OGG1 Ser326Cys polymorphism interacts with cigarette smoking to increase oxidative DNA damage in human sperm and the risk of male infertility

8-Oxoguanine DNA glycosylase 1 (OGG1) plays an important role in repairing oxidative DNA damage induced by chemical agents, such as tobacco. This study examined the effects of OGG1 Ser326Cys polymorphism and cigarette smoking, alone or combined, on sperm oxidative DNA damage and the risk of male infertility. A total of 620 idiopathic infertile subjects and 480 fertile controls were recruited in this study. Sperm 8-hydroxydeoxyguanine (8-OHdG) was measured by immunofluorescent assay using flow cytometry and genotypes were determined by OpenArray platform with a chip-based Taq-Man genotyping technology. Our results demonstrated that both cigarette smoking and OGG1 polymorphism can affect the sperm 8-OHdG levels. Individuals with variant Cys/Cys homozygote showed higher levels of sperm 8-OHdG than wide-type homozygote carriers (Ser/Ser). Stratified analysis found that the association between OGG1 polymorphism and sperm 8-OHdG levels was only observed among smokers with pack-years ≥5 but not among those subjects with pack-years < 5 (pack-years = packs smoked per day × years as a smoker). Further analysis based on the case–control study revealed that variant allele (Cys) of OGG1 was significantly associated with male infertility risk in a dominant model (OR = 1.35, 95% CI: 1.01–1.82; trend P < 0.001). Furthermore, we found a significant gene–environment interaction between OGG1 Ser326Cys polymorphism and cigarette smoking in relation to male infertility risk (P_interation = 0.0003). These findings provided the first evidence about potential interactive effects of OGG1 polymorphism and cigarette smoking on male infertility risk.     

Genetic polymorphisms in hMTH1, hOGG1 and hMYH and risk of chronic benzene poisoning in a Chinese occupational population

Oxidative damage to DNA induced by benzene is an important mechanism of its genotoxicity, which leads to chronic benzene poisoning (CBP). Therefore, genetic variation in DNA repair genes may contribute to susceptibility to CBP in the exposed population. We hypothesized that single nucleotide polymorphisms (SNPs) in hMTH1, hOGG1 and hMYH genes are associated with risk of CBP. We genotyped SNPs at codon 83 of hMTH1, codon 326 of hOGG1, and codon 324 of hMYH in 152 CBP patients and 152 healthy workers occupationally exposed to benzene without poisoning manifestations. The genotypes were determined by polymerase chain reaction-restrained fragment length polymorphism (PCR-RFLP) technique. There were 2.51-fold [adjusted odds ratio (OR_adj), 2.51; 95% CI, 1.14-5.49; P = 0.02] and 2.49-fold (OR_adj, 2.49; 95% CI: 1.52-4.07; P < 0.01) increased risk of CBP for individuals carrying genotypes of hMTH1 83Val/Met + Met/Met and hOGG1 326Cys/Cys, respectively. Compared with individuals carrying genotypes of hOGG1 326Cys/Cys and hMYH 324His/His at the same time, there was a 0.33-fold (OR_adj, 0.33; 95% CI: 0.15-0.72; P < 0.05) decreased risk of CBP for those with genotypes of hOGG1 326Ser/Cys + Ser/Ser and hMYH 324His/Gln + Gln/Gln. In the smoking group, there was a 0.15-fold (OR_adj, 0.15; 95% CI, 0.03-0.68; P = 0.01) decreased risk of CBP for subjects carrying genotypes of hMYH 324His/Gln + Gln/Gln compared with those of genotype of hMYH 324His/His. Therefore, our results suggested that polymorphisms at codons 83 of hMTH1 and codon 326 of hOGG1 might contribute to CBP in a Chinese occupational population.     

