bluuebunny/crossref_metadata_2025_split huggingface dataset:
Intranuclear localization of apoptosis‐inducing factor (AIF) and large scale dna fragmentation after traumatic brain injury in rats and in neuronal cultures exposed to peroxynitrite
Authors: Zhang Xiaopeng , Chen Jun , Graham Steven H. , Du Lina , Kochanek Patrick M. , Draviam Romesh , Guo Fengli , Nathaniel Paula D. , Szabó Csaba , Watkins Simon C. , Clark Robert S. B. 
Published: March 2003

AbstractProgrammed cell death occurs after ischemic, excitotoxic, and traumatic brain injury (TBI). Recently, a caspase‐independent pathway involving intranuclear translocation of mitochondrial apoptosis‐inducing factor (AIF) has been reported in vitro; but whether this occurs after acute brain injury was unknown. To address this question adult rats were sacrificed at various times after TBI. Western blot analysis on subcellular protein fractions demonstrated intranuclear localization of AIF in ipsilateral cortex and hippocampus at 2–72 h. Immunocytochemical analysis showed AIF labeling in neuronal nuclei with DNA fragmentation in the ipsilateral cortex and hippocampus. Immunoelectronmicroscopy verified intranuclear localization of AIF in hippocampal neurons after TBI, primarily in regions of euchromatin. Large‐scale DNA fragmentation (∼50 kbp), a signature event in AIF‐mediated cell death, was detected in ipsilateral cortex and hippocampi by 6 h. Neuron‐enriched cultures exposed to peroxynitrite also demonstrated intranuclear AIF and large‐scale DNA fragmentation concurrent with impaired mitochondrial respiration and cell death, events that are inhibited by treatment with a peroxynitrite decomposition catalyst. Intranuclear localization of AIF and large‐scale DNA fragmentation occurs after TBI and in neurons under conditions of oxidative/nitrosative stress, providing the first evidence of this alternative mechanism by which programmed cell death may proceed in neurons after brain injury.
Regulation of regulators of G protein signaling mRNA expression in rat brain by acute and chronic electroconvulsive seizures
Authors: Gold Stephen J. , Heifets Boris D. , Pudiak Cindy M. , Potts Bryan W. , Nestler Eric J. 
Published: March 2003

AbstractG protein‐coupled receptor (GPCR) signaling cascades may be key substrates for the antidepressant effects of chronic electroconvulsive seizures (ECS). To better understand changes in these signaling pathways, alterations in levels of mRNA's encoding regulators of G protein signaling (RGS) protein subtypes‐2, ‐4, ‐7, ‐8 and ‐10 were evaluated in rat brain using northern blotting andin situhybridization. In prefrontal cortex, RGS2 mRNA levels were increased several‐fold 2 h following an acute ECS. Increases in RGS8 mRNA were of lesser magnitude (30%), and no changes were evident for the other RGS subtypes. At 24 h following a chronic ECS regimen, RGS4, ‐7, and ‐10 mRNA levels were reduced by 20–30%; only RGS10 was significantly reduced 24 h after acute ECS. Levels of RGS2 mRNA were unchanged 24 h following either acute or chronic ECS. In hippocampus, RGS2 mRNA levels were markedly increased 2 h following acute ECS. More modest increases were seen for RGS4 mRNA expression, whereas levels of the other RGS subtypes were unaltered. At 24 h following chronic ECS, RGS7, ‐8 and ‐10 mRNA levels were decreased in the granule cell layer, and RGS7 and ‐8 mRNA levels were decreased in the pyramidal cell layers. Only RGS8 and ‐10 mRNA levels were significantly reduced in hippocampus 24 h following an acute ECS. Paralleling neocortex, RGS2 mRNA content was unchanged in hippocampus 24 h following either acute or chronic ECS. In ventromedial hypothalamus, RGS4 mRNA content was increased 24 h following chronic ECS, whereas RGS7 mRNA levels were only increased 24 h following an acute ECS. The increased RGS4 mRNA levels in hypothalamus were significant by 2 h following an acute ECS. These studies demonstrate subtype‐, time‐, and region‐specific regulation of RGS proteins by ECS, adaptations that may contribute to the antidepressant effects of this treatment.
Ceramide‐induced apoptosis of D283 medulloblastoma cells requires mitochondrial respiratory chain activity but occurs independently of caspases and is not sensitive to Bcl‐xL overexpression
Authors: Poppe Monika , Reimertz Claus , Münstermann Gudrun , Kögel Donat , Prehn Jochen H. M. 
Published: March 2003

