Enantiomeric CopA3 dimer peptide suppresses cell viability and tumor xenograft growth of human gastric cancer cells.

The CopA3 dimer peptide is a coprisin analog that has an anticancer effect against human cancer cells in vitro. In this study, we investigated the anticancer activity of the enantiomeric CopA3 dimer peptide in human gastric cancer cell lines as well as in an in vivo tumor xenograft model. Enantiomeric CopA3 reduced gastric cancer cell viability and exhibited cytotoxicity against cancer cells. Enantiomeric CopA3-induced cell death was mediated by specific interactions with phosphatidylserine and phosphatidylcholine, membrane components that are enriched in cancer cells, in a calcein leakage assay. Moreover, acridine orange/ethidium bromide staining, flow cytometric analysis, and Western blot analysis showed that enantiomeric CopA3 induced apoptotic and necrotic gastric cancer cell death. The antitumor effect was also observed in a mouse tumor xenograft model in which intratumoral inoculation of the peptide resulted in a significant decrease in the SNU-668 gastric cancer tumor volume. In addition, periodic acid-Schiff and hematoxylin staining and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay revealed apoptotic and necrotic cell death in tumor masses treated with greater than 150 µg CopA3. Collectively, these results indicate that the enantiomeric CopA3 dimer peptide induces apoptosis and necrosis of gastric cancer cells in vitro and in vivo, indicating that the peptide is a potential candidate for the treatment of gastric cancer, which is a common cause of cancer and cancer deaths worldwide.

Therapeutic efficacy of halocidin-derived peptide HG1 in a mouse model of Candida albicans oral infection.

OBJECTIVES: HG1 is an antimicrobial peptide derived from halocidin, which is naturally found in tunicates. The purpose of this study was to evaluate the therapeutic potential of HG1 as a novel antifungal agent for treating oral candidiasis. METHODS: The pharmacokinetic properties of HG1 were explored in mice, which were orally administered a single dose of HG1. Anti-Candida activity of HG1 was investigated in a time-dependent manner in the presence of saliva obtained from healthy donors or patients with oral candidiasis. In addition, HG1 was evaluated for its anti-Candida activity in the presence of proteins extracted from the culture supernatant of Candida albicans. The therapeutic potential in vivo and ex vivo of HG1 against oral candidiasis was investigated using a mouse model of oral candidiasis. RESULTS: Our data showed that absorption of HG1 into the blood did not occur following oral administration. In addition, HG1 exerted marked anti-Candida activity after short-term incubation at a concentration of 20 mg/L and it also caused a considerable reduction in fungal burden in the oral candidiasis mouse model when treated with 1 mg or 0.5 mg. CONCLUSIONS: This study suggests that HG1, as a novel component of mouthwash, might become an alternative antifungal agent to conventional drugs used to manage oral candidiasis.

An insect multiligand recognition protein functions as an opsonin for the phagocytosis of microorganisms.

We characterize a novel pathogen recognition protein obtained from the lepidopteran Galleria mellonella. This protein recognizes Escherichia coli, Micrococcus luteus, and Candida albicans via specific binding to lipopolysaccharides, lipoteichoic acid, and beta-1,3-glucan, respectively. As a multiligand receptor capable of coping with a broad variety of invading pathogens, it is constitutively produced in the fat body, midgut, and integument but not in the hemocytes and is secreted into the hemolymph. The protein was confirmed to be relevant to cellular immune response and to further function as an opsonin that promotes the uptake of invading microorganisms into hemocytes. Our data reveal that the mechanism by which a multiligand receptor recognizes microorganisms contributes substantially to their phagocytosis by hemocytes. A better understanding of an opsonin with the required repertoire for detecting diverse invaders might provide us with critical insights into the mechanisms underlying insect phagocytosis.

Therapeutic efficacy of halocidin-derived peptide HG1 in a mouse model of surgical wound infection with methicillin-resistant Staphylococcus aureus.

