Leukocyte 8-OHdG Research Articles

Leukocyte 8-hydroxy-2'-deoxyguanosine as an oxidative stress marker to predict cardiovascular events and death in chronic hemodialysis patients.

Hemodialysis patients have a markedly increased risk of cardiovascular (CV) morbidity and mortality. Oxidative stress plays a pathogenic role in the progression of atherosclerosis and CV disease among chronic hemodialysis patients. The 8-hydroxy-2'-deoxyguanosine (8-OHdG) content in leukocyte deoxyribonucleic acid (DNA) has been shown as a sensitive and well-known biomarker of oxidant-induced DNA damage in chronic hemodialysis patients. We conducted a retrospective cohort study to investigate the association of leukocyte 8-OHdG and CV events and deaths in patients of chronic hemodialysis. In this study, 217 chronic hemodialysis patients were recruited from 2016 to 2021. The 8-OHdG content of leukocyte DNA was measured by a high-performance liquid chromatography electrochemical detection method. Study outcomes were CV events as well as CV and all-cause deaths. The patients were followed until May 2021. The median follow-up period was 34.8 months. At the end of May 2021, 57 first CV events and 89 all-CV events occurred. Among the first and all CV events, 17 (29.8%) and 32 (36.0%) were fatal, respectively. Multivariate Cox regression analysis showed per 1/10 5 dG increment in leukocyte 8-OHdG values increased risk of CV events (adjusted hazard ratio [aHR], 1.19; 95% CI, 1.10-1.41; p < 0.001), CV death (aHR, 1.27; 95% CI, 1.03-1.72; p = 0.034), and all-cause death (aHR, 1.11; 95% CI, 1.01-1.30; p = 0.038). This is the first study to demonstrate that oxidative stress assessed by 8-OHdG levels of leukocyte DNA predicted CV events as well as CV and all-cause deaths among chronic hemodialysis patients.

Telomere Shortening and Increased Oxidative Stress in Lumbar Disc Degeneration.

Lumbar disc degeneration (LDD) contributes to low back pain. This study aimed to determine relative telomere length (RTL), oxidative stress status, and antioxidant levels and examine the relationships between RTL, oxidative stress, and the severity in LDD patients. A total of 100 subjects, 50 LDD patients and 50 healthy controls, were enrolled in the case–control study. Blood leukocyte RTL was analyzed using quantitative real-time polymerase chain reaction. Lipid peroxidation was determined by malondialdehyde (MDA) assay. Plasma 8-hydroxy 2′-deoxyguanosine (8-OHdG) values were determined using enzyme-linked immunosorbent assay. Total antioxidant capacity (TAC) and ferric reducing antioxidant power (FRAP) in plasma were also measured. The LDD patients had significantly shorter telomeres than the healthy controls (p = 0.04). Blood leukocyte RTL was inversely correlated with the LDD severity (r = −0.41, p = 0.005). Additionally, plasma MDA and 8-OHdG levels were markedly greater in LDD patients than in the controls (p = 0.01 and p = 0.002, respectively). Furthermore, the plasma MDA level showed a positive correlation with the radiographic severity (r = 0.49, p = 0.001). There was a positive correlation between plasma 8-OHdG and the severity (r = 0.60, p < 0.001). Moreover, plasma TAC and FRAP levels were significantly lower in LDD patients than in the controls (p = 0.04). No significant differences in plasma TAC and FRAP were observed among the three groups of LDD severity. We found that RTL was negatively correlated with the severity while plasma MDA and 8-OHdG levels were positively correlated with the severity. These findings suggest that blood leukocyte RTL, plasma MDA, and 8-OHdG may have potential as noninvasive biomarkers for the assessment of severity in LDD.

