Nuclear factor-kappa B contributes to excitotoxin-induced apoptosis in rat striatum

Caspase-1 inhibitor Ac-YVAD-CHO attenuates quinolinic acid-induced increases in p53 and apoptosis in rat striatum

AIM

To study the effects of the caspase-1 inhibitor Ac-YVAD-CHO on quinolinic acid (QA)-induced apoptosis.

METHODS

Rats were pre-treated with intrastriatal infusion of Ac-YVAD-CHO (2-8 microg) before intrastriatal injection of QA (60 nmol). Striatal total proteins, genomic DNA, and nuclear proteins were isolated. The effects of Ac-YVAD-CHO on QA-induced caspase-1 activity, internucleosomal DNA fragmentation, IkappaB-alpha degradation, NF-kappaB, and AP-1 activation, and increases in p53 protein levels were measured with enzyme assays, agarose gel electrophoresis, electrophoresis mobility shift assays, and Western blot analysis.

RESULTS

Pre-treatment with Ac-YVAD-CHO inhibited QA-induced internucleosomal DNA fragmentation. Ac-YVAD-CHO inhibited QA-induced increases in caspase-1 activity and p53 protein levels, but had no effect on QA-induced IkappaB-alpha degradation, NF-kappaB or AP-1 activation.

CONCLUSION

Caspase-1 is involved in QA-induced p53 upregulation but not IkappaB-alpha degradation. Inhibition of caspase-1 attenuates QA-induced apoptosis in rat striatum.

Delivery of bioactive molecules into the cell: the Trojan horse approach

In recent years, vast amounts of data on the mechanisms of neural de- and regeneration have accumulated. However, only in disproportionally few cases has this led to efficient therapies for human patients. Part of the problem is to deliver cell death-averting genes or gene products across the blood-brain barrier (BBB) and cellular membranes. The discovery of Antennapedia (Antp)-mediated transduction of heterologous proteins into cells in 1992 and other "Trojan horse peptides" raised hopes that often-frustrating attempts to deliver proteins would now be history. The demonstration that proteins fused to the Tat protein transduction domain (PTD) are capable of crossing the BBB may revolutionize molecular research and neurobiological therapy. However, it was only recently that PTD-mediated delivery of proteins with therapeutic potential has been achieved in models of neural degeneration in nerve trauma and ischemia. Several groups have published the first positive results using protein transduction domains for the delivery of therapeutic proteins in relevant animal models of human neurological disorders. Here, we give an extensive review of peptide-mediated protein transduction from its early beginnings to new advances, discuss their application, with particular focus on a critical evaluation of the limitations of the method, as well as alternative approaches. Besides applications in neurobiology, a large number of reports using PTD in other systems are included as well. Because each protein requires an individual purification scheme that yields sufficient quantities of soluble, transducible material, the neurobiologist will benefit from the experiences of other researchers in the growing field of protein transduction.

Ethyl pyruvate protects PC12 cells from dopamine-induced apoptosis

Pyruvate acid can protect cells against oxidative damage. However, its instability limits its usefulness as a therapeutic agent. In this study, we examined the effect of ethyl pyruvate, an aliphatic ester derived from pyruvate acid, on dopamine-induced cytotoxicity in rat pheochromocytoma PC12 cells. The results demonstrated that dopamine induced apoptosis in PC12 cells accompanied with increases of intercellular reactive oxygen species, nuclear translocation of nuclear transcription factor kappa B (NF-kappaB) and expression of p53 and decrease of mitochondrial transmembrane potential. Ethyl pyruvate markedly reduced the dopamine-induced production of reactive oxygen species, nuclear translocation of NF-kappaB, upregulation of p53, loss of mitochondrial transmembrane potential and apoptosis in PC12 cells. The results suggested that ethyl pyruvate might protect PC12 cells against dopamine by suppressing intercellular oxidative stress and modulating key signal pathways of apoptosis, and that ethyl pyruvate might be used as a potential therapeutic agent for Parkinson's disease.

N-Propargyl-1 (R)-aminoindan, rasagiline, increases glial cell line-derived neurotrophic factor (GDNF) in neuroblastoma SH-SY5Y cells through activation of NF-kappaB transcription factor

N-Propargyl-l(R)-aminoindan, rasagiline, an anti-Parkinson drug, was found to increase the protein and mRNA levels of glial cell line-derived neurotrophic factor (GDNF) in human neuroblastoma SH-SY5Y cells, whereas an analogue without a propargyl residue, aminoindan, did not. GDNF is known to protect dopaminergic neurons in animal and cellular models of Parkinson's disease, and the supplement has been tried for the treatment of degenerating dopamine neurons in Parkinsonian patients. In this paper, intracellular mechanism underlying the induction of GDNF was studied. Rasagiline induced phosphorylation of inhibitory subunit (IkappaB) of nuclear factor-kappaB (NF-kappaB), and translocation of active p65 subunit from cytoplasm into nuclei. Activation of NF-kappaB was also quantitatively determined by NF-kappaB p65 transcription assay. Sulfasalazine, an inhibitor of IkappaB kinase, suppressed the activation of NF-kappaB and the increase of GDNF by rasagiline simultaneously, further indicating the involvement of the IkappaB kinase-NF-kappaB pathway. The results on the activation of the transcription factor by rasagiline are discussed in relation to its possible application as a neuroprotective drug to halt declining of neurons in neurodegenerative disorders, such as Parkinson's and Alzheimer's diseases.

Inhibition of NFkappaB increases the efficacy of cisplatin in in vitro and in vivo ovarian cancer models

Whether or not inhibition of NFkappaB increases the efficacy of cisplatin in in vitro and in vivo ovarian cancer models was investigated. We compared the basal levels of phosphorylation of IkappaBalpha and activity of NFkappaB between cisplatin-sensitive A2780 cells and cisplatin-resistant Caov-3 cells. The basal levels of phosphorylation of IkappaBalpha and activity of NFkappaB in Caov-3 cells were significantly higher than those in A2780 cells. Cisplatin caused a more marked decrease in the phosphorylation of IkappaBalpha and activity of NFkappaB in A2780 cells than in Caov-3 cells. Thus, high basal levels of phosphorylation of IkappaBalpha and activation of NFkappaB and less marked inhibition of the phosphorylation of IkappaBalpha and activation of NFkappaB by cisplatin seem to reduce the sensitivity of cells to cisplatin. Inhibition of NFkappaB activity either by treatment with the IkappaBalpha phosphorylation inhibitor (BAY 11-7085) or a specific NFkappaB nuclear translocation inhibitor (SN-50) or by transfection of p50DeltaNLS (which lacks the nuclear localization signal domain) increased the efficacy of both the cisplatin-induced attenuation of IkappaBalpha phosphorylation and NFkappaB activity and the cisplatin-induced apoptosis. In addition, treatment with BAY 11-7085 increased the efficacy of the cisplatin-induced attenuation of both the expression of X-linked inhibitor of apoptosis protein (XIAP) and cell invasion through Matrigel. Moreover, treatment with BAY 11-7085 increased the efficacy of the cisplatin-induced inhibition of the intra-abdominal dissemination and production of ascites using athymic nude mice inoculated intraperitoneally with Caov-3 cells. These results suggest that combination therapy of cisplatin with the NFkappaB inhibitor should increase the therapeutic efficacy of cisplatin.

NF-kappaB site interacts with Sp factors and up-regulates the NR1 promoter during neuronal differentiation

The NR1 gene undergoes induction in neurogenesis mainly via promoter de-repression, and up-regulation during neuronal differentiation by undefined mechanism(s). Here, we show that in the distal region the NR1 promoter has an active NF-kappaB site sharing the consensus with the immunoglobulin (Ig)/human immunodeficiency virus NF-kappaB site. Mutation of this site significantly reduced NR1 promoter up-regulation during neuronal differentiation of P19 cells. Electrophoretic mobility shift assays revealed that P19 nuclei constitutively contained p50 and that neuronal differentiation not only increased nuclear p50 but also induced p65 nuclear translocation. Responding to this change was an up-regulation of NF-kappaB-dependent promoter activity. However, inhibition of NF-kappaB nuclear translocation by an IkappaBalpha super-repressor or decoy DNA only moderately inhibited NR1 promoter up-regulation. Interestingly, the NR1 NF-kappaB site strongly interacted with Sp3/Sp1, instead of NF-kappaB factors, in P19 nuclear extracts. This interaction was reduced for Sp3 following neuronal differentiation, accompanied by dynamic expression of Sp factors. Cotransfection of Sp factors (Sp1, 3, or 4) upregulated the NR1 NF-kappaB site dramatically in differentiated neurons, but only moderately in undifferentiated P19 cells. This up-regulation was strong for Sp1 in differentiated cells and for Sp3 in undifferentiated cells. Chromatin-immunoprecipitation assays further demonstrated that Sp1 and Sp3 interacted with the NR1 NF-kappaB site in situ, and Sp3 lost its interaction after neuronal differentiation. We conclude that the NF-kappaB site positively regulates the NR1 promoter during neuronal differentiation via interacting mainly with Sp factors and neuronal differentiation reduces the effect of Sp3 factor on this site.