Polymorphic trial in oxidative damage of arsenic exposed Vietnamese

Arsenic causes DNA damage and changes the cellular capacity for DNA repair. Genes in the base excision repair (BER) pathway influence the generation and repair of oxidative lesions. Single nucleotide polymorphisms (SNPs) in human 8-oxoguanine DNA glycosylase (hOGG1) Ser326Cys; apurinic/apyrimidinic endonuclease (APE1) Asp148Glu; X-ray and repair and cross-complementing group 1 (XRCC1) Arg280His and Arg399Gln in the BER genes were analyzed, and the relationship between these 4 SNPs and the urinary 8-hydroxy-2′-deoxyguanosine (8-OHdG) concentrations of 100 Vietnamese population exposed to arsenic was investigated. Individuals with hOGG1 326Cys/Cys showed significantly higher urinary 8-OHdG concentrations than did those with 326 Ser/Cys and Ser/Ser. As for APE1 Asp148Glu, heterozygous subjects showed significantly higher urinary 8-OHdG concentrations than did those homozygous for Asp/Asp. Moreover, global ethnic comparison of the allelic frequencies of the 4SNPs was performed in 10 population and previous reported data. The mutant allele frequencies of hOGG1 Ser326Cys in the Asian populations were higher than those in the African and Caucasian populations. As for APE1 Asp148Glu, Caucasians showed higher mutant frequencies than those shown by African and Asian populations. Among Asian populations, the Bangladeshi population showed relatively higher mutant allele frequencies of the APE1 Asp148Glu polymorphism. This study is the first to demonstrate the existence of genetic heterogeneity in a worldwide distribution of SNPs (hOGG1 Ser326Cys, APE1 Asp148Glu, XRCC1 Arg280His, and XRCC1 Arg399Gln) in the BER genes.     

Association of <Emphasis Type="Italic">hOGG1</Emphasis> genotype with life style and oxidative DNA damage among Chinese ethnic populations

To assess the natural variation of hOGG1 gene and the gene–environmental interactions, the hOGG1 codon 326 polymorphism and urinary 8-OHdG levels were investigated in large samples (n = 953) of healthy individuals from five Chinese ethnic populations by using PCR-RFLP and HPLC-ECD. Life-style parameters under study were obtained through a questionnaire. The allelic frequencies of the hOGG1 gene in the Chinese populations were found to be 0.16 (Ser/Ser), 0.49 (Ser/Cys) and 0.35 (Cys/Cys), respectively. The frequencies of Ser326Cys polymorphism were significantly different among the five Chinese ethnic populations (P = 0.002). No association was found between the hOGG1 gene polymorphism and other life-style parameters except for the association between Ser326Cys and smoking (P = 0.027). A significant increase of urinary 8-OHdG level was observed in Cys326Cys allelic healthy subjects (P = 0.033). These results suggest that there are natural variations of hOGG1 gene among Chinese ethnic populations. Smoking relates to Cys/Cys polymorphism frequencies, and oxidative DNA damage is repaired less in individuals with the hOGG1 Cys326Cys genotype.     

Rapid detection of the hOGG1 Ser326Cys polymorphism using LightCycler technology

Human 8-oxoguanine DNA glycosylase 1 (hOGG1) plays an important role in the repair of 8-oxo-7, 8-dihydro-2'-deoxyguanosine (8-oxodGuo), one of the major constituents in DNA damage. A recent in vitro study showed that the hOGG1 326Cys polymorphism (rs1052133) exhibits reduced 8-oxodGuo repair activity. This study aimed to develop a LightCycler (LC) assay to analyze the C>G polymorphism (Ser326Cys) in exon 7 of the hOGG1 gene followed by validation of the method using DNA samples from 260 polycyclic aromatic hydrocarbons(PAH)-exposed workers with known 8-oxodGuo DNA-adduct values measured by HPLC. Twenty DNA samples were analyzed by a PCR-RFLP analysis with Fnu4H I to generate control DNA. LC melting curve analyses of the hOGG1 exon 7 PCR product were characteristic of the probes hybridized to the non-mutated Ser-type (CC) at 65 degrees C, or to the Cys mutant (GG) at 59 degrees C. The distribution in the population of PAH-exposed workers (N=260) was 58% (CC), 38%(CG), and 4% (GG). The minor G allele displayed a frequency of 23 %. The distribution of 8-oxodGuo adducts for the Ser326Cys variants of hOGG1 revealed geometric means (GM) of 5.83 (CC), 5.27 (CG), and 6.53 (GG) 8-oxodGuo adducts/10(6)dGuo. Corresponding GM values of current smokers were 5.7 (CC), 5.6 (CG) and 7.0 (GG) 8-oxodGuo adducts/10(6) dGuo. The analysis of the Ser326Cys polymorphism in 260 DNA samples with this new LC assay revealed that this method is reliable for high throughput analysis of this key polymorphism in the hOGG1 gene.     

