Ralf Dringen

Universität Bremen, Bremen, Bremen, Germany

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Publications (176)624.97 Total impact

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    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 · 3.55 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; DOI:10.1021/acsami.5b01900 · 5.90 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 · 2.55 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 · 3.51 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 · 11.34 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 01/2015; 48(3). DOI:10.1080/00032719.2014.951449 · 0.98 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 · 2.55 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 · 2.65 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 · 2.55 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 · 5.68 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 · 2.55 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 · 2.73 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 · 2.73 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 · 2.55 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; DOI:10.1016/j.neuint.2014.06.013 · 2.65 Impact Factor
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    ABSTRACT: Nanodiamonds are a class of carbon-based nanoparticles that are rapidly gaining attention, particularly for biomedical applications, i.e., as drug carriers, for bio imaging, or as implant coatings. Nanodiamonds have generally been considered biocompatible for a broad variety of eukaryotic cells. We show that, depending on their surface composition, nanodiamonds kill Gram-positive and -negative bacteria rapidly and efficiently. We investigated six different types of nanodiamonds exhibiting diverse oxygen-containing surface groups that were created using standard pretreatment methods for forming nanodiamond dispersions. Our experiments suggest that the antibacterial activity of nanodiamond is linked to the presence of partially oxidized and negatively charged surfaces, specifically those containing acid anhydride groups. Furthermore, proteins were found to control the bactericidal properties of nanodiamonds by covering these surface groups, which explains the previously reported biocompatibility of nanodiamonds. Our findings describe the discovery of an exciting property of partially oxidized nanodiamonds as a potent antibacterial agent.
    ACS Nano 05/2014; 8(6). DOI:10.1021/nn502230m · 12.03 Impact Factor
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    ABSTRACT: Inorganic arsenicals are environmental toxins that have been connected with neuropathies and impaired cognitive functions. To investigate whether such substances accumulate in brain astrocytes and affect their viability and glutathione metabolism, we have exposed cultured primary astrocytes to arsenite or arsenate. Both arsenicals compromised the cell viability of astrocytes in a time- and concentration-dependent manner. However, the early onset of cell toxicity in arsenite-treated astrocytes revealed the higher toxic potential of arsenite compared with arsenate. The concentrations of arsenite and arsenate that caused within 24h half-maximal release of the cytosolic enzyme lactate dehydrogenase were around 0.3mM and 10mM, respectively. The cellular arsenic contents of astrocytes increased rapidly upon exposure to arsenite or arsenate and reached after 4h of incubation almost constant steady state levels. These levels were about 3-times higher in astrocytes that had been exposed to a given concentration of arsenite compared with the respective arsenate condition. Analysis of the intracellular arsenic species revealed that almost exclusively arsenite was present in viable astrocytes that had been exposed to either arsenate or arsenite. The emerging toxicity of arsenite 4h after exposure was accompanied by a loss in cellular total glutathione and by an increase in the cellular glutathione disulfide content. These data suggest that the high arsenite content of astrocytes that had been exposed to inorganic arsenicals causes an increase in the ratio of glutathione disulfide to glutathione which contributes to the toxic potential of these substances.
    Journal of Trace Elements in Medicine and Biology 05/2014; 28(3). DOI:10.1016/j.jtemb.2014.04.007 · 2.49 Impact Factor
  • Michaela C. Hohnholt, Ralf Dringen