We evaluated the therapeutic potential of HG1, an antimicrobial peptide, as a novel topical antibiotic by the use of a mouse surgical wound model of infection with methicillin-resistant Staphylococcus aureus. First, we attempted to determine whether or not HG1 infiltrated into the dermis when topically administered. Second, we evaluated the antibiotic effects of HG1 on skin infection via bacterial-enumeration and microscopic analyses. The results showed that topically administered HG1 was capable of penetrating into the dermis at the infection site, where it exerted its antimicrobial effects.

Antiseptic effect of antimicrobial peptide psacotheasin 2 derived from the yellow-spotted longicorn beetle (Psacothea hilaris).

Given the challenges posed by antibiotic resistant microbes and the high mortality rate associated with sepsis, there is an urgent need to develop novel peptide antibiotics that exhibit both antimicrobial and anti-inflammatory activities. Herein, we evaluated antimicrobial activity and anti-inflammatory activity of psacotheasin 2, one of the antimicrobial peptide candidates identified previously using an in silico analysis on the transcriptome of Psacothea hilaris. In addition to exhibiting antimicrobial activities against microorganisms without inducing hemolysis, psacotheasin 2 also decreased the nitric oxide production in lipopolysaccharide (LPS)-induced Raw264.7 cells. Moreover, ELISA and western blot analysis revealed that psacotheasin 2 reduced the expression levels of pro-inflammatory enzymes such as inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). Further, we found that psacotheasin 2 markedly reduced the expression levels of pro-inflammatory cytokines (IL-6 and IL-1ß) by regulating mitogen-activated protein kinases (MAPKs) and nuclear factor-kB (NF-kB) signaling in LPS-induced Raw264.7 cells. We also confirmed that the binding of psacotheasin 2 to bacterial cell membranes occurs via a specific interaction with LPS. In mouse models of LPS-induced shock, psacotheasin 2 significantly enhanced the survival rate and recovered weight by attenuating pro-inflammatory cytokines. Thus, psacotheasin 2 could be a promising candidate as a peptide antiseptic agent.

De novo assembly and functional annotation of the Red-striped golden stink bug (Poecilocoris lewisi) transcriptome.

Insect antimicrobial peptides (AMPs) have a wide range of functions and potential applications, and have recently attracted attention as alternative foods and medicines for humans. Our study performed transcriptome analysis to explore the potential of the red-striped golden stink bug (Poecilocoris lewisi), and as a result, we have discovered new features of P. lewisi that have not been identified. Specifically, defensin found in P. lewisi is a well-known AMP and is expressed by various plants, animals and fungi for host defense. Moreover, the discovery of defensin in P. lewisi provides new research and important information. In this study, we identified AMP and related DEG in P. lewisi that are closely related to human disease and immune response. These findings will provide the basis and important information for future research on P. lewisi that has not yet been studied.

Antimicrobial activity of a halocidin-derived peptide resistant to attacks by proteases.

Cationic antimicrobial peptides (AMPs) have attracted a great deal of interest as a promising candidate for a novel class of antibiotics that might effectively treat recalcitrant infections caused by a variety of microbes that are resistant to currently available drugs. However, the AMPs are inherently limited in that they are inevitably susceptible to attacks by proteases generated by human and pathogenic microbes; this vulnerability severely hinders their pharmaceutical use in human therapeutic protocols. In this study, we report that a halocidin-derived AMP, designated HG1, was found to be resistant to proteolytic degradation. As a result of its unique structural features, HG1 proved capable of preserving its antimicrobial activity after incubation with trypsin, chymotrypsin, and human matrix metalloprotease 7 (MMP-7). Additionally, HG1 was observed to exhibit profound antimicrobial activity in the presence of fluid from human skin wounds or proteins extracted from the culture supernatants of Staphylococcus aureus and Pseudomonas aeruginosa. Greater understanding of the structural motifs of HG1 required for its protease resistance might provide feasible ways to solve the problems intrinsic to the development of an AMP-based antibiotic.

Immune evasion of Enterococcus faecalis by an extracellular gelatinase that cleaves C3 and iC3b.

