Showing papers on "Antimicrobial peptides published in 2003"
TL;DR: This review, inspired by a spate of recent studies ofdefensins in human diseases and animal models, focuses on the biological function of defensins.
Abstract: The production of natural antibiotic peptides has emerged as an important mechanism of innate immunity in plants and animals. Defensins are diverse members of a large family of antimicrobial peptides, contributing to the antimicrobial action of granulocytes, mucosal host defence in the small intestine and epithelial host defence in the skin and elsewhere. This review, inspired by a spate of recent studies of defensins in human diseases and animal models, focuses on the biological function of defensins.
2,718 citations
TL;DR: The intention of this review is to illustrate the contemporary structural and functional themes among mechanisms of antimicrobial peptide action and resistance.
Abstract: Antimicrobial peptides have been isolated and characterized from tissues and organisms representing virtually every kingdom and phylum, ranging from prokaryotes to humans. Yet, recurrent structural and functional themes in mechanisms of action and resistance are observed among peptides of widely diverse source and composition. Biochemical distinctions among the peptides themselves, target versus host cells, and the microenvironments in which these counterparts convene, likely provide for varying degrees of selective toxicity among diverse antimicrobial peptide types. Moreover, many antimicrobial peptides employ sophisticated and dynamic mechanisms of action to effect rapid and potent activities consistent with their likely roles in antimicrobial host defense. In balance, successful microbial pathogens have evolved multifaceted and effective countermeasures to avoid exposure to and subvert mechanisms of antimicrobial peptides. A clearer recognition of these opposing themes will significantly advance our understanding of how antimicrobial peptides function in defense against infection. Furthermore, this understanding may provide new models and strategies for developing novel antimicrobial agents, that may also augment immunity, restore potency or amplify the mechanisms of conventional antibiotics, and minimize antimicrobial resistance mechanisms among pathogens. From these perspectives, the intention of this review is to illustrate the contemporary structural and functional themes among mechanisms of antimicrobial peptide action and resistance.
2,687 citations
TL;DR: Analysis of this defence by molecular genetics has now provided a global picture of the mechanisms by which this insect senses infection, discriminates between various classes of microorganisms and induces the production of effector molecules, among which antimicrobial peptides are prominent.
Abstract: Drosophila mounts a potent host defence when challenged by various microorganisms. Analysis of this defence by molecular genetics has now provided a global picture of the mechanisms by which this insect senses infection, discriminates between various classes of microorganisms and induces the production of effector molecules, among which antimicrobial peptides are prominent. An unexpected result of these studies was the discovery that most of the genes involved in the Drosophila host defence are homologous or very similar to genes implicated in mammalian innate immune defences. Recent progress in research on Drosophila immune defence provides evidence for similarities and differences between Drosophila immune responses and mammalian innate immunity.
1,393 citations
TL;DR: Antibacterial peptides: basic facts and emerging concepts (Review).
Abstract: 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.
1,041 citations
TL;DR: The role of membrane lipid composition, specifically non-bilayer lipids, on peptide activity will also be discussed, and structure-activity studies of these peptides reveal two main requirements for antimicrobial activity, a cationic charge and an induced amphipathic conformation.
843 citations
TL;DR: It is demonstrated that LL-37/hCAP-18 is a multifunctional antimicrobial peptide with a central role in innate immunity by linking host defense and inflammation with angiogenesis and arteriogenesis.
Abstract: Antimicrobial peptides are effector molecules of the innate immune system and contribute to host defense and regulation of inflammation. The human cathelicidin antimicrobial peptide LL-37/hCAP-18 is expressed in leukocytes and epithelial cells and secreted into wound and airway surface fluid. Here we show that LL-37 induces angiogenesis mediated by formyl peptide receptor-like 1 expressed on endothelial cells. Application of LL-37 resulted in neovascularization in the chorioallantoic membrane assay and in a rabbit model of hind-limb ischemia. The peptide directly activates endothelial cells, resulting in increased proliferation and formation of vessel-like structures in cultivated endothelial cells. Decreased vascularization during wound repair in mice deficient for CRAMP, the murine homologue of LL-37/hCAP-18, shows that cathelicidin-mediated angiogenesis is important for cutaneous wound neovascularization in vivo. Taken together, these findings demonstrate that LL-37/hCAP-18 is a multifunctional antimicrobial peptide with a central role in innate immunity by linking host defense and inflammation with angiogenesis and arteriogenesis.
