A new cryptic cationic antimicrobial peptide from human apolipoprotein E with antibacterial activity and immunomodulatory effects on human cells

Sensory Dysfunction, Microbial Infections, and Host Responses in Alzheimer's Disease

Sensory functions of organs of the head and neck allow humans to interact with the environment and establish social bonds. With aging, smell, taste, vision, and hearing decline. Evidence suggests that accelerated impairment in sensory abilities can reflect a shift from healthy to pathological aging, including the development of Alzheimer's disease (AD) and other neurological disorders. While the drivers of early sensory alteration in AD are not elucidated, insults such as trauma and infections can affect sensory function. Herein, we review the involvement of the major head and neck sensory systems in AD, with emphasis on microbes exploiting sensory pathways to enter the brain (the "gateway" hypothesis) and the potential feedback loop by which sensory function may be impacted by central nervous system infection. We emphasize detection of sensory changes as first-line surveillance in senior adults to identify and remove potential insults, like microbial infections, that could precipitate brain pathology.

Engineered endolysin of Klebsiella pneumoniae phage is a potent and broad-spectrum bactericidal agent against "ESKAPEE" pathogens

The rise of antimicrobial resistance in ESKAPEE pathogens poses significant clinical challenges, especially in polymicrobial infections. Bacteriophage-derived endolysins offer promise in combating this crisis, but face practical hurdles. Our study focuses on engineering endolysins from a Klebsiella pneumoniae phage, fusing them with ApoE23 and COG133 peptides. We assessed the resulting chimeric proteins' bactericidal activity against ESKAPEE pathogens in vitro. ApoE23-Kp84B (CHU-1) reduced over 3 log units of CFU for A. baumannii, E. faecalis, K. pneumoniae within 1 h, while COG133-Kp84B (CHU-2) showed significant efficacy against S. aureus. COG133-L1-Kp84B, with a GS linker insertion in CHU-2, exhibited outstanding bactericidal activity against E. cloacae and P. aeruginosa. Scanning electron microscopy revealed alterations in bacterial morphology after treatment with engineered endolysins. Notably, CHU-1 demonstrated promising anti-biofilm and anti-persister cell activity against A. baumannii and E. faecalis but had limited efficacy in a bacteremia mouse model of their coinfection. Our findings advance the field of endolysin engineering, facilitating the customization of these proteins to target specific bacterial pathogens. This approach holds promise for the development of personalized therapies tailored to combat ESKAPEE infections effectively.

Effects of dietary cecropin on growth performance, diarrhea rate and intestinal health of nursery Hainan pigs

Antimicrobial peptides could inhibit the growth of harmful bacteria and promote the growth performance in weaned piglets. Here, we investigated the effects of dietary supplementation with cecropin antimicrobial peptides (CAP) on growth performance, diarrhea rate, intestinal health in nursery Hainan piglets. For this, 120 healthy nursery Hainan male piglets (13.29 ± 0.29 kg, 44 days old) were randomly divided into 5 groups-a control (CON) group (fed a basal diet), an antibiotic control (AC) group (fed a basal diet supplemented with 250 mg/kg colistin sulfate); and 3 experimental groups (provided the basal diet supplemented with 250, 500, or 1,000 mg/kg CAP). Pre-feeding lasted 7 days and the official period lasted 40 days. The results showed that compared with the CON group, dietary supplementation of 500 mg/kg CAP had significantly increased the average daily gain (ADG, p < 0.05), while the feed conversion ratio (FCR) and diarrhea rate were markedly reduced (p < 0.05), serum total protein (TP), albumin, IgA, IgM, and globulin concentrations were significantly increased (p < 0.05), where serum aspartate aminotransferase (AST) level was significantly reduced (p < 0.05), and it also increased the villus height and the villus height-to-crypt depth ratio in the jejunum, reduced the serum D-lactic acid concentrations and diamine oxidase activity, and increased the expression level of ZO-1 and occludin in the jejunum and ileum (p < 0.05), the relative abundance of Firmicutes, Lactobacillus, and Limoslactobacillus in the colon were increased (p < 0.05), whereas that of Streptococcus and Escherichia-Shigella were reduced (p < 0.05). These results indicated that dietary supplementation with 500 mg/kg CAP could improve the growth performance, reduce the diarrhea rate, improve the serum immunity, intestinal health of nursery pigs.

Antimicrobial peptides in bone regeneration: mechanism and potential

INTRODUCTION

Antimicrobial peptides (AMPs) are small-molecule peptides with a unique antimicrobial mechanism. Other notable biological activities of AMPs, including anti-inflammatory, angiogenesis, and bone formation effects, have recently received widespread attention. These remarkable bioactivities, combined with the unique antimicrobial mechanism of action of AMPs, have led to their increasingly important role in bone regeneration.

AREAS COVERED

In this review, on the one hand, we aimed to summarize information about the AMPs that are currently used for bone regeneration by reviewing published literature in the PubMed database. On the other hand, we also highlight some AMPs with potential roles in bone regeneration and their possible mechanisms of action.

EXPERT OPINION

The translation of AMPs to the clinic still faces many problems, but their unique antimicrobial mechanisms and other conspicuous biological activities suggest great potential. An in-depth understanding of the structure and mechanism of action of AMPs will help us to subsequently combine AMPs with different carrier systems and perform structural modifications to reduce toxicity and achieve stable release, which may be a key strategy for facilitating the translation of AMPs to the clinic.

ApoE Mimetic Peptide COG1410 Kills Mycobacterium smegmatis via Directly Interfering ClpC's ATPase Activity

Antimicrobial peptides (AMPs) hold promise as alternatives to combat bacterial infections, addressing the urgent global threat of antibiotic resistance. COG1410, a synthetic peptide derived from apolipoprotein E, has exhibited potent antimicrobial properties against various bacterial strains, including Mycobacterium smegmatis. However, our study reveals a previously unknown resistance mechanism developed by M. smegmatis against COG1410 involving ClpC. Upon subjecting M. smegmatis to serial passages in the presence of sub-MIC COG1410, resistance emerged. The comparative genomic analysis identified a point mutation in ClpC (S437P), situated within its middle domain, which led to high resistance to COG1410 without compromising bacterial fitness. Complementation of ClpC in mutant restored bacterial sensitivity. In-depth analyses, including transcriptomic profiling and in vitro assays, uncovered that COG1410 interferes with ClpC at both transcriptional and functional levels. COG1410 not only stimulated the ATPase activity of ClpC but also enhanced the proteolytic activity of Clp protease. SPR analysis confirmed that COG1410 directly binds with ClpC. Surprisingly, the identified S437P mutation did not impact their binding affinity. This study sheds light on a unique resistance mechanism against AMPs in mycobacteria, highlighting the pivotal role of ClpC in this process. Unraveling the interplay between COG1410 and ClpC enriches our understanding of AMP-bacterial interactions, offering potential insights for developing innovative strategies to combat antibiotic resistance.

