Doris Marko

Publications (51)184.23 Total impact

• Article: Application of low-energy scanning transmission electron microscopy for the study of Pt-nanoparticle uptake in human colon carcinoma cells.

  Holger Blank, Reinhard Schneider, Dagmar Gerthsen, Helge Gehrke, Katharina Jarolim, Doris Marko
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  ABSTRACT: Abstract High-angle annular dark-field scanning transmission electron microscopy (HAADF STEM) in a scanning electron microscope facilitates the acquisition of images with high chemical sensitivity and high resolution. HAADF STEM at low electron energies is particularly suited to image nanoparticles in thin cell sections which are not subjected to poststaining procedures as demonstrated by comparison with bright-field transmission electron microscopy. High membrane contrast is achieved and distinction of nanoparticles with different chemical composition is possible at first sight. Low-energy HAADF STEM was applied to systematically study the uptake of Pt-nanoparticles with a broad size distribution in HT29 colon carcinoma cells as a function of incubation time and incubation temperature. The cellular dose was quantified, i.e. the amount and number density of nanoparticles taken up by the cells, as well as the particle-size distribution. The results show a strong dependence of the amount of incubated nanoparticles on the exposure time which can be understood by considering size-dependent diffusion and gravitational settling of the nanoparticles in the cell culture medium.
  Nanotoxicology 04/2013; · 5.76 Impact Factor
• Article: Effect of microformulation on the bioactivity of an anthocyanin-rich bilberry pomace extract (Vaccinium myrtillus L.) in vitro.

  Christopher Kropat, Michael Betz, Ulrich Kulozik, Sabine Leick, H Rehage, Ute Böttler, Nicole Teller, Doris Marko
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  ABSTRACT: In cell culture we compared the different release rates of anthocyanins from a bilberry pomace extract encapsulated either in food-grade whey protein-based matrix capsules (WPC) or pectin amid-based hollow spherical capsules (PHS). The impact of the formulations on typical anthocyanin-associated biological endpoints such as inhibition of the epidermal growth factor receptor (EGFR) and suppression of cell growth in HT29 colon carcinoma cells was assessed. Purpose was to find out whether the release rates are sufficient to maintain biological activity and whether encapsulation affected EGFR inhibitory and growth suppressive properties of the extract. Even though anthocyanin release from extract-loaded capsules was proven under cell culture conditions, the inhibitory potential towards the EGFR was diminished. However, non-encapsulated extract as well as both extract-loaded encapsulation systems diminished the growth of HT29 cells to a comparable extent. The loss of EGFR inhibitory properties by encapsulation despite anthocyanin release indicates substantial contribution of other further constituents not monitored so far. Taken together, both applied encapsulation strategies allowed anthocyanin release and maintained biological activity with respect to growth inhibitory properties. However, the loss of EGFR inhibitory effects underline the need of biological profiling to estimate process-induced changes of plant constituent's beneficial potencies.
  Journal of Agricultural and Food Chemistry 04/2013; · 2.82 Impact Factor
• Source

  Available from: Laurent Meijer

  Dataset: 078-Supplementary Material

  Ralph Hoessel, Sophie Leclerc, Jane A Endicott, Martin E. M. Nobel, Alison Lawrie, Paul Tunnah, Maryse Leost, Eve Damiens, Dominique Marie, Doris Marko, Ellen Niederberger, Weici Tang, Gerhard Eisenbrand, Laurent Meijer
• Article: Apple procyanidins affect several members of the ErbB receptor tyrosine kinase family in vitro.