818 citations
TL;DR: Its extensive antimicrobial activities were originally attributed to its ability to sequester essential iron, however, it is now established that it possesses bactericidal activities as a result of a direct interaction between the protein or lactoferrin-derived peptides.
681 citations
TL;DR: Domesticated animals have a large variety of antimicrobial peptides that serve as natural innate barriers limiting microbial infection or, in some instances, act as an integral component in response to inflammation or microbial infection.
437 citations
TL;DR: Bacteriocins, antimicrobial peptides, and bacteriophage have attracted attention as potential substitutes for, or as additions to, currently used antimicrobial compounds as mentioned in this paper.
430 citations
TL;DR: The two‐component regulatory system PhoP‐PhoQ of Pseudomonas aeruginosa regulates resistance to cationic antimicrobial peptides, polymyxin B and aminoglycosides in response to low Mg2+ conditions is identified and the putative LPS modification operon, PA3552‐PA3559, was showed to be induced by cionic peptides.
Abstract: Summary The two-component regulatory system PhoP-PhoQ of Pseudomonas aeruginosa regulates resistance to cationic antimicrobial peptides, polymyxin B and aminoglycosides in response to low Mg 2+ conditions. We have identified a second two-component regulatory system, PmrA-PmrB, that regulates resistance to polymyxin B and cationic antimicrobial peptides. This system responds to limiting Mg 2 + , and is affected by a phoQ , but not a phoP mutation. Inactivation of the pmrB sensor kinase and pmrA response regulator greatly decreased the expression of the operon encoding pmrA-pmrB while expression of the response regulator pmrA in trans resulted in increased activation suggesting that the pmrA-pmrB operon is autoregulated. Interposon mutants in pmrB , pmrA , or in an intergenic region upstream of pmrApmrB exhibited two to 16-fold increased susceptibility to polymyxin B and cationic antimicrobial peptides. The pmrA-pmrB operon was also found to be activated by a number of cationic peptides including polymyxins B and E, cattle indolicidin and synthetic variants as well as LL-37, a component of human innate immunity, whereas peptides with the lowest minimum inhibitory concentrations tended to be the weakest inducers. Additionally, we showed that the putative LPS modification operon, PA3552-PA3559, was also induced by cationic peptides, but its expression was only partially dependent on the PmrA-PmrB system. The discovery that the PmrA-PmrB twocomponent system regulates resistance to cationic peptides and that both it and the putative LPS modification system are induced by cationic antimicrobial peptides has major implications for the development of these antibiotics as a therapy for P. aeruginosa infections.
420 citations
TL;DR: LL-37 may constitute one of the mediators by which neutrophils regulate epithelial cell activity in the lung, and data suggest that LL-37 transactivates the EGFR via metalloproteinase-mediated cleavage of membrane-anchored EGFR-ligands.
Abstract: Antimicrobial peptides produced by epithelial cells and neutrophils represent essential elements of innate immunity, and include the defensin and cathelicidin family of antimicrobial polypeptides. The human cathelicidin cationic antimicrobial protein-18 is an antimicrobial peptide precursor predominantly expressed in neutrophils, and its active peptide LL-37 is released from the precursor through the action of neutrophil serine proteinases. LL-37 has been shown to display antimicrobial activity against a broad spectrum of microorganisms, to neutralize LPS bioactivity, and to chemoattract neutrophils, monocytes, mast cells, and T cells. In this study we show that LL-37 activates airway epithelial cells as demonstrated by activation of the mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) and increased release of IL-8. Epithelial cell activation was inhibited by the MAPK/ERK kinase (MEK) inhibitors PD98059 and U0126, by the epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor AG1478, by blocking anti-EGFR and anti-EGFR-ligand Abs, and by the metalloproteinase inhibitor GM6001. These data suggest that LL-37 transactivates the EGFR via metalloproteinase-mediated cleavage of membrane-anchored EGFR-ligands. LL-37 may thus constitute one of the mediators by which neutrophils regulate epithelial cell activity in the lung.
TL;DR: In conclusion, cathelicidin antimicrobial peptides qualify as prototypes of innovative drugs that may be used to treat infection and/or modulate the immune response and the structures of their genes and peptides are provided.
