			Home About us Contact

Defensins

Distribution by Scientific Domains

Medical Sciences	50%
Life Sciences	36%
Chemistry	13%

Distribution within Medical Sciences

Immunology	26%
Dermatology	20%
Periodontology	10%
Oral Sciences & Technology	4%
9 Other Subdomains	40%

Selected Abstracts

The malaria vector mosquito Anopheles gambiae expresses a suite of larval-specific defensin genes

INSECT MOLECULAR BIOLOGY, Issue 2 2008
J. M. Meredith
Abstract cDNAs of Anopheles gambiae Defensin 2 (AgDef2), Defensin 3 (AgDef3) and Defensin 4 (AgDef4), identified in the genome sequence, have been characterized and their expression profiles investigated. In contrast to both typical defensins and insect antimicrobial peptides generally, the newly identified defensins were not upregulated with acute-phase kinetics following immune challenge in insects or cell culture. However, mRNA abundance of AgDef2, AgDef3 and AgDef4 increased significantly during the larval stages. Promoter analysis of all three genes failed to identify putative immune response elements previously identified in other mosquito defensin genes. As previous studies failed to identify these larval-specific defensins, it seems likely that further antimicrobial peptide genes with nontypical expression profiles will be identified as more genome sequences become available. [source]

A novel association between clustered NF-,B and C/EBP binding sites is required for immune regulation of mosquito Defensin genes

INSECT MOLECULAR BIOLOGY, Issue 4 2006
J. M. Meredith
Abstract A comparative analysis identified key cis -acting regulatory elements responsible for the temporal control of mosquito Defensin gene expression. The promoters of Anopheles gambiae Defensin 1 and two isoforms of Aedes aegypti Defensin A are up-regulated by immune challenge. This stimulated activity depends upon a cluster of three NF-,B binding sites and closely associated C/EBP-like motifs, which function as a unit for optimal promoter activity. Binding of NF-,B and C/EBP like transcription factors is confirmed by electrophoretic mobility shift assay, including supershifts with antibodies to C/EBP. ,B-like motifs are abundant within antimicrobial peptide gene promoters and most are very closely associated with putative C/EBP binding sites. This novel association between NF-,B and C/EBP binding sites may, therefore, be of widespread significance. [source]

Expression of ,-defensin 1 and 2 mRNA by human monocytes, macrophages and dendritic cells

IMMUNOLOGY, Issue 4 2002
Louise A. Duits
Summary Human ,-defensins are broad-spectrum antimicrobial peptides known to be produced by epithelial cells. It was recently shown that ,-defensins also display chemotactic activity for dendritic cells (DC) and T cells, and thus may serve to link innate and adaptive immunity. The aim of the present study was to explore expression of mRNA for these peptides in mononuclear phagocytes and DC. The results revealed that monocytes, monocyte-derived-macrophages (MDM), and monocyte-derived-dendritic cells (DC) all express human-,-defensin-1 (hBD-1) mRNA. hBD-1 mRNA expression by monocytes and MDM was increased after activation with interferon-, (IFN-,) and/or lipopolysaccharide (LPS) in a dose- and time-dependent fashion. Alveolar macrophages showed an intense hBD-1 expression, which could not be further increased. Expression of hBD-1 mRNA by immature DC was low, and increased considerably after maturation. Monocytes, MDM, alveolar macrophages and DC showed a limited expression of human ,-defensin-2 (hBD-2) mRNA, which could only be increased in monocytes and alveolar macrophages by IFN-, and/or LPS in a dose- and time-dependent fashion. Immunocytochemical stainings demonstrated the expression of hBD-2 peptide by freshly isolated blood monocytes and alveolar macrophages in cytospin preparations. [source]

Pyrosequencing and characterization of immune response genes from the American dog tick, Dermacentor variabilis (L.)

INSECT MOLECULAR BIOLOGY, Issue 5 2010
D. C. Jaworski
Abstract Ticks continue to be a threat to animal and human health, and new and novel control strategies are needed for ticks and tick-borne pathogens. The characterization of the tick,pathogen interface and the tick immune response to microbial infections is fundamental toward the formulation of new control strategies for ticks and the pathogens they transmit. Our overall hypothesis for this research is that the tick immune system manages the maintenance of pathogens. Therefore, discovery of tick immune response genes may provide targets for novel control strategies directed toward reducing vector competency and pathogen transmission. In these studies, 454 pyrosequencing, a high-throughput genomic sequencing method was used to discover tick genes expressed in response to bacterial and fungal infections. Expressed sequence tags (ESTs) were analysed from Dermacentor variabilis ticks that had been injected with bacteria (Escherichia coli, Bacillus subtilis, Micrococcus luteus) or fungi (Saccharomyces cerevisiae and Candida albicans) and ticks that were naturally infected with the intracellular bacterium, Anaplasma marginale. By this approach, ESTs were assembled into 5995 contigs. Contigs fell into the five main functional categories of metabolism, genetic information processing, environmental information processing, cellular processes and human diseases. We identified more than 30 genes that are likely to encode for proteins involved in tick immune function. We further analysed by reverse transcriptase PCR (RT-PCR) the expression of 22 of these genes in each of our bacterial or fungal treatment groups and found that seven were up-regulated. Up-regulation of these seven genes was confirmed for bacterial, but not fungal treatment by quantitative PCR (qPCR). One of these products was novel, encoding a new tick defensin. Our results clearly demonstrate the complexities of the tick immune system and mark new directions for further study and characterization of proteins that modulate microbial infections in the American dog tick. [source]

