Antibacterial and lipopolysaccharide (LPS)-neutralising activity of human cationic antimicrobial peptides against periodontopathogens

In this study, we investigated the antibacterial activity of eight antimicrobial peptides (AMPs), comprising four human beta-defensins (HBDs), three human neutrophil defensins (HNPs) and the cathelicidin LL-37, against two representative periodontopathogens, Prevotella intermedia and Tannerella forsythia. The neutralising effect of these AMPs on expression of interleukin (IL)-1 beta, IL-8 and intercellular adhesion molecule 1 (ICAM-1) induced by lipopolysaccharide (LPS) from P. intermedia and T. forsythia was also tested in THP-1 cells and human gingival fibroblasts. Prevotella intermedia was susceptible to HBD-3 and LL-37 but was resistant to HBD-1, HBD-2, HBD-4, HNP-1, HNP-2 and HNP-3 at concentrations up to 10 mu M. However, all of the AMPs except HNP-2 at 5 mu M significantly inhibited the expression of IL-1 beta, IL-8 and ICAM-1 induced by P. intermedia LPS. Tannerella forsythia showed marked susceptibility to the AMPs tested in the following order: LL-37, HBD-3, HBD-2, HBD-1, HNP-1 and HBD-4. All of the AMPs except HNP-3 had significant neutralising effects on T. forsythia LPS activity. The AMPs showing LPS-neutralising activity inhibited LPS binding to the cells. These results suggest that AMPs may be considered as preventive and therapeutic agents against mixed bacterial infections such as periodontitis by eliminating the pathogens themselves as well as reducing the activity of LPS. Crown Copyright (C) 2009 Published by Elsevier B.V. on behalf of International Society of Chemotherapy. All rights reserved.