AbstractCeramides are potent lipid second messengers that are involved in apoptotic and hypoxic/ischaemic neurone death. We investigated the role of mitochondria and the mitochondrial apoptosis pathway in ceramide‐induced cell death using human D283 medulloblastoma cells with a reduced mitochondrial DNA copy number (ρ– cells) and a corresponding defect in mitochondrial respiration. Treatment with the complex I inhibitor rotenone, C2‐ or C8‐ceramide induced cell death in D283 control cells, while ρ– cells were significantly protected. In contrast, activation of the mitochondrial apoptosis pathway by transient overexpression of the pro‐apoptotic Bax protein or exposure to the kinase inhibitor staurosporine induced apoptosis to a similar extent in control and ρ– cells. Overexpression of the antiapoptotic protein Bcl‐xL failed to inhibit the toxic effect of C2‐ceramide in D283 control cells, and no significant increase in caspase‐3‐like protease activity could be detected during the death process. Despite this, C2‐ceramide induced significant chromatin condensation and cell shrinkage in D283 control cells, reminiscent of apoptosis. These morphological alterations were associated with the activation of calpains. Both apoptotic morphology and calpain activation were attenuated in ρ– cells. Our data indicate that the apoptosis‐inducing effect of C2‐ceramide may require mitochondrial respiratory chain activity and can occur independently of the mitochondrial apoptosis pathway, but involves the activation of calpains.
Activity‐dependent NMDA receptor‐mediated activation of protein kinase B/Akt in cortical neuronal cultures
Authors: Sutton Greg , Chandler L. Judson 
Published: March 2003

AbstractThe serine/threonine protein kinase B (PKB)/Akt is a phosphoinositide 3‐kinase (PI3K) effector that is thought to play an important roll in a wide variety of cellular events. The present study examined whether PKB activation in cortical neuronal cultures is coupled with synaptic activity. A 1‐h incubation of neuronal cultures with tetrodotoxin (TTX), the PI3K inhibitor wortmannin, the NMDA receptor antagonist MK‐801 or removal of extracellular calcium significantly reduced basal levels of phospho(Ser473)‐PKB, indicating that activity‐dependent glutamate release maintains PKB activation through an NMDA receptor‐PI3K pathway. A 5‐min exposure to NMDA (50 µm) in the presence of TTX increased phospho‐PKB back to levels observed in the absence of TTX. NMDA stimulation of phospho‐PKB was blocked by wortmannin, the CaMKII inhibitor KN‐93, MK‐801, and removal of extracellular calcium. We have previously shown that NMDA receptors can bi‐directionally regulate activation of extracellular‐signal regulated kinase (ERK), and NMDA receptor stimulation of PKB in the present study appeared to mirror activation of ERK. These results suggest that in cultured cortical neurons, PKB activity is dynamically regulated by synaptic activity and is coupled to NMDA receptor activation. In addition, NMDA receptor activation of ERK and PKB may occur through overlapping signaling pathways that bifurcate at the level of Ras.
Peroxynitrite enhances astrocytic volume‐sensitive excitatory amino acid release via a src tyrosine kinase‐dependent mechanism
Authors: Haskew Renée E. , Mongin Alexander A. , Kimelberg Harold K. 
Published: March 2003

AbstractVolume‐regulated anion channels (VRACs) are critically important for cell volume homeostasis, and under pathological conditions contribute to neuronal damage via excitatory amino (EAA) release. The precise mechanisms by which brain VRACs are activated and/or modulated remain elusive. In the present work we explored the possible involvement of nitric oxide (NO) and NO‐related reactive species in the regulation of VRAC activity and EAA release, using primary astrocyte cultures. The NO donors sodium nitroprusside and spermine NONOate did not affect volume‐activatedd‐[3H]aspartate release. In contrast, the peroxynitrite (ONOO–) donor 3‐morpholinosydnomine hydrochloride (SIN‐1) increased volume‐dependent EAA release by approx. 80–110% under identical conditions. Inhibition of ONOO–formation with superoxide dismutase completely abolished the effects of SIN‐1. Both the volume‐ and SIN‐1‐induced EAA release were sensitive to the VRAC blockers NPPB and ATP. Further pharmacological analysis ruled out the involvement of cGMP‐dependent reactions and modification of sulfhydryl groups in the SIN‐1‐inducedmodulation of EAA release. The src family tyrosine kinase inhibitor 4‐amino‐5‐(4‐chlorophenyl)‐7‐(t‐butyl)pyrazolo [3,4‐d]pyrimidine (PP2), but not its inactive analog PP3, abolished the effects of SIN‐1. A broader spectrum tyrosine kinase inhibitor tyrphostin A51, also completely eliminated the SIN‐1‐induced EAA release. Our data suggest that ONOO–up‐regulates VRAC activity via a src tyrosine kinase‐dependent mechanism. This modulation may contribute to EAA‐mediated neuronal damage in ischemia and other pathological conditions favoring cell swelling and ONOO–production.
Presenilin‐binding protein forms aggresomes in monkey kidney COS‐7 cells
Authors: Namekata Kazuhiko , Nishimura Noriyuki , Kimura Hideo 
Published: March 2003

