Activation of transcription factors in human bronchial epithelial cells exposed to aqueous extracts of mainstream cigarette smoke in vitro.

This study aimed to identify the most sensitive transcription factor activated by cigarette smoke extract (CSE) and to explore cigarette smoke components that have high biological activities in a cell-base assay. Previously, we found evidence that implicated 10 different transcription factors as having a high biological activity to CSE in vitro, based on the results of a comprehensive gene expression profile. For this study, luciferase reporter assays for each transcription factor were developed in two types of human bronchial epithelial cells: NCI-H292 and BEAS-2B cells. The results demonstrated that the nuclear factor erythroid 2-related factor 2 (NRF2)/anti-oxidant response element (ARE) pathway was the most sensitive in response to CSE. Consistently, hemo oxygenase-1 (HO-1), a downstream target gene of NRF2, was effectively up-regulated in BEAS-2B cells exposed to CSE. Moreover, among 1395 cigarette smoke components, naphthoquinones including 9,10-phenaotrenquinone, quinones, benzenediols and α, β-unsaturated carbonyls, were identified as major smoke components that contribute to activating the NRF2/ARE pathway, as indicated by the ARE-reporter assay in BEAS-2B cells. Taken together, NRF2 appears to be a key molecule in the CSE-induced cellular response, and the employed methodology is helpful for the analysis of molecular and cellular effects by CSE.