Protective role of ergothioneine from tobacco smoke‐induced oxidative stress in vitro and in vivo

Abstract

Tobacco smoke is a major contributing factor for chronic obstructive pulmonary disease (COPD) and exposure leads to oxidative stress, which contributes to alveolar wall destruction, mucus hyper secretion, inflammation and defective tissue repair.Ergothioneine (ET), an amino acid transported across cell membranes by the OCTN1 (SLC22A4) transporter, has been shown to exhibit antioxidant capacities. The objective of this study is to investigate the role of OCTN1‐transported ET on lung epithelial cells subjected to tobacco smoke‐induced oxidative stress.For in vitro studies, human NCI‐H441 cells were cultured for at least 5 days in the presence or absence ET and then exposed to cigarette smoke extract (CSE). Reactive oxygen species were measured using H2DCFDA, enzymes involved in oxidative stress defence (e.g. thioredoxin, sulfiredoxin 1). In addition markers of xenobiotic defense (e.g. MRP1, BCRP, and PXR) were studied by qPCR and immunoblot. Moreover, octn1 knock‐out mice were exposed for 3 and 6 months to second hand smoke. The total cell numbers in broncho‐alveolar lavage fluid (BALF) were counted and smoke induced changes in lung morphology were assessed in hematoxylin‐eosin (HE) stained lung sections.q‐PCR and immunoblot revealed elevated expression levels of sulfiredoxin 1 and thioredoxin as well as PXR after ET treatment of NCI‐H441 cells. Moreover, lower levels of oxidative stress were observed in cells, which were cultured in the presence of ET prior to CSE exposure. When exposed to room air, KO mice showed no differences in HE staining or cell numbers in BALF compared to wild type (WT) animals. However, total cell numbers in BALF as well as increased alveolar damage and immune cell infiltration were observed in KO animals compared to WT mice when exposed to second hand smoke.These data suggest that ET can protect lung epithelial cells from oxidative damage and consequently, variants of OCTN1 might play a role in the pathogenesis of tobacco smoke‐induced COPD by regulating ET transport.Support or Funding InformationThis work has been financially supported by a Clinical Investigator Awards from the Flight Attendant Medical Research Institute (FAMRI CIA 130016). M.A.S. is the recipient of a PhD bursary from the Iraqi Ministry of Higher Education and Scientific Research (MOHESR) and C.G.C. is supported by a Trinity College Research Studentship Award.