Erratum to: Oxya chinensis sinuosa (OC) Extracts Protects ARPE-19 Cells against Oxidative Stress via Activation of the Mitogen-Activated Protein Kinases (MAPKs)/Nuclear Factor-κB (NF-κB) Pathway.

[This corrects the article DOI: 10.5851/kosfa.2024.e15.].

Oxya chinensis sinuosa (OC) Extracts Protects ARPE-19 Cells against Oxidative Stress via Activation of the Mitogen-Activated Protein Kinases (MAPKs)/ Nuclear Factor-κB (NF-κB) Pathway.

Oxya chinensis sinuosa (OC) is a well-known edible insect. Several researches on the health benefits of OC consumption have been performed to date; however, their effect on eye health remains largely unknown. This study aimed to assess the protective effects of OC extracts on the oxidative stress on the retinal pigment epithelium (RPE) cells. Oxidative damage has been identified as one of the key regulatory factors in age-related macular degeneration. H2O2-induced reactive oxygen species (ROS) production, a well-known oxidative stress factor, can cause cell death in retinal pigment epithelia cells. In this study, we found that three OC extracts effectively prevented H2O2-induced ROS production and subsequent death of ARPE-19 cells in a dose-dependent manner. In addition, the OC extracts inhibited the phosphorylation of mitogen-activated protein kinases including p38, JNK, and ERK. The OC extracts restored IκBα degradation induced by H2O2, indicating that OC extracts suppressed the activation of nuclear factor-κB. Furthermore, the three OC extracts were shown to have antioxidant effects by up-regulating the intracellular expression of key antioxidant proteins such as SOD, NQO, and HO-1. Here we demonstrated the antioxidant and anti-apoptotic effects of the OC extracts on ARPE-19, indicating their potential role in improving eye health. These results suggest that three OC extracts plays a critical role in oxidative stress-induced cell death protects in ARPE-19 cells.

Protaetia brevitarsis seulensis larvae ethanol extract inhibits RANKL-stimulated osteoclastogenesis and ameliorates bone loss in ovariectomized mice.

Modulation of osteoclast formation could be a therapeutic target for inhibiting pathological bone destruction. The receptor activator of nuclear factor (NF)-κB ligand (RANKL) is known to be an essential factor in osteoclast differentiation and activation inducers. However, whether Protaetia brevitarsis seulensis (P. brevitarsis) larvae-a traditional animal-derived medicine used in many Asian countries-can inhibit RANKL-induced osteoclast formation and prevent ovariectomy (OVX)-induced bone loss has not been evaluated. Here, we aimed to investigate the anti-osteoporotic effects of P. brevitarsis larvae ethanol extract (PBE) in RANKL-stimulated RAW264.7 cells and OVX mice. In vitro, PBE (0.1, 0.5, 1, and 2 mg/mL) decreased RANKL­induced tartrate-resistant acid phosphatase (TRAP) activity and expression of osteoclastogenesis-associated genes and proteins. Furthermore, PBE (0.1, 0.5, 1, and 2 mg/mL) significantly inhibited the phosphorylation of p38 and NF-κB. Female C3H/HeN mice were divided into five groups (n = 5 per group), namely, sham-operated, OVX, OVX+PBEL (100 mg/kg, oral gavage), OVX+PBEH (200 mg/kg, oral gavage), and OVX+estradiol (0.03 µg/day, subcutaneous injection). High doses of PBE significantly increased femoral bone mineral density (BMD) and bone volume/tissue volume (BV/TV), whereas femoral bone surface/bone volume (BS/BV) and osteoclastogenesis-associated protein expression decreased compared to those in the OVX group. Moreover, PBE (200 mg/kg) significantly increased estradiol and procollagen type I N-terminal propeptide and decreased N-terminal telopeptide of type I collagen and C-terminal telopeptide of type I collagen compared to those in the OVX group. Our results suggest that PBE can be an effective therapeutic candidate for preventing or treating postmenopausal osteoporosis.

Transcriptome profiling for developmental stages Protaetia brevitarsis seulensis with focus on wing development and metamorphosis.

A white-spotted flower chafer Protaetia brevitarsis seulensis widely distributed in Asian countries is traditionally used in oriental medicine. This study explored gene expression abundance with respect to wing development and metamorphosis in P. b. seulensis based on the large-scale RNA-seq data. The transcriptome assembly consists of 23,551 high-quality transcripts which are approximately 96.7% covered. We found 265 wing development genes, 19 metamorphosis genes, and 1,314 candidates. Of the 1,598 genes, 1,594 are included exclusively in cluster 4 with similar gene co-expression patterns. The network centrality analyses showed that wing development- and metamorphosis-related genes have a high degree of betweenness centrality and are expressed most highly in eggs, moderately in pupa and adults, and lowest in larva. This study provides some meaningful clues for elucidating the genetic modulation mechanism of wing development and metamorphosis in P. b. seulensis.