  Nicole Teller, Matthias Roth, Melanie Esselen, Diana Fridrich, Ute Boettler, Volker Blust, Frank Will, Helmut Dietrich, Francis Raul, Wolfgang Hümmer, Elke Richling, Peter Schreier, Doris Marko
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  ABSTRACT: Complex polyphenol-rich extracts from apples are known to inhibit the activity of the epidermal growth factor receptor (EGFR) in vitro. The aim of the present study was to identify the bioactive constituents of the apple juice extract which contribute substantially to this potentially chemopreventive effect and to address the question whether the effect is specific to the EGFR or whether other members of the ErbB-receptor family might also be affected. Apple-derived dihydrochalcones and their respective glycosides were found to decrease EGFR activity under cell-free conditions with IC(50)-values ranging from 0.4 ± 0.1 to 267.0 ± 50.0 μM but showed no activity on human cancer cells. The concentration of quercetin or its glycosides in the extract was too low to contribute substantially to the EGFR-inhibitory properties. In contrast, fractions derived from the apple juice extract comprising ≥86% oligomeric procyanidins (OPCs) suppressed the activity of the EGFR in cell culture with an IC(50) ∼ 100 μg mL(-1). In addition, the activity of further members of the ErbB-receptor family was potently inhibited, with ErbB3 receptor activity being most potently decreased (IC(50) ∼ 10 μg mL(-1)). From the apple polyphenols identified so far OPCs were found to add the highest contribution to the inhibitory effects towards members of the ErbB-receptor family. Considering the crucial role of the ErbB-receptors in carcinogenesis, these results support the hypothesis that apple-derived OPCs as well as OPC-rich apple preparations might be of interest with respect to chemoprevention.
  Food & function. 02/2013;
• Article: Anthocyanins suppress the cleavable complex formation by irinotecan and diminish its DNA strand breaking activity in the colon of Wistar rats.

  Melanie Esselen, Stephan W Barth, Swantje Winkler, Simone Baechler, Karlis Briviba, Bernhard Watzl, Susanne Skrbek, Doris Marko
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  ABSTRACT: In the present study the question was addressed whether anthocyanins interfere with the topoisomerase I poison irinotecan in vivo. "In vivo Complexes of Enzyme to DNA" bioassay was used to detect irinotecan-induced stabilization of topoisomerase I/DNA complexes and single cell gel electrophoresis to determine DNA strand break induction in the colon of male Wistar rats. Furthermore, analysis of anthocyanin concentrations in rat plasma and rat colon was included in the testing, demonstrating that anthocyanins reach the colon and the concentrations do not differ between rats that only received anthocyanins and the anthocyanin/irinotecan group. Blackberry extract was found to significantly reduce irinotecan-mediated topoisomerase I / DNA cleavable complex formation.. Overall, anthocyanins did not notably increase cleavable complex formation. However, a significant increase of DNA damage was shown after a single dose of irinotecan as well as the single compounds cy and cy-3-g. Furthermore, a significant reduction of irinotecan-induced DNA-strand breaks after a pre-treatment with cy, cy-3-g and blackberry extract was observed. Thus the question arises whether anthocyanin-rich preparations might interfere with chemotherapy or whether, due to low systemic bioavailability, the preparations might provide protective potential in the gastrointestinal tract.
  Carcinogenesis 12/2012; · 5.70 Impact Factor
• Article: Synthesis, topoisomerase-targeting activity and growth inhibition of lycobetaine analogs.

  Simone A Baechler, Markus Fehr, Michael Habermeyer, Andreas Hofmann, Karl-Heinz Merz, Heinz-Herbert Fiebig, Doris Marko, Gerhard Eisenbrand
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  ABSTRACT: The plant alkaloid lycobetaine has potent topoisomerase-targeting properties and shows anticancer activity. Based on these findings, several lycobetaine analogs were synthesized mainly differing in their substituents at 2, 8 and 9 position and their biological activities were evaluated. The topoisomerase-targeting properties and cytotoxicity of these structural analogs were assessed in the human gastric carcinoma cell line GXF251L. Performing a plasmid relaxation assay, an increased inhibition of topoisomerase I was found with N-methylphenanthridinium chlorides bearing a 8,9-methylenedioxy moiety or a methoxy group in 2-position. Furthermore, quaternized phenanthridinium derivatives bearing either a 2-methoxy or a 8,9-methylenedioxy moiety in conjunction with a 2-hydroxy or 2-methoxy group display potent topoisomerase II inhibition as shown by decatenation of kinetoplast DNA. In general, the N-methylphenanthridinium chlorides possess more potency in inhibiting topoisomerase I than topoisomerase II. All quaternized derivatives also exhibited potent inhibition of tumor cell growth in the low micromolar concentration range. Hence, N-methylphenanthridinium compounds were found to represent a promising class of compounds, potently inhibiting both, topoisomerases I and II, and may be further developed into clinically useful topoisomerase inhibitors.
  Bioorganic & medicinal chemistry 11/2012; · 2.82 Impact Factor
• Article: Modulation of the cellular redox status by the Alternaria toxins alternariol and alternariol monomethyl ether.

