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Aims: Urinary 8-oxo-7,8-dihydro-2¢-deoxyguanosine (8-oxodG) is a widely used biomarker of oxidative stress. However, variability between chromatographic and ELISA methods hampers interpretation of data, and this variability may increase should urine composition differ between individuals, leading to assay interference. Furthermore, optimal urine sampling conditions are not well defined. We performed inter-laboratory comparisons of 8-oxodG measurement between mass spectrometric-, electrochemical-and ELISA-based methods, using common within-technique calibrants to analyze 8-oxodG-spiked phosphate-buffered saline and urine samples. We also investigated human subject-and sample collection-related variables, as potential sources of variability. Results: Chromatographic assays showed high agreement across urines from different subjects, whereas ELISAs Kronos Science, Phoenix, Arizona. ANTIOXIDANTS & REDOX SIGNALINGVolume 18, Number 18, 2013 ª Mary Ann Liebert, Inc. DOI: 10.1089/ars.2012.4714 2377showed far more inter-laboratory variation and generally overestimated levels, compared to the chromatographic assays. Excretion rates in timed 'spot' samples showed strong correlations with 24 h excretion (the 'gold' standard) of urinary 8-oxodG (r p 0.67-0.90), although the associations were weaker for 8-oxodG adjusted for creatinine or specific gravity (SG). The within-individual excretion of 8-oxodG varied only moderately between days (CV 17% for 24 h excretion and 20% for first void, creatinine-corrected samples). Innovation: This is the first comprehensive study of both human and methodological factors influencing 8-oxodG measurement, providing key information for future studies with this important biomarker. Conclusion: ELISA variability is greater than chromatographic assay variability, and cannot determine absolute levels of 8-oxodG. Use of standardized calibrants greatly improves intra-technique agreement and, for the chromatographic assays, importantly allows integration of results for pooled analyses. If 24 h samples are not feasible, creatinine-or SG-adjusted first morning samples are recommended.

The activation of NF-κB transcription factor is critical for a wide range of processes such as immunity, inflammation, cell development, growth and survival. It is activated by a variety of stimuli including cytokines, ionizing radiation and oxidative stress. Redox modulations of NF-κB pathway have been widely demonstrated. Studies carried out during last years have advanced our knowledge about possible connections between NF-κB pathway and the impact of free radicals. This review is an endeavor to gather recent results focused on this issue, although an important question, whether oxidative stress plays a physiological role in NF-κB activation, seems to be still unanswered.

Oxidative stress is involved in the pathogenesis of colon cancer. We wanted to elucidate at which stage of the disease this phenomenon occurs. In the examined groups of patients with colorectal cancer (CRC, n = 89), benign adenoma (AD, n = 77) and healthy volunteers (controls, n = 99), we measured: vitamins A, C and E in blood plasma, 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) and 8-oxo-7,8-dihydroguanine (8-oxoGua) in leukocytes and urine, leukocyte 8-oxoGua excision activity, mRNA levels of APE1, OGG1, 8-oxo-7,8-dihydrodeoxyguanosine 5'-triphosphate pyrophosphohydrolase (MTH1) and OGG1 polymorphism. The vitamin levels decreased gradually in AD and CRC patients. 8-OxodG increased in leukocytes and urine of CRC and AD patients. 8-OxoGua was higher only in the urine of CRC patients. 8-OxoGua excision was higher in CRC patients than in controls, in spite of higher frequency of the OGG1 Cys326Cys genotype, encoding a glycosylase with decreased activity. mRNA levels of OGG1 and APE1 increased in CRC and AD patients, which could explain increased 8-oxoGua excision rate in CRC patients. MTH1 mRNA was also higher in CRC patients. The results suggest that oxidative stress occurs in CRC and AD individuals. This is accompanied by increased transcription of DNA repair genes, and increased 8-oxoGua excision rate in CRC patients, which is, however, insufficient to counteract the increased DNA damage.

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Is oxidative damage of DNA responsible for physiological changes associated with aging? The authors note a positive correlation between the age of human subjects with the level of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) in leukocyte DNA. The levels of urinary 8-oxo-7,8-dihydroguanine and 8-oxodG followed the same pattern of correlation. Age-dependent decline in the concentration of plasma vitamin C was also evident. These interesting observations in humans point towards the need to scrutinize in detail the role of oxidative DNA damage and compromised antioxidant defense systems in age-related physiological disorders.

Several different components contribute to the maintenance of 8-oxoG levels in human DNA, with the greatest contributor being the removal of 8-oxodGTP from the cellular nucleotide pool by hMTH1.

SummaryBackgroundThe broad spectrum of oxidative damage DNA biomarkers: urinary excretion of 8-oxodG (8-oxo-7,8-dihydro-2′-deoxyguanosine), 8-oxoGua (8-oxo-7,8-dihydroguanine) as well as the level of oxidative damage DNA in leukocytes, was analyzed in cancer patients and healthy subjects.Material/Methods222 cancer patients and 134 healthy volunteers were included in the analysis, using methodologies which involve HPLC (high-performance liquid chromatography) prepurification followed by gas chromatography with isotope dilution mass spectrometry detection and HPLC/EC.ResultsFor the whole patient population (n=222) the median values of 8-oxoGua and 8-oxodG in urine samples were 12.44 (interquartile range: 8.14–20.33) [nmol/24 hr] and 6.05 (3.12–15.38) [nmol/24 hr], respectively. The median values of 8-oxoGua and 8-oxodG in urine samples of the control group (n=85) were 7.7 (4.65–10.15) [nmol/24 hr] and 2.2 (1.7–2.8) [nmol/24 hr], respectively. The level of 8-oxodG in DNA isolated from leukocytes of the patient population (n=179) and of the control group (n=134) was 4.93 (3.46–9.27) per 10’6 dG and 4.46 (3.82–5.31) per 10’6 dG, respectively.ConclusionsThe results suggest that oxidative stress in cancer patients, demonstrated by augmented amounts of these modifications in urine, could be typical not only for affected tissue but also for other tissues and even the whole organism. An assay that enables the determination of levels of basic markers of oxidative stress might be applied in clinical practice as an additional, helpful marker to diagnose cancer.