Cadmium, mercury, and lead in kidney cortex are not associated with urinary 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) in living kidney donors

Arsenic exposure and biomarkers for oxidative stress and telomere length in indigenous populations in Bolivia

BACKGROUND

Women living in the Bolivian Andes are environmentally exposed to arsenic, yet there is scarce information about arsenic-related effects in this region. Several biomarkers for telomere length and oxidative stress (mitochondrial DNA copy number, mtDNAcn; 8-Oxo-2'-deoxyguanosine, 8-oxo-dG; and 4-hydroxy nonenal mercapturic acid, 4-HNE-MA) have been previously linked to arsenic, and some of which are prospective biomarkers for cancer risk.

OBJECTIVE AND HYPOTHESIS

To evaluate associations between arsenic exposure and telomere length, mtDNAcn, 8-oxo-dG, and 4-HNE-MA in Bolivians. Arsenic exposure was hypothesized to be positively associated with all four toxicity biomarkers, particularly in individuals with a less efficient arsenic metabolism.

METHODS

The study encompassed 193 indigenous women. Arsenic exposure was assessed in urine as the sum of inorganic arsenic metabolite concentrations (U-As) measured by HPLC-HG-ICP-MS, and in whole blood as total arsenic (B-As) measured by ICP-MS. Efficiency of arsenic metabolism was evaluated by a polymorphism (rs3740393) in the main arsenic methylating gene AS3MT measured by TaqMan allelic discrimination, and by the relative fractions of urinary inorganic arsenic metabolites. Telomere length and mtDNAcn were determined in peripheral blood leukocytes by quantitative PCR, and urinary 8-oxo-dG and 4-HNE-MA by LC-MS/MS.

RESULTS

U-As and B-As were associated with longer telomeres and higher mtDNAcn, particularly in women with a less efficient arsenic metabolism. Urinary 8-oxo-dG and 4-HNE-MA were positively associated with U-As, but only 4-HNE-MA was associated with B-As. Arsenic metabolism efficiency did not have a clear effect on the concentrations of either of these biomarkers.

CONCLUSION

Bolivian women showed indications of arsenic toxicity, measured by four different biomarkers. Telomere length, mtDNAcn, and 4-HNE-MA were positively associated with both U-As and B-As. The association of arsenic exposure with telomere length and mtDNAcn was only present in Bolivian women with a less efficient metabolism. These findings call for additional efforts to evaluate and reduce arsenic exposure in Bolivia.

Oxidative DNA Damage Is Increased in Living Kidney Donors

BACKGROUND

Long-term consequences of donor nephrectomy might be reduced kidney function, increased risk for cardiovascular disease, and impaired quality of life. The purpose of the current cross-sectional study was to evaluate the relationship between clinical, laboratory, and donation-specific outcomes of living kidney donors and systemic oxidative DNA damage.

METHODS

We conducted a cross-sectional study and assessed retrospectively pre- and postdonation data from 60 donors who donated between 2010 and 2015. Plasma malondialdehyde levels and 8-hydroxy-2'-deoxyguanosine/deoxyguanosine ratio (8-OHdG/dG ratio) were determined as oxidative stress markers. Catalase, carbonic anhydrase, and paraoxonase (PON) activities were measured as antioxidants.

RESULTS

Approximately 3 years after donation, the hypertensive donor ratio was 12%, and 11% of the donors had glomerular filtration rate <60 mL/min/1.73 m². Mean serum urea (P = .001) and serum creatinine levels (P = .001) were increased; creatinine clearance level (126.2 ± 35.5 vs 94.6 ± 26.8, P = .001) was decreased in the postdonation period. There was a significant positive correlation between predonation serum urea and 8-0HdG/dG ratio (r = 0.338, P = .016) and predonation serum creatinine and 8-0HdG/dG ratio (r = 0.442, P = .001), while there was a significant negative correlation between serum creatinine and PON activity (r = -0.545, P < .001).

CONCLUSION

Our data have demonstrated that kidney donors exhibit increased oxidative DNA damage and decreased antioxidant activity. We propose that predonation serum creatinine is positively correlated with 8-0HdG/dG ratio and negatively correlated with antioxidant PON activity. This is the first study to demonstrate that plasma oxidative DNA damage increases in healthy kidney donors.