Biochemical and Molecular Studies of Different Parameters as Markers for Nephropathy in Type 1 Diabetic Patients

Albuminuria is the most characteristic marker of diabetic nephropathy (DN), which is a diabetic complication associated with DN progression. However, renal functions decreased by about one-third of diabetic patients before the occurrence of albuminuria. We study the role of telomere length (TL) of blood leukocytes, some inflammatory markers in the progression of DN in patients with type 1 diabetes (T1D). Volunteers were selected and distributed into four groups: group 1 included 20 healthy subjects as control, group 2: 20 T1D patients with albumin excretion rate (AER) &lt; 30 mg/gm creatinine, group 3: 15 T1D patients with (300 &gt; AER &gt; 30 mg/gm creatinine), group 4: 15 T1D patients with (AER &gt; 300 mg/gm creatinine) and group 5 (DN group), which is a collective group between group 3 and group 4. Glycated haemoglobin (HbA1c), serum urea, creatinine, malondialdehyde (MDA), 8-OHdG, and TL in leukocytes were measured. Results showed a significant increase in HbA1c, creatinine, urea, 8-OHdG, transforming growth factor β1 (TGF-β1), MDA and decrease in TL in G2, G3, G4, and G5 compared with control with a p-value &lt; 0.05.

Oxidative Stress and Antioxidant Status in High-Risk Prostate Cancer Subjects.

The oxidant/antioxidant balance has been implicated in the pathophysiology of prostate cancer. We investigated oxidative damage and antioxidant status in high-risk prostate cancer subjects. Reduced glutathione (GSH) levels were measured in erythrocytes, 8-hydroxydeoxyguanosine (8-OHdG) in leukocytes and plasma levels of catalase (CAT), glutathione peroxidase (GSH-Px), glutathione reductase (GSH-R), glutathione S-transferase (GST), superoxide dismutase (SOD), and lipid peroxide products were measured in high-risk and age-matched healthy subjects. Serum PSA levels were significantly higher (p < 0.0001) in high-risk subjects, whereas GST (p < 0.0001) and GSH (p < 0.002) were higher in healthy controls. Levels of 8-OHdG, an oxidized nucleoside of DNA, were significantly increased (p < 0.0001) in high-risk subjects. No marked difference in the levels of CAT (p = 0.237), GSH-Px (p = 0.74), GSH-R (p = 0.344), SOD (p = 0.109), and lipid peroxide products (p = 0129) were observed between two groups. Pearson’s correlation between GST and PSA (r = −0.69 (p < 0.0001)), GST and 8-OHdG (r = −0.62 (p < 0.0004)), GSH and 8-OHdG (r= −0.39 (p = 0.038)), and CAT and GSH-Px (r= −0.33 (p = 0.04)) were found to be negatively correlated, whereas 8-OHdG and PSA were positively associated (r= 0.57 (p < 0.002). These results indicate a significant role of oxidative damage in prostate carcinogenesis, particularly during the early stages of development. In conclusion, our data support the importance of antioxidant defense as a valuable diagnostic and/or prognostic marker in prostate cancer.

Mitochondrial 8-hydroxy-2\u2032-deoxyguanosine and coronary artery disease in patients with type 2 diabetes mellitus

BackgroundLittle is known about whether mitochondria 8-hydroxy-2′-deoxyguanosine (8-OHdG), a biomarker of mitochondrial DNA (mtDNA) oxidative damage, contributes to the development of coronary artery disease (CAD) in diabetic patients. Here, we explored the associations of mtDNA 8-OHdG in leukocytes with obstructive CAD, coronary stenosis severity, cardiovascular biomarkers, and 1-year adverse outcomes after coronary revascularization in patients with type 2 diabetes mellitus (T2DM).MethodsIn a total of 1920 consecutive patients with T2DM who underwent coronary angiography due to symptoms of angina or angina equivalents, the presence of obstructive CAD, the number of diseased vessels with ≥ 50% stenosis, and modified Gensini score were cross-sectionally evaluated; the level of mtDNA 8-OHdG was quantified by quantitative PCR. Then, 701 of 1920 diabetic patients who further received coronary revascularization completed 1-year prospective follow-up to document major adverse cardiovascular and cerebral events (MACCEs). In vitro experiments were also performed to observe the effects of mtDNA oxidative damage in high glucose-cultured human umbilical vein endothelial cells (HUVECs).ResultsCross-sectionally, greater mtDNA 8-OHdG was associated with increased odds of obstructive CAD (odds ratio [OR] 1.38, 95% CI confidence interval 1.24–1.52), higher degree of coronary stenosis (number of diseased vessels: OR 1.29, 95% CI 1.19–1.41; modified Gensini scores: OR 1.28, 95% CI 1.18–1.39), and higher levels of C-reactive protein (β 0.18, 95% CI 0.06–0.31) after adjusting for confounders. Sensitivity analyses using propensity score matching yielded similar results. Stratification by smoking status showed that the association between mtDNA 8-OHdG and obstructive CAD was most evident in current smokers (Pinteration < 0.01). Prospectively, the adjusted hazards ratio per 1-SD increase in mtDNA 8-OHdG was 1.59 (95% CI 1.33–1.90) for predicting 1-year MACCEs after revascularization. In HUVECs, exposure to antimycin A, an inducer for mtDNA oxidative damage, led to adverse alterations in markers of mitochondrial and endothelia function.ConclusionGreater mtDNA 8-OHdG in leukocytes may serve as an independent risk factor for CAD in patients with T2DM.

