Experimental study of oxidative DNA damage

Traffic Density Exposure, Oxidative Stress Biomarkers and Plasma Metabolomics in a Population-Based Sample: The Hortega Study

Exposure to traffic-related air pollution (TRAP) generates oxidative stress, with downstream effects at the metabolic level. Human studies of traffic density and metabolomic markers, however, are rare. The main objective of this study was to evaluate the cross-sectional association between traffic density in the street of residence with oxidative stress and metabolomic profiles measured in a population-based sample from Spain. We also explored in silico the potential biological implications of the findings. Secondarily, we assessed the contribution of oxidative stress to the association between exposure to traffic density and variation in plasma metabolite levels. Traffic density was defined as the average daily traffic volume over an entire year within a buffer of 50 m around the participants' residence. Plasma metabolomic profiles and urine oxidative stress biomarkers were measured in samples from 1181 Hortega Study participants by nuclear magnetic resonance spectroscopy and high-performance liquid chromatography, respectively. Traffic density was associated with 7 (out of 49) plasma metabolites, including amino acids, fatty acids, products of bacterial and energy metabolism and fluid balance metabolites. Regarding urine oxidative stress biomarkers, traffic associations were positive for GSSG/GSH% and negative for MDA. A total of 12 KEGG pathways were linked to traffic-related metabolites. In a protein network from genes included in over-represented pathways and 63 redox-related candidate genes, we observed relevant proteins from the glutathione cycle. GSSG/GSH% and MDA accounted for 14.6% and 12.2% of changes in isobutyrate and the CH2CH2CO fatty acid moiety, respectively, which is attributable to traffic exposure. At the population level, exposure to traffic density was associated with specific urine oxidative stress and plasma metabolites. Although our results support a role of oxidative stress as a biological intermediary of traffic-related metabolic alterations, with potential implications for the co-bacterial and lipid metabolism, additional mechanistic and prospective studies are needed to confirm our findings.

Velvet antler water extract protects porcine oocytes from lipopolysaccharide-induced meiotic defects

Previous studies have demonstrated that lipopolysaccharide (LPS), as a central toxic factor of gram-negative bacteria, can induce oxidative stress and cellular inflammation to result in the impairment of female fertility in different organisms. Particularly, it has harmful effects on the oocyte quality and subsequent embryonic development. However, the approach concerning how to prevent oocytes from LPS-induced deterioration still remains largely unexplored. We assessed the effective influences of velvet antler water extract (VAWE) by immunostaining and fluorescence intensity quantification on the meiotic maturation, mitochondrial function and sperm binding ability of oocytes under oxidative stress. Here, we report that VAWE treatment restores the quality of porcine oocytes exposed to LPS. Specifically, LPS exposure contributed to the failed oocyte maturation, reduced sperm binding ability and fertilization capability by disturbing the dynamics and arrangement of meiotic apparatuses and organelles, including spindle assembly, chromosome alignment, actin polymerization, mitochondrial dynamics and cortical granule distribution, the indicators of oocyte nuclear and cytoplasmic maturation. Notably, VAWE treatment recovered these meiotic defects by removing the LPS-induced excessive ROS and thus inhibiting the apoptosis. Collectively, our study illustrates that VAWE treatment is a feasible strategy to improve the oocyte quality deteriorated by the LPS-induced oxidative stress.

Mutagenic and DNA repair activity in traffic policemen: a case-crossover study

Background

Emissions from vehicles are composed of heterogeneous mixtures of hazardous substances; several pollutants such as Polycyclic Aromatic Hydrocarbons (PAHs) are amongst the most dangerous substances detected in urban monitoring. A cohort of traffic policemen usually occupationally exposed to PAHs present in the urban environment were examined in order to assess the mutagenicity and DNA capacity repair.

Methods

Seventy-two urban traffic policemen working in Catania's metropolitan area were enrolled in the study. Two spot urine samples were collected from each subject during the whole working cycle as follows: sample 1 (S1), pre-shift on day 1; sample 2 (S2) post-shift on day 6. 1-hydroxypyrene (1-OHP) was measured to serve as an indirect exposure indicator. Urinary mutagenic activity was assessed through the plate incorporation pre-incubation technique with S9, using YG1024 Salmonella typhimurium strain over-sensitive to PAH metabolite. Concentrations of urinary 8-oxodG were measured using liquid chromatography tandem mass spectrometry.

Results

As regards the exposure to PAHs, results highlighted a statistically significant difference (p < 0.001) between pre-shift on day 1 and post-shift on day 6 levels. Mutagenic activity was detected in 38 (66%) workers on S1 and in 47 (81%) on S2. Also 8-oxodG analysis showed a statistically significant difference between S1 and S2 sampling.

Conclusions

This study demonstrated that occupational exposure to pollutants from traffic emission, assessed via 1-OHP measurements in urine, may lead to DNA repair and mutagenic activity, in line with other studies.

Human 8-oxoguanine DNA glycosylase gene polymorphism (Ser326Cys) and cancer risk: updated meta-analysis

Genetic polymorphism of human 8-oxoguanine glycosylase 1 (hOGG1) has been reported to have a relationship with the risk of the development of various cancers. Many studies have described the influence of Ser326Cys polymorphism of the hOGG1 gene on cancer susceptibility. However, the results have remained inconclusive and controversial. Therefore, we performed a meta-analysis to more precisely determine the relationship between the hOGG1 polymorphism and the development of cancer.Electronic databases including PubMed, Embase, Google Scholar, and the Korean Studies Information Service System (KISS) were searched. The odds ratio (OR), 95% confidence interval (CI), and p value were calculated to assess the strength of the association with the risk of cancer using Comprehensive Meta-analysis software (Corporation, NJ, USA). The 127 studies including 38,757 cancer patients and 50,177 control subjects were analyzed for the meta-analysis.Our meta-analysis revealed that G allele of Ser326Cys polymorphism of the hOGG1 gene statistically increased the susceptibility of cancer (all population, OR = 1.092, 95% CI = 1.051-1.134, p < 0.001; in Asian, OR = 1.095, 95% CI = 1.048-1.145, p < 0.001; in Caucasian, OR = 1.097, 95% CI = 1.033-1.179, p = 0.002). Also, other genotype models showed significant association with cancer (p < 0.05, respectively).The present meta-analysis concluded that the G allele was associated with an increased risk of cancer. It suggested that the hOGG1 polymorphism may be a candidate marker of cancer.

Effect of Cruciferous Vegetable Intake on Oxidative Stress Biomarkers: Differences by Breast Cancer Status

This post hoc analysis examined cruciferous vegetable intake on urinary oxidative metabolites in postmenopausal women. Intervention participants (n = 69) received cruciferous vegetables (≥14 cups/week) during a 3-week period. First morning urine measured 8-isoprostane and 8-hydroxy-2'-deoxyguanosine. Dietary intake was estimated using 24-h recalls. When stratified by history of breast cancer, those with breast cancer had significantly lower post-intervention urinary 8-hydroxy-2'-deoxyguanosine values in the intervention arm versus. the control arm (1.1 ng/mL vs. 3.2 ng/mL, p = .01) after adjustment for baseline 8-hydroxy-2'-deoxyguanosine. This was not observed in those without breast cancer. Further work is needed to understand the role of breast cancer in these relationships.

Nitro-, Azo-, and Amino Derivatives of Ebselen: Synthesis, Structure, and Cytoprotective Effects

Novel azo-bis-ebselen compounds 7 were prepared by reduction of 7-nitro-2-aryl-1,2-benzisoselenazol-3(2H)-ones 3 and 6 with sodium benzenetellurolate, NaTeC₆H₅, and by reaction of 2-bromo-3-nitrobenzamides with Na₂Se₂. The X-ray structure of 7b showed that the molecule, due to strong intramolecular secondary Se···N interactions, is completely planar. Azo-compounds 7 upon further reaction with NaTeC₆H₅ were reductively cleaved to provide 2 equiv of the corresponding aromatic amine. The weak Se-N bond was not stable enough to survive the reaction conditions, and diselenides 8 were isolated after workup. Whereas azo-bis-ebselens 7 were poor mimics of the glutathione peroxidase (GPx)-enzymes, nitroebselens 3, 6, and 11b and diselenides 8 were 3-6-fold more active than ebselen. Based on ⁷⁷Se NMR spectroscopy, a catalytic cycle for diselenide 8b, involving aminoebselen 14, was proposed. As assessed by chemiluminescence measurements, the good GPx-mimics could reduce production of reactive oxygen species (ROS) in stimulated human mononuclear cells more efficiently than Trolox. No toxic effects of the compounds were seen in MC3T3-cells at 25 μM.

