Evaluation of the antimicrobial activity of the mastoparan Polybia-MPII isolated from venom of the social wasp Pseudopolybia vespiceps testacea (Vespidae, Hymenoptera)

Wasp Venom: Future Breakthrough in Production of Antimicrobial Peptides

The emergence of multi-drug-resistant pathogens and the decrease in the discovery of newer antibiotics have led to a quest for novel alternatives. Recently, wasp venom has spiked interest due to the presence of various active compounds, showcasing a diverse range of therapeutic effects. Wasps are creatures of the Hymenoptera order, and their venom chemically comprises antimicrobial peptides such as Anoplin, Mastoparan, Polybia-CP, Polydim-I, and Polybia MP1 that play a significant role in the biological effects of the venom. AMPs belong to the family of cationic peptides with α-helical structure, which exhibits a diversity of structural motifs and are crucial for innate immunity and defence in these creatures. These peptides demonstrate not only antimicrobial properties but also a wide range of other biological activities like anti-biofilm and anti-inflammatory, linked to their varying capacity to interact with biological membranes. Although wasp venom has the potential to be a cutting-edge natural source for the creation of new drugs, its usage is still restricted due to its availability and the lack of sophisticated methods for synthesizing its therapeutic components. Therefore, this review article provides insights about the therapeutic use of the wasp venom peptides against the antimicrobial-resistant pathogens, as well as its constraints and opportunities for future pharmacological development.

New Frontiers in Fighting Mycobacterial Infections: Venom-Derived Peptides

Notwithstanding the indefatigable endeavors to develop effective anti-mycobacterial therapies, mycobacterial infections still present a tough problem for medicine today. The problem is further complicated by the disquieting surge of drug-resistant mycobacterial pathogens, which considerably narrows the existing therapeutic options. Thus, there is a genuine need to discover novel anti-mycobacterial drugs. Animal venoms are considered a treasure trove of structurally variable and biologically active peptides, which may hold promise for therapeutic applications. Over the past two decades, abundant evidence has been amassed regarding anti-mycobacterial effects of various peptides derived from the venoms of honeybees, wasps, scorpions, pseudoscorpions, cone snails, and snakes. This review intends to consolidate the state-of-the-art knowledge on the anti-mycobacterial peptides of animal venoms and to sketch potentially fruitful directions for future investigations. The available data indicate that micromolar concentrations of particular venom-derived peptides can effectively inhibit the in vitro growth of Mycobacterium tuberculosis and non-tuberculous mycobacteria. The proposed mechanisms of action of venom-derived peptides include reduced activity of plasma membrane ATPase, depolarization of the cell membrane, disruption of the cell wall, and increased generation of reactive oxygen species. Interestingly, administering certain peptides (≤ 2 mg/kg body weight) through daily intraperitoneal injections to mice for 8 consecutive days resulted in lower levels of mycobacterial infections and inflammation, hitting two targets with one arrow. Indubitably, such peptides can usher in new possibilities for the prevention and treatment of recalcitrant mycobacterial infections.

Anti-Tumor Effects of Vespa bicolor Venom on Liver Cancer: In Vitro and In Vivo Studies

Despite the popular belief in the anti-tumor properties of Vespa bicolor venom (VBV), there is limited scientific evidence to support this claim. This study is the first to examine the anti-tumor effects of VBV on liver cancer, both alone and in combination with cisplatin (DDP), through in vitro and in vivo experiments. In vitro experiments evaluated VBV and its combination with DDP on HepG2 cell proliferation, invasion, migration, and apoptosis. Animal studies examined the tumor-suppressive effects, safety (hepatotoxicity and nephrotoxicity), and immune impact of these treatments in tumor-bearing mice. VBV monotherapy significantly inhibited the growth of HepG2 cells by suppressing their proliferation and invasion and induced apoptosis in vitro. Notably, low VBV concentrations significantly promoted the proliferation of normal liver cells (L-02), suggesting a hepatoprotective effect. In vivo, VBV monotherapy enhanced immune function and exhibited tumor suppression comparable to DDP monotherapy but did not induce significant liver or kidney damage. In addition, VBV combined with DDP synergistically enhanced the anti-tumor effects of DDP, compensating for its limited apoptosis-inducing activity and insufficient enhancement of immune function. Initial studies have shown the strong potential of VBV as an anti-liver-tumor drug, highlighting its unique clinical value.

Novel Synthetic Peptide Agelaia-12 Has Improved Activity Against Mycobacterium abscessus Complex

Fast-growing mycobacteria cause difficult-to-treat infections due to their high intrinsic resistance to antibiotics as well as disinfectant agents. Mycobacterium abscessus complex (MAC) is the main cause of nontuberculous mycobacteria diseases. In this work, we evaluated the activity of the novel synthetic antimicrobial peptide, Agelaia-12, against Mycobacterium abscessus and M. massiliense. Agelaia-12 showed a minimum inhibitory concentration (MIC) of 25 μM detected against M. abscessus and M. massiliense with no cytotoxicity. The scanning electronic microscopy analysis of mycobacterial treated with Agelaia-12 demonstrated the presence of filamentous structures and aggregation of the cells. Congo red binding assay of M. abscessus exhibited altered dye accumulation after treatment with Agelaia-12. Treatment of M. abscessus- or M. massiliense-infected murine macrophages with Agelaia-12 decreased the mycobacterial load by 92% for the tested strains. Additionally, IFN-y KO mice infected with M. abscessus or M. massiliense and treated with Agelaia-12 showed a 98% reduction in lung bacterial load. Thus, the synthetic peptide Agelaia-12 may be a promising biomolecule for the treatment of mycobacteriosis, and its structural properties may serve as a foundational model for the design and development of novel pharmaceutical agents aimed at combating this disease.

