Bench Mark Dose Modeling Approaches for Volatile Organic Chemical Exposed Human Airway Epithelial Cells at Air-Liquid Interface
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Currently, volatile organic chemicals (VOCs) pose a unique problem for traditional in vitro chemical safety testing which is predominantly performed in high-throughput submerged exposures. Most VOCs are insoluble in DMSO or water and inhalation is the most concerning route of exposure. To address the difficulties in screening toxic effects of VOCs, the cell culture exposure system (CCES) permits cells to be exposed to multiple concentrations at air-liquid interface (ALI) in a 24-well format. ALI exposure methods permit direct pollutant-to-cell interaction with the test article at physiological conditions, providing a more realistic exposure paradigm. In the on-going study, BEAS-2B and 16HBE cell lines, as well as primary normal human bronchial epithelial (HBE) and MatTek Epi-Airway™ cells are used to assess comparative responses to a variety of volatile chemicals. 1-bromopropane, 1,3-butadiene, carbon tetrachloride, dichloromethane, acrolein, acetaldehyde, trichloroethylene, and formaldehyde have been screened using BEAS-2B and HBE cells. The results show that CCES exposures of in vitro cell lines exhibit variable toxicity across cell types. Cell viability and cytotoxicity are measured via the CellTiter-Glo assay and lactate dehydrogenase release. For most chemicals tested, the highest concentration shows between a 10-30% change in Beas2B cell viability while contrastingly, primary HBECs show less cytotoxicity when exposed to almost all chemicals tested. Cell lysates were collected for TempO-Seq™ analysis designed to be used with Bench Mark Dose (BMD) modeling response and comparison across cell types. The BMD for the most sensitive gene collection was achieved for all B2B cells exposed except for formaldehyde. Most striking is the comparison of BMD to TLV and in vivo exposure results from existing in-vivo studies. Overall, the BMD measured for our chemicals was within one order of magnitude of the TLV reported by ACGIH and our targeted dose response reflects the same rank order of chemical potency as the relevant rodent in vivo exposures reported in the literature. Additional studies in comparison with Mattek™ Epi-Airway cells have been conducted for comparison. Overall, our study provides novel approaches to evaluate the capability of the transcriptomic data to identify concentration-dependent changes in gene expression for volatile chemicals and provides a jumping off point to evaluate the ability of the transcriptomic data to group chemicals with similar bioactivity profiles for potential read across applications. [Abstract does not reflect views or policies of the U.S. EPA.]