bluuebunny/crossref_metadata_2025_split huggingface dataset:
Apoptotic signaling in dopamine‐induced cell death: the role of oxidative stress, p38 mitogen‐activated protein kinase, cytochrome c and caspases
Authors: Junn Eunsung , Mouradian M. Maral 
Published: March 2003

Oxidative stress generated by dopamine (DA) oxidation could be one of the factors underlying the selective vulnerability of nigral dopaminergic neurons in Parkinson's diseases. Here we show that DA induces apoptosis in SH‐SY5Y neuroblastoma cells demonstrated by activation of caspase‐9 and caspase‐3, cleavage of poly(ADP‐ribose) polymerase as well as nuclear condensation. We also show that p38 mitogen‐activated protein kinase is activated within 10 min of DA treatment, which precedes the onset of apoptosis because the potent p38 kinase inhibitor SB203580 protects against DA‐induced cell death as well as against caspase‐9 and caspase‐3 activation. In addition, the antioxidant N‐acetyl‐l‐cysteine (NAC) effectively blocks DA‐induced p38 kinase activation, caspase‐9 and caspase‐3 cleavage and subsequent apoptosis, indicating that DA triggers apoptosis via a signaling pathway that is initiated by the generation of reactive oxygen species (ROS). Dopamine exerts its toxicity principally intracellularly as the DA uptake inhibitor, nomifensine significantly reduces DA‐induced cell death as well as activation of p38 kinase and caspase‐3. Furthermore, DA induces mitochondrial cytochrome c release, which is dependent on p38 kinase activation and precedes the cleavage of caspases. These observations indicate that DA induces apoptosis primarily by generating ROS, p38 kinase activation, cytochrome c release followed by caspase‐9 and caspase‐3 activation.
Amyloid β proteins inhibit Cl−‐ATPase activity in cultured rat hippocampal neurons
Authors: Yagyu K. , Kitagawa K. , Irie T. , Wu B. , Zeng X. T. , Hattori N. , Inagaki C. 
Published: March 2003

Cl−‐ATPase in the CNS is a candidate for an outwardly directed neuronal Cl− transporter requiring phosphatidylinositol‐4‐phosphate (PI4P) for its optimal activity. To test its pathophysiological changes in a phosphatidylinositol (PI) metabolism disorder, the effects of neurotoxic factors in Alzheimer's disease (AD), amyloid β proteins (Aβs), on the Cl−‐ATPase activity were examined using primary cultured rat hippocampal neurons. Amyloid β proteins (1–40, 1–42 and 25–35) concentration‐dependently (1–100 nm) and time‐dependently (from 1 h to 6 day) decreased Cl−‐ATPase activity and elevated intracellular Cl− concentrations ([Cl−]i), Aβ25–35 being the most potent. Addition of inositol or 8‐Br‐cyclic GMP completely reversed these Aβ‐induced changes. The recoveries in enzyme activity were attenuated by an inhibitor of PI 4‐kinase, 10 µm wortmannin or 20 µm quercetin, but not by a PI 3‐kinase inhibitor, 50 nm wortmannin or 10 µm LY294002. The PI, PIP and PIP2 levels of the plasma membrane‐rich fraction were lower in the Aβ‐treated cells as compared with each control. In the Aβ‐exposed culture, but not in control, stimulation by 10 µm glutamate for 10 min significantly increased fragmentation of DNA and decreased cell viability. Addition of inositol or 8‐Br‐cyclic GMP prevented the effect of Aβ‐treatment on the neurotoxicity of glutamate. Thus, Aβs reduce neuronal Cl−‐ATPase activity, resulting in an increase in [Cl−]i probably by lowering PI4P levels, and this may reflect a pre‐apoptotic condition in early pathophysiological profiles of AD.
The inhibition of phosphatidylinositol‐3‐kinase induces neurite retraction and activates GSK3
Authors: Sanchez S. , Sayas C. L. , Lim F. , Diaz‐Nido J. , Avila J. , Wandosell F. 
Published: March 2003

