OCTN1‐Mediated Ergothioneine Uptake Protects Lung Epithelial Cells From Tobacco Smoke‐Induced Damage

Abstract

Smoking is a major contributing factor for chronic obstructive pulmonary disease (COPD). Tobacco smoke exposure causes oxidative stress which results in alveolar wall destruction, mucus hyper secretion, inflammation and defective tissue repair. Ergothioneine (ET), an amino acid transported by OCTN1, has been shown to exhibit antioxidant and cytoprotective capacities in vitro. Hence, the objective of this study is to understand the role of OCTN1 and the effect of ET on human alveolar cells when subjected to tobacco smoke‐induced oxidative stress.Confocal microscopy and Western blot was used to determine the presence of OCTN1 in A549 cells and freshly isolated human alveolar epithelial type II (ATII) and type I‐like (ATI‐like) cells in primary culture. A549 cells were cultured in medium containing 1 mM of ET and its intracellular accumulation was measured by LC‐MS/MS over a 3‐week period. A549 cells were also was exposed to various concentrations of cigarette smoke extract (CSE). Prior to the experiment, cells were either cultured for 1 week in the presence or absence of 1 mM ET. An MTT assay was used to assess cell viability for the difference exposures to CSE.Immunoblot and CLSM showed OCTN1 expression in A549, ATII and ATI‐like cells. The uptake of ET by A549 epithelial cells was saturated after approximately 7 days of culture. Western blot data supported the CLSM results and also indicated that OCTN1 levels were increased in the presence of ET. The MTT assay showed that cells pre‐treated with ET were less affected by the cytotoxic effects of CSE.These preliminary data indicate that OCTN1 might play a role in the pathogenesis of tobacco smoke‐induced COPD by regulating ergothioneine transport.