TY  - JOUR
A1  - Adam, W.
A1  - Ahrweiler, M.
A1  - Saha-Möller, C. R.
A1  - Sauter, M.
A1  - Schönberger, A.
A1  - Epe, B.
A1  - Müller, E.
A1  - Schiffmann, D.
A1  - Stopper, Helga
A1  - Wild, D.
T1  - Genotoxicity studies of benzofuran dioxetanes and epoxides with isolated DNA, bacteria and mammalian cells
N2  - 1.2-Dioxetanes, very reactive and high energy molecules. are involved as labile intermediates in dioxygenase- activated aerobic metabolism and in physiological processes. Various toxico1ogica1 tests reveal that dioxetanes are indeed genotoxic. In supercoiled DNA of bacteriophage PM2 they induce endonucleasesensitive sites, most of them are FPG protein-sensitive base modifications (8-hydroxyguanine, fonnamidopyrimidines). Pyrimidinedimersand sites ofbase loss (AP sites) which were probed by UV endonuclease and exonuclease 111 are minor lesions in this system. While the alky1-substituted dioxetanes do not show any significant mutagenic activity in different Salmonella typhimurium strains, heteroarene dioxetanes such as benzofuran and furocoumarin dioxetanes are strongly mutagenic in S. typhimurium strain TA I 00. DNA adducts formed with an intermediary alkyJating agent appear to be responsible for the mutagenic activity of benzofuran dioxetane. We assume that the benzofuran epoxides, generated in situ from benzofuran dioxetanes by deoxygenation are the ultimate mutagens of the latter. since benzofuran epoxides are highly mutagenic in the S. typhimurium strain TAIOO and they form DNA adducts. as detected by the 212Ppostlabelling technique. Our results imply that the type of D NA darnage promoted by dioxetanes is dependent on the structural feature of dioxetanes. Furthermore, the direct photochemical DNA darnage by energy transfer. i.e., pyrimidine dimers, plays a minor role in the genotoxicity of dioxetanes. Instead, photooxidation dominates in isolated DNA. while radical darnage and alkylation prevail in the cellular system.
KW  - Toxikologie
KW  - 1
KW  - 2-Dioxetane
KW  - Benzefuran dioxetane
KW  - Benzefuran epoxide
KW  - DNA damage
KW  - Mutagenicity
KW  - DNA adduct . Repair endonuclease
KW  - FPG protein
Y1  - 1993
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-63420
ER  - 
TY  - JOUR
A1  - Awad, Eman
A1  - Othman, Eman M.
A1  - Stopper, Helga
T1  - Effects of resveratrol, lovastatin and the mTOR-inhibitor RAD-001 on insulin-induced genomic damage in vitro
JF  - Molecules
N2  - Diabetes mellitus (DM) is one of the major current health problems due to lifestyle changes. Before diagnosis and in the early years of disease, insulin blood levels are elevated. However, insulin generates low levels of reactive oxygen species (ROS) which are integral to the regulation of a variety of intracellular signaling pathways, but excess levels of insulin may also lead to DNA oxidation and DNA damage. Three pharmaceutical compounds, resveratrol, lovastatin and the mTOR-inhibitor RAD-001, were investigated due to their known beneficial effects. They showed protective properties against genotoxic damage and significantly reduced ROS after in vitro treatment of cultured cells with insulin. Therefore, the selected pharmaceuticals may be attractive candidates to be considered for support of DM therapy.
KW  - genomic damage
KW  - insulin
KW  - resveratrol
KW  - lovastatin
KW  - mTOR-inhibitor RAD-001
Y1  - 2017
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-159260
VL  - 22
IS  - 12
ER  - 
TY  - JOUR
A1  - Balasubramanian, Srikkanth
A1  - Othman, Eman M.
A1  - Kampik, Daniel
A1  - Stopper, Helga
A1  - Hentschel, Ute
A1  - Ziebuhr, Wilma
A1  - Oelschlaeger, Tobias A.
A1  - Abdelmohsen, Usama R.
