PMCCPMCCPMCC

Search tips
Search criteria 

Advanced

 
Logo of nihpaAbout Author manuscriptsSubmit a manuscriptNIH Public Access; Author Manuscript; Accepted for publication in peer reviewed journal;
 
Periodontol 2000. Author manuscript; available in PMC Nov 4, 2013.
Published in final edited form as:
PMCID: PMC3816379
NIHMSID: NIHMS515176
Epithelial cell-derived antimicrobial peptides are multi-functional agents that bridge innate and adaptive immunity
Thomas S. McCormick* and Aaron Weinberg
*Department of Dermatology, Case Western Reserve University and University Hospitals Case Medical Center, Cleveland, OH. 10900 Euclid Ave., Cleveland, OH 44106, USA
Department of Biological Sciences, Case Western Reserve University School of Dental Medicine, Cleveland, OH. 10900 Euclid Ave., Cleveland, OH 44106, USA
Corresponding Author: Thomas S. McCormick Department of Dermatology, Case Western Reserve University and University Hospitals Case Medical Center, 10900 Euclid Ave., Cleveland, OH 44106, USA. tsm4/at/case.edu
Mucosal barriers are not only physical; they are the source of potent antimicrobial peptides. These ancient compounds are important for the innate defense of an eukaryotic host. They function within a matter of hours, on a broad spectrum of bacteria, fungi, and encapsulated viruses (reviewed in (34, 94, 102)). The innate immune system works in conjunction with the adaptive immune system in mammals, by permitting the host to curb, delay, or avoid microbial growth shortly after an infection. For example, human β-defensins, specific epithelial cell-derived antimicrobial peptides (see below), have been shown to “cross-talk” with the adaptive immune system by interacting with specific chemokine and Toll-like receptors, resulting in modulation of immunocompetent cell responses of the host (6, 27, 29, 98). It is theorized therefore, that surveillance through epithelial cell-derived antimicrobial peptides functions to keep the natural flora of microorganisms in a steady state in different niches such as the skin, the intestines, and the mouth. This review will highlight recent findings, by our group and others, demonstrating that antimicrobial peptides are not just antimicrobial; they play an added role of cross-talking with a number of cell types in functions as diverse as regulating epithelial cell proliferation, enhancing wound healing, inhibiting/inducing pro-inflammatory cytokines, promoting/inhibiting angiogenesis, stimulating chemokine production, promoting chemotaxis of various leukocytes, degranulating mast cells or modulating host cell gene expression.
It is important to note, at the outset, that human epithelial cells, oral epithelial cells notwithstanding, are a rich source of antimicrobial peptides. While this review will focus principally on recent data highlighting the newly discovered regulatory functions of human β-defensins and LL-37 (see below), the field has yet to discover if other epithelial derived AMP's also harbor immunoregulatory functions. It stands to reason that the aforementioned peptides may work in concert with other epithelial cell-derived antimicrobial peptides. These include S100 proteins such as calprotectin (73) and psoriasin (S100A7) (25, 55), the cathelicidin LL-37 (28), adrenomedullin (3, 45), secretory leukocyte protease inhibitor (80), neutrophil gelatinase-associated lipocalin (10, 32), and the host-defense-related angiogenin, RNase 7 (37). Table I summarizes the antimicrobial peptides discussed in this article. We have intentionally omitted antimicrobial peptides of salivary gland origin such as histatins (69), as this review focuses on oral epithelial cell-derived antimicrobial peptides. S100 proteins regulate a number of epithelial cell functions including intracellular Ca2+ signaling, differentiation, cell-cycle progression, cytoskeletal membrane interactions, leukocyte chemotaxis (25, 40) and, in the case of psoriasin and calprotectin, they also contribute to innate host defense. Psoriasin, initially characterized as a psoriasis specific marker, is secreted by skin keratinocytes and is very effective in killing Escherichia coli, which could explain why skin is naturally resistant to E. coli colonization (31). Calprotectin exhibits biostatic activity against the oral fungal opportunist Candida albicans (17, 82). LL-37, LL-37 (named after the first two N-terminal residues and the total number of residues of the mature peptide) is a member of the cathelin family of antimicrobial peptides with a characteristic α-helix (101). While highly expressed in psoriatic lesions, LL-37 is decreased in lesions of atopic dermatitis, similar to what has been described for the inducible human β-defensins (66, 68). Decreased expression of human β-defensins and LL-37 appear therefore to predispose atopic dermatitis patients to skin infections; complications not encountered in psoriasis patients (66). Adrenomedullin is a pluripotent peptide that can be induced in human oral epithelial cells by oral bacteria (45). It demonstrates broad spectrum antimicrobial activity in low micromolar concentrations (3). Secretory leukocyte protease inhibitor, a member of the Kazal superfamily of serine protease inhibitors generally containing 3–7 tandem Kazal domains, structures originally named in reference to a pancreatic secretory trypsin inhibitor first isolated by Kazal et al (48), is highly expressed in respiratory secretions and saliva and exhibits anti-bacterial, anti-retroviral and anti-inflammatory properties (41, 92). Interestingly, salivary concentrations of secretory leukocyte protease inhibitor have been shown to decrease with advanced age (81). Neutrophil gelatinase-associated lipocalin, is a siderophore-binding protein that exerts a bacteriostatic effect by sequestering iron (10). It is found in human saliva and is secreted from oral epithelial cells (95). Interestingly, human β-defensin 3, secretory leukocyte protease inhibitor and neutrophil gelatinase-associated lipocalin are all regulated via the epidermal growth factor receptor by transforming growth factor-α and insulin-like growth factor-I (83). RNase 7, a member of the RNase A superfamily, exhibits broad-spectrum antimicrobial activity against gram-negative bacteria and the yeast C. albicans at low micromolar concentrations (37). It is expressed in various mucosal sites, including the oral cavity, and is induced by proinflammatory cytokines and bacteria (37).
Table I
Table I
Epithelia-derived antimicrobial peptides discussed in this review
The discoveries that β-defensins originate in mammalian mucosal epithelium (8, 23, 30, 35, 36, 38, 57, 67, 75, 103) has led to the hypothesis that these antimicrobial peptides function to protect the host against microbial pathogenesis at critical confrontational sites. We have extended this hypothesis to also encompass the oral epithelium (20, 51, 52, 94). This tissue, and cells derived from it, constitutively express human β-defensin 1 and can be induced to express human β-defensins 2 and 3 (24, 51, 52, 94). In addition to antimicrobial properties, β-defensins engage the CCR6 receptor on selected immune effector cells, such as immature dendritic cells and T cells and, in a chemokine manner, lead to recruitment of these cells to the site of interest (98). Moreover, we have demonstrated that human β-defensin 3 can down modulate the human immunodeficiency virus (HIV) co-receptor CXCR4, leading to antagonism of cellular activity (27). In addition, antigen presenting cells undergo maturation in the presence of human β-defensin 3 via Toll-like receptors 1 and 2 (29). With the identification of 28 new human β-defensin genes in five syntenic chromosomal regions (76), it is likely that new and well characterized beta defensins are playing a key role in mediating the complex interaction between diverse microorganisms in our environment, the innate host defense system and the acquired immune response necessary to protect hosts from foreign invaders.
