Regulatory mechanisms in mucosal secretions and tissues recognize antigens and attenuate pro-inflammatory cytokine responses. Here, we asked whether human b-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 (Po0.05) the interleukin (IL)-6, IL-10, granulocyte macrophage colony stimulating factor (GM-CSF) and tumor-necrosis factor-a (TNF-a) 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.

Human neutrophil peptide α-defensins and human β-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 antigenpresenting 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 β defensin DEFB103 acts as both a stimulant and an attenuator of chemokine and cytokine responses: a dichotomy that is not entirely understood. Our predicted results using an in silico simulation model of dendritic cells and our observed results in human myeloid dendritic cells, show that DEFB103 significantly (p < 0.05) enhanced 6 responses, attenuated 7 responses, and both enhanced/attenuated the CXCL1 and TNF responses to Porphyromonas gingivalis hemagglutinin B (HagB). In murine JAWSII dendritic cells, DEFB103 significantly attenuated, yet rarely enhanced, the Cxcl2, Il6, and Csf3 responses to HagB; and in C57/BL6 mice, DEFB103 significantly enhanced, yet rarely attenuated, the Cxcl1, Csf1, and Csf3 responses. Thus, DEFB103 influences pro-inflammatory activities with the concentration of DEFB103 and order of timing of DEFB103 exposure to dendritic cells, with respect to microbial antigen exposure to cells, being paramount in orchestrating the onset, magnitude, and composition of the chemokine and cytokine response.

Histone deacetylase inhibitors (HDACI) are potential therapeutic agents that inhibit tumor cell growth and survival. Although there are several publications regarding the effects of HDACIs on prostate cancer cell growth, their mechanism(s) of action remains undefined. We treated several human prostate cancer cell lines with the HDACI trichostatin A and found that trichostatin A induced cell death in androgen receptor (AR) -positive cell lines to higher extent compared with AR-negative cell lines. We then discovered that trichostatin A and other HDACIs suppressed AR gene expression in prostate cancer cell lines as well as in AR-positive breast carcinoma cells and in mouse prostate. Trichostatin A also induced caspase activation, but trichostatin A -induced AR suppression and cell death were caspase independent. In addition, we found that doxorubicin inhibited AR expression, and p21 protein completely disappeared after simultaneous treatment with trichostatin A and doxorubicin. This effect may be attributed to the induction of protease activity under simultaneous treatment with these two agents. Further, simultaneous treatment with trichostatin A and doxorubicin increased cell death in AR-positive cells even after culturing in steroid-free conditions. The protease/proteasome inhibitor MG132 protected AR and p21 from the effects of trichostatin A and doxorubicin and inhibited trichostatin A -induced cell death in AR-positive prostate cells. Taken together, our data suggest that the main mechanism of trichostatin A -induced cell death in AR-positive prostate cancer is inhibition of AR gene expression. The synergistic effect of simultaneous treatment with trichostatin A and doxorubicin is mediated via inhibition of AR expression, induction of protease activity, increased expression of p53, and proteolysis of p21.

Aim-Our aim is to assess the ability of human neutrophil peptide α-defensins (HNPs) and human β-defensins (HBDs) to attenuate proinflammatory cytokine responses and enhance antibody responses to recombinant hemagglutinin B (rHagB) or recombinant fimbrillin A (rFimA) from Porphyromonas gingivalis 381 in mice.Materials & methods-In the first study, C57BL/6 mice were given 10 μg rHagB or rFimA without and with 1 μg HNP1, HNP2, HBD1, HBD2 or HBD3. At 24 h, mice were euthanized and cytokine concentrations were determined in nasal wash fluid (NWF), bronchoalveolar lavage fluids, saliva and serum. In the second study, C57BL/6 mice were given 10 μg rHagB or rFimA without and with 1 μg HNPs or HBDs similarly on days 0, 7 and 14. At 21 days, mice were euthanized and rHagB-and rFimA-specific antibody responses were determined in NWF, bronchoalveolar lavage fluids, saliva and serum.Results-Mice given rHagB + HNP2, rHagB + HBD1 and rHagB + HBD3 produced significantly lower (p < 0.05) IL-6 responses than mice given rHagB alone. Mice given rHagB + HNP1, rHagB + HNP2, rHagB + HBD1 and rHagB + HBD3 produced significantly lower (p < 0.05) keratinocytederived chemokine responses than mice given rHagB alone. Mice given rFimA produced very low levels of IL-6 and only moderate levels of keratinocyte-derived chemokine in NWF that were not attenuated by prior incubation of rFimA with any defensin. Mice given rHagB + HNP1 produced a significantly higher (p < 0.05) serum IgG antibody response than mice given rHagB alone and mice given rFimA + HNP2 produced a higher, but not significant, antibody response. Conclusion-The ability of HNPs andHBDs to attenuate proinflammatory cytokine responses in murine NWF and enhance IgG antibody responses in serum was dependent upon both the defensin and antigen of P. gingivalis. Keywords defensins; fimbriae A; hemagglutinin B; immunity; Porphyromonas gingivalisDefensins are small, host-derived peptides with broad antimicrobial activity against Gramnegative and Gram-positive bacteria, fungi and enveloped viruses [1][2][3][4]. In humans, there are human neutrophil peptide α-defensins (HNPs), human θ-defensins (HBDs) and human θdefensins. HNPs are found in neutrophil granules, macrophages, mucosal crypt cells and Paneth cells and contain 29-35 amino acids. HNP1-4 are found in azurophil granule fractions of human neutrophils and human defensins (HD)5 and 6 are found in human Paneth cells. HBDs are expressed in epithelia of many organs and in nonepithelial tissues [5][6][7][8][9]. The latter tissues include articular cartilage, synovial membranes and bone [10][11][12]. HBDs contain 36-45 amino acids. Although 28 β-defensin genes have been described in humans, HBD1-4 are among the more closely studied HBDs.Defensins regulate innate immune mechanisms [3,13]. In addition to their antimicrobial activity, they chemoattract CD4/CD45 RA + cells, CD8 + T cells, monocytes and immature dendritic cells, enhance phagocytosis by macrophages, activate and degranulate mast cells; regulate cytokine production, regulate comp...