Expression and characterization of cecropinXJ, a bioactive antimicrobial peptide from Bombyx mori (Bombycidae, Lepidoptera) in Escherichia coli

Bombyx mori Cecropin D could trigger cancer cell apoptosis by interacting with mitochondrial cardiolipin

Cecropin D is an antimicrobial peptide from Bombyx mori displaying anticancer and pro-apoptotic activities and, together with Cecropin XJ and Cecropin A, one of the very few peptides targeting esophageal cancer. Cecropin D displays poor similarity to other cecropins but a remarkable similarity in the structure and activity spectrum with Cecropin A and Cecropin XJ, offering the possibility to highlight key motifs at the base of the biological activity. In this work we show by NMR and MD simulations that Cecropin D is partially structured in solution and stabilizes its two-helix folding upon interaction with biomimetic membranes. Simulations show that Cecropin D strongly interacts with the surface of cancer cell biomimetic bilayers where it recognises the phosphatidylserine headgroup often exposed in the outer leaflet of cancerous cells by means of specific salt bridges. Cecropin D is also able to penetrate deeply in bilayers containing cardiolipin, a phospholipid found in mitochondria, causing significant destabilization in the lipid packing which might account for its pro-apoptotic activity. In bacterial membranes, phosphatidylglycerol and phosphatidylethanolamine act synergically by electrostatically attracting cecropin D and providing access to the membrane core, respectively.

Effect of Silkworm Pupa Protein Hydrolysates on Proliferation of Gastric Cancer Cells In Vitro

The proliferation inhibition effects of the hydrolysates from silkworm pupa proteins on MGC-803 gastric cancer cells were investigated in this study. The specific morphological changes (cell membrane, cell nucleus and cytoskeleton) of cells were measured. In vitro, the proliferation of MGC-803 cells was inhibited by silkworm pupa protein hydrolysates (SPPHs) in a dose-dependent manner. The flow cytometry analysis showed that the blocking effect of SPPHs on the MGC-803 cells was mainly in the G₀/G₁-phase. The morphological changes, disintegration of the cytoskeleton and retardant cell cycles were probably related to the activation of apoptosis. Thus, SPPHs could be promising as a chemopreventive agent due to their ability to promote apoptosis of tumor cells.

Molecular mechanism and potential application of bacterial infection in the silkworm, Bombyx mori

As a representative species of Lepidoptera, Bombyx mori has been widely studied and applied. However, bacterial infection has always been an important pathogen threatening the growth of silkworms. Bombyx mori can resist various pathogenic bacteria through their own physical barrier and innate immune system. However, compared with other insects, such as Drosophila melanogaster, research on the antibacterial mechanism of silkworms is still in its infancy. This review systematically summarized the routes of bacterial infection in silkworms, the antibacterial mechanism of silkworms after ingestion or wounding infection, and the intestinal bacteria and infection of silkworms. Finally, we will discuss silkworms as a model animal for studying bacterial infectious diseases and screening antibacterial drugs.

Bioactivities of Mealworm (Alphitobius diaperinus L.) Larvae Hydrolysates Obtained from Artichoke (Cynara scolymus L.) Proteases

In this study, we aimed to obtain hydrolysates with bioactive peptides from mealworm (Alphitobius diaperinus L.) larvae using an artichoke (Cynara scolymus L.) enzyme extract. Two types of substrates were used: the raw larvae flour (LF) and its protein extract (PE). The hydrolysis yield, considering the peptide concentration of the hydrolysates, was higher in PE hydrolysates than in LF hydrolysates (6.39 ± 0.59 vs. 3.02 ± 0.06 mg/mL, respectively). However, LF showed a higher antioxidant activity against the DPPH radical than PE (59.10 ± 1.42 vs. 18.79 ± 0.81 µM Trolox Eq/mg peptides, respectively). Regarding the inhibitory activity of angiotensin-I-converting enzyme (ACE), an IC50 value of 111.33 ± 21.3 µg peptides/mL was observed in the PE. The identification of the peptide sequence of both hydrolysates was conducted, and LF and its PE presented 404 and 116 peptides, respectively, most with low molecular weight (<3 kDa), high percentage of hydrophobic amino acids, and typical characteristics of well-known antioxidant and ACE-inhibitory peptides. Furthermore, the potential bioactivity of the sequences identified was searched in the BIOPEP database. Considering the antioxidant and ACE-inhibitory activities, LF hydrolysates contained a larger number of sequences with potential bioactivity than PE hydrolysates.