It has been extensively described that neuronal differentiation involves the signalling through neurotrophin receptors to a Ras‐dependent mitogen‐activated protein kinase (MAPK) cascade. However, signalling pathways from other neuritogenic factors have not been well established. It has been reported that cAMP may activate protein kinase (PKA), and it has been shown that PKA‐mediated stimulation of MAPK pathway regulates not only neuritogenesis but also survival. However, extracellular regulated kinases (ERKs) mediated pathways are not sufficient to explain all the processes which occur in neuronal differentiation. Our present data show that: in cAMP‐mediated neuritogenesis, using the SH‐SY5Y human neuroblastoma cell line, there exists a link between the activation of PKA and stimulation of phosphatidylinositol 3‐kinase (PI3K). Both kinase activities are essential to the initial elongation steps. Surprisingly, this neuritogenic process appears to be independent of ERKs. While the activity of PI3K is essential for elongation and maintenance of neurites, its inhibition causes retraction. In this neurite retraction process, GSK3 is activated. Using both a pharmacological approach and gene transfer of a dominant negative form of GSK3, we conclude that this induced retraction is a GSK3‐dependent process which in turn appears to be a common target for transduction pathways involved in lysophosphatidic acid‐mediated and PI3K‐mediated neurite retraction.
Green tea polyphenol (–)‐epigallocatechin‐3‐gallate prevents N‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine‐induced dopaminergic neurodegeneration
Authors: Levites Yona , Weinreb Orly , Maor Gila , Youdim Moussa B. H. , Mandel Silvia 
Published: March 2003

In the present study we demonstrate neuroprotective property of green tea extract and (–)‐epigallocatechin‐3‐gallate in N‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine mice model of Parkinson's disease. N‐Methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine neurotoxin caused dopamine neuron loss in substantia nigra concomitant with a depletion in striatal dopamine and tyrosine hydroxylase protein levels. Pretreatment of mice with either green tea extract (0.5 and 1 mg/kg) or (–)‐epigallocatechin‐3‐gallate (2 and 10 mg/kg) prevented these effects. In addition, the neurotoxin caused an elevation in striatal antioxidant enzymes superoxide dismutase (240%) and catalase (165%) activities, both effects being prevented by (–)‐epigallocatechin‐3‐gallate. (–)‐Epigallocatechin‐3‐gallate itself also increased the activities of both enzymes in the brain. The neuroprotective effects are not likely to be caused by inhibition of N‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine conversion to its active metabolite 1‐methyl‐4‐phenylpyridinium by monoamine oxidase‐B, as both green tea and (–)‐epigallocatechin‐3‐gallate are very poor inhibitors of this enzyme in vitro (770 µg/mL and 660 µM, respectively). Brain penetrating property of polyphenols, as well as their antioxidant and iron‐chelating properties may make such compounds an important class of drugs to be developed for treatment of neurodegenerative diseases where oxidative stress has been implicated.
Early ethanolamine phospholipid translocation marks stress‐induced apoptotic cell death in oligodendroglial cells
Authors: Brand Annette , Yavin Ephraim 
Published: March 2003

