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Probe molecules (PrM) approach in adverse outcome pathway (AOP) based high throughput screening (HTS): in vivo discovery for developing in vitro target methods
Citation:
Angrish, M., M. Madden, AND J. Pleil. Probe molecules (PrM) approach in adverse outcome pathway (AOP) based high throughput screening (HTS): in vivo discovery for developing in vitro target methods. CHEMICAL RESEARCH IN TOXICOLOGY. American Chemical Society, Washington, DC, 2015(28):551-559, (2015).
Impact/Purpose:
The National Exposure Research Laboratory’s (NERL’s) Human Exposure and Atmospheric Sciences Division (HEASD) conducts research in support of EPA’s mission to protect human health and the environment. HEASD’s research program supports Goal 1 (Clean Air) and Goal 4 (Healthy People) of EPA’s strategic plan. More specifically, our division conducts research to characterize the movement of pollutants from the source to contact with humans. Our multidisciplinary research program produces Methods, Measurements, and Models to identify relationships between and characterize processes that link source emissions, environmental concentrations, human exposures, and target-tissue dose. The impact of these tools is improved regulatory programs and policies for EPA.
Description:
Efficient and accurate adverse outcome pathway (AOP) based high-throughput screening (HTS) methods use a systems biology based approach to computationally model in vitro cellular and molecular data for rapid chemical prioritization; however, not all HTS assays are grounded by relevant in vivo exposure data. The challenge is to develop HTS assays with unambiguous quantitative links between in vitro responses and corresponding in vivo effects, which is complicated by metabolically insufficient systems, in vitro to in vivo (IVIV) extrapolation, cross-species comparisons, and other inherent issues correlating IVIV findings. This article introduces the concept of ultrasensitive gas phase probe molecules (PrM) to bridge the current HTS assay IVIV gap. The PrM concept assesses metabolic pathways that have already been well defined from intact human or mammalian models. Specifically, the idea is to introduce a gas phase probe molecule into a system, observe normal steady state, add chemicals of interest, and quantitatively measure (from headspace gas) effects on PrM metabolism that can be directly linked back to a well-defined and corresponding in vivo effect. As an example, we developed the pharmacokinetic (PK) parameters and differential equations to estimate methyl-tertiary butyl ether (MTBE) metabolism to tertiary butyl alcohol (TBA) via cytochrome (CYP) 2A6 in the liver from human empirical data. Because MTBE metabolic pathways are well characterized from in vivo data, we can use it as a PrM to explore direct and indirect chemical effects on CYP pathways. The PrM concept could be easily applied to in vitro and alternative models of disease and phenotype, and even test for volatile chemicals while avoiding liquid handling robotics. Furthermore, a PrM can be designed for any chemical with known empirical human exposure data, and used to assess chemicals for which no information exists. Herein, we propose an elegant gas phase probe molecule-based approach to in vitro toxicity testing.
URLs/Downloads:
FINAL FINAL ANGRISH-PLEIL AOP 02182015A.PDF (PDF, NA pp, 373.791 KB, about PDF)Chemical Research in Toxicology
