Simultaneous HPLC analysis of 8-hydroxydeoxyguanosine and 7-methylguanine in urine from humans and rodents

Natural Guanine Derivatives Exert PARP-Inhibitory and Cytoprotective Effects in a Model of Cardiomyocyte Damage under Oxidative Stress

Inhibitors of human poly(ADP-ribose) polymerase (PARP) are considered as promising agents for treatment of cardiovascular, neurological, and other diseases accompanied by inflammation and oxidative stress. Previously, the ability of natural compounds 7-methylguanine (7mGua) and 8-hydroxy-7-methylguanine (8h7mGua) to suppress activity of the recombinant PARP protein was demonstrated. In the present work, we have investigated the possibility of PARP-inhibitory and cytoprotective action of 7mGua and 8h7mGua against the rat cardiomyoblast cultures (undifferentiated and differentiated H9c2). It was found that 7mGua and 8h7mGua rapidly penetrate into the cells and effectively suppress the H2O2-stimulated PARP activation (IC50 = 270 and 55 μM, respectively). The pronounced cytoprotective effects of 7mGua and 8h7mGua were shown in a cellular model of oxidative stress, and effectiveness of 8h7mGua exceeded the classic PARP inhibitor 3-aminobenzamide. The obtained data indicate promise for the development of PARP inhibitors based on guanine derivatives and their testing using the models of ischemia-reperfusion tissue damage.

Inhibitory Effects of 7-Methylguanine and Its Metabolite 8-Hydroxy-7-Methylguanine on Human Poly(ADP-Ribose) Polymerase 1

Previously, we have found that a nucleic acid metabolite, 7-methylguanine (7mGua), produced in the body can have an inhibitory effect on the poly(ADP-ribose) polymerase 1 (PARP1) enzyme, an important pharmacological target in anticancer therapy. In this work, using an original method of analysis of PARP1 activity based on monitoring fluorescence anisotropy, we studied inhibitory properties of 7mGua and its metabolite, 8-hydroxy-7-methylguanine (8h7mGua). Both compounds inhibited PARP1 enzymatic activity in a dose-dependent manner, however, 8h7mGua was shown to be a stronger inhibitor. The IC₅₀ values for 8h7mGua at different concentrations of the NAD+ substrate were found to be 4 times lower, on average, than those for 7mGua. The more efficient binding of 8h7mGua in the PARP1 active site is explained by the presence of an additional hydrogen bond with the Glu988 catalytic residue. Experimental and computational studies did not reveal the effect of 7mGua and 8h7mGua on the activity of other DNA repair enzymes, indicating selectivity of their inhibitory action.

Toxicological Properties of 7-Methylguanine, and Preliminary Data on its Anticancer Activity

7-Methylguanine (7-MG) competitively inhibits the DNA repair enzyme poly(ADP-ribose) polymerase (PARP) and RNA-modifying enzyme tRNA-guanine transglycosylase (TGT) and represents a potential anticancer drug candidate. Furthermore, as a natural compound, it could escape the serious side effects characteristic for approved synthetic PARP inhibitors. Here we present a comprehensive study of toxicological and carcinogenic properties of 7-MG. It was demonstrated that 7-MG does not induce mutations or structural chromosomal abnormalities, and has no blastomogenic activity. A treatment regimen with 7-MG has been established in mice (50 mg/kg per os, 3 times per week), exerting no adverse effects or changes in morphology. Preliminary data on the 7-MG anticancer activity obtained on transplantable tumor models support our conclusions that 7-MG can become a promising new component of chemotherapy.