Peptidomic analysis of endogenous and bacterial protease activity in human plasma and wound fluids

Endogenous and bacterial proteases play important roles in wound healing and infection. Analysis of alterations in the low-molecular-weight peptidome by individual enzymes could therefore provide insight into proteolytic events occurring in wounds and may aid in the discovery of biomarkers. Using liquid chromatography with tandem mass spectrometry, we characterized the peptidome of plasma and acute wound fluids digested ex vivo with human (neutrophil elastase and cathepsin G) and bacterial proteases (Pseudomonas aeruginosa LasB and Staphyloccocus aureus V8). We identified over 100 protein targets for each enzyme and characterized enzyme specific peptides and cleavage patterns. Moreover, we found unique peptide regions in V8 digested samples that were also present in dressing extracts from S. aureus infected wounds. Finally, the work indicates that peptidomic analysis of qualitative differences of proteolytic activity of individual enzymes may aid in the discovery of potential diagnostic biomarkers for wound healing status.

Study of the Antimicrobial Activity of the Human Peptide SQQ30 against Pathogenic Bacteria

Given the continuous increase in antibiotic resistance, research has been driven towards the isolation of new antimicrobial molecules. Short, charged, and very hydrophobic antimicrobial peptides have a direct action against biological membranes, which are less prone to developing resistance. Using a bioinformatic tool, we chose the SQQ30 peptide, isolated from the human SOGA1 protein. The antimicrobial activity of this peptide against various Gram-negative and Gram-positive bacterial strains and against a fungal strain was studied. A mechanism of action directed against biological membranes was outlined. When administered in combination with the antibiotic ciprofloxacin and with the TRS21 (buforin II), another antimicrobial peptide, SQQ30 can be used with a lower MIC, showing additivity and synergism, respectively. Particularly interesting is the ability of SQQ30 to bind LPS in Gram-negative strains, preventing the eukaryotic cell from releasing inflammatory mediators. Our study indicates SQQ30 as a novel and promising antimicrobial agent.

Identification of gene signatures and molecular mechanisms underlying the mutual exclusion between psoriasis and leprosy

Leprosy and psoriasis rarely coexist, the specific molecular mechanisms underlying their mutual exclusion have not been extensively investigated. This study aimed to reveal the underlying mechanism responsible for the mutual exclusion between psoriasis and leprosy. We obtained leprosy and psoriasis data from ArrayExpress and GEO database. Differential expression analysis was conducted separately on the leprosy and psoriasis using DEseq2. Differentially expressed genes (DEGs) with opposite expression patterns in psoriasis and leprosy were identified, which could potentially involve in their mutual exclusion. Enrichment analysis was performed on these candidate mutually exclusive genes, and a protein-protein interaction (PPI) network was constructed to identify hub genes. The expression of these hub genes was further validated in an external dataset to obtain the critical mutually exclusive genes. Additionally, immune cell infiltration in psoriasis and leprosy was analyzed using single-sample gene set enrichment analysis (ssGSEA), and the correlation between critical mutually exclusive genes and immune cells was also examined. Finally, the expression pattern of critical mutually exclusive genes was evaluated in a single-cell transcriptome dataset. We identified 1098 DEGs in the leprosy dataset and 3839 DEGs in the psoriasis dataset. 48 candidate mutually exclusive genes were identified by taking the intersection. Enrichment analysis revealed that these genes were involved in cholesterol metabolism pathways. Through PPI network analysis, we identified APOE, CYP27A1, FADS1, and SOAT1 as hub genes. APOE, CYP27A1, and SOAT1 were subsequently validated as critical mutually exclusive genes on both internal and external datasets. Analysis of immune cell infiltration indicated higher abundance of 16 immune cell types in psoriasis and leprosy compared to normal controls. The abundance of 6 immune cell types in psoriasis and leprosy positively correlated with the expression levels of APOE and CYP27A1. Single-cell data analysis demonstrated that critical mutually exclusive genes were predominantly expressed in Schwann cells and fibroblasts. This study identified APOE, CYP27A1, and SOAT1 as critical mutually exclusive genes. Cholesterol metabolism pathway illustrated the possible mechanism of the inverse association of psoriasis and leprosy. The findings of this study provide a basis for identifying mechanisms and therapeutic targets for psoriasis.

Neurobiochemical characteristics of arginine-rich peptides explain their potential therapeutic efficacy in neurodegenerative diseases

Neurodegenerative diseases, including Alzheimer̕ s disease (AD), Parkinson̕ s disease (PD), Huntington̕ s disease (HD), and Amyotrophic Lateral Sclerosis (ALS) require special attention to find new potential treatment methods. This review aims to summarize the current knowledge of the relationship between the biochemical properties of arginine-rich peptides (ARPs) and their neuroprotective effects to deal with the harmful effects of risk factors. It seems that ARPs have portrayed a promising and fantastic landscape for treating neurodegeneration-associated disorders. With multimodal mechanisms of action, ARPs play various unprecedented roles, including as the novel delivery platforms for entering the central nervous system (CNS), the potent antagonists for calcium influx, the invader molecules for targeting mitochondria, and the protein stabilizers. Interestingly, these peptides inhibit the proteolytic enzymes and block protein aggregation to induce pro-survival signaling pathways. ARPs also serve as the scavengers of toxic molecules and the reducers of oxidative stress agents. They also have anti-inflammatory, antimicrobial, and anti-cancer properties. Moreover, by providing an efficient nucleic acid delivery system, ARPs can play an essential role in developing various fields, including gene vaccines, gene therapy, gene editing, and imaging. ARP agents and ARP/cargo therapeutics can be raised as an emergent class of neurotherapeutics for neurodegeneration. Part of the aim of this review is to present recent advances in treating neurodegenerative diseases using ARPs as an emerging and powerful therapeutic tool. The applications and progress of ARPs-based nucleic acid delivery systems have also been discussed to highlight their usefulness as a broad-acting class of drugs.

The Antimicrobial, Antibiofilm and Anti-Inflammatory Activities of P13#1, a Cathelicidin-like Achiral Peptoid

Cationic antimicrobial peptides (CAMPs) are powerful molecules with antimicrobial, antibiofilm and endotoxin-scavenging activities. These properties make CAMPs very attractive drugs in the face of the rapid increase in multidrug-resistant (MDR) pathogens, but they are limited by their susceptibility to proteolytic degradation. An intriguing solution to this issue could be the development of functional mimics of CAMPs with structures that enable the evasion of proteases. Peptoids (N-substituted glycine oligomers) are an important class of peptidomimetics with interesting benefits: easy synthetic access, intrinsic proteolytic stability and promising bioactivities. Here, we report the characterization of P13#1, a 13-residue peptoid specifically designed to mimic cathelicidins, the best-known and most widespread family of CAMPs. P13#1 showed all the biological activities typically associated with cathelicidins: bactericidal activity over a wide spectrum of strains, including several ESKAPE pathogens; the ability to act in combination with different classes of conventional antibiotics; antibiofilm activity against preformed biofilms of Pseudomonas aeruginosa, comparable to that of human cathelicidin LL-37; limited toxicity; and an ability to inhibit LPS-induced proinflammatory effects which is comparable to that of "the last resource" antibiotic colistin. We further studied the interaction of P13#1 with SDS, LPSs and bacterial cells by using a fluorescent version of P13#1. Finally, in a subcutaneous infection mouse model, it showed antimicrobial and anti-inflammatory activities comparable to ampicillin and gentamicin without apparent toxicity. The collected data indicate that P13#1 is an excellent candidate for the formulation of new antimicrobial therapies.