Investigation of the effect of the efficiency of noise at different intensities on the DNA of the newborns

Hearing loss can occur in newborns exposed to high-level noise; noise exposure can cause more physiological stress and can lead to DNA damage. This study was designed to determine DNA damage in newborn rats exposed to sound at different concentrations. For this purpose, 28 newborn (3-6 days old) rats were divided into four groups of 7 rats in each group (Control and Groups of 40 decibel (dB), 70 dB, and 110 dB]. In the experimental groups, 40 dB, 70 dB, and 110 dB (7.5-15 kHz) of sound was applied to the experimental groups for 30 min a day for 7 days. DNA damage levels in the serums obtained from this study were determined by the enzyme-linked immunosorbent assay (ELISA) method. According to this, it was determined that DNA damage in the group exposed to 110 dB showed a statistically significant increase (P < 0.05) compared to the compared to the control, 40 dB, and 70 dB groups. Related to the subject, it was concluded that DNA damage may occur in newborns exposed to 110 dB or higher sound in neonatal units, wards, and home environments with newborn babies. Mothers should be warned about this situation and noise should be kept under 110 dB volume in the environments with the newborns.

Single nucleotide polymorphisms in the Trx2/TXNIP and TrxR2 genes of the mitochondrial thioredoxin antioxidant system and the risk of diabetic retinopathy in patients with Type 2 diabetes mellitus

BACKGROUND

Oxidative stress plays an important role in the pathogenesis of diabetes and its complications. The aim of this study was to examine the possible association between seven single nucleotide polymorphisms (SNPs) of the Trx2/TXNIP and TrxR2 genes encoding proteins involved in the thioredoxin antioxidant defence system and the risk of diabetic retinopthy (DR).

DESIGN

Cross-sectional case-control study.

PARTICIPANTS

A total of 802 Slovenian patients with Type 2 diabetes mellitus; 277 patients with DR and 525 with no DR were enrolled.

METHODS

Patients genotypes of the SNPs; including rs8140110, rs7211, rs7212, rs4755, rs1548357, rs4485648 and rs5748469 were determined by the competitive allele specific PCR method.

MAIN OUTCOME MEASURES

Each genotype of examined SNPs was regressed in a logistic model, assuming the co-dominant, dominant and the recessive models of inheritance with covariates of duration of diabetes, HbA1c, insulin therapy, total cholesterol and LDL cholesterol levels.

RESULTS

In the present study, for the first time we identified an association between the rs4485648 polymorphism of the TrxR2 gene and DR in Caucasians with Type 2 DM. The estimated ORs of adjusted logistic regression models were found to be as follows: 4.4 for CT heterozygotes, 4.3 for TT homozygotes (co-dominant genetic model) and 4.4 for CT+TT genotypes (dominant genetic model).

CONCLUSIONS

In our case-control study we were not able to demonstrate any association between rs8140110, rs7211, rs7212, rs4755, rs1548357, and rs5748469 and DR, however, our findings provide evidence that the rs4485648 polymorphism of the TrxR2 gene might exert an independent effect on the development of DR.

Sulfur and selenium antioxidants: challenging radical scavenging mechanisms and developing structure-activity relationships based on metal binding

Because sulfur and selenium antioxidants can prevent oxidative damage, numerous animal and clinical trials have investigated the ability of these compounds to prevent the oxidative stress that is an underlying cause of cardiovascular disease, Alzheimer's disease, and cancer, among others. One of the most common sources of oxidative damage is metal-generated hydroxyl radical; however, very little research has focused on determining the metal-binding abilities and structural attributes that affect oxidative damage prevention by sulfur and selenium compounds. In this review, we describe our ongoing investigations into sulfur and selenium antioxidant prevention of iron- and copper-mediated oxidative DNA damage. We determined that many sulfur and selenium compounds inhibit Cu(I)-mediated DNA damage and that DNA damage prevention varies dramatically when Fe(II) is used in place of Cu(I) to generate hydroxyl radical. Oxidation potentials of the sulfur or selenium compounds do not correlate with their ability to prevent DNA damage, highlighting the importance of metal coordination rather than reactive oxygen species scavenging as an antioxidant mechanism. Additional gel electrophoresis, mass spectrometry, and UV-visible studies confirmed sulfur and selenium antioxidant binding to Cu(I) and Fe(II). Ultimately, our studies established that both the hydroxyl-radical-generating metal ion and the chemical environment of the sulfur or selenium significantly affect DNA damage prevention and that metal coordination is an essential mechanism for these antioxidants.

Exposure to mitochondrial genotoxins and dopaminergic neurodegeneration in Caenorhabditis elegans

Neurodegeneration has been correlated with mitochondrial DNA (mtDNA) damage and exposure to environmental toxins, but causation is unclear. We investigated the ability of several known environmental genotoxins and neurotoxins to cause mtDNA damage, mtDNA depletion, and neurodegeneration in Caenorhabditis elegans. We found that paraquat, cadmium chloride and aflatoxin B₁ caused more mitochondrial than nuclear DNA damage, and paraquat and aflatoxin B₁ also caused dopaminergic neurodegeneration. 6-hydroxydopamine (6-OHDA) caused similar levels of mitochondrial and nuclear DNA damage. To further test whether the neurodegeneration could be attributed to the observed mtDNA damage, C. elegans were exposed to repeated low-dose ultraviolet C radiation (UVC) that resulted in persistent mtDNA damage; this exposure also resulted in dopaminergic neurodegeneration. Damage to GABAergic neurons and pharyngeal muscle cells was not detected. We also found that fasting at the first larval stage was protective in dopaminergic neurons against 6-OHDA-induced neurodegeneration. Finally, we found that dopaminergic neurons in C. elegans are capable of regeneration after laser surgery. Our findings are consistent with a causal role for mitochondrial DNA damage in neurodegeneration, but also support non mtDNA-mediated mechanisms.

The hOGG1 Ser326Cys polymorphism contributes to digestive system cancer susceptibility: evidence from 48 case-control studies

The Ser326Cys polymorphism in the human 8-oxogunaine DNA glycosylase (hOGG1) gene had been implicated in cancer susceptibility. Studies investigating the associations between the Ser326Cys polymorphism and digestion cancer susceptibility showed conflicting results. Therefore, a meta-analysis was performed to derive a more precise estimation of the relationship. We conducted a meta-analysis of 48 studies that included 12,073 cancer cases and 19,557 case-free controls. We assessed the strength of the association using odds ratios (ORs) with 95% confidence intervals (CIs). In our analysis, the hOGG1 Ser326Cys polymorphism was significantly associated with the risk of digestive system cancers (Cys/Cys vs. Ser/Ser: OR = 1.17, 95% CI = 1.00-1.35, P < 0.001; Cys/Cys vs. Cys/Ser + Ser/Ser: OR = 1.14, 95% CI = 1.00-1.29, P < 0.001). In subgroup analyses by cancer types, we found that the hOGG1 Ser326Cys polymorphism may increase hepatocellular cancer and colorectal cancer risks, but decrease the risk of oral cancer. These findings supported that hOGG1 Ser326Cys polymorphism may contribute to the susceptibility of digestive cancers.

Plasma selenium levels and oxidative stress biomarkers: a gene-environment interaction population-based study

The role of selenium exposure in preventing chronic disease is controversial, especially in selenium-repleted populations. At high concentrations, selenium exposure may increase oxidative stress. Studies evaluating the interaction of genetic variation in genes involved in oxidative stress pathways and selenium are scarce. We evaluated the cross-sectional association of plasma selenium concentrations with oxidative stress levels, measured as oxidized to reduced glutathione ratio (GSSG/GSH), malondialdehyde (MDA), and 8-oxo-7,8-dihydroguanine (8-oxo-dG) in urine, and the interacting role of genetic variation in oxidative stress candidate genes, in a representative sample of 1445 men and women aged 18-85 years from Spain. The geometric mean of plasma selenium levels in the study sample was 84.76 µg/L. In fully adjusted models the geometric mean ratios for oxidative stress biomarker levels comparing the highest to the lowest quintiles of plasma selenium levels were 0.61 (0.50-0.76) for GSSG/GSH, 0.89 (0.79-1.00) for MDA, and 1.06 (0.96-1.18) for 8-oxo-dG. We observed nonlinear dose-responses of selenium exposure and oxidative stress biomarkers, with plasma selenium concentrations above ~110 μg/L being positively associated with 8-oxo-dG, but inversely associated with GSSG/GSH and MDA. In addition, we identified potential risk genotypes associated with increased levels of oxidative stress markers with high selenium levels. Our findings support that high selenium levels increase oxidative stress in some biological processes. More studies are needed to disentangle the complexity of selenium biology and the relevance of potential gene-selenium interactions in relation to health outcomes in human populations.

