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STRESS PATHWAY-BASED REPORTER ASSAYS TO ASSESS TOXICITY OF ENVIRONMENTAL CHEMICALS.
Citation:
SIMMONS, S. AND T. V. RAMABHADRAN. STRESS PATHWAY-BASED REPORTER ASSAYS TO ASSESS TOXICITY OF ENVIRONMENTAL CHEMICALS. Presented at Society of Toxicology, Charlotte, NC, March 25 - 29, 2007.
Description:
There is an increasing need for assays for the rapid and efficient assessment of toxicities of large numbers of environmental chemicals. To meet this need, we are developing cell-based reporter assays that measure the activation of key molecular stress pathways. We are using promoter regions from various stress-responsive genes such as heme oxygenase I (HO), heat shock protein 70 (hsp70), and nuclear factor-kappa B, etc. with the ultimate goal of building and characterizing a panel of reporter assays that can be multiplexed within the same cell line for use in high-throughput chemical screening. Our preliminary work towards this goal with the heme oxygenase 1- reporter shows that several toxic compounds can activate HO expression of a in a dose-dependent manner. Cadmium sulfate significantly activated HO expression at a LOAEL concentration of 250 nM, compared to hsp70, which was activated at a LOAEL concentration of 10 uM, indicating the differential sensitivities of these two stress pathways. Less toxic metallic compounds such as copper sulfate did not appreciably affect HO activity at identical concentrations. Additionally, HO expression was induced by a polychlorinated biphenyl (PCB) mixture, Aroclor 1254, at a LOAEL concentration of 10 uM indicating the broad responsiveness of the HO-1 promoter to metal and non-metal stressors. The data presented will show that in vitro stress reporter assays can discriminate toxic compounds at sub-lethal concentrations, provide a quantitative method to assess cellular toxicity and infer mechanism(s) of toxicity. (This is an abstract of a proposed presentation and does not necessarily reflect EPA policy).