicity and modulation of NF-kappaB activity by cocaine in PC 12 cells. Treatment with cocaine (1 mM) for 24 hours induced DNA fragmentation, cellular membrane rupture and reduction of mitochondrial activity. A decrease in Bcl-2 protein and mRNA levels, and an increase in caspase 3 activity and cleavage were also observed. In addition, cocaine (after 6 hours treatment) activated the p50/p65 subunit of NF-kappaB complex and the pretreatment of the cells with SCH 23390, a D1 receptor antagonist, attenuated the NF-kappaB activation. Inhibition of NF-kappaB activity by using PDTC and Sodium Salicilate increased cell death caused by cocaine. These results suggest that cocaine induces cell death (apoptosis and necrosis) and activates NF-kappaB in PC12 cells. This activation occurs, at least partially, due to activation of D1 receptors and seems to have an anti-apoptotic effect on these cells.

NF-kappaB dimers in the regulation of neuronal survival

Nuclear factor-kappaB (NF-kappaB) is a dimeric transcription factor composed of five members, p50, RelA/p65, c-Rel, RelB, and p52 that can diversely combine to form the active transcriptional dimer. NF-kappaB controls the expression of genes that regulate a broad range of biological processes in the central nervous system such as synaptic plasticity, neurogenesis, and differentiation. Although NF-kappaB is essential for neuron survival and its activation may protect neurons against oxidative-stresses or ischemia-induced neurodegeneration, NF-kappaB activation can contribute to inflammatory reactions and apoptotic cell death after brain injury and stroke. It was proposed that the death or survival of neurons might depend on the cell type and the timing of NF-kappaB activation. We here discuss recent evidence suggesting that within the same neuronal cell, activation of diverse NF-kappaB dimers drives opposite effects on neuronal survival. Unbalanced activation of NF-kappaB p50/RelA dimer over c-Rel-containing complexes contributes to cell death secondary to the ischemic insult. While p50/RelA acts as transcriptional inducer of Bcl-2 family proapoptotic Bim and Noxa genes, c-Rel dimers specifically promote transcription of antiapototic Bcl-xL gene. Changes in the nuclear content of c-Rel dimers strongly affect the threshold of neuron vulnerability to ischemic insult and agents, likewise leptin, activating a NF-kappaB/c-Rel-dependent transcription elicit neuroprotection in animal models of brain ischemia.

Erythropoietin improves oxidative stress following spinal cord trauma in rats

Spinal cord injury (SCI) is a very destructive process for both patients and society. Lipid peroxidation is the main cause of the further secondary damage which starts after mechanical destruction of tissues. Recent studies have shown that erythropoietin (EPO) has neuroprotective properties. In this study, we aimed to see the effect of EPO treatment after spinal cord injury on the oxidant and anti-oxidant enzyme systems and the relationship with the N-methyl-D-Aspartate (NMDA) blockage. Spinal cord injury was produced by epidural compression with a cerebral vascular clip that has a closing force of 40 g for 30s after a limited multilevel laminectomy (T9-11). Experiment was done in 5 groups: Group 1: Sham-operated untraumatised, Group 2: SCI untreated, Group 3: 150 i.u./kg EPO injected i.p. at the end of the first hour following the trauma. Group 4: NMDA receptor antagonist ketamine (100mg/kg) i.p. Group 5: EPO+ketamine i.p. The experiments were finished after 12h of the trauma. The spinal cords were excised for biochemical examinations. Anti-oxidant enzymes; catalase and reduced glutathione (GSH) levels increased and lipid peroxidation product, malonyldialdehyde (MDA) level decreased in EPO treated group when compared to the other groups. TNF-alpha levels decreased in EPO treated group. Application of ketamine before EPO treatment decreased effects of EPO. In conclusion, our results suggest that 150 i.u./kg i.p. EPO, a therapeutic dose in anaemic patients, applied after 1h of spinal cord injury significantly attenuated the oxidative damage of spinal cord injuries in rats. This activity is abolished via ketamine pretreatment.