The consequences of H2O2/Fe2+‐induced oxidative stress on translocation of ethanolamine phosphoglyceride (EPG) and serine phosphoglyceride (SPG) were studied in an oligodendroglia‐like cell line (OLN 93) following 3 days of supplementation with 0.1 mm docosahexaenoic acid (DHA) and a series of polar head group precursors, including N‐monomethyl‐ and N,N‐dimethylethanolamine at millimolar concentrations. Added DHA was predominantly esterified in EPG species and those cells enriched in DHA showed enhanced sensitivity to oxidative stress and eventually died by apoptosis. Co‐supplements with ethanolamine and DHA resulted in a rapid, but transient, EPG translocation with a maximum at 30 min following stress, as characterized by a trinitrobenzenesulfonic acid reagent. There was no significant translocation of SPG as evidenced by annexin V binding. Unlike SPG, which is usually irreversibly translocated to subserve as a tag for phagocytosis, EPG acted as a signaling molecule with biphasic kinetic characteristics. N‐Monomethyl‐ and N,N‐dimethylethanolamine supplements reduced EPG synthesis, prevented its externalization and rescued cells from apoptotic death. Following stress, the fatty acid profile of the externalized EPG showed marked losses in polyunsaturated fatty acids and aldehydes compared with the remaining intracellular EPG. Prevention of EPG species selective translocation to the outer membrane leaflet by altering phospholipid asymmetry may be important in the mechanism of rescue from cell death.
The catalytic domain of human neuropathy target esterase mediates an organophosphate‐sensitive ionic conductance across liposome membranes
Authors: Forshaw Philip J. , Atkins Jane , Ray David E. , Glynn Paul 
Published: March 2003

In humans and other vertebrates, reaction of organophosphates with a neuronal membrane protein, neuropathy target esterase (NTE), initiates events which culminate in axonal degeneration. The initiation process appears to involve modification of a property of the protein distinct from its esterase activity, subsequent to formation of a negatively charged adduct with the active site serine residue. Here, we show that membrane patches from liposomes containing NEST, a recombinant hydrophobic polypeptide comprising the esterase domain of human NTE, display a transmembrane ionic conductance with both stable and high‐frequency flickering components. An asymmetric current–voltage relationship suggested that ion flow was favoured in one direction relative to the membrane and its associated NEST molecules. Flow of anions was slightly favoured compared with cations. The flickering current formed a much larger proportion of the overall conductance in patches containing wild‐type NEST compared with the catalytically inactive S966A mutant form of the protein. The conductance across patches containing NEST, but not those with the S966A mutant, was significantly reduced after adding neuropathic organophosphates to the bathing medium. By contrast, non‐neuropathic covalent inhibitors of the catalytic activity of NEST did not reduce NEST‐mediated conductance. Future work may establish whether NTE itself mediates an organophosphate‐sensitive ion flux across intracellular membranes within intact cells.
Iodoacetate protects hippocampal neurons against excitotoxic and oxidative injury: involvement of heat‐shock proteins and Bcl‐2
Authors: Guo Zhihong , Lee Jaewon , Lane Mark , Mattson Mark P. 
Published: March 2003

Mild metabolic stress may increase resistance of neurons in the brain to subsequent, more severe insults, as demonstrated by the ability of ischemic pre‐conditioning and dietary restriction to protect neurons in experimental models of stroke‐ and age‐related neurodegenerative disorders. In the present study we employed iodoacetic acid (IAA), an inhibitor of glyceraldehyde‐3‐phosphate dehydrogenase, to test the hypothesis that inhibition of glycolysis can protect neurons. Pre‐treatment of cultured hippocampal neurons with IAA can protect them against cell death induced by glutamate, iron and trophic factor withdrawal. Surprisingly, protection occurred with concentrations of IAA (2–200 nm) much lower than those required to inhibit glycolysis. Pre‐treatment with IAA results in suppression of oxyradical production and stabilization of mitochondrial function in neurons after exposure to oxidative insults. Levels of the stress heat‐shock proteins HSP70 and HSP90, and of the anti‐apoptotic protein Bcl‐2, were increased in neurons exposed to IAA. Our data demonstrate that IAA can stimulate cytoprotective mechanisms within neurons, and suggest the possible use of IAA and related compounds in the prevention and/or treatment of neurodegenerative conditions.
Human immunodeficiency virus type‐1 Tat protein induces nuclear factor (NF)‐κB activation and oxidative stress in microglial cultures by independent mechanisms
Authors: Nicolini Alessia , Ajmone‐Cat Maria Antonietta , Bernardo Antonietta , Levi Giulio , Minghetti Luisa 
Published: March 2003