The first evidence of β-defensins in a mammalian oral cavity was described in 1995 by Schonwetter et al. (75). Since then, we and others have described the presence of β-defensins in the human oral cavity (9, 20, 24, 52, 56, 60, 74). In gingival tissue, mRNA for both human β-defensins 1 and 2 is localized in suprabasal stratified epithelium and the peptides are detected in upper epithelial layers consistent with the formation of the stratified epithelial barrier (20) (Fig. 1). β-defensins 1 and 2 are not detected in junctional epithelium that serves as the attachment to the tooth surface. Our investigations into the distribution of β-defensin 3 expression in oral epithelium suggests that while β-defensin 2 compartmentalizes to the more differentiated stratum granulosum and spinosum, β-defensin 3 is expressed in the less differentiated stratum basale (47) (Fig. 1); further suggesting “cross-talk” capacity between this peptide and resident immunocompetent cells. Most recently, β-defensin 3 has been shown to be overwhelmingly produced in premalignant epithelial cells in carcinoma in situ and that this correlates with recruitment and infiltration of monocytes/macrophages exclusively to the lesion site (47). We are currently assessing the ability of β-defensin 3 to promote chemotaxis of monocytes/macrophages via a novel G protein coupled receptor (unpublished data).
Figure 1
Figure 1
Immunofluorescence detection of human β-defensin (hBD) 2 and 3 in normal oral epithelium
α-defensins are detected only in polymorphonuclear neutrophils that migrate through the junctional epithelium (20), a localization that persists during inflammation, when the junctional epithelium and surrounding tissue are highly infiltrated with polymorphonuclear neutrophils. Therefore, the undifferentiated junctional epithelium contains exogenously expressed α-defensins and the stratified epithelium contain endogenously expressed β-defensins. These results demonstrate that defensins are localized in specific sites in the gingiva, are synthesized in different cell types, and are likely to serve different roles in various regions of the periodontium.
The distribution of β-defensins in salivary glands also suggests a degree of specificity for these peptides. While human β-defensin 1 is ubiquitous to all salivary glands (74), human β-defensin 3 expression is rarely found in salivary glands (24), and human β-defensin 2 is expressed only in minor salivary glands (9, 56).
A notable difference between oral and most other epithelia is the expression of human β-defensins 2 and 3. These defensins are expressed only in the presence of infection or inflammation in most tissues, including skin, trachea and gut epithelium (4, 54, 67, 68, 93). However, both human β-defensins 2 and 3 are expressed in normal uninflamed gingival tissue (20). We are currently testing the hypothesis that the baseline level of human β-defensin 2 expression in oral epithelium is due to the chronic exposure of the tissue to specific oral commensal bacteria that induce its expression (unpublished data) (see Fig. 2).
Figure 2
Figure 2
AMP's direct chemotaxis indirectly
Prior to the year 2000, most reviews of antimicrobial peptides described these host derived peptides as the body's “natural antibiotics;” i.e., as microbicidal agents that can function rapidly against multiple microbial species at epithelial barriers or during phagocytosis. However, early pioneering work (86) demonstrated that neutrophil derived α-defensins were chemotactic towards human monocytes. This finding, however, could not be appreciated nor put into context until a number of years later when other laboratories started realizing that antimicrobial peptides indeed had additional properties related to directing adaptive immune responses (i.e., cross-talk).
As more information is gathered from such findings, it is anticipated that exploiting antimicrobial peptide immune regulatory strategies will become more commonplace as translational options in bolstering the native host response, without incurring concerns of bacterial resistance. In fact, the first landmark in vivo report using an anti-infective peptide to selectively modulate the innate immune response, was published by Scott et al. (78). The authors described the utility of a 13 amino acid non-toxic peptide, innate defense-regulator peptide 1 (KSRIVPAIPVSLL-NH2), in a mouse model of aggressive bacterial infection. Interestingly, while the peptide showed little antimicrobial activity, it was reported to attenuate pro-inflammatory cytokine production by microbial products, while promoting selective recruitment of monocytes over neutrophils and thereby enhancing and sustaining the levels of monocyte chemokines. While mechanisms for this selective activity still need to be elucidated, results are reminiscent of findings attributed to LL-37 and its anti-inflammatory capacity. Overall, this novel study demonstrated that inflammation can be attenuated in vivo through the use of anti-infective peptides.
It is important to state at the outset that works highlighted herein that focus on antimicrobial peptide capacity to regulate epithelial cell proliferation, enhanced wound healing, inhibition/induction of pro-inflammatory cytokines, angiogenesis/antiangiogenesis, stimulation of chemokine production, chemotaxis of various leukocytes, mast cell degranulation or modulation of host cell gene expression were determined in physiological conditions, not in media of low ionic strength that are often used to determine antimicrobial peptide antimicrobial activity. Therefore, positive outcomes in the presence of serum and physiological salts suggest that results obtained are actually relevant to in vivo functions and conditions.
Antimicrobial peptide neutralization of lipopolysaccharide
The ability of antimicrobial peptides, particularly LL-37, to neutralize endotoxin, was first believed to be due to their cationic and amphipathic capacities to interact with anionic lipopolysaccharide (58), as well as their ability to block lipopolysaccharide binding to lipopolysaccharide-binding protein, as an initial step in activating immune cells (79). Further investigation revealed that antimicrobial peptides can actually dampen pro-inflammatory responses induced by lipopolysaccharide. Lipopolysaccharide-induced genes in macrophages can be suppressed by LL-37, as it directly up-regulates macrophage gene expression, including certain anti-inflammatory genes (77). Importantly, these observations were reported in whole blood and in low micromolar concentrations of LL-37. These results suggest that LL-37 has anti-inflammatory properties. Interestingly, although LL-37 was able to inhibit tumor necrosis factor-α production in bacteria challenged macrophages (77), polymyxin B, another antimicrobial peptide that inhibits lipopolysaccharide binding to lipopolysaccharide-binding protein (79), could not, thereby suggesting specificity of LL-37 activity. Additionally, LL-37 was also found to induce expression of potent chemokines such as interleukin-8 (CXCL8) and monocyte chemoattractant protein-1 (CCL2) in vitro(77). One could speculate, therefore, that the action of LL-37 in the context of neutralizing endotoxin, may be part of a feedback mechanism intended to limit the induction of septic levels of pro-inflammatory cytokines. By re-balancing an obviously dangerous scenario, LL-37 and other antimicrobial peptides could then participate in recruiting cells intended to initiate healing and repair processes.
Antimicrobial peptide related chemotaxis activity and associated receptors
As stated above, the first non-microbicidal related activity attributed to antimicrobial peptides was that α-defensin human neutrophil peptide-1 and -2, but not -3, were chemotactic towards human monocytes. Subsequently, these peptides were found to also chemoattract naïve (CD4+/CD45RA+) CD4+ and CD8+ T cells, as well as immature dendritic cells, but not memory (CD4+/CD45RO+) T cells (97). Later, LL-37 was found to also chemoattract monocytes, T cells and neutrophils, but not dendritic cells, and that this recruitment was dependent upon the G protein coupled receptor formyl peptide receptor-like 1 (16, 22, 99). In addition to formyl peptide receptor-like 1, LL-37 also utilizes the purinergic receptor P2X7 to activate a number of cell types (26, 59, 104). Interestingly, Elssner et al. (26) showed that by trans-activating P2X7, LL-37 promotes interleukin-1β processing and secretion; a result that may enhance inflammatory effectors through synergy between LL-37 and released interleukin-1β (100).