Cell death and proliferation in NF-kappaB p50 knockout mouse after cerebral ischemia

The transcription factor NF-kappaB is a key regulator of inflammation and cell survival. NF-kappaB activation increases following cerebral ischemia. We previously showed accelerated aging process in NF-kappaB p50 subunit knockout (p50 -/-) mice under physiological condition. The present investigation concerned the role of NF-kappaB p50 gene in ischemia-induced neuronal cell death. In an animal model of permanent middle cerebral artery occlusion (MCAO), infarct formation, apoptotic cell death and cell proliferation were examined in adult wild type (WT) and p50-/- mice. The ischemic infarct volume was significantly larger in p50-/- mice than that in WT mice. Consistently, the numbers of cells in the penumbra region positive to terminal deoxynucleotidyltransferase (TdT)-mediated dUTP-biotin nick end-labeling (TUNEL) and caspase-3 staining were significantly more in p50-/- mice than that in WT mice. To identify proliferation after cerebral ischemia, bromodeoxyurindine (BrdU) was intraperitoneal injected daily after MCAO. Ischemia increased BrdU positive cells in the penumbra, subventricular zone, corpus callosum, and cerebral cortex, while cell proliferation was hampered in p50-/- mice. These results suggest that NF-kappaB signaling is a neuroprotective mechanism and may play a role in cell proliferation in the stroke model of permanent MCAO.

Proteasome inhibitors prevent oxidative stress-induced nerve cell death by a novel mechanism

The role of the proteasome in neurodegenerative diseases is controversial. On the one hand, there is evidence that a dysfunction of proteasome activity can lead to neurodegeneration but there is also data showing that proteasome inhibition can protect nerve cells from a variety of insults. In an attempt to clarify this issue, we studied the effects of four different proteasome inhibitors in a well characterized model of oxidative stress-induced nerve cell death. Consistent with the hypothesis that proteasome inhibition can be neuroprotective, we found that low concentrations of proteasome inhibitors were able to protect nerve cells from oxidative stress-induced death. Surprisingly, the neuroprotective effects of the proteasome inhibitors appeared to be at least partially mediated by the induction of NF-kappaB since protection was significantly reduced in cells expressing a specific NF-kappaB repressor. The activation of NF-kB by proteasome inhibitors was mediated by IkappaB alpha and IKK and was blocked by antioxidants and inhibitors of mitochondrial reactive oxygen species production. These data suggest that low concentrations of proteasome inhibitors induce a moderate level of mitochondrial oxidative stress which results in the activation of neuroprotective pathways.

Antiamnestic effect of alpha7-nicotinic receptor agonist RJR-2403 in middle-aged ovariectomized rats with Alzheimer type dementia

The effects of chronic combined treatment with alpha7-nicotinic cholinergic receptor agonist RJR-2403 (1.0 mg/kg intraperitoneally) or alpha7-nicotinic cholinergic receptor antagonist mecamylamine (1.0 mg/kg intraperitoneally) and 17beta-estradiol (0.5 microg per rat intramuscularly) for 10 days on passive avoidance retention were studied in middle-aged (15 months) ovariectomized rats with experimental Alzheimer type dementia. Chronic treatment with RJR-2403 and 17beta-estradiol had a pronounced antiamnestic effect under conditions of Alzheimer type dementia in middle-aged ovariectomized rats.

Memory and learning impairment induced by dexamethasone in senescent but not young mice

In this study, the memory and learning impairment induced by dexamethasone in young mice and senescent mice were evaluated by step-down inhibitory avoidance task and passive avoidance test. Colorimetric MTT(tetrazole 3-(4,5-dimethylthiazol-2-yl-)-2,5-diphenyltetrazolium bromide) assay and TUNEL staining were used to investigate the influence of dexamethasone on hippocampal neuronal cell death with amyloid beta-protein. It was determined the effect of dexamethasone on intracellular calcium ([Ca(2+)](i)) with amyloid beta-protein 25-35 by fluorescence imaging with a confocal laser microscope using fluo-3 acetoxymethylester (AM) as a fluorescent dye. The effect of dexamethasone on amyloid beta-protein 25-35-induced nuclear factor kappaB (NF-kappaB) was analyzed by western blot. The results showed that twenty one days dexamethasone exposure resulted in an impairment of memory and learning in senescent but not young mice. Pretreatment of isolated hippocampal neurons with dexamethasone increased the vulnerability of the hippocampal neurons to amyloid beta-protein 25-35, enhanced [Ca(2+)](i) and down-regulated the increased level of nuclear NF-kappaB p65 proteins induced by amyloid beta-protein 25-35. These results demonstrated that glucocorticoids could potentiate the neurotoxic action of amyloid beta-protein by further increasing the level of [Ca(2+)](i) and down-regulating the level of nuclear NF-kappaB protein. Since amyloid beta-protein increases in the brain with aging, glucocorticoids potentiation of the neurotoxic action of amyloid beta-protein maybe one of the mechanisms responsible for glucocorticoids-induced memory and learning impairment in senescent but not young mice, which maybe relevance to the etiology of Alzheimer's disease.

