Inducible expression of an antibiotic peptide gene in lipopolysaccharide-challenged tracheal epithelial cells

Mechanisms and regulation of defensins in host defense

As a family of cationic host defense peptides, defensins are mainly synthesized by Paneth cells, neutrophils, and epithelial cells, contributing to host defense. Their biological functions in innate immunity, as well as their structure and activity relationships, along with their mechanisms of action and therapeutic potential, have been of great interest in recent years. To highlight the key research into the role of defensins in human and animal health, we first describe their research history, structural features, evolution, and antimicrobial mechanisms. Next, we cover the role of defensins in immune homeostasis, chemotaxis, mucosal barrier function, gut microbiota regulation, intestinal development and regulation of cell death. Further, we discuss their clinical relevance and therapeutic potential in various diseases, including infectious disease, inflammatory bowel disease, diabetes and obesity, chronic inflammatory lung disease, periodontitis and cancer. Finally, we summarize the current knowledge regarding the nutrient-dependent regulation of defensins, including fatty acids, amino acids, microelements, plant extracts, and probiotics, while considering the clinical application of such regulation. Together, the review summarizes the various biological functions, mechanism of actions and potential clinical significance of defensins, along with the challenges in developing defensins-based therapy, thus providing crucial insights into their biology and potential clinical utility.

Vitamin A- and D-Deficient Diets Disrupt Intestinal Antimicrobial Peptide Defense Involving Wnt and STAT5 Signaling Pathways in Mice

Vitamin A and D deficiencies are associated with immune modulatory effects and intestinal barrier impairment. However, the underlying mechanisms remain unclear. C57BL/6J mice were fed either a diet lacking in vitamin A (VAd), vitamin D (VDd) or a control diet (CD) for 12 weeks. Gut barrier function, antimicrobial peptide (AMP) defense and regulatory pathways were assessed. VAd mice compared to CD mice showed a reduced villus length in the ileum (p < 0.01) and decreased crypt depth in the colon (p < 0.05). In both VAd- and VDd-fed mice, ileal α-defensin 5 (p < 0.05/p < 0.0001 for VAd/VDd) and lysozyme protein levels (p < 0.001/p < 0.0001) were decreased. Moreover, mRNA expression of lysozyme (p < 0.05/p < 0.05) and total cryptdins (p < 0.001/p < 0.01) were reduced compared to controls. Furthermore, matrix metalloproteinase-7 (Mmp7) mRNA (p < 0.0001/p < 0.001) as well as components of the Wnt signaling pathway were decreased. VAd- and VDd-fed mice, compared to control mice, exhibited increased expression of pro-inflammatory markers and β-defensins in the colon. Organoid cell culture confirmed that vitamins A and D regulate AMP expression, likely through the Jak/STAT5 signaling pathway. In conclusion, our data show that vitamin A and D regulate intestinal antimicrobial peptide defense through Wnt and STAT5 signaling pathways.

A Scoping Analysis of Cathelicidin in Response to Organic Dust Exposure and Related Chronic Lung Illnesses

Over two billion people worldwide are exposed to organic dust, which can cause respiratory disorders. The discovery of the cathelicidin peptide provides novel insights into the lung’s response to organic dust; however, its role in the lung’s response to organic dust exposure and chronic lung diseases remains limited. We conducted a scoping review to map the current evidence on the role of cathelicidin LL-37/CRAMP in response to organic dust exposure and related chronic lung diseases: hypersensitivity pneumonitis (HP), chronic obstructive pulmonary disease (COPD) and asthma. We included a total of n = 53 peer-reviewed articles in this review, following the process of (i) a preliminary screening; (ii) a systematic MEDLINE/PubMed database search; (iii) title, abstract and full-text screening; (iv) data extraction and charting. Cathelicidin levels were shown to be altered in all clinical settings investigated; its pleiotropic function was confirmed. It was found that cathelicidin contributes to maintaining homeostasis and participates in lung injury response and repair, in addition to exerting a positive effect against microbial load and infections. In addition, LL-37 was found to sustain continuous inflammation, increase mucus formation and inhibit microorganisms and corticosteroids. In addition, studies investigated cathelicidin as a treatment modality, such as cathelicidin inhalation in experimental HP, which had positive effects. However, the primary focus of the included articles was on LL-37’s antibacterial effect, leading to the conclusion that the beneficial LL-37 activity has not been adequately examined and that further research is required.

Study on the mechanism of Mycoplasma gallisepticum infection on chicken tracheal mucosa injury

ABSTRACTMycoplasma gallisepticum (MG) is a pathogenic microorganism that causes serious harm to the poultry industry. It is mainly adsorbed on the cilia and mucosa of respiratory epithelial cells, causing tracheal mucosal damage or cilia loss, causing chronic respiratory disease (CRD). In order to study the effect of MG infection on chicken tracheal mucosa injury and explore its possible mechanism, specific-pathogen-free (SPF) chickens were challenged with Mycoplasma gallisepticum wild-type strain MG-HY. Then, transcriptome sequencing analysis was performed to study the mechanism of MG tracheal mucosal damage. During infection, MG localizes and proliferates in the chicken trachea, and induces mucosal damage. A total of 3112 significantly (P < 0.01) differentially expressed genes (DEGs) were selected by RNA-seq, including 1646 up-regulated genes and 1466 down-regulated genes. Functional analysis showed increased expression levels of genes involved in immune defense response and mechanical barrier of tracheal mucosa in infected chicks. The expression level of pro-inflammatory cytokines (TNF-α) increased, activating the upstream protein Ras of the ERK-MLCK signaling pathway, Ras causing ERK phosphorylation levels to rise and MLCK activation, thus causing phosphationalization of MLC, and further regulating the expression and mucous distribution of tight junction protein (TJ), leading to tracheal mucosal injury in chicks. The results of qRT-PCR assay and immunohistochemical analysis were consistent with the results of transcriptome analysis. Overall, Our findings provide a basis for further research on the underlying mechanism of chick tracheal mucosal damage caused by MG infection, and help to understand how MG induces respiratory immune damage in birds.

Polyalanine peptide variations may have different mechanisms of action against multidrug-resistant bacterial pathogens

OBJECTIVES

The number of bacterial pathogens resistant to the currently available antibiotics has dramatically increased, with antimicrobial peptides (AMPs) being among the most promising potential new drugs. In this study, the applicability and mechanisms of action of Pa-MAP 2 and Pa-MAP 1.9, two AMPs synthetically designed based on a natural AMP template, were evaluated.

METHODS

Pa-MAP 2 and Pa-MAP 1.9 were tested against a clinically isolated multidrug-resistant (MDR) Escherichia coli strain. Biophysical approaches were used to evaluate the preference of both peptides for specific lipid membranes, and bacterial surface changes imaged by atomic force microscopy (AFM). The efficacy of both peptides was assessed both in vitro and in vivo.