Injury‐induced NF‐κB activation in the hippocampus: implications for neuronal survival

Nuclear factor (NF)-kappaB p50 protein is involved in promoting survival in hippocampal neurons after trimethyltin (TMT)-injury. In the current study, hippocampal NF-kappaB activity was examined and quantitated from transgenic kappaB-lacZ reporter mice after chemical-induced injury. NF-kappaB activity was localized primarily to hippocampal neurons and significantly elevated over that in saline-treated mice between 4 and 21 days after TMT injection. Seven days after TMT injection, a timepoint of elevated NF-kappaB activity, gene expression in the hippocampus was studied by microarray analysis through comparison of expression profiles between treated nontransgenic and p50-null mice with their saline-injected controls. Seventeen genes increased in nontransgenic TMT-treated mice relative to saline-treated as well as showing no increase in p50-null mice, indicating a role for p50 in their regulation. One of these genes, the Na+, K+-ATPase-gamma subunit, was detected in brain for the first time. Several of the genes modulated by NF-kappaB are potentially related to neuroplasticity, providing additional evidence that this transcription factor is a neuroprotective signal in the hippocampus.

Expression of Nuclear Factor-Kappa B and Placental Apoptosis in Pregnancies Complicated with Intrauterine Growth Restriction and Preeclampsia: An Immunohistochemical Study

Preeclampsia affects 7-10% of all pregnancies, and is a major cause of maternal and fetal morbidity and mortality. Although enhanced apoptosis is well known in placentas with preeclampsia, the role of transcription factor nuclear factor-kappa B (NF-kappa B) in the process is still being debated. In this work, we investigate the relationship between NF-kappa B expression and trophoblastic cell apoptosis in pregnancies complicated with preeclampsia or intrauterine growth restriction (IUGR) by immunohistochemical analysis of NF-kappa B and three apoptosis related markers: bcl-2, caspase-3, and M30 CytoDeath antibody that identifies early apoptotic changes in the cytoskeleton related to action of caspase. The study was conducted on placental samples from 19 preeclamptic, 5 IUGR-complicated and 10 normal pregnant women. The three conclusions from the statistical analysis of the data are obtained; (i) Significantly higher expression of NF-kappa B in IUGR-complicated (p = 0.003) and preeclamptic placentas (p = 0.004) than the control placentas, (ii) significantly higher M30 index and caspase 3 expression in IUGR and preeclampsia placentas (p = 0.003), and (iii) decreased expression of bcl-2 in IUGR and preeclampsia placentas (p = 0.001). Based on these observations, we suggest that increased trophoblastic apoptosis is at least partially induced by NF-kappa B and reduced bcl-2 expression.

Caffeic acid phenethyl ester (CAPE) prevents inflammatory stress in organotypic hippocampal slice cultures

Caffeic acid phenethyl ester (CAPE) is an antioxidant component of propolis, a natural product secreted by honeybee. Recent literature shows that CAPE inhibits nuclear factor kappa B (NFkappaB) activation in cell lines. Since NFkappaB was shown to be a crucial factor in neuroinflammation and to be associated with some neuropathologies, CAPE might reduce these disorders in brain too and have therapeutic applications. To test this hypothesis we used a model of endotoxic insult (interferon-gamma, followed by lipopolysaccharide) on rat organotypic hippocampal cultures. Cerebral inflammatory responses were strongly inhibited by CAPE (100 microM): reductions of NFkappaB nuclear activity, tumor necrosis factor alpha and nitric oxide productions were observed. At the dose of maximal effects (100 microM), an increase of cAMP-responsive element binding protein (CREB) activity, which anti-inflammatory role is well known, was seen. We compared CAPE effects with those of other drugs: anti-inflammatory as acetyl-salicylate and dexamethasone (glucocorticoid), antioxidant as pyrrolidine dithiocarbamate, or selective permeant inhibitor of NFkappaB as SN 50 peptide. These studies lead us to conclude that CAPE presents an interesting and original neuropharmacological profile compared to these drugs and might be helpful in the prevention of neurotoxic events due to excessive inflammatory reaction in brain. CAPE interferes with several effectors of neuroinflammation that might have complementary and synergic effects and allows a rather durable control since an acute treatment at the time of endotoxin exposure allows to control inflammatory factors for over 48 h.

Activation of p38 plays a pivotal role in the inhibitory effect of lipopolysaccharide and interleukin-1 beta on long term potentiation in rat dentate gyrus

Lipopolysaccharide (LPS), a component of the cell wall of Gram-negative bacteria, has been shown to induce profound changes both peripherally and centrally. It has recently been reported that intraperitoneal injection of LPS inhibited long term potentiation (LTP) in perforant path-granule cell synapses and that this effect was coupled with an increase in the concentration of the proinflammatory cytokine, interleukin-1 beta (IL-1 beta). The LPS-induced effects were abrogated by inhibition of caspase-1, suggesting that IL-1 beta may mediate the effects of LPS. Here we report that the inhibition of LTP induced by LPS and IL-1 beta was coupled with stimulation of the stress-activated protein kinase p38 in hippocampus and entorhinal cortex and that this effect was abrogated by the p38 inhibitor SB203580, while the effect of LPS was markedly attenuated in C57BL/6 IL-1RI-/- mice. The data also indicate that activation of the transcription factor, nuclear factor kappa B (NF kappa B), may play a role, since the inhibitory effect of LPS and IL-1 beta on LTP was attenuated by the NF kappa B inhibitor, SN50; consistently, LPS and IL-1 beta led to activation of NF kappa B in entorhinal cortex. We suggest that one consequence of these LPS and IL-1 beta-induced changes is a compromise in glutamate release in dentate gyrus, which was coupled with the inhibition of LTP. The evidence is consistent with the idea that the LPS-induced impairment in LTP is mediated by IL-1 beta and is a consequence of activation of p38.

The novel neuroprotective action of sulfasalazine through blockade of NMDA receptors

Sulfasalazine is widely used to treat inflammatory diseases. Besides anti-inflammatory actions such as blockade of nuclear factor-kappaB and cyclooxygenases, we found that 30 to 1000 micro M sulfasalazine dose dependently blocked N-methyl-D-aspartate receptor-mediated excitotoxicity without intervening kainate or alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid neurotoxicity. The neuroprotective effects of sulfasalazine were attributable to prevention of Ca(2+) influx and accumulation through N-methyl-D-aspartate receptors as a low-affinity antagonist. The systemic administration of sulfasalazine reduced neuronal death following transient cerebral and retinal ischemia in adult rat. The present findings suggest that the neuroprotective action of sulfasalazine can be therapeutically applied to halt devastating neuronal death following hypoxic ischemia, trauma, and neurodegenerative diseases.

Signal transduction and neurosurvival in experimental models of brain injury

Brain injury and neurodegenerative disease are linked by their primary pathological consequence-death of neurons. Current approaches for the treatment of neurodegeneration are limited. In this review, we discuss animal models of human brain injury and molecular biological data that have been obtained from their analysis. In particular, signal transduction pathways that are associated with neurosurvival following injury to the brain are presented and discussed.

