[Role of p53 in silica-induced cell cycle alternation and DNA double-strand break repair in human embryo lung fibroblasts].
OBJECTIVE
To study the role of p53 in silica-induced cell cycle alternation and DNA double strand breaks repair in human embryo lung fibroblasts (HELF).


METHODS
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.


RESULTS
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).


CONCLUSIONS
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.
Zhang
Feng-Mei
FM
National Institute of Occupation Health and Poison Control, Chinese Center for Disease Control and Prevention, Beijing 100050, China.
Liu
Bing-Ci
BC
Liu
Hai-Feng
HF
Jia
Xiao-Wei
XW
Ye
Meng
M
D002453:Cell Cycle; D002460:Cell Line; D020552:Comet Assay; D053903:DNA Breaks, Double-Stranded; D004249:DNA Damage; D004260:DNA Repair; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism*; D006801:Humans; D008168:Lung / Q000166:cytology; D012822:Silicon Dioxide / Q000633:toxicity*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*
C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D012822:Silicon Dioxide