SERMs attenuate estrogen-induced malignant transformation of human mammary epithelial cells by upregulating detoxification of oxidative metabolites

The risk of developing hormone-dependent cancers with long-term exposure to estrogens is attributed both to proliferative, hormonal actions at the estrogen receptor (ER) and to chemical carcinogenesis elicited by genotoxic, oxidative estrogen metabolites. Nontumorigenic MCF-10A human breast epithelial cells are classified as ER(-) and undergo estrogen-induced malignant transformation. Selective estrogen receptor modulators (SERM), in use for breast cancer chemoprevention and for postmenopausal osteoporosis, were observed to inhibit malignant transformation, as measured by anchorage-independent colony growth. This chemopreventive activity was observed to correlate with reduced levels of oxidative estrogen metabolites, cellular reactive oxygen species (ROS), and DNA oxidation. The ability of raloxifene, desmethylarzoxifene (DMA), and bazedoxifene to inhibit this chemical carcinogenesis pathway was not shared by 4-hydroxytamoxifen. Regulation of phase II rather than phase I metabolic enzymes was implicated mechanistically: raloxifene and DMA were observed to upregulate sulfotransferase (SULT 1E1) and glucuronidase (UGT 1A1). The results support upregulation of phase II metabolism in detoxification of catechol estrogen metabolites leading to attenuated ROS formation as a mechanism for inhibition of malignant transformation by a subset of clinically important SERMs.

Genetic variant in APE1 gene promoter contributes to cervical cancer risk

OBJECTIVE

Apurinic/apyrimidinic endonuclease 1 (APE1) is an essential enzyme in the base excision repair pathway, which plays an important role in repairing DNA damage caused by oxidation and alkylation. However, the exact mechanism of APE1 associated with cervical cancer risk is still unknown. In this study, we explored whether the APE1 -656T>G polymorphism contributed to the risk of cervical cancer.

STUDY DESIGN

In the hospital-based case-control study, 306 cervical cancer cases and 306 cancer-free controls were genotyped for the APE1 -656T>G polymorphism using the polymerase chain reaction restriction fragment length polymorphism method. Luciferase reporter assay and electrophoretic mobility shift assay were used to evaluate the APE1 transcriptional activity and the binding ability of transcriptional factors to the APE1 promoter, respectively.

RESULTS

Logistic regression analysis showed that individuals with the APE1 -656 TG/GG genotypes had a significantly reduced risk of cervical cancer compared with the TT genotype (adjusted odds ratio, 0.61; 95% confidence interval, 0.42-0.89). The luciferase assays in 3 cell lines showed that the APE1 -656T>G substitution can increase the expression of APE1, which was consistent with the finding of association study. Electrophoretic mobility shift assay further indicated that the APE1 -656T>G polymorphism enhanced the binding affinity of transcriptional factors to the promoter region.

CONCLUSION

These findings suggested that the APE1 -656T>G polymorphism was associated with cervical cancer risk in a Chinese population by affecting the binding affinity of transcriptional factors to the promoter, leading to an increased expression level of APE1.

Oxidatively damaged DNA in animals exposed to particles

Exposure to combustion-derived particles, quartz and asbestos is associated with increased levels of oxidized and mutagenic DNA lesions. The aim of this survey was to critically assess the measurements of oxidatively damaged DNA as marker of particle-induced genotoxicity in animal tissues. Publications based on non-optimal assays of 8-oxo-7,8-dihydroguanine by antibodies and/or unrealistically high levels of 8-oxo-7,8-dihydroguanine (suggesting experimental problems due to spurious oxidation of DNA) reported more induction of DNA damage after exposure to particles than did the publications based on optimal methods. The majority of studies have used single intracavitary administration or inhalation with dose rates exceeding the pulmonary overload threshold, resulting in cytotoxicity and inflammation. It is unclear whether this is relevant for the much lower human exposure levels. Still, there was linear dose-response relationship for 8-oxo-7,8-dihydroguanine in lung tissue without obvious signs of a threshold. The dose-response function was also dependent on chemical composition and other characteristics of the administered particles, whereas dependence on species and strain could not be equivocally determined. Roles of cytotoxicity or inflammation for oxidatively induced DNA damage could not be documented or refuted. Studies on exposure to particles in the gastrointestinal tract showed consistently increased levels of 8-oxo-7,8-dihydroguanine in the liver. Collectively, there is evidence from animal experimental models that both pulmonary and gastrointestinal tract exposure to particles are associated with elevated levels of oxidatively damaged DNA in the lung and internal organs. However, there is a paucity of studies on pulmonary exposure to low doses of particles that are relevant for hazard/risk assessment.

Polymorphism of the DNA repair genes RAD51 and XRCC2 in smoking- and drinking-related laryngeal cancer in a Polish population

INTRODUCTION

Cigarette smoke and alcohol can generate reactive oxygen species, which may induce DNA double-strand breaks (DSBs), the most serious DNA lesion. In humans, DSBs are repaired mainly by non-homologous end joining and homologous recombination repair (HRR). Several polymorphisms in the DNA repair gene have been extensively studied in the association with various human cancers. In the present work we investigated the association between polymorphisms of two HRR genes, XRCC2 and RAD51, and tobacco- and alcohol-related larynx cancer in a Polish population.

MATERIAL AND METHODS

Two polymorphisms of the XRCC2 gene, -41657C > T (rs718282) and 31479G > A (rs3218536), as well as one polymorphism of the RAD51 gene, -135G > C (rs1801320), were investigated by PCR-RFLP in 253 patients with larynx cancer and 253 age- and sex-matched non-cancer controls.

RESULTS

Analysis of the gene-smoking and -drinking interactions revealed a weak association between larynx cancer and the -41657C > T polymorphisms of the XRCC2 gene among the moderate alcohol drinkers. The C allele of the -135G > C polymorphism of RAD51 increased cancer risk in the smoker group. Increased risk was also found for heavy drinkers. Additionally, there were no significant differences between distributions of genotypes in subgroups assigned to different TNM stages and grades.

CONCLUSIONS

The results indicated that the -135G > C polymorphism of the RAD51 gene may be associated with smoking- and drinking-related larynx cancer in Poland.

Meta-analysis of the association between hOGG1 Ser326Cys polymorphism and risk of colorectal cancer based on case--control studies. J Cancer Res Clin Oncol. 2012;138:1443-1448. [PMID: 22526153 DOI: 10.1007/s00432-012-1197-z]

PURPOSE

Oxidative DNA damage caused by reactive oxygen species plays an important role in cancer development. The association between colorectal cancer and hOGG1 Ser326Cys polymorphisms has been analyzed in several published studies, but mixed findings have been reported. The main purpose of this study was to integrate previous results and explore whether the polymorphism of hOGG1 is associated with susceptibility to colorectal cancer.

METHODS

PubMed, Embase, Google Scholar, and Cbmdisc were searched for studies on the relationship of hOGG1 SNPs and the incidence of colorectal cancer (CRC). Eligible articles were included for data extraction. The main outcome was the frequency of hOGG1 Ser326Cys polymorphisms between cases and controls. Comparison of the distribution of SNP was mainly performed using Review Manager 5.0.

RESULTS

A total of 4,174 cases and 6,196 controls from 12 studies were included for this meta-analysis. Overall, stratified by ethnicity or population source, no significant associations between the hOGG1 Ser326Cys polymorphism and colorectal cancer risk were found for Cys/Cys allele (OR = 1.146; 95 % CI: 0.978-1.342, P = 0.091), Cys/Cys + Cys/Ser versus Ser/Ser (OR = 1.045; 95 % CI: 0.975-1.121, P = 0.213) Cys/Cys Versus Ser/Ser (OR = 1.243; 95 % CI: 0.979-1.578, P = 0.074) and Cys/Cys versus Cys/Ser + Ser/Ser (OR = 1.198; 95 % CI: 0.959-1.496, P = 0.111) in a recessive model and (OR = 1.494; 95 % CI: 1.023-2.181, P = 0.038) in a homozygote contrast. However, if apart from sensitivity analysis, there was some evidence to indicate that significantly increased risks were found among European plus American subjects, who are mostly Caucasian (OR = 1.444; 95 % CI: 1.017-2.05 Cys/Cys vs. Ser/Cys + Ser/Ser; P = 0.04). In the subgroup analyses, we also did not found any association between hOGG1 Ser326Cys polymorphism and certain populations and smokers.

CONCLUSIONS

This meta-analysis suggests that there is no robust association between hOGG1 Ser326Cys polymorphism and colorectal cancer. Because of the limitation of meta-analysis, this finding demands further investigation.

Longevity in mice is promoted by probiotic-induced suppression of colonic senescence dependent on upregulation of gut bacterial polyamine production. PLoS One. 2011;6:e23652. [PMID: 21858192 PMCID: PMC3156754 DOI: 10.1371/journal.pone.0023652]

Background

Chronic low-grade inflammation is recognized as an important factor contributing to senescence and age-related diseases. In mammals, levels of polyamines (PAs) decrease during the ageing process; PAs are known to decrease systemic inflammation by inhibiting inflammatory cytokine synthesis in macrophages. Reductions in intestinal luminal PAs levels have been associated with intestinal barrier dysfunction. The probiotic strain Bifidobacterium animalis subsp. lactis LKM512 is known to increase intestinal luminal PA concentrations.