RESULTS

Experimental results showed that both peptides have antimicrobial activity against the E. coli MDR strain. Zeta potential and surface plasmon resonance assays showed that they interact extensively with negatively charged membranes, changing from a random coil structure, when free in solution, to an α-helical structure after membrane interaction. The antibacterial efficacy was evaluated in vitro, by several techniques, and in vivo, using a wound infection model, showing a concentration-dependent antibacterial effect. Different membrane properties were evaluated to understand the mechanism underlying peptide action, showing that both promote destabilization of the bacterial surface, as imaged by AFM, and change properties such as membrane surface and dipole potential.

CONCLUSIONS

Despite their similarity, data indicate that the mechanisms of action of the peptides are different, with Pa-MAP 1.9 being more effective than Pa-MAP 2. These results highlight their potential use as antimicrobial agents against MDR bacteria.

Host Defense Peptides as Templates for Antifungal Drug Development

Current treatment for invasive fungal diseases is limited to three classes of antifungal drugs: azoles, polyenes, and echinocandins. The most recently introduced antifungal class, the echinocandins, was first approved nearly 30 years ago. The limited antifungal drug portfolio is rapidly losing its clinical utility due to the inexorable rise in the incidence of invasive fungal infections and the emergence of multidrug resistant (MDR) fungal pathogens. New antifungal therapeutic agents and novel approaches are desperately needed. Here, we detail attempts to exploit the antifungal and immunoregulatory properties of host defense peptides (HDPs) in the design and evaluation of new antifungal therapeutics and discuss historical limitations and recent advances in this quest.

Bacteria-induced expression of the pig-derived protegrin-1 transgene specifically in the respiratory tract of mice enhances resistance to airway bacterial infection

About 70% of all antibiotics produced in the world are used in the farm animal industry. The massive usage of antibiotics during farm animal production has caused rapid development of antibiotic resistance in bacteria, which poses a serious risk to human and livestock health when treating bacterial infections. Protegrin-1 (PG-1) is a potent antimicrobial peptide (AMP). It was initially identified in pig leukocytes with a broad-spectrum antibacterial and antiviral activity, and a low rate of inducing bacterial resistance. To develop a genetic approach for reducing the use of antibiotics in farm animal production, we produced transgenic mice carrying a bovine tracheal AMP gene promoter-controlled PG-1 transgene. The PG-1 transgene was specifically expressed in the respiratory tract of transgenic mice upon induction by bacterial infection. These PG-1 transgenic mice exhibited enhanced resistance to nasal bacterial infection as the transgenic mice showed a higher survival rate (79.17% VS. 34.78%), lower bacterial load and milder histological severity than their wild-type control littermates. The improved resistance to bacterial infection in the PG-1 transgenic mice could be resulted from the direct bacteria-killing activities of PG-1, and the immunomodulatory effects of PG-1 via stimulating interleukin 1 beta secretion. The present study provides a promising genetic strategy to prevent airway bacterial infections in farm animals by bacteria-inducible tissue-specific expression of PG-1 transgene. This approach may also be helpful for decreasing the possibility of inducing bacterial resistance during farm animal production.

The expression of β-Defensin-2, IL-22, IL-22R1 and IL-10R2 in rat model of Klebsiella pneumonia and their correlation with histological grades

Backgrounds and Aims:Klebsiella pneumoniae represents the most common opportunistic pathogen contributing to Klebsiella pneumonia in hospital-acquired infections. Klebsiella pneumonia has a rapidly progressive clinical course and multi-drug resistant (MDR). Identification of the effective biochemical markers is crucial for improving early diagnosis and treatment of Klebsiella pneumonia. The aims of our study are to 1) investigate the expression of β-Defensin-2(rβD2), IL-22, IL-22R1 and IL-10R2 in Klebsiella pneumonia-infected rats and 2) their association with the histological grades of Klebsiella pneumonia.Methods and Materials: Fifty specific pathogen free (SPF) male SD rats were randomly divided into two groups: control group (treated with normal saline) and pneumonia group (treated with K. pneumoniae). All animals were sacrificed 1 h, 12 h, 1 d, 3 d, 5 d post infection. The severity and property of pneumonia was evaluated by histopathologic observation and pathogen identification. The mRNA expression of rβD2, IL-22, IL-22R1 and IL-10R2 was measured by RT-qPCR assay. The expression of rβD2 in rat lung tissue was determined by Western blot analysis, and the level of IL-22 in rat serum was determined by ELISA.Results: Histopathologic examination and bacterial counting of lung tissues confirmed the successful establishment of rat pneumonia model. The gene expression of rβD2, IL-22, IL-22R1 and IL-10R2 in pneumonia rats were significantly higher than those in healthy control mice (P < 0.05). The expression of rβD2 was correlated with histological grades of Klebsiella pneumonia and the level of IL-22. RT-qPCR results showed that the peak expression of IL-22R1 appeared earlier than IL-10R2 in rat pneumonia model.Conclusions: The expression of rβD2 and IL-22 was increased significantly at early stage in rat Klebsiella pneumonia model, suggesting that IL-22 and rβD2 might serve as potential biomarkers for the early diagnosis of Klebsiella pneumonia.

Expression of Defensin Antimicrobial Peptides in the Peritoneal Cavity of Patients on Peritoneal Dialysis

Objective

To investigate the expression and regulation of defensins in the peritoneal cavity of peritoneal dialysis (PD) patients.

Design

The presence of defensins in the peritoneal cavity was assessed using reverse transcription polymerase chain reaction (RT-PCR). In vivo defensin expression was analyzed in human peritoneal membrane biopsies and in peritoneal cavity leukocytes isolated from spent dialysate. Defensin expression in vitro was assessed in cultured human peritoneal mesothelial cells (HPMC) and confirmed with PCR Southern blot and DNA sequencing. The effect of tumor necrosis factor alpha (TNFa) and epidermal growth factor (EGF) on b2 defensin expression in HPMC was analyzed by Northern blot analysis and RT-PCR respectively.

Results

Both a and b classes of defensins are expressed in the peritoneal cavity of PD patients. Messenger RNA for the a-defensin human neutrophil peptide 3 and for b-defensin-1 (hbD-1) were found in preparations containing predominantly peritoneal leukocytes, whereas b-defensin-2 (hbD-2) is expressed by HPMC. HPMC isolated from different individuals displayed variability in both basal hbD-2 expression and in response to stimulation by TNFa. Conversely, EGF consistently downregulated the level of hbD-2 message in HPMC.

Conclusion

a- and b-defensins are expressed in the peritoneal cavity, and hbD-2 is the main defensin present in the peritoneal membrane. Variable levels of expression of hbD-2 by mesothelial cells were seen, with evidence of regulation by cytokines and growth factors. This provides evidence for a previously unknown mechanism of innate immunity at that site.

