| Comparative study of the oxidative damages of nanosized and microsized particles on lung and liver DNAObjectiveNanosized materials are composed of particles with a diameter between 0.1nm and 100nm, which have many particular characteristics. Because of the special structure, nanosized materials show a variety of correspondent characteristics, such as surface effects and quanta sized effects. As is reported widely, nanosized particles can deposit in different segments of respiratory tract and even in the lung alveolus, and then initiate oxidative damages and inflammations.By now, studies of toxicities of nano particles on liver and lung have just started and are far away from agreement, especially for DNA oxidative damages. We chose 8-OHdG as a marker of DNA oxidative damages, aiming to compare the differences between the effects on DNA oxidative damages of nanosized and microsized particles, and also the probable mechanisms.Materials and Methods1 Animal treatment50 healthy Kunming mice with a weight scale of 18-22g were obtained. Animal facilities were controlled for temperature (20℃-24℃) and relative humidity (40%-60%), and operated under a 12-h light-dark cycle. Rats were administered with nanosized and microsized particles at the dose of 50mg/m3 and 200 mg/m3 by inhalation for 28 days, 2 hours for every other day. After the administration all animals were sacrificed.2 Methods(1) Pathological changes were detected by HE dyeing in lung.(2) Pathological changes were detected by HE dyeing in liver.(3) DNA oxidative damages were detected by 8-OHdG Elisa kits.3 StatisticsThe data sign to mean with the mean±SE. Changes in every array were analyzed by analysis of variance (ANOVA) followed by Fisher's least significant difference (LSD) after those have been showed as the normal distribution by the SPSS 13.0. If the analysis of normal distribution was not appropriate, the Kruskal-Wallis test was used identify the statistical significance of the individual groups.Results1 HE dyeing of lung tissuesIn control group, cells in alveolar wall were well-distributed, no inflammatory cell infiltrate founded in alveolar spaces. Bronchi epithelial cells' structures were integrated, no inflammatory cell infiltrate founded. Nevertheless, in nano 200mg/m3, thickenings and fragmentations were seen in alveolar septum with an increase of inflammatory cells. chronic inflammatory changes can be seen in small bronchi.2 HE dyeing of liver tissuesIn control group, limiting plates of hepatic lobules showed a clear strucrure. No damages were seen in portal vein zones and hepatic nucleus. In micro SiO2 50mg/m3 and higher groups, karyolysis were detected. In nano SiO2 50mg/m3 group, hepatic cells showed apomorphosis in a large scale, mainly cellularedema. Cell volumes increased, and hepatic sinusoid became narrow, Karyolysis and necrosis also founded. Nano SiO2 200mg/m3 group showed Karyolysis, karyorrhexis and pyknosis. Large quantities of eosinophilic bodys presented in hepatic lobules. 3 DNA oxidative damages in lung and liver tissues(1) Lung 8-OHdG positive cell counts in bronchi and alveoli epithelial cells of experimental groups were bigger than those of control group(p＜0.01), and nano group bigger than micro group at the equivalent dose level(p＜0.05), 200mg/m3 group bigger than 50mg/m3 respectively.(2) Liver 8-OHdG positive cell counts in nano groups were bigger than those of control group(p＜0.01), and bigger than micro groups too. But micro groups showed no significant changes compared with control group(p＞0.05).Conclusion1 Nano and micro sized particles can initiate DNA oxidative damages in lung and liver tissues of mice.2 The DNA oxidative damages initiated by Nano and micro sized particles do not agree. |
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