Emerging and alternative strategies for the treatment of nontuberculous mycobacterial infections

INTRODUCTION

Nontuberculous mycobacteria (NTM) infections have emerged as a significant clinical challenge due to their intrinsic multidrug resistance and the limited efficacy of existing treatments. These infections are becoming increasingly prevalent, with a need for new and effective therapeutic strategies.

AREAS COVERED

This review addresses several key aspects of NTM infections: i) pathogenesis and epidemiology; ii) the limitations and challenges of current treatment options; iii) emerging and alternative therapeutic strategies; iv) advanced drug delivery systems such as nanoparticles and efflux pump inhibitors; v) innovative antibacterial alternatives like antimicrobial peptides, bacteriophage therapy, and phytochemicals; and vi) other potential treatment modalities such as inhaled nitric oxide, small molecules, surgical debridement, phototherapy, and immunomodulatory therapy.

EXPERT OPINION

Personalized medicine, advanced drug delivery systems, and alternative therapies hold promise for the future of NTM treatment. Early and accurate identification of NTM species, enabled by improved diagnostic methods, is critical for tailoring treatment regimens. Emerging therapies show promise against drug-resistant NTM strains, but overcoming barriers like clinical trials, regulatory hurdles, and high production costs is crucial. Continued research and innovation are essential to improve treatment efficacy and patient outcomes.

Heterologous expression of the novel dimeric antimicrobial peptide LIG in Pichia pastoris

The antimicrobial peptide (AMP) LI is a fusion product of antimicrobial peptide LL37 produced by human neutrophils and Indolicidin secreted by bovine neutrophils. LI retained the antimicrobial activity of the parental peptides and showed high cell selectivity. In this study, the flexible linker Gly-Ser-Gly (G-S-G) was used to ligate LI into dimeric LIG, and constructed the Pichia pastoris (P. pastoris) expression vector pPIC9K-6×His-3×FLAG-LIG. The total protein expression of P. pastoris GS115 reached the highest level (189.6 mg/L) after 96 h induction with 3 % methanol at the initial pH value of 7.0. Finally, 5.9 mg/L of recombinant LIG (rLIG) was obtained after enterokinase digestion and purification. The rLIG had high antimicrobial activity and low hemolytic activity. Compared with monomer LI, GSG linked dimeric LIG, which had no significant change in antimicrobial activity and had good salt ions stability. In this study, the dimeric antimicrobial peptide LIG was successfully expressed, which provided a new idea for the expression of AMPs in the P. pastoris expression system, and had important significance for the application of AMPs.

Unwrapping the structural and functional features of antimicrobial peptides from wasp venoms

The study of wasp venoms has captured attention due to the presence of a wide variety of active compounds, revealing a diverse array of biological effects. Among these compounds, certain antimicrobial peptides (AMPs) such as mastoparans and chemotactic peptides have emerged as significant players, characterized by their unique amphipathic short linear alpha-helical structure. These peptides exhibit not only antibiotic properties but also a range of other biological activities, which are related to their ability to interact with biological membranes to varying degrees. This review article aims to provide updated insights into the structure/function relationships of AMPs derived from wasp venoms, linking this knowledge to the potential development of innovative treatments against infections.

Mycobacterium abscessus Opsonization Allows an Escape from the Defensin Bactericidal Action in Drosophila

Mycobacterium abscessus, an intracellular nontuberculous mycobacterium, is considered the most pathogenic species among the group of rapidly growing mycobacteria. The resistance of M. abscessus to the host innate response contributes to its pathogenicity in addition to several virulence factors. We have recently shown in Drosophila that antimicrobial peptides (AMPs), whose production is induced by M. abscessus, are unable to control mycobacterial infection. This could be due to their inability to kill mycobacteria and/or the hidden location of the pathogen in phagocytic cells. Here, we demonstrate that the rapid internalization of M. abscessus by Drosophila macrophages allows it to escape the AMP-mediated humoral response. By depleting phagocytes in AMP-deficient flies, we found that several AMPs were required for the control of extracellular M. abscessus. This was confirmed in the Tep4 opsonin-deficient flies, which we show can better control M. abscessus growth and have increased survival through overproduction of some AMPs, including Defensin. Furthermore, Defensin alone was sufficient to kill extracellular M. abscessus both in vitro and in vivo and control its infection. Collectively, our data support that Tep4-mediated opsonization of M. abscessus allows its escape and resistance toward the Defensin bactericidal action in Drosophila. IMPORTANCE Mycobacterium abscessus, an opportunistic pathogen in cystic fibrosis patients, is the most pathogenic species among the fast-growing mycobacteria. How M. abscessus resists the host innate response before establishing an infection remains unclear. Using Drosophila, we have recently demonstrated that M. abscessus resists the host innate response by surviving the cytotoxic lysis of the infected phagocytes and the induced antimicrobial peptides (AMPs), including Defensin. In this work, we demonstrate that M. abscessus resists the latter response by being rapidly internalized by Drosophila phagocytes. Indeed, by combining in vivo and in vitro approaches, we show that Defensin is able to control extracellular M. abscessus infection through a direct bactericidal action. In conclusion, we report that M. abscessus escapes the host AMP-mediated humoral response by taking advantage of its internalization by the phagocytes.