Orchestration of the inflammatory response in ischemia-reperfusion injury

Ischemia to nerve can cause fiber degeneration and reperfusion following ischemia [ischemia-reperfusion (IR)] adds the additional insult of an inflammatory response and oxidative injury. Limited information is available on the molecular mediators and their endoneurial targets. In this study, using a highly reproducible animal model of IR injury to nerve and selective immunolabeling methods [for nuclear factor kappa B (NF-kappaB), intercellular adhesion molecule-1 (ICAM-1), cytokines, and inflammatory cells] over an expanded time frame, we evaluated the temporal pattern and localization of mediators of the inflammatory response. Sixty rats were used. Nine groups (N=6 each) underwent complete hind limb ischemia for 4 h, followed by reperfusion durations of 0, 3, 12, 24, and 48 h, and 7, 14, 28, and 42 days. One group underwent sham operation (N=6). The earliest change was ICAM-1 expression in the microvessel (endothelial cell) followed almost immediately by NF-kappaB activation with axonal expression (24 and 48 h), followed by endoneurial edema and ischemic fiber degeneration (7 and 14 days). Granulocytic infiltration was followed by endoneurial infiltration of mononuclear phagocytes (14 days), expression of interleukin 6 (IL-6) (microvessels), and subsequent Schwann cell NF-kappaB expression. Granulocytes, tumor necrosis factor alpha, and IL-6-positive cells were observed primarily within the epineurium. IR results in changes in a number of interacting networks of targets and inflammatory mediators. NF-kappaB activation has a central orchestrating role involving both the axon and the Schwann cell in effecting the inflammatory response.

Nuclear factor kappa-B p50 and p65 subunits expression in dementia with Lewy bodies

Dementia with Lewy bodies (DLB) is the second most common cause of neurodegenerative dementia after Alzheimer's disease (AD). Parkinsonism in DLB is mainly caused by neuronal loss with Lewy bodies (LBs) in the substantia nigra, thereby inducing degeneration of the nigrostriatal dopaminergic pathway similar to that in Parkinson's disease (PD). To clarify the pathogenesis of DLB, it is important to investigate the mechanisms involved in the degenerative process of LB-bearing neurones. Several reports suggest a role for nuclear factor kappa-B (NFkappaB) in the manifestation of neurodegenerative conditions such as AD and PD. The aim of the present study was to investigate whether NFkappaB subunits are involved in the pathogenesis of neurodegeneration in DLB by measuring tyrosine hydroxylase (TH), NFkappaB p65 and p50 protein expression in frontal cortex and substantia nigra pars compacta of DLB and control human brains. An increase, although not statistically significant, in nigral TH expression in DLB cases was observed. There were no differences in the cortical and nigral expression levels of NFkappaB p65 subunit between control and DLB cases. Western blots of the frontal cortex showed no differences in the expression levels of NFkappaB p50 subunit. However, NFkappaB p50 levels were significantly decreased (P < 0.05) in the pars compacta of the substantia nigra in the DLB cases in comparison with controls. The decrease in the expression of the p50 subunit in the substantia nigra of DLB cases achieved in the present study may increase the vulnerability of the dopaminergic neurones to a possible neurotoxic effect of p65 subunit. Thus, normal levels of NFkappaB p65 might be toxic in neurones with a low expression of the NFkappaB p50 subunit.

Histone deacetylase inhibitors: insights into mechanisms of lethality

Histone deacetylases (HDACs) have recently emerged as an important target for therapeutic intervention in cancer and potentially other human diseases. By modulating the acetylation status of histones, histone deacetylase inhibitors (HDACIs) alter the transcription of genes involved in cell growth, maturation, survival and apoptosis, among other processes. Early clinical results suggest a potentially useful role for HDACIs in the treatment of certain forms of lymphoma (e.g., cutaneous T cell lymphoma) and acute leukaemia. An unresolved question is how HDACIs induce cell death in tumour cells. Recent studies suggest that acetylation of nonhistone proteins may play an important role in the biological effects of this class of compounds, and may explain lack of correlation between histone acetylation and induction of cell death by HDACIs in some circumstances. Recently, attention has focussed on the effects of HDACIs on disruption of co-repressor complexes, induction of oxidative injury, upregulation of the expression of death receptors, generation of lipid second messengers such as ceramide, interference with the function of chaperone proteins and modulation of the activity of NF-kappaB as critical determinants of lethality. Aside from providing critical insights into the mechanism of action of HDACIs in neoplastic disease, these findings may provide a foundation for the rational development of combination studies, involving HDACIs in combination with either conventional cytotoxic drugs as well as more novel targeted agents.

