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.

Scorpion venom constitutes a rich source of biologically active compounds with high potential for therapeutic and biotechnological applications that can be used as prototypes for the design of new drugs. The aim of this study was to characterize the structural conformation, evaluate the antimicrobial activity, and gain insight into the possible action mechanism underlying it, for two new analog peptides of the scorpion peptide Stigmurin, named StigA25 and StigA31. The amino acid substitutions in the native sequence for lysine residues resulted in peptides with higher positive net charge and hydrophobicity, with an increase in the theoretical helical content. StigA25 and StigA31 showed the capacity to modify their structural conformation according to the environment, and were stable to pH and temperature variation—results similar to the native peptide. Both analog peptides demonstrated broad-spectrum antimicrobial activity in vitro, showing an effect superior to that of the native peptide, being non-hemolytic at the biologically active concentrations. Therefore, this study demonstrates the therapeutic potential of the analog peptides from Stigmurin and the promising approach of rational drug design based on scorpion venom peptide to obtain new anti-infective agents.

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In Brazil, envenomation by snakes of the genus Bothrops is clinically relevant, particularly for the species Bothrops jararaca and B. erythromelas. The most effective treatment for envenomation by snakes is the administration of antivenoms associated with adjuvants. Novel adjuvants are required to reduce side effects and maximize the efficiency of conventional serum and vaccine formulations. The polymer chitosan has been shown to have immunoadjuvant properties, and it has been used as a platform for delivery systems. In this context, we evaluated the potential immunoadjuvant properties of chitosan nanoparticles (CNPs) loaded with B. jararaca and B. erythromelas venoms in the production of sera against these venoms. Stable CNPs were obtained by ionic gelation, and mice were immunized subcutaneously for 6 weeks with 100 µL of each snake venom at concentrations of 5.0 or 10.0% (w/w), encapsulated in CNPs or associated with aluminium hydroxide (AH). The evaluation of protein interactions with the CNPs revealed their ability to induce antibody levels equivalent to those of AH, even with smaller doses of antigen. In addition, the CNPs were less inflammatory due to their modified release of proteins. CNPs provide a promising approach for peptide/protein delivery from snake venom and will be useful for new vaccines.

Anionic Peptides are molecules rich in aspartic acid (Asp) and/or glutamic acid (Glu) residues in the primary structure. This work presents, for the first time, structural characterization and biological activity assays of an anionic peptide from the venom of the scorpion Tityus stigmurus, named TanP. The three-dimensional structure of TanP was obtained by computational modeling and refined by molecular dynamic (MD) simulations. Furthermore, we have performed circular dichroism (CD) analysis to predict TanP secondary structure, and UV-vis spectroscopy to evaluate its chelating activity. CD indicated predominance of random coil conformation in aqueous medium, as well as changes in structure depending on pH and temperature. TanP has chelating activity on copper ions, which modified the peptide's secondary structure. These results were corroborated by MD data. The molar ratio of binding (TanP:copper) depends on the concentration of peptide: at lower TanP concentration, the molar ratio was 1:5 (TanP:Cu), whereas in concentrated TanP solution, the molar ratio was 1:3 (TanP:Cu). TanP was not cytotoxic to non-neoplastic or cancer cell lines, and showed an ability to inhibit the in vitro release of nitric oxide by LPS-stimulated macrophages. Altogether, the results suggest TanP is a promising peptide for therapeutic application as a chelating agent.

Microbial resistance to conventional antibiotics is a public health problem worldwide, motivating the search for new therapeutic alternatives in varied natural sources. Cationic peptides without disulfide bridges from scorpions have been targeted in this context, mainly due to their multifunctional action and the limited ability of microorganisms to develop resistance against them. The present study was focused on Stigmurin and TsAP-2, cationic peptides found in the transcriptome of the venom gland from the scorpion Tityus stigmurus. The aims were: to assess the secondary structure of TsAP-2 and the structural stability of both peptides by circular dichroism; to evaluate their antiproliferative effect, and antimicrobial activities in vitro, ex vivo and in vivo; and to investigate their therapeutic potential in a murine model of polymicrobial sepsis. Stigmurin and TsAP-2 secondary structures responded similarly to environment polarity changes, and were stable to temperature and pH variation. Both peptides showed antiproliferative effect on tumor cells. TsAP-2 showed lower cytotoxicity to normal cells, and had a mitogenic activity on murine macrophages. Stigmurin demonstrated bactericidal and bacteriostatic activity, depending on the microorganism, whereas TsAP-2 had bactericidal action upon different bacterial strains analyzed. Both peptides were able to reduce leukocyte migration, TNF-α levels and microorganism load in the peritoneal cavity after induction of experimental sepsis, decreasing inflammation in the lung and cecum of septic animals. TsAP-2 also reduced the release of nitric oxide in the peritoneal cavity. Taken together, these data suggest that Stigmurin and TsAP-2 are structurally stable molecules and are efficient in the control of the infectious focus in polymicrobial sepsis, with potential use as a prototype for the rational design of novel therapeutic agents.

The global rise of infectious disease outbreaks and the progression of microbial resistance reinforce the importance of researching new biomolecules. Obtained from the hydrolysis of chitosan, chitooligosaccharides (COSs) have demonstrated several biological properties, including antimicrobial, and greater advantage over chitosan due to their higher solubility and lower viscosity. Despite the evidence of the biotechnological potential of COSs, their effects on trypanosomatids are still scarce. The objectives of this study were the enzymatic production, characterization, and in vitro evaluation of the cytotoxic, antibacterial, antifungal, and antiparasitic effects of COSs. NMR and mass spectrometry analyses indicated the presence of a mixture with 81% deacetylated COS and acetylated hexamers. COSs demonstrated no evidence of cytotoxicity upon 2 mg/mL. In addition, COSs showed interesting activity against bacteria and yeasts and a time-dependent parasitic inhibition. Scanning electron microscopy images indicated a parasite aggregation ability of COSs. Thus, the broad biological effect of COSs makes them a promising molecule for the biomedical industry.

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