Previous studies indicate that ascorbic acid, when combined with copper or iron cleaves several v... more Previous studies indicate that ascorbic acid, when combined with copper or iron cleaves several viral DNA. ln this study, we generated the ascorbate radical anion electrochemically in a simple chemical environment without the participation of a metal ion. This solution possesses viral DNA scission activity. Ohe absence of catalytic metal ions [Fe (IIl) and Cu(II)] in the incubation medium was evidenced by metal chelating agents such as desferrioxamine and EDTA. Ohe radical quenching at high EDTA concentration was attributed to ionic strength of EDTA rather than metal chelation. Ohe effects of antioxidants, radical scavangers, catalase, superoxide dismutase and some proteins on DNA cleavage have been tested. Cleavage may not arise directly from ascorbate free radical but the reaction of the radical form of ascorbate with oxygen may produce the actual reactive species. Aerobic oxidation of ascorbate itself strictly requires transition metal catalysts, however electrochemically produced ascorbyl radical avoided the kinetic barrier that prevented direct oxidation of ascorbic acid with oxygen and eliminated the need for the transition metal ion catalysts.
Oxidative DNA damage is an inescapable consequence for cells constantly exposed to oxidative stre... more Oxidative DNA damage is an inescapable consequence for cells constantly exposed to oxidative stress derived from normal metabolic processes and from environmental factors. Phenolic compounds, which have strong antioxidant activity, prevent DNA damage by protecting the cells against harmful effects of oxidative stress. In this study, the effect of virgin olive oil phenolic extract (OOPE) was investigated on H2O2-induced mitochondrial DNA (mtDNA) and nuclear DNA (nDNA) damage in HeLa cells. DNA damage was assessed in mitochondria and two nuclear regions by using quantitative PCR (QPCR) assay. The cells were pre-treated with non-cytotoxic doses of OOPE for 4 h, and DNA damage was determined. OOPE alone does not change the steady-state level of DNA damage. The oxidative stress generated with 750 μM H2O2 caused two times greater damages in mtDNA compared to nDNA, which included the nonexpressed β-globin region (1.507±0.110 lesions/10 kb) and the expressed APEX1 gene (1.623±0.243 lesions/10 kb) with respect to the control region. When cells were preincubated with OOPE for 4 h, nDNA damage under stress condition was completely inhibited; however, mtDNA damage was not affected by this procedure. These results suggest that OOPE has a protective effect against nDNA damage in HeLa cells.
A new deletion of the β-globin gene cluster was characterized in a Turkish family. A 6-year-old m... more A new deletion of the β-globin gene cluster was characterized in a Turkish family. A 6-year-old male and his father were heterozygotes for this deletion. They presented with mild hypochromic microcytic anemia associated with elevated Hb F (15%) and normal Hb A2 levels (2.0%). This newly described Turkish type (δβ)°-thalassemia has a deletion of about 30 kb. The 5´ breakpoint
Many recent studies have focused on the investigation of the biological effects of electromagneti... more Many recent studies have focused on the investigation of the biological effects of electromagnetic field. Although the several types of biological effects of electromagnetic fields have been shown, the molecular mechanisms of these effects have not been explained yet. Some epidemiological studies have suggested that exposure to ambient, lowlevel 50-60 Hz electromagnetic fields increase risk of disease including cancer such as leukemia among children who live close to power lines or among men whose jobs expose them to electromagnetic field, while others have suggested that electromagnetic fields exposure could increase both the concentration of free radicals and oscillating free radicals. Electromagnetic fields are known to affect radical pair recombination and they may increase the concentration of oxygen free radicals in living cells. In this study, oxidative stress was formed by the oxidation of ascorbic acid and the effect of 50 Hz, 0.3 mT electromagnetic fields on the oxidative ...
