AurH1: a new heptapeptide derived from Aurein1.2 antimicrobial peptide with specific and exclusive fungicidal activity

Due to the increasing incidence of fungal opportunistic infections and emergence of antibiotic‐resistant fungal strains, antimicrobial peptides (AMPs) are considered as ideal candidates for antifungal compounds. In silico methods can reduce the limitations of natural AMPs such as toxicity and instability and improve their antimicrobial properties and selectivity. In this study, we designed AurH1, a new truncated peptide, based on the six‐amino acid sequence of Aurein1.2. Further , the antimicrobial activities and toxicity effects of AurH1 on human skin fibroblast cells and red blood cells were investigated. Finally, field emission scanning electron microscopy (FE‐SEM) and flow cytometry were performed in order to study the mechanism of action of AurH1. The results indicated that AurH1 had only antifungal activity (at a minimal inhibitory concentration (MIC) of 7.3‐125 μg/mL) without any antibacterial effects on the selected bacteria, while Aurein1.2 had both antifungal and antibacterial activities as positive control. Furthermore, AurH1 did not show any toxicity on Hu02 cells and human red blood cells at its MIC range. In conclusion, it became clear that AurH1 is a selective peptide against fungi with no toxic effects on the selected bacteria and human cells.     

Increased potency of a novel d-β-naphthylalanine-substituted antimicrobial peptide against fluconazole-resistant fungal pathogens

The antifungal activities of the known antimicrobial peptide, P-113, as well as a new type of Trp-rich peptide, Ac-KWRRWVRWI-NH₂, Pac-525, and its modified peptide, d -Nal-Pac-525, were determined using the broth microdilution method in three different media. All peptides had similar activities against yeast pathogens in low-salt LYM media. However, only d -Nal-Pac-525 retained its antifungal activity in the media containing high concentrations of salt. Hence, d -Nal-Pac-525 has the potential of becoming a promising antifungal agent, especially for fungal pathogens with intrinsic resistance to fluconazole.     

细菌对抗菌肽的耐受机制

抗菌肽广谱、高特异、高生物活性等特点决定其具极大的临床应用潜力,然而抗菌肽的耐受是其药物开发必须重视和亟待克服的问题。从生物学的观点看,部分细菌可以产生抗菌肽,其必定存在逃避自身抗菌肽作用的机制;从进化的观点看,宿主和病原体之间是相互抑制、相互逃避、相互适应的关系,细菌在漫长的进化中会形成应对抗菌肽的特殊机制。抗菌肽对细菌存在多种作用机制,其核心是依赖于与细胞膜相互作用或进入细胞,进而改变膜完整性或干扰胞内生理生化反应导致细菌死亡;而细菌通过减弱抗菌肽结合、降低抗菌肽有效浓度等方式产生对抗菌肽的耐受。这些耐受机制也为抗菌肽类药物开发提供重要的启示。     

猪源抗菌肽PMAP-36的序列设计及其结构优化的研究进展

抗生素的耐药性和动物源性食品中的药物残留问题严重威胁全球公共卫生系统.因此,开发出不易产生耐药性、抗菌活性高的新型抗菌药物迫在眉睫.抗菌肽因其分子量小、抗菌谱广、不易产生耐药性等优点受到科学家们的广泛关注,但天然抗菌肽具有抗菌活性低、溶血活性和细胞毒性等缺陷.随着抗菌肽序列和结构的不断优化,多种具有显著体内外抗菌活性且...     

抗菌肽结构改造与人工智能研发策略

抗菌肽是一类广泛存在于生物体内的小分子肽,参与构成生物体先天免疫,可以有效抵抗病原微生物的入侵。抗菌肽具有广谱抗菌活性,且不易产生耐药性等特点,在治疗感染性疾病方面具有独特的优势,有望成为理想的抗感染药物。然而,由于部分抗菌肽尚存在稳定性差、毒性高等问题,限制了抗菌肽的广泛应用。由于人工智能算法能有效合成具有高稳定性、低毒性的抗菌肽,在探索天然抗菌肽中展现了巨大的潜力,因此本文简述了抗菌肽的抗菌机制、结构改造以及利用机器学习和深度学习等人工智能算法进行新型抗菌肽研发的优化策略,以期为抗菌肽结构优化及研发提供新思路。     

Crabrolin,a natural antimicrobial peptide: structural properties

A joint application of experimental and computational approaches has revealed the exceptionally high attitude of crabrolin, a 13‐residue peptide with sequence FLPLILRKIVTAL‐NH₂, to adopt alpha‐helix conformation not only in membrane‐mimicking solvents but also in the presence of a not negligible amount of water. Our study shows that this propensity essentially resides in the intrinsic thermodynamic stability of alpha‐helix conformation whose kinetic stability is drastically reduced in water solvent. Our analysis suggests that this is due to two effects enhanced by water: a more local effect consisting of the demolition of intra‐peptide H‐bonds, essential for the alpha‐helix formation, and a bulk – electrostatic – effect favoring conformational states more polar than alpha‐helix. Copyright © 2017 European Peptide Society and John Wiley & Sons, Ltd.     

