Mechanism Research Of Cigarette Somke Extract-induced Pulmonary Epithelial Cells Apoptosis

Background and objective:Cigarette smoke(CS) is the major cause of chronic obstructive pulmonary disease (COPD), cigarette smoke contains reactive oxygen (ROS) that can cause oxidative stress. It increases the number of apoptotic and necrotic lung cells and further induces the development of chronic airway disease. However, the mechanism of cigarette smoke-induced lung epithelial cells apoptosis remains unclear. The aim of this study was to explore the mechanism of cigarette smoke extract (CSE)-induced lung epithelial cells apoptosis.Methods:In this study, we investigated the effects of cigarette smoke extract (CSE) on apoptosis in human bronchial epithelial cells (BEAS-2B). Analysis of ROS level and apoptosis was detected by flow cytometry. Western blot was used in the tests of apoptosis-regulating signal kinase 1(ASK-1),c-jun N-terminal kinase (JNK), p38 mitogen-activated protein kinase (p38 MAPK) signaling pathway. ROS scavenger and p38 siRNA-based knockout were used to to explore the mechanism of apoptosis.Results:1) CSE exposure induced apoptosis in BEAS-2B cells in a concentrtions-dependent manner.2) In BEAS-2B cells, CSE induced ROS production in concentrtions-dependent manner compared with untreated cells; NAC, a ROS scavenger, significantly relieved the 4% CSE-induced ROS accumulation and cells apoptosis.3) Treatment with CSE led to the activation of ASK-1, p38 MAPK and JNK in a concentration-dependent manner; Pretreatment with 5 mM and 10 mM NAC significantly decreased the activation of phosphorylated ASK1 and p38 MAPK induced by 4% CSE.4) BEAS-2B cells apoptosis induced by CES was significantly suppressed by p38 siRNA, whereas the pooled negative control siRNA had no detectable effects. 5) 4% and 8% CSE treatment significantly up-regulated Nrf-2 expression; 10 mM NAC partially supressed the CSE -induced Nrf-2 protein production; p38MAPK inhibitor and p38 siRNA preparation blocked the CSE-induced alteration of Nrf-2 expression.Conclusion:1) In this study, we demonstrate that ROS generated in response to CSE exposure can activate ASK-1 in BEAS-2B cells, leading to the activation of p38 MAPK and ultimately cell apoptosis;2) Nrf-2 is up-regulated following CSE exposure, and this up-regulation is also regulated through the ROS/p38 MAPK pathways.