A novel cecropin B-derived peptide with antibacterial and potential anti-inflammatory properties

Modified polymeric biomaterials with antimicrobial and immunomodulating properties

The modification of the surgical polypropylene mesh and the polytetrafluoroethylene vascular prosthesis with cecropin A (small peptide) and puromycin (aminonucleoside) yielded very stable preparations of modified biomaterials. The main emphasis was placed on analyses of their antimicrobial activity and potential immunomodulatory and non-cytotoxic properties towards the CCD841 CoTr model cell line. Cecropin A did not significantly affect the viability or proliferation of the CCD 841 CoTr cells, regardless of its soluble or immobilized form. In contrast, puromycin did not induce a significant decrease in the cell viability or proliferation in the immobilized form but significantly decreased cell viability and proliferation when administered in the soluble form. The covalent immobilization of these two molecules on the surface of biomaterials resulted in stable preparations that were able to inhibit the multiplication of Staphylococcus aureus and S. epidermidis strains. It was also found that the preparations induced the production of cytokines involved in antibacterial protection mechanisms and stimulated the immune response. The key regulator of this activity may be related to TLR4, a receptor recognizing bacterial LPS. In the present study, these factors were produced not only in the conditions of LPS stimulation but also in the absence of LPS, which indicates that cecropin A- and puromycin-modified biomaterials may upregulate pathways leading to humoral antibacterial immune response.

Cecropin AD reduces viral load and inflammatory response against H9N2 avian influenza virus in chickens

Introduction

This study focuses on evaluating the therapeutic efficacy of cecropin AD, an antimicrobial peptide, against H9N2 avian influenza virus (AIV) in chickens. Given the global impact of H9N2 AIV on poultry health, identifying effective treatments is crucial.

Methods

To assess the impact of cecropin AD, we conducted in vivo experiments involving 108 5-week-old chickens divided into control, infected, and various treatment groups based on cecropin AD dosage levels (high, medium, and low). The methodologies included hemagglutination (HA) tests for viral titers, histopathological examination and toluidine blue (TB) staining for lung pathology, real-time PCR for viral detection, and enzyme-linked immunosorbent assays for measuring serum levels of inflammatory markers.

Results

The findings revealed that cecropin AD substantially reduced lung pathology and viral load, especially at higher dosages, comparing favorably with the effects seen from conventional treatments. Moreover, cecropin AD effectively modulated mast cell activity and the levels of inflammatory markers such as IL-6, TNF-α, IFN-γ, and 5-HT, indicating its potential to diminish inflammation and viral spread.

Discussion

Cecropin AD presents a significant potential as an alternative treatment for H9N2 AIV in chickens, as evidenced by its ability to lessen lung damage, decrease viral presence, and adjust immune responses. This positions cecropin AD as a promising candidate for further exploration in the management of H9N2 AIV infections in poultry.

Multiple resistance factors collectively promote inoculum-dependent dynamic survival during antimicrobial peptide exposure in Enterobacter cloacae

Antimicrobial peptides (AMPs) are a promising tool with which to fight rising antibiotic resistance. However, pathogenic bacteria are equipped with several AMP defense mechanisms, whose contributions to AMP resistance are often poorly defined. Here, we evaluate the genetic determinants of resistance to an insect AMP, cecropin B, in the opportunistic pathogen Enterobacter cloacae. Single-cell analysis of E. cloacae's response to cecropin revealed marked heterogeneity in cell survival, phenotypically reminiscent of heteroresistance (the ability of a subpopulation to grow in the presence of supra-MIC concentration of antimicrobial). The magnitude of this response was highly dependent on initial E. cloacae inoculum. We identified 3 genetic factors which collectively contribute to E. cloacae resistance in response to the AMP cecropin: The PhoPQ-two-component system, OmpT-mediated proteolytic cleavage of cecropin, and Rcs-mediated membrane stress response. Altogether, this evidence suggests that multiple, independent mechanisms contribute to AMP resistance in E. cloacae.