  Christine Tiessen, Markus Fehr, Christoph Schwarz, Simone Baechler, Katharina Domnanich, Ute Böttler, Gudrun Pahlke, Doris Marko
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  ABSTRACT: The mycotoxin alternariol (AOH) has been reported to possess genotoxic properties, inducing enhanced levels of DNA damage after only 1h of incubation. In the present study we addressed the question whether the induction of oxidative stress might contribute to the genotoxic effects of AOH or its naturally occurring monomethylether AME. In the DCF assay, treatment of HT29 cells for 1h enhanced the formation of dichlorofluorescein, indicative for ROS formation. The total glutathione (tGSH) was transiently decreased. In accordance with the results of the DCF assay, AOH and AME enhanced the proportion of the transcription factor Nrf2 in the nucleus. Concomitantly, the Nrf2/ARE-dependent genes γ-glutamylcysteine ligase (γ-GCL) and glutathione-S-transferase (GSTA1/2) showed enhanced transcript levels. After 24h of incubation this effect was also reflected on the protein level by an increase of GST-activity. However, in spite of the positive DCF assay and the activation of the redox-sensitive Nrf2/ARE-pathway, the level of oxidative DNA damage, measured in the comet assay by the addition of formamidopyrimidine-DNA-glycosylase (fpg) remained unaffected. Of note, after 3h of incubation no significant DNA damaging potential of AOH and AME was detectable, indicating either inactivation of the compounds or enhanced DNA repair. In summary, the mycotoxins AOH and AME were found to modulate the redox balance of HT29 cells but without apparent negative effect on DNA integrity.
  Toxicology Letters 11/2012; · 3.23 Impact Factor
• Article: Characterization of a genotoxic impact compound in Alternaria alternata infested rice as Altertoxin II.

  Christoph Schwarz, Christine Tiessen, Martin Kreutzer, Timo Stark, Thomas Hofmann, Doris Marko
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  ABSTRACT: Toxicity-guided fractionation was used to identify DNA strand breaking impact compounds in extracts obtained from rice heavily infested with the Alternaria alternata strains DSM 62006 and DSM 62010. The major genotoxic potential measured in the comet assay using human colon carcinoma cells (HT29) could be attributed to three unknown peaks, whereas the fractions containing alternariol, its monomethylether or tenuazonic acid showed no significant DNA damaging effects. According to (1)H and (13)C-NMR spectroscopy, one genotoxic impact compound was identified as Altertoxin II (ATXII). ATXII showed potent DNA damaging properties in HT29 cells with substantial induction of formamidopyrimidine DNA glycosylase (FPG)-sensitive sites. However, no effect was observed with respect to the cellular redox status, measured in the DCF assay and as total glutathione. The induction of apoptosis could be excluded as a potential reason for enhanced DNA damage. After 24 h of incubation with 1 μM ATX II, a significant increase of cells in the G(0)/G(1) phase was observed together with an inhibition of cell proliferation in the sulforhodamine B assay. Taken together, ATX II was found to contribute substantially to the genotoxic effects of complex extracts obtained from Alternaria alternata infested rice. The results demonstrate the high genotoxic potency of ATX II in human cells, underlining the necessity for further studies on the occurrence in food and its relevance for food safety.
  Archive für Toxikologie 10/2012; · 4.67 Impact Factor
• Article: Effect of Coffee Combining Green Coffee Bean Constituents with Typical Roasting Products on the Nrf2/ARE Pathway in Vitro and in Vivo.

