bluuebunny/crossref_metadata_2025_split huggingface dataset:
Role of capacitative calcium entry on glutamate‐induced calcium influx in type‐I rat cortical astrocytes
Authors: Pizzo Paola , Burgo Andrea , Pozzan Tullio , Fasolato Cristina 
Published: March 2003

Capacitative calcium entry (CCE) has been described in a variety of cell types. To date, little is known about its role in the CNS, and in particular in the cross‐talk between glia and neurons. We have first analyzed the properties of CCE of astrocytes in culture, in comparison with that of the rat basophilic leukemia cell line (RBL‐2H3), a model where calcium release‐activated Ca2+ (CRAC) channels have been unambiguously correlated with CCE. We here show that (i) in astrocytes CCE activated by store depletion and Ca2+ influx induced by glutamate share the same pharmacological profile of CCE in RBL‐2H3 cells and (ii) glutamate‐induced Ca2+ influx in astrocytes plays a primary role in glutamate‐dependent intracellular Ca2+ concentration ([Ca2+]i) oscillations, being these latter reduced in frequency and amplitude by micromolar concentrations of La3+. Finally, we compared the expression of various mammalian transient receptor potential genes (TRP) in astrocytes and RBL‐2H3 cells. Despite the similar pharmacological properties of CCE in these cells, the pattern of TRP expression is very different. The involvement of CCE and TRPs in glutamate dependent activation of astrocytes is discussed.
Anandamide, but not 2‐arachidonoylglycerol, accumulates during in vivo neurodegeneration
Authors: Hansen Henrik H. , Schmid Patricia C. , Bittigau Petra , Lastres‐Becker Isabel , Berrendero Fernando , Manzanares Jorge , Ikonomidou Chrysanthy , Schmid Harald H. O. , Fernández‐Ruiz J. Javier , Hansen Harald S. 
Published: March 2003

Endogenous cannabinoid receptor ligands (endocannabinoids) may rescue neurons from glutamate excitotoxicity. As these substances also accumulate in cultured immature neurons following neuronal damage, elevated endocannabinoid concentrations may be interpreted as a putative neuroprotective response. However, it is not known how glutamatergic insults affect in vivo endocannabinoid homeostasis, i.e. N‐arachidonoylethanolamine (anandamide) and 2‐arachidonoylglycerol (2‐AG), as well as other constituents of their lipid families, N‐acylethanolamines (NAEs) and 2‐monoacylglycerols (2‐MAGs), respectively. Here we employed three in vivo neonatal rat models characterized by widespread neurodegeneration as a consequence of altered glutamatergic neurotransmission and assessed changes in endocannabinoid homeostasis. A 46‐fold increase of cortical NAE concentrations (anandamide, 13‐fold) was noted 24 h after intracerebral NMDA injection, while less severe insults triggered by mild concussive head trauma or NMDA receptor blockade produced a less pronounced NAE accumulation. By contrast, levels of 2‐AG and other 2‐MAGs were virtually unaffected by the insults employed, rendering it likely that key enzymes in biosynthetic pathways of the two different endocannabinoid structures are not equally associated to intracellular events that cause neuronal damage in vivo. Analysis of cannabinoid CB1 receptor mRNA expression and binding capacity revealed that cortical subfields exhibited an up‐regulation of these parameters following mild concussive head trauma and exposure to NMDA receptor blockade. This may suggest that mild to moderate brain injury may trigger elevated endocannabinoid activity via concomitant increase of anandamide levels, but not 2‐AG, and CB1 receptor density.
ΔΨm‐Dependent and ‐independent production of reactive oxygen species by rat brain mitochondria
Authors: Votyakova Tatyana V. , Reynolds Ian J. 
Published: March 2003

