Cultured Mouse Neuroblastoma Cells Research Articles

Thiamine and benfotiamine prevent stress-induced suppression of hippocampal neurogenesis in mice exposed to predation without affecting brain thiamine diphosphate levels.

Thiamine is essential for normal brain function and its deficiency causes metabolic impairment, specific lesions, oxidative damage and reduced adult hippocampal neurogenesis (AHN). Thiamine precursors with increased bioavailability, especially benfotiamine, exert neuroprotective effects not only for thiamine deficiency (TD), but also in mouse models of neurodegeneration. As it is known that AHN is impaired by stress in rodents, we exposed C57BL6/J mice to predator stress for 5 consecutive nights and studied the proliferation (number of Ki67-positive cells) and survival (number of BrdU-positive cells) of newborn immature neurons in the subgranular zone of the dentate gyrus. In stressed mice, the number of Ki67- and BrdU-positive cells was reduced compared to non-stressed animals. This reduction was prevented when the mice were treated (200mg/kg/day in drinking water for 20days) with thiamine or benfotiamine, that were recently found to prevent stress-induced behavioral changes and glycogen synthase kinase-3β (GSK-3β) upregulation in the CNS. Moreover, we show that thiamine and benfotiamine counteract stress-induced bodyweight loss and suppress stress-induced anxiety-like behavior. Both treatments induced a modest increase in the brain content of free thiamine while the level of thiamine diphosphate (ThDP) remained unchanged, suggesting that the beneficial effects observed are not linked to the role of this coenzyme in energy metabolism. Predator stress increased hippocampal protein carbonylation, an indicator of oxidative stress. This effect was antagonized by both thiamine and benfotiamine. Moreover, using cultured mouse neuroblastoma cells, we show that in particular benfotiamine protects against paraquat-induced oxidative stress. We therefore hypothesize that thiamine compounds may act by boosting anti-oxidant cellular defenses, by a mechanism that still remains to be unveiled. Our study demonstrates, for the first time, that thiamine and benfotiamine prevent stress-induced inhibition of hippocampal neurogenesis and accompanying physiological changes. The present data suggest that thiamine precursors with high bioavailability might be useful as a complementary therapy in several neuropsychiatric disorders.

Comparative Neuroprotective Effects of Dietary Curcumin and Solid Lipid Curcumin Particles in Cultured Mouse Neuroblastoma Cells after Exposure to Aβ42.

Aggregation of amyloid beta protein (Aβ) and phosphorylated tau (p-Tau) plays critical roles in pathogenesis of Alzheimer's disease (AD). As an antiamyloid natural polyphenol, curcumin (Cur) has a potential role in prevention of neurodegeneration in AD. However, due to limited absorption of the dietary Cur, the solid lipid Cur particles (SLCP) have been suggested as being more effective for AD therapy. In the present study, we compared the role of dietary Cur and SLCP on oxidative stress, neuronal death, p-Tau level, and certain cell survival markers in vitro, after exposure to Aβ42. Mouse neuroblastoma cells were exposed to Aβ42 for 24 h and incubated with or without dietary Cur and/or SLCP. Reactive oxygen species (ROS), apoptotic cell death, p-Tau, and tau kinase (including GSK-3β and cell survival markers, such as total Akt, phosphorylated Akt, and PSD95 levels) were investigated. SLCP showed greater permeability than dietary Cur in vitro, decreased ROS production, and prevented apoptotic death. In addition, SLCP also inhibited p-Tau formation and significantly decreased GSK-3β levels. Further, the cell survival markers, such as total Akt, p-Akt, and PSD95 levels, were more effectively maintained by SLCP than dietary Cur in Aβ42 exposed cells. Therefore, SLCP may provide greater neuroprotection than dietary Cur in Alzheimer's disease.