Scale-up production of and dietary supplementation with the recombinant antimicrobial peptide tilapia piscidin 4 to improve growth performance in Gallus gallus domesticus

Antimicrobial peptides (AMPs) are short and positively charged peptides with broad-spectrum antimicrobial activities. AMPs have been investigated as potential antibiotic alternatives to improve growth performance and prevent pathogen infection in the poultry industry. The antimicrobial peptide tilapia piscidin 4 (TP4) was derived from Oreochromis niloticus, possesses antimicrobial activities and immunomodulatory properties, promotes intestinal health, and protects against pathogen infection. The codon-optimized sequence of TP4 was introduced into the pPICZαA vector and transformed into Pichia pastoris. Large-scale expression was induced following culture with methanol in a 500-liter fermenter. Freeze drying of fermented rTP4 broth and then rTP4 evaluation as a feed additive for Gallus gallus domesticus were performed. The in vitro antimicrobial activity of recombinant TP4 (rTP4) against gram-positive and gram-negative pathogens was evaluated. Evaluation of the effect of temperature on the antimicrobial activity of rTP4 showed its high stability at high temperatures. rTP4 significantly enhanced the phagocytic activity of macrophage cells, indicating that rTP4 has a remarkable ability to stimulate macrophages. rTP4 was used as a dietary supplement at 0.75, 1.5, 3.0, 6.0 and 12% in G. g. domesticus for five weeks, and growth performance, gut microbiota composition, and histology were assessed. The 3.0% rTP4 supplement group showed a significant increase in weight gain ratio and feed efficiency compared to those of the basal broiler diet group. Crude rTP4 was expressed by yeast to significantly promote growth efficiency and resistance against pathogens in G. g. domesticus, which could indicate its use as a suitable alternative to antibiotics as feed additives in the poultry industry.

Molecular Basis of the Anticancer and Antibacterial Properties of CecropinXJ Peptide: An In Silico Study

Esophageal cancer is an aggressive lethal malignancy causing thousands of deaths every year. While current treatments have poor outcomes, cecropinXJ (CXJ) is one of the very few peptides with demonstrated in vivo activity. The great interest in CXJ stems from its low toxicity and additional activity against most ESKAPE bacteria and fungi. Here, we present the first study of its mechanism of action based on molecular dynamics (MD) simulations and sequence-property alignment. Although unstructured in solution, predictions highlight the presence of two helices separated by a flexible hinge containing P24 and stabilized by the interaction of W2 with target biomembranes: an amphipathic helix-I and a poorly structured helix-II. Both MD and sequence-property alignment point to the important role of helix I in both the activity and the interaction with biomembranes. MD reveals that CXJ interacts mainly with phosphatidylserine (PS) but also with phosphatidylethanolamine (PE) headgroups, both found in the outer leaflet of cancer cells, while salt bridges with phosphate moieties are prevalent in bacterial biomimetic membranes composed of PE, phosphatidylglycerol (PG) and cardiolipin (CL). The antibacterial activity of CXJ might also explain its interaction with mitochondria, whose phospholipid composition recalls that of bacteria and its capability to induce apoptosis in cancer cells.

Antimicrobial Peptide K11 Selectively Recognizes Bacterial Biomimetic Membranes and Acts by Twisting Their Bilayers

K11 is a synthetic peptide originating from the introduction of a lysine residue in position 11 within the sequence of a rationally designed antibacterial scaffold. Despite its remarkable antibacterial properties towards many ESKAPE bacteria and its optimal therapeutic index (320), a detailed description of its mechanism of action is missing. As most antimicrobial peptides act by destabilizing the membranes of the target organisms, we investigated the interaction of K11 with biomimetic membranes of various phospholipid compositions by liquid and solid-state NMR. Our data show that K11 can selectively destabilize bacterial biomimetic membranes and torque the surface of their bilayers. The same is observed for membranes containing other negatively charged phospholipids which might suggest additional biological activities. Molecular dynamic simulations reveal that K11 can penetrate the membrane in four steps: after binding to phosphate groups by means of the lysine residue at the N-terminus (anchoring), three couples of lysine residues act subsequently to exert a torque in the membrane (twisting) which allows the insertion of aromatic side chains at both termini (insertion) eventually leading to the flip of the amphipathic helix inside the bilayer core (helix flip and internalization).

