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Case study using transcriptomics from acute in vivo and in vitro exposures to inform points of departure
Citation:
Wehmas, L. Case study using transcriptomics from acute in vivo and in vitro exposures to inform points of departure. Genetics and Environmental Mutagenesis Society, NA, North Carolina, May 24, 2021. https://doi.org/10.23645/epacomptox.17391311
Impact/Purpose:
With the increasing use of cell-based methods in chemical toxicity testing, there is a need to translate results to human health risk. Understanding the amount of chemical (i.e. dose or concentration) that causes changes in gene expression compared to control in cell assays through benchmark dose (BMD) analysis helps address this challenge, but data-gaps exist like how amount of chemical is delivered to the cells and how cell metabolism effects the results. To address this problem, we compared gene expression results from livers of an existing 7 day Di(2-ethylhexyl) phthalate (DEHP) mouse study in which mice were exposed to multiple dose levels of DEHP by feed (0 to 564.3 mg/kg-d, n=4/dose level) to gene expression results from DEHP (0-10 µM) and Mono(2-ethylhexyl)phthalate (MEHP; 0-35 µM) exposed primary mouse liver cells (n=4 assays). While primary liver cells maintain some metabolism, most of the metabolism of DEHP to MEHP is believed to occur in the gut not the liver. Therefore, testing MEHP as well as DEHP in the cell assay helped confirm how much gut vs. liver metabolism is affecting gene response when compared to the animal study. Media from the cell assays was collected to confirm exposure concentrations. Analysis of DEHP induced genes found several genes (Acots) consistent with known DEHP effects. BMD analysis identified a dose threshold for DEHP of 24.2 mg/kg-d which caused a change in gene sets that was 10% different from controls. This was 1.5 fold lower than the 2 yr BMD for liver adenoma or carcinoma. Gene response in cell culture was less robust with only Acot1 and Acot2 showing significant differential expression for MEHP and none for DEHP. Nominal benchmark concentration analysis found 11.7 and 0.5 µM of MEHP and DEHP, respectively resulted in a 10% increase in gene expression compared to control. Calculating delivered dose to cells from exposure concentrations of MEHP and DEHP is in progress but made difficult by the presence of DEHP in a lot of plastics used for cell culture. These results show that gut metabolism may be important in understanding cell based chemical toxicity and human health risk.
Description:
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URLs/Downloads:
DOI: Case study using transcriptomics from acute in vivo and in vitro exposures to inform points of departure
20210521_GEMS_WEHMAS.PDF (PDF, NA pp, 1945.618 KB, about PDF)