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

The Multiple Roles of Autophagy in Neural Function and Diseases

Autophagy involves the sequestration and delivery of cytoplasmic materials to lysosomes, where proteins, lipids, and organelles are degraded and recycled. According to the way the cytoplasmic components are engulfed, autophagy can be divided into macroautophagy, microautophagy, and chaperone-mediated autophagy. Recently, many studies have found that autophagy plays an important role in neurological diseases, including Alzheimer's disease, Parkinson's disease, Huntington's disease, neuronal excitotoxicity, and cerebral ischemia. Autophagy maintains cell homeostasis in the nervous system via degradation of misfolded proteins, elimination of damaged organelles, and regulation of apoptosis and inflammation. AMPK-mTOR, Beclin 1, TP53, endoplasmic reticulum stress, and other signal pathways are involved in the regulation of autophagy and can be used as potential therapeutic targets for neurological diseases. Here, we discuss the role, functions, and signal pathways of autophagy in neurological diseases, which will shed light on the pathogenic mechanisms of neurological diseases and suggest novel targets for therapies.

The Effect of Super-Repressor IkB-Loaded Exosomes (Exo-srIκBs) in Chronic Post-Ischemia Pain (CPIP) Models

Complex regional pain syndrome (CRPS) is a condition associated with neuropathic pain that causes significant impairment of daily activities and functioning. Nuclear factor kappa B (NFκB) is thought to play an important role in the mechanism of CRPS. Recently, exosomes loaded with super-repressor inhibitory kappa B (Exo-srIκB, IκB; inhibitor of NFκB) have been shown to have potential anti-inflammatory effects in various inflammatory disease models. We investigated the therapeutic effect of Exo-srIκB on a rodent model with chronic post-ischemia pain (CPIP), a representative animal model of Type I CRPS. After intraperitoneal injection of a vehicle, Exo-srIκB, and pregabalin, the paw withdrawal threshold (PWT) was evaluated up to 48 h. Administration of Exo-srIκB increased PWT compared to the vehicle and pregabalin, and the relative densities of p-IκB and IκB showed significant changes compared to the vehicle 24 h after Exo-srIκB injection. The levels of several cytokines and chemokines were reduced by the administration of Exo-srIκB in mice with CPIP. In conclusion, our results showed more specifically the role of NFκB in the pathogenesis of CRPS and provided a theoretical background for novel treatment options for CRPS.

Quinolinic Acid-Induced Huntington Disease-Like Symptoms Mitigated by Potent Free Radical Scavenger Edaravone-a Pilot Study on Neurobehavioral, Biochemical, and Histological Approach in Male Wistar Rats

In this study, we demonstrated for the first time the neuroprotective role of edaravone (Eda) (5 and 10 mg/kg b.w.), a potent free radical scavenger against the unilateral stereotaxic induction of quinolinic acid (QA) (300 nm/4 μl saline)-induced Huntington disease (HD)-like symptoms in behavioral, biochemical, and histological features in male Wistar rats striatum. QA induction, which mimics the early stage of HD, commonly causes oxidative stress to the cell and decreases the antioxidant defense mechanism by altering the level of lipid peroxidation (LPO), protein carbonyls, and nitrate concentration (NO) and the activities of glutathione family enzymes (GPx, GST, GR) and acetyl choline esterase concentration (AChE) which was found to be ameliorated by Eda treatment in both the tested doses 5 and 10 mg/kg b.w. in the significance of P < 0.05 and P < 0.01, respectively. Finally histopathological analysis by hematoxylin and eosin stain concluded the promising neurodefensive role of Eda in rat striatum at the dosage of 10 mg/kg b.w., with the decreased tissue damage and the number of damaged granular cells when compared to QA-induced groups.

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.

Microglia activation contributes to quinolinic acid-induced neuronal excitotoxicity through TNF-α

It has been reported that activation of NF-κB is involved in excitotoxicity; however, it is not fully understood how NF-κB contributes to excitotoxicity. The aim of this study is to investigate if NF-κB contributes to quinolinic acid (QA)-mediated excitotoxicity through activation of microglia. In the cultured primary cortical neurons and microglia BV-2 cells, the effects of QA on cell survival, NF-κB expression and cytokines production were investigated. The effects of BV-2-conditioned medium (BCM) on primary cortical neurons were examined. The effects of pyrrolidine dithiocarbamate (PDTC), an inhibitor of NF-κB, and minocycline (MC), an inhibitor of microglia activation, on QA-induced excitotoxicity were assessed. QA-induced NF-κB activation and TNF-α secretion, and the roles of TNF-α in excitotoxicity were studied. QA at the concentration below 1 mM had no apparent toxic effects on cultured primary neurons or BV-2 cells. However, addition of QA-primed BCM to primary neurons did aggravate QA-induced excitotoxicity. The exacerbation of QA-induced excitotoxicity by BCM was partially ameliorated by inhibiting NF-κB and microglia activation. QA induced activation of NF-κB and upregulation of TNF-α in BV-2 cells. Addition of recombinant TNF-α mimicked QA-induced excitotoxic effects on neurons, and neutralizing TNF-α with specific antibodies partially abolished exacerbation of QA-induced excitotoxicity by BCM. These studies suggested that QA activated microglia and upregulated TNF-α through NF-κB pathway in microglia. The microglia-mediated inflammatory pathway contributed, at least in part, to QA-induced excitotoxicity.

Suppression of LASP-1 attenuates the carcinogenesis of prostatic cancer cell lines: Key role of the NF-κB pathway

Prostate cancer (PCa) is one of the most frequently diagnosed cancers among males worldwide and causes a considerable number of deaths each year. One of the newly explored targets for the development of therapies against PCa is LIM and SH3 protein 1 (LASP-1). In the present study, the function of LASP-1 in the oncogenesis and metastasis of PCa was investigated using a series of in vitro experiments. Moreover, the mechanism through which LASP-1 exerted its effect on the carcinogenesis of PCa was also explored. The expression levels of LASP-1 in clinical PCa specimens were determined both at the mRNA and protein levels. Afterwards, the activity of LASP-1 in human PCa cell lines PC3 and DU145 was inhibited using a short hairpin RNA (shRNA) interfering method. The effects of LASP-1 knockdown on the cell growth, apoptosis, cell cycle distribution, migration and invasion were assessed. It was demonstrated that the expression of LASP-1 was significantly higher in the clinical PCa tissues than the level in the corresponding para-carcinoma tissues. Following the knockdown of the LASP-1 gene in human PCa cell lines, the viability, migration and invasion of the cancer cells were decreased. It was also demonstrated that the change in the cell viability and motile ability were associated with an induction of cell apoptosis and G1 phase cell cycle arrest. Based on the results of the detection of the expression of NF-κB-related factors, it was indicated that LASP-1 may affect the carcinogenesis of PCa through a NF-κB inhibition-dependent manner. Although the detailed explanation of the mechanism of LASP-1 in the carcinogenesis of PCa requires further elucidation, the present study highlights the potential of LASP-1 as a promising therapeutic target to ameliorate the oncogenesis and metastasis of PCa.

