Abstract
Anionic peptides of scorpions are molecules rich in aspartic and/or glutamic acid residues and correspond to a class of peptides without disulfide bonds that are still little explored. TanP is a linear anionic peptide (50 amino acid residues and net charge −20) present in the venom gland of the scorpion, Tityus stigmurus, with chelating properties for Cu2+ ion and immunomodulatory properties. The therapeutic application of chelating molecules is related to cases of acute or chronic intoxication by metals, neurodegenerative diseases, hematological diseases, healing of skin wounds, cardiovascular diseases, and cancer. In this approach, the chelating activity of TanP was evaluated in relation to new metal ions (Fe2+ and Zn2+) of biological importance, as well as its antioxidant, hemostatic, immunomodulatory, and healing potential, aiming to expand the biological and biotechnological potential of this peptide. TanP (25 µM) was able to form stable complexes with Fe2+ in a ratio of 1:5 (TanP: Fe2+). Theoretical results suggest that TanP can work as a sensor to identify and quantify Fe2+ ions. The fluorescence intensity of TanP (1.12 µM) decreased significantly after the addition of Fe2+, obtaining the highest ratio 1: 7.4 (TanP: Fe2+) that led to the lowest fluorescence intensity. For Zn2+, no relevant spectral change was noted. TanP (50 µM) showed a maximum of 3% of hemolytic activity, demonstrating biocompatibility, as well as exhibiting a 1,1-diphenyl-2-picrylhydrazyl radical–scavenging activity of above 70% at all the concentrations tested (1–25 μM), and 89.7% iron-chelating activity at 25 μM and 96% hydroxyl radical–scavenging activity at 73.6 μM. In addition, TanP (12.5 and 25 µM) revealed an anticoagulant effect, prolonging the clotting time in prothrombin time and activated partial thromboplastin time assays, with no fibrinogenolytic activity. TanP (12.5 and 25 µM) induced the release of TNF-α by murine macrophages, in the absence of lipopolysaccharides, with a concentration-dependent increase and also stimulated the migration of 3T3 cells in the in vitro healing assay. Thus, TanP revealed a multifunctional potential, being useful as a prototype for the development of new therapeutic and biotechnological agents.
Highlights
Anionic, or acidic, peptides are a new class of scorpion venom peptides, which have been rarely identified and poorly characterized so far but are widely present in the venom glands of all detected species of scorpions (Shi et al, 2018)
As on the Zn2+ complexes, dication iron interacts with one oxygen of each acetate carboxylate; four water molecules are present on the first hydration shell and form an octahedral complex
High concentrations of Fe2+ and Cu2+ ions cause these metals to react with molecular oxygen, generating reactive oxygen species (ROS) that damage DNA, lipids, and proteins (Di Bella et al, 2017)
Summary
Acidic, peptides are a new class of scorpion venom peptides, which have been rarely identified and poorly characterized so far but are widely present in the venom glands of all detected species of scorpions (Shi et al, 2018). These molecules are peptides without disulfide bonds, rich in aspartic and glutamic acid residues, with an isoelectric point less than 5.0, showing high hydrophilic properties and secondary structures composed by random regions, α-helix domains, and spiral structures (Nie et al, 2012; Shi et al, 2018). In vitro assays have demonstrated that TanP has the chelating activity of Cu2+ ions and revealed an immunomodulatory potential, since it induced the proliferation of macrophages and reduced the release of nitric oxide by these cells, in the presence of lipopolysaccharides (LPS) (Melo et al, 2017)
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