Apolipoprotein E plays a central role in lipid metabolism by serving as a ligand for the binding ... more Apolipoprotein E plays a central role in lipid metabolism by serving as a ligand for the binding of lipoproteins to lipoprotein receptors. We investigated the polymorphism of the apolipoprotein E (ApoE) gene using a PCR-RFLP method and the relation between ApoE polymorphism and plasma lipoproteinlipid levels in patients with cardiovascular disease (CD). As a result, there were significant differences between plasma lipid profiles in allelic groups of the patients although the frequency of ε4 allele in CD patients was higher than control subject. These results and other recent observation present that one or more factors other than the ApoE gene contribute to the pathogenesis of cardiovascular disease. Running title: Relationship between ApoE and Cardiovascular Disease
Oxidants and Antioxidants in Medical Science, 2015
Objective: Oxidative DNA damages occur in the cells constantly exposed to reactive oxygen species... more Objective: Oxidative DNA damages occur in the cells constantly exposed to reactive oxygen species that can originate from normal metabolic processes and from environmental agents. Accumulation of oxidative DNA damages has been observed in several pathologies, such as aging, carcinogenesis and degenerative diseases. In this study the hypothesis that gallic acid (GA), one of the most distributed phenolics in plants, could prevent the H 2 O 2-induced both mitochondrial DNA (mtDNA) and nuclear DNA (nDNA) damage was investigated. Materials and Methods: The cells were pretreated with GA (28 μg/ml) for 4 h before the induction of oxidative stress by H 2 O 2 (300 μM) exposure for 1 h. DNA damage was assessed in the mtDNA and two nuclear regions using quantitative polymerase chain reaction (qPCR) assay. Results: Pretreatment with GA significantly reduced both nDNA and mtDNA damages occurred with H 2 O 2 exposure. Conclusion: The results clearly demonstrate that GA has a protective effect against oxidative damage for both nDNA and mtDNA in HeLa cells. GA is most likely to act as an antimutagenic/anticarcinogenic agent through the protection of the genome against the damaging effect of chronic oxidative stress.
Previous studies indicate that ascorbic acid, when combined with copper or iron cleaves several v... more Previous studies indicate that ascorbic acid, when combined with copper or iron cleaves several viral DNA. ln this study, we generated the ascorbate radical anion electrochemically in a simple chemical environment without the participation of a metal ion. This solution possesses viral DNA scission activity. Ohe absence of catalytic metal ions [Fe (IIl) and Cu(II)] in the incubation medium was evidenced by metal chelating agents such as desferrioxamine and EDTA. Ohe radical quenching at high EDTA concentration was attributed to ionic strength of EDTA rather than metal chelation. Ohe effects of antioxidants, radical scavangers, catalase, superoxide dismutase and some proteins on DNA cleavage have been tested. Cleavage may not arise directly from ascorbate free radical but the reaction of the radical form of ascorbate with oxygen may produce the actual reactive species. Aerobic oxidation of ascorbate itself strictly requires transition metal catalysts, however electrochemically produced ascorbyl radical avoided the kinetic barrier that prevented direct oxidation of ascorbic acid with oxygen and eliminated the need for the transition metal ion catalysts.
International Journal of Biological Macromolecules, 1996
Scanning Tunneling Microscopy (STM) was used for the investigation of oxidative DNA damage. A PCR... more Scanning Tunneling Microscopy (STM) was used for the investigation of oxidative DNA damage. A PCR ampfified fragment of human 0-globin gene was used as a model for time dependent cleavage reaction by ascorbate and copper. Cleavage reactions were carried out in a medium containing 0.5 ~tg/20 ~1 DNA, 20 mM Tris-HCl pH, 7.8 and ascorbate-Cu (II) in the final concentrations of I mM and 30/~M, respectively. The mixtures were incubated at 37°C for 5, 15 and 30 min. For STM studies, 3 pg/5 td DNA samples were deposited on the gold coated mica and dried in a water flow vacuum drier. The STM was operated in air at atmospheric pressure with a tip-to-substrate bias of 100 mV and tunneling currents of < 10 pA. Etched tips of Pt/Ir wires were used in a constant current mode. The degradated DNA structure can be distinguished from the intact DNA and the sizes of the degradation products can be identified in the STM micrographs. The size of fragments decreased from approximately 3000 ~ to 34 ,/~ in ascorbate-Cu (II) medium, after 30 rain of incubation.
