Exploring the neuroprotective potential of antimicrobial peptides from Dinoponera quadriceps venom against pentylenetetrazole-induced seizures in vivo

Epilepsy affects around 50 million people worldwide and 30% of patients have difficulty controlling the disease. The search for substances that can fill the existing gaps in the treatment of epilepsy is of great importance. Arthropod venoms are promising sources for this purpose due to the presence of small peptides that modulate the activity of ion channels and neuron receptors. The aim of this study was to investigate dinoponeratoxins from the Dinoponera quadriceps ant venom (M-PONTX-Dq3a, M-PONTX-Dq3b and M-PONTX-Dq3c) as potential anticonvulsants. We evaluated them in a seizure model induced by pentylenetetrazole (PTZ) in male swiss mice. Interestingly, intraperitoneal treatment with each peptide increased the time until the first seizure and the percentage of survival, with M-PONTX-Dq3b showing the best results. M-PONTX-Dq3a was discarded due to the appearance of some signs of toxicity with the increase in malondialdehyde (MDA) levels in the striatum. Both, M-PONTX-Dq3b and M-PONTX-Dq3c decreased iNOS and TNF-α in the hippocampus. Notably, M-PONTX-Dq3c treatment decreased the levels of MDA and nitrite in the cortex and hippocampus. Our results indicate that, M-PONTX-Dq3b and M-PONTX-Dq3c have anticonvulsant activity and exhibit anti-inflammatory effects in epilepsy, offering new perspectives for biopharmaceutical development.

Effect from dinoponeratoxin M-PONTXDq3a arginine and lysine substituted analogues against Staphylococcus aureus strains

The growing incidence of methicillin-resistant Staphylococcus aureus (MRSA) infections is associated with increased mortality rates, which has generated interest in the development of antimicrobial peptides (AMP), such as those found in the giant ant Dinoponera quadríceps. In order to improve the net positive charge and the antibacterial activity of the AMP, amino acids with positive side chain single substituted analogues have been proposed, mainly arginine or lysine. The present work aims to study the antimicrobial activity of the analogues of M-PONTX-Dq3a, a 23 amino acid AMP identified in the D. quadriceps venom. M-PONTX-Dq3a[1-15], a fragment containing the 15 central amino acids, and eight derivatives of single arginine or lysine substituted analogues were proposed. The antimicrobial activity of peptides was evaluated against Staphylococcus aureus ATCC 6538 P (MSSA) and ATCC 33591 (MRSA) strains, followed by minimum inhibitory concentration (MIC), minimum lethal concentration (MLC), and minimum biofilm inhibitory concentration (MBIC) measurement. The membrane permeability was then assessed via crystal violet assay and flow cytometry analysis. The effect of exposure time on microbial viability (Time-Kill) was evaluated. Finally, ultrastructural alterations were evaluated through scanning electron microscopy (SEM). Both arginine-substituted peptides [Arg]3M-PONTX-Dq3a[1-15] and [Arg]4M-PONTX-Dq3a[1-15], showed lowest MIC and MLC values (each 0.78 μM). In the biofilm formation assays, the peptide [Arg]3M-PONTX-Dq3a [1-15] showed MBIC of 3.12 μM against the two tested strains. Both peptides were able to alter the membrane permeability approximately by 80%. The treatment with MIC was able to eliminate bacteria after 2 h of contact on the other hand, treatment with half of the MIC, the population of both bacterial strains remained constant for up to 12 h, indicating a possible bacteriostatic effect. The SEM results showed that the treatment with the lowest concentration (0.78 μM) of both peptides caused disruption of the cell membrane, destabilization of the intercellular interaction and the CLM of [Arg]4M-PONTX-Dq3a [1-15] resulted in the complete eradication of the bacteria. Thus, this study describes two AMPs active against MSSA and MRSA and also inhibits the biofilm formation of these stains. This study finds [Arg]3M-PONTX-Dq3a[1-15] and [Arg]4M-PONTX-Dq3a[1-15] as alternative substances to treat resistant and/or biofilm-forming strains.