hOGG1 promoter methylation,hOGG1 genetic variants and their interactions for risk of coal-borne arsenicosis: A case-control study

To identify the effect of hOGG1 methylation, Ser326Cys polymorphism and their interactions on the risk of coal-borne arsenicosis, 113 coal-borne arsenicosis subjects and 55 reference subjects were recruited. Urinary arsenic contents were analyzed with ICP-MS. hOGG1 methylation and Ser326Cys polymorphism was measured by mehtylation-specific PCR and restriction fragment length polymorphism PCR in PBLCs, respectively. The results showed that the prevalence of methylated hOGG1 and variation genotype (326 ^Ser/Cys & 326 ^Cys/Cys) were increased with raised levels of urinary arsenic in arsenicosis subjects. Increased prevalence of methylated hOGG1 and variation genotype were associated with raised risk of arsenicosis. Moreover, the results revealed that variant genotype might increase the susceptibility to hOGG1 methylation. The interactions of methylated hOGG1 and variation genotype were also found to contribute to increased risk of arsenicosis. Taken together, hOGG1 hypermethylation, hOGG1 variants and their interactions might be potential biomarkers for evaluating risk of coal-borne arsenicosis.     

The human 8-oxoguanine DNA N-glycosylase 1 (hOGG1) DNA repair enzyme and its association with lung cancer risk

OBJECTIVE: The human 8-oxoguanine DNA N-glycosylase 1 gene encodes a DNA glycosylase that is involved in the base excision repair of 8-hydroxy-2-deoxyguanine from oxidatively-damaged DNA and expressed in lung tissue. The codon 326 polymorphism in the hOGG1 gene has been suggested to reduce DNA repair enzyme activity based on in vitro functional analysis. The goal of the present study is to determine whether the codon 326 polymorphism was significantly associated with alterations in individual risk for lung cancer. METHODS: To determine whether hOGG1 plays a role in risk for lung cancer, we measured the prevalence of the Ser326Cys polymorphism in incident lung cancer patients and matched non-cancer controls. hOGG1 genotyping was performed by PCR-restriction fragment length polymorphism analysis of genomic DNA isolated from 179 Caucasian lung cancer cases and 358 controls individually matched in a 1:2 ratio by race-, sex- and age (+/- 5 years). RESULTS: Significantly increased risk for lung cancer was observed for both the hOGG1 326 (odds ratio [OR] = 1.9, 95% confidence interval [CI] = 1.2-2.9) and hOGG1 326 genotypes (OR = 3.8, 95% CI = 1.4-10.6). The increased risk for lung cancer was observed for subjects with both the hOGG1 326 (OR = 1.7, 95% CI = 1.1-2.8) and hOGG1 326 genotypes (OR = 4.9, 95% CI = 1.5-16.1) in ever-smokers. A significant association was found between hOGG1 genotypes and lung cancer risk with a dose-dependent effect with smoking. Significantly increased risk for variant hOGG1 genotypes was observed for all non-small cell lung cancer patients. CONCLUSION: These results suggest that the hOGG1 Ser326Cys polymorphism plays an important role in the risk for lung cancer and is linked to exposure to tobacco smoke.     

hOGG1 SER326CYS genetic polymorphism in a Turkish population

Oxidative DNA damage, caused by either endogenous or exogenous sources of reactive oxygen species (ROS), has been linked to aging, chronic degenerative diseases, inflammatory diseases and cancers. 8-Hydroxydeoxyguanine (8-OHdG) is a major lesion produced by ROS. Among various types of DNA base modifications, 8-OHdG has been the most widely studied and is considered a key biomarker of oxidative DNA damage. Human 8-oxoguanine DNA glycosylase 1 (hOGG1) is a key component of the base excision repair (BER) pathway and catalyzes the removal of 8-OHdG. Ethnic and inter-individual differences in hOGG1 activity and several kinds of polymorphisms at the hOOG1 gene locus have been observed in the different populations studied so far. Since no information is available on the inter-individual variability of the hOGG1 genotype in the Turkish population, we genotyped 206 healthy, unrelated Turkish individuals. The allelic frequencies of the hOGG1 gene in the Turkish population were found to be 0.50, 0.41 and 0.09 (Ser/Ser, Ser/Cys and Cys/Cys, respectively). Our results are similar to those for Caucasians studied previously but are different from Asian populations. It seems that there is a growing need for extensive genotype studies with respect to the hOGG1 gene due to its importance to various types of cancer and to smoking habits.     