  Nadine Volz, Ute Boettler, Swantje Winkler, Nicole Teller, Christoph Schwarz, Tamara Bakuradze, Gerhard Eisenbrand, Larissa Haupt, Lyn R Griffiths, Herbert Stiebitz, Gerhard Bytof, Ingo Lantz, Roman Lang, Thomas Hofmann, Veronika Somoza, Doris Marko
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  ABSTRACT: This study investigated Nrf2-activating properties of a coffee blend combining raw coffee bean constituents with 5-O-caffeoylquinic acid (CGA) as a lead component with typical roasting products such as N-methylpyridinium (NMP). In cell culture (HT29) the respective coffee extract (CN-CE) increased nuclear Nrf2 translocation and enhanced the transcription of ARE-dependent genes as exemplified for NAD(P)H:quinone oxidoreductase and glutathione-S-transferase (GST)A1, reflected in the protein level by an increase in GST enzyme activity. In a pilot human intervention study (29 healthy volunteers), daily consumption of 750 mL of CN-coffee for 4 weeks increased Nrf2 transcription in peripheral blood lymphocytes on average. However, the transcriptional response pattern of Nrf2/ARE-dependent genes showed substantial interindividual variations. The presence of SNPs in the Nrf2-promoter, reported recently, as well as the detection of GSTT1*0 (null) genotypes in the study collective strengthens the hypothesis that coffee acts as a modulator of Nrf2-dependent gene response in humans, but genetic polymorphisms play an important role in the individual response pattern.
  Journal of Agricultural and Food Chemistry 09/2012; 60(38):9631-41. · 2.82 Impact Factor
• Article: Induction of antioxidative Nrf2 gene transcription by coffee in humans: depending on genotype?

  Ute Boettler, Nadine Volz, Nicole Teller, Larisa M Haupt, Tamara Bakuradze, Gerhard Eisenbrand, Gerhard Bytof, Ingo Lantz, Lyn R Griffiths, Doris Marko
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  ABSTRACT: The Nrf2/ARE pathway is a major cellular defense mechanism that prevents damage by reactive oxygen species through induction of antioxidative phase II enzymes. However, the activity of the Nrf2/ARE system is not uniform with variability in response presumed to be dependent on the Nrf2 genotype. We recently completed a pilot human coffee intervention trial with healthy humans, where large interindividual differences in the antioxidative response to the study coffee were examined. Here, we address the question whether differences in the modulation of Nrf2 gene transcription, assessed as an induction of Nrf2 gene transcription by Q-PCR, might be correlated with specific Nrf2 genotypes. To date, nine single nucleotide polymorphisms (SNPs) have been identified in the Nrf2 (NFE2L2) gene. Two of these, the -617C/A and -651G/A SNPs are located within the promoter region and have previously been reported to influence the activity of the Nrf2/ARE pathway by reducing Nrf2 transcriptional activity. Sequencing of the critical Nrf2 gene promoter region not only confirmed the existence of these SNPs within the participants of the trial at the expected frequency (33% carrying the -617C/A, 17% the -651G/A and 56% the -653A/G SNP) but also indicated reduced Nrf2 gene transcription associated with a normal diet if the SNPs at position -617, -651 or -653 were present. Of note, the data also indicated the study coffee increased Nrf2 gene transcription even in SNP carriers. This further highlights the relevance of genotype-dependent induction of Nrf2 gene transcription that appears to be largely influenced by dietary factors.
  Molecular Biology Reports 02/2012; 39(6):7155-62. · 2.93 Impact Factor
• Article: In vitro toxicity of amorphous silica nanoparticles in human colon carcinoma cells.