Identification and characterization of antimicrobial peptide, defensin, in the taiga tick, Ixodes persulcatus

INSECT MOLECULAR BIOLOGY, Issue 4 2009
Y. Saito
Abstract Ixodes persulcatus is the primary vector for human tick-borne diseases in Japan. A cDNA library was constructed from whole body homogenates of fed nymphs of I. persulcatus. From this library, one cDNA encoding defensin-like antimicrobial peptide was identified. The amino-acid sequence showed high similarity to those of the defensins of other ticks and arthropods. I. persulcatus defensin mRNA transcripts were detected at all life cycle stages of fed ticks and found to be predominantly expressed in the midguts of adult female ticks, but not in the salivary glands, a finding corroborated by Western blotting analysis. To investigate the function of I. persulcatus defensin, we examined its antibacterial activity by evaluation of growth of several bacterial strains in the presence of the synthetic peptide. The defensin from I. persulcatus markedly inhibited the growth of Gram-positive bacteria including Staphylococcus aureus, Bacillus subtilis and Corynebacterium renale, but not Gram-negative bacteria except Escherichia coli O157. In conclusion, these results suggest that I. persulcatus defensin may be playing a significant role in the defence against microbes from bloodmeals. [source]

A p38 MAP kinase regulates the expression of the Aedes aegypti defensin gene in mosquito cells

INSECT MOLECULAR BIOLOGY, Issue 4 2007
R. Chen-Chih Wu
Abstract An Aedes aegypti p38 (Aap38) mitogen-activated protein kinase was isolated and characterized in this study. The 1761 bp long full-length Aap38 cDNA encodes an open reading frame of 358 amino acids, exhibiting characteristics of Thr/Tyr dual kinase specificities. We showed that bacteria activate both the kinase activity of Aap38 and the expression of the Aedes aegypti defensin A (AaDefA) gene, which is inhibited by a p38 kinase inhibitor SB203580 and dsRNA interference of Aap38. A similar result was obtained by a reporter construct containing the AaDefA regulatory region linked to Ds-Red. The lipopolysaccharide-activated reporter gene was inhibited by SB203580. In addition, Aap38 translocated to the nucleus after lipopolysaccharide induction. Our findings suggest that the p38 protein kinase pathway is involved in the antibacterial peptide synthesis in mosquitoes. [source]

Gene organization of a novel defensin of Ixodes ricinus: first annotation of an intron/exon structure in a hard tick defensin gene and first evidence of the occurrence of two isoforms of one member of the arthropod defensin family

INSECT MOLECULAR BIOLOGY, Issue 4 2007
N. Rudenko
Abstract Antimicrobial peptides (defensins) are effectors of the immune system. Herein, we describe a novel Ixodes ricinus defensin gene(s), analyse its structure and compare it with other known antimicrobial peptides from different tick species. For the first time, an intron/exon structure is discovered in a hard-tick defensin gene. The intron/exon genomic organization of the gene is similar to the organization in Ornithodoros moubata, but not to that of the intronless defensins of Dermacentor variabilis and Ixodes scapularis. The analysis of the deduced amino acid sequences of different recombinants from the I. ricinus cDNA library reveals the presence of two defensin isoforms with three amino acid substitutions. Whether or not these substitutions affect the biological properties of the peptides is currently unknown. The expression of the defensin gene is strongly induced in the tick midgut after infection with Borrelia burgdorferi. [source]

An optimized method for intensive screening of molecules that stimulate , -defensin 2 or 3 (hBD2 or hBD3) expression in cultured normal human keratinocytes