Leukocyte Mitochondrial DNA Copy Number and Risk of Thyroid Cancer: A Two-Stage Case-Control Study.

Background: Mitochondrial DNA copy number (mtDNA-CN) may contribute to the development of various cancer types in a tumor-specific manner. However, little is known about whether leukocyte mtDNA content confers susceptibility to thyroid cancer (TC). This study aimed to investigate the associations of leukocyte mtDNA-CN with the risk and clinicopathological features of TC in a Chinese population.Methods: In this two-stage case-control study with a total of 402 TC patients and 406 controls, leukocyte mtDNA-CN content was measured with a quantitative PCR method. In a subset of 100 cases and 100 controls, levels of leukocyte 8-hydroxy-2′-deoxyguanosine (8-OHdG) and plasma malondialdehyde, as two biomarkers for oxidative stress, were determined by ELISA and colorimetric kits, respectively.Results: In a combined analysis of discovery and validation sets, high mtDNA-CN content was positively associated with increased TC risk, after adjusting for confounders (OR for per SD increment: 1.43; 95%CI, 1.23–1.66; P < 0.001; OR for tertile 3 vs. tertile 1: 2.10; 95%CI, 1.48–3.00; Ptrend < 0.001). This linear dose-response relationship was more pronounced in subtype analyses for papillary and follicular thyroid carcinoma (P < 0.001 for all), as well as in subgroup analyses for subjects with overweight and obesity (Pinteraction = 0.015). In TC patient, we observed the positive correlations of mtDNA-CN with advanced TNM stage (P = 0.006) and the presence of lymph node metastasis (P = 0.012). Leukocyte mtDNA-CN content was also identified to increase with the levels of leukocyte 8-OHdG (P < 0.001), a biomarker for oxidative DNA damage.Conclusion: Our data suggest that the increase in leukocyte mtDNA-CN content may correlate with oxidative DNA damage, and serve as an independent risk factor for TC.

Leukocyte telomere length, mitochondrial DNA copy number, and coronary artery disease risk and severity: A two-stage case-control study of 3064 Chinese subjects

Background and aimsLeukocyte telomere length (TL) and mitochondrial DNA copy number (mtDNA-CN), as hallmarks of cellular aging, may be involved in the development of coronary artery disease (CAD) by modulating oxidative stress. This study aimed to investigate the effects of leukocyte TL and mtDNA-CN alone or in combination on CAD risk and severity in the Chinese population. MethodsIn this two-stage case-control study with 1511 CAD patients and 1553 controls, leukocyte TL and mtDNA-CN were determined by a quantitative PCR assay. Three oxidative parameters, including leukocyte 8-hydroxy-2′-deoxyguanosine (8-OHdG), plasma malondialdehyde, and plasma reactive oxygen species (ROS), were quantified by ELISA or colorimetric kits in a subset of 129 cases and 129 controls. ResultsIn the combined cohort, each 1-SD decrease in TL and mtDNA-CN was significantly associated with a 1.17-fold and 1.14-fold increased risk of CAD (p < 0.001 for all), respectively, after adjusting for confounders. The aggregated score, which reflected the cumulative dosage of the tertiles of TL and mtDNA-CN, showed inverse dose-response correlations with CAD risk (ptrend < 0.001), and severity, as determined by the severity of clinical presentations (ptrend = 0.037), the presence of multi-vessel CAD (ptrend = 0.004), and modified Gensini scores (ptrend = 0.009). Similar dose-response relations of the aggregated score to leukocyte 8-OHdG and plasma ROS were also identified. ConclusionsOur data suggested reductions in both TL and mtDNA-CN as independent risk factors for CAD. The combination of TL and mtDNA-CN might jointly contribute to CAD risk, CAD severity, and oxidative stress.