T1  - Marine sponge-derived Streptomyces sp SBT343 extract inhibits staphylococcal biofilm formation
JF  - Frontiers in Microbiology
N2  - Staphylococcus epidermidis and Staphylococcus aureus are opportunistic pathogens that cause nosocomial and chronic biofilm-associated infections. Indwelling medical devices and contact lenses are ideal ecological niches for formation of staphylococcal biofilms. Bacteria within biofilms are known to display reduced susceptibilities to antimicrobials and are protected from the host immune system. High rates of acquired antibiotic resistances in staphylococci and other biofilm-forming bacteria further hamper treatment options and highlight the need for new anti-biofilm strategies. Here, we aimed to evaluate the potential of marine sponge-derived actinomycetes in inhibiting biofilm formation of several strains of S. epidermidis, S. aureus, and Pseudomonas aeruginosa. Results from in vitro biofilm-formation assays, as well as scanning electron and confocal microscopy, revealed that an organic extract derived from the marine sponge-associated bacterium Streptomyces sp. SBT343 significantly inhibited staphylococcal biofilm formation on polystyrene, glass and contact lens surfaces, without affecting bacterial growth. The extract also displayed similar antagonistic effects towards the biofilm formation of other S. epidermidis and S. aureus strains tested but had no inhibitory effects towards Pseudomonas biofilms. Interestingly the extract, at lower effective concentrations, did not exhibit cytotoxic effects on mouse fibroblast, macrophage and human corneal epithelial cell lines. Chemical analysis by High Resolution Fourier Transform Mass Spectrometry (HRMS) of the Streptomyces sp. SBT343 extract proportion revealed its chemical richness and complexity. Preliminary physico-chemical characterization of the extract highlighted the heat-stable and non-proteinaceous nature of the active component(s). The combined data suggest that the Streptomyces sp. SBT343 extract selectively inhibits staphylococcal biofilm formation without interfering with bacterial cell viability. Due to absence of cell toxicity, the extract might represent a good starting material to develop a future remedy to block staphylococcal biofilm formation on contact lenses and thereby to prevent intractable contact lens-mediated ocular infections.
KW  - medicine
KW  - marine sponges
KW  - actinomycetes
KW  - Streptomyces
KW  - staphilococci
KW  - biofilms
KW  - contact lens
Y1  - 2017
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-171844
VL  - 8
ER  - 
TY  - JOUR
A1  - Bankoglu, Ezgi Eyluel
A1  - Arnold, Charlotte
A1  - Hering, Ilona
A1  - Hankir, Mohammed
A1  - Seyfried, Florian
A1  - Stopper, Helga
T1  - Decreased chromosomal damage in lymphocytes of obese patients after bariatric surgery
JF  - Scientific Reports
N2  - The number of bariatric surgeries being performed worldwide has markedly risen. While the improvement in obesity-associated comorbidities after bariatric surgery is well-established, very little is known about its impact on cancer risk. The peripheral lymphocyte micronucleus test is a widely used method for the monitoring of chromosomal damage levels in vivo, and micronucleus frequency positively correlates with cancer risk. Therefore, the aim of this study was to compare the micronucleus frequency before and after bariatric surgery in obese subjects. Peripheral blood mononuclear cells were collected from 45 obese subjects before and at two time-points after bariatric surgery (6 and 12 months) to assess spontaneous micronucleus frequency. Consistent with the increased cancer risk previously shown, bariatric surgery-induced weight loss led to a significant reduction in lymphocyte micronucleus frequency after 12 months. Interestingly, comorbidities such as type 2 diabetes mellitus and metabolic syndrome further seemed to have an impact on the lymphocyte micronucleus frequency. Our findings may indicate a successful reduction of cancer risk in patients following weight loss caused by bariatric surgery.
KW  - obesity
KW  - bariatric surgery
KW  - cancer risk
Y1  - 2018
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-177090
VL  - 8
IS  - 11195
ER  - 
TY  - JOUR
A1  - Bankoglu, Ezgi Eyluel
A1  - Schuele, Carolin
A1  - Stopper, Helga
T1  - Cell survival after DNA damage in the comet assay
JF  - Archives of Toxicology
N2  - The comet assay is widely used in basic research, genotoxicity testing, and human biomonitoring. However, interpretation of the comet assay data might benefit from a better understanding of the future fate of a cell with DNA damage. DNA damage is in principle repairable, or if extensive, can lead to cell death. Here, we have correlated the maximally induced DNA damage with three test substances in TK6 cells with the survival of the cells. For this, we selected hydrogen peroxide (H\(_{2}\)O\(_{2}\)) as an oxidizing agent, methyl methanesulfonate (MMS) as an alkylating agent and etoposide as a topoisomerase II inhibitor. We measured cell viability, cell proliferation, apoptosis, and micronucleus frequency on the following day, in the same cell culture, which had been analyzed in the comet assay. After treatment, a concentration dependent increase in DNA damage and in the percentage of non-vital and apoptotic cells was found for each substance. Values greater than 20-30% DNA in tail caused the death of more than 50% of the cells, with etoposide causing slightly more cell death than H\(_{2}\)O\(_{2}\) or MMS. Despite that, cells seemed to repair of at least some DNA damage within few hours after substance removal. Overall, the reduction of DNA damage over time is due to both DNA repair and death of heavily damaged cells. We recommend that in experiments with induction of DNA damage of more than 20% DNA in tail, survival data for the cells are provided.