Cloning, expression, and purification of cold inducible RNA-binding protein and its neuroprotective mechanism of action

Background: Cold-inducible RNA-binding protein (CIRP) is induced in response to hypothermia, where it exerts neuroprotective effects. Our preliminary studies revealed that it inhibits H2O2-induced apoptosis in rat neurons. In the current study, we report effective expression and purification approaches for the synthesis of CIRP, and assess its potential protective effects against oxidative stress. Methods: CIRP-encoding was expressed using the prokaryotic expression system pGEX-4T-1, and SP-Sepharose and Sephacryl S-200 columns were used to purify rCIRP. To mimic ischemia/reperfusion injury-associated oxidative stress, neuro2a cells (N2a) were pre-treated with rCIRP for 2h, followed by hydrogen peroxide (H2O2 60μmol/ml) for 24h. Cell viability was then quantified using an MTT assay. In addition, western blotting was performed to measure the cell cycle related signal transduction pathways. Results: N2a cells exhibited decreased viability following H2O2 treatment, whereas rCIRP significantly improved viability following H2O2 treatment. CIRP also accelerated cell cycle progression from S to G2/M phase in cultured mouse neuroblastoma cells. In addition, CIRP increased levels of p-ERK and p-Akt, and also re-activated the cell cycle-related protein cyclin D1 and c-Myc. These results suggest that CIRP activated the Akt and ERK signal transduction pathways in N2a cells. Conclusions: Our findings suggest that CIRP could exert protective effects against oxidative stress, and that it might be a novel neuroprotective agent.

The Components ofFlemingia macrophyllaAttenuate Amyloidβ-Protein Accumulation by Regulating Amyloidβ-Protein Metabolic Pathway

Flemingia macrophylla (Leguminosae) is a popular traditional remedy used in Taiwan as anti-inflammatory, promoting blood circulation and antidiabetes agent. Recent study also suggested its neuroprotective activity against Alzheimer's disease. Therefore, the effects of F. macrophylla on Aβ production and degradation were studied. The effect of F. macrophylla on Aβ metabolism was detected using the cultured mouse neuroblastoma cells N2a transfected with human Swedish mutant APP (swAPP-N2a cells). The effects on Aβ degradation were evaluated on a cell-free system. An ELISA assay was applied to detect the level of Aβ1-40 and Aβ1-42. Western blots assay was employed to measure the levels of soluble amyloid precursor protein and insulin degrading enzyme (IDE). Three fractions of F. macrophylla modified Aβ accumulation by both inhibiting β-secretase and activating IDE. Three flavonoids modified Aβ accumulation by activating IDE. The activated IDE pool by the flavonoids was distinctly regulated by bacitracin (an IDE inhibitor). Furthermore, flavonoid 94-18-13 also modulates Aβ accumulation by enhancing IDE expression. In conclusion, the components of F. macrophylla possess the potential for developing new therapeutic drugs for Alzheimer's disease.