hOGG1基因多态性与胃癌遗传易感性的关系

目的探讨人类8-羟基鸟嘌呤DNA糖苷酶1（hOGG1）基因多态性与胃癌遗传易感性的关系。方法收集河南郑州和开封地区98例胃癌患者和80例非肿瘤对照组志愿者外周血样,应用聚合酶链反应一限制性片段长度多态性（PCR—RFLP）检测法检测胃癌人群的外周血中DNA损伤修复酶基因多态性,分析其与肿瘤遗传易感性的关系。结果hOGGISer326Cys基因的各基因型频率在胃癌组和对照组间的分布差异有统计学意义（P〈0．05）。携带Cys326Cys基因型者胃癌的发病风险增加1．7倍（OR=I．706,95％CI=0．341～2．462,P=0．002）。hOGGlSer326Cys基因多态性与酒的交互作用增加胃癌的发病风险（S〉1,API=0．38）。结论Cys326Cys基因型是胃癌发病的危险基因型,携带Cys易感基因与饮酒交互作用时可能增加患胃癌的易感性。     

Modulation of DNA repair capacity and mRNA expression levels of XRCC1, hOGG1 and XPC genes in styrene-exposed workers

Decreased levels of single-strand breaks in DNA (SSBs), reflecting DNA damage, have previously been observed with increased styrene exposure in contrast to a dose-dependent increase in the base-excision repair capacity. To clarify further the above aspects, we have investigated the associations between SSBs, micronuclei, DNA repair capacity and mRNA expression in XRCC1, hOGG1 and XPC genes on 71 styrene-exposed and 51 control individuals. Styrene concentrations at workplace and in blood characterized occupational exposure. The workers were divided into low (below 50 mg/m³) and high (above 50 mg/m³) styrene exposure groups. DNA damage and DNA repair capacity were analyzed in peripheral blood lymphocytes by Comet assay. The mRNA expression levels were determined by qPCR. A significant negative correlation was observed between SSBs and styrene concentration at workplace (R = − 0.38, p = 0.001); SSBs were also significantly higher in men (p = 0.001). The capacity to repair irradiation-induced DNA damage was the highest in the low exposure group (1.34 ± 1.00 SSB/10⁹ Da), followed by high exposure group (0.72 ± 0.81 SSB/10⁹ Da) and controls (0.65 ± 0.82 SSB/10⁹ Da). The mRNA expression levels of XRCC1, hOGG1 and XPC negatively correlated with styrene concentrations in blood and at workplace (p < 0.001) and positively with SSBs (p < 0.001). Micronuclei were not affected by styrene exposure, but were higher in older persons and in women (p < 0.001). In this study, we did not confirm previous findings on an increased DNA repair response to styrene-induced genotoxicity. However, negative correlations of SSBs and mRNA expression levels of XRCC1, hOGG1 and XPC with styrene exposure warrant further highly-targeted study.     

Quercetin inhibits hydrogen peroxide-induced DNA damage and enhances DNA repair in Caco-2 cells

Flavonoids are known to have antioxidant activity that may limit DNA damage and help prevent degenerative diseases, including cancer. However, our knowledge of flavonoids’ role in DNA protection/repair mechanism(s) is limited. This study investigated the effects of quercetin on DNA oxidation and DNA repair in Caco-2 cells with or without oxidant (H₂O₂) challenge. Quercetin (1, 100 μM) significantly reduced oxidative DNA damage, as measured by the number of single-strand breaks identified by single cell gel electrophoresis. Quercetin treatment also caused a measurable increase in the mRNA expression of human 8-oxoguanine DNA glycosylase (hOGG1) at 0 and 4 h after H₂O₂ treatment (measured using RT-PCR). In addition, the highest level of quercetin tested (100 μM) maintained hOGG1 expression at basal levels or higher for up to 12 h after H₂O₂ treatment, while oxidant treatment alone resulted in significant reduction of hOGG1 at 8 h. Our study indicates that quercetin could protect DNA both by reducing oxidative DNA damage and by enhancing DNA repair through modulation of DNA repair enzyme expression.     