Neglected Zoonotic Diseases: Advances in the Development of Cell-Penetrating and Antimicrobial Peptides against Leishmaniosis and Chagas Disease

In 2020, the WHO established the road map for neglected tropical diseases 2021-2030, which aims to control and eradicate 20 diseases, including leishmaniosis and Chagas disease. In addition, since 2015, the WHO has been developing a Global Action Plan on Antimicrobial Resistance. In this context, the achievement of innovative strategies as an alternative to replace conventional therapies is a first-order socio-sanitary priority, especially regarding endemic zoonoses in poor regions, such as those caused by Trypanosoma cruzi and Leishmania spp. infections. In this scenario, it is worth highlighting a group of natural peptide molecules (AMPs and CPPs) that are promising strategies for improving therapeutic efficacy against these neglected zoonoses, as they avoid the development of toxicity and resistance of conventional treatments. This review presents the novelties of these peptide molecules and their ability to cross a whole system of cell membranes as well as stimulate host immune defenses or even serve as vectors of molecules. The efforts of the biotechnological sector will make it possible to overcome the limitations of antimicrobial peptides through encapsulation and functionalization methods to obtain approval for these treatments to be used in clinical programs for the eradication of leishmaniosis and Chagas disease.

Unravelling the potential of insects for medicinal purposes - A comprehensive review

Entomotherapy, the use of insects for medicinal purposes, has been practised for centuries in many countries around the world. More than 2100 edible insect species are eaten by humans, but little is known about the possibility of using these insects as a promising alternative to traditional pharmaceuticals for treating diseases. This review offers a fundamental understanding of the therapeutic applications of insects and how they might be used in medicine. In this review, 235 insect species from 15 orders are reported to be used as medicine. Hymenoptera contains the largest medicinal insect species, followed by Coleoptera, Orthoptera, Lepidoptera, and Blattodea. Scientists have examined and validated the potential uses of insects along with their products and by-products in treating various diseases, and records show that they are primarily used to treat digestive and skin disorders. Insects are known to be rich sources of bioactive compounds, explaining their therapeutic features such as anti-inflammatory, antimicrobial, antiviral, and so on. Challenges associated with the consumption of insects (entomophagy) and their therapeutic uses include regulation barriers and consumer acceptance. Moreover, the overexploitation of medicinal insects in their natural habitat has led to a population crisis, thus necessitating the investigation and development of their mass-rearing procedure. Lastly, this review suggests potential directions for developing insects used in medicine and offers advice for scientists interested in entomotherapy. In future, entomotherapy may become a sustainable and cost-effective solution for treating various ailments and has the potential to revolutionize modern medicine.

The mechanism underlying toxicity of a venom peptide against insects reveals how ants are master at disrupting membranes

Hymenopterans represent one of the most abundant groups of venomous organisms but remain little explored due to the difficult access to their venom. The development of proteo-transcriptomic allowed us to explore diversity of their toxins offering interesting perspectives to identify new biological active peptides. This study focuses on U9 function, a linear, amphiphilic and polycationic peptide isolated from ant Tetramorium bicarinatum venom. It shares physicochemical properties with M-Tb1a, exhibiting cytotoxic effects through membrane permeabilization. In the present study, we conducted a comparative functional investigation of U9 and M-Tb1a and explored the mechanisms underlying their cytotoxicity against insect cells. After showing that both peptides induced the formation of pores in cell membrane, we demonstrated that U9 induced mitochondrial damage and, at high concentrations, localized into cells and induced caspase activation. This functional investigation highlighted an original mechanism of U9 questioning on potential valorization and endogen activity in T. bicarinatum venom.