Abstract: One component of host defence at mucosal surfaces are epithelial-derived antimicrobial peptides. Cathelicidins are one family of antimicrobial peptides characterized by conserved pro-peptide sequences that have been identified in several mammalian species. LL-37/hCAP-18 is the only cathelicidin found in humans and is expressed in inflammatory and epithelial cells. Besides their direct antimicrobial function, cathelicidins have multiple roles as mediators of inflammation influencing diverse processes such as cell proliferation and migration, immune modulation, wound healing, angiogenesis and the release of cytokines and histamine. Finally, cathelicidin antimicrobial peptides qualify as prototypes of innovative drugs that may be used to treat infection and/or modulate the immune response. This review provides an overview of antimicrobial peptides of the cathelicidin family, the structures of their genes and peptides and their biological functions.
TL;DR: A number of antimicrobial peptides such as defensins have multiple functions in host defence, which endows them with the capacity to marshall adaptive host defences against microbial invaders.
Abstract: A number of antimicrobial peptides such as defensins have multiple functions in host defence. Defensins are produced not only by phagocytic cells and lymphocytes, but also by the epithelial cell lining of the gastrointestinal and genitourinary tracts, the tracheobronchial tree, and keratinocytes. Some are produced constitutively, whereas others are induced by proinflammatory cytokines and exogenous microbial products. Defensins produced by cells in the course of innate host defence serve as signals which initiate, mobilise, and amplify adaptive immune host defences. Administration of defensins with antigens to mice enhances both cellular (Th1-dependent) and humoral (Th2-dependent) cytokine production and immune responses. Linkage of defensins to weak tumour antigens potentiates their immunoadjuvant effects. Defensins use multiple cellular receptors, which endows them with the capacity to marshall adaptive host defences against microbial invaders.
TL;DR: It is found that the growth factors important in wound healing, insulin-like growth factor I and TGF-α, induce the expression of the antimicrobial peptides/polypeptides human cationic antimicrobial protein hCAP-18/LL-37, human β-defensin 3, neutrophil gelatinase-associated lipocalin, and secretory leukocyte protease inhibitor in human keratinocytes.
Abstract: In addition to acting as a physical barrier against microorganisms, the skin produces antimicrobial peptides and proteins. After wounding, growth factors are produced to stimulate the regeneration of tissue. The growth factor response ceases after regeneration of the tissue, when the physical barrier protecting against microbial infections is re-established. We found that the growth factors important in wound healing, insulin-like growth factor I and TGF-alpha, induce the expression of the antimicrobial peptides/polypeptides human cationic antimicrobial protein hCAP-18/LL-37, human beta-defensin 3, neutrophil gelatinase-associated lipocalin, and secretory leukocyte protease inhibitor in human keratinocytes. Both an individual and a synergistic effect of these growth factors were observed. These findings offer an explanation for the expression of these peptides/polypeptides in the skin disease psoriasis and in wound healing and define a host defense role for growth factors in wound healing.
TL;DR: The use of two-peptide antimicrobial peptides as replacement for clinical antibiotics is promising, though their applications in preservation of foods, in veterinary medicine, and in dentistry are more immediate.
TL;DR: Model phospholipid membranes have been used to study the mode of action of antimicrobial peptides and it is demonstrated that peptides that act preferentially on bacteria are also able to interact with and permeate efficiently anionicospholipids, whereas peptide that lyse mammalian cells bind and permeates efficiently both acidic and zwitterionic phospholIPids membranes.
TL;DR: It now appears that the general patterns of antimicrobial responses of invertebrates have been preserved in vertebrates (“innate immunity”) where they contribute to host defense both independently and in complex interplay with adaptive immunity.