Review : Gene Expression after Cerebral Ischemia

Global and focal ischemias induce a variety of gene families, including immediate early genes, cytokines, neurotransmitter receptors, and heat-shock proteins. The Janus-like effects of several of these gene prod ucts promote neuronal survival and degeneration. Therefore, determining the molecular pathways respon sible for the differential regulation of these genes is of paramount importance. The discovery of apoptosis as a mediator of delayed neuronal death has led to the identification of a number of other genes involved in postischemic brain damage. Future neuroprotective therapies for cerebral ischemia may be directed at preventing alterations in gene expression. NEUROSCIENTIST 5:238-253, 1999

Oct-2 transcription factor binding activity and expression up-regulation in rat cerebral ischaemia is associated with a diminution of neuronal damage in vitro

Brain plasticity provides a mechanism to compensate for lesions produced as a result of stroke. The present study aims to identify new transcription factors (TFs) following focal cerebral ischaemia in rat as potential therapeutic targets. A transient focal cerebral ischaemia model was used for TF-binding activity and TF-TF interaction profile analysis. A permanent focal cerebral ischaemia model was used for the transcript gene analysis and for the protein study. The identification of TF variants, mRNA analysis, and protein study was performed using conventional polymerase chain reaction (PCR), qPCR, and Western blot and immunofluorescence, respectively. Rat cortical neurons were transfected with small interfering RNA against the TF in order to study its role. The TF-binding analysis revealed a differential binding activity of the octamer family in ischaemic brain in comparison with the control brain samples both in acute and late phases. In this study, we focused on Oct-2 TF. Five of the six putative Oct-2 transcript variants are expressed in both control and ischaemic rat brain, showing a significant increase in the late phase of ischaemia. Oct-2 protein showed neuronal localisation both in control and ischaemic rat brain cortical slices. Functional studies revealed that Oct-2 interacts with TFs involved in important brain processes (neuronal and vascular development) and basic cellular functions and that Oct-2 knockdown promotes neuronal injury. The present study shows that Oct-2 expression and binding activity increase in the late phase of cerebral ischaemia and finds Oct-2 to be involved in reducing ischaemic-mediated neuronal injury.

Glycemia-dependent nuclear factor κB activation contributes to mechanical allodynia in rats with chronic postischemia pain

BACKGROUND

Ischemia-reperfusion injury causes chronic postischemia pain (CPIP), and rats with higher glycemia during ischemia-reperfusion injury exhibit increased allodynia. Glycemia-induced elevation of nuclear factor κB (NFκB) may contribute to increased allodynia.

METHODS

Glycemia during a 3-h ischemia-reperfusion injury was manipulated by: normal feeding; or normal feeding with administration of insulin; dextrose; or insulin/dextrose. In these groups, NFκB was measured in ipsilateral hind paw muscle and spinal dorsal horn by enzyme-linked immunosorbent assay (ELISA), and SN50, an NFκB inhibitor, was administered to determine its differential antiallodynic effects depending on glycemia.

RESULTS

CPIP fed/insulin rats (12.03 ± 4.9 g, N = 6) had less allodynia than fed, fed/insulin/dextrose, and fed/dextrose rats (6.29 ± 3.37 g, N = 7; 4.57 ± 3.03 g, N = 6; 2.95 ± 1.10 g, N = 9), respectively. Compared with fed rats (0.209 ± 0.022 AU, N = 7), NFκB in ipsilateral plantar muscles was significantly lower for fed/insulin rats, and significantly higher for fed/dextrose rats (0.152 ± 0.053 AU, N = 6; 0.240 ± 0.057 AU, N = 7, respectively). Furthermore, NFκB in the dorsal horn of fed, fed/insulin/dextrose, and fed/dextrose rats (0.293 ± 0.049 AU; 0.267 ± 0.037 AU; 0.315 ± 0.015 AU, respectively, N = 6 for each) was significantly higher than in fed/insulin animals (0.267 ± 0.037 AU, N = 6). The antiallodynic SN50 dose-response curves of CPIP rats in the fed/insulin/dextrose, fed/dextrose, and fed conditions exhibited a rightward shift compared with the fed/insulin group. The threshold SN50 dose of CPIP fed/dextrose, fed/insulin/dextrose, and fed rats (328.94 ± 92.4 ng, 77.80 ± 44.50 ng, and 24.89 ± 17.20 ng, respectively) was higher than that for fed/insulin rats (4.06 ± 7.04 ng).

CONCLUSIONS

NFκB was activated in a glycemia-dependent manner in CPIP rats. Hypoglycemic rats were more sensitive to SN50 than rats with higher glycemia. The finding that SN50 reduces mechanical allodynia suggests that NFκB inhibitors might be useful for treating postischemia pain.

Cathepsin L plays a role in quinolinic acid-induced NF-Κb activation and excitotoxicity in rat striatal neurons

The present study seeks to investigate the role of cathepsin L in glutamate receptor-induced transcription factor nuclear factor-kappa B (NF-κB) activation and excitotoxicity in rats striatal neurons. Stereotaxic administration of the N-methyl-d-aspartate (NMDA) receptor agonist Quinolinic acid (QA) into the unilateral striatum was used to produce the in vivo excitotoxic model. Co-administration of QA and the cathepsin L inhibitor Z-FF-FMK or 1-Naphthalenesulfonyl-IW-CHO (NaphthaCHO) was used to assess the contribution of cathepsin L to QA-induced striatal neuron death. Western blot analysis and cathepsin L activity assay were used to assess the changes in the levels of cathepsin L after QA treatment. Western blot analysis was used to assess the changes in the protein levels of inhibitor of NF-κB alpha isoform (IκB-α) and phospho-IκB alpha (p-IκBα) after QA treatment. Immunohistochemical analysis was used to detect the effects of Z-FF-FMK or NaphthaCHO on QA-induced NF-κB. Western blot analysis was used to detect the effects of Z-FF-FMK or NaphthaCHO on QA-induced IκB-α phosphorylation and degradation, changes in the levels of IKKα, p-IKKα, TP53, caspase-3, beclin1, p62, and LC3II/LC3I. The results show that QA-induced loss of striatal neurons were strongly inhibited by Z-FF-FMK or NaphthaCHO. QA-induced degradation of IκB-α, NF-κB nuclear translocation, up-regulation of NF-κB responsive gene TP53, and activation of caspase-3 was strongly inhibited by Z-FF-FMK or NaphthaCHO. QA-induced increases in beclin 1, LC3II/LC3I, and down-regulation of p62 were reduced by Z-FF-FMK or NaphthaCHO. These results suggest that cathepsin L is involved in glutamate receptor-induced NF-κB activation. Cathepsin L inhibitors have neuroprotective effects by inhibiting glutamate receptor-induced IκB-α degradation and NF-κB activation.