Apoptosis in cerebellar granule neurons is associated with reduced interaction between CREB-binding protein and NF-kappaB

Cerebellar granule neurons undergo apoptosis when switched from medium containing depolarizing levels of potassium (high K+ medium, HK) to medium containing low K+ (LK). NF-kappaB, a ubiquitously expressed transcription factor, is involved in the survival-promoting effects of HK. However, neither the expression nor the intracellular localization of the five NF-kappaB proteins, or of IkappaB-alpha and IkappaB-beta, are altered in neurons primed to undergo apoptosis by LK, suggesting that uncommon mechanisms regulate NF-kappaB activity in granule neurons. In this study, we show that p65 interacts with the transcriptional co-activator, CREB-binding protein (CBP), in healthy neurons. The decrease in NF-kappaB transcriptional activity caused by LK treatment is accompanied by a reduction in the interaction between p65 and CBP, an alteration that is accompanied by hyperphosporylation of CBP. LK-induced CBP hyperphosphorylation can be mimicked by inhibitors of protein phosphatase (PP) 2A and PP2A-like phosphatases such as okadaic acid and cantharidin, which also causes a reduction in p65-CBP association. In addition, treatment with these inhibitors induces cell death. Treatment with high concentrations of the broad-spectrum kinase inhibitor staurosporine prevents LK-mediated CBP hyperphosphorylation and inhibits cell death. In vitro kinase assays using glutathione-S-transferase (GST)-CBP fusion proteins map the LK-regulated site of phosphorylation to a region spanning residues 1662-1840 of CBP. Our results are consistent with possibility that LK-induced apoptosis is triggered by CBP hyperphosphorylation, an alteration that causes the dissociation of CBP and NF-kappaB.

Characterization of the molecular events following impairment of NF-kappaB-driven transcription in neurons

Nuclear factor-kappaB (NF-kappaB) is a transcription factor with a pivotal role in neuronal homeostasis. Indeed, NF-kappaB trans-activates several antiapoptotic genes in neurons and inhibition of NF-kappaB transcriptional activity triggers neuronal apoptosis. However, the exact mechanisms by which neurons undergo apoptosis in conditions of NF-kappaB inhibition are poorly understood. To further clarify how NF-kappaB operates in neurons, and to gather information on the molecular events occurring during NF-kappaB inhibition-dependent neuronal apoptosis, this study evaluated the effects of recently identified NF-kappaB inhibitors such as parthenolide, SN50, BAY 11-7082 and helenalin on primary cultures of rat cortical neurons. Data show that NF-kappaB was constitutively activated in neurons, and demonstrate for the first time that drug-dependent NF-kappaB inhibition induced rapid mitochondrial release of cytochrome c, caspase-9 and -3 activation, poly(ADP-ribose) polymerase-1 cleavage, membrane blebbing and nuclear fragmentation, without evidence of procaspase-8 and Bid processing. Interestingly, a burst of Akt activation occurred in neurons exposed to NF-kappaB inhibitors. These events were preceded by selective reduction of mRNAs of NF-kappaB-dependent, antiapoptotic Bcl-2 family members such as Bcl-x(L), Bcl-2 and, in particular, A1/Bfl-1. The present study reports a novel, detailed temporal analysis of the molecular events following impairment of NF-kappaB-driven transcription in neurons and demonstrates that inhibition of constitutive neuronal NF-kappaB activity triggers selective activation of the intrinsic apoptotic program.

Prostaglandin A1 inhibits rotenone-induced apoptosis in SH-SY5Y cells

The degeneration of nigral dopamine neurons in Parkinson's disease (PD) reportedly involves a defect in brain mitochondrial complex I in association with the activation of nuclear factor-kappaB (NF-kappaB) and caspase-3. To elucidate molecular mechanisms possibly linking these events, as well as to evaluate the neuroprotective potential of the cyclopentenone prostaglandin A1 (PGA1), an inducer of heat shock proteins (HSPs), we exposed human dopaminergic SH-SY5Y cells to the complex I inhibitor rotenone. Dose-dependent apoptosis was preceded by the nuclear translocation of NF-kappaB and then the activation of caspase-3 over the ensuing 24 h. PGA1 increased the expression of HSP70 and HSP27 and protected against rotenone-induced apoptosis, without increasing necrotic death. PGA1 blocked the rotenone-induced nuclear translocation of NF-kappaB and attenuated, but did not abolish, the caspase-3 elevation. Unexpectedly, the caspase-3 inhibitor, Ac-DEVD.CHO (DEVD), at a concentration that completely prevented the caspase-3 elevation produced by rotenone, failed to protect against apoptosis. These results suggest that complex I deficiency in dopamine cells can induce apoptosis by a process involving early NF-kappaB nuclear translocation and caspase-3 activation. PGA1 appears to protect against rotenone-induced cell death by inducing HSPs and blocking nuclear translocation of NF-kappaB in a process that attenuates caspase-3 activation, but is not mediated by its inhibition.

Oxidative modulation of nuclear factor-kappaB in human cells expressing mutant fALS-typical superoxide dismutases

Previous evidence supports the notion of a redox regulation of protein phosphatase calcineurin that might be relevant for neurodegenerative processes where an imbalance between generation and removal of reactive oxygen species occurs. We have recently observed that calcineurin activity is depressed in human neuroblastoma cells expressing Cu,Zn superoxide dismutase (SOD1) mutant G93A and in brain areas from G93A transgenic mice, and that mutant G93A-SOD1 oxidatively inactivates calcineurin in vitro. We have studied the possibility that, by interfering directly with calcineurin activity, mutant SOD1 can modulate pathways of signal transduction mediated by redox-sensitive transcription factors. In this paper, we report a calcineurin-dependent activation of nuclear factor-kappaB (NF-kappaB) induced by the expression of familial amyotrophic lateral sclerosis (fALS)-SOD1s in human neuroblastoma cell lines. Alteration of the phosphorylation state of IkappaBalpha (the inhibitor of NF-kappaB translocation into the nucleus) and induction of cyclooxygenase 2 are consistent with the up-regulation of this transcription factor in this system. All of these modifications might be relevant to signaling pathways involved in the pathogenesis of fALS.

Constitutive nuclear factor-kappaB activity is crucial for human retinoblastoma cell viability

Retinoblastoma (Rb) is the most common intraocular malignancy of childhood. Although systemic and intrathecal chemotherapy with local and cranial radiotherapy have improved overall survival, the prognosis for patients with central nervous system involvement is still poor. We investigated the role of the transcription factor nuclear factor (NF)-kappaB, which promotes cell survival in several other models, in the pathophysiology of Rb. The human Rb cell lines Y79 and WERI-Rb1 were treated with the cell permeable peptide SN50, that specifically inhibits the transcriptional activity of NF-kappaB by blocking its translocation into the nucleus. We found that NF-kappaB inhibition up-regulated Bax; down-regulated the anti-apoptotic proteins Bcl-2, A1, and cIAP-2; and induced loss of the mitochondrial transmembrane potential and caspase-independent, calpain-dependent apoptosis in Rb cells. Inhibition of the p38 kinase sensitized cells to SN50-induced cell death, whereas insulin-like growth factor-1 activated NF-kappaB and attenuated the proapoptotic effect of SN50. Finally, NF-kappaB inhibition sensitized Rb cells to doxorubicin. In conclusion, inhibition of NF-kappaB activity in Rb cells leads to loss of mitochondrial transmembrane potential and caspase-independent, calpain-dependent apoptosis. Therapeutic strategies targeting NF-kappaB could be beneficial in the clinical management of Rb, either alone or in combination with conventional chemotherapy.

Propapoptotic effects of NF-kappaB in LNCaP prostate cancer cells lead to serine protease activation

LNCaP prostate cancer cells are resistant to induction of apoptosis by gamma-irradiation and partially sensitive to TNF-alpha or FAS antibody, irradiation sensitizes cells to apoptosis induced by FAS antibody or TNF-alpha. LNCaP cell clones stably expressing IkappaBalpha super repressor were resistant to apoptosis induced by death ligands in the presence or absence of irradiation. IkappaBalpha super repressor expression also increased clonogenic survival after exposure to TNF-alpha+irradiation, but had no effect on survival after irradiation alone. IkappaBalpha super repressor expression blocked the increase of whole cell and cell surface FAS expression induced by TNF-alpha, but did not effect induction of FAS expression and cell surface FAS expression that resulted from irradiation. In cells expressing IkappaBalpha super repressor there was diminished activation of caspases-8 and -7 and diminished production of proscaspases-8 and -7, usually required for death induction in LNCaP cells. Peptide inhibitors of caspase activation complemented the IkappaBalpha super repressor inhibition of apoptosis, but peptide inhibitors of serine proteases had no effect on LNCaP cells expressing IkappaBalpha super repressor. Moreover, cleavage of a serine protease substrate was induced by treatment of LNCaP cells with TNF-alpha and irradiation. The data suggest that in LNCaP cells NF-kappaB mediates a proapoptotic pathway that leads to activation of proapoptotic serine proteases.