Patchy Core/Shell, Magnetite/Silver Nanoparticles via Green and Facile Synthesis: Routes to Assure Biocompatibility

Nanomedicine is entering a high maturity stage and is ready to reach full translation into the clinical practice. This is because of the ample spectrum of applications enabled by a large arsenal of nanostructured materials. In particular, bimetallic patchy core/shell nanoparticles offer tunable surfaces that allow multifunctional responses. Despite their attractiveness, major challenges regarding the environmental impact and biocompatibility of the obtained materials are yet to be solved. Here, we developed a green synthesis scheme to prepare highly biocompatible patchy core/shell magnetite/silver nanoparticles for biological and biomedical applications. The magnetite core was synthesized by the co-precipitation of ferric chloride and ferrous chloride in the presence of NaOH. This was followed by the patchy silver shell’s growth by a green synthesis approach based on natural honey as a reducing agent. A purification process allowed selecting the target patchy nanoparticles and removing excess toxic reagents from the synthesis very efficiently. The obtained patchy magnetite/silver nanoparticles were characterized by UV-Vis spectrophotometry, dynamic light scattering (DLS), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope equipped with energy-dispersive spectroscopy (SEM + EDS), and transmission electron microscopy (TEM). The morphology, patchiness level, and size of the nanoparticles were determined via SEM and TEM. In addition, the spectrophotometric characterization confirmed the presence of the patchy silver coating on the surface of the magnetite core. The nanoparticles show high biocompatibility, as evidenced by low cytotoxicity, hemolytic effect, and platelet aggregation tendency. Our study also provides details for the conjugation of multiples chemistries on the surface of the patchy bimetallic nanoparticles, which might be useful for emerging applications in nanomedicine, where high biocompatibility is of the utmost importance.

Antimicrobial peptides fromBombyx mori: a splendid immune defense response in silkworms

Bombyx mori L., a primary producer of silk, is the main tool in the sericulture industry and provides the means of livelihood to a large number of people. Silk cocoon crop losses due to bacterial infection pose a major threat to the sericulture industry. Bombyx mori L., a silkworm of the mulberry type, has a sophisticated inherent innate immune mechanism to combat such invasive pathogens. Among all the components in this defense system, antimicrobial peptides (AMPs) are notable due to their specificity towards the invading pathogens without harming the normal host cells. Bombyx mori L. so far has had AMPs identified that belong to six different families, namely cecropin, defensin, moricin, gloverin, attacin and lebocin, which are produced by the Toll and immune deficiency (IMD) pathways. Their diverse modes of action depend on microbial pathogens and are still under investigation. This review examines the recent progress in understanding the immune defense mechanism of Bombyx mori based on AMPs.

AMPs produced by B. mori induced by microbial challenge in the fat body.

An auto-inducible expression and high cell density fermentation of Beefy Meaty Peptide with Bacillus subtilis

Currently, some cases about the expression of flavor peptides with microorganisms were reported owing to the obvious advantages of biological expression over traditional methods. However, beefy meaty peptide (BMP), the focus of umami peptides, has neither been concerned in its safe expression nor its overproduction in fermenter. In this study, multi-copy BMP (8BMP) was successfully auto-inducibly expressed and efficiently produced in Bacillus subtilis 168. First, 8BMP was successfully auto-inducibly expressed with srfA promoter in B. subtilis 168. Further, the efficient production of 8BMP was researched in a 5-L fermenter: the fermentation optimized by Pontryagin's maximum principle obtained the highest 8BMP yield (3.16 g/L), which was 1.2 times and 1.8 times than that of two-stage feeding cultivation (2.67 g/L) and constant-rate feeding cultivation (1.75 g/L), respectively. Overall, the auto-inducible expression of 8BMP in B. subtilis and fermentation with Pontryagin's maximum principle are conductive for overproduction of BMP and other peptides.

