Regina Ebert-Dümig

University of Wuerzburg, Würzburg, Bavaria, Germany

Are you Regina Ebert-Dümig?

Claim your profile

Publications (7)11.61 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: The expression of thioredoxin reductases and other selenoproteins in cells of the bone microenvironment may represent an important means of regulation of bone resorption and remodeling in health and disease. Selenoproteins and their substrates may influence intracellular and extracellular redox-dependent signaling, transcription factor activity, posttranslational modification of proteins, and general or compartmentalized scavenging from ROIs. However, the evaluation of their biological role in bone and their potential in terms of therapeutic approaches is just beginning.
    Methods in Enzymology 02/2002; 347:168-79. · 2.00 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Monocytes differentiate from myeloid precursors towards the macrophage state of differentiation under the influence of 1,25-dihydroxy vitamins D3 (1,25 [OH]2 vitamin D3) and other factors and this is further propagated by colony stimulating factors (MCSF and GMCSF). Macrophage activation and phagocytosis of foreign particles are regularly accompanied by a so called "respiratory burst", an increase in the production of reactive oxygen species (ROS), exerted by the enzyme complex NADPH oxidase. A number of antioxidant enzymes is expressed at the same time to protect the cells from the cytotoxic effects of ROS directed against engulfed microorganisms. The selenium-dependent glutathione peroxidases and thioredoxin reductases are important examples. The cytosolic GPx isoenzyme (cGPx) and thioredoxin reductase alpha (TrxR alpha) are upregulated during the process of differentiation and under the influence of 1.25 (OH)2 vitamin D3. GPx isoenzymes neutralize H2O2. TrxR reduce sulfhydryl-groups like in cysteins either directly or via their cofactor thioredoxin and thus are involved in protein folding and critical protein-protein and protein-DNA interactions, e.g. modulation of dimerization and/or DNA-binding and ligand binding of transcription factors (glucocorticoid receptor and other steroid receptors, NF kappa B). In addition, the antibiotic peptide NK-lysin was shown to be a substrate for TrxR alpha, suggesting that TrxR protects the cell itself from the cytotoxic effects of NK-lysin. Selenium is incorporated into selenocysteine (Secys) in a regulated fashion in the presence of a hairpin structure (Secis element) in the 3'UTR of selenoprotein genes. Secis elements direct the insertion of Secys at UGA codons, which function as opal stop codons in the absence of a suitable Secis element and in selenium deficiency. The above mentioned processes might therefore be altered in relative selenium deficiency or vice versa be upregulated through selenium supplementation. We have shown that TrxR alpha is a 1.25 (OH)2 vitamin D3-responsive early gene in monocytic cells and that TrxR activity as well as GPx activity in these cells can be upregulated by the addition of selenium in vitro and ex vivo. Recent work demonstrates that thioredoxin rapidly enters the cell nucleus upon treatment of cells with H2O2, but little is known about the compartimentalization of the respiratory burst and the intracellular localization of antioxidant enzymes during that process. Macrophage function is insufficient if the generation of a respiratory burst is altered like in hereditary chronic granulomatous disease on one hand, but on the other hand is as well disturbed, if there is a lack in antioxidant enzyme activity. Thioredoxin has been identified as a lymphocyte growth factor and might therefore be involved in the crosstalk between macrophages and lymphocytes. The relevance of the above mentioned and other yet undefined monocytic selenoproteins remains to be elucidated in detail as well as the relevance of selenium supplementation in nutrition in general and in situations of critical infectious disease and autoimmunity.
