阳离子抗菌肽的研究进展

阳离子抗菌肽是一类具抗微生物活性的小分子多肽，按结构特征可分为α－螺旋肽和β－折叠肽，不同来源或同一抗菌肽的不同结构形式生物活性差别较大，部分抗菌肽之间或抗菌肽与抗生素之间存在协同作用，特别是最近发现一些抗菌肽具有抗内毒素活性。阳离子抗菌肽的结构特征是其发挥作用的重要基础，α－螺旋肽通过其两亲性的α－螺旋上的正电茶与细菌细胞膜磷脂分子的负电荷之间的静电吸引而结合在细菌膜上，并借助于疏水段分子中连接结构的柔性插入到细胞膜中，最终通过膜内分子间的相互位移使抗菌肽分子相互聚集在一起形成离子通道，使细菌失去膜势，不能保持正常的渗透压而死亡。一般认为β－折叠肽也是和细胞膜结合后，结构发生变化而发挥作用。抗菌肽和细胞膜结合及形成离子通道受多种因素的影响，如阳离子抗菌肽的结构、浓度，环境 pH、温度，介质的离子强度。阳离子抗菌肽杀菌力强，抗菌谱广，不良反应少，因此在食品、农业，特别是在医药领域都有很好的应用前景，极可能发展成为一类全新的抗生素。     

抗菌肽作为新型抗感染药物的研究进展

抗菌肽(AMPs)作为传统抗生素的潜在取代物,已引起广泛关注。尽管抗生素彻底改变了人类对抗细菌感染的斗争,但细菌物种的快速适应及抗生素的滥用导致了耐药菌株的出现和广泛存在。AMPs已被证明是一种替代方案,其具有明显的杀菌抗感染作用,还可抑制生物膜的形成,诱导现有生物膜的溶解。综述旨在阐明AMPs的作用机制和目前的临床应用,及多肽开发中遇到的问题与解决方法,为AMPs的临床开发应用提供理论依据。     

常见抗生素与新型抗菌药物在临床上的研究应用进展

摘要：抗生素的研发与使用有效杀灭和抑制了众多病原菌，挽救了无数人的生命，但由于抗生素的不合理使用，导致细菌耐 药不断出现，耐药菌的感染已严重地威胁人类的生命健康。为此，本文主要对近年来临床上常用的抗生素如β-内酰胺类、喹诺酮 类、氨基糖苷类药物以及新型抗菌药物如抗菌肽和纳米颗粒的应用研究进行总结分析与探讨，为临床上治疗疾病提供一些参考。     

家蝇抗菌肽抗菌活性及抗菌机制的初步研究

目的　研究家蝇抗菌肽的抗菌活性及抗菌机制。方法　用损伤感染的方法诱导家蝇幼虫表达抗菌肽 ,通过 Sephadex过滤层析和 HL PC技术纯化提取 ,用平板法和稀释法作抗菌活性试验 ,并用电子扫描技术研究抗菌肽的抗菌机制。结果　家蝇抗菌肽对铜绿假单胞菌、大肠埃希氏菌、耐甲氧西林金黄色葡萄球菌( MRSA)均有明显的抗菌活性。大肠埃希氏菌与 5 0 μg/ml的纯化抗菌肽溶液一起 37℃孵育 6 0 min后 ,大肠埃希氏菌不能存活。经电镜扫描观察发现 ,细菌的细胞膜出现破损和穿孔现象。结论　家蝇抗菌肽具有明显的广谱抗菌活性 ,对阴性杆菌和阳性球菌均有杀伤作用。抗菌肽的抗菌机制是通过破坏细菌的细胞膜而杀伤细菌的     

抗菌肽作用机制及应用研究进展

在这抗生素耐药性病菌不断出现的时代,新型抗菌药物的发现已迫在眉睫。而抗菌肽为大多数生物对入侵病原体的自然防御系统的重要组成部分,具有独特的抗菌作用机制,迅速杀菌且不易引发细菌的耐药性,可单独或与抗生素联合使用杀伤病原体,是一类极具发展潜力的生物药物。本文根据抗菌肽的理化性质,作用机制及抗菌肽的设计等进行综述,并对几种有前景的抗菌肽作一简单介绍。     