The Contribution of Antimicrobial Peptides to Immune Cell Function: A Review of Recent Advances

The development of novel antimicrobial agents to replace antibiotics has become urgent due to the emergence of multidrug-resistant microorganisms. Antimicrobial peptides (AMPs), widely distributed in all kingdoms of life, present strong antimicrobial activity against a variety of bacteria, fungi, parasites, and viruses. The potential of AMPs as new alternatives to antibiotics has gradually attracted considerable interest. In addition, AMPs exhibit strong anticancer potential as well as anti-inflammatory and immunomodulatory activity. Many studies have provided evidence that AMPs can recruit and activate immune cells, controlling inflammation. This review highlights the scientific literature focusing on evidence for the anti-inflammatory mechanisms of different AMPs in immune cells, including macrophages, monocytes, lymphocytes, mast cells, dendritic cells, neutrophils, and eosinophils. A variety of immunomodulatory characteristics, including the abilities to activate and differentiate immune cells, change the content and expression of inflammatory mediators, and regulate specific cellular functions and inflammation-related signaling pathways, are summarized and discussed in detail. This comprehensive review contributes to a better understanding of the role of AMPs in the regulation of the immune system and provides a reference for the use of AMPs as novel anti-inflammatory drugs for the treatment of various inflammatory diseases.

Characterization and Classification In Silico of Peptides with Dual Activity (Antimicrobial and Wound Healing)

The growing challenge of chronic wounds and antibiotic resistance has spotlighted the potential of dual-function peptides (antimicrobial and wound healing) as novel therapeutic strategies. The investigation aimed to characterize and correlate in silico the physicochemical attributes of these peptides with their biological activity. We sourced a dataset of 207 such peptides from various peptide databases, followed by a detailed analysis of their physicochemical properties using bioinformatic tools. Utilizing statistical tools like clustering, correlation, and principal component analysis (PCA), patterns and relationships were discerned among these properties. Furthermore, we analyzed the peptides' functional domains for insights into their potential mechanisms of action. Our findings spotlight peptides in Cluster 2 as efficacious in wound healing, whereas Cluster 1 peptides exhibited pronounced antimicrobial potential. In our study, we identified specific amino acid patterns and peptide families associated with their biological activities, such as the cecropin antimicrobial domain. Additionally, we found the presence of polar amino acids like arginine, cysteine, and lysine, as well as apolar amino acids like glycine, isoleucine, and leucine. These characteristics are crucial for interactions with bacterial membranes and receptors involved in migration, proliferation, angiogenesis, and immunomodulation. While this study provides a groundwork for therapeutic development, translating these findings into practical applications necessitates additional experimental and clinical research.

Antimicrobial peptides as drugs with double response against Mycobacterium tuberculosis coinfections in lung cancer

Tuberculosis and lung cancer are, in many cases, correlated diseases that can be confused because they have similar symptoms. Many meta-analyses have proven that there is a greater chance of developing lung cancer in patients who have active pulmonary tuberculosis. It is, therefore, important to monitor the patient for a long time after recovery and search for combined therapies that can treat both diseases, as well as face the great problem of drug resistance. Peptides are molecules derived from the breakdown of proteins, and the membranolytic class is already being studied. It has been proposed that these molecules destabilize cellular homeostasis, performing a dual antimicrobial and anticancer function and offering several possibilities of adaptation for adequate delivery and action. In this review, we focus on two important reason for the use of multifunctional peptides or peptides, namely the double activity and no harmful effects on humans. We review some of the main antimicrobial and anti-inflammatory bioactive peptides and highlight four that have anti-tuberculosis and anti-cancer activity, which may contribute to obtaining drugs with this dual functionality.

Antibacterial 3D-Printed Silver Nanoparticle/Poly Lactic-Co-Glycolic Acid (PLGA) Scaffolds for Bone Tissue Engineering