LL-37 chemoattracts mast cells, but apparently in an formyl peptide receptor-like 1 receptor independent manner (62), and promotes mast cell activation (15, 64). Human β-defensin 1, 2 and 3 were found to recruit memory T cells and immature dendritic cells via the G protein coupled receptor CCR6 (98). Human β-defensin 2 can also recruit mast cells (61) and induce mast cell degranulation, prostaglandin D2 production and intracellular Ca2+ mobilization (64). Recently, human β-defensins 3 and 4 have been shown to induce mast cell degranulation, prostaglandin D2 production, intracellular Ca2+ mobilization and promote chemotaxis (14). Moreover, human β-defensin 2 is chemotactic for human neutrophils via CCR6 (63). Interestingly, human β-defensin 3 has been shown to recruit monocytes in an isoform dependent manner; i.e., different disulfide bond motif forms of human β-defensin 3 chemoattract monocytes to varying degrees (96). This suggests that oxidative conditions in mucosae of chronic disease could impact conformational outcomes of antimicrobial peptides during folding, which could then impact their ability to recruit innate and adaptive immune cells.
The specificity of antimicrobial peptides for receptors and respective outcomes of these interactions is noteworthy, and best exemplified when comparing LL-37 and human β-defensin 3. As stated above, LL-37 recruits a number of peripheral blood mononuclear cells through interaction with the G protein coupled receptor formyl peptide receptor-like 1. However, we recently showed that human β-defensin 3 has no effect on formyl-met-leu-phe receptors, such as formyl peptide receptor-like 1 (27). Instead, human β-defensin 3 interacts with another G protein coupled receptor, CXCR4, resulting in antagonism of T cell migration, rather than promotion of chemotaxis (27). CXCR4 is an important co-receptor used by HIV-1 to allow cell fusion and replication of the virus in CD4+ T cells (72). We previously showed that human β-defensin 3 protects T cells from HIV-1 infection (72) by promoting CXCR4 internalization, without cellular activation (27). Since CXCR4 also plays an important role in hemopoiesis, neurogenesis, cardiogenesis and angiogenesis, human β-defensin 3 or its derivatives offer a new paradigm in immunoregulatory therapeutics and provide the opportunity to enhance future drug design.
Antimicrobial peptides can also direct chemotaxis, indirectly
Antimicrobial peptides have been shown to induce a variety of chemokines in epithelial cells, thereby enhancing their own chemotactic capacity and possibly prolonging chemotaxis overall. Interleukin-8 can be produced in epithelial cells upon challenge with either LL-37 or α-defensins (77, 89). Human β-defensin and LL-37 can induce chemokines such as monocyte chemotactic protein-1, macrophage inflammatory protein-3α (MIP-3α; CCL20) and interferon-γ inducible protein-10 (IP-10; CXCL10) in human epidermal keratinocytes (65) (Fig. 2).
These data, along with findings discussed in the previous section, collectively, indicate that antimicrobial peptides likely have a multifaceted role in controlling microbial infections. Aside from their direct antimicrobial activity, antimicrobial peptides are capable of initially promoting leukocyte migration to combat infection, as evidenced by up-regulation of interleukin-8 and monocyte chemotactic protein-1, and also have the capacity to, at a later point in the inflammatory process, act as feedback inhibitors to control inflammation by attenuating immune cell activation.
Antimicrobial peptide related epidermal growth factor receptor interactions
LL-37 can induce lung epithelial cell signaling by transactivating the epidermal growth factor receptor. This is apparently carried out in a multi-step fashion, where LL-37 activates membrane-bound metalloproteinases, which then cleave membrane-anchored epidermal growth factor receptor-ligands (87), which in turn activate the cell by binding epidermal growth factor receptor. Since neutrophils are the major source of LL-37, it is conceivable that infiltrating neutrophils, by releasing LL-37, could contribute to lung epithelial cell signaling. In addition, neutrophil derived matrix metalloproteinase-9 and matrix metalloproteinase-25 (44, 49) could aid in releasing epithelial membrane bound epidermal growth factor receptor ligands and thereby contribute to epidermal growth factor receptor activation and cell signaling. These intriguing results suggest that epithelial cell activation and cytokine release in the lungs, and possibly elsewhere, is the result of neutrophil derived LL-37. Furthermore, LL-37 can induce keratinocyte migration via heparin-binding-epidermal growth factormediated transactivation of epidermal growth factor receptor, and can also promote cell proliferation via epidermal growth factor receptor (12). Importantly, the first in vivo verification of an antimicrobial peptide promoting wound healing was recently demonstrated when adenoviral transfer of LL-37 to excisional wounds in mice promoted re-epithelialization and granulation tissue formation (12).
Clearly, it is probable that other antimicrobial peptides, in conjunction with LL-37, function collectively to promote wound healing. Evidence to support this include the following: (i), epidermal growth factor, when released in areas of infection, has been shown to induce epithelial cell proliferation and wound healing (85); (ii), Sorensen et al. (83) found that in addition to epidermal growth factor, additional epidermal growth factor receptor ligands, such as insulin growth factor-1 and transforming growth factor-α, induce expression of a host of epithelial cell derived antimicrobial peptides, including LL-37, human β-defensin 3, neutrophil gelatinase-associated lipocalin and secretory leukocyte protease inhibitor, suggesting a common epidermal growth factor receptor dependent mechanism for AMP induction; (iii), both LL-37 (88) and human β-defensin 3 (65) promote epithelial cell migration and proliferation; (iv), wound closure; i.e., epithelial cell migration, appears to require epidermal growth factor receptor activation and downstream signaling pathways (2); (v), alpha defensins from human neutrophils, which induce lung epithelial cell proliferation in an epidermal growth factor receptor independent fashion (1), promote the expression of MUC5B and MUC5AC, two mucins that contribute to regeneration of the epithelium (2). Therefore, collective AMP induction and activation may work in synergy to support the growth and antimicrobial potential of epithelial cells when endangered through microbial challenges and wounding.
Evidence and implications for antimicrobial peptide expression in wounds
LL-37 is (i) highly expressed in skin wounds in vivo, reaching its peak by 48 hrs post-injury and declining to its lowest level upon wound closure; (ii) detected in the inflammatory infiltrate and in epithelial cells migrating over the wound; (iii) blocked using specific antibodies which leads to inhibition of re-epithelialization in a concentration dependent manner (39). However, in chronic ulcers, LL-37 expression is very low and is not detected in ulcer edge epithelium (39). Since angiogenesis is an important component in tissue repair and wound healing, Koczulla et al. (50) investigated the neo-vascularization capacity of LL-37 in in vitro and in vivo models. They found that LL-37 caused endothelial cell activation and proliferation, resulting in the formation of vessel-like structures. Interestingly, mice deficient in cathelin-related antimicrobial peptide, the mouse orthologue of human cathelicidin LL-37, are deficient in wound neo-vascularization (50).