Effect of the fluorescent tracer Fast Blue on the Pseudorabies virus infection

Event Abstract Back to Event Effect of the fluorescent tracer Fast Blue on the Pseudorabies virus infection Gabor Marton1, Dora Tombacz2, Judit Toth2, Andrea Szabo1, Zsolt Boldogkoi2 and Antal Nógrádi1* 1 Department of Ophthalmology, University of Szeged, Hungary 2 Department of Medical Biology, University of Szeged, Hungary The Pseudorabies virus (Prv) inoculated into peripheral tissue infects neurons and spreads through synaptically linked cells. Retrograde fluorescent tracers can be used for the identification of the infected first-order neurons. The question can be raised whether these fluorescent tracers have an effect on the Prv infection. In this study we applied the fluorescent tracer Fast Blue to the cut sciatic nerve 24 or 48 hours after inoculation of Prv (Bartha strain) into hindlimb muscles of SD rats. The virus infection was studied also in the trigeminal tract: the Kaplan strain of the virus was inoculated into the cornea of SD rats and after 2 or 6 hours FB was applied into the cornea. In cultured mouse neuroblastoma cells the expression of different viral kinetic genes was investigated in the presence of FB. The application of the FB 24 hours after the PrV injection into the hindlimb muscles prevented the infection of lumbar motoneurons, while FB treatment applied 48 hours after virus inoculation was not able to inhibit infection of lumbar motoneurons. In the trigeminal nuclei the number of the virus infected neurons significantly decreased when FB was applied 2 or 6 hours after the inoculation of the Prv into the cornea. In the neuroblastoma cultures treated with FB the expression of the viral RNAs and amount of the viral DNAs was repressed. Our results show that Fast Blue delivered to the primarily infected rat neurons at an early stage of virus replication is able to prevent infection of motoneurons. The infection of the trigeminal nuclear neurons can also be effectively inhibited using FB. The molecular investigations confirmed our morphological findings. Conference: 12th Meeting of the Hungarian Neuroscience Society, Budapest, Hungary, 22 Jan - 24 Jan, 2009. Presentation Type: Poster Presentation Topic: Developmental neurobiology and subcortical functions Citation: Marton G, Tombacz D, Toth J, Szabo A, Boldogkoi Z and Nógrádi A (2009). Effect of the fluorescent tracer Fast Blue on the Pseudorabies virus infection. Front. Syst. Neurosci. Conference Abstract: 12th Meeting of the Hungarian Neuroscience Society. doi: 10.3389/conf.neuro.01.2009.04.065 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 02 Mar 2009; Published Online: 02 Mar 2009. * Correspondence: Antal Nógrádi, Department of Ophthalmology, University of Szeged, Szeged, Hungary, nogradi.antal@med.u-szeged.hu Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Gabor Marton Dora Tombacz Judit Toth Andrea Szabo Zsolt Boldogkoi Antal Nógrádi Google Gabor Marton Dora Tombacz Judit Toth Andrea Szabo Zsolt Boldogkoi Antal Nógrádi Google Scholar Gabor Marton Dora Tombacz Judit Toth Andrea Szabo Zsolt Boldogkoi Antal Nógrádi PubMed Gabor Marton Dora Tombacz Judit Toth Andrea Szabo Zsolt Boldogkoi Antal Nógrádi Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

The effects of acute phase phosphoplipids from patients with chronic fatigue syndrome on the sodium channel in tissue culture

Acute phase phospholipids isolated from the sera of patients with clinically diagnosed chronic fatigue syndrome (CFS) were examined for effects on the sodium channel of mouse neuroblastoma cells in tissue culture after studies suggested a structural correlation between CFS lipids and the lipophilic marine toxin, ciguatoxin. The neuroblastoma cell bioassay is a directed cytotoxicity assay that records sensitive changes in the sodium channel of neuroblastoma cells in the presence of sodium channel activators or inhibitors. The ciguatoxins are characterized by their ability to cause the persistent activation of voltage‐sensitive sodium channels, leading to increased cell Na+ permeability. Ciguatera fish poisoning in humans is characterized by neurological, gastrointestinal, and cardiovascular manifestations that are similar to the symptoms of CFS.Several lipids were examined for sodium channel activity: ciguatoxin, cholesterol, cholesterol myristate, and the phospholipids isolated from CFS patients as well as antagonists gluconate, ursodeoxycholic acid, d‐ribose, and anti‐CTX antibody. Results indicate that cholesterol and cholesterol myristate have weak but observable interactions at the sodium channel as activators, and that CTX and CFS lipids both have strong activity as sodium channel activators. However, studies revealed that none of the potential antagonists evaluated were effective at blocking the activity of the lipids at the sodium channel.[Supported in part by National CFIDS Foundation, and the Hokama‐Yagawa Fund]

The antitrypanosomal drug melarsoprol competitively inhibits thiamin uptake in mouse neuroblastoma cells

