Protective eff ect and mechanism of nanoantimicrobial peptide ND-C14 against Streptococcus pneumoniae infection

BACKGROUND:Streptococcus pneumoniae(S.pneumoniae)is a common pathogen that causes bacterial pneumonia.However,with increasing bacterial resistance,there is an urgent need to develop new drugs to treat S.pneumoniae infections.Nanodefensin with a 14-carbon saturated fatty acid(ND-C14)is a novel nanoantimicrobial peptide designed by modifying myristic acid at the C-terminus of humanα-defensin 5(HD5)via an amide bond.However,it is unclear whether ND-C14 is effective against lung infections caused by S.pneumoniae.METHODS:In vitro,three groups were established,including the control group,and the HD5 and ND-C14 treatment groups.A virtual colony-count assay was used to evaluate the antibacterial activity of HD5 and ND-C14 against S.pneumoniae.The morphological changes of S.pneumoniae treated with HD5 or ND-C14 were observed by scanning electron microscopy.In vivo,mice were divided into sham,vehicle,and ND-C14 treatment groups.Mice in the sham group were treated with 25μL of phosphate-buffered saline(PBS).Mice in the vehicle and ND-C14 treatment groups were treated with intratracheal instillation of 25μL of bacterial suspension with 2×108 CFU/mL(total bacterial count:5×10^(6) CFU),and then the mice were given 25μL PBS or intratracheally injected with 25μL of ND-C14(including 20μg or 50μg),respectively.Survival rates were evaluated in the vehicle and ND-C14 treatment groups.Bacterial burden in the blood and bronchoalveolar lavage fluid were counted.The lung histology of the mice was assessed.A propidium iodide uptake assay was used to clarify the destructive eff ect of ND-C14 against S.pneumoniae.RESULTS:Compared with HD5,ND-C14 had a better bactericidal eff ect against S.pneumoniae because of its stronger ability to destroy the membrane structure of S.pneumoniae in vitro.In vivo,ND-C14 significantly delayed the death time and improved the survival rate of mice infected with S.pneumoniae.ND-C14 reduced bacterial burden and lung tissue injury.Moreover,ND-C14 had a membrane permeation eff ect on S.pneumoniae,and its destructive ability increased with increasing ND-C14 concentration.CONCLUSION:The ND-C14 may improve bactericidal eff ects on S.pneumoniae both in vitro and in vivo.

Design of pH-responsive antimicrobial peptide melittin analog-camptothecin conjugates for tumor therapy

Melittin,a classical antimicrobial peptide,is a highly potent antitumor agent.However,its significant toxicity seriously hampers its application in tumor therapy.In this study,we developed novel melittin analogs with pH-responsive,cell-penetrating and membranelytic activities by replacing arginine and lysine with histidine.After conjugation with camptothecin(CPT),CPT-AAM-1 and CPT-AAM-2 were capable of killing tumor cells by releasing CPT at low concentrations and disrupting cell membranes at high concentrations under acidic conditions.Notably,we found that the C-terminus of the melittin analogs was more suitable for drug conjugation than the N-terminus.CPT-AAM-1 significantly suppressed melanoma growth in vivo with relatively low toxicity.Collectively,the present study demonstrates that the development of antitumor drugs based on pH-responsive antimicrobial peptide-drug conjugates is a promising strategy.

The dual antimicrobial and immunomodulatory roles of host defense peptides and their applications in animal production

Host defense peptides(HDPs)are small molecules with broad-spectrum antimicrobial activities against infectious bacteria,viruses,and fungi.Increasing evidence suggests that HDPs can also indirectly protect hosts by modulating their immune responses.Due to these dual roles,HDPs have been considered one of the most promising antibiotic substitutes to improve growth performance,intestinal health,and immunity in farm animals.This review describes the antimicrobial and immunomodulatory roles of host defense peptides and their recent applications in animal production.

