OBJECTIVETo investigate the roles of activated protein 1 (AP-1) in cell cycle changes on human embryo lung fibroblasts (HELF) induced by benzo (a) pyrene [B (a) P], and relationships between AP-1 and cyclin D1/CDK4-E2F-1/4.

METHODSCells transfected with AP-1 luciferase reporter plasmid (AP-H) were cultured with serum-free RPMI1640 for 48 h, and treated with 2 micromol/L B (a) P for 24 h. AP-1 relative activity was detected by luciferase assay. Changes of cell cycle and the expression of cyclin D1, CDK4 and E2F-1/4 were checked using the flow cytometer and Western blot assay.

RESULTSAfter B (a) P was treated for 24 h, the ratio of G1 phase cells (71 +/- 2)% was decreased to (48 +/- 3)% (P < 0.05), and an increase was observed in the ratio of S phase. AP-1 activity and cyclin D1/E2F-1 expression were increased significantly, but CDK4/E2F-4 expression did not change after B (a) P treatment. When AP-1 activity was inhibited by curcumin, decreases of G1 phase in response to B (a) P treatment were blocked, and overexpression of cyclin D1/E2F-1 was attenuated, but CDK4/E2F-4 expression was not changed significantly.

CONCLUSIONAP-1 is involved in B (a) P induced cell cycle changes, and is the upstream signals of cyclin D1/E2F-1, but not CDK4/E2F-4.