AbstractA novel presenilin‐binding protein (PBP) is specifically expressed in the brain, and its level in the soluble fraction of Alzheimer's disease (AD) brains is much less than that in the age‐matched controls. Recently, several proteins, including presenilin (PS), have been found to form structures of aggregated proteins, called aggresomes, when the production of the proteins exceeds their rate of degradation by proteasomes. Based on these observations it has been proposed that the aggresome may represent one of the mechanisms forthe formation of cytoplasmic deposits which are linked to the pathogenesis of neurodegenerative disorders including AD. It is shown here that the overexpression of PBP or the suppression of proteasome activity in monkey kidney COS‐7 cells leads to the accumulation of detergent‐insoluble and multiubiquitinated PBP aggregates. PBP also forms aggregates in primary cultures of neurons in the presence of a proteasome inhibitors. PBP aggregates have the characteristics of aggresomes, including the localization to microtubule organization centers and the disruption of intermediate filaments. These observations suggest that the malfunctioning of the proteasome can cause the formation of PBP aggresomes, which may lead to AD.
Inositol and higher inositol phosphates in neural tissues: homeostasis, metabolism and functional significance
Authors: Fisher Stephen K. , Novak James E. , Agranoff Bernard W. 
Published: March 2003

AbstractInositol phospholipids and inositol phosphates mediate well‐established functions in signal transduction and in Ca2+homeostasis in the CNS and non‐neural tissues. More recently, there has been renewed interest in other roles that bothmyo‐inositol and its highly phosphorylated forms may play in neural function. We review evidence thatmyo‐inositol serves as a clinically relevant osmolyte in the CNS, and that its hexakisphosphate and pyrophosphorylated derivatives may play roles in such diverse cellular functions as DNA repair, nuclear RNA export and synaptic membrane trafficking.
Selective loss of neurofilament expression in Cu/Zn superoxide dismutase (SOD1) linked amyotrophic lateral sclerosis
Authors: Menzies Fiona M. , Grierson Andrew J. , Cookson Mark R. , Heath Paul R. , Tomkins Janine , Figlewicz Denise A. , Ince Paul G. , Shaw Pamela J. 
Published: March 2003

AbstractNeurofilament pathology is a hallmark of sporadic and familial amyotrophic lateral sclerosis (SALS and FALS). The disease mechanisms underlying this pathology are presently unclear, but recent evidence in SALS patients suggest that reductions in neurofilament light subunit (NFL) mRNA may contribute to the death of motor neurones. Mutations in the gene encoding Cu‐Zn superoxide dismutase (SOD1) represent the best‐studied cause of FALS, and a number of laboratory models of SOD1‐mediated disease exist. Here we have used microdissected lumbar spinal cord motor neurones from human SOD1 FALS patients as well as G93A SOD1 transgenic mice and demonstrated that reduced NFL mRNA levels are seen in both. To probe the molecular mechanisms underpinning these observations, we generated NSC34 motor neurone‐like cell lines expressing wild‐type and mutant SOD1. NSC34 cells expressing G37R or G93A SOD1 showed selective reductions in NFL and NFM mRNA and protein. These data suggest that NFL mRNA reductions are common to SALS and FALS patients, and that cells and mice expressing mutant SOD1 may enable us to characterize the molecular mechanism(s) responsible for the loss of neurofilament mRNA.
Activation of group II metabotropic glutamate receptors underlies microglial reactivity and neurotoxicity following stimulation with chromogranin A, a peptide up‐regulated in Alzheimer's disease
Authors: Taylor D. L. , Diemel L. T. , Cuzner M. L. , Pocock J. M. 
Published: March 2003