Infectious bone defects present a major challenge in the clinical setting currently. In order to address this issue, it is imperative to explore the development of bone tissue engineering scaffolds that are equipped with both antibacterial and bone regenerative capabilities. In this study, we fabricated antibacterial scaffolds using a silver nanoparticle/poly lactic-co-glycolic acid (AgNP/PLGA) material via a direct ink writing (DIW) 3D printing technique. The scaffolds' microstructure, mechanical properties, and biological attributes were rigorously assessed to determine their fitness for repairing bone defects. The surface pores of the AgNPs/PLGA scaffolds were uniform, and the AgNPs were evenly distributed within the scaffolds, as confirmed via scanning electron microscopy (SEM). Tensile testing confirmed that the addition of AgNPs enhanced the mechanical strength of the scaffolds. The release curves of the silver ions confirmed that the AgNPs/PLGA scaffolds released them continuously after an initial burst. The growth of hydroxyapatite (HAP) was characterized via SEM and X-ray diffraction (XRD). The results showed that HAP was deposited on the scaffolds, and also confirmed that the scaffolds had mixed with the AgNPs. All scaffolds containing AgNPs exhibited antibacterial properties against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). A cytotoxicity assay using mouse embryo osteoblast precursor cells (MC3T3-E1) showed that the scaffolds had excellent biocompatibility and could be used for repairing bone tissue. The study shows that the AgNPs/PLGA scaffolds have exceptional mechanical properties and biocompatibility, effectively inhibiting the growth of S. aureus and E. coli. These results demonstrate the potential application of 3D-printed AgNPs/PLGA scaffolds in bone tissue engineering.

The Cell Wall Deacetylases Spy1094 and Spy1370 Contribute to Streptococcus pyogenes Virulence

Streptococcus pyogenes, or Group A Streptococcus (GAS), is a strictly human pathogen that causes a wide range of diseases, including skin and soft tissue infections, toxic shock syndrome and acute rheumatic fever. We have recently reported that Spy1094 and Spy1370 of S. pyogenes serotype M1 are N-acetylglucosamine (GlcNAc) deacetylases. We have generated spy1094 and spy1370 gene deletion mutants in S. pyogenes and gain-of-function mutants in Lactococcus lactis. Similar to other cell wall deacetylases, our results show that Spy1094 and Spy1370 confer lysozyme-resistance. Furthermore, deletion of the genes decreased S. pyogenes virulence in a human whole blood killing assay and a Galleria mellonella (Greater wax moth) larvae infection model. Expression of the two genes in L. lactis resulted in increased lysozyme resistance and survival in whole human blood, and reduced survival of infected G. mellonella larvae. Deletion of the spy1370, but not the spy1094 gene, decreased resistance to the cationic antimicrobial peptide cecropin B, whereas both enzymes increased biofilm formation, probably resulting from the increase in positive charges due to deacetylation of the cell wall. In conclusion, Spy1094 and Spy1370 are important S. pyogenes virulence factors and might represent attractive targets for the development of antibacterial agents.

Antimicrobial peptide HI-3 from Hermetia illucens alleviates inflammation in lipopolysaccharide-stimulated RAW264.7 cells via suppression of the nuclear factor kappa-B signaling pathway

Hermetia illucens-3 (HI-3), an active insect antimicrobial peptide extracted from H. illucens larvae, exerts antibacterial and anticancer activity. However, the inflammatory effects and their relative molecular mechanisms remain unclear. To explore the inflammatory effects of HI-3, an inflammatory model was induced using 1 ng/mL LPS in RAW264.7 cells. The cell viability and phagocytosis of LPS-stimulated RAW264.7 cells were then detected after HI-3 treatment. Furthermore, the antioxidant activity, the levels of proinflammatory cytokines, and the expression levels of both p65 and inhibitor of nuclear factor kappa B (IκB) were measured. Results showed that HI-3 could inhibit the differentiation, proliferation, phagocytosis, and antioxidant ability, as well as the secretion and messenger RNA expression levels of IL-6, TNF-α, and IL-1β of LPS-induced RAW264.7 cells in a dose-dependent manner. At the same time, the level of the anti-inflammatory cytokine IL-10 was increased after HI-3 treatment. Western blotting results showed that HI-3 suppressed LPS-induced p65 and IκB activation in a dose-dependent manner. Therefore, HI-3 exerts its anti-inflammatory effect by inhibiting the expression of proinflammatory cytokines and the activation of p65 and IκB, which indicated that HI-3 could be a promising therapeutic medicine for inflammation.

Antibacterial and Anti-Inflammatory Properties of Peptide KN-17

Peri-implantitis, an infectious disease originating from dental biofilm that forms around dental implants, which causes the loss of both osseointegration and bone tissue. KN-17, a truncated cecropin B peptide, demonstrated efficacy against certain bacterial strains associated with peri-implantitis. This study aimed to assess the antibacterial and anti-inflammatory properties and mechanisms of KN-17. The effects of KN-17 on oral pathogenic bacteria were assessed by measuring its minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). Moreover, the cytotoxicity and anti-inflammatory effects of KN-17 were evaluated. KN-17 inhibited the growth of Streptococcus gordonii and Fusobacterium nucleatum during in vitro biofilm formation and possessed low toxicity to hBMSCs cells. KN-17 also caused RAW264.7 macrophages to transform from M1 to M2 by downregulating pro-inflammatory and upregulating anti-inflammatory factors. It inhibited the NF-κB signaling pathway by reducing IκBα and P65 protein phosphorylation while promoting IκBα degradation and nuclear P65 translocation. KN-17 might be an efficacious prophylaxis against peri-implant inflammation.