抗菌肽对耐甲氧西林金黄色葡萄球菌的抗菌机制研究进展

目的:了解抗菌肽对耐甲氧西林金黄色葡萄球菌(MRSA)的抗菌机制,以期为抗菌肽临床治疗MRSA肺炎提供参考。方法:查阅近年来国内外相关文献,就各种抗菌肽对MRSA的抗菌机制的相关研究进行归纳和总结。结果与结论:抗菌肽相对于抗菌药物拥有较多优势——(1)抗菌肽是生物天然免疫系统的组成部分,容易获得;抗菌肽氨基酸数较少、肽链较短,减小了合成抗菌肽的难度,为大量人工合成抗菌肽提供了可能性。(2)抗菌肽表面富含正电荷,YD1、Melittin和Bac8c均通过其表面的正电荷与MRSA表面的负电荷结合并黏附于细菌表面,进一步破坏细胞膜从而杀灭细菌;LL-37能抑制MRSA生物膜的形成并破坏已经形成的MRSA生物膜;h BD3-CBD通过在MRSA周围聚集进而发挥杀菌作用;J-AA、J-RR和J-AR利用其结构特殊性,通过内/外膜透化机制,破坏MRSA细胞膜,从而杀伤细菌。上述机制皆不涉及受体与配体之间的结合,避免了MRSA对抗菌肽产生耐药性。(3)大部分抗菌肽在极低的MIC下即已对MRSA展示出了强大的杀菌作用。抗菌肽的使用也存在一定的局限性——(1)抗菌肽的肽链较短,增加了提取难度,人工合成抗菌肽则提高了药物成本。(2)抗菌肽的短肽链和简单结构,使其稳定性较差。(3)抗菌肽是一种异种蛋白,可能诱发患者产生一系列的免疫反应和毒性作用。     

中药抑菌作用特点及其开发优势研究

随着细菌耐药性危机加剧，人类生活与生产受到严重危害，抗菌药物的规范使用逐渐受到重视。国家颁布相关规定约束抗菌药物的使用，减弱药物滥用造成的耐药性问题。中药是我国传统药物，作为抑菌药物具有多种优势，可单独作为抗菌药物，亦可联合抗生素减弱细菌耐药性，其作用机制也逐渐得到了阐释。因此，加大对中药抑菌作用的研究，是研发新的抗菌药物的重要途径。本文通过介绍中药抗菌优势，分析中药抑菌作用的研究价值，为中药抑菌研究提供参考。     

人β防御素-3的研究进展

人β防御素-3是存在于皮肤和上皮黏膜组织的小分子抗菌肽,作为人体重要的内源性抗生素可以有效抵御细菌的侵染。不仅在自身免疫而且在获得性免疫过程中也发挥作用。它作用于微生物细胞膜的防御机理以及不易引起耐药性的特点已引起各国研究者的日益重视。本文对其分子结构、表达调控、抗菌作用机理和药用价值作一综述。     

合成棕点湍蛙抗菌肽的抗菌活性评价

目的对合成棕点湍蛙抗菌肽的抗菌作用进行分析,探讨合成产物与天然产物的一致性以及临床应用价值。方法体外抗菌试验测定合成抗菌肽及与庆大霉素、青霉素和链霉素联合应用对金色葡萄球菌和大肠埃希菌的最小杀菌浓度(MBC)。结果合成抗菌肽对金黄色葡萄球菌和大肠埃希菌均有一定的杀菌作用,MBC值分别为200 mg.L-1和100 mg.L-1,但活性低于生物化学方法提取的天然产物。合成抗菌肽与青霉素、链霉素联合使用后抗菌作用有增强趋势,其中与青霉素联合使用的效果较明显,MBC值达到青霉素/合成肽为0.625 mg.L-1/25 mg.L-1。结论抗菌肽的联合应用可能有助于改善病原性细菌对传统抗生素的耐药性。     

应对细菌耐药——研发新药与合理使用抗生素

抗生素的滥用不仅浪费医药资源,增加患者的医疗费用,更会导致细菌耐药。从开始利用抗生素治疗疾病到第五代头孢菌素的成功研发,人类一直在应对细菌耐药这一问题。当前,研究者致力于研究新型杀菌药物,监管部门加强医疗机构对抗菌药物使用的管理,努力寻找遏制细菌耐药的措施。     