Methodology/Principal Findings

We supplemented the diet of 10-month-old Crj:CD-1 female mice with LKM512 for 11 months, while the controls received no supplementation. Survival rates were compared using Kaplan–Meier survival curves. LKM512-treated mice survived significantly longer than controls (P<0.001); moreover, skin ulcers and tumors were more common in the control mice. We then analyzed inflammatory and intestinal conditions by measuring several markers using HPLC, ELISA, reverse transcription-quantitative PCR, and histological slices. LKM512 mice showed altered 16S rRNA gene expression of several predominant intestinal bacterial groups. The fecal concentrations of PAs, but not of short-chain fatty acids, were significantly higher in LKM512-treated mice (P<0.05). Colonic mucosal function was also better in LKM512 mice, with increased mucus secretion and better maintenance of tight junctions. Changes in gene expression levels were evaluated using the NimbleGen mouse DNA microarray. LKM512 administration also downregulated the expression of ageing-associated and inflammation-associated genes and gene expression levels in 21-month-old LKM512-treated mice resembled those in 10-month-old untreated (younger) mice.

Conclusion/Significance

Our study demonstrated increased longevity in mice following probiotic treatment with LKM512, possibly due to the suppression of chronic low-grade inflammation in the colon induced by higher PA levels. This indicates that ingestion of specific probiotics may be an easy approach for improving intestinal health and increasing lifespan. Further studies are required to clarify its effectiveness in humans.

Monocrotophos induced apoptosis in PC12 cells: role of xenobiotic metabolizing cytochrome P450s

Monocrotophos (MCP) is a widely used organophosphate (OP) pesticide. We studied apoptotic changes and their correlation with expression of selected cytochrome P450s (CYPs) in PC12 cells exposed to MCP. A significant induction in reactive oxygen species (ROS) and decrease in glutathione (GSH) levels were observed in cells exposed to MCP. Following the exposure of PC12 cells to MCP (10⁻⁵ M), the levels of protein and mRNA expressions of caspase-3/9, Bax, Bcl₂, P⁵³, P²¹, GSTP1-1 were significantly upregulated, whereas the levels of Bclw, Mcl1 were downregulated. A significant induction in the expression of CYP1A1/1A2, 2B1/2B2, 2E1 was also observed in PC12 cells exposed to MCP (10⁻⁵ M), whereas induction of CYPs was insignificant in cells exposed to 10⁻⁶ M concentration of MCP. We believe that this is the first report showing altered expressions of selected CYPs in MCP-induced apoptosis in PC12 cells. These apoptotic changes were mitochondria mediated and regulated by caspase cascade. Our data confirm the involvement of specific CYPs in MCP-induced apoptosis in PC12 cells and also identifies possible cellular and molecular mechanisms of organophosphate pesticide-induced apoptosis in neuronal cells.

Oxidative damage to DNA and lipids: correlation with protein glycation in patients with type 1 diabetes

Diabetic hyperglycemia is associated with increased production of reactive oxygen species (ROS). ROS reacts with DNA resulting in various products, such as 8-hydroxydeoxyguanosine (8-OHdG), that excrete in urine owing to DNA repair processes. Urinary 8-OHdG has been proposed as an indicator of oxidative damage to DNA. This study aimed to evaluate relationship between oxidative damage to DNA and protein glycation in patients with Type 1 diabetes. We measured urinary 8-OHdG level in diabetic patients and healthy subjects and discussed its relationship to glycated hemoglobin (HbA(1c)) and glycated serum protein (GSP) levels. Furthermore plasma malondialdehyde (MDA) level monitored as an important indicator of lipid peroxidation in diabetes. We studied 32 patients with Type 1 diabetes mellitus and compared the measured factors with those of 48 age-matched nondiabetic controls. GSP and MDA were measured bycolorimetric assay. Urinary 8-OHdG measurement was carried out using ELISA. In this study urinary 8-OHdG, HbA(1c), plasma MDA, and GSP levels were progressively higher in diabetics than in control subjects (P<0.05). Furthermore we found significant correlation between urinary 8-OHdG and HbA(1c) (P<0.05) in diabetic group. Correlation between fasting blood sugar and GSP were significant. We also found significant correlation between fasting blood sugar and MDA. This case-control study in young diabetic patients showed increased blood glucose and related metabolic disorders result in oxidative stress and oxidative damage to DNA and lipids. Furthermore oxidative damage to DNA is associated to glycemic control level, whereas lipid peroxidation level was not significantly correlated with glycemic control level. J. Clin. Lab. Anal. 24:72-76, 2010. (c) 2010 Wiley-Liss, Inc.

The impact of dietary and lifestyle risk factors on risk of colorectal cancer: a quantitative overview of the epidemiological evidence

Colorectal cancer is a major cause of cancer mortality and is considered to be largely attributable to inappropriate lifestyle and behavior patterns. The purpose of this review was to undertake a comparison of the strength of the associations between known and putative risk factors for colorectal cancer by conducting 10 independent meta-analyses of prospective cohort studies. Studies published between 1966 and January 2008 were identified through EMBASE and MEDLINE, using a combined text word and MESH heading search strategy. Studies were eligible if they reported estimates of the relative risk for colorectal cancer with any of the following: alcohol, smoking, diabetes, physical activity, meat, fish, poultry, fruits and vegetables. Studies were excluded if the estimates were not adjusted at least for age. Overall, data from 103 cohort studies were included. The risk of colorectal cancer was significantly associated with alcohol: individuals consuming the most alcohol had 60% greater risk of colorectal cancer compared with non- or light drinkers (relative risk 1.56, 95% CI 1.42-1.70). Smoking, diabetes, obesity and high meat intakes were each associated with a significant 20% increased risk of colorectal cancer (compared with individuals in the lowest categories for each) with little evidence of between-study heterogeneity or publication bias. Physical activity was protective against colorectal cancer. Public-health strategies that promote modest alcohol consumption, smoking cessation, weight loss, increased physical activity and moderate consumption of red and processed meat are likely to have significant benefits at the population level for reducing the incidence of colorectal cancer.

Use of conventional and -omics based methods for health claims of dietary antioxidants: a critical overview

This article describes the principles and limitations of methods used to investigate reactive oxygen species (ROS) protective properties of dietary constituents and is aimed at providing a better understanding of the requirements for science based health claims of antioxidant (AO) effects of foods. A number of currently used biochemical measurements aimed of determining the total antioxidant capacity and oxidised lipids and proteins are carried out under unphysiological conditions and are prone to artefact formation. Probably the most reliable approaches are measurements of isoprostanes as a parameter of lipid peroxidation and determination of oxidative DNA damage. Also the design of the experimental models has a strong impact on the reliability of AO studies: the common strategy is the identification of AO by in vitro screening with cell lines. This approach is based on the assumption that protection towards ROS is due to scavenging, but recent findings indicate that activation of transcription factors which regulate genes involved in antioxidant defence plays a key role in the mode of action of AO. These processes are not adequately represented in cell lines. Another shortcoming of in vitro experiments is that AO are metabolised in vivo and that most cell lines are lacking enzymes which catalyse these reactions. Compounds with large molecular configurations (chlorophylls, anthocyans and polyphenolics) are potent AO in vitro, but weak or no effects were observed in animal/human studies with realistic doses as they are poorly absorbed. The development of -omics approaches will improve the scientific basis for health claims. The evaluation of results from microarray and proteomics studies shows that it is not possible to establish a general signature of alterations of transcription and protein patterns by AO. However, it was shown that alterations of gene expression and protein levels caused by experimentally induced oxidative stress and ROS related diseases can be normalised by dietary AO.

Noninvasive markers of oxidative DNA stress, RNA degradation and protein degradation are differentially correlated with resting metabolic rate and energy intake in children and adolescents

Urinary excreted RNA and DNA catabolites are used as noninvasive markers for metabolic processes: 8-oxo-2'-deoxyguanosine (8-oxodG) potentially represents oxidative stress to DNA/deoxyribonucleotidetriphosphate pool, modified ribonucleoside pseudouridine (psi) originating mainly from degraded rRNA and tRNA reflects RNA turnover. Modified amino acid gamma-carboxyglutamic acid (Gla) stems from degraded proteins reflecting turnover of proteins. Aim of the present study was to investigate (44 healthy males, 3-18 y) how excretion rates of 8-oxodG, psi, and Gla are related to resting metabolic rate and energy intake. Excretion rates of 8-oxodG (pmol/kg/d), psi (micromol/kg/d), and Gla (micromol/kg/d) were significantly correlated with resting metabolic rate (kJ/kg/d): r = 0.108 (p = 0.029), 0.691 and 0.552 (p < 0.0001), respectively. Excretion rates of 8-oxodG, psi, and Gla were also significantly correlated with energy intake (kJ/kg/d): r = 0.108 (p = 0.036), 0.602 and 0.462 (p < 0.0001). 8-oxodG and Gla excretion was significantly correlated with psi excretion: r = 0.174 (p = 0.005) and 0.709 (p < 0.0001). These results indicate close relationships between whole-body RNA and protein degradation and metabolic rate. The relationship between 8-oxodG excretion and metabolic rate, however, is less strong suggesting that factors other than metabolic rate considerably affect the oxidative stress to DNA.

