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1.  Human Neutrophil Peptide-1 (HNP-1): A New Anti-Leishmanial Drug Candidate 
The toxicity of available drugs for treatment of leishmaniasis, coupled with emerging drug resistance, make it urgent to find new therapies. Antimicrobial peptides (AMPs) have a strong broad-spectrum antimicrobial activity with distinctive modes of action and are considered as promising therapeutic agents. The defensins, members of the large family of AMPs, are immunomodulatory molecules and important components of innate immune system. Human neutrophil peptide-1 (HNP-1), which is produced by neutrophils, is one of the most potent defensins. In this study, we described anti-parasitic activity of recombinant HNP-1 (rHNP-1) against Leishmania major promastigotes and amastigotes. Furthermore, we evaluated the immunomodulatory effect of rHNP-1 on parasite-infected neutrophils and how neutrophil apoptosis was affected. Our result showed that neutrophils isolated from healthy individuals were significantly delayed in the onset of apoptosis following rHNP-1 treatment. Moreover, there was a noteworthy increase in dying cells in rHNP-1- and/or CpG–treated neutrophils in comparison with untreated cells. There is a considerable increase in TNF-α production from rHNP-1-treated neutrophils and decreased level of TGF-β concentration, a response that should potentiate the immune system against parasite invasion. In addition, by using real-time polymerase chain reaction (real-time PCR), we showed that in vitro infectivity of Leishmania into neutrophils is significantly reduced following rHNP-1 treatment compared to untreated cells.
Author Summary
In Iran, cutaneous leishmaniasis (CL) is a widespread and highly endemic disease in young individuals. To date, treatment strategy is based on chemotherapy accompanied with high incidence of toxicity and drug resistance. Distinctive mode of action of defensins (members of antimicrobial peptides) with low susceptibility to resistance and low toxicity to mammalian cells makes them suitable candidates for anti-leishmanial agents. The most active human defensin is human neutrophil peptide-1 (HNP-1) produced by neutrophils; the first effector cells during Leishmania infection. In this work, we used recombinant HNP-1 (rHNP-1) against both the promastigote and amastigote forms of Leishmania (L.) major. Furthermore, immunomodulatory effect of rHNP-1 on Leishmania-infected neutrophils was investigated. Our result showed that rHNP-1 has anti-parasitic effect against L. major promastigotes and amastigotes and also reduces infectivity rate of Leishmania-infected neutrophils. Moreover, assessment of cytokine production from Leishmania-infected neutrophils reveals an increase in TNF-α and a decrease in TGF-β production after rHNP-1 treatment; a cytokine pattern anticipated to facilitate control of parasites. The immunomodulatory effect of rHNP-1 on cytokine production from parasite-infected neutrophils besides its direct effect on free parasites is considered as promising step towards developing new anti-leishmanial agents.
PMCID: PMC3798388  PMID: 24147170
2.  Human Neutrophil Peptides 1–3 as Gastric Cancer Tissue Markers Measured by MALDI-Imaging Mass Spectrometry: Implications for Infiltrated Neutrophils as a Tumor Target 
Disease markers  2012;32(1):21-31.
Objective: Human neutrophil peptides (HNPs) -1, -2 and -3 are significantly upregulated and were reported as biomarkers in gastric cancer (GC). However, the tissue location and function of HNPs 1-3 are still unclear in GC, and the spatial distribution of the triad needs to be disclosed. The aims of this study were to investigate the distribution and relationships among HNPs-1, -2 and -3, and assess whether infiltrated neutrophils accumulate in gastric tumor.
Methods: In this study, paired samples (n=33) of the GC tissues and adjacent normal tissues from the same patients were obtained from surgery. Expression of HNPs 1-3 were detected by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS). The distributions of the HNPs 1-3 in GC tissues were investigated. After verification of HNPs-1 by immunohistochemistry, infiltrated neutrophils were also detected. Then, an in vitro assay was used to observe the binding capacity and measure the cytotoxic effect of HNPs-1 against AGS cells.
Results: Comparing to neighboring normal tissue, expressional level of HNPs 1-3 were significantly higher and their distributions overlapped in cancerous tissues of GC patients with high abundance in the lamina propria, whereas HNPs-1 was identified as the highest major peak. Moreover, HNPs-1, -2 and -3 correlated with each other. Besides, we also observed that increased infiltrated neutrophils accumulating in GC tissues, indicating that a strong positive correlation between HNPs 1-3 and infiltrated neutrophils. In addition, the further investigated demonstrated that the major peptide, HNPs-1, was statistically increased with the advance of tumor development from the early to advanced stage of GC (p < 0.05). Moreover, we also noticed that HNPs-1 with a great binding capacity to GC AGS cells in vitro can inhibit tumor cell growth.
Conclusions: Our results suggest that neutrophil secreted peptides, HNPs 1-3, increased in the GC tissues and could be used as potential biomarkers detected using MALDI-TOF MS, implying that elevated neutrophils may be used as a tumor target for tumor treatment. The binding capacity of HNPs-1 with GC cells implies that tracking molecules conjugated with HNPs-1 could be applied as a specific probe for GC diagnoses.
PMCID: PMC3826590  PMID: 22297599
Gastric cancer; human neutrophil peptides 1–3; MALDI-TOF MS; biomarker
3.  Intramolecular inhibition of human defensin HNP-1 by its propiece. 
Journal of Clinical Investigation  1996;97(7):1624-1629.
We examined mechanisms that protect host defense cells from their cytotoxic effector molecules. Human neutrophil peptides (HNP) 1-3 are microbicidal and cytotoxic defensins, initially synthesized as 94-amino acid preproHNP(1-94), cotranslationally proteolyzed to proHNP(20-94), then converted by removal of the anionic propiece to mature HNP(65-94)(HNP-1 and -3) and HNP(66-94) (HNP-2). We hypothesized that during synthesis and subcellular sorting the anionic propiece inhibits the cytotoxicity of the cationic defensin. We expressed preproHNP-1 cDNA in recombinant baculovirus-infected insect cells that secreted the normally transient proHNP-1(20-94) into the medium. Cyanogen bromide cleaved proHNP-1(20-94) at the fortuitously located Met64 to yield mature recombinant HNP-1(65-94) and unlinked propiece. Recombinant and native HNP-1 purified from PMN were identical as judged by mass spectrometry, retention time in reverse-phase high performance liquid chromatography, migration on acid-urea polyacrylamide gels, and reaction with a conformation-specific antibody. Recombinant and native HNP-1 had comparable microbicidal activity towards Listeria monocytogenes and were similarly potent in permeabilizing K562 leukemia cells, but proHNP-1(20-94) was virtually inactive in both assays. Addition of unlinked propiece (proHNP-1(20-64) with Met64-->homoserine) inhibited the bactericidal and cell-permeabilizing activity of mature HNP-1 in a dose-dependent manner. Linked, and to a lesser extent unlinked, propiece interfered with the binding of HNP-1 to target cells. The propiece thus acts as an efficient intramolecular inhibitor of defensin HNP-1 cytotoxicity.
