Stigmurin and TsAP-2 from Tityus stigmurus scorpion venom: Assessment of structure and therapeutic potential in experimental sepsis

Abstract

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.

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

“…Antimicrobial peptides have been discovered in the venom of different scorpion species, being linked to the innate immune response against pathogens [ 18 , 19 , 20 , 21 , 22 ]. In the transcriptome study of the T. stigmurus venom gland, an AMP denominated Stigmurin (+1 net charge and 0.571 hydrophobic moment) was identified [ 4 , 13 , 14 ]. From this peptide we designed two analog peptides, denominated StigA6 and StigA16.…”

“…Using CD, we could also observe StigA6 and StigA16 stability at pH range 3–9, as well as in temperature change; once heated to 98 °C and subsequently cooled to 2 °C, they did not appear to change their secondary structure. Stigmurin had already been seen to be stable to pH and temperature variation [ 13 , 14 ], indicating that the addition of lysine in the native peptide sequence did not cause impairment to the peptide stability.…”

“…Other antimicrobial peptides from scorpions had already shown activity against Gram-positive and Gram-negative bacteria [ 18 , 25 , 26 , 27 , 28 ]. TsaP2, a peptide found in T. serrulatus that shows high identity with Stigmurin, presented MIC of 17.30 and 69.23 µM for S. aureus and E. faecalis , respectively; therefore, both StigA6 and StigA16 are more effective than TsaP2 [ 14 ]. The capacity of scorpion AMPs to inhibit fungal growth has also been seen [ 29 , 30 ].…”

“…For the normal cell line tested, 3T3, both analog peptides showed an IC 50 that was twice the value observed for Stigmurin, demonstrating that they are less toxic for this normal cell than the native peptide. Other scorpion AMPs demonstrated activity on cancerous and normal cells [ 14 , 15 , 38 ]. A study with analog scorpion AMPs showed that the peptides with lysine substitutions were less effective on the BHK21 normal cell [ 38 ].…”

“…Stigmurin is an antimicrobial peptide discovered by our research group in the venom gland transcriptome study of T. stigmurus [ 4 ]. It is a cationic peptide containing 17 amino acid residues (FFSLIPSLVGGLISAFK-NH 2 ), with +1 net charge and hydrophobic moment of 0.571 [ 13 , 14 ], which presented antimicrobial activity in vitro and in vivo, as well as antiproliferative properties in normal and cancerous cells, with low hemolytic activity [ 13 , 14 ]. The rational design of molecules has been seen to potentiate their activity and biotechnological use; the increase in α-helix, cationic character, and hydrophobic moment can empower the antimicrobial activity [ 15 , 16 , 17 ].…”