Advanced in vitro exposure systems.

Nrf2 Responses of Commercial Cigarette Whole Smoke and Aerosol from Six Electronic Nicotine Delivery Systems (ENDS) in a 3D Human Airway Model

27. Mar. 2022

Poster SOT 2022, 61st Annual Meeting and ToxExpo, March 27-31, San Diego, USA

Brian M. Keyser1, John Wertman1, Michael Hollings2, Robert Bedford2, and Kristen Jordan1
1 Scientific & Regulatory Affairs, RAI Services Company, Winston-Salem, NC; 
2 Labcorp Early Development Laboratories Ltd., Harrogate, UK

In this study whole smoke from a marketed combustible cigarette and whole aerosol from four different ENDS were evaluated on cell viability and Nrf2 response in a 3D human airway model transfected with a luciferase Nrf2 promoter.
Whole aerosol was generated using a Vitrocell ® VC10® Smoke Exposure System. The tissues were exposed to whole smoke from a market combustible generated under Health Canada Intense regime.These data show that the 3D Nrf2 EpiAirway™ in vitro model can be used to assess and discriminate responses from a biomarker (oxidative stress) for disease pathways associated with tobacco product usage.

 

Abstract
The nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway, activated in human lung cells by cigarette smoke, regulates genes involved in the antioxidative stress response. Here, we evaluated whole smoke from a marketed combustible cigarette (CC) and whole aerosol from four different ENDS (Vuse Alto®) flavors varying in nicotine concentrations on cell viability and Nrf2 response in a 3D human airway model (EpiAirway™) transfected with a luciferase Nrf2 promoter.
EpiAirway™ tissues were exposed to whole smoke or aerosol generated under the Health Canada Intense or a modified ISO 20768:2018 regimen, respectively. Whole smoke/aerosol doses were controlled using dilution airflows of 0.5 to 6 L/min for CC, and undiluted to 3 L/min for Vuse Alto®. Eighteen hours postexposure, luciferase activity and cell viability were measured. Relative luciferase fold activity was expressed as fold change over the air exposed control. Post-exposure, whole smoke/aerosol deposition was quantified using chemical analysis (e.g., glycerol, nicotine, carbonyls).
Differential Nrf2 activation was observed following exposure to whole smoke compared to the ENDS aerosol. A peak response for the CC was ~79 times higher and occurred at ~164 lower equivalent nicotine concentration than Vuse Alto®. Cell viability remained >80% at all airflows for all ENDS test articles and >60% for the CC. Moreover, the minimum exposure-correlated nicotine concentration required to induce a >2-fold increase (threshold response) in Nrf2 activation was >100x lower for CC than the four different Vuse Alto® flavors. These data show that the 3D Nrf2 EpiAirway™ in vitro model can be used to assess and discriminate responses from a biomarker (oxidative stress) for disease pathways associated with tobacco product usage (e.g., respiratory and cardiovascular disease).

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