Defensins as anti-inflammatory compounds and mucosal adjuvants.

Human neutrophil peptide alpha-defensins and human beta-defensins are small, well-characterized peptides with broad antimicrobial activities. In mixtures with microbial antigens, defensins attenuate proinflammatory cytokine responses by dendritic cells in culture, attenuate proinflammatory cytokine responses in the nasal fluids of exposed mice and enhance antibody responses in the serum of vaccinated mice. Although the exact mechanisms are unknown, defensins first start by binding to microbial antigens and adhesins, often attenuating toxic or inflammatory-inducing capacities. Binding is not generic; it appears to be both defensin-specific and antigen-specific with high affinities. Binding of defensins to antigens may, in turn, alter the interaction of antigens with epithelial cells and antigen-presenting cells attenuating the production of proinflammatory cytokines. The binding of defensins to antigens may also facilitate the delivery of bound antigen to antigen-presenting cells in some cases via specific receptors. These interactions enhance the immunogenicity of the bound antigen in an adjuvant-like fashion. Future research will determine the extent to which defensins can suppress early events in inflammation and enhance systemic antibody responses, a very recent and exciting concept that could be exploited to develop therapeutics to prevent or treat a variety of oral mucosal infections, particularly where inflammation plays a role in the pathogenesis of disease and its long-term sequelae.

Human beta-defensin 3 binds to hemagglutinin B (rHagB), a non-fimbrial adhesin from Porphyromonas gingivalis, and attenuates a pro-inflammatory cytokine response.

Regulatory mechanisms in mucosal secretions and tissues recognize antigens and attenuate pro-inflammatory cytokine responses. Here, we asked whether human beta-defensin 3 (HBD3) serves as an upstream suppressor of cytokine signaling that binds and attenuates pro-inflammatory cytokine responses to recombinant hemagglutinin B (rHagB), a non-fimbrial adhesin from Porphyromonas gingivalis strain 381. We found that HBD3 binds to immobilized rHagB and produces a significantly higher resonance unit signal in surface plasmon resonance spectroscopic analysis, than HBD2 and HBD1 that are used as control defensins. Furthermore, we found that HBD3 significantly attenuates (P<0.05) the interleukin (IL)-6, IL-10, granulocyte macrophage colony stimulating factor (GM-CSF) and tumor-necrosis factor-alpha (TNF-alpha) responses induced by rHagB in human myeloid dendritic cell culture supernatants and the extracellular signal-regulated kinases (ERK 1/2) response in human myeloid dendritic cell lysates. Thus, HBD3 binds rHagB and this interaction may be an important initial step to attenuate a pro-inflammatory cytokine response and an ERK 1/2 response.

Carbamoylcholine chloride induces a rapid increase in IL6 in the nasal cavity of C57BL/6 mice.

Mice are widely used as models to study the roles of chemokines and cytokines in immune and inflammatory responses. In our work to determine the basal levels of cytokines in saliva, nasal wash fluid (NWF), bronchoalveolar lavage fluid (BALF), and serum of mice, we found that injection of carbamoylcholine chloride, used to stimulate saliva production, induced variations in the interleukin (IL) 6 levels of NWF and BALF supernatants. To characterize this response, C57BL/6 mice were given 10 microg carbamoylcholine chloride intraperitoneally and euthanized at 0, 1, 3, 6, 12, 24, 48, 72, and 96 h after injection. IL6 was increased in NWF supernatants by 2 to 3 h, remained elevated for 24 h, and declined by 48 h after injection. To determine whether carbamoylcholine chloride increased Th1 cytokine (IL2, IL12[p70], and interferon gamma), Th2 cytokine (IL4, IL5, and IL10), granulocyte-macrophage colony-stimulating factor (GM-CSF), or proinflammatory cytokine (IL1beta, tumor necrosis factor alpha, and IL6 in saliva and serum) levels, mice were given 10 microg carbamoylcholine chloride and euthanized. In 47 mice, all cytokine levels in saliva supernatants, NWF supernatants, BALF supernatants, and serum were within normal reported levels (range, 1 to 364 pg/ml); in the serum of the remaining 3 mice, GM-CSF, IL1beta, and IL2 levels were increased. In summary, carbamoylcholine chloride induces a rapid, elevated IL6 response in the nasal cavity and respiratory tract of mice but does not alter the levels of other Th1, Th2, or proinflammatory cytokines.