Neuronal store-operated calcium entry pathway as a novel therapeutic target for Huntington's disease treatment

Huntington's disease (HD) is a neurodegenerative disorder caused by a polyglutamine expansion within Huntingtin (Htt) protein. In the phenotypic screen we identified a class of quinazoline-derived compounds that delayed a progression of a motor phenotype in transgenic Drosophila HD flies. We found that the store-operated calcium (Ca(2+)) entry (SOC) pathway activity is enhanced in neuronal cells expressing mutant Htt and that the identified compounds inhibit SOC pathway in HD neurons. The same compounds exerted neuroprotective effects in glutamate-toxicity assays with YAC128 medium spiny neurons primary cultures. We demonstrated a key role of TRPC1 channels in supporting SOC pathway in HD neurons. We concluded that the TRPC1-mediated neuronal SOC pathway constitutes a novel target for HD treatment and that the identified compounds represent a novel class of therapeutic agents for treatment of HD and possibly other neurodegenerative disorders.

Ketogenic diet-induced peroxisome proliferator-activated receptor-γ activation decreases neuroinflammation in the mouse hippocampus after kainic acid-induced seizures

Similar to fasting, the ketogenic diet (KD) has anti-inflammatory effects and protects against excitotoxicity-mediated neuronal cell death. Recent studies have shown that peroxisome proliferator-activated receptor (PPAR)γ has anti-inflammatory effects in seizure animal models. However, the exact mechanisms underlying the anti-inflammatory effects of the KD have not been determined for seizures. Here we investigated the effect of the KD and acetoacetate (AA) on neuroinflammation in a seizure animal model and glutamate-treated HT22 cells, respectively. Mice were fed the KD for 4 weeks and sacrificed 2 or 6h after KA injection. The KD reduced hippocampal tumor necrosis factor alpha (TNF-α) levels and nuclear factor (NF)-κB translocation into the nucleus 2h after KA treatment. KD-induced PPARγ activation was decreased by KA in neurons as assessed by western blotting and immunofluorescence. Finally, the KD inhibited cyclooxygenase (COX)-2 and microsomal prostaglandin E(2) synthase-1 (mPGES-1) expression in the hippocampus 6h after KA treatment. AA treatment also protected against glutamate-induced cell death in HT22 cells by reducing TNF-α and PPARγ-mediated COX-2 expression. Thus, the KD may inhibit neuroinflammation by suppressing a COX-2-dependent pathway via activation of PPARγ by the KD or AA.

Protection by neuroglobin and cell-penetrating peptide-mediated delivery in vivo: a decade of research. Comment on Cai et al: TAT-mediated delivery of neuroglobin protects against focal cerebral ischemia in mice. Exp Neurol. 2011; 227(1): 224-31

Over the last decade, numerous studies have suggested that neuroglobin is able to protect against the effects of ischemia. However, such results have mostly been based on models using transgenic overexpression or viral delivery. As a therapy, new technology would need to be applied to enable delivery of high concentrations of neuroglobin shortly after the patient suffers the stroke. An approach to deliver proteins in ischemia in vivo in a timely manner is the use of cell-penetrating peptides (CPP). CPP have been used in animal models for brain diseases for about a decade as well. In a recent issue of Experimental Neurology, Cai and colleagues test the effect of CPP-coupled neuroglobin in an in vivo stroke model. They find that the fusion protein protects the brain against the effect of ischemia when applied before stroke onset. Here, a concise review of neuroglobin research and the application of CPP peptides in hypoxia and ischemia is provided.

Impact of simulated microgravity on microvascular endothelial cell apoptosis

Cardiovascular deconditioning is known to occur in astronauts exposed to microgravity. Endothelial dysfunction at microcirculatory sites might contribute to cardiovascular deconditioning induced by weightlessness. Recent studies have reported changes in the morphology and gene expression of endothelial cells exposed to conditions of simulated microgravity. The present study was aimed at examining the effects of microgravity on the apoptosis of microvascular endothelial cells and the mechanism underlying these effects. We simulated a microgravity environment and found that microgravity induced microvascular endothelial cell apoptosis and that this effect was correlated with the downregulation of the PI3K/Akt pathway, increased expression of NF-κB, and depolymerization of F-actin. These findings may provide important insights into the origin of the adverse physiological changes occurring due to exposure to microgravity conditions.

NF-kappaB signaling in neurite growth and neuronal survival

The nuclear factor kappa B (NF-kappaB) transcription factor system plays multiple roles in the function of the nervous system during development and postnatal physiology. In the developing nervous system, neurite outgrowth could be regulated by both canonical and alternative NF-kappaB signaling pathways. The degree and site of NF-kappaB activation could promote or inhibit neuronal survival in a complex, signal and subunit-dependent manner. The significance and mechanistic basis of some of NF-kappaB activity in neurons have remained controversial. We discuss our current understanding and recent findings with regard to the roles of NF-kappaB in the neurite outgrowth and neuronal survival, and how NF-kappaB activation is associated with the pathophysiology of ischemic/ traumatic injuries and neurodegenerative diseases.