KW  - Cell death and comet assay
KW  - DNA damage
KW  - DNA repair
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-265339
VL  - 95
IS  - 12
ER  - 
TY  - JOUR
A1  - Bankoglu, Ezgi Eyluel
A1  - Stipp, Franzisca
A1  - Gerber, Johanna
A1  - Seyfried, Florian
A1  - Heidland, August
A1  - Bahner, Udo
A1  - Stopper, Helga
T1  - Effect of cryopreservation on DNA damage and DNA repair activity in human blood samples in the comet assay
JF  - Archives of Toxicology
N2  - The comet assay is a commonly used method to determine DNA damage and repair activity in many types of samples. In recent years, the use of the comet assay in human biomonitoring became highly attractive due to its various modified versions, which may be useful to determine individual susceptibility in blood samples. However, in human biomonitoring studies, working with large sample numbers that are acquired over an extended time period requires some additional considerations. One of the most important issues is the storage of samples and its effect on the outcome of the comet assay. Another important question is the suitability of different blood preparations. In this study, we analysed the effect of cryopreservation on DNA damage and repair activity in human blood samples. In addition, we investigated the suitability of different blood preparations. The alkaline and FPG as well as two different types of repair comet assay and an in vitro hydrogen peroxide challenge were applied. Our results confirmed that cryopreserved blood preparations are suitable for investigating DNA damage in the alkaline and FPG comet assay in whole blood, buffy coat and PBMCs. Ex vivo hydrogen peroxide challenge yielded its optimal effect in isolated PBMCs. The utilised repair comet assay with either UVC or hydrogen peroxide-induced lesions and an aphidicolin block worked well in fresh PBMCs. Cryopreserved PBMCs could not be used immediately after thawing. However, a 16-h recovery with or without mitotic stimulation enabled the application of the repair comet assay, albeit only in a surviving cell fraction.
KW  - human biomonitoring
KW  - DNA damage
KW  - DNA repair
KW  - comet assay
KW  - blood samples
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-265326
VL  - 95
IS  - 5
ER  - 
TY  - JOUR
A1  - Bankoglu, Ezgi Eyluel
A1  - Tschopp, Oliver
A1  - Schmitt, Johannes
A1  - Burkard, Philipp
A1  - Jahn, Daniel
A1  - Geier, Andreas
A1  - Stopper, Helga
T1  - Role of PTEN in Oxidative Stress and DNA Damage in the Liver of Whole-Body Pten Haplodeficient Mice
JF  - PLoS One
N2  - Type 2 diabetes (T2DM) and obesity are frequently associated with non-alcoholic fatty liver disease (NAFLD) and with an elevated cancer incidence. The molecular mechanisms of carcinogenesis in this context are only partially understood. High blood insulin levels are typical in early T2DM and excessive insulin can cause elevated reactive oxygen species (ROS) production and genomic instability. ROS are important for various cellular functions in signaling and host defense. However, elevated ROS formation is thought to be involved in cancer induction. In the molecular events from insulin receptor binding to genomic damage, some signaling steps have been identified, pointing at the PI3K/AKT pathway. For further elucidation Phosphatase and Tensin homolog (Pten), a tumour suppressor phosphatase that plays a role in insulin signaling by negative regulation of PI3K/AKT and its downstream targets, was investigated here. Dihydroethidium (DHE) staining was used to detect ROS formation in immortalized human hepatocytes. Comet assay and micronucleus test were performed to investigate genomic damage in vitro. In liver samples, DHE staining and western blot detection of HSP70 and HO-1 were performed to evaluate oxidative stress response. DNA double strand breaks (DSBs) were detected by immunohistostaining. Inhibition of PTEN with the pharmacologic inhibitor VO-OHpic resulted in increased ROS production and genomic damage in a liver cell line. Knockdown of Pten in a mouse model yielded increased oxidative stress levels, detected by ROS levels and expression of the two stress-proteins HSP70 and HO-1 and elevated genomic damage in the liver, which was significant in mice fed with a high fat diet. We conclude that PTEN is involved in oxidative stress and genomic damage induction in vitro and that this may also explain the in vivo observations. This further supports the hypothesis that the PI3K/AKT pathway is responsible for damaging effects of high levels of insulin.
KW  - insulin
KW  - mouse models DNA damage
KW  - oxidative stress
KW  - mammalian genomics
KW  - fatty liver
KW  - micronuclei
KW  - insulin signaling
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-146970
VL  - 11
IS  - 11
ER  - 
TY  - JOUR
A1  - Cheng, Cheng
A1  - Othman, Eman M.