INTERNATIONAL JOURNAL OF COSMETIC SCIENCE, Issue 3 2005
I. Pernet
Synopsis Normal human skin controls the intrusion of microorganisms by the production of peptide antibiotics such as defensins. The aim of our study was to develop a culture model of normal human keratinocytes for optimal , -defensin mRNA detection which allows the screening of molecules able to stimulate hBD2 and hBD3 without inducing pro-inflammatory cytokines. A keratinocyte culture model in 96-well plates, in high calcium medium (1.7 mm) allowed to analyze hBD2 and hBD3 mRNA expression in basal condition and after cell stimulation by products from diverse vegetal extracts. The release of IL-8 and the chemokine MIP-3, was also evaluated in cell supernatants by ELISA. Among the 184 extracts tested, 75 showed a stimulatory effect on , -defensin expression: 40 on hBD2, 26 on hBD3 and nine on both defensins. Fifteen of these substances which also induced the release of pro-inflammatory cytokines were eliminated. Among the other substances, four were selected and were analyzed in a dose-dependent study (n = 4) by real-time quantitative RT-PCR and completed by a measure of MIP-3,, IL-8 and IL-1, levels. These data underline the important necessity of screening result controls by a quantitative method reproduced at least three times. This new method of intensive screening allowed us to exhibit vegetal extracts that were able to stimulate epidermal , -defensin expression without inducing an up-secretion of pro-inflammatory cytokines. Résumé La peau humaine normale exerce une fonction barrière contre l'intrusion de microorganismes par la production de peptides antibiotiques comme les défensines. Le but de cette étude a consistéà mettre au point un modèle de culture de kératinocytes humains normaux permettant une détection optimale des ARNm des défensines en général, et adapté au screening de molécules aptes à stimuler les défensines épidermiques hBD2 et hBD3 en particulier, sans induire de cytokines pro-inflammatoires. Un modèle de culture de kératinocytes en plaques 96 puits, en milieu riche en calcium (1,7 mm) permet une analyse de l'expression des ARNm de hBD2 et hBD3 en condition basale et après stimulation par divers extraits végétaux. La sécrétion d'IL-8 et de la chimiokine MIP-3, a étéévaluée dans les surnageants de culture par ELISA. Parmi les 184 extraits testés, 75 montrent un effet stimulant sur l'expression des , -défensines : 40 ont un effet sur hBD2, 26 sur hBD3 et 9 sur les 2 types de défensines. Quinze de ces actifs qui induisent aussi la sécrétion de cytokines pro-inflammatoires ont étééliminés. Parmi les autres molécules, 4 ont été sélectionnées pour faire l'objet d'une étude de leurs effets-doses (n = 4) sur l'expression des , -défensines par une technique quantitative de RT-PCR en temps réel. Cette étude est complétée par le dosage des cytokines IL-1,, IL-8 et MIP-3,. Les résultats obtenus soulignent l'importante nécessitée de contrôler au moins trois fois par une méthode quantitative les résultats d'un screening. Cette nouvelle méthode de screening intensif nous a permis de mettre en évidence des extraits végétaux capables de stimuler les défensines épidermiques sans induire de cytokines pro-inflammatoires. [source]

SNPs in human ,-defensin 1 gene (DEFB1): frequencies in a Mexican population and new PCR,RFLPs assays

INTERNATIONAL JOURNAL OF IMMUNOGENETICS, Issue 5 2006
E. Prado-Montes de Oca
Summary Polymerase chain reaction,restriction fragment length polymorphism assays for two single nucleotide polymorphisms in the human ,-defensin 1 gene have been validated with real-time PCR in 101 healthy individuals from western Mexico. Allele frequencies were 52.5% (692-A) and 98.5% (1836-A). These assays can be confidently used as a cheaper alternative genotyping method for these sites. [source]

Arthropod defensins illuminate the divergence of scorpion neurotoxins

JOURNAL OF PEPTIDE SCIENCE, Issue 12 2004
Dr Oren Froy
Abstract Defensins are phylogenetically ancient antibacterial polypeptides found in plants and animals. Isolation of the cDNA and genomic sequences encoding the scorpion (Leiurus quinquestriatus hebraeus) defensin revealed similarity to scorpion neurotoxins in gene organization (two exons and a phase I intron) and intron characteristics (conserved acceptor, donor and putative branch sites). This commonality, alongside a similar core structure, protein sequence and bioactivity suggest that arthropod defensins and scorpion neurotoxins share a common ancestor. Interestingly, phylogenetic analysis of defensins and scorpion neurotoxins illuminates for the first time a putative evolutionary trajectory for scorpion sodium and potassium channel neurotoxins. Copyright © 2004 European Peptide Society and John Wiley & Sons, Ltd. [source]