Ferritin from Mycobacterium abscessus is involved in resistance to antibiotics and oxidative stress

Mycobacterium abscessus subsp. massiliense (Mycma) is a rapidly growing Mycobacterium belonging to the M. abscessus complex that is often associated with lung and soft tissue infection outbreaks. Mycma is resistant to many antimicrobials, including those used for treating tuberculosis. Therefore, Mycma infections are difficult to treat and may lead to high infectious complication rates. Iron is essential for bacterial growth and establishment of infection. During infection, the host reduces iron concentrations as a defense mechanism. To counteract the host-induced iron deficiency, Mycma produces siderophores to capture iron. Mycma has two ferritins (encoded by mycma_0076 and mycma_0077) modulated by different iron concentrations, which allow the survival of this pathogen during iron scarcity. In this study, we constructed knockout (Mycma 0076KO) and complemented (Mycma 0076KOc) gene strains for mycma_0076 to understand the function of 0076 ferritin. Deletion of mycma_0076 in Mycma led to the transition in colony morphology from smooth to rough, alteration of the glycopeptidolipids spectra, increased permeability of the envelope, reduction in biofilm formation, increased susceptibility to antimicrobials and hydrogen peroxide-induced oxidative stress, and decreased internalization by macrophages. This study shows that Mycma_0076 ferritin in Mycma is involved in resistance to oxidative stress and antimicrobials, and alteration of cell envelope architecture. KEY POINTS: • Deletion of the mycma_0076 gene altered colony morphology to rough; • Mycma 0076KO changed GPL profile; • Absence of Mycma_0076 ferritin results in increased susceptibility to antimicrobials and oxidative stress in Mycma. Legend: a In wild-type M. abscessus subsp. massiliense strain, iron is captured from the environment by carboxymycobactins and mycobactins (1). Iron-dependent regulator (IdeR) proteins bind to ferrous iron (Fe⁺²) in the bacterial cytoplasm leading to the activation of the IdeR-Fe⁺² complex (2). The activated complex binds to the promoter regions of iron-dependent genes, called iron box, which in turn help in the recruitment of RNA polymerase to promote transcription of genes such as mycma_0076 and mycma_0077 ferritin genes (3). Mycma_0076 and Mycma_0077 ferritins bind to excess iron in the medium and promote Fe²⁺ oxidation into ferric iron (Fe³⁺) and store iron molecules to be released under iron scarcity conditions. (4) Genes related to biosynthesis and transport of glycopeptidolipids (GPL) are expressed normally and the cell envelope is composed of different GPL species (colored squares represented on the cell surface (GPLs). Consequently, WT Mycma present smooth colony phenotype (5). b In Mycma 0076KO strain, the lack of ferritin 0076 causes overexpression of mycma_0077 (6), but does not restore wild-type iron homeostasis and thus may result in free intracellular iron, even in the presence of miniferritins (MaDps). The excess iron potentiates oxidative stress (7) by generating hydroxyl radicals through Fenton Reaction. During this process, through an unknown mechanism, that could involve Lsr2 (8), the expression of GPL synthesis locus is regulated positively and/or negatively, resulting in alteration of GPL composition in the membrane (as represented by different colors of squares on the cell surface), resulting in a rough colony phenotype (9). The changes of GPL can increase cell wall permeability, contributing to antimicrobial susceptibility (10).

Mycobacterium abscessus Infections in Cystic Fibrosis Individuals: A Review on Therapeutic Options

Mycobacterium abscessus is an opportunistic pathogen that mainly colonizes and infects cystic fibrosis patients' lungs. M. abscessus is naturally resistant to many antibiotics such as rifamycin, tetracyclines and β-lactams. The current therapeutic regimens are not very effective and are mostly based on repurposed drugs used against Mycobacterium tuberculosis infections. Thus, new approaches and novel strategies are urgently needed. This review aims to provide an overview of the latest ongoing findings to fight M. abscessus infections by analyzing emerging and alternative treatments, novel drug delivery strategies, and innovative molecules.

Pelgipeptins, a Nonribosomal Lipopeptide Family, Show Larvicidal Activity against Vectors Transmitting Viruses

Aedes aegypti and Culex quinquefasciatus are vectors of numerous diseases of worldwide public importance, such as arboviruses and filariasis. The main strategy for controlling these vectors is the use of chemicals, which can induce the appearance of resistant insects. The use of Bacillus thuringiensis (Bt) and Lysinibacillus sphaericus (Ls) with larvicidal activity against arboviral-transmitting insects has been successful in many studies. In contrast, the use and knowledge of peptides with insecticidal activity are so far scarce. In this work, 25 peptides and 5 strains of each bacterial species were prospected individually or together regarding their insecticidal activity. Initially, in vitro assays of cellular cytotoxicity of the peptides against SF21 cells of Spodoptera frugiperda were performed. The peptides Polybia-MPII and pelgipeptin caused 69 and 60% of cell mortality, respectively, at the concentration of 10 μM. Thus, they were evaluated in vivo against second-stage larvae of the two Culicidae. However, in the in vivo bioassays, only pelgipeptin showed larvicidal mortality against both larvae (LC₅₀ 6.40 μM against A. aegypti, and LC₅₀ 1.22 μM against C. quinquefasciatus). The toxin-producing bacterial strain that showed the lowest LC₅₀ against A. aegypti was Bt S8 (LC₅₀ = 0.71 ng/mL) and against C. quinquefasciatus, it was Ls S260 (LC₅₀ = 2.32 ng/mL). So, the synergistic activity between the association of the bacterial toxins and pelgipeptin was evaluated. A synergic effect of pelgipeptin was observed with Ls strain S260 against C. quinquefasciatus. Our results demonstrate the possibility of synergistic or individual use of both biologically active larvicides against C. quinquefasciatus and A. aegypti.

Biologically Active Peptides from Venoms: Applications in Antibiotic Resistance, Cancer, and Beyond

Peptides are potential therapeutic alternatives against global diseases, such as antimicrobial-resistant infections and cancer. Venoms are a rich source of bioactive peptides that have evolved over time to act on specific targets of the prey. Peptides are one of the main components responsible for the biological activity and toxicity of venoms. South American organisms such as scorpions, snakes, and spiders are important producers of a myriad of peptides with different biological activities. In this review, we report the main venom-derived peptide families produced from South American organisms and their corresponding activities and biological targets.

