EGF receptor signalling in elastase initiated lung injury

肺气肿是一种进行性的人类致残性疾病，其特征是肺泡壁的破坏和肺内周围空间的扩大。蛋白水解酶/抗蛋白水解酶失衡在肺气肿的发病机制中起重要作用。细胞外基质(ECM)和细胞表面分子被丝氨酸蛋白酶和金属蛋白酶(主要是中性粒细胞和巨噬细胞来源)的蛋白水解性加工，涉及多种受体介导的细胞内重要事件，这些事件调节基因表达，影响受损细胞的增殖、迁移、分化和存活。损伤后，受损的肺组织修复不当会导致呼吸道重塑和器官功能障碍。前期研究发现，在体外培养的肺成纤维细胞和损伤肺组织中，中性粒细胞弹性蛋白酶(NE)诱导EGF受体(EGFR)表达下调，细胞外信号调节蛋白1和2(ERK)激活。我们还发现，NE启动的信号导致培养细胞中弹性蛋白mRNA的减少。我们假设NE启动的EGFR介导的ERK通路可以抑制NE损伤的肺组织中弹性蛋白的重新合成，从而促进肺气肿的进展。我们目前的工作模型预测，NE通过降解特定的ECM成分释放细胞表面锚定的EGFR来启动其内吞作用并向ERK传递信号。项目3的重点将是确定NE启动的EGFR介导的ERK在培养的肺成纤维细胞中激活的机制，并研究这一信号通路在NE诱导的小鼠肺气肿进展中的影响。提出了三个具体目标。1.探讨NE诱导的肺成纤维细胞EGFR下调及其信号转导机制。2.探讨EGFR信号通路在NE损伤的肺成纤维细胞弹力、增殖和凋亡反应中的作用；3.检测EGFR信号通路在NE诱导的肺气肿动物模型中的作用。

Pulmonary emphysema is a progressive disabling disorder in humans characterized by destruction of the alveolar walls in enlargement of the peripheral airspaces in the lung. Protease/anti-protease imbalance significantly contributes to the pathogenesis of pulmonary emphysema. Proteolytic processing of extracellular matrix (ECM) and cell surface molecules by serine proteases and metalloproteinases (primarily of neutrophil and macrophage origin_ involves a variety of receptor- mediated intracellular significant events which regulate gene expression and affect proliferation, migration, differentiation, as well as viability of the injured cells. After injury inadequate repair of damaged lung tissue results in remodeling of airways and organ dysfunction. In preliminary studies we found that neutrophil elastase (NE) induces the down- regulation of EGF receptor (EGFR) and activation of extracellular signal regulated kinases 1 and 2 (ERK) in vitro in cultured pulmonary fibroblasts and in vivo of the injured lung. We also found that NE- initiated signaling leads to the decrease of elastin mRNA in cultured cells. We hypothesize that the NE-initiated EGFR-mediated ERK pathway can suppress elastin re-synthesis in NE-injured lung, and thus contribute to the progression of pulmonary emphysema, Our current working model predicts that NE by degrading specific ECM components releases the cell surface anchored EGFR to initiate its endocytosis and signaling towards ERK. The focus of Project 3 will be to determine the mechanism of NE-initiated EGFR-mediated ERK activation in cultured lung fibroblasts and to examine the impact of this signaling pathway on the progression of NE-induced emphysema in mice. Three specific aims are proposed. 1. Determine the mechanism of NE-initiated EGFR down- regulation and signaling in pulmonary fibroblasts. 2. Investigate the role of EGFR signaling pathway in elastogenic, proliferative, and apoptotic responses of NE-injured pulmonary fibroblasts; 3. Examine the role of EGFR signaling in an animal model of NE-induced pulmonary emphysema.