  Helge Gehrke, Anne Frühmesser, Joanna Pelka, Melanie Esselen, Lena L Hecht, Holger Blank, Heike P Schuchmann, Dagmar Gerthsen, Clarissa Marquardt, Silvia Diabaté, Carsten Weiss, Doris Marko
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  ABSTRACT: Abstract The use of nanostructured silica (SiO(2)) particles is no longer restricted to biomedical and (bio-) technological fields but rather finding applications in products of the food industry. Thus, our studies on the toxicological relevance of SiO(2) nanoparticles focused on cytotoxic effects, the modulation of the cellular redox status and the impact on DNA integrity in human colon carcinoma cells (HT29). The results indicate that these SiO(2) nanoparticles stimulate the proliferation of HT29 cells, depending on the incubation time and the particle size. The cytotoxicity of the investigated SiO(2) nanoparticles was found to depend on the concentration, size and on the FCS content of the culture medium. Furthermore, SiO(2) seem to interfere with glutathione biosynthesis. The results indicate further that effects of SiO(2) NPs are not mediated by oxidative stress but by interference with the MAPK/ERK1/2 as well as the Nrf2/ARE signalling pathways. Additionally, investigations regarding DNA integrity revealed no substantial (oxidative) DNA damage.
  Nanotoxicology 01/2012; · 5.76 Impact Factor
• Article: DNA damaging properties of single walled carbon nanotubes in human colon carcinoma cells.

  Joanna Pelka, Helge Gehrke, Anja Rechel, Manfred Kappes, Frank Hennrich, Christian G Hartinger, Doris Marko
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  ABSTRACT: Abstract Single walled carbon nanotubes were studied with respect to cytotoxic and genotoxic properties in cells of the gastrointestinal tract as exemplified for the human colon carcinoma cell line HT29. No effect on cell growth in the sulphorhodamine B assay was observed after 24 h of incubation, whereas growth inhibitory properties were found after 48 and 72 h. After 24 h incubation a decrease of mitochondrial activity (WST-1) was measured (≥0.1 μg/ml), whereas membrane integrity (lactate dehydrogenase) was not affected. In cytotoxic concentrations, the formation of reactive oxygen species and a slight increase of total glutathione and nuclear Nrf2 were observed. However, already in subcytotoxic concentrations substantial DNA damaging effects were found in the alkaline comet assay, which were not associated with enhanced formation of formamidopyrimidine-DNA-glycosylase-sensitive sites. In addition, an increase of kinetochore-negative micronuclei (V79) and phosphorylation of the tumour suppressor protein p53 (HT29) underlined the genotoxic potential of these nanostructures.
  Nanotoxicology 10/2011; · 5.76 Impact Factor
• Article: Dark roast coffee is more effective than light roast coffee in reducing body weight, and in restoring red blood cell vitamin E and glutathione concentrations in healthy volunteers.

  Christine Kotyczka, Ute Boettler, Roman Lang, Herbert Stiebitz, Gerhard Bytof, Ingo Lantz, Thomas Hofmann, Doris Marko, Veronika Somoza
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  ABSTRACT: Recent results from prospective cohort studies have shown that moderate coffee consumption is associated with a reduced risk for diabetes mellitus type II or Alzheimer's disease. Since reactive oxygen species (ROS) are believed to be involved in the pathogenesis of these diseases, antioxidants in coffee might contribute to this risk reduction. We aimed at elucidating whether a dark roast coffee beverage (CB) rich in N-methylpyridinium ions (NMP: 785 μmol/L) and low in chlorogenic acids (CGA: 523 μmol/L) has stronger antioxidant effects on human erythrocytes than a CB prepared from a light roast with opposite proportions (CGA: 4538 μmol/L; NMP: 56 μmol/L). Following a 2-wk wash out period, 500 mL of the respective CB was administered to 30 subjects daily for 4-wk. Blood and spot urine samples were collected at the beginning and at the end of each intervention. Intake of the dark roast CB most effectively improved the antioxidant status of erythrocytes: superoxide dismutase and glutathione peroxidase activity decreased by 5.8 and 15%, respectively, whereas tocopherol and total glutathione concentrations increased by 41 and 14%, respectively. Furthermore, administration of the NMP-rich CB led to a significant body weight reduction in pre-obese subjects, whereas the CGA-rich CB did not.
  Molecular Nutrition & Food Research 08/2011; 55(10):1582-6. · 4.30 Impact Factor
• Article: Anthocyanin-rich blackberry extract suppresses the DNA-damaging properties of topoisomerase I and II poisons in colon carcinoma cells.