Melarsoprol is the main drug used for the treatment of late-stage sleeping sickness, although it causes severe side-effects such as encephalopathy and polyneuropathy leading to death in some patients. Recent data suggest that melarsoprol and its active metabolite melarsenoxide interfere with thiamin transport and metabolism in E. coli and yeast, but there are no data concerning their possible effects on thiamin metabolism in mammalian cells. We tested both drugs on thiamin transport in cultured mouse neuroblastoma cells using (14)C-labeled thiamin. Melarsoprol, competitively inhibits high-affinity thiamin transport in mouse neuroblastoma cells with a K(i) of 44 micromol/L. However, the active compound melarsenoxide has no inhibitory effect. This suggests that the side effects of melarsoprol treatment are unlikely to be due to inhibition of thiamin transport by melarsenoxide, its main metabolite in the brain.

Prion clearance in bigenic mice

The clearance of prions from the brain was investigated in bigenic mice designated Tg(tTA : PrP(+/0))3, in which expression of the cellular prion protein (PrP(C)) was regulated by oral doxycycline administration. With suppression of PrP(C) expression, the incubation time for RML prions was prolonged almost threefold from approximately 150 to approximately 430 days. To determine the clearance rate of disease-causing PrP(Sc), bigenic mice were given oral doxycycline beginning 98 days after inoculation with RML prions and sacrificed at various time points over the subsequent 56 days. The half-life (t1/2) for PrP(Sc) was approximately 1.5 days in mouse brain, in reasonable agreement with the apparent t1/2 of 30 h that was determined in a separate study for scrapie-infected mouse neuroblastoma (ScN2a) cells in culture. Both protease-sensitive and -resistant conformers of PrP(Sc) were cleared at the same rate. The t1/2 value for PrP(C) clearance from brain was approximately 18 h, which was considerably longer than the t1/2 of 5 h found in ScN2a cells. The capability of the brain to clear prions raises the possibility that PrP(Sc) is normally made at low levels and continually cleared, and that PrP(Sc) may have a function in cellular metabolism. Moreover, these bigenic mice make it possible to determine both components of PrP(Sc) accumulation, i.e. the rates of formation and clearance, for various strains of prions exhibiting different incubation times.

Endogenous parathyroid hormone-related protein functions as a neuroprotective agent

Parathyroid hormone-related protein (PTHrP) was discovered a dozen years ago as a product of malignant tumors. It is now known that PTHrP is a paracrine factor with multiple biological functions. One such function is to relax smooth muscle by inhibiting calcium influx into the cell. In the central nervous system, PTHrP and its receptor are widely expressed in neurons in the cerebral cortex, hippocampus and cerebellum. The function of PTHrP in the CNS is not known. Previous work has shown that expression of the PTHrP gene is depolarization-dependent in cultured cerebellar granule cells and depends specifically on L-type voltage sensitive calcium channel (L-VSCC) Ca 2+ influx. PTHrP has also been found to be capable of protecting these cells against kainic acid-induced excitotoxicity. Here, we tested the idea that mice with a PTHrP-null CNS might display hypersensitivity to kainic acid excitotoxicity. We found that these mice were six-fold more sensitive than control littermate mice to kainic-acid-induced seizures as well as hippocampal c-Fos expression. PTHrP-null embryonic mixed cerebral cortical cultures were more sensitive to kainic acid than control cultures, and PTHrP addition was found to be protective against kainate toxicity in both PTHrP-null and control cultures. By whole-cell techniques, PTHrP was found to reduce L-VSCC Ca 2+ influx in cultured mouse neuroblastoma cells. We conclude that PTHrP functions as a component of a neuroprotective feedback loop that is structured around the L-type calcium channel. This loop appears to be operative in vivo as well as in vitro.