Antibacterial spectrum of human omentum and differential expression of beta defensins

BACKGROUND

Human β defensins (hBD1 and hBD2) are cationic, cysteine-rich peptides and form an integral part of the mammalian innate immune system. hBD1 is constitutively expressed in epithelial cells, whereas hBD2 increases in response to bacterial infection. Human omentum is known for its anti-inflammatory properties and also possesses an antibacterial activity of its own. We hypothesized that antimicrobial peptides, β defensins, may govern host defense mechanism in the microbe-rich environment of the peritoneal cavity. Therefore, we analyzed the expression of hBD1 and hBD2 in omentum tissue in vivo and also studied the antibacterial activity of omentum against common pathogens.

METHODOLOGY

Omentum tissues were obtained from 30 patients (15 cases and 15 controls). Real-time polymerase chain reaction (PCR) was used to evaluate the mRNA expression of hBD1 and hBD2. Protein quantification was done using Western blotting technique. Antibacterial susceptibility was performed to check the antibacterial activity of omentum.

RESULT

Significantly higher expression of hBD2 was observed in cases compared to controls at both the transcriptional and translational levels. In comparison with an array of antibiotics, activated omentum also showed antibacterial property even at lower concentration of its extract.

CONCLUSION

Omentum directly responds to bacterial infection, which may be due to differential expression of hBD1 and hBD2 in human omental tissue. These peptides (hBD1 and hBD2) may be an ideal candidate for novel antibiotic class with a broad-spectrum activity.

Comparison of Efficacy of Doxycycline and Isotretinoin on Cutaneous Human Beta-Defensin-1 and -2 Levels in Acne Vulgaris

Background:

Recent studies have shown that human beta-defensin-1 (hBD-1) and (human beta-defensin-2 hBD-2), which are antimicrobial peptides produced by the skin, play a role in the pathogenesis of acne vulgaris (AV).

Objective:

The aim of this study was to determine the role of antimicrobial peptides in the pathogenesis of AV and enlighten the effects of doxycycline and isotretinoin in the expression of these defensins in AV.

Materials and Methods:

A total of 44 patients (22 patients in each group) with Grade 6 and 8 AV who were indicated doxycycline or isotretinoin for their treatment, and 20 healthy volunteers were included in this study. Pretreatment cutaneous samples were obtained from pustular lesions and uninvolved skin of AV patients and were repeated after the treatment. Only one biopsy was obtained from controls.

Results:

Cutaneous levels of hBD-1 and hBD-2 were significantly increased in AV patients when compared with healthy controls (P<0.05). Doxycycline therapy achieved a decrease in hBD-1 levels (P<0.05), whereas isotretinoin therapy achieved a reduction in hBD-2 levels when compared with pretreatment levels (P<0.05). Posttreatment hBD-1 and hBD-2 levels were not different between doxycycline and isotretinoin groups (P>0.05).

Conclusion:

In the light of these results, it was reasonable to assume the role of hBD-1 and hBD-2 in the pathogenesis of AV. Our results showing a significant reduction in hBD-1 staining with doxycycline treatment and in hBD-2 with isotretinoin suggested that some part of their anti-acne effect worked through these mechanisms.

Benzo(a)pyrene suppresses tracheal antimicrobial peptide gene expression in bovine tracheal epithelial cells

Respiratory disease is an important cause of morbidity and mortality in cetaceans, which are also threatened by environmental degradation caused by crude oil spills. Following oil spills, cetaceans at the water surface may inhale droplets of oil containing toxic polycyclic aromatic hydrocarbons (PAHs), which could potentially alter respiratory immunity via activation of the aryl hydrocarbon receptor (AHR) and its subsequent interaction with nuclear factor kappa B (NF-κB). β-defensins are antimicrobial peptides secreted by airway epithelial cells and their expression is known to be dependent on NF-κB. We hypothesized that PAHs may suppress the expression of β-defensins, and thereby contribute to the pathogenesis of pneumonia. This hypothesis was modeled by measuring the in vitro effects of benzo(a)pyrene (BAP), phenanthrene, and naphthalene on tracheal antimicrobial peptide (TAP) gene expression in bovine tracheal epithelial cells. Stimulation with lipopolysaccharide (LPS) induced 20 ± 17-fold (mean ± SD) increased TAP gene expression. Exposure of tracheal epithelial cells to 5 μM BAP for 4 or 8 h, followed by incubation with a combination of LPS and 5 μM BAP for another 16 h, significantly (P = 0.002) suppressed LPS-induced TAP gene expression by 40.6 ± 21.8% (mean ± SD) in tracheal epithelial cells from 9 calves tested. BAP-induced suppression of TAP gene expression coincided with induction of cytochrome P450 1A1 gene expression. In contrast, phenanthrene and naphthalene had no consistent effect, and exposure to PAHs did not significantly affect constitutive TAP gene expression (i.e. without LPS). These findings characterize the suppressive effects of BAP-a toxic pollutant found in crude oil-on this respiratory innate immune response.

Cytotoxic and biological effects of bulk fill composites on rat cortical neuron cells

The aim of this study was to investigate potential cellular responses and biological effects of new generation dental composites on cortical neuron cells in two different exposure times. The study group included five different bulk-fill flow able composites; Surefil SDR Flow, X-tra Base Flow, Venus Bulk Flow, Filtek Bulk Flow and Tetric-Evo Flow. They were filled in Teflon molds (Height: 4 mm, Width: 6 mm) and irradiated for 20 s. Cortical neuron cells were inoculated into 24-well plates. After 80% of the wells were coated, the 3 µm membrane was inserted and dental filling materials were added. The experiment was continued for 24 and 72 h. Cell viability measured by MTT assay test, total antioxidant and total oxidant status were examined using real assay diagnostic kits. The patterns of cell death (apoptosis) were analyzed using annexin V-FITC staining with flow cytometry. Β-defensins were quantitatively assessed by RT-PCR. IL-6, IL-8 and IL-10 cytokines were measured from the supernatants. All composites significantly affected analyses parameters during the exposure durations. Our data provide evidence that all dental materials tested are cytotoxic in acute phase and these effects are induced cellular death after different exposure periods. Significant cytotoxicity was detected in TE, XB, SS, FBF and VBF groups at 24 and 72 h, respectively.

