CCN1 Secretion Induced by Cigarette Smoking Extracts Augments IL-8 Release from Bronchial Epithelial Cells

Inflammation involves in many cigarette smoke (CS) related diseases including the chronic obstructive pulmonary disease (COPD). Lung epithelial cell released IL-8 plays a crucial role in CS induced lung inflammation. CS and cigarette smoke extracts (CSE) both induce IL-8 secretion and subsequently, IL-8 recruits inflammatory cells into the lung parenchyma. However, the molecular and cellular mechanisms by which CSE triggers IL-8 release remain not completely understood. In this study, we identified a novel extracellular matrix (ECM) molecule, CCN1, which mediated CSE induced IL-8 secretion by lung epithelial cells. We first found that CS and CSE up-regulated CCN1 expression and secretion in lung epithelial cells in vivo and in vitro. CSE up-regulated CCN1 via induction of reactive oxygen spices (ROS) and endoplasmic reticulum (ER) stress. p38 MAPK and JNK activation were also found to mediate the signal pathways in CSE induced CCN1. CCN1 was secreted into ECM via Golgi and membrane channel receptor aquaporin4. After CSE exposure, elevated ECM CCN1 functioned via an autocrine or paracrine manner. Importantly, CCN1 activated Wnt pathway receptor LRP6, subsequently stimulated Wnt pathway component Dvl2 and triggered beta-catenin translocation from cell membrane to cytosol and nucleus. Treatment of Wnt pathway inhibitor suppressed CCN1 induced IL-8 secretion from lung epithelial cells. Taken together, CSE increased CCN1 expression and secretion in lung epithelial cells via induction of ROS and ER stress. Increased ECM CCN1 resulted in augmented IL-8 release through the activation of Wnt pathway.

炎症与多种香烟烟雾(CS)相关性疾病的发生密切相关，包括慢性阻塞性肺疾病(COPD)。肺上皮细胞释放的白细胞介素8(IL-8)在CS诱导的肺部炎症进程中发挥核心调控作用。CS与香烟烟雾提取物(CSE)均能诱导IL-8的分泌，随后IL-8可招募炎症细胞浸润肺实质。然而，CSE触发IL-8释放的分子与细胞机制尚未完全明确。本研究鉴定出一种新型细胞外基质(ECM)分子CCN1，其可介导肺上皮细胞中CSE诱导的IL-8分泌。我们首次证实，CS与CSE可在体内及体外环境中上调肺上皮细胞内CCN1的表达与分泌。CSE通过诱导活性氧(ROS)生成与内质网(ER)应激，上调CCN1的表达；此外，p38丝裂原活化蛋白激酶(p38 MAPK)与c-Jun氨基末端激酶(JNK)的活化同样参与介导了CSE诱导CCN1表达的信号通路。CCN1经高尔基体与膜通道受体水通道蛋白4(AQP4)分泌至细胞外基质中。经CSE处理后，上调的细胞外基质CCN1可通过自分泌或旁分泌的方式发挥生物学功能。尤为关键的是，CCN1可激活Wnt通路受体LRP6，随后激活Wnt通路组分散乱蛋白2(Dvl2)，并触发β-连环蛋白从细胞膜向胞质及细胞核转位。使用Wnt通路抑制剂可有效抑制CCN1诱导的肺上皮细胞分泌IL-8。综上，CSE可通过诱导ROS生成与ER应激，上调肺上皮细胞中CCN1的表达与分泌；升高的细胞外基质CCN1则通过激活Wnt通路，进而促进IL-8的释放。