The use of technetium-99m radiolabeled human antimicrobial peptides for infection specific imaging

Bacterial resistance to conventional antibiotics poses a challenge medicine to search for alternatives. Cationic antimicrobial peptides (AMPs) are promising for the development of a new class of antibiotics. This review focuses on the use of technetium-99m labeled synthetic AMPs, derived from human natural cationic AMPs, for target-delivery to and in vivo detection of infection sites caused by (drug-resistant) micro-organisms. The scintigraphic approach has proven to be a reliable method for evaluating AMPs in pharmacological studies and for optimizing target-delivery of radiolabeled AMPs to pathological sites in animals and humans. In addition, the effect of alterations in amphipathicity, amino acid substitution, and dimerization on the biological performance of AMPs is reported. Radiolabeled AMPs offer good perspectives for diagnosis of infections, for monitoring therapy, and, most importantly, for the ability to discriminate between infections and sterile inflammatory processes.     

Design and synthesis of cationic antimicrobial peptides with improved activity and selectivity against Vibrio spp

Extensive use of classical antibiotics has led to the growing emergence of many resistant strains of pathogenic bacteria. Evidence has suggested that cationic antimicrobial peptides (AMPs) are of greatest potential to represent a new class of antibiotics. The largest group of AMPs comprises peptides that fold into an amphipathic alpha-helical conformation when interacting with the target microorganism. In the current study, a series of cationic AMPs of 20 amino acids was designed and synthesised based on four structural parameters, including charge, polar angle, hydrophobicity and hydrophobic moment. The effect of these parameters on antimicrobial activity and selectivity was assessed by structural and biological analyses. Our results indicated that high hydrophobicity and amphipathicity (hydrophobic moment) were correlated with increased haemolytic activity, whilst antimicrobial activity was found to be less dependent on these factors. Three of the synthetic AMPs (GW-Q4, GW-Q6 and GW-H1) showed higher antimicrobial activity and selectivity against a broad spectrum of Gram-positive and Gram-negative bacteria compared with the naturally occurring AMPs magainin 2a and pleurocidin. This study also demonstrates that these rationally designed cationic and amphipathic helical AMPs exhibited high selectivity against several Vibrio spp. and are potential agents for future use in the treatment of these marine pathogens.     

Current state of a dual behaviour of antimicrobial peptides—Therapeutic agents and promising delivery vectors

Micro‐organism resistance is an important challenge in modern medicine due to the global uncontrolled use of antibiotics. Natural and synthetic antimicrobial peptides (AMPs) symbolize a new family of antibiotics, which have stimulated research and clinical interest as new therapeutic options for infections. They represent one of the most promising antimicrobial substances, due to their broad spectrum of biological activity, against bacteria, fungi, protozoa, viruses, yeast and even tumour cells. Besides, being antimicrobial, AMPs have been shown to bind and neutralize bacterial endotoxins, as well as possess immunomodulatory, anti‐inflammatory, wound‐healing, angiogenic and antitumour properties. In contrast to conventional antibiotics, which have very defined and specific molecular targets, host cationic peptides show varying, complex and very rapid mechanisms of actions that make it difficult to form an effective antimicrobial defence. Importantly, AMPs display their antimicrobial activity at micromolar concentrations or less. To do this, many peptide‐based drugs are commercially available for the treatment of numerous diseases, such as hepatitis C, myeloma, skin infections and diabetes. Herein, we present an overview of the general mechanism of AMPs action, along with recent developments regarding carriers of AMPs and their potential applications in medical fields.     

