Airway epithelia regulate expression of human beta-defensin 2 through Toll-like receptor 2

The goal of this study is to investigate whether TLR2 mediates hBD2 induction through NF-kappaB in response to bacterial components in the human airway epithelia. We showed that hTLR2 is expressed in the airway epithelial cells by immunohistochemical staining and RT-PCR. The biology of hTLR2 in this context was studied initially in 293 cells transfected with a plasmid expressing hTLR2 together with an hBD2 promoter-driven luciferase reporter (hBD2-promoter-LUC). Upon incubation with lipoteichoic acid (LTA), the major cell wall component of gram-positive bacteria, luciferase activity was greatly increased compared with mock stimulation. Analysis of mutation constructs of the hBD2 promoter revealed that NF-kappaB sites are important for hTLR2-mediated hBD2 up-regulation upon LTA stimulation. When hBD2-promoter-LUC was transfected into primary human airway epithelia cells (EC), the luciferase activity was greatly increased upon LTA stimulation compared with mock stimulation. The hBD2 promoter mutation constructs were also tested in EC, which confirmed the studies in 293 cells. When a plasmid expressing a dominant-negative mutant of hTLR2 was co-transfected with hBD2-promoter-LUC into EC, LTA could not stimulate hBD2 expression. These data provide convincing evidence that up-regulation of hBD2 can be induced through hTLR2-mediated NFkappaB/IkappaB pathway in the human airway epithelial cells.