Biomonitoring of complex occupational exposures to carcinogens: the case of sewage workers in Paris

Background

Sewage workers provide an essential service in the protection of public and environmental health. However, they are exposed to varied mixtures of chemicals; some are known or suspected to be genotoxics or carcinogens. Thus, trying to relate adverse outcomes to single toxicant is inappropriate. We aim to investigate if sewage workers are at increased carcinogenic risk as evaluated by biomarkers of exposure and early biological effects.

Methods/design

This cross sectional study will compare exposed sewage workers to non-exposed office workers. Both are voluntaries from Paris municipality, males, aged (20–60) years, non-smokers since at least six months, with no history of chronic or recent illness, and have similar socioeconomic status. After at least 3 days of consecutive work, blood sample and a 24-hour urine will be collected. A caffeine test will be performed, by administering coffee and collecting urines three hours after. Subjects will fill in self-administered questionnaires; one covering the professional and lifestyle habits while the a second one is alimentary. The blood sample will be used to assess DNA adducts in peripheral lymphocytes. The 24-hour urine to assess urinary 8-oxo-7, 8-dihydro-2'-deoxy-Guanosine (8-oxo-dG), and the in vitro genotoxicity tests (comet and micronucleus) using HeLa S3 or HepG2 cells. In parallel, occupational air sampling will be conducted for some Polycyclic Aromatic Hydrocarbons and Volatile Organic Compounds. A weekly sampling chronology at the offices of occupational medicine in Paris city during the regular medical visits will be followed. This protocol has been accepted by the French Est III Ethical Comitee with the number 2007-A00685-48.

Discussion

Biomarkers of exposure and of early biological effects may help overcome the limitations of environmental exposure assessment in very complex occupational or environmental settings.

Low-dose aspirin prevents age-related endothelial dysfunction in a mouse model of physiological aging

The age-related impairment of endothelium-dependent vasodilatation contributes to increased cardiovascular risk in the elderly. For primary and secondary prevention, aspirin can reduce the incidence of cardiovascular events in this patient population. The present work evaluated the effect of low-dose aspirin on age-related endothelial dysfunction in C57B/J6 aging mice and investigated its protective antioxidative effect. Age-related endothelial dysfunction was assessed by the response to acetylcholine of phenylephrine-induced precontracted aortic segments isolated from 12-, 36-, 60-, and 84-wk-old mice. The effect of low-dose aspirin was examined in mice presenting a decrease in endothelial-dependent relaxation (EDR). The effects of age and aspirin treatment on structural changes were determined in mouse aortic sections. The effect of aspirin on the oxidative stress markers malondialdehyde and 8-hydroxy-2'-deoxyguanosine (8-OhdG) was also quantified. Compared with that of 12-wk-old mice, the EDR was significantly reduced in 60- and 84-wk-old mice (P < 0.05); 68-wk-old mice treated with aspirin displayed a higher EDR compared with control mice of the same age (83.9 +/- 4 vs. 66.3 +/- 5%; P < 0.05). Aspirin treatment decreased 8-OHdG levels (P < 0.05), but no significant effect on intima/media thickness ratio was observed. The protective effect of aspirin was not observed when treatment was initiated in older mice (96 wk of age). It was found that low-dose aspirin is able to prevent age-related endothelial dysfunction in aging mice. However, the absence of this effect in the older age groups demonstrates that treatment should be initiated early on. The underlying mechanism may involve the protective effect of aspirin against oxidative stress.

hOGG1 Ser326Cys polymorphism and susceptibility to gallbladder cancer in a Chinese population

The human oxoguanine glycosylase 1(hOGG1) gene encodes a DNA glycosylase that is involved in excision repair of 8-OH-dG (8-hydroxy-2-deoxyguanine) from oxidatively-damaged DNA. To determine whether hOGG1 plays a role in the risk for adenocarcinoma of the gallbladder, we tested the association of this polymorphism with gallbladder cancer in a Chinese population-based, case control study of 204 cases and 209 controls. The subjects were genotyped with a polymerase chain reaction-restriction fragment length polymorphism (PCR-RELP) assay. The association between the genetic polymorphism of this gene and risk of the cancer was examined by using a multivariate analysis. We found that the distribution of hOGG1 Ser326Cys genotypes among controls (Ser/Ser, 37.3%; Ser/Cys, 53.6% and Cys/Cys, 9.1%) was significantly different from that among gallbladder cancer cases (Ser/Ser, 43.1%; Ser/Cys, 36.3% and Cys/Cys, 20.6%). Significantly increased risk for gallbladder cancer was both the hOGG1 326Ser/Cys (Odds ratio [OR] = 1.9, 95% confidence interval (CI) = 1.0-3.7) and hOGG1 326Cys/Cys genotypes (OR = 4.5, 95% CI = 1.1-22.4). We observed no statistically significant association between hOGG1 genotype and gallbladder cancer association in gallstone absence. In contrast, a near-significant increase in risk for gallbladder cancer was observed for gallstone presence with the hOGG1 326Ser/Cys genotype (OR = 2.2, CI = 1.4-3.5) whereas a significant increase in association for gallbladder cancer was observed for gallstone presence with the 326Cys/Cys genotype (OR = 6.1, CI = 2.1-27.2). These data corresponded with the fact that a significant trend towards increased association for gallbladder cancer was observed with potentially higher-risk hOGG1 genotypes in gallstone presence(p < 0.001, chi(2) trend test)but not in gallstone absence(p = 0.89, chi(2) trend test). A significant increase in risk for gallbladder cancer was observed for larger gallstone (those with stone diameters 2 cm or greater) with the hOGG1 326Ser/Cys(OR = 1.9, 95% CI = 1.1-2.9) and hOGG1 326Cys/Cys genotypes(OR = 5.9, 95% CI = 1.6-18.0). These data are consistent with the observation that a significant trend towards increased risk for gallbladder cancer was observed with potentially higher-risk hOGG1 genotypes in gallbladder cancer patients with larger gallstone (p < 0.001, chi(2) trend test). However, we observed no statistically significant association between hOGG1 genotype and gallbladder cancer risk in gallbladder cancer patients with smaller gallstone (those with stone diameters 2 cm smaller) (hOGG1 326Ser/Cys:OR = 2.2, 95% CI = 0.8-4.0; hOGG1 326Cys/Cys:OR = 2.9, 95% CI = 0.6-29.4; p = 0.06, chi(2) tread test). These results suggest that hOGG1 Ser326Cys polymorphism is associated with gallbladder cancer risk.

In vitro approaches to develop weight of evidence (WoE) and mode of action (MoA) discussions with positive in vitro genotoxicity results

A recent analysis by Kirkland et al. [Kirkland, D., Aardema, M., Henderson, L. and Müller, L. (2005) Evaluation of the ability of a battery of 3 in vitro genotoxicity tests to discriminate rodent carcinogens and non-carcinogens. I. Sensitivity, specificity and relative predictivity. Mutat. Res. 584, 1-256] demonstrated an extremely high false positive rate for in vitro genotoxicity tests when compared with carcinogenicity in rodents. In many industries, decisions have to be made on the safety of new substances, and health risk to humans, without rodent carcinogenicity data being available. In such cases, the usual way to determine whether a positive in vitro genotoxicity result is relevant (i.e. indicates a hazard) for humans is to develop weight of evidence (WoE) or mode of action (MoA) arguments. These are based partly on further in vitro investigations, but usually rely heavily on tests for genotoxicity in one or more in vivo assays. However, for certain product types in the European Union, the use of animals for genotoxicity testing (as well as for other endpoints) will be prohibited within the next few years. Many different examples have been described that indicate DNA damage and genotoxic responses in vitro can arise through non-relevant in vitro events that are a result of the test systems and conditions used. The majority of these non-relevant in vitro events can be grouped under a category of 'overload of normal physiology' that would not be expected to occur in exposed humans. However, obtaining evidence in support of such MoAs is not easy, particularly for those industries prohibited from carrying out in vivo testing. It will become necessary to focus on in vitro studies to provide evidence of non-DNA, threshold or in vitro-specific processes and to discuss the potential for such genotoxic effects to occur in exposed humans. Toward this end, we surveyed the published literature for in vitro approaches that may be followed to determine whether a genotoxic effect observed in vitro will occur in humans. Unfortunately, many of the approaches we found are based on only a few published examples and validated approaches with consensus recommendations often do not exist. This analysis highlights the urgent need for developing consensus approaches that do not rely on animal studies for dealing with in vitro genotoxins.