8-oxoguanine and 8-oxodeoxyguanosine Biomarkers of Oxidative DNA Damage: A Review on HPLC-ECD Determination

Reactive oxygen species (ROS) are continuously produced in living cells due to metabolic and biochemical reactions and due to exposure to physical, chemical and biological agents. Excessive ROS cause oxidative stress and lead to oxidative DNA damage. Within ROS-mediated DNA lesions, 8-oxoguanine (8-oxoG) and its nucleotide 8-oxo-2'-deoxyguanosine (8-oxodG)-the guanine and deoxyguanosine oxidation products, respectively, are regarded as the most significant biomarkers for oxidative DNA damage. The quantification of 8-oxoG and 8-oxodG in urine, blood, tissue and saliva is essential, being employed to determine the overall effects of oxidative stress and to assess the risk, diagnose, and evaluate the treatment of autoimmune, inflammatory, neurodegenerative and cardiovascular diseases, diabetes, cancer and other age-related diseases. High-performance liquid chromatography with electrochemical detection (HPLC-ECD) is largely employed for 8-oxoG and 8-oxodG determination in biological samples due to its high selectivity and sensitivity, down to the femtomolar range. This review seeks to provide an exhaustive analysis of the most recent reports on the HPLC-ECD determination of 8-oxoG and 8-oxodG in cellular DNA and body fluids, which is relevant for health research.

Ultrasensitive electrochemiluminescence aptasensor for 8-hydroxy-2'-deoxyguanosine detection based on target-induced multi-DNA release and nicking enzyme amplification strategy

8-Hydroxy-2'-deoxyguanosine (8-OH-dG) is a principal stable marker of DNA oxidative damage. Sensitive and specific detection of 8-OH-dG is of great importance for early disease diagnosis. In this paper, we developed an electrochemiluminescence aptasensor for 8-OH-dG detection based on target induced multi-DNA release and nicking enzyme signaling amplification strategy. First, three kinds of short DNAs were aligned on the aptamers immobilized on the magnetic beads. In the presence of 8-OH-dG, the aptamer recognized and specifically bound with 8-OH-dG, leading to the release of three kinds of short DNAs and three-fold signal amplification. Then the released short DNAs hybridized with ferrocence (Fc) labeled hairpin DNA (Fc-HP) immobilized on the gold electrode to form a double strand DNA. Subsequently, nicking endonuclease (Nt.AlwI) recognized the asymmetric sequence in the dsDNA and cleaved the substrate strand (Fc-HP) into two parts, one fragments containing Fc would leave the surface of electrode. Based on the quenching effect of Fc on the electrochemiluminescence (ECL) of Ru(bpy)₃²⁺/TPA, a signal-on ECL aptasensor was developed. At the same time, three kinds of short DNAs were released again and reused to initiate the repeated cycles of hybridization-cleavage. Under double signal amplification, this aptasensor achieved a low detection of 25 fM and a wide linear range from 100 fM to 10 nM for 8-OH-dG. Besides, the amount of 8-OH-dG in urine samples derived from different people were determined with satisfactory results.

Leisure-time physical activity and DNA damage among Japanese workers

BACKGROUND

It remains unclear whether daily physical activity is associated with DNA damage. This cross-sectional study examined the association between leisure-time physical activity and urinary 8-hydroxydeoxyguanosine (8-OH-dG), a biomarker of oxidative DNA damage, or urinary 7-methylguanine (m7Gua), a biomarker of methylating DNA damage.

METHODS

Participants included 501 workers (294 men and 207 women), aged 20-65 years, from municipal offices in Japan. Urinary 8-OH-dG and m7Gua were measured using column-switching HPLC. Physical activity was evaluated using a self-reported questionnaire. The associations between leisure-time physical activity and urinary DNA damage markers were assessed by multiple linear regression analysis, with stratification by occupational physical activity.

RESULTS

After adjusting for covariates, leisure-time physical activity showed a suggestive inverse correlation with urinary 8-OH-dG levels (P for trend = 0.06), and a significant inverse association with urinary m7Gua levels (P for trend = 0.03). In analysis stratified by occupation, inverse correlations were observed in sedentary workers (walking < 30 min/day at work: P for trend = 0.06 and = 0.03 for urinary 8-OH-dG and m7Gua, respectively), but not in physically active workers (walking ≥ 30 min/day at work). In analysis for each intensity of leisure-time physical activity, light-intensity exercise was associated with lower levels of urinary 8-OH-dG (P for trend = 0.03), whereas moderate-to-high-intensity exercise was associated with lower levels of urinary m7Gua (P for trend = 0.02).

