Determination of 8-hydroxydeoxyguanosine by an immunoaffinity chromatography-monoclonal antibody-based ELISA

The earliest stage of cognitive impairment in transition from normal aging to Alzheimer disease is marked by prominent RNA oxidation in vulnerable neurons

Although neuronal RNA oxidation is a prominent and established feature in age-associated neurodegenerative disorders such as Alzheimer disease (AD), oxidative damage to neuronal RNA in aging and in the transitional stages from normal elderly to the onset of AD has not been fully examined. In this study, we used an in situ approachto identify an oxidized RNA nucleoside 8-hydroxyguanosine (8OHG) in the cerebral cortex of 65 individuals without dementia ranging in age from 0.3 to 86 years. We also examined brain samples from 20 elderly who were evaluated for their premortem clinicaldementia rating score and postmortem brain pathologic diagnoses to investigate preclinical AD and mild cognitive impairment. Relative density measurements of 8OHG-immunoreactivity revealed a statistically significant increase in neuronal RNA oxidation during aging in the hippocampus and the temporal neocortex. In subjects with mild cognitive impairment but not preclinical AD, neurons of the temporal cortex showed a higher burden of oxidized RNA compared to age-matched controls. These results indicate that, although neuronal RNA oxidation fundamentally occurs as an age-associated phenomenon, more prominent RNA damage than in normal aging correlates with the onset of cognitive impairment in the prodromal stage of AD.

Resistance loading and signaling assays for oxidative stress in rodent skeletal muscle

Resistance loading provides an important tool for understanding skeletal muscle responses and adaptations to various perturbations. A model using anesthetized rodents provides the means to control the input parameters carefully, and to measure the output parameters of each muscle contraction. Unilateral models of anesthetized loading also provide the advantage of comparing an unloaded and loaded muscle from the same animal. Voluntary models for resistance loading arguably provide a more "physiological response" but it also introduces more variability in the input parameters, which can be affected by the stimulus used to motivate the animal to exercise. After either acute or chronic periods of muscle loading, the loaded muscles can be removed and various signaling proteins can be determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) or enzyme assays. Several assays are described, which provide an indication of downstream markers for oxidative stress.

Immunochemical detection of oxidatively damaged DNA

Oxidatively damaged DNA is implicated in various diseases, including neurodegenerative disorders, cancer, diabetes, cardiovascular and inflammatory diseases as well as aging. Several methods have been developed to detect oxidatively damaged DNA. They include chromatographic techniques, the Comet assay, (32)P-postlabelling and immunochemical methods that use antibodies to detect oxidized lesions. In this review, we discuss the detection of 8-oxo-7,8-dihydro-29-deoxyguanosine (8-oxodG), the most abundant oxidized nucleoside. This lesion is frequently used as a marker of exposure to oxidants, including environmental pollutants, as well as a potential marker of disease progression. We concentrate on studies published between the years 2000 and 2011 that used enzyme-linked immunosorbent assay (ELISA) and immunohistochemistry to detect 8-oxodG in humans, laboratory animals and in cell lines. Oxidative damage observed in these organisms resulted from disease, exposure to environmental pollutants or from in vitro treatment with various chemical and physical factors.

Microfluidic tool based on the antibody-modified paramagnetic particles for detection of 8-hydroxy-2'-deoxyguanosine in urine of prostate cancer patients

Guanosine derivatives are important for diagnosis of oxidative DNA damage including 8-hydroxy-2'-deoxyguanosine (8-OHdG) as one of the most abundant products of DNA oxidation. This compound is commonly determined in urine, which makes 8-OHdG a good non-invasive marker of oxidation stress. In this study, we optimized and tested the isolation of 8-OHdG from biological matrix by using paramagnetic particles with an antibody-modified surface. 8-OHdG was determined using 1-naphthol generated by alkaline phosphatase conjugated with the secondary antibody. 1-Naphthol was determined by stopped flow injection analysis (SFIA) with electrochemical detector using a glassy carbon working electrode and by stationary electrochemical detection using linear sweep voltammetry. A special modular electrochemical SFIA system which needs only 10  μL of sample including working buffer for one analysis was completely designed and successfully verified. The recoveries in different matrices and analyte concentration were estimated. Detection limit (3 S/N) was estimated as 5  pg/mL of 8-OHdG. This method promises to be very easily modified to microfluidic systems as "lab on valve". The optimized method had sufficient selectivity and thus could be used for determination of 8-OHDG in human urine and therefore for estimation of oxidative DNA damage as a result of oxidation stress in prostate cancer patients.

Expression of XRCC5 in peripheral blood lymphocytes is upregulated in subjects from a heavily polluted region in the Czech Republic

Air pollution causes oxidative damage to macromolecules, chromosomal aberrations and changes in gene expression. We investigated the levels of oxidative stress markers [8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG), 15-F(2t)-isoprostane (15-F2t-IsoP), protein carbonyls] and cytogenetic parameters [genomic frequency of translocations (F(G)/100), percentage of aberrant cells (%AB.C.) and acentric fragments (ace)] in subjects living in Prague and in the heavily polluted Ostrava region. We also compared the expression of genes participating in base excision repair (BER) and non-homologous end-joining (NHEJ). We analyzed 64 subjects from Prague and 75 subjects from Ostrava. We measured oxidative stress markers by ELISA, cytogenetic parameters by fluorescence in situ hybridization and gene expression by quantitative PCR. The levels of air pollutants (benzo[a]pyrene, B[a]P; carcinogenic polycyclic aromatic hydrocarbons, c-PAHs; benzene) measured by personal monitors were significantly elevated in Ostrava compared to Prague (p<0.001). Despite this fact, we observed no differences in biomarkers of oxidative stress between the two locations. Moreover, subjects from Ostrava were less likely to have above-median levels of %AB.C. (OR; 95% CI: 0.18; 0.05-0.67; p=0.010). Multivariate analyses revealed that subjects living in Ostrava had increased odds of having above-median levels of XRCC5 expression (OR; 95% CI: 3.33; 1.03-10.8; q=0.046). Above-median levels of 8-oxodG were associated with decreased levels of vitamins C (OR; 95% CI: 0.37; 0.16-0.83; p=0.016) and E (OR; 95% CI: 0.25; 0.08-0.75; p=0.013), which were elevated in subjects from Ostrava. We suggest that air pollution by c-PAHs affects XRCC5 gene expression, which probably protects subjects from Ostrava against the induction of a higher frequency of translocations; elevated vitamin C and E levels in the Ostrava subjects decrease the levels of 8-oxodG.

