Regulation of Eclipta prostrata L. components on cigarette smoking-induced autophagy of bronchial epithelial cells via keap1-Nrf2 pathway.

Cigarette smoking extract (CSE)-induced autophagic injury has been regarded as an important contributor to the pathogenesis of lung cancer. We previously found that Eclipta prostrata L. component (CCE) reduced CSE-induced bronchial epithelial cells damage. However, the mechanism remains unknown. Human normal bronchial epithelial cells (NHBE) were exposed to CSE to establish stress model. Nrf2-siRNA and Keap1-siRNA transfection were performed. mRFP-GFP-LC3 dual fluorescence and transmission electron microscopy were used to observe the autophagic characteristics. CCE prevented CSE-induced Nrf2 transfer into cytoplasm and up-regulated Keap1 level of NHBE cells. Furthermore, CCE significantly increased p-p16, p-p21 and p-p53 phosphorylation levels in Nrf2-siRNA- or Keap1-siRNA-transfected cells. As demonstrated by transmission electron microscopy and mRFP-GFP-LC3 dual fluorescence assays, CCE mitigated autophagic injury, and also down-regulated autophagy-related Beclin-1, LC3II/LC3I ratio, Atg5 and ATF4 levels. Our findings showed the attenuation of CCE on CSE-induced NHBE cells injury was associated with Nrf-2-mediated oxidative signaling pathway.