Antimicrobial peptides act on the rumen the performance of castrated bulls

Background Many countries have already banned the use of antibiotics in animal husbandry,making it extremely difficult to maintain animal health in livestock breeding.In the livestock industry,there is an urgent need to develop alternatives to antibiotics which will not lead to drug resistance on prolonged use.In this study,eighteen castrated bulls were randomly divided into two groups.The control group(CK)was fed the basal diet,while the antimicrobial peptide group(AP)was fed the basal diet supplemented with 8 g of antimicrobial peptides in the basal diet for the experimental period of 270 d.They were then slaughtered to measure production performance,and the ruminal contents were isolated for metagenomic and metabolome sequencing analysis.Result The results showed that antimicrobial peptides could improve the daily weight,carcass weight,and net meat weight of the experimental animals.Additionally,the rumen papillae diameter and the micropapillary density in the AP were significantly greater than those in the CK.Furthermore,the determination of digestive enzymes and fermentation parameters showed that the contents of protease,xylanase,andβ-glucoside in the AP were greater than those in the CK.However,lipase content in the CK was greater than that in the AP.Moreover,the content of acetate,propionate,butyrate,and valerate was found to be greater in AP than those in CK.The metagenomic analysis annotated 1993 differential microorganisms at the species level.The KEGG enrichment of these microorganisms revealed that the enrichment of drug resistance-related pathways was dramatically decreased in the AP,whereas the enrichment of immune-related pathways was significantly increased.There was also a significant reduction in the types of viruses in the AP.187 probiotics with significant differences were found,135 of which were higher in AP than in CK.It was also found that the antimicrobial mechanism of the antimicrobial peptides was quite specific.Seven low-abundance microorganisms(Acinetobactersp.Ac1271,Aequorivita soesokkakensis,Bacillus lacisalsi,Haloferax larsenii,Lysinibacillussp.3DF0063,Parabacteroidessp.217,Streptomycessp.So13.3)were found to regulate growth performance of the bull negatively.Metabolome analysis identified 45 differentially differential metabolites that significantly different between the CK and the AP groups.Seven upregulated metabolites(4-pyridoxic acid,Ala-Phe,3-ureidopropionate,hippuric acid,terephthalic acid,L-alanine,uridine 5-monophosphate)improve the growth performance of the experimental animals.To detect the interactions between the rumen microbiome and metabolism,we associated the rumen microbiome with the metabolome and found that negative regulation between the above 7 microorganisms and 7 metabolites.Conclusions This study shows that antimicrobial peptides can improve the growth performance of animals while resisting viruses and harmful bacteria and are expected to become healthy alternatives to antibiotics.We demonstrated a new antimicrobial peptides pharmacological model.We demonstrated low-abundance microorganisms may play a role by regulating the content of metabolites.

Design methods for antimicrobial peptides with improved performance

The recalcitrance of pathogens to traditional antibiotics has made treating and eradicating bacterial infections more difficult.In this regard,developing new antimicrobial agents to combat antibiotic-resistant strains has become a top priority.Antimicrobial peptides(AMPs),a ubiquitous class of naturally occurring compounds with broadspectrum antipathogenic activity,hold significant promise as an effective solution to the current antimicrobial resistance(AMR)crisis.Several AMPs have been identified and evaluated for their therapeutic application,with many already in the drug development pipeline.Their distinct properties,such as high target specificity,potency,and ability to bypass microbial resistance mechanisms,make AMPs a promising alternative to traditional antibiotics.Nonetheless,several challenges,such as high toxicity,lability to proteolytic degradation,low stability,poor pharmacokinetics,and high production costs,continue to hamper their clinical applicability.Therefore,recent research has focused on optimizing the properties of AMPs to improve their performance.By understanding the physicochemical properties of AMPs that correspond to their activity,such as amphipathicity,hydrophobicity,structural conformation,amino acid distribution,and composition,researchers can design AMPs with desired and improved performance.In this review,we highlight some of the key strategies used to optimize the performance of AMPs,including rational design and de novo synthesis.We also discuss the growing role of predictive computational tools,utilizing artificial intelligence and machine learning,in the design and synthesis of highly efficacious lead drug candidates.