Oxidative DNA damage is an inescapable consequence for cells constantly exposed to oxidative stre... more Oxidative DNA damage is an inescapable consequence for cells constantly exposed to oxidative stress derived from normal metabolic processes and from environmental factors. Phenolic compounds, which have strong antioxidant activity, prevent DNA damage by protecting the cells against harmful effects of oxidative stress. In this study, the effect of virgin olive oil phenolic extract (OOPE) was investigated on H2O2-induced mitochondrial DNA (mtDNA) and nuclear DNA (nDNA) damage in HeLa cells. DNA damage was assessed in mitochondria and two nuclear regions by using quantitative PCR (QPCR) assay. The cells were pre-treated with non-cytotoxic doses of OOPE for 4 h, and DNA damage was determined. OOPE alone does not change the steady-state level of DNA damage. The oxidative stress generated with 750 μM H2O2 caused two times greater damages in mtDNA compared to nDNA, which included the nonexpressed β-globin region (1.507±0.110 lesions/10 kb) and the expressed APEX1 gene (1.623±0.243 lesions/10 kb) with respect to the control region. When cells were preincubated with OOPE for 4 h, nDNA damage under stress condition was completely inhibited; however, mtDNA damage was not affected by this procedure. These results suggest that OOPE has a protective effect against nDNA damage in HeLa cells.
Purpose Olive oil contains several phenolic compounds possessing antioxidant activity. The aim of... more Purpose Olive oil contains several phenolic compounds possessing antioxidant activity. The aim of this study was to investigate the protective effects of olive oil phenolic extract (OOPE) and one of its constituents, gallic acid (GA) against H 2 O 2-induced oxidative stress and apoptotic cell death in HeLa cells, a model for human epithelial cells. Methods The cells were pretreated with nontoxic doses of OOPE or GA for 4, 24 and 48 h, and the intracellular reactive oxygen species (ROS) level was determined, before and after oxidative stress induction with H 2 O 2. As an indicator of apoptosis, caspase 9 activity was measured. Results All pretreatments reduced ROS generation. Four hour incubation with OOPE or GA completely inhibited ROS generation. Increases in caspase 9 activity by OOPE and GA pretreatment under harsh stress conditions were inhibited 92 and 67.8%, respectively. Conclusions These results suggest that OOPE and GA act as powerful antioxidants against oxidative stress and exert anti-apoptotic effects.
Previous studies indicate that ascorbic acid, when combined with copper or iron cleaves several v... more Previous studies indicate that ascorbic acid, when combined with copper or iron cleaves several viral DNA. ln this study, we generated the ascorbate radical anion electrochemically in a simple chemical environment without the participation of a metal ion. This solution possesses viral DNA scission activity. Ohe absence of catalytic metal ions [Fe (IIl) and Cu(II)] in the incubation medium was evidenced by metal chelating agents such as desferrioxamine and EDTA. Ohe radical quenching at high EDTA concentration was attributed to ionic strength of EDTA rather than metal chelation. Ohe effects of antioxidants, radical scavangers, catalase, superoxide dismutase and some proteins on DNA cleavage have been tested. Cleavage may not arise directly from ascorbate free radical but the reaction of the radical form of ascorbate with oxygen may produce the actual reactive species. Aerobic oxidation of ascorbate itself strictly requires transition metal catalysts, however electrochemically produced ascorbyl radical avoided the kinetic barrier that prevented direct oxidation of ascorbic acid with oxygen and eliminated the need for the transition metal ion catalysts.
Oxidative DNA damage is an inescapable consequence for cells constantly exposed to oxidative stre... more Oxidative DNA damage is an inescapable consequence for cells constantly exposed to oxidative stress derived from normal metabolic processes and from environmental factors. Phenolic compounds, which have strong antioxidant activity, prevent DNA damage by protecting the cells against harmful effects of oxidative stress. In this study, the effect of virgin olive oil phenolic extract (OOPE) was investigated on H2O2-induced mitochondrial DNA (mtDNA) and nuclear DNA (nDNA) damage in HeLa cells. DNA damage was assessed in mitochondria and two nuclear regions by using quantitative PCR (QPCR) assay. The cells were pre-treated with non-cytotoxic doses of OOPE for 4 h, and DNA damage was determined. OOPE alone does not change the steady-state level of DNA damage. The oxidative stress generated with 750 μM H2O2 caused two times greater damages in mtDNA compared to nDNA, which included the nonexpressed β-globin region (1.507±0.110 lesions/10 kb) and the expressed APEX1 gene (1.623±0.243 lesions/10 kb) with respect to the control region. When cells were preincubated with OOPE for 4 h, nDNA damage under stress condition was completely inhibited; however, mtDNA damage was not affected by this procedure. These results suggest that OOPE has a protective effect against nDNA damage in HeLa cells.