Antifungal metabolites, their novel sources, and targets to combat drug resistance

Excessive antibiotic prescriptions as well as their misuse in agriculture are the main causes of antimicrobial resistance which poses a growing threat to public health. It necessitates the search for novel chemicals to combat drug resistance. Since ancient times, naturally occurring medicines have been employed and the enormous variety of bioactive chemicals found in nature has long served as an inspiration for researchers looking for possible therapeutics. Secondary metabolites from microorganisms, particularly those from actinomycetes, have made it incredibly easy to find new molecules. Different actinomycetes species account for more than 70% of naturally generated antibiotics currently used in medicine, and they also produce a variety of secondary metabolites, including pigments, enzymes, and anti-inflammatory compounds. They continue to be a crucial source of fresh chemical diversity and a crucial component of drug discovery. This review summarizes some uncommon sources of antifungal metabolites and highlights the importance of further research on these unusual habitats as a source of novel antimicrobial molecules.

Alternatives to Antibiotics against Mycobacterium abscessus

Mycobacterium abscessus complex is extremely difficult to treat. Intrinsic and acquired bacterial resistance makes this species one of the most challenging pathogens and treatments last from months to years, associated with potential risky antibiotic toxicity and a high number of failures. Nonantibiotic antimicrobial agents against this microorganism have recently been studied so as to offer an alternative to current drugs. This review summarizes recent research on different strategies such as host modulation using stem cells, photodynamic therapy, antibiofilm therapy, phage therapy, nanoparticles, vaccines and antimicrobial peptides against M. abscessus both in vitro and in vivo.

Mastoparans: A Group of Multifunctional α-Helical Peptides With Promising Therapeutic Properties

Biologically active peptides have been attracting increasing attention, whether to improve the understanding of their mechanisms of action or in the search for new therapeutic drugs. Wasp venoms have been explored as a remarkable source for these molecules. In this review, the main findings on the group of wasp linear cationic α-helical peptides called mastoparans were discussed. These compounds have a wide variety of biological effects, including mast cell degranulation, activation of protein G, phospholipase A₂, C, and D activation, serotonin and insulin release, and antimicrobial, hemolytic, and anticancer activities, which could lead to the development of new therapeutic agents.

Bioactive Peptides and Proteins from Wasp Venoms

Wasps, members of the order Hymenoptera, use their venom for predation and defense. Accordingly, their venoms contain various constituents acting on the circulatory, immune and nervous systems. Wasp venom possesses many allergens, enzymes, bioactive peptides, amino acids, biogenic amines, and volatile matters. In particular, some peptides show potent antimicrobial, anti-inflammatory, antitumor, and anticoagulant activity. Additionally, proteinous components from wasp venoms can cause tissue damage or allergic reactions in organisms. These bioactive peptides and proteins involved in wasp predation and defense may be potential sources of lead pharmaceutically active molecules. In this review, we focus on the advances in bioactive peptides and protein from the venom of wasps and their biological effects, as well as the allergic reactions and immunotherapy induced by the wasp venom.

Characterization of the Composition and Biological Activity of the Venom from Vespa bicolor Fabricius, a Wasp from South China

We analyzed, for the first time, the major components and biological properties of the venom of Vespa bicolor, a wasp from South China. Using HPLC and SDS-PAGE, combined with LC–MS/MS, MALDI-TOF-MS, and NMR data to analyze V. bicolor venom (VBV), we found that VBV contains three proteins (hyaluronidase A, phospholipase A1 (two isoforms), and antigen 5 protein) with allergenic activity, two unreported proteins (proteins 5 and 6), and two active substances with large quantities (mastoparan-like peptide 12a (Vb-MLP 12a), and 5-hydroxytryptamine (5-HT)). In addition, the antimicrobial activity of VBV was determined, and results showed that it had a significant effect against anaerobic bacteria. The minimum inhibitory concentration and minimum bactericidal concentration for Propionibacterium acnes were 12.5 µg/mL. Unsurprisingly, VBV had strong antioxidant activity because of the abundance of 5-HT. Contrary to other Vespa venom, VBV showed significant anti-inflammatory activity, even at low concentrations (1 µg/mL), and we found that Vb-MLP 12a showed pro-inflammatory activity by promoting the proliferation of RAW 264.7 cells. Cytotoxicity studies showed that VBV had similar antiproliferative effects against all tested tumor cell lines (HepG2, Hela, MCF-7, A549, and SASJ-1), with HepG2 being the most susceptible. Overall, this study on VBV has high clinical importance and promotes the development of Vespa bicolor resources.

The effects of incorporation of the counterparts and mimics of L-lysine on the antimicrobial activity, hemolytic activity, cytotoxicity and tryptic stability of antimicrobial peptide polybia-MPII

Due to the limited effects of conventional antibiotics on the increasing emergence of drug-resistant bacteria and fungi, novel antimicrobial agents were urgently needed to alleviate this phenomenon. Nowadays, antimicrobial peptides are believed to be a promising candidate for a new generation of antimicrobial drugs. Antimicrobial peptide polybia-MPII (MPII) was first isolated from the venom of the social wasp Polybia paulista with a broad spectrum of antimicrobial activity. In the present study, the counterparts and mimics of cationic amino acids of Lys, such as Arg, His, Orn, Dab and Dap were employed to substitute Lys in the sequence of MPII. The effects of the incorporation of these amino acids on its antimicrobial activity, hemolytic activity, cytotoxicity, enzyme stability and therapeutic potential were explored. Our results showed that although the incorporation of Arg could improve its antimicrobial activity, there is no improvement in enzyme stability. The incorporation of His makes MPII exert its antimicrobial activity in a pH-dependent manner. Notably, incorporating Dap could effectively decrease its hemolytic activity and cytotoxicity and enhance its enzyme stability against trypsin. In conclusion, this study would provide an effective strategy to improve the bioavailability and metabolic stability of AMPs while decrease their hemolytic activity and cytotoxicity.

