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Zhang F.M.,National Institute of Occupation Health and Poison Control
Zhonghua lao dong wei sheng zhi ye bing za zhi = Zhonghua laodong weisheng zhiyebing zazhi = Chinese journal of industrial hygiene and occupational diseases | Year: 2010

To study the role of p53 in silica-induced cell cycle alternation and DNA double strand breaks repair in human embryo lung fibroblasts (HELF). Neutral comet assay was applied to detect silica-induced DNA double strand breaks. According to the neutral comet experimental result, the DNA repair competence was calculated. The expression levels and phosphorylation of protein in HELF were determined by Western blot. Cell cycle changes were identified by flow cytometry in HELF. After treatment with 200 microg/ml silica for different times (0, 1, 2, 6, 12 and 24 h), the expression levels and phosphorylation of p53 increased in a time-dependent manner, reaching maximum at 12 h and then decreasing at 24 h. After treatment with 0, 25, 50, 100, 200, 300 and 400 microg/ml silica for 12 h, the expression levels and phosphorylation of p53 increased in concentration-dependent manner. After p53 expression was inhibited, silica-induced DNA damage repair competence was markedly increased (DRC = 87.68%), compared with the negative control cell induced by silica (DRC = 57.19%). Silica increased the percentage of S phase (31.8 +/- 1.1)% compared with the controls (24.3 +/- 3.8)% (P < 0.05). When p53 expression was inhibited, the number of S phase cells was significantly increased, (41.4 +/- 0.6)% compared with the controls (25.4 +/- 1.9)% (P < 0.05). The silica dramatically increases the expression levels and phosphorylation of p53. The increased expression of p53 mediates silica-induced cell cycle change and inhibits silica-induced DNA double strand breaks repair. Source


Liu H.F.,National Institute of Occupation Health and Poison Control
Zhonghua lao dong wei sheng zhi ye bing za zhi = Zhonghua laodong weisheng zhiyebing zazhi = Chinese journal of industrial hygiene and occupational diseases | Year: 2010

To study the role of Phosphatidylinositol 3 kinase (PI3K) in silica-induced DNA double strand break repair in human embryo lung fibroblasts (HELF). Control HELF cells and DN-Deltap85 (HELF transfected with Dominant negative mutant of PI3K) were treated with 200 microg/ml silica for different times. The expression levels of phosphor-H2AX (H2AX), Ku70, Ku80 and DNA-PKcs were determined by Western blot. Furthermore, DNA double strand breaks were measured by neutral comet assay after cells were treated with 200 microg/ml silica for 0, 12 and 24 h. After treatment with 200 microg/ml silica for different times, the levels of H2AX were increased in a time-dependent manner and the expression levels of H2AX were obviously suppressed in DN-Deltap85 compared with control cells. The levels of Ku70 and Ku80 were also significantly suppressed in DN-Deltap85 (0.37 +/- 0.14, 0.55 +/- 0.17) compared with control cells (0.58 +/- 0.09, 0.95 +/- 0.21) after treatment with 200 microg/ml silica for 12 h (P < 0.05). Both the percentage of tail DNA in HELF and DN-Deltap85 increased significantly at 12 h (9.78 +/- 1.15, 11.79 +/- 4.90) compared with groups without treatment with silica (2.40 +/- 0.69, 3.31 +/- 1.35) and then decreased at 24 h (4.19 +/- 0.47, 7.58 +/- 4.32), but only the decrease of HELF at 24 h was significant compared with HELF at 12 h (P < 0.05). DNA repair competence of HELF was 75.74% and that of DN-Deltap85 declined to 49.64%. Silica dust can induce DNA double strand breaks in human embryo lung fibroblasts. PI3K might play a role in silica-induced DNA double strand break repair by regulating the expression levels of Ku70 and Ku80. Source


Liu H.F.,National Institute of Occupation Health and Poison Control
Zhonghua lao dong wei sheng zhi ye bing za zhi = Zhonghua laodong weisheng zhiyebing zazhi = Chinese journal of industrial hygiene and occupational diseases | Year: 2011

To study the roles of Ku80/p53 pathway in silica-induced cell cycle changes in human embryo lung fibroblasts (HELF). Ku80 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. The 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. Ku80/p53 pathway plays a role in the cell cycle charges induced by silica in human embryo lung fibroblasts. Source


Liu H.F.,National Institute of Occupation Health and Poison Control
Zhonghua lao dong wei sheng zhi ye bing za zhi = Zhonghua laodong weisheng zhiyebing zazhi = Chinese journal of industrial hygiene and occupational diseases | Year: 2011

To study the roles of DNA dependent protein kinase (DNA-PK)in silica-induced cell cycle changes and expressions of CyclinE and CDK2 in human embryo lung fibroblasts (HELF). The expressions of Ku80 and DNA-PKcs proteins were inhibited by siRNA plasmids, respectively. Flow cytometry was used to detect the distributions of cell cycle and western blot assay was used to determine the expression levels of CyclinE and CDK2 after cells were exposed to 200 microg/ml silica for 0, 3, 6, 12, 24 h. The proportion of G1 phases in negative control cells decreased from 83.53% +/- 2.24% to 69.11% +/- 3.12% after exposure to silica; the proportion of G1 phases in H-Ku80 and H-PKcs cells exposed to silica decreased from 85.16% +/- 3.73% to 59.92% +/- 3.31% and from 75.06% +/- 2.23% to 58.32% +/- 1.35%, respectively (P < 0.05). The exposure to silica resulted in the increasing protein expression levels of CyclinE and CDK2 in negative control cells, and the expression levels of CyclinE were obviously suppressed in H-Ku80 and H-PKcs as compared with control cells. However, the expression level of CDK2 protein did not change significantly. DNA-PK might play a role in silica-induced alternations of cell cycle and regulate silica-induced overexpression of CyclinE in human embryo lung fibroblasts. Source


Jia X.W.,National Institute of Occupation Health and Poison Control
Zhonghua lao dong wei sheng zhi ye bing za zhi = Zhonghua laodong weisheng zhiyebing zazhi = Chinese journal of industrial hygiene and occupational diseases | Year: 2011

To investigate the roles of mitogen-activated protein kinases (MAPK) on silica-induced cell cycle changes. After cells were treated with 200 microg/ml silica, Western blot and Immunofluorescence assays were utilized to detect the expression of cyclin D1, CDK4 and E2F-4, Flow cytometry was used to detect cell cycle progression, the dominant negative mutants techniques were used to investigate silica-induced signal pathway and the effects of which in silica-induced cell cycle changes. After cells were exposed to 200 microg/ml silica 24 h, the results of present study showed the proportion of cells in G1 phases was decreased. Silica-induced cell cycle alternation was markedly impaired by stable expression of a dominant negative mutants of ERK or JNK, but not p38. It was found that ERK and JNK were involved in silica-induced cyclin D1 and CDK4 overexpression and the decreased expression of E2F-4. ERK and JNK, but not p38, mediated silica-induced cell cycle changes in human embryo lung fibroblasts. Source

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