A new deletion of the β-globin gene cluster was characterized in a Turkish family. A 6-year-old m... more A new deletion of the β-globin gene cluster was characterized in a Turkish family. A 6-year-old male and his father were heterozygotes for this deletion. They presented with mild hypochromic microcytic anemia associated with elevated Hb F (15&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;percnt;) and normal Hb A2 levels (2.0&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;percnt;). This newly described Turkish type (δβ)°-thalassemia has a deletion of about 30 kb. The 5´ breakpoint
Many recent studies have focused on the investigation of the biological effects of electromagneti... more Many recent studies have focused on the investigation of the biological effects of electromagnetic field. Although the several types of biological effects of electromagnetic fields have been shown, the molecular mechanisms of these effects have not been explained yet. Some epidemiological studies have suggested that exposure to ambient, lowlevel 50-60 Hz electromagnetic fields increase risk of disease including cancer such as leukemia among children who live close to power lines or among men whose jobs expose them to electromagnetic field, while others have suggested that electromagnetic fields exposure could increase both the concentration of free radicals and oscillating free radicals. Electromagnetic fields are known to affect radical pair recombination and they may increase the concentration of oxygen free radicals in living cells. In this study, oxidative stress was formed by the oxidation of ascorbic acid and the effect of 50 Hz, 0.3 mT electromagnetic fields on the oxidative ...
Apolipoprotein E plays a central role in lipid metabolism by serving as a ligand for the binding ... more Apolipoprotein E plays a central role in lipid metabolism by serving as a ligand for the binding of lipoproteins to lipoprotein receptors. We investigated the polymorphism of the apolipoprotein E (ApoE) gene using a PCR-RFLP method and the relation between ApoE polymorphism and plasma lipoproteinlipid levels in patients with cardiovascular disease (CD). As a result, there were significant differences between plasma lipid profiles in allelic groups of the patients although the frequency of ε4 allele in CD patients was higher than control subject. These results and other recent observation present that one or more factors other than the ApoE gene contribute to the pathogenesis of cardiovascular disease. Running title: Relationship between ApoE and Cardiovascular Disease
Oxidants and Antioxidants in Medical Science, 2015
Objective: Oxidative DNA damages occur in the cells constantly exposed to reactive oxygen species... more Objective: Oxidative DNA damages occur in the cells constantly exposed to reactive oxygen species that can originate from normal metabolic processes and from environmental agents. Accumulation of oxidative DNA damages has been observed in several pathologies, such as aging, carcinogenesis and degenerative diseases. In this study the hypothesis that gallic acid (GA), one of the most distributed phenolics in plants, could prevent the H 2 O 2-induced both mitochondrial DNA (mtDNA) and nuclear DNA (nDNA) damage was investigated. Materials and Methods: The cells were pretreated with GA (28 μg/ml) for 4 h before the induction of oxidative stress by H 2 O 2 (300 μM) exposure for 1 h. DNA damage was assessed in the mtDNA and two nuclear regions using quantitative polymerase chain reaction (qPCR) assay. Results: Pretreatment with GA significantly reduced both nDNA and mtDNA damages occurred with H 2 O 2 exposure. Conclusion: The results clearly demonstrate that GA has a protective effect against oxidative damage for both nDNA and mtDNA in HeLa cells. GA is most likely to act as an antimutagenic/anticarcinogenic agent through the protection of the genome against the damaging effect of chronic oxidative stress.