Antimicrobial Peptides: Recent Insights on Biotechnological Interventions and Future Perspectives

With the unprecedented rise of drug-resistant pathogens, particularly antibiotic-resistant bacteria, and no new antibiotics in the pipeline over the last three decades, the issue of antimicrobial resistance has emerged as a critical public health threat. Antimicrobial Peptides (AMP) have garnered interest as a viable solution to this grave issue and are being explored for their potential antimicrobial applications. Given their low bioavailability in nature, tailoring new AMPs or strategizing approaches for increasing the yield of AMPs, therefore, becomes pertinent. The present review focuses on biotechnological interventions directed towards enhanced AMP synthesis and revisits existing genetic engineering and synthetic biology strategies for production of AMPs. This review further underscores the importance and potential applications of advanced gene editing technologies for the synthesis of novel AMPs in future.

Immune responses to bacterial and fungal infections in the silkworm, Bombyx mori

The silkworm Bombyx mori, an economically important insect that is usually reared indoors, is susceptible to various pathogens, including bacteria, fungi, viruses, and microsporidia. As with other insects, the silkworm lacks an adaptive immune system and relies solely on innate immunity to defend itself against infection. Compared to other intensively studied insects, such as the fruit fly and tobacco hornworm, the principal immune pathways in the silkworm remain unclear. In this article, we review the literature concerning silkworm immune responses to bacteria and fungi and present our perspectives on future research into silkworm immunity.

Therapeutic effects of antimicrobial peptide on malignant ascites in a mouse model

The primary objective of the treatment of malignant ascites in advanced stages is to alleviate symptoms using procedures such as diuresis, paracentesis of subretinal fluid and vena cava anastomosis. The effectiveness of systemic or intraperitoneal chemotherapy treatment is limited, and more efficacious therapies are required. The authors of the present study demonstrated that an antimicrobial peptide, cecropinXJ, isolated from the larvae of Bombyx mori, selectively inhibits the proliferation of gastric cancer cells. However, the effects of antibacterial peptides on gastric ascites tumor remains unclear. In the present study, the therapeutic effects of cecropinXJ were investigated in mice bearing malignant ascites. Compared with bovine serum albumin treatment, cecropinXJ and doxorubicin (Dox) significantly inhibited the formation and growth of malignant ascites, and prolonged the survival time of ascites tumor‑bearing mice. In addition, cecropinXJ treatment normalized the hematological and biochemical phenotypes, induced tumor cell apoptosis in ascites and improved the survival of mice bearing malignant ascites when compared with Dox treatment. These results suggested that cecropinXJ might be a promising therapeutic candidate for the treatment of gastric cancer‑associated ascites.

Anti-Salmonella Activity Modulation of Mastoparan V1-A Wasp Venom Toxin-Using Protease Inhibitors, and Its Efficient Production via an Escherichia coli Secretion System

A previous study highlighted that mastoparan V1 (MP-V1), a mastoparan from the venom of the social wasp Vespula vulgaris, is a potent antimicrobial peptide against Salmonella infection, which causes enteric diseases. However, there exist some limits for its practical application due to the loss of its activity in an increased bacterial density and the difficulty of its efficient production. In this study, we first modulated successfully the antimicrobial activity of synthetic MP-V1 against an increased Salmonella population using protease inhibitors, and developed an Escherichia coli secretion system efficiently producing active MP-V1. The protease inhibitors used, except pepstatin A, significantly increased the antimicrobial activity of the synthetic MP-V1 at minimum inhibitory concentrations (determined against 10⁶ cfu/mL of population) against an increased population (10⁸ cfu/mL) of three different Salmonella serotypes, Gallinarum, Typhimurium and Enteritidis. Meanwhile, the E. coli strain harboring OmpA SS::MP-V1 was identified to successfully secrete active MP-V1 into cell-free supernatant, whose antimicrobial activity disappeared in the increased population (10⁸ cfu/mL) of Salmonella Typhimurium recovered by adding a protease inhibitor cocktail. Therefore, it has been concluded that our challenge using the E. coli secretion system with the protease inhibitors is an attractive strategy for practical application of peptide toxins, such as MP-V1.

