Association of hOGG1 genotype with life style and oxidative DNA damage among Chinese ethnic populations

Blood concentrations of lead, cadmium, mercury and their association with biomarkers of DNA oxidative damage in preschool children living in an e-waste recycling area

Reactive oxygen species (ROS)-induced DNA damage occurs in heavy metal exposure, but the simultaneous effect on DNA repair is unknown. We investigated the influence of co-exposure of lead (Pb), cadmium (Cd), and mercury (Hg) on 8-hydroxydeoxyguanosine (8-OHdG) and human repair enzyme 8-oxoguanine DNA glycosylase (hOGG1) mRNA levels in exposed children to evaluate the imbalance of DNA damage and repair. Children within the age range of 3-6 years from a primitive electronic waste (e-waste) recycling town were chosen as participants to represent a heavy metal-exposed population. 8-OHdG in the children's urine was assessed for heavy metal-induced oxidative effects, and the hOGG1 mRNA level in their blood represented the DNA repair ability of the children. Among the children surveyed, 88.14% (104/118) had a blood Pb level >5 μg/dL, 22.03% (26/118) had a blood Cd level >1 μg/dL, and 62.11% (59/95) had a blood Hg level >10 μg/dL. Having an e-waste workshop near the house was a risk factor contributing to high blood Pb (r _s  = 0.273, p < 0.01), while Cd and Hg exposure could have come from other contaminant sources. Preschool children of fathers who had a college or university education had significantly lower 8-OHdG levels (median 242.76 ng/g creatinine, range 154.62-407.79 ng/g creatinine) than did children of fathers who had less education (p = 0.035). However, we did not observe a significant difference in the mRNA expression levels of hOGG1 between the different variables. Compared with children having low lead exposure (quartile 1), the children with high Pb exposure (quartiles 2, 3, and 4) had significantly higher 8-OHdG levels (β _Q2 = 0.362, 95% CI 0.111-0.542; β _Q3 = 0.347, 95% CI 0.103-0.531; β _Q4 = 0.314, 95% CI 0.087-0.557). Associations between blood Hg levels and 8-OHdG were less apparent. Compared with low levels of blood Hg (quartile 1), elevated blood Hg levels (quartile 2) were associated with higher 8-OHdG levels (β _Q2 = 0.236, 95% CI 0.039-0.406). Compared with children having low lead exposure (quartile 1), the children with high Pb exposure (quartiles 2, 3, and 4) had significantly higher 8-OHdG levels.

Haplotype CGC from XPD, hOGG1 and ITGA2 polymorphisms increases the risk of nasopharyngeal carcinoma in Malaysia

BACKGROUND

8-oxoG, a common DNA lesion resulting from reactive oxygen species (ROS), has been shown to be associated with cancer initiation. hOGG1 DNA glycosylase is the primary enzyme responsible for excision of 8-oxoG through base excision repair (BER). Integrins are members of a family of cell surface receptors that mediate the cell-cell and extracellular matrix (ECM) interactions. Integrins are involved in almost every aspect of carcinogenesis, from cell differentiation, cell proliferation, metastasis to angiogenesis. Loss of ITGA2 expression was associated with enhanced tumor intravasation and metastasis of breast and colon cancer. XPD gene encodes DNA helicase enzyme that is involved in nucleotide excision repair (NER). It is shown in previous research that XPD homozygous wildtype Lys/Lys genotype was associated with higher odds of NPC.

METHODS

We conducted a 1 to N case-control study involving 300 nasopharyngeal carcinoma (NPC) cases and 533 controls matched by age, gender and ethnicity to investigate the effect of hOGG1 Ser326Cys, ITGA2 C807T and XPD Lys751Gln polymorphisms on NPC risk. Linkage disequilibrium and haplotype analysis were conducted to explore the association of allele combinations with NPC risk. Restriction fragment length polymorphism (RFLP-PCR) was used for DNA genotyping.

RESULTS

No significant association was observed between hOGG1 Ser326Cys and ITGA2 C807T polymorphisms with NPC risk after adjustment for age, gender, ethnicity, cigarette smoking, alcohol and salted fish consumption. Lys/Lys genotype of XPD Lys751Gln polymorphism was associated with increased NPC risk (OR = 1.60, 95% CI = 1.06-2.43). Subjects with history of smoking (OR = 1.81, 95% CI = 1.26-2.60), and salted fish consumption before age of 10 (OR = 1.77, 95% CI = 1.30-2.42) were observed to have increased odds of NPC. The odds of developing NPC of CGC haplotype was significantly higher compared to reference AGC haplotype (OR = 2.20, 95% CI = 1.06-4.58).

CONCLUSION

The allele combination of CGC from hOGG1, ITGA2 and XPD polymorphisms was significantly associated with increased odds of NPC.

Compensatory effects of hOGG1 for hMTH1 in oxidative DNA damage caused by hydrogen peroxide

OBJECTIVE

To investigate the potential compensatory effects of hOGG1 and hMTH1 in the repair of oxidative DNA damage.

METHODS

The hOGG1 and hMTH1 gene knockdown human embryonic pulmonary fibroblast cell lines were established by lentivirus-mediated RNA interference. The messenger RNA (mRNA) levels of hOGG1 and hM1TH1 were analyzed by the real-time polymerase chain reaction, and 8-hydroxy-2'-deoxyguanosine (8-oxo-dG) formation was analyzed in a high-performance liquid chromatography-electrochemical detection system.

