bluuebunny/crossref_metadata_2025_split huggingface dataset:
Zn2+‐induced ERK activation mediated by reactive oxygen species causes cell death in differentiated PC12 cells
Authors: Seo Su Ryeon , Chong Seon Ah , Lee Syng‐Ill , Sung Jee Young , Ahn Young Soo , Chung Kwang Chul , Seo Jeong Taeg 
Published: March 2003

Recent studies have provided evidence that Zn2+ plays a crucial role in ischemia‐ and seizure‐induced neuronal death. However, the intracellular signaling pathways involved in Zn2+‐induced cell death are largely unknown. In the present study, we investigated the roles of mitogen‐activated protein kinases (MAPKs), such as c‐Jun N‐terminal kinase (JNK), p38 MAPK and extracellular signal‐regulated kinase (ERK), and of reactive oxygen species (ROS) in Zn2+‐induced cell death using differentiated PC12 cells. Intracellular accumulation of Zn2+ induced by the combined application of pyrithione (5 µm), a Zn2+ ionophore, and Zn2+ (10 µm) caused cell death and activated JNK and ERK, but not p38 MAPK. Preventing JNK activation by the expression of dominant negative SEK1 (SEKAL) did not attenuate Zn2+‐induced cell death, whereas the inhibition of ERK with PD98059 and the expression of dominant negative Ras mutant (RasN17) significantly prevented cell death. Inhibition of protein kinase C (PKC) and phosphatidylinositol‐3 kinase had little effect on Zn2+‐induced ERK activation. Intracellular Zn2+ accumulation resulted in the generation of ROS, and antioxidants prevented both the ERK activation and the cell death induced by Zn2+. Therefore, we conclude that although Zn2+ activates JNK and ERK, only ERK contributes to Zn2+‐induced cell death, and that ERK activation is mediated by ROS via the Ras/Raf/MEK/ERK signaling pathway.
Antagonists of protein kinase C inhibit rat retinal glutamate transport activity in situ
Authors: Bull Natalie D. , Barnett Nigel L. 
Published: March 2003

AbstractNeuronal and glial high‐affinity transporters regulate extracellular glutamate concentration, thereby terminating synaptic transmission and preventing neuronal excitotoxicity. Glutamate transporter activity has been shown to be modulated by protein kinase C (PKC) in cell culture. This is the first study to demonstrate such modulation in situ, by following the fate of the non‐metabolisable glutamate transporter substrate,	d‐aspartate. In the rat retina, pan‐isoform PKC inhibition with chelerythrine suppressed glutamate uptake by GLAST (glutamate/aspartate transporter), the dominant excitatory amino acid transporter localized to the glial Müller cells. This effect was mimicked by rottlerin but not by Gö6976, suggesting the involvement of the PKCδ isoform, but not PKCα, β or γ. Western blotting and immunohistochemical labeling revealed that the suppression of glutamate transport was not due to a change in transporter expression. Inhibition of PKCδ selectively suppressed GLAST but not neuronal glutamate transporter activity. These data suggest that the targeting of specific glutamate transporters with isoform‐specific modulators of PKC activity may have significant implications for the understanding of neurodegenerative conditions arising from compromised glutamate homeostasis, e.g. glaucoma and amyotrophic lateral sclerosis.
Metabotropic glutamate receptor 5 and calcium signaling in retinal amacrine cells
Authors: Sosa Romina , Hoffpauir Brian , Rankin Michele L. , Bruch Richard C. , Gleason Evanna L. 
Published: March 2003