Controlled Release of a Therapeutic Peptide in Sprayable Surgical Sealant for Prevention of Postoperative Abdominal Adhesions

Formation of asymmetric, rigid scar tissue known as surgical adhesions is caused by traumatic disruption of mesothelial-lined surfaces in surgery. A widely adopted prophylactic barrier material (Seprafilm) for the treatment of intra-abdominal adhesions is applied operatively as a pre-dried hydrogel sheet but has reduced translational efficacy due its brittle mechanical properties. Topically administered peritoneal dialysate (Icodextrin) and anti-inflammatory drugs have failed to prevent adhesions due to an uncontrolled release profile. Hence, inclusion of a targeted therapeutic into a solid barrier host matrix with improved mechanical properties could provide dual utility in adhesion prevention and as a surgical sealant. Spray deposition of poly(lactide-co-caprolactone) (PLCL) polymer fibers through solution blow spinning has yielded a tissue-adherent barrier material with previously reported adhesion prevention efficacy due to a surface erosion mechanism that inhibits deposition of inflamed tissue. However, such an approach uniquely presents an avenue for controlled therapeutic release through mechanisms of diffusion and degradation. Such a rate is kinetically tuned via facile blending of "high" molecular weight (HMW) and "low" molecular weight (LMW) PLCL with slow and fast biodegradation rates, respectively. Here, we explore viscoelastic blends of HMW PLCL (70% w/v) and LMW PLCL (30% w/v) as a host matrix for anti-inflammatory drug delivery. In this work, COG133, an apolipoprotein E (ApoE) mimetic peptide with potent anti-inflammatory properties was selected and tested. In vitro studies with PLCL blends presented low (∼30%) and high (∼80%) percent release profiles over a 14-day period based on the nominal molecular weight of the HMW PLCL component. Two independent mouse models of cecal ligation and cecal anastomosis significantly reduced adhesion severity versus Seprafilm, COG133 liquid suspension, and no treatment control. The synergy of physical and chemical methods in a barrier material with proven preclinical studies highlights the value of COG133-loaded PLCL fiber mats in effectively dampening the formation of severe abdominal adhesions.

ApoE Mimetic Peptide COG1410 Exhibits Strong Additive Interaction with Antibiotics Against Mycobacterium smegmatis

Background

Drug-resistant tuberculosis (TB) is an emerging threat to public health worldwide. Antimicrobial peptide (AMP) is a promising solution to solve the antimicrobial resistance crisis. The apolipoprotein E mimetic peptide COG1410 has been confirmed to simultaneously have neuroprotective, anti-inflammatory, and antibacterial activity. However, whether it is effective to inhibit growth of mycobacteria has not been investigated yet.

Methods

The peptide COG1410 was synthesized with conventional solid-phase peptide synthesis and qualified by HPLC and mass spectrometry. Micro-dilution method was used to determine the minimal inhibitory concentration. A time-kill assay was used to determine the bactericidal dynamics of antimicrobial peptide and relative antibiotics. Static biofilm formation was conducted in 24-well plate and the biofilm was separated from planktonic cells and collected. The mechanism of action of COG1410 was explored by TEM observation and ATP leak assay. The localization of COG1410 was observed by confocal laser scan microscopy. The drug-drug interaction was determined by a checkerboard assay.

Results

COG1410 was a potent bactericidal agent against M. smegmatis in vitro and within the macrophages with MIC 16 μg/mL, but invalid against M. abscess and M. tuberculosis. A time-kill assay showed that COG1410 killed M. smegmatis as potent as clarithromycin, but faster than LL-37, another short synthetic cationic peptide. 1× MIC COG1410 almost reduced 90% biofilm formation of M. smegmatis. Additionally, COG1410 was able to penetrate the cell membrane of macrophage and inhibit intracellular M. smegmatis growth. TEM observation and ATP leak assay found that COG1410 disrupted cell membrane and caused release of cell contents. Confocal fluorescence microscopy showed that FITC-COG1410 aggregated around cell membrane instead of entering the cytoplasm. Although COG1410 had relative high cytotoxicity, it exhibited strong additive interaction with regular anti-TB antibiotics, which reduced the working concentration of COG1410 and expanding safety window. After 30 passages, there was no induced drug resistance for COG1410.

Conclusion

COG1410 was a novel and potent AMP against M. smegmatis by disrupting the integrity of cell membrane.

A Novel Cryptic Clostridial Peptide That Kills Bacteria by a Cell Membrane Permeabilization Mechanism

This work reports detailed characteristics of the antimicrobial peptide Intestinalin (P30), which is derived from the LysC enzyme of Clostridium intestinale strain URNW. The peptide shows a broader antibacterial spectrum than the parental enzyme, showing potent antimicrobial activity against clinical strains of Gram-positive staphylococci and Gram-negative pathogens and causing between 3.04 ± 0.12 log kill for Pseudomonas aeruginosa PAO1 and 7.10 ± 0.05 log kill for multidrug-resistant Acinetobacter baumannii KPD 581 at a 5 μM concentration. Moreover, Intestinalin (P30) prevents biofilm formation and destroys 24-h and 72-h biofilms formed by Acinetobacter baumannii CRAB KPD 205 (reduction levels of 4.28 and 2.62 log CFU/mL, respectively). The activity of Intestinalin is combined with both no cytotoxicity and little hemolytic effect against mammalian cells. The nuclear magnetic resonance and molecular dynamics (MD) data show a high tendency of Intestinalin to interact with the bacterial phospholipid cell membrane. Although positively charged, Intestinalin resides in the membrane and aggregates into small oligomers. Negatively charged phospholipids stabilize peptide oligomers to form water- and ion-permeable pores, disrupting the integrity of bacterial cell membranes. Experimental data showed that Intestinalin interacts with negatively charged lipoteichoic acid (logK based on isothermal titration calorimetry, 7.45 ± 0.44), causes membrane depolarization, and affects membrane integrity by forming large pores, all of which result in loss of bacterial viability. IMPORTANCE Antibiotic resistance is rising rapidly among pathogenic bacteria, becoming a global public health problem that threatens the effectiveness of therapies for many infectious diseases. In this respect, antimicrobial peptides appear to be an interesting alternative to combat bacterial pathogens. Here, we report the characteristics of an antimicrobial peptide (of 30 amino acids) derived from the clostridial LysC enzyme. The peptide showed killing activity against clinical strains of Gram-positive and Gram-negative pathogens. Experimental data and computational modeling showed that this peptide forms transmembrane pores, directly engaging the negatively charged phospholipids of the bacterial cell membrane. Consequently, dissipation of the electrochemical gradient across cell membranes affects many vital processes, such as ATP synthesis, motility, and transport of nutrients. This kind of dysfunction leads to the loss of bacterial viability. Our firm conviction is that the presented study will be a helpful resource in searching for novel antimicrobial peptides that could have the potential to replace conventional antibiotics.

