In vitro activity of phospholipase A(2) and of peptides from Crotalus durissus terrificus venom against amastigote and promastigote forms of Leishmania (L.) infantum chagasi

BACKGROUND: American visceral leishmaniasis is caused by the intracellular parasite Leishmania (L.) infantum chagasi, and transmitted by the sand fly Lutzomyia longipalpis. Since treatment is based on classical chemotherapeutics with significant side effects, the search for new drugs remains the greatest global challenge. Thus, this in vitro study aimed to evaluate the leishmanicidal effect of Crotalus durissus terrificus venom fractions on promastigote and amastigote forms of Leishmania (L.) infantum chagasi. METHODS: Phospholipase A(2) (PLA(2)) and a pool of peptide fraction (<3 kDa) were purified from Crotalus venom. Furthermore, promastigotes and peritoneal macrophages of mice infected by amastigotes were exposed to serial dilutions of the PLA(2) and peptides at intervals varying between 1.5625 μg/mL and 200 μg/mL. Both showed activity against promastigotes that varied according to the tested concentration and the time of incubation (24, 48 and 72 h). RESULTS: MTT assay for promastigotes showed IC(50) of 52.07 μg/mL for PLA(2) and 16.98 μg/mL for the peptide fraction of the venom. The cytotoxicity assessment in peritoneal macrophages showed IC(50) of 98 μg/mL and 16.98 μg/mL for PLA(2) and peptide by MTT assay, respectively. In peritoneal macrophages infected by Leishmania (L.) infantum chagasi amastigotes, the PLA(2) stimulated growth of parasites, and at higher doses reduced growth by 23 %. The peptide fraction prevented 43 % of the intracellular parasite growth at a dose of 16.98 μg/mL, demonstrating the toxicity of this dose to macrophages. Both fractions stimulated H(2)O(2) production by macrophages but only PLA(2) was able to stimulate NO production. CONCLUSION: We have demonstrated the in vitro leishmanicidal activity of the PLA(2) and peptide fraction of Crotalus venom. The results encourage further studies to describe the metabolic pathways involved in cell death, as well as the prospecting of molecules with antiparasitic activity present in the peptide fraction of Crotalus durissus terrificus venom.