NF-ΚB is involved in induction of hBD-2 during monocyte differentiation

Objectives: Human beta-defensins (hBDs) belong to a group of antimicrobial peptide. We previously observed that the expression of hBD-2 was induced during monocyte differentiation. Inducible expression of hBD-2 by bacteria occurs at the NF-ΚB binding site. The present study examined whether the NF-ΚB pathway is involved in the induction of hBD-2 during monocyte differentiation. Method: THP-1 cells used as a model for the monocyte system were cultured in RPMI 1640. In order to induce cell differentiation, the cells were treated with 0.2mM phobol 12-myristate 13-acetate (PMA) for 48h. Signal transduction inhibitors (PDTC, MG123)were added and induction of hBD-2 mRNA were quantificated by TaqMan PCR. The plasmids which have hBD-2 promoter regions of various length or mutation at three NF-ΚB binding site were transfected into THP-1 cells. Promoter activity was analysed by luciferase reporter assay. The statistical significance of the difference was analyzed using One-way ANOVA. Results: Significant expression was observed in the luciferase vector with the -1500bp fragment and the luciferase activity of the vector with NF-ΚB mutants dramatically decreased (p<0.01). Induction of hBD-2 mRNA was inhibited with NF-ΚB inhibitor. Conclusion: These results indicate that the binding site for NF-ΚB may play a crucial role in the induction of hBD-2 expression during monocyte differentiation.