Benzo[a]pyrene diol-epoxide (B[a]PDE) upregulates COX-2 expression through MAPKs/AP-1 and IKKβ/NF-κB in mouse epidermal Cl41 cells

Benzo[a]pyrene-7,8-cliol-9,10-epoxide (B[a]PDE), the major metabolite of benzo[a]pyrene (13[a]P), shows an ultimate complete carcinogen in various animals and is a causative agent for human cancers. However, its effects on the activation of signal pathways and the expression of genes involved in its carcinogenic effect remain largely unknown. In this study, the effects of B[a]PDE on induction of cyclooxygenase (COX)-2 and the signal pathways leading to the induction were investigated. Treatment of mouse epidermal C141 cells with B[a]PDE caused an increase in the expression of COX-2 at both transcription and protein levels, while its parental compound B[a]P did not show significant inductive effect. The COX-2 induction by B[a]PDE was dependent on the activation of mitogen-activated protein kinases (MAPK)s/activation protein (AP)-1 pathway, because inhibition of AP-1 by either overexpression of TAM67 (dominant negative mutant of c-jun), or pretreatment of cells with PD98059 (MEK1/2-ERKs pathway inhibitor) lor SB202190 (p38K inhibitor), markedly inhibited B[a]PDE-induced COX-2 expression. In addition, impairment of NF-kappa B pathway by either NEMO-BDBP (an NF-kappa B specific inhibitor) or I kappa B kinase (IKK)beta-KM (dominant negative mutant of IKK beta) also caused marked reduction of COX-2 induction by B[a]PDE. In contrast, inhibition of nuclear factor of activated T cells (NFAT) with FK506, did not show any effect on B[a]PDE-induced COX-2 expression. Collectively, these data indicate that exposure of CI41 cells to B[a]PDE can induce COX-2 expression by increasing its transcription, which requires the activation of MAPKs/AP-1 and IKK beta/NF-kappa B pathways, but not NFAT pathway. In view of the importance of COX-2 in carcinogenesis, we anticipate that the induction of COX-2 by B[a]PDE may coordinate its mutagenic effects to facilitate the development of skin cancer. (c) 2006 Wiley-Liss, Inc.