Detection of 8-hydroxydeoxyguanosine (8-OHdG) as a biomarker of oxidative damage in peripheral leukocyte DNA by UHPLC-MS/MS.

8-Hydroxydeoxyguanosine (8-OHdG) is a widely-used biomarker of oxidative DNA damages. 8-OHdG in peripheral blood leukocyte is associated with mutation and cancer risk. The level of 8-OHdG in peripheral blood leukocytes can indicate a long-term response to oxidative stress rather than that in urine. Accurate identification and quantification of leukocyte 8-OHdG are essential for understanding its mechanism of formation, repair, and biological consequences. In this study, a fast and accurate ultra-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method was developed and validated to detect 8-OHdG in human peripheral leukocyte. DNA in blood samples were extracted and digested, then subjected onto UHPLC-MS/MS using an isocratic elution on a Zorbax Eclipse Plus C18 column (2.1×100mm, 1.8μm). Multiple reaction monitoring (MRM) mode was adopted by using [15N5]-8-OHdG as an internal standard. The assay was linear over the concentration range of 1.0-100nM with R2=0.999. The accuracy for spiked samples was 90.9%-94.8%, and the intra-day precision was within 3.7%. The limit of detection (LOD) is 0.30nM and limit of quantification (LOQ) is 1.0nM with 5μl of sample injection. By the analysis of human leukocyte 8-OHdG (n=121) using the developed UHPLC-MS/MS method, it demonstrates that the level of leukocyte 8-OHdG of the cancer patients group (n=46) is significantly higher than that of the health control (n=75).

Pancreatic Cancer is Associated with Peripheral Leukocyte Oxidative DNA Damage

Background:DNA damage accumulation has been linked to the cancer phenotype. The purpose of this study was to compare the levels of DNA base 8-hydroxy-2’-deoxyguanosine (8-OHdG) and C-reactive protein (CRP) inflammatory markers in healthy controls and pancreatic cancer patients from a hospital-based case-control study.Materials and Methods:Fifty-five pancreatic cancer patients and 55 healthy controls were enrolled from a pool of patients referred to the Endoscopic Ultrasound (EUS) center. Analysis of DNA content of peripheral blood cells was conducted for 8-OHdG with the 32P-postlabelling assay. Serum CRP levels were measured by high-sensitivity assays and demographic data for comparison were collected from individual medical records.Results:The group of cases showed significant increased median (IQR) 8-OHdG DNA adducts/106 nucleotides and CRP compared to the controls (208.8 (138.0-340.8) vs 121.8 (57.7-194.8) RAL value; P<0.001) and (3.5 (1.5-8.6) vs 0.5 (0.2-1.5) mg/L P<0.001). A number of conditional regression models confirmed associations of pancreatic cancer with oxidative DNA damage in peripheral leukocytes.Conclusions:Our findings suggest the importance of leukocyte 8-OHdG adducts as an indicator for systemic oxidative DNA damage in pancreatic cancer patients. In addition to increase in the CRP inflammatory marker, this supports the impact of inflammation in the occurrence of pancreatic cancer as well as inflammatory responses during cancer development.

Increased 8-hydroxy-2'-deoxyguanosine in leukocyte DNA from patients with type 2 diabetes and microangiopathy.

