Association of Oxidative Damage Measured by 8-hydroxyguanosine Formation with Altered Risks to Hepatocellular Carcinoma in Malaysian Study Population

@#Introduction: Oxidative damage is an important factor contributing to ageing and many degenerative diseases. It can be detected by the DNA base damage, which is formation of 8-oxo-7,8-dihydro-2’deoxyguanosine (8-oxodG). The 8-oxodG is an important indicator of oxidative stress and has been competently specified as a recognized initiator of the carcinogenic process and premutagenic injury in mammalian cells. Aims: In this preliminary study, we investigated the possible association of oxidative DNA damage in hepatocellular carcinoma (HCC) patients in comparison with Malaysian healthy controls taking into account the different races and genders in both groups. Method: DNA of peripheral white blood cells was isolated from 91 HCC patients and 304 controls. The level of oxidative DNA damage was determined by ELISA procedure. Results: Quantitative measurement of 8-oxodG was higher in HCC patients at mean value of 3.30 ± 2.32 ng/ml. In controls, the average value is 1.57 ± 1.92 ng/ml. Comparison between gender showed that there was a significant difference observed in the level of 8-oxodG between male and female in controls, where p = 0.003. The level of 8-oxodG was higher in male than in female controls. There was a significant difference in the average value of 8-oxodG level between the controls and HCC patients where p<0.001. However, no significant difference in the level of 8-oxodG value was observed when compared between Malays and the non-Malays. Conclusion: HCC patients showed greater oxidative damage to DNA as compared to controls and this suggests oxidative DNA damage may contribute to the pathogenesis of HCC.

Iron Indices and Urinary 8-Oxo-7, 8-Dihydro-2’- Deoxyguanosine (8-Oxodg) in Patients with Cervical Intraepithelial Neoplasia.

Aim: To investigate the role of iron status in cervical carcinogenesis through its involvement in the Haber-Weis and Fenton reactions serving as a pathway to carcinogenesis and using 8-oxo-7, 8- dihydro-2’-deoxyguanosine (8-oxodG) as a marker of DNA oxidation in a population where iron deficiency is prevalent. Study Design: It is a cross sectional study. Place of Study: The patients were recruited from the colposcopy clinic of the University College Hospital (UCH), Ibadan and Obafemi Awolowo University Teaching Hospitals Complex, Ile-Ife, Nigeria. The laboratory investigations were carried out at the Haematology and Chemical Pathology laboratories of UCH, Ibadan and Oxidative Stress Group, Department of Cancer Studies and Molecular Medicine, University of Leicester, Leicester, UK. Methodology: Forty-five subjects with CIN and 41 with normal Pap smear result (non-CIN) were recruited. A structured questionnaire was administered to collect information on demographic characteristics, dietary, social and medical history. Fasting blood sample were collected to assess for serum iron, total iron binding capacity and transferrin saturation. Urine was also collected to analyze for creatinine and 8-oxodG. Results: The CIN subjects had more babies; > 5 than non-CIN subjects (P=.003). The individuals with > 5 children were 4 times more likely to have CIN [OR 3.79 (95% CI 1.3-10.33), P=.01]. CIN subjects had higher serum iron and transferrin saturation than non-CIN subjects. Though the mean urinary 8-oxodG level similar between the two groups, there was a trend towards higher levels in individuals with high grade CIN. Conclusion: High serum iron level was linked to frequent ingestion of iron supplement and may contribute to progression of CIN with a potential role for urinary 8-oxodG as a useful bio indicator of altered iron homeostasis and associated DNA damage.

Telomeres and Oxidative Stress.

Telomeres are long repetitive DNA sequences of TTAGGG located at the end of the linear chromosomes and bound by shelterin proteins. Shelterin proteins function as the protection for the loop structure of telomere, which prevents the chromosome ends uncapped; resemble a DNA break and activates DNA repair mechanism. Telomere length is maintained by an enzyme called telomerase. There are several factors that can shorten the telomeres which include telomere attrition during cell division, deficiency of Rad 54, which is involved in DNA repair and the methylation of histones H3 and histones H4, which can diminish telomerase activity. Three major mechanisms which influence the telomere length are the end-replication problem, the action of C-strand-specific exonuclease and oxidative DNA damage induced by environmental risk factors. However, oxidative stress has been shown to be the major mechanism which can influence the telomere length. This review explores the association between telomere length a oxidative stress.

Modulatory effect of plasma folate and polymorphisms in one-carbon metabolism on catecholamine methyltransferase (COMT) H108L associated oxidative DNA damage and breast cancer risk.

The present study was aimed to investigate the modulatory role of plasma folate and eight putatively functional polymorphisms of one-carbon metabolism on catecholamine methyltransferase (COMT)-mediated oxidative DNA damage and breast cancer risk. Plasma folate and 8-oxo-2’-deoxyguanosine (8-oxodG) were estimated by commercially available kits, while polymorphisms were screened by PCR-RFLP and PCR-AFLP methods. COMT H108L polymorphism showed independent association with breast cancer (OR: 1.73, 95% CI: 1.31-2.30). No significant interaction was observed between folate status and COMT genotype. Multifactor dimensionality reduction (MDR) analysis gave evidence for the significant epistatic (gene-gene) interactions (p<0.0001) of COMT H108L with reduced folate carrier 1 (RFC1) G80A, thymidylate synthase (TYMS) 5’-UTR 3R2R, TYMS 3’-UTR ins6/del6. Increased plasma 8-oxodG were observed in cases compared to controls (mean ± SE: 5.59 ± 0.60 vs. 3.50 ± 0.40 ng/ml, p<0.004). Plasma folate deficiency alone was not a significant predictor of 8-oxodG elevation. The genotype combinations namely, RFC1 G80A/methionine synthase reductase (MTRR) A66G, RFC1 G80A/SHMT C1420T/TYMS 3R2R and serine hydroxymethyltransferase (SHMT) C1420T/TYMS 3R2R/methionine synthase (MTR) A2756G/COMT H108L were strong predictors of 8-oxodG elevation in the order of risk. To conclude, the current study provides substantial evidence for a cross talk between one-carbon metabolism and COMT catalysis that might influence oxidative DNA damage and breast cancer risk.

Ginsenoside-Rg1 protects human dermal fibroblasts against 8-methoxypsoralen plus ultraviolet A-induced photoaging through p53-dependent signaling pathways / 中国药理学通报

Aim To investigate the roles of p53-dependent signaling pathways in the process of ginsenoside Rg1 protection against 8-methoxypsoralen(8-MOP) and subsequent ultraviolet A(UVA) irradiation induced photoaging model in human dermal fibroblasts(HDFs).Methods Photoaging model was established by 8-MOP/UVA in skin HDFs.Flow cytometry, enzyme cytochemistry, immunofluorescence and Western blot were employed.Results Pretreatment with ginsenoside Rg1 could significantly reduce the amount of UVA-generated 8-oxo-dG and relieve the photoaging representation.Compared with 8-MOP/UVA treatment group, pretreatment with Ginsenoside Rg1 could decrease the expression of SA β-galatosides(SA-β-Gal), and down-regulate the level of senescence associated proteins(p16 and p21).Conclusions Ginsenoside Rg1 has prominent dose-dependent antagonism on senescence of skin HDFs induced by 8-MOP/UVA, and its mechanism may be due to its antioxidation which reduces the production of photoproducts to protect telomere against abnormal shortening.