A new cell culture exposure system for studying the toxicity of volatile chemicals at the air–liquid interface

Abstract

A cell culture exposure system (CCES) was developed to expose cells established at an air–liquid interface (ALI) to volatile chemicals. We characterized the CCES by exposing indigo dye-impregnated filter inserts inside culture wells to 125 ppb ozone (O₃) for 1 h at flow rates of 5 and 25 mL/min/well; the reaction of O₃ with an indigo dye produces a fluorescent product. A 5-fold increase in fluorescence at 25 mL/min/well versus 5 mL/min/well was observed, suggesting higher flows were more effective. We then exposed primary human bronchial epithelial cells (HBECs) to 0.3 ppm acrolein for 2 h at 3, 5, and 25 mL/min/well and compared our results against well-established in vitro exposure chambers at the U.S. EPA’s Human Studies Facility (HSF Chambers). We measured transcript changes of heme oxygenase-1 (HMOX1) and interleukin-8 (IL-8), as well as lactate dehydrogenase (LDH) release, at 0, 1, and 24 h post-exposure. Comparing responses from HSF Chambers to the CCES, differences were only observed at 1 h post-exposure for HMOX1. Here, the HSF Chamber produced a ∼6-fold increase while the CCES at 3 and 5 mL/min/well produced a ∼1.7-fold increase. Operating the CCES at 25 mL/min/well produced a ∼4.5-fold increase; slightly lower than the HSF Chamber. Our biological results, supported by our comparison against the HSF Chambers, agree with our fluorescence results, suggesting that higher flows through the CCES are more effective at delivering volatile chemicals to cells. This new CCES will be deployed to screen the toxicity of volatile chemicals in EPA’s chemical inventories.

Keywords:

• Air–liquid interface
• acrolein
• volatile organic compounds
• in vitro exposure
• toxicity screening
• air pollution

Acknowledgements

The authors would like to thank TRC Environmental Corporation, particularly Mr. Scott Meade, for the design, construction, and maintenance of the EPA Human Studies Facility in vitro exposure chambers.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported in part by an Oak Ridge Institute for Science and Education (ORISE) postdoctoral fellowship to Jose Zavala and the intramural research program of the Office of Research and Development at the U.S. Environmental Protection Agency (EPA). This manuscript was reviewed by the National Health and Environmental Effects Research Laboratory of the U.S. EPA and approved for publication. Approval does not signify that the contents reflect the views of any agency, nor does mention of trade names or commercial products constitute endorsement or recommendation for use.