Antibodies inhibit prion propagation and clear cell cultures of prion infectivity

Prions are the transmissible pathogenic agents responsible for diseases such as scrapie and bovine spongiform encephalopathy. In the favoured model of prion replication, direct interaction between the pathogenic prion protein (PrPSc) template and endogenous cellular prion protein (PrPC) is proposed to drive the formation of nascent infectious prions. Reagents specifically binding either prion-protein conformer may interrupt prion production by inhibiting this interaction. We examined the ability of several recombinant antibody antigen-binding fragments (Fabs) to inhibit prion propagation in cultured mouse neuroblastoma cells (ScN2a) infected with PrPSc. Here we show that antibodies binding cell-surface PrPC inhibit PrPSc formation in a dose-dependent manner. In cells treated with the most potent antibody, Fab D18, prion replication is abolished and pre-existing PrPSc is rapidly cleared, suggesting that this antibody may cure established infection. The potent activity of Fab D18 is associated with its ability to better recognize the total population of PrPC molecules on the cell surface, and with the location of its epitope on PrPC. Our observations support the use of antibodies in the prevention and treatment of prion diseases and identify a region of PrPC for drug targeting.

Aminohexanoic hydroxamate is a potent inducer of the differentiation of mouse neuroblastoma cells

Deoxyhypusine synthase is the key enzyme for modifying a lysine residue to hypusine in the cellular protein eukaryotic initiation factor 5A (eIF-5A). Deletion of the deoxyhypusine synthase or the eIF-5A gene in yeast produces lethal phenotype. Inhibition of deoxyhypusine synthase by 1-guanidino-7-aminoheptane (GC7) suppresses tumor cell growth. Hypusine formation represents one of the most specific polyamine-dependent biochemical reactions. In view of the importance of polyamines in growth regulation and cancer biology, deoxyhypusine synthase has been considered to be a good target for chemotherapeutic drug design. Using GC7 as a prototype we have synthesized and tested three classes of diamine analogs, namely, guanidino-, pyrimidino-, and hydroxamate derivatives, as potential inhibitors for deoxyhypusine synthase. Our study shows that (i) among all the compounds tested, GC7 remained to be the most potent inhibitor for deoxyhypusine synthase; (ii) N, N′-bispyrimidino-1,9-diaminononane, although a poor inhibitor of deoxyhypusine synthase, was a potent growth inhibitor; and (iii) one of the hydroxamate derivatives, 6-aminohexanoic hydroxamate (HC6), prominently induced the differentiation of mouse neuroblastoma cells at sub-millimolar concentrations. Interestingly, other hydroxamates with different chain length were not nearly as effective as HC6 in inducing neuroblastoma cell differentiation. The effect of HC6 was also unique in that it could induce neurite outgrowth and the expression of neuron-specific genes such as synapsin I and MAP-2 in neuroblastoma cells in the absence of other promoting agents such as cAMP. The effect of HC6 on neuroblastoma cell differentiation was comparable with, or better than that of N 6, O 2′-dibutyryl cAMP (Bt 2cAMP), a standard reagent commonly used for inducing the differentiation of mouse and human neuroblastoma cells in culture.

Morphological, biochemical and molecular effects of cocaine on mouse neuroblastoma cells culture in vitro

In order to compare the effects of cocaine at morphological, basal cytotoxicity, biochemical and molecular levels, cultured mouse neuroblastoma cells (Neuro-2a) were exposed to a range of concentrations of cocaine hydrochloride. Neuroblastoma cell proliferation, evaluated by quantification of total protein content, was very sensitive to cocaine, being increasingly inhibited from 12 to 72 hr of exposure (EC 50 = 3.1 m m at 24 hr). Cytoplasmic membrane permeability to lactate dehydrogenase was not particularly increased and lysosomal function was stimulated from 0.05 to 1.5 m m, and inhibited from 2.5 m m. A shift to anaerobiosis was detected as intracellular lactate dehydrogenase (LDH) activity was increased and mitochondrial succinate dehydrogenase (SDH) activity decreased. Hexosaminidase (HEX), a lysosomal enzyme involved in sphingolipid degradation, was stimulated only at 1 m m and neural acetylcholinesterase (AChE) activity was stimulated from 2.5 m m. Morphological examination of exposed cultures revealed that most cells became bipolar and multipolar neurons by extension of neurites, but also suffered cytoplasmic vacuolization, hydropic degeneration and nuclear pyknosis. Although cells developing apoptosis were observed, no DNA oligonucleosomal fragmentation was detected by agarose gel electrophoresis of DNA from cells exposed to cocaine. In conclusion, in addition to predominance of anaerobiosis, little disruption of membranes and severe morphologic injury, biochemical and morphological differentiation-like effects were the most prominent alterations produced by cocaine on mouse neuroblastoma cells.