Mitochondria are widely believed to be the source of reactive oxygen species (ROS) in a number of neurodegenerative disease states. However, conditions associated with neuronal injury are accompanied by other alterations in mitochondrial physiology, including profound changes in the mitochondrial membrane potential ΔΨm. In this study we have investigated the effects of ΔΨm on ROS production by rat brain mitochondria using the fluorescent peroxidase substrates scopoletin and Amplex red. The highest rates of mitochondrial ROS generation were observed while mitochondria were respiring on the complex II substrate succinate. Under this condition, the majority of the ROS signal was derived from reverse electron transport to complex I, because it was inhibited by rotenone. This mode of ROS generation is very sensitive to depolarization of ΔΨm, and even the depolarization associated with ATP generation was sufficient to inhibit ROS production. Mitochondria respiring on the complex I substrates, glutamate and malate, produce very little ROS until complex I is inhibited with rotenone, which is also consistent with complex I being the major site of ROS generation. This mode of oxidant production is insensitive to changes in ΔΨm. With both substrates, ubiquinone‐derived ROS can be detected, but they represent a more minor component of the overall oxidant signal. These studies demonstrate that rat brain mitochondria can be effective producers of ROS. However, the optimal conditions for ROS generation require either a hyperpolarized membrane potential or a substantial level of complex I inhibition.
Potentiation of PGE2‐mediated cAMP production during neuronal differentiation of human neuroblastoma SK‐N‐BE(2)C cells
Authors: Choi, Se‐Young , Choi, Bo‐Hwa , Suh, Byung‐Chang , Chae, Hee‐Don , Kim, Jong‐So , Shin, Min‐Jung , Kang Shin‐Sung , Negishi Manabu , Kim Kyong‐Tai 
Published: March 2003

The prostaglandin‐evoked cAMP production was studied in human neuroblastoma SK‐N‐BE(2)C cells during neuronal differentiation induced by all‐trans retinoic acid. The incubation with 5 µm all‐trans retinoic acid for 4–6 days promoted neurite outgrowth of cells. After differentiation, prostaglandin E2 (PGE2)‐induced cAMP production was dramatically increased, whereas forskolin‐ and AlF

‐induced cAMP productions were not changed. The increase reached maximum after 4‐days of incubation with all‐trans retinoic acid. The differentiation caused an increase in the maximal response and a decrease in the half‐maximal effective concentration of the PGE2‐induced cAMP production. In addition, the binding of [3H]PGE2 to membrane receptors was enhanced in differentiated cells. However, the order of potency of the various prostaglandins (PGE1 = PGE2 > PGD2 = PGF2α = PGI2) in cAMP production did not change during the differentiation, suggesting that mainly E‐prostanoid (EP) receptors were involved. Butaprost, an EP2 receptor specific agonist, increased the cAMP level in a concentration dependent manner and had a similar potentiating effect on cAMP production as PGE2 upon differentiation. Northern blot analysis using the human cDNA probes shows that the EP2 mRNA level was about seven times higher in differentiated cells, while the dopamine β‐hydroxylase (DBH) mRNA completely disappeared. Our results, thus, suggest that elevated gene expression of the prostanoid EP2 receptor results in an increase in the PGE2‐evoked cAMP production in SK‐N‐BE(2)C cells during neuronal differentiation.
Differential effects of unaggregated and aggregated amyloid β protein (1–40) on K+ channel currents in primary cultures of rat cerebellar granule and cortical neurones
Authors: Ramsden Martin , Plant Leigh D. , Webster Nicola J. , Vaughan Peter F. T. , Henderson Zaineb , Pearson Hugh A. 
Published: March 2003

The effects of amyloid β protein on voltage‐gated K+ channel currents were studied using the whole‐cell patch‐clamp technique. The 1–40 amino acid form of amyloid β protein was applied to primary cultures of rat cerebellar granule and cortical neurones for 24 h. Both the unaggregated and aggregated forms of the peptide, which have differing biological activities, were used. In cerebellar granule neurones, 24‐h pre‐incubation with 1 µm unaggregated amyloid β protein resulted in a 60% increase in the ‘A’‐type component of K+ current. Increased delayed rectifier activity was Cd2+‐sensitive and was presumed to be secondary to an increase in voltage‐gated Ca2+ channel current activity. Unaggregated amyloid β protein had no effect on any component of the K+ channel current in cortical neurones. One micromolar of aggregated amyloid β protein had no effect on K+ channel current in either cell type but reduced cell survival within 24 h as measured using the 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) and terminal deoxynucleotidyl transferase‐mediated dUTP nick end labelling (TUNEL) assays. The unaggregated form of amyloid β protein had no neurotoxic effects when applied to either neurone type for up to 72 h. These data indicate that the unaggregated, non‐pathological form of amyloid β protein causes changes in the ion channel function of neurones, possibly reflecting a physiological role for the peptide.
The role of dopamine in motor symptoms in the R6/2 transgenic mouse model of Huntington's disease
Authors: Hickey Miriam A. , Reynolds Gavin P. , Morton A. Jennifer 
Published: March 2003