PMCID: PMC507226  PMID: 8601627
4.  Sub-Inhibitory Concentrations of Human α-defensin Potentiate Neutralizing Antibodies against HIV-1 gp41 Pre-Hairpin Intermediates in the Presence of Serum 
PLoS Pathogens  2013;9(6):e1003431.
Human defensins are at the forefront of the host responses to HIV and other pathogens in mucosal tissues. However, their ability to inactivate HIV in the bloodstream has been questioned due to the antagonistic effect of serum. In this study, we have examined the effect of sub-inhibitory concentrations of human α-defensin HNP-1 on the kinetics of early steps of fusion between HIV-1 and target cells in the presence of serum. Direct measurements of HIV-cell fusion using an enzymatic assay revealed that, in spite of the modest effect on the extent of fusion, HNP-1 prolonged the exposure of functionally important transitional epitopes of HIV-1 gp41 on the cell surface. The increased lifetime of gp41 intermediates in the presence of defensin was caused by a delay in the post-coreceptor binding steps of HIV-1 entry that correlated with the marked enhancement of the virus' sensitivity to neutralizing anti-gp41 antibodies. By contrast, the activity of antibodies to gp120 was not affected. HNP-1 appeared to specifically potentiate antibodies and peptides targeting the first heptad repeat domain of gp41, while its effect on inhibitors and antibodies to other gp41 domains was less prominent. Sub-inhibitory concentrations of HNP-1 also promoted inhibition of HIV-1 entry into peripheral blood mononuclear cells by antibodies and, more importantly, by HIV-1 immune serum. Our findings demonstrate that: (i) sub-inhibitory doses of HNP-1 potently enhance the activity of a number of anti-gp41 antibodies and peptide inhibitors, apparently by prolonging the lifetime of gp41 intermediates; and (ii) the efficiency of HIV-1 fusion inhibitors and neutralizing antibodies is kinetically restricted. This study thus reveals an important role of α-defensin in enhancing adaptive immune responses to HIV-1 infection and suggests future strategies to augment these responses.
Author Summary
Human neutrophil peptide 1 (HNP-1) is a small cationic peptide that can directly block HIV-1 entry in the absence of serum. However, since serum attenuates the anti-HIV activity of this peptide, HNP-1 is unlikely to inhibit infection in the bloodstream. Here, we demonstrate that sub-inhibitory doses of HNP-1 in the presence of serum can strongly enhance the activity of neutralizing antibodies and inhibitors targeting transiently exposed intermediate conformations of HIV-1 gp41. HNP-1 appears to exert this effect by delaying post-coreceptor binding steps of fusion and thereby prolonging the exposure of gp41 intermediates. These results imply that the HIV-1 fusion kinetics is an important determinant of sensitivity to neutralizing antibodies and peptides against transiently exposed functional domains of gp41. The surprising synergy between sub-inhibitory concentrations of HNP-1 and anti-gp41 antibodies suggests new strategies to sensitize the virus to circulating antibodies by developing compounds that prolong the exposure of conserved gp41 epitopes on the cell surface.
PMCID: PMC3681749  PMID: 23785290
5.  Follicular fluid expression of alpha-defensins and their role in ovulation 
Defensins are cytotoxic peptides and have a well-defined role in host defense. Human alpha defensins 1–3 (HNP1–3) are primarily produced by peripheral neutrophils and constitute about 50% of the azurphil granule protein. Studies have suggested that peripheral neutrophils and the resident neutrophils in the ovary enhance the release of IL-8 and TNF-α that play a role in ovulation and influence fertilisation rate and IVF outcome. The production of HNP1–3 by follicular fluid and its role in ovulation has never studied. The aim of this study was to demonstrate the presence of HNP1–3 in follicular fluid and to ascertain its correlation with fertilisation rate and IVF outcome.
Women attending the Reproductive Medicine Unit at Liverpool Women’s Hospital UK, for IVF treatment were invited to participate in the study. Sixty-three patients were recruited for the study and underwent controlled ovarian stimulation and oocyte retrieval according to the unit’s protocol. Fluid from the first follicle only was collected to minimise blood contamination of the sample and HNP1–3 was estimated using ELISA technique.
HNP1–3 was detected in follicular fluid samples. The concentration did not correlate with the fertilisation rate (r = 0.01). The concentrations were also not significantly different in the women who did or did not become pregnant following treatment. Subgroup analysis showed that women with endometriosis were not more likely to have higher levels of the HNP1–3 when compared with controls (male factor infertility group).
This is the first study to show the expression of HNP1–3 in follicular fluid. HNP1–3 concentrations did not correlate with fertilisation rate or IVF outcome. It did not show an increased expression of HNP1–3 in fluid collected from women with endometriosis suggesting that inflammatory processes associated with endometriosis do not influence HNP1–3 concentration in the follicular fluid. Further studies to evaluate the correlation between HNP1–3 and IL-8 and TNF-α may clarify the role of defensins in ovulation.
PMCID: PMC2582110  PMID: 18228126
Alpha-defensin; Ovulation; Follicular fluid; Interleukin-8; Tumor necrosis factor
6.  High Fidelity Processing and Activation of the Human α-Defensin HNP1 Precursor by Neutrophil Elastase and Proteinase 3 
PLoS ONE  2012;7(3):e32469.
