Production of beta-defensins by human airway epithelia

T2R38 taste receptor polymorphisms underlie susceptibility to upper respiratory infection

Innate and adaptive defense mechanisms protect the respiratory system from attack by microbes. Here, we present evidence that the bitter taste receptor T2R38 regulates the mucosal innate defense of the human upper airway. Utilizing immunofluorescent and live cell imaging techniques in polarized primary human sinonasal cells, we demonstrate that T2R38 is expressed in human upper respiratory epithelium and is activated in response to acyl-homoserine lactone quorum-sensing molecules secreted by Pseudomonas aeruginosa and other gram-negative bacteria. Receptor activation regulates calcium-dependent NO production, resulting in stimulation of mucociliary clearance and direct antibacterial effects. Moreover, common polymorphisms of the TAS2R38 gene were linked to significant differences in the ability of upper respiratory cells to clear and kill bacteria. Lastly, TAS2R38 genotype correlated with human sinonasal gram-negative bacterial infection. These data suggest that T2R38 is an upper airway sentinel in innate defense and that genetic variation contributes to individual differences in susceptibility to respiratory infection.

The Helicobacter pylori virulence effector CagA abrogates human β-defensin 3 expression via inactivation of EGFR signaling

Antimicrobial peptides are constituents of the first-line innate mucosal defense system that acts as a barrier to establishment of infection. The highly successful human gastric pathogen, Helicobacter pylori, is able to persistently colonize its host despite inducing expression of several antimicrobial peptides, including human β-defensin 3 (hBD3). We find that hBD3 is highly active against H. pylori in vitro and is rapidly induced during early infection via EGFR-dependent activation of MAP kinase and JAK/STAT signaling. However, during prolonged infection, hBD3 was subsequently downregulated by the H. pylori virulence determinant CagA. Upon translocation into host cells, CagA activated the cellular tyrosine phosphatase, SHP-2, terminating EGFR activation and downstream signaling and increasing bacterial viability. Chemical inhibition and knockdown of SHP-2 expression rescued hBD3 synthesis and bactericidal activity. Thus, we reveal how cagPAI-positive H. pylori strains use CagA to evade a key innate mucosal defense pathway to support the establishment of persistent infection.

Clinical application of human β-defensin and CD14 gene polymorphism in evaluating the status of chronic inflammation

Background

Periodontitis is a common disease that affects the periodontal tissue supporting the teeth. This disease is attributed to multiple risk factors, including diabetes, cigarette smoking, alcohol, pathogenic microorganisms, genetics and others. Human beta-defensin-1 (hBD-1) is a cationic antimicrobial peptide with cysteine-rich ß-sheets and broad-spectrum antimicrobial activity. CD14 is a protein involved in the detection of bacterial lipopolysaccharide (LPS) and has also been associated with periodontitis. This study investigates the single nucleotide polymorphic (SNP) region, -1654(V38I), of the human beta-defensin-1 (hBD-1) gene as well as the -159 region of the CD14 gene in subjects with chronic periodontitis.

Methods

Blood samples from periodontally healthy subjects and periodontitis patients were obtained. DNA was extracted from the blood and was used to perform restriction digest at the polymorphic G1654A site of DEFB1 with the enzyme HincII. The polymorphic site 159TT of CD14 was digested with the enzyme AvaII. Enzyme-linked immunosorbent assay (ELISA) was performed on soluble samples to determine the protein expressions.

Results

The control and patient groups expressed 35% and 38% 1654 A/A genotype of DEFB1, respectively. The A allele frequency of the control group was 40%, while the patient blood group was 54%. The mean hBD-1 protein levels of the control and patient samples were 102.83 pg/mL and 252.09 pg/mL, respectively. The genotype distribution of CD14 in healthy subjects was 16% for C/C, 26% for T/T and 58% for C/T. The genotype frequencies of CD14 in periodontitis patients were 10% for C/C, 43% for T/T and 47% for C/T. The CD14 protein expression determined by ELISA showed a mean protein level of the control samples at 76.28ng/mL and the patient blood samples at 179.27ng/mL with a p value of 0.001.

Our study demonstrated that patients suffering from chronic periodontitis present more commonly with the 1654A/A genotype on the DEFB1 gene and the 159T/T genotype on the CD14 gene.

Conclusions

This study purely investigated the association between periodontitis and one polymorphic site on both DEFB1 and CD14 gene, with the purpose of expanding knowledge for the future development in diagnostic markers or therapeutic interventions to combat this disease.

Effect of human defensins on lactobacilli and liposomes

AIMS

To study the effect of human β-defensins (HBD-1 and HBD-2) on lactobacilli membranes as well as on liposomes prepared from purified bacterial lipids.

METHODS AND RESULTS

Lactobacillus delbrueckii subsp. bulgaricus CIDCA 331 and Lact. delbrueckii subsp. lactis CIDCA 133 were grown in Man, Rogosa, Sharpe broth for 16 h at 37 °C. After being washed, micro-organisms were treated with 0.1-10 μg ml(-1) of HBD-1 and HBD-2 (30 min, 37 °C). Bacterial damage was determined by flow cytometry after propidium iodide staining. In parallel experiments, release of carboxyfluorescein from liposomes prepared from bacterial lipids was determined fluorometrically (excitation 485/20 nm, emission 528/20 nm) in the presence of HBD-1, HBD-2 or Nisin. Exposure of lactobacilli to HBD-2 resulted in a significant membrane permeabilization being Lact. delbrueckii subsp. bulgaricus CIDCA 331 the most susceptible strain. Liposomes prepared with lipids from strain CIDCA 133 were destabilized neither by HBD-1 nor by HBD-2, whereas liposomes derived from strain CIDCA 331 were susceptible to HBD-2 but not to HBD-1. Effect of defensins was strongly inhibited in the presence of NaCl, and the activity increased in water.

CONCLUSIONS

Results reported in the presented work indicate that lipid composition of bacterial membranes lead to a different interaction with cationic peptides such as defensins.

SIGNIFICANCE AND IMPACT OF THE STUDY

The results represent an advance in the understanding of the differential effect of HBDs on micro-organisms. Differences in susceptibility to anti-microbial peptides could modify the fate of micro-organisms after the interaction with host's cells.

Characterization of released polypeptides during an interferon-γ-dependent antibacterial response in airway epithelial cells

When pathogenic bacteria breach the epithelial lining at mucosal surfaces, rapidly available innate immune mechanisms are critical to halt the infection. In the present study, we characterized the production of antibacterial polypeptides released by epithelial cells. IFN-γ, but neither TNF nor IL-1β alone, induced release of antibacterial activity to a cell culture medium, causing a lytic appearance of killed bacteria as revealed by electron microscopy. Addition of the protein streptococcal inhibitor of complement, derived from Streptococcus pyogenes, known for its ability to neutralize antimicrobial polypeptides (AMPs), reduced the antibacterial activity of the medium. Characterization of the antibacterial incubation medium using mass spectrometric approaches and ELISAs, displayed presence of several classical AMPs, antibacterial chemokines, as well as complement factors and proteases that may interfere with bacterial killing. Many were constitutively produced, that is, being released by cells incubated in a medium alone. While a combination of IFN-γ and TNF did not increase bacterial killing, the presence of TNF boosted the amounts and detectable number of AMPs, including antibacterial chemokines. However, the methods applied in the study failed to single out certain AMPs as critical mediators, but rather demonstrate the broad range of molecules involved. Since many AMPs are highly amphiphatic in nature (i.e., cationic and hydrophobic), it is possible that difficulties in optimizing recovery present limitations in the context investigated. The findings demonstrate that epithelial cells have a constitutive production of AMPs and that IFN-γ is an important inducer of an antibacterial response in which is likely to be a critical part of the innate host defense against pathogenic bacteria at mucosal surfaces.