CONCLUSIONS

Our results suggest that high levels of leisure-time physical activity are associated with decreased levels of DNA damage in individuals with low physical activity at work.

Oxidative Stress and DNA Damage in Human Gastric Carcinoma: 8-Oxo-7'8-dihydro-2'-deoxyguanosine (8-oxo-dG) as a Possible Tumor Marker

We characterized the oxidative stress (OS) status by the levels of reduced/oxidized glutathione (GSH/GSSG), malondialdehyde (MDA) and the mutagenic base 8-oxo-7′8-dihydro-2′-deoxyguanosine (8-oxo-dG) in human gastric carcinoma (HGC) samples and compared the results with normal tissue from the same patients. We also analyzed 8-oxo-dG in peripheral mononuclear cells (PMNC) and urine from healthy control subjects and in affected patients in the basal state and one, three, six, nine and twelve months after tumor resection. The levels of DNA repair enzyme mRNA expression (hOGG1, RAD51, MUYTH and MTH1) were determined in tumor specimens and compared with normal mucosa. Tumor specimens exhibited increased levels of MDA and 8-oxo-dG compared with normal gastric tissue. GSH levels were also increased, while GSSG levels remained stable. DNA repair enzyme mRNA expression was induced in the tumor tissues. Levels of 8-oxo-dG were significantly elevated in both urine and PMNC of gastric cancer patients compared with healthy controls. After gastrectomy, the levels of the damaged base in urine and PMNC decreased progressively to values close to those found in the healthy population. The high levels of 8-oxo-dG in urine may be related to the increased induction of DNA repair activity in tumor tissue, and the changes observed after tumor resection support its potential use as a tumor marker.

Rapid measurement of 8-oxo-7,8-dihydro-2'-deoxyguanosine in human biological matrices using ultra-high-performance liquid chromatography-tandem mass spectrometry

Interaction of reactive oxygen species with DNA results in a variety of modifications, including 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG), which has been extensively studied as a biomarker of oxidative stress. Oxidative stress is implicated in a number of pathophysiological processes relevant to obstetrics and gynecology; however, there is a lack of understanding as to the precise role of oxidative stress in these processes. We aimed to develop a rapid, validated assay for the accurate quantification of 8-oxodG in human urine using solid-phase extraction and ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) and then investigate the levels of 8-oxodG in several fluids of interest to obstetrics and gynecology. Using UHPLC-MS/MS, 8-oxodG eluted after 3.94 min with an RSD for 15 injections of 0.07%. The method was linear between 0.95 and 95 nmol/L with LOD and LOQ of 5 and 25 fmol on-column, respectively. Accuracy and precision were 98.7-101.0 and <10%, respectively, over three concentrations of 8-oxodG. Recovery from urine was 88% with intra- and interday variations of 4.0 and 10.2%, respectively. LOQ from urine was 0.9 pmol/ml. Rank order from the greatest to lowest 8-oxodG concentration was urine>seminal plasma>amniotic fluid>plasma>serum>peritoneal fluid, and it was not detected in saliva. Urine concentrations normalized to creatinine (n=15) ranged between 0.55 and 1.95 pmol/μmol creatinine. We describe, for the first time, 8-oxodG concentrations in human seminal plasma, peritoneal fluid, amniotic fluid, and breast milk, as well as in urine, plasma, and serum, using a rapid UHPLC-MS/MS method that will further facilitate biomonitoring of oxidative stress.

Inhibition by wheat sprout (Triticum aestivum) juice of bisphenol A-induced oxidative stress in young women

