Avaliação do mastoparano-L e seus derivados frente a cepas de Staphylococcus aureus associadas a mastite bovina

Abstract

Bovine mastitis (BM) consists in a disease characterized by mammary gland inflammation caused by pathogenic bacteria, resulting in substantial economic losses in the dairy production systems. Among the bacterial species associated with bovine mastitis, S. aureus represents one of the most common bacterial etiological agents found at infection sites. Conventional antibiotics remain the main tool for BM treatment and control. Nevertheless, the bacterial resistance evolution, as well as the possible presence of such drugs residues and pathogenic microorganisms in milk leads to the need of developing alternative treatment strategies. In this sense, antimicrobial peptides (AMPs) represent promising therapeutic candidates for the treatment of diseases like BM. In the present study, the peptide isolated from wasp venom, mastoparan-L, and three of its derivates previously obtained through rational design strategies, were functionally and structurally characterized. Thus, it was evaluated the mastoparan-L peptide efficiency, as well as its three derivates, denominated mastoparan-MO, mastoparan-R1 and [I5, R8] MP, against S. aureus strains isolated from bovine with mastitis. Initially, it was observed that the mastoparan-L parental peptide sequence modifications, to obtain the derivates, led to physicochemical properties alterations such as charge, hydrophobicity and hydrophobic moment of these peptides. Regarding structural comparison, all derivatives exhibit theoretical three-dimensional -helix structures. Moreover, mastoparan-R1 and [I5, R8] MP derivates have higher percentages of -helix (64.3% for mastoparan-L and 78.6% for mastoparan-R1 and [I5, R8] MP), being the mastoparan-MO, the derivate with the lowest percentage of -helix (57.9%). In addition, the structural peptide evaluation results indicate that the structural models generated for the analogs are stereochemically possible and reliable. Thus, the results of the minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) showed that the mastoparan-MO exhibited a slight increase in its antibacterial activity (16 μM) when compared to parental peptide (32 μM). Otherwise, the mastoparan-R1 derivate was uncapable of inhibiting the tested strains growth. Finally, the highest activities were reported for the [I5, R8] MP peptide, exhibiting MICs between 4-16 μM and MBCs between 8-16 μM. Thus, the bactericidal activity of this derivate ([I5, R8] MP) against S. aureus Aurora was evaluated during 90 min. Therefore, it was determined that the peptide [I5, R8] MP, at a concentration of 8 μM, totally reduced the initial bacterial load (4 log10) of S. aureus Aurora after 70 min of incubation. In hemolytic assays it was observed that at a concentration of 100 μM, the parental peptide (mastoparan-L) and the mastoparan-MO derivate resulted in the highest percentages of hemolysis (62% and 50%, respectively); whereas mastoparan-R1 and [I5, R8] MP derivates caused less than 20% hemolysis of bovine erythrocytes. In this way, the therapeutic potential of the [I5, R8] MP derivate observed in the present study makes possible the application of this peptide in future studies, aiming BM treatment.