The Asian wasp Vespa velutina nigrithorax: Entomological and allergological characteristics

The yellow-legged or Asian wasp (Vespa velutina nigrithorax) has spread rapidly across Europe since its first introduction in France, in 2004. Originally from South-East Asia, it is considered an invasive species outside its native region. Apart from the ecological and economic implications of its presence, it may cause health problems to humans due to the toxic and allergenic components of its venom. Vespa velutina nigrithorax has become the most prevalent cause of anaphylaxis due to Hymenoptera venom in some regions of Spain. Although sIgE against both antigen 5 (Vesp v 5) and A1-phospholipase (Vesp v 1) has been detected in these patients, only Vesp v 5 may be considered a dominant allergen. Interestingly, Vesp v 1 appears to be a glycosylated allergen different from A1-phospholipases from other species. Inhibition studies suggest that Vespula spp venom could behave as primary sensitizer. Besides, changes in sIgE and sIgG4 during Vespula venom immunotherapy in patients with anaphylaxis due to V. velutina support the use of Vespula venom extracts to treat these patients. The purpose of this review is to explore the biological behaviour of V. velutina and to summarize the current knowledge of the allergic reactions provoked by this wasp.

Wasp Venom Biochemical Components and Their Potential in Biological Applications and Nanotechnological Interventions

Wasps, members of the order Hymenoptera, are distributed in different parts of the world, including Brazil, Thailand, Japan, Korea, and Argentina. The lifestyles of the wasps are solitary and social. Social wasps use venom as a defensive measure to protect their colonies, whereas solitary wasps use their venom to capture prey. Chemically, wasp venom possesses a wide variety of enzymes, proteins, peptides, volatile compounds, and bioactive constituents, which include phospholipase A2, antigen 5, mastoparan, and decoralin. The bioactive constituents have anticancer, antimicrobial, and anti-inflammatory effects. However, the limited quantities of wasp venom and the scarcity of advanced strategies for the synthesis of wasp venom’s bioactive compounds remain a challenge facing the effective usage of wasp venom. Solid-phase peptide synthesis is currently used to prepare wasp venom peptides and their analogs such as mastoparan, anoplin, decoralin, polybia-CP, and polydim-I. The goal of the current review is to highlight the medicinal value of the wasp venom compounds, as well as limitations and possibilities. Wasp venom could be a potential and novel natural source to develop innovative pharmaceuticals and new agents for drug discovery.

Antimicrobial and Anticancer Properties of Synthetic Peptides Derived from the Wasp Parachartergus fraternus

Agelaia-MPI and protonectin are antimicrobial peptides isolated from the wasp Parachartergus fraternus that show antimicrobial and neuroactive activities. Previously, two analogues of these peptides, neuroVAL and protonectin-F, were designed to reduce nonspecific toxicity and improve potency. Here, the three-dimensional structures of neuroVAL, protonectin and protonectin-F were determined by using circular dichroism and NMR spectroscopy. Antibacterial, antifungal, cytotoxic and hemolytic activities were tested for the parent peptides and analogues. All peptides showed moderate antimicrobial activity against Gram-positive bacteria, with agelaia-MPI being the most active. Protonectin and protonectin-F were found to be toxic to cancerous and noncancerous cell lines. Internalization experiments revealed that these peptides accumulate inside both cell types. By contrast, neuroVAL was nontoxic to all tested cells and was able to enter cells without accumulating. In summary, neuroVAL has potential as a nontoxic cell-penetrating peptide, while protonectin-F needs further modification to realize its potential as an antitumor peptide.

EcDBS1R4, an Antimicrobial Peptide Effective against Escherichia coli with In Vitro Fusogenic Ability

Discovering antibiotic molecules able to hold the growing spread of antimicrobial resistance is one of the most urgent endeavors that public health must tackle. The case of Gram-negative bacterial pathogens is of special concern, as they are intrinsically resistant to many antibiotics, due to an outer membrane that constitutes an effective permeability barrier. Antimicrobial peptides (AMPs) have been pointed out as potential alternatives to conventional antibiotics, as their main mechanism of action is membrane disruption, arguably less prone to elicit resistance in pathogens. Here, we investigate the in vitro activity and selectivity of EcDBS1R4, a bioinspired AMP. To this purpose, we have used bacterial cells and model membrane systems mimicking both the inner and the outer membranes of Escherichia coli, and a variety of optical spectroscopic methodologies. EcDBS1R4 is effective against the Gram-negative E. coli, ineffective against the Gram-positive Staphylococcus aureus and noncytotoxic for human cells. EcDBS1R4 does not form stable pores in E. coli, as the peptide does not dissipate its membrane potential, suggesting an unusual mechanism of action. Interestingly, EcDBS1R4 promotes a hemi-fusion of vesicles mimicking the inner membrane of E. coli. This fusogenic ability of EcDBS1R4 requires the presence of phospholipids with a negative curvature and a negative charge. This finding suggests that EcDBS1R4 promotes a large lipid spatial reorganization able to reshape membrane curvature, with interesting biological implications herein discussed.