Differential expression of antimicrobial peptides in human synovial membranes is governed by specific diseases. Human β-defensin 3 and/or LL-37 are detected in synovial membrane samples from pyogenic arthritis, osteoarthritis or rheumatoid arthritis, while bactericidal permeability-increasing protein, HD5, HD6 and human β-defensin 2 are absent from all of these samples (70). Under inflammatory conditions, human β-defensin 3 is induced in pyogenic arthritis, LL-37 in rheumatoid arthritis and both in osteoarthritis (70). More recently, cytokines involved in the pathogenesis of osteoarthritis, tumor necrosis factor-α and interleukin-1, were shown to induce human β-defensin 3 in cultured chondrocytes and human β-defensin 3 was shown to mediate tissue remodeling in articular cartilage by increasing chondrocyte derived cartilage-degrading matrix- metalloproteases and reducing levels of their endogenous inhibitors (91). The authors concluded that human β-defensin 3 links host defense mechanisms and inflammation with tissue-remodeling processes in articular cartilage and suggest that human β-defensin 3 is a new factor in the pathogenesis of osteoarthritis.
Role of antimicrobial peptides in adaptive immunity
From a series of studies conducted over the last seven years, we can now point to the ability of antimicrobial peptides to modulate adaptive immune functions. A number of studies have reported that co-administering antimicrobial peptides with relatively benign antigens results in enhancement of the host's cell mediated and humoral immune responses to these antigens. Co-administering ovalbumin with α-defensins human neutrophil peptide-1-3 in mice leads to enhanced IgG antibody response to ovalbumin when compared to ovalbumin alone (53). Ovalbumin-specific CD4+ T cells were found to produce elevated cytokine levels as well (53). These data suggest that the human neutrophil peptides may act as adjuvants. Another study showed enhanced ovalbumin-specific IgG response in mice when ovalbumin was co-nasally administered with either 1 μg of either human neutrophil peptide-1, human β-defensin 1 or human β-defensin 2 (11) suggesting that β-defensins may also share the ability to modulate antigen presentation and direct the adaptive immune response. Furthermore, intraperitoneal administration of a B-cell lymphoma idiotype antigen combined with daily injections of human neutrophil peptides increased IgG levels to that antigen and augmented resistance to tumor challenge in mice (84). These findings strongly implicate α-defensins as immune adjuvants that promote T cell-dependent cellular immunity as well as antigen-specific immunoglobulin production.
Using a DNA-vaccine strategy, Biragyn et al. (7) immunized mice with constructs encoding murine β-defensins or various chemokines fused to non-immunogenic lymphoma antigens, and studied their capacity to deliver antigens to subsets of immune cells in order to elicit antitumor immunity. This elegant study demonstrated that DNA immunization, where the vaccine contained murine defensins or chemokines that chemoattract immature dendritic cells via CCR6; i.e., mβ-defensin-2, macrophage inflammatory protein-3α, but not mature dendritic cells, elicit humoral and protective immunity against lymphoma (7). The authors speculated that the targeting of immature dendritic cells by these specific defensins and chemokines via CCR6 (98), results in increased uptake of antigen and induces the expression of co-stimulatory molecules that have been reported by others to induce a robust immune response against weak immunogens (5, 13, 42, 71). Interestingly, this group showed in the murine model that mβ-defensin-2, which does not appear to have a human orthologue, can activate murine immature dendritic cells directly via Toll-like receptor 4 (6). More recently, we showed that human β-defensin 3 induces expression of costimulatory molecules CD40, CD80 and CD86 on human immature dendritic cellss and monocytes, and that human β-defensin-3 promotes expression of pro-inflammatory cytokines by antigen presenting cells (29). LL-37 has been shown to modulate dendritic cell differentiation by enhancing endocytic capacity, upregulating co-stimulatory molecule expression, enhancing secretion of pro-inflammatory cytokines and promoting Th1 responses in vitro (21). Human α-defensins have also been shown to promote expression of costimulatory molecules on lymphocytes (53) as well as the production of proinflammatory cytokines (90). Chemokines, such as monocyte chemotactic protein-1, can promote interleukin-4 production (46) and induce Th2 polarization (33), while macrophage-derived chemokines (CCL22) selectively chemoattract Th2 cells toward antigen presenting cells (43).
While the mechanisms for these intriguing outcomes have not be established, we can speculate that antimicrobial peptides may be modulating lymphocyte responses, modifying cytokine expression during the antigen presenting cell encounter with the antigen, and possibly, as we recently reported with human β-defensin-3 (29), causing the maturation of immature dendritic cells by inducing co-stimulatory molecules, resulting in more effective antigen presentation and subsequent robust T cell activation. These collective observations lead us to conclude that specific defensin molecules and chemokines, or their active homologs, could one day be used as adjuvants to both target antigen to antigen presenting cells as well as selectively prime for humoral or cellular immune responses in vivo. Clearly, these and future studies will lead to an enhanced interest in antimicrobial peptides and their homologs as immuno-therapeutic candidates to bolster the host's immune response.
Antimicrobial peptides in oral cancer
New evidence is emerging that tumor cells produce innate response elements and bioactive peptides, other than chemokines, that alter the tumor micromilieu and contribute to tumor-related inflammatory processes including angiogenesis, recruitment and infiltration of leukocytes, and invasion of tumor cells (19). LL-37 was most recently shown to be produced by ovarian cancer cells, and has the capacity to recruit mesenchymal stem cells to the tumor site, resulting in increased production of pro-tumor cytokines, growth factors and enhanced vascularization (18). We recently reported that human β-defensin 3 is overexpressed in oral carcinoma in situ (Fig. 3) resulting in specific macrophage recruitment to the lesion site (47). Moreover, human β-defensin 3 over expression is also associated with increased tumor size and vascularization, and an investigation into the mechanism of human β-defensin 3 chemoattraction of tumor associated macrophages has revealed a novel receptor related to this activity (Jin et al, unpublished data). Collectively, these observations suggest, for the first time, that tumor cell-derived factors, other than chemokines, are associated with chemoattraction and activation of important cells that contribute to tumor-related inflammation and protection of tumors from immune surveillance.
Figure 3
Figure 3
Expression of human β-defensin (hBD) 2 and human β-defensin 3 in carcinoma in situ
Conclusion
Antimicrobial peptides cross-talk with numerous cell types and function diversely to regulate proliferation, wound healing, pro- and anti-inflammatory cytokine response, angiogenesis, chemokine production, mast cell degranulation and chemotaxis of various leukocytes. Therefore, antimicrobial peptides clearly function to modulate host cell response at the both the molecular and cellular level. This diverse class of regulatory peptides will likely be exploited to modulate immune regulatory strategies as a translational option to bolster the native host response, without incurring concerns of bacterial resistance. Clearly, current and future studies will lead to an enhanced interest in antimicrobial peptides and their homologs as immuno-therapeutic candidates.
Acknowledgments
Studies reported in this manuscript from our group were supported by NIH/NIDCR R01DE18276, R01DE16334, R01DE15510 and P01DE019089 (AW).