Differential expression of antimicrobial peptides in human fungal keratitis

AIM:To analyze a series of antimicrobial peptides(AMPs)in corneal tissue from individuals with fungal keratitis(FK)during the active phase of the fungus infection and after healing.METHODS:Patients undergone lamellar keratoplasty for the treatment of severe FK or corneal scar had their corneal buttons sampled.Quantitative real-time polymerase chain reaction(PCR)was used to ascertain the gene expression of human beta-defensin(HBD)-1,-2,-3,-9,S100A7,8,9,and LL-37.RESULTS:All AMPs’messenger ribonucleic acid(mRNA)expression was considerably elevated in all samples(n=12).In contrast to controls,where HBD-2,-3,and S100A7 mRNAs were expressed at very low levels,it was discovered that HBD-1,-9,S100A8,S100A9,and LL-37 were constitutively expressed in all healed samples(n=4).HBD-1,-2-3,S100A7,and LL-37 mRNAs were significantly increased in all active FK samples(n=8).The levels of HBD-9,S100A8,and S100A9 mRNAs were moderately upregulated in all active FK samples.Subgroup comparison showed that HBD-2 was significantly increased in Fusarium keratitis samples(n=5),and LL-37 mRNAs were significantly enhanced in Aspergillus keratitis samples(n=3).Whereas there was not significantly increased of HBD-1,-3,-9,S100A7,8,9 mRNA in Aspergillus keratitis samples compared with Fusarium keratitis samples.CONCLUSION:AMPs expression is increased in active FK,but not all AMPs are equally expressed.HBD-2 and LL-37 expression levels are the highest,showing some specificity of AMP expression related to FK.Human AMPs,particularly HBD-2 may play a significant role in Fusarium keratitis and LL-37 might be the key player in Aspergillus keratitis.

Effects of Antimicrobial Peptides on Production,Slaughter Performance and Blood Routine of Tan Sheep

[Objectives]This study was conducted to analyze effects of antimicrobial peptides added to the diet of Tan sheep on their production, slaughter performance and blood composition. [Methods] Ninety two four-month-old Tan sheep were randomly divided into two treatment groups according to their body weight, 46 in each group. The control check group(CK) was feed with conventional diet, and the experimental group was fed with the addition of antimicrobial peptide on the basis of the conventional diet, with the added amount of 2.5 g/sheep per day. The experimental period was 60 d. [Results] The incidence rate was 75.06% lower in the experimental group than in the CK. The average daily weight gain per sheep was 11.27% higher in the experimental group than in the CK(P<0.05). The feed conversion ratio was 8.45% lower in the experimental group than in the CK(P<0.05). The average daily gross profit per sheep was 12.12% higher in the experimental group than in the CK. For slaughter performance, the data difference of each item was not significant. The PH at 45 min and 24 h after slaughter was within the normal range of fresh mutton. The cooked meat percentage and water loss rate showed no significant differences(P>0.05). The marbling ranged from 2.45 to 2.50, indicating that the fat content was moderate, and the difference between groups was not significant(P>0.05). The flesh color ranged from 3.00 to 3.15, between light red and bright red, belonging to the normal color of mutton, and the difference between groups was not significant(P>0.05). The shear force was between 2.50 and 2.65, without a significant difference between groups(P>0.05). The white blood cells, lymphocytes and platelets in the experimental group were lower than those in the CK(P<0.01). The erythrocytes and hemoglobin in the erythrocyte group were higher than those in the CK(P<0.05). The neutrophils and monocytes in the experimental group were lower than those in the CK(P<0.05). [Conclusions] This study provides a technical basis for the rational use of antimicrobial peptides and their application in ruminants.

Analysis of the Antimicrobial Activity of Antimicrobial Peptides Extracted from Immunized Tenebrio molitor Induced by Different Microbial Treatments Against 26 Pathogens

[Objective] The study was to explore whether antimicrobial activity of the antimicrobial peptides extracted from immunized Tenebrio molitor varied with different pathogens as inducers.[Method]By inducing T.molitor hungry larvaes to generate immune response via feeding with bacteria and with fungi or actinomycete post to pricking,the antimicrobial peptides extracts were obtained by grinding and centrifuging the cultures.Its antimicrobial activity against 26 pathogens was measured by bacteriostatic ring,and evaluated by trisection to four types and inhibitory spectrum.[Result]Both the antimicrobial activity and antimicrobial spectrum of the antimicrobial peptides extracts varied remarkably among different pathogens as inducers.[Conclusion]Bio-control used strains have obvious advantage in inducing the insect to express body fluid immunity material-antimicrobial peptides.