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 24 h, 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.     

Biomarkers of nucleic acid oxidation, polymorphism in, and expression of, hOGG1 gene in styrene-exposed workers

This study investigated nucleic acid oxidation associated with styrene exposure, mRNA expression levels of hOGG1 gene and the role of the genetic polymorphism Ser326Cys of human 8-oxoguanine DNA N-glycosylase 1 (hOGG1) in 60 styrene-exposed workers and 50 unexposed clerks. Biomarkers of exposure (styrene in blood, mandelic and phenylglyoxylic acids and 4-vinylphenol in urine) and urinary biomarkers of nucleic acid oxidation, namely 8-oxo-7,8-dihydro-2′-deoxyguanosine (U-8-oxodGuo), 8-oxo-7,8-dihydroguanosine (U-8-oxoGuo) and 8-oxo-7,8-dihydroguanine (U-8-oxoGua) were determined by liquid chromatography–tandem mass spectrometry. The levels of 8-oxodGuo adduct and 2′-deoxyguanosine (dGuo) were measured by HPLC in DNA from white blood cells (WBC). Genomic DNA and RNA from blood samples were used to characterize the Ser326Cys polymorphism and the mRNA expression levels of the hOGG1 gene, respectively, by PCR-based methods. Exposed workers showed lower values of 8-oxodGuo/10⁵ dGuo ratio in WBC-DNA but higher concentrations of U-8-oxoGuo compared to controls (p = 0.002 and p = 0.008, respectively, t-test for independent samples). In the whole group, all urinary biomarkers of nucleic acid oxidation correlated with both the sum of mandelic and phenylglyoxylic acids (rho > 0.33, p < 0.0001) and 4-vinylphenol (rho > 0.29, p < 0.001), whereas 8-oxodGuo/10⁵ dGuo in WBC showed a negative correlation with exposure parameters (rho < −0.24, p < 0.02). Subjects bearing the hOGG1 Ser/Ser genotype showed lower values of 8-oxodGuo/10⁵ dGuo in WBC than those with at least one variant Cys allele (0.34 ± 0.16 vs 0.45 ± 0.21, p = 0.008). In the subgroup of hOGG1 Ser/Ser subjects, laminators showed lower levels of WBC 8-oxodGuo/10⁵ dGuo ratio and significantly higher concentrations of U-8-oxoGua than controls (p = 0.07 and p = 0.01, respectively, t-test for independent samples). Interestingly, workers showed higher levels of hOGG1 expression compared to controls (p < 0.0005). Styrene exposure seems to be associated with oxidation damage to nucleic acids, particularly to RNA and with an induction of the BER system.     

Dose-dependent influence of genetic polymorphisms on DNA damage induced by styrene oxide, ethylene oxide and gamma-radiation

Styrene oxide (SO), ethylene oxide (EO) and gamma-radiation (G) are agents with a well-described metabolism and genotoxicity. EPHX1 and GSTs play an important role in the detoxification of electrophiles and oxidative stress. Enzymes involved in base excision repair (hOGG1, XRCC1), in rejoining single strand breaks (XRCC1) and in repair of cross-links and chromosomal double strand breaks (XRCC3) might have an impact on genotoxicity as well. In this study we assessed the dose-dependent effect of genetic polymorphisms in biotransforming (EPHX (Tyr113/His113 and His139/Arg139), GSTP1 (Ile105/Val105), GSTM1 and GSTT1) and DNA repair enzymes (hOGG1 (Ser326/Cys326), XRCC1 (Arg194/Trp194, Arg280/His280, Arg399/Gln399), XRCC3 (Thr241/Met241)) on the induced genotoxicity. Peripheral blood mononuclear cells from 20 individuals were exposed to 3 doses per agent (+control). Genotoxicity was evaluated by measuring comet tail length (TL) and micronucleus frequencies in binucleated cells (MNCB). Dose-dependent DNA damage was found for all agents and end-points, with the exception of MNCB induced by EO. Repeated measure ANOVA revealed a significant contribution of hOGG1 and XRCC3 genotypes to the inter-individual variability of TL and MNCB in cells exposed to EO and G. Homozygous hOGG1326 wild cells showed significantly lower EO-induced TL than the heterozygous cells. Significantly higher TL and MNCB were found in EO-exposed cells carrying the XRCC3(241)Met variant and the influence on TL was more pronounced at higher dose. In G-irradiated cells, TL was significantly higher in the hOGG1326 homozygous wild types compared with mutated genotypes. The influence of hOGG1326 on TL was borderline dose-dependent. We conclude that the influence of genetic polymorphisms of enzymes involved in DNA repair on induced genotoxicity depends on exposure dose.     