    Medizinische Klinik 11/1999; 94 Suppl 3:29-34. · 0.34 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: □ Monozyten differenzieren unter dem Einfluß von 1,25(OH)2 Vitamin D3 und anderen Faktoren aus myeloischen Vorläuferzellen. Koloniestimulierende Faktoren wie (Granulozyten-)Makrophagen-stimulierender Faktor (GMCSF und MCSF) propagieren die weitere Differenzierung zu Makrophagen. Die Aktivierung von Makrophagen und die Phagozytose von fremden Partikeln sind regelmä\ig begleitet von einem sogenannten „respiratory burst“, einer erhöhten Produktion von reaktiven Sauerstoffspezies (ROS), die durch den Enzymkomplex NADPH-Oxidase bewerkstelligt wird. Gleichzeitig wird eine Anzahl antioxidativer Enzyme exprimiert, um die Zelle vor den zytotoxischen Effekten der ROS zu schützen, die gegen die eingeschlossenen Mikroorganismen gerichtet sind und möglicherweise auch Genregulationen bewirken. Gut charakterisierte Selenoproteine, die in die antioxidative „Defense“-Reaktion der Zelle involviert sind, sind die selenabhängigen Glutathionperoxidasen (zytosolische [cGPx] und plasmatische [pGPx]) und die Thioredoxinreduktasen α und β (TrxRα/β). Das zytosolische Isoenzym der GPx (cGPx) und die TrxRα werden beide im Rahmen der Differenzierung durch 1,25 (OH)2 Vitamin D3 stimuliert. GPx-Isoenzyme neutralisieren H2O2. TrxR sind entweder direkt oder indirekt über ihren Kofaktor Thioredoxin in die Proteinfaltung involviert. Sie reduzieren Sulfhydrylgruppen und beeinflussen so zum Beispiel kritische Protein/Protein-Interaktionen und Protein/DNA-Interktionen; sie modulieren somit die Dimerisation und/oder die DNA-Bindung von Transkriptionsfaktoren (Glukokortikoidrezeptor und andere Steroidhormonrezeptoren, NFκB). Darüber hinaus wurde gezeigt, daß das antibiotische und zytotoxische Peptid NK-Lysin ein Substrat für die TrxRα ist (mit der Folge der Inaktivierung des Peptids), was nahelegt, daß TrxR ein protektiver Faktor für die Zelle selbst ist. Selen wird kontrolliert und spezifisch in Selenoproteine in Form von Selenozystein (Secys) eingebaut, welches in Anwesenheit einer dredimensionalen Haarnadelstruktur der 3′UTR (Secis-Element) am Codon UGA abgelesen wird, das ohne ein geeignetes Secis-Element und im Selenmangel als opales Stop-Codon fungiert. Die oben diskutierten Prozesse können also im Selenmangel alteriert sein und andererseits durch Selensupplementation moduliert werden. □ Wir haben die TrxRα als 1,25(OH)2 Vitamin D3-responsives Protein in Monozyten charakterisiert und gezeigt, daß die Aktivität der GPx und der TrxR durch Selensupplementation in vitro und ex vivo stimuliert wird. Neuere Arbeiten zeigen, daß Thioredoxin, ein wichtiges Substrat der TrxR, nach Behandlung von Zellen mit H2O2 schnell in den Zellkern wandert. Darüber hinaus ist aber wenig bekannt über die Kompartimentalisierung des „respiratory burst“ in der Zelle und die intrazelluläre Lokalisation der antioxidativen Enzyme während dieses Vorgangs. Die Makrophagenfunktion ist alteriert, wenn der „respiratory burst“ insuffizient ist, wie zum Beispiel bei der hereditären chronischen granulomatösen Erkrankung. Andererseits ist diese aber auch gestört, wenn ein Defizit an antioxidativen Enzymen besteht. Thioredoxin wurde als Wachstumsfaktor für Lymphozyten identifiziert und ist in den „Crosstalk“ zwischen Makrophagen und Lymphozyten involviert. Die Relevanz der beschriebenen und anderer noch nicht charakterisierter Selenoproteine von Monozyten bleibt näher zu charakterisieren, wie auch die der Supplementation von Selen generell in der Nahrungskette und speziell in Situationen von kritischen Infektionen und bei der Entwicklung der Autoimmunität. □ Monocytes differentiate from myeloid precursors towards the macrophage state of differentiation under the influence of 1,25-dihydroxy vitamin D3 (1,25 [OH]2 vitamin D3) and other factors and this is further propagated by colony stimulating factors (MCSF and GMCSF). Macrophage activation and phagocytosis of foreign particles are regularly accompanied by a so called “respiratory burst”, an increase in the production of reactive oxygen species (ROS), exerted by the enzyme complex NADPH