Antimicrobial peptides: new hope in the war against multidrug resistance

The discovery of antibiotics marked a golden age in the revolution of human medicine. However,decades later, bacterial infections remain a global healthcare threat, and a return to the pre-antibiotic era seems inevitable if stringent measures are not adopted to curb the rapid emergence and spread of multidrug resistance and the indiscriminate use of antibiotics. In hospital settings, multidrug resistant(MDR) pathogens, including carbapenem-resistant Pseudomonas aeruginosa, vancomycin-resistant enterococci(VRE), methicillin-resistant Staphylococcus aureus(MRSA), and extendedspectrum β-lactamases(ESBL) bearing Acinetobacter baumannii, Escherichia coli, and Klebsiella pneumoniae are amongst the most problematic due to the paucity of treatment options,increased hospital stay, and exorbitant medical costs. Antimicrobial peptides(AMPs) provide an excellent potential strategy for combating these threats. Compared to empirical antibiotics, they show low tendency to select for resistance, rapid killing action, broad-spectrum activity, and extraordinary clinical efficacy against several MDR strains. Therefore, this review highlights multidrug resistance among nosocomial bacterial pathogens and its implications and reiterates the importance of AMPs as next-generation antibiotics for combating MDR superbugs.

The application of antimicrobial peptides as growth and health promoters for swine

With the widespread ban on the use of antibiotics in swine feed, alternative measures need to be sought to maintain swine health and performance, Antimicrobial peptides （AMPs） are part of the nonspecific defense system and are natural antibiotics produced by plants, insects, mammalians, and micro-organisms as well as by chemical synthesis. Due to their broad microbicidal activity against various fungi, bacteria and enveloped viruses AMPs are a potential alternative to conventional antibiotics for use in swine production. This review focuses on the structure and mechanism of action of AMPs, as well as their effects on performance, immune function and intestinal health in pigs. The aim is to provide support for the application of AMPs as feed additives replacing antibiotics in swine nutrition.

Tissue expression and developmental regulation of chicken cathelicidin antimicrobial peptides

Cathelicidins are a major family of antimicrobial peptides present in vertebrate animals with potent microbicidal and immunomodulatory activities. Four cathelicidins, namely fowlicidins 1 to 3 and cathelicidin B1, have been identified in chickens. As a first step to understand their role in early innate host defense of chickens, we examined the tissue and developmental expression patterns of all four cathelicidins. Real-time PCR revealed an abundant expression of four cathelicidins throughout the gastrointestinal, respiratory, and urogenital tracts as well as in all primary and secondary immune organs of chickens. Fowlicidins 1 to 3 exhibited a similar tissue expression pattern with the highest expression in the bone marrow and lung, while cathelicidin B1 was synthesized most abundantly in the bursa of Fabricius. Additionally, a tissue-specific regulatory pattern was evident for all four cathelicidins during the first 28 days after hatching. The expression of fowlicidins 1 to 3 showed an age-dependent increase both in the cecal tonsil and lung, whereas all four cathelicidins were peaked in the bursa on day 4 after hatching, with a gradual decline by day 28. An abrupt augmentation in the expression of fowlicidins 1 to 3 was also observed in the cecum on day 28, while the highest expression of cathelicidin B1 was seen in both the lung and cecal tonsil on day 14. Collectively, the presence of cathelicidins in a broad range of tissues and their largely enhanced expression during development are suggestive of their potential important role in early host defense and disease resistance of chickens.

Antimicrobial peptides: mechanism of action, activity and clinical potential

The management of bacterial infections is becoming a major clinical challenge due to the rapid evolution of antibiotic resistant bacteria.As an excellent candidate to overcome antibiotic resistance,antimicrobial peptides(AMPs)that are produced from the synthetic and natural sources demonstrate a broad-spectrum antimicrobial activity with the high specificity and low toxicity.These peptides possess distinctive structures and functions by employing sophisticated mechanisms of action.This comprehensive review provides a broad overview of AMPs from the origin,structural characteristics,mechanisms of action,biological activities to clinical applications.We finally discuss the strategies to optimize and develop AMP-based treatment as the potential antimicrobial and anticancer therapeutics.