AbstractTo begin to understand the modulatory role of glutamate in the inner retina, we examined the mechanisms underlying metabotropic glutamate receptor 5 (mGluR5)‐dependent Ca2+ elevations in cultured GABAergic amacrine cells. A partial sequence of chicken retinal mGluR5 encompassing intracellular loops 2 and 3 suggests that it can couple to both Gq and Gs. Selective activation of mGluR5 stimulated Ca2+ elevations that varied in waveform from cell to cell. Experiments using high external K+ revealed that the mGluR5‐dependent Ca2+ elevations are distinctive in amplitude and time course from those engendered by depolarization. Experiments with a Ca2+‐free external solution demonstrated that the variability in the time course of mGluR5‐dependent Ca2+ elevations is largely due to the influx of extracellular Ca2+. The sensitivity of the initial phase of the Ca2+ elevation to thapsigargin indicates that this phase of the response is due to the release of Ca2+ from the endoplasmic reticulum. Pharmacological evidence indicates that mGluR5‐mediated Ca2+ elevations are dependent upon the activation of phospholipase C. We rule out a role for L‐type Ca2+ channels and cAMP‐gated channels as pathways for Ca2+ entry, but provide evidence of transient receptor potential (TRP) channel‐like immunoreactivity, suggesting that Ca2+ influx may occur through TRP channels. These results indicate that GABAergic amacrine cells express an avian version of mGluR5 that is linked to phospholipase C‐dependent Ca2+ release and Ca2+ influx, possibly through TRP channels.
Alteration of amino acid metabolism in neuronal aggregate cultures exposed to hypoglycaemic conditions
Authors: Honegger Paul , Braissant Olivier , Henry Hugues , Boulat Olivier , Bachmann Claude , Zurich Marie‐Gabrielle , Pardo Beatriz 
Published: March 2003

AbstractThe neuronal effects of glucose deficiency on amino acid metabolism was studied on three‐dimensional cultures of rat telencephalon neurones. Transient (6 h) exposure of differentiated cultures to low glucose (0.25 mm instead of 25 mm) caused irreversible damage, as judged by the marked decrease in the activities of two neurone‐specific enzymes and lactate dehydrogenase, 1 week after the hypoglycemic insult. Quantification of amino acids and ammonia in the culture media supernatants indicated increased amino acid utilization and ammonia production during glucose‐deficiency. Measurement of intracellular amino acids showed decreased levels of alanine, glutamine, glutamate and GABA, while aspartate was increased. Added lactate (11 mm) during glucose deficiency largely prevented the changes in amino acid metabolism and ammonia production, and attenuated irreversible damage. Higher media levels of glutamine (4 mm instead of 0.25 mm) during glucose deprivation prevented the decrease of intracellular glutamate and GABA, while it further increased intracellular aspartate, ammonia production and neuronal damage. Both lactate and glutamine were readily oxidized in these neuronal cultures. The present results suggest that in neurones, glucose deficiency enhances amino acid deamination at the expense of transamination reactions. This results in increased ammonia production and neuronal damage.
Alpha7 nicotinic receptor activation inhibits ethanol‐induced mitochondrial dysfunction, cytochrome c release and neurotoxicity in primary rat hippocampal neuronal cultures
Authors: Li Yangxin , Meyer Edwin M. , Walker Don W. , Millard William J. , He Yun‐Ju , King Michael A. 
Published: March 2003

AbstractPrimary hippocampal neuronal cultures exhibited a concentration‐ and time‐dependent loss of cells when exposed to ethanol (EtOH). EtOH‐induced neurotoxicity was attenuated by 2,4‐dimethoxybenzilidene anabaseine (DMXB) which selectively activates alpha7 nicotinic receptors in a concentration‐dependent manner. We further investigated the mechanisms of the protective effect of DMXB on EtOH‐ induced neurotoxicity. We found that EtOH decreased the mitochondrial membrane potential and released cytochrome c from mitochondria at neurotoxic concentrations. DMXB (3 μm) attenuated both of these actions in a manner that was in turn blocked with the nicotinic antagonist methyllyconitine (MLA) 100 nm. Neither DMXB nor MLA alone affected these parameters. These results suggest that the neuroprotection conferred by alpha7 nicotinic receptor activation may be mediated, at least in part, through preventing the decrease in the mitochondrial membrane potential and the increase in the release of cytochrome c caused by EtOH.
Induction of apoptosis in human and rat glioma by agonists of the nuclear receptor PPARγ
Authors: Zander Thomas , Kraus Jürgen A. , Grommes Christian , Schlegel Uwe , Feinstein Douglas , Klockgether Thomas , Landreth Gary , Koenigsknecht Jessica , Heneka Michael T. 
Published: March 2003

