Ralf Dringen

Universität Bremen, Bremen, Bremen, Germany

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Publications (180)649.42 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: In this study we use a straightforward experimental method to probe the presence and activity of the proteolytic enzyme α-chymotrypsin adsorbed on titania colloidal particles. We show that the adsorption of α-chymotrypsin on the particles is irreversible and pH-dependent. At pH 8 the amount of adsorbed chymotrypsin is threefold higher compared to the adsorption at pH 5. However, we observe that the adsorption is accompanied by a substantial loss of enzymatic activity, and only around 6-9% of the initial enzyme activity is retained. A Michaelis-Menten kinetics analysis of both unbound and TiO2-bound chymotrypsin shows that the KM value is increased from ∼10μM for free chymotrypsin to ∼40μM for the particle bound enzyme. Such activity decrease could be related by the hindered accessibility of substrate to the active site of adsorbed chymotrypsin, or by adsorption-induced structural changes. Our simple experimental method does not require any complex technical equipment, can be applied to a broad range of hydrolytic enzymes and to various types of colloidal materials. Our approach allows an easy, fast and reliable determination of particle surface-bound enzyme activity and has high potential for development of future enzyme-based biotechnological and industrial processes. Copyright © 2015 Elsevier Inc. All rights reserved.
    Journal of Colloid and Interface Science 10/2015; 455. DOI:10.1016/j.jcis.2015.05.022 · 3.37 Impact Factor
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    ABSTRACT: Copper is essential for several important cellular processes, but an excess of copper can also lead to oxidative damage. In brain, astrocytes are considered to play a pivotal role in the copper homeostasis and antioxidative defence. To investigate whether antioxidants and copper chelators can modulate the uptake and the toxicity of copper ions in brain astrocytes, we used primary astrocytes as cell culture model. These cells accumulated substantial amounts of copper during exposure to copper chloride. Copper accumulation was accompanied by a time- and concentration-dependent loss in cell viability, as demonstrated by a lowering in cellular MTT reduction capacity and by an increase in membrane permeability for propidium iodide. During incubations in the presence of the antioxidants ascorbate, trolox or ebselen, the specific cellular copper content and the toxicity in copper chloride-treated astrocyte cultures were strongly increased. In contrast, the presence of the copper chelators bathocuproine disulfonate or tetrathiomolybdate lowered the cellular copper accumulation and the copper-induced as well as the ascorbate-accelerated copper toxicity was fully prevented. These data suggest that predominantly the cellular content of copper determines copper-induced toxicity in brain astrocytes. Copyright © 2015 Elsevier GmbH. All rights reserved.
    Journal of Trace Elements in Medicine and Biology 10/2015; 32:168-76. DOI:10.1016/j.jtemb.2015.07.001 · 2.37 Impact Factor
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    ABSTRACT: A protein corona forms spontaneously around silica nanoparticles (SNPs) in serum-containing media. To test whether this protein corona can be utilized for the loading and release of anticancer drugs we incorporated the hydrophilic doxorubicin, the hydrophobic meloxicam as well as their combination in the corona around SNPs. The application of corona-covered SNPs to osteosarcoma cells revealed that drug-free particles did not affect the cell viability. In contrast, SNPs carrying a protein corona with doxorubicin or meloxicam lowered the cell proliferation in a concentration-dependent manner. In addition, these particles had an even greater antiproliferative potential than the respective concentrations of free drugs. The best antiproliferative effects were observed for SNPs containing both doxorubicin and meloxicam in their corona. Co-localization studies revealed the presence of doxorubicin fluorescence in the nucleus and lysosomes of cells exposed to doxorubicin-containing coated SNPs, suggesting that endocytotic uptake of the SNPs facilitates the cellular accumulation of the drug. Our data demonstrate that the protein corona, which spontaneously forms around nanoparticles, can be efficiently exploited for loading the particles with multiple drugs for therapeutic purposes. As drugs are efficiently released from such particles they may have a great potential for nanomedical applications.