oxidase. A number of antioxidant enzymes is expressed at the same time to protect the cells from the cytotoxic effects of ROS directed against engulfed microorganisms. The selenium-dependent glutathione peroxidases and thioredoxin reductases are important examples. The cytosolic GPx isoenzyme (cGPx) and thioredoxin reductase α (TrxRα) are upregulated during the process of differentiation and under the influence of 1,25 (OH)2 vitamin D3. GPx isoenzymes neutralize H2O2. TrxR reduce sulfhydryl-groups like in cysteins either directly or via their cofactor thioredoxin and thus are involved in protein folding and critical protein-protein and protein-DNA interactions, e. g. modulation of dimerization and/or DNA-binding and ligand binding of transcription factors (glucocorticoid receptor and other steroid receptors, NFκB). In addition, the antibiotic peptide NK-lysin was shown to be a substrate for TrxRα, suggesting that TrxR protects the cell itself from the cytotoxic effects of NK-lysin. Selenium is incorporated into selenocysteine (Secys) in a regulated fashion in the presence of a hairpin structure (Secis element) in the 3′UTR of selenoprotein genes. Secis elements direct the insertion of Secys at UGA codons, which function as opal stop codons in the absence of a suitable Secis element and in selenium deficiency. The above mentioned processes might therefore be altered in relative selenium deficiency or vice versa be upregulated through selenium supplementation. □ We have shown that TrxRα is a 1,25 (OH)2 vitamin D3-responsive early gene in monocytic cells and that TrxR activity as well as GPx activity in these cells can be upregulated by the addition of selenium in vitro and ex vivo. Recent work demonstrates that thioredoxin rapidly enters the cell nucleus upon treatment of cells with H2O2, but little is known about the compartimentalization of the respiratory burst and the intracellular localization of antioxidant enzymes during that process. Macrophage function is insufficient if the generation of a respiratory burst is altered like in hereditary chronic granulomatous disease on one hand, but on the other hand is as well disturbed, if there is a lack in antioxidant enzyme activity. Thioredoxin has been identified as a lymphocyte growth factor and might therefore be involved in the crosstalk between macrophages and lymphocytes. The relevance of the above mentioned and other yet undefined monocytic selenoproteins remains to be elucidated in detail as well as the relevance of selenium supplementation in nutrition in general and in situations of critical infectious disease and autoimmunity.
    10/1999; 94:29-34.
  • [Show abstract] [Hide abstract]
    ABSTRACT: 1,25(OH)2 Vitamin D3 (1,25(OH)2D3) and adhesion propagate monocyte differentiation. We identified the selenoprotein thioredoxin reductase (TrxR) as a new molecular target for 1,25(OH)2D3 in monocytes during this process. In THP1 monocytic leukemia cells 1,25(OH)2D3 stimulated TrxR mRNA levels 2-4-fold by 4-8 h and enhanced TrxR activity (60%) (as measured by the dithionitrobenzole-assay) after 24 h, which declined below baseline after 96 h. The addition of 100 nM selenite enhanced (approx. 50%) basal and stimulated enzyme activity in THP1 cells. The relative stimulation by 1,25(OH)2D3 was very similar but peak levels were sustained in THP1 cells up to 48 h. Human peripheral blood monocytes (PBM) of different donors showed very low basal TrxR steady state mRNA levels which were markedly enhanced (as analyzed by Northern blotting) after 4 h of adherence to culture dishes. 1,25(OH)2D3 (100 nM) further stimulated TrxR mRNA expression (4 h, 3-fold). TrxR enzyme activity mirrored the mRNA changes. Basal activity was stimulated approx. 25% by adhesion in culture alone and was further stimulated (approximately 15%) by 1,25(OH)2D3 after 4 h. By 24 h similar results were achieved but the effect of 1,25(OH)2D3 could be seen in the presence of 100 nM selenium only. The expression of TrxR and its regulation by 1,25(OH)2D3 and selenite in monocytes might be important for their induction of differentiation and maintenance of function.