Extracellular DNA within a nontypeable Haemophilus influenzae-induced biofilm binds human beta defensin-3 and reduces its antimicrobial activity

Biofilms formed by nontypeable Haemophilus influenzae (NTHI) are associated with multiple chronic infections of the airway, including otitis media. Extracellular DNA (eDNA) is part of the biofilm matrix and serves as a structural component. Human β-defensin-3 (hBD-3) is a cationic antimicrobial host defense protein (AMP) critical to the protection of the middle ear. We hypothesized that anionic eDNA could interact with and bind hBD-3 and thus shield NTHI in biofilms from its antimicrobial activity. We demonstrated that recombinant hBD-3 [(r)hBD-3] bound eDNA in vitro and that eDNA in biofilms produced by NTHI in the chinchilla middle ear co-localized with the orthologue of this AMP. Incubation of physiological concentrations of (r)hBD-3 with NTHI genomic DNA abrogated the ability of this innate immune effector to prevent NTHI from forming robust biofilms in vitro. Establishment of NTHI biofilms in the presence of both DNase I and (r)hBD-3 resulted in a marked reduction in the overall height and thickness of the biofilms and rescued the antimicrobial activity of the AMP. Our results demonstrated that eDNA in NTHI biofilms sequestered hBD-3 and thus diminished the biological activity of an important effector of innate immunity. Our observations have important implications for chronicity of NTHI-induced diseases.

Arginine-specific mono ADP-ribosylation in vitro of antimicrobial peptides by ADP-ribosylating toxins

Among the several toxins used by pathogenic bacteria to target eukaryotic host cells, proteins that exert ADP-ribosylation activity represent a large and studied family of dangerous and potentially lethal toxins. These proteins alter cell physiology catalyzing the transfer of the ADP-ribose unit from NAD to cellular proteins involved in key metabolic pathways. In the present study, we tested the capability of four of these toxins, to ADP-ribosylate α- and β- defensins. Cholera toxin (CT) from Vibrio cholerae and heat labile enterotoxin (LT) from Escherichia coli both modified the human α-defensin (HNP-1) and β- defensin-1 (HBD1), as efficiently as the mammalian mono-ADP-ribosyltransferase-1. Pseudomonas aeruginosa exoenzyme S was inactive on both HNP-1 and HBD1. Neisseria meningitidis NarE poorly recognized HNP-1 as a substrate but it was completely inactive on HBD1. On the other hand, HNP-1 strongly influenced NarE inhibiting its transferase activity while enhancing auto-ADP-ribosylation. We conclude that only some arginine-specific ADP-ribosylating toxins recognize defensins as substrates in vitro. Modifications that alter the biological activities of antimicrobial peptides may be relevant for the innate immune response. In particular, ADP-ribosylation of antimicrobial peptides may represent a novel escape mechanism adopted by pathogens to facilitate colonization of host tissues.

The antimicrobial activity of the appetite peptide hormone ghrelin

The present study examined the antimicrobial activity of the peptide ghrelin. Both major forms of ghrelin, acylated ghrelin (AG) and desacylated ghrelin (DAG), demonstrated the same degree of bactericidal activity against Gram-negative Escherichia coli (E. coli) and Pseudomonas aeruginosa (P. aeruginosa), while bactericidal effects against Gram-positive Staphylococcus aureus (S. aureus) and Enterococcus faecalis (E. faecalis) were minimal or absent, respectively. To elucidate the bactericidal mechanism of AG and DAG against bacteria, we monitored the effect of the cationic peptides on the zeta potential of E. coli. Our results show that AG and DAG similarly quenched the negative surface charge of E. coli, suggesting that ghrelin-mediated bactericidal effects are influenced by charge-dependent binding and not by acyl modification. Like most cationic antimicrobial peptides (CAMPs), we also found that the antibacterial activity of AG was attenuated in physiological NaCl concentration (150mM). Nonetheless, these findings indicate that both AG and DAG can act as CAMPs against Gram-negative bacteria.

Expression of hBD-2 induced by 23-valent pneumococcal polysaccharide vaccine, Haemophilus influenzae type b vaccine and split influenza virus vaccine

Human β-defensin-2 (hBD-2) is an antimicrobial peptide with high activity and broad spectrum activity. hBD-2 expression may be highly elevated by microorganisms and inflammation. We reported that the majority of common vaccines used, including 23-valent pneumococcal polysaccharide vaccine, Haemophilus influenzae type b vaccine and split influenza virus vaccine, could induce the expression of hBD-2 in epithelial cells. Among them, the 23-valent pneumococcal polysaccharide vaccine was effective at a lower concentration (0.5 µg/ml), while Haemophilus influenzae type b vaccine and split influenza virus vaccine were effective at the concentration of 1 µg/ml. However, bacteriostatic experiments revealed that the split influenza virus vaccine was capable of inducing the highest antimicrobial activity. The medium of the 23-valent pneumococcal polysaccharide vaccine treatment group had a higher antimicrobial activity than the medium of the Haemophilus influenzae type b vaccine treatment group. The transcriptional regulator of hBD-2, that is, the NF-κB subunit, had a high level of activity, while the normal epithelial cells showed barely detectable activity, indicating that these vaccines have potential for clinical application.

Specific-sized hyaluronan fragments promote expression of human β-defensin 2 in intestinal epithelium

Hyaluronan (HA) is a glycosaminoglycan polymer found in the extracellular matrix of virtually all mammalian tissues. Recent work has suggested a role for small, fragmented HA polymers in initiating innate defense responses in immune cells, endothelium, and epidermis through interaction with innate molecular pattern recognition receptors, such as TLR4. Despite these advances, little is known regarding the effect of fragmented HA at the intestinal epithelium, where numerous pattern recognition receptors act as sentinels of an innate defense response that maintains epithelial barrier integrity in the presence of abundant and diverse microbial challenges. Here we report that HA fragments promote expression of the innate antimicrobial peptide human β-defensin 2 (HβD2) in intestinal epithelial cells. Treatment of HT-29 colonic epithelial cells with HA fragment preparations resulted in time- and dose-dependent up-regulated expression of HβD2 protein in a fragment size-specific manner, with 35-kDa HA fragment preparations emerging as the most potent inducers of intracellular HβD2. Furthermore, oral administration of specific-sized HA fragments promotes the expression of an HβD2 ortholog in the colonic epithelium of both wild-type and CD44-deficient mice but not in TLR4-deficient mice. Together, our observations suggest that a highly size-specific, TLR4-dependent, innate defense response to fragmented HA contributes to intestinal epithelium barrier defense through the induction of intracellular HβD2 protein.

Human antimicrobial peptides LL-37 and human β-defensin-2 reduce viral replication in keratinocytes infected with varicella zoster virus

BACKGROUND

There is mounting evidence that antimicrobial peptides have an important role in cutaneous defence, but the expression of these antimicrobial peptides in atopic eczema (AE) is still unclear. There are several families of antimicrobial peptides, including cathelicidins and human β-defensins. Patients with AE are more susceptible to severe cutaneous viral infections, including varicella zoster virus (VZV).

AIM

To characterize the functional activity of the antimicrobial peptides LL-37 (human cathelicidin) and human β-defensin (hBD)-2 keratinocytes were infected with VZV, in a skin-infection model.