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

Background

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

Results

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

Conclusions

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

Obovatol enhances docetaxel-induced prostate and colon cancer cell death through inactivation of nuclear transcription factor-kappaB

Nuclear transcription factor-kappaB (NF-kappaB) is constitutively activated in prostate and colon cancers and is related with the resistance of cancer cells against chemotherapeutics. Previously, we found that obovatol, an active compound isolated from Magnolia obovata, inhibited cancer cell growth through inhibition of NF-kappaB activity. We investigated here whether obovatol could sensitize cancer cells against docetaxel through inhibition of NF-kappaB activity in prostate cancer (LNCaP and PC-3) and colon cancer (SW620 and HCT116) cells. The combination treatment with each drug at one half the respective IC(50) dose (5 microM obovatol + 5 nM docetaxel) was more effective and significant (60%-70%) in the inhibition of cancer cell growth than single treatment by each drug (20%-40%); inhibition was exerted through a significant increase of apoptosis induction (60%-80%) by the combination treatment compared to the single treatment (10%-30%). Correlating well with the synergistic inhibition (combination indices are less than 1 in all cell types), the combination significantly inhibited NF-kappaB activities as well as expression of NF-kappaB target apoptotic cell death proteins, but decreased anti-apoptotic cell death proteins. Similar combination effects of obovatol with other chemotherapeutic agents (paclitaxel, cisplatin, and doxorubicin) on the inhibition of cell growth and NF-kappaB activity were also found. These results indicate that obovatol augments cell growth inhibition by chemotherapeutics through inactivation of NF-kappaB and suggest that obovatol may have therapeutic advantages in the combination treatment with other chemotherapeutics. [Supplementary Figure: available only at http://dx.doi.org/10.1254/jphs.09048FP].

p53 induction contributes to excitotoxic neuronal death in rat striatum through apoptotic and autophagic mechanisms

The present study sought to investigate mechanisms by which p53 induction contributes to excitotoxic neuronal injury. Rats were intrastriatally administered the N-methyl-D-aspartate (NMDA) receptor agonist quinolinic acid (QA), the changes in the expression of p53 and its target genes involved in apoptosis and autophagy, including p53-upregulated modulator of apoptosis (PUMA), Bax, Bcl-2, damage-regulated autophagy modulator (DRAM) and other autophagic proteins including microtubule-associated protein 1 light chain 3 (LC3) and beclin 1 were assessed. The contribution of p53-mediated autophagy activation to apoptotic death of striatal neurons was assessed with co-administration of the nuclear factor-kappaB (NF-kappaB) inhibitor SN50, the p53 inhibitor Pifithrin-alpha (PFT-alpha) or the autophagy inhibitor 3-methyladenine (3-MA). The increased formation of autophagosomes and secondary lysosomes were observed with transmission electron microscope after excitotoxin exposure. QA induced increases in the expression of p53, PUMA, Bax and a decrease in Bcl-2. These changes were significantly attenuated by pre-treatment with SN50, PFT-alpha or 3-MA. SN50, PFT-alpha or 3-MA also reversed QA-induced upregulation of DRAM, the ratio of LC3-II/LC3-I and beclin 1 protein levels in the striatum. QA-induced internucleosomal DNA fragmentation and loss of striatal neurons were robustly inhibited by SN50, PFT-alpha or 3-MA. These results suggest that overstimulation of NMDA receptors can induce NF-kappaB-dependent expression of p53. p53 participates in excitotoxic neuronal death probably through both apoptotic and autophagic mechanisms.

Inhibition of NF-kappaB by ginsenoside Rg3 enhances the susceptibility of colon cancer cells to docetaxel

Ginsenoside Rg3, the main constituent isolated from Panax ginseng, has been of interest for use as a cancer preventive or therapeutic agent. We investigated here whether Rg3 can inhibit the activity of NF-kappaB, a key transcriptional factor constitutively activated in colon cancer that confers cancer cell resistance to chemotherapeutic agents. To investigate whether RG3 can suppress activation of NF-kappaB, and thus inhibit cancer cell growth, we examined the susceptibility of colon cancer cells (SW620 and HCT116) to treatment with Rg3 (25, 50, 75, 100 microM) and RG3-induced activation of NF-kappaB. RG3 dose-dependently inhibited cancer cell growth through induction of apoptosis and decreased NF-kappaB activity. In a further study of compounds in colon cancer, we used half of the IC(50) dose, values in combined treatments of Rg3 (50 microM) with conventional agents - docetaxel (5 nM), paclitaxel (10 nM) cisplatin (10 microM) and doxorubicin (2 microM). Compared to treatment with Rg3 or chemotherapy alone, combined treatment was more effective (i.e., there were synergistic effects) in the inhibition of cancer cell growth and induction of apoptosis and these effects were accompanied by significant inhibition of NF-kappaB activity. NF-kappaB target gene expression of apoptotic cell death proteins (Bax, caspase-3, caspase-9) was significantly enhanced, but the expression of anti-apoptotic genes and cell proliferation marker genes (Bcl-2, inhibitor of apoptosis protein (IAP-1) and X chromosome IAP (XIAP), Cox-2, c-Fos, c-Jun and cyclin D1) was significantly inhibited by the combined treatment compared to Rg3 or docetaxel alone. These results indicate that ginsenoside Rg3 inhibits NF-kappaB, and enhances the susceptibility of colon cancer cells to docetaxel and other chemotherapeutics. Thus, ginsenoside Rg3 could be useful as an anti-cancer or adjuvant anti-cancer agent.

Molecular mechanisms of excitotoxicity and their relevance to pathogenesis of neurodegenerative diseases

A pivotal role for excitotoxicity in neurodegenerative diseases is gaining increasingly more acceptance, but the underlying mechanisms through which it participates in neurodegeneration still need further investigation. Excessive activation of glutamate receptors by excitatory amino acids leads to a number of deleterious consequences, including impairment of calcium buffering, generation of free radicals, activation of the mitochondrial permeability transition and secondary excitotoxicity. Recent studies implicate excitotoxicity in a variety of neuropathological conditions, suggesting that neurodegenerative diseases with distinct genetic etiologies may share excitotoxicity as a common pathogenic pathway. Thus, understanding the pathways involved in excitotoxicity is of critical importance for the future clinical treatment of many neurodegenerative diseases. This review discusses the current understanding of excitotoxic mechanisms and how they are involved in the pathogenesis of neurodegenerative diseases.

Reduction in Cerebral Atrophy Associated with Ethyl-Eicosapentaenoic Acid Treatment in Patients with Huntington's Disease

Ultra-pure ethyl-eicosapentaenoic acid (ethyl-EPA), a semi-synthetic ethyl ester of eicosapentaenoic acid, is associated with clinical improvement in motor functioning in Huntington's disease. The aim was to determine the extent to which it might reduce the rate of progress of cerebral atrophy. High-resolution cerebral magnetic resonance imaging scans were acquired at baseline, 6 months and 1 year in up to 34 patients with stage I or II Huntington's disease who took part in a randomized, double-blind, placebo-controlled trial of ethyl-EPA. For each subject and each pair of structural images, the two-timepoint brain volume change was calculated in a double-blind manner. Significant group-level reductions in brain atrophy were observed in the head of the caudate nucleus and the posterior thalamus. These findings show that treatment with ethyl-EPA is associated with significant reduction in brain atrophy, particularly in the caudate and thalamus. No other drug tested in Huntington's disease has shown this effect.