Abstract: SYNOPSIS. Production of antimicrobial peptides and proteins is an important means of host defense in eukaryotes. The larger antimicrobial proteins, containing more than 100 amino acids, are often lytic enzymes, nutrient-binding proteins or contain sites that target specific microbial macromolecules. The smaller antimicrobial peptides act largely by disrupting the structure or function of microbial cell membranes. Hundreds of antimicrobial peptides have been found in the epithelial layers, phagocytic cells and body fluids of multicellular animals, from mollusks to humans. Some antimicrobial peptides are produced constitutively, others are induced in response to infection or inflammation. Studies of the regulation of antimicrobial peptide synthesis in Drosophila have been particularly fruitful, and have provided a new paradigm for the analysis of mammalian host defense responses. It now appears that the general patterns of antimicrobial responses of invertebrates have been preserved in vertebrates (‘‘innate immunity’’) where they contribute to host defense both independently and in complex interplay with adaptive immunity. ANTIMICROBIAL PEPTIDES—B ACKGROUND AND DEFINITION Multicellular organisms continually defend themselves against parasitization by potentially harmful microbes. In the absence of penetrating injury, the most common sites of initial encounter with microbes are the epithelial surfaces (skin, the moist surfaces of the eyes, nose, airways and the lungs, mouth and the digestive tract, and the urinary and reproductive systems). Because mechanisms requiring specific antigen recognition depend on clonal proliferation of immunocytes, and therefore take days to weeks to develop fully, the initial host resistance mechanisms must recognize or target microbe-specific class characteristics and employ mechanisms that are either constitutive or rapidly inducible. Some unique microbial molecular features are recognized by complementary receptors that trigger localized effector mechanisms (‘‘pattern recognition’’) while other structural or metabolic characteristics make the microbes selectively susceptible to the action of injurious antimicrobial substances including chemically highly reactive molecules, lytic enzymes, pore-forming molecules, or substances that sequester essential nutrients. Certain antimicrobial substances may be present constitutively; the local synthesis or release of others is provoked by invading microbes; and yet other antimicrobial substances can be brought into the area of invasion by mobile cells. Unlike innate immunity, adaptive immunity (antibodies and antigen-recognizing cytotoxic lymphocytes) is a late evolutionary development developed fully only in higher vertebrates. Specific antigen recognition by lymphocytes probably plays a limited role during the initial encounter but it is especially effective against 1 From the Symposium Comparative Immunologypresented at the Annual Meeting of the Society for Integrative and Comparative Bi
TL;DR: This review summarises the current knowledge about the basic and applied biology of AMPs and qualifies as prototypes of innovative drugs that may be used as antimicrobials, anti-lipopolysaccharide drugs or modifiers of inflammation.
Abstract: Antimicrobial peptides (AMPs) are effector molecules of the innate immune system. A variety of AMPs have been isolated from species of all kingdoms and are classified based on their structure and amino acid motifs. AMPs have a broad antimicrobial spectrum and lyse microbial cells by interaction with biomembranes. Besides their direct antimicrobial function, they have multiple roles as mediators of inflammation with impact on epithelial and inflammatory cells influencing diverse processes such as cell proliferation, immune induction, wound healing, cytokine release, chemotaxis and protease-antiprotease balance. AMPs qualify as prototypes of innovative drugs that may be used as antimicrobials, anti-lipopolysaccharide drugs or modifiers of inflammation. Several strategies have been followed to identify lead candidates for drug development, to modify the peptides' structures, and to produce sufficient amounts for pre-clinical and clinical studies. This review summarises the current knowledge about the basic and applied biology of AMPs.
TL;DR: It is found that JNK signaling is not required for antimicrobial peptide gene expression but is required for the activation of other immune inducible genes, including Punch, sulfated, and malvolio.
TL;DR: Antimicrobial peptides are attractive candidates for clinical development because of their selectivity, their speed of action and because bacteria may not easily develop resistance against them, but some strains of bacteria already have resistance.
Abstract: Many different types of organisms use antimicrobial peptides, typically 20–40 amino acids in length, for defence against infection. Most are capable of rapidly killing a wide range of microbial cells. They have been classified according to their active structures into six extensive groups. It is not yet clear how these peptides kill bacterial cells, but it is widely believed that some cationic antimicrobial peptides kill by disrupting bacterial membranes, allowing the free exchange of intra- and extra-cellular ions. The selectivity of these peptides appears to relate to differences between the external membranes of prokaryotic and eukaryotic cells. The action of the peptides may involve the formation of ‘barrel-stave’ or ‘torroidal’ pores, the introduction of packing defects in the membrane phospholipids, or large-scale disruption of the membrane by a very dense aggregation of parallel-oriented peptide, called the ‘carpet mechanism’.
TL;DR: The presence of antimicrobial peptides with such different structures and spectra of action represents the successful evolution of multidrug defense by providing frogs with maximum protection against infectious microbes and minimizing the chance of microorganisms developing resistance to individual peptides.