The azurophilic granules of human neutrophils contain four α-defensins called human neutrophil peptides (HNPs 1–4). HNPs are tridisulfide-linked antimicrobial peptides involved in the intracellular killing of organisms phagocytosed by neutrophils. The peptides are produced as inactive precursors (proHNPs) which are processed to active microbicides by as yet unidentified convertases. ProHNP1 was expressed in E. coli and the affinity-purified propeptide isolated as two species, one containing mature HNP1 sequence with native disulfide linkages (“folded proHNP1”) and the other containing non-native disulfide linked proHNP1 conformers (misfolded proHNP1). Native HNP1, liberated by CNBr treatment of folded proHNP1, was microbicidal against Staphylococcus aureus, but the peptide derived from misfolded proHNP1 was inactive. We hypothesized that neutrophil elastase (NE), proteinase 3 (PR3) or cathepsin G (CG), serine proteases that co-localize with HNPs in azurophil granules, are proHNP1 activating convertases. Folded proHNP1 was converted to mature HNP1 by both NE and PR3, but CG generated an HNP1 variant with an N-terminal dipeptide extension. NE and PR3 cleaved folded proHNP1 to produce a peptide indistinguishable from native HNP1 purified from neutrophils, and the microbicidal activities of in vitro derived and natural HNP1 peptides were equivalent. In contrast, misfolded proHNP1 conformers were degraded extensively under the same conditions. Thus, NE and PR3 possess proHNP1 convertase activity that requires the presence of the native HNP1 disulfide motif for high fidelity activation of the precursor in vitro.
PMCID: PMC3308943  PMID: 22448222
7.  Human α-Defensin Expression Is Not Dependent on CCAAT/Enhancer Binding Protein-ε in a Murine Model 
PLoS ONE  2014;9(3):e92471.
Specific granule deficiency (SGD) is a rare congenital disorder characterized by recurrent infections. The disease is caused by inactivating mutations of the CCAAT/enhancer binding protein-ε (C/EBP-ε) gene. As a consequence, specific and gelatinase granules lack most matrix proteins. Furthermore, azurophil granules contain diminished amounts of their most abundant proteins, α-defensins, also known as human neutrophil peptides (HNPs). In accordance with this, in vitro models have demonstrated induction of HNPs by C/EBP-ε. Since mice do not express myeloid defensins, they cannot per se be used to characterize the role of C/EBP-ε in controlling HNP expression in vivo. We therefore crossed a transgenic HNP-1-expressing mouse with the Cebpe-/- mouse to study the in vivo significance of C/EBP-ε for HNP-1 transcription and expression. Surprisingly, neither expression nor processing of HNP-1 was affected by lack of C/EBP-ε in these mice. Transduction of C/EBP-ε into primary bone marrow cells from HNP-1 mice induced some HNP-1 expression, but not to levels comparable to expression human cells. Taken together, our data infer that the HNP-1 of the transgenic mouse does not show an expression pattern equivalent to endogenous secondary granule proteins. This limits the use of these transgenic mice as a model for human conditions.
PMCID: PMC3962403  PMID: 24658030
8.  Direct inactivation of viruses by human granulocyte defensins. 
Journal of Virology  1986;60(3):1068-1074.
Human neutrophils contain a family of microbicidal peptides known as defensins. One of these defensins, human neutrophil peptide (HNP)-1, was purified, and its ability to directly inactivate several viruses was extensively tested. Herpes simplex virus (HSV) types 1 and 2, cytomegalovirus, vesicular stomatitis virus, and influenza virus A/WSN were inactivated by incubation with HNP-1. Two nonenveloped viruses, echovirus type 11 and reovirus type 3, were resistant to inactivation. Purified homologous peptides HNP-2 and HNP-3 were found to have HSV-1-neutralizing activities approximately equal to that of HNP-1. Inactivation of HSV-1 by HNP-1 depended on the time, temperature, and pH of incubation. Antiviral activity was abrogated by low temperature or prior reduction and alkylation of the defensins. Addition of serum or serum albumin to the incubation mixtures inhibited neutralization of HSV-1 by HNP-1. We used density gradient sedimentation techniques to demonstrate that HNP-1 bound to HSV-1 in a temperature-dependent manner. We speculate that binding of defensin peptides to certain viruses may impair their ability to infect cells.
PMCID: PMC253347  PMID: 3023659
9.  ProHNPs are specific markers of normal myelopoiesis 
Blood Cancer Journal  2014;4(3):e193-.
Pro human neutrophil peptides (proHNP)s are proforms of α-defensins produced by precursors of human neutrophils. They are secreted to bone marrow plasma in large amounts by myelocytes. We hypothesized that the plasma concentration of proHNPs might serve as a specific marker of myelopoietic activity, heralding the onset of normal myelopoiesis before reappearance of neutrophils, in the setting of bone marrow regeneration. To investigate this, plasma levels of proHNPs were measured by enzyme-linked immunosorbent assay in blood samples collected from patients undergoing allogeneic (n=11) or autologous (n=16) stem cell transplantations (SCTs) and patients receiving chemotherapy for acute leukemia (n=14). To compare proHNPs with previously suggested myeloid markers, myeloperoxidase (MPO), lysozyme and neutrophil gelatinase-associated lipocalin (NGAL) were also assayed. In all but one patient, chemotherapy led to the complete disappearance of ProHNPs from plasma. It reappeared in plasma on average 6.3 days before reappearance of neutrophils in the allogeneic setting, whereas this was reduced to an average of 2.8 days in the autologous SCT patients who received granulocyte colony-stimulating factor. Patients with acute myeloid leukemia (n=19) had significantly lower levels of plasma proHNPs than healthy controls, indicating that proHNPs are not produced by leukemic blasts. We conclude that plasma concentration of proHNPs is a clinically useful marker of normal myelopoiesis.
PMCID: PMC3972697  PMID: 24658371
10.  MDP-NOD2 stimulation induces HNP-1 secretion which contributes to NOD2 anti-bacterial function 
Inflammatory bowel diseases  2010;16(5):736-742.
Human Neutrophil Peptide 1 (HNP-1) is a defensin with antibacterial activity secreted by various cells as a component of the innate immune host defense. NOD2 is a cytoplasmic protein that recognizes bacterial derived muramyl dipeptide, and is involved in bacterial clearance. The aim of the present study was to investigate the relationship between antibacterial activity of NOD2 and HNP-1 expression in epithelial cell lines.