Enterococcus faecalis (Ef) accounts for most cases of enterococcal bacteremia, which is one of the principal causes of nosocomial bloodstream infections (BSI). Among several virulence factors associated with the pathogenesis of Ef, an extracellular gelatinase (GelE) has been known to be the most common factor, although its virulence mechanisms, especially in association with human BSI, have yet to be demonstrated. In this study, we describe the complement resistance mechanism of Ef mediated by GelE. Using purified GelE, we determined that it cleaved the C3 occurring in human serum into a C3b-like molecule, which was inactivated rapidly via reaction with water. This C3 convertase-like activity of GelE was shown to result in a consumption of C3 and thus inhibited the activation of the complement system. Also, GelE was confirmed to degrade an iC3b that was deposited on the Ag surfaces without affecting the bound C3b. This proteolytic effect of GelE against the major complement opsonin resulted in a substantial reduction in Ef phagocytosis by human polymorphonuclear leukocytes. In addition, we verified that the action of GelE against C3, which is a central component of the complement cascade, was human specific. Taken together, it was suggested that GelE may represent a promising molecule for targeting human BSI associated with Ef.

Deciphering Novel Antimicrobial Peptides from the Transcriptome of Papilio xuthus.

An insect's innate immune system is the front line of defense against many invading microorganisms. One of the important components of this defense system is antimicrobial peptides (AMPs). Papiliocin is a well-studied antimicrobial peptide (AMP) isolated from the swallowtail butterfly, Papilio xuthus, and it was previously reported to be effective against Gram-positive bacteria, Gram-negative bacteria, and fungi, particularly in drug resistant Gram-negative bacteria. Hence, we aimed to identify novel AMPs from Papilio xuthus using its transcriptome. We immunized the swallowtail butterfly with Escherichia coli, Staphylococcus aureus, Candida albicans, and the total RNA was isolated. De novo transcriptome assembly and functional annotations were conducted, and AMPs were predicted using an in-silico pipeline. The obtained 344,804,442 raw reads were then pre-processed to retrieve 312,509,806 (90.6%) total clean reads. A total of 38,272 unigenes were assembled with the average length of 1010 bp. Differential gene expression analysis identified 584 and 1409 upregulated and downregulated genes, respectively. The physicochemical, aggregation, and allergen propensity were used as filtration criteria. A total of 248 peptides were predicted using our in-house pipeline and the known AMPs were removed, resulting in 193 novel peptides. Finally, seven peptides were tested in vitro and three peptides (Px 5, 6, and 7) showed stronger antimicrobial activity against Gram-negative bacteria and yeast. All the tested peptides were non-allergens. The identified novel AMPs may serve as potential candidates for future antimicrobial studies.

Transcriptome Analysis of Psacothea hilaris: De Novo Assembly and Antimicrobial Peptide Prediction.

Antimicrobial peptides (AMPs) are the frontline innate defense system evolutionarily preserved in insects to combat invading pathogens. These AMPs could serve as an alternative to classical antibiotics to overcome the burden of treating multidrug resistant bacteria. Psacotheasin, a knottin type AMP was isolated from Psacothea hilaris and shown to exhibit antimicrobial activity, especially against fungi through apoptosis mediated cell death. In this study, we aimed to identify novel probable AMPs from Psacothea hilaris, the yellow spotted longicorn beetle. The beetle was immunized with the two bacterial strains (E. coli and S. aureus), and the yeast strain C. albicans. After immunization, total RNA was isolated and sequenced in Illumina platform. Then, beetle transcriptome was de novo assembled and searched for putative AMPs with the known physiochemical features of the AMPs. A selection of AMP candidates were synthesized and tested for antimicrobial activity. Four peptides showed stronger activity against E. coli than the control AMP, melittin while one peptide showed similar activity against S. aureus. Moreover, four peptides and two peptides showed antifungal activity stronger than and similar to melittin, respectively. Collectively one peptide showed both antibacterial and antifungal activity superior to melittin; thus, it provides a potent antimicrobial peptide. All the peptides showed no hemolysis in all the tested concentrations. These results suggest that in silico mining of insects' transcriptome could be a promising tool to obtain and optimize novel AMPs for human needs.