1. Aarbiou J, Ertmann M, van Wetering S, van Noort P, Rook D, Rabe KF, Litvinov SV, van Krieken JH, de Boer WI, Hiemstra PS. Human neutrophil defensins induce lung epithelial cell proliferation in vitro. J Leukoc Biol. 2002;1:167–174. [PubMed]
2. Aarbiou J, Verhoosel RM, Van Wetering S, De Boer WI, Van Krieken JH, Litvinov SV, Rabe KF, Hiemstra PS. Neutrophil defensins enhance lung epithelial wound closure and mucin gene expression in vitro. Am J Respir Cell Mol Biol. 2004;2:193–201. [PubMed]
3. Allaker RP, Zihni C, Kapas S. An investigation into the antimicrobial effects of adrenomedullin on members of the skin, oral, respiratory tract and gut microflora. FEMS Immunol Med Microbiol. 1999;4:289–293. [PubMed]
4. Bajaj-Elliott M, Fedeli P, Smith GV, Domizio P, Maher L, Ali RS, Quinn AG, Farthing MJ. Modulation of host antimicrobial peptide (beta-defensins 1 and 2) expression during gastritis. Gut. 2002;3:356–361. [PMC free article] [PubMed]
5. Banchereau J, Steinman RM. Dendritic cells and the control of immunity. Nature. 1998;6673:245–252. [PubMed]
6. Biragyn A, Ruffini PA, Leifer CC, Klyushnenkova E, Shakhov A, Chertov O, Shirakawa AK, Farber JM, Segal DM, Oppenheim FG, Kwak LW. Toll-like receptor 4-dependent activation of dendritic cells by beta-defensin 2. Science. 2002:1025–1029. [PubMed]
7. Biragyn A, Surenhu M, Yang D, Ruffini PA, Haines BA, Klyushnenkova E, Oppenheim JJ, Kwak LW. Mediators of innate immunity that target immature, but not mature, dendritic cells induce antitumor immunity when genetically fused with nonimmunogenic tumor antigens. Journal of Immunology. 2001;11:6644–6653. [PubMed]
8. Boe R, Silvola J, Yang J, Moens U, McCray PB, Jr, Stenfors LE, Seljfelid R. Human beta-defensin-1 mRNA is transcribed in tympanic membrane and adjacent auditory canal epithelium. Infect Immun. 1999;9:4843–4846. [PMC free article] [PubMed]
9. Bonass WA, High AS, Owen PJ, Devine DA. Expression of beta-defensin genes by human salivary glands. Oral Microbiol Immunol. 1999;6:371–374. [PubMed]
10. Borregaard N, Cowland JB. Neutrophil gelatinase-associated lipocalin, a siderophore-binding eukaryotic protein. Biometals. 2006;2:211–215. [PubMed]
11. Brogden KA, Heidari M, Sacco RE, Palmquist D, Guthmiller JM, Johnson GK, Jia HP, Tack BF, McCray PB. Defensin-induced adaptive immunity in mice and its potential in preventing periodontal disease. Oral Microbiol Immunol. 2003;2:95–99. [PubMed]
12. Carretero M, Escamez MJ, Garcia M, Duarte B, Holguin A, Retamosa L, Jorcano JL, Rio MD, Larcher F. In vitro and in vivo wound healing-promoting activities of human cathelicidin LL-37. J Invest Dermatol. 2008;1:223–236. [PubMed]
13. Caux C, Massacrier C, Vanbervliet B, Dubois B, Van Kooten C, Durand I, Banchereau J. Activation of human dendritic cells through CD40 cross-linking. J Exp Med. 1994;4:1263–1272. [PMC free article] [PubMed]
14. Chen X, Niyonsaba F, Ushio H, Hara M, Yokoi H, Matsumoto K, Saito H, Nagaoka I, Ikeda S, Okumura K, Ogawa H. Antimicrobial peptides human beta-defensin (hBD)-3 and hBD-4 activate mast cells and increase skin vascular permeability. Eur J Immunol. 2007;2:434–444. [PubMed]
15. Chen X, Niyonsaba F, Ushio H, Nagaoka I, Ikeda S, Okumura K, Ogawa H. Human cathelicidin LL-37 increases vascular permeability in the skin via mast cell activation, and phosphorylates MAP kinases p38 and ERK in mast cells. J Dermatol Sci. 2006;1:63–66. [PubMed]
16. Chertov O, Michiel DF, Xu L, Wang JM, Tani K, Murphy WJ, Longo DL, Taub DD, Oppenheim JJ. Identification of defensin-1, defensin-2, and CAP37/azurocidin as T-cell chemoattractant proteins released from interleukin-8-stimulated neutrophils. J Biol Chem. 1996;6:2935–2940. [PubMed]
17. Clohessy PA, Golden BE. Calprotectin-mediated zinc chelation as a biostatic mechanism in host defence. Scand J Immunol. 1995;5:551–556. [PubMed]
18. Coffelt SB, Marini FC, Watson K, Zwezdaryk KJ, Dembinski JL, LaMarca HL, Tomchuck SL, Honer zu Bentrup K, Danka ES, Henkle SL, Scandurro AB. The proinflammatory peptide LL-37 promotes ovarian tumor progression through recruitment of multipotent mesenchymal stromal cells. Proc Natl Acad Sci U S A. 2009;10:3806–3811. [PubMed]
19. Coussens LM, Werb Z. Inflammation and cancer. Nature. 2002;6917:860–867. [PMC free article] [PubMed]
20. Dale BA, Kimball JR, Krisanaprakornkit S, Roberts F, Robinovitch M, O'Neal R, Valore EV, Ganz T, Anderson GM, Weinberg A. Localized antimicrobial peptide expression in human gingiva. J Periodontal Res. 2001;5:285–294. [PubMed]
21. Davidson DJ, Currie AJ, Reid GS, Bowdish DM, MacDonald KL, Ma RC, Hancock RE, Speert DP. The cationic antimicrobial peptide LL-37 modulates dendritic cell differentiation and dendritic cell-induced T cell polarization. J Immunol. 2004;2:1146–1156. [PubMed]
22. De Y, Chen Q, Schmidt AP, Anderson GM, Wang JM, Wooters J, Oppenheim JJ, Chertov O. LL-37, the neutrophil granule- and epithelial cell-derived cathelicidin, utilizes formyl peptide receptor-like 1 (FPRL1) as a receptor to chemoattract human peripheral blood neutrophils, monocytes, and T cells. J Exp Med. 2000;7:1069–1074. [PMC free article] [PubMed]
23. Diamond G, Zasloff M, Eck H, Brasseur M, Maloy WL, Bevins CL. Tracheal antimicrobial peptide, a cysteine-rich peptide from mammalian tracheal mucosa: peptide isolation and cloning of a cDNA. Proc Natl Acad Sci U S A. 1991;9:3952–3956. [PubMed]
24. Dunsche A, Acil Y, Dommisch H, Siebert R, Schroder JM, Jepsen S. The novel human beta-defensin-3 is widely expressed in oral tissues. Eur J Oral Sci. 2002;2:121–124. [PubMed]
25. Eckert RL, Broome AM, Ruse M, Robinson N, Ryan D, Lee K. S100 proteins in the epidermis. J Invest Dermatol. 2004;1:23–33. [PubMed]
26. Elssner A, Duncan M, Gavrilin M, Wewers MD. A novel P2X7 receptor activator, the human cathelicidin-derived peptide LL37, induces IL-1 beta processing and release. J Immunol. 2004;8:4987–4994. [PubMed]
