DNA damage and cytotoxicity in type II lung epithelial (A549) cell cultures after exposure to diesel exhaust and urban street particles

<p>Abstract</p> <p>Background</p> <p>Exposure to air pollution particles has been acknowledged to be associated with excess generation of oxidative damage to DNA in experimental model systems and humans. The use of standard reference material (SRM), such as SRM1650 and SRM2975, is advantageous because experiments can be reproduced independently, but exposure to such samples may not mimic the effects observed after exposure to authentic air pollution particles. This study was designed to compare the DNA oxidizing effects of authentic street particles with SRM1650 and SRM2975. The authentic street particles were collected at a traffic intensive road in Copenhagen, Denmark.</p> <p>Results</p> <p>All of the particles generated strand breaks and oxidized purines in A549 lung epithelial cells in a dose-dependent manner and there were no overt differences in their potency. The exposures also yielded dose-dependent increase of cytotoxicity (as lactate dehydrogenase release) and reduced colony forming ability with slightly stronger cytotoxicity of SRM1650 than of the other particles. In contrast, only the authentic street particles were able to generate 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) in calf thymus DNA, which might be due to the much higher level of transition metals.</p> <p>Conclusion</p> <p>Authentic street particles and SRMs differ in their ability to oxidize DNA in a cell-free environment, whereas cell culture experiments indicate that the particle preparations elicit a similar alteration of the level of DNA damage and small differences in cytotoxicity. Although it cannot be ruled out that SRMs and authentic street particles might elicit different effects in animal experimental models, this study indicates that on the cellular level, SRM1650 and SRM2975 are suitable surrogate samples for the study of authentic street particles.</p

Effects of physicochemical properties of TiO2 nanomaterials for pulmonary inflammation, acute phase response and alveolar proteinosis in intratracheally exposed mice

Nanomaterial (NM) characteristics may affect the pulmonary toxicity and inflammatory response, including specific surface area, size, shape, crystal phase or other surface characteristics. Grouping of TiO2 in hazard assessment might be challenging because of variation in physicochemical properties. We exposed C57BL/6 J mice to a single dose of four anatase TiO2 NMs with various sizes and shapes by intratracheal instillation and assessed the pulmonary toxicity 1, 3, 28, 90 or 180 days post-exposure. The quartz DQ12 was included as benchmark particle. Pulmonary responses were evaluated by histopathology, electron microscopy, bronchoalveolar lavage (BAL) fluid cell composition and acute phase response. Genotoxicity was evaluated by DNA strand break levels in BAL cells, lung and liver in the comet assay. Multiple regression analyses were applied to identify specific TiO2 NMs properties important for the pulmonary inflammation and acute phase response. The TiO2 NMs induced similar inflammatory responses when surface area was used as dose metrics, although inflammatory and acute phase response was greatest and more persistent for the TiO2 tube. Similar histopathological changes were observed for the TiO2 tube and DQ12 including pulmonary alveolar proteinosis indicating profound effects related to the tube shape. Comparison with previously published data on rutile TiO2 NMs indicated that rutile TiO2 NMs were more inflammogenic in terms of neutrophil influx than anatase TiO2 NMs when normalized to total deposited surface area. Overall, the results suggest that specific surface area, crystal phase and shape of TiO2 NMs are important predictors for the observed pulmonary effects of TiO2 NMs.Peer reviewe

Baseline-adjusted SB (A) and FPG sites (B) in A549 cell cultures exposed 24 hours to SRM1650, SRM2975 and ASPM

The data are obtained from figure 4 and table 1. Data points are mean ± SEM (SRMs, n = 9; ASPM, n = 6). There was no significant difference between the particle's ability to induce SB and FPG sites at any doses (> 0.05, Kruskal-Wallis test).<p><b>Copyright information:</b></p><p>Taken from "DNA damage and cytotoxicity in type II lung epithelial (A549) cell cultures after exposure to diesel exhaust and urban street particles"</p><p>http://www.particleandfibretoxicology.com/content/5/1/6</p><p>Particle and Fibre Toxicology 2008;5():6-6.</p><p>Published online 8 Apr 2008</p><p>PMCID:PMC2323018.</p><p></p

