Response of HepG2/C3A cells supplemented with sodium selenite to hydrogen peroxide-induced oxidative stress.

Oxidative stress (OS) is involved in the onset of various pathological processes, and sodium selenite (Na2 SeO3 ) is known to have antioxidant activity. This study evaluated the cellular response of human HepG2/C3A cells supplemented with Na2 SeO3 when exposed to hydrogen peroxide (H2 O2 )-induced OS. We analyzed cytotoxicity, cell proliferation, and genotoxicity in comparison with molecular data of mRNA and protein expression. The MTT and comet assays revealed that Na2 SeO3 conferred cytoprotective and anti-genotoxic effects. In contrast, RTCA (Real-Time Cell Analysis) and flow cytometry analysis revealed that Na2 SeO3 did not inhibit H2 O2 -induced anti-proliferative effects or cell cycle arrest (G2/M). Cells exposed simultaneously to Na2 SeO3 and H2 O2 showed overexpression of GPX1 mRNA, indicating that Na2 SeO3 influenced the cellular antioxidant system. Furthermore, downregulation of CAT mRNA and SOD1 and PRX2 proteins induced by H2 O2 , was minimal after the Na2 SeO3 +H2 O2 treatment. Although normalization of CCN2B mRNA expression by Na2 SeO3 was observed after the Na2 SeO3 +H2 O2 treatment, this was not observed for other genes such as CDKN1A, CDKN1C, and CDKN2B, which are related to cell cycle control, nor for GADD45A, which is involved in the cellular response to DNA damage. Furthermore, both CDKN1B and CDKN1C expression were downregulated in HepG2/C3A cells treated with Na2 SeO3 only. Our results indicate that cellular response to Na2 SeO3 involved the modulation of the antioxidant system. Na2 SeO3 was unable completely recover HepG2/C3A cells from H2 O2 -induced oxidative damage, as evidenced by analysis of cell proliferation kinetics, cell cycle assay, and expression of key genes involved in cell cycle progression and response to DNA damage.