[ERK, JNK/AP-1 pathway was involved in silica-induced cell cycle changes].
OBJECTIVE
To investigate the alteration of activator protein-1 (AP-1) luciferase activity in human embryo lung fibroblasts (HELF) after exposed to silica, and the role of mitogen activated protein kinase (MAPK)/AP-1 pathway on silica-induced cell cycle changes.


METHODS
After HELF cells were treated with 200 microg/ml silica, immunofluorescence assays were employed to detect the translocation and the phosphorylation level of extracellular signal-regulated protein kinase (ERK) and c-Jun N-terminal kinase (JNK), flow cytometry was used to detect the distributions of cell cycle, the dominant negative mutant of ERK, JNK and p38 were applied to detect the upstream or downstream relationship of signaling pathways.


RESULTS
After HELF-AP-1 cells were exposed to 200 microg/ml silica 6, 12, 24 h respectively, silica exposure lead to AP-1 activation in a time-dependent manner, inducing significant AP-1 activation at 6 h, reaching a maximum activation at 12 h, and having a little decrease at 24 h. After silica exposure 1 h, phosphorylation level of ERK and JNK increased mainly in cytoplasm, however, after exposure 2 h, they translocated to nucleus. The proportion of cells in G1 phases was decreased from (63.80 +/- 9.57)% to (32.23 +/- 7.22)%, and the proportion of cells in S phases was increased from (35.17 +/- 10.33)% to (66.00 +/- 8.07)% after exposed to silica 24 h. Curcumin, a chemical inhibitor of AP-1, impaired the decrease of cells in G1 phases. Furthermore we found expression of dominant-negative mutant of ERK and JNK impaired silica-induced AP-1 activation, whereas, dominant-negative mutant of p38 did not show the effect.


CONCLUSIONS
These result suggested that 200 microg/ml silica exposure can induce AP-1 activation, induce cell cycle changes through ERK, JNK/AP-1-dependent pathway.
Jia
Xiao-wei
XW
National Institute of Occupation Health and Poison Control, Chinese Center for Disease Control and Prevention, Beijing, 100050, China.
Liu
Bing-ci
BC
Shi
Xiang-lin
XL
Gao
Ai
A
Ye
Meng
M
Zhang
Feng-mei
FM
Liu
Hai-feng
HF
Jiao
Shi
S
D002453:Cell Cycle / Q000187:drug effects; D002478:Cells, Cultured; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D005347:Fibroblasts / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D008168:Lung / Q000166:cytology; D011791:Quartz / Q000494:pharmacology*; D015398:Signal Transduction / Q000187:drug effects; D018808:Transcription Factor AP-1 / Q000378:metabolism*
D018808:Transcription Factor AP-1; D011791:Quartz; D048049:Extracellular Signal-Regulated MAP Kinases; D048031:JNK Mitogen-Activated Protein Kinases