Lipidation of Antimicrobial Peptides as a Design Strategy for Future Alternatives to Antibiotics

Multi-drug-resistant bacteria are becoming more prevalent, and treating these bacteria is becoming a global concern. One alternative approach to combat bacterial resistance is to use antimicrobial (AMPs) or host-defense peptides (HDPs) because they possess broad-spectrum activity, function in a variety of ways, and lead to minimal resistance. However, the therapeutic efficacy of HDPs is limited by a number of factors, including systemic toxicity, rapid degradation, and low bioavailability. One approach to circumvent these issues is to use lipidation, i.e., the attachment of one or more fatty acid chains to the amine groups of the N-terminus or a lysine residue of an HDP. In this review, we examined lipidated analogs of 66 different HDPs reported in the literature to determine: (i) whether there is a link between acyl chain length and antibacterial activity; (ii) whether the charge and (iii) the hydrophobicity of the HDP play a role; and (iv) whether acyl chain length and toxicity are related. Overall, the analysis suggests that lipidated HDPs with improved activity over the nonlipidated counterpart had acyl chain lengths of 8–12 carbons. Moreover, active lipidated peptides attached to short HDPs tended to have longer acyl chain lengths. Neither the charge of the parent HDP nor the percent hydrophobicity of the peptide had an apparent significant impact on the antibacterial activity. Finally, the relationship between acyl chain length and toxicity was difficult to determine due to the fact that toxicity is quantified in different ways. The impact of these trends, as well as combined strategies such as the incorporation of d- and non-natural amino acids or alternative approaches, will be discussed in light of how lipidation may play a role in the future development of antimicrobial peptide-based alternatives to current therapeutics.     

Mechanism of Antimicrobial Peptides: Antimicrobial,Anti-Inflammatory and Antibiofilm Activities

Antimicrobial peptides (AMPs) are regarded as a new generation of antibiotics. Besides antimicrobial activity, AMPs also have antibiofilm, immune-regulatory, and other activities. Exploring the mechanism of action of AMPs may help in the modification and development of AMPs. Many studies were conducted on the mechanism of AMPs. The present review mainly summarizes the research status on the antimicrobial, anti-inflammatory, and antibiofilm properties of AMPs. This study not only describes the mechanism of cell wall action and membrane-targeting action but also includes the transmembrane mechanism of intracellular action and intracellular action targets. It also discusses the dual mechanism of action reported by a large number of investigations. Antibiofilm and anti-inflammatory mechanisms were described based on the formation of biofilms and inflammation. This study aims to provide a comprehensive review of the multiple activities and coordination of AMPs in vivo, and to fully understand AMPs to realize their therapeutic prospect.     

Two Male-Specific Antimicrobial Peptides SCY2 and Scyreprocin as Crucial Molecules Participated in the Sperm Acrosome Reaction of Mud Crab Scylla paramamosain

Antimicrobial peptides (AMPs) identified in the reproductive system of animals have been widely studied for their antimicrobial activity, but only a few studies have focused on their physiological roles. Our previous studies have revealed the in vitro antimicrobial activity of two male gonadal AMPs, SCY2 and scyreprocin, from mud crab Scylla paramamosain. Their physiological functions, however, remain a mystery. In this study, the two AMPs were found co-localized on the sperm apical cap. Meanwhile, progesterone was confirmed to induce acrosome reaction (AR) of mud crab sperm in vitro, which intrigued us to explore the roles of the AMPs and progesterone in AR. Results showed that the specific antibody blockade of scyreprocin inhibited the progesterone-induced AR without affecting intracellular Ca²⁺ homeostasis, while the blockade of SCY2 hindered the influx of Ca²⁺. We further showed that SCY2 could directly bind to Ca²⁺. Moreover, progesterone failed to induce AR when either scyreprocin or SCY2 function was deprived. Taken together, scyreprocin and SCY2 played a dual role in reproductive immunity and sperm AR. To our knowledge, this is the first report on the direct involvement of AMPs in sperm AR, which would expand the current understanding of the roles of AMPs in reproduction.     

Emerging Antifungal Targets and Strategies

Despite abundant research in the field of antifungal drug discovery, fungal infections remain a significant healthcare burden. There is an emerging need for the development of novel antifungals since those currently available are limited and do not completely provide safe and secure protection. Since the current knowledge regarding the physiology of fungal cells and the infection mechanisms is greater than ever, we have the opportunity to use this for the development of novel generations of antifungals. In this review, we selected and summarized recent studies describing agents employing different antifungal mechanisms. These mechanisms include interference with fungal resistance, including impact on the efflux pumps and heat shock protein 90. Additionally, interference with virulence factors, such as biofilms and hyphae; the impact on fungal enzymes, metabolism, mitochondria, and cell wall; and antifungal vaccines are explored. The agents investigated belong to different classes of natural or synthetic molecules with significant attention given also to plant extracts. The efficacy of these antifungals has been studied mainly in vitro with some in vivo, and clinical studies are needed. Nevertheless, there is a large quantity of products employing novel antifungal mechanisms that can be further explored for the development of new generation of antifungals.     