Cyclic stretch induced IL-33 production through HMGB1/TLR-4 signaling pathway in murine respiratory epithelial cells

Interleukin 33 (IL-33), an inflammatory and mechanically responsive cytokine, is an important component of a TLR4-dependent innate immune process in mucosal epithelium. Although TLR4 also plays a role in sensing biomechanical stretch, a pathway of stretch-induced TLR4-dependent IL-33 biosynthesis has not been revealed. In the current study, we show that short term (6 h) cyclic stretch (CS) of cultured murine respiratory epithelial cells (MLE-12) increased intracellular IL-33 expression in a TLR4 dependent fashion. There was no detectable IL-33 in conditioned media in this interval. CS, however, increased release of the notable alarmin, HMGB1, and a neutralizing antibody (2G7) to HMGB1 completely abolished the CS mediated increase in IL-33. rHMGB1 increased IL-33 synthesis and this was partially abrogated by silencing TLR4 suggesting additional receptors for HMGB1 are involved in its regulation of IL-33. Collectively, these data reveal a HMGB1/TLR4/IL-33 pathway in the response of respiratory epithelium to mechanical stretch.

Bacterial modification of LPS and resistance to antimicrobial peptides

Antimicrobial peptides (APs) are ubiquitous in nature and are thought to kill micro-organisms by affecting membrane integrity. These positively charged peptides interact with negative charges in the LPS of Gram-negative bacteria. A common mechanism of resistance to AP killing is LPS modification. These modifications include fatty acid additions, phosphoethanolamine (PEtN) addition to the core and lipid A regions, 4-amino-4-deoxy-L-arabinose (Ara4N) addition to the core and lipid A regions, acetylation of the O-antigen, and possibly hydroxylation of fatty acids. In Salmonella typhimurium, LPS modifications are induced within host tissues by the two-component regulatory systems PhoPQ and PmrAB. PmrAB activation results in AP resistance by Ara4N addition to lipid A through the activation of at least 8 genes, 7 of which are transcribed as an operon. Loss of this operon and, therefore, Ara4N LPS modification, affects S. typhimurium virulence when administered orally. Transposon mutagenesis of Proteus mirabilis also suggests that LPS modifications affect AP resistance and virulence phenotypes. Therefore, LPS modification in Gram-negative bacteria plays a significant role during infection in resistance to host antimicrobial factors, avoidance of immune system recognition, and maintenance of virulence phenotypes.

Anti-endotoxin properties of cationic host defence peptides and proteins

The innate immune system of mammals contains a series of peptides with overall positive charge and an amphipathic structure which have a variety of important properties in host defences. Although these are often termed cationic antimicrobial peptides, they have numerous roles in innate defences in all complex species of life and thus we prefer to refer to them as host defence peptides. These roles include: (i) an ability to kill micro-organisms directly, ranging from bacteria to viruses, fungi, parasites and helminths; (ii) an adjuvant activity in the adaptive response; and (iii) a multiplicity of roles in modulating innate immunity, including an apparent ability to stimulate protective innate immunity while suppressing harmful inflammatory/septic responses. This latter property may be one of the more important activities of these peptides in vivo. Innate immunity is thought to be triggered by the interaction of conserved bacterial components with particular receptors including Toll-like receptors (TLRs) on host cells. However, the initiation of the innate immune response through this route may trigger a pro-inflammatory cascade that is the principle cause of harmful conditions such as sepsis. Since we are exposed to potentially dangerous pathogens on a daily basis, the host response must contain certain checks and balances. We propose that host defence peptides have a role in feed-back modulation of inflammation under normal (low-pathogen exposure) conditions. This review surveys the available information regarding the antiendotoxic/anti-inflammatory properties of host defence peptides, and will address whether this potential might be exploited for therapeutic benefit in sepsis.

Fecal Human β-Defensin 2 in Children with Cystic Fibrosis: Is There a Diminished Intestinal Innate Immune Response?

BACKGROUND

Defects in bacterial host defenses in the cystic fibrosis (CF) airways have been extensively investigated, but the role of the intestinal innate immune system in CF is unknown. Human β-defensin 2 (HBD-2) is an antimicrobial protein produced by epithelial surfaces and upregulated by inflammation. Its expression in the CF intestine is unknown.

AIM

To determine whether HBD-2 was present in the feces of patients with CF, and to compare fecal HBD-2 levels between CF and healthy controls (HC). To compare fecal HBD-2 levels in inflamed and noninflamed states, as measured by fecal calprotectin, as a secondary aim.

METHODS

Feces from children with CF and HC were collected for analysis.

RESULTS

Thirty-three CF patients and 33 HC were recruited. All CF patients had detectable fecal HBD-2. There was no difference between fecal HBD-2 in CF and HC (median (IQR) 49.1 (19.7-77.2) versus 43.4 (26.5-71.9) ng/g; P = 0.7). Fecal calprotectin was significantly higher in the CF cohort than in HC (median (IQR) 61.3 (43.8-143.8) versus 19.5 (19.5-35.1) mg/kg; P < 0.0001). There was no difference in fecal HBD-2 levels between CF subjects with fecal calprotectin ≥50 mg/kg and <50 mg/kg (50.5 (19.6-80.2) versus 43.0 (19.0-70.4); P = 0.7). There was no correlation between fecal HBD-2 and calprotectin in CF (r = 0.14; P = 0.4).

CONCLUSION

Fecal HBD-2 levels were not increased in children with CF, in inflamed or noninflamed states. The lack of HBD-2 induction and upregulation under inflammatory conditions may suggest a diminished intestinal innate immune response in CF.

Antimicrobial peptide resistance in Neisseria meningitidis

Antimicrobial peptides (AMPs) play an important role as a host defense against microbial pathogens and are key components of the human innate immune response. Neisseria meningitidis frequently colonizes the human nasopharynx as a commensal but also is a worldwide cause of epidemic meningitis and rapidly fatal sepsis. In the human respiratory tract, the only known reservoir of N. meningitidis, meningococci are exposed to human endogenous AMPs. Thus, it is not surprising that meningococci have evolved effective mechanisms to confer intrinsic and high levels of resistance to the action of AMPs. This article reviews the current knowledge about AMP resistance mechanisms employed by N. meningitidis. Two major resistance mechanisms employed by meningococci are the constitutive modification of the lipid A head groups of lipooligosaccharides by phosphoethanolamine and the active efflux pump mediated excretion of AMPs. Other factors influencing AMP resistance, such as the major porin PorB, the pilin biogenesis apparatus, and capsular polysaccharides, have also been identified. Even with an inherently high intrinsic resistance, several AMP resistance determinants can be further induced upon exposure to AMPs. Many well-characterized AMP resistance mechanisms in other Gram-negative bacteria are not found in meningococci. Thus, N. meningitidis utilizes a limited but highly effective set of molecular mechanisms to mediate antimicrobial peptide resistance. This article is part of a Special Issue entitled: Bacterial Resistance to Antimicrobial Peptides.

Cathelicidin related antimicrobial peptide, laminin, Toll-like receptors and chemokines levels in experimental hypersensitivity pneumonitis in mice

INTRODUCTION

Hypersensitivity pneumonitis (HP) is an interstitial lung disease caused by unresolved inflammation and tissue repair pathologies triggered by repeated organic dust exposure. The aim of the study was to investigate changes in levels of the cathelicidin related antimicrobial peptide (CRAMP), laminin (LAM-A1), selected Toll-like receptors (TLR) and chemokines in experimental HP in mice.