Bioactivity Profiling of In Silico Predicted Linear Toxins from the Ants Myrmica rubra and Myrmica ruginodis

The venoms of ants (Formicidae) are a promising source of novel bioactive molecules with potential for clinical and agricultural applications. However, despite the rich diversity of ant species, only a fraction of this vast resource has been thoroughly examined in bioprospecting programs. Previous studies focusing on the venom of Central European ants (subfamily Myrmicinae) identified a number of short linear decapeptides and nonapeptides resembling antimicrobial peptides (AMPs). Here, we describe the in silico approach and bioactivity profiling of 10 novel AMP-like peptides from the fellow Central European myrmicine ants Myrmica rubra and Myrmica ruginodis. Using the sequences of known ant venom peptides as queries, we screened the venom gland transcriptomes of both species. We found transcripts of nine novel decapeptides and one novel nonapeptide. The corresponding peptides were synthesized for bioactivity profiling in a broad panel of assays consisting of tests for cytotoxicity as well as antiviral, insecticidal, and antimicrobial activity. U-MYRTX-Mrug5a showed moderately potent antimicrobial effects against several bacteria, including clinically relevant pathogens such as Listeria monocytogenes and Staphylococcus epidermidis, but high concentrations showed negligible cytotoxicity. U-MYRTX-Mrug5a is, therefore, a probable lead for the development of novel peptide-based antibiotics.

Profiling hymenopteran venom toxins: Protein families, structural landscape, biological activities, and pharmacological benefits

Hymenopterans are an untapped source of venom secretions. Their recent proteo-transcriptomic studies have revealed an extraordinary pool of toxins that participate in various biological processes, including pain, paralysis, allergic reactions, and antimicrobial activities. Comprehensive and clade-specific campaigns to collect hymenopteran venoms are therefore needed. We consider that data-driven bioprospecting may help prioritise sampling and alleviate associated costs. This work established the current protein landscape from hymenopteran venoms to evaluate possible sample bias by studying their origins, sequence diversity, known structures, and biological functions. We collected all 282 reported hymenopteran toxins (peptides and proteins) from the UniProt database that we clustered into 21 protein families from the three studied clades - wasps, bees, and ants. We identified 119 biological targets of hymenopteran toxins ranging from pathogen membranes to eukaryotic proteases, ion channels and protein receptors. Our systematic study further extended to hymenopteran toxins' therapeutic and biotechnological values, where we revealed promising applications in crop pests, human infections, autoimmune diseases, and neurodegenerative disorders.

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The hymenopteran toxin diversity includes 21 protein families from 81 species.

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Some toxins are shared across wasps, bees and ants, others are clade-specific.

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Their venoms contain membrane-active peptides, neurotoxins, allergens and enzymes.

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Hymenopteran toxins have been tested against a total of 119 biological targets.

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Hymenopteran toxins were predominantly evaluated as anti-infective agents.

Multipurpose peptides: The venoms of Amazonian stinging ants contain anthelmintic ponericins with diverse predatory and defensive activities

In the face of increasing drug resistance, the development of new anthelmintics is critical for controlling nematodes that parasitise livestock. Although hymenopteran venom toxins have attracted attention for applications in agriculture and medicine, few studies have explored their potential as anthelmintics. Here we assessed hymenopteran venoms as a possible source of new anthelmintic compounds by screening a panel of ten hymenopteran venoms against Haemonchus contortus, a major pathogenic nematode of ruminants. Using bioassay-guided fractionation coupled with liquid chromatography-tandem mass spectrometry, we identified four novel anthelmintic peptides (ponericins) from the venom of the neotropical ant Neoponera commutata and the previously described ponericin M-PONTX-Na1b from Neoponera apicalis venom. These peptides inhibit H. contortus development with IC₅₀ values of 2.8-5.6 μM. Circular dichroism spectropolarimetry indicated that the ponericins are unstructured in aqueous solution but adopt α-helical conformations in lipid mimetic environments. We show that the ponericins induce non-specific membrane perturbation, which confers broad-spectrum antimicrobial, insecticidal, cytotoxic, hemolytic, and algogenic activities, with activity across all assays typically correlated. We also show for the first time that ponericins induce spontaneous pain behaviour when injected in mice. We propose that the broad-spectrum activity of the ponericins enables them to play both a predatory and defensive role in neoponeran ants, consistent with their high abundance in venom. This study reveals a broader functionality for ponericins than previously assumed, and highlights both the opportunities and challenges in pursuing ant venom peptides as potential therapeutics.

