Liquid application dosing alters the physiology of air-liquid interface (ALI) primary human bronchial epithelial cell/lung fibroblast co-cultures and in vitro testing relevant endpoints

Nicholas M Mallek; Elizabeth M Martin; Lisa A Dailey; Shaun D McCullough

doi:10.3389/ftox.2023.1264331

Liquid application dosing alters the physiology of air-liquid interface (ALI) primary human bronchial epithelial cell/lung fibroblast co-cultures and in vitro testing relevant endpoints

Front Toxicol. 2024 Jan 23:5:1264331. doi: 10.3389/ftox.2023.1264331. eCollection 2023.

Authors

Nicholas M Mallek¹, Elizabeth M Martin², Lisa A Dailey³, Shaun D McCullough^{3

4}

Affiliations

¹ Curriculum in Toxicology and Environmental Medicine, University of North Carolina, Chapel Hill, NC, United States.
² Epigenetics and Stem Cell Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Durham, NC, United States.
³ Public Health and Integrated Toxicology Division, Center for Public Health and Environmental Assessment, United States Environmental Protection Agency, Chapel Hill, NC, United States.
⁴ Exposure and Protection, RTI International, Durham, NC, United States.

Abstract

Differentiated primary human bronchial epithelial cell (dpHBEC) cultures grown under air-liquid interface (ALI) conditions exhibit key features of the human respiratory tract and are thus critical for respiratory research as well as efficacy and toxicity testing of inhaled substances (e.g., consumer products, industrial chemicals, and pharmaceuticals). Many inhalable substances (e.g., particles, aerosols, hydrophobic substances, reactive substances) have physiochemical properties that challenge their evaluation under ALI conditions in vitro. Evaluation of the effects of these methodologically challenging chemicals (MCCs) in vitro is typically conducted by "liquid application," involving the direct application of a solution containing the test substance to the apical, air-exposed surface of dpHBEC-ALI cultures. We report that the application of liquid to the apical surface of a dpHBEC-ALI co-culture model results in significant reprogramming of the dpHBEC transcriptome and biological pathway activity, alternative regulation of cellular signaling pathways, increased secretion of pro-inflammatory cytokines and growth factors, and decreased epithelial barrier integrity. Given the prevalence of liquid application in the delivery of test substances to ALI systems, understanding its effects provides critical infrastructure for the use of in vitro systems in respiratory research as well as in the safety and efficacy testing of inhalable substances.

Keywords: IVIVE; air-liquid interface (ALI); bronchial; epithelial; inhalation; new approach methodologies (NAMs); respiratory tract; risk assessment.

Grants and funding

The author(s) declare financial support was received for the research, authorship, and/or publication of this article. NM was supported by a NIEHS T32 training grant (#2T32ES007126) and a cooperative agreement between the US Environmental Protection Agency and the UNC Center for Environmental Medicine, Asthma, and Lung Biology (#CR82952201). EM was supported through the Intramural Research Program of the National Institute of Environmental Health Sciences, NIH (ES103372-01). SM and LD were supported by intramural research funding through the US Environmental Protection Agency. SM was also supported by RTI International.