METHODS

Flow-cytometry analysis was used to investigate LL-37 expression in normal human keratinocytes, and quantitative PCR was used to determine viral loads in infected HaCaT keratinocytes and B cells, with and without exogenous LL-37 and hBD-2.

RESULTS

LL-37 expression was present in keratinocytes, and both exogenous LL-37 and hBD-2 significantly reduced VZV load in infected keratinocytes and B cells. Specific antibodies blocked the antiviral action exhibited by these antimicrobial peptides. Pre-incubation of VZV with LL-37, but not hBD-2, further reduced VZV load.

CONCLUSIONS

Both LL-37 and hBD-2 have an antiviral effect on VZV replication in the keratinocyte HaCaT cell line and in B cells, but their mechanism of action is different. Evidence of the relationship between antimicrobial peptide expression and higher susceptibility to infections in AE skin is still emerging. Developing novel antiviral therapies based on antimicrobial peptides may provide improved treatment options for patients with AE.

Localization of inflammatory mediators in pediatric sinus mucosa

OBJECTIVES

Microarray analyses of sinus mucosa in pediatric patients with chronic rhinosinusitis (CRS) have recently demonstrated increased messenger RNA expression of the inflammatory chemokines CXCL5 and CXCL13 and of the innate immune mediators β-defensin 1 (DEFB1), serum amyloid A2 (SAA2), and serpin B4. The objectives of this study were to determine whether these gene products were expressed at the protein level in pediatric sinus mucosa and to determine their localization.

DESIGN

Immunohistochemical analysis was used to identify protein expression and cellular localization of CXCL5, CXCL13, DEFB1, SAA2, and serpin B4. Coimmunofluorescence staining of inflammatory cells was performed to further evaluate expression of CXCL5 and CXCL13.

SETTING

Pediatric tertiary care facility.

PATIENTS

Fifteen children with CRS who underwent endoscopic sinus surgery and 8 children who underwent craniofacial or neurosurgical procedures for abnormalities other than sinusitis.

MAIN OUTCOME MEASURES

Protein expression and cellular localization of CXCL5, CXCL13, DEFB1, SAA2, and serpin B4 in pediatric sinus mucosa.

RESULTS

Ciliated and basal cells in the pseudostratified epithelium stained positively for the 5 mediators examined in both cohorts. Except for serpin B4, goblet cells did not stain for any mediators in either cohort. Glandular cells stained positively for all 5 mediators in both cohorts. Coimmunofluorescence staining of inflammatory cells showed that CXCL13 was expressed in macrophages, T and B cells but not in neutrophils. CXCL5 was detected only in T cells.

CONCLUSIONS

CXCL5, CXCL13, DEFB1, SAA2, and serpin B4 were expressed at the protein level in the sinus mucosa of controls and pediatric patients with CRS and exhibited cell-specific localization. These mediators, not typically associated with pediatric CRS, may be involved in the inflammatory response and mucus hypersecretion seen in pediatric CRS.

Mechanistic exploration of AhR-mediated host protection against Streptococcus pneumoniae infection

Streptococcus pneumoniae is a primary cause of invasive bacterial infection and pneumonia and is one of the leading causes of death worldwide. In prior studies we showed that pre-treating mice with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a potent agonist of the aryl hydrocarbon receptor (AhR), protects against S. pneumoniae-induced mortality and reduces pulmonary bacterial burden. The current studies were conducted to help elucidate the mechanism for this protective effect, and to characterize the response in the lung during the first 10h following infection. C57Bl/6 mice were treated with TCDD one day prior to intranasal infection with serotype 3 S. pneumoniae. Monitoring of bacteria in the lung airways revealed that bacterial growth was inhibited in the TCDD-treated animals within 10h of infection. To address the mechanism of this rapid protective response, macrophages, neutrophils, and invariant Natural Killer T (iNKT) cells were quantified, and levels of natural antibodies produced by B-1 B cells were evaluated. Functional assays addressed whether AhR activation reduced the capacity of lung epithelial cells to bind bacteria, and whether TCDD treatment enhanced production of antimicrobial agents in the lung or blood. None of the hypothesized mechanisms was able to explain the protective effect. Finally, the exposure paradigm was manipulated to test whether administration of TCDD after instillation of the bacteria was also protective. Results showed that TCDD must be administered in advance of exposure to bacteria, suggesting that the lung environment is rendered inhospitable to the pathogens.

Lactoferrin: an alternative view of its role in human biological fluids

Lactoferrin is a major component of biologically important mucosal fluids and of the specific granules of neutrophils. Understanding its biological function is essential for understanding neutrophil- and mucosal-mediated immunity. In this review, we reevaluate the in vivo functions of human lactoferrin (hLF) emphasizing in vivo studies and in vitro studies performed in biologically relevant fluids. We discuss the evidence in the literature that supports (or does not support) proposed roles for hLF in mucosal immunity and in neutrophil function. We argue that the current literature supports a microbiostatic role, but not a microbicidal role, for hLF in vivo. The literature also supports a role for hLF in inhibiting colonization and infection of epithelial surfaces by microorganisms and in protecting tissues from neutrophil-mediated damage. Using this information, we briefly discuss hLF in the context of the complex biological fluids in which it is found.

Antiviral effects of β-defensin derived from orange-spotted grouper (Epinephelus coioides)

Defensins are a group of small antimicrobial peptides playing an important role in innate host defense. In this study, a β-defensin cloned from liver of orange-spotted grouper, Epinephelus coioides, EcDefensin, showed a key role in inhibiting the infection and replication of two kinds of newly emerging marine fish viruses, an enveloped DNA virus of Singapore grouper iridovirus (SGIV), and a non-enveloped RNA virus of viral nervous necrosis virus (VNNV). The expression profiles of EcDefensin were significantly (P < 0.001) up-regulated after challenging with Lipopolysaccharide (LPS), SGIV and Polyriboinosinic Polyribocytidylic Acid (polyI:C) in vivo. Immunofluorescence staining observed its intracellular innate immune response to viral infection of SGIV and VNNV. EcDefensin was found to possess dual antiviral activity, inhibiting the infection and replication of SGIV and VNNV and inducting a type I interferon-related response in vitro. Synthetic peptide of EcDefensin (Ec-defensin) incubated with virus or cells before infection reduced the viral infectivity. Ec-defensin drastically decreased SGIV and VNNV titers, viral gene expression and structural protein accumulation. Grouper spleen cells over-expressing EcDefensin (GS/pcDNA-EcDefensin) support the inhibition of viral infection and the upregulation of the expression of host immune-related genes, such as antiviral protein Mx and pro-inflammatory cytokine IL-1β. EcDefensin activated type I IFN and Interferon-sensitive response element (ISRE) in vitro. Reporter genes of IFN-Luc and ISRE-Luc were significantly up-regulated in cells transfected with pcDNA-EcDefenisn after infection with SGIV and VNNV. These results suggest that EcDefensin is importantly involved in host immune responses to invasion of viral pathogens, and open the new avenues for design of antiviral agents in fisheries industry.