AbstractIn both Huntington's disease (HD) patients and genetic mouse models of HD, there is a pre‐symptomatic loss of dopamine (DA) receptors, suggesting that dysfunctional dopaminergic neurotransmission may be involved in early HD presentation. However, the role of DA in HD symptoms is not fully understood. In this study, we examined the possibility that dysfunctional dopaminergic neurotransmission contributes to the progressive decline in motor function of a transgenic mouse model of HD (R6/2 line). We found that R6/2 mice display an age‐dependent abnormal behavioural response to (+)‐methamphetamine (METH) and a dose‐dependent increase in sensitivity to METH toxicity compared with wildtype (WT) mice. R6/2 mice also showed an attenuated response to cocaine, indicating that DA release may be compromised. Striatal DA levels were reduced in R6/2 mice by 9 weeks of age. Replacement of DA by chronic treatment with laevodopa (l‐DOPA, administered as Sinemet) caused short‐term improvements in activity and rearing behaviour, and abolished abnormal spontaneous hindlimb grooming. However, long‐term treatment with l‐DOPA had deleterious effects on survival and rotarod performance of R6/2 mice. These results suggest that dysfunctional DA neurotransmission contributes to phenotype development in R6/2 mice and thus also may be important in symptom progression in HD.
GM1 ganglioside induces phosphorylation and activation of Trk and Erk in brain
Authors: Duchemin Anne‐Marie , Ren Qun , Mo Lili , Neff Norton H. , Hadjiconstantinou Maria 
Published: March 2003

AbstractWe investigated the ability of GM1 to induce phosphorylation of the tyrosine kinase receptor for neurotrophins, Trk, in rat brain, and activation of possible down‐stream signaling cascades. GM1 increased phosphorylated Trk (pTrk) in slices of striatum, hippocampus and frontal cortex in a concentration‐ and time‐dependent manner, and enhanced the activity of Trk kinase resulting in receptor autophosphorylation. The ability of GM1 to induce pTrk was shared by other gangliosides, and was blocked by the selective Trk kinase inhibitors K252a and AG879. GM1 induced phosphorylation of TrkA > TrkC > TrkB in a region‐specific distribution. Adding GM1 to brain slices activated extracellular‐regulated protein kinases (Erks) in all three brain regions studied. In striatum, GM1 elicited activation of Erk2 > Erk1 in a time‐and concentration‐dependent manner. The GM1 effect on Erk2 was mimicked by other gangliosides, and was blocked by the Trk kinase inhibitors K252a and AG879. Pertussis toxin, as well as Src protein tyrosine kinase and protein kinase C inhibitors, did not prevent the GM1‐induced activation of Erk2, apparently excluding the participation of Gi and Gq/11 protein‐coupled receptors. Intracerebroventricular administration of GM1 induced a transient phosphorylation of TrkA and Erk1/2 in the striatum and hippocampus complementing the in situ studies. These observations support a role for GM1 in modulating Trk and Erk phosphorylation and activity in brain.
Protection against 3,4‐methylenedioxymethamphetamine‐induced neurodegeneration produced by glutathione depletion in rats is mediated by attenuation of hyperthermia
Authors: O'Shea E. , Easton N. , Fry J. R. , Green A. R. , Marsden C. A. 
Published: March 2003

Abstract3,4‐Methylenedioxymethamphetamine (MDMA) administration produces neurotoxic degeneration of serotonin terminals in rat brain. These effects occur only after systemic administration and not after central injection, suggesting that peripheral metabolism, possibly hepatic, is required for toxicity. Glutathione is one of the principal cellular defence mechanisms, but conjugation with glutathione can, on some occasions, increase the reactivity of certain molecules. Previous studies have shown that central administration of glutathione adducts of a MDMA metabolite produces a neurotoxicity profile similar to that of systemic MDMA. In the present study, depletion of peripheral (hepatic) glutathione by 43% with dl‐buthionine‐(S,R)‐sulfoximine (an inhibitor of glutathione synthesis) did not attenuate MDMA‐induced neurotoxicity as indicated by the 34% loss of [3H]paroxetine binding to the serotonin uptake sites in Dark Agouti rats treated with the inhibitor. However, a more profound depletion (92%) of glutathione by diethylmaleate (direct conjugation) administration significantly reduced the serotonergic neurotoxicity produced by MDMA. This depletion protocol also attenuated the hyperthermic response to MDMA. A combination protocol utilising both buthionine‐(S,R)‐sulfoximine and diethylmaleate that did not alter the hyperthermic response of the rats given MDMA also failed to attenuate the neurotoxicity. These findings indicate that glutathione depletion does not offer specific protection against MDMA‐induced serotonin neurotoxicity in Dark Agouti rats.
Tissue transglutaminase differentially modulates apoptosis in a stimuli‐dependent manner
Authors: Tucholski Janusz , Johnson Gail V. W. 
Published: March 2003