Regulation of clusterin/apolipoprotein J, a functional homologue to the small heat shock proteins, by oxidative stress in ageing and age-related diseases

Clusterin/apolipoprotein J (CLU) gene has a nearly ubiquitous expression pattern in human tissues. The two main CLU protein isoforms in human cells include the conventional glycosylated secreted heterodimer (sCLU) and a truncated nuclear form (nCLU). CLU has been implicated in various physiological processes and in many severe physiological disturbance states including ageing, cancer progression, vascular damage, diabetes, kidney and neuron degeneration. Although unrelated in their etiology and clinical manifestation, these diseases represent states of increased oxidative stress, which in turn, promotes amorphous aggregation of target proteins, increased genomic instability and high rates of cellular death. Among the various properties attributed to CLU so far, those mostly investigated and invariably appreciated are its small heat shock proteins-like chaperone activity and its involvement in cell death regulation, which are both directly correlated to the main features of oxidant injury. Moreover, the presence of both a heat shock transcription factor-1 and an activator protein-1 element in the CLU gene promoter indicate that CLU gene can be an extremely sensitive biosensor to reactive oxygen species. This review emphasizes on CLU gene regulation by oxidative stress that is the common link between all pathological conditions where CLU has been implicated.

Garlic supplementation prevents oxidative DNA damage in essential hypertension

Oxygen-free radicals and other oxygen/nitrogen species are constantly generated in the human body. Most are intercepted by antioxidant defences and perform useful metabolic roles, whereas others escape to damage biomolecules like DNA, lipids and proteins. Garlic has been shown to contain antioxidant phytochemicals that prevent oxidative damage. These include unique water-soluble organosulphur compounds, lipid-soluble organosulphur compounds and flavonoids. Therefore, in the present study, we have tried to explore the antioxidant effect of garlic supplementation on oxidative stress-induced DNA damage, nitric oxide (NO) and superoxide generation and on the total antioxidant status (TAS) in patients of essential hypertension (EH). Twenty patients of EH as diagnosed by JNC VI criteria (Group I) and 20 age and sex-matched normotensive controls (Group II) were enrolled in the study. Both groups were given garlic pearls (GP) in a dose of 250 mg per day for 2 months. Baseline samples were taken at the start of the study, i.e. 0 day, and thereafter 2 months follow-up. 8-Hydroxy-2'-deoxyguanosine (8-OHdG), lipids, lipid peroxidation (MDA), NO and antioxidant vitamins A, E and C were determined. A moderate decline in blood pressure (BP) and a significant reduction in 8-OHdG, NO levels and lipid peroxidation were observed in Group I subjects with GP supplementation. Further, a significant increase in vitamin levels and TAS was also observed in this group as compared to the control subjects. These findings point out the beneficial effects of garlic supplementation in reducing blood pressure and counteracting oxidative stress, and thereby, offering cardioprotection in essential hypertensives.

Increased excretion of a lipid peroxidation biomarker in autism

It is thought that autism could result from an interaction between genetic and environmental factors with oxidative stress as a potential mechanism linking the two. One genetic factor may be altered oxidative-reductive capacity. This study tested the hypothesis that children with autism have increased oxidative stress. We evaluated children with autism for the presence of two oxidative stress biomarkers. Urinary excretion of 8-hydroxy-2-deoxyguanosine (8-OHdG) and 8-isoprostane-F2alpha (8-iso-PGF2alpha) were determined in 33 children with autism and 29 healthy controls. 8-iso-PGF2alpha levels were significantly higher in children with autism. The isoprostane levels in autistic subjects were variable with a bimodal distribution. The majority of autistic subjects showed a moderate increase in isoprostane levels while a smaller group of autistic children showed dramatic increases in their isoprostane levels. There was a trend of an increase in 8-OHdG levels in children with autism but it did not reach statistical significance. There was no significant correlation between the levels of the biomarkers and vitamin intake, dietary supplements, medicine, medical disorders, or history of regression. These results suggest that the lipid peroxidation biomarker is increased in this cohort of autistic children, especially in the subgroup of autistic children.

Oxidative DNA modifications

Oxidative DNA modifications are frequent in mammalian DNA and have been suggested an important mechanism in carcinogenesis, diabetes and ageing. The foundations for this suggestion are: Evidence for the importance of oxidative DNA modifications in cancer development is: high levels of oxidative lesions in cancer tissue; highly conserved and specific DNA repair systems targeting oxidative lesions; high levels of oxidative DNA lesions in oxidative DNA repair knock-out animals; defective repair of oxidative lesions in cancer-prone progeria syndromes; reduced cancer incidence in populations with high dietary antioxidant intake; and increased oxidative stress to DNA in tobacco smokers. Conflicting evidence for a relation between oxidative stress to DNA and cancer is: disagreement about the true levels and occurrence of the oxidative lesions in vivo; failure to identify the localization of oxidative lesions in important genes, e.g. tumor suppressor and oncogenes; lack of evidence that the oxidative lesions induce mutations in vivo; no cancer development in animals knocked-out for specific DNA repair enzymes in spite of high tissue levels of oxidative lesions; and unchanged cancer rates after antioxidant interventions in large clinical controlled and randomized trials. The rate of DNA oxidation has been estimated from urinary excretion of repair products and it is evident that if these lesions were not repaired, a large part of DNA would be oxidized to a degree not compatible with living. The methodologies by which oxidative DNA modifications are measured cover a wide and different range, advantages and disadvantages will be presented. One particular problem is artificial oxidation, and methods to prevent such artifacts will be presented together with results from a large interlaboratory standardization program. The methodology by which the lesions can be measured is complicated and prone to artifacts during DNA isolation, digestion, derivatization and maybe even during the separation procedure proper prior to detection. A large effort from 20+ laboratories supported by a grant from the EU has reduced artifacts considerably and work towards interlaboratory standardization of the methodology is in progress. The presently agreed "normal" levels of the most frequent known lesion 8-oxodG is about 5 per million dG's in DNA. A comprehensive evaluation of the evidence, from chemistry to clinical and epidemiological trials, linking oxidative modifications to cancer will be given. Finally, an estimate of the quantitative role oxidative DNA modifications play among the multiplicity of other insults is given. While there is no question that all of these oxidative mechanisms do exist, quantitative data on their importance for the human situation do not exist. Prospective human studies that can provide such quantitative data on different mechanisms are underway.

hOGG1 Ser326Cys polymorphism, interaction with environmental exposures, and gastric cancer risk in Japanese populations

Oxidative DNA damage caused by reactive oxygen species (ROS) generated by Helicobacter pylori (H. pylori ) infection or smoking may be a cause of gastric cancer development. 8-Hydroxydeoxyguanine (8-OHdG) formation is one of the most common types of oxidative DNA damage, while human oxoguanine glycosylase 1 (hOGG1) is responsible for repairing 8-OHdG lesions. Among several hOGG1 gene polymorphisms, the Ser-->Cys polymorphism at position 326 is related to biological function. To investigate the association between Ser326Cys hOGG1 polymorphism and gastric cancer in relation to the potential risk factors of gastric cancer and antioxidant dietary or nutrient intakes, we conducted a case-control study with 142 histologically-confirmed gastric cancer cases and 271 age, sex-matched healthy controls in Japanese populations. Overall, neither the hOGG1 Ser/Cys nor the Cys/Cys genotype was associated with risk of gastric cancer, compared with the Ser/Ser genotype. A significant interaction was observed between hOGG1 Ser/Cys or Cys/Cys genotype and atrophic gastritis (P for interaction=0.03). No significant interaction was found between hOGG1 genotype and antioxidant dietary or nutrient intakes. The results of the present study suggest that patients with atrophic gastritis in conjunction with the hOGG1 Cys allele might have a higher susceptibility to gastric cancer.

Linking exposure to environmental pollutants with biological effects

Exposure to ambient air pollution has been associated with cancer. Ambient air contains a complex mixture of toxics, including particulate matter (PM) and benzene. Carcinogenic effects of PM may relate both to the content of PAH and to oxidative DNA damage generated by transition metals, benzene, metabolism and inflammation. By means of personal monitoring and biomarkers of internal dose, biologically effective dose and susceptibility, it should be possible to characterize individual exposure and identify air pollution sources with relevant biological effects. In a series of studies, individual exposure to PM(2.5), nitrogen dioxide (NO(2)) and benzene has been measured in groups of 40-50 subjects. Measured biomarkers included 1-hydroxypyrene, benzene metabolites (phenylmercapturic acid (PMA) and trans-trans-muconic acid (ttMA)), 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) in urine, DNA strand breaks, base oxidation, 8-oxodG and PAH bulky adducts in lymphocytes, markers of oxidative stress in plasma and genotypes of glutathione transferases (GSTs) and NADPH:quinone reductase (NQO1). With respect to benzene, the main result indicates that DNA base oxidation is correlated with PMA excretion. With respect to exposure to PM, biomarkers of oxidative damage showed significant positive association with the individual exposure. Thus, 8-oxodG in lymphocyte DNA and markers of oxidative damage to lipids and protein in plasma associated with PM(2.5) exposure. Several types of DNA damage showed seasonal variation. PAH adduct levels, DNA strand breaks and 8-oxodG in lymphocytes increased significantly in the summer period, requiring control of confounders. Similar seasonal effects on strand breaks and expression of the relevant DNA repair genes ERCC1 and OGG1 have been reported. In the present setting, biological effects of air pollutants appear mainly related to oxidative stress via personal exposure and not to urban background levels. Future developments include personal time-resolved monitors for exposure to ultrafine PM and PM(2.5,) use of GPS, as well as genomics and proteomics based biomarkers.

hOGG1 Ser326Cys polymorphism modifies the significance of the environmental risk factor for colon cancer

AIM: To determine the association of hOGG1 (8-oxoguanine glycosylase I, OGG1) polymorphism of Ser326Cys substitution with colon cancer risk and possible interaction with known environmental risk factors.