27. Feng Z, Dubyak GR, Lederman MM, Weinberg A. Cutting edge: human beta defensin 3--a novel antagonist of the HIV-1 coreceptor CXCR4. J Immunol. 2006;2:782–786. [PubMed]
28. Frohm M, Agerberth B, Ahangari G, Stahle-Backdahl M, Liden S, Wigzell H, Gudmundsson GH. The expression of the gene coding for the antibacterial peptide LL-37 is induced in human keratinocytes during inflammatory disorders. J Biol Chem. 1997;24:15258–15263. [PubMed]
29. Funderburg N, Lederman MM, Feng Z, Drage MG, Jadlowsky J, Harding CV, Weinberg A, Sieg SF. Human -defensin-3 activates professional antigen-presenting cells via Toll-like receptors 1 and 2. Proc Natl Acad Sci U S A. 2007;47:18631–18635. [PubMed]
30. Garcia JR, Jaumann F, Schulz S, Krause A, Rodriguez-Jimenez J, Forssmann U, Adermann K, Kluver E, Vogelmeier C, Becker D, Hedrich R, Forssmann WG, Bals R. Identification of a novel, multifunctional beta-defensin (human beta-defensin 3) with specific antimicrobial activity. Its interaction with plasma membranes of Xenopus oocytes and the induction of macrophage chemoattraction. Cell & Tissue Research. 2001;2:257–264. [PubMed]
31. Glaser R, Harder J, Lange H, Bartels J, Christophers E, Schroder JM. Antimicrobial psoriasin (S100A7) protects human skin from Escherichia coli infection. Nat Immunol. 2005;1:57–64. [PubMed]
32. Goetz DH, Holmes MA, Borregaard N, Bluhm ME, Raymond KN, Strong RK. The neutrophil lipocalin NGAL is a bacteriostatic agent that interferes with siderophore-mediated iron acquisition. Mol Cell. 2002;5:1033–1043. [PubMed]
33. Gu L, Tseng S, Horner RM, Tam C, Loda M, Rollins BJ. Control of TH2 polarization by the chemokine monocyte chemoattractant protein-1. Nature. 2000;6776:407–411. [PubMed]
34. Hancock RE, Brown KL, Mookherjee N. Host defence peptides from invertebrates--emerging antimicrobial strategies. Immunobiology. 2006;4:315–322. [PubMed]
35. Harder J, Bartels J, Christophers E, Schroder JM. Isolation and characterization of human beta -defensin-3, a novel human inducible peptide antibiotic. J Biol Chem. 2001;8:5707–5713. [PubMed]
36. Harder J, Bartels J, Christophers E, Schroder JM. A peptide antibiotic from human skin. Nature. 1997;6636:861. [PubMed]
37. Harder J, Schroder JM. RNase 7, a novel innate immune defense antimicrobial protein of healthy human skin. J Biol Chem. 2002;48:46779–46784. [PubMed]
38. Haynes RJ, McElveen JE, Dua HS, Tighe PJ, Liversidge J. Expression of human beta-defensins in intraocular tissues. Invest Ophthalmol Vis Sci. 2000;10:3026–3031. [PubMed]
39. Heilborn JD, Nilsson MF, Kratz G, Weber G, Sorensen O, Borregaard N, Stahle-Backdahl M. The cathelicidin anti-microbial peptide LL-37 is involved in re-epithelialization of human skin wounds and is lacking in chronic ulcer epithelium. J Invest Dermatol. 2003;3:379–389. [PubMed]
40. Heizmann CW, Fritz G, Schafer BW. S100 proteins: structure, functions and pathology. Front Biosci. 2002:d1356–1368. [PubMed]
41. Hiemstra PS, Maassen RJ, Stolk J, Heinzel-Wieland R, Steffens GJ, Dijkman JH. Antibacterial activity of antileukoprotease. Infect Immun. 1996;11:4520–4524. [PMC free article] [PubMed]
42. Hodge JW, Rad AN, Grosenbach DW, Sabzevari H, Yafal AG, Gritz L, Schlom J. Enhanced activation of T cells by dendritic cells engineered to hyperexpress a triad of costimulatory molecules. J Natl Cancer Inst. 2000;15:1228–1239. [PubMed]
43. Imai T, Nagira M, Takagi S, Kakizaki M, Nishimura M, Wang J, Gray PW, Matsushima K, Yoshie O. Selective recruitment of CCR4-bearing Th2 cells toward antigen-presenting cells by the CC chemokines thymus and activation-regulated chemokine and macrophage-derived chemokine. Int Immunol. 1999;1:81–88. [PubMed]
44. Kang T, Yi J, Guo A, Wang X, Overall CM, Jiang W, Elde R, Borregaard N, Pei D. Subcellular distribution and cytokine- and chemokine-regulated secretion of leukolysin/MT6-MMP/MMP-25 in neutrophils. J Biol Chem. 2001;24:21960–21968. [PubMed]
45. Kapas S, Bansal A, Bhargava V, Maher R, Malli D, Hagi-Pavli E, Allaker RP. Adrenomedullin expression in pathogen-challenged oral epithelial cells. Peptides. 2001;9:1485–1489. [PubMed]
46. Karpus WJ, Lukacs NW, Kennedy KJ, Smith WS, Hurst SD, Barrett TA. Differential CC chemokine-induced enhancement of T helper cell cytokine production. J Immunol. 1997;9:4129–4136. [PubMed]
47. Kawsar HI, Weinberg A, Hirsch SA, Venizelos A, Howell S, Jiang B, Jin G. Overexpression of human beta-defensin-3 in oral dysplasia: Potential role in macrophage trafficking. Oral Oncology. 2009;8:50–56. [PubMed]
48. Kazal LA, Spicer DS, Brahinsky RA. Isolation of a crystalline trypsin inhibitor-anticoagulant protein from pancreas. J Am Chem Soc. 1948;9:3034–3040. [PubMed]
49. Kjeldsen L, Bainton DF, Sengelov H, Borregaard N. Structural and functional heterogeneity among peroxidase-negative granules in human neutrophils: identification of a distinct gelatinase-containing granule subset by combined immunocytochemistry and subcellular fractionation. Blood. 1993;10:3183–3191. [PubMed]
50. Koczulla R, von Degenfeld G, Kupatt C, Krotz F, Zahler S, Gloe T, Issbrucker K, Unterberger P, Zaiou M, Lebherz C, Karl A, Raake P, Pfosser A, Boekstegers P, Welsch U, Hiemstra PS, Vogelmeier C, Gallo RL, Clauss M, Bals R. An angiogenic role for the human peptide antibiotic LL-37/hCAP-18. J Clin Invest. 2003;11:1665–1672. [PMC free article] [PubMed]
51. Krisanaprakornkit S, Kimball JR, Weinberg A, Darveau RP, Bainbridge BW, Dale BA. Inducible expression of human beta-defensin 2 by Fusobacterium nucleatum in oral epithelial cells: multiple signaling pathways and role of commensal bacteria in innate immunity and the epithelial barrier. Infect Immun. 2000;5:2907–2915. [PMC free article] [PubMed]
52. Krisanaprakornkit S, Weinberg A, Perez CN, Dale BA. Expression of the peptide antibiotic human beta-defensin 1 in cultured gingival epithelial cells and gingival tissue. Infect Immun. 1998;9:4222–4228. [PMC free article] [PubMed]