Antimicrobial potential of a ponericin-like peptide isolated from Bombyx mori L. hemolymph in response to Pseudomonas aeruginosa infection

The main effectors in the innate immune system of Bombyx mori L. are antimicrobial peptides (AMPs). Here, we infected B. mori with varied inoculum sizes of Pseudomonas aeruginosa ATCC 25668 cells to investigate changes in morpho-anatomical responses, physiological processes and AMP production. Ultraviolet-visible spectra revealed a sharp change in λ_max from 278 to 285 nm (bathochromic shift) in the hemolymph of infected B. mori incubated for 24 h. Further, Fourier Transform InfraRed studies on the hemolymph extracted from the infected B. mori showed a peak at 1550 cm^-1, indicating the presence of α-helical peptides. The peptide fraction was obtained through methanol, acetic acid and water mixture (90:1:9) extraction, followed by peptide purification using Reverse Phase High Performance Liquid Chromatography. The fraction exhibiting antibacterial properties was collected and characterized by Matrix-Assisted Laser Desorption/Ionization-Time of Flight. A linear α-helical peptide with flexible termini (LLKELWTKMKGAGKAVLGKIKGLL) was found, corresponding to a previously described peptide from ant venom and here denominated as Bm-ponericin-L1. The antibacterial activity of Bm-ponericin-L1 was determined against ESKAPE pathogens. Scanning electron microscopy confirmed the membrane disruption potential of Bm-ponericin-L1. Moreover, this peptide also showed promising antibiofilm activity. Finally, cell viability and hemolytic assays revealed that Bm-ponericin-L1 is non-toxic toward primary fibroblasts cell lines and red blood cells, respectively. This study opens up new perspectives toward an alternative approach to overcoming multiple-antibiotic-resistance by means of AMPs through invertebrates' infection with human pathogenic bacteria.

Functional diversity of apolipoprotein E: from subcellular localization to mitochondrial function

Human apolipoprotein E (APOE), originally known for its role in lipid metabolism, is polymorphic with three major allele forms, namely, APOEε2, APOEε3, and APOEε4, leading to three different human APOE isoforms. The ε4 allele is a genetic risk factor for Alzheimer's disease (AD); therefore, the vast majority of APOE research focuses on its role in AD pathology. However, there is increasing evidence for other functions of APOE through the involvement in other biological processes such as transcriptional regulation, mitochondrial metabolism, immune response, and responsiveness to dietary factors. Therefore, the aim of this review is to provide an overview of the potential novel functions of APOE and their characterization. The detection of APOE in various cell organelles points to previously unrecognized roles in mitochondria and others, although it is actually considered a secretory protein. Furthermore, numerous interactions of APOE with other proteins have been detected, providing indications for new metabolic pathways involving APOE. The present review summarizes the current evidence on APOE beyond its original role in lipid metabolism, to change the perspective and encourage novel approaches to future research on APOE and its isoform-dependent role in the cellular metabolism.

Apolipoprotein E mimetic peptide COG1410 combats pandrug-resistant Acinetobacter baumannii

The emergence of pandrug-resistant bacteria breaks through the last line of defense and raises fear among people of incurable infections. In the post-antibiotic era, the pharmaceutical field turns to seek non-conventional anti-infective agents. Antimicrobial peptides are considered a prospective solution to the crisis of antimicrobial resistance. In this study, we evaluated the antimicrobial efficiency of an ApoE mimetic peptide, COG1410, which has been confirmed to exhibit strong neural protective activity and immunomodulatory function. COG1410 showed potent antimicrobial activity against pandrug-resistant Acinetobacter baumannii, even eliminating large inocula (108 CFU/ml) within 30 min. LC99.9 in PBS and 50% pooled human plasma was 2 μg/ml (1.4 μM) and 8 μg/ml (5.6 μM), respectively. Moreover, COG1410 exhibited biofilm inhibition and eradication activity, excellent stability in human plasma, and a low propensity to induce resistance. Although COG1410 easily entered bacterial cytoplasm and bound to DNA nonspecifically, the major mechanism of COG1410 killing was to disrupt the integrity of cell membrane and lead to leakage of cytoplasmic contents, without causing obvious pores on the cell surface or cell lysis. Additionally, transcriptome analysis showed that treatment with COG1410-enriched genes involved a series of oxidation–reduction processes. DCFH-DA probe detected an increased ROS level in the presence of COG1410, indicating ROS was another hit of this AMP. Furthermore, the action of COG1410 did not depend on the electronic interaction with the LPS layer, in contrast to polymyxin B. The strong synergistic interaction between COG1410 and polymyxin B dramatically reduced the working concentration of COG1410, expanding the safety window of the application. C. elegans infection model showed that combined therapy of COG1410 and polymyxin B was capable of significantly rescuing the infected nematodes. Taken together, our study demonstrates that COG1410 is a promising drug candidate in the battle against pandrug-resistant A. baumannii.

Synthetic Antimicrobial Immunomodulatory Peptides: Ongoing Studies and Clinical Trials

The increasingly widespread antimicrobial resistance forces the search for new antimicrobial substances capable of fighting infection. Antimicrobial peptides (AMPs) and their synthetic analogs form an extensive group of compounds of great structural diversity and multifunctionality, different modes of antimicrobial action, and considerable market potential. Some AMPs, in addition to their proven antibacterial, antifungal, and antiviral activity, also demonstrate anti-inflammatory and immunomodulatory capabilities; these are called innate defense regulator (IDR) peptides. IDR peptides stimulate or inhibit the body’s immune system, e.g., by stimulating leukocyte migration to the site of infection, driving macrophage differentiation and activation, providing chemotactic action for neutrophils, degranulation and activation of mast cells, altering chemokine and cytokine production, and even induction of angiogenesis and wound healing. Such multifunctional immunomodulatory peptide molecules are currently being investigated and developed. Exploring and utilizing IDR peptides as an indirect weapon against infectious diseases could represent a completely new strategy to cope with the issue of antimicrobial resistance.

Antibacterial and Anti-Inflammatory Effects of Apolipoprotein E

Apolipoprotein E (APOE) is a lipid-transport protein that functions as a key mediator of lipid transport and cholesterol metabolism. Recent studies have shown that peptides derived from human APOE display anti-inflammatory and antimicrobial effects. Here, we applied in vitro assays and fluorescent microscopy to investigate the anti-bacterial effects of full-length APOE. The interaction of APOE with endotoxins from Escherichia coli was explored using surface plasmon resonance, binding assays, transmission electron microscopy and all-atom molecular dynamics (MD) simulations. We also studied the immunomodulatory activity of APOE using in vitro cell assays and an in vivo mouse model in combination with advanced imaging techniques. We observed that APOE exhibits anti-bacterial activity against several Gram-negative bacterial strains of Pseudomonas aeruginosa and Escherichia coli. In addition, we showed that APOE exhibits a significant binding affinity for lipopolysaccharide (LPS) and lipid A as well as heparin. MD simulations identified the low-density lipoprotein receptor (LDLR) binding region in helix 4 of APOE as a primary binding site for these molecules via electrostatic interactions. Together, our data suggest that APOE may have an important role in controlling inflammation during Gram-negative bacterial infection.

Valorization of lignins from energy crops and agro-industrial byproducts as antioxidant and antibacterial materials

BACKGROUND

Developing eco-friendly antioxidant and antimicrobial substances originating from biomass residues has recently attracted considerable interest. In this study, two lignosulfonates and various oxidized water-soluble lignins were investigated for their antioxidant properties, as assessed by ABTS, DPPH and Folin-Ciocalteu methods, and their antimicrobial activity against some bacterial strains responsible for human pathologies.

RESULTS

The lignosulfonates showed the largest antiradical/antimicrobial capacity, whereas the other substrates were less effective. The observed antioxidant/antibacterial properties were positively correlated with lignin aromatic/phenolic content. The positive correlation between antiradical and antimicrobial activities suggests that lignin scavenging capacity was also involved in its antibacterial activity. A greater antimicrobial performance was generally observed against Gram-positive bacterial strains, and it was attributed to the intrinsic larger susceptibility of Gram-positive bacteria to lignin phenols. A significant though lesser inhibitory activity was also found against Escherichia coli.