AbstractMalignant astrocytomas are among the most common brain tumours and few therapeutic options exist. It has recently been recognized that the ligand‐activated nuclear receptor PPARγ can regulate cellular proliferation and induce apoptosis in different malignant cells. We report the effect of three structurally different PPARγ agonists inducing apoptosis in human (U87MG and A172) and rat (C6) glioma cells. The PPARγ agonists ciglitazone, LY171 833 and prostaglandin‐J2, but not the PPARα agonist WY14643, inhibited proliferation and induced cell death. PPARγ agonist‐induced cell death was characterized by DNA fragmentation and nuclear condensation, as well as inhibited by the synthetic receptor‐antagonist bisphenol A diglycidyl ether (BADGE). In contrast, primary murine astrocytes were not affected by PPARγ agonist treatment. The apoptotic death in the glioma cell lines treated with PPARγ agonists was correlated with the transient up‐regulation of Bax and Bad protein levels. Furthermore, inhibition of Bax expression by specific antisense oligonucleotides protected glioma cells against PPARγ‐mediated apoptosis, indicating an essential role of Bax in PPARγ‐induced apoptosis. However, PPARγ agonists not only induced apoptosis but also caused redifferentiation as indicated by outgrowth of long processes and expression of the redifferentiation marker N‐cadherin in response to PPARγ agonists. Taken together, treatment of glioma cells with PPARγ agonists may hold therapeutic potential for the treatment of gliomas.
Identification of a novel SNAP25 interacting protein (SIP30)
Authors: Lee Ho‐Ki , Safieddine Saaid , Petralia Ronald S. , Wenthold Robert J. 
Published: March 2003

AbstractSoluble N‐ethylmaleimide‐sensitive factor attachment protein receptors (SNAREs), including synaptosome‐associated proteins of 25 kDa (SNAP25), syntaxins, and vesicle‐associated membrane proteins (VAMP), are essential for regulated exocytosis of synaptic vesicles in neurotransmission. We identified a cDNA coding for a novel protein of 266 amino acids that we have named SIP30 (SNAP25 interacting protein of 30 kDa). SIP30 is expressed abundantly in brain and slightly in testis and kidney. In brain, SIP30 is highly expressed in the inferior and superior colliculi, which contain important relay nuclei of the auditory and visual systems. GST–pull‐down and immunoprecipitation assays showed direct binding of SIP30 to SNAP25. Although SIP30 does not directly interact with syntaxin based on pull‐down assays, syntaxin does co‐immunoprecipitate with SIP30 suggesting that syntaxin is indirectly associated with SIP30, perhaps through SNAP25.
BDNF‐mediated signal transduction is modulated by GSK3β and mood stabilizing agents
Authors: Mai Lian , Jope Richard S. , Li Xiaohua 
Published: March 2003

AbstractBrain‐derived neurotrophic factor (BDNF) is a major neurotrophin in the brain and abnormal regulation of BDNF may contribute to the pathophysiology of mood disorders. In the present study, we examined if alterations in the activity of glycogen synthase kinase‐3‐beta (GSK3β) or treatment with mood stabilizers modulated BDNF‐mediated signal transduction pathways in differentiated human neuroblastoma SH‐SY5Y cells. BDNF increased the phosphorylation of the forkhead transcription factor FKHRL1 through activation of the phosphatidylinositol 3‐kinase (PI3K)/Akt signaling pathway, and the phosphorylation of the cyclic AMP response element binding protein (CREB) through activation of extracellular signal‐regulated kinase1/2 (ERK1/2). BDNF also increased serine9‐phosphorylation of GSK3β, which inhibits GSK3β activity. Overexpression of GSK3β did not affect BDNF‐induced phosphorylation of Akt, ERK1/2, or FKHRL1, but abolished CREB phosphorylation induced by BDNF. This inhibition of BDNF‐induced CREB phosphorylation in GSK3β‐overexpressing SH‐SY5Y cells was blocked by treatment with lithium. In contrast to lithium, sodium valproate and lamotrigine did not affect BDNF‐mediated signaling, whereas carbamazepine induced a rapid and prolonged phosphorylation of ERK1/2 and CREB in the absence or the presence of BDNF. Therefore, increased GSK3β selectively attenuates BDNF‐induced CREB phosphorylation, and lithium and carbamazepine can facilitate activation of CREB.
Measuring nicotinic receptors with characteristics of α4β2, α3β2 and α3β4 subtypes in rat tissues by autoradiography
Authors: Perry David C. , Xiao Yingxian , Nguyen Henry N. , Musachio John L. , Dávila‐García Martha I. , Kellar Kenneth J. 
Published: March 2003