  Melanie Esselen, Ute Boettler, Nicole Teller, Simone Bachler, Melanie Hutter, Corinna E Rufer, Susanne Skrbek, Doris Marko
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  ABSTRACT: In the present study, we addressed the question whether cyanidin-3-glucoside (C3G) or complex C3G-rich blackberry extracts affect human topoisomerases with special emphasis on the contribution of the potential degradation products phloroglucinol aldehyde (PGA) and protocatechuic acid (PCA). In HT29 colon carcinoma cells a C3G-rich blackberry extract suppressed camptothecin- (CPT-) or doxorubicin- (DOX-) induced stabilization of the covalent DNA-topoisomerase intermediate, thus antagonizing the effects of these classical topoisomerase poisons on DNA integrity. As a single compound, C3G (100 μM) decreased the DNA-damaging effects of CPT as well, but did not significantly affect those induced by DOX. At the highest applied concentration (100 μM), cyanidin protected DNA from CPT- and DOX-induced damage. Earlier reports on DNA-damaging properties of cyanidin were found to result most likely from the formation of hydrogen peroxide as an artifact in the cell culture medium when the incubation was performed in the absence of catalase. The suppression of hydrogen peroxide accumulation, achieved by the addition of catalase, demonstrated that cyanidin does not exhibit DNA-damaging properties in HT29 cells (up to 100 μM). The observed effects on topoisomerase interference and DNA protection against CPT or DOX were clearly limited to the parent compound and were not observed for the potential cyanidin degradation products PGA and PCA.
  Journal of Agricultural and Food Chemistry 06/2011; 59(13):6966-73. · 2.82 Impact Factor
• Article: Genotoxicity of dietary, environmental and therapeutic topoisomerase II poisons is uniformly correlated to prolongation of enzyme DNA residence.

  Faiza M Kalfalah, Christian Mielke, Morten O Christensen, Simone Baechler, Doris Marko, Fritz Boege
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  ABSTRACT: DNA damage by genistein and etoposide is determined by the half-life of topoisomerase II-DNA linkage induced [Bandele O. J. and Osheroff N., Biochemistry 2008, 47, 11900]. Here, we test whether this applies generally to dietary flavonoids and therapeutic compounds enhancing topoisomerase II-DNA cleavage (Topo II poisons). We compared the impact of Topo II poisons on DNA residence kinetics of biofluorescent human topoisomerases IIα and IIβ (delineating duration of the DNA-linked enzyme state) with histone 2AX phosphorylation (delineating DNA damage response). Prolongation of topoisomerase II-DNA residence was correlated to DNA damage response, whereas topoisomerase II-DNA linkage was not. Catalytic inhibitors stabilizing topoisomerase II on unbroken DNA also exhibited such a correlation, albeit at a lower level of DNA damage response. Therapeutic Topo II poisons had stronger and more durable effects on enzyme II DNA residence and elicited stronger DNA damage responses than natural or dietary ones. Topoisomerase II-mediated DNA damage appears related to the prolongation of enzyme DNA residence more than to enzyme-DNA cleavage. Due to this reason, genistein and other tested natural and dietary Topo II poisons have a much lower genotoxic potential than therapeutic ones under the conditions of equal topoisomerase II-DNA linkage.
  Molecular Nutrition & Food Research 05/2011; 55 Suppl 1:S127-42. · 4.30 Impact Factor
• Article: Coffee constituents as modulators of Nrf2 nuclear translocation and ARE (EpRE)-dependent gene expression.