CONCLUSION

Our results confirmed the dependence of lignin antioxidant/antibacterial power on its extraction method and chemical structure, as well as on the type of bacterial strains. Identifying the relationship between lignin molecular composition and its antioxidant/antibacterial features represents an advance on the potential future use of renewable and eco-compatible lignin materials in nutraceutical, pharmaceutical and cosmetic sectors. © 2021 Society of Chemical Industry.

Synthetic Antibiotic Derived from Sequences Encrypted in a Protein from Human Plasma

Encrypted peptides have been recently found in the human proteome and represent a potential class of antibiotics. Here we report three peptides derived from the human apolipoprotein B (residues 887-922) that exhibited potent antimicrobial activity against drug-resistant Klebsiella pneumoniae, Acinetobacter baumannii, and Staphylococci both in vitro and in an animal model. The peptides had excellent cytotoxicity profiles, targeted bacteria by depolarizing and permeabilizing their cytoplasmic membrane, inhibited biofilms, and displayed anti-inflammatory properties. Importantly, the peptides, when used in combination, potentiated the activity of conventional antibiotics against bacteria and did not select for bacterial resistance. To ensure translatability of these molecules, a protease resistant retro-inverso variant of the lead encrypted peptide was synthesized and demonstrated anti-infective activity in a preclinical mouse model. Our results provide a link between human plasma and innate immunity and point to the blood as a source of much-needed antimicrobials.

Mammals' humoral immune proteins and peptides targeting the bacterial envelope: from natural protection to therapeutic applications against multidrug‐resistant Gram ‐negatives

Mammalian innate immunity employs several humoral ‘weapons’ that target the bacterial envelope. The threats posed by the multidrug‐resistant ‘ESKAPE’ Gram‐negative pathogens (Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp.) are forcing researchers to explore new therapeutic options, including the use of these immune elements. Here we review bacterial envelope‐targeting (peptidoglycan and/or membrane‐targeting) proteins/peptides of the mammalian immune system that are most likely to have therapeutic applications. Firstly we discuss their general features and protective activity against ESKAPE Gram‐negatives in the host. We then gather, integrate, and discuss recent research on experimental therapeutics harnessing their bactericidal power, based on their exogenous administration and also on the discovery of bacterial and/or host targets that improve the performance of this endogenous immunity, as a novel therapeutic concept. We identify weak points and knowledge gaps in current research in this field and suggest areas for future work to obtain successful envelope‐targeting therapeutic options to tackle the challenge of antimicrobial resistance.

Computational Methods and Tools in Antimicrobial Peptide Research

The evolution of antibiotic-resistant bacteria is an ongoing and troubling development that has increased the number of diseases and infections that risk going untreated. There is an urgent need to develop alternative strategies and treatments to address this issue. One class of molecules that is attracting significant interest is that of antimicrobial peptides (AMPs). Their design and development has been aided considerably by the applications of molecular models, and we review these here. These methods include the use of tools to explore the relationships between their structures, dynamics, and functions and the increasing application of machine learning and molecular dynamics simulations. This review compiles resources such as AMP databases, AMP-related web servers, and commonly used techniques, together aimed at aiding researchers in the area toward complementing experimental studies with computational approaches.

The role of full-length apoE in clearance of Gram-negative bacteria and their endotoxins

ApoE is a well-known lipid-binding protein that plays a main role in the metabolism and transport of lipids. More recently, apoE-derived peptides have been shown to exert antimicrobial effects. Here, we investigated the antibacterial activity of apoE using in vitro assays, advanced imaging techniques, and in vivo mouse models. The formation of macromolecular complexes of apoE and endotoxins from Gram-negative bacteria was explored using gel shift assays, transmission electron microscopy, and CD spectroscopy followed by calculation of the α-helical content. The binding affinity of apoE to endotoxins was also confirmed by fluorescent spectroscopy detecting the quenching and shifting of tryptophan intrinsic fluorescence. We showed that apoE exhibits antibacterial activity particularly against Gram-negative bacteria such as Pseudomonas aeruginosa and Escherichia coli. ApoE protein folding was affected by binding of bacterial endotoxin components such as lipopolysaccharide (LPS) and lipid A, yielding similar increases in the apoE α-helical content. Moreover, high-molecular-weight complexes of apoE were formed in the presence of LPS, but not to the same extent as with lipid A. Together, our results demonstrate the ability of apoE to kill Gram-negative bacteria, interact with their endotoxins, which leads to the structural changes in apoE and the formation of aggregate-like complexes.

Recent Innovations in Bacterial Infection Detection and Treatment

Bacterial infections are a major threat to human health, exacerbated by increasing antibiotic resistance. These infections can result in tremendous morbidity and mortality, emphasizing the need to identify and treat pathogenic bacteria quickly and effectively. Recent developments in detection methods have focused on electrochemical, optical, and mass-based biosensors. Advances in these systems include implementing multifunctional materials, microfluidic sampling, and portable data-processing to improve sensitivity, specificity, and ease of operation. Concurrently, advances in antibacterial treatment have largely focused on targeted and responsive delivery for both antibiotics and antibiotic alternatives. Antibiotic alternatives described here include repurposed drugs, antimicrobial peptides and polymers, nucleic acids, small molecules, living systems, and bacteriophages. Finally, closed-loop therapies are combining advances in the fields of both detection and treatment. This review provides a comprehensive summary of the current trends in detection and treatment systems for bacterial infections.

Multifunctional mats by antimicrobial nanoparticles decoration for bioinspired smart wound dressing solutions

Developing advanced materials for wound dressings is a very challenging, yet unaddressed task. These systems are supposed to act as temporary skin substitutes, performing multiple functions, including fluid absorption and antimicrobial action, supporting cell proliferation and migration in order to promote the skin regeneration process. Following a global bioinspired approach, in this study, we developed a multifunctional textile for wound dressing applications. Biodegradable polyhydroxybutyrate/poly-3-caprolactone (PHB/PCL) mats were fabricated by electrospinning to mimic the extracellular matrix (ECM), thus providing structural and biochemical support to tissue regeneration. Furthermore, inspired by nature's strategy which exploits melanin as an effective weapon against pathogens infection, PHB/PCL mats were modified with hybrid Melanin-TiO₂ nanostructures. These were combined to PHB/PCL mats following two different strategies: in-situ incorporation during electrospinning process, alternately ex-post coating by electrospraying onto obtained mats. All samples revealed huge water uptake and poor cytotoxicity towards HaCat eukaryotic cells. Melanin-TiO₂ coating conferred PHB/PCL mats significant antimicrobial activity towards both Gram(+) and Gram(-) strains, marked hydrophilic properties as well as bioactivity which is expected to promote materials-cells interaction. This study is going to provide a novel paradigm for the design of active wound dressings for regenerative medicine.

Cryptic Host Defense Peptides: Multifaceted Activity and Prospects for Medicinal Chemistry

Host defense peptides (HDPs) comprise a heterogeneous group of evolutionarily conserved and biologically active small molecules that are produced by different organisms. HDPs are widely researched because they often have multiple biological activities, for example antimicrobial, immunomodulatory and anticancer activity. In this context, in this review we focus on cryptic HDPs, molecules derived specifically from proteolytic processing of endogenous precursor proteins. Here, we explore the biological activity of such molecules and we further discuss the development of optimized sequences based on these natural cryptic HDPs. In addition, we present clinical-phase studies of cryptic HDPs (natural or optimized), and point out the possible applicability of these molecules in medicinal chemistry.

