Análise estrutural e avaliação das atividades biológicas de peptídeos análogos de stigmurina

Abstract

Resistance to antimicrobials and antineoplastic agents is considered a worldwide public health problem and the search for new molecules that are more effective or that supplement existing therapies is necessary. In this context, Stigmurin, a peptide native to the venom of the yellow scorpion Tityus stigmurus, showed antibacterial activity on gram-positive bacteria, with antiproliferative effect on different cancer cells, low toxicity in human erythrocytes,and trypanocidal activity on Trypanossoma cruzi. In order to expand the potential of the native peptide, analogs to Stigmurin were designed and analyzed for structure and different biological activities. The structural analysis of the analog peptides, named StigA8 and StigA18, was obtained by structural prediction, molecular modeling, and circular dichroism. In vitro biocompatibility was evaluated in human red blood cells, murine fibroblasts, and in vivo on Galleria mellonella larvae. The antibacterial activity against grampositive and gram-negative strains was performed by microdilution in broth, the antibiofilm activity in cell culture plate and analyzed by scanning electron microscopy, as well as the antibacterial effect in vivo on G. mellonella larvae infected with Staphylococcus aureus. The antiparasitic action of analog peptides on the epimastigote and trypomastigote forms of T. cruzi was evaluated by counting viable cells and the antiproliferative effect in cancer cell lines was evaluated by the 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyl-tetrazolium (MTT) salt reduction method. StigA8 and StigA18 showed higher rates of cationicity (+4 and +5, respectively) and hydrophobic moment (0.652 and 0.708, respectively) in relation to the lead molecule (+2 and 0.571, respectively) and a conformation mostly in α-helix in environments that mimic biological membranes. In addition, the peptides showed hemolytic activity of 11.5-22% in a concentration range of 9.37-150 µM, with a cytotoxicity index of 50% in murine fibroblasts at a concentration of 20 µM and 12.3 µM for StigA8 and StigA18, respectively. In addition, no signs of toxicity were observed on G. mellonella larvae at a dose of 120 mg/kg. Both analog peptides showed significant antibacterial activity in strains of gram-positive and gram-negative bacteria in concentrations ranging from 0.93-9.37 µM, with antibiofilm action against S. aureus in concentrations of 7.5-12.5 µM, causing damage such as matrix destruction, cell membrane invaginations, roughness, and reduction of the cell diameter by 12.5 µM. StigA8 and StigA18 showed antibacterial effect in vivo, increasing larval survival at 120 mg/kg by 75% and 60%, respectively, at the peak of infection. Trypanocidal activity on the epimastigote and trypomastigote forms of T. cruzi was observed at 6.25 µM for both peptides and antiproliferative potential from the concentration of 2 µM for StigA8 and 4 µM for StigA18. Therefore, StigA8 and StigA18 are molecules with the potential for the development of new antimicrobial and anticancer drugs.