    Nanoscale 09/2015; DOI:10.1039/C5NR04726A · 7.39 Impact Factor
  • Charlotte Petters · Karsten Thiel · Ralf Dringen
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    ABSTRACT: Iron oxide nanoparticles (IONPs) are used for various biomedical and neurobiological applications. Thus, detailed knowledge on the accumulation and toxic potential of IONPs for the different types of brain cells is highly warranted. Literature data suggest that microglial cells are more vulnerable towards IONP exposure than other types of brain cells. To investigate the mechanisms involved in IONP-induced microglial toxicity, we applied fluorescent dimercaptosuccinate-coated IONPs to primary cultures of microglial cells. Exposure to IONPs for 6 h caused a strong concentration-dependent increase in the microglial iron content which was accompanied by a substantial generation of reactive oxygen species (ROS) and by cell toxicity. In contrast, hardly any ROS staining and no loss in cell viability were observed for cultured primary astrocytes and neurons although these cultures accumulated similar specific amounts of IONPs than microglia. Co-localization studies with lysotracker revealed that after 6 h of incubation in microglial cells, but not in astrocytes and neurons, most IONP fluorescence was localized in lysosomes. ROS formation and toxicity in IONP-treated microglial cultures were prevented by neutralizing lysosomal pH by the application of NH4Cl or Bafilomycin A1 and by the presence of the iron chelator 2,2′-bipyridyl. These data demonstrate that rapid iron liberation from IONPs at acidic pH and iron-catalyzed ROS generation are involved in the IONP-induced toxicity of microglia and suggest that the relative resistance of astrocytes and neurons against acute IONP toxicity is a consequence of a slow mobilization of iron from IONPs in the lysosomal degradation pathway.
    Nanotoxicology 08/2015; DOI:10.3109/17435390.2015.1071445 · 6.41 Impact Factor
  • Felix Bulcke · Ralf Dringen
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    ABSTRACT: Copper is an essential trace element for many important cellular functions. However, excess of copper can impair cellular functions by copper-induced oxidative stress. In brain, astrocytes are considered to play a prominent role in the copper homeostasis. In this short review we summarise the current knowledge on the molecular mechanisms which are involved in the handling of copper by astrocytes. Cultured astrocytes efficiently take up copper ions predominantly by the copper transporter Ctr1 and the divalent metal transporter DMT1. In addition, copper oxide nanoparticles are rapidly accumulated by astrocytes via endocytosis. Cultured astrocytes tolerate moderate increases in intracellular copper contents very well. However, if a given threshold of cellular copper content is exceeded after exposure to copper, accelerated production of reactive oxygen species and compromised cell viability are observed. Upon exposure to sub-toxic concentrations of copper ions or copper oxide nanoparticles, astrocytes increase their copper storage capacity by upregulating the cellular contents of glutathione and metallothioneins. In addition, cultured astrocytes have the capacity to export copper ions which is likely to involve the copper ATPase 7A. The ability of astrocytes to efficiently accumulate, store and export copper ions suggests that astrocytes have a key role in the distribution of copper in brain. Impairment of this astrocytic function may be involved in diseases which are connected with disturbances in brain copper metabolism.
    Neurochemical Research 08/2015; DOI:10.1007/s11064-015-1688-9 · 2.59 Impact Factor
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    ABSTRACT: To study the importance of the surface charge for cellular uptake of silica nanoparticles (NPs) we synthesised five different single- or multi-functionalised fluorescent silica NPs (FFSNPs) by introducing various ratios of amino and sulfonate groups into their surface. These FFSNPs were tailored in their zeta potential values from highly positive to highly negative, while other physicochemical properties remained almost constant. Irrespective of the original surface charge, serum proteins adsorbed onto the surface, neutralised the zeta potential values and prevented the aggregation of the tailor-made FFSNPs. Depending on the surface charge and on the absence or presence of serum, two opposite trends were found concerning the cellular uptake of FFSNPs. In the absence of serum, positively charged NPs were stronger accumulated by human osteoblast (HOB) cells than negatively charged NPs. In contrast, in serum-containing medium anionic FFSNPs were internalised by HOB cells more strongly, despite the similar size and surface charge of all types of protein-covered FFSNPs. Thus, at physiological condition, when the presence of proteins is inevitable sulfonate-functionalised silica NPs are the favourite choice to achieve a desired high rate of NP internalisation.
