ABSTRACT
8-Oxo-7,8-dihydroguanine (8-oxo-G) is a key biomarker of oxidative damage to DNA in cells, and its genotoxicity is well-studied. In recent years, it has been confirmed experimentally that free 8-oxo-G and molecules containing it are not merely inert products of DNA repair or degradation, but they are actively involved in intracellular signaling. In this review, data are systematized indicating that free 8-oxo-G and oxidized (containing 8-oxo-G) extracellular DNA function in the body as mediators of stress signaling and initiate inflammatory and immune responses to maintain homeostasis under the action of external pathogens, whereas exogenous 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxo-dGuo) exhibits pronounced antiinflammatory and antioxidant properties. This review describes known action mechanisms of oxidized guanine and 8-oxo-G-containing molecules. Prospects for their use as a therapeutic target are considered, as well as a pharmaceutical agent for treatment of a wide range of diseases whose pathogenesis is significantly contributed to by inflammation and oxidative stress.
Subject(s)
Deoxyguanosine/analogs & derivatives , 8-Hydroxy-2'-Deoxyguanosine , Animals , Biomarkers , DNA Damage/drug effects , DNA Repair/drug effects , Deoxyguanosine/pharmacology , Deoxyguanosine/therapeutic use , Guanine/analogs & derivatives , Humans , Inflammation/drug therapy , Oxidative Stress/drug effectsABSTRACT
It is demonstrated that hydroxyl radicals and hydrogen peroxide are formed under the action of uranyl ions in aqueous solutions containing no reducing agents. In the presence of uranyl ions, formation of 8-oxoguanine in DNA and long-lived protein radicals are observed in vitro. It is shown that the pro-oxidant properties of uranyl at micromolar concentrations mostly result from the physico-chemical nature of the compound rather than its radioactive decay. Uranyl ions lead to damage in DNA and proteins causing death of HEp-2 cells by necrotic pathway. It is revealed that the uranyl ions enhance radiation-induced oxidative stress and significantly increase a death rate of mice exposed to sublethal doses of X-rays.
Subject(s)
Reactive Oxygen Species/chemistry , Uranium/chemistry , Uranium/toxicity , Animals , Blood Proteins/chemistry , Bone Marrow/drug effects , Bone Marrow/radiation effects , DNA Damage/drug effects , Guanine/analogs & derivatives , Hot Temperature , Hydrogen Peroxide/chemistry , Hydroxyl Radical/analysis , Ions , Lasers , Male , Mice , Mortality , Mutagenicity Tests , Uranyl Nitrate/chemistry , X-RaysABSTRACT
Employing enhanced chemiluminescence in luminol-p-iodophenol peroxidase system and coumarine-3-carboxylic acid, it was shown that guanosine-5'-monophosphate (GMP) appreciably reduces formation of H2O2 and hydroxyl radicals induced by x-ray irradiation. Using immunoenzyme assay, we revealed that GMP lowered 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo) formation in DNA in vitro after irradiation. The results of survival test have shown that mice being injected intraperitoneally with GMP after irradiation with a dose of 7 Gy had better survival rate than the control mice. GMP reduced leucopoenia and thrombocytopenia in irradiated mice. Obtained results give premises that GMP may be promising therapeutic agent for treatment of radiation injuries.