The roles of the proteasome pathway in signal transduction and neurodegenerative diseases

There are two degradation systems in mammalian cells, autophagy/lysosomal pathway and ubiquitin-proteasome pathway. Proteasome is consist of multiple protein subunits and plays important roles in degradation of short-lived cellular proteins. Recent studies reveal that proteasomal degradation system is also involved in signal transduction and regulation of various cellular functions. Dysfunction or dysregulation of proteasomal function may thus be an important pathogenic mechanism in certain neurological disorders. This paper reviews the biological functions of proteasome in signal transduction and its potential roles in neurodegenerative diseases.

Bilobalide inhibits 6-OHDA-induced activation of NF-kappaB and loss of dopaminergic neurons in rat substantia nigra

AIM

To investigate the effects of bilobalide on the activation of NF-kappaB, and apoptosis of dopaminergic neurons induced by 6-hydroxydopamine (6-OHDA).

METHODS

A rat model of Parkinson's disease was produced with a unilateral infusion of 6-OHDA (8 mug) into the substantia nigra par compact. Bilobalide was administered 5, 10, and 20 mg/kg (ip) once a day for 7 d, starting 6 d prior to the 6- OHDA infusion. The rats were subjected to locomotor activity and rotational behavior testing 2 or 3 weeks after the 6-OHDA infusion. The expressions of tyrosine hydroxylase (TH) and NF-kappaB p65 were examined by immunofluorescence. The loss of dopaminergic neurons was detected by Nissl's staining. Terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling was used to identify apoptosis.

RESULTS

The behavioral changes due to 6-OHDA were significantly restored by bilobalide pretreatment. Bilobalide inhibited the 6-OHDA-induced loss of TH-positive neurons, decreased the activation of NF-kappaB, and protected dopaminergic neurons from apoptosis remarkably.

CONCLUSION

NF-kappaB activation contributes to the 6-OHDA-induced loss of dopaminergic neurons, and the inhibition of the NF-kappaB pathway is likely to be involved in the neuroprotective effect of bilobalide.

IDO expands human CD4+CD25high regulatory T cells by promoting maturation of LPS-treated dendritic cells

We have previously shown that human monocyte-derived dendritic cells (DC) express indoleamine 2,3-dioxygenase (IDO), as well as several other enzymes of the kynurenine pathway at the mRNA level upon maturation. The tolerogenic mechanisms of this pathway remain unclear. Here we show that LPS-treated DC metabolize tryptophan as far as quinolinate. We found that IDO contributes to LPS and TNF-alpha + poly(I:C)-induced DC maturation since IDO inhibition using two different inhibitors impairs DC maturation. IDO knock-down using short-hairpin RNA also led to diminished LPS-induced maturation. In line with these results, the tryptophan-derived catabolites 3-hydroxyanthranilic acid and 3-hydroxykynurenine increased maturation of LPS-treated DC. Concerning the molecular mechanisms of this effect, IDO acts as an intermediate pathway in LPS-induced production of reactive oxygen species and NF-kappaB activation, two processes that lead to DC maturation. Finally, we show that mature DC expand CD4(+)CD25(high) regulatory T cells in an IDO-dependent manner. In conclusion, we show that IDO constitutes an intermediate pathway in DC maturation leading to expansion of CD4(+)CD25(high) regulatory T cells.

HIV-1 envelope glycoprotein 120 induces cyclooxygenase-2 expression in astrocytoma cells through a nuclear factor-kappaB-dependent mechanism

Human immunodeficiency virus-1 gp120 alters astroglial function, which compromises the function of the nearby of neuronal cells contributing to the cognitive impairment in human immunodeficiency virus-1 infection. Cyclooxygenase (COX)-2 has been involved in this process, although the intracellular pathways and second messengers involved are yet unknown. We have investigated the role of gp120-induced COX-2 in the astrocytoma human cell line U-87, and the different pathways involved in this activation. COX-2 mRNA and protein expression were detected in gp120-stimulated cells. Moreover, gp120 induces COX-2 promoter transcription. The effect of gp120 was abrogated by a neutralizing antibody against the chemokine receptor CXCR4 neutralizing antibody. Analysis of the promoter show that deletion or mutation of a proximal nuclear factor (NF)-kappaB site completely abrogated gp120-dependent transcription. NF-kappaB but neither Activating protein-1 nor nuclear factor of activated T-cells-dependent transcription was induced by gp120, as shown by reporter and electrophoretic mobility shift assays. In addition, transfection assays with the NF-kappaB inhibitor, IkappaBalpha, prevented gp120-mediated COX-2 induction. In contrast, there was no inhibition of COX-2 promoter transcription by expressing a dominant negative c-Jun, or nuclear factor of activated T-cells constructs. The antioxidant pyrrolidine dithiocarbamate inhibited COX-2 protein expression and COX-2 transcriptional activity induced by gp120. Thus, our results indicate that gp120 induced COX-2 transcription through NF-kappaB activation in astrocytoma cells.

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

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

Triptolide inhibits NF-kappaB activation and reduces injury of donor lung induced by ischemia/reperfusion

AIM

To investigate the protective effect of triptolide (TRI) on ischemia/reperfusion-induced injury of transplanted rabbit lungs and to investigate the mechanisms underlying the actions of TRI.

METHODS

We established the rabbit lung transplantation model and studied lung injury induced by ischemia/reperfusion and the inhibitory effect of TRI on NF-kappaB. The severity of lung injury was determined by a gradual decline in PvO2, the degree of lung edema, the increase in the myeloperoxidase (MPO) activity, and the ultrastructural changes of transplanted lungs. The activation of NF-kappaB was measured by immunohistochemistry. The increase in intercellular adhesion molecule-1 (ICAM-1), which is the target gene of NF-kappaB, was evaluated by ELISA.

RESULTS

After reperfusion, there was a gradual decline in the PvO2 level in the control group (group I). The level of PvO2 in the group treated with lipopolysaccharide (group II) was significantly decreased, whereas that of the group treated with TRI (group III) was markedly improved (P<0.01). In group III, the activity of MPO was downregulated, and the pulmonary edema did not become severe and the ultrastructure of the donor lung remained normal. The activity of NF-kappaB and the expression of ICAM-1 was significantly increased in the donor lungs. TRI blocked NF-kappaB activation and ICAM-1 expression.

