Comparison of biological responses between submerged, pseudo-air-liquid interface, and air-liquid interface exposure of A549 and differentiated THP-1 co-cultures to combustion-derived particles

Abstract

Air liquid interface (ALI) exposure systems are gaining interest, and studies suggest enhanced response of lung cells exposed to particles at ALI as compared to submerged exposure, although the results have been somewhat inconsistent. Previous studies have used monocultures and measured particle deposition using assumptions including consistent particle deposition, particle density, and shape. This study exposed co-cultures of A549 and differentiated THP-1 cells to flame-generated particles using three exposure methods: ALI, pseudo-ALI, and submerged. The dose at ALI was measured directly, reducing the need for assumptions about particle properties and deposition. For all exposure methods an enhanced pro-inflammatory response (TNFα) and Cytochrome P450 (CYP1A1) gene expression, compared to their corresponding negative controls, was observed. ALI exposure induced a significantly greater TNFα response compared to submerged exposure. The submerged exposures exhibited greater induction of CYP1A1 than other exposure methods, although not statistically significant. Some of the factors behind the observed difference in responses for the three exposure methods include differences in physicochemical properties of particles in suspending media, delivered dose, and potential contribution of gas-phase species to cellular response in ALI exposure. However, given the difficulty and expense of ALI exposures, submerged exposure may still provide relevant information for particulate exposures.

Keywords:

• Cell uptake
• electrostatic deposition
• pro-inflammatory marker
• exposure method
• CYP1A1 gene expression
• mass dose

Acknowledgments

The authors acknowledge the use of the University of Utah shared facilities of the Micron Microscopy Suite and the University of Utah USTAR shared facilities supported in part by the MRSEC Program of the NSF under Award (No. DMR-1121252).

Competing interest

The authors declare no conflict of interest. Dr. Kelly has a financial Interest in Tetrad Sensor Network Solutions, LLC. None of Tetrad’s technologies were used in this study.

Data availability statement

The author confirms that the data supporting the findings of this study are available within the article and appendix.

Additional information

Funding

This research was supported by grants from the National Institute of Environmental Health Sciences, National Institutes of Health (5K25ES027504-02, R01ES024681, ES017431, and ES027015). This work was also supported by a Merit Research Grant from the Department of Veterans Affairs (660-D64122). This work was also supported by the University of Utah Flow Cytometry Facility and the National Cancer Institute through Award Number 5P30CA042014-24.