Subject(s)
Antioxidants/pharmacology , Guanosine Monophosphate/pharmacology , Radiation-Protective Agents/pharmacology , 8-Hydroxy-2'-Deoxyguanosine , Animals , Antioxidants/administration & dosage , Antioxidants/metabolism , Blood Cell Count , Bone Marrow Cells/drug effects , Bone Marrow Cells/metabolism , Bone Marrow Cells/radiation effects , Cattle , DNA/metabolism , Deoxyguanosine/analogs & derivatives , Deoxyguanosine/metabolism , Guanosine Monophosphate/administration & dosage , Guanosine Monophosphate/metabolism , Male , Mice , Radiation-Protective Agents/administration & dosage , Radiation-Protective Agents/metabolism , Reactive Oxygen Species/metabolism , Serum Albumin, Bovine/metabolism , Survival Analysis , X-RaysSubject(s)
Free Radicals/chemistry , Guanosine/pharmacology , Inosine Diphosphate/pharmacology , Ovalbumin/drug effects , Proteins/radiation effects , Radiation Injuries/prevention & control , Radiation-Protective Agents/pharmacology , Animals , Cattle , Cricetinae , DNA Damage/drug effects , DNA Damage/radiation effects , Dose-Response Relationship, Drug , Dose-Response Relationship, Radiation , Free Radical Scavengers/pharmacology , Free Radicals/metabolism , Free Radicals/pharmacokinetics , Guanosine/metabolism , Half-Life , Humans , Inosine Diphosphate/metabolism , Ovalbumin/metabolism , Ovalbumin/radiation effects , Oxidation-Reduction , Oxidative Stress/drug effects , Oxidative Stress/radiation effects , Proteins/drug effects , Time Factors , Water , X-RaysABSTRACT
A test system has been developed to determine 8-oxoguanine in DNA, the most important biomarker of damage to DNA bases by reactive oxygen species. The system is based on a chemiluminescence enzyme immunoassay with the use of monoclonal antibodies (mcAB) against 8-oxoguanine. The test involves several stages: 1) immobilization of DNA on nitrocellulose membrane filters using an efficient technique with preliminary formation of a complex with protamine sulfate; 2) formation of antigen--antibody complexes (mcAB with 8-oxoguanine in DNA) with secondary antibodies and with a peroxidase--antiperoxidase complex (PAP method); 3) detection of increased chemiluminescence in a solution of hydrogen peroxide, luminol, and p-iodophenol. The increased chemiluminescence is determined with a conventional liquid scintillation counter for measuring beta-radioactivity. The system was tested by determining 8-oxoguanine formation in DNA upon gamma-irradiation and upon photosensitized oxidation of guanine under visible light in the presence of methylene blue. A linear dose dependence of 8-oxoguanine formation in DNA was shown for gamma-irradiation. The radiation-chemical yield of 8-oxoguanine (G = 0.57 molecule per 100 eV) is convenient to use for calibration of the amount of 8-oxoguanine formed under other conditions. The sensitivity of the method permits the detection of several femtomoles of 8-oxoguanine in a 40 microg sample of DNA.
Subject(s)
DNA/chemistry , Guanine/analogs & derivatives , Animals , Collodion , DNA/radiation effects , DNA Damage , Gamma Rays , Guanine/analysis , Immunoenzyme Techniques , Luminescent Measurements , Methylene Blue/chemistry , Salmon , Sensitivity and SpecificityABSTRACT
Formation of 8-hydroxyguanine derivatives caused by the exposure of aqueous solutions of guanine nucleosides and nucleotides (Guo, dGuo, GMP, dGMP, GDP, and GTP) to gamma-radiation was studied by differential UV-spectroscopy. 8-hydroxyguanine had linear dose-yield relationship with G-value (radiation-chemical yield) of 0.2-0.4 molecules per 100 eV. Data on irradiation of D2O solutions of nucleotides show that the mechanism of gamma-radiation-induced formation of 8-hydroxyguanine is probably different from that of heat-induced one. Levels of intracellular guanine nucleotide pool damage caused by natural background radiation and induced by heat were compared for different temperatures. Level of DNA precursor pool damage by natural background radiation at 37 degrees C is insignificant and comprises approximately 0.2% of the heat-induced damage but rises sharply as the temperature decreases. The possible biological consequences of gamma-radiation-induced damage of guanine and deoxyguanine nucleotide cell pools are discussed.
Subject(s)
DNA Damage , Guanine Nucleotides/radiation effects , Guanine/analogs & derivatives , Gamma Rays , Guanine/biosynthesis , Hot Temperature , Spectrophotometry, UltravioletABSTRACT
Detailed analysis of the kinetics of inhibition of E. coli RNA-polymerase-catalyzed synthesis of dinucleotide pppApU by 8-oxy-GTP and 8-Br-GTP on promoter A1 of the bacteriophage T7 delta D111 with an incomplete set of substrates was carried out. In accordance with the mathematical models obtained, we calculated quantitative parameters of binding of these nucleotide analogs to the centers whose geometry is suitable for incorporation of ATP and UTP. 8-oxy-GTP and 8-Br-GTP compete with ATP for the binding center (their steady-state dissociation constant ratios are 2.1 and 2.4, respectively, whereas the constant for ATP is 0.3 mM) but, unlike ATP, they are not incorporated into the product. 8-oxy-GTP competes also with UTP (its steady-state dissociation constant ratio is 21.6, the constant for UTP is 0.03 mM). 8-Br-GTP does not interact with the binding center of UTP.