Differential regulation of immune responses by odontoblasts

MOLECULAR ORAL MICROBIOLOGY, Issue 1 2007
O. Veerayutthwilai
Odontoblasts (OBs) are cells lining the inner surface of the tooth. Their potential role in host defenses within the tooth is suggested by their production of antimicrobial , -defensins, but their role needs confirmation. The present study sought to define the roles of human OBs in microbial recognition and innate host responses. Toll-like receptor 2 (TLR2) and TLR4, as well as CCR6, were immunolocalized in human OBs and their dentinal processes in situ. To examine OB function we used organotypic tooth crown cultures to maintain human OBs within their dentin scaffold. Cells in the OB layer of cultured and non-cultured crown preparations expressed mRNA for several markers of innate immunity including chemokine CCL20, chemokine receptor CCR6, TLR2, TLR4 and the OB marker dentin sialophosphoprotein (DSPP). Expression of human , -defensin 1 (hBD1), hBD2, hBD3, interleukin-8 (IL-8), and CCL20 increased with time in culture. Tooth crown odontoblast (TcOB) cultures were stimulated with agonist that was specific for TLR2 (Pam3CSK4) or TLR4 [Escherichia coli lipopolysaccharide (LPS)]. Nuclear factor- ,B assays confirmed the TLR2 activity of Pam3CSK4 and the TLR4 activity of LPS. LPS up-regulated IL-1,, tumor necrosis factor- , (TNF- ,), CCL20, hBD2, IL-8, TLR2 and TLR4; however, Pam3CSK4 down-regulated these mRNAs. IL-1,, TNF- ,, CCL20 were also up-regulated from six-fold to 30-fold in TcOB preparations from decayed teeth. Our results show for the first time that OBs express microbial pattern recognition receptors in situ, thus allowing differential responses to gram-positive and gram-negative bacteria, and suggest that pro-inflammatory cytokines and innate immune responses in decayed teeth may result from TLR4 signaling. [source]

Expression of human ,-defensin -1, -2, and -3 in non-inflamed pseudocyst, mucoceles

ORAL DISEASES, Issue 7 2008
MK Frederic
Objectives and design:, The expressions of human beta defensin-1 (HBD-1), -2 (HBD-2) and -3 (HBD-3) in non-inflamed pseudocysts such as mucoceles were investigated immunohistochemically in this study. Materials and methods:, Mucocele specimens were obtained from 21 patients. The expression of HBDs was studied immunohistochemically by using antibodies directed against HBD-1, -2, and -3. Statistical analyses were carried out on serial sections stained with antibodies. Results:, Cells expressing HBDs were found in mucoceles. The expression of HBD-2 was observed in floating cells in all the specimens, whereas HBD-1 and HBD-3-expressing cells were detected in 93% and 73% of the mucoceles, respectively. The HBD-2 signal was the most intense and the HBD-3 signal intensity was weaker than that of HBD-1. HBDs were expressed in neutrophils and in other floating cells. Interestingly, the signal intensity and the population of positive cells located close to the centers of cysts were higher than those located in the peripheral areas of cysts. Conclusion:, The expression of HBDs was found even in non-inflamed pseudocysts such as mucoceles. These results suggest that an unknown mechanism not involved in biophylaxis for the expression of HBDs may exist. [source]

Molecular analysis of resistance mechanisms to Orobanche cumana in sunflower

PLANT PATHOLOGY, Issue 3 2007
P. Letousey
Resistance to the dicotyledenous parasite Orobanche cumana in sunflower is characterized by a low number of parasitic attachments and a confinement of the parasite in host tissues leading to its necrosis. To help understand what determines such resistance mechanisms, molecular, biochemical and histological approaches were employed before (early response) and after (late response) attachment of the broomrape parasite to susceptible (2603) and resistant (LR1) sunflower genotypes. The expression patterns of 11 defence-related genes known to be involved in different metabolic pathways (phenylpropanoids, jasmonate, ethylene) and/or in resistance mechanisms against microorganisms were investigated. RT-PCR and cDNA blot experiments revealed that the resistant genotype exhibited a stronger overall defence response against O. cumana than the susceptible one, involving marker genes of the jasmonate (JA) and salicylic acid (SA) pathways. Among them, the SA-responsive gene, def. (defensin), appeared to be characteristic of LR1 sunflower resistance. However, no JA accumulation and similar SA contents (250,300 ng g,1 FW) were measured by GC/MS in both genotypes, parasitized or not. In addition, three cDNAs, isolated by a suppression-subtractive hybridization, were shown to be strongly induced only in the resistant genotype 8 days post-inoculation, when the first O. cumana attachments occurred. These genes, putatively encoding a methionine synthase, a glutathione S-transferase and a quinone oxidoreductase, might be involved in detoxification of reactive oxygen species, suggesting the occurrence of an oxidative burst during the incompatible interaction. Finally, host cell-wall modifications leading to parasite-confinement were correlated with more intense callose depositions in the resistant genotype, concomitant with over-expression of the callose synthase cDNA HaGSL1. [source]