METHODS: A case-control study with 125 colon cancer cases and 247 controls was conducted.

RESULTS: There was no major difference in Ser326Cys genotype distribution between cases and controls. The meat intake tended to increase the odds ratio for colon cancer with an OR of 1.72 (95% confidence interval; CI = 1.12-2.76). Such tendency was more prominent in Cys/Cys carriers (OR = 4.31, 95%CI = 1.64-11.48), but meat intake was not a significant risk factor for colon cancer in Ser/Ser or Ser/Cys carriers. The OR for colon cancer was elevated with marginal significance in smokers who were Cys/Cys carriers (OR = 2.75, 95%CI = 1.07-7.53) but not in Ser/Ser or Ser/Cys carriers.

CONCLUSION: These results suggest that the hOGG1 Ser326Cys polymorphism is probably not a major contributor to individual colon cancer susceptibility overall, but the Cys/Cys genotype may alter the impact of some environmental factors on colon cancer development.

Limited repair of 8-hydroxy-7,8-dihydroguanine residues in human testicular cells

Oxidative damage in testicular DNA is associated with poor semen quality, reduced fertility and increased risk of stillbirths and birth defects. These DNA lesions are predominantly removed by base excision repair. Cellular extracts from human and rat testicular cells and three enriched populations of rat male germ cells (primary spermatocytes, round spermatids and elongating/elongated spermatids) all showed proficient excision/incision of 5-hydroxycytosine, thymine glycol and 2,6-diamino-4-hydroxy-5-formamidopyrimidine. DNA containing 8-oxo-7,8-dihydroguanine was excised poorly by human testicular cell extracts, although 8-oxoguanine-DNA glycosylase-1 (hOGG1) was present in human testicular cells, at levels that varied markedly between 13 individuals. This excision was as low as with human mononuclear blood cell extracts. The level of endonuclease III homologue-1 (NTH1), which excises oxidised pyrimidines, was higher in testicular than in somatic cells of both species. Cellular repair studies of lesions recognised by formamidopyrimidine-DNA glycosylase (Fpg) or endonuclease III (Nth) were assayed with alkaline elution and the Comet assay. Consistent with the enzymatic activities, human testicular cells showed poor removal of Fpg-sensitive lesions but efficient repair of Nth-sensitive lesions. Rat testicular cells efficiently repaired both Fpg- and Nth-sensitive lesions. In conclusion, human testicular cells have limited capacity to repair important oxidative DNA lesions, which could lead to impaired reproduction and de novo mutations.

Progress in the analysis of urinary oxidative DNA damage

Oxidative DNA damage has been implicated to be important in the pathogenesis of many diseases, including cancer and heart disease. The assessment of damage in various biological matrices, such as DNA, serum, and urine, is vital to understanding this role and subsequently devising intervention strategies. Despite the numerous techniques to measure oxidative DNA damage products in urine, it remains unclear what these measurements truly represent. Sources of urinary lesions may include the diet, cell death, and, of most interest, DNA repair. Were it possible to exclude the two former contributions, a noninvasive assay for DNA repair would be invaluable in the study of DNA damage and disease. This review highlights that, although progress has been made, significant work remains. Diet, cell death, and repair need continued examination to further elucidate the kinetics of lesion formation and clearance in vivo. Studies from our laboratory and others are making appreciable progress towards the interpretation of urinary lesion measurements along with the development of urinary assays to evaluate DNA repair. Upon establishment of these details, urinary oxidative DNA damage measurements may become more than a reflection of generalized oxidative stress.

Opportunities for nutritional amelioration of radiation-induced cellular damage

The closed environment and limited evasive capabilities inherent in space flight cause astronauts to be exposed to many potential harmful agents (chemical contaminants in the environment and cosmic radiation exposure). Current power systems used to achieve space flight are prohibitively expensive for supporting the weight requirements to fully shield astronauts from cosmic radiation. Therefore, radiation poses a major, currently unresolvable risk for astronauts, especially for long-duration space flights. The major detrimental radiation effects that are of primary concern for long-duration space flights are damage to the lens of the eye, damage to the immune system, damage to the central nervous system, and cancer. In addition to the direct damage to biological molecules in cells, radiation exposure induces oxidative damage. Many natural antioxidants, whether consumed before or after radiation exposure, are able to confer some level of radioprotection. In addition to achieving beneficial effects from long-known antioxidants such as vitamins E and C and folic acid, some protection is conferred by several recently discovered antioxidant molecules, such as flavonoids, epigallocatechin, and other polyphenols. Somewhat counterintuitive is the protection provided by diets containing elevated levels of omega-3 polyunsaturated fatty acids, considering they are thought to be prone to peroxidation. Even with the information we have at our disposal, it will be difficult to predict the types of dietary modifications that can best reduce the risk of radiation exposure to astronauts, those living on Earth, or those enduring diagnostic or therapeutic radiation exposure. Much more work must be done in humans, whether on Earth or, preferably, in space, before we are able to make concrete recommendations.

Mutagenicity of 2-amino-3-methylimidazo[4,5-f]quinoline in colon and liver of Big Blue rats: role of DNA adducts, strand breaks, DNA repair and oxidative stress

The contribution of oxidative stress, different types of DNA damage and expression of DNA repair enzymes in colon and liver mutagenesis induced by 2-amino-3-methylimidazo [4,5-f]quinoline (IQ) was investigated in four groups of six Big Blue rats fed diets with 0, 20, 70, and 200 mg IQ/kg for 3 weeks. There were dose-response relationships of DNA adducts ((32)P-postlabeling) and DNA strand breaks (comet assay) in colon and liver tissues, with the highest levels of DNA adducts and strand breaks in the colon. There was dose-dependent induction of mutations in both the colon and the liver, and the same IQ dose produced two-fold more cII mutations in the liver compared with the colon. The IQ-induced mutation spectrum in the colon was not significantly different to that of control rats. The expression of ERCC1 and OGG1 was higher in the colon than liver, and was unaffected by the IQ diet. Investigations of oxidative stress biomarkers produced inconclusive results. Oxidative DNA damage detected by the endonuclease III enzyme and 7-hydro-8-oxo-2'-deoxyguanosine in colon, liver and/or urine was unaltered by IQ. However, there was increased level of gamma-glutamyl semialdehyde in liver proteins, indicating a higher rate of protein oxidation in the liver following IQ administration. In plasma and erythrocytes there were unaltered levels of oxidized protein, malondialdehyde, and antioxidant enzyme activities (superoxide dismutase, glutathione peroxidase, catalase, glutathione reductase) indicating no systemic oxidative stress. However, the level of total vitamin C was increased in plasma, with the largest fraction being in the reduced form. In conclusion, our results indicate that DNA adducts rather than oxidative stress are responsible for the initiation of IQ-induced carcinogenesis of the liver and colon. A lower frequency of mutations in the colon than in the liver could be related to higher expression of DNA repair enzymes in the former.

Renal excretion of 8-oxo-7,8-dihydro-2(')-deoxyguanosine: degradation rates of RNA and metabolic rate in humans

Renally excreted 8-oxo-7,8-dihydro-2(')-deoxyguanosine (oxo(8)dG) is a potential marker of oxidative DNA damage by reactive oxygen species. Whole-body degradation rates of t- and rRNA are potential indicators of the resting metabolic rate (RMR). Excretion rates of oxo(8)dG and degradation rates of t- and rRNA were determined in healthy non-smoking adults and children. RMR (indirect calorimetry; 14 children, 16 adults), total energy expenditure (TEE; doubly labelled water technique; 4 children, 6 adults), and lean body mass (LBM; dual-energy X-ray absorptiometry; 14 children, 16 adults) were also measured. Degradation of t- and rRNA (micromol/d/kg LBM; 4 children, 6 adults) was highly correlated with RMR (kJ/d/kg LBM), r=0.867 (p<0.005) and 0.959 (p<0.001), respectively. Excretion of oxo(8)dG (pmol/d/kg LBM; 14 children, 16 adults) was not significantly correlated with RMR (p>0.05). Neither excretion of oxo(8)dG nor degradation of RNA was significantly correlated with TEE (kJ/d/ kg LBM) (p>0.05). In healthy subjects further factors, other than the metabolic rate, seem to influence the excretion rate of oxo(8)dG. The degradation rates of t- and rRNA seem to be appropriate indicators of the RMR.

