Study On Mechanism Of Oxidative Stress In Pulmonary Fibrosis

AIM: Pulmonary fibrosis (PF) is a chronic inflammatory interstitial disease of lung with potential fatal prognosis and poor response to available medical therapy. It is characterized by an altered cellular composition of the alveolar region with excessive deposition of collagen. Although the pathogenesis of pulmonary fibrosis has not yet been well clarified, it has been hypothesized that activated inflammatory cells which accumulate in the lower airways, release harmful amount of reactive oxygen species (ROS) that result in lung injury, and proliferation of fibroblast in alveolar walls. Many possible treatment protocols for PF have been investigated, but none has succeeded in clinical trials. Therefore, it has an important significance to study mechanisms of pulmonary fibrosis and novel therapeutic agents with improved efficacy being needed to ameliorate or slow down the progress of fibrosis. METHODS: Through successful establishment of animal model of PF in rats induced by bleomycine, relative parameters of oxidative stress were determinated. The antioxidation activity of a-lipoic acid (LA) was observed by using microsomal lipid peroxidation models in vitro. Fibroblasts were isolated from rats' lung and cultured, adding H₂O₂, BLM and LA to observe their effects on cell proliferation and collagen synthesis, using flow cytometer todetect cellular ROS. Then experiment treatment by using H₂O₂ or LA was practiced on animal model of PR At the 7^th, 14^th and 28^th days after administration, lung tissues were removed and the levels of tissue hydroxyproline (HYP), malondialdehyde (MDA), the reduced glutathione (GSH) and oxidized glutathione (GSSG) and the ratio of GSH/GSSG, as well as total antioxidative capability (T-AOC) were determined. Also, the expression changes of matrix metalloproteinase-1, 3(MMP-1, 3) and tissue inhibitor of matrix metalloproteinase (TIMP-1) of rats' lung were observed. By determination of oxidative stress change as factor of pathogenesis, to study mechanism of PF and observe experimental treatment effects of antioxidant, so as to provide preliminary experiment data and theoratical evidence for elevating remedy level and improving survival quality. RESULTS: (1) The animal model of PF on rats induced by BLM has been successfully established. Pathological changes and the high level of HYP appeared in PF model has been observed. (2) Oxidative damages were also found in these animals. At the 14l days after BLM administration, MDA contents of lung increased significantly, the ratio of GSH/GSSG descended, those implied that efflux of GSSG from lung and consume of GSH raised. And total superoxide dismutase (T-SOD) activity in lung showed descendent tendency. (3) The inhibitory effect of LA on lipid peroxidation models which were stimulated by CCl₄/NADP and V_C/Fe²⁺, has been proved. The antioxidative mechanism of LA made its application in PF possible. (4) Low dose of H2O2 stimulated fibroblasts proliferation, while high dose may kill cells. The same effect on cells was of BLM. However, different doses of LA all have inhibitory effects on cells proliferation, and HYP in cultural medium decreased.Through detecting by flow cytometer, it is found that H2O2 and BLM increased cellular ROS, yet LA reduced. (5) The therapeutical action of...