Determination of Phosphofructokinase and Enolase Activities in Cultured Mouse Neuroblastoma Cells: Application to the In Vitro Detection of Neurotoxic Effects

Simple methods for the determination of phosphofructokinase (PFK) and total enolase (END activities in cultured mouse neuroblastoma cells have been developed. The influences of changes in glucose metabolism, induced by chlorpromazine, cycloheximide, 2,4-dinitrophenol and iodoacetic acid, on PFK and ENL activities in vitro were compared as a practical application of the methods. Mouse neuroblastoma cell cultures (Neuro-2a) were exposed for 24 hours and cytotoxic effects were evaluated. All the determinations were carried out in the same 96-well tissue culture plates in which exposure took place. Chlorpromazine and cycloheximide produced opposite effects on both PFK and ENL activities. While chlorpromazine increased PFK activity by 50% and decreased ENL activity by 30%, cycloheximide inhibited PFK activity by 50% and increased ENL activity by 45%. The response to dinitrophenol was quite different; both PFK and ENL activities were increased, by 45% and 35% respectively. After exposure of the cells to iodoacetic acid, neither PFK nor ENL activities showed statistically significant differences from the levels in control cells. The different responses elicited by the four toxicants suggest that the two enzymes selected are useful for differentiating among diverse types of mechanism of action.

Unique Conductance, Gating, and Selective Permeability Properties of Gap Junction Channels Formed by Connexin40

Connexin40 is selectively expressed in specialized cardiac conduction (nodal and His-Purkinje) tissues and the atrium, yet the channel properties formed by this gap junction protein have not been investigated. The conductance, gating, and selective permeability of rat connexin40 (Cx40) gap junction channels between pairs of Cx40-transfected mouse neuroblastoma (N2A) cells in culture were studied by using dual whole-cell voltage-clamp techniques. The macroscopic steady state junctional conductance gating was dependent on transjunctional voltage with a Boltzmann half-inactivation voltage of +/- 50 mV, a residual voltage-insensitive normalized junctional conductance of 35% of maximum, and a gating charge valence of 3. In the presence of 120 mmol/L potassium glutamate, the slope conductance of single rat Cx40 gap junction channels measured 158 +/- 2 pS (n = 4). Lower conductance states equal to 21% to 48% of the main open-state conductance were also occasionally observed in two of the four cell pairs. Multichannel open probabilities were found to be heterogeneous. Ion substitution and dye transfer experiments were performed to determine the relative chloride/potassium conductance and dye permeability of anionic fluorescein derivatives in rat Cx40 channels. The rat Cx40 channel had a maximum conductance of 180 +/- 18 pS (n = 3) in 120 mmol/L KCl and a detectable chloride permeability of 0.29 relative to potassium, indicating some selectivity for cations over anions. Cx40 gap junctions were permeable to 2',7'-dichlorofluorescein (diCl-F) and also to the more polar 6-carboxyfluorescein dye; however, diCl-F dye transfer was not observed to increase with increasing junctional conductance.