Activation of NF-kappaB and upregulation of intracellular anti-apoptotic proteins via the IGF-1/Akt signaling in human multiple myeloma cells: therapeutic implications

Interleukin-6 (IL-6) and insulin-like growth factor-1 (IGF-1) promote the proliferation of multiple myeloma (MM) cells and protect them against dexamethasone (Dex)-induced apoptosis. We have previously shown that Apo2 ligand/TNF-Related apoptosis inducing ligand (Apo2L/TRAIL) induces apoptosis of MM cells, including cells either sensitive or resistant to Dex and cytotoxic drugs, and overcomes the growth and survival effect of IL-6; conversely, NF-kappaB transcriptional activity attenuates their Apo2L/TRAIL-sensitivity. In the current study, we demonstrate that IGF-1 stimulates sustained activation of NF-kappaB and Akt; induces phosphorylation of the FKHRL-1 Forkhead transcription factor; upregulates a series of intracellular anti-apoptotic proteins including FLIP, survivin, cIAP-2, A1/Bfl-1, and XIAP; and decreases Apo2L/TRAIL-sensitivity of MM cells. In contrast, IL-6 does not cause sustained NF-kappaB activation, induces less pronounced Akt activation and FKHRL-1 phosphorylation than IGF-1, and increases the expression of only survivin. Forced overexpression of constitutively active Akt in MM-1S cells reduced their sensitivity to Apo2L/TRAIL and to doxorubicin (Doxo). In contrast, the Akt inhibitor IL-6-Hydroxymethyl-chiro-inositol 2-(R)-2-O-methyl-3-O-octadecylcarbonate induced cell death of both Dex- and Doxo-sensitive and -resistant cells; opposed the protective effect of constitutive Akt activity against Apo2L/TRAIL; and abrogated the NF-kappaB activation, increase of anti-apoptotic proteins and protection against Apo2L/TRAIL induced by IGF-1. These findings therefore define an important role of the Akt pathway in modulating tumor cell responsiveness to Apo2L/TRAIL, delineate molecular mechanisms for the survival effects of IGF-1, and characterize differential pathophysiologic sequelae of IGF-1 vs IL-6 on MM cells. Importantly, they provide the basis for future clinical trials in MM combining conventional or novel agents with strategies designed to neutralize IGF-1.

Lack of NF-kappaB p50 exacerbates degeneration of hippocampal neurons after chemical exposure and impairs learning

The roles of activated NF-kappaB subunits in the CNS remain to be discerned. Members of this family of transcription factors are essential to diverse physiological processes and can be activated by pathogens, stress, pharmacological agents, and trauma. We are particularly interested in long-term NF-kappaB activation and its involvement in neuroplastic changes in the brain resulting from acquisition of memory as well as injury. Here, we use lesioning by the limbic-specific neurotoxicant trimethyltin (TMT) as a model in which to examine activation of the NF-kappaB p50 subunit before, during, and after neuronal degeneration. Neurons in wild-type mice that survived TMT-induced injury contained activated p50 and did not label with Fluoro-Jade, a histochemical marker of degenerating neurons. Granule cells of the wild-type dentate gyrus subregion, an area particularly vulnerable to TMT-induced degeneration, contained less activated p50 protein than CA regions. We compared the extent of degeneration in wild-type and p50-null mice and found a fivefold increase in death of hippocampal neurons in mice lacking p50. The hippocampus is key to processes of learning and memory, and NF-kappaB has reported involvement in these processes. The enhanced hippocampal degeneration in p50-null mice prompted us to evaluate their basal learning abilities, and we discovered that difficulties in task acquisition were an additional consequence of p50 ablation. These results indicate that absence of p50 negatively modulates learning ability as well as hippocampal responsiveness to brain injury after a chemical-induced lesion.

Biologic sequelae of nuclear factor-kappaB blockade in multiple myeloma: therapeutic applications

The transcription factor nuclear factor-kappaB (NF-kappaB) confers significant survival potential in a variety of tumors. Several established or novel anti-multiple myeloma (anti-MM) agents, such as dexamethasone, thalidomide, and proteasome inhibitors (PS-341), inhibit NF-kappaB activity as part of their diverse actions. However, studies to date have not delineated the effects of specific inhibition of NF-kappaB activity in MM. We therefore investigated the effect of SN50, a cell-permeable specific inhibitor of NF-kappaB nuclear translocation and activity, on MM cells. SN50 induced apoptosis in MM cell lines and patient cells; down-regulated expression of Bcl-2, A1, X-chromosome-linked inhibitor-of-apoptosis protein (XIAP), cellular inhibitor-of-apoptosis protein 1 (cIAP-1), cIAP-2, and survivin; up-regulated Bax; increased mitochondrial cytochrome c release into the cytoplasm; and activated caspase-9 and caspase-3, but not caspase-8. We have previously demonstrated that tumor necrosis factor-alpha (TNF-alpha) is present locally in the bone marrow microenvironment and induces NF-kappaB-dependent up-regulation of adhesion molecules on both MM cells and bone marrow stromal cells, with resultant increased adhesion. In this study, TNF-alpha alone induced NF-kappaB nuclear translocation, cIAP-1 and cIAP-2 up-regulation, and MM cell proliferation; in contrast, SN50 pretreatment sensitized MM cells to TNF-alpha-induced apoptosis and cleavage of caspase-8 and caspase-3, similar to our previous finding of SN50-induced sensitization to apoptosis induced by the TNF-alpha family member TNF-related apoptosis-inducing ligand (TRAIL)/Apo2L. Moreover, SN50 inhibited TNF-alpha-induced expression of another NF-kappaB target gene, intercellular adhesion molecule-1. Although the p38 inhibitor PD169316 did not directly kill MM cells, it potentiated the apoptotic effect of SN50, suggesting an interaction between the p38 and NF-kappaB pathways. Our results therefore demonstrate that NF-kappaB activity in MM cells promotes tumor-cell survival and protects against apoptotic stimuli. These studies provide the framework for targeting NF-kappaB activity in novel biologically based therapies for MM.

Basal levels and patterns of anticancer drug-induced activation of nuclear factor-kappaB (NF-kappaB), and its attenuation by tamoxifen, dexamethasone, and curcumin in carcinoma cells

Nuclear factor-kappaB (NF-kappaB) has been implicated in the development of drug resistance in cancer cells. We systematically examined the baseline levels of NF-kappaB activity of representative carcinoma cell lines, and the change of NF-kappaB activity in response to a challenge with four major anticancer drugs (doxorubicin, 5-fluorouracil, cisplatin, and paclitaxel). We found that the basal level of NF-kappaB activity was heterogeneous and roughly correlated with drug resistance. When challenged with various drugs, all the cell lines examined responded with a transient activation of NF-kappaB which then declined to basal level despite variation in the concentration of the agent and the timing of the treatment. In contrast to tumor necrosis factor-alpha (TNF-alpha), which activates NF-kappaB in minutes, NF-kappaB activation induced by anticancer drugs usually occurred more than 1hr after stimulation. A gradual increase of total NF-kappaB and its nuclear translocation, and cytoplasmic translocation of nuclear IkappaBalpha and its degradation were involved in this process. In particular, when cells were pretreated with common biologic modulators such as tamoxifen, dexamethasone, and curcumin, the doxorubicin-induced NF-kappaB activation was attenuated significantly. This inhibition may play a role in sensitizing cancer cells to chemotherapeutic drugs. This study has demonstrated that activation of NF-kappaB is a general cellular response to anticancer drugs, and the mechanism of activation appears to be distinct from that induced by TNF-alpha. These observations may have implications for improving the efficacy of systemic chemotherapy for cancer patients.

