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 125ppb ozone (O-3) for 1h at flow rates of 5 and 25mL/min/well; the reaction of O-3 with an indigo dye produces a fluorescent product. A 5-fold increase in fluorescence at 25mL/min/well versus 5mL/min/well was observed, suggesting higher flows were more effective. We then exposed primary human bronchial epithelial cells (HBECs) to 0.3ppm acrolein for 2h at 3, 5, and 25mL/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 24h post-exposure. Comparing responses from HSF Chambers to the CCES, differences were only observed at 1h post-exposure for HMOX1. Here, the HSF Chamber produced a approximate to 6-fold increase while the CCES at 3 and 5mL/min/well produced a approximate to 1.7-fold increase. Operating the CCES at 25mL/min/well produced a approximate to 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.