Gentamicin protection assay using Salmonella Typhimurium was performed in Caco-2 cells. mRNA level was determined by quantitative RT-PCR and defensin expression was assessed by Western Blot and ELISA. Nuclear Factor-κB activation was assessed using pIV luciferase and renilla plasmids. NOD2 mutant was generated by site-directed mutagenesis.
Among the defensins tested, only HNP-1 expression is induced in colonic epithelial model HCT116 cells after MDP-LD stimulation. HNP-1 secretion is significantly increased after MDP-LD stimulation in the cell supernatant of intestinal epithelial cells expressing endogenous NOD2, but not in cells which lack endogenous NOD2 expression. HNP-1 is required for NOD2 dependent NF-κB activation after MDP-LD stimulation since hnp-1 siRNA transfection abrogated response to MDP-LD stimulation. The antibacterial function of NOD2 against S. Typhimurium was impaired when expression of HNP-1 was blocked by siRNA.
HNP-1 secretion depends on NOD2 stimulation by MDP-LD and contributes to antibacterial activity in intestinal epithelial cells expressing endogenous NOD2, but not NOD2 3020insC mutant associated with increased susceptibility to Crohn’s disease.
PMCID: PMC2895931  PMID: 19856414
Crohn’s disease; NOD2; HNP-1; invasive bacteria
11.  Salivary Antimicrobial Peptide Expression and Dental Caries Experience in Children 
Dental caries is a major worldwide oral disease problem in children. Although caries are known to be influenced by dietary factors, the disease results from a bacterial infection; thus, caries susceptibility may be affected by host factors such as salivary antimicrobial peptides. This study aimed to determine a possible correlation between caries prevalence in children and salivary concentrations of the antimicrobial peptides human beta-defensin-3 (hBD-3), the cathelicidin LL37, and the alpha-defensins HNP1-3 (a mixture of HNP1, 2, 3). Oral examinations were performed on 149 middle school children, and unstimulated whole saliva was collected for immunoassays of the three peptides and for assay of caries-causing bacteria in saliva. The median salivary levels of hBD-3, LL37, and HNP1-3 were in the microgram/ml range but were highly variable in the population. While levels of LL37 and hBD-3 did not correlate with caries experience, the median HNP1-3 levels were significantly higher in children with no caries than in children with caries. Children with high caries levels did not have high levels of salivary Streptococcus mutans, and the HNP1-3 level was not correlated with salivary S. mutans. By immunohistochemistry we localized HNP1-3 in submandibular salivary duct cells. HNPs are also released by neutrophils into the gingival crevicular fluid. Both sources may account for their presence in saliva. Low salivary levels of HNP1-3 may represent a biological factor that contributes to caries susceptibility. This observation could lead to new ways to screen for caries susceptibility and to new means of assessing the risk for this common oral problem.
PMCID: PMC1195389  PMID: 16127066
12.  Molecular determinants for the interaction of human neutrophil α defensin 1 with its pro peptide 
Journal of molecular biology  2008;381(5):1281-1291.
Human neutrophil α-defensins (HNPs) are cationic antimicrobial peptides that are synthesized in vivo as inactive precursors (proHNPs). Activation requires proteolytic excision of their anionic N-terminal inhibitory pro peptide. The pro peptide of proHNP1 also specifically interacts with and inhibits the antimicrobial activity of HNP1 intermolecularly. In the light of the opposite net charges segregated in proHNP1, functional inhibition of the C-terminal defensin domain by its pro peptide is generally thought to be of electrostatic nature. Using a battery of analogs of the pro peptide and of proHNP1, we identified residues in the pro peptide region important for HNP1 binding and inhibition. Only three anionic residues in the pro peptide, Glu15, Asp20 and Glu23, were modestly important for interactions with HNP1. By contrast, the hydrophobic residues in the central part of the pro peptide, and the conserved hydrophobic motif Val24Val25Val26Leu28 in particular, were critical for HNP1 binding and inhibition. Neutralization of all negative charges in the pro peptide only partially activated the bactericidal activity of proHNP1. Our data indicate that hydrophobic forces play a dominant role in mediating the interactions between HNP1 and its pro peptide – a finding largely contrasting the commonly held view that the interactions are of electrostatic nature.
PMCID: PMC2754386  PMID: 18616948
defensin; HNP; antimicrobial peptide; pro peptide; electrostatic interaction; hydrophobic interaction
13.  Antibacterial activity of human neutrophil defensins in experimental infections in mice is accompanied by increased leukocyte accumulation. 
Journal of Clinical Investigation  1998;102(8):1583-1590.
Neutrophil defensins (or human neutrophil peptides-HNP) are major constituents of the azurophilic granules of human neutrophils and have been shown to display broad-spectrum antimicrobial activity. Other activities of these defensins, which are released from stimulated neutrophils, include cytotoxic, stimulatory, and chemotactic activities toward a variety of target cells. We studied the potential use of HNP-1 for antibacterial therapy of experimental bacterial infections in mice. In experimental peritoneal Klebsiella pneumoniae infections in mice, HNP-1 injection was shown to markedly reduce bacterial numbers in the infected peritoneal cavity 24 h after infection. This antibacterial effect was found to be associated with an increased influx of macrophages, granulocytes, and lymphocytes into the peritoneal cavity. These leukocytes appeared to be a requirement for the antibacterial effect, since in leukocytopenic mice administration of HNP-1 did not display antibacterial activity. HNP-1 treatment also reduced bacterial numbers in experimental K. pneumoniae or Staphylococcus aureus thigh muscle infections. In this model, radiolabeled HNP-1 was found to accumulate at the site of infection, whereas most of the injected HNP-1 was rapidly removed from the circulation via renal excretion. These results demonstrate that neutrophil defensins display marked in vivo antibacterial activity in experimental infections in mice and that this activity appears to be mediated, at least in part, by local leukocyte accumulation.
PMCID: PMC509009  PMID: 9788972
14.  Human α- and β-Defensins Bind to Immobilized Adhesins from Porphyromonas gingivalis▿  
Infection and Immunity  2008;76(12):5714-5720.