Expression of toll-like receptor 2, NOD2 and dectin-1 and stimulatory effects of their ligands and histamine in normal human keratinocytes

BRITISH JOURNAL OF DERMATOLOGY, Issue 2 2009
M. Kobayashi
Summary Background, Epidermal keratinocytes are involved in the skin innate immunity and express toll-like receptors (TLRs) and other innate immune proteins. The epidermis is continuously exposed to pathogenic Gram-positive bacteria or fungi. However, few studies have examined the function and expression of innate immune proteins in keratinocytes. Histamine, which is well known for itch and allergy, is closely associated with innate immunity, but its influence on epidermal innate immunity is still unclear. Objectives, To clarify the expression of innate immune proteins in keratinocytes stimulated by ligand pathogen-associated molecules, and the function of histamine in this process. Methods, We investigated the effects of lipopeptide (MALP-2, 1,100 ng mL,1; ligand for TLR2), peptidoglycan (PGN, 0·02,2 ,g mL,1; ligand for NOD2) and ,-glucan (1,100 ,g mL,1; ligand for dectin-1) in the presence or absence of histamine on mRNA expression of TLR2, NOD2 and dectin-1 as well as human ,-defensin 2 by quantitative real-time polymerase chain reaction in cultured normal human epidermal keratinocytes. TLR2 expression was also examined at the cell surface and intracellularly, as determined by flow cytometry and confocal microscopy. The quantities of interleukin (IL)-1, and IL-8 produced by keratinocytes were measured using enzyme-linked immunosorbent assay. Results, At the mRNA level, TLR2 was enhanced by PGN but not by its ligand MALP-2 or by ,-glucan; NOD2 was easily induced by all three ligands; and dectin-1 was enhanced by its ligand ,-glucan. These enhanced expressions were further augmented by histamine at 1 ,g mL,1. While the surface expression of TLR2 was barely detectable by flow cytometry even after stimulation, the intracellular expression of TLR2 was apparently elevated by PGN and further promoted by histamine. A confocal microscopic analysis also revealed the enhanced expression of TLR2 in the cytoplasm. The expression of TLR2, NOD2 and dectin-1 was functional, as these pathogen-associated molecules induced the production of IL-1,, IL-8 and defensin, and again, histamine greatly enhanced this production. Conclusions, Our study demonstrated that the expression of functional innate immune receptors is augmented by the pathogen-associated molecules in a ligand-feed forward or nonrelated manner in keratinocytes, and histamine promotes their expression and the resultant production of cytokines and defensins. [source]

Bacterial exotoxins downregulate cathelicidin (hCAP-18/LL-37) and human ,-defensin 1 (HBD-1) expression in the intestinal epithelial cells

CELLULAR MICROBIOLOGY, Issue 12 2008
Krishnendu Chakraborty
Summary Cathelicidin (hCAP-18/LL-37) and ,-defensin 1 (HBD-1) are human antimicrobial peptides (AMPs) with high basal expression levels, which form the first line of host defence against infections over the epithelial surfaces. The antimicrobial functions owe to their direct microbicidal effects as well as the immunomodulatory role. Pathogenic microorganisms have developed multiple modalities including transcriptional repression to combat this arm of the host immune response. The precise mechanisms and the pathogen-derived molecules responsible for transcriptional downregulation remain unknown. Here, we have shown that enteric pathogens suppress LL-37 and HBD-1 expression in the intestinal epithelial cells (IECs) with Vibrio cholerae and enterotoxigenic Escherichia coli (ETEC) exerting the most dramatic effects. Cholera toxin (CT) and labile toxin (LT), the major virulence proteins of V. cholerae and ETEC, respectively, are predominantly responsible for these effects, both in vitro and in vivo. CT transcriptionally downregulates the AMPs by activating several intracellular signalling pathways involving protein kinase A (PKA), ERK MAPKinase and Cox-2 downstream of cAMP accumulation and inducible cAMP early repressor (ICER) may mediate this role of CT, at least in part. This is the first report to show transcriptional repression of the AMPs through the activation of cellular signal transduction pathways by well-known virulence proteins of pathogenic microorganisms. [source]

Two mitogen-activated protein kinase signalling cascades mediate basal resistance to antifungal plant defensins in Fusarium graminearum