Measurement of oxidatively generated base damage in cellular DNA

This survey focuses on the critical evaluation of the main methods that are currently available for monitoring single and complex oxidatively generated damage to cellular DNA. Among chromatographic methods, HPLC-ESI-MS/MS and to a lesser extent HPLC-ECD which is restricted to a few electroactive nucleobases and nucleosides are appropriate for measuring the formation of single and clustered DNA lesions. Such methods that require optimized protocols for DNA extraction and digestion are sensitive enough for measuring base lesions formed under conditions of severe oxidative stress including exposure to ionizing radiation, UVA light and high intensity UVC laser pulses. In contrast application of GC-MS and HPLC-MS methods that are subject to major drawbacks have been shown to lead to overestimated values of DNA damage. Enzymatic methods that are based on the use of DNA repair glycosylases in order to convert oxidized bases into strand breaks are suitable, even if they are far less specific than HPLC methods, to deal with low levels of single modifications. Several other methods including immunoassays and (32)P-postlabeling methods that are still used suffer from drawbacks and therefore are not recommended. Another difficult topic is the measurement of oxidatively generated clustered DNA lesions that is currently achieved using enzymatic approaches and that would necessitate further investigations.

Oxidative DNA damage in early pregnancy and risk of gestational diabetes mellitus: A pilot study

OBJECTIVES

To examine the association of maternal early pregnancy oxidative stress with risk of gestational diabetes mellitus (GDM).

DESIGN AND METHODS

A pilot prospective, nested case-control study was conducted. Study participants were recruited before 20weeks gestation. Maternal urinary 8-hydroxydeoxyguanosine (8-OHdG), a biomarker of systemic oxidative DNA damage and repair, was measured using competitive immunoassays. Logistic regression was used to calculate odds ratio (OR) and 95% confidence intervals (95%CI).

RESULTS

Elevations in early pregnancy urinary 8-OHdG concentrations were associated with increased GDM risk. After adjusting for confounders, the OR for extreme quartiles (≥8.01 vs. <4.23ng/mg creatinine) of 8-OHdG was 3.79 (95%CI 1.03-14.00). The risk for GDM was highest for overweight women with urine 8-OHdG concentrations ≥8.01ng/mg creatinine (OR=5.36, 95%CI 1.33-21.55) when compared with lean women who had 8-OHdG concentrations <8.01ng/mg creatinine.

CONCLUSIONS

Elevated urine 8-OHdG concentrations in early pregnancy appear to be associated with increased GDM risk.

Factors affecting the frequency of micronuclei in asthmatic and healthy children from Ostrava

A higher incidence of asthma is one of the serious problems confronting urban populations worldwide. The aim of the present study was to analyze the effect of age, gender, smoking, vitamin intake, genetic polymorphisms in genes related to the metabolic activation of polycyclic aromatic hydrocarbons (PAHs) and their detoxification and oxidative damage to DNA, lipids and proteins on the frequency of micronuclei (MN) in a group of 175 children (81 with bronchial asthma and 94 healthy controls) aged 6-15 years. The study group from the most polluted region of the Czech Republic, Ostrava, was followed in November 2008, when the mean concentration of benzo[a]pyrene (B[a]P) measured by stationary monitoring was 11.4±9.8ng/m(3). The results of cotinine analysis revealed active smoking in 15 children. The frequency of MN per 1000 binucleated cells (MN/1000 BNC), measured by automated image analysis, indicated a significant risk for smoking children with asthma in comparison with smoking control children (4.25±1.54 and 3.00±0.77, respectively, p<0.05). Girls in the control group had 16% higher levels of MN in comparison with boys. Markers of oxidative damage to DNA, proteins and lipids were not associated with asthma in this study. Higher levels of MN were associated with increased levels of protein carbonyl groups. We conclude that smoking asthmatic children are at higher risk of DNA damage measured as the frequency of micronuclei in peripheral blood lymphocytes.

A post-entry step in the mammalian orthoreovirus replication cycle is a determinant of cell tropism

Mammalian reoviruses replicate in a broad range of hosts, cells, and tissues. These viruses display strain-dependent variation in tropism for different types of cells in vivo and ex vivo. Early steps in the reovirus life cycle, attachment, entry, and disassembly, have been identified as pivotal points of virus-cell interaction that determine the fate of infection, either productive or abortive. However, in studies of the differential capacity of reovirus strains type 1 Lang and type 3 Dearing to replicate in Madin-Darby canine kidney (MDCK) cells, we found that replication efficiency is regulated at a late point in the viral life cycle following primary transcription and translation. Results of genetic studies using recombinant virus strains show that reovirus tropism for MDCK cells is primarily regulated by replication protein μ2 and further influenced by the viral RNA-dependent RNA polymerase protein, λ3, depending on the viral genetic background. Furthermore, μ2 residue 347 is a critical determinant of replication efficiency in MDCK cells. These findings indicate that components of the reovirus replication complex are mediators of cell-selective viral replication capacity at a post-entry step. Thus, reovirus cell tropism may be determined at early and late points in the viral replication program.

