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Cellular Stress Responses Elicited by Engineered Nanomaterials
Citation:
Prasad, R. Y., K. Wallace, C. F. BLACKMAN, D. M. DEMARINI, AND S. SIMMONS. Cellular Stress Responses Elicited by Engineered Nanomaterials. Presented at 42nd Annual Meeting of Environmental Mutagen Society, Montreal, QC, CANADA, October 15 - 19, 2011.
Impact/Purpose:
This presentation will highlight the advances made in developing high- throughput assays for toxicity screening based on cellular stress response pathways and how these assays are used to establish quantitative biological activity relationships to characterize toxicant mode of action.
Description:
Engineered nanomaterials are being incorporated continuously into consumer products, resulting in increased human exposures. The study of engineered nanomaterials has focused largely on oxidative stress and inflammation endpoints without further investigation of underlying pathways. Here we examine time-sensitive biological response pathways affected by engineered nanomaterials using a battery of stable luciferase-reporter HepG2 cell lines. We measured the activation of three key stress-responsive transcription factors (NFKB, NRF2, and AP-1) and the human IL-8 promoter after exposure to 6 titanium dioxide nanomaterials (nanoTiO2) and 2 cerium oxide nanomaterials (nano-CeO2-) from various manufacturers. Exposure concentrations ranged from 1-100 ug/ml per nanomaterial over a time course of 6, 16 and 24 h. Cytotoxicity was measured in parallel using the MTT assay at 24 h. Dynamic light scattering was used to determine the size and zeta potential of the nanomaterials. There were significant changes in transcriptional activation at concentrations as low as 1 ug/ml. The 10 nm anatase nano-TlO2 elicited the highest effect, a ~2-fold increase in NFkB transcriptional activation, at a concentration of 100 ug/ml after 24 h exposure. NRF2 transcriptional activity was stimulated by one nano-CeO2; (~1.5-fold activation) at 100 ug/ml after 24 h. 1 ug/ml anatase/rutile nano-TiO2 elicited a 1.3-fold increase in AP-1 activity after 24 h. IL-8 activity mirrored NFkB transcriptional activation signature at longer exposures. Both anatase/rutile nano-Ti02 were cytotoxic at 100 ug/ml after 24 h. Our results demonstrate the potential for engineered nanomaterials to elicit cellular stimulation through the NFKB pathway and other stress response pathways. [Abstract does not necessarily reflect the policies of the U.S. EPA.]