AbstractTissue transglutaminase is a unique member of the transglutaminase family as it not only catalyzes a transamidating reaction, but also binds and hydrolyzes GTP and ATP. Tissue transglutaminase has been reported to be pro‐apoptotic, however, conclusive evidence is still lacking. To elucidate the role of tissue transglutaminase in the apoptotic process human neuroblastoma SH‐SY5Y cells were stably transfected with vector only (SH/pcDNA), wild‐type tissue transglutaminase (SH/tTG) and tissue transglutaminase that has no transamidating activity but retains its other functions (SH/C277S). In these studies three different apoptotic stimuli were used osmotic stress, staurosporine treatment and heat shock to delineate the role of tissue transglutaminase as a transamidating enzyme in the apoptotic process. In SH/tTG cells, osmotic stress and staurosporine treatments resulted in significantly greater caspase‐3 activation and apoptotic nuclear changes then in SH/pcDNA or SH/C277S cells. This potentiation of apoptosis in SH/tTG cells was concomitant with a significant increase in thein situtransamidating activity of tissue transglutaminase. However, in the heat shock paradigm, which did not result in any increase in the transamidating activity in SH/tTG cells, there was a significant attenuation of caspase‐3 activity, LDH release and apoptotic chromatin condensation in SH/tTG and SH/C277S cells compared with SH/pcDNA cells. These findings indicate for the first time that the effect of tissue transglutaminase on the apoptotic process is highly dependent on the type of the stimuli and how the transamidating activity of the enzyme is affected. Tissue transglutaminase facilitates apoptosis in response to stressors that result in an increase in the transamidating activity of the enzyme. However, when the stressors do not result in an increase in the transamidating activity of tissue transglutaminase, than tissue transglutaminase can ameliorate the apoptotic response through a mechanism that is independent of its transamidating function. Further, neither the phosphatidylinositol‐3‐kinase pathway nor the extracellular‐regulated kinase pathway is downstream of the modulatory effects of wild‐type tissue transglutaminase or C277S‐tissue transglutaminase in the apoptotic cascade.
Patterns of gene expression are altered in the frontal and motor cortices of human alcoholics
Authors: Mayfield R. Dayne , Lewohl Joanne M. , Dodd Peter R. , Herlihy Amy , Liu Jianwen , Harris R. Adron 
Published: March 2003

AbstractAlcoholism is a major health problem in Western countries, yet relatively little is known about the mechanisms by which chronic alcohol abuse causes the pathologic changes associated with the disease. It is likely that chronic alcoholism affects a number of signaling cascades and transcription factors, which in turn result in distinct gene expression patterns. These patterns are difficult to detect by traditional experiments measuring a few mRNAs at a time, but are well suited to microarray analyses. We used cDNA microarrays to analyze expression of approximately 10 000 genes in the frontal and motor cortices of three groups of chronic alcoholic and matched control cases. A functional hierarchy was devised for classification of brain genes and the resulting groups were compared based on differential expression. Comparison of gene expression patterns in these brain regions revealed a selective reprogramming of gene expression in distinct functional groups. The most pronounced differences were found in myelin‐related genes and genes involved in protein trafficking. Significant changes in the expression of known alcohol‐responsive genes, and genes involved in calcium, cAMP, and thyroid signaling pathways were also identified. These results suggest that multiple pathways may be important for neuropathology and altered neuronal function observed in alcoholism.
Age‐dependent decline of DNA repair activity for oxidative lesions in rat brain mitochondria
Authors: Chen Dexi , Cao Guodong , Hastings Teresa , Feng Yiqin , Pei Wei , O'Horo Cristine , Chen Jun 
Published: March 2003