Pulmonary surfactant protein A protects lung epithelium from cytotoxicity of human β-defensin 3

Defensins are important molecules in the innate immune system that eliminate infectious microbes. They also exhibit cytotoxicity against host cells in higher concentrations. The mechanisms by which hosts protect their own cells from cytotoxicity of defensins have been poorly understood. We found that the cytotoxicity of human β-defensin 3 (hBD3) against lung epithelial cells was dose-dependently attenuated by pulmonary surfactant protein A (SP-A), a collectin implicated in host defense and regulation of inflammatory responses in the lung. The direct interaction between SP-A and hBD3 may be an important factor in decreasing this cytotoxicity because preincubation of epithelial cells with SP-A did not affect the cytotoxicity. Consistent with in vitro analysis, intratracheal administration of hBD3 to SP-A(-/-) mice resulted in more severe tissue damage compared with that in WT mice. These data indicate that SP-A protects lung epithelium from tissue injury caused by hBD3. Furthermore, we found that the functional region of SP-A lies within Tyr(161)-Lys(201). Synthetic peptide corresponding to this region, tentatively called SP-A Y161-G200, also inhibited cytotoxicity of hBD3 in a dose-dependent manner. The SP-A Y161-G200 is a candidate as a therapeutic reagent that prevents tissue injury during inflammation.

Genetic variability in beta-defensins is not associated with susceptibility to Staphylococcus aureus bacteremia

Introduction

Human beta-defensins are key components of human innate immunity to a variety of pathogens, including Staphylococcus aureus. The aim of the present study was to investigate a potential association between gene variations in DEFB1 and DEFB103/DEFB4 and the development of S. aureus bacteremia (SAB) employing a case-control design.

Methods

Cases were unique patients with documented SAB, identified with the National S. aureus Bacteremia Register, a comprehensive dataset of all episodes of community associated-SABs (CA-SAB) occurring in children (≤20 yrs) in Denmark from 1990 to 2006. Controls were age-matched healthy individuals with no history of SAB. DNA obtained from cases and controls using the Danish Newborn Screening Biobank were genotyped for functional polymorphisms of DEFB1 by Sanger sequencing and copy number variation of the DEFB103 and DEFB4 genes using Pyrosequencing-based Paralogue Ratio Test (P-PRT).

Results

193 ethnic Danish SAB cases with 382 age-matched controls were used for this study. S. aureus isolates represented a variety of bacterial (i.e., different spa types) types similar to SAB isolates in general. DEFB1 minor allele frequencies of rs11362 (cases vs. controls 0.47/0.44), rs1800972 (0.21/0.24), and rs1799946 (0.32/0.33) were not significantly different in cases compared with controls. Also, DEFB4/DEFB103 gene copy numbers (means 4.83/4.92) were not significantly different in cases compared with controls.

Conclusions

Using a large, unique cohort of pediatric CA-SAB, we found no significant association between DEFB1 genetic variation or DEFB4/DEFB103 gene copy number and susceptibility for SAB.

Expression of β-defensin-4 in "an in vivo and ex vivo model" of human osteoarthritic knee meniscus

PURPOSE

To investigate, for the first time, the expression of β-defensins-4, by immunohistochemistry and western blotting, in OA meniscus versus control meniscus, thus providing new insights into the physiological processes of meniscus repairing.

METHOD

β-defensins-4 was studied in vivo, in knee osteoarthritic menisci obtained from 30 patients (20 men and 10 women) who underwent isolated arthroscopic partial medial or lateral meniscectomy, and in vitro on fibrochondrocyte cells from human OA knee menisci. The study was conducted using morphological, immunohistochemical, and Western blot analysis.

RESULTS

The histological results demonstrated structural alterations and cracks of OA menisci accompanied by a very strong β-defensin-4 immunohistochemical staining. The Western blot analysis confirmed also a strong expression of β-defensin-4 in OA fibrochondrocyte cells.

CONCLUSION

The present study suggests an activation of β-defensin-4 induction, in human knee meniscus induced by the OA inflammatory process. It may represent an endogenous antibiotic defense mechanism accompanied by an intrinsic effort of tissue remodeling in OA articular joints. In conclusion, the present paper suggests the clinical relevance of β-defensin-4 in the prospective of future alternative medical treatment for OA.

Multiple trauma induces serum production of host defence peptides

Today multiple trauma still is associated with a high mortality. Although severe open fractures and wounds can give rise to local infections and sepsis, the overall infection rate of multiply injured patients is surprisingly low. We have investigated serum of multiply injured patients with respect to antibacterial properties and screened for host defence peptides (HDP) that constitute a class of fast acting and rapidly available molecules preventing bacterial infection. Serum specimens were obtained from multiply injured patients. Radial diffusion assays were performed to investigate antimicrobial properties. Ultrafiltration and heat-inactivation were used to rule out antimicrobial activity of large proteins i.e. complement factors. ELISA was performed to analyse serum concentrations of the human beta-defensins 2 and 3 (hBD-2 and hBD-3), LL-37 and the proinflammatory cytokines interferon-gamma (IFN-γ) and interleukin-6 (IL-6). Serum of multiply injured patients showed greater zones of inhibition in antimicrobial testing against Gram negative und positive bacteria. This effect was mediated by proteins smaller than 10 kDa, inactivation of the complement system does not significantly reduce antibacterial action. hBD-2, hBD-3 and LL-37 concentrations were significantly elevated after trauma and followed different characteristic concentration curves. Similar patterns of concentration profiles were recorded for hBD-2/IL-6 and hBD-3/IFN-γ suggesting a stimulatory influence within their induction process. With this study we provide evidence, that serum of multiply injured patients has by far higher antibacterial capacity than that of healthy donors. As possible mediators we have detected the HDP hBD-2, hBD-3 and LL-37 and their inducers in serum of multiply injured patients.

Host evasion by Burkholderia cenocepacia

Burkholderia cenocepacia is an opportunistic respiratory pathogen of individuals with cystic fibrosis (CF). Some strains of B. cenocepacia are highly transmissible and resistant to almost all antibiotics. Approximately one-third of B. cenocepacia infected CF patients go on to develop fatal "cepacia syndrome." During the last two decades, substantial progress has been made with regards to evasion of host innate defense mechanisms by B. cenocepacia. Almost all strains of B. cenocepacia have the capacity to survive and replicate intracellularly in both airway epithelial cells and macrophages, which are primary sentinels of the lung and play a pivotal role in clearance of infecting bacteria. Those strains of B. cenocepacia, which express both cable pili and the associated 22 kDa adhesin are also capable of transmigrating across airway epithelium and persist in mouse models of infection. In this review, we will discuss how this type of interaction between B. cenocepacia and host may lead to persistence of bacteria as well as lung inflammation in CF patients.

Antimicrobial peptide defensin: identification of novel isoforms and the characterization of their physiological roles and their significance in the pathogenesis of diseases

Defensins comprise a family of cationic antimicrobial peptides containing a specific six-cysteine motif. Their contribution to the host defense against microbial invasion and the control of normal flora have been previously described. Some of the β-defensin isoforms are predominantly expressed in the epididymis and showed a region-specific expression pattern in the epididymis, which thus suggested that these isoforms may possess epididymis-specific functions in addition to antimicrobial activities. A sequence variant of the β-defensin 126 gene has been shown to be associated with reductions in the human sperm function, thus supporting this hypothesis. Furthermore, defensins have the capacity to chemoattract immune cells and induce the secretion of inflammatory cytokines. Mice expressing human neutrophil α-defensin showed more severe lung injuries after the aspiration of acidic contents than did control mice. Recent investigations regarding copy number variations of human defensin genes also suggest the significance of defensin in the pathogenesis or the worsening of chronic obstructive pulmonary diseases, sepsis and psoriasis.

