Atividade in vitro da pterocarpanoquinona LQB-118 sobre o Trypanosoma cruzi

• Autor(a) principal: Azevedo, Bruno Fonseca de
• Data de Publicação: 2013
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UERJ
• Texto Completo: http://www.bdtd.uerj.br/handle/1/14414
• topic: Trypanosoma cruzi; Pterocarpanoquinone; Treatment; Macrophages; Antiparasitic effect; Trypanosoma cruzi; Pterocarpanoquinona; Tratamento; Macrófagos; Efeito antiparasitário; Trypanosoma cruzi; Macrófagos; Antiparasitários; CNPQ::CIENCIAS BIOLOGICAS::PARASITOLOGIA

Chagas disease is endemic in Latin America being considered a neglected disease with high socioeconomic impact. The infection is caused by the protozoan Trypanosoma cruzi, which is transmitted by the vector form, among other mechanisms. The treatment basically consists of using two drugs, benznidazole and nifurtimox which presenting several side effects and acts very little on intracellular amastigotes what makes the current treatment is restricted and unsatisfactory. Several pharmacological activities have been attributed to lapachol and pterocarpans, such as antitumor and antiparasitic activity. Because of this therapeutic potential an hybrid molecule was synthesized, a pterocarpanquinone LQB-118, and some derived molecules. The LQB-118 previously showed antitumor and anti-Leishmania activity. The objective of this study was to investigate the in vitro activity of LQB-118 and its derived molecules on Trypanosoma cruzi Dm28c clone. For initial evaluation of the antiparasitic effect of the molecules, intracellular amastigotes, epimastigotes and metacyclic trypomastigotes were incubated with 20 µM of LQBs 118, 168, 187, 182 and 236. The LQB-118 showed antiparasitic activity on the three evolutionary forms (90% on amastigote form, 44% on trypomastigote form and 70% on epimastigote form) of the parasite, while derived molecules showed no significant activity. Thus, studies were continued with the molecule LQB-118. The action of LQB-118 on intracellular amastigotes was dose dependent, with reduction of infection index into 81 and 88% at concentrations of 20 and 30 µM respectively. In trypomastigotes, LQB-118 was less active reducing the mobility of these forms up to 45% at 30 µM. In epimastigote form, the action was dose dependent reaching 96% to inhibit the growth of parasites at 20 µM, with morphological changes such as rounding of the cell body and loss of the flagellum. The dose able to inhibit 50% was 4,2 µM to intracellular amastigote and 38,1 µM to trypomastigote. To macrophages, LC50 was 40 µM, a concentration about ten times higher than the IC50 to amastigotes.The ability of intracellular amastigotes differentiate on trypomastigotes and break macrophages was evaluated after the treatment with LQB-118 for 72 hours. There was a delay on intracellular cycle of the parasite in a dose dependent way, where in the concentration of 30 µM the trypomastigote emergence was on the 9th day while in controls was on the 5th day of culture. To delineate the mechanism of action, it was evaluated the direct effect on the parasite such as the induction of DNA fragmentation. Analysis of the induction of DNA fragmentation by TUNEL labeling showed that the treatment with LQB-118 induced selectively fragmentation of amastigotes s nuclei while macrophages s nuclei remained without fragmentation. Peritoneal macrophages pretreated with LQB-118 for 24 hours were able to reduce the number of amastigotes after 72 hours of culture in absence of the molecule, but without alteration in nitric oxide production. These results show that LQB-118 is active against T. cruzi, mainly on intracellular amastigote form, which is present in the chronic phase of infection. The mechanism of action suggests that LQB-118 can be selectively toxic to parasite and also activate the microbicidal mechanisms of macrophages independently of nitric oxide production.