We have extended our previous findings and shown that human immunodeficiency virus Tat protein, in addition to nitric oxide (NO), stimulated rat microglial cultures to release pro‐inflammatory cytokine interleukin‐1β and tumour necrosis factor‐α in a nuclear factor (NF)‐κB‐dependent manner. At the same time, Tat stimulated the accumulation of free radicals, as indicated by the increased levels of isoprostane 8‐epi‐prostaglandin F2α (8‐epi‐PGF2α), a reliable marker of lipid peroxidation and oxidative stress, by a mechanism unrelated to NF‐κB activation. The presence of free radical scavengers abrogated Tat‐induced 8‐epi‐PGF2α accumulation without affecting NO and cytokine production. Consistently, Tat‐induced IκBα degradation – an index of NF‐κB activation – was not affected by free radical scavengers, but was prevented by an NF‐κB‐specific inhibitor. Our observations indicate that NF‐κB plays a key role in Tat‐dependent microglial activation, and that oxidative stress and NF‐κB activation induced by Tat occur by independent mechanisms.
Cysteine and mercapturate conjugates of oxidized dopamine are in human striatum but only the cysteine conjugate impedes dopamine trafficking in vitro and in vivo
Authors: Sidell Kathrin R. , Olson Sandra J. , Ou Joyce J. , Zhang Yueli , Amarnath Ventkataraman , Montine Thomas J. 
Published: March 2003

Recent results have suggested that some products of mercapturic acid pathway (MAP) metabolism of oxidized dopamine (DA) may contribute to mesostriatal dopaminergic neurodegeneration, and that at least one product, 5‐S‐cysteinyldopamine (Cys‐DA), is elevated in patients with advanced Parkinson's disease (PD) who have been treated with l‐DOPA. Here we investigated MAP enzymes and products in the midbrain and striatum of control individuals and patients with dementia with Lewy bodies (DLB) who had less severe dopaminergic degeneration than PD patients and who were not treated with l‐DOPA. We also determined the biological activity of MAP metabolites of oxidized DA using primary rat mesencephalic cultures, rat cerebral synaptosomes, and rat striatum in vivo microdialysis. Our results showed that the human mesostriatal dopaminergic pathway generates Cys‐DA but has limited enzymatic capacity for mercapturate formation, that striatal levels of MAP products of oxidized DA are not elevated in DLB patients compared with controls, and that Cys‐DA interferes with trafficking of DA in vitro and in vivo. These results indicate that while Cys‐DA is not increased in striatum of patients with mild dopaminergic neurodegeneration, it may interfere with uptake of DA in patients with advanced PD.
Species‐scanning mutagenesis of the serotonin transporter reveals residues essential in selective, high‐affinity recognition of antidepressants
Authors: Mortensen Ole V. , Kristensen Anders S. , Wiborg Ove 
Published: March 2003

The serotonin transporter (SERT) is a high‐affinity sodium/chloride‐dependent neurotransmitter transporter responsible for reuptake of serotonin from the extracellular space. SERT is a selective target of several clinically important antidepressants. In a cross‐species analysis comparing human and bovine SERTs, the kinetic parameters for serotonin uptake were found to be similar, however, the pharmacological profiles of the two transporters differ. Following transient expression in COS‐1 cells, IC50 values were determined for several antidepressants and psychostimulants. The potencies of the antidepressants citalopram, fluoxetine, paroxetine and imipramine were several‐fold higher at hSERT compared with bSERT. No species selectivity was observed for the antidepressants fluvoxamine, and sertraline or for the psychostimulants cocaine, the cocaine analogue β‐carbomethoxy‐3β‐(4‐iodophenyl)tropane, or for 3,4‐methylenedioxymethamphetamine (MDMA). Analysis of six hSERT/bSERT chimeras and subsequent species‐scanning mutagenesis of each isoform revealed methionine‐180, tyrosine‐495, and phenylalanine‐513 to be responsible for the increase in citalopram and paroxetine potencies at hSERT and methionine‐180 and phenylalanine‐513 to confer species selectivity at hSERT for fluoxetine and imipramine. Results were obtained by doing the forward, bovine to human, mutations and confirmed by doing the reverse mutations. Citalopram analogues were used to define the roles of methionine‐180, tyrosine‐495, and phenylalanine‐513 and to reveal molecular interactions with individual functional groups of citalopram. We suggest that methionine‐180 interacts with the heterocyclic nucleus of citalopram or stabilizes the binding pocket and phenylalanine‐513 to be a steric blocker of antidepressant recognition.
Pro‐apoptotic effect of presenilin 2 (PS2) overexpression is associated with down‐regulation of Bcl‐2 in cultured neurons
Authors: Araki Wataru , Yuasa Katsutoshi , Takeda Shin'ichi , Takeda Kazuya , Shirotani Keiro , Takahashi Keikichi , Tabira Takeshi 
Published: March 2003