AbstractComparison of [125I]epibatidine and 5‐[125I]iodo‐3‐(2‐azetidinylmethoxy)pyridine ([125I]A‐85380) autoradiography showed evidence for nicotinic receptor heterogeneity. To identify the receptor subtypes, we performed [125I]epibatidine autoradiography in the presence of cytisine or A‐85380. By comparing these results with binding data from human embryonic kidney (HEK) 293 cells stably transfected with different combinations of rat nicotinic receptor subunits, we were able to quantify three distinct populations of [125I]epibatidine binding sites with characteristics of α4β2, α3β2 and α3β4 receptors. Although the predominant subtype in rat brain was α4β2, non‐α4β2 binding sites were prominent in many regions. In the habenulo‐peduncular system, cerebellum, substantia gelatinosa, and many medullary nuclei, α3β4‐like binding accounted for more than 40% of [125I]epibatidine binding, and nearly all binding in superior cervical ganglion and pineal gland. Other regions enriched in α3β4‐like binding included locus ceruleus, dorsal tegmentum, subiculum and anteroventral thalamic nucleus. Regions enriched in α3β2‐like binding included the habenulo‐peduncular system, many visual system structures, certain geniculate nuclei, and dopaminergic regions. The combination of autoradiography using a broad spectrum radioligand in the presence of selectivecompetitors, and data from binding to defined receptor subtypes in expression systems, allowed us to quantify the relative populations of these three subtypes.
Effects of systemic and central nervous system localized inflammation on the contributions of metabolic precursors to the l‐kynurenine and quinolinic acid pools in brain
Authors: Kita Tomoyuki , Morrison Paul F. , Heyes Melvyn P. , Markey S. P. 
Published: March 2003

Abstract l‐Kynurenine and quinolinic acid are neuroactive l‐tryptophan‐kynurenine pathway metabolites of potential importance in pathogenesis and treatment of neurologic disease. To identify precursors of these metabolites in brain, [2H3]‐l‐kynurenine was infused subcutaneously by osmotic pump into three groups of gerbils: controls, CNS‐localized immune‐activated, and systemically immune‐activated. The specific activity of l‐kynurenine and quinolinate in blood, brain and systemic tissues at equilibrium was then quantified by mass spectrometry and the results applied to a model of metabolism to differentiate the relative contributions of various metabolic precursors. In control gerbils, 22% of l‐kynurenine in brain was derived via local synthesis from l‐tryptophan/formylkynurenine versus 78% from l‐kynurenine from blood. Quinolinate in brain was derived from several sources, including: local tissue l‐tryptophan/formylkynurenine (10%), blood l‐kynurenine (35%), blood 3‐hydroxykynurenine/3‐hydroxyanthranilate (7%), and blood quinolinate (48%). After systemic immune‐activation, however, l‐kynurenine in brain was derived exclusively from blood, whereas quinolinate in brain was derived from three sources: blood l‐kynurenine (52%), blood 3‐hydroxykynurenine or 3‐hydroxyanthranilate (8%), and blood quinolinate (40%). During CNS‐localized immune activation, > 98% of both l‐kynurenine and quinolinate were derived via local synthesis in brain. Thus, immune activation and its site determine the sources from which l‐kynurenine and quinolinate are synthesized in brain. Successful therapeutic modulation of their concentrations must take into account the metabolic and compartment sources.
Estrogen‐mediated neuroprotection against β‐amyloid toxicity requires expression of estrogen receptor α or β and activation of the MAPK pathway
Authors: Fitzpatrick Jennifer L. , Mize Amy L. , Wade Christian B. , Harris Julie A. , Shapiro Robert A. , Dorsa Daniel M. 
Published: March 2003