  Ute Boettler, Katharina Sommerfeld, Nadine Volz, Gudrun Pahlke, Nicole Teller, Veronika Somoza, Roman Lang, Thomas Hofmann, Doris Marko
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  ABSTRACT: Oxidative cellular stress initiates Nrf2 translocation into the nucleus, thus inducing antioxidant response element (ARE)-mediated expression of Phase II enzymes involved in detoxification and antioxidant defence. We investigated whether coffee extracts (CEs) of different proveniences and selected constituents have an impact on the Nrf2/ARE pathway in human colon carcinoma cells (HT29). Assessed as increased nuclear Nrf2 protein, Nrf2 nuclear translocation was modulated by different CEs as observed by Western blot analysis. In addition to the known Nrf2 activator 5-O-caffeoylquinic acid (CGA), pyridinium derivatives like the N-methylpyridinium ion (NMP) were identified as potent activators of Nrf2 nuclear translocation and ARE-dependent gene expression of selected antioxidative Phase II enzymes in HT29. Thereby, the substitution pattern at the pyridinium core structure determined the impact on Nrf2-signalling. In contrast, trigonelline was found to interfere with Nrf2 activation, effectively suppressing the NMP-mediated induction of Nrf2/ARE-dependent gene expression. In conclusion, several coffee constituents, partly already present in the raw material as well as those generated during the roasting process, contribute to the Nrf2-translocating properties of consumer-relevant coffee. A fine tuning in the degradation/formation of activating and deactivating constituents of the Nrf2/ARE pathway during the roasting process appears to be critical for the chemopreventive properties of the final coffee product.
  The Journal of nutritional biochemistry 05/2011; 22(5):426-40. · 4.29 Impact Factor
• Article: Coffees rich in chlorogenic acid or N-methylpyridinium induce chemopreventive phase II-enzymes via the Nrf2/ARE pathway in vitro and in vivo.

  Ute Boettler, Nadine Volz, Gudrun Pahlke, Nicole Teller, Christine Kotyczka, Veronika Somoza, Herbert Stiebitz, Gerhard Bytof, Ingo Lantz, Roman Lang, Thomas Hofmann, Doris Marko
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  ABSTRACT: Recently, the coffee constituents 5-O-caffeoylquinic acid (CGA) and N-methylpyridinium (NMP) were identified as inducers of the Nrf2/antioxidant-response element (ARE) detoxifying pathway under cell-culture condition. To study the impact of CGA and NMP on the Nrf2-activating properties of a complex coffee beverage, two different model coffees were generated by variation of the roasting conditions: a low-roast coffee rich in CGA and a heavy-roast low in CGA but containing high levels of NMP. Activation of the Nrf2/antioxidant-response element pathway was monitored in vitro and in vivo.
  Molecular Nutrition & Food Research 03/2011; 55(5):798-802. · 4.30 Impact Factor
• Article: Anthocyanin-rich extracts suppress the DNA-damaging effects of topoisomerase poisons in human colon cancer cells.

  Melanie Esselen, Jessica Fritz, Melanie Hutter, Nicole Teller, Simone Baechler, Ute Boettler, Tim H Marczylo, Andreas J Gescher, Doris Marko
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  ABSTRACT: The effect of two anthocyanin-rich berry extracts (A, bilberry; B, red grape) on topoisomerases was investigated in a cell-free system and in human HT29 colon carcinoma cells. In parallel, their impact on DNA integrity was determined. The berry extracts suppressed the activity of topoisomerase I at concentrations ≥50 μg/mL. The activity of the topoisomerase II isoform was preferentially diminished (≥1 μg/mL). Within HT29 cells, the extracts were found to act as catalytic inhibitors without stabilizing the cleavable complex. Although topoisomerase activity was inhibited, none of the extracts induced DNA strand breaks up to 50 μg/mL. Moreover, pre- and coincubation of HT29 cells with A (≥1 μg/mL) significantly suppressed (p-value ≤0.001) the strand-breaking effects of camptothecin, whereas B was found to be less effective (1 μg/mL; p-value ≤0.05). Both extracts were found to significantly diminish doxorubicin-mediated DNA strand breaks at concentrations ≥1 μg/mL (p-value ≤0.001). Consistent with these results, the extracts suppressed doxorubicin-mediated enhancement of levels of topoisomerase II covalently linked to DNA in HT29 cells. These results raise the possibility that high intake of berry extracts may protect DNA and thus counteract the therapeutic effectiveness of orally applied topoisomerase poisons during chemotherapy.
  Molecular Nutrition & Food Research 01/2011; 55 Suppl 1:S143-53. · 4.30 Impact Factor
• Article: Platinum nanoparticles and their cellular uptake and DNA platination at non-cytotoxic concentrations.