Abstract: The dermal glands of frogs produce antimicrobial peptides that protect the skin against noxious microorganisms and assist in wound repair. The sequences of these peptides are very dissimilar, both within and between species, so that the 5000 living anuran frogs may produce ≈ 100 000 different antimicrobial peptides. The antimicrobial peptides of South American hylid frogs are derived from precursors, the preprodermaseptins, whose signal peptides and intervening sequences are remarkably conserved, but their C-terminal domains are markedly diverse, resulting in mature peptides with different lengths, sequences and antimicrobial spectra. We have used the extreme conservation in the preproregion of preprodermaseptin transcripts to identify new members of this family in Australian and South American hylids. All these peptides are cationic, amphipathic and α-helical. They killed a broad spectrum of microorganisms and acted in synergy. 42 preprodermaseptin gene sequences from 10 species of hylid and ranin frogs were analyzed in the context of their phylogeny and biogeography and of geophysical models for the fragmentation of Gondwana to examine the strategy that these frogs have evolved to generate an enormous array of peptide antibiotics. The hyperdivergence of modern antimicrobial peptides and the number of peptides per species result from repeated duplications of a ≈ 150-million-year-old ancestral gene and accelerated mutations of the mature peptide domain, probably involving a mutagenic, error-prone, DNA polymerase similar to Escherichia coli Pol V. The presence of antimicrobial peptides with such different structures and spectra of action represents the successful evolution of multidrug defense by providing frogs with maximum protection against infectious microbes and minimizing the chance of microorganisms developing resistance to individual peptides. The hypermutation of the antimicrobial domain by a targeted mutagenic polymerase that can generate many sequence changes in a few steps may have a selective survival value when frogs colonizing a new ecological niche encounter different microbial predators.
TL;DR: CDNA sequences of five highly disulphide-bonded hepcidin-like peptides from winter flounder, Pseudopleuronectes americanus and two from Atlantic salmon are presented, indicating that they are widespread among fish.
Abstract: Antimicrobial peptides play a crucial role as the first line of defense against invading pathogens. Several types of antimicrobial peptides have been isolated from fish, mostly of the cationic α-helical variety. Here, we present the cDNA sequences of five highly disulphide-bonded hepcidin-like peptides from winter flounder, Pseudopleuronectes americanus (Walbaum) and two from Atlantic salmon, Salmo salar (L.). These hepcidin-like molecules consist of a 24 amino acid signal peptide and an acidic propiece of 38–40 amino acids in addition to the mature processed peptide of 19–27 amino acids. Exhaustive data mining of GenBank with these sequences revealed that similar peptides are encoded in the genomes of Japanese flounder, rainbow trout, hybrid striped bass and medaka, indicating that they are widespread among fish. Southern hybridization analysis suggests that closely related hepcidin-like genes are present in other flatfish species, and that they exist as a multigene family clustered on the winter flounder genome. Hepcidin variants are differentially expressed during bacterial challenge, during larval development of P. americanus and in different tissues of adult fish.
TL;DR: Collectively, CCL28 may play dual roles in mucosal immunity as a chemoattractant for cells expressing CCR10 and/or CCR3 such as plasma cells and also as a broad-spectrum antimicrobial protein secreted into low-salt body fluids.
Abstract: CCL28 is a CC chemokine signaling via CCR10 and CCR3 that is selectively expressed in certain mucosal tissues such as exocrine glands, trachea, and colon. Notably, these tissues commonly secrete low-salt fluids. RT-PCR analysis demonstrated that salivary glands expressed CCL28 mRNA at the highest levels among various mouse tissues. Single cells prepared from mouse parotid glands indeed contained a major fraction of CD3(-)B220(low) cells that expressed CCR10 at high levels and CCR3 at low levels and responded to CCL28 in chemotaxis assays. Morphologically, these cells are typical plasma cells. By immunohistochemistry, acinar epithelial cells in human and mouse salivary glands were strongly positive for CCL28. Furthermore, human saliva and milk were found to contain CCL28 at high concentrations. Moreover, the C terminus of human CCL28 has a significant sequence similarity to histatin-5, a histidine-rich candidacidal peptide in human saliva. Subsequently, we demonstrated that human and mouse CCL28 had a potent antimicrobial activity against Candida albicans, Gram-negative bacteria, and Gram-positive bacteria. The C-terminal 28-aa peptide of human CCL28 also displayed a selective candidacidal activity. In contrast, CCL27, which is most similar to CCL28 and shares CCR10, showed no such potent antimicrobial activity. Like most other antimicrobial peptides, CCL28 exerted its antimicrobial activity in low-salt conditions and rapidly induced membrane permeability in target microbes. Collectively, CCL28 may play dual roles in mucosal immunity as a chemoattractant for cells expressing CCR10 and/or CCR3 such as plasma cells and also as a broad-spectrum antimicrobial protein secreted into low-salt body fluids.