NF-kappaB-mediated up-regulation of Bcl-X(S) and Bax contributes to cytochrome c release in cyanide-induced apoptosis

Cyanide induces apoptosis through cytochrome c activated caspase cascade in primary cultured cortical neurons. The underlying mechanism for cytochrome c release from mitochondria after cyanide treatment is still unclear. In this study, the roles of endogenous Bcl-2 proteins in cyanide-induced apoptosis were investigated. After cyanide (100-500 microm) treatment for 24 h, two pro-apoptotic Bcl-2 proteins, Bcl-X(S) and Bax were up-regulated as shown by western blot and RT-PCR analysis. The expression levels of two antiapoptotic Bcl-2 proteins, Bcl-2 and Bcl-X(L), remained unchanged after cyanide treatment, whereas the mRNA levels of Bcl-X(S) and Bax began to increase within 2 h and their protein levels increased 6 h after treatment. NF-kappaB, a redox-sensitive transcription factor activated after cyanide treatment, is responsible for the up-regulation of Bcl-X(S) and Bax. SN50, which is a synthetic peptide that blocks translocation of NF-kappaB from cytosol to nucleus, inhibited the up-regulation of Bcl-X(S) and Bax. Similar results were obtained using a specific kappaB decoy DNA. NMDA receptor activation and reactive oxygen species (ROS) generation are upstream events of NF-kappaB activation, as blockade of these two events by MK801, l-NAME or PBN inhibited cyanide-induced up-regulation of Bcl-X(S) and Bax. Up-regulation of pro-apoptotic Bcl-X(S) and Bax contributed to cyanide-induced cytochrome c release, because SN50 and a specific Bax antisense oligodeoxynucleotide significantly reduced release of cytochrome c from mitochondria as shown by western blot analysis. It was concluded that NF-kappaB-mediated up-regulation of Bcl-X(S) and Bax is involved in regulating cytochrome c release in cyanide-induced apoptosis.

Nuclear factor kappaB activation is mediated by NMDA and non-NMDA receptor and L-type voltage-gated Ca(2+) channel following severe global ischemia in rat hippocampus

Recent studies suggest that nuclear factor NF-kappaB may be involved in excitotoxin-induced cell apopotosis. To analyze the variation of NF-kappaB, levels of NF-kappaB were measured after the rats were subjected to 30 min of four-vessel occlusion and sacrificed in selected reperfusion time points. Induction of NF-kappaB consisting mainly of p65 and p50 subunits was detected by Western blot with anti p65, p50 antibodies, respectively. DNA binding activity of NF-kappaB was performed by electrophoretic mobility-shift analysis. Our studies indicate that ischemia-induced NF-kappaB nuclear translocation is time-dependent. Inductions or binding activity of NF-kappaB in nucleus increased about 10-fold from 6 to 12 h as compared with that of the control group, then gradually declined in the following 24, 72 h. To further analyze the regulation by ionotropic glutamate receptor and L-type voltage-gated Ca(2+) channel (L-VGCC) in vivo, N-methyl-D-aspartate (NMDA) receptor antagonist ketamine, alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate/kainate receptor antagonist 6,7-dinitroquinoxaline-2,3 (1H,4H)-dione and L-VGCC antagonist nifedipine were given 20 min prior to 30 min of ischemia. The NF-kappaB nuclear translocation was completely blocked by these three antagonists in a dose-dependent manner after ischemia/reperfusion 6 h. Increased phosphorylation of the NF-kappaB regulatory unit IkappaB-alpha was detected by Western blot. Decrement of IkappaB-alpha was found after 3 h reperfusion in the cytoplasm following global ischemia, which was also blocked by such three antagonists. These results illustrate that glutamate-gated ionotropic NMDA or non-NMDA receptors and voltage-gated Ca(2+) channels are important routes to mediate NF-kappaB activation during brain ischemic injury. Active NF-kappaB may attend the excitotoxin-induced cell death in turn. Our studies also suggest that IkappaB-alpha is an important regulatory unit that controls the activation of NF-kappaB after its phosphorylation and degradation and resynthesis in rat hippocampus following global ischemia.

Automated analysis of global ischemia-induced CA1 neuronal death using terminal UTP nick end labeling (TUNEL)

In the brain, DNA fragmentation is associated with apoptotic cell death following ischemic/excitotoxic damage. Fragmented DNA can be detected in situ by labeling the 3'OH termini of the internucleosomal generated fragments with deoxynucleotides, through a process known as terminal deoxynucleotidyl transferase (TdT) dUTP nick end labeling, or TUNEL. TUNEL is frequently being used to assess neuronal death following cerebral ischemia in a number of animal models. However, conventional techniques for TUNEL can be time consuming, and are often subjective and thus can lead to inconsistencies among investigators. Moreover, the lack of tools for its quantification and standardization limits the use of this technique in assessing the magnitude of cell death. In the present report, we describe an improved higher throughput technique for TUNEL staining at room temperature on a BioGenex automated stainer, and its subsequent quantitative analysis using NORTHERN ECLIPSE, an imaging analysis program. Its implementation allows us to effectively quantify TUNEL positive cells in the CA1 region of the hippocampus following global forebrain ischemia in rats. We conclude that this general histological technique can be applied to the study of cell death in numerous other experimental models.

NF-kappaB and IkappaBalpha expression following traumatic brain injury to the immature rat brain

NF-kappaB is one of the most important modulators of stress and inflammatory gene expression in the nervous system. In the adult brain, NF-kappaB upregulation has been demonstrated in neurons and glial cells in response to experimental injury and neuropathological disorders, where it has been related to both neurodegenerative and neuroprotective activities. Accordingly, the aim of this study was to evaluate the cellular and temporal patterns of NF-kappaB activation and the expression of its endogenous inhibitor IkappaBalpha following traumatic brain injury (TBI) during the early postnatal weeks, when the brain presents elevated levels of plasticity and neuroprotection. Our results showed that cortical trauma to the 9-day-old rat brain induced a very fast upregulation of NF-kappaB, which was maximal within the first 24 hours after injury. NF-kappaB was mainly observed in neuronal cells of the degenerating cortex as well as in astrocytes located in the corpus callosum adjacent to the injury, where a pulse-like pattern of microglial NF-kappaB activation was also found. In addition, astrocytes of the corpus callosum, and microglial cells to a lower extent, also showed de novo expression of IkappaBalpha within the time of NF-kappaB activation. This study suggests an important role of NF-kappaB activation in the early mechanisms of neuronal death or survival, as well as in the development of the glial and inflammatory responses following traumatic injury to the immature rat brain.

Dual role of the NF-kappaB transcription factor in the death of immature neurons

We have previously shown that the extent of axotomy-induced death of retinal ganglion cells is reduced by cycloheximide, an inhibitor of protein synthesis, and that an earlier sublethal oxidative insult induced by buthionine sulfoximine, a glutathione synthesis inhibitor, enhances the protective effects of cycloheximide. Thus, axotomy-induced ganglion cell death seems to involve an interaction between the redox status and genetic expression. The redox-sensitive transcription factor nuclear factor-kappaB (NF-kappaB) is a logical candidate for providing this interaction. In the present study, we injected intraocularly selective inhibitors of NF-kappaB in chick embryos either unlesioned, or after a unilateral tectal lesion, which axotomizes ganglion cells. The number of dying cells in the retina contralateral to the lesion was reduced in embryos receiving NF-kappaB inhibitors as compared with vehicle-injected controls. In contrast, the same NF-kappaB inhibitors administered as pretreatment before intraocular injection of buthionine sulfoximine and cycloheximide drastically raised neuronal death and induced fulgurant degenerative changes in the retina. The most parsimonious interpretation of our results is that in axotomized retinal ganglion cells of chick embryos NF-kappaB may have either death-promoting or death-inhibiting effects. We propose a theoretical model to explain these dual effects assuming the existence of parallel death pathways differently affected by NF-kappaB. These results may have implications for future redox-based therapeutic strategies for neuroprotection.

Lithium suppresses excitotoxicity-induced striatal lesions in a rat model of Huntington's disease

Huntington's disease is a progressive, inherited neurodegenerative disorder characterized by the loss of subsets of neurons primarily in the striatum. In this study, we assessed the neuroprotective effect of lithium against striatal lesion formation in a rat model of Huntington's disease in which quinolinic acid was unilaterally infused into the striatum. For this purpose, we used a dopamine receptor autoradiography and glutamic acid decarboxylase mRNA in situ hybridization analysis, methods previously shown to be adequate for quantitative analysis of the excitotoxin-induced striatal lesion size. Here we demonstrated that subcutaneous injections of LiCl for 16 days prior to quinolinic acid infusion considerably reduced the size of quinolinic acid-induced striatal lesion. Furthermore, these lithium pre-treatments also decreased the number of striatal neurons labeled with the terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling assay. Immunohistochemistry and western blotting demonstrated that lithium-elicited neuroprotection was associated with an increase in Bcl-2 protein levels. Our results raise the possibility that lithium may be considered as a neuroprotective agent in treatment of neurodegenerative diseases such as Huntington's disease.