Human neutrophil peptide α-defensins (HNPs) and human β-defensins (HBDs) are small well-characterized peptides with broad antimicrobial activities and a diversity of innate immune functions. Although the interactions of defensins with bacteria and their membranes have been well characterized, the interactions of defensins with bacterial adhesins have not. Here we determine if HNPs and HBDs bind to the immobilized adhesins of Porphyromonas gingivalis strain 381, recombinant hemagglutinin B (rHagB) and recombinant fimbrillin A (rFimA), by surface plasmon resonance spectroscopy. Association of HNPs and HBDs with rHagB or rFimA was dose dependent and defensin specific. HBD3, HNP-2, and HNP-1 bound more readily to immobilized rHagB than HBD2 and HBD1 did. HNP-2, HNP-1, and HBD3 bound more readily to immobilized rFimA than HBD1 and HBD2 did. Binding of defensins to adhesins may serve to prevent microbial adherence to tissues, attenuate proinflammatory cytokine responses, and facilitate delivery of bound antigen to antigen-presenting cells with defensin receptors.
PMCID: PMC2583589  PMID: 18852241
15.  Upregulated expression of human neutrophil peptides 1, 2 and 3 (HNP 1-3) in colon cancer serum and tumours: a biomarker study 
BMC Cancer  2005;5:8.
Molecular markers for localized colon tumours and for prognosis following therapy are needed. Proteomics research is currently producing numerous biomarker studies with clinical potential. We investigate the protein composition of plasma and of tumour extracts with the aim of identifying biomarkers for colon cancer.
By Surface Enhanced Laser Desorption/Ionisation – Time Of Flight / Mass spectrometry (SELDI-TOF/MS) we compare the protein profiles of colon cancer serum with serum from healthy individuals and the protein profiles of colon tumours with normal colon tissue. By size exclusion chromatography, we investigate the binding of HNP 1-3 to high mass plasma proteins. By microflow we investigate the effect of HNP 1-3 on mammalian cells.
Human Neutrophil Peptides -1, -2 and -3 (HNP 1-3), also known as alfa-defensin-1, -2 and -3, are present in elevated concentrations in serum from colon cancer patients and in protein extracts from colon tumours. A fraction of HNP 1-3 in serum is bound to unidentified high mass plasma proteins. HNP 1-3 purified from colon tumours are lethal to mammalian cells.
HNP 1-3 may serve as blood markers for colon cancer in combination with other diagnostic tools. We propose that HNP 1-3 are carried into the bloodstream by attaching to high mass plasma proteins in the tumour microenvironment. We discuss the effect of HNP 1-3 on tumour progression.
PMCID: PMC548152  PMID: 15656915
16.  Suppression of Hepatic Glucose Production by Human Neutrophil α-Defensins through a Signaling Pathway Distinct from Insulin 
The Journal of biological chemistry  2008;283(18):12056-12063.
In this study, we tested the hypothesis that Human Neutrophil α-Defensins (HNPs) inhibit hepatic glucose production through a signaling pathway distinct from insulin. The effect of HNP-1 on fasting blood glucose levels and expression of hepatic gluconeogenic genes was first examined. Using hyperinsulin-emiceuglycemic clamps, we determined the effect of HNP-1 on endogenous glucose production, hepatic expression of key gluconeogenic genes, and glucose uptake in skeletal muscle in Zucker Diabetic Fatty (ZDF) rats. In isolated primary hepatocytes, we studied the effect of HNP-1 and -2 on glucose production, expression of gluconeogenic genes, and phosphorylation of Akt, c-Src, and FoxO1. Our results show that HNP-1 reduced blood glucose levels of both normal mice and ZDF rats predominantly through suppression of hepatic glucose production. HNPs inhibited glycogenolysis and gluconeogenesis in isolated hepatocytes. HNPs also suppressed expression of key gluconeogenic genes including phosphoenoylpyruvate carboxy kinase (PEPCK) and glucose-6-phosphatase (G6Pase). To investigate the mechanism, we found that HNPs stimulated phosphorylation of Akt and FoxO1 without activating IRS1. Nevertheless, HNPs activated c-Src. Blockade of c-Src activity with either a chemical inhibitor PP2 or an alternative inhibitor CSK prevented the inhibitory effect of HNPs on gluconeogenesis. Together, our results support the hypothesis that HNPs can suppress hepatic glucose production through an intracellular mechanism distinct from the classical insulin signaling pathway.
PMCID: PMC2335365  PMID: 18347011
17.  Monocyte-chemotactic activity of defensins from human neutrophils. 
Journal of Clinical Investigation  1989;84(6):2017-2020.
We investigated the monocyte-chemotactic activity of fractionated extracts of human neutrophil granules. Monocyte-chemotactic activity was found predominantly in the defensin-containing fraction of the neutrophil granules. Purified preparations of each of the three human defensins (HNP-1, HNP-2, HNP-3) were then tested. HNP-1 demonstrated significant chemotactic activity for monocytes: Peak activity was seen at HNP-1 concentrations of 5 X 10(-9) M and was 49 +/- 20% (mean +/- SE, n = 9) of that elicited by 10(-8) M FMLP. HNP-2 (peak activity at 5 X 10(-9) M) was somewhat less active, yielding 19 +/- 10% (n = 11). HNP-3 failed to demonstrate chemotactic activity. Checkerboard analysis of monocyte response to HNP-1 and HNP-2 confirmed that their activity was chemotactic rather than chemokinetic. Neutrophils demonstrated a low level of response to defensins but this reaction was primarily chemokinetic. Defensins may play a role in the recruitment of monocytes by neutrophils into inflammatory sites.
PMCID: PMC304087  PMID: 2592571
18.  Defensins attenuate cytokine responses yet enhance antibody responses to Porphyromonas gingivalis adhesins in mice 
Future microbiology  2010;5:115.
Our aim is to assess the ability of human neutrophil peptide α-defensins (HNPs) and human β-defensins (HBDs) to attenuate proinflammatory cytokine responses and enhance antibody responses to recombinant hemagglutinin B (rHagB) or recombinant fimbrillin A (rFimA) from Porphyromonas gingivalis 381 in mice.