AbstractIt is well documented that estrogen can activate rapid signaling pathways in a variety of cell types. These non‐classical effects of estrogen have been reported to be important for cell survival after exposure to a variety of neurotoxic insults. Since direct evidence of the ability of the estrogen receptors (ERs) α and/or β to mediate such responses is lacking, the hippocampal‐derived cell line HT22 was stably transfected with either ERα (HTERα) or ERβ (HTERβ). In HTERα and HTERβ cells, but not untransfected cells, an increase in ERK2 phosphorylation was measured within 15 min of 17β‐estradiol treatment. The ER antagonist ICI 182, 780 (1 µm) and the MEK inhibitor, PD98059 (50 µm) blocked this increase in ERK2 phosphorylation. Treatment of HT22, HTERα and HTERβ cells with the β‐amyloid peptide (25–35) (10 µm) resulted in a significant decrease in cell viability. Pre‐treatment for 15 min with 10 nm 17β‐estradiol resulted in a 50% increase in the number of living cells in HTERα and HTERβ cells, but not in HT22 cells. Finally, ICI 182, 780 and PD98059 prevented 17β‐estradiol‐mediated protection. This study demonstrates that both ERα and ERβ can couple to rapid signaling events that mediate estrogen‐elicited neuroprotection.
GABA–opioid interactions in the globus pallidus: [D‐Ala2]‐Met‐enkephalinamide attenuates potassium‐evoked GABA release after nigrostriatal lesion
Authors: Schroeder J. A. , Schneider J. S. 
Published: March 2003

AbstractThe motor signs of Parkinson's disease have been partly attributed to an overinhibition of the external globus pallidus (GP) that results from hyperactivity of striatopallidal GABA/enkephalinergic neurons. The goals of this study were to measure basal levels of extracellular fluid GABA in the GP of normal cats, 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine (MPTP)‐treated parkinsonian cats and cats spontaneously recovered from MPTP‐induced parkinsonism, and to examine the effects of opioid receptor activation on potassium (K+)‐evoked GABA release in the GP in these animals. Basal GP GABA levels were increased 75% from normal in parkinsonian animals 1 week after MPTP administration and returned to control levels in recovered animals 6 weeks afterMPTP administration. No significant differences were observed in K+‐evoked GABA release across conditions. The opioid receptor agonist [D‐Ala2]‐Met‐Enkephalinamide (DALA) significantly attenuated K+‐evoked GABA release in the GP of MPTP‐treated symptomatic and recovered cats, but had no significant effect on GABA release in normal animals. These data show that basal GP GABA levels are elevated coincident with expression of parkinsonian signs and return to normal in animals that have functionally compensated for a nigrostriatal lesion. DALA‐induced inhibition of pallidal GABA release after a dopamine‐depleting lesion, suggests that enkephalin may attenuate GABA release in the GP specifically after striatal dopamine loss.
Blockade by ferrous iron of Ca2+ influx through N‐methyl‐d‐aspartate receptor channels in immature cultured rat cortical neurons
Authors: Nakamichi Noritaka , Ohno Hiroshi , Nakamura Yoichi , Hirai Takao , Kuramoto Nobuyuki , Yoneda Yukio 
Published: March 2003