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    ABSTRACT: Hydrogen peroxide is a normal by-product of cellular metabolism that in higher concentrations can cause oxidative stress. Cultured cerebellar granule neurons efficiently disposed of micromolar concentrations of hydrogen peroxide with half-times in the minute range in a process that predominately involved catalase. Application of up to 100 µM hydrogen peroxide did not affect the cell viability for up to 4 h, but caused a time- and concentration-dependent increase in the extracellular glutathione (GSH) content that was accompanied by a matching decrease in the cellular GSH content. Hydrogen peroxide at 100 µM stimulated maximally the GSH export from viable neurons, but did not affect GSH export from cultured astrocytes. The peroxide-induced extracellular GSH accumulation from neurons was lowered by 70% in the presence of MK571, an inhibitor of multidrug resistance protein (Mrp) 1. The extracellular GSH content determined after 4 h of incubation was already significantly increased after a 5-min exposure of neurons to hydrogen peroxide and became maximal after 15 min of peroxide application. These data demonstrate that just a short exposure of viable cerebellar granule neurons to micromolar concentrations of hydrogen peroxide stimulates a prolonged Mrp1-mediated export of cellular GSH. This process may compromise the antioxidative potential of neurons and increase their sensitivity toward drugs and toxins.
    Free Radical Biology and Medicine 05/2014; 70. DOI:10.1016/j.freeradbiomed.2014.02.005 · 5.71 Impact Factor
  • Christian Arend, Eric Ehrke, Ralf Dringen
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    ABSTRACT: The pyruvate analogue 3-bromopyruvate (3-BP) is a electrophilic alkylator which is considered as a promising anti-cancer drug as it was reported to efficiently kill cancer cells while having little toxic effects on non-tumor cells. Regarding a potential treatment of brain tumor with 3-BP it is important to know about potential adverse consequences of 3-BP on normal brain cells. Therefore, we have exposed cultured primary rat astrocytes to 3-BP and investigated the effects of this compound on the cell viability, the glucose metabolism and the glutathione (GSH) content. Presence of 3-BP severely compromised the cell viability and slowed the cellular glucose consumption and lactate production in a time- and concentration-dependent manner with half-maximal effects observed after exposure to around 100 µM 3-BP. The cellular hexokinase activity was not affected in 3-BP-treated astrocytes, while already a 30 min treatment with 3-BP strongly inactivated glyceraldehyde-3-phosphate dehydrogenase and depleted cellular GSH contents with half-maximal effects observed for astrocytes that had been exposed to around 30 µM 3-BP. The depletion of cellular GSH by 100 µM 3-BP was not prevented by the presence of 10 mM of the monocarboxylates lactate or pyruvate, suggesting that monocarboxylate transporters are not involved in 3-BP uptake into astrocytes. Our data suggest that the 3-BP-induced inhibition of glycolysis and depletion of cellular GSH contribute to the toxicity observed for 3-BP-treated cultured astrocytes. Such alterations in the metabolism of brain astrocytes should be considered as potential side-effects of an application of 3-BP for anti-tumor treatment.
    11th International Conference on Brain Energy Metabolism, Bymosehegn, Helsinge, Denmark (Mai 2014); 05/2014
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    ABSTRACT: Antiretroviral protease inhibitors are crucial components of the antiretroviral combination therapy that is successfully used for the treatment of patients with HIV infection. To test whether such protease inhibitors affect the glutathione (GSH) metabolism of neurons, cultured cerebellar granule neurons were exposed to indinavir, nelfinavir, lopinavir or ritonavir. In low micromolar concentrations these antiretroviral protease inhibitors did not acutely compromise the cell viability, but caused a time- and concentration-dependent increase in the accumulation of extracellular GSH which was accompanied by a matching loss in cellular GSH. The stimulating effect by indinavir, lopinavir and ritonavir on GSH export was immediately terminated upon removal of the protease inhibitors, while the nelfinavir-induced stimulated GSH export persisted after washing the cells. The stimulation of neuronal GSH export by protease inhibitors was completely prevented by MK571, an inhibitor of the multidrug resistance protein 1, suggesting that this transporter mediates the accelerated GSH export during exposure of neurons to protease inhibitors. These data suggest that alterations in brain GSH metabolism should be considered as potential side-effects of a treatment with antiretroviral protease inhibitors.
    Neurochemical Research 03/2014; DOI:10.1007/s11064-014-1284-4 · 2.55 Impact Factor

Publication Stats

8k Citations
624.97 Total Impact Points

Institutions

  • 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
    • Helmholtz-Zentrum für Umweltforschung
      Leipzig, Saxony, Germany
  • 2011
    • Ludwig Boltzmann Institute for Experimental and Clinical Traumatology
      Wien, Vienna, Austria
  • 2004–2011
    • Monash University (Australia)
      • School of Psychology and Psychiatry
      Melbourne, Victoria, Australia
    • University of Vic
      Vic, Catalonia, Spain
  • 2005
    • Max Planck Institute for Experimental Medicine
      • Department of Neurogenetics
      Göttingen, Lower Saxony, Germany
  • 1992–2005
    • University of Tuebingen
      • • Institute for Physiology
      • • Institute of Physical and Theoretical Chemistry
      • • Interfaculty Institute for Biochemistry
      Tübingen, Baden-Württemberg, Germany