OBJECTIVETo analyze the early expression differences of lung tissue proteins in rats exposed to silica using comparative proteomics method, to explore the effects of Chinese traditional medicine (Gymnadenia conopse alcohol extract, GcAE) on silicosis (50 mg/ml).

METHODSAdult male Wistar rats were randomly divided into silica-treated group and GcAE-treated group, four rats a group. The rats were exposed to silica by intratracheal (IT) instillation of 1 ml silica suspension for 24 h. After exposure, the rats in GcAE-treated group were intragastric administration with 0.8 ml GcAE (0.8 ml/100 g a day) and the rats in silica-treated group were intragastric administration with 2 ml sterilized saline a day for 14 days. Then all rats were sacrificed and lung tissues were collected. 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). Western blotting was used to validate the expression of certain candidate proteins in lung tissues.

RESULTSObvious pathological changes of lung could be observed in silica-treated group, such as the thicken of interalveolar septum, which was infiltrated with lymphocytes, macrophages and a few neutrophils with the proliferation of fibroblasts and smooth muscle cells. The accumulation of collagen, the destruction of alveolus structure and the more dotted fibrosis or granuloma could also be found. However, the pathological changes of lung in GcAE-treated group were lighter than those of silica-treated group. Thirty three differentially expressed proteins were identified, including cathepsin D precursor, peroxiredoxin-1 (Prx-1) and SEC14-like protein 3. Compared with silica-treated group, cathepsin D precursor and Prx-1 were significantly downregulated in GcAE-treated group, and SEC14-like protein 3 was significantly upregulated (P < 0.01). The results of western blot indicated that the expression level of Prx-1 in GcAE-treated group was 0.26 ± 0.02, which was significantly lower than that (0.35 ± 0.04) in silica-treated group (P < 0.01).

CONCLUSIONGcAE may inhibit the progress of silicosis in the early period and cathepsin D precursor, SEC14-like protein 3 and Prx-1 may participate in this process.