E-cigarette aerosols of propylene glycol impair BK channel activity and parameters of mucociliary function.

Introduction:
This article examines the effects of propylene glycol (PG), a common delivery vehicle for nicotine and flavorings in e-cigarette (e-cig) liquids, on airway function. The study utilizes a large animal model (sheep) and primary human bronchial epithelial cells (hBECs) to assess the impact of pure PG e-cig aerosols on mucociliary function and airway inflammation.

Key Points:

* Five-day exposure of sheep to e-cig aerosols of 100% PG increased mucus concentrations (percentage of mucus solids) in tracheal secretions, as well as the activity of matrix metalloproteinase-9 (MMP-9).
* In vitro exposure of hBECs to e-cig aerosols of 100% PG decreased ciliary beating and increased mucus concentrations.
* PG e-cig aerosols further reduced the activity of large conductance, Ca2þ-activated, and voltage-dependent Kþ(BK) channels.
* PG can be metabolized to methylglyoxal (MGO) in airway epithelia, which disrupts the interaction between the major pore-forming BK subunit human Slo1 (hSlo1) and the gamma regulatory subunit LRRC26, reducing BK channel conductance.
* PG exposures caused a significant increase in mRNa expression levels of MMP9 and interleukin 1 beta (IL1B).

Main Message:
The study shows that PG e-cig aerosols can cause mucociliary dysfunction by impairing BK channel function via the production of the cytotoxic molecule MGO. This highlights the potential for PG, even in the absence of nicotine or flavorings, to contribute to harmful effects on the airway. The findings underscore the need for further research and regulation regarding e-cigarettes and their components.

Kim MD, Chung S, Baumlin N, et al. E-cigarette aerosols of propylene glycol impair BK channel activity and parameters of mucociliary function. american journal of physiology Lung cellular and molecular physiology. 2023;324(4):L468-L479. doi:10.1152/ajplung.00157.2022