[Overexpression and higher phosphorylation of p53 induced by benzo(a) pyrene through activated protein 1 independent pathway]

Abstract

Objective: To investigate changes of p53 expression, p53 phosphorylation, and their subcellular localizations and activated protein 1 (AP-1) activity on human embryo lung fibroblasts (HELF) induced by benzo(a)pyrene (B(a)P), and relationships between p53 and AP-1.

Methods: Cells transfected with p53 small interference RNA (p53 siRNA) plasmid (p53-H), CMV vector (HELF/CMV) and AP-1 luciferase reporter plasmid (AP-H) were cultured with serum free RPMI-1640 for 48h, then treated with 2 micromol/L B (a)P for 24h. Changes of p53 expression and p53 phosphorylation were checked by immunofluorescence and Western blot assay. The subcellular localizations of p53 and phosphorylated p53 were checked by cytoplasmic and nuclear extraction. AP-1 relative activities were detected by luciferase assay. Chemical inhibitors of p53 (pifithrin-alpha (PFT)) and AP-1 (curcumin) were used to observe relationships of p53 and AP-1.

Results: The cells were treated with 2 micromol/L B(a)P for 24h, expression of p53 and phosphorylated p53 at 20 site were significantly increased, and they were entirely localized in the nucleus. AP-1 activities significantly increased after B (a)P treatment. When AP-1 activities were inhibited by curcumin, overexpression of p53 induced by B(a)P was not markedly changed. When p53 expression was inhibited by PFY, AP-1 activities were not significantly changed.

Conclusion: Overexpression of p53 in HELF induced by B(a)P could be through AP-1 independent pathways.