8-hydroxyadenine and 5-hydroxyuracil

In the present study, we have studied the level of oxidative DNA base damage in lymphocytes of HIV-infected intravenous drug users (IDUs) and a seronegative control group. Chromatin was isolated from the lymphocytes and then analyzed by gas chromatography/isotope-dilution mass spectrometry with selected-ion monitoring (GC/IDMS-SIM). Significantly greater levels of four oxidatively modified DNA bases were observed in chromatin samples from the symptomatic HIV-infected patients than in those from the seronegative patients. These were 5-hydroxyuracil, 5-hydroxycytosine, 8-hydroxyadenine and 8-hydroxyguanine. In the case of 5-hydroxyuracil and 8-hydroxyguanine, a statistically significant difference was also found between the control group and the asymptomatic HIV-positive patients. These results suggest that oxidative stress may play an important role in the pathogenesis of acquired immune deficiency syndrome (AIDS), and that administration of antioxidant drugs to HIV-infected patients may offer protection against AIDS-related carcinogenesis.

Topics: Adenine; Adolescent; Adult; Chromatin; Cytosine; DNA Damage; Guanine; HIV Infections; Humans; Lymphocytes; Male; Oxidation-Reduction; Oxidative Stress; Substance Abuse, Intravenous; Uracil

Taurine has been suggested to have cytoprotective actions via a number of different mechanisms. The role of taurine in protecting DNA from oxidative damage has received only limited attention. The aim of the present studies was to test the hypothesis that taurine might act to attenuate oxidative damage to DNA caused by free radicals generated by iron-stimulated catecholamine oxidation in the presence of H2O2. Calf thymus DNA (100 microg/tube) was exposed to a reaction mixture containing: ferric chloride (60 microM), H2O2 (2.8 mM) and L-dopa (100 microM). Taurine and taurine analogs were added simultaneously to determine their effects to prevent oxidative damage to DNA. The reaction was carried out for 1 hour at 37 degrees C and terminated by rapid freezing in an ethanol/dry ice bath. The DNA was precipitated with ethanol and subsequently hydrolyzed with formic acid under vacuum. The hydroxylated bases were separated by HPLC and detected electrochemically. All experiments were replicated a minimum of 5 times. Taurine (20 mM) was found to reduce (p<0.05) damage to DNA as indexed by reductions in the formation of 5-OH-uracil (49% decrease), 8-OH adenine (37% decrease), and 8-OH guanine (21% decrease). Taurine had minimal effects to reduce the formation of 5-OH cytosine (<7% decrease). Taurine (20 mM) also increased total DNA recovery after damage 36-40% and increased total undamaged guanine approximately 32%. 5-OH Uracil formation could be reduced (p<0.05) by 1 mM taurine and 8-OH-adenine formation was reduced (p<0.05) by 5 mM taurine. Studies were conducted with various amino acid analogs and total base adduct formation was reduced by 20 mM beta-alanine (30% decrease), lysine (58% decrease) and glutathione (88% decrease). When tested at 20 mM, both hypotaurine and homotaurine provided greater protection against DNA damage than taurine, whereas isethionic acid provided a similar level of protection as taurine. Using identical conditions as the assays for base hydroxylation, we tested whether inhibition of quinone formation could account for taurine's mechanism of action. Taurine (49% decrease), homotaurine (24% decrease) and hypotaurine (79% decrease) all reduced quinone formation. Thus, inhibition of quinone formation could account for part of taurine's mechanism of action to inhibit oxidative damage, but it could not account for homotaurine's greater efficacy in preventing DNA damage. Overall, these studies show that taurine at concentrations normally foun

Topics: Adenine; Animals; Antioxidants; Cattle; DNA Adducts; DNA Damage; Dose-Response Relationship, Drug; Hydrogen Peroxide; Oxidants; Oxidative Stress; Structure-Activity Relationship; Taurine; Uracil

Recently we found that KMnO4 oxidation of DNA oligomers containing a 7,8-dihydro-8-oxoguanine (8-oxo-G) residue induces damage to the neighboring base residues; other modified bases, 7,8-dihydro-8-oxoadenine (8-oxo-A) and 5-hydroxyuracil (5-oh-U), show similar behavior in DNA. The present study indicated that the ability to induce damage, which could also occur by the oxidation of a 5-oh-C residue, was low as in the case of 5-oh-U. On the other hand, in order to examine the pathways and the intermediates for the oxidative degradation of 8-oxo-A, we have carried out the KMnO4 oxidation using an 8-oxo-2'-deoxyadenosine derivative as a model and have determined the structures of the three major products.

Topics: Adenine; Base Sequence; DNA; DNA Damage; Guanine; Oligodeoxyribonucleotides; Oxidation-Reduction; Potassium Permanganate; Uracil

This aim of this study was to measure the typical free radical-induced products of DNA bases in cellular DNA of cervical cancer tissues directly irradiated by applying brachytherapy to the patients. Significant increases in the amounts of modified bases over the control level were observed in the samples isolated after irradiation for all patients. These increases differed among patients and among products. The repair capacity and/or the amount of hypoxic cells inside the tumor may account for the different levels of modified bases. It is possible that the observed variabilities may account for the differences in clinical responses to brachytherapy.

Topics: Adenine; Brachytherapy; Cytosine; DNA Damage; DNA, Neoplasm; Female; Gas Chromatography-Mass Spectrometry; Guanine; Humans; Oxidation-Reduction; Pyrimidines; Uracil; Uterine Cervical Neoplasms

The extent of DNA modification in cancerous rat live and lung tissues was investigated and compared to their respective normal tissues. Liver tumors were induced by 2-fluorenylacetamide (2-FAA) or N-nitroso-N-2-fluorenylacetamide (N-NO-2-FAA), and lung tumors were induced by sodium nitrite plus trimethylamine. In the DNA samples isolated from these tissues, two pyrimidine-derived and four purine-derived modified DNA bases were identified and quantified by gas chromatography/mass spectrometry with selected-ion monitoring. These compounds were characterized as 5-hydroxyuracil (5-OHUra), thymine glycol (TG), 4,6-diamino-5-formamidopyrimidine (FapyAde), 2,6-diamino-4-hydroxy-5- formamidopyrimidine (FapyGua), 8-hydroxyadenine (8-OHAde), and 8-hydroxyguanine (8-OHGua). Elevated amounts of modified DNA bases were found in most cancerous tissues when compared to the controls. Chemicals used for tumor induction were responsible for inducing DNA lesions that could be promutagenic in vivo and could lead to various types of mutations. When endogenous oxidative damage to DNA during aging was examined, a roughly 2-fold increase of thymine glycol, 8-OHAde and 8-OHGua was found in aged (12 months) rat liver tissues compared to young tissues (1 month). The same results were also found in lung tissues, except that the amount of thymine glycol exhibited more than a 10-fold increase in aged tissues when compared to young tissues. The association of the modified bases with the processes of aging and carcinogenesis deserves further investigation.

Topics: 2-Acetylaminofluorene; Adenine; Aging; Animals; Antineoplastic Agents; Disease Models, Animal; DNA Damage; DNA, Neoplasm; Gas Chromatography-Mass Spectrometry; Guanine; Hydrolysis; Liver; Liver Neoplasms, Experimental; Lung; Lung Neoplasms; Male; Methylamines; Nitrates; Oxidation-Reduction; Pyrimidines; Random Allocation; Rats; Rats, Sprague-Dawley; Rats, Wistar; Thymine; Uracil