| Summary: | 碩士 === 長庚大學 === 醫學生物技術研究所 === 97 === Pulmonary fibrosis is a progressive diffuse parenchymal lung disorder with unknown etiology. It is characterized by an intricate cytokine network and abnormal deposition of mesenchymal cells. Recent study indicated that neutrophil- and macrophage-derived nitrogen free radicals play an important role in cytotoxicity and in the pathogenesis of a whole host of lung diseases. Furthermore, recently study also indicated that NO production may augment TGF-β1 activity, which is proven to be a strong stimulator of collagen, fibronectin, and proteoglycan synthesis. On the other hand, several studies indicated that hepatocyte growth factor (HGF), a multifunctional growth factor produced by mesenchymal cells, is protective against lung damage, and preventing subsequent fibrogenesis. Despite of its well-known protective effect on lung against bleomycin-induced fibrosis, the constitutive overexpression of HGF has some side effects, such as increased susceptibility to lung cancer in transgenic mice model. To avoid these side-effects, we hypothesized that controllable overexpressed HGF under modified iNOS promoter regulation in lung epithelial cells may against the bleomycin-induced pulmonary fibrosis. To examine this hypothesis, we studied: (1) to test whether genetic modified iNOS promoter enhances gene induction upon lung injury related cytokines and fibrotic-related factors challenge, (2) whether the inducible overexpressed HGF in the alveolar epithelial cells have cytoprotective ability to against fibrotic environment challenge. Our data demonstrated that the genetic modified multiple cytokine-responsive elements in rat iNOS promoter have better responded to alone or combination of cytokine (TNF-α, IL-1β, and IFN-γ) induction. Exogenous HGF activated the HGFR (c-met) and urokinase plasminogen activator (uPA) gene expression in the A549 cells. Furthermore, the cytokine-induced HGF overexpression also shown that not only improve the repair of alveolar epithelial and prevent epithelial-mesenchymal transition related fibrosis, but also protect against bleomycin-induced cell death in vitro. In conclusion, we have successfully developed a fibrotic related factors-inducible cytoprotective gene expression system might be applied as a novel therapeutic strategies in pulmonary fibrosis.
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