Nuclear factor-kappaB activation in neonatal mouse lung protects against lipopolysaccharide-induced inflammation

RATIONALE

Injurious agents often cause less severe injury in neonates as compared with adults.

OBJECTIVE

We hypothesized that maturational differences in lung inflammation induced by lipopolysaccharide (LPS) may be related to the nature of the nuclear factor (NF)-kappaB complex activated, and the profile of target genes expressed.

METHODS

Neonatal and adult mice were injected with intraperitoneal LPS. Lung inflammation was assessed by histology, and apoptosis was determined by TUNEL (terminal deoxynucleotidyl transferase UTP nick-end labeling). The expression of candidate inflammatory and apoptotic mediators was evaluated by quantitative real-time polymerase chain reaction and Western immunoblot.

RESULTS

Neonates demonstrated reduced inflammation and apoptosis, 24 hours after LPS exposure, as compared with adults. This difference was associated with persistent activation of NF-kappaB p65p50 heterodimers in the neonates in contrast to early, transient activation of p65p50 followed by sustained activation of p50p50 in the adults. Adults had increased expression of a panel of inflammatory and proapoptotic genes, and repression of antiapoptotic targets, whereas no significant changes in these mediators were observed in the neonates. Inhibition of NF-kappaB activity in the neonates decreased apoptosis, but heightened inflammation, with increased expression of the same inflammatory genes elevated in the adults. In contrast, inhibition of NF-kappaB in the adults resulted in partial suppression of the inflammatory response.

CONCLUSIONS

NF-kappaB activation in the neonatal lung is antiinflammatory, protecting against LPS-mediated lung inflammation by repressing similar inflammatory genes induced in the adult.

Expression of expanded polyglutamine proteins suppresses the activation of transcription factor NFkappaB

A major pathological hallmark of the polyglutamine diseases is the formation of neuronal intranuclear inclusions of the disease proteins that are ubiquitinated and often associated with various transcription factors, chaperones, and proteasome components. However, how the expanded polyglutamine proteins or their aggregates elicit complex pathogenic responses in the neuronal cells is not fully understood. Here, we have demonstrated that the expression of expanded polyglutamine proteins down-regulated the NFkappaB-dependent transcriptional activity. The expression of expanded polyglutamine proteins increased the stability and the levels of IkappaB-alpha and its phosphorylated derivatives. We have also found that various NFkappaB subunits and IkappaB-alpha aberrantly interacted with the expanded polyglutamine proteins and associated with their aggregates. Finally, we have shown that several NFkappaB-dependent genes are down-regulated in the expanded polyglutamine protein-expressing cells and down-regulation of NFkappaB activity enhances expanded polyglutamine protein-induced cell death. Because the NFkappaB pathway plays a very important role in cell survival, altered regulation of this pathway in expanded polyglutamine protein-expressing cells might be linked with the disease pathogenesis.

Nuclear factor kappaB signaling in opioid functions and receptor gene expression

Opiates are the most powerful of all known analgesics. The prototype opiate morphine has been used as a painkiller for several thousand years. Chronic usage of opiates not only causes drug tolerance, dependence, and addiction, but also suppresses immune functions and affects cell proliferation and cell survival. The diverse functions of opiates underscore the complexity of opioid receptor signaling. Several downstream signaling effector systems, including adenylyl cyclase, mitogen-activated protein kinase, Ca2+ channels, K+ channels, and phosphatidylinositol 3-kinase/Akt, have been identified to be critical in opioid functions. Nuclear factor-kappaB (NF-kappaB), one of the most diverse and critical transcription factors, is one of the downstream molecules that may either directly or indirectly transmit the receptor-mediated upstream signals to the nucleus, resulting in the regulation of the NF-kappaB-dependent genes, which are critical for the opioid-induced biological responses of neuronal and immune cells. In this minireview, we focus on current understanding of the involvement of NF-kappaB signaling in opioid functions and receptor gene expression in cells.