Anti-Inflammatory Activity of Antimicrobial Peptide Periplanetasin-5 Derived from the Cockroach Periplaneta americana.

Previously, we performed an in silico analysis of the Periplaneta americana transcriptome. Antimicrobial peptide candidates were selected using an in silico antimicrobial peptide prediction method. It was found that periplanetasin-5 had antimicrobial activity against yeast and grampositive and gram-negative bacteria. In the present study, we demonstrated the anti-inflammatory activities of periplanetasin-5 in mouse macrophage Raw264.7 cells. No cytotoxicity was observed at 60 µg/ml periplanetasin-5, and treatment decreased nitric oxide production in Raw264.7 cells exposed to lipopolysaccharide (LPS). In addition, quantitative RT-PCR and enzyme-linked immunosorbent assay revealed that periplanetasin-5 reduced cytokine (tumor necrosis factor-α, interleukin-6) expression levels in the Raw264.7 cells. Periplanetasin-5 controlled inflammation by inhibiting phosphorylation of MAPKs, an inflammatory signaling element, and reducing the degradation of IκB. Through LAL assay, LPS toxicity was found to decrease in a periplanetasin-5 dose-dependent manner. Collectively, these data showed that periplanetasin-5 had antiinflammatory activities, exemplified in LPS-exposed Raw264.7 cells. Thus, we have provided a potentially useful antibacterial peptide candidate with anti-inflammatory activities.

Characterization of Kunitz-type protease inhibitor purified from hemolymph of Galleria mellonella larvae.

We characterized a Kunitz-type protease inhibitor (Gm KTPI) obtained from the hemolymph of Galleria mellonella larvae immunized with Escherichia coli. The structural analysis of the cloned cDNA showed that it consists of 56 residues derived from the precursor of 75 amino acids. The peptide was constitutively produced in the fat bodies, but not in the midgut nor the integument of larvae. In our analysis of stage-dependent expression, its transcript was detected within the midgut, the fat bodies and the integument of the prepupae, which undergo tissue remodeling. The inhibition assays showed that Gm KTPI was capable of inhibiting only the trypsin-like activity of the larval midgut extracts. Furthermore, it was determined that Gm KTPI induced the activation of extracellular signal-regulated kinase (ERK) in the fat bodies and integument cells, and this kinase is known to perform a central role in cell proliferation signaling. Its effect on ERK activation was also verified in a control experiment using a human endothelial cell culture. Collectively, it was suggested that Gm KTPI might be responsible for the protection of other tissues against proteolytic attack by trypsin-like protease(s) from larval midgut during metamorphosis, and might play a role in the proliferation of cells in the fat body and integument.

Antimicrobial effect of halocidin-derived peptide in a mouse model of Listeria infection.

Halocidin is an antimicrobial peptide found in the tunicate. A series of experiments were previously conducted in an attempt to develop a novel antibiotic derived from halocidin, as the peptide was determined to evidence profound antimicrobial activity against a variety of antibiotic-resistant microbes, with significantly less toxicity to human blood cells. In this study, we assessed the validity of one of the halocidin congeners, called Khal, as a new antibiotic for the treatment of systemic bacterial infections. Our in vitro antimicrobial tests showed that the MICs of Khal against several gram-positive bacteria were below 16 microg/ml in the presence of salt. We also determined that Khal retained sufficient target selectivity to discern microbial and human blood cells and was therefore capable of efficiently killing invading pathogens. Furthermore, Khal caused no aggregation problems upon incubation with human serum and also proved to be resistant to proteolysis by enzymes occurring in human serum. In the following experiments conducted with a mouse model of Listeria monocytogenes infection, we demonstrated that a single intravenous inoculation with Khal resulted in significant therapeutic effects on the survival of mice. In addition, our bacterial-enumeration analysis showed that after Listeria infection, livers and spleens from Khal-treated mice generated a great deal fewer recoverable CFU. Finally, the antibiotic effects of Khal were evaluated under confocal microscopy after we immunostained the liver sections with anti-Khal antibody. It was concluded that Khal bound specifically to the surfaces of bacteria colonized in the mouse liver and killed the bacteria rapidly.