RESUMO
OBJECTIVES: The pterocarpanquinone LQB-118, previously demonstrated to be effective in vivo via oral delivery, was investigated for its mechanism in selective parasite killing. METHODS: Oxidative stress in Leishmania amazonensis was analysed by evaluating reactive oxygen species (ROS) production (2',7'-dichlorodihydrofluorescein diacetate) and the loss of mitochondrial membrane potential (ΔΨm) using rhodamine, JC-1 and MitoCapture. Ultrastructural analysis was performed using transmission electron microscopy (TEM). DNA fragmentation was evaluated using terminal deoxyribonucleotidyl transferase-mediated dUTP nick-end labelling (TUNEL). RESULTS: Treatment with LQB-118 induced ROS production in the promastigotes of L. amazonensis in a concentration-dependent manner for the first 4 h and was sustained for 24 h. TEM analysis revealed several alterations typical of apoptosis. Promastigotes presented a reduction of ΔΨm after 24 h of incubation with 2.5 µM (18.7%), 5 µM (63.7%) or 10 µM (70.7%) LQB-118. A sub-G0/G1 cell cycle phenotype was observed in 21%-83% of the promastigotes incubated with 1.25-10 µM LQB-118. Concentration-dependent DNA fragmentation was observed in promastigotes treated with 2.5-10 µM LQB-118, and selective DNA fragmentation was observed in intracellular amastigotes after 72 h with 2.5 µM treatment. CONCLUSIONS: Our results suggest that LQB-118 selectively induces ROS-triggered and mitochondria-dependent apoptosis in this parasite.