A1  - Stopper, Helga
A1  - Edrada-Ebel, RuAngelie
A1  - Hentschel, Ute
A1  - Abdelmohsen, Usama Ramadan
T1  - Isolation of petrocidin A, a new cytotoxic cyclic dipeptide from the marine sponge-derived bacterium \(Streptomyces\) sp. SBT348
JF  - Marine Drugs
N2  - A new cyclic dipeptide, petrocidin A (\(\textbf{1}\)), along with three known compounds—2,3-dihydroxybenzoic acid (\(\textbf{2}\)), 2,3-dihydroxybenzamide (\(\textbf{3}\)), and maltol (\(\textbf{4}\))—were isolated from the solid culture of \(Streptomyces\) sp. SBT348. The strain \(Streptomyces\) sp. SBT348 had been prioritized in a strain collection of 64 sponge-associated actinomycetes based on its distinct metabolomic profile using liquid chromatography/high-resolution mass spectrometry (LC-HRMS) and nuclear magnetic resonance (NMR). The absolute configuration of all α-amino acids was determined by HPLC analysis after derivatization with Marfey’s reagent and comparison with commercially available reference amino acids. Structure elucidation was pursued in the presented study by mass spectrometry and NMR spectral data. Petrocidin A (\(\textbf{1}\)) and 2,3-dihydroxybenzamide (\(\textbf{3}\)) exhibited significant cytotoxicity towards the human promyelocytic HL-60 and the human colon adenocarcinoma HT-29 cell lines. These results demonstrated the potential of sponge-associated actinomycetes for the discovery of novel and pharmacologically active natural products.
KW  - biology
KW  - sponges
KW  - actinomycetes
KW  - streptomyces
KW  - cyclic dipeptide
KW  - cytotoxic
Y1  - 2017
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-172644
VL  - 15
IS  - 12
ER  - 
TY  - JOUR
A1  - Djelić, Ninoslav
A1  - Borozan, Sunčica
A1  - Dimitrijević-Srećković, Vesna
A1  - Pajović, Nevena
A1  - Mirilović, Milorad
A1  - Stopper, Helga
A1  - Stanimirović, Zoran
T1  - Oxidative stress and DNA damage in peripheral blood mononuclear cells from normal, obese, prediabetic and diabetic persons exposed to thyroid hormone in vitro
JF  - International Journal of Molecular Sciences
N2  - Diabetes, a chronic group of medical disorders characterized byhyperglycemia, has become a global pandemic. Some hormones may influence the course and outcome of diabetes, especially if they potentiate the formation of reactive oxygen species (ROS). There is a close relationship between thyroid disorders and diabetes. The main objective of this investigation was to find out whether peripheral blood mononuclear cells (PBMCs) are more prone to DNA damage by triiodothyronine (T\(_3\)) (0.1, 1 and 10 μM) at various stages of progression through diabetes (obese, prediabetics, and type 2 diabetes mellitus—T2DM persons). In addition, some biochemical parameters of oxidative stress (catalase-CAT, thiobarbituric acid reactive substances—TBARS) and lactate dehydrogenase (LDH) were evaluated. PBMCs from prediabetic and diabetic patients exhibited increased sensitivity for T\(_3\) regarding elevated level of DNA damage, inhibition of catalase, and increase of TBARS and LDH. PBMCs from obese patients reacted in the same manner, except for DNA damage. The results of this study should contribute to a better understanding of the role of thyroid hormones in the progression of T2DM.
KW  - diabetes
KW  - oxidative stress
KW  - DNA damage
KW  - lymphocytes
KW  - thyroid hormone
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-285988
SN  - 1422-0067
VL  - 23
IS  - 16
ER  - 
TY  - JOUR
A1  - Epe, B.
A1  - Harttig, U.
A1  - Stopper, Helga
A1  - Metzler, M.
T1  - Covalent binding of reactive estrogen metabolites to microtubular protein as a possible mechanism of aneuploidy induction and neoplastic cell transformation
N2  - Neoplastic cell transfonnation induced by estrogens and some other carcinogen& such as benzene appears to involve the induction of mitotic aneuploidy rather than DNA damage and point mutations. As metabolic activation may also play an important roJe in the mechanism of carcinogenesis of these nongenotoxic compounds, we have studied the Interaction of reactive quinone metabolites of various estrogens and of benzene with the major microtubular protein, tubulin, in a cell-free system. Covalent binding of the radioactively labeled metabolites to the a- and 13-subunit of tubulin was found to depend on the structure of the metabolite. When the adducted tubulins were tested in vitro for their ability to polymerize to microtubules, Inhibition of microtubule assembly was obsened in every case, although to varying extents. It is proposed that the fonnation of covalent tubulin adducts may impair the formation of mitotic spindies and thus contribute to chromosomal nondisjunction and aneuploidy induction.
KW  - Toxikologie
Y1  - 1990
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-63478
ER  -