Concentration‐ and time‐dependent effects of benzalkonium chloride in human lung epithelial cells; fate of necrosis, apoptosis, or epithelial mesenchymal transition

Abstract

Benzalkonium chloride (BAC), an antimicrobial agent in inhalable medications and household sprays, has been reported to be toxic to pulmonary organs. Although cell membrane damage has been considered as the main cytotoxic action of BAC, its concentration‐ and time‐dependent cellular effects on lung epithelium has been not fully understood. In the present study, human lung epithelial (H358) cells were exposed to 0.2–40 μg/mL of BAC for 30 min to 21 days. Cell membranes were rapidly disrupted by 30 min exposure, but 24 h incubation of BAC (4–40 μg/mL) dominantly caused apoptosis rather than necrosis. BAC (2–4 μg/mL) induced mitochondrial depolarization which may be related to the increased pro‐apoptotic proteins (caspase‐3, PARP, Bax, p53, and p21), and the decreased anti‐apoptotic Bcl‐2. IRE1α, BiP, CHOP, and p‐JNK proteins were also elevated by BAC (2–4 μg/mL) suggesting the possible involvement of ER stress in the apoptosis. Long‐term (7–21 days) incubations of BAC (0.2–0.6 μg/mL) did not affect the cell viabilities but led to epithelial mesenchymal transition (EMT) as shown as the decrease of E‐cadherin, and the increases of N‐cadherin, fibronectin, and vimentin by up‐regulating the EMT transcription factors, Snail, Slug, Twist1, Zeb1, and Zeb2. Therefore, we conclude that apoptosis can be an important mechanism of acute BAC cytotoxicity in lung epithelial cells, and chronic exposure to BAC even at sub‐toxic doses can promote pulmonary EMT.Support or Funding InformationThis study was funded by Nano‐Material Technology Development Program through the National Research Foundation of Korea (NRF) funded by Ministry of Science and ICT (NRF‐ 2018M3A7B4071233).