CELLULAR MICROBIOLOGY, Issue 6 2007
Vellaisamy Ramamoorthy
Summary Antifungal defensins, MsDef1 and MtDef4, from Medicago spp., inhibit the growth of Fusarium graminearum, which causes head blight disease in cereals. In order to determine the signalling cascades that are modulated by these defensins, we have isolated several insertional mutants of F. graminearum that exhibit hypersensitivity to MsDef1, but not to MtDef4. The molecular characterization of two of these mutants, designated enhanced sensitivity to defensin (esd), has revealed that the Mgv1 and Gpmk1 MAP kinase signalling cascades play a major role in regulating sensitivity of F. graminearum to MsDef1, but not to MtDef4. The Hog1 MAP kinase signalling cascade, which is responsible for adaptation of this fungus to hyperosmotic stress, does not participate in the fungal response to these defensins. Significantly, the esd mutants also exhibit hypersensitivity to other tested defensins and are highly compromised in their pathogenesis on wheat heads and tomato fruits. The studies reported here for the first time implicate two MAP kinase signalling cascades in a plant defensin-mediated alteration of fungal growth. Based on our findings, we propose that specific MAP kinase signalling cascades are essential for protection of a fungal pathogen from the antimicrobial proteins of its host plant. [source]

Probiotic lactobacilli and VSL#3 induce enterocyte ,-defensin 2

CLINICAL & EXPERIMENTAL IMMUNOLOGY, Issue 3 2008
M. Schlee
Summary Recent evidence suggests that probiotic bacteria may stabilize gut barrier function via induction of anti-microbial peptides such as defensins. This study aimed to elucidate the induction mechanism of the human beta defensin-2 (hBD-2) gene by different probiotic lactobacillus strains. The expression of hBD-2 mRNA peaked at 6 h of incubation upon treatment of Caco-2 cells and increased with higher dosage of various probiotic bacteria. Deletion of nuclear factor (NF)-,B and activator protein-1 (AP-1) binding sites on the hBD-2 promoter resulted in a complete abrogation of promoter activation by probiotics. As revealed by the use of specific mitogen-activated protein kinase (MAPK) inhibitors the hBD-2 induction was dependent on the MAPK extracellular regulated kinase (ERK 1/2), p38 and c-Jun N-terminal kinase (JNK), although to varying degrees. Several Lactobacillus strains and VSL#3, a probiotic cocktail of four lactobacilli, three bifidum and one streptococcus species, induced the secretion of the hBD-2 peptide into the culture media as shown by enzyme-linked immunosorbent assay (ELISA). Thus, the present study suggests that lactobacilli and the VSL#3 bacterial mixture strengthen intestinal barrier functions through the up-regulation of hBD-2 via induction of proinflammatory pathways including NF-,B and AP-1 as well as MAPKs. [source]

The antimicrobial activity of CCL28 is dependent on C-terminal positively-charged amino acids

EUROPEAN JOURNAL OF IMMUNOLOGY, Issue 1 2010
Bin Liu
Abstract Several chemokines have been shown to act as antimicrobial proteins, suggesting a direct contribution to innate immune protection. Based on the study of defensins and other antimicrobial peptides, it has been proposed that cationic amino acids in these proteins play a key role in their antimicrobial activity. The primary structure requirements necessary for the antimicrobial activity of chemokines, however, have not yet been elucidated. Using mouse CCL28, we have identified a C-terminal region of highly-charged amino acids (RKDRK) that is essential to the antimicrobial activity of the murine chemokine. Additionally, other positively-charged amino acids in the C-terminus of the protein contribute to the observed antimicrobial effect. Charge reversal and deletion mutations support our hypothesis that C-terminal positively-charged amino acids are essential for the antimicrobial activity of CCL28. Results also demonstrate that although the C-terminal region of the chemokine is essential, it is not sufficient for full antimicrobial activity of CCL28. [source]

Peptides of human gingival crevicular fluid determined by HPLC-ESI-MS

EUROPEAN JOURNAL OF ORAL SCIENCES, Issue 6 2005
Elisabetta Pisano
The acidic-soluble protein content of human gingival crevicular fluid was analyzed by reverse-phase high-performance liquid chromatography (RP-HPLC), and the eluent deriving from the chromatography separation was directly introduced into an ion-trap mass spectrometer through electrospray ionization (ESI-IT MS). By this technique the molecular weight of peptides/proteins was determined with a precision of ,,1/10,000 amu. On the basis of the chromatographic behavior and the knowledge of the molecular mass value, some peptides and proteins soluble in acidic solution were unambiguously recognized. Besides high quantities of human serum albumin, , -defensins 1,4 and minor amounts of cystatin A, statherin, basic PB salivary peptide and other unidentified components were detected. The presence of , -defensins in gingival crevicular fluid is in agreement with their relevant contribution to protein composition deriving from granulocyte secretions. Other peptides and proteins abundant in human saliva, such as proline-rich proteins (PRPs) and histatins, were not detected in gingival crevicular fluid. Further investigations will be necessary to establish the origin of statherin and PB salivary peptide in gingival crevicular fluid. [source]