A novel role for the NLRC4 inflammasome in mucosal defenses against the fungal pathogen Candida albicans

Candida sp. are opportunistic fungal pathogens that colonize the skin and oral cavity and, when overgrown under permissive conditions, cause inflammation and disease. Previously, we identified a central role for the NLRP3 inflammasome in regulating IL-1β production and resistance to dissemination from oral infection with Candida albicans. Here we show that mucosal expression of NLRP3 and NLRC4 is induced by Candida infection, and up-regulation of these molecules is impaired in NLRP3 and NLRC4 deficient mice. Additionally, we reveal a role for the NLRC4 inflammasome in anti-fungal defenses. NLRC4 is important for control of mucosal Candida infection and impacts inflammatory cell recruitment to infected tissues, as well as protects against systemic dissemination of infection. Deficiency in either NLRC4 or NLRP3 results in severely attenuated pro-inflammatory and antimicrobial peptide responses in the oral cavity. Using bone marrow chimeric mouse models, we show that, in contrast to NLRP3 which limits the severity of infection when present in either the hematopoietic or stromal compartments, NLRC4 plays an important role in limiting mucosal candidiasis when functioning at the level of the mucosal stroma. Collectively, these studies reveal the tissue specific roles of the NLRP3 and NLRC4 inflammasome in innate immune responses against mucosal Candida infection.

In this manuscript we describe a new role for a group of molecules termed the “inflammasome” that process key immune response proteins including interleukin-1-β. In previous work, we and others have shown that the NLRP3 inflammasome is important in protecting from severe fungal infections. We now show that, in addition to the NLRP3 inflammasome, a different inflammasome containing NLRC4 is also important in protecting against infection with Candida albicans, and appears to be functioning in the mucosal lining of the mouth and intestines, rather than in immune cells. Our research explains a new mechanism of mucosal immunity to fungal infections and has broad implications for developing new treatments against fungal infections, which are a serious cause of illness and death, particularly in immunocompromised persons. Additionally, this research may also lead to new ways to identify those individuals who are at the highest risk for serious fungal infections.

Antimicrobial aspects of inflammatory resolution in the mucosa: a role for proresolving mediators

Mucosal surfaces function as selectively permeable barriers between the host and the outside world. Given their close proximity to microbial Ags, mucosal surfaces have evolved sophisticated mechanisms for maintaining homeostasis and preventing excessive acute inflammatory reactions. The role attributed to epithelial cells was historically limited to serving as a selective barrier; in recent years, numerous findings implicate an active role of the epithelium with proresolving mediators in the maintenance of immunological equilibrium. In this brief review, we highlight new evidence that the epithelium actively contributes to coordination and resolution of inflammation, principally through the generation of anti-inflammatory and proresolution lipid mediators. These autacoids, derived from ω-6 and ω-3 polyunsaturated fatty acids, are implicated in the initiation, progression, and resolution of acute inflammation and display specific, epithelial-directed actions focused on mucosal homeostasis. We also summarize present knowledge of mechanisms for resolution via regulation of epithelial-derived antimicrobial peptides in response to proresolving lipid mediators.

Antimicrobial peptides: key components of the innate immune system

Life-threatening infectious diseases are on their way to cause a worldwide crisis, as treating them effectively is becoming increasingly difficult due to the emergence of antibiotic resistant strains. Antimicrobial peptides (AMPs) form an ancient type of innate immunity found universally in all living organisms, providing a principal first-line of defense against the invading pathogens. The unique diverse function and architecture of AMPs has attracted considerable attention by scientists, both in terms of understanding the basic biology of the innate immune system, and as a tool in the design of molecular templates for new anti-infective drugs. AMPs are gene-encoded short (<100 amino acids), amphipathic molecules with hydrophobic and cationic amino acids arranged spatially, which exhibit broad spectrum antimicrobial activity. AMPs have been the subject of natural evolution, as have the microbes, for hundreds of millions of years. Despite this long history of co-evolution, AMPs have not lost their ability to kill or inhibit the microbes totally, nor have the microbes learnt to avoid the lethal punch of AMPs. AMPs therefore have potential to provide an important breakthrough and form the basis for a new class of antibiotics. In this review, we would like to give an overview of cationic antimicrobial peptides, origin, structure, functions, and mode of action of AMPs, which are highly expressed and found in humans, as well as a brief discussion about widely abundant, well characterized AMPs in mammals, in addition to pharmaceutical aspects and the additional functions of AMPs.

Spatial distribution of antimicrobial peptides and mast cells in the skin of the external auditory canal

Objective:

The direct activity of antimicrobial peptides against microbes is thought to be an essential first line of defence in the skin; however, little is known about antimicrobial peptide secretion in the skin of the external auditory canal. Evidence suggests that mast cells contribute to the secretion of antimicrobial peptides. This study aimed to examine the distribution of mast cells and antimicrobial peptides, including human β-defensin-1 and -2 and LL-37, in the external auditory canal skin.

Methods:

External auditory canal skin samples from 12 patients undergoing middle-ear surgery with canaloplasty were immunohistochemically stained to detect expression of mast cell markers (tryptase and chymase) and antimicrobial peptides (human β-defensin-1 and -2 and LL-37).

Results:

Mast cells and human β-defensin-1 were present in the ceruminous glands but not in the sebaceous glands. The increased presence of mast cells, human β-defensin-1 and LL-37 in ceruminous glands suggests that mast cells may participate in the secretion of antimicrobial peptides from ceruminous glands.

Conclusion:

These findings suggest that mast cells contribute to the secretion of antimicrobial peptides in the ceruminous glands of the external auditory canal skin.

Host Defense and the Airway Epithelium: Frontline Responses That Protect against Bacterial Invasion and Pneumonia

Airway epithelial cells are the first line of defense against invading microbes, and they protect themselves through the production of carbohydrate and protein matrices concentrated with antimicrobial products. In addition, they act as sentinels, expressing pattern recognition receptors that become activated upon sensing bacterial products and stimulate downstream recruitment and activation of immune cells which clear invading microbes. Bacterial pathogens that successfully colonize the lungs must resist these mechanisms or inhibit their production, penetrate the epithelial barrier, and be prepared to resist a barrage of inflammation. Despite the enormous task at hand, relatively few virulence factors coordinate the battle with the epithelium while simultaneously providing resistance to inflammatory cells and causing injury to the lung. Here we review mechanisms whereby airway epithelial cells recognize pathogens and activate a program of antibacterial pathways to prevent colonization of the lung, along with a few examples of how bacteria disrupt these responses to cause pneumonia.

Effects of lipopolysaccharide and CpG-DNA on burn-induced skin injury

Destruction of the skin barrier by thermal injury induces microbial invasion, which can lead to the development of systemic infection and septic shock. Microbial pathogens possess pathogen-associated molecular patterns (PAMPs), which are recognized by conserved receptors. To understand the role of PAMPs in thermal injury-induced mice, LPS or CpG-DNA were topically applied to dorsal skin after thermal injury. We observed an increase in the number of inflammatory cell infiltrates as well as thickening in the dermis upon treatment with LPS or CpG-DNA. We also found that expression of IL-1β, MIP-2, and RANTES induced by thermal injury was enhanced by LPS or CpG-DNA. In addition, the proportions of CD4(+) and CD8(+) T cells in the spleen and lymph nodes were altered by LPS or CpG-DNA. These results provide important information concerning PAMPs-induced inflammation upon thermal injury and provide a basis for studying the role of PAMPs in thermal injury-induced complications.