8-oxodG formation in calf thymus DNA measured with HPLC/ED after 30 minutes exposure to A) SRM2975 and B) SRM1650 and C) ASPM; ■ filter 1, ▲ filter 2, △ filter 3, ○ filter 4, ◆ filter 5

For SRM2975 and SRM1650 dots represents mean ± SEM; n = 3. The DNA was incubated at 37°C with 5 mM HO. For ASPM, the DNA was incubated at 37°C with 10 μM HO.<p><b>Copyright information:</b></p><p>Taken from "DNA damage and cytotoxicity in type II lung epithelial (A549) cell cultures after exposure to diesel exhaust and urban street particles"</p><p>http://www.particleandfibretoxicology.com/content/5/1/6</p><p>Particle and Fibre Toxicology 2008;5():6-6.</p><p>Published online 8 Apr 2008</p><p>PMCID:PMC2323018.</p><p></p

DNA damage measured by the comet assay in A549 cells exposed to SRM2975 and SRM1650 for 3, 24 or 48 hours

(A) SB, SRM2975, (B) FPG sites, SRM2975, (C) SB, SRM1650 and (D) FPG sites, SRM1650. Mean ± SEM, n = 9. * Dose where all exposure times are statistically significant compared to control (< 0.01, ANOVA, except for 3 hours exposure to 100 μg/ml where SRM1650 is tested with Kruskal-Wallis test, < 0.05). Dose where a single time point is statistically significant compared to the respective control (ANOVA): (A) SRM2975, SB, 2.5 μg/ml, 48 h, < 0.05, (C) SRM1650, SB, 2.5 μg/ml, 3 h, < 0.05 and SRM1650, SB, 25 μg/ml, 48 h, < 0.01, (D) SRM1650, FPG, 2.5 μg/ml, 3 h, < 0.05 and SRM1650, FPG, 25 μg/ml, 24 h, < 0.05.<p><b>Copyright information:</b></p><p>Taken from "DNA damage and cytotoxicity in type II lung epithelial (A549) cell cultures after exposure to diesel exhaust and urban street particles"</p><p>http://www.particleandfibretoxicology.com/content/5/1/6</p><p>Particle and Fibre Toxicology 2008;5():6-6.</p><p>Published online 8 Apr 2008</p><p>PMCID:PMC2323018.</p><p></p

Bioanalysis in Oxidative Stress Biomarkers of oxidative damage to DNA and repair

Abstract Oxidative-stress-induced damage to DNA includes a multitude of lesions, many of which are mutagenic and have multiple roles in cancer and aging. Many lesions have been characterized by MS-based methods after extraction and digestion of DNA. These preparation steps may cause spurious base oxidation, which is less likely to occur with methods such as the comet assay, which are based on nicking of the DNA strand at modified bases, but offer less specificity. The European Standards Committee on Oxidative DNA Damage has concluded that the true levels of the most widely studied lesion, 8-oxodG (8-oxo-7,8-dihydro-2 -deoxyguanosine), in cellular DNA is between 0.5 and 5 lesions per 10 6 dG bases. Base excision repair of oxidative damage to DNA can be assessed by nicking assays based on oligonucleotides with lesions or the comet assay, by mRNA expression levels or, in the case of, e.g., OGG1 (8-oxoguanine DNA glycosylase 1), responsible for repair of 8-oxodG, by genotyping. Products of repair in DNA or the nucleotide pool, such as 8-oxodG, excreted into the urine can be assessed by MS-based methods and generally reflects the rate of damage. Experimental and population-based studies indicate that many environmental factors, including particulate air pollution, cause oxidative damage to DNA, whereas diets rich in fruit and vegetables or antioxidant supplements may reduce the levels and enhance repair. Urinary excretion of 8-oxodG, genotype and expression of OGG1 have been associated with risk of cancer in cohort settings, whereas altered levels of damage, repair or urinary excretion in case-control settings may be a consequence rather than the cause of the disease