ObjectiveTo evaluate oxidative damage in leukocytes from patients with type 2 diabetes by examining 8-hydroxy-2’-deoxyguanosine (8-OHdG) levels.MethodsPatients with type 2 diabetes and healthy controls were assessed for demographic, clinical and biochemical characteristics. Levels of 8-OHdG in extracted leukocyte DNA were determined by enzyme linked immunosorbent assay.ResultsOf 108 patients with type 2 diabetes (56 with microangiopathy, 52 without) and 65 healthy controls, leukocyte 8-OHdG levels were higher in patients with type 2 diabetes versus controls (median ± interquartile range [IQR], 3.19 ± 2.17 versus 0.38 ± 1.00 ng/ml), and higher in patients with type 2 diabetes and microangiopathy versus those without microangiopathy (median ± IQR, 3.34 ± 1.87 versus 2.71 ± 2.26 ng/ml). Patients with type 2 diabetes and microangiopathy had higher serum creatinine and urinary albumin levels versus those without microangiopathy. Leukocyte 8-OHdG levels, duration of type 2 diabetes, albuminuria, use of insulin and use of angiotensin-converting enzyme (ACE) inhibitors/angiotensin receptor blockers (ARBs) were independently associated with microangiopathy in patients with type 2 diabetes after adjustment for smoking.ConclusionsLeukocyte oxidative DNA damage was high in patients with type 2 diabetes and microangiopathy. Presence of microangiopathy was associated with leukocyte 8-OHdG levels, duration of type 2 diabetes, albuminuria and use of ACE inhibitors/ARBs or insulin.

DNA damage in children with obstructive adenotonsillar hypertrophy.

The objective of this prospective, controlled study was to evaluate oxidative DNA damage in children with obstructive adenotonsillar hypertrophy. This study included 30 patients with obstructive adenotonsillar hypertrophy (male/female ratio, 3:2; age range, 3-9 y) scheduled to undergo tonsillectomy and adenoidectomy and 25 control subjects of similar age and sex with no adenotonsillar disease or airway obstruction. Urine and blood samples were obtained from each child for 8-hydroxy 2-deoxyguanosine (8-OhdG) and malondialdehyde (MDA) concentrations. There were significant differences in leukocyte (3.28 [0.69/10] vs 0.70 [0.15/10] dG) and urine 8-OhdG (8.22 [2.27/10] vs 5.26 [1.3/10] dG) levels in patients with obstructive adenotonsillar hypertrophy and healthy subjects (P < 0.001 for both). Plasma (2.98 [1.31] vs 1.14 [0.64] μM) and urine (1.77 [0.84] vs 0.56 [0.32] μM) MDA levels were also different (P < 0.001 for both). There were positive correlations between 8-OhdG in leukocyte DNA and plasma MDA (r = 0.648, P < 0.001) and between levels of urine 8-OhdG excretion and urine MDA (r = 0.588, P < 0.001). The DNA damage in children with adenotonsillar hypertrophy should be kept in mind, but further studies must be done with larger patient groups.

Oxidative markers in spontaneous intracerebral hemorrhage: leukocyte 8-hydroxy-2'-deoxyguanosine as an independent predictor of the 30-day outcome.

Oxidative stress may play a role in spontaneous intracerebral hemorrhage (ICH), but data on oxidative burden in cerebral hemorrhage are limited, and it is not clear whether oxidative markers add predictive power regarding ICH outcome beyond that of traditional factors. The authors therefore examined redox status and traditional factors in ICH patients within 3 days of hemorrhage onset to delineate redox status in ICH and investigate the predictive value with respect to 30-day functional outcome. Sixty-four patients with ICH and 114 controls were prospectively enrolled in this study. Blood samples were collected within 3 days of ICH onset and processed for isolation of plasma, erythrocytes, and leukocytes. The authors evaluated levels or activities of leukocyte 8-hydroxy-2'-deoxyguanosine (8-OHdG), erythrocyte glucose-6-phosphate dehydrogenase (G6PD), erythrocyte glutathione peroxidase (GPx), plasma malondialdehyde (MDA), vitamin E, and vitamin A, as well as traditional factors including the presence of hypertension or diabetes mellitus, total cholesterol level, and measures of liver function. A general linear model and multivariable logistic regression were used for analyses where appropriate. After adjustment for age and sex and traditional risk factors, ICH was significantly associated with an increased level of 8-OHdG (p < 0.0001), decreased GPx activity (p = 0.0002), and a decreased level of vitamin E (p = 0.003). There was no association of ICH risk with G6PD activity or MDA or vitamin A level. Considering all the oxidative markers and traditional risk factors together, logistic regression showed an independent association of ICH with 8-OHdG (OR 2.7, 95% CI 1.7-4.2, p < 0.0001). The association between increased 8-OHdG level and lower 30-day Barthel Index was also independent of the effects of age, sex, hemorrhage location and size, and traditional factors (p = 0.026). Unfavorable outcome (modified Rankin Scale score ≥ 3) at 30 days after ICH onset was not significantly associated with any of the examined oxidative markers. Increased leukocyte 8-OHdG levels, as well as decreased GPx activity and vitamin E levels, were found during acute ICH. Only 8-OHdG was associated with ICH and the 30-day outcome independently from the other oxidative markers and traditional factors. Leukocyte 8-OHdG may add power beyond the traditional factors in predicting ICH outcome and thus may be used as an independent surrogate for clinical ICH study.