MATERIALS AND METHODS

Three and 18-month-old female C57BL/6J mice underwent inhalations of the saline extract of Pantoea agglomerans cells, Gram-negative bacterium common in organic dust and known for its pathogenic impact. The inhalations were repeated daily (28 days). ELISA was used for measuring in lung tissue homogenates concentration of CRAMP, LAM-A1, TLR2, TLR4, TLR8, CXCL9 (chemokine [C-X-C motif] ligand) and CXCL10.

RESULTS

Levels of TLR2, TLR4 and CXCL9 were significantly higher in both young and old mice lungs already after 7 days of inhalations, while significant increase of LAM-A1 and CXCL10 was noted after 28 days, compared to untreated samples. TLR8 level was significantly augmented only in young mice. Only CRAMP level significantly declined. Significantly higher TLR8 and CXCL9 concentration in untreated samples were noted in old animals compared to young ones.

CONCLUSION

Significant alterations of the examined factors levels indicate their role in HP pathogenesis.

An evolutionary history of defensins: a role for copy number variation in maximizing host innate and adaptive immune responses

Defensins represent an evolutionary ancient family of antimicrobial peptides that play diverse roles in human health and disease. Defensins are cationic cysteine-containing multifunctional peptides predominantly expressed by epithelial cells or neutrophils. Defensins play a key role in host innate immune responses to infection and, in addition to their classically described role as antimicrobial peptides, have also been implicated in immune modulation, fertility, development, and wound healing. Aberrant expression of defensins is important in a number of inflammatory diseases as well as modulating host immune responses to bacteria, unicellular pathogens, and viruses. In parallel with their role in immunity, in other species, defensins have evolved alternative functions, including the control of coat color in dogs. Defensin genes reside in complex genomic regions that are prone to structural variations and some defensin family members exhibit copy number variation (CNV). Structural variations have mediated, and continue to influence, the diversification and expression of defensin family members. This review highlights the work currently being done to better understand the genomic architecture of the β-defensin locus. It evaluates current evidence linking defensin CNV to autoimmune disease (i.e., Crohn’s disease and psoriasis) as well as the contribution CNV has in influencing immune responses to HIV infection.

CC Chemokine Ligand 20 and Its Cognate Receptor CCR6 in Mucosal T Cell Immunology and Inflammatory Bowel Disease: Odd Couple or Axis of Evil?

Chemokines and their cognate receptors have been identified as major factors initiating and governing cell movement and interaction. These ligands and their receptors are expressed on a wide variety of cells and act during steady-state migration as well as inflammatory recruitment. CCR6 is a non-promiscuous chemokine receptor that has only one known chemokine ligand, CCL20, and is present on B and T cells as well as dendritic cells (DCs). Two CD4⁺ T cell populations with opposing functions present in the intestines and the mesenteric lymph nodes express CCR6: the pro-inflammatory T_H17 and regulatory T_reg cells. CCL20 is also present in the intestine and is strongly up-regulated after an inflammatory stimulus. Interestingly, this ligand is also expressed by T_H17 cells, which opens up the possibility of autocrine/paracrine signaling and, consequently, a self-perpetuating cycle of recruitment, thereby promoting inflammation. Recently, CCR6 has been implicated in inflammatory bowel disease (IBD) by genome wide association studies which showed an association between SNPs in the genomic region of the CCR6 gene and the inflammation. Furthermore, recent research targeting the biological function of CCR6 indicates a significant role for this chemokine receptor in the development of chronic IBD. It is therefore possible that IBD is facilitated by a disordered regulation of T_H17 and T_reg cells due to a disruption in the CCL20-CCR6 axis and consequently disturbed mucosal homeostasis. This review will summarize the literature on CCL20-CCR6 in mucosal immunology and will analyze the role this receptor-ligand axis has in chronic IBD.

Biotic stress resistance in agriculture through antimicrobial peptides

Antimicrobial peptides (AMPs) are the hosts' defense molecules against microbial pathogens and gaining extensive research attention worldwide. These have been reported to play vital role of host innate immunity in response to microbial challenges. AMPs can be used as a natural antibiotic as an alternative of their chemical counterpart for protection of plants/animals against diseases. There are a number of sources of AMPs including prokaryotic and eukaryotic organisms and are present, both in vertebrates and invertebrates. AMPs can be classified as cationic or anionic, based on net charges. Large number of databases and tools are available in the public domain which can be used for development of new genetically modified disease resistant varieties/breeds for agricultural production. The results of the biotechnological research as well as genetic engineering related to AMPs have shown high potential for reduction of economic losses of agricultural produce due to pathogens. In this article, an attempt has been made to introduce the role of AMPs in relation to plants and animals. Their functional and structural characteristics have been described in terms of its role in agriculture. Different sources of AMPs and importance of these sources has been reviewed in terms of its availability. This article also reviews the bioinformatics resources including different database tools and algorithms available in public domain. References of promising biotechnology research in relation to AMPs, prospects of AMPs for further development of genetically modified varieties/breeds are highlighted. AMPs are valuable resource for students, researchers, educators and medical and industrial personnel.

The antimicrobial peptide pheromone Plantaricin A increases antioxidant defenses of human keratinocytes and modulates the expression of filaggrin, involucrin, β-defensin 2 and tumor necrosis factor-α genes

Plantaricin A (PlnA) is a peptide with antimicrobial and pheromone activities. PlnA was synthesized chemically and used as a pure peptide or synthesized biologically using Lactobacillus plantarum DC400 co-cultured with Lactobacillus sanfranciscensis DPPMA174. Cell-free supernatant (CFS) was used as a crude PlnA preparation. As estimated using the 3-(4,5-dimethyl-2-yl)-2,5-diphenyltetrazolium bromide and the 2',7'-dichlorofluorescein diacetate assays, both PlnA preparations increased the antioxidant defenses of human NCTC 2544 keratinocytes. PlnA (10 μg/ml) had a higher activity than hyaluronic acid or 125 μg/ml α-tocopherol. Effects on the transcriptional regulation of filaggrin (FLG), involucrin (IVL), hyaluronan synthase (HAS2), human β-defensin-2 (HBD-2) and tumor necrosis factor-alpha (TNF-α) genes were assayed. Compared with the control, expression of the FLG gene in NCTC 2544 cells increased in cells treated with hyaluronic acid, 1 or 10 μg/ml PlnA. Compared with the control, the level of IVL gene expression increased in NCTC 2544 cells treated with 10 μg/ml PlnA. No significant difference was found between the level of the HAS2 gene expressed by control cells and cells treated with PlnA. Compared with chemically synthesized PlnA, the up-regulation of the HBD-2 gene by CFS was higher. Compared with the control, expression of TNF-α decreased in NCTC 2544 cells after treatment with 1 or 10 μg/ml of chemically synthesized PlnA. In contrast, the level of TNF-α was highest in the presence of 10 μg/ml CFS-PlnA. These findings suggest that the PlnA was positively sensed by human keratinocytes, promoting antioxidant defenses, barrier functions and antimicrobial activity of the skin.