Host Defence Cryptides from Human Apolipoproteins: Applications in Medicinal Chemistry

Several eukaryotic proteins with defined physiological roles may act as precursors of cryptic bioactive peptides released upon protein cleavage by the host and/or bacterial proteases. Based on this, the term "cryptome" has been used to define the unique portion of the proteome encompassing proteins with the ability to generate bioactive peptides (cryptides) and proteins (crypteins) upon proteolytic cleavage. Hence, the cryptome represents a source of peptides with potential pharmacological interest. Among eukaryotic precursor proteins, human apolipoproteins play an important role, since promising bioactive peptides have been identified and characterized from apolipoproteins E, B, and A-I sequences. Human apolipoproteins derived peptides have been shown to exhibit antibacterial, anti-biofilm, antiviral, anti-inflammatory, anti-atherogenic, antioxidant, or anticancer activities in in vitro assays and, in some cases, also in in vivo experiments on animal models. The most interesting Host Defence Peptides (HDPs) identified thus far in human apolipoproteins are described here with a focus on their biological activities applicable to biomedicine. Altogether, reported evidence clearly indicates that cryptic peptides represent promising templates for the generation of new drugs and therapeutics against infectious diseases.

Design, Engineering and Discovery of Novel α-Helical and β-Boomerang Antimicrobial Peptides against Drug Resistant Bacteria

In an era where the pipeline of new antibiotic development is drying up, the continuous rise of multi-drug resistant (MDR) and extensively drug resistant (XDR) bacteria are genuine threats to human health. Although antimicrobial peptides (AMPs) may serve as promising leads against drug resistant bacteria, only a few AMPs are in advanced clinical trials. The limitations of AMPs, namely their low in vivo activity, toxicity, and poor bioavailability, need to be addressed. Here, we review engineering of frog derived short α-helical AMPs (aurein, temporins) and lipopolysaccharide (LPS) binding designed β-boomerang AMPs for further development. The discovery of novel cell selective AMPs from the human proprotein convertase furin is also discussed.

Cationic Arginine-Rich Peptides (CARPs): A Novel Class of Neuroprotective Agents With a Multimodal Mechanism of Action

There are virtually no clinically available neuroprotective drugs for the treatment of acute and chronic neurological disorders, hence there is an urgent need for the development of new neuroprotective molecules. Cationic arginine-rich peptides (CARPs) are an expanding and relatively novel class of compounds, which possess intrinsic neuroprotective properties. Intriguingly, CARPs possess a combination of biological properties unprecedented for a neuroprotective agent including the ability to traverse cell membranes and enter the CNS, antagonize calcium influx, target mitochondria, stabilize proteins, inhibit proteolytic enzymes, induce pro-survival signaling, scavenge toxic molecules, and reduce oxidative stress as well as, having a range of anti-inflammatory, analgesic, anti-microbial, and anti-cancer actions. CARPs have also been used as carrier molecules for the delivery of other putative neuroprotective agents across the blood-brain barrier and blood-spinal cord barrier. However, there is increasing evidence that the neuroprotective efficacy of many, if not all these other agents delivered using a cationic arginine-rich cell-penetrating peptide (CCPPs) carrier (e.g., TAT) may actually be mediated largely by the properties of the carrier molecule, with overall efficacy further enhanced according to the amino acid composition of the cargo peptide, in particular its arginine content. Therefore, in reviewing the neuroprotective mechanisms of action of CARPs we also consider studies using CCPPs fused to a putative neuroprotective peptide. We review the history of CARPs in neuroprotection and discuss in detail the intrinsic biological properties that may contribute to their cytoprotective effects and their usefulness as a broad-acting class of neuroprotective drugs.

Epigenetic-sensitive pathways in personalized therapy of major cardiovascular diseases

The complex pathobiology underlying cardiovascular diseases (CVDs) has yet to be explained. Aberrant epigenetic changes may result from alterations in enzymatic activities, which are responsible for putting in and/or out the covalent groups, altering the epigenome and then modulating gene expression. The identification of novel individual epigenetic-sensitive trajectories at single cell level might provide additional opportunities to establish predictive, diagnostic and prognostic biomarkers as well as drug targets in CVDs. To date, most of studies investigated DNA methylation mechanism and miRNA regulation as epigenetics marks. During atherogenesis, big epigenetic changes in DNA methylation and different ncRNAs, such as miR-93, miR-340, miR-433, miR-765, CHROME, were identified into endothelial cells, smooth muscle cells, and macrophages. During man development, lipid metabolism, inflammation and homocysteine homeostasis, alter vascular transcriptional mechanism of fundamental genes such as ABCA1, SREBP2, NOS, HIF1. At histone level, increased HDAC9 was associated with matrix metalloproteinase 1 (MMP1) and MMP2 expression in pro-inflammatory macrophages of human carotid plaque other than to have a positive effect on toll like receptor signaling and innate immunity. HDAC9 deficiency promoted inflammation resolution and reverse cholesterol transport, which might block atherosclerosis progression and promote lesion regression. Here, we describe main human epigenetic mechanisms involved in atherosclerosis, coronary heart disease, ischemic stroke, peripheral artery disease; cardiomyopathy and heart failure. Different epigenetics mechanisms are activated, such as regulation by circular RNAs, as MICRA, and epitranscriptomics at RNA level. Moreover, in order to open new frontiers for precision medicine and personalized therapy, we offer a panoramic view on the most innovative bioinformatic tools designed to identify putative genes and molecular networks underlying CVDs in man.

Mechanisms of Action for Antimicrobial Peptides With Antibacterial and Antibiofilm Functions

The antibiotic crisis has led to a pressing need for alternatives such as antimicrobial peptides (AMPs). Recent work has shown that these molecules have great potential not only as antimicrobials, but also as antibiofilm agents, immune modulators, anti-cancer agents and anti-inflammatories. A better understanding of the mechanism of action (MOA) of AMPs is an important part of the discovery of more potent and less toxic AMPs. Many models and techniques have been utilized to describe the MOA. This review will examine how biological assays and biophysical methods can be utilized in the context of the specific antibacterial and antibiofilm functions of AMPs.

Titanium based complexes with melanin precursors as a tool for directing melanogenic pathways

Bioinspired melanin based hybrid materials hold huge promise for developing multifunctional systems for a considerable set of applications. Yet, control of melanogenic pathway is a big challenge to allow rational design of nanostructured systems with tuned structures and improved properties. This study proves the ability of titanium ions interactions with melanin precursors in directing melanogenic pathway. To this purpose complementary spectroscopic evidences were collected to reveal that in the presence of a TiO2-sol, amino-acid complex of Ti(IV) ions and DOPA actually inhibits its cyclization, during oxidative process, thus leading to DOPA-based polyphenols, stable even in oxidative environment, rather than eumelanin. This hugely impacts on the biological properties of the final hybrid systems which, discloses relevant and durable antioxidant behavior but poor antimicrobial activity differently from DHICA-based hybrid nanostructures. Overall this study, discloses the high potential of ceramic templated approach in combination with the selection of melanin precursor in achieving a fine tuning of physico-chemical as well as bioactivity of melanin-TiO2 nanostructures, opening new scenarios towards the design of cutting-edge biomaterials with tailored biological properties.