The neural basis of heat seeking in a human-infective parasitic worm.

Soil-transmitted parasitic nematodes infect over one billion people and cause devastating morbidity worldwide. Many of these parasites have infective larvae that locate hosts using thermal cues. Here, we identify the thermosensory neurons of the human threadworm Strongyloides stercoralis and show that they display unique functional adaptations that enable the precise encoding of temperatures up to human body temperature. We demonstrate that experience-dependent thermal plasticity regulates the dynamic range of these neurons while preserving their ability to encode host-relevant temperatures. We describe a novel behavior in which infective larvae spontaneously reverse attraction to heat sources at sub-body temperatures and show that this behavior is mediated by rapid adaptation of the thermosensory neurons. Finally, we identify thermoreceptors that confer parasite-specific sensitivity to body heat. Our results pinpoint the parasite-specific neural adaptations that enable parasitic nematodes to target humans and provide the foundation for drug development to prevent human infection.

Mealworm Ethanol Extract Enhances Myogenic Differentiation and Alleviates Dexamethasone-Induced Muscle Atrophy in C2C12 Cells.

Aging, and other disease-related muscle disorders are serious health problems. Dexamethasone (DEX), a synthetic glucocorticoid, can trigger skeletal muscle atrophy. This study examined the effects of mealworm (Tenebrio molitor larva) ethanol extract (TME) on C2C12 myoblast differentiation and DEX-induced myotube atrophy. TME induced myotube formation compared to the differentiation medium (DM) group. TME also significantly increased the mRNA expression of muscle creatine kinase (CKm) and myogenic regulatory factors (MRFs), such as myogenin (MyoG), myogenic factor (Myf)5, and MRF4 (Myf6). TME dramatically increased the muscle-specific protein, MyoG, compared to the control, whereas the expression of myogenic differentiation 1 (MyoD) remained unchanged. It also activated the mammalian target of rapamycin (mTOR) signaling pathway. In the DEX-induced muscle atrophy C2C12 model, TME reduced the gene expression of atrogin-1, muscle RING finger protein-1 (MuRF-1), and myostatin, which are involved in protein degradation in skeletal muscles. Furthermore, TME elevated the phosphorylation of forkhead box O3 (FoxO3α) and protein kinase B (Akt). These findings suggest that TME can enhance myotube hypertrophy by regulating the mTOR signaling pathway, and can rescue DEX-induced muscle atrophy by alleviating atrophic muscle markers mediated by Akt activation. Thus, TME can be a potential therapeutic agent for treating muscle weakness and atrophy.

Anticancer Activity of Periplanetasin-5, an Antimicrobial Peptide from the Cockroach Periplaneta americana.

Cockroaches live in places where various pathogens exist and thus are more likely to use antimicrobial compounds to defend against pathogen intrusions. We previously performed an in silico analysis of the Periplaneta americana transcriptome and detected periplanetasin-5 using an in silico antimicrobial peptide prediction method. In this study, we investigated whether periplanetasin-5 has anticancer activity against the human leukemia cell line K562. Cell growth and survival of K562 cells treated with periplanetasin-5 were decreased in a dose-dependent manner. By using flow cytometric analysis, acridine orange/ethidium bromide (AO/EB) staining and DNA fragmentation, we found that periplanetasin-5 induced apoptotic and necrotic cell death in leukemia cells. In addition, these events were associated with increased levels of the pro-apoptotic proteins Fas and cytochrome c and reduced levels of the anti-apoptotic protein Bcl-2. Periplanetasin-5 induces the cleavage of pro-caspase-9, pro-caspase-8, pro-caspase-3, and poly (ADP-ribose) polymerase (PARP). The above data suggest that periplanetasin-5 induces apoptosis via both the intrinsic and extrinsic pathways. Moreover, caspase-related apoptosis was further confirmed by using the caspase inhibitor carbobenzoxy-valyl-alanyl-aspartyl-[O-methyl]- fluoromethylketone (Z-VAD-FMK), which reversed the periplanetasin-5-induced reduction in cell viability. In conclusion, periplanetasin-5 caused apoptosis in leukemia cells, suggesting its potential utility as an anticancer therapeutic agent.

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.

The insect peptide CopA3 blocks programmed cell death by directly binding caspases and inhibiting their proteolytic activation.

