Inhibitory effects of selenium on cadmium-induced cytotoxicity in PC12 cells via regulating oxidative stress and apoptosis

Purpose of this study is to investigate mechanism/s of cyto-protection by selenium (Na2SeO3; Se4+) against cadmium (CdCL2; Cd2+)-induced cytotoxicity using PCl2 cells. In addition, Se (5, 10, 20 and 40 mu M) and Cd (2.5, 5 and 10 mu M) -induced cytotoxicity is determined. Cytotoxicity assays and western blot analyses confirmed that Se (>= 10 mu M) promotes autophagic cell death via inhibition of mTOR activation and p62 accumulation due to increase of cellular oxidative stress. On the other hand, co-presence of non-toxic Se (5 mu M) and toxic Cd (5 mu M) showed to increase cell viability, glutathione and glutathione peroxidase 1 (GPx1) levels, and to decrease DNA fragmentation and lactate dehydrogenase (LDH) activity compared to Cd-treated (5 mu M) cells alone. Furthermore, western blot analyses of cytochrome c and ERK1 indicated that Cd-induced apoptotic cell death in PC12 cells. However, the co-exposure of Se with Cd significantly decreases the release of cytochrome c into cytosol from mitochondria, and up-regulates ERK1 protein to inhibit Cd-induced apoptosis. In conclusion, Se (>= 10 mu M) possess cytotoxicity in PC12 cells; however, co-presence of Se (5 mu M) with Cd (5 mu M) protects against Cd-induced apoptosis in PC12 cells due to inhibition of Cd-induced oxidative stress and subsequently suppression of mitochondrial apoptosis pathway.