Oxidative DNA damage in patients with cataract

This study examines the levels of oxidative damage in patients with cataract. Blood samples were collected from 60 patients with cataract and 60 age- and gender-matched healthy individuals to measure 8-hydroxy 2-deoxyguanosine (8-OHdG) and malondialdehyde (MDA) levels. A significant difference was observed in leukocyte 8-OHdG levels in patients with cataract in comparison with healthy persons (p < 0.001). Similarly, a significant difference was observed in plasma MDA levels in patients with cataract in comparison with healthy persons (p<0.001). In addition, a significant correlation was found between levels of 8-OHdG in leukocyte DNA and plasma MDA (r = 0.859, p < 0.001). This study measured the oxidative DNA damage by measuring the 8-OHdG in the leukocyte DNA in patients with cataract. In addition, the level of MDA - a marker for lipid peroxidation - was measured to determine lipid peroxidation.

Effect of an antioxidant functional food beverage on exercise-induced oxidative stress: A long-term and large-scale clinical intervention study

The efficacy of long-term intake of a novel functional food supplement Funciona™ containing vitamins and juiced fruits was evaluated in order to assess the net effect of physical activity and antioxidant potentials in healthy older adult population. The long-term (2 years) and large-scale (400 older adult subjects) interventional study was based on both moderate-intensity exercise practice and concurrent supplementation. Sustained exercise-induced oxidative stress as reflected in significantly increased blood thiobarbituric acid-reactive substances (TBARS) (+15%), protein carbonyl groups (PC) (+18%) and oxidized glutathione (GSSG) (+112%) concentrations, and leukocyte 8-OHdG contents (23%). Exercise decreased the reduced/oxidized glutathione (GSH/GSSG) molar ratio (−43%) and plasma vitamin C levels (−22%). Supplementation with Funciona™ was significant in preventing oxidative damage to lipid, protein and DNA, and normalizing blood GSSG, GSH/GSSG and vitamin C levels. Thus daily intake of the antioxidant functional beverage counteracts the exercise-induced oxidative stress in free-living older subjects, and might be necessary to restore impaired antioxidant balance due long-term regular exercise.

Oxidative DNA Damage in Retinopathy of Prematurity

This study examines the levels of oxidative damage in patients with retinopathy of prematurity (ROP). Fifty patients were recruited with a birthweight below 1500 g or gestational age below 32 weeks. The cases were classified into those who developed ROP (n=25) and those without ROP (n=25). The authors obtained blood and urine samples from each infant, for measuring 8-hydroxy 2-deoxyguanosine (8-OHdG) and malondialdehyde (MDA) levels, at the time of the first examination at 4-6 postnatal weeks. A significant difference was observed in leukocyte and urine 8-OHdG levels in patients with ROP compared to those without ROP (p<0.001 for both). Similarly, a significant difference was observed in plasma and urine MDA levels in patients with ROP compared to those without ROP (p<0.001 for both). In addition, significant correlations were found between levels of 8-OHdG in leukocyte DNA and plasma MDA (r=0.859, p<0.001), and between levels of urine 8-OHdG excretion and urine MDA (r=0.563, p<0.001). 8-OHdG in leukocyte DNA and urine levels in premature infants can be useful as an indicator for ROP screening.