RESULTS

The hOGG1 and hMTH1 knockdown cells were obtained through blasticidin selection. After transfection of hOGG1 and hMTH1 small interfering RNA, the expression levels of the mRNA of hOGG1 and hMTH1 genes were decreased by 97.2% and 96.2%, respectively. The cells then were exposed to 100 μmol/L of hydrogen peroxide (H2O2) for 12 h to induce oxidative DNA damage. After H2O2 exposure, hMTH1 mRNA levels were increased by 25% in hOGG1 gene knockdown cells, whereas hOGG1 mRNA levels were increased by 52% in hMTH1 gene knockdown cells. Following the treatment with H2O2, the 8-oxo-dG levels in the DNA of hOGG1 gene knockdown cells were 3.1-fold higher than those in untreated HFL cells, and 1.67-fold higher than those in H2O2-treated wild-type cells. The 8-oxo-dG levels in hMTH1 gene knockdown cells were 2.3-fold higher than those in untreated human embryonic pulmonary fibroblast cells, but did not differ significantly from those in H2O2-treated wild-type cells.

CONCLUSION

Our data suggested that hOGG1 could compensate for hMTH1 during oxidative DNA damage caused by H2O2, whereas hMTH1 could not compensate sufficiently for hOGG1 during the process.

hOGG1 Ser326Cys polymorphism is associated with risk of bladder cancer in a Chinese population: a case-control study

Human oxoguanine glycosylase 1 (hOGG1) is a DNA repair enzyme, which plays important roles in the base excision repair (BER) pathway. Several studies reported a common polymorphism Ser326Cys (rs1052133) in hOGG1, which conferred the susceptibility of bladder cancer. We hypothesized that the polymorphism is associated with risk of bladder cancer in a Chinese population. In a case-control study of 1050 histologically confirmed bladder cancer patients and 1404 age and sex matched healthy controls, we genotyped the hOGG1 Ser326Cys polymorphism using TaqMan technology and assessed its association with bladder cancer risk. We found that the hOGG1 Ser/Cys + Ser/Ser genotypes were associated with a significantly increased risk of bladder cancer (adjusted odds ratio [OR] = 1.19, 95% confidence interval [CI] = 1.01-1.41), compared with the Cys/Cys genotype. Furthermore, the increased risk was more pronounced among subjects over age 65 years (OR = 1.31, 95% CI = 1.04-1.66), male subjects (OR = 1.21, 95% CI = 1.00-1.47), ever smokers (OR = 1.29, 95% CI = 1.00-1.68) and heavy smokers (>20 pack-years) (OR = 1.45, 95% CI = 1.03-2.04). No significant association was observed in the stratification of tumor grade and tumor stage for bladder cancer. In conclusion, our results suggest that hOGG1 Ser326Cys polymorphism may contribute to the susceptibility to bladder cancer in a Chinese population.

Role of OGG1 Ser326Cys polymorphism and 8-oxoguanine DNA damage in risk assessment of squamous cell carcinoma of head and neck in North Indian population

Squamous cell carcinoma of head and neck (SCCHN), one of the leading cancers worldwide, is most prevalent in Indian sub-continent. The major risk factors involved are smoking and consumption of alcohol, since they provide high free radical generating environment. We studied 8-oxoguanine DNA-glycosylase (OGG1) Ser326Cys polymorphism in 278 SCCHN cases and 278 matched controls by PCR-RFLP and observed that the variant genotype Ser/Cys exhibited an enhanced risk of ∼1.7 folds (OR=1.71, 95% CI=1.20-2.93) and Cys/Cys ∼2.5 folds (OR=2.55, 95% CI=1.29-5.00). Furthermore, we found a significant increase in salivary cell 8-OHdG with respect to Ser/Cys and Cys/Cys genotypes of OGG1 in SCCHN cases, when compared to Ser/Ser and Ser/Cys genotypes of the control population. Our results demonstrate that Ser326Cys variant genotype is associated with an increased risk of SCCHN in north India. Ser326Cys variant genotype was found to accumulate more of 8-OHdG, which may serve as a biomarker for early diagnosis of SCCHN.

The 8-oxoguanine glycosylase I (hOGG1) Ser326Cys variant affects the susceptibility to multi-vessel disease in Taiwan coronary artery disease patients

8-hydroxydeoxyguanosine, the key lesion of oxidative DNA damage, contributes to the development of coronary artery disease (CAD). In humans, 8-hydroxydeoxyguanosine is repaired by the enzyme 8-oxoguanine glycosylase I (hOGG1). We investigated the association between the hOGG1 Ser(326)Cys polymorphism and the presence and the severity of CAD in a Taiwan population. Genotypes of the hOGG1 Ser(326)Cys polymorphism were determined from 1397 participants enrolled in this study (378 CAD patients and 1019 controls). CAD severity was indicated both by number of vessels affected (single-vessel disease, SVD vs. multi-vessel disease, MVD), and by individual diffuse score. Real-time polymerase chain reaction was used to determine genotype, using allele-specific TaqMan probes. We found that presence of the hOGG1 Ser(326)Cys polymorphism was associated with a significantly increased risk of CAD and multi-vessel disease when assuming a dominant model of inheritance (OR: 1.52 [95%:1.082~2.133], p=0.015; OR: 2.26 [95%:1.232~4.156], p=0.007). This result was confirmed by multivariate analysis, after adjustment for age, gender, body-mass index, diabetes hypertension, hypercholesterolemia and smoking (OR: 1.78 [95%:1.127~2.806], p<0.005; OR: 2.44 [95%:1.276~4.651], p<0.001). In the present study, hOGG1 Ser(326)Cys polymorphism is a novel genetic marker to be independently associated with the development and severity of CAD in Taiwanese population.