Natural antimicrobial peptides from bacteria: characteristics and potential applications to fight against antibiotic resistance

Because of the emergence of antibiotic‐resistant pathogens worldwide, a number of infectious diseases have become difficult to treat. This threatening situation is worsened by the fact that very limited progress has been made in developing new and potent antibiotics in recent years. However, a group of antimicrobials, the so‐called bacteriocins, have been much studied lately because they hold a great potential in controlling antibiotic‐resistant pathogens. Bacteriocins are small antimicrobial peptides (AMPs) produced by numerous bacteria. They often act toward species related to the producer with a very high potency (at pico‐ to nanomolar concentration) and specificity. The common mechanisms of killing by bacteriocins are destruction of target cells by pore formation and/or inhibition of cell wall synthesis. Several studies have revealed that bacteriocins display great potential in the medical sector as bacteriocinogenic probiotics and in the clinic as therapeutic agents. In this review, we discuss the emerging antibiotic resistance and strategies to control its dissemination, before we highlight the potential of AMPs from bacteria as a new genre of antimicrobial agents.     

Mechanisms of antimicrobial and antiendotoxin activities of a triazine-based amphipathic polymer

TZP4 is a triazine-based amphipathic polymer designed to mimic the amphipathic structure found in antimicrobial peptides. TZP4 showed potent antimicrobial activity comparable to melittin against antibiotic-resistant bacteria, such as methicillin-resistant Staphylococcus aureus and multidrug-resistant Pseudomonas aeruginosa. TZP4 showed high resistance to proteolytic degradation and low tendency to develop drug resistance. The results from membrane depolarization, SYTOX Green uptake, flow cytometry, and gel retardation revealed that the mechanism of antimicrobial action of TZP4 involved an intracellular target rather than the bacterial cell membrane. Furthermore, TZP4 suppressed the messenger RNA levels of inducible nitric oxide synthase and tumor necrosis factor-α (TNF-α) and inhibited the release of nitric oxide and TNF-α in lipopolysaccharide (LPS)-stimulated RAW264.7 cells. BODIPY-TR-cadaverine displacement and dissociation of fluorescein isothiocyanate (FITC)-labeled LPS assays revealed that TZP4 strongly bound to LPS and disaggregated the LPS oligomers. Flow cytometric analysis demonstrated that TZP4 inhibits the binding of FITC-conjugated LPS to RAW264.7 cells. These observations indicate that TZP4 may exert its antiendotoxic activity by directly binding with LPS and inhibiting the interaction between LPS and CD14⁺ cells. Collectively, TZP4 is a promising drug candidate for the treatment of endotoxic shock and sepsis caused by Gram-negative bacterial infections.     

深度学习在药物活性预测研究中的应用

药物从研发到临床应用需要耗费较长的时间，研发期间的投入成本可高达十几亿元。而随着医药研发与人工智能的结合以及生物信息学的飞速发展，药物活性相关数据急剧增加，传统的实验手段进行药物活性预测已经难以满足药物研发的需求。借助算法来辅助药物研发，解决药物研发中的各种问题能够大大推动药物研发进程。传统机器学习方法尤其是随机森林、支持向量机和人工神经网络在药物活性方面能够达到较高的预测精度。深度学习由于具有多层神经网络，模型可以接收高维的输入变量且不需要人工限定数据输入特征，可以拟合较为复杂的函数模型，应用于药物研发可以进一步提高各个环节的效率。在药物活性预测中应用较为广泛的深度学习模型主要是深度神经网络（deep neural networks，DNN）、循环神经网络（recurrent neural networks，RNN）和自编码器（auto encoder，AE），而生成对抗网络（generative adversarial networks，GAN）由于其生成数据的能力常常被用来和其他模型结合进行数据增强。近年来深度学习在药物分子活性预测方面的研究和应用综述表明，深度学习模型的准确度和效率均高于传统实验方法和传统机器学习方法。因此，深度学习模型有望成为药物研发领域未来十年最重要的辅助计算模型。     