Molecular Characterization and SNP Detection of CD14 Gene of Crossbred Cattle

CD14 is an important molecule for innate immunity that can act against a wide range of pathogens. The present paper has characterized CD14 gene of crossbred (CB) cattle (Bos indicus×Bos taurus). Cloning and sequence analysis of CD14 cDNA revealed 1119 nucleotide long open reading frame encoding 373 amino acids protein and 20 amino acids signal peptide. CB cattle CD14 gene exhibited a high percentage of nucleotide identity (59.3–98.1%) with the corresponding mammalian homologs. Cattle and buffalo appear to have diverged from a common ancestor in phylogenetic analysis. 25 SNPs with 17 amino acid changes were newly reported and the site for mutational hot-spot was detected in CB cattle CD14 gene. Non-synonymous substitutions exceeding synonymous substitutions indicate the evolution of this protein through positive selection among domestic animals. Predicted protein structures obtained from deduced amino acid sequence indicated CB cattle CD14 molecule to be a receptor with horse shoe-shaped structure. The sites for LPS binding, LPS signalling, leucine-rich repeats, putative N-linked glycosylation, O-linked glycosylation, glycosyl phosphatidyl inositol anchor, disulphide bridges, alpha helix, beta strand, leucine rich nuclear export signal, leucine zipper and domain linker were predicted. Most of leucine and cysteine residues remain conserved across the species.

The synthetic peptides bovine enteric β-defensin (EBD), bovine neutrophil β-defensin (BNBD) 9 and BNBD 3 are chemotactic for immature bovine dendritic cells

Human and murine immature DCs (iDCs) are highly efficient in antigen capture and processing, while as mature cells they present antigen and are potent initiators of cell-mediated immune responses. Consequently, iDCs are logical targets for vaccine antigens. Originally discovered for their antimicrobial activity, and thought of as strictly part of the innate immune system, studies with defensins such as human β (beta)-defensin 2 (hBD2) and murine β-defensin 2 (mBD2) have shown that they can function as chemo-attractant for iDCs and, in vaccination strategies, can enhance antigen-specific adaptive immune responses. Most studies to date have been conducted in mice. In contrast, little is known about defensins in cattle. To expand our understanding of the role of defensins in modulating immune responses in cattle, DCs were generated from bovine monocytes and the immature state of these bovine DCs was characterized phenotypically and through functional assays. By day 3 (DC3), bovine monocyte-derived DCs stained positively for DC-specific receptors CD1, CD80/86, CD205, DC-Lamp and MMR. When compared to conventional 6-day DC cultures or DCs cultured for 10 days with and without maturation factors, these DC3 were functionally at their most immature stage. Fourteen of the 16 known bovine β-defensins were synthesized and the synthetic peptides were screened for their ability to attract bovine iDCs. Bovine DC3 were consistently attracted to BNBD3, an analog of BNBD3 (aBNBD3), BNBD9 and bovine EBD in vitro and to aBNBD3 in vivo. These results are the first to describe chemotactic ability of synthetic bovine β-defensins for immature bovine monocyte-derived DCs.

L-isoleucine-supplemented oral rehydration solution in the treatment of acute diarrhoea in children: a randomized controlled trial

Antimicrobial peptides represent an important component of the innate immune defenses of living organisms, including humans. They are broad-spectrum surface-acting agents secreted by the epithelial cells of the body in response to infection. Recently, L-isoleucine and its analogues have been found to induce antimicrobial peptides. The objectives of the study were to examine if addition of L-isoleucine to oral rehydration salts (ORS) solution would reduce stool output and/or duration of acute diarrhoea in children and induce antimicrobial peptides in intestine. This double-blind randomized controlled trial was conducted at the Dhaka Hospital of ICDDR,B. Fifty male children, aged 6-36 months, with acute diarrhoea and some dehydration, attending the hospital, were included in the study. Twenty-five children received L-isoleucine (2 g/L)-added ORS (study), and 25 received ORS without L-isoleucine (control). Stool weight, ORS intake, and duration of diarrhoea were the primary outcomes. There was a trend in reduction in mean +/- standard deviation (SD) daily stool output (g) of children in the L-isoleucine group from day 2 but it was significant on day 3 (388 +/- 261 vs. 653 +/- 446; the difference between mean [95% confidence interval (CI) (-)265 (-509, -20); p = 0.035]. Although the cumulative stool output from day 1 to day 3 reduced by 26% in the isoleucine group, it was not significant. Also, there was a trend in reduction in the mean +/- SD intake of ORS solution (mL) in the L-isoleucine group but it was significant only on day 1 (410 +/- 169 vs. 564 +/- 301), the difference between mean (95% CI) (-)154 (-288, -18); p = 0.04. The duration (hours) of diarrhoea was similar in both the groups. A gradual increase in stool concentrations of beta-defensin 2 and 3 was noted but they were not significantly different between the groups. L-isoleucine-supplemented ORS might be beneficial in reducing stool output and ORS intake in children with acute watery diarrhoea. A further study is warranted to substantiate the therapeutic effect of L-isoleucine.

Innate immunity in the respiratory epithelium

The airway epithelium represents the first point of contact for inhaled foreign organisms. The protective arsenal of the airway epithelium is provided in the form of physical barriers and a vast array of receptors and antimicrobial compounds that constitute the innate immune system. Many of the known innate immune receptors, including the Toll-like receptors and nucleotide oligomerization domain-like receptors, are expressed by the airway epithelium, which leads to the production of proinflammatory cytokines and chemokines that affect microorganisms directly and recruit immune cells, such as neutrophils and T cells, to the site of infection. The airway epithelium also produces a number of resident antimicrobial proteins, such as lysozyme, lactoferrin, and mucins, as well as a swathe of cationic proteins. Dysregulation of the airway epithelial innate immune system is associated with a number of medical conditions that can result in compromised immunity and chronic inflammation of the lung. This review focuses on the innate immune capabilities of the airway epithelium and its role in protecting the lung from infection as well as the outcomes when its function is compromised.