Materials & methods
In the first study, C57BL/6 mice were given 10 μg rHagB or rFimA without and with 1 μg HNP1, HNP2, HBD1, HBD2 or HBD3. At 24 h, mice were euthanized and cytokine concentrations were determined in nasal wash fluid (NWF), bronchoalveolar lavage fluids, saliva and serum. In the second study, C57BL/6 mice were given 10 μg rHagB or rFimA without and with 1 μg HNPs or HBDs similarly on days 0, 7 and 14. At 21 days, mice were euthanized and rHagB- and rFimA-specific antibody responses were determined in NWF, bronchoalveolar lavage fluids, saliva and serum.
Mice given rHagB + HNP2, rHagB + HBD1 and rHagB + HBD3 produced significantly lower (p < 0.05) IL-6 responses than mice given rHagB alone. Mice given rHagB + HNP1, rHagB + HNP2, rHagB + HBD1 and rHagB + HBD3 produced significantly lower (p < 0.05) keratinocyte-derived chemokine responses than mice given rHagB alone. Mice given rFimA produced very low levels of IL-6 and only moderate levels of keratinocyte-derived chemokine in NWF that were not attenuated by prior incubation of rFimA with any defensin. Mice given rHagB + HNP1 produced a significantly higher (p < 0.05) serum IgG antibody response than mice given rHagB alone and mice given rFimA + HNP2 produced a higher, but not significant, antibody response.
The ability of HNPs and HBDs to attenuate proinflammatory cytokine responses in murine NWF and enhance IgG antibody responses in serum was dependent upon both the defensin and antigen of P. gingivalis.
PMCID: PMC2822342  PMID: 20020833
defensins; fimbriae A; hemagglutinin B; immunity; Porphyromonas gingivalis
19.  Mast cell activation and its relation to proinflammatory cytokine production in the rheumatoid lesion 
Arthritis Research  1999;2(1):65-74.
Mast cell (MC) activation in the rheumatoid lesion provides numerous mediators that contribute to inflammatory and degradative processes, especially at sites of cartilage erosion. MC activation in rheumatoid synovial tissue has often been associated with tumour necrosis factor (TNF)-α and interleukin (IL)-1β production by adjacent cell types. By contrast, our in situ and in vitro studies have shown that the production of IL-15 was independent of MC activation, and was not related to TNF-α and IL-1β expression. Primary cultures of dissociated rheumatoid synovial cells produced all three proinflammatory cytokines, with production of IL-1β exceeding that of TNF-α, which in turn exceeded that of IL-15. In vitro cultures of synovial macrophages, synovial fibroblasts and articular chondrocytes all produced detectable amounts of free IL-15, macrophages being the most effective.
Increased numbers of mast cells (MCs) are found in the synovial tissues and fluids of patients with rheumatoid arthritis (RA), and at sites of cartilage erosion. MC activation has been reported for a significant proportion of rheumatoid specimens. Because the MC contains potent mediators, including histamine, heparin, proteinases, leukotrienes and multifunctional cytokines, its potential contributions to the processes of inflammation and matrix degradation have recently become evident.
Proinflammatory cytokines are important mediators of inflammation, immunity, proteolysis, cell recruitment and proliferation. Tumour necrosis factor (TNF) reportedly plays a pivotal role in the pathogenesis of RA, especially its ability to regulate interleukin (IL)-1β expression, this being important for the induction of prostanoid and matrix metalloproteinase production by synovial fibroblasts and chondrocytes. IL-15 has been assigned numerous biological effects and has been implicated as an important factor in TNF-α expression by monocyte/macrophages. Some in vitro studies have placed IL-15 upstream from TNF-α in the cytokine cascade, suggesting an interdependence between TNF, IL-1 and IL-15 for the promotion of proinflammatory cytokine expression in the rheumatoid joint.
To examine the in situ relationships of TNF-α, IL-1β and IL-15 in relation to MC activation in rheumatoid tissues by use of immunolocalization techniques; and to compare quantitatively the proinflammatory cytokine production by specific cell cultures and rheumatoid synovial explants with and without exposure to a MC secretagogue.
Materials and methods:
Samples of rheumatoid synovial tissue and cartilage–pannus junction were obtained from patients (n = 15) with classic late-stage RA. Tissue sections were immunostained for MC (tryptase) and the proinflammatory cytokines IL-1, TNF-α and IL-15. Rheumatoid synovial tissue explants were cultured in Dulbecco's modified Eagles medium (DMEM) containing either the MC secretagogue rabbit antihuman immunoglobulin (Ig)E, or control rabbit IgG. Primary rheumatoid synovial cell cultures, human articular chondrocytes, synovial fibroblasts and synovial macrophages were prepared as described in the full article. Conditioned culture media from these cultures were collected and assayed for IL-1β, TNF-α and IL-15 using enzyme-linked immunosorbent assay methodology.
Immunohistological studies of rheumatoid synovial tissues have demonstrated local concentrations of MCs in most specimens of the rheumatoid lesion. Sites of MC activation were associated with localized oedema, and TNF-α, IL-1α and IL-1β production by a proportion of mononuclear inflammatory cells. By contrast, no evidence was found for IL-15 production in tissue sites containing either intact or activated MCs, and IL-15 expression, when observed, bore no relation to tissue sites where TNF-α and IL-1β were evident. The immunodetection of IL-15 was restricted to microfocal sites and was not typical of most junctional specimens, but was associated with a proportion of articular chondrocytes in a minority of junctional specimens.
MC activation within synovial explant cultures was induced by the addition of polyclonal antibody to human IgE. MC activation significantly reduced the levels of TNF-α and IL1β released into the medium, this representing approximately 33% of control values. By contrast, MC activation had little effect on the levels of IL-15 released into the culture medium, the average value being very low in relation to the release of TNF-α and IL-1β . Thus, induced MC activation brings about changes in the amounts of released tryptase, TNF-α and IL-1β , but not of IL-15.
Four preparations of primary rheumatoid synovial cell cultures produced more IL-1β than TNF-α, with only modest values for IL-15 production, indicating that all three cytokines are produced and released as free ligands by these cultures. Of specific cell types that produced IL-15 in vitro, macrophages produced more than fibroblasts, which in turn produced more than chondrocytes. This demonstrates that all three cell types have the potential to produce IL-15 in situ.