Cecropin-Loaded Zeolitic Imidazolate Framework Nanoparticles with High Biocompatibility and Cervical Cancer Cell Toxicity

Cecropins (CECs) are insect venom-derived amphiphilic peptides with numerous pharmacological effects, including anti-inflammatory, antibacterial, antiviral, and anti-tumor activities. Cecropins induce tumor cell death by disrupting phospholipid membrane integrity. However, non-specific cytotoxicity and in vivo rapid degradation limit clinical application. Nanotechnologies provide novel strategies for tumor eradication, including nanocarriers that can precisely target drugs to tumor tissue. We report the fabrication of CEC-encapsulated zeolitic imidazolate framework 8 (ZIF-8) nanoparticles (CEC@ZIF-8 NPs) via the preparation of CEC@ZIF-8 NPs in pure water by one-pot stirring. This method yielded morphologically uniform NPs with 20 wt% drug loading capacity and 9% loading efficiency. The NP formulation protected CECs from proteasome degradation, enhanced peptide bioavailability, promoted HeLa tumor cell uptake, and increased antitumor efficacy compared to free CECs. In conclusion, this ZIF-8 encapsulation strategy may enhance the clinical applicability of CECs and other antitumor peptides.

Novel antimicrobial cecropins derived from O. curvicornis and D. satanas dung beetles

Antibiotic resistance is an increasing global problem and therapeutic alternatives to traditional antibiotics are needed. Antimicrobial and host defense peptides represent an attractive source for new therapeutic strategies, given their wide range of activities including antimicrobial, antitumoral and immunomodulatory. Insects produce several families of these peptides, including cecropins. Herein, we characterized the sequence, structure, and biological activity of three cecropins called satanin 1, 2, and curvicin, found in the transcriptome of two dung beetle species Dichotomius satanas and Onthophagus curvicornis. Sequence and circular dichroism analyses show that they have typical features of the cecropin family: short length (38-39 amino acids), positive charge, and amphipathic α-helical structure. They are active mainly against Gram-negative bacteria (3.12-12.5 μg/mL), with low toxicity on eukaryotic cells resulting in high therapeutic indexes (TI > 30). Peptides also showed effects on TNFα production in LPS-stimulated PBMCs. The biological activity of Satanin 1, 2 and Curvicin makes them interesting leads for antimicrobial strategies.

Novel Antimicrobial Peptides from a Cecropin-Like Region of Heteroscorpine-1 from Heterometrus laoticus Venom with Membrane Disruption Activity

The increasing antimicrobial-resistant prevalence has become a severe health problem. It has led to the invention of a new antimicrobial agent such as antimicrobial peptides. Heteroscorpine-1 is an antimicrobial peptide that has the ability to kill many bacterial strains. It consists of 76 amino acid residues with a cecropin-like region in N-terminal and a defensin-like region in the C-terminal. The cecropin-like region from heteroscorpine-1 (CeHS-1) is similar to cecropin B, but it lost its glycine-proline hinge region. The bioinformatics prediction was used to help the designing of mutant peptides. The addition of glycine-proline hinge and positively charged amino acids, the deletion of negatively charged amino acids, and the optimization of the hydrophobicity of the peptide resulted in two mutant peptides, namely, CeHS-1 GP and CeHS-1 GPK. The new mutant peptide showed higher antimicrobial activity than the native peptide without increasing toxicity. The interaction of the peptides with the membrane showed that the peptides were capable of disrupting both the inner and outer bacterial cell membrane. Furthermore, the SEM analysis showed that the peptides created the pore in the bacterial cell membrane resulted in cell membrane disruption. In conclusion, the mutants of CeHS-1 had the potential to develop as novel antimicrobial peptides.