Antimicrobial Peptides and Skin: A Paradigm of Translational Medicine

Antimicrobial peptides (AMPs) are small, cationic, amphiphilic peptides with broad-spectrum microbicidal activity against both bacteria and fungi. In mammals, AMPs form the first line of host defense against infections and generally play an important role as effector agents of the innate immune system. The AMP era was born more than 6 decades ago when the first cationic cyclic peptide antibiotics, namely polymyxins and tyrothricin, found their way into clinical use. Due to the good clinical experience in the treatment of, for example, infections of mucus membranes as well as the subsequent understanding of mode of action, AMPs are now considered for treatment of inflammatory skin diseases and for improving healing of infected wounds. Based on the preclinical findings, including pathobiochemistry and molecular medicine, targeted therapy strategies are developed and first results indicate that AMPs influence processes of diseased skin. Importantly, in contrast to other antibiotics, AMPs do not seem to propagate the development of antibiotic-resistant micro-organisms. Therefore, AMPs should be tested in clinical trials for their efficacy and tolerability in inflammatory skin diseases and chronic wounds. Apart from possible fields of application, these peptides appear suited as an example of the paradigm of translational medicine for skin diseases which is today seen as a 'two-way road' - from bench to bedside and backwards from bedside to bench.     

Research advances in the development of peptide antibiotics

Bacterial resistance to antibiotics is a growing concern in both nosocomial and community acquired infections. Resistance began to emerge as early as the 1950s. Much research has been dedicated to the improvement of existing classes of antibiotics. Antimicrobial peptides (AMPs) are part of the innate immune system, and an important component of immune defense. They are produced by plants, animals, insects, and single celled organisms, and possess anti-microbial properties. As such, they are an ideal target for future antibiotic production. Bacteriocins are a subgroup of AMPs, produced by various bacteria. It has been shown that the production of chimeric peptides consisting of bacteriocins and pheromones can be targeted toward the killing of specific bacterial species. In contrast to the clonal, acquired adaptive immunity, endogenous peptide antibiotics provide a fast and energy-effective mechanism as front line defense. This review will provide an overview of AMPs and their potential for target-specific anti-infective therapy.     

Alignment-based design and synthesis of new antimicrobial Aurein-derived peptides with improved activity against Gram-negative bacteria and evaluation of their toxicity on human cells

Considering the worldwide increasing prevalence of resistance to traditional antibiotics, it is necessary to find new antibiotics to deal with this issue. Recently, antimicrobial peptides (AMPs) have been proposed as new antimicrobial agents. Aureins are a family of AMPs that are isolated from Green and Golden Bell Frogs. These peptides have a favorable antibacterial activity against Gram-positive bacteria. We designed two peptides derived from natural Aurein enjoying alignment-based design method. After synthesis of the peptides, their secondary structure was checked by circular dichroism. Consequently, the antibacterial effects of these peptides were investigated by determining the minimum inhibitory concentration (MIC) and bactericidal concentration. Eventually, the toxicity of these peptides was determined by MTT (3-[4, 5-dimethylthiazol-2-yl]-2, 5-diphenyltetrazolium bromide) assay on normal human skin cells (Hu02 cell line). Natural Aurein1.2 was used as a natural control to compare the properties in all stages. The results indicated that these new peptides had medium-upward antimicrobial activity against Escherichia coli, Pseudomonas aeruginosa, and Bacillus subtilis (MIC of 8–64 μg/mL) and weak bactericidal activity against Staphylococcus aureus (MIC of 128–256 μg/mL). Also, MTT assays results showed that AureinN2 is less toxic than AureinN1 and Aurein1.2. Toxicity of AureinN2 for Hu02 cell lines was between 20 and 40% at the concentration of 8–500 μg/mL. In this study, we were able to improve antimicrobial activity of two synthetic derivatives of the Aurein family against Gram-negative bacteria by using machine-learning algorithm and other in silico methods.     

Bacterial cell wall compounds as promising targets of antimicrobial agents II. Immunological and clinical aspects

The bacterial cell wall represents the primary target for antimicrobial agents. Microbial destruction is accompanied by the release of potent immunostimulatory membrane constituents. Both Gram-positive and Gram-negative bacteria release a variety of lipoproteins and peptidoglycan fragments. Gram-positive bacteria additionally provide lipoteichoic acids, whereas Gram-negative bacteria also release lipopolysaccharide (LPS, endotoxin), essential component of the outer leaflet of the bacterial cell wall and one of the most potent immunostimulatory molecules known. Immune activation therefore can be considered as an adverse effect of antimicrobial destruction and killing during anti-infective treatment. In contrast to antibiotics, the use of cationic amphiphilic antimicrobial peptides allows both effective bacterial killing and inhibition of the immunostimulatory effect of the released bacterial membrane constituents. The administration of antimicrobial peptides alone or in combination with antibiotic agents thus represents a novel strategy in the antiinfective treatment with potentially important beneficial aspects. Here, data are presented which describe immunological and clinical aspects of the use of antimicrobial peptides (AMPs) as therapeutic agents to treat bacterial infection and neutralize the immunostimulatory activity of released cell wall constituents.     