    ACS Applied Materials & Interfaces 06/2015; 7(25). DOI:10.1021/acsami.5b01900 · 6.72 Impact Factor
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    ABSTRACT: The inorganic arsenic species arsenate and arsenite are common environmental toxins which contaminate the drinking water in many countries. Chronic intoxication with arsenicals has been connected with various diseases, but causes also neurological complications and impairs cognitive development, learning and memory. In brain, astrocytes have a pivotal role as partners of neurons in homeostatic and metabolic processes. In addition, astrocytes are the first parenchymal brain cell type which encounters substances which cross the blood-brain barrier and are considered as first line of defence against the toxic potential of xenobiotics. Therefore, astrocytes are likely to play a prominent role in the metabolism and potential detoxification of arsenicals in brain. This article summarizes the current knowledge on the uptake and toxicity of arsenate and arsenite in astrocytes and discusses the modulation of the astrocytic glucose and glutathione metabolism by arsenicals.
    Neurochemical Research 04/2015; DOI:10.1007/s11064-015-1570-9 · 2.59 Impact Factor
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    ABSTRACT: The immobilization of enzymes on solid materials is a promising strategy in biotechnological applications and proteomics. It can improve the enzymes’ stability, and enables a more convenient handling, easy separation from the reaction solution, and cyclic reuse of the enzymes. In order to investigate the proteolytic properties of a particle-bound protease, chymotrypsin was covalently immobilized on silica and alumina colloidal particles. The enzymatic activity of the bound chymotrypsin at different times, in consecutive proteolytic cycles, and after storage up to several weeks was investigated by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-ToF MS). Using this approach, the proteolysis products were identified without using artificial protease substrates or intermediate chemicals. Lysozyme was used as a model protein to perform enzymatic digestion using immobilized chymotrypsin and the peptides generated from the proteolytic digestion were determined. Compared to the activity of chymotrypsin applied for the immobilization reactions, more active chymotrypsin was bound to alumina (between 1 and 10% of the initial concentration) than to silica (below 1%) colloidal particles. Compared to an excess of unbound chymotrypsin, the digestion of lysozyme was slower with chymotrypsin immobilized on colloidal particles and only 60% of the maximal amounts of lysozyme peptides were detected. The proteolytic activity of chymotrypsin immobilized on colloidal particles was maintained during storage at room temperature for up to at least seven weeks, while it was lowered during consecutive digestions.
    Analytical Letters 02/2015; 48(3). DOI:10.1080/00032719.2014.951449 · 1.03 Impact Factor
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    ABSTRACT: Based on the chemical structure and the known chemical synthesis of the marine sponge alkaloid ageladine A, we synthesized the ageladine A-derivative 4-(naphthalene-2-yl)-1H-imidazo[4,5-c]pyridine trifluoroacetate (LysoGlow84). The two-step synthesis started with the Pictet-Spengler reaction of histamine and naphthalene-2-carbaldehyde to a tetrahydropyridine intermediate, which was dehydrogenated with activated manganese (IV) oxide to LysoGlow84. Structure and purity of the synthesized LysoGlow84 were confirmed by NMR spectroscopy and mass spectrometry. The fluorescence intensity emitted by LysoGlow84 depended strongly on the pH of the solvent with highest fluorescence intensity recorded at pH 4. The fluorescence maximum (at 315 nm excitation) was 921 observed at 440 nm. Biocompatibility of LysoGlow84 was investigated using cultured rat brain astrocytes and the marine flatworm Macrostomum lignano. Exposure of the astrocytes for up to 6 h to micromolar concentrations of LysoGlow84 did not compromise cell viability, as demonstrated by several viability assays, but revealed a promising property of this compound for staining of cellular vesicles. Conventional fluorescence microscopy as well as confocal scanning microscopy of LysoGlow84-treated astrocytes revealed co-localization of LysoGlow84 fluorescence with that of LysoTracker ® Red DND-99. LysoGlow84 stained unclear structures in Macrostomum lignano, which were identified as lysosomes by co-staining with LysoTracker. Strong fluorescence staining by LysoGlow84 was further observed around the worms' anterior gut and the female genital pore which were not counterstained by LysoTracker Red. Thus, LysoGlow84 is a new promising dye that stains lysosomes and other acidic compartments in cultured cells and in worms.