Platelets display potent antimicrobial activity and release human beta-defensin 2

Platelet-rich plasma (PRP) is a potent agent that improves soft tissue and bone healing. By the release of growth factors and cytokines, PRP is believed to locally boost physiologic healing processes. Recently, antimicrobial activity of PRP has been demonstrated against S. aureus strains. Major scientific effort is being put into the understanding and prevention of infections i.e. by delivery of antimicrobial substances. In previous studies we showed the ideal antibacterial activity-profile of the human beta-defensin 2 (hBD-2) for orthopaedic infections and therefore hypothesized that hBD-2 may be the effector of antimicrobial platelet action. Platelet concentrates were produced from human platelet phresis obtained from a hospital blood bank. They were screened by immunohistochemistry, Western Blot and ELISA for the human beta defensin-2. In vitro susceptibility to PRP was investigated by a standard disc diffusion test with or without pre-incubation of PRP with anti-hBD-2 antibody. SPSS statistical software was used for statistical analysis. PRP contains hBD-2 470 pg/10(9) platelets or 1786 pg/ml, respectively, (ELISA), which was confirmed by immunohistochemistry and Western Blot. In antimicrobial testing, PRP demonstrates effective inhibition of E. coli, B. megaterium, P. aeruginosa, E. faecalis and P. mirabilis. With this study we confirm the previously reported antimicrobial action of platelet concentrates i.e. PRP. In opposition to previously reported effects against gram positive bacteria our study focuses on gram negative and less common gram positive bacteria that do frequently cause clinical complications. We provide a possible molecular mechanism at least for E. coli and P. mirabilis for this effect by the detection of an antimicrobial peptide (hBD-2). This study may advocate the clinical use of PRP by highlighting a new aspect of platelet action.

Human beta-Defensin-2 Induction in Human Foreskin Keratinocyte by Synergetic Stimulation with Foods and Escherichia Coli

We established a real-time quantitative RT-PCR assay that permits rapid and sensitive screening of foods that increase the human beta-defensin-2 (hBD-2) mRNA level in human foreskin keratinocyte (HFK) cells. The range of hBD-2 mRNA concentrations suitable for the assay was between 8 x 10(-11) M (39-cycle amplification) and 8 x 10(-18) M (13-cycle amplification) as calibrated with standard hBD-2 cDNA. With this assay system, it was found that the stimulation of HFK cells by the addition of yeast powder at 5 g l(-1) to the culture medium resulted in about 40 times increase in hBD-2 mRNA level, though stimulation with Escherichia coli attained the same level of induction. The active component of yeast was insoluble in water. Simultaneous co-stimulation of HFK cells with E. coli and grains, such as amaranth, millet, soybean and sesame, boosted hBD-2 mRNA induction significantly (6.1, 2.5, 3.3, and 3.3 times, respectively) above the level attained with E. coli alone. The results of successive fractionations of amaranth grain powder by ether extraction and amylase digestion showed that the boosting activity of amaranth grain resided in its insoluble fraction. Significant boosting of hBD-2 mRNA induction in epithelial cells with foods opens a new possibility of developing functional foods that can protect the human body against microbial infection at the oral cavity, skin, and respiratory tract among others.

Analysis of the networks controlling the antimicrobial-peptide-dependent induction of Klebsiella pneumoniae virulence factors

Antimicrobial peptides (APs) impose a threat to the survival of pathogens, and it is reasonable to postulate that bacteria have developed strategies to counteract them. Polymyxins are becoming the last resort to treat infections caused by multidrug-resistant Gram-negative bacteria and, similar to APs, they interact with the anionic lipopolysaccharide. Given that polymyxins and APs share the initial target, it is possible that bacterial defense mechanisms against polymyxins will be also effective against host APs. We sought to determine whether exposure to polymyxin will increase Klebsiella pneumoniae resistance to host APs. Indeed, exposure of K. pneumoniae to polymyxin induces cross-resistance not only to polymyxin itself but also to APs present in the airways. Polymyxin treatment upregulates the expression of the capsule polysaccharide operon and the loci required to modify the lipid A with aminoarabinose and palmitate with a concomitant increase in capsule and lipid A species containing such modifications. Moreover, these surface changes contribute to APs resistance and also to polymyxin-induced cross-resistance to APs. Bacterial loads of lipid A mutants in trachea and lungs of intranasally infected mice were lower than those of wild-type strain. PhoPQ, PmrAB, and the Rcs system govern polymyxin-induced transcriptional changes, and there is a cross talk between PhoPQ and the Rcs system. Our findings support the notion that Klebsiella activates a defense program against APs that is controlled by three signaling systems. Therapeutic strategies directed to prevent the activation of this program could be a new approach worth exploring to facilitate the clearance of the pathogen from the airways.

Evidence of in vitro differential secretion of human beta-defensins-1, -2, and -3 after selective exposure to Streptococcus agalactiae in human fetal membranes

OBJECTIVE

The aim of this work was to characterize the individual contribution of the amnion (AMN) and choriodecidua (CHD) regions to the secretion of human beta defensins (HBD)-1, -2, and -3, after stimulation with Streptococcus agalactiae.

METHODS

Full-thickness membranes were mounted on a Transwell device, constituted by two independent chambers; 1 × 10(6) CFU/ml of S. agalactiae were added to either the AMN or CHD face or to both. Secretion profiles of HBD-1, HBD-2, and HBD-3 to the culture medium were quantified by enzyme-linked immunosorbent sandwich assay (ELISA).

RESULTS

Secretion profile of HBD-1 remained without significant changes; HBD-2 secretion level by the CHD increased 2.0 (2.73 ± 0.19 pg/μg) and 2.6 (3.62 ± 0.60 pg/μg) times when the stimulus was applied only to the CHD region and simultaneously to both compartments, respectively. The bacterial stimulation in the AMN induced a 2.0 times (2.06 ± 0.29 pg/μg) increase in this region. HBD-3 secretion level increased significantly in the CHD (15.65 ± 2.68 pg/μg) and the AMN (14.94 ± 1.85 pg/μg) only when both regions were stimulated simultaneously.

CONCLUSION

The stimulation of human fetal membranes with S. agalactiae induced a differential and tissue-specific profile of HBD-1, HBD-2, and HBD-3 secretion.

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.

Interleukins, from 1 to 37, and interferon-γ: receptors, functions, and roles in diseases

Advancing our understanding of mechanisms of immune regulation in allergy, asthma, autoimmune diseases, tumor development, organ transplantation, and chronic infections could lead to effective and targeted therapies. Subsets of immune and inflammatory cells interact via ILs and IFNs; reciprocal regulation and counter balance among T(h) and regulatory T cells, as well as subsets of B cells, offer opportunities for immune interventions. Here, we review current knowledge about ILs 1 to 37 and IFN-γ. Our understanding of the effects of ILs has greatly increased since the discoveries of monocyte IL (called IL-1) and lymphocyte IL (called IL-2); more than 40 cytokines are now designated as ILs. Studies of transgenic or knockout mice with altered expression of these cytokines or their receptors and analyses of mutations and polymorphisms in human genes that encode these products have provided important information about IL and IFN functions. We discuss their signaling pathways, cellular sources, targets, roles in immune regulation and cellular networks, roles in allergy and asthma, and roles in defense against infections.