Antimicrobial peptides and the gut microbiome in inflammatory bowel disease

Antimicrobial peptides(AMP)are highly diverse and dynamic molecules that are expressed by specific intestinal epithelial cells,Paneth cells,as well as immune cells in the gastrointestinal(GI)tract.They play critical roles in maintaining tolerance to gut microbiota and protecting against enteric infections.Given that disruptions in tolerance to commensal microbiota and loss of barrier function play major roles in the pathogenesis of inflammatory bowel disease(IBD)and converge on the function of AMP,the significance of AMP as potential biomarkers and novel therapeutic targets in IBD have been increasingly recognized in recent years.In this frontier article,we discuss the function and mechanisms of AMP in the GI tract,examine the interaction of AMP with the gut microbiome,explore the role of AMP in the pathogenesis of IBD,and review translational applications of AMP in patients with IBD.

Advances in Antimicrobial Peptides and Expression Strategy

Antimicrobial peptides are widely distributed in nature,existing in organisms of plants,insects,and vertebrates.It has been approved that antimicrobial peptides have broad spectrum antimicrobial activities,and play a key modulatory role in the innate immune response and tumor inhibiting activity.Due to the special action mechanism,the antimicrobial peptides become a hot field of genetic engineering.In the present paper,the general properties,mechanism of action,application value,existing problems,the latest progress and the expression strategy were discussed.

Expression profiles of antimicrobial peptides (AMPs) and their regulation by Relish

Antimicrobial peptides （AMPs）, as key immune effectors, play important roles in the innate immune system of invertebrates. Different types of AMPs, including Penaeidin, Crustin, ALF （anti- lipopolysaccharide factor） have been identified in different penaeid shrimp; however, systematic analyses on the function of different AMPs in shrimp responsive to different types of bacteria are very limited. In this study, we analyzed the expression profiles of AMPs in the Chinese shrimps, Fenneropenaeus chinensis, simultaneously by real-time RT-PCR （reverse transcription-polymerase chain reaction） when shrimp were challenged with Micrococcus lysodeikticus （Gram-positive, G＋） or Hbrio anguillarium （Gram-negative, G-）. Different AMPs showed different expression profiles when shrimp were injected with one type of bacterium, and one AMP also showed different expression profiles when shrimp were challenged with different bacteria. Furthermore, the expression of these AMPs showed temporal expression profiles, suggesting that different AMPs function coordinately in bacteria-infected shrimp. An RNA interference approach was used to study the function of the Relish transcription factor in regulating the transcription of different AMPs. The current study showed that Relish could regulate the transcription of different AMPs in shrimp. Differential expression profiles of AMPs in shrimp injected with different types of bacteria indicated that a complicated antimicrobial response network existed in shrimp. These data contribute to our understanding of immunity in shrimp and may provide a strategy for the control of disease in shrimp.

Natural Antimicrobial Peptides: Pleiotropic Molecules in Host Defense

Natural antimicrobial peptides (AMPs) are small cationic molecules that display antimicrobial activity against a wide range of bacteria, fungi and viruses. AMPs are multifunctional molecules that have an essential activity in infection and inflammation: they play an important role in the innate immune response, not only as antimicrobial agents, but also as immunomodulating molecules and as an important link between the innate and adaptive immune response. In this article, we will discuss the antimicrobial activity, together with the novel properties of some of these molecules as immune modulators on the innate and adaptive immune response.

Degradation of naturally occurring and engineered antimicrobial peptides by proteases

We hypothesized that current antimicrobial peptides should be susceptible to proteolytic digestion. The antimicrobial peptides: Griffithinsin, RC-101, LL-37, LSA-5, PSC-RANTES and DJ007 were degraded by commercially available proteases. Two different species of anaerobic vaginal flora, Prevotella bivia and Porphyromonas asaccharolytica also degraded the materials. Griffithsin was resistant to digestion by 8 of the 9 proteases and the bacteria while LL-37 was the most sensitive to protease digestion. These data suggests most of the molecules may not survive for very long in the proteolytic rich environments in which they are intended to function.