Expression of Antimicrobial Peptide (AMP), Cecropin B, in a Fused Form to SUMO Tag With or Without Three-Glycine Linker in Escherichia coli and Evaluation of Bacteriolytic Activity of the Purified AMP

Current antibiotics have limited action mode, which makes it difficult for the antibiotics dealing with the emergence of bacteria resisting the existing antibiotics. As a need for new bacteriolytic agents alternative to the antibiotics, AMPs have long been considered substitutes for the antibiotics. Cecropin B was expressed in a fusion form to six-histidine and SUMO tags in Escherichia coli. Six-histidine tag attached to SUMO was for purification of SUMO-cecropin B fusion proteins and removal of the SUMO tag from cecropin B. Chimeric gene was constructed into pKSEC1 vector that was designed to be functional in both Escherichia coli and chloroplast. To maximize translation of the fusion protein, sequences were codon-optimized. Four different constructs were tested for the level of expression and solubility, and the construct with a linker, 6xHisSUMO3xGly-cecropin B, showed the highest expression. In addition, cleavage of the SUMO tag by SUMOase in the three fusion constructs which have no linker sequence (3xGly, three glycines) was not as efficient as the construct with the linker between SUMO and cecropin B. The cleaved cecropin B showed bacteriolytic activity against Bacillus subtilis at a concentration of 0.0625 μg/μL, while cecropin B fused to SUMO had no activity at a higher concentration, 0.125 μg/μL. As an expression system for AMPs in prokaryotic hosts, the use of tag proteins and appropriate codon-optimization strategy can be employed and further genetic modification of the fusion construct should help the complete removal of the tag proteins from the AMP in the final step of purification.

Insect antimicrobial peptides: potential weapons to counteract the antibiotic resistance

Misuse and overuse of antibiotics have contributed in the last decades to a phenomenon known as antibiotic resistance which is currently considered one of the principal threats to global public health by the World Health Organization. The aim to find alternative drugs has been demonstrated as a real challenge. Thanks to their biodiversity, insects represent the largest class of organisms in the animal kingdom. The humoral immune response includes the production of antimicrobial peptides (AMPs) that are released into the insect hemolymph after microbial infection. In this review, we have focused on insect immune responses, particularly on AMP characteristics, their mechanism of action and applications, especially in the biomedical field. Furthermore, we discuss the Toll, Imd, and JAK-STAT pathways that activate genes encoding for the expression of AMPs. Moreover, we focused on strategies to improve insect peptides stability against proteolytic susceptibility such as D-amino acid substitutions, N-terminus modification, cyclization and dimerization.

OMN6 a novel bioengineered peptide for the treatment of multidrug resistant Gram negative bacteria

New antimicrobial agents are urgently needed, especially to eliminate multidrug resistant Gram-negative bacteria that stand for most antibiotic-resistant threats. In the following study, we present superior properties of an engineered antimicrobial peptide, OMN6, a 40-amino acid cyclic peptide based on Cecropin A, that presents high efficacy against Gram-negative bacteria with a bactericidal mechanism of action. The target of OMN6 is assumed to be the bacterial membrane in contrast to small molecule-based agents which bind to a specific enzyme or bacterial site. Moreover, OMN6 mechanism of action is effective on Acinetobacter baumannii laboratory strains and clinical isolates, regardless of the bacteria genotype or resistance-phenotype, thus, is by orders-of-magnitude, less likely for mutation-driven development of resistance, recrudescence, or tolerance. OMN6 displays an increase in stability and a significant decrease in proteolytic degradation with full safety margin on erythrocytes and HEK293T cells. Taken together, these results strongly suggest that OMN6 is an efficient, stable, and non-toxic novel antimicrobial agent with the potential to become a therapy for humans.