IkappaB kinase activation is involved in regulation of paclitaxel-induced apoptosis in human tumor cell lines

Paclitaxel (Taxol), a naturally occurring antimitotic agent, has shown significant cell-killing activity against human solid tumor cells through induction of apoptosis. The molecular mechanism underlying paclitaxel-induced apoptosis is not entirely clear. Using the unique inhibitory effect of glucocorticoids on paclitaxel-induced apoptosis, we recently discovered that paclitaxel-induced inhibitor kappaBalpha (IkappaBalpha) degradation and nuclear factor-kappaB (NF-kappaB) activation might contribute to the mediation of paclitaxel-induced apoptosis. In this study, using a novel IkappaBalpha phosphorylation inhibitor, we demonstrated that the blockage of paclitaxel-induced IkappaBalpha degradation inhibited apoptotic cell death in human breast cancer BCap37 and ovarian cancer OV2008 cell lines. Furthermore, in vitro kinase assays showed that the activity of IkappaB kinase (IKK), which is responsible for the phosphorylation and degradation of IkappaB proteins, was significantly activated by paclitaxel in these paclitaxel-sensitive tumor cells. Stable transfection of a mutant IkappaBalpha lacking Ser(32) and Ser(36) that was insensitive to IKK-mediated phosphorylation and degradation resulted in reduced sensitivity of tumor cells to paclitaxel-induced apoptosis. Moreover, we also found that the expression of mitogen-activated protein kinase/extracellular signal-regulated kinase kinase kinase 1, an upstream regulator of IKK, was up-regulated by paclitaxel. These findings suggest that the activation of IKK might play a critical role in the regulation of paclitaxel-induced NF-kappaB activation that subsequently mediates paclitaxel-induced apoptotic cell death in solid tumor cells.

Inhibition of intimal hyperplasia after balloon injury in rat carotid artery model using cis-element 'decoy' of nuclear factor-kappaB binding site as a novel molecular strategy

The transcription factor, NFkB, plays a pivotal role in the coordinated transactivation of cytokine and adhesion molecule genes involved in atherosclerosis and lesion formation after vascular injury. We hypothesized that synthetic double-stranded DNA with high affinity for NFkB may be introduced as a 'decoy' cis element to bind the transcription factor, and block gene activation, resulting in an effective therapeutic agent for treating intimal hyperplasia. In vivo transfection of NFkB decoy oligodeoxynucleotides (ODN) into balloon-injured rat carotid artery resulted in the inhibition of neointimal formation at 14 days after injury as compared with vessels transfected with scrambled ODN (P < 0.01). It is of importance to note that in the vessels transfected with NFkB decoy ODN, the expression of p53, a pro-apoptotic gene, was upregulated in neointimal area, followed by increased apoptosis at 14 days. In addition, gene expression of ICAM-1 and VCAM-1 was markedly decreased in blood vessels transfected with NFkB decoy ODN compared with scrambled ODN, whereas balloon injury induced ICAM and VCAM expression in the neointimal area. More importantly, the migration of macrophages and T-lymphocytes into the neointima and media was significantly inhibited by NFkB decoy ODN as compared with scrambled ODN. Here, we demonstrated that in vivo transfer of NFkB decoy ODN successfully inhibited neointimal formation after balloon injury, accompanied by (1) induction of apoptosis through p53 upregulation, and (2) inhibition of local inflammatory actions through the downregulation of adhesion molecules. These results suggest that decoy treatment against NFkB provides a new therapeutic strategy to inhibit neointimal hyperplasia after angioplasty.

Triflusal posttreatment inhibits glial nuclear factor-kappaB, downregulates the glial response, and is neuroprotective in an excitotoxic injury model in postnatal brain

BACKGROUND AND PURPOSE

Nuclear factor-kappaB (NF-kappaB) and the signal transducer and activator of transcription 3 (STAT3) are important transcription factors regulating inflammatory mechanisms and the glial response to neural injury, determining lesion outcome. In this study we evaluate the ability of triflusal (2-acetoxy-4-trifluoromethylbenzoic acid), an antiplatelet agent inhibitor of NF-kappaB activation, to improve lesion outcome after excitotoxic damage to the immature brain.

METHODS

Postnatal day 9 rats received an intracortical injection of the excitotoxin N-methyl-D-aspartate (NMDA) and oral administration of triflusal (30 mg/kg) either as 3 doses before NMDA injection (pretreatment) or as a single dose 8 hours after NMDA injection (posttreatment). After survival times of 10 and 24 hours, brains were processed for toluidine blue staining, tomato lectin histochemistry, and glial fibrillary acidic protein, NF-kappaB, and STAT3 immunocytochemistry.

RESULTS

NMDA-lesioned animals that were not treated with triflusal showed activation of NF-kappaB in neuronal cells at first and in glial cells subsequently. Animals that received pretreatment with triflusal showed a strong downregulation of neuronal and glial NF-kappaB but a similar development of the glial response and an equivalent lesion volume compared with nontreated animals. In contrast, animals receiving triflusal posttreatment showed increased early neuronal NF-kappaB but a reduction in the subsequent glial NF-kappaB, accompanied by important downregulation of the microglial and astroglial response and a drastic reduction in the lesion size. STAT3 activation was not affected by triflusal treatment.

CONCLUSIONS

Triflusal posttreatment diminishes glial NF-kappaB, downregulates the glial response, and improves the lesion outcome, suggesting a neuroprotective role of this compound against excitotoxic injury in the immature brain.

Molecular pathways involved in the neurotoxicity of 6-OHDA, dopamine and MPTP: contribution to the apoptotic theory in Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder characterized by a preferential loss of the dopaminergic neurons of the substantia nigra pars compacta. Although the etiology of PD is unknown, major biochemical processes such as oxidative stress and mitochondrial inhibition are largely described. However, despite these findings, the actual therapeutics are essentially symptomatical and are not able to block the degenerative process. Recent histological studies performed on brains from PD patients suggest that nigral cell death could be apoptotic. However, since post-mortem studies do not allow precise determination of the sequence of events leading to this apoptotic cell death, the molecular pathways involved in this process have been essentially studied on experimental models reproducing the human disease. These latter are created by using neurotoxic compounds such as 6-hydroxydopamine (6-OHDA), 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) or dopamine (DA). Extensive study of these models have shown that they mimick, in vitro and in vivo, the histological and/or the biochemical characteristics of PD and thus help to define important cellular actors of cell death presumably critical for the nigral degeneration. This review reports recent data concerning the biochemical and molecular apoptotic mechanisms underlying the experimental models of PD and correlates them to the phenomena occurring in human disease.

Suppression of cytokine production and neural cell death by the anti-inflammatory alkaloid cepharanthine: a potential agent against HIV-1 encephalopathy

Inflammatory cytokines and human immunodeficiency virus type 1 (HIV-1) gp120 are considered to play an important role in the pathogenesis of HIV-1-associated CNS disorders. These substances are produced predominantly by HIV-1-infected or activated macrophages and microglia in the brain and induce neural cell death. Cepharanthine is a biscoclaurine alkaloid isolated from Stephania cepharantha Hayata and has been shown to have anti-inflammatory, anti-allergic, and immunomodulatory activities in vivo. We previously reported that this compound could inhibit tumor necrosis factor (TNF)-alpha- or phorbol 12-myristate 13-acetate-induced HIV-1 replication in latently infected U1 cells through the inhibition of nuclear factor-kappaB, a potent inducer of HIV-1 gene expression. In the present study, we demonstrated that cepharanthine suppresses the production of inflammatory cytokines and a chemokine, i.e. TNF-alpha, interleukin (IL)-1beta, IL-6, and IL-8, in human monocytic cell cultures, including primary monocyte/macrophage cultures. This effect of cepharanthine was concentration-dependent, and significant suppression was observed at 0.1 microg/mL. Furthermore, the compound also inhibited TNF-alpha- and gp120-induced death of differentiated human neuroblastoma cells at a concentration of 0.04 to 0.2 microg/mL. It penetrates the blood-brain barrier, and a medicine containing cepharanthine as a major component has been used in Japan for the treatment of patients with chronic inflammatory diseases. Thus, cepharanthine should be investigated further for its therapeutic and prophylactic potential in HIV-1-associated CNS disorders.

Enhanced expression of I-kappaB with neurofibrillary pathology in Alzheimer's disease

Inflammatory and immune responses are known to be involved in the pathogenesis of Alzheimer's disease (AD). NF-kappaB is a major transcription factor that plays a central role in the inflammatory and immune responses and is regulated by I-kappaB through an autoregulatory feedback system. Southwestern immunohistochemistry and immunohistochemistry in our study demonstrated activated NF-kappaB in AD brains. However, there was also activated expression of I-kappaB in a distribution that corresponded to the neurofibrillary pathology of AD. These observations indicate that disruption of the autoregulatory mechanism of NF-kappaB in brain regions with neurofibrillary pathology may play a role in the pathogenesis of AD.

