In the present study, we used the method involving HPLC pre-purification followed by gas chromatography with isotope dilution mass spectrometric detection for the determination of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo) and 8-oxo-7,8-dihydroguanine (8-oxoGua) in human urine. The mean levels of 8-oxoGua and 8-oxodGuo in the urine samples of the subjects on unrestricted diet were respectively 1.87 nmol/kg 24 h (+/-0.90) and 0.83 nmol/kg 24 h (+/-0.49), and in the case of the groups studied, they did not depend on the applied diet. The sum of the amounts of both compounds in urine can give information about the formation rate of 8-oxoGua in cellular DNA. It is also likely that the levels of modified nucleo-base/side in urine sample are reflective of the involvement of different repair pathways responsible for the removal of 8-oxodGuo from DNA, namely base excision repair (BER) and nucleotide excision repair (NER).

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Abnormal spermatozoa frequently display typical features of oxidative stress, i.e. excessive level of reactive oxygen species (ROS) and depleted antioxidant capacity. Moreover, it has been found that a high level of oxidatively damaged DNA is associated with abnormal spermatozoa and male infertility. Therefore, the aim of our study was the comparison of oxidative stress/DNA damage in semen and blood of fertile and infertile men. The broad range of parameters which describe oxidative stress and oxidatively damaged DNA and repair were analyzed in the blood plasma and seminal plasma of groups of fertile and infertile subjects. These parameters include: (i) 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxodG) and 8-oxo-7,8-dihydroguanine (8-oxoGua) levels in urine; (ii) 8-oxodG level in DNA isolated from leukocytes and spermatozoa; (iii) antioxidant vitamins (A, C and E) and uric acid. Urinary excretion of 8-oxodG and 8-oxoGua and the level of oxidatively damaged DNA in leukocytes as well as the level of antioxidant vitamins were analyzed using HPLC and HPLC/GC/MS methods.The results of our study demonstrate that 8-oxodG level significantly correlated with every parameter which describe sperm quality: sperm count, motility and morphology. Moreover, the data indicate a higher level of 8-oxodG in sperm DNA compared with DNA of surrogate tissue (leukocytes) in infertile men as well as in healthy control group. For the whole study population the median values of 8-oxodG/106 dG were respectively 7.85 and 5.87 (p = 0.000000002). Since 8-oxodG level in sperm DNA is inversely correlated with urinary excretion rate of 8-oxoGua, which is the product of OGG1 activity, we hypothesize that integrity of spermatozoa DNA may be highly dependent on OGG1 activity. No relationship between the whole body oxidative stress and that of sperm plasma was found, which suggests that the redox status of semen may be rather independent on this characteristic for other tissues.

Aging is a complex process involving morphologic and biochemical changes in single cells and in the whole organism. One of the most popular explanations of how aging occurs at the molecular level is the oxidative stress hypothesis. Oxidative stress leads in many cases to an age-dependent increase in the cellular level of oxidatively modified macromolecules including DNA, and it is this increase which has been linked to various pathological conditions, such as aging, carcinogenesis, neurodegenerative and cardiovascular diseases. It is, however, possible that a number of short-comings associated with gaps in our knowledge may be responsible for the failure to produce definite results when applied to understanding the role of DNA damage in aging and age-related diseases.

Numerous DNA repair pathways exist to prevent the persistence of damage, and are integral to the maintenance of genome stability, and hence prevention of disease. Excised lesions arising from repair may ultimately appear in the urine where their measurement has been acknowledged to be reflective of overall oxidative stress. The development of reliable assays to measure urinary DNA lesions, such as HPLC prepurification followed by gas chromatography/mass spectrometry, offers the potential to assess whole body oxidative DNA damage. However, some studies suggest a possibility that confounding factors may contribute to urinary levels of 7,8-dihydro-8-oxoguanine (8-oxoGua) and 7,8-dihydro-8-oxo-2 -deoxyguanosine (8-oxodG). This article considers several possible sources of urinary lesions: (a) the repair of oxidatively damaged DNA; (b) a possible dietary influence; and (c) cell death. The authors conclude that data from their laboratories, along with a number of literature reports, form an argument against a contribution from cell death and diet. In the absence of these confounding factors, urinary measurements may be attributed entirely to the repair of DNA damage and suggests their possible use in studying associations between DNA repair and disease.

The aim of this work was to answer the question whether the broad range of parameters which describe oxidative stress and oxidatively damaged DNA and repair are appropriate prognosis factors of colon cancer (CRC) patients survival? The following parameters were analyzed for 89 CRC patients: concentration of uric acid and vitamins A, E, C in plasma; levels of 8-oxodGuo (8-oxo-7,8-dihydro-2 0 -deoxyguanosine) in DNA of leukocyte and colon tissues; urinary excretion rates of 8-oxodGuo and 8-oxoGua (8-oxo-7,8-dihydroguanine); the activity and mRNA or protein level of repair enzymes OGG1, APE1, ANPG, TDG and PARP1. All DNA modifications and plasma antioxidants were analyzed using high performance liquid chromatography (HPLC) or HPLC/gas chromatography-mass spectrometry techniques. Expression of repair proteins was analyzed by QPCR, Western or immunohistochemistry methods. Longer survival coincided with low levels of 8-oxodGuo/8oxoGua in urine and 8-oxodGuo in DNA as well as with high concentration of uric acid plasma level. In contrast to expectations, longer survival coincided with lower mRNA level in normal colon tissue of the main 8-oxoGua DNA glycosylase, OGG1, but no association was found for PARP-1 expression. When analyzing simultaneously two parameters the discriminating power increased significantly. Combination of low level of urinary 8-oxoGua together with low level of 8-oxodGuo in leukocyte (both below median value) or high concentration of plasma uric acid (above median value) have the best prediction power. Since prediction value of these parameters seems to be comparable to conventional staging procedure, they could possibly be used as markers to predict clinical success in CRC treatment.