Dinoponera quadriceps venom as a source of active agents against Staphylococcus aureus

Staphylococcus aureus is a highly virulent pathogen, capable of biofilm formation and responsible for thousands of deaths each year. The prevalence of Methicillin-Resistant S. aureus (MRSA) strains has increased in recent years and thus, the development of new antibiotics has become necessary. Antimicrobial Peptides (AMPs) are effective against a variety of multidrug-resistant bacteria and low levels of resistance have been reported regarding these molecules. Dinoponera quadriceps ant venom (DqV) has been described regarding its effect against S. aureus. In this study, we have evaluated the antibacterial effect of DqV-AMPs, the dinoponeratoxins (DNTxs), against Methicillin-Sensitive and a Methicillin-Resistant S. aureus strains. Our results show DNTx M-PONTX-Dq3a as a potent inhibitor of both strains, being able to prevent biofilm formation at low micromolar range (0.78-3.12 μM). It also showed a short-time effect through membrane disruption. M-PONTX-Dq3a opens up new perspectives for the prevention of biofilm formation through the development of anti-adhesive surface coatings on medical devices, as well as the treatment of resistant strains in skin or soft tissue infections.

Arg-substituted VmCT1 analogs reveals promising candidate for the development of new antichagasic agent

VmCT1 is an antimicrobial peptide (AMP) isolated from the venom of the scorpion Vaejovis mexicanus with antimicrobial, anticancer and antimalarial activities, which the rational design with Arg-substitution has yielded AMPs with higher antimicrobial activity than VmCT1. Chagas is a neglected tropical disease, becoming the development of new antichagasic agents is urgent. Thus, we aimed to evaluate the antichagasic effect of VmCT1 and three Arg-substituted analogues, as well their action mechanism. Peptides were tested against the epimastigote, trypomastigote, amastigote forms of Trypanossoma cruzi Y strain and against LLC-MK2 mammalian cells. The mechanism of action of these peptides was evaluated by means of flow cytometry and scanning electron microscopy. VmCT1 presented activity against all three forms of T. cruzi, with EC50 against trypomastigote forms of 1.37 μmol L-1 and selectivity index (SI) of 58. [Arg]3-VmCT1, [Arg]7-VmCT1 and [Arg]11-VmCT1 also showed trypanocidal effect, but [Arg]11-VmCT1 had the best effect, being able to decrease the EC50 against trypomastigote forms to 0.8 μmol L-1 and increase SI to 175. Necrosis was cell death pathway of VmCT1, as well [Arg]7-VmCT1 and [Arg]11-VmCT1, such as observed by membrane damage in flow cytometry analyses and scanning-electron-microscopy. In conclusion, [Arg]11-VmCT1 revealed promising as a candidate for new antichagasic therapeutics.

Comprehensive analysis of peptides and low molecular weight components of the giant ant Dinoponera quadriceps venom

Ants (Hymenoptera, Apocrita, Aculeata, Formicoidea) comprise a well-succeeded group of animals. Like bees and wasps, ants are mostly venomous, having a sting system to deliver a mixture of bioactive organic compounds and peptides. The predatory giant ant Dinoponera quadriceps belongs to the subfamily Ponerinae that includes one of the largest known ant species in the world. In the present study, low molecular weight compounds and peptides were identified by online peptide mass fingerprint. These include neuroactive biogenic amines (histamine, tyramine, and dopamine), monoamine alkaloid (phenethylamine), free amino acids (e.g. glutamic acid and proline), free thymidine, and cytosine. To the best of our knowledge, most of these components are described for the first time in an ant venom. Multifunctional dinoponeratoxin peptide variants (pilosulin- and ponericin-like peptides) were characterized that possess antimicrobial, hemolytic, and histamine-releasing properties. These venom components, particularly peptides, might synergistically contribute to the overall venom activity and toxicity, for immobilizing live prey, and for defending D. quadriceps against aggressors, predators, and potential microbial infection.