Multiple-metal exposure, diet, and oxidative stress in Uruguayan school children

Oxidative stress (OS) is an important consequence of exposure to toxic metals but it is unclear to what extent low-level metal exposures contribute to OS in children. We examined the cross-sectional association between urinary concentrations of arsenic (As), cadmium (Cd), and lead (Pb) and urinary markers of OS: F₂-8α isoprostane and 8-hydroxy-2-deoxy-guanosine (8-OHdG). We also tested effect modification by dietary intakes. Of the 211 children aged 6-8 years living in Montevideo who were eligible for the study because they had at least one OS marker measured via ELISA, 143 were included in a complete-case analysis. Urinary metals were measured with inductively coupled plasma mass spectrometry (ICP-MS: Pb, Cd) and high-performance liquid chromatography online with hydride generation ICP-MS (As-metabolites); concentrations were log₂-transformed. All urinary markers were adjusted for specific gravity of urine. Two 24-h dietary recalls were conducted to estimate children's dietary intakes, including total fruit and vegetable consumption and vitamin C, zinc and fiber intake. Ordinary least square (OLS) and weighted quantile sum (WQS) regressions were used to estimate the association between metals and each OS marker as outcome. Metal exposure was generally low: median urinary As, Cd, Pb 9.6 μg/L, 0.06 μg/L and 1.9 μg/L, respectively. Median 8-isoprostane concentration was 1.1 and 8-OHdG 39.6 ng/mL. Log₂-transformed urinary As concentrations were positively associated with 8-OHdG concentrations (10.90 [3.82, 17.97]) in covariate-adjusted OLS models which also took account of exposure to Cd and Pb. In WQS, a mixture index was also associated with higher 8-OHdG (8.71 [1.12, 16.3] for each 25% increase in index value), mostly driven by As exposure. There was little evidence of effect modification by dietary antioxidants. In sum, even at low-level, As exposure is associated with detectable oxidative damage to the DNA.

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.

The Relation Between Low-Level Lead Exposure and Oxidative Stress: a Review of the Epidemiological Evidence in Children and Non-Occupationally Exposed Adults

Experimental studies in animals and observational studies in occupationally exposed adults indicate that higher lead exposure results in higher biomarkers of oxidative stress. However, this evidence cannot be extended to the general population who typically experience lower levels of lead exposure. This systematic review evaluates the epidemiological evidence on the association between lead and oxidative stress in non-occupationally exposed general population, with a particular focus on the pediatric population. Studies were identified through a systematic search of Medline and Web of Science. Ultimately, evidence from 15 studies conducted in children and 22 studies in adults from the general population was reviewed. Overall, the published findings are inconsistent, and there are very few well-designed studies on the relation between lead exposure and oxidative stress in the general population. The strength of the current evidence is discussed in light of the methodological approaches employed, and recommendations are made for future research directions. These include designing prospective studies with repeat measurements of clinically relevant oxidative stress markers to answer the question of causality and sensitive windows and reanalyzing previously published data, but using multivariable statistical approaches and adjustment for relevant explanatory factors.

Toxicity of Glutathione-Binding Metals: A Review of Targets and Mechanisms

Mercury, cadmium, arsenic and lead are among priority metals for toxicological studies due to the frequent human exposure and to the significant burden of disease following acute and chronic intoxication. Among their common characteristics is chemical affinity to proteins and non-protein thiols and their ability to generate cellular oxidative stress by the best-known Fenton mechanism. Their health effects are however diverse: kidney and liver damage, cancer at specific sites, irreversible neurological damages with metal-specific features. Mechanisms for the induction of oxidative stress by interaction with the cell thiolome will be presented, based on literature evidence and of experimental findings.

Relationship between serum ferritin level and blood mercury concentration using data from the Korean national health and nutrition examination survey (2010-2012)

BACKGROUND

Studies on the association between serum ferritin levels (S-Ft) and blood mercury concentrations (B-Hg) are scarce. The objective of this study was to investigate the relationships between these two parameters using a large-scale nationwide representative sample of the Korean males.

METHOD

A nationwide cross-sectional study was conducted to examine the relationship between S-Ft and B-Hg in 2832 men over 19 years of age (aged 20-87 years), using data from the 2010-2012 Korean National Health and Nutrition Examination Survey. The odds ratios (ORs) and 95% confidence intervals (CIs) for high B-Hg (>75th percentile) were calculated across S-Ft quartiles using multiple logistic regression analyses.

RESULTS

Mean values of B-Hg gradually increased in accordance with the quartiles of S-Ft (P-trend<0.001). The odds ratio (95% CI) for high B-Hg with the doubling of S-Ft was 1.51 (1.25-1.84) after adjusting for age, fish/shellfish consumption, rice consumption, waist circumference, cigarette smoking, alcohol intake, regular exercise, blood pressure, fasting plasma glucose, triglyceride, and high-density lipoprotein cholesterol. Compared with the lowest quartiles of B-Hg, the ORs (95% CI) for high S-Ft in the 3rd and 4th quartiles were 2.09 (1.17-3.73) and 2.73 (1.55-4.79) after adjusting for the same co-variables.

CONCLUSION

We found a positive relationship between S-Ft and B-Hg in a representative population sample of Korean adult men. Our results suggested S-Ft as a tool for environmental Hg exposure assessment.