Strong Associations Exist among Oxidative Stress and Antioxidant Biomarkers in the Circulating, Cellular and Urinary Anatomical Compartments in Guatemalan Children from the Western Highlands.

BACKGROUND: A series of antioxidant enzymes and non-enzymatic compounds act to protect cells from uncontrolled propagation of free radicals. It is poorly understood, though, to what extent and how their interaction is harmonized. OBJECTIVES: To explore associative interactions among a battery of urinary and blood biomarkers of oxidative stress and enzymatic and non-enzymatic markers of the antioxidant defense system in children from low income households. METHODS: For this cross-sectional descriptive study, urine, red cells, and plasma were sampled in 82 preschool children attending three daycare centers in Quetzaltenango Guatemala. The urinary oxidative stress biomarkers studied were F2-isoprostanes and 8-hydroxy-deoxy-guanosine. Red cell enzyme activities measured were: catalase, superoxide dismutase, glutathione peroxidase and glutathione reductase. Circulating non-enzymatic antioxidants selected were: retinol, tocopherols, ß-carotene and coenzymes Q9 and Q10. RESULTS: In a Spearman rank-order correlation hemi-matrix, of 55 paired combinations of the 11 biomarkers, 28 (51%) were significantly correlated among each other (p ≤ 0.05), with the strongest association being retinol and tocopherols (r = 0.697, p<0.001), and 4 associations (9%) showed a trend (p> 0.5 to ≤ 0.10). F2-isoprostanes showed the greatest number of cross-associations, having significant interactions with 8 of the 10 remaining biomarkers. Goodness-of-fit modeling improved or maintained the r value for 24 of the significant interactions and for one of the 5 borderline associations. Multiple regression backward stepwise analysis indicated that plasma retinol, ß-carotene and coenzyme Q10 were independent predictors of urinary F2-isoprostanes. CONCLUSION: Numerous significant associations resulted among biomarkers of oxidation and responders to oxidation. Interesting findings were the apparent patterns of harmonious interactions among the elements of the oxidation-antioxidation systems in this population.

Effective utilization of N2-ethyl-2'-deoxyguanosine triphosphate during DNA synthesis catalyzed by mammalian replicative DNA polymerases.

Acetaldehyde is produced by metabolic oxidation of ethanol after drinking alcoholic beverages. This agent reacts with nucleosides and nucleotides, resulting in the formation of N2-ethyl-guanine residues. N2-ethyl-2'-deoxyguanosine (N2-ethyl-dG) adduct has been detected in the lymphocyte DNA of alcoholic patients [Fang, J. L., and Vaca, C. E. (1997) Carcinogenesis 18, 627-632]. Thus, the nucleotide pool is also expected to be modified by acetaldehyde. N2-Ethyl-2'-deoxyguanosine triphosphate (N2-ethyl-dGTP) was chemically synthesized. The utilization of N2-ethyl-dGTP during DNA synthesis was determined by steady-state kinetic studies. N2-Ethyl-dGTP was efficiently incorporated opposite template dC in reactions catalyzed by mammalian DNA polymerase alpha and delta. When pol alpha was used, the insertion frequency of N2-ethyl-dGTP was 400 times less than that of dGTP, but 320 times higher than that of 7,8-dihydro-8-oxo-2'-deoxyguanosine triphosphate (8-oxo-dGTP), an oxidative damaged nucleotide. Using pol delta, the insertion frequency of N2-ethyl-dGTP was only 37 times less than that of dGTP. The chain extension from dC:N2-ethyl-dG pair occurred much more rapidly: the extension frequencies for pol alpha and pol delta were only 3.8 times and 6.3 times, respectively, lower than that of dC:dG pair. We also found that N2-ethyl-dG can be detected in urine samples obtained from healthy volunteers who had abstained from drinking alcohol for 1 week before urine collection. This indicates that humans are exposed constantly to acetaldehyde even without drinking alcoholic beverages. Incorporation of N2-ethyl-dG adducts into DNA may cause mutations and may be related to the development of alcohol- and acetaldehyde-induced human cancers.

Excretion kinetics of the DNA adducts of cis-diamminedichloroplatinum(II) formed in vitro in rat urine.

The main adduct of cis-diamminedichloroplatinum(II) (cis-Pt) with DNA, cis-[Pt(NH3)2(dGpdG)], was administered i.p. to rats. Urine was collected daily for 4 days. The adduct was purified by a weak cation exchanger and quantitated by HPLC with UV detection. The recovery of the adduct was 30.0 +/- 7.0% (mean +/- SEM). The main reason for the low recovery was the chemical instability of cis-[Pt(NH3)2 (dGpdG)] in urine as shown in an in vitro incubation. Adjusted for this instability the recovery in urine was greater than 70% of the dose. When cis-Pt-DNA (the molar ratio of cis-Pt to nucleotide = 1:50) was administered i.p. to rats only 1.25 +/- 0.23% of platinum was excreted in urine in the form of cis-[Pt(NH3)2(dGpdG)] and cis-[Pt(NH3)2(dApdG)] during the first 4 days. If the removal of the cis-Pt-DNA adducts from human tissues is to be followed, their possible slow excretion and chemical instability in urine needs to be considered.