Computational Study of Helical and Helix-Hinge-Helix Conformations of an Anti-Microbial Peptide in Solution by Molecular Dynamics and Vibrational Analysis

Many classical antimicrobial peptides adopt an amphipathic helical structure at a water-membrane interface. Prior studies led to the hypothesis that a hinge near the middle of a helical peptide plays an important role in facilitating peptide-membrane interactions. Here, dynamics and vibrations of a designed hybrid antimicrobial peptide LM7-2 in solution were simulated to investigate its hinge formation. Molecular dynamics simulation results on the basis of the CHARMM36 force field showed that the α-helix LM7-2 bent around two or three residues near the middle of the peptide, stayed in a helix-hinge-helix conformation for a short period of time, and then returned to a helical conformation. High-resolution computational vibrational techniques were applied on the LM7-2 system when it has α-helical and helix-hinge-helix conformations to understand how this structural change affects its inherent vibrations. These studies concentrated on the calculation of frequencies that correspond to backbone amide bands I, II, and III: vibrational modes that are sensitive to changes in the secondary structure of peptides and proteins. To that end, Fourier transforms were applied to thermal fluctuations in C-N-H angles, C-N bond lengths, and C═O bond lengths of each amide group. In addition, instantaneous all-atom normal mode analysis was applied to monitor and detect the characteristic amide bands of each amide group within LM7-2 during the MD simulation. Computational vibrational results indicate that shapes and frequencies of amide bands II and especially III were altered only for amide groups near the hinge. These methods provide high-resolution vibrational information that can complement spectroscopic vibrational studies. They assist in interpreting spectra of similar systems and suggest a marker for the presence of the helix-hinge-helix motif. Moreover, radial distribution functions indicated an increase in the probability of hydrogen bonding between water and a hydrogen atom connected to nitrogen (HN) in such a hinge. The probability of intramolecular hydrogen bond formation between HN and an amide group oxygen atom within LM7-2 was lower around the hinge. No correlation has been found between the presence of a hinge and hydrogen bonds between amide group oxygen atoms and the hydrogen atoms of water molecules. This result suggests a mechanism for hinge formation wherein hydrogen bonds to oxygen atoms of water replace intramolecular hydrogen bonds as the peptide backbone folds.

Antimicrobial peptide temporin-1CEa isolated from frog skin secretions inhibits the proinflammatory response in lipopolysaccharide-stimulated RAW264.7 murine macrophages through the MyD88-dependent signaling pathway

Temporin-1CEa, which is isolated from the skin secretions of the Chinese brown frog Rana chensinensis, exhibits broad-spectrum antimicrobial activity against gram-positive and gram-negative bacteria and antitumor activity. LK2(6) and LK2(6)A(L) are the analogs of temporin-1CEa obtained by replacing amino acids and displayed an improved anticancer activity. In the present study, the anti-inflammatory activity and mechanism of action of temporin-1CEa and its analogs LK2(6) and LK2(6)A(L) in lipopolysaccharide (LPS)-stimulated RAW264.7 murine macrophages were investigated. The results showed that temporin-1CEa and its analogs decreased the production of the cytokines tumor necrosis factor-α and interleukin-6 by inhibiting the protein expression of nuclear factor-κB and mitogen-activated protein kinase and the MyD88-dependent signaling pathway. Isothermal titration calorimetry studies revealed that temporin-1CEa, LK2(6) and LK2(6)A(L) exhibited binding affinities to LPS, an important inflammatory inducer, with Kd values of 0.1, 0.03 and 0.06 μM, respectively. Circular dichroism and zeta potential experiments showed that temporin-1CEa and its analogs interacted with LPS by electrostatic binding between the positively charged peptides and negatively charged LPS, resulting in the neutralization of LPS toxicity.

Antimicrobial peptide activity is anticorrelated with lipid a leaflet affinity

The activity of antimicrobial peptides (AMPs) has significant bacterial species bias, the mechanisms of which are not fully understood. We employed single-molecule tracking to measure the affinity of three different AMPs to hybrid supported bilayers composed of lipid A extracted from four different Gram negative bacteria and observed a strong empirical anticorrelation between the affinity of a particular AMP to a given lipid A layer and the activity of that AMP towards the bacterium from which that lipid A was extracted. This suggested that the species bias of AMP activity is directly related to AMP interactions with bacterial outer membranes, despite the fact that the mechanism of antimicrobial activity occurs at the inner membrane. The trend also suggested that the interactions between AMPs and the outer membrane lipid A (even in the absence of other components, such as lipopolysaccharides) capture effects that are relevant to the minimum inhibitory concentration.