For health of future generation, fertile young women should be monitored for exposure of endocrine disrupting chemicals (EDCs). Among EDCs, bisphenol A (BPA) is suggested to induce reactive oxygen species (ROS) which play an important role in pathologies of female diseases such as endometriosis. On the other hand, previous studies suggested that sprouts of wheat (Triticum aestivum) have antimutagenicity and antioxidant activity. We performed the 2 weeks intervention of wheat sprout juice (100ml/day) to investigate its effects on BPA-exposure and -oxidative toxicity in young women (N=14, age=24.4±4.0). Geometrical mean of urinary BPA levels was 1.81 (GSTD, 4.34)μg/g creatinine. We observed that irregular meals significantly increased levels of urinary BPA approximate 3 times (p=0.03). In addition, we found BPA-induced oxidative stress is correlated with levels of 8-hydroxydeoxyguanosine (8-OHdG) or malondialdehyde (MDA) levels (p=0.18 or 0.03, respectively). We also observed a continuous reduction of urinary BPA during the wheat sprout intervention (p=0.02). In summary, our data suggested potential detoxification of wheat sprouts on BPA-toxicity via antioxidative and interference of absorption, distribution, metabolism and excretion (ADME)-mediated mechanisms in young women.

Effect of age, smoking and other lifestyle factors on urinary 7-methylguanine and 8-hydroxydeoxyguanosine

Urinary 8-hydroxydeoxyguanosine (8-OH-dG) and 7-methylguanine (m7Gua) were measured by a column-switching high performance liquid chromatography method as markers of oxidative and methylating DNA damage, respectively. We investigated the associations between urinary 8-OH-dG or m7Gua and various lifestyle and demographic factors, such as age and sex. The urinary 8-OH-dG excretion level was positively correlated with cigarette smoking, but inversely correlated with fruit consumption, physical activity and total energy consumed per day. A multiple regression analysis revealed that daily physical activity and healthy meal combinations decreased the urinary 8-OH-dG level, whereas alcohol consumption increased it. In terms of the urinary m7Gua measurement, cigarette smoking, age and consumption of meat, fish, egg, soybean, etc. were positively correlated with the urinary m7Gua level, whereas body weight, BMI, physical activity, and dietary index score, which indicates good nutritional balance, were negatively correlated with the amount of m7Gua. Based on a multiple regression analysis, cigarette smoking and age correlated with the m7Gua level, while high BMI and healthy meal combinations have significant reducing effects on m7Gua level. Therefore, the urinary m7Gua level is considered to be a useful marker of DNA methylation, not only from smoking, but also from aging and unhealthy dietary habits.

Neopterin, a marker of immune response, and 8-hydroxy-2'-deoxyguanosine, a marker of oxidative stress, correlate at high age as determined by automated simultaneous high-performance liquid chromatography analysis of human urine

Using an established high-performance liquid chromatography (HPLC) method based on anion exchange chromatography, fraction collection, and electrochemical detection, the oxidative DNA damage marker 8-hydroxy-2'-deoxyguanosine (8-OH-dG) can be analyzed rapidly and precisely in human urine samples. In addition, by ultraviolet (UV) detection, it was shown recently that it is possible to simultaneously analyze creatinine and 7-methylguanine (m(7)Gua), an RNA degradation product, in urine. By adding a fluorescence detector to the HPLC system, we now report that it is also possible to detect pteridins such as neopterin and biopterin. The fluorescence detection was evaluated in detail for neopterin, an immune response and tumor marker. The urinary content of neopterin, assessed by using the HPLC method, was verified with a commercial neopterin enzyme-linked immunosorbent assay (ELISA) kit as indicated by the high correlation between the two methods (r=0.98). In urinary samples from 58 young healthy individuals (male and female nonsmokers, ages 19-39 years), it was found that there was no significant correlation (r=-0.04) between the levels of 8-OH-dG and neopterin (as normalized to urinary creatinine levels). In contrast, in urinary samples from 60 old healthy individuals (male and female nonsmokers, ages 60-86 years), there was a significant correlation (r=0.47) found between the levels of 8-OH-dG and neopterin (as normalized to urinary creatinine levels). These findings strongly indicate that the higher level of immune response that was correlating with old age contributes significantly to the higher level of oxidative damage as assessed in the form of 8-OH-dG. Using this type of HPLC system, it is possible to evaluate oxidative DNA damage and immune response simultaneously using the respective urinary markers. These data may contribute to understanding of the pathophysiology of diseases such as infections and tumor progression where both oxidative stress and immune response occur simultaneously.