Presenilin 2 (PS2) is a polytopic membrane protein that is mutated in some cases of familial Alzheimer's disease (AD). The normal functions of PS2 and its pathogenic role in AD remain unclear. We investigated the biological role of this protein in neurons, using adenovirus‐mediated transduction of the PS2 gene into rat primary cortical neurons. Immunocytochemical analyses demonstrated increased PS2 immunoreactivity in most neurons infected with recombinant adenoviruses expressing PS2. Neurons infected with wild‐type or mutant (N141I) PS2‐expressing adenoviruses showed a significant increase in basal cell death, compared with those infected with control β‐galactosidase‐expressing adenovirus. Moreover, PS2 overexpression markedly increased neuronal susceptibility to staurosporine‐induced apoptosis. Mutant PS2 was more effective in enhancing apoptosis than its wild‐type counterpart. Staurosporine‐induced death was significantly inhibited by a specific caspase 3 inhibitor. Western analyses revealed that Bcl‐2 protein expression was specifically down‐regulated in neurons overexpressing PS2, which temporally corresponded to the accumulation of C‐ and N‐terminal fragments of PS2. Additionally, expression of mutant, but not wild‐type PS2, increased the production of β‐amyloid protein (Aβ) 42. These data collectively suggest that the pro‐apoptotic effect of PS2 is mediated by down‐regulation of Bcl‐2. PS2 mutations may increase the susceptibility of neurons to apoptotic stimuli by perturbing the regulation of cell death.
Focal neurometabolic alterations in mice deficient for succinate semialdehyde dehydrogenase
Authors: Gibson K. M. , Schor D. S. M. , Gupta M. , Guerand W. S. , Senephansiri H. , Burlingame T. G. , Bartels H. , Hogema B. M. , Bottiglieri T. , Froestl W. , Snead O. C. , Grompe M. , Jakobs C. 
Published: March 2003

AbstractMetabolite profiling in succinate semialdehyde dehydrogenase (SSADH; Aldh5a1–/–) deficient mice previously revealed elevated γ‐hydroxybutyrate (GHB) and total GABA in urine and total brain and liver extracts. In this study, we extend our metabolic characterization of these mutant mice by documenting elevated GHB and total GABA in homogenates of mutant kidney, pancreas and heart. We quantified β‐alanine (a GABA homolog and putative neurotransmitter) to address its potential role in pathophysiology. We found normal levels of β‐alanine in urine and total homogenates of mutant brain, heart and pancreas, but elevated concentrations in mutant kidney and liver extracts. Amino acid analysis in mutant total brain homogenates revealed no abnormalities except for significantly decreased glutamine, which was normal in mutant liver and kidney extracts. Regional amino acid analysis (frontal cortex, parietal cortex, hippocampus and cerebellum) in mutant mice confirmed glutamine results. Glutamine synthetase protein and mRNA levels in homogenates of mutant mouse brain were normal. We profiled organic acid patterns in mutant brain homogenates to assess brain oxidative metabolism and found normal concentrations of Kreb's cycle intermediates but increased 4,5‐dihydroxyhexanoic acid (a postulated derivative of succinic semialdehyde) levels. We conclude that SSADH‐deficient mice represent a valid metabolic model of human SSADH deficiency, manifesting focal neurometabolic abnormalities which could provide key insights into pathophysiologic mechanisms.
Injury‐induced ‘switch’ from GTP‐regulated to novel GTP‐independent isoform of tissue transglutaminase in the rat spinal cord
Authors: Festoff Barry W. , SantaCruz Karen , Arnold Paul M. , Sebastian Cyril T. , Davies Peter J. A. , Citron Bruce A. 
Published: March 2003