Increased oxidative damage in peripheral blood correlates with severity of Parkinson's disease

Increased oxidative stress contributes to neuronal dysfunction in Parkinson's disease (PD). We investigated whether the pathological changes in PD brains may also be present in peripheral tissues. Leukocyte 8-hydroxydeoxyguanosine (8-OHdG), plasma malondialdehyde (MDA), erythrocyte glutathione peroxidase (GPx) and plasma vitamin E (Vit E) were measured for 211 PD patients and 135 healthy controls. Leukocyte 8-OHdG and plasma MDA were elevated, whereas erythrocyte GPx and plasma Vit E were reduced in PD patients when compared to the controls. After adjusting for environmental factors, logistic regression analysis showed that PD severity was independently correlated with 8-OHdG and MDA level, and inversely correlated with GPx activity and Vit E level. Leucocyte 8-OHdG level was continuously increased with advanced PD Hoehn–Yahr stages, while plasma MDA level peaked at early disease stages, among PD patients. These results suggest increased oxidative damage and decreased anti-oxidant capacity in peripheral blood, and a significant correlation between leucocyte 8-OHdG level and disease severity in PD.

GST M1 Polymorphism Associates with DNA Oxidative Damage and Mortality among Hemodialysis Patients

Leukocyte 8-hydroxy-2'-deoxyguanosine (8-OHdG) is a surrogate marker of oxidant-induced DNA damage in patients undergoing maintenance hemodialysis (MHD). Glutathione S-transferase M1 (GST M1) is a member of the GST family of proteins, which protect cellular DNA against oxidative damage. This study tested the association of a common GST M1 gene polymorphism [GST M1(-)], known to produce a dysfunctional enzyme, with levels of 8-OHdG in peripheral blood leukocytes and all-cause mortality among MHD patients. Among 488 MHD patients and 372 gender-matched healthy subjects, the frequency of the GST M1(-) genotype was 63.1 and 60.2%, respectively. The GST M1(-) genotype was associated with significantly higher levels of leukocyte 8-OHdG compared with the GST M1(+) genotype, even after adjustment for potential confounders (P < 0.001). Moreover, GST M1(-) patients who also had a common polymorphism in the DNA repair enzyme 8-oxoguanine DNA glycosylase 1 or who underwent dialysis with a bioincompatible cellulose membrane had the highest median levels of leukocyte 8-OHdG. Multivariate Cox regression revealed that among MHD patients, GST M1(-) genotype approximately doubled the risk for all-cause mortality (hazard ratio 2.24; 95% confidence interval 1.30 to 4.51) during the mean follow-up of 34 mo. In conclusion, patients without GST M1 activity are more vulnerable to oxidative stress and are at greater risk for death compared with those who possess GST M1 activity.

Oxidative DNA damage and influence of genetic polymorphisms among urban and rural schoolchildren exposed to benzene

Traffic related urban air pollution is a major environmental health problem in many large cities. Children living in urban areas are exposed to benzene and other toxic pollutants simultaneously on a regular basis. Assessment of benzene exposure and oxidative DNA damage in schoolchildren in Bangkok compared with the rural schoolchildren was studied through the use of biomarkers. Benzene levels in ambient air at the roadside adjacent to Bangkok schools was 3.95-fold greater than that of rural school areas. Personal exposure to benzene in Bangkok schoolchildren was 3.04-fold higher than that in the rural schoolchildren. Blood benzene, urinary benzene and urinary muconic acid (MA) levels were significantly higher in the Bangkok schoolchildren. A significantly higher level of 8-hydroxy-2′-deoxyguanosine (8-OHdG) in leukocytes and in urine was found in Bangkok children than in the rural children. There was a significant correlation between individual benzene exposure level and blood benzene ( r s = 0.193, P < 0.05), urinary benzene ( r s = 0.298, P < 0.05), urinary MA ( r s = 0.348 , P < 0.01), and 8-OHdG in leukocyte ( r s = 0.130, P < 0.05). In addition, a significant correlation between urinary MA and 8-OHdG in leukocytes ( r s = 0.241, P < 0.05) was also found. Polymorphisms of various xenobiotic metabolizing genes responsible for susceptibility to benzene toxicity have been studied; however only the GSTM1 genotypes had a significant effect on urinary MA excretion. Our data indicates that children living in the areas of high traffic density are exposed to a higher level of benzene than those living in rural areas. Exposure to higher level of benzene in urban children may contribute to oxidative DNA damage, suggesting an increased health risk from traffic benzene emission.