TL;DR: Of several genes associated with methicillin resistance, inactivation of the fmtC gene in MRSA strain COL increased susceptibility to the antimicrobial effect mediated by hBD3 or CAP18.
Abstract: The antimicrobial peptides human β-defensin-1 (hBD1), hBD2, hBD3, and CAP18 expressed by keratinocytes have been implicated in mediation of the innate defense against bacterial infection. To gain insight into Staphylococcus aureus infection, the susceptibility of S. aureus, including methicillin-resistant S. aureus (MRSA), to these antimicrobial peptides was examined. Based on quantitative PCR, expression of hBD2 mRNA by human keratinocytes was significantly induced by contact with S. aureus, and expression of hBD3 and CAP18 mRNA was slightly induced, while hBD1 mRNA was constitutively expressed irrespective of the presence of S. aureus. Ten clinical S. aureus isolates, including five MRSA isolates, induced various levels of expression of hBD2, hBD3, and CAP18 mRNA by human kertinocytes. The activities of hBD3 and CAP18 against S. aureus were found to be greater than those of hBD1 and hBD2. A total of 44 S. aureus clinical isolates, including 22 MRSA strains, were tested for susceptibility to hBD3 and CAP18. Twelve (55%) and 13 (59%) of the MRSA strains exhibited more than 20% survival in the presence of hBD3 (1 μg/ml) and CAP18 (0.5 μg/ml), respectively. However, only three (13%) and two (9%) of the methicillin-sensitive S. aureus isolates exhibited more than 20% survival with hBD3 and CAP18, respectively, suggesting that MRSA is more resistant to these peptides. A synergistic antimicrobial effect between suboptimal doses of methicillin and either hBD3 or CAP18 was observed with 10 MRSA strains. Furthermore, of several genes associated with methicillin resistance, inactivation of the fmtC gene in MRSA strain COL increased susceptibility to the antimicrobial effect mediated by hBD3 or CAP18.
TL;DR: The presence of all of these antimicrobial polypeptides in vernix suggests that they are important for surface defense and may have an active biologic role against microbial invasion at birth.
Abstract: Antimicrobial peptides/proteins are widespread in nature and play a critical role in host defense. To investigate whether these components contribute to surface protection of newborns at birth, we have characterized antimicrobial polypeptides in vernix caseosa (vernix) and amniotic fluid (AF). Concentrated peptide/protein extracts were obtained from 11 samples of vernix and six samples of AF and analyzed for antimicrobial activity using an inhibition zone assay. Proteins/peptides in all vernix extracts exhibited strong antibacterial activity against Bacillus megaterium (strain Bm11), in addition to antifungal activity against Candida albicans, whereas AF-derived proteins/peptides showed only the former activity. Fractions obtained after separation by reverse-phase HPLC exhibited antibacterial activity, with the most pronounced activity in a fraction containing alpha-defensins (HNP1-3). The presence of HNP1-3 was proved by dot blot analysis and confirmed by mass spectrometry. Lysozyme and ubiquitin were identified by sequence analysis in two fractions with antibacterial activity. Fractions of vernix and AF were also positive for LL-37 with dot blot and Western blot analyses, and one fraction apparently contained an extended form of LL-37. Interestingly, psoriasin, a calcium-binding protein that is up-regulated in psoriatic skin and was found recently to exhibit antimicrobial activity, was characterized in the vernix extract. The presence of all of these antimicrobial polypeptides in vernix suggests that they are important for surface defense and may have an active biologic role against microbial invasion at birth.
TL;DR: A resulting new generation of anti microbial peptides (AMPs) with higher specific activity and wider microbe-range of action could be constructed, and hopefully endogenously expressed in genetically-modified organisms.
TL;DR: The cellular uptake of fluorescent analogues of the two representative antimicrobial peptides magainin 2 and buforin 2 in comparison with the representative Arg-rich cell-penetrating Tat-(47–57) peptide (YGRKKRRQRRR) suggested that the three peptides cross cell membranes through different mechanisms.