CONCLUSION

The effects of TRI on reducing injury to donor lungs induced by ischemia/reperfusion may possibly be mediated by inhibiting the activity of NF-kappaB and the expression of the NF-kappaB target gene ICAM-1. Thus, TRI could be used in lung transplantations for improving the function of donor lungs.

Nuclear factor-kappa B regulates seizure threshold and gene transcription following convulsant stimulation

We evaluated a role for the nuclear factor-kappa B (NF-kappaB) pathway in the regulation of seizure susceptibility and transcriptional activation during prolonged, continuous seizures (status epilepticus). Using two functionally distinct NF-kappaB inhibitors we observed a decrease in latency to onset of kainate-induced seizures and status epilepticus. To assess NF-kappaB transcriptional activation, we evaluated inhibitor kappa B alpha (IkappaBalpha) and brain-derived neurotrophic factor (bdnf) gene targets. Inhibition of the NF-kappaB signaling pathway significantly attenuated the increases in IkappaBalpha and bdnf mRNA levels that occurred during prolonged seizure activity, suggesting that the NF-kappaB pathway was involved in the up-regulation of these transcripts during status epilepticus. DNA-binding studies and chromatin immunoprecipitation assays using hippocampal extracts from animals with status epilepticus revealed that NF-kappaB subunits were associated with the candidate kappaB-binding elements within promoter 1 of the bdnf gene. The pattern of association was different for the p50 and p65 subunits supporting complex NF-kappaB modifications within promoter 1. In summary, our findings provide additional insights into the role of NF-kappaB transcriptional regulation in hippocampus following status epilepticus and suggest that NF-kappaB pathway activation contributes to seizure susceptibility.

Nuclear factor-kappaB-dependent cyclin D1 induction and DNA replication associated with N-methyl-D-aspartate receptor-mediated apoptosis in rat striatum

Cell cycle reentry has been found during apoptosis of postmitotic neurons under certain pathological conditions. To evaluate whether nuclear factor-kappaB (NF-kappaB) activation promotes cell cycle entry and neuronal apoptosis, we studied the relation among NF-kappaB-mediated cyclin induction, bromodeoxyuridine (BrdU) incorporation, and apoptosis initiation in rat striatal neurons following excitotoxic insult. Intrastriatally injected N-methyl-D-aspartate receptor agonist quinolinic acid (QA, 60 nmol) elicited a rise in cyclin D1 mRNA and protein levels (P<0.05). QA-induced NF-kappaB activation occurred in striatal neurons and nonneuronal cells and partially colocalized with elevated cyclin D1 immunoreactivity and TUNEL-positive nuclei. QA triggered DNA replication as evidenced by BrdU incorporation; some striatal BrdU-positive cells were identified as neurons by colocalization with NeuN. Blockade of NF-kappaB nuclear translocation with the recombinant peptide NF-kappaB SN50 attenuated the QA-induced elevation in cyclin D1 and BrdU incorporation. QA-induced internucleosomal DNA fragmentation was blunted by G(1)/S-phase cell cycle inhibitors. These findings suggest that NF-kappaB activation stimulates cyclin D1 expression and triggers DNA replication in striatal neurons. Excitotoxin-induced neuronal apoptosis may thus result from, at least partially, a failed cell cycle attempt.

Bile salts induce resistance to apoptosis through NF-kappaB-mediated XIAP expression

Apoptosis plays a critical role in intestinal mucosal homeostasis. We previously showed that the bile salt taurodeoxycholate has a beneficial effect on the intestinal mucosa through an increase in resistance to apoptosis mediated by nuclear factor (NF)-kappaB. The current study further characterizes the effect of bile salts on intestinal epithelial cell susceptibility to apoptosis and determines if the X-linked inhibitor of apoptosis protein (XIAP) regulates bile salt-induced resistance to apoptosis. Exposure of normal intestinal epithelial cells (IEC-6) to the conjugated bile salts taurodeoxycholate (TDCA) and taurochenodeoxycholate (TCDCA) resulted in an increase in resistance to tumor necrosis factor (TNF)-alpha and cycloheximide (CHX)-induced apoptosis, and NF-kappaB activation. Treatment with TDCA and TCDCA resulted in an increase in XIAP expression. Specific inhibition of NF-kappaB by infection with an adenoviral vector that expresses the IkappaBalpha super-repressor (IkappaBSR) prevented the induction of XIAP expression and the bile salt-mediated resistance to apoptosis. Treatment with the specific XIAP inhibitor Smac also overcame this increase in enterocyte resistance to apoptosis. Bile salts inhibited formation of the active caspase-3 from its precursor procaspase-3. Smac prevented the inhibitory effect of bile salts on caspase-3 activation. These results indicate that bile salts increase intestinal epithelial cell resistance to apoptosis through NF-kappaB-mediated XIAP expression. Bile salt-induced XIAP mediates resistance to TNF-alpha/CHX-induced apoptosis, at least partially, through inhibition of caspase-3 activity. These data support an important beneficial role of bile salts in regulation of mucosal integrity. Decreased enterocyte exposure to luminal bile salts, as occurs during starvation and parenteral nutrition, may have a detrimental effect on mucosal integrity.

NF-κB contributes to 6-hydroxydopamine-induced apoptosis of nigral dopaminergic neurons through p53

To evaluate the contribution of NF-kappaB and the NF-kappaB target gene p53 to nigral dopaminergic neuron degeneration in rodent models of Parkinson's disease, time-course of dopaminergic neuron loss as well as changes in the expression of some NF-kappaB-regulated proapoptotic proteins were assayed after unilateral infusion of 6-hydroxydopamine into rat medial forebrain bundle. Substantial loss of tyrosine hydroxylase immunoreactivity in nigral was observed 24 h after 6-hydroxydopamine treatment. The degenerative processes began 12 h after 6-hydroxydopamine administration as evidenced by a positive silver staining. Apoptotic death of dopaminergic neurons was suggested by the appearance of TUNEL-positive nuclei in substantia nigra and internucleosomal DNA fragmentation as detected by agarose gel electrophoresis. NF-kappaB activation in dopaminergic neurons as revealed by immunohistochemistry and electrophoresis mobility shift assay, began at 12 h after 6-hydroxydopamine administration. Levels of c-Myc and p53 immunoreactivities increased after 6-hydroxydopamine treatment, mainly in dopaminergic neurons as indicated by co-localization with tyrosine hydroxylase immunoreactivity. Blockade of NF-kappaB nuclear translocation with recombinant cell-permeable peptide NF-kappaB SN50 inhibited NF-kappaB nuclear translocation and p53 induction. SN50 and the p53 antagonist pifithrin-alpha significantly reduced nigral dopaminergic neuron degeneration. These results suggest that NF-kappaB activation contributes, at least in part, to oxidative stress-induced degeneration of dopaminergic neurons through a NF-kappaB-dependent p53-signaling pathway.