Modulation of human beta-defensin-1 (hBD-1) in plasmacytoid dendritic cells (PDC), monocytes, and epithelial cells by influenza virus, Herpes simplex virus, and Sendai virus and its possible role in innate immunity

hBD comprise a family of antimicrobial peptides that plays a role in bridging the innate and adaptive immune responses to infection. The expression of hBD-2 increases upon stimulation of numerous cell types with LPS and proinflammatory cytokines. In contrast, hBD-1 remains constitutively expressed in most cells in spite of cytokine or LPS stimulation; however, its presence in human PDC suggests it plays a role in viral host defense. To examine this, we characterized the expression of hBD-1 in innate immune cells in response to viral challenge. PDC and monocytes increased production of hBD-1 peptide and mRNA as early as 2 h following infection of purified cells and PBMCs with PR8, HSV-1, and Sendai virus. However, treatment of primary NHBE cells with influenza resulted in a 50% decrease in hBD-1 mRNA levels, as measured by qRT-PCR at 3 h following infection. A similar inhibition occurred with HSV-1 challenge of human gingival epithelial cells. Studies with HSV-1 showed that replication occurred in epithelial cells but not in PDC. Together, these results suggest that hBD-1 may play a role in preventing viral replication in immune cells. To test this, we infected C57BL/6 WT mice and mBD-1((-/-)) mice with mouse-adapted HK18 (300 PFU/mouse). mBD-1((-/-)) mice lost weight earlier and died sooner than WT mice (P=0.0276), suggesting that BD-1 plays a role in early innate immune responses against influenza in vivo. However, lung virus titers were equal between the two mouse strains. Histopathology showed a greater inflammatory influx in the lungs of mBD-1((-/-)) mice at Day 3 postinfection compared with WT C57BL/6 mice. The results suggest that BD-1 protects mice from influenza pathogenesis with a mechanism other than inhibition of viral replication.

Criterion for amino acid composition of defensins and antimicrobial peptides based on geometry of membrane destabilization

Defensins comprise a potent class of membrane disruptive antimicrobial peptides (AMPs) with well-characterized broad spectrum and selective microbicidal effects. By using high-resolution synchrotron small-angle X-ray scattering to investigate interactions between heterogeneous membranes and members of the defensin subfamilies, α-defensins (Crp-4), β-defensins (HBD-2, HBD-3), and θ-defensins (RTD-1, BTD-7), we show how these peptides all permeabilize model bacterial membranes but not model eukaryotic membranes: defensins selectively generate saddle-splay ("negative Gaussian") membrane curvature in model membranes rich in negative curvature lipids such as those with phosphoethanolamine (PE) headgroups. These results are shown to be consistent with vesicle leakage assays. A mechanism of action based on saddle-splay membrane curvature generation is broadly enabling, because it is a necessary condition for processes such as pore formation, blebbing, budding, and vesicularization, all of which destabilize the barrier function of cell membranes. Importantly, saddle-splay membrane curvature generation places constraints on the amino acid composition of membrane disruptive peptides. For example, we show that the requirement for generating saddle-splay curvature implies that a decrease in arginine content in an AMP can be offset by an increase in both lysine and hydrophobic content. This "design rule" is consistent with the amino acid compositions of 1080 known cationic AMPs.

Nuclear factor kappa B plays a pivotal role in polyinosinic-polycytidylic acid-induced expression of human β-defensin 2 in intestinal epithelial cells

Intestinal epithelial cells (IECs) play an important role in protecting the intestinal surface from invading pathogens by producing effector molecules. IECs are one of the major sources of human beta-defensin 2 (hBD-2), and can produce it in response to a variety of stimuli. Although IECs express Toll-like receptor 3 (TLR-3) and can respond to its ligand, double-stranded RNA (dsRNA), hBD-2 expression in response to dsRNA has not been elucidated. In the present study, using an artificial analogue of dsRNA, polyinosinic-polycytidylic acid (poly I:C), we investigated whether the human IEC line, HT-29, can produce hBD-2 in response to poly I:C. HT-29 cells can express hBD-2 mRNA only when stimulated with poly I:C. The induction of hBD-2 mRNA expression was observed at 3 h after stimulation and peaked at 12 h of post-stimulation. Pre-incubation of the cells with nuclear factor kappa B (NF-κB)-specific inhibitor, l-1-4'-tosylamino-phenylethyl-chloromethyl ketone (TPCK) and isohelenine abolished the expression of hBD-2. Detection of the poly I:C signal by TLR-3 on the surface of HT-29 cells was revealed by pre-incubating the cells with anti-TLR-3 antibody. The 5'-regulatory region of the hBD-2 gene contains two NF-κB binding sites. A luciferase assay revealed the importance of the proximal NF-κB binding site for poly I:C-induced expression of hBD-2. Among NF-κB subunits, p65 and p50 were activated by poly I:C stimulation and accumulated in the nucleus. Activation of the p65 subunit was investigated further by determining its phosphorylation status, which revealed that poly I:C stimulation resulted in prolonged phosphorylation of p65. These results indicate clearly that NF-κB plays an indispensable role in poly I:C induced hBD-2 expression in HT-29 cells.

Mycobacterium tuberculosis components stimulate production of the antimicrobial peptide hepcidin

We investigated the in vitro production of the antimicrobial peptide hepcidin by cells of the innate immune system that harbor Mycobacterium tuberculosis. Stimulation of mouse lung macrophages with M. tuberculosis or IFN-γ + M. tuberculosis induced hepcidin mRNA. In human alveolar A549 epithelial cells, lipoglycans of M. tuberculosis, in particular mannose-capped lipoarabinomannan and phosphatidyl-myo-inositol mannosides, were strong inducers of hepcidin mRNA. In mouse dendritic cells, hepcidin mRNA was increased by subcellular fractions and culture filtrate proteins of M. tuberculosis and by TLR2 and TLR4 agonists, but not by TLR9 agonists, IL-1α, IL-6 or TNF-α. Flow cytometry evaluation of human peripheral blood mononuclear cells demonstrated that CD11c(+) myeloid dendritic cells stimulated with killed M. tuberculosis or live M. bovis BCG produced hepcidin. The production of the antimicrobial peptide hepcidin by cells that interact with M. tuberculosis suggests a host defense mechanism against mycobacteria.

Additive effects of orexin B and vasoactive intestinal polypeptide on LL-37-mediated antimicrobial activities

The present study examined the bactericidal effects of orexin B (ORXB) and vasoactive intestinal peptide (VIP) alone or combined with cationic antimicrobial peptides, such as LL-37, on Escherichia coli, Pseudomonas aeruginosa, Streptococcus mutans and Staphylococcus aureus. The bactericidal effect of ORXB or VIP alone was detected in low NaCl concentration, but attenuated in physiological NaCl concentration (150 mM). However, such attenuated bactericidal activities of ORXB and VIP in 150 mM NaCl were regained by adding LL-37. Therefore, our results indicate that VIP and ORXB appear to mediate bactericidal effects in concert with LL-37 in the physiological context of mucosal tissue.

High-Glucose Environment Inhibits p38MAPK Signaling and Reduces Human β-Defensin-3 Expression [corrected] in Keratinocytes

Diabetes mellitus is characterized by elevated plasma glucose and increased rates of skin infections. Altered immune responses have been suggested to contribute to this prevalent complication, which involves microbial invasion. In this study we explored the effects of a high-glucose environment on the innate immunity of keratinocytes by focusing on β defensin-3 (BD3) using in vivo and in vitro models. Our results demonstrated that the perilesional skins of diabetic rats failed to show enhanced BD3 expression after wounding. In addition, high-glucose treatment reduced human BD3 (hBD3) expression of cultured human keratinocytes. This pathogenic process involved inhibition of p38MAPK signaling, an event that resulted from increased formation of advanced glycation end products. On the other hand, toll-like receptor-2 expression and function of cultured keratinocytes were not significantly affected by high-glucose treatment. In summary, high-glucose conditions inhibited the BD3 expression of epidermal keratinocytes, which in turn contributed to the frequent occurrences of infection associated with diabetic wounding.