Detection of extracellular 8-oxo-7,8-dihydro-2'-deoxyguanosine as a biomarker of oxidative damage in X-irradiated fibroblast cultures: optimization of analytical procedure

We have developed a simple methodology, based on single-step solid-phase extraction followed by isocratic high-performance liquid chromatography coupled with electrochemical detection (HPLC-ECD), to determine extracellular 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) in culture supernatants of normal human dermal fibroblasts. A standard addition method, using externally added 8-oxodG (0.5 and 1 pmol) was employed to eliminate matrix effects arising from the chemically complex, protein-rich medium. Secondly, applying this procedure to X-ray irradiated fibroblasts, we report a significant twofold increase in the levels of 8-oxodG at the radiobiologically relevant dose of 6 Gy. This suggests that extracellular 8-oxodG might be a useful biomarker for oxidative stress following moderate doses of X-irradiation.

Salvage of oxidized guanine derivatives in the (2'-deoxy)ribonucleotide pool as source of mutations in DNA

Recent evidence suggests that salvage of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) and 8-oxo-7,8-dihydro-guanine (8-oxoGua) can contribute substantially to levels of 8-oxoGua in DNA and RNA. However, it remains to be determined if this mechanism contributes to mutagenesis and disease. This review covers the predominant methods for detecting 8-oxoGua and its derivatives, summarizes some of the relevant recent DNA repair studies and discusses the mechanisms for metabolism of oxidized guanine derivatives in the (2'-deoxy)ribonucleoside and (2'-deoxy)ribonucleotide pools.

Loss of nuclear p27(kip1) and α-dystroglycan is a frequent event and is a strong predictor of poor outcome in renal cell carcinoma

Expression levels of p27(kip1) , a negative regulator of the G1 phase of the cell cycle, and 8-hydroxydeoxyguanosine (8-OHdG), a marker of oxidative DNA damage, were assessed by immunostaining in a series of renal cell carcinomas (RCCs) and their prognostic significance was evaluated. Expression of p27(kip1) as well as of the α-subunit of the dystroglycan (DG) complex, previously reported to be altered in RCC, was also evaluated by western blot analysis. Nuclear expression of p27(kip1) was reduced in a significant fraction of tumors and low p27(kip1) staining correlated with higher tumor grade (P < 0.01). Recurrence and death from clear cell RCCs were significantly more frequent in p27(kip1) -low expressing tumors and Kaplan-Meier curves showed a significant separation between high vs low expressor groups for both disease-free (P = 0.011) and overall (P = 0.002) survival. Low nuclear expression of p27(kip1) as well as loss of α-DG were confirmed to be independent prognostic parameters at a multivariate analysis and the simultaneous loss of both molecules defined a "high-risk" group of patients with increased risk of recurrence (RR = 28.7; P = 0.01) and death (RR = 12.9; P = 0.03). No significant correlation with clinical or pathological parameters was found for 8-OHdG staining. Western blot analyses suggested a post-translational mechanism for the loss of α-DG expression and demonstrated that cytoplasmic dislocation of the protein contributes to the loss of active nuclear p27(kip1) . Loss of nuclear p27(kip1) is a frequent event in human RCCs and is a powerful predictor of poor outcome which, in combination with low DG expression, could help to identify high-risk patients with clear cell RCC.

Oxidative damage to biological macromolecules in Prague bus drivers and garagemen: impact of air pollution and genetic polymorphisms

DNA integrity was investigated in the lymphocytes of 50 bus drivers, 20 garagemen and 50 controls using the comet assay with excision repair enzymes. In parallel, 8-oxo-7,8-dihydro-2'-deoxyguanosine and 15-F(2t)-isoprostane levels in the urine and protein carbonyl levels in the plasma were assessed as markers of oxidative damage to DNA, lipids and proteins. Exposure to carcinogenic polycyclic aromatic hydrocarbons (cPAHs) and volatile compounds was measured by personal samplers for 48 and 24h, respectively, before the collection of biological specimens. Both exposed groups exhibited a higher levels of DNA instability and oxidative damage to biological macromolecules than the controls. The incidence of oxidized lesions in lymphocyte DNA, but not the urinary levels of 8-oxodG, correlated with exposure to benzene and triglycerides increased this damage. Oxidative damage to lipids and proteins was associated with exposure to cPAHs and the lipid peroxidation levels positively correlated with age and LDL cholesterol, and negatively with vitamin C. The carriers of at least one variant hOGG1 (Cys) allele tended to higher oxidative damage to lymphocyte DNA than those with the wild genotype, while XPD23 (Gln/Gln) homozygotes were more susceptible to the induction of DNA strand breaks. In contrast, GSTM1 null variant seemed to protect DNA integrity.

Mitochondrial base excision repair assays

The main source of mitochondrial DNA (mtDNA) damage is reactive oxygen species (ROS) generated during normal cellular metabolism. The main mtDNA lesions generated by ROS are base modifications, such as the ubiquitous 8-oxoguanine (8-oxoG) lesion; however, base loss and strand breaks may also occur. Many human diseases are associated with mtDNA mutations and thus maintaining mtDNA integrity is critical. All of these lesions are repaired primarily by the base excision repair (BER) pathway. It is now known that mammalian mitochondria have BER, which, similarly to nuclear BER, is catalyzed by DNA glycosylases, AP endonuclease, DNA polymerase (POLgamma in mitochondria) and DNA ligase. This article outlines procedures for measuring oxidative damage formation and BER in mitochondria, including isolation of mitochondria from tissues and cells, protocols for measuring BER enzyme activities, gene-specific repair assays, chromatographic techniques as well as current optimizations for detecting 8-oxoG lesions in cells by immunofluorescence. Throughout the assay descriptions we will include methodological considerations that may help optimize the assays in terms of resolution and repeatability.

Oxidatively generated base damage to cellular DNA

Search for the formation of oxidatively base damage in cellular DNA has been a matter of debate for more than 40 years due to the lack of accurate methods for the measurement of the lesions. HPLC associated with either tandem mass spectrometry (MS/MS) or electrochemical detector (ECD) together with optimized DNA extraction conditions constitutes a relevant analytical approach. This has allowed the accurate measurement of oxidatively generated single and clustered base damage in cellular DNA following exposure to acute oxidative stress conditions mediated by ionizing radiation, UVA light and one-electron oxidants. In this review the formation of 11 single base lesions that is accounted for by reactions of singlet oxygen, hydroxyl radical or high intensity UVC laser pulses with nucleobases is discussed on the basis of the mechanisms available from model studies. In addition several clustered lesions were found to be generated in cellular DNA as the result of one initial radical hit on either a vicinal base or the 2-deoxyribose. Information on nucleobase modifications that are formed upon addition of reactive aldehydes arising from the breakdown of lipid hydroperoxides is also provided.