Relation of PON1 and CYP1A1 genetic polymorphisms to clinical findings in a cross-sectional study of a Greek rural population professionally exposed to pesticides

Allelic variants of CYP1A1 and PON1 have been extensively studied as susceptibility factors in toxic response, although little is known about the role of these variants as risk factors for the plethora of diseases appearing in the human population. In this study we investigated the hypothesis of correlation of CYP1A1 and PON1 enzymes with the incidence of various medical examination findings in a Greek rural population professionally exposed to a variety of pesticides. The medical history of 492 individuals, randomly selected for the total population of 42,000, was acquired by interviews and their genotype determined for the CYP1A1*2A, PON1 M/L and PON1 Q/R polymorphisms. The assessment of exposure to pesticides of the population was verified by analytical methods. Analysis of the genetic data revealed that the allele frequencies of PON1 R, M and CYP1A1*2A alleles were 0.243, 0.39 and 0.107 respectively. The CYP1A1*2A polymorphism was found to have significant association with chronic obstructive pneumonopathy (p = 0.045), peripheral circulatory problems (trend p = 0.042), arteritis (p = 0.022), allergies (trend p = 0.046), hemorrhoids (trend p = 0.026), allergic dermatitis (p = 0.0016) and miscarriages (p = 0.012). The PON1 Q/R polymorphism was found to have significant association with hypertension (p = 0.046) and chronic constipation (p = 0.028) whereas, the L/M polymorphism, with diabetes (p = 0.036), arteritis (trend p = 0.022) and hemorrhoids (trend p = 0.027). Our results demonstrated an association between the CYP1A1/PON1 polymorphisms and several medical examination findings, thus indicating the possible involvement of the human detoxification system to health effects in a rural population exposed professionally to pesticides.     

Oxidative DNA damage and its repair in rat spleen following subchronic exposure to aniline

The mechanisms by which aniline exposure elicits splenotoxic response, especially the tumorigenic response, are not well-understood. Splenotoxicity of aniline is associated with iron overload and generation of reactive oxygen species (ROS) which can cause oxidative damage to DNA, proteins and lipids (oxidative stress). 8-Hydroxy-2′-deoxyguanosine (8-OHdG) is one of the most abundant oxidative DNA lesions resulting from ROS, and 8-oxoguanine glycosylase 1 (OGG1), a specific DNA glycosylase/lyase enzyme, plays a key role in the removal of 8-OHdG adducts. This study focused on examining DNA damage (8-OHdG) and repair (OGG1) in the spleen in an experimental condition preceding a tumorigenic response. To achieve that, male Sprague-Dawley rats were subchronically exposed to aniline (0.5 mmol/kg/day via drinking water for 30 days), while controls received drinking water only. Aniline treatment led to a significant increase in splenic oxidative DNA damage, manifested as a 2.8-fold increase in 8-OHdG levels. DNA repair activity, measured as OGG1 base excision repair (BER) activity, increased by ∼ 1.3 fold in the nuclear protein extracts (NE) and ∼ 1.2 fold in the mitochondrial protein extracts (ME) of spleens from aniline-treated rats as compared to the controls. Real-time PCR analysis for OGG1 mRNA expression in the spleen revealed a 2-fold increase in expression in aniline-treated rats than the controls. Likewise, OGG1 protein expression in the NEs of spleens from aniline-treated rats was ∼ 1.5 fold higher, whereas in the MEs it was ∼ 1.3 fold higher than the controls. Aniline treatment also led to stronger immunostaining for both 8-OHdG and OGG1 in the spleens, confined to the red pulp areas. It is thus evident from our studies that aniline-induced oxidative stress is associated with increased oxidative DNA damage. The BER pathway was also activated, but not enough to prevent the accumulation of oxidative DNA damage (8-OHdG). Accumulation of mutagenic oxidative DNA lesions in the spleen following exposure to aniline could play a critical role in the tumorigenic process.     

