Dust ; Humans ; Pneumoconiosis ; etiology

Animals ; Antigens, Nuclear ; DNA ; genetics ; metabolism ; DNA Breaks, Double-Stranded ; DNA Repair ; DNA-Binding Proteins ; Humans ; Ku Autoantigen

Animals ; DNA Damage ; DNA Repair ; DNA-Activated Protein Kinase ; Humans

Genomics ; Proteomics ; Toxicology

Apoptosis ; Cell Cycle ; Cell Differentiation ; Cell Proliferation ; Humans ; Neoplastic Processes ; Proto-Oncogene Proteins c-jun ; genetics ; metabolism ; physiology

Dust ; Humans ; Occupational Exposure ; prevention & control ; Pneumoconiosis ; prevention & control

Attitude to Health ; China ; Dust ; prevention & control ; Humans ; Needs Assessment ; Occupational Exposure ; prevention & control ; Occupational Health Services ; Pneumoconiosis ; prevention & control ; Surveys and Questionnaires

China ; epidemiology ; Dust ; prevention & control ; Humans ; Silicon Dioxide ; chemistry ; Silicosis ; epidemiology ; prevention & control

OBJECTIVETo study the role of DNA-dependent protein kinase catalytic subunit (DNA-PKcs) in silica-induced DNA double-strand break repair in human embryo lung fibroblasts (HELF).

METHODSTwo stable transfectants, HELF transfected with DNA-PKcs siRNA (HELF-PKcs) and with negative control siRNA (HELF-NC), were established. HELF cells were treated with 0, 25, 50, 100, 200, 300 and 400 microg/ml silica for 12 h and with 200 microg/ml silica for different times (0, 1, 2, 6, 12 and 24 h). HELF-PKcs and HELF-NC were treated with 200 microg/ml silica for 0, 12 and 24 h. The expression levels of DNA-PKcs and phosphor-H2AX (H2AX) were determined by Western blot. DNA double strand breaks were measured by neutral comet assay.

RESULTSAfter treatment with different doses of silica for 12 h, the levels of H2AX and the percentages of tail DNA increased in concentration-dependent manner. After treatment with 200 microg/ml silica for different times, the levels of H2AX increased in a time-dependent manner. The percentages of tail DNA increased significantly at 6 h, and reaching maximum at 12 h and then decreasing at 24 h. The expression level of DNA-PKcs was suppressed in HELF-PKcs. After treatment with silica at 12 h, the level of H2AX was lower in HELF-PKcs than in HELF-NC, and the percentages of tail DNA increased obviously in both HELF-PKcs and HELF-NC compared with non-treated cells, but no significant difference was found in the percentages of tail DNA between them. The percentages of tail DNA decreased markedly in silica-treated HELF-NC and was significantly lower than in HELF-PKcs at 24 h (P < 0.05).

CONCLUSIONSilica can induce DNA double strand breaks in human embryo lung fibroblasts. DNA-PKcs might play a major role in silica-induced DNA double strand break repair. Silica-induced histone H2AX phosphorylation was dependent on DNA-PKcs.

Cell Line ; DNA Breaks, Double-Stranded ; drug effects ; DNA Repair ; DNA-Activated Protein Kinase ; genetics ; metabolism ; Fibroblasts ; drug effects ; physiology ; Histones ; metabolism ; Humans ; Phosphorylation ; Silicon Dioxide ; pharmacology ; Transfection

OBJECTIVETo study the roles of Ku80/p53 pathway in silica-induced cell cycle changes in human embryo lung fibroblasts (HELF).

METHODSKu80 siRNA expression vectors were transfected into HELF by lipofectamine. Flow cytometry was used to detect the distributions of cell cycle and western blot assay was used to determine the expression level of Ku80, p53 and p21 proteins or the phosphorylation levels of p53-ser15 after cells were exposed to silica.

RESULTSThe expression levels of Ku80 protein increased in concentration-dependent and time-dependent manners after cells were exposed to silica. The proportion of G1 phases in H-NC cells (controls) decreased from 89.28% +/- 2.19% to 68.93% +/- 3.79% after exposure to silica, and the proportion of G1 phases in HELF cells (H-Ku80) decreased from 85.16% +/- 3.73% to 59.92% +/- 3.31% after exposure to silica (P<0.05). The expression levels of Ku80, p53 proteins or p21 proteins or phosphorylation level of p53-ser15 were obviously suppressed in H-Ku80, as compared with H-NC.

CONCLUSIONKu80/p53 pathway plays a role in the cell cycle charges induced by silica in human embryo lung fibroblasts.

Antigens, Nuclear ; metabolism ; Cell Cycle ; drug effects ; Cells, Cultured ; Cyclin-Dependent Kinase Inhibitor p21 ; metabolism ; DNA-Binding Proteins ; metabolism ; Fibroblasts ; cytology ; drug effects ; metabolism ; Flow Cytometry ; Humans ; Ku Autoantigen ; Lung ; cytology ; metabolism ; Phosphorylation ; Quartz ; toxicity ; Signal Transduction ; Tumor Suppressor Protein p53 ; metabolism