Cigarette smoke-induced human bronchial epithelial cell injury mediated by AhR/CYP1B1

Background Studies have shown that smoking is associated with dozens of pathological conditions. Cigarette smoke contains nearly 5000 chemicals, including carcinogens and aryl hydrocarbon receptor (AhR) ligands.

Objective This study is designed to explore potential mediating mechanism of AhR/CYP1B1 in cigarette smoke-induced injury of human bronchial epithelial cells.

Methods Three smoking-related datasets, viz. GSE994, GSE17913, and GSE10072, were downloaded from the Gene Expression Omnibus (GEO), and protein expression data of normal tissues of lung cancer patients were obtained from the Clinical Proteomic Tumor Analysis Consortium (CPTAC). The samples from the four datasets were categorized by smoking history and compared for CYP1B1 expressions. Human immortalized lung epithelial (BEAS-2B) cells were exposed to 0%, 20% and 40% (v/v) cigarette smoke in a cell-smoke dynamic exposure system, and pretreated with 10 μmol·L^-1 AhR antagonist CH223191 (CH22). The expression levels of CYP1B1 mRNA and protein were assessed by quantitative PCR and Western blotting; the reactive oxygen species (ROS) level and apoptosis rate were analyzed by flow cytometry; the proliferative ability was measured by EdU assay.

Results In all four datasets, the expression levels of CYP1B1 mRNA and protein in airway epithelial cell, oral epithelial cell, and lung tissues of smoking patients were significantly higher than that of never and former smokers (all Ps < 0.05). The mRNA and protein expressions of CYP1B1 in the 20% and 40% cigarette smoke exposure groups were significantly up-regulated (all Ps < 0.05), while the expressions in the cigarette smoke exposure groups pretreated with CH22 were significantly down-regulated than those in the CH22-unpretreated groups (all Ps < 0.05). Similarly, the ROS levels and apoptosis rates in the 20% and 40% cigarette smoke exposure groups were increased (all Ps < 0.05), while the two indicators were decreased after the pretreatment with CH22 (all Ps < 0.05). Furthermore, the 20% and 40% cigarette smoke exposure groups showed significant down-regulation of cell proliferative ability (all Ps < 0.05), while the CH22 pretreatment groups showed increased proliferative ability (all Ps < 0.05).

Conclusion CYP1B1 is up-regulated in the lung tissues of smoking patients. The cigarette smoke-induced damage in human bronchial epithelial cells is mediated by the activation of AhR/CYP1B1 signaling pathway.