6-hydroxydopamine-induced nuclear factor-kappa B activation in PC12 cells

The involvement of nuclear Factor-kappa B (NF-kappa B) transcription factor in PC12 cell death triggered by the dopaminergic neurotoxin 6-hydroxydopamine (6-OHDA) was investigated. Results show that oxidative stress generated by 6-OHDA activates NF-kappa B. When the NF-kappa B activation was inhibited by parthenolide, PC12 cell death induced by 6-OHDA was significantly increased, thus suggesting an involvement of this transcription factor in a protective mechanism against 6-OHDA toxicity. To further assess this hypothesis, we studied the involvement of NF-kappa B in the protective effect of two anti-apoptotic genes, bcl-2 and bfl-1. Although Bcl-2 and Bfl-1 expression normally protects PC12 cells from 6-OHDA, parthenolide strongly decreased the beneficial effects afforded by transgene expression. These results suggest: (1) that the transcription factor NF-kappa B is likely associated with the protection of catecholaminergic PC12 cells and (2) that the protective effects afforded by bcl-2 and bfl-1 expression may be dependent on NF-kappa activation.

Preconditioning-induced neuroprotection is mediated by reactive oxygen species and activation of the transcription factor nuclear factor-kappaB

Preconditioning by a sublethal stimulus induces tolerance to a subsequent, otherwise lethal insult and it has been suggested that reactive oxygen species (ROS) are involved in this phenomenon. In the present study, we determined whether preconditioning activates the transcription factor nuclear factor-kappaB (NF-kappaB) and how this activation contributes to preconditioning-induced inhibition of neuronal apoptosis. Preconditioning was performed by incubating mixed cultures of neurons and astrocytes from neonatal rat hippocampus with xanthine/xanthine oxidase or FeSO4 for 15 min followed by 24 h of recovery which protected the neurons against subsequent staurosporine-induced (200 nM, 24 h) apoptosis. The cellular ROS content increased during preconditioning, but returned to basal levels after removal of xanthine/xanthine oxidase or FeSO4. We detected a transient activation of NF-kappaB 4 h after preconditioning as shown by immunocytochemistry, by a decrease in the protein level of IkappaBalpha as well as by electrophoretic mobility shift assay. Preconditioning-mediated neuroprotection was abolished by antioxidants, inhibitors of NF-kappaB activation and cycloheximide suggesting the involvement of ROS, an activation of NF-kappaB and de novo protein synthesis in preconditioning-mediated rescue pathways. Furthermore, preconditioning increased the protein level of Mn-superoxide dismutase which could be blocked by antioxidants, cycloheximide and kappaB decoy DNA. Our data suggest that inhibition of staurosporine-induced neuronal apoptosis by preconditioning with xanthine/xanthine oxidase or FeSO4 involves an activation of NF-kappaB and an increase in the protein level of Mn-superoxide dismutase.

Endothelial apoptosis induced by oxidative stress through activation of NF-kappaB: antiapoptotic effect of antioxidant agents on endothelial cells

Injury of endothelial cells has been assumed to be an initial trigger of the development of atherosclerosis. In this study, we investigated the molecular mechanisms of endothelial cell death induced by hypoxia, which leads to oxidative stress. To study the relation between hypoxia-induced cell death and activation of nuclear factor-kappaB (NF-kappaB) in a hypoxic state, we evaluated the effect of 2 antioxidant drugs, probucol and pyrrolidine dithiocarbamate (PDTC), on human endothelial apoptosis. Although hypoxic treatment of human aortic endothelial cells resulted in a significant decrease in cell number and a significant increase in apoptotic cells compared with that of cells under normoxia (P<0.01), treatment with probucol (50 micromol/L) or PDTC (100 micromol/L) significantly attenuated the decrease in cell number (P<0.01) and was accompanied by inhibition of NF-kappaB activation. Furthermore, downregulation of bcl-2 caused by hypoxia was inhibited by these drugs. We further investigated the translocation of bax protein from the cytoplasm to the mitochondrial heavy fraction membrane, as translocation of bax protein is considered to be a determinant of apoptosis. Interestingly, we found that antioxidant treatment inhibited the translocation of bax protein caused by hypoxia. Moreover, upregulation of p53, a proapoptotic molecule, was observed in hypoxia, whereas treatment with probucol attenuated the expression of p53 accompanied by suppression of NF-kappaB activation. These data suggest functional links between p53 and endothelial apoptosis through the activation of NF-kappaB. Overall, the current study demonstrated that oxidative stress induced apoptosis in human aortic endothelial cells through the downregulation of bcl-2, translocation of bax, and upregulation of p53, probably through NF-kappaB activation. Oxidative stress may play an important role in endothelial apoptosis mediated by hypoxia, through the activation of NF-kappaB.

Mitochondrial involvement in brain function and dysfunction: relevance to aging, neurodegenerative disorders and longevity

It is becoming increasingly evident that the mitochondrial genome may play a key role in neurodegenerative diseases. Mitochondrial dysfunction is characteristic of several neurodegenerative disorders, and evidence for mitochondria being a site of damage in neurodegenerative disorders is partially based on decreases in respiratory chain complex activities in Parkinson's disease, Alzheimer's disease, and Huntington's disease. Such defects in respiratory complex activities, possibly associated with oxidant/antioxidant balance perturbation, are thought to underlie defects in energy metabolism and induce cellular degeneration. Efficient functioning of maintenance and repair process seems to be crucial for both survival and physical quality of life. This is accomplished by a complex network of the so-called longevity assurance processes, which are composed of genes termed vitagenes. A promising approach for the identification of critical gerontogenic processes is represented by the hormesis-like positive effect of stress. In the present review, we discuss the role of energy thresholds in brain mitochondria and their implications in neurodegeneration. We then review the evidence for the role of oxidative stress in modulating the effects of mitochondrial DNA mutations on brain age-related disorders and also discuss new approaches for investigating the mechanisms of lifetime survival and longevity.

NF-kappaB activation and susceptibility to apoptosis after polyamine depletion in intestinal epithelial cells

The maintenance of intestinal mucosal integrity depends on a balance between cell renewal and cell death, including apoptosis. The natural polyamines, putrescine, spermidine, and spermine, are essential for mucosal growth, and decreasing polyamine levels cause G(1) phase growth arrest in intestinal epithelial (IEC-6) cells. The present study was done to determine changes in susceptibility of IEC-6 cells to apoptosis after depletion of cellular polyamines and to further elucidate the role of nuclear factor-kappaB (NF-kappaB) in this process. Although depletion of polyamines by alpha-difluoromethylornithine (DFMO) did not directly induce apoptosis, the susceptibility of polyamine-deficient cells to staurosporine (STS)-induced apoptosis increased significantly as measured by changes in morphological features and internucleosomal DNA fragmentation. In contrast, polyamine depletion by DFMO promoted resistance to apoptotic cell death induced by the combination of tumor necrosis factor-alpha (TNF-alpha) and cycloheximide. Depletion of cellular polyamines also increased the basal level of NF-kappaB proteins, induced NF-kappaB nuclear translocation, and activated the sequence-specific DNA binding activity. Inhibition of NF-kappaB binding activity by sulfasalazine or MG-132 not only prevented the increased susceptibility to STS-induced apoptosis but also blocked the resistance to cell death induced by TNF-alpha in combination with cycloheximide in polyamine-deficient cells. These results indicate that 1) polyamine depletion sensitizes intestinal epithelial cells to STS-induced apoptosis but promotes the resistance to TNF-alpha-induced cell death, 2) polyamine depletion induces NF-kappaB activation, and 3) disruption of NF-kappaB function is associated with altered susceptibility to apoptosis induced by STS or TNF-alpha. These findings suggest that increased NF-kappaB activity after polyamine depletion has a proapoptotic or antiapoptotic effect on intestinal epithelial cells determined by the nature of the death stimulus.