Exfoliated Buccal Mucosa Cells as a Source of DNA to Study Oxidative Stress

The extent of oxidative DNA damage is considered a biomarker of carcinogenic process and could be investigated in population studies using easily obtained cells. The oxidized DNA base adduct 8-hydroxy-2-deoxyguanosine (8-OHdG) released by enzymatic hydrolysis of DNA is commonly assayed by high performance liquid chromatography with electrochemical detection. It is expressed as a ratio of 8-OHdG to unoxidized deoxyguanosine. We modified and improved this method, determined the optimal time for harvesting buccal mucosa cells (BMC), assessed whether they mirror peripheral circulating blood cell DNA damage, and compared the anticoagulants, heparin, and EDTA for consistency in measurement of leukocyte 8-OHdG. Thirty-one healthy participants, randomized into two groups, donated BMC and blood samples. Samples were collected at baseline and either 3 or 7 days after baseline. Results showed no correlation between 8-OHdG/deoxyguanosine ratios in BMC and peripheral blood leukocytes at any time point regardless of harvest time. BMC had much higher oxidative DNA damage, but displayed a 25.6% reduction in the oxidized DNA adduct level (P < 0.04) at 3 days after baseline. Leukocytes collected in heparin and EDTA had similar 8OHdG/deoxyguanosine ratios; however, EDTA was preferred, as it produced a clean nuclear pellet without hemoglobin contamination, and the results were less variable. This improved assay shows within subject stability over time in both leukocyte and BMC DNA damage, increasing the probability that small intervention differences can be detected in healthy subjects. Buccal cells provide an accessible pool of epithelial cells that represents higher levels of DNA damage than circulating leukocytes.

Evaluation of oxidative stress in a group of adolescents exposed to a high level of aflatoxin B1 a multi-center and multi-biomarker study

The association between aflatoxin B1 (AFB1) exposure and oxidative stress was extensively examined in 84 adolescents from an area at high risk for hepatocellular carcinoma in China. Plasma level of aflatoxin B1-albumin adducts (AAAs) was associated with AFB1 excretion in urine (r = 0.394, P < 0.001). Urinary AFB1 was also associated with both the urinary excretion of 8-hydroxydeoxyguanosine (8-OHdG) (r > or = 0.479, P < 0.001) and 8-OHdG and hOGG1 levels in peripheral leukocytes (r > or = 0.308, P < or = 0.005). Similarly, AAA was significantly associated with both the urinary excretion of 8-OHdG (r > or = 0.259, P < or = 0.018) and the 8-OHdG and hOGG1 levels in peripheral leukocytes (r > or = 0.313, P < or = 0.004). In addition, urinary 8-OHdG was correlated with both the level of DNA 8-OHdG (r > or = 0.24, P < or = 0.05) and the expression of hOGG1 in peripheral leukocytes (r > or = 0.429, P < 0.001). Protein carbonyl content (PCC) level was significantly associated with not only the level of DNA 8-OHdG (r > or = 0.366, P < 0.001) and the urinary 8-OHdG (r > or = 0.258, P < or = 0.018) but also the expression of hOGG1 in peripheral leukocytes (r = 0.485, P < 0.001). A significant but weak association was found between high-performance liquid chromatograph-electrochemical detection (HPLC-ECD) and enzyme-linked immunosorbent assay (ELISA) for urinary 8-OHdG (r = 0.334, P = 0.002) and between HPLC-ECD and flow cytometry assays for 8-OHdG in leucocytes (r = 0.395, P < 0.001). Significant associations were observed between AAA and PCC and liver function indices (alanine aminotransferase and aspartate aminotransferase). These findings suggest significant contribution from AFB1 exposure to oxidative stress and subsequent repair among adolescents that may impose substantial risk for hepatocarcinogenesis in adulthood in this region.