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.

Drug targeting of dysregulated transcription in Huntington's disease

Transcriptional dysregulation in Huntington's disease (HD) is a well documented and broadly studied phenomenon. Its basis appears to be in huntingtin's aberrant protein-protein interactions with a variety of transcription factors. The development of therapeutics targeting altered transcription, however, faces serious challenges. No single transcriptional regulator has emerged as a primary actor in HD. The levels of literally hundreds of RNA transcripts are altered in affected cells and it is uncertain which are most relevant. The protein-protein interactions of mutant huntingtin with transcriptional factors do not constitute conventional and easy targets for drug molecules. Nevertheless, potential therapeutic advances, targeting transcriptional deregulation in HD, have been made in recent years. In this chapter we review current progress in this area of therapeutic development. We also discuss possible drug discovery strategies targeting altered transcriptional pathways.

Ethyl-EPA in Huntington disease: potentially relevant mechanism of action

The pathomechanisms involved in the neuronal dysfunction in Huntington disease (HD) are still unresolved and may be heterogeneous. One potential mechanism might be related to the induction of mitochondrial dysfunction in the CNS. This might lead firstly to neuronal dysfunction and finally to the activation of apoptotic pathways. Several compounds, which should alleviate mitochondrial dysfunction, have been tested in preclinical models as well as in clinical trials of different scale. Recently we reported the efficacy of Ethyl-eicosapentaenoic acid (Ethyl-EPA) in patients with HD. Ethyl-EPA is a polyunsaturated fatty acid from the n-3 group, which is in clinical development for HD and melancholic depression. In our trial with Ethyl-EPA in HD responding patients could be characterized by either a lower CAG repeat number or a chorea-predominant clinical expression of the disease. Here we would like to describe some evidence on the potential mechanism of action of Ethyl-EPA in HD. We specifically focus on pathways, which are known to be influenced in HD and are modified by Ethyl-EPA and which points to an involvement of mitochondrial function as a common target. Some attention is given to the NF-kappa B pathway and the c-Jun amino-terminal kinases (JNK) pathway, which both may lead to an activation of the antiproliferative factor p53 and consequently mitochondrial dysfunction. Further the effects of EPA or Ethyl-EPA in preclinical models of HD are described. The evidence from these studies led to the design of phase III clinical trials, which are ongoing.

Role of nigral NFkappaB p50 and p65 subunit expression in haloperidol-induced neurotoxicity and stereotyped behavior in rats

Long-term use of typical neuroleptics such as haloperidol may be limited by unwanted motor side effects like tardive dyskinesia (TD) characterized by repetitive involuntary movements, involving the mouth, face and tongue. TD generally persists after haloperidol withdrawal indicating long lasting changes in brain function that are no longer related to the presence of the drug. The precise mechanisms of the neuronal toxicity induced by haloperidol are poorly understood. Haloperidol has been shown to induce the expression of the transcription factor nuclear factor-kappaB (NFkappaB). NFkappaB resembles a heterodimer protein composed of a 50 and a 65 kDa subunits and the role of the NFkappaB subunits on haloperidol-induced toxicity remains still unknown. The aim of the present study is to investigate the role of the p65 and p50 subunits of NFkappaB on the toxicity induced by chronic haloperidol administration in an experimental model of TD. Rats were treated for 21 days with: haloperidol (1mg/kg), clozapine (1mg/kg) or saline. Apomorphine-induced stereotyped behavior was evaluated. Striatal expression of the dopamine transporter (DAT) and the nigral expression of the NFkappaB p65 and p50 subunits were measured by Western Blot. Haloperidol, but not clozapine, increased stereotyped behavior associated to a decreased striatal DAT expression (p<0.01). Haloperidol did not modify the nigral expression of the p65 subunit whereas clozapine decreased it (p<0.01). Both drugs induced a significant decrease in the nigral expression of the NFkappaB p50 (p<0.05 and p<0.01, respectively). The decrease in nigral expression of the p50 subunit may increase the vulnerability of the dopaminergic neurons to a possible neurotoxic effect of p65 subunits in the haloperidol-treated rats.

Animal models of Huntington's disease: implications in uncovering pathogenic mechanisms and developing therapies

Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder, which is caused by an abnormal expansion of Cytosine Adenine Guanine (CAG) trinucleotide repeat in the gene making huntingtin (Htt). Despite intensive research efforts devoted to investigate molecular mechanisms of pathogenesis, effective therapy for this devastating disease is still not available at present. The development of various animal models of HD has offered alternative approaches in the study of HD molecular pathology. Many HD models, including chemical-induced models and genetic models, mimic some aspects of HD symptoms and pathology. To date, however, there is no ideal model which replicates all of the essential features of neuropathology and progressive motor and cognitive impairments of human HD. As a result, our understanding of molecular mechanisms of pathogenesis in HD is still limited. A new model is needed in order to uncover the pathogenesis and to develop novel therapies for HD. In this review we discussed usefulness and limitations of various animal and cellular models of HD in uncovering molecular mechanisms of pathogenesis and developing novel therapies for HD.

Prostaglandin A1 inhibits increases in intracellular calcium concentration, TXA(2) production and platelet activation

AIM

In our previous studies we found that cyclopentenane prostaglandin A1 (PGA1) had neuroprotective effects in a rodent ischemic model. In the present study we aimed to investigate the inhibitory effect of PGA1 on platelet function.

METHOD

The rate of aggregation of human platelets was measured by using turbidimetry. The rate of adhesion of platelets to cultured endothelial cells was determined by using [(3)H]-adenine labeled platelets. 5-Hydroxytryptamine release from platelets was measured with O-phthaldialdehyde fluorospectrophotometry. The levels of TXB(2), a stable metabolite of TXA(2), were determined by radioimmuno-assay. Alternations in platelet morphology were observed using an electron microscope, and the intraplatelet free calcium concentrations were measured with Fluo-3/AM FCM assay.

RESULTS

PGA1 significantly inhibited thrombin-, collagen- and ADP-induced aggregation and adhesion of platelets. The morphological changes of platelets induced by thrombin were blocked by PGA1. PGA1 inhibited the release of 5-hydroxytyptamine from dense granules and the synthesis of TXA(2).