    BioFactors 02/1999; 10(4):329-38. · 3.09 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: 1,25(OH)2 Vitamin D3 (1,25(OH)2D3) and adhesion propagate monocyte differentiation. We identified the selenoprotein thioredoxin reductase (TrxR) as a new molecular target for 1,25(OH)2D3 in monocytes during this process. In THP1 monocytic leukemia cells 1,25(OH)2D3 stimulated TrxR mRNA levels 2—4-fold by 4—8 h and enhanced TrxR activity (60%) (as measured by the dithionitrobenzole-assay) after 24 h, which declined below baseline after 96 h. The addition of 100 nM selenite enhanced (approx. 50%) basal and stimulated enzyme activity in THP1 cells. The relative stimulation by 1,25(OH)2D3 was very similar but peak levels were sustained in THP1 cells up to 48 h. Human peripheral blood monocytes (PBM) of different donors showed very low basal TrxR steady state mRNA levels which were markedly enhanced (as analyzed by Northern blotting) after 4 h of adherence to culture dishes. 1,25(OH)2D3 (100 nM) further stimulated TrxR mRNA expression (4 h, 3-fold). TrxR enzyme activity mirrored the mRNA changes. Basal activity was stimulated approx. 25% by adhesion in culture alone and was further stimulated (∼15%) by 1,25(OH)2D3 after 4 h. By 24 h similar results were achieved but the effect of 1,25(OH)2D3 could be seen in the presence of 100 nM selenium only. The expression of TrxR and its regulation by 1,25(OH)2D3 and selenite in monocytes might be important for their induction of differentiation and maintenance of function.
    BioFactors 01/1999; 10(4):329-338. · 3.09 Impact Factor
  • R Ebert-Dümig, N Schütze, F Jakob
    BioFactors 01/1999; 10(2-3):227-35. · 3.09 Impact Factor
  • Source
    Regina Ebert-Dümig
    [Show abstract] [Hide abstract]
    ABSTRACT: Das Secosterid Vitamin D3 wird durch die Nahrung aufgenommen oder im Organismus synthetisiert, wobei eine Reaktion in der Haut durch einen photochemischen Prozess katalysiert wird.Durch zwei Hydroxylierungsschritte in Leber und Niere wird Vitamin D3 über 25(OH) Vitamin D3 zum aktiven 1,25(OH)2 Vitamin D3-Hormon. 1,25(OH)2 Vitamin D3 hat eine wichtige Funktion im Knochenstoffwechsel, es reguliert die Ca2+-Resorption im Dünndarm. Die 1,25(OH)2 Vitamin D3-Synthese in der Niere wird durch Parathormon (PTH) kontrolliert. Ist die Serum Ca2+-Konzentration niedrig, wird PTH ausgeschüttet und die 1a-Hydroxylase, das 25(OH) Vitamin D3-aktivierende Enzym, stimuliert. Das Prinzip der (Seco)steroid-Aktivierung und -Inaktivierung in glandulären Organen, wie Leber und Niere mit anschließender Freisetzung der aktiven Hormone und Transport zu den jeweiligen Zielgeweben gilt heute nicht mehr uneingeschränkt. Auch Einzelzellen sind in der Lage Steroid-modifizierende Enzyme, die Hydroxylasen und Dehydrogenasen, zu exprimieren. Monozytäre Zellen exprimieren das 1,25(OH)2 Vitamin D3-aktivierende und das -inaktivierende Enzym, die 1a-Hydroxylase und die 24-Hydroxylase. Sie sind somit in der Lage, 1,25(OH)2 Vitamin D3 zu sezernieren, welches parakrin auf Nachbarzellen wirken kann. In diesem Zusammenhang wurde die Expression und Regulation der 1a-Hydroxylase in peripheren Blutmonozyten (PBM) und monozytären THP1-Zellen untersucht. Durch Supplementation der Zellen mit dem Substrat 25(OH) Vitamin D3 konnte die Produktion an aktivem 1,25(OH)2 Vitamin D3-Hormon in PBM signifikant gesteigert werden. In PBM konnte im Gegensatz zum systemischen Ca2+-Stoffwechsel nur ein geringer Einfluss auf die 1a-Hydroxylase-Aktivität beobachtet werden. Durch RT-PCR-Amplifikation konnte eine Expression des PTH Rezeptors Typ 1 (PTHR1) in PBM und Dendritischen Zellen nachgewiesen werden. Ein weiterer Ligand des PTHR1 ist PTH related Protein (PTHrP), ein Faktor der die Tumorhyperkalzämie propagiert. Durch Markierungsexperimente mit