Diversity of compounds in Vespa spp. venom and the epidemiology of its sting: a global appraisal

Poisonous animals imply a risk to human life, because their venom is a complex mixture of low molecular weight components, peptides and proteins. Hornets use the venom for self-defence, to repel intruders and to capture prey, but they can cause poisoning and allergic reactions to people. In particular, they seem to be a health problem in the countries where they are native due to their sting, which in the most severe cases can lead to severe or fatal systemic anaphylaxis. But this situation is being an emerging problem for new countries and continents because hornet incursions are increasing in the global change scenario, such as in Europe and America. Furthermore, 55 detailed cases of hornet sting were found in 27 papers during the current review where 36.4% died due to, mainly, a multi-organ failure, where renal failure and liver dysfunction were the most common complications. Moreover, the great taxonomic, ecological diversity, geographical distribution and the wide spectrum of pathophysiological symptoms of hornets have been the focus of new research. Considering this, the present systematic review summarizes the current knowledge about the components of Vespa venom and the epidemiology of its sting to serve as reference for the new research focused on the development of techniques for diagnosis, new drugs and treatments of its sting.

Involvement of the gabaergic, serotonergic and glucocorticoid mechanism in the anxiolytic-like effect of mastoparan-L

Mastoparan-L (mast-L) is a cell-penetrating tetradecapeptide and stimulator of monoamine exocytosis. In the present study, we evaluated the anxiolytic-like effect of mast-L. Preliminary pharmacological tests were conducted to determine the most appropriate route of administration, extrapolate dose and detect potential toxic effects of this peptide. Oral and intracerebroventricular administration of mast-L (0.1, 0.3 or 0.9 mg.kg^-1), diazepam (1 or 5 mg.kg^-1), buspirone (10 mg.kg^-1) or vehicle 10 mL.kg^-1 was carried out prior to the exposure of mice to the anxiety models: open field, light-dark box and elevated plus-maze. To characterize the mechanism underlying the antianxiety-like effect of mast-L, pharmacological antagonism, blood plasma analysis, molecular docking, and receptor binding assays were performed. The absence of a neurotoxic sign, animal's death as well as lack of significant changes in the relative organ weight, hematological and biochemical parameters suggest that mast-L is relatively safe. The anxiolytic-like effect of mast-L was attenuated by flumazenil (antagonist of benzodiazepine binding site) and WAY100635 (selective antagonist of 5-HT_1A receptors) pretreatments. Mast-L reduced plasma corticosterone and lowered the scoring function at GABA_A -18.48 kcal/mol (Ki = 155 nM), 5-HT_1A -22.39 kcal/mol (Ki = 130 nM), corticotropin-releasing factor receptor subtype 1 (CRF1) -11.95 kcal/mol (Ki = 299 nM) and glucocorticoid receptors (GR) -14.69 kcal/mol (Ki = 3552 nM). These data fit the binding affinity (Ki) and demonstrate the involvement of gabaergic, serotonergic and glucocorticoid mechanisms in the anxiolytic-like property of mast-L.

Antimicrobials from Venomous Animals: An Overview

The inappropriate or excessive use of antimicrobial agents caused an emerging public health problem due to the resulting resistance developed by microbes. Therefore, there is an urgent need to develop effective antimicrobial strategies relying on natural agents with different mechanisms of action. Nature has been known to offer many bioactive compounds, in the form of animal venoms, algae, and plant extracts that were used for decades in traditional medicine. Animal venoms and secretions have been deeply studied for their wealth in pharmaceutically promising molecules. As such, they were reported to exhibit many biological activities of interest, such as antibacterial, antiviral, anticancer, and anti-inflammatory activities. In this review, we summarize recent findings on the antimicrobial activities of crude animal venoms/secretions, and describe the peptides that are responsible of these activities.

Wasp Venom Possesses Potential Therapeutic Effect in Experimental Models of Rheumatoid Arthritis

Rheumatoid arthritis (RA) is an autoimmune disease. Wasp venom (WV), which is considered as a traditional folk medicine in Jingpo nationality in Yunnan, China, relieves rheumatoid arthritis. The current study aimed to investigate the effect of wasp venom ameliorating rheumatoid arthritis symptoms in experimental rats. We established a model of type II collagen- (CII-) induced arthritis (CIA) in SD rats and examined the inhibition of inflammation and autoimmune response. The antiarthritic effects of WV were evaluated through the paw swelling, and histopathological score and histopathology changes of the affected paw were assessed. The anti-inflammation effects were assayed by the level of IL-6, TNF-α, IL-1β, and the number of inflammatory cells in peripheral blood. The alteration of the T cell subset ratio in the spleen of rats was detected by flow cytometry, and at the same time, the viscera index and immune serum globulin levels were evaluated. The results suggested that various doses of WV (0.125, 0.25, and 0.5 mg/kg) significantly alleviated paw swelling and arthritis score in CIA rats with the untreated control (P < 0.05). WV (0.25 and 0.5 mg/kg) relieved synovial tissue lesions of ankle joints and histopathology scores of synoviocyte hyperplasia and inflammatory cell infiltration with vehicle group (P < 0.05). Regarding immunological regulation, 0.5 mg/kg WV lowered the immune serum globulin levels (P < 0.05), and we further found that WV (0.5 mg/kg) suppressed the immune response of Th cells, while enhancing the functions of Tc cells and Treg cells in spleen cells markedly (P < 0.05). The immunosuppressive action of WV displayed was analogous to its inhibitory effect on IL-1β, TNF-α, IL-8, IL-6, COX-2, and PGE2 levels in rat serum. In conclusion, these findings demonstrated that WV exhibited antiarthritic activity, which might be associated with their inhibitory effects on immunoregulation and anti-inflammatory action.