Structural studies of a peptide with immune modulating and direct antimicrobial activity

The structure and function of the synthetic innate defense regulator peptide 1018 was investigated. This 12 residue synthetic peptide derived by substantial modification of the bovine cathelicidin bactenecin has enhanced innate immune regulatory and moderate direct antibacterial activities. The solution state NMR structure of 1018 in zwitterionic dodecyl phosphocholine (DPC) micelles indicated an α-helical conformation, while secondary structures, based on circular dichroism measurements, in anionic sodium dodecyl sulfate (SDS) and phospholipid vesicles (POPC/PG in a 1:1 molar ratio) and simulations revealed that 1018 can adopt a variety of folds, tailored to its different functions. The structural data are discussed in light of the ability of 1018 to potently induce chemokine responses, suppress the LPS-induced TNF-α response, and directly kill both Gram-positive and Gram-negative bacteria.

Interplay of protease-activated receptors and NOD pattern recognition receptors in epithelial innate immune responses to bacteria

Protease-activated receptors (PARs), nucleotide-binding oligomerization domain (NOD) receptors and Toll-like receptors (TLRs) play a role in innate immunity, but little is known about interaction between these receptors. The goal of this study was to investigate how silencing one receptor affects the expression of other receptors and downstream innate immune markers in response to bacteria. Human gingival epithelial cells (GECs) were transfected with siRNA specific for PAR1 or PAR2, then stimulated with periopathogen Porphyromonas gingivalis, bridging organism between pathogens and non-pathogens Fusobacterium nucleatum, or non-pathogen Streptococcus gordonii. PAR1 or PAR2 knock-down resulted in up-regulated NOD1 and NOD2 expression with P. gingivalis or F. nucleatum stimulation (p<0.01), as well as enhanced TLR2 and TLR4 expression when cells were stimulated by bacteria that utilize TLR2 or TLR4, respectively. Involvement of PARs for induction of CC chemokine ligand 20 (CCL20), a cytokine with antimicrobial properties, was observed following stimulation of the three bacterial species. Furthermore, results from multiple cytokine ELISA array showed receptors utilized in the induction of various innate immune markers are tailored to individual bacterium tested. Our data suggest complex interplay of several receptors is required for appropriate innate immune responses to the different types of bacteria present within the oral cavity and that receptor expression itself is altered depending on which organism the cell encounters.

Inducible innate resistance of lung epithelium to infection

Most studies of innate immunity have focused on leukocytes such as neutrophils, macrophages, and natural killer cells. However, epithelial cells play key roles in innate defenses that include providing a mechanical barrier to microbial entry, signaling to leukocytes, and directly killing pathogens. Importantly, all these defenses are highly inducible in response to the sensing of microbial and host products. In healthy lungs, the level of innate immune epithelial function is low at baseline. This is indicated by low levels of spontaneous microbial killing and cytokine release, reflecting low constitutive stimulation in the nearly sterile lower respiratory tract when mucociliary clearance mechanisms are functioning effectively. This contrasts with the colon, where bacteria are continuously present and epithelial cells are constitutively activated. Although the surface area of the lungs presents a large target for microbial invasion, activated lung epithelial cells that are closely apposed to deposited pathogens are ideally positioned for microbial killing.

Measuring antimicrobial peptide activity on epithelial surfaces in cell culture

To more accurately assess the activity and role of epithelial cell-derived antimicrobial peptides in their native settings, it is essential to perform assays at the surfaces under relevant conditions. In order to carry this out, we utilize three-dimensional cultures of airway and gingival epithelium, which are grown at an air-liquid interface. Under these conditions, the cultures can be subjected to challenge with a variety of factors known to cause an increase in antimicrobial peptide gene expression. The functional relevance of this induction can then be assessed by quantifying antibacterial activity either directly on the surface of the cells or using the fluid secreted onto the apical surface of the cultures. The relative contribution of the peptides can also be measured by pre-incubation of the secreted fluid with specific inhibitory antibodies. Thus, a relatively inexpensive in vitro model can be used to evaluate the role of antimicrobial peptides in mucosal epithelium.

Molecular analysis and recombinant expression of bovine neutrophil β-defensin 12 and its antimicrobial activity

To analyze molecular characteristics and antimicrobial activity of bovine neutrophil β-defensin 12 (BNBD12), Pro-BNBD12 gene was amplified from Chinese Holstein cow using reverse transcription polymerase chain reaction. Based on the sequence of mature BNBD12 and codon preference in E. coli, a modified mature BNBD12 cDNA was synthesized, cloned into pET32a (+) vector and expressed in E. coli BL21 as a 26 kD fusion protein after isopropyl β-D-1-thiogalactopyranoside induction. The expressed mature BNBD12 accounted for 21.4% of total protein. 0.05 mg/ml purified BNBD12 had antimicrobial activity against both E. coli and S. aureus in vitro assayed by agar diffusion method. Electron microscopy found that BNBD12 treatment of E. coli and S. aureus could induce cell content leakage. Taking together, BNBD12 protein was successfully expressed in E. coli and it has antimicrobial activity against both Gram-positive and negative bacteria and potentials in control of mastitis clinically.

Lipopolysaccharide (LPS) increases the invasive ability of pancreatic cancer cells through the TLR4/MyD88 signaling pathway

BACKGROUND

Inflammation plays a multifaceted role in cancer progression, and NF-kappaB is one of the key factors connecting inflammation with cancer progression. We have shown that lipopolysaccharide (LPS) promotes NF-kappaB activation in colon cancer cells and pancreatic cancer cells. However, it is unclear why inflammatory stimuli can induce NF-kappaB activation in cancer cells.

METHODS

We used two human pancreatic cancer cells, Panc-1 and AsPC-1, as target cells. LPS was used as an inflammatory stimulus. To confirm the participation of TLR4/NF-kappaB signaling pathway, we used three different NF-kappaB inhibitors (PDTC, IkappaBalpha mutant, and NF-kappaB decoy ODN) and siRNAs (against TLR4, MyD88, and MMP-9). Effect of LPS on pancreatic cancer cell invasive ability was determined by Matrigel invasion assay.

RESULTS

LPS increased the invasive ability of pancreatic cancer cells, while blockade of NF-kappaB pathway decreased the LPS-dependent increased invasive ability. Blockade of TLR4 or MyD88 by siRNA also decreased the LPS-dependent increased invasive ability.

CONCLUSION

These results suggest that TLR/MyD88/NF-kappaB signaling pathway plays a significant role in connecting inflammation and cancer invasion and progression.

Human defensins and LL-37 in mucosal immunity

Defensins are widespread in nature and have activity against a broad range of pathogens. Defensins have direct antimicrobial effects and also modulate innate and adaptive immune responses. We consider the role of human defensins and the cathelicidin LL-37 in defense of respiratory, gastrointestinal, and genitourinary tracts and the oral cavity, skin, and eye. Human beta-defensins (hBDs) and human defensins 5 and 6 (HD5 and -6) are involved most obviously in mucosal responses, as they are produced principally by epithelial cells. Human alpha-defensins 1-4 (or HNPs 1-4) are produced principally by neutrophils recruited to the mucosa. Understanding the biology of defensins and LL-37 is the beginning to clarify the pathophysiology of mucosal inflammatory and infectious diseases (e.g., Crohn's disease, atopic dermatitis, lung or urinary infections). Challenges for these studies are the redundancy of innate defense mechanisms and the presence and interactions of many innate defense proteins in mucosal secretions.