Antifungal and antibacterial functions of medicinal leech recombinant destabilase-lysozyme and its heated-up derivative

Antifungal activity of recombinant medicinal leech destabilase-lysozyme (rec.Dest-Lys) was investigated by using fungi: Botrytis cinerea, and Verticillium lateriticum, including yeasts Candida guillermoudii and Shizosaccharomyces pombe. Its antibacterial activity was investigated on gram-negative bacteria Pseudomonas fluorescens. These activities were assessed by radial agar diffusion assay, and scanning and transmission electron microscopy. Therefore, destabilase-lysozyme not only is endo-isopeptidase and lysozyme, but also has antifungal and antibacterial activities. Muramidase activity of rec.Dest-Lys disappeared after heat-treating at 90°C for 50 min without the loss of its antimicrobial activity. Furthermore we showed for the first time that the heated-up derivative of rec.Dest-Lys exhibited more potent activities against the above enumerated fungi and gram-negative bacteria than original protein.     

Short Peptides Make a Big Difference: The Role of Botany-Derived AMPs in Disease Control and Protection of Human Health

Botany-derived antimicrobial peptides (BAMPs), a class of small, cysteine-rich peptides produced in plants, are an important component of the plant immune system. Both in vivo and in vitro experiments have demonstrated their powerful antimicrobial activity. Besides in plants, BAMPs have cross-kingdom applications in human health, with toxic and/or inhibitory effects against a variety of tumor cells and viruses. With their diverse molecular structures, broad-spectrum antimicrobial activity, multiple mechanisms of action, and low cytotoxicity, BAMPs provide ideal backbones for drug design, and are potential candidates for plant protection and disease treatment. Lots of original research has elucidated the properties and antimicrobial mechanisms of BAMPs, and characterized their surface receptors and in vivo targets in pathogens. In this paper, we review and introduce five kinds of representative BAMPs belonging to the pathogenesis-related protein family, dissect their antifungal, antiviral, and anticancer mechanisms, and forecast their prospects in agriculture and global human health. Through the deeper understanding of BAMPs, we provide novel insights for their applications in broad-spectrum and durable plant disease prevention and control, and an outlook on the use of BAMPs in anticancer and antiviral drug design.     

Atomic-Resolution Structures and Mode of Action of Clinically Relevant Antimicrobial Peptides

Global rise of infections and deaths caused by drug-resistant bacterial pathogens are among the unmet medical needs. In an age of drying pipeline of novel antibiotics to treat bacterial infections, antimicrobial peptides (AMPs) are proven to be valid therapeutics modalities. Direct in vivo applications of many AMPs could be challenging; however, works are demonstrating encouraging results for some of them. In this review article, we discussed 3-D structures of potent AMPs e.g., polymyxin, thanatin, MSI, protegrin, OMPTA in complex with bacterial targets and their mode of actions. Studies on human peptide LL37 and de novo-designed peptides are also discussed. We have focused on AMPs which are effective against drug-resistant Gram-negative bacteria. Since treatment options for the infections caused by super bugs of Gram-negative bacteria are now extremely limited. We also summarize some of the pertinent challenges in the field of clinical trials of AMPs.     

木塑复合材料的霉腐真菌危害及防霉抗菌剂的应用进展

木塑复合材料(WPCs)是近年来广泛应用的一种新型复合材料,兼有木材和高分子材料二者的优点,但同时也存在一个很大的弊端:易受霉腐真菌的危害。本文主要介绍了霉腐真菌对WPCs的危害情况及防霉抗菌剂的开发生产情况,同时简要阐述了防霉抗菌剂的发展趋势,最后指出开发防霉抗菌剂的必要性和重要性。     

The Antimicrobial Peptide 1018-K6 Interacts Distinctly with Eukaryotic and Bacterial Membranes,the Basis of Its Specificity and Bactericidal Activity