Study of mastoparan analog peptides against Candida albicans and safety in zebrafish embryos (Danio rerio)

Aim: In this work, mastoparan analog peptides from wasp venom were tested against Candida albicans and safety assays were performed using cell culture and model zebrafish. Materials & methods: Minimal inhibitory concentration was determined and toxicity was performed using human skin keratinocyte and embryo zebrafish. Also, permeation of peptides through embryo chorion was performed. Results: The peptides demonstrated anti-C. albicans activity, with low cytotoxicity and nonteratogenicity in Danio rerio. The compounds had different permeation through chorion, suggesting that this occurs due to modifications in their amino acid sequence. Conclusion: The results showed that the studied peptides can be used as structural study models for novel potential antifungal agents.

Looking beyond Typical Treatments for Atypical Mycobacteria

The genus Mycobacterium comprises not only the deadliest of bacterial pathogens, Mycobacterium tuberculosis, but several other pathogenic species, including M. avium and M. abscessus. The incidence of infections caused by atypical or nontuberculous mycobacteria (NTM) has been steadily increasing, and is associated with a panoply of diseases, including pulmonary, soft-tissue, or disseminated infections. The treatment for NTM disease is particularly challenging, due to its long duration, to variability in bacterial susceptibility profiles, and to the lack of evidence-based guidelines. Treatment usually consists of a combination of at least three drugs taken from months to years, often leading to severe secondary effects and a high chance of relapse. Therefore, new treatment approaches are clearly needed. In this review, we identify the main limitations of current treatments and discuss different alternatives that have been put forward in recent years, with an emphasis on less conventional therapeutics, such as antimicrobial peptides, bacteriophages, iron chelators, or host-directed therapies. We also review new forms of the use of old drugs, including the repurposing of non-antibacterial molecules and the incorporation of antimicrobials into ionic liquids. We aim to stimulate advancements in testing these therapies in relevant models, in order to provide clinicians and patients with useful new tools with which to treat these devastating diseases.

Antifungal Activity, Toxicity, and Membranolytic Action of a Mastoparan Analog Peptide

Invasive fungal infections, such as cryptococcosis and paracoccidioidomycosis are associated with significant rates of morbidity and mortality. Cryptococcosis, caused by Cryptococcus neoformans, is distributed worldwide and has received much attention as a common complication in patients with HIV. Invasive fungal infections are usually treated with a combination of amphotericin B and azoles. In addition, 5-fluorocytosine (5-FC) is applied in cryptococcosis, specifically to treat central nervous system infection. However, host toxicity, high cost, emerging number of resistant strains, and difficulty in developing new selective antifungals pose challenges. The need for new antifungals has therefore prompted a screen for inhibitory peptides, which have multiple mechanisms of action. The honeycomb moth Galleria mellonella has been widely used as a model system for evaluating efficacy of antifungal agents. In this study, a peptide analog from the mastoparan class of wasps (MK58911) was tested against Cryptococcus spp. and Paracoccidioides spp. In addition, peptide toxicity tests on lung fibroblasts (MRC5) and glioblastoma cells (U87) were performed. Subsequent tests related to drug interaction and mechanism of action were also performed, and efficacy and toxicity of the peptide were evaluated in vivo using the G. mellonella model. Our results reveal promising activity of the peptide, with an MIC in the range of 7.8-31.2 μg/mL, and low toxicity in MRC and U87 cells (IC₅₀ > 500 μg/mL). Taken together, these results demonstrate that MK58911 is highly toxic in fungal cells, but not mammalian cells (SI > 16). The mechanism of toxicity involved disruption of the plasma membrane, leading to death of the fungus mainly by necrosis. In addition, no interaction with the drugs amphotericin B and fluconazole was found either in vitro or in vivo. Finally, the peptide showed no toxic effects on G. mellonella, and significantly enhanced survival rates of larvae infected with C. neoformans. Although not statistically significant, treatment of larvae with all doses of MK58911 showed a similar trend in decreasing the fungal burden of larvae. These effects were independent of any immunomodulatory activity. Overall, these results present a peptide with potential for use as a new antifungal drug to treat systemic mycoses.

Structure and mode of action of a novel antibacterial peptide from the blood of Andrias davidianus

Andrias davidianus is widely recognized in traditional medicine as a cure-all to treat a plethora of ailments. In a previous study, a novel antibacterial peptide named andricin B was isolated from A. davidianus blood. In this study, we investigated andricin B structure and its mode of action. Circular dichroism spectra suggested that andricin B adopts a random coil state in aqueous solution and a more rigid conformation in the presence of bacteria. Moreover propidium iodide/fluorescein diacetate double staining indicated that bacteria treated with andricin B were not immediately eliminated. Rather, there is a gradual bacterial death, followed by a sublethal stage. Scanning electronic microscope imaging indicates that andricin B might form pores on cell membranes, leading to the release of cytoplasmic contents. These results were consistent with flow cytometry analysis. Furthermore, Fourier transform infrared spectroscopy suggests that andricin B induces changes in the chemical properties in the areas surrounding these "pores" on the cell membranes. SIGNIFICANCE AND IMPACT OF THE STUDY: The results of this study suggested the new perspectives about the mode of action of antimicrobial peptide (AMP) active against sensitive bacteria. The AMP was able to be in a random coiled state in aqueous solution but to change to a more rigid one in the presence of sensitive bacteria. Exposure to AMP might not lead to immediate death of treated bacteria, rather bacteria concentration decreased gradually flattening at a sublethal stage. These findings will help people to understand better how the AMPs activate against sensitive bacteria.