Effects of cobalt on mouse neuroblastoma cells cultured in vitro

To compare the effects of cobalt at different cellular levels, cultured mouse neuroblastoma cells (Neuro-2a) were exposed for 24 hr to cobalt(II) chloride. The following toxicity indicators were assessed: cell proliferation by quantification of total protein content; cytoplasmic membrane integrity to cytosolic lactate dehydrogenase leakage; lysosomal hexosaminidase release; lactate dehydrogenase activity (LDH); mitochondrial succinate dehydrogenase activity (SDH); relative neutral red uptake by lysosomes (RNRU); lysosomal hexosaminidase activity (HEX), and acetylcholinesterase activity (AChE). The effect of cobalt on the various indicators differed. Cobalt was not very toxic to neuroblastoma cell proliferation (EC 50 = 200 μ m). Cytoplasmic membrane permeability was not specifically increased, and LDH leakage occurred only at high concentrations, prior to the stimulation of HEX activity, an enzyme involved in sphingolipid degradation. In contrast, cobalt was lysosomotropic, with HEX release. The effects on lysosomal function were also studied with the RNRU, showing stimulation at low concentrations and inhibition at high concentrations. Neural AChE was decreased after an initial stimulation at low concentrations. LDH and SDH intracellular activities were both stimulated from low concentrations, mitochondrial SDH activity being the most sensitive marker studied. Metabolic stimulatory effects induced by cobalt were, therefore, more marked than changes in cytoplasmic and lysosomal membrane permeability.

In vitro effects of thallium on mouse neuroblastoma cells

To compare the effects of thallium at different cellular levels, cultured mouse neuroblastoma cells (Neuro-2A) were exposed for 24 hr to thallium(I) acetate. The following toxic indicators were assessed in the in vitro test system: cell proliferation by quantification of total protein content of the culture; cytoplasmic membrane integrity to cytosolic lactate dehydrogenase (LDH) leakage; lysosomal hexosaminidase release; lactate dehydrogenase activity; mitochondrial succinate dehydrogenase activity; relative neutral red uptake by lysosomes; lysosomal hexosaminidase sphingolipid degradation activity; acetylcholinesterase activity. The effects of thallium on the various indicators differed. Neural acetylcholinesterase activity was extremely sensitive to T1 inhibition. In contrast, hexosaminidase, an enzyme involved in glycosphingolipid degradation, was stimulated prior to cytoplasmic membrane disruption detected as LDH leakage. Relative neutral red uptake was slightly more sensitive than cell growth inhibition and the reduction in hexosaminidase release suggests an interaction with lysosomes. The low degree of sensitivity of cell proliferation, as judged by the protein content of the cultures, may reflect inhibition of protein degradation. LDH glycolytic activity was severely inhibited, but succinate dehydrogenase activity in the citric acid cycle was increased, probably owing to the mitochondrial accumulation of thallium.

Interaction between enantiomers of mianserin and ORG3770 at 5-HT 3 receptors in cultured mouse neuroblastoma cells

Stereoselective effects of mianserin and ORG3770 on serotonin 5-HT 3 receptors in mouse neuroblastoma N1E-115 cells have been investigated in radioligand binding and in whole-cell voltage clamp experiments. The specific binding of [ 3H]GR65630 to 5-HT 3 recognition sites in N1E-115 cell homogenates is reduced by mianserin and ORG3770 and their enantiomers. The p K i values of the more potent ( R)enantiomers of mianserin and ORG3770 are 8.44 and 8.62, respectively. The ( R)enantiomers of mianserin and ORG3770 are 15 and 37 times more potent than their respective( S)enantiomers. The racemates are only 1.9 and 3.3 times less potent than the corresponding ( R)enantiomers. In voltage clamp experiments the ( R)enantiomers block the 5-hydroxytryptamine(5-HT)-induced ion current with pIC 50 values of 8.52 for ( R)mianserin and 8.26 for the ( R)enantiomer of ORG3770. The ( R)enantiomers of mianserin and ORG3770 are 24 and 145 times more potent in blocking the 5-HT-induced ion current than their respective ( S)enantiomers. The racemates are 6 and 13 times less potent than the corresponding ( R)enantiomers. In addition, the block of 5-HT-induced ion current by the ( R)enantiomer of ORG3770 is partially reversed by a low concentration of its ( S)enantiomer. The results indicate that the two enantiomers block the 5-HT 3 receptor-mediated ion current in a mutually dependent manner.

