| Silicosis, a systematic disease caused by long-time inhalation of free silica dust, is characterized mainly by pulmonary interstitial fibrosis. The Ministry of Public Health announced a total of 14,296 cases of occupational diseases in 2007, of which 10,963 cases were new cases of pneumoconiosis, 875 cases died and 860 cases promoted period. Among these reported 10,963 cases, coal worker's pneumoconiosis and silicosis accounted for 89.37%, for 5,351 cases and 4,447 cases respectively. The proportion which new pneumoconiosis accounted is increased by 0.44 % than 2006, up to 76.69%. Therefore, pneumoconiosis is still the most serious occupational diseases and the incidence is still grim. Studies have shown that the loss caused by this disease per year is about 14 billion yuan directly and the loss caused by new cases is increased at a rate of 0.6 billion yuan per year. The pathogenesis of silicosis is very complex and yet there has been no theory to explain all these phenomena. However, up to date, there is no specific methods for early diagnose and treatment. Till now, though there were several drugs could be used in clinical, and yet these drugs with high toxicity. So, it is urgent to develop new skills and tracing new treatments to interfere with this disease.ObjectiveTo analyse the differential protein expression profiling in pulmonary tissue of rats exposed to silica in early period by comparative proteomics method, to explore the molecular mechanism of silicosis and the role of Chinese traditional medicine (GcAE) on this disease.MethodsA total of 120 wistar rats were randomly divided into three experimental groups: control group, silica group and GcAE-treated group. The rat model of silicosis was established by intratracheal instillation of silica suspension. After the model was established 24h, the rats in GcAE-treated groups were intragastric administration with GcAE (8g/kg body weight per day, orally) and the silica and control groups were intragastric administration with 2 ml sterilized saline per day orally. At the 7th d, 14th d, 21th d, 28th d and 60th d after establishment of animal models, rats in each group were sacrificed, and lungs were removed and stored immediately in liquid nitrogen. The changes of lung histomorphology were observed by HE staining of histological section. Sirius red staining detected I and III type collagens.We selected 14d as the exact time point for early period of rats exposed to silica. The total proteins were separated by means of two-dimensional gel electrophoresis (2-DE) and the differentially expressed proteins were identified using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). In addition,Western blotting was performed to verify the expression of certain candidate protein.Results1. HE staining proved that the rat model of silicosis was successfully established by intratracheal instillation of silica suspension.2. Six differentially expressed proteins were identified. Compared with the control group, cathepsin D precursor, peroxiredoxin-1, heat shock cognate 71 kDa protein, fatty acid-binding protein (epidermal) and heterogeneous nuclear ribonucleoprotein A3 were upregulated in silica group, though SEC14-like protein 3 was downregulated. Western blot further validated the upregulation of peroxiredoxin-1 in silica group.3. GcAE has reverse effect to silicosis, and this process involved cathepsin D precursor, SEC14-like protein 3 and peroxiredoxin-1. The results were verified using western blot for peroxiredoxin-1 with the same trend.Conclusions1. In this study, we successfully found six differentially expressed proteins, mainly refer to oxidative stress, cell signal transduction, apoptosis and so on.2. Cathepsin D precursor, peroxiredoxin-1 and SEC14-like protein 3 may be the target proteins, for the mechanism may be: (1) anti-free radical; (2) anti-apoptosis; (3) anti-oxidation.In a word, our study have provided basic data and study direction for further exploring the pathogenesis of silicosis and discovering the target proteins that GcAE acts.
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