  Helge Gehrke, Joanna Pelka, Christian G Hartinger, Holger Blank, Felix Bleimund, Reinhard Schneider, Dagmar Gerthsen, Stefan Bräse, Marlene Crone, Michael Türk, Doris Marko
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  ABSTRACT: Three differently sized, highly dispersed platinum nanoparticle (Pt-NP) preparations were generated by supercritical fluid reactive deposition (SFRD) and deposited on a β-cyclodextrin matrix. The average particle size and size distribution were steered by the precursor reduction conditions, resulting in particle preparations of <20, <100 and >100 nm as characterised by TEM and SEM. As reported previously, these Pt-NPs were found to cause DNA strand breaks in human colon carcinoma cells (HT29) in a concentration- and time-dependent manner and a distinct size dependency. Here, we addressed the question whether Pt-NPs might affect directly DNA integrity in these cells and thus behave analogous to platinum-based chemotherapeutics such as cisplatin. Therefore, DNA-associated Pt as well as the translocation of Pt-NPs through a Caco-2 monolayer was quantified by ICP-MS. STEM imaging demonstrated that Pt-NPs were taken up into HT29 cells in their particulate and aggregated form, but appear not to translocate into the nucleus or interact with mitochondria. The platinum content of the DNA of HT29 cells was found to increase in a time- and concentration-dependent manner with a maximal effect at 1,000 ng/cm(2). ICP-MS analysis of the cell culture medium indicated the formation of soluble Pt species, although to a limited extent. The observations suggest that DNA strand breaks mediated by metallic Pt-NPs are caused by Pt ions forming during the incubation of cells with these nanoparticles.
  Archive für Toxikologie 01/2011; 85(7):799-812. · 4.67 Impact Factor
• Article: Repair of DNA damage induced by the mycotoxin alternariol involves tyrosyl-DNA phosphodiesterase 1.

  Markus Fehr, Simone Baechler, Christopher Kropat, Christian Mielke, Fritz Boege, Gudrun Pahlke, Doris Marko
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  ABSTRACT: Alternariol (AOH) was reported recently to act as a topoisomerase poison. To underline the relevance of topoisomerase targeting for the genotoxic properties of AOH, we addressed the question whether human tyrosyl-DNA phosphodiesterase 1 (TDP1), an enzyme vital to the repair of covalent DNA-topoisomerase adducts, affects AOH-mediated genotoxicity. The relevance of TDP1 activity on AOH-induced genotoxicity was investigated by the comet assay in human cells overexpressing GFP chimera of TDP1 or the inactive mutant TDP1(H263A) as well as in cells subjected to siRNA-mediated knock-down of endogenous TDP1. Cells overexpressing TDP1 exhibited significantly less DNA damage after treatment with AOH in comparison to cells expressing the inactive mutant TDP1(H263A). In accordance with these results, levels of AOH inducing DNA strand breaks were increased in TDP1-suppressed cells in comparison to cells transfected with control siRNA. The specific topoisomerase poisons camptothecin and etoposide caused comparable effects, underlining that TDP1 plays an important role in the repair of topoisomerase-mediated DNA damage. In summary, the repair enzyme TDP1 was identified as a factor for the modulation of AOH-mediated DNA damage in human cells.
  Mycotoxin Research 11/2010; 26(4):247-56.