    Marine Drugs 02/2015; 13(2):920-935. DOI:10.3390/md13020920 · 2.85 Impact Factor
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    ABSTRACT: Colloidosomes are microcapsules consisting of nanoparticle shells. These microcarriers can be self-assembled from a wide range of colloidal particles with selective chemical, physical, and morphological properties and show promise for application in the field of theranostic nanomedicine. Previous studies have mainly focused on fairly large colloidosomes (>1 μm) based on a single kind of particle; however, the intrinsic building-block nature of this microcarrier has not been exploited so far for the introduction of tailored functionality at the nanoscale. We report a synthetic route based on interfacial shear rheology studies that allows the simultaneous incorporation of different nanoparticles with distinct physical properties, that is, superparamagnetic iron oxide and fluorescent silica nanoparticles, in a single submicron colloidosome. These tailor-made microcapsules can potentially be used in various biomedical applications, including magnetic hyperthermia, magnetic particle imaging, drug targeting, and bioimaging.
    Angewandte Chemie International Edition 01/2015; 127(1). DOI:10.1002/anie.201408515 · 11.26 Impact Factor
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    ABSTRACT: Arsenate is an environmental pollutant which contaminates the drinking water of millions of people worldwide. Numerous in vitro studies have investigated the toxicity of arsenate for a large number of different cell types. However, despite the known neurotoxic potential of arsenicals, little is known so far about the consequences of an exposure of neurons to arsenate. To investigate acute effects of arsenate on the viability and the glutathione (GSH) metabolism of neurons, we have exposed primary rat cerebellar granule neuron cultures to arsenate. Incubation of neurons for up to 6 h with arsenate in concentrations of up to 10 mM did not acutely compromise the cell viability, although the cells accumulated substantial amounts of arsenate. However, exposure to arsenate caused a time- and concentration-dependent increase in the export of GSH from viable neurons with significant effects observed for arsenate in concentrations above 0.3 mM. The arsenate-induced stimulation of GSH export was abolished upon removal of arsenate and completely prevented by MK571, an inhibitor of the multidrug resistance protein 1. These results demonstrate that arsenate is not acutely toxic to neurons but can affect the neuronal GSH metabolism by stimulating GSH export.
    Neurochemical Research 12/2014; 40(3). DOI:10.1007/s11064-014-1501-1 · 2.59 Impact Factor
  • Charlotte Petters · Ralf Dringen
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    ABSTRACT: Magnetic iron oxide nanoparticles (IONPs) are frequently used for biomedical applications. Although nanoparticles can enter the brain, little is known so far on the uptake of IONPs in neurons and on their neurotoxic potential. Hence, we applied dimercaptosuccinate (DMSA)-coated IONPs to cultured primary rat cerebellar granule neurons. These IONPs had average hydrodynamic diameters of around 80 nm and 120 nm when dispersed in incubation medium in the absence and the presence of 10% fetal calf serum, respectively. Acute exposure of neurons with IONPs for up to 6 h did neither alter the cell morphology nor compromise cell viability, although neurons accumulated large amounts of IONPs in a time- and concentration-dependent manner which caused delayed toxicity. For the first 30 min of incubation of neurons at 37°C with IONPs the cellular iron content increased proportionally to the concentration of IONPs applied irrespective of the absence and the presence of serum. IONP-exposure in the absence of serum generated maximal cellular iron contents of around 3000 nmol iron/mg protein after 4 h of incubation, while the accumulation in presence of 10% serum was slower and reached already within 1 h maximal values of around 450 nmol iron/mg protein. For both incubation conditions was the increase in cellular iron contents significantly lowered by reducing the incubation temperature to 4°C. Application of inhibitors of endocytotic pathways did not affect neuronal IONP accumulation in the absence of serum, while inhibitors of clathrin-mediated endocytosis lowered significantly the IONP accumulation in the presence of serum. These data demonstrate that DMSA-coated IONPs are not acutely toxic to cultured neurons and that a protein corona around the particles strongly affects their interaction with neurons. Copyright © 2014. Published by Elsevier Ltd.
    Neurochemistry International 12/2014; 81. DOI:10.1016/j.neuint.2014.12.005 · 3.09 Impact Factor
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    ABSTRACT: Astrocytes have a pivotal role in brain as partners of neurons in homeostatic and metabolic processes. Astrocytes also protect other types of brain cells against the toxicity of reactive oxygen species and are considered as first line of defence against the toxic potential of xenobiotics. A key component in many of the astrocytic detoxification processes is the tripeptide glutathione (GSH) which serves as electron donor in the GSH peroxidase-catalyzed reduction of peroxides. In addition, GSH is substrate in the detoxification of xenobiotics and endogenous compounds by GSH-S-transferases which generate GSH conjugates that are efficiently exported from the cells by multidrug resistance proteins. Moreover, GSH reacts with the reactive endogenous carbonyls methylglyoxal and formaldehyde to intermediates which are substrates of detoxifying enzymes. In this article we will review the current knowledge on the GSH metabolism of astrocytes with a special emphasis on GSH-dependent detoxification processes.