AbstractRat cortical neurons cultured for 3 days in vitro were loaded with the fluorescent indicator fluo‐3 for assessment of intracellular free calcium ion (Ca2+) concentrations with the aid of a confocal laser‐scanning microscope. In the absence of added MgCl2, the addition of NMDA induced a rapid but sustained increase in the number of fluorescent neurons in a concentration‐dependent manner at a concentration range of 1–100 µm with the increase by KCl being transient. The addition of FeCl2, but not FeCl3, markedly inhibited the increase by NMDA in a reversible manner at concentrations of 10–200 µm, without affecting that by KCl. Extensive analyses revealed clear differentiation between inhibitions by ferrous iron and other channel blockers known to date. The inhibition by FeCl2 was completely prevented by the addition of two different iron chelators. Exposure to NMDA alone did not lead to cell death in immature cultured neurons, however, while further addition of FeCl2 invariably induced neuronal cell death 24 h after exposure. These results give support to our previous proposal that NMDA receptor complex may contain a novel site sensitive to blockade by ferrous iron in rat brain.
Mitochondrial permeability transition mediates apoptosis induced by N‐methyl(R)salsolinol, an endogenous neurotoxin, and is inhibited by Bcl‐2 and rasagiline, N‐propargyl‐1(R)‐aminoindan
Authors: Akao Yukihiro , Maruyama Wakako , Shimizu Shigeomi , Yi Hong , Nakagawa Yoshihito , Shamoto‐Nagai Masayo , Youdim Moussa B. H. , Tsujimoto Yoshihide , Naoi Makoto 
Published: March 2003

AbstractThe role of mitochondrial permeability transition (PT) in apoptosis induced by an endogenous neurotoxin, N‐methyl(R)salsolinol [NM(R)Sal], was studied by use of dopaminergic neuroblastoma SH‐SY5Y cells. NM(R)Sal reduced mitochondrial membrane potential, ΔΨm, in the early phase of apoptosis, which was not suppressed by a pan‐caspase inhibitor, but was antagonized by Bcl‐2 and cyclosporin A, suggesting the involvement of the PT in NM(R)Sal‐induced loss of ΔΨm. NM(R)Sal‐induced apoptosis was completely inhibited not only by Bcl‐2 and a pan‐caspase inhibitor, but also by cyclosporin A, suggesting the essential role of the PT in NM(R)Sal‐induced apoptosis. In mitochondria isolated from rat liver, NM(R)Sal induced swelling and reduced ΔΨm, which was inhibited by cyclosporin A and Bcl‐2 overexpression. These results indicate that NM(R)Sal induced the PT by direct action on the mitochondria. Rasagiline, N‐propargyl‐1(R)‐aminoindan, which is a now under a clinical trial for Parkinson's disease, suppressed the ΔΨm reduction, release of cytochrome c, and apoptosis induced by NM(R)Sal in SH‐SY5Y cells. Rasagiline also inhibited the NM(R)Sal‐induced loss of ΔΨm and swelling in the isolated mitochondria, proving that rasagiline directly targets the mitochondria also. Altogether, mitochondrial PT plays a key role both in NM(R)Sal‐induced cell death and the neuroprotective effect of rasagiline.
Molecular characterization of MARTA1, a protein interacting with the dendritic targeting element of MAP2 mRNAs
Authors: Rehbein Monika , Wege Konstanze , Buck Friedrich , Schweizer Michaela , Richter Dietmar , Kindler Stefan 
Published: March 2003

AbstractIn neurones, the somatodendritic microtubule‐associated protein 2 regulates the stability of the dendritic cytoskeleton. Its extrasomatic localization appears to be a multicausal mechanism that involves dendritic mRNA trafficking, a process that depends on a dendritic targeting element in the 3′ untranslated region. Two rat MAP2‐RNA trans‐acting proteins, MARTA1 and MARTA2, exhibit specific high‐affinity binding to the dendritic targeting element. We have now affinity‐purified MARTA1 from rat brain. Analysis of proteolytic peptides revealed that rat MARTA1 is the orthologue of the human RNA‐binding protein KSRP. Rat MARTA1 is a 74‐kDa protein that contains four putative RNA‐binding domains and is 98% identical to human KSRP. Both purified rat MARTA1 and human KSRP preferentially bind to the dendritic targeting element, but do not strongly interact with other investigated regions of mRNAs encoding microtubule‐associated protein 2 and α‐tubulin. In rat brain neurones and cultured neurones derived from superior cervical ganglia, MARTA1 is primarily intranuclear, but is also present in the somatodendritic cytoplasm. Thus, MARTA1 may play a role in nucleocytoplasmic mRNA targeting.