fluoreszenz-markiertem PTHrP konnte gezeigt werden, dass PTHrP an die Zellmembran von PBM und Dendritischen Zellen bindet und in den Zellkern von Dendritischen Zellen transportiert wird. Im Rahmen dieser Arbeit wurde die Expression 1,25(OH)2 Vitamin D3-responsive Gene in Monozyten/Makrophagen untersucht. Die Expression der 24-Hydroxylase wird innerhalb der Differenzierung von myeloischen THP1-Zellen zu Makrophagen- bzw. Osteoklasten-ähnlichen Zellen transient induziert. Als weiteres 1,25(OH)2 Vitamin D3-responsives Gen wurde die Expression von Osteopontin (OPN) untersucht. OPN ist ein vor allem in Knochen vorkommendes Matrixprotein, das wesentlich an der Zelladhäsion beteiligt ist. OPN wird in THP1-Zellen im Zuge der Differenzierung zunehmend exprimiert. Durch immunhistochemische Untersuchungen konnte OPN in Granulomen von Morbus Crohn- und Leberschnitten detektiert werden. Es spielt hier eine wesentliche Rolle bei der Granulomentstehung. Die Thioredoxin Reduktase 1 (TR1) ist ein Selenoenzym, welches maßgeblich an der Reduktion von Disulfidbindungen in Proteinen beteiligt ist. Es moduliert Protein/Protein- und Protein/DNA-Interaktionen wie die Bindung der Transkriptionsfaktoren AP1 und NFkB an DNA-responsive Elemente. Die Expression der TR1 wird in THP1-Zellen im Rahmen der Differenzierung induziert und ist in differenzierten Zellen maximal. Aktivitätsmessungen deckten sich mit dieser Beobachtung. In peripheren Blutmonozyten steigt die TR-Aktivität alleine durch Adhäsion der Zellen an das Kulturgefäß und nach Behandlung mit 1,25(OH)2 Vitamin D3. Die Untersuchungen der vorliegenden Arbeit zeigten eine Abhängigkeit der TR-Aktivität vom Differenzierungsgrad der Zellen und der Supplementation des Mediums mit dem Spurenelement Selen. Die Expression weiterer Selenoproteine in monozytären Zellen wurde nachgewiesen. So konnten durch 75Selenit-Markierungsexperimente neun Selenoproteine in THP1-Zellen detektiert werden, von denen fünf sezerniert werden. Ein weiteres, in monozytären Zellen charakterisiertes Selenoprotein ist die zelluläre Glutathionperoxidase. Ihre Aktivität konnte in Selenit-supplementierten Zellen um das 70fache gesteigert werden. Die Kultivierung monozytärer Zellen unter Selenit-Supplementation beeinflusst die Funktion dieser Zellen wesentlich. So konnte beobachtet werden, dass die Anzahl an phagozytierenden, zu Makrophagen differenzierten THP1-Zellen nach Selenit-Supplementation abnahm, während die Phagozytoserate der einzelnen Zellen anstieg. Die erzielten Ergebnisse zeigen, dass monozytäre Zellen mit Komponenten des 1,25(OH)2 Vitamin D3 Stoffwechsels ausgestattet sind und aktives 1,25(OH)2 Vitamin D3-Hormon produzieren, sezernieren und inaktivieren können. Die lokale Kontrolle der 1,25(OH)2 Vitamin D3 Stoffwechsels ausgestattet sind und aktives 1,25(OH)2 Vitamin D3-responsiver Gene, wie die Expression des Selenoproteins TR1, das einen direkten Einfluss auf den Redoxstatus und den Abbau reaktiver Sauerstoffverbindungen in diesen und Nachbarzellen ausübt. The secosteroid 1,25(OH)2 vitamin D3 is either taken up by our daily diet or it is formed by a photochemical prosess in the skin. In liver and kidney vitamin D3 is hydroxylated in two steps to 25(OH) vitamin D3 and the active hormone 1,25(OH)2 vitamin D3. 