Biochemical Effects of Silver Nanomaterials in Human Hepatocellular Carcinoma (HepG2) Cells.
Kirk T Kitchin, Judy A Richards, Brian L Robinette, Kathleen A Wallace, Najwa H Coates, Benjamin T Castellon, Eric A Grulke, Jiahui Kou, Rajender S Varma
Author Information
Kirk T Kitchin: 109 Alexander Drive, Mail Drop B105-03, Integrated Systems Toxicology Division, National Health and Environmental Effects Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711, USA.
Judy A Richards: Environmental Public Health Division, National Health and Environmental Effects Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711, USA.
Brian L Robinette: 109 Alexander Drive, Mail Drop B105-03, Integrated Systems Toxicology Division, National Health and Environmental Effects Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711, USA.
Kathleen A Wallace: 109 Alexander Drive, Mail Drop B105-03, Integrated Systems Toxicology Division, National Health and Environmental Effects Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711, USA.
Najwa H Coates: Environmental Public Health Division, National Health and Environmental Effects Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711, USA.
Benjamin T Castellon: Institute of Biomedical Studies and Department of Environmental Science, Baylor University, Waco, TX 76798, USA.
Eric A Grulke: Chemical & Materials Engineering, University of Kentucky, Lexington, KY 20506, USA.
Jiahui Kou: State Key Laboratory of Materials-Orient Chemical Engineering, College of Materials Science and Engineering, Nanjing Tech University, Nanjing 210009, P. R. China.
Rajender S Varma: 26 West M.L.K. Drive, MS 443, Water Systems Division, National Risk Management Research Laboratory, U.S. Environmental Protection Agency, 26 West M.L.K. Dr., MS 443, Cincinnati, Ohio 45268, USA.
In dose-response and structure-activity studies, human hepatic HepG2 cells were exposed to between 0.01 and 300 ug/ml of different silver nanomaterials and AgNO��� for 3 days. Treatment chemicals included a custom synthesized rod shaped nano Ag, a glutathione capped nano Ag, polyvinylpyrrolidone (PVP) capped nano Ag (75 nm) from Nanocomposix and AgNO���. Various biochemical parameters were then evaluated to study cytotoxicity, cell growth, hepatic function and oxidative stress. Few indications of cytotoxicity were observed between 0.1 ug/ml and 6 ug/ml of any nano Ag. At 10 ug/ml and above, Ag containing nanomaterials caused a moderate to severe degree of cytotoxicity in HepG2 cells. Lactate dehydrogenase and aspartate transaminase activity alterations were the most sensitive cytotoxicity parameters. Some biochemical parameters were altered by exposures to both nano Ag and AgNO��� (statistically significant increases in alkaline phosphatase, gamma glutamyltranspeptidase, glutathione peroxidase and triglycerides; in contrast both glutathione reductase and HepG2 protein concentration were both decreased). Three parameters were significantly altered by nano Ag but not by AgNO��� (decreases in glucose 6-phosphate dehydrogenase and thioredoxin reductase and increases in catalase). Cytotoxicity per se did not appear to fully explain the patterns of biological responses observed. Some of the observations with the three nano Ag (increases in alkaline phosphatase, catalase, gamma glutamyltranspeptidase, as well as decreases in glucose 6-phosphate dehydrogenase and glutathione reductase) are in the same direction as HepG2 responses to other nanomaterials composed of TiO���, CeO���, SiO���, CuO and Cu. Therefore, these biochemical responses may be due to micropinocytosis of nanomaterials, membrane damage, oxidative stress and/or cytotoxicity. Decreased G6PDH (by all three nano Ag forms) and GRD activity (only nano Ag R did not cause decreases) support and are consistent with the oxidative stress theory of Ag nanomaterial action.