    Neurochemical Research 11/2014; DOI:10.1007/s11064-014-1481-1 · 2.59 Impact Factor
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    ABSTRACT: Fluorescently labeled nanoparticles (NPs) are used in a wide range of biomedical and nanotoxicological studies to elucidate their interactions with cellular components and their intracellular localization. As commonly used fluorescence microscopes are usually limited in their performance to a few channels which detect the emitted fluorescence light in the red, green and blue color range, the simultaneous colocalization of accumulated fluorescent NPs with cellular markers is often difficult and remains a challenge due to spectral overlay of NP-fluorescence and fluorescence of stained cellular components. To overcome this problem we have synthesized three different photostable dual-labeled fluorescent core/shell silica NPs with high fluorescence intensity (FI) and well defined shape, size and surface chemistry. The synthesis route of dual fluorophore doped silica (DFDS) NPs was based on a water in oil microemulsion method and includes the separate incorporation of two fluorophores in core or shell. The suitability of DFDS for colocalization studies was assessed and successfully demonstrated with human osteoblast (HOB) cells. Parallel visualization of DFDS NPs with two separate microscope channels allowed cellular NPs uptake and discrimination from fluorescently stained cellular components, even in triple stained cells that show fluorescence for the cytoskeleton protein actin (green), the nucleus (blue) and collagen (red). Our results demonstrate the feasibility and straightforwardness of the approach for colocalization studies at single-cell-level to discern clearly the accumulation of NPs from triple stained cellular components. Such NPs with multiple fluorescence characteristics have a great potential to replace single fluorescent NPs for in vitro studies, when multiple staining of cellular components is required. Copyright © 2014. Published by Elsevier Ltd.
    Acta Biomaterialia 11/2014; 14. DOI:10.1016/j.actbio.2014.11.037 · 6.03 Impact Factor
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    ABSTRACT: PVP-capped silver nanoparticles with a diameter of the metallic core of 70 nm, a hydrodynamic diameter of 120 nm and a zeta potential of -20 mV were prepared and investigated with regard to their biological activity. This review summarizes the physicochemical properties (dissolution, protein adsorption, dispersability) of these nanoparticles and the cellular consequences of the exposure of a broad range of biological test systems to this defined type of silver nanoparticles. Silver nanoparticles dissolve in water in the presence of oxygen. In addition, in biological media (i.e., in the presence of proteins) the surface of silver nanoparticles is rapidly coated by a protein corona that influences their physicochemical and biological properties including cellular uptake. Silver nanoparticles are taken up by cell-type specific endocytosis pathways as demonstrated for hMSC, primary T-cells, primary monocytes, and astrocytes. A visualization of particles inside cells is possible by X-ray microscopy, fluorescence microscopy, and combined FIB/SEM analysis. By staining organelles, their localization inside the cell can be additionally determined. While primary brain astrocytes are shown to be fairly tolerant toward silver nanoparticles, silver nanoparticles induce the formation of DNA double-strand-breaks (DSB) and lead to chromosomal aberrations and sister-chromatid exchanges in Chinese hamster fibroblast cell lines (CHO9, K1, V79B). An exposure of rats to silver nanoparticles in vivo induced a moderate pulmonary toxicity, however, only at rather high concentrations. The same was found in precision-cut lung slices of rats in which silver nanoparticles remained mainly at the tissue surface. In a human 3D triple-cell culture model consisting of three cell types (alveolar epithelial cells, macrophages, and dendritic cells), adverse effects were also only found at high silver concentrations. The silver ions that are released from silver nanoparticles may be harmful to skin with disrupted barrier (e.g., wounds) and induce oxidative stress in skin cells (HaCaT). In conclusion, the data obtained on the effects of this well-defined type of silver nanoparticles on various biological systems clearly demonstrate that cell-type specific properties as well as experimental conditions determine the biocompatibility of and the cellular responses to an exposure with silver nanoparticles.
