Isolation and characterisation of proline/arginine-rich cathelicidin peptides from ovine neutrophils

Cathelicidins are a family of gene-encoded antimicrobial peptides found in mammals. Seven cathelicidin genes have been identified in sheep, but up to now only two variants of one of these predicted peptides (OaBac5) have been purified from ovine neutrophils. In this work numerous proline/arginine-rich cathelicidin peptides were purified, including the originally predicted OaBac5 and another OaBac5 variant. As well as this, the C-terminus of the predicted OaBac7.5 and various truncated forms of OaBac11 were purified. Even though these peptides were much smaller than those predicted, they still displayed antimicrobial activity.     

Synergistic effects of ovine-derived cathelicidins and other antimicrobials against Escherichia coli O157:H7 and Staphylococcus aureus 1056 MRSA

Synergistic effects of ovine-derived cathelicidins SMAP29 and OaBac5mini with the antimicrobials polymyxin B, lysozyme, nisin and lactoferrin were investigated against E. coli O157:H7 and S. aureus 1056 MRSA. Lysozyme showed synergy against E. coli O157:H7 with SMAP29, polymyxin B and lactoferrin. Synergy was also found between SMAP29 and lactoferrin against this host. Against S. aureus 1056 MRSA, lysozyme showed synergy with OaBac5mini, polymyxin B and nisin, while synergy was also found between nisin and OaBac5mini and polymyxin B. Other combinations of the antimicrobials were either additive or non-synergistic.     

The human cathelicidin LL-37 enhances airway mucus production in chronic obstructive pulmonary disease

Airway mucus overproduction is a distinguishing feature of chronic obstructive pulmonary disease (COPD). LL-37 is the only member of human cathelicidins family of antimicrobial peptides and plays a central role in many immune and inflammatory reactions. Increasing evidence suggests the involvement of LL-37 in the pathogenesis of COPD. Here, we investigated the effects of LL-37 on airway mucus overproduction in COPD. We observed overexpression of both LL-37 and MUC5AC mucin (a major mucin component of mucus) in airways of COPD patients and found a correlation between them. We showed in vitro that LL-37 induces MUC5AC mucin production by airway epithelial NCI-H292 cells in the absence and presence of cigarette smoke extract, with TNF-α converting enzyme (TACE)–EGFR–ERK1/2 pathway and IL-8 required for the induction. Therefore, we concluded that LL-37 enhances the mucus production in COPD airways, thus contributing to the progression of COPD.     

Antimicrobial fragments of the pro-region of cathelicidins and other immune peptides

In addition to the numerous cathelicidin peptides that are associated with the antimicrobial activity exhibited by a crude extract from ovine blood, a further three peptides with antimicrobial activity have been identified. These were part of the precursor cathelin domain of cathelicidins, a large fragment of platelet factor 4 and a small peptide similar to signal peptide of the T-cell glycoprotein CD4 precursor. Fragments of proteins that are involved in protecting the host from infection may have a secondary purpose as antimicrobial agents once they have carried out their primary purpose and are cleaved the main protein.     

BMAP-28 improves the efficacy of vancomycin in rat models of gram-positive cocci ureteral stent infection

An experimental study was performed to evaluate the efficacy of BMAP-28 alone and in combination with vancomycin in animal models ureteral stent infection due to Enterococcus faecalis and Staphylococcus aureus. Study included a control group without bacterial challenge to evaluate the sterility of surgical procedure, a challenged control group that did not receive any antibiotic prophylaxis and for each bacterial strain three challenged groups that received (a) 10 mg/kg vancomycin intraperitoneally, immediately after stent implantation, (b) BMAP-28-coated ureteral stents where 0.2-cm(2) sterile ureteral stents were incubated in 1mg/l BMAP-28 solution for 30 min immediately before implantation and (c) intraperitoneal vancomycin plus BMAP-28-coated ureteral stent at the above concentrations. Experiments were performed in duplicate. Ureteral stents were explanted at day 5 following implantation and biofilm bacteria enumerated. Our data showed that rats that received intraperitoneal vancomycin showed the lowest bacterial numbers. BMAP-28 combined with vancomycin showed efficacies higher than that of each single compound. These results highlight the potential usefulness of this combination in preventing ureteral stent-associated in gram-positive infections.     