Differential expression of antimicrobial peptides in margins of chronic wounds

EXPERIMENTAL DERMATOLOGY, Issue 7 2010
Stefanie Dressel
Please cite this paper as: Differential expression of antimicrobial peptides in margins of chronic wounds. Experimental Dermatology 2010; 19: 628,632. Abstract:, Skin wounds usually heal without major infections, although the loss of the mechanical epithelial barrier exposes the tissue to various bacteria. One reason may be the expression of antimicrobial peptides (AMP) of which some [human ,-defensins (hBD) and LL-37] were recently shown to support additionally certain steps of wound healing. There are no studies which have compared expression patterns of different classes of AMP in chronic wounds. The aim of our study was therefore to analyse the expression profile of hBD-2, hBD-3, LL-37, psoriasin and RNase 7 by immunohistochemistry from defined wound margins of chronic venous ulcers. We detected a strong induction of psoriasin and hBD-2 in chronic wounds in comparison with healthy skin. Except for stratum corneum, no expression of RNase 7 and LL-37 was detected in the epidermis while expression of hBD-3 was heterogeneous. Bacterial swabs identified Staphylococcus aureus and additional bacterial populations, but no association between colonization and AMP expression was found. The differential expression of AMP is noteworthy considering the high bacterial load of chronic ulcers. Clinically, supplementation of AMP with the capability to enhance wound healing besides restricting bacterial overgrowth could present a physiological support for treatment of disturbed wound healing. [source]

Identification of a cowpea ,-thionin with bactericidal activity

FEBS JOURNAL, Issue 15 2006
Octávio L. Franco
Antimicrobial peptides are an abundant group of proteinaceous compounds widely produced in the plant kingdom. Among them, the ,-thionin family, also known as plant defensins, represents one typical family and comprises low molecular mass cysteine-rich proteins, usually cationic and distributed in different plant tissues. Here, we report the purification and characterization of a novel ,-thionin from cowpea seeds (Vigna unguiculata), named Cp-thionin II, with bactericidal activity against Gram-positive and Gram-negative bacteria. Once the primary structure was elucidated, molecular modelling experiments were used to investigate the multimerization and mechanism of action of plant ,-thionins. Furthermore, Cp-thionin II was also localized in different tissues in cowpea seedlings during germination in contrasting conditions, to better understand the plant protection processes. The use of plant defensins in the construction of transgenic plants and also in the production of novel drugs with activity against human pathogens is discussed. [source]

Rhinovirus increases human ,-defensin-2 and -3 mRNA expression in cultured bronchial epithelial cells

FEMS IMMUNOLOGY & MEDICAL MICROBIOLOGY, Issue 1 2003
Louise A Duits
Abstract Human ,-defensins (hBDs) are antimicrobial peptides that play important roles in host defense against infection, inflammation and immunity. Previous studies showed that micro-organisms and proinflammatory mediators regulate the expression of these peptides in airway epithelial cells. The aim of the present study was to investigate the modulation of expression of hBDs in cultured primary bronchial epithelial cells (PBEC) by rhinovirus-16 (RV16), a respiratory virus responsible for the common cold and associated with asthma exacerbations. RV16 was found to induce expression of hBD-2 and -3 mRNA in PBEC, but did not affect hBD-1 mRNA. Viral replication appeared essential for rhinovirus-induced ,-defensin mRNA expression, since UV-inactivated rhinovirus did not increase expression of hBD-2 and hBD-3 mRNA. Exposure to synthetic double-stranded RNA (dsRNA) molecule polyinosinic:polycytidylic acid had a similar effect as RV16 on mRNA expression of these peptides in PBEC. In line with this, PBEC were found to express TLR3, a Toll-like receptor involved in recognition of dsRNA. This study shows that rhinovirus infection of PBEC leads to increased hBD-2 and hBD-3 mRNA expression, which may play a role in both the uncomplicated common cold and in virus-associated exacerbations of asthma. [source]

Expression of ,-defensin 1 and 2 mRNA by human monocytes, macrophages and dendritic cells

Inducible and constitutive ,-defensins are differentially expressed in Crohn's disease and ulcerative colitis