Combination of cecropinXJ and LY294002 induces synergistic cytotoxicity, and apoptosis in human gastric cancer cells via inhibition of the PI3K/Akt signaling pathway

The aim of the present study was to investigate the cytotoxic and apoptotic effects of cecropinXJ against human gastric cancer BGC823 cells, either alone, or in combination with a specific phosphatidylinositol 3-kinase (PI3K) inhibitor, LY294002. Cell viability and the apoptosis rate were measured using flow cytometry with Annexin-V staining. Additionally, the expression levels of several RAC-α serine/threonine kinase (Akt) phosphorylation-associated proteins and apoptosis-regulating proteins were evaluated by western blot analysis. It was observed that the combination of cecropinXJ and LY294002 resulted in significant synergistic cytotoxic and apoptosis effects, as compared with any single agent alone, in a dose-dependent manner. Corresponding to enhanced apoptosis, the expression levels of certain apoptosis-regulating proteins were changed, the most notable being the upregulation of caspase-3, B-cell lymphoma-2 (Bcl-2)-associated death promotor, Bcl-2 homologous antagonist killer, Bcl-2 interacting killer, Bcl-2-like protein 11, Bcl-2-like protein 4 and cytochrome c, and the downregulation of phosphorylated-Bad and Bcl-2 proteins. The present study provided a novel therapeutic regimen for the use of the cecropinXJ in combination with LY294002 for the treatment of gastric cancer.

Optimization of culturing conditions of recombined Escherichia coli to produce umami octopeptide-containing protein

Using synthesized peptides to verify the taste of natural peptides was probably the leading cause for tasting disputes regarding umami peptides. A novel method was developed to prepare the natural peptide which could be used to verify the taste of umami peptide. A controversial octopeptide was selected and gene engineering was used to structure its Escherichia coli. expressing vector. A response surface method was adopted to optimize the expression conditions of the recombinant protein. The results of SDS-PAGE for the recombinant protein indicated that the recombinant expression system was successfully structured. The fitting results of the response surface experiment showed that the OD₆₀₀ value was the key factor which influenced the expression of the recombinant protein. The optimal culturing process conditions predicted with the fitting model were an OD₆₀₀ value of 0.5, an IPTG concentration of 0.6mM, a culturing temperature of 28.75°C and a culturing time of 5h.

A potential food biopreservative, CecXJ-37N, non-covalently intercalates into the nucleotides of bacterial genomic DNA beyond membrane attack

The antibacterial activities and mechanism of an amide-modified peptide CecXJ-37N were investigated in this study. CecXJ-37N showed small MICs (0.25-7.8μM) against eight harmful strains common in food industry. The α-helix proportion of CecXJ-37N increased by 11-fold in prokaryotic membrane comparable environments; cytotoxicity studies demonstrated the MHC was significantly higher than that of non-amidated isoform. Moreover, CecXJ-37N possessed stronger capacities to resist trypsin and pepsin hydrolysis within two hours. Flow cytometry and scanning electron microscopy demonstrated that CecXJ-37N induced pore-formation, morphological changes, and lysed E. coli cells. Fluorescence microscopy indicated that CecXJ-37N penetrated E. coli membrane and accumulated in cytoplasm. Further ultraviolet-visible spectroscopy suggested that CecXJ-37N changed the action mode of parental peptide interacting with bacterial genome from outside binding to a tightly non-covalent intercalation into nucleotides. Overall, this study suggested that amide-modification enhanced antimicrobial activity and reduced the cytotoxicity, thus could be potential strategies for developing novel food preservatives.

