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Abstract Background DNA is constantly exposed to reactive oxygen species (ROS), spontaneously arising during the normal oxygen metabolism. ROS may result in temporary as well as permanent modifications in various cellular components such as lipids, proteins and DNA, which may have deleterious consequences. Demonstrating that a dietary supplementation of antioxidants can reduce oxidative DNA damage may provide evidence for the value of such supplementation in prevention of cancer and age related diseases. Findings The present study was conducted to address whether tomato juice protects against ROS induced by extensive physical exercise in untrained individuals. As a marker of oxidative stress, serum levels of 8-oxodG were monitored using a modified ELISA. An intervention was performed involving 15 untrained healthy subjects who performed a 20 min physical exercise at 80% of maximum pulse using an ergometer bicycle. Blood samples were taken before and one hour after the exercise. The procedure was repeated after 5 weeks with a daily intake of 150 ml tomato juice and followed by a 5 weeks wash-out period and another 5 weeks with a daily intake of tomato juice. The results indicated that a daily intake of tomato juice, equal to 15 mg lycopene per day, for 5 weeks significantly reduced the serum levels of 8-oxodG after an extensive physical exercise. Conclusion These data strongly suggest that tomato juice has a potential antioxidant effect and may reduce the elevated level of ROS induced by oxidative stress.

Formation of 7,8-dihydro-8-oxo-2′-deoxyguanosine (8-oxo-dG) in solutions of free 2′-deoxyguanosine (dG) and calf thymus DNA (DNA) was compared for the diffusion-dependent and localised production of oxygen radicals from phosphate-mediated oxidation of ferrous iron (Fe2+) to ferric iron (Fe3+). The oxidation of Fe2+ to Fe3+ was followed at 304 nm at pH 7.2 under aerobic conditions. Given that the concentration of Fe2+ ≥phosphate concentration, the rate of Fe2+ oxidation was significantly higher in DNA-phosphate as compared for the same concentration of inorganic phosphate. Phosphate catalysed oxidation of ferrous ions in solutions of dG or DNA led through the production of reactive oxygen species to the formation of 8-oxo-dG. The yield of 8-oxo-dG in solutions of dG or DNA correlated positively with the inorganic-/DNA-phosphate concentrations as well as with the concentrations of ferrous ions added. The yield of 8-oxo-dG per unit oxidised Fe2+ were similar for dG and DNA; thus, it differed markedly from radiation-induced 8-oxo-dG, where the yield in DNA was several fold higher.For DNA in solution, the localisation of the phosphate ferrous iron complex relative to the target is an important factor for the yield of 8-oxo-dG. This was supported from the observation that the yield of 8-oxo-dG in solutions of dG was significantly increased over that in DNA only when Fe2+ was oxidised in a high excess of inorganic phosphate (50 mM) and from the lower protection of DNA damage by the radical scavenger (hydroxymethyl)aminomethane (Tris)–HCl. [Copyright &y& Elsevier]

Highlights: [•] hMTH1 protects cells from mutagenesis induced by UVA and UVB, but not UVC. [•] No protective role of hMTH1 in cell survival post UVB and UVC irradiation. [•] hMTH1 prevents induction of transition-type mutations at AT and GC post UVA irradiation. [•] 2-OH-dATP rather than 8-oxo-dGTP in the nucleotide pool likely contributes in UVA-induced mutations. [ABSTRACT FROM AUTHOR]

Abstract: The aim of the study was to compare the radiation-induced oxidative stress response in blood samples from breast cancer patients that developed severe acute skin reactions during the radiotherapy, with the response in blood samples from patients with no side effects. Peripheral blood was collected from 12 breast cancer patients showing no early skin reactions after radiotherapy (RTOG grade 0) and from 14 breast cancer patients who developed acute severe skin reactions (RTOG grade 3–4). Whole blood was irradiated with 0, 5 and 2000mGy γ-radiation and serum was isolated. The biomarker for oxidative stress, 8-oxo-dG, was analyzed in the serum by a modified ELISA. While a significant radiation-induced increase of serum 8-oxo-dG levels was observed in serum of the RTOG 0 patients, no increase was seen in serum of the RTOG 3–4 patients. The radiation induced increase in serum 8-oxo-dG levels after 5mGy did not differ significantly from the increase observed for 2000mGy in the RTOG 3–4 cohort, thus no dose response relation was observed. A receiver operating characteristic (ROC) value of 0.97 was obtained from the radiation-induced increase in 8-oxo-dG indicating that the assay could be used to identify patients with severe acute adverse reactions to radiotherapy. The results show that samples of whole blood from patients, classified as highly radiosensitive (RTOG 3–4) based on their skin reactions to radiotherapy, differ significantly in their oxidative stress response to ionizing radiation compared to samples of whole blood from patients with no skin reactions (RTOG 0). Extracellular 8-oxo-dG is primarily a biomarker of nucleotide damage and the results indicate that the patients with severe acute skin reactions differ in their cellular response to ionizing radiation at the level of induction of oxidative stress or at the level of repair or both. [Copyright &y& Elsevier]

Abstract: UVA has been suggested to play an important role in UV-induced mutagenesis. The mechanisms by which UVA induces mutations are still a matter of debate. Our aim was to investigate the protective capacity of hMTH1, a nucleotide pool sanitization enzyme with 8-oxodGTPase activity. Human B lymphoblastoid cells were stably transfected with shRNA directed against hMTH1. Clonogenic survival, mutations, intracellular and extracellular levels of 8-oxodG (8-oxo-7, 8-dihydro-2′-deoxyguanosine) and dG in the nucleotide pool of UVA-irradiated transfected and non-transfected cells were investigated. Mutations were determined in the thymidine kinase locus. Intracellular 8-oxodG and dG were measured using a modified ELISA and HPLC, respectively, after extraction of the nucleotide pool and conversion of nucleotides to their corresponding nucleosides. 8-oxodG in the medium was measured using ELISA. UVA-induced mutations were significantly higher while the survival was slightly lower in transfected compared to non-transfected cells. The increased mutation rate in transfected cells at increased exposure correlated with enhanced levels of 8-oxodG in the nucleotide pool, and a somewhat reduced level of 8-oxodG in the medium. The results indicate that the nucleotide pool is a significant target for UVA-induced mutations and implicates that hMTH1 plays an important role in protecting cells from UVA-induced oxidative stress. [Copyright &y& Elsevier]

Abstract: Oxidative stress is considered to be one of the most important phenomena involved in the process of aging and age-related diseases. 8-Oxo-7,8-dihydro-2′-deoxyguanosine (8-oxo-dG) has been frequently used as a marker for oxidative stress. However, the origin of extracellular 8-oxo-dG is not well understood. The aim of this work was to investigate the nucleotide pool and the role of the human mutT homologue protein (hMTH1) in the appearance of extracellular 8-oxo-dG in a cellular model system. For this purpose we used primary human fibroblast cells, which were transfected by siRNAs homologous to hMTH1. Extracellular 8-oxo-dG in cell culture media after exposure of the cells to ionizing radiation was measured as enzyme-linked immunosorbent assay reactivity. Our results demonstrate the profound effect of both hMTH1 expression and nucleotide pool size on the cellular excretion of 8-oxo-dG, suggesting that the nucleotide pool is a significant target for the formation of extracellular 8-oxo-dG. [Copyright &y& Elsevier]