The biological consequences of MC activation in vivo are extremely complex, and in all probability relate to the release of various combinations of soluble and granular factors, as well as to the expression of appropriate receptors by neighbouring cells. The subsequent synthesis and release of cytokines such as TNF-α and IL-1 may well follow at specific stages after activation, or may be an induced cytokine response by adjacent macrophagic or fibroblastic cells. However, because no IL-15 was detectable either in or around activated or intact MCs, and the induced MC activation explant study showed no change in IL-15 production, it seems unlikely that the expression of this cytokine is regulated by MCs. The immunohistochemistry (IHC) demonstration of IL-15 at sites of cartilage erosion, and especially by some chondrocytes of articular cartilage, showed no spatial relationship with either T cells or neutrophils, and suggests other functional properties in these locations. The lack of evidence for an in situ association of IL-15 with TNF and IL-1 does not support a role for IL-15 in a proinflammatory cytokine 'cascade', as proposed by other in vitro experiments. We believe that sufficient evidence is available, however, to suggest that MC activation makes a significant contribution to the pathophysiological processes of the rheumatoid lesion.
PMCID: PMC17805  PMID: 11219391
interleukin-15; interleukin-1β; mast cells; rheumatoid arthritis; tumour necrosis factor-α
20.  Modulation of the in vitro candidacidal activity of human neutrophil defensins by target cell metabolism and divalent cations. 
Journal of Clinical Investigation  1988;81(6):1829-1835.
We tested the in vitro susceptibility of Candida albicans to three defensins from human neutrophilic granulocytes (HNP-1, 2, and 3), a homologous defensin from rabbit leukocytes (NP-1), and four unrelated cationic peptides. Although the primary amino acid sequences of HNP-1, 2, and 3 are identical except for a single amino-terminal amino acid alteration, HNP-1 and HNP-2 killed C. albicans but HNP-3 did not. C. albicans blastoconidia were protected from HNP-1 when incubations were performed in the absence of oxygen or in the presence of inhibitors that blocked both of its mitochondrial respiratory pathways. Neither anaerobiosis nor mitochondrial inhibitors substantially protected C. albicans exposed to NP-1, poly-L-arginine, poly-L-lysine, or mellitin. Human neutrophilic granulocyte defensin-mediated candidacidal activity was inhibited by both Mg2+ and Ca2+, and was unaffected by Fe2+. In contrast, Fe2+ inhibited the candidacidal activity of NP-1 and all of the model cationic peptides, whereas Mg2+ inhibited none of them. These data demonstrate that susceptibility of C. albicans to human defensins depends both on the ionic environment and on the metabolic state of the target cell. The latter finding suggests that leukocyte-mediated microbicidal mechanisms may manifest oxygen dependence for reasons unrelated to the production of reactive oxygen intermediates by the leukocyte.
PMCID: PMC442632  PMID: 3290255
21.  Defensins. Natural peptide antibiotics of human neutrophils. 
Journal of Clinical Investigation  1985;76(4):1427-1435.
We extracted a granule-rich sediment from normal human neutrophils and subjected it to chromatographic, electrophoretic, and functional analysis. The extract contained three small (molecular weight less than 3,500) antibiotic peptides that were named human neutrophil peptide (HNP)-1, HNP-2, and HNP-3, and which will be referred to as "defensins." HNP 1-3, a mixture of the three defensins, killed Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli effectively in vitro when tested in 10 mM phosphate buffer containing certain nutrients, but it had little or no bactericidal activity in nutrient-free buffer. In contrast, the nutrient-free buffer supported a high degree of activity by HNP 1-3 against Cryptococcus neoformans. In addition to its antibacterial and antifungal properties, HNP 1-3 directly inactivated herpes simplex virus, Type 1. Two of the individual purified defensins, HNP-1 and HNP-2, were as microbicidal as the mixture HNP 1-3. HNP-3 was less active than the other defensins against most but not all of the microbes tested. Immunoperoxidase stains revealed HNP 1-3 to have a granular localization in the neutrophil's cytoplasm by light microscopy. Frozen thin section immunogold transmission electron microscopy showed HNP 1-3 to be localized in azurophil granules. These studies define a broad-spectrum antimicrobial system in human neutrophils. The defensin system may operate in conjunction with or independently from oxygen-dependent microbicidal processes to enable human neutrophils to inactivate and destroy potential pathogens.
PMCID: PMC424093  PMID: 2997278
22.  Human α-Defensins Inhibit Hemolysis Mediated by Cholesterol-Dependent Cytolysins▿  
Infection and Immunity  2009;77(9):4028-4040.
Many pathogenic gram-positive bacteria release exotoxins that belong to the family of cholesterol-dependent cytolysins. Here, we report that human α-defensins HNP-1 to HNP-3 acted in a concentration-dependent manner to protect human red blood cells from the lytic effects of three of these exotoxins: anthrolysin O (ALO), listeriolysin O, and pneumolysin. HD-5 was very effective against listeriolysin O but less effective against the other toxins. Human α-defensins HNP-4 and HD-6 and human β-defensin-1, -2, and -3 lacked protective ability. HNP-1 required intact disulfide bonds to prevent toxin-mediated hemolysis. A fully linearized analog, in which all six cysteines were replaced by aminobutyric acid (Abu) residues, showed greatly reduced binding and protection. A partially unfolded HNP-1 analog, in which only cysteines 9 and 29 were replaced by Abu residues, showed intact ALO binding but was 10-fold less potent in preventing hemolysis. Surface plasmon resonance assays revealed that HNP-1 to HNP-3 bound all three toxins at multiple sites and also that solution-phase HNP molecules could bind immobilized HNP molecules. Defensin concentrations that inhibited hemolysis by ALO and listeriolysin did not prevent these toxins from binding either to red blood cells or to cholesterol. Others have shown that HNP-1 to HNP-3 inhibit lethal toxin of Bacillus anthracis, toxin B of Clostridium difficile, diphtheria toxin, and exotoxin A of Pseudomonas aeruginosa; however, this is the first time these defensins have been shown to inhibit pore-forming toxins. An “ABCDE mechanism” that can account for the ability of HNP-1 to HNP-3 to inhibit so many different exotoxins is proposed.
PMCID: PMC2738040  PMID: 19581399
23.  Evaluation of susceptibility of gram-positive and -negative bacteria to human defensins by using radial diffusion assay. 
Antimicrobial Agents and Chemotherapy  1996;40(10):2280-2284.
