Biochemical effects of some CeO2, SiO2, and TiO2 nanomaterials in HepG2 cells.

Abstract

The potential mammalian hepatotoxicity of nanomaterials was explored in dose-response and structure-activity studies in human hepatic HepG2 cells exposed to between 10 and 1000μg/ml of five different CeO2, three SiO2, and one TiO2-based particles for 3days. Various biochemical parameters were then evaluated to study cytotoxicity, cell growth, hepatic function, and oxidative stress. Few indications of cytotoxicity were observed between 10 and 30μg/ml. In the 100 to 300μg/ml exposure range, a moderate degree of cytotoxicity was often observed. At 1000μg/ml exposures, all but TiO2 showed a high degree of cytotoxicity. Cytotoxicity per se did not seem to fully explain the observed patterns of biochemical parameters. Four nanomaterials (all three SiO2) decreased glucose 6-phosphate dehydrogenase activity with some significant decreases observed at 30μg/ml. In the range of 100 to 1000μg/ml, the activities of glutathione reductase (by all three SiO2) and glutathione peroxidase were decreased by some nanomaterials. Decreased glutathione concentration was also found after exposure to four nanomaterials (all three nano SiO2 particles). In this study, the more responsive and informative assays were glucose 6-phosphate dehydrogenase, glutathione reductase, superoxide dismutase, lactate dehydrogenase, and aspartate transaminase. In this study, there were six factors that contribute to oxidative stress observed in nanomaterials exposed to hepatocytes (decreased glutathione content, reduced glucose 6-phosphate dehydrogenase, glutathione reductase, glutathione peroxidase, superoxide dismutase, and increased catalase activities). With respect to structure-activity, nanomaterials of SiO2 were more effective than CeO2 in reducing glutathione content, glucose 6-phosphate dehydrogenase, glutathione reductase, and superoxide dismutase activities.