Pseudomonas aeruginosa- and IL-1beta-mediated induction of human beta-defensin-2 in keratinocytes is controlled by NF-kappaB and AP-1.

Human beta-defensin-2 (hBD-2) is an inducible epithelial peptide antibiotic involved in cutaneous defense. Expression of hBD-2 in keratinocytes is strongly induced by IL-1beta and culture supernatants of Pseudomonas aeruginosa (PA). The use of an IL-1 receptor antagonist revealed that PA-mediated induction of hBD-2 is not dependent on IL-1. Luciferase gene reporter experiments, demonstrated that a 2,338 bp promoter fragment of hBD-2 containing three putative NF-kappaB as well as one activator protein-1 (AP-1) binding site was strongly activated by IL-1beta and PA. Mutation of all NF-kappaB binding sites together with mutation of the AP-1 binding site completely abolished hBD-2 promoter activation by IL-1beta and PA. Treatment with the NF-kappaB inhibitor Helenalin as well as with the c-Jun N-terminal kinase (JNK) inhibitor SP600125 and the p38 mitogen-activated protein kinase inhibitor SB 202190 blocked hBD-2 induction by IL-1beta and PA. PD 98059, a selective inhibitor of extracellular signal-regulated kinase 1/2 demonstrated no significant influence. Transcription factor ELISAs indicated that the NF-kappaB heterodimer p50-p65 binds to all three NF-kappaB sites in the hBD-2 promoter upon stimulation of primary keratinocytes with IL-1beta and PA. We conclude that the activation of NF-kappaB (p50-p65) and AP-1 are crucial events for induction of hBD-2 in keratinocytes upon IL-1beta and PA stimulation.