AbstractRegulation of microglial reactivity and neurotoxicity is critical for neuroprotection in neurodegenerative diseases. Here we report that microglia possess functional group II metabotropic glutamate receptors, expressing mRNA and receptor protein for mGlu2 and mGlu3, negatively coupled to adenylate cyclase. Two different agonists of these receptors were able to induce a neurotoxic microglial phenotype which was attenuated by a specific antagonist. Chromogranin A, a secretory peptide expressed in amyloid plaques in Alzheimer's disease, activates microglia to a reactive neurotoxic phenotype. Chromogranin A‐induced microglial activation and subsequent neurotoxicity may also involve an underlying stimulation of group II metabotropic glutamate receptors since their inhibition reduced chromogranin A‐induced microglial reactivity and neurotoxicity. These results show that selective inhibition of microglial group II metabotropic glutamate receptors has a positive impact on neuronal survival, and may prove a therapeutic target in Alzheimer's disease.
The homeobox containing gene Lbx1 is required for correct dorsal–ventral patterning of the neural tube
Authors: Krüger Markus , Schäfer Konstanze , Braun Thomas 
Published: March 2003

AbstractThe specification of distinct classes of neurones in the neural tube is governed by extracellular signals and transcriptional mediators including neurogenic bHLH‐ and homeobox‐containing genes. Despite recent insights in the transcriptional code that controls generation of neuronal subtypes in the dorsal neural tube, the mechanisms that underlie regional identity in dorsal and lateral regions of the mammalian neural tube are not well understood. The homeobox gene Lbx1 is expressed in a subset of interneurons in the early neural tube and later in dorsal parts of the spinal cord. Here we show that Lbx1 is part of the machinery that controls formation of neurones in the dorsal horn. Targeted inactivation of Lbx1 leads to a severe reduction of neurones in the dorsal horn and to down‐regulation of dorsal markers such as Lmx1a from E11.5 onwards. In contrast, Pax3, another dorsally expressed homeobox gene, was up‐regulated in Lbx1 mutant mice at E18.5, suggesting the existence of a negative regulatory feedback loop. Lbx1/Pax3 double‐mutant mice showed an enhanced Pax3 phenotype characterized by a completely open neural tube. We suggest that Lbx1 plays a critical role in the specification of dorsal interneurons and that Lbx1 and Pax3 might act together synergistically to promote neural tube closure.
Proteasomal degradation of tau protein
Authors: David Della C. , Layfield Robert , Serpell Louise , Narain Yolanda , Goedert Michel , Spillantini Maria Grazia 
Published: March 2003

AbstractFilamentous inclusions composed of the microtubule‐associated protein tau are a defining characteristic of a large number of neurodegenerative diseases. Here we show that tau degradation in stably transfected and non‐transfected SH‐SY5Y cells is blocked by the irreversible proteasome inhibitor lactacystin. Further, we find that in vitro, natively unfolded tau can be directly processed by the 20S proteasome without a requirement for ubiquitylation, and that a highly reproducible pattern of degradation intermediates is readily detectable during this process. Analysis of these intermediates shows that 20S proteasomal processing of tau is bi‐directional, proceeding from both N‐ and C‐termini, and that populations of relatively stable intermediates arise probably because of less efficient digestion of the C‐terminal repeat region. Our results are consistent with an in vivo role for the proteasome in tau degradation and support the existence of ubiquitin‐independent pathways for the proteasomal degradation of unfolded proteins.
D1 dopamine receptor stimulation increases GluR1 surface expression in nucleus accumbens neurons
Authors: Chao Steven Z. , Ariano Marjorie A. , Peterson Daniel A. , Wolf Marina E. 
Published: March 2003

AbstractThe goal of this study was to understand how dopamine receptors, which are activated during psychostimulant administration, might influence glutamate‐dependent forms of synaptic plasticity that are increasingly recognized as important to drug addiction. Regulation of the surface expression of the α‐amino‐3‐hydroxy‐5‐methylisoxazole‐4‐propionate (AMPA) receptor subunit GluR1 plays a critical role in long‐term potentiation, a well‐characterized form of synaptic plasticity. Primary cultures of rat nucleus accumbens neurons were used to examine whether dopamine receptor stimulation influences cell surface expression of GluR1, detected using antibody to the extracellular portion of GluR1 and fluorescence microscopy. Surface GluR1 labeling on processes of medium spiny neurons and interneurons was increased by brief (5–15 min) incubation with a D1 agonist (1 µm SKF 81297). This effect was attenuated by the D1 receptor antagonist SCH 23390 (10 µm) and reproduced by the adenylyl cyclase activator forskolin (10 µm). Labeling was decreased by glutamate (10–50 µm, 15 min). These results are the first to demonstrate modulation of AMPA receptor surface expression by a non‐glutamatergic G protein‐coupled receptor. Normally, this may enable ongoing regulation of AMPA receptor transmission in response to changes in the activity of dopamine projections to the nucleus accumbens. When dopamine receptors are over‐stimulated during chronic drug administration, this regulation may be disrupted, leading to inappropriate plasticity in neuronal circuits governing motivation and reward.
Axin negatively affects tau phosphorylation by glycogen synthase kinase 3β
Authors: Stoothoff William H. , Bailey Craig D. C. , Mi Kaihong , Lin Sheng‐Cai , Johnson Gail V. W. 
Published: March 2003