Evaluation of the mutagenic effects of myosmine in human lymphocytes using the HPRT gene mutation assay

The minor tobacco alkaloid myosmine is implicated in DNA damage through pyridyloxobutylation similar to the tobacco-specific nitrosamines (TSNA). In contrast to TSNA, occurrence of myosmine is not restricted to tobacco. Myosmine is genotoxic to human cells in the comet assay. In this study, the mutagenic effect of myosmine was evaluated using the cloning hypoxanthine-guanine phosphoribosyltransferase (HPRT) gene mutation assay. Four hour exposure of isolated peripheral blood lymphocytes from 14 subjects homozygous for the Leu84 wild-type of the O⁶-methylguanine-DNA-methyltransferase (MGMT) gene to 1 mM of myosmine increased mutant frequency from 0.73 ± 0.58 × 10⁻⁶ in control to 1.14 ± 0.89 × 10⁻⁶ lymphocytes (P < 0.05). These new data further confirm the mutagenic effects of myosmine.     

Oxidative DNA damage and repair in children exposed to low levels of arsenic in utero and during early childhood: Application of salivary and urinary biomarkers

The present study aimed to assess arsenic exposure and its effect on oxidative DNA damage and repair in young children exposed in utero and continued to live in arsenic-contaminated areas. To address the need for biological specimens that can be acquired with minimal discomfort to children, we used non-invasive urinary and salivary-based assays for assessing arsenic exposure and early biological effects that have potentially serious health implications. Levels of arsenic in nails showed the greatest magnitude of difference between exposed and control groups, followed by arsenic concentrations in saliva and urine. Arsenic levels in saliva showed significant positive correlations with other biomarkers of arsenic exposure, including arsenic accumulation in nails (r = 0.56, P < 0.001) and arsenic concentration in urine (r = 0.50, P < 0.05). Exposed children had a significant reduction in arsenic methylation capacity indicated by decreased primary methylation index and secondary methylation index in both urine and saliva samples. Levels of salivary 8-OHdG in exposed children were significantly higher (~ 4-fold, P < 0.01), whereas levels of urinary 8-OHdG excretion and salivary hOGG1 expression were significantly lower in exposed children (~ 3-fold, P < 0.05), suggesting a defect in hOGG1 that resulted in ineffective cleavage of 8-OHdG. Multiple regression analysis results showed that levels of inorganic arsenic (iAs) in saliva and urine had a significant positive association with salivary 8-OHdG and a significant negative association with salivary hOGG1 expression.     

Modulation of oxidative DNA damage by repair enzymes XRCC1 and hOGG1

The influence of DNA repair gene polymorphisms (XRCC1: Arg194Trp, Arg280His, Arg399Gln; APE1: Asp148Glu; hOGG1: Ser326Cys) on oxidative DNA damage is controversial and was investigated in 214 German workers with occupational exposure to vapors and aerosols of bitumen,compared to 87 German construction workers without exposure, who were part of the Human Bitumen Study. Genotypes were determined by real-time polymerase chain reaction (PCR), and actual smoking habits by a questionnaire and cotinine analysis. Oxidative DNA damage in white blood cells (WBC) collected pre- and postshift was measured as 8-oxodGuo adducts/10(6) dGuo by a hjigh-performance liquid chromatography electron capture detection (HPLC-ECD) method, followed by calculation of the difference between post- and preshift values (Δ8-oxodGuo/10(6) dGuo). The 214 bitumen exposed workers showed higher median Δ8-oxodGuo values than the 87 references. In the whole study group (n=301) there was a trend for increasing adduct values for XRCC1 Arg(GG)399Gln(AA) during a shift, especially in nonsmokers (n=108. Referents (n=87) displayed a similar trend for hOGG1 Ser(CC)326Cys(GG). In contrast, XRCC1 Arg(GG)280His(AA) showed a decrease of median Δ8-oxodGuo/10(6) dGuo values in workers with exposure to vapors and aerosols of bitumen (n=214), especially in smokers (n=145). XRCC1 Arg194Trp and APE1 Asp148Glu displayed no marked association with Δ8-oxodGuo levels. Data indicate that the combination of different variants in DNA damage repair enzymes may modulate the production of 8-oxoguanine adducts in WBC produced by xenobiotics during a shift.