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Engineered Nanomaterials Elicit Cellular Stress Responses
Citation:
Prasad, R. Y., R. Prasad, C. F. BLACKMAN, D. M. DEMARINI, AND S. SIMMONS. Engineered Nanomaterials Elicit Cellular Stress Responses. Presented at Society of Toxicology (SOT) Annual Meeting, Washington, DC, March 06 - 10, 2011.
Impact/Purpose:
Oxidative stress and inflammation are thought to be one of the causes of the potential toxic effects of nanomaterials. In this study we aim to identify timesensitive biological response pathways affected by engineered nanomaterials by measuring increased levels of mRNA expression in luciferase reporter gene assays.
Description:
Engineered nanomaterials are being developed continuously and incorporated into consumer products, resulting in increased human exposures. The study of engineered nanomaterials has focused largely on toxicity endpoints without further investigating potential mechanisms or pathways. Additionally, most in vitro studies have examined time points of 24 hours post-exposure and longer. Oxidative stress and inflammation are thought to be one of the causes of the potential toxic effects of nanomaterials. In this study we aim to identify timesensitive biological response pathways affected by engineered nanomaterials by measuring increased levels of mRNA expression in luciferase reporter gene assays. We developed a battery of stable luciferase-reporter cell lines using HepG2 cells that measure the activation of three key stress responsive transcription factors (Nrf2, NFkB, and AP-1) and the human IL-8 promoter. We are examining titanium dioxide (rutile, anatase, and rutile/anatase mixtures), cerium dioxide, and possibly silver nanomaterials, at concentrations ranging from 1-100 ug/ml. To determine if nanomaterials affect different pathways over time, we will also assess reporter expression at 6, 12, and 24 hours post-exposure. Cytotoxicity will be measured using the CellTiter GL™ assay. Dynamic light scattering will be used to determine the size and zeta potential of the nanomaterials in media. Initial results show increases in AP1 activity with titanium dioxide and cerium dioxide nanomaterials at 1-10 ug/ml and increases in NFkB signaling at 30 ug/ml 24 hours post-exposure. Titanium dioxide nanomaterials cause overt cytotoxicity at 100 ug/ml under our treatment conditions. We are currently investigating the time-dependent effects of nanomaterials on the activation status of these cellular stress response pathways. [Abstract does not necessarily reflect the policies of the U.S. EPA.]