Benzodifurans for biomedical applications: BZ4, a selective anti-proliferative and anti-amyloid lead compound

AIM

Our goal is to evaluate benzodifuran-based scaffolds for biomedical applications.

METHODOLOGY

We here explored the anticancer and anti-amyloid activities of a novel compound (BZ4) in comparison with other known benzodifuran analogs, previously studied in our group, and we have explored its ability to interact with different DNA model systems.

RESULTS

BZ4 shows antiproliferative activity on different cancer cells; does not affect noncancerous control cells and alters the aggregation properties of β-amyloid, as ascertained by circular dichroism, fluorescence spectroscopy and scanning electron microscopy analysis. An overall, qualitative picture on the mechanistic aspects related to the biological activities is discussed in light of the dynamic light scattering, UV, circular dichroism and fluorescence data, as well as of the metal ion-binding properties of BZ4.

Reassessing the Host Defense Peptide Landscape

Current research has demonstrated that small cationic amphipathic peptides have strong potential not only as antimicrobials, but also as antibiofilm agents, immune modulators, and anti-inflammatories. Although traditionally termed antimicrobial peptides (AMPs) these additional roles have prompted a shift in terminology to use the broader term host defense peptides (HDPs) to capture the multi-functional nature of these molecules. In this review, we critically examined the role of AMPs and HDPs in infectious diseases and inflammation. It is generally accepted that HDPs are multi-faceted mediators of a wide range of biological processes, with individual activities dependent on their polypeptide sequence. In this context, we explore the concept of chemical space as it applies to HDPs and hypothesize that the various functions and activities of this class of molecule exist on independent but overlapping activity landscapes. Finally, we outline several emerging functions and roles of HDPs and highlight how an improved understanding of these processes can potentially be leveraged to more fully realize the therapeutic promise of HDPs.

Antifungal and anti-biofilm activity of the first cryptic antimicrobial peptide from an archaeal protein against Candida spp. clinical isolates

Candida species cause cutaneous and systemic infections with a high mortality rate, especially in immunocompromised patients. The emergence of resistance to the most common antifungal drugs, also due to biofilm formation, requires the development of alternative antifungal agents. The antimicrobial peptide VLL-28, isolated from an archaeal transcription factor, shows comparable antifungal activity against 10 clinical isolates of Candida spp. Using a fluoresceinated derivative of this peptide, we found that VLL-28 binds to the surface of planktonic cells. This observation suggested that it could exert its antifungal activity by damaging the cell wall. In addition, analyses performed on biofilms via confocal microscopy revealed that VLL-28 is differentially active on all the strains tested, with C. albicans and C. parapsilosis being the most sensitive ones. Notably, VLL-28 is the first example of an archaeal antimicrobial peptide that is active towards Candida spp. Thus, this points to archaeal microorganisms as a possible reservoir of novel antifungal agents.

Cell-Selective Pore Forming Antimicrobial Peptides of the Prodomain of Human Furin: A Conserved Aromatic/Cationic Sequence Mapping, Membrane Disruption, and Atomic-Resolution Structure and Dynamics

Antimicrobial peptides are promising molecules in uprising consequences of drug-resistant bacteria. The prodomain of furin, a serine protease, expressed in all vertebrates including humans, is known to be important for physiological functions. Here, potent antimicrobial peptides were mapped by extensive analyses of overlapping peptide fragments of the prodomain of human furin. Two peptides, YR26 and YR23, were active against bacterial cells including MRSA-resistant Staphylococcus aureus and Staphylococcus epidermis 51625. Peptides were largely devoid of hemolytic and cytotoxic activity. Bacterial cell killing occurred as a result of the disruption of the permeability barrier of the lipopolysaccharide (LPS)-outer membrane and fragmentation of LPS into small micelles. Furthermore, antibacterial peptides specifically interacted with the negatively charged lipids causing membrane leakage and fusion. The YR26 peptide in sodium dodecyl sulfate micelles demonstrated a long-helix-turn-short-helix structure exhibiting restricted backbone motions. The cell-selective activity of the furin peptides and their unique mode of action on membranes have a significant potential for the development of therapeutics.

Identification of Novel Cryptic Multifunctional Antimicrobial Peptides from the Human Stomach Enabled by a Computational-Experimental Platform

Novel approaches are needed to combat antibiotic resistance. Here, we describe a computational-experimental framework for the discovery of novel cryptic antimicrobial peptides (AMPs). The computational platform, based on previously validated antimicrobial scoring functions, indicated the activation peptide of pepsin A, the main human stomach protease, and its N- and C-terminal halves as antimicrobial peptides. The three peptides from pepsinogen A3 isoform were prepared in a recombinant form using a fusion carrier specifically developed to express toxic peptides in Escherichia coli. Recombinant pepsinogen A3-derived peptides proved to be wide-spectrum antimicrobial agents with MIC values in the range 1.56-50 μM (1.56-12.5 μM for the whole activation peptide). Moreover, the activation peptide was bactericidal at pH 3.5 for relevant foodborne pathogens, suggesting that this new class of previously unexplored AMPs may contribute to microbial surveillance within the human stomach. The peptides showed no toxicity toward human cells and exhibited anti-infective activity in vivo, reducing by up to 4 orders of magnitude the bacterial load in a mouse skin infection model. These peptides thus represent a promising new class of antibiotics. We envision that computationally guided data mining approaches such as the one described here will lead to the discovery of antibiotics from previously unexplored sources.

Human apolipoprotein E as a reservoir of cryptic bioactive peptides: The case of ApoE 133-167

Bioactive peptides derived from the receptor-binding region of human apolipoprotein E have previously been reported. All these peptides, encompassing fragments of this region or designed on the basis of short repeated cationic sequences identified in the same region, show toxic activities against a broad spectrum of bacteria and interesting immunomodulatory effects. However, the ability of these molecules to exert antibiofilm properties has not been described so far. In the present work, we report the characterization of a novel peptide, corresponding to residues 133 to 167 of human apolipoprotein E, here named ApoE (133-167). This peptide, besides presenting interesting properties comparable with those reported for other ApoE-derived peptides, such as a direct killing activity against a broad spectrum of bacteria or the ability to downregulate lipopolysaccharide-induced cytokine release, is also endowed with significant antibiofilm properties. Indeed, the peptide is able to strongly affect the formation of the extracellular matrix and also the viability of encapsulated bacteria. Noteworthy, ApoE (133-167) is not toxic toward human and murine cell lines and is able to assume ordered conformations in the presence of membrane mimicking agents. Taken together, collected evidences about biological and structural properties of ApoE (133-167) open new perspectives in the design of therapeutic agents based on human-derived bioactive peptides.

Exploring the role of unnatural amino acids in antimicrobial peptides

Cationic antimicrobial peptides (CAMPs) are a promising alternative to treat multidrug-resistant bacteria, which have developed resistance to all the commonly used antimicrobial, and therefore represent a serious threat to human health. One of the major drawbacks of CAMPs is their sensitivity to proteases, which drastically limits their half-life. Here we describe the design and synthesis of three nine-residue CAMPs, which showed high stability in serum and broad spectrum antimicrobial activity. As for all peptides a very low selectivity between bacterial and eukaryotic cells was observed, we performed a detailed biophysical characterization of the interaction of one of these peptides with liposomes mimicking bacterial and eukaryotic membranes. Our results show a surface binding on the DPPC/DPPG vesicles, coupled with lipid domain formation, and, above a threshold concentration, a deep insertion into the bilayer hydrophobic core. On the contrary, mainly surface binding of the peptide on the DPPC bilayer was observed. These observed differences in the peptide interaction with the two model membranes suggest a divergence in the mechanisms responsible for the antimicrobial activity and for the observed high toxicity toward mammalian cell lines. These results could represent an important contribution to unravel some open and unresolved issues in the development of synthetic CAMPs.