53. Lillard JW, Jr, Boyaka PN, Chertov O, Oppenheim JJ, McGhee JR. Mechanisms for induction of acquired host immunity by neutrophil peptide defensins. Proc Natl Acad Sci U S A. 1999;2:651–656. [PubMed]
54. Liu L, Wang L, Jia HP, Zhao C, Heng HHQ, Schutte BC, McCray PB, Jr, Ganz T. Structure and mapping of the human beta-defensin HBD-2 gene and its expression at sites of inflammation. Gene. 1998;2:237–244. [PubMed]
55. Madsen P, Rasmussen HH, Leffers H, Honore B, Dejgaard K, Olsen E, Kiil J, Walbum E, Andersen AH, Basse B, et al. Molecular cloning, occurrence, and expression of a novel partially secreted protein “psoriasin” that is highly up-regulated in psoriatic skin. J Invest Dermatol. 1991;4:701–712. [PubMed]
56. Mathews M, Jia HP, Guthmiller JM, Losh G, Graham S, Johnson GK, Tack BF, McCray PB., Jr Production of beta-defensin antimicrobial peptides by the oral mucosa and salivary glands. Infect Immun. 1999;6:2740–2745. [PMC free article] [PubMed]
57. McCray PB, Jr, Bentley L. Human airway epithelia express a beta-defensin. Am J Respir Cell Mol Biol. 1997;3:343–349. [PubMed]
58. Nagaoka I, Hirota S, Niyonsaba F, Hirata M, Adachi Y, Tamura H, Heumann D. Cathelicidin family of antibacterial peptides CAP18 and CAP11 inhibit the expression of TNF-alpha by blocking the binding of LPS to CD14(+) cells. J Immunol. 2001;6:3329–3338. [PubMed]
59. Nagaoka I, Tamura H, Hirata M. An antimicrobial cathelicidin peptide, human CAP18/LL-37, suppresses neutrophil apoptosis via the activation of formyl-peptide receptor-like 1 and P2X7. J Immunol. 2006;5:3044–3052. [PubMed]
60. Nishimura M, Abiko Y, Kusano K, Yamazaki M, Saitoh M, Mizoguchi I, Jinbu Y, Noguchi T, Kaku T. Localization of human beta-defensin 3 mRNA in normal oral epithelium, leukoplakia, and lichen planus: an in situ hybridization study. Med Electron Microsc. 2003;2:94–97. [PubMed]
61. Niyonsaba F, Hirata M, Ogawa H, Nagaoka I. Epithelial cell-derived antibacterial peptides human beta-defensins and cathelicidin: multifunctional activities on mast cells. Curr Drug Targets Inflamm Allergy. 2003;3:224–231. [PubMed]
62. Niyonsaba F, Iwabuchi K, Someya A, Hirata M, Matsuda H, Ogawa H, Nagaoka I. A cathelicidin family of human antibacterial peptide LL-37 induces mast cell chemotaxis. Immunology. 2002;1:20–26. [PubMed]
63. Niyonsaba F, Ogawa H, Nagaoka I. Human beta-defensin-2 functions as a chemotactic agent for tumour necrosis factor-alpha-treated human neutrophils. Immunology. 2004;3:273–281. [PubMed]
64. Niyonsaba F, Someya A, Hirata M, Ogawa H, Nagaoka I. Evaluation of the effects of peptide antibiotics human beta-defensins-1/-2 and LL-37 on histamine release and prostaglandin D(2) production from mast cells. Eur J Immunol. 2001;4:1066–1075. [PubMed]
65. Niyonsaba F, Ushio H, Nakano N, Ng W, Sayama K, Hashimoto K, Nagaoka I, Okumura K, Ogawa H. Antimicrobial peptides human beta-defensins stimulate epidermal keratinocyte migration, proliferation and production of proinflammatory cytokines and chemokines. J Invest Dermatol. 2007;3:594–604. [PubMed]
66. Nomura I, Goleva E, Howell MD, Hamid QA, Ong PY, Hall CF, Darst MA, Gao B, Boguniewicz M, Travers JB, Leung DY. Cytokine milieu of atopic dermatitis, as compared to psoriasis, skin prevents induction of innate immune response genes. J Immunol. 2003;6:3262–3269. [PubMed]
67. O'Neil DA, Porter EM, Elewaut D, Anderson GM, Eckmann L, Ganz T, Kagnoff MF. Expression and regulation of the human beta-defensins hBD-1 and hBD-2 in intestinal epithelium. J Immunol. 1999;12:6718–6724. [PubMed]
68. Ong PY, Ohtake T, Brandt C, Strickland I, Boguniewicz M, Ganz T, Gallo RL, Leung DY. Endogenous antimicrobial peptides and skin infections in atopic dermatitis. New England Journal of Medicine. 2002;15:1151–1160. see comments. [PubMed]
69. Oppenheim FG, Xu T, McMillian FM, Levitz SM, Diamond RD, Offner GD, Troxler RF. Histatins, a novel family of histidine-rich proteins in human parotid secretion. Isolation, characterization, primary structure, and fungistatic effects on Candida albicans. J Biol Chem. 1988;16:7472–7477. [PubMed]
70. Paulsen F, Pufe T, Conradi L, Varoga D, Tsokos M, Papendieck J, Petersen W. Antimicrobial peptides are expressed and produced in healthy and inflamed human synovial membranes. J Pathol. 2002;3:369–377. [PubMed]
71. Porgador A, Irvine KR, Iwasaki A, Barber BH, Restifo NP, Germain RN. Predominant role for directly transfected dendritic cells in antigen presentation to CD8+ T cells after gene gun immunization. J Exp Med. 1998;6:1075–1082. [PMC free article] [PubMed]
72. Quinones-Mateu ME, Lederman MM, Feng Z, Chakraborty B, Weber J, Rangel HR, Marotta ML, Mirza M, Jiang B, Kiser P, Medvik K, Sieg SF, Weinberg A. Human epithelial beta-defensins 2 and 3 inhibit HIV-1 replication. Aids. 2003;16:F39–48. [PubMed]
73. Ross KF, Herzberg MC. Calprotectin expression by gingival epithelial cells. Infect Immun. 2001;5:3248–3254. [PMC free article] [PubMed]
74. Sahasrabudhe KS, Kimball JR, Morton TH, Weinberg A, Dale BA. Expression of the antimicrobial peptide, human beta-defensin 1, in duct cells of minor salivary glands and detection in saliva. J Dent Res. 2000;9:1669–1674. [PubMed]
75. Schonwetter BS, Stolzenberg ED, Zasloff MA. Epithelial antibiotics induced at sites of inflammation. Science. 1995;5204:1645–1648. [PubMed]
76. Schutte BC, Mitros JP, Bartlett JA, Walters JD, Jia HP, Welsh MJ, Casavant TL, McCray PB., Jr Discovery of five conserved beta-defensin gene clusters using a computational search strategy. Proc Natl Acad Sci U S A. 2002;4:2129–2133. [PubMed]
77. Scott MG, Davidson DJ, Gold MR, Bowdish D, Hancock RE. The human antimicrobial peptide LL-37 is a multifunctional modulator of innate immune responses. J Immunol. 2002;7:3883–3891. [PubMed]