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.

Antioxidant pyrrolidine dithiocarbamate activates Akt-GSK signaling and is neuroprotective in neonatal hypoxia-ischemia

Pyrrolidine dithiocarbamate (PDTC), an antioxidant and inhibitor of transcription factor nuclear factor kappa-B (NF-kappaB), has been reported to reduce inflammation and apoptosis. Because PDTC was recently found to protect in various models of adult brain ischemia with a wide therapeutic time window, we tested the effect of PDTC in a rodent model of neonatal hypoxia-ischemia (HI) brain injury. T2-weighed magnetic resonance imaging (T2-MRI) 7 days after the insult showed that a single PDTC (50 mg/kg) injection 2.5 h after the HI reduced the mean brain infarct size by 59%. PDTC reduced the HI-induced dephosphorylation of Akt and glycogen synthase kinase-3beta (GSK-3beta), expression of cleaved caspase-3, and nuclear translocation of NF-kappaB in the neonatal brain. PDTC targeted directly neurons, as PDTC reduced hypoxia-reoxygenation-induced cell death in pure hippocampal neuronal cultures. It is suggested that in addition to the previously indicated NF-kappaB inhibition as a protective mechanism of PDTC treatment, PDTC may reduce HI-induced brain injury at least partially by acting as an antioxidant, which reduces the Akt-GSK-3beta pathway of apoptotic cell death. The clinically approved PDTC and its analogues may be beneficial after HI insults with a reasonable time window.

4-Hydroxyestradiol induces oxidative stress and apoptosis in human mammary epithelial cells: possible protection by NF-kappaB and ERK/MAPK

Catechol estrogens, the hydroxylated metabolites of 17beta-estradiol (E2), have been considered to be implicated in estrogen-induced carcinogenesis. 4-Hydroxyestradiol (4-OHE2), an oxidized metabolite of E2 formed preferentially by cytochrome P450 1B1, reacts with DNA to form depurinating adducts thereby exerting genotoxicity and carcinogenicity. 4-OHE2 undergoes 2-electron oxidation to quinone via semiquinone, and during this process, reactive oxygen species (ROS) can be generated to cause DNA damage and cell death. In the present study, 4-OHE2 was found to elicit cytotoxicity in cultured human mammary epithelial (MCF-10A) cells, which was blocked by the antioxidant trolox. MCF-10A cells treated with 4-OHE2 exhibited increased intracellular ROS accumulation and 8-oxo-7,8-dihydroxy-2'-deoxyguanosine formation, and underwent apoptosis as determined by poly(ADP-ribose)polymerase cleavage and disruption of mitochondrial transmembrane potential. The redox-sensitive transcription factor nuclear factor kappaB (NF-kappaB) was transiently activated by 4-OHE2 treatment. Cotreatment of MCF-10A cells with the NF-kappaB inhibitor, L-1-tosylamido-2-phenylethyl chloromethyl ketone, exacerbated 4-OHE2-induced cell death. 4-OHE2 also caused transient activation of extracellular signal-regulated protein kinases (ERK) involved in transmitting cell survival or death signals. A pharmacological inhibitor of ERK aggravated the 4-OHE2-induced cytotoxicity, supporting the pivotal role of ERK in protecting against catechol estrogen-induced oxidative cell death.

NF-kappaB is required for survival of immature auditory hair cells in vitro

Damage to auditory hair cells in the inner ear as a consequence of aging, disease, acoustic trauma, or exposure to ototoxins underlies most cases of hearing impairment. Because the mammalian ear cannot replace damaged hair cells, loss of hearing is irreversible and progressive throughout life. One of the current goals of inner ear biology is to develop therapeutic strategies to prevent hair cell degeneration. Although important progress has been made in discovering factors that mediate hair cell death, very little is known about the molecular pathway(s) that signal survival. Here we considered the role of NF-kappaB, a ubiquitous transcription factor that plays a major role in the regulation of many apoptosis- and stress-related genes, in mediating hair cell survival. NF-kappaB was detected in a constitutively active form in the organ of Corti of 5-day-old rats. Selective inhibition of NF-kappaB through use of a cell-permeable inhibitory peptide in vitro caused massive degeneration of hair cells within 24 h of inhibitor application. Hair cell death occurred through an apoptotic pathway through activation of caspase-3 and may involve transcriptional down-regulation of the gadd45beta gene, an anti-apoptotic NF-kappaB target. In view of our results, it seems likely that NF-kappaB may participate in normal hair cell function.