INFLAMMATORY BOWEL DISEASES, Issue 4 2003
Jan Wehkamp
Abstract Antimicrobial peptides such as defensins provide nonspecific mucosal defense against a multitude of microorganisms. Recently, it has been shown that luminal bacteria may invade the mucosa in inflammatory bowel diseases, suggesting a defect in innate mucosal immunity. The aim of this study was to investigate the expression of human ,-defensins (HBD) in controls, Crohn's disease (CD), ulcerative colitis (UC), and unspecific inflammation. Up to 4 biopsies were taken from 103 patients (33 controls, 24 with Crohn's disease, 36 with ulcerative colitis, 10 with unspecific colitis). Mucosal mRNA was measured using real-time fluorescence temperature cycler reverse-transcription polymerase chain reaction with primers for HBD-1, HBD-2, HBD-3, tumor necrosis factor ,, and interleukin 8. Mucosal HBD-1 expression was marginally decreased in both CD and UC. HBD-2 was increased exclusively in UC but not in CD. The expression of the novel defensin HBD-3 was strongly correlated with HBD-2 and also raised predominantly in UC. The expression of both inducible ,-defensins was enhanced in the state of inflammation. Expression of HBD-2 showed a weak correlation with interleukin 8 only in inflamed CD biopsies but not with tumor necrosis factor ,. The missing induction of both inducible ,-defensins in CD as compared with UC may cause a defect in barrier function that predisposes to bacterial invasion. [source]

Identification and characterization of antimicrobial peptide, defensin, in the taiga tick, Ixodes persulcatus

The malaria vector mosquito Anopheles gambiae expresses a suite of larval-specific defensin genes

Gene organization of a novel defensin of Ixodes ricinus: first annotation of an intron/exon structure in a hard tick defensin gene and first evidence of the occurrence of two isoforms of one member of the arthropod defensin family

An optimized method for intensive screening of molecules that stimulate , -defensin 2 or 3 (hBD2 or hBD3) expression in cultured normal human keratinocytes

Analysis of DEFB1 regulatory SNPs in cystic fibrosis patients from North-Eastern Italy

INTERNATIONAL JOURNAL OF IMMUNOGENETICS, Issue 3 2010
L. Segat
Summary Cystic fibrosis (CF) transmembrane regulator protein (CFTR) gene is undoubtedly the main genetic factor involved in the modulation of CF phenotype. However, other factors such as human defensins and the genes encoding for these antimicrobial peptides have been hypothesized as possible modifiers influencing airways infection in CF patients, but their role in the pathogenesis of lung disease is still debated. Since DEFB1 gene encoding for human beta-defensin 1 displays features such as antimicrobial or chemotactic activity playing a role in inflammation, it has been considered as a possible candidate CF modifier gene. We analysed three single nucleotide polymorphisms (SNPs) in the 5,-untranslated region of the DEFB1 gene (namely g-52G>A, g-44C>G and g-20G>A) in a group of 62 CF patients from North Eastern Italy, and in 130 healthy controls, with the aim of verifying the possible association of these functional SNPs with the pulmonary phenotype of CF patients. DEFB1 SNPs have been genotyped by using Taqman allele-specific fluorescent probes and a real-time PCR platform. No significant differences were found for allele, genotype and haplotype frequencies of DEFB1 g-52G>A, g-44C>G and g-20G>A SNPs in CF patients stratified for Pseudomonas aeruginosa infection, as well as in patients with a severe and mild clinical phenotype or in patients stratified for CFTR genotypes. DEFB1 allele, genotype and haplotype frequencies of CF patients globally considered were similar to those of healthy controls. Our findings are discordant with respect to another recent study performed on CF patients coming from Southern Italy, probably due to different ethnicity of the patients. [source]

Antibacterial peptides: basic facts and emerging concepts

JOURNAL OF INTERNAL MEDICINE, Issue 3 2003
H. G. Boman
Abstract., Boman HG (Microbiology and Tumor Biology Center, Karolinska Institutet, Stockholm, Sweden). Antibacterial peptides: basic facts and emerging concepts (Review). J Intern Med 2003; 254: 197,215. Antibacterial peptides are the effector molecules of innate immunity. Generally they contain 15,45 amino acid residues and the net charge is positive. The cecropin type of linear peptides without cysteine were found first in insects, whilst the defensin type with three disulphide bridges were found in rabbit granulocytes. Now a database stores more than 800 sequences of antibacterial peptides and proteins from the animal and plant kingdoms. Generally, each species has 15,40 peptides made from genes, which code for only one precursor. The dominating targets are bacterial membranes and the killing reaction must be faster than the growth rate of the bacteria. Some antibacterial peptides are clearly multifunctional and an attempt to predict this property from the hydrophobicity of all amino acid side chains are given. Gene structures and biosynthesis are known both in the fruit fly Drosophila and several mammals. Humans need two classes of defensins and the cathelicidin-derived linear peptide LL-37. Clinical cases show that deficiencies in these peptides give severe symptoms. Examples given are morbus Kostmann and atopic allergy. Several antibacterial peptides are being developed as drugs. [source]