Oxidative damage to RNA in neurodegenerative diseases

Since 1999, oxidative damage to RNA molecules has been described in several neurological diseases including Alzheimer's disease, Parkinson's disease, Down syndrome, dementia with Lewy bodies, prion disease, subacute sclerosing panencephalitis, and xeroderma pigmentosum. An early involvement of RNA oxidation of vulnerable neuronal population in the neurodegenerative diseases has been demonstrated, which is strongly supported by a recent observation of increased RNA oxidation in brains of subjects with mild cognitive impairment. Until recently, little is known about consequences and cellular handling of the RNA damage. However, increasing body of evidence suggests detrimental effects of the RNA damage in protein synthesis and the existence of several coping mechanisms including direct repair and avoiding the incorporation of the damaged ribonucleotides into translational machinery. Further investigations toward understanding of the consequences and cellular handling mechanisms of the oxidative RNA damage may provide significant insights into the pathogenesis and therapeutic strategies of the neurodegenerative diseases.

Increased urinary 8-hydroxy-2'-deoxyguanosine excretion in long-distance bus drivers in Taiwan

Professional bus drivers are exposed to environments containing air pollution and reactive oxygen species (ROS) that can induce cellular oxidative stress and DNA damage. This study investigated environmental factors associated with oxidative DNA damage in a cohort of long-distance bus drivers. In a comparison study, urinary 8-hydroxydeoxyguanosine (8-OHdG), a biomarker of DNA oxidative damage, was examined in 120 male long-distance bus drivers and 58 male office workers in Taiwan. Multivariate logistic regression was used to analyze association between urinary 8-OHdG levels and environmental factors. Bus drivers had higher urinary 8-OHdG levels (adjusted odds ratio (aOR)=9.4, 95% confidence interval (CI)=3.5-28.2) compared with office workers. Increased urinary 8-OHdG level was significantly related to cigarette smoking (aOR=18.0, 95% CI=7.1-52.1), consumption of energy drinks (aOR=5.0, 95% CI=2.1-12.6), and regular exercise (aOR=3.8, 95% CI=1.5-10.2). A strong exposure-response relationship was found between urinary 8-OHdG and urinary cotinine (p<0.0001). Among nonsmokers, bus drivers (aOR=3.9, 95% CI=1.0-17.7) had higher urinary 8-OHdG than office workers. Among both bus drivers and office workers, those who drank energy drinks (aOR=3.7, 95% CI=1.2-12.2) had higher 8-OHdG levels than those who did not drink energy drinks. Adjusted for smoking, levels of 8-OHdG were increased in long-distance bus drivers exposed to traffic exhaust and ingested energy drinks. Future studies should explore what aspects of energy drinks may contribute to increased urinary 8-OHdG.

Oxidative damage to RNA: mechanisms, consequences, and diseases

Overproduction of free radicals can damage cellular components resulting in progressive physiological dysfunction, which has been implicated in many human diseases. Oxidative damage to RNA received little attention until the past decade. Recent studies indicate that RNA, such as messenger RNA and ribosomal RNA, is very vulnerable to oxidative damage. RNA oxidation is not a consequence of dying cells but an early event involved in pathogenesis. Oxidative modification to RNA results in disturbance of the translational process and impairment of protein synthesis, which can cause cell deterioration or even cell death. In this review, we discuss the mechanisms of oxidative damage to RNA and the possible biological consequences of damaged RNA. Furthermore, we review recent evidence suggesting that oxidative damage to RNA may contribute to progression of many human diseases.

Detection and localization of markers of oxidative stress by in situ methods: application in the study of Alzheimer disease

Oxidative stress is a key factor involved in the development and progression of Alzheimer disease (AD), and it is well documented that free radical oxidative damage, particularly of neuronal lipids, proteins, nucleic acids, and sugars, is extensive in brains of AD patients. The complex chemistry of peroxynitrite has been the subject of intense study and is now evident that there are two principal pathways for protein modification: the first one involves homolytic hydroxyl radical-like chemistry that results in protein-based carbonyls and the second involves electrophilic nitration of vulnerable side chains, in particular the electron-rich aromatic rings of Tyr and Trp. In the presence of buffering bicarbonate, peroxynitrite forms a CO(2) adduct, which augments its reactivity. Formation of 3-nitrotyrosine by this route has become the classical protein marker specifically for the presence of peroxynitrite. Protein-based carbonyls can be detected by two methods: (i) derivatization with 2,4-dinitrophenylhydrazine (DNPH) and detection of the protein-bound hydrazones using an enzyme-linked anti-2,4-dinitrophenyl antibody and (ii) derivatization with biotin-hydrazide and detection of the protein-bound acyl hydrazone with enzyme-linked avidin or streptavidin. Glycation of proteins by reducing sugars (Maillard reaction) results in a profile of time-dependent adduct evolution rendering susceptibility to oxidative elaboration. In addition, oxidative stress can result in oxidized sugar derivatives which can subsequently modify protein through a process known as glycoxidation. Of more general importance, oxidative stress results in lipid peroxidation and the production of a range of electrophilic and mostly bifunctional aldehydes that modify numerous proteins. The more important protein modifications are referred to as advanced glycation end products (AGEs) and advanced lipoxidation end products (ALEs). Protein modification can result in both non-cross-link and cross-link AGEs and ALEs, the latter arising from the potential bifunctional reactivity, such as that of the lipid-derived modifiers 4-hydroxy-2-nonenal (HNE) and malondialdehyde (MDA). Oxidative damage to nucleic acids results in base modification, substitutions, and deletions. Among the most common modifications, 8-hydroxyguanosine (8OHG) is considered a signature of oxidative damage to nucleic acid.Cells are not passive to increased oxygen radical production but rather upregulate protective responses. In neurodegenerative diseases, heme oxygenase-1 (HO-1) induction is coincident with the formation of neurofibrillary tangles. This enzyme that converts heme, a prooxidant, to biliverdin/bilirubin (antioxidants) and free iron has been considered an antioxidant enzyme. But seen in the context of arresting apoptosis, HO-1 and tau may play a role in maintaining the neurons free from the apoptotic signal (cytochrome c), since tau has strong iron-binding sites. Given the importance of iron as a catalyst for the generation of reactive oxygen species, changes in proteins associated with iron homeostasis can be used as an index of cellular responses. One such class of proteins is the iron regulatory proteins (IRPs) that respond to cellular iron concentrations by regulating the translation of proteins involved in iron uptake, storage, and utilization. Therefore, IRPs are considered to be the central control components of cellular iron concentration.