AbstractEndogenous oxidative damage to brain mitochondrial DNA and mitochondrial dysfunction are contributing factors in aging and in the pathogenesis of a number of neurodegenerative diseases. In this study, we characterized the regulation of base‐excision‐repair (BER) activity, the predominant repair mechanism for oxidative DNA lesions, in brain mitochondria as the function of age. Mitochondrial protein extracts were prepared from rat cerebral cortices at the ages of embryonic day 17 (E17) or postnatal 1‐, 2‐, and 3‐weeks, or 5‐ and 30‐months. The total BER activity and the activity of essential BER enzymes were examined in mitochondria using in vitro DNA repair assay employing specific repair substrates. Mitochondrial BER activity showed marked age‐dependent declines in the brain. The levels of overall BER activity were highest at E17, gradually decreased thereafter, and reached to the lowest at the age of 30‐month (∼80% reduction). The decline of overall BER activity with age was attributed to the decreased expression of repair enzymes such as 8‐OHdG glycosylase and DNA polymerase‐γ and, consequently, the reduced activity at the steps of lesion‐base incision, DNA repair synthesis and DNA ligation in the BER pathway. These results strongly suggest that the decline in BER activity may be an important mechanism contributing to the age‐dependent accumulation of oxidative DNA lesions in brain mitochondria.
The metabotropic glutamate receptor mGluR7b binds to the catalytic γ‐subunit of protein phosphatase 1
Authors: Enz Ralf 
Published: March 2003

AbstractCorrect targeting of enzymes represents an important biological mechanism to control post‐translational modifications of neurotransmitter receptors. The metabotropic glutamate receptor type 7 (mGluR7) exists in two splice variants (mGluR7a and mGluR7b), defined by different C‐termini that are phosphorylated by protein kinase C (PKC). Recently, the search for mGluR7a binding partners yielded several proteins that interacted with its C‐terminus. Here, a yeast two‐hybrid screen using the mGluR7b C‐terminus identified both variants of the catalytic γ‐subunit of protein phosphatase 1 (PP1γ1 and PP1γ2) as binding partners. The minimal interacting region of PP1γ1/2 contained the core domain and was homologous to a region of PP1α that is needed for functional expression. Although this core domain is highly conserved within the protein phosphatase family, PP1α1 and PP1β did not interact with mGluR7b. Binding between PP1γ1 and mGluR7b might be regulated by alternative splicing, as the variant‐specific distal part of the mGluR7b C‐terminus mediated the interaction. Within this domain, amino acids involved in the binding to PP1γ1 were mapped and biochemical assays using recombinant and native proteins verified the proposed interaction. Finally, the expression pattern of PP1γ1, PP1γ2 and mGluR7b was analysed in various CNS regions. In summary, these results suggest a regulation of mGluR7b by PP1γ.
Effects of desipramine treatment on norepinephrine transporter gene expression in the cultured SK‐N‐BE(2)M17 cells and rat brain tissue
Authors: Zhu Meng‐Yang , Kim Chun‐Hyung , Hwang Dong‐Youn , Baldessarini Ross J. , Kim Kwang‐Soo 
Published: March 2003

AbstractThe antidepressant desipramine (DMI) is a selective inhibitor of norepinephrine (NE) transport that down‐regulates the norepinephrine transporter (NET) protein in a concentration‐ and time‐dependent mannerin vitro. In this study, possible regulatory effects of DMI onNETmRNA and protein levels were investigated with the NET‐expressing SK‐N‐BE(2)M17 cell line and rat brain tissue. Northern blot analysis showed that incubation of the cultured cells with DMI (5–500 nm) for 3 days reduced levels ofNETmRNA in both its 5.8‐kb (by up to 58%) and 3.6‐kb forms (to 68%), whereas incubation for 14 days increased both levels (to 40% and 100%) in a concentration‐dependent manner. In contrast, NET protein levels decreased after 3–14 days of exposure of the cells to DMI, as determined by western blotting. Thein vitrofindings were supported byin vivotreatment of rats with DMI. Thus,in situhybridization demonstrated initially decreased, and later increased,NETmRNA levels in locus coeruleus (LC) tissue of rats treated with DMI; whereas NET protein levels in the LC were reduced after 14 days, but unchanged after three daily DMI treatments. Thus, DMI had similar effects on NET expressionin vitroandin vivo, with opposite changes inNETmRNA and protein levels, suggesting that the regulatory mechanisms involved are complex and non‐congruent.