ERK and JNK/AP-1 pathways involved in benzo(a)pyrene induced cell cycle changes in human embryo lung fibroblasts

OBJECTIVE: To study the role of mitogen activated protein kinase (MAPK)/activator protein-1 (AP-1) pathway in benzo(a)pyrene (B(a)P)-induced changes of cell cycle in human embryo lung fibroblasts (HELF). METHODS: AP-1 luciferase activity was determined by the Luciferase reporter gene assay using a luminometer. The expression levels and activity of extracellular signal-regulated protein kinase (ERK), c-Jun NH2-terminal kinase (JNK) and p38 were determined by Western blot. Flow cytometric analysis was employed to detect the distributions of cell cycle. The dominant negative mutant of ERK2, JNK1 and p38 were applied to detect the upstream or downstream relationship of signaling pathways. RESULTS: B(a)P treatment resulted in a marked activation of AP-1 and its upstream MAPK, including ERK, JNK and p38 in human embryo lung fibroblasts (HELF). B(a)P exposure also led to increase the population of cells at S phase compared to control (P < 0.01) with a concomitant decline of cells at G(1) phase. B(a)P-induced cell cycle alternation was markedly impaired by stable expression of a dominant negative mutant of ERK2 or JNK1, but not p38. B(a)P-induced AP-1 transactivation was inhibited by the overexpression of dominant-negative mutant of ERK2 or JNK1, but not p38. Inhibition of the activation of AP-1 by curcumin, a chemical inhibitor of AP-1, significantly inhibited the cell cycle changes in response to B(a)P treatment. CONCLUSION: ERK and JNK, but not p38, mediated benzo(a)pyrene-induced cell cycle changes by AP-1 transactivation in HELF.