Since penicillin was discovered, antibiotics have been critical in the fight against infections. However, antibiotic misuse has led to drug resistance, which now constitutes a serious health problem. In this context, antimicrobial peptides (AMPs) constitute a natural group of short proteins, varying in structure and length, that act against certain types of bacterial pathogens. The antimicrobial peptide 1018-K6 (VRLIVKVRIWRR- NH2) has significant bactericidal and antibiofilm activity against Listeria monocytogenes isolates, and against different strains and serotypes of Salmonella. Here, the mechanism of action of 1018-K6 was explored further to understand the peptide–membrane interactions relevant to its activity, and to define their determinants. We combined studies with model synthetic membranes (liposomes) and model biological membranes, assessing the absorption maximum and the quenching of 1018-K6 fluorescence in aqueous and lipid environments, the self-quenching of carboxyfluorescein, as well as performing lipid sedimentation assays. The data obtained reflect the differential interactions of the 1018-K6 peptide with eukaryotic and prokaryotic membranes, and the specific interactions and mechanisms of action in the three prokaryotic species studied: Salmonella Typhimurium^2GN, Escherichia coli^3GN, and Staphylococcus aureus^3GP. The AMP 1018-K6 is a candidate to prevent (food preservation) or treat (antibiotic use) infections caused by certain pathogenic bacteria, especially some that are resistant to current antibiotics.     

家蝇抗菌肽祛痘功效性评价及其产品开发

采用肉汤稀释法测得家蝇抗菌肽对痤疮丙酸杆菌(Propionibacterium acnes)的最低抑菌浓度(MIC)为0.078 mg/mL.根据GB 15979-2002《一次性使用卫生用品卫生标准》中附录C4“溶出性抗(抑)菌产品抑菌性能试验方法”,测得家蝇抗菌肽在添加质量分数为1％,2％,3％和5％时的抑菌率分别为34.21％,42.42％,99.99％和99.99％.根据QB/T1857-2004中润肤膏霜的卫生指标及感官、理化指标的试验方法及检验标准对该祛痘产品进行检测,结果表明各项指标均符合标准中的要求,且进一步的加速稳定性试验表明,产品的稳定性较好,未见分层、变色、变质和变味等现象的发生.     

乌司他丁和泰索帝对乳腺癌细胞增殖、侵袭的影响及其机制

目的探讨乌司他丁(Ulinastatin for injection,UTI)和泰索帝(Taxotere,TXT)对人乳腺癌细胞MDA-MB-231(ER-)增殖、侵袭及血管内皮生长因子-C(Vascular endothelial growth factor-C,VEGF-C)、碱性成纤维细胞生长因子(Basic fibroblastgrowth factor,bFGF)、神经生长因子(Nerve growth factor,NGF)mRNA转录水平的影响。方法体外培养MDA-MB-231细胞,随机分为4组:对照组(只加RPMI1640培养液)、UTI组(终浓度800 U/ml)、TXT组(3.7μg/ml)、UTI+TXT组(800 U/ml UTI+3.7μg/ml TXT)。给药后24、48、72 h,采用MTT法检测细胞增殖水平;24 h,采用Transwell侵袭小室法检测细胞侵袭能力,实时荧光定量PCR法检测细胞VEGF-C、bFGF、NGF基因mRNA的转录水平。结果 UTI、TXT及UTI+TXT呈时间依赖性抑制MDA-MB-231细胞的增殖(P均<0.05),并显著抑制MDA-MB-231细胞的侵袭能力(P均<0.01)及VEGF-C、bFGF、NGF基因mRNA的转录水平(P均<0.05);TXT组与UTI+TXT组NGF基因mRNA转录水平比较,差异无统计学意义(P>0.05);对细胞增殖、侵袭及VEGF-C、bFGF、NGF基因mRNA转录的抑制作用UTI+TXT>TXT>UTI。结论 UTI和TXT均可显著抑制乳腺癌细胞MDA-MB-231增殖、侵袭,UTI可增强TXT的抑制作用,其机制可能与下调VEGF-C、bFGF、NGF mRNA的表达有关。     

聚丙烯灰分的来源及控制手段

本文对环管聚丙烯装置PP产品的灰分来源进行定性的分析,并在此基础上推导出定量的计算方法,从而为控制好聚丙烯产品的灰分含量,提高出厂产品优级品率提供了有实际意义的指导。     

Porous polymer particles—A comprehensive guide to synthesis, characterization, functionalization and applications

This review is written to fulfill the need of a comprehensive guide for the manufacture of porous polymer particles. The synthesis section discusses and for the first time compares microfluidics, membrane/microchannel, suspension, dispersion, precipitation, multistage polymerizations and a few other less known methods, microfluidics being in greater detail. The comparison includes on one hand simplicity, scaling-up possibilities and the ability to yield nonspherical particles for these methods and on the other hand size, size monodispersity, pore characteristics and chemical functionality of the obtained particles. This extensive comparison certainly makes this review also useful for the preparation of nonporous particles. In addition, functionalization/characterization techniques and applications of porous particles are also discussed, including some visionary recommendations. The review is expected not only to enable individual experts of each field to compare their methods with the other ones, but also to be a handbook for the newcomers to this field to guide them from the synthesis to the applications.