Intraneuronal amyloid beta accumulation and oxidative damage to nucleic acids in Alzheimer disease

In an analysis of amyloid pathology in Alzheimer disease, we used an in situ approach to identify amyloid-beta (Abeta) accumulation and oxidative damage to nucleic acids in postmortem brain tissue of the hippocampal formation from subjects with Alzheimer disease. When carboxyl-terminal-specific antibodies directed against Abeta40 and Abeta42 were used for immunocytochemical analyses, Abeta42 was especially apparent within the neuronal cytoplasm, at sites not detected by the antibody specific to Abeta-oligomer. In comparison to the Abeta42-positive neurons, neurons bearing oxidative damage to nucleic acids were more widely distributed in the hippocampus. Comparative density measurements of the immunoreactivity revealed that levels of intraneuronal Abeta42 were inversely correlated with levels of intraneuronal 8-hydroxyguanosine, an oxidized nucleoside (r=- 0.61, p<0.02). Together with recent evidence that the Abeta peptide can act as an antioxidant, these results suggest that intraneuronal accumulation of non-oligomeric Abeta may be a compensatory response in neurons to oxidative stress in Alzheimer disease.

Determinants of urinary 8-hydroxy-2'-deoxyguanosine in Chinese children with acute leukemia

The 8-hydroxy-2'-deoxyguanosine (8-OHdG), an oxidized nucleoside of DNA, not only is a widely used biomarker for the measurement of endogenous oxidative DNA damage, but might also be a risk factor for many diseases including cancer. Elevated level of urinary 8-OHdG has been detected in patients with various malignancies. In the present study, the level of urinary 8-OHdG was examined in 116 Chinese children with acute leukemia (94 acute lymphoid leukemia, ALL, 22 acute myeloid leukemia, AML), and its correlation with urinary metal elements was investigated. Our result showed that the level of urinary 8-OHdG in children with acute leukemia before treatment was significantly elevated compared with that in normal controls (11.92 +/- 15.42 vs. 4.03 +/- 4.70 ng/mg creatinine, P < 0.05). In particular, urinary 8-OHdG was higher in children with acute leukemia aged under 3 years (20.86 +/- 21.75 ng/mg creatinine) than in those aged 3-15 years (8.09 +/- 9.65 ng/mg creatinine), whereas no differences were shown in terms of gender, parental smoking and education, household income, place of residence, and use of paracetamol. In addition, urinary 8-OHdG levels were similar among different subtypes of acute lymphoid leukemia (ALL) patients. Furthermore, linear regression analysis revealed a significant correlation between urinary 8-OHdG and urinary Cr, but not Fe or As, in group aged <3 years compared with group aged 3-15 years (P = 0.041), indicating that the metal elements may be involved in increasing urinary 8-OHdG level in younger children with acute leukemia. Our results suggest that children with acute leukemia undergo an increased risk of oxidative DNA damage, which may be correlated with high level of Cr exposure in Chinese children with acute leukemia.

RNA oxidation in Alzheimer disease and related neurodegenerative disorders

RNA oxidation and its biological effects are less well studied compared to DNA oxidation. However, RNA may be more susceptible to oxidative insults than DNA, for RNA is largely single-stranded and its bases are not protected by hydrogen bonding and less protected by specific proteins. Also, cellular RNA locates in the vicinity of mitochondria, the primary source of reactive oxygen species. Oxidative modification can occur not only in protein-coding RNAs, but also in non-coding RNAs that have been recently revealed to contribute towards the complexity of the mammalian brain. Damage to coding and non-coding RNAs will cause errors in proteins and disturbances in the regulation of gene expression. While less lethal than mutations in the genome and not inheritable, such sublethal damage to cells might be associated with underlying mechanisms of degeneration, especially age-associated neurodegeneration that is commonly found in the elderly population. Indeed, oxidative RNA damage has been described recently in most of the common neurodegenerative disorders including Alzheimer disease, Parkinson disease, dementia with Lewy bodies and amyotrophic lateral sclerosis. Of particular interest, the accumulating evidence obtained from studies on either human samples or experimental models coincidentally suggests that oxidative RNA damage is a feature in vulnerable neurons at early-stage of these neurodegenerative disorders, indicating that RNA oxidation actively contributes to the onset or the development of the disorders. Further investigations aimed at understanding of the processing mechanisms related to oxidative RNA damage and its consequences may provide significant insights into the pathogenesis of neurodegenerative disorders and lead to better therapeutic strategies.