Electrochemical performance of 8-hydroxy-2′-deoxyguanosine and its detection at poly(3-methylthiophene) modified glassy carbon electrode

8-Hydroxy-2'-deoxyguanosine (8-OH-dG) has attracted enormous attention in recent years because it has been acknowledged as a typical biomarker of oxidative DNA damage. In this paper, the electrochemical performance of 8-OH-dG at the poly(3-methylthiophene) (P3MT) modified glassy carbon electrode (GCE) was investigated by cyclic voltammetry (CV) and linear sweep voltammetry (LSV). The conducting polymer P3MT can effectively decrease the oxidation peak potential of 8-OH-dG and greatly enhance its peak current. In 0.1 M pH 7.0 phosphate buffer solution (PBS), the anodic peak currents of cyclic voltammograms are linear with the 8-OH-dG concentration in two intervals, viz. 0.700-35.0 microM and 35.0-70.0 microM, with the correlative coefficients of 0.9992 and 0.9995, respectively. The detection limit of 8-OH-dG can be estimated to be 0.100 microM (S/N=3). This modified electrode can be used to detect the amount of 8-OH-dG in human urine. Furthermore, the effects of scan rate, pH, and interference of uric acid (UA) for the voltammetric behavior and detection of 8-OH-dG are also discussed. This proposed modified electrode also shows excellent reproducibility and stability that makes it an ideal candidate for amperometric detection of 8-OH-dG in flow injection analysis (FIA) and high performance liquid chromatography (HPLC).

Prospective study of urinary excretion of 7-methylguanine and the risk of lung cancer: Effect modification bymu class glutathione-S-transferases

Nitrosamines are mainly mutagenic through methylation of DNA. 7-Methylguanine (m(7)Gua) is a product of base excision repair and spontaneous depurination of such lesions in DNA and a metabolite from RNA. Associations between urinary excretion of m(7)Gua and risk of lung cancer were examined in a population-based cohort of 25,717 men and 27,972 women aged 50-64 years. During 3-7 years follow-up 260 cases with lung cancer were identified and a subcohort of 263 individuals matched on sex, age and smoking duration was selected for comparison. Urine collected at entry was analyzed for m(7)Gua by HPLC. Effect modification by glutathione-S-transferases GSTM1, GSTM3, GSTT1 and GSTP1 was investigated. We found higher excretion of m(7)Gua among current smokers than among former smokers. The IRR (incidence rate ratio) of lung cancer was 1.20 (95% CI: 1.00-1.43) per doubling of m(7)Gua excretion in unadjusted analysis and 1.12 (95% CI: 0.93-1.35) after adjustment for smoking status, intensity and duration at entry. This association was mainly present among current smokers. Comparing the highest with the lowest tertile of m(7)Gua excretion the IRR of lung cancer was 1.75 (95% CI: 1.04-2.95) irrespective of genotype and 2.75 (95% CI: 1.33-5.81) in subjects with GSTM1 null genotype. If not caused by residual confounding by smoking a possible association between m(7)Gua excretion and lung cancer supports the importance of methylation of guanine. The finding of an association between m(7)Gua excretion and lung cancer risk mainly among current smokers and subjects with GSTM1 null genotype supports causality in this respect.

Urinary 8-hydroxyguanine may be a better marker of oxidative stress than 8-hydroxydeoxyguanosine in relation to the life spans of various species

Oxidative DNA damage is believed to be involved in the aging process. Species with shorter potential life spans generally have a higher specific metabolic rate (SMR), and would be expected to have increased levels of oxidative stress and DNA damage, as compared to long-lived species. An automatized HPLC method based on electrochemical detection was used to measure the levels of the oxidative DNA damage markers 8-hydroxydeoxyguanosine (8-OH-dG) and 8-hydroxyguanine (8-OH-Gua) in urinary samples from mammals with various potential life spans (mice, rats, guinea pigs, cats, chimpanzees, and humans). There was no significant linear correlation (r = -0.71, p = 0.11) between the species' potential life spans (log transformed) and the urinary levels of 8-OH-dG as normalized to creatinine (8-OH-dG/creatinine), although the species with longer life spans, such as chimpanzee and human, had among the lowest levels detected. In contrast, the negative linear correlation between the species' potential life span (log transformed) and the urinary levels of 8-OH-Gua as normalized to creatinine (8-OH-Gua/creatinine), was significant (r = -0.97, p = 0.002). In addition, there was a positive linear and significant correlation between SMR and 8-OH-dG/creatinine (r = 0.91, p = 0.01) or 8- OH-Gua/creatinine (r = 0.90, p = 0.01). These results suggest that 8-OH-Gua, rather than 8-OH-dG, may be a more general marker for oxidative damage.