It Takes Two: Dimerization Is Essential for the Broad-Spectrum Predatory and Defensive Activities of the Venom Peptide Mp1a from the Jack Jumper Ant Myrmecia pilosula

Ant venoms have recently attracted increased attention due to their chemical complexity, novel molecular frameworks, and diverse biological activities. The heterodimeric peptide ∆-myrtoxin-Mp1a (Mp1a) from the venom of the Australian jack jumper ant, Myrmecia pilosula, exhibits antimicrobial, membrane-disrupting, and pain-inducing activities. In the present study, we examined the activity of Mp1a and a panel of synthetic analogues against the gastrointestinal parasitic nematode Haemonchus contortus, the fruit fly Drosophila melanogaster, and for their ability to stimulate pain-sensing neurons. Mp1a was found to be both insecticidal and anthelmintic, and it robustly activated mammalian sensory neurons at concentrations similar to those reported to elicit antimicrobial and cytotoxic activity. The native antiparallel Mp1a heterodimer was more potent than heterodimers with alternative disulfide connectivity, as well as monomeric analogues. We conclude that the membrane-disrupting effects of Mp1a confer broad-spectrum biological activities that facilitate both predation and defense for the ant. Our structure-activity data also provide a foundation for the rational engineering of analogues with selectivity for particular cell types.

Venom alkaloids against Chagas disease parasite: search for effective therapies

Chagas disease is an important disease affecting millions of patients in the New World and is caused by a protozoan transmitted by haematophagous kissing bugs. It can be treated with drugs during the early acute phase; however, effective therapy against the chronic form of Chagas disease has yet to be discovered and developed. We herein tested the activity of solenopsin alkaloids extracted from two species of fire ants against the protozoan parasite Trypanosoma cruzi, the aetiologic agent of Chagas disease. Although IC₅₀ determinations showed that solenopsins are more toxic to the parasite than benznidazole, the drug of choice for Chagas disease treatment, the ant alkaloids presented a lower selectivity index. As a result of exposure to the alkaloids, the parasites became swollen and rounded in shape, with hypertrophied contractile vacuoles and intense cytoplasmic vacuolization, possibly resulting in osmotic stress; no accumulation of multiple kinetoplasts and/or nuclei was detected. Overexpressing phosphatidylinositol 3-kinase-an enzyme essential for osmoregulation that is a known target of solenopsins in mammalian cells-did not prevent swelling and vacuolization, nor did it counteract the toxic effects of alkaloids on the parasites. Additional experimental results suggested that solenopsins induced a type of autophagic and programmed cell death in T. cruzi. Solenopsins also reduced the intracellular proliferation of T. cruzi amastigotes in infected macrophages in a concentration-dependent manner and demonstrated activity against Trypanosoma brucei rhodesiense bloodstream forms, which is another important aetiological kinetoplastid parasite. The results suggest the potential of solenopsins as novel natural drugs against neglected parasitic diseases caused by kinetoplastids.

Antifungal In Vitro Activity of Pilosulin- and Ponericin-Like Peptides from the Giant Ant Dinoponera quadriceps and Synergistic Effects with Antimycotic Drugs

Venoms from ants comprise a rich source of bioactive peptides, including antimicrobial peptides. From the proteome and peptidome of the giant ant Dinoponera quadriceps venom, members of five known classes of antimicrobial peptides were disclosed (e.g., dermaseptin-, defensin-, ICK-, pilosulin- and ponericin-like types). Based on comparative analysis, these family members have structural determinants that indicate they could display antimicrobial activities. In previous works, pilosulin- and ponericin-like peptides were demonstrated to be active against bacteria, fungi, and parasites. Herein, the antifungal activity of ponericin- and pilosulin-like peptides were assessed, aiming at the expansion of the knowledge about AMPs in predatory ants and the development of new microbicide strategies to deal with difficult-to-treat fungal infections. Synthetic pilosulin- (Dq-2562, Dq-1503, and Dq-1319) and ponericin-like (Dq-3162) peptides were evaluated for their fungicide and fungistatic activities against different species of Candida, including a drug-resistant clinical strain. The MICs and MLCs were determined for all peptides individually and in combination with general antifungal drugs by the microdilution method. The time-kill kinetic curves were set up by means of a luminescent reagent, of which the light signal is proportional to the number of viable cells. The candicidal synergism observed by the combination of subinhibitory concentrations of peptides and general antimycotic drugs were quantified by the checkerboard test and fluorescent dye permeation assay. The influence of ergosterol on the antifungal activity was verified by supplementation of culture medium. The pilosulin- (Dq-2562 and Dq-1503) and ponericin-like (Dq-3162) were the most active peptides, displaying a broad spectrum of antifungal activity in vitro, with MICs in the range of 0.625 to 10 µM. The combination of peptides and conventional antimycotic drugs displayed a synergistic reduction in the MIC values of individual peptides and drugs, while soluble ergosterol in the culture medium increased the MICs. The fungicide and fungistatic activity of the individual peptides and peptides in combination with antimycotics were time-dependent with a rapid onset of action and long-lasting effect, which involved membrane disruption as an underlying mechanism of their action. Altogether, pilosulin- and ponericin-like peptides from the giant ant D. quadriceps venom display a broad-spectrum of candicidal activity, what allows their inclusion in the row of the antifungal peptides and gives support for further studies on the development of strategies to fight candidiasis.