Novel bioactive peptides from PD-L1/2, a type 1 ribosome inactivating protein from Phytolacca dioica L. Evaluation of their antimicrobial properties and anti-biofilm activities

Antimicrobial peptides, also called Host Defence Peptides (HDPs), are effectors of innate immune response found in all living organisms. In a previous report, we have identified by chemical fragmentation, and characterized the first cryptic antimicrobial peptide in PD-L4, a type 1 ribosome inactivating protein (RIP) from leaves of Phytolacca dioica L. We applied a recently developed bioinformatic approach to a further member of the differently expressed pool of type 1 RIPs from P. dioica (PD-L1/2), and identified two novel putative cryptic HDPs in its N-terminal domain. These two peptides, here named IKY31 and IKY23, exhibit antibacterial activities against planktonic bacterial cells and, interestingly, significant anti-biofilm properties against two Gram-negative strains. Here, we describe that PD-L1/2 derived peptides are able to induce a strong dose-dependent reduction in biofilm biomass, affect biofilm thickness and, in the case of IKY31, interfere with cell-to-cell adhesion, likely by affecting biofilm structural components. In addition to these findings, we found that both PD-L1/2 derived peptides are able to assume stable helical conformations in the presence of membrane mimicking agents (SDS and TFE) and intriguingly beta structures when incubated with extracellular bacterial wall components (LPS and alginate). Overall, the data collected in this work provide further evidence of the importance of cryptic peptides derived from type 1 RIPs in host/pathogen interactions, especially under pathophysiological conditions induced by biofilm forming bacteria. This suggests a new possible role of RIPs as precursors of antimicrobial and anti-biofilm agents, likely released upon defensive proteolytic processes, which may be involved in plant homeostasis.

Antimicrobial Peptides and Their Therapeutic Potential for Bacterial Skin Infections and Wounds

Alarming data about increasing resistance to conventional antibiotics are reported, while at the same time the development of new antibiotics is stagnating. Skin and soft tissue infections (SSTIs) are mainly caused by the so called ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) which belong to the most recalcitrant bacteria and are resistant to almost all common antibiotics. S. aureus and P. aeruginosa are the most frequent pathogens isolated from chronic wounds and increasing resistance to topical antibiotics has become a major issue. Therefore, new treatment options are urgently needed. In recent years, research focused on the development of synthetic antimicrobial peptides (AMPs) with lower toxicity and improved activity compared to their endogenous counterparts. AMPs appear to be promising therapeutic options for the treatment of SSTIs and wounds as they show a broad spectrum of antimicrobial activity, low resistance rates and display pivotal immunomodulatory as well as wound healing promoting activities such as induction of cell migration and proliferation and angiogenesis. In this review, we evaluate the potential of AMPs for the treatment of bacterial SSTIs and wounds and provide an overview of the mechanisms of actions of AMPs that contribute to combat skin infections and to improve wound healing. Bacteria growing in biofilms are more resistant to conventional antibiotics than their planktonic counterparts due to limited biofilm penetration and distinct metabolic and physiological functions, and often result in chronification of infections and wounds. Thus, we further discuss the feasibility of AMPs as anti-biofilm agents. Finally, we highlight perspectives for future therapies and which issues remain to bring AMPs successfully to the market.

Bioinspired hybrid eumelanin–TiO2 antimicrobial nanostructures: the key role of organo–inorganic frameworks in tuning eumelanin's biocide action mechanism through membrane interaction

Intrinsic biocide efficacy of eumelanins can be markedly enhanced through a templated formation in the presence of a TiO₂-sol, leading to hybrid TiO₂–melanin nanostructures. However, mechanisms and processes behind biocide activity still remain poorly understood. This paper discloses the fundamental mechanism of action of these systems providing mechanistic information on their peculiar interaction with Escherichia coli strains. To this purpose biocide characterization is combined with Electron Paramagnetic Resonance (EPR) spectroscopy to investigate radical species produced by the hybrids as well as their interactions with Gram(−) external bacterial membranes. Experimental results indicate that TiO₂ mediated eumelanin polymerization leads to a peculiar mechanism of action of hybrid nanostructures, whose strong interactions with bacterial membranes enhance the action of reactive oxygen species (ROS) produced by eumelanin degradation itself, also concurring with the final biocide action. These findings provide strategic information for the development of eumelanin-based systems with enhanced activity against drug-resistant strains.

Hybrid TiO₂/eumelanin nanostructures showed a peculiar biocide mechanism against Gram(−) bacteria, based on the ROS action, produced by eumelanin degradation under visible light irradiation, and the interactions with external bacterial membranes.

Chemical Modification for Proteolytic Stabilization of the Selective αvβ3 Integrin RGDechi Peptide: in Vitro and in Vivo Activities on Malignant Melanoma Cells

Herein, we report the synthesis and biological characterization of the new peptide ψRGDechi as the first step toward novel-targeted theranostics in melanoma. This pseudopeptide is designed from our previously reported RGDechi peptide, known to bind selectively α_vβ₃ integrin, and differs for a modified amide bond at the main protease cleavage site. This chemical modification drastically reduces the enzymatic degradation in serum, compared to its parental peptide, resulting in an overall magnification of the biological activity on a highly expressing α_vβ₃ human metastatic melanoma cell line. Selective inhibition of cell adhesion, wound healing, and invasion are demonstrated; near-infrared fluorescent ψRGDechi derivative is able to detect α_vβ₃ integrin in human melanoma xenografts in a selective fashion. More, molecular docking studies confirm that ψRGDechi recognizes the receptor similarly to RGDechi. All these findings pave the way for the future employment of this novel peptide as promising targeting probe and therapeutic agent in melanoma disease.

Evolution of human apolipoprotein E (APOE) isoforms: Gene structure, protein function and interaction with dietary factors

Apolipoprotein E (APOE) is a member of the vertebrate protein family of exchangeable apolipoproteins that is characterized by amphipathic α-helices encoded by multiple nucleotide tandem repeats. Its equivalent in flying insects - apolipophorin-III - shares structural and functional commonalities with APOE, suggesting the possibility of an evolutionary relationship between the proteins. In contrast to all other known species, human APOE is functionally polymorphic and possesses three major allelic variants (ε4, ε3 and ε2). The present review examines the current knowledge on APOE gene structure, phylogeny and APOE protein topology as well as its human isoforms. The ε4 allele is associated with an increased age-related disease risk but is also the ancestral form. Despite increased mortality in the elderly, ε4 has not become extinct and is the second-most common allele worldwide after ε3. APOE ε4, moreover, shows a non-random geographical distribution, and similarly, the ε2 allele is not homogenously distributed among ethnic populations. This likely suggests the existence of selective forces that are driving the evolution of human APOE isoforms, which may include differential interactions with dietary factors. To that effect, micronutrients such as vitamin D and carotenoids or dietary macronutrient composition are elucidated with respect to APOE evolution.