Antimicrobial and Antibiofilm Effects of Peptides from Venom of Social Wasp and Scorpion on Multidrug-Resistant Acinetobacter baumannii

Intravascular stent infection is a rare complication with a high morbidity and high mortality; bacteria from the hospital environment form biofilms and are often multidrug-resistant (MDR). Antimicrobial peptides (AMPs) have been considered as alternatives to bacterial infection treatment. We analyzed the formation of the bacterial biofilm on the vascular stents and also tested the inhibition of this biofilm by AMPs to be used as treatment or coating. Antimicrobial activity and antibiofilm were tested with wasp (Agelaia-MPI, Polybia-MPII, Polydim-I) and scorpion (Con10 and NDBP5.8) AMPs against Acinetobacter baumannii clinical strains. A. baumannii formed a biofilm on the vascular stent. Agelaia-MPI and Polybia-MPII inhibited biofilm formation with bacterial cell wall degradation. Coating biofilms with polyethylene glycol (PEG 400) and Agelaia-MPI reduced 90% of A. baumannii adhesion on stents. The wasp AMPs Agelaia-MPI and Polybia-MPII had better action against MDR A. baumannii adherence and biofilm formation on vascular stents, preventing its formation and treating mature biofilm when compared to the other tested peptides.

The role of natural antimicrobial peptides during infection and chronic inflammation

Natural antimicrobial peptides (AMPs), a family of small polypeptides that are produced by constitutive or inducible expression in organisms, are integral components of the host innate immune system. In addition to their broad-spectrum antibacterial activity, natural AMPs also have many biological activities against fungi, viruses and parasites. Natural AMPs exert multiple immunomodulatory roles that may predominate under physiological conditions where they lose their microbicidal properties in serum and tissue environments. Increased drug resistance among microorganisms is occurring far more quickly than the discovery of new antibiotics. Natural AMPs have shown promise as 'next generation antibiotics' due to their broad-spectrum curative effects, low toxicity, the fact that they are not residual in animals, and the low rates of resistance exhibited by many pathogens. Many types of synthetic AMPs are currently being tested in clinical trials for the prevention and treatment of various diseases such as chemotherapy-associated infections, diabetic foot ulcers, catheter-related infections, and other conditions. Here, we provide an overview of the types and functions of natural AMPs and their role in combating microorganisms and different infectious and inflammatory diseases.

Peptidomic analysis of the venom of the solitary bee Xylocopa appendiculata circumvolans

Background

Among the hymenopteran insect venoms, those from social wasps and bees – such as honeybee, hornets and paper wasps – have been well documented. Their venoms are composed of a number of peptides and proteins and used for defending their nests and themselves from predators. In contrast, the venoms of solitary wasps and bees have not been the object of further research. In case of solitary bees, only major peptide components in a few venoms have been addressed. Therefore, the aim of the present study was to explore the peptide component profile of the venom from the solitary bee Xylocopa appendiculata circumvolans by peptidomic analysis with using LC-MS.

Methods

A reverse-phase HPLC connected to ESI-OrbiTrap MS was used for LC-MS. On-line mass fingerprinting was made from TIC, and data-dependent tandem mass spectrometry gave MSMS spectra. A major peptide component was isolated by reverse-phase HPLC by conventional way, and its sequence was determined by Edman degradation, which was finally corroborated by solid phase synthesis. Using the synthetic specimen, biological activities (antimicrobial activity, mast cell devaluation, hemolysis, leishmanicidal activity) and pore formation in artificial lipid bilayer were evaluated.

Results

On-line mass fingerprinting revealed that the crude venom contained 124 components. MS/MS analysis gave 75 full sequences of the peptide components. Most of these are related to the major and novel peptide, xylopin. Its sequence, GFVALLKKLPLILKHLH-NH₂, has characteristic features of linear cationic α-helical peptides; rich in hydrophobic and basic amino acids with no disulfide bond, and accordingly, it can be predicted to adopt an amphipathic α-helix secondary structure. In biological evaluation, xylopin exhibited broad-spectrum antimicrobial activity, and moderate mast cell degranulation and leishmanicidal activities, but showed virtually no hemolytic activity. Additionally, the peptide was able to incorporate pores in artificial lipid bilayers of azolectin, confirming the mechanism of the cytolytic activity by pore formation in biological membranes.

Conclusions

LC-ESI-MS and MS/MS analysis of the crude venom extract from a solitary bee Xylocopa appendiculata circumvolans revealed that the component profile of this venom mostly consisted of small peptides. The major peptide components, xylopin and xylopinin, were purified and characterized in a conventional manner. Their chemical and biological characteristics, belonging to linear cationic α-helical peptides, are similar to the known solitary bee venom peptides, melectin and osmin. Pore formation in artificial lipid bilayers was demonstrated for the first time with a solitary bee peptide.

Isolation and chemical characterization of agelaiatoxin8 (AvTx8) from Agelaia vicina wasp venom and its biological effects on GABA neurotransmission

Arthropod venoms are sources of molecules that may be useful tools to investigate molecular mechanisms of putative new medicines and laboratory drugs. Here we show the effects of the compound agelaiatoxin-8 (AVTx8), isolated from Agelaia vicina venom, on γ-aminobutyric acid (GABA) neurotransmission in rat brain synaptosomes. Analysis reveals that AvTx8 is composed by 14 amino acid residues with a molecular weight (MW) of 1567 Da. AvTx8 increased GABA release and inhibited GABA uptake in synaptosomes from rat cerebral cortex. AvTx8 inhibited GABA uptake and increased GABA release in the presence of Ca⁺ , Na⁺ , and K⁺ channel blockers, suggesting that it acts directly on GABA transporters. In addition, AvTx8 significantly decreases GABA binding in synaptic membranes from rat brain cortex, suggesting that it also modulates the activity of GABA receptors. Moreover, AvTx8 decreased GAT-1- and GAT-3-mediated GABA uptake in transfected COS-7 cells. Accordingly, we suggest that AvTx8 modulates GABA neurotransmission and might provide a novel entry point for identifying a new class of GABA-modulating neuroprotective drugs.