蛙皮抗菌肽促胰岛素分泌功能研究进展

随着对蛙皮抗菌肽功能研究的不断深入,陆续发现部分肽具有促胰岛素分泌活性,该活性对于2型糖尿病治疗具有较好的应用前景。蛙皮抗菌肽即可以通过克服注射胰岛素产生的低血糖反应,又能改善2型糖尿病胰岛素抵抗的问题,这使其有希望成为安全、高效治疗2型糖尿病药物的新药物。本文综述了具有促胰岛素分泌功能的蛙皮抗菌肽的序列特征和工作机制的研究进展,为进一步开展相关研究提供参考。     

Alpha-helical cationic antimicrobial peptides: relationships of structure and function

Antimicrobial peptides (AMPs), with their extraordinary properties, such as broad-spectrum activity, rapid action and difficult development of resistance, have become promising molecules as new antibiotics. Despite their various mechanisms of action, the interaction of AMPs with the bacterial cell membrane is the key step for their mode of action. Moreover, it is generally accepted that the membrane is the primary target of most AMPs, and the interaction between AMPs and eukaryotic cell membranes (causing toxicity to host cells) limits their clinical application. Therefore, researchers are engaged in reforming or de novo designing AMPs as a ‘single-edged sword’ that contains high antimicrobial activity yet low cytotoxicity against eukaryotic cells. To improve the antimicrobial activity of AMPs, the relationship between the structure and function of AMPs has been rigorously pursued. In this review, we focus on the current knowledge of α-helical cationic antimicrobial peptides, one of the most common types of AMPs in nature.     

Short AntiMicrobial Peptides (SAMPs) as a class of extraordinary promising therapeutic agents

The emergence of multidrug resistant bacteria has a direct impact on global public health because of the reduced potency of existing antibiotics against pathogens. Hence, there is a pressing need for new drugs with different modes of action that can kill microorganisms. Antimicrobial peptides (AMPs) can be regarded as an alternative tool for this purpose because they are proven to have therapeutic effects with broad‐spectrum activities. There are some hurdles in using AMPs as clinical candidates such as toxicity, lack of stability and high budgets required for manufacturing. This can be overcome by developing shorter and more easily accessible AMPs, the so‐called S hort A nti M icrobial P eptides (SAMPs) that contain between two and ten amino acid residues. These are emerging as an attractive class of therapeutic agents with high potential for clinical use and possessing multifunctional activities. In this review we attempted to compile those SAMPs that have exhibited biological properties which are believed to hold promise for the future. Copyright © 2016 European Peptide Society and John Wiley & Sons, Ltd.     

Synthesis,characterization and in vitro activity of a surface-attached antimicrobial cationic peptide

Infection associated with implanted biomaterials is common and costly and such infections are extremely resistant to antibiotics and host defenses. Consequently, there is a need to develop surfaces which resist bacterial adhesion and colonization. The broad spectrum synthetic cationic peptide melimine has been covalently linked to a surface via two azide linkers, 4-azidobenzoic acid (ABA) or 4-fluoro-3-nitrophenyl azide (FNA), and the resulting surfaces characterized by X-ray photoelectron spectroscopy and contact angle measurements. The quantity of bound peptide was estimated by a modified Bradford assay. The antimicrobial efficacy of the two melimine-modified surfaces against Pseudomonas aeruginosa and Staphylococcus aureus was compared by scanning electron microscopy (SEM) and fluorescence microscopy. Attachment of melimine via ABA gave an approximately 4-fold greater quantity of melimine bound to the surface than attachment via FNA. Surfaces melimine-modified by either attachment strategy showed significantly reduced bacterial adhesion for both strains of bacteria. P. aeruginosa exposed to ABA–melimine and FNA–melimine surfaces showed marked changes in cell morphology when observed by SEM and a reduction of approximately 15-fold (p < 0.001) in the numbers of adherent bacteria compared to controls. For the ABA–melimine surface there was a 33% increase in cells showing damaged membranes (p = 0.0016) while for FNA–melimine there was no significant difference. For S. aureus there were reductions in bacterial adhesion of approximately 40-fold (p < 0.0001) and 5-fold (p = 0.008) for surfaces modified with melimine via ABA or FNA, respectively. There was an increase in cells showing damaged membranes on ABA–melimine surfaces of approximately 87% (p = 0.001) compared to controls, while for FNA–melimine there was no significant difference observed. The data presented in this study show that melimine has excellent potential for development as a broad spectrum antimicrobial coating for biomaterial surfaces. Further, it was observed that the efficacy of antimicrobial activity is related to the method of attachment.     

