Analysis of oxidative DNA damage and HPRT mutant frequencies in cancer patients before and after radiotherapy.

Department of Health Risk Analysis and Toxicology, Maastricht University, Netherlands. Various markers of radiation-induced DNA damage including DNA oxidation were investigated in peripheral lymphocytes of 23 cancer patients prior to and one week after receiving radiotherapy with a cumulative dose of 54-70 Gy. Exposure to ionizing radiation nonsignificantly increased the ratio 2'deoxy-7-dihydro-8-oxoguanosine/2'deoxyguanosine (8-oxodG/dG) from 1.73 x 10(-5) to 3.33 x 10(-5). Frequencies of micronuclei significantly (p = 0.0003) increased from 6.4 to 38.9 per 1000 cells. The frequency of hypoxanthine-guanine-phosphoribosyltransferase (HPRT) mutant lymphocytes measured as 6-thioguanine resistant variant cells by 5-bromodeoxyuridine labeling, was elevated eight-fold, from 4.7 x 10(-6) to 36.2 x 10(-6) (p = 0.008) after termination of the radiotherapy, thus showing a clear response to the radiation treatment. No correlation between levels of oxidative DNA damage and frequencies of HPRT mutant lymphocytes or micronuclei could be established

Exposure-route-dependent DNA adduct formation by polycyclic aromatic hydrocarbons

Understanding the kinetics of aromatic-DNA adducts in target tissues and white blood cells (WBC) would enhance the applicability of DNA adducts in WBC as surrogate source of DNA in biomonitoring studies. In the present study, rats were acutely exposed to benzo[a]pyrene (B[a]P; 10 mg/kg body wt) via intratracheal (i.t.), dermal and oral administration. DNA adducts were analyzed in relevant target organs and WBC by nuclease P1 enriched P-32-post-labeling at 1, 2, 4, 11 and 21 days after exposure. Additionally, the internal dose was assessed by measurement of urinary excretion of 3-hydroxy-B[a]P (3-OH-B[a]P), Total B[a]P-DNA adduct levels in WBC were highest after i.t. and oral administration, whereas DNA adducts were hardly detectable after dermal exposure. Highest adduct levels were reached at 2 days after exposure. In lung tissue, DNA adduct levels reached maximal values at 2 days and were highest after i.t., oral and dermal exposure, respectively. DNA adduct levels were significantly lower in WBC as compared with lung. Nonetheless, overall B[a]P-DNA adduct levels in WBC were significantly correlated with those in lung. In target organs, highest DNA adduct levels were observed in skin after topical application, and lowest in stomach after oral administration of B[a]P, Furthermore, DNA adduct levels in WBC were correlated with DNA adduct levels in skin after dermal exposure and stomach after oral administration of B[a]P, Two-fold higher levels of 3-OH-B[a]P were excreted after i.t. administration of B[a]P as compared with dermal or oral exposure, Urinary 3-OH-B[a]P concentrations were correlated with DNA adduct levels at the site of B[a]P application. Overall, it can be concluded that aromatic-DNA adduct levels in WBC can be applied as a surrogate source of DNA for the site of application of B[a]P and reflect binding to lung DNA, independently of the exposure route

Oxidative DNA damage and cytogenetic effects in flight engineers exposed to cosmic radiation.

Department of Health Risk Analysis and Toxicology, Maastricht University, The [email protected] This study set out to analyze biomarkers for genotoxic events, e.g., oxidative DNA damage, chromosomal damage and hprt mutations, among flight personnel, who are known to be occupationally exposed to ionizing radiation of cosmic origin. Twenty-three flight engineers were recruited while ground personnel served as a matched control group. Cumulative radiation doses during flight were calculated on the basis of subjects' flight records assuming an exposure rate of 6 microSv per hour of flight. Oxidative DNA damage in peripheral lymphocytes from flight engineers appeared significantly increased in comparison with controls and was associated with cumulative exposure to cosmic radiation. Frequencies of peripheral lymphocyte chromosome aberrations, micronuclei and hprt mutations appeared also to be increased in flight engineers, but not significantly. It was also observed that DNA damage was higher in flight engineers with a relatively shorter flight history in comparison with flight engineers with higher cumulative exposures to radiation, suggesting adaptation to DNA damage caused by ionizing radiation. DNA repair activities measured as unscheduled DNA synthesis were clearly increased in the higher-exposed subgroup of flight engineers, and appeared significantly correlated with cumulative radiation dose, as well as inversely with oxidative DNA damage. The implications for cancer risk assessment in relation to exposure to cosmic radiation are discussed