Previous studies indicate that ascorbic acid, when combined with copper or iron cleaves several v... more Previous studies indicate that ascorbic acid, when combined with copper or iron cleaves several viral DNA. ln this study, we generated the ascorbate radical anion electrochemically in a simple chemical environment without the participation of a metal ion. This solution possesses viral DNA scission activity. Ohe absence of catalytic metal ions [Fe (IIl) and Cu(II)] in the incubation medium was evidenced by metal chelating agents such as desferrioxamine and EDTA. Ohe radical quenching at high EDTA concentration was attributed to ionic strength of EDTA rather than metal chelation. Ohe effects of antioxidants, radical scavangers, catalase, superoxide dismutase and some proteins on DNA cleavage have been tested. Cleavage may not arise directly from ascorbate free radical but the reaction of the radical form of ascorbate with oxygen may produce the actual reactive species. Aerobic oxidation of ascorbate itself strictly requires transition metal catalysts, however electrochemically produced ascorbyl radical avoided the kinetic barrier that prevented direct oxidation of ascorbic acid with oxygen and eliminated the need for the transition metal ion catalysts.
International Journal of Biological Macromolecules, 1996
Scanning Tunneling Microscopy (STM) was used for the investigation of oxidative DNA damage. A PCR... more Scanning Tunneling Microscopy (STM) was used for the investigation of oxidative DNA damage. A PCR ampfified fragment of human 0-globin gene was used as a model for time dependent cleavage reaction by ascorbate and copper. Cleavage reactions were carried out in a medium containing 0.5 ~tg/20 ~1 DNA, 20 mM Tris-HCl pH, 7.8 and ascorbate-Cu (II) in the final concentrations of I mM and 30/~M, respectively. The mixtures were incubated at 37°C for 5, 15 and 30 min. For STM studies, 3 pg/5 td DNA samples were deposited on the gold coated mica and dried in a water flow vacuum drier. The STM was operated in air at atmospheric pressure with a tip-to-substrate bias of 100 mV and tunneling currents of < 10 pA. Etched tips of Pt/Ir wires were used in a constant current mode. The degradated DNA structure can be distinguished from the intact DNA and the sizes of the degradation products can be identified in the STM micrographs. The size of fragments decreased from approximately 3000 ~ to 34 ,/~ in ascorbate-Cu (II) medium, after 30 rain of incubation.
Oxidative DNA damage is an inescapable consequence for cells constantly exposed to oxidative stre... more Oxidative DNA damage is an inescapable consequence for cells constantly exposed to oxidative stress derived from normal metabolic processes and from environmental factors. Phenolic compounds, which have strong antioxidant activity, prevent DNA damage by protecting the cells against harmful effects of oxidative stress. In this study, the effect of virgin olive oil phenolic extract (OOPE) was investigated on H2O2-induced mitochondrial DNA (mtDNA) and nuclear DNA (nDNA) damage in HeLa cells. DNA damage was assessed in mitochondria and two nuclear regions by using quantitative PCR (QPCR) assay. The cells were pre-treated with non-cytotoxic doses of OOPE for 4 h, and DNA damage was determined. OOPE alone does not change the steady-state level of DNA damage. The oxidative stress generated with 750 μM H2O2 caused two times greater damages in mtDNA compared to nDNA, which included the nonexpressed β-globin region (1.507±0.110 lesions/10 kb) and the expressed APEX1 gene (1.623±0.243 lesions/10 kb) with respect to the control region. When cells were preincubated with OOPE for 4 h, nDNA damage under stress condition was completely inhibited; however, mtDNA damage was not affected by this procedure. These results suggest that OOPE has a protective effect against nDNA damage in HeLa cells.
Purpose Olive oil contains several phenolic compounds possessing antioxidant activity. The aim of... more Purpose Olive oil contains several phenolic compounds possessing antioxidant activity. The aim of this study was to investigate the protective effects of olive oil phenolic extract (OOPE) and one of its constituents, gallic acid (GA) against H 2 O 2-induced oxidative stress and apoptotic cell death in HeLa cells, a model for human epithelial cells. Methods The cells were pretreated with nontoxic doses of OOPE or GA for 4, 24 and 48 h, and the intracellular reactive oxygen species (ROS) level was determined, before and after oxidative stress induction with H 2 O 2. As an indicator of apoptosis, caspase 9 activity was measured. Results All pretreatments reduced ROS generation. Four hour incubation with OOPE or GA completely inhibited ROS generation. Increases in caspase 9 activity by OOPE and GA pretreatment under harsh stress conditions were inhibited 92 and 67.8%, respectively. Conclusions These results suggest that OOPE and GA act as powerful antioxidants against oxidative stress and exert anti-apoptotic effects.
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Papers by Günhan Erdem