Walker-256 tumor growth causes oxidative stress in rat brain

The elevated rate of oxygen consumption and high amount of polyunsaturated fatty acids make the central nervous system vulnerable to oxidative stress. The effect of Walker-256 tumor growth on oxi-reduction indexes in the hypothalamus (HT), cortex (CT), hippocampus (HC) and cerebellum (CB) of male Wistar rats was investigated. The presence of the tumor caused an increase in thiobarbituric acid reactant substances (TBARs) in the HT, CB and HC. Due to tumor growth, the activity of glucose-6-phosphate dehydrogenase increased in the HT and CB, whereas citrate synthase activity was reduced in the HT, CT and CB. Therefore, the potential for generation of reducing power is increased in the cytosol and decreased in the mitochondria of various brain regions of Walker-256 tumor-bearing rats. These changes occurred concomitantly with an unbalance in the brain enzymatic antioxidant system. The tumor decreased the activities of catalase in the HT and CB and of glutathione peroxidase in the HT, CB and HC, and raised the CuZn-superoxide dismutase activity in the HT, CB and HC. These combined findings indicate that Walker-256 tumor growth causes oxidative stress in the brain.

Activation of nuclear transcription factor kappa B (NF-kappaB) is essential for dopamine-induced apoptosis in PC12 cells

The etiology of Parkinson's disease is still unknown, though current investigations support the notion of the pivotal involvement of oxidative stress in the process of neurodegeneration in the substantia nigra (SN). In the present study, we investigated the molecular mechanisms underlying cellular response to a challenge by dopamine, one of the local oxidative stressors in the SN. Based on studies showing that nuclear factor kappa B (NF-kappaB) is activated by oxidative stress, we studied the involvement of NF-kappaB in the toxicity of PC12 cells following dopamine exposure. We found that dopamine (0.1-0.5 m M) treatment increased the phosphorylation of the IkappaB protein, the inhibitory subunit of NF-kappaB in the cytoplasm. Immunoblot analysis demonstrated the presence of NF-kappaB-p65 protein in the nuclear fraction and its disappearance from the cytoplasmic fraction after 2 h of dopamine exposure. Dopamine-induced NF-kappaB activation was also evidenced by electromobility shift assay using radioactive labeled NF-kappaB consensus DNA sequence. Cell-permeable NF-kappaB inhibitor SN-50 rescued the cells from dopamine-induced apoptosis and showed the importance of NF-kappaB activation to the induction of apoptosis. Furthermore, flow cytometry assay demonstrated a higher level of translocated NF-kappaB-p65 in the apoptotic nuclei than in the unaffected nuclei. In conclusion, our findings suggest that NF-kappaB activation is essential to dopamine-induced apoptosis in PC12 cells and it may be involved in nigral neurodegeneration in patients with Parkinson's disease.

Induction of nitric-oxide synthase and activation of NF-kappaB by interleukin-12 p40 in microglial cells

Interleukin-12 (IL-12) is composed of two different subunits, p40 and p35. Expression of p40 mRNA but not that of p35 mRNA in excessive amount in the central nervous system of patients with multiple sclerosis (MS) suggests that IL-12 p40 may have a role in the pathogenesis of the disease. However, the mode of action of p40 is completely unknown. Because nitric oxide produced from the induction of nitric-oxide synthase (iNOS) also plays a vital role in the pathophysiology of MS, the present study was undertaken to explore the role of p40 in the induction of NO production and the expression of iNOS in microglia. Both IL-12 and p40(2), the p40 homodimer, dose-dependently induced the production of NO in BV-2 microglial cells. This induction of NO production was accompanied by an induction of iNOS protein and mRNA. Induction of NO production by the expression of mouse p40 cDNA but not that of the mouse p35 cDNA suggests that the p40 but not the p35 subunit of IL-12 is involved in the expression of iNOS. In addition to BV-2 glial cells, p40(2) also induced the production of NO in mouse primary microglia and peritoneal macrophages. However, both IL-12 and p40(2) were unable to induce the production of NO in mouse primary astrocytes. Because activation of NF-kappaB is important for the expression of iNOS, we investigated the effect of p40(2) on the activation of NF-kappaB. Induction of the DNA binding as well as the transcriptional activity of NF-kappaB by p40(2) and inhibition of p40(2)-induced expression of iNOS by SN50, a cell-permeable peptide carrying the nuclear localization sequence of p50 NF-kappaB, but not by SN50M, a nonfunctional peptide mutant, suggests that p40(2) induces the expression of iNOS through the activation of NF-kappaB. This study delineates a novel role of IL-12 p40 in inducing the expression of iNOS in microglial cells, which may participate in the pathogenesis of neuroinflammatory diseases.

Evidence for non-oxidative dopamine cytotoxicity: potent activation of NF-kappa B and lack of protection by anti-oxidants

A stable aromatic acid decarboxylase expressing the Chinese hamster ovary cell line was developed to study the cytotoxic properties of intracellular and extracellular dopamine. The relative impermeability of cells to dopamine, but not to L-DOPA, allows the differentiation of extracellular and intracellular dopamine cytotoxicity. In contrast to extracellular dopamine, intracellular dopamine toxicity was resistant to antioxidant protection, and did not require melanin formation for its toxicity. Furthermore, we demonstrated a rapid and potent activation of the stress-inducible transcription factor NF-kappa B by intracellular dopamine, which was also largely insensitive to antioxidant inhibition. A distinctly slower and less potent NF-kappa B activation by extracellular dopamine was blocked by antioxidants and acetylsalicylic acid. Our results indicate the existence of a non-oxidative mechanism of dopamine cytotoxicity. Mitigating intracellular dopamine toxicity could be a novel strategy of slowing the progressive degeneration of dopaminergic neurons in Parkinson's disease.

Nuclear factor-kappaB-mediated X-linked inhibitor of apoptosis protein expression prevents rat granulosa cells from tumor necrosis factor alpha-induced apoptosis

Although X-linked inhibitor of apoptosis protein (Xiap) is an important intracellular suppressor of apoptosis in a variety of cell types and is present in ovary, its physiological role in follicular development remains unclear. The purpose of the present studies was to examine the modulatory role of Xiap in the proapoptotic action of tumor necrosis factor-alpha (TNFalpha) in rat granulosa cells. Granulosa cells from equine CG-primed immature rats were plated in RPMI 1640 medium containing 10% FCS and subsequently cultured in serum-free RPMI in the absence or presence of TNFalpha (20 ng/ml), the protein synthesis inhibitor cycloheximide (10 microM), and/or adenoviral Xiap sense or antisense complementary DNA. TNFalpha alone failed to induce granulosa cell death, but in the presence of cycloheximide, it markedly increased the number of apoptotic granulosa cells (as assessed by in situ terminal deoxynucleotidyl transferase-mediated deox-UTPbiotin end labeling and DNA fragmentation analysis). Western analysis indicated that TNFalpha alone increased the Xiap protein level, a response significantly reduced by adenoviral Xiap antisense expression. Down-regulation of Xiap expression by antisense complementary DNA induced granulosa cell apoptosis, which was potentiated by the cytokine. Inhibition of nuclear factor-kappaB activation by N-acetyl-cysteine and SN50 suppressed Xiap protein expression and enhanced apoptosis induced by TNFalpha. The latter phenomenon was readily attenuated by adenoviral Xiap sense expression. In conclusion, these findings suggest that Xiap is an important intracellular modulator of the TNFalpha death signaling pathway in granulosa cells. Its expression is regulated by the TNFalpha via a nuclear factor-kappaB-mediated mechanism.

NF-kappaB transcription factors: critical regulators of hematopoiesis and neuronal survival

The Rel/NF-kappaB family of transcription factors has been implicated in the regulation of genes involved in immune and inflammatory responses, and of processes such as cell survival, apoptosis, development, differentiation, cell growth and neoplastic transformation. In this report we will summarize recent findings which highlight critical roles of NF-kappaB in different processes in hematopoietic and neuronal cells.

Differential induction of NF-kappaB activity and neural cell death by antidepressants in vitro

Tricyclic antidepressants and selective serotonin reuptake inhibitors are here shown to induce cell death in a neural cell line. The exposure to these drugs led to increased generation of reactive oxygen species and a concomitant reduction of intracellular glutathione levels. Furthermore, these antidepressants induced DNA fragmentation and increased the transcriptional and DNA-binding activity of NF-kappaB. In contrast, treatment with type A and B monoamine oxidase inhibitors did not induce changes in NF-kappaB activity and did not exert a detrimental influence on cell viability. These results indicate that some antidepressant drugs may cause both oxidative stress and changes in cellular antioxidative capacity, resulting in altered NF-kappaB activity and, ultimately, cell death.