Biomarkers of exposure to tobacco smoke and environmental pollutants in mothers and their transplacental transfer to the foetus. Part II. Oxidative damage

Oxidative damage to macromolecules may have numerous negative health consequences. We measured oxidative damage to DNA, proteins and lipids in 80 newborns and 79 mothers, analyzed the effect of mother's tobacco smoke exposure on oxidative stress, and assessed correlations between oxidative stress markers and bulky and PAH (polycyclic aromatic hydrocarbons)-specific DNA adducts. Mean levels (+/-S.D.) of 8-oxodeoxyguanosine (8-oxodG) per 10(5) dG in the placenta were 2.85+/-0.78; we did not see a difference between 8-oxodG levels in newborns born to mothers exposed and unexposed to tobacco smoke. Protein carbonyl levels, a marker of protein oxidation, were comparable in the umbilical cord and in maternal venous blood plasma (17.4+/-3.2 and 17.6+/-4.2nmol/ml plasma in newborns and mothers, respectively, p=0.66). Lipid peroxidation measured as levels of 15-F(2t)-isoprostane (15-F(2t)-IsoP) in plasma was significantly higher in newborns than in mothers (362+/-129 and 252+/-130pg/ml in newborns and mothers, respectively, p<0.001). We did not find any effect of tobacco smoke exposure on either biomarker in any group. Levels of both protein carbonyls and 15-F(2t)-IsoP in cord blood significantly correlated with those in maternal plasma (p<0.001). 8-oxodG levels positively correlated with plasma carbonyls in cord plasma, as well as with cotinine levels (marker of tobacco smoke exposure) in maternal plasma. 8-oxodG levels also correlated with bulky DNA adducts in lymphocyte DNA of newborns and mothers and with PAH-DNA adducts in the placenta. Our results showed higher lipid peroxidation in newborns than in mothers, close correlation of analyzed oxidative stress markers between newborns and mothers, and a relationship between oxidative stress and induction of DNA adducts.

8-hydroxy-2' -deoxyguanosine (8-OHdG): A critical biomarker of oxidative stress and carcinogenesis

There is extensive experimental evidence that oxidative damage permanently occurs to lipids of cellular membranes, proteins, and DNA. In nuclear and mitochondrial DNA, 8-hydroxy-2' -deoxyguanosine (8-OHdG) or 8-oxo-7,8-dihydro-2' -deoxyguanosine (8-oxodG) is one of the predominant forms of free radical-induced oxidative lesions, and has therefore been widely used as a biomarker for oxidative stress and carcinogenesis. Studies showed that urinary 8-OHdG is a good biomarker for risk assessment of various cancers and degenerative diseases. The most widely used method of quantitative analysis is high-performance liquid chromatography (HPLC) with electrochemical detection (EC), gas chromatography-mass spectrometry (GC-MS), and HPLC tandem mass spectrometry. In order to resolve the methodological problems encountered in measuring quantitatively 8-OHdG, the European Standards Committee for Oxidative DNA Damage was set up in 1997 to resolve the artifactual oxidation problems during the procedures of isolation and purification of oxidative DNA products. The biomarker 8-OHdG or 8-oxodG has been a pivotal marker for measuring the effect of endogenous oxidative damage to DNA and as a factor of initiation and promotion of carcinogenesis. The biomarker has been used to estimate the DNA damage in humans after exposure to cancer-causing agents, such as tobacco smoke, asbestos fibers, heavy metals, and polycyclic aromatic hydrocarbons. In recent years, 8-OHdG has been used widely in many studies not only as a biomarker for the measurement of endogenous oxidative DNA damage but also as a risk factor for many diseases including cancer.

Oxidative stress biomarkers and lifestyles in Japanese healthy people

The urinary concentrations of 8-isoprostane and 8-hydroxy-2’-deoxyguanosine (8-OHdG), which are biomarkers of oxidative stress, were measured in 677 Japanese people without any diseases, and their correlations with lifestyle facotrs, lifestyle-related blood biochemical parameters, and dietary intake of antioxidative vitamins were investigated. The mean urinary concentration of 8-isoprostane and 8-OHdG was 0.58 ng/mg creatinine and 8.43 ng/mg creatinine, respectively. Mean urinary 8-isoprostane was significantly different in terms of age, gender, smoking and alcohol consumption but not different in terms of body mass index (BMI) and exercise. By multiple regression analysis, urinary 8-isoprostane was significantly influenced by smoking and age. On the other hand, mean urinary 8-OHdG showed differences only by age group. Multiple regression analysis revealed that urinary 8-OHdG was significantly influenced by age, smoking, body weight, levels of high-sensitivity C-reactive protein (Hs-CRP) and low density lipoprotein-cholesterol in females, although it was significantly influenced by body weight in males. The present study shows that urinary 8-isoprostane is associated with lipid peroxidation related-lifestyles such as smoking, and urinary 8-OHdG is associated with arteriosclerosis related-factors such as Hs-CRP. Our findings suggest that 8-isoprostane and 8-OHdG appear to be prospective biomarkers for early prediction of lifestyle related-disease risk at the population level.

Urinary 8-oxodeoxyguanosine levels in children exposed to air pollutants

Oxidative stress is believed to be one of the mechanisms of effects of air pollution to human health. We investigated levels of 8-oxodeoxyguanosine (8-oxodG), a marker of oxidative damage to DNA, in urine samples of 894 children from two districts in the Czech Republic: Teplice and Prachatice. We assessed the association between 8-oxodG levels and exposure to particulate matter of different size: <or=10 microm (PM10), <or=2.5 microm (PM2.5) and carcinogenic polycyclic aromatic hydrocarbons (c-PAHs); as well as between 8-oxodG levels and individual lifestyle, health and pregnancy outcomes. An ELISA technique was used for analysis of 8-oxodG levels. Median levels (range) of 8-oxodG in children from Teplice vs. Prachatice were as follows: 14.6 (3.1-326.5) nmol/mmol vs. 15.2 (3.0-180.8) nmol/mmol creatinine (p=0.34). Levels of 8-oxodG were elevated in children exposed to environmental tobacco smoke (ETS) (p<0.05) and among the Gypsy population (p<0.01). Levels of 8-oxodG decreased with the child's age (p<0.001) and increasing level of the mother's education (p<0.01). Multivariate statistical analyses confirmed the effect of the child's age and ETS exposure on 8-oxodG levels. The exposure to PM10 and PM2.5 measured by stationary monitors during a 7-day period before urine collection, as well as the exposure to c-PAHs measured during 3-day periods 1-3 and 7-9 days before urine collection were identified as factors affecting 8-oxodG levels in multivariate models. The obtained results indicate that 8-oxodG is a sensitive biomarker for measuring the exposure of children to air pollution.