Antichagasic effect of hemocyanin derived from antimicrobial peptides of penaeus monodon shrimp

Trypanosoma cruzi, the etiological agent of Chagas disease, is responsible for the infection of millions of people worldwide and it is a public health problem, without an effective cure. Four fragments with antimicrobial potential from the hemocyanin of Penaeus monodon shrimp were identified using a computer software AMPA. The present study aimed to evaluate the antichagasic effect of these four peptides (Hmc364-382, Hmc666-678, Hmc185-197 and Hmc476-498). The peptides were tested against the epimastigote, trypomastigote and amastigote forms of Trypanosoma cruzi Y strain (benznidazole-resistant strain) and cytotoxicity in mammalian cells was evaluated against LLC-MK2 lineage cells. Two fragments (Hmc364-382, Hmc666-678) showed activity against the epimastigote and trypomastigote forms and their selectivity index (SI) was calculated. The Hmc364-382 peptide was considered the most promising (SI > 50) one and it was used for further studies, using flow cytometry analyses with specific molecular probes and scanning electron microscopy (SEM). Hmc364-382 was able to induce cell death in T. cruzi through necrosis, observed by loss of membrane integrity in flow cytometry analyses and pore formation in SEM. Overall, Hmc364-382 open perspectives to the development of new antichagasic agents.

Wasp venom peptide as a new antichagasic agent

Chagas disease is caused by Trypanosoma cruzi and affects approximately 10 million people a year worldwide. The only two treatment options, benznidazole and nifurtimox, have low efficacy and high toxicity towards human cells. Mastoporan peptide (MP) a small cationic AMP from the venom of the wasp Polybia paulista has been reported as a potent trypanocidal agent. Thus, we evaluated the antichagasic effect of another AMP from the venom of the same wasp Polybia paulista, polybia-CP (ILGTILGLLSKL-NH₂), and investigated its mechanism of action against different stages of the trypanosomal cells life cycle. Polybia-CP was tested against the epimastigote, trypomastigote and amastigote forms of the T. cruzi Y strain (benznidazole-resistant strain) and inhibited the development of these forms. We also assessed the selectivity of the AMP against mammalian cells by exposing LLC-MK2 cells to polybia-CP, the peptide presented a high selectivity index (>106). The mechanism of action of polybia-CP on trypanosomal cells was investigated by flow cytometry, scanning electron microscopy (SEM) and enzymatic assays with T. cruzi GAPDH (tcGAPDH), enzyme that catalyzes the sixth step of glycolysis. Polybia-CP induced phosphatidylserine exposure, it also increased the formation of reactive species of oxigen (ROS) and reduced the transmembrane mitochondrial potential. Polybia-CP also led to cell shrinkage, evidencing apoptotic cell death. We did not observe the inhibition of tcGAPDH or autophagy induction. Altogether, polybia-CP has shown the features of a promising template for the development of new antichagasic agents.