TL;DR: It is demonstrated that H BD-2 and HBD-3 are susceptible to degradation and inactivation by the cysteine proteases cathepsins B, L, and S, which may be important in the regulation of β-defensin activity in chronic lung diseases associated with infection.
Abstract: beta-Defensins are antimicrobial peptides that contribute to the innate immune responses of eukaryotes. At least three defensins, human beta-defensins 1, 2, and 3 (HBD-1, -2, and -3), are produced by epithelial cells lining the respiratory tract and are active toward Gram-positive (HBD-3) and Gram-negative (HBD-1, -2, and -3) bacteria. It has been postulated that the antimicrobial activity of defensins is compromised by changes in airway surface liquid composition in lungs of patients with cystic fibrosis (CF), therefore contributing to the bacterial colonization of the lung by Pseudomonas and other bacteria in CF. In this report we demonstrate that HBD-2 and HBD-3 are susceptible to degradation and inactivation by the cysteine proteases cathepsins B, L, and S. In addition, we show that all three cathepsins are present and active in CF bronchoalveolar lavage. Incubation of HBD-2 and -3 with CF bronchoalveolar lavage leads to their degradation, which can be completely (HBD-2) or partially (HBD-3) inhibited by a cathepsin inhibitor. These results suggest that beta-defensins are susceptible to degradation and inactivation by host proteases, which may be important in the regulation of beta-defensin activity. In chronic lung diseases associated with infection, overexpression of cathepsins may lead to increased degradation of HBD-2 and -3, thereby favoring bacterial infection and colonization.
TL;DR: This review provides an overview of antimicrobial peptides identified in the hemolymph of venomous arthropods, and especially of cytolytic peptides in their venom, and a dual role is proposed: acting as antimicrobials as well as increasing the potency of the venom by influencing excitable cells.
Abstract: As a response to invading microorganisms, the innate immune system of arthropods has evolved a complex arrangement of constitutive and inducible antimicrobial peptides that immediately destroy a large variety of pathogens. At the same time, venomous arthropods have developed an additional offensive system in their venom glands to subdue their prey items. In this complex venom system, several enzymes, low-molecular-mass compounds, neurotoxins, antimicrobial and cytolytic peptides interact together, resulting in extremely rapid immobilization and/or killing of prey or aggressors. This review provides an overview of antimicrobial peptides identified in the hemolymph of venomous arthropods, and especially of cytolytic peptides in their venom. For these peptides a dual role is proposed: acting as antimicrobials as well as increasing the potency of the venom by influencing excitable cells.
TL;DR: The simple composition of the diastereomeric peptides and their stability regarding enzymatic degradation by serum components make them excellent candidates for new chemotherapeutic drugs.
Abstract: Despite significant advances in cancer therapy, there is an urgent need for drugs with a new mode of action that will preferentially kill cancer cells. Several cationic antimicrobial peptides, which bind strongly to negatively charged membranes, were shown to kill cancer cells slightly better than normal cells. This was explained by a slight increase (3-9%) in the level of the negatively charged membrane phosphatidylserine (PS) in many cancer cells compared to their normal counterparts. Unfortunately, however, these peptides are inactivated by serum components. Here we synthesized and investigated the anticancer activity and the role of peptide charge, peptide structure, and phospholipid headgroup charge on the activity of a new group of diastereomeric lytic peptides (containing D- and L-forms of leucine and lysine; 15-17 amino acids long). The peptides are highly toxic to cancer cells, to a degree similar to or larger than that of mitomycin C. However, compared with mitomycin C and many native antimicrobial peptides, they are more selective for cancer cells. The peptides were investigated for (i) their binding to mono- and bilayer membranes by using the surface plasmon resonance (SPR) technique, (ii) their ability to permeate membranes by using fluorescence spectroscopy, (iii) their structure and their effect on the lipid order by using ATR-FTIR spectroscopy, and (iv) their ability to bind to cancer versus normal cells by using confocal microscopy. The data suggest that the peptides disintegrate the cell membrane in a detergent-like manner. However, in contrast to native antimicrobial peptides, the diastereomers bind and permeate similarly zwitterionic and PS-containing model membranes. Therefore, cell selectivity is probably determined mainly by improved electrostatic attraction of the peptides to acidic components on the surface of cancer cells (e.g., O-glycosylation of mucines). The simple composition of the diastereomeric peptides and their stability regarding enzymatic degradation by serum components make them excellent candidates for new chemotherapeutic drugs.