Antibacterial Activity of a Cationic Antimicrobial Peptide against Multidrug-Resistant Gram-Negative Clinical Isolates and Their Potential Molecular Targets

Antimicrobial resistance reduces the efficacy of antibiotics. Infections caused by multidrug-resistant (MDR), Gram-negative bacterial strains, such as Klebsiella pneumoniae (MDRKp) and Pseudomonas aeruginosa (MDRPa), are a serious threat to global health. However, cationic antimicrobial peptides (CAMPs) are promising as an alternative therapeutic strategy against MDR strains. In this study, the inhibitory activity of a cationic peptide, derived from cecropin D-like (ΔM2), against MDRKp and MDRPa clinical isolates, and its interaction with membrane models and bacterial genomic DNA were evaluated. In vitro antibacterial activity was determined using the broth microdilution test, whereas interactions with lipids and DNA were studied by differential scanning calorimetry and electronic absorption, respectively. A strong bactericidal effect of ΔM2 against MDR strains, with minimal inhibitory concentration (MIC) and minimal bactericidal concentrations (MBC) between 4 and 16 μg/mL, was observed. The peptide had a pronounced effect on the thermotropic behavior of the 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC)/1,2-dimyristoyl-sn-glycero-3-phosphorylglycerol (DMPG) membrane models that mimic bacterial membranes. Finally, the interaction between the peptide and genomic DNA (gDNA) showed a hyperchromic effect, which indicates that ΔM2 can denature bacterial DNA strands via the grooves.

Inhibitory effects of Bombyx mori antimicrobial peptide cecropins on esophageal cancer cells

Bombyx mori antimicrobial peptides (BmAMPs) are important effectors in silkworm immune system. They can inhibit and kill a variety of bacteria and fungi. Recent studies have shown that some kinds of BmAMPs exert strong inhibitory effects on a variety of tumor cells. In the present study, the antitumor activity of BmAMP Cecropin A (BmCecA) and BmAMP Cecropin D (BmCecD) was investigated against human esophageal cancer cells and their antitumor mechanism preliminary explored. Cell Counting Kit-8 and colony formation assays indicated that BmCecA and BmCecD suppressed cell proliferation and reduced colony formation of both Eca109 and TE13 cells in a dose-dependent manner, but exhibited no inhibitory effect on normal human embryonic kidney 293T cells. Wound healing and invasion experiments indicated that both BmCecA and BmCecD inhibited migration and invasion of Eca109 and TE13 cells in vitro. Annexin V/propidium iodide staining and flow cytometry detection suggested that BmCecA induced the apoptosis of Eca109 cells in a dose-dependent manner. RT-qPCR and western blot analysis showed that BmCecA induced apoptosis of Eca109 cells through the activation of a mitochondria-mediated caspase pathway, the upregulation of B-cell lymphoma 2 (Bcl-2)-associated X protein and the downregulation of Bcl-2. In addition, BmCecA significantly inhibited the growth of xenograft tumors in Eca109-bearing mice. These results suggested that BmCecA and BmCecD might serve as potential therapeutic agents for the treatment of cancer in the future.

A Novel Cecropin D-Derived Short Cationic Antimicrobial Peptide Exhibits Antibacterial Activity Against Wild-Type and Multidrug-Resistant Strains of Klebsiella pneumoniae and Pseudomonas aeruginosa

Infections caused by multidrug-resistant (MDR) Pseudomonas aeruginosa and Klebsiella pneumoniae are a serious worldwide public health concern due to the ineffectiveness of empirical antibiotic therapy. Therefore, research and the development of new antibiotic alternatives are urgently needed to control these bacteria. The use of cationic antimicrobial peptides (CAMPs) is a promising candidate alternative therapeutic strategy to antibiotics because they exhibit antibacterial activity against both antibiotic susceptible and MDR strains. In this study, we aimed to investigate the in vitro antibacterial effect of a short synthetic CAMP derived from the ΔM2 analog of Cec D-like (CAMP-CecD) against clinical isolates of K pneumoniae (n = 30) and P aeruginosa (n = 30), as well as its hemolytic activity. Minimal inhibitory concentrations (MICs) and minimal bactericidal concentrations (MBCs) of CAMP-CecD against wild-type and MDR strains were determined by the broth microdilution test. In addition, an in silico molecular dynamic simulation was performed to predict the interaction between CAMP-CecD and membrane models of K pneumoniae and P aeruginosa. The results revealed a bactericidal effect of CAMP-CecD against both wild-type and resistant strains, but MDR P aeruginosa showed higher susceptibility to this peptide with MIC values between 32 and >256 μg/mL. CAMP-CecD showed higher stability in the P aeruginosa membrane model compared with the K pneumoniae model due to the greater number of noncovalent interactions with phospholipid 1-Palmitoyl-2-oleyl-sn-glycero-3-(phospho-rac-(1-glycerol)) (POPG). This may be related to the boosted effectiveness of the peptide against P aeruginosa clinical isolates. Given the antibacterial activity of CAMP-CecD against wild-type and MDR clinical isolates of P aeruginosa and K pneumoniae and its nonhemolytic effects on human erythrocytes, CAMP-CecD may be a promising alternative to conventional antibiotics.