Development of beta-amyloid-induced neurodegeneration in Alzheimer's disease and novel neuroprotective strategies

Alzheimer's disease (AD) is a form of dementia in which people develop rapid neurodegeneration, complete loss of cognitive abilities, and are likely to die prematurely. At present, no treatment for AD is known. One of the hallmarks in the development of AD is the aggregation of amyloid protein fragments in the brain, and much evidence points towards beta-amyloid fragments being one of the main causes of the neurodegenerative processes. This review summarises the present concepts and theories on how AD develops, and lists the evidence that supports them. A cascade of biochemical events is initiated that ultimately leads to neuronal death involving an imbalance of intracellular calcium homeostasis via activation of calcium channels, intracellular calcium stores, and subsequent production of free radicals by calcium-sensitive enzymes. Secondary processes include inflammatory responses that produce more free radicals and the induction of apoptosis. Recently, several new strategies have been proposed to try to ameliorate the neurodegenerative developments associated with AD. These include the activation of neuronal growth factor receptors and insulin-like receptors, both of which have neuroprotective properties. Furthermore, the role of cholesterol and potential protective properties of cholesterol-lowering drugs are under intense investigation. Other promising strategies include the inhibition of beta- and gamma-secretases which produce beta-amyloid, activation of proteases that degrade beta-amyloid, glutamate receptor selective drugs, antioxidants, and metal chelating agents, all of which prevent formation of plaques. Novel drugs that act at different levels of the neurodegenerative processes show great promise to reduce neurodegeneration. They could help to prolong the time of unimpaired cognitive abilities of people who develop AD, allowing them to lead an independent life.

Regulation of the human taurine transporter by oxidative stress in retinal pigment epithelial cells stably transformed to overexpress aldose reductase

In diabetes, overexpression of aldose reductase (AR) and consequent glucose-induced impairment of antioxidant defense systems may predispose to oxidative stress and the development of diabetic complications, but the mechanisms are poorly understood. Taurine (2-aminoethanesulfonic acid) functions as an antioxidant, osmolyte, and calcium modulator such that its intracellular depletion could promote cytotoxicity in diabetes. The relationships of oxidative stress and basal AR gene expression to Na+-taurine cotransporter (TT) gene expression, protein abundance, and TT activity were therefore explored in low AR-expressing human retinal pigment epithelial (RPE) 47 cells and RPE 47 cells stably transformed to overexpress AR (RPE 75). Changes in TT gene expression were determined using a 4.6-kb TT promoter-luciferase fusion gene. Compared with RPE 47 cells, in high AR-expressing RPE 75 cells, TT promoter activity was decreased by 46%, which was prevented by an AR inhibitor. TT promoter activity increased up to 900% by prooxidant exposure, which was associated with increased TT peptide abundance and taurine transport. However, induction of TT promoter activity by oxidative stress was attenuated in high AR-expressing cells and partially corrected by AR inhibitor. Finally, exposure of RPE 75 cells to high glucose increased oxidative stress, but down-regulated TT expression. These studies demonstrate for the first time that the TT is regulated by oxidative stress and that overexpression of AR and high glucose impair this response. Abnormal expression of AR may therefore impair antioxidant defense, which may determine tissue susceptibility to chronic diabetic complications.

The p75 neurotrophin receptor in human development and disease

The functional effects of nerve growth factor (NGF) and its precursor, pro-NGF, are thought to be mediated through binding of these ligands to one or both of their receptors, TrkA and p75NTR. While the signaling pathways and downstream effects of NGF binding to TrkA are reasonably well known, those related to the binding of NGF and pro-NGF to p75NTR are less well understood. Furthermore, p75NTR appears to play functional roles that are unrelated to its ability to bind NGF and pro-NGF, some of which are ligand-independent and others of which are dependent upon binding to other neurotrophins. As these functional roles and their biochemical mechanisms become better known, the importance of p75NTR, related receptors, and both extracellular ligands and intracellular interactors and effectors for human development and health has become increasingly apparent. A complete understanding of p75NTR and its cellular partners is best served by approaching the remaining questions from both sides, with studies of function in normal states and studies of dysfunction in aberrant states mutually informing one another.