Urinary level of nickel and acute leukaemia in Chinese children

The 8-hydroxy-2′-deoxyguanosine (8-OHdG), an oxidized nucleoside of DNA, not only is a widely used biomarker for the measurement of endogenous oxidative DNA damage but might also be a risk factor for many diseases including cancer. Metal exposure may play an important role in oxidative DNA damage among children. However, few studies on urinary 8-OHdG and metals have been conducted in children with acute leukemia. In the present study, urinary Ni and 8-OHdG were examined in 116 children with acute leukaemia (94 acute lymphoid leukaemia [ALL] and 22 acute myeloid leukaemia [AML]) and 51 healthy child controls. Our result showed that urinary Ni in acute leukaemia patients (ALL: 68.40 ± 133.98, AML: 41.48 ± 76.31 ng/mg creatinine) was significantly higher than that in controls (62.47 ± 124.90 vs 17.63 ± 46.17 ng/mg creatinine, P < 0.05). Similarly, the pretherapy level of urinary 8-OHdG in patients (ALL: 11.83 ± 16.23, AML: 12.36 ± 11.36 ng/mg creatinine) was significantly elevated compared with controls (11.92 ± 15.42 vs 4.03 ± 4.70 ng/mg creatinine, P < 0.05). Moreover, urinary 8-OHdG and urinary Ni showed a weak but significant association with increased risk of childhood leukaemia. The present study suggests that Ni may be an etiologic factor for childhood acute leukaemia by oxidative DNA damage.

Seasonal variability of oxidative stress markers in city bus drivers. Part I. Oxidative damage to DNA

We investigated the seasonal variability of 8-oxodeoxyguanosine (8-oxodG), a marker of oxidative damage to DNA, in urine of 50 bus drivers and 50 controls in Prague, Czech Republic, in three seasons with different levels of air pollution: winter 2005, summer 2006 and winter 2006. The exposure to environmental pollutants (carcinogenic polycyclic aromatic hydrocarbons, c-PAHs, particulate matter (PM), and volatile organic compounds (VOC)) was monitored by personal and/or stationary monitors. For the analysis of 8-oxodG levels, the ELISA technique was used. Bus drivers were exposed to significantly higher levels of c-PAHs in winter 2006, while in the other two seasons the exposure of controls was unexpectedly higher than that of bus drivers. We did not see any difference in VOC exposure between both groups in summer 2006 and in winter 2006; VOC were not monitored in winter 2005. 8-OxodG levels were higher in bus drivers than in controls in all seasons. The median levels of 8-oxodG (nmol/mmol creatinine) in bus drivers vs. controls were as follows: winter 2005: 7.79 vs. 6.12 (p=0.01); summer 2006: 6.91 vs. 5.11 (p<0.01); winter 2006: 5.73 vs. 3.94 (p<0.001). Multivariate logistic regression analysis identified PM2.5 and PM10 levels, measured by stationary monitors during a 3-day period before urine collection, as the only factors significantly affecting 8-oxodG levels, while the levels of c-PAHs had no significant influence.

Oxidative stress biomarkers in sporadic ALS

We aimed to investigate oxidative stress biomarkers in a cross-sectional pilot study of 50 participants with sporadic ALS (SALS) compared to 46 control subjects. We measured urinary 8-oxodeoxyguanosine (8-oxodG), urinary 15-F(2t)-isoprostane (IsoP), and plasma protein carbonyl by ELISA methods. We also determined if ELISA measurement of 8-oxodG could be validated against measures from high-pressure liquid chromatography coupled with electrochemical detection, the current standard method. We found that 8-oxodG and IsoP levels adjusted for creatinine were significantly elevated in SALS participants. These differences persisted after age and gender were controlled in regression analyses. These markers are highly and positively correlated with each other. 8-oxodG measured by the two techniques from the same urine sample were positively correlated (p<.0001). Protein carbonyl was not different between SALS participants and controls. In conclusion, using ELISA, we confirmed that certain oxidative stress biomarkers were elevated in SALS participants. ELISA may be reliable and thus useful in epidemiology studies requiring large numbers of samples to determine the significance of increased oxidative stress markers in SALS. Further studies are required.

Sublethal RNA oxidation as a mechanism for neurodegenerative disease

Although cellular RNA is subjected to the same oxidative insults as DNA and other cellular macromolecules, oxidative damage to RNA has not been a major focus in investigations of the biological consequences of free radical damage. In fact, because it is largely single-stranded and its bases lack the protection of hydrogen bonding and binding by specific proteins, RNA may be more susceptible to oxidative insults than is DNA. Oxidative damage to protein-coding RNA or non-coding RNA will, in turn, potentially cause errors in proteins and/or dysregulation of gene expression. While less lethal than mutations in the genome, such sublethal insults to cells might be associated with underlying mechanisms of several chronic diseases, including neurodegenerative disease. Recently, oxidative RNA damage has been described in several neurodegenerative diseases including Alzheimer disease, Parkinson disease, dementia with Lewy bodies, and prion diseases. Of particular interest, oxidative RNA damage can be demonstrated in vulnerable neurons early in disease, suggesting that RNA oxidation may actively contribute to the onset of the disease. An increasing body of evidence suggests that, mechanistically speaking, the detrimental effects of oxidative RNA damage to protein synthesis are attenuated, at least in part, by the existence of protective mechanisms that prevent the incorporation of the damaged ribonucleotides into the translational machinery. Further investigations aimed at understanding the processing mechanisms related to oxidative RNA damage and its consequences may provide significant insights into the pathogenesis of neurodegenerative and other degenerative diseases and lead to better therapeutic strategies.