    Beilstein Journal of Nanotechnology 11/2014; 5:1944-65. DOI:10.3762/bjnano.5.205 · 2.67 Impact Factor
  • Felix Bulcke · Ralf Dringen
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    ABSTRACT: Copper oxide nanoparticles (CuO-NPs) are frequently used for industrial or medical applications and are known for their high toxic potential. As little is known so far on the consequences of an exposure of brain cells to such particles, we applied CuO-NPs to cultured primary rat astrocytes and investigated whether such particles affect cell viability and alter their metabolic properties. Astrocytes efficiently accumulated CuO-NPs in a time- and concentration-dependent manner. The cells remained viable during a 24 h incubation with 100 µM copper in the form of CuO-NPs, while higher concentrations of CuO-NPs severely compromised the cell viability. Astrocytes that were exposed for 24 h to 100 µM CuO-NPs showed significantly enhanced extracellular lactate concentrations and increased cellular levels of glutathione and metallothioneins. The CuO-NP-induced increase in lactate release and metallothionein content were prevented by the presence of the membrane-permeable copper chelator tetrathiomolybdate, while this chelator increased already in the absence of CuO-NPs the cellular glutathione content. After removal of the CuO-NPs following a 24 h pre-incubation with 100 µM CuO-NPs, astrocytes maintained during a further 6 h incubation an elevated glycolytic lactate release and exported significantly more glutathione than control cells that had been pre-incubated without CuO-NPs. These data suggest that copper ions which are liberated from internalized CuO-NPs stimulate glycolytic flux as well as the synthesis of glutathione and metallothioneins in cultured viable astrocytes.
    Neurochemical Research 10/2014; 40(1):15-26. DOI:10.1007/s11064-014-1458-0 · 2.59 Impact Factor
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    ABSTRACT: To clarify discrepancies in the literature on the adverse effects of hydrogen peroxide on neurons, this study investigated the application of this peroxide to cultured cerebellar granule neurons with six assays frequently used to test for viability. Cultured neurons efficiently cleared exogenous H2O2. Although viability was not affected by exposure to 10 µM hydrogen peroxide, an exposure to the peroxide in higher concentrations rapidly lowered, within 15 min, the cellular 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltertrazolium bromide (MTT) reduction capacity to 53% ± 1% (100 µM) and 31% ± 1% (1,000 µM) and the 3-amino-7-dimethylamino-2-methyl-phenazine hydrochloride (neutral red; NR) uptake to 84% ± 6% (100 µM) and 33% ± 1% (1,000 µM) of control cells. The release of glycolytically generated lactate was stopped within 30 min in neurons treated with 1,000 µM peroxide. In contrast, even hours after peroxide application, the cell morphology, the number of propidium iodide-positive cells, and the extracellular activity of the cytosolic enzyme lactate dehydrogenase (LDH) were not significantly altered. The rapid loss in MTT reduction and NR uptake after exposure of neurons to H2O2 for 5 or 15 min correlated well with a strongly compromised MTT reduction and a very high extracellular LDH activity observed after further incubation in peroxide-free medium for a total incubation period of 24 hr. These data demonstrate that cultured neurons do not recover from damage that is inflicted by a short exposure to H2O2 and that the rapid losses in the capacities of neurons for MTT reduction and NR uptake are good predictors of delayed cell damage. © 2014 Wiley Periodicals, Inc.
    Journal of Neuroscience Research 10/2014; 93(7). DOI:10.1002/jnr.23502 · 2.59 Impact Factor
  • Eric Ehrke · Christian Arend · Ralf Dringen
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    ABSTRACT: The pyruvate analogue 3-bromopyruvate (3-BP) is an electrophilic alkylator that is considered a promising anticancer drug because it has been shown to kill cancer cells efficiently while having little toxic effect on nontumor cells. To test for potential adverse effects of 3-BP on brain cells, we exposed cultured primary rat astrocytes to 3-BP and investigated the effects of this compound on cell viability, glucose metabolism, and glutathione (GSH) content. The presence of 3-BP severely compromised cell viability and slowed cellular glucose consumption and lactate production in a time- and concentration-dependent manner, with half-maximal effects observed at about 100 µM 3-BP after 4 hr of incubation. The cellular hexokinase activity was not affected in 3-BP-treated astrocytes, whereas within 30 min after application of 3-BP the activity of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was inhibited, and cellular GSH content was depleted in a concentration-dependent manner, with half-maximal effects observed at about 30 µM 3-BP. The depletion of cellular GSH after exposure to 100 µM 3-BP was not prevented by the presence of 10 mM of the monocarboxylates lactate or pyruvate, suggesting that 3-BP is not taken up into astrocytes predominantly by monocarboxylate transporters. The data suggest that inhibition of glycolysis by inactivation of GAPDH and GSH depletion contributes to the toxicity that was observed for 3-BP-treated cultured astrocytes. © 2014 Wiley Periodicals, Inc.
