Evaluation of Inhalation Exposures and Potential Health Impacts of Ingredient Mixtures Using in vitro to in vivo Extrapolation

Jingjie Zhang; Xiaoqing Chang; Tessa L Holland; David E Hines; Agnes L Karmaus; Shannon Bell; K Monica Lee

doi:10.3389/ftox.2021.787756

Evaluation of Inhalation Exposures and Potential Health Impacts of Ingredient Mixtures Using in vitro to in vivo Extrapolation

Front Toxicol. 2022 Feb 2:3:787756. doi: 10.3389/ftox.2021.787756. eCollection 2021.

Authors

Jingjie Zhang¹, Xiaoqing Chang², Tessa L Holland³, David E Hines², Agnes L Karmaus², Shannon Bell², K Monica Lee¹

Affiliations

¹ Altria Client Services, LLC, Richmond, VA, United States.
² Integrated Laboratory Systems, LLC, Morrisville, NC, United States.
³ Lancaster Laboratories, c/o Altria Client Services, LLC, Regulatory Affairs, VA, Richmond, United States.

Abstract

In vitro methods offer opportunities to provide mechanistic insight into bioactivity as well as human-relevant toxicological assessments compared to animal testing. One of the challenges for this task is putting in vitro bioactivity data in an in vivo exposure context, for which in vitro to in vivo extrapolation (IVIVE) translates in vitro bioactivity to clinically relevant exposure metrics using reverse dosimetry. This study applies an IVIVE approach to the toxicity assessment of ingredients and their mixtures in e-cigarette (EC) aerosols as a case study. Reported in vitro cytotoxicity data of EC aerosols, as well as in vitro high-throughput screening (HTS) data for individual ingredients in EC liquids (e-liquids) are used. Open-source physiologically based pharmacokinetic (PBPK) models are used to calculate the plasma concentrations of individual ingredients, followed by reverse dosimetry to estimate the human equivalent administered doses (EADs) needed to obtain these plasma concentrations for the total e-liquids. Three approaches (single actor approach, additive effect approach, and outcome-oriented ingredient integration approach) are used to predict EADs of e-liquids considering differential contributions to the bioactivity from the ingredients (humectant carriers [propylene glycol and glycerol], flavors, benzoic acid, and nicotine). The results identified critical factors for the EAD estimation, including the ingredients of the mixture considered to be bioactive, in vitro assay selection, and the data integration approach for mixtures. Further, we introduced the outcome-oriented ingredient integration approach to consider e-liquid ingredients that may lead to a common toxicity outcome (e.g., cytotoxicity), facilitating a quantitative evaluation of in vitro toxicity data in support of human risk assessment.

Keywords: electronic cigarette; in vitro to in vivo extrapolation (IVIVE); in vitro toxicity mechanism; mixture assessment; new approach methodologies (NAMs); physiologically based pharmacokinetic (PBPK) model.