Capillary electrophoresis of oxidative DNA damage

Urinary 8-hydroxy-2'-deoxyguanosine (8OHdG) is an excellent marker of oxidative DNA damage. Until now, urinary 8OHdG has been measured by high-performance liquid chromatography with electrochemical detection. A simple and sensitive method for the analysis of urinary 8OHdG by capillary electrophoresis with end-column amperometric detection has been developed and is described in this chapter. A single-step solid-phase extraction procedure was optimized and used for extracting 8OHdG from human urine. To improve the sensitivity of this method, a new focusing technique based on a dynamic pH junction was used. In the end, the urinary concentration of 8OHdG in healthy persons, patients with cancer, patients with diabetic nephropathy, and smokers was determined. Emphasis is focused on the establishment and application of the methods.

Hepatitis B virus infection contributes to oxidative stress in a population exposed to aflatoxin B1 and high-risk for hepatocellular carcinoma

Biomarkers of hepatitis B virus (HBV) infection, aflatoxin B1 (AFB1) exposure and oxidative stress were detected in 71 hepatocellular carcinoma (HCC) patients and 694 controls from southern China. Plasma level of AFB1-albumin-adducts (AAA) and protein carbonyl content (PCC) were significantly higher in the 71 HCC cases than in any age/gender matched HBV sero-status groups (p<0.001). HCC patients positive for the p53-249 G-T mutation had a marginally higher level of PCC than those negative for the mutation (p=0.077). HBV infection had a prominent influence on the association between AFB1 exposure and oxidative stress biomarkers in the controls. Our study indicates a significant contribution from HBV infection to oxidative stress in a population with AFB1 exposure which might substantially increase risk for HCC in this region.

Urinary biomarker of oxidative stress correlating with outcome in critically septic patients

OBJECTIVE

To determine whether urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG), an in vivo parameter of oxidative stress, is correlated with the outcome of critically septic patients.

DESIGN AND SETTING

Clinical outcome study in an adult medical ICU.

PATIENTS

Eighty-five consecutive septic patients: 59 men and 26 women.

MEASUREMENTS AND RESULTS

Urinary 8-OHdG was analyzed using isotope-dilution liquid chromatography with tandem mass spectrometry (LC/MS/MS). ICU mortality in these 85 septic patients was 25.9% (n = 22) and hospital mortality 38.8% (n = 33). APACHE II scores of survivors on day 1, on day 3, and the difference between them differed significantly from those of nonsurvivors (day 1, 21.0 +/- 7.1 vs. 25.9 +/-8.0; day 3, 15.0 +/- 5.8 vs. 23.2 +/- 8.3; difference, 6.0 +/- 5.5 vs. 1.7 +/- 6.6). Urinary 8-OHdG was significantly lower in survivors than in nonsurvivors on day 1 (1.8 +/- 2.4 vs. 3.0 +/- 2.4). The area under receiver operating characteristic curve analysis for the association between day 1 urinary 8-OHdG and ICU mortality was 0.71. The comparison performed upon discharge from hospital revealed similar results.

CONCLUSIONS

This is a preliminary study. The excretion of the urinary 8-OHdG, as measured using isotope-dilution LC/MS/MS, as the APACHE II score, were correlated with the outcome of critically septic patients in medical ICU.

Assessing biomarkers of oxidative stress: analysis of guanosine and oxidized guanosine nucleotide triphosphates by high performance liquid chromatography with electrochemical detection

Oxidation of the guanosine moiety in DNA has become a hallmark biomarker in assessing oxidative stress. The oxidation of guanosine in the nucleotide triphosphate pool has been overlooked due to the lack of a reliable methodology. This method describes a sample processing and high performance liquid chromatography with electrochemical detection protocol for the analysis of the cellular pool of guanosine triphosphates and oxidized guanosine triphosphates. Validation of this method is demonstrated along with evaluation of these analytes in control and oxidizing conditions in vitro and in HEK 293T cells. Oxidation of this triphosphate pool occurred independently of oxidation to DNA.

Cancer prevention with freeze-dried berries and berry components

Our laboratory is developing a food-based approach to the prevention of esophageal and colon cancer utilizing freeze-dried berries and berry extracts. Dietary freeze-dried berries were shown to inhibit chemically induced cancer of the rodent esophagus by 30-60% and of the colon by up to 80%. The berries are effective at both the initiation and promotion/progression stages of tumor development. Berries inhibit tumor initiation events by influencing carcinogen metabolism, resulting in reduced levels of carcinogen-induced DNA damage. They inhibit promotion/progression events by reducing the growth rate of pre-malignant cells, promoting apoptosis, reducing parameters of tissue inflammation and inhibiting angiogenesis. On a molecular level, berries modulate the expression of genes involved with proliferation, apoptosis, inflammation and angiogenesis. We have recently initiated clinical trials; results from a toxicity study indicated that freeze-dried black raspberries are well tolerated in humans when administered orally for 7 days at a dose of 45 g per day. Several Phase IIa clinical trials are underway in patients at high risk for esophagus and colon cancer; i.e., Barrett's esophagus, esophageal dysplasia and colonic polyps, to determine if berries will modulate various histological and molecular biomarkers of development of these diseases.

DNA damage, a biomarker of carcinogenesis: its measurement and modulation by diet and environment

Free radicals and other reactive oxygen or nitrogen species are constantly generated in vivo and can cause oxidative damage to DNA. This damage has been implicated to be important in many diseases, including cancer. The assessment of damage in various biological matrices, such as tissues, cells, and urine, is vital to understanding this role and subsequently devising intervention strategies. During the last 20 years, many analytical techniques have been developed to monitor oxidative DNA base damage. High-performance liquid chromatography-electrochemical detection and gas chromatography-mass spectrometry are the two pioneering contributions to the field. Currently, the arsenal of methods available include the promising high-performance liquid chromatography-tandem mass spectrometry technique, capillary electrophoresis, 32P-postlabeling, antibody-base immunoassays, and assays involving the use of DNA repair glycosylases such as the comet assay. The objective of this review is to discuss the biological significance of oxidative DNA damage, evaluate the effectiveness of several techniques for measurement of oxidative DNA damage in various biological samples and review current research on factors (dietary and non-dietary) that influence DNA oxidative damage using these techniques.