AbstractGlycogen synthase kinase 3β (GSK3β) is an essential protein kinase that regulates numerous functions within the cell. One critically important substrate of GSK3β is the microtubule‐associated protein tau. Phosphorylation of tau by GSK3β decreases tau–microtubule interactions. In addition to phosphorylating tau, GSK3β is a downstream regulator of the wnt signaling pathway, which maintains the levels of β‐catenin. Axin plays a central role in regulating β‐catenin levels by bringing together GSK3β and β‐catenin and facilitating the phosphorylation of β‐catenin, targeting it for ubiquitination and degradation by the proteasome. Although axin clearly facilitates the phosphorylation of β‐catenin, its effects on the phosphorylation of other GSK3β substrates are unclear. Therefore in this study the effects of axin on GSK3β‐mediated tau phosphorylation were examined. The results clearly demonstrate that axin is a negative regulator of tau phosphorylation by GSK3β. This negative regulation of GSK3β‐mediated tau phosphorylation is due to the fact that axin efficiently binds GSK3β but not tau and thus sequesters GSK3β away from tau, as an axin mutant that does not bind GSK3β did not inhibit tau phosphorylation by GSK3β. This is the first demonstration that axin negatively affects the phosphorylation of a GSK3β substrate, and provides a novel mechanism by which tau phosphorylation and function can be regulated within the cell.
The levels of mature glycosylated nicastrin are regulated and correlate with γ‐secretase processing of amyloid β‐precursor protein
Authors: Arawaka Shigeki , Hasegawa Hiroshi , Tandon Anurag , Janus Christopher , Chen Fusheng , Yu Gang , Kikuchi Kenji , Koyama Shingo , Kato Takeo , Fraser Paul E. , St George‐Hyslop Peter 
Published: March 2003

AbstractNicastrin, a type‐I transmembrane glycoprotein, is a necessary component of the high molecular weight presenilin (PS) complexes that mediate intramembranous cleavage of β‐amyloid precursor protein (βAPP) and Notch. Nicastrin undergoes trafficking‐dependent glycosylation maturation, and PS1 interacts preferentially with these maturely glycosylated forms of nicastrin. We investigated the effects of differing levels of the immature and mature endoglycosidase‐H‐resistant forms of nicastrin on Aβ40‐ and Aβ42‐peptide secretion in several cell lines stably expressing a mutant nicastrin (D336A/Y337A) that increases Aβ secretion. There was no correlation between Aβ secretion and the level of over‐expression of the immature forms of nicastrin. The total level of mature nicastrin remained constant, but mutant nicastrin replaced endogenous mature nicastrin in varying degrees. Differences in the levels of mature mutant nicastrin positively correlated with Aβ secretion, but did not influence either βAPP trafficking or processing by α‐ and β‐secretases. Proper trafficking and terminal maturation of nicastrin is therefore a necessary event for the regulated intramembranous proteolysis of βAPP.
Binge ethanol exposure decreases neurogenesis in adult rat hippocampus
Authors: Nixon Kimberly , Crews Fulton T. 
Published: March 2003

AbstractAlcoholism is associated with cognitive deficits and loss of brain mass. Recent studies have indicated that neural progenitor cells proliferate throughout life forming neurons, astrocytes, and oligodendrocytes. The dentate gyrus is one neurogenic region of the adult brain containing neural progenitor cells. To determine if binge ethanol (EtOH) exposure alters neural progenitor cell proliferation and survival, bromodeoxyuridine was administered to adult male rats following an acute or chronic binge exposure paradigm. For an acute binge, rats were gavaged with a 5 g/kg dose of EtOH or vehicle, administered bromodeoxyuridine, and killed either 5 h or 28 days after EtOH treatment. In a 4‐day, chronic‐binge paradigm, rats were infused with EtOH three times per day (mean dose 9.3 g/kg/day) or isocaloric control diet. Rats were given bromodeoxyuridine once a day for the 4 days of chronic binge treatment, then perfused either immediately following the last dose of EtOH or 28 days later. In both EtOH treatment groups, binge EtOH decreased neural progenitor cell proliferation. Following the chronic four‐day binge, neural progenitor cell survival was decreased. These studies are the first to show EtOH inhibition of neural progenitor cell proliferation and survival in the adult, a possible new mechanism underlying alcoholic cognitive dysfunction.