Effect of diet on cancer development: is oxidative DNA damage a biomarker?

Free radicals and other reactive species are generated in vivo and many of them can cause oxidative damage to DNA. Although there are methodological uncertainties about accurate quantitation of oxidative DNA damage, the levels of such damage that escape immediate repair and persist in DNA appear to be in the range that could contribute significantly to mutation rates in vivo. The observation that diets rich in fruits and vegetables can decrease both oxidative DNA damage and cancer incidence is consistent with this. By contrast, agents increasing oxidative DNA damage usually increase risk of cancer development. Such agents include cigarette smoke, several other carcinogens, and chronic inflammation. Rheumatoid arthritis and diabetes are accompanied by increased oxidative DNA damage but the pattern of increased cancer risk seems unusual. Other uncertainties are the location of oxidative DNA damage within the genome and the variation in rate and level of oxidative damage between different body tissues. In well-nourished human volunteers, fruits and vegetables have been shown to decrease oxidative DNA damage in several studies, but data from short-term human intervention studies suggest that the protective agents are not vitamin C, vitamin E, beta-carotene, or flavonoids.

Growing old with nuclear factor-kappaB

The transcription factor nuclear factor-kappa B (NF-kappaB) is involved in the regulation of a broad spectrum of genes that play important roles in a myriad of physiological and pathological events ranging from the immune response to carcinogenesis. Interestingly, many processes in which NF-kappa B plays a central role have long been noted for their alteration with age. A number of research groups have reported rather dramatic changes in NF-kappaB activity as humans and animals age, with tissue-specific increases and decreases in NF-kappaB activity being reported. The extent to which changes in NF-kappaB activity drive aging and influence life span in humans and other mammals is not clear. However, given the dramatic impact that NF-kappaB can have on the function of numerous tissues and organs, understanding how NF-kappaB activity changes with age will undoubtedly enhance our understanding of the many diseases associated with growing old.

Role of endogenous oxidative DNA damage in carcinogenesis: what can we learn from repair-deficient mice?

Basal steady-state levels of oxidative DNA base modifications such as 7,8-dihydro-8-oxo-2'-deoxyguanosine (8-oxoG) are observed in all types of cells, most probably due to a continuous generation of reactive oxygen species (ROS) in the cellular oxygen metabolism, and it has long been suspected that they might play an important role in the initiation of carcinogenesis. Experimental evidence for this assumption can be obtained by studying the effects of a modulation of the steady-state levels, either by in- or decreasing the generation of oxidative DNA damage, on spontaneous mutation rates and cancer incidence. However, clear answers have not yet been obtained by these strategies. It is still doubtful whether an efficient reduction of the in vivo steady-state levels can be achieved by application of antioxidants, and effects observed under oxidative stress conditions (i.e. increased oxidative DNA damage) are inconclusive due to the pronounced epigenetic effects of ROS on signal transduction and gene expression (tumor promotion). In addition, the reliable quantification of the basal levels of oxidative DNA modifications is still a major problem. Recently, the generation of mice deficient in the repair 8-oxoG (ogg1-/- mice) has opened the door for an alternative approach. Results obtained so far indicate that an increase by less than five 8-oxoG residues per 106 bp in the liver of the knockout animals is associated with a two- to threefold higher spontaneous mutation frequency in transgenic genes. However, the increase in the ogg1-/- mice of the steady-state level of 8-oxoG and the spontaneous mutation frequency was only observed in the liver and apparently too small to enhance the spontaneous cancer incidence significantly. The limited effect seems to be due to a back-up repair system for 8-oxoG in the ogg1-/- mice, and it can be expected that the inactivation of this pathway in double-knockout mice will lead to higher effects and a better assessment of the risk associated with endogenous oxidative DNA damage.

Benzo(a)pyrene-coated onto Fe(2)O(3) particles-induced lung tissue injury: role of free radicals

Lipid peroxidation (as malondialdehyde; MDA), activities of some antioxidant enzymes (as superoxide dismutase; SOD, glutathione peroxidase; GPx, glutathione reductase; GR), glutathione status, and oxidative DNA damage (as 8-hydroxy-2'-deoxyguanosine; 8-OHdG) were investigated in the lungs of rats exposed to hematite (Fe(2)O(3); 3 mg), benzo(a)pyrene (B(a)P; 3 mg), or B(a)P (3 mg)-coated onto Fe(2)O(3) particles (3 mg). Approximately 2-fold increases in MDA production were seen in animals exposed to Fe(2)O(3), B(a)P, or B(a)P-coated onto Fe(2)O(3) particles (P<0.01). Decreases in SOD activities were observed in rats treated with Fe(2)O(3) (1.66-fold, P<0.01), B(a)P (1.66-fold, P<0.001) or B(a)P-coated onto Fe(2)O(3) particles (1.43-fold, P<0.01). GPx and GR activities could not be detected. No alteration of the glutathione status was observed. Significant increases in the 8-OHdG formation occurred in response to exposure to B(a)P (2.0-fold, P<0.01) or B(a)P-coated onto Fe(2)O(3) particles (23.7-fold, P<0.001). Our results demonstrate also that Fe(2)O(3) generates free radical (FR)-induced lung injury and is not an inert carrier. We established that exposure to B(a)P or B(a)P-coated onto Fe(2)O(3) particles resulted in lipid peroxidation and SOD inactivation, thereby leading to oxidative damages in DNA. The main findings of this work was that B(a)P-coated onto Fe(2)O(3) particles caused higher lung concentrations of 8-OHdG than B(a)P by itself. Hence, our data may explain why exposure to B(a)P-coated onto Fe(2)O(3) particles resulted in a decreased latency and an increased incidence of lung tumors in rodents compared to exposure to B(a)P.

Minor role of oxidative stress during intermediate phase of acute pancreatitis in rats

Reactive oxygen species have been implicated in the pathogenesis of acute pancreatitis. Few studies have focused on the loss of endogenous antioxidants and molecular oxidative damage. Two acute pancreatitis models in rats; taurocholate (3% intraductal infusion) and cerulein (10 microg/kg/h), were used to study markers of oxidative stress: Glutathione, ascorbic acid, and their oxidized forms (glutathione disulfide and dehydroascorbic acid), malondialdehyde, and 4-hydroxynoneal in plasma and pancreas, as well as 7-hydro-8-oxo-2'-deoxyguanosine in pancreas. In both models, pancreatic glutathione depleted by 36-46% and pancreatic ascorbic acid depleted by 36-40% (p <.05). In the taurocholate model, plasma glutathione was depleted by 34% (p <.05), but there were no significant changes in plasma ascorbic acid or in plasma and pancreas dehydroascorbic acid, malondialdehyde, and 4-hydroxynoneal, and no significant changes in the pancreas glutathione disulfide/glutathione ratio. While pancreas glutathione disulfide/glutathione ratio increased in the cerulein model, there were no significant changes in plasma glutathione, plasma, or pancreas ascorbic acid, dehydroascorbic acid, 4-hydroxynoneal, and malondialdehyde, or in pancreas 7-hydro-8-oxo-2'-deoxyguanosine. Reactive oxygen species have a minor role in the intermediate stages of pancreatitis models.

hOGG1 polymorphism and loss of heterozygosity (LOH): significance for lung cancer susceptibility in a caucasian population

Oxidative damage is implicated in several chronic diseases including cancer. 8-Hydroxyguanine (8-oxoG) is one of the major promutagenic DNA lesions, which is produced by reactive oxygen species, causes G:C to T:A transversions and is excised by OGG1, an 8-oxoG specific DNA glycosylase/AP-Lyase. In a nested case-control study, gDNA from 105 Caucasian primary non-small cell lung cancer cases and 105 matched controls was screened for 6 possible new polymorphic sites in the human OGG1 gene, detected previously mainly in tumour tissue. The previously described Ser(326)Cys polymorphism was found to be common (allele frequency 0.22) in Caucasians. However, no major difference in Ser(326)Cys genotype distribution could be detected between cases and controls. Two 5;-end polymorphisms previously found in Japanese as well as Arg(131)Gln could not be detected in this population. An Ala(85)Ser polymorphism was found in 2 controls, whereas Arg(46)Gln was detected in only 1 case. As the hOGG1 gene is mapped (3p26.2) to a region frequently lost in primary lung tumours, the frequency of loss of heterozygosity (LOH) was investigated. Forty-three percent of the studied lung tumours exhibited loss of one of the hOGG1 alleles. The wt Ser(326) allele was not predominantly lost in our sample set, which suggests a minor role of this polymorphism in tumourgenesis. Our results show that LOH at the hOGG1 gene locus is a very common occurrence in lung tumourgenesis, possibly leading to increased mutational damage due to ROS in smokers. However, the hOGG1 polymorphisms studied are probably not major contributors to individual lung cancer susceptibility in Caucasians.