78. Scott MG, Dullaghan E, Mookherjee N, Glavas N, Waldbrook M, Thompson A, Wang A, Lee K, Doria S, Hamill P, Yu JJ, Li Y, Donini O, Guarna MM, Finlay BB, North JR, Hancock RE. An anti-infective peptide that selectively modulates the innate immune response. Nat Biotechnol. 2007;4:465–472. [PubMed]
79. Scott MG, Vreugdenhil AC, Buurman WA, Hancock RE, Gold MR. Cutting edge: cationic antimicrobial peptides block the binding of lipopolysaccharide (LPS) to LPS binding protein. J Immunol. 2000;2:549–553. [PubMed]
80. Shugars DC, Wahl SM. The role of the oral environment in HIV-1 transmission. J Am Dent Assoc. 1998;7:851–858. [PubMed]
81. Shugars DC, Watkins CA, Cowen HJ. Salivary concentration of secretory leukocyte protease inhibitor, an antimicrobial protein, is decreased with advanced age. Gerontology. 2001;5:246–253. [PubMed]
82. Sohnle PG, Hunter MJ, Hahn B, Chazin WJ. Zinc-reversible antimicrobial activity of recombinant calprotectin (migration inhibitory factor-related proteins 8 and 14) J Infect Dis. 2000;4:1272–1275. [PubMed]
83. Sorensen OE, Cowland JB, Theilgaard-Monch K, Liu L, Ganz T, Borregaard N. Wound healing and expression of antimicrobial peptides/polypeptides in human keratinocytes, a consequence of common growth factors. J Immunol. 2003;11:5583–5589. [PubMed]
84. Tani K, Murphy WJ, Chertov O, Salcedo R, Koh CY, Utsunomiya I, Funakoshi S, Asai O, Herrmann SH, Wang JM, Kwak LW, Oppenheim JJ. Defensins act as potent adjuvants that promote cellular and humoral immune responses in mice to a lymphoma idiotype and carrier antigens. Int Immunol. 2000;5:691–700. [PubMed]
85. Tarnawski A, Szabo IL, Husain SS, Soreghan B. Regeneration of gastric mucosa during ulcer healing is triggered by growth factors and signal transduction pathways. J Physiol Paris. 2001;1-6:337–344. [PubMed]
86. Territo MC, Ganz T, Selsted ME, Lehrer R. Monocyte-chemotactic activity of defensins from human neutrophils. J Clin Invest. 1989;6:2017–2020. [PMC free article] [PubMed]
87. Tjabringa GS, Aarbiou J, Ninaber DK, Drijfhout JW, Sorensen OE, Borregaard N, Rabe KF, Hiemstra PS. The antimicrobial peptide LL-37 activates innate immunity at the airway epithelial surface by transactivation of the epidermal growth factor receptor. J Immunol. 2003;12:6690–6696. [PubMed]
88. Tokumaru S, Sayama K, Shirakata Y, Komatsuzawa H, Ouhara K, Hanakawa Y, Yahata Y, Dai X, Tohyama M, Nagai H, Yang L, Higashiyama S, Yoshimura A, Sugai M, Hashimoto K. Induction of keratinocyte migration via transactivation of the epidermal growth factor receptor by the antimicrobial peptide LL-37. J Immunol. 2005;7:4662–4668. [PubMed]
89. van Wetering S, Manness-Lazeroms SP, van Sterkenburg MA, Daha MR, Dijkman JH, PS H. Effect of defensins on interleukin-8 synthesis in airway epithelial cells. Am J Physiol. 1997:L888–896. [PubMed]
90. van Wetering S, Sterk PJ, Rabe KF, Hiemstra PS. Defensins: key players or bystanders in infection, injury, and repair in the lung? J Allergy Clin Immunol. 1999;6:1131–1138. [PubMed]
91. Varoga D, Pufe T, Harder J, Schroder JM, Mentlein R, Meyer-Hoffert U, Goldring MB, Tillmann B, Hassenpflug J, Paulsen F. Human beta-defensin 3 mediates tissue remodeling processes in articular cartilage by increasing levels of metalloproteinases and reducing levels of their endogenous inhibitors. Arthritis Rheum. 2005;6:1736–1745. [PubMed]
92. Wahl SM, McNeely TB, Janoff EN, Shugars D, Worley P, Tucker C, Orenstein JM. Secretory leukocyte protease inhibitor (SLPI) in mucosal fluids inhibits HIV-I. Oral Dis. 1997:S64–69. [PubMed]
93. Wehkamp J, Fellermann K, Herrlinger KR, Baxmann S, Schmidt K, Schwind B, Duchrow M, Wohlschlager C, Feller AC, Stange EF. Human beta-defensin 2 but not beta-defensin 1 is expressed preferentially in colonic mucosa of inflammatory bowel disease. Eur J Gastroenterol Hepatol. 2002;7:745–752. [PubMed]
94. Weinberg A, Krisanaprakornkit S, Dale BA. Epithelial antimicrobial peptides: review and significance for oral applications. Crit Rev Oral Biol Med. 1998;4:399–414. [PubMed]
95. Westerlund U, Ingman T, Lukinmaa PL, Salo T, Kjeldsen L, Borregaard N, Tjaderhane L, Konttinen YT, Sorsa T. Human neutrophil gelatinase and associated lipocalin in adult and localized juvenile periodontitis. J Dent Res. 1996;8:1553–1563. [PubMed]
96. Wu Z, Hoover DM, Yang D, Boulegue C, Santamaria F, Oppenheim JJ, Lubkowski J, Lu W. Engineering disulfide bridges to dissect antimicrobial and chemotactic activities of human beta-defensin 3. Proc Natl Acad Sci U S A. 2003;15:8880–8885. [PubMed]
97. Yang D, Chen Q, Chertov O, Oppenheim JJ. Human neutrophil defensins selectively chemoattract naive T and immature dendritic cells. Journal of Leukocyte Biology. 2000;1:9–14. [PubMed]
98. Yang D, Chertov O, Bykovskaia SN, Chen Q, Buffo MJ, Shogan J, Anderson M, Schroder JM, Wang JM, Howard OM, Oppenheim JJ. Beta-defensins: linking innate and adaptive immunity through dendritic and T cell CCR6. Science. 1999;5439:525–528. [PubMed]
99. Yang D, Chertov O, Oppenheim JJ. Participation of mammalian defensins and cathelicidins in anti-microbial immunity: receptors and activities of human defensins and cathelicidin (LL-37) J Leukoc Biol. 2001;5:691–697. [PubMed]
100. Yu J, Mookherjee N, Wee K, Bowdish DM, Pistolic J, Li Y, Rehaume L, Hancock RE. Host defense peptide LL-37, in synergy with inflammatory mediator IL-1beta, augments immune responses by multiple pathways. J Immunol. 2007;11:7684–7691. [PubMed]
101. Zanetti M. Cathelicidins, multifunctional peptides of the innate immunity. J Leukoc Biol. 2004;1:39–48. [PubMed]
102. Zasloff M. Antimicrobial peptides of multicellular organisms. Nature. 2002;6870:389–395. [PubMed]
103. Zhao C, Wang I, Lehrer RI. Widespread expression of beta-defensin hBD-1 in human secretory glands and epithelial cells. FEBS Lett. 1996;2-3:319–322. [PubMed]
104. Zuyderduyn S, Ninaber DK, Hiemstra PS, Rabe KF. The antimicrobial peptide LL-37 enhances IL-8 release by human airway smooth muscle cells. J Allergy Clin Immunol. 2006;6:1328–1335. [PubMed]