AbstractWe recently found that alternative transcripts of tissue transglutaminase (tTG or TG2) were present in hippocampal brain regions of Alzheimer's disease (AD), but not in control, non‐demented, age‐matched brains. Since antecedent non‐severe trauma has been implicated in AD and other neurodegenerative diseases, such as Parkinson's disease (PD) and amyotrophic lateral sclerosis (ALS), we were interested in whether alternative transcripts might be detected in a model of neurotrauma, controlled‐contusion spinal cord injury (SCI) in the rat. Implicated in diverse roles from growth and differentiation to apoptotic cell death, only bifunctional tTG, of the nine member TG family, has dual catalytic activities: guanine trinucleotide (GTP) hydrolyzing activity (GTPase), as well as protein cross‐linking. These functions imply two physiological functions: programmed cell life and death. These may have profound roles in the nervous system since studies in cultured astrocytes found tTG short (S) mRNA transcripts induced by treatment with injury‐related cytokines. In the developing rat spinal cord, tTG activity is concentrated in ventral horn alpha motoneurons, but neither studies of spinal cord tTG gene expression, nor evaluation of the GTP‐regulated isoforms in tissues, have been reported. We now report increased tTG protein and gene expression occurring rapidly after SCI. In parallel, novel appearance of a second, short form transcript, in addition to the normal long (L) isoform, occurs by 8 h of injury. Up‐regulation of tTG message and activity following neural injury. with appearance of a truncated GTP‐unregulated S form, may represent new approaches to drug targets in neurotrauma.
Regulation of DARPP‐32 dephosphorylation at PKA‐ and Cdk5‐sites by NMDA and AMPA receptors: distinct roles of calcineurin and protein phosphatase‐2A
Authors: Nishi Akinori , Bibb James A. , Matsuyama Seiichiro , Hamada Miho , Higashi Hideho , Nairn Angus C. , Greengard Paul 
Published: March 2003

AbstractGlutamatergic inputs from corticostriatal and thalamostriatal pathways have been shown to modulate dopaminergic signaling in neostriatal neurons. DARPP‐32 (dopamine‐ and cAMP‐regulated phosphoprotein of Mr 32 kDa) is a signal transduction molecule that regulates the efficacy of dopamine signaling in neostriatal neurons. Dopamine signaling is mediated in part through phosphorylation of DARPP‐32 at Thr34 by cAMP‐dependent protein kinase, and antagonized by phosphorylation of DARPP‐32 at Thr75 by cyclin‐dependent protein kinase 5. We have now investigated the effects of the ionotropic glutamate NMDA and AMPA receptors on DARPP‐32 phosphorylation in neostriatal slices. Activation of NMDA and AMPA receptors decreased the state of phosphorylation of DARPP‐32 at Thr34 and Thr75. The decrease in Thr34 phosphorylation was mediated through Ca2+‐dependent activation of the Ca2+‐/calmodulin‐dependent phosphatase, calcineurin. In contrast, the decrease in Thr75 phosphorylation was mediated through Ca2+‐dependent activation of dephosphorylation by protein phosphatase‐2A. The results provide support for a complex effect of glutamate on dopaminergic signaling through the regulation of dephosphorylation of different sites of DARPP‐32 by different protein phosphatases.