Defensins are small cationic bactericidal peptides present abundantly in the granules of polymorphonuclear neutrophils (PMNs). Human PMNs contain four defensins termed HNP-1 to HNP-4. We used a new assay system in agar plates, the radial diffusion assay, to evaluate the effects of human defensins against gram-positive and -negative bacteria. A crude mixture of HNP-1, -2, and -3 (crude HNPs) was purified from human PMN extracts by reversed-phase high-pressure liquid chromatography (RP-HPLC). The different components were later separated by RP-HPLC and gel permeation chromatography. We compared the antibacterial activities of purified HNP-1, -2, and -3 against Escherichia coli, Pseudomonas aeruginosa, methicillin-susceptible Staphylococcus aureus, and methicillin-resistant S. aureus strains using the radial diffusion assay. The antibacterial activities of HNP-1 and HNP-2 against all strains tested were similar to those of the crude HNPs, but the activity of HNP-3 was less than those of the other defensins. To quantitate the activities of HNPs against different bacteria, we defined the minimal dose of crude HNPs forming a detectable clear zone around the bacteria as the minimal inhibitory dose (MID) and determined the MIDs for 10 strains of E. coli, 12 strains of P. aeruginosa, 10 strains of methicillin-susceptible S. aureus, and 12 strains of methicillin-resistant S. aureus isolates, including clinical isolates. In general, the MIDs of the HNPs were similar against similar bacterial species. However, the MIDs for P. aeruginosa were higher than those for the other organisms tested. The radial diffusion assay is suitable as a screening test for measuring the susceptibilities of isolates to defensins, because it is sensitive and simple and has good reproducibility.
PMCID: PMC163519  PMID: 8891130
24.  Impact Of Pro Segments On The Folding And Function Of Human Neutrophil α-Defensins 
Journal of molecular biology  2007;368(2):537-549.
Human neutrophil α-defensins (HNPs) are synthesized in vivo as inactive precursor proteins, i.e., preproHNPs. A series of sequential proteolytic events excise the N-terminal inhibitory pro peptide, leading to defensin maturation and storage in azurophilic granules. The anionic pro peptide, required for correct sub-cellular trafficking and sorting of proHNPs, inhibits the antimicrobial activity of cationic defensins, either inter- or intra-molecularly, presumably through charge neutralization. To better understand the role of the pro peptide in the folding and functioning of α-defensins and/or pro α-defensins, we chemically attached the proHNP1 pro peptide or wtpro peptide and the following artificial pro segments to the N-terminus of HNP1: polyethylene glycol (PEG), Arg10 (polyR), Ser10 (polyS), and crpro peptide – a charge-reversing mutant of the pro peptide where Arg/Lys residues were changed to Asp, and Asp/Glu residues to Lys. Comparative in vitro folding suggested that while all artificial pro segments chaperoned defensin folding, with PEG being the most efficient, the pro peptide catalyzed the folding of proHNPs likely through two independent mechanisms: solubilization of and interaction with the C-terminal defensin domain. Further, the N-terminal artificial pro segments dramatically altered the bactericidal activity of HNP1 against both E. coli and S. aureus. Surprisingly, crpro peptide and wtpro peptide showed similar properties with respect to intra-molecular and inter-molecular catalysis of defensin folding as well as α-defensin binding, although their binding modes appeared different. Our findings identify a dual chaperone activity of the pro peptide and may shed light on the molecular mechanisms by which pro α-defensins fold in vivo.
PMCID: PMC2754399  PMID: 17355880
defensin; HNP; pro peptide; native chemical ligation; chaperone
25.  In Vitro Antibacterial Activities of Platelet Microbicidal Protein and Neutrophil Defensin against Staphylococcus aureus Are Influenced by Antibiotics Differing in Mechanism of Action 
Thrombin-induced platelet microbicidal protein-1 (tPMP-1) and human neutrophil defensin-1 (HNP-1) are small, cationic antimicrobial peptides. These peptides exert potent in vitro microbicidal activity against a broad spectrum of human pathogens, including Staphylococcus aureus. Evidence suggests that tPMP-1 and HNP-1 target and disrupt the bacterial membrane. However, it is not yet clear whether membrane disruption itself is sufficient to kill the bacterium or whether subsequent, presumably intracellular, events are also involved in killing. We investigated the staphylocidal activities of tPMP-1 and HNP-1 in the presence or absence of pretreatment with antibiotics that differ in their mechanisms of action. The staphylocidal effects of tPMP-1 and HNP-1 on control cells (no antibiotic pretreatment) were rapid and concentration dependent. Pretreatment of S. aureus with either penicillin or vancomycin (bacterial cell wall synthesis inhibitors) significantly enhanced the anti-S. aureus effects of tPMP-1 compared with the effects against the respective control cells over the entire tPMP-1 concentration range tested (P < 0.05). Similarly, S. aureus cells pretreated with these antibiotics were more susceptible to HNP-1 than control cells, although the difference in the effects against cells that received penicillin pretreatment did not reach statistical significance (P < 0.05 for cells that received vancomycin pretreatment versus effects against control cells). Studies with isogenic pairs of strains with normal or deficient autolytic enzyme activities demonstrated that enhancement of S. aureus killing by cationic peptides and cell wall-active agents could not be ascribed to a predominant role of autolytic enzyme activation. Pretreatment of S. aureus cells with tetracycline, a 30S ribosomal subunit inhibitor, significantly decreased the staphylocidal effect of tPMP-1 over a wide peptide concentration range (0.16 to 1.25 μg/ml) (P < 0.05). Furthermore, pretreatment with novobiocin (an inhibitor of bacterial DNA gyrase subunit B) and with azithromycin, quinupristin, or dalfopristin (50S ribosomal subunit protein synthesis inhibitors) essentially blocked the S. aureus killing resulting from exposure to tPMP-1 or HNP-1 at most concentrations compared with the effects against the respective control cells (P < 0.05 for a tPMP-1 concentration range of 0.31 to 1.25 μg/ml and for an HNP-1 concentration range of 6.25 to 50 μg/ml). These findings suggest that tPMP-1 and HNP-1 exert anti-S. aureus activities through mechanisms involving both the cell membrane and intracellular targets.
PMCID: PMC89119  PMID: 10223922

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