Peptide-based Antifungal Therapies against Emerging Infections

Acquired drug resistance to mycotic infections is rapidly emerging as a major medical problem. Opportunistic fungal infections create therapeutic challenges, particularly in high risk immunocompromised patients with AIDS, cancer, and those undergoing transplantation. Higher mortality and/or morbidity rates due to invasive mycosis have been increasing over the last 20 years, and in light of growing resistance to commonly used antibiotics, novel antifungal drugs and approaches are required. Currently there is considerable interest in antifungal peptides that are ubiquitous in plant and animal kingdoms. These small cationic peptides may have specific targets or may be multifunctional in their mechanism of action. On the basis of recent advances in protein engineering and solid phase syntheses, the utility and potential of selected peptides as efficient antifungal drugs with acceptable toxicity profiles are being realized. This review will discuss recent advances in peptide therapy for opportunistic fungal infections.

Differential antimicrobial peptide gene expression patterns during early chicken embryological development

The adaptive immune system is not completely developed when chickens hatch, so the innate immune system has evolved a range of mechanisms to deal with early pathogenic assault. Avian beta-defensins (AvBDs) and cathelicidins (CTHLs) are two major sub-classes of antimicrobial peptides (AMPs) with a fundamental role in both innate and adaptive immune responses. In this study, we demonstrate distinct expression patterns of innate immune genes including - Toll-like receptors (TLRs) (TLR2, TLR15 and TLR21, but not TLR4), the complete repertoire of AvBDs, CTHLs and both pro- and anti-inflammatory cytokines (IL1B, IL8, IFNG and IL10) during early chicken embryonic development. AvBD9 was significantly increased by over 150 fold at day 9; and AvBD10 was increased by over 100 fold at day 12 in the abdomen of the embryo, relative to day 3 expression levels (P<0.01). In contrast, AvBD14 was preferentially expressed in the head of the embryo. This is the first study to demonstrate differential patterns of AMP gene expression in the sterile environment of the developing embryo. Our results propose novel roles for AMPs during development and reveal the innate preparedness of developing embryos for pathogenic assault in ovo, or post-hatching.

Host defense peptides in the oral cavity and the lung: similarities and differences

Peptides with broad-spectrum antimicrobial activity are found in the mucosal surfaces at many sites in the body, including the airway, the oral cavity, and the digestive tract. Based on their in vitro antimicrobial and other immunomodulatory activities, these host defense peptides have been proposed to play an important role in the innate defense against pathogenic microbial colonization. The genes that encode these peptides are up-regulated by pathogens, further supporting their role in innate immune defense. However, the differences in the local microbial environments between the generally sterile airway and the highly colonized oral cavity suggest a more complex role for these peptides in innate immunity. For example, beta-defensin genes are induced in the airway by all bacteria and Toll-like receptor (TLR) agonists primarily through an NF-kappaB-mediated pathway. In contrast, the same genes are induced in the gingival epithelium by only a subset of bacteria and TLR ligands, via different pathways. Furthermore, the environments into which the peptides are secreted--specifically saliva, gingival crevicular fluid, and airway surface fluid--differ greatly and can effect their respective activities in host defense. In this review, we examine the differences and similarities between host defense peptides in the oral cavity and the airway, to gain a better understanding of their contributions to immunity.

Host defense peptides in wound healing

Host defense peptides are effector molecules of the innate immune system. They show broad antimicrobial action against gram-positive and -negative bacteria, and they likely play a key role in activating and mediating the innate as well as adaptive immune response in infection and inflammation. These features make them of high interest for wound healing research. Non-healing and infected wounds are a major problem in patient care and health care spending. Increasing infection rates, growing bacterial resistance to common antibiotics, and the lack of effective therapeutic options for the treatment of problematic wounds emphasize the need for new approaches in therapy and pathophysiologic understanding. This review focuses on the current knowledge of host defense peptides affecting wound healing and infection. We discuss the current data and highlight the potential future developments in this field of research.

Differential utilization of nuclear factor-kappaB signaling pathways for gingival epithelial cell responses to oral commensal and pathogenic bacteria

INTRODUCTION

Human beta-defensin-2 (hBD-2) is an antimicrobial peptide, induced by bacterial stimuli and inflammation, that plays a role in mucosal and skin innate immune defense. The nuclear factor-kappaB (NF-kappaB) transcription factor family is important in innate and adaptive immune responses to bacteria and proinflammatory cytokines. NF-kappaB operates via the traditional IKKbeta signaling, as well as an alternative pathway utilizing IKKalpha signaling, which is important in keratinocyte differentiation. Our previous studies showed that pathogenic, but not commensal, bacteria used NF-kappaB signaling in hBD-2 induction. The objective of this study was to understand which arm of the NF-kappaB pathway is involved in gingival epithelial cell responses to pathogenic bacteria, including hBD-2 induction.

METHODS

Cultured oral epithelial cells were transfected with synthetic small interfering RNAs (siRNAs) specific for various steps in each pathway, namely IKKbeta, TRAF6 and MyD88 in the canonical, and IKKalpha and TRAF3 in the alternative pathway, and subsequently stimulated with various oral bacteria.

RESULTS

The hBD-2 induction level was reduced to 21-61% in cells in which the alternative NF-kappaB pathway was blocked and subsequently stimulated with pathogenic bacteria, while cells in which the canonical pathway was blocked showed reduction to 78-99%. Cells stimulated with commensals showed little change in hBD-2 induction level regardless of the siRNA used. Microarray analysis showed that oral epithelia differentially regulated numerous innate immune markers in response to pathogens and commensals.

CONCLUSION

Our data suggest a role for the IKKalpha/TRAF3 pathway in NF-kappaB activation by pathogenic bacteria, while commensal bacteria do not utilize either NF-kappaB pathway, for hBD-2 induction.

Psoriasin (S100A7) is a principal antimicrobial peptide of the human tongue

The human tongue is particularly resistant to bacterial infections although the mouth is continuously exposed to a complex and abundant ensemble of microbes, such as the common intestinal bacterium Escherichia coli. We show that lingual epithelia produce and release, as a primary E. coli-killing compound, the S100 protein psoriasin. No significant reduction in psoriasin release could be achieved through repeated rinsing of the epithelial surface of the tongue. Psoriasin is produced in the upper layers of the lingual epithelia but is lacking in the most superficial and basal cells. It displays a gradient pattern of expression with decreasing expression from the anterior one-third to the posterior portion of the tongue. Thus, psoriasin may be the key to the resistance of the human tongue toward E. coli.