CONCLUSION

PGA1 inhibits the activation of platelets probably through blocking increases in intracellular calcium concentration and TXA(2) synthesis.

Selenium reduces the proapoptotic signaling associated to NF-kappaB pathway and stimulates glutathione peroxidase activity during excitotoxic damage produced by quinolinate in rat corpus striatum

Quinolinate (QUIN) neurotoxicity has been attributed to degenerative events in nerve tissue produced by sustained activation of N-methyl-D-aspartate receptor (NMDAr) and oxidative stress. We have recently described the protective effects that selenium (Se), an antioxidant, produces on different markers of QUIN-induced neurotoxicity (Santamaría et al., 2003, J Neurochem 86:479-488.). However, the mechanisms by which Se exerts its protective actions remain unclear. Since some of these events are thought to be related with inhibition of deadly molecular cascades through the activation of antioxidant selenoproteins, in this study we investigated the effects of Se on QUIN-induced cell damage elicited by the nuclear factor kappaB (NF-kappaB) pathway, as well as the time-course response of striatal glutathione peroxidase (GPx) activity. Se (sodium selenite, 0.625 mg/kg/day, i.p.) was administered to rats for 5 days, and 120 min after the last administration, animals received a single striatal injection of QUIN (240 nmol/mul). Twenty-four hours later, their striata were tested for the expression of IkappaB-alpha (the NF-kappaB cytosolic binding protein), the immunohistochemical expression of NF-kappaB (evidenced as nuclear expression of P65), caspase-3-like activation, and DNA fragmentation. Additional groups were killed at 2, 6, and 24 h for measurement of GPx activity. Se reduced the QUIN-induced decrease in IkappaB-alpha expression, evidencing a reduction in its cytosolic degradation. Se also prevented the QUIN-induced increase in P65-immunoreactive cells, suggesting a reduction of NF-kappaB nuclear translocation. Caspase-3-like activation and DNA fragmentation produced by QUIN were also inhibited by Se. Striatal GPx activity was stimulated by Se at 2 and 6 h, but not at 24 h postlesion. Altogether, these data suggest that the protective effects exerted by Se on QUIN-induced neurotoxicity are partially mediated by the inhibition of proapoptotic events underlying IkappaB-alpha degradation, NF-kappaB nuclear translocation, and caspase-3-like activation in the rat striatum, probably involving the early activation of GPx.

Susceptibility of striatal neurons to excitotoxic injury correlates with basal levels of Bcl-2 and the induction of P53 and c-Myc immunoreactivity

The present studies evaluated the potential contribution of Bcl-2, p53, and c-Myc to the differential vulnerability of striatal neurons to the excitotoxin quinolinic acid (QA). In normal rat striatum, Bcl-2 immunoreactivity (Bcl-2-i) was most intense in large aspiny interneurons including choline acetyltransferase positive (CAT+) and parvalbumin positive (PARV+) neurons, but low in a majority of medium-sized neurons. In human brain, intense Bcl-2-i was seen in large striatal neurons but not in medium-sized spiny projection neurons. QA produced degeneration of numerous medium-sized neurons, but not those enriched in Bcl-2-i. Many Bcl-2-i-enriched interneurons including those with CAT+ and PARV+ survived QA injection, while medium-sized neurons labeled for calbindin D-28K (CAL D-28+) did not. In addition, proapoptotic proteins p53-i and c-Myc-i were robustly induced in medium-sized neurons, but not in most large neurons. The selective vulnerability of striatal medium spiny neurons to degeneration in a rodent model of Huntington's disease appears to correlate with their low levels of Bcl-2-i and high levels of induced p53-i and c-Myc-i.

Involvement of spinal cord nuclear factor κB activation in rat models of proinflammatory cytokine-mediated pain facilitation

Proinflammatory cytokines, such as interleukin-1beta and tumour necrosis factor-alpha, are released by activated glial cells in the spinal cord and play a major role in pain facilitation. These cytokines exert their actions, at least partially, through the activation of the transcription factor, nuclear factor kappaB (NF-kappaB). In turn, NF-kappaB regulates the transcription of many inflammatory mediators, including cytokines. We have previously shown that intrathecal injection of the human immunodeficiency virus-1 (HIV-1) envelope glycoprotein, gp120, induces mechanical allodynia via the release of proinflammatory cytokines. Here, we investigated whether NF-kappaB is involved in gp120-induced pain behaviour in Sprague-Dawley rats. Intrathecal administration of NF-kappaB inhibitors, pyrrolidinedithiocarbamate (PDTC) and SN50, prior to gp120 partially attenuated gp120-induced allodynia. In addition, PDTC delayed and reversed allodynia in a model of neuropathic pain induced by sciatic nerve inflammation. These observations suggest that intrathecal gp120 may lead to activation of NF-kappaB within the spinal cord. To reveal NF-kappaB activation, we assessed inhibitory factor kappaBalpha (IkappaBalpha) mRNA expression by in situ hybridization, as NF-kappaB activation up-regulates IkappaBalpha gene expression as part of an autoregulatory feedback loop. No or low levels of IkappaBalpha mRNA were detected in the lumbar spinal cord of vehicle-injected rats, whereas IkappaBalpha mRNA expression was markedly induced in the spinal cord following intrathecal gp120 in predominantly astrocytes and endothelial cells. Moreover, IkappaBalpha mRNA expression positively correlated with proinflammatory cytokine protein levels in lumbosacral cerebrospinal fluid. Together, these results demonstrate that spinal cord NF-kappaB activation is involved, at least in part, in exaggerated pain states.

Peptide-enhanced cellular internalization of proteins in neuroscience

Over the last 15 years, many publications described the use of peptide sequences that have been dubbed cell penetrating peptides (CPP), Trojan Horse peptides, protein transduction domains, or membrane-translocating sequences. These mostly positively charged domains bring attached cargo across biological membranes. One of the reasons for the interest in CPP is their potential as delivery tools to enhance the pharmacodynamics of drugs otherwise poorly bioavailable. In particular, the neuroscientist aiming to deliver a protein or other compound into the brain for analytical or therapeutic reasons is faced with the challenge that few drugs cross the blood-brain barrier. CPP are valuable tools to overcome the plasma membrane or the blood-brain barrier in basic research, and in relevant models of neural disease, and will hopefully help to increase the precious few treatments or even cures for people with diseases of the brain and nervous system. Here, we review applications in neuroscience and recent insights into the mechanism of CPP-mediated trafficking.