Mechanisms of antimicrobial peptides as characterized by solid-state NMR

Antimicrobial peptides(AMP)are small proteins that play critical roles in host defense against microbe invasion.Many AMPs disrupt the cellular membrane of microbe,while the mechanism of action of AMPs can be very sophisticated.Solid-state NMR(SSNMR)technique is powerful in characterizing the mechanism of AMPs in vivo and in vitro.This review summarizes the recent advance of SSNMR technique in AMP mechanisms characterization.We highlight the sample preparation approaches,the SSNMR spectroscopic methods,and a number of outstanding examples of AMP mechanisms elucidated via SSNMR spectroscopy.

Intestine metrnl acts as a local regulator released into gut lumen and maintaining gut antimicrobial peptides

OBJECTIVE Metrnl is a novel secreted protein with limited researches.In this study,we investigated metrnl tissue expression pattern in humans,and exploredthe possible role of its highest expression using animal models.METHODS We examined metrnl tissue expression pattern in a human tissue microarray containing 19types of tissues from 69 donors,and verified the highest expression in fresh human and mouse tissues.We then created an animal model of cell-specific knockout mice to study the role of metrnl.RESULTS Metrnl was the highest expressed in human gastrointestinal tract,and specifical y expressed in the intestinal epithelium.Consistently,Metrnl expression was also the highest expressed in mouse gastrointestinal tract among the detected tissues of 14 types.We developed intestinal epithelial cellspecific metrnl knockout mice with Vil in-Cre.In this animal model,metrnl levels displayed a statistically significant reduction in gut fluid,but not in blood serum.This cell specific deletion of metrnl did not affect body weight,food intake,blood glucose,colon length and histology,intestinal permeability,mucus production and mucin 2 expression under physiological conditions,but markedly reduced the expression of antimicrobial peptides,such as regenerating islet-derived 3 gamma and lactotransferrin.CONCLUSION Metrnl is rich in intestinal epithelial cells of humans and mice,mainly contributing to local gut metrnl level,and less affecting systemic circulating metrnl level.Metrnl plays a role in maintaining gut antimicrobial peptides.

Identification and molecular cloning of novel antimicrobial peptides from skin secretions of the Chinese bamboo leaf odorous frog (Odorrana versabilis) and the North American pickerel frog (Rana palustris)

Objective:Amphibian skin secretions are an abundant source of bioactive peptides,some of which could be developed as candidate drugs.Among these natural peptides,cytolytic peptides have attracted the most attention given that they might replace conventional antibiotics and help deal with the problem of microbial resistance.This study discovered two bioactive peptides,Brevinin-1-PLr and Nigrocin-2-OV,from two species frogs,the Chinese bamboo leaf odorous frog (Odorrana versabilis) and the North American pickerel frog (Rana palustris),respectively.Their antimicrobial,anticancer and hemolytic activities were also investigated.Methods:cDNA sequences encoding peptides were cloned from cDNA libraries constructed from the lyophilized secretions of the Chinese bamboo leaf odorous frog and the North American pickerel frog.By reversed-phase HPLC and MS/MS fragmentation sequencing,the encoded novel peptides,named Nigrocin-2-OV and Brevinin-1-PLr,were identified in skin secretions and their structures were confirmed.Replicates of both peptides were produced through solid phase peptide synthesis.Their antimicrobial and anticancer activity was studied against three types of microorganisms (Staphylococcus aureus,Candida albicans,and Escherichia coli) and five cancer cell lines (NCI-H157,PC-3,MDA-MB-435s,MCF-7,and U251MG).Their hemolytic activity was investigated using whole horse blood.Results:In this research,cDNA sequences encoding two novel 24-mer peptides were cloned from cDNA libraries constructed from the lyophilized skin secretions of the Chinese bamboo leaf odorous frog and the North American pickerel frog.Both of the peptides had the strongest inhibitory effect against C.albicans,and IC50 values against five cancer cell lines were all under 6 μM.Conclusions:Nigrocin-2-OV and Brevinin-1-PLr had the strong ability to inhibit the proliferation of studied microorganisms and tumor cell lines,with slight hemolytic activity.Compared with Brevinin-1-PLr,Nigrocin-2-OV exhibited higher antimicrobial and anticancer activity but slightly higher hemolytic activity.