    Journal of Neuroscience Research 09/2014; 93(7). DOI:10.1002/jnr.23474 · 2.59 Impact Factor
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    ABSTRACT: Magnetic iron oxide nanoparticles (IONPs) are used for various applications in biomedicine, for example as contrast agents in magnetic resonance imaging, for cell tracking and for anti-tumor treatment. However, IONPs are also known for their toxic effects on cells and tissues which are at least in part caused by iron-mediated radical formation and oxidative stress. The potential toxicity of IONPs is especially important concerning the use of IONPs for neurobiological applications as alterations in brain iron homeostasis are strongly connected with human neurodegenerative diseases. Since IONPs are able to enter the brain, potential adverse consequences of an exposure of brain cells to IONPs have to be considered. This article describes the pathways that allow IONPs to enter the brain and summarizes the current knowledge on the uptake, the metabolism and the toxicity of IONPs for the different types of brain cells in vitro and in vivo.
    Neurochemical Research 07/2014; 39(9). DOI:10.1007/s11064-014-1380-5 · 2.59 Impact Factor
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    ABSTRACT: Intoxication with inorganic arsenicals leads to neuropathies and impaired cognitive functions. However, little is known so far on the cellular targets that are involved in the adverse effects of arsenite to brain cells. To test whether arsenite may affect neural glucose and glutathione (GSH) metabolism, primary astrocyte cultures from rat brain were used as a model system. Exposure of cultured astrocytes to arsenite in concentrations of up to 0.3mM did not compromise cell viability during incubations for up to 6 h, while 1 mM arsenite damaged the cells already within 2 h after application. Determination of cellular arsenic contents of astrocytes that had been incubated for 2 h with arsenite revealed an almost linear concentration-dependent increase in the specific cellular arsenic content. Exposure of astrocytes to arsenite stimulated the export of GSH and accelerated the cellular glucose consumption and lactate production in a time- and concentration-dependent manner. Half-maximal stimulation of GSH export and glycolytic flux were observed for arsenite in concentrations of 0.1 mM and 0.3 mM, respectively. The arsenite-induced stimulation of both processes was abolished upon removal of extracellular arsenite. The strong stimulation of GSH export by arsenite was prevented by MK571, an inhibitor of the multidrug resistance protein 1, suggesting that this transporter mediates the accelerated GSH export. In addition, presence of MK571 significantly increased the specific cellular arsenic content, suggesting that Mrp1 may also be involved in arsenic export from astrocytes. The data observed suggest that alterations in glucose and GSH metabolism may contribute to the reported adverse neural consequences of intoxication with arsenite.
    Neurochemistry International 07/2014; 76. DOI:10.1016/j.neuint.2014.06.013 · 3.09 Impact Factor

Publication Stats

8k Citations
649.42 Total Impact Points


  • 1998–2015
    • Universität Bremen
      • • Advanced Ceramics
      • • Center for Biomolecular Interactions CBIB
      • • Institut für Organische und Analytische Chemie
      Bremen, Bremen, Germany
  • 2012
    • Jacobs University
      Bremen, Bremen, Germany
  • 2011
    • Ludwig Boltzmann Institute for Experimental and Clinical Traumatology
      Wien, Vienna, Austria
  • 2006–2011
    • Monash University (Australia)
      • School of Psychology and Psychiatry
      Melbourne, Victoria, Australia
  • 1992–2005
    • University of Tuebingen
      • • Institute for Physiology
      • • Institute of Physical and Theoretical Chemistry
      Tübingen, Baden-Württemberg, Germany
  • 2004
    • University of Vic
      Vic, Catalonia, Spain