Decreasing urinary PAH metabolites and 7-methylguanine after smoking cessation

OBJECTIVE

Humans are exposed to various carcinogens by smoking. Urinary metabolites of polycyclic aromatic hydrocarbons (PAH), one of the major carcinogens in cigarette smoke, were measured as the environmental carcinogen exposure marker for humans. We evaluated urinary exposure markers for smoking cessation.

METHOD

In this study, we measured cigarette smoke exposure markers, such as urinary cotinine, PAH exposure markers, such as urinary 1-hydroxypyrene (1-OHP), 2-naphthol (2-NP) and 1-naphthol (1-NP), as well as a methylating chemical exposure marker, 7-methylguanine (7-MeG). The before smoking cessation levels of these markers, and the after smoking cessation levels were then compared. Eighteen subjects participated in this smoking cessation program.

RESULTS

Levels of all of four markers were found to have decreased by 19-54% after smoking cessation. Urinary cotinine, 1-OHP, 2-NP and 7-MeG levels were found to have significantly decreased after smoking cessation. There were positive correlations between cotinine and three urinary PAH markers and between 1-OHP, 2-NP and 7-MeG.

CONCLUSION

PAH metabolites were better biomarkers of smoking cessation than 7-MeG. Analyzing urinary metabolites or urinary DNA adducts is suitable for epidemiological studies.

Prospective study of 8-oxo-7,8-dihydro-2'-deoxyguanosine excretion and the risk of lung cancer

Oxidative damage to DNA may be important in carcinogenesis and a possible risk factor for lung cancer. The urinary excretion of products of damaged nucleotides in cellular pools or in DNA may be important biomarkers of exposure to relevant carcinogens reflecting the rate of damage in steady state and may predict cancer risk. Oxidation of guanine in DNA or the nucleotide pool may give rise to 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) for urinary excretion. Oxoguanine glycosylase (OGG1) is the base excision enzyme repairing 8-oxodG in DNA by release of 8-oxoguanine. In a nested case-cohort design we examined associations between urinary excretion of 8-oxodG and risk of lung cancer as well as potential interaction with the OGG1 Ser326Cys polymorphism in a population-based cohort of 25 717 men and 27 972 women aged 50-64 years with 3-7 years follow-up. We included 260 cases with lung cancer and a sub-cohort of 263 individuals matched on sex, age and smoking duration for comparison. Urine collected at entry was analysed for 8-oxodG by HPLC with electrochemical detection. The excretion of 8-oxodG was higher in current smokers, whereas OGG1 genotype had no effect. Overall the incidence rate ratio (IRR) (95% confidence interval) of lung cancer was 0.99 (0.80-1.22) per doubling of 8-oxodG excretion and there was no interaction with OGG1 genotype. However, among never-smokers (eight cases and eight sub-cohort members) the IRR was 11.8 (1.21-115) per doubling of 8-oxodG excretion. The association between 8-oxodG excretion and lung cancer risk among never-smokers suggests that oxidative damage to DNA nucleotides is important in this group.

Simultaneous determination of 8-hydroxydeoyguanosine, a marker of oxidative stress, and creatinine, a standardization compound, in urine

Recently, H. Kasai reported an automatic, precise method of 8-hydroxydeoxyguanosine (8-OH-dG) analysis in urine by high performance liquid chromatography coupled to an electrochemical detector (HPLC-ECD). It is based on a cleaning-up step by anion-exchange chromatography and a further purification step using reverse phase chromatography before detection, by the ECD. In this communication, we report a method for the simultaneous determination of 8-OH-dG and creatinine, an internal standard for normalizing the excretion of 8-OH-dG in urine.