The Role of Antimicrobial Peptides in
Periodontal Disease
333
As with LL-37, neutrophil
-defensins also exert their immunomodulating effects on
various types of immune cells. For example, HNP-1 and HNP-2 can induce chemotaxis of T-
lymphocytes (Chertov et al, 1996), dendritic cells (Yang et al, 2000), macrophages, and mast
cells (Grigat et al, 2007). Neutrophil
-defensins enhance cytokine expression in T-
lymphocytes and immunoglobulin G production in B-lymphocytes (Tani et al, 2000), induce
IL-8 expression in lung epithelial cells (van Wetering et al, 1997), and promote IL-1
release
through posttranslational processing (Perregaux et al, 2002).
With regard to the immunoregulatory effects of human
-defensins, hBD-1 and hBD-2
chemoattract immature dendritic cells and memory T-lymphocytes through a G-protein
coupled chemokine receptor, i.e., CCR6, indicating the ability of these two
-defensins to
bridge innate and acquired immunity (Yang et al, 1999). HBD-1 activates monocyte-derived
dendritic cells and promotes the synthesis of several cytokines (Presicce et al, 2009).
Moreover, hBD-1 up-regulates expression of CD91, a scavenger receptor that recognizes
defensins, on the dendritic cell surface, indicating a positive feedback of dendritic cell
activation (Presicce et al, 2009). However, hBD-2, but not hBD-1, enhances chemotaxis of
mast cells (Niyonsaba et al, 2002b) and neutrophils treated with TNF-
(Niyonsaba et al,
2004), possibly via a CCR6 that mediates the signal through activation of phospholipase C.
Furthermore, hBD-2 induces histamine release from mast cells and prostaglandin D synthesis
(Niyonsaba et al, 2001). As with the dissociation of antimicrobial activities from the host
immunostimulatory activities of LL-37 (Braff et al, 2005), it has recently been demonstrated
that the chemoattractant and antimicrobial activities of
-defensins are exerted by distinct
domains, and both of these activities do not rely on the intramolecular disulfide bridges of
-
defensins (Taylor et al, 2008).
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