Emanuel Paula Magalhães¹, Evelline Araújo Edson², Bruna Viana Barroso Martins¹, Ramon Róseo Paula Pessoa Bezerra de Menezes^1,3, Alice Maria Costa Martins^1,2,3

Introduction: Chagas’ disease (CD), caused by Trypanosoma cruzi, is an illness that is spreading worldwide, for which benznidazole (Bz) remains the only available treatment. However, the limited efficacy and toxicity of Bz underscore the urgent need for the development of  novel trypanocidal compounds. Regarding the therapeutic potential of antimicrobial peptides, novel analogues of M-PONTX-Dq4e [1–10] peptide ofDinoponera quadriceps venom, were synthesized. This study aims to evaluate the cytotoxicity andtrypanocidal effect, effect of [R]⁴ M-PONTX-Dq4e [1-10] peptide against T. cruzi Y strain.Material and Methods: Cytotoxicity of [R]⁴ M-PONTX-Dq4e [1-10] was assessed in LLC-MK2 cells (ATCC CCL-7) cultivated in DMEM 10% FBS medium in 96-wells plate (10⁵ cells/mL at 37°C in 5% CO₂ incubator). Experimental groups were treated with the peptide (400 – 1.56 µM) for 24 hours, when were submitted to MTT reduction assay. Percentual of cell viability was used to estimate CC50 (concentration that reduces cell viability in 50%). For trypanocidal effect, trypomastigotes (10⁶/mL), obtained by host cells infection, were treated with [R]⁴ M-PONTX-Dq4e [1-10] for 24 hours (at 37°C and 5% CO₂), and the percentual of viable parasites was determined by counting in Neubauer’s chamber for estimative of LC50 (lethal concentration to 50% of trypomastigotes). Selectivity Index (SI) was calculated by CC₅₀/LC₅₀ ratio. Antiamastigote effect was measured through infection of host cells, and treatment of parasites with LC50 and 2 x LC50 of the peptide. After 24 hours, amastigotes were stained with Giemsa, and the percentual of infected cells, and intracellular amastigotes was obtained by counting of 100 cells. Bz was used as the reference drug. Experiments were performed in triplicate (n = 3), and results, expressed as mean ± SEM, were analyzed by One-way ANOVA (Dunnet’s post-test). Results: [R]⁴ M-PONTX-Dq4e [1-10] reduced cell viability at 400 and 200 µM, with CC50 > 400 µM. The peptide reduced parasites viability in all concentrations higher than 0.78 µM (LC50 = 13.56 ± 1.27 µM), and SI > 29.50. For Bz, CC50, LC50 and SI were 502.60 ± 57.80 µM; 161.40 ± 31.80 µM; and 3.11. In amastigote forms, all tested concentrations of [R]⁴ M-PONTX-Dq4e [1-10] were able to reduce the number of infected cells in more than 30%, with reduction of viable amastigotes, the lifeform associated with persistence and chronic phase of CD, in 50%. Conclusions: [R]⁴ M-PONTX-Dq4e [1-10] presented effect against trypomastigote forms of T. cruzi Y strain, with selectivity higher than Bz. So, this molecule presents as potential candidate for the development of novel antichagasic tools.

Agradecimentos: Authors thanks to CNPQ, CAPES and FUNCAP for their financial support.