Characterization and regulation of expression of an antifungal peptide from hemolymph of an insect, Manduca sexta

Insects secrete antimicrobial peptides as part of the innate immune response. Most antimicrobial peptides from insects have antibacterial but not antifungal activity. We have characterized an antifungal peptide, diapausin-1 from hemolymph of a lepidopteran insect, Manduca sexta (tobacco hornworm). Diapausin-1 was isolated by size exclusion chromatography from hemolymph plasma of larvae that were previously injected with a yeast, Saccharomyces cerevisiae. Fractions containing activity against S. cerevisiae were analyzed by SDS-PAGE and MALDI-TOF MS/MS and found to contain a 45-residue peptide that was encoded by sequences identified in M. sexta transcriptome and genome databases. A cDNA for diapausin-1 was cloned from cDNA prepared from fat body RNA. Diapausin-1 is a member of the diapausin family of peptides, which includes members known to have antifungal activity. The M. sexta genome contains 14 genes with high similarity to diapausin-1, each with 6 conserved Cys residues. Diapausin-1 was produced as a recombinant protein in Escherichia coli. Purified recombinant diapausin-1 was active against S. cerevisiae, with IC50 of 12 μM, but had no detectable activity against bacteria. Spores of some plant fungal pathogens treated with diapausin-1 had curled germination tubes or reduced and branched hyphal growth. Diapausin-1 mRNA level in fat body strongly increased after larvae were injected with yeast or with Micrococcus luteus. In addition, diapausin-1 mRNA levels increased in midgut and fat body at the wandering larval stage prior to pupation, suggesting developmental regulation of the gene. Our results indicate that synthesis of diapausin-1 is part of an antifungal innate immune response to infection in M. sexta.

Insect antimicrobial peptides: potential tools for the prevention of skin cancer

Antimicrobial peptides/proteins (AMPs) are biologically active molecules with diverse structural properties that are produced by mammals, plants, insects, ticks, and microorganisms. They have a range of antibacterial, antifungal, antiviral, and even anticancer activities, and their biological properties could therefore be exploited for therapeutic and prophylactic applications. Cancer and cancer drug resistance are significant current health challenges, so the development of innovative cancer drugs with minimal toxicity toward normal cells and novel modes of action that can evade resistance may provide a new direction for anticancer therapy. The skin is the first line of defense against heat, sunlight, injury, and infection, and skin cancer is thus the most common type of cancer. The skin that has been exposed to sunlight is particularly susceptible, but lesions can occur anywhere on the body. Skin cancer awareness and self-efficacy are necessary to improve sun protection behavior, but more effective preventative approaches are also required. AMPs may offer a new prophylactic approach against skin cancer. In this mini review, we draw attention to the potential use of insect AMPs for the prevention and treatment of skin cancer.

The antibacterial peptide from Bombyx mori cecropinXJ induced growth arrest and apoptosis in human hepatocellular carcinoma cells

CecropinXJ is a cationic antimicrobial peptide originally isolated from the larvae of Bombyx mori. The anticancer effect of cecropinXJ has been reported in various tumor cells, including leukemia, gastric and esophageal cancer cells. However, the activity of cecropinXJ on hepatocellular carcinoma (HCC) and its underlying mechanism have not been investigated to date. Therefore, the present study investigated the efficacy and associated mechanism of cecropinXJ in Huh-7 cells. Flow cytometric analysis was performed to determine the presence of cell cycle arrested and apoptotic cells. CecropinXJ significantly inhibited the growth of Huh-7 cells in a dose- and time-dependent manner. CecropinXJ treatment for 24 h induced S cell cycle arrest and apoptosis, in addition to loss of the mitochondrial membrane potential, in hepatoma cells. CecropinXJ induced HCC cell apoptosis by activating caspase-3 and poly(ADP-ribose) polymerase. Furthermore, cecropinXJ downregulated the expression of B-cell lymphoma 2 (Bcl-2), while upregulated the expression of Bcl-2-associated death promoter and Bcl-2-associated X protein. In conclusion, the results of the present study suggest that cecropinXJ may be an active anti-HCC agent and provide novel insights into the mechanism of cecropinXJ.