Cathelicidin family of antimicrobial peptides: proteolytic processing and protease resistance

Cathelicidins are a gene family of antimicrobial peptides produced as inactive precursors. Signal peptidase removes the N-terminal signal sequence, while peptidylglycine alpha-amidating monooxygenase often amidates and cleaves the C-terminal region. Removal of the cathelin domain liberates the active antimicrobial peptide. For mammalian sequences, this cleavage usually occurs through the action of elastase, but other tissue-specific processing enzymes may also operate. Once released, these bioactive peptides are susceptible to proteolytic degradation. We propose that some mature cathelicidins are naturally resistant to proteases due to their unusual primary structures. Among mammalian cathelicidins, proline-rich sequences should resist attack by serine proteases because proline prevents cleavage of the scissile bond. In hagfish cathelicidins, the unusual amino acid bromotryptophan may make the active peptides less susceptible to proteolysis for steric reasons. Such protease resistance could extend the pharmacokinetic lifetimes of cathelicidins in vivo, sustaining antimicrobial activity.     

两栖类动物Cathelicidins家族 抗菌肽研究进展

两栖类动物皮肤裸露和湿润的特性易于微生物的生长,它们为了抵御病原微生物的侵袭,在长期自然进化过程中形成了以抗菌肽(AMPs)为主要防御机制的免疫系统。抗菌肽广泛分布于动物、植物、微生物中,是生物用于抵御细菌、真菌、病毒和原虫等病原体侵袭的重要武器之一,在进化上是一类非常古老而有效的天然防御物质。Cathelicidins是脊椎动物特有的重要抗菌肽家族之一,除具有高效广谱的抗菌活性,还具有如抗炎、抗氧化、伤口修复、抑制组织损伤和促进血管生成等多种重要活性,因此Cathelicidins家族抗菌肽已成为抗感染多肽类新药的研发热点。本文将从两栖类动物Cathelicidins家族抗菌肽的一般特点、来源分布、生物合成与结构、生物学活性、作用机制及应用前景等几个方面,综合阐述国内外的研究动态。     

Antimicrobial peptides: clinical relevance and therapeutic implications

Antimicrobial peptides (AMPs) are molecules that provide protection against environmental pathogens, acting against a large number of microorganisms, including bacteria, fungi, yeast, virus and others. Two major groups of antimicrobial peptides are found in humans: cathelicidins and defensins. Recently, several studies have furnished information that besides their role in infection diseases, antimicrobial peptides play a role in diseases as diverse as inflammatory disorders, autoimmunity and cancer. Here, we discuss the role of antimicrobial peptides and vitamin D have in such complex diseases and propose their use should be more explored in the diagnosis and treatment of such conditions.     

Analysis of antimicrobial peptides from porcine neutrophils

Cationic host defence peptides are important components of innate immunity in pigs and other mammalians. Most of these peptides have a direct antimicrobial activity and they also have a broad spectrum of effects on the host immune system, which may be taken into account in the introduction of novel therapeutics. Our method permits simultaneous isolation of six antibacterial peptides, i.e. prophenin-1, prophenin-2, PR-39, and protegrins 1-3 from a porcine neutrophil crude extract and characterisation of them. Among the obtained peptides the greatest bactericidal activity expressed as MBC was seen in protegrins (10 μg/ml), whereas in the other studied peptides MBC was on the level of 20 μg/ml. Minimal inhibitory concentrations (MIC) reached 10 μg/ml for protegrins 1-3 and 20 μg/ml for prophenins, and PR-39. Within the bactericidal range all isolated peptides didn't show cytotoxicity on cell lines used in our experiment.     

Ribosomally synthesized antimicrobial peptides: their function, structure, biogenesis, and mechanism of action

Ribosomally synthesized peptides with antimicrobial activity are produced by prokaryotes, plants, and a wide variety of animals, both vertebrates and invertebrates. These peptides represent an important defense against micro-organisms. Although the peptides differ greatly in primary structures, they are nearly all cationic and very often amphiphilic, which reflects the fact that many of these peptides kill their target cells by permeabilizing the cell membrane. Moreover, many of these peptides may roughly be placed into one of three groups: (1) those that have a high content of one (or two) amino acid(s), often proline, (2) those that contain intramolecular disulfide bonds, often stabilizing a predominantly β-sheet structure, and (3) those with amphiphilic regions if they assume an α-helical structure. Most known ribosomally synthesized antimicrobial peptides have been identified and characterized during the past 15 years. As a result of these studies, insight has been gained into fundamental aspects of biology and biochemistry such as innate immunity, membrane-protein interactions, and protein modification and secretion. Moreover, it has become evident that these peptides may be developed into useful antimicrobial additives and drugs. This review presents a broad overview of the main types of ribosomally synthesized antimicrobial peptides produced by eukaryotes and prokaryotes. Received: 30 August 1996 / Accepted: 26 November 1996