Study on Cecropin B2 Production via Construct Bearing Intein Oligopeptide Cleavage Variants

In this study, genetic engineering was applied to the overexpression of the antimicrobial peptide (AMP) cecropin B2 (cecB2). pTWIN1 vector with a chitin-binding domain (CBD) and an auto-cleavage Ssp DnaB intein (INT) was coupled to the cecB2 to form a fusion protein construct and expressed via Escherichia coli ER2566. The cecB2 was obtained via the INT cleavage reaction, which was highly related to its adjacent amino acids. Three oligopeptide cleavage variants (OCVs), i.e., GRA, CRA, and SRA, were used as the inserts located at the C-terminus of the INT to facilitate the cleavage reaction. SRA showed the most efficient performance in accelerating the INT self-cleavage reaction. In addition, in order to treat the INT as a biocatalyst, a first-order rate equation was applied to fit the INT cleavage reaction. A possible inference was proposed for the INT cleavage promotion with varied OCVs using a molecular dynamics (MD) simulation. The production and purification via the CBD-INT-SRA-cecB2 fusion protein resulted in a cecB2 yield of 58.7 mg/L with antimicrobial activity.

Insect Cecropins, Antimicrobial Peptides with Potential Therapeutic Applications

The alarming escalation of infectious diseases resistant to conventional antibiotics requires urgent global actions, including the development of new therapeutics. Antimicrobial peptides (AMPs) represent potential alternatives in the treatment of multi-drug resistant (MDR) infections. Here, we focus on Cecropins (Cecs), a group of naturally occurring AMPs in insects, and on synthetic Cec-analogs. We describe their action mechanisms and antimicrobial activity against MDR bacteria and other pathogens. We report several data suggesting that Cec and Cec-analog peptides are promising antibacterial therapeutic candidates, including their low toxicity against mammalian cells, and anti-inflammatory activity. We highlight limitations linked to the use of peptides as therapeutics and discuss methods overcoming these constraints, particularly regarding the introduction of nanotechnologies. New formulations based on natural Cecs would allow the development of drugs active against Gram-negative bacteria, and those based on Cec-analogs would give rise to therapeutics effective against both Gram-positive and Gram-negative pathogens. Cecs and Cec-analogs might be also employed to coat biomaterials for medical devices as an approach to prevent biomaterial-associated infections. The cost of large-scale production is discussed in comparison with the economic and social burden resulting from the progressive diffusion of MDR infectious diseases.

Cecropin-like antimicrobial peptide protects mice from lethal E.coli infection

Resistance of pathogenic bacteria to standard antibiotics is an issue of great concern, and new treatments for bacterial infections are needed. Antimicrobial peptides (AMPs) are small, cationic, and amphipathic molecules expressed by metazoans that kill pathogens. They are a key part of the innate immune system in both vertebrates and invertebrates. Due to their low toxicity and broad antimicrobial activities, there has been increasing attention to their therapeutic usage. Our previous research demonstrated that four peptides-DAN1, DAN2, HOLO1 and LOUDEF1-derived from recently sequenced arthropod genomes exhibited potent antimicrobial effects in-vitro. In this study, we show that DAN2 protected 100% of mice when it was administered at a concentration of 20 mg/kg thirty minutes after the inoculation of a lethal dose of E. coli intraperitoneally. Lower concentrations of DAN2-10mg/kg and 5mg/kg protected more than 2/3s of the mice. All three dose levels reduced bacterial loads in blood and peritoneal fluid by 10-fold or more when counted six hours after bacterial challenge. We determined that DAN2 acts by compromising the integrity of the E. coli membrane. This study supports the potential of DAN2 peptide as a therapeutic agent for treating antibiotic resistant Gram-negative bacterial infections.