Helicobacter pylori-mediated transcriptional regulation of the human β-defensin 2 gene requires NF-κB

Abstract

Human β-defensin 2 (hBD-2) is an antimicrobial peptide involved in host defence against bacterial infection in epithelial tissues. Its levels are dramatically increased after bacterial infection. The involvement of NF-κB in Helicobacter pylori-mediated induction of hBD-2 promoter activity was examined. A luciferase reporter plasmid containing the hBD-2 promoter extending from -2110 base pairs to -1 was transiently expressed in MKN45 cells, and promoter activity was determined after incubation with H. pylori for 6 h. Deletion or mutation of the NF-κB site at -208 abolished activation of the hBD-2 promoter. Only H. pylori strains carrying a cag pathogenicity island (PAI) induced activation of the NF-κB site of the hBD-2 promoter gene. By gel retardation analyses, H. pylori increased NF-κB binding to hBD-2 promoter gene sequences. Supershift analysis demonstrated that whereas H. pylori activated NF-κB p65-p65 and p50-p50 homodimers, and the p65-p50 heterodimer of NF-κB, only the p65-p65 homodimer bound to the NF-κB site of the hBD-2 promoter. Thus, specific NF-κB proteins are important cis-elements for induction of hBD-2 gene transcription by H. pylori.