Collection of antimicrobial peptides database and its derivatives: Applications and beyond

Collection of antimicrobial peptides (CAMP), CAMPSign, and ClassAMP are open‐access resources that have been developed to enhance research on antimicrobial peptides (AMPs). Comprehensive information on AMPs and machine learning‐based predictive models are made available for users through these resources. As of date, CAMP_R3 has 10,247 sequences, 757 structures, and 114 family‐specific signatures of AMPs along with associated tools for AMP sequence and structure analysis. CAMPSign uses family‐specific sequence conservation, in the form of patterns and hidden Markov models for identification of AMPs. ClassAMP can be used to classify AMPs as antibacterial, antifungal, or antiviral based on sequence information. Here we describe CAMP and its derivatives and illustrate, with a few examples, the contribution of these online resources to the advancement of our current understanding of AMPs.     

Activities of a broad-spectrum antimicrobial peptide analogue SAMP-A4-C8 and its combat against pneumonia in Staphylococcus aureus-infected mice

Antimicrobial peptides and their analogues have become substitutes for antibiotics in recent years. The antimicrobial peptide analogue SAMP-A4-C8 (n-octanoic-VRLLRRRI) with high antimicrobial activity was found in our lab. We speculate that it may kill pathogens by some lethal mechanism of action. In the present investigation, the microbicidal activities of SAMP-A4-C8 and its mechanism of action were investigated. The results demonstrated that SAMP-A4-C8 had lethal activities against Staphylococcus aureus and Candida albicans by cell disruption. Based on its microbicidal activities, we believe that it is worth further research for its potential as drug candidate. The results showed that SAMP-A4-C8, with low propensity to induce the resistance of S. aureus and C. albicans, could kill the persister cells of S. aureus and C. albicans, exhibited biofilm forming inhibition activity and preformed biofilm eradication ability against S. aureus and C. albicans, and displayed therapeutic potential on pneumonia in S. aureus-infected mice by reducing lung inflammation. The present study provided a promising drug candidate in the war against multidrug resistance.     

Activity optimization of an undecapeptide analogue derived from a frog-skin antimicrobial peptide

While natural antimicrobial peptides are potential therapeutic agents, their physicochemical properties and bioactivity generally need to be enhanced for clinical and commercial development. We have previously developed a cationic, amphipathic α-helical, 11-residue peptide (named herein GA-W2: FLGWLFKWASK-NH₂) with potent antimicrobial and hemolytic activity, which was derived from a 24-residue, natural antimicrobial peptide isolated from frog skin. Here, we attempted to optimize peptide bioactivity by a rational approach to sequence modification. Seven analogues were generated from GA-W2, and their activities were compared with that of a 12-residue peptide, omiganan, which is being developed for clinical and commercial applications. Most of the modifications reported here improved antimicrobial activity. Among them, the GA-K4AL (FAKWAFKWLKK-NH₂) peptide displayed the most potent antimicrobial activity with negligible hemolytic activity, superior to that of omiganan. The therapeutic index of GA-K4AL was improved more than 53- and more than 31-fold against Gram-negative and Gram-positive bacteria, respectively, compared to that of the starting peptide, GA-W2. Given its relatively shorter length and simpler amino acid composition, our sequence-optimized GA-K4AL peptide may thus be a potentially useful antimicrobial peptide agent.     

Identification of a cysteine-rich antimicrobial peptide from salivary glands of the tick Rhipicephalus haemaphysaloides

The presence of an effective immune response in the hemocoel of ticks is crucial for survival, as it prevents the invasion of pathogens throughout the animal's body. Antimicrobial peptides (AMPs) play an important role in this response by rapidly killing invading microorganisms. In this study, a subtraction hybridization cDNA library was constructed from the salivary glands of the unfed and fed female tick Rhipicephalus haemaphysaloides, and a novel cysteine-rich AMP designated Rhamp (R. haemaphysaloides antimicrobial peptide) was isolated and identified. The Rhamp was encoded by a gene with an open reading frame of 303 bp which encoded a mature peptide with 8 kDa molecular weight. No identity was found by BLAST search to any database entries. The sequence encoding the Rhamp was subcloned into the pGEX-4T vector and expressed in Escherichia coli. The recombinant protein of Rhamp showed chymotrypsin and elastase-inhibitory activity and markedly inhibited the growth of Gram-negative bacteria, including Pseudomonas aeruginosa, Salmonella typhimurium, and E. coli. Moreover, the recombinant protein also exerted low hemolytic activity. These results indicate the Rhamp is a novel antimicrobial peptide with proteinase activity from the tick R. haemaphysaloides.