Green fluorescent protein as a scaffold for high efficiency production of functional bacteriotoxic proteins in Escherichia coli

The availability of simple, robust, and cost-effective methods for the large-scale production of bacteriotoxic peptides such as antimicrobial peptides (AMPs) is essential for basic and pharmaceutical research. However, the production of bacteriotoxic proteins has been difficult due to a high degree of toxicity in bacteria and proteolytic degradation. In this study, we inserted AMPs into the Green fluorescent protein (GFP) in a loop region and expressed them as insoluble proteins in high yield, circumventing the inherent toxicity of AMP production in Escherichia coli. The AMPs inserted were released by cyanogen bromide and purified by chromatography. We showed that highly potent AMPs such as Protegrin-1, PMAP-36, Buforin-2, and Bactridin-1 are produced in high yields and produced AMPs showed similar activities compared to chemically synthesized AMPs. We increased the yield more than two-fold by inserting three copies of Protegrin-1 in the GFP scaffold. The immunogold electron micrographs showed that the expressed Protegrin-1 in the GFP scaffold forms large and small size aggregates in the core region of the inclusion body and become entirely nonfunctional, therefore not influencing the proliferation of E. coli. Our novel method will be applicable for diverse bacteriotoxic peptides which can be exploited in biomedical and pharmaceutical researches.

CecropinXJ inhibits the proliferation of human gastric cancer BGC823 cells and induces cell death in vitro and in vivo

We have shown that an antimicrobial peptide (AMP) cecropinXJ isolated from the larvae of Bombyx mori selectively inhibits the proliferation of cancer cells. However, the mechanism remains to be determined. In the present study, we examined the antitumor activity of cecropinXJ against human gastric cancer BGC823 cells and explored the mechanism. The results showed that cecropinXJ inhibited the growth of gastric cancer BGC823 cells in vitro and in vivo. MTT and colony formation assays indicated that cecropinXJ suppressed cell proliferation and reduced colony formation of BGC823 cells in a dose- and time-dependent manner, but without inhibitory effect on normal gastric epithelia GES-1 cells. S-phase arrest in BGC823 cells was observed after treatment with cecropinXJ. Annexin V/PI staining suggested that cecropinXJ induced both early and late phases of apoptosis through activation of mitochondrial-mediated caspase pathway, upregulation of Bax expression and downregulation of Bcl-2 expression. Additionally, cecropinXJ treatment increased reactive oxygen species (ROS) production, disrupted the mitochondrial membrane potential (Δψm) and led to release of cytochrome c. Importantly, in vivo study showed that cecropinXJ significantly prevented the growth of xenograft tumor in the BGC823-bearing mice, possibly mediated by the induction of apoptosis and inhibition of angiogenesis. These results suggest that cecropinXJ may be a promising therapeutic candidate for the treatment of gastric cancer.

CecropinXJ, a silkworm antimicrobial peptide, induces cytoskeleton disruption in esophageal carcinoma cells

Antimicrobial peptides exist in the non-specific immune system of organism and participate in the innate host defense of each species. CecropinXJ, a cationic antimicrobial peptide, possesses potent anticancer activity and acts preferentially on cancer cells instead of normal cells, but the mechanism of cancer cell death induced by cecropinXJ remains largely unknown. This study was performed to investigate the cytoskeleton-disrupting effects of cecropinXJ on human esophageal carcinoma cell line Eca109 using scanning electron microscopy observation, fluorescence imaging, cell migration and invasion assays, western blotting, and quantitative reverse transcription polymerase chain reaction (qRT-PCR) analysis. The electronic microscope and fluorescence imaging observation suggested that cecropinXJ could result in morphological changes and induce damage to microtubules and actin of Eca109 cells in a dose-dependent manner. The cell migration and invasion assays demonstrated that cecropinXJ could inhibit migration and invasion of tumor cells. Western blot and qRT-PCR analysis showed that there was obvious correlation between microtubule depolymerization and actin polymerization induced by cecropinXJ. Moreover, cecropinXJ might also cause decreased expression of α-actin, β-actin, γ-actin, α-tubulin, and β-tubulin genes in concentration- and time-dependent manners. In summary, this study indicates that cecropinXJ triggers cytotoxicity in Eca109 cells through inducing the cytoskeleton destruction and regulating the expression of cytoskeleton proteins. This cecropinXJ-mediated cytoskeleton-destruction effect is instrumental in our understanding of the detailed action of antimicrobial peptides in human cancer cells and cecropinXJ might be a potential therapeutic agent for the treatment of cancer in the future.