Modulation of early β-defensin-2 production as a mechanism developed by type I Toxoplasma gondii to evade human intestinal immunity

We investigated the early innate immune responses induced in human intestinal epithelial cells (IEC) by the three defined Toxoplasma gondii genotype strains. Transcriptome analysis revealed that among differentially expressed genes, β-defensins distinguished the most IEC infected by fast- or slow-replicating T. gondii genotypes. Although β-defensin 1 and 3 genes were not expressed in host cells at early time points postinfection, the slow-replicating type II and III parasites induced high levels of β-defensin 2 gene expression. Notably, no β-defensin 2 gene expression occurred early after infection with the fast-replicating type I parasite. However, activation of this gene in IEC by poly(I:C) treatment prior to infection substantially decreased parasite viability, and pretreatment of parasites with synthetic β-defensin 2 significantly reduced their infectivity of IEC. These findings strongly support the modulation of early β-defensin 2 expression as a mechanism used by type I T. gondii parasites to mediate immune evasion.

Molecular cloning and characterization of novel cathelicidin-derived myeloid antimicrobial peptide from Phasianus colchicus

Cathelicidins were initially characterized as a family of antimicrobial peptides. Now it is clear that they fulfill several immune functions in addition to their antimicrobial activity. In the current work, three cDNA sequences encoding pheasant cathelicidins were cloned from a constructed bone marrow cDNA library of Phasianus colchicus, using a nested-PCR-based cloning strategy. The three deduced mature antimicrobial peptides, Pc-CATH1, 2 and 3 are composed of 26, 32, and 29 amino acid residues, respectively. Unlike the mammalian cathelicidins that are highly divergent even within the same genus, Pc-CATHs are remarkably conserved with chicken fowlicidins with only a few of residues mutated according to the phylogenetic analysis result. Synthetic Pc-CATH1 exerted strong antimicrobial activity against most of bacteria and fungi tested, including the clinically isolated (IS) drug-resistant strains. Most MIC values against Gram-positive bacteria were in the range of 0.09-2.95 μM in the presence of 100mM NaCl. Pc-CATH1 displayed a negligible hemolytic activity against human erythrocytes, lysing 3.6% of erythrocytes at 3.15 μM (10 μg/ml), significantly higher than the corresponding MIC. Pc-CATH1 was stable in the human serum for up to 72 h, revealing its extraordinary serum stability. These specific features of Pc-CATH1 may make its applications much wider given the potency and breadth of the peptide's bacteriocidal capacity and its resistance towards serum and high-salt environments.

Implications of the innate immune response to adenovirus and adenoviral vectors

Adenovirus (AdV) is a common cause of respiratory illness in both children and adults. Respiratory symptoms can range from those of the common cold to severe pneumonia. Infection can also cause significant disease in the immunocompromised and among immunocompetent subjects in close quarters. Fortunately, infection with AdV in the normal host is generally mild. This is one reason why its initial use as a gene-therapy vector appeared to be so promising. Unfortunately, both innate and adaptive responses to the virus have limited the development of AdV vectors as a tool of gene therapy by increasing toxicity and limiting duration of transgene expression. This article will focus on the innate immune response to infection with wild-type AdV and exposure to AdV gene-therapy vectors. As much of the known information relates to the pulmonary inflammatory response, this organ system will be emphasized. This article will also discuss how that understanding has led to the creation of new vectors for use in gene therapy.

Reduction of disulphide bonds unmasks potent antimicrobial activity of human β-defensin 1

Human epithelia are permanently challenged by bacteria and fungi, including commensal and pathogenic microbiota. In the gut, the fraction of strict anaerobes increases from proximal to distal, reaching 99% of bacterial species in the colon. At colonic mucosa, oxygen partial pressure is below 25% of airborne oxygen content, moreover microbial metabolism causes reduction to a low redox potential of -200 mV to -300 mV in the colon. Defensins, characterized by three intramolecular disulphide-bridges, are key effector molecules of innate immunity that protect the host from infectious microbes and shape the composition of microbiota at mucosal surfaces. Human β-defensin 1 (hBD-1) is one of the most prominent peptides of its class but despite ubiquitous expression by all human epithelia, comparison with other defensins suggested only minor antibiotic killing activity. Whereas much is known about the activity of antimicrobial peptides in aerobic environments, data about reducing environments are limited. Herein we show that after reduction of disulphide-bridges hBD-1 becomes a potent antimicrobial peptide against the opportunistic pathogenic fungus Candida albicans and against anaerobic, Gram-positive commensals of Bifidobacterium and Lactobacillus species. Reduced hBD-1 differs structurally from oxidized hBD-1 and free cysteines in the carboxy terminus seem important for the bactericidal effect. In vitro, the thioredoxin (TRX) system is able to reduce hBD-1 and TRX co-localizes with reduced hBD-1 in human epithelia. Hence our study indicates that reduced hBD-1 shields the healthy epithelium against colonisation by commensal bacteria and opportunistic fungi. Accordingly, an intimate interplay between redox-regulation and innate immune defence seems crucial for an effective barrier protecting human epithelia.

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.

Glucose depletion in the airway surface liquid is essential for sterility of the airways

Diabetes mellitus predisposes the host to bacterial infections. Moreover, hyperglycemia has been shown to be an independent risk factor for respiratory infections. The luminal surface of airway epithelia is covered by a thin layer of airway surface liquid (ASL) and is normally sterile despite constant exposure to bacteria. The balance between bacterial growth and killing in the airway determines the outcome of exposure to inhaled or aspirated bacteria: infection or sterility. We hypothesized that restriction of carbon sources--including glucose--in the ASL is required for sterility of the lungs. We found that airway epithelia deplete glucose from the ASL via a novel mechanism involving polarized expression of GLUT-1 and GLUT-10, intracellular glucose phosphorylation, and low relative paracellular glucose permeability in well-differentiated cultures of human airway epithelia and in segments of airway epithelia excised from human tracheas. Moreover, we found that increased glucose concentration in the ASL augments growth of P. aeruginosa in vitro and in the lungs of hyperglycemic ob/ob and db/db mice in vivo. In contrast, hyperglycemia had no effect on intrapulmonary bacterial growth of a P. aeruginosa mutant that is unable to utilize glucose as a carbon source. Our data suggest that depletion of glucose in the airway epithelial surface is a novel mechanism for innate immunity. This mechanism is important for sterility of the airways and has implications in hyperglycemia and conditions that result in disruption of the epithelial barrier in the lung.

The airway epithelium: soldier in the fight against respiratory viruses

The airway epithelium acts as a frontline defense against respiratory viruses, not only as a physical barrier and through the mucociliary apparatus but also through its immunological functions. It initiates multiple innate and adaptive immune mechanisms which are crucial for efficient antiviral responses. The interaction between respiratory viruses and airway epithelial cells results in production of antiviral substances, including type I and III interferons, lactoferrin, β-defensins, and nitric oxide, and also in production of cytokines and chemokines, which recruit inflammatory cells and influence adaptive immunity. These defense mechanisms usually result in rapid virus clearance. However, respiratory viruses elaborate strategies to evade antiviral mechanisms and immune responses. They may disrupt epithelial integrity through cytotoxic effects, increasing paracellular permeability and damaging epithelial repair mechanisms. In addition, they can interfere with immune responses by blocking interferon pathways and by subverting protective inflammatory responses toward detrimental ones. Finally, by inducing overt mucus secretion and mucostasis and by paving the way for bacterial infections, they favor lung damage and further impair host antiviral mechanisms.