Use of antimicrobial peptides against microbial biofilms: advantages and limits

The formation of surface-attached cellular agglomerates, the so-called biofilms, contributes significantly to bacterial resistance to antibiotics and innate host defenses. Bacterial biofilms are associated to various pathological conditions in humans such as cystic fibrosis, colonization of indwelling medical devices and dental plaque formation involved in caries and periodontitis. Over the last years, natural antimicrobial peptides (AMPs) have attracted considerable interest as a new class of antimicrobial drugs for a number of reasons. Among these, there are the broad activity spectrum, the relative selectivity towards their targets (microbial membranes), the rapid mechanism of action and, above all, the low frequency in selecting resistant strains. Since biofilm resistance to antibiotics is mainly due to the slow growth rate and low metabolic activity of bacteria in such community, the use of AMPs to inhibit biofilm formation could be potentially an attractive therapeutic approach. In fact, due to the prevalent mechanism of action of AMPs, which relies on their ability to permeabilize and/or to form pores within the cytoplasmic membranes, they have a high potential to act also on slow growing or even non-growing bacteria. This review will highlight the most important findings obtained testing AMPs in in vitro and in vivo models of bacterial biofilms, pointing out the possible advantages and limits of their use against microbial biofilm-related infections.     

Lipo-γ-AApeptides as a new class of potent and broad-spectrum antimicrobial agents

There is increasing demand to develop antimicrobial peptides (AMPs) as next generation antibiotic agents, as they have the potential to circumvent emerging drug resistance against conventional antibiotic treatments. Non-natural antimicrobial peptidomimetics are an ideal example of this, as they have significant potency and in vivo stability. Here we report for the first time the design of lipidated γ-AApeptides as antimicrobial agents. These lipo-γ-AApeptides show potent broad-spectrum activities against fungi and a series of Gram-positive and Gram-negative bacteria, including clinically relevant pathogens that are resistant to most antibiotics. We have analyzed their structure-function relationship and antimicrobial mechanisms using membrane depolarization and fluorescent microscopy assays. Introduction of unsaturated lipid chain significantly decreases hemolytic activity and thereby increases the selectivity. Furthermore, a representative lipo-γ-AApeptide did not induce drug resistance in S. aureus, even after 17 rounds of passaging. These results suggest that the lipo-γ-AApeptides have bactericidal mechanisms analogous to those of AMPs and have strong potential as a new class of novel antibiotic therapeutics.     

Enhancing the antibacterial activity of PMAP‐37 by increasing its hydrophobicity

With increasing resistance against conventional antibiotics, there is an urgent need to discover novel substances to replace antibiotics. This need provides an opportunity for the development of antimicrobial peptides (AMPs). To develop new AMPs with effective and safe therapeutic effects, two PMAP‐37 analogs called PMAP‐37(R13‐I) and PMAP‐37(K20/27‐I) were designed to increase hydrophobicity. Antimicrobial susceptibility testing and animal infection models were used to assess their antibacterial activity. The results showed that the minimal inhibitory concentrations of PMAP‐37(R13‐I) were lower than those of PMAP‐37 for two gram‐negative strains. Compared with PMAP‐37, PMAP‐37(K20/27‐I) not only inhibited the growth of most bacterial strains, but also exhibited antibacterial activity against Shigella flexneri CICC21534. In addition, PMAP‐37(K20/27‐I) exhibited pH and thermal stability. PMAP‐37(R13‐I) had a therapeutic effect only in mice infected with Salmonella typhimurium SL1344. However, PMAP‐37(K20/27‐I) exhibited the therapeutic effects, whether in the clinical symptoms, the tissue lesions, or the tissue bacterial loads and the survival rates in mice infected with Staphylococcus aureus ATCC25923 or S. typhimurium SL1344. Therefore, PMAP‐37(K20/27‐I) can be used as a substitute for antibiotics against infection with bacterial strains.