Estudo in vitro da atividade tripanocida da batroxicidina – catelecidina da glândula de veneno da serpente Bothrops atrox

Abstract

Chagas disease, also known as American trypanosomiasis, is a potentially fatal disease caused by the parasite Trypanosoma cruzi. There are two drugs available for the treatment of the disease, nifurtimox and benzonidazole. Both are toxic and have limited efficacy, requiring the search for new therapeutic alternatives. Antimicrobial peptides (AMPs) may be potential alternatives to conventional treatments already available, as they have a rapid action mode, a low resistance development and can work with existing drugs. The aim of this study was to investigate the effects of Batroxicidin (BatxC), a catalicidine peptide of the venom Bothrops atrox venom gland, on the different forms of of Trypanosoma cruzi Y strains. The treatment with BatxC at 24, 48 and 72 h caused a decrease in the viability of the parasites in almost all the studied concentrations (1.56, 3.12, 6.25, 12.5, 25 and 50 μM) with an IC50 of 11, 3; (0.045, 0.09, 0.18, 0.39, 0.78 and 1.56 μM), respectively, with a selectivity index of 315. Assays with trypomastigote forms at different concentrations demonstrated that BatxC is toxic from concentrations of 0.18 μM, approaching 100% lethality at the concentration of 1.56 μM. Amastigote forms were also performed following cytotoxicity study in LLC-MK2 and RAW264.7 cells, showing that the studied concentrations (0.44 and 0.88 μM) in 24h, was a reduction of 40% and 45% of infected cells, respectively. In 48h, there was no decrease in the percentage of cell infection. The percentage inhibition of amastigote forms treated with BatxC was 33% (IC50) and 43.5% (2xIC50) in 24h, and 23% (IC50) and 33% (2xIC50) in 48h. These results demonstrated a reduction in the survival rate of amastigote forms. Subsequently, flow cytometric assays with Annexin V-PE and 7- aminoactinomycin (7-AAD) demonstrated a higher population of 7ADAD-labeled parasites at IC 50 (11.3μM) and 2x IC 50 (22.6μM ) demonstrating that death induced by BatxC was predominantly by necrosis. Then, the experiments were performed with DCF and Rhodamine 123 to investigate the involvement of reactive oxygen species (EROS) and alteration of the mitochondrial membrane potential in cell death mechanism. The results showed that there was an increase in EROS and alteration of mitochondrial transmembrane potential. The T.cruzi cell death pathway by a necrotic mechanism was finally confirmed by scanning electron microscopy (SEM) that observed loss of cellular membrane integrity. In conclusion, BatxC inhibited all forms of T. cruzi Y strain, with high selectivity index, inducing necrosis.