Analysis of oxidative DNA damage after human dietary supplementation with linoleic acid

Analysis of oxidative DNA damage after human dietary supplementation with linoleic acid. de Kok TM, Zwingman I, Moonen EJ, Schilderman PA, Rhijnsburger E, Haenen GR, Kleinjans JC. Department of Health Risk Analysis and Toxicology, University Maastricht, PO Box 616, 6200 MD Maastricht, The Netherlands. [email protected] It has been hypothesized that oxygen radicals generated by peroxidation of dietary linoleic acid may induce genetic damage and thereby increase cancer risk. We examined the effect of dietary supplementation with linoleic acid on the levels of oxidative DNA damage in peripheral lymphocytes and on the blood plasma antioxidant potential. Thirty volunteers received during 6 weeks either a high dose of linoleic acid (15 g/day), an intermediate dose of linoleic acid (7.5 g/day) or an isocaloric supplement without linoleic acid (15 g palmitic acid/day). After the intervention, no significant increase in oxidative DNA damage, measured as relative amounts of 7,8-dihydro-8-oxo-2'-deoxyguanosine (8-oxodG) in DNA from peripheral lymphocytes, was observed in both high and intermediate linoleic acid-supplemented groups (increase of respectively 13 and 21%; P>0.05). Also, the differences between levels of oxidative DNA damage in the high or intermediate linoleic acid-supplemented group and the control group receiving palmitic acid (23% decrease) were not significant. Furthermore, no statistically significant differences were found between the total antioxidant capacities of blood plasma from the different experimental groups. Plasma levels of malondialdehyde, an important end-product of lipid peroxidation, were not increased after supplementation, nor were effects found on the plasma concentrations of retinol, alpha-tocopherol and beta-carotene. Despite the experimental design that excludes several forms of bias introduced in studies based on modulation of dietary composition, our results provide no indication of increased oxidative stress or genetic damage as a result of increased dietary intake of linoleic acid. Therefore, we see no scientific basis to reconsider the public health policy to stimulate the intake of polyunsaturated fatty acids aimed at the reduction of coronary heart diseases

In vitro effects of coal fly ashes: hydroxyl radical generation, iron release, and DNA damage and toxicity in rat lung epithelial cells.

Department of Health Risk Analysis and Toxicology, Maastricht University, The Netherlands. Oxygen radical generation due to surface radicals, inflammation, and iron release has been suggested as the mechanism of adverse effects of quartz, such as emphysema, fibrosis, and carcinogenic effects. Therefore, we measured iron release, acellular generation of hydroxyl radicals, and oxidative DNA damage and cytotoxicity in rat lung epithelial (RLE) cells by different coal fly ashes (CFA) that contain both quartz and iron. Seven samples of CFA with different particle size and quartz content (up to 14.1%) were tested along with silica (alpha-quartz), ground coal, and coal mine dust (respirable) as positive control particles, and fine TiO(2) (anatase) as a negative control. Five test samples were pulverized fuel ashes (PFA), two samples were coal gasification (SCG) ashes (quartz content <0.1%), and one sample was a ground coal. No marked differences between SCG and PFA fly ashes were observed, and toxicity did not correlate with physicochemical characteristics or effect parameters. Stable surface radicals were only detected in the reference particles silica and coal mine dust, but not in CFA. On the other hand, hydroxyl radical generation by all fly ashes was observed in the presence of hydrogen peroxide, which was positively correlated with iron mobilization and inhibited by deferoxamine, but not correlated with iron or quartz content. Also a relationship between acellular hydroxyl radical generation and oxidative DNA damage in RLE cells by CFA was observed. Differences in hydroxyl radical generation and oxidative damage by the CFA were not related to iron and quartz content, but the respirable ashes (MAT023, 38, and 41) showed a very extensive level of hydroxyl radical generation in comparison to nonrespirable fly ashes and respirable references. This radical generation was clearly related to the iron mobilization from these particles. In conclusion, the mechanisms by which CFA and the positive references (silica, coal mine dust) affect rat lung epithelial cells seem to be different, and the data suggest that quartz in CFA does not act the same as quartz in silica or coal mine dust. On the other hand, the results indicate an important role for size and iron release in generation and subsequent effects of reactive oxygen species caused by CFA