Tetraethylammonium ions block 5-HT 3 receptor-mediated ion current at the agonist recognition site and prevent desensitization in cultured mouse neuroblastoma cells

Effects of tetraethylammonium ions on 5-hydroxytryptamine 3 (5-HT 3) receptor-mediated ion current have been studied in whole-cell voltage clamped N1E-115 cells. Inward currents evoked by superfusion with 10 μM 5-HT are rapidly blocked by external tetraethylammonium and the kinetics of the partially blocked inward currents are slowed down. External tetraethylammonium also prevents, but is unable to reverse, agonist-induced desensitization of the 5-HT 3 receptor-mediated ion current. Both effects depend on tetraehtylammonium concentration and attain half maximum values at 2.6–2.8 mM tetraethylammonium. Tetraethylammonium acts externally, since substituting internal monovalent cations by 107 mM tetraethylammonium fails to block 5-HT 3 receptor-mediated ion current. This ion substitution causes a shift in the current reversal potential towards a more positive value, indicating that the receptor-operated ion channel is permeable to tetraethylammonium. An IC 50 effect of external tetraethylammonium is reduced to 28% blockade when currents are evoked by 50 μM instead of 10 μM 5-HT, indicating that tetraethylammonium and 5-HT compete for the same site. It is concluded that tetraethylammonium shows low affinity for (part of) the agonist binding site involved in the activation as well as in the desensitization of the receptor-operated ion channel.

A scanning electron-microscopic study of the effects of methylmercury on the neuronal cytoskeleton

Cultured mouse neuroblastoma cells, Neuro-2a (c1300), were exposed to 2.5 and 5.0 μM methylmercury (MeHg) with or without the concomitant administration of 10 mM glutathione for 24 h. Treated cells viewed by scanning electron microscopy (SEM) appeared sponge-like and were surrounded by fragments of cytoplasmic processes. SEM cytoskeletal preparations of treated cells showed a collapsed matrix containing globular bodies. Microtubules were not seen in treated cells, but intermediate and microfilaments were observed. SDS-PAGE analysis of cytoskeletal extracts revealed bands ranging in size from 90 to 27 kDa in all treatment groups except in the 5.0 μM-MeHg-treated group. This group showed a single band co-migrating with actin. Cells exposed to glutathione alone or concomitantly with MeHg appeared similar to control cells under all experimental conditions. These observations suggest that MeHg may predominantly affect microtubules to form a condensation product.

Activation of cyclic GMP formation in mouse neuroblastoma cells by a labile nitroxyl radical. An electron paramagnetic resonance/spin trapping study

The receptor-mediated generation of an endothelial-derived relaxing factor (EDRF)-free radical intermediate in a neuronal cell line detected by spin trapping techniques has been reported. Here we report the time course of the appearance of the 3,5-dibromo-4-nitrosobenzene sulfonate (DBNBS) spin adduct and cyclic GMP formation following addition of carbamylcholine to suspensions of cultured mouse neuroblastoma cells (clone N1E-115). The time course of the appearance of the DBNBS spin adduct shows that spin adduct formation decreases possibly reaching a minimum approximately between 35 and 40 s. This is inversely proportional to cGMP formation which reaches a maximum at approximately 40 s after carbamylcholine activation. In addition, the inhibitory effect of N G-monomethyl-L-arginine (NMMA), potassium ferricyanide, K 3Fe(CN) 6 and methylene blue in cytosol preparation was investigated. A mechanism is proposed that essentially accounts for the combined results observed by spin trapping/electron paramagnetic resonance (EPR) study providing direct evidence for the muscarinic receptor-mediated formation of a labile, diffusible precursor of nitric oxide (NO) derived from L-arginine that activates soluble guanylate cyclase.