Natural Occurrence in Venomous Arthropods of Antimicrobial Peptides Active against Protozoan Parasites

Arthropoda is a phylum of invertebrates that has undergone remarkable evolutionary radiation, with a wide range of venomous animals. Arthropod venom is a complex mixture of molecules and a source of new compounds, including antimicrobial peptides (AMPs). Most AMPs affect membrane integrity and produce lethal pores in microorganisms, including protozoan pathogens, whereas others act on internal targets or by modulation of the host immune system. Protozoan parasites cause some serious life-threatening diseases among millions of people worldwide, mostly affecting the poorest in developing tropical regions. Humans can be infected with protozoan parasites belonging to the genera Trypanosoma, Leishmania, Plasmodium, and Toxoplasma, responsible for Chagas disease, human African trypanosomiasis, leishmaniasis, malaria, and toxoplasmosis. There is not yet any cure or vaccine for these illnesses, and the current antiprotozoal chemotherapeutic compounds are inefficient and toxic and have been in clinical use for decades, which increases drug resistance. In this review, we will present an overview of AMPs, the diverse modes of action of AMPs on protozoan targets, and the prospection of novel AMPs isolated from venomous arthropods with the potential to become novel clinical agents to treat protozoan-borne diseases.

Bottom-Up Proteomic Analysis of Polypeptide Venom Components of the Giant Ant Dinoponera Quadriceps

Ant species have specialized venom systems developed to sting and inoculate a biological cocktail of organic compounds, including peptide and polypeptide toxins, for the purpose of predation and defense. The genus Dinoponera comprises predatory giant ants that inoculate venom capable of causing long-lasting local pain, involuntary shaking, lymphadenopathy, and cardiac arrhythmias, among other symptoms. To deepen our knowledge about venom composition with regard to protein toxins and their roles in the chemical-ecological relationship and human health, we performed a bottom-up proteomics analysis of the crude venom of the giant ant D. quadriceps, popularly known as the "false" tocandiras. For this purpose, we used two different analytical approaches: (i) gel-based proteomics approach, wherein the crude venom was resolved by denaturing sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and all protein bands were excised for analysis; (ii) solution-based proteomics approach, wherein the crude venom protein components were directly fragmented into tryptic peptides in solution for analysis. The proteomic data that resulted from these two methodologies were compared against a previously annotated transcriptomic database of D. quadriceps, and subsequently, a homology search was performed for all identified transcript products. The gel-based proteomics approach unequivocally identified nine toxins of high molecular mass in the venom, as for example, enzymes [hyaluronidase, phospholipase A1, dipeptidyl peptidase and glucose dehydrogenase/flavin adenine dinucleotide (FAD) quinone] and diverse venom allergens (homologous of the red fire ant Selenopsis invicta) and venom-related proteins (major royal jelly-like). Moreover, the solution-based proteomics revealed and confirmed the presence of several hydrolases, oxidoreductases, proteases, Kunitz-like polypeptides, and the less abundant inhibitor cysteine knot (ICK)-like (knottin) neurotoxins and insect defensin. Our results showed that the major components of the D. quadriceps venom are toxins that are highly likely to damage cell membranes and tissue, to cause neurotoxicity, and to induce allergic reactions, thus, expanding the knowledge about D. quadriceps venom composition and its potential biological effects on prey and victims.

Analogs of the Scorpion Venom Peptide Stigmurin: Structural Assessment, Toxicity, and Increased Antimicrobial Activity

Scorpion venom is a rich source of biologically active components and various peptides with high-potential therapeutic use that have been characterized for their antimicrobial and antiproliferative activities. Stigmurin is a peptide identified from the Tityus stigmurus venom gland with high antibacterial and antiproliferative activities and low toxicity. Amino acid substitutions in peptides without a disulfide bridge sequence have been made with the aim of reducing their toxicity and increasing their biological activities. The purpose of this study was to evaluate the structural conformation and structural stability, as well as antimicrobial, antiproliferative, and hemolytic activities of two peptide analogs to Stigmurin, denominated StigA6 and StigA16. In silico analysis revealed the α-helix structure for both analog peptides, which was confirmed by circular dichroism. Data showed that the net charge and hydrophobic moment of the analog peptides were higher than those for Stigmurin, which can explain the increase in antimicrobial activity presented by them. Both analog peptides exhibited activity on cancerous cells similar to the native peptide; however, they were less toxic when tested on the normal cell line. These results reveal a potential biotechnological application of the analog peptides StigA6 and StigA16 as prototypes to new therapeutic agents.