[Vitamin C reverses benzo (a) pyrene-induced cell cycle changes by E2F pathway].
OBJECTIVE
To study the role of E2F1/4 pathway in vitamin C reversing benzo (a) pyrene [B (a) P]-induced changes of cell cycle in human embryo lung fibroblasts (HELF) and the relationship between E2F1 and cyclin D1/CDK4.


METHODS
The stable transfectants, HELF transfected with antisense cyclin D1 and antisense CDK4, were established to detect the relationship of signaling pathway. Cells were cultured and pretreated with vitamin C before stimulation with B (a) P for 24 hours. The expression levels of cyclin D1, CDK4, E2F1 and E2F4 were determined by Western blot and the band intensity was analysed as the relative value to control by using the Gel-Pro 3.0 software. Flow Cytometric Analysis was employed to detect the distributions of cell cycle.


RESULTS
B (a) P significantly elevated the expression levels of cyclin D1, CDK4, E2F1 and E2F4 in HELF cells. Vitamin C decreased the expression levels of above proteins in B (a) P-stimulated HELF cells. The expression levels of these proteins in B (a) P-treated above transfectants were lower than those in B (a) P-treated HELF cells. The expression levels of above proteins with vitamin C combined with antisense cyclin D1 were decreased as compared to those with antisense cyclin D1 alone. B (a) P increased the percentage of S phase as compared to the controls [(41.1 +/- 0.2)% vs (33.5 +/- 3.2)%, P < 0.05]. Both vitamin C [(33.2 +/- 0.6)% vs (41.1 +/- 0.2)%, P < 0.05] and antisense cyclin D1 [(31.2 +/- 1.3)% vs (41.1 +/- 0.2)%, P < 0.05] suppressed the changes of cell cycle induced by B (a) P. Vitamin C combined with antisense CDK4 markedly suppressed B (a) P-induced changes of cell cycle as compared to those with antisense CDK4 alone.


CONCLUSIONS
Vitamin C might reserve the B (a) P-induced changes of cell cycle via intracellular signaling pathway of cyclin D1-CDK4/E2F-1/4.
Gao
Ai
A
National Institute of Occupation Health and Poison Control, Chinese Center for Disease Control and Prevention, Beijing 100050, China.
Liu
Bing-ci
BC
Shen
Fu-hai
FH
Du
Hong-ju
HJ
Huang
Chuan-shu
CS
Jia
Xiao-wei
XW
You
Bao-rong
BR
Ye
Meng
M
D001205:Ascorbic Acid / Q000494:pharmacology*; D001564:Benzo(a)pyrene / Q000037:antagonists & inhibitors / Q000633:toxicity; D002453:Cell Cycle / Q000187:drug effects*; D019938:Cyclin D1 / Q000378:metabolism; D050687:E2F1 Transcription Factor / Q000378:metabolism*; D050704:E2F4 Transcription Factor / Q000378:metabolism*; D006801:Humans; D008168:Lung / Q000166:cytology / Q000196:embryology; D015398:Signal Transduction
D050687:E2F1 Transcription Factor; D050704:E2F4 Transcription Factor; D019938:Cyclin D1; D001564:Benzo(a)pyrene; D001205:Ascorbic Acid