香烟诱导3-磷酸肌醇依赖蛋白激酶1表达和气道粘液高分泌的分子机制研究

Chronic obstructive pulmonary disease (COPD) represents a characteristic symbol of mucus hypersecretion of airway remodeling. Prostaglandin E2 (PGE2), a lipid mediator derived from metabolism of arachidonic acid by the cyclooxygenase (COX), is found increased in lungs from patients with COPD,and correlates with the severity of airflow obstruction and mucus hypersecretion.3-phosphoinositede dependent protein kinase-1 (PDK1), an ankyrin repeat-containing Ser/Thr kinase has been implicated in the induction of apoptosis and the cell proliferation. We found that PDK1 small interfering RNA (siRNA) and the PDK1 inhibitor (OSU03012) blocked the effects of cigarette smoking on human airway epithelial cells induction of mucus hypersecretion. In view of its perceived importance, we speculate that cigarette smoking increases mucus hypersecretion in airway epithelial cells through induction of PGE2 with binding to EP2 or EP4 receptors, followed with induction of PDK1. In addition, we expected that induction of PDK1 by cigarette smoking might be associated with induction of the transcription factor, activating protein 2 (AP-2) or c-Jun expression. Silencing of AP-2 or c-Jun using siRNA and point mutations in the PDK1 promoter might result in blockade of PDK1 expression and promoter activity induced by cigarette smoking. Phoshatidyl-inositol-3 kinase (PI3K)，Mitogen-activated protein kinase (MAPK)，or PKC pathway might be involved in this procedure. So we hypothesis that cigarette smoking stimulates mucus hypersecretion in airway epithelial cells through induction of PGE2, with binding to EP2 orEP4 receptors, stimulation the PI3K/ MAPK, induction of AP-2 or c-jun, increase of PDK1. This study might unveil a novel role of PDK1 in mediating mucus hypersecretion.

气道黏液高分泌、气道上皮杯状细胞化生是慢性阻塞性肺疾病（COPD）气道重塑的重要特征之一。近年来研究发现，COPD患者气道PGE2分泌增加，PGE2可能参与了COPD的气道粘液高分泌。我们在既往的研究中发现AKT/PKB信号参与了气道粘液高分泌的调控，作为AKT/PKB的上游调节物的PDK1是否参与了吸烟所致PGE2分泌增加从而刺激气道粘液高分及气道重塑的过程？预实验中我们初步证实PDK1在这一过程中的作用，本研究拟通过体外实验和烟熏诱导建立慢性阻塞性肺疾病大鼠粘液高分泌模型，首次系统性探讨PDK1信号在香烟诱导的慢性阻塞性肺疾病大鼠模型黏液高分泌的分子机制，为进一步探讨COPD的气道重塑机制和有效防治提供新的思路。

气道黏液高分泌、气道上皮杯状细胞化生是慢性阻塞性肺疾病（COPD）气道重塑的重要特征之一。本研究拟通过体外实验和烟熏诱导建立慢性阻塞性肺疾病大鼠粘液高分泌模型，首次系统性探讨了PDK1信号在香烟诱导的慢性阻塞性肺疾病大鼠模型黏液高分泌的分子机制。在体外实验中我们发现，香烟提取物（CSE）可刺激人气道上皮细胞（HBE）PDK1表达增加和黏蛋白MUC5AC表达增加，呈剂量依赖性和时间依赖性；PDK1siRNA 和PDK1抑制剂OSU03012能抑制CSE引起的MUC5AC表达增加，PDK1过表达质粒能上调CSE引起的MUC5AC表达增加。CSE能刺激HBE PGE2分泌增加，EP4 siRNA能部分抑制CSE引起的PDK1和MUC5AC表达增加。CSE可促进核转录因子AP-2表达增加，呈时间依赖性和剂量依赖性；AP-2siRNA 能抑制CSE引起的PDK1和MUC5AC表达增加，PDK1过表达质粒能上调CSE引起的PDK1和MUC5AC表达增加；CSE能增加AP-2的结合能力。在烟熏小鼠动物模型中发现PDK1抑制剂OSU03012能抑制小鼠气道上皮Mucus5ac表达增加和杯状细胞化生，呈剂量依赖性。以上发现证实了PDK1在CSE诱导的气道粘液高分泌中的关键性作用，为进一步探讨COPD的气道重塑机制和有效防治提供新的思路。