1,25(OH)2 vitamin D3 plays an important role in bone metabolism. It is a key regulatorof the resorption of Ca2+ in the intestine. In the kidney 1,25(OH)2 vitamin D3 synthesis is controlled by parathyroid hormone (PTH). When the concentration of serum Ca2+ is low, PTH is secreted and 1a-hydroxylase, the 25(OH) vitamin D3 activating enzyme is induced in kidney. The picture of (seco)steroid activation and inactivation in glandular organs, like the liver and kidney, and the release and transport of the activated hormone to the target tissues has been modified recently. Single cells are also able to express steroid-modifying enzymes like hydroxylases and dehydrogenases. Monocytes express the 1,25(OH)2 vitamin D3-activating and the inactivating enzyme, i.e. the 1a-hydroxylase and the 24-hydroxylase. Thus they are able to build and secrete 1,25(OH)2 vitamin D3 which can act on neighbouring cells in a paracrine way. In this context the expression and regulation of the 1a-hydroxylase in peripheral blood monocytes (PBM) and THP1 cells was investigated. By supplementation of cells with the substrate 25(OH) vitamin D3 the production of active 1,25(OH)2 vitamin D3 hormone could be enhanced significantly in PBM. In PBM only a slight influence of PTH on 1a-hydroxylase activity could be observed, in contrast to the regulation in systemic Ca2+-metabolism. An expression of PTH receptor type 1 (PTHR1) could be verified by RT-PCR from whole RNA isolated from PBM and dendritic cells. A further ligand of PTHR1 is PTH related protein (PTHrP), a factor which propagates the humoral hypercalcemia of malignancy. Labeling experiments with a fluorescently marked PTHrP showed clustered membrane staining of PBM and dendritic cells and a transport to the nucleus of dendritic cells. The expression of 1,25(OH)2 vitamin D3-responsive genes in monocytes/macrophages was investigated. 24-hydroxylase is induced transiently during the differentiation of myeloid THP1 cells to macrophages and osteoclast-like cells, respectively. Next, the expression of osteopontin (OPN), a further 1,25(OH)2 vitamin D3 responsive gene was studied. OPN is a matrix protein that is mainly found in bone, it carries a RGD-motive in its aminoacid sequence which can bind to integrins and is involved in cell adhesion. The expression of OPN is increased during differentiation of THP1 cells. By immunohistochemistry OPN could be detected in Crohn's disease and liver granulomas where it also plays an important role in granuloma formation. The thioredoxin reductase 1 (TR1) is a selenoenzyme that is mainly involved in the reduction of disulfide bonds of proteins. It modulates protein/protein and protein/DNA interactions like the binding of the transkription factors AP1 and NFkB to DNA-responsive elements. The expression of TR1 mRNA is induced during differentiation and is maximal in differentiated cells. Activity measurments parallel these observations. In PBM TR-activity is increased by the event of adhesion of cells to the culture dish and after treatment with 1,25(OH)2 vitamin D3. A dependence of TR-activity on the degree of differentiation of cells and the supplementation of the medium with the trace element selenium was observed. The expression of further selenoproteins in monocytic cells was investigated. In THP1 cells nine selenoproteins could be detected By labeling experiments with 75selenite. Five were found as secreted proteins in the culture supernatant. In monocytes cellular glutathione peroxidase (cGPx) is a well characterized selenoprotein. Activity could be increased 70fold by selenit supplementation. Under selenite supplementation the number of differentiated THP1 cells capable of phagocytosis was diminished while the rate of phagocytosis of single cells was enhanced. Taken together, the experiments clearly indicate that monocytic cells are equipped with the components of 1,25(OH)2 vitamin D3 metabolism and thus are capable of 1,25(OH)2 vitamin D3 hormone synthesis, secretion and turnover. Moreover, local control of 1,25(OH)2 vitamin D3 synthesis and inactivation directly regulates the expression of 1,25(OH)2 vitamin D3-responsive genes like the selenoprotein TR and thus even impacts on the cellular redox-status and defense against reactive oxygen species in these and neighbouring cells.