Abstract

Nanomaterials, including zinc oxide (ZnO) nanoparticles, are being developed for a variety of commercial products. Recent reports showed that cells exposed to ZnO nanoparticles produced severe cytotoxicity accompanied by oxidative stress and genotoxicity. To understand the possible mechanism underlying oxidative stress of ZnO nanoparticles, the present investigation focused on the direct bioactivity of ZnO nanoparticles using a rat retinal ganglion cell (RGC-5) culture. At concentrations relevant to those used in vitro exposure of RGC-5 cells to ZnO nanoparticles, it was found that ZnO nanoparticles could inhibit cell proliferation in time- and concentration-dependent manners. Meanwhile, cell cycle arrest of S and G2/M phases occurred in RGC-5 cells induced by ZnO nanoparticles. Moreover, our results also demonstrated that the overproduction of reactive oxygen species (ROS) and elevated level of caspase-12 as well as decreased levels of bcl-2 and caspase- 9 occurred after treatment with different concentrations of ZnO nanoparticles when compared to those in untreated cells. In summary, our findings suggest that ZnO nanoparticles could lead to the over generations of ROS and caspase-12 as well as decreased levels of bcl-2 and caspase- 9. These results indicate that bcl-2, caspase-9 and caspase-12 may play significant roles in ZnO nanoparticle-induced RGC-5 cell damage.

Materials and methods

different concentrations of ZnO nanoparticles in RGC-5 cells. Briefly, after 4 h of exposure to different concentrations (0, 2.5, 5.0 and 10.0

g/mL, respectively) of ZnOnanoparticles, the equivalent amounts of cells in each flask were harvested, washed with PBS twice, resuspended in 0.5 mL of cold PBS, and sonicated on the ice for 10 min.After centrifugation at 3000 g for 20 min, the level of Bcl- 2, Caspase-9 and Caspase-12 from cell extracts in 40

Lof the supernatant was determined by ELISA according to the manufacturer’s instructions (Rat Bcl-2 ELISA Kit,Rat Caspase-9 ELISA Kit and Rat Caspase-12 ELISA Kit, Wuhan ColorfulGene biological technology Co., Ltd., China).