Caspases play essential roles in apoptotic processes, which is necessary for cellular homeostasis. However, over-activation of caspases and subsequent excessive apoptosis is considered a main cause of Parkinson's disease and liver diseases. Here, we found that the insect-derived peptide, CopA3, which has shown antiapoptotic effects in many apoptosis models, directly binds to caspases. The resulting complexes do not dissociate during denaturing polyacrylamide gel electrophoresis, as evidenced by a distinct shift in the migration of caspase reflecting an increase in their molecular weight. Surface plasmon resonance and experiment using cysteine-substituted mutants of CopA3 collectively revealed that binding of CopA3 to caspases is dependent on an internal cysteine residue. Notably, CopA3 binding significantly inhibited proteolytic activation of downstream caspases by upstream caspases. In summary, the demonstration that CopA3 directly binds to caspases and inhibits their activating cleavage suggests a possible therapeutic approach for treating human diseases resulting from uncontrolled apoptosis.

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.

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.

Anti-Inflammatory Activity of Antimicrobial Peptide Allomyrinasin Derived from the Dynastid Beetle, Allomyrina dichotoma.

In a previous work, we performed de novo RNA sequencing of Allomyrina dichotoma using next generation sequencing and identified several antimicrobial peptide candidates based on transcriptome analysis. Among them, a cationic antimicrobial peptide, allomyrinasin, was selected bioinformatically based on its physicochemical properties. Here, we assessed the antimicrobial and anti-inflammatory activities of allomyrinasin against microorganisms and mouse macrophage Raw264.7 cells. Allomyrinasin showed antimicrobial activities against various microbes and decreased the nitric oxide production of the lipopolysaccharide-induced Raw264.7 cells. Furthermore, quantitative RT-PCR and ELISA revealed that allomyrinasin reduced cytokine expression levels in the Raw264.7 cells. We also identified inducible nitric oxide synthase, cyclooxygenase-2 expression, and PGE2 production through western blot analysis and ELISA. We confirmed that allomyrinasin bound to bacterial cell membranes via a specific interaction with lipopolysaccharides. Taken together, these data indicate that allomyrinasin has antimicrobial and anti-inflammatory activities as exemplified in lipopolysaccharide-induced Raw264.7 cells. We have provided a potentially useful antimicrobial peptide candidate that has both antimicrobial and anti-inflammatory activities.

The Antimicrobial Peptide CopA3 Inhibits Clostridium difficile Toxin A-Induced Viability Loss and Apoptosis in Neural Cells.

Numerous studies have reported that enteric neurons involved in controlling neurotransmitter secretion and motility in the gut critically contribute to the progression of gut inflammation. Clostridium difficile toxins, which cause severe colonic inflammation, are also known to affect enteric neurons. Our previous study showed that C. difficile toxin A directly induces neural cell toxicities, such as viability loss and apoptosis. In the current study, we attempted to identify a potent inhibitor of toxin A-induced neural cell toxicity that may aid in managing toxin A-induced gut inflammation. In our recent study, we found that the Korea dung beetle-derived antimicrobial peptide CopA3 completely blocked neural cell apoptosis caused by okadaic acid or 6-OHDA. Here, we examined whether the antimicrobial peptide CopA3 inhibited toxin A-induced neural cell damage. In neuroblastoma SH-SY5Y cells, CopA3 treatment protected against both apoptosis and viability loss caused by toxin A. CopA3 also completely inhibited activation of the pro-apoptotic factor, caspase-3. Additionally, CopA3 rescued toxin A-induced downregulation of neural cell proliferation. However, CopA3 had no effect on signaling through ROS/p38 MAPK/p27kip1, suggesting that CopA3 inhibits toxin A-induced neural cell toxicity independent of this well-characterized toxin A pathway. Our data further suggest that ability of CopA3 to rescue toxin A-induced neural cell damage may also ameliorate the gut inflammation caused by toxin A.

A novel antimicrobial peptide acting via formyl peptide receptor 2 shows therapeutic effects against rheumatoid arthritis.

In oriental medicine, centipede Scolopendra subspinipes mutilans has long been used as a remedy for rheumatoid arthritis (RA), a well-known chronic autoimmune disorder. However, the molecular identities of its bioactive components have not yet been extensively investigated. We sought to identify bioactive molecules that control RA with a centipede. A novel antimicrobial peptide (AMP) (scolopendrasin IX) was identified from Scolopendra subspinipes mutilans. Scolopendrasin IX markedly activated mouse neutrophils, by enhancing cytosolic calcium increase, chemotactic cellular migration, and generation of superoxide anion in neutrophils. As a target receptor for scolopendrasin IX, formyl peptide receptor (FPR)2 mediates neutrophil activation induced by the AMP. Furthermore, scolopendrasin IX administration strongly blocked the clinical phenotype of RA in an autoantibody-injected model. Mechanistically, the novel AMP inhibited inflammatory cytokine synthesis from the joints and neutrophil recruitment into the joint area. Collectively, we suggest that scolopendrasin IX is a novel potential therapeutic agent for the control of RA via FPR2.

A novel role for earthworm peptide Lumbricusin as a regulator of neuroinflammation.

Recently, we reported that Lumbricusin, an antimicrobial peptide isolated from earthworm Lumbricus terrestris, enhanced neuronal proliferation and ameliorated motor dysfunction and dopaminergic neurodegeneration. Accumulating evidence suggests that neurodegeneration is the primary pathological feature of acute or chronic inflammation mediated by microglia, the resident macrophage of the central nervous system. Therefore, microglial activation inhibitors may be useful as therapeutic agents for neurodegenerative diseases. To determine whether Lumbricusin ameliorates neuroinflammation through inhibition of microglial activation by lipopolysaccharides (LPS), we newly synthesized 9-mer Lumbricusin analogues based on the amino acid sequence of Lumbricusin. One of these, Lumbricusin Analogue 5 (LumA5; QLICWRRFR-NH2), markedly reduced expression of enzymes (COX-2, iNOS), cytokines (IL-6, IL-1ß, TNF-α), and signal transduction factors (AKT, MAPKs, NF-κB) involved in inflammation triggered by LPS in vitro and in vivo. In addition, LumA5 inhibited the cytotoxicity of conditioned medium prepared by LPS-activated BV-2 microglia to neuronal SH-SY5Y cells and improved cell viability. These results indicate that LumA5 may be a potential therapeutic agent for the treatment of various neuroinflammatory conditions.

Stilbene epoxidation and detoxification in a Photorhabdus luminescens-nematode symbiosis.

Members of the gammaproteobacterial Photorhabdus genus share mutualistic relationships with Heterorhabditis nematodes, and the pairs infect a wide swath of insect larvae. Photorhabdus species produce a family of stilbenes, with two major components being 3,5-dihydroxy-4-isopropyl-trans-stilbene (compound 1) and its stilbene epoxide (compound 2). This family of molecules harbors antimicrobial and immunosuppressive activities, and its pathway is responsible for producing a nematode "food signal" involved in nematode development. However, stilbene epoxidation biosynthesis and its biological roles remain unknown. Here, we identified an orphan protein (Plu2236) from Photorhabdus luminescens that catalyzes stilbene epoxidation. Structural, mutational, and biochemical analyses confirmed the enzyme adopts a fold common to FAD-dependent monooxygenases, contains a tightly bound FAD prosthetic group, and is required for the stereoselective epoxidation of compounds 1 and 2. The epoxidase gene was dispensable in a nematode-infective juvenile recovery assay, indicating the oxidized compound is not required for the food signal. The epoxide exhibited reduced cytotoxicity toward its producer, suggesting this may be a natural route for intracellular detoxification. In an insect infection model, we also observed two stilbene-derived metabolites that were dependent on the epoxidase. NMR, computational, and chemical degradation studies established their structures as new stilbene-l-proline conjugates, prolbenes A (compound 3) and B (compound 4). The prolbenes lacked immunosuppressive and antimicrobial activities compared with their stilbene substrates, suggesting a metabolite attenuation mechanism in the animal model. Collectively, our studies provide a structural view for stereoselective stilbene epoxidation and functionalization in an invertebrate animal infection model and provide new insights into stilbene cellular detoxification.

Antimicrobial Activity of the Scolopendrasin V Peptide Identified from the Centipede Scolopendra subspinipes mutilans.

In a previous study, we analyzed the transcriptome of Scolopendra subspinipes mutilans using next-generation sequencing technology and identified several antimicrobial peptide candidates. One of the peptides, scolopendrasin V, was selected based on the physicochemical properties of antimicrobial peptides using a bioinformatics strategy. In this study, we assessed the antimicrobial activities of scolopendrasin V using the radial diffusion assay and colony count assay. We also investigated the mode of action of scolopendrasin V using flow cytometry. We found that scolopendrasin V's mechanism of action involved binding to the surface of microorganisms